• 대한수학회보
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• 제56권3호
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• pp.789-799
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• 2019

In this paper, we deal with unicity of a nonconstant zero-order meromorphic function f(z) and its shift f(qz) when they share four distinct values IM or share three distinct values with multiplicities truncated to level 4 in the extended complex plane, where $q{\in}\mathbb{C}{\setminus}\{0\}$. We also give an uniqueness result for f(z) sharing sets with its shift.

• 한국사회복지학
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• 제69권2호
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• pp.9-30
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• 2017

체제의 전환은 정책의 변화나 정부의 교체보다는 덜 자주 발생한다. 사회경제 연합, 정치경제 제도, 공공정책의 양상이라는 체제를 구성하는 세 가지 요소 모두의 변화가 이루어질 때 체제의 전환은 가능하다. 이 연구는 한국 생활보장체제의 전환 가능성이 상당히 높은 지금의 시점에서 필요한 과제를 모색하는 것을 목적으로 한다. 이를 위해 2절에서는 한국 생활보장체제의 전개과정과 특성을 필자의 선행연구들에서 주장한 '개발국가형 생활보장체제'의 관점에서 살펴보았다. 3절에서는 한국 생활보장체제의 전환을 위해 필요하다고 생각하는 3가지의 과제를 제시하였는데, 그것은 정치제도의 개혁, 재정지출 구조의 개혁, 그리고 비공식 취업의 축소 등이다. 이러한 과제들은 사회경제 연합의 변화와 새로운 정치경제 제도의 등장을 요구한다는 점에서 체제전환과 관련한 정책적 과제이다. 한편, 4절에서는 한국 사회복지의 새판 짜기와 관련하여 우리 학문 공동체에 붙여보고 싶은 두 가지의 토론거리를 결론을 대신하여 제기하였다.

• Safety and Health at Work
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• 제10권1호
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• pp.109-113
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• 2019

Background: In both developed and developing countries, noise is regarded as the most common occupational hazard in various industries. The present study aimed to examine the effect of sound pressure level (SPL) on serum cortisol concentration in three different times during the night shift. Methods: This case-control study was conducted among 75 workers of an industrial and mining firm in 2017. The participants were assigned to one of the three groups (one control and two case groups), with an equal number of workers (25 participants) in each group. Following the ISO 9612 standard, dosimetry was adopted to evaluate equivalent SPL using a TES-1345 dosimeter. The influence of SPL on serum cortisol concentration was measured during the night shift. The serum cortisol concentration was measured using a radioimmunoassay (RIA) test in the laboratory. Repeated measure analysis of variance and linear mixed models were used with ${\alpha}=0.05$. Results: The results indicated a downward trend in the serum cortisol concentration of the three groups during the night shift. Both SPL and exposure time significantly affected cortisol concentration (p < 0.0001, p < 0.0001). Conversely, age and body mass index had no significant influence on cortisol concentration (p = 0.360, p = 0.62). Conclusion: Based on the obtained results, increasing SPL will lead to enhancement of serum cortisol concentration. Given that cortisol concentration varies while workers are exposed to different SPLs, this hormone can be used as a biomarker to study the effect of noise-induced stress.

• 한국직업건강간호학회지
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• 제31권3호
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• pp.125-136
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• 2022

Purpose: The aim of this systematic literature review was to synthesize and investigate the effects of shift workers' sleep in Korea. Methods: A search was conducted through three electronic databases using keywords such as "shift work" or "rotation work" and "sleep", with sleep as the independent variable, and 17 papers were reviewed. Results: The design of those 17 studies was analyzed in a cross-sectional analysis. The most commonly measured characteristic was quality of sleep, whereas the others were sleep disturbance, sleep efficiency, and sleepiness. The study outcome variables were job-related factors, mental health, wellness, stress, fatigue, and metabolic syndrome. Conclusion: The results inform sleep and health-promoting behaviors and improvement in shift workers' working condition.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.96-100
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• 1997

The shadow moire is one of the optical techniques which is able to give contour lines of an object with respect to a master grating plane. The moire patterns are issued from the superposition of a master grating and its shadow projected on the surface of an object. In case of the classical shadow moire method, the sensitivity was a few tenths millimeters. generally, it is difficult to use a phase shift method in shadow moire because it is impossible to obtain uniform phase shifts on the whole field. But in this study we use the fact that if the depth of object is much less than the distance between the observer and the master grating, and the object is displaced perpendicularly to the grating plane, phase shifts are almost uniform. Finally we obtained a better resolution by using a phase shift procedure and applied the phase shifting shadow moire to three dimensional shape measurement.

• Journal of Power Electronics
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• 제19권6호
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• pp.1337-1350
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• 2019

This paper proposes a Phase-Shift Triple Full-Bridge (PSTB) Zero-Voltage Zero-Current-Switching (ZVZCS) converter with a high switching frequency and high efficiency. In the proposed converter, all three bridge legs are shared leading-legs, and all three transformers work in the Discontinuous Conduction Mode (DCM). Thus, all of the switches and diodes in the PSTB ZVZCS can be soft switched. Moreover, since all of the transformers can pass energy from the primary-side to the secondary-side when their primary-side currents are not zero, there is no circulating current. As a result, the PSTB ZVZCS converter can achieve a high efficiency at high operating frequencies. A theoretical analysis and the characteristics of the proposed converter are presented and verified on a 1MHz 200~300V/24V 1.2kW hardware prototype. The proposed converter can reach a peak efficiency of 96.6%.

