• 한국농공학회논문집
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• 제60권2호
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• pp.103-110
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• 2018

Most of the intake facilities of small agricultural reservoirs are conduits and they are regarded as serious defects due to the structural weakness that penetrates the body of the dam, and countermeasures are needed. This study suggests the application method of siphon type water intake facility by hydraulic model test and physical scale model test of siphon type water intake facility which has high safety and easy maintenance. Experimental results show that sufficient flow rate can be secured for the purpose of intaking water according to the differential head between the reservoir and the discharge part, and the flow rate can be controlled by the valve. The negative pressure was -31.5 kPa, and vibration and noise did not occur during the operation of the siphon. The maximum flow velocity in the discharge outlet was 1.11 m/s which meets the criterion for irrigation canals. Therefore, scour risk would be very low. As a result of the inflow distribution experiment, even if the inflow part is separated by only about 0.8 m, the flow velocity is remarkably decreased, so that the clogging by debris would not appear. When the pump was operated only once for the first time and the inside of the siphon was filled with water, continuous operation was possible by only valve operation. The results of this study are expected to be used for the design guidelines of the water intake facilities and improve safety and maintenance convenience of agricultural reservoirs.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.372-378
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• 2018

Life management technology is required as the failure risk of aged power transformers increases. Asset management technology is developed to evaluate the remaining life, establish the replacement strategies, and decide the optimal investment based on the reliability and economy of power transformers. The remaining life assessment uses data such as installation, operation, maintenance, refurbishment, and failure of power transformers. The optimal investment also uses data such as maintenance, outage, and social costs. To develop the asset management system for power transformers, determining the degradation parameters related to the aging of power transformers and evaluating the condition of power transformers using these parameters are important. In this study, since 1983, 110,000 Dissolved Gas Analysis (DGA) data have been analyzed to determine the degradation parameters related to the aging of power transformers. The alarm rates of combustible gases ($H_2$, $C_2H_2$, $C_2H_4$, $CH_4$, and $C_2H_6$), TCG, CO, and $CO_2$ were analyzed. The end of life and failure rate (bathtub curve) of power transformers were also calculated based on the failure data from 1981 to 2014. The DGA gases related to discharge, overheating, and insulation degradation were determined based on alarm and failure rates. $C_2H_2$, $C_2H_6$, and $CO_2$ were discharge, oxidation, and insulation degradation parameters related to the aging of power transformers.

• 환경위생공학
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• 제11권1호
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• pp.9-15
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• 1996

The purpose of this study was to evaluate the decomposition efficiency of $NH_3$ odor gas using high frequency surface discharge body. The results from this study are as follows; 1, Voltage and frequency of electric elements have effects on removal of $NH_3$ odor. The higher these two elements were set up, the more efficiently deodorizing processing worked. In this experiment, the optimum voltage and frequency applicable were observed around AC 6.0 kVp-p and 24.0 kHz respectively. 2. The temperature, humidity and residence time were observed strong variables for NH$_3$ removal process. Its performance had limits at high temperature and humidity conditions. The longer the residence time continued, the more efficiently deodorization process worked. The experimental results showed that the deodorization was efficiently processed under such conditions as $30.0^{\circ}C$ in temperature, 60rh% in humidity and 0.3 sec in residence time. 3. It was observed that in deodorization experiment, $NH_3$ odor gas was perfectly decomposed under the concentration condition below 15.0ppm. Moreover it was considered as economic and practical in terms of maintenance cost when compared with other deodorization methods.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1487-1496
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• 2013

In this paper, a novel algorithm for PD localization in power transformers based on wavelet de-noising technique and energy criterion is proposed. Partial discharge is one of the main failures in power transformers. The localization of which could be very useful for maintenance systems. Acoustic signals due to a PD event are transient, irregular and non-repetitive. So wavelet transform is an efficient tool for this signal processing problem that gives a time-frequency demonstration. First, different wavelet based de-noising methods are analyzed. Then, a reasonable structure for threshold value determining and applying manner on signals is presented. Evaluated errors are good evidences for choices. Next, applying the elimination low energy frequency bands is discussed and developed as a de-noising method. Time differences between signals are used for PD localization. Different ways in time arrival detection are introduced and a novel approach in energy criterion method is presented. At the end, the quality of algorithm is verified through the different assays in lab.

• 전기학회논문지P
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• 제65권4호
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• pp.340-345
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• 2016

Railway vehicle battery is supplying the power required for the initial start-up of the train, in the event of a fault in the vehicle, or catenary for supplying emergency power is one of the components are very important. Currently, the railway vehicles such as nickel-cadmium batteries are being used [1,2]. Ni-Cd batteries as a battery installed in the railway vehicles have a strong corrosion resistance is included, The charge-discharge performance is significantly degraded in cold weather, there is a danger of deterioration or explosion. Train accidents have been caused a lot of damage due to rapid deterioration and cracking of the battery and memory due to the effect of Ni-Cd batteries. In order to solve the problems, There is no risk of degradation, deterioration and leakage, cracking and exploding. maintenance is simple and applied measures proposed to apply Lithium Polymer battery of high performance. In addition, the lack of capacity problems identified by testing the different special systems is replaced by a 70Ah lithium-polymer battery is possible without changing the batteries of 50Ah caused by installing additional equipment in existing older trains were applied to the vehicle.

