• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.3
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• pp.1-7
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• 2002

This paper presents a new PLL clock generator that can improve a jitter noise characteristics and acquisition process by designing a multi-PFD(Phase Frequency Detector) and an adaptive charge pump circuit. The conventional PLL has not only a jitter noise caused from such a demerit of the wide dead zone and duty cycle, but also a long delay interval that makes a high speed operation unable. An advanced multi-structured PFD circuit using the TSPC(True Single Phase Clocking) circuit is proposed, in which it shows an excellent functionalities in terms of the jitter noises by designing its circuit with the exact dead zone and duty cycle. Our new designed adaptive charge pump in the loop filter of a PLL can improve an acquisition characteristic by adaptively increasing of current. The Hspice simulation is done to evaluate the performance of the proposed circuit. Simulation result shows that our PLL has under 0.01ns in the dead zone, no influence from the duty cycle of input signals and under 50ns in the acquisition time. This circuit will be able to be used in develops of high-performance microprocessors and digital systems.  

• Journal of IKEEE
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• v.15 no.1
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• pp.104-112
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• 2011

During the ground operation of Korean army, the voice message is mainly used for exchanging informations related to the surveillance and reconnaissance, command and control, and precision strike. However, in order to the battlefield visualization among fighting powers participating in the ground force operation, automatic situational awareness and variable message format (VMF) for command and control are required. For securing core technologies necessary for the battlefield visualization, message standard and message handler are established through several applied researches. Besides, the VMF for equipping a weapon system is in development. In this paper, a study on the Korean variable message format (KVMF), where interoperability of integrated battle management system (BMS) is guaranteed due to performing joint, ground, and combined operations so that the situation awareness and strike system can be automated in almost real time, is presented. From the modeling and simulation (M&S) results of the message processor, delay time is varied in accordance with the number of nodes in unit platoon network, message length, and generation interval of routine messages. Therefore, it is shown that the system performance can be optimized by establishing proper network protocol for each situation.

• Childhood Kidney Diseases
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• v.21 no.1
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• pp.15-20
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• 2017

Purpose: Febrile urinary tract infection (UTI) is one of the commonest bacterial infections in children. The purpose of this study is to investigate the clinical characteristics of the first episode of febrile UTI occurring in children over 5 years compared to those in infants younger than a year. Methods: We retrospectively reviewed the medical records of 10 patients over 5 years, having febrile UTI, and 25 controls under 1 year. Clinical characteristics including symptoms at admission, the time interval between symptom onset and hospital visit and/or diagnosis, duration of fever, urinalysis, and other laboratory and imaging test results were compared between the two groups. Results: Most patients in the control group showed only high fever at the time of presentation to the hospital. However, 60% of the case group had fever along with gastrointestinal (GI) symptoms such as abdominal and flank pain, vomiting, as well as relatively mild pyuria. The case group showed a longer duration between symptom onset and hospital visit and/or diagnosis. Conclusions: Delay in diagnosis and initiation of treatment of UTI increases the risk of permanent renal scarring and associated complications. Therefore, early diagnosis and treatment of febrile UTI is vital for very young infants, as well as children considering that febrile UTI could be an important cause of febrile illness in children over 5 years.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.9
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• pp.1846-1855
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• 2015

In this paper, a precise relative positioning with TD(time differenced) carrier phase measurements from a low-cost GNSS(Global Navigation Satellite System) receiver is proposed and analysed. The proposed method is using carrier phase measurement from a single GNSS receiver that reference receiver is not required and stand alone positioning is possible. TD operation removes the troublesome integer ambiguity resolution problem, and if the time interval is short, other error, such as, ionospheric, tropospheric delay and ephemeris error are effectively eliminated. The error analysis of the proposed method shows that a precise and positioning with carrier phase is possible. The implemented system is evaluated using a real car experiments. The results show that the horizontal positioning error was less than 3m during 10 minutes experiments, which is 4 times more precise than the results of normal code based absolute positioning.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.118-123
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• 1987

In relation to the dust detonatians which have imposed severe damages on the industry, the ignitability of various dusts has been investigated on a horizontal shock tube in this study. By using a newly designed air injector, very well-distributed clouds could be obtained. The proper reflected shock conditions have been generated by placing a reflector 1.5cm behind the air injector, which reflected the incident shock wave. The incident shock waves in the range of Mach number 2.8-3.3 created the postreflected shock temperature of 1200-1600K. Experimentally the ignition delay was defined as the time interval between the arrival of a reflected shock wave at dusts and the detection of visible light. Measured ignition delays of dusts investigated were located lower than 1msec under the above conditions. These values are one-order higher than those in the incident shock wave condition. In this type of ignitiion process the following three processes are considered to play important roles; heating of a particle, generation of volatile gas by endothermic devolatilization process, and its diffusion from the particle surface and the formation of stoichiometric mixture with oxidizer.

