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This study the impact on the real earnings management credit rating (RANK), and looked at the impact on the real earnings management grade credit rating changes (decrease, increase) the effects in detail. firm for a total of 06 years for firm that are listed on the Korea Stock Exchange from 2008 to 2013 for the hypothesis - using the proceeds of the year 2,583 sample were analyzed to study A regression analysis of the relevance of the credit rating (RANK) and real earnings measured results between the credit rating and a measure of real earnings management ACFO and ADE (+) between AMC (-)IFRS and receive relevant ADE between(+) between AMC (-) if the credit rating (RANK) is increased ACFO and is significantly sound level at 1% showed the relevance of (+) did not significantly ADE (+) 10% of AMC if the credit rating fell ACFO is (-) from AMC show the relevance of positive credit rating is dropped capital letter showed for performing real earnings management of positive even give up the future cash flow in order to reduce the cost.

Aim of the present work is to optimize the shape of inlet part of a printed circuit heat exchanger to enhance the thermal–hydraulic performance using surrogate modeling. The fluid flow was analyzed using three-dimensional Reynolds-averaged Navier–Stokes analysis with the shear stress transport turbulence model. The non-dimensional parameters related to the angle and radius of curvature of the inlet plenum wall, and diameter of the inlet pipes were selected as design variables for the optimization. The objective function was defined as a weighted-sum of two objectives related to uniformity of the mass flow rate distribution and pressure loss, respectively. Twenty six design points were obtained by Latin hypercube sampling method. The Kriging and the radial basis neural networks were used as surrogate models to approximate the value of the objective function. The results of the optimization with a weighting factor show that the objective function values of the optimum designs obtained by the two surrogate models were similar to each other and improved from that of the reference design.

Purpose: The purpose of this study was to propose supply chain management efficiency by analyzing moderat-ing effect on the training support project in small and midium-sized enterprise.Methods: The collected data through the survey were analyzed using multi ‐regression analysis. The measure-ment tools used for this study were divided into three dimensions such as personal characteristics, supportive environment and training effect.Results: The results of this study are as follows; first, it was found that the effects of personal characteristics and supportive environment were significant on training effect. Second, significant differences were found between supply chain management active group and inactive group. Third, moderating effect of supply chain manage efficiency was found between variables.Conclusion: SME supporting project in training program needs supply chain management efficiency for training effect. Supply chain management needs to be promoted in SMEs not only for performance but also for their workplace learning and learning culture.Key Words: Supply Chain Management, Small and Medium-Sized Enterprise Training, HRD

This paper presents a multi-objective optimization procedure for the design of a sigma micromixer. The procedure combines three-dimensional analyses of fluid flow and mixing, polynomial approximation of objective functions, and a multi-objective genetic algorithm (MOGA). MATLAB Optimization Toolbox (version 7.7, The Mathworks, Inc., MA, USA) was used to invoke MOGA for optimization. A brief discussion on the application of Toolbox is introduced in the paper. Three geometric design parameters concerning the shape of the sidewalls were exploited for optimization. Mixing index and non-dimensional pressure loss were selected as objective functions. For mixing analysis, steady Navier-Stokes equations with a convection-diffusion model for scalar transport were solved at the Reynolds number Re = 0.91. The design space was explored through parametric study, and the Latin hypercube sampling method was used as a design-of-experiment technique for selection of the design points in the design space. Surrogate modelin...

A multidisciplinary optimization to simultaneously enhance the aerodynamic and aeroacoustic performance of an axial-flow fan was performed. Flow analysis through the axial-flow fan was conducted by solving three-dimensional steady and unsteady Reynolds-averaged Navier–Stokes equations with the shear-stress transport turbulence model. Starting with the results for the unsteady flow, aeroacoustic analysis was performed by solving the Ffowcs Williams–Hawkings equations. A single-objective optimization for high-efficiency design was carried out before the multi-objective optimization. The single-objective optimization was conducted using a weighted average surrogate model with five design variables defining the hub-to-tip ratio, hubcap installation distance, hubcap ratio, and angle distributions at the midspan and blade tip. The objective function (i.e., the efficiency) was evaluated at the design points, sampled by Latin hypercube sampling in the design space, to construct the surrogate model. Then, multi-ob...

Numerical simulations were carried out to investigate the flow dynamics and mixing behavior in T-shaped and serpentine microchannels with non-Newtonian working fluids using shear-dependent viscosity models. As an illustrative case study, the microfluidic transport of blood was considered. The Carreau–Yasuda and Casson non-Newtonian blood viscosity models were used to capture the non-Newtonian characteristics. Steady Navier–Stokes equations with a diffusion-convection model for species concentration were solved in flow and mixing analyses. Under similar operating conditions, flow dynamics and mixing were compared between the working fluids: water (a Newtonian fluid), and blood using the Carreau–Yasuda non-Newtonian model. For a mass flow rate of m 10 − 2 k g / h , the mixing performances of both the fluids were found to be nearly equivalent, and decreased with flow rate. With increased flow rate, the mixing with water was significantly improved. However, a negligible change in mixing performance was observed using the Carreau–Yasuda model for blood. Also, the pumping power needed was considerably higher for the blood sample (~1 bar) than for water (~0.40 bar) at the same flow rate. The mixing behavior with the Carreau–Yasuda blood model was compared for T-shaped and serpentine channels over a fixed mixing length. The serpentine channel showed better mixing performance over the flow rate range considered.

