• Journal of the Korean Society of Radiology
• /
• v.2 no.2
• /
• pp.5-10
• /
• 2008

Most of the diagnostic medical radiography are rapidly replaced by digital imaging systems recently. Although with the current transition of analog to digital most of the exposure conditions and parameters are still on the basis of film-screen analog system. Moreover the evaluation of acquired digital radiographic image is not fulfilled normally because of the difficulties in handling the digital raw data. The user friendly windows program for the evaluations of digital radiographic image was developed on the MatLab platform. The program has functions for the calculation of the contrast profile, NPS(noise power spectrum), MTF(modulation transfer function), and NEQ(noise equivalent quanta).

• Journal of the Korean Chemical Society
• /
• v.30 no.2
• /
• pp.195-200
• /
• 1986

MO studies have been carried out on 1,5-hydrogen shifts between tautomeric forms (6${\pi}$ system) of ${\beta}$-diketones, ${\beta}$-thioxoketones and ${\beta}$-dithioketones by determining transition state and analyzing structural stability effects on the activation barriers using MNDO method. The barrier was found to increase with the stability of the ground state having greater charge separation and with the increase (less stabilization) in the one electron energy ${\Delta}(2\sum\limits^{occ}{\varepsilon}i)^{\neq}$ in the activation process.

• Journal of the Korean Chemical Society
• /
• v.33 no.6
• /
• pp.582-587
• /
• 1989

Rates for aquation of $[Cr(NH_3)_5(DMF)]^{3+}$ ion in aqueous acidic solution have been measured by spectrophotometric method at various temperatures and pressures. The volume of activation for the aquation is small negative and lies in the limited range -2.76 ∼ -3.65 $cm^3mol^{-1}$. The entropy and compressibility coefficient of activation are small negative values. From the results of thermodynamic activation parameters, it can be inferred that the aquation of $[Cr(NH_3)_5(DMF)]^{3+}$ ion proceeds through an associative interchange($I_a$) mechanism.

• Bulletin of the Korean Chemical Society
• /
• v.9 no.1
• /
• pp.1-4
• /
• 1988

Rates of solvolysis of trans-[Co$(N-eten)_2Cl_2$]$^+$ have been investigated using spectrophotometric method at various pressures and temperatures in the mixtures of water with the t-butyl alcohol which possesses a high structure inducing capacity in water. The values of ${\Delta}V^{\neq}$ obtained from pressure effect on the rate constants were 2.55∼ 5.83 $cm^3mol^{-1}$. These values were discussed in terms of dissociative mechanism. Extrema found in the variation of ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$ with solvent composition correlated with extrema in the variation of the physical properties of the mixtures. The logarithms of rate constants correlated linearly with both Grunwald-Winstein parameter and the reciprocal of dielectric constant ($Ds^{-1}$). The gradient, m of Grunwald-Winstein plot for the trans-[Co$(N-eten)_2Cl_2$]$^+$ was 0.09, which is significantly lower than those for the other cobalt (Ⅲ)-dichloro complexes. It was suggested that the reaction is an Id mechanism with long extension of Co-Cl bond in the transition state, as found for the C-Cl bond in the transition state for the solvolysis of t-butyl chloride.

• Journal of the Korean Chemical Society
• /
• v.20 no.3
• /
• pp.173-184
• /
• 1976

A steel capillary viscometer was built for the study of rheological properties of greases. Bentone greases with thickener concentration of 2.0, 4.0, 6.0, 8.0, and 10.0 weight percent and lime-soap greases with soap concentrations of 2.4, 7.0, 9.3, 12.1 and 15.2 weight percent were studied. Capillaries with various radii R and lengths L were used to study the resident-time effect on the flow properties of lime soap greases. Detailed studies on bentone greases were conducted using a capillary with a fixed size. The results were analyzed by using Ree-Eyring flow equation. The factors appearing in the latter, ($X_1{\beta}_1/{\alpha}_1$ for Newtonian units, $X_2/{\alpha}_2$ and ${\beta}_2$ both for non-Newtonian units), were studied in order to investigate how they change with thickener concentrations and temperatures. Through this analysis, we have found that TEX>${\Delta}H_1^{\neq}$ and ${\Delta}H_2^{\neq}$, the activation enthalpies for flow of type-1 unit and of type-2 unit, respectively, are approximately equal to that of the base oil, the solvent. From this fact, it is concluded that these type units flow into the holes which were produced by the movement of solvent molecules. For bentone greases, the ${\beta}_2$ is about constant independent of concentration at a given temperature as found in the literature. The resident-time effect has not been clearly demonstrated in this research; this is due partly to the nature of the greases used in our research and partly to the small values of L/R of our capillaries, the resident time being proportional to the value L/R.

