• Journal of Power System Engineering
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• v.8 no.1
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• pp.24-29
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• 2004

In this study, a computer analysis has been developed for predicting the pipe pressure of the intake and exhaust manifold. To obtain the boundary conditions for a numerical analysis, one dimensional and non-steady gas dynamic calculation is performed by using the MOC(Method Of Characteristic). The main numerical parameters are the variation of the engine revolution to calculate the pulsating flow which the intake and exhaust valves arc working. The comparison of exhaust pressure in case of numerical results is quite matched with in case of experimental results. When engine revaluation is increased, the pressure amplitude showed a high value, but the pressure frequency was decreased.

• Journal of the Korean Professional Engineers Association
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• v.10 no.1
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• pp.15-18
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• 1977

국내에서 현재 생산중인 산화방간 4종을 비롯한 기타 여러 지역에 부존된 산화망간 시료와 수입한 산화망간 7종류 중에서 이산화망간의 건전지에 대한 활성도를 각각 실험해 보았다. 실험 방법은 강알카리성에서 Hydrazine Sulfate의 환원력을 이용하여 Activity Index Value를 구하였다. 그 결과 이산화 망간으로 직접 건전지를 만들어 방전시킨 방전곡선과 또한 $\alpha$.$\beta$.${\gamma}$.등의 결정구조가 활성도에 미치는 영향과의 관계가 잘 일치함을 알 수 있고 지금까지는 건전지용 이산화망간의 활성도를 시험하기 위하여 직접 건전지를 제작하여 장시간의 방전시험을 하였던 것을 본 실험에 따르면 Activity Index Value만 측정하여 비교 검토만 하므로서 간단히 그리고 빠른시간 내에 이산화망간의 건전지에 대한 활성도를 확인 결정할 수 있다.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.230-230
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• 1999

PDP 미세면방전에서 방전의 전기, 광학적 특성을 이해하기 위해서는 근본적으로 면방전에 대한 기초적인 이해와 연구가 뒤따라야 한다. 따라서 본 연구에서는 일차적으로 방전 전극구조에서 방전 전압변화에 가장 중요한 변수인 방전 유지 전극 간격에 대해서 구동 진동수, 유전체 두께, 전극폭, MgO 보호막 두께 등과 같은 다른 변수들은 고정시켜 놓고 방전기체종류(Ne,Xe, He)와 Xe 기체혼합 비율 (1%, 4%, 7%등)에 따라서 방전유지 전극간격(50, 100, 150, 200$mu extrm{m}$)을 변화시켜가며 실험을 수행했다. 방전 유지 전극의 간격(d)이 좁을수록 방전개시(Vf), 유지 전압(Vs)은 낮아지고 전극간격을 점차로 넓게 하면 방전개시, 유진 전압이 높아지게 되는 즉 전극 간격에 따라서 가스 압력(P)에 따른 파센 최저방전 개시전압과 최저방전 유지전압 특성곡선이 존재함을 알 수 있었다. 또한 단일종의 기체를 사용했을 때 보다는 혼합기체를 사용했을 때 Penning effect에 의해서 방전 전압이 상대적으로 낮아지는 경향을 관측 할 수 있었으며, Xe 기체 혼합 비율에 따른 방전전압 특성 또한 관측하였다.

• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.116-123
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• 1997

세계적으로 수요가 증대하고 있는 고속선의 설계시 승선감 또는 내항성은 필수적으로 고려되어야 하는 중요요소이다. 고속선은 필연적으로 과도한 운동을 동반하며 그로 인해 승객들은 극심한 멀미와 구토 등 불쾌한 승선감을 경험하게 된다. 근래에 항공 및 육상 교통수단들의 고급화에 따라 해양 운항선사들도 선박품질의 고급화와 괘적한 승선감 확보에 비상한 관심을 보이며 승객 유치 및 승선률 제고를 도모하고 있다. 본 논문은 고속쌍동선에 대한 내항성능을 추정하고 그 해석결과를 실험과 비교하였다. 상하동요 및 종동요 간의 선형 연성 운동방정식을 사용하였고, 규칙파에 대한 상하동요의 응답특성 곡선을 구하였다. 또한 불규칙파에 대한 운동응답을 추정하기 위하여 ITTC파도 스펙트럼을 적용하였으며, 본 고속쌍동선의 운동성능에 미치는 선수 및 선수각의 영향을 고찰하였다.

