• 대한방사선기술학회지:방사선기술과학
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• 제8권2호
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• pp.71-72
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• 1985

This study was performed on the dose distribution of various field size and the effect of penumbra shield in the telecobalt unit. The results obtained are as follows. 1. Errors of the light and ${\gamma}-ray$ field size was below the regulation as 0.52 percentage. 2. The coefficient of field area was increased with the larger field area, and this coefficient was showed the more difference in larger SSD. 3. The rectangular field areas, which were described by level of the same percentage depth does, were decreased with the more elongation factor. At the same elongation factor, the compensating factor was decreased with the larger field size. 4. The lead block or extension collimator was able to shield r-ray exposure of outside field size from 50 to 80 percentage. 5. On the matching adjacent fields, while the gap between beam edges are contacted, that overlapped beam edges indicated up to 140 percentage, and while the gap was 1 cm, it could be reduced to 90 Percentage. The lead-libocking on the overlapped area was more effective to lower dose, as 80 percentage in this case. 6. Percentage depth dose of various trimming field sizes were increased linearlly according to area 1 perimeter size, but the center split field size did not maintain linearlly.

• Steel and Composite Structures
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• 제31권6호
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• pp.617-628
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• 2019

As an extremely destructive accident, progressive collapse is defined as the spread of an initial local failure from element to element, resulting eventually in the collapse of an entire structure or disproportionately large of it. To prevent the occurrence of it and evaluate the ability of structure resisting progressive collapse, the nonlinear static procedure is usually adopted in the whole structure design process, which considered dynamic effect by utilizing Dynamic Increase Factor (DIF). In current researches, the determining of DIF is performed in full-rigid frame, however, the performance of beam-column connection in the majority of existing frame structures is not full-rigid. In this study, based on the component method proposed by EC3 guideline, the expression of extended endplate connection performance is further derived, and the connection performance is taken into consideration when evaluated the performance of structure resisting progressive collapse by applying the revised plastic P-M hinge. The DIF for structures with extended endplate beam-column connection have been determined and compared with the DIF permitted in current GSA guideline, the necessity of considering connection stiffness in determining the DIF have been proved.

• 한국의학물리학회지:의학물리
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• 제5권1호
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• pp.87-99
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• 1994

목적 : 선형가속기 ML-15MDX의 전자선에너지 대한 출력선량계수가 Applicator크기에 따라 결정되도록 하며 각 Applicator에서 정방형조사면과 직사각형조사변에 대한 출력선량계수는 측정값으로 부터 다항식을 이용하여 결정되었다. 방법 : 실험에서, 출력선량의 측정은 전자선에너지 4, 6, 9, l2MEV대해 2$\times$2$cm^2$에서 20$\times$20$cm^2$까지 이루어졌다. 출력선량계수는 각 아프리케이터의 조사면중심선속의 최대선량에 대한 임의 조사면의 최대선량의 비로 얻어졌고 각 아프리케이터의 출력선량계수는 기준 아프리케이터(10$\times$10$cm^2$)와 비교되었다. 전자선조사면의 차폐는 모든 실험에너지 영역에서 균등하게 10mm 두께의 Lipowitz(밀도 9.4g/$cm^2$)를 사용하였으며, 조사면크기 및 모양 결정이 용이하도록 고안하여 사용되었다. 임의의 전자선조사면에 대한 출력선량계수는 조사면의 한변을 고정한 직사각형의 출력선량 계수를 이용한 1-Dimension방법에 의한 다항식으로 부터 구하였다. 결과 : 직사각형의 전자선조사면에 대한 출력선량계수는 4$\times$4$cm^2$에서 20$\times$20$cm^2$의 범위에서는 2%이내의 불확실성을 보였으며, 이들 보다 작은 직사각형조사면에서는 약 3%의 오차를 보였다. 결론 : 전자선에너지의 정사각형 및 직사각형조사변에 대한 출력선량계수가 실험자료를 이용한 다항식으로 부터 실제값에 매우 근사한 예상값을 얻을 수 있었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.568-571
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• 1997

