• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.6
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• pp.1081-1086
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• 2008

This paper presents the $3^{rd}$ 4bit sigma delta modulator with the block and timing diagrams of DWA(Data Weighted Averaging) to optimize a operating time. In the modulator, the proposed DWA structure has a stable operation and timing margin so as to remove three latches and another clock. Because the modulator with proposed DWA structure improve timing margin about 23%. It can increase sampling frequency up to 244MHz. Through the MATLAB modeling, the optimized coefficients are obtained to design the modulator. The fully differential SC integrators, DAC, switch, quantizer, and DWA are designed by considering the nonideal characteristics. The designed $3^{rd}$ order 4bit modulator has a power consumption of 40mW and SNR(signal to noise ratio) of 77.2dB under 1.2V supply and 64MHz sampling frequency.

• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.237-239
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• 2007

This paper focuses on maintenance scheduling using PSO algorithm for power plants from an economic (operating cost) and reliable(variance of operating reserve margin) point of view. We also apply regional reserve margin and transfer capability to maintenance scheduling problem. The proposed method has been applied to IEEE-RTS(1996) with 32-generators and a real -world large scale power system with 291 generators.

• Korea Journal of Hospital Management
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• v.18 no.3
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• pp.43-61
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• 2013

The purpose of this study is to analyze the relations between publicness and profitability of national university hospitals in Korea. Finance and management data from 2008 to 2010 were collected from balancing accounts and annual reports in 13 national university hospitals. The dependant variables are used profitability indicators which are operating margin, net profit to gross revenues, normal profit to gross revenues. The independent variables are publicness indicators which are medical social work, ratio of medical aid in inpatients, ratio of medical aid in outpatients, publicness index. The results show that operating margin, net profit to gross revenues in profitability indicators are affected by medical social work in publicness indicators. Normal profit to gross revenues in profitability indicators is strong related to medical social work and hospital province in publicness indicators. Based on these results, this study suggests implications to balance the publicness and the profitability in national university hospitals.

• The KSFM Journal of Fluid Machinery
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• v.14 no.2
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• pp.35-40
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• 2011

This study analyzed the influence of firing biogas on the performance and operation of a gas turbine combined heat and power (CHP) system. A reference CHP system designed with natural gas fuel was set up and off-design simulation was made to investigate the impact of firing biogas in the system. Changes in critical operating parameters such as compressor surge margin and turbine blade temperature caused by firing biogas were examined, and a couple of operating schemes to mitigate their changes were simulated. Part load operation of the biogas-fired system was compared with that of natural-gas fired system, and it was found that as long as the two system produce the same electric power output, they exhibit nearly the same heat recovery.

• The KSFM Journal of Fluid Machinery
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• v.14 no.6
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• pp.68-75
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• 2011

This study simulated the effect of steam injection on the performance and operation of a gas turbine combined heat and power (CHP) system. A commercial simple cycle gas turbine was analyzed. A full off-design analysis was carried out to investigate the variations in not only engine performance but also the operating characteristics of the compressor caused by steam injection. Variation in engine performance and operation characteristics according to various operation modes were examined. First, the impact of full steam injection was investigated. Then, operations aiming to guarantee a minimum compressor surge margin, such as under-firing and partial steam injection, were investigated. The former and latter were turned out to be relatively superior to each other in terms of power and efficiency, respectively.

• Korea Journal of Hospital Management
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• v.25 no.4
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• pp.48-59
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• 2020

Purposes: The purposes of this study is analysis of business performance in national university hospitals in Korea. Methodology: Data from 2010 to 2019 were collected from balance sheet, income statement, and annual reports in 11 national university hospitals. The dependant variables are business performance which are operating margin to total assets, operating margin to gross revenue, and net income to gross revenue. The independent variables are the number of bed, hospital location, opening, liquidity, stability, and activity. Findings: In recent years, activity has been shown to have a lot of influence on management performance. National university hospitals increase profitability by using resources as efficiently as possible. The short-term debt and fixed assets have been increased rapidly in recent years. It was found that management performance has been increased through active investment using financial leverage. Practical Implications: Based on these results, this study will be the basic data for efficient management of national university hospitals.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.11
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• pp.1015-1022
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• 2013

This study simulates the operation of a 200 kW class micro gas turbine that is currently under development. The performance and operating characteristics depending on the load control scheme (constant turbine inlet temperature versus constant turbine exit temperature) and ambient condition were investigated using detailed component performance data. The sensitivities of operating parameters, such as the compressor surge margin and flow path temperatures, according to unit fuel flow change were predicted for a wide load range. The sensitivity analysis showed that the steady state calculation provided useful information about the maximum surge margin reduction during load change.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.11
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• pp.223-234
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• 2021

This study aims to examine whether operating cash flows influence banks' financial stability in Pakistan. The study employed annual panel data collected from annual reports of 20 commercial banks listed on the Pakistan Stock Exchange for the year 2011 to 2019. Free cash flow yield was taken as the dependent variable while cash flow ratio was selected as the independent variable, and net interest margin, income diversification, asset quality, financial leverage, the cost to income ratio, advance net of provisions to total assets ratio, capital ratio, financial performance, breakup value per share and bank size were taken as control variables. The study performed ordinary least square technique, random and fixed effects models, Hausman test, Lagrange multiplier test, descriptive and correlation analysis. Results showed that operating cash flows and net interest margin significantly and positively influenced banks' financial stability while the cost to income ratio and advances net of provisions to total assets ratio significantly and negatively associated with banks' financial stability. To improve financial stability, banks should become more cost-effective and enhance their liquidity levels by lowering lending activities. In the future, it would be useful to compare commercial and investment banks, also Islamic and conventional banks in the same research setting.

• The Journal of the Korea Contents Association
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• v.9 no.6
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• pp.196-206
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• 2009

The profitability of a hospital refers to business administration results achieved through its medical care and other management activities during applicable fiscal year. This study focused on operating margin as a measurement index of hospital profitability, which is a genuine medical return obtained by subtracting medical expenses from medical profits achieved during business administration of hospital. Based on the index, this study could deduce certain factors on hospital profitability in terms of various indices affecting profitability. And based on those factors, this study sought to provide more useful reference materials which allow us to devise possible ways to improve hospital profitability. As a result, it was found that public hospitals attained lower profitability than private ones. To analyze profitability depending on each index, this study divided hospitals broadly into deficit group and surplus group. As a result, it was found that there were significant differences in hospital profitability between two groups depending upon relevant indices such as labor cost ratio, maintenance expense ratio, number of operations per medical specialist and medical instrument turnover. According to analysis on potential effects of relevant indices upon profitability, it was found that each index had its explanatory power ranging from 25% to 74.5% depending on given model.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.3-6
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• 2000

In this paper the concept of voltage stability operating limit in optimal power flow problem is described. A methodology of optimal power flow considering voltage stability margin is proposed based on auxiliary constraint to get a secure dispatch solution. The look-ahead margin is used to shift dispatch solutions to the secure direction in proposed framework. The a1gorithm proposed is successfully tested on IEEE 30-bus system.