Experimental and numerical analysis of a helical spring failure

Results of experimental and numerical analysis of a broken motor vehicle helical spring are presented in this paper. Location of the fracture is on a first active coil of the spring. Experimental part of the research employed optical microscopy that revealed fractured surface microstructure and allowed for detection of inclusions. Corroded fracture surface limited scanning electron microscopy examination (SEM). Nevertheless, corrosion pits on the edge of the spring wire which served as crack initiation points could be detected by SEM along with radiating ridges left by the fracture front that propagated to the opposite edge of the wire. Optical emission spectrometer with glow discharge source sample stimulation was used to determine material chemical composition that is adequate to spring steel 61SiCr7. Additionally, hardness test was performed and obtained value was used to derive maximum tensile strength of the steel. Experimentally collected data served as input for numerical analysis of helical spring. Finite element analysis of a helical spring model was performed. Stress distribution was determined and fatigue life of the undamaged helical spring predicted. Results were compared with those obtained analytical. Causes of failure are outlined assessing the results of the performed experimental and numerical analysis. Insufficient corrosion protection and excessive contact between the coils caused damage that developed from initial crack to final fracture of the spring. Results obtained by this research are valuable in understanding fracture behavior of helical spring mounted in suspension system of various motor vehicles. Given the presented results, further improvements of spring design can be made in order to reduce failures

Questing with Grandma: Building Closer Families Through Intergenerational Video Gaming

While small and large technological miracles have undoubtedly made our lives easier, they have potentially also made a significant part of our daily social routine obsolete. People live in the same space but rarely spend quality time together, interacting and bonding. One of the solutions to diminishing family relationships may lie in the technology itself—video games. Previous research having shown the sociability of video games, and in this study, we examined their potential in creating closer family relationships, especially among different generations. Participants (n = 183), mainly grandparents and grandchildren, were asked to play video games together over a period of six weeks. Participants completed a modified version of the self-other overlap, self-disclosure, and relationship closeness inventories before and after the treatment and responded to a series of open-ended questions post-treatment. Results indicate a significant increase in the inclusion of other in the self, as well as an increase in breadth and depth of self-disclosure for both younger and older adults. A comparison group (n = 88), comprising also mostly grandparents and grandchildren, was tasked with having conversations either face-to-face or in a mediated setting. The comparison group completed the same questionnaires, with results indicating a significantly smaller increase in the inclusion of other in the self and depth of self-disclosure, while breadth of self-disclosure experienced the same increase as in the gaming group. The findings suggest that video games can provide a platform for family communication, resulting in the rejuvenation and maintenance of intergenerational relationships. Gathering around a novel shared activity, both younger and older adults found new ways of connecting to their family members, whether through more frequent conversations, broader selection of topics, shared subjects, or pure entertainment

Generalizations of Steffensen's inequality via Fink's identity and related results II

We use Fink's identity to obtain new identities related to generalizations of Steffensen's inequality. Ostrowski-type inequalities related to these generalizations are also given. Using inequalities for the Cebysev functional we obtain bounds for these identities. Further, we use these identities to obtain new generalizations of Steffensen's inequality for n-convex functions. Finally, we use the segeneralizations to construct a linear functional that generates exponentially convex functions.We use Fink’s identity to obtain new identities related to generalizations of Steffensen’s inequality. Ostrowski-type inequalities related to these generalizations are also given. Using inequalities for the Cebysev functional we obtain bounds for these identities. Further, we use these identities to obtain new generalizations of Steffensen’s inequality for n-convex functions. Finally, we use these generalizations to construct a linear functional that aenerates exvonentiallv convex functions

On generalizations of Ostrowski inequality via Euler harmonic identities

Copyright © 2002 L. J. Dedić et al. This work is licensed under a Creative Commons License.Some generalizations of Ostrowski inequality are given, by using some Euler identities involving harmonic sequences of polynomials.L. J. Dedić, M. Matić, J. Pečarić, and A. Vukeli

Extending genome-wide association study (GWAS) results to test classic anthropological hypotheses: Human third molar agenesis and the ‘probable mutation effect’

