• Journal of Advanced Marine Engineering and Technology
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• v.35 no.8
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• pp.1022-1027
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• 2011

A diesel engine works in high compression ratio due to injection of diesel fuel after compression of air. Therefore the engine has a high thermal efficiency, while nitrogen oxide is produced a lot in high flame temperature regions. In order to solve the problem this study HHO gas is added into the intake air of the industrial diesel engine. The test conditions are loads of 0%, 50% and 100% and engine speeds of 700 to 1900 rpm. The results show the maximum torque and pressure is increased, fuel consumption, smoke and CO emissions are decreased and NOx emission is remained at same level.

• Journal of Bio-Environment Control
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• v.7 no.3
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• pp.214-218
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• 1998

This study was performed to stabilize the physical properties of Sodium Carbonate Decahydrate that was selected as a highly concentrative thermal energy storage medium. The addition of ARS(additives to prevent supercooling) showed to prevent the supercooling of Na$_{2}$CO$_{3}$.10H$_{2}$O, and the supercooling was decreased below $1.5^{\circ}C$ with ARS of 3 wt% and the addition of PSC(phase separation controller) of 1.5 wt% controlled the phase separation of Na$_{2}$CO$_{3}$ .10H$_{2}$O with the phase change cycles increased from 0 to 1,500, the phase change temperature and the latent heat has changed in the range of 30$\pm$1.$0^{\circ}C$ and 54$\pm$2.0Kcal.kg$^{-1}$ respectively.

• Journal of Korea Multimedia Society
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• v.14 no.2
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• pp.258-268
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• 2011

Underwater acoustic sensor networks can be used disaster prevention and environmental monitoring systems in underwater environments. Because, the underwater environment is different from the ground, the long propagation delay, low transfer rates and limited bandwidth characteristics should be considered. In this, paper will propose the MAC protocol that allocates time slot into each node according to priority policy through the period of contention-free slot reservation in underwater acoustic sensor networks in order to avoid collision and minimize energy consumption waste. We perform mathematical analysis to evaluate the performance of the proposed protocol with regard to the collision probability, the energy consumption by collision, throughput and channel utilization. We compare the proposed protocol with the conventional protocol, and the performance results show that the proposed protocol outperforms the conventional protocol.

• Journal of Navigation and Port Research
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• v.35 no.3
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• pp.265-270
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• 2011

The purpose of this study is to compare and analyze the differences of a building's heating and cooling loads depending on the weather variation. Followings are the results. The temperature, humidity and wind speeds of standard year are bigger than those of 2006~2009. The 2006~2009's total horizontal solar irradiance is greater than that of standard year, and the direct solar irradiance of standard year is bigger in winter and vice versa in summer. As results of simulation on heating and cooling loads, it is difficult to find out the bilateral influences between maximum thermal loads and annual's. The equivalent-time operating ratio(EOR) is defined on this study to estimate the differences between year and year, and the EOR of standard year shows low value comparing to 2006~2009 years'.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.39-47
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• 2004

In this paper, the defects of two-dimensional anisotropic elastic bodies are identified by using the boundary element method. The use of numerical models that contain only boundary integral terns reduces the dimensionality of the problem by one. This advantage is particularly important in problems such as crack mechanics. Avoiding domain meshing is also particularly advantageous in the solution of inverse problems since it overcomes mesh perturbations and simplifies the procedure. In this paper, nondestructive approaches for the existing isotropic materials are extended to analyze the elastic bodies made of anisotropic materials such as composites. After verifying that the proposing boundary element model is in good agreement with numerical results reported by other investigators, the effect of noise in the measurements on the identifiability is studied with respect to different design parameters of layered composites. Sample studies are carried out for various layup configurations and loading conditions. The effects of the layup sequences in detecting flaw of composites is explored in this paper.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.10
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• pp.901-909
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• 2013

Owing to the Increasing use of fossil fuels, worldwide concerns over environmental pollution are increasing. As a solution, ligneous biomass has emerged as a promising alternative fuel in recent times. Therefore, in this study, a moisture evaporation model that largely influences the energy density and efficiency of ligneous biomass is studied using a numerical approach. Furthermore, the thermal characteristics are analyzed in terms of torrefaction temperature and moisture fractions in the wood, and the type of wood species. The results show that the temperature and moisture fractions of wood decrease with an increase in the torrefaction temperature. In particular, when the torrefaction temperature is lower than 423K, there were little changes in the moisture fraction in the wood. Furthermore, it was found that charcoal is produced more slowly as the moisture fraction in the wood increases.

