• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.281-291
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• 1995

The objective of this work is to obtain the experimental data for the heat transfer processes occurring both on the inside and outside surfaces of containment steel wall with dry and wet outer surface conditions in the passive containment cooling system. The test model represented a 60$^{\circ}$ section of a containment vessel based on the AP 600 geometry. Major linear dimensions of the test model ore reduced tv a factor of ten. To simulate the decay heat a steam generator heated by electricity was placed in the test model. The maximum heat flux was 8.91 kW/$m^2$. Two types of tests were performed. The one was the tort on the natural convection of air without water film flow. The other was the evaporative heat transfer test with the falling water film flow and natural air draft. no test result shooed that the heat transfer capability by the natural convection from the containment to the air without oater film flow was limited at about 1.48 kW/$m^2$ heat flux. It was found that the heat removal capability was remarkably enhanced in the tests with the waster film flow and air draft. The obtained heat transfer data ore compared with the existing correlations.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.3
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• pp.227-234
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• 2006

Two candidate glasses, AG8W1 and DG-2, have been developed for vitrifying the mixture of low activity resin, zeolite and Dry Active Waste(DAW), and DAW solely, respectively. In order to evaluate the chemical durability of the glasses, two different leaching tests, Product Consistency Test(PCT) and Vapor Hydration Test(VHT), have been performed. As the results of PCT performed from 7 to 120 days, the leach rates of B, Na, Si and Li in the glasses were much lower than those of the benchmark glass(SRL-EA). As the result of VHT peformed for 7 days, the leach rates were 2 and $10g/m^2/day$ for AG8W1 and DG-2, respectively, The results of VHT met the regulatory guideline( $<50g/m^2/day$) for the low activity glasses of Hanford in the USA. Consequently, two candidate glasses to be used at a commercial operation in the future showed that their chemical durability is satisfactory according to the results of two leaching tests.

• Restorative Dentistry and Endodontics
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• v.27 no.2
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• pp.158-174
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• 2002

The aim of this study was to investigate the effect of light irradiation modes on polymerization shrinkage, degree of cure and microleakage of a composite resin. VIP$^{TM}$ (Bisco Dental Products, Schaumburg, IL, USA) and Optilux 501$^{TM}$ (Demetron/Kerr, Danbury, CT, USA) were used for curing Filtek$^{TM}$ Z-250 (3M Dental Products, St. Paul., MN, USA) composite resin using following irradiation modes: VIP$^{TM}$ (Bisco) 200mW/$\textrm{cm}^2$ (V2), 400mW/$\textrm{cm}^2$ (V4), 600mW/$\textrm{cm}^2$ (V6), Pulse-delay (200 mW/$\textrm{cm}^2$ 3 seconds, 5 minutes wait, 600mW/$\textrm{cm}^2$ 30seconds, VPD) and Optilux 501$^{TM}$ (Demetron/Kerr) C-mode (OC), R-mode (OR). Linear polymerization shrinkage of the composite specimens were measured using Linometer (R&B, Daejeon, Korea) for 90 seconds for V2, V4, V6, OC, OR groups and for up to 363 seconds for VPD group (n=10, each). Degree of conversion was measured using FTIR spectrometer (IFS 120 HR, Bruker Karlsruhe, Germany) at the bottom surface of 2 mm thick composite specimens V2, Y4, V6, OC groups were measured separately at five irradiation times (5, 10, 20, 40, 60 seconds) and OR, VPD groups were measured in the above mentioned irradiation modes (n=5 each). Microhardness was measured using Digital microhardness tester (FM7, Future-Tech Co., Tokyo, Japan) at the top and bottom surfaces of 2mm thick composite specimens after exposure to the same irradiation modes as the test of degree of conversion(n=3, each). For the microleakage test, class V cavities were prepared on the distal surface of the ninety extracted human third molars. The cavities were restored with one of the following irradiation modes : V2/60 seconds, V4/40 seconds, V6/30 seconds, VPD , OC and OR. Microleakage was assessed by dye penetration along enamel and dentin margins of cavities. Mean polymerization shrinkage, mean degree of conversion and mean microhardness values for all groups at each time were analyzed using one-way ANOVA and Duncan's multiple range test, and using chi-square test far microleakage values. The results were as follows : . Polymerization shrinkage was increased with higher light intensity in groups using VIP$^{TM}$ (Bisco) : the highest with 600mW/$\textrm{cm}^2$, followed by Pulse-delay, 400mW/$\textrm{cm}^2$ and 200mW/$\textrm{cm}^2$ groups, The degree of polymerization shrinkage was higher with Continuous mode than with Ramp mode in groups using Optilux 501$^{TM}$ (Demetron/Kerr). . Degree of conversion and microhardness values were higher with higher light intensity. The final degree of conversion was in the range of 44.7 to 54.98% and the final microhardness value in the range of 34.10 to 56.30. . Microleakage was greater in dentin margin than in enamel margin. Higher light intensity showed more microleakage in dentin margin in groups using VIP$^{TM}$ (Bisco). The microleakage was the lowest with Continuous mode in enamel margin and with Ramp mode in dentin margin when Optilux 501$^{TM}$ (Demetron/Kerr) was used.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.13 no.4
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• pp.92-99
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• 2005