The overall aim of this paper is to determine coupling loss factor using loss factor and structural loss factor. For this purpose, two kinds of loss factor were adopted. One is loss factor of each sub structure, another is structural loss factor based on the complex welded or assembled structure. Using these two parameters, it is possible to derive the coupling loss factor which represent characteristic condition of SEA theory. Coupling loss factor of conjunction in complex structure was expressed as power balance equation. The derived equation for a coupling loss factor has been simplified on the assumption of one directional power flow between two sub structures. Using these conditions, it is possible to find the coupling loss factor equation. The comparison between theory of power transmission on conjunction and above equation, show a good agreement in simple beam structure. To check the effectiveness of above equation, it was adopted rotary compressor. Rotary compressor has three main conjunctions between shell and internal vibration part. This equation was applied to find out the optimum welding point with respect to reduce the noise propagation. It shows the effective tool to evaluate the coupling loss factor in complex structure.

• 한국염색가공학회지
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• 제27권2호
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• pp.119-125
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• 2015

The effects of e-beam irradiation on water-repellency and washing durability of water-repellent finished chemically-recycled PET(CR-PET) fabrics were investigated. As results, more doses of e-beam irradiation damaged the fabric surface more severely. It was thought because the high densed energy was formed, where the more e-beam was converged. The contact angle measurement showed that as the dose of e-beam irradiation increased, water wettability of the CR-PET fabric increased slightly. It was thought to be due that the surface etching by e-beam irradiation let water droplet permeate into the fabric surface better. The concentration of the water-repellent finishing agent was more important factor than curing temperature as finishing parameter. It was considered because the water-repellent finishing agent used in this study got to cure sufficiently at low temperature. Consequently, e-beam irradiation improved the washing durability of water-repellent finishing on the CR-PET fabrics.

• Earthquakes and Structures
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• 제15권4호
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• pp.369-382
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• 2018

A free vibration analysis and wave propagation of functionally graded porous beams has been presented in this work using a high order hyperbolic shear deformation theory. Unlike other conventional shear deformation theories, a new displacement field that introduces indeterminate integral variables has been used to minimize the number of unknowns. The constituent materials of the beam are assumed gradually variable along the direction of height according to a simple power law distribution in terms of the volume fractions of the constituents. The variation of the pores in the direction of the thickness influences the mechanical properties. It is therefore necessary to predict the effect of porosity on vibratory behavior and wave velocity of FG beams in this study. A new function of the porosity factor has been developed. Hamilton's principle is used for the development of wave propagation equations in the functionally graded beam. The analytical dispersion relationship of the FG beam is obtained by solving an eigenvalue problem. Illustrative numerical examples are given to show the effects of volume fraction distributions, beam height, wave number, and porosity on free vibration and wave propagation in a functionally graded beam.

• 한국전자파학회논문지
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• 제21권12호
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• pp.1412-1422
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• 2010

펄스 체이싱을 이용한 바이스태틱 레이더는 탐지 영역을 효과적으로 스캔하기 위해 수신 빔을 이용하여 송신 펄스를 추적함으로써 표적을 탐지한다. 수신 빔을 이용한 펄스 추적시 펄스-펄스간 빔 포인팅 오차에 의해 수신 펄스의 타이밍 오차와 신호 세기의 변화가 발생할 수 있다. 본 논문에서는 수신 빔 포인팅 오차에 의해 발생된 에러가 MTI 필터의 성능을 제한할 수 있음을 제안하였고, 바이스태틱 구조만의 고유한 특성인 기하학적 요소와 MTI 성능의 관계식을 유도하였다. 시뮬레이션을 통해 수신 빔 조향 오차에 의한 개선 성능 제한을 고찰하였고, 수신 빔의 조향 오차를 0.5도 이하로 유지함으로써 성능 개선에 기여할 수 있음을 확인하였다.

