• 설비공학논문집
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• 제9권1호
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• pp.43-54
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• 1997

This paper presents an approximate analytical solution to a two-region one-dimensional model for the charging process of stratified thermal storage tanks with variable inlet temperature in the presence of momentum-induced mixing. Based on the superposition principle, an arbitrary-varying inlet temperature is decomposed into inherent discontinuous steps and continuous intervals approximated as a finite number of piecewise linear functions. This approximation allows the temperature of the upper perfectly-mixed layer to be expressed in terms of constant, linear and exponential functions with respect to time. Applying the Laplace transform technique to the model equation for the lower thermocline layer subject to each of three representative interfacial conditions yields compact-form solutions, a linear combination of which constitutes the final temperature profile. A systematic method for deriving solutions to the plug-flow problem having polynomial-type boundary conditions is also established. The effect of adiabatic exit boundary on solution behaviors proves to be negligible under the actual working conditions, which justifies the assumption of semi-infinite domain introduced in the solution procedure. Finally, the approximate solution is validated by comparing it with an exact solution obtained for a specific variation of inlet temperature. Excellent agreements between them suffice to show the necessity and utility of this work.

• 한국자동차공학회논문집
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• 제10권4호
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• pp.114-121
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• 2002

This paper describes the control system of the toroidal traction driver continuously variable-speed transmission(CVT) fur a tractor. The instrumentation system, the hydraulic power control system and the principle control scheme were introduced. Experimental tests in the bench and the tractor were conducted to validate the performance of the CVT utilizing the proposed controller. The speed of the vehicle was continuously changed to follow the speed set by driver under various operating conditions. Given the reduction ratio of the variator from 2.0 to 1.0, the settling time was about just 0.52 seconds which was satisfactory value for working with the tractor. It was also proved that the tractor could work with continuously variable speed under heavy load disturbances.

• Steel and Composite Structures
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• 제31권2호
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• pp.149-158
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• 2019

The force-deformation behavior, strain distribution and failure modes of a variable damping self-centering brace (VD-SCB) are theoretically analyzed, experimentally studied, and numerically simulated to guide its design. The working principle of the brace is explained by describing the working stages and the key feature points of the hysteretic curve. A large-scale brace specimen was tested under different sinusoidal excitations to analyze the recentering capability and energy dissipation. Results demonstrate that the VD-SCB exhibits a full quasi-flag-shaped hysteretic response, high ultimate bearing capacity, low activation force and residual deformation, and excellent recentering and energy dissipation capabilities. Calculation equations of the strain distribution in different parts of the brace are proposed and are compared with the experimental data and simulated results. The developments of two failure modes are compared. Under normal circumstances, the brace fails due to the yielding of the spring blocking plates, which are easily replaced to restore the normal operating conditions of the brace. A brief description of the design procedure of the brace is proposed for application.

• 한국사회복지학
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• 제57권2호
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• pp.41-70
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• 2005

본 연구는 사회경제적 구조변화에 따른 빈곤형태의 변화를 고찰하고 신빈곤층의 탈빈곤을 위한 정책을 모색하는데 목적이 있다. 그동안 빈곤정책은 노령, 실업, 장애, 질병 등 노동능력 상실과 관련된 절대빈곤층에 초점을 두어 왔다. 그러나 경제위기 후 증가하는 빈곤의 특성은 노동시장 참여가 더 이상 탈빈곤의 요인으로 작용하지 않게 되었다. 본 연구는 근로빈민을 대상으로 경제위기이후 경제상황변화, 복지상황, 사회적 위험에 대한 경험 및 대응방식에 대해 경험적으로 조사하고 이를 기반으로 탈빈곤정책을 모색하고자 하였다. 연구결과 근로빈민층은 경제위기이후 실업, 소득감소 등 다양한 형태의 사회적 위험을 경험했으며 불안정한 고용상황, 취약한 복지상황을 보여주고 있으며 이를 기반으로 탈빈곤정책으로 소득안정정책, 직업훈련 및 기술교육정책, 적극적인 사회복지정책 등을 제시하였다.

• 한국보육지원학회지
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• 제10권6호
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• pp.57-80
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• 2014

본 연구의 목적은 영아반 보육교사의 교사효능감과 직무스트레스에 영향을 미치는 관련 배경 변인 분석을 통해 영아반 보육교사의 직무여건 개선 및 교사교육의 기초자료를 제공하기 위함이다. 이러한 목적을 위해 경상북도에 소재한 어린이집에 재직 중인 영아반 보육교사 488명을 대상으로 2013년 3월11일부터 29일까지 설문조사를 실시하였다. 연구결과 첫째, 영아반 보육교사의 교사효능감은 전반적으로 조금 높게 나타났으며, 일반효능감이 개인효능감보다 높게 나타났다. 교사효능감은 개인변인인 연령과 결혼여부에서, 근무여건 변인인 어린이집 유형, 평균근무시간, 월평균보수, 반 원아수에서 유의한 차이를 보였다. 둘째, 영아반 보육교사의 직무스트레스 역시 전반적으로 조금 높게 나타났으며, 직무스트레스는 경제, 학부모, 업무, 원아, 개인, 행정업무 순이며, 가장 낮은 요인은 동료스트레스로 나타났다. 직무스트레스는 개인변인 연령, 결혼여부, 경력, 이수한 연수회수에서, 근무여건 변인은 어린이집 유형, 평균근무시간, 반 원아수, 월평균보수에서 유의한 차이가 나타났다. 이러한 결과를 통해 영아반 보육교사의 교사효능감 향상을 위해 영아반 보육교사의 직무여건 개선이 무엇보다 중요하다는 시사점을 얻을 수 있다.

