• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.607-614
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• 2013

Nowadays, automotive manufacturers have developed various technologies to improve fuel economy and reduce harmful emissions. The ultra-lean direct injection engine is a promising technology because it has the advantage of improving thermal efficiency through the deliberate control of fuel and ignition. This study aims to investigate the development of a spray-guided-type lean-burn LPG direct injection engine through the redesign of the combustion system. This engine uses a central-injection-type cylinder head in which the injector is installed adjacent to the spark plug. Fuel consumption and combustion stability were estimated depending on the ignition timing and injection timing at various air-fuel ratios. The optimal injection timing and ignition timing were based on the best fuel consumption and combustion stability.

• Journal of The Korean Society of Grassland and Forage Science
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• v.27 no.4
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• pp.275-280
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• 2007

This experiment was conducted to investigate the selection of regional double cropping system for production of organic forage in middle part of Korea. The species of forage crop used in this experiment were corn, $sorghum\;{\times}\;sudangrass$ hybrid and japanese millet for summer crops and rye and Italian ryegrass for winter crops. $Sorghum\;{\times}\;sudangrass$ hybrid showed higher DM (dry matter) and TDN (total digestible nutrient) yield than that of corn. Dry matter yield of corn decreased to 56% that of control because of weed. In winter crops, DM and TDN yield of rye is higher than that of Italian ryegrass. Rye was more adequate to produce organic forage in middle part of Korea. We could not find out the difference of nutrient value between each treatments. It means that the amount of nutrient is affected by DM productivity of each crop. The result of this study indicated that $sorghum{\times}sudangrass$ hybrid (summer crop) and rye (winter crop) cropping system could be recommended as producing high yield of organic forage in middle part of Korea.

• Membrane Journal
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• v.23 no.1
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• pp.12-23
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• 2013

On the subject of river bed water in Seomjin river, it had accomplished the verifying experiment of membrane filtration pilot plant for evaluating the applicability of its process throughout the prediction of membrane fouling as a function of the pore size of membrane and the determination of optimum coagulant dosage. On the result of the experiment for the evaluation of the membrane fouling as a function of the pore size, a increasing rate of irreversible resistance of membrane pore size $0.1{\mu}m$ and $0.01{\mu}m$ was measured each $0.44{\times}10^{12}/m^2$ and $0.42{\times}10^{12}/m^2$, respectively. And on the result of Flux-test, it showed that the optimum coagulant dosage was measured lower than the it of the Jar-test. The result to be operated in a condition of a permeate flux $1.0{\sim}1.5m^3/m^2{\cdot}day$ without coagulation and a permeate flux $1.0{\sim}2.0m^3/m^2{\cdot}day$ with coagulation was maintained at stable trans-membrane pressure (TMP) value for 6 months up to. Therefore it showed that the stable operation without the coagulation was possible on permeate flux $1.0{\sim}1.5m^3/m^2{\cdot}day$ in the operation of membrane filtration process.

• International Journal of Highway Engineering
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• v.10 no.3
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• pp.57-68
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• 2008

The stabilization techniques in the pavement foundations have advantages in increasing pavement performance and reducing pavement thickness. By mixing the geomaterials and stabilizer, the economical and structurally sound layer can be added in the pavement system. Until now, these techniques have been applied in the field empirically and the design criteria for stabilization has not been established. The purposes of this paper are to evaluate the mechanistic properties of stabilizers used for geomaterials and determine the type and optimum amount of stabilizer for each technique. The unconfined compressive testing and repeated load resilient modulus test were conducted on the coarse grained soils mixed with various types of stabilizer to investigate the strength and deformation characteristics of stabilized geomaterials. It is found from the test that the unconfined compressive strength of stabilized geomaterials is more than ten times higher than that of gradation modified geomaterials. The resilient modulus of stabilized geomaterials increases by $6{\times}10$ times compared to the original soils and tends to increase with increase of volumetric and deviatoric stress, and amount of stabilizer.

• Journal of radiological science and technology
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• v.38 no.4
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• pp.437-442
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• 2015

Accurate volume measurement of the prostate is a significant role in determining the result of diagnosis and treatment of benign prostate hyperplasia. The purpose of this study was to determine, when measuring prostate volume by TRUS, whether location is more accurately determined by transaxial or longitudinal scanning. With reference to the patient's image, it was produced six prostate model. It compares the actual volume and the measurement volume, and find the optimal measurement position of each specific model. Prostate volume measured by TRUS closely correlates with prostate phantom volume. There was no significant difference(p = .156). To measure the accurate volume of prostate with focal protrusion, its length should be measured exclude the protrusions.

• Journal of Korea Water Resources Association
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• v.49 no.8
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• pp.645-656
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• 2016

The study performed a regional flood frequency analysis and proposed a regression equation to estimate design floods corresponding to return periods for ungauged basins in Geum-river basin. Five preliminary tests were employed to investigate hydrological independence and homogeneity of streamflow data, i.e. the lag-one autocorrelation test, time homogeneity test, Grubbs-Beck outlier test, discordancy measure test ($D_i$), and regional homogeneity measure (H). The test results showed that streamflow data were time-independent, discordant and homogeneous within the basin. Using five probability distributions (generalized extreme value (GEV), three-parameter log-normal (LN-III), Pearson type 3 (P-III), generalized logistic (GLO), generalized Pareto (GPA)), comparative regional flood frequency analyses were carried out for the region. Based on the L-moment ratio diagram, average weighted distance (AWD) and goodness-of-fit statistics ($Z^{DIST}$), the GLO distribution was selected as the best fit model for Geum-river basin. Using the GLO, a regression equation was developed for estimating regional design floods, and validated by comparing the estimated and observed streamflows at the Ganggyeong station.

