• 한국화재소방학회논문지
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• 제31권6호
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• pp.16-22
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• 2017

국내에서는 복잡해지고 다양해지고 있는 건축물에서의 화재위험에 대응하기 위해 성능기반 화재안전 설계가 논의되고 있지만, 건축물에서의 다양한 인자들에 의한 화재특성의 에측의 어려움으로 인하여 성능기반 화재안전 설계의 도입이 제한되고 있다. 본 연구에서는 뉴질랜드에서 제시하고 있는 화재위험도별 화재하중 값의 실대형 화재실험을 통해 성능기반 설계 도입을 위한 기준 방향 설정 및 기초 자료로 사용하고자 하였다. 실대형 화재실험은 10 MW급의 실대형 칼로리미터에서 $0.8(L){\times}2.0(H)m$의 단일 개구부를 포함하고 있는 $2.4(L){\times}3.6(W){\times}2.4(H)m$ 크기의 시험체 틀의 내부에 목재 크립을 화재하중에 따라 배치시켜, 목재 크립이 전소할 때 까지 진행하였다. 화재실험에서 열방출률의 변화는 목재 크립에 화염이 착화 된 후 외부로 출화되는 약 90초 이후부터 급격히 증가하였으며, 위험도 레벨 1에서는 최대 4743.4 kW의 열발출률이 실험시작 후 244 초에 측정되었고 위험도 레벨 2에서는 5050.9 kW의 최대 열방출률이 497 초에 측정되었다. 또한 위험도 레벨 3에서는 최대 열방출률이 4446.9 kW로 실험시작 677 초에 측정되었다.

• 터널과지하공간
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• 제14권1호
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• pp.54-68
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• 2004

본 연구에서는 경제성장기에 고층 구조물 시공에서 널리 사용된 철근콘크리트(RC, Reinforced Concrete) 구조물을 대상으로 발파해체 축소모형실험을 수행하고 전산실험결과와 이를 비교하였다. 발파해체 공법으로는 파괴거동을 비교적 쉽게 확인할 수 있는 점진붕괴공법을 적용하였으며, 축소모형실험은Hobbs(1969)에 의한 축소율의 개념에 따라 차원해석을 실시하여 축소된 강도특성을 계산하였다. 사용재료로는 석고, 모래, 물의 혼합액을 콘크리트 대용으로 사용하였다. 모래와 석고의 중량 비를 다양하게 변화시키면서 이에 따른 강도의 변화를 측정하고 최적의 강도 값을 갖는 배합 비를 결정하였다. 또한 연성을 가지고 있으며 축소강도로 비교할 때 철근과 유사한 특성을 지니는 땜용 납선을 철근대용 재료로 사용하였다. 수치해석 프로그램으로는 요소의 파괴거동을 육안으로 확인할 수 있는 개별 요소법(DEM Distinct Element Method)에 의해 수행되는 상용코드인 PFC2D(Particle Flow Code 2-Dimension)을 사용하였다. 모형의 제작은 실내에서 미리 양생된 부재들을 현장으로 옮겨 연결부만을 타설하여 일체화시키는 방법으로 이루어졌다. 먼저 3차원 무근 콘크리트 라멘 구조의 모형을 설계하고 그 축소 모형을 발파해체하여 그 거동을 촬영하였다. 이를 수치적인 해석과 비교하는 과정을 통해 2차원 해석이라는 한계성은 존재하지만 대체로 유사한 형태의 거동을 보임을 알 수 있었다. 사전해석의 경험과 RC 보의 실내 굴곡 실험결과를 근거로 하여 RC 구조모형의 발파해체 사전해석을 실시하였다. 시차는 200㎳로 하여 점진적으로 붕괴되도록 설계하였다. 모형실험과는 달리 2차원 해석이라는 한계에도 불구하고 900㎳까지 매우 유사한 거동을 보이며 붕괴되었다.

