• 수산해양교육연구
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• 제18권1호
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• pp.58-64
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• 2006

In order to examine the effect of humidity on hydrogen embrittlement of STS 444 weld zone for boiler with dry and wet welding conditions, this paper was carried out the accelerated hydrogen osmosis test and the electrochemical Tafel polarization test. In 0.5M $H_2SO_4$ + 0.01M $As_20_3$ solution, this test is added to load of $1400kg/cm^2$ together with hydrogen osmosis by current of $50 {mA/cm^2}$ for 60 min.. The electrochemical Tafel polarization test was carried out in 0.5M $H_2SO_4$ + 0.01M $As_20_3$ solution. Therefore, the effect of humidity on hydrogen embrittlement of STS 444 was considered. The main results are as following: On the basis of hydrogen embrittlement mechanism, that is, integrated electrochemical polarization characteristics with the established mechanism of hydrogen embrittlement, the reduction rate of corrosion current density of weld zone in the wet weld condition is larger than in the dry condition. We can nondestructively predict the degree of hydrogen embrittlement of STS 444 weld zone for boiler through the reduction rate of electrochemical corrosion current density.

• 한국유체기계학회 논문집
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• 제11권6호
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• pp.7-17
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• 2008

Fan performances are obtained with various tip clearance gaps and stagger angles of the rotor. A tested fan is an axial-type fan of which the casing diameter is 806 mm. Two different rotors are applied to this test. One is designed on the basis of the free vortex method along the radial direction and the other is designed using the forced vortex method. The operating conditions are varied to the ultimate off-design point as well as the deign point. Overall efficiency, total pressure and input power are compared with the tip clearance gaps and different stagger angle. The experimental results show that changing of the stagger angle has minor influence to the performance when the same rotor is applied. When the tip clearance gap is less than 5% of the rotor span, the overall efficiency, total pressure loss and input power reduction are varied linearly with the variation of the tip clearance gaps. On the design point, the overall efficiency is decreased to the rate of 2.8-2.9 to the increasing of the tip clearance, but the changing rate of the overall efficiency is alleviated when the fan operates at off-design points. In particular, this rate is more quickly declined on a fan with the rotor designed using the forced vortex method. The result of the total pressure shows that the pressure reduction rate is a 0.08-0.1 according to the tip clearance, and additionally the input power reduction rate is a 0.045-0.065 at design point.

• 한국자동차공학회논문집
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• 제10권1호
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• pp.24-31
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• 2002

An experimental study was conducted to investigate the effects of EGR (Exhaust Gas Recirculation) variables on performance and emission characteristics in a 2-liter 4-cylinder spark-ignition LPG fuelled engine. The effects of EGR on the reduction of thermal loading at exhaust manifold were also investigated because the reduced gas temperature is desirable for the reliability of an engine in light of both thermal efficiency and material issue of exhaust manifold. The steady-state tests show that the brake thermal efficiency increased and the brake specific fuel consumption decreased with the increase of EGR rate in hot EGR and with the decrease of EGR temperature in case of cooled EGR, while the stable combustion was maintained. The increase of EGR rate or the decrease of EGR temperature results in the reduction of NOx emission even in the increase of HC emission. Furthermore, decreasing EGR temperature by $180^{\circ}C$ enabled the reduction of exhaust gas temperature by $15^{\circ}C$ in cooled EGR test at 1600rpm/370kPa BMEP operation, and consequently the reduction of thermal load at exhaust. The optimization strategy of EGR application is to be discussed by the investigation on the effect of geometrical characteristics of EGR-supplying pipe line.

• 대한기계학회논문집B
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• 제33권10호
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• pp.748-756
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• 2009

The effect of idling stop on $CO_2$ reduction was estimated, especially in the area of in-use vehicles. In order to know the fuel saving for each class of vehicles, a methodology to calculate the fuel saving was used along with a standard test using NIER-07 mode. Idling stop execution rate was estimated by analyzing the driving pattern of the in-use city buses, which shows about 75% at maximum. And this corresponds to about 5.4% reduction of the daily total fuel consumption. Finally, $CO_2$ reduction in the automotive sector was estimated, which concludes that, when idling stop device is used, about 480 thousand and 450 thousand tons of $CO_2$ could be reduced with in-use city buses and taxis, respectively. This amount corresponds to about 1.2% of $CO_2$ reduction in the automotive sector.

