ACCELERATED LIFE TESTING OF A MILD HYBRID POWERTRAIN USING ARRHENIUS EQUATION

Habib Kaymaz 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.5

Electrification of city buses, which play a major role in public transportation, is imperative for efficient use of limited resources and reducing adverse effects of fossil fuels on the environment. One of the vital processes in electrification projects in the automotive industry is testing. The main target of testing is to achieve a reliable and reproducible test that simulates real-world driving conditions to disclosure any weakness of the product at the early stage of the life cycle. Other side targets of testing are to achieve the main target with low cost and environmentally friendly testing. In this study, results of research and development in accelerated life test stand for a mild hybrid system is described. The realized test stand serves to product reliability by enabling life tests with in excess of its normal service parameters real-world driving conditions such as revolution, electrical power, high ambient temperature, cooling effect, and rest-bus CAN simulation. By using temperature as a stress factor for the mild hybrid powertrain under test, life test duration was shortened 4.65 times according to the Arrhenius equation. Thanks to the realized test stand, the mild hybrid life test was achieved by decreasing time and cost.

Neuroprotective Effects of Quetiapine on Neuronal Apoptosis Following Experimental Transient Focal Cerebral Ischemia in Rats

Yilmaz, Muhammet Bahadir,Tonge, Mehmet,Emmez, Hakan,Kaymaz, Figen,Kaymaz, Memduh The Korean Neurosurgical Society 2013 Journal of Korean neurosurgical society Vol.54 No.1

Objective : This study was undertaken in the belief that the atypical antipsychotic drug quetiapine could prevent apoptosis in the penumbra region following ischemia, taking into account findings that show 5-hydroxytryptamine-2 receptor blockers can prevent apoptosis. Methods : We created 5 groups, each containing 6 animals. Nothing was done on the K-I group used for comparisons with the other groups to make sure adequate ischemia had been achieved. The K-II group was sacrificed on the 1st day after transient focal cerebral ischemia and the K-III group on the 3rd day. The D-I group was administered quetiapine following ischemia and sacrificed on the 1st day while the D-II group was administered quetiapine every day following the ischemia and sacrificed on the 3rd day. The samples were stained with the immunochemical TUNEL method and the number of apoptotic cells were counted. Results : There was a significant difference between the first and third day control groups (K-II/K-III : p=0.004) and this indicates that apoptotic cell death increases with time. This increase was not encountered in the drug groups (D-I/D-II : p=1.00). Statistical analysis of immunohistochemical data revealed that quetiapine decreased the apoptotic cell death that normally increased with time. Conclusion : Quetiapine is already in clinical use and is a safe drug, in contrast to many substances that are used to prevent ischemia and are not normally used clinically. Our results and the literature data indicate that quetiapine could help both as a neuronal protector and to resolve neuropsychiatric problems caused by the ischemia in cerebral ischemia cases.

Determining the Optimum Process Parameters of Selective Laser Melting via Particle Swarm Optimization Based on the Response Surface Method

Fahri Murat,İrfan Kaymaz,Abdullah Tahir Şensoy,İsmail H. Korkmaz 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.1

Manufacturing high-quality and desired products from additive manufacturing necessitate careful adjustment of the processparameters. Various methods can be utilised to determine optimum process parameters, such as the Taguchi method, Designof Experiments (DoE). Rather than evaluating limited information obtained from statistical analysis of the experiments, optimisationmethods can help find the best possible combination for the process parameters. Therefore, an optimisation approachbased on Particle Swarm Optimization (PSO) was utilised to find the optimum process parameters. The most importantprocess parameters of Selective Laser Melting (SLM) such as laser power, layer thickness, scan speed, and build orientationwere selected as input parameters, and their effects on the tensile properties of the manufactured part were investigated to findout the optimal operating conditions for the SLM process. Since there is not any explicit mathematical expression relatingthese process parameters to the tensile strength, the Response Surface Method (RSM) was used to obtain a meta-model sothat it can be used as an objective function in the optimisation formulation. This approach enabled us to predict the optimumprocess parameters to maximise the tensile strength without conducting an excessive number of experiments. Moreover, themathematical model can also predict tensile strength corresponding to the parameter values that are not tested according tothe DoE chosen for such studies. Furthermore, it was also shown that the PSO outperforms the Genetic Algorithm (GA),which is widely employed to find out the optimum process parameters, in terms of less number of iteration.

