• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.444-444
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• 2011

Recently, patterned magnetic films and elements attract a wide interest due to their technological potentials in ultrahigh-density magnetic recording and spintronic devices. Among those patterned magnetic structures, magnetic anti-dot patterning induces a strong shape anisotropy in the film, which can control the magnetic properties such as coercivity, permeability, magnetization reversal process, and magneto-resistance. While majority of the previous works have been concentrated on anti-dot arrays with a single magnetic layer, there has been little work on multilayered anti-dot arrays. In this work, we report on study of the magnetic properties of bilayered anti-dot system consisting of upper perforated Co layer of 40 nm and lower continuous Ni layer of 5 nm thick, fabricated by photolithography and wet-etching processes. The magnetic hysteresis (M-H) loops were measured with a superconducting-quantum-interference-device (SQUID) magnetometer (Quantum Design: MPMS). For comparison, investigations on continuous Co thin film and single-layer Co anti-dot arrays were also performed. The magnetic-domain configuration has been measured by using a magnetic force microscope (PSIA: XE-100) equipped with magnetic tips (Nanosensors). An external electromagnet was employed while obtaining the MFM images. The MFM images revealed well-defined periodic domain networks which arise owing to the anisotropies such as magnetic uniaxial anisotropy, configurational anisotropy, etc. The inclusion of holes in a uniform magnetic film and the insertion of a uniform thin Ni layer, drastically affected the coercivity as compared with single Co anti-dot array, without severely affecting the saturation magnetization ($M_s$). The observed changes in the magnetic properties are closely related to the patterning that hinders the domain-wall motion as well as to the magneto-anisotropic bilayer structure.

• 한국건설관리학회논문집
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• 제5권2호
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• pp.194-201
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• 2004

코어월 선행공사는 공기단축, 비용 절감 효과 등과 같은 이점 등으로 인하여 국내 초고층건물공사에서 널리 적용되고 있다. 그러나 본 연구에서 수행한 사례조사연구에 따르면 초고층건물 코어월 선행공사 수행 과정에서 작업 공간 및 작업 동선 등의 미확보로 인한 생산성 저하, 코어월 선행공사의 세부 작업 및 양중장비 등의 작업 간섭으로 인한 공기 지연, 추가 가설 공사 및 비용 발생, 콘크리트 타설 작업의 지연 등으로 인한 공사비 증가와 공기 지 연 등의 문제가 발생하고 있었다. 이러한 문제의 발생원인을 분석한 결과, 시공계획 과정에서 좀더 치밀하고 세심한 주의를 기울여서 계획을 수립하고 공사에 임했을 경우, 이것들의 상당수는 발생을 미연에 방지할 수 있음을 알 수 있었다. 이에 본 연구에서는 이러한 문제점들을 해결하기 위한 기초 단계로서 시공계획 과정에서의 도급자와 하도급자간의 협력체계 개선 방향과 시공계획 과정의 개선 방향 등을 제안하였다.

• 대한기계학회논문집
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• 제16권2호
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• pp.325-335
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• 1992

In this work, direct contact 4-stage fluidized bed heat exchanger is experimentally studied to develop a new type of heat exchanger which recovers the energy contained in the high temperature waste gas exhausted from the industrial furnaces. A sand is used as a heat transfer medium in this experiment. To determine the optimum operating condition, 11 different perforated plates which have a different free area ratio with different hole diameter are used in the experiment. From the room temperature experiment, the pressure drop which is caused by fluidized bed formation is observed. The high temperature experiment is carried out to seek the optimum operating condition of high heat efficiency at low heat exchanger operation cost. The results of experiment are as following. The pressure drop in the high temperature condition can be predicted from the results of the room temperature experiment. And Nusselt number becomes smaller due to the increased interference between sand particles as Reynolds number increases when the dilute phase fluidized beds are formed in nigh temperature condition. But heat transfer amount through the total sand surface area become larger due to the large resident amount of sand. Considering the heat transfer amount and the heat exchanger operation cost, perforated plates which have either a 30% or 35% of free area ratio with 15mm of hole diameter are best fitted for our goal of this work. The values of .phi. which is a dimensionless number representing the absorption heat amount per unit sand rate are in the range from 0.4 to 0.5, when Reynolds number of waste gas ranges from 25-30 with these perforated plates.

