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        • SCOPUSKCI등재

          The Investigation of a Novel Indicator System for Trace Determination and Speciation of Selenium in Natural Water Samples by Kinetic Spectrophotometric Detection

          Gurkan,,Ramazan,Ulusoy,,Halil,Ibrahim Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.7

          A novel catalytic kinetic method is proposed for the determination of Se(IV), Se(VI) and total inorganic selenium in water based on the catalytic effect of Se(IV) on the reduction of bromate by p-nitrophenylhydrazine at pH 3.0. The generated bromine, $Br_2$ or $Cl_2$ plus $Br_2$ in 0.1 M NaCl (or NaBr) environment efficiently decolorized Calmagite and the reaction was monitored spectrophotometrically at 523 nm as a function of time. In this indicator reaction, bromide acted as an activator for the catalysis of selenium (IV) and a reducing agent for selenium (VI) at pH 3.0, which allowed the determination of total selenium. The fixed time method was adopted for the determination and speciation of inorganic selenium. Under the optimum conditions, the calibration graph are linear in the range 1 - 35 ${\mu}gL^{-1}$ of Se(IV) for the fixed time method at $25^{\circ}C$. The detection limit based on statistical $3S_{blank}$/m-criterion was 0.215 ${\mu}gL^{-1}$ for the fixed time method (7 min). All of the variables that affect the sensitivity at 523 nm were investigated, and the optimum conditions were established. The interference effect of various cations and anions on the Se (IV) determination was also studied. The selectivity of the selenium determination was greatly improved with the use of the strongly cation exchange resin such as Amberlite IR120 plus. The proposed kinetic method was validated statistically and through recovery studies in natural water samples. The RSDs for ten replicate measurements of 5, 15 and 25 ${\mu}gL^{-1}$ of Se(IV) and Se(VI) was changed between 2.1 - 4.85%. Analyses of a certified standard reference material (NIST SRM 1643e) for selenium using the fixed-time method showed that the proposed kinetic method has good accuracy. Se(IV), Se(VI) and total inorganic selenium in environmental water samples have been successfully determined by this method after selective reduction of Se(VI) to Se(IV).

        • KCI등재SCOPUS

          Expansive Networks: Exploiting Spectrum Sharing for Capacity Boost and 6G Vision

          Gurkan,Gur 한국통신학회 2020 Journal of communications and networks Vol.22 No.6

          Adaptive capacity with cost-efficient resource provisioning is a crucial capability for future 6G networks. In this work, weconceptualize “expansive networks” which refers to a networkingparadigm where networks should be able to extend their resourcebase by opportunistic but self-controlled expansive actions. To thisend, we elaborate on a key aspect of an expansive network as aconcrete example: Spectrum resource at the PHY layer. Evidently,future wireless networks need to provide efficient mechanisms tocoexist in the licensed and unlicensed bands and operate in expansive mode. In this work, we first describe spectrum sharing issuesand possibilities in 6G networks for expansive networks. We thenpresent security implications of expansive networks, an importantconcern due to more open and coupled systems in expansive networks. We also discuss two key enablers, namely distributed ledgertechnology (DLT) and network intelligence via machine learning,which are promising to realize expansive networks for the spectrum sharing aspect.

        • SCOPUSKCI등재

          Catalytic Spectrophotometry for the Determination of Manganese at Trace Levels by a Novel Indicator Reaction

