The results indicated that wild boar meat was characterised by the highest percentage of IA fibres and it contained the higher percentage of MUFA, but a low of PUFA and SFA, and was characterised by a(n-6)/(n-3) ratio lower than in the case of deer meat and greater susceptibility to oxidative changes. The highest percentage of SFA, and the lowest of MUFA and PUFA, was recorded in fallow deer meat, which was also characterised by the highest percentage of white fibres. The curing and drying processes increased the percentage share of SFA and the susceptibility of muscle lipids to oxidation, decreased the percentage of PUFA, and caused insignificant changes in the (n-6)/(n-3) ratio of fatty acids. The products were also characterised by a low amount of fat.The aim of the study was to describe the effect of fibre type on the fatty acid profile and lipid oxidation observed in dry-cured ham produced from individual  The characteristics of dry-cured hams are shaped by the selection of appropriate processing conditions , raw matPork is the basic raw material for the production of cured meats ,9. In maIn recent years in Europe, there has been an increase in consumer interest in wild game meat as an alternative to pork and beef, mainly due to its relatively high nutritional value. New ranges of fermented and dried products from various species of game are beginning to appear on the market . DespiteAn important aspect in assessing the quality of raw material from wild game is taking into account the histochemical profile of the meat. According to the research of Żochowska-Kujawska et al. , a greatA total of 48 carcasses from roe deer (Capreolus capreolus), fallow deer (Dama dama), deer (Cervus elaphus) bucks and wild boar (Sus scrofa) males (twelve carcasses in each group) were used for the experiment. The carcasses selected from among the hunted animals weighed 14.7 kg (standard deviation = 0.8), 54.1 kg (SD = 1.7), 97.7 kg (SD = 4.2) and 73.2 kg (SD = 3.9), while their ages were approximately 24–30 months, respectively. The age of hunting animals was determined by tooth wear and replacement on the jaw teeth . AnimalsFor the purposes of histochemistry analysis, three samples of 1 × 1 × 0.5 cm were taken from the mid-part of the semimembranosus (SM) muscle of each carcass (45–60 min after being shot), then immediately frozen in liquid nitrogen and stored at −80 °C. The carcasses were transported to the laboratory facilities at the West Pomeranian University of Technology in Szczecin. Approximately 44-h post mortem, carcasses were taken from the cool room to be skinned, halved and jointed according to the standards of the Polish Department of Hunting and used to obtain 96 hams . Each cut was deboned, and cleaned of external fat. The SM muscles of normal pH were dissected out of each of the hams. Before the salting stage, each muscle was shaped into a block by trimming off the edges.w/w) of salt mixture, and the salting mixture contained 150 ppm of NaNO2 as a curing agent and NaCl as a salt base. The process conditions of production were determined in a previous experiment [The muscles obtained as described above were divided in a completely randomised design into three groups of eight SM and BF muscles of each species of animal. Each group of muscles was cured with 6%  were placed on glass slides, stained using the myosin ATP-ase method , and claFat content was determined according to the AOAC (2005) procedure .v/v) solution. The extraction mixture contained 0.001% (w/v) of butylated hydroxytoluene as an antioxidant. The organic solvent was evaporated under a stream of nitrogen. The crude lipid extracts were then saponified with a 0.5 mol KOH solution in methanol. Afterward, the methyl esters of fatty acids (FAMEs) were prepared by transesterification with boron trifluoride (BF3) solution in methanol according to the AOCS official method Ce 2–66 [The intramuscular fat from raw, post-salted and dry-cured SM muscles of all tested species of animals was extracted  using a  Ce 2–66 .3/min, split ratio 1:50. Interpretation of chromatograms was made by comparing the retention times and the mass spectra of individual FAMEs of the examined sample with the retention times and mass spectra of the respective Sigma FAME standards (Lipid Standard). The results were recorded and processed using ChemStation (E.01.00) software and thus the fatty acids (mg/100 g of muscle tissue) as well as the n-6/n-3 fatty acid ratio were calculated. As an internal standard, C 19:0 was used. Only FAME representing > 0.01% of total FAME was included in the results.Fatty Acid Methyl Esters (FAME) were prepared according to the AOCS method . GC analg for 25 min. The supernatant absorbance was determined on a SEMCO spectrocolorimeter at a wavelength λ = 535 nm in a cuvette with a layer thickness of 1 cm. The amount of lipid peroxidation products reacting with thiobarbituric acid (TBA-RS) was calculated from the absorbance value using the molar absorption coefficient (ε = 1.56 × 105 M − 1 × cm − 1) and expressed in milligrams of malondialdehyde (MDA) per 1 kg of sample weight. TBA-RS concentration determinations were made for each variant in duplicate.The degree of lipid oxidation was determined according to the methodology presented by Buege & Aust . ImmediaMuscle pH was measured using a portable pH metre  equipped with a pH penetration probe and an automatic temperature compensation probe. Before each measurement, the pH metre was calibrated with standard buffer solutions of pH 7.0 and pH 4.0  stored at room temperature.The instrumental measurement data were analysed statistically with the single effects given by species and the fixed effects by species and production phase, and their interaction . The meaThe study compares the histochemical profile (percentage of three types of muscle fibres) of the SM muscles of four game species . The data in There is little data in the literature on the simultaneous comparison of the histochemical muscle profiles of different species of wild animals, with the majority of them describing the histochemical state of the meat of wild boar, deer, or fallow deer ,23,34,35There was a significant effect of the species on the fat content, fatty acid composition and the value of the TBA-RS coefficient . Deer meIt seems that the greater share of MUFA in venison meat and the higher TBA-RS ratio can be attributed to the greater percentage of red fibres it contains. In turn, a higher percentage of white fibres in the muscle was associated with a higher content of SFA. Moreover, Hernández et al.  and AndrIn turn, a higher value of the TBA-RS index in muscles with a higher percentage of red fibres can be explained by a greater number of mitochondria in them, and consequently, a greater number of membranes being the main source of phospholipids , becauseApart from the above-mentioned influence of the histochemical profile, another cause of the interspecies differences in the quality of venison meat found during the study may be, among others, a diet associated mainly with a preference for a certain type of food, which, in turn, determines its nutritional value. Game has been shown to have a generally low fat content, which is also confirmed by data in the literature ,48,49. HThe observed differences in the fatty acid composition can be ascribed, as mentioned above, to the different diets of wild animals. Wild boar, despite being an omnivorous animal, prefer plant food, especially cultivated plants, but also acorns and chestnuts . As a coThe curing and drying processes caused changes in the quality of muscles in all tested groups of animals, while both the phase of the production process and the type of meat were factors that differentiated the examined quality parameters . It is kThe effect of drying time on changes in the fatty acid profile presented in the study and in the literature is ambiguous. It seems that one of the factors determining the nature of these changes is the type of raw material. For example, in curing and drying the horse tenderloin “cecina”, Lorenzo  found thThe result of the oxidation of unsaturated fatty acids, which accompanies the drying of cured meat, is associated with the increase in the value of the TBA-RS index observed in this study, compared to the raw material , which wThe species of game was another factor that, apart from the production process phase, influenced the quality of dry-cured meats. It seems that deer and wild boar meat products had better nutritional value, as they had a higher content of MUFA and PUFA, and a lower content of SFA. It is worth emphasising that the interspecies differences in the selection of raw material for the production of dry-cured meats had a significant effect on its nutritional value. The method of processing the raw material did not generally cause a significant deterioration in the fatty acid profile of dry-cured meats, regardless of the type of meat used. However, it can be noticed that dry-cured wild boar and deer meat had a slightly “better” profile of fatty acids.One of the reasons for the differences in the fatty acid profile of dry-cured meats produced from different species of game animals indicated in the study may be the previously described differences in the quality of the raw material, which are a consequence of the diet preferred by game. Moreover, Ventanas et al.  believe The results indicated that the species of game is a factor that has a significant impact on the differentiation of the histochemical profile of muscles. However, the histochemical properties of game meat may determine its culinary quality and the possibility of using it in processing for the production of dry-cured meats. The production process is a factor that varies the fatty acid composition and the susceptibility of meat to oxidation. The processing of this raw material in the curing and drying process causes changes in the quality of the raw material but does not significantly deteriorate the fat quality of dry-cured meats.


