Interobserver agreement was analyzed quantitatively using Cohen’s kappa and Krippendorf’s canonical concordance. Once data reliability was confirmed, lag sequential analysis using GSEQ5 software was performed to search for behavior patterns. The results show (a) different behavior patterns in the clarification, confrontation, and interpretation interventions by T1 and T2; and (b) different behavior patterns when T1 and T2 are considered as the focal subject (CT). Our study offers a new perspective on the impact of therapist interventions on participants in this kind of group.A child diagnosed with autism may have a negative psychological and behavioral impact on their siblings, whose participation in a group with children in the same situation is a preventive measure. Our group study was conducted by two therapists (T1 and T2) assigned to co-therapy (CT) work. Both therapists shared the theoretical bases and understanding of the group and the needs of the individual subjects, and complemented each other in terms of the direction of their interventions, given that shared impressions and continuous exchanges that integrate countertransference aspects are essential to successful co-therapy. The objectives of this study were as follows: (a) to detect patterns of clarification, confrontation, and interpretation interventions by T1 and T2 in the group; and (b) to detect patterns of clarification, confrontation and interpretation interventions considering T1 and T2 as the only focal subject of the CT. Design was mixed-methods based on systematic observation, for which we developed a qualitative  Family centered care in the autism spectrum disorder (ASD) field has attracted growing interest in the past decade in early care units . StudiesSupport groups for ASD-Sibs are key to the prevention and early detection of developmental and emotional disorders and also in terms of therapeutic strategies when difficulties appear . TraditiThe goal of our sibling support group is to offer a space where ASD-Sibs can freely express feelings and thoughts that may remain silenced in their everyday life or that may be perceived as contradictory. In the group the children explore the ambivalence of wanting to care for their sibling with special needs while also feeling guilt, anger and maybe even hate because of the special treatment their sibling receives from parents or at school. In this research, we wanted to study the spontaneous interaction between children and psychoanalytical therapists in a group. This required a flexible methodology adaptable to all behaviors and contexts. Mixed methods research offers an excellent combination of rigor and flexibility while allowing qualitative and quantitative techniques to be used within the same paradigm . Indeed,The conceptual framework for this study gave rise to four essential dimensions reflected in the observation instrument: ASD-Sib, turn-taking, group, and play. However, although all the small children in the support group shared the fact of having a sibling with ASD, there were few explicit interventions about the sibling. Group activities focused on plasticine models and wooden doll families. The plasticine figures made by the children were kept, which led to some becoming characters in the group .In this mixed-methods study we focus on the group and turn-taking dimensions of the therapists. From a psychoanalytical theory perspective, the group interventions of the therapists were divided into clarification (I1), confrontation (I2), and interpretation (I3). Clarification allows the therapist to emphasize essential elements in communications and perceptions, confrontation stimulates an interest in thinking, reflecting, and understanding behavior in relation to others, and interpretation is a hypothesis as to how a group participant may feel in the here and now of a session .In this study we were especially interested in observing how the two therapists related and interacted as co-therapists with each other and with the children.Co-therapy is very frequent in group work , with adThe Society of Group Psychology and Group Psychotherapy provides some arguments against psychotherapy groups conducted with a single therapist : (a) lonad hoc crisis intervention groups, are designed to offer emotional support to persons sharing a common problem or handicap  and four children aged 6–9 years old .The therapists are clinical psychologists with decades of experience with groups and with autism from a psychoanalytical perspective, and T1, who is older than T2, is also a psychoanalyst.Regarding the participating children, inclusion criteria were (a) age 6–9 years, (b) attendance at a standard school, and (c) having an ASD-Sib. Exclusion criteria were a diagnosis of pervasive developmental disorder (PDD) and attendance at psychotherapy. The therapists requested the permission of the parents to include their children in the group.The support group intervention was offered in Carrilet Education and Therapy Center , which specializes in the care of people with autism and their families. A sibling support group offers siblings a space where they can express their feelings and talk about issues in their relationship with the ADS-Sib without fear of hurting their parents. The group has both an educational and therapeutic focus. Autism is discussed with other children who are living a similar experience and with adults who are not members of the family. In words and through play, using plasticine, drawings, etc., the children express feelings, including fear, jealousy, anger, guilt, etc. The psychoanalytical therapists legitimize the ambivalence of the children’s feelings and help them understand and contain their emotions. Through conversation and play these children share feelings that could easily be silenced within the family and this helps them develop their own differentiated identity .The setting is a 1-h monthly meeting over 2 years. Before each session, the therapists send a reminder letter to the children’s home regarding the upcoming session. As material, the group uses two shared boxes, one with colored plasticine and the other with two foldable wooden figures of families , paper, colored crayons and pencils, rubbers, scissors, and a folder for drawings. The group’s activities focus mostly on the wooden dolls and the plasticine, and the plasticine figures made by the children are kept, with some becoming like persons in the group.At the family level, there are three meetings with parents, two in groups (one each before and after the main sessions) and an individual meeting .In accordance with the principles of the Declaration of Helsinki and the Ethical Code of the General Council of the Official College of Psychologists of Spain, the participants were informed that they were being filmed and parents signed a written informed consent, authorizing the participation of their children in this research. In relation to this study, on the first day of therapy, the reason for filming was explained to the subjects, along with the privacy and confidentiality conditions regarding session content. During the sessions, an observer (a psychologist in training) sat at a distance from the table where the group’s conversation was taking place and took notes.We used both observation and recording instruments.ad hoc observation instrument, following observational methodology canons  and on specific communications between therapists in relation to the emotional field of the children. To better exemplify the data analyzed below, Used as the recording instrument – to ensure maximum accuracy in data collection – was a video camera. To minimize the reactivity bias of the participants, the camera was positioned discreetly at a high viewing angle in the room.For the purposes of this study, we used recordings of six sessions from the first year with the group, but excluded three of these as not being fully audible.All sessions were video-recorded and subsequently transcribed in full. For the transcribed conversations between the children and the therapists, intervention turns were considered as the units of analysis, which were assigned the codes reflecting each dimension from the observation instrument.Data quality control was implemented to ensure that codes were correctly assigned. Three observers, previously trained using the approach described by Interobserver agreement was measured using Cohen’s kappa (k) , 1968, fSince our goal was to detect the existence of possible patterns of behavior in communicative interactions between the therapists and the children, we used intersessional sequential analysis, considered to be the most suitable data analysis technique for our purposes. The sequential analysis technique, developed by In our study we applied it to an analysis of concurrent and event-based quadrant II data. For our analysis, we used GSEQ v.5.1 software , in whicSince the study refers to communication processes, in an initial analysis, we separately considered the intervention turns of the therapists (T1 and T2) and of the grouped children (children) as the criterion and conditional behaviors. In a second analysis, we separately considered the criterion behavior of each therapist for the three forms of intervention, i.e., clarification , confrontation  and interpretation , and used the remaining codes as the conditional behaviors. In a third analysis, the co-therapy (CT) macro-category was taken as the criterion behavior for the three intervention forms  and the remaining codes were taken as the conditional behaviors.Using the binomial test and the Allison-Liker correction , residuaOur results are described in four sections: the first reflects turn-taking between the therapists and the children, while the remaining three reflect behavior patterns in relation to use of clarification, confrontation, and interpretation by each therapist separately (T1 and T2) and then together in co-therapy (CT). The analysis yielded ten distinct interactive behavior patterns between lags −1 and +1 responding to the question: what precedes and what succeeds therapeutic interventions?This first set of patterns with arrows, as shown in The second set of results, depicted in The use pattern of confrontation by T1 is this time much more complex. T1 confrontations follow T2 interpretation interventions (T2 I3) or involuntary behaviors, such as a cough or sneeze (T2 S2), and lead to clarification (I1) and confrontation (I2) interventions by T2. Regarding the children, we see that P1 stimulates T1 with brief interventions (B1) or follow-ups to the conversation (R3), P2 uses non-verbal resources  and verbal follow-ups to the conversation (R3), whereas P4 laughs. After the therapist has intervened, one of the children (P2) responds with non-verbal approval gestures (C3). The pattern also reflects the possibility of a response in the form of silence (S1) or of a comment regarding the game (M1).A posteriori, the interpretation generates brief expressions of disagreement or doubt (B2) in two of the children (P1 and P4) and interruptions (R2) by another child (P3).In relation to T1 interpretations, we also see that these follow interpretation interventions (I3) or laughs (S3) by T2 and, in turn, generate confrontation (I2) and interpretation (I3) interventions. As for the