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Ahmet A. Kiykim,Ahmet Camsari,Serkan Kahraman,Mustafa Arici,Bulent Altun,Dilek Cicek,Yunus Erdem,Unal Yasavul,Cetin Turgan,Sali Caglar,Aytekin Oto 연세대학교의과대학 2004 Yonsei medical journal Vol.45 No.2
Cardiovascular disease (CVD) is still the major cause of the morbidity and mortality in hemodialysis (HD) patients. The characteristics of major arterial changes, atherosclerosis and related risk factors in HD patients remain unclear. We aimed to evaluate the atherosclerotic process in asymptomatic HD patients and healthy volunteers, and to determine the association between the risk factor(s) and the atherosclerotic process in these groups. 92 HD patients (female: 43, male: 49) and 62 age and sex matched healthy volunteers (female: 27, male: 35) were enrolled in this study. Diabetics, smokers, and patients with symptomatic CVD were excluded. The right and left carotid intima-media thicknesses (CIMTs) were measured and plaque structures were studied by B-mode ultrasound. The mean CIMT in patients and control group were 0.79±0.16 mm and 0.54±0.09mm, respectively. Mean CIMT in HD patients was thicker (p<0.001) and the presence ratio of plaque was higher in patients group (n=38, %61.2 vs n=9, %17.3) (p<0.001). Calcified type of plaque was more frequent in HD patients than control group. Age (r=0.48, p<0.001), left ventricular mass (r=0.42, p<0.05), and homocysteine (r=0.46, p<0.01), mean hematocrit (r=-0.36, p<0.05), plasma CRP (r=0.50, p<0.001), ESR (r=0.43, p<0.01) and albumin (r= -0.34, p<0.05) levels were correlated with the CIMT measurements and plaque presence, significantly. -CIMT as an atherosclerotic process indicator is thicker in asymptomatic HD patients than healthy subjects. We concluded that in addition to various classical risk factors, uremic environment may also contribute to acceleration of the atherosclerotic process.
M. Mufit Kahraman,M. Ozgur Ozygit,Ahmet Akkoc,Bulent Ediz,Deniz Misirlioglu,Gursel Sonmez,Aylin Alasonyalilar,Rahsan Yilmaz 대한수의학회 2007 JOURNAL OF VETERINARY SCIENCE Vol.8 No.2
Bovine spongiform encephalopathy (BSE), a member of the transmissible spongiform encepahlopathies, has been a notifiable disease in Turkey since 1997. In 2002, the BSE status of Turkey was assessed by the EU Scientific Steering Committee as “it is likely but not confirmed”.This study presents the results of a targeted surveillance study to assess the presence of BSE in the age risk population of Bursa, Turkey. In the assessment procedure, the immunohistochemical detection of protease-resistant prion protein (PrP-Sc) was aimed at and applied to 420 brain tissues of cattle slaughtered in Bursa at an age of 30-months and older. None of the samples were positive for BSE.
Hyun Sik Kwon,Ahmet Kahraman 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.12
Automotive automatic transmissions typically use a planetary gear train to transmit power at a number of desired output-to-input speed ratios. This is achieved by connecting the gear sets forming the train in various ways as well as connecting certain members to the input and outputs shafts as well as friction elements to hold them stationary. As the gear train is coaxial, the connections between the members of the gear sets as well as input, output and fixed member connections must be planar (i.e. do not intersect) for the transmission to be assemblable. This paper proposes a methodology to perform such planarity (assembly) checks to examine if kinematic configurations of a given concept design for an automatic planetary gear train be mechanically assembled by using a vertex addition algorithm based on graph theory. The proposed methodology is demonstrated through selected planar and non-planar transmission examples.