This paper deals with the problem of vertical oscillation of rail and road vehicles under symmetrical and asymmetrical loading and symmetrical and asymmetrical kinematic excitation. The term asymmetry is understood as the asymmetric distribution of vehicle mass and elastic and dissipative elements with respect to the axes of geometric symmetry, including asymmetric kinematic excitation. The various models used  are discussed and their analytical solutions are outlined. The theory of the spatial model is applied to the chassis of a model railway vehicle. The basic relations for the calculation of the equations of motion of this vehicle are given. In the next section, the experimental solution of a four-axle platform rail car is described and the measurements of vertical displacement and accelerations when crossing wedges (representing unevenness) are given. The problem of vibration in wheeled vehicles, both road and rail, is solved based on different assumptions and models, under different operating conditions. There is extensive literature on this issue, e.g., ,4,5,6,7.An overview of the solution to the vibrations of a spatially elastic body with consideration of various influences are given, for example, in . The supA major disadvantage of the current models, i.e., most often quarter-plane or planar, but also spatial, is the neglect of the effect of asymmetry on their driving characteristics. Therefore, only solutions to partial problems are given, mostly for half-plane (planar) models, which assume planar symmetry with one longitudinal axis of symmetry, respect the effect of the displacement of the centre of gravity from the centre of geometry, or consider different intensities of viscous damping and their combination. However, the most common solutions to the oscillation of vehicle models are based on quaternion models, usually vertical and elastic coupling with dissipative elements, and with different numbers of bodies—these are models with multiple degrees of freedom with coupled vertical displacements. In the application of the quaternary model, two axes of vehicle symmetry are assumed, i.e., full symmetry and its kinematic excitation.It is known from practice that vehicle crashes, both road and rail, often occur for reasons that are difficult to explain. In the case of road vehicles, the cause is often cited as not adapting the speed to the road conditions, etc. In the case of railway vehicles, the causes are often more difficult to determine, apart from the obvious causes such as rail breakage, rail gauge collapse, etc. The cause is often due to incorrect load distribution and the resulting asymmetry of the load on the individual axles or wheels. In the case of vehicle oscillation, vertical vibrations can cause loss of wheel contact with the road (loss of vehicle controllability), and in the case of railway vehicles, loss of wheel contact with the rail due to unevenness of the rail, resulting in derailment.Therefore, the investigation of the effect of asymmetry on the vertical oscillation of the model vehicle must be carried out by analysing the various causes and their consequences on spatial models.Asymmetry of the vehicle weight distribution with respect to the axes of geometric symmetry, the position of the centre of gravity, the directions of the main central axes of inertia, both of the vehicle structure itself and of the loaded vehicleAsymmetry of the geometry of the distribution of elastic and dissipative elements of the couplings of the individual bodies of the vehicle system, their mechanical properties, spring stiffnesses, intensity of viscous damping assuming linear couplings of the individual quantities, and small displacements and rotations of the parts of the systemAsymmetry of kinematic excitation, i.e., the field of unevenness of the road or track surface, which define the kinematic excitation of the system at the point of contact between wheel-vehicle or wheel-track.When analysing the effect of asymmetry on the vertical oscillation of vehicles, we must distinguish three basic cases of the effect of asymmetry with respect to the axes of geometric symmetry, which are determined by two mutually perpendicular axes, the symmetry of the vehicle’s track and wheelbase, and the intersection at the geometric centre of the vehicle:The above types of asymmetry can exist separately or together, and the third case is the most common.The basic prerequisite for investigating the influence of asymmetry on the vibration of a system of bodies (a vehicle) is the choice of a suitable simple spatial model that allows for the investigation of different cases of asymmetry and the comparison or verification of the results obtained by different methods, i.e., theoretical  and experimental. Most often, we compare the vertical displacement of the centre of gravity and the rotation about the axes passing through the centre of gravity and the vertical movements of any point of the vehicle.In this study, a methodology for solving the vertical vibration of a vehicle was developed and this methodology was applied to several real vehicle cases (wheeled and tracked) to verify its applicability to a large set of vehicles. The methodology also allows for the determination of the magnitude and time history of wheel forces, the deformation magnitude or allowability of the individual elements of the spring links and parts of the structures, and the damping intensity criteria, including the fulfilment of the physiological requirements for the vehicle ride.We use the basic theory of motion equations of an elastically supported rigid body when solving the vertical vibration of the vehicles, both road and rail. A rigid body of general shape can be elastically supported or suspended in an inertial orthonormal Cartesian space, which is defined by a stationary component system. In our case, it is a more complex system where we solve the vertical oscillation of the vehicle (model) including the effect of asymmetry based on various assumptions. As already mentioned, a quarter, half, or full 3D model of the mechanical system with several degrees of freedom, with different mass distributions and with different elastic and dissipative elements (bindings) is used. The kinetic excitation is considered, and the solution will be demonstrated analytically, numerically, and experimentally.For the basic analytical derivation, a simple but sufficiently general 3D model was designed to meet the requirements outlined in the previous section. The proposed model  is suitak1–k4). The springs are supplemented by dampers (b1–b4). Weights z1 and z2 are placed on the plate to simulate the imbalance of the vehicle. The centre of gravity of the vehicle T is displaced in the x-axis direction by xe and in the y-axis direction by ye relative to the geometric centre C. The x and y axes passing through the geometric are the axle base and wheel spacing axes. The rotation of the model about the x-axis is xφ and about the y-axis is yφ. The value of h is the height of the road unevenness.The model consists of a rigid plate, which is supported on four springs (Tw(t) and the rotation of the model about the central axes of inertia xφ(t), yφ(t), was chosen as the criterion for comparing the individual cases.The time course of vertical displacement, i.e., the change in the position of the centre of gravity xA, yA) in terms of its vertical displacement, velocity, and acceleration versus time (e.g. at the suspension location) and determine the wheel pressures of the vehicle (Equations (1)–(3)).In general, we can describe the motion of any point A , a planar model, and a quartic model. The solution is found by determining the equations of motion of a mechanical system with three degrees of freedom.p—number of degrees of freedom, jq—generalised coordinate, kE—kinetic energy, pE—potential energy, dR—Rayleigh dissipated energy, jQ—excitation forces.The equations of motion for the vibration of a spatial model of an elastically supported rigid body were determined from the Lagrange equations of the second kindMh—mass matrix, Mb—damping matrix, Mk—stiffness matrix, Qj—vector of generalised excitation function  of the third order, whose elements are equal to the inverse of the diagonal elements of the matrix Mh.To solve Equation (5), we use Laplace integral transforms, modifying the elements of the matrix D from the left, we getIn the case of a symmetrical mechanical system, the mass matrix is unitary. If we multiply Equation (5) by the diagonal matrix M—mass matrix, B—damping matrix, K—stiffness matrix, Fj—vector of generalised kinematic excitation function.We rewrite this equation in the formijb and the stiffness matrix ija. The calculation of these elements is given, e.g., in  and is given by the ratio of the product of the vertical components of the wheel forces and the mass of the vehicle modelIf the vertical component of the force at the F2(t)—the physical component of the angular acceleration with respect to the x-axis [s−2]—is given by the ratio of the product of the moments of the components of the wheel forces to the x-axis and the moment of inertia of the vehicle model to this axisThe component of the generalised function F3(t)—physically the component of the angular acceleration with respect to the y-axis [s−2]—is given by the ratio of the product of the moments of the wheel force components to the y-axis and the moment of inertia of the vehicle model to this axisxml a yml for m = 1, 2, 3, 4 are the distances of the support (elastic viscoelastic damping) from the axes C, xJ, yJ—moments of inertia of the vehicle mass to the respective axes xml, yml.The component of the generalised function M, B, K and the components of the vector F, a system of simultaneous linear inhomogeneous differential equations, the equations of motion of a spatial model of a vehicle with three degrees of freedom, with complete asymmetry: the mass distribution of the system (h(x) → h(t) is determined.By defining the elements of the matrices It should be emphasised that the investigation of vehicle oscillations assuming a planar vehicle model with a longitudinal axis of symmetry, and especially assuming a quarter vehicle model with both longitudinal and transverse axes of symmetry, will substantially change the definition of the elements of the matrices of the equations of motion (7) and thus the required solution. This can be documented by comparing the matrix elements of the single-individual vehicle models.w(t) and yφ(t), the following can be assumed:M is diagonal and unit, and for mass distribution is valid xyD = yxD = 0, => S23 = S32 = 0, ye = 0.Mass matrix yl1 = yl4, yl2 = yl3, xl1 = xl4, xl2 = xl3.The geometry of support is defined by dimensions b1 = b4, b2 = b3.Damping intensity k1 = k4, k2 = k3.Stiffness of elastic support is given by formulas For spatial mode of vehicle with a longitudinal axis of symmetry, which has only two degrees of freedom, B elements areThen damping matrix K elements areStiffness matrix m-th wheel between the wheel and the road (rail) for crossing over unevenness of height h1 = h4, h2 = h3Based on the above relations, we can determine the components of the vertical forces acting at the location of the w(t) the following is assumed:xyD = yxD = 0 → S23 = S32 = 0, xe = 0, ye = 0.Mass distribution M is unit, the centre of gravity of the system is identical to the centre of geometric gravity C, the main central axes of inertia are identical to axes of geometrical symmetry.Mass matric xj = lx, lyj = lyl for j = 1, 2, 3, 4.The support geometry is determined by dimensions j = b, for j = 1, 2, 3, 4.Damping intensity j = kk.Stiffness of elastic support is given by For quarter model of vehicle with a longitudinal and transverse axis of symmetry, i.e., for a system of one degree of freedom B elements areThen, damping matrix K elements areStiffness matrix jk = hComponents of the generalised kinematic excitation function vector for From the brief analysis of the equations of motion discussed above, and the forces on the individual wheels, it follows that both the plane and quarter models require complete symmetry along the longitudinal axis (plane model) or along both the longitudinal and transverse axes (quarter model).Due to the distribution of the different structural groups in the vehicle, no vehicle is geometrically symmetrical, it is clear that neither the quarter nor the half model are able to determine the dynamic properties of the vehicle with sufficient accuracy. In addition, the asymmetry in the loading of the vehicle (both cargo and possibly passengers) must be taken into account. For this reason, it is advisable to use a full spatial model for the further solution, which may be generally unsymmetrical  or only unsymmetrical but with parallel inertia and geometric symmetry axes.We will show the solution of this system on the chassis of a model of a railway vehicle, considering the effect of asymmetry. We assume a forced oscillation of the model, which is represented by a spatially elastically supported rigid plate with single and multiple primary linear suspension by coil springs (two-axle railway vehicle model). It is a kinematically excited system of three rigid bodies elastically supported and bounded, considering the effect of asymmetry ,23,24. Hm1 and m2 with symmetric