• Nuclear Engineering and Technology
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• 제27권3호
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• pp.393-402
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• 1995

원자로냉각재계통의 설계를 위한 구조해석 분야에는 원자로의 정상운전 과정에서 발생하는 유체의 온도와 압력의 변화에 의해 냉각재계통에 발생하는 정적하중해석, 지진과 가상적인 분지관 파단사고에 의해 냉각재계통에 발생하는 동적하중해석분야로 구분할 수 있다. 원자로냉가재계통의 구조해석은 원자력발전소의 안전성 화보 측면을 중시하여 해석시 충분한 여유도를 고려한 보수적인 해석 방법을 원용한다. 지진이나 가상적인 분지관 파단사고에 의한 냉각재계통의 구조해석은 사고시 냉각재계통의 안전성을 유지하는 방어적인 개념으로서 기기의 건전성을 확보하기 위하여 충분한 보수성과 안전여유가 해석시 고려된다 정상운전에 의해 냉각재계통에 발생하는 하중은 원자력 발전소의 상존하는 하중의 개념으로서 냉각재계통의 기본 설계 하중으로 인식된다. 특히 고온 고압의 유체로 인하여 발생하는 냉각재 계통의 열팽창 현상은, 정상운전 하중으로 인하여 나타나는 전형적인 거동으로서, 냉각재계통 구조해석 결과읜 중요한 지표로서 인식된다. 따라서 냉각재계통의 열팽창 현상을 정확히 예측하는 것은 원자로 냉각재계통 구조해석의 가장 중요한 목표중의 하나이다. 본 연구에서는 정상운전 하중에 의한 원자로 냉가재계통의 열팽창 거동을 해석하기 위한 냉각재계통의 모델링 방법과 해석 방법을 제시하였다. 해석 결과의 타당성을 검토하기 위하여 최근 건설 완료 단계에 돌입한 표준형 1000 MWe 급 가압경수로(Pn)의 고온기능시험 (Hot Function Test)과정에서 실측한 자료를 근거로 하여 원자로냉각재계통의 열팽창 거동 해석의 타당성을 입증코자 하였다.

• 접착 및 계면
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• 제13권2호
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• pp.58-63
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• 2012

탄소섬유강화플라스틱(CFRP)의 홀 가공 시 chip이 발생된다. 이때 발생되는 chip은 단순 폐기용 차원이 아닌 미세탄소섬유와 에폭시의 조성으로 이루어져 있다. Chip을 강화재로 활용하기 위해서는 탄소섬유만의 조성을 이루어야 고분자 기지와 계면접착력이 증가될 수 있다. Chip 내 탄소섬유의 길이를 일정하게 하기 위해 막자 사발을 이용한 절단 과정 후 $H_2O_2$를 이용한 표면처리를 하여 탄소섬유에 붙어있는 에폭시를 제거하였다. Chip을 이용하여 페놀수지를 기지로 한 페놀복합재료를 제조하였으며, 내열성 및 난연성 재료로 활용 가능성을 평가하였다. 기존의 페놀보다 표면처리를 한 chip복합재료가 기계적, 열적 물성이 향상됨을 확인하였으며, 젖음성 평가를 이용하여 표면물성에 따른 재료의 물성을 평가하였다. 불균질한 표면 조성에 의해 표면 거칠기가 달라지기 때문에 페놀복합재료의 접촉각이 증가되었다. 난연성 평가는 ASTM D635-06 방법으로 수행하였다. 평가결과, chip의 첨가 및 표면처리의 영향에 의해 난연성이 향상되었다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제28권1호
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• pp.53-60
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• 2002

