• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.3
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• pp.209-217
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• 2013

This paper presents an optimal design of a magnetorheological(MR) fluid-based mount(MR mount) that can be used for to vibration control in diesel engines of ships. In this work, a mount that uses mixed-modes(squeeze mode, flow mode, and shear mode) is proposed and designed. To determine the actuating damping force of the MR mount required for efficient vibration control, the excitation force from a diesel engine is analyzed. In this analysis, a model of a V-type engine is considered. The relationship between the velocity and pressure of gas in terms of the torque acting on the piston is derived. Subsequently, by integrating the field-dependent rheological properties of commercially available MR fluid with the excitation force, the appropriate size of the MR mount is designed. In addition, to achieve the maximum actuating force under geometric constraints, design optimization is undertaken using the ANSYS parametric design language software. Through magnetic density analysis, optimal design parameters such as the bottom gap and radius of coil are determined.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.9
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• pp.1-5
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• 2011

In this paper, we investigated the characteristics of AlGaN/GaN HEMTs to optimize their DC and RF characteristics by using a two-dimensional device simulator. First, we analyzed the variation of the DC characteristics with respect to the variation of 2DEG concentrations when varying the Al mole fraction and the thickness of the AlGaN layer. Then, we examined the variation of the RF characteristics by varying the size and the location of the gate, source and drain electrodes. When the Al mole fraction increased from 0.2 to 0.45, both the transconductance and I-V characteristics increased. On the other hand, the I-V characteristics were improved but transconductance was decreased as the thickness of the AlGaN layer increased from 10nm to 50nm. In the RF characteristics, the gate length was found to be the most influential parameter, and the RF characteristics were improved when the gate length was shorten.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.11
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• pp.1135-1140
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• 2016

The main challenge in designing wearable WBANs is to guarantee the balance of QoS demands in the network with the low power constraints of limited battery powered nodes. Low power devices implanted in or attached to the body should be designed to meet minimum energy requirements due to their limited battery life and be small in size to be easily wearable. In this paper, we propose a method for optimizing channel allocation method that is compatible with the IEEE 802.15.6 standard, enables the maximum amount of power charge at idle, guarantees the QoS of a WBAN, and provides the reliable date transmission between nodes and hubs in the network. Our extensive simulations will show that the method we propose not only maximizes the QoS in packet transmission but also improves the level of energy efficiency.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.8
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• pp.1068-1073
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• 2010

A welding neck flange is widely used for an interconnection between pipes. It is produced by a hot forging process, and required high yield strength under the high pressure condition, like a deep-sea. Generally, to increase yield strength, a increasing of carbon content is used, however a carbon content of welding neck flange is limited to 0.47. So, in this study, a strengthening by grain refinement without changing carbon content is used to increase yield strength. Taguchi method and FEM are used for the optimization of forging process and the experiment for the yield strength of the prototype with the optimal forging process is performed for validity.

• Progress in Medical Physics
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• v.29 no.2
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• pp.66-72
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• 2018

The proper position of a multi-leaf collimator (MLC) is essential for the quality of intensity-modulated radiation therapy (IMRT) and volumetric modulated arc radiotherapy (VMAT) dose delivery. Task Group (TG) 142 provides a quality assurance (QA) procedure for MLC position. Our study investigated the QA validation of the mechanical leaf gap measurement and the maintenance procedure. Two $VitalBeam^{TM}$ systems were evaluated to validate the acceptance of an MLC position. The dosimetric leaf gaps (DLGs) were measured for 6 MV, 6 MVFFF, 10 MV, and 15 MV photon beams. A solid water phantom was irradiated using $10{\times}10cm^2$ field size at source-to-surface distance (SSD) of 90 cm and depth of 10 cm. The portal dose image prediction (PDIP) calculation was implemented on a treatment planning system (TPS) called $Eclipse^{TM}$. A total of 20 VMAT plans were used to confirm the accuracy of dose distribution measured by an electronic portal imaging device (EPID) and those predicted by VMAT plans. The measured leaf gaps were 0.30 mm and 0.35 mm for VitalBeam 1 and 2, respectively. The DLG values decreased by an average of 6.9% and 5.9% after mechanical MLC adjustment. Although the passing rates increased slightly, by 1.5% (relative) and 1.2% (absolute) in arc 1, the average passing rates were still within the good dose delivery level (>95%). Our study shows the existence of a mechanical leaf gap error caused by a degenerated MLC motor. This can be recovered by reinitialization of MLC position on the machine control panel. Consequently, the QA procedure should be performed regularly to protect the MLC system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.921-931
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• 2011

