The counting and size measurement of microalga cells and NPs were performed by flow cytometry. The biochemical endpoints were measured by a UV-VIS microplate spectrophotometer. The highest toxicity was observed for SMB24  and CdS . A combined toxicity bioassay demonstrated that TiO2 and the SMB3 NPs had a synergistic toxic effect in combinations with all the tested samples except SMB24, probably caused by a “Trojan horse effect”. Sample SMB24 had antagonistic toxic action with CdS and ZnS, which was probably caused by metal ion scavenging.The investigation of the combined toxic action of different types of nanoparticles (NPs) and their interaction between each other and with aquatic organisms is an important problem of modern ecotoxicology. In this study, we assessed the individual and mixture toxicities of cadmium and zinc sulfides (CdS and ZnS), titanium dioxide (TiO According to existing data , the totManufactured nanomaterials enter the aquatic environment during their production and application as a result of emissions and discharges during environmental cleanup or as waste . In the The knowledge about the environmental behavior of NPs and the interaction of metal-based NPs with aquatic organisms is summarized in a review by Peng et al. (2017) . It shou2) is considered a safe NP, having a variety of applications including food additives and drug delivery [2 NPs can cause cytotoxicity, ROS generation, and other health risks in human cells and rats [It was reported that the toxic effects of metal-oxide nanoparticles are a result of oxidative stress and membrane damage, provoked by releasing metal ions into the media . Howeverdelivery . Howeverand rats ,41.Nowadays, few studies have investigated the combined effects of binary and complex mixtures of NPs on organisms. There are previous studies that used bacteria , microalHeterosigma akashiwo and five types of NPs. H. akashiwo was chosen as a common test species used in toxicity bioassays with different chemicals and substances, including NPs [This work set out with the aim of assessing the interaction between different types of NPs in a microalga bioassay. Microalga was selected as a reliable, sensitive, and wildly used test model ,47 whichding NPs ,50. The 2), and two types of mesoporous silicon dioxide (SMB3 and SMB24), which caused 10% (EC10) and 50% (EC50) inhibition of microalgal growth, are given in The calculated effective concentrations of the five used NPs, namely cadmium and zinc sulfides (CdS and ZnS), titanium dioxide  calculated by Equation (1) and expected growth inhibition (Pe) calculated by Equation (2) is demonstrated in The comparison between the observed growth inhibition  and expected toxicity (Pe). The cases with no significant difference between Po and Pe, the cases with Po levels significantly higher than the Pe levels, and the cases with Po levels significantly lower than the Pe levels could be assumed to be additive, synergistic, and antagonistic toxic actions, respectively.The obtained results  demonstrbioassay . The resbioassay  demonstrThe highest antagonistic action was observed for the combination of ZnS and SMB24 b. Subseq2 and SMB3, including the combination of TiO2 with SMB3. At the same time, the combinations of SMB24 with TiO2 and with SMB3 had an additive effect .The synergistic action was observed for the combinations of CdS and ZnS with TiO2 and SMB3 had either synergistic or additive effects.In general, the mixture toxicity bioassay demonstrated that all the combinations of the used NPs with SMB24 had either antagonistic or additive effects. On the contrary, all the combinations of the used NPs with TiOH. akashiwo exposed to the single and binary mixtures of the NPs were calculated by Equation (3) and are represented in The changes in esterase activity, membrane potential, and ROS generation in the cells of 2. The presence of TiO2 almost normalized the esterase activity of H. akashiwo exposed to CdS, and the combination of TiO2 with SMB24 significantly increased the esterase activity of microalga cells.It should be noted that CdS and SMB24, as well as the combinations of all the used NPs with these two samples, significantly reduced the esterase activity of microalga cells a. The ex2 should reduce the toxicity by antagonistic action. However, this assumption did not correlate with the binary toxicity data (The highest esterase activity inhibition caused by a single exposure of CdS and SMB24 a correlaity data a. NevertSignificant membrane depolarization b was obsp < 0.0001) was caused by the influence of CdS and the combinations of all the other NPs with CdS. The insignificant influence on ROS generation was observed only for SMB3 and the combinations of ZnS with TiO2 and SMB3. It should be highlighted that all the combinations of NPs with ZnS, except for the combination with CdS, had normalized or increased ROS generation compared with the single exposure of microalgae to these NPs. Interestingly, the combination of ZnS with SMB24, which caused the highest increase in ROS generation, demonstrated the highest antagonistic interaction in the growth rate inhibition bioassay (A significant increase in reactive oxygen species (ROS) generation was observed for the microalga cells exposed to ZnS and the mixture of ZnS with SMB24 c. Most obioassay b. These The influence of single and binary mixtures of the NPs on the size of the microalga cells is represented in H. akashiwo cells in the size range between 10 and 15 µm. According to the results, the highest increase in the microalga cell size was caused by the influence of single SMB24 NPs and the binary mixtures of SMB24 with TiO2 and CdS with TiO2. In these cases, there was a significant (p < 0.0001) increase in the number of cells in the size range of more than 15 µm. It should be noticed that single exposure of microalgae to CdS did not show any significant cell size change, and TiO2 even caused a decrease in cell size, although the mixture influence of TiO2 with CdS increased the size of H. akashiwo. In general, all the cases with an increase in the cell size of the microalga correlated with high mortality and growth inhibition ) was observed for the samples ZnS, TiOThe initial particle size distribution and particle size changes after 96 h of exposure are represented in 2 NPs. The single TiO2 sample and all the combinations with the other NPs demonstrated the highest number of particles in the size ranges of 500–1000 nm and 1–10 µm, compared with the other samples and their combinations. At the same time, a single TiO2 sample and all the binary combinations with TiO2 had the lowest number of particles in a size range of 100–200 nm, which also demonstrates that the TiO2 sample facilitated the aggregation of the other NPs. The samples of CdS, ZnS, SMB3, SMB24, and their combinations in the used concentrations had a similarly high number of particles in the size range of 100–200 nm.The initial particle size distribution a demonst2 with ZnS, followed by the combination of TiO2 with CdS and the single TiO2 sample. All these cases demonstrated the same pattern, with an increase in the particles in size ranges of more than 10 µm and 100–200 nm and a simultaneous decrease in the number of particles in the size ranges between 200 nm and 10 µm.2, and the combination of SMB3 with SMB24 had no significant difference in the number of 100–200 nm particles, but all these samples demonstrated a decrease in 200–500 nm particles. The samples of ZnS and SMB3 and their combinations with each other and with CdS and SMB24 demonstrated a high decrease in the number of 500–1000 nm particles.CdS demonstrated a slight increase in the number of particles in the size range of 100–200 nm and a 50% decrease in the particles in the 200–500 nm size range, which might be explained by the dissolution of the aggregated NPs. The samples of ZnS, SMB3, the combinations of CdS and ZnS with the other particles except for TiO2 with ZnS, compared with the summation of the measurements of these NPs individually. The combination of TiO2 with SMB3 increased the number of 500–1000 nm particles. The other samples in combinations had a lower number of particles compared with the sum of their single measurements, which can mean that interaction between the used NPs supported their faster dissociation compared with single NPs.H. akashiwo had an extremely high influence on the aggregation of sample SMB3 and all the combinations of the other used samples with SMB3. The increase in the particles in the size range of 1–10 µm of 13–25 times and particles more than 10 µm of 25–175 times for these samples should be assessed, considering the very low number of such particles in the initial suspensions  for all the used samples and their combinations.pensions a. It meaThe obtained results were summarized in This study focused on the single and combined toxic effects of metal-containing, metal oxide, and silicon oxide NPs on microalgae. Moreover, this research work evaluated the influence of the interaction between different types of NPs and between NPs and microalga cells on the agglomeration of the NPs.2 NPs SMB24 had inclusions of ZnO and Ag represent strong antimicrobial and cytotoxic properties, according to the manufacturer information . This sample of NPs can be considered a mixture by itself because of the impurities. The obtained results of the bioassay correlate with the manufacturer information, as this sample demonstrated the highest toxicity among the tested NPs .The recent concept suggested considering even pure NPs as a mixture due to their transformation, dissociation, agglomeration with environmental components, and impurities in their composition . In thisH. akashiwo cells among the tested NPs . It was reported that ZnO is predominantly present in biological media in ionic form and binds with proteins by electrostatic attraction [Scenedesmus obliquus and crustacean Daphnia magna and had an antagonistic effect in the fish Danio rerio [2+ ions and ZnO inclusions from SMB24, which made the properties of SMB24 closer to the relatively safe SMB3. The ability of ZnO and ZnS to form nanocomposites in water under normal conditions was reported previously [2+, which were absorbed by graphene oxide NPs [We can conclude that the toxic properties of SMB24 were caused directly by the metal impurities of ZnO and Ag, because sample SMB3 with