• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1689-1696
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• 2008

Heat pumps transfer heat by circulating a substance called a refrigerant through a cycle of evaporation and condensation. But Heat pumps system by only using heat-source is not efficient. Because the mean temperature of North Korean winter season is low, economy of air heat-source heat pump descend. This paper is practiced the simulation on evaluation criteria for Heat pump heating and cooling systems to Rolling Stock. Efficiency of the heat pump in order improving from certainly the development of the technique will be able to prevent a freezing actual condition must proceed. As a result, Below $-10^{\circ}C$ used heating and cooling systems of heat pump format even in cold winter season and is serviceable confirmed with heat source supply circle of the Rolling Stock.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.132-137
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• 2006

Supercooled type ice slurry system is hard to keep a proper supercooling degree when solution becomes supercooling state. This is the reason of the ice blockage in pipe or cooling part due to an unstable cooling state. In this study, a cooling experiment was performed to pressurized solution in a stationary state. The behaviors during the supercooled aqueous solution were investigated at fixed flow rate of brine and aqueous solution of ethylene glycol 7 mass%. Also the effect to the freezing point of supercooled aqueous solution was investigated to the different pressure 101, 202, 303, and 404 kPa. At results, the pressure of the aqueous solution in the cylinder increased the supercooling degree increased and dissolution of supercooled point decreased.

• Current Photovoltaic Research
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• v.9 no.2
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• pp.36-44
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• 2021

To endorse the reliability and durability of the solar photovoltaic (PV) device several tests were conducted before exposing to the outdoor field in a non-ideal condition. The PV module has high probability that intend to perform adequately for 30 years under operating conditions. To evaluate the long term performance of the PV module in diversified terrestrial conditions, one should use the outdoor performance data. However, no one wants to wait for 25 years to determine the module reliability. The accelerating stress tests performing in the laboratory by mimicking different field conditions are thus important to understand the performance of a PV module. In this review, we will discuss briefly about different accelerating stress types, levels and prioritization that are used to evaluate the PV module reliability and durability before using them in real field.

• Korean Journal of Weed Science
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• v.16 no.2
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• pp.114-121
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• 1996

This study was conducted to investigate seed germination, seedling growth, and responses to herbicides of Bidens tripartita L. When the field-collected seeds were stored under a dry-room temperature, dry-low temperature, wet-low temperature, or dry-high temperature condition, no seeds were germinated in a growth chamber with 14 hr photoperiod up to 35 days after the storage. Exceptionally, however, some seeds stored under a wet-room temperature condition were germinated after 25 days of the storage. This might be due to the fact that the seed coats were damaged by fungi which developed during the storage. Seeds stored under a wet-low temperature condition (stratification) began to be germinated after 3 months of the storage and the germination rate increased with a prolonged stratification. Almost all seeds were germinated after 9 months of the stratification. These results suggest that the dormancy of B. tripartita L. seeds relate to the seed coat and thus several attempts were made to induce seed germination through damaging or weakening the seed coat. Freezing($-20^{\circ}C$), drying($100^{\circ}C$), or swelling($40^{\circ}C$) of the seeds was not effective to induce the germination. Treatments of concentrated sulfuric acid, $KNO_3$, or gibberellin to the seeds had no effect on inducing the germination. However, ethrel had a stimulatory effect on the germination of the seeds with an optimum concentration of 250ppm. A seed cutting was also effective to induce the germination, but seedlings from the seeds had cutted cotyledons. Germination of the stratified seeds varied with the temperature condition to which they were subjected, but not with light. The germination rate was the highest at 35 - $40^{\circ}C$. Although the seeds were not able to germinate under a submerged condition, seedlings after 2-leaf-stage exhibited better growth under a submerged or a subirrigated condition than under an upland condition. Among the herbicides tested, pyrazosulfuton-ethyl, linuron, and bentazone were found to be effective for controlling B. tripartita L., having more herbicidal effect with an earlier application.