A genome-wide association study (GWAS) identifies regions of the genome that likely affect the variable state of a phenotype of interest. These regions can then be studied with population genetic methods to make inferences about the evolutionary history of the trait. There are increasing opportunities to use GWAS results – even from clinically-motivated studies – for tests of classic anthropological hypotheses. One such example, presented here as a case study for this approach, involves tooth development variation related to dental crowding. Specifically, more than 10% of humans fail to develop one or more permanent third molars (M3 agenesis). M3 presence/absence variation within human populations has a significant genetic component (heritability estimate h2 = 0.47). The evolutionary significance of M3 agenesis has a long history of anthropological speculation. First, the modern frequency of M3 agenesis could reflect a relaxation of selection pressure to retain larger and more teeth following the origins of cooking and other food-softening behaviors (i.e., the genetic drift hypothesis, or classically, the “probable mutation effect”). Alternatively, commensurate with increasing hominin brain size and facial shortening, M3 agenesis may have conferred an adaptive fitness advantage if the risk of M3 impaction and potential health complications was reduced (i.e., the positive selection hypothesis). A recent GWAS identified 70 genetic loci that may play a role in human M3 presence/absence variation. To begin evaluating the contrasting evolutionary scenarios for M3 agenesis, we used the integrated haplotype score (iHS) statistic to test whether those 70 genetic regions are enriched for genomic signatures of recent positive selection. None of our findings are inconsistent with the null hypothesis of genetic drift to explain the high prevalence of human M3 agenesis. This result might suggest that M3 impaction rates for modern humans don’t accurately retrodict those of the pre-agricultural past. Alternatively, the absence of support for the positive selection hypothesis could reflect a lack of power; this analysis should be repeated following the completion of more comprehensive GWAS analyses for human M3 agenesis

An Innovative Photogrammetric System for 3D Digitization of Dental Models

This paper presents an innovative system for 3D reconstruction of a physical dental model. The innovative system is based on close-range photogrammetry and enables the projection of digital light texture on the objects surface. It is based on the application of mirrors that direct the digital light texture to the vertical surfaces of the physical model. In this way, high coverage of the object is achieved, and 3D reconstruction from one set of photographs is possible. 3D digitization, verification and comparison of the proposed methodology was performed on dental models that are characterized by extremely complex surfaces. It was performed by comparing the proposed approach with active stereovision, and the efficiency was evaluated in relation to the reference 3D model obtained by the structured light 3D scanner. The comparison of the results was performed on the basis of the mean deviation and standard deviation for the 3D model with combined teeth and for the 3D model with metal caps. The absolute mean deviations for the 3D model with combined teeth are 0.004-0.021 mm, with a standard deviation of 0.055-0.058 mm, and for the 3D model with metal caps absolute mean deviations are 0.015-0.033 mm, with a standard deviation of 0.095-0.113 mm, respectively. Absolute minimum values of mean deviation of 0.004 mm and standard deviations of 0.055 mm were obtained by 3D model with combined teeth,which was reconstructed by the proposed innovative approach. The obtained results indicate a higher accuracy of the innovative approach in relation to the use of a commercial 3D scanner that uses active stereovision principle

Multi-Criteria Evaluation of Design Complexity for Patient-Specific Bone Graft

With the rise of modern computer-aided technologies, their use in various different fields is becoming more and more apparent, but more profoundly in the field of medicine. The use of such technology enables the design of complex anatomical structures, often found in different areas of medicine. Maxillofacial and oral fields are becoming more and more popular with the use of such technologies, all leaning toward designing and fabrication of patient-specific implants from a biocompatible material. The level of complexity in personal graft design depends on criteria that describe the bone graft\u27s various properties. This research applies multi-criteria decision aiding in selection of patient-specific bone graft optimal design.Twelve different patient-specific bone-grafts designs have been evaluated by four decision makers who expressed their preferences with direct weighting and revised Simos procedure. Well known VIKOR method was used for multi-criteria decision aiding and the final results verified that the fully curved shape graft design is the least complex while the complex shape is the most demanding from the graft design perspective