광주지역 태양열 온수 급탕시스템에 관한 연구

김창오,서동표,정낙규,오율권,김진흥 朝鮮大學校 機械技術硏究所 2001 機械技術硏究 Vol.4 No.2

One way to reduce abroad dependence for energy is to utilize solar energy when we are now confronted with not only insufficiency of natural resources but also the serious problems of environmental pollution. Therefore, full attention must now be paid to the development of solar energy system as alternative energy resource. To achieve this, solar hot water heating system was established at Chosun university, Gwang-ju. and experimental data were obtained based on meteorological data and solar radiation. This study has used the monthly mean values of the daily measurements obtained by data acquisition software Labview. Experimental study shows Gwang-ju is a good region for the utilization of solar energy.

저장 온도 및 상대습도가 비타민 정제 중 지용성 비타민 함량의 변화에 미치는 영향

김동섭,이재황,김세곤,이동언,박석준,이진희,이강표,최성원,백무열 경희대학교식량자원개발연구소 2007 硏究論文集 Vol.26 No.1

요추부 유합 후 인접분절 각운동의 변화

김홍태,박봉훈,천동욱,김형표,정재호 대한척추외과학회 1995 대한척추외과학회지 Vol.2 No.1

A lumbar fusion may influence biomechanically on the remained unfused segments to take over the lost motions. The adjacent segments to fusion particulatly will experience an additional motional stress following a fusion, and then various late complications can occur. Moreover, the amount of this stress may differ according to the levels and extents of the fusions. The aim of this study is to evalu- ate this motional stress in different levels of fusion. A retrospective review of flexion and extension lateral radiograghs was undertaken for 142 consec- utive patients who had undergone various fusions in the lumbar region. Included in this study were the patients who had performed active daily livings after surgery and followed for minimum of two years. They were 60 males and 82 females, having mean age of 46.7(range 14-72). There were three posterior fusions, 123 lateral fusions, and 16 interbody fusions. The extent of fusions were one seg- ment in 71, two segments in 53, three segments in 16, and four segments in two patients. The follow- up period was 53 months in average(range 2-15 years). The intervertebral angles were measured on the flexion/extension lateral radiographs, and then the calculated intervertebral angular motions at follow-up periods were compared with those of preoperative values. The average increases of angular motion at the adjacent segments to fusions were 2.3˚at L1-2 seg- ment(ranging 0˚to 5˚increase),2.5˚at L2-3 segment(ranging 1˚decrease to 8˚increase), 2.9˚at L3-4 segment (ranging 3˚decrease to 12˚increase), 6.7˚at L4-5 segment(ranging 2˚to 18˚ increase), and 1.5˚at L5-S1 segment(ranging 5˚decrease to 7˚increase). The average increases of the above and below adjacent segments to fusions were 3.3˚(ranging 3˚decrease to 18˚increase) and 1.7˚(ranging 5˚decrease to 12˚increase) respectively. There were no significant differences in the changes of angular motion according to the extents of fusion and during these follow-up periods. In conclusion, the angular motions at the adjacent segment to fusions increased most signficantly at L4-5 segment regardless of the fusion sites whether it is below or above a fusion. Excluding the L4-5 segment, the angular motions at the above adjacent segments to fusion increased significantly compared to those at the below adjacent segments. The late complications at adjacent segments to lumbar fusions are expected to appear preferably at these segments.

調和 集中 荷重을 받고 回轉하는 타이어에서 音響 放射

김병삼,홍동표 全北大學校 1992 論文集 Vol.34 No.-

The Problem of sound radiation from rotational tire under the action of harmonic point forces is studied. The reaction on the vibratory response of the rotational tire is taken into account. The rotational tire is assumed to occupy the plane y = 0. The rotational tire material and the elastic foundation are assumed to be lossless and Bernoulli-Euler beam theory including a tension force (T), damping coefficient (C) and stiffness of foundation (k_s) will be employed. The non- dimensional sound power is derived through integration of the surface intensity distribution over the entire rotational tire. The expression for sound power is integrated numerically and the results examined as a function of wavenumber ratio (γ) and stiffness factor (ψ). Here, our purpose is to explain the response of sound power over a number of non-dimensional parameters describing tension, stiffness, damping and foundation stiffness.

