• 한국결정성장학회지
• /
• 제7권2호
• /
• pp.224-234
• /
• 1997

적은 양의 침입형 불순물을 함유한 고순도 재료를 제조하기 위해 70 ㎾ 걸자 빔용해기를 제작하였으며 이를 이용해서 sponge Ti와 Ti-6Al-4V 합금을 용융시켰다. 전자 빔 용해법을 이용해 정련된 sponge Ti에 대한 실험 결과를 바탕으로 초기 용해 180초 동안에는 Ti의 순도가 증가하였지만 그 이후로는 크게 변화지 않는 것을 알 수 있었다. 그리고 Ti의 정련 결과, 침입형 불순물과 금속 불순물의 양을 포함한 전체 불순물의 양이 900 ppm인 고순도(99.9 wt%)의 Ti를 얻었다. Ti-6Al-4V 합금의 전자 빔 용해에 대한 실험 결과로부터 손실되는 Al의 양은 열역학적 데이터, regular solution model 그리고 model of solute removal kinetics를 통해서 판단할 수 있음을 알 수 있었으며, 이 모델들로부터 계산된 합금 조성과 실험을 통해서 구한 합금 조성이 일치하였다. 그리고 Ti-6Al-4V 합금의 조성은 매우 균일하였으며 이것은 EPMA line scanning을 통해서 확인하였다.

• Carbon letters
• /
• 제7권3호
• /
• pp.171-179
• /
• 2006

A carbonaceous sorbent was prepared from rice husk via sulphuric acid treatment. After preparation and washing, the wet carbon with moisture content 85% was used in its wet status in this study due to its higher reactivity towards Cr(VI) than the dry carbon. The interaction of Cr(VI) and the carbon was studied and two processes were investigated in terms of kinetics and equilibrium namely Cr(VI) removal and chromium sorption. Cr(VI) removal and chromium sorption were studied at various initial pH (1.6-7), for initial Cr(VI) concentration (100 mg/l). At equilibrium, maximum Cr(VI) removal occurred at low initial pH (1.6-2) where, Cr(III) was the only available chromium species in solution. Cr(VI) removal, at such low pH, was related to the reduction to Cr(III). Maximum chromium sorption (60.5 mg/g) occurred at initial pH 2.8 and a rise in the final pH was recorded for all initial pH studied. For the kinetic experiments, approximate equilibrium was reached in 60-100 hr. Cr(VI) removal data, at initial pH 1.6-2.4, fit well pseudo first order model but did not fit pseudo second order model. At initial pH 2.6-7, Cr(VI) removal data did not fit, anymore, pseudo first order model, but fit well pseudo second order model instead. The change in the order of Cr(VI) removal process takes place in the pH range 2.4-2.6 under the experimental conditions. Other two models were tested for the kinetics of chromium sorption with the data fitting well pseudo second order model in the whole range of pH. An increase in cation exchange capacity, sorbent acidity and base neutralization capacity was recorded for the carbon sorbent after the interaction with acidified Cr(VI) indicating the oxidation processes on the carbon surface accompanying Cr(VI) reduction.

• 한국분무공학회지
• /
• 제5권2호
• /
• pp.35-42
• /
• 2000

A number of atomization and droplet breakup models have been developed and used to predict the diesel spray characteristics. Of the many atomization and droplet breakup models based on the breakup mechanism due to aerodynamic liquid and gas interaction, four models classified as mathematical models, such as TAB, modified TAB, DDB, WB and one of the hybrid model based on WB and TAB models were selected for the assessment of prediction ability of diesel spray dynamics. The assessment of these models by using KIVA-II code was performed by comparing with the experimental data of spray tip penetration and sauter mean diameter(SMD) from the literature. It is found that the prediction of spray tip penetration and SMD by the hybrid model was only influenced by the initial parcel number. All the atomization and droplet breakup models considered here was strongly dependent on the grid resolution. Therefore it is important to check the grid resolution to get an acceptable results in selecting the models. At low injection pressure, modified TAB model could only give the good agreement with experimental data of spray tip penetration and both of modified TAB and DDB models were recommendable for the prediction of SMD. At high injection pressure, hybrid model could only give the good agreement with the experimental data of spray tip penetration and the prediction of all of the selected models did not match the experimental data. Spray tip penetration was increased with the increase the $B_1$ and the increase of $B_1$ did not affected the prediction of SMD.