similar structural parameters but without any impurities had the lowest toxicity toward traction . Ye et aio rerio . In our s EC50, 2.8 mg/L. xide NPs . Therefo2 NPs had synergistic toxic action in combinations with all the used samples except SMB24  also demonstrated synergistic toxic action. In this case, the particles by themselves were dissociated with time in all the combinations b, but thnhardtii . The autaddition . Our stuand SMB3 b. In thiH. akashiwo, was previously reported in our work [2 , and two types of mesoporous silicon dioxide (SMB3 and SMB24).For the bioassays, we used five samples of NPs , namely Particle acquisitions were supported by the team staff of Far Eastern Federal University, working under the state task of the Russian Ministry of Science and Higher Education (project 0657-2020-0013).H. akashiwo (Raphidophyceae) [The culture of a raphidophyte microalga phyceae)  was provH. akashiwo was described in detail [H. akashiwo does not have a shell like most of the algae species, but it has amorphous vesicles under the cell wall. H. akashiwo has a mixed form of feeding, which includes photosynthesis, direct nutrition uptake, and the eating of bacterium [The morphology of n detail . Howeveracterium .Culturing of the microalgae and toxicity test conditions were maintained following the guidance of OECD No. 201  with minThe tested NPs were added to 0.22 µm of filtered seawater to obtain the working suspensions with a concentration of 1000 mg/L. Before each series of bioassays, the working suspensions of the NPs were sonicated with a Bandelin Sonopuls GM 3100 ultrasound homogenizer  with a high-frequency power of 100 W for 30 min. The sonication was performed to prevent the initial particle agglomeration according to the protocols of particle suspension testing .All the bioassays were performed in 24-well plates in quadruplicate. The volume of the microalga aliquots in each well was 2 mL. The wells with only f/2 medium  were takThe first stage of the bioassay involved single NP testing. Here, we used the concentrations of 10, 25, 50, 100, 125, and 150 mg/L for all the tested NPs. The preliminary results demonstrated that the highly cytotoxic sample SMB24 required reduction of the used concentrations and, therefore, the concentrations of 1 and 5 mg/L were additionally applied for this sample. Based on the results of the first stage of the bioassay, we calculated the effective concentrations of the NPs, which caused 10% (EC10) and 50% (EC50) inhibition of microalgal growth. The calculation of the EC10 and EC50 values was performed by nonlinear regression fitting in GraphPad Prism 8.0.2 . The control group was taken as 100%.The second stage of the bioassay was the testing of the binary mixtures of the NPs. Here, we used the EC10 concentrations calculated for each NP sample in the first stage. Hence, the microalga cells were exposed to the calculated EC10 concentrations of each NP sample individually (comparative control) and in binary combinations with the other samples.o) was calculated as a percent of growth inhibition compared with the control of Equation (1):To assess the toxic effects of single and binary mixtures on the second stage of the bioassay, the observed toxicity (Po) of the binary mixtures was compared with the theoretically expected toxicity (Pe) calculated by Equation (2) based on probability theory [1 is the mean observed toxicity caused by NP sample N1 and P2 is the mean observed toxicity caused by NP sample N2. The observed toxic effect was considered synergistic or antagonistic if Po was significantly (p < 0.05) higher or lower than Pe, respectively. If there was no significant difference (p > 0.05) between Po and Pe, then the interaction was determined to be additive.Then, the observed toxicity (Py theory :(2)Pe1+2Before all the measurements, 100 µL of exposed microalga aliquot from each well of the 24-well plate was transferred into a 96-well plate and stained with specific fluorescent dyes as described below. The used endpoints, biomarkers, and parameters of their registration are represented in a (emission channel: 690 nm) as described previously [The counting of the microalga cells and the evaluation of their morphological changes were performed with a CytoFLEX flow cytometer  with the software package CytExpert v.2.0. The determination of the microalga cells in the analyzed samples was carried out using the parameters of the microalga cell size, granularity, and fluorescence of chlorophyll eviously . Each saThe registration of the biochemical endpoints was performed with a GloMax Multi+ UV-VIS microplate reader E9032 . According to the similar emission maximum of the used dyes, the measurements of all endpoints by the GloMax microplate reader were made as separate independent series. The results were obtained as the mean fluorescent intensity represented in arbitrary units.The growth inhibition changes of the microalga cells were measured both in the first and second stages of the bioassay. The size, esterase activity, membrane potential, and ROS generation in the exposed microalga cells were registered only on the second stage of the bioassay.The changes in microalgal esterase activity, membrane potential, and ROS generation were estimated as an observed relative effect  by Equation (3) :(3)RE=yxTo assess the size distribution of the used NPs and their size changes after exposure, we used a CytoFLEX flow cytometer in two different working configurations. The particles in the size range of 100–1000 nm were registered by the forward scatter intensity of the violet laser (405 nm) and used a mixture of fluorescent particles Megamix-Plus SSC and Megamix-Plus FSC . The particles in the size range of 1–10 µm were registered by the forward scatter intensity of the blue laser (485 nm) and size calibration kit . All the measurements were performed in these two configurations independently in triplicate. Each measurement was performed at a flow rate of 50 μL/min for 30 s.a fluorescence in the emission channel of 690 nm.The particle size distribution was assessed for the EC10 concentrations of the NPs calculated in the first stage of the bioassay and for all their binary combinations. To assess the changes in the particle sizes with time and to assess the effect of binary combinations on the particle size, the measurements were carried out immediately after the dispersion of single and binary mixtures of NPs and after 96 h of exposure in the same condition as the microalgae bioassay but without adding the aliquot of microalga cells. To assess the impact of the microalga cells on the particle size, the measurements of the particle sizes were performed after 96 h of exposure of the microalga cells with single and binary mixtures of NPs. In this case, the microalga cells were excluded from counting in the CytExpert software by chlorophyll H. akashiwo compared with 96 h of exposure without the alga were estimated as a relative difference  by Equation (4):i is the number of particles in a size range i registered in the compared group and The changes in the size distribution of the NPs after 96 h compared with 0 h and after 96 h of exposure with (1+2), times) by Equation (5):(1+2) is the number of particles in a size range i registered in the binary mixture of NPs after 96 h of exposure and i in single-NP samples N1 and N2, respectively.The relative particle size change in the binary mixtures compared with the sum of the individual NPs after 96 h of exposure was calculated as a relative difference of the mixtures .In the first stage of the bioassay, the statistical significance of the microalga growth rate’s dependence on the concentrations of the NPs was tested by one-way ANOVA.t-tests were used to assess the significance of the difference between Po and Pe, the control and exposed groups in terms of esterase activity, the membrane potential, ROS generation, and algal cell size assessment, the particle numbers in the corresponding size ranges before and after 96 h of exposure, the particle numbers in corresponding size ranges with and without microalga cells, and between the calculated sum of the numbers of particles in the corresponding size ranges of two single NPs and the observed number of particles in the same size ranges of a binary mixture of these NPs.In the second stage of the bioassay, multiple Student’s p ≤ 0.05 was considered statistically significant.Normality was checked using the Shapiro–Wilk test. A value of H. akashiwo demonstrated the highest toxicity of a mesoporous silicon dioxide sample with metal inclusions SMB24  and sample CdS . The toxicity assessment of the binary mixtures of NPs revealed that the toxicity of SMB24 was reduced in the presence of CdS and ZnS by probable scavenging of additional Zn2+ ions and ZnO inclusions from SMB24. The tested TiO2 and mesoporous silicon dioxide sample without any inclusions of SMB3 demonstrated synergistic toxic action in all the combinations with the other NPs except SMB24. The used TiO2 NPs and the NPs in all the combinations of TiO2 with the other samples strongly agglomerated after 96 h of exposure in seawater. The NPs of SMB3 and the NPs in the combination of SMB3 with the other samples did not agglomerate by themselves in seawater but strongly agglomerated after the exposure with microalga cells. The supposed reason for synergistic toxic action of TiO2 and SMB3 combined with the other NPs is a “Trojan horse effect” which increases the bioavailability of other metal-containing NPs for aquatic organisms. Moreover, all the used NPs and their combinations agglomerated after the exposure with H. akashiwo compared with the similarly exposed NPs without the microalga.The individual aquatic toxicity assessment of the NPs in the marine microalga The used methodology can be modified and reproduced for other types of NPs and their combinations to support a better understanding of the toxicity mechanisms and interaction between NPs and aquatic organisms. Further studies should include more species from different trophic levels, more types of NPs and their combinations, broader biomarker and target characteristic boards, omics approaches, and chronic toxicity bioassays with low doses of the toxicants. The standardization of the protocol of the mixture toxicity of NPs is one of the major issues that should be addressed to support faster study in this area.


