• 제어로봇시스템학회논문지
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• 제15권12호
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• pp.1163-1168
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• 2009

The power quality of wind energy becomes more and more important in connecting wind-farms to the grid, especially weak grid. This paper presents the simulation of a wind farm of a permanent magnet synchronous generator (PMSG) and a doubly fed induction generator (DFIG). Flicker mitigation is performed by using PMSG as a static synchronous compensator (STATCOM) to regulate the voltage at the point of common coupling (PCC). A benefit of the measure is that integrating two function of to control the active power flow and to reduce the voltage flicker in a wind farm. Simulation results show that controlling PMSG is an effective and economic measure in reducing the flicker during continuous operation of grid connected wind turbines regardless of short circuit capacity ratio, turbulence intensity and grid impedance angle.

• 환경영향평가
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• 제23권3호
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• pp.227-235
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• 2014

Interest has been growing worldwide in unconventional natural gas that has become an increasingly important source of energy in the world. Unconventional gas development, including shale gas, generally involves a larger environmental impact, compared to conventional gas development, due to its intensity and scale of the operation. There are a growing number of studies on identifying and minimizing the environmental impacts of unconventional gas development. This study aims to examines the current environmental policies and regulatory systems related to the unconventional gas development. The study shows that few environmental regulation exists concerning unconventional gas development, even in the USA where unconventional gas development is most actively pursued. Regulations, however, are being developed based on studies currently underway on health and environmental risks of unconventional gas development and on guidelines designed to reduce the risks. In a world where environmental regulations are ever strengthening, review the environmental regulatory systems and guidelines about unconventional gas need to be established for Korean firms to understand environmental impacts of unconventional gas development they invest or take part in, enabling them to manage and operate gas activities in a way that minimizes environmental damages.

• 한국환경보건학회지
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• 제36권4호
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• pp.264-270
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• 2010

Agricultural workers are often exposed to high levels of dust during field operations. A systematic exposure assessment of annual task-weighted exposure has not been thoroughly examined. The occupational dust exposure in two wine grape vineyards was measured. Exposure levels to total and respirable dust were determined for a 1-year cycle of work. An operation profile including the frequency of tasks was established. The means of total and respirable dust exposure were $1.08\;mg/m^3$ and $0.07\;mg/m^3$, respectively. Based on the exposure for each task and the task frequency, task-weighted mean exposures to total and respirable dust were estimated as $1.115\;mg/m^3$ and $0.079\;mg/m^3$, respectively. The task-weighted exposure was significantly represented by three operations and could be attributed to the exposure frequency rather than the exposure intensity of operations. The measurement of a few of the most frequent tasks may be an alternative method of estimating task-weighted exposure. Agricultural dust exposure can be significantly reduced by targeting those tasks most important to task-weighted dust exposure.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1759-1761
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• 1996

Md:YAG laser has been used in many applications such as micromachining, nonlinear optical experiments, holography, and rangefinding. These applications quite often require operation of the laser at the $TEM_{00}$ mode since this mode produces the smallest beam divergence, the highest power density, and, hence, the highest brightness. In this study, a pinhole is put between a rod and a half mirror to make the $TEM_{00}$ mode, and then we measured the intensity distribution of the output beam as reducing the diameter of the pinhole from 6mm to 1.5mm. As a result, the optimum size of the pinhole fixed in a resonator to make the $TEM_{00}$ mode was obtained, and we found out that the output beam of the pulsed Nd:YAG laser with a single elliptical cavity has a Gaussian distribution.

• 대한산업공학회지
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• 제36권1호
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• pp.59-68
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• 2010

The medical emergency departments are suffering from the crowdness of patients, hence the quality of medical service the patients are receiving are getting poorer. Overcrowding of medical emergency departments may incur the waiting time for the treatment, and the improper treatment in time. For the operational control of the emergency department, the crowding index is commonly used to identify the crowding intensity, with which the operation process is managed, and future process can be expected. In this study the composite crowding index is suggested, in which the trend of inpatients rate, the age and acuity of patients, and resource of ED are considered. The validity of the suggested crowding index is discussed by the regression analysis for the index and the actual number of inpatients, and by the simulation study using the process model and the real data.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.324-333
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• 2014

In this study, physiological status of locomotive engineers were measured through EEG, ECG, EDA, PPG and respiration signals from 6 subjects to evaluate their arousal status during train operating. Existence of tunnels and mechanical vibration of train using 3-axes acceleration sensors were recorded simultaneously and were correlated with operator's physiological status. As the result of the analyzed subjects' physiological signals, mean SCR was increased in the section where more body movement is required. The RR interval was decreased before and after train stop due to the higher level of mental tension. The intensity of beta wave of EEG was found to be higher before and after train stop and tunnel section due to the increased mental arousal and tension. Therefore, it is expected that the outcomes of the physiological signals explored in this study can be utilized as the quantitative assessment methods for the arousal status to be used for sleepiness prevention system for vehicles operators which can greatly contribute to public transportation system safety.