Neurosensory dysfunction of the injured inferior alveolarnerve(IAN) is a common and distrssing consequence of traumatic or iatrogenic injury. Conventional neurosensory testing has been used to detect and monitor sensory impairments of the injured IAN. However, these tests had low reliability and are not qualitative at best because they are based on solely on the patient's subjective assesment of symptoms. Consequently, there is need for more reliable, sensitive, and objective test measures to document and to monitor sensory dysfunction of the trigeminal nerve. This study was to investigate DITI's (digital infrared thermographic imaging) potential as a diagnostic alternative for evaluating of the nerve injures and sensory disturbance. Subjects were 30 patients who had been referred to Ewha Medical Center due to sensory disturbance of the lower lip and chin followed after unobserved inferior alveolar nerve injuries. The patients were examined by clinical neurosensory tests as SLTD (static light touch discrimination), MDD (moving direction discrimination), PPN (pin prick nociception) and DITI (digital infrared thermographic imaging). The correlation between clinical sensory dysfunction scores(Sum of SLTD, MDD, PPN, NP, Tinel sign) and DITI were tested by Spearman nonparametric rank correlation anaylsis & Kruskal-Wallis test, Wilcoxon 2-sample test. This study resulted in as follows; (1) The difference of thermal difference between normal side and affected side was as ${\Delta}-3.2{\pm}0.13$. (2) The DITI differences of the subjects presenting dysesthesia of the lip and chin were correlated significantly with the neurosensory dysfunction scores(r=0.419, p=0.021)and SLTD (r=0.429, p<0.05). (3) The MDD, PPN, NP, Tinel sign, duration, gender were not correlated with DITI(p> 0.05). Therefore, the DITI(digital infrared thermographic imaging) can be an option of the useful objective diagnostic methods to evaluate the injured inferior alveolar nerve and sensory dysfunction of trigerminal nerve.

• 한국추진공학회지
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• 제18권3호
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• pp.70-77
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• 2014

본 논문은 한국형 2.75 인치 로켓 추진기관의 독자 모델 개발에 관하여 기술하였다. 개발된 한국형 2.75 인치 로켓 추진기관은 추진제 그레인의 형상변경을 통하여 화염안정성을 증대시켰으며, 점화장치에 EMI 필터를 장착하여 우발점화 방지기능을 추가하였다. 그리고 노즐 형상 변경 및 날개 수 증가를 통하여 비행안정성의 향상을 가질 수 있었다. 지상연소시험 및 온도충격시험을 통해 추진제의 성능을 검증하였으며, 약 210 발의 비행시험을 통해 기 배치된 추진기관과 비행성능이 동일함을 입증하였다. 성능개량과 더불어 한국형 독자모델 개발로 인한 지적재산권 문제 극복에 기여할 수 있는 근간을 마련했다는데 그 의의가 있다.

• 한국정밀공학회지
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• 제24권12호
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• pp.95-103
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• 2007

This paper presents a liquid cooling concept for heat rejection of high power electronic devices existing in notebook computers etc. The design, fabrication, and performance of the planar ECF pump and farced-liquid cooling system are summarized. The electro-conjugate fluid (ECF) is a kind of dielectric and functional fluids, which generates jet flows (ECF-jets) by applying static electric field through a pair of rod-like electrodes. The ECF-jet directly acts on the working fluid, so the proposed planar ECF pump needs no moving part, produces no vibration and noise. The planar ECF pump, consists of a pump housing and electrode substrate, achieves maximum flow rate and output pressure of $5.5\;cm^3/s$ and 7.2 kPa, respectively, at an applied voltage of 2.0 kV. The farced-liquid cooling system, constructed with the planar ECF pump, liquid-cooled heat sink and thermal test chip, removes input power up to 80 W keeping the chip surface temperature below $70\;^{\circ}C$. The experimental results demonstrate that the feasibility of forced-liquid cooling system using ECF is confirmed as an advanced cooling solution on the next-generation high power electronic devices.

• 전기학회논문지
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• 제60권6호
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• pp.1112-1121
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• 2011

A microgrid is an aggregation of multiple distributed generators (DGs) such as renewable energy sources, conventional generators, and energy storage systems that provide both electric power and thermal energy. Generally, a microgrid operates in parallel with the main grid. However, there are cases in which a microgrid operates in islanded mode, or in a disconnected state. Islanded microgrid can change its operational mode to grid-connected operation by reconnection to the grid, which is referred to as synchronization. Generally, a single machine simply synchronizes with the grid using a synchronizer. However, the synchronization of microgrid that operate with multiple DGs and loads cannot be controlled by a traditional synchronizer, but needs to control multiple generators and energy storage systems in a coordinated way. This is not a simple job, considering that a microgrid consists of various power electronics-based DGs as well as alternator-based generators that produce power together. This paper introduces the results of research examining an active synchronizing control system that consists of the network-based coordinated control of multiple DGs. Consequently, it provides the microgrid with a deterministic and reliable reconnection to the grid. The proposed method is verified by using the test cases with the experimental setup of a microgrid pilot plant.

