On the Use of Homogeneous Polynomial Yield Functions in Sheet Metal Forming Analysis

Sheet metal forming techniques are a major class of stamping and manufacturing processes of numerous parts such as doors, hoods, and fenders in the automotive and related supplier industries. Due to series of rolling processes employed in the sheet production phase, automotive sheet metals, typically, exhibit a significant variation in the mechanical properties especially in strength and an accurate description of their so-called plastic anisotropy and deformation behaviors are essential in the stamping process and methods engineering studies. One key gradient of any engineering plasticity modeling is to use an anisotropic yield criterion to be employed in an industrial content. In literature, several orthotropic yield functions have been proposed for these objectives and usually contain complex and nonlinear formulations leading to several difficulties in obtaining positive and convex functions. In recent years, homogenous polynomial type yield functions have taken a special attention due to their simple, flexible, and generalizable structure. Furthermore, the calculation of their first and second derivatives are quite straightforward, and this provides an important advantage in the implementation of these models into a finite element (FE) software. Therefore, this study focuses on the plasticity descriptions of homogeneous second, fourth and sixth order polynomials and the FE implementation of these yield functions. Finally, their performance in FE simulation of sheet metal cup drawing processes are presented in detail

Evaluation of Agreement Between Sweep Visual Evoked Potential Testing and Subjective Visual Acuity

Objectives:The primary objective of this study was to evaluate the agreement of visual acuity (VA) obtained with the sweep visual evoked potential (sVEP) method with the VA obtained with the Snellen chart. The secondary objective was to examine the effect of age and gender on agreement.Materials and Methods:Best corrected VAs of subjects were recorded with the Snellen chart, and sVEP testing was performed according to the recommendations of the International Society for Clinical Electrophysiology of Vision (ISCEV). Snellen VAs and sVEP measurements were analyzed using logMAR conversion for statistical analysis. Agreement was evaluated with Bland-Altman analysis.Results:The study included 49 subjects with a mean age of 53.5±17.3 years (range: 19-75 years) and mean Snellen VA of 0.31±0.32 logMAR (range: 1.3-0.0 logMAR). In the Bland-Altman analysis, the mean differences between the VA and sVEP measurements (VA-sVEP) were significantly different and outside the limits of agreement (p=0.035). A significant proportional bias (p=0.0007) was found in the regression analysis performed between VA-sVEP and the mean VA. According to the Bland-Altman analysis of sex subgroups, there was a significant difference between VA and sVEP measurements in female subjects (p=0.006). The difference between VA and sVEP measurement increased significantly with older age (R2: 0.306, p<0.001, β: 0.05 [0.03, 0.08]).Conclusion:In conclusion, sVEP measurements and VAs did not show statistical agreement. Cranial anatomy and endocrine differences of the subjects may affect their sVEP measurements. The difference between the methods varies according to VA level. Directly using sVEP results instead of VA would not be appropriate

Çocuklarda ve Genç Erişkinlerde Subaksiller Sağ Torakotomi Yaklaşımıyla (Bikini İnsizyonu) Minimal İnvaziv Atriyal Septal Defekt Onarımı

Aim: The minimally invasive techniques in the treatment of congenital heart diseases have widely expanded recently both in terms of cosmetic results and patient comfort. In this report, we aimed to present our results of patients with the diagnosis of atrial septal defect and associated intracardiac pathologies who were operated through subaxillary mini thoracotomy.Materials and Methods: Seven patients who underwent subaxillary mini thoracotomy out of 53 patients with atrial septal defect that were operated with minimally invasive techniques in our clinic between 2009 and 2020 were identified. Six of the patients (85%) were girls and one was a boy (15%) and the mean age at operation was 8. 1 15.8 years.Results: Three patients had secundum atrial septal defect with a deficient septal rim; two patients had primum atrial septal defect, mitral cleft and mild mitral regurgitation and two patients had atrial septal defect, partial pulmonary venous return of the right pulmonary veins. All of the intracardiac pathologies were treated through right subaxillary mini thoracotomy. The mean cardiopulmonary bypass times and aortic cross clamp times were 71.5 19.2 and 44.4 22.1 minutes, respectively. Our patients were uneventfully discharged in 5.2 0.4 days. We did not encounter and morbidity or mortality in a mean follow up period of 4.4 3.1 years.Conclusion: The postoperative wound healing is faster and wound related complications are less frequently seen in patients undergoing cardiac surgery performed with minimally invasive techniques. The selection of subaxillary thoracotomy provides advantages both in terms of cosmetic aspects and breast development not being affected negatively

