Proceedings of the Korean Society of Propulsion Engineers Conference
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1999.10a
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pp.33-33
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1999
The Coanda effect is the tendency for a fluid jet to atach itself to an adjacent surface and follow its contour without causing an appreciable flow separation. The jet is pulled onto the surface by the low pressure region which develops as entrainment pumps fluid from the region between the jet and the surface. Then the jet is held to the wall surface by the resulting radial pressure gradient which balance the inertial resistance of the jet to turning. The jet may attach to the surface and may be deflected through more than 180 dog, when the radius of the Coanda surface is sufficiently large compared to the height of the exhaust nozzle. However, if the radius of curvature is small, the jet turns through a smaller angle, or may not attach to the surface at all. In general, the limitations in size and weight of a device will limit the radius of the deflection surface. Thus much effort has been paid to improve the jet deflection in a variety of engineering fields. The Coanda effect has long been applied to improve aerodynamic characteristics, such as the drag/lift ratio of flight body, the engine exhaust plume thrust vectoring, and the aerofoil/wing circulation control. During the energy crisis of the seventies, the Coanda jet was applied to reduce vehicle drag and led to drag reductions of as much as about 30% for a trailer configuration. Recently a variety of industrial applications are exploiting another characteristics of the Coanda jets, mainly the enhanced turbulence levels and entrainment compared with conventional jet flows. Various industrial burners and combustors are based upon this principle. If the curvature of the Coanda surface is too great or the operating pressure too high, the jet flow will break away completely from the surface. This could have catastrophic consequences for a burner or combustor. Detailed understanding of the Coanda jet flow is essential to refine the design to maximize the enhanced entrainment in these applications.
The fisheries industry has been changed drastically during the so - called Golden Growth Era of Korea. Recently, WTO/DDA agenda drove industries out of their safe refuges toward infinite competitions in the world. This paper aims at finding out distinguished features in the structural changes of fisheries since 70s. Furthermore, policy implications are investigated in order for the fisheries to survive in the outdoors. The paper consists of the following sections. First, we consider why and for what the structural change of fisheries in historical perspective should be investigated. And we introduce how we can approach to the goal in various aspects in the second section. In the third section, we examine the historical change of Korean fisheries in respect of national economy, resource allocation mechanism, industrial structure, and fisheries society. In the fourth section, we extract the development steps in fisheries from the periodic characteristics, using various methods of the above approaches. And we deduce the next step for Korean fisheries in the future. Finally, we conclude that there needs some turning point of fisheries policies in Korea, striving to foster the fisheries industry in the future. As results of empirical analysis in this paper, we find that fisheries industry in Korea has experienced some momentous changes during 30 years, using I/O data of B.O.K. The weight of fisheries sector in the whole economy of Korea increased during early 70s, initially leading the national economy to export - oriented engine for growth. But fisheries sector has shrunk rapidly since late 70s. Almost resources in Korea were allocated to expanding manufacturing industries. Further, fisheries industry has encountered perfect international competitions since the late 90s. This paper draws that fisheries industry in Korea will jump across to next step of qualitative growth in the future. Therefore, we recommend that the policies should be focused on enhancing the industrial competitiveness, switching quantitative growth to qualitative advance in fisheries.
Magazine of the Korean Society of Agricultural Engineers
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v.16
no.1
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pp.3293-3301
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1974
An experimental work was conducted by using a laboratory-made model dryer to investigate the effect of the rate of natural forced-air on the drying rate of rough rice which was deposited in the deep-bed. The dryer consisted of 8 cylinderical containers with grain holding screen at their bottoms, each of which having 30cm in diameter and 15cm in height. The containers were sacked vertically with keeping them air-tight by using paper tape during dryer operation. Two separate layers of containers were operated in the same time to have two replications. The moisture contents of grains within each bins after predetermined period of dryer operation were determined indirectly by measuring the weight of the individual containers. The air-rates were maintained at 6 levels, or 5, 8, 10, 15, 18 and 20 millimenters of static head of water. The roomair conditions during dryer operation were maintained in the range of 10-l5$^{\circ}C$ in temperature and 40-60% in relative humidity. The results of the study are summarized as follows: 1. Drying characteristics of the grains in the bottom layers were approximately the same regardless of airdelivery rates, giving the average drying rate as about 0.35 percent per hour after 40-hour drying period, during which moisture content (w. b.) reduced from 24 percent to about 10 percent. 2. After about 40-hour drying period, the mean drying rates increased from 0.163 percent per hour to 0.263 percent per hour as air-flow rates increased from 5mm to 87.16mm of static head of water. In the same time, the moisture differences of grains between lower and upper layers varied from 12.7 percent at the air rate of 5mm of water head to 7.5 percent at the air-flow rate of 20mn of water head. Thus, the greater the air-flow rate was, the more overall improvement in drying performance was. Additionally, from the result of ineffectiveness of drying grain positioned at 70cm depth or above by the air rate of 5mm of static head of water it may be suggested in practical application that the height of grain deposit would be maintained adequately within the limits of air-rates that may be actually delivered. 3. Drying after layer-turning operation was continued for about 30 hours to test the effectiveness of reducing moisture differences in the thick layers. As a result of this layer-turning operation, moisture distribution through layers approached to narrow ranges, giving the moisture range as about 7 percent at air-flow rate of 5mm head of water, about 3 percent at 10mm head about 2 percent at 15mm head, and less than 1 percent at 20mm head. In addition, from the desirable results that drying rate was rapid in the lower layers and dully in the upper layers, layer-turning operation may be very effective in natural air drying with deep-layer grain deposit, especially when the forced air was kept in low rate. 4. Even though the high rate of air delivery is very desirable for deep-layer natural-air drying of rough rice, it can be happened that the required air delivery rate could not be attained because of limitation of power source available on farms. To give a guide line for the practical application, the power required to perform the drying with the specified air rate was analyzed for different sizes of drying bin and is given in Table (5). If a farmer selects a motor of which size is 1 or {{{{1 { 1} over {2 } }}}} H.P. and air-delivery rate which ranges from 8~10mm of head, the diameter of grain bin may be suggested to choose about 2.4m, also power tiller or other moderate size of prime motor may be recommended when the diameter of grain bin is about 5.0m or more for about 120cm grain deposit.
