• Journal of the Korean Society of Industry Convergence
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• v.23 no.1
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• pp.83-91
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• 2020

The evaluation of the compression behavior of the cushioning material is of importance to achieve appropriate packaging design. In order to change packaging design from polymeric-based to more eco-friendly cellulose-based nire effectively, comparative study on the compression behavior between these two packaging materials is crucial. In this study, the stress-strain behavior, hysteresis loss, and response characteristics for cyclic loading were analyzed through compression tests on multi-layered corrugated structure (MLCS) and expanded polystyrene (EPS) packaging materials. MLCS produced in Korea is produced by winding a certain number of single-faced corrugated paperboard, and the compression behavior of this material was turned out to be 6 stages: elastic stage, first buckling stage, sub-buckling stage, densification stage, last buckling stage and high densification stage. On the other hand, EPS's compression behavior was in 3 stages: linear elastic stage, collapse plateau, and densification stage. The strain energy per unit volume (strain energy density) of MLCS did not differ depending on the material thickness, but it showed a clear difference depending on the raw material and flute type. Hysteresis loss of MLCS ranged from 0.90 to 0.93, and there were no significant differences in the raw material and flute type. These values were about 5 to 20% greater than the hysteresis of the EPS (about 0.78 to 0.87).

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.2
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• pp.259-264
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• 2020

In this study, comparison study has been performed between two-stage compression and a vapor-recompression refrigeration cycle and a liquefaction using LNG cold heat. When using a first method using two-stage compression and a refrigeration cycle, at least three compressors are required, however when using LNG cold heat, no compressor is required since carbon dioxide can be pumped after condensing with the heat exchange with -160℃ of LNG. Through this study, we can save more than one hundred million KRW annually by using LNG cold heat instead of using gas compression and refrigeration cycle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.345-348
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• 2010

Light gas guns have a large number of applications in various fields of engineering. A two-stage light gas gun can develop an extremely high pressure in a very short interval of time. This can be employed efficiently in the application of ultra-high pressure liquid jets. In general, the two-stage light gas gun is made up of a high pressure tube, a compression tube and a launch tube, each stage being separated by diaphragms. The first diaphragm is installed downstream of the high pressure tube and the second, downstream of the compression tube. In the present study, experiments are carried out to investigate the projectile velocity and pressure behavior in the tubes according to the pressure changes at diaphragm opening. It is found that the rupture pressure of the first diaphragm has a dominant influence on projectile velocity. It is also observed that at pressures greater than 14 bar, the pressure in the launch tube exceeds that in the compression tube.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2101-2104
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• 2003

Experimental investigations are performed for the rarefied gas flows in a disk-type drag pump (DTDP). The pump considered in this paper consists of grooved spiral channel on rotors and planar stators. The flow-metre method is adopted to calculate the pumping speed. Compression ratio and pumping speeds for the nitrogen gas are measured under the inlet pressure range of $0.001{\sim}4$ Torr. The maximum of compression ratio was about 3300 for three-stage DTDP, 1000 for two-stage and 100 for single-stage DTDP at zero throughput. The number of stage influences the pumping speed of DPDT

• Journal of Power System Engineering
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• v.20 no.2
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• pp.85-90
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• 2016

Coefficient of performance (COP) for two-stage compression system is investigated in this paper to develop seawater ice machine. The system performance is analyzed with respect to degrees of superheating and subcooling, condensing and evaporating temperatures, compression and mechanical efficiencies and mass flow ratio in an inter-cooler. The main results are summarized as follows : The COP of the system grows when the mass flow ratio, subcooling degree and evaporating temperature edge up. Contrariwise, the system performance descends in case that superheating degree and condensing temperature increase. The most effective factor for the COP is the mass flow rate ratio. Each refrigerant has different limitation for a value of the mass flow ratio in the inter-cooler because of difference in material property.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.3
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• pp.1243-1263
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• 2018

The two-stage linear discrimination analysis (TSLDA) is a feature extraction technique to solve the small size sample problem in the field of image recognition. The TSLDA has retained all subspace information of the between-class scatter and within-class scatter. However, the feature information in the four subspaces may not be entirely beneficial for classification, and the regularization procedure for eliminating singular metrics in TSLDA has higher time complexity. In order to address these drawbacks, this paper proposes an improved two-stage linear discriminant analysis (Improved TSLDA). The Improved TSLDA proposes a selection and compression method to extract superior feature information from the four subspaces to constitute optimal projection space, where it defines a single Fisher criterion to measure the importance of single feature vector. Meanwhile, Improved TSLDA also applies an approximation matrix method to eliminate the singular matrices and reduce its time complexity. This paper presents comparative experiments on five face databases and one handwritten digit database to validate the effectiveness of the Improved TSLDA.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.577-580
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• 2002

In this paper, the pumping performance of the disk-type drag pump which works in the outlet pressure range from 4 to 0.001 Torr is studied experimentally. The pumping characteristics of various drag pumps are performed. The inlet pressures are measured for various outlet pressures of the test pump. The flow-meter method is adopted to calculate the pumping speed. Compression ratios and pumping speeds for the nitrogen gas are measured. The present experimental data show the leak-limited value of the compression ratio in the molecular transition region. The rotational speed of the pump is 24,000rpm. The inlet pressures are measured for various outlet pressures of the test pump. The ultimate Pressures for zero throughput are measured for three-stage, two-stage and single-stage disk-type, respectively.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.203-208
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• 2001

In this paper, the pumping performance of the three-stage disk-type drag pump which works in the outlet pressure range from 4 to 0.01 Torr is studied experimentally. The rotational speed of the pump is 24,000rpm, and nitrogen is used as a test gas, The pumping characteristics of various drag pumps are investigated. The inlet pressures are measured for various outlet pressures of the test pump. The maximum compression ratios for zero throughput are measured for three-stage, two-stage BSC type, helical-type, one-stage BSC type and one-stage OSC type, respectively.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.258-263
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• 2000

River water is higher in temperature than the surrounding environment during the winter. It is highly suitable a heat source for heat pump system. Despite its suitability, however, it is not widely used, due to its fouling and corrosive nature in heat exchanger tubes of evaporator. It is designed prior-treatment system which come into direct contact with the river water, such as auto-seamer, ozone generator for bactericidal test and auto-cleaning system. And it is analyzed treatment effects for its operation. It is designed two-stage compression heat pump system using R-134a with heating load 35.16kW, ad analyzed its performance. As a result it is obtained 3.08 COP when mid-point pressure is 1,200kPa, and bypass ratio of flowing refreigerant to high-stage compressor is 25.1%

• Journal of the Korean Society of Visualization
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• v.3 no.2
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• pp.79-87
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• 2005

Two engines, one is conventional DOHC 4 valve and the other is narrow valve angle, were used to compare the characteristics of swirl motion generation in the cylinder. One intake port is deactivated to induce swirl flow. A PIV (Particle Image Velocimetry) was applied to measure in-cylinder velocity field according to inlet valve angle during intake and compression stroke. The results show that the flow patterns of narrow valve engine are much more stable and well arranged compared with the normal engine over the entire intake and compression stroke except early intake stage, and very strong swirl motion is generated at the end of compression stage in this engine nevertheless using straight port which is unfavorable for swirl generating. In the normal engine, however, strong swirl motion induced during intake stroke is destroyed as the compression progresses.