• 대한기계학회논문집
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• 제18권10호
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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.

• 음성과학
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• 제9권4호
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• pp.165-173
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• 2002

Strong compression effects in a stressed vowel due to the addition of syllables have been adopted as evidence for stress-timing. In relation to this, Yun (2002) investigated the compression effects of number of syllables on Korean vowel. The results generally revealed that Korean had neither significant nor consistent anticipatory or backwards compression effects, especially when it came to the sentence level. This led us to claim that Korean would not be a stress-timed language. But the language investigated in the study was only Korean, and further cross-linguistic research was needed to confirm the claim. In this study, Yun's (2002) sentence level data are compared with Fowler's (1981) English data. The comparison reveals that Korean seems to be similar to English in the backwards compression effect, whereas the two languages are markedly different in the anticipatory compression effect. Thus, if English is a stress-timed language and the strong anticipatory compression effect is evidence in favour of stress-timing as is claimed, the present cross-linguistic study confirms Yun's (2002) suggestion-Korean is unlikely to be stress-timed. On the other hand, compression effects are revisited: the differences in vowel compression between English and Korean are discussed from the syntactic and phonological points of view.

• The Journal of Korean Physical Therapy
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• 제23권6호
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• pp.43-47
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• 2011

Purpose: The aim of this preliminary study was to use hand function tests to Hand dexterity levels provided by the type of compression garment and compression bandages in asymptomatic subjects and to collect baseline data for the comparison of hand functions in the patients with chronic arm lymphedema. Methods: The subjects of this study were 32 healthy volunteer female with a mean age of 45.8 years. Grip strength and hand functions were tested in three conditions-no compression, compression garment, and compression bandages-using the nine-hole peg test (NHPT), the box and block test (B&BT), Minnesota Manual Dexterity test (MMDT), and the hand-held Jamar dynamometer. Results: The grip strength was significantly low in the bandage condition (p<0.05). The performance in both compression groups (i.e., bandage and compression garment) decreased as the thickness of the compression material increased (p<0.05). Conclusion: The findings of this study suggest that grip strength and hand function scores are influenced by the characteristics of the compression applied. Future study is needed to determine the level of hand function between patients with chronic arm lymphedema and healthy individuals.

• 한국응급구조학회지
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• 제16권3호
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• pp.103-115
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• 2012

Purpose : Inadequate chest compression during cardiopulmonary resuscitation(CPR) may result in the insufficient blood flow to preserve critical organ function. The study evaluated changes of quality of cardiopulmonary resuscitation over time in 30:2 CPR by laypersons and analyzed rescuer factors affecting the quality of chest compressions over time. Methods : This study was designed to know quality of CPR changes during 5 minutes. 47 students completed CPR training courses. They were performed 30:2 CPR using a manikin with Skill-Reporter for 5 minutes continuously to get data of depth, rate of chest compression, volume and correct rate of ventilation. Results : Time dependent analysis showed significant ineffective compression depth in females and under weight rescuers. In case of female, we found effective compression depth has maintained up to 2 minutes, but it decreased significantly after 2 minutes. However, underweight rescuers maintained effective compression depth up to a minute but it decreased after 1 minute. Conclusion : Although compression rate maintained over time, chest compression quality declined significantly. It suggested switching compression at an interval of 2 minutes is reasonable for 30:2 CPR by layperson but underweight rescuers may provide effective chest compression by switching shift every one minute.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권3호
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• pp.124-130
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• 2006

A wavelet-based image compression system allowing both lossless and lossy image compression is proposed in this paper. The proposed algorithm consists of the two stages. The first stage uses the wavelet packet transform and the quad-tree coding scheme for the lossy compression. In the second stage, the residue image taken between the original image and the lossy reconstruction image is coded for the lossless image compression by using the integer wavelet transform and the context based predictive technique with feedback error. The proposed wavelet-based algorithm, allowing an optional lossless reconstruction of a given image, transmits progressively image materials and chooses an appropriate wavelet filter in each stage. The lossy compression result of the proposed algorithm improves up to the maximum 1 dB PSNR performance of the high frequency image, compared to that of JPEG-2000 algorithm and that of S+P algorithm. In addition, the lossless compression result of the proposed algorithm improves up to the maximum 0.39 compression rates of the high frequency image, compared to that of the existing algorithm.