In recent years, single-incision laparoscopic appendectomy has been used as an improved form of conventional laparoscopic appendectomy (CLA). We have started to perform gasless laparoscopy-assisted transumbilical appendectomy (GLATUA) in patients with uncomplicated appendicitis. This study aimed to evaluate the feasibility, safety, cosmetic results, and cost-effectiveness of this novel technique of GLATUA.In total, 30 patients with a diagnosis of acute appendicitis without evidence of periappendiceal abcess or perforation and indicated for operation were enrolled in the study. Attempts to operate by the GLATUA technique initially were made in all of the patients. When it was technically difficult to perform appendix extraction via the umbilicus, the procedures were converted to the CLA technique (conversion group). The following factors between the successful group and conversion group were investigated to evaluate feasibility and predictable factors for the success of GLATUA: age, gender, duration from symptom onset to hospital visit, preoperative ileus, preoperative white blood cell count, neutrophil count (%), body mass index, fat infiltration in abdominal computed tomography or ultrasonography, pathologic characteristics of the resected appendix, and postoperative complications.Among the 30 patients, 19 patients underwent operation by the GLATUA technique (63.3%). There were no significant differences between the two groups in terms of demographics, duration from symptom onset to hospital visit, preoperative white blood cell count, neutrophil count (%), and pathologic characteristics of the appendix. Significant differences were observed between the two groups for preoperative ileus in simple abdominal x-ray and fat infiltration in preoperative diagnostic modality. There were no postoperative complications in both groups.GLATUA is a feasible, safe, and cost-effective technique for appendectomy in uncomplicated appendicitis and shows good cosmetic results. It did not increase the rate of complications and represents a possible alternative to the CLA technique in cases without fat infiltration in abdominal tomography or ultrasonography and small bowel ileus in simple abdominal x-ray.

A multiobjective optimization of a micromixer with convergent–divergent sinusoidal walls has been conducted using flow and mixing analyses, surrogate modeling, and multiobjective genetic algorithm. The ratios of amplitude to wavelength of the sinusoidal walls, throat width to depth of the convergent–divergent sections, and diameter of the inner circular wall to wavelength were chosen as the design variables for optimization. The full-factorial method was used to discretize the design space. The mixing index and nondimensional pressure loss were selected as objective functions. Radial basis neural network functions were used to train the objective functions. The optimization was carried out at a Reynolds number of 30. A concave Pareto-optimal front representing the trade-off between the two objective functions was obtained. The analysis of representative designs along the Pareto-optimal front showed significant variation in the ratio of throat width to depth of the convergent–divergent sections, whereas th...

The heat transfer performance of a new fan-shaped pin–fin in a rectangular cooling channel is evaluated using three-dimensional Reynolds-averaged Navier–Stokes equations in comparison with a circular pin–fin. A multi-objective optimization of the fan-shaped pin–fin was performed using a hybrid evolutionary algorithm with surrogate modeling to maximize the heat transfer and to minimize the friction loss simultaneously. The fluid flow and heat transfer were analyzed using the shear stress transport turbulence model in the Reynolds number range of 5000–100,000. The results of our analysis indicate that the averaged Nusselt number with the fan-shaped pin–fin was improved considerably in comparison with that of the circular pin–fin over the whole range of Reynolds numbers. For the optimization of the fan-shaped pin–fin, the ratio of the radius of front part of the pin–fin to that of the rear part, and the lateral reduction angle of the pin–fin, were selected as the design variables. Fifteen design points were generated using Latin hypercube sampling, and the values of the objective function were evaluated at these points. The surrogate models for the objective functions were constructed using the radial basis neural network method. The Pareto-optimal solutions of the fan-shaped pin–fin show that the designs were improved with respect to heat transfer and pressure drop in comparison with the circular and reference pin–fins.

A new design for a printed circuit heat exchanger is proposed, and the thermal characteristics of the proposed design are evaluated using three-dimensional Reynolds-averaged Navier–Stokes analysis. Further, the effect of overlapping the areas of the hot and cold channels on the thermal effectiveness in a conventional printed circuit heat exchanger is analyzed to investigate the usefulness of increasing the overlapping between channel areas. The proposed printed circuit heat exchanger is designed to maximize the overlapping area and to reduce the distance between the hot and cold channels. The four thermal performance parameters of the new design, namely, the Nusselt number, Colburn j-factor, thermal effectiveness, and net exergy gain, are evaluated and compared to a reference, which is a conventional printed circuit heat exchanger design. The proposed design shows remarkably higher thermal performance than the reference design.

The heat transfer and friction loss performances of rib-roughened rectangular cooling channels having a variety of cross-sectional rib shapes were analyzed using three-dimensional Reynolds-averaged Navier–Stokes equations. Numerical simulations were conducted for sixteen rib shapes: square, isosceles triangular, fan-shaped, house-shaped, reverse cut-trapezoidal, cut-trapezoidal, reverse boot-shaped, boot-shaped, reverse right-angle triangular, right-angle triangular, reverse pentagonal, pentagonal, reverse right-angle trapezoidal, right-angle trapezoidal, isosceles trapezoidal, and semicircular ribs. The ratios of pitch, height, and width of the rib to hydraulic diameter of the channel were set to 10, 0.047, and 0.047, respectively. The Reynolds stress model was used with the Speziale–Sarkar–Gatski pressure–strain model to analyze the turbulence. The computational results for the area-averaged Nusselt number were validated by comparison with the experimental data under the same conditions. The effects of the Reynolds number and rib pitch-to-width ratio on the performances of various ribs were also investigated for Reynolds numbers of 5000–50,000 and rib pitch-to-width ratios of 5.0–10.0, respectively. The new boot-shaped rib design showed the best heat transfer performance with a pressure drop similar to that of the square rib.

