• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.2
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• pp.346-363
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• 2015

We have performed integrated dynamics modeling for a supercavitating vehicle. A 6-DOF equation of motion was constructed by defining the forces and moments acting on the supercavitating body surface that contacted water. The wetted area was obtained by calculating the cavity size and axis. Cavity dynamics were determined to obtain the cavity profile for calculating the wetted area. Subsequently, the forces and moments acting on each wetted part-the cavitator, fins, and vehicle body-were obtained by physical modeling. The planing force-the interaction force between the vehicle transom and cavity wall-was calculated using the apparent mass of the immersed vehicle transom. We integrated each model and constructed an equation of motion for the supercavitating system. We performed numerical simulations using the integrated dynamics model to analyze the characteristics of the supercavitating system and validate the modeling completeness. Our research enables the design of high-quality controllers and optimal supercavitating systems.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.856-862
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• 2013

A cavity-backed two-arm spiral antenna for partial discharge diagnosis is presented. The proposed antenna consists of a two-arm Archimedean spiral, a tapered microstrip balun as spiral antenna feed, and a ring-shaped absorber-loaded cavity. The Archimedean spiral antenna is designed for the operating frequency band of 0.3 GHz to 1.5 GHz and fed by the tapered microstrip balun. The cavity is utilized to transform the bidirectional beam into a unidirectional beam, thereby enhancing gain. The ring-shaped absorber is stacked in the cavity to reduce the reflected waves from the cavity wall. The proposed antenna is designed and simulated using CST Microwave Studio. A prototype of the proposed antenna is likewise fabricated and tested. The measured radiation patterns are directional to the positive z-axis, and the measured peak gain is 8.13 dBi at a frequency of 1.1 GHz.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.474-479
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• 2005

Experimental and theoretical studies of internal cavity pressure during injection molding of a spiral tube cavity were carried out. The frozen layer thickness and the evolution of internal cavity pressure were calculated using a commercial software (C-MOLD). The evolution of the internal cavity pressure was recorded during injection molding of polystyrene into a spiral tube mold. To explain the differences observed between the calculated and measured internal cavity pressure, a pressure correction factor (PCF) was introduced based on the plane stress theory. This factor was determined by analyzing the stress state in the melt and calculating the frozen layer thickness near the mold wall. The corrected and experimental pressures have been compared to validate the applicability of the pressure correction factor.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.142-147
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• 2001

Natural convection of a magnetic fluid is different from that of Newtonian fluids because magnetic body force exists in an addition to gravity and buoyancy. In this paper, natural convection of a magnetic fluids(W-40) in a cubic cavity is examined by numerical and experimental method. One side wall was kept at a constant temperature($25^{\circ}C$), and the opposite side wall was also held at a constant but lower temperature($20^{\circ}C$). Under above conditions, various magnitudes of the magnetic fields were applied up. GSMAC scheme is used for a numerical method, and the thermo-sensitive liquid crystal film(R20C5A) is utilized in order to visualize wall-temperature distributions as an experimental method. This study has resulted in the following fact that the natural convection of a magnetic fluids is controlled by the direction and intensity of the magnetic fields.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1084-1089
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• 2000

The basic equations are derived for the analysis of a stepped labyrinth gas seal which are generally used in high performance compressors, gas turbines, and steam turbines. The Bulk-flow is assumed for a single cavity control volume and the flow is assumed to be completely turbulent in circumferential direction. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses in the single cavity control volume. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about a centered position. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the stepped labyrinth gas seal. The leakage and rotordynamic characteristic results of the stepped labyrinth gas seal are presented and compared with Scharrer's theoretical analysis using Blasius' wall-friction-factor formula.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.4
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• pp.693-698
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• 2006