The viscoelastic properties of open graded friction course (OGFC) are closely related to anti-permanent deformation ability, noise reduction ability and durability. To study the viscoelastic parameters of OGFC under dynamic and static loads and to establish the functional relationship between them, uniaxial compression creep tests and dynamic modulus tests were performed to obtain the creep compliance and the dynamic modulus of OGFC. In addition, the Burgers model, modified Burgers model, second-order extensive Maxwell model, Scott-Blair model and modified Sigmoid model were employed to quantitatively analyze the dynamic and static viscoelastic properties of OGFC. Subsequently, the relaxation modulus of OGFC was deduced by the viscoelastic theory. Then, the dynamic modulus of OGFC was calculated according to the deduced relaxation modulus. Based on the calculated values and the measured values of dynamic modulus, the functional relationship of viscoelastic parameters of OGFC under dynamic and static loads was established. The results show that the increase in test temperature has adverse effects on the viscoelastic indexes of OGFC, such as creep compliance, relaxation modulus, and dynamic modulus; the dynamic modulus derived from static creep compliance has a good linear correlation with that obtained by dynamic modulus tests, but the correlation of the phase angle is poor. Open-graded friction course (OGFC) is a kind of open-graded asphalt mixture composed of aggregate and high viscosity modified asphalt. It has been widely used in permeable pavement engineering because of its many advantages, such as high permeability, skid resistance, and noise reduction ,2. CompaRelevant studies have pointed out that the viscoelastic parameters, such as creep compliance, relaxation modulus, dynamic modulus, and phase angle, are closely related to the anti-permanent deformation ability, noise reduction ability, and durability of OGFC. The creep compliance and relaxation modulus of OGFC can be obtained by the static uniaxial compression tests; and the dynamic modulus and phase angle used to describe the resistance to dynamic load deformation and to characterize the rheological properties of asphalt mixture can be tested through dynamic uniaxial compression tests. Biligiri et al. measured the phase angle of OGFC based on the dynamic modulus tests and analyzed the correlation between the phase angle of OGFC and pavement noise level . Some reAt present, many researchers are also committed to using meso-mechanical models and mathematical algorithms to predict viscoelastic parameters (such as dynamic modulus and phase angle of OGFC), which can provide a good help for the study of viscoelastic properties of OGFC. Naik et al. and Venudharan et al. used robust mathematical functions and operators in the form of beta distribution to predict the elastic modulus and phase angle parameters of OGFC ,14. The However, the related studies have pointed out that there is an inherent relationship between dynamic modulus parameters and static creep compliance parameters of asphalt mixtures, and the creep compliance in the time domain can be transformed into dynamic modulus in the frequency domain according to the relevant mathematical theories ,17. FurtTherefore, to establish the functional relationship of viscoelastic parameters of OGFC under dynamic and static loads and realize the rapid prediction of dynamic parameters of OGFC, the creep compliance and the dynamic modulus of OGFC is tested by uniaxial compression creep tests and dynamic modulus tests at different temperatures. In addition, the relaxation modulus data of OGFC is needed to construct this function, but there is still a lack of effective testing equipment for testing the relaxation modulus. Thus, according to the viscoelastic theory, the relaxation modulus of OGFC is deduced by the convolution integral and Simpson quadrature formula. Then, the dynamic modulus parameters of OGFC are calculated and compared with the measured results. Based on the calculated values and the measured values, the functional relationship of viscoelastic parameters of OGFC under dynamic and static loads is established to realize the prediction of the dynamic modulus parameters from static creep compliance.In this study, rubber modified asphalt was applied as the binder to prepare the open graded asphalt mixtures. The physical performance parameters of rubber modified asphalt was tested and is shown in To evaluate the viscoelastic properties of asphalt mixtures under static load, uniaxial compression creep tests at 10 °C, 20 °C, 30 °C, 40 °C, and 50 °C were carried out for three specimens in each group. For the static creep tests, the asphalt mixture specimen should be kept at the corresponding test temperature for 4 h before the test, so that the internal and external temperature of the specimen are uniform and reach the value required by the test. During the test, the contact pressure of 0.2 MPa was implemented on the cylindrical specimen, which was continued for 3600 s in the environment box at the corresponding test temperature . All theTo analyze the viscoelastic properties of OGFC under dynamic loads and compare the viscoelastic parameters between dynamic and static loads, dynamic modulus tests at 10 °C, 20 °C and 30 °C were performed for three specimens in each group according to the specification JTG E20-2011. The stress control was adopted throughout the tests, the loading amplitude was set to 0.2 MPa, and the loading frequencies were 0.1 Hz, 0.5 Hz, 1 Hz, 5 Hz, 10 Hz and 25 Hz, respectively ,23. BefoE(ξ) is the relaxation modulus of OGFC at loading time ξ, and J(t − ξ) is the creep compliance of OGFC at loading time t − ξ. According to the principle of integral superposition, Equation (4) can be divided into Equation (5):Creep and relaxation are two kinds of mechanical responses of viscoelastic materials, such as asphalt mixtures, under different loading modes. Some studies have pointed out that there is a function relationship between the creep compliance and the relaxation modulus as shown in Equation (1) ,18,24,25According to the numerical integration algorithm and the Simpson rule summary, the relaxation modulus of OGFC can be calculated. The calculation method is shown in Equation (6):n unknown parameters, which can be written as Equation (7) [Equation (6) is a system of linear equations with tion (7) :(7)Ax=BSome studies have pointed out that the variation of relaxation modulus of asphalt mixtures with loading time can be fitted by the generalized Maxwell model shown in ion (12) ,27:(11)The dynamic modulus According to the coefficients of the generalized Maxwell model, the storage modulus (15) and , respectectively ,29:(15)GAccording to the uniaxial compression creep tests, the creep compliance of OGFC at 10 °C, 20 °C, 30 °C, 40 °C, and 50 °C was tested and calculated, and the average results are shown in To further quantitatively analyze the influence of temperature on creep characteristics of OGFC, the Burgers model and modified Burgers model, shown in According to When the load time t tends to infinity, the modified Burgers model, as shown in Equation (18), can be written as Equation (20). From Equation (20), it can be found that the creep strain of asphalt mixtures is mainly composed of instantaneous elastic strain According to the relationship between the creep compliance and relaxation modulus of asphalt mixture in Equation (6), the relaxation modulus of OGFC at 10 °C, 20 °C, 30 °C, 40 °C, and 50 °C is calculated by using MATLAB software , as shown in In general, the attenuation process of the relaxation modulus of asphalt mixture can be divided into three stages. The first stage is the rapid decline stage, which is usually completed in tens of seconds, and the decline in the relaxation modulus is the greatest at this stage. The second stage is the turning stage of the decrease in the relaxation modulus. The decrease speed of the relaxation modulus gradually slows down, and the decrease range of the relaxation modulus is about 30% of the initial relaxation modulus. The third stage is the slow decline stage of the relaxation modulus, which indicates that the change of the relaxation modulus of asphalt mixtures has tended to be stable, and the decline of the relaxation modulus in this process is the smallest. At the end of the relaxation test, about 10% of the initial relaxation modulus remains.To further quantitatively analyze the effect of test temperature on relaxation characteristics of OGFC, the second-order extensive Maxwell model ,35,36,372 in According to Equations (21) and (22), the parameters of the two models are calculated by programming algorithm in Excel. The calculated results are shown in From the fitting results of the second-order generalized Maxwell model in For the fitting results of the Scott-Blair model, it can be observed that the viscosity coefficient of OGFC decrease with the increase in test temperature, which indicates that the asphalt mixture changes from solid elastomer to fluid with the increase in temperature, its elastic properties and viscous resistance will decrease, and the anti-rutting deformation ability will weaken.According to Equations (2) and (3), the dynamic modulus test results are calculated at 10 °C, 20 °C, and 30 °C, and the variation of dynamic modulus and phase angle of OGFC with loading frequency is plotted, as shown in It can be seen from From −3–105 Hz), the dynamic modulus of OGFC is still increasing with the increase in loading frequency.The change in dynamic modulus of asphalt mixtures, as a typical viscoelastic material, with loading frequency meets the time-temperature equivalence principle of polymer materials, and the master curve of dynamic modulus of asphalt mixtures can be constructed by the shift factor, which can be used to study the development of dynamic modulus of asphalt mixtures in the range of higher or lower loading frequency. According to the time-temperature equivalence principle, the dynamic modulus master curves of OGFC are constructed in the double logarithmic coordinate axis based on the dynamic modulus curves at 10 °C, 20 °C and 30 °C, as shown in In order to further analyze the variation of the dynamic modulus and phase angle of OGFC with the loading frequency and the influence of test temperature on the dynamic modulus and phase angle of OGFC, the modified Sigmoid model, as shown in Equations (23) and (24), is employed to fit the master curve of dynamic modulus and phase angle of OGFC ,40. The It can be seen from From the fitting results of the second-order generalized Maxwell model, it can be seen that when the order of the generalized Maxwell model is small, it is poor to characterize the change of relaxation modulus in the short-term loading process. Therefore, in order to accurately establish the functional relationship of viscoelastic parameters of asphalt mixture under dynamic and static loading modes, the sixth order generalized Maxwell model was selected for subsequent calculation. Equation (10) is used to fit the relaxation modulus of OGFC at 10 °C, 20 °C, 30 °C, 40 °C, and 50 °C, and the fitting