The performances of four liquid-jet cooling systems for light emitting diodes (direct, indirect, hybrid double-side, and hybrid jet-fin cooling) were evaluated using three-dimensional Reynolds-averaged Navier-Stokes analysis. The steady incompressible turbulent flow and conjugate heat transfer in the cooling systems were calculated using the shear stress transport turbulence model. The numerical results for the maximum temperatures at the chips were validated by comparison with experimental data. The maximum temperatures at the chips and the pressure drops through the systems were selected as the performance parameters, and were evaluated at four different flow rates. Connection methods for the inlet ports were also tested to enhance the uniform cooling of the chips. The hybrid double-side cooling method showed the best cooling performance. The best inlet connection method depended upon the mass flow rate.

Shape optimization of a staggered herringbone micromixer (SHM) was performed using the three-dimensional numerical analysis of fluid flows and mixing of two fluids, surrogate modeling, and a multi-objective genetic algorithm. Two design variables related to dimensions of the grooves, i.e., depth and width, were chosen for optimization. Three performance parameters, i.e., the mixing index at the exit of the micromixer, overall friction factor, and mixing sensitivity, which is the mixing index at a specified axial location in upstream part of the micromixer, were employed as the objective functions. Surrogate modeling was performed for the objective functions using response surface approximation. Multi-objective genetic algorithm was used to find the Pareto-optimal solutions. Representative Pareto-optimal designs were analyzed using numerical analysis and a particle tracking method. The optimization results indicate that wide and deep grooves are desirable to promote faster mixing with a low pressure drop inside the SHM.

A numerical investigation of the mixing and fluid flow in a new design of passive micromixer employing several cylindrical obstructions within a curved microchannel is presented in this work. Mixing in the channels is analyzed using Navier–Stokes equations and the diffusion equation between two working fluids (water and ethanol) for Reynolds numbers from 0.1 to 60. The proposed micromixer shows far better mixing performance than a T-micromixer with circular obstructions and a simple curved micromixer. The effects of cross-sectional shape, height, and placement of the obstructions on mixing performance and the pressure drop of the proposed micromixer are evaluated.

The three-dimensional geometry of a micromixer with an asymmetrical split-and-recombine mechanism was optimized to enhance the fluid-mixing capability at a Reynolds number of 20. Single and multi-objective optimizations were carried out by using particle swarm optimization and a genetic algorithm on a modeled surrogate surface. Surrogate modeling was performed using the computational results for the mixing. Mixing and flow analyses were carried out by solving the convection&ndash, diffusion equation in combination with the three-dimensional continuity and momentum equations. The optimization was carried out with two design variables related to dimensionless geometric parameters. The mixing effectiveness was chosen as the objective function for the single-objective optimization, and the pressure drop and mixing index at the outlet were chosen for the multi-objective optimization. The sampling points in the design space were determined using a design of experiment technique called Latin hypercube sampling. The surrogates for the objective functions were developed using a Kriging model. The single-objective optimization resulted in 58.9% enhancement of the mixing effectiveness compared to the reference design. The multi-objective optimization provided Pareto-optimal solutions that showed a maximum increase of 48.5% in the mixing index and a maximum decrease of 55.0% in the pressure drop in comparison to the reference design.

The impeller and volute of a single-channel pump used for wastewater treatment were simultaneously optimized to improve the hydraulic efficiency and reduce unsteady radial force sources due to the impeller–volute interaction. Steady and unsteady Reynolds-averaged Navier–Stokes equations were solved with the shear stress transport turbulence model as the turbulence closure model using tetrahedral grids to analyze the internal flow in the single-channel pump. Five design variables related to the internal flow cross-sectional areas of the impeller and volute were selected to simultaneously optimize the hydraulic efficiency, the sweep area of the radial force during one revolution, and the distance of the mass center of the sweep area from the origin as the three objective functions. The response surface approximation model and genetic algorithm were employed to obtain three-dimensional Pareto-optimal solutions representing the trade-off between the efficiency and the radial force sources. The results of the three-objective optimization show that the representative clustered optimum designs enhanced the efficiency and reduced the radial force sources simultaneously in most cases, compared to the reference design. In addition, it was confirmed that the trade-off between the efficiency and the radial force sources clarifies with controlling the internal flow cross-sectional areas of the impeller and volute of the single-channel pump.

The effects of geometric parameters on the performance of a printed circuit heat exchanger have been analyzed using three-dimensional Reynolds-averaged Navier–Stokes equations. The shear stress transport model is used for accurate prediction of the turbulent flows. The numerical solutions are validated in comparison with the available experimental data, and different lengths of the calculation domain have been tested to determine the optimum length of the domain. The effects of two design parameters, namely, the channel angle and the semi-ellipse aspect ratio of the cold channel, on the heat transfer and friction performance in the cold channel have been evaluated. The results indicate that the effectiveness of the heat exchanger is maximized when the cold channel angle is similar to the hot channel angle.

