• Journal of Welding and Joining
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• 제6권2호
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• pp.30-39
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• 1988

Generally, as the welded region of weld structures has the incomplete bead and welded deposit which are able to behave like the surface cracks occasinally, there is a high possibility that the fatigue fracture of the weld structures is due to the surface cracks on the wlded region. This study was done to investigate the effects of post weld heat treatment (PWHT) on the fatigue behaviors of the surface crack of the heat affected zone (HAZ) for the multi-pass welds under the repetitive pure bending moment. The obtained results are summarized as follows : 1. The crack grows to the depth direction initially as the number of cylces increase, the amount of crack length is increased for the surface dir3ction and cive versa for the depth direction. 2. The fatigue life is increased in a order of as weld, PWHT specimens and parent. 3. As the number of cycles increase, the crack length is increased to th surface direction. The increase of the depth length is blunted at the center of specimen thickness. 4. The fatigue crack growth of PWHT specimens to the surface direction is dependent upon the holding time and applied stress during PWHT. In order words, the crack growth rate decreases with the holding time and increases with the applied stress during PWHT. 5. As the crack grows, the aspect formed in the course of crack propagation approaches to semicircle for parent and ellipse with the largest semidiameter for PWHT ($1/4hr, 15kgf/mm^2$) 6. At depth direction, it is difficult to apply to the paris' equation because of the scattered data between the crack growth rate and the stress intensity factor range.

• Toxicological Research
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• 제17권4호
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• pp.317-323
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• 2001

The skin penetration rate of methidathion in vitro and pharmacokinetics of methidathion in vivo were studied with male Sprague-Dawley rats by dermal treatment. The in vitro skin penetration rates for Sprague-Dawley rats of methidathion technical (50 mg, 100 ${mu}ell$) and emulsifable concentrate (EC,40mg, 100${mu}ell$) were determined as 18.4 $\mu\textrm{g}$/c $m^2$/h (RSD : 6.5) and 18.5 $\mu\textrm{g}$/c $m^2$/h (RSD : 3.2), respectively. Dose-related systemic exposure (AUC) was observed in rats after dermal treatment. The corresponding AUC, $T_{max}$, $C_{max}$, and $T_{1}$2/ of methidathion in plasma were 1.5$\mu\textrm{g}$.hr/ml, 6 h, 0.10 $\mu\textrm{g}$/ml, and 16 h, for 116mg/kg doses, 3.2 $\mu\textrm{g}$. hr/ml, 8 h, 0.12 $\mu\textrm{g}$/ml, and 23 h, for 232 mg/kg doses and 10 $\mu\textrm{g}$. hr/ml, 12 h, 0.32 $\mu\textrm{g}$/ml, and 20 h, for 1,160 mg/kg doses respectively. The urinary excretion of methidathion, estimated wing an equation derived from the in vitro skin penetration study was 0.24~0.35% of the absorbed dose. The concentration of methidathion in kidney was higher than that in liver. Dose-dependent absorption and excretion of methidathion without saturation was observed under in vivo experimental condition.n.n.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제41권3호
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• pp.165-172
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• 2017

In this study, centrifugal fan blades used to circulate cold air inside a household refrigerator were optimized to achieve high performance and low noise by using the response surface method, which is frequently employed as an optimization algorithm when multiple independent variables affect one dependent variable. The inlet and outlet blade angles, and the inner radius, were selected as the independent variables. First, the fan blades were optimized to achieve the maximum volume flow rate. Based on this result, a prototype fan blade was manufactured using a 3-D printer. The measured P-Q curves confirmed the increased volume flow rate of the proposed fan. Then, the rotation speed of the new fan was decreased to match the P-Q curve of the existing fan. It was found that a noise reduction of 1.7 dBA could be achieved using the new fan at the same volume flow rate.

