• Journal of Forest and Environmental Science
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• 제27권2호
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• pp.113-118
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• 2011

This study was carried out to analyze annual diameter growth characteristics for major 11 tree species using the data for Gangwon province of the National Forest Resources Inventory in 2007. The annual diameter growth of coniferous species was 5.02 mm, 4.70 mm, and 3.90 mm in Korean white pine, Japanese larch, and Korean red pine, respectively. In growths of the deciduous trees, dogwood, basswood, and cork oak had 3.55 mm, 3.48 mm and 3.01 mm, respectively. Average of the annual diameter growths for all species was 3.38 mm. The relationship between diameter growth and age class showed that the growth rate decreased for all species as age increased. The age class II had the highest annual diameter rate. In relation of the stand density(trees per hectare) and diameter growth, the diameter growth tended to decrease as the stand density increased for most species, especially Korean white pine, cork oak, and basswood. Finally age had the highest value in the correlation coefficients between measurement factor and growth rate regardless of species.

• 대한기계학회논문집B
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• 제24권7호
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• pp.957-966
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• 2000

The effect of rotation on the discharge coefficient of orifices with various length-to-diameter ratios and two different inlet corner radii was studied. Length-to-diameter ratios of the orifices range from 0.2 to 10, while the inlet shapes are square edged, or round edges of radius-to-diameter ratio of 0.5. From the experiment, we found that rotational discharge coefficient and Rotation number, when based on ideal exit velocity of the orifice considering momentum transfer from the rotor, describe the effect of rotation very well. In this study, the discharge coefficients of rotating orifices are shown to behave similar to those of the well-known non-rotating orifices. For both rotating and non-rotating orifices, the discharge coefficients increase with the length-to-diameter ratio until a maximum is reached. The flow reattachments in the relatively short orifices are responsible for the increase. The coefficient then decreases with the length-to-diameter ratio due to the friction loss along the orifice bore. The length-to-diameter ratio that yields maximum discharge coefficient, however, increases with the Rotation number because the increased flow-approaching angle requires larger length-to-diameter ratio for complete reattachment. The length-to-diameter ratio for complete reattachment is shorter for round edged orifices than that of square edged orifices by about a unit length-to-diameter ratio.

• 한국연소학회지
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• 제21권4호
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• pp.16-22
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• 2016

Pressure and temperature variations in a shock tube have been studied numerically by changing the diameter ratio of a driven part to a driver part. There are five cases where the adopted diameter ratios are 40%, 50%, 60%, 80%, and 100% respectively. The diameter of the driver part remains unchanged meanwhile the shock tube driven part diameter increases from 40% to 100% of the driver part. In the 100% ratio case, the driver part and driven parts have the same diameter of 66.9 mm. As the diameter ratio decreases, the pressure in the shock tube and available test time are increased.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 총회 및 춘계학술발표회
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• pp.213-217
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• 2004

Laboratory scale study for an area of influence and flowing aspect of groundwater saturated zone was conducted for three sediment grains. On the AMG(Average Modal diameter Grains) 0.34, 1.38, 3.89mm diameter samples, the affected area of the aquifer were 15.2, 37.0, 30.0%/m2 each. Air flow for AMG 0.34mm diameter grain size provides indication of pattern of channelized air flow in saturated zone and expansion state in above saturated zone. For AMG of 1.38, 3.89mm diameter grains, air flow are pervasive air flow, forming a symmetrical cone of influence around the injection point. And also AMG 1.38, 3.89mm diameter samples show onset of collapse and approach to steady state in above saturated zone, respectively. In this study, optimal sites for in situ air sparging, may be grain diameters between about AMC 1.5～2.5mm diameter.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
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• pp.134-139
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• 2000

Evaporating heat transfer characteristics of R-22 were measured inside smooth horizontal copper tubes with inner diameters of 3.36 mm and 5.35 mm respectively. The experiments were conducted in the closed loop which was driven by a magnetic gear pump. Experiments were performed for the following range of variables ; mass velocity of refrigerants (200 to 400 $kg/m^2$ .s) saturation temperature ($0^{\circ}C, \; 5^{\circC$}) and quality (0 to 1.0) The main results obtained are as follows : Evaporating heat transfer coefficients in the small diameter tubes (ID<7 mm) were observed to be strongly affected by a variety of diameters and to differ from those in the large diameter tubes. The heat transfer coefficients of the small diameter tubes are higher than those of the large diameter tubes. Comparing the heat transfer coefficients between experimental results and some well-known previous predictions (Shah's correlation Gungor-Winterton's and Kandlikar's correlation) it was very difficult to apply those to small diameter tubes.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.225-230
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• 2001

