• Journal of Ship and Ocean Technology
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• 제9권3호
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• pp.1-13
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• 2005

A design procedure for a ship with minimum total resistance has been developed using a numerical optimization method called SQP (Sequential Quadratic Programming) to search for optimized hull form and CFD(Computational Fluid Dynamics) technique. The friction resistance is estimated using the ITTC 1957 model-ship correlation line formula and the wave making resistance is evaluated using a potential-flow panel method based on Rankine sources with nonlinear free surface boundary conditions. The geometry of hull surface is represented and modified using B-spline surface patches during the optimization process. Using the Series 60 hull ($C_B$ =0.60) as a base hull, the optimization procedure is applied to obtain an optimal hull that produces the minimum total resistance for the given constraints. To verify the validity of the result, the original model and the optimized model obtained by the optimization process have been built and tested in a towing tank. It is shown that the optimal hull obtained around $13\%$ reduction in the total resistance and around $40\%$ reduction in the residual resistance at a speed tested compared with that of the original one, demonstrating that the present optimization tool can be effectively used for efficient hull form designs.

• 유통과학연구
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• 제19권5호
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• pp.13-21
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• 2021

Purpose: The sports leadership theories are crucial in ensuring the success of corporations. This study shall discuss the various leadership theories employed in the sports industry and how they can be incorporated within the retailing sector to enhance the service quality and promote substantial customer value towards all the consumers visiting the retailing stores. Research design, data and methodology: The present researcher gathered textual data on potential solutions for coding of development through web searching method and coded and produced various topics as solution providers. Methods were then established to enhance quality on customer value by the leadership within their businesses, and the researcher subsequently presented the findings. Results: This study provides a total of nine solutions which are helpful systemically for practitioners in the retailer service sector. These numerous solutions can be incorporated within the retail industry through the sports leadership theories employed in the sports industry to help achieve a full and strong customer value. Conclusions: Finally, the present study concludes that the retail industry and management need to ensure that a substantial customer value is built through high-quality services rendered towards the clientele base, employing sports leadership theories such as path-goal, authentic leadership, transformation, situational and leader-member exchange theories.

• Steel and Composite Structures
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• 제32권6호
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• pp.731-741
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• 2019

Shear deformation effects are neglected in most structural system identification methods. This assumption might lead to important errors in some structures like built up steel or composite deep beams. Recently, the observability techniques were presented as one of the first methods for the inverse analysis of structures including the shear effects. In this way, the mechanical properties of the structures could be obtained from the nodal movements measured on static tests. One of the main controversial features of this procedure is the fact that the measurement set must include rotations. This characteristic might be especially problematic in those structures where rotations cannot be measured. To solve this problem and to increase its applicability, this paper proposes an update of the observability method to enable the structural identification including shear effects by measuring only vertical deflections. This modification is based on the introduction of a numerical optimization method. With this aim, the inverse analysis of several examples of growing complexity are presented to illustrate the validity and potential of the updated method.

• Advances in concrete construction
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• 제14권2호
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• pp.115-130
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• 2022

This paper presents an application of the maturation effect on the strength of high-strength concrete which is produced with different origin aggregates. While investigating the maturation effect on HSC 384 specimens were prepared with 22 different origin aggregates. These prepared specimens were subjected to the standard compressive tests which were applied after curing for 2, 7, 28, and 56 days under appropriate conditions. The test results revealed that bright surface-low adherence behavior is valid in normal strength concretes, but is not as effective as expected in high-strength concretes. The application of artificial neural networks (ANNs) to predict 2, 7, 28, and 56 day compressive strength of HSC is also investigated in this paper. An ANN model is built, trained, and tested using the available test data gathered from experimental studies. The ANN model is found to predict 2, 7, 28, and 56 days of compressive strength of high-strength concrete well within the ranges of the input parameters considered. These comparisons show that ANNs have strong potential as a feasible tool for predicting the compressive strength of high-strength concrete within the range of the input parameters considered.

• Macromolecular Research
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• 제8권1호
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• pp.6-11
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• 2000

In this study, we examined the charging behavior of chopped carbon fibers during electro-flocking process, which is one of the key processes of the novel technique for fabricating conductive polymer composite films. Short carbon fibers (CF) during electroflocking were electrically charged by the combined effect of contact charging, corona charging and tribocharging. The specific charge built on CF surface was measured by using Faraday cup method. Specific charge increased not only with increasing electric field strength and potential impressed to mesh electrode as expected from theoretical considerations in literature, but with decreasing mesh opening size due to the improved contact charging condition. However, CF length was found unexpectedly to influence the amount of CF specific charge due to the agglomerated nature of CF flocks leading to the change in charging conditions.

