• 한국전산유체공학회지
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• 제2권1호
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• pp.8-12
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• 1997

The three-dimensional Euler equations are solved numerically for the analysis of contraction flows in wind or water tunnels. A second-order finite difference method is used for the spatial discretization on the nonstaggered grid system and the 4-stage Runge-Kutta scheme for the numerical integration in time. In order to speed up the convergence, the local time stepping and the implicit residual-averaging schemes are introduced. The pressure field is obtained by solving the pressure-Poisson equation with the Neumann boundary condition. For the evaluation of the present Euler solver, numerical computations are carried out for three contraction geometries, one of which was adopted in the Large Cavitation Channel for the U.S. Navy. The comparison of the computational results with the available experimental data shows good agreement.

• Journal of Advanced Marine Engineering and Technology
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• 제23권6호
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• pp.794-805
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• 1999

Pneumatic cushioning cylinders are commonly employed for vibration and shock control. A mathematical simulation model of a double acting pneumatic cushioning cylinder designed to absorb shock loads is presented which is based on the following assumptions; ideal equation of state isentropic flow through a port conservation of mass polytropic thermodynamics single degree of freedom piston dynamics and energy equivalent linear damping. These differential equation can be solved through numerical integration using the fourth order Runge-Kutta method. An experimental study was conducted to validate the results obtained by the numerical integra-tion technique. Simulated results show good agreement with experimental data. The computer simulation model presented here has been extremely useful not only in understanding the has been extremely useful not only in understanding the basic cushioning but also in evaluating different designs.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.528-534
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• 2001

Basic equations and its solution procedure are derived for the analysis of an annular pump seal in which the rotor has a large static displacement from the centered position. The Bulk-flow is assumed for a control volume set in the seal clearance and the flow is assumed to be completely turbulent in axial and circumferential direction. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses in the control volume. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about an eccentric position. Flow variables are expanded by using Fourier series for the solution procedure. Integration of the resultant first-order pressure distribution along and around the seal defines the 12 elements of rotordynamic coefficients of the eccentric annular pump seal. The results of leakage and rotordynamic coefficients are presented and compared with the Marquette's experimental results and the San Andres' theoretical analysis.

• ETRI Journal
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• 제10권2호
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• pp.13-19
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• 1988

This paper describes on the interworking services. interworking issues and the design concepts in the Interworking System (IWS) between Pubilc Switched Telephone Network (PSTN) and Packet Switched Data Network (PSDN), which has been developed at the Electronics and Tedecommunications Research Institute (ETRI). As a gateway between PSTN and PSDN, IWS provides the interconnection between PSTN and PSDN. In addition to the provision of basic interconnection services (i.e. dial-in/dial-out services), IWS provides the Maintenance and Administration (M&A) services for system itself and the supplementary services such as the call barring, direct call and closed user group. The architecture of IWS is based on the multiprocessor system with single system bus. And a multiprocessor real time kernel is used to support the inter-board communication as well as the inter-process commmunications. Especially, the operation and maintenance functions of IWS are treated in detail.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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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.

• 천문학논총
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• 제8권1호
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• pp.137-151
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• 1993

We have calculated the astronomical almanac 1994 and simulated the trajectory of a satellite orbit considering all perturbative forces with various initial conditions. In this work, Gauss Jackson multistep integration method has been used to calculate our basic equation of motion with high numerical accuracy. It has beer. found that our results agree well with the Astronomical Almanac Data distributed by JPL of NASA and the orbit simulations have been carried out with fast speed, stability and excellent round-off error accumulation, comparing with other numerical methods. In order to be carried out our works on almanac and orbit calculations easily by anyone who uses a personal computer, we have made a computer program on graphical user interface to provide various menus for detail works selected by a mouse.

• ALGAE
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• 제21권4호
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• pp.349-375
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• 2006

The application of modern ecological, ultrastructural and molecular methods, aided by the cultivation of numerous cyanobacterial morphotypes, has substantially changed our knowledge of these organisms. It has led to major advances in cyanobacterial taxonomy and criteria for their phylogenetic classification. Molecular data provide basic criteria for cyanobacterial taxonomy; however, a correct phylogenetic system cannot be constructed without combining genetic data with knowledge from the previous 150 years research of cyanobacterial diversity. Thus, studies of morphological variation in nature, and modern morphological, ultrastructural, ecophysiological and biochemical characters need to be combined in a “polyphasic” approach. Taxonomic concepts for generic and infrageneric ranks are re-evaluated in light of combined phenotypic and molecular criteria. Despite their usefulness in experimental studies, the limitations of using strains from culture collections for systematic and nomenclatural purposes is highlighted. The need for a continual revision of strain identification and proper nomenclatural practice associated with either the bacteriological or botanical codes is emphasized. Recent advances in taxonomy are highlighted in the context of prospects for understanding cyanobacterial diversity from natural habitats, and the evolutionary and adaptational processes that cyanobacteria undergo.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.884-889
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• 2000

This paper describes the design and implementation of PCOAMC(PC-based Open Architecture Machine Controller) to be flexible and independent from the vendor-oriented hardware and software structure. This openness approach is able to enhance an intelligence and integration of a manufacturing system. The development methodology of PcOAMC is an Object-Oriented approach, and all modules in PcOAMC are modelled using UML(Unified Modelling Language) that provides an easy understanding and modification. In order to demonstrate an applicability of PcOAMC, a simple test has been executed by using the Client-Server system consisting of two PcOAMCS and bus monitoring system. The good results have been obtained, so that the developed controller is expected to be embedded into IMS(Intelligent Manufacturing System) as a basic unit.

• 한국항해학회지
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• 제18권3호
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• pp.31-49
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• 1994

In the meantime Korean Insurance Industry has been developed a steady growth under government's political protection. But insurance market seems to be opened unavoidably owing to the liberalization of international trade by the Agreements of UR and the bloc of economy by EC Integration and the Organization of NAFTA. By the above reason, especially, in case of hull insurance, the rate of hull insurance is being instituted as a problem. Accordingly the recognition for the problem like this, in thsi study, explained the major objectives of rate making and described the basic rate making methods that are used in property and liability insurance, and searched the rate making schemes of hull insurance rate of the major nations by comparing method. And as a conclusion, the writer presented several schemes including new rate making scheme of hull insurance rate and the security of statistical data about loss ratio, and the establishment of Korean Hull Insurance Association.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.682-687
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• 2000

In this paper, the simulation methods using transmission lines are studied and realized, which are necessary in design and analysis of hydraulic control systems. The basic idea of this method is that system components are separated by transmission line element for simulation. The PI-controller can keep inductance level as low as desired. It can also handle nonlinearities and discontinuities without flag signal when restarting integration. Parallel hydraulic circuits are simulated using parallel processing algorithm. To shoe that using variable timestep size in each subsystem, simulation time can be reduced. Performance of the simulation results is compared with that of Runge Kutta method.