Small diameter drilling which take high precision in cutting work is needed more small hole and high speed working. Especially, small hole deep drilling is one of the most important machining types and its necessity and importance become more and more increasing in the whole field of industry. This paper shows the limit depths with small diameter drills using experimental analysis. The results are gained by tool dynamometer and Labview system and obtained during small diameter twist drilling system on SM45C steel for different machining conditions. The machine and tools are the CNC machining center and twist drill of diameter 1.5mm. And additionally, tool microscope show the relationship between shapes of chips and breakage shapes of small diameter drills.

• 한국안전학회지
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• 제13권4호
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• pp.9-18
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• 1998

The vortex tube is a simple device for separating a compressed gaseous fluid stream into two flows of high and low temperature without any chemical reactions. Recently, vortex tube is widely used to local cooler of industrial equipments and air supply system. The phenomena of energy separation through the vortex tube was investigated experimentally. This study is focused on the effect of the diameter of cold end orifice diameter on the energy separation. The experiment was carried out with various cold end orifice diameter ratio from 0.22 to 0.78 for different input pressure and cold air flow ratio. The experimental results were indicated that there are an optimum diameter of cold end orifice for the best cooling performance. The maximum cold air temperature difference was appeared when the diameter ratio of the cold end orifice was 0.5. The maximum cooling capacity was obtained when the diameter ratio of the cold end orifice was 0.6 and cold air flow ratio was 0.7.

• 한국농공학회지
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• 제17권3호
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• pp.3872-3877
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• 1975

This study was conducted to examine the effects of the change of cap hole diameter and pressure on the travelling distance and the sprayed particle size for the medium range nozzle. The results of this study are summarized as follows; 1) The effective travelling distance was about from 1 meter to 8 meters and centro-position of the travelling distance was about 3 or 5 meters. 2) Main effect of change of cap hole diameter for the travelling distance was a slight convex quadratic curve. 3) Main effect of change of pressure increased linearly, its increasing rate about 1.6 was large. 4) Sizes of sprayed particles were less than 250${\mu}$ generally and the sizes decreased according to the increasing of travelling distance. 5) Changes of diameter of sprayed particles by cap hole diameter increased in accordance with increasing of cap hole diameter. 6) Changes of diameter of sprayed particles by the groove depth of swirl plate was very slight.

• 한국연소학회지
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• 제1권1호
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• pp.41-49
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• 1996

Effects of ambient geometry on the liftoff characteristics are experimentally studied for nonpremixed turbulent jet flames. To clarify the inconsistency of the nozzle diameter effect on the liftoff height, the ambiences of finite and infinite domains are studied. For nonpremixed turbulent jet issuing from a straight nozzle to infinite domain, flame liftoff height increases linearly with nozzle exit mean velocity and is independent of nozzle diameter. With the circular plate installed on the upstream of nozzle exit, flame liftoff height is lower with plate at jet exit than without, but flame liftoff characteristics are similar to the case of infinite domain. For the confined jet having axisymmetric wall boundary, the ratio of the liftoff height and nozzle diameter is proportional to the nozzle exit mean velocity demonstrating the effect of the nozzle diameter on the liftoff height. The liftoff height increases with decreasing outer axisymmetric wall diameter. At blowout conditions, the blowout velocity decreases with decreasing outer axisymmetric wall diameter and liftoff heights at blowout are approximately 50 times of nozzle diameter.

• 한국전기전자재료학회논문지
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• 제26권2호
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• pp.87-91
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• 2013

Carbon-nanotube field-effect transistors (CNFETs) have drawn wide attention as one of the potential substitutes for metal-oxide-semiconductor field-effect transistors (MOSFETs) in the sub-10-nm era. Output characteristics of coaxially gated CNFETs were simulated using FETToy simulator to reveal the dependence of drain current on the nanotube diameter and gate oxide thickness. Nanotube diameter and gate oxide thickness employed in the simulation were 1.5, 3, and 6 nm. Simulation results show that drain current becomes large as the diameter of nanotube increases or insulator thickness decreases, and nanotube diameter affects the drain current more than the insulator thickness. An equation relating drain saturation current with nanotube diameter and insulator thickness is also proposed.