• 전자공학회논문지
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• 제52권10호
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• pp.148-158
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• 2015

수중음향 채널환경에서 운영되는 검파시스템 성능분석은 실험의 제약으로 인해 모의 도구를 활용하여 시스템 성능을 결정한다. 본 논문은 수중음향 채널에 대한 탐지 효과도 분석을 위하여 수중환경 데이터베이스를 기반 수중음향 탐지 효과도 분석 모의 도구를 제안한다. 먼저, HYCOM 수중환경 데이터베이스 기반으로 수중 환경을 구축하고, 음선이론을 이용하여 수중음향 전달 경로/음압 계산을 통한 다중경로 지연 특성을 고려하였다. 또한, 실 환경에서 발생하는 수중 잡음 특성을 반영하기 위해 운용 주파수에 따른 수중청음기/수중음향 채널 잡음 특성인 열잡음/수중 주변 잡음을 적용하였다.

• 마이크로전자및패키징학회지
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• 제11권1호
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• pp.43-47
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• 2004

We have been using Moisture Barrier Bags for dry packing of semiconductor packages to prevent moisture from absorbing during shipping. Moisture barrier bag material is required to be waterproof, vapor proof and offer superior ESD (Electro-static discharge) and EMI shielding. Also, the bag should be formed easily to the shape of products for vacuum packing while providing excellent puncture resistance and offer very low gas ＆ moisture permeation. There are some problems like pinholes and punctured bags after sealing and before the surface mount process. This failure may easily result in package pop corn crack during board mounting. The bags should be developed to meet the requirements of excellent electrical and physical properties by means of optimization of their raw material composition and their thickness. This study investigates the performance of moisture barrier bags by characterization of their mechanical endurance, tensile strength and through thermal analysis. By this study, we arrived at a robust material composition (polyester/Aluminate) for better packing.

• 대한기계학회논문집A
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• 제31권8호
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• pp.880-888
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• 2007

This article describes the load capability of bending piezoelectric actuators with a thin sandwiched PZT plate in association with the stored elastic energy induced by an increased dome height after a curing process. The stored elastic energy within the actuators is obtained via a flexural mechanical bending test. The load capability is evaluated indirectly in terms of an actuating displacement with a load of mass at simply supported and fixed-free boundary conditions. Additionally, a free displacement under no load of mass is measured for a comparison with an actuating displacement. The results reveal that an actuator with a top layer having a high elastic modulus and a low coefficient of thermal expansion exhibits a better performance than the rest of actuators in terms of free displacement as well as actuating displacement due to the formation of the large stored elastic energy within the actuator system. When actuators are excited at AC voltage, the actuating displacement is rather higher than the free displacement for the same actuating conditions. In addition, the effect of PZT ceramic softening results in a slight reduction in the resonance frequency of each actuator as the applied electric field increases. It is thus suggested that the static and dynamic actuating characteristics of bending piezoelectric composite actuators with a thin sandwiched PZT plate should be simultaneously considered in controlling the performance.

• Macromolecular Research
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• 제14권6호
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• pp.640-645
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• 2006

Polyethylene of bimodal molecular weight distribution was irradiated with an electron beam. The thermal and mechanical properties were examined by DSC, small and wide angle X-ray scattering and static tensile test according to the crystal morphology of the irradiated samples. The crystal morphology change upon irradiation, as revealed by wide angle X-ray scattering, correlated well with the changes in melting enthalpy, whereas the lamellar thickness and the amorphous gap thickness remained virtually unchanged at irradiation doses up to 500 kGy. Crosslinks in the crystal domains became evident at an energy level of 250 kGy, resulting in reduced crystallinity and crystal size of the (110) and (200) planes. The samples became stiff and brittle with increased irradiation dose, which seem to be more relevant to the amount of cross links than the crystal morphology changes.