A closed-circuit type wind tunnel is designed, which has a test section with the dimensions $1.2(W){\times}1.2(H){\times}3.4(L)$. A subsonic wind tunnel is designed to improves educational circumstances and promote ground tests. It is constituted of an exchangeable test section, first and second diffusers, a fan, a settling chamber, a contraction, and 4 corners. The maximum velocity in the test section is 70m/s and the contraction ratio is 6.25:1. Input power in the wind tunnel is about 96.1 kw (128.8 hp) and its energy ratio is 3.89. It has the dimension of about $7.4(W){\times}3.6(H){\times}21.7m(L)$. The wind tunnel designed in this investigation will be an effective educational and investigational equipment.

• Transactions of the KSME C: Technology and Education
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• v.4 no.1
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• pp.43-47
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• 2016

Ground source heat pump(GSHP) systems is known as environmental friendly and energy saving. Especially a ground heat exchanger is an important unit that determines the thermal performance of a system and initial cost. In design phase of vertical GSHP system, it is recommended that the effective borehole thermal resistance, be determined from in-situ thermal response test. In this study, ground effective thermal conductivity was categorized by a region. As a result of the study, the ground thermal conductivity of national average was analyzed as 2.56 W/mK. The highest regional average of thermal conductivity is 2.68 W/mK in Seoul, and the lowest is 2.28 W/mK in Busan. Also, the thermal conductivity on the coast has been analyzed approximately 30% lower than the average.

• Fire Science and Engineering
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• v.26 no.1
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• pp.89-95
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• 2012

In this study, we were manufactured wood flour-HDPE composites by modular co-rotating twin screw extruder with L/D ratio of 42. We was measured cone calorimeter test and thermogravimetric analysis (TGA) to find the combustion characteristics and thermal properties for wood flour-HDPE composites. We then evaluated the effect of three additive-type flame retardants on fire resistance performance. The cone calorimeter test showed that the heat release rate (HRR) of untreated composites was the highest Peak HRR ($446.6kW/m^2$) as well as Mean HRR ($185.5kW/m^2$). From the TGA, it was shown that composites added flame retardants began early thermal decomposition and improved thermal stability.

• Journal of Powder Materials
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• v.9 no.5
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• pp.307-314
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• 2002

The high temperature deformation behavior of the activated sintered W powder compacts was investigated. The W compact showed the relative density of 94% with the average W grain size of $23\mutextrm{m}$ by activated sintering at $1400^{\circ}C$ for 1 hour. Compression tests were carried out in the temperature range of $900-1100^{\circ}C$ at the strain rate range of $10^{0}$/sec - $10^{-3}$/sec. True stress-strain curve and microstructure exhibited the grain boundary brittleness which was dependent on the compression test temperature. The activated sintered W compact showed that the maximum stress as well as the strain at the maximum stress was abruptly decreased as the test temperature increase from $900^{\circ}C$ to 1000 and $1100^{\circ}C$ regardless of the strain rate. The discrepancy of the microstructure in the specimen center was obviously observed with the increase of the test temperature. After compression test at $900^{\circ}C$ the W grain was severely deformed normally against the compression axis. However, after compression test at $1000^{\circ}C$ and $1100^{\circ}C$ the W grain was not deformed, but the microcrack was formed in the W grain boundary. The Ni-rich second phase segregated along the W grain boundary could be partly unstable over $900^{\circ}C$ and affect the poor mechanical property of the activated sintered W compact.

