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Experimental and theoretical analyses of a double-cylindrical trough solar concentrator
Cuma Çetiner 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.11
Parabolic trough, Fresnel, heliostat mirror, or dish-type collectors are used to obtain high temperature in solar thermal applications. The operation of this system is similar to that of a Fresnel collector, except for its reflective mirror, which is cylindrical and not flat. The experiments were carried out in the solar energy system manufactured for producing hot water, superheated water, and steam in the cylindrical trough solar concentrator. According to the test results, the thermal power of the system and the average thermal efficiency of the collector were a maximum of 15 kW and approximately 35 %, respectively.
Perimortem Cesarean Delivery Following Severe Maternal Penetrating Injury
Cuma Yildirim,Sitki Goksu,Hasan Kocoglu,Ahmet Gocmen,Melek Akdogan,Nurullah Gunay 연세대학교의과대학 2004 Yonsei medical journal Vol.45 No.SUP
The case of a severely traumatized pregnant patient, in whom a perimortem cesarean section, in the emergency department, led to the birth of a viable baby, with long-term survivor, is described. A postmortem cesarean section, resulting in fetal survival, performed after 45 minutes of maternal cardiopulmonary resuscitation is reported in a patient with multiple penetrating injuries. A 27-year-old primigravida suffered cardiopulmonary arrest at the 34th week of gestation following multiple knife injuries. Although extensive advanced cardiopulmonary resuscitation was performed for 45 minutes, her vital signs did not return to normal levels. A low segment cesarean delivery was performed, and a female baby was delivered. The time interval between cardiopulmonary arrest and delivery, prior maternal health status, and continued cardiopulmonary resuscitation are important determinants of fetal survival. A perimortem cesarean section is advised in case of multiple penetrating injuries, even after 45 minutes of cardiopulmonary resuscitation, since it may result in fetal salvage.
Cuma, M. Ugras,Teke, Ahmet,Meral, M. Emin,Bayindir, K. Cagatay,Tumay, Mehmet The Korean Institute of Power Electronics 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.2
The most common power quality problems in distribution systems are related to unbalanced voltage sags. Voltage sags must be detected quickly and corrected in a minimum amount of time. One of the most widely used methods for sag detection is based on the d-q transformation. This method has the disadvantage of missing the detection of unbalanced faults, because this method uses a voltage sag level signal obtained from the average of 3 phases for sag detection. In this paper, an adaptive filter sag detection method is proposed for Dynamic Voltage Restorers (DVR) under unbalanced fault conditions. The proposed DVR controller is able to detect balanced, unbalanced and single phase voltage sags. A novel reference voltage generation method is also presented. To validate the proposed control methods, a 3-phase DSP controlling a DVR prototype with a power rating of 1.5-kVA has been developed. Finally, experimental results are presented to verify the performance of the proposed control methods.
M. Ugras Cuma,Ahmet Teke,M. Emin Meral,K. Cagatay Bayindir,Mehmet Tumay 전력전자학회 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.2
The most common power quality problems in distribution systems are related to unbalanced voltage sags. Voltage sags must be detected quickly and corrected in a minimum amount of time. One of the most widely used methods for sag detection is based on the d-q transformation. This method has the disadvantage of missing the detection of unbalanced faults, because this method uses a voltage sag level signal obtained from the average of 3 phases for sag detection. In this paper, an adaptive filter sag detection method is proposed for Dynamic Voltage Restorers (DVR) under unbalanced fault conditions. The proposed DVR controller is able to detect balanced, unbalanced and single phase voltage sags. A novel reference voltage generation method is also presented. To validate the proposed control methods, a 3-phase DSP controlling a DVR prototype with a power rating of 1.5-kVA has been developed. Finally, experimental results are presented to verify the performance of the proposed control methods.
Transient response of functionally graded non-uniform cylindrical helical rods
Yavuz C. Cuma,Faruk Firat Calim 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.4
This paper have the objective of investigating forced vibration behaviour of axially functionally graded cylindrical helices with variable cross-section. An algorithm is developed in order to solve corresponding problems. The ordinary differential equations governing the dynamic behaviour of cylindrical helices are determined in Laplace domain by using Timoshenko beam theory. Then transfer matrix method is implemented for the solution, including shear and axial deformation effects. Obtained results are transferred to time domain using Durbin’s modified numerical inverse algorithm for Laplace transform. A benchmark problem has been solved to check the accuracy of developed algorithm then a parametric study is conducted considering the effects of material gradient index ( ), section variation parameter ( ) and number of active turns ( ). Results are compared with solutions attained from ANSYS for verification
Mechanical Behaviour of Non-Oxide Boride Type Ceramics Formed on The AISI 1040 Plain Carbon Steel
Sen, Saduman,Usta, Metin,Bindal, Cuma,UciSik, A.Hikmet The Korean Ceramic Society 2000 The Korean journal of ceramics Vol.6 No.1
A series experiments were performed to evaluate mechanical behavior of non-oxide boride type ceramics formed on the AISI 1040 plain carbon steel. Boronizing was performed in a slurry salt bath consisting of borax, boric acid, and ferro-silicon at $950^{\circ}C$ for 2-6h. The AISI 1040 steel used as substrate material was containing 0.4%C, 0.13%Si, 0.65%Mn, 0.02%P, 0.014%S. The presence of non-oxide boride type ceramics $Fe_2B $ and FeB formed on the surface of steel was confirmed by metallographic technique and X-ray diffraction (XRD) analysis. The hardness of borides measured via Vickers indenter with a load of 2N reached a microhardness of up to 1800 DPN. The hardness of unborided steel was 185 DPN. The fracture toughness of borides measured by means of Vickers indenter with a load of 10N was about 2.30 MPa.$m^{1/2}$. The thickness of boride layers ranged from 72$\mu\textrm{m}$ to 145$\mu\textrm{m}$. Boride layers have a columnar morphology.
이종네트워크에서 펨토셀의 스펙트럼 공유할당 비용 최적화 알고리즘
박상혁 ( Sang Hyuk Park ),맹세영 ( Seayoung Myeong ),라지브 ( Rajeev ),쿠마 ( Cuma ),원종호 ( Jongho Won ),바트 ( Bate ),김경호 ( Gyeongho Kim ),이연우 ( Yeonwoo Lee ) 한국정보처리학회 2013 한국정보처리학회 학술대회논문집 Vol.20 No.2
본 논문에서는 최근 주파수 자원에 대한 수요가 급증하면서 효율적으로 주파수를 이용하기 위해 주파수 공유를 하면서 생길 수 있는 비용문제의 최고의 이득을 발생시킬 수 있도록 하기 위하여 이종 네크워크(Heterogeneous Network)에서 매크로셀과 펨토셀 환경에서 스펙트럼 공유에 있어서 매크로셀이 사용하지 않는 스펙트럼을 펨토셀에 공유해줌으로써 이득을 취할 수 있는데 이러한 이득에 있어서 최고의 이득을 발생시킬 수 있도록 하기 위하여 펨토셀의 스펙트럼 공유당 비용 최적화 알고리즘을 제안 하였다.