• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.97-98
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• 2006

Fusion of decisions from multiple distributed sensor nodes is studied in this work. Based on the canonical parallel fusion model, we derive the optimal likelihood ratio based fusion rule with the assumptions of the generalized Gaussian noise model and the arbitrary fading channel. This optimal fusion rule, however, requires the complete knowledge of the channels and the detection performance of local sensor nodes. To mitigate these requirements and to provide near optimum performance, we derive suboptimum fusion rules by using high and low signal-to-noise ratio (SNR) approximations to the optimal fusion rule. Performance evaluation is conducted through simulations.

• Journal of Information Processing Systems
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• v.16 no.6
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• pp.1261-1270
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• 2020

The physical security layer of industrial wireless sensor networks in the event of an eavesdropping attack has been investigated in this paper. An optimal sensor selection scheme based on the maximum channel capacity is proposed for transmission environments that experience Nakagami fading. Comparing the intercept probabilities of the traditional round robin (TRR) and optimal sensor selection schemes, the system secure performance is analyzed. Simulation results show that the change in the number of sensors and the eavesdropping ratio affect the convergence rate of the intercept probability. Additionally, the proposed optimal selection scheme has a faster convergence rate compared to the TRR scheduling scheme for the same eavesdropping ratio and number of sensors. This observation is also valid when the Nakagami channel is simplified to a Rayleigh channel.

• Journal of the East Asian Society of Dietary Life
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• v.13 no.3
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• pp.191-196
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• 2003

The purpose of this study was to propose the optimal blending ratio of honey, dextrose syrup and salt with regard to the amount of soybean powder for the manufacture of soybean Dasik. For the establishment of addition amount of honey, dextrose syrup and salt, the sensory characteristics were compared in relation to the physiochemical characteristics and color values. The results were summarized as follows: Soybean Dasik contained 16.77 % protein. As the results of sensory evaluation in according to color values, taste and moistness, the optimal blending ratio of honey and dextrose syrup was 80~90%, and that of salt 0.06% in proportion to the total weight of soybean powder. As the test results of mechanical characteristics, hardness of soybean Dasik decreased as the increasing of the addition amount of honey and dextrose syrup. Cohesiveness, gumminess, brittleness and springiness did not show any significant differences statistically. Lightness(L) decreased as the increasing of addition amount of honey and dextrose syrup. Redness(a) was high at the 90% addition level, but yellowness(b) not significantly different at the 70, 80 and 90% level of honey and dextrose syrup to the total weight of soybean powder. Therefore, the optimal blending ratio of soybean Dasik was proposed at the levels of 45% honey, 45% dextrose syrup and 0.06% salt to the total weight of soybean powder.

• Journal of Environmental Science International
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• v.16 no.9
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• pp.1091-1098
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• 2007

Activated carbon was prepared from waste citrus peels by chemical activation with $ZnCl_2$. The optimal condition of carbonization was at $300^{\circ}C$ for 1.5 hr. Activation experiments with carbonized samples prepared at optimal carboniztion condition were carried out under various conditions such as activation temperature of 400 to $900^{\circ}C$, activation time of 0.5 to 2.0 hr, and $ZnCl_2$ ratio of 100 to 300%. In order to investigate the physical properties of the activated carbons prepared, iodine adsorptivities and specific surface areas were measured and their morphologies were observed from scanning electron microscopy. As $ZnCl_2$ ratio increased, activation yield decreased, while iodine adsorptivity and specific surface area increased. The optimal condition of activation was at 300% $ZnCl_2$ ratio and $300^{\circ}C$ for 1.5 hr, and then iodine adsorptivity and specific surface area was measured as about 862 mg/g and $756m^2/g$, respectively. SEM photography showed that the surface morphology was changed and many active pore were produced by chemical activation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.909-914
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• 2006

Vibration isolation tables are mostly required in precise measurement and manufacturing system. Among the vibration isolation tables, an air spring is the most favorable equipment because of low resonant frequency and high damping ratio. However, it is difficult to design the air spring with the required stiffness and damping ratio. Futhermore, whenever conventional active control methods are applied to the air spring, it may be difficult to obtain effective control performance due to high nonlinearity of air spring. In this paper, the optimal design of the air spring is performed using genetic algorithm to bring out low resonant frequency and high damping ratio. Also, active control of the vibration isolation table with 3-DOF model is proposed using the adaptive control method. Through experiments, optimal design is shown to be effective. And performance of the proposed control method is verified to be better than those of the passive control method and the conventional active control methods.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.11
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• pp.1222-1227
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• 2005

