• Journal of the Korean Chemical Society
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• v.41 no.7
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• pp.337-342
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• 1997

Acryloylmethylbenzo-15-crown-5 was prepared from the reaction of 4'-hydroxymethylbenzo-15-crown-5 with acryloyl chloride. And, poly(acryloylmethylbenzo-15-crown-5) [poly(AMB15C5)] was synthesized by radical polymerization using AIBN as initiator in benzene. Coated wire lead(II) ion-selective electrodes ($Pb^{2+}$-CWISEs) using either poly(AMB15C5) or B15C5 as neutral carrier were prepared, respectively. $Pb^{2+}$-CWISEs gave linear responses with slopes of 28$\pm$ 1mV per decade within the concentration range of $10^{-5} M{\sim}10^{-1}$ M, respectively. Also, the detection limits were $10^{-6}$ M and response times were either 3 or 5 min. for B15C5 and poly(AMB15C5), respectively. $Pb^{2+}$-CWISE base on B15C5 was rather unstable than poly(AMB15C5)'s due to solubility of the B15C5 in water. The selectivity coefficients of a variety of interfering ions such as $Mg^{2+},\; Ca^{2+},\; Co^{2+},\; Ni^{2+},\; Cu^{2+},\; Zn^{2+}$ and $Cd^{2+}$ were small ($10^{-4}{\sim}10^{-5}$), while those of $Na^+$ and $K^+$ were large (0.1∼0.01). In addition, the electrode responses depended upon the pH of test solution and the composition of the membrane. In the range pH 3∼6 of test solution, potentials of Pb2+-CWISEs were hardly changed. The optimal contents of B15C5 and poly(AMB15C5) were 7.7 wt% and 13.1 wt%, respectively.

• Journal of the Korean Mathematical Society
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• v.54 no.4
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• pp.1063-1079
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• 2017

Two standard Bessel sequences in a Hilbert $C^*$-module are approximately duals if the distance (with respect to the norm) between the identity operator on the Hilbert $C^*$-module and the operator constructed by the composition of the synthesis and analysis operators of these Bessel sequences is strictly less than one. In this paper, we introduce (a, m)-approximate duality using the distance between the identity operator and the operator defined by multiplying the Bessel multiplier with symbol m by an element a in the center of the $C^*$-algebra. We show that approximate duals are special cases of (a, m)-approximate duals and we generalize some of the important results obtained for approximate duals to (a, m)-approximate duals. Especially we study perturbations of (a, m)-approximate duals and (a, m)-approximate duals of modular Riesz bases.

• Journal of the Korean Ceramic Society
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• v.22 no.3
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• pp.13-18
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• 1985

Semiconductive $Ba_{0.9}Sr_{0.1}TiO_3$ was prepared by both the Calcining of mixed Oxides (C. M. O) and the Molten Salt Synthesis(M.S.S) methods to investigate the PTCR effects. In the Molten Salt Synthesis method the temperature of calcination for Synthesis of $BaTiO_3$ could be lowered from 110$0^{\circ}C$ to 80$0^{\circ}C$. The M.S.S Specimens had smaller grain size and more homogeneous size distribution at the same sintering temperature as compared with the C. M. O specimens. The M. S. S. specimens showed greater PTCR effects and current variations in the time vs. current charac-teristics than those of C. M. O Specimens.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.19 no.4
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• pp.443-457
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• 2015

We consider the M/M/c/c queues in which the customers blocked to enter the service facility retry after a random amount of time and some of idle servers can leave the vacation. The vacation time and retrial time are assumed to be of phase type distribution. Approximation formulae for the distribution of the number of customers in service facility and the mean number of customers in orbit are presented. We provide an approximation for M/M/c/c queue with general retrial time and general vacation time by approximating the general distribution with phase type distribution. Some numerical results are presented.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.241-243
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• 2000

In this paper, we analyze three-dimensional magnetic field distribution of a convergence purity maget(C.P.M) which is used for a cathode ray tube. The magnetization vector distribution of the C.P.M is obtained from the result of magnetization process analysis using the 2D F.E.M. Then the motion of electron beam passing through the inner space of the C.P.M is determined and compared with experimental result.

