• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.555-560
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• 2002

Brazing of Al to Cu using AI-Si-Mg-Bi brazing alloy has been carried out in the vacuum furnace. In the bonded interlayer, there were two kinds of intermetallic compounds. One of these intermetallic compounds was e phase and the other was b phase. The growth of b phase was controlled by diffusion Al into Cu. Deformation behavior of Al-Cu brazing joint was brittle without deformation of the base metal. Shear strength of the joint was only about 20MPa. The shear specimen broken in the intermetallic compound, which was mainly e phase. Shear strength did not depend on the bonding temperature.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.464-467
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• 2007

All image data acquisition systems for example the digital camera and digital camcorder, use the image sensor to convert the image data (light) into electronic data. These image sensors are used in satellite camera for high quality and resolution image data. There are two kinds of image sensors, the one is the CCD (charge coupled device) detector sensor and the other is the CMOS (complementary metal-oxide semiconductor) image sensor. The CCD sensor control system has more complex than the CMOS sensor control system. For the high quality image data on CCD sensor, the precise timing control signal and the several voltage sources are needed in the control system. In this paper, the comparison of the CCD with CMOS sensor, the CCD sensor characteristic, and the control system will be described.

• Bulletin of the Korean Chemical Society
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• 제19권7호
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• pp.743-746
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• 1998

The Belousov-Zhabotinskii (BZ) reaction, which is composed of a bromate-organic acid-metal catalyst and an acidic solution is a commonly employed chemical oscillating reaction system. Cyclohexanedione (CHD) has been used as an initial organic substrate in oscillation systems. We studied each system of 1,4-CHD/BrO3-/Ce4/H+ and 1,3-CHD/BrO3-/Ce4+/H+ oscillating reactions, and studied the control of oscillating characters in a CHD/BrO3-/Ce4+/H+ batch system using a mixed substrate of 1,4-CHD and 1,3-CHD under a fixed total CHD concentration. In the mixed reactions, 1,4-CHD was used as a main substrate and small amounts of 1,3-CHD were used in order to vary the oscillatory behaviours by changing the mixing amount ratio of two substrates.

• The Journal of Advanced Prosthodontics
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• 제3권4호
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• pp.196-203
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• 2011

PURPOSE. This study evaluated marginal fit of glass infiltrated alumina cores fabricated using two techniques and their marginal stability after firing cycles of veneering porcelain. MATERIALS AND METHODS. Fifteen standardized all-ceramic crowns were fabricated on a metal die using each technique: slip cast technique of VITA In-Ceram sprint Alumina (Group A as control) and plastic foil matrix technique of Turkom-Cera fused alumina core system (Group B). Copings were compared between groups and within groups at coping stage and after firing each layer of veneering porcelain. A device was used to standardize seating of copings on the metal die and positioning of the specimens under the microscope after each stage of fabrication. The specimens were not cemented and marginal gap was measured using an image analyzing software (Imagepro Express) on the photographs captured under an optical microscope. Two tailed unpaired 't test' was used to compare marginal gaps in two groups and one way ANOVA was used to analyze marginal distortion within each group at 95% confidence interval. RESULTS. The marginal gap was smaller at the coping stage in group B ($60+30{\mu}M$) than group A ($81+21{\mu}M$) with statistical significance. After firing of veneering porcelain the difference was insignificant. At the final stage, both groups exhibited lower mean marginal gaps than at the initial coping stage with the difference of $11.75{\mu}M$ for group A and $11.94{\mu}M$ for group B, but it was statistically insignificant due to high value of standard deviation. CONCLUSION. Within the limitations of this study, it was concluded that both techniques produced copings with comparable and acceptable marginal fit and marginal stability on firing veneering porcelain.

