• Title/Summary/Keyword: compression delay time

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Energy-aware Selective Compression Scheme for Solar-powered Wireless Sensor Networks (태양 에너지 기반 무선 센서 네트워크를 위한 에너지 적응형 선택적 압축 기법)

  • Kang, Min Jae;Jeong, Semi;Noh, Dong Kun
    • Journal of KIISE
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    • v.42 no.12
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    • pp.1495-1502
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    • 2015
  • Data compression involves a trade-off between delay time and data size. Greater delay times require smaller data sizes and vice versa. There have been many studies performed in the field of wireless sensor networks on increasing network life cycle durations by reducing data size to minimize energy consumption; however, reductions in data size result in increases of delay time due to the added processing time required for data compression. Meanwhile, as energy generation occurs periodically in solar energy-based wireless sensor networks, redundant energy is often generated in amounts sufficient to run a node. In this study, this excess energy is used to reduce the delay time between nodes in a sensor network consisting of solar energy-based nodes. The energy threshold value is determined by a formula based on the residual energy and charging speed. Nodes with residual energy below the threshold transfer data compressed to reduce energy consumption, and nodes with residual energy above the threshold transfer data without compression to reduce the delay time between nodes. Simulation based performance verifications show that the technique proposed in this study exhibits optimal performance in terms of both energy and delay time compared with traditional methods.

Wavelet Compression Method with Minimum Delay for Mobile Tele-cardiology Applications (이동형 Tele-cardiology 시스템 적용을 위한 최저 지연을 가진 웨이브릿 압축 기법)

  • Kim Byoung-Soo;Yoo Sun-Kook;Lee Moon-Hyoung
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.53 no.11
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    • pp.786-792
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    • 2004
  • A wavelet based ECG data compression has become an attractive and efficient method in many mobile tele-cardiology applications. But large data size required for high compression performance leads a serious delay. In this paper, new wavelet compression method with minimum delay is proposed. It is based on deciding the type and compression ratio(CR) of block organically according to the standard deviation of input ECG data with minimum block size. Compression performances of the proposed algorithm for different MIT ECG Records were analyzed comparing other ECG compression algorithm. In addition to the processing delay measurement, compression efficiency and reconstruction sensitivity to error were also evaluated via random noise simulation models. The results show that the proposed algorithm has both lower PRD than other algorithm on same CR and minimum time in the data acquisition, processing and transmission.

Mobile Robot Teleoperation to Consider the Stability over the Time-Delay of Wireless Network (무선네트워크의 시간지연을 고려한 원격이동로봇의 안정성에 대한 연구)

  • Ro, Young-Shick;Kang, Hee-Jun;Suh, Young-Soo;Yoo, Sun-Kuk
    • Proceedings of the KIEE Conference
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    • 2007.04a
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    • pp.340-342
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    • 2007
  • When a system is teleoperated in the indoor environment through the wireless LAN, the communication time delay that is due to the inherent characteristic and surrounding environment is random and unbounded. The time delay has a significant effect on the stability and performance of the teleoperating system. In this paper, we present the method that is the image compression, measuring time delay and switching control-mode corresponding to time delay automatically, to improve stability and performance, and the simple experiment is conducted to demonstrate the feasibility

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Observation on the Ignition Delay Time of Cool and Thermal Flame of n-heptane/alcohol Blended Fuel at Low Temperature Combustion Regime (저온연소조건에서 n-heptane/alcohol 혼합연료의 냉염과 열염에 대한 착화지연 관찰)

  • Song, Jaehyeok;Kang, Kijoong;Ryu, Seunghyup;Choi, Gyungmin;Kim, Duckjool
    • Journal of the Korean Society of Combustion
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    • v.18 no.4
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    • pp.12-20
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    • 2013
  • The ignition delay time is an important factor to understand the combustion characteristics of internal combustion engine. In this study, ignition delay times of cool and thermal flame were observed separately in homogeneous charge compression ignition(HCCI) engine. This study presents numerical investigation of ignition delay time of n-heptane and alcohol(ethanol and n-butanol) binary fuel. The $O_2$ concentration in the mixture was set 9-10% to simulate high exhaust gas recirculation(EGR) rate condition. The numerical study on the ignition delay time was performed using CHEMKIN codes with various blending ratios and EGR rates. The results revealed that the ignition delay time increased with increasing the alcohol fraction in the mixture due to a decrease of oxidation of n-heptane at the low temperature. From the numerical analysis, ethanol needed more radical and higher temperature than n-butanol for oxidation. In addition, thermal ignition delay time is sharply increasing with decreasing $O_2$ fraction, but cool flame ignition delay time changes negligibly for both binary fuels. Also, in high temperature regime, the ignition delay time showed similar tendency with both blends regardless of blending ratio and EGR rate.

The investigation on the Ignition Delay of n-heptane/n-butanol Blend Fuel using a Rapid Compression Machine at Low Temperature Combustion Regime (저온연소조건에서 급속압축기를 이용한 n-heptane/n-butanol 혼합연료의 착화지연에 관한 연구)

  • Song, Jaehyeok;Kang, Kijoong;Yang, Zheng;Lu, Xingcai;Choi, Gyungmin;Kim, Duckjool
    • 한국연소학회:학술대회논문집
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    • 2013.06a
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    • pp.25-28
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    • 2013
  • This study presents both experimental and numerical investigation of ignition characteristics of n-heptane and n-butanol mixture. The $O_2$ concentration was fixed to 9-10% to make high exhaust gas recirculation(EGR) rate condition. Experiments were performed using a rapid compression machine. In addition, a numerical study of the ignition delay time was performed using CHEMKIN codes to validate experimental results and predict chemical species after combustion process. The results showed that the ignition delay time increased with increasing n-butanol ratio and the reactivity decreased by low $O_2$ concentration.