The present numerical analysis addresses free convection flow of a viscous incompressible fluid along an inclined semi-infinite flat plate considering the variation of viscosity and thermal diffusivity with temperature. The governing equations are developed with the corresponding boundary conditions are transformed to non-dimensional form using the appropriate dimensionless quantities. Due to complexity in the transformed governing equations, analytical solution will fail to produce a solution. Hence, most efficient and unconditionally stable implicit finite difference method of Crank-Nicolson scheme has been used to solve the governing equations. Numerical results are obtained for different values of the viscosity, thermal conductivity, inclination angle, Grashof number, and Prandtl number. The overall investigation of the variation of velocity, temperature, shearing stress and Nusselt number are presented graphically. To examine the accuracy of the present approximate results, the present results are compared with the available results.

The present study investigates the thermal performance of a silicon-based multiple microjet impingement heat sink for the thermal management of electronics. A three-dimensional numerical analysis was performed on the steady incompressible laminar flow and the conjugate heat transfer in multiple microjet impingement heat sinks. One side of the silicon substrate receives a moderate heat flux of 100 W/cm2; the other side contains the designed jet impingement system. The jet plate consists of many jet holes, so the computational domain was simplified by using symmetric boundary conditions. The effects of the design parameters such as the jet diameter, jet pitch, and standoff (that is, the distance of the nozzle exit to the heated surface) were analyzed under laminar flow conditions. Because of the low pumping power available in the micropumping system, the analysis was carried out at a low Reynolds number. The crossflow effects of the spent flow and the inline jet sweeping were investigated to determine the ...

Purpose: This study aims to develop measuring tools for 'Consumer Issues' of ISO 26000, the international standards for corporate social responsibility(CSR), and propose strategic suggestions on the CSR implemention by analyzing the differences among various industries. Methods: In order to test the research models, structured questionnaires were used and nationwide surveys were conducted targeting at customers who have had experiences in using the products and services from the companies which published CSR reports. In addition, for the empirical analysis of data, the models were verified with AMOS confirmatory factor analysis(CFA). Results: From the result of the analysis of differences among industries, it was shown that level of CSR activities was high in public sectors, followed by service industries and manufacturing. It was also shown high in air transport and the electrical and electronic industries, while it was confirmed low in energy and environment related industries such as energy, automobile and chemical industries. As a result, strategic approaches are suggested, considering the different characteristics of each industry in implementing CSR. Conclusion: This study has developed measuring tools for 'Consumer Issues' to research the core subjects and issues of ISO 26000, the international standards for CSR. It has confirmed the characteristics and differ- ences regarding 'Consumer Issues ' among industries and proved that industries can provide guidelines for the implementation of CSR activities through approaching and researching various issues from interested parties. This study has also suggested the importance of customer awareness of CSR activities and active communications by industries.

In this paper , we have developed the application of a remote multi-lingual video guide that allows interaction with Set Top Box of a thin client by using the WebRTC, an web browser-based communication method. A server accesses a web camera in conjunction with digital information display of a thin client connected remotely and is exchanged guide information with user. This server can be played in thin client STB using virtualization based the high-quality video compression technology. Further, it is not dependent on the performance of the STB and provides a video guide remotely.

A Parametric study of a passive micromixer with convergent-divergent channel walls of sinusoidal variation is conducted numerically using combined Navier-Stokes equations and convection-diffusion model for a Reynolds number range, 10 ≤ Re ≤ 70. Water and ethanol are used as working fluids for mixing analysis. Mixing performance was used to compare different configurations (layout) of the micromixer. In comparison with previously published design, which was based on Dean vortices in the sub-channels, the new configurations offered Dean vortices in the sub-channels and recirculation zones in the recesses of the channel for effective mixing. The proposed configurations are competitive in terms mixing performance and pressure loss. Finally, effect of two geometrical parameters viz. the ratio of throat-width to diameter of circular wall and the ratio of diameter of circular wall to amplitude, on mixing performance was studied over a chosen Reynolds number range.

A rotating equilateral triangular cooling channel with staggered square ribs inside the leading edge of a turbine blade has been optimized in this work based on surrogate modeling. The fluid flow and heat transfer in the channel have been analyzed using three-dimensional Reynolds-averaged Navier–Stokes (RANS) equations under uniform heat flux condition. Shear stress transport turbulence model has been used as a turbulence closure. Computational results for area-averaged Nusselt number have been validated compared to the experimental data. The objectives related to the heat transfer rate and pressure drop has been linearly combined with a weighting factor to define the objective function. The angle of the rib, the rib pitch-to-hydraulic diameter ratio, and the rib width-to-hydraulic diameter ratio have been selected as the design variables. Twenty-two design points have been generated by Latin Hypercube sampling, and the values of the objective function have been calculated by the RANS analysis at these points. The surrogate model for the objective function has been constructed using the radial basis neural network method. Through the optimization, the objective function value has been improved by 21.5 % compared to that of the reference geometry.