This paper presents a data-fitting technique in which a B-spline hypervolume is used to approximate a given data set of scattered data samples. We describe the implementation of the data structure of a B-spline hypervolume, and we measure its memory size to show that the representation is compact. The proposed technique includes two algorithms. One is for the determination of the knot vectors of a B-spline hypervolume. The other is for the control points, which are determined by solving a linear least-squares minimization problem where the solution is independent of the data-set complexity. The proposed approach is demonstrated with various data-set configurations to reveal its performance in terms of approximation accuracy, memory use, and running time. In addition, we compare our approach with existing methods and present unconstrained optimization examples to show the potential for various applications.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.4
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• pp.636-641
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• 2002

Optimum extraction condition and clarification process were investigated to manufacture liquid extract tea using Phellinus linteus. Carbohydrates content in the raw Phellinus linteus was 80.9%. Major minerals were K, Ca, Fe and Na, but vitamin B$_1$, B$_2$, and C were not detected. The best extraction condition was 5% raw material at 10$0^{\circ}C$ within 3 hr. To clarify the extract, three methods of filtration with depth filter pad, centrifugation and addition of several filter aids were studied. Filtration with depth filter pad and centrifugation were highly effective on the clarification and the changes in the turbidity for 7 weeks at 4$0^{\circ}C$ were not occurred. The optimum clarification condition was centrifugation above 6,000 rpm or filtration with 8 ${\mu}{\textrm}{m}$ depth filter pad.

• Membrane Journal
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• v.18 no.1
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• pp.35-43
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• 2008

In this study, we tried to solve membrane fouling with membranes made by fine nano-particle in MBR process. And we confirmed good fouling resistance in pilot test. In this test, we confirmed our membrane with titania out-standing quality by testing in the pilot long-term test by comparing to other company product. Our membrane keep up steadily $20{\sim}25 L/m^2{\cdot}hr$ high flux in $7,000{\sim}13,000mg/L$ MLSS high sludge concentration. In addition to this quality, we studied membrane flux character related membrane arrangement, membrane-air line arrangement, air-line hole size, cleaning solution concentration, treatment method, etc. Using the optimization of this additional parameter, we tried to search method of maximizing membrane quality.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.56-62
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• 2012

The results presented in this paper form part of an investigation into the optimization of a ternary blended cementitious system based on ordinary Portland cement (OPC)/blast furnace slag(BFS)/fly ash(FA) for the development of ultra high strength concrete. Concrete covering a wide range of BFS/FA blending proportions were investigated. Compressive strength at the ages of 3, 7 and 28 days for concrete specimens containing 0%, 10%, 20% and 30%FA along with 0%, 30%, 40% and 50%BFS as partial cement replacement at a water-binder ratio of 0.18 were investigated. Tests on porosity and pore size distribution were conducted using mercury intrusion porosimetry. The results show that the combination of FA10 and BFS30 can improve both short- and long-term properties of concrete as results of reducing of pores larger than 50nm.

• Journal of Distribution Science
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• v.14 no.10
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• pp.147-152
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• 2016

Purpose - High quality films are affected by both the production stage and various variables such as the size of the movie investment and marketing that changes consumers' perceptions. Consumer preferences should be recognized first to ensure that the movie is successful. If a film is produced without pre-investigation and analysis of consumer demand and taste, the probability of success will be low. This study investigates the balance of production costs, marketing costs, and profits using game theory, suggesting an optimization strategy using the simplex method of linear programming. Research design, data, and methodology - Before the release of the movie, initial demand is assumed to be driven largely by marketing costs. In the next phase, demand is assumed to be driven purely by a movie's production cost and quality, which might also further determine consumer demand. Thus, it is essential to determine how to distribute pure production costs and other costs (marketing) in a limited movie production budget. Moreover, it should be taken into account how to optimally distribute under the assumption that the audience and production company's input resources are limited. This research simplifies the assumptions for large-scale and relatively small-scale movie investments and examines how movie distribution participant profits differ when each cost is invested differently. Results - When first movers or market leaders have to choose both quality and marketing, it has been proven that pursuing a strategy choosing only one is more likely than choosing both. In this situation, market leaders should maximize marketing costs under the premise that market leaders will not lag their quality behind the quality of second movers. Additionally, focusing on movie marketing that produces a quick effect while ceding creative activity to increase movie quality is a natural outcome in the movie distribution environment since a cooperative strategy between market competitors is not feasible. Conclusions - Government film development policy should ignore quality competition between movie production companies and focus on preventing marketing competition. If movie production companies focus on movie production quality improvement then a creative competition would ensue.