• Journal of information and communication convergence engineering
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• v.8 no.5
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• pp.519-523
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• 2010

In Gen-2 RFID system, the initial value of $Q_{fp}$, which is the slot-count parameter of Q-algorithm, is not defined in the standard. In this case, if the number of tags within the reader's identification range is small and we let the initial $Q_{fp}$ be large, the number of empty slot will be large. On the other hand, if we let the initial $Q_{fp}$ be small in spite of many tags, almost all the slots will be collided. As a result, the performance will be declined because the frame size does not converge to the optimal point quickly during the query round. In this paper, we propose a scheme to allocate the optimal initial $Q_{fp}$ through the tag number estimation before the query round begins. Through computer simulations, it is demonstrated that the proposed scheme achieves more stable performance than Gen-2 Q-algorithm.

• Communications for Statistical Applications and Methods
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• v.27 no.3
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• pp.365-376
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• 2020

Interval-valued data, a type of symbolic data, is given as an interval in which the observation object is not a single value. It can also occur frequently in the process of aggregating large databases into a form that is easy to manage. Various regression methods for interval-valued data have been proposed relatively recently. In this paper, we introduce a nonparametric regression model using the kernel function and a nonlinear regression model for the interval-valued data. We also propose applying the local linear regression model, one of the nonparametric methods, to the interval-valued data. Simulations based on several distributions of the center point and the range are conducted using each of the methods presented in this paper. Various conditions confirm that the performance of the proposed local linear estimator is better than the others.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.67.1-67.1
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• 2010

Understanding the nature of MHD turbulence is of fundamental importance in astrophysics. The results of these studies can be used to develop the star formation theory. While most of previous studies have considered turbulence in uniform media, the stratification of media can play an important role. We performed three-dimensional numerical simulations of isothermal, compressible, MHD turbulence with different plasma beta's and different flow Mach numbers in stratified media to study the effects of stratification on turbulence. We found Statistics of turbulent flow in stratified media is different from in uniform media. In this talk, we present the statistical properties of the MHD turbulence, such as the PDF, power spectrum, and structure function.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.339-341
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• 1997

From this first studies, We have investigated the latch-up characteristics of various CMOS well structures possible with high energy ion implantation processes. In this study, we also investigated those of STI(Shallow Trench Isolation} structures with varing n+/p+ spacing and the depth of trench. STI structure is formed by T-SUPREM4 process simulator, and then latch-up simulations for each case were performed by MEDICI device simulator for latch-up immunity improvement. STI is very effective to preventing the degradation of latch-up characteristics as the n+/p+ spacing is reduced. These studies will allow us to evaluate each technology and suggest guidelines for the optimization of latch-up susceptibility.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.16-21
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• 2005

The performance of reciprocating internal combustion engine is a strong function of the air intake system configuration. In order to improve engine power, it is essential to optimize the air induction system. In this study, a numerical investigation has been carried out for the three-dimensional flow and pressure characteristics in air intake system of a large-sized commercial bus. CFD simulations using STAR-CD were also perform ed to evaluate effects of intake duct geometry and structure variation inside air cleaner on the negative pressure distribution of overall intake system. Studies for improving the back pressure distribution have been proposed and quantitatively examined based on intensive case studies.

• Food Industry
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• s.206
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• pp.26-41
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• 2008

Recently, Korea have experienced numbers of FTAs with other countries, including Chile, EFTA(European Free Trade Association), Singapore, ASEAN(Association of South-East Asian Nations), and U.S. In particular, FTA with U.S. are expected to cause huge impact on food markets as well as agricultural sector in Korea. Many researches have analyzed and discussed about the impact on agricultural sector after Korean-U.S. FTA, but very small number of studies focus on the impact of Korean-U.S. FTA on food markets. The purpose of the paper is to discuss the impact of Korea-U.S. FTA on Korean dairy market. For the numerical simulations, this paper focus on the impact on cheese and butter markets. The results of numerical analysis in the paper will be helpful for the future research, because few (maybe no) studies conduct the numerical analysis to measure the impact of Korea-U.S. FTA on Korean food market.

• Korean Management Science Review
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• v.10 no.1
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• pp.107-125
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• 1993

Modern telecommunication switching systems are SPC(Stored Program Control) machines handling voice, data and other kinds of traffic, in an environment which tends to be fully digital switching and transmission. The throughput of such systems is determined by the real time capacity of its centralized or distributed control processors and by the traffic capacity of the switching network. Designers must verify the traffic and call processing capacity of the switching system and check its performance under traffic load before it is put into service. Verification of traffic and call processing capacity of switching systems is one of the problems treated by teletraffic studies ; teletraffic studies are based on stochastic process, queueing theory, simulations and other quantitative methods of decision making. This study suggests the general methodology to evaluate the throughput and performance of the ISDN switching system. TDX-10 ISDN switching system are employed to give illustrative examples of the methodologies discussed in this study.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.6
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• pp.815-822
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• 2016

The cationic biopolymer chitosan has several applications in medicine. Chitosan is the deacetylated derivative of chitin, the second most abundant naturally occurring polymer. Recent studies have investigated the relationship between chitosan and antibacterial activity. However, the molecular interactions and mechanisms have not been detailed. This study used molecular dynamics simulations to study interactions between chitosan and anionic bacterial membranes (POPE-POPG) and electrically neutral non-bacterial membranes (POPC). We calculated the free energy using umbrella sampling to compare the interactions between membranes and chitosan in different protonation states. Fully protonated chitosan interacted most strongly with the bacterial membranes, but weakly with non-bacterial membranes. These results suggest that electrostatic interactions are the main mechanism of the antibacterial activity of chitosan, and they provide insights into the design of novel antibacterial and antimicrobial agents.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.39.2-39.2
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• 2016

The central regions of barred-spiral galaxies contain interesting gaseous structures such as dust lanes located at the leading side of the bar and nuclear rings that are sites of intense star formation. Our previous studies showed how gas structures form under the influence of a non-axisymmetric bar potential and temporal/spatial behavior of the star formation in nuclear rings. However, previous works were limited to 2-dimensional infinitesimally-thin, unmagnetized and isothermal disks. To study effects of cooling/heating, vertical motions of gas structures and magnetic field, we use Mesh-Free magneto-hydrodynamic simulation code GIZMO. We find that temporal variations of the star formation rates in the nuclear ring in the three-dimensional model are overall similar those in the previous two-dimensional results, although the former shows more violent small-scale fluctuations near the early primary peak. We will present our recent results about evolution of gaseous structures and star formation rate compare with results of previous studies.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.27-27
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• 2014

The past three decades have witnessed a renaissance in the field of extragalactic globular clusters (GCs). GC systems have now been investigated in galaxies ranging from dwarfs to giants and spanning all the morphological types. Detailed studies of GCs provide strong constraints on galaxy formation that can be obtained in the near-field. In this talk I will review some of the pivotal studies performed with the HST and large ground-based telescopes and state-of-the-art simulations. Also, I will attempt to introduce my new solution to a long-standing puzzle in this field----the origin of GC bimodality in color. I will show that the theory gives a simple, cohesive explanation for the key observations of extragalactic GCs. The implication of the results will be discussed in the context of formation of GC systems and their parent galaxies.