• 한국정보과학회논문지:소프트웨어및응용
• /
• 제34권3호
• /
• pp.275-302
• /
• 2007

본 논문은 고품질 텍스트 압축 기능을 지원하는 우수한 정지영상 압축 시스템을 제안한다. 영상에서 텍스트 부분을 분리하여 압축을 수행함으로서 고품질의 텍스트 압축 기능을 지원한다. 시스템은 코드블록 단위로 적응 이진 산술부호화를 수행하여 48:1 이상의 높은 정지영상 압축률을 보여주고 있다. 코드블록은 비트평면을 구성하는 비트들을 서브블록 단위로 파악하여 산술부호에 적합한 코드블록을 구성한 것이다. 산술부호기는 구성된 코드블록을 문맥을 기반으로 압축한다. 시스템의 입력 모드는 분할(Segmentation) 모드와 ROI(Region Of Interest) 모드로 구성된다. 분할 모드는 입력 영상을 텍스트 부분과 배경 영상 부분으로 분할하여 입력할 수 있게 한다. ROI 모드는 입력 영상을 관심 영역과 그 밖의 영역으로 구분하여 입력할 수 있게 한다. 현재 시스템이 나타내는 텍스트 압축 기능과 높은 압축률은 다른 JPEG2000 시스템들과 충분히 비교할 수 있는 수준이다. 시스템은 그 밖에 그레이 코딩을 수행하여 압축률을 향상시킨다.

• Journal of Advanced Marine Engineering and Technology
• /
• 제30권1호
• /
• pp.42-49
• /
• 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.

• 대한방사선기술학회지:방사선기술과학
• /
• 제22권2호
• /
• pp.9-15
• /
• 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.

• International Journal of Automotive Technology
• /
• 제7권3호
• /
• pp.295-301
• /
• 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.

• 대한기계학회논문집B
• /
• 제20권1호
• /
• pp.275-283
• /
• 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.

• International Journal of Internet, Broadcasting and Communication
• /
• 제16권2호
• /
• pp.22-30
• /
• 2024

Image compression-decompression methods have become increasingly crucial in modern times, facilitating the transfer of high-quality images while minimizing file size and internet traffic. Historically, early image compression relied on rudimentary codecs, aiming to compress and decompress data with minimal loss of image quality. Recently, a novel compression framework leveraging colorization techniques has emerged. These methods, originally developed for infusing grayscale images with color, have found application in image compression, leading to colorization-based coding. Within this framework, the encoder plays a crucial role in automatically extracting representative pixels-referred to as color seeds-and transmitting them to the decoder. The decoder, utilizing colorization methods, reconstructs color information for the remaining pixels based on the transmitted data. In this paper, we propose a novel approach to image compression, wherein we decompose the compression task into grayscale image compression and colorization tasks. Unlike conventional colorization-based coding, our method focuses on the colorization process rather than the extraction of color seeds. Moreover, we employ the Denoising Diffusion Null-Space Model (DDNM) for colorization, ensuring high-quality color restoration and contributing to superior compression rates. Experimental results demonstrate that our method achieves higher-quality decompressed images compared to standard JPEG and JPEG2000 compression schemes, particularly in high compression rate scenarios.

• 에너지공학
• /
• 제24권3호
• /
• pp.61-66
• /
• 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.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제10권10호
• /
• pp.5063-5073
• /
• 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.

• 대한기계학회논문집
• /
• 제18권10호
• /
• pp.2686-2697
• /
• 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.

• 한국자동차공학회논문집
• /
• 제13권4호
• /
• pp.145-151
• /
• 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.