• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2023-2028
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• 2013

A kinetic study is reported for the nucleophilic substitution reactions of phenyl Y-substituted-phenyl carbonates (5a-5k) with piperidine in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. The plots of $k_{obsd}$ vs. [piperidine] for the reactions of substrates possessing a strong electron-withdrawing group (EWG) in the leaving group (i.e., 5a-5i) are linear and pass through the origin. In contrast, the plots for the reactions of substrates bearing a weak EWG or no substituent (i.e., 5j or 5k) curve upward, indicating that the electronic nature of the substituent Y in the leaving group governs the reaction mechanism. Thus, it has been suggested that the reactions of 5a-5i proceed through a stepwise mechanism with a zwitterionic tetrahedral intermediate (i.e., $T^{\pm}$) while those of 5j and 5k proceed through a stepwise mechanism with two intermediates (i.e., $T^{\pm}$ and its deprotonated form $T^-$). The slope of the Br${\o}$nsted-type plot for the second-order rate constants (i.e., $k_N$ or $Kk_2$) changes from -0.41 to -1.89 as the leaving-group basicity increases, indicating that a change in the rate-determining step (RDS) occurs. The reactions of 5a-5k with piperidine result in larger $k_1$ values than the corresponding reactions with ethylamine.

• Bulletin of the Korean Chemical Society
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• v.25 no.7
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• pp.1019-1024
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• 2004

The present paper is focused on simultaneous sorption concentration of gold (III) and silver (I) from thiocyanate solutions using high-selective anion exchanger AN-25 and subsequent separation of these ions at various concentrations of thiocarbamide (eluent). As a result, silver (I) ions are completely eluted from AN-25 and gold (III) ions remain in the resin phase and can be determined directly in the solid phase by diffuse reflection spectroscopy. It is proposed to use the sorption-spectroscopic method for Au(III) determination in aqueous solutions. The calibration curve is linear in the concentration range of 1-19 mg/L (sample volume is 10.0 mL) and the detection limit is 0.05 ${\mu}g/mL$. The presence of Cu(II), Co(II), Fe(II) do not hinder this determination. Au(III) was determined in industrial solutions.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.154-157
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• 1990

This paper describes a new method of calculating expected energy generation and loss of load probability (L.O.L.P) for electric power system operation and expansion planning. The method represents an equivalent load duration curve (E.L.D.C) as a mixture of cumulants approximation (M.O.C.A), which is the general case of mixture of normals approximation (M.O.N.A). By regarding a load distribution as many normal distributions-rather than one normal distribution-and representing each of them in terms of Gram-Charller expansion, we could improve the accuracy of results. We developed an algorithm which automatically determines the number of distribution and demarcation points. In modelling of a supply system, we made subsets of generators according to the number of generator outage: since the calculation of each subset's moment needs to be processed rapidly, we futher developed specific recursive formulae. The method is applied to the test systems and the results are compared with those of cumulant, M.O.N.A and Booth-Baleriaux method. It is verified that the M.O.C.A method is faster and more accurate than any other methods.

• Analytical Science and Technology
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• v.8 no.3
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• pp.313-319
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• 1995

Surface-enhanced Raman scattering(SERS) spectroscopy was employed to analyze the genotoxic nucleobase adducts of benzo[a]pyrene(BP) formed through one-electron oxidation pathway. SERS spectroscopy provided sufficient resolution to distinguish if BP intermediate was bound to different nucleobases(e. g. adenine or guanine). Furthermore, SERS specroscopy was also able to detect the difference in the binding position of the adduct to the various sites of the nucleobase. The linearity of the calibration curve for N7Ade-BP ranged from 20 picogram to 800 nanogram per microliter and the detection limit under the current conditions was determined 20 picogram per microliter in a solution volume of 20 microliter.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.145-146
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• 2000

Primary emphasis was placed on the electrophoretic deposition of low voltage phosphor to indium-tin oxide-coated glass for the application of field emission display. The phosphor deposited by various parameters, such as deposition time and applied voltages was examined in detail. In addition, a comparison was made by analyzing luminance properties of the phosphor mixed with and without conducting $In_2O_3$ powder of less than 1um size. The measurement was performed as a function of $In_2O_3$ concentration from 3% to 15% by weight. The enhanced impact of indium powder mixing on the phosphor was clearly demonstrated by aging performance curve at 1000V excitation voltages with a current density of $1\;mA/cm^2$

• Steel and Composite Structures
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• v.19 no.2
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• pp.485-501
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• 2015

Channels are implemented in composite beams as shear connectors in two arrangements, face to face and back to back. No relevant explanation is found in the design codes to clarify the preference of the mentioned arrangements. Besides, the designers do not have a common opinion on this subject; i.e., some recommend the face to face and others, back to back status. In this research, channel shear connectors in composite beams are studied analytically for both arrangements using ABAQUS software. For this purpose, they have been modeled in simply supported beams in the arrangements of face to face and back to back; their effects on the crack initiation load of concrete slabs were monitored. The stiffness values of composite beams were also compared in the two arrangements using force-displacement curve; the results are relatively the same in both cases. Furthermore, the effects of compressive strength of concrete, channel size, length and spacing of channels as well as steel type of channels on the performance of composite beams have been investigated. According to the results obtained in this research, the face to face status shows better performance in comparison with that of back to back, considering the load of concrete fracturing.

