• 전력전자학회논문지
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• 제25권1호
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• pp.37-43
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• 2020

This study proposes a 7kW low-voltage DC-DC converter (LDC) using a coupled inductor (CI) for heavy hydrogen electric transport vehicles. The LDC uses a phase-shift manner for soft switching. SiC-MOSFET is used to reduce the loss of reverse recovery current through the use of a high switching frequency. LDC is require large transformer and inductor because of large output current. The size of transformer and inductor can be reduced by deviding the transformer and inductor into two pieces each. This work presents the experimental results of the proposed circuit.

• Safety and Health at Work
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• 제13권1호
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• pp.3-8
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• 2022

Background: This study aims to allow the development of efficient measures to improve occupational health of shift-working nurses focusing on job stress, health promotion behavior, resilience, and sleep disturbance. Methods: It was conducted on a subject panel of 137 nurses who were aware of the purpose of the study and agreed to participate. They worked three shifts at a tertiary hospital or a general hospital located in metropolitan city B. The collected data were analyzed by the independent t test and one-way analysis of variance and post-tested by Scheffe's test, Pearson's correlation coefficients, and multiple linear regression analysis using SPSS/WIN 25.0. Results: The significant influencing factors on sleep disturbance were of those whose subjective health status was 'normal' (b = 0.29, p < .001), 'not healthy' (β = .40, p < .001), who have job stress (β = .22, p = .003), and who have health promotion behavior (β = -0.17, p = .023). The overall explanatory power was 31.1% (F = 16.31, p < .001). Conclusion: Through this study, nurses' subjective health status and job stress of working shifts were found to be important factors influencing the sleep disturbance level, and the most influencing factor was identified as the subjective health status.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.1022-1028
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• 2024

A neutronics study of a supercritical CO₂-cooled fast reactor core for nuclear propulsion has been performed in this work. The thermal power of the reactor core is 30 MWth and a ceramic UO₂ fuel can be used to achieve a 20-year lifetime without refueling. In order to make a compact core with inherent safety features, the drum-type reactivity control system and folding-type shutdown system are adopted. In addition, we suggest a cold shutdown system using gadolinium as a spectral shift absorber (SSA) against flooding. Although there is a penalty of U-235 enrichment for the core embedded with the cold shutdown system, it effectively mitigates the increment of reactivity at the flooding of seawater. In this study, the neutronics analyses have been performed by using the continuous energy Monte Carlo Serpent 2 code with the evaluated nuclear data file ENDF/B-VII.1 Library. The supercritical CO₂-cooled fast reactor core is characterized in view of important safety parameters such as the reactivity worth of reactivity control systems, fuel temperature coefficient (FTC), coolant temperature coefficient (CTC), and coolant temperature-density coefficient (CTDC). We can say that the suggested core has inherent safety features and enough flexibility for load-following operation.

• 한국의료질향상학회지
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• 제5권1호
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• pp.28-40
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• 1998

Background : Many patients have been frequently complaining that they have to spend couples of hours in hospital on visiting outpatient clinic. Among several steps, two major time consuming steps were waiting to see a doctor and/or waiting at pharmacy to get medicine. Therefore not only to provide the proper guidance for medication or counseling on health affairs but also to make waiting time short is very important for the better hospital services. The aim of this study is to validate several time-saving processes to reduce waiting time at outpatient pharmacy and its efficacy. Methods : We surveyed the time interval actually taken to receive medicine after issuing prescription by doctors, and analyzed the data on the bases of relevant or possible causative factors. Then following processes were given to reduce waiting time and resurveyed and compared both data to validate efficacy of those processes : 1. No work-off on Monday and Tuesday 2. Work hour shift to start 30 minutes earlier 3. Changeable work shift between outpatient pharmacy and ward pharmacy according to work load 4. Use of pre-made medicines prescribed more frequently by certain doctors at certain time 5. Cooperation with doctors to use set prescriptions. Results : Before the process, mean waiting time at pharmacy was 29.2 minutes and most time consuming period was from noon to 1 PM, 3 to 4 PM, 1 to 2 PM in order of frequency. Only 37.7 % of patients could get the medicine within 20 minutes. Three times of surveys after process showed mean waiting time at pharmacy were 18.1 minutes, 19.0 minutes, and 17.6 minutes, respectively. And 72.7 %, 81.3%, and 82.2% of patients could get the medicine within 20 minutes. Conclusion : The mean waiting time was markedly reduced with above mentioned processes which applied intradepartmently event hough with little cooperation from other department. Consequently, the complaints of patients were decreased with increasing the satisfaction degree. In conclusion, those suggestions were recommanded to improve the degree of satisfaction of patients.