children, of note is humor (S3), short answers (R1) and comments regarding the game (M1) by P3 or involuntary reflexes, such as coughs or sneezes (S2) by P4 prior to the interpretation by T1. This third set of results, depicted in A priori of the confrontation intervention, the children (P1) briefly express agreement (B1) or doubt (B2), or respond non-verbally, defensively or with laughter (P2), or express their collaboration with the conversation (P3). The confrontational interventions by T2 generate short responses, positive answers or interruptions by P1, collaborative responses by P3, coughing or sneezing by P4 or silence in the whole group.As for confrontations (I2) by T2, these follow interpretation or laughter by T1. In relation to the children, the interpretations of T2 arise from brief expressions of gratitude or collaborative interventions by one child (P1), interruptions by another child (P4) and a non-verbal response by yet another child that stimulates laughter (P2). The interpretations of T2 stimulate interpretation (I3) or confrontation (I2) interventions, and also coughing or sneezing (S2) by T1 and laughter or other sounds reflecting humor in P2.This final set of results shows that when T1 and T2 are grouped together , communicative patterns are simplified somewhat, as shown in When the focal subject is CT, confrontation interventions arise after non-verbal responses by P2 or brief interventions expressing doubt or disagreement by two of the children , generating silence in the group.Finally, CT interpretation interventions arise after laughter or other sounds reflecting humor in one of the children or the therapists , or brief interventions expressing doubt or disagreement (B2) by one of the children (P3) or interruptions (by P4). These interpretations generate other brief interventions expressing doubt or disagreement , laughter  or other confrontation interventions by the therapists (CT).The intervention macro-category was designed as a resource and as a means of communication for psychoanalytical therapists T1 and T2. Unlike the other categories, interventions introduce new variables and new emotional experiences and help to develop new mental models. The changes seen in the children were the result of the attitudes and verbal interventions of the therapists, whether clarification (I1), confrontation (I2), or interpretation (I3).In the group, both therapists perform clarification after a brief communication (body or sound). As the therapists do not introduce feelings or ideas that the children have not expressed, these continue with a similar discourse in the form of a brief response, some sound or silence, followed by manipulation of the material. Given its simplicity and neutrality, this intervention generates confidence and helps improve connections between participants .Confrontation arises when thoughts are explored in depth . In the Confrontation helps children overcome their difficulties in expressing themselves. It also facilitates clarification and interpretation interventions . InterprThe therapist’s efforts focus on bringing the patient to an understanding of how to balance their inner fantasies with influences from the external world.The emergence of behavioral patterns of silence or of responses that reflect collaboration or dissatisfaction in the children in response to the interventions of the therapists is consistent with results obtained in previous research on the role of the psychoanalytic therapist in group sessions , 2005 anIn our sequential analysis it was found that T1 activates clarification and confrontation interventions by T2 but does not follow up on these interventions. The opposite happens in the interpretation interventions, where T1 does not activate T2 interventions, but does follow up. T2 activates all the three types of interventions by T1 and follows up on confrontation and interpretation interventions.Both therapists are women. T1 (the older therapist) seems to assume a greater role in containment, tolerance, and follow-up. The younger T2 seems to play a role that is more activating, verbal and available . As noteThe co-therapy (CT) analysis, more global than the analysis of individual relationships within the group, is characterized by more general aspects and issues reflecting the group as a whole. Along these lines, it can be observed that in the CT clarification intervention, P1 is hidden in previous analyses of this category, and, at the same time, the leadership of the other children is obscured. While the subsequent responses are similar to those of the therapists in isolation, there is no room for the silence represented above.In the confrontation, the two protagonists of separate interventions by the therapists stand out, but therapists conceal what the other children express and leave silence evident. In this case, if the game is not followed up, then this is the only possible response.Interpretation implies deeper intervention. The co-therapeutic result helps protect the children, since previous and subsequent follow-ups to the interpretation intervention take place between the therapists themselves . Thus, TThese functions do not follow a rule, nor are they permanent. The therapists adapt them to the requirements of the children and complement them in their interventions. Noteworthy is the sum of the attitudes of T1 and T2 in their co-therapeutic work. The fact that they share a theoretical framework and have experience of working together boosts their expertise in creating a facilitating space and in allowing interactions through dialog and play . HoweverOf course, there is no differentiation of functions other than those determined by the personal and professional characteristics of each therapist; however, alternating between different functions means they participate in the transference process.As observed in our results, analyzing the profiles of the therapeutic partners (co-therapists) draws attention to children and responses not observed in the individual analyses of each therapist’s interventions.The results also show that children speak little of their siblings with autism and participate in the sessions spontaneously with all kinds of interventions . The communicative richness evident in their behavior patterns reinforces the importance of offering this type of intervention for children with ASD-Sibs . The supIn addition to our sequential study of the interventions, we were able to observe parallels and interwoven relationships for the two therapists, who complement each other in the direction in which their interventions are intended. Basic aspects of co-therapy include shared impressions, continuous exchanges and integrated countertransference aspects . As noteA limitation of our study is the fact that results cannot be generalized, given the small size of our sample, both in terms of the number of sessions and the variety of attitudes. Rather, the group should be considered as a unique case analyzed in depth in terms of individual processes.ad hoc instrument and so evolve to new lines of research.The methodological characteristics used are highly appropriate for a study of group processes and human interactions . HoweverThis study was carried out in accordance with the recommendations of “Comitè d’Ètica de la Recerca (CER-URL)” with written informed consent from all subjects. All subjects gave written informed consent in accordance with the Declaration of Helsinki. The protocol was approved by the “Comitè d’Ètica de la Recerca (CER-URL).”MV developed the project and performed the sequential analysis. VC and XC contributed to the documenting and writing of the manuscript. EA-P supervised the project, designed the study, developed the methodology, and drafted the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


This study presents a set of experimental and numerical investigations to study the sensitivity of the piezoelectric-based smart interface device to structural damage in a bolted connection. The study aims to identify the proper geometric sizes of smart interfaces for damage detection tasks. First, the fundamentals of the damage monitoring technique via lead zirconate titanate (PZT) interface is briefly described for a bolted connection. Second, a lab-scaled girder connection is selected as the test structure for the experimental investigation. PZT interface prototypes with varying geometric sizes are designed for the test connection. Under the bolt-loosening inflicted in the connection, the impedance responses of the PZT interfaces are analyzed to understand the effect of geometric parameters on the damage sensitivity of the impedance responses. Subsequently, the bolt-loosening detection capabilities of the PZT interfaces are comparatively evaluated for identifying the proper geometric sizes of the devices. Finally, a finite element model of the PZT interface-bolted connection system is established for the numerical investigation. The damage sensitivity of the numerical impedance responses is compared with the experimental results for the verification. Civil structures are important facilities that support the economic and social activities of a nation. During their operation, these structures are often exposed to severe environmental and loading conditions. Extreme events, such as earthquakes and tsunamis, could result in inevitable structural deficiencies, causing seriously negative damage to social properties and loss of human life. Structural health monitoring (SHM) systems have been shown to have an important role in the integrity assessment of in-service civil structures. Basically, an SHM system implements a process of damage detection and characterization. The damage-induced sensitive features of the monitored structure are recorded via the SHM system, and the health status of the structure is assessed by analyzing these features.hot spots’ in steel structures. Bolted connections that are poorly maintained, in fact, are originators that could lead to serious failures of the load-bearing elements, or even the collapse of the entire structural system. Many studies have been carried out to develop efficient SHM tools for damage assessment of critical joints, including a vibration/ultrasonic-based method, a vision-based method, a guided wave-based method, and an impedance-based method [Critical bolted connections are concerned to be the ‘d method ,5,6,7,8.d method ,12,13,14d method ,18,19,20Typically, the impedance-based method uses a cheap, fast-response, non-intrusive, and linear piezoelectric ) patch to acquire the electromechanical (EM) impedance signatures from a target structure. Subsequently, damage-sensitive features, such as frequency shifts, amplitude changes, and statistical damage metrics, are extracted from the EM impedance signatures and used for damage detection. Traditionally, the PZT patch is permanently bonded to the host structure (directly bonded attachment) in the impedance-based SHM system. This often causes barriers in the desired modification of an existing sensor placement, and influences the repeatability of impedance signals ,22. MoreTo deal with the above-mentioned issues, piezoelectric-based portable devices have been developed and recently gained significant attention from SHM academy. Annamdas et al.  developeOwning to