• Steel and Composite Structures
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• v.18 no.2
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• pp.345-355
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• 2015

In this study, the effects of weld parameters on nugget size and tensile-shear strength of welding joint in electrical resistance spot welding of galvanized DP 600 steel sheets having 1.2 mm were investigated. Taguchi design method has been employed to examine the effects of five parameters of welding current, electrode pressure, welding time, clamping time and holding time by using the $L_{27}(5^3)$ orthogonal array. Results showed that the most effective parameters on tensile shear strength and the nugget size ratio (hn/dn) were found as welding current and welding time, whereas electrode pressure, clamping time and holding time were less effective factors. Max. 545 MPa strength was obtained through proposed optimum conditions by Taguchi technique.

• Advances in Computational Design
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• v.2 no.4
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• pp.313-331
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• 2017

In this study, teaching-learning based optimization (TLBO) is improved by incorporating model of multiple teachers, adaptive teaching factor, self-motivated learning, and learning through tutorial. Modified TLBO (MTLBO) is applied for simultaneous topology, shape, and size optimization of space and planar trusses to study its effectiveness. All the benchmark problems are subjected to stress, displacement, and kinematic stability constraints while design variables are discrete and continuous. Analyses of unacceptable and singular topologies are prohibited by seeing element connectivity through Grubler's criterion and the positive definiteness. Performance of MTLBO is compared to TLBO and state-of-the-art algorithms available in literature, such as a genetic algorithm (GA), improved GA, force method and GA, ant colony optimization, adaptive multi-population differential evolution, a firefly algorithm, group search optimization (GSO), improved GSO, and intelligent garbage can decision-making model evolution algorithm. It is observed that MTLBO has performed better or found nearly the same optimum solutions.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.685-691
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• 2013

Ibuprofen, non-steroidal anti-inflammatory drugs; NSAIDs, is a highly crystalline substance with the pharmaceutical properties of poor solubility and low bioavailability. The size reduction of ibuprofen is needed to improve the solubility. The objective of this study is to optimize the grinding condition of ibuprofen. Grinding of ibuprofen was carried out using a planetary mill. Grinding parameters were optimized using Box-Behnken experimental design method. The physical characteristics of ground ibuprofen were investigated for the particle size by particle size analyzer, for the crystal size by X-ray diffraction (XRD), and for the tensile strength by tensile/compression tester. The optimum conditions for the milling of ibuprofen were 290 rpm of the revolution number of mill, 24.6 g of the weight of sample, and 10 minutes of grinding time. The measured value of the particle size of ground ibuprofen at these optimum conditions was $13.5{\mu}m$. The results showed that the crystal size of ibuprofen was reduced by the planetary milling process. In case the relative density of the tablets formulated of ground ibuprofen was range of 0.85~0.90, the tensile strength of them was range of 1$2{\sim}14Kg_f/cm^2$.

• International Journal of Fluid Machinery and Systems
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• v.10 no.3
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• pp.240-253
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• 2017

Latin hypercube sampling is widely used design-of-experiment technique to select design points for simulation which are then used to construct a surrogate model. The exploration/exploitation properties of surrogate models depend on the size and distribution of design points in the chosen design space. The present study aimed at evaluating the performance characteristics of various surrogate models depending on the Latin hypercube sampling (LHS) procedure (sample size and spatial distribution) for a diverse set of optimization problems. The analysis was carried out for two types of problems: (1) thermal-fluid design problems (optimizations of convergent-divergent micromixer coupled with pulsatile flow and boot-shaped ribs), and (2) analytical test functions (six-hump camel back, Branin-Hoo, Hartman 3, and Hartman 6 functions). The three surrogate models, namely, response surface approximation, Kriging, and radial basis neural networks were tested. The important findings are illustrated using Box-plots. The surrogate models were analyzed in terms of global exploration (accuracy over the domain space) and local exploitation (ease of finding the global optimum point). Radial basis neural networks showed the best overall performance in global exploration characteristics as well as tendency to find the approximate optimal solution for the majority of tested problems. To build a surrogate model, it is recommended to use an initial sample size equal to 15 times the number of design variables. The study will provide useful guidelines on the effect of initial sample size and distribution on surrogate construction and subsequent optimization using LHS sampling plan.

