• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.10a
• /
• pp.139-141
• /
• 2007

Compression tests were carried out to investigate morphologies of compressed specimen, deformation microstructure and stress-strain relation in high-nitrogen austenite stainless steel. Tests were performed under a wide range of temperature and, with true strain rates up to $\dot{\varepsilon}$ =0.05, 0.1, 0.5 and $1.0s^{-1}$. The activation energy of loading force was equal to plastic deformation energy within the temperature range of $900^{\circ}C$ to $1250^{\circ}C$. Dynamically recrystallized grain size decreased with an increasing strain rate and temperature. Flow stresses and deformation microstructures, were used to quantify the critical strain rate and recrystallized grain size. The grain size versus strain rate-temperature map obtained in the study was in good agreement with the deformation microstructures of compressed specimens.

• Journal of the Korean Wood Science and Technology
• /
• v.51 no.2
• /
• pp.98-108
• /
• 2023

In this study, the boards were manufactured according to the mandarin peels addition rate using sawdust and mandarin orange peel. After that, the mechanical properties and density profile of ceramics prepared by conditions through resin impregnation process and carbonization process were investigated. The bending and compression strengths of ceramics tended to increase as the resin impregnation rate increased. When the resin impregnation rate was 70%, the highest values were 8.58 MPa and 14.77 MPa, respectively. Also, the mechanical properties of ceramics according to carbonization temperature showed the highest values at 1,200℃ for bending strength of 11.09 MPa and compression strength of 17.20 MPa. The bending strength and compression strength according to the mandarin peels addition rate showed the highest values at 8.62 MPa and 14.16 MPa, respectively, when the mandarin orange peel addition rate was 5%. The mechanical properties tended to decrease when the addition rate of mandarin orange was increased. The density profile of ceramics showed a similar tendency to the mechanical properties. It can be seen that the density distribution from the surface layer to the center layer is more uniform as the resin impregnation rate and carbonization temperature increase and the mandarin peels addition rate decreases.

• Transactions of Materials Processing
• /
• v.16 no.5 s.95
• /
• pp.354-359
• /
• 2007

Effects of forging and mechanical properties of 6061 aluminum alloy wheel for automobiles were investigated in the present study. Microstructural and tensile characteristics of automobile wheel after hot forging process using dynamic screw press were analyzed to evaluate effect of metal flow on mechanical properties. The results showed advanced mechanical properties of 6061 alloy wheel because of $Mg_2Si$ precipitation by T6, elongated grain by forging, and work hardening by dense metal flow, etc. Hot compression tests were conducted in order to characterize high temperature compression deformation behaviors and microstructural variation in the range of $300{\sim}450^{\circ}C$, in the strain rate range of $10^{-3}{\sim}10^1\;sec^{-1}$. As strain rate increased, maximum compression stress increased but it was shown the reverse linear relation between temperature and maximum stress irrelevant to strain rate variation. On the other hand, temperature and yield stress didn't have any linear relation and its relation showed big deviation by a function of strain rate and test temperature.

• The KIPS Transactions:PartA
• /
• v.13A no.3 s.100
• /
• pp.185-190
• /
• 2006

JPEG 2000 is used as an alternative to solve the blocking artifact problem with the existing still image compression JPEG algorithm. However, it has shortcomings such as longer floating point computation time and more complexity in the procedure of enhancing the image compression rate and decompression rate. To compensate for these we implemented with hardware the JPEG 2000 algorithm's filter part which requires a lot of floating point computation. This DWT Filter[1] chip is designed on the basis of Daubechies 9/7 filter[6] and is composed of 3-stage pipeline system to optimize the performance and chip size. Our implemented Filter was 7 times faster than software based Filter in the floating point computation.

• Geomechanics and Engineering
• /
• v.29 no.4
• /
• pp.451-461
• /
• 2022

The roadways surrounded by rock and coal will lose their stability or even collapse under rock burst. Rock burst mainly involves an evolution of dynamic loading which behaves quite differently from static or quasi-static loading. To compare the dynamic response of coal and rocks with different static strengths, three different rocks and bituminous coal were selected for testing at three different dynamic loadings. It's found that the dynamic compression strength of rocks and bituminous coal is much greater than the static compression strength. The dynamic compression strength and dynamic increase factor of the rocks both increase linearly with the increase of the strain rate, while those of the bituminous coal are irregular due to the characteristics of multi-fracture and heterogeneity. Moreover, the absorbed energy of the rocks and bituminous coal both increase linearly with an increase in the strain rate. And the ratio of absorbed energy to the total energy of bituminous coal is greater than that of rocks. With the increase of dynamic loading, the failure degree of the sample increases, with the increase of the static compressive strength, the damage degree also increases. The static compassion strength of the bituminous coal is lower than that of rocks, so the number of small-scale fragments was the largest after bituminous coal rupture.

