• Journal of Power Electronics
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• 제18권2호
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• pp.482-491
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• 2018

The practical design methodology of a three-phase dual active bridge (3ph-DAB) converter applied to low voltage direct current (LVDC) applications is proposed by using a mathematical model based on the steady-state operation. An analysis of the small-signal model (SSM) is important for the design of a proper controller to improve the stability and dynamics of the converter. The proposed lead-lag controller for the 3ph-DAB converter is designed with a simplified SSM analysis including an equivalent series resistor (ESR) for the output capacitor. The proposed controller can compensate the effects of the ESR zero of the output capacitor in the control-to-output voltage transfer function that can cause high-frequency noises. In addition, the performance of the power converter can be improved by using a controller designed by a SSM analysis without additional cost. The accuracy of the simplified SSM including the ESR zero of the output capacitor is verified by simulation software (PSIM). The design methodology of the 3ph-DAB converter and the performance of the proposed controller are verified by experimental results obtained with a 5-kW prototype 3ph-DAB converter.

• 대한기계학회논문집B
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• 제22권4호
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• pp.450-467
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• 1998

The characteristics of the unstable impinging circular jet is investigated based on the frequency characteristics and the sound field of the impinging-tones. Two symmetric modes S1 and S2, associated with low frequency and high frequency respectively, and one helical mode H have been observed. At low speed the S2 mode is dominant and switched by the S1 mode as the speed increases. When the jet speed is high the S1 mode is very active over the impinging distance from half the nozzle diameter to its ten times, while the S2 mode occurs at shorter distance corresponding to stage 2 and 3. The helical mode H seems unstable, likely to be influenced much by the experimental environment, and occurs at relatively high speed with almost the same frequency characteristics as the S2 mode. By estimating the convection speed of the unstable jet, it is found that the ratio of the convection speed to the jet speed decreases with both Strouhal number and Reynolds number and the speed of S2 mode is faster than the Si mode. When the present experimental results are compared with the previous investigations performed for the hole tone and the impinging tone with a small plate, the S1 mode is found to be associated with the ring vortex of large diameter with low speed, but the S2 mode with the vortex of small diameter with high speed. In addition, the frequency is found to be influenced by the nozzle configuration but the characteristics is almost the same. From the impinging distance and frequency range, it can be deduced that S1 mode is related with the jet column mode and S2 mode with the shear mode.

• 한국지역사회생활과학회지
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• 제27권spc호
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• pp.651-663
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• 2016

This study explores the background and the processes underpinning the educational reform movement based on local community. This educational community initiated the alternative education reform movement, which is referred to as the small school movement. A qualitative case study was implemented by collecting data from thirty articles, three focused interviews. This study drew out three key factors as the operation of educational community in regional area. First, it claimed a total of 30 papers related to the educational community for content analysis. Second, key words were derived in the local educational community context. They developed their own alternative educational programs, such as self-supportive meeting, season carnivals, community revitalization activities, and so on. Their focus was on finding out and establishing better educational relationships among the concerned communities. Third, the community continues to reinforce the internal rules and climate through meta-education, a process, in which education educates itself. As a result, they could enjoy substantial success in a visible educational community. This small school revival movement later grew into the new school movement. Furthermore, a variety of teachers, parents groups, and interested scholars have been engaged in the community movement through professional networking. This study suggests that the key innovator-initiated movement, which involves education reform, upgraded Korean education, and improved their own expertise and autonomy, is expected to be the first step to solve the current Korean educational problems by the educational community.

• 대한기계학회논문집B
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• 제34권9호
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• pp.817-824
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• 2010

본 연구에서는 개선된 액막 분열 모델을 개발하였고 그에 따른 계산격자 의존성을 고찰하였다. 액막 및 액적 추적을 위해 라그랑지-오일러 액적 추적 모델을 사용하였기 때문에 계산격자의 크기에 한계가 있으므로 매우 작은 격자를 사용하는데 제약을 받는다. 또한 유동장내로의 분사기의 액막 주입 시선회유동이 존재하므로 선회 유동을 정확히 예측하기 위해서는 계산격자가 충분히 작아야 한다. 이러한 상반된 조건으로부터 두 목적을 달성하기 위해 10$\times$10mm부터 0.625$\times$0.625mm까지 다양한 계산격자를 구성하여 수치적 고찰을 수행하였고 가장 효율적인 격자의 크기는 1.25$\times$1.25mm인 것을 알 수 있었다.

• 한국산업보건학회지
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• 제19권4호
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• pp.328-334
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• 2009

There are various methods for welding fume control. These methods can be divided into local exhaust system, general ventilation system and integrated control system. With the general ventilation system, we should have a good prediction tool for testing various appropriate control options. But, until now there are not many studies about how to predict the welding fume concentrations. Especially, the prediction of welding fume concentration is not a very easy task because welding fume is the particulate matters. In this study, we tried to measure $CO_2$ concentrations and welding fume concentrations in a small single room with a small ventilation opening. Using commercially available CFD (Computational Fluid Dynamics) software, we tried to predict $CO_2$ concentrations under the exactly same conditions. Then, we tried to compare the numerical $CO_2concentrations$ with the experimental results to know whether we could predict $CO_2$ concentrations. Then we tried to compare $CO_2$ concentrations with experimental welding fume concentrations to know whether we can use the numerical $CO_2concentrations$ to predict the welding fume concentration indirectly.