The effects of the ejection and lateral ejection angles of double-jet film-cooling holes on the film-cooling effectiveness was evaluated, and the shape of the double-jet film-cooling holes was optimized using three-dimensional Reynolds-averaged Navier–Stokes equations with a shear stress transport turbulence model and a radial basis neural network surrogate model. The numerical results for the film-cooling effectiveness were validated by a comparison with experimental data. To optimize the double jet film-cooling holes, the spatially-averaged, film-cooling effectiveness was considered as the objective function. Latin hypercube sampling was performed to determine the design points in the design space. A radial basis neural network model was constructed using the objective function values calculated at the design points. The optimal point was obtained from the constructed surrogate using sequential quadratic programming. The cooling performance of the double-jet film-cooling holes was improved considerably by optimization compared to the reference geometry. The constructed surrogate model was found to be sufficiently reliable.

This study evaluated a silicon-based micro-jet impingement heat sink for electronic cooling applications. First, the pressure-drop and thermal characteristics were investigated for steady incompressible and laminar flow by solving three-dimensional Navier–Stokes equations, and the performance enhancement was carried out through parametric and optimization studies. Several parallel and staggered micro-jet configurations consisting of a maximum of 16 jet impingements were tested. The effectiveness of the micro-jet configurations, i.e. inline 2 × 2, 3 × 3 and 4 × 4 jets, and staggered 5-jet and 13-jet arrays with nozzle diameters 50, 76, and 100 μm, were analyzed at various flow rates for the maximum temperature-rise and pressure-drop characteristics. A design with a staggered 13-jet array showed the best performance among the various configurations investigated in the present study. The design optimization based on three-dimensional numerical analysis, surrogate modeling and a multi-objective evolutionary algorithm were carried out to understand the thermal resistance and pumping power correlation of the micro-jet impingement heat sink. Two design variables, the ratio of height of the channel and nozzle diameter, and the ratio of nozzle diameter and interjet spacing, were chosen for design optimization. The global Pareto-optimal front was achieved for overall thermal resistance and required pumping power of the heat sink. The Pareto-optimal front revealed existing correlation between pumping power and thermal resistance of the heat sink. Of the range of Pareto-optimal designs available, some representative designs were selected and their functional relationships among the objective functions and design variables were examined to understand the Pareto-optimal sensitivity and optimal design space. A minimum of 66 °C of maximum-temperature-rise was obtained for a heat flux of 100 W/cm2 at a pressure drop of about 24 kPa.

The film cooling performance of cylindrical holes embedded in a transverse trench is evaluated for various shapes of the trench and blowing ratios, and an optimum geometry for the trenched film-cooling hole is suggested. In order to analyze the turbulent flow and film cooling performance, three-dimensional Reynolds-averaged Navier-Stokes analysis is performed using the shear stress transport turbulence model. Tetrahedral and hexahedral computational meshes are tested, and the numerical solution is validated by comparison with experimental data. A parametric study with two geometric variables, the height and width of the trench, is performed. From the results of the parametric study and flow field analysis, shifting the film cooling hole toward the upstream end of the trench is proposed to enhance film cooling performance. In addition, the optimum downstream trench width is determined.

A multiobjective optimization to enhance the stall margin and peak adiabatic efficiency of an axial compressor with a casing groove combined with injection was performed in this work. The geometry of the casing groove was optimized using a hybrid multiobjective evolutionary algorithm coupled with a surrogate model. Reynolds-averaged Navier–Stokes equations with a k– ɛ turbulence model were discretized by finite volume approximations and solved on hexahedral grids to analyze the flow in the compressor. The stall margin and peak adiabatic efficiency were selected as objective functions with three design variables related to the geometry of the casing groove. Latin hypercube sampling was applied as a design-of-experiment technique to generate 25 design points within the design space. Response surface approximation models as the surrogate models for the objectives were constructed based on the objective function values at the design points. A fast nondominated sorting genetic algorithm for the local search coupled with the surrogate models was applied to determine the global Pareto-optimal solutions. The tradeoff between the two objectives was determined and is described with respect to the Pareto-optimal solutions. The multiobjective optimization results showed that the stall margin and peak adiabatic efficiency of the axial compressor with an optimized casing groove combined with injection were simultaneously improved compared to the compressor with a smooth casing.

Core bypass flow in block type very high temperature reactor (VHTR) occurs due to the inevitable gaps between the hexagonal core blocks for the block installation and refueling. Since the core bypass flow affects the reactor safety and efficiency, it should be minimized to enhance the core thermal margin. In this regard, the core bypass flow reduction method applying the labyrinth seal mechanism was developed and optimized by using the single-objective shape optimization method. Response surface approximation (RSA) method was adopted as the optimization method. Side wall of the replaceable reflector block was redesigned and response surface approximate model was adopted to optimize the shape of the reflector wall. Computational fluid dynamics (CFD) analyses were carried out not only to assess the limitation of existing method of bypass flow reduction, but also to optimize the design of a newly developed reduction method. The experiment with Seoul National University (SNU) multi-block experimental facility was performed to demonstrate the performance of the reduction method. It was found that the effect of the existing bypass flow reduction method by sealing the bypass gap exit was restricted nearby the lower region of the core. However, the flow resistance factor of the bypass gap increased from 18.04 to 26.24 by the optimized reduction method. The results of the performance test showed that the bypass flow distribution was reduced throughout the entire core regions. The bypass flow ratios at the inlet and the outlet were reduced by 36.19% and 14.66%, respectively. In conclusion, it is expected that the core thermal margin and efficiency of VHTR reactor cooling can be enhanced by applying the developed bypass flow reduction method.

