• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.311-314
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• 2006

This paper concerns about total dynamic analysis of integrated mining system. This system consists of vertical steel pipe, intermediate buffer station, flexible pipe and self-propelled miner. The self-propelled miner and buffer are assumed as rigid-body of 6-dof. Discrete models of vertical steel pipe and flexible pipe are adopted, which are obtained by means of lumped-parameter method. The motion of mining vessel is not considered. Instead, the motion of mining vessel is taken into account in form of various boundary conditions (e.g. forced excitation in slow motion and/or fast oscillation and so on). A terramechanics model of extremely soft cohesive soil is applied to the self-propelled miner. The hydrodynamic forces and moments are included in the dynamic models of vehicle and lifting pipe system. Hinged and fixed constraints are used to define the connections between sub-systems (vertical steel pipe, buffer, flexible pipe, miner). Equations of motion of the coupled model are derived with respect to the each local coordinates system. Four Euler parameters are used to express the orientations of the sub-systems. To solve the equations of motion of the total dynamic model, an incremental-iterative formulation is employed. Newmark-b method is used for time-domain integration. The total dynamic responses of integrated mining system are investigated.

• 국제지역연구
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• 제22권3호
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• pp.3-27
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• 2018

이 논문은 쿠바의 기존의 발전 전략과 국가사회주의의 본질적 문제를 개선하기 위한 시장개혁 조처를 분석하고 발전전략으로서 산업정책의 효과성을 논의하였다. 국가사회주의의 계획 경제는 기본적으로 동기부여 체계(incentive system) 결여와 연성예산제약(soft budget constraint) 문제를 극복하기 쉽지 않다. 이 두 가지 문제는1990년대 주된 무역 대상국가인 소련과 동구 국가사회주의 국가의 몰락 초래하였다. 사회주의국가 블록의 몰락이후 쿠바는 식량부족, 에너지부족, 생필품 부족 등 심각한 경제위기에 봉착하였다. 이를 극복하기 위해 쿠바는 국가사회주의를 유지하는 수준에서 경제개혁을 단행하여 시장개혁 정책을 실행하고자 하였다. 특히, 수출주도형 산업정책으로 자유무역지대법을 통과시키고 강력한 외자 유치의 산업정책과 이를 통한 발전전략을 추진하였다. 그러나 마리엘특구 등 4개의 경제특구 설치에 의한 산업정책과 발전전략은 크게 성공을 거두지 못하였다고 평가되고 있다. 이는 기본적으로 이중적 고용과 임금, 그리고 이중화폐제도의 문제에서 비롯된다. 외국기업은 노동자를 쿠바의 고용청을 통해 간접적으로 고용하거나 해고할 수 있는 고용방식은 선진적인 인사 조직관리 기법 적용을 제한하게 되고 결국은 근로의욕 저하, 노동자의 생산성 하락과 효율성 하락으로 이어질 수 있다는 것이다. 또한 이중화폐제도로 인한 이중적 임금구조는 외국인투자기업에 인건비가 높이기 때문에 외국인이 쿠바에 적극적으로 직접투자를 꺼린 것이다. 또한 쿠바의 불균형 산업구조와 생산구조, 편중된 노동력 구조, 도심화와 농촌인구 슬림화, 농업생산의 중앙집권화 등으로 Lewis가 제안한 2부문모형인 아시아 농업주도 발전전략을 적용하기 쉽지 않아 보인다. 다시 말해, 쿠바는 산업정책을 통한 발전 전략을 수행하기 위해서 여러 가지 난점을 극복해야 할 것이다.

• 인터넷정보학회논문지
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• 제5권1호
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• pp.67-84
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• 2004

실시간 데이터베이스 시스템의 트랜잭션은 마감시간과 같은 시간 제약조건을 갖는다. 따라서 트랜잭션은 마감시간 내에 완료되어야 하며 동시에 데이터 일관성 제약조건을 만족해야 한다. 빠른 평균 응답시간 제공을 목표로 하는 기존 데이터베이스 시스템과 달리 실시간 데이터베이스 시스템은 트랜잭션의 마감시간 초과 비율과 마감시간을 초과한 트랜잭션에 의해 발생되는 비용에 의해 평가된다. 따라서 실시간 트랜잭션은 공정성과 시스템 처리율의 저하를 발생시킨다 하더라도 트랜잭션의 중요도 및 마감시간에 따라 스케줄링 되어야 하고, 항상 높은 우선 순위 트랜잭션의 선행 처리가 보장되어야 한다. 본 논문에서는 기존 실시간 스케줄링 알고리즘들이 갖는 문제점을 개선시킬 수 있는 새로운 스케줄링 알고리즘(Multi-level EFDF)과 펌, 소프트 실시간 트랜잭션온 고려한 병행실행제어 알고리즘(2PL-FT)을 제안한다. 또한 성능평가를 통해 2PL-FT와 AVCC방법에 대한 트랜잭션의 재시작 비율 및 마감시간 초과 비율을 비교한다. 이 실험들을 통해 제안하는2PL-FT알고리즘이 기존에 제안된 방법들보다 더 우수함을 보인다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 1996년도 추계학술대회발표논문집; 고려대학교, 서울; 26 Oct. 1996
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• pp.199-202
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• 1996