result is shown in To better analyze the correlation of viscoelastic parameters of OGFC under dynamic and static loads, the linear correlation function is adopted to fit the scatter diagram. From the fitting results, it is found that the correlation coefficient of the dynamic modulus is 0.9632, while the correlation coefficient of the phase angle is only 0.7568, which shows that the dynamic modulus of OGFC obtained under the dynamic and static loads has a good linear correlation. The dynamic modulus obtained by the dynamic modulus test can be calculated by reasonably modifying that derived from creep compliance. The modified equation is shown in To analyze and compare the viscoelastic properties of OGFC under dynamic and static loads, uniaxial compression creep tests and the dynamic modulus tests were carried out to obtain the creep compliance, dynamic modulus, and phase angle. Furthermore, the viscoelastic theory and models were applied to study the effect of test temperature on viscoelastic properties of OGFC and to construct the functional relationship of viscoelasticity parameters of OGFC under dynamic and static loads. The following results can be summarized:(1)With the increase in test temperature, the creep compliance of OGFC increases significantly, and the corresponding anti-instantaneous elastic deformation ability ((2)With the increase in loading time, the relaxation modulus of OGFC decreased rapidly at first and then slowly; with the increase in test temperature, the relaxation modulus of OGFC decreased significantly. The Scott-Blair model can better describe the change in OGFC relaxation modulus with loading time than the second-order extensive Maxwell model, and the fractional order of the Scott-Blair model can adequately characterize the transition of OGFC from solid to fluid with the increase in temperature.(3)5 MPa at high frequency, and converges to the static modulus around 2 MPa at low frequency.With the increase in loading frequency, the dynamic modulus of OGFC increases and the phase angle decreases. The increase in test temperature will have an adverse effect on the dynamic modulus of OGFC. The fitting analysis results show that the dynamic modulus of OGFC at different temperatures almost converges to the same value at very high or very low loading frequency, converges to the glassy modulus around 10(4)The dynamic modulus derived from static creep compliance has a good linear correlation with that obtained by dynamic modulus tests, but the correlation of the phase angle is poor. The actual dynamic modulus of OGFC can be calculated and obtained by the linear function modified the dynamic modulus derived from creep compliance, which can provide a new way to obtain the parameters needed for the structural design of asphalt pavement.


The paper investigated the possibility of obtaining large-sized blocks of C11000 copper on stainless steel substrates via electron beam wire-feed additive technology. The features of the microstructure and grain texture formation and their influence on the mechanical properties and anisotropy were revealed. A strategy of printing large-sized C11000 copper was determined, which consists of perimeter formation followed by the filling of the internal layer volume. This allows us to avoid the formation of defects in the form of drops, underflows and macrogeometry disturbances. It was found that the deposition of the first layers of C11000 copper on a steel substrate results in rapid heat dissipation and the diffusion of steel components  into the C11000 layers, which promotes the formation of equiaxed grains of size 8.94 ± 0.04 μm. As the blocks grow, directional grain growth occurs close to the <101> orientation, whose size reaches 1086.45 ± 57.13 μm. It is shown that the additive growing of large-sized C11000 copper leads to the anisotropy of mechanical properties due to non-uniform grain structure. The tensile strength in the opposite growing direction near the substrate is 394 ± 10 MPa and decreases to 249 ± 10 MPa as the C11000 blocks grows. In the growing direction, the tensile strength is 145 ± 10 MPa. Additive manufacturing (AM) covers an increasing range of tasks in industry. Currently, common additive manufacturing technologies are electron beam melting (EBM) , selectiCu is one of the most widely used constructional materials due to its excellent electrical conductivity, thermal conductivity, ductility, machinability and formability. Due to this, Cu has a wide range of practical applications, and it is used in various engineering industries, such as in the automotive, aerospace, electrical power, electronics and defense industries, etc. The high thermal conductivity of copper and copper alloys allows for the manufacture of various components, such as heat exchangers (combustion chambers for liquid rocket engines), power units, springs and bearings and electronic connectors in the above sectors. These high heat flux environments require a high-strength, high-conductivity alloy to properly cool the thrust chamber walls with high-pressure rocket fuel or an oxidizer. The higher thermal conductivity of pure copper leads to faster heat dissipation and a higher localized temperature gradient, which causes the twisting and delamination of the deposited layer . The higThe microstructure during solidification in manufacturing is determined by the temperature gradient, solidification rate, cooling and other material-related parameters ,20. The The grain structure and crystallographic texture of the component depend on the melting and crystallization of the melt pool. The shape of the melt pool in this case varies depending on the printing parameters, and can be oval or curved on the top surface and semicircular or keyhole-shaped in cross-section, depending on the intensity of the heat source and the rate of movement. Growth occurs during solidification because of previously deposited layers, and this determines the crystallographic essence of the structure through the partial or complete melt feedback of the previously formed layer. In addition, crystallographic texture is also determined by the scanning strategies used during sample fabrication. In the case of IN718, it was observed that the texture was designed with a unidirectional scanning strategy, whereas the rotated cube texture was designed with bidirectional scanning. These textures are a consequence of the compromise between the directions of easy grain growth and the directions of maximum heat flux near the boundaries of the melt pool . Growth However, little is known about the use of crystallographic texture and grain size as a tool for designing a functional microstructure, and even less is known about the relationship between the preferred anisotropy, microstructure and mechanical properties. Therefore, the goal of this work was to obtain large-sized workpieces to investigate texture formation and its effect on the anisotropy of mechanical properties under tension in different directions relative to growth.Large-sized samples of C11000 copper were obtained through electron beam wire-feed additive manufacturing with experimental equipment at the Institute of Strength Physics and Materials Science, Siberian Branch of the Russian Academy of Sciences  .An AISI 304 stainless steel substrate and technical grade C11000 copper wire were used to obtain the samples . The diaI = 90 A and υI = 300 mm/min, respectively. Further, as the height of the large samples increased, the current and printing speed were changed to III = 60 A and υII = 400 mm/min, respectively. The wire feed rate was 1.5–2.0 mm/min, depending on the printing speed. The width of the melt pool was 6 mm and the distance between passes was 5 mm. The formation of the melt pool was performed by sweeping an electron beam, in the form of a circle with a diameter of 5 mm, at a frequency of 1 kHz. The thickness of the deposited layer was 1 mm. Large copper blocks were obtained according to three types  of scanning strategy . To determine the elemental composition of the specimens, a Zeiss LEO EVO 50  scanning electron microscope (SEM) was used. Microhardness was measured using a Duramin5  machine. Microhardness measurements were carried out via the Vickers method at a load of 50 g for 10 s. The tensile specimens were in the shape of a double-sided blade. The working part of the double-sided blade was 12 mm . Tests were performed on a universal testing machine, UTS 110M . The strain rate was 1.4 × 10−3 c−1. Macroscopic images of the specimens were taken with a Pentax K-3 camera with a lens focal length of 100 mm. Microstructural studies were performed using a scanning electron microscope, Tescan MIRA 3 LMU , equipped with a system of registration of back-reflected electrons, Oxford Instruments Nordlys, and an energy dispersive X-ray spectrometer, Oxford Instruments Ultim Max 40 . The scans were performed at an accelerating voltage (HV) of 20 kV and a beam current of 10 nA. Electron backscattered diffraction (EBSD) samples were prepared using the standard technique: sandpaper grinding to #2000, diamond polishing from 9 to 1 µm and 50 nm col-K suspension fine polishing. The final stage of sample preparation was ion polishing for 10 min at 10 kV by using a Technoorg Linda SEMPrep2 ion mill  with a wide plane-parallel argon ion beam. Before the structural studies, the samples were ground and polished with diamond paste followed by the etching of the polished surfaces of the samples in a solution of 10 mL HCl + 1 g FeClThe general view of the large-sized copper blocks grown through electron beam wire-feed additive technology is shown in Printing type B blocks using strategy 2  involvedThe correction of such defects was achieved by changing the printing scheme. In type C blocks, the perimeter was formed first, followed by the filling of the inner layer volume. The blocks obtained using this printing scheme did not show the presence of geometric distortions, even when reaching a height of 80 mm . The surThus, for the production of blocks with correct geometry and compliance with the proportion of the shape of large-sized copper blocks using electron beam wire-feed additive technology, suitable scanning involves the initial formation of the perimeter and the subsequent filling of the inner layer volume . Since the type C printing strategy proved to be preferable, in the following section, we will consider the structure and mechanical properties of the blocks obtained through strategy 3 only.In the structure of C-type copper blocks, a coarse grain structure is formed with preferential growth in the direction of heat removal . TypicalThe analysis of the macrostructure in the longitudinal section b shows tThe actual grain growth direction can differ significantly from the local maximum temperature gradient, depending on the scanning strategy. “Zigzag” patterns have major grain directions that are perpendicular to each other in successive layers, resulting in a 45° angle to the scanning direction. This results in epitaxial grain growth in the first layer shifting to grain formation in a different direction in the second layer, or vice versa, with a 15° deviation