• 한국전자통신학회논문지
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• 제16권1호
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• pp.25-36
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• 2021

Broadcast traffic을 분산하는 라우터의 대체 솔루션으로 개발된 VLAN(Virtual LAN)은 물리적인 망과 무관하게 논리적으로 구성하는 가상 근거리 통신망으로, Broadcast domain을 분할하여 Broadcast traffic으로 인한 네트워크의 성능저하를 막을 수 있어 대역폭을 보다 효율적으로 사용할 수 있으며, 서로 다른 VLAN에 속한 장비들 간의 통신이 불가능하므로 보안 강화에도 도움이 된다. 본 논문은 학생들이 VLAN이 적용된 네트워크를 보다 쉽게 이해할 수 있도록 패킷 트레이서에 기반 한 토폴로지와 이를 구현하기 위한 5단계 시나리오 모델을 제안하였다. 또한 시나리오 별로 가상 망을 추가로 설계해 가면서 스위치와 라우터를 설정하고 ping/telnet/tracert test와 시뮬레이션을 통해서 VLAN의 다양한 기능들을 이해하고 검증하는 효율적인 구현사례를 제시하였다.

• 한국컴퓨터정보학회논문지
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• 제14권10호
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• pp.23-29
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• 2009

본 논문에서는 임베디드 네트워크 기술 교육용 시스템 설계를 제시하였다. 본 논문에서 제시한 교육용 임베디드 네트워크 실습장비는 사용자가 인터넷 환경에서 네트워크 구성과 임베디드 네트워크 프로그래밍 실습 교육을 할 수 있도록 설계 및 구현되었다. 네트워크 기술 교육용 시스템 설계를 임베디드 환경에서 이더넷 인터페이스를 바탕으로 제시하였다. 개발 환경으로는 PXA255를 CPU로, 디버깅 환경은 ADSv1.2를, RTOS는 uC/OS276를, 개발 언어는 C언어를 사용하였다. 교육 환경으로는 Ping 프로그램을 제공하여 실습생으로 하여금 컴파일 및 로딩이후 데모 동작을 우선 실행하도록 하였다. 이후 이의 데모 기능의 프로그래밍 기술을 교육하기 위해 단계별로 교육시키도록 하였다. 즉, ARP 프로그래밍 기법을 다룬 후 IP 기반위에서 ICMP 프로그래밍 기법의 프로그래밍을 완성하도록 하였다.

• Journal of Microbiology
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• 제44권6호
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• pp.685-688
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• 2006

The aim of this study was to characterize the molecular features of serogroup C Neisseria meningitidis strains circulating in Beijing, China. Twenty out of 23 strains belonged to ST 4821. The causative serosubtype for meningococcal meningitis was P1.12-1,16-8. All of the strains expressed class 3 PorB protein. Among the five pulsed-field gel electrophoresis patterns observed, pattern III predominated.

• Communications for Statistical Applications and Methods
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• 제15권2호
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• pp.147-159
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• 2008

We consider using ranked set sampling methods to draw inference about the three well-known measures of overlap, namely Matusita's measure $\rho$, Morisita's measure $\lambda$ and Weitzman's measure $\Delta$. Two exponential populations with different means are considered. Due to the difficulties of calculating the precision or the bias of the resulting estimators of overlap measures, because there are no closed-form exact formulas for their variances and their exact sampling distributions, Monte Carlo evaluations are used. Confidence intervals for those measures are also constructed via the bootstrap method and Taylor series approximation.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 1998년도 The 12th Asia Quality Management Symposium* Total Quality Management for Restoring Competitiveness
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• pp.269-276
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• 1998

This paper proposes an opportunistic age replacement policy. The system has two types of failures. Type I failures (minor failures) are removed by minimal repairs, whereas type II failures are removed by replacements. Type I and type II failures are age-dependent. A system is replaced at type II failure (catastrophic failure) or at the opportunity after age T, whichever occurs first. The cost of the minimal repair of the system at age z depends on the random part C(z) and the deterministic part c(z). The opportunity arises according to a Poisson process, independent of failures of the component. The expected cost rate is obtained. The optimal $T^{\ast}$ which would minimize the cost rate is discussed. Various special cases are considered. Finally, a numerical example is given.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제19권4호
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• pp.267-278
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• 2015

