• Journal of the Korean Society for Railway
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• v.19 no.2
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• pp.170-186
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• 2016

This paper introduces a multi-phase fuzzy risk graph model, representing a method for determining for SIL values for railway industry systems. The purpose of this paper is to compensate for the shortcomings of qualitative determination, which are associated with input value ambiguity and the subjectivity problem of expert judgement. The multi-phase fuzzy risk graph model has two phases. The first involves the determination of the conventional risk graph input values of the consequence, exposure, avoidance and demand rates using fuzzy theory. For the first step of fuzzification this paper proposes detailed input parameters. The fuzzy inference and the defuzzification results from the first step will be utilized as input parameters for the second step of the fuzzy model. The second step is to determine the safety integrity level and tolerable hazard rate corresponding to be identified hazard in the railway industry. To validate the results of the proposed the multi-phase fuzzy risk graph, it is compared with the results of a safety analysis of a level crossing system in the CENELEC SC 9XA WG A0 report. This model will be adapted for determining safety requirements at the early concept design stages in the railway business.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.293-298
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• 1999

Reaction mechanism was elucidated and reaction condition were optimized for the catalytic reaction synthesizing 2-methyl-4-methoxy-diphenylamine (MMDPA) which is an intermediate of Fluoran heat-sensitive dyestuff. Reactants consisted of 2-methyl-4-methoxyaniline (MMA), 3-methyl-4-nitroanisole (MNA), and cyclohexanone, and 5 wt % Pd/C was used as a catalyst. Experiments were run in an open slurry reactor equipped with reflux condenser, and products were analyzed by means of GC/MS and NMR. MMDPA yield of 90 mole % could be obtained after reaction time of 8~10 hours under the optimal reaction conditions comprising the reaction mass composition of MMA : MNA : cyclohexanone = 1 : 2 : 150 based on MMA input of 0.01 gmoles in xylene solvent, reaction temperature of $160^{\circ}C$, and catalyst amount of 0.5 g. It was found that the rate-determining step of overall reaction was dehydrogenation of the intermediate product obtained from condensation of MMA and cyclohexanone. Overall reaction rate and MMDPA yield were enhanced owing to hydrogen transfer reaction by introducing MNA together with MMA in the reaction mass. Excess cyclohexanone in the reaction mass played an important role of promoting the condensation of MMA and cyclohexanone.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3588-3592
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• 2010

Second-order rate constants ($k_N$) have been measured spectrophotometrically for nucleophilic substitution reactions of 2-pyridyl X-substituted benzoates 8a-e with a series of alicyclic secondary amines in $H_2O$ at $25.0{\pm}0.1^{\circ}C$. The $k_N$ values for the reactions of 8a-e are slightly smaller than the corresponding reactions of 4-nitrophenyl X-substituted benzoates 1a-e (e.g., $kN^{1a-e}/k_N^{8a-e}$ = 1.1 ~ 3.1), although 2-pyridinolate in 8a-e is ca. 4.5 $pK_a$ units more basic than 4-nitrophenolate in 1a-e. The Br$\o$nsted-type plot for the aminolysis of 8c (X = H) is linear with $\beta_{nuc}$ = 0.77 and $R^2$ = 0.991 (Figure 1), which is typical for reactions reported previously to proceed through a stepwise mechanism with breakdown of a zwitterionic tetrahedral intermediate $T^{\pm}$ being the rate-determining step (RDS), e.g., aminolysis of 4-nitrophenyl benzoate 1c. The Hammett plot for the reactions of 8a-e with piperidine consists of two intersecting straight lines (Figure 2), i.e., $\rho$ = 1.71 for substrates possessing an electron-donating group (EDG) while $\rho$ = 0.86 for those bearing an electron-withdrawing group (EWG). Traditionally, such a nonlinear Hammett plot has been interpreted as a change in RDS upon changing substituent X in the benzoyl moiety. However, it has been proposed that the nonlinear Hammett is not due to a change in RDS since the corresponding Yukawa-Tsuno plot exhibits excellent linear correlation with $\rho$ = 0.85 and r = 0.62 ($R^2$ = 0.995, Figure 3). Stabilization of substrates 8a-e in the ground state has been concluded to be responsible for the nonlinear Hammett plot.

• Journal of the Korean Ceramic Society
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• v.27 no.1
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• pp.79-85
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• 1990

A study on the oxidation of SiO2 sensing layer was done at 950, 1000, 105$0^{\circ}C$ under dry O2 atmosphere. The rate determining step around the oxide layer thickness, 1000$\AA$ was different with the oxidation temperature, as follows ; ⅰ) linear growth at 95$0^{\circ}C$ and ⅱ) parabolic growth at 100$0^{\circ}C$ and 105$0^{\circ}C$. The flatness of SiO2 film was observed within $\pm$1% and surface state charge density was reduced by annealing in N2 atmosphere. Finally, pH sensitivity of SiO2 film, in the range of pH 3-9, was 20mV/pH.