between the maximum heat flux temperatures. Thus, texture evolution is strongly influenced by the scanning strategies that correlate with the directions of easy growth and maximum heat flux. Full alignment results in a texture similar to the norm. The final solidification texture is determined by local heat flux directions and competitive grain growth.The horizontal section is distinguished by the main structural components of the blocks . In the In general, the structure of the sample is a columnar grain crossing most of the layers. In the lower part of the blocks, i.e., part 1 , area 1,Near the interface in the copper part of the bimetal, we also observed inclusions with weak etching, and a morphology close to the structure of austenitic steel below the interface “substrate-additive layers” . The preAt a distance of approximately 1.5 mm from the interface, the Cu content is 98.9 (wt. %), which is close to the grade composition of C11000 copper. A clear transition zone, indicating the formation of a solid solution of iron in copper, on the metallographic thin sections is not revealed.Thus, the first layers have a high concentration of substrate chemical elements, such as Fe, Ni and Cr, whose concentration decreases as the C11000 blocks is printed a.The analysis of the distribution of microhardness at transition through an interface of a bimetallic sample testifies to the sharp change in the strength properties in a material, which goes from 2.29 GPa, corresponding to austenitic steel, to 0.54 GPa in the copper part of a sample. The transition zones near the interface described above are characterized by scattered microhardness values  and elevated microhardness values  b. The vaThe increased concentration of Fe with Cu dilution in this region explains the presence of small globular inclusions due to its increased tendency to partition. This phenomenon, with the intrusion of the underlying layers, including the substrate, has also been observed in the previous works of various additive products consisting of austenitic stainless steels, nickel-based heat resistant alloys and copper and bronze alloys ,41,42.The barrier effect  affects the copper part of the sample. According to the microstructure shown in In addition, the transition boundary from the substrate to the first layers, in which a supersaturated solid solution is formed, is considered separately . The depI = (11.91 ± 0.03) μm  μm . At the II = (27.76 ± 0.04) μm, are observed in the process of collective recrystallization  twins. The twin structure is equivalent to a packing defect. The coherent surfaces of the twins turn out to be little mobile when heated, but the incoherent surfaces often migrate, which can lead to the disappearance of small twins as a result of the development of this process. Since the latter always exist in the deformed matrix, a favorable situation for twin formation is created when the growing grain meets a packing defect. However, there are a number of other features of the grain growth process that can determine the formation of twins. Further, larger equiaxed grains, with an average size of dlization . With smThe formation of large grains is possible both at the expense of neighboring nuclei, where coalescence is observed, and of gradual growth. Additionally, it should be noted that the content of iron and alloying elements in the steel substrate decreases, which reduces the obstacle to the migration of grain boundaries. The predominance of chaotic grain orientation remains, but it is worth noting the formation of a predominant orientation along <101> and <111>, as evidenced by the distribution of the MUD function .III = (338.54 ± 13.83) μm. The fraction of low-angle boundaries is insignificant, and twin boundaries are practically absent. Based on the IPF analysis, it is clear that the fraction of preferential orientation increases significantly, and the MUD function value differs by a factor of 25. The direction of recrystallization does not coincide with the vertical direction of the cladding due to the temperature gradient during printing. After the completion of secondary recrystallization, abnormally large, elongated grains are formed, with average length and width values of dIV = (1086.45 ± 57.13) μm at the beginning of formation; in the finished workpiece, they are up to 3.5 mm and 0.3 mm in length and thickness, respectively . The temperature gradient plays a key role in the morphology and size of the structure and determines the crystallization mode. During the deposition of the first layers of C11000 copper on stainless steel substrate AISI 304, rapid heat dissipation occurs, which, together with the alloying of copper with austenitic steel components (primarily Fe) and the formation of inclusions of the second phase, leads to the formation of a fine-grained structure. As the blocks grows, the influence of these factors decreases and directional grain growth occurs. Directed grain growth is facilitated by the slow heat dissipation and temperature gradient formed during additive blocks growth .Region II represents the orientations of those grains that can have moving boundaries, with all or most of the texture components of <101> and <111>. In region III, grains with texture orientation <101> prevent the formation of grains with texture orientation <111>. The choice of structure orientation is related to several factors. The relative volume of the texture component is related to the number of these grains, that is, the rate of their formation. In area IV, the predominant texture orientation is <101>. In this case, the growth of grains of this orientation has a minimum energy of growth.UTStrans reaches 534 ± 10 MPa at 2–4 mm  from the substrate and 394 ± 10 MPa at 10–12 mm (bottom) for the transverse samples cut in the scanning direction 2 along the OY axis.In region IV, the predominant texture orientation is 101. In this case, the growth of grains of this orientation has minimal growth energy. Since the additive growth in the copper part of the blocks forms a significantly heterogeneous grain structure, its mechanical properties may differ markedly from the properties of cast copper, and it may have anisotropy. The conducted studies of mechanical properties of samples , cut accUTStrans to 249 ± 10 MPa. Since the introduction of steel particles no longer leads to an increase in strength, there is a hardening due to the refinement of the grain structure of the copper near the substrate. The strength of σUTStrans in further samples decreases gradually (to 145 ± 10 MPa) in the upper part of the blocks, with quite similar plasticity values. This situation is due to the fact that the block structure above 20–25 mm stabilizes, and becomes a set of large grains oriented almost parallel to the direction of heat removal. A large crystal structure, defect-free, with directional growth, has high parameters of plasticity, thermal and electrical conductivity, but has lower values of ultimate strength compared to the fine-grained structure formed near the substrate. At the same time, the tensile strength of 120 MPa or more is characteristic of cast copper [Further, at a distance of 18–20 mm from the substrate, there is an increase in ductility and a decrease in the tensile strength σI = (11.91 ± 0.03) μm. As the blocks grows, the influence of these factors decreases and directional grain growth up to 3.5 mm occurs close to the <101> orientation. Directed grain growth is facilitated by the slow heat dissipation and temperature gradient formed in the process of the additive growth of the blocks. It was established that the mechanical properties of the samples depend on the cutout area and are significantly higher in the area near the substrate (394 ± 10 MPa) at 10–12 mm (bottom) for transverse samples than the 145 ± 10 MPa recorded for the upper part of the blocks. The strength values when tested in both the horizontal and vertical directions are at the level of cast copper.The paper presented the production of large-sized blocks of C11000 copper on stainless steel substrates using electron beam wire-feed AM using separate perimeter formation and separate filling of the inner volume, which avoids disturbances in the macrogeometry of the samples in the printing process. It was found that the strategy of sample scanning during printing determines the formation of the structure at the macro level, and the distribution of large grains in the horizontal and vertical section of the sample. Separate filling of the perimeter does not lead to separate structure formation in the central and peripheral parts of the sample due to the smooth thermal gradient within the layer during printing. With the deposition of the first layers of C11000 copper on stainless steel substrate AISI 304, a rapid heat dissipation occurs that, together with the alloying of copper with austenitic steel components  and the formation of inclusions of the second phase, leads to the formation of a fine-grained structure d


The influence of compaction methods such as the Marshall compaction method (MCM), vibration compaction method (VCM) and gyration compaction method (GCM), on the performance of stone mastic asphalt (SMA-13) mixture has yet to be explored. Therefore, to compare the influences of compaction methods and work on the physical and mechanical properties of SMA-13 mixture, the volume parameters, mechanical properties, and gradation changes of SMA-13 mixture specimens prepared under different vibration compaction times, Marshall double-compaction numbers, and gyration compaction numbers were studied. The compaction method for SMA-13 mixture design was also proposed under the principle of optimum properties. Results demonstrate that the asphalt aggregate ratio and compaction work directly affect the volumetric properties  of asphalt mixture specimens while the raw material and mineral aggregate gradation were fixed. The influence of compaction work on physical properties is greater than that of asphalt aggregate ratio. The mechanical strength of VCM and GCM specimens is higher than that of MCM specimens under the same compaction work and the optimum asphalt aggregate ratio. With the increase in compaction work, the mechanical properties of SMA-13 mixture are improved at the same compaction method and the optimum asphalt aggregate ratio. The aggregate gradation of the SMA-13 mixture before and after compacted using VCM and GCM changes minimally compared with that of the SMA-13 mixture compacted by MCM. Thus, the compaction methods of VCM65 and GCM130 were recommended for SMA-13 mixture design. With the aggravating trend of China’s traffic toward the direction of “large flow, large-scale vehicles, heavy load, and overload”  and the However, the Marshall compaction method (MCM), which is easy to operate for researchers, is mostly used in the research of SMA mixture at present . Wu explRc) and splitting strength (RT) similar to those obtained using GCM . Th. Th21]. This study adopted the MCM established in JTGE20-2011. The specimens were prepared using a Marshall compactor, in which the working parameters are listed in The compaction numbers of 50, 75, 90, 105, 