Although numerous studies demonstrate that one technique outperforms the others for a given data set, there is often no way to tell a priori which of these techniques will be most effective to solve a specific problem. Alternatively, it has been suggested that a better approach to classification problem might be to integrate several different forecasting techniques by combining their results. The issues of interest are how to integrate different modeling techniques to increase the prediction performance. This paper proposes the post-model integration method, which means integration is performed after individual techniques produce their own outputs, by finding the best combination of the results of each method. To get the optimal or near optimal combination of different prediction techniques. Genetic Algorithms (GAs) are applied, which are particularly suitable for multi-parameter optimization problems with an objective function subject to numerous hard and soft constraints. This study applied three individual classification techniques (Discriminant analysis, Logit and Neural Networks) as base models to the corporate failure prediction context. Results of composite prediction were compared to the individual models. Preliminary results suggests that the use of integrated methods will offer improved performance in business classification problems.

• 한국경영과학회지
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• 제22권3호
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• pp.163-173
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• 1997

Although numerous studies demonstrate that one technique outperforms the others for a given data set, it is hard to tell a priori which of these techniques will be the most effective to solve a specific problem. It has been suggested that the better approach to classification problem might be to integrate several different forecasting techniques by combining their results. The issues of interest are how to integrate different modeling techniques to increase the predictive performance. This paper proposes the post-model integration method, which tries to find the best combination of the results provided by individual techniques. To get the optimal or near optimal combination of different prediction techniques, Genetic Algorithms (GAs) are applied, which are particularly suitable for multi-parameter optimization problems with an object function subject to numerous hard and soft constraints. This study applies three individual classification techniques (Discriminant analysis, Logit model and Neural Networks) as base models for the corporate failure prediction. The results of composite predictions are compared with the individual models. Preliminary results suggests that the use of integrated methods improve the performance of business classification.

• Computers and Concrete
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• 제25권4호
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• pp.303-310
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• 2020

In this research, a hybrid mathematical model is derived using the higher-order polynomial kinematic model in association with soft computing technique for the prediction of best fiber volume fractions and the minimal mass of the layered composite structure. The optimal values are predicted further by taking the frequency parameter as the constraint and the projected values utilized for the computation of the eigenvalue and deflections. The optimal mass of the total layered composite and the corresponding optimal volume fractions are evaluated using the particle swarm optimization by constraining the arbitrary frequency value as mass/volume minimization functions. The degree of accuracy of the optimal model has been proven through the comparison study with published well-known research data. Further, the predicted values of volume fractions are incurred for the evaluation of the eigenvalue and the deflection data of the composite structure. To obtain the structural responses i.e. vibrational frequency and the central deflections the proposed higher-order polynomial FE model adopted. Finally, a series of numerical experimentations are carried out using the optimal fibre volume fraction for the prediction of the optimal frequencies and deflections including associated structural parameter.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1776-1781
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• 2008

To reduce interior noise of running vehicles, a floating floor construction has been widely used in recent railway industry. Among the key factors of the floating floor design, dynamic stiffness is of most important in acoustical point of view. Sometimes hard rubber type supports have often been selected due to the other design constraints such as heavy load condition, durability of rubber element and its cost etc., even though it seems like the softer support, the better isolation of noise and vibration. In this paper two representative floor supports have been considered to evaluate their effectiveness in interior noise contribution: one is a soft rubber and another is a relatively hard one. From the measured dynamic stiffness of the specimens, equivalent stiffness of actual floating floor has been derived to use in the analytical models. Calculated air-borne and structure-borne noise insulation properties of the floating floors have been compared with experiments in prototype car. In full car model interior noise levels of running vehicles have been predicted to quantify the effectiveness of the two different floating support materials and verified through the measured inside noise levels of actual train as well. By comparison with difference of running noise levels two materials for floor support can be investigated quantitatively so that it could be applied in floating floor design.