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The investigation on the Ignition Delay of n-heptane/n-butanol Blend Fuel Using a Rapid Compression Machine at Low Temperature Combustion Regime (저온연소조건에서 급속압축기를 이용한 n-heptane/n-butanol 혼합연료의 착화지연에 관한 연구)

  • Song, Jae Hyeok;Kang, Ki Joong;Yang, Zheng;Lu, XingCai;Choi, Gyung Min;Kim, Duck Jool
    • Journal of the Korean Society of Combustion
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    • v.18 no.2
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    • pp.32-41
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    • 2013
  • This study presents both experimental and numerical investigation of ignition delay time of n-heptane and n-butanol binary fuel. The $O_2$ concentration in the mixture was set to 9-10% to make high exhaust gas recirculation( EGR) rate condition which leads low NOx and soot emission. Experiments were performed using a rapid compression machine(RCM) at compressed pressure 20bar, several compressed temperature and three equivalence ratios(0.4, 1.0, 1.5). In addition, a numerical study on the ignition delay time was performed using CHEMKIN codes to validate experimental results and predict chemical species in the combustion process. The results showed that the ignition delay time increased with increasing the n-butanol fraction due to a decrease of oxidation of n-heptane at the low temperature. Moreover, all of the binary fuel mixtures showed the combustion characteristics of n-heptane such as cool flame mode at low temperature and negative-temperature-coefficient(NTC) behavior. Due to the effect of high EGR rate condition, the operating region is reduced at lean condition and the ignition delay time sharply increased compared with no EGR condition.

Measurement of Compression Temperature in Cylinder by using the Compensation Circuit of Thermocouple (열전대 보상회로에 의한 실린더 내에서의 압축온도 측정)

  • Kwon, Soon-Ik
    • Journal of the Korean Society of Industry Convergence
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    • v.3 no.2
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    • pp.149-154
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    • 2000
  • The purpose of this study is to measure the compression temperature in cylinder by using the fine thermocouple. As for using the thermocouple, it's response time delay should be regarded, even if it is a fine one. So, the output of thermocouple needs some compensation. The compensation circuit, which consists of a differential and an adding circuit is used for the compensate the time lag. And the time constant of the compensation circuit is determined the time between the TDC and the maximum point of the thermocouple output. Using this compensation circuit, the compression temperature is investigated of the cylinder in the diesel engine.

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Simplified Reaction Scheme of Hydrocarbon Fuels and Its Application to Autoignition of n-Heptane (탄화수소계 연료의 축소반응모텔과 노말-헵탄(n-Heptane)의 자발화 현상)

  • 여진구
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.1
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    • pp.76-83
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    • 2002
  • Mathematically and chemically simplified reaction scheme for n(heptane that simulates autoignitions of the end gases in spark ignition engines has been developed and studied computationally. The five(equation model is described, to predict the essential features of hydrocarbon oxidation. This scheme has been calibrated against autoignition delay times measured in rapid compression machines. The rate constants, activation temperatures, Ta, Arrhenius pre-exponential constants, A, and heats of reaction for stoichiometric nheptane/air has all been optimized. Comparisons between computed and experimental autoignition delay times have validated the present simplified reaction scheme. The influences of heat loss and concentration of chain carrier at the beginning of compression upon autoignition delay times have been computationally investigated.

Investigation of Molding Characteristics in Injection Compression Molding According to Molding Conditions through Birefringence (사출압축성형에서 복굴절을 통한 성형조건에 따른 성형특성 고찰)

  • Lee, Dan Bi;Nam, Yun Hyo;Lyu, Min-Young
    • Polymer(Korea)
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    • v.38 no.2
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    • pp.193-198
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    • 2014
  • Lens and DVD require high quality of optical property. Conventional injection molded products contain high residual stress and this invokes birefringence since high cavity pressure and high temperature variation are involved in a molding process. Thus these products are often molded by injection compression molding in order to minimize the residual stress through reducing cavity pressure and uniform cavity pressure. In this study, molding parameters affecting molding quality such as property uniformity in injection compression molding were investigated through experiment. Molding quality deviations among the cavities in multi-cavity mold were also studied. Transparent resins, PC and PS were used in this study. Compression gap, compression speed, compression force, and compression delay time for processing variables in injection compression molding were applied in experiment. Compression force, compression delay time, and compression gap significantly affected the optical property of product. The degree of influence of process variable on the product quality was different in different resins. This implies that the optimal operational conditions in injection compression molding existed for each resin according to flow property.

Simplified Reaction Scheme of Hydrocarbon Fuels and Its Application to Autoignition of Gasoline with Different Octane Numbers (탄화수소계 연료의 축소반응모델과 가솔린연료의 옥탄가 변화에 따른 자발화 지연시간)

  • 여진구
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.3
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    • pp.13-19
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    • 2003
  • Mathematically simplified reaction scheme that simulates autoignitions of the end gases in spark ignition engines has been studied computationally. The five equation model is described, to predict the essential features of hydrocarbon oxidation. This scheme has been calibrated against autoignition delay times measured in rapid compression machines. The rate constants, activation temperatures, Ta, Arrhenius preexponential constants, A, and heats of reaction for stoichiometric n-heptane/air, iso-octane/air, and their mixtures have all been optimised. The optimisation has been guided by Morley's correlation of the ratio of chain branching to linear termination rates with octane number. Comparisons between computed and experimental autoignition delay times have validated the Present simplified reaction scheme and the influences of octane number upon autoignition delay times have been computationally investigated. It has been found that both cool flame and high temperature direct reactions can have an effect on autoignition delay times.