Optimal sludge recycling ratio for maximum total nitrogen(TN) removal efficiency was calculated stoichiometrically using nitrification and denitrification reaction with given influent water qualities in anoxic-oxic process which was one of the popular nitrogen removal system. The water quality items for stoichiometric calculation were ammonia, nitrite, nitrate, alkalinity, COD, and dissolved oxygen which could affect nitrification and denitrification. Optimal sludge recycling ratio for maximum TN removal efficiency was expressed by those five influent water qualities. TN concentration calculated stoichiometrically had kept good relationship with reported TN concentration in each tank and final effluent. In addition, it was possible to expect the TN concentration in final effluent by stoichiometric calculation within ${\pm}5.0\;mg/L$.

• Structural Engineering and Mechanics
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• v.58 no.2
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• pp.259-276
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• 2016

Lead-rubber bearings (LRBs) have been used worldwide in seismic design of buildings and bridges owing to their stable mechanical properties and good isolation effect. We have investigated the effectiveness of LRBs in framed underground structures on controlling structural seismic responses. Nonlinear dynamic time history analyses were carried out on the well-documented Daikai Station, which collapsed during the 1995 Hyogoken-Nanbu earthquake. Influences of strength ratio (ratio of yield strength of LRBs to yield strength of central column) and shear modulus of rubber on structural seismic responses were studied. As a displacement-based passive energy dissipation device, LRBs reduce dynamic internal forces of framed underground structures and improve their seismic performance. An optimal range of strength ratios was proposed for the case presented. Within this range, LRBs can dissipate maximum input earthquake energy. The maximum shear and moment of the central column can achieve more than 50% reduction, whereas the maximum shear displacement of LRBs is acceptable.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.539-546
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• 2016

With the growing interest of microgrid systems all over the world, many studies on microgrid operation are being carried out. The battery energy storage system(BESS) and the diesel generator are key equipments in the microgrid. In this paper, we analyze the characteristics of fuel consumption according to the power ratio of the diesel generator. Then, the formula to represent the unit cost of generation according to the power ratio of the diesel generator is derived. A new modeling of battery operation is presented considering the lifetime reduction according to increasing the cycles of charge/discharge operation of the battery. The methodology of determining the optimal operation of the battery and the diesel generator is presented by the use of the formula of fuel consumption of the diesel generator and the new modeling of battery operation. It is shown that this optimization methodology can be applied effectively for economical operation of the BESS and the diesel generator of a microgrid by case studies.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.3
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• pp.113-122
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• 2015

HVAC&R systems account for more than 50% of the energy consumption of buildings. The purpose of this study is to propose an optimal design method for the HVAC&R system and to examine the possibility for the energy conservation of a selected system. The energy demand for cooling and heating is determined by using TRNSYS and HEET. By an interaction between total system efficiency and cooling-to-heating load ratio, the optimal HVAC&R systems will be decided. The results showed that this proposed method is significantly capable of determining optimal system and building design for saving energy.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.130-136
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• 1998

A procedure of stress and strength analysis has been proposed for the centrifuge rotor of composite materials of quasi-isotropic laminates. The goal in this study is to maximize the allowable rotating speed, that is, to minimize maximum strength ratio with the given path length by changing the geometric parameter-outer radius and ply angles in quasi-isotropic laminates. Optimum values of the geometric parameter-outer radius and ply angles are obtained by multilevel optimization. All the geometric dimensions and stresses are normalized such that the result can be extended to a general case. Two dimensional analysis at each cross section with an elliptic tube hole subjected to internal hydrostatic pressures by samples as well as the centrifugal body forces has been performed along the height to calculate the stress distribution with the plane stress assumption, and Tsai-Wu failure criterion is used to calculate the strength ratio. The maximum allowable rotating speed can be increased by changing the radii of the outer surface along the height with the maximum strength ratio under the unit value : The optimal number of ply angles maximizing the allowable rotating speed in quasi-isotropic laminates is found to be the half number of tube hole, and the optimal laminate rotation angle is the half of $[{\pi}/m]$. A $[{\pi}/3]$ laminate, for instance, is stronger than a $[{\pi}/4]$ laminate for the centrifuge rotor of 6 tube hole number even though they have the same stiffness.