• Journal of Korea Water Resources Association
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• v.43 no.3
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• pp.275-282
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• 2010

The purpose of culvert design is to determine optimum size for a safe drainage of flood discharge. The present method of culvert design in Korea is generally carried out by using "Road Drainage Design" of Korea Expressway Corporation (1991), which is based on the manual of Federal Highway Association (FHWA) of USA. However, this method may result in subjective error because of using graphs and the usage of nomograph can be a major obstacle for computer modelling. Some errors found in the previous works of culvert design are corrected, and a new logic has been developed for a simple determination of culvert size in this study. FHWA (1985) presents a nomograph to determine the critical water depth and the velocity head for a circular pipe, but in this study simple explicit equations have been developed to determine both respectively.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.21-32
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• 2004

In this study, a continuous optimum design model with its application program for plane steel frame structures developed. In the model, the sequential unconstrained minimization technique (SUMT) transforming the nonlinear optimization problem with multidesign variables and constraints into an unconstrained minimization problem and the refined plastic hinge analysis method as one of the most effective second-order inelastic analysis methods for steel frame structures were implemented. The total weight of a steel frame structure was taken as the objective function, and the AISC-LRFD code requirements for the local and member buckling, flexural strength, shear strength, axial strength and size of the cross-sectional shapes of members were used for the derivation of constraint equations. To verify the appropriateness of the present model, the optimum designs of serveral plane steel frame structures subject to vertical and horizontal loads were conducted.

• Journal of Families and Better Life
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• v.28 no.3
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• pp.179-187
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• 2010

Since the late 20th century, construction companies have developed different brands of apartments while keeping the LOHAS, well-being, ubiquitous, and one-stop-living concepts in mind. From this point of view, this study intends to define the diverse space planning needs of apartment residents. The purpose of this study is to suggest optimum guidelines regarding the subject of space requirements and planning by conducting in-depth interviews of residents whose apartment floor size is between $66m^2$ (20 Pyong) and $165m^2$ (50 Pyong) and whose apartment is less than 5 years old. The major findings were as follows: (1) The shortage of storage space in different types of apartment housing units was found to be a chronic problem. Thus, closet sizes mustbe increased. (2) The size of the master bedroom needs to be decreased, whereas the size of the kitchen and dining room as well as the size of the second and/or third bedroom must be increased. More space is required in common areas occupied by the family and larger closets are needed. Less space is required for the master bedroom.

• Korean Institute of Interior Design Journal
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• v.20 no.5
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• pp.152-159
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• 2011

Housing construction companies have been providing master bedroom walk-in closet as a selling point in modest sized apartments as small as 74m$^2$. It is noticeable that master bedroom walk-in closet in apartments provided by public sectors showed much variety in its size. This study tries to set up the guide line of master bedroom walk-in closet size. It is quite reasonable to assume that the biggest space-occupiers in walk-in closet are blankets and clothing. The survey conducted in this study shows that the number of clothes people keep in their closet does not show any significant difference regardless of square footage of their apartments. 34.7% of respondent answered they keep about 50-60 clothes using coat hangers, where 20-30 of those are winter clothes. It is calculated the required optimum length of the walk-in closet is 3.8m$^2$. Considering the most popular longitudinal dimension of master bedroom, 3.9m, and the space needed to accommodate blankets, it can be concluded that the required length of storage in master bedroom walk-in closet is 2.1m. The length can be adjusted reflecting the length of the master bedroom.

• Journal of Magnetics
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• v.21 no.3
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• pp.374-378
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• 2016

The transformer used in an inverter type arc welding machine is designed to use high frequency in order to reduce its size and cost. Also, selecting core materials that fit frequency is important because core loss increases in a high frequency band. An inrush current can occur in the primary coil of transformer during arc welding and this inrush current can cause IGBT, the switching element, to burn out. The transformer design was carried out in $A_P$ method and amorphous core was used to reduce the size of transformer. In addition, sheet coil was used for primary winding and secondary winding coil considering the skin effect. This paper designed the transformer core with an air gap to prevent IGBT burnout due to the inrush current during welding and proposed the optimum air gap length.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.269-276
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• 2007

Optimal thickness and shape of the pedal arm of an automotive clutch is determined, using the numerical optimization technique, by solving the size and shape optimization problems to minimize its weight. For the optimization problems, two cases of stress and displacement constraints are considered: one from the vertical, and the other from the transverse stiffness test condition. The result of the transverse case is shown to be more conservative than that from the vertical case, being determined as the final optimum.