          Gurkan,,Ramazan,Caylak,,Osman Korean Chemical Society 2010 대한화학회지 Vol.54 No.5

          새로운 동적 분광 광도 측정법은 천연의 물 샘플에서 망간(II)의 측정을 위해 개발되었다. 그 방법은 620 nm에서 활성화제로서 nitrilotriacetic acid (NTA)를 사용하면서 $KIO_4$에 의한 갈로시아닌(Gallocyanin)의 산화와 함께 망간(II)의 촉매 효과에 기초했다. 최적조건은 갈로시아닌(Gallocyanin) $4.00{\times}1^{-5}\;M$, $KIO_4$ $1.00{\times}10^{-4}\;M$, NTA $1.00{\times}10^{-4}\;M$, pH = 3.50인 0.1 M HAc/NaAc 완충용액, 5분의 반응시간 그리고 $30^{\circ}C$의 온도에서 얻어졌다. 최적조건 하에서 제안된 방법은 $0.1\;-\;4.0\;ng\;mL^{-1}$의 범위에서 망간(II)의 측정을 허용했고 $0.025\;ng\;mL^{-1}$이하의 검출한계를 가지고 있다. 표준 망간(II) 용액을 측정하는 것에서 회수율은 98.5 - 102% 범위에 있다. 그리고 상대표준편차(RSD)는 0.76 - 1.25%의 범위에 있다. 새롭게 개발된 동적 방법은 약간의 주위의 물과 만족할 만한 결과를 갖는 JAC-0031의 공인된 표준 기준 강물 샘플 둘 다에서 망간(II)의 측정에 성공적으로 응용되었다. 또한, 얼마 안 되는 양이온과 음이온은 망간(II)의 측정을 방해한다. 다른 촉매-동적 방법과 기기적 방법과 비교했을 때, 제안된 동적 방법은 상당히 좋은 선택성과 감도, 낮은 가격, 저렴함, 낮은 검출한계와 신속함을 보인다. 상대적으로 낮은 염분을 갖는 진짜 물 샘플과 병으로 된 마시는 물, 차갑고 뜨거운 용천수, 호수, 강물 샘플 같은 복잡한 모체들에 적용하는 것은 쉽고 성공적으로 적용될 수 있다. A new kinetic spectrophotometric method is developed for the measurement of Mn(II) in natural water samples. The method is based on the catalytic effect of Mn(II) with the oxidation of Gallocyanin by $KIO_4$ using nitrilotriacetic acid (NTA) as an activation reagent at 620 nm. The optimum conditions obtained are $4.00{\times}1^{-5}\;M$ Gallocyanin, $KIO_4$, $1.00{\times}10^{-4}\;M$ NTA, 0.1 M HAc/NaAc buffer of pH = 3.50, the reaction time of 5 min and the temperature of $30^{\circ}C$. Under the optimum conditions, the proposed method allows the measurement of Mn(II) in a range of $0.1\;-\;4.0\;ng\;mL^{-1}$ and with a detection limit of down to $0.025\;ng\;mL^{-1}$. The recovery efficiency in measuring the standard Mn(II) solution is in a range of 98.5 - 102%, and the RSD is in a range of 0.76 - 1.25%. The newly developed kinetic method has been successfully applied to the measurement of Mn(II) in both some environmental water samples and certified standard reference river water sample, JAC-0031 with satisfying results. Moreover, few cations and anions interfere with the measurement of Mn(II). Compared with the other catalytic-kinetic methods and instrumental methods, the proposed kinetic method shows fairly good selectivity and sensitivity, low cost, cheapness, low detection limit and rapidity. It can easily and successfully be applied to the real water samples with relatively low salt content and complex matrices such as bottled drinking water, cold and hot spring waters, lake water, river water samples.

        • KCI등재SCOPUS

          Synthesis and anticancer effects of some novel 2-(4- phenoxyphenyl)-1H-benzimidazole derivatives on K562 cell line

          A.,Selen,Gurkan-Alp,Hakan,Go¨ker,Mehmet,Alp,Tulin,Ozkan,Asuman,Sunguroglu 대한약학회 2015 Archives of Pharmacal Research Vol.38 No.5

          A series of novel 2-(4-phenoxyphenyl)-1Hbenzimidazolederivatives was synthesized and testedin vitro on human chronic myelogenous leukemia (CML)cell line K562. Benzimidazoles containing 5-amidino (10),5-N-isopropylamidino (11), 5-bromo (13), and 5,6-dimethyl(14) derivatives exhibited remarkable cytotoxicactivity. The quantitative analysis of apoptosis by flowcytometrydemonstrated that the percentages of early andlate apoptotic K562 cells treated with these compoundswere significantly higher than cells without treatment. Wealso investigated the effects of these compounds on theexpression of apoptosis-related genes BAX, BCL-2, BADand BIM. Treatment of K562 cells wih compounds 10–14significantly increased the expression levels of the proapoptoticgenes BAX, BAD and BIM, whereas compound20 increased BAX and BAD.

        • KCI등재SCOPUS

          Modeling and Implications of Airport Ground Egress Mode Choice

          Ilgin,Gokasar,Gurkan,Gunay 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.2

          Mode choice of airport ground access has been covered by several studies, but there is a lack of research in the case of airport ground egress; that is, mode choices of inbound passengers for ground trips from the airport to the city center. This study aimed to cover this gap by modeling the ground egress mode choice of passengers, employing mixed logit and comparing it with the multinomial logit model. The data for this research was collected at Istanbul's Sabiha Gokcen International Airport (SAW) in 2015. Analyses included six modes, namely automobile, pick-up, public transit, taxi, shuttle and public transit (SP), and shuttle and taxi (ST). An important outcome was that a mixed logit model with error components outperformed the multinomial logit model. Results showed that significant variables affecting the ground egress mode choice included the income of the passenger, the cost of a ground trip from the airport, auto ownership status, number of luggage and trip purpose. Passengers are less constrained by ground travel time in their airport egress trips than in their airport access trips. By this, a significant finding was that prioritizing egress trip cost over travel time affected the mode choice.

        • KCI등재SCOPUS

          Effect of layer thickness and print orientation on strength of 3D printed and adhesively bonded single lap joints

          Volkan,Kovan,Gurkan,Altan,Eyup,Sabri,Topal 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.5

          Three-dimensional printing is the common name given to various techniques used to manufacture different objects. Fused deposition technique is a commonly used additive manufacturing technology in prototyping and production. Fused deposition modelling systems are limited in terms of shape and size of parts. Printing parts with less support material, for parts too large to print in a single operation or for parts with fine details, sectioning and adhesively bonding is the solution for manufacturing. According to adhesion theory, the strength of adhesively bonding between three-dimensional printed parts is affected by surface roughness. Effects of layer thickness and print orientation on adhesion strength of parts manufactured with three-dimensional printing were experimentally studied. As a result of the study, it was found that the edgewise orientation had the highest bonding strength in lower layer thicknesses, while flatwise orientation had the highest bonding strength in higher layer thicknesses.