its advantages, the PZT interface technique has been applied to pre-determine the damage-sensitive frequency bands for damage monitoring of bolted connections ,30. AlthThis study presents a set of experimental and numerical investigations to study the influence of a PZT interface’s geometric parameters on the damage sensitivity of the EM impedance. First, the PZT interface-based impedance monitoring technique for bolted joints is briefly described. Second, a lab-scaled girder connection is selected as the host structure of the PZT interface for the experimental investigation. A few PZT interface prototypes, which are different in geometric size and boundary conditions, are designed for the tested girder connection. In the damage cases, the impedance responses of the different PZT interfaces are recorded. The damage sensitivity of the impedance responses is analyzed to determine the suitable sizes of the PZT sensor and the interface for damage detection. Finally, the impedance response of the PZT interface-bolted connection system is numerically simulated, using the finite element method to confirm the experimental observations. The damage sensitivity of the numerical impedance responses is analyzed for the different PZT interfaces and compared with the experimental results.The piezoelectric-based, smart interface technique has been proposed to pre-determine the sensitive frequency bands in the damage monitoring of a bolted connection . The intAs the bolts are loosened, the contact parameters (including contact stiffness and contact damping) at the interface between the connecting members are altered ,32. Thisim, ic, ik), and the other represents the host structure . The effect of bolt torque is simulated by the contact damping and contact stiffness in the connection . Under the voltage-induced harmonic elongation of the PZT, a harmonic excitation force if(ω) is generated and drives the interface-bolted connection system, making the interface couple with the bolted joint. The structural impedance of the entire system eqZ is computed as [j signifies the imaginary unit and ω is the angular frequency of the voltage excitation.puted as (1)Zeq=−aw, al, and at signify the length, width, and thickness of the PZT, respectively; η and δ denote the mechanical loss factor and the dielectric loss factor of the PZT material, respectively; and k, ω, and aZ are wave number, angular frequency, and mechanical impedance of the PZT material, respectively. Equations (1) and (2) theoretically demonstrate that the measured impedance signatures will contain the structural information of the whole system, including the structural properties and contact parameters of the connection. As the PZT interface’s structural parameters are assumed to be unchanged, alternation in the measured impedance signatures should be an indicator for the structural damage existing in the bolted connection. The total EM impedance of the PZT interface as coupled with the bolted connection is computed as ,33(2)Z(Z(ωi) and Z*(iω) are the pre- and post-damage EM impedances at the ith angular frequency, respectively, and N denotes the number of swept frequency points. When the structure is not damaged, the impedance signatures Z(ωi) and Z*(iω) are almost similar, leading to an ignorable value for the RMSD. In contrast, the RMSD value will become significant as the structure is damaged. For damage detection, a well-known statistical damage index, the so-called root-mean-square deviation (RMSD), is often used to quantify the damage-induced variations in impedance responses. The RMSD index is defined as follows :(3)RMSD and the width of the interface  were selected to vary. This is because the width of the interface deeply determines the local dynamic behaviors of the interface, while the size of the PZT is heavily associated with the piezoelectric driving force on the interface (the excitation capability) [Among various geometric parameters, the size of PZT  . As listB) of the interface was varied from 18 mm to 33 mm, with an interval of 5 mm (interfaces 1–4), while other geometric parameters of the PZT interface prototype remained unchanged, as shown in In Case 1, to examine the effect of the interface’s size, the width  of the square PZT was changed from 10 mm to 25 mm, with an interval of 5 mm (PZTs 1–4), while the other dimensional parameters of the PZT interface prototype were unchanged, as shown in In Case 2, to examine the effect of the PZT’s size, the edge , 60 Nm (62% torque change), and 0 Nm (100% torque change), sequentially. Next, bolt 1 was refastened to 160 Nm. Then, Bolt 2 was loosened to 110 Nm (31% torque change), 60 Nm (62% torque change), and 0 Nm (100% torque change), sequentially. The preload changes in the bolted connection are detailed in The impedance signatures in 10–100 kHz (901 swept points) obtained from four PZT interfaces under a healthy state are shown in The changes in frequencies of the two impedance peaks (Peak 1 and Peak 2) were plotted according to the increment of the interface’s width, as shown in The variations of the two impedance peaks (Peak 1 and Peak 2) under the bolt 2 loosening events are shown in The RMSD index of impedance signatures was computed under bolt 1 and bolt 2 loosening events, as shown in B/L) of the flexible section, as shown in B/L ratio of 1.1 provided the highest sensitivity of the impedance signatures to the bolt loosening. This means the plate-type flexible section of the interface could result in higher damage sensitivity than the beam-type flexible section.To estimate the suitable width of the interface, the RSMD index was computed by using the impedance signatures in 10–100 kHz. The RMSD index was plotted according to the variation of the width/length ratio  under bolt 2 loosening events are shown in The RMSD index of the EM impedance signatures was computed under bolt 1 and bolt 2 loosening events for PZTs 1–4. The RMSD values of the four PZT sensors were compared, as shown in To estimate the suitable size of the PZT, the RSMD index was computed by using the impedance signatures in the whole frequency range of 10–100 kHz. The RMSD index was plotted according to the ratio of surface areas between the PZT and the flexible section, as shown in From the previous experimental investigation, it was shown that when increasing the width of the interface, as well as the PZT size, the damage sensitivity of impedance responses was improved. In this section, a finite element (FE) model of the test model was established to numerically analyze the influence of the PZT interface’s geometry, and to verify the experimental results.xk, yk, and zk) and dashpot  system, as shown in The simulation of piezoelectric effects of the PZT interface requires electrical–mechanical coupled physics, which act simultaneously during the PZT excitation. The FE modeling of the PZT interface-bolted connection was carried out using COMSOL, which is commonly accepted by many researchers due to its electrical–mechanical simulation capabilities for modeling piezoelectric effects ,41,42,43xk = yk = 2.5 × 1011 N/m2/m and zk = 5.0 × 1011 N/m2/m for the healthy state. The effect of damping is represented by the damping loss factor η, shown in The material properties of the interface, the connection splice, and the adhesive layer are shown in Two simulation cases  following the experiment were investigated. The first simulation case (Case 1) was performed to numerically analyze the effect of the interface’s size on the sensitivity of impedance signatures. Accordingly, the four different interfaces (Interfaces 1–4) of the experiment were simulated, as shown in The second simulation case (Case 2) was conducted to numerically examine the effect of the PZT’s size on the sensitivity of the impedance signatures. The four different PZT sensors (PZTs 1–4) of the experiment were simulated, as shown in The numerical impedance in 10–100 kHz (901 swept points) obtained from the four interfaces under the intact case is shown in For each interface, two clear impedance peaks  can be observed in For Interfaces 1–4, the RMSD index of impedance signatures was computed as shown in B/L) ratio of the flexible section, as shown in B/L) ratio. To estimate the suitable width of the interface, the RSMD index was computed using the numerical impedance signatures in 10–100 kHz. The RMSD index was plotted versus the width/length (When the PZT size was increased from 10 mm × 10 mm (PZT 1) to 25 mm × 25 mm (PZT 4), the first peak frequency (Peak 1) slightly decreased, while the second one (Peak 2) slightly increased, as observed in For PZTs 1–4, the RMSD of the impedance signatures was quantified, as shown in As the PZT was increased from 10 mm × 10 mm (PZT 1) to 25 mm × 25 mm (PZT 4), the PZT driving force on the interface was also increased 6.25 times, computed based on reference . This inTo estimate the suitable size of the PZT sensor, the RSMD index was computed using the numerical impedance signatures in 10–55 kHz. The damage index was plotted according to the ratio of surface areas between the PZT and the flexible section, as shown in Conclusively, the results of the experimental model agreed well with the FE model. Therefore, the FE results verified the experimental results, and also demonstrated that the experimental model was set up with acceptable errors.(1)When the width of the interface increased, the flexible section of the interface changed from the beam-like structure to the plate-like structure. As a result, the resonant frequency of Peak 1 was slightly increased, while the resonant frequency of Peak 2 was significantly decreased. The longitudinal flexural motion of Peak 1 remained unchanged, while the lateral flexural motion of Peak 2 became more distinct, along with an increase of the interface’s width. The more distinct motions of the impedance peaks might cause improved sensitivity of the impedance signatures.(2)When the size of the PZT was increased, the impedance pattern shifted down, and the resonant frequency of Peak 1 slightly decreased, while the resonant frequency of Peak 2 slightly increased. The PZT driving force on the interface increased, along with an increase in the PZT size, making the flexural motions of the two peaks became more distinct. This increased piezoelectric driving force would make stronger excitations to the PZT interface that could result in higher damage sensitivity of the PZT interface.(3)To maximize its damage detection performance, the PZT interface should be designed to have the flexible section of a near-square shape, and the PZT patch covering 40% of the surface area of the flexible section. This study presents a set of experimental and numerical investigations to study the effect of the PZT interface’s geometric parameters on the damage sensitivity of the EM impedance. From the experimental and numerical investigations on a bolted connection, the following concluding remarks can be drawn, as follows:These obtained results above can be used for other bolted structures with similar configurations. For future study, a more complicated simulation should be implemented into the FE model to assess the stiffness change during by the PZT vibration. Also, the comprehensive analysis of the bonding effect on the impedance characteristics will be investigated.