• Polymer(Korea)
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• v.25 no.6
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• pp.803-810
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• 2001

A nonlinear optical hyperbranched polyester (PE-Azo/Hyper) was synthesized from 4-[N,N-bis(hydroxyethyl)amino-4'-formyl] azobenzene and cyanoacetic acid by a Knoevenagel polycondensation using 4-(dimethylamino) pyridine as a base. The resulting polymer was soluble in polar aprotic solvents such as N,N-dimethylformamide and 1-methyl-2-pyrrolidinone and could be processed into optical quality films by spin coating. The molecular weight was determined to be $M_w$=61,800 ($M_W/M_n{=1.86}$) by gel permeation chromatography using polystyrene as a standard. No melting point was detected by differential scanning Calorimeter, indicating that this polymer presents an amorphous state. It shows a glass transition temperature of $121^{\circ}C$. The second-order nonlinear optical coefficient $d_{33}$ of the poled polymer determined by the second harmonic generation at 1064 nm was 25.4 pm/V.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.2
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• pp.91-97
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• 2013

Self-heating effects during operation of high current AlGaN/GaN power transistors degrade the current-voltage characteristics. In particular, this problem becomes serious when a low thermal conductivity Si substrate is used. In this work, AlGaN/GaN-on-Si devices were fabricated with various channel widths and Si substrate thicknesses in which the structure dependent self-heating effects were investigated by temperature dependent measurements as well as thermal simulation. Accordingly, a device structure that can effectively dissipate the heat was proposed in order to achieve the maximum current in a multi-channel, large area device. Employing via-holes and common electrodes with a 100 ${\mu}m$ Si substrate thickness improved the current level by 75% reducing the channel temperature by 68%.

• Korean Journal of Construction Engineering and Management
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• v.10 no.1
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• pp.126-135
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• 2009

Recently, operation of highway is the complex digital Infrastructure based on complicated IT. The application of IT is increasing more and more in digital Infrastructure. Though IT is very convenient, if unpredicted operating risk of highway occurs, widespread damage can be large. When operating risk of highway occurs, road users are out of smoothly-run service because of the operating interruption. This risk causes unpredicted operating management cost and additional maintenance cost. It will excess over the planned operating cost, which may leads to users's unsafety and operator's insolvency because of income loss. Until now, related studies to find out the risk are not sufficient. The purpose of this study is to suggest risk cost items and to estimate the reasonable risk cost by using simulation method in case of occurring the huge power failure at the operating digitalized highway. This study indicates the several plans to hedge against risk cost and the management of highway project. From now on, it will be used as basic data to confirm the soundness of operating system in Digital Infrastructure.

• Journal of Korean Biological Nursing Science
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• v.5 no.1
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• pp.35-44
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• 2003

Objectives : Though Tsutsugamushi disease has been reported with increasing frequencies in rural communities in Korea, it is not easy to find the nursing investigations. Methods : We have conducted a survey on 30 cases who had the fever as a chief complaint, then clinically ruled out the Tsutsugamushi disease in autumn of $2000{\sim}2001$. Data were collected retrospectively by investigation of the general characteristics, clinical and laboratory findings, their nursing care. Findings: Of 30 cases, 46.7% were farmers, and 60.0% had chances of exposure to fields or mountains. The characteristic symptoms and signs were febrile sense and chill(100.0%), headache(80.0%), and eschar(66.7%). Abnormal laboratory findings were anemia (23.3%), elevated AST(60.6%), ALT(63.3%), and abnormal urinalysis findings(50.0%). 53.3% were serologically confirmed as Tsutsugamushi disease. Therapeutic nursing cares were composed with warm up by blancket(50.0%), Ice bag(50.0%) and doxycycline antibiotic therapy(100.0%). Other nursing care for them included fluid therapy(100.0%) and nutritional support with regular(56.7%) or soft diet(43.3%). Conclusion: The above results indicate nurses who take care of acute febrile clients should make her responsible for the fever and pain management as well as give education for infection control for the community inhabitants.