• Journal of the Korea Institute of Building Construction
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• v.12 no.2
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• pp.194-202
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• 2012

This paper predicts the cementing efficiency of fly-ash(FA) based on mortar test considering binder-water ratio and FA replacement ratio as experimental variables. The cementing efficiency prediction model proposed by statistical analysis enables us to estimate the value according to the binder-water ratio and FA replacement ratio of matrix. When FA replacement ratio is the same, the lower the binder-water ratio, the higher the estimated cementing efficiency. There are significant differences in the values according to binder-water ratio at FA replacement ratios of 15% or less, but there are almost no differences when FA replacement ratio is more than 15%. As the binder-water ratio increases, the variations in the values according to FA replacement ratio are great at FA replacement ratios of 15% or less. As the FA replacement ratios increase, the values increase for FA replacement ratios of 15% or less, but decrease for more than 15%. The values range from -0.71 to 1.24 at binder-water ratio of 1.67-2.86 and FA replacement ratio of 0-70%. The RMSE of the 28-day compressive strength predicted by modified water-cement ratio is 2.2 MPa. The values can be trusted, as there is good agreement between predicted strength and experimental strength.

• Journal of Korean Society of Water and Wastewater
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• v.37 no.6
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• pp.311-324
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• 2023

As an advanced study on the method of calculating the target revenue water ratio of local waterworks through the leakage component analysis method proposed by Kim et al. (2022), this study developed a model to calculate the achievable revenue water ratio within the specified project cost, the required project cost to achieve the specified target revenue water ratio, and the economically appropriate target revenue water ratio level by considering the leakage reduction cost and leakage reduction benefit for each revenue water ratio improvement strategy, and conducted an applicability evaluation of the developed model using actual field data. The procedure for calculating the target revenue water ratio of local waterworks considering economics proposed in this study consists of three stages: physical data linkage model construction, leakage component analysis, and economic analysis, and the applicability was evaluated for Zone H with branch type and the Zone M network type. As a result of the application, it was calculated that approximately 32.5 billion won would be required to achieve the target revenue water ratio of 70% in the Zone H, and approximately KRW 10.5 billion would be required to achieve the target revenue water ratio of 75% in the Zone M. If the business scale of Zones H and M was corrected to 10,000 m³/day of water usage, the required project cost for a 1% improvement in the revenue water ratio of Zone H was calculated to be 0.7642 billion won and 0.4715 billion won for Zone M.

• Journal of Korean Society on Water Environment
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• v.28 no.2
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• pp.202-212
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• 2012

Due to the deterioration of water supply network and the deficiency of raw water, the water utility of local governments have performed various projects to improve their revenue water ratio. However, it is very difficult to estimate the cost for maintaining the revenue water ratio at higher level after completing the project, because local governments have different conditions affecting the operating and maintenance cost of water supply network. The purpose of this study is to present a procedure to estimate the operating and maintenance cost required to maintain the target revenue water ratio of the water supply network. For this purpose, we estimated the cost used only for operation and maintenance of water supply network of 164 local governments with the aid of K-Mean Clustering Analysis and the data from 40 representative local governments. Then, the regression analysis was performed to find relationship between revenue water ratio and the operating and maintenance cost with two different data sets generated by two classification methods; the first method classifies the local governments by means of k-means clustering, and the other classifies the local governments according to the index standardized by the operating and maintenance cost per unit length of water mains per revenue water ratio. The results shows that the method based on the index standardized by the cost and revenue water ratio of each government produces more reliable results for finding regression equations between revenue water ratio and the operating and maintenance cost only for water supply network. The estimated regression equations for each group can be used to estimate the cost required to keep the target revenue water ratio of the local government.

