• Korean Chemical Engineering Research
• /
• v.46 no.2
• /
• pp.414-422
• /
• 2008

Adsorption experiments for $H_2$, $CH_4$, CO, $CO_2$ on activated carbon and zeolite 5A were performed by static volumetric method. A 4-bed pressure swing adsorption (PSA) process was to study separation of hydrogen from multi-component mixture gases ($H_2$ 72.2%, $CH_4$ 4.06%, CO 2.03%, $CO_2$ 21.6%). Dual-site langmuir (DSL) isotherm showed good or fair agreement with the experimental results. The optimum height of activated carbon layer was 55 cm with breakthrough results on the packing ratio of activated carbon to zeolite 5A. In PSA process, the effects of the process parameters such as total cycle time ($T_c$), ${\Delta}P$ at the provide purge step and adsorption pressure on the PSA performance were studied experimentally and theoretically.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.4
• /
• pp.589-598
• /
• 2000

A pilot-scale Spray Drying Sorber (SDS) system was set up to evaluate the effect of spray characteristics on the desulfurization yield. The size distribution and the Sauter Mean Diameters of slurry droplets were measured in advance using the optical size measurement system, Malvern 2600. The desulfurization yield of the drying chamber by size was measured for the conditions of inlet gas and spray injection. As a reagent, 10% limestone slurry of $Ca(OH)_2$ was treated with flue gas containing $SO_2$, and the combustion gas analyzer and gas detectors were attached to measure the $SO_2$ concentration. With a flow rate of 144 Nm3/h and a temperature range of $200{\sim}300^{\circ}C$, the experiments were performed for the Stoichiometric Ratio (SR) of 1.0 to 3.0 and droplet mean diameter of 6.5 to $34.3{\mu}m$. In case of smaller spray droplets, the desulfurization efficiency improved due to the increase of total droplet surface area, while the reduction in evaporation time reduced the contact time between the droplets and $SO_2$ gas. In some typical region of droplet diameter, this negative effect, reduction of contact time, became dominant and the desulfurization yield decreases the desulfurization yield in spite of the expansion in absorption area. These results revealed that there exists the optimal size of spray droplets for a given state, which is determined by the compromise between the total surface area of slurry droplets and the evaporation time of droplets. The measurements also indicated that the inlet temperature of flue gas changes the optimal injection condition by varying the driving force for evaporation. The results confirm that the effect of the evaporation time of slurry droplets should be considered in analyzing the desulfurization yield as well as the total surface area, for it is a significant aspect of the correlation with the capabilities of $SO_2$ absorption in wet droplets. In conclusion, the optimal condition of spray can be determined based on these results, which might be applied to design or scale-up of SDS system.

• Resources Recycling
• /
• v.27 no.3
• /
• pp.8-15
• /
• 2018

Solvent extraction behavior of light rare earth elements (Pr, Nd) and medium rare erath elements (Tb, Dy) in the HCl-PC88A-kerosene extraction system was investigated in order to separate high-purity light rare earths (Pr, Nd) and medium rare earths (Tb, Dy) in the mixed rare earth chloride solution. In the batch test step, it was confirmed that the separation efficiency was good when the extractant concentration (PC88A) was 0.5 M, the equilibrium pH after extraction was 0.8 to 1.0 (initial pH 1.3 of the feed), the concentrations of hydrochloric acid in scrubbing solution was set as 0.1 M, the concentrations of hydrochloric acid in stripping solution was set as 2.0 M or more. Based on the experimental data obtained from the batch test, the mixer-settler was composed as follows; 4 stages of extraction, 8 stages of scrubbing, 4 stages of stripping, and 3 stages of pickling organic solution. The Mixer-settler was operated for 180 hours, and the operating conditions were continuously adjusted to obtain the high-purity light/medium rare earths. Finally, the purity of light (Pr, Nd) and medium rare earth elements (Tb, Dy) was reached as 3 N class.