Journal of the Korea Academia-Industrial cooperation Society
/
v.19
no.4
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pp.571-577
/
2018
A gyratory compactor was developed to reflect the field compaction roller, which is commonly used in road construction. Unlike the compaction of the proctor using a conventional impact load, the gyratory compactor simulated the field roller compaction characteristics using the compressive force by the roller weight and the shear force through the rotation of a roller. The purpose of this study was to evaluate the shear stress and density change characteristics during compaction, which are difficult to obtain in the existing compaction process of the proctor, and to utilize it as a basic data for road design. The compaction characteristics of sand and subgrade soils were also analyzed and evaluated using the gyratory compactor. The compaction characteristics obtained using the gyratory compaction are basically the number of gyrations, height of the specimen, compaction density, void ratio, degree of saturation, and shear stress. As the number of gyrations increased, the height of the specimen decreased, the compaction density increased, the void ratio decreased, the degree of saturation increased, and the shear stress tended to increase. The shear stress of the compacted specimens started at 200 kPa in the initial stage of compaction and increased to approximately 330 to 350 kPa at 50 gyrations. The compaction density, degree of saturation and shear stress tended to increase with increasing water content in the same specimens. Compaction using turning compaction has the advantage of measuring the physical properties required for road design, such as density and shear stress, so that more engineering road design will be possible if it is reflected in road design.
The Journal of the Institute of Internet, Broadcasting and Communication
/
v.15
no.1
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pp.179-186
/
2015
This paper proposes the target path detection algorithm using statistical characteristics of an activated time lag along a moving path of target from a neighboring sensor in PDR(Pulse Doppler Radar) sensor node environment based on USN(Ubiquitous Sensor Network) with a limitation detecting only an existence of moving target. In the proposed algorithm, detection and non-detection time lag obtained from the experimental data are used. The experimental data are through repetitive action of each 500 times about three path scenarios such as passing in between two sensors, moving parallel to two sensors, and turning through two sensors. From this experiments, error detection percentages of three path scenarios are 5.67%, 5.83%, and 7.17%, respectively. They show that the proposed algorithm can exactly detect a target path using the limited PDR sensor nodes.
This study was conducted to examine and compare the characteristics in the cognitive functions of peritoneal dialysis, hemodialysis and normal kidney function groups as basic data for effectively educating dialysis patients. The data were collected from May 10 to October 30. 2000, collected from each of 20 patients with peritoneal dialysis, hemodialysis and normal Kidney function and who registered for the dialysis room at a general hospital affiliated to a university in Seoul and sampled by age and educational level through personal interviews with the researchers of this study. As a measuring tool, MMSE developed by Folstein et al.(1975) to measure cognitive function disorder was used, slightly revised for hemodialysis patients. Collected data were processed into frequency, percentage, mean, and standard deviation by the use of SAS. The results of this study are as follows : 1. With a maximum of 30 points for cognitive function, the mean of the peritoneal dialysis patients was $27.06{\pm}2.06$, while that of the hemodialysis patients was $27.25{\pm}2.76$; that of the normal Kidney function patients was $27.85{\pm}2.00$, indicating no significant difference among those three groups. 2. As for the subjects who scored 23 points, the turning point of confirming the cognitive disorder, the percentage was 5% in the case of the peritoneal dialysis, 10% in the case of the hemodialysis and 5% in the case of the normal Kidney function group. 3. Differences between the peritoneal dialysis and hemodialysis patients by gender, occupation, spouse, diabetes, hypertension, the period of dialysis, number of hospitalizations, and the use of erythropoietin were not significant in the scoring of cognitive function. 4. There was no significant correlation between the level of Hb, Hct, albumin, aluminium, PTH, BUN, Cr, dialysis adequacy and the cognitive function. Considering such results, it is clear that there is no significant difference in the cognitive functions of the sampled subjects. Therefore, the nurse in the dialysis room should continually carry out assessment and intervention against elements degrading the effect of patients' education to improve self- care.
