• Proceedings of the KSME Conference
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• 2002.08a
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• pp.259-262
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• 2002

Application of combustion stabilization devices such as baffle and acoustic cavity to liquid propellant rocket engine is investigated to suppress high-frequency combustion instability, i.e., acoustic instability. First, these damping devices are designed based on linear damping theory. As a principal design parameter, damping factor is considered and calculated numerically in the chambers with various specifications of these devices. Next, the unbaffled chambers with/without acoustic cavities are tested experimentally for several operating conditions. The unbaffled chamber shows the specific stability characteristics depending on the operating condition and has small dynamic stability margin. The most hazardous frequency is clearly identified through Fast Fourier Transform. As a result, the acoustic cavity with the present design has little stabilization effect in this specific chamber. Finally, stability rating tests are conducted with the baffled chamber, where evident combustion stabilization is observed, which indicates sufficient damping effect. Thrust loss caused by baffle installation is about $2{\%}$.

• The Korean Journal of Health Service Management
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• v.8 no.2
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• pp.1-10
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• 2014

This study examined nonpatient revenues of university hospitals in korea. The data source for this study was 22 university hospitals over the period 2010-2012. In this study, patient revenues, patient expenses, operating profit, nonpatient revenues, total revenues, operating margin, normal profit to gross revenues, ratio of the nonpatient revenues in the total revenues were analysed by the annual and three-year average. The analysis of nonpatient revenue differences by hospital type, bed size, location, management performance was performed by T-test and oneway ANOVA. The results were as follows. First, nonpatient revenues of university hospitals were increased during the period 2010-2012. Second, nonpatient revenues according to hospital type, bed size, location in the university hospitals had significant difference. Third, hospital type was significantly associated with normal profit to gross revenues which was profitability index about nonpatient revenues. Based on these results, this study suggests implications to diversify for management performance in hospitals.

• Nuclear Engineering and Technology
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• v.27 no.1
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• pp.96-104
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• 1995

EPRI URD requires that the reactor be capable of accommodating an unintended CEA drop without initiating a trip and operating at a reduced power with ay single CEA fully inserted. YGN 3 and 4 reactors have 12-finger CEAs, and the CPCS will trip the reactor due to their large reactivities when one of them is dropped at a high power. The ABB-CE reactor power cutback system has been proposed to be used against the 12-Finger CEA drop to avoid the reactor trips. The results of study show that the reactor power cutback can prevent the reactor trips of the 12-Finger CEA drop when the CPCS has enough operating thermal margin (more than 9％ for YGN 3&4 Cycle 1). It is noted, however, that the probability of a 12-Finger CEA drop is very low, less than one per 100 reactor years for YGN 3& and System 80$^{+}$ plants.

• Journal of the Korea Institute of Building Construction
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• v.15 no.1
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• pp.65-71
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• 2015

This study suggests business strategies by interaction analysis of indicators related construction business and business performance for specialty contractors that provide labor, materials and small sized equipments. To do this research, the data was analyzed for construction orders and business performance indicators of specialty contractors with KRW 7 bil. or more of assets during 1997 through 2010. For specialty contractors that provide labor, materials and smaller sized equipments, the amount of construction orders affects profitability the most and therefore some sort of strategy needs to be established to respond to decrease in operating margin due to dwindling construction orders. In other words, it is determined that increase in the amount of construction orders enhances operation of gross assets as well as the operating margin, ultimately increasing the profitability.

• Health Policy and Management
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• v.20 no.3
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• pp.123-137
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• 2010

The main purpose of this article is for deriving functions related to the prediction of the closure of the hospitals, and finding out how the discriminant functions affect the closure of the hospitals. Empirical data were collected from 3 years financial statements of 41 private hospitals closed down from 2000 till 2006 and 62 private hospitals in business till now. As a result, the functions related to the prediction of the closure of the private hospital are 4 indices: Return on Assets, Operating Margin, Normal Profit Total Assets, Interest expenses to Total borrowings and bonds payable. From these discriminant functions predicting the closure, I found that the profitability indices - Return on Assets, Operating Margin, Normal Profit Total Assets - are the significant affecting factors. The discriminant functions predicting the closure of the group of the hospitals, 3 years before the closure were Normal Profit to Gross Revenues, Total borrowings and bonds payable to total assets, Total Assets Turnover, Total borrowings and bonds payable to Revenues, Interest expenses to Total borrowings and bonds payable and among them Normal Profit to Gross Revenues, Total borrowings and bonds payable to total assets, Total Assets Turnover, Total borrowings and bonds payable to Revenues are the significant affecting factors. However 2 years before the closure, the discriminant functions predicting the closure of the hospital were Interest expenses to Total borrowings and bonds payable and it was the significant affecting factor. And, one year before the closure, the discriminant functions predicting the closure were Total Assets Turnover, Fixed Assets Turnover, Growth Rate of Total Assets, Growth Rate of Revenues, Interest expenses to Revenues, Interest expenses to Total borrowings and bonds payable. Among them, Total Assets Turnover, Growth Rate of Revenues, Interest expenses to Revenues were the significant affecting factors.