• Journal of Biosystems Engineering
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• 제36권5호
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• pp.342-347
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• 2011

The effect of SNC(silver nano colloid) on the emission reduction of odors such as ammonia ($NH_3$), hydrogen sulfide ($H_2S$), and methane ($CH_4$) from swine excreta was studied. Silver has been used as an universal antibiotic substance and can reduce the emission of some gases by sterilizing action. Therefore, an apparatus which produces SNC was developed and was conducted its performance test. Also, the SNC made by the apparatus was applied to swine excreta sampled from a piggery in oder to find the effect on the reduction of odor emission. An electrolysis apparatus was developed to produce SNC and its capacity was 0.024 ppm/$hr{\cdot}L$. The effects of SNC on the reduction of odor emission from swine excreta were tested for bad smell gases of ammonia ($NH_3$), hydrogen sulfide ($H_2S$) and methane ($CH_4$). For ammonia gas, factorial experiments were conducted to find the effects of concentration and application rate of SNC. The test results for the different concentrations of 20 ppm, 50 ppm, and 100 ppm showed that the more concentration of SNC was increased, the more emission reduction of ammonia gas increased. From the test results about the effect of application rate, the more SNC was applied, the more emission reduction of $NH_3$ increased. In order to reduce the concentration of $NH_3$ below 5 ppm, SNC of 50 ppm is recommended to be applied at an interval of 6 hours, and is mixed with swine excreta in the volumetric ratio of 4:1. For hydrogen sulfide gas, the concentration was decreased as time went by and was reduced rapidly in the first stage of the tests for all applied concentrations of SNC (20 ppm, 50 ppm, and 100 ppm). Especially, when 100 ml of SNC with 100 ppm was applied, emission of hydrogen sulfide gas was reduced rapidly during early 4 hours after the application of SNC. And, concentration of hydrogen sulfide gas was maintained below 20 ppm after 12 hours. For methane gas, t-test showed that there was no significance on the effect of its application for all applied concentrations of SNC. Therefore, it was concluded that the application of SNC on swine excreta had no effect on the emission reduction of $CH_4$.

• 한국한의학연구원논문집
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• 제17권2호
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• pp.173-181
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• 2011

Objective : The purpose of this study is to evaluate the effect of Yuebijiashu-tang with Low-Glycemic Diet on the obesity and to improve the oriental medical methods of treatment in obesity patients. Methods : Forty one patients were classified into four groups(Normal, Overweight, 1st Obesity, 2nd Obesity) by Body Mass Index(BMI). Weight, Body Fat Mass, Body Fat Rate, Waist Hip Rate, BMI and Obesity Index were compared in each group by t-test. Results : In distribution of sex, male was 7(17.1%), female was 34(82.9%). Mean age was 37${\pm}$11 and the patients in twenties were the most. Among four groups, the number of 1st obesity groups was the most. In the change of body composition, the reduction of weight was 6.82${\pm}$2.67kg, the reduction of body fat mass was 5.53${\pm}$2.30kg, the reduction of BMI was $2.51{\pm}0.85kg/m^2$, the reduction of body fat rate was 4.61${\pm}$2.17%, the reduction of waist hip rate was 0.019${\pm}$0.013. Conclusion : This study shows that Yu$\'{e}$biji$\~{a}$sh$\`{u}$-t$\~{a}$ng with low-glycemic diet is effective on weight reduction.

