• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.5
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• pp.586-592
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• 2018

In this paper, HIC with various functions is proposed for the design 140W LED power control circuit. The proposed HIC integrates constant voltage/constant current circuit, short circuit protection circuit, internal constant voltage circuit, and dimmer circuit, thereby reducing the horizontal length of the PCB by 16% comparing with the conventional system. Through various experiments, we verified the performance of each block implemented inside of HIC with numerical results. (Constant voltage variation ratio: 2.9%, dimmer circuit duty variation within 5%, stable short protection at 720 mA) Since the PCB area can be significantly reduced by applying the proposed HIC. It is possible to reduce the PCB manufacturing time which takes up most of the manufacturing time, however, It is expected that the faulted power module can be replaced without replacing the whole PCB, so that maintenance / repair can be made easier.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.11
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• pp.6-17
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• 2015

In this paper, colors of broadcast lightings composed of Red, Green, and Blue LED(Light Emitted Diode) can be linearly and quantitatively controlled in low illuminance. Because LED cannot emit uniform illuminance in low illuminance, the colors of RGB LED are unmixable. Furthermore, the illuminances are nonlinear with the dimming values of the RGB LED due to the nonlinearity of the output illuminance with the current through the LED. This nonlinearity generated errors of the target colors and illuminances. The proposed algorithm set up the target colors, which is expressed by the color coordinates in CIE 1931 color space, and the target illuminances. Then the illuminances of RGB LED were calculated using color mixing theory. The calculated illuminances determined the dimming values of the RGB LED for transmission via DMX512 communication. After the broadcasting lighting received the dimming values of the RGB LED via DMX512 communication,.RGB LED can emit target color and illuminance, and be controlled by calculating the PWM(Pulse Width Modulation) duty ratio of the hybrid LED driver which be considered the nonlinearity for the illuminances of the LED. As a result, the proposed algorithm can linearly and quantitatively control the colors and illuminances in full range of illuminance. Then we verify experimentally that the errors of the emitted color coordination x, y and illuminance are 2.27%, 3.6% and 1.5%, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.5
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• pp.31-40
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• 2008

Recently, Contactless Power Supply(CPS) system has been broadly studied as a power supply system for Flat Panel Display(FPD) material transfer equipments. In mass production line, CPS systems on material transfer equipment are applied only in the straight sections with single operating vehicle. The formal CPS system was not adequate for curved section nor multiple operating vehicles. Therefore, this paper presents CPS system that consists of straight and curved section with multiple operation vehicles. The circuit topology of CPS system consists of full bridge configured serial-parallel resonant DC/DC converter. The control method for CPS system consists of duty control method on the primary power supply system to maintain constant resonant current. And the secondary power supply systems of multiple vehicles are self controled to maintain constant output voltage. Practically, the test result of dual vehicles on straight and curved section of material transfer equipments were satisfactory, and proved it's applicability on commercial use.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.2
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• pp.82-89
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• 2021

This study proposes a DAB two-stage series structure with insulated bidirectional DC-DC converter for two-way power transfer between the renewable energy of high voltages (1 kV and above). The proposed circuit transforms the existing DAB converter into a two-stage series structure to reduce the pressure in the switch. The problem of power imbalance occurring in the design of the DAB converter second-stage series is improved by applying the cell balancing method circuit and the common mode coupled inductor using an external flying capacitor instead of reflecting the existing improvement measures, voltage balance control, and inductor current control. In addition, a no-load supercharging sequence is proposed in high voltages and high-speed switching by using the fixed duty output method. This study presents the analysis results through the structure of the proposed circuit, the principle of improving the power imbalance problem, and simulations. Prototypes were manufactured to meet the specifications of input/output voltage of 1700 V, maximum load of 65 kW, and switching frequency of 51kHz, and the validity of the topology was verified using the experimental results and efficiency data.

• Safety and Health at Work
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• v.13 no.2
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• pp.148-154
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• 2022

Background: Bus driving is a mentally demanding activity that requires prolonged attention to ensure safety. The aim of the study was to assess mental fatigue caused by driving a public bus and to find a profile of workers at higher risk. Methods: We evaluated changes of critical flicker fusion (CFF) (index of central arousal) and heart rate variability (HRV) (index of autonomic balance) in a 6-hour driving shift on a real route, in 31 professional bus drivers, and we tested the influence of personal factors such as sleep quality, BMI, and age. Paired t-test was used to test differences of CFF and HRV between both initial and final phase of driving, while multiple linear regression tested the influence of personal variables on the indexes of mental fatigue. Results: Results showed that CFF significantly decreased after 6 hours of bus driving (41.91 Hz, sd 3.31 vs. 41.15 Hz, sd 3.15; p = 0.041), and heart rate significantly decreased in the final phase of driving, with respect to the initial phase (85 vs. 78 bpm, p = 0.027). Increasing age (beta = -0.729, p = 0.022), risk of obstructive sleep apnea syndrome (beta = -0.530, p = 0.04), and diurnal sleepiness (beta = -0.406, p = 0.017) showed a significant effect on influencing mental fatigue. Conclusion: Elderly drivers at higher risk of sleep disorders are more prone to mental fatigue, when exposed to driving activity. Monitoring indexes of central arousal and autonomic balance, coupled with the use of structured questionnaires can represent a useful strategy to detect profile of workers at higher risk of mental fatigue in such duty.