• Journal of the Korea Concrete Institute
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• v.26 no.5
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• pp.591-598
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• 2014

In this study, the relationship between compressive strength and water-cement ratio according to water reducing ratio was evaluated, concrete mix was prepared according to 3 level of water reducing ratio (0%, 8% and 16%) and 3 level of water-cement ratio (40%, 45% and 50%). In addition, concrete mix was carried out repetition test of three times in order to secure the reliability. As a result, compressive strength according to water reducing ratio was shown that difference of strength was about 20% occurred, effect of compressive strength according to water reducing ratio was found more than the water-cement ratio. Therefore, reflected the effect of water reducing ratio, relationship equation between new compressive strength and water-cement ratio was proposed.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.2
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• pp.121-133
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• 2021

This study set up the estimates of leakage management efficiency evaluation and leakage management goal that could be used in local water distribution networks efficiency business and modernization business. The data were analyzed using data envelopment analysis and multiple regression analysis. To this end, with leakage management input indices concerning leakage reduction activities (e.g., aged pipe replacement, water meter replacement, leakage restoration, and leakage detection) and leakage management calculation indices (e.g., the increase of revenue water ratio and the reduction of leakage ratio), the data on 22 K-water consignment local water supply systems were analyzed for the years from 2004 through 2018. Using the results of efficiency analysis by data envelopment analysis, the other DMUs (Decision Making Unit) benchmarked the DMU with the highest efficiency to maximize the leakage management efficiency for all DMUs. Through this, leakage management goal estimates were drawn with the input indices of four leakage reduction activities and calculation indices of the increase of revenue water ratio and the reduction of leakage ratio by multiple regression analysis for each group based on the revenue water ratio and leakage ratio. The correlation coefficients of the leakage management goal estimate for the criteria for the revenue water ratio amounted to 0.553 and 0.771. The correlation coefficients of the leakage management goal estimate for the criteria for leakage ratio were 0.397 and 0.865. Accordingly, we estimated the quantity and priority of four leakage reduction activities for the target leakage ratio and revenue water ratio.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.194.2-194.2
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• 2011

Heating and cooling performance has been analyzed for the water-source heat pump system using raw water from Daechung reservoir. During heating operation from March to May, water temperature is not good condition for a heat source due to the higher atmospheric temperature. Avearged heating load ratio is only 14.3%, and the averaged unit COP and system COP are estimated to be 2.46 and 2.15 respectively. The COP is affected considerably by the water temperature, and the unit COP is increased from 2.16 at $5^{\circ}C$ to 2.95 at $11^{\circ}C$. Cooling performance is analyzed with the measured data from June to August. During cooling operation, raw water has lower temperature by 4. $5^{\circ}C{\sim}4.7^{\circ}C$ than the atmosphere. The load ratio is 39.2%, and the averaged unit COP and system COP are estimated to be 7.25 and 6.13 respectively. The heating COP is affected by the load ratio rather than water temperature. The COP is increased for 20%~40% load ratio, while is decreased for 40%~60% load ratio. It is estimated that the compressor operation combination for 3 (two constant speed and one inverter) compressors is changed for the load ratio.

• Journal of Korea Foundry Society
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• v.4 no.2
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• pp.89-95
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• 1984

A Study on the Mechanical Properties of Molding Sand with Various Water/Clay Ratio A standard sample of molding sand was prepared by adding a various amount of bentonite, which has water/clay ratio from 0.4 to 0.6, into artificial sand, Hanyoung #6. The results obtained by measuring the room temperature properties of green mold are as follows. 1. This compressive strength of green molds which have 4% and 10% of bentonite decreased with increasing water/clay ratio, but the maximum strengths of 4.3 (psi) and 7.2 (psi) were observed in the samples with 6%, 8% bentonite respectively when the water/clay is 0.45. 2. The optimum water/clay ratio for strength and permeability increased from 0.4 to 0.5 with increasing clay. 3. The green compressive strength was proportional to the hardness. 4. Deformation increased with increasing water/clay ratio. 5. Flowability decreased with increasing water/clay ratio and clay content in molding sand.

