• 한국지구물리탐사학회:학술대회논문집
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• 2000.09a
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• pp.112-131
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• 2000

In spite of its many strong points, pole-pole electrode configuration is not often used for ground electrical resistivity survey except for bore hole survey as normal logging and for archaeological investigation. Above all, poor spatial resolution of pole-pole survey may be responsible for this. But recent experiences so far gained by the present authers lead them to think that pole-pole survey can be at least a viable means of reconnaissance survey in near-surface conductive environment and an effective interpretational scheme may augment its resolution. As well known, a response of any other electrode configuration is a linear combination of pole-pole responses. Based on this principle of linear superposition and the principle of reciprocity, the other 'responses' can be derived with simple additions and subtractions of pole-pole responses. Though such responses are not always correct due to the adverse effects of noises, combined with the potential decay curves, they can be helpful to interprete better pole-pole survey data especially in connection of the resolution. This can be comparable to the use of the first or second derivatives of gravity and magnetic intensity surveys.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.777-787
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• 2012

The transient analysis for the output voltage of a piezoresistive microaccelerometer takes a relatively high computation time because at least two iterations are required to calculate the piezoresistive-structural coupled response at each time step. In this study, the high computational cost for calculating the transient output voltage is considerably reduced by an approach integrating the mode superposition method and the least square method. In the approach, data on static displacement and output voltage calculated by piezoresistive-structural coupled simulation for three acceleration inputs are used to develop a quadratic regression model, relating the output voltage to the displacement at a certain observation point. The transient output voltage is then approximated by a regression model using the displacement response cheaply calculated by the mode superposition method. A high-impact microaccelerometer subject to several types of acceleration inputs such as 100,000 G shock, sine, step, and square pulses are adopted as a numerical example to represent the efficiency and accuracy of the suggested approach.

• Journal of The Korean Digital Architecture Interior Association
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• v.4 no.1
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• pp.36-45
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• 2004

Allowable stress design method have been most widely used in steel structure in Korea. Recently, not only high-rise buildings but also medium or low-rise buildings were designed as steel structure. Most of low-rise steel buildings are designed as ordinary moment resisting frames(MRF). But MRFs don't have any lateral force resisting devices such as bracing in braced frames. This study focuses mainly on nonlinear seismic response analyses of small scale steel frames which will be used later as specimens for the evaluation of MRF's seismic performances. The main parameters of analyses are arrangement of column axis, $P-{\Delta}$ effect, acceleration factor etc. The object of this paper is to estimate the seismic performances of MRFs, which are mostly designed in Korea, through the results of response analyses.

• Computational Structural Engineering
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• v.11 no.1
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• pp.46-57
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• 1998

노스리지 지진하의 모멘트 저항 강 뼈대 구조물에 대한 사례연구결과를 요약하면 다음과 같다. 1) 탄성과 비탄성 동적해석 방법의 신뢰도가 구조물의 동적거동의 모형화에 크게 영향을 받는다는 것을 알 수 있었고 구조물의 동적거동의 모형화를 위한 보다 개선된 지침과 기준의 필요성이 부각되었다. 2) 비탄성 횡방향 정적해석은 6층높이의 건물까지는 비탄성동적해석과 유사한 결과를 보였으나 10층 이상의 건물에서는 고차 모드 효과를 고려하지 못하여 상당히 상이한 결과를 나타냈다. 3) 응답스펙트럼 해석은 노스리지 지진하에서 탄성 시간이력 해석에 비하여 100%까지 상이한 결과를 보였다. 특정지진에 대한 구조물거동의 상세조사시 응답 스펙트럼 해석 대신 시간이력해석을 수행하는 것이 바람직하다. 4) 탄성 부재력의 저항능력 비와 소성 회전각 등의 거동지수 등은 현존하는 건물의 연결부 손상을 검사하기 위한 지침을 마련하는데 도움을 줄 수 있지만 특정 연결부를 검사에서 배제시키는 유일한 근거로 사용되어서는 안될 것으로 판단된다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.602-605
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• 2011

본 논문에서는 마찰감쇠기가 설치된 건물이 붕괴하중을 받을 때의 에너지소산능력을 고려하여 등가감쇠비를 유도하였다. 마찰감쇠기는 주로 지진과 같은 수평하중에 대한 에너지를 소산하기위해 설치된다. 마찰감쇠기를 대각 가새형으로 설치하면 수평하중에 대한 저항력뿐 만아니라 수직하중에 대한 저항성능도 발휘된다. 건물에 설치된 마찰감쇠기는 외력의 크기에 따라 정지와 운동의 상태를 반복하여 외부 입력에너지를 소산시키기 때문에 외력과 응답관계가 비선형이다. 건물은 고유의 점성감쇠를 가지므로 마찰감쇠기가 설치된 건물은 마찰과 점성감쇠를 동시에 고려해야하므로 해석적인 정해를 구하기가 어렵다. 에너지 평형을 이용하여 등가감쇠비를 구하고 운동방정식을 등가선형화하면 쉽게 저항 성능을 파악할 수 있다. 우선 건물에 영향을 미치는 것은 감쇠이므로 감쇠의 영향력을 마찰력비, ${\gamma}_c$로 나타내었다. 둘째, 정해를 마찰력비로 표현하여 유도하고 응답특성을 파악하였다. 셋째, 에너지 균형식을 통해 등가감쇠비를 산정하였다. 마지막으로 등가감쇠비를 검증하기 위하여 등가감쇠비를 이용하여 등가선형화한 응답과 실제 마찰감쇠기를 설치하여 비선형 수치해석한 결과와 비교, 검증하였다.