• Journal of Biosystems Engineering
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• 제42권4호
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• pp.251-257
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• 2017

Purpose: A chisel mounted on working implement, such as agricultural machinery used in irregular farming conditions, is subjected to highly variable fatigue loading during work. To ensure the safety of the chisel on a working implement for the duration of its service life, fatigue testing must be performed with the proper fatigue test load conditions. In this study, working loads for a chisel were developed by reconstructing loads from strain gage data collected during field tests and used to conduct fatigue tests on the chisel component. Methods: FE analysis with nCode software was utilized to select the proper quantity and locations of strain gages for load measurements. A fatigue test was performed to experimentally verify the fatigue strength of the chisel and to evaluate the validity of the load history developed with the load reconstruction technique. Results: A strain history for the chisel was obtained from data collected during field tests. The data was filtered for the 14-16 km/h speed range, connected, and merged. The chisel load history was developed using the load reconstruction technique. The resulting load history was expressed as a load spectrum using the rain-flow counting method. Conclusions: A fatigue test was conducted on a chisel under a constant load condition with an equivalent load amplitude and number of cycles, as calculated by Miner's Rule for linear damage accumulation. During the fatigue test, there were no cracks at any position. It is concluded that the fatigue test method proposed in this study can be utilized successfully as a durability evaluation method for the chisel.

• 생물정신의학
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• 제16권4호
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• pp.238-245
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• 2009

Objectives : Mild Alzheimer's disease(AD) is uncertain to be related to visuospatial working memory subsystem dysfunction. We used the self ordered pointing test(SOPT) to find the characteristics of visuospatial working memory in mild AD. Methods : We compared the visuospatial working memory abilities of 20 patients with mild AD and 20 normal elderly controls(NC) using SOPT, of which stimuli consisted of two stimuli types(A : abstract, C : concrete) and two stimuli numbers(8 and 12). Therefore, working memory was tested using C8, C12, A8, and A12 stimuli conditions in SOPT. Mixed-model ANOVA was conducted with the AD and NC groups as between-subjects factor, with stimuli types and stimuli numbers as the within-subjects factors and with SOPT error rates as the dependent variable. Results : The AD group showed higher error rates in SOPT than the NC group. The NC group showed low error rates in concrete stimuli than in abstract stimuli and in small stimuli numbers than in large stimuli numbers. And the AD group showed no differences between stimuli types or stimuli numbers. Conclusion : AD patients showed a poor performance in visuospatial working memory using concrete stimuli. The result suggests that there is a non-transformation from visual input to phonological working memory in AD. Patients with AD showed a poor performance although in small stimuli number condition of SOPT. It suggests that in AD, visuospatial working memory is not working well although in low central executive loads.

• The Journal of Asian Finance, Economics and Business
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• 제8권7호
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• pp.295-302
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• 2021

In the context of economic growth, the banking system has greatly contributed to a substantial rise in living conditions, connecting savings and investment, and economic growth. Since economic reform in 1986, Vietnam's banking system has increasingly expanded in quality and quantity of banks including state-owned, private-owned, and foreign banks. The aim of this study is to evaluate the main factors affecting employee's performance in the banking system in the case of an emerging economy of Vietnam. Using the pilot study by investigating three experts in a few banks in order to correct the questionnaires, and a mega sample data of 170 observations conducted from bank's staffs, and managers in Hanoi capital of Vietnam, empirical results demonstrate that the independent variables included in the model can explain 67% of the change of the dependent variable of employee's performance, and the rest (31%) can be explained by other reasons. Further, motivation (MO), and working ability (WA) have a positive and insignificant impact on employee's performance, reflecting that motivation, and working ability have insignificantly affected employee's performance. In contrast, four factors, namely, welfare, working environment, cooperation, and education have a positive and significant impact on employee's performance in the case of Hanoi, Vietnam.

• 아동학회지
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• 제28권3호
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• pp.149-162
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• 2007

A questionnaire was distributed to 102 teachers who worked in non-profit, for-profit and company-operated child care centers. The relationships of demographic, work conditions, and social support variables were examined by correlation, one-way ANOVA, and multiple regressions. Results showed that working hours, salary and social support were the most important factors influencing emotional exhaustion. Higher levels of burnout were found among teachers of infants and toddlers who worked for more than 12 hours on average, teachers with lower salary, and those with a lower level of social support. Results in general indicated that shorter working hours was a very important variable for reduction in burnout among teachers of infants and toddlers.

• 한국산업정보학회논문지
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• 제4권4호
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• pp.154-163
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• 1999

본 연구는 산소결핍이 운전자에 미치는 영향을 여러 가지 모형으로 산소 테스트기로 실험하였다. 자동차 실내 유해물질 중 인체와 가장 밀접한 관련이 있는 산소의 농도와 소비량에 대하여 고찰하였고 아울러 산소가 생체내에서 소비되는 다양한 형태를 파악함으로써 본 연구에 대한 이해를 돕고자 한다. 이 시스템에서 고려되는 것은 운전자에게 건강상 유해를 일으키는 기체상 인자의 농도범위를 조사·연구하여 운전자가 얼마간의 운전후에 휴식을 실시거나 환기를 시켜야 한다는 것을 분석한다.