Aerodynamic performance of a transonic axial compressor with a casing groove combined with injection has been investigated in this work. Three-dimensional Reynolds-averaged Navier–Stokes equations with k-ε turbulence model are discretized by finite volume approximations and solved on hexahedral grids for the flow analyses. For parametric study, the front and rear lengths and height of the casing groove are selected as the geometric parameters and are changed with constant injection to investigate their effects on the stall margin and peak adiabatic efficiency. As a result of the parametric study, the maximum stall margin and peak adiabatic efficiency are found to be obtained in the axial compressor having 70% height of the reference groove. The results show that the application of the casing groove combined with injection to an axial compressor is effective for the simultaneous improvement of both the stall margin and peak adiabatic efficiency of the compressor.

A transonic axial compressor with circumferential casing grooves is optimized to improve operating stability. Numerical analysis is conducted by solving three-dimensional Reynolds-averaged Navier–Stokes equations using the shear stress transport turbulence model. An optimization process based on a weighted-average surrogate model and steady flow analysis are performed with three design variables defining the tip clearance, blade tip angle, and depth of the grooves. The steady stall inception point is identified from the last converged point, and values of the stall margin as the objective function are predicted using steady flow analysis at the design points sampled by Latin hypercube sampling in the design space. The surrogate model is constructed based on these objective function values. Optimization of this model found the optimum design, which yields a considerable increase in the stall margin compared to the smooth casing. To investigate unsteady behavior of the flow in the optimized compressor with casing grooves, an unsteady flow analysis is performed, and the stall inception point is re-predicted using this analysis.

Hydraulic performance of an inlet plenum in a printed-circuit heat exchanger has been analyzed using three-dimensional Reynolds-Averaged Navier-Stokes equations. The numerical model of the inlet plenum was constructed through grid dependency test, calculation domain tests, and turbulence model and numerical scheme selections. Shear stress transport turbulence model was used for analysis of turbulence. Non-uniformity of the flow in zigzag flow channels was evaluated for the reference case. Parametric studies have been performed with the angle of the inlet plenum wall, radius of curvature of the inlet plenum wall, and width of the inlet pipes. The effects of these parameters on the flow uniformity and friction performance were evaluated.

A parametric study on the geometry of an impeller in a forward-curved blades centrifugal fan for residential ventilation has been carried out in this work. Numerical analysis of a forward-curved blades centrifugal fan was carried out by solving three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. A validation of numerical results was conducted by comparison with experimental data for the pressure and efficiency. The impeller separated by an annular plate was employed, and the annular plate height and the angle between the upper and lower impellers were selected as the geometric parameters to investigate their effects on the efficiency of the forward-curved blades centrifugal fan. Additionally, the impeller geometry having the highest efficiency was tested with the number and exit angle of blades. The results show that the impeller with properly installed annular plate improves the aerodynamic performance of the forward-curved blades centrifugal fan.

Effect of semicircular rib or groove on the performance of a rim-seal was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations. The turbulence was modeled using the one-equation Spalart-Allmaras turbulence closure model. Reynolds number based on the axial chord of the turbine blade was 500,000 at the mainstream outlet. The numerical results for a sealing effectiveness was validated in comparison with experimental data. To examine the effect of the semicircular rib or groove on sealing effectiveness of the rim-seal, location and diameter of the rib or groove were selected as the parameters to be performed. The rim-seals with the semicircular groove showed a higher sealing effectiveness than that with the semicircular rib. The semicircular groove installed on the stator side showed best sealing effectiveness among the numerical simulation results.

Mechanism of thymic compartmentalization was studied in the transgenic system using the promoter of thymic stromal cotransporter (TSCOT), a cortical thymic epithelium-specific gene. The transgenic 3.1 kb TSCOT (3.1T) and 4.4 kb TSCOT (4.4T) promoters recapitulated the thymic organ and the cortical epithelial cell-specific expression at the newborn stage. However, the 3.1T driving enhanced green fluorescent protein (EGFP; 3.1T-EGFP) or Cre-recombinase (3.1T-CreE) redistributed the expression into the medulla at the adult stages. Two Cre-transgenic lines (3.1T-CreE and 4.4T-CreE), when crossed with the ROSA LacZ or EGFP lines, showed the reporter expression in both the cortex and the medulla. TSCOT promoter activities were also verified in the transient thymic epithelial cell (TEC) population expressing keratin 5 and keratin 8. These indicate that the TSCOT promoter is turned on in the bipotent TEC precursors and regulated in a compartment-specific, developmentally regulated fashion. These transgenic lines provide the useful systems for delineating the specific pathways for TEC lineage development and function.

Multi-objective shape optimization of a row of laidback fan-shaped film cooling holes has been performed using a hybrid multi-objective evolutionary approach in order to achieve an acceptable compromise between two competing objectives: the enhancement of film cooling effectiveness and the reduction of aerodynamic loss. In order to perform comprehensive optimization of a film cooling hole shape, the injection angle of the hole, lateral expansion angle of the diffuser, forward expansion angle of the hole, and pitch-to-hole diameter ratio are chosen as design variables. Forty experimental designs within the design spaces are selected using the Latin hypercube sampling method. The response surface approximation method is used to construct the surrogate using objective function values calculated at the experimental points using Reynolds-averaged Navier-Stokes analysis. The shear stress transport turbulence model is used as a turbulence closure. The optimization results are processed using the Pareto-optimal m...