Gultekin, Guldal Inal,Yilmaz, Seda Gulec,Kahraman, Ozlem Timirci,Atasoy, Hande,Dalan, A. Burak,Attar, Rukset,Buyukoren, Ahmet,Ucunoglu, Nazli,Isbir, Turgay Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.3
Uterine leiomyomas (ULM), are benign tumors of the smooth muscle cells of the myometrium. They represent a common health problem and are estimated to be present in 30-70% of clinically reproductive women. Abnormal angiogenesis and vascular-related growth factors have been suggested to be associated with ULM growth. The angiotensin-I converting enzyme (ACE) is related with several tumors. The aim of this study was to identify possible correlation between ULM and the ACE I/D polymorphism, to evaluate whether the ACE I/D polymorphism could be a marker for early diagnosis and prognosis. ACE I/D was amplified with specific primer sets recognizing genomic DNA from ULM (n=72) and control (n=83) volunteers and amplicons were separated on agarose gels. The observed genotype frequencies were in agreement with Hardy-Weinberg equilibrium ($x^2=2.162$, p=0.339). There was no association between allele frequencies and study groups ($x^2=0.623$; p=0.430 for ACE I allele, $x^2=0.995$; p=0.339 for ACE D allele). In addition, there were no significant differences between ACE I/D polymorphism genotype frequencies and ULM range in size and number ($X^2=1.760;$ p=0.415 for fibroid size, $X^2=0.342;$ p=0.843 for fibroid number). We conclude that the ACE gene I/D polymorphism is not related with the size or number of ULM fibroids in Turkish women. Thus it cannot be regarded as an early diagnostic parameter nor as a risk estimate for ULM predisposition.
해석적 접근을 통한 기어 마찰 동력 손실 예측 및 최소화
박기종(Kijong Park),자니 하리안토(Jonny Harianto),아멧 칼만(Ahmet Kahraman) 한국자동차공학회 2017 한국 자동차공학회논문집 Vol.25 No.4
A highly efficient parallel-axis gear train is widely used in automobile transmissions. Power losses in a parallel-axis gear train are mainly generated by gears and bearings. In this study, an analytical methodology is introduced to predict the friction-related mechanical power loss of a gear pair in a parallel-axis gear train. The mechanical power loss of a gear under typical operating and lubrication conditions is estimated through a gear contact analysis model and a friction coefficient formulation. A design parameter study is performed to identify the effect of the parameters on gear mechanical power loss. Design optimization is also conducted to minimize the mechanical power loss of the gear pair.
평행축 기어트레인을 갖는 변속기의 마찰 및 쳐닝 동력 손실 예측
박기종(Kijong Park),강마루(Maru Kang),이승호(Sueng Ho Lee),손우철(Woochurl Son),권여현(Yeo Hyeon Kwon),아멧칼만(Ahmet Kahraman) 한국자동차공학회 2018 한국 자동차공학회논문집 Vol.26 No.1
The automotive industry is currently focusing on the development of a highly efficient gearbox to reduce the fuel consumption of vehicles. A transmission system with a parallel-axis geartrain has higher efficiency than the one with a planetary geartrain. Power losses of the transmission with a parallel-axis geartrain are mainly generated by the gears and bearings. In this study, a process was developed to analyze the efficiency of an entire parallel-axis gearbox, considering the power losses of all the components, such as the gear mesh, gear spin, bearings, and synchronizer. The analytical models that were used were based on the component power loss models developed in previous studies and published in many papers. The process included the power flow analysis of a parallel geartrain. The power losses and transmission efficiency of a few automotive gearboxes with a parallel geartrain were estimated through the process. The results were compared with the experiment data.
토크 변동조건에서의 유성기어세트 동적 거동 해석 모델링에 대한 연구
이현구(Hyun Ku Lee),김무석(Moo Suk Kim),홍사만(Sa Man Hong),유동규(Dong Kyu Yoo),아멧 칼만(Ahmet Kahraman),데이빗 탈봇(David Talbot) 한국소음진동공학회 2019 한국소음진동공학회 논문집 Vol.29 No.4
In this paper, to reduce planetary gear noise under the neutral control condition, a dynamic analysis model for multi-stage planetary gear trains of the HMC 6th speed automatic transmissions under a torque fluctuations condition is proposed. The natural frequencies of its system are computed by solving the corresponding eigenvalue problem. Moreover, some forced torque fluctuation response to the planetary gear system is applied to check its influence during neutral control. By undertaking some parameter studies for analysis modeling, an underdrive brake torque fluctuation and underdrive hub inertia are observed to be the most effective factors of the HMC 6th speed automatic transmission’s planetary gear noise under the neutral control condition. To reduce neutral control planetary gear noise, the underdrive torque fluctuation should be reduced whereas underdrive hub inertia should be increased. However, every transmission has some torque fluctuations caused by the valve body control response and friction component characteristic and those also have some manufacturing quality distributions. Therefore, control component inertia is an important item in the neutral control condition. To adapt the neutral control to a next-generation transmission, its control component inertia should be above a certain value.
