• 대한화학회지
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• 제22권2호
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• pp.67-77
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• 1978

착물의 분자궤도함수를 중심 금속이온의 핵을 원점으로 하는 함수들을 기저함수 집합으로 하여 일점 전개하고, 그 결과를 섭동론적인 입장에서 해석했다. $KNiF_3$의 결정구조 (perovskite structure)내에 존재하는 공유결합성이 비교적 작은 $[NiF_6]^{4-}$의 경우에도, 리간드의 배위로 인한 섭동으로 중심 금속이온의 $e_g$궤도함수와 $t_{2g}$궤도함수에 g궤도함수 이상의 각운동량을 갖는 들뜬상태 배치가 상당히 크게 섞여 들어온다는 것과, 이들 궤도함수들이 갖는 변형이 서로 다르다는 것을 발견했다. 여기서 MO계산에 의해 얻어지는 $e^*_g$궤도함수와 $t^*_{2g}$궤도함수 사이의 에너지차는 결정장 이론에서 정의되는 단일한 파라미터로서 10Dq의 의미는 갖지 못하며, 엄밀한 입장에선 그와 같은 파라미터는 정의될 수 없음을 밝혔다.

• 공업화학
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• 제20권5호
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• pp.465-472
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• 2009

본 총설에서는 최근 주로 연구되고 있는 활성탄, 탄소나노튜브, 팽창 흑연 및 활성 탄소 섬유 등 다공성 탄소재료를 중심으로 수소 저장량을 증대시키기 위한 기술 및 기 발표된 수소저장량과 그 장 단점에 대하여 고찰하였다. 수소저장능을 향상시키기 위한 탄소 내 기공의 최적의 크기는 0.6~0.7 nm로 조사되었다. 촉매의 경우 전이금속 및 그 금속산화물이 많이 이용되었으며, 주로 다공성 탄소재료에 도핑을 통해 수소저장능을 향상시켰다. 수소저장 매체인 다공성 탄소재료 중에서 활성탄은 대량생산이 가능하여 가격이 비교적 저렴한 장점이 있고 탄소나노튜브는 튜브의 튜브간 공간 외에도 내부공간에 수소를 저장할 수 있는 공간이 수소저장에 활용될 수 있다는 장점이 있다. 팽창 흑연은 흑연의 층 사이에 알칼리 금속의 삽입 시 층간 거리가 팽창하여 수소저장에 용이하고, 활성탄소섬유는 높은 비표면적과 발달된 미세기공이 수소흡착에 크게 기여한다는 점이 있다. 이러한 기존의 연구로 고려해 볼 때 다공성 탄소재료는 아직 달성되지 못한 DOE의 수소저장 목표치에 도달하기 위한 주요 유망한 후보재료 중의 하나이다.

• 대한전자공학회논문지
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• 제25권9호
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• pp.1115-1124
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• 1988

A two-dimensional systolic array for fast Fourier transform, which has a regular and recursive VLSI architecture is presented. The array is constructed with identical processing elements (PE) in mesh type, and due to its modularity, it can be expanded to an arbitrary size. A processing element consists of two data routing units, a butterfly arithmetic unit and a simple control unit. The array computes FFT through three procedures` I/O pipelining, data shuffling and butterfly arithmetic. By utilizing parallelism, pipelining and local communication geometry during data movement, the two-dimensional systolic array eliminates global and irregular commutation problems, which have been a limiting factor in VLSI implementation of FFT processor. The systolic array executes a half butterfly arithmetic based on a distributed arithmetic that can carry out multiplication with only adders. Also, the systolic array provides 100% PE activity, i.e., none of the PEs are idle at any time. A chip for half butterfly arithmetic, which consists of two BLC adders and registers, has been fabricated using a 3-um single metal P-well CMOS technology. With the half butterfly arithmetic execution time of about 500 ns which has been obtained b critical path delay simulation, totla FFT execution time for 1024 points is estimated about 16.6 us at clock frequency of 20MHz. A one-PE chip expnsible to anly size of array is being fabricated using a 2-um, double metal, P-well CMOS process. The chip was layouted using standard cell library and macrocell of BLC adder with the aid of auto-routing software. It consists of around 6000 transistors and 68 I/O pads on 3.4x2.8mm\ulcornerarea. A built-i self-testing circuit, BILBO (Built-In Logic Block Observation), was employed at the expense of 3% hardware overhead.

• Nuclear Engineering and Technology
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• 제41권4호
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• pp.427-446
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• 2009

In order to meet the increasing demand for electricity, Korea has to rely on nuclear energy due to its poor natural resources. In order for nuclear energy to be expanded in its utilization, issues with uranium supply and waste management issues have to be addressed. Fast reactor system is one of the most promising options for electricity generation with its efficient utilization of uranium resources and reduction of radioactive waste, thus contributing to sustainable development. The Korea Atomic Energy Research Institute (KAERI) has been performing R&Ds on Sodium-cooled Fast Reactors (SFRs) under the national nuclear R&D program. Based on the experiences gained from the development of KALIMER conceptual designs of a pool-type U-TRU-10%Zr metal fuel loaded reactor, KAERI is currently developing Advanced SFR design concepts that can better meet the Generation IV technology goals. This also includes developing, Advanced SFR technologies necessary for its commercialization and basic key technologies, aiming at the conceptual design of an Advanced SFR by 2011. KAERI is making R&D efforts to develop advanced design concepts including a passive decay heat removal system and a supercritical $CO_2$ Brayton cycle energy conversion system, as well as developing design methodologies, computational tools, and sodium technology. The long-term Advanced SFR development plan will be carried out toward the construction of an Advanced SFR demonstration plant by 2028.