• Journal of Internet Computing and Services
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• v.9 no.5
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• pp.153-163
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• 2008

Almost literature has so far proposed the modifications to IEEE 802.11 DCF MAC protocol to improve system throughput and average delay. Jitter(variance in packet delays) is, however, considered as an important QoS parameter for real-time streaming service which is popularized increasingly. Unfortunately, legacy access protocol for WLAN can't support the jitter. This paper proposes two schemes modifying the DCF MAC protocol to reduce the average value of jitter for multimedia frames arrived at received nodes. The one scheme, referred to as DCW-DCF(Decreasing Contention Window-DCF), reduces CW(Contention Window) size by half whenever a transmitted frame collided against other frames and back-off happens. Also, it increase initial CW size according as the link utilization and the collision probability increase. The other scheme, referred to as D-DIFS(Differential-DIFS), assigns different values to DIFS. That is, the DIFS interval is deceased as the number of back-off for a frame increases. In this paper, the two schemes are evaluated through simulation using ns2 and simulation results show that the proposed schemes are effective for improving the jitter property of standard WLAN.

• Journal of Advanced Navigation Technology
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• v.18 no.5
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• pp.429-436
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• 2014

This paper proposes three methods of the time synchronization for Pseudolite and GPS and analyzes pseudolite time synchronization error factors for software based performance evaluation on proposed time synchronization methods. Proposed three time synchronization methods are pseudolite time synchronization station construction method, method by using UTC(KRIS) clock source and GPS timing receiver based time synchronization method. Also, we analyze pseudolite time synchronization error factors such as errors of pseudolite clock and reference clock, time delay as clock transmission line, measurement error of time interval counter and error as clock synchronization algorithm to design simulation platform for performance evaluation of pseudolite time synchronization.

• Journal of KIISE:Software and Applications
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• v.26 no.12
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• pp.1404-1417
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• 1999

웹과 같은 분산 환경에서는, 웹 브라우저 상에서 SQL 형식의 공간 질의를 수행시키는 것과 또한 서버로부터 그 질의 결과를 보는 것이 가능하다. 그러나, 격자 이미지(raster image)와 같은 대용량 공간 데이타를 포함하는 질의 결과를 웹 브라우징할 때 발생하는 많은 문제점들 중에서, 사용자 응답 시간의 지연은 매우 중요한 문제이다. 본 논문에서는 사용자의 재요청(callback) 접근 패턴이 공간적 근접성(spatial locality)을 따른다는 가정하에서의, 사용자 응답 시간을 최소화하기 위한 새로운 프리페치(prefetch) 전략에 대해서 서술한다. 본 논문의 프리페치 전략은 다음과 같이 요약될 수 있다. 첫째, 프리페치 알고리즘은 사용자의 접근 패턴을 잘 반영하는 힐버트 곡선(Hilbert-curve) 모델을 바탕으로 한다. 둘째, 프리페치 전송 비용을 줄이기 위해서 사용자의 재요청 시간 간격(think time)을 이용한다. 본 논문에서는, 힐버트 곡선을 이용한 프리페치 전략의 성능 평가를 위해서 다양한 실험을 하였으며, 그 결과로 프리페치를 하지 않는 방식보다 높은 성능 향상이 있음을 보인다.Abstract In distributed environment(e.g., WWW), it would be possible for the users to submit SQL-like spatial queries and to see their query results from the server on the Web browser. However, of many obstacles which result from browsing query results including large spatial data such as raster image, the delay of user response time is very critical. In this paper we present a new prefetch policy which can alleviate user response time on the assumption that user's callback access pattern has spatial locality. Our prefetch policy can be summerized as follows: 1) our prefetch algorithm is based on the Hibert-curve model which well replects user's access pattern, and 2) it utilizes user's callback interval to reduce prefetch network transmission cost. In this paper we conducted diverse experiments to show that our prefetch policy achieves higher performance improvement compared to other non-prefetch methods.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1559-1570
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• 2013

The family of ISO/IEEE11073 standards is the basis of the e-health system and provides interoperability for personal health devices. In the early stage of e-health business, it was expected that people would use a health device individually. In this case, a measurement datum was episodically acquired and generally transmitted for one person at a time. Recently, a health device is expected to be used by multiple people, and large amounts of measurement data are gathered in a short time interval. In addition, mobile health devices have become more popular, so that energy efficient measurement data transmission is required, to prolong the use of a device. In IEEE11073 PHD standards, data transmission is classified into three different types: immediate individual transfer, small block transfer, and large block transfer. The large block transfer using PM-store concept provides efficient transmission. However, an existing PM-store has problem when a device is used by multiple people. To address the defined problem, a modified PM-segment that is in compliance with 11073 standards is proposed in this paper. In particular, the proposed PM-segment is designed to minimize the additional complexity of an agent instead of a manager and it is interoperable with the existing manager. The proposed PM-segment shows better performance than the existing PM-segment, in terms of memory requirements and expected queue time. Also, performance comparison among the three transfers is performed in regard to the delay time and communication power consumption points of view.

• Explosives and Blasting
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• v.34 no.4
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• pp.40-45
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• 2016

Sites, where explosives are used, are constantly under constraint of vibration and noise levels. If a sensitive area is located nearby the sites, mechanical excavation has been preferred rather than blasting. Recently, however, blasting using electronic detonators is applicable in the areas, where previously should be excavated by mechanical methods. $HiTRONIC^{TM}$ is a fourth-generation detonator that utilizes Hanwha Corporation's advanced electronic technology. The detonator contains IC-Chip, which allows delay times between 0~15,000ms with 1ms interval. Furthermore, the product can provide high accuracy(0.01%) for accurate-blasting. Electronic detonator is widely used in highway and railway construction sites, large limestone quarries, and other works. In this paper, several sites, in which HiTRONIC was used, are introduced in order to enhance understanding of electronic detonator.