120, 135, and 150 were used for the specimens compacted using MCM; the compaction times of 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, 70 s, and 80 s were used for the specimens compacted using VCM; the gyratory compaction numbers of 25, 50, 75, 100, 125, and 150 were used for the specimens compacted using GCM. The gross bulk density of the specimens was measured. The relationship between compaction number or time and the density of the specimens is shown in From For simplicity, the specimens compacted using a Marshall double-compaction number of 75, vibration compaction time of 65s, and gyratory compaction number of 65 were replaced with MCM75, VCM65, and GCM 65, respectively. The same replacement applied to the others.The compaction method and work have a considerable influence on the particle arrangement of asphalt mixtures and the breakage of aggregates in the compaction process, which can inevitably affect the volume parameters of the mixtures. Thus, the structure of mixture specimens and the mechanical properties and optimal asphalt aggregate ratio of mixtures are also affected. The effects of compaction method and work on the physical properties of asphalt mixtures are studied under certain material composition.The variation in density of SMA-13 mixture with asphalt aggregate ratio under different compaction methods and compaction work is shown in Although the compaction mechanisms of GCM50 and MCM50 are not identical, the variation in the density of SMA-13 mixture specimens compacted using the two methods with asphalt aggregate ratio is basically the same. The asphalt aggregate ratio of the maximum density of specimens is 5.8%, that of the maximum density of VCM10, GCM65, and MCM75 specimens is 5.7%, and that of the maximum density of VCM65, GCM130, and MCM155 specimens is 5.4%. This result occurs because although the compaction methods are different, the compaction work of diverse compaction methods is basically the same. Nonetheless, the compaction work of VCM65, GCM130, and MCM155 is greater than that of VCM10, GCM65, and MCM75, and the maximum density of asphalt mixtures increases with the increase in compaction work. Specifically, the average density of VCM65, GCM130, and MCM155 specimens is 1.02 times that of VCM10, GCM65, and MCM75 specimens; the maximum density corresponding to the asphalt aggregate ratio decreases with the increase in compaction work. The asphalt aggregate ratio of the maximum density of VCM10, GCM65, and MCM75 specimens is 5.7%, and the asphalt aggregate ratio of the maximum density of VCM65, GCM130, and MCM155 specimens is 5.4%. This result shows that when the compaction work is small, the aggregates hardly reach the close contact state, and substantial asphalt lubrication and filling are needed to increase the density of asphalt mixtures.As an important volume parameter index of asphalt mixtures, VV has been considered to have direct effects, such as water seepage and aging, on the durability of pavement. VV becomes a weak point in pavements; the voids are prone to stress concentration and microdamage under the load action. The repeated action of stress gradually accumulates and expands the microdamage, which continuously reduces the effective stress bearing area and causes further damage after repeated action for a certain number of times. The variation in VV with asphalt aggregate ratio under different compaction methods and compaction work is shown in VMA is a key index in the design process of SMA-13 mixture, which is directly related to asphalt aggregate ratio and is one of the most important indexes reflecting the overall quality of the asphalt mixture. The variation in VMA with asphalt aggregate ratio under different compaction methods and compaction work is shown in Asphalt can be divided into structural and free asphalt. Structural asphalt has greater cohesion than free asphalt, and free asphalt can fill voids and reduce pavement water seepage and aging. Excessive free asphalt will affect the pavement strength; insufficient free asphalt will affect the pavement durability . TherefoIn conclusion, the volumetric properties of asphalt mixture specimens are a function of asphalt aggregate ratio and compaction work while the raw material and mineral aggregate gradation are fixed. When the asphalt content is the same but the compaction work is different, the volumetric properties  of the compacted mixture are also different. Different compaction standards should have distinct volumetric properties and the optimum asphalt aggregate ratio.The effect of compaction on mechanical properties under different compaction methods is shown in Figs Figs When the asphalt aggregate ratio of SMA-13 mixture is small, its VMA and VV are large, the VFA is low, and the mechanical properties are low. With the increase in asphalt aggregate ratio, the thickness of the asphalt film increases gradually, the friction among aggregate particles decreases, the VMA and VV of the mixture decrease, the VFA increases, and the mechanical properties first increase and then decline as a single-peak curve. The content of free asphalt increases and the cohesion of the asphalt weakens with the increase in asphalt aggregate ratio after the mechanical properties peak.The asphalt aggregate ratio of the mechanical property peak of MCM50 and GCM50 specimens is 5.8%, that of VCM10, GCM65, and MCM75 specimens is 5.7%, and that of VCM65, GCM130, and MCM155 specimens is 5.4%. This result shows that the optimum asphalt aggregate ratio of the mechanical property peak is a function of compaction work. The greater the compaction work is, the smaller the optimum asphalt aggregate ratio of the SMA-13 mixture is. When the compaction work is small, the friction of aggregates is high, and substantial asphalt is needed to make the aggregate dense. Consequently, the optimum asphalt aggregate ratio corresponding to the optimum mechanical properties of SMA-13 mixture under various compaction methods is different. Different compaction methods have distinct mechanical properties under the optimum asphalt aggregate ratio and the same compaction work.Under the same compaction work, the Marshall stability, compressive strength, shear strength and splitting strength of VCM10 specimens are 1.16, 1.06, 1.09, and 1.19 times higher than those of MCM75 specimens, respectively, with an average value of 1.13 times. The Marshall stability, compressive strength, shear strength and splitting strength of GCM65 specimens are 1.15, 1.07, 1.06, and 1.13 times higher than those of MCM75 specimens, respectively, with an average value of 1.10 times. The mechanical properties of GCM50 specimens are 1.08 times higher than those of MCM50 specimens; the mechanical properties of GCM130 specimens are 1.08 times higher than those of MCM155 specimens; the mechanical properties of VCM65 specimens are 1.12 times higher than those of MCM155 specimens. This result shows that the compaction method plays an important role in the positioning and arrangement of internal particle structure, and VCM and GCM are more conducive to the rearrangement of internal particles and the formation of stable structure than MCM .The effect of compaction work on mechanical properties under different compaction methods is shown in Figs Figs At the same compactness of SMA-13 mixture, different compaction methods have diverse mechanical properties. The mechanical properties of the mixture compacted using VCM are best compared with those of the mixtures compacted using GCM and MCM. Therefore, the compaction method plays a key role in the positioning and arrangement of internal particle structure, and VCM and GCM are more conducive to the rearrangement of internal particles and the formation of stable structure than MCM.The performance of SMA-13 mixture, especially the rutting resistance of the mixture, is affected by gradation. The compaction method and work influence the gradation of the asphalt mixture during the compaction progress and hence the performance of the mixture. The gradation of SMA-13 mixture with different compaction methods and compaction work is shown in σ declines, the compressive resistance diminishes, and the displacement of aggregates is more sufficient, making it easy to achieve density of SMA-13 mixture [From  mixture . AccordiIn this study, the performance of SMA-13 mixtures that were compacted using MCM, GCM, and VCM was compared. Their physical properties, mechanical properties, and gradation changes under different vibration compaction times, gyratory compaction numbers, and Marshall double-compaction numbers were discussed. The compaction method for SMA-13 mixture design was recommended under the principle of optimum properties. The main findings acquired from the above work were summarized as follows:The influence of vibration compaction time, gyratory compaction number, and Marshall double-compaction number on the density of SMA-13 mixture was analyzed. The Marshall double-compaction number corresponding to the density specified in the heavy traffic compaction standard was 155, which was called heavy MCM. The vibration compaction times corresponding to the density of MCM75 and MCM155 were 10 s and 65 s, respectively. The gyratory compaction numbers corresponding to the density of MCM50, MCM75, and MCM155 were 50, 65, and 130, respectively.Asphalt aggregate ratio and compaction work directly affect the volumetric properties  of asphalt mixture specimens while the raw material and mineral aggregate gradation were fixed. Under the same compaction work and the optimum asphalt aggregate ratio, the mechanical properties of GCM50 were 8% higher than those of MCM50; the mechanical properties of GCM65 and VCM10 were 10% and 13% higher than those of MCM75, respectively; the mechanical properties of GCM130 and VCM65 were 8% and 12% higher than those of MCM155, respectively.Under the same compaction method and the optimum asphalt aggregate ratio, if the compactness of the SMA-13 mixture increased by 1%, the Marshall stability, compressive strength, shear strength and splitting strength were improved on average by 8.1%– 11.3%, 6.5%– 8.0%, 14%– 18.0%, and 7.6%– 13.7%, respectively.The gradations of SMA-13 mixture were changed compared with the original gradation, which showed that the aggregates of the mixture were crushed during the compaction progress. The aggregate gradation of the SMA-13 mixture before and after compacted using VCM and GCM changed minimally compared with that of the SMA-13 mixture compacted using MCM. Compared with the breakage of the MCM specimen, the breakage of larger than 4.75 mm size aggregates of the GCM specimen was reduced by 1.9%, and that of the VGM specimen is reduced by 2.8% in the same compaction work.Through comparing the volume parameters, mechanical properties, and gradation changes of SMA-13 mixtures prepared under different compaction methods, the compaction methods of VCM65 and GCM130 were recommended for SMA-13 mixture design. They provide a reference for SMA-13 mixture design. The influence of these compaction methods on road performance, such as rutting-resistance and durability, will be evaluated in future studies.