• Applied Chemistry for Engineering
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• 제25권2호
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• pp.167-173
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• 2014

The adsorption characteristics of the pellet-type adsorbent prepared from water treatment sludge for trimethylamine and ammonia were studied. The surface area and pore volume of the pellet-type adsorbent increased during calcination at $500^{\circ}C$. It was confirmed that the adsorbent prepared from water treatment sludge contained Br$\ddot{o}$nsted and Lewis acid sites. The breakthrough time of the adsorbent for both trimethylamine and ammonia was measured at different adsorbent weights and linear velocities while maintaining constant amounts of trimethylamine and ammonia. The kinetic saturation capacity and the adsorption rate constant for trimethylamine and ammonia were determined at different linear velocities by using the Wheeler equation. It was found that the kinetic saturation capacity and the adsorption rate constant were dependent on the linear velocity. An experimental equation could be derived to predict the breakthrough time of the adsorbent prepared from water treatment sludge for trimethylamine and ammonia at different adsorption conditions.

• Journal of the Korean Wood Science and Technology
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• 제26권3호
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• pp.63-72
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• 1998

In order to evaluate the biodegradability and mechanism of 4,5,6-trichloroguaiacol (TCG) produced from bleaching process in pulp mill by Phanerochaete chrysosporium, Trametes versicolor, and Inonotus cuticularis, changes in TCG and its metabolites during biodegradation were analyzed by HPLC, and GC/MS spectrometry. By three fungi, the maximum biodegradability against TCG were very quickly reached, compared with other chlorinated aromatic compounds such as PCP. Within 24 hrs, T versicolor indicated up to 95% of TCG removal rate, and P. chrysosporium and I. cuticularis also showed more than 80%, and 90%, respectively. Particularly, in case of T. versicolor, the removal rate of TCG after 1 hr. incubation was reached to approximately 90%, implying very rapid metabolization of TCG. However, by analyzing the filtrates extracted from TCG containing culture by GC/MS, the major metabolites at initial stage of biodegradation were dimers, indicating that the added TCG monomers were quickly polymerized. The others were trichloroveratrole, dichloroguaiacol, and trichlorobenzoic acid, suggesting that TCG may be biodegraded by several sequential reactions such as polymerization, oxidation, methylation, dechlorination, and hydroxylation. In other experiments, the extracellular fluid which did not contain any fungal mycelia was used to evaluate the effect of mycelia on TCG biodegradation. The extracellular fluid of T. versicolor also biodegraded TCG up to 90% within 24hrs, but those of P. chrysosporium and I. cuticularis did not show any good biodegradability. T versicolor showed the highest value of laccase, and other two fungi indicated a little activity of lignin peroxidase (LiP) and manganese peroxidase (MnP). In addition, the laccase activity of T. versicolor was very linearly proportional to the removal rate of TCG during incubation, in other words, showing the induction effect against TCG. Consequently, the biodegradation of TCG was very dependent upon the activity of laccase.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.159-159
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• 2011

Among the semiconductor ternary compounds in the I-III-$VI_2$ series, $CulnS_2$ ($CulnSe_2$) are one of the promising materials for photovoltaic applications because of the suitability of their electrical and optical properties. The $CuInS_2$ thin film is one of I-III-$VI_2$ type semiconductors, which crystallizes in the chalcopyrite structure. Its direct band gap of 1.5 eV, high absorption coefficient and environmental viewpoint that $CuInS_2$ does not contain any toxic constituents make it suitable for terrestrial photovoltaic applications. A variety of techniques have been applied to deposit $CuInS_2$ thin films, such as single/double source evaporation, coevaporation, rf sputtering, chemical vapor deposition and chemical spray pyrolysis. This is the first report that $CuInS_2$ thin films have been prepared by Aerosol Jet Deposition (AJD) technique which is a novel and attractive method because thin films with high deposition rate can be grown at very low cost. In this study, $CuInS_2$ thin films have been prepared by Aerosol Jet Deposition (AJD) method which employs a nozzle expansion. The mixed fluid is expanded through the nozzle into the chamber evacuated in a lower pressure to deposit $CuInS_2$ films on Mo coated glass substrate. In this AJD system, the characteristics of $CuInS_2$ films are dependent on various deposition parameters, such as compositional ratio of precursor solution, flow rate of carrier gas, stagnation pressure, substrate temperature, nozzle shape, nozzle size and chamber pressure, etc. In this report, $CuInS_2$ thin films are deposited using the deposition parameters such as the compositional ratio of the precursor solution and the substrate temperature. The deposited $CuInS_2$ thin films will be analyzed in terms of deposition rate, crystal structure, and optical properties.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제30권1호
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• pp.88-94
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• 2002

