• 대한산업공학회지
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• 제33권1호
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• pp.153-163
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• 2007

An adaptive framework paradigm where the bandwidth values of the ongoing calls vary according to the trafficsituations is one of the promising concepts for overcoming poor resource conditions due to handoffs in mobilecellular networks. However, quantifying the level of bandwidth degradation of the ongoing calls in an adaptiveframework is important in view of Quality of Service (QoS) Provisioning. Therefore we introduce new QoSparameters, the Degradation Degree Ratio (DDR), which represents the average portion of the degradationdegree during degradation pehod of a call, and the Degradation Area Ratio (DAR), which represents the averageratio of a call's degradation level considering both the period and the degree of degradation jointly in multi-levelbandwidth service. We also develop a new analytical model for estimating the QoS measures such as theDegradation Pehod Ratio (DPR), DDR and DAR. We show how to calculate the QoS measures and illustrate themethod by numerical examples. The proposed model can be used to determine the optimal parameter of theCAC scheme and analyze the sensitivity ofthe QoS parameters in adaptive networks.

• 대한산업공학회지
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• 제23권1호
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• pp.23-37
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• 1997

In this paper, performance analysis of video traffic shaper for Motion Picture Experts Group (MPEG) video traffic in on ATM network are investigated. Traffic shaping for MPEG video traffic is proposed as a traffic control function in ATM networks. The proposed shaper smoothes video traffics by controling the output rate of the buffer, which is placed in an MPEG source, according to I,B,P frame sequences of MPEG. In performance analysis of an video traffic shaper, a periodic botch arrival model is suggested to describe cell streams in a frame of MPEG video traffic. The queueing model which has periodic independent botch arrival and periodic deterministic service time is used to obtain the cell loss ratio, the mean cell delay, and the measure of smoothing effect. Simulation results are used to validate this queueing model. The cell loss performance of ATM multiplexer is measured by simulation study with real MPEG-1 data. From the viewpoint of traffic load, the cell loss ratio is observed to be considerably high, which is considered to result from the burstiness of MPEG video traffic. As a result, it is shown that the shaping decreases cell loss ratio of multiplexer. The results of this paper can be employed to establish a basic guideline in the implementation of a traffic control scheme and the design of ATM multiplexer for MPEG video traffic.

• Structural Engineering and Mechanics
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• 제12권5호
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• pp.559-572
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• 2001

A numerical model, in the form of a computer program, for evaluating the fire resistance of insulated wide-flange steel columns is presented. The three stages associated with the thermal and structural analysis in the calculation of fire resistance of columns is explained. The use of the computer program for tracing the response of an insulated steel column from the initial pre-loading stage to collapse, due to fire, is demonstrated. The validity of the numerical model used in the program is established by comparing the predictions from the computer program with results from full-scale fire tests. Details of fire tests carried out on wide-flange steel columns protected with ceramic fibre insulation, together with results, are presented. The computer program can be used to evaluate the fire resistance of protected wide-flange steel columns for any value of the significant parameters, such as load, section dimensions, column length, type of insulation, and thickness of insulation without the necessity of testing.

• 산업경영시스템학회지
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• 제44권4호
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• pp.169-176
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• 2021

Maritime monitoring requirements have been beyond human operators capabilities due to the broadness of the coverage area and the variety of monitoring activities, e.g. illegal migration, or security threats by foreign warships. Abnormal vessel movement can be defined as an unreasonable movement deviation from the usual trajectory, speed, or other traffic parameters. Detection of the abnormal vessel movement requires the operators not only to pay short-term attention but also to have long-term trajectory trace ability. Recent advances in deep learning have shown the potential of deep learning techniques to discover hidden and more complex relations that often lie in low dimensional latent spaces. In this paper, we propose a deep autoencoder-based clustering model for automatic detection of vessel movement anomaly to assist monitoring operators to take actions on the vessel for more investigation. We first generate gridded trajectory images by mapping the raw vessel trajectories into two dimensional matrix. Based on the gridded image input, we test the proposed model along with the other deep autoencoder-based models for the abnormal trajectory data generated through rotation and speed variation from normal trajectories. We show that the proposed model improves detection accuracy for the generated abnormal trajectories compared to the other models.