A parametric analysis and optimization of double-jet film-cooling holes was performed using three-dimensional Reynolds averaged Navier–Stokes equations with the shear stress transport turbulence model. The numerical results for film-cooling effectiveness were validated in comparison with experimental data. The lateral and streamwise distances between the centers of the holes, along with two lateral ejection angles, were chosen as the design variables. The effects of these four variables on the film-cooling effectiveness were evaluated. For optimization of double-jet film-cooling holes, film-cooling effectiveness was considered as the objective function. Latin hypercube sampling was used to determine the design points. A weighted average surrogate model was constructed using the objective function values calculated at the design points. Sequential quadratic programming was used to search for the optimal point from the constructed surrogate. The cooling performance of double-jet film-cooling holes was impro...

The present study investigates the thermal and hydraulic performance of the microjet array cooling system for thermal management of a high-power light-emitting diode array. Three-dimensional numerical analyses were performed for steady incompressible turbulent flow and conjugate heat transfer through a finite volume solver. The performances of several microjet array configurations, viz., 1-jet, 4-jet, 9-jet, 13-jet, and 16-jet arrays, were analyzed at two flow rates and top-cavity heights. The design optimization of a 4-jet array cooling system was performed using a multi-objective evolutionary algorithm. For the optimization, two design variables, viz., ratio of the nozzle diameter and height of the top cavity and ratio of the height and length of the top cavity, were selected. The thermal resistance and pressure drop were selected as the objective functions of the design. The Pareto-optimal solutions were obtained and discussed in view of the thermal resistance and pressure drop and sensitivity of desig...

A liquid flow manifold microchannel heat sink is optimized with the help of 3-D numerical analysis, a surrogate method, and a multiobjective evolutionary algorithm. The performance of the manifold microchannel heat sink is optimized for the overall thermal resistance and the pumping power required for driving the coolant. The design variables related to the width of the microchannel, depth of the microchannel, width of fins, length of the nozzles, and height of the nozzles, which contribute to objective functions, are identified and optimized for minimum thermal resistance and pumping power. A Latin hypercube sampling method is used to exploit the design space. The numerical solutions obtained at these design points are utilized to construct a surrogate model, i.e., response surface approximation. The Navier-Stokes and energy equations for laminar flow and conjugate heat transfer are solved using a finite-volume solver. A hybrid multi objective evolutionary algorithm coupled with a surrogate model is applied to find out global Pareto-optimal designs (PODs). Trade-off analysis is performed in view of the conflicting nature of the two objectives, which yields PODs with low thermal resistance at various pumping powers. The ratio of the microchannel width to the microchannel height and that of the nozzle height to the microchannel height are found to be more Pareto-optimal sensitive (sensitive along the Pareto-optimal front) than others. In contrast, the ratio of the fin width to the microchannel height and that of the nozzle length to the microchannel width are found to be less Pareto-optimal sensitive than other design variables. The PODs showed lower thermal resistance and pumping power than the reference designs at various mass flow rates.

Inlet part of a printed circuit heat exchanger has been optimized by using three-dimensional Reynolds-Averaged Navier-Stokes analysis and surrogate modeling techniques. Kriging model has been used as the surrogate model. The objective function for the optimization has been defined as a linear combination of uniformity of mass flow rate and the pressure loss with a weighting factor. For the optimization, the angle of the inlet plenum wall, radius of curvature of the inlet plenum wall, and width of the inlet pipes have been selected as design variables. Twenty six design points are obtained by Latin Hypercube Sampling in design space. Through the optimization, considerable improvement in the objective function has been obtained in comparison with the reference design of PCHE.

Comparative study has been performed with various channel cross-sectional shapes and channel configurations of a zigzag printed circuit heat exchanger (PCHE), which has been considered as a heat exchanging device for the gas turbine based generation systems. Three-dimensional Reynolds-averaged Navier–Stokes equations and heat transfer equations are solved to analyze conjugate heat transfer in the zigzag channels. The shear stress transport model with a low Reynolds number wall treatment is used as a turbulence closure. The global Nusselt number, Colburn j-factor, effectiveness, and friction factor are used to estimate the thermal–hydraulic performance of the PCHE. Four different shapes of channel cross section (semicircular, rectangular, trapezoidal, and circular) and four different channel configurations are tested to determine their effects on thermal–hydraulic performance. The rectangular channel shows the best thermal performance but the worst hydraulic performance, while the circular channel shows the worst thermal performance. The Colburn j-factor and friction factor are found to be inversely proportional to the Reynolds number in cold channels, while the effectiveness and global Nusselt number are proportional to the Reynolds number.

Performance analysis of double-layer microchannel heat sinks was performed under non-uniform heating conditions having randomly distributed hotspots. Two parallel-channel (parallel-flow and counter-flow) and one cross-channel (transverse-flow) designs of double-layer heat sink were evaluated with three sets of heating schemes. Each set of heating scheme consisted of eleven randomly distributed hotspots generated by Latin hypercube sampling. The heat flux, area, and location of the hotspots were selected as the design parameters. Conjugate heat transfer analysis of the heat sinks was performed by solving three-dimensional Navier–Stokes and energy equations. Water with temperature-dependent properties was selected as the coolant. The thermal resistance, pressure drop, maximum temperature rise, and temperature variation among hotspots were evaluated for all the heat sinks. The transverse-flow microchannel heat sink exhibited the lowest thermal resistance, temperature rise and temperature variation among the hotspots throughout the specified range of flow rate. The lowest pressure drop was exhibited by the counter-flow heat sink.