• Nuclear Engineering and Technology
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• 제41권8호
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• pp.1053-1064
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• 2009

The existence of a large sodium pool in the KALIMER, a pool-type LMR developed by the Korea Atomic Energy Research Institute, plays an important role in reactor safety and operability because it determines the grace time for operators to cope with an abnormal event and to terminate a transient before reactor enters into an accident condition. A two-dimensional hot pool model has been developed and implemented in the SSC-K code, and has been successfully applied for the assessment of safety issues in the conceptual design of KALIMER and for the analysis of anticipated system transients. The other important models of the SSC-K code include a three-dimensional core thermal-hydraulic model, a reactivity model, a passive decay heat removal system model, and an intermediate heat transport system and steam generation system model. The capability of the developed two-dimensional hot pool model was evaluated with a comparison of the temperature distribution calculated with the CFX code. The predicted hot pool coolant temperature distributions obtained with the two-dimensional hot pool model agreed well with those predicted with the CFX code. Variations in the temperature distribution of the hot pool affect the reactivity feedback due to an expansion of the control rod drive line (CRDL) immersed in the pool. The existing CRDL reactivity model of the SSC-K code has been modified based on the detailed hot pool temperature distribution obtained with the two-dimensional pool model. An analysis of an unprotected transient over power with the modified reactivity model showed an improved negative reactivity feedback effect.

• 대한치과보철학회지
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• 제47권2호
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• pp.164-173
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• 2009

연구 목적: 심미적 장점을 지닌 지르코니아 지대주와 금속 지대주 사이에 반복 하중 전, 후의 풀림 회전력을 비교하여 지대주 재질에 따른 나사 안정성에 차이가 있는지를 비교 분석해 보고자 하는 것이다. 연구 재료 및 방법: 실험군은 크게 외측 연결 구조(US II, Osstem Implant, Korea)와 내측 연결 구조(GS II, Osstem Implant, Korea)의 임플란트 시스템을 두 군으로 나누었다. 각각의 군에서 지르코니아 지대주군와 금속 지대주군으로 나누어 실험하였다. 각군당5개씩의 시편을 제작하였다. 임플란트 고정체를 별도 제작된 지그에 고정시킨다. 디지털 토크게이지를 이용하여 30 Ncm의 조임 회전력을 가하고 10분 후 동일 조임 회전력을 한번 더 적용하였다. 다음 각 지대주 나사의 초기 풀림 회전력을 디지털 토크게이지로 측정하였다. 동일 시편을 다시 30 Ncm의 조임 회전력을 가하여 체결한 후, 유압식 동적 재료시험기(Instron, USA)에 임플란트 매식체를 치과용 임플란트 피로시험에 관한 ISO/FPIS 14801:2003(E)규정을 참고하여 고정시켰다. 최소 하중은 10 N, 최대 하중은 250 N의 sine형 반복 하중을 $30^{\circ}$의 경사각도로, 하중 주기는 14 Hz로, 100만 회의 반복 하중을 적용한 후 풀림 회전력을 측정하였다. 결과: 1. 모든 시스템에서 지대주 나사의 풀림 회전력이 조임 회전력 보다 감소하였으나, 나사 풀림 현상은 나타나지 않았다. 2. 반복 하중 전과 후의 나사 풀림 회전력은 두 임플란트 시스템 모두에서 지르코니아 지대주가 금속 지대주보다 더 컸다(P<.05). 3. 반복 하중에 따른 풀림 회전력 상실률은 두 임플란트 시스템 모두에서 지르코니아 지대주와 금속 지대주가 차이가 없는 것으로 나타났다(P>.05). 4. 금속 지대주에서 반복 하중에 따른 풀림 회전력 상실률은 내측 연결 형태의 GS II 시스템이 외측 연결형태의 US II 시스템보다 작았다(P<.05). 5. 지르코니아 지대주에서는 반복 하중에 따른 풀림 회전력 상실률은 두 임플란트 시스템 간에 차이가 없는 것으로 나타났다(P>.05). 결론: 본 실험을 통해 100만회 반복 하중 하에서 지르코니아 지대주가 금속 지대주에 비해 나사 결합부 안정성이 더 크다는 결론을 내릴 수 있다.

• 한국토양환경학회지
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• 제5권3호
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• pp.55-64
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• 2001

많은 유기 염소계 농약들은 환경에서 매우 지속적이며, 먹이 사슬을 통해서 중요하게 생물학적으로 농축하는 경향이 있다. 농업에 적용되는 농약은 지표수의 유출이나 지하수의 흐름을 통해서 사실상 수 계로 이동되어지기 때문에 수환경에 특히 많은 영향을 끼치게 된다. 이 논문의 연구 목적은 두 가지 다른 휴믹산에 의한 유기 염소계 농약인 lindane과 dieldrin의 수중 용해도 증가에 중금속인 납 이온이 미치는 영향에 대해 알아보고자 하는 것이다. 또한 유기 염소계 농약이 두 가지 혼합물로 존재할 때 각각의 용해도에 서로의 상호작용에 대해서도 연구해 보고자 하였다. 휴믹산에 의한 lindane의 용해도 증가 정도는 거의 일정하였지만, 이에 비해 휴믹산에 의한 dieldrin의 수중 용해도 증가는 훨씬 증가함을 보여주었다. 또한 수중에 휴믹산과 납이 공존하면 dieldrin의 용해도는 납이 존재하지 않을 때보다 더욱 감소하였다.

