• Journal of Environmental Health Sciences
• /
• v.29 no.2
• /
• pp.94-102
• /
• 2003

This study was carried out to investigated the distribution and characteristics of Vibrio spp. isolated from fish and shellfish, seawater and brackish water samples collected from Pohang, Uljin, Yeongduk and Gyeongju in Gyeongbuk Province from April 2000 to October 2000. Total 155 strains of genus Vibrio were isolated from 439 collected samples, and numbers of isolated strains of V. parahaemolyticus and V. vulnificus were 140 and 15, respectively. The isolation rate from the samples collected in Pohang was the highest as 41.5% (76 strains), and wat the highest as 71.4% (30 strains) in brackish water, and was the highest as 55.7% (34 strains) in August. And the optimal pH, temperature, and NaCl concentration for growth of V. parahaemolyticus and V. cholerae were 8.0, 3$0^{\circ}C$ and 2.0％, respectively. In a resistance test for environmental factors, heat and cold resistants of V. parahaemolyticus were higher than those of V. vulnificus, withstanding for 15 minutes at 6$0^{\circ}C$ and 6 days at -18$^{\circ}C$. The pH range for existence of V. parahaemolyticus and V. vulnificus were 4.5~l1.0 and 4.5~10.0, showing the similar resistance to pH. V. parahaemolyticus and V. vulnificus could grow in media containing up to 10.0% and 7.0% NaCl, respectively, Salt-tolerance of V. parahaemolyticus was higher than that of V. vulnificus. In an antibiotics sensitivity test against 16 strains of V. parahaemolyticus, twelve strains were resistant to ampicillin, eight strains were resistant to cephalothin. one strain was resistant to streptomycin, and one strain was resistant to ticarcillin.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.14 no.4
• /
• pp.375-395
• /
• 2012

According to the local highway tunnel ventilation guideline, ventilation capacity calculation should be performed at the speed ranging from 10 km/h to 80 km/h. This is so reasonable method considering uncongested and congested traffic conditions in urban tunnels. But recently due to low traffic volume and very low congestion frequency in rural highway tunnels, it seems to be an inadequate way to apply the guideline. Therefore the calculation should be performed separately for the free flow and congested traffic cases classified by the appropriate decision model. This paper aims at determining unnecessary running speed range for reasonable tunnel ventilation design, considering free flow and congested traffic conditions. Firstly, traffic volumes in highway tunnels were collected and if any, the causes of congestion were investigated. And with concept of 'margin speed'($u-u_m$), the decision model on traffic congestion was developed. Applicability of the decision model was also analyzed with case study. According to the results, when design speed is 100 km/h, with V/C less than 0.1, then the range of unnecessary speed in tunnel ventilation design is less than 40 km/h; for $V/C{\leqq}0.35$, $V/C{\leqq}0.6$ and $V/C{\leqq}0.75$, the unnecessary speed ranges are found to be ${\leqq}30$, ${\leqq}20$ and ${\leqq}10km/h$, respectively.

• Journal of Korean Society of Transportation
• /
• v.23 no.3 s.81
• /
• pp.125-136
• /
• 2005

The current traffic accident reduction procedure in economic feasibility study does not consider the characteristics of road and V/C ratio. For solving this problem, this paper suggests methods to be able to evaluate safety of each road in construction and improvement through developing accident Prediction model in reflecting V/C ratio Per road types and traffic characters. In this paper as primary process, model is made by tke object of urban roads. Most of all, factor effecting on accident relying on road types is selected. At this point, selecting criteria chooses data obtained from road planning procedure, traffic volume, existence or non-existence of median barrier, and the number of crossing point, of connecting road. and of traffic signals. As a result of analyzing between each factor and accident. all appear to have relatives at a significant level of statistics. In this research, models are classified as 4-categorized classes according to roads and V/C ratio and each of models draws accident predicting model through Poisson regression along with verifying real situation data. The results of verifying models come out relatively satisfactory estimation against real traffic data. In this paper, traffic accident prediction is possible caused by road's physical characters by developing accident predicting model per road types resulted in V/C ratio and this result is inferred to be used on predicting accident cost when road construction and improvement are performed. Because data using this paper are limited in only province of Jeollabuk-Do, this paper has a limitation of revealing standards of all regions (nation).