• The Journal of Korean Physical Therapy
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• v.24 no.5
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• pp.325-333
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• 2012

Purpose: The purpose of this study was to determine the concurrent validity between Figure-of-8 Walking Test (F8W), Berg Balance Scale (BBS), Four Squared Step Test (FSST), and Timed UP and GO Test (TUG) in patients with stroke. Methods: Forty two participants (26 men, 16 women, $55.0{\pm}11.72$) with at least three months post stroke who were able to walk at least 10 m without walking aid participated in this study. Assessment of concurrent validity between the F8W (time and steps) and BBS was performed using Spearman rank order correlation and between the F8W (time and steps), FSST and TUG assessed using Pearson correlation. Results: The time of the F8W showed correlation with BBS (r=-0.46, p<0.01), FSST (r=0.64, p<0.01), and TUG (r=0.81, p<0.01), and steps of the F8W showed correlation with BBS (r=-0.43, p<0.01), FSST (r=0.47, p<0.01), and TUG (r=0.51, p<0.01). Conclusion: The F8W is a valid measure of balance and walking skill among patients with stroke and may provide complementary information with regard to dynamic balance and functional walking for the real life of stroke patients.

• Nuclear Engineering and Technology
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• v.31 no.6
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• pp.561-571
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• 1999

Microstructure and mechanical properties of five Cr-Mo steels for nuclear industry applications have been investigated. Transmission electron microscopy, energy dispersive spectrometer, differential scanning calorimeter, hardness, tensile, and impact test were used to evaluate the Cr and W effect on the microstructure and mechanical properties. Microstructures of Cr-Mo steels after tempering are classified into three types : bainitic 2.25Cr-lMo steel, martensitic Mod.9Cr-lMo, HT9M, and HT9W steels, and dual phase HT9 steel. The majority of the precipitates were found to be M$_{23}$C$_{6}$ carbides. As minor phases, fine needle-like V(C,N), spherical NbC, fine needle-like Cr-rich Cr$_2$N, and Cr-rich M$_{7}$C$_3$were also found. Addition of 2wt.% W in Cr-Mo steels retarded the formation of subgrain and dissolution of Cr$_2$N precipitates. Hardness and ultimate tensile strength increased with increasing Cr content. Though Cr content of HT9W steel was lower than that of HT9 steel, the hardness of HT9W was higher due to the higher W content. W added HT9W steel had the highest ultimate tensile strength above $600^{\circ}C$. But impact toughness of W added steel (HT9W) and high Cr steel (HT9) was low.w.w.

• Journal of the Korean Wood Science and Technology
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• v.40 no.1
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• pp.19-25
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• 2012

The fire retardant bamboo charcoal (BC) boards were manufactured for interior building materials in this study, The BC boards were manufactured by mixing and pressing of the bamboo charcoal, expanded vermiculite, and inorganic binder. The combustion behaviors of the BC boards were investigated using a cone calorimeter at an incident heat flux of 50 kW/$m^2$. Three building materials (plywood, BC board of Japan, and gypsum board) were used to observe the burning behaviors of weight loss, total heat release rate, and maximum heat release rate. Surface test and toxicity evaluation of the BC board were also conducted. The weight loss of the BC board (12.0%) was lower than the nonflammable gypsum board (15.6%) after burning of 10 min. Total heat release of the BC was 3 MJ/$m^2$ (KS standard 8 MJ/$m^2$) and total heat release rate of the BC was 20 kW/$m^2$ (KS standard 200 kW/$m^2$). Therefore, the BC boards were adjustable for the third-grade flame retardant building materials. External appearance change and mouse toxicity were not found in the BC boards after the combustion test.