• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.877-882
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• 2014

The reduction of CO2 emission has been discussed in the Marine Environment Protection committee in the International Maritime Organization as the biggest causes of GHG for the purpose of indexing CO2 amounts released into the atmosphere from ships. Accordingly, various methods including the change in the hull design to improve energy efficiency, the coating development to reduce friction resistances, the additives development for improving thermal efficiency in an engine, the low-speed operation to reduce fuel consumptions, and etc. have been applied. The main engine of a ship is an electronic engine for improving the efficiency of the whole load area. However, marine generator engines still use mechanical drive engines in intake, exhaust, and fuel injection valve drive cams. In addition, most of marine generator engines in ships apply a part-load operation of less then 80% due to an overload protection system. Therefore, marine auxiliary diesel engine set at 100% load is necessary to readjust in order to efficient operation because of part-load operation. The objective of this study is to report the results of the part-load fuel consumption improvement by injection timing readjust to identifying the operational characteristics of a marine generator engine currently operated in a ship.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.9
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• pp.56-65
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• 2005

A dynamic analysis method that freezes a time domain by discretization and solves the spatial propagation equation has a unique feature that provides a degree of freedom on spatial domain compared with the space discretization or space-time discretization finite element method. Using this feature, the time finite element analysis can be effectively applied to optimize the spatial characteristics of distributed type actuators. In this research, the time domain finite element method was used to discretize the model. A state variable vector was used in the discretization to include arbitrary initial conditions. A performance index was proposed on spatial domain to consider both potential and vibrational energy, so that the resulting shape of the distributed actuator was optimized for dynamic control of the structure. It is assumed that the structure satisfies the final rest condition using the realizable control scheme although the initial disturbance can affect the system response. Both equations on states and costates were derived based on the selected performance index and structural model. Ricatti matrix differential equations on state and costate variables were derived by the reconfiguration of the sub-matrices and application of time/space boundary conditions, and finally optimal actuator distribution was obtained. Numerical simulation results validated the proposed actuator shape optimization scheme.

• Journal of Aquaculture
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• v.10 no.2
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• pp.143-151
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• 1997

A six week feeding trial was conducted to determine the amount of fish meal analog (FMA) that can be replacing fish meal protein (FM) in Korean Rockfish. Seven experimental diets were formulated on isonitrogenous 52% crude protein and isocaloric basic 16.8KJ/g diet. Also, foreign commercial fish meal analog (CFMA) and attractants (ATT) were tested in this experiment. Percentage of the graded level of replacement of FM by FMA/CFMA on the basis of crude protein were as following : Diet 1, 100%FM ; Diet by 2, 60%FM : 40% CFMA ; Diet 3, 60%FM : 40$ CFMA+ATT ; Diet 4, 80%FM : 20%FMA ; Diet 5, 80%FM : 20% FMA+ATT ; Diet 6, 60%FM : 40%FMA+ATT ; Diet 7, 40%FM : 60% FMA+ATT. The FMA was made by mixing six animal protein source such as th blood meal, squid liver powder, meat and bond meal, leather meal, feather meal, poultry by-product and 3 essential amino acids (Met, Lys, Ile). Weight gain, feed efficiency, specific growth rate and protein efficiency ratio of fish fed diets 4, 5 and 6 were not significantly different (P>0.05) from those of fish fed the control (100% FM), while those of fish fed diets 2 and 3 were significantly lower (P<0.05) than those of fish fed the diet 6. There was no significant ATT effects in this study (P>0.05). Significant differences were found in hepatosomatic index, hemoglobin and condition factor. Therefore, these, results indicated that FMA can be used up to 40% as a substitute of fish meal protein in Korean Rockfish diets.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.11
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• pp.12-19
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• 2015

In network-centric warfare, the communication network has played a significant role in defeating an enemy. Especially, the urgent and important data should be preferentially delivered in time. Thus, we proposed a priority MAC protocol based on CSMA/CA with Binary Exponential Back-off for tactical wireless networks. This MAC protocol suggested a PCW(Prioritized Contention Window) with differentiated back-off time by priority and a RBR(Repetitive Back-off Reset) to reset the remaining back-off time. The results showed that this proposed MAC has higher performance than those of DCF(Distributed Coordination Function) in the transmission success rate and the number of control packet transmission by reducing the packet collision. Thus, it produced more effective power consumption. In comparison with DCF, this proposed protocol is more suitable in high-traffic network.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.161-163
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• 2021

This urban centralization is expected to develop rapidly, with 75% of the population living in the city by 2035. Large cities are becoming unsustainable due to side effects such as environmental pollution, severe traffic jams, excessive energy depletion, and destruction of the natural ecosystem. In addition, the happiness index of citizens of large cities is also falling because of high crime rates and safety accidents, the work-life imbalance caused by inequality and polarization, and overly competitive education. To solve this problem, Smart City, an IT-based future city model, was born. The Korean government is also actively attempting to improve urban competitiveness and promote sustainable development through efficient construction and operation of smart cities as a national focus project. To support the effort, we review the basic directions and strategies of Sejong City's Smart City service infrastructure based on the comprehensive national land plan, Smart City plan, and Smart City strategy plan.

