• Title/Summary/Keyword: high compression

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A Still Image Compression System with a High Quality Text Compression Capability (고 품질 텍스트 압축 기능을 지원하는 정지영상 압축 시스템)

  • Lee, Je-Myung;Lee, Ho-Suk
    • Journal of KIISE:Software and Applications
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    • v.34 no.3
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    • pp.275-302
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    • 2007
  • We propose a novel still image compression system which supports a high quality text compression function. The system segments the text from the image and compresses the text with a high quality. The system shows 48:1 high compression ratio using context-based adaptive binary arithmetic coding. The arithmetic coding performs the high compression by the codeblocks in the bitplane. The input of the system consists of a segmentation mode and a ROI(Region Of Interest) mode. In segmentation mode, the input image is segmented into a foreground consisting of text and a background consisting of the remaining region. In ROI mode, the input image is represented by the region of interest window. The high quality text compression function with a high compression ratio shows that the proposed system can be comparable with the JPEG2000 products. This system also uses gray coding to improve the compression ratio.

A Chancteristic of Thermal Efficiency in Order to High Expansion Realization with a Retard of Intake Valve Closing Time in the Low Speed Diesel Engine (저속 디젤기관에서 흡기밸브 닫힘시기 지연시 고팽창 실현을 위한 열효율 특성)

  • Jang Tae-Ik
    • Journal of Advanced Marine Engineering and Technology
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    • v.30 no.1
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    • pp.42-49
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    • 2006
  • In this research. the diesel cycle was thermodynamically interpreted to evaluate the possibility of high efficiency by converting diesel engines to the high expansion diesel cycle, and general cycle features were analyzed after comparing these two cycles. Based on these analyses. an experimental single cylinder a long stroke with high expansion-diesel engine. of which S/B ratio was more than 3, was manufactured. After evaluating the base engine through basic experiments, a diesel engine was converted into the high expansion diesel engine by establish VCR device and VVT system Accordingly, the high expansion diesel cycle can be implemented when the quantity of intake air is compensated by supercharge and the effective compression ratio is maintained at its initial level through the reduction of the clearance volume. In this case, heat efficiency increased by $5.0\%$ at the same expansion-compression ratio when the apparent compression ratio was 20 and the fuel cut off ratio was 2. As explained above, when the atkinson cycle was used for diesel cycle, heat efficiency was improved. In order to realize high expansion through retarding the intake value closing time, the engine needs to be equipped with variable valve timing equipment, variable compression ratio equipment and supercharged pressure equipment. Then a high expansion diesel cycle engine is realized.

A study on the Application of Prone Compression Study for Obese Patients in Upper Gastrointestinal Series (비만환자의 위장조영술에 있어 복와위 압박법의 적용에 관한 연구)

  • Son, Soon-Yong;Jung, Hong-Ryang
    • Journal of radiological science and technology
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    • v.22 no.2
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    • pp.9-15
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    • 1999
  • The aim of this study is to measure the application of prone compression study using compression paddle for obese patients in upper gastrointestinal series. Prone compression study using compression paddle was performed in fifty patients, who were not examined completely erect compression study for obesity. The radiographs of stomach were classified into the lower, middle, and high body and then we gave five points included 'very poor', 'poor', 'suspicious', 'good', and 'complete' according to level of detection for area gastrica and mucosal fold. Statistic analysis was performed using T-test and ANOVA, and confidence rate was fixed in 95%(P<0.05) for the significance. The results were as follows : 1. The compression marks on high body was 'poor' grades in erect and prone compression study. The points were 1.64 and 1.86, respectively. 2. The compression marks on middle body was 1.68 in erect compression study, and 'suspicious' in prone compression study. 3. The compression marks on lower body was 'poor' in erect compression study, and 'good' in prone compression study. 4. There was a high statistic signification between the two study on middle and lower body except for high body(P<0.01). 5. The average abdominal thickness of subjects was 23.98 centimeter. There was no statistic signification between the difference of average marks by the abdominal thickness(P>0.05). As these results, the prone compression study in upper gastrointestinal serie seem to be an useful study for obese patients, because it decreases pain and the feeling of uneasiness, and improve compression efficiency remarkably.