• 한국사회복지학
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• 제51권
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• pp.157-182
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• 2002

본 연구는 세계적으로 변화해 가고 있는 장애인에 대한 사회적 인식을 검토하고, 이러한 사회적 인식의 변화가 우리나라에서 장애인을 위한 사회복지실천 현장에 어떤 과제들을 요구하고 있는가를 제시하고자 한다. 이러한 연구 목적을 달성하기 위해서는 먼저, 보편적인 차원에서 장애에 대한 사회적 반응에 따라 장애인에 대한 서비스 패러다임이 어떤 방향으로 변화하고 있는지를 살펴본다. 이러한 논의를 바탕으로 장애에 대한 사회적 반응 및 서비스 패러다임의 변화가 우리나라의 실천현장에 요구하고 있는 함의들을 모색한다. 장애인에 대한 20세기 이전의 사회적 반응은 사회적으로 부적합하며, 장애는 개인의 책임으로 생각하였다. 그러다가 20세기 중반기와 후반기를 거치면서 장애에 대한 사회적 책임이 중요하게 제기되었다. 이러한 장애에 대한 사회적 반응의 변화는 장애를 설명하는 개념적 모델에서도 변화를 초래하였는데, 이른바 개별적 모델에서 사회적 모델로의 변화이다. 또한 사회적 반응 및 개념적 모델의 변화는 세계보건기구의 장애정의 및 분류에 영향을 미쳐서 1980년, 1997년, 2001년에 걸쳐서 새로운 정의와 분류체계들이 제시되었다. 이러한 변화들은 장애인에 대한 사회복지서비스 패러다임의 변화와 관련이 있으며, 이러한 흐름은 강점중심의 접근, 능력강화접근법, 사례관리, 자립생활모델 등을 통해서 설명된다. 장애에 대한 사회적 반응, 장애 개념, 서비스 패러다임의 변화는 동일한 방향으로 일관되게 전개되고 있다. 이러한 일관된 변화에 대한 논의를 통해서 본 연구에서 제기하는 실천현장에서의 함의는 사정과정에서 장애 당사자의 참여 강화, 사회 환경적 관점을 강조하는 방향으로의 사정 도구의 재검토, 장애당사자의 자기결정능력을 극대화하기 위한 정보제공 기능의 강화, 장애 당사자의 공식적 및 비공식적 원조망에 대한 지원 강화, 자조집단 프로그램의 강화, 배치모델에서 지원모델로의 전환 등으로 요약될 수 있다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.111.1-111.1
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• 2010

This paper focuses on a systematic configuration of steam reforming fuel processor, particularly designed for small and medium sized hydrogen production application. In a typical integration of the fuel processor, there exist significant temperature gradients over the entire system which has negative effect on both catalyst life-time and system performance. Also, the volumetric inefficiency should be avoided to obtain the possible compactness for the commercial purpose. In the present work, the computational analysis will be performed to gain the fundamental insight on the transport phenomena and chemical reactions in the reformer consisting of preheating, steam reforming (SR), and water gas shift (WGS) reaction beds in the flow direction. Also, the fuel processing system includes a top-fired burner providing necessary thermal energy for endothermic catalytic reactor. A fully two-dimensional numerical modeling for a integrated fuel processing system is introduced for in-depth analysis of the heat and mass transport phenomena based on surface kinetics and catalytic process. In the model, water gas shift reaction and decomposition reaction were assumed to be at equilibrium. A kinetic model was developed and then computational results were compared with the experimental data available in the literature. Finally, the case study was done by considering the key parameters, i.e. steam to carbon (S/C) ratio and temperature. The computer-aided models developed in this study can be greatly utilized for the design of advanced fast-paced compact fuel processors research.

• 대한간호학회지
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• 제47권4호
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• pp.476-487
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• 2017

Purpose: This study aimed to examine the effects of cognitive behavior therapy for insomnia (CBT-I) based on the mobile social networking service (SNS) on dysfunctional beliefs and attitudes about sleep, sleep quality, daytime sleepiness, depression, and quality of life among rotatingshift nurses in a hospital in Korea. Methods: A nonequivalent control group pre-post test design was used. The participants included 55 nurses with rotating three-shift work (25 in the experimental group and 30 in the control group). For the experimental group, CBT-I using mobile SNS was provided once a week for 60 minutes over six weeks. Data were analyzed using descriptive statistics, $x^2-test$, independent samples t-test, and Mann-whitney U test with the SPSS 21.0 program. Results: In the homogeneity test of the general characteristics and study variables, there were no significant differences between the two groups. Nurses in the experimental group had significantly lower scores on dysfunctional beliefs and attitudes regarding sleep and sleepiness than nurses in the control group. Nurses in the experimental group had significantly higher scores on sleep quality and quality of life than nurses in the control group. Conclusion: These findings indicate that using the mobile SNS-based CBT-I is feasible and has significant and positive treatment-related effects on rotating-shift nurses' irrational thoughts and beliefs in association with sleep, sleep quality, daytime sleepiness, and quality of life. These contribute to expanding our knowledge of rotating-shift nurses' sleep issues and their preferences for intervention.