• Journal of Environmental Impact Assessment
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• v.22 no.5
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• pp.397-408
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• 2013

The purpose of this study is to analyze water cycle area ratio and spatial evaluation of water cycle in urban area of Changwon-si, Gyeongsangnam-do. Water cycle area ratio are analyzed by using spatial data of land-cover and land-use, and Hot spot analysis of GIS program was used for spatial evaluation of water cycle. The results are as below. Firstly, the high water cycle area ratio areas were forests, parks, and rivers, but urban areas covered asphalt and concrete were low under 40%. Public institutions and co-residential of urban areas were higher than others because of high area ratio of pervious land-cover. Spatial evaluation of water cycle was analyzed to vulnerable areas there are dense residential and commercial area. These areas are really occurring frequently flooding and immersion, therefore, is required water management facilities and improvement of land-cover from impervious to pervious. In the future, it will require additionally analysis of water cycle area ratio supplemented data of water management facility and ground water.

• Restorative Dentistry and Endodontics
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• v.5 no.1
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• pp.29-34
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• 1979

The purpose of this study was to measure thermal expansions of dental investments, Biovest(Casting Investment. Dentsply International INC, U.S.A.), Multi-Best (Use for all dental chrome-cobalt alloys, The Ransom & Randolph Co. U.S.A.), Kerr(Inlay Investment. Sybron Kerr, U.S.A.), O. K. (Inlay Investment. Shofu Dental MFG, Co. Japan), Whip-Mix (Cristobalite Inlay Investment. Whip-Mix Corporation. U.S.A.). Thermal expansion of specimens(5mm in diameter and 50mm in length) was measured by a dilatometer at the temperature range from $20^{\circ}C$ to $700^{\circ}C$ by comparing expansion between standardized quartz and experimental specimens with heating rate about $300^{\circ}C$/hr. The following results were obtained. 1. The coefficient of thermal expansion of Biovest was $15{\times}10^{-6}/^{\circ}C$ in the water powder ratio 18/100 and $14{\times}10^{-6}/^{\circ}C$ in the water powder ratio 28/100. Those of Multi-Best were $9{\times}10^{-6}/^{\circ}C$ in the water powder ratio 14/100 and $7{\times}10^{-6}/^{\circ}C$ in the water powder ratio 24/100. 2. The coefficient of thermal expansion of Kerr were $17{\times}10^{-6}/^{\circ}C$ in the water powder ratio 38/100 and $14{\times}10^{-6}/^{\circ}c$ in the water powder ratio 48/100. Those of O. K. were $9{\times}10^{-6}/^{\circ}C$ in the water powder ratio 33/100 and $7{\times}10^{-6}/^{\circ}C$ in the water powder ratio 43/100 3. The coefficient of thermal expansion of Whip-Mix were $14{\times}10^{-6}/^{\circ}C$ in the water powder ritio 40/100 and $12{\times}10^{-6}/^{\circ}c$ Fein the water powder ratio 50/100. Those of Hi-Heat were $11{\times}10^{-6}/^{\circ}c$ in the water powder ratio 28/100 and $10{\times}10^{-6}/^{\circ}c$ in the water powder ratio 38/100.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.63-64
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• 2023

In order to reduce the high absorption ratio of spent coffee grounds, this study examined the compressive strength and absorption ratio of mortar replacing coated spent coffee grounds according to the type of water repellent. In order to examine this, as the water repellent used, a silane-based water repellent (fluorine-based water repellent) and an acrylic-based water repellent, which are film-type water repellents, and a silane/siloxane-based water repellent, which are penetration-type water repellents, were used. The spent coffee grounds were coated with each of three water repellents, and mortar was prepared by mixing cement and fine aggregate. As a result of the experiment, the compressive strength and absorption ratio of the mortar replaced with coated spent coffee grounds coated with the film-type water repellent were superior to the penetration-type water repellent. Therefore, in order to reduce the high absorption ratio of spent coffee grounds, a suitable water repellent is a film-type water repellent. Among them, it is judged that the acrylic type has excellent water repellency and is suitable.