• Journal of computational fluids engineering
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• v.19 no.2
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• pp.1-7
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• 2014

This study is to analyze the local convective heat transfer for a circular cylinder with annular fins. The relation between wall heat transfer and three-dimensional flow is investigated for different distances of annular fins. Depending on the fin spacing, the flow structure is strongly changed by the variation of horseshoe vortices. As the fin spacing increases, the heat transfer rate is maximized at a certain condition. This is clearly obtained as the Reynolds number increases, and it is closely related to the development of horseshoe vortices.

• Journal of computational fluids engineering
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• v.8 no.1
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• pp.8-15
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• 2003

Three-dimensional endwall flow within a linear cascade passage of high performance turbine blade is simulated with a 3-D Wavier-Stokes CFD code (MOSA3D), which is based on body-fitted coordinate system, pressure-correction and finite volume method. The endwall flow characteristics, including the development and generation of horseshoe vortex, passage vortex, etc. are clearly simulated, consistent with the generally known tendency. The effects of both turbulence model and convective differencing scheme on the prediction performance of endwall flow are systematically analyzed in the present paper. The convective scheme is found to have stronger effect than the turbulence model on the prediction performance of endwall flow. The present simulation result also indicates that the suction leg of the horseshoe vortex continues on the suction side until it reaches the trailing edge.

• Applied Microscopy
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• v.9 no.1
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• pp.21-34
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• 1979

The cyclic changes of the epithelium of seminiferous tubule in the Korean greater horseshoe bat (Rhinolophus ferrumequinum korai) were investigated by means of the light and electron microscopic observations and the following results were obtained. 1) The spermatogenic function of the horseshoe bats captured in September was moderate but considerable amount of the ultrastructural findings were obtained in both the spermatocytogenic and the spermiogenic phases. 2) The spermatogenic function of the horseshoe bats captured in December was depressed representing a resting status. 3) The light and electron microscopic findings suggest that the epithelium of seminiferous tubule varies cyclically, which is closely related to their peculiar way of reproductive habit during hibernation.

• Animal Systematics, Evolution and Diversity
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• v.31 no.1
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• pp.42-45
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• 2015

A tri-spine horseshoe crab, Tachypleus tridentatus (Leach, 1819) was collected from a sandy beach of Udo Island of Jeju during the full moon tides in November 1997. Three spines on the posterior margin of the opisthosoma were characterized indicating that the specimen was T. tridentatus. This specimen was a female with the total length of 49.5 cm and prosoma width of 23.0 cm. Tachypleus tridentatus was the first record from Korean waters. A brief description and figures of the species were given. This finding indicates that Korea is included to the distribution range of the species.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.4
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• pp.415-422
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• 2015

The flow field structures of dual jet-in-cross-flow were examined experimentally for in-lined perforated damage holes configuration using particle image velocimetry. Ensemble averaged in-plane velocity and vorticity data in the jet were determined to study the mean jet structure. Jets are formed by pressure differences between upper and lower airfoil surface. The flow structure of vicinity of the thru holes consist of a vortical structure that wrap around the jets like a horseshoe and develop further downstream through a pair of stream-wise vortices. The shape, size and location of the horseshoe vortex were found to be dependent on the angle of attack. In spite of the existence of battle damage holes, the effect on the control force was insignificant when the damage size was not large enough.

• Geomechanics and Engineering
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• v.38 no.1
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• pp.57-68
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• 2024

Tunnels offer myriad benefits for modern countries, and understanding their behavior under loads is critical. This paper analyzes and evaluates the damage to buried horseshoe tunnels under soil pressure and traffic loading. To achieve this, a numerical model of this type of tunnel is first created using ABAQUS software. Then, fracture mechanics theory is applied to investigate the fracture and damage of the horseshoe tunnel. The numerical analysis is based on the damage plasticity model of concrete, which describes the inelastic behavior of concrete in tension and compression. In addition, the reinforcing steel is modeled using the bilinear plasticity model. Damage contours, stress contours, and maximum displacements illustrate how and where traffic loading alters the response of the horseshoe tunnel. Based on the results, the fracture mechanism proceeded as follows: initially, damage started at the center of the tunnel bottom, followed by the formation of damage and micro-cracks at the corners of the tunnel. Eventually, the damage reached the top of the concrete arch with increasing loading. Therefore, in the design of this tunnel, these critical areas should be reinforced more to prevent cracking.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.6
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• pp.795-801
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• 2019

The aim of this study was to investigate the possibility of the skin-friction reduction by vortex control. A vortical system such as a horseshoe vortex, a hairpin vortex, and a wake region was induced around a hemisphere attached on a Perspex flat plate in the circulating water channel. Hairpin vortices were developed from the wake region and horseshoe vortices were formed by an adverse pressure gradient in front of the hemisphere. The horseshoe vortices located on the flank of the hemisphere induced a high momentum flow in the wake region by the direction of their vorticity. This process increased the frequency of the hairpin vortices as well as the frictional drag on the surface of the wake region. To reduce the skin-friction drag, suction control in front of the hemisphere was applied through a hole. Flow visualization was performed to optimize the free-stream velocity, size of the hemisphere, and size of the suction hole. Once the wall suction control mitigated the strength of the horseshoe vortex, the energy supplied to the wake region was reduced, causing the frequency of the hairpin vortex generation to decrease by 36.4 %. In addition, the change in the skin-friction drag, which was measured with a dynamometer connected to a plate in the wake region, also decreased by 2.3 %.