• 보건행정학회지
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• 제2권2호
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• pp.57-89
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• 1992

This study is aimed both to reorient the Health net-works focused to Health Subcenters in times of development of local autonomy in Korea and to collect the fundamental data such as attitude and practice of the directors of Health Subcenter. The materials are collected from 134 out of 258 sampling directors of Health Subcenters with a questionaire by mailing(respond rate 51.9%). The major findings of this fundamental data are as follows. 1. Current average number of outpatients cared by a director of Health Subcenter is found to be 21.6. 2. The directors of Health Subcenter have little deducted hours for Public Health Programme. 3. Number of the Preventive Health Programme worked by a director of Health Subcenter is from 0 to 3. The most major group worked only 1 programme marked at 69.4%. 4. The directors of Health Subcenter express approval opinin marked at 80.2% that their qualification to appoint has to finish intern course. 5. The average diagnosis allowance a month is approximately twenty hundred thousand won. 6. Most of Health Subcenter(market at 94%) adopted a self-supporting account system. 7. The most complaining subject of directors of Health Subcenter is their working environment. The second complaining subject is governmental officier's interference. 8. The average number of outpatients cared by a director of Health Subcenter is found to be certain differentials by their marriage and the duration of employment. Some proposals of development on Health Subcenter based on the result of this research is as follows : 1. The reorganization on Health Subcenter under line of National Health Center Net-work 2. The psychological reorientation of directors of Health Sucenter and officers. 3. Autonomy management of Health Subcenter. 4. Reorientation of status on directors of Health Subcenter.

• Journal of Korean Society for Atmospheric Environment
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• 제23권E2호
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• pp.66-73
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• 2007

The introduction of tracer gas techniques to ventilation studies in indoor environments provides valuable information that used to be unattainable from conventional testing environments. Data acquisition systems (DASs) containing analogue-to-digital (A/D) converters are usually used to function the key role that records signals to storage in digital format. In the testing process, there exist a number of components in the measuring equipment which may produce system-based inference to the monitored results. These unwanted fluctuations may cause significant error in data analysis, especially when non-linear algorithms are involved. In this study, a pre-processor is developed and applied to separate the unwanted fluctuations (noise or interference) in raw measurements and to reduce the uncertainty in the measurement. Moving average, notch filter, FIR (Finite Impulse Response) filters, and IIR (Infinite Impulse Response) filters are designed and applied to collect the desired information from the raw measurements. Tracer gas concentrations are monitored during leakage and ventilation tests in the model test room. The signal analysis functions are introduced to carry out the digital signal processing (DSP) work. Overall the FIR filters process the $CO_2$ measurement properly for ventilation rate and mean age of air calculations. It is found that, the Kaiser filter was the most applicable digital filter for pre-processing the tracer gas measurements. Although the IIR filters help to reduce the random noise in the data, they cause considerable changes to the filtered data, which is not desirable.

• 한국사회복지학
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• 제43권
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• pp.157-192
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• 2000

This Study concerns therapeutic effects of the Therapy Dog Assisted Program (TDAP) on autistic children. Subjects participating in the study are two groups of Korean elementary schoolboys of the same age (twelve years old) : an experimental group and a control1ed group of equal number of children (sex children in total). Thirteen different sessions of TDAP interventions were performed over a three-month period. Evidence from the present study indicates that the children participating in the TDAP program achieved a greater degree of improvement in their social interactions as well as in their individual activities in comparison with the preTDAP counterparts. The present study also demonstrates significant changes in the TDAP group in comparison with those in the non-participating control group. The results from this study supports that the proposition that the Therapy Dog Assisted Program can be applied effectively in treating people experiencing severely damaged social functioning. Such a program may serve as an effective treatment modality in a variety of clinical social work settings. The questions of long-term effects of the TDAP intervention and possible interference with other behavioral side-effects on the part of the intervened subjects need to be addressed in future studies.