• 복식문화연구
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• 제17권2호
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• pp.216-224
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• 2009

This study was accomplished to examine the dyeing property and functionality of both cotton and silk fabrics dyed with clove extract. The purpose of this study was to investigate the effects of dyeing property, antibiosis, and sun protection effectiveness for a clove. The study method used in this study was the experimental research to extract dyestuffs from a clove, to treat dyestuffs with a mordant, and then to measure dyeing colorfastness, antibiosis, and sun protection for dyed fabrics. As a result of the test for dyeing colorfastness, in the case of colorfastness to laundry, the degree of discoloration showed grade $1\sim4$ and the degree of pollution showed grade $4\sim5$. Colorfastness to perspiration for both cotton and silk fabrics dyed showed grade $1\sim2$ to $4\sim5$. Colorfastness to sunlight showed grade 2 to $4\sim5$. Colorfastness to rubbing showed grade $3\sim4$ to $4\sim5$. In the colorfastness to dry cleaning, the degree of discoloration showed grade $3\sim4$ and the degree of pollution showed grade $4\sim5$. As a result of the antibiosis test, for the Staphylococcus aureus, both cotton and silk showed the bacteria reduction rate of 99.9% even after five times laundry, and for the Escherichia coli, cotton fabrics showed the bacteria reduction rate of 99.9% only after one time laundry, but silk fabrics showed the bacteria reduction rate of 99.9% even after five times laundry. As a result of the test for sun protection effectiveness, dyed silk fabrics showed the result more excellent than dyed cotton fabrics.

• 한국산학기술학회논문지
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• 제8권2호
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• pp.201-206
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• 2007

본 논문에서는 NoC(Network-on Chip) 구조로 구현된 core-based 시스템에 대한 효율적인 저전력 테스트 방법을 제안한다 NoC의 라우터 채널로 전송되는 테스트 데이터의 전력소모를 줄이기 위해서 스캔 벡터들을 채널 폭만큼의 길이를 갖는 flit으로 분할하고 nit간 천이율(switching rate)이 최소화 되도록 don't care 입력을 할당하였다. ISCAS 89 벤치마크에 대하여 실험을 한 결과, 제안된 방법은 약 35%의 전력 감소를 나타내었다.

• 한국자동차공학회논문집
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• 제21권5호
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• pp.176-180
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• 2013

After-treatment apparatus ceramic DPF (diesel particulate filter) have been applied to reduce harmful particulate matters(PM) among emissions from diesel engines so far, but they are easy to be fragile and weak in thermal shock. This research aims to investigate a metal type filter which is superior in mechanical strength and heat conduction rate and is beneficial economically in manufacturing. Basic performance of metal DPF such asloading test, temperature gradient test, thermal shock test, heat resistant test and back pressure was carried out. And then their experimental data provided key informations in designing and manufacturing such as detailed structures of metal mesh filter. Also diesel engine and vehicle of 2957cc displacement was tested under lug-down 3 mode and CVS-75 mode. PM reduction efficiency was 54.5% using metal DPF without loss of performance and fuel consumption.

• Earthquakes and Structures
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• 제4권6호
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• pp.607-627
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• 2013

The application of shape memory alloys (SMAs) to the seismic response reduction of civil engineering structures has attracted growing interest due to their self-centering feature and excellent fatigue performance. The loading rate dependence of SMAs raises a concern in the seismic analysis of SMA-based devices. However, the implementation of micromechanics-based strain-rate-dependent constitutive models in structural analysis software is rather complicated and computationally demanding. This paper investigates the feasibility of replacing complex rate-dependent models with rate-independent constitutive models for superelastic SMA elements in seismic time-history analysis. Three uniaxial constitutive models for superelastic SMAs, including one rate-dependent thermomechanical model and two rate-independent phenomenological models, are considered in this comparative study. The pros and cons of the three nonlinear constitutive models are also discussed. A parametric study of single-degree-of-freedom systems with different initial periods and strength reduction factors is conducted to examine the effect of the three constitutive models on seismic simulations. Additionally, nonlinear time-history analyses of a three-story prototype steel frame building with special SMA-based damping braces are performed. Two suites of seismic records that correspond to frequent and design basis earthquakes are used as base excitations in the seismic analyses of steel-braced frames. The results of this study show that the rate-independent constitutive models, with their parameters properly tuned to dynamic test data, are able to predict the seismic responses of structures with SMA-based seismic response modification devices.