Torsion of circular open cross-section with corrugated inner and outer surface

Yaşar Pala,Abdullah Pala 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.1

In this study, the problem of torsion of bars with open cross section surrounded by corrugated boundaries is analyzed. An approximate analytical solution is given using perturbation technique. First, the stress analysis for circular open cross-section for arbitrary opening angle is formulated and the problem is analytically solved. Second, the open cross-section with corrugated cross section is analyzed using perturbation method. First order contributions to the stresses and the torques have been added. The results have been exemplified and compared by considering special examples.

Effect of Deposition Technique of SiN x Passivation Layer on the Electrical DC and RF Properties of AlGaN/GaN HEMTs

Yağmur Güler,Barış Onaylı,Mehmet Taha Haliloğlu,Doğan Yılmaz,Tarık Asar,Ekmel Özbay 한국전기전자재료학회 2024 Transactions on Electrical and Electronic Material Vol.25 No.2

In this paper, we present the results of a comparative analysis of two alternative SiN x passivation techniques of AlGaN/GaN high electron mobility transistor (HEMT) manufactured using identical epitaxial structure and fabrication processes. AlGaN/GaN HEMT has demonstrated excellent device characteristics, making them excellent candidates for high power, high frequency, and low noise applications. However, the full potential of GaN HEMT s in large signal operation at high frequency is limited by trapping effects and leakage currents at the interface between the epitaxial structure and passivation layer. A SiN x passivation layer has commonly been used to prevent electron trapping at the surface by providing extra positive charges to neutralize trapped negative electrons on the surface. This comparative study investigates the effects of a 75 nm SiN x passivation layer fabricated using both plasma-enhanced chemical vapor deposition ( PECVD ) and inductively coupled plasma chemical vapor deposition ( ICPCVD ) techniques on the DC and RF performance of the transistor.

Migration of Rod into Retroperitoneal Region: A Case Report and Review of the Literature

Yaşar Bayri,Murat Sakir Eksi,Ramazan Doğrul,Demet Yalçinkaya Koç,Deniz Konya 대한척추신경외과학회 2014 Neurospine Vol.11 No.4

Spinal stabilization with fusion is the widely used method for traumatic or pathologic fracture of spine, spinal stenosis, and spondylolisthesis. Complications may emerge during or after the operations. Infection, hematoma and neurological deficits are early noticed findings. Screw and/or rod fractures present in long-term after surgery. Rod migration in out of the spinal column is a rare entity. A 67-year-old woman was visited our clinic for right leg pain. She had a previous spinal instrumentation surgery for spondylolisthesis in another center 6 years before. After radiological work-up, a distally migrated rod piece was observed in the retroperitoneal portion. The patient was operated for degenerative change; old instruments were replaced and extended to the L2 level with posterior spinal fusion. After the operation, her right leg pain improved. The asymptomatic migrated rod piece has regularly been followed clinically and radiologically, since then. Although it has rarely been reported, migration of the instrumentation material should be kept in mind. Spinal fixation without fusion makes the mechanical system vulnerable to motion effects of spine, especially in a degenerative and osteoporotic background. Long-term, even life-long follow-up is necessary for late term complications.

Elevated Serum Galectin-1 and Galectin-3 Levels in Children With Specific Learning Disorder: A Case Control Study

Yaşar Tanır,Zeynep Nur Gülle,Gökçe Sultan Uncu,Adile Merve Baki,Pervin Vural,Nusret Soylu,Abdurrahman Cahid Örengül 대한신경정신의학회 2023 PSYCHIATRY INVESTIGATION Vol.20 No.7