• Management & Information Systems Review
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• v.32 no.1
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• pp.135-151
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• 2013

The study has been carried out to understand productivity-related factors that have been connected to improve financial independence rate of national university hospital. In order to achieve such research purpose as working out implications of efficient resource management, data from the four years between 2007 to 2010 of 12 national university hospitals were reviewed. According to the results, the hospitals came up with significant differences in Value Added to Total Asset, Value Added to Tangible Fixed Assets, Value Added to Personnel Expenses and Value Added Ratio to Patient Revenues. In addition, after the relation between the investment efficiency and profitability of the national university hospitals was investigated, it was learned that application of basic environmental factors would have an influence on a profitability index Operating Margin. As long as the basic environmental factors are adopted, Operating Margin of the national university hospitals is improved under the condition that the Value Added to Tangible Fixed Assets for Production and the Value Added to Personnel Expenses gets higher but the Value Added Ratio to Patient Revenues gets lowered.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.7
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• pp.857-864
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• 2016

In the present work, vibration analysis of high speed rotary bell cup model for paint atomizer application is carried out through numerical simulation. At first, eight bell cup models, considering four different cup shapes and two different cup diameters, are proposed and corresponding dynamic characteristics are investigated. To evaluate the operating stability, critical speed analysis is conducted using Campbell diagram and separation margin between operating speed and critical speed is identified. Unbalance vibration responses are also studied according to operating speed and balancing quality grade of G. Finally, the stability and adequacy of the proposed bell cup models are discussed for field application.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.2
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• pp.9-14
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• 2007

Recently, in order to improve the characteristics of operating voltage, brightness, discharge time lag, luminous efficacy of ac PDP, the PDP with high Xe partial pressure has been investigated. However, the serious problems in this case is to increase the operating voltage of ac PDP. In this study, in order to meet this problem the influences of kr gas in Ne-Xe-Kr ternary gas system is investigated for wide range of Xe partial pressure in terms of operating voltage, driving margin, luminance and luminous efficacy.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3164-3182
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• 2023

The CRUD on the fuel cladding under the pressurized water reactor (PWR) operating condition causes several issues. The CRUD can act as thermal resistance and increases the local cladding temperature which accelerate the corrosion process. The hideout of boron inside the CRUD results in axial offset anomaly and reduces the plant's shutdown margin. Recently, there are efforts to revise the acceptance criteria of emergency core cooling systems (ECCS), and additionally require the modeling of the thermal resistance effect of the CRUD during the performance analysis. There is an urgent need for the evaluation of the effect of the CRUD deposition on the cladding heat transfer under PWR operating conditions, but the experimental database is very limited. The experimental facility called DISNY was designed and constructed to analyze the CRUD-related multi-physical phenomena, and the performance analysis of the constructed DISNY facility was conducted. The thermal-hydraulic and water chemistry conditions to simulate the CRUD growth under PWR operating conditions were established. The design characteristics and feasibility of the DISNY facility were validated by the MARS-KS code analysis and separate performance tests. In the current study, detailed design features, design validation results, and future utilization plans of the proposed DISNY facility are presented.

• The KSFM Journal of Fluid Machinery
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• v.17 no.5
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• pp.27-36
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• 2014

This paper presents a numerical investigation of the effect of the rotation speed on the performance in a transonic axial compressor with the dihedral stator. Four stator geometries with different stacking line variables were tested in the flow simulations over the whole operating range. It was found that a large shroud loss at the rotor outlet and the subsequent shroud corner separation in the stator passage occurred at low mass flow rate with the 100 % design speed. The hub dihedral stator could suppress the shroud loss region and consequently improve the stall margin. In case of the 70 % design speed condition as the mass flow rate decreased, it was seen that the high loss region was placed at the midspan of the rotor passage. The dihedral stator slightly affected the local diffusion factor, but the performance of the compressor was not changed.