• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.10
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• pp.985-995
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• 2003

In this paper, a study on optimization of three dimensional multi-layered metallic disk array structure(MDAS) excited by circular waveguides was performed to shape efficient flat-topped element patterns(FTEP) of ${\pm}$20$^{\circ}$ beam width. Each radiating element of the MDAS is composed of input, transition and radiation circular waveguides and finite metal disks stacked on radiation circular waveguide. It has an array structure of a hexagonal lattice appropriate for the conical beam scanning. The analytic algorithm for the MDAS was proposed and the code was also programmed using it. Optimal design parameters of the MDAS were determined through the optimal simulation process to obtain ${\pm}$20$^{\circ}$ FTEP. Also, bandwidth characteristics for FTEP and reflection coefficients of the MDAS were investigated and, as the results, it was shown that the MDAS could shape good FTEPs of ${\pm}$20$^{\circ}$ beam width in main planes at least within a 5.6 % frequency band.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.965-970
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• 2010

Bolts and nuts are widely used to fasten mechanical parts together in machines and structures. The primary role of a nut is to maintain the axial force of a bolt. In this paper, a new type of a lock nut that uses a spring is studied. To have a spring within a nut, a cocking process to narrow the top of the nut is adopted, but cracking occurred in the process. In this study, strain of an initial model is measured using the finite element analysis program, MSC/Marc. The occurrence of the crack was studied by comparing the maximum observed strain of a model with the maximum strain indicated by an accurate stress-strain diagram of 1020 steel. Then, the structure of the lock nut was optimized by response surface analysis to prevent cracking. The prototype of the lock nut was manufactured on the basis of the optimization result, and cracking did not occur.

• Korean Journal of Construction Engineering and Management
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• v.17 no.1
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• pp.101-109
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• 2016

During road construction, minimizing haul and return distances as well as keeping a balance between cut and fill quantities are two of the key tasks for earthmoving operation planning. The result of the earthwork planning has a significant impact on the construction cost and duration. Although there have been research efforts regarding optimized earthwork planning using linear programming, the current practice of selecting earthwork planning methods typically depends on a field manager's intuitive and/or experimental knowledge. Furthermore, there is no system considering earthwork influential field factors including the transportation distance, the earthwork quantity, and the recycling ratio of earth volume. Therefore, this research focuses on the development of such a model for planning the optimized earthwork to increase the efficiency of a road construction. The proposed model is developed based upon the transportation problem method which is a part of Linear Programming. The application result of optimization model on a case study shows that the duration and cost for earthwork ha sbeen reduced approximately 19% and 11% respectively

• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.119-126
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• 2009

A district energy system plays very important role to fulfill energy demand in regional areas. This paper diagnoses the necessity of the development of an economical operation system for the efficient operation of district energy plants located in Seoul. The effect anticipated from the use of the optimal operation system is also analyzed. Production and consumption of energy are estimated for the district energy plants at Suseo, Bundang, Ilwon and Jungang located near in Seoul, Korea. The problem is formulated as a mixed integer linear programming(MILP) problem where the objective is to minimize the overall cost of the district energy system. From the results of numerical simulations we can see that the energy efficiency is improved due to the application of the optimal operation conditions provided by the proposed model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.3
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• pp.213-218
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• 2017

In this study, a reverse design of the F-theta lens was proposed for a 2D scanner in remote welding applications. The curvature and distance of the lens were set as variables, and the focal length of the lens was set as the marginal ray height. The ZEMAX commercial software was used to perform a simulation with unlimited iterations for the optimization process. The target value was optimized using the internal Merit function with the weight factors of focal length and spot diameter. The number of lenses was four, and the focal length obtained from the results was 135mm that is slightly less than that of the commercial lens, which is set with a focal length of 185 mm. The calculated spot diameters are $1.3{\mu}m$, $6.2{\mu}m$, and $16.1{\mu}m$ for $0^{\circ}$, $12.5^{\circ}$ and $23^{\circ}$ of incident laser beam, respectively. It is expected that an optimized lens design is possible by performing the reverse design of a lens by the ray tracing method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.9
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• pp.11-19
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• 2006

