• Journal of information and communication convergence engineering
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• v.10 no.1
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• pp.21-26
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• 2012

As the new requirements for wireless sensor networks are emerging, real-time communications is becoming a major research challenge because resource-constrained sensor nodes are not powerful enough to accommodate the complexity of the protocol. In addition, an efficient energy management scheme has naturally been a concern in wireless sensor networks for a long time. However, the existing schemes are limited to meeting one of these two requirements. To address the two factors together, we propose real-time communications with two approaches, a protocol for satisfied conditions and one for unsatisfied. Under the satisfied requirement, existing real-time protocol is employed. On the other hand, for the unsatisfied requirement, the newly developed scheme replaces the existing scheme by adjusting the transmission range of some surplus nodes. By expanding the transmission range, the end-to-end delay is shortened because the number of intermediate nodes decreases. These nodes conserve their energy for real-time communications by avoiding other activities such as sensing, forwarding, and computing. Finally, simulation results are given to demonstrate the feasibility of the proposed scheme in high traffic environments.

• The Journal of Information Technology and Database
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• v.8 no.2
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• pp.103-114
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• 2001

In this paper, we propose an efficient index mechanism for real-time main memory database systems. Existing main memory index structures based on the tree can effectively support range searches. However, it doesn't guarantee the real-time characteristic because difference between the access time of a node and an average access time can be high. The index structures based on the hash have always a regular random access time on the simple searches and that speed is very fast. However they do not support range searches. To solve such problems, we propose a new index mechanism called Hyper Tree-Hash (Hyper-TH) that combines ECBH (Extendible Chained Bucket Hashing) and T＊-tree. ECBH can be dynamically extended and has a very fast access time. T＊-tree effectively supports the range searches. We show through our experiments that the proposed mechanism outperforms existing other index structures.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.4
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• pp.116-123
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• 2008

In this paper we study the performance of the measurement time-delay estimation of tightly-coupled GPS/INS(Global positioning system/Inertial Navigation system) system. Generally, the heading error estimation performance of loosely-coupled GPS/INS system using GPS's Navigation Solution is poor. In the case of tightly-coupled GPS/INS system using pseudo-range and pseudo-range rate, the heading error estimation performance is better. However, the time-delay error on the measurement(pseudo-range rate) make the heading error estimation performance degraded. So that, we propose the time-delay model on the measurement and compose the time-delay estimator. And we confirm that the heading error estimation performance in the case of measurement time-delay existence is similar with the case of no-delay by Monte-Carlo simulation.

• Journal of the Korean Institute of Telematics and Electronics
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• v.15 no.5
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• pp.13-18
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• 1978

A delay switching PLL (DSPLL) is proposed for improvement of the frequency acquisition Performance (pull-in range) while keeping a narrow bandwidth LPF. It has, between the phase detector and the LPF, just a simple RC delay circuit, a switch and another phase detector controlling the switching time. For the common second order PLL, the pull-in capability of the DSPLL is analyzed approximately, without considering additive white noise effect, and verified experimentally. It is shown that the delay switching extends the pull-in range significantly, as much as a half of lock-range. At the phase tracking mode, the delay switching does not function, to make the DSPLL be a normal PLL.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.273-274
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• 2007

영상 신호에서 Dynamic Range는 이미지가 포함하고 있는 휘도의 최소 레벨과 최대 레벨의 비이다. 이미지 촬상 장치가 표현할 수 있는 Dynamic Range는 한정되어 있기 때문에 한정된 범위를 벗어나는 영역에 대해서는 이미지의 왜곡 혹은 손실이 발생한다. 본 논문에서는 Line별로 다른 Integration Time을 적용하는 방법으로 영상의 계조 표현 범위를 넓게 향상시켜 Wide Dynamic Range를 갖는 영상을 얻는 방법을 기술한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.11
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• pp.54-61
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• 2012