• Journal of Animal Science and Technology
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• v.46 no.4
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• pp.503-508
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• 2004

This study was conducted to estimate the growth curve parameters of crossbreds between Korean native boars and Landrace sows and their relationships with meat qualities. The data used were weight-age data and carcass data from 131 males and 122 females raised at N.L.R.I in Korea. Growth curve parameters were estimated from nonlinear regression using Gompertz model individually. Average mature weight(A), average maturing rate(k), and average inflection point(u) showing maximum growth rate estimated were 179.54${\pm}$6.06kg, 0.3154${\pm}$0.0059, and 5.50${\pm}$0.11 months in females, and 179.84${\pm}$6.33kg, 0.3049${\pm}$0.0061, and 5.24${\pm}$0.13 months in males, respectively. For the growth curve parameters and derived statistics, the phenotypic correlations of maturing rate with gain rate at inflection, mature weight, and inflection point were - .30, - .77, and - .93 in male, and - .31, - .78 and - .94 in female, respectively. Matrure weight was positively correlated to the inflection point as + .89 in both male and female, indicating that late maturing pigs with lower k had longer maturing period with increasing gain rate and reached point of inflection later than early maturing pigs with higher k, and grew to larger mature weight. Backfat thickness and erode fat contents were correlated with mature weight positively in male and negatively in female, and correlated with gain rate at inflection point positively in both male and female, of which coefficients were as high as .42 and .50 in male, respectively.

• The Journal of Engineering Research
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• v.3 no.1
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• pp.97-106
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• 1998

In this paper, we analyze the WLL systems with high chip rate, which virtually eliminates the multipath fading effects by appling space diversity functions. First, we found out the capacity of reverse link which resulted from performing computer simulation of the transmission and reception of the WLL systems to evaluate the performance of the WLL systems in real environment. Besides, we analyze the radio propagation medium and the link budget and from the results, made RCSU for providing of the AWGN multipath fading channel. This RCSU is produced to characterize the urban radio propagation medium in various environments. From the simulation results, diversity gains increase as depth of fading becomes deeper. We also confirm that the systems applied diversity reduce the effects of multipath fading phenomena which cause to degrade the performance of WLL systems, based on the results $E_b/N_o$ and BER curve.

• Economic and Environmental Geology
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• v.14 no.2
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• pp.55-76
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• 1981

Southwestern contact zone of the Boeun granodiorite occurs near the thrust fault between the Ogcheon Group and Majeonri Limestone Formation. Ogcheon Group, metasediments composed of the Munjuri Formation, Changri Formation, and unconformably overlying Hwanggangri Formation, belongs to greenschist facies of regional metamorphism accompanied with deformation of two fold axes, $N10^{\circ}E$ and $N45-65^{\circ}E$ directions. Basic metamorphic rocks occurring in the Changri and Limestone Formations are the meta-basalts and meta-diabases of tholeiitic basalt series. The meta-basalts intruded in the Changri Formation as sills, whereas the meta-diabases in the Changri and Limestone Formations as stocks in appearance. They are considered to have emplaced before the formation of two fold axes and related with the thrust fault, based on the geologic setting of the area. The metamorphic facies are identified to be greenschist facies to epidote-amphibolite facies for the meta-basalt, and epidote-amphibolite facies for the meta-diabases. It is interpreted that such a variety of facies was related from the combination of earlier deuteric alteration and later regional metamorphism. The metasediments in southwestern contact zont of the Boeun granodiorite which is a product of later syntectonic intrusion of middle Jurassic in age, show pyroxene-hornfels facies near the contact and amphibole-horenfels facies away from the contact to the mineral zoning in the contact metamorphic aureole of the Limestone Formation, based on the paragenetic analysis of mineral assemblages. The Limestone in the area appears to be considerably $SiO_2-CaO-MgO-CO_2-H_2O$ can be adopted to evaluate equilibrium conditions of the mineral assemblages in each mineral zone. It is revealed that a temperature gradient was existed accross the contact aureole ranging from the higher igneous side to lower sedimentary side, whereas no clear trend of $XCO_2$ variation appears but high mole fraction. The tremolite diopside-quartz-calcite assemblages occurs in common through the most mineral zones of contact aureole that is in good agreement with the equivalent reaction curve which extends over a wide range of $T-XCO_2$ conditions.

• Journal of Yeungnam Medical Science
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• v.36 no.3
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• pp.231-240
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• 2019

Background: We sought to determine the value of combining diffusion-weighted (DW) and perfusion-weighted (PW) sequences with a conventional magnetic resonance (MR) sequence to assess solid components of borderline ovarian tumors (BOTs) and stage I carcinomas. Methods: Conventional, DW, and PW sequences in the tumor imaging studies of 70 patients (BOTs, n=38; stage I carcinomas, n=32) who underwent surgery with pathologic correlation were assessed. Two independent radiologists calculated the parameters apparent diffusion coefficient (ADC), $K^{trans}$ (vessel permeability), and $V_e$ (cell density) for the solid components. The distribution on conventional MR sequence and mean, standard deviation, and 95% confidence interval of each DW and PW parameter were calculated. The inter-observer agreement among the two radiologists was assessed. Area under the receiver operating characteristic curve (AUC) and multivariate logistic regression were performed to compare the effectiveness of DW and PW sequences for average values and to characterize the diagnostic performance of combined DW and PW sequences. Results: There were excellent agreements for DW and PW parameters between radiologists. The distributions of ADC, $K^{trans}$, and $V_e$ values were significantly different between BOTs and stage I carcinomas, yielding AUCs of 0.58 and 0.68, 0.78 and 0.82, and 0.70 and 0.72, respectively, with ADC yielding the lowest diagnostic performance. The AUCs of the DW, PW, and combined PW and DW sequences were $0.71{\pm}0.05$, $0.80{\pm}0.05$, and $0.85{\pm}0.05$, respectively. Conclusion: Combining PW and DW sequences to a conventional sequence potentially improves the diagnostic accuracy in the differentiation of BOTs and stage I carcinomas.