• Advances in materials Research
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• 제6권1호
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• pp.79-91
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• 2017

In the present work, a design of experiment (DOE) technique using Taguchi method, has been applied to optimize the properties of ODS tungsten heavy alloys(WHAs). In this work Taguchi method involves nine experiments groups for four processing parameters (compaction pressure, sintering temperature, binding material type, and oxide type) with three levels was implemented. The signal-to-noise (S/N) ratio and analysis of variance (ANOVA) were employed to obtain the optimal process parameter levels and to analyze the effect of these parameters on density, electrical conductivity, hardness and compressive strength values. The results showed that all the chosen factors have significant effects on all properties of ODS tungsten heavy alloys samples. The density, electrical conductivity and hardness increases with the increase in sintering temperature. The analysis of the verification experiments for the physical properties (density and Electrical conductivity) has shown that Taguchi parameter design can successfully verify the optimal parameters, where the difference between the predicted and the verified values of relative density and electrical conductivity is about 1.01% and 1.15% respectively.

• International Journal of Aeronautical and Space Sciences
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• 제17권3호
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• pp.341-351
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• 2016

In this present work, the effect of hole shapes, orientation and hole arrangements on film cooling effectiveness has been carried out. For this work a flat plate has been considered for the computational model. Computational analysis of film cooling effectiveness using different hole shapes with no streamwise inclination has been carried out. Initially, the model with an inclination of $30^{\circ}$ has been verified with the experimental data. The validation results are well in agreement with the results taken from literature. Five different hole shapes viz. Cylindrical, Elliptic, Triangular, Semi-Cylindrical and Semi-Elliptic have been compared and validated over a wide range of blowing ratios. The blowing ratios ranged from 0.67 to 1.67. Later, orientation of holes have also been varied along with the number of rows and hole arrangements in rows. The performance of film cooling scheme has been given in terms of centerline and laterally averaged adiabatic effectiveness. Semi-elliptic hole utilizes half of the mass flow as in other hole shapes and gives nominal values of effectiveness. The triangular hole geometry shows higher values of effectiveness than other hole geometries. But when compared on the basis of effectiveness and coolant mass consumption, Semi-elliptic hole came out to give best results.

• Journal of Power Electronics
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• 제18권4호
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• pp.975-984
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• 2018

This work presents a high efficiency phase shifted full bridge (PSFB) DC-DC converter for use in the second stage of a battery charger for neighborhood electrical vehicle (EV) applications. In the design of the converter, Lithium-ion battery cells are preferred due to their high voltage and current rates, which provide a high power density. This requires wide range output voltage regulation for PSFB converter operation. In addition, the battery charger works with a light load when the battery charge voltage reaches its maximum value. The soft switching of the PSFB converter depends on the dead time optimization and load condition. As a result, the converter has to work with soft switching at a wide range output voltage and under light conditions to reach high efficiency. The operation principles of the PSFB converter for the continuous current mode (CCM) and the discontinuous current mode (DCM) are defined. The performance of the PSFB converter is analyzed in detail based on wide range output voltage and load conditions in terms of high efficiency. In order to validate performance analysis, a prototype is built with 42-54 V / 15 A output values at a 200 kHz switching frequency. The measured maximum efficiency values are obtained as 94.4% and 76.6% at full and at 2% load conditions, respectively.

• International Journal of Human Ecology
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• 제8권1호
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• pp.109-116
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• 2007

Leisure time is a critical part of modern life and is increasingly important in modern society. Therefore, analyzing expectations and values of leisure and researching leisure practices are integral in measuring the quality of life. In this respect, differences between values and attitudes leading to the ideal leisure life and the actual leisure life could provoke negative influence on our lives, further, decreasing quality of life. Therefore, classifying leisure lifestyle through analyzing value of lifestyle and the actual state of leisure precisely is very necessary. Leisure lifestyle could be very useful standard satisfying various desires and demands related to leisure. In the research, we surveyed 3,000 people over 10 years of age, one on one interview method, asking value of life behaviors (Individualism vs. Collectivism, Pro-Stability vs. Pro-Change, Statistical way of life vs. Active way of life, Family-centered life vs. Work-centered life) and practices of leisure life (With whom, How frequently, Where, For what) in respect to both value and behaviors. Through this survey, five groups of leisure life type have been identified; "Community-oriented Type", "Cocoon Type", "Family-oriented Type", "Personal-stability Type" and "Multiplicity Type". These leisure lifestyles would provide effectual alternatives for reducing gaps between expectations for ideal leisure life and actual life. Furthermore, this could be used for ground work to develop measurements for satisfying various leisure demands.

