• 농업과학연구
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• 제37권3호
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• pp.501-508
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• 2010

A swirl chamber type diesel engine attachable to 18 kW agricultural tractors was improved to reduce exhaust emissions. Compression ratio and throat area ratio of the combustion chamber were varied to determine optimum combustion conditions. Tests were composed of full load and 8-mode emission tests. Compression ratio was fixed as 21, but the swirl chamber volume was increased by 3.8%. Output power, torque, specific fuel consumption, exhaust gas temperature, and smoke level were not considerably different for compression ratios of 21.5 (reference condition) and 21 (test condition), while NOx, HC, CO and PM levels for the compression ratio of 21 were decreased by 11%, 46%, 28%, 11%, respectively, from those for the compression ratio of 21.5. The tests were also conducted with a compression ratio of 22 and 4.3% increased chamber volume. Output power, torque, exhaust gas temperature and smoke level were greater, while specific fuel consumption was less for the compression ratio of 22 than those for the compression ratio of 21.5. Increase of compression ratio decreased HC and CO levels by 24%, 39%, but increased NOx and PM levels by 24%, 39%. Based on these results, a compression ratio of 21 was selected as an optimum value. Then, full load tests with the selected compression ratio of 21 were carried out for different throat ratios of 1.0%, 1.1%, 1.2%. Output power and torque were greatest and smoke was lowest when throat area ratio was 1.1%, which satisfied the target values of specific fuel consumption (less than 272 g/$kW{\cdot}h$) and exhaust gas temperature (less than $550^{\circ}C$). Therefore, a throat area ratio of 1.1% was selected as an optimum value.

• 한국융합학회논문지
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• 제7권5호
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• pp.51-57
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• 2016

본 연구는 초음파 영상(ultrasound imaging)을 이용하여 네발기기 자세(quadruped position)에서 골반압박벨트(pelvic compression belt)가 뭇갈래근과 척추세움근의 근두께에 융합적으로 미치는 영향을 알아보기 위해 실시되었다. 대상자는 30명의 남자대학생으로 실험에 자발적으로 참여한 자로 선정하였다. 골반압박벨트를 위앞엉덩뼈가시아래(anterior superior iliac spines)에 착용한 상태와 착용하지 않은 상태에서 네발기기 자세를 실시하였고, 초음파영상 진단장치를 이용하여 근 두께를 측정하였다. 자료분석은 반복측정분산분석을 이용하였다. 연구결과, 뭇갈래근의 경우 골반압박벨트를 착용하였을 때가 착용하지 않았을 때보다 근두께가 유의하게 증가하였고(p<.05), 척추세움근의 경우도 골반압박벨트를 착용하였을 때가 착용하지 않았을 때보다 근두께가 유의하게 증가하였다(p<.05). 따라서 본 연구결과를 통해 골반압박벨트의 착용이 요통환자에게 효과적이며, 임상에서 다양한 네발기기 자세운동의 처방과 적용 시에 유용한 자료로 활용하고자 한다.

• Journal of the Korean Wood Science and Technology
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• 제29권3호
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• pp.1-13
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• 2001

Compression, lateral, and opposite woods in the stem and branch of rimu (Dacrydium cupressinum Lamb.), a softwood species indigenous to New Zealand, were described and compared in the anatomical aspects. Qualitatively, growth rings were wide in the compression wood, intermediate in the lateral wood, and narrow in the opposite wood. Tracheid transition from early wood to late wood was very gradual in the compression wood but was more abrupt in both the lateral and opposite woods. When viewed transversely, compression wood tracheids showed a roundish outline except at the growth ring boundary but lateral and opposite wood tracheids were angular to rectangular in outline. Intercellular spaces were occasionally detected in the compression wood except in the late wood at the growth ring boundary but were absent from both the lateral and opposite woods. Slit-like extensions of the bordered pit openings caused by the location of pit apertures within short and narrow helical grooves were observed in the compression wood tracheids but not in the opposite or lateral wood tracheids. In the compression wood tracheids, fine striations in the form of fine checks or grooves were observed on the lumen surfaces and the innermost $S_3$ layer of secondary wall was absent. In the tracheids of lateral and opposite woods, the $S_3$ layer was sometimes absent but occasionally highly developed. Cross-field pits in the compression wood appeared to be piceoid due to slit-like pit apertures but those in the lateral and opposite wood tracheids showed cupressoid to taxodioid. Quantitatively, compression wood tracheids were somewhat shorter than those of opposite or lateral wood in stem but not different from the opposite or lateral wood tracheids in branch. The walls were thicker in the compression wood than in the lateral or opposite wood. Uniseriate rays in the compression wood were fewer than in the lateral or opposite wood.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.918-927
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• 2018