This study investigated the relationship between the response time of DVR (Dynamic Voltage Restorer) and the possible compensation range for voltage dips by the DVR system which protects the 3-phase phase-controlled rectifier from said dips. As a result, the permissible range of voltage dip is presented in a 3-phase phase-controlled rectifier. When the DVR compensates for voltage dip, the range of voltage dip can be compensated according to the DVR's response time. Using the proposed method, DVR response time can be determined from the parameters of the 3-phase phase-controlled rectifier and the possible compensatory range of voltage dip, while at the same time it is possible to use a control system having an appropriate speed. Therefore, the use of excessively fast equipment can be avoided, improving the stability of the overall system. The reliability of the DVR concerning the 3-phase phase-controlled rectifier can be verified by simulation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.4
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• pp.639-642
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• 2012

Optical coherence tomography(OCT) can provide real-time and non-invasive subsurface imaging with ultra-high resolution of micrometer scale. However, conventional OCT systems generally have a limited imaging depth range within a depth of only 1-2 mm. To overcome the limitation, we have proposed an active surface tracking algorithm used in common-path Fourier-domain OCT system in order to extend the imaging depth range. The surface tracking algorithm based on the threshold and Savitzky-Golay filter of A-scan data was applied to real-time tracking. The algorithm has controlled a moving stage according to the sample's surface variance in real time. An OCT image obtained by the algorithm clearly show an extended imaging depth range. Consequently, the proposed algorithm demonstrated the potential for improving the conventional OCT systems with limitary depth range.

• Bulletin of the Korean Chemical Society
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• v.25 no.9
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• pp.1403-1407
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• 2004

Dielectric relaxation measurements on 3-nitrotoluene (3-NT) mixture of dimethylacetamide (DMA), dimethylformamide (DMF) and dimethysulphoxide (DMSO) have been carried out across the entire concentration range using Time domain reflectometry technique at 15, 25, 35 and $45^{\circ}C$ over the frequency range from 10 MHz to 20 GHz. For all the mixtures, only one dielectric loss peak was observed in this frequency range and the relaxation in these mixtures can be well described by a single relaxation time using Debye model. Bilinear calibration method is used to obtain complex permittivity ${\varepsilon}^{*}({\omega})$ from complex reflection coefficient ${\rho}^{*}({\omega})$ over frequency range 10 MHz to 20 GHz. The excess permittivity, excess inverse relaxation time, Kirkwood correlation factor, molar energy of activation are also calculated for these mixtures to study the solute-solvent interaction.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.11
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• pp.19-28
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• 2003

The limitation on the dynamic range improvement of the complementary correlation optical time domain reflectometer(CCOTDR) is presented. In CCOTDR, the improvement of dynamic range is function of both the averaging number of measurement cycles and the length of codes. The trade off between the averaging number and the code length restricts the improvement of the dynamic range and a very long code is not effective to improve the dynamic range. In this paper, the improvement limitation on dynamic range caused by the trade off between the averaging number and the code length is presented. For derivation of the trade off, the number of one measurement cycles employing a conventional single pulse method and employing a complementary code method are presented and compared. And the effective maximum code length is presented in addition.

• Proceedings of the Korean Society of Environment and Ecology Conference
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• 2007.04a
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• pp.136-142
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• 2007

The main aim of this study is to estimate home-range of the Korean raccoon dog(Nyctereutes procyonoides koreensis) at a rural area of Gurye in the southern part of South Korea. A radio-tracking was regularly carried out on 4 raccoon dogs for 2 days every 2 months in 2006. During the days, the radio-tracking was usually conducted every 1-3 hours through day-time to night-time. Among the 4 raccoon dogs, 2 individuals(a permanent breeding pair) could be extensively tracked for 5 to 7 months, including all 4 seasons. The result showed that total home-range sizes of the pair were 0.732 $km^2$ and 0.373 $km^2$ for 100% minimum convex polygons(MCP) and 100% kernel(K), respectively, during the monitoring period. Mean home-range sizes of the 2 raccoon dogs were 0.035-0,688 $km^2$ and 0.012-0.341 $km^2$ for MCP and K, respectively. Yearly home-range sizes of the male and female were similar to each other. However, home-range sizes of the raccoon dogs between day-time and night-time were quite different. Furthermore, the raccoon dogs showed a much broader home-range size in spring, summer and fall than in winter season. Finally, the pair had a broad overlapping home-range(about 70-95%), and 1 core area and 4 different feeding areas.