Design program was developed to determine the external shape of the supersonic axisymmetric inlet by combining conical flow solver and approximation technique of conical shock with gradient-based optimization algorithm. Inlet designs were carried out under various operation conditions through optimization with respectively two object functions which consist of pressure recovery and cowl drag and with constraints about shock position, cowl shape, and minimum throat area. New object function consisting of pressure recovery and drag of the external cowl was proposed and the optimized shapes from new object function were compared to the ones from the old object function which maximize only the pressure recovery. Through computations of inviscid and turbulent flow, was tested performance of the design program and performance estimated in design program agreed well with computation results for inlets designed under various flight conditions.

• Journal of the Korean Solar Energy Society
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• v.34 no.5
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• pp.117-126
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• 2014

This study developed a KRESS program designed to find the optimization ratio for new and renewable energy systems and analyze the effects of building energy consumption characteristics on the ratio. In spite of clear differences in predicted energy consumption and energy consumption by the loads among 18 facilities, the current formula for obligatory supply ratios applies a correction coefficient according to the building purposes based on energy consumption per each unit area in medical facilities and thus reflects no energy consumption characteristics according to the building purposes. The optimization ratio for new and renewable energy systems was the same for all facilities when the correction coefficients by the building purposes and new and renewable energy sources were all applied. When the correction coefficients were not applied, however, the optimization ratio varied according to building energy consumption characteristics. The findings raise a need to test the correction coefficients in order to select new and renewable energy systems that take into account energy consumption characteristics by the building purposes and loads and reflect economy, environmental performance, and technology.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.756-763
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• 2008

The aim of this work was to obtain uniform and well-dispersed spherical silver nanoparticles using statistical design-of-experiment methods. We performed the experiments using 2 k fractional factorial designs with respect to key factors of a general chemical reduction method. The nanoparticles prepared were characterized by SEM, TEM and UV-visible absorbance for particle size, distribution, aggregation and anisotropy. The data obtained were analyzed and optimized using a statistical software, Minitab. The design-of-experiment methods using quantified data enabled us to determine key factors and appreciate interactions between factors. The measured properties of nanoparticles were dominated not only by individual one or two main factors but also by interactions between factors. The appropriate combination of the factors produced small, narrow-distributed and non-aggregated silver nanoparticles of about 30 nm with approximately 10% standard deviation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.1 s.71
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• pp.47-54
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• 2006

In this study, an optimum support design problem is considered to minimize displacement of stacked plates under self weight condition. During the displacement analysis, several kinds of contact arise between the plates themselves and support bar. These can be easily considered if commercial analysis software, which provides capability to solve the contact problem, is used. It is found, however, that the computing time is extraordinarily long due possibly to the generality of the software and also to the ignorance of the control parameters used in the software. In this paper, the contact condition is imposed directly by the authors, while the software is used only to solve the ordinary displacement analysis problem. In this way, the computing time is decreased remarkably by more than 30 times, while yielding the same accurate results. Optimization is conducted based on this efficient analysis method to find minimum number of supporting bars using the response surface algorithm.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.105-111
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• 2003

Wheel for passenger car support the car weight with tires, and they transmit rolling and braking power into the ground. Whittling away at wheel weight is more effective to boost fuel economy than lighting vehicle body structure. A shape of hole in disk is optimized for minimizing the weight of steel wheel. Pro/ENGINEER program is used for formulating the design model, and ANSYS package is selected for analyzing the design model. It has difficulties to interface these commercial software directly. For Combining both programs, response surface methodology is applied to construct approximation functions for maximum stresses and maximum displacements are obtained by full factorial design of five levels. This steel wheel is modeled in 14-inch diameter of rim, and wide parameter of hole in disk is only selected as design variable for reducing the weight of steel whee. PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm, which used the second-order information in the direction finding problem and uses the active set strategy, is used for solving optimization problems.