mass distribution . However, we consider the asymmetry of the spring stiffness parameter and their geometrical support. The model of the vehicle body is considered as a rigid plate of mass m for which an asymmetric mass distribution is considered . The computational model is shown in A simple computational model of the vehicle chassis was chosen for the calculation. The model consists of two two-axle chassis with simple primary suspension and simple vehicle body suspension. The chassis are replaced by rigid plates of mass w, w1 and w2, the rotations φx, φx1, φx2, yφ, φy1, φy2 about the central axes of inertia of individual masses m, m1, m2 and its distance from these axes. Thus, we solve a system of bodies with nine degrees of freedom.The derivation of the following relationships is based on general assumptions, i.e., body stiffness, small displacements and rotations, and linear spring characteristics. We consider only the vertical displacements of arbitrary points of individual bodies. This vertical change in the position of a point of a body is determined by the displacement of the body’s centre of gravity xJ, yJ—moments of inertia, xyD—deviation moment to central axes of inertia of chassis with mass m, xJ1, yJ1, xJ2 and yJ2—inertia moments to the main central axes of bogies with mass m1, m2.The equations of motion are derived from the Lagrange equations of the second kind (4). Kinetic energy of the systemjkiA, their coordinates jkix, jkiy, vertical displacements jkiw and stiffness constants jkik. The individual indices correspond to masses j = 1, 2, quadrants k = 1, 2, 3, 4 and spring order i = 1, 2, ...., n (for the case of multiple support).The potential energy of the system depends on the displacements of the individual masses in the places of their elastic support, i.e., in the places of their elastic bound. In our case, in the chassis model we have chosen the system of marking for points jkih is marked, which is at the point of contact of the axle (spring) with the rigid base, to which we relate the position of the body. This vertical change represents crossing over an unevenness in the road (rail)—kinematic excitation.Similarly, the vertical change m1, j = 1PointVertical displacementStiffness constantA111(19)A121A131A141We can therefore determine the displacements of the individual points of the chassis, which are given by the relations for body m2, j = 2PointVertical displacementStiffness constantA211(20)A221A231A241For body jkiB, jkix, jkiy, jkik, j = 0 body, mass m, k = 1, 2 marking of chassis 1 and 2, respectively, i = 1, 4 belonging to the half-point A111, respectively, A141 follows from In the case of a model of a body with a simple spring suspension in the axis of the chassis, the division into quadrants cannot be used to mark the individual points of action of the springs. Marking of the points, coordinates, and stiffness constants PointVertical displacementStiffness constantB011(21)B014B021B024Displacement of individual point of body are given bym1, m2 and body m isPotential energy of bogies j—degree of system freedom, qj = T and jQ—generalised forces.Kinetic energy from (18) and potential energy from (22) are substituted into the Equation (4) resulting inThe solution  is given by motion equations in matrix formijκ are functions of stiffness constants jkik, the dimensions of support jkix, jkiy and the eccentricities xe and ye. The detailed solution of the individual elements is given, e.g., in [The individual elements of the stiffness matrix e.g., in .jQ ((23) and (24)) are again functions of the stiffness constants of the chassis springs jkik and functions of the road unevenness (elevation) at time h(t) at the location of the wheel springs. Then the kinematic excitation functions in Equation (24) are given byjkihjkik(t)—the shape of the time function of kinematic excitation at individual axle points and their sequence.The generalised force functions Equation (24) can be rearranged toD (ijd) from the left, where ijd = 1/ijα—diagonal elements of mass matrix Mh(ijα). After arrangement, the result is [Then the equation is multiplied by matrix esult is ,26(27)MM = E + S and is substituted into (26)S are ijs. These elements are given by equations s11 = s22 = 0; ijs = 0 for i = 3, …, 9; j = 3, …, 9; s12 = xyD/xJ; s21 = xyD/yJ. These quantities represent the effect of asymmetric distribution of mass, i.e., rotation of main central inertia axes to central axes parallel with geometric axes of the plate (vehicle). Similarly, the elements ija of matrix K are determined by division of i-th row of stiffness matrix by i-th element at diagonal of inertia matrix. Excitation function of time jF(t) is determined by the same procedure with function jQ(t).Mass matrix can be expressed in form System of motion equations in case of symmetry is transformed intok12 and k0 and function of displacement x12, y12, x0, y0. In the case of complete symmetry, the system of nine differentiated simultaneous equations is transformed to the system of seven simultaneous equations and two independent equations of harmonic motion for q7 and q9(y9).Elements of stiffness matrix are function of spring stiffness The solution of the system of Equation (26) can be performed by any of the numerical methods . Analytical solution is possible by applying matrix calculus, Lagrange’s method of variance of constants, or by Laplace transform. The Laplace transformation yields a system of linear algebraic equations for zero initial conditions .jq(t) and jF(t) for j = 4 … 9, p—parameter of Laplace transformation. By rewriting the Equation (32) into the matrix form, it is recommended to solve the system of linear algebraic equations by Cramer ruleD(p)—determinant of matrix of above-mentioned system of equations, which is defined asAs indicated, the solution can also be done by applying the Laplace transformation, where Equation (27) after modifications becomesAn − i)22 by reverse transformation of the images jiD(p) and D(p) so that the product of the expression and image To determine the search required function The polynomial in Equation (34) with real coefficients can be replaced by the product of quadratic binomialsAfter performing the product on the right side, a polynomial is obtained2(n − i)p on both sides of Equation (36) An − i)2( = Bn − i)2 with the relations determining the coupling of the coefficients of the algebraic equation and its root factors, the algebraic equation is obtainedω2—the circular frequencies of the functions jy(t), for j = 1, 2, 3, …, n. The next solution, after modifications and back-transformation, would give the convolution integralkω is the solution of Equation (38). From the known functions jq(t), i.e., the solution of the system of Equation (26), the required quantities of the system of Equation (24) are determined.Determining the roots of the frequency Equation (38) is the most complicated part of the proposed solution, especially in terms of numerical accuracy, i.e., This method makes it possible to determine the vertical displacements of arbitrary points of the chassis or body of the vehicle, for example, the displacements of the points described by Equations (19)–(21). Thus, a program can be developed to calculate the vertical displacements of arbitrary points of railway vehicle chassis models with a large range of design variations.The above method was experimentally verified on a real railway vehicle. A four-axle railway freight car of the Smmps series was used for the experiment. The aim of the measurements was to determine the geometrical, mass, and stiffness parameters of the single-individual parts of the freight car. The main objective was to establish the oscillations of the individual parts of the wagon when crossing the wedges at different wedge locations and load placements on the wagon platform . The measurement requirements were specified, and the wagon was modified for these specific requirements.Due to the requirements for suspension linearity, the original chassis with leaf springs (type 26-2.8) were replaced by chassis with coil springs (Y25). For the new chassis, the outer springs of the primary suspension were removed a, and a The bogies were fixed to the body (car platform) by a network of steel cables with cable tensioners—For all springs  of both chassis, their characteristics and stiffnesses were determined, and based on these characteristics the selection was made so that the resulting stiffnesses of the primary and secondary suspension on the wheel, wheelset, chassis, and car were distributed with maximum symmetry to the longitudinal and transverse axes of the car.The flatcar was loaded with two loading units b, each wThe modified vehicle was subjected to wedge crossing tests . The carThe relative vertical displacement of the chassis frame relative to the wheelset (9 sensors), the car body relative to the chassis frame (4 sensors), and the vertical acceleration of selected points on the body (5 sensors) and chassis (2 sensors) were measured. The location of the sensors can be seen in Strain gauge track sensors (chassis frame × wheelset) and cable track sensors (box frame × chassis frame) were used to measure vertical displacement. Acceleration was measured with B12/200 Hz inductive sensors .The experiments were carried out according to an optimised test plan. Selected combinations of experiments arose from statistical analysis of combinations of all possible experimental settings. These combinations were sufficient to achieve the goals, i.e., to identify critical situations in which derailment may occur . The tesDue to the scope of the measurements, only selected results for symmetrical and asymmetrical loading and for symmetrical and asymmetrical excitation are presented in this paper. The labels of the locations where the relative deflections between the case and chassis, chassis, and wheelset were measured are shown in (a)The time trend of the deflections when the car crosses the wedges under symmetrical loading of the car and symmetrical kinematic excitation is shown in In this case, the symmetrical load is represented by the symmetrical positioning of the load with respect to the geometric centre of the car. (b)Time trends of displacement when the car crosses the wedges under symmetrical loading, asymmetrical kinematic excitation—From the above time trend , it is c(c)Time trends of displacement when the car crosses the wedges under asymmetrical loading, symmetrical kinematic excitation—The displacement of the front wheelset relative to the chassis frame  show a dThe relative deflection between the chassis frame and the car body is again shifted relative to the axis through the centre of gravity in the case D-I, i.e., under asymmetrical loading and symmetrical kinematic excitation . The dis(d)Time trends of displacement when the car crosses the wedges under asymmetrical loading, asymmetrical kinematic excitation—The load distribution is the same as in the previous case, but the kinematic excitation is asymmetrical . DisplacThe difference in the position of the vertical displacement between the car body and the chassis frame  at pointIn addition to the measurements of the relative vertical displacement, measurements of the vertical acceleration were also carried out. Most of the acceleration measurement points were located on the vehicle body . In this paper we present the vertical acceleration waveform of the vehicle body in its transverse axis on the left and right side (points 3L and 3R) for asymmetrical loading and asymmetrical kinematic excitation (variant B-III). To illustrate this situation, the time history of the relative displacements at points 1L, 1R , 2L, 2R The relative displacement between the car body and the chassis frame  are relaThe vertical acceleration in the middle of the car body on both the left and right sides  was highThe paper deals with the theory of oscillations of mechanical systems of elastically supported and bound bodies. The application of this solution to vehicle models has been carried out. The methodology of the model solution is proposed and the application of this methodology to a real vehicle under different operating conditions has been carried out. The application has been made, among other things, to a railway chassis vehicle—its solution is the subject of this paper. Based on the developed methodology, an experimental solution of a four-axle railway vehicle without damping (shock absorbers) was implemented. The results of the experimental solution, i.e., the time course of vertical displacement, are presented in the previous section.From the given results, it can be seen that in the case of asymmetrical kinematic excitation , the vertical oscillation of the car will cause the vertical oscillation. The consequence of this oscillation is the loss of contact between the wheel and the rail (loss of adhesion). In any case where the critical value of vertical displacement of the wheel, which is equal or higher than height of axle, is achieved, the vehicle may be derailed. These vertical deflections are also strongly influenced by the asymmetry of the weight distribution of the vehicle and, in particular, by the asymmetry of the load. From the results obtained, it is necessary to pay particular attention to the distribution of the load  on the railway carriage.