• The Korean Journal of Pain
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• 제19권2호
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• pp.241-243
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• 2006

Central pain is defined as pain associated with lesions of the central nervous system, and is among the most intractable of chronic pain syndromes. A 47 year-old-female, who had right arm and shoulder pain, was diagnosed with syringomyelia of the Arnold Chiari malformation type I and received foramen magnum decompression and a syringo-subarachnoid shunt. After the operation, the evoked pain was improved, but she complained of a continuous burning pain, coupled with cold and tactile allodynia. This symptom failed to fully subside on administration of oral medicine; therefore, brachial plexus block was performed, which relieved her pain transiently. Through repeated trials, a gradual decrease in the pain intensity and frequency was found. However, the way in which brachial plexus block improves spinal central pain is not completely known.

• Agricultural and Biosystems Engineering
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• 제6권1호
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• pp.1-7
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• 2005

Assessing health condition of crop in the field is one of core operation in precision fanning. A sensing system was proposed to remotely detect the crop health condition in terms of SP AD readings directly related to chlorophyll contents of crop using a multispectral camera equipped on ground-based platform. Since the image taken by a camera was sensitive to changes in ambient light intensity, it was needed to convert gray scale image data into reflectance, an index to indicate the reflection characteristics of target crop. A reference reflectance panel consisting of four pieces of sub-panels with different reflectance was developed for a dynamic calibration, by which a calibration equation was updated for every crop image captured by the camera. The system performance was evaluated in a field by investigating the relationship between com canopy reflectance and SP AD values. The validation tests revealed that the com canopy reflectance induced from Green band in the multispectral camera had the most significant correlation with SPAD values $(r^2=0.75)$ and NIR band could be used to filter out unwanted non-crop features such as soil background and empty space in a crop canopy. This research confirmed that it was technically feasible to develop a ground-based remote sensing system for assessing crop health condition.

• Journal of Biosystems Engineering
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• 제17권4호
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• pp.344-353
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• 1992

This study was carried out to develop a fully-controlled plant growth system for studying the effects of environmental factors on plant growth. The plant growth system consists of the growth chamber, the measurement system for sensing and signal conditioning the environmental factors and the control system which includes control algorithm required for optimum operation and on-line monitoring. The results of the study on the performance of the controlled plant growth system are summarized as follows : 1. Under the light intensity of 18,000~20,000 lux, the temperature was controlled in the range of $22{\pm}0.4^{\circ}C$, the relative humidity of $70{\pm}5%$ respectively. 2. The $CO_2$ concentration was controlled in the range of $1,000{\pm}40ppm$(from 1st to 4th day) and $1,500{\pm}40ppm$(from 4th to 9th day). 3. The electric conductivity(EC) and pH of the nutrient solution were controlled in the range of $1.9{\pm}0.2mS/cm$ and $6.8{\pm}0.5pH$ respectively. 4. Under the above environmental conditions, the average fresh weight of leaf lettuce increased from 10g to 74g in 9 days with 24 hour lighting.

• 한국생산제조학회지
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• 제22권3_1spc호
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• pp.509-517
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• 2013

This paper presents upgraded equipment to assist a patient in rehabilitating of their knee-joint by themselves. A new automatic mechanism is suggested and developed in order to add functions for enforcing the leg muscles, which were absent in previous rehabilitation machines. Using the Pro-engineer software, we analyze the displacements and speeds of several moving points of the equipment during various planned exercises. In addition, an appropriate control panel for operation is developed. Three motors andthree motor drivers are used in a tilting part for the ankle joint, sliding guide part for the knee joint, and up-down moving part for the whole leg. Finally, various newly upgraded motions can be generated by controlling the three motors simultaneously. we show that by using this equipment, we can adjust the proper length of the equipment according to the user's height and the intensity of the rehabilitation exercise.