• Journal of Advanced Navigation Technology
• /
• v.14 no.1
• /
• pp.49-56
• /
• 2010

Severe energy constraints and the low power consumption require the significance of the energy efficient error control mechanisms in wireless sensor network (WSN). In this paper, an automatic repeat request (ARQ) methodology for the analysis of error control schemes in WSN is presented such that the effects of packet length, the modulation scheme and the interference effect of the wireless channel are investigated. Moreover, an analyis of ARQ error control is provided by considering two major architectures for wireless sensor network, i.e., Mica2 and MicaZ sensor nodes. And the throughput performance of WSN with asynchronous FSK signal and DSSS-OQPSK signal with selective repeat ARQ scheme are analyzed in multiple interference environment, and the probability of receiving a correct bit and packet from target node to sink node is evaluated as a function of the channel parameter, the number of wireless sensor node, and the spreading factor.

• Proceedings of the KIPE Conference
• /
• 2014.07a
• /
• pp.41-42
• /
• 2014

본 논문에서는 종전의 3상 PWM 정류기의 문제점을 극복하기 위하여 3상 Z-Source PWM 정류기를 제안하였다. 제안된 정류기는 시스템의 간소화, 안정화, 비용상승을 고려하여 상태관측기가 적용된 센서리스 제어 기법을 적용하였다. 3상 Z-Source PWM 정류기는 교류측 전압센서 없이 DC-link단 전압센서와 입력단 전류 센서만을 이용하여 교류측 전압을 추종한다. 제안된 3상 Z-Source PWM 정류기는 PSIM 시뮬레이션을 통하여 검증 하였다.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.26 no.1
• /
• pp.66-73
• /
• 2021

This study presents a novel four-channel light-emitting diode (LED) current balancing topology using a current-fed hybrid quasi-Z-source converter. With the proposed structure, currents flowing through four LED strings are automatically balanced owing to the charge (amp-sec) balance condition on capacitors. Thus, automatic current balancing of the proposed driver is simple and precise. In addition, the proposed LED driver uses only one active switch and three diodes. The operating principle and characteristics of the proposed four-channel LED driver are analyzed in detail. To verify the operation of the proposed LED driver, a prototype is built and tested with different numbers of LEDs.

• Proceedings of the KIEE Conference
• /
• 1987.07a
• /
• pp.201-204
• /
• 1987

To improve the reliability of boiler controller of a power plant, FTCS(Fault Tolerant Control System) is proposed. We studied to implement a Multi-processor scheme for FTCS. This paper presents the total system to experiment the performance of FTCS and the Multi-processor scheme implemented.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.2
• /
• pp.29.3-30
• /
• 2015

We introduce an advanced one-to-one galaxy correspondence method that populates dark matter halos with galaxies by tracing merging histories of most bound member particles (MBPs) identified in simulated virialized halos. To estimate the survival time of a satellite galaxy, we adopt several models of tidal-destruction time derived from an analytic calculation, isolated galaxy simulations, and cosmological simulations. We build mock galaxy samples for each model by using a merging tree information of MBPs from our new Horizon Run 4 N-body simulation from z = 12 to 0. For models of galaxy survival time derived from cosmological and isolated galaxy simulations, about 40% of satellites galaxies merged into a certain halo are survived until z = 0. We compare mock galaxy samples from our MBP-galaxy correspondence scheme and the subhalo-galaxy scheme with SDSS volume-limited galaxy samples around z = 0 with $M_r-5{\log}h$ < -21 and -20. Compared to the subhalo-galaxy correspondence method, our method predicts more satellite galaxies close to their host halo center and larger pairwise peculiar velocity of galaxies. As a result, our method reproduces the observed galaxy group mass function, the number of member galaxies, and the two-point correlation functions while the subhalo-galaxy correspondence method underestimates them.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2017.04a
• /
• pp.463-465
• /
• 2017

