• Proceedings of the Korea Forestry Energy Research Society Conference
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• 2011.02a
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• pp.34-36
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• 2011

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.129-132
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• 2006

This paper is to investigate passing performance of high performance concrete between reinforcing bar depending on maximum size of coarse aggregates. Increase in maximum size of coarse results in decrease in water demand and sand to aggregate to secure target slump flow. The larger the maximum size of coarse aggregates is, the denser the space between reinforcing bar is, the amount of concrete passed through the reinforcing bar cage shows to decrease. HPC has favorable passing performance, regardless of aggregate size, when only vertical reinforcing bar is arranged. Whereas, when vertical and horizontal reinforcing bar is arranged at the same time, proper space between reinforcing bar is considered larger than 32mm in case of using 20mm coarse aggregate, 38mm in case of using 25mm aggregate. The increase in maximum size of coarse aggregate leads to increase compressive strength slightly. Length change shows to be decreased with the increase in maximum size of coarse aggregate.

• Journal of Biosystems Engineering
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• v.9 no.2
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• pp.1-7
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• 1984

The engines mounted on power-tillers are used as power source in various kinds of works such as plowing, harrowing, transporting, spraying, water pumping and threshing, etc. But the engines have not been used effectively from a standpoint of fuel consumption because of lack of proper power transmission system and lack of understanding of fuel consumption characteristics of the engines. Therefore, this study was attempted to establish proper power transmission system between the power-tiller engines and various implements. In order to accomplish the above objective, firstly, power requirement and pulley sizes for various implements, which are driven by the power-tiller engines, were investigated to find out whether the power transmission system is proper. Secondly, partload variable engine-speed test was conducted for 3 different sizes of diesel engines to measure to specific fuel consumption. Thirdly, the present power transmission systems were analyzed in terms of specific fuel consumption, and proper power transmission systems were suggested for various implements. The results of this study are summarized as follows: 1. Power requirement for each fixed-type implement of power-tiller varied from 1.5 ps to 11 ps according to its type and operating conditions, but generally in the range of 2.5 ps to 7 ps. 2. Each power tiller and implement were equipped with only one size of pully with few exeptions. With the present power transmission systems, the engines can't be utilized effectively in terms of fuel economy. The pulley size of engine or implement should be diversified to provide the optimum engine speed for different implements. 3. For a diesel eninge with the rated power output of 6 ps, the optimum engine speed to minimize specific fuel consumption was 2200 rpm for the power reguirement in the range of 6 ps or more, 1700 rpm in the range of 4 to 6 ps, and 1200 rpm in the range of 4 ps or less. 4. For a diesel engine with the rated power output of 8 ps, the optimum engine speed was 2200 rpm for the power requirement in the range of 7 ps or more, 1700 rpm in the range of 4.8 to 7 ps, and 1200 rpm in the range of 4.8 ps or less. 5. For a diesel engine with the rated power output of 10 ps, the optimum engine speed was 2200 rpm for the power requirement in the range of 8.4 ps or more, 1700 rpm in the range of 5.4 ps to 8.4 ps, and 1200 rpm in thr range of 5.4 ps or less. 6. Provided the existing implements are dirven by 8 ps diesel engines, the optimum size of engine pulley should be larger than 120mm for the works of requiring less than 4 ps and 90-110mm for the works requiring 4.5-6.5 ps in order to minimize fuel consumption.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.1
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• pp.135-143
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• 2006

The objective of this study is to develop PSCF (potential source contribution function) program and determine the optimal values of control parameters to enhance the prediction of PSCF modeling. This study provides an important information and methodologies that can be used to get better results of locating influencing sources, especially unknown and fugitive sources. To determine proper values of control parameters in PSCF model, the diagnostic assessment on the results obtained by the various input conditions was carried out. PSCF model has created and improved from version 1.0 to version 7.0 since 200 I and the measured data (at least > 100) of receptor, and the values of control input parameters should be arranged and determined to obtain reliable results in PSCF modeling. The size of modeling domain must be determined to include enough trajectories to get reliable results. And the size of grid is recommended to be 2.5 $\sim$ 5 degrees for global scale, 0.2 $\sim$ 1 degrees for regional scale and 0.05 degree for local scale.

• Journal of the Korean Applied Science and Technology
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• v.15 no.4
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• pp.87-93
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• 1998

In spite of various applications of chitin derivatives from waste marine sources, commercial use of chitin has been limited due to resistance to chemicals and the absense of proper solvents. We prepared chitin through decalcification, bleaching and deproteination from protunus trituberculatus shells by the application of Hackman's method. Structural and chemical properties of chitin were investigated to have proper specific surface area and particle size by IR, BET and PSA. The amount of absorbed water of chitin reached equilibrium by stirring about 15 minutes. The amount of absored water of the prepared chitin were large than the commercial chitin. When prepared chitin tested on dyeing wastewater, they showed better treatment efficiency in COD, suspended solid, and color tests than the commercial chitin. The adsorption capacity increased with decreasing particle size for the prepared chitin. Treatment efficiency for color was increased as the sitirring rate increased. Results show the possibility of the prepared chitin from waste marine sources as a treatment system for dyeing wastewater.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.359-361
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• 2006

