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For reduced mechanical stress, some chains with links made of metallic materials could be replaced by chains made of polymeric materials. A lower weight and a higher corrosion resistance would characterize such chains. From this point of view, research on the behavior of chain links made of polymeric materials under the action of tensile stresses can become important. Modeling by the finite element method highlighted some specific aspects of the behavior of a chain link subjected to tensile stresses. Later, we resorted to the manufacture by 3D printing of some chain links from four distinct polymeric materials, with the modification of the size of the chain link and, respectively, of the values of some of the input factors in the 3D printing process. The tensile strength of the chain links was determined using specialized equipment. The experimental results were processed mathematically to determine some empirical mathematical models that highlight the influence of the values of the input factors in the 3D printing process on the tensile strength of the samples in the form of chain links. It thus became possible to compare the results obtained for the four polymeric materials considered and identify the polymeric material that provides the highest tensile strength of the sample in the form of a chain link. The results of the experimental research showed that the highest mechanical resistance was obtained in the case of the links made of polyethylene terephthalate glycol (PETG). According to experimental results, when tested under identical conditions, PETG links can break for a force value of 40.9 N. In comparison, polylactic acid links will break for a force value of 4.70 N. Links printed in the horizontal position were almost 9-fold stronger than those printed in the vertical position. Under the same test conditions, according to the determined empirical mathematical models, PETG links printed in a horizontal position will break for a force of 300.8 N, while links printed in a vertical position will break for force values of 35.8 N.

Background People who smoke drugs (PWSD) are at high risk of both infectious disease and overdose. Harm reduction activities organized by their peers in the community can reduce risk by providing education, safer smoking supplies, and facilitate access to other services. Peers also provide a network of people who provide social support to PWSD which may reinforce harm reducing behaviors. We evaluated the numbers of supportive network members and the relationships between received support and participants’ harm-reducing activities. Methods Initial peer-researchers with past or current lived drug use experience were employed from communities in Abbotsford and Vancouver to interview ten friends from their social networks who use illegal drugs mainly through smoking. Contacts completed a questionnaire about people in their own harm reduction networks and their relationships with each other. We categorized social support into informational, emotional, and tangible aspects, and harm reduction into being trained in the use of, or carrying naloxone, assisting peers with overdoses, using brass screens to smoke, obtaining pipes from service organizations and being trained in CPR. Results Fifteen initial peer researchers interviewed 149 participants who provided information on up to 10 people who were friends or contacts and the relationships between them. People who smoked drugs in public were 1.46 (95% CI, 1.13-1.78) more likely to assist others with possible overdoses if they received tangible support; women who received tangible support were 1.24 (95% CI; 1.02-1.45) more likely to carry and be trained in the use of naloxone. There was no relationship between number of supportive network members and harm reduction behaviors. Conclusions In this pilot study, PWSD who received tangible support were more likely to assist peers in possible overdoses and be trained in the use of and/or carry naloxone, than those who did not receive tangible support. Future work on the social relationships of PWSD may prove valuable in the search for credible and effective interventions.

Rigorous design of flexible rockfall protection systems requires an adequate understanding of the system performance. In recent decades, finite element simulations have complemented experimental testing for economical and practical reasons. However, complex modelling techniques are required to capture the dynamic response of such systems, which leads to considerable computational costs. This paper presents a new approach called “hybrid method” to improve the computational efficiency of FE models with minimum effects on the results accuracy. The method is based on the idea to model the exact architecture of the wire net in the vicinity of impact (zone undergoing plastic deformation and failure) and to model the mesh with less computationally expensive elements far from the impact (zones undergoing elastic deformation). To this aim, a three-dimensional model of chain-link mesh was developed using commercial finite element code ABAQUS. The real architecture of the wires is modelled and discretised using three-dimensional beam elements. Homogenised shell surfaces are used to model the chain-link away from the impact zone. The model was calibrated and validated against published experimental data. The results prove that the proposed hybrid method leads to considerable reduction in computational costs of the finite element analysis while producing accurate results.

Rotary draw bending is one of the methods used for bending of thin wall tubes. In this process, the mandrel is positioned inside the tube, and the bend die, clamp die, pressure die, and wiper die surround the tube. The bending is conducted around the bend die. Conventional mandrels are mostly ball link type whose manufacture needs high precision and cost. Links of ball link mandrels are exposed to failure in necking areas due to particular form of the links. In this paper, a new mandrel type called “chain link mandrel” is presented, manufactured, and tested. The main difference of this mandrel with conventional mandrels is in the degrees of freedom of the mandrel’s ball segments. Finite element simulation of the bending process, using proposed mandrel and ball link mandrel, has been conducted in ABAQUS software, and some parameters, including required bending moment for tube bending, tube’s ovality, the variations in tube wall’s thickness, and spring back have been measured and compared between two types of mandrels. The clearance between external surface of the mandrel and internal wall of the tube and other influential process parameters has been set equal in both simulations. The simulation results showed that the amounts of thinning in outer wall of the bend, thickening in inner wall of the bend, tube’s ovality, and spring back are equal for both of mandrels. This fact proves the proposed mandrel’s effectiveness, despite its lower cost and simplicity compared to ball link mandrels. Experimental tests are also carried out, and the findings are compared with those obtained in the finite element simulations. There is good agreement between the simulation and experimental results. Practical operation of the proposed chain link mandrel shows that it has good performance for bending thin wall tubes. This mandrel is less expensive and stronger than the conventional ball link types, and the quality of the tubes bent by using this mandrel is acceptable.