When the total dosage of MK and SF admixture is 6%, these beneficial effects on workability, mechanical performance, and microstructure are more significant when SF and MK are applied together.This study explores the effects of metakaolin (MK) and silica fume (SF) on rheological behaviors and microstructure of self-compacting concrete (SCC). The rheology, slump flow, V-funnel, segregation degree (SA), and compressive strength of SCC are investigated. Microstructure characteristics, including hydration product and pore structure, are also studied. The results show that adding MK and SF instead of 4%, 6% and 8% fly ash (FA) reduces flowability of SCC; this is due to the fact that the specific surface area of MK and SF is larger than FA, and the total water demand increases as a result. However, the flowability increases when replacement ratio is 2%, as the small MK and SF particles will fill in the interstitial space of mixture and more free water is released. The fluidity, slump flow, and SA decrease linearly with the increase of yield stress. The total amount of SF and MK should be no more than 6% to meet the requirement of self-compacting. Adding MK or SF to SCC results in more hydration products, less Ca(OH) Self-compacting concrete (SCC) is usually characterized as a high-performance concrete that can pass through the gaps between steel bars and fill the formwork completely, only relying on its own gravity during pouring process ,2,3. It The rheological properties of paste have significant influence on the workability of SCC ,11,12,13On the other hand, supplementary cementitious material (SCM) has become an important component in the design of modern SCC . Fly ashThe preparation of high-performance SCC usually requires the addition of SF and MK admixtures, but the negative influence on the workability is also a deterrent. Hence, it is of great significance to propose a design criterion of high-performance SCC with consideration of SF and MK. In this study, the effect of SF and MK on the rheology and workability of high-performance SCC is investigated, and importance of the rheology on the workability of SCC is discussed. Then, the enhanced mechanical properties and microstructure of high-performance SCC containing SF and MK admixtures are evaluated.In this study, P·II 42.5 cement is used as binding material; fly ash (FA), silica fume (SF), and metakaolin (MK) are used as SCMs, their particle size distributions and chemical constituents are measured by laser particle size analyzer and X-ray fluorescence spectrometer, respectively, as shown in 3 are prepared, and demoulded after 24 h, then they are cured under standard conditions (25 ± 2 °C and relative humidity of 98%) until testing.The mix composition of paste and concrete mixtures are shown in The rheological property of paste is measured by a rotor viscometer. The testing instrument is R/S-SST soft-solid rheometer produced by Brookfield Company . The range of shear stress is 6–200 Pa and the shear rate is 0–1000 rpm. The data obtained by the rheometer can be transmitted to the master computer in real time and analyzed by Rheo V2.8 software. The rheological test procedure of rheometer is shown in m0 is the average weight of dried aggregate in concrete, and m1 and m2 are the weight of dried aggregates in the bottom and top layer of the segregation barrel, respectively.In order to evaluate the workability of SCC, slump flow test and V-funnel test were carried out. Segregation degree of coarse aggregate (SA) was also measured to evaluate the homogeneity of SCC. The tests process was referred to BS EN 12350:2010 . SA was A 3000 kN capacity machine was employed to measure the compressive strength of cube specimens according to ASTM C39 . The tesThe samples of paste were crushed into small grains after curing for 28 days, and soaked in alcohol to stop hydration. Then, the samples were dried at 60 °C for 24 h in an oven. Afterwards, the samples were grounded into powder and examined by XRD and thermal analysis.XRD analysis is carried out by D/max-RB type X-ray diffractometer  with scanning step of 0.02, the speed of 10 °/min, the current of 30 mA, and the voltage of 35 kV. Thermal analysis is carried out by Simultaneous Thermal Analyzer  under nitrogen atmosphere with gas flow of 30 mL/min, heating rate of 10 °C/min, and temperature range of 0~1000 °C.The small grains with several micrometers in diameter, crushed from 28-day concrete samples, were dried in an oven at 60 °C for 24 h before pore structure examination. The Micromeritics AutoPore-9500  was used for mercury intrusion porosimetry test (MIP) test, with the generating pressures of mercury intrusion porosimeter ranging from 3 Pa to 379 MPa.The effect of MK and SF on the fluidity of pastes is shown in R2 is 0.99939. It shows that the mathematic relationships between shear stress (τ) with shear rate (γ) of pastes can be determined from being fitted by Bingham model (τ = τ0 + η·γ), where slope of the curve, η, represents the viscosity and the vertical intercept; τ0, represents the yield stress of the paste [he paste .The viscosity and yield stress of different pastes are shown in R2, is 0.913. This demonstrates that the fluidity of paste is mainly affected by yield stress, which is consist with [Overall, it can be found that there is an obvious linear relationship between fluidity and yield stress, as shown in the ist with . Hence, The slump flow, V-flow, and SA values of SCC are shown in R2 is 0.948, and it shows a significant linear relationship between yield stress and slump flow, and the slump flow decreases with the increase of yield stress. This phenomenon illustrates that the yield stress of paste is the key factor to determining the slump of SCC. The reason is that when the driving force is greater than the yield stress of SCC, the flow continues; conversely, it stops [it stops .R2 = 0.864. A linear relationship can also be seen between yield stress and SA of SCC. The fitting curve indicates that the SA decreases with the increase of yield stress, and the segregation of aggregate will not occur (SA = 0) when the yield stress is greater than 34.6 Pa. This phenomenon is attributed to by the fact that yield stress is the precondition for the stability of aggregate in concrete, and segregation of aggregate happens only when the difference between gravity and buoyancy of the aggregate is greater than the yield stress [d stress . Neverthd stress . At thisd stress .The compressive strength of 3 and 28 days of SCC that contain different amounts of MK and SF are shown in the 2 (marked as CH), and CaCO3 (marked as C). The diffraction peak of AFt in PSF6 is lower than P0, which indicates that the employment of SF decreases the formation of AFt. This should be attributed to reduction in active aluminum phases and more significant absorption of aluminum by C-S-H gels in SF system. This is in accordance with a previous study [2 in PMK6 and PSF6 is inferior to P0, that is, the employment of MK and SF will reduce the content of Ca(OH)2. This is because MK and SF are more active than FA, and doping MK and SF can increase the content of high activity SiO2 and Al2O3 in SCC. Thus, more Ca(OH)2 produced by cement hydration is consumed by pozzolanic reaction and better performances, such as with mechanical properties, can result (as shown in The XRD patterns of different mixtures after curing for 28 days are presented in us study . It can DTG (derivative thermogravimetry) curves of specimens after curing for 28 days are presented in 3) in PMK6 and PSF6 is more remarkable than P0, which means that the addition of MK and SF induces much more abundant hydration products [2, indicating that the content of Ca(OH)2 in hydration products decreases, and is accordant with the XRD results  have a relatively lower coarse pore volume and smaller average diameter, which means that MK has better capacity to refine pores, and a similar phenomenon has been observed in previous research . HoweverHigh performance SCC with MK and SF addition are designed and characterized. The effect of MK and SF on the rheology, workability, compressive strength, and microstructure is investigated. The following conclusions can be drawn based on the results:The employment of MK and SF, instead of FA, increases the yield stress and viscosity of SCC, resulting in the reduction of fluidity, slump flow, and SA of SCC, which is due to that the utilized MK and SF in this study are finer and more active than FA, so more water is adsorbed by the powder itself and more flocculating products are produced. When the dosage of MK and SF is 2%, the small particles will fill in the interstitial space of mixtures, and more free water is released, leading to an increasement of fluidity. The total amount of SF and MK should be no more than 6% to meet the requirement of self-compacting.The fluidity, slump flow and SA decreases linearly with the increase of yield stress, based on rheology and workability results. This is owing to that yield stress is the key factor determining flow and aggregate settlement of concrete.The addition of 6% MK and 6% SF instead of FA increases the compressive strength of SCC by 15.1% and 17.0% at 28 days, respectively. On the one hand, the particle size of MK and SF are smaller than FA and can fill the voids between powers. On the other hand, MK and SF are more active, and more hydration products are generated by pozzolanic reaction and fill the voids in the hardened concrete. All of these effects will lead to an optimized pore structure and higher strength. The compressive strength decreases when the contents exceed 8%, and this is due to the excessive yield stress and viscosity, which make it difficult to discharge bubbles and form a compact structure.The property of SCC, including workability, mechanical performance, and microstructure, could be further improved when SF and MK are applied together. As the particle size of SF is smaller than MK, the accumulation of the powder becomes more compact by compounding MK and SF and, as a result, more free water is released and fluidity is increased. Moreover, the small MK particle can be the kernel of the early pozzolanic reaction and the formation of C-S-H gels, which can further accelerate the cement hydration and fill the pores. Hence, the mechanical performance and microstructure of SCC are improved.


