• Journal of Electrical Engineering and Technology
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• 제2권2호
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• pp.145-151
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• 2007

Electric load components have different characteristics according to the variation of voltage and frequency. This paper presents the load modeling of an electric locomotive by the parameter identification method. The proposed method for load modeling is very simple and easy for application. The proposed load model of the electric locomotive is represented by the combination of the loads that have static and dynamic characteristics. This load modeling is applied to the KTX in Korea to verify the effectiveness of the proposed method. The results of proposed load modeling by the parameter identification follow the field measurements very exactly.

• Clinical and Experimental Reproductive Medicine
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• 제50권4호
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• pp.213-222
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• 2023

Cryopreservation is an option for the preservation of pre- or post-pubertal female or male fertility. This technique not only is beneficial for human clinical applications, but also plays a crucial role in the breeding of livestock and endangered species. Unfortunately, frozen germ cells, including oocytes, sperm, embryos, and spermatogonial stem cells, are subject to cryoinjury. As a result, various cryoprotective agents and freezing techniques have been developed to mitigate this damage. Despite extensive research aimed at reducing apoptotic cell death during freezing, a low survival rate and impaired cell function are still observed after freeze-thawing. In recent decades, several cell death pathways other than apoptosis have been identified. However, the relationship between these pathways and cryoinjury is not yet fully understood, although necroptosis and autophagy appear to be linked to cryoinjury. Therefore, gaining a deeper understanding of the molecular mechanisms of cryoinjury could aid in the development of new strategies to enhance the effectiveness of the freezing of reproductive tissues. In this review, we focus on the pathways through which cryoinjury leads to cell death and propose novel approaches to enhance freezing efficacy based on signaling molecules.

• BMB Reports
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• 제49권4호
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• pp.220-225
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• 2016

Cancer cells have different characteristics due to the genetic differences where these unique features may strongly influence the effectiveness of therapeutic interventions. Here, we show that the spontaneous reactivation of extracellular signalregulated kinase (ERK), distinct from conventional ERK activation, represents a potent mechanism for cancer cell survival. We studied ERK1/2 activation in vitro in SW480 colorectal cancer cells. Although ERK signaling tends to be transiently activated, we observed the delayed reactivation of ERK1/2 in epidermal growth factor (EGF)-stimulated SW480 cells. This effect was observed even after EGF withdrawal. While phosphorylated ERK1/2 translocated into the nucleus following its primary activation, it remained in the cytoplasm during late-phase activation. The inhibition of primary ERK1/2 activation or protein trafficking, blocked reactivation and concurrently increased caspase 3 activity. Our results suggest that the biphasic activation of ERK1/2 plays a role in cancer cell survival; thus, regulation of ERK1/2 activation may improve the efficacy of cancer therapies that target ERK signaling.

• 대한화장품학회지
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• 제37권3호
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• pp.275-282
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• 2011

MC1R의 길항제 역할을 하는 펩타이드와 tyrosinase를 저해하는 효능을 가지는 천연유래 물질을 유도체화하여 신규 미백소재를 개발하였다. 또한 이러한 새로운 기작에 의한 미백 효능을 평가할 수 있는 방법을 cAMP 신호전달 과정을 활용하여 제시하였다. 총 24종의 유도체를 합성하였고, cAMP assay의 결과를 통해 11종의 유도체를 선별하였으며, 선별된 유도체에 대하여 멜라닌 형성 억제 효능을 평가하여 본 평가 방법의 유효성을 확인하였다. 이 과정에서 RW를 서열에 포함하는 펩타이드 유도체가 특별히 멜라닌 형성 억제 효능이 높은 것을 알 수 있었다. 또한, cAMP assay는 MC1R의 antagonist라는 특정 타겟 물질을 디자인한 소재의 스크리닝 방법에는 활용할 수 있음을 알 수 있었다. 하지만, 미백소재로서의 가능성을 확인하기 위해서는 멜라닌 생성저해 시험과 병행하여야 할 것으로 판단된다.