• 한국구조물진단유지관리공학회 논문집
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• 제7권2호
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• pp.219-229
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• 2003

The objective of this work is to verify the Code specified girder distribution factors for short and medium span bridges. To accomplish this objective, field tests were carried out on seventeen simply supported highway bridges. This paper presents the procedure and results of field tests that were performed to verify girder distribution factors. Finite Element analyses previously performed at the University of Michigan indicated that in most cases currently used girder distribution factors specified in AASHTO Codes are too conservative. However, these studies also showed that for short spans and short girder spacings, the girder distribution factors can be too permissive. Therefore, this paper focused on experimental evaluation of girder distribution factors for short and medium span steel girder bridges. The results were compared with the distribution factors specified by AASHTO Standard (2000) and AASHTO LRFD Code (1998). It has been found that the measured girder distribution factors are lower than AASHTO values in most cases, and sometimes the code specified values are overly conservative. The research work involved formulation of the testing procedure, selection of structure, installation of equipment, measurements, and interpretation of the results.

• 한국농공학회지
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• 제36권1호
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• pp.83-94
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• 1994

The first part of this study dealt with the determination of soil parameters for Lade's double work-hardening model using the raw data obtained from cubical and cylinderal triaxial tests At present, it should be investigated which test can simulated satisfactorily the behavior of soft clayey foundation. In this regard, plate bearing test on the 2-dimentional model foundation(218cm long, 40cm wide, 19&m high) was performed, and finite element analysis carried out to abtain the behavior of the foundation. Settlement, lateral displacement, displacement vector and mode of failure were measured and these values were compared with numerical values in order to validate the numerical program developed by authors. The FEM technique was based on Christain-Boehmer's method, in which the displacement is obtained at each nodal point while stress and pore water pressure at each element.In this research, Biot's equation, which explains was elahorately the phisical meaning of consolidation, was selected, as a governing equation, coupled with Lade's double surface work-hardening constitutive model.

• Journal of Electrochemical Science and Technology
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• 제2권1호
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• pp.20-25
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• 2011

This work focuses on the behavior of the overpotential increase due to a utilization rise in a molten carbonate fuel cell. The behavior is generally explained by Nernst loss, which is a kind of voltage loss due to the thermodynamic potential gradients in a polarization state due to the concentration distribution of reactant species through the gas flow direction. The evaluation of Nernst loss is carried out with a traditional experimental method of constant gas utilization (CU). On the other hand, overpotential due to the gas-phase mass-transport resistance at the anode and cathode shows dependence on the utilization, which can be measured using the inert gas step addition (ISA) method. Since the Nernst loss is assumed to be due to the thermodynamic reasons, the voltage loss can be calculated by the Nernst equation, referred to as a simple calculation (SC) in this work. The three values of voltage loss due to CU, ISA, and SC are compared, showing that these values rise with increases in the utilization within acceptable deviations. When we consider that the anode and cathode reactions are significantly affected by the gas-phase mass transfer, the behavior strongly implies that the voltage loss is attributable not to thermodynamic reasons, namely Nernst loss, but to the kinetic reason of mass-transfer resistance in the gas phase.

• 한국직업건강간호학회지
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• 제20권3호
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• pp.240-249
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• 2011

Purpose: The purpose of this study was to identify the factors influencing the nursing students' job-esteem. Methods: The data were collected from March 1 to 30, 2011 using questionnaires. The subjects were recruited from the department of nursing at a college in Kyungnam. The collected data were analyzed using SPSS descriptive statistics, mean and standard deviation, t-test and ANOVA, Pearson's Correlation Coefficient, and Stepwise Multiple Regression Analysis. Results: The significantly factor which is a variable predicting best job-esteem of college nursing students by ability and opportunity to getting accounting for 13.4% (${\beta}$=.277) of the prediction, followed by work conditions, lifestyles, and sense of honor that accounted for 27.6%. Conclusion: Based on the results of this study, nursing educational program and curriculum development should give nursing students a variety of experience for their career.

