• Applied Microscopy
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• v.37 no.2
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• pp.53-63
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• 2007

The culticular substructure of the venom apparatus in the orb-web spider Araneus ventricosus are studied with scanning electron microscopy. The apparatus is composed of chelicera and paired venom glands in the cephalothorax. Each chelicera consists of a basal segment and a movable fang that articulates with each other. The chelicera of this spider is labidognathous form that moves at right angles to the body axis, and has two segments similar to that of a folding jackknife. Each cylindrical fang has a specialized hinge joint which articulate with the cheliceral groove which contains numerous small protrusions. In addition, each side of cheliceral groove is covered with a total of 7 cuticular teeth in two rows which composed of 4 promarginal and 3 retromarginal teeth. It has been also observed that a single venom pore is always located toward the direction of retromarginal teeth, and surface cuticular pits are distributed on the cuticular depressive area of cheliceral groove.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.55-63
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• 1995

This paper describes the procedure to analyze the performance of the end-plated propeller(EPP) by a boundary integral method. The screw blade(SB) and end-plate(EP) are represented by a set of quadrilateral panels, where the source and normal dipole of uniform strength are distributed. The perturbation velocity potential, being the only unknown via the potential-based formulation, is determined by satisfying the flow tangency condition on the blade and the end-plate at the same time. The Kutta condition is satisfied through an iterative process by requiring the null pressure jump across the upper and lower sides of the trailing edges of both the SH and the EP. Sample calculations indicate that the EP increases the loading near the tip of the SB while spreading the trailing vortices along the trailing edge of the EP, thus avoiding the strong tip-vortex formation. Predicted performance of the EPP shows good correlations with the experimental results. The method is therefore considered applicable in designing and analyzing the EPP which may be an alternative for energy-saving propulsive devices.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.2
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• pp.60-67
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• 2019

To understand the low frequency instability(LFI) characteristics in hybrid rockets combustion, effects of equivalence ratio variations on the phase shift between pressure and heat release oscillations were investigated by using the direct numerical simulation. The change in the equivalence ratio of the main chamber was simulated by the temperature and composition variation of the combustion gas introduced into the post-combustion chamber. In the results, additional combustion appeared along with vortex generation at the backward step, and combustion pressure and heat release oscillations were observed as the vortex moved. In addition, the results confirmed that the phase difference between the pressure and heat release oscillation shifts because of the changes in the propagation velocity of pressure wave as the temperature of combustion gas changes.

• Korean Journal of Ichthyology
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• v.35 no.4
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• pp.366-371
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• 2023

A shrimp goby, Amblyeleotris japonica is reported firstly from Korea, based on a single specimen (70.3 mm in SL) collected at a depth of 14 m in the southern Jejudo Island. The species is characterized by having a lower number of scales in longitudinal series, a rather compressed body, anterior limit of opercular opening located below between posterior margin of eye and preopercle, second dorsal fin with a single spine and 13 soft rays, anal fin with a single spine and 14 soft rays, and five brownish vertical bands on lateral body between head and caudal peduncle when fresh. New Korean names, "Se-u-but-i-mang-dug-sog" and "Bulg-eun-dong-gal-se-u-but-i-mang-dug", are proposed for the genus and the species, respectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.1
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• pp.43-57
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• 2002

This paper introduces an analysis method to predicting the flow characteristic of flow field around otter board In order to develope a high performance model. In this experiment, it is used a numerical analysis of flow field through CFD(Computational Fluid Dynamic), PIV method in which quantitative, qualitative evaluation is possible. In this experiment, it is used PIV method with flow filed image around otter board in order to analysis of flow characteristic. The result compared flow pattern with analysis result through CFD and also measurement result of lift and drag force coefficient carried out in CWC(Circulating Water Channel). The numerical analysis result is matched well with experiment result of PIV in the research and it is able to verify In the physical aspect. The result is as follows ; (1) It was carried out visibility experiment using laser light sheet, and picture analysis through PIV method in order to analysis fluid field of otter-board. As a result, the tendency of qualitative fluid movement only through the fluid particle's flow could be known. (2) Since PIV analysis result is quantitative, this can be seen in velocity vector distributions, instantaneous streamline contour, and average vorticity distributions through various post processing method. As a result, the change of flow field could be confirmed. (3) At angle of attack 24$^{\circ}$ where It Is shown maximum spreading force coefficient, the analysis result of CFD and PIV had very similar flow pattern. In both case, at the otter-board post edge a little boundary layer separation was seen, but, generally they had a good flow (4) As the result of post processing with velocity vector distributions, instantaneous streamline contour and average vorticity distributions by PIV, boundary layer separation phenomenon started to happen from angle of attack 24$^{\circ}$, and from over angle of attack 28$^{\circ}$, it happen at leading edge side with the width enlarged.