Carbon fiber-reinforced composite has an excellent X-ray transmission rate as well as specific modulus and strength. The major components of medical devices, X-ray systems, and computed tomography (CT) equipment that require superior X-ray transmission performance also require structural performance for deformation. Therefore, medical components consist of a sandwich composite structure with carbon fiber composites applied as a face material. The X-ray transmission ratios of face material and foam material were measured according to thickness, and the relation equation for thickness and X-ray transmission rate was derived. The X-ray transmission rate for the sandwich composite structure consisting of face and core material was measured and the relationship between the X-ray transmission rate and the dimension for thickness of sandwich cradle was derived. Using the optimization process, the thicknesses of face and core materials for sandwich cradles were determined to minimize the cost of used materials. They also met the criteria that the deflection should not be more than 20 mm, and the X-ray transmission rate of the cradle should be equal to or greater than that of aluminum at 1.5 mm thickness. The sequence pattern of face material was proposed through structural analysis. The face material of the sandwich cradle was manufactured by a resin infusion and vacuum bagging method, followed by inserting the core between the cured faces. Next, the sandwich cradle assembly was completed and re-cured. The sandwich cradle met the criteria that the deflection at the end was 19.04 mm and the X-ray transmission was 78.7% greater than the X-ray transmission of 1.5 mm aluminum. Historically, composite materials were lightweight and of superior stiffness and strength. Composite materials were used in aircraft parts and defense components where such characteristics are required . In receIn this paper, the development process of the sandwich cradle for medical devices composed of carbon fiber reinforced plastics CFRP for the face material and foam material as the core was explored. The X-ray transmittance analysis was conducted experimentally to measure the transmission rate according to the thickness of the materials for face material and core material. The specifications were determined to meet the criteria for structural performance and to minimize the cost of applied material for the sandwich cradle. The face material was formed using an infusion and vacuum bagging method. Next, the foam core was inserted between the faces. Finally, the sandwich cradle was assembled and cured to ensure uniform X-ray transmission performance to the X-ray measurement area of the sandwich cradle.As the purpose of this study, the designing technology of a CFRP sandwich cradle with better X-ray transmission performance than the conventional metallic cradle and the fabricating process of a CFRP sandwich cradle for the uniform X-ray transmission are examined.Among the used fiber materials, CU 125NS  and MCU 125NS  were unidirectional (UD) prepreg 0.153 mm and 0.155 mm thick, respectively, as shown in The X-ray transmission equipment used in performance evaluation is a digital X-ray system made by Listem Inc . The configuration of the device for performance evaluation of X-ray transmission is shown in 0) without specimen applied for 0.1 s at 100 kV, 200 mA and the transmission value (I1) measured through each specimen was analyzed under the same conditions. The transmission rate is the ratio of I1/I0. In the case of the CU 125NS composite, the X-ray transmission rate decreased rapidly from 96.8% to 74.7% as thickness increased from 0.7 mm to 4.5 mm. Regardless of the type of molding technique and material, the transmission rate was approximately the same for the same thickness. Therefore, the relation between the transmission rate and thickness of face material is expressed in the following equation and predicted in The face materials were chosen from 6 types of UD materials manufactured through vacuum bagging, 2 types of UD + fabric prepreg through vacuum bagging, and 4 types of fabric materials made by infusion as shown in 3 and PVC (Polyvinyl chloride) foam with a density of 40 kg/m3. Thicknesses of 2, 11, 30, and 45 mm were considered for PMI Foam 31 IG and an evaluation was performed for PVC foam at thicknesses of 30 and 50 mm. For the PMI 31IG foam, as the thickness of core increased, the transmission rate decreased slightly as shown in 3 showed a transmission rate of 90.1% for a thickness of 30 mm when compared to the transmission rate of PMI 31IG with the same thickness. The relationship between the transmission rate and thickness of core material for PMI 31IG is explained in the following equation and predicted in The X-ray transmission rate of core materials was compared for different thicknesses and densities of foam. These were compared and analyzed for PMI foam 31IG with a density of 32 kg/mUsing the results for X-ray transmission performance of face materials and core materials, several cases of sandwich structure were constructed as shown in the Using the optimization process, the thicknesses of face and core materials for the sandwich cradle were determined to meet the deflection of end point for sandwich cradles were determined not more than 20 mm for the external 135 kg load and the X-ray transmission rate of sandwich cradle was equal to or greater than the X-ray transmission rate of 99.9% aluminum 1.5 mm thickness.2 and that of the core material is 1 US$/(1mm thick) per 1 m2.For optimization of the total thickness of the sandwich cradle, the total thickness  (5)Δ = ΔEquation (6) represents the first constraint, related to the total deflection and structural requirement.As the second constraint, the X-ray transmission rate must be greater than that of aluminum 1.5 mm thick (≅ 75.22%).The relationship between X-ray transmission rate and the thickness of core material is represented by Equation (9).The third constraint is the limitation of the total thickness (T) of the sandwich cradle. Total thickness of the sandwich cradle must not exceed 50 mm. Therefore, this constraint is expressed by Equation (10).The optimization solution used in this study has been applied with linear programming (LP) using Microsoft Excel . As shown in The structural performance criteria of the cradle that the end point deflection should not exceed 20 mm when the total load applied at a specific location is 135 kg is shown in In The cradle designed as a sandwich structure is composed of the top face, bottom face, and the foam core between faces. The first layers of upper and lower face were formed by infusion and the remaining layers were formed using prepreg. The upper and lower faces were molded as shown in A stiffness test of the cradle determined whether it satisfied the criteria, which is that the end deflection is 20 mm or less when a total load of 135 kg was applied. The loading bar connected to the loadcell and LVDT  were equipped and the applied load and deflection at the prescribed point were measured as shown in The X-ray transmission rate for the final product was measured as shown in Uniform X-ray transmission performance of the sandwich cradle whose first ply for the upper face and lower faces was laid by infusion and the remaining layers used prepreg is shown in This paper evaluated the X-ray transmission rate for face, core and sandwich structure to determine the thickness of the sandwich cradle by repeatedly calculating the thickness of face and core materials to satisfy the structural performance, X-ray transmission conditions, and to propose the manufacturing process for the sandwich cradle.The X-ray transmission performance of several face materials and some cases of core materials was measured. Measurements of the X-ray transmission rate of individual materials show that X-ray transmission performance was significantly affected by the density and thickness of the materials. The equations describing the relationship between thickness of face and core material and the X-ray transmission rate were derived through the measured value. X-ray transmission rates were measured for a sandwich structure combined with several cases of face and core, and the relation equation for X-ray transmission performance of sandwich structure was estimated.The 3D shape of the sandwich cradle of CT instruments was decided with consideration to the bolting conditions and interface with other parts. The thicknesses of face and core materials were optimized to minimize the cost of the materials on meeting the requirements that the deflection of sandwich cradle should be not more than 20 mm and the X-ray transmission rate of cradle should be equal to or greater than that of aluminum 1.5 mm thick.The first layers of upper and lower skin were formed by infusion and the remaining layers were used prepreg. After the upper and lower skins were molded, they were integrally bonded to the core and the sandwich cradle was formed. X-ray transmission performance of the final fabricated cradle was uniform over its entire surface. The X-ray transmission rate of the sandwich cradle is 78.8%, which is better than the 75.22% transmission rate of aluminum (1.5 mm thick). Additionally, it satisfied the criteria by finding the deflection at the end point of the cradle to be 19.49 mm.The improvement of the CT cradle increases the accuracy of the medical device rather than the improvement of the CT system and an improvement in X-ray transmission rates can have an effect on reducing the amount of X-ray applied to patients.


