• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.2
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• pp.53-62
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• 2020

The purpose of this study is to estimate the channel water loss of agricultural water supply in the command areas belong to Yechon irrigation channel of Gyeongcheon reservoir located Mungyeong-si, which area experienced a severe drought in 2015. The channel water loss was estimated by comparison of the irrigation water requirements (IWR) and agricultural water supply of the field data from 2012 to 2015. Further analysis was conducted to define the conveyance loss estimated based on the leakage holes and illegal pumping spots investigated through the field survey, and the distribution loss obtained by subtracting conveyance loss from the channel water loss. The annual rainfall decreased gradually, but the contribution of effective rainfall, available rain water to crop, increased to IWR during the study period. These phenomena resulted in the increase of agricultural water supply, and hence made greater the channel water loss simultaneously. The average channel water losses estimated as 36.8 % with 7.1 % of the conveyance loss and 29.7 % of distribution loss respectively. The distribution loss seems to be related to total number of rainy days, and irrigation schedules, while the conveyance loss was caused by irrigation channel aging conditions and illegal intake problems. In order to achieve sustainable agricultural water resources, the channel water loss needs to be reduced through the restoration of aged irrigation facilities and effective water managements in the fields.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.507-510
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• 2003

This paper presents a novel prototype of tile three-phase bridge power block module type a auxiliary resonant AC link snubber circuit, which is effectively used for the three-phase voltage source type sinewave soft switching PWM inverter using IGBTs. Its operating principle Is described for current source load model, along with its practical design approach based on the simulation data. The performance evaluation of the three-phase voltage source type snewave soft switching PWM inverter incorporating a single three-phase bridge mo여le of active auxiliary resonant AC link snubber treated here Is illustrated, which is concerned with power duality efficiency power loss analysis. This inverter is discussed as compared with those of tile three-phase voltage source type sinewave hard switching PWM inverter. The power loss analysis of this soft switching PWM Inverter using IGBT power modules is evaluated on the basis of the measured v-i characteristics and switching power losses of IGBT, and antiparaliel diodes. The practical effectiveness of this inverter is proven by the power loss analysis for distributed power supply.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.4
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• pp.337-343
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• 2015

The multi-level inverters are highly efficient for high-power and medium-voltage AC driving applications, such as high-speed railway systems and renewable energy resources, because such inverters generate lower total harmonic distortion (THD) and electromagnetic interface (EMI). Lower switching stress occurs on switching devices compared with conventional two-level inverters. Depending on the multi-level inverter topology, the required components and number of switching devices are different, influencing the overall efficiency. Comparative studies of multi-level inverters based on loss analysis and output characteristic are necessary to apply multi-level inverters in high-power AC conversion systems. This paper proposes a theoretical loss analysis method based on piecewise linearization of characteristic curves of power semiconductor devices as well as loss analysis and output performance comparison of five-level neutral-point clamped, flying capacitor inverters, and high-level cascaded H-bridge multi-level inverters.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.12 no.2
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• pp.140-144
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• 2001

Backgrounds & Objectives : Prolonged hearing loss was considered as one of the factors which have the potential to cause vocal changes. However, the analysis of quality of phonation in hearing loss patients has not been achieved enough. The purpose of the study was to evaluate the difference in objective acoustic parameters between long-term hearing impaired patients and normal control group. Material & Methods : The material of this investigation comprised a group of 20 patients (M : F=10 : 10) with moderate or profound hearing loss(over 50dB). The duration of all hearing loss was over 1 year. All of them underwent the acoustic examinations comprising electroglottography, multidimensional voice program and formant analysis during phonation of the bowels /a/ with free confortable tone and /i/ with voluntary high tone. The results of the acoustic examinations were compared with those of a control group, composed of 20 sex- and age-matched normal hearing subjects. Results : In the male hearing loss subjects, the significant increase was detected in pitch and shimmer during phonation of /a/ and in pitch during phonation of /i/. In addition, this group was characterized by decreased fundamental frequency during phonation of /i/. In female, there was no difference between hearing loss group and normal control group except a decreased formant 1 frequency. Conclusion : Long-term moderate and profound sensorineural hearing loss could affect the objective voice parameters.