• 성인간호학회지
• /
• 제13권2호
• /
• pp.277-290
• /
• 2001

This study was conducted to examine if the revised HPM was appropriate to explain smoking quitting behavior. A convenience sample of 400 college students enrolled in the universities located in Seoul and Kyunggi-Inchon province was selected. According to the study results, smoking-specific cognitions and affect included in the study could significantly explain commitment to a plan to quit smoking which was one of the behavioral outcomes in the revised HPM. The study result showed that among predictors, smoking-related affect, perceived benefit of quitting smoking, and perceived self-efficacy significantly explained commitment to a plan to quit smoking, but perceived barriers and interpersonal influences did not. The model for smoking quitting behavior formulated with smoking-specific cognitions and affect was statistically significant and the model explained 48 percent of variance in smoking quitting behavior. More specifically, it was shown that among smoking-specific cognitions and affect, only smoking-related affect, interpersonal influences, and perceived self-efficacy were the significant predictors to explain smoking quitting behavior. Smoking-related affect was the most important variable to explain smoking quitting behavior, followed by perceived self-efficacy. However, the influence of commitment to a plan to quit smoking on smoking quitting behavior was not statistically significant. Lastly, the model for smoking quitting behavior formulated with individual characteristics and experiences could explain 13 percent of the variance in behavior to quit smoking. Although the model is statistically significant, only the number of quitting attempts had significant and direct influence on behavior to quit smoking, while the remaining variables did not.

• 경영정보학연구
• /
• 제25권2호
• /
• pp.163-180
• /
• 2023

본 연구는 TOE(Technology-Organization-Environment) 모델을 기반으로 원격근무 솔루션(RWS)의 기술적, 조직적, 환경적 측면을 고려해 위드 코로나 시대 이용자들의 지속사용 의도를 설명할 수 있는 연구 모형을 제안하였다. 연구 모형 및 가설 검증을 위해 국내 원격근무 솔루션 사용자를 대상으로 온라인 설문을 실시하였고 부분최소자승법(Partial Least Square, PLS)을 이용해 411개 수집 데이터를 분석하였다. 분석 결과, 기능성과 보안성은 생산성 향상과 만족도에 모두 유의한 양의 상관관계가 있음이 밝혀졌다. 또한 조직 준비성은 생산성 향상에 긍정적인 영향을 끼치나 만족도에는 영향을 주지 못하는 것으로 드러났다. 정부지원은 원격근무 솔루션의 지속사용의도에 긍정적인 영향을 미치는 것이 확인되었으나 건강에 대한 우려와 지속사용의도와의 상관관계는 유의하지 않은 것으로 나타났다. 마지막으로 생산성 향상과 만족도, 지속사용의도 간의 상관관계들은 모두 유의한 것으로 확인되어 총 11개 가설 중 9개 가설이 지지되었다.

• 설비공학논문집
• /
• 제29권10호
• /
• pp.515-529
• /
• 2017

EnergyPlus, which is widely used in various fields, provides Simple Window Model, a window model that can be used practically. However, the results of building load using the model are different from those of the standard model. The main cause of the deviation by Simple Window Model was analyzed to be due to the assumption that all windows were considered as single layer. The purpose of this study is to propose a window model that improves the cause of deviation by Simple Window Model and can be easily calculated from the algebraic relations. The proposed window model solved the heat balance equation algebraically by using seven window characteristic coefficients. The coefficient relationships consisted of the heat transmission coefficient and solar heat gain coefficient as input parameters make practical use and calculation possible. As a result of comparing the deviation between each window model by implementing the dynamic analysis method, the proposed window model showed that the deviation of the total heating/cooling energy consumption was reduced to 1/3 compared to Simple Window Model for one year. Although the maximum energy consumption did not show any significant improvement, the indoor temperature evaluation showed significantly reduced deviation.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 춘계학술대회논문집
• /
• pp.1045-1049
• /
• 2001

Before building houses or apartments, we need to predict noise propagation to eliminate possible noise problems to residents. However, we do not try to predict noise propagation during estimation of noise effect for the developing area since we did not have a good mathematical model to predict noise level due to a traffic noise. In this article, an adequate mathematical model has been developed and proved to predict noise effect to living area due to a traffic noise.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
• /
• pp.344-344
• /
• 2000

Recently, the demand for high precision and large stroke in linear positioning systems is increasing in industry. A coarse-fine position control system composed of a linear motor and a piezoelectric actuator has such characteristics. Many optimal control laws have been applied to the position control of coarse-fine actuators but most of them did not take account into constraints. In this study, model predictive control (MPC) method with constraints is applied to the position control of the coarse-fine actuator and the performance of MPC is compared with those of conventional control laws.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 춘계학술대회 논문집
• /
• pp.2500-2503
• /
• 2008

Currently the railway system's operational strategy for developing various scenarios did not establish how the development. This is a realistic time constraints and thus virtually no model for development due to operational activities and functions because of the lack of a clear understanding. Therefore, activities and functions of the definition for how to take advantage of it through the development of the situation is urgent.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2004년도 추계학술대회 논문집
• /
• pp.1546-1552
• /
• 2004

Railway schedule is periodically modified so that it could yield more profit by means of adjusting the schedule to demand. Most of related works are applicable under the given demand, but did not deal with dynamic relation between demand and schedule. To our knowledge, the methodology considering the relation is only the profitability evaluation model developed by SNCF. Our study suggests how to adjust the schedule to demand and therefore obtain more benefits using the profitability evaluation model.