• Journal of Sericultural and Entomological Science
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• v.42 no.1
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• pp.1-5
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• 2000

To investigate the possibility of crypreservation of mulberry seeds in liquid nitrogen(LN$_2$), characteristics of the seeds were examined after picking mulberry syncarps and drying-heat treatment. Storage in LN$_2$has the potential of providing indifinite preservation of valuable seed germplasm. Determining the tolerance of seeds among given cultivars to LN$_2$cooling and subsequent rewarming is the first step to establishing the feasibility of LN$_2$storage. Seeds of 4 mulberry varities were treated to LN$_2$(-196$\^{C}$) for 24 hours after drying heat treatment. Seed moisture content of Daeryukppong was the highest. As moisture content of mulberry seed was below 1%, storage in LN$_2$was safe. And drying heat treatment for 60 minutes was suitable to prevent decreased germination rate and germination vigor of seeds. The seeds of Cheongilppong were unsuibable to cryopreserve in LN$_2$for longterm storage.

• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.38-42
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• 2008

The voltammetic behavior of Vitamin B6 (VB6) was studied at a glassy carbon electrode in phosphate buffers using cyclic, linear sweep and differential pulse voltammetry. The oxidation process was shown to be irreversible over the entire pH range studied (4.0-10.0) and was adsorption controlled. The adsorption amount of VB6 on the glassy carbon electrode was examined by chronocoulometry and the value of n, product of transfer coefficient and number of electrons transferred in the rate determining step, was determined from Tafel plot. VB6 was determined by differential pulse voltammetry and the peak current was found linearly with its concentration in the range of 3 10-7-2 10-4 mol L-1. The detection limit was 1 10-7 mol L-1. The procedure was successfully applied for the assay of VB6 in tablets.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.6
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• pp.316-324
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• 2003

This paper applied Elite-based Simplex-GA hybrid approach combined with Muptipop-GA (ESGA) to determining the location, size and number of capacitors to improve voltage profile and minimize power losses in unbalanced distribution systems. One of the main obstacles in applying GA to complex problems has been the high computational cost due to their slow convergence rate. To alleviate this difficulty, ESGA approach was developed that combines Elite-based Simplex-GA hybrid approach with Muptipop-GA. The objective function formulated consists of two terms: cost for energy losses and cost related to capacitor purchase and capacitor installation. The cost function associated with capacitor placement is considered as a step function due to banks of standard discrete capacities. Its efficiency was proved through the application in IEEE 13 bus and 34 bus test systems and was compared with several methods using GA.

• Bulletin of the Korean Chemical Society
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• v.23 no.5
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• pp.715-720
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• 2002

Kinetic studies of the reaction of Z-aryl cyclobutanecarboxylates with X-pyridines in acetonitrile at $55.0^{\circ}C$ have been carried out. The reaction proceeds by a stepwise mechanism in which the rate-determining step is the breakdown of the zwitterion ic tetrahedral intermediate, T $\pm$ . These mechanistic conclusions are drawn based on (i) the large magnitude of ${\rho}X$ and $\rhoZ$, (ⅱ) the positive sign of ${\rho}XZ$ and the larger magnitude of $\rhoXZ$ than normal SN2 processes, (ⅲ) a small positive enthalpy of activation, ${\Delta}H{\neq}$, and a large negative, ${\Delta}S{\neq}$, and lastly (iv) adherence to the reactivity-selectivity principle (RSP) in all cases.

• Journal of the Korean institute of surface engineering
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• v.41 no.6
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• pp.279-286
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• 2008

Numerical analysis is done to investigate which would be the most influencing process parameter in determining the uniformity of deposition thickness in TiN ICP-CVD(inductively coupled plasma chemical vapor deposition). Two configurations of ICP antenna are modeled; side and top planar. Side and top gas inlets are considered with each ICP antenna geometries. Precursor for TiN deposition was TDMAT(Tetrakis Diethyl Methyl Amido Titanium). Two step volume dissociation of TDMAT is used and absorption, desorption and deposition surface reactions are included. Most influencing factors are H and N concentration dissociated by electron impact collisions in plasma volume which depends on the relative positions of gas inlet and ICP antenna generated hot plasma region. Low surface recombination of N shows hollow type concentration, but H gives a bell type distribution. Film thickness at substrate edges is sensitive to gas flow rate and at high pressures getting more dependent on flow characteristics.

• Journal of the Korean Chemical Society
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• v.32 no.6
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• pp.567-574
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• 1988

Kinetic studies on the vanadium(IV)-catalyzed oxidation of dimethylsulfoxide by hydrogen peroxide in water and aqueous methanol and ethanol show that the reaction is the first order in the concentration of dimethylsulfoxide and hydrogen peroxide, respectively. Activation parameters are also measured for the oxidation of dimethylsulfoxide. It is suggested that the rate determining step is a process involving oxidation of dimethylsulfoxide as the result of nucleophilic attack by the sulfur on the O-O bond of vanadium(V)-peroxide complex.