The Comparison of Clinical Variables in Two Classifications: GOLD 2017 Combined Assessment and Spirometric Stage of Chronic Obstructive Pulmonary Disease

Candemir, Ipek,Ergun, Pinar,Kaymaz, Dicle,Tasdemir, Filiz,Egesel, Nurcan The Korean Academy of Tuberculosis and Respiratory 2018 Tuberculosis and Respiratory Diseases Vol.81 No.4

Background: There are limited number of studies that investigate clinical variables instead of chronic obstructive lung disease (COPD) management according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2017 classification. The aim of the study was to investigate whether there was a difference between GOLD 2017 classification and spirometric stage in clinical variables in patients with COPD. The data of 427 male patients with stable COPD were investigated retrospectively. Methods: Patients were allocated into combined assessment of GOLD 2017 and spirometric stage. Age, amount of smoking, pulmonary function, modified Medical Research Council (mMRC), incremental shuttle walk test (ISWT), Hospital Anxiety-Depression Scale (HADS), St. George's Respiratory Questionnaire (SGRQ), body mass index (BMI), and fat free mass index (FFMI) were recorded. Results: Seventy-three (17%) patients were in group A, 103 (24%) constituted group B, 38 (9%) were included in group C, and 213 (50%) comprised group D according to the combined assessment of GOLD 2017. Twenty-three patients (5%) were in stage 1, 95 (22%) were in stage 2, 149 (35%) were in stage 3, and 160 (38%) were in stage 4 according to spirometric stage. According to GOLD 2017, age, amount of smoking, mMRC, BMI, FFMI, SGRQ, HADS, forced vital capacity, forced expiratory volume in 1 second ($FEV_1$), and ISWT were significantly different between groups. Ages, amount of smoking, FFMI, BMI, HADS of group A were different from B and D. Smiliar values of $FEV_1$ were found in A-C and B-D. A and C had smiliar ISWT. According to spirometric stage, BMI, FFMI of stage 4 were statistically different. mMRC, ISWT, and SGRQ of stages 3 and 4 were different from other stages, amongst themselves. $FEV_1$ was correlated with mMRC, SGRQ, anxiety scores, BMI, FFMI, and ISWT. Conclusion: This study showed that the GOLD ABCD classification might not represent the severity of COPD sufficiently well in terms of lung function or exercise capacity. The combination of both spirometric stage and combined assessment of GOLD 2017 is important, especially for estimating clinical variables.

An improved response surface method for reliability analysis of structures

Basaga, Hasan Basri,Bayraktar, Alemdar,Kaymaz, Irfan Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.2

This paper presents an algorithm for structural reliability with the response surface method. For this aim, an approach with three stages is proposed named as improved response surface method. In the algorithm, firstly, a quadratic approximate function is formed and design point is determined with First Order Reliability Method. Secondly, a point close to the exact limit state function is searched using the design point. Lastly, vector projected method is used to generate the sample points and Second Order Reliability Method is performed to obtain reliability index and probability of failure. Five numerical examples are selected to illustrate the proposed algorithm. The limit state functions of three examples (cantilever beam, highly nonlinear limit state function and dynamic response of an oscillator) are defined explicitly and the others (frame and truss structures) are defined implicitly. ANSYS finite element program is utilized to obtain the response of the structures which are needed in the reliability analysis of implicit limit state functions. The results (reliability index, probability of failure and limit state function evaluations) obtained from the improved response surface are compared with those of Monte Carlo Simulation, First Order Reliability Method, Second Order Reliability Method and Classical Response Surface Method. According to the results, proposed algorithm gives better results for both reliability index and limit state function evaluations.