Based on the actual operating environment of transformer, the aging tests of nitrile butadiene rubber (NBR) were conducted systematically under four conditions: in air, in transform oil, under compression in air and under compression in transform oil to studythe effect of high temperature, transform oil and compression stress simultaneously on the thermal aging behaviors of nitrile butadiene rubber and predict the lifetime. The effects of liquid media and compression stress simultaneously on the thermal aging behaviors of nitrile butadiene rubber were studied by using characterization methods such as IR spectrosc-opy, thermogravimetric measurements, Differential Scanning Calorimetry (DSC) measurements and mechanical property measurements. The changes in physical properties during the aging process were analyzed and compared. Different aging conditions yielded materials with different properties. Aging at $70^{\circ}C$ under compression stress in oil, the change in elongation at break was lower than that aging in oil, but larger than that aging under compression in air. The compression set or elongation at break as evaluation indexes, 50% as critical value, the lifetime of NBR at $25^{\circ}C$ was predicted and compared. When aging under compression in oil, the prediction lifetime was lower than in air and under compression in air, and in oil. It was clear that when predicting the service lifetime of NBR in oil sealing application, compression and media liquid should be involved simultaneously. Under compression in oil, compression set as the evaluation index, the prediction lifetime of NBR was shorter than that of elongation at break as the evaluation index. For the life prediction of NBR, we should take into account of the performance trends of NBR under actual operating conditions to select the appropriate evaluation index.

• 정보과학회 논문지
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• 제42권9호
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• pp.1078-1089
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• 2015

본 연구에서는 쓰기 데이터양 감소를 통해 낸드 플래시 기반 저장장치의 수명향상을 도모할 수 있는 MADE(Min-hash Assisted Delta-compression Engine) 모듈을 제안한다. MADE 모듈은 델타압축기법(delta compression)을 통해 중복되는 데이터 패턴을 최소화하여 실제 낸드 플래시에 인가되는 쓰기 명령 횟수를 획기적으로 줄일 수 있을 뿐만 아니라, 중복제거기법(deduplication) 및 무손실압축기법(lossless compression)의 통합적용과 유사한 효과를 볼 수 있도록 설계되었다. 또한 델타압축기법 과정 중 필요한 참조 페이지 탐색 및 압축 기법을 최적화하여, 저장되는 데이터양을 최대한 줄이는 동시에 부가적인 오버헤드를 최소화 하였다. 시뮬레이션 결과, MADE가 적용된 플래시 변환계층(Flash Transition Layer, FTL)은 실제 낸드 플래시 칩에 저장되는 데이터를 최소 50% 줄일 수 있었으며, 순차적인 중복제거기법과 무손실압축 기법을 단순 통합하여 적용한 경우에 비해 추가적으로 12%의 쓰기 데이터양을 감소시킬 수 있었다.

• 한국응급구조학회지
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• 제24권3호
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• pp.107-116
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• 2020

Purpose: We compared three chest compression methods to find an efficient method for performing infant cardiopulmonary resuscitation (CPR) for single rescuers and improving chest compressions quality. Methods: Thirty new marine police trainees at the Korea Coast Guard Education Institute were tested for five sessions using three methods of single rescuer infant CPR: two-finger chest compression, two-thumb encircling chest compression, and two-finger support chest compression. Results: The depth, accuracy, and number of compressions per minute of resuscitation were analyzed for the above three methods. The depth of two-finger chest compression, two-thumb encircling chest compression, and two-finger support chest compression was 3.53±0.20cm, 4.10±0.13cm, and 4.22±0.15cm, respectively. Accuracy was 23.86±12.59%, 54.11±10.8%, 71.55±18.81%, respectively, while the time for one cycle of 30 chest compression was 16.01±10.5 seconds, 16.45±0.85 seconds, and 16.56±0.91 seconds, respectively. Chest compression interruptions were 6.59±0.78 seconds, 7.17±0.37 seconds, and 6.97±0.35 seconds, respectively. The interruptions were consistent with the range of 5-10 seconds suggested by the American Heart Association. Conclusion: When one rescuer performs CPR for an infant in cardiac arrest, a comparative analysis of three methods showed that two-thumb encircling chest compression is the best for accuracy and efficiency of chest compressions.