Obtained natural sands can present different particle size distributions (PSD), although they have the same mineralogical origin. These differences directly influence the physical and mechanical behavior of mortars and, therefore, the performance of mortar and ceramic renderings. Standardizing the particle size of sands based on pre-established requirements in normative standards (NBR 7214 or ASTM C778) is one way to minimize these effects. However, these standards do not consider the optimization of the granular skeleton through the analysis of bulk density and PSD, which may be insufficient to obtain satisfactory results. Therefore, this paper analyzes the effects of using different particle size ranges on the physical and mechanical behavior of cement and hydrated lime mortars. The properties of consistency index, bulk density, air content, capillary water absorption, water absorption by immersion, flexural strength, compressive strength, and dynamic modulus of elasticity were evaluated. For this purpose, standardized sands of the same mineralogical origin were made with different particle size ranges, being: (i) standardized sand constituted by 25% of coarse and fine fractions (S25-control), (ii) standardized sand constituted by 30% of coarse fraction and 20% of fine fraction (S30-20), and (iii) standardized sand composed by 40% of coarse fraction, and 10% of fine fraction (S40-10), respectively. The results indicated that variations in the particle size composition of the standardized sands are necessary to obtain mixtures with higher compactness and, therefore, mortars with better physical and mechanical performance. Thus, the dosage of the particle size fractions of standardized sand should consider the optimization of the granular skeleton, being the unit mass and the granulometric composition as important parameters to meet this premise. The consumption of natural resources and energy worldwide has increased considerably due to urban and economic growth. It is estimated that the construction industry consumes 40% of these natural resources , and thiFor example, Brazil is considered one of the countries that extract and consume the most natural resources in an uncontrolled, non-optimized way. Aggregates, for example, are materials with high consumption in the country. In 2019 only, about 2.5 tons of aggregates were consumed per inhabitant , which cAmong the various materials used in the construction industry, mortar is one of the main materials used due to its mechanical properties, durability, cost-effectiveness, and availability . CementiSome of the properties of aggregates such as textural parameters of aggregate grains, such as grain size (expressed in terms of grain size composition), shape, surface texture, and mineralogical composition significantly affect the behavior of construction materials ,14,15,16Notwithstanding, currently one seeks to produce construction materials with less cement and simultaneously present adequate mechanical and physical performance. In this context, optimizing the properties of a mortar mixture considering the maximum packing density of the constituent materials  is an imThe shape and particle size distribution of the aggregates are parameters that are related to obtaining the maximum packing density. Such influence is of great interest since the internal microstructure of cement-based mortar is a function of its porosity and pore size distribution  . Thus, aIn this perspective, the Brazilian (NBR 7214) and American (ASTM C778) standards determine that natural or artificial sands should be standardized in terms of particle size fraction before being used in tests for determining the strength class of cements or evaluation of the pozzolanic activity of supplementary cementitious materials (SCM). For example, Brazilian standards recommend that standardized sand should have four size fractions: fraction #16 with particle size between 2.4 and 1.2 mm, fraction #30 with particle size between 1.2 and 0.6 mm, fraction #50 with particle size between 0.6 and 0.3 mm, and fraction #100 with particle size between 0.3 and 0.15 mm. However, these standards do not take into account the effects of the particle size distribution (PSD) on mortar behavior, which can be a determining factor for the acceptance or not of a particular cement or SCM.Thus, the effects of using standardized natural sands (SS) with different size fractions on the physical and mechanical properties of cement and lime mortars were investigated. The results obtained show that the production of SS based on the maximum packing density concept is extremely necessary for the rational use of natural aggregates and for obtaining mortars with better physical and mechanical properties. This initiative can, in the long run, contribute to mitigating environmental impacts and avoiding waste of one of the main materials in the construction industry.The main novelties of the research are related to the development of an experimental program that looks for the effect of the granulometry of the sands in the main mortar properties. Marvila et al.  carried 3, a specific surface BET of 4.362 m2/g, Blaine fineness of 4000 cm2/g, and compressive strength of 32.7 MPa at 28 days. The cement used has approximately 20% of pozzolanic material and the rest of clinker and was chosen due to its high use in the region where the research was carried out. As the complementary binder, hydrated-lime (HL) type CH-I (similar to ASTM C207-6) with a specific gravity of 2.30 g/cm3, bulk density of 0.56 g/cm3 and CaO and MgO oxide contents higher than 95% were used. The use of HL is justified by its beneficial effect on mortar properties  and by reducing cement consumption [Pozzolanic Portland cement (PC) (similar to ASTM C 595 Portland Pozzolanic) was used, with a specific gravity of 2.93 g/cmsumption ,25,26,273. After collection, this sand was dried in an oven (105 ± 5) °C for 48 h and then sieved to remove particles with size >4.75 mm. After this procedure, three types of standardized natural sands (SS) with different particle size distributions (PSD) were made, based on the Brazilian standardization NBR 7214 [As fine aggregate was used, quartz sand obtained from the riverbed with a specific gravity of 2.62 g/cmNBR 7214 . Table 1It should be noted that the SS-25 composition was chosen because it is the standard used in different international standards, as previously highlighted. Therefore, it is necessary to highlight the criteria for choosing SS30-20 and SS40-10 compositions: (i) set the fine particle limit established by ASTM C144-3 ; and , MSS30-20 and MSS40-10;The consistency index of the mortars was kept constant at 260 mm in all mixtures according to NBR 16541 ;The ideal amount of water for mortar mixture was determined experimentally to ensure workability. The procedures adopted followed the specifications of NBR 13,276 The following criteria were established to produce the mortars:The increase in the number of coarse particles increased the water consumption for the mortars to reach the consistency of 260 mm , which cThe tests performed for the characterization of the mortars in the fresh and hardened states are listed in The molding and compaction of the specimens followed the recommendations of NBR 13279 . During The mortars’ dynamic modulus of elasticity was evaluated using ultrasonic dynamic technique and non-destructive tests. The dry density of the hardened mortar  was determined based on Equation (1).n) days and the weight of the anhydrous binder in the mortar, respectively.The test of weight variation of the mortars over time was based on the weighing in precision analytical balance of prismatic specimens (40 mm × 40 mm × 160 mm) during a period of 28 days counted from the demolding, according to the specific Modalités D’essais of the CSTB . This te3, while Ferreira et al. [3. Therefore, the results obtained are coherent.These results reveal that all mortars studied can be classified as normal , thus noa et al.  obtainedIt is also observed that by increasing the continuity of the granular skeleton of the sands, there is a decrease in the trapped air content of the mortars, confirming that there is an improvement in the behavior in terms of air incorporated into the mixture when the particle size distribution of the sands is optimized. These observations are consistent with a previous study .It is also important to note that, generally, a higher content of air incorporated into fresh mortars can improve their workability , however3, similar to the present research.Thus, in terms of capillary water absorption, the use of standardized sand with 30% of the “coarse” fraction and 20% of the “fine” fraction (SS30-20) results in mortars with reduced permeability, which hinders the entry of aggressive agents inside . This beMortars produced with SS25 and SPS 40-10 absorb a greater amount of water and are therefore more porous. The lower water absorption and porosity of the MSS30-20 mortars are due to the better particle size distribution of the SS30-20 sand and the higher mass densities in the fresh state of these mixtures. Thus, these results show that better particle packing favors the compaction of the mortar in the fresh state, thus reducing the porosity in the hardened state. Comparing the results, the research by Aquino et al.  obtaineddm/dt) evaluates the behavior of the mortars regarding the loss and gain of weight during hardening. This behavior is related to the water retention capacity that, the higher it is, the lower the mass variation rate will be. The weight variation occurs due to a physical process in which the mixing water evaporates over time, being more evident in the initial stages of curing [The rate of weight variation  and the mortars are less dense when compared to the others. These results corroborate those of water absorption and porosity and confirm that these properties are related to the weight variation rate of mortars.The behavior of the mortars studied is similar, especially those produced with sands with better particle size composition (SS25 and SS30-20), which is beneficial for the hardening of the cement and contributes to preventing the appearance of cracks by drying shrinkage. However, mortars with higher percentages of “coarse” particles (MSSP40-10) showed higher fc) and flexural strength (ft) of the mortars studied are shown in The results of the compressive strength , less porous and with higher mechanical strengths. For Santos et al.  when usiSugrañez et al.  reveal tIt is noteworthy that the results obtained are like the research by Ferreira et al. ,27, wherEd) of the mortars is shown in Ed was obtained by the mortars produced with MSS30-20 due to the increased stiffness of the internal structure of the mortar caused by the packing of the particles.The dynamic modulus of elasticity . It is known that a low modulus of elasticity contributes to better deformability, while a high flexural strength indicates better mechanical strength to support the applied load, therefore, the mortar tends to present a higher susceptibility to cracking when the ratio E/ft is high [E/ft ratio is lower when compared to the other mortars, which suggests a more ductile behavior and less susceptibility to cracking. This shows that the higher flexural strength may be important to reduce the susceptibility to cracking of mortars that have higher modulus of deformation.On the other hand, the parameter proposed by the Centre Scientifique et Technique du Bâtiment (CSTB) can better characterize the behavior of mortars in terms of cracking. One of the criteria proposed by CSTB is based on the ratio between the modulus of elasticity and flexural strength ( is high . The resfc), flexural strength (ft), and dynamic elastic modulus (Ed) tests of the samples at 28 days were selected. Then, the data obtained were normalized and presented by means of a ternary diagram, as shown in In order to determine the mix proportion with the better performance of the standardized mortars, a comparative analysis of the studied hardened properties was initially performed. For this analysis, the results of compressive strength , obtained a better content of incorporated air of approximately 0.5%;In the hardened state, the SS30-20 sand obtained better performance in all analyzed properties. This behavior was due to the better particle size distribution of this sand compared to the other sands;Ed), based on the E/ft ratio these mortars have higher deformation capacity and therefore have lower susceptibility to cracking. The E/ft ratio for the MSS30-20 composition was 4815, while for the MSS-25 composition, they were 5304, illustrating this information.Although the mortars with SS30-20 showed higher dynamic modulus of elasticity , being the unit mass and the granulometric composition of the aggregates important parameters to guarantee this premise and to obtain economic mixtures and mortars with better physical and mechanical performances.


