• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1155-1157
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• 1999

The UPFC is known to have the ability to control both the real power flow and the reactive power flow. [1],[2] The power flow in the system is heavily related with the system security. [4] This paper deals with the operation of the UPFC to increase the power system security. The concept of the power system security is verified and the index to indicate the power system security level is suggested. And the algorithm to find the optimum operation point of the UPFC improving the system security level is presented.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.313-317
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• 2005

This study aimed to estimate applicability of a model to simulate circulation in estuarine lake caused by operation of drainage gates. The model consists of 2D (depth-averaged) hydrodynamic models, Delft3D-FLOW model and operation model for drainage gates. The flow through drainage gates was calculated using weir formulae with discharge coefficient, 0.8. The simulations are performed under two conditions: uncontrolled condition and controlled by periods of two days. The results on simulation of the model showed that the water level in estuarine lake was tend to increase above mean sea level. Therefore it was proved that the calibration and verification were needed in order to applicate this model for Saemankeum area.

• Journal of Electrical Engineering and Technology
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• v.1 no.4
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• pp.546-549
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• 2006

In this paper the neuron operation based on Brillouin-active fiber in optical fiber is described. The inherent optical feedback by the backscattered stokes wave in optical fiber leads to instabilities in the form of optical chaos. Controlling of chaos induced transient instability in Brillouin-active fiber is implemented with Kerr nonlinearity having a non-instantaneous response in network systems. The controlling chaotic instabilities can lead to multistable periodic states; create optical logic 'on' or high level '1' or 'off', or low level '0'. It is theoretically possible to apply the multi-stability regimes as an optical memory device for encoding and decoding series and complex data transmission in optical systems.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.2
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• pp.120-126
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• 2019

This study proposes a neutral voltage balance control scheme for stable fault-tolerant operation of an active neutral point clamped (ANPC) inverter using carrier-based pulse width modulation. The proposed scheme maintains the neutral voltage balance by reconfiguring the switching combination and modulating the reference output voltage in order to solve the degradation of the output characteristic in the fault tolerant operation due to the fault of the power semiconductor switch constituting the ANPC inverter. The feasibility of the proposed control scheme is confirmed by HIL experiment using RT-BOX.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.12
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• pp.852-858
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• 2010

In an absorption chiller, solution is circulated by a solution pump with an inverter to vary flow rate depending on operating conditions. For optimal operation, the solution level in the high temperature generator should be kept constant. However, a sensor for measuring continuous level is not available because of varying solution concentration. Instead, level switches are used and hence feedforward control associated with limit checking is a common practice. In the study, inverter frequencies are estimated from a dynamic simulation model and pump performance. Designed frequencies are compared with those implemented in real chillers. It was found that the frequencies used in real chillers are larger than those needed in circulation flow rates. It was intended to prevent system shut-off caused by dry-out. However, it is necessary to minimize the excessive frequency setting in order to reduce frequent pump stops and the range of solution level for continuous pump operation.

• Journal of Korean Society for Atmospheric Environment
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• v.3 no.1
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• pp.65-73
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• 1987

Indoor air pollution problems, in fact, have been neglected due to the unawareness of its seriousness and the lack of accumulated data. Recently, some movement of research and regulations, however, have been made for several indoor air pollutants. In this study, one of the carcinogenic polynuclear aromatic hyrocarbon, Benzo(a) pyrene in indoor airborne particulate, was measured and analyzed to estimate emission strength of BaP from an unvented kerosene heater and to know its level in indoor environment with use of a kerosene heater and a wood-burning fireplace. By the measurement of BaP level in a dark room with air exchange rate of app. 3.0, BaP emission strength of a kerosene heater (11,000Btu/hr) was estimated to be 326.6ng/hr (or 29.7 ng/$10^3$ Btu). With 4-hr operation a day of the kerosene heater in an apartment, the BaP level became 2.97ng/m$^3$ from 0.27ng/m$^3$ of background level. The operation of a wood-burning fireplace app. 2hr a day, on the other hand, increased the BaP level from 0.16ng/m$^3$ of background to 3.53ng/m$^3$. So proper ventilation must be considered seriously when unvented heating facilities are used in indoor environment.