• Journal of Acupuncture Research
• /
• v.35 no.4
• /
• pp.219-225
• /
• 2018

Background: The purpose of this study was to review whether Korean medicine treatment was effective to maintain the spinal stability and to relieve spinal symptom by reviewing medical records of 18 vertebral compression fracture patients. Methods: The subjects were 18 thoracolumbar compression fracture patients who were taken more than two lateral view x-rays of fractured vertebra from Jan, 2010 to June, 2018. They were divided into two groups: the time admitted into Department of Acupuncture & Moxibustion Medicine, Pohang Korean Medical Hospital of Daegu Hanny University from onset (Research 1) and whether or not they have a past history of osteoporosis (Research 2). Then, they were follow-up observed and compared by compression ratio and numerical rating scale (NRS) and so on. Results: The amount of weekly compression rate increase of 18 patients was 1.76% per week. According to the result of Research 1, the patients group (14 patients) who were admitted into the hospital within 1-2 weeks from getting injury was 1.88% per week whereas the patients group(4 patients) who were admitted into the hospital within 3-4 weeks from getting injury was 1.22% per week. By Research 2 result, the patients group (7 patients) who had been diagnosed as an osteoporosis patient was 2.19% per week, and those (11 patients) who had not was 1.49% per week. There was a statistical significance in the change of the amount of compression rate increase in the case of Research 1, but there was not in the case of Research 2. NRS was decreased without significant difference regardless of the time admitted into the hospital and whether or not the patients had the past history of osteoporosis. Conclusion: Considering that there were more amount of compression rate increase at 1-4 weeks from onset, it is necessary to offer treatment more actively on early time from onset. Further research is needed into the increase of compression rate by the patients' having a past history of osteoporosis or not. Given that NRS decreased without significant difference, it is assumed that Korean medicine treatment has a meaningful effect on relieving subjective symptom of patients who are diagnosed as vertebral compression fractures.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.2
• /
• pp.83-90
• /
• 2004

A flywheel-driven rapid compression and expansion machine is developed and utilized for experimental study of homogeneous charge compression ignition combustion. Compression ignition of homogeneous charge in IC engines offers possibilities of realizing ultra-lean engine operation with greatly reduced NOx and particulate formation. Fundamental investigations are carried out in order to better understand this ideal engine combustion mechanism. Perfectly premixed propane-air mixtures of various equivalence ratio are compression-ignited in the rapid compression and expansion machine, and the characteristics of the auto-ignition and the following combustion process are analyzed.

• Journal of Internet Computing and Services
• /
• v.21 no.4
• /
• pp.35-41
• /
• 2020

This paper proposes an algorithm to improve the compression performance of the adaptive multi-rate (AMR) speech coding using the context tree weighting (CTW) method. AMR is the voice encoding standard adopted by IMT-2000, and supports 8 transmission rates from 4.75 kbit/s to 12.2 kbit/s to cope with changes in the channel condition. CTW as a kind of the arithmetic coding, uses a variable-order Markov model. Considering that CTW operates bit by bit, we propose an algorithm that re-orders AMR data and compresses them with CTW. To verify the validity of the proposed algorithm, an experiment is conducted to compare the proposed algorithm with existing compression methods including ZIP in terms of compression ratio. Experimental results indicate that the average additional compression rate in AMR data is about 3.21% with ZIP and about 9.10% with the proposed algorithm. Thus our algorithm improves the compression performance of AMR data by about 5.89%.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.15 no.3
• /
• pp.77-83
• /
• 2015

Block Truncation Coding, or BTC, is a type of lossy image compression technique for grayscale images. It divides the original images into blocks and then reduces the number of grey levels in each block to compute the mean and standard deviation. BTC has also been adapted to video compression. Another variation of BTC is Absolute Moment Block Truncation Coding. AMBTC is computationally simpler than BTC. In this paper, we proposed new image compression method based on BTC, which is applied patterns to improve compression rate and image quality. This method make two codebooks to extract 36 and 64 patterns from the highest frequency patterns in BTC. When you are compressing an image, you compare many block patterns to that of codebook and use to compress indexes of identical patterns. We experiment our proposed scheme with 36 patterns and the experimental results showed the compression rate of 1.37 bpp. In this paper, our proposed scheme showed higher compression rate rather than that of BTC. In experiment, we used standard images for the performance evaluation.

• Journal of Convergence for Information Technology
• /
• v.9 no.11
• /
• pp.227-233
• /
• 2019

The purpose of this study is to evaluate the quality of chest compression by conducting comparison research between mechanical chest compressor(LUCAS) and manuale cardiopulmonary resuscitation(CPR) in a out-of-hospital environment and suggest effective advanced cardiac life support using mechanical chest compressors. For this, a out-of-hospital cardiac arrest was simulated with a team of 3 ambulance workers, and manuale CPR and CPR using LUCAS were performed on site and during transport in an ambulance. The research results are as follows: the comparison of manuale CPR between on site and in an ambulance revealed that on-site manuale CPR showed significant differences in the average compression depth, compression rate, and relaxation rate. Second, the comparison between manuale CPR and LUCAS in an ambulance showed significant differences in the average compression depth, compression rate, the number of compression per minute.