Objective Specific learning disorder (SLD) is a neurodevelopmental disorder in which underlying pathogenesis and etiological factors are not fully understood. Neuroinflammatory response (measured with serum levels of galectin-1 and galectin-3), which is associated with learning and memory, may play an important role in the etiopathogenesis of SLD. Aim of the present study is to examine whether serum galectin-1 and galectin-3 levels are related to SLD.Methods The current study consisted of 42 treatment-naive children with SLD and 42 control subjects. All of the subjects were assessed using semi-structured psychiatric examination to diagnose SLD and exclude attention-deficit hyperactivity disorder. Serum galectin-1 and galectin-3 levels were measured via venous blood samples.Results The SLD and control group did not differ significantly in terms of age, sex, and body mass index (BMI). The SLD group had significantly higher serum levels of galectin-1 (8.78±2.97 vs. 7.40±2.03, p=0.019) and galectin-3 (1.86±0.93 vs. 1.32±0.69, p=0.003) than the control group when controlled for age, sex, and BMI.Conclusion Higher serum levels of galectin-1 and galectin-3 in children with SLD may indicate the role of neuroinflammatory response in the pathogenesis of SLD. Other mechanisms involving galectin-1 and galectin-3 related to learning may play a part in the etiology of SLD.

Thrust force modelling and surface roughness optimization in drilling of AA-7075: FEM and GRA

Nafiz Yaşar 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10

AA7075 aluminum alloy attracts scientific interest to participate in production of crucial components in aerospace, construction and automotive domains. Specifically, final products need to display equal quality to ensure the basic standards of safety in the aircraft industry. Despite the high machinability of the AA7075 alloy, hole quality may vary according to tool geometry and drilling parameters. In this study, the effects of different feed rate levels and cutting speeds on the surface roughness (Ra) and thrust (Fz) were investigated. Drilling experiments were conducted with drills of three different quality and geometry. The effects of drilling variables on the surface roughness and the thrust force according to “the smaller-the better” approach of the gray relation analysis (GRA) method have been investigated. Consequently, the highest and lowest gray relations degrees obtained were 0.828 and 0.338, respectively. Numerical analyzes for thrust force were performed with the ThirdWave AdvantEdge simulation software based on the finite element method. We also outlined that there exists an average difference of 4.9 % between the experimental and simulation thrust force values, and we proved the applicability of the finite element model.

간호사의 소진과 감정노동 및 자기효능감에 대한 연구

양야기 한국간호과학회 간호행정학회 2011 간호행정학회지 Vol.17 No.4

Purpose: This study was conducted to investigate the relationship of burn out, emotional labor and self-efficacy in nurses, and to identify predictors of burnout. Method: The participants were 268 nurses working in C university hospital in G city. Data were collected from May 1 to May 31, 2010, and analyzed using SPSS/WIN 12.0. Results: The mean score per item for burnout was 3.13, the mean emotional labor score was 3.15, and the mean of self-efficacy score was 3.42. Burnout showed negative correlation with self-efficacy (r=-.339, p=.000), and showed positive correlation with emotional labor (r=.511, p=.000). Variables that predicted burnout were emotional labor, self-efficacy, gender, number of assigned patient per duty (37.8%). Conclusion: The findings of this study indicate a need to develop programs for nurses to increase self-efficacy and to control the emotion, and the need for further studies to examine causal relationship among burn out, emotional labor and self-efficacy.

Simultaneous Eco-friendly Bleaching and Retting Wastewater Treatment of Hemp Fiber with Ozone Application

Görkem Gedik,Yağmur Meltem Aydın Kızılkaya,Vedat Uyak,Ahmet Koluman 한국섬유공학회 2023 Fibers and polymers Vol.24 No.1

The main aim of this study was to reduce the biological load in the retting effluents by eliminating the microorganism and at the same time, to bleach hemp fibers in the retting liquor, with ozone treatment. In addition to prevention of the environmentalpollution, time, energy, water and chemical consumption decrease were targeted by the ozone bleaching of hemp fiber in the retting liquor. For this purpose, retting liquor was treated with ozone gas in different concentrations (5–25 g/h) anddurations (5–90 min) while hemp stems were still in it. The environmental impact was investigated by TOC (Total Organic Carbon), BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) measurements. Ozone applicationresulted in dramatic reductions on BOD and TOC values. Total bacteria count in the untreated retting liquor and ozonetreated samples was determined, up to 100% sanitation effect was achieved by ozone application. Whiteness degrees of the hemp fibers increased up to 72% with ozone application compared with the retted sample. The chemical compositions of the fibers were stated by chemical tests and oxidative damage related to ozone treatment was investigated. The lignin ratio was significantly reduced after ozone application. The results of the chemical tests were supported by FTIR measurements. The mechanical properties such as tenacity and elongation were analyzed with tensile tests. The crystallographic characteristics were investigated with XRD, the crystallinity index was increased with ozone treatment.