• Animal cells and systems
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• 제9권3호
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• pp.153-160
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• 2005

Most living organisms exhibit the circadian rhythm in their physiology and behavior. Recent identification of several clock genes in mammals has led to the molecular understanding of how these components generate and maintain the circadian rhythm. Many reports have implicated the photic induction of either mPer1 or mPer2 in the hypothalamic region called the suprachiasmatic nucleus (SCN) to phase shift the brain clock. It is now established that peripheral tissues other than the brain also express these clock genes and that the clock machinery in these tissues work in a similar way to the SCN clock. To determine the role of the two canonical clock genes, mPer1 and mPer2, in the peripheral clock shift, stable HEK293EcR cell lines that can be induced and stably express these proteins were prepared. By regulating the expression of these proteins, it could be shown that induction of the clock genes, either mPer1 or mPer2 alone is not sufficient to cause clock phase shifting in these cells. Our real-time PCR analysis on these cells indicates that the induction of mPER proteins dampens the expression of the clock-specific transcription factor mBmal1. Altogether, our present data suggest that mPer1 and mPer2 may not function in clock shift or take part in differential roles on the peripheral circadian clock.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.122-122
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• 2008

Recently, Metal/Alumina/Silicon-Nitride/Silicon-Oxide/Silicon (MANOS) structures are one of the most attractive candidates to realize vertical scaling of high-density NAND flash memory [1]. However, as ANO layers are miniaturized, negative and positive bias temperature instability (NBTI/PBTI), such as the flat band voltage shift, ${\Delta}V_{FB}$, the interfacial trap density increase, ${\Delta}D_{it}$, the gate leakage current, ${\Delta}I_G$. and the retention characteristics, in MONOS capacitors, becomes an important issue in terms of reliability. It is well known that tunnel oxide degradation is a result of the oxide and interfacial traps generation during FN (Fowler-Nordheim) stress [2]. Because the bias temperature stress causes an increase of both interfacial-traps and fixed oxide charge could be a factor, witch can degrade device reliability during the program and erase operation. However, few studies on NBTI/PBTI have been conducted on improving the reliability of MONOS devices. In this work, we investigate the effect of post-annealing gas on bias temperature instability (BTI), such as the flat band voltage shift, ${\Delta}V_{FB}$, the interfacial trap density shift, ${\Delta}I_G$ retention characteristics, and the gate leakage current characteristics of MANOS capacitors. MANOS samples annealed at $950^{\circ}C$ for 30 s by a rapid thermal process were treated via additional annealing in a furnace, using annealing gases $N_2$ and $N_2-H_2$ (2 % hydrogen and 98 % nitrogen mixture gases) at $450^{\circ}C$ for 30 min. MANOS samples annealed in $N_2-H_2$ ambient had the lowest flat band voltage shift, ${\Delta}V_{FB}$ = 1.09/0.63 V at the program/erase state, and the good retention characteristics, 123/84 mV/decade at the program/erase state more than the sample annealed at $N_2$ ambient.

• Korean Chemical Engineering Research
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• 제49권1호
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• pp.21-27
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• 2011

메탄올 수증기 개질반응에 대한 적용가능성을 파악하기 위하여 메탄올 합성용 촉매인 ICI-M45와 수성가스 전환반응용 촉매인 MDC-3와 MDC-7을 비교 연구하였다. 또한 수성가스전환 반응에 대한 세 촉매의 비교실험도 수행하였다. 그 결과 MDC-7이 메탄올 수증기 개질반응에서 가장 높은 전화율을 보였으며, $H_2$와 $CO_2$ 생성속도 또한 높게 나타났다. 수성가스 전환반응용 촉매인 MDC-7과 메탄올 합성촉매인 ICI-M45를 이용하여 촉매 충진 방법에 따른 메탄올의 전화율에서의 변화를 살펴본 결과, MDC-7 단독보다 낮은 메탄올의 전화율을 보였다. 수성가스 전환반응에서도 DC- 7, MDC-3, 그리고 ICI-M45의 순으로 반응성이 감소하였다. 상기 두 반응에서 MDC-7이 가장 우수한 이유로는 높은 비표면적과 Cu의 분산도, 그리고 적절한 Cu와 Zn의 비율에 기인함을 확인할 수 있었다.