This paper presents a performance evaluation of non-axisymmetric casing grooves combined with airflow injection in a transonic axial compressor with NASA Rotor 37, using three-dimensional Reynolds-averaged Navier-Stokes equations with the k-ε turbulence model. An axisymmetric casing groove was divided circumferentially into 36 non-axisymmetric grooves. The numerical results for adiabatic efficiency and total pressure ratio were validated with experimental data. A parametric study for stall margin, stable range extension, peak adiabatic efficiency, and total pressure ratio at peak adiabatic efficiency of the compressor was performed using five parameters: the front and rear lengths, the height of the casing groove, the injection mass flow rate, and the injection angle. The non-axisymmetric casing grooves combined with injection improve greatly the stall margin and stable range extension of the transonic axial compressor, but reduce only slightly the peak adiabatic efficiency in all cases, compared to the results for a smooth casing.

The objective of this study is to determine a tracking method using kernelized correlation filter based on object's appearance and motion model used to track multi-object. This system largely consists of 4 modules: motion model, background subtraction, hijacking handling and occlusion handling. Lab colour model is applied to subtract background, and histogram of oriented gradient (HoG) is used to extract object feature. If occlusion among objects occurs, we use a method that tracks again after removing the overlapping objects in consideration of the depth between objects: The head of the closer object is being taken from a camera positioned below the head of the distant object. Thus, among occluded tracking objects, we find that the most upper located object is considered as the furthest object in captured camera image. If hijacking among objects is occurred, it has been solved by removing the overlapping region of the bounding box between two objects that maintain their relative positions for a period of time. These results indicate that this method may allow a solution for tracking of multi-object to be more robust to real-world tracking environments.

Optimization of a microchannel heat sink has been performed based on the analyses of fluid flow and heat transfer with phase change using three-dimensional Reynolds-averaged Navier-Stokes equations. The uniform heat flux condition is applied at the bottom of the heat sink. Three design variables, viz. ratio of microchannel width to height of the heat sink, ratio of fin height to heat sink height, and ratio of fin width to height of the heat sink are selected for the shape optimization. Latin hypercube sampling was used to determine the training points as a design of experiment, and the surrogate model is constructed using the objective function values at the training points. Sequential quadratic programming is used to search for the optimal point from the constructed surrogate model. The thermal resistance is set as the objective function. It was found that the thermal resistance increased with increasing ratios of the microchannel width-to-height of the heat sink and fin height to heat sink height, while the thermal resistance decreased with increasing ratio of the fin width-to-height of the heat sink. Through the optimization, the thermal resistance has been decreased by 37.3% compared to the reference geometry.

This paper presents a parametric study on aerodynamic performance of a transonic axial compressor combined with a casing groove and tip injection using three-dimensional Reynolds-average Navier-Stokes equations. The front and rear lengths and height of the groove are selected as the geometric parameters to investigate their effects on the stall margin and peak adiabatic efficiency. These parameters are changed with constant injection. The validation of the numerical results is performed in comparison with experimental data for the total pressure ratio and adiabatic efficiency. As the results of the parametric study, the maximum stall margin and peak adiabatic efficiency are obtained in the axial compressor having 70% groove height of the reference groove. The stall margin and peak adiabatic efficiency in other cases are also improved in comparison with the axial compressors with the smooth casing and reference groove. The results show that both the stall margin and the peak adiabatic efficiency are considerably improved by the application of the casing groove combined with tip injection in an axial compressor.

A multi-objective design optimization of a rotating two-pass cooling channel with airfoil-shaped guide vanes in the turning region has been performed to enhance heat transfer and reduce pressure drop in the channel. An optimization procedure using three-dimensional Reynolds-averaged Navier–Stokes analysis, a surrogate method, and a multi-objective evolutionary algorithm is presented. Two objective functions related to heat transfer and friction loss are considered to estimate the cooling performance of the rotating two-pass channel. For the optimization, four design variables, the angles and radii of the airfoil-shaped guide vanes, are selected. A comparison of the friction factors between the experimental data and numerical results for a smooth channel is made to validate the numerical results. The optimized airfoil-shaped guide vanes in the turning region reduce pressure loss and enhance heat transfer throughout the channel.

This work investigates the effects of circumferential casing grooves on stall flow characteristics of a transonic axial compressor. Numerical analysis is conducted by solving three-dimensional steady Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. The results of flow analysis for an axial compressor with smooth casing are validated in comparison with experimental data for the pressure ratio and adiabatic efficiency. The numerical stall inception point is identified from the last converged point by convergence criteria, and the stall margin is predicted numerically. The peak adiabatic efficiency point is also obtained by reducing the normalized mass flow in the high mass flow region. In order to explore the influence of number of the circumferential casing grooves on the performance of the compressor, the stall margins and peak adiabatic efficiencies are evaluated compared to the case smooth casing. The stability of the axial compressor with circumferential casing grooves is found to be sensitively influenced by the number of grooves.