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DRASTIC IMPROVEMENT OF THERMAL EFFICIENCY BY RAPID PISTON-MOVEMENT NEAR TDC

  • Moriyoshi, Y.;Sano, M.;Morikawa, K.;Kaneko, M.
    • International Journal of Automotive Technology
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    • v.7 no.3
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    • pp.295-301
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    • 2006
  • A new combustion method of high compression ratio SI engine was studied and proposed in order to achieve high thermal efficiency, comparable to that of CI engine. Compression ratio of SI engine is generally restricted by the knocking phenomena. A combustion chamber profile and a cranking mechanism were studied to avoid knocking with high compression ratio. Because reducing the end-gas temperature will suppress knocking, a combustion chamber was considered to have a wide surface at the end-gas region. However, wide surface will lead to large heat loss, which may cancel the gain of higher compression ratio operation. Thereby, a special cranking mechanism was adapted which allowed the piston to move rapidly near TDC. Numerical simulations were performed to optimize the cranking mechanism for achieving high thermal efficiency. An elliptic gear system and a leaf-shape gear system were employed in numerical simulations. Livengood-Wu integral, which is widely used to judge knocking occurrence, was calculated to verify the effect for the new concept. As a result, this concept can be operated at compression ratio of fourteen using a regular gasoline. A new single cylinder engine with compression ratio of twelve and TGV(Tumble Generation Valve) to enhance the turbulence and combustion speed was designed and built for proving its performance. The test results verified the predictions. Thermal efficiency was improve over 10% with compression ratio of twelve compared to an original engine with compression ratio of ten when strong turbulence was generated using TGV, leading to a fast combustion speed and reduced heat loss.

The Fundamental Study on Generation of High Turbulence at Vicinity of Ignition Timing (점화시기 근방의 고난류 생성을 위한 기초연구)

  • Hong, Jae-Ung;Song, Yeong-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.1
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    • pp.275-283
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    • 1996
  • The turbulence in the engine cylinder is generated by intake pressure and inertia effects during intake stroke, and is generated and decreased by piston compression effect during the compression stroke. The classified needed to generate high turbulence flow at vicinity of ignition timing. Therefore, A single-shot Rapid Intake Compression Expansion Machine (RICEM), which is able to realize the intake, compression, expansion or intake-compression stroke under high piston speed respectively, was manufactured and evaluated in order to find methods to generate high turbulence at around spark timing. It was found that the characteristics of RICEM such as reapperance, leakage, piston displacement with crank angle was corresponding to those of real engine and RICEM simulates not only high temperature and high pressure field but also flow patterns of the actual engine by increasing of pressure in intake line.

Effect of Compression Ratio on the Combustion Characteristics of a Thermodynamics-Based Homogeneous Charge Compression Ignition Engine

  • Han, Sung Bin
    • Journal of Energy Engineering
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    • v.24 no.3
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    • pp.61-66
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    • 2015
  • Homogeneous charge compression ignition (HCCI) engine combines the combustion characteristics of a compression ignition engine and a spark ignition engine. HCCI engines take advantage of the high compression ratio and heat release rate and thus exhibit high efficiency found in compression ignition engines. In modern research, simulation has be come a powerful tool as it saves time and also economical when compared to experimental study. Engine simulation has been developed to predict the performance of a homogeneous charge compression ignition engine. The effects of compression ratio, cylinder pressure, rate of pressure rise, flame temperature, rate of heat release, and mass fraction burned were simulated. The simulation and analysis show several meaningful results. The objective of the present study is to develop a combustion characteristics model for a homogeneous charge compression ignition engine running with isooctane as a fuel and effect of compression ratio.

