• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1997.12a
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• pp.255-262
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• 1997

A low-cost and precise metering device, which is suitable to automatic mixing of nutrient-solution for hydroponic culture, was developed for small-scale growers. The metering device was composed of three parts those were supply pumps, metering cylinders and venturi tube. Those parts were controlled by personal computer with time-based odoff control method. To verify the performance of the developed metering device, the relationship between operating time and discharge was examined and the accuracy of the developed metering device was compared with commercial metering pumps. The results of this study are as follows. 1. The correlation coefficient between the flow rate and operating time was 0.9999, and the linear regression equation computed was y=21.759x, where y is the discharge(g) and x is the operating time(s). 2. The developed device has greater accuracy than commercial metering pumps in terms of the full-scale error. Calculated errors for the developed metering device and two commercial pump were $\pm$0.3 %, $\pm$2.45 % and $\pm$1.38 % respectively. 3. Above results show developed metering device is a useful tool for nutrient-solution control system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.1
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• pp.12-21
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• 2010

This paper focuses on the hover performance experiment of a small-scale single rotor in partial ground conditions. In this study, small-scale rotor blade rotating device and floor panel are used to include partial ground effect. Thrust and torque were measured with varying collective pitch angles at fixed rotor rotating speed. The overlap distance between rotor and ground is d, the rotor diameter is D. It was shown that the ground effects have little effect on the rotor performance until d/D is 0.25. Four blade rotor has more increased thrust and more reduced power than those of two blade rotor because of stronger ground effect. In addition, it was also found that the thrust increases as a collective pitch angle become smaller. Based on these experiment results, we deduced new empirical equation considered blade number and partial ground effect.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.631-634
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• 2001

This paper presents a maximum power point tracking without a current sensor for a small scale photovoltaic power system. The small scale photovoltaic power systems are used in parallel, and so the cost and the reliability are strongly demanded. In the proposed inverter, the current is controlled with open loop, and then the power of photovoltaic array is calculated by the equation using the voltage of the photovoltaic array. Therefore, the system can obtain the power by detecting only the voltage of the photovoltaic array. As a result, we may obtain the performance of the MPPT with a current sensor as well as with a current sensor.

• Korean Journal of Occupational Health Nursing
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• v.8 no.2
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• pp.169-175
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• 1999

The study was purposed to know the status of health management in small-scale-industries which have less than 50 employees. A total of 330 small-scale-industries were surveyed by nurses and industrial-hygienists who were affiliated with industrial health care agency from January, 1993 to December, 1994. The contents of survey include status of work environment, occupational accident and its disease availability, protective evice, health education and settlements. The results were as follows: 1. The number of industrial accidents(death, injury arid occup. disease) in 1994 was 83 which was reduced from that of the 1993 which was 126. 2. As a result of the measurement of work environment the excessive ratio of permitted criteria was reduced to 20.6% in 1994 from 264% in 1993, and the improvement ratio of work environment was increased to 39.5% in 1994 from 29.7% in 1993. 3. The contents of health education at work place were as follows: general disease(25.4%), work environment(20.2%), protective device(16.7%), disease prevension(14.2%), occupational disease(85%), and health promotion(8.3%). 4. In terms of industrial safty and prevention of occupational disease, only 10.6% was satisfactory or excellent, and the 89.4% was poor, inadequate or required reexamination.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1778-1783
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• 2000

When visual intrusion is an important factor, it is desirable to find alternative methods of improving the insertion loss of a noise barrier without increasing the height. Therefore, the primary object of the work attenuates the noise due to transport vehicle by small interference device installed at noise barrier edge. In this paper the performance of noise barriers with attached interference device, in terms of shape, absorptive material and split panel, are examined using the boundary element approach. Also, the scale models are moanted in an anechoic chamber and the frequency of the sound sources are appropriately scaled to simulate full scale site conditions. Lastly, experimental measurements of the designs are executed for a range of frequencies and receiver positions, and are compared with the results of numerical modeling.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.537-542
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• 2000

When visual intrusion Is an Important factor, it is desirable to find alternative methods of Improving the insertion loss of a noise barrier without Increasing the height. Therefore, the primary object of the work attenuate the noise due to railway by small interference device installed at noise barrier edge. In this paper the performance of noise barriers with attached interference device, in terms of shape, absorptive material and split panel, we examined using the boundary element approach. Also, the scale models are mounted in an anechoic chamber and the frequency of the sound sources are appropriately scaled to simulate full scale site conditions. Lastly, experimental measurements of the designs are executed for a range of frequencies and receiver positions, and are compared with the results of numerical modeling.

• Journal of the Regional Association of Architectural Institute of Korea
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• v.20 no.6
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• pp.105-112
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• 2018

The purpose of this study is to develop an application that supports a user in the maintenance of small photovoltaic device. To this end, this study analyzed the maintenance status, related regulations and existing application contents in Korea. According to the analysis results, most users did not maintain device for themselves. In addition, the maintenance market has not been activated due to its low profitability. Regulations on the maintenance of photovoltaic device prescribed by the KESCO and Japanese counterpart were analyzed to establish the standards for photovoltaic device inspection, and an application was developed based on the existing applications and research results. In order to evaluate the completeness and satisfaction of the developed application, it surveyed 52 users and 22 experts. The survey results showed that the completeness was calculated to be 90 points, and the level of satisfaction was 93 points on a 100-point scale. Therefore, it is expected that the maintenance application developed in this study will be useful for users to maintain the photovoltaic device.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.975-983
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• 2009

This paper presents the work being carried out in order to deduce hover performance of a small-scale single rotor blade as a preliminary study of a small coaxial rotor helicopter development. As an initial research, a test stand capable of measuring thrust and torque of a small-scale rotor blade in hover state was constructed and fabricated. The test stand consists of three parts; a rotating device, a load measuring sensor and a data acquisition system. Thrust and torque were measured with varying collective pitch angle at fixed RPM. Through this research, hover performance tests were conducted for a small-scale single rotor blade operating in low Reynolds number ($Re\;{\approx}3{\times}10^5$), as well as for verifying the test stand itself for acquiring hover performance.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.161-162
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• 2008

• Journal of the Korean Institute of Rural Architecture
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• v.21 no.3
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• pp.17-24
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• 2019

This study aimed to develop a mobile separating and sorting device for discharge sites to separate and sort mixed construction waste generated in small and medium scale in small provincial cities into inorganic materials and combustible materials. The study results can be summarized as follows: 1) As a result of analyzing the existing domestic technology for the separating and sorting mixed construction waste, a device sorting the waste by fusing the vibration screen, disc screen, air blowing methods and the separating and sorting the combustible waste is applied in Korea. 2) In foreign countries, the air blowing, screen, gravity sorters are used for separating and sorting combustible waste in the same way as in Korea. Especially German T Company suggests a construction waste separating and sorting system using an optical sorter. 3) As for the test device for separating and sorting mixed construction waste to be buried in landfill, the processing capacity was set as 16 tons per day. 4) For separating and sorting inorganic materials by granularity, this study set a trommel with two types of diameter as a basic. To operate the mobile all-in-one system, the device is designed to locate a conveyor, a combustible waste conveying device, inside of the trommel. 5) The device is designed in a mobile mode under the concept of primary separating and sorting device, and it can be transported using a 2.5-ton truck minimum. The diameter and length of the trommel are designed to be within 1500mm and 3000mm, respectively. In a further study, an optimized separating and sorting technology is planned to be presented through an experimental study for processing efficiency analysis at the mixed construction waste site by manufacturing the pilot experiment facility reflecting the design elements in the result of this study.