• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1065-1075
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• 2017

In this study, high velocity impact tests along with modeling of material behavior and numerical analyses were conducted to predict the dispersion behavior of the debris resulting from a high velocity impact fracture. For the impact tests, two different materials were employed for both the projectile and the target plate - the first setup employed aluminum alloy while the second employed steel. The projectile impacts the target plate with a velocity of approximately 1 km/s were enforced to generate the impact damages in the aluminum witness plate through the fracture debris. It was confirmed that, depending on the material employed, the debris dispersion behavior as well as the dispersion radii on the witness plate varied. A numerical analysis was conducted for the same impact test conditions. The smoothed particle hydrodynamics (SPH)-finite element (FE) coupled technique was then applied to model the fracture and damage upon the debris. The experimental and numerical results for the diameters of the perforation holes in the target plate and the debris dispersion radii on the witness plate were in agreement within a 5％ error. In addition, the impact test using steel was found to be more threatening as proven by the larger debris dispersion radius.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.12
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• pp.829-838
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• 2022

This study conducts Hypervelocity Impact(HVI) simulations considering space objects with various shapes and different impact angles. A commercial nonlinear structural dynamics analysis code, LS-DYNA, is used for the present simulation study. The Smoothed Particle Hydrodynamic(SPH) method is applied to represent the impact phenomena with hypervelocity. Mie-Grüneisen Equation of State and Johnson-Cook material model are used to consider nonlinear structural behaviors of metallic materials. The space objects with various shapes are modeled as a sphere, cube, cylinder, and cone, respectively. The space structure is modeled as a thin plate(200 mm×200 mm×2 mm). HVI simulations are conducted when space objects with various shapes with 4.119 km/s collide with the space structures, and the impact phenomena such as a debris cloud are analyzed considering the space objects with various shapes having the same mass at the different impact angles of 0°, 30° and 45° between the space object and space structure. Although space objects have the same kinetic energy, different debris clouds are generated due to different shapes. In addition, it is investigated that the size of the debris cloud is decreased by impact angles.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.5
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• pp.932-940
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• 2011

This study describes computational simulation results in 2-dimensional and 3-dimensional space concerning large scale gap test(LSGT) by using commercial hydrocode such as AUTODYN and LS-DYNA to analyze the detonation phenomenons of high explosives. To consider the possibilities of LSGT simulation, we used Lee - Tarver reaction rate model of PBX-9404 and Comp-B which were implemented AUTODYN's material library. Also we have tried the diverse numerical schemes such as Lagrangian, Eulerian and ALE(Arbitary Lagrangian Eulerian), SPH(Smoothed Particle Hydrodynamics) in LSGT simulations. After LSGT simulations, we compared the simulation results with published results to verify the LSGT simulations. According to the LSGT simulations, we have concluded as follows. In 2-dimensional and 3-dimensional space, Lagrangian solver provided the most reliable results based on analysis time and accuracy. When using two hydrocodes in 2-dimensional space, the simulation results are almost same except one explosive model. We have verified the modeling method and simulation results of the LSGT by using the commenrcial hydrocode in this study.

• Journal of Korean Society of Rural Planning
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• v.25 no.1
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• pp.67-74
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• 2019

This study is to identify the heat vulnerability area as represented by heat risk factors which could be attributable to heat-related deaths. The heat risk factors were temperature, Older Adults(OA), Economic Disadvantage(ED), Accessibility of Medical Services(AMS), The population Single Person Households(SPH). The factors are follow as; the temperature means to the number of days for decades average daily maximum temperature above $31^{\circ}C$, the Older Adults means to population ages 65 and above, furthermore, the Economic Disadvantage means to the population of Basic Livelihood Security Recipients(BLSR), the Accessibility of Medical Services(AMS) means to 5 minutes away from emergency medical services. The results of the analysis are showed that the top-level of temperature vulnerability areas is Dong, the top-level of vulnerability OA areas is Eup, the top-level of AMS vulnerability is Eup. Moreover, the top-level of vulnerability ED area appears in the Eup and Dong. The result of analysing relative importance to each element, most of the Eup were vulnerable to heat. Since, there are many vulnerable groups such as Economic Disadvantage, Older Adults in the Eup. We can be figured out estimated the number of heat-related deaths was high in the Eup and Dong by the data of emergency activation in the Chungcheongnam-do Fire Department. Therefore, the result of this study could be reasonable.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.9
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• pp.682-686
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• 2014

Nowadays, the needs to revise the classification criteria for noise emission facilities have been suggested by the related industries. Because there existed many reasonable factors in the criteria regarding the noise emission facilities. And the noise emission facility classification criterion of the print machine changed from 50 HP to 100 HP in 2013. But the increasement of the noise emission facility classification criterion of the print machine can cause adverse effects like the bigger noise. So, in this paper, we measured the print machine's sound power level according to the changes of the print machine's power to assess the adverse effects. The measurement method applied with KS I ISO 9614-2(1996). The corelation between the sound power level and the power of print machines was analyzed by regression analysis. In this paper, we found that the sound power level of the print machines can increase about 1.3 dB in the condition of that the power of print machine increases from 50 HP to 100 HP. And we found that the sound power level of the print machines can increase about 1.0 dB for a increasement of 1,000 SPH(sheet per hour) of printing speed. The noise emission characteristics of print machine stuied in this paper will be useful to design the noise reduction plan in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.709-713
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• 2017