• 한국직업건강간호학회지
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• 제7권2호
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• pp.155-163
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• 1998

In order to investigate the effects of rotating shift work on the subjective characteristics of sleep and mental depression questionnaire survey was carried out on 405 shift workers and 153 nonshift workers who were nurses employed. in three university hospital. The questionnaire forms used in this study were the self rating depression scale(SDS) and circadian type questionnaire(CTQ) factor R(rigidity/flexbility of sleeping habit) and factor V(inability/ability to overcome drowsiness). The results were as follows ; 1. Mean score of CTQ R in shift workers was significantly lower than that in nonshift workers, however, no significant difference in CTQ V was observed between two groups. 2. Mean score of SDS was significantly higher in shift workers(44.1) than in nonshift workers(39.8). 3. Mean self rating depression scale scores of pervasive affect, physiologic equivalents and psychological equivalents were significantly higher in shift workers than in nonshift workers. 4. In shift worker, mean SDS score was the highest in confusion and followed by diurnal variation, retardation, and indeciveness in the descending order. In nonshift worker, that score was the highest in decreased libido and followed by confusion, and indeciveness in the descending order. 5. Circadian type questionnaire scores was significantly and negatively correlated with significantly and negatively correlating with Self-rating depression scale scores(r=-0.473).

• 한국항만경제학회지
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• 제27권2호
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• pp.137-161
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• 2011

본 연구의 목적은 국내 외 전환교통의 추진실태의 분석과 시사점을 토대로 한국에서 전환교통을 수립하기 위한 기본정책방향을 제시하는 데 있다. 중요한 연구내용은 전환교통정책의 이론적 고찰, 국내 외 전환교통실태와 정책분석, 한국의 전환교통정책의 수립방향 등을 포함하고 있다. 전환교통(modal shift)은 여객 또는 화물을 운송하는 데서 운송수단을 화물차에서 철도 또는 선박으로 전환하는 것이다. 전환교통은 범세계적인 환경규제의 시대에 친환경 물류체계를 달성할 수 있는 중요한 정책수단이다. 한국에서 기존 전환교통정책은 대상화물의 선정, 지원금의 지급대상과 산정기준 등에서 문제점이 나타나고 있다. 선진 외국의 전환교통정책을 살펴보면, 전환교통정책방향의 명확화, 실천 가능한 정책목표의 설정, 전환교통의 간접지원 강화 등의 시사점이 발견된다. 따라서 한국에서 전환교통정책을 활성화시키기 위해서는 정책의 수립단계부터 계획과 관리 측면에서 정책방향을 강구하는 것이 중요하다. 계획 측면의 전환교통정책의 수립방향은 전환교통정책 수립방향의 명확화, 운송수단별 사회적 비용 등 기초연구의 실시 및 철도시설정비방향의 설정 등으로 제시되고 있다. 한편 관리 측면에서 전환교통정책의 수립방향은 도로운송 지원정책과의 사전 상호조정 및 전환교통 대상화물의 전략적 관리 등으로 확인되어진다. 본 연구는 학술적인 정책연구의 특성이 강하다. 그래서 전환교통정책을 수립하는 데필요한 기본이론을 제공하며, 정책수립의 중요한 기본방향을 강구하는 데 연구의의가 있다.

• 대한의용생체공학회:의공학회지
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• 제30권6호
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• pp.461-468
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• 2009

Magnetic resonance electrical impedance tomography (MREIT) enables us to perform high-resolution conductivity imaging of an electrically conducting object. Injecting low-frequency current through a pair of surface electrodes, we measure an induced magnetic flux density using an MRI scanner and this requires a sophisticated MR phase imaging method. Applying a conductivity image reconstruction algorithm to measured magnetic flux density data subject to multiple injection currents, we can produce multi-slice cross-sectional conductivity images. When there exists a local region of fat, the well-known chemical shift phenomenon produces misalignments of pixels in MR images. This may result in artifacts in magnetic flux density image and consequently in conductivity image. In this paper, we investigate chemical shift artifact correction in MREIT based on the well-known three-point Dixon technique. The major difference is in the fact that we must focus on the phase image in MREIT. Using three Dixon data sets, we explain how to calculate a magnetic flux density image without chemical shift artifact. We test the correction method through imaging experiments of a cheese phantom and postmortem canine head. Experimental results clearly show that the method effectively eliminates artifacts related with the chemical shift phenomenon in a reconstructed conductivity image.

• Journal of Power Electronics
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• 제15권5호
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• pp.1392-1401
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• 2015

Inverter configurations for multiple-load induction cooking applications need development. Inverter configurations for induction cooking applications are used in home appliances based on single coil inverters. For multiple-load configurations, multiple coils are used. They require proper inverters, which provide independent control for each load and have fewer components. This paper presents a three-leg inverter configuration for three load induction cooking applications. Each induction coil powers one induction cooking load. This configuration operates with constant switching frequency and powers individual loads. The output power of the required load is controlled with a phase-shift control technique. This configuration is simulated and experimentally tested with three induction loads. The simulation and experimental results are in good agreement. This configuration can be extended to more loads.