• Nuclear Engineering and Technology
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• 제49권3호
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• pp.504-516
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• 2017

The Jordan Research and Training Reactor (JRTR) is the first research reactor in Jordan, the commissioning of which is ongoing. The reactor is a 5-MWth, open-pool type, light-water-moderated, and cooled reactor with a heavy water reflector system. The neutron measurement system (NMS) applied to the JRTR employs a wide-range fission chamber that can cover from source range to power range. A high-sensitivity boron trifluoride counter was added to obtain more accurate measurements of the neutron signals and to calibrate the log power signals; the NMS has a major role in the entire commissioning stage. However, few case studies exist concerning the application of the NMS to a research reactor. This study introduces the features of the NMS and the boron trifluoride counter in the JRTR and shares valuable experiences from lessons learned from the system installation to its early commissioning. In particular, the background noise relative to the signal-to-noise ratio and the NMS signal interlock are elaborated. The results of the count rates with the neutron source and the effects of the discriminator threshold are summarized.

• 정보보호학회논문지
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• 제30권6호
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• pp.1237-1246
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• 2020

최근 마이크로 아키텍처의 취약점을 이용하여 내부의 비밀 정보를 노출시키는 캐시 부채널 공격들이 제안되었다. 캐시 부채널 공격 중 Flush+Reload 공격은 높은 해상도와 낮은 노이즈 특성으로 인해 여러 악의적 응용 공격에 활용되고 있다. 본 논문에서는 CPU 캐시 활동을 관측할 수 있는 PCM(Performance Counter Monitor) 기능을 이용하여 캐시 기반 부채널 공격을 찾아낼 수 있는 탐지기를 구현하였다. 특히, Spectre 공격과 AES 암호 연산 중 비밀 키 추출 공격이 발생했을 때를 가정하여 PCM 카운터 값의 변화를 관측하였다. 실험 결과, PCM의 4가지 카운터 특성이 캐시 부채널 공격에 크게 반응함을 확인하였고, SVM(Support Vector Machine). RF(Random Forest), MLP(Multi Level Perceptron)와 같은 머신 러닝 기반 검출기를 통해 높은 정확도로 캐시 부채널 공격을 탐지할 수 있었다.

• 항공우주시스템공학회지
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• 제15권3호
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• pp.30-44
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• 2021

동축 반전 프로펠러는 기존의 단일 프로펠러와 달리 추가적인 설계 변수의 증가로 인해 실험적 성능평가에 비용과 시간 측면에서 여러 제약이 따른다. 또한 상/하단 프로펠러 사이의 상호 간섭으로 인하여 수치 해석에 있어서도 많은 시간과 자원이 요구된다. 본 연구에서는 시간 효율적인 수치해석기법인 actuator 기법을 활용하여 제자리 비행하는 동축 반전 프로펠러의 공력 성능에 관한 수치적 연구를 수행하였다. 상용 CFD 코드인 ANSYS Fluent 결과와 비교하여 해석기법의 정확성을 검증하였다. 해석 변수로는 동축 반전 프로펠러의 축 간극과 회전속도를 선정하였으며, 다양한 조건에서 동축 반전 프로펠러의 공력 성능을 획득하였다. 획득한 공력 성능을 바탕으로 단일 프로펠러와 동축 반전 프로펠러의 제자리 비행 효율 계수를 획득하고, 단일 프로펠러의 성능으로 동축 반전 프로펠러의 성능을 예측할 수 있는 예측 인자를 도출하여 actuator 기법의 활용성을 평가하였다.

• 한국정밀공학회지
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• 제18권3호
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• pp.90-98
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• 2001

In this paper, the development of exclusive control valve for improving the performance of truck cab tilting system is discussed. Cab tilting system is implemented to the heavy truck for the convenience of driver. However when tilting up or down, sudden swing of cab has brought discredit on user. To improve this phenomena it is inevitable to use counter balance valve. But because of high pressure and low flow characteristic, general counter balance valve is unsuitable to cab tilting system. Therefore, this paper presents the developments of exclusive return pressure control valve which prevents sudden swing of cab and verify the validity of design through the computer simulation.