• Journal of Microbiology and Biotechnology
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• 제33권3호
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• pp.339-347
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• 2023

Transforming growth factor-β is a key factor in regulating adhesion formation during tendon healing. We investigated the effectiveness of SMAD family members, SMAD7 and SMAD3, in the TGF-β/Smad signaling during flexor tendon repair. Mouse flexor toe deep tendon rupture anastomosis models were made. On days 3, 7, 14, 21, and 28, the expressions of smad7 and smad3 in flexor tendon tissues were detected by RT-qPCR and western blot. Furthermore, postoperative intraperitoneal injections of SMAD7 agonists or SMAD3 antagonists were given. The degree of tendon healing was evaluated by adhesion testing and biomechanical experiments. Hematoxylin and eosin (HE) staining was used to observe the pathological changes. Immunohistochemistry was used to evaluate the expressions of collagen III, SMAD3, and SMAD7. The mRNA levels of matrix metalloproteinases, Mmp2 and Mmp9, and scleraxis (SCX) in flexor tendon tissue were detected by RT-qPCR. Smad3 expression increased and Smad7 expression decreased in flexor tendon tissue after injury. In addition, the SMAD7 agonist blocked SMAD3 phosphorylation. SMAD7 agonist and SMAD3 antagonist both improved adhesion formation during flexor tendon healing, and decreased the expressions of collagen III, Mmp9, and SCX, while increasing Mmp2 expression. This study provides a possible theoretical basis for the SMAD7-SMAD3 signal cascade during flexor tendon adhesion healing.

• 한국철도학회논문집
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• 제19권2호
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• pp.145-158
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• 2016

철도 신호 시스템의 안전 확보 기준으로 사용되는 안전무결성수준(SIL, Safety Integrity Level) 할당에 사용되는 기존 정성적 평가방법인 리스크 그래프에 대하여 소개하고, 정성적 평가의 문제점인 입력 변수의 모호성 및 안전무결성수준간 경계성 문제에 대하여 퍼지 이론 적용을 통해 문제점을 보완하는 것을 목적으로 한다. 본 모델의 퍼지 입력변수는 4가지인 심각도, 노출도, 회피도, 요구율로 구성되며, 퍼지추론(Fuzzy Inference)은 IEC 61511의 계량적 리스크 그래프를 적용하여 48개의 퍼지 규칙을 생성한다. 퍼지추론은 최대 최소 합성(Max-Min Composition)의 퍼지관계 합성연산을 적용한다. 추론 모델을 통해 도출된 최종적인 추론 결과는 퍼지 값이므로 실제 상황에 적용 가능하도록 다시 실수 값으로 변환하는 역 퍼지화 과정을 통해 최종 출력값인 안전무결성수준과 그에 해당하는 허용 해저드율을 생성하여, 최종적인 해당 해저드에 대한 안전성 요구사항을 도출한다. 마지막으로 본 평가모델 검증을 위해 CENELEC SC 9XA WG A10 보고서에 소개된 단선구간에서의 신호시스템을 대상으로 한 안전성 평가 결과와 비교한다.

• 한국산학기술학회논문지
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• 제19권11호
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• pp.574-582
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• 2018

