• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1B
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• pp.34-46
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• 2009

The remarkable growth of Korean telecommunication market has based on the introduction of competition as well as mobile technology like CDMA. It was well Down that such a conspicuous growth has been towed by mobile service rather than fixed telephone service. In telecommunications service the number of subscribers to mobile was over 40 millions in 2006 and also, while the traffic amount of fixed telephone has been more decreased, that of mobile, which already outnumbers the fixed, has been constantly increased and will be much more in future. It will accelerate the substitution of access and call demand of fixed service by mobile. This change of technology and demand does affect directly the market performance of telecommunications. And regulation has also an effect on market structure, which finally affects on market performance. In this paper we suppose the fixed and mobile telecommunications services are in a same industry. After reviewing the relations among the demand, cost, charge structure and revenue structure in the one fixed and mobile telecommunications market using the framework of an industrial structure analysis, we discuss the current issues of telecommunications regulation and implications for the future regulation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.35-42
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• 1992

The effectiveness of the support-isolation system for the equipment mounted on the primary structure is evaluated to reduce its responses under the earthquake load with considering the interaction between the primary structure and the internal equipment in this paper. A computer code (KBISAP) is developed to analyze the above system using the matrix condensation technique and constant average acceleration method. To evaluate the effectiveness of the support-isolation system, three systems are used in this study as follows: i) fixed-base structure with support-fixed equipment, ii) base-isolated structure with support-fixed equipment and iii) fixed-base structure with support-isolated equipment. The results of case study show that the acceleration of equipment with the support-isolation system is less than that of the support-fixed equipment in the base-isolated structure and significantly reduced the response compared with that of the support-fixed equipment in the fixed-base structure with the reduction factor of 8. The support-isolation system used in this study can reduce the response and also increase the safety margin of the important safety-related internal equipments.

• Coupled systems mechanics
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• v.2 no.1
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• pp.111-126
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• 2013

The structural design requirements of an offshore platform subjected to wave induced forces and moments in the jacket can play a major role in the design of the offshore structures. For an economic and reliable design; good estimation of wave loadings are essential. A nonlinear response analysis of a fixed offshore platform under structural and wave loading is presented, the structure is discretized using the finite element method, wave plus current kinematics (velocity and acceleration fields) are generated using 5th order Stokes wave theory, the wave force acting on the member is calculated using Morison's equation. Hydrodynamic loading on horizontal and vertical tubular members and the dynamic response of fixed offshore structure together with the distribution of displacement, axial force and bending moment along the leg are investigated for regular and extreme conditions, where the structure should keep production capability in conditions of the 1-yr return period wave and must be able to survive the 100-yr return period storm conditions. The result of the study shows that the nonlinear response investigation is quite crucial for safe design and operation of offshore platform.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.272-272
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• 2000

since the controller is part or the overall closed-Loop system, it is necessary that the designed controller be able to tolerate some uncertainty in its coefficients. The adequate stability and performance margins are required for the designed nominal controllers. In the paper. we study the method to design the non-fragile fixed-structured controller for real parametric uncertain systems. When we impose the controller parameter perturbation, the structure of the controller must be given. Therefore, we assume that the controller has fixed-structure. The fixed-structure controller is practically necessary especially when the robust controller synthesis results in a high-order controller. In SISO systems, we propose the robust controller design method using the Mapping theorem. In the method, the plant uncertainty and controller Parameter are of the multilineal form in the stability and performance conditions. Then, the controller synthesis problem is easily recast to Linear Programming Problem.

• Journal of the Korean Society of Safety
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• v.25 no.5
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• pp.54-61
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• 2010

The additional axial force of CWR(continuous welded rail) is occurred by structure-track interaction, in reverse, fixed supports of structure are applied the large load by that. Ratio of load which transferred on support through the bridge superstructure with one-side REJ by acceleration and braking load are stated in High-Speed Rail Design Criteria(2005). On the other hand the horizontal forces of support delivered to the load due to thermal loads has been no report about the criteria. Therefore, this study was performed the review of the reaction and displacement on support by structure-track interaction in a special bridge(composite brdiges, 45+55+55+45=200m) with REJ acting on the temperature load. As a result, because fixed support of a special bridge or a continuous bridge with REJ under the temperature load which is constant load has been acted the large lateral load by structure-track interaction, when determining the fixed bearing capacity of structure should be reflected in the results to secure the safety of structures was confirmed.