Estimating the Optimal Dexketoprofen Pharmaceutical Formulation with Machine Learning Methods and Statistical Approaches

Atakan Başkor,Yağmur Pirinçci Tok,Burcu Mesut,Yıldız Özsoy,Tamer Uçar 대한의료정보학회 2021 Healthcare Informatics Research Vol.27 No.4

Objectives: Orally disintegrating tablets (ODTs) can be utilized without any drinking water; this feature makes ODTs easy touse and suitable for specific groups of patients. Oral administration of drugs is the most commonly used route, and tabletsconstitute the most preferable pharmaceutical dosage form. However, the preparation of ODTs is costly and requires longtrials, which creates obstacles for dosage trials. The aim of this study was to identify the most appropriate formulation usingmachine learning (ML) models of ODT dexketoprofen formulations, with the goal of providing a cost-effective and timereducingsolution. Methods: This research utilized nonlinear regression models, including the k-nearest neighborhood (k-NN), support vector regression (SVR), classification and regression tree (CART), bootstrap aggregating (bagging), randomforest (RF), gradient boosting machine (GBM), and extreme gradient boosting (XGBoost) methods, as well as the t-test, topredict the quantity of various components in the dexketoprofen formulation within fixed criteria. Results: All the modelswere developed with Python libraries. The performance of the ML models was evaluated with R2 values and the root meansquare error. Hardness values of 0.99 and 2.88, friability values of 0.92 and 0.02, and disintegration time values of 0.97 and10.09 using the GBM algorithm gave the best results. Conclusions: In this study, we developed a computational approach toestimate the optimal pharmaceutical formulation of dexketoprofen. The results were evaluated by an expert, and it was foundthat they complied with Food and Drug Administration criteria.

A pilot study of the two OB associations Cygnus OB2 and Carina OB1 using the Gaia data

Beomdu Lim,Yaël Nazé,Eric Gosset,Gregor Rauw 한국천문학회 2019 天文學會報 Vol.44 No.1

Investigation of the Mechanical, Electronic and Phonon Properties of X2ScAl (X = Ir, Os, and Pt) Heusler Compounds

Arikan Nihat,Ocak Hamza Yaşar,Dikici Yıldız Gökçen,Yıldız Yasin Göktürk,Ünal Rahmi 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.10

In the present study, the second-order elastic constants and the electronic band structures of the X2ScAl (x = Ir, Os, and Pt) compounds crystallized in the L21 phase were calculated separately by using the ab-initio density functional theory. According to the results for the second-order elastic constants, these compounds met the Born mechanical stability criteria. Also, according to the Pugh criteria, they were found to have a ductile structure and to show anisotropic behavior. The microhardneses of the compounds were between 2 and 14 GPa, and the highest hardness was found in the Ir2ScAl (14.290 GPa) compound. In addition, the energy band structures of these compounds were calculated, and the crystals were found to have a metallic bond structure. All the computed data were compared with previously calculated results obtained with different methods. According to the findings obtained in the present study, in terms of its mechanical and electronic behaviors, Ir2ScAl was found to have better physical properties than Os2ScAl and Pt2ScAl. The phonon dispersion curves and their corresponding total and projected densities of states were investigated for the first time by using a linear-response approach in the context of density functional perturbation theory. The frequencies of the optical phonon modes of all compounds at the Γ point were 4.767, 7.504 and 9.271 THz for Ir2ScAl, 2.761, 7.985 and 9.184 THz for Os2ScAl and 2.012, 5.6952 and 8.118 THz for Pt2ScAl. The heat capacity Cv at constant volume versus temperature was calculated using a quasi-harmonic approach and the results are discussed.