• Applied Microscopy
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• v.22 no.2
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• pp.97-117
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• 1992

In order to study process of spermiogenesis of the Korean greater horseshoe bat, Rhinolophus ferrumequinum korai, the cycle of seminiferous epithelium was examined by the light and electron microscope and the following results were obtained based on the epithelial cell differentiation. 1. Spermiogenesis occurred from early July to mid-Octber, and spermatogenic activity was vigorous from mid-August to late September. Spermatocytes including spermatogonia were found to be degenerated in only July. It is deduced that the degeneration serves as the mechanism to regulate effective use of energy to prepare for mating and hibernating periods, and regulation of breeding cycle. 2. Spermiogenesis of the Korean greater horseshoe bat was divided according to differentiation of the cell structure, into Golgi, cap, acrosome, maturation and spermiation phases; Golgi, cap and spermiation phases were further divided into two steps of early and late phase respectively, and acrosome phase into three steps of early, mid and late phases, and maturation phase has only one step. Hence, the spermiogenesis consists of ten phases. The first research was done in this article on the changes of chromatin with nucleus, the time of appearance and disappearance of chromatin granules, in case of Korean greater horseshoe bat (Rhinolophus ferrumequinum korai). Chromatin granule began to be condensed in late Golgi and the condensation proceeded to form an irregular mass of a electron-dense chromatin in a form of circular cylinder in the center of nucleus at the phase of maturation. Finally, the chromatin condensation proceeded and perfect nucleus of sperm with homogeneous density was formed when the sperm was separated from Sertoli cell. Therefore, appearance and disappearance of chromatin granules occurred in the period of time between late Golgi and maturation phase, The tail of sperm began to develop in early cap phase, Numerous lipid droplets were obseved in the cytoplasm of spermatids during the maturation phase, which seemed to be used as energy source necessary to make mature sperm during spermiogenesis.

• Molecules and Cells
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• v.26 no.4
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• pp.373-379
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• 2008

Recently, we reported the existence of AII "rod" amacrine cells in the retina of the greater horseshoe bat Rhinolophus ferrumequinum (Jeon et al., 2007). In order to enhance our understanding of bat vision, in the present study, we report on a quantitative analysis of cone and rod photoreceptors. The average cone density was $9,535cells/mm^2$, giving a total number of cones of 33,538 cells/retina. The average rod density was $368,891cells/mm^2$, giving a total number of rods of 1,303,517 cells. On average, the total populations of rods were 97.49%, and cones were 2.51% of all the photoreceptors. Rod: cone ratios ranged from 33.85:1 centrally to 42.26:1 peripherally, with a mean ratio of 38.96:1. The average regularity index of the cone mosaic in bat retina was 3.04. The present results confirm the greater horseshoe bat retina to be strongly rod-dominated. The rod-dominated retina, with the existence of AII cells discovered in our previous study, strongly suggests that the greater horseshoe bat retina has a functional scotopic property of vision. However, the existence of cone cells also suggests that the bat retina has a functional photopic property of vision.

• Korean Journal of Ecology and Environment
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• v.49 no.4
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• pp.385-392
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• 2016

Geographical isolation may lead to the populations having different ecological characteristics. Geographic isolation have been known to cause echolocation call differences in bats. In order to look at geographic differences of echolocation calls of Great Horseshoe Bats (Rhinolophus ferrumequinum), populations of inland and Jeju island habitats were examined in Korea. The study areas were some abandoned mines in the inland and caves of Jeju island, which were known as rest sites of Great Horseshoe Bats during the active season. Recording was done in two ways: Hand-held, Free-flying. Recording pulse was analyzed into five parameters: Maximum Frequency (FMAX), Minimum Frequency (FMIN), Peak Frequency (PF), Duration (D), Inter pulse Interval (IPI). Interestingly, The present study shows that the difference in echolocation between the inland and island populations. The PF of bats inhabited inland was 69 kHz. but, the PF of bats inhabited island (Jeju) was 71 kHz. There was a difference between regions. Discriminant analyses also showed clear difference between the inland and the island populations. Especially, PF of Korea population is lower than that of Europe (82 kHz) and higher than that of Japan (65 kHz).