In areas where the concentration coefficient of rice or corn is greater than 1, the number of fire spots has a strong correlation with the urban pollution index. The correlation coefficient R between the number of burned fire spots and the pollutant concentration has a certain relationship with the urban distribution. Cities are aggregated in geospatial space with different R values.Northeast China is China’s primary grain production base. A large amount of crop straw is incinerated every spring and autumn, which greatly impacts air quality. To study the degree of influence of straw burning on urban pollutant concentrations, this study used The Moderate-Resolution Imaging Spectroradiometer/Terra Thermal Anomalies & Fire Daily L3 Global 1 km V006 (MOD14A1) and The Moderate-Resolution Imaging Spectroradiometer/Aqua Thermal Anomalies and Fire Daily L3 Global 1 km V006 (MYD14A1) data from 2015 to 2017 to extract fire spot data on arable land burning and to study the spatial distribution characteristics of straw burning on urban pollutant concentrations, temporal variation characteristics and impact thresholds. The results show that straw burning in Northeast China is concentrated in spring and autumn; the seasonal spatial distributions of PM The poland PM10 . In addiand PM10 . In receIn recent years, scholars have conducted studies on the weather caused by straw burning and have obtained a series of research results. Some scholars found that open-air biomass burning significantly impacts urban air quality by monitoring biomass produced by forests and farmland biomass burning in southeastern Queensland, Australia . Under hTraditional straw burning monitoring methods  have the disadvantages of low efficiency, low coverage, and high costs. Satellite remote sensing has enabled quick and extensive burning monitoring due to its timeliness, wide coverage and high resolution . The ModBased on MOD14A1 and MYD14A1 thermal anomaly product data, surface cover change data and pollutant monitoring site data in Northeast China, this study explores the distribution characteristics and relationship of straw burning with urban pollutant concentrations in time and space, conducts in-depth research on rice and corn concentrated planting areas, and performs a quantitative analysis of typical cities. The research results can be used to implement policies prohibiting straw burning by government departments at all levels, to establish a limited burning zone for straw burning zones, to generate scientific support for controlling straw burning, and to aid in monitoring and early warning of pollutant disasters. The factors that affect the serious pollution in the spring and autumn seasons in Northeast China have been determined to aid the development of straw harmless treatment technology at the source, to contribute to maintaining people’s health and to improve the ecological environment.The research objectives of this paper are as follows: (1) Explore the temporal and spatial distribution of straw burning fire spots and 41 city or regional pollutant concentrations in Northeast China. The relationship between straw burning and pollutant concentrations has been explored on temporal and spatial scales; (2) study the degree of influence of straw burning on pollutants in urban centres at different radius buffers and explore the maximum threshold value of straw burning on urban pollutant concentrations; (3) explore the relationship between rice- and corn-concentrated planting areas and fire spots and pollutants, and quantitatively study the extent of the impact of fire spots around typical cities in Northeast China on the city pollutants.The northeastern region includes Heilongjiang Province, Jilin Province, Liaoning Province and Hulunbeier, Wulanhaote, Tongliao and Chifeng cities in the eastern part of the Inner Mongolia Autonomous Region, located at 115°05′–135°02′E, 38°40′–53°34′N  Figure . The norThis study used MOD14A1 and MYD14A1 data for 2015–2017 with a spatial resolution of 1 km to extract straw-burned fire spots. The land cover type data were derived from the surface coverage change data of MCD12Q1  with a spatial resolution of 500 m, which was used to extract agricultural land in the study area. MOD14A1 and MYD14A1 products are based on the 3.9 μm and 11 μm bands of MODIS sensors on the Terra satellite and Aqua satellite, respectively. By setting the thresholds for fire spots and background temperature difference, the MODIS research team extracts the temperature anomaly area and fire spot data for day and night. The following table is the metadata description of the FireMask data set of MOD14A1 and MYD14A1 products. 2.5 and PM10 data. Pollutant data for 41 cities in the study area were selected from March 2015 to March 2017.The pollutant data were derived from the China Air Quality Online Monitoring and Analysis Platform . This reIn the MODIS thermal anomaly and fire product data, the values of “7, 8, 9” are fire spots; they were reassigned as 1, and the other values are non-fire spots, which were assigned a value of 0. The MOD14A1 and MYD14A1 data from the same period were combined, and the obtained data only contains the fire spot and non-fire spot data. The crop area in the MCD12Q1 land cover type data at 500-m resolution was used as a mask to extract the fire spots in the agricultural land to determine the number of fire spots of crop straw burning in the northeastern region for each day.The spring, summer, autumn and winter seasons in this study were divided according to “March, April, May”, “June, July, August”, “September, October, November”, and “December, January (the next year), February (the next year)”. According to the seasonal superposition of the fire spots in 2015 and 2016, fire spot spatial distribution maps of the four seasons of spring, summer, autumn and winter were obtained, and the annual data were superimposed to obtain the annual fire spot distribution map.2.5, PM10 and AQI, in 41 cities or regions in Northeast China were processed to obtain the AQI, PM2.5 and PM10 in the four seasons and the whole year for all cities in 2015 and 2016. The average value was interpolated in the Kriging space to obtain a spatial distribution map of the seasonal and annual air pollution concentrations in Northeast China.The daily monitoring data of pollutants, such as PMWe counted the number of fire spots in different buffer zones in different cities, summed the fire spots and urban pollutant data in the buffer every 8 days, and then conducted correlation analysis to obtain the correlation coefficient between the fire spots in different buffers and the pollutants in the central city. A two-dimensional map of the correlation coefficients between the fire spots in different buffers and the pollutants in the central city was obtained.2.5, PM10, AQI and the correlation coefficient of the number of burned fire spots in different buffer zones were evaluated, and cities with R values greater than 0.5 for two or more pollutants were selected; (3) considering that the provincial capital has a large population, industrial development and many vehicles, the provincial capitals were also considered typical cities. Finally, eight typical cities including Harbin, Changchun, Shenyang, Songyuan, Shuangyashan, Jiamusi, Qitaihe and Suihua were selected.To analyse the quantitative relationship between fire spots and pollutants, some typical cities were selected for analysis. The selection of typical cities considered three conditions: (1) From March 2015 to March 2017, the number of straw burning points in a 150-km radius was ranked as the top 16 (number of fire points greater than 1700); (2) PMAccording to the situation of farmers burning straw in the northeastern region, the straw obtained in the autumn harvest was burned in the autumn of that year and the spring of the following year. Here, a straw burning year is defined from September 1 of the current year to August 31 of the following year. According to our statistics, the total number of fire points in the burning years of 2013, 2014, 2015 and 2016 was 71,599, 122,137, 123,131 and 101,588, respectively. From 2013 to 2016, the graph of the number of fire spots in Northeast China  shows thThe fire spots in 2015 and 2016 were summed to obtain a fire spot distribution map for 2 years. We recorded the frequency of fire occurrences in 2 years and used nuclear density analysis to obtain a frequency map of the fire spots. The combination of the two figures resulted in The fire points in the spring, summer, autumn and winter seasons of 2015 and 2016 were summed to obtain the fire spot distribution maps in different seasons . We reco2.5 and PM10, from March 2015 to March 2017 were selected. 2.5, PM10 and AQI peaked in autumn and spring in 2015 and 2016. The 2015 and 2016 air quality parameters  show that the air pollution in most cities in 2015 was the most serious in early November, followed by December; the air pollution in most cities in 2016 was the most serious in December, followed by the first half of January in the following year. There are obvious time series differences between 2015 and 2016. Three parameters of pollutants, AQI, PMThe 41 cities or regions in Northeast China are coded in the order of north to south and west to east .2.5, PM10 and AQI  of a certain regional industry to the corresponding per capita output value (or output) of the country. If the concentration coefficient is greater than 1, that crop type is concentrated in the region and the degree of specialization is high . PreviouThe change in the number of fire spots in different buffers of a typical city  shows thThe 2015–2016 typical urban pollution index change chart  shows th2.5, PM10, and AQI and the number of fire spots in different radii of the typical cities, except for Shenyang, have a maximum correlation coefficient R of 0.7 or greater (p < 0.05), as shown in R in the different buffer radii of a typical city as a function of the radius at p < 0.05.Considering the combination of temporal and spatial factors, there are also peaks in the spring and autumn corresponding to the number of typical city straw fire spots. The pollutants PMR value with the radius, both Harbin and Suihua have a trend of increasing first and then decreasing, which has strong consistency. Changchun decreases first at 0–20 km and increases at 20 km–50 km. After 50 km, the correlation coefficient R value is basically unchanged at approximately 0.7. The correlation coefficient R of Shenyang shows a tendency to increase slowly with the radius. The R values of Songyuan and