• Computers and Concrete
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• 제33권5호
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• pp.605-619
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• 2024

The increase of reclaimed asphalt pavement (RAP) content in recycled asphalt concrete (RAC) is accompanied by the degradation of low-temperature cracking resistance, which has become an obstacle to the development of RAC. This paper aims to reveal the meso-scale mechanisms of the low-temperature fracture behavior of RAC and provide a theoretical basis for the economical recycling of RAP. For this purpose, micromechanical heterogeneous peridynamic model of RAC was established and validated by comparing three-point bending (TPB) test results against corresponding numerical simulation results of RAC with 50% RAP content. Furthermore, the models with different aggregate shapes (i.e., average aggregates circularity (${\bar{C_r}}=1.00$, 0.75, and 0.50) and RAP content (i.e., 0%, 15%, 30%, 50%, 75%, and 100%) were constructed to investigate the effect of aggregate shape and RAP content on the low-temperature cracking resistance. The results show that peridynamic models can accurately simulate the low-temperature fracture behavior of RAC, with only 2.9% and 13.9% differences from the TPB test in flexural strength and failure strain, respectively. On the meso-scale, the damage in the RAC is mainly controlled by horizontal tensile stress and the stress concentration appears in the interface transition zone (ITZ). Aggregate shape has a significant effect on the low-temperature fracture resistance, i.e., higher aggregate circularity leads to better low-temperature performance. The large number of microcracks generated during the damage evolution process for the peridynamic model with circular aggregates contributes to slowing down the fracture, whereas the severe stress concentration at the corners leads to the fracture of the aggregates with low circularity under lower stress levels. The effect of RAP content below 30% or above 50% is not significant, but a substantial reduction (16.9% in flexural strength and 16.4% in failure strain) is observed between the RAP content of 30% and 50%. This reduction is mainly attributed to the fact that the damage in the ITZ region transfers significantly to the aggregates, especially the RAP aggregates, when the RAP content ranges from 30% to 50%.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2011년도 한국우주과학회보 제20권1호
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• pp.23.4-23.4
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• 2011

MIRIS is the main payload of the Science and Technology Satellite-3 (STSAT-3). which is being developed by KASI for infrared survey observation of the Galactic plane at Paschen alpha wavelength. Wideband filters in I and H band will also be used to observe cosmic infrared background. The MIRIS will perform astronomical observations in the near-infrared wavelengths of 0.9~2 ${\mu}m$ using a 256 ${\times}$ 256 Teledyne PICNIC FPA sensor providing a 3.67 ${\times}$ 3.67 degree field of view with a pixel scale of 51.6 arcsec. The flight model of the MIRIS has been recently developed, The system performance tests have been made in the laboratory, including opto-mechanics test, vibration test, thermal vacuum test and passive cooling test down to 200K, using a thermally controlled vacuum chamber. Several focus tests showed good agreements compared to initial design parameters. Recent efforts are being concentrated to improve the system performances, particularly to reduce readout noise level in electronics. After assembly and integration into the satellite bus, the MIRIS will be launched in 2012.

• 한국철도학회논문집
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• 제16권1호
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• pp.47-51
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• 2013

본 논문은 연약지반 쉴드 TBM 축소 모형실험을 통하여 슬러리에 의해 가해지는 막장 지보압의 변화에 따른 터널 막장면 안정성 변화 양상을 파악하고자 토피고에 따라 0.5D, 0.75D, 1.0D, 1.25D, 1.5D의 총 5개 Case에 대하여 모형실험을 수행하였으며, 이론적인 터널 막장면 지보압 및 모형실험으로 선정된 적정 지보압 값을 상호 비교하였다. 암반 쉴드 TBM과 달리 연약지반 쉴드 TBM의 경우 균질한 지반조건임에 따라 모형실험으로부터 산정된 적정 지보압이 터널 심도에 따른 막장면 토압 및 수압으로부터 이론적으로 산정된 막장압 범위($P_{min}{\leq}P_{slurry\;pressure}{\leq}P_{max}$)와 잘 일치하고 있음을 확인하였다.

• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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• pp.512-521
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• 2017

This paper reports development process of a university-based sounding rocket using simplified hybrid rocket propulsion system for low-altitude flight application. A hybrid propulsion system was tried to be designed with as few components as possible for more economical, simpler and safer propulsion system, which is essential for the small scale sounding rocket operation as a CanSat carrier. Using blow-down feeding system and catalytic ignition as combustion starter, 250 N class hybrid rocket system was composed of three components: a composite tank, valves, and a thruster. With a composite tank filled with both hydrogen peroxide($H_2O_2$) as an oxidizer and nitrogen gas($N_2$) as a pressurant, the feeding pressure was operated in blowdown mode during thruster operation. The $MnO_2/Al_2O_3$ catalyst was fabricated for propellant decomposition, and ground test of propulsion system showed the almost theoretical temperature of decomposed $H_2O_2$ at the catalyst reactor, indicating sufficient catalyst efficiency for propellant decomposition. Auto-ignition of the high density polyethylene(HDPE) fuel grain successfully occurred by the decomposed $H_2O_2$ product without additional installation of any ignition devices. Performance test result was well matched with numerical internal ballistics conducted prior to the experimental propulsion system ground test. A sounding rocket using the developed hybrid rocket was designed, fabricated, flight simulated and launch tested. Six degree-of-freedom trajectory estimation code was developed and the comparison result between expected and experimental trajectory validated the accuracy of the developed trajectory estimation code. The fabricated sounding rocket was successfully launched showing the effectiveness of the simplified hybrid rocket propulsion system.

• 대한물리의학회지
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• 제7권3호
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• pp.259-265
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• 2012

Purpose : Patients with Parkionson's disease have a temporal and spatial restriction for their's exercise treatment. The aim of this study is to verify the effectiveness of e-exercise program on balance, gait, and endurance ability in people with Parkinson's disease. Methods : Eighteen participants, with Parkinson's disease that ranged from stage to on the Hoehn & Yahr scale, were assigned to two group. Two group were divided into on-line group that exercised in home by computer video, and off-line group that exercised in clinical center. Exercise program that included 3 sections (warm-up, main exercise, cool down)-5 parts(stretch, strength, balance, gait, stretch) was used to train for participants. We used the functional reach test for balance ability, timed up and go test for gait ability, 6 minute walking test for endurance ability. Wilkoxon sign lank tests were used to assess the difference of balance, gait, and endurance ability in pre-and post test each groups. Mann-whitney tests were used to assess the difference of balance, gait, and endurance ability between groups. Results : Wilkoxon sign lank tests revealed that both group were improved the balance, gait and endurance agility by e-exercise program intervention. Mann-whitney tests showed that there were no differences between groups in the variation of balance, gait, endurance ability. Conclusion : We believe that exercise program with on-line(e-exercise program) is an effective intervention for people with Parkinson's disease and is no different than off-line exercise group in the variation of balance, gait, endurance ability.

• Wind and Structures
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• 제38권2호
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• pp.129-146
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• 2024

Aiming at the problem of non-stationary wind field simulation of downbursts, a non-stationary down-burst generation system was designed by adding a nozzle and program control valve to the inlet of the original wall jet model. The computational fluid dynamics (CFD) method was used to simulate the downburst. Firstly, the two-dimensional (2D) model was used to study the outflow situation, and the database of working conditions was formed. Then the combined superposition of working conditions was carried out to simulate the full-scale measured downburst. The three-dimensional (3D) large eddy simulation (LES) was used for further verification based on this superposition condition. Finally, the wind tunnel test is used to further verify. The results show that after the valve is opened, the wind ve-locity at low altitude increases rapidly, then stays stable, and the wind velocity at each point fluctuates. The velocity of the 2D model matches the wind velocity trend of the measured downburst well. The 3D model matches the measured downburst flow in terms of wind velocity and pulsation characteris-tics. The time-varying mean wind velocity of the wind tunnel test is in better agreement with the meas-ured time-varying mean wind velocity of the downburst. The power spectrum of fluctuating wind ve-locity at different vertical heights for the test condition also agrees well with the von Karman spectrum, and conforms to the "-5/3" law. The vertical profile of the maximum time-varying average wind veloci-ty obtained from the test shows the basic characteristics of the typical wind profile of the downburst. The effectiveness of the downburst generation system is verified.

