• 음성과학
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• 제13권4호
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• pp.177-186
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• 2006

In an effort to enhance the quality of feature vector classification and thereby reduce the recognition error rate of the speaker-independent speech recognition, we employ the Mahalanobis distance in the calculation of the similarity measure between feature vectors. It is assumed that the metric matrix of the Mahalanobis distance be diagonal for the sake of cost reduction in memory and time of calculation. We propose that the diagonal elements be given in terms of the variations of the feature vector components. Geometrically, this prescription tends to redistribute the set of data in the shape of a hypersphere in the feature vector space. The idea is applied to the speech recognition by hidden Markov model with fuzzy vector quantization. The result shows that the recognition is improved by an appropriate choice of the relevant adjustable parameter. The Viterbi score difference of the two winners in the recognition test shows that the general behavior is in accord with that of the recognition error rate.

• 대한토목학회논문집
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• 제26권5D호
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• pp.771-781
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• 2006

본 연구는 대도시 아스팔트 포장에 대한 포장공법에 대한 LCC 분석모델 개발 및 VE 평가에 관한 연구로 대도시 포장의 공용연수 동안에 발생하는 총 생애주기비용을 고려하여, 지역 특성과 교통량 등 포장의 수명에 영향을 주는 인자에 대해 보다 효율적으로 대처할 수 있는 포장공법 선정에 대한 의사 결정을 지원하기 위해 수행되었다. 이를 위해 우리나라의 대표적 대도시라고 할 수 있는 서울시의 관련 자료를 토대로 LCC 분석모델을 개발하였고, 관련 실무자의 의견을 반영하여 VE 평가를 실시하였다. LCC 분석모델 개발은 포장공법별로 공통되는 비용항목을 제외한 포장공법 선정에 직접적으로 영향을 주는 비용항목으로 구성하였으며, 이렇게 개발된 LCC 분석모델을 서울시에 현재 공용중인 사례 대상노선을 선정하여 적용해 그 타당성을 검토하였다. 분석에 사용되는 비용항목의 근거자료는 서울시 통계자료와 단가산출 기준자료 등을 이용하여 분석의 신뢰성을 높였다. 개발된 LCC 분석 모델은 대도시 아스팔트 포장에 국한적으로 사용되고 있는 개질 아스팔트와 재생 아스팔트를 일반아스팔트와 비교 분석하여 대도시의 지역 특성과 교통량 등을 고려한 최적 포장공법의 선정을 지원할 수 있을 것이라 판단된다.

• Journal of Power Electronics
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• 제15권4호
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• pp.1006-1017
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• 2015

This paper presents a finite control set model predictive control (FCS-MPC) strategy for the AC/DC matrix converter used in grid-connected battery energy storage system (BESS). First, to control the grid current properly, the DC current is also included in the cost function because of input and output direct coupling. The DC current reference is generated based on the dynamic relationship of the two currents, so the grid current gains improved transient state performance. Furthermore, the steady state error is reduced by adding a closed-loop. Second, a Luenberger observer is adopted to detect the AC input voltage instead of sensors, so the cost is reduced and the reliability can be enhanced. Third, a switching state pre-selection method that only needs to evaluate half of the active switching states is presented, with the advantages of shorter calculation time, no high dv/dt at the DC terminal, and less switching loss. The robustness under grid voltage distortion and parameter sensibility are discussed as well. Simulation and experimental results confirm the good performance of the proposed scheme for battery charging and discharging control.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권3호
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• pp.118-123
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• 1999

This paper describes the finite element procedure including the magnetic hysteresis phenomena. The magnetization-dependent Preisach model is employed to simulate the magnetic hysteresis and applied to each elements. Magnetization is calculated by the Fibonacci search method for the applied field in the implementation of the magnetization-dependent model. This can calculate the magnetization very accurately with small iteration numbers. The magnetic field intensity and the magnetization corresponding to the magnetic flux density obtained by the finite element analysis(FEA) are computed at the same time under the condition that these balues must satisfy the constitutive equation. In order to reduce the total calculation cost, pseudo-permeability is used for the input for the FEA. It is found that the presented method is very useful in combining the hysteresis model with the finite element method.

• Journal of Advanced Marine Engineering and Technology
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• 제9권3호
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• pp.214-224
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• 1985

In this paper, some theoretical equations are derived to calculate natural frequencies and their modes of a portal type derrick system and developed a computer program to carry out their calculations. The ship's structures, such as funnels, upper decks, engine structures, shaft systems suffer local vibrations of the ship. The exciting forces of vibrations are induced by the bearing force and the surface force of propeller or by the main engine. For solving the vibration problem of riggings like the derrick system the natural frequency of its system must be exactly estimated as far as possible and its resonance condition must be kept out of the normal engine operating speed range. When some severe resonances are encountered after the ship's launching, it may be required a tremendous cost to amend their condition. An experimental model of the portal type derrick is made, which is composed of two posts and a truss. This experimental model is excited by an electrical-magnet, and its vibration responses are found out. The calculating results of the model by the developed computer program are compared with those of measured values of model experiment, and they show fairly good agreements.