• Journal of Korean Academy of Nursing Administration
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• v.5 no.2
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• pp.389-400
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• 1999

The purpose of this study is to examine a possibility of applying the ABC system to analyze the cost of nursing service on one obstetrics and gynecology (OB/GYN) unit in a major medical center. The activities of nurses on an OB/GYN unit were analyzed for 4 days for 96 hours. 2 week days and 2 days on weekend. Total cases included in the study were activities of 12 charge nurses and 12 staff nurses. Activities were categorized into direct and indirect activities in order to calculate the cost of activities. Nursing activities were defined multidimesionally in order to utilize the ABC system. The 60 nursing activities were classified into the direct nursing activities and the indirect nursing activities based on a literature review, interview, and survey results. The direct activities were further categorized into the single nursing activities and the multiple nursing activities. The indirect activities were classified into the indirect nursing service activities and the general management activities. The major findings of this study were as follows : 1. There were differences in activities according to the positions and duties of the nurses. The charge nurses mostly performed the indirect nursing service activities and the general management activities. Almost all of their indirect nursing activities spent on each patient were similar. The staff nurses performed the single nursing activities and the multiple nursing activities. 2. The activities of staff nurses included medication, patient assessment, rounding and organizing the unit. patient education, nursing treatment, admission and discharging of patients. There was no differences in types and amount of time spent between the nurses on day-time duty and evening-time duty, but the patient assessment activity increased during the night-time. 3. The cost of post partum nursing services for women who had a normal vaginal delivery using the ABC system included the cost incurred by direct nursing activities provided by the staff nurses (85.9%), indirect nursing activities incurred by the staff nurses(19.0%) and the nursing activities by the charge nurses and the head nurse(14.1%). The ABC system is a relatively new method of cost analysis. The results of this study can provide the nursing and hospital managers with useful information on cost control. It is suggested that more studies should be done using the ABC system and extend the scope of studies to include value analysis to aid the Activity-Based Management(ABM) and/or the reengineering of hospital process.

• The Korean Society of Law and Medicine
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• v.9 no.1
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• pp.319-382
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• 2008

As a withdrawing care's study, the purpose of this study is searching about withdrawing care's acceptance and circumstances through Bora-mae hospital case(chapter 1). Withdrawing life-sustaining treatment has various forms. Though the meaning of euthanasia, death with dignity, natural death, physician assisted suicide are duplicated, the meaning of those are different slightly. Firstly, this study looks about the difference of the those meaning and acceptance range(condition) by withdrawing care's forms(chapter 2). Bora-mae hospital case sentenced guilty about physician who discharged incompetent patient who was after surgery by patient's wife determination. This Bora-mae case that sentenced guilty about discharge against medical advise(DAMA) that is regarded to custom has brought intensive confliction of legal, social, medical aspect, Bora-mae hospital case has many legal problems. First, as to criminal law rule 250(murder), the problem is whether discharge and withdrawing life-sustaining treatment is commission or omission. this study concluded omission(district court: omission, appeal, supreme court: commission). Because legal denounce point of discharge and medical treatment withdrawing is omission that physician who is obligatory on patient to cure. If physician's act is regarded omission, it is necessary to determine whether he has guardian status and obligation. Without guardian status and obligation, omission crime can't exist. This study decided that physician had guardian status and obligation and foundation of guardian status was pre-action or acceptance of emergency patient. Physician's medical treatment duty finished when patient(or patient's guardian) demands discharge. But when patient death is foreseen and other possible treatment does not exist, his duty of life prolonging treatment does not finish. This originate from physician's social responsibility and public status that limits patient's private liberty. This study regarded physician's action as accomplice about whether physician's discharging action is accomplice or the principal offender(district court: the principal offender, appeal, supreme court: accomplice). Though the principal offender needs criminal determination and action, there is no this common determination and functional action control of physician in Bora-mae case(chapter 3). Bora-mae hospital case partly originated from deficiency of legal, institutive system including medical security system shortage, the instruction is 1. medical security system strengthening, 2. hospital ethical committee's activity strengthening, 3. institutionalization of withdrawing life-sustaining treatment, 4. acceptance of pre-decision making system, 5. sufficient persuasion of physician for patient and faithful writing of medical paper, 6. respect for patients' self-determination and rights, 7. consciousness's changing for withdrawing life-sustaining treatment and persistent education about medical ethics(chapter 4). Considering Bora-mae case, medical sector is not the dead ground of a criminal punishment. Intervention of criminal law in medical sector give rise to ill effect, that is, excess medical examination and treatment, safeguard treatment, delay of discharge from a hospital. Because sufficient guarantee of life becomes mere empty slogan under situation that impose a burden of heavy cost to family or hospital, public and systematic solution should be given(chapter 5).