Steel wire meshes are a key component of rockfall protection barriers. The efficiency in reproducing the structure response with numerical methods relies upon the specific modelling technique employed to capture the wire mesh behaviour. The fabric of some rockfall meshes, such as chain-links is quite complex, which leads to sophisticated and costly numerical models, if modelled accurately. This paper presents an efficient approach to model the response of steel wire meshes to rockfall impacts by using shell elements to develop an equivalent continuum model. An elastoplastic behaviour is prescribed to the shell elements to reproduce the results of a set of experimental data, carried out on mesh portions under various load paths and boundary conditions. The idea is that simple laboratory tests can be used to calibrate an effective numerical model of the steel wire mesh with a significantly lower computational cost if compared to other effective solutions. The model’s ability in yielding consistent results when implemented at the structure scale is then assessed, based on the data of full-scale impact tests on a three-span low-energy rockfall barrier. The method can be extended to other wire mesh types and can find convenient application on exploring the response of a rockfall barrier with a cost-effective tool.

Purpose The purpose of this study was to discuss the distribution characteristics and the anatomical angioarchitecture of cutaneous branches arising from the second dorsal metacarpal artery for the repair of small tissue defects in the hand or fingers using the second dorsal metacarpal artery chain-link flap. Methods Fifteen fresh human cadaveric hands were studied using three methods: latex perfusion for microanatomical analysis, denaturation of material and vinyl chloride mixed packing for cast specimens, and latex perfusion creating pellucid specimens. Cutaneous perforators with a diameter of 0.2 mm or greater were evaluated using statistical analysis. Cluster analysis was conducted to determine the overall distribution of the perforators. Results Two main clusters of perforators distributed at a relative distance of 40.8 and 68.6 % from the second web space edge to the midpoint of the second metacarpal bone as a unit. The Chi-square analysis revealed no significant differences in either the radial or ulnar side distribution of the cutaneous perforators from the second dorsal metacarpal artery ( p  = 0.779). Chain-links formed among adjacent perforators were parallel to the axis of the second metacarpal bone on the dorsum of the hand. Based on the anatomic characteristic, we designed the second dorsal metacarpal artery chain-link flap to recover the defect in the index finger. As a result, the patient was satisfied with the appearance and function. Conclusion This study indicates that there are two main clusters of arterioles in the distal second dorsal metacarpal artery that can be helpful for the second dorsal metacarpal artery pedicle cutaneous chain-link perforator flaps in the repair of defects in the fingers.

This paper studies the temperature field variation of the chain link as well as the stress and deformation distribution of the pin which works in hot forging and stamping production line with heat recovery function. The approach is to build the model of the chain link with Pro/Engineer and apply it to the simulation with Pro/Mechanica. To be specific, it is to stimulate the thermal conduction of the chain link and the stress state of the pin under high temperature with Pro/Mechanica-Thermal and Pro/Mechanica-Structure module, respectively. The results are the temperature filed nephogram of the chain link as well as the stress and deformation nephogram of the pin. The simulation shows that:1) the temperature reaches 420°C at the contacts of the outer and inner plates at 600s, 2) the maximum stress of the pin is 112Mpa at the ends where the pin meets the outer and inner plates,3) the pins max deformation is 0.0159mm at the middle of the pin. Comparing the simulation to the actual temperature at the contacts of the outer and inner plates,which is measured ten times in advance with average of 439°C ,the simulation is favorable. According to the results above, graphite lubrication should be chosen for the chain and the pin can work properly with deformation rate of 0.795. By this way of simulating with Pro/Mechanica, complicated calculations and repeated tests can be reduced largely, meanwhile, useful parameters and mathematical model can also be provided for manufacturing and process control.

In spite of the ongoing, periodic efforts by social justice advocates to ‘reform’ public education, public schools continue to grapple with issues pertinent to student success including the need for an increase in reading, writing and analytic abilities.

With this dramatic epigraph, Art Spiegelman begins My Father Bleeds History (1986), the first single-volume publication of the graphic novel Maus (serialised from 1980–91) that tells the story of the author’s life through the lens of the experiences of his Jewish parents in Poland in the Second World War. I quote this line in particular because it raises a central tenet of Nazi policy, the purported racial hierarchy that justified ‘The Final Solution’, and this is a fallacy that Spiegelman explores through the graphic aspect of his work: the Jewish people — Spiegelman’s parents included — are portrayed as mice, Germans are pictured as cats, and non-Jewish Poles are pigs, among other bestial representations of racial difference. I do not wish to focus extensively on the question of race in Maus, Spiegelman’s use of animal imagery, or the racial typing inherent in far-right European ideology of the early twentieth century; apart from the fact that these subjects lie beyond the bounds of this chapter, they are covered thoroughly by extensive criticism of Maus in the decade following its publication.2 Spiegelman’s foregrounding of the issue of race, through the graphical forms populating his work, though, shows how useful graphic novel literature can be in exploring relationships between those of different races.