• Journal of Wetlands Research
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• v.13 no.1
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• pp.45-52
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• 2011

Seawater circulations between a bay and the open sea play an important role to make the ecosystem healthy, providing nutrient and oxygen to the benthic environments and cleaning up pollutions. The health of the benthic environment in a bay is closely related to the flushing characteristics of seawater. In this study, to estimate the seawater distribution and circulation characteristics of benthic environment in the Geunso bay, we calculated the hydraulic turn-over time by a hydro-hypsographic analysis. Digital elevation model (DEM) which was generated using waterline method based upon remotely sensed data and water depth of the subtidal zone estimated by echo-sounding survey was applied to the hydro-hypsograhic analysis through a geographic information system (GIS) spatial analysis. The results showed that 95% of the total area of the bay was tidal flat and the hydraulic turn-over time was 1.03 tidal cycle, which indicated that the flushing characteristics of the Geunso bay was very good. Geunso bay was revealed to occupy relatively wide area of benthic environment and to have relatively big tidal range over other domestic and foreign coastal environment, therefore it could have a better seawater circulation characteristics. This result can be effectively applied as fundamental information to establish the system for a quantitative estimate of health of coastal environment in the west coast of Korea and manage the ecosystem in benthic environments.

• Journal of Power Electronics
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• v.17 no.2
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• pp.561-569
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• 2017

Power converter design requires simulation accuracy. In addition to the requirement of accurate models of power semiconductor devices, this paper highlights the role of considering a very good description of the converter circuit layout for an accurate simulation of its electrical behavior. This paper considers a simple experimental circuit including one switching cell where a MOSFET transistor controls the diode under test. The turn-off transients of the diode are captured, over which the circuit wiring has a major influence. This paper investigates the necessity for accurate modeling of the experimental test circuit wiring and the MOSFET transistor. It shows that a simple wiring inductance as the circuit wiring representation is insufficient. An adequate model and identification of the model parameters are then discussed. Results are validated through experimental and simulation results.

• Journal of Ecology and Environment
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• v.36 no.1
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• pp.89-94
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• 2013

Diatoms have become an integral part of the UK's freshwater monitoring strategy over the past two decades, mostly in response to increasingly stringent European Union (EU) legislation. The use of diatoms is based on strong correlations between diatom assemblages and environmental variables, and from knowledge of the "expected" (= "reference") state of each river. The nationwide overview of the ecological health of rivers this gives allows those stretches of rivers which fail to meet EU criteria to be identified. This, in turn, allows appropriate remediation measures to be planned. Because diatom assemblages vary in space and time, even within a single water body, effective use of diatoms requires a consistent approach in order to minimise uncertainty. This includes the use of methods which comply with European Standards, a training and accreditation scheme for analysts, and a suite of quality assurance methods. Those aspects of uncertainty that cannot be readily controlled have been quantified and all estimates of ecological status are accompanied by the appropriate "confidence of class" and "risk of misclassification". This, in turn, helps planners prioritise those locations which are most likely to benefit from remediation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.04a
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• pp.84-87
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• 2003

Carbon-nitrogen (CN) nanofibers have been produced using a water cooled hot isostatic pressure (HIP) apparatus. The CN nanofibers were grown in random with the diameter of about 100-150nm and length over $10{\mu}m$. Emission properties of CN nanofibers were investigated for spacing, between anode and cathode, variation. Then turn-on fields about $1.4V/{\mu}m$. The time reliability and light emission test were carried out for above 100 hours. We suggest that CN nanofibers can be possibly applied to high brightness flat lamp because of low turn-on field and time reliability.

• Journal of The Korean Astronomical Society
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• v.47 no.5
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• pp.195-199
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• 2014

We present a GUI-based interactive Python program, VIMAP, which generates radio spectral index maps of active galactic nuclei (AGN) from Very Long Baseline Interferometry (VLBI) maps obtained at different frequencies. VIMAP is a handy tool for the spectral analysis of synchrotron emission from AGN jets, specifically of spectral index distributions, turn-over frequencies, and core-shifts. In general, the required accurate image alignment is difficult to achieve because of a loss of absolute spatial coordinate information during VLBI data reduction (self-calibration) and/or intrinsic variations of source structure as function of frequency. These issues are overcome by VIMAP which in turn is based on the two-dimensional cross-correlation algorithm of Croke & Gabuzda (2008). In this paper, we briefly review the problem of aligning VLBI AGN maps, describe the workflow of VIMAP, and present an analysis of archival VLBI maps of the active nucleus 3C 120.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.5
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• pp.37-42
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• 2012

In this paper, a new charge pump is proposed to reduce the timing mismatch in the conventional current-steering charge pumps. Conventional current-steering charge pumps used NMOS input stages both for UP and DOWN signals, which resulted in different numbers of stage for UP and DOWN delay paths. The proposed charge pump has equalized the numbers of stages for UP and DOWN signals by using a PMOS stage for the DOWN signal. The simulation results show that the conventional current-steering charge pump has 14ns and 6ns for optimized timing mismatches between UP and DOWN signals for turn-on and turn-off, respectively. On the other hand, the proposed charge pump has improved timing mismatches of 6ns and 5ns for turn-on and turn-off, respectively. As a result, the reference spurs are reduced from -26dBc to -39dBc for the proposed charge pump. The proposed charge pump was designed by using $0.18{\mu}m$ CMOS technology. The measurement results show that the maximum variation of the charging and discharging current over the charge pump output voltage range of 0.3~1.5V is approximately 1.5%.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.1
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• pp.46-56
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• 2015