Partial least squares regression was used to elucidate the linkages between water contaminants and the factors. As shown in the results, the temporal mutations of NH3-N and TP were obvious in the middle reaches, with 4 out of 7 catchments in the middle reaches have a larger number of mutations of NH3-N than other catchments. The cluster analysis results of NH3-N and TP among catchments were similar. This study also indicated that although the Huangshui River basin was located in the upper reaches of the Yellow River, the influences of rainfall-runoff relationship on spatiotemporal changes of NH3-N and TP in its sub-basins were limited. Only the temporal change of NH3-N in Jintan catchment in the upstream area was significantly affected by runoff coefficient. The indexes of proportion of water area (PWA), proportion of impervious area (PIA), and proportion of primary industry (PPI) were the top three influencing factors of temporal variation of NH3-N and TP for most catchments in the middle reaches. The temporal change of NH3-N in Jintan catchment in the upstream area was obviously affected by runoff coefficient. The spatial variation of NH3-N and TP were all affected by PWA and proportion of secondary industry significantly. The results of this study can provide theoretical basis and technical support for the control and management of nitrogen and phosphorus pollution in upper reaches of rivers.The foundation of managing excess nutrients in river is the identification of key physical processes and the control of decisive influencing factors. The existing studies seldom consider the influence of rainfall-runoff relationship and only focus on a few anthropogenic activities and natural attributes factors. To address this issue, a comprehensive set of influencing factors including rainfall-runoff relationship (represented by runoff coefficient), basic physical and chemical parameters of water quality, land use types, landscape patterns, topography, and socioeconomic development was constructed in this study. M–K test and cluster analysis were conducted to identify the temporal mutation and spatial clustering characteristics of NHThe online version contains supplementary material available at 10.1007/s10661-021-09067-1. Mn influence the transformation and mobilization of nitrogen and phosphorus in rivers , Partial least squares regression (PLSR) was used to quantify the impacts of the influencing factor set on spatiotemporal variation of NH3-N and TP concentration in the Huangshui River basin from 2015 to 2018. The importance rankings of the influencing factors on NH3-N and TP were obtained and then the main influencing factors were acquired. The main objectives of this paper are to (1) identify temporal and spatial variation patterns of ammonia nitrogen and total phosphorus in Huangshui River basin with the available monitoring dataset and (2) determine how the temporal and spatial variation of specific water contaminant attributed to multiple factors referred in this study using PLSR. This work can provide theoretical basis and technical support for the control and management of nitrogen and phosphorus pollution in upper reaches of rivers.In this study, a comprehensive set of influencing factors which consisted of six types of factors including rainfall-runoff relationship (represented by runoff coefficient), basic physical and chemical parameters of water quality, land use types, landscape patterns, topography, and socioeconomic development were constructed. To test whether it is applicable to the upper reaches of rivers, we selected Huangshui River basin in the upper reaches of the Yellow River as an example. According to China Ecological and Environmental Status Bulletin from 2015 to 2018 . With the rapid development of Xining urban agglomeration in recent years, the water environment and aquatic ecology of the Huangshui River Basin have been threatened. The main stream length of this region is 278 km with a drainage area of 15,558 km2, as shown in Fig. 3 (1956–2000 records). According to the land use classification results of 2017, forest was the mainly type of land use, followed by grasslands and cropland, occupying 92.91% in total.This study was conducted in Huangshui River basin, which rises in the Haibei Tibetan Autonomous Prefecture of Qinghai Province Fig. . Huangsh3-N), total phosphorus (TP), pondus hydrogenii (pH), the dissolved oxygen (DO), and potassium permanganate index (CODMn) were analyzed in this study. The specific analysis methods for water quality items were presented as follows: NH3-N, spectrophotometric method with salicylic acid; TP, spectrophotometric method with ammonium molybdate; pH, glass electrode method; DO, electrochemical probe method; CODMn, acidic  potassium permanganate method.We collected all water contaminant data and other spatial data from several government agencies , and that in 2017 was from Department of Natural Resources of Qinghai Province, China.For the basin scale, the boundary of each catchment was depicted by means of the DEM data in the ArcGIS, and each water quality monitoring station was deemed to be the outlet of the corresponding catchments Fig. . Digital3-N and TP in each catchment were obtained through M–K test. Moreover, the spatial clustering characteristics of NH3-N and TP in catchments were obtained by cluster analysis. On this basis, PLSR was used to quantify the complex interdependencies between the influencing factor set, and spatiotemporal variation of ammonia nitrogen and total phosphorus concentration in the basin. From the perspectives of temporal and spatial variation, the importance rankings of the influencing factors on NH3-N and TP were obtained and the main controlling factors were acquired accordingly, which lay the foundation for the accurate attribution of the temporal and spatial variation of NH3-N and TP , the sequence of NH3-N or TP is on the rise (down) trend, when it exceeds the critical line (p < 0.05), it indicates the rise or fall of the trend is significant.The Mann–Kendall test, which is a robust and non-parametric test method, was used to diagnose the temporal trends of water quality parameters  are analyzed. PLSR was developed for econometric modeling of multivariate time series and later was applied in chemometrics Wold,  and hype3-N) and total phosphorus (TP) was established respectively to identify the main influencing factors temporally and spatially in order to obtain the attribution of spatiotemporal variation of NH3-N and TP. Before PLSR analyses, predictors were centered and scaled to unit variance to give them the same relative importance. The percentage of variance explained for the response variables, the cross-validated root mean squared error (RMSE), which is the difference between the predicted and observed values of each individual pass. The predictor coefficients (magnitude and direction) were used to examine the influence of predictors on responses. The PLSR was performed using Matlab algorithm.A PLSR model for ammonia nitrogen   CSEPB, , Table 2The results of cluster analysis of TP showed that Jintan, Zhamalong, and Taerqiao catchment at the upstream section belonged to nearly entire qualified class (subject to Class III standards for surface water bodies in GB3838-2002) . The basic excess class of NH3-N in 7 catchments out of 13 catchments were mainly affected by three factors: PWA, PIA, PPI. The importance rankings of these three factors were different among catchments. The temporal variation characteristics of NH3-N in other catchments were significantly affected by RC, PSI, PTI, SHDI, and PGA factors , which was similar to the relevant studies  and middle PIA (about 0.06). Moreover, the temporal variation of NH3-N in Jintan catchment was significantly affected by PWA, PIA, and RC. The Jintan catchment was located in the upper reaches of the Huangshui River with low average concentration of NH3-N. It may due to its lowest population density and livestock density among all the catchments. Meanwhile, the land use type of this catchment was mainly grassland and woodland (>0.85), and the impervious ground area only accounted for a small proportion (<0.01). This is in accord with that agriculture land and urban land were negatively correlated with surface water quality, whereas forested land, water area, and grassland were positively correlated with water quality , and the larger value of the sum of PTI and PSI in Wanziqiao catchment (>0.9). The results were similar with  in the catchment. The temporal variation of TP in the Minheqiao catchment was obviously affected by PGA which maybe related with the lower mean value of PGA. The temporal change of NH3-N concentration. The temporal changes of NH3-N in 12 catchments out of 13 catchments were significantly influenced by PWA. Therefore, the spatial variability of NH3-N concentration was also affected by PWA to some extent. The natural attributes of the watershed  are closely related to the factor HI. According to Yu et al.  through the M–K test. The catchments in the upstream and downstream areas except Jintan and Taerqiao had fewer mutations of NH3-N and TP. The cluster analysis results of NH3-N and TP of all catchments were similar according to hierarchical agglomerative cluster analysis. The concentration of NH3-N and TP in the upstream and at the outlet of the basin has a higher possibility to meet the Class III standards for surface water bodies in GB3838-2002)  of all catchments were significantly affected by PWA. In the middle reaches of the Huangshui River basin, the temporal variations of NH3-N and TP in most catchments  were also significantly affected by PIA and PPI. The temporal variation characteristics of TP in other catchments were significantly affected by PCA and PGA factors. The spatial variation of NH3-N was mainly affected by PWA, HI, and PSI. The spatial variation of TP was significantly affected by PWA, PSI, and PTI. The conclusions of this study may provide a reference for the control and management of nitrogen and phosphorus pollution in similar upstream river basins.This study showed that although the Huangshui River Basin was located in the upper reaches of the Yellow River, the influences of rainfall-runoff relationship on spatiotemporal changes of NHSupplementary file1 (DOCX 16 KB)Supplementary file2 (DOCX 21 KB)Below is the link to the electronic supplementary material.