• Journal of Welding and Joining
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• v.16 no.3
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• pp.74-84
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• 1998

The microstructures of the HAZ (Heat Affected Zone) are generally different from the base metal due to rapid thermal cycle during welding process. Particuraly, CGHAZ (Coarsened Grain Heat Affected Zone) near the fusion line is the most concerned region in which many metallurgical and mechanical discontinuities have been normally generated. A computer program by the numerical formularization of phase transformation during cooling with different rates was developed to generate the CCT diagram, and to predict microstructural (phase) changes in the CGHAZ. In order to verify simulated results, isothermal and continuous cooling transformation experiments were conducted. The simulated and experimental results showed that the developed computer model could successfully predict the room temperature microstructural changes (changes in volume fraction of phases) under various welding conditions (heat input & cooling rate $(Δt_{8/5})$).

• Korean Journal of Environment and Ecology
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• v.25 no.6
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• pp.861-866
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• 2011

Using skeletochronology in the Daejung-eup, Jeju, we determined the age structure of Kaloula borealis. The study was performed during the breed season in June 2009. We measured the snout-vent length(SVL) and body weigth(BW) and analyzed the age structure of 38 male and 58 female frogs. The mean value of SVL is $43.69{\pm}3.44mm$ in males and $46.32{\pm}4.23mm$ in females. The age at first reproduction was estimated to be 2 years of age in males and 3 years in females. The oldest males and females were 8 and 10 years of age, respectively. Therefore, the longevity in this species was estimated to be more than 8 years for males and 10 years for females. So, females live longer than males. Also, this difference between the male and the female in age structure was significant. We estimated the growth curve for Kaloula borealis using von Bertalanffy growth model. The growth coefficient (K) was 0.56 in male and 0.41 in female. The asymptotic size was 46.41 mm in male and 50.22 mm in female.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.221-227
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• 1996

Micellization range and cmc for the dilute aqueous solution of N-acyl amino acid type anionic surfactants, that is, sodium N-acyl-N-methyl-${\beta}$-alaninate, sodium N-acyl sarcosinate and sodium N-acyl-N-methyl taurate were investigated by computer programming. The extreme of the curvature of ${\sigma}(C)$ as a new suggested method to determine the cmc and the micellization range was accomplished with computer programming. The values of cmc and micellization range can be obtained by the extreme of the curve by direct processing of only a few experimental data. The values of cmc particulary was in good agreement with those deduced intuitively from the shape of experimental curves of ${\sigma}(C)$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3155-3160
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• 2010

Nowadays, most car manufactures have tried to improve fuel efficiency and corrosion resistance of car body. Therefore, use of high strength steels and coated steel becomes more and more increased. In this study, spot weld characteristics according to lap sequence of sheets were analyzed using simulation method for three different steel sheet of car body which were EDDQ class coated steel with 0.7t, high strength steel 440R with 1.2t and advanced high strength steel DP 590 with 1.0t. Using simulation, weldability was evaluated by nugget size of welded zone according to nugget growth curve and welding current with respect to lap sequence of sheets. Contact resistance of each sheets contact point was used to analyze formation of nugget and optimal lap sequence was suggested.

• International Journal of Highway Engineering
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• v.8 no.2 s.28
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• pp.87-93
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• 2006

To evaluate the deformational characteristics of subgrade soils, four subgrade samples in Korea were tested using the RC and TS tests with various dry unit weight and water content. Both the maximum modulus and normalized modulus reduction curves of subgrade soils were affected by the dry unit weight. The normalized modulus was decreased about 20% with increasing of relative compaction of 5%. It was founded that the variations of modulus of subgrade soils in Korea were over 40% with water content variation of $\pm$2%, and those effects can be estimated by exponential model. However, the normalized modulus reduction curves were almost identical and independent of water content. It was also founded that confining pressure, loading frequency, dry unit weight, and water content have an affect on modulus of subgrade soils independently. Therefore, it can be considered that those effects are independent variables.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.939-945
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• 2009

The dome stretching tests and tension tests have been performed to obtain a forming limit curve(FLC) for the copper alloy which is used for manufacturing the regenerative cooling thrust chamber. For experimental investigation of the forming limit curve, we have used in-plane tension specimen to obtain tension-compression strain state as well as out-of-plane specimen to obtain tension-tension strain state through dome stretching test. All specimens were divided into longitudinal and transverse directions according to the orientation of test specimen. The test results showed that in the tension-tension region, copper alloy revealed a maximum major strain of 62.3% and a maximum minor strain of 58.6%. In the tension-compression region, the maximum major strain and the maximum minor strain were measured to be 60.5% and 25.8%, respectively.