• 경영정보학연구
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• 제14권2호
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• pp.65-92
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• 2012

저출산, 고령화 사회 진입 등 사회문화적 환경 변화에 대응코자 최근 스마트워크 도입에 대한 관심이 고조되고 있다. 스마트워크는 정보통신기술을 활용하여 시간과 장소의 제약 없이 동료 직원들과 원활하게 협업하고 끊김 없이 업무를 수행하는 근로 형태로서 원격근무, 재택근무 또는 스마트워크 센터근무 등의 형태로 구현된다. 그러나 이러한 관심에도 불구하고 도입 추진 1년이 지난 지금 일부 기업들은 스마트워크 도입을 통해 업무 생산성과 근무 만족도를 효과적으로 개선하는 반면, 일부 기업들은 도입을 보류하거나 사실상 실패하는 사례들이 나타나고 있다. 이러한 차이를 해결하기 위해서는 스마트워크 도입 성공 요인을 밝히고 비즈니스 모델에 어떻게 적용시킬 수 있을지에 대한 고려가 필요하지만, 스마트워크 도입의 성공 요인을 밝히고자 하는 연구들은 매우 제한되어 있는 상황이다. 따라서, 본 고에서는 우선, 최근 스마트워크 도입 추진 연구를 바탕으로 스마트워크의 정의, 적용 가능 산업영역 및 파급효과의 크기, 도입 추진을 위한 시사점들을 종합하였다. 동시에, 원격근무(Telework), 가상팀 (Virtual team) 활동 등 선행 연구를 취합하여 성공사례와 성공 요소를 수집하였다. 정리된 결과를 바탕으로 국내외 시범사업 추진 사례를 비교함으로써 스마트워크 도입 시 기대효과를 극대화 할 수 있는 핵심 요소를 도출하고자 하였다. 본 연구 결과는 스마트워크 도입의 핵심 요소를 가시화 함으로써 실제 도입을 추진하고 있는 기업이 보다 원활하게 스마트워크를 도입하고 스마트워크를 기반으로 한 업무 프로세스 개선을 가능케 할 뿐만 아니라, 스마트워크 지원 서비스 비즈니스 모델 구축에도 도움을 줄 수 있을 것으로 기대한다.

• 한국산업보건학회지
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• 제31권4호
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• pp.317-330
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• 2021

Objectives: By law, companies in Korea must periodically measure workers' exposure to harmful chemicals (the system is called the Work Environment Monitoring Program (WMP)[a]) and report the results to the government. The government also measures exposure to monitor the WMP's reliability (called Reliability Assessment (RA) for WMP[b]). The issue is that measured data from these two sources are so different that the objectivity of WMP needs to be confirmed by comparing the results using the European Centre for Ecotoxicology and Toxicology of Chemicals' Targeted Risk Assessment (ECETOC TRA). Methods: Step 1: Data collection from WMP reports submitted by companies (n=586) and RA for WMP written by the government (n=33). Step 2: Data Standardization by key information included. Step 3: Data conversion to input-variables required to run the ECETOC TRA model, and run the model with specific data (n=514) which meet the predetermined exposure scenario. Step 4: Statistical data analysis by process category (PROC) and ventilation type from each source ([A] and [B]). Step 5: Additional analysis of any unexpected results. Results: The process categories of the production and handling of Dichloromethane were classified into 12 PROCs, and ten of them were selected to run ECETOC TRA. Modeled values tended to be higher than measured values from both sources. For the measured values from WMP, RCR distribution by PROC was narrow (0.197-0.267, 95% CI) and did not have a relationship with ventilation type, which differs from the tendency of the modeling result. Meanwhile, the measured values from RA for WMP were relatively widely distributed (0.301-1.177, 95% CI) by PROC. In particular PROCs (13,19) were high enough to exceed 1. Also, they become low with better ventilation types and appear differently depending on the ventilation type, similar to the model result. Conclusions: This study revealed that ECETOC TRA might have the potential to serve as a screening tool for exposure assessment and to be used as assistive method for WMP to estimate exposure. Further empirical study is required to confirm its availability as a screening tool.