철도, 자동차, 항공 등의 시스템에서는 시스템의 고장이 사고로 이어져 심각한 인명피해와 경제적 손실로 직결되는 경우가 많기 때문에 시스템 안전의 확보가 매우 중요하다. 기존 연구들에서는 구성품 수준의 정보를 활용해서 고장 분석 및 안전조치를 도출하고 이를 통해 고장이 발생했을 때 피해를 경감시키기 위한 안전설계가 주로 수행되었다. 그러나 기능안전 개념에 의한 설계는 위험원 식별 및 평가 그리고 안전기능을 생성한 후 안전 설계를 통해 안전 목표를 달성하고자 하는 것이다. 따라서 시스템의 기능수준에서 고장의 현재 빈도를 수용 가능한 목표수준으로 빈도를 낮출 수 있는 안전기능을 결정하고 이를 설계에 반영하기 위한 방법에 대한 연구가 필요하다. 이를 달성하기 위하여 본 연구에서는 먼저 시스템모델링 언어인 SysML을 활용하여 안전기능 들에 대해 고장빈도를 반영하기 위한 고장 모델링 방법을 연구하였다. 그리고 나서 생성된 SysML 고장모델 대안들의 시뮬레이션을 통해 각 안전기능 들이 달성할 수 있는 고장빈도의 감축능력을 평가해서 안전목표를 충족하는 대안을 결정하는 방법을 제시하였다. 사례 연구로서 대표적인 안전중시 시스템인 철도신호시스템에 적용하여 유용성을 확인하였다. 철도신호시스템의 안전기능 형태의 설계 대안들에 대해 안전 목표를 충족하는 지를 M&S를 통해 비교평가 하였다. 본 연구의 결과는 시스템의 개념설계 단계에서부터 적용 가능한 방법으로 안전기능을 수행하기 위한 다양한 설계대안 들 중에서 적절한 것을 선택함으로써 안전 목표를 충족하는 시스템의 안전 설계에 유용하게 활용될 수 있을 것이다.

• ETRI Journal
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• 제40권3호
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• pp.318-329
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• 2018

Femtocell (FC) technology envisaged as a cost-effective approach to attain better indoor coverage of mobile voice and data service. Deployment of FCs over macrocell forms a heterogeneous network. In urban areas, the key factor limits the successful deployment of FCs is inter-cell interference (ICI), which severely affects the performance of victim users. Autonomous FC transmission power setting is one straightforward way for coordinating ICI in the downlink. Application of intelligent control using soft computing techniques has not yet explored well for wireless networks. In this work, autonomous FC transmission power setting strategy using Adaptive Neuro Fuzzy Inference System is proposed. The main advantage of the proposed method is zero signaling overhead, reduced computational complexity and bare minimum delay in performing power setting of FC base station because only the periodic channel measurement reports fed back by the user equipment are needed. System level simulation results validate the effectiveness of the proposed method by providing much better throughput, even under high interference activation scenario and cell edge users can be prevented from going outage.

• 전기학회논문지
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• 제67권11호
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• pp.1549-1554
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• 2018

Recently the design of railway systems have been performed, based on the analysis of operational conditions and service targets, it is to optimize the effectiveness and efficiency of system operation. Many RAMS requirements have been developed to transform operation conditions into system design characteristics. However, our railway industry has not actived the application of RAMS into system design performance. According to short of RAMS application, many technologies that have been developed are not only applied the existing systems that is operating, but also have not succeed to apply for new systems. In order to design the effective and efficient railway systems that are optimized to operation conditions and service targets, a systems approach and RAMS management are necessary in railway development, operation and maintenance. Therefore, in this study, the RAMS performance requirement design methods are discussed. the allocation methods from system level to each devices of subsystems.

• 조명전기설비학회논문지
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• 제28권8호
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• pp.90-97
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• 2014

This paper presents a compensation method of unbalanced phase currents in interleaved bi-directional converters. Phase currents in interleaved bi-directional converter are apt to be unbalanced due to circuit parameter error and switch operation difference. This problem causes the switch element failure and the reduced efficiency of the converter. Therefore, it is necessary that a certain balance control algorithm is provided in interleaved bi-directional converter system. In this paper, a balance control algorithm based on the circular chain control method is proposed. Further, in order to reduce the number of phase current sensors, this paper shows a simple method in which phase currents can be extracted indirectly through a DC-link current sensor in both charging and discharging modes. The validity and the effectiveness of the proposed phase currents balance control algorithm are illustrated through the simulation results.