• 대한공업교육학회지
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• v.45 no.2
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• pp.1-20
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• 2020

The purpose of this study is to develop an assembly-type liquid level control experimental equipment and a hands-on activity task that can be applied to the class so that students studying the chemical industry can easily understand the liquid level control. For this purpose, the content elements related to liquid level control in the chemical industry practice course of the 2015 revised curriculum was analyzed, a hands-on activity task with an assembly-type liquid level control experimental equipment was and developed. And then, expert verification was also performed and the hands-on activity task was applied to 19 students of S meister high school. The results obtained through this are as follows. First, the existing completion-type liquid level control experimental equipment was explored, and based on this, a new assembly-type liquid level control experimental equipment that can be assembled by students and used for practices was designed and manufactured. Second. by analyzing the contents of the NCS-based 'Chemical Process Maintenance Operation' practical course of the 2015 revised curriculum, learning contents related to level control were extracted. Among the contents related to the level control, the practice with understanding the process flow chart, manufacturing the level control experimental equipment, measuring the flow rate, and checking the level control phenomenon were conducted with the assembly-type liquid level control experimental equipment to systematically learn the level control.

• Journal of Navigation and Port Research
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• v.41 no.2
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• pp.63-70
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• 2017

Despite the remarkable continual growth of the world cruise industry, studies have yet to be attempted on many revenue management problems in cruise operations. This paper suggests two schemes that can be easily applied to cruise revenue management: optimal dual pricing and passenger safety level. In optimal dual pricing, a pair of higher and lower prices is applied to cabin reservation through market segmentation. This scheme can be executed with a linear price-response function for the current unreserved cabins. A cruise line could benefit from this scheme to maximize reservation revenue while attaining full occupancy. The dual pricing scheme is also devised to produce only integer demands to suit real management practices. The life boat capacity is an additional service capacity unique to the cruise industry, catering to passengers' safety. The concept of passenger safety level is defined and computed for any passenger life boat capacity of a cruise ship. It can be used to evaluate the passenger safety of a cruise ship in operation, as well as to determine the number of life boat seats required for a new cruise ship. Hypothetical examples are used to illustrate the operation of these two schemes.

• Health Policy and Management
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• v.11 no.2
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• pp.16-28
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• 2001

This study was to compare multidimensional outcomes of patient's satisfaction after cataract surgery and to identify factors influencing satisfaction after operation. Patient's satisfaction was measured with three dimensions : interpersonal care, physician explanation and hospital care. Overall satisfaction was measured as means of three dimensional scores. For the study, a prospective study was performed with 389 patients who had undergone cataract surgery for either one eye or both eyes. The surgery was performed by 20 ophthalmologists who were practicing at university hospitals and general hospitals. Patients were interviewed and clinical data (the visual acuity of operated eye, visual function, symptom score and satisfaction with vision) were obtained. The doctors were questioned with self-reported questionnaire forms. Medical records were also examined to understand surgery Process. The survey was conducted before(389) and after operation(327). Alter excluding cases with incomplete data, 3n cases were enrolled In this study. Both the overall satisfaction and the satisfaction with physician explanation increased after the operation whereas the satisfaction with interpersonal care and hospital care did not change significantly. Multiple regression analysis showed that the level of education, baseline satisfaction scores and the degree of vision improvement were statistically significant variables. The preoperative lower level of education, higher level of overall satisfaction (interpersonal care, physician explanation, hospital care scores) and the more the satisfaction with vision improvement were associated with the improvement of postoperative satisfaction scores.

• Korean Journal of Agricultural Science
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• v.48 no.3
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• pp.617-627
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• 2021

In the field of on-road motor vehicles, the level for autonomous driving technology is defined according to J3016, proposed by Society of Automotive Engineers (SAE) International. However, in the field of agricultural machinery, different standards are applied by country and manufacturer, without a standardized classification for autonomous driving technology which makes it difficult to clearly define and accurately evaluate the autonomous driving technology, for agricultural machinery. In this study, a method to classify the autonomy levels for autonomous agricultural machinery (ALAAM) is proposed by modifying the SAE International J3016 to better characterize various agricultural operations such as tillage, spraying and harvesting. The ALAAM was classified into 6 levels from 0 (manual) to 5 (full automation) depending on the status of operator and autonomous system interventions for each item related to the automation of agricultural tasks such as straight-curve path driving, path-implement operation, operation-environmental awareness, error response, and task area planning. The core of the ALAAM classification is based on the relative roles between the operator and autonomous system for the automation of agricultural machines. The proposed ALAAM is expected to promote the establishment of a standard to classify the autonomous driving levels of self-propelled agricultural machinery.