For the pressurized propellant supply system of liquid rocket, feed pressure is determined with respect to the chamber pressure of normal combustion state. However, during ignition period the initial chamber pressure is atmosopheric. This may cause overflow, hard-start and even critical damage for the engine. This paper proposes an improved propellant feed system for the stable combustion of liquid rocket. The proposed system utilizes the cavitating venturi to provide stable mass flow rate. Cavitating venturi offers unique flow control capabilities at normal and abnormal combustion state, because flow rate is soley dependent on the upstream absolute pressure and fluid properties, but independent on th downstream condition. Experimental variables are propellant feed pressure and chamber pressure. The effectiveness of cavitating venturi increased when the ratio of actual feed pressure to the cavitating venturi design pressure is increased. It is also found that Kerosene if more effective to supply stable mass flow rate than LOx.

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.2983-2988
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• 2013

Second-order rate constants ($k_N$) have been measured spectrophotometrically for the reactions of 4-chloro-2-nitrophenyl X-substituted-benzoates (1a-1h) with a series of cyclic secondary amines in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. The Hammett plot for the reactions of 1a-1h with piperidine consists of two intersecting straight lines, while the Yukawa-Tsuno plot exhibits an excellent linear correlation with ${\rho}_X $ = 1.25 and r = 0.58, indicating that the nonlinear Hammett plot is not due to a change in the rate-determining step (RDS) but is caused by ground-state stabilization through resonance interactions for substrates possessing an electron-withdrawing group in the benzoyl moiety. The Br${\o}$nsted-type plot for the reactions of 4-chloro-2-nitrophenyl benzoate (1d) with a series of cyclic secondary amines curves downward with ${\beta}_2$ = 0.85, ${\beta}_1$ = 0.24, and $pK_a{^o}$ = 10.5, implying that a change in RDS occurs from the $k_2$ step to the $k_1$ process as the $pK_a$ of the conjugate acid of the amine exceeds 10.5. Dissection of $k_N$ into the microscopic rate constants $k_1$ and $k_2/k_{-1}$ ratio associated with the reaction of 1d reveals that $k_2$ is dependent on the amine basicity, which is contrary to generally held views.

• Polymer(Korea)
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• 제27권6호
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• pp.509-520
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• 2003

The study was made to compare the crystallization behavior of polypropylene (PP) with different stereo-regularity. The unit cell parameters, lamellar structure of PP, and the growth of thieir spherulites were strongly dependent upon the crystallization condition. It was shown that metastable structure appeared with increasing cooling rate. The structural change of isotactic PP (iPP) was larger than that of syndiotactic PP (sPP). The crystal structure of sPP showed body centered cell III when it is cooled down with 1 $^{\circ}C$/min. When sPP was grown to primitive cell II structure, both unit cell and lamellar structure were less affected by a cooling rate. The overall crystallization rate of ipp was faster than that of sPP.

• Journal of Korean Society for Atmospheric Environment
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• 제17권E3호
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• pp.109-115
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• 2001

Acidic air pollutants were collected to characterize indoor air quality at a private house in Seoul during the spring period. All indoor and outdoor samples were measured simultaneously using an annular denuder system. The data set was collected on twelve different days with a 24-hr sampling period in April and May 1997. The chemical species measured were HN $O_3$, HN $O_2$, S $O_2$ and N $H_3$in the gas phase and P $M_{2.5}$ (dp 2.5 ${\mu}{\textrm}{m}$), S $O_4$$^{2-}$, N $O_3$$^{[-10]}$ and N $H_4$$^{+}$ in the particulate phase. Indoor concentrations of HN $O_2$, N $H_3$, and P $M_{2.5}$ were greater than outdoor levels. However, indoor concentrations of HN $O_3$, S $O_2$, N $O_3$$^{[-10]}$ and N $H_4$$^{+}$ were less than those found from outdoors. In the case of S $O_4$$^{2-}$, the indoor and outdoor concentrations were similar. Indoor concentrations of P $M_{2.5}$ , S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ were dependent upon the outdoor concentrations. A tracer-gas decay technique with sulfur hexafluoride (S $F_{6}$ ) as the tracer gas was used to estimate the air exchange rate of a private home in the spring. The average air exchange rate was computed to be 2.87 h $r^{-1}$ .X> .