• Ocean and Polar Research
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• 제28권3호
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• pp.245-258
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• 2006

We investigated seasonal variations of the upper ocean temperature and the mixed layer depth (MLD) in an eddy-permitting global ocean general circulation model (OGCM) to assess the OGCM perfermance. The OGCM is based on the GFDL MOM3 which has a horizontal resolution of 0.5 degree and 30 vertical levels. The OGCM was integrated for 68 years using a monthly-mean climatological wind stress forcing. The model sea surface temperature (SST) and sea surface salinity were restored to the Levitus climatology with a time scale of 30 days. Annual-mean model SST shows a cold bias $(<\;-2^{\circ}C)$ in the summer hemisphere and a warm bias $(>\;1^{\circ}C)$ in the winter hemisphere mainly due to the restoring boundary condition of temperature. The model MLD captures well the observed features in most areas, with a slightly deep bias. However, in the Ross Sea and Weddell Sea, the model shows significantly deeper MLD than the climatology-mainly due to weak salinity stratifications in the model. For amplitude of seasonal variation, the model SST is smaller $(1{\sim}3^{\circ}C)$ than the observation largely due to the restoring surface boundary condition while the model MLD has larger seasonal variation $({\sim}50m)$. It is suggested that for more realistic simulation of the upper ocean structure in the present eddy-permitting ocean model, more refinements in the surface boundary condition for the thermohaline forcing and parameterization for vertical mixing are required, together with the incorporation of a sea-ice model.

• 콘크리트학회논문집
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• 제12권5호
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• pp.35-46
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• 2000

In this paper, an analytical model is proposed to predict the shear strenth of RC beams strengthened by FRP. This predictional model is composed of two basic models-the upper bound theorem for shear failure (shear tension or shear compression criteria) and a truss model based on the lower bound theorem for diagonal tension creteria. Also, a simple flexural theory based on USD is used to explain flexural failure. The major cause of destruction of RC beams shear strengthened by FRP does not lie in FRP fracture but in the loss of load capacity incurred by rip-off failure of shear strengthening material. Since interfacial shear stree between base concrete and the FRP is a major variable in rip-off failure mode, it is carefully analyzed to derive the shear strengthening effect of FRP. The ultimate shear strength and failure mode of RC beams, using different strengthening methods, estimated in this predictional model is then compared with the result derived from destruction experiment of RC beams shear strengthened using FRP. To verify the accuracy and consistency of the analysis, the estimated results using the predictional model are compared with various other experimental results and data from previous publications. The result of this comparative analysis showed that the estimates from the predictional model are in consistency with the experimental results. Therefore, the proposed shear strength predictional model is found to predict with relative accuracy the shear strength and failure mode of RC beams shear strengthened by FRP regardless of strengthening method variable.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권3호
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• pp.253-257
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• 2005

By using a coupled circuit, time-stepping, two-dimensional finite element method (2-D FEM), the performance of a stand-alone permanent-magnet synchronous generator (PMSG) with inset rotor can be computed without involving the classical two-axis model. The effects of interpolar air gap length and armature resistance on the load characteristics are investigated. It is shown that the interpolar flux density, and hence the amount of voltage compensation, is affected by magnetic saturation. Validity of the coupled circuit and field analysis is confirmed by experiments on a prototype generator. The machine exhibits an approximately level load characteristic when it is supplying an isolated unity-power-factor load.

• 영어어문교육
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• 제13권3호
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• pp.41-56
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• 2007

This paper, drawing on various secondary sources related to bilingualism and bilingual education, proposes a semi-CLIL (Content and Language Integrated Learning) model as an initial option for Korea's ELT instruction at a primary level, with a subsequent application to a secondary level in mind. It is reported that the current pedagogy focused on early English education and communicative language teaching does not meet the needs of students' EFL proficiency. The main reasons for this are considered to lie in the social and educational environment which impedes EFL students' meaningful and authentic communication in target language. Thus, by exploring a conceptual approach to such a problem, this paper suggests a paradigm of integrating content and language for a reasonable solution.

• 한국CDE학회논문집
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• 제11권1호
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• pp.20-26
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• 2006

This paper presents a procedure to compute pencil curves from a triangular mesh which is offset with the radius of a given ball-end mill. An offset triangular mesh has numerous self-intersections caused by an abundance of invalid triangles, which do not contribute to the valid CL-surface. Conceptually, we can obtain valid pencil curves by combining all intersections tying on the outer skin of the offset triangular mesh, i.e., the valid CL-surface. The underlying concept of the proposed algorithm is that visible intersections are always valid for pencil curves, because visible intersections lie on the outer skin of the offset model. To obtain the visibility of intersections efficiently, the proposed algorithm uses a graphics board, which performs hidden surface removal on up to a million polygons per second.

• 아동학회지
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• 제31권2호
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• pp.183-195
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• 2010

This study sought to investigate the environmental predictors of atopic dermatitis in children. The participants were 1050 (age 3-5) children taken from data data from the Ministry for Health, Welfare and Family Affairs. A data mining decision tree model revealed that the factors of medical neglect, breakfast, attachment to mother, and mother's depression influenced atopic dermatitis in children. Our results revealed that in the factors considered above, medical neglect had the greatest influence upon atopic dermatitis in children.