• Steel and Composite Structures
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• 제38권1호
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• pp.103-120
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• 2021

This research examines the eccentric compression performance of composite columns composed of recycled aggregate concrete (RAC)-filled square steel tube and profile steel. A total of 17 specimens on the composite columns with different recycled coarse aggregate (RCA) replacement percentage, RAC strength, width to thickness ratio of square steel tube, profile steel ratio, eccentricity and slenderness ratio were subjected to eccentric compression tests. The failure process and characteristic of specimens under eccentric compression loading were observed in detail. The load-lateral deflection curves, load-train curves and strain distribution on the cross section of the composite columns were also obtained and described on the basis of test data. Results corroborate that the failure characteristics and modes of the specimens with different design parameters were basically similar under eccentric compression loads. The compression side of square steel tube yields first, followed by the compression side of profile steel. Finally, the RAC in the columns was crushed and the apparent local bulging of square steel tube was also observed, which meant that the composite column was damaged and failed. The composite columns under eccentric compression loading suffered from typical bending failure. Moreover, the eccentric bearing capacity and deformation of the specimens decreased as the RCA replacement percentage and width to thickness ratio of square steel tube increased, respectively. Slenderness ratio and eccentricity had a significantly adverse effect on the eccentric compression performance of composite columns. But overall, the composite columns generally had high-bearing capacity and good deformation. Meanwhile, the mechanism of the composite columns under eccentric compression loads was also analysed in detail, and the calculation formulas on the eccentric compression capacity of composite columns were proposed via the limit equilibrium analysis method. The calculation results of the eccentric compression capacity of columns are consistent with the test results, which verify the validity of the formulas, and the conclusions can serve as references for the engineering application of this kind of composite columns.

• 한국CDE학회논문집
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• 제13권1호
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• pp.1-7
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• 2008

Data compression becomes increasingly an important issue for reducing data storage spaces as well as transmis-sion time in network environments. In 3D geometric models, the normal vectors of faces or meshes take a major portion of the data so that the compression of the vectors, which involves the trade off between the distortion of the images and compression ratios, plays a key role in reducing the size of the models. So, raising the compression ratio when the normal vector is compressed and minimizing the visual distortion of shape model's shading after compression are important. According to the recent papers, normal vector compression is useful to heighten com-pression ratio and to improve memory efficiency. But, the study about distortion of shading when the normal vector is compressed is rare relatively. In this paper, new normal vector compression method which is clustering normal vectors and assigning Representative Normal Vector (RNV) to each cluster and using the angular deviation from actual normal vector is proposed. And, using this new method, Visually Undistinguishable Lossy Compression (VULC) algorithm which distortion of shape model's shading by angular deviation of normal vector cannot be identified visually has been developed. And, being applied to the complicated shape models, this algorithm gave a good effectiveness.

• 대한의용생체공학회:의공학회지
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• 제31권5호
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• pp.407-411
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• 2010

During the cardiopulmonary resuscitation (CPR), the correct chest compression depth and period are very important to increase the resuscitation possibility. For the feedback of chest compression depth, the depth monitoring device based on the accelerometer is developed and widely used. But this method tends to overestimate the compression depth on the bed. To overcome this limitation, the chest compression depth estimation method using two accelerometers is suggested With the additional accelerometer between the patient and mattress on the bed, the compression of the mattress is also measured and it is used to compensate the overestimation error. The experimental results show that the single accelerometer estimates as 61.4mm for the actual compression depth of 43.6mm on the mattress. The depth estimation with the dual accelerometer was 44.6mm which is close to the actual depth. With the automatic zeroing in every single compression, the integration error for the depth can be reduced. The dual accelerometer method is effective to increase the accuracy of the chest compression depth estimation.

• 대한기계학회논문집
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• 제19권8호
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• pp.1972-1981
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• 1995

As 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. The impulsive noise is closely related to the pressure gradient of the compression wave propagating the tunnel. In order to investigate the characteristics of the compression waves, in the present study an experiment was made using a shock tube. The results show that the strength of a compression wave decreases with the distance from the tunnel entrance and the nonlinear effect of compression wave appears to be significant if strength of the initial compression wave is greater than 7 kPa. Furthermore if the wave pattern is known, attenuation of the compression wave propagating in a tunnel can be reasonably predicted by a theoretical equation considering viscous action and heat transfer in boundary layer.