• Structural Engineering and Mechanics
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• v.3 no.2
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• pp.107-120
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• 1995

A soil-structure interaction formulation is used here which is based on consideration of the dynamics of the structure with a free, rather than a fixed, base. This approach is shown to give a quite simple procedure for coupling the dynamic characteristics of the structure to those of the foundation and soil in order to obtain a matrix formulation for the complete system. In fixed-base studies it is common to presume that each natural mode of the structure has a given fraction of critical damping, and since the interaction formulation uses a free-base model, it seems natural for this situation to assign the equal modal damping values to free-base modes. It is shown, though, that this gives a structural model which is significantly different than the one having equal modal damping in the fixed-base modes. In particular, it is found that the damping matrix resulting in equal modal damping values for free-based modes will give a very significantly smaller damping value for the fundamental distortional mode of the fixed-base structure. Ignoring this fact could lead one to attribute dynamic effects to interaction which are actually due to the choice of damping.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.437-438
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• 2012

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2675-2680
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• 2010

Computation steps for 3D graphic processing consist of two stages - fixed operation stage and programming required stage. Using this characteristic of 3D pipeline, a hybrid structure between graphics hardware designed by fixed structure and programmable hardware based on instructions, can handle graphic processing more efficiently. In this paper, fragment Shader is designed under this hybrid structure. It also supports OpenGL ES 2.0. Interior interface is optimized to reduce the delay of entire pipeline, which may be occurred by data I/O between the fixed hardware and the Shader. Interior register group of the Shader is designed by an interleaved structure to improve the register space and processing speed.

• Journal of Distribution Science
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• v.15 no.11
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• pp.41-48
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• 2017

Purpose - Capital structure adjustment costs influence the test of the standard trade-off theory of capital structure. We investigate whether there exist economically significant capital adjustment costs in the Korean retail industry. Research design, data, and methodology - This paper adopts the model of Leary and Roberts(2005) to obtain the hazard rate of capital structure variations. The retail firms traded in the KOSPI and KOSDAQ markets are analyzed from 2000 to 2016. Results - The empirical analysis shows infrequent capital structure adjustments in the Korean retail firms. The duration analysis emphasizes that the fixed adjustment cost plays an important role in the determination of capital structure adjustments for the Korean retail firms. Yet, even after taking account of infrequent capital structure adjustments, the trade off theory only weakly explains the capital structure variations of the Korean retail firms. Conclusions - This paper confirms the existence of capital structure adjustment costs for the Korean retail firms. Our results argue for the significance of fixed adjustment costs in capital structure adjustments. Such emphasis on the fixed cost is inconsistent with the existing studies. The trade off theory does not successfully explain capital structure policy in the Korean retail firms even after considering adjustment costs.

• Journal of Ocean Engineering and Technology
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• v.34 no.4
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• pp.263-271
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• 2020

In this study, we performed a three-dimensional (3D) topology optimization of a fixed offshore structure to enhance its structural stiffness. The proposed topology optimization is based on the solid isotropic material with penalization (SIMP) method, where a volume constraint is applied to utilize an equivalent amount of material as that used for the rule-based scantling design. To investigate the effects of the main legs of the fixed offshore structure on its structural stiffness, the leg region is selectively considered in the design domain of the topology optimization problem. The obtained optimal designs and the rule-based scantling design of the structure are manufactured by 3D metal printing technology to experimentally validate the topology optimization. The behaviors under compressive loading of the obtained optimal designs are compared with those of the rule-based scantling design using a universal testing machine (UTM). Based on the structural experiments, we concluded that by employing the topology optimization method, the structural stiffness of the structure was enhanced compared to that of the rule-based scantling design for an equal amount of the fabrication material. Furthermore, by effectively combining the topology optimization and rule-based scantling methods, we succeeded in enhancing the structural stiffness and improving the breaking load of the fixed offshore structure.