• Journal of Korean Society of Transportation
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• v.26 no.6
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• pp.113-122
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• 2008

This study extended Park et al.(2007c), which analyzed the efficiency of a hierarchical transit network, showed the result of a real data, and analyzed its applicability. Operating cost was estimated using a model which was established in this study, and minimum transit demand was derived from the operating cost. The minimum transit demand value is just a sample calculation, thus it varies by many inside and outside factors of the model. Looking at the inside of the model, operating cost and travel speed are major factors, and the possibility of introducing urban subway becomes high when the operating cost of the transit system is low and its travel speed is high. As far as the outside factors are concerned, according to the analysis on the network structure, transit demand, and transit mode share, the minimum transit demand value which was derived in this study will be the maximum value among the possible values. In the feasibility study, the benefit is likely to be overestimated and the cost is likely to be underestimated than those of this study. It could be concluded that the methodology of a feasibility study is appropriate in the field standard. This study analyzed the efficiency of introduction of urban subway using analytical approach, thus has many shortcomings and limitations. However the practical approach, like feasibility study, has some limitations as well. This study could be a basis on establishing an analysis framework that is more accurate and reasonable by comparing analytical approach and practical approach.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.4
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• pp.54-61
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• 2023

In this paper, the compressive strength, pore characteristics, and chloride diffusion coefficient were measured at 28 days of age in order to examine the influence of curing conditions for the chloride diffusion and pores in concrete cured under extreme condition. According to the test results, the compressive strength was improved as the relative humidity increased. Additionally, higher compressive strength was observed when the specimens were cured at 35℃. However, the compressive strength of specimens cured at 45℃ was decreased. Meanwhile, the chloride diffusion coefficient decreased with an increase in curing temperature and relative humidity, indicating a difference compared to the trend observed for compressive strength. On the other hand, the excellent correlation showed between compressive strength and chloride diffusion coefficient, porosity and chloride diffusion coefficient when the concrete cured under water. However, when the concrete cured under extreme condition, this correlation was significantly reduced compared to the water curing case. In contrast, it has been determined that there is no significant correlation between the average pore size and chloride diffusion coefficient, regardless of the curing conditions.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.487-490
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• 2001

본 논문에서는 기존의 Caussian Mixture Model을 이용한 실시간문맥독립화자인식시스템의 성능을 향상시키기 위하여 화자검증시스템에서 좋은 결과를 나타내는 유사도정규화 ( Likelihood Normalization )방법을 화자식별시스템에 적용하여 시스템을 구현하였으며, 인식실험한 결과에 대해 보고한다. 시스템은 화자모델생성단과 화자식별단으로 구성하였으며, 화자모델생성단에서는, 화자발성의 음향학적 특징을 잘 표현할 수 있는 GMM(Gaussian Mixture Model)을 이용하여 화자모델을 작성하였으며. GMM의 파라미터를 최적화하기 위하여 MLE(Maximum Likelihood Estimation)방법을 사용하였다. 화자식별단에서는 학습된 데이터와 테스트용 데이터로부터 ML(Maximum Likelihood)을 이용하여 프레임단위로 유사도를 계산하였다. 계산된 유사도는 유사도 정규화 과정을 거쳐 스코어( SC)로 표현하였으며, 가장 높은 스코어를 가지는 화자를 인식화자로 결정한다. 화자인식에서 발성의 종류로는 문맥독립 문장을 사용하였다. 인식실험을 위해서는 ETRI445 DB와 KLE452 DB를 사용하였으며. 특징파라미터로서는 켑스트럼계수 및 회귀계수값만을 사용하였다. 인식실험에서는 등록화자의 수를 달리하여 일반적인 화자식별방법과 프레임단위유사도정규화방법으로 각각 인식실험을 하였다. 인식실험결과, 프레임단위유사도정규화방법이 인식화자수가 많아지는 경우에 일반적인 방법보다 향상된 인식률을 얻을수 있었다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1255-1265
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• 1992

Under uniform heat flow, the thermal stress intensity factors for the interfacial crack on a rigid cusp-type inclusion are determined by Hilbert problem expressed with complex variable. The thermal stress intensity factors are expressed in terms of the periodic function of heat flow angle. When the tip of the interfacial crack meets that of the cusp crack, the thermal stress intensity factors have singularities. The thermal stress intensity factors at the interfacial crack tip located in the distance from the cusp crack tip vary with the location of the interfacial crack tip. From the results of the analysis, the complex potential functions and the thermal stress intensity factors for the cusp-type inclusion without the interfacial crack are derived under the cusp surface boundary conditions insulated or fixed to zero relative temperature.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.2
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• pp.149-154
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• 2004