• 한국자동차공학회논문집
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• 제13권4호
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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.

• International Journal of Computer Science & Network Security
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• 제21권8호
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• pp.196-202
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• 2021

DNA sequencing provides fundamental data in genomics, bioinformatics, biology and many other research areas. With the emergent evolution in DNA sequencing technology, a massive amount of genomic data is produced every day, mainly DNA sequences, craving for more storage and bandwidth. Unfortunately, managing, analyzing and specifically storing these large amounts of data become a major scientific challenge for bioinformatics. Those large volumes of data also require a fast transmission, effective storage, superior functionality and provision of quick access to any record. Data storage costs have a considerable proportion of total cost in the formation and analysis of DNA sequences. In particular, there is a need of highly control of disk storage capacity of DNA sequences but the standard compression techniques unsuccessful to compress these sequences. Several specialized techniques were introduced for this purpose. Therefore, to overcome all these above challenges, lossless compression techniques have become necessary. In this paper, it is described a new DNA compression mechanism of pattern matching extended Compression algorithm that read the input sequence as segments and find the matching pattern and store it in a permanent or temporary table based on number of bases. The remaining unmatched sequence is been converted into the binary form and then it is been grouped into binary bits i.e. of seven bits and gain these bits are been converted into an ASCII form. Finally, the proposed algorithm dynamically calculates the compression ratio. Thus the results show that pattern matching extended Compression algorithm outperforms cutting-edge compressors and proves its efficiency in terms of compression ratio regardless of the file size of the data.

• 한국농공학회논문집
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• 제65권6호
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• pp.51-63
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• 2023

To improve the problem that the settlement curve of the consolidation theory of Terzaghi does not match well with the actual settlement curve, we included a secondary compression settlement and analyzed it by varying the beginning point and then obtained the following results. The current methods of calculating the compression index from the  log𝜎 curve and the coefficient of consolidation from the time-dependent settlement curve for each consolidation pressure proved that the final settlement amount will be consistent after a long time, but the actual settlement amount will always be smaller than the predicted settlement amount during the settlement progress stage. The consolidation factors estimated by the curve fitting with the condition that the secondary compression begins in the second half of the primary compression showed similar values to the consolidation factors estimated by the curve fitting for the primary compression only, and the settlement curves were in better agreement throughout the compression. It showed different values, showing low validity. It can be inferred that secondary compression acts from the point when a significant portion of the excess pore water pressure is dissipated, and the loading stress begins to have more influence on the skeletal structure of the soil. Analysis results show that secondary compression begins at the range of 91 % to 98 % on the average degree of primary consolidation.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.331-334
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• 2003

In the finite element simulation of hot forging processes using hexahedron, remeshing of a flash is very difficult. The mesh compression method is a remeshing technique to construct an effective hexahedral mesh. However, because mesh is distorted during the compression procedure or the mesh compression method, mesh smoothing is necessary to improve the mesh Qualify. in this study, several geometric mesh smoothing techniques and a matrix norm optimization technique are applied and compared which is more adaptive to the mesh compression method.

• 한국정보기술응용학회:학술대회논문집
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• 한국정보기술응용학회 2005년도 6th 2005 International Conference on Computers, Communications and System
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• pp.169-172
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• 2005

Genetic algorithm based predictor for lossless image compression is propsed. We describe a genetic algorithm to learn predictive model for lossless image compression. The error image can be further compressed using entropy coding such as Huffman coding or arithmetic coding. We show that the proposed algorithm can be feasible to lossless image compression algorithm.