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.28 no.1
• /
• pp.15-22
• /
• 1995

To study ecological properties of Vibrio cholerae non-Ol and Vibrio mimicus which have been described as new food poisoning bacteria recently, the influence of factors such as temperature, salinity, pH and chemical oxygen demand (COD) on detection rate and density of these bacteria were evaluated. Fifty four seawater samples and 49 bottom deposit samples from estuary of Kum river from March 26th, 1993 to February 22nd, 1994 were used for this study. The detection rate of V cholerae non-O1 were $16.7\%$ for seawater and $10.2\%$ for bottom deposit, respertively. The total detertion rate of V. cholerae non-O1 $(11.7\%)$ was a little higher than V mimicus $(10.7\%)$. Both V choierae non-O1 and V. mimicus were mainly detected in estuary water of which showed temperature $24^{\circ}C$ above and salinity $10\%o$ below. These bacteria were also detected in bottom deposit on January when the water temperature was $3.5^{\circ}C$. From these results, we supposed that temperature, salinity and organic material were important factors to growth of V. cholerae non-O1 and V. mimicus. V cholerae non-O1 might be grown better than V. mimicus under the fluctuating aquatic environmental condition such as salinity.

• Transactions of the Korean hydrogen and new energy society
• /
• v.7 no.1
• /
• pp.81-92
• /
• 1996

The Ar/Ar-$H_2$ plasma method was applied to reduce oxides and refine metals of V, Ta and B. In addition, the high temperature chemical reaction in Ar plasma and of the refining reaction in the Ar-(20%)$H_2$ plasma were analyzed. The crude V of 96wt% purity was obtained at the ratio of $C/V_{2}O_{5}=4.50$ by the Ar plasma reduction grade and the maximum reduction was obtained at $C/V_{2}O_{5}=4.50$ due to the $O_{2}$ loss from the thermal decomposition of vanadium oxide. In the Ar-(20%)$H_2$ plasma refining, the metallic V of 99.2wt% was produced at the ratio of $C/V_{2}O_{5}=4.40$. It was considered that a main refining reaction resulted from the chemical reaction between the residual carbon and residual oxygen. The metallic Ta of 99.8wt% was obtained at the ratio of $C/Ta_{2}O_{5}=5.10$ in a Ar plasma reduction and the Oz loss from the thermal decomposition of tantalum pentoxide did not take place. The deoxidation reaction was more significant than the decarburization reaction in the Ar-(20%)$H_2$ plasma refining and the metallic Ta of 99.9wt% was produced within the range of $C/Ta_{2}O_{5}$ ratio of 4.50 to 5.10. The Vickers hardness of Ta in the above mentioned range was about 220Hv due to the decrease in a residual oxygen by the deoxidation reaction. On the other hand, C is no suitable agent for the reduction of $B_{2}O_{3}$ by the Ar and Ar-$H_2$ plasma. But Fe-B-Si alloy was produced with the reduction of $B_{2}O_{3}$ in the melt when Fe, C, $B_{2}O_{3}$, and ferroboron mixtures were melted by the high frequency induction melting.

• Journal of the Korean Vacuum Society
• /
• v.5 no.3
• /
• pp.213-217
• /
• 1996

HgS and HgS: Co crystals and films grown by the slow cooling and the chemical bath deposition method were used to measure their crystal structure and their optical absorption spectra. HgS and HgS: Co crystals are hexagonal structure with the lattice constant $a_0=4.155{\AA}$, $c_0=9.505{\AA}$ for HgS and $a_0=4.148{\AA}$, $c_0=9.462{\AA}$ for HgS and $a_0=4.135{\AA}$, $c_0=9.442{\AA}$ for HgS: Co, respectively. The optical energy gap of these crystals are given as 2.040 eV for HgS and 1.900 eV for HgS: Co, and the optical energy gap of these films were 2.440 eV for HgS and 1.940 eV for HgS: Co at room temperature, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.6 no.2
• /
• pp.220-228
• /
• 1996

CdTe single crystals were grown by vertical Bridgman method using double furnace with two siliconit heating elements. When the peak temperature of the upper furnace was fixed at $1150^{\circ}C$ and that of the lower furnace was $800^{\circ}C$, the temperature gradient was about $22.5^{\circ}C$/cm. The lattice constant $a_0$ was $6.482\AA$ from the X-ray diffraction and the band gap energy obtained from the optical absorption experiment at room temperature was 1.478 eV. PL spectrum showed that the bound exciton emission peak was resolved into ($A^0,X$) (1.5902, 1.5887 eV), ($h\;D^0$) (1.5918 eV) and ($D^0,X$ (1.5928, 1.5932 eV), and we have also calculated binding energy and ionization energy of the neutral donor and acceptor.

