• Journal of Biosystems Engineering
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• v.15 no.1
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• pp.1-13
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• 1990

Aerodynamic property is the most important factor in designing the pneumatic separator and handling equipment for grains and seeds. Particularly the correct information about the terminal velocities of the corresponding grains and seeds is indispensible. However, a few studies with relation to the terminal velocities of grains and seeds were conducted in this country, even though the terminal velocities of the domestic grains and seeds are required to design those equiments which can be used for the domestic grains and seeds having specific aerodynamic properties. In this study, the terminal velocities for four varieties of varley and six varieties of paddy were investigated by means of two different methods, the suspension method and the drop method in an upward current of air. For measuring the terminal velocities, the vertical wind tunnel which had been examined about the uniform air flow in the previous study was used. In addition, the effect of the size of grains and the moisture content of grain kernel on the terminal velocity was examined. The following conclusions were derived from the study : 1. The different terminal velocities of grains are resulted from the different measuring methods. The terminal velocity measured by the drop method is smaller than that by the suspension method. It is considered that the difference in the terminal velocities is caused by the difference in the projection area of grain which is faced to the air stream. 2. The terminal velocity of grain increases as the size and the moisture content of the kernel increase. 3. The linear regression equations for the terminal velocities of grains were derived in terms of the moisture content of grains by the variety of grains and the measuring method. Also, the linear regression equations for the terminal velocity, based on the weighted size of grains, were derived in terms of the moisture contents of granis.

• Journal of Korean Physical Therapy Science
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• v.12 no.4
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• pp.79-87
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• 2005

The purposes of this study were to test the effects of the low power laser and exercise on the recovery in the cerebellar injured rats by 3-Acetylpyridine. Cerebellar injury was induced by 3-Acetylpyridine chemoablation of the inferior olive. Thirty Sprague-Dawley rats were assigned to the normal control and 3AP control and 3 experimental groups. Each experimental group was treated from 5 days after being injured for the 5 min(laser group), 10 min(exercise group) and 15min(exercise with laser) everyday during the 2 weeks. The Hindlimb splay test, Vestibular drop test, Hindlimb stride width test, Maximal Height Vertical Jump test were examined at pre-treatment on 1st day and 5th, 10th, 14th days after treatment on the cerebellar injured rats by 3AP. The results of this experiment were as follows; There were significantly increased exercise on the 3 experimental groups comparied with the 3AP control group, in the Hindlimb splay test, Vestibular drop test, Hindlimb stride width test, and Maximal Height Jump test(P<.05).

• Journal of Information Display
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• v.10 no.3
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• pp.111-116
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• 2009

In this paper, a plasma-assisted patterning method for the organic layers of organic light-emitting diodes (OLEDs) and its effect on the OLED performances are reported. Oxygen plasma was used to etch the organic layers, using the top electrode consisting of lithium fluoride and aluminum as an etching mask. Although the current flow at low voltages increased for the etched OLEDs, there was no significant degradation of the OLED efficiency and lifetime in comparison with the conventional OLEDs. Therefore, this method can be used to reduce the ohmic voltage drop along the common top electrodes by connecting the top electrode with highly conductive bus lines after the common organic layers on the bus lines are etched by plasma. To further analyze the current increase at low voltages, the plasma patterning effect on the OLED performance was investigated by changing the device sizes, especially in one direction, and by changing the etching depth in the vertical direction of the device. It was found that the current flow increase at low voltages was not proportional to the device sizes, indicating that the current flow increase does not come from the leakage current along the etched sides. In the etching depth experiment, the current flow at low voltages did not increase when the etching process was stopped in the middle of the hole transport layer. This means that the current flow increase at low voltages is closely related to the modification of the hole injection layer, and thus, to the modification of the interface between the hole injection layer and the bottom electrode.