Generating landmark labels for short distance queries in a distributed setting

Distance queries are a fundamental part of many network analysis applications. Distances can be used to infer the closeness of two users in social networks, the relation between two websites in a web graph, or the importance of the interaction between two proteins or molecules. As a result, being able to answer these queries rapidly has many benefits to the area of network analysis as a whole. Pruned landmark labeling is a technique used to generate an index for a given graph that allows the shortest path queries to be completed in a fraction of the time when compared to a standard BFS (Breadth First Search) based algorithm. PSL (Parallel Shortest-distance Labeling) is a pruned landmark labeling algorithm that is designed to be implemented in a multithreaded environment and works particularly well on social networks. Unfortunately, even for a medium-size, 50 million vertex graph, the index size can be as large as 300GB. On the same graph, a single CPU core takes more than 12 days to generate the index. This thesis aims to implement PSL in a distributed environment by partitioning the input graph and distributing the partitions to the nodes. Our method can provide improvements in both the execution time and the memory consumption by distributing both across multiple nodes of a cluster. Furthermore, we develop techniques and conduct experiments that can help increase the performance of the PSL algorithm

MKE Sanayi ve Teknoloji Müzesi

Ankara : İhsan Doğramacı Bilkent Üniversitesi İktisadi, İdari ve Sosyal Bilimler Fakültesi, Tarih Bölümü, 2018.This work is a student project of the Department of History, Faculty of Economics, Administrative and Social Sciences, İhsan Doğramacı Bilkent University.The History of Turkey course (HIST200) is a requirement for all Bilkent undergraduates. It is designed to encourage students to work in groups on projects concerning any topic of their choice that relates to the history of Turkey. It is designed as an interactive course with an emphasis on research and the objective of investigating events, chronologically short historical periods, as well as historic representations. Students from all departments prepare and present final projects for examination by a committee, with 10 projects chosen to receive awards.Includes bibliographical references (page 16)by Fatma Özden Mercan

Direct Determination of Peroxide Explosives on Polycarbazole/Gold Nanoparticle-Modified Glassy Carbon Sensor Electrodes Imprinted for Molecular Recognition of TATP and HMTD

© 2022 American Chemical Society. All rights reserved.Since peroxide-based explosives (PBEs) lack reactive functional groups, they cannot be determined directly by most detection methods and are often detected indirectly by converting them to H2O2. However, H2O2 may originate from many sources, causing false positives in PBE detection. Here, we developed a novel electrochemical sensor for the direct sensitive and selective determination of PBEs such as triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD) using electrochemical modification of the glassy carbon (GC) electrode with PBE-memory polycarbazole (PCz) films decorated with gold nanoparticles (AuNPs) by cyclic voltammetry (CV). The prepared electrodes were named TATP-memory-GC/PCz/AuNPs (used for TATP determination) and HMTD-memory-GC/PCz/AuNPs (used for HMTD detection). The calibration lines of TATP and HMTD were found in the concentration range of 0.1-1.0 mg L-1 using the net current intensities of differential pulse voltammetry (DPV) versus analyte concentrations. The limit of detection (LOD) commonly found was 15 μg L-1 for TATP and HMTD. The sensor electrodes could separately determine intact TATP and HMTD in the presence of nitro-aromatic, nitramine, and nitrate ester energetic materials. The proposed electrochemical sensing method was not interfered by electroactive substances such as paracetamol, caffeine, acetylsalicylic acid, aspartame, d-glucose, and detergent (containing perborate and percarbonate) used as camouflage materials for PBEs. This is the first molecularly imprinted polymeric electrode for PBEs accomplishing such low LODs, and the DPV method was statistically validated in contaminated clay soil samples against the GC-MS method for TATP and a spectrophotometric method for HMTD using t- and F-tests