To explore the clinical effect of electroacupuncture in promoting the healing of the osteotomy area after high tibial osteotomy.  50 patients with knee osteoarthritis who underwent open wedge high tibial osteotomy (OWHTO) were selected and randomly divided into the observation group and control group. The control group got the common postoperative treatment, and the observation group was added electroacupuncture from the 3rd day after the operation on the basis of the control group. The electroacupuncture acupoints were selected SP10, ST34, ST32, EX-LE2, ST40,KI6, KI3, SP6, and ST41, once a day, and 14 days were a course of treatment. And then we contrasted the index of the Lane-Sandhu X-ray score, the skin incision healing time, the swelling subsided time, Visual Analogue Scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index Score (WOMAC), and Lysholm in different time. P < 0.05), and the time to achieve bone healing was about 2 weeks earlier than that of the control group. The skin healing and swelling were the subsided time in the osteotomy area. Both were better than the control group, and the difference was statistically significant (P < 0.05). The VAS score, WOMAC score, and Lysholm score of the two groups were significantly improved compared with preoperatively, and the difference was statistically significant (P < 0.05). The improvement of the observation group's VAS score, WOMAC score, and Lysholm score at 1 week, 4 weeks, and 8 weeks after the end of the treatment course was better than that of the control group, and the difference was statistically significant (P < 0.05).  The Lane-Sandhu X-ray score of the observation group was better than that of the control group at all time points ( Electroacupuncture can quicken the healing of bone tissue and surrounding soft tissues in the osteotomy area after high tibial osteotomy, and at the same time, it can help the relief of knee joint pain and improve knee joint function. Knee osteoarthritis (KOA) is a common cartilage degenerative disease which causes a high disability rate –4. It usAlthough the strong internal fixation of the osteotomy area is the guarantee for the success of the operation, the healed time of the osteotomy is also an important factor to finish the treatment of KOA. Nowadays, allograft bone is used to fill the area to speed up the healing of the fracture area. However, is there an effectively methods such as physical treatment to do it well? We used acupuncture to do it.In traditional Chinese medicine, acupuncture and moxibustion have been studied –12 to prIn the paper, electroacupuncture was used as an intervention treatment after tibial osteotomy to explore the effect of promoting the healing of the osteotomy area after high tibial osteotomy.P > 0.05).50 patients with MSCKOA were treated in the Department of Minimally Invasive Arthritis of The Third Affiliated Hospital of Beijing University of Chinese Medicine from January 2020 to October 2020. The patients were randomly divided into the observation group and observation group using the randomized envelope method, 25 cases in each group. The difference in baseline data between the two groups was not statistically significant (The inclusion criteria were as follows: (1) patients with MSCKOA, (2) receiving high tibial osteotomy, (3) age 40 to 70 years old, (4) consciously able to cooperate with treatment, and (5) signed informed consent book.The exclusion criteria were as follows: (1) knee osteoarthritis and destruction of lateral cartilage; (2) combined with knee gouty arthritis, rheumatoid arthritis, and other diseases; (3) combined with severe diabetes, hypertension and severe liver and kidney insufficiency, and other diseases; and (4) combined with chronic wasting diseases such as tuberculosis and tumors as shown by Routine rehabilitation program begins after surgery. On the first day after the surgery, the patient underwent an ankle pump exercise. The day after the operation, a knee flexion and extension exercise were performed. The third day after the operation, patient began to walk to the ground with the help of a walker. Two weeks after surgery, the patient walked with the assistance of double crutches. At 8–10 weeks after the surgery, the patient walked autonomously.On the basis of the treatment of the control group, electroacupuncture treatment was started on the 3rd day after operation. Acupoint selection is as follows: SP10, ST34, ST32, EX-LE2, ST40, KI6, KI3, SP6, and ST41. Acupuncture procedure is to get the patient's cooperation firstly and then mark the right acupuncture points; secondly, next step is to select 0.3 × 40 mm disposable acupuncture needles and then to puncture the needles that is 90° to the skin, and the depth is about 3 cm. After that, the pulse electroacupuncture device , and the time to achieve bone healing was about 2 weeks faster than that of the control group as shown by The bone healing in the osteotomy area of the observation group was better than that of the control group at all time points (P < 0.05) as shown by The skin healing time of the observation group and the time to reduce swelling were better than those of the control group, and the difference was statistically significant (P < 0.05); the VAS score of the observation group, WOMAC score, and Lysholm score was better than the control group at 1, 4, and 8 weeks after treatment (P < 0.05) as shown by 3At 1 week, 4 weeks, and 8 weeks after the treatment, the VAS score, WOMAC score, and Lysholm score of the observation group and the control group were significantly improved compared with preoperatively, and the difference was statistically significant P < 0.0; the VASWith the continuous advancement of the concept of enhanced recovery after surgery (ERAS) and the search for comprehensive treatment methods to promote the rapid healing of the osteotomy area, the recovery of knee joint function and relieve pain has attracted more and more attention from clinicians. In order to seek rapid healing of the osteotomy area after THO, we have made efforts to do it.We used strong internal fixation and bone grafting in the osteotomy area to promote the healing of the osteotomy as other surgeons do. Studies have shown that , 14 stroβ-catenin signal pathway protein, and regulating the level of cell growth factors [Acupuncture, as a traditional Chinese medicine therapy, has the functions of dredging the meridians, reconciling qi and blood, and promoting blood circulation . Study  has foun factors .Electrical stimulation therapy is a type of physical therapy, which has been widely used in clinical practice , 24. StuStudies have suggested that –31 the mβ (TGF-β), BMP2, and BMP4 in osteoblasts, thereby accelerating the process of fracture healing. Kuzyk et al. [Studies have also found that  electrick et al.  believedk et al. .In addition, the normal effect of the electromagnetic field can also speed up the fracture healing process. The bone structure integrity is heavily influenced by the material properties that are dependent on certain characteristics , 37. PreThis study has its limitations, such as one of the barriers to demonstrating rapid healing of the fracture area in surgical and medical image diagnosis is plate occlusion limiting the evaluation of more points in the fracture area and having an impact on the data.We found that electroacupuncture can significantly promote the healing of bone tissue and surrounding soft tissues in the osteotomy area after HTO, which also can speed up the relief of knee joint pain and improve knee joint function. As a clinically effective and simple and inexpensive treatment method, it is worthy to be clinical promotion.