• 유공압시스템학회논문집
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• 제5권1호
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• pp.13-19
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• 2008

The typical hydraulic system of hoist is composed of a hydraulic supply unit, a directional control valve, counter balance valve, and flow control valves. The flow capacity coefficients of flow control valves should be adjusted so that the hoist is operated at moderate speed and the hydraulic energy loss is minimized. However, it is difficult to adjust the flow coefficients of flow control valves by trial and error for optimal operation. Here, the steady state model of the hoist hydraulic system including the differential cylinder circuit is derived and the optimal flow capacity coefficients of flow control valves are obtained using the complex method that is one kind of constrained direct search method.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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• pp.255-258
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• 2005

In this study, new types of counter electrode discharge cells for PDP were designed. The counter electrode discharge cells were designed to realize long-gap discharge mode, low firing voltage and moderate conductance for evacuation and sealing process of the panel. In order to test the concept of the design, macro discharge cells were prepared and the discharge characteristics were evaluated. The results indicate that discharge behavior may be modified significantly by changing the morphology of discharge cells.

• 전자공학회논문지D
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• 제35D권12호
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• pp.53-58
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• 1998

다결정 실리콘 박막 트랜지스터를 이용한 회로의 성능 향상을 위하여 새로운 구조의 4-terminal buried channel poly-Si TFT(BCTFT)를 설계하고 제작하였다. BCTFT는 moderate 도핑이 된 buried channel을 이용하므로 기존의 다결정 실리콘 TFT보다 ON-전류와 전계 효과 이동도가 n-형과 p-형 소자 각각 5배와 10배 향상되었다. BCTFT는 moderate 도핑된 buried 채널과 counter 도핑된 body 사이의 junction 공핍에 의하여 캐리어의 이동이 억제 되므로 OFF-전류가 증가하지 않았다.

• 설비공학논문집
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• 제11권5호
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• pp.598-604
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• 1999

The thermal performance of cooling towers is affected by the temperature of inlet water, wet bulb temperature of entering air add water-air flow rate. In this study, the effects of these variables are simulated using NTU-method and experimentally investigated for the counter-flow cooling towers. The simulation program to evaluate these variables which affect the performance of cooling tower was developed. The maximum errors between the results of simulations and experiments were 3.8% under the standard design conditions and 5.4% under the other conditions. The performance was increased up to 46~50% as the water loading was increased from $6.8m^3$/$hr\cdot m^2$ to $15.9m^3$/$hr\cdot m^2$. The range was reduced up to 56~42% when the wet bulb temperature of the entering air was increased from $22^{\circ}C\; to\; 29^{\circ}C.$

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.192.1-192.1
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• 2010

Micro hydraulic turbines take a growing interest because of its small and simple structure as well as high possibility of applying to micro and small hydropower resources. The differential pressure exiting within the city water pipelines can be used efficiently to generate electricity like the energy generated through gravitational potential energy in dams. In order to reduce water pressure at the inlet of water cleaning centers, pressure reducing valves are used widely. Therefore, pressure energy is wasted. Instead of using the pressure reduction valve, a micro counter-rotating hydraulic turbine can be replaced to get energy caused by the large differential pressure found in the city water pipelines. In this paper, detail studies have been carried out to acquire basic design data of micro counter-rotating hydraulic turbine, output power, head, and efficiency characteristics on various number of runner vane. Moreover, the influences of pressure, tangential and axial velocity distributions on turbine performance are also investigated.

• 유통과학연구
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• 제16권2호
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• pp.25-33
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• 2018

Purpose - This study focused on the effect of counter-factual thinking on post-purchase behavior producing consumer regret at HMR selection and purchase. We have analyzed the factors that HMR production and distribution businesses should consider because distribution and marketing strategy reflecting consumers' demand. Research design, data, and methodology - For the purpose of carrying out this research, we conducted a direst structured questionnaire to students at 'J' college. A total of 237 valid questionnaires were collected for students and their parents at 'J' university. For the hypothesis test, exploratory factor analysis, t-test, regression and structure equation path analysis were performed. Results - The consumers who often resented HMR purchase did counter-factual thinking on post-purchase behavior were likely to do switching purchases. Counter-factual thinking on post-purchase behavior had a negative influence upon consumer's satisfaction with HMR safety and marketing characteristics. Conclusions - Consumers who had been satisfied to a certain degree might have cognitive dissonance of minor mistakes of HMR product were likely to have downward counter-factual thinking through contrast effects. Therefore, HMR producer and distribution businesses that had production, distribution and marketing strategy to satisfy consumers by raw material, freshness and safety were likely to switch to another product at one time mistake of selection, purchase and use.