• Solar Energy
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• v.15 no.1
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• pp.29-38
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• 1995

This paper concerns the study of a two-stage binary absorption cycle employing the refrigerant/absorbent combinations of $LiBr/H_2O$ and $NH_3/H_2O$. This cycle consists of coupling two single-effect absorption cycles so that the first stage absorber and condenser produces heating water to evaporate refrigerant in the evaporator of the second stage. The effect of operating variables such as evaporator temperature, condenser and absorber temperature, and generator temperature on the coefficient of performance and temperature lift have been studied for two-stage binary absorption heat pump systems. It is found that this cycle has a large temperature lift at $105^{\circ}C$ of optimum generator temperature to obtain $50^{\circ}C$ of condenser temperature.

• 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.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.4
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• pp.10-15
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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 produce an extremely high pressure in a very short interval of time. 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. This can be employed efficiently in the application of ultra-high pressure liquid jets. 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 the frist diaphragm opening. In the present study result was found that the rupture pressure of the first diaphragm has a dominant influence on piston acceleration.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.10a
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• pp.307-309
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• 1996

This paper analyses a deterministic scheduling problem concerned with manufacturing two types of components at a pre-assembly stage which consists of two independent feeding machines each producing its own type of component. Each type represents a unique component which may have variations in its size or quality. Therefore, the completion time of each component depends on both its type and quality (size) variations. Such manufactured components are subsequently assembled into various component dependent products. The problem has the objective measure of minimizing the total weighted completion time of a finite number of jobs(products) where the completion time of each job is measured by the latest completion time of its two components at the pre-assembly stage. The problem is shown to be NP-complete in the strong sense. A WSPT rule coupled with a machine-aggregation idea is developed for good heuristics which show the error bound of 2.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.932-937
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• 2004

In situ extraction by organic solvent was studied in order to improve the recovery yield of hydrocarbon from the culture of Botryococcus braunii, a green colonial microalga. When the solvent mixture of octanol as an extractive solvent and n-octane as a biocompatible solvent was added to a two-phase column, the algal growth was seriously inhibited, even at a low concentration of polar octanol. Therefore, a two-stage cell-recycle extraction process was proposed to improve the contact area between the organic phase and the aqueous phase. The hydrocarbon recovery with in situ cell-recycle extraction showed a three-fold increase (57% of cell) in yield over that with two-phase extraction. In addition, over 60% of the hydrocarbon could be recovered without serious cell damage by downstream separation when this process was applied to the culture broth after batch fermentation.

• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.2
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• pp.353-358
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• 1999

We produced the apple vinegar with only apple fruits, no adding sugar and others through two stages fermentation(alcohol fermentation and acetic acid fermentation). At the first stage, apple wine contained 5% alcohol was produced at the 5th day. And through the second stage, acetic acid fer mentation, apple vinegars of which total acidity is 5.88% were produced. In comparision with com mercial vinegars for physicochemical quality, it was the lowest in total acidity. But contents of oxalic, tartaric, malic, citric, succinic acid in it were higher than other vinegars. Especially the content of malic acid in it was higher 5 times than other vinegars. Malic acid was known that it was abundant in apple fruits. Also the contents of free amino acids were distinctly high such as 21.97mg% in two stages fermented apple vingars. Potassium content in it was higher 4 times than other vinegars. So it was supposed that two stages fermented vinegar had much higher quality than commercial vinegars.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.237-242
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• 2000

The areal recording density of HDD(Hard Disk Drive) has been increasing by about 60% a year. In order to achieve high areal density, less track pitch is expected and more servo bandwidth is required. Dual stage actuator and servo controller for HDD have been suggested for achieving high track density as a possible solution. Dual-loop servo system is generally classified into a two-input-two-output system, but if we use an estimator for a two-input-two-output system, it can be converted into two input one output system. Since we can't control the dual stage servo system by the classical method, it requires a special technique; for example, Parallel Loop System, Master-Slave Loop System, Decoupled Master-Slave Loop System, and Dual Feedback Loop System. In this paper, we performed experimental evaluations of several types of control algorithm. Further experiments will be made in the future.

• Communications for Statistical Applications and Methods
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• v.18 no.4
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• pp.423-431
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• 2011

For procuring more sensitive information and estimating stratum target population proportion as well as an overall one form a sensitive population composed of several strata we suggest a two-stage stratified unrelated question model that uses stratified random sampling instead of simple random sampling in the two-stage unrelated question model by Kim et al. (1992) and extend it to the three-stage stratified unrelated question model. We also deal with the proportional and optimal allocation problems in each suggested model, compare the relative efficiency of the suggested two models, and show that the three-stage stratified unrelated question model is more efficient than the two-stage one in view of the variance.

• Journal of Microbiology and Biotechnology
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• v.10 no.1
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• pp.75-80
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• 2000

An improved method of refolding recombinant human proinsulin from E. coli was presented. It was based on a two-stage stirred tank reactor in which denatured proinsulin-s-sulfonate was mixed instantaneously with a reaction buffer in the first stage reactor, and then fed to the second stage reactor. The mixture was stirred further for a total of 30h in the second stage reactor. In this system, unfavorable effects present due to the increase in reaction volume and protein concentration for protein refolding, which becomes significant in a large-scale operation, were avoided. Refolding yields of over 80% was obtained for achieving reaction volume of upto 50 l at protein concentration of 1 mg/ml. The optimum urea concentration was 1M. Refolding yield at the 1-1 reaction volume and protein concentration of 0.5mg/ml was increased about 2.5-fold, compared to that in a batch reactor. By increasing protein concentration in a two-stage refolding reaction, the cost for insulin production could be reduced, therefore, making this process economical.

• Journal of the Korean Wood Science and Technology
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• v.19 no.2
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• pp.56-64
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• 1991

The destructed chips(Pinus rigida Mill) were sulfonated under different conditions and defiberated. The yields and strengths of pulp, fatty acid and resin acid in sulfonated chips were determined. The results of this work were as follows: 1) A sulfonation caused a yield reduction to 97.9~88.2% at single stage. and to 94.9~88.2% at two stage pretreatment. The pulp yields were rapidly draped with increasing cooking temperature from $130^{\circ}C$ to $150^{\circ}C$ 2) Pulp strengths were improved with iacreasing cooking temperature. A sulfonation with 5% $Na_2SO_3$/NaOH(8/2) at single stage and 2% NaOH-5% $Na_2SO_3$ at two stage were most effective and gave the best combination of strength properteis. 3) Fatty acid esters in chips were mostly consisted of palmitic and olleic acid. During a sulfonation the former increased extensively, and the latter was lost with increase of cooking times. The amount of pimaric type in the chips was relatively decreased by the pretreatnent and abietic-type increased. But the changes between two resin acid types were insignificant. 4) The effciency of pitch removal was dependant upon cooking liquor pH. To remove sufficiently the resinous substance, the chips must be sulfonated at over pH 12. Therefore, taking account of pitch removel, two stage sulfonation is considered suitable as reinforcement pulp for newsprint manufacture from pitch pine chips : 2% NaOH($60^{\circ}C$ 1 hr) at first stage and 5% $Na_2SO_3$ ($130^{\circ}C$, 1hr) at secund stage.