• 대한기계학회논문집B
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• 제23권6호
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• pp.713-721
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• 1999

A composite plastic, where long metallic fibers are used as filling materials, is transformed from nonconducting to conducting medium as the volume fraction of filling metallic fibers is increased from zero : such drastic change in property is called the percolation. It is desired both for practical and theoretical purposes to understand the physics underlying the percolation and to estimate the percolation threshold that is defined by the minimum volume fraction of the metallic fibers for which the percolation occurs. In this study, percolation thresholds are calculated by Monte Carlo Computer simulation. Both lattice and continuum spaces are considered and detailed microstructures of metallic fibers are modelled as rigid and flexible bodies for both model spaces. Simulations are carried out for wide range of aspect ratios and discussions are given.

• 한국생산제조학회지
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• 제7권2호
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• pp.91-99
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• 1998

This paper presents a methodology for identifying the cutter runout geometry in end milling process. Cutter runout is common but undesirable phenomenon in multi-tooth machining because it introduces variable chip loading to insert which results in a accelerated tool wear. amplification of force variation and hence enlargement vibration amplitude From understanding of chip load change kinematics, the analytical cutting force convolution model was formulated as the angular domain convolution model was formulated as the angular domain convolution of three dynamic cutting force component functions. By virtue of the convolution integration property, the frequency domain expression of the local cutting forces and the chip width density of the cutter. Experimental study is presented to validate the analytical model. This study provides the in-process monitoring and compensation of dynamic cutter runout to improve machining tolerance and surface quality for industrial application.

• 한국공작기계학회논문집
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• 제13권1호
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• pp.88-93
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• 2004

In general, a fundamental structural design consideration for an automobile is the overall dynamic behavior in bending and torsion. Dynamic behavior of the automobile are mainly influenced by the structural stiffness of B.I.W.(body-in-white) and the physical property of trim components. In this paper, the modeling techniques for various trim components of middle-sized bus are presented, and the dynamic effects of the trim components on the vibration characteristics of the bus are investigated. The $1^{st}$ torsional frequency is decreased by attaching windshield and backlite to the B.I.W., but the $1^{st}$ vertical bending frequency and the $1^{st}$ lateral bending frequency are increased. The natural frequencies of the bus are decreased by attaching doors and windows. And also, the natural frequencies of the bus are large decreased by attaching seats, instrument panel etc. The study shows that the dynamic characteristics of the bus can be effectively predicted in the initial design stage.

• 한국생산제조학회지
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• 제20권6호
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• pp.740-744
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• 2011

Carbon-carbon composite material is the reinforced carbon fiber. Because of its high strength, elasticity and the excellent heat-resisting property in high temperature, carbon-carbon composite material has been used in many fields such as aerospace and automotive industries, etc. Especially, aircraft brake discs used at aerospace can be cracked due to its fatigue and vibration under various loading condition. This research is focused on the influence of the vibration of carbon-carbon composite material by using accelerometer with impact hammer excitation. And the change of vibration mode will be known by applying tensile loading test.

• The Journal of the Acoustical Society of Korea
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• 제15권3E호
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• pp.78-85
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• 1996

The set of admissible time-variations in the input signal can be separated into two categories : slow parameter changes and large parameter changes which occur infrequently. A common approach used in the tracking of slowly time-varying parameters is the exponential recursive least-squares(RLS) algorithm. There have been a variety of research works on the error analysis of the exponential RLS algorithm for the slowly time-varying parameters. In this paper, the focus has been given to the error analysis of exponential RLS algorithms for the input data with abrupt property changes. The voiced speech signal is chosen as the principal application. In order to analyze the error performance of the exponential RLS algorithm, deterministic properties of the exponential RLS algorithms is first analyzed for the case of abrupt parameter changes, the impulsive input(or error variance) synchronous to the abrupt change of parameter vectors actually enhances the convergence of the exponential RLS algorithm. The analysis has also been verified through simulations on the synthetic speech signal.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2011년도 학술발표회
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• pp.344-348
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• 2011

본 연구에서의 낙동강 본류에 설치예정인 N보를 중심으로 수문조건에 따른 흐름특성을 연구하기 위하여 N수위표에서 상류방향으로 약 4km구간을 채택하였다. 분석에서는 수위표 상류 약2.5km지점에 보를 설치하여 수문의 개방도와 수문조건에 따라 보의 상 하류 구간의 수리학적 특성 및 하상변화의 분석을 실시하였다. 그 결과 유속 수심 및 하상변동은 보에서 배수되는 유량과 밀접한 관계가 있다고 판단되며 차후 유황에 따른 수문의 개방도를 적절히 계획 설계하여 보다 안정적인 치수계획을 수립해야 할 것으로 판단된다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 춘계 학술논문 발표대회
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• pp.278-279
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• 2017

Result from Amendment of Apartment Houses Decree Customer Service, Recently, the starting point of Defects Liability changed "Criteria of Completion date" to "Delivery date to Divided property". Through the Law amended, There are some inconsistency between "Claim for repairing defects" and "Period of security deposit for repairing defects claim". If someone bought a house after Completion date, Purchasing period of "Claim to security deposit for repairing defects" lapsed without renewal. This research is to identify problems and solutions for improving the system.

• 정보처리학회논문지A
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• 제8A권2호
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• pp.179-188
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• 2001

We analyze the property of candidate node set in the network graph, and propose an algorithm to decrease shortest path-finding computation time by using multiple dynamic-range queue(MDRQ) structure. This MDRQ structure is newly created for effective management of the candidate node set. The MDRQ algorithm is the shortest path-finding algorithm that varies range and size of queue to be used in managing candidate node set, in considering the properties that distribution of candidate node set is constant and size of candidate node set rapidly change. This algorithm belongs to label-correcting algorithm class. Nevertheless, because re-entering of candidate node can be decreased, the shortest path-finding computation time is noticeably decreased. Through the experiment, the MDRQ algorithm is same or superior to the other label-correcting algorithms in the graph which re-entering of candidate node didn’t frequently happened. Moreover the MDRQ algorithm is superior to the other label-correcting algorithms and is about 20 percent superior to the other label-setting algorithms in the graph which re-entering of candidate node frequently happened.

• 한국전기전자재료학회논문지
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• 제18권6호
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• pp.493-498
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• 2005

Al doped Zinc Oxide, which is widely used as a transparent conductor in opto-electronic devices. In this paper, we find that the lateral variations of the parameters of the ZnO:Al films prepared by the rf magnetron sputtering can be reduced to acceptable levels by optimising the deposition parameters. The effect of bias voltage on the electrical, optical and morphological properties were investigated experimentally. we investigated sample properties of Bias Voltage change in 0 to 50 V.

• 한국주조공학회지
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• 제28권4호
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• pp.170-174
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• 2008

Mechanical properties of high strength ductile cast iron for the brake caliper of truck were investigated. Meanwhile the nodularity and nodule count decreased respectively from 92 and 95 to 80% and $60/mm^2$ with increased thickness, the volume fractions of graphite, pearlite and ferrite didn't change much and were in the ranges of 12.0-13.5, 52.6-55.0 and 33.0-35.2, respectively. Hardness, tensile strength and elongation in the mechanical properties of the castings of brake caliper were BHN 241, 710 MPa and 9.5%, respectively.