• Korean Journal of Environmental Agriculture
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• v.35 no.3
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• pp.223-233
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• 2016

BACKGROUND: This study was to develop a analytical reference material including twenty pesticides in tomato. To use it for proficiency test, the suitability of homogeneity, storage stability, assigned values and uncertainty for analytical reference material were important.METHODS AND RESULTS: In order to develop a analytical reference material of tomato for multi-residue analysis of pesticides, twenty-pesticides were treated in tomato and the samples were frozen and homogenized. The homogeneity, stability, assigned value and uncertainty were calculated according to the requirements of the KS A ISO Guide 35, KS Q ISO 13528 and EURL-PT protocol. The values of the within-bottle standard variation(s_wb) and the between-bottle standard variation(s_bb) were 0.9~6.5% of assigned value and the uncertainty(u*_bb) due to inhomogeneity was also calculated as 0.6~1.9% for all pesticides. This indicated that it was satisfactory to be used as a analytical reference material. The storage stabilities of twenty-pesticides at room temperature and freezing conditions were assessed according to the requirement of the KS Q ISO Guide 35. All pesticides were stable at room temperature (20~30℃) for 8 days and freezing (-20℃) for 23 days.CONCLUSION: The feasibility of analytical reference material for pesticide multi-residue analysis in a tomato matrix was investigated. Homogeneity of within/between-bottle, uncertainty and stabilities at room temperature and freezing condition were satisfactory for a use of proficiency test and quality control. From these results, a analytical reference material would be applicable to monitor the proficiency test of pesticide analysis organizations to improve the reliability and consistency.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.457-465
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• 2007

In this paper, polymer-modified repair materials using polymer dispersions with six repair methods are prepared with various polymer-cement ratios, and tested for compressive and flexural strengths through each curing condition such as dry cure, water cure, and freezing and thawing cyclic action. And, the adhesive interface between the polymer-modified mortar and mortar substrate is observed by a scanning electron microscope. From the test results, the compressive and flexural strengths of cement mortar repaired by polymer-modified mortar are improved with a rise in the polymer-cement ratio regardless of the type of polymer and curing conditions. Such an improvement in the strengths of polymer-modified repair materials to ordinary cement mortar is explained by the high adhesion of polymer-modified mortar. Strength reduction of polymer-modified repair materials after freezing and thawing cyclic actions is recognized, but it is lower than that of unmodified mortar. Especially, cement mortar repaired by polymer-modified mortar with a St/BA emulsion has good strength properties compared with those of SBR latex and PA emulsion. Accordingly, it is judged that polymer-modified mortars with a St/BA emulsion are possible to use as repair materials to ordinary cement mortar and concrete.

• Korean Journal of Animal Reproduction
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• v.26 no.2
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• pp.119-124
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• 2002

This study was carried out to investigate the effects of packing materials of frozen boar semen to improve reproductive performance efficiency in pig. Boars were raised at Swine Artificial Insemination Center in National Livestock Research Institute, Sunghwan, Chungnam, Korea. We compared packing protocols for frozen boar semen among 5$m\ell$ maxi-straw, 5$m\ell$ cryogenic-vial, and aluminum-pack. Cryogenic-vial packing material showed similar sperm characteristics compared with maxi-straw packing material when the sperm was frozen above 15cm from liquid nitrogen and thawed at 52$^{\circ}C$ for 190 seconds. We investigated different thawing times to find out the optimal condition of freezing and thawing protocol with cryogenic-vial. Freezing above 15cm from liquid nitrogen and thawing at 52$^{\circ}C$ for 190 seconds were the optimal protocol compared with 120 and 150 seconds. However, normal acrosome rates did not show any differences among thawing times. Post-thawing results of maxi-straw in water at 52$^{\circ}C$ for 45 seconds had better total motility and curve linear velocity than those of cryogenic-vial in water 52$^{\circ}C$ for 190 seconds. However, there were no differences on straightness and normal apical ridge of sperm between maxi-straw and cryogenic vial. Non-return rate, farrowing rate and litter size of sows inseminated with frozen boar semen of commercial farms were higher in the maxi-straw than cryogenic-vial, but there were no significant differences between maxi-straw and cryogenic-vial. In conclusion, there were no significant differences between maxi-straw and cryogenic-vial and so, we may replace cryogenic-vial packing method instead of maxi-straw packing method by improvement of freezing and thawing rate.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.51-59
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• 2019

