• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2440-2443
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• 2008

This paper presents a three dimensional shape optimization procedure for a low-speed axial flow fan blade with a weighted average surrogate model. Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are discretized by finite volume approximations. Six variables from airfoil profile and lean are selected as design variables. 3D RANS solver is used to evaluate the objective functions of total pressure efficiency. Surrogate approximation models for optimization have been employed to find the optimal design of fan blade. A search algorithm is used to find the optimal design in the design space from the constructed surrogate models for the objective function. The total pressure efficiency is increased by 0.31% with the weighted average surrogate model.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.3
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• pp.1-8
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• 1999

Mixing efficiency of the unlike Impinging split triplet injector(FOOF type) were measured to investigate the effect of the momentum ratio variation. $H_2$O/kerosene were used as a propellant simulant. The maximum mixing efficiency occured at the momentum ratio 1.5 (total mixture ratio 1.89). Calculated mixing efficiency of real propellant LOX/Kerosene showed similar trend but maximum efficiency of characteristic velocity occurs at the momentum ratio 2.0(total mixture ratio 2.17). Although there exist a little discrepancy between calculated mixing efficiency based on simulant cold test and hot fire test results, this calculated mixing efficiency can be used to predict hot fire mixing efficiency.

• The Journal of Information Systems
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• v.29 no.3
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• pp.145-157
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• 2020

Purpose This study proposed an approach for predicting the efficiency rating of the cultural tourism festivals using DEA and machine learning techniques. The cultural tourism festivals are selected for the best festivals through peer reviews by tourism experts. However, only 10% of the festivals which are held in a year could be evaluated in the view of effectiveness without considering the efficiency of festivals. Design/methodology/approach Efficiency scores were derived from the results of DEA for the prediction of efficiency ratings. This study utilized BCC models to reflect the size effect of festivals and classified the festivals into four ratings according the efficiency scores. Multi-classification method were considered to build the prediction of four ratings for the festivals in this study. We utilized neural networks and SVMs with OAO(one-against-one), OAR(one-against-rest), C&S(crammer & singer) with Korea festival data from 2013 to 2018. Findings The number of total visitors in low efficient rating of DEA is more larger than the number of total visitors in high efficient ratings although the total expenditure of visitors is the highest in the most efficient rating when we analyzed the results of DEA for the characteristics of four ratings. SVM with OAO model showed the most superior performance in accuracy as SVM with OAR model was not trained well because of the imbalanced distribution between efficient rating and the other ratings. Our approach could predict the efficiency of festivals which were not included in the review process of culture tourism festivals without rebuilding DEA models each time. This enables us to manage the festivals efficiently with the proposed machine learning models.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3357-3368
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• 1994

Total pressure losses required to calculate the total-to-total efficiency are estimated by integrating empirical loss coefficients of four loss mechanisms along the mean-line of blades as follows; blade profile loss, secondary flow loss, end wall loss and tip clearance loss. The off-design points are obtained on the basis of Howell's off-design performance of a compressor cascade. Also, inlet-outlet air angles and camber angle are obtained from semi-empirical relations of transonic airfoils' minimum loss incidence and deviation angles. And nominal point is replaced by the design point. It is concluded that relatively simple loss models and Howell's off-design data permit us to calculate the off-design performance with satisfactory accuracy. And this method can be easily extended for off-design performance prediction of multi-stage compressors.

• KIEAE Journal
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• v.6 no.3
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• pp.43-48
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• 2006

This paper aims to suggest ways of institutionally improving standards that must be applied when installing Water Reclamation/Reuse (WRR) system based on efficiency analysis. Currently, the standard for WRR system establishment requires that the system should treat more than 10% of used water in the building of over $60,000m^2$ in total area of all floors, but our research has found that it would be more effective to change the standard to $150-m^3-per-day$ reclaimed water or the total area of all floors of $30,000m^2$ ($50,000m^2$ in the case of an office building). In other words, what this paper suggests is not a one-size-fits-all standard based on the total area of all floors, but a reasonable and flexible standard that takes into account efficiency and a unit water usage according to a building's purpose. Furthermore, this paper recommends a new WRR standard that can be applied to large-scale land development for housinglots, like the New Town. The recommendation is based on the economic analysis that the WRR system will ensure efficiency only if the amount of reclaimed water is over 4,000 tons per day, which corresponds to 4 millions square meters of housinglots. Regarding the size of the established facility, this paper suggests changing the standard, which is now set at over 10% of water usage, to what is relative to the total amount of use of reclaimed water in order to ensure efficiency and promote use of reclaimed water. In addition, this paper proposes that governmental support should be offered not only to facility owners, who are recipients at present, but also to facility builders. By doing so, those who donate a facility to the government, central or local, after building it, can be provided with substantial aid. Therefore, the application of the institutional improvement suggested in this paper is expected to create environment-friendly living conditions and boost the quality of life by encouraging people to secure water resources efficiently in buildings, and in a wider range, in cities.