• Proceedings of the Korean Magnestics Society Conference
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• 2001.04a
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• pp.34-35
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• 2001

• Journal of the Korean Magnetics Society
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• v.4 no.3
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• pp.239-243
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• 1994

$NiFe/TbCo/Si_3N_4$ thin films were fabricated, which can be employed as dualOongitudinal and transverse) biased magnetoresistive elements utilizing surface magnetic exchange at the interface of NiFe/TbCo films. When Tb area percent was 36 % and substrate bias was not applied, magnetic exchange fields of 100~180 Oe were obtained. The thicknesses of NiFe, TbCo and $Si_3N_4$(Protective layer) were $470\;{\AA},\;2400\;{\AA}\;and\;600\;{\AA}$, respectively. Magnetoresistance ratio of 1.45 % was obtained using NiFe films fabricated with 1000 W power and 2.5 mTorr of Ar pressure. The MR ratio of microstructured elements was reduced to 1.31 % and the MR response curves were shown not to saturate due to demagnetizing fields of the elements. When elements were fabricated with $36^{\circ}$ of misalignment with respect to the exchange field direction using films having 150 Oe exchange field, MR response curve was shifted by 85 Oe, and the operating point of the device shifted to the linear region of the response. Also, the Barkhausen noise was eiminated due to longitudinal bias field originating from the exchange field.

• Environmental and Resource Economics Review
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• v.20 no.3
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• pp.595-628
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• 2011

This study investigates the issues and suggests reform measures in applying CV methods to the Korea Development Institute's (KDI's) Preliminary Feasibility Test (PFT) of public projects. Most public projects on culture, science and environment evaluated under the PFT system belong to the category of "nonstandard" projects whose outputs are non-marketed, and CV is currently the main tool used for their benefit estimation. A careful discussion and investigation is recommended for the selection of target population, payment vehicle, and number of payment times. Operating expert reviews, focus group interviews, and pre-tests is highly recommended to reduce the potential bias involved in the CV studies. A single or double bounded dichotomous choice format is the most popular design of questionnaire, but we identify several undissolved issues in designing and implementing the format. Some other forms of inducing WTPs may still deserve our consideration. Various specifications of the WTP function need to be tried and tested based on their stability, in particular. Employing a nonparametric approach is also recommended. Treatments of 0 or negative WTPs and protest bids are shown to be the most serious issues that affect the estimation results significantly. We review diverse measures of handling those issues and summarize their advantages and shortcomings.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.353-353
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• 2013

최근 고밀도 메모리 반도체의 재료와 빠른 응답을 요구하는 나노입자를 이용한 비휘발성 메모리 소자의 제작에 대한 연구가 활발히 진행되고 있다. 특히, 비휘발성 메모리 소자 중 하나인 저항 변화 메모리 소자는 인가되는 전압에 따라 저항이 급격히 변화하여 적어도 서로 다른 두 저항 상태를 스위칭할 수 있는 물질을 이용하는 소자이다. 따라서 본 연구에서는 화합물 중에서 비휘발성 메모리 장치의 전기적 특성을 향상시킬 수 있는 실리사이드 계열의 바나듐 실리사이드($V_3Si$) 박막을 열처리 과정을 통하여 수 nm 크기의 나노입자로 제작하여, 그래핀을 하부 전극으로 하는 저항 변화 메모리 소자를 제작하였다. p-type (100) 실리콘 기판에 단일층으로 형성되어 있는 그래핀 상에 약 10 nm 두께의 저항 변화층($SiO_2$)을 각각 초고진공 스퍼터링 방법으로 성장시킨 후 $V_3Si$ 나노입자를 제작하기 위해서 $V_3Si$ 금속 박막을 스퍼터링 방법으로 4~6 nm의 두께로 저항 변화층 사이에 증착시켰으며, 급속 열처리 방법으로 질소 분위기에서 $800^{\circ}C$로 5초 동안 열처리하여 $V_3Si$ 나노 입자를 형성하였다. 마지막으로 200 nm 두께의 Pt을 증착하였다. 하부 전극으로 형성되어 있는 그래핀은 라만 분광법을 이용하여 확인하였으며, 제작된 소자의 전기적인 측정은 Agilent E4980A LCR meter, 1-MHz HP4280A와 HP 8166A pulse generator, HP4156A precision semiconductor parameter analyzer을 이용하여 전기적인 특성을 확인하였다.

• Economic and Environmental Geology
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• v.27 no.5
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• pp.491-498
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• 1994

The integral equation method is used for magnetotelluric (MT) modeling of a finite inhomogeneity in a two-layered earth. An integral equation relates the incident plane-wave field and the scattering currents in the three-dimensional (3-D) inhomogeneity through the electric tensor Green's function appropriate to a layered earth. This paper describes an effect of overburden and basement on MT responses of 3-D body. The effect of overburden is to reduce the detectability of target, and the reduction of detectability is more apparent for conductive overburden than for resistive one. The effect of basement, on the other hand, may enhance the anomaly due to 3-D body in the upper layer. In case of the resistive basement current perturbations about the body tend to be confined to the more conductive upper layer.