Jiamusi tend to be stable after a slow increase with the radius. Shuangyashan appears to increase first and then decrease, and finally, the R value remains basically unchanged. The correlation coefficient of Qitaihe has the largest R value, and the overall trend tends to remain unchanged after it first decreases. The correlation coefficient R values of Changchun, Songyuan, Jiamusi, Shuangyashan and Qitaihe all tend to remain basically unchanged as the radius becomes larger. Since some correlation coefficient R values do not satisfy the condition of p < 0.05, there is data missing in the fold line in Among these cities, from the change of the correlation coefficient 2.5, under the premise of p < 0.05, we fitted and analysed the curve of the correlation coefficient R with the radius to obtain the functional relationship between them. The function formula is shown in R and the radius of Songyuan is well fitted, and there is an obvious positively correlated relationship. The fitting curve of the R values and radii of Harbin and Suihua shows that R is positively correlated with a radius in the range of 80 km and negatively correlated with those more than 80 km . It is indicated that the more concentrated rice and corn are planted around the city in Northeast China, the greater the amount of straw, the more fire spots generated by rice or corn stover burning and the greater the impact of the generated pollutants on the urban pollutant concentration.In cities with a concentration coefficient of rice and corn greater than 1 in the northeastern region, the number of straw burning fire spots in the same buffer zone is higher than that in other cities. In cities with a rice or corn concentration coefficient greater than 1 in Northeast China, the correlation coefficient between the number of fire points and PMR values in Qitaihe, Shuangyashan, Harbin and Suihua is within 100 km. The radius of the buffer corresponding to the maximum R values in Changchun, Jiamusi and Songyuan is within 100–200 km. The impact radius of straw burning on urban pollutants varies in different cities. Varied policies can be adopted to control straw burning and pollutants according to different city characteristics.The quantitative analysis of the eight selected typical cities shows that the impact radius of straw burning varies in different cities. The radius of the buffer corresponding to the maximum One of the main causes of urban pollutant concentrations is the pollution source. In addition to burning straw in Northeast China, there are some effects from automobile exhaust, winter heating (October–April of the following year) and factories. The effects of other sources of pollution were not considered in this study. The capital cities in Northeast China are densely populated, and there are many heavy industries that produce a large amount of industrial exhaust and automobile exhaust.10 concentrations in the North Plain vary greatly with wind direction and humidity [Meteorological conditions are also an important factor in changing pollutant concentrations in urban cities. In windy weather, pollutants are quickly blown away by the wind, reducing pollutant concentrations. Wang et al. studied the effects of wheat straw burning on regional aerosols in northern China. The results show that the average AOD and PMhumidity .2.5, PM10 and AQI in 2015–2016 was higher than that in winter and peaked in spring and autumn. We speculate that straw burning promotes pollutant generation to some extent. We used 41 cities in Northeast China as the centres and made buffer zones with radii increasing every 10 km. The correlation coefficient R values of PM2.5, PM10 and AQI in the central cities and the number of fire spots in different buffers were calculated, respectively. According to the variation of the R values with the radii, 41 cities were clustered and analysed. We found that the cities were clustered and distributed in regions with different R values. Radius cluster analysis shows that adjacent radii are clustered into one class. In cities with a concentration factor of rice and corn planting greater than 1 in Northeast China, the correlation coefficient of the number of fire spots and pollutants is generally higher.The fire spots of straw burning in Northeast China are concentrated in spring and autumn. The fire spots in spring are mainly distributed in southwestern Heilongjiang Province. The fire spots in autumn are mainly distributed in northeastern Heilongjiang Province, northwestern and central Jilin Province, and central Liaoning Province. From 2013–2016, for the fire spots of straw burning in northeastern China in the northeastern region, the level of PMThe main innovations and contributions of this research are: A quantitative study on the temporal and spatial distribution characteristics of fire spots and pollutants in Northeast China that was carried out to provide a reference for studying the relationship between straw and pollutants. By clustering the relationship between pollutants and straw burning, the geospatial law of the effects of straw burning on pollutants has been revealed.


The aging process led to the formation of carbonates (Na2CO3 and CaCO3) and hydrocarbonates (NaHCO3). The amount and composition of nucleated species evolved with time, affecting the structure, properties, and bioactivity of the scaffolds. This study provides a first structured report of aging effects on the structure and chemico-physical properties of bioactive glass-based scaffolds, offering an insight about the importance of their storage and packaging.Bioactive glasses (BG) possess significant bone-bonding and osteogenic properties that support their use for bone defects repair in orthopaedic and dental procedures. Recent advancement enables the manufacturing of BG-based scaffolds providing structural support during bone regeneration. Despite the wide number of studies on BG and BG-based materials, little information on their aging mechanisms and shelf life is available in the literature. In this study, the evolution of chemical species on BG-based foams was investigated via accelerated tests in the presence of CO The treatment of traumatic and pathological conditions that do not lead to spontaneous bone regeneration represents a major clinical challenge . The useBioactive glasses and bioactive glass–ceramics have been widely studied as bone substitute materials . A rapid2 and water (formed by the condensation of air moisture on the glass surface) was reported to result in the formation of crystalline products, such as carbonates and hydrocarbonates.Despite the fact that there is a growing interest in bioactive glass and derived glass-ceramic structures  and thei2 was investigated, together with the impact of these species on the properties of bioactive glass-based foams. Physical and chemical characterizations were used to follow the kinetics of carbonate formation during the aging process. Morphological characterization and uniaxial compression test provided insights in the evolution of the scaffold structure and its mechanical properties with time. Finally, the impact of aging on scaffold bioactivity was assessed by immersion tests in simulated body fluid (SBF).In this study, the evolution of the chemical species on the surface of scaffolds aged in atmosphere containing humidity and CO® powder   and CaCO3 [JCPDS #98-002-0179] after aging . This approach does not take into consideration the density of the other species, i.e., CaCO3 (2.71 g cm−3), Na2CO3 (2.54 g cm−3), and NaHCO3 (2.20 g cm−3) [3 and comparable amounts of CaCO3 and Na2CO3, both having a theoretical density near the density of Bioglass. The density of the composite materials should thus be similar to the density of Bioglass. The general dependence of compressive strength on porosity is qualitatively reported in The reduction of porosity with aging affected the mechanical strength of the foams. The porosity of aged samples was evaluated using Equation (1), assuming the material had the same theoretical density of Bioglass (2.7 g cm g cm−3) . This apCompressive strength is used as a preliminary yet powerful mechanical characterization technique, since it offers an easy way to compare the mechanical properties of the obtained materials with those of cortical and trabecular bone and structures previously published . In all 2O is related to the exchange of Na+/H+ ions and to the absence of a buffer in the solution. Differences in pH behavior for aged specimens can be explained by the different quantity and nature of the carbonates formed on the surface of the foams, as supported by XRD and MIR analysis. The pH and solubility values of carbonate species are reported in 3, which has lower pH and solubility values than Na2CO3. On the contrary, higher pH values reached with samples aged 4 and 8 weeks can be explained considering a substitution of NaHCO3 with Na2CO3 . As observed by Cerruti et al. , the fash Na2CO3 a. Since 3 and Na2CO3, respectively, whose high solubility . This phenomenon preferentially occurs at the subgrain boundaries of the crystalline phases, leading to the degradation of non-sintered crystalline structures. Furthermore, ions exchange contributes to punctual defects increase, distorting the periodic structure of the crystalline phase and leading to the amorphization. Cations exchange, in particular Na+ and Ca2+, from glass and carbonates with protons from the solution resulted in a fast increase of pH  of immersion because of its low solubility  and hydrocarbonates (NaHCO3) in the presence of CO2 and humidity. The carbon measured in the aged specimens was strictly related to the formation of carbonates on the surface of the scaffolds. Moreover, the presence of carbonates increased the scaffolds’ mechanical compressive strength, reduced the pH after dissolution in the presence of NaHCO3, and had an influence on scaffolds’ bioactivity. The results indicate that the kinetics of formation of carbonate was slow enough to prevent the formation of a large amount of carbonates if the exposure was short at room temperature.This study presents the impact of aging on the structure and properties of bioactive glass-based scaffolds. Aging of bioactive glass-ceramic scaffolds leads to the formation of carbonates .The aging process could, nevertheless, be minimized by adequate packaging, thus preventing the reaction of glass with humidity and COFurther investigations could be performed to assess the overall effects on the in vitro and in vivo behavior of aged bioactive glass and determine the effects of nucleated species.


