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Yang, Seo-Yun,Lee, Jae-Jin,Lee, Jin-Hee,Lee, Kyungeun,Oh, Seung ,Hoon,Lim, Yu-Mi,Lee, Myung-Shik,Lee, Kong-Joo Portland Press Ltd. 2016 Biochemical journal Vol.473 No.12
<P>Secretagogin (SCGN), a Ca2+-binding protein having six EF-hands, is selectively expressed in pancreatic beta-cells and neuroendocrine cells. Previous studies suggested that SCGN enhances insulin secretion by functioning as a Ca2+-sensor protein, but the underlying mechanism has not been elucidated. The present study explored the mechanism by which SCGN enhances glucose-induced insulin secretion in NIT-1 insulinoma cells. To determine whether SCGN influences the first or second phase of insulin secretion, we examined how SCGN affects the kinetics of insulin secretion in NIT-1 cells. We found that silencing SCGN suppressed the second phase of insulin secretion induced by glucose and H2O2, but not the first phase induced by KCl stimulation. Recruitment of insulin granules in the second phase of insulin secretion was significantly impaired by knocking down SCGN in NIT-1 cells. In addition, we found that SCGN interacts with the actin cytoskeleton in the plasma membrane and regulates actin remodelling in a glucose-dependent manner. Since actin dynamics are known to regulate focal adhesion, a critical step in the second phase of insulin secretion, we examined the effect of silencing SCGN on focal adhesion molecules, including FAK (focal adhesion kinase) and paxillin, and the cell survival molecules ERK1/2 (extracellular-signal-regulated kinase 1/2) and Akt. We found that glucose-and H2O2-induced activation of FAK, paxillin, ERK1/2 and Akt was significantly blocked by silencing SCGN. We conclude that SCGN controls glucose-stimulated insulin secretion and thus may be useful in the therapy of Type 2 diabetes.</P>
An investigation of energy efficiency of a wheel loader with automated manual transmission
Kwangseok Oh,Seung Jae Yun,Kyungeun Ko,김판영,Jaho Seo,Kyongsu Yi 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.7
This paper describes an investigation of energy efficiency by applying an advanced powertrain system in a conventional wheel loader. A conventional powertrain of a wheel loader consists of an engine, torque converter and transmission. A torque converter in a conventional system generally causes a significant amount of energy loss, as determined by analyzing energy flow based on V-pattern working. To prevent energy loss in a torque converter, Automated manual transmission (AMT) was proposed and modeled in this paper as an advanced powertrain. A wheel loader based on AMT does not need to use a torque converter since the single clutch system is used between the engine and transmission with subsystems of engine controller, clutch actuator and controller. A simplified single clutch system and controller were constructed for V-pattern working of a wheel loader. Additionally, a PI-controller was used as a control algorithm for engine speed control to prevent energy loss while the clutch is not engaged. All simulation models have been constructed in the Matlab/Simulink environment, and simulation studies were conducted by using a simulation model of a wheel loader with a driver model based on V-pattern working. Simulation results of the AMT-based wheel loader were analyzed by comparison with the results of the torque converter-based wheel loader, and the results show that the AMT-based wheel loader is more energy efficient than the conventional wheel loader.
오광석(Kwangseok Oh),윤승재(Seungjae Yun),김학구(Hakgu Kim),고경은(Kyungeun Ko),이경수(Kyongsu Yi) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.5
본 논문은 Matlab/simulink 기반 휠로더 시뮬레이션 모델의 개발과 검증에 대한 논문이다. 휠로더 시뮬레이션 모델의 개발 및 검증은 실제 휠로더의 생산단계에 앞서 휠로더의 성능을 평가하고 개선하기 위한 목적을 두고 있다. 휠로더 시뮬레이션 모델은 전체적으로 주행부/유압부 동력전달계 모델, 주행부/작업장부 동역학 모델을 포함한 4 가지 모델로 나뉘어져 있다. 휠로더의 주행 및 작업성능을 평가하고 개선하기 위해서는 언급된 4 가지 모델의 통합 시뮬레이션이 필요하며 통합된 시뮬레이션 모델은 성능평가 외의 연료효율의 최적화, 하이브리드 시스템 및 지능형 휠로더 모델의 개발로써 작업효율 향상에 기여할 수 있을 것이다. 본 논문에 제안된 시뮬레이션 모델은 주행부와 작업부 실험 데이터와의 비교를 통해 검증 되었다. This paper presents the development and validation of a wheel loader simulation model. The objective of doing so is to evaluate the performance of the wheel loader and improve its overall performance using Matlab/Simulink. The wheel loader simulation model consists of 4 parts: mechanical/hydraulic powertrain model and vehicle/working dynamic model. An integrated simulation model is required to evaluate and improve the performance of the wheel loader. It is expected that this model will be applied to fuel economizing, improving the pace of operation by using the hybrid system, and the intelligent wheel loader. The performance of the proposed simulation model has been validated by using Matlab/Simulink to compare the driving and the working experimental data.
Biocompatability of carbon nanotubes with stem cells to treat CNS injuries
Kiran Kumar Bokara,Jong Youl Kim,Young Il Lee,Kyungeun Yun,Tom J Webster,Jong Eun Lee 대한해부학회 2013 Anatomy & Cell Biology Vol.46 No.2
Cases reporting traumatic injuries to the brain and spinal cord are extended range of disorders that affect a large percentage of the world's population. But, there are only few effective treatments available for central nervous system (CNS) injuries because the CNS is refractory to axonal regeneration and relatively inaccessible to many pharmacological treatments. The use of stem cell therapy in regenerative medicine has been extensively examined to replace lost cells during CNS injuries. But, given the complexity of CNS injuries oxidative stress, toxic byproducts, which prevails in the microenvironment during the diseased condition, may limit the survival of the transplanted stem cells affecting tissue regeneration and even longevity. Carbon nanotubes (CNT) are a new class of nanomaterials, which have been shown to be promising in different areas of nanomedicine for the prevention, diagnosis and therapy of certain diseases, including CNS diseases. In particular, the use of CNTs as substrates/scaffolds for supporting the stem cell differentiation has been an area of active research. Single-walled and multi-walled CNT's have been increasingly used as scaffolds for neuronal growth and more recently for neural stem cell growth and differentiation. This review summarizes recent research on the application of CNT-based materials to direct the differentiation of progenitor and stem cells toward specific neurons and to enhance axon regeneration and synaptogenesis for the effective treatment of CNS injuries. Nonetheless, accumulating data support the use of CNTs as a biocompatible and permissive substrate/scaffold for neural cells and such application holds great potential in neurological research.