• Transactions on Electrical and Electronic Materials
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• 제13권5호
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• pp.256-261
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• 2012

Recently, many photovoltaic systems (PV systems) including solar parks and PV farms have been built to prepare for the post fossil fuel era. To investigate the degradation process of the PV systems and thus, efficiently operate PV systems, there is a need to visually monitor PV systems in the range of infrared ray through the Internet. For efficient visual monitoring, this paper explores a multithreaded implementation of a recently developed HEVC standard whose compression efficiency is almost two times higher than H.264. For an efficient parallel implementation under a meshbased 64 multicore system, this work takes into account various design choices which can solve potential problems of a two-dimensional interconnects-based 64 multicore system. These problems may have not occurred in a small-scale multicore system based on a simple bus network. Through extensive evaluation, this paper shows that, for an efficient multithreaded implementation of HEVC intra prediction in a mesh-based multicore system, much effort needs to be made to optimize communications among processing cores. Thus, this work provides three design choices regarding communications, i.e., main thread core location, cache home policy, and maximum coding unit size. These design choices are shown to improve the overall parallel performance of the HEVC intra prediction algorithm by up to 42%, achieving a 7 times higher speed-up.

• 대한조선학회논문집
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• 제40권4호
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• pp.16-21
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• 2003

The very large container ships have been built recently and those ships have very small structural rigidity compared with the other conventional ships. As a result, the destruction of ship hull is occurred by the springing including to warping phenomena due to encounter waves. In this study, the solutions of hydrodynamic coefficients are obtained by solving the three dimensional source distribution method and the forward speed Green function representing a translating and pulsating source potential for infinite water depth is used to calculating the integral equation. The vessel is longitudinally divided into various sections and the added mass, wave damping and wave exciting forces of each section is calculated by integrating the dynamic pressures over the mean wetted section surface. The equations for six degree freedom of motions is obtained for each section in the frequency domain and stiffness matrix is calculated by Euler beam theory. The computations are carried out for very large ship and effects of bending and torsional ridigity on the wave frequency and angle are investigated.

• Journal of Power Electronics
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• 제18권4호
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• pp.1154-1164
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• 2018

In single-phase magnetically coupled resonant (MCR) wireless power transfer (WPT) systems, the transfer characteristics, including the output power and transfer efficiency, are significantly influenced by the spatial scales of its coils. As a potential alternative, a three-phase MCR WPT system with cylinder-shaped coils that are excited in a voltage-fed manner has been proposed to satisfy the requirements of compact space. This system adopts a phase-shifted angle control scheme to generate a rotating magnetic field and to realize omnidirectional WPT that is immune to spatial scales. The magnetic field model and equivalent circuit models are built to holistically analyze the system characteristics under different angular misalignments. Research results show that the transfer characteristics can be improved by modulating the phase-shifted angle in each phase. Experiments have also been carried out to evaluate the accuracy of the theoretical analysis and to confirm the validity of the system modeling method.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.82-82
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• 2008

One-dimensional (1D) nanowires have been received much attention due to their potential for applications in various field. Recently some logic applications fabricated on various nanowires, such as ZnO, CdS, Si, are reported. These logic circuits, which consist of two- or three field effect transistors(FETs), are basic components of computation machine such as central process unit (CPU). FETs fabricated on nanowire generally have surrounded shapes of gate structure, which improve the device performance. Highly integrated circuits can also be achieved by fabricating on nano-scaled nanowires. But the numerical and SPICE simulation about the logic circuitry have never been reported and analyses of detailed parameters related to performance, such as channel doping, gate shapes, souce/drain contact and etc., were strongly needed. In our study, NAND and NOT logic circuits were simulated and characterized using 2- and 3-dimensional numerical simulation (SILVACO ATLAS) and built-in spice module(mixed mode).

• 대한기계학회논문집A
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• 제20권5호
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• pp.1392-1400
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• 1996

The need of companies shorten the design-to-manufacturing process for new products with improved quality in cost effective manner places increasing demends on engineers to simulate the performance characteristics of a design before it is built of a prototype is developed. For theses demands CAE(Computer-Aided Engineering) offers engineers not only giving confidence of their design but also eliminating potential errors due totesting prototypes in small numbers. This paper present the method to predict the fatigue life using dynamics simulation and FEA(Finite Element Analysis) for construciton equipment in the computer before building prototype. The dynamicsimulatio is to get the load-time history corresponding to the maneuvering and driving of the construction equipment. The FEA is to build a model of the structure and then analyse to define the local stress response to applied loadings using linear static analysis.