• 조명전기설비학회논문지
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• 제26권12호
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• pp.37-43
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• 2012

UV-IR diagnostic technology is being used for predictive maintenance of high voltage equipment together with IR-thermography and ultrasonic devices. In this paper, the UV-IR camera design, fabrication, and perform a simple test to be take advantage of the diagnostic equipment. UV-IR camera developed a $6.4^{\circ}{\times}4.8^{\circ}$ of the field of view as a conventional camera to diagnose a wide range of slightly enlarged, and power equipment to measure the distance between the camera and the distance meter has been attached. In a distance of 5m with the UV-IR it is possible to detect partial discharge with a PD level of 2.5 pC and a RIV(Radio Influence Voltage) level of $3.6dB{\mu}V$.

• 한국농공학회논문집
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• 제54권4호
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• pp.29-38
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• 2012

Drip irrigation is a affordable irrigation under structured cultivation. Drip irrigation system with high uniformity can be achieved through effective design, maintenance and management of irrigation systems. Nevertheless the design guidelines have not been established for the drip irrigation system products in domestic and imported considering cultivation method and greenhouse environment in Korea. The objectives of this study were to evaluate the performance of drip irrigation system with uniformity through an experiment. The experiment was conducted to study with nine different types of emitters produced in domestic and imported. Hazen-Williams coefficients were also estimated for the drip emitter through hydraulic simulation for design use. It was found that approximately 91.5 % for 10 cm emitter spacing and 96.2 % for 30 cm emitter spacing of statistical uniformity were observed in respectively. Average emission uniformity was decreased as the reduction of emitter spacing. The results would be used in the drip irrigation system design and guideline construction.

• 수산해양교육연구
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• 제27권1호
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• pp.253-261
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• 2015

The chemical water quality and fish assemblage of Dong Stream to assessment of environmental improvement after discharge seawater were investigated from July to December 2013. BOD and DO were significantly different between before and after discharge seawater, while pH and SS did not significant. A total of 11 fish species, 218 individuals and 10,525.1g were collected. Dominant fish species were Mugil cephalus, Konosirus punctatus, Acanthogobius flavimanus and Leiognathus nuchalis which account for 77.5% of total individuals collected, and they were estuarian species. Peak number of species and individuals, and biomass occurred in September, whereas diversity index were highest in November. The water ecosystem of Dong Stream have been changed estuarian environment. As a result of stream assessment on water quality and ecosystem, water quality have been improved as 'III' grade. These results suggested that stream restoration policies such as drain pipes maintenance, management of pollution sources and riverbed dredging to improve environment and recover habitate of Dong Stream were need for set up and establishment of regular monitoring system.

• 한국환경과학회지
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• 제15권9호
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• pp.887-895
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• 2006

Through this research of the analysis on the frequency flood discharges regarding basin property factors, a linear regression system was introduced, and as a result, the item with the highest correlation with the frequency flood discharges from Nakdong river basin is the basin area, and the second highest is the average width of basin and the river length. The following results were obtained after looking at the multi correlation between the flood discharge and the collected basin property factors using the data from the established river maintenance master plan of the one hundred twenty-five rivers in the Nakdong river basin. The result of analysis on multivariate correlation between the flood discharges and the most basic data in determining the flood discharges as basin area, river length, basin slope, river slope, average width of basin, shape factor and probability precipitation showed more than 0.9 of correlation in terms of the multi correlation coefficient and more than 0.85 for the determination coefficient. The model which induced a regression system through multi correlation analysis using basin property factors is concluded to be a good reference in estimating the design flood discharge of unmeasured basin.

• 환경위생공학
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• 제7권2호
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• pp.37-52
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• 1992

Since the first sewage treatment plant was constructed in 1976, the sewerage systems of Korea have been rapidly expanded. As of the end of 1991, 22 sewage treatment plants with total capacity of 5.4 million tons/day are in operation which is equivalent of 3395 total daily sewage generation. Total extension of sewer 39.534 km in 1990 which is 55% of the target extension for the year 2001. However, the most sewage treatment plants employ activated sludge process which may not be suitable for medium and/or small scale plants. The poor existing sewer systems do not effectively collect and transport sewage to adversely affect the function of sewage treatment plant. To select the appropriate treatment system, the cities are classified into 3 categories such as large and medium size inland cities, small size cities and coastal cities. Considering the criteria suggested during this study, appropriate treatment processes were selected for each category. Conventional activated sludge process and step aeration process were found to be the most appropriate for big inland cities while biological nutrient removal processes should be considered for the cities discharge the effluent to lakes or reservoirs. RBC or Oxidation Ditch process might be appropriate for the medium size cities while several processes which do not require skilled operation and maintenance were suggested for the small cities. Ocean discharge after primary treatment can be considered for some east coast cities, Appropriate methodology to rehabilitate the existing sewers and strategy to convert combined sewer system to separate sewer system were proposed. This paper also include the appropriate management system for industrial wastewater, sludge and nightsoil.