• 소성∙가공
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• 제28권6호
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• pp.347-353
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• 2019

The porthole extrusion process is a classic metal forming process to produce complex cross-section shaped aluminum profile. It is very difficult to design porthole die and extrusion process because of the complex shape of extrusion die and internal metal flow. The main variables in this process are ram speed, initial billet and tool temperature, and die shape. In general, the metal flow of porthole extrusion process can be divided into two steps. During the first step, the billet is divided into several parts in the porthole die bridge. During the second step, the divided billets are welded in the welding chamber. In the welding chamber, the level of welding pressure is very important for the quality of the final product. The purpose of this study is to increase the welding pressure in the welding chamber by using a two stage welding chamber. The porthole extrusion die was designed by using the Taguchi method with orthogonal array. The effectiveness of the optimized porthole die was verified by using the finite element analysis.

• 한국시뮬레이션학회논문지
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• 제23권2호
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• pp.47-55
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• 2014

한국군의 분석용 시뮬레이션모델을 포함한 대개의 전투시뮬레이션 모델들은 통합화력과 같은 복잡한 전투상황을 모델링, 분석하기에는 어려움이 많다. 본 연구에서는 Fire Eagle과 같은 지상화력과 육군항공의 통합화력전투훈련의 분석을 위한 모델링 및 시뮬레이션 요구사항을 분석한다. 이에 기반하여 Fire Eagle을 위한 시뮬레이션 모델을 제안, 개발하고 통합화력을 개선하기 위한 전략을 도출한다. 이 시뮬레이션 모델을 이용하여 특정 작전계획 및 시나리오의 효과성을 분석한다. 이 시뮬레이션 실험 결과를 바탕으로 효율적이고 효과적인 작전계획을 개발하는 시범을 보인다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2014년도 추계학술발표대회
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• pp.928-931
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• 2014

The detection of human behavior from social media revolutionized health, business, criminal and political prediction. Significance of it, in incentive transformation of public opinion had already proven for developed countries in improving democratic process of elections. In $3^{rd}$ World countries, voters poll votes for personal interests being unaware of party manifesto or national interest. These issues can be addressed by social media, resulting as ongoing process of improvement for presently adopted electoral procedures. On the optimistic side, people of such countries applied social media to garner support and campaign for political parties in General Elections. Political leaders, parties, and people empowered themselves with social media, in disseminating party's agenda and advocacy of party's ideology on social media without much campaigning cost. To study effectiveness of social media inferred from individual's political behavior, large scale analysis, sentiment detection & tweet classification was done in order to classify, predict and forecast election results. The experimental results depicts that social media content can be used as an effective indicator for capturing political behaviors of different parties positive, negative and neutral behavior of the party followers as well as party campaign impact can be predicted from the analysis.

• Steel and Composite Structures
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• 제10권4호
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• pp.361-371
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• 2010

Enhancement in the seismic buckling capacity of steel tanks caused by the addition of fiber reinforced polymers (FRP) retrofit layers attached to the outer walls of the steel tank is investigated. Three-dimensional non-linear finite element modeling is utilized to perform such analysis considering non linear material properties and non-linear large deformation large strain analysis. FRP composites which possess high stiffness and high failure strength are used to reduce the steel hoop stress and consequently improve the tank capacity. A number of tanks with varying dimensions and shell thicknesses are examined using FRP composites added in symmetric layers attached to the outer surface of the steel shell. The FRP shows its effectiveness in carrying part of the hoop stresses along with the steel before steel yielding. Following steel yielding, the FRP restrains the outward bulging of the tank and continues to resist higher hoop stresses. The percentage improvement in the ultimate base moment capacity of the tank due to the addition of more FRP layers is shown to be as high as 60% for some tanks. The percentage of increase in the tank moment capacity is shown to be dependent on the ratio of the shell thickness to the tank radius (t/R). Finally a new methodology has been explained to calculate the location of Elephant foot buckling and consequently the best location of FRP application.

• 한국지반환경공학회 논문집
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• 제16권1호
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• pp.29-36
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• 2015

현재 국내 연구는 1차원 수치해석을 통한 침수방지대책의 효과분석 및 효율성을 입증하는 형태로 본 연구에서는 2차원 도시유출모형인 XP-SWMM 모형을 침수지역에 적용, 침수방지대책을 상호 비교 분석함으로써 수자원관리자의 효율적인 정책결정에 반영할 수 있도록 하는 것이 본 연구의 목적이다. 기상데이터는 지난 1967년부터 2011년까지 45년간 청주 기상대에서 수집한 것으로 통계 분석하여 사용하였다. 대상 배수구역 통수능력 분석을 50년 빈도 모의 결과 침수면적 $539,548m^2$, 최대침수심 1.0m, 침수시간 48분으로 분석되었다. 침수대책으로 A1 소배수구역의 통수능력 증대를 위해 우회수로 및 지하저류시설 건설을 비교한 결과 대상유역에 용량이 $13,500m^3$인 지하저류시설을 설치할 경우 50년 빈도의 강우까지 침수가 완전 해소될 것으로 판단된다. 향후 침수 저감대책으로 이상기후에 대비할 수 있는 지하저류조 설치가 효율성이 좋을 것으로 판단된다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제2권1호
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• pp.24-33
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• 2010

