• Bulletin of the Korean Mathematical Society
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• v.26 no.2
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• pp.127-134
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• 1989

This paper proposes a deformation method for solving practical nonlinear programming problems. Utilizing the nonlinear parametric programming technique with Quasi-Newton method [6,7], the method solves the problem by imbedding it into a suitable one-parameter family of problems. The approach discussed in this paper was originally developed with the aim of solving a system of structural optimization problems with frequently appears in various kind of engineering design. It is assumed that we have to solve more than one structural problem of the same type. It an optimal solution of one of these problems is available, then the optimal solutions of thel other problems can be easily obtained by using this known problem and its optimal solution as the initial problem of our parametric method. The method of nonlinear programming does not generally converge to the optimal solution from an arbitrary starting point if the initial estimate is not sufficiently close to the solution. On the other hand, the deformation method described in this paper is advantageous in that it is likely to obtain the optimal solution every if the initial point is not necessarily in a small neighborhood of the solution. the Jacobian matrix of the iteration formula has the special structural features [2, 3]. Sectioon 2 describes nonlinear parametric programming problem imbeded into a one-parameter family of problems. In Section 3 the iteration formulas for one-parameter are developed. Section 4 discusses parametric approach for Quasi-Newton method and gives algorithm for finding the optimal solution.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.11
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• pp.1517-1522
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• 2018

This paper describes the improvement of the arithmetic for emergency generator capacity. This formula which calculates emergency generator is dependent on the Korean Design Standard of building electrical equipment issued by the Ministry of Land, Infrastructure and Transport, and the technical data related to the generator. when appling the formula, the capacity of the generator is insufficient at the starting conditions of the load facility. In case of emergency, the generator is not operated normally. $PG_2$ of the formula ($PG_1$, $PG_2$, $PG_3$) applied in determining the capacity of the emergency generator is selected by calculating the capacity of the generator based on only biggest one motor among the load equipment and $PG_3$ may not be able to start the generator normally in case of emergency because there is an error such that the power factor is applied at the last start of the motor having the maximum capacity of the load. We analyze the problem of capacity calculation of emergency generators used for general purposes. As a consequence, the improved formulas have been presented for safety of electrical installation.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.292-299
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• 1998

In this study, the size effect in flexural and shear behaviors of reinforced concrete beams with stirrup has been studied. The specimens of different size with same longitudinal reinforcement ratio are tested. The major variables of test include the size(relative depth) of the members as well as the longitudinal reinforcement ratios. The nominal resistances in flexure and shear are obtained for various sizes and steel ratios. It is found from the present study that the size effect is also very pronounced for the flexural resistance in reinforced concrete structures. The prediction formulas for the size effect of reinforced concrete beams in flexure and shear are proposed. The proposed equations agree relatively well with experimental data. The present study will provide useful bases for more accurate analysis and design of reinforced concrete structures.

• Wind and Structures
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• v.11 no.2
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• pp.153-178
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• 2008

Based on the empirical formulas for power spectra of generalized modal forces and local fluctuating wind forces in across-wind and torsional directions, the wind-induced lateral-torsional coupled response analysis of a representative rectangular tall building was conducted by setting various parameters such as eccentricities in centers of mass and/or rigidity and considering different torsional to lateral stiffness ratios. The eccentricity effects on the lateral-torsional coupled responses of the tall building were studied comprehensively by structural dynamic analysis. Extensive computational results indicated that the torsional responses at the geometric center of the building may be significantly affected by the eccentricities in the centers of mass and/or rigidity. Covariance responses were found to be in the same order of magnitude as the along-wind or across-wind responses in many eccentricity cases, suggesting that the lateral-torsional coupled effects on the overall wind-induced responses can not be neglected for such situations. The calculated results also demonstrated that the torsional motion contributed significantly to the total responses of rectangular tall buildings with mass and/or rigidity eccentricities. It was shown through this study that the framework presented in this paper provides a useful tool to evaluate the wind-induced lateral-torsional coupled responses of rectangular buildings, which will enable structural engineers in the preliminary design stages to assess the serviceability of tall buildings, potential structural vibration problems and the need for a detailed wind tunnel test.