• 대한기계학회논문집A
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• 제34권9호
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• pp.1235-1240
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• 2010

와이어직조 카고메(WBK)는 나선형으로 성형된 와이어를 6 방향에서 조립하여 제작된다. 지금까지의 WBK 는 수작업으로 조립되어 왔지만, 산업적 적용을 위해서는 조립공정의 자동화가 필수적이다. 또한, 유연한 와이어로 WBK를 제작할 경우 기하학적 형상을 유지할 수 없으므로 직조기와 같은 자동화 기계의 개발이 절실하다. 이번 연구에서는, 유연한 와이어를 이용하여 WBK 를 제작하는 직조기를 설계 및 제작하였다. 이 직조기는 상부 플레이트의 회전운동과 와이어를 삽입하는 장치의 병진운동으로 작동 된다. 그리고 이미 삽입된 와이어 간의 간섭을 방지하기 위한 빗살장치는 다층의 카고메망 사이에 위치된다. 또한 이 직조기는 나선형 와이어와 직선형 와이어로 구성된 semi-WBK 의 제작에도 이용될 수 있다.

• 수산해양기술연구
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• 제49권2호
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• pp.116-125
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• 2013

Jigging and angling fishery is prevalent in the East Sea of Korea and this fishery needs many lamps to attract the fish. And the fishing boat uses 24~47 ballasts by the vessel's tonnage to turn on the fishing lamp. A 3.5kW magnetic-type ballast being currently used at many fishing boats can drive two 1.5kW metal-halide lamps. Meanwhile, this ballast has large weight (25kg) and volume. Therefore it is one of reason for the over-consumption of energy and the fire, resulted from overheat and electrical short, occurs occasionally because the ballast is installed at narrow and hot engine room. In addition, most of magnetic ballast has several problems such as periodic condenser replacement, low energy efficiency and making lamp short life, etc. So it is necessary to improve or develop newly the electronic ballast, which has to be smaller, lighter and more efficient. An electronic ballast was designed for the fishing boat by considering duration and electromagnetic interference in the study. Its weight and volume are respectably 40% and 66% compared to current ballast on the basis of PCB. The metal-halide lamp's spectrum of the designed ballast was nearly same to that of the current ballast in the test of lighting. In particular, the light stability was improved and there isn't any radio interference. As mentioned above, it is expected that the developed electronic ballast can replace current magnetic ballast because of many advantages related to energy-saving.

• Imaging Science in Dentistry
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• 제45권3호
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• pp.147-151
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• 2015

Purpose: The aim of this study was to investigate the effects of metal artifacts on the accurate diagnosis of root fractures using cone-beam computed tomography (CBCT) images with large and small/limited fields of view (FOVs). Materials and Methods: Forty extracted molar and premolar teeth were collected. Access canals were made in all teeth using a rotary system. In half of the teeth, fractures were created by the application of mild pressure with a hammer. The teeth were then randomly put into a wax rim on an acryl base designed in the shape of a mandible. CBCT scans were obtained using a Newtom 5G system with FOVs of $18cm{\times}16cm$ and $6cm{\times}6cm$. A metal pin was then placed into each tooth, and CBCT imaging was again performed using the same fields of view. All scans were evaluated by two oral and maxillofacial radiologists. The specificity, sensitivity, positive predictive value, negative predictive value, and likelihood ratios (positive and negative) were calculated. Result: The maximum levels of sensitivity and specificity (100% and 100%, respectively) were observed in small-volume CBCT scans of teeth without pins. The highest negative predictive value was found in the small-volume group without pins, whereas the positive predictive value was 100% in all groups except the large-volume group with pins. Conclusion: The specificity of CBCT decreased with the presence of a pin in the large-volume group, but not in the small-volume group.