In urgent situations such as crashes, the integrity of an aircraft's fuel tank is directly related to the survivability of the crew. Thus, an external auxiliary fuel tank should be robust against bird strikes. In this study, a numerical analysis was carried out using impact analysis software to analyze the influence of bird strike on a composite container for an external auxiliary fuel tank. The structure was modeled as a shell element, and the fluid and bird were modeled by the particle method. The behavior of the internal fluid was also examined. The maximum stress, deformation, and strain of the composite container were also calculated.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.7 no.1
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• pp.33-48
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• 1997

Korean diffusive sampler (KDS) and charcoal tube (CT) were used for sampling n-hexane, trichloroethylene and toluene in air KDS was made by Department of Environmental Health, SNU-SPH in 1995. Surveys were conducted at ten industrial plants with organic solvents. The relationship between two sampling methods was examined by linear regression analysis, and concentrations by two sampling methods were compared using paired t-test. The results are as follows: 1. The geometric means by CT and KDS methods were 3.26ppm and 3.32ppm for n-hexane, 5.07ppm and 6.34ppm for toluene, and 7.18ppm and 7.90ppm for toluene, respectively. There was no significant difference between results by CT and KDS methods in three organic vapors (p>0.05). When linear regression analysis was performed, two sampling methods were highly related ; correlation coefficients were 0.98, 0.90 and 0.96 for n-hexane, toluene and trichloroethylene, respectively. 2. Airborne concentrations of n-hexane (n=21) were below 0.5 TLV level. The GM by two methods were almost same (3.09 ppm). And there was no significant difference between results by two methods (p>0.05). 3. Since toluene and trichloroethylene concentrations showed several levels, appropriate sampling rates were applied for each level. The GM of toluene concentrations by two methods at 0.5 TLV level were 3.75ppm and 5.48ppm. The KDS method overestimated the toluene concentrations at 0.5 TLV level (p<0.05). The GM values of toluene concentrations at 1 TLV level were 31.80ppm and 25.38ppm and at 2 TLV level were 64.13 ppm and 51.37 ppm. The KDS method underestimated concentration at both level (p<0.05). For trichloroethylene, the GM at 0.5 TLV level were 4.97 ppm and 7.11ppm. The KDS method overestimated the concentration of trichloroethylene (p<0.05). In conclusion, concentrations of three organic vapors measured by CT and KDS were not significantly different and results by two methods were highly related. But at contain concentrations, the levels by method were significantly different. Therefore, it is suggested that sampling rate of KDS should be studied simultaneously using CT method for organic vapors.

• Journal of Microbiology and Biotechnology
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• v.14 no.2
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• pp.302-311
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• 2004

Comamonas testosteroni (formerly Pseudomonas sp.) NCIMB 10643 can grow on biphenyl and alkylbenzenes $(C_2-C_7)$ via 3-substituted catechols. Thus, to identify the genes encoding the degradation, transposon-mutagenesis was carried out using pAG408, a promoter-probe mini-transposon with a green fluorescent protein (GFP), as a reporter. A mutant, NT-1, which was unable to grow on alkylbenzenes and biphenyl, accumulated catechols and exhibited an enhanced expression of GFP upon exposure to these substrates, indicating that the gfp had been inserted in a gene encoding a broad substrate range catechol 2,3-dioxygenase. The genes (2,826 bp) flanking the gfp cloned from an SphI-digested fragment contained three complete open reading frames that were designated bphCDorfl. The deduced amino acid sequences of bphCDorfl were identical to 2,3-dihydroxybiphenyl 1,2-dioxygenase (BphC), 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate hydrolase (BphD), and OrfI, respectively, that are all involved in the degradation of biphenyl/4-chlorobiphenyl (bph) by Ralstonia oxalatica A5. The deduced amino acid sequence of the orfl revealed a similarity to those of outer membrane proteins belonging to the OmpW family. The introduction of the bphCDorfl genes enabled the NT-l mutant to grow on aromatic hydrocarbons. In addition, PCR analysis indicated that the DNA sequence and gene organization of the bph operon were closely related to those in the bph operon from Tn4371 identified in strain A5. Furthermore, strain A5 was also able to grow on a similar set of alkylbenzenes as strain NCIMB 10643, demonstrating that, among the identified aromatic hydrocarbon degradation pathways, the bph degradation pathway related to Tn4371 was the most versatile in catabolizing a variety of aromatic hydrocarbons of mono- and bicyclic benzenes.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.1
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• pp.39-45
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• 2009