Fatma Sezer Şenol,Ilkay Erdogan Orhan,Sinem Aslan Erdem,Murat Kartal,Bilge Şener,Yu¨ksel Kan,Ferhat Celep,Ahmet Kahraman,Musa Dogan 한국식품영양과학회 2011 Journal of medicinal food Vol.14 No.11
In European folk medicine, Salvia species have traditionally been used to enhance memory. In our previous study of 55 Salvia taxa, we explored significant anticholinesterase activity of cultivated S. fruticosa. In this study, we compared the inhibitory activity of dichloromethane, ethyl acetate, and ethanol extracts of 3 wild-grown samples and 1 cultivated sample of S. fruticosa against acetylcholinesterase and butyrylcholinesterase enzymes (which are associated with pathogenesis of Alzheimer's disease) by using the spectrophotometric Ellman method. Antioxidant activities were assessed by determining 2,2-diphenyl-1-picrylhydrazyl radical–scavenging activity, iron-chelating capacity, and ferric-reducing antioxidant power. The dichloromethane extract of the cultivated sample was then subjected to fractionation by using open column chromatography and medium-pressure liquid chromatography to obtain the most active fraction by activity-guided fractionation. All fractions and subfractions were tested in the same manner, and inactive subfractions were discarded. The essential oil of the cultivated sample was analyzed by gas chromatography–mass spectrometry.
유성기어 소음과 효율을 고려한 pRMC 프로그램 개발 및 적용에 관한 연구
이현구(Hyun Ku Lee),김무석(Moo Suk Kim),홍사만(Sa Man Hong),박영지(Young Ji Park),천성경(Seong Kyeong Cheon),아멧칼만(Ahmet Kahraman),하리안토자니(Jonny Harianto) 한국자동차공학회 2021 한국자동차공학회 부문종합 학술대회 Vol.2021 No.6
이 연구는 자동변속기 및 미래 신개념 변속기의 핵심 구성 요소 중 하나인 유성기어 시스템에 대하여 컨셉 단계에서부터 소음과 효율을 동시에 고려할 수 있는 유성기어 제원 설계용 프로그램을 개발하고 이를 검증한 것을 기술한 것이다. 기존의 pRMC(planetary run many cases) 프로그램에 효율 분석인자를 추가하여 유성기어 제원 상세 설계 시 상대적으로 효율이 우수한 제원을 선정하여 설계 검토할 수 있도록 하였다. 현대자동차의 전륜 8속 자동변속기에 탑재된 유성기어세트 2세트를 각각 재설계하고 자동변속기 소음과 효율 평가를 통하여 검증하였다. 첫번째 유성기어세트는 효율이 0.23 %, 전달오차가 0.07㎛ 개선되었고, 두번째 유성기어세트는 효율이 0.47 % 개선되나, 전달오차는 0.05㎛ 악화되는 제원으로 설계를 하였다. 자동변속기 연비와 관련된 효율에 대한 해석과 실험을 통하여 신규로 설계한 유성기어 세트가 탑재된 변속기의 효율이 상대적으로 약 0.3% 이상 우세한 것을 확인하였다. 진동 소음 대상 평가를 통하여 첫번째 유성기어세트가 10dB 개선되고 차량 평가를 통하여 전 구간에서 소음이 5dBA이상 개선됨을 확인하였다. pRMC with EHL 프로그램을 개발하고 상관성 검증 평가를 통하여 컨셉 단계부터 유성기어 세트의 소음과 효율에 대하여 강건 설계를 할 수 있는 역량을 확보하여 보다 진보된 유성기어 설계 프로세스를 구축하였다. Photo.1은 개발된 프로그램의 사용과정에 대한 것을 보인 것이고, Photo.2는 이전 제원과 새로 설계된 제원의 효율 평가 결과를 나타낸 것이다. Photo.3은 첫번째 유성기어세트의 대상 진동 소음 평가 결과 비교를 보인 것이다.