• Applied Microscopy
• /
• v.33 no.1
• /
• pp.25-39
• /
• 2003

Cell differentiation and ultrastructural characteristics in the seminiferous epithelium of Myotis macrodactylus was investigated with the light and electron microscopes. Spermatogenesis has begun at April and finished at September. The nuclei of A spermatogonia (dark and pale type of spermatogonia) were oval, applied to the basal lamina, and surrounded by Sertoli cells. By comparison with other types of spermatogonia, the cell and nucleus of B type of spermatogonium is globular and larger than A types of spermatogonia. The nucleolus appears as a coarse and touches the nuclear membrane. The cell and nucleus of spermatocytes was globular and larger, but primary spematocyte is larger than secondary spermatocyte. Spermiogenesis was divided according to the level of fine structural difference, into Golgi, cap, acrosomal, maturation and spermiation phases; Golgi, cap, acrosomal and spermiation phases were further subdivided into steps of early and late phase respectively, and maturation phase has only one step. Hence, the spermiogenesis has been divided into a total of nine phases. In the change of karyoplasm, the chromatin granules are condensed at late Golgi phase and completed at spermiation phase. The sperm tail began to develop in early Golgi phase and completed in spermiation phase. The process of degeneration of spermatogenic cells in the seminiferous tubules was continually observed from October, before the beginning of hibernation, to hibernation phase (November, December, January, February, March). Immatured spermatogenic cells in the seminiferous tubules have been engulfed by phagocytosis of Sertoli cells during period of degeneration. It is deduced that the adaptative strategy serves as the mechanism to regulate the effective use of energy to prepare for long hibernation and regulation of breeding cycle.

• Clinical and Experimental Reproductive Medicine
• /
• v.25 no.2
• /
• pp.171-177
• /
• 1998

The combination of testicular sperm extraction (TESE) with ICSI can achieve normal fertilization and pregnancy rate and is effective method in obstructive and non-obstructive azoospermic patients. But, when pregnancy was not occurred, repeated testicular biopsies are not evitable. Therefore, in this study, we observed the survival rate of testicular spemratozoa and spermatozoa extracted from the seminiferous tubules after cryopreserved-thawed used for next IVF cycle with ICSI. In a total of 23 cases, obstructive azoospermia was 17 cases and non-obstructive azoospermia was 6 cases. In obstructive azoospermia, after thawing, motile spermatozua was observed in 13 cases (76.5%). The fertilization rate with 2PN was 67.6% and 5 pregnancies (29.4%) were achieved. In non-obstructive azoospermia, motile spermatozoa was observed in 2 case (33.3%) after thawing. The fertilization rates with 2PN was 53.7% and 3 pregnancies (50.0%) were achieved. A comparison of the results of motile spermatozoa after thawed testicular spermatozoa and spermatozoa extracted from the thawed seminiferous tubule section were 3 cases (60.0%) and 12 cases (66.6%), respectively. The fertilization and pregnancy rates of thawed testicular spermatozoa and spermatozoa extracted from the thawed seminiferous tubule section were 69.4% and 20.0%, 62.5% and 38.8%, respectively. Conclusively, thawed testicular spermatozoa and spermatozoa extracted from the thawed seminiferous tubule section can achieve normal fertilization and pregnancy and cryopreservation of testicular spermatozoa and seminiferous tubule may avoid repetition of testicular biopsies in azoospermic patients in whom the only source of spermatozoa is the testis.

• Journal of the Korean Chemical Society
• /
• v.48 no.6
• /
• pp.590-598
• /
• 2004

The preconcentration and determination of trace Cu(II) and Pb(II) on calcium alginate beads in aqueous solution were studied. A calcium alginate beads were prepared by adding an alginic acid to sample solution contained Ca(II). Some following conditions were optimized: the pH of sample solution, amount of alginic acid, and stirring time for effective adsorption; the type and concentration of acid, and sonication time in an ultrasonic vibrator for the perfect de-sorption. A sample solution was prepared with Cu(II) and Pb(II) in DI water. And Ca(II) and ethanol was added into the sample solution. The pH of the final sample solution was controlled with buffer solution. The alginic acid were dispersed in the sample solution by a magnetic stirrer. This mixture was stored in room temperature for 30 min to form a calcium alginate. After the beads were filtered and washed on a membrane filter, the analytes were redissolved from the beads by an ultrasonic vibration of 10 minutes in 1.0M $HNO_3$ solution. The effect of diverse ions on the adsorption of analytes were studied. This procedure was applied for the analysis of two real samples. The recoveries in spiked samples were $90.4{\sim}104.3%$ for analytes.