• 한국건축시공학회지
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• 제13권3호
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• pp.291-305
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• 2013

This paper presents the continuous hoop reinforcement method as a means to overcome the difficulty of rebar construction due to the seismic detail of lateral reinforcement. Because the continuous hoop has no seismic hook, and there is less interference during the rebar work, rebar quantities and construction time can be reduced. Since the details of column and beam continuous hoops are different from those of conventional lateral reinforcements, the construction method should be developed through mock-up tests. The length of the beam mock-up is 8m and the section size is $500mm{\times}700mm$, the height of the column mock-up is 2.8m and 4m, and the section size is $800{\times}800mm$. The length and the size are determined based on the elements that are generally used in reinforced concrete basement parking lots and office buildings. The results of the mock-up test showed that the quantities of rebar could be reduced by 20% and the time could be reduced by up to 40% compared with conventional lateral reinforcements.

• 전자공학회논문지T
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• 제36T권3호
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• pp.64-71
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• 1999

본 논문에서는 DD(Direct-drive)의 기구로서 2자유도 평행링크 기구를 사용하였다. 평행링크 기구는 2개의 모터가 각각 기저부에 설치되어 있기 때문에 모터 자체의 질량이 다른 모터에 부하가 되지 않고, 링크의 수는 증가하지만 arm의 질량이 가볍게 되어, 링크 파라미터의 설정에 의하여 원심력 등의 비선형력이 없어지며 동시에 모터사이의 비간섭화를 실현할 수 있다. 그리고 평행링크 DD로븟 매니퓰레이터의 고정도 운전의 실현을 위하여 신경회로망을 이용한 학습제어계를 설계하여 학습속도의 개선과 함께 변화한 작업대상에의 적응력을 개선하기 위하여 신경회로망과 피드백제어기로 학습제어 알고리즘을 구성한다.

• 전력전자학회논문지
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• 제24권6호
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• pp.396-405
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• 2019

Single-phase full-bridge inverters have shoot-through problems. Dead time is an essential way of solving these issues, but it distorts the output voltage and current. Dual-buck inverters are designed to eliminate the abovementioned problems. However, these inverters result in switching power loss and electromagnetic interference due to the diode reverse-recovery problem. Previous studies have suggested reducing the switching power loss from diode reverse-recovery, but their proposed methods have complex circuit configurations and high system costs. To alleviate the switching power loss from diode reverse-recovery, the current work proposes a dual-buck inverter with a coupled inductor. In the structure of the proposed inverter, the current flowing into the original diode is divided into a new diode. Therefore, the switching power loss is reduced, and the efficiency of the proposed inverter is improved. Simulation waveforms and experimental results for a 1.0 kW prototype inverter are discussed to verify the performance of the proposed inverter.

• 전력전자학회논문지
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• 제24권6호
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• pp.459-462
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• 2019

This work presents methods for reducing overshoot voltages across the drain-source of silicon carbide (SiC) MOSFETs in grid-connected hybrid active neutral-point-clamped (ANPC) inverters. Compared with 3-level NPC-type inverter, the hybrid ANPC inverter can realize the high efficiency. However, SiC MOSFETs conduct its switching operation at high frequencies, which cause high overshoot voltages in such devices. These overshoot voltages should be reduced because they may damage switching devices and result in electromagnetic interference (EMI). Two major strategies are used to reduce the overshoot voltages, namely, adjusting the gate resistor and using a snubber capacitor. In this paper, advantages and disadvantages of these methods will be discussed. The effectiveness of these strategies is verified by experimental results.