• Asian Pacific Journal of Cancer Prevention
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• 제13권5호
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• pp.2157-2162
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• 2012

Objective: The PI3K/PTEN/AKT/mTOR signaling pathway has been implicated in resistance to cisplatin. In the current study, we determined whether common genetic variations in this pathway are associated with platinum-based chemotherapy response and clinical outcome in advanced non-small cell lung cancer (NSCLC) patients. Methods: Seven common single nucleotide polymorphisms (SNPs) in core genes of this pathway were genotyped in 199 patients and analyzed for associations with chemotherapy response, progression-free survival (PFS) and overall survival (OS). Results: Logistic regression analysis revealed an association between AKT1 rs2494752 and response to treatment. Patients carrying heterozygous AG had an increased risk of disease progression after two cycles of platinum-based chemotherapy compared to those with AA genotype (Adjusted odds ratio (OR)=2.18, 95% confidence interval (CI): 1.00-4.77, which remained significant in the stratified analyses). However, log-rank test and cox regression detected no association between these polymorphisms in the PI3K pathway genes and survival in advanced NSCLC patients. Conclusions: Our findings suggest that genetic variants in the PI3K/PTEN/AKT/mTOR pathway may predict platinum-based chemotherapy response in advanced NSCLC patients in a Chinese population.

• Asian Pacific Journal of Cancer Prevention
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• 제14권2호
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• pp.701-705
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• 2013

Polymorphisms in XPG are considered to contribute to the clinical outcome of patients receiving platinum drug chemotherapy. We aimed to investigate the role of five potential SNPs of XPG gene on the response to platinum-based chemotherapy in advanced Chinese NSCLC patients. A total of 451 patients with newly diagnosed and histopathologically confirmed primary NSCLC were consecutively collected. XPG rs2296147, rs4150261, rs17655, rs1047768 and rs2094258 were genotyped by the Taqman real-time polymerase chain reaction (PCR). In our study, we found patients carrying rs1057768 TT genotype had a significantly lower treatment response when compared with the CC genotype (OR=0.38, 95% CI=0.18-0.78). Patients carrying rs1047768 TT genotype showed a significantly short median PFS (11.2 months) and OS (13.6 months) than CC genotype, and the hazard ratios (HR) for PFS and OS were 2.06 (1.01-4.50) and 2.29 (1.21-2.49), respectively. Moreover, we found a significant decreased risk of death from NSCLC among patients carrying the rs2296147 TT genotype when compared with the CC genotype, the HR (95% CI) for OS being 0.50 (0.27-0.95). In conclusion, our study found that polymorphisms in rs1047768 C/T and rs2296147 C/T are associated with response to platinum-based chemotherapy in advanced NSCLC, and XPG polymorphisms could be predictive of prognosis.

• 한국산학기술학회논문지
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• 제18권12호
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• pp.423-433
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• 2017

오늘날 기업은 내부 기능 간 협력만으로는 경쟁우위를 달성하기 어려운 실정이다. 또한, 기업이 속한 공급사슬 즉, 공급자와 고객에 이르는 참여자들과 협력하여 공급사슬의 프로세스를 통합하는 것이 중요하다. 이에 따라 본 연구는 중소 벤처기업의 공급사슬 탐색 및 활용전략이 조직역량과 기업운영성과에 미치는 영향력을 밝히는데 목적을 갖고 부산 지역 소재 중소 벤처기업 298개 업체의 중간 관리자를 대상으로 설문조사 방법을 통해 조사하였다. 실증분석 결과 공급사슬 탐색 및 활용전략이 조직역량과 기업 운영성과에 긍정적인 영향을 미쳐 가설은 모두 채택되었다. 그리고 조직역량이 공급사슬 탐색 전략과 활용전략에 따른 기업운영성과의 매개효과에 있어서도 긍정적인 영향을 미쳐 공급사슬 전략으로서의 탐색과 활용이 조직역량의 결집을 통해 기업성과를 높여주는 매개변수로서의 촉진요인임을 확인시켜 주었다. 이 같은 결과는 공급사슬 전략의 탐색과 활용이 조직과 기업 성과를 높이는 촉진 변수로서의 역할과 동시 중소 벤처기업의 공급 사슬 전략이 적극 응용될 필요가 있음을 시사한 것으로 평가할 수 있다.

• Current Photovoltaic Research
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• 제2권2호
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• pp.59-62
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• 2014

Minority carrier diffusion length is one of the most important parameters of solar cells, especially for short circuit current density (Jsc). In this report, we proposed the calculating method of the minority carrier diffusion length ($L_n$) in CIGS solar cells through biased quantum efficiency (QE). To verify this method's reliability, we chose two CIGS samples which have different grain size and calculated $L_n$ for each sample. First of all, we calculated out that $L_n$ was 56nm and 97nm for small and large grain sized-cell through this method, respectively. Second, we found out the large grain sized-cell has about 7 times lower defect density than the small grain sized-cell using drive level capacitance profiling (DLCP) method. Consequently, we confirmed that $L_n$ was mainly affected by the micro-structure and defect density of CIGS layer, and could explain the cause of Jsc difference between two samples having same band gap.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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• pp.205-206
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• 2000

The capacitance-temperature (C-T) measurement technique is proposed in the present work to investigate the thermal stability of organic and polymeric thin films for organic electroluminescent display (OELD). The single layer devices with the individual materials were subjected to the C-T measurement, prior to the examination of the complete OELD. The single layer devices with the small molecules destroyed below $180\;^{\circ}C$ depending on the kinds of materials. However, the device with the hole-transporting polyimide did not show any relaxation up to $200\;^{\circ}C$. The small molecule based OELDs failed to emit light after annealing, whereas that with the hole-transporting polyimide worked well in spite of large reduction in intensity.