• Communications of the Korean Mathematical Society
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• v.37 no.1
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• pp.229-257
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• 2022

Let M be a semi-invariant submanifold of codimension 3 with almost contact metric structure (𝜙, 𝜉, 𝜂, g) in a complex space form M_n+1(c), c ≠ 0. We denote by A and R_𝜉 the shape operator in the direction of distinguished normal vector field and the structure Jacobi operator with respect to the structure vector 𝜉, respectively. Suppose that the third fundamental form t satisfies dt(X, Y) = 2𝜃g(𝜙X, Y) for a scalar 𝜃(< 2c) and any vector fields X and Y on M. In this paper, we prove that if it satisfies R_𝜉A = AR_𝜉 and at the same time ∇_𝜉R_𝜉 = 0 on M, then M is a Hopf hypersurface of type (A) provided that the scalar curvature s of M holds s - 2(n - 1)c ≤ 0.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.620-626
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• 1988

GaAs solar cells may be the most attractive and efficient power source of a satellite. GaAs is more radiation tolerant and less temperature sensitive than widely used silicon. $Al_{x}$ Ga$_{1-x}$ As/GaAs solar cells have been designed and fabricated by Liquid Phase Epitaxial method. GaAs solar cells, of which structure is about 0.2 .mu.m p$^{+}$ - window layer, 0.6-1.O .mu.m Ge-doped p-layer. 3.mu.m n-GaAs layer and n$^{+}$ - buffer layer, have been characterized as a function of operating temperature from 25 .deg.C to 130 .deg.C. Open circuit voltage decreases linearly with increasing temperature by 1.4-1.51 mV/ .deg.C while degradation of silicon solar cells is about 2.2-2.5 mV/ .deg.C, short circuit current does not increase much with increasing temperature. Relative efficiency decreases with increasing of temperature by about 0.21-0.29 %/ .deg.C. Efficiency degradation of silicon solar cells with temperature is known to be about 0.5%/ .deg.C and our results show GaAs solar cells may be an excellent candidate for concentrated solar cells.ells.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.5
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• pp.31-36
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• 1983

The indirect M.R.A.C. method using the W.L.S. algorithm is applied to the speed control of a D.C. motor on the assumption that the motor is the 1-st order, completely controllable and observable, non-minimum phase plant. By the help of M6809 microprocessor system the experiments are performed with respect to the sinusoidal and square reference input. The results show that the speed of a D.C. motor is well controlled by the indirect M.R.A.C. method using W.L.S, algorithm, and that the W.L.S. algorithm is quite suitable to the time-varying plant.

• Communications of the Korean Mathematical Society
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• v.9 no.4
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• pp.831-836
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• 1994

In this paper we characterize the quasiaffine transforms of quasisubscalar operators. Let H and K be separable, complex Hilbert spaces and L(H,K) denote the space of all linear, bounded operators from H to K. If H = K, we write L(H) in place of L(H,K). A linear bounded operators S on H is called scalar of order m if there is a continuous unital morphism of topological algebras $$ \Phi : C^m_0(C) \to L(H) $$ such that $\Phi(z) = S$, where as usual z stands for identity function on C, and $C^m_0(C)$ stands for the space of compactly supproted functions on C, continuously differentiable of order m, $0 \leq m \leq \infty$.

• Journal of the Korean Wood Science and Technology
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• v.9 no.3
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• pp.24-30
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• 1981

This experiment was carried out to determine the drying time from green to oven dry and estimate the moisture content of wood, such as red lauan (Shorea Spp.), Douglas fir (Pseudotsuga menziesii), Birch (Betula platyphylla), and oak (Quercus aliena), at various thickness, paralleled to fiber, of specimen for M.C. by oven dry method (100-105$^{\circ}C$). The results obtained are summarized as follows: 1. The drying time from green to oven dry decreases as the thickness of specimen for M.C. becomes to be thined, and that time at 10mm thickness are 14 hrs, for birch wood and 24 hrs, for oak wood. 2. The relative formulae between thickness (X) of specimen for M.C. and drying lime (Y) from 12% to oven dry are showed in Fig. 3. 3. The M.C. based on the weight of specimen for M.C. at t% can be obtained from the formula (2), and the drying time to 1% are shorter than that time to oven dry by approximately three times.