• Journal of the Korean Magnetics Society
• /
• v.8 no.2
• /
• pp.62-66
• /
• 1998

We have studied on the magnetic properties of the specimen with additives Bi$_2$O$_3$and$V_2O_5$ that sintered at 900 $^{\circ}C$ for 4 hours for sybthesizing optimal Ni-Zn-Cu ferrite. Curie temperature rises from 240 $^{\circ}C$ to 270 $^{\circ}C$ as Ni contents increase. Magentic maximum induction$(B_m)$ increases from 2650 G to 3300 G, 3500 G in the specimens with $V_2O_5$ and Bi$_2$O$_3$resectively. On the contrary coercive force $(H_c)$ lowers to 2.05 Oe~1.05 Oe. Permeability all increase in the specimen with additives. In the specimen with additive Bi$_2$O$_3$, we have obtained the low relative loss factor of $6.3{\times}10^{-5}~7.84{\times}10^{-5}$ in the range of 1MHz due to increase of resistivity in grain boundary. In the specimen with additive $V_2O_5$ in spite of increase permeability relative loss factor increase of due to decrease of Q-value.

• Korean Journal of Metals and Materials
• /
• v.46 no.8
• /
• pp.477-481
• /
• 2008

The secondary hardening and fracture behavior in P/M high speed steels bearing V content of 9 to 10 wt% have been investigated in terms of austenitizing temperature and precipitation behavior. Austenitizing was conducted at 1,100 and $1,175^{\circ}C$ of relatively low and high temperatures. Coarse primary carbides retained after austenitization were mainly V-rich MC type. They give a significant influence on hardeness and toughness, as well as wear resistance. Tempering was performed in the range of $500{\sim}600^{\circ}C$. The peak hardness resulting from the precipitation of the fine MC secondary carbides was observed near 520, irrespective of austenitizing temperature. Aging acceleration(or deceleration) did not occur with increasing austenitizing temperature because it mainly influences contents of V and C of matrix through the dissloution of coarse primary MC containing lots of V and C. The precipitation of secondary MC carbides, which also contain V and C, did not change the aging kinetics itself. In the 10V alloy containing much higher C content, the impact toughness was lower than 9V alloy, because of the larger amount of primary carbide and high hardness.

• Journal of the Korean Chemical Society
• /
• v.67 no.6
• /
• pp.407-414
• /
• 2023

The present study uses quasi-classical trajectory procedures to examine the vibrational relaxation and dissociation of the methyl and ring C-H bonds in excited methylpyrazine (MP) during collision with either N₂ or O₂. The energy-loss (-ΔE) of the excited MP is calculated as the total vibrational energy (E_T) of MP is increased in the range of 5,000 to 40,000cm^-1. The results indicate that the collision-induced vibrational relaxation of MP is not large, increasing gradually with increasing E_T between 5,000 and 30,000 cm^-1, but then decreasing with the further increase in E_T. In both N₂ and O₂ collisions, the vibrational relaxation of MP occurs mainly via the vibration-to-translation (V→T) and vibration-to-vibration (V→V) energy transfer pathways, while the vibration-to-rotation (V→R) energy transfer pathway is negligible. In both collision systems, the V→T transfer shows a similar pattern and amount of energy loss in the ET range of 5,000 to 40,000cm^-1, whereas the pattern and amount of energy transfer via the V→V pathway differs significantly between two collision systems. The collision-induced dissociation of the C-H_methyl or C-H_ring bond occurs when highly excited MP (65,000-72,000 cm^-1) interacts with the ground-state N₂ or O₂. Here, the dissociation probability is low (10^-4-10^-1), but increases exponentially with increasing vibrational excitation. This can be interpreted as the intermolecular interaction below E_T = 71,000 cm^-1. By contrast, the bond dissociation above E_T = 71,000 cm^-1 is due to the intramolecular energy flow between the excited C-H bonds. The probability of C-H_methyl dissociation is higher than that of C-H_ring dissociation.