The study is about the influence of literal, symbolic and graphics languages on mathematics reading. The results show that the scores of symbolic language volume are significantly lower than that of literal language volume. The abstractness of the mathematical symbols will not have a significant impact on the students with excellent mathematical academic, but as for the medium and poor students, abstract mathematics symbols will cause their cognitive impairment. Due to picture-superiority-effect, the test scores of the graphics language volume are significantly higher than that of the symbolic language volume. Graphics language will have a significant impact on the excellent and medium students, but has no impact on the poor students.

• Journal of Power Electronics
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• 제15권3호
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• pp.644-651
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• 2015

This paper introduces a novel digital one cycle control (DOCC) boost power factor correction (PFC) converter. The proposed PFC converter realizes the FPGA-based DOCC control approach for single-phase PFC rectifiers without input voltage sensing or a complicated two-loop compensation design. It can also achieve a high power factor and the operation of low harmonic input current ingredients over universal loads in continuous conduction mode. The trailing triangle modulation adopted in this approach makes the acquisition of the average input current an easy process. The controller implementation is based on a boost topology power circuit with low speed, low-resolution A/D converters, and economical FPGA development board. Experimental results demonstrate that the proposed PFC rectifier can obtain a PF value of up to 0.999 and a minimum THD of at least 1.9% using a 120W prototype.

• Structural Engineering and Mechanics
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• 제48권1호
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• pp.103-124
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• 2013

This paper studies the static and dynamic characteristics of composite plates subjected to an arbitrary periodic load in hygrothermal environments. The material properties of composite plates are depended on the temperature and moisture. The governing equations of motion of Mathieu-type are established by using the Galerkin method with reduced eigenfunction transforms. A periodic load is taken to be a combination of axial pulsating load and bending stress in the example problem. The regions of dynamic instability of laminated composite plates are determined by solving the eigenvalue problems based on Bolotin's method. The effects of temperature rise and moisture concentration on the dynamic instability of laminated composite plates are investigated and discussed. The influences of various parameters on the instability region and dynamic instability index are also investigated. The numerical results reveal that the influences of hygrothermal effect on the dynamic instability of laminated plates are significant.

• Bulletin of the Korean Chemical Society
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• 제27권3호
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• pp.377-380
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• 2006

The semiconductor PbS nanobelts (width 50-120 nm and length over 3 $\mu$m) were self-assembled in a simple reverse micelle solvent system containig the surfactant of polyoxyethylene (9) dodecy ether $(C_{12}E_9)$. The nanobelts synthesized were found to possess cube galena poly-crystal structure with high purity when analyzed by ED and X-ray diffraction. Significant “blue shift” from bulk material was observed on the PbS nanobelts using photoluminescence and UV-Vis spectroscopy. A mechanism involving the possible formation of nanobelts based on surfactant template was also proposed.

• Smart Structures and Systems
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• 제20권1호
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• pp.43-52
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• 2017

Structural health monitoring has drawn great attention in the field of civil engineering in past two decades. These structural health monitoring methods evaluate structural integrity through high-quality sensor measurements of structures. Due to electronic deterioration or aging problems, sensors may yield biased signals. Therefore, the objective of this study is to develop a fault detection method that identifies malfunctioning sensors in a sensor network. This method exploits the autoregressive modeling technique to generate a bank of Kalman estimators, and the faulty sensors are then recognized by comparing the measurements with these estimated signals. Three types of faults are considered in this study including the additive, multiplicative, and slowly drifting faults. To assess the effectiveness of detecting faulty sensors, a numerical example is provided, while an experimental investigation with faults added artificially is studied. As a result, the proposed method is capable of determining the faulty occurrences and types.