        • SCOPUSSCIEKCI등재

          Growing Hemorrhagic Choroidal Fissure Cyst

          Karatas,,Ayse,Gelal,,Fazil,Gurkan,,Gokhan,Feran,,Hamit The Korean Neurosurgical Society 2016 Journal of Korean neurosurgical society Vol.59 No.2

          Choroidal fissure cysts are often incidentally discovered. They are usually asymptomatic. The authors report a case of growing and hemorrhagic choroidal fissure cyst which was treated surgically. A 22-year-old female presented with headache. Cranial MRI showed a left-sided choroidal fissure cyst. Follow-up MRI showed that the size of the cyst had increased gradually. Twenty months later, the patient was admitted to our emergency department with severe headache. MRI and CT showed an intracystic hematoma. Although such cysts usually have a benign course without symptoms and progression, they may rarely present with intracystic hemorrhage, enlargement of the cyst and increasing symptomatology.

        • KCI등재SSCISCOPUS

          Hippocampal Neurochemical Pathology in Patients with Panic Disorder

          Murad,Atmaca,Hanefi,Yildirim,M.,Gurkan,Gurok,Muammer,Akyol,Filiz,Koseoglu 대한신경정신의학회 2012 PSYCHIATRY INVESTIGATION Vol.9 No.2

          '스콜라' 이용 시 소속기관이 구독 중이 아닌 경우, 오후 4시부터 익일 오전 7시까지 원문보기가 가능합니다.

          Objective In the present study, we measured hippocampal N-acetyl-l-aspartate (NAA), choline (CHO) and creatine (CRE) values in patients with panic disorder and healthy control subjects using in vivo 1H MRS. Methods We scanned 20 patients meeting Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) criteria for panic disorder and 20 matched healthy controls with a 1.5 Tesla GE Signa Imaging System and measured of NAA, CHO, and CRE in hippocampal regions. ResultsaaWhen NAA, CHO and CRE values were compared between groups, statistically significant lower levels for all ones were detected for both sides. Conclusion Consequently, in the present study we found that NAA, CHO and CRE values of the patients with panic disorder were lower than those healthy controls. Future studies involving a large number of panic patients may shed further light on the generalizability of the current findings to persons with panic disorder. Objective In the present study, we measured hippocampal N-acetyl-l-aspartate (NAA), choline (CHO) and creatine (CRE) values in patients with panic disorder and healthy control subjects using in vivo 1H MRS. Methods We scanned 20 patients meeting Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) criteria for panic disorder and 20 matched healthy controls with a 1.5 Tesla GE Signa Imaging System and measured of NAA, CHO, and CRE in hippocampal regions. ResultsaaWhen NAA, CHO and CRE values were compared between groups, statistically significant lower levels for all ones were detected for both sides. Conclusion Consequently, in the present study we found that NAA, CHO and CRE values of the patients with panic disorder were lower than those healthy controls. Future studies involving a large number of panic patients may shed further light on the generalizability of the current findings to persons with panic disorder.

        • SCIESCOPUS

          Investigation of possible causes of sinkhole incident at the Zonguldak Coal Basin, Turkey

          Genis,,Melih,Akcin,,Hakan,Aydan,,Omer,Bacak,,Gurkan Techno-Press 2018 Geomechanics & engineering Vol.16 No.2

          The subsidence mechanism of ground surface is a complex phenomenon when multiple seam coal mining operations are carried out. Particularly, the coal mining beneath karstic formations causes a very special form of subsidence. The subsidence causes elasto-plastic deformation of the karstic layers and the collapse of cavities leads to dolinization and/or sinkhole formation. In this study, a sinkhole with a depth of 90 m and a width of 25 m formed in Gelik district within the coal-basin of Zonguldak (NW, Turkey) induced by multiple seam coal mining operations in the past has been presented as a case-history together with two-dimensional numerical simulations and InSAR monitoring. The computational results proved that the sinkhole was formed as a result of severe yielding in the close vicinity of the faults in contact with karstic formation due to multiple seam longwall mining at different levels.

        • KCI등재SCOPUS

          Performance functions for laterally loaded single concrete piles in homogeneous clays

          Gokhan,mancli,M.,Rifat,Kahyaoglu,Gurkan,Ozden,Arif,S.,Kayalar 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.4

          A key parameter in the design of a laterally loaded pile is the determination of its performance level. Performance level of a pile is usually expressed as the maximum head deflection and bending moment. In general, uncertainties in the performance of a pile originates from many factors such as inherent variability of soil properties, inadequate soil exploration programs, errors taking place in the determination of soil parameters, limited calculation models as well as uncertainties in loads. This makes it difficult for practicing engineers to decide for the reliability of laterally loaded piles both in cohesive and cohesionless soils. In this paper, limit state functions and consequent performance functions are obtained for single concrete piles to predict the maximum bending moment, a widely accepted design criterion along with the permissible pile head displacement. Analyses were made utilizing three dimensional finite element method and soil-structure-interaction (SSI) effects were accounted for.

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