• 한국간호교육학회지
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• 제7권1호
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• pp.68-80
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• 2001

This study is aimed to evaluate the effects of the educational program that is designed to help the patients of T.K.R.A. to improve their self-nursing ability. The research will show how well this program can contribute to raising of their adaptability of everyday life by decreasing the difficulties that the patients had before in their daily life. The sample persons for this research were 40 adult patients who had T.K.R.A. in our hospital, and the data were collected through the questionnaires which were given to them. For the surveying tool, Jette's scale was applied to measure the degree of uncomforting that the patients experienced in their daily life. The materials of report had been gathered from May 1st to December 10th. The collected data were analyzed with real numbers, percentage, average, the standard deviation, TorF test and Pearsons correlation. The results of this study can be summarized like follows: The survey of self-caring exercise part were processed with two groups containing experiment group and contrast group. The exercise which took the highest points in experiment group was repetition of stretching and bending knees with laid down position while taking a walk, repetition of stretching and bending knees with seated on chair position and repetition of stretching and bending knees with laid down position got high points in contrast group. There were distinctive differences in statistics between repetition of stretching and bending knees in laid down position and taking a walk. There was no significant statistical gap between the degrees of inconveniences of daily life that each two groups experienced when we compared the average of the two groups, but 12 out of 20 questions got considerable differences. According to common characters of self-caring, there was a distinctive gap in the group who left the hospital in 14days and the ones who spend more than 30 minutes with exercise. The patient group who left the hospital in fourteen days after T.K.R.A. spent more time doing self-caring exercise. In the relationship between common characters and the degree of difficulties of daily life, Exercising is effective and Spending more that 30 minutes for exercise showed visible differences. The patients who answered that exercise are effective and put more time for it experienced less pain in their everyday life. The data proved by Pearson's correlation showed the relationship between self- caring and the degree of pain of daily life. According to the result, the increasing of self-caring activities helped to down the degree of inconveniences of daily life. This data show that T.K.R.A. reduced self-caring exercise ability and daily life activities. Therefore, the medical staffs who would take care the T.K.R.A. patients should offer stable nursing through well scheduled and education materials for patients. It is also important to encourage the patients to participate to the exercise by showing them how exercise after T.K.R.A. The education program is expecting to guarantee not only the right of patients to get enough information but also effective result to decrease uncomfortable of daily life.

• Journal of Acupuncture Research
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• 제15권2호
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• pp.105-116
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• 1998

Purpose In this study, We observed the recovery process in the ability to move in the hind limbs of the rats whose spinal cord injuries were treated by Radix acouniti(RA). The purpose of this study is to see the effects of Radix acouniti(RA) water extract on the contraction of rat's spinal cord injury. Procedure First, the rats were subjected to hemisectional spinal cord injuries by a scalpel blade. Those rats, then, were divided into three groups: Sham operated rats group and the experimental group, which received the Radix acouniti(RA) water extract, and the control group, which had no treatment. Their recovery in the ability to walk was observed by the Open Field Test (OFT) for 14 days after the injuries. Method The OFT was applied at four points: the hip, knee, ankle joint, and the tail. Each joint was given a movement rating of from 0 to 3, depending on the amount of movement. A movement rating of 0 designates no movement, a 1 designates slight movement, a 2 designates increased movement, and a 3 designates active movement. Slight movement is defined as a joint displaying less than or equal to 30% of that joint range, increased movement is displaying less than or equal to 60% of that joint's range, and active movement is greater than or equal to 90% of that joint's range. Tail movement is also graded on a scale of 0 to 3. A rating of 0 indicates that the tail is down 100% of the time, one of 1 indicates that the tail is down more than 10%, one of 2 shows that the tail is down less than 50% but more than 10% of the time, and one of 3 shows that the tail is down less than 10% of the time. All four ratings were added together and then averaged to arrive at a single score. Results The sham group which did not go through spinal cord injuries showed near normal results on all 3 joints and tail from right after the operation, which one would expect. The RA oral application group showed more effective recovery of movememt function than the control group around 4 days after the spinal cord injuries. However, after 14 days, both groups displayed almost the same degree of movement recovery. The results of this study are summarized as follows: 1. After 14days the spinal cord injuries, movement was recovered in sham operated group, control group, and experimented group in the hip, the knee, the tail and then the ankle of rats, in that order. 2. Around 7 days after the spinal cord injuries, the experimental group proved the effectiveness of the therapy in terms of movement recovery. 3. The level of ALT, ALP, AST in RA treated group was slightly increased. 4. The level of BUN and creatinine in RA treated group was slightly increased. The above results indicate that RA therapy at an early stage can bring about better movement recovery in patients with spinal cord injuries from traffic accidents or industrial disasters. But there is apparent side effect of RA on clinical, therefore the study on this should be continued.