• The Transactions of the Korea Information Processing Society
• /
• v.6 no.11S
• /
• pp.3260-3268
• /
• 1999

As the proliferation of multimedia traffic over High-speed Internet increases, ATM network will be vital to adopt as backbone network over various parts of Internet. In this paper, we investigate the performance of TCP/IP traffic flow over ABR and UBR of ATM service to study for the high throughput and good fairness by simulation technique. Although TCP is run in the transport layer, it is controlled by several methods, e.g, EPD, PPD, RED, EFCI, ER etc, in ATM layer when TCP uses the ABR/UBR service. Therefore, if one cell is discarded in ATM layer, a packet of TCp will be laost. And, also, along with the increasing of the number of VC among switches, the throughput and fairness will be degraded. In order to improve these degradations, we propose the effective parameter control operations of EFCI and ER on ABR service, and also suggest the buffer management methods on UBR service. Finally, through the simulation results, the improved throughput and fairness are shown.

• Journal of Korean Institute of Industrial Engineers
• /
• v.27 no.1
• /
• pp.95-102
• /
• 2001

The design of automobile body assembly line is one of essential parts for improving the process performance. The major objective of this research is to develop a performance evaluation model for automobile assembly line using a closed queueing network(CQN) and simulation method. In this study we used a two-step approach to compute the performance of the assembly line : first, we used CQN model considering assembly line equipments and the line operating time under the assumption of no failure, and second we used a well-known simulator FACTOR/AIM. Finally we implemented this model on a K automobile company and we have shown the sample results of automobile body assembly line.

• Environmental and Resource Economics Review
• /
• v.9 no.5
• /
• pp.973-997
• /
• 2000

The carbon tax is one of several measures to reduce the green-house gases emitted from burning the fossil fuels, which has been much discussed internationally. The analyses of the effects of a carbon tax on individual countries have been carried out by applying the computable general equilibrium(CGE) models, especially models with the assumption of non-existence of scale economies. However, the introduction of scale economies to CGE models changes the simulation results drastically. In this paper, two CGE models are used to compute and compare the economic and $CO_2$ reduction effects of a carbon tax, one of with is the model with scale economies and the other is without scale economies. One of main results is that the analysis using the CGE model without scale economies may underestimate the effects of a carbon tax on GDP and reducing the emission of $CO_2$.

• Journal of information and communication convergence engineering
• /
• v.6 no.2
• /
• pp.177-181
• /
• 2008

The more improved the Internet and the information technology, the stronger cryptographic system is required which can satisfy the information security on the platform of personal hand-held devices or smart card system. This paper introduces a case study of designing an elliptic curve cryptographic processor of a high performance that can be suitably used in a wireless communicating device or in an embedded system. To design an efficient cryptographic system, we first analyzed the operation hierarchy of the elliptic curve cryptographic system and then implemented the system by adopting a serial cell multiplier and modified Euclid divider. Simulation result shows that the system was correctly designed and it can compute thousands of operations per a second. The operating frequency used in simulation is about 66MHz and gate counts are approximately 229,284.

• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.2
• /
• pp.65.2-65.2
• /
• 2014

We present a new hydrodynamic simulation code based on the Voronoi tessellation for estimating the density precisely. The code employs both of Lagrangian and Eulerian description by adopting the movable mesh scheme, which is superior to the conventional SPH (smoothed particle hydrodynamics) and AMR (adaptive mesh refinement) schemes. The code first generates unstructured meshes by the Voronoi tessellation at every time step, and then solves the Riemann problem for all surfaces of each Voronoi cell so as to update the hydrodynamic states as well as to move current meshes. Besides, the IEM (incremental expanding method) is devised to compute the Voronoi tessellation to desired degree of speed, thereby the CPU time is turned out to be just proportional to the number of particles, i.e., O(N). We discuss the applications of our code in the context of cosmological simulations as well as numerical experiments for galaxy formation.

• 한국데이터정보과학회:학술대회논문집
• /
• 2005.10a
• /
• pp.71-84
• /
• 2005

The Fieller-Creasy problem involves statistical inference about the ratio of two independent normal means. It is difficult problem from either a frequentist or a likelihood perspective. As an alternatives, a Bayesian analysis with noninformative priors may provide a solution to this problem. In this paper, we extend the results of Yin and Ghosh (2001) to unbalanced sample case. We find various noninformative priors such as first and second order matching priors, reference and Jeffreys' priors. The posterior propriety under the proposed noninformative priors will be given. Using real data, we provide illustrative examples. Through simulation study, we compute the frequentist coverage probabilities for probability matching and reference priors. Some simulation results will be given.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2000.11a
• /
• pp.12-15
• /
• 2000

In this paper, we have evaluated the performance of an OFDM system using hierarchical 16QAM (OFDM/HL-16QAM) for achieving high quality and high speed data and image transmission in multipath fading channel. The wireless channel for performance evaluation is assumed to include AWGN and two ray multipath fading. Through simulation we have obtained the BER performance of the system according to $E_{b}$, $N_{0}$, then compared the received image quality of proposed system with that of conventional system. From the result, it is shown that the OFDM/HL-16QAM system is more effective for data and image transmission.n.n.

• 한국전산유체공학회:학술대회논문집
• /
• 2010.05a
• /
• pp.508-516
• /
• 2010

An efficient code has been developed to predict dispersion of indoor air pollutants The computing capability of the code has been compared with that of a commercial code inn a benchmark test. After that, the code has been employed to compute dispersion of a pollutant released from a new furniture, a kind of Sick Building Syndrome (SBS). A sofa which generates formaldehyde is implemented by using an immersed boundary method. Large Eddy Simulation (LES) is employed to obtain time-dependent velocity and scalar fields. LES has bee regarded as an academic tool, but the newly-developed code reveals a possibility of application of LES to practical problems, especially dispersion of indoor pollutants.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.4 no.2
• /
• pp.35-43
• /
• 1984

The purpose of this paper is to develop a mathematical model which can be used to compute the position of the free surface due to water level fluctuations in the canal and the transient pressure distributions along the canal lining. The diagnostic equation has been solved by the point successive over-relaxation method, and the linearized prognostic equation has been solved by the implicit Lax-Wendroff scheme. Four different cases in the simulation conditions are presented for both permeable and impermeable canal lining to predict the transient seepage surface development.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.1076-1079
• /
• 2003

The vector field histogram(VFH) uses a two-dimensional Cartesian histogram grid as a world model. The VFH method subsequently employs a two-stage data-reduction process in order to compute the desired control commands for the vehicle. In the first stage the histogram grid is reduced to a one dimensional polar histogram that is constructed around the robot's momentary location. Each sector in the polar histogram contains a value representing the polar obstacle density in that direction. In the second stage, the algorithm selects the most suitable sector from among all polar histogram sectors with a low polar obstacle density, and the steering of the robot is aligned with that direction. We applied this algorithm to our simulation program and tested..