As circuits become increasingly complex and devices sizes shrinks, the demands placed on global planarization of higher level. Chemical Mechanical Polishing (CMP) is an indispensable manufacturing process used to achieve global planarity. In the CMP process, Diamond Disk (DD) plays an important role in the maintenance of removal rate. According to studies, the cause of removal rate decrease in the early or end stage of diamond disk lifetime comes from pad surface change. We also presented pad cutting rate (PCR) as a useful cutting ability index of DD and studied PCR trend about variable parameters that including size, hardness, shape of DD and RPM, pressure of conditioner It has been shown that PCR control ability of pressure and shape is superior to RPM and size. High pressure leads to a decrease of cell open ratio of pad surface because polyurethane of pad is destroyed by pressure. So low pressure high RPM condition is a proper removal rate sustain. By examining correlations between RPM and pressure of conditioner, it has been shown that PCR safe zoneto satisfy proper removal rate has the range 0.06mm/hr to 0.12mm/hr.

• Journal of the Korean housing association
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• v.23 no.5
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• pp.87-94
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• 2012

The primary purposes of this study are to suggest a medium-sized regeneration project which includes the excluded small sites near existing regeneration site, to identify urban improvement type which fits local conditions, and to suggest proper regeneration strategies for the improvement type. Main findings of this study are follows. First, the size of the living environment improvement project in urban area should be larger than 3ha and government's incentives are required for parcel merges to make the medium-size project site. Second, independent type of urban regeneration project should consider local characteristics while center-spread type of urban regeneration project should build a center by providing neighborhood facilities and proper housings. Third, urban regeneration project should be able to utilize local assets, such as cultural heritages, natural landscapes, transportation facilities. Fourth, standards for public support should be prepared to improve local competitiveness. Last, further studies are required for urban regeneration system improvement.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.292-295
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• 2001

A Study on the precipitation characteristics of nickel hydroxide as well as carbonate and sulfide is carried out to determine the proper treatment condition of the wastewater induced from nickel-plating industry. The nickel concentrations in the effluent could be kept lower than 5ppm when the value of pH was maintained higher than 10. The precipitation of nickel salts by alkaline addition to the nickel containing model wastewater was conducted by using proper amount of sodium hydroxide, sodium carbonate, sodium bicarbonate and sodium sulfide. In case of the sulfide treatment, the residual nickel concentration in the clear water after precipitates removed showed the lowest value. The influences of the precipitation condition upon the particle size of the crystals precipitated were also investigated. In spite of the various precipitation conditions were adopted, the particle size of the precipitated crystals showed no great differences. The sedimentation rates of the precipitated particle bed were observed and the free sedimentation period was terminated within 20 minutes. Although the hindered sedimentation as well as bed compaction progressed subsequently, the bed heights were maintained almost the same level after two hours of sedimentation.

• Fashion & Textile Research Journal
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• v.11 no.2
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• pp.301-307
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• 2009

The purpose of this study is to investigate the problem and complaint of current flight suit derived with the questionnaires. The survey was carried out to the 137 aviators in Army Aviation School from April to May, 2007. The questionnaires were composed of personal characteristics, usage characteristics, wearing characteristics and free comments. Regard to the questionnaires of usage characteristics, they wore the flight suit over 6 hours a day and over 5 days a week. For wearing convenience item in usage characteristics it was revealed that fitness, ease and the location of pocket were not proper, Also, it showed that the material characteristics(e.g. insulation, absorption, and sensation) for flight suit was not proper. Regard to the questionnaire of wearing characteristics, the most inconvenient part is crotch as the answer on the question of "unfitting part in size" and "inconvenient part when wearing". Free comments for the improvement requests are various size, material, stitch strengthening, pattern modifying, and accessories.

• Computers and Concrete
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• v.15 no.2
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• pp.231-257
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• 2015

This paper discusses the spatial variability of the carbonation depth caused by the mesoscopic structure of the concrete and the influence of the spatial variability on the thickness of the concrete cover. To conduct the research, a method to generate the random aggregate structure (RAS) based on polygonal particles and a simplified numerical model of the concrete carbonation at meso-scale are firstly developed. Based on the method and model, the effect of the aggregate properties including shape, content and gradation on the spatial variability of the carbonation depth is comprehensively studied. The results show that a larger degree of the spatial variability will be obtained by using (1) the aggregates with a larger aspect ratio; (2) a larger aggregate content; (3) the gradation which has more large particles. The proper sample size and model size used in the analysis are also studied. Finally, a case study is conducted to demonstrate the influence of the spatial variability of the carbonation depth on the proper thickness of the concrete cover. The research in this paper not only provides suggestions on how to decrease the spatial variability, but also proposes the method to consider the effect of the spatial variability in designing the thickness of the concrete cover.