Resin-based binders are one of the main materials used in foundry molding and core sands. This work adds to the research on self-curing sands with furfuryl resin, which dominates in the production of large-size castings. The work concerns the possibility of using biodegradable polymers as a component of resin-based binders. Biodegradable or partially biodegradable polymers are a group of materials which have an increasing level of importance in many areas of life and technology. This is mainly due to the increase in waste deposited in landfills, water and soil. This problem also concerns waste from the casting production process with the use of disposable molds with resin-based binders, which are mainly residues from their mechanical regeneration process. The aim of the research presented in this paper was to determine the effect of polycaprolactone (PCL) on the structure of post-regeneration dust from molding sands before and after the biodegradation process carried out in a water environment. Structure studies were carried out by Fourier transform infrared spectroscopy (FTIR) and the changes in the mass by TG/DTA-QMS analysis. The article also presents the results of the research of the morphology carried out by scanning electron microscopy (SEM) and the chemical oxygen demand index (COD) in water extracts of dust samples. Resin-based binders are one of the main materials used in foundry molding and core sands. This work supplements to the research on self-curing molding sands with furfuryl resin, which dominates in the production of large-size castings. Furfuryl resins and resins modified with furfuryl alcohol used as foundry binders contain 7–90%  furfuryl alcohol. The addition of alcohol accelerates the hardening process and increases the bonding capacity, which makes it possible to reduce the addition of binder to the molding sand. Furfuryl resins undergo spatial cross-linking under the influence of heating or chemical agents.The technology of self-curing molding and core sands with furfuryl resins ensures the attainment of castings with high dimensional accuracy, the ability to prepare complex forms, bonding at ambient temperature, an easy process of making molds, good knockout properties and the ability to mechanical regeneration of the used molding sands. The disadvantages of this technology include, first of all, the high harmfulness of gases emitted, mainly when pouring with liquid melt, and the problem with the disposal of post-regeneration waste from the applied molding sands.Post-production waste from used molding and core sands is the main group of waste generated by foundry industry. It is assumed that, on average, one ton of castings generates 0.6–1.0 ton of used sand ,3. The w2, H2O, mineral salts with the formation of new biomass, or under anaerobic conditions  to CO2, CH4, inorganic salts and biomass [This problem is particularly important as most of the commonly used raw materials for their production are not decomposable or are difficult to decompose. These materials are resistant to numerous environmental factors; most of them are not damaged by water, air, sunlight or the action of microorganisms. Degradation is defined as an irreversible, often multi-step process leading to marked changes in chemical structure, usually resulting in a loss of performance in the material. The degradation can be caused by various factors in the environment. When the degradation takes place under the influence of electromagnetic radiation, mechanical forces, heat, and active chemical compounds, it is defined as abiotic degradation. When the degradation process is caused by the action of biological factors (living organisms), mainly enzymes produced by various microorganisms, i.e., bacteria or fungi, it is a biotic degradation . The potential biodegradability of a material, which has been established or is predicted on the basis of appropriate laboratory tests under strictly defined, controlled conditions, is called specific biodegradability. In turn, total  biodegradability is the total decomposition of the material by microorganisms, either in the presence of oxygen (aerobic biodegradation) to CO biomass ,6.The growing interest in photodegradable and biodegradable materials with a controlled lifetime, in which their degradation should start only after fulfilling their task, also includes materials for obtaining molds for large-size castings. Therefore, another current direction of research and development in the field of foundry molding materials is the possibility of obtaining biodegradable, environmentally friendly materials.Works on this issue began in the 1990s ,8,9 and In previous studies, K. Major-Gabryś proposed a new approach to the issue consisting of the use of biodegradable polymer (polycaprolactone) as a component of resin-based binders available on the market. Such a solution will reduce the number of harmful residues after mechanical regeneration of molding sands and accelerate the biodegradation process of the synthetic binder ,14,15,16Due to the fact that residues of post-regeneration materials are an unresolved problem from the point of view of environmental protection, taking up the topic of adding biodegradable material in order to reduce the amount of harmful waste and accelerate its biodegradation seems fully justified.The article presents the results of research on the influence of polycaprolactone (PCL) on the structure of post-regeneration dust from molding sands before and after the biodegradation process. Dust after regeneration of standard molding sand with resin-based binders and dust after the sand regeneration process with the addition of biodegradable material (PCL) were tested. The biodegradation process was carried out in an environment reflecting real environmental conditions. The structure was determined by Fourier transform infrared (FTIR) spectroscopy. The paper also presents preliminary studies of the morphology and grain size by scanning electron microscopy (SEM) and the results of determination of the chemical oxygen demand index (COD) of aqueous extracts of dust samples after the (bio) degradation process.Furfuryl resin, without the presence of nitrogen; free formaldehyde in the range of 0.05–0.15%; the amount of furfuryl alcohol 78%;Hardener—an aqueous solution of paratoluenesulfonic acid;n; molecular weight 50,000 Da and melting point 58–60 °C; a biodegradable polymer in solid form with an end of hydroxyl group from Polysciences Inc., Warrington, PA, USA.Polycaprolactone (PCL)—a biodegradable additive and plasticizer with the formula –(O(CH2)5CO)-The following materials were selected as components for molding sands that were subjected to mechanical regeneration:The dust samples after the process of mechanical regeneration of molding sands: standard molding sand with organic binders (MS no. 1) and molding sand with organic binder and the addition of polycaprolactone PCL (MS no. 2) were the subjects of our examination. The composition of the molding sands and dust-sample types are presented in The material has been processed the biodegradation process. Three g samples of dust were placed in polypropylene containers and filled 100 mL of water from the Vistula River, with a confirmed composition and specific physicochemical properties . The sam−1 with a resolution of 4 cm−1.Structure studies were carried out by Fourier transform infrared spectrometry (FTIR) using Digilab Excalibur FTS 3000  spectrometer with a standard DTGS detector. The test specimens were obtained at room temperature by the KBr pelletization method. The number of scans was the same for all samples, the results were recorded in the wavenumber range from 4000 to 400 cm® thermal analyzer coupled to QMS 403C Aëolos by Netzsch  equipped with a TG-DTA sensor. The test was proceeded under the following conditions: pressure 10−2 mbar; inert gas Ar (99.9992%) 70 mL/min; heating speed 15 K/min. Measurements were determined using the Netzsch  Proteus Thermal Analysis 6.1.0 software. The residual gas analysis was carried out on the basis of the literature data from [Selected samples were subjected to the thermogravimetric test and the differential thermal analysis (TG/DTA) in order to determine the changes in the mass of the tested sample and the thermal effects related to the changes in the sample . The TG/DTA-QMS measurements were carried out using the STA 449 F3 Jupiterata from .The determination of the morphology and chemical composition by X-ray microanalysis in selected microareas of the dust samples before and after the biodegradation process was performed using the Jeol JSM 6460LV  scanning electron microscope (SEM) with the INCA X- EDS-act Energy 350 by Oxford Instruments  spectrometer. The powder samples were attached to a carbon tape and vaporized with platinum.3 of the aqueous extract were collected into the reaction flask, to which 5 cm3 of the potassium dichromate solution and a few porous glass spheres were added. After thorough mixing, 15 cm3 of a solution of silver sulphate in sulfuric acid were added very slowly to the solution. The reaction flask was then connected to a reflux condenser and the reaction mixture was heated to reflux and then held at 148 °C for 110 min. At this time, the reaction mixture was cooled rapidly to about 60 °C, diluted to about 75 cm3, and then cooled to room temperature. The course of the first stage of the determination-heating of the mixture in the reaction flask is shown in The determination of the COD of the water extracts after the biodegradation process of dust samples from molding sand MS no. 1 and MS no. 2 was carried out in accordance with the PN-ISO 6060:2006 standard “Water quality. Determination of the chemical oxygen demand” . In the The excess of potassium dichromate (VI) was titrated with ammonium and iron (II) sulfate. Ferroin was used as an indicator . Chemica3c—concentration of ammonium and iron (II) sulphate (VI) expressed in mol/dm0—the volume of the analytical sample expressed in cm3V1—volume of ammonium and iron (II) sulphate (VI) used for titration in the blank sample, expressed in cm3V2—volume of ammonium and iron (II) sulphate (VI) used to titrate the analytical sample, expressed in cm3V2 expressed in mg/dm38000—molar mass ½ OThe FTIR spectra obtained for dust samples after the regeneration of molding sand are presented in −1 [−1 region, there is a band corresponding to the stretching vibration of the O-H bond [−1 [−1, on the other hand, OH- group bands are visible, which correspond to vibrations originating from the furan or phenol ring [In the spectra obtained for all the dust samples obtained after the regeneration of the standard molding sand (dust from MS no. 1) and the molding sand with a 5% addition to the resin of a biodegradable component (dust from MS no. 2), the most characteristic is the band originating from the binder characteristic for phenol-furfuryl resin. These vibrations occur in the area of 1149–1142 cm−1 . In the O-H bond . Anotherbond [−1 . In the nol ring . These bnol ring ,32.The comparison of the absorption bands for dust samples before and after the biodegradation process is shown in O-H) groups was found [−1 coming from the C−H group. In the case of dust after the regeneration process of the molding sand with the addition of a biodegradable component, an increase in the intensity of the band originating from the C−H group was observed in this area. An increase in the band intensity in the area of 1142 cm−1 and in the area of 1730 cm−1 was found for dust samples obtained from the standard molding sand MS no. 1. These bands correspond to vibrations originating from