• The KSFM Journal of Fluid Machinery
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• v.18 no.5
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• pp.54-58
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• 2015

The objective of this paper is to investigate the flow characteristics of the multi nozzle. The configurations of the single, the 3- and the 6-nozzle were selected under Mach number of 2.5. Under-expanded pressure ratio such as 1.2, 1.6 and 2.0 were selected to elucidate interference of the free jet. The flow visualization was carried out with the Schlieren system and a supersonic cold-flow system. Also, the flow characteristics were studied computationally with the density measurements. Reasonable agreement between experimental and theoric equation has been achieved qualitatively.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.698-703
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• 2000

The characteristics of NOx emission in reburning process have been experimentally studied. The design point of burner is creative of three distinct reaction zones; a primary flame zone that NOx producted, reburn zone to reduce the primary zone NOx and burnout zone. Liquefied Petroleum Gas(LPG) was used as main and reburn fuels. Process parameters investigated included main/reburn fuel ratio, primary/secondary air ratio, reborn fuel injector position and different designed quarl. The NOx emission characteristic of aerodynamic designed burner relied on reborn fuel ratio and was slightly affected by a reburn fuel injector position and quarl shape.

• Journal of Environmental Impact Assessment
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• v.22 no.6
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• pp.695-703
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• 2013

Soil erosion and sediment delivery ratio(SDR) were estimated by using HSPF model in 3 tributaries of upper stream of Geum river-basin. Meteorological data and other input data were constructed from 2006 to 2011 year by the HSPF model. Flow and suspended solid results were relatively matched with the measurement data through the calibration and validation of the model. Soil erosion was proportional to the amount of rainfall and the area of watershed based on the results of model calibration and validation. SDR in Moojunamdea stream was the highest and one in Cho stream was the lowest. This was effected by the geographical characteristic. SDR was 17.6% Moojunamdea stream, 9.1% Cho stream and 13.2 % Bocheong stream. As the SDR was effected by watershed area and shape factor in this study area.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.1
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• pp.16-21
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• 2004

In order to investigate the characteristics of diamond wheel grinding of ceramic materials, grinding resistance, surface roughness of ground surface and image of grinding wheel were acquired using experimental method. Through the experiments, this makes it possible to observe grinding wheel behavior by grinding resistance, surface roughness and cutting edge ratio. In case of $Al_2O_3$, cutting edge ratio is bigger than that of $ZrO_2$ and $Si_3N_4$. That's because $Al_2O_3$ has a characteristic of low fracture toughness and bending stress.

• Transactions of Materials Processing
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• v.20 no.8
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• pp.575-580
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• 2011

Direct laser melting(DLM) is promising as a joining method for producing parts for automobiles, aerospace, marine and medical applications. An advantageous characteristic of DLM is that it affects the parent metal very little. The mechanical properties of parts made by DLM are strongly affected by the porosity and surface roughness of the laser melted beads. This is a systematic study of the effects of the porosity and surface roughness of laser melted beads using various processing parameters, such as laser power, scan rate and overlapping ratio of the fill spacing. The specimens were fabricated with 316L and 304L austenitic stainless steel powder. Dense parts with low porosity were obtained at low laser scan speed, as it increased the aspect ratio of the parental material and the depth of penetration. The variations of surface roughness were examined at various processing parameters such as overlapping ratio and laser power.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.3
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• pp.301-312
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• 2009

This paper presents a theoretical approach to calculate the resonant frequency of a thickness vibration mode in the radial direction for a 1-3 piezoelectric composite transducer of circular arch shape. For the composite transducer composed of a piezoelectric ceramic and a polymer, vibration parameters were derived according to the volume ratio of a ceramic, and a vibration characteristic equation was derived from the piezoelectric governing equations with adequate boundary conditions. The fundamental resonant frequencies were calculated numerically and verified by comparing them with those obtained from the finite element analysis and the experiment. The volume ratio and the thickness are more substantial than the curvature radius to determine the fundamental resonant characteristics, and the fundamental resonant frequency becomes higher for the larger volume ratio of the piezoelectric ceramic and for the smaller thickness.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.131-138
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• 2001

In this paper, performance of a dry CVT vehicle with torque cam is investigated. Based on belt transmission mechanism and torque cam actuator characteristics, an algorithm which is able to calculate the speed ratio from given thrust and load torque is suggested and a 3-D map is constructed for the speed ratio-thrust-torque. Using the 3-D map, a steady state characteristic of torque cam and a transient response of a dry CVT vehicle are investigated by simulation. It is found that initial spring compression plays a key role in determining the sliding criteria and the speed ratio velocity.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.215-219
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• 2004

In this study, Types of irrigation water development in islands district were classified. The types were reservior, fleshwater lake, pumped storage, etc. Most of islands district has delveloped reuse irrigation system as a pumped storage system. But. Irrigation water-reuse ratio doesn't define a basis clearly and the value of measurement for water-reuse ratio doesn't exist so far. so, we measured Irrigation water-reuse to clarify for water-reuse ratio in a pumped storage system. Also, we need to develop hydrologic analysis and water balance method with characteristic factor of islands district. that make use of plan about security of agriculture water efficiently in islands district.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.369-372
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• 1996

We prepared LiMn$_2$O$_4$ by reacting stoichiometric mixture of LiOH.$H_2O$ and MnO$_2$ (mole ratio 1 : 1) and heating at 80$0^{\circ}C$ for 24h, 36h, 48h, 60h and 70h. We obtained through X-ray diffraction that lattice parameter varied as function of heat treatment time. heated cathode active materials at 80$0^{\circ}C$ for 36h, (111)/(311) peak ratio was 0.37. It expected good charge/discharge characteristics. When (111)/(311) peak ratio was 0.37, it will be that crystal structure is farmed very well. In the result of charge/discharge test When heated at 80$0^{\circ}C$ for 36h, charge/discharge characteristic of LiMn$_2$O$_4$is the most property. It agree with our expectation.

• The Journal of Korean Medicine
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• v.29 no.5
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• pp.104-110
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• 2008

Objectives : The purpose of this study is to develop the method of selecting representative pulse wave. Methods : The pulse waves were acquired at the right and the left Guan point(關部) with 1420 people who were apparently healthy. The shape agreement of right and left pulse wave and the floating-sinking ratio were compared with three cases, which were the pulse height based method, the pulse area based method, and the pulse time based method. Results : In the point of the shape accordance, the pulse time based method was the best, and the pulse area based method was the worst. In the point of the floating-sinking ratio, the pulse height based method was the worst, and the pulse time based method was the best. Conclusions : So, the pulse time based method was recommended for selecting the representative pulse wave. This study compared the selection methods of representative pulse using the physiological characteristics of pulse wave. Further studies are required, because the representative pulse wave is the main factor of determining the shape and the floating-sinking characteristic of the pulse wave.