• Journal of Veterinary Clinics
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• v.28 no.6
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• pp.566-570
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• 2011

The objective of this study was to assess the complications of titanium clip application after ovariohysterectomy (OHE) and find the proper surgical technique to minimize the complications by comparing the ligation method of ovarian pedicle. Six female beagle dogs were used for this study and they were divided randomly into two groups by ligation techniques: ligation and non-ligation of the suspensory ligament of ovary including ovarian pedicle. To evaluate the difference between two techniques, the location and embedded pattern of applied clips in the abdominal cavity were identified through radiographic tests and autopsy. Hematology tests were also performed to check the existence of inflammation by applied clips and all tests were carried out monthly for 1 year. There were few changes in location of clips of both groups on X-ray views without any migration. Almost all values in hematology of two groups were within the normal range and there were no inflammatory symptoms. All of applied clips in two groups were found near the kidney, but the embedded forms of them showed slight differences. The clips ligating suspensory ligament and ovarian pedicle were located in deep place and thickly surrounded with thin layers of peritoneum. But the clips ligating only ovarian pedicle were found with ease on surface of layer and located in lower place compared with the clips ligating suspensory ligament. These results indicate that the suspensory ligament holds applied clips and minimizes the movement of them. Therefore, ligation of suspensory ligament would be the preferred technique in titanium clip application for OHE.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.3
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• pp.234-240
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• 2002

The static stability of the otter board in relation to the angle of attack ($\alpha$) was studied analytically and experimentally from the moments of tensions and hydrodynamic force acting on it. Three flat plates of 0.5, 1.0, and 1.5 aspect ratios (λ) and four cambered plates of 5, 10, 15, and 20% camber ratios (CR) with the same aspect ratio (λ=1.5) were tested in a circulating water tank for measuring the hydrodynamic forces and moments relevant to the position of hydrodynamic center. And, center-of-pressure coefficients ($C_p$) and moment coefficients ($C_M$) of each plate as a function of the angle of attack were calculated for estimating the static stability from hydrodynamic forces. The obtained results are summarized as follows ； 1． When the angle of attack for otter board is changed from equilibrium for some reason, moments depending upon tensions of warp and sweep line always act in order to have the static stability, respectively. 2. Position of center-of-pressure of each flat plate moves from leading edge to center of plate with the increase of the angle of attack. It means that the moment of hydrodynamic force acting on flat plates also increases the static stability of plate. 3. With the increase of the angle of attack for cambered plates, the positions of center of-pressure move from trailing to leading edge, and then turn toward center of plate. As the camber ratios increase, the ranges of the angle of attack of the static un stability depending on moment of hydrodynamic force become wide.

• Korean Journal of Ichthyology
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• v.8 no.1
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• pp.83-89
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• 1996

The early life history of Korean bullhead, Pseudobagrus fulvidraco was studied to obtain some information required in aquaculture and reinforcement of natural population. The fertilized eggs were almost spherical in shape and demersal. The egg membranes were transparent with minute folds on the surface, causing them to stick to other substrates. Yolk is yellowish without oil droplets. The eggs just after fertilization were measuring $1.4{\pm}0.03mm$(1.3~1.5mm, n=10) and expanded to $1.7{\pm}0.08mm$(1.6~1.8mm, n=10) in diameter in 1.5 hr. The blastodisc was formed in 30 min and cleavage started in 1 hr after fertilization, and the intervals of each stage of cleavage was about 30 min at $25.0^{\circ}C$. The yolk from 32-cell stage to gastrula stage partly depressed and the depressed part moved clockwise. Hatching occurred in 53 hr after fertilization and hatched embryos had 18~19+20~21(38~40) myomeres measuring 4.2~4.3mm in total length. At the age 7 d after hatching, 4 pairs of barbels were already formed ; 1 pair on the posterior part of the nostril, 1 pair on the upper jaw, and 2 pairs on the lower jaw. And the posterior margin of caudal fin changed into two folds. The lateral band and the form of all fins were completed in 3 weeks.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.12 no.4
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• pp.297-303
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• 1979

Early morphological changes of Omobranchus slogans (STEINDACHNER) (Family Blennidae) were studied based on the samples of 125 individuals collected from Changseon channel of Nam-hae in June 1973 and May 1979. Descriptions were made with particular emphasis on developmental changes of supraorbital region, fin rays, development of chromatophores and the preopercular spine. In the early stages the lateral profile of the supraorbital region is perpendicular to tile sagittal plane, however, in the later stages it becomes curved. In the early stage of 5.55 mm in total length the number of soft rays of dorsal fin is 18, and that of the anal fin 15. Ventral fin first appears as a premoidal proturberance. It fully developes into a fin composed of two soft rays in the stages of 12.9 mm in total length. The caudal fin rays first appear in the ventral part and in the stages of 6.15 mm in total length it gets one or two soft rays which bear 1-2 segments. In the later stages each ray bears more than 5 segments. Melanophores first appear as two black spots on the central part of the head. They are distributed on the opercle and the antero-dorsal surface of the trunk in the stage of 18mm in total length. At this stage the general chromatophore. pattern is identical to the adult stage. The anal fin bears melanophores at the basal part of the rays, and it is one of the remarkable morphological characters of this species. In early stages the preopercular spine develops reaching the basal part of the pectoral fin. In the later stages of 15 mm in total length relative length of the spine decreases to total length, and ie reaches only the distal margin of the opercular.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.7
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• pp.585-592
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• 2016

Visualization was done by using $CH^*$ chemiluminescence images and PMT measurements in order to understand the origin of fluctuating pressure and chemical luminosity at about 500 Hz frequency even in stable combustion, which was observed in recent experimental tests, and to find the physical correlation leading to Low Frequency Instability(LFI) in terms of phase angle. In stable combustion, chemical reactions are distributed along the shear layer flow showing a negative coupling(about 180 degree in phase angle) with combustion pressure. However, phase difference is shifted to a positive coupling showing less than 90 degree in unstable case. Also a periodic change in the distribution of chemical reactions is observed along with local flame extinction and the appearance of big scale vortex flow. In the transition to LFI, local flame extinction and small vortex flow start to appear in a row. As seen in the bluff body wake in reactive flow, the periodic appearance of vortex flow seems to share the same physical process of BVK(Bernard Von Karman) instability generation. Thus, the appearance of local extinction in 500 Hz fluctuations is gradually amplified to complete extinctions of about 20 Hz, and it leads into LFI.