• Clean Technology
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• v.23 no.2
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• pp.163-171
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• 2017

Currently, researches on recycling and reuse of waste energetic materials have recently gained a great attention from advanced countries due to ever tightening environmental regulations. In this study, as a part of a recycling technology, the experiments and dynamic simulation of simulated moving bed (SMB) process were performed to efficiently separate TNT and RDX from their mixture, which are main components of ammunition. In order to determine the operation zone of SMB process, the retention times of TNT and RDX were measured using HPLC at different flow rates and the adsorption equilibrium of each component was obtained by using a moment method. According to the adsorption equilibrium and the triangle theory of SMB process, four operation points were determined and separation experiments were carried out by the SMB process using the solvent consisting of acetonitrile and water. Two different mixing ratios (6:4 and 1:1) of acetonitrile and water were chosen for the experiment due to the great impact of mixing ratio of the solvent on separation. The performance of SMB process was evaluated by purity, recovery, productivity and solvent consumption. Pure TNT and RDX were successfully obtained from the SMB process and the dynamic simulation for the SMB process agreed well with the experimental results. Therefore, the dynamic model could be applied for predicting the dynamic behavior of the SMB process and designing a large scale SMB process.

• Journal of the Korean Society of Radiology
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• v.6 no.1
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• pp.73-77
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• 2012

Recently, Interest to the photoconductor, which is used to flat form X-ray detector such as a-Se, $HgI_2$, PbO, CdTe, $PbI_2$ etc. is increasing. In this study, the film layer by using the photoconductive material with particle sedimentation was fabricated and evaluated. The quantization efficiency of the continuous X-ray with the 70 kVp energy bandwidth was analyzed by using the Monte Carlo simulation. With the results, the thickness of film with 64 % quantization efficiency was 180 ${\mu}m$ which is similar to the efficiency of 500 ${\mu}m$ a-Se film. And $HIg_2$ film has the high quantization efficiency of 74 % on 240 ${\mu}m$ thickness. The electrical characteristics of the 239 ${\mu}m$ $Hgl_2$ films produced by particle sedimentation were shown as very low dark current(under 10 $pA/mm^2$), and high sensitivity(19.8 mC/mR-sec) with 1 $V/{\mu}m$ input voltage. The SNR, which is influence to the contrast of X-ray image, was shown highly as 3,125 in low driving voltage on 0.8 $V/{\mu}m$. With the results of this study, the development of the low-cost, high-performance image detector with film could be possible by replacing the film produced by particle sedimentation instead to a-Se detector.

• Journal of Animal Science and Technology
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• v.50 no.4
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• pp.499-508
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• 2008

This study was conducted to evaluate the effect of bio-starch from corn processing to replace dried whey in weaned pigs. A total of 120 crossbred [(Landrace×Yorkshire)×Duroc] pigs were weaned at 21 days of age weighing 6.01±0.34 kg in average. Five week feeding trial consisted of phase 1(0~2 wks) and phase 2(3~5 wks). Dietary treatments included 1) CON(basal diet), 2) BS5(whey 5%, partial substitution of bio-starch), 3) BS10(whey 10%, partial substitution of bio-starch) and 4) BS15(whey 15%, partial substitution of bio-starch). There were four dietary treatments with six replicate pens per treatment and five pigs per pen. During the overall period, there were no significant differences in the ADG(average daily gain) and gain/feed ratio among the treatments(P>0.05). However, the ADFI(average daily feed intake) was higher in BS5 and BS15 treatments than in CON treatment(P<0.05). At the 2nd week, dry matter and nitrogen digestibility were increased(quadratic effect, P=0.03 and P=0.01, respectively; cubic effect, P<0.001 and P=0.01, respectively) with the highest at 10% of bio-starch inclusion in the diets. At the last week of the experiment, dry matter, nitrogen and energy digestibility were increased(P<0.05) with the highest at 5% of bio-starch inclusion in the diets. At the 2nd week total protein concentration was increased(linear effect, P=0.04; cubic effect, P=0.01) with the highest at 10% of bio-starch inclusion in the diets. Also, BUN(blood urea nitrogen) was increased(linear effect, P=0.01) as the level of bio-starch inclusion increased in the diets. Fecal consistency score was inclined to lowers CON treatment than other treatments. In conclusion, the result of trial indicates that bio-starch can be included at the level of 5~10% of weaning pig diet replacing part of the dried-whey, and digestibilities were positively affected by bio-starch at growth stage.