• 대한안전경영과학회지
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• 제8권5호
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• pp.167-180
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• 2006

This study expands limitation of OASIS(Optimal Allocation of Spares for Initial Supports) program, which calculates CSP(Concurrent Spare Part), not only availability but also cost, and developed the program enabling run in WINDOW OS. By considering multi-step repair and logistics support system, repairing capability at the time of deployment, and procurement period, this model is the first local model reflecting circumstances of the armed forces of the Republic of Korea. Furthermore, the programmed model was selected as the military standard software and has being essentially used for CSP calculation.

• 한국안전학회지
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• 제23권6호
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• pp.7-13
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• 2008

It is important to prevent roll failure in hot rolling process for reducing maintenance cost and production loss. The relationship between rolling pass schedule and the work roll wear profile will be presented. The roll wear pattern is related with roll catastrophic failure. The irregular and deep roll wear pattern should be removed by On-line Roll Grinder(ORG) for roll failure prevention. In this study, a computer roll wear prediction model under real process working condition is developed and evaluated with hot rolling pass schedule. The method of building wear calculation functions for center portion abrasion and marginal abrasion respectively was used to develop a work roll wear prediction mathematical model. The three type rolling schedule are evaluated by wear prediction model. The optimum roll grinding methods is suggested for schedule tree rolling technique.

• 상하수도학회지
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• 제37권6호
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• pp.311-324
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• 2023

As an advanced study on the method of calculating the target revenue water ratio of local waterworks through the leakage component analysis method proposed by Kim et al. (2022), this study developed a model to calculate the achievable revenue water ratio within the specified project cost, the required project cost to achieve the specified target revenue water ratio, and the economically appropriate target revenue water ratio level by considering the leakage reduction cost and leakage reduction benefit for each revenue water ratio improvement strategy, and conducted an applicability evaluation of the developed model using actual field data. The procedure for calculating the target revenue water ratio of local waterworks considering economics proposed in this study consists of three stages: physical data linkage model construction, leakage component analysis, and economic analysis, and the applicability was evaluated for Zone H with branch type and the Zone M network type. As a result of the application, it was calculated that approximately 32.5 billion won would be required to achieve the target revenue water ratio of 70% in the Zone H, and approximately KRW 10.5 billion would be required to achieve the target revenue water ratio of 75% in the Zone M. If the business scale of Zones H and M was corrected to 10,000 m³/day of water usage, the required project cost for a 1% improvement in the revenue water ratio of Zone H was calculated to be 0.7642 billion won and 0.4715 billion won for Zone M.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권4호
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• pp.491-498
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• 2018

The cost evaluation for voyage route planning in an ice-covered sea is one of the major topics among ship owners. Information of the ice properties, such as ice type, concentration of ice, ice thickness, strength of ice, and speed-power relation under ice conditions are important for determining the optimal route in ice and low operational cost perspective. To determine achievable speed at any designated pack ice condition, a model test of resistance, self-propulsion, and overload test in ice and ice-free water were carried out in a KRISO ice tank and towing tank. The available net thrust for ice and an estimation of the ice resistance under any pack ice condition were also performed by I-RES. The in-house code called 'I-RES', which is an ice resistance estimation tool that applies an empirical formula, was modified for the pack ice module in this study. Careful observations of underwater videos of the ice model test made it possible to understand the physical phenomena of underneath of the hull bottom surface and determine the coverage of buoyancy. The clearing resistance of ice can be calculated by subtracting the buoyance and open water resistance form the pre-sawn ice resistance. The model test results in pack ice were compared with the calculation results to obtain a correlation factor among the pack ice resistance, ice concentration, and ship speed. The resulting correlation factors were applied to the calculation results to determine the pack ice resistance under any pack ice condition. The pack ice resistance under the arbitrary pack ice condition could be estimated because software I-RES could control all the ice properties. The available net thrust in ice, which is the over thrust that overcomes the pack ice resistance, will change the speed of a ship according to the bollard pull test results and thruster characteristics (engine & propulsion combination). The attainable speed at a certain ice concentration of pack ice was determined using the interpolation method. This paper reports a procedure to determine the attainable speed in pack ice and the sample calculation using the Araon vessel was performed to confirm the entire process. A more detailed description of the determination of the attainable speed is described. The attainable speed in 1.0 m, 90% pack ice and 540 kPa strength was 13.3 knots.

• Structural Engineering and Mechanics
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• 제36권1호
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• pp.37-55
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• 2010

For large-scale structures, the calculation of the eigensolution and the eigensensitivity is usually very time-consuming. This paper develops the Kron's substructuring method to compute the first-order derivatives of the eigenvalues and eigenvectors with respect to the structural parameters. The global structure is divided into several substructures. The eigensensitivity of the substructures are calculated via the conventional manner, and then assembled into the eigensensitivity of the global structure by performing some constraints on the derivative matrices of the substructures. With the proposed substructuring method, the eigenvalue and eigenvector derivatives with respect to an elemental parameter are computed within the substructure solely which contains the element, while the derivative matrices of all other substructures with respect to the parameter are zero. Consequently this can reduce the computation cost significantly. The proposed substructuring method is applied to the GARTEUR AG-11 frame and a highway bridge, which is proved to be computationally efficient and accurate for calculation of the eigensensitivity. The influence of the master modes and the division formations are also discussed.