the bond characteristic for the resin and from the C=O group, respectively. For these samples, an increase in the intensity of the band in the region of 885 cm−1 derived from the C-H group corresponding to the deformation vibration occurring in the furan ring was also found [C=O characteristic for aliphatic polyesters [The analysis of FTIR spectra of the dust samples after the regeneration process and after the biodegradation process showed slight shifts of a small number of absorption bands towards lower wavenumber values. On the other hand, slight changes were visible in the intensity of some absorption bands. In all spectra, an increased intensity of the band originating from the stretching vibration of the OH−  and 1-H+; 2-H2+, He+; 16-O+, CH4+, CO2, CO; 17-OH+; 18-H2O+; 20—Ar (sample after biodegradation).1-HThe total mass change for Sample no. 5 up to 900°C before biodegradation process was 5.15% and for the same sample after biodegradation process was 6.84% . The QMS+; 2-H2+, He+; 16-O+, CH4+, CO2, CO; 17-OH+; 18-H2O+; 20—Ar (sample before biodegradation) and 1-H+; 2-H2+, He+; 16-O+, CH4+, CO2, CO; 17-OH+; 18-H2O+; 20—Ar (sample after biodegradation).1-HThe morphology studies were carried out in order to determine the changes that could have occurred under the influence of the environmental factor during the biodegradation process. For comparative purposes, observations of dust samples for both molding sands MS no. 1 and MS no. 2 after initial regeneration were present. In the case of sample no. 1 , it can In the case of sample no. 5 derived from the molding sand MS no. 2, in which a biodegradable agent was applied to the binder, it can be observed that, as a result of the regeneration process, a much greater amount of organic residue was obtained than in the case of the sample no. 1 from MS no. 1 . There a2Cr2O7, potassium periodate  that is needed to oxidize these compounds to the highest degree of oxidation under given conditions [The scope and speed of biodegradation transformations, as it has already been presented in the theoretical part, is conditioned by a number of factors that should characterize the environment in which the process is carried out. In addition to factors, such as the content of nutrients, temperature and pH, the access of oxygen plays an important role. Chemical oxygen demand (COD) is an indicator that determines the amount of oxygen necessary for the oxidation of organic and inorganic compounds contained in water. Laboratory methods determine it by determining the amount of oxygen taken from oxidants (potassium dichromate (VI) Knditions .The results of the chemical oxygen demand determination are presented in 3. The COD value then decreases with the regeneration time and remains constant after 10 min of the regeneration process. The addition of a biodegradable component (MS no. 2) to the molding sand will significantly affect the value of chemical oxygen demand. For sample 5, that is a dust sample taken directly after the initial regeneration process, the determined COD value was 1152 mg/dm3. This is consistent with the conducted microscopic observations; sample no. 5 is characterized by an increased amount of organic residue in relation to the sample no. 1 and therefore the COD value is much higher. As in the case of the dust from the standard molding sand (MS no. 1), the index value decreased with the duration of the regeneration process and after 15 min, it amounted to 413 mg/dm3.The data presented in –1 corresponding to the vibration of the CH2 group in PCL. The analysis of FTIR spectra also showed a slight increase in the band intensity at the wavenumber of 1720 cm–1 caused by the C=O stretching vibration of the carbonyl group characteristic for aliphatic esters. However, no significant changes were found in the dust structure after the biodegradation process in relation to the initial dust samples. Research has shown that, first of all, the intensity of some absorption bands changes, while their positions and shapes remain practically unchanged. In all spectra, an increased intensity of the band originating from the stretching vibration of the OH− (νO-H) groups was found, which may indicate a partial degradation of the structure, mainly PCL. On the other hand, fragments of biodegradable chains migrate to the incubation solution.The aim of the research was to determine the effect of polycaprolactone on the structural changes in dust from molding sand with a resin-based binder before and after the biodegradation process in a water environment. The tests were carried out on dust samples after the process of mechanical regeneration of molding sands with a resin-based binder of a standard composition and with the addition of biodegradable material. The analysis of FTIR spectra carried out for the original dust samples showed that the addition of polycaprolactone in the amount of 5% to the furfuryl resin causes the appearance of a band at the wavenumber of 1104 cmFor both molding sands MS no. 1 and 2, the weight loss of the dust sample before biodegradation was lower (3.36% for MS no. 1 and 5.15% for MS no. 2) than after the biodegradation process (4.52% for MS no. 1 and 6.84% for MS no. 2)—the differences are appropriately on the levels 1.16% (MS no. 1) and 1.69% (MS no. 2). Higher losses of total mass up to 900 °C were recorded for MS no. 2 with the PCL addition. QMS analysis confirmed the presence of gaseous components that are normal for this type of molding sand with an organic binder.Scanning electron microscopy examinations showed that dust sample no. 5 from molding sand MS no. 2 (with the addition of PCL in the binder) after initial regeneration had a larger amount of organic residue than dust sample no. 1 from molding sand MS no. 1 (without the addition of PCL) after initial regeneration. The analysis of the local chemical composition in the micro-areas showed the presence of the following elements: silicon (Si), oxygen (O) and carbon (C) as the main components of the molding sand based on quartz sand. Irregular, porous structures observed on the photomicrographs obtained for dust samples after the regeneration process, mainly of the molding sand with the addition of a biodegradable component, indicate the presence of Cl, Na, F, Mg, K and Ca as well, characteristic elements of river water . The sulThe conducted measurements of the determination of the chemical oxygen demand index showed a decrease in the COD value along with the duration of the mechanical regeneration process for all tested water extracts. The decrease in the index value is the result of the decreasing number of organic substances in the water extract sample, which can oxidize. The tests were carried out in closed systems; the samples were placed in water of known chemical composition. The presence of chlorides at the level of 369 mg/L was found in water and it could act as an oxidant in the tested environment. The highest COD value was reported for the dust sample no. 5 from the molding sand MS no. 2 with the addition of a biodegradable component after the initial regeneration and biodegradation process. This is consistent with the results of the microscopy observations about the amount of organic residue. The COD value for the sample no. 5 resulted in a faster oxidation of organic compounds. At the same time, the obtained results indicate no influence of polycaprolactone on the organic substance of the molding sand, including the process of its decomposition into inorganic compounds. This would be confirmed by the lower COD values.It is possible to use biodegradable polymer as a component of foundry resin-based binder.O-H) was found. This effect may confirm the partial degradation of the structure, mainly PCL.There were no significant changes in the dust samples’ structures before and after the biodegradation process. An increased intensity of the band originating from stretching vibrations of the OH− groups (νDust samples after the biodegradation process had higher weight loss than the same samples before biodegradation. Dust samples from molding sand with PCL addition had higher weight loss than dust samples from molding sand without PCL addition.Morphology studies showed the presence of irregular, porous structures mainly in the dust samples from molding sand MS no. 2 after the biodegradation process.It was found that increasing the regeneration time reduces the amount of organic matter in the tested samples, which has a significant impact on the decrease in the COD value along with the duration of the process.Aeromonas, Pseudomonas, Flavobacterium and Bacillus.The conducted research and the obtained results indicate the directions of further research and work in the selection of components of molding sand with biodegradable properties, which should be carried out in terms of determining the minimum and maximum amount of polycaprolactone as an addition of a biodegradable component to the molding sand. It would be also essential to carry out a biodegradation process in longer time - between 6 and 12 months. Important for determining the properties of biodegradable materials is the biodegradation process in which the inoculum should be activated sludge used in sewage treatment plants or under the influence of microorganisms that break down aromatic hydrocarbons, e.g., bacteria such as The next step of research would be a structural and molecular weight analysis of the polymer.The conducted research of the biodegradation process in a water environment and the analysis of the obtained results allowed for the formulation of the following conclusions:


X-axis), 3.65 mm (Z-axis), and 4.03 mm (X-axis), respectively; and the percentage differences in the size of the ablation volume are greater than 6.9%. Under the condition of the pulse, the amplitude is 1000 V, the total PFA duration is 1 s, and the pulse train interval is 198.4 ms; the differences in the temperature increase between AC and IC in LA are less than 2.46 °C. Hence, this study suggests that in further exploration of the computational study of PFA in AF treatment using the same or similar conditions as those used here , to obtain more accurate computational results, it is necessary to adopt AC rather than IC to investigate the size of the surface ablation area, the size of the ablation isosurface, or the size of the ablation volume generated by PFA in LA. Moreover, if only investigating the temperature increase generated by PFA in LA, adopting IC instead of AC for simplifying the model construction process is reasonable.Pulsed field ablation (PFA) is a promising new ablation modality for the treatment of atrial fibrillation (AF); however, the effect of fiber orientation on the ablation characteristics of PFA in AF treatment is still unclear, which is likely an essential factor in influencing the ablation characteristics. This study constructed an anatomy-based left atrium (LA) model incorporating fiber orientation and selected various electrical conductivity and ablation targets to investigate the effect of anisotropic electrical conductivity (AC), compared with isotropic electrical conductivity (IC), on the ablation characteristics of PFA in AF treatment. The results show that the percentage differences in the size of the surface ablation area between AC and IC are greater than 73.71%; the maximum difference in the size of the ablation isosurface between AC and IC at different locations in the atrial wall is 3.65 mm ( Atrial fibrillation (AF) is one of the most common arrhythmias in the clinic. Aside from medication, left atrium (LA) radiofrequency ablation (RFA) is currently the gold