Background: The increasing significance of didactic aspects in medical education has also led to the development of special postgraduate programs. Completion rates represent an important outcome criterion for these programs of study. Up to today, detailed studies on what factors influence these completion rates have been lacking.Methods: Within the framework of outcomes research, a semi-structured online survey of students was conducted in the Master of Medical Education Germany program. Of the 90 items, 21 referred to the master's thesis that is required for graduation. Results: 157 out of 246 (63.8%) of students from classes 1-10 of the program (study period 2004-2014) participated in the survey. 109 participants had submitted a master's thesis, whereas 45 participants had not completed their studies by submitting a master's thesis. Influencing factors of successful completion were, among other things, little difficulty in choosing the topic, retention of the originally chosen topic, general support by the program administration in the modules and ensuring timely feedback from the advisor, and the provision of temporal, staff and financial resources by the home faculty. The failure to turn in the project report and a lengthy interruption of master thesi's work could be identified as critical parameters.Conclusion: Taking into account these results can contribute to increasing completion rates in medical education graduate programs. Systematic outcomes research leads, moreover, to quality assurance. Such studies should be conducted in a standardized manner in the future, in order to facilitate comparisons between medical education programs. The increased significance of didactic aspects in medical education in recent decades has also led to the development of special postgraduate programs , 2], , . In 2013Besides commonalities, there are also considerable differences between the various medical education programs with respect to organization, structure and core contents , 9], , , 11]. I. I11]. IThe study of the influencing factors was combined with two other thematic complexes in a joint project on outcomes research concerning the MME program. These other thematic complexes concerned career and development of the graduates, as well as professional and personal inhibiting factors. A common catalogue of questions was conceived for a semi-structured online survey. The questionnaire mainly consists of closed questions and has some free text elements. Already validated and established scales, like KarMed, the Graduate Survey Cooperation Project (KOAB) questionnaire of the International Centre for Higher Education Research (INCHER) Kassel , and the E-PROM project questionnaire , were partially drawn upon here , 16], , . In a multi-stage process, the questionnaire was discussed, modified and tested by six current students and graduates of the program. The final version of the questionnaire comprised 90 individual questions, of which 35 items dealt with sociodemographic and professional information, 21 items with the MME master's thesis, 11 items with professional and personal inhibiting factors, and 23 items with career and development opportunities of the MME graduates . 35 questions from the general part and 21 questions from the section on the master's thesis were used for the present study. The study was approved by the ethics committee of the Medical Faculty of Heidelberg University. 246 former students from classes 1-10 (2004/05 to 2013/14 from the Heidelberg University) were invited by e-mail to participate in the study; the study was conducted using the “LimeSurvey” survey tool and was open for a period of six weeks (18/04-29/05/2016). Data entry took place using pseudonyms and was monitored by the program's administrative office. In addition, with the consent of the participants, internal comparative data was gathered for cohorts 1-10 and used for purposes of validation. Statistical analysis of the collected data was conducted using the free R environment (Version 3.4.3). Besides a descriptive analysis, this comprises an assessment of potential influencing factors on the completion of studies in form of the submission of the master's thesis. Since we do not only have the information about ‘submitted / not submitted’ but also on the individual submission dates, our analysis accounts for these temporal aspects. Therefore, we apply time-to-event analysis using log-rank tests and Kaplan-Meier curves. Both are common techniques used to identify differences in events – in our case submission of the master thesis – over the observation period among groups , 19]. D. D19]. D157 of the 246 former students participated in the survey (response rate of 63.8%). At least 11 and at most 20 participants were represented from every class. 109 participants (70.8%) had submitted a master's thesis, whereas 45 participants (29.2%) had not completed their studies by submitting a master's thesis (no response for 3 participants). Submission of the master's thesis was equated with a successful completion of studies; only 4 of 246 participants were eliminated during the module phase. Figure 1 100 men (64.5%) and 55 women (35.5%) took part in the survey  and 36.2% with the with additional habilitation . In the case of 73.2%, advanced studies of the participants were in medicine (112 of 153), whereas dentists (n=17), at 11.1%, and other fields of study were less frequently represented. 79.5% of the participants were working in a clinical specialization (89 of 112). 75.7% of the participants had turned in the project work (115 of 152). The comparative data for the total cohorts 1-10 (n=246) displayed similar results. Of the 108 participants who completed the master's thesis, all but two participants had turned in all eight follow-up assignments. By contrast, of the 49 participants who did not complete the master's thesis, in 26 cases at least one follow-up assignment was missing. The large majority (66.4%) of the participants responded that the choice of topic derived from an idea of their own (95 of 143). With respect to the degree of difficulty, participants responded that in almost half of the cases (48.3%), the choice of topic was made easily or rather easily (72 of 149). For 32.8% of the participants, the choice of topic was difficult or rather difficult (n=49). More than half of the participants (63.7%) retained the originally chosen topic (86 of 135). 26 participants (19.2%) changed the topic once; 23 participants (17.0%) changed topic several times. With respect to the study design used, it was shown that in 72.1% of cases (98 of 136), the study design was conceived in the sense of a “clarification”  took place in specifically education-related journals , BMC Medical Education (n=4), European Journal of Dental Education (n=4), Medical Teacher (n=3), Advances in Health Sciences Education (n=1), Advances in Physiology Education (n=1), Medical Education (n=1), Patient Education and Counseling (n=1). In half of the cases (n=15), publication took place in a journal with an impact factor. The latter was between 0.96 and 3.18 and 0.81 on average (including publications with no impact factor). 20 participants (40%), on the other hand, published in a journal of their own specialization  or thematically-related interdisciplinary journals . In these cases, publication only took place in journals with an impact factor. This factor was between 0.14 and 5.12 and 1.93 on average.The time-to-event analysis (Table 2) showed that participants with a higher academic degree (doctorate or Habilitation) turned in a master’s thesis more frequently than participants with a first degree (master or diploma) or who have passed a state examination. A strong association was observed between turning in the project work and submitting the master's thesis. Further influence could be observed with respect to the issue of topic choice. Participants who had little difficulty in choosing a topic or were not in need for a change of topic had more frequently submitted their master’s thesis. With respect to study design, a “clarification” or “justification study” was more frequently represented among participants who completed their master's thesis as compared to a “descriptive study.”With respect to support for the master's thesis by the home faculty (see table 1 With respect to support for the master's thesis by the program administration (see table 1 With respect to further influencing factors (see table 1 The previous sections discussed the descriptive findings (see table 1 Presently, there are only a few studies on the outcome of postgraduate programs in medical education available , 24], , . An infoWith respect to the sociodemographic factors, no significant correlations to the submission of the master’s thesis could be observed. With respect to the individual factors, significant differences were found in the case of the highest academic degree obtained as well as turning in the project work. It should be kept in mind here that the project workwas supposed to be prepared during the intensive phase of the program. This suggests that the deficiencies indicate an excessive burden or insufficient structuring and self-organization of the participants , 14]. I. I14]. IWith respect to the external factors, serious deficiencies in the participant's perceived support by their home faculties is apparent in the descriptive treatment. Both in the provision of temporal resources and in the granting of staff, funding, materials and office space, the share of inadequate or even completely non-existent support was around 50% or higher. In this connection, the failure to grant temporal resources and support in the form of staff and funding also displayed a significant association to the submission of the master's thesis. The few existing publications on the outcome of medical education programs also mention insufficient time, due to a combination of work and study, and conditions at the home institutions as the most important reasons for not completing one's studies . With reIn considering the program-immanent characteristics, the demands, the organization and the conception of the program have to be taken into account. The program administration initially placed the emphasis on the academic freedom of participants and the scientific rigour of the program . In combWith respect to the support provided by the supervisor, it was striking that over two-thirds of the participants chose their supervisor via personal contacts, which showed a significant association to the submission of the master's thesis was also apparent. This suggests the already existing experience on the evaluation of adequate advising, which, given the high proportion of participants with doctorates or Habilitation, is entirely understandable. With respect to ensuring timely feedback and the support and competence of the supervisor, a high to very high proportion of the assessments were positive. The few critical assessments indicate, however, that in individual cases, there is still a discrepancy between the competence in the field, which is actually present, and the implementation of the advising. The cause is probably an excessive burden as a result of the simultaneous supervision of too many theses or as a result of other professional demands . It was With respect to the other factors, a long-term interruption of work on the master's thesis is clearly associated with non-submission of the thesis. This fact should be communicated to the students both in the classroom modules and in the advising. An excessive workload as a result of other professional projects, a change in profession and the start of parenthood could be identified as other hindering or delaying factors. In the present study, it was possible to identify a number of influencing factors for a successful completion of the Master of Medical Education Germany postgraduate program. These include a higher academic degree, little difficulty in choosing a topic, and retention of the originally chosen topic and study design. Choice of the supervisor via personal contacts and ensuring timely feedback by the supervisor proved to be further positive factors. It was also shown that the provision of temporal, staff and financial resources by the home faculty favours the completion of studies. The failure to turn in the project work and a lengthy interruption of master's work could be identified as critical parameters. The evaluation of the actual success of additional program-immanent support measures should be accompanied by further studies on the program outcome. These findings can contribute to increasing the graduation rates in medical education graduate programs. It is plausible that these results can also be applied to other post-graduate programs, since the issue of graduation rates is also reported for dentistry and other degree programs , 35], , . In ordeThe authors declare that they have no competing interests.


Journal of the American Academy of Child and Adolescent Psychiatry , an error appeared in the Results section of the Abstract. The sentence as published reads: “High levels of NC  and NS  were associated with increased odds of high depressive symptoms at 18 years in a dose-response fashion.” The sentence should instead read: “Low levels of NC  and high levels of NS  were associated with increased odds of high depressive symptoms at 18 years in a dose-response fashion.”In the research article “Trajectories of Neighborhood Cohesion in Childhood, and Psychotic and Depressive Symptoms at Age 13 and 18 Years” by Francesca Solmi, Ian Colman, Murray Weeks, Glyn Lewis, and James B. Kirkbride, published in the July 2017 issue of the