The purpose of this study is to find out the effectiveness of drivers' satisfaction over protected and permissive left-turn (PPLT) traffic signal operation. A structural equation model was established for analyzing the effectiveness of various drivers' factors (e.g., personal characteristics, driving attitude, expectation to PPLT, etc.) on the PPLT preference based on questionnaire survey. As a result, the analysis is satisfied with the critical values, such as Q value, RMR, GIF, AGIF, and NFI. The study reveals that PPLT preference increases in case of driver who is male with long social carrier related to transportation affaire and long driving experience without traffic accident involvement. Moreover, PPLT preference increases as the expectation of PPLT to improvement of traffic safety, traffic operation, and traffic environment increases. Therefore, it is recommended that the PPLT should be preferentially operated in urban area of less traffic accidents and the promotion of PPLT be actively conducted for positive effectiveness.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.4
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• pp.175-180
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• 2011

A large AC generator is an important component of the power system. It is a need for research of AC generator protection relay for the next-generation ECMS and an efficient operation of protection control system. However, most of protection and control systems used in power plants have been still imported as turn-key and operated in domestic. This may cause the lack of the correct understanding on the protection systems and methods, and thus have difficulties in optimal operation. In this paper, over-excitation protection relaying is one of the protective factors in generator protection IED was presented. The cause and protection principles were dealt and, DFT-based gain compensation algorithm was adopted for the frequency measurement. The Republic of Korea 345kV modeling data by EMTP-RV was used for performance evaluation.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.3
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• pp.33-42
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• 2011

This study focused to find the main factors causing job stress to ROKAF pilots and of which factors affects to turnover intention. As a results, the factors of job stress are job characteristics, over loaded ground work, payment, promotion and employee benefits & service system. All of these 5 factors are positively related to the causes of a pilot stress. Among the job stress factors, payment, promotion and over loaded ground work are positively related as the same order. But, job characteristics and employee benefits & service system are not. Even though ROKAF pilots are stressed by annual requirement and night flying, and also are stressed by unfulfilled welfare, those two stress factors are not related to the turnover intention.

• Journal of Korean Academy of Nursing Administration
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• v.5 no.3
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• pp.477-500
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• 1999

Korean labor market has showed remarkable change of the increase in the amount of unemployment and contingent employment since IMF bailout agreement. There is a theoretical position to explain this increase in contingent employment at hospitals with the notion of flexibility. The high flexibility of employment due to the increase of contingent employees is becoming very important part in new business strategy of hospitals. The types of contingent employment of the nurse are part-time employment temporary employment, fixed-term employment, and internship which was introduced in early 1999. Recently, Korean health care industry managers have paid attention to the customer oriented service, rationalization of business administration, service quality control so that they can adjust their business to outer environment. Especially their efforts concentrate on the wage reduction through efficient and scientific control of man power because wage shares about 40% of total cost. This dissertation aims at verifying the phenomena of the contingent employment of the nurse and analyzing the related factors and problems. To rephrase these aims in ordinal: First, verifying the phenomena of contingent employment of the nurse. Second, verifying the problems of that phenomena. Third, analyzing the related factors of the contingent employment of the nurse. To accomplish these research goals, a statistical survey was executed. in which 384 questionnaires-66 for manager nurses, 318 for contingent nurses - were given to nurses working at 66 hospitals-which have at least 100 beds-in Seoul. Among them, 187 questionnaires-38 from manager nurses, 149 from contingent nurses'- 'were returned. Then, the data coded and submitted to T-test, $X^2$ -test, variance analysis(ANOVA), correlation analysis, multiple regression analysis, Logistic Regression with SAS program. The research results of the contingent nurses are followings: 1. The average career term at the present hospital 8.4 months: duty-on days per month are 24.2 days: working time per day is 7.9 hours. These results showed little difference from regular nurses. 2. Their wage level is about 70% of regular nurses except for internship nurses whose wage level is 41% of regular nurses. To break down the wage composition, part-time nurses and internship nurses get few allowance and bonus. And contingent nurses get very low level of additional pay except for fixed-term nurses who are under similar condition of employment to regular nurses. These results show that hospital managers are trying to reduce the labor cost not only through the direct way of wage reduction but through differential treatment of bonus, retirement allowance, and other additional pay. 3. The problem of contingent employment: low level of pay; high level of turn-over rate: weakening of union; low level of working condition: heavy burden of work; inhuman treatment. The contingent nurses consider these problems more seriously than manager nurses do. What manager nurses regard problematic is the absence of feeling-belonged and responsibility of the contingent nurses. 4. The factors strongly related with the rate of the number of contingent nurses for the number of regular nurses; gross turn-over nurses; average in-patients per day; staring wage of graduate from professional college: the type of hospital ownership; the number of beds; the gap between gross newcomer nurses and gross turn-over nurses. The factors related with their gross wage per month; the number of beds; applying of health insurance; applying of industrial casualty insurance; applying of yearly-paid leave; the type of hospital ownership; average out-patients per day; gross turn-over nurses. The meaningful factors which make difference by employment type: monthly-paid leave; physiological leave. The logistic regression analysis using these two factors shows that monthly-paid leave is related with the type of hospital ownership; the number of beds; average out-patient per day, and physiological leave is related with the gross newcomer nurses; gross turn-over nurses; the number of beds.