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.4
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• pp.456-465
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• 2019

PHEV(Plug in Hybrid Electric Vehicle) and BEV(Battery Electric Vehicle) equip high voltage batteries to drive motor and vehicle electric system. Those vehicle require OBC(On-Board Charger) for charging batteries and LDC(Low DC/DC Converter) for converting from high voltage to low voltage. Since the charger and the converter actually separate each other in electrical vehicles, there is a margin to reduce the vehicle weight and area of installation by integration two systems. This paper studies a 1.5kW LDC converter that can be integrated into an OBC using an isolated current-fed converter by simplifying the design of LDC transformers. The proposed LDC can control the final output voltage of the LDC by using a fixed arbitrary output voltage of the bidirectional buck-boost converter, so that Compared to the existing OBC-LDC integrated system, it has the advantage of simplifying the transformer design considering the battery voltage range, converter duty ratio and OBC output turn ratio. Prototype of the proposed LDC was made to confirm normal operation at 200V ~ 400V input voltage and maximum efficiency of 91.885% was achieved at rated load condition. In addition, the OBC-LDC integrated system achieved a volume of about 6.51L and reduced the space by 15.6% compared to the existing independent system.

• Journal of Aquaculture
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• v.15 no.1
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• pp.49-60
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• 2002

Research on practices for improving water quality in channel catfish Ictalurus punctatus ponds was conducted at the Auburn University Fisheries Research Station, Auburn, Alabama, in 1998 and 1999. The objective of this two-year study was to determine better management practices to enhance water quality and improve production efficiency. In the first year, oxidation of bottom soil by drying, tilling, and applying sodium nitrate was performed (dry-till and dry-till with sodium nitrate treatments). The second year, based on the results obtained during the first year, precipitation of phosphorus (P) from water by applying gypsum was compared to the dry-till treatment (dry-till and dry-till with gypsum treatments). Control ponds were not subjected to bottom drying, tilling, sodium nitrate, or gypsum treatment. Channel catfish fingerings were stocked at 15,000/ha. In the first year, water in ponds from dry-till and dry-till with sodium nitrate treatments had lower concentrations (P < 0.01) of soluble reactive P, nitrate ($NO_{3} ^{-}) and nitrite ($NO_{2} ^{-}) nitrogen (N), total ammonia ($NH_3$) nitrogen, total suspended solids and turbidity, and higher values of pH, Secchi disk visibility, total alkalinity, total hardness, and calcium ($Ca^{2+}) hardness than water in control ponds. Ponds of the dry-till treatment also had lower concentrations (P < 0.01) of total P and total N than control ponds. Total fish production and survival rate did not differ among the treatments (P > 0.05). The findings suggested that drying and tiling pond bosoms between crops could achieve water quality improvement. Applying sodium nitrate to dry, tilled pond bosoms did not provide water quality improvement. In the second year, the treatment with the best results from the first year, dry-till, was compared with a dry-till with gypsum treatment. Enough gypsum was applied to give a total hardness of about 200 mg/L, and gypsum was reapplied as needed to maintain the hardness. Compared to the control, dry-till and dry-till with gypsum treatments had lower concentrations (P < 0.01) of total and soluble reactive P, total N, and total $NH_3$-N, and higher concentrations (P < 0.01) of dissolved oxygen. Ponds of the duty-till with gypsum treatment also had lower concentrations (P < 0.01) of chlorophyll $\alpha$, chemical oxygen demand, and total alkalinity than the control. Total fish production and survival rate did not differ (P > 0.05) among the treatments. These findings suggest that drying and tilling pond bosoms between crops and treating low hardness waters with gypsum could achieve water Quality improvement.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.1-9
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• 2015

To satisfy stricter $NO_X$ emission regulations for light- and heavy-duty diesel vehicles, a control algorithm needs to be developed based on a selective catalytic reaction (SCR) dynamics model for chemical reactions. This paper presents the development and validation of a SCR dynamics model through test rig experiments and MATLAB simulations. A nonlinear state space model is proposed based on the mass conservation law of chemical reactions in the SCR dynamics model. Experiments were performed on a test rig to evaluate the effects of the $NO_X$ and $NH_3$ concentrations, gas temperature, and space velocity on the $NO_X$ conversion efficiency for the urea-SCR system. The parameter values of the proposed SCR model were identified using the experimental datasets. Finally, a control-oriented model for an SCR system was developed and validated from the experimental data in a MATLAB simulation. The results of this study should contribute toward developing a closed-loop control strategy for $NO_X$ and $NH_3$ slip reduction in the urea-SCR system for an actual engine test bench.