ICT기술이 빠르게 발전함으로써 헬스케어, 스마트홈, 스마트 씨티, 스마트카, 웨어러블과 같이 다양한 인간중심의 서비스가 개발되고 있다. 이러한 인간중심 서비스를 제공하기 위해 여러 센서들을 이용하여 작은 네트워크를 구현한다. 일반적으로 많은 무선 프로토콜 중 Z-Wave를 많이 사용한다. 센서들의 정보를 AES기반으로 암호화하여 Controller와 Device간 통신하는데 가장 효율적이지만 Z-Wave통신으로 데이터를 보내기위해 암호화 키를 생성할 때 사용되는 값이 평문으로 전송되기 때문에 보안위협이 존재한다. 따라서 이러한 보안 위협을해결하기 위해 Controller와 Device간 암호화 키를 생성할 시 Diffie-Hellman을 이용하여 보다 안전한 프로토콜을 제안한다.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.5
• /
• pp.47-56
• /
• 2003

Geometric cutting-simulation and verification play an important role in detecting NC machining errors in mold & die manufacturing and thereby reducing correcting time & cost on the shop floor. Current researches in the area may be categorized into view-based, solid-based, and discrete vector-based methods mainly depending on workpiece models. Each methodology has its own strengths and weaknesses in terms of computing speed, representation accuracy, and its ability of numerical inspection. The paper proposes a hybrid modeling scheme for workpiece representation with z-map model and discrete vector model, which performs 3-axis and 5-axis cutting-simulation via tool swept surface construction by connecting a sequence of silhouette curves.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.26 no.1
• /
• pp.9-15
• /
• 2021

In multi-string light-emitting diode (LED) driver system, current balancing is crucial because the brightness of LED is directly related to its forward current. This paper presents a novel LED current balancing topology using current-fed Z-source converter. With the proposed structure, currents flowing through two LED strings are automatically balanced owing to the charge-balance condition on capacitors. Operation of the proposed converter is simple and the proposed converter uses only one active switch and one diode. Moreover, low-side gate driving can be used to operate the active switch. To verify the operation of the proposed LED current balancing converter, a prototype is built and tested with different numbers of LEDs.

• Journal of the Korean Statistical Society
• /
• v.35 no.4
• /
• pp.441-452
• /
• 2006

Here an efficient regression type estimator for a stratified population mean is proposed under the two-phase sampling scheme. While constructing the proposed estimator, it is assumed that the first auxiliary variable x is directly and highly correlated with the study variable y, and the second auxiliary variable z is directly and highly correlated with the first auxiliary variable x. However the variable z is not directly correlated with the variable y, but they are just correlated with each other only due to their direct and high correlation with the variable x. The proposed regression type estimator is found to be always more efficient than the existing estimators defined under the same situation.

• Journal of The Korean Astronomical Society
• /
• v.11 no.1
• /
• pp.1-30
• /
• 1978

The four dimensional classification of globular dusters with the parameters, Z, Y, age and HB type is presented defining two new parameters. $(B-V)_{1/2}\;and\;S_{3/2}$ which are shown to be tightly correlated with Kinman's spectral types and the helium abundances obtained from the R-method, respectively. The Z- and Y- abundances are derived from $(B-V)_{1/2}\;and\;S_{3/2}$, respectively, and the latter parameters determine the age class of clusters with help of Dickens' HB type, which is a function of Z. Y and age. For the examined forty two globular clusters the computed range at Z and Y are $1.5{\times}10^{-4}{\leq}Z{\leq}4.5{\times}10^{-2}\;and\;0.23<Y{\leq}0.41$. The age difference between the oldest (HB type 1) and the youngest (HB type 7) clusters is roughly estimated to be $2-4{\times}10^9$ years. Using these four parameters the known anomalous C-M diagrams seem to be reasonably interpreted without taking into account some complicate parameters such as unusually overabundant heavy elements, mass loss and mass spread, etc. The four dimensional scheme strongly suggests the slow successive collapses of the proto-Galaxy rather than a single fast collapse, and by this slow collapse model the inversion of chemical abundance gradient in the Galaxy can be explained. It is also shown that the clump position along the RGB near the HB level removes down to the fainter magnitude as the Z(Y)- abundance increases (decreases).