• Bulletin of the Korean Chemical Society
• /
• v.2 no.3
• /
• pp.96-104
• /
• 1981

(1) The flow data of f (stress) and ${\dot{s}$ (strain rate) for Fe and Ti alloys were plotted in the form of f vs. -ln ${\dot{s}$ by using the literature values. (2) The plot showed two distinct patterns A and B; Pattern A is a straight line with a negative slope, and Pattern B is a curve of concave upward. (3) According to Kim and Ree's generalized theory of plastic deformation, pattern A & B belong to Case 1 and 2, respectively; in Case 1, only one kind of flow units acts in the deformation, and in Case 2, two kinds flow units act, and stress is expressed by $f={X_1f_1}+{X_2f_2}$where $f_1\;and\;f_2$ are the stresses acting on the flow units of kind 1 and 2, respectively, and $X_1,\;X_2$ are the fractions of the surface area occupied by the two kinds of flow units; $f_j=(1/{\alpha}_j) sinh^{-1}\;{\beta}_j{{\dot{s}}\;(j=1\;or\;2)$, where $1/{\alpha}_j\;and\;{\beta}_j$ are proportional to the shear modulus and relaxation time, respectively. (4) We found that grain-boundary flow units only act in the deformation of Fe and Ti alloys whereas dislocation flow units do not show any appreciable contribution. (5) The deformations of Fe and Ti alloys belong generally to pattern A (Case 1) and B (Case 2), respectively. (6) By applying the equations, f=$(1/{\alpha}_{g1}) sinh^-1({\beta}_{g1}{\dot{s}}$) and $f=(X_{g1}/{\alpha}_{g1})sinh^{-1}({\beta}_{g1}{\dot{s}})+ (X_{g2}/{\alpha}_{g2})\;shih^{-1}({\beta}_{g2}{\dot{s}})$ to the flow data of Fe and Ti alloys, the parametric values of $x_{gj}/{\alpha}_{gj}\;and\;{\beta}_{gs}(j=1\;or\;2)$ were determined, here the subscript g signifies a grain-boundary flow unit. (7) From the values of ($({\beta}_gj)^{-1}$) at different temperatures, the activation enthalpy ${\Delta}H_{gj}^{\neq}$ of deformation due to flow unit gj was determined, ($({\beta}_gj)^{-1}$) being proportional to , the jumping frequency (the rate constant) of flow unit gj. The ${\Delta}H_{gj}\;^{\neq}$ agreed very well with ${\Delta}H_{gj}\;^{\neq}$ (self-diff) of the element j whose diffusion in the sample is a critical step for the deformation as proposed by Kim-Ree's theory (Refer to Tables 3 and 4). (8) The fact, ${\Delta}H_{gj}\;^{\neq}={\Delta}H_{j}\;^{\neq}$ (self-diff), justifies the Kim-Ree theory and their method for determining activation enthalpies for deformation. (9) A linear relation between ${\beta}^{-1}$ and carbon content [C] in hot-rolled steel was observed, i.e., In ${\beta}^{-1}$ = -50.2 [C] - 40.3. This equation explains very well the experimental facts observed with regard to the deformation of hot-rolled steel..

• Life and Agrochemicals
• /
• s.247
• /
• pp.32-35
• /
• 2009

• Kyungpook Mathematical Journal
• /
• v.56 no.4
• /
• pp.1047-1067
• /
• 2016

In this paper, a new class of diagram algebras which are subalgebras of signed brauer algebras, called the Walled Signed Brauer algebras denoted by ${\overrightarrow{D}}_{r,s}(x)$, where $r,s{\in}{\mathbb{N}}$ and x is an indeterminate are introduced. A presentation of walled signed Brauer algebras in terms of generators and relations is given. The cellularity of a walled signed Brauer algebra is established. Finally, ${\overrightarrow{D}}_{r,s}(x)$, is quasi- hereditary if either the characteristic of a field, say p, p = 0 or p > max(r, s) and either $x {\neq}0$ or x = 0 and $r{\neq}s$.

• Journal of the Korean Mathematical Society
• /
• v.55 no.5
• /
• pp.1031-1043
• /
• 2018

Let R be a commutative ring with $1{\neq}0$, I a proper ideal of R, and m and n positive integers. In this paper, we define I to be a weakly (m, n)-closed ideal if $0{\neq}x^m\;{\in}I$ for $x{\in}R$ implies $x^n{\in}I$, and R to be an (m, n)-von Neumann regular ring if for every $x{\in}R$, there is an $r{\in}R$ such that $x^mr=x^n$. A number of results concerning weakly(m, n)-closed ideals and (m, n)-von Neumann regular rings are given.

• Bulletin of the Korean Mathematical Society
• /
• v.53 no.1
• /
• pp.21-28
• /
• 2016

It is known that no two of the roots of the polynomial equation (1) $$\prod\limits_{l=1}^{n}(x-r_l)+\prod\limits_{l=1}^{n}(x+r_l)=0$$, where 0 < $r_1{\leq}r_2{\leq}{\cdots}{\leq}r_n$, can be equal and all of its roots lie on the imaginary axis. In this paper we show that for 0 < h < $r_k$, the roots of $$(x-r_k+h)\prod\limits_{{l=1}\\{l{\neq}k}}^{n}(x-r_l)+(x+r_k-h)\prod\limits_{{l=1}\\{l{\neq}k}}^{n}(x+r_l)=0$$ and the roots of (1) in the upper half-plane lie alternatively on the imaginary axis.