The Comparison of Clinical Variables in Two Classifications: GOLD 2017 Combined Assessment and Spirometric Stage of Chronic Obstructive Pulmonary Disease

( Ipek Candemir ),( Pinar Ergun ),( Dicle Kaymaz ),( Filiz Tasdemir ),( Nurcan Egesel ) 대한결핵 및 호흡기학회 2018 Tuberculosis and Respiratory Diseases Vol.81 No.4

Background: There are limited number of studies that investigate clinical variables instead of chronic obstructive lung disease (COPD) management according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2017 classification. The aim of the study was to investigate whether there was a difference between GOLD 2017 classification and spirometric stage in clinical variables in patients with COPD. The data of 427 male patients with stable COPD were investigated retrospectively. Methods: Patients were allocated into combined assessment of GOLD 2017 and spirometric stage. Age, amount of smoking, pulmonary function, modified Medical Research Council (mMRC), incremental shuttle walk test (ISWT), Hospital Anxiety-Depression Scale (HADS), St. George’s Respiratory Questionnaire (SGRQ), body mass index (BMI), and fat free mass index (FFMI) were recorded. Results: Seventy-three (17%) patients were in group A, 103 (24%) constituted group B, 38 (9%) were included in group C, and 213 (50%) comprised group D according to the combined assessment of GOLD 2017. Twenty-three patients (5%) were in stage 1, 95 (22%) were in stage 2, 149 (35%) were in stage 3, and 160 (38%) were in stage 4 according to spirometric stage. According to GOLD 2017, age, amount of smoking, mMRC, BMI, FFMI, SGRQ, HADS, forced vital capacity, forced expiratory volume in 1 second (FEV1), and ISWT were significantly different between groups. Ages, amount of smoking, FFMI, BMI, HADS of group A were different from B and D. Smiliar values of FEV1 were found in A- C and B-D. A and C had smiliar ISWT. According to spirometric stage, BMI, FFMI of stage 4 were statistically different. mMRC, ISWT, and SGRQ of stages 3 and 4 were different from other stages, amongst themselves. FEV1 was correlated with mMRC, SGRQ, anxiety scores, BMI, FFMI, and ISWT. Conclusion: This study showed that the GOLD ABCD classification might not represent the severity of COPD sufficiently well in terms of lung function or exercise capacity. The combination of both spirometric stage and combined assessment of GOLD 2017 is important, especially for estimating clinical variables.

Investigation of Blood Betatrophin Levels in Obese Children with Non-Alcoholic Fatty Liver Disease

Fatih Battal,Hakan Türkön,Nilüfer Aylanç,Hakan Aylanç,Şule Yıldırım,Nazan Kaymaz,Sema Uysal 대한소아소화기영양학회 2018 Pediatric gastroenterology, hepatology & nutrition Vol.21 No.2

Purpose: The prevalence of obesity has significantly increased among children and adolescents worldwide and is becoming an important health care problem in parallel with the increased prevalence of obesity pediatric non-alco-holic fatty liver disease. Betatrophin is a newly define hormone that is commonly secreted by liver and plays role in glucose tolerance. This study aimed to investigate the relationship between serum betatrophin levels and non-alco-holic fatty liver disease in obese children.Methods: The study included 40 obese children with a body mass index (BMI) above 95th centile, and 35 non-obese subjects with a BMI 3-85th centile, whose age and gender were similar to those of the patient group. For the evaluation of metabolic parameters fasting serum glucose, insulin, alanine aminotransferase, aspartate aminotransferase, lipid profile and serum betatrophin levels were measured. Total cholesterol: high-density lipoprotein cholesterol and low-density lipoprotein cholesterol: high-density lipoprotein cholesterol ratios were calculated as “atherogenicindices.”Results: Serum betatrophin levels of the obese subjects were similar to that of non-obese subjects (p=0.90). Betatrophin levels were not correlated with the metabolic parameters.Conclusion: In the present study, levels of betatrophin are not different between obese and insulin resistant children and non-obese subjects, and they are not correlated with atherogenic indices. To elucidate the exact role of beta-trophin in obesity, further studies are required to identify the betatrophin receptor and/or other possible cofactors.