standard for AF clinical treatment, which works by destroying the local myocardium to isolate abnormal electrical signals causing arrhythmia. However, RFA still has important limitations, exceptionally high recurrence rates, significant complication rates, and lengthy procedure times . Pulsed With the rapid development of PFA in AF treatment in recent years, several computational studies based on 3D medical imaging reconstruction combined with finite element analysis (FEA) have emerged to investigate the ablation characteristics generated by PFA in the pulmonary veins (PVs), in combination with experimental results . HoweverAlthough it is reasonable to consider the electrical conductivity of the LA model as AC in the computational study of PFA in AF treatment, incorporating fiber orientation into the LA model has so far been complex and time consuming. In a review of relevant studies, AC induced by fiber orientation on the ablation characteristics of PFA in AF treatment was not investigated. Accordingly, this study investigates in the computational study of PFA in AF treatment (1) the effect of AC compared with IC on ablation characteristics; (2) the effect of AC with a different size and anisotropy ratio on ablation characteristics; the objective is to provide reasonable advice on which electrical conductivity to choose in further studies, in order to achieve the optimal choice of obtaining results that are as consistent as possible with actual ablation, or to simplify the model construction process without compromising the reasonableness of the results.CTA images of a female patient with persistent AF provided by the hospital were used to reconstruct the LA model. CTA scans were performed using a SOMATOM Drive ; the number of slices is 298, the slice resolution is 512 × 512 pixels, the slice thickness is 0.75 mm, and the pixel size is 0.326172 mm.Semi-automatic segmentation of the LA region from CTA images was performed using CemrgApp v2.2 a 10]. T. T10]. TA segmentation of the LA epicardial surface from traditional CTA images is usually not feasible due to an insufficient spatial resolution and a limited signal-to-noise ratio. To build the epicardial surface, this study assumes that the thickness of the LA wall is homogeneous; the endocardial surface of the mesh was dilated by 2.4 mm at each point along the normal direction, which is the mean measured wall thickness of the human LA . To builTo incorporate fiber orientation into the LA model, 13 seed points corresponding to specific anatomical positions were manually marked on the LA model c. Then, The pulsatile blood flow profile at the MV y record  consistiThe pulsatile blood flow profiles at the four PVs and MV in the LA model are shown in This study used the AC/DC module, bio-heat transfer module, and computational fluid dynamics (CFD) module in COMSOL Multiphysics v5.6  to solve the electric field intensity distribution, temperature distribution generated by PFA in LA, and the cooling effect of the pulsatile blood flow in the cardiac chamber on the myocardium and the electrode during the application of PFA.Electrical EquationsThe electrical, thermal, and CFD equations involved in PFA in AF treatment are expressed as follows:The current density No other electric source existed inside the LA, so its potential was regulated by the Laplace equation :(3)∇⋅σa=σtTherefore, on each node, Thermal EquationsCFD Equations−3 kg/m/s), and The physical phenomena of the thermoelectric coupling problem are expressed by the Pennes biological heat transfer equation :(7)ρc∂T∂LA model .The LA model was composed of myocardium and blood, and a catheter model was added in the LA endocardium consistent with the straight pressure catheter used in the actual PFA experiment. The catheter consists of two electrodes and is connected by an insulated plastic catheter in the middle; the diameter of the electrode and the plastic catheter is 7 F (1 F = 1/3 mm), and the length of the single electrode and the plastic catheter is 2 mm and 2.5 mm, respectively. To simulate the effect of slight electrode pressure on the endocardium, the catheter was inserted into the endocardium at a depth of 0.5 mm at all ablation targets and placed parallel to the epicardium to ensure consistent electrode–endocardium contact volume for all ablation target sites. The ablation model is illustrated in Electrical Boundary ConditionsThe biphasic pulsed voltage In the computation of the electric field intensity distribution, the amplitude of the periment ,28.In the computation of the temperature distribution, the amplitude of the periment . The wavThermal Boundary Conditionst = 0, the initial temperature of the myocardium T0 and the blood Tb was set to 37 °C.Initial temperature boundary condition: At The second type of thermal boundary condition (constant heat flux boundary condition): The boundary of the plastic catheter and the epicardium represented the zero heat flux conditions and is expressed as:Thermal boundary conditions comprised an initial temperature boundary condition and one type of thermal boundary condition:CFD Boundary ConditionsA no slip condition was applied on the myocardium–blood and electrode–blood interfaces. For fluid dynamics, the blood flow in the LA was simulated by setting the four PVs as inflows with a condition of 10 mmHg , and theThe fluid type was determined by calculating the Reynolds number in the PV as:The electrical and thermal properties of the ablation model are listed in Before applying PFA, the cell membrane is intact and acts as an electrical insulator; the electrical conductivity of the tissue corresponds to that of low frequency, while after the PFA-induced creation of the pores, the pores in the cell membrane allow the passage of electric current through the cytoplasm and the extracellular space. Hence, the cell becomes more permeable to electrical currents, and the electrical conductivity of the tissue is similar to that of high frequency. It is usual to use a sigmoid function that relates the electrical conductivity of the tissue  to the electric field magnitude during PFA and is expressed as :(13)σ(E)ectively .In this study, rections , i.e., and are expressed as mean ± standard deviation. The size of the ablation isosurface is in mm, and the difference in size between AC and IC is the absolute value. The size of the surface ablation area is in square mm, and the percentage difference in the size of the surface ablation area between AC and IC is calculated as This study considered that the differences in the size of the ablation isosurface are insignificant for values less than 1 mm, since this value is approximate to the deviation (±0.5 mm) observed in experimental studies on RFA . This stAccording to Equation (6), the AC is essentially reflected by the distribution of fiber orientation throughout the entire LA; therefore, the correctness of the fiber orientation incorporated into the LA model is crucial for the subsequent investigation. In this study, the generated fiber orientation conforms to the realistic fiber orientation based on the descriptions in the literature and histological observations ,37,38. FAs shown in The previous section shows significant differences in shape and fiber orientation at each ablation target; these two factors will lead to the difference in the electric field intensity distribution generated by PFA under the condition of the same electrical conductivity at each ablation target. Presently, a specific electric field intensity threshold is usually used to estimate whether PFA causes effective myocardial ablation ,3,4,39; To determine the surface ablation area, this study first created the surface and isoline in the result of the electric field intensity distribution in COMSOL and set the value of isoline to 1000 V/cm, then selected the different plane views for each ablation target . Finally, this study enlarged and adjusted the view of the electric field intensity distribution at each ablation target under the condition of different groups of electrical conductivity, and the magnification of the view is the same in all cases. To determine the size of the surface ablation area, this study used the surface integral function built into COMSOL to integrate the area with electric field intensity greater than 1000 V/cm in the surface of the LA model. The electrical conductivity groups in Specifically, at ablation target 1 the catheter is placed parallel to the LSPV ostium. Under the condition of IC, the surface ablation area extends along the catheter to both sides of the LSPV ostium. Under the condition of AC, with the increase in the anisotropy ratio, the surface ablation area near the positive electrode gradually extends obliquely towards the top of LSPV along the circumferential fibers.At ablation target 2, the catheter is placed parallel to the LA roof. Under the condition of IC, the surface ablation area is perpendicular to the LA roof. Under the condition of AC, with the increase in the anisotropy ratio, the surface ablation region located at the plastic catheter gradually extends obliquely towards the PW along the direction of the septopulmonary bundle, which is located on the LA roof.At ablation target 3, the catheter is placed on the PW and is perpendicular to the RIPV ostium. Under the condition of IC, the surface ablation region is primarily perpendicular to the plastic catheter. Under the condition of AC, the surface ablation area located in the upper part of the catheter gradually extends to the left of the PW along the direction of the septopulmonary bundle branch, and the lower part of the catheter gradually extends to the lower left of the PW along the direction of the septoatrial bundle.The previous section shows that AC significantly impacts the surface ablation area more than IC at each ablation target generated by PFA in LA. This study further investigates the ablation isosurface and ablation volume generated by AC compared with IC at each ablation target; the definition of the ablation isosurface is the same as before (1000 V/cm).To determine the ablation isosurface, this study first created the isosurface in the result of the electric field intensity distribution in COMSOL and set the value of isosurface to 1000 V/cm, then adjusted the view and obtained isosurfaces of IC and each group of AC in three different plane views  under the condition of a different ablation target; finally, the study exported the isosurfaces and superimposed the isosurfaces of IC on the isosurfaces of each group of AC in three different plane views based on the position of the catheter. Figures 9, 11 and 13 show that under the condition of the PFA the amplitude is 1000 V, and the ablation isosurface (1000 V/cm) distribution is generated by different ACs and ICs at each ablation target, respectively.X-axis, Y-axis, and Z-axis of each isosurface, respectively, and finally obtained the difference between the maximum and minimum of the three axes as the three sizes of each isosurface. Figures 10, 12 and 14 show the statistical results of the size of the ablation isosurface under the condition of different PFA amplitudes at each ablation target, respectively.To determine the size of the ablation isosurface, this study first exported the coordinate data of the isosurfaces of IC and each group of AC under the condition of different PFA amplitudes and ablation targets, then sorted the coordinates of the X-axis, Y-axis, and Z-axis) , 0.35 ± 0.48 mm (Y-axis), and 1.29 ± 0.16 mm (Z-axis), respectively, and the maximum difference is 3.65 mm (X-axis), 1.25 mm (Y-axis), and 1.53 mm (Z-axis), respectively.Specifically, as