• Journal of the Korean Institute of Gas
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• v.2 no.4
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• pp.53-59
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• 1998

Flow pattern of air-water two phase flow depends on the conditions of pressure drop, void fraction, and channel geometry. Drag reduction in the two phase flow can be applied to the transport of crude oil, phase change systems such as chemical reactor, pool and boiling flow, and to present cavitation which occurs in pump impellers. But the research on drag reduction in two phase flow is not intensively investigated. Therefore, experimental investigations have been carried out to analyze the drag reduction produced and void fraction by Co-polymer(A611p) addition in the two phase flow system. We find that the maximum point position of local void friction moves from the wall of the pipe to the center of the pipe when polymer concentration increases. Also we find that the polymer solution changes the characteristics of the two phase flow. And then we predict that it is closely related with the drag reduction.

• Computers and Concrete
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• v.22 no.1
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• pp.123-132
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• 2018

Reinforced concrete (RC) columns which are the main vertical structural members are exposed to several static and dynamic effects such as earthquake and wind. However, impact loading that is sudden impulsive dynamic one is the most effective loading type acting on the RC columns. Impact load is a kind of impulsive dynamic load which is ignored in the design process of RC columns like other structural members. The behavior of reinforced concrete columns under impact loading is an area of research that is still not well understood; however, work in this area continues to be motivated by a broad range of applications. Examples include reinforced concrete structures designed to resist accidental loading scenarios such as falling rock impact; vehicle or ship collisions with buildings, bridges, or offshore facilities; and structures that are used in high-threat or high-hazard applications, such as military fortification structures or nuclear facilities. In this study, free weight falling test setup is developed to investigate the behavior effects on RC columns under impact loading. For this purpose, eight RC column test specimens with 1/3 scale are manufactured. While drop height and mass of the striker are constant, application point of impact loading, stirrup spacing and concrete compression strength are the experimental variables. The time-history of the impact force, the accelerations of two points and the displacement of columns were measured. The crack patterns of RC columns are also observed. In the light of experimental results, low-velocity impact behavior of RC columns were determined and interpreted. Besides, the finite element models of RC columns are generated using ABAQUS software. It is found out that proposed finite element model could be used for evaluation of dynamic responses of RC columns subjected to low-velocity impact load.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1535-1548
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• 2004

Condensation heat transfer experiments were conducted with the oblong shell and plate heat exchanger without oil in a refrigerant loop using R-l34a, R-407C and R-410A. An experimental refrigerant loop has been developed to measure the condensation heat transfer coefficient h$_{r}$ and frictional pressure drop $\Delta$p$_{f}$ of the various refrigerants in a vertical oblong shell and plate heat exchanger. The effects of the refrigerant mass flux(40∼80kg/$m^2$s), average heat flux(4∼8kW/$m^2$), refrigerant saturation temperature(30∼4$0^{\circ}C$) and vapor quality of refrigerants on the measured data were explored in detail. Similar to the case of a plate heat exchanger, even at a very low Reynolds number, the flow in the oblong shell and plate heat exchanger remains turbulent. A comparison of the performance of the various refrigerants revealed that R-410A had the highest heat transfer performance followed by R-l34a, and R-407C had the lowest performance of the refrigerants tested. The pressure drops were also reported in this paper. The pressure drops for R-410A were approximately 45% lower than those of R-l34a. R-407C had 30% lower pressure drops than R-l34a. Experimental results were compared with several correlations which predicted condensation heat transfer coefficients and frictional pressure drops. Comparison with the experimental data showed that the previously proposed correlations gave unsatisfactory results. Based on the present data, empirical correlations of the condensation heat transfer coefficient and the friction factor were proposed.tor were proposed.sed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.1
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• pp.13-20
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• 2000