• Korean journal of applied entomology
• /
• v.56 no.4
• /
• pp.403-412
• /
• 2017

To investigate the control effect of insect pests by natural enemies, sticky traps were used in commercial tomato greenhouses in Chun-cheon and the experiment fields of Gangwon-do Agricultural Research and Extension Services, Republic of Korea using semi-forcing culture (February to June). We selected low toxicity pesticides, environment-friendly agricultural materials (EFAM), and natural enemies of the study species, combinations of which have been previously used in farms to control insect pests. In this study, Trialeurodes vaporariorum and thrips, which are major agricultural insect pests, were studied in experimental greenhouses. The adult T. vaporariorum population was observed in mid-April and the population of thrips showed occurrences in early April. Regarding seasonal fluctuation, T. vaporariorum peaked in mid-May and thrips peaked after June. one insecticide, spiromesifen suspension concentrate (SC); one fungicide, cyazofamid SC; and two EFAMs containing neem tree extract were shown to be slightly toxic to Encarsia formosa and Orius laevigatus. The results of this study could be used to develop management models using natural enemies of control the insect pests; T. vaporariorum and thrips in semi-forcing culture of tomato.

• Food Science and Preservation
• /
• v.9 no.4
• /
• pp.357-361
• /
• 2002

This study was carried out to understand the problems, and find out the solution of post - Harvest related procedures for barley in Korea. Consecutive post - harvest procedures in harvesting, drying, milling, packaging and marketing methods were collaborately surveyed at Bujeok (Chungchongnamdo) and Kunsuh (Cholanamdo) agricultural cooperative federation where Chalssalbori (waxy barley) and Ssalbori (non waxy barley) were collectively cultivated in a group farming area, respectively. An early harvesting and relatively short harvesting period within 15 to 20 days to transplanting rice plants as a succeeding crop lead to produce undergrade barley and 2 to 3％ harvesting loss were considered as the problem that should be improved. In drying of barley, wide moisture content range of harvested barley among the different farmers and cultivation land was made difficult barley drying unifomly when they were dried in same dryer and drying temperature was slightely higher with 50 to 70$\^{C}$ than that of optimum temperature (under 50$\^{C}$) fer barley drying for producing the high quality barley. Dried barley packaged in ton-bag or 3P bag and put into the rectangular grain bin were stored in ambient temperature warehouse and milled for marketing through whole you. The physico-chemical properties and taste of stored barley were fairly maintained until May next year.

• Journal of Korean Society of Transportation
• /
• v.31 no.5
• /
• pp.60-70
• /
• 2013

This study aims to develop a truck priority on left-turn algorithm that can reduce greenhouse gas emissions by reducing heavy duty truck's stops at signalized intersection. The signal priority is granted for a left-turn phase, because heavy duty trucks can deteriorate left-turn traffic flow due to the low acceleration or deceleration rate and large turn radius. Truck priority allows to provide the stable speed control for heavy duty truck, and reduces emissions at the signal intersection. Also, two signal recovery strategies are compared for various traffic conditions. This study analyzes the effectiveness of truck priority such as greenhouse gas emissions and fuel consumption reduction, and total travel time saving using the PARAMICS and Comprehensive Modal Emissions Model (CMEM). The results show that signal priority for heavy duty trucks has an effect on reducing greenhouse gas emissions and fuel consumptions at non-peak hour. Also, it shows decreasing total travel time due to reducing truck stops.

• Journal of Adhesion and Interface
• /
• v.12 no.3
• /
• pp.99-104
• /
• 2011

Currently, automotive pre-primed coatings has been developed to overcome environmental regulations and to reduce manufacturing cost in automotive industry. By these reasons, an automotive pre-primed system has been investigated to remove the wash and pre-treatment process using a roll coating application. It is required to develop non-weldable pre-primed system for automotive structural adhesives, because pre-primed sheet coated with organic compounds is hard to be assembled by welding process. Primer 1 (polyester type) and primer 2 (urethane type) were designed to satisfy flexibility and formability for non-weldable pre-primed system. According to the results of physical property test of the primers, adhesion test such as single-lap shear test and T-peel test, primer 1 (polyester type) had better physical properties such as pencil hardness, solvent resistance, flexibility and adhesion with automotive adhesive than that of primer 2 (polyurethane type). In addition, the possibility of the non-weldable pre-primed system was applicable to automotive assembly process in place of welding process.