Usefulness of End-to-Side Bridging Anastomosis of Sural Nerve to Tibial Nerve : An Experimental Research

Civi, Soner,Durdag, Emre,Aytar, Murat Hamit,Kardes, Ozgur,Kaymaz, Figen,Aykol, Sukru The Korean Neurosurgical Society 2017 Journal of Korean neurosurgical society Vol.60 No.4

Objective : Repair of sensorial nerve defect is an important issue on peripheric nerve surgery. The aim of the present study was to determine the effects of sensory-motor nerve bridging on the denervated dermatomal area, in rats with sensory nerve defects, using a neural cell adhesion molecule (NCAM). Methods : We compared the efficacy of end-to-side (ETS) coaptation of the tibial nerve for sural nerve defect repair, in 32 Sprague-Dawley rats. Rats were assigned to 1 of 4 groups : group A was the sham operated group, group B rats had sural nerves sectioned and buried in neighboring muscles, group C experienced nerve sectioning and end-to-end (ETE) anastomosis, and group D had sural nerves sectioned and ETS anastomosis was performed using atibial nerve bridge. Neurological evaluation included the skin pinch test and histological evaluation was performed by assessing NCAM expression in nerve terminals. Results : Rats in the denervated group yielded negative results for the skin pinch tests, while animals in the surgical intervention groups (group C and D) demonstrated positive results. As predicted, there were no positively stained skin specimens in the denervated group (group B); however, the surgery groups demonstrated significant staining. NCAM expression was also significantly higher in the surgery groups. However, the mean NCAM values were not significantly different between group C and group D. Conclusion : Previous research indicates that ETE nerve repair is the gold standard for peripheral nerve defect repair. However, ETS repair is an effective alternative method in cases of sensorial nerve defect when ETE repair is not possible.

Investigation of Blood Betatrophin Levels in Obese Children with Non-Alcoholic Fatty Liver Disease

Battal, Fatih,Turkon, Hakan,Aylanc, Nilufer,Aylanc, Hakan,Yildirim, Sule,Kaymaz, Nazan,Uysal, Sema The Korean Society of Pediatric Gastroenterology 2018 Pediatric gastroenterology, hepatology & nutrition Vol.21 No.2

Purpose: The prevalence of obesity has significantly increased among children and adolescents worldwide and is becoming an important health care problem in parallel with the increased prevalence of obesity pediatric non-alcoholic fatty liver disease. Betatrophin is a newly define hormone that is commonly secreted by liver and plays role in glucose tolerance. This study aimed to investigate the relationship between serum betatrophin levels and non-alcoholic fatty liver disease in obese children. Methods: The study included 40 obese children with a body mass index (BMI) above 95th centile, and 35 non-obese subjects with a BMI 3-85th centile, whose age and gender were similar to those of the patient group. For the evaluation of metabolic parameters fasting serum glucose, insulin, alanine aminotransferase, aspartate aminotransferase, lipid profile and serum betatrophin levels were measured. Total cholesterol: high-density lipoprotein cholesterol and low-density lipoprotein cholesterol: high-density lipoprotein cholesterol ratios were calculated as "atherogenic indices." Results: Serum betatrophin levels of the obese subjects were similar to that of non-obese subjects (p=0.90). Betatrophin levels were not correlated with the metabolic parameters. Conclusion: In the present study, levels of betatrophin are not different between obese and insulin resistant children and non-obese subjects, and they are not correlated with atherogenic indices. To elucidate the exact role of betatrophin in obesity, further studies are required to identify the betatrophin receptor and/or other possible cofactors.