• Wind and Structures
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• v.17 no.2
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• pp.203-225
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• 2013

An analysis framework for vehicle-bridge dynamic interaction system under turbulent wind is proposed based on the relevant theory of wind engineering and dynamics. Considering the fluctuating properties of wind field, the stochastic wind velocity time history is simulated by the Auto-Regressive method in terms of power spectral density function of wind field. The bridge is represented by three-dimensional finite element model and the vehicle by a multi-rigid-body system connected by springs and dashpots. The detailed calculation formulas of unsteady aerodynamic forces on bridge and vehicle are derived. In addition, the form selection of wind barriers, which are applied as the windbreak measures of newly-built railways in northwest China, is studied based on the suggested evaluation index, and the suitable values about height and porosity rate of wind barriers are studied. By taking a multi-span simply-supported box-girder bridge as a case study, the dynamic response of the bridge and the running safety indices of the train traveling on the bridge with and without wind barriers are calculated. The limit values of train speed with respect to different wind velocities are proposed according to the allowance values in the design code.

• Computers and Concrete
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• v.12 no.2
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• pp.187-209
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• 2013

This paper presents a study on the prediction of transfer length of 13 mm seven-wire prestressing steel strand in pretensioned prestressed concrete members with rectangular cross-section including several material properties and design and manufacture parameters. To this end, a carefully selected database consisting of 207 different cases coming from 18 different sources spanning a variety of practical transfer length prediction situations was compiled. 16 single input features and 5 combined input features are analyzed. A widely used feedforward neural regression model was considered as a representative of several machine learning methods that have already been used in the engineering field. Classical multiple linear regression was also considered in order to comparatively assess performance and robustness in this context. The results show that the implemented model has good prediction and generalization capacity when it is used on large input data sets of practical interest from the engineering point of view. In particular, a neural model is proposed -using only 4 hidden units and 10 input variables-which significantly reduces in 30% and 60% the errors in transfer length prediction when using standard linear regression or fixed formulas, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.1
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• pp.139-147
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• 1997

Sediment transport around artificial habitat which is induced by the change ol flow due to installation of the structure plays a role not only as a defect function of subsidence and burial but also bottom-environment control function. This study examined the characteristics of local scouring and deposition with sediment sizes, current velocities and installation direction of artificial habitat in flow field. Resultant subsidence and burial processes are investigated and discussed with Reynolds number. Together with sediment number and dimensionless time elapse, prediction formulas are established by combining these relationships. Bottom control function as cultivating effects is discussed with installation direction, and applicability of countermeasures is compared and stone pavement method is recommended.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.1
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• pp.52-58
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• 2020

In this paper, a 2-dimensional phase comparison direction finding receiver was designed and fabricated. For 2-D comparison direction finding, direction finding formulas were derived from a uniformly arranged of four antennas. Based on this, a direction finding receiver was designed using Matlab simulink, and the direction finding receiver was fabricated. To analyze the performance of the designed direction finding receiver, the injection direction finding accuracy and simulation results were compared. As a result of the test, the fabricated direction finding receiver showed a maximum of 3° RMS precision, and the result of both tests showed similar trends. Also, it was confirmed that the direction finding accuracy of elevation angle is about 2.7 times better than azimuth angle, and both models performed well within 0.7° RMS at the boresight.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.44-57
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• 2010

The purpose of this paper is to introduce case studies on 2 projects for the construction of port facilities in Colombo, Sri lanka. In Queen Elizabeth quay development project in 2000, the damage at the bottom of steel tubular piles were occurred when piles were driven into subsoil for piled wharf structure in Stage 1. In order to prevent same incident in Stage 2 & 3, the pile driveability analysis were executed by dynamic formulas, analysis program, test driving and pile load tests. Through pile driveability analysis, prevention plans were proposed. In Colombo port expansion project in 2008, the mv method was applied to predict a primary consolidation settlement of a subsoil under a breakwater in the calculation stage. The $m_v$ was estimated from results of cone penetration tests and the final settlement by consolidation was calculated with it.

• Journal of Power Electronics
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• v.13 no.5
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• pp.746-756
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• 2013

The modularized subunit of an electronic power transformer (EPT) is a series connection of two H-bridge voltage-source converters and a DC-DC converter with a high-frequency isolation transformer (HFIT). On the basis of cascading and paralleling the modularized subunits, EPT can be used in high-voltage and large-current applications in the power system. This paper discusses the steady state analysis of the modularized subunit of EPT. Theoretical analysis considers the influences of the two H-bridge voltage-source converters on the two sides of the DC-DC converter. We deduce the formulas of the theoretical calculation on the internal electrical characteristics of EPT (e.g., the voltages of the DC-bus capacitor and the primary side peak current of the HFIT). This paper provides guidance on the design and selection of EPT key elements (e.g., the DC-bus capacitors and HFIT). Experimental results are obtained from a single subunit of a laboratory model rated at 962 V, 15 kVA. All calculations, simulations, and experiments confirm the theoretical analysis of the subunit of EPT.