• Analytical Science and Technology
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• v.16 no.5
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• pp.399-406
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• 2003

This study was conducted to find out the analysis condition of selenium(Se) in oil refinery wastewater with a high concentration of Se using the atomic absorption spectrometry with hydride generation system (HG-AAS). From various experiments that reduced Se(VI) to Se(IV), the optimum pretreatment condition was determined to be a sample volume of 10 mL, HCl 10 mL, with a 30 min heating time in a water bath. In oil refinery wastewater, as the concentration of organics and constitution became higher, the recovery rates of Se decreased. Therefore, three acid digestion methods ($HNO_3/HClO_4$ digestion, $KMnO_4$ digestion, and microwave acid digestion) were tested on the recovery rates of Se in reference to the digestion of organics, petroleum and oxidation from organic Se(org.), Se(IV) to Se(VI). The experiment results showed that the average recovery rate of Se was the highest in microwave acid digestion, although all of the digestions were more than 90%. In consequence, the pretreatment procedure of microwave digestion followed by HCl addition was the most suitable for selenium analysis in oil refinery wastewater by using HG-AAS.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.86-92
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• 2012

A characteristic study of chlorine dioxide generation by the electrolysis system was performed after chlorite ($ClO_2^-$) is adsorbed from sodium chlorite by a polymer ion exchange resin. A strongly basic anion exchange resin was used and a Ti plate coated with Ru and Ir was used as an electrode. Various parameters such as reaction stirring velocity, reaction temperature, chlorine dioxide product concentration, ion exchange resin content and product maker type for the adsorption quantity in the chlorite adsorption of ion exchange resin were investigated and found the ion exchange resin with the maximum adsorption quantity. A generation trend of chlorine dioxide was observed by the electrolysis system and optimum conditions on the desired value were found using response surface design of DOE (Design of Experiments). The strongly basic anion exchange resin with the maximum adsorption quantity was SAR-20 (TRILITE Gel type II) and the adsorption quantity was around 110 mg/IER (g). Observed generation optimum conditions of chlorine dioxide were constant-current (electrode area base; $A/dm^2$) and flow rate of $N_2$ gas (4.7 L/min) at the desired value of sterilization (900~1000 ppm, 1 h).

• Journal of The Korean Society of Grassland and Forage Science
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• v.37 no.1
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• pp.80-91
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• 2017

The objective of this study was to select a model showing high-levels of interpretability which is high in R-squared value in terms of predicting the yield in the mixed pasture using the factors of fertilization, seeding rate and years after pasture establishment in steps, as well as the climate as a basic factor. The processes of constructing the yield prediction model for the mixed pasture were performed in the sequence of data collection (forage and climatic data), preparation, analysis, and model construction. Through this process, six models were constructed after considering climatic variables, fertilization management, seeding rates, and periods after pasture establishment years in steps, thereafter the optimum model was selected through considering the coincidence of the models to the forage production theories. As a result, Model VI (R squared = 53.8%) including climatic variables, fertilization amount, seeding rates, and periods after pasture establishment was considered as the optimum yield prediction model for mixed pastures in South Korea. The interpretability of independent variables in the model were decreased in the sequence of climatic variables(24.5%), fertilization amount(17.8%), seeding rates(10.7%), and periods after pasture establishment(0.8%). However, it is necessary to investigate the reasons of positive correlation between dry matter yield and days of summer depression (DSD) by considering cultivated locations and using other cumulative temperature related variables instead of DSD. Meanwhile the another research about the optimum levels of fertilization amounts and seeding rates is required using the quadratic term due to the certain value-centered distribution of these two variables.

• Korean Journal of Food Science and Technology
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• v.42 no.5
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• pp.565-570
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• 2010

A coenzyme Q10 nanoemulsion was prepared using high pressure homogenization with different valve type conditions (A, B, and C) and cycle numbers (1, 2, and 3). The particle size, transmittance, zeta potential, and coenzyme Q10 content of the prepared coenzyme Q10 nanoemulsion were measured. The stability of the prepared coenzyme Q10 nanoemulsion was evaluated on heating ($95^{\circ}C$), freezing ($-20^{\circ}C$), and different pH (2-10) conditions. Also, the prepared coenzyme Q10 nanoemulsion was stored at different temperatures of 4, 25, and $40^{\circ}C$ for 12 weeks to evaluate its storage stability. In this study, the optimal conditions of high pressure homogenization for the preparation of a coenzyme Q10 nanoemulsion were identified to be 150 MPa, C valve, and a cycle number of 3. The results showed that the prepared coenzyme Q10 nanoemulsion had an average particle size of 40 nm, generated no deposits or floating matter when stored at either 4 or $25^{\circ}C$ for 12 weeks, and displayed excellent dispersibility and transparency when processed at different pHs (4-10) or heating ($95^{\circ}C$) and, freezing ($-20^{\circ}C$) conditions. Our results indicated that a coenzyme Q10 nanoemulsion prepared by high pressure homogenization can be used for preparing beverages in the food industry.