승용차용 알루미늄 합금 휠의 진동특성에 관한 실험적 연구

金秉三,홍동표 全北大學校 1993 論文集 Vol.36 No.-

Vibration characteristics of a wheel play an important role to judge a ride comfortability and quality for a passenger car. In this study, the vibration characteristics of al-alloy and steel wheel for passenger car are studied. Natural frequency, damping and mode shape are determined experimentally by frequency response function. Results show that wheel material property, size and design are parameter for shift of natural frequency and damping.

X선 프렉토그래피기법을 이용한 금속복합재료의 피로손상 해석에 관한 연구

김광영,박동성,박영철,윤두표,김득진 韓國非破壞檢査學會 1998 한국비파괴검사학회지 Vol.18 No.3

본 연구에서는 비파괴방법중 대단히 효과적인 방법이라 할 수 있는 X선 프렉토그래피 방법을 이용하여 파괴역학적 파라메타인 ΔK, Kmax의 정량적인 평가의 가능성에 대하여 검토하였다. 이를 위하여 Al2009-15v/o SiCw 복합재료와 SS41 불림재를 이용하여 피로균열진전시험을 실시하고 그 결과로부터 파면상의 X선 프렉토그래피 파라메타와 파면형성시의 파괴역학적 파라메타를 비교 ㆍ검토하여 X선 프렉토그래피에 의한 ΔKdhk Kmax의 평가 방법에 대하여 연구하였다. 또한, 정적하중부에 의한 소성변형률의 비파괴적 평가법에 대하여도 검토하였다. 이를 위하여 인장시험으로 소성변형을 부하한 후, X선 프렉토그래피 파라메타를 이용하여 부하된 소성변형량의 비파괴평가법에 대하여 검토하였다. 그 결과 피로파괴시의 부하된 Kmax와 피로손상 정도를 X선 프렉토그래피에 의하여 정량적으로 평가할 수 있는 방법을 제시하였다. It is attempted to verify the Quantitative relationship between fracture mechanical parameters(ΔK, Kmax)and X-ray parameters (residual stress, half-value breadth) of Al2009-15v/o SiCw composite, and normalized SS41 steel. In this study, fatigue crack propagation test were carried out X-ray diffraction was applied to fatigue fractured surface in order to investigate the change of residual stress and half-value breadth on fatigue fractured surface. And it is loaded prestrain to each tensile specimen, Al2009-15v/o SiCw composite(0.3,0.5,1,1.5,2%) and normalized SS41 steel(0.63,7.50,13.7,20%),for investigating plastic strain rate using nondestructive measurement method. X-ray diffraction was applied to the prestrained tensile specimens in order to measure the change of residual stress and half-value breadth.

폐염균의 항생제 감수성 검색

김수남,이동권,표석능 성균관대학교 약학연구소 1993 成均藥硏論文集 Vol.5 No.1

Streptococcus pneumoniae remains a major cause of bacteremia, meningitis, penumonia, sinusitis, and otitis media. Although this organism was originally exquisitely susceptible to penicillin, the last two decades have witnessed the emergence of strains resistant to penicillin as well as other antimicrobial agents in many parts of the world. 102 isolates obtained from patients with invasive pneumococcal disease have been examined the susceptibility to various antibiotics. 52% to 85% of isolates tested were resistant to various antibiotics. These data suggest that more powerful antibiotics should be used for the treatment of pneumococal infection.