In this paper, we demonstrated an analytical description method of forward votage drop and reverse leakage current of the junction barrier controlled schottky rectifier with linearly graded junction and abrupt junction models. In this case, the vertical depths of device are 1[${\mu}{\textrm}{m}$] and 2[${\mu}{\textrm}{m}$], respectively. Through ion implantation and annealing process, we obtain the data of lateral and depth from implanted 2-dimensional profiles. Also we applied these data to models that indicate the change of depletion each on linearly-graded and abrupt juction as the forward and revers bias. After applied depletion changes to electric characteristics of JBS rectifiers, we calculated the forward I-V, the reverse leakage current and temperatures vs. power dissipations according to each junction. When we compared the rectifier with calculated and measured data, from the calculated results, forward votage drop with linearly graded junction is lower than that of abrupt junction and reverse leakage current with linearly graded junction is lower(≒1$\times$10\ulcorner times) than that of abrupt junction. Also, the power dissipations according to different juction depth(1[${\mu}{\textrm}{m}$], 2[${\mu}{\textrm}{m}$]) of device are calculated. Seeing the calculated results, we confirmed it from analytic model that the rectifier with linearly graded junction retained a low power dissipation up to 600[$^{\circ}C$] in comparison with the rectifier with abrupt junction.

• Korean Journal of Applied Biomechanics
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• v.16 no.1
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• pp.65-79
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• 2006

The purpose of this study was firstly to investigate correctional function of custom semi-rigid foot orthotics for excessively pronated people during gait by observing comfort, navicular movement and leg muscles' activity according to short-term and mid-term wearing duration and secondly to understand positive and/or negative point of view of a recently proposed paradigm related to foot orthotics more profoundly. Sixteen subjects who showed excessive pronation at navicular drop test were recruited for this study. Custom semi-rigid foot orthotics were made fitting for foot characteristics of the subjects by podiatry division of Otto Bock Korea company. While wearing the foot orthotics for two months, comfort of wearing were questioned and vertical navicular movement and electromyography of leg muscles during gait were measured at the condition of both immediately after and 2 months after including a control condition, respectively. The subjects were required to walk on a treadmill at the speed of 1.5m/s and four digital video camera filmed the movement of navicular process at the speed of 60 frames/s. In conclusion, in excessively pronated group continuous increase of comfort from short-term to mid-term wearing of custom foot orthotics is assumed to be closely related with short-term and mid term correctional action, of which are consisted the decrease of the range of navicular drop and navicular raisins- the faster timing of minimum navicular position occurring, and the decrease of leg muscles' activities. This conclusion could lead to positively accept new paradigm related to foot orthotics suggested by Nigg and the author suggest that in the future study the variable which could observe navicular movement would be one of major variables to study preferred path of skeleton in the paradigm.

• Journal of Biomedical Engineering Research
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• v.17 no.1
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• pp.85-92
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• 1996

A monoleaflet polymer artificial heart valve which showed the remarkable improvement in pressure drop compared with other types of artificial valve was designed to minimize the deflection in vertical direction and the displacement of the valve tip in horizontal direction obtained by using finite element method as the location of the supporting members of the valve frame changed stress distribution change was also studied on each model generated by changing the distance between the frame and supporting members. It was found that by using the valve tip horizontal displacement the minimum valve thickness could be obtained in order to prevent the gap between the valve tip and the frame wall.

• Journal of Ocean Engineering and Technology
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• v.25 no.5
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• pp.15-20
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• 2011

This study carried out a series of experiments involving impact tests (Drop Weight type & Charpy type with a standard specimen and newly designed I-type specimen), hardness tests, and fracture surface observations of French-made roll shell steel (F), abnormal roll shell steel (M), reheated roll shell steel (R), and S25C steel under heat treatment conditiAn experimental study was carried out to study the solid-liquid mixture upward hydraulic transport of solid particles in vertical and inclined annuli with a rotating inner cylinder. The lift forces acting on a fluidized particle play a central role in many important applications such as the removal of drill cuttings in horizontal drill holes, sand transport in fractured reservoirs, sediment transport, the cleaning of particles from surfaces, etc. In this study a clear acrylic pipe was used to observe the movement of solid particles. Annular velocities varied from 0.4 to 1.2 m/s. The effect of the annulus inclination and drill pipe rotation on the carrying capacity of a drilling fluid, particle rising velocity, and pressure drop in a slim hole annulus were measured for fully-developed flows of water and aqueous solutions of CMC (sodium carboxymethyl cellulose) and bentonite. The rotation of the inner cylinder was efficient at carrying particles to some degree. For a higher particle volume concentration, the hydraulic pressure loss of the mixture flow increased because of the friction between the wall and solids or between solids.