Intra-picture Block-matching Method for Codebook-based Texture Compression

  • Cui, Li;Jang, Euee S.
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.10 no.10
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    • pp.5063-5073
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    • 2016
  • In this paper, an efficient texture compression method is proposed for fast rendering, which exploits the spatial correlation among blocks through intra-picture block matching. Texture mapping is widely used to enhance the visual quality of results in real-time rendering applications. For fast texture mapping, it is necessary to identify an effective trade-off between compression efficiency and computational complexity. The conventional compression methods utilized for image processing (e.g., JPEG) provide high compression efficiency while resulting in high complexity. Thus, low complexity methods, such as ETC1, are often used in real-time rendering applications. Although these methods can achieve low complexity, the compression efficiency is still lower than that of JPEG. To solve this problem, we propose a texture compression method by reducing the spatial redundancy between blocks in order to achieve the better compression performance than ETC1 while maintaining complexity that is lower than that of JPEG. Experimental results show that the proposed method achieves better compression efficiency than ETC1, and the decoding time is significantly reduced compared to JPEG while similar to ETC1.

Study of Shock Tube for Wave Phenomenon in High Speed Railway Tunnel(1) - On the characteristics of Compression Wave - (고속철도 터널에서 발생하는 파동현상에 관한 충격파관의 연구(1) - 압축파의 특성에 대하여 -)

  • ;松尾一泰
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.10
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    • pp.2686-2697
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    • 1994
  • When a railway train enters a tunnel at high speed, a compression wave is formed in front of the train and propagates along the tunnel. The compression wave subsequently emerges from the exit of the tunnel, which causes an impulsive noise. In order to estimate the magnitudes of the noises and to effectively minimize them, the characteristics of the compression wave propagating in a tunnel must be understood. In the present paper, the experimental and analytical investigations on the attenuation and distortion of the propagating compression waves were carried out using a model tunnel. This facility is a kind of open-ended shock tube with a fast-opening gate valve instead of a general diaphragm. One-dimensional flow model employed in the present study could appropriately predict the strength of the compression wave, Mach number and flow velocity induced by the compression wave. The experimental results show that the strength of a compression wave decreases with the distance from the tunnel entrance. The decreasing rate of the wave strength and pressure gradient in the wave is strongly dependent on the strength of the initial compression wave at the tunnel entrance.

Performance Characteristics of CNG Engine at Various Compression Ratios (압축비 변경에 따른 CNG기관의 특성 연구)

  • Kim Jin-young;Ha Jong-yul
    • Transactions of the Korean Society of Automotive Engineers
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    • v.13 no.4
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    • pp.145-151
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    • 2005
  • Natural gas is one of clean fuels that can replace petroleum-based fuels, because it has low exhaust emission, comparatively high thermal efficiency and abundant deposits. In this addition, owing to high octane number and wide lean flammability limit, it has a strong point to increase the compression ratio. For this reason, the research is being actively executed to increase the generating power and thermal efficiency of the engine by raising the compression ratio through utilization of high octane number relevant to development of CNG engine. In this study, 0.63L single cylinder diesel engine has been used to alter easily compression ratio. Compression ratio has gotten under control by modifying the thickness of gasket between cylinder head and block without major structural modifications. As the result, as compression ratio has increased, generating power and fuel consumption ratio have been improved. As for emission concentration, as compression ratio has increased, THC concentration has been decreased while exhause concentration of NOx increased. In case compression ratio has excessively increased, brake output decrease and cycle variation have been increased. As the result acquired by analyzing brake output, fuel consumption ratio, cycle variation and exhaust, the engine driving condition has acquired $\varepsilon=13$ as the optimal compression ratio in this study.

One-Dimensional Numerical Study of Compression Wave Propagating in High-Speed Railway Tunnel (고속철도 터널내를 전파하는 압축파의 일차원 수치해석)

  • 김희동;엄용균;송미일태
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.5
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    • pp.1280-1290
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    • 1995
  • In order to investigate the compression wave propagating in a high-speed railway tunnel, a numerical calculation was applied to the wave phenomenon occurring in a model tunnel. Unsteady, one-dimensional inviscid or viscous flows were solved by an explicit TVD scheme, and the calculated flows were compared with the results of measurement in real tunnels. Tunnel noises caused by emission of the compression wave were characterized in terms of excess pressure of compression wave, pressure gradient in the wave front and width of the compression wave. Calculated attenuation, pressure gradient and width of compression wave with the propagating distance agreed with the results of measurement in the real tunnels. The results also show that tunnel noises are proportional to the train velocity entering the tunnel.