• 한국전산유체공학회지
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• 제19권4호
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• pp.68-74
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• 2014

This computational study features the transient compressible and inviscid flow analysis on a metallic plasma discharge from the opposing composite electrodes which is subjected to pulsed electric power. The computations have been performed using the flux corrected transport algorithm on the axisymmetric two-dimensional domain of electrode gap and outer space along with the calculation of plasma compositions and thermophysical properties such as plasma electrical conductivity. The mass ablation from aluminum electrode surfaces are modeled with radiative flux from plasma column experiencing intense Joule heating. The computational results shows the highly ionized and highly under-expanded supersonic plasma discharge with strong shock structure of Mach disk and blast wave propagation, which is very similar to muzzle blast or axial plasma jet flows. Also, the geometrical effects of composite electrodes are investigated to compare the amount of mass ablation and penetration depth of plasma discharge.

• 한국정밀공학회지
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• 제26권8호
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• pp.96-103
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• 2009

The roll forming process is commonly used for the conventional 'Fe' metal products such as a furniture drawer guide or an up-down slide guide. Recently its applications are variously expanded to the sanitary facilities or electronic devices. It is essentially required the cleanness for the high technology application and any corrosion or rust are not allowed. Therefore, in those applications the stainless steel materials are strongly demanded as the substitution of 'Fe' steel. However the mechanical properties of stainless steel are not suitable for forming process compared with those of 'Fe' steel. Up to now, the conventional F.E.M.(Finite Element Method) has been used to analyze and design the roll forming process. The purpose of this research is to obtain the proper production process and the shape of rolls to manufacture the high precision slide rails made of stainless steel material. The commercial program, SHARPE-RF, is used to analyze the entire roll forming process. The results show that the rolling process and the roll design by F.E.M. are useful from the good agreement between the shapes of products estimated by F.E.M. and those of the actual products.

• 비파괴검사학회지
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• 제35권3호
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• pp.215-220
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• 2015

최근 널리 사용되는 모든 비파괴검사 기술 중 적외선열화상 카메라는 점차 적용 범위를 확대하고 있다. 초음파적외선 열화상은 절대온도 0 K 이상의 모든 물체가 방출하는 적외선 에너지를 검출하여 검사자가 볼 수 있는 화상으로 이미지를 만들어 검사하는 기술에 초음파를 접목하여 결함 부위만을 검출하는 방법으로 비접촉으로 넓은 범위를 빠른 시간에 검사할 수 있는 장점이 있는 기술이다. 본 연구에서는 고유주파수를 변화할 수 있는 터패놀-D 소재의 가변초음파 가진검사 방법을 이용하여 결함 검출의 적용가능성을 연구하였다.

• 센서학회지
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• 제26권3호
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• pp.155-159
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• 2017

The analog-to-digital converter (ADC) is an important component in various fields of sensor signal processing. This paper presents an expandable flash analog-to-digital converter (E-flash ADC) for sensor signal processing using a comparator, a subtractor, and a multiplexer (MUX). The E-flash ADC was simulated and designed in $0.35-{\mu}m$ standard complementary metal-oxide semiconductor (CMOS) technology. For operating the E-flash ADC, input voltage is supplied to the inputs of the comparator and subtractor. When the input voltage is lower than the reference voltage, it is outputted through the MUX in its original form. When it is higher than the reference voltage, the reference voltage is subtracted from the input value and the resulting voltage is outputted through the MUX. Operation of the MUX is determined by the output of the comparator. Further, the output of the comparator is a digital code. The E-flash ADC can be expanded easily.

• 한국재료학회지
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• 제13권7호
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• pp.442-446
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• 2003

Tin dioxide ($SnO _2$) thin films were deposited at $375^{\circ}C$ on alumina substrate by metal-organic chemical vapor deposition. A few hillocks like a cauliflower were observed and the number of hillock on thin film surface increased with annealing temperature in air atmosphere. The oxygen content and the binding energy during air annealing at$ 500^{\circ}C$ came to close the stoichiometric $SnO_2$. The cauliflower hillocks seem to be the result of the continuous migration of the tiny grains to release the stress of an expanded grain. Sensitivity of CO gas depended on annealing temperature and increased with increasing annealing temperature.

• Nuclear Engineering and Technology
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• 제41권8호
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• pp.1005-1014
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• 2009

The Dual Unit Optimizer 2000 MWe (DUO2000) is put forward as a new design concept for large power nuclear plants to cope with economic and safety challenges facing the $21^{st}$ century green and sustainable energy industry. DUO2000 is home to two nuclear steam supply systems (NSSSs) of the Optimized Power Reactor 1000 MWe (OPR1000)-like pressurized water reactor (PWR) in single containment so as to double the capacity of the plant. The idea behind DUO may as well be extended to combining any number of NSSSs of PWRs or pressurized heavy water reactors (PHWRs), or even boiling water reactors (BWRs). Once proven in water reactors, the technology may even be expanded to gas cooled, liquid metal cooled, and molten salt cooled reactors. With its in-vessel retention external reactor vessel cooling (IVR-ERVC) as severe accident management strategy, DUO can not only put the single most querulous PWR safety issue to an end, but also pave the way to very promising large power capacity while dispensing with the huge redesigning cost for Generation III+ nuclear systems. Five prototypes are presented for the DUO2000, and their respective advantages and drawbacks are considered. The strengths include, but are not necessarily limited to, reducing the cost of construction by decreasing the number of containment buildings from two to one, minimizing the cost of NSSS and control systems by sharing between the dual units, and lessening the maintenance cost by uniting the NSSS, just to name the few. The latent threats are discussed as well.