Design of a Pump Jet Propulsor (PJP) was undertaken for an underwater body with axisymmetric configuration using axial/low compressor design techniques supported by Computational Fluid Dynamics (CFD) analysis for performance prediction. Experimental evaluation of the PJP was earned out through experiments in a Wind Tunnel Facility (WTF) using momentum defect principle for propulsive performance prior to proceeding with extensive experimental evaluation in towing tank and cavitation tunnel. Experiments were particularly conducted with respect to Self Propulsion Point (SPP), residual torque and thrust characteristics over a range of vehicle advance ratio in order to ascertain whether sufficient thrust is developed at the design condition with least possible imbalance torque left out due to residual swirl in the slip stream. Pumpjet and body models were developed for the propulsion tests using Aluminum alloy forged material. Tests were conducted from 0 m/s to 30 m/s at four rotational speeds of the PJP. SPP was determined confirming the thrust development capability of PJP. Estimation of residual torque was carried out at SPP corresponding to speeds of 15, 20 and 25 m/s to examine the effectiveness of the stator. Estimation of thrust and residual torque was also carried out at wind speeds 0 and 6 m/s for PJP RPMs corresponding to self propulsion tests to study the propulsion characteristics during the launch of the vehicle m water where advance ratios are close to Zero. These results are essential to assess the thrust performance at very low advance ratios to accelerate the body and to control the body during initial stages. This technique has turned out to be very useful and economical method for quick assessment of overall performance of the propulsor and generation of exhaustive fluid dynamic data to validate CFD techniques employed.

• 대한간호학회지
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• 제30권5호
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• pp.1254-1264
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• 2000

This study investigated the relationship between the nurse's followership, job satisfaction and organizational commitment. The sample consisted of 173 nurses of 2 private university hospitals. The instruments used in this study were the followership scale (Kelly, 1994), the job satisfaction scale (Slavitts et al., 1978), the organizational commitment questionnaire (Mowday et al., 1979) and the demographic questionnaire. SPSS/WIN program was used for descriptive statistics, ANOVA, and Pearson correlation analysis of data. The results were as follows: 1) The styles of followership were classified as pragmatist followers (73.4%), exemplary followers (19.7%), passive followers (4.6%), and alienated followers (2.3%). 2) The mean of independent/critical thinking was 3.32 (M=3.0), and active involvement was 3.04 (M=3.0). As a whole, the mean of followership was 3.18 (M=3.0), job satisfaction was 2.82 (M=2.5), and organizational commitment was 3.97 (M=3.5). 3) Significant differences were found in the degree of clinical nurses' perception of followership according to the demographic characteristics such as age, education, position, and career. 4) Significant differences were found in the degree of clinical nurses' perception of followership according to followership styles. 5) The followership was significantly related to job satisfaction and organizational commitment. In conclusion, the nurse's followership is considered as an important concept and this suggested that the concept could be used as a major variable in measuring effectiveness of nursing organization.

• 대한통합의학회지
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• 제8권2호
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• pp.169-185
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• 2020

Purpose : This study aimed to conduct a comprehensive meta-analysis to evaluate the effect size for pulmonary function and gait capacity of treadmill exercise in stroke patients. In addition, we aimed to examine the current status of treadmill interventions and compare the effect sizes of treadmill training to provide evidence-based practice for future development and application. Methods : The meta-analysis study was conducted using research articles that applied treadmill exercise to stroke patients and were published between January 2005 and February 2020. For a systematic meta-analysis, we conducted a search using the PICOS framework and selected 25 domestic stroke- and treadmill-related studies. The Comprehensive Meta-Analysis program was used to calculate the effect sizes for lung function and gait capacity (6-minute walk test and 10 m walk test). As Cohen's d has a tendency to overestimate the effect size, we used Hedge's g to increase the accuracy in computing the effect size. Results : Based on the results of the meta-analysis, the total effect size of treadmill exercise was 0.535, which was statistically significant, with a medium effect size (p<0.05). The effects of treadmill exercise in stroke patients were divided into dependent variables, namely pulmonary function (0.372) and gait capacity (0.584). In addition, for gait capacity, the effect sizes were evaluated for both the 6-minute walk test (0.756) and the 10 m walk test (0.514). Conclusion : This study provides objective evidence of the effectiveness of treadmill-based gait training programs. We hope that the results of this study will help support the development and implementation of treadmill-based gait training in stroke patients. Treadmill training is expected to improve not only pulmonary function, but also the gait capacity of stroke patients. Long-term investigations on the effects of treadmill training in stroke patients are necessary.

• 한국산학기술학회논문지
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• 제13권9호
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• pp.4349-4358
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• 2012

ASRP 데이터는 야전에 저장 운용되고 있는 탄약을 평가한 유일한 필드 데이터이자 탄약성능 중심의 포병전력을 객관적으로 판단할 수 있는 자료이다. 하지만 ASRP 데이터는 야전에 저장된 탄약에 대한 저장상태를 판단하는 잣대로 활용될 뿐, 축적된 데이터에 대한 재평가와 깊이 있는 연구가 진행되지 못하고 있다. 본 연구는 포병탄약 성능 중심의 현존 포병전력을 분석하고 관리하기 위한 ASRP 데이터의 활용 방법 연구로 야전에 저장되고 있는 탄약의 시험주기 설정, 탄약수명 예측 및 M&S(Modeling & Simulation) 기법의 전투모의를 통한 전력효과 분석 등 3가지 방안을 제시하였다.

• 한국군사과학기술학회지
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• 제17권6호
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• pp.751-763
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• 2014

The paper is written to determine the optimal search pattern through search effects assessment on underwater targets. 5 types of search patterns are introduced such as, M-type pattern, W-type pattern, rectangular pattern, 4-type pattern and square pattern, In addition, Operational effectiveness analysis model is developed to obtain the optimum search pattern. The algorithms and mathematical models are also suggested to analyze the required search times, AUV's movement patterns, moving distances, overlapping areas and so on.