In Class I cavity, the highest C-factor could be obtained and it means the highest polymerization shrinkage stress. In this study, high C-factor model was designed. The pulpose of present study was to determine differences of Microtensile bond strength (MTBS) of class I cavity pulpal and axial wall specimens in primary molar. Twenty clean mandibular 2nd primary molars were randomly divided into two groups Different composite Resins (Filtek Z250, 3M ESPE & Filtek Supreme, 3M ESPE) were bulk filled and photo cured. Axial wall specimens and pulpal specimens were prepared at the same teeth, All specimens were divided into 4 groups and MTBS were evaluated. Group ZP : Filtek Z250-Pulpal wall Group ZA : Filtek Z250-Axial wall Group SP : Filtek Supreme - Pulpal wall Group SA : Filtek Supreme - Axial wall The results were as follows: 1. Mean MTBS of ZP & ZA and SP & SA were significantly different(p<.001). 2. There was no significant difference between MTBS of ZP & SP and ZA & SA.

• Korean Journal of Animal Reproduction
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• v.18 no.4
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• pp.245-250
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• 1995

The appearance and function of corpora lutea(CL) with a central cavity in the ovaries of Korean Native Cattle (KNC) were investigated endocrinologically and histochemically. The CL were enucleated from KNC ovaries within 2~3 hrs local slaughter house and classified with central cavity CL or not. Enzymatically dispersed luteal cell (1$\times$106 live cell/ml of Dulbecco's Modified Eagle Media) with or without cavity of CL cultured at 37$^{\circ}C$ in a humidified incubation (5% CO2 : 95% air) for 72hr. A central cavity in the CL of KNC was found in 58.8% of CL-1, 34.9% of CL 2, 39.1% of CL-3, and 11.1% of CL-4, respectively. There were no significant difference between protein content of CL with and without a central cavity. Mean progesterone secretion after 36h of in vitro luteal cell culture were significantly (p<0.05) higher in CL with central cavity than without cavity. However, the luteal cavitic wall was composed of the connective tissue band of the reticular and collagen fibers and then these connective tissue band extended into the CL with cavity. These results suggest that the central cavity of CL may be caused infertility in KNC.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.3
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• pp.392-404
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• 1997

The flow induced by the oscillatory motion of a solid body is important in a number of practical problems. As the solid boundary oscillates harmonically, there is steady streaming motion invoked by the Reynolds stresses, which could cause extensive migration of the fluid during a period of fluid motion. We here analyzed the flow in a square cavity with an oscillating top wall for the parameters which make the time derivatives and the convective terms equally important in the entire cavity flow. The full Navier-Stokes equations are solved by the second-order time accurate Momentum Coupling Method which is devised by the authors. The particular numerical scheme does not need subiteration at each time step which is usually a required process to calculate the incompressible Navier-Stokes equations. The effect of two parameters, the Reynolds number and the frequency parameter, on the oscillatory flow has been investigated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.44-52
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• 1987

For the favorable performance of a D.I. diesel engine, it is important to improve the mixture formation process and the ensuing early stage of combustion process. In the present paper, high speed photography was employed to investigate the effectiveness of a cavity digged in a piston crown for some more useful utilization of air. The cavity would function to improve mixing of fuel and air by the increase of turbulence of air and by the impingement of fuel spray on the cavity wall. The results obtained are summarized as follows: (1) From an aspect of thermal efficiency, it is effective to inject the spray tangentially to the cavity wall to enlarge the area of spray evaporation. (2) some deductions obtained from previous investigations using a hot air stream duct are supported by the present results. For example, it is effective for the quick development of flames throughout the combustion chamber to mix the evaporated fuel of main spray with the intermediates brought about by the early stage of combustion of the preceded auxiliary fuel spray.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1601-1604
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• 2005

The demand increasing of optical applications like as display devices derives interest for fabrication process. The product s development is apt to fabricate numerous thin and wide surfaces with micro pattern. Naturally that needs injection molding fabrication for the mass production. In existing manufacturing, the product quality is controlled by input fabrication condition from the outside. That can be called as a try and error method and not fundamentally solve the troubles; imperfect replication, war page, short shot, etc. To understand the cause and bring a solution, it is needed that check of changing in the cavity. This study can catch them. Data acquisition system about temperature and pressure distribution is settled and can get some data. From this research, other studies related with DAQ in cavity can start on the easier step.