There is increasingly more research focusing on the application of FRP reinforcing bars as an alternative material for steel reinforcing bars, but most such research look at short term behavior of FRP reinforced structures. In this study, the microscopic analysis and tensile behavior of Basalt and Glass FRP bars under freezing-thawing and alkaline conditions were experimentally evaluated. After 100 cycles of the freezing and thawing, the tensile strength and elastic modulus of FRP bars decreased by about 5%. In the case of microstructure of FRP bars during the initial 20 days, no significant damages of FRP bar sections were found under $20^{\circ}C$ alkaline solution; however, the specimens immersed in $60^{\circ}C$ alkaline solution were found to experience resin dissolution, fiber damage and the separation of the resin-fiber interface. In the alkaline environment, the strength decrease of about 10% occurred in the environment at $20^{\circ}C$ for 100 days, but the tensile strength of FRPs exposed for 500 days decreased by 50%. At temperature of $40^{\circ}C$ and $60^{\circ}C$, an abrupt decrease in the strength was observed at 50 and 100 days. Especially, the tensile strength decrease of Basalt fiber Reinforced Polymer bars showed more severe degradation due to the damage caused by dissolution of resin matrix and fiber swelling in alkaline solution. Therefore, in order to improve the long-term performance of the surface braided FRPr reinforcing bars, surface treatment is required to ensure alkali resistance.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.9 no.1
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• pp.17-21
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• 2023

In this study, we evaluated the targeting of prostate cancer (PCa) using [¹⁸F]Florastamin in non-clinical study, for the purpose of therapeutic monitoring of [¹⁷⁷Lu]Ludotadipep, a therapeutic radiopharmaceutical for PCa, [¹⁸F]Florastamin/[¹⁷⁷Lu]Ludotadipep was co-administered to a single-individual prostate tumor bearing mouse model, mimicking clinical condition. Considering the difference in half-life of the two isotopes (¹⁸F or ¹⁷⁷Lu), image scan of whole-body autoradiography was performed at 24 or 48 h after preparation of frozen section, respectively. Then, it was confirmed whether they showed the same targeting efficiency for the area of tumor. A tumor xenograft model was prepared using PSMA-overexpressing PC3-PIP prostate cancer cells. [¹⁸F]Florastamin [111 MBq (3 mCi) in 100 µL]/¹⁷⁷Lu]Ludotadipep [3.7 MBq (100 µCi) in 100 µL] was co-administered through the tail vein, and 2 hours after administration, the mice were frozen, and after freezing for 24 hours, whole-body cryosection was performed at 24 h after freezing. Image scanning using cryosection was performed after 24 or 48 hours after freezing, respectively. In the scan image after 24 hours, tumor uptake of [¹⁸F] Florastamin/[¹⁷⁷Lu]Ludotadipep were simultaneously observed specific uptake in the tumor. In the scan image after 48 hours in the same section, signal of ¹⁸F was lost by decay of radioisotope, and specific uptake image for [¹⁷⁷Lu]Ludotadipep was observed in the tumor. Uptake of [¹⁷⁷Lu]Ludotadipep was specific to the same tumor region where [¹⁸F]Florastamin/[¹⁷⁷Lu]Ludotadipep was uptake. These results suggested that [¹⁸F]Florastamin showed the same tumor uptake efficiency to PCa as [¹⁷⁷Lu]Ludotadipep, and effective therapeutic monitoring is expected to be enable using [¹⁸F]Florastamin during [¹⁷⁷Lu]Ludotadipep therapy for PCa.

• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.73-79
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• 2011

Based on the results of Part 1 of our two-parts paper, the possibility on field applicability of CMDS(Coal Mine Drainage Sludge) mixed with bentonite and cement as a liner in landfill sites was investigated. The optimum moisture content that met the landfill liner condition was obtained when the ratio of CMDS: bentonite: cement was 1: 0.5: 0.3 in a lab-scale. The relative compaction was measured in 90.1%, which results for construction field have been generally acceptable. In this study, a large-scale Lysimeter($1.0m{\times}1.5m{\times}2.0m$) was used to simulate the effects of the layer on the freeze/thaw by -20 average temperature. The mixture after freezing/thawing showed compressive strength more than $5kg/cm^2$, which was satisfied with EPA standards. Initial permeability of CMDS was $7.10{\times}10^{-7}cm/s$ and permeability its mixture after freezing/thawing was increased to $9.80{\times}10^{-7}cm/s$. The change of temperature in the layers rises and falls with linear and temperature gradient keep maintain the present state. Moisture contents in the layers have not been radically changed. Through the leaching test determined by KSLT method, it was found that heavy metals excluding Zn and Ni were not leached out or leached out less than the standards during 7 cycles of freezing/thawing process. Since it shows the increased permeability about 1.5 times and slight change in moisture content, but it was satisfied with EPA standar through 7 cycles of freezing/thawing process, this mixture can be applied as a liner in landfill final cover system.