• Geomechanics and Engineering
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• 제33권4호
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• pp.401-414
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• 2023

Organic clays are ideal habitat for flora and fauna. From a geotechnical perspective, organic clays are soft, weak, variable, heterogeneous and flocculated. Portland cement is a universally common stabiliser. However, some organic acids in soil inhibit full hydration and expose cementation products to rapid dissolution. This paper investigates scopes for use of C₃S cement to enable durable cementation. Prospects of using PP fibre alongside with C₃S cement, scopes for partial replacement of C₃S cement with a plant-based nanosilica and evolution of binders are then investigated. Binding mixtures here mimic the natural functions of rhizoliths, amorphous phases, and calcites. Testing sample population include natural and fibre-reinforced clays, compact mixes of clay - C₃S cement, clay - nanobiosilica, and clay, C₃S cement and nanobiosilica. Benefits and constraints of C₃S cement and fibres for retaining the naturally flocculated structure of organic clays are discussed. Nanobiosilica provides an opportunity to cut the C₃S content, and to transition of highly compressive organic clays into an engineered, open-structured medium with >0.5 MPa compressive strength across the strains spanning from peak to 1.5-times peak.

• Geomechanics and Engineering
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• 제33권5호
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• pp.453-462
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• 2023

Intermediate Geomaterials (IGMs) are natural formation materials that exhibit the engineering behavior (strength and compressibility) between soils and rocks. The engineering behavior of such material is highly unpredictable as the IGMs are stiffer than soils and weaker/softer than rocks. Further, the characterization of such material needs exposure to both soil and rock mechanics. In most conventional designs of geotechnical structures, the engineering properties of the IGMs are either aligned with soils or rocks, and this assumption may end up either in an over-conservative design or under-conservative design. Hence, many researchers have attempted to evaluate its actual engineering properties through laboratory tests. However, the test results are partially reliable due to the poor core recovery of IGMs and the possible sample disturbance. Subsequently, in-situ tests have been used in recent years to evaluate the engineering properties of IGMs. However, the respective in-situ test finds its limitations while exploring IGMs with different geological formations at deeper depths with the constraints of sampling. Standard Penetration Test (SPT) is the strength-based index test that is often used to explore IGMs. Moreover, it was also observed that the coefficient of variation of the design parameters (which represents the uncertainties in the design parameters) of IGMs is relatively high, and also the studies on the probabilistic characterization of IGMs are limited compared with soils and rocks. With this perspective, the present article reviews the laboratory and in-situ tests used to characterize the IGMs and explores the shear strength variation based on their geological origin.

• 콘크리트학회논문집
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• 제26권3호
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• pp.401-409
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• 2014

이 연구는 초고층 건물의 철근콘크리트 기둥 단면을 최적화하기 위한 알고리즘을 개발하고 이를 실제 프로젝트에 적용하는 과정에서 검증, 보완한 실용화 연구이다. 최적설계변수는 콘크리트 강도와 단면형상으로 구조엔지니어에 의해 수행된 1차적인 구조설계 결과를 바탕으로 상기 설계변수들을 순수하게 수치적 관점에서 전산최적화한 실례를 소개, 제시하는 것이 이 논문의 목적이다. 이를 위해 외부의 해석 솔버로부터 원 해석모델에서 산출한 부재 응력을 받아오고 이를 기준으로 최소 비용을 만족하는 단면형상을 찾는 전산최적설계 컴포넌트를 새롭게 개발하였다. 이를 활용하여 콘크리트 강도를 사전 가정하고 각 강도별로 1차 최적 단면형상을 산출한 다음 그 결과들을 비교 검토해 서로 다른 두 강도에 대한 단면형상이 최대한 유사한 지점에서 콘크리트 강도를 변경하는 최적설계 시나리오를 제안하였다. 이상의 프로세스는 현업 프로젝트를 수행하는 과정에서 특정 부재의 최적설계만을 위해 집중적으로 개발된 것이므로 구조적 관점에서 미시적이고 수학적 관점에 치중하였다는 한계를 가진다. 그러나 현업에의 적용을 위해 실용적 관점에서 알고리즘 및 프로세스를 강도 높게 검증, 보완한 결과물이므로 차후 발전적 적용 및 개발이 가능할 것으로 판단된다.