• Steel and Composite Structures
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• 제44권4호
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• pp.451-471
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• 2022

In the present paper, the static bending and buckling responses of functionally graded carbon nanotubes-reinforced composite (FG-CNTRC) beam under various boundary conditions are investigated within the framework of higher shear deformation theory. The significant feature of the proposed theory is that it provides an accurate parabolic distribution of transverse shear stress through the thickness satisfying the traction-free boundary conditions needless of any shear correction factor. Uniform (UD) and four graded distributions of CNTs which are FG-O, FG-X, FG- and FG-V are selected here for the analysis. The effective material properties of FG-CNTRC beams are estimated according to the rule of mixture. To model the FG-CNTRC beam realistically, an efficient Hermite-Lagrangian finite element formulation is successfully developed. The accuracy and efficiency of the present model are demonstrated by comparison with published benchmark results. Moreover, comprehensive numerical results are presented and discussed in detail to investigate the effects of CNTs volume fraction, distribution patterns of CNTs, boundary conditions, and length-to-thickness ratio on the bending and buckling responses of FG-CNTRC beam. Several new referential results are also reported for the first time which will serve as a benchmark for future studies in a similar direction. It is concluded that the FG-X-CNTRC beam is the strongest beam that carries the lowest central deflection and is followed by the UD, V, Λ, and FG-O-CNTRC beam. Besides, the critical buckling load belonging to the FG-X-CNTRC beam is the highest, followed by UD and FG-O.

• 국제학술발표논문집
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• The 8th International Conference on Construction Engineering and Project Management
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• pp.333-342
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• 2020

Due to the enhancing environmental concerns worldwide with the need of increasing demand for sustainability of building design, maintenance and operation, key stakeholders including the government and developers in many countries strike for the benefits in implementing the green design and building concepts in constructing, infrastructure as well as the buildings. Different countries have their standards or certifications for green buildings while the adoption rate of BEAM-Plus in HK is relatively less compared with other developed countries such as Europe, USA and Japan. Therefore, in the present research, BEAM-Plus, the beginning assessment method of green standard implemented in HK, will be mainly discussed. Current situation of BEAM-Plus implementation in HK will be reviewed and then adopt a systematic approach via literature review and research paper, questionnaire with Analytic Hierarchy Process (AHP) method to depict the opportunities and challenges from the perspective of government and developers regarding implementing BEAM-Plus in HK and thus investigate the implementation gaps. It is found that for both the macro level of opportunity and challenge, the most important criterion is political, in which the weighting value are 0.3114 and 0.2321 respectively. It is obvious that government plays a critical and significant role in affecting the development of BEAM plus. Technological difficulty is also an important factor that challenging and hindering the implementation of BEAM plus, the weighting value is 0.2194 under challenge hierarchy. More experts and professionals should be imported to Hong Kong to enhance the technique is building green buildings. At the end of this paper, solutions and actions will also be suggested and concluded in alleviating the challenges. Finally, solutions and actions are suggested and concluded in alleviating the challenges. Findings from this research can guide developers to consider adopting green elements, government and Green Building Council in HK to review green buildings' policy.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1733-1735
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• 2002

The important parameters deciding the fluctuation of laser beam are smoothing capacitor, frequency and the characteristics of laser resonator. In this thesis, we control the fluctuation of $CO_2$ laser in realtime by changing Duty-Ratio of IGBT and switching frequency with fixed the smoothing capacitor to improve the fluctuation of laser beam. We detect the light on laser resonator using a CdS photo sensor to improve ripple factor of laser beam and feedback fluctuated signals refined by a band pass filter into the control circuit to stabilize fluctuation actively. There is much to be desired in the realtime controlling technique of the light on laser discharge tube in electrical signal. We propose switching control technique with microprocessor and photo sensing technique by controlling switch devices optimum operation and feedback signals detected by a photo sensor into the laser power supply in order to improve ripple factor of the $CO_2$ laser beam.