shown in X-axis, Y-axis, and Z-axis between AC and IC are greater than 1 mm in all cases. Overall, the mean difference in the size of the ablation isosurface in the four electrical conductivity groups is 2.39 ± 0.65 mm (X-axis), 2.54 ± 0.35 mm (Y-axis), and 2.59 ± 0.78 mm (Z-axis), respectively, and the maximum difference is 3.18 mm (X-axis), 3.03 mm (Y-axis), and 3.65 mm (Z-axis), respectively.As shown in Y-axis between AC and IC are less than 1 mm; in other conditions, the size differences in the Y-axis between the two are greater than 1 mm. The size differences in the X-axis and Z-axis between AC and IC are greater than 2 mm in all cases. Overall, the mean difference in the size of the ablation isosurface in the four electrical conductivity groups is 3.6 ± 0.45 mm (X-axis), 1.02 ± 0.13 mm (Y-axis), and 3.37 ± 0.42 mm (Z-axis), respectively, and the maximum difference is 4.03 mm (X-axis), 1.15 mm (Y-axis), and 3.89 mm (Z-axis), respectively.As shown in To obtain the size of the ablation volume, this study used the volume integral function built into COMSOL to integrate the area with an electric field intensity greater than 1000 V/cm in the myocardial domain of the LA model. As shown in In terms of the type of myocardial electrical conductivity, under the condition of the same PFA amplitude, at each ablation target the ablation volumes generated by the AC of the normal myocardial electrical conductivity groups are all smaller than that of the myocardium with AF electrical conductivity groups.3 (ablation target 1), 148.64 ± 52.86 mm3 (ablation target 2), and 157.54 ± 59.99 mm3 (ablation target 3).In terms of the size of the ablation volume, under the condition of different PFA amplitudes, the mean percentage difference of the ablation volume generated by AC compared with IC amplitude at each ablation target is 152.19 ± 45.45 mmIn terms of the difference in ablation volume, with the increase in the anisotropy ratio, under the condition of different PFA amplitudes, the mean percentage difference of the ablation volume generated by AC compared with the IC amplitude at each ablation target is 16 ± 7% (ablation target 1), 49 ± 8% (ablation target 2) and 68 ± 13% (ablation target 3), respectively, and the maximum percentage difference is 26.44% (ablation target 1), 61.45% (ablation target 2) and 88.49% (ablation target 3), respectively.In a review of relevant studies, the temperature distribution under the condition of AC compared with IC generated by PFA in LA has not been investigated. To investigate the influence of AC and IC on temperature increase, this study compares the temperature under the condition of the same PFA parameters (see “Boundary Conditions”) and AC and the corresponding IC from the fourth electrical conductivity group with the highest anisotropy ratio, the final temperature distribution generated in the myocardium at three ablation targets , and theAs shown in As shown in In the computational studies of PFA in AF treatment, to shorten the model construction process and reduce the computational complexity, the LA model is usually defined as a regular shape model such as a sphere  or a cylSince the atrial wall is significantly thinner than the ventricular wall, and atrial fiber architecture is highly complex , the maiTo investigate the effect of AC induced by fiber orientation on the ablation characteristics of PFA in AF treatment, this study used a robust semi-automatic method to incorporate fiber orientation into the patient-specific LA model reconstructed by CTA images; compared with the above method, this method significantly minimizes the challenge of incorporating fiber orientation into the LA. The defect of defining LA as a regular shape model and/or ignoring fiber orientation is that it cannot reflect the effect of realistic LA shape and fiber orientation on the electric field intensity and temperature distribution generated by PFA in LA. From the results of this study, it can be concluded that both influence the electric field intensity and temperature distribution, which tends to extend towards the fiber orientation at the ablation target. Therefore, to reflect the actual ablation results as consistently as possible, constructing the anatomy-based LA model incorporating fiber orientation may be the correct trend for further studies in the computational study of PFA in AF treatment, and an essential step to introducing the reliable patient-specific LA model into clinical practice.Most triggers for paroxysmal AF come from the PVs, so ablation involves creating circumferential lesions around the PVs to isolate them from the rest of the LA electrically. Catheter ablation for persistent AF is more challenging and has less favorable outcomes. To improve these outcomes, ablation targeting the substrate that maintains AF  is often added to PVI; the two most common techniques for substrate modification are the creation of linear lesions in the LA and focal ablation to eliminate atrial signals that show CFAE . GuideliIn terms of the distance from the ablation target to the PV ostium, ablation target 1 belongs to the circumferential PVI strategy, and the distance from the catheter to the PV ostium is in the range of 0.5–1 cm, which requires complete circumferential ablation of the LA around the upper and lower PVs on both sides . AblatioAccording to the type of myocardium, the myocardium electrical conductivity selected in this study can be divided into the normal myocardial electrical conductivity and myocardium with AF electrical conductivity. Compared with the normal myocardial electrical conductivity, in the myocardium with AF electrical conductivity, the formation of fibrosis in the myocardium leads to the increase in the anisotropy ratio of myocardial conduction velocity, which further leads to the increase in the anisotropy ratio of myocardial electrical conductivity . As showIn terms of ablation characteristics, IC ignores the influence of fiber orientation, resulting in the surface ablation area and ablation isosurface generated by IC being more uniform than that of AC at each ablation target. Under the condition of AC, the above two ablation characteristics are affected by the fiber orientation and tend to extend towards the fiber orientation at the ablation target; at the same time, the myocardial fiber orientation is usually highly concentrated in a specific direction at the ablation target, resulting in the percentage differences in the size of the surface ablation area and ablation volume between AC and IC being greater than 5% in all cases, and the maximum differences in the size of the ablation isosurface between AC and IC are all greater than 1 mm at each ablation target. Hence, this study suggests that in future research on the computational study of PFA in AF treatment, to obtain more accurate computational results, it is necessary to adopt AC rather than IC to investigate the size of the surface ablation area, the size of the ablation isosurface, or the size of the ablation volume generated by PFA in LA.At the same time, due to using the function of electrical conductivity, which changes with electric field magnitude, in each group of AC with a different anisotropy ratio, the difference between the myocardial transverse and longitudinal electrical conductivity after electroporation is reduced, and both of them are close to the post-electroporation electric conductivity In terms of temperature increase, under the conditions of specific PEF parameters applied in this study (see “Boundary Conditions”), the difference in the temperature increase between AC and IC in LA are insignificant in all cases. Hence, this study suggests that in the future research on the computational study of PFA in AF treatment, if only investigating the temperature increase generated by PFA in LA, adopting IC instead of AC for simplifying the model construction process is reasonable.The anatomy-based LA model constructed by CTA images in this study is from a female patient. In a review of relevant studies, no studies have shown that the LA fiber orientation of the males is significantly different from that of the females. Although the mean LA volume is slightly larger in males than in females in most humans, the difference is not statistically significant .Therefore, this study preliminarily considers that if we happen to use an LA model of a male patient with an LA volume slightly larger than the current LA model, then the shape and the size of the surface ablation area and ablation isosurface will be changed somewhat compared with the result in the current study, because in LAs with a larger volume, the curvature of the LA wall where the catheter is attached is smaller.The electrode direction relative to the fiber orientation of tissue has proved to have a significant effect on the ablation effect; in general, when the electrode is parallel to the fiber orientation of tissue, the generated ablation area is larger than that which is perpendicular to the fiber orientation of tissue ,47. The This study also had some limitations. The most prominent limitation is that we did not use the experimental results to support the reliability of the computational results in this study. In fact, the ablation of living rabbit myocardium using the PFA generator and the straight pressure catheter was originally part of this study plan; however, due to the impact of COVID-19, we have so far been unable to carry out this experiment. The second limitation is that the results and conclusions in this study are based on specific myocardial electrical conductivity, pulse parameters, and electric field intensity damage threshold. However, to date, the myocardial electrical conductivities are not well characterized for low frequencies (as is the case for PFA) since they are based on estimations of those obtained experimentally above 1 MHz . The PFAThe third limitation is that fiber orientation changes depending on the atrial depth in different atrial areas; however, due to the limitation of the current semi-automatic algorithms for generating fiber orientation into the patient-specific atrial model, we cannot investigate the influence of this factor on the ablation characteristics of PFA in AF treatment.The fourth limitation is that the ablation model constructed in this study is macro and does not include the myocardial cell models, so it is impossible to investigate the influence of other PFA parameters other than the PFA amplitude on ablation characteristics.This study constructed an anatomy-based LA model incorporating fiber orientation and selected various electrical conductivity and ablation targets to investigate the effect of AC compared with IC on the ablation characteristics of PFA in AF treatment. According to quantifications, the results show that the difference in the size of the surface ablation area, the size of the ablation isosurface, and the size of the ablation volume between AC and IC are significant; however, the difference in the temperature increase between the two are insignificant. Hence, this study suggests that in further studies in the computational study of PFA in AF treatment using the same or similar conditions as those used in this study , to obtain more accurate computational results, it is necessary to adopt AC rather than IC to investigate the size of the surface ablation area, the size of the ablation isosurface, or the size of the ablation volume generated by PFA in LA. Moreover, if only investigating the temperature increase generated by PFA in LA, adopting IC instead of AC for simplifying the model construction process is reasonable.