Fungicide-resistant Alternaria alternata impede the practical control of the Alternaria diseases in crop fields. This study aimed to investigate cytological fungicide resistance mechanisms of A. alternata against dicarboximide fungicide iprodione. A. alternata isolated from cactus brown spot was cultured on potato-dextrose agar (PDA) with or without iprodione, and the fungal cultures with different growth characteristics from no, initial and full growth were observed by light and electron microscopy. Mycelia began to grow from one day after incubation (DAI) and continued to be in full growth (control-growth, Con-G) on PDA without fungicide, while on PDA with iprodione, no fungal growth (iprodione-no growth, Ipr-N) occurred for the first 3 DAI, but once the initial growth (iprodione-initial growth, Ipr-I) began at 4-5 DAI, the colonies grew and expanded continuously to be in full growth (iprodione-growth, Ipr-G), suggesting Ipr-I may be a turning moment of the morphogenetic changes resisting fungicidal toxicity. Con-G formed multicellular conidia with cell walls and septa and intact dense cytoplasm. In Ipr-N, fungal sporulation was inhibited by forming mostly undeveloped unicellular conidia with degraded and necrotic cytoplasm. However, in Ipr-I, conspicuous cellular changes occurred during sporulation by forming multicellular conidia with double layered (thickened) cell walls and accumulation of proliferated lipid bodies in the conidial cytoplasm, which may inhibit the penetration of the fungicide into conidial cells, reducing fungicide-associated toxicity, and may be utilized as energy and nutritional sources, respectively, for the further fungal growth to form mature colonies as in Ipr-G that formed multicellular conidia with cell walls and intact cytoplasm with lipid bodies as in Con-G.
We try to analyse the localization phenomenon of a lightwave in random media by means of considering the solution of the propagation equation on a transmission line in which the propagation constants are randomly distributed. Lightwave localization is generated at the turning point where the solution is changed suddenly from an increase to a decrease. First, in order to investigate the changing process of the solution, we have derived the approximated one-dimensional Schrodinger equation from the two-dimensional wave equation by using the Brags condition. Considering the many types of solutions of the wave equation, we have investigated the conditions that allow the solutions to exist. Also, we have investigated the relationships between the localization of the solution and the variation of the propagation constant. In case of the exponential solution, we know that the permittivity $\varepsilon$=(0,0$\varepsilon$$_{0}$) is a very important parameter to influence the phase of the lightwave and to generate the localization.
The purpose of this study is to examine the characteristics of man's boots in the Joseon Dynasty and compared them with those of the Ming and Qing Dynasty to find the influential relationships between them. Boots in the Joseon Dynasty are divided into several kinds such as Heukgwejapihwa, Hheuksapihwa(黑斜皮靴), Heukpihwa(黑皮靴), Mokhwa(木靴), Hyeopgeumhwa(挾金靴), Suhwaja (水靴子), Jeonpihwa, Gijahwa(起子靴), and Baekhwa(白靴). In addition, Jeong(精: footwear) was put inside boots. They tend to be named according to their materials or ornaments on them. First, Jeong put inside the boots is regarded as footwear for the comfort of the feet or protection against cold. Mokhwa appears in literature around the 19th century. As shown by remains and paintings of those days, it is considered to have become the common name of boots as it underwent many changes. On the other hand, a book in the era of King Gojong includes pictures of Suhwaja. Compared to Hukpihwa in the same book. The topside seems to have been raised in order to make the wearer who put on a military uniform feel comfortable when walking, since the bottom piece is hard. Baekhwa is worn not only with funeral garments but also with Sibok(時服), one of official uniforms. Boots in the Joseon Dynasty had been made following the design of the Ming Dynasty since official uniforms were conferred upon King Gongmin in the late Koryo Dynasty. But turning the late Joseon Dynasty its detailed design changed little by little. The topside of the boots became more round, the entrance part became wider, height of the shoes became taller, and the bottom piece became parallel to the ground.
Journal of the Korea Academia-Industrial cooperation Society
/
v.10
no.12
/
pp.3594-3599
/
2009
The train control system used in Gyeongbu-line is classified in ATC, IXL and CTC. The ATC data related to speed and space control for trains are transmitted from wayside to onboard by way of UM71 AF track circuits and BSP Loop. The information transferred by track circuits is composed of operation data which directly influence to the train operation and the information transferred by BSP Loop is used in the section which requires the additional data transmission about the particular track-side environment such as tunnel, hot box detector or insulated section. In this paper, for the BA type turning unit of the UM71 AF track circuits which is mainly used in the linking section of existing and high-speed lines from the opening of the Gyeongbu line till the present, we not only analyze the characteristics of BA but also compare and analyze baseline values and the measured values. With this analysis, we will be able to propose how to solve the problems about operation and maintenance such as track circuit malfunctions of the relevant sections.
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