• Progress in Medical Physics
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• v.9 no.4
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• pp.217-225
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• 1998

In this paper, the analysis of the relation between noise induced hearing loss and noise exposure is described for the A-weighted noise levels and exposure duration. The hearing loss and sensitivity threshold shift is investigated by changing the various parameters such as the effects of aging and noise exposure. Total hearing loss is proportional to a function of exposure level based upon the integral of pressure with time. If the noise exposure term is large so that the presbycusis may be neglected, the hearing loss due to aging and noise exposure becomes the noise induced hearing loss. It is shown that exposure to excessive noise can cause temporary loss of hearing that may become permanent if the exposure is prolonged or intense. An audiogram taken from a person suffering from noise induced hearing loss will usually show the greatest loss of hearing sensitivity in the 4kHz region, which is typically the region most sensitive to damage resulting from many types of industrial noise.

• Journal of the Korean Institute of Landscape Architecture
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• v.24 no.3
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• pp.115-132
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• 1996

The purpose of this study is to estimate the soil loss amount with Geographic Information System according to the land use change of Buju mountain area in Mokpo city. To estimate the soil loss, Universal Soil Loss Equation which is the most proper technique to predict soil loss in this site condition is adopted and IDRISI, a raster GIS software, is used. GIS application with USLE is very efficient to estimate soil loss accurately and fastly. In order to decide value and to find application method of USLE factors, we used existing rainfall erosion index, soil erodibility analysis, slope length, slope steepness, vegetation management and practices, which are rated by GIS through the analysis of various studies related USLE. The result of this study was compared with the previous other researches to verify our method of constructing numerical data of USLE's factors. The result of verification of our way showed significance for the soil loss in forest area. But the result of verification for the soil loss in forest area. But the result of verification for the soil loss of cultivated area showed some errors. It seems that this result was due to local variation of topographical map.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.136-148
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• 1997

The present study has been carried out to develop a computational procedure for the analysis of the off-design performance in centrifugal compressors with vaneless diffusers by integrating empirical loss models and analytical equations. Losses in centrifugal compressors stem from a number of sources and their exact calculation is not yet possible. This study investigates several modeling schemes and shows that a fairly good prediction can be achieved by a proper selection of the most important flow parameters resulting form a meanline one-dimensional analysis. The performance maps for compressors are calculated and compared with measured performance maps. The off-design performance characteristics in terms of the pressure ratio vs. mass flow produced have generally correct forms. However, no universal means have been found to predict accurately the onset of surge. The prediction method developed through this study can serve as a tool to ensure good matching between parts and it can assist the understanding of the operational characteristics of general purpose centrifugal compressors.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.2
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• pp.115-118
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• 2020

As interest in the reduction of energy loss has increased in recent years, analysis of losses in power cables is becoming more important. The overall loss in the transmission system can be measured, but there are many difficulties in researching the loss in each internal structure. There are various factors in the type of loss, and the loss of external factors by previous research has been studied. However, there is little research on the cable internal loss. Since the metal sheath inside the cable is made of aluminum having a high conductivity, an eddy current is generated due to the current flowing in the conductor, thereby causing an eddy current loss inevitably. In this paper, the eddy current loss in metal sheath of 154 kV Cable was researched through FEM (Finite Element Method) electromagnetic analysis.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.122-125
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• 2004

This paper presents the loss analysis comparison for Three-Level Converter and Full-Bridge converter. The result of the analysis is verified with 2.5kW prototype.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.247-250
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• 2015

The characteristics of opposed nonpremixed tubular flames with radiation heat loss are investigated using linear stability analysis and 2-D numerical simulations. Two extinction limits, as the $Damk{\ddot{o}}hler$ number is small or large, are confirmed using finite difference method with a simple continuation method. It is verified that the results of linear stability analysis predict the number of flame cells and the critical Da starting cellular instability or amplification of temperature near both extinction limits with good resolution.