• The KSFM Journal of Fluid Machinery
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• v.7 no.2 s.23
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• pp.21-26
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• 2004

In this study the effects of fluid viscosity on the pump performances for a conventional centrifugal pump were experimentally investigated. The study aimed to compare the pump characteristics between water and viscosity fluids. In order to measure the flow rate and pressure, v-notch welt and bourdon pressure gauges were used for the codes of KS B6301 and KS B6302. The working fluids were water, aqueous sugar and glycerin solutions. The results were summarized as follows : The experimental results were summarized as follows : the pump characteristics of the total head, shaft power, and efficiency with high viscosity fluids were different from those of water. When the viscosity of the applied fluid was increased, the total head and efficiency were more decreased than those of water. The decreasing gradients of the total head and the efficiency were larger than water due to the increased disk friction losses at the duty operation point. However, the shut-off head was almost constant regardless the viscosity of applied fluids. Each efficiency curves for the sugar $20w\%$ and glycerin $20w\%$ solutions was decreased up to $15.1\%$ and $34.4\%$ than that of water, respectively.

• The KSFM Journal of Fluid Machinery
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• v.4 no.4 s.13
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• pp.28-36
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• 2001

Performance analysis is conducted on an axial-type turbine which is used for fire extinction by injecting water or steam into the turbine. Loss models developed by Hacker and Okapuu are applied for predicting the performance of turbine. Pressure loss generated through a turbine is converted to the thermal efficiency, and thermal and gas properties are calculated within a turbine passage. Total-to-total efficiency, total-to-static efficiency, static temperature at the exit of turbine, output power, flow coefficient, blade loading coefficient, and expansion ratio are predicted with changing the amount of injected steam and the rotational speed. The 74 kW class gas turbine developed at KIMM is chosen for performance analysis. The 74 kW class turbine consists of 1 stage like a current developing gas turbine for fire extinction. Water or steam is injected at the end of combustor, and results show that efficiency and output power are dependent on the temperature of injected water or steam and the static temperature at the exit is decreased.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.4
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• pp.361-367
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• 2016

Pollutants removal and disinfection effect of secondary effluent from final settling tank of sewage treatment plant of W city were investigated in Loop Reactor using ordinary granular activated carbon(GAC) and GAC coated with silver nanoparticles. The results showed that the removal efficiency of $COD_{Mn}$, T-N and T-P using GAC with silver nanoparticles were higher than using the ordinary GAC. The removal efficiency of T-P using GAC with silver nanoparticles is 45.4% and that of T-P using ordinary GAC is 30.9% in the same case of the input amount of 20 g/L of GAC. The total califorms is reduced according to increasing input amount of GAC with silver nanoparticles and ordinary GAC. The disinfection efficiency of total coliforms in case of GAC with silver nanoparticles is much higher than that in case of ordinary GAC. For all experiments using the silver nanoparticles, the total coliforms is under 26 cfu/mL and this shows very excellent disinfection effect.

• The Korean Journal of Health Service Management
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• v.10 no.3
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• pp.1-12
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• 2016

Objectives : This study examined relations between investment efficiency and management performance as indexes related to productivity of Korean regional public hospitals. Methods : The analysis data are financial information of Korean regional public hospitals from 2011 to 2014. For the indicators, value added to total assets, value added to productive activity tangible fixed assets, and value added to personnel expenses, operating margin to revenues, net profit to total earnings, and ratio of value added. Results : Significant relevance was not shown among indicators of investment efficiency. However, Significant relevance was shown between value added to personnel expense and productivity per value added. Conclusions : It confirmed that outside support funds like subsidy did not have effect on improving the management performance. Also, it could be known that availability about input of capital and labor was not realized organically.

• Journal of Veterinary Clinics
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• v.21 no.2
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• pp.115-121
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• 2004

The purpose of this study was to ascertain the breeding efficiency in Thoroughbred mare. A total of 106 mares were investigated for the status of follicle (462 cases), ovulation (179 cases) and pregnancy (346 cases). Of total examination, 46.8% was follicle measure to determine breeding time, and mating rate per cases examined was 39.9%. There was no correlation between reproductive results and size of follicles or endometrial edema or degrees of teasing alone. 143 cases were ovulated among 179 cases which were performed ovulation examination, and ovulation rate and fertilization rate per mating times were 79.9% and 39.0%, respectively. The use of hCG(human chorionic gonadotropin), to facilitate ovulation, presented to increase occurrence of double ovulations and twin fertilizations In conclusion, though more examination to estimate the optimal breeding time and higher mating rate was performed, fertilization rate per mating times was lower and then reproductive efficiency also became decreased. Therefore, it seemed that accurate examination of reproductive tracks, appropriate teasing programme and hCG administration before ovulation were of help to improve ovulation rate and fertilization rate.