Purpose: The purpose of this study is to compare the visual performance by contrast sensitivity (CS) and disability glare (DG) in low astigmatic eyes corrected with toric soft lenses and other optical corrections. Methods: Twenty university students with myopia (-1.00 to -6.50D Sph. with astigmatism up to 1.50 cyl) were enrolled and corrected by five different methods: 1) soft toric lenses; 2) spherical soft contact lenses; 3) RGP lenses; 4) best spectacle corrected visual acuity; 5) spherical equivalent spectacles. All subjects had corrected vision acuity of 20/20 or better. Contrast sensitivity and disability glare were measured using the OPTEC 6500 contrast sensitivity view-in tester included the EyeView Functional Vision Analysis software at photopic or mesopic conditions with glare. Results: At photopic condition, best corrected spectacle wearers had the highest monocular contrast sensitivity at all spatial frequency followed by soft toric lenses, RGP lenses, spherical equivalent spectacles, and spherical soft contact lenses. However, all of them were in normal contrast sensitivity value at photopic condition. At mesopic condition with glare, toric soft lenses were the highest and followed by RGP lenses, spherical equivalent spectacles, best spectacle corrected visual acuity and spherical soft contact lenses. It was observed that spherical soft contact lens wearers demonstrated lower range than normal contrast sensitivity value at mesopic condition with glare. Conclusion: Toric soft lenses gave better visual performance than spherical soft lenses in low astigmatic eyes. Subjects requiring the use of contact lenses under mesophic conditions could benefit from toric soft lenses.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1995.06b
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• pp.77-96
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• 1995

To obtain basic informations for the improvement of seed potato production in Korea, some etiological properties of potato virus Y(PVY) distributed in the major seed potato production area(Daekwanryeong) were characterized, and the nucleotide and amino acid sequences of the coat protein gene of the PVY strains isolated were analyzed. PVY strains in Daekwonryeong, an alpine area, were identified to be two strains, PVYo and PVYN by symptoms of indicator plants, and their distribution in potato fields was similar. Major symptom on potato varieties by PVY was grouped as either mosaic alone or mosaic accompanied with veinal necrosis in the lower leaves. The symptom occurrence of the two symptoms was similar with Irish Cobbler, but Superior showed a higher rate of mosaic symptom than the other. The PVY strain which was isolated from potato cv. Superior showing typical mosaic symptoms produced symptoms of PVY-O on the indicator plants of Chenopodium amaranticolor, Nicotiana tabacum cv. Xanthi nc and Physalis floridana, but no symptom o Capsicum annum cv. Ace. Moreover, results from the enzyme-linked immunosorbent assay with monoclonal and polyclonal antibodies showed that the isolated PVY reacts strongly with PYV-O antibodies but does not react specifically with PVY-T antibodies. The purified virus particles were flexious with a size of 730$\times$11nm. On the basis of the above characteristics, the strain was identified to be a PVY-O and named as of PVY-K strain. The flight of vector aphids was observed in late May, however, the first occurrence of infected plants was in mid June with the bait plants surrounded with PVY-infected potato plants and early July with the bait plants surrounded with PVY-free potato plants. PVY infection rates by counting symptoms on bait plants (White Burley) were 1.1% with the field surrounded with PVY-free potato plants and 13.7% the fields surrounded with PVY-infected potato plants, showing the effect of infection pressure. The propagated PVY-K strain on tobacco(N. sylvestris) was purified, and the RNA of the virus was extracted by the method of phenol extraction. The size of PVY-K RNA was measured to be 9, 500 nucleotides on agarose gel electrophoresis. The double-stranded cDNAs of PVY-K coat protein(CP) gene derived by the method of polymerase chain reaction were transformed into the competent cells of E. coli JM 109, and 2 clones(pYK6 and pYK17) among 11 clones were confirmed to contain the full-length cDNA. Purified plasmids from pYK17 were cut with Sph I and Xba I were deleted with exonuclease III and were used for sequencing analysis. The PVY-K CP gene was comprised of 801 nucleotides when counted from the clevage site of CAG(Gln)-GCA(Ala) to the stop codon of TGA and encoded 267 amino acids. The molecular weight of the encoded polypeptides was calculated to be 34, 630 daltons. The base composition of the CP gene was 33.3% of adenine, 25.2% of guanine, 20.1% of cytosine and 21.4% of uracil. The polypeptide encoded by PVY-K CP gene was comprised of 22 alanines, 20 threonines, 19 glutamic acids and 18 glycines in order. The homology of nucleotide sequence of PVY-K CP gene with those of PVY-O(Japan), PVY-T(Japan), PVY-TH(Japan), PVYN(the Netherlands), and PVYN(France) was represented as 97.3%, 88.9%, 89.3%, 89.6% and 98.5%, respectively. The amino acid sequence homology of the polypeptide encoded by PVY-K CP gene with those encoded by viruses was represented as 97.4%, 92.5%, 92.9%, 92.9%, and 98.5%, respectively.