鎔接殘留應力이 應力比에 따라 疲勞龜裂傳播에 미치는 影響

表東根,李龍福,金鍾鉉,吳湞淵 弘益大學校 1989 弘大論叢 Vol.21 No.2

To examine the effects of the welding residual stress on Mode I fatigue crack propagation behavior, 3mm thickness SS41 steel plate was welded by an Auto-matic Submerged Arc Welding. Initial residual stress and relaxation residual stresses according to each stress ratio were measured. The fatigue crack propagation behavior from the region of compressive residual stress to region of tensile residual stress was analyzed. The results predicted by the Forman's equation using the superposition approach of the respective stress intensity factors for the initial residual stress and for the applied stress according to each stress ratio were compared with experimental data. The validity of the superposition approach was investigated. The conclusion are summerized as follows: 1. When the component is subjected to a constant amplitude cyclic tensile loading, the welding residual stress is reduced as stress ratio increase. 2. As the fatigue crack is propagation through the compressive residual stress field, it was found that the effects of welding compressive residual stress on fatigue crack growth in weldments, and the stress ratio decreases, become larger and delay the fatigue crack growth rate. 3. For negative values of the effective stress ratio, R? in the welding compressive residual stress field, the prediction of fatigue crack growth rate by the Forman's equation were found to be corresponded to experimental data for stress ratio R?0.3, as the effective stress ratio R? approached zero, when the stress ratio R>0.3 the prediction of the fatigue crack growth rate by Forman's equation were found to be impossible.

고밀도 플라즈마에 의해 식각된 SrBi_2Ta_2O_9 박막의 표면 반응 연구

김동표,김창일,장의구 중앙대학교 기술과학연구소 2000 기술과학연구소 논문집 Vol.30 No.-

본 연구에서 SBT 박막은 Cl_2양을 변화하면서 Cl_2/Ar 가스 플라즈마를 이용하여 식각하였다. 최대 식각 속도는 Cl_2(20%)/Ar(80%) 가스혼합비에서 883A˚/min 이었다. Cl_2 가스양이 증가함에 따라서 SBT 박막의 식각 속도는 감소하였다. 이는 Ar 이온의 물리적 스퍼터링에 의한 영향이 화확 반응에 의한 식각보다 우세하게 작용함을 의미한다. 식각 메커니즘을 규명하기 위하여 optical emission spectroscopy (OES), x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS)와 atomic force microscopy (AFM) 분석을 하였다. AFM 분석결과에서 Ar이나 Cl12 플라즈마를 이용하여 식각된 시료의 표면 거칠기 rms 값이 식각전의 시료나 Cl_2/Ar 플라즈마로 식각된 시료보다 크다. 이는 식각된 시료에서의 Bi 양의 감소나 비휘발성 식각 잔류물에 의한 영향이다. XPS와 SIMS 분석을 통하여 검증하였다. SBT thin films were etched at different content of Cl_2 in Cl_2/Ar. The maximum etch rate of SBT was 883A˚/min in Cl_2(20%)/Ar(80%). As Cl_2 gas increased in Cl_2/Ar gas plasma, the etch rate decreased. The result indicates that physical sputtering of Ar ion is dominant to chemical reaction in etching SBT thin films. To evaluate the etching mechanism of SBT thin films, optical emission spectroscopy (OES), x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and atomic force microscopy (AFM) were carried out. From the result of AFM, the rms values of etched samples in Ar only or Cl_2 only plasma were higher than that of as-deposited, Cl_2/Ar. This can be illustrated by a decrease of Bi content or nonvolatile etching products(Sr-Cl and Ta-Cl), which are revealed by XPS and SIMS.

보강재의 형상이 평판의 고유진동수에 미치는 영향에 관한 연구

金泰玩,姜俊洙,表東根 弘益大學校 科學技術硏究所 1995 科學技術硏究論文集 Vol.6 No.-

An analysis is presented for the free vibration of a cantilever plate. For this papers, there are compared with the stiffener, I-shape and T-shape of the plate. The method is applied to cantilever plate with stiffened plate, I-shape and T-shape, and the natural frequencies and mode shapes of vibration are calculated numerically, given the results and confirmed experimentally.