Results of a numerical simulation of a flowing of the underwater vehicles hull with the pump-jet nozzle are presented. It was calculate velocity distributions coefficients of the lift force the longitudinal moment of the hull with the pump-jet nozzle and isolated hull for some values of angle of attack. It was shown that the area of the influence of the nozzle on the velocities distribution of the hull and character of changing of coefficients of the lift force and the longitudinal moment and their derivatives depending on angle of attack.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.5
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• pp.535-541
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• 2010

In this paper, we have derived a continuum-based adjoint design sensitivity of general performance functionals with respect to Young' modulus and heat conduction coefficient for steady-state nonlinear thermoelastic problems. An adjoint equation for temperature and displacement fields is defined for the efficient computation of the coupled field design sensitivity. Through numerical examples, we investigated the mesh dependency of the topology optimization method in the thermoelastic problems. Also, comparing the dominant loading cases of thermal and mechanical ones, the loading dependency of topology design optimization in coupled multi-physics problems is investigated.

• Journal of KSNVE
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• v.5 no.3
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• pp.303-311
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• 1995

Tests on flow-induced vibration of inclined cylinders in uniform flow were performed in the cavitation tunnel at the Korea Instituteof Machinery and Metals. The test program was intended to investigate flow-induced vibration characteristic of the cylinders with three different inclined angles of 10$^\circ$, 20$^\circ$ and 30$^\circ$ and to estimate the fluid force coefficients acting on the cylinders. Important observations are as follows: 1) Numal drag is dominant compared with viscous drag for the inclined angle over 20.deg. and it has the value from 1.7 to 2.0 as was observed by other researchers. 2) Lift force coefficient has large value at the lock-in range determined by 4$\Theta/f_nD$<8. Measured maximum lift force coefficients at the inclined angle of 30.$^\circ$ and 20$^\circ$ were 0.9 and 0.4 respectively.

• The Journal of Bigdata
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• v.2 no.1
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• pp.41-48
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• 2017

Recently, the popularity of the recommendation system and the evaluation of the performance of the algorithm of the recommendation system have become important. In this study, we used modeling and RMSE to verify the effectiveness of various algorithms in movie data. The data of this study is based on user-based collaborative filtering using Pearson correlation coefficient, item-based collaborative filtering using cosine correlation coefficient, and item-based collaborative filtering model using singular value decomposition. As a result of evaluating the scores with three recommendation models, we found that item-based collaborative filtering accuracy is much higher than user-based collaborative filtering, and it is found that matrix recommendation is better when using matrix decomposition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5B
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• pp.324-329
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• 2005

In the traditional telephone services, the settlement method for usage of facilities has been systematically and reasonably arranged based on the cost. Through the advanced technology, the telecommunication services such as the convergence of voice-data, wire-wireless, communication-broadcasting, etc are offering. So, new settlement method in the broadband convergence network (BCN) should be necessary. This paper suggests inter-companies settlement method in the broadband network using interconnection bandwidth and transmission distance factor. By reflecting the facility cost weight on each BCN level, the cost settlement for various services can be easily done. As the settlement model for BCN, the inter-companies interconnection and settlement can be normalized by interconnection bandwidth and transmission distance factors.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.497-504
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• 1988

The steady state thermal stress intensity factors (TSIF's) are analyzed for hypocycloid, symmetric airfoil and symmetric lip type rigid inclusions embedded in infinite elastic solids, using Boganoff's complex variable approach in plane thermoplasticity. Two thermal conditions are considered, one with an uniform heat flow disturbed by an insulated rigid inclusion of cusp crack shape and the other with an uniform heat flow disturbed by a rigid inclusion of cusp crack shape with fixed boundary temperature. The tendencies of TSIF's for rigid inclusions of cusp crack shape are somewhat different from those of traction free cusp cracks. However, if k=-1, the non-dimensionalized TSIF's for rigid inclusions of cusp crack shape become those of traction free cusp cracks like the tendencies of the SIF's under mechanical loading conditions. The thermal stress and displacement components for a rigid circular inclusion of radius Ro are drived from the results of a hypocycloid crack type rigid inclusion.