• Korean Journal of Mathematics
• /
• v.25 no.2
• /
• pp.215-227
• /
• 2017

Let D be an integral domain with quotient field K, X be an indeterminate over D, K[X] be the polynomial ring over K, and $R=\{f{\in}K[X]{\mid}f(0){\in}D\}$; so R is a subring of K[X] containing D[X]. For $f=a_0+a_1X+{\cdots}+a_nX^n{\in}R$, let C(f) be the ideal of R generated by $a_0$, $a_1X$, ${\ldots}$, $a_nX^n$ and $N(H)=\{g{\in}R{\mid}C(g)_{\upsilon}=R\}$. In this paper, we study two rings $R_{N(H)}$ and $Kr(R,{\upsilon})=\{{\frac{f}{g}}{\mid}f,g{\in}R,\;g{\neq}0,{\text{ and }}C(f){\subseteq}C(g)_{\upsilon}\}$. We then use these two rings to give some examples which show that the results of [4] are the best generalizations of Nagata rings and Kronecker function rings to graded integral domains.

• Bulletin of the Korean Mathematical Society
• /
• v.42 no.4
• /
• pp.807-815
• /
• 2005

Let R be a ring with identity, X the set of all nonzero, nonunits of Rand G the group of all units of R. We will consider two group actions on X by G, the regular action and the conjugate action. In this paper, by investigating two group actions we can have some results as follows: First, if G is a finitely generated abelian group, then the orbit O(x) under the regular action on X by G is finite for all nilpotents x $\in$ X. Secondly, if F is a field in which 2 is a unit and F $\backslash\;\{0\}$ is a finitley generated abelian group, then F is finite. Finally, if G in a unit-regular ring R is a torsion group and 2 is a unit in R, then the conjugate action on X by G is trivial if and only if G is abelian if and only if R is commutative.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.312-315
• /
• 2008

The flow structure behind circular and elliptical type rings embedded in a cross-flow was investigated experimentally using two-frame particle image velocimetry (PIV). The experiments were performed in a circulating water channel with a test section of 0.35m height ${\times}$ 0.3m width ${\times}$ 1.1m length. PIV measurements were carried out with varying the Reynolds number in the range of 4.5 ${\times}$ $10^2$ - 4.5 ${\times}$ $10^3$. In the present study, turbulent flow structures in the stream-wise direction and span-wise direction were investigated. The mean velocity field distribution was obtained by statistical-averaging instantaneous velocity fields. The spatial distributions of turbulent statistics such as turbulent intensities and turbulent kinetic energy were also investigated.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.12 no.3
• /
• pp.370-377
• /
• 2001

This paper proposed an eccentric annular ring microstrip antenna which has an asymmetric slot and a tuning stub for improving bandwidth and size of the circular microstrip patch antenna. The field characteristics of the eccentric annular ring microstrip antenna have been calculated by using the method of FDTD (finite difference time domain). The calculated results showed good agreement with the measured results. As a result of measurement, the antenna size and the bandwidth has been improved to that of 12.2 % and 4.8 % respectively, comparing to circular microstrip patch antenna.

• Korean Journal of Veterinary Research
• /
• v.9 no.2
• /
• pp.55-59
• /
• 1969

For the establishment of simpler and more reliable methods for the diagnosis of Brucellosis, diagnostic antigen for Milk Ring Test (M.R.T.) was prepared according to working document recommended by Ministry of Agriculture U.S.A., and applied in the field for the test of its's applicability. The results are summarized as follows. 1. Of fifty two dairy cattle ranches in the vicinity of Seoul, five ranges were shown positive reaction to M.R.T. 2. Even though one volume of positive milk was mixed with five to ten volumes of negative milk, the positive reactions were also observed. 3. Antigenicity of the antigen was maintained without deteriolation for 13 months at $5^{\circ}C$ and three months at both $22^{\circ}C$ and $37^{\circ}C$. 4. Three positive cows to M.R.T. were also shown suspective reaction by Serum Agglutination Test.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.81-84
• /
• 2005

We suggest flux quantum-based mechanism for force realization in the sub-pico-Newton range. By controlling the number of flux quantum in a superconducting ring, a force can be created as an integer multiple of a constant force step. For a 50 nm-thick Nb ring with the inner and outer radii of $5{\mu}m\;and\;10{\mu}m$, respectively, the force step is estimated to be 165 fN, assuming the magnetic field gradient of 10 T/m. We also estimated a maximum force limit to be $1\sim2$ pN.

• Bulletin of the Korean Chemical Society
• /
• v.18 no.10
• /
• pp.1076-1082
• /
• 1997

The infrared, Raman, and jet-cooled laser-induced fluorescence excitation spectra of 1,2,3,4-tetrahydronaphthalene have been recorded and analyzed. The observed vibrations have been assigned to understand the conformational behaviors in its electronic ground (S0) and excited (S1) states. Ab initio at the HF/6-31G** level and molecular mechanics (MM3) force field calculations have been carried out to generate the complete normal mode frequencies of the molecule in its S0 state. The vibrational frequencies calculated from the ab initio method show a better agreement with the observed infrared and Raman frequencies than those calculated from the MM3 method. In several cases, the normal mode calculations were very helpful to clarify some ambiguities of previous assignments. In addition, the ring inversion process between two twisted conformers of 1,2,3,4-tetrahydronaphthalene has been reexamined utilizing ab initio calculation. The results show that the ring inversion energy is in the range of 3.7-4.3 kcal/mol which is higher than the previously reported AM1 value of 2.1 kcal/mol.

• Bulletin of the Korean Chemical Society
• /
• v.18 no.6
• /
• pp.657-662
• /
• 1997

Gas-phase phenyl group migration within the protonated ketones has been studied MO theoretically using the AM1 method. The initial state structure shows relatively strong resonance delocalization of positive charge into the nonmigrating (Y) ring, while the ring migration (Z-ring) is nearly complete in the transition state. These results are reflected in the large $p^+_Z$ (<0) and $p^+_$Y (>0) values and in the predominant contribution of resonance (r) over inductive (field, f) effect, r/f ranging from 1.3 ($p^+_r$) to 1.5 ($p^+_z$). The cross-interaction constant $p_{YZ}$ is vanishingly small ($p_{YZ}$=0.03) which is in contrast to the larger magnitudes for benzilic ($p_{YZ}$=-0.48) and azibenzil ($p_{YZ}$=-0.53) rearrangement processes. The relationship found between the extent of resonance contribution in the initial state and the magnitude of $p_{YZ}$ provides strong support for the proportionality between the magnitude of $p_{YZ}$ and the change in the intensity of interaction, ${\Delta}I^{\cdot}_{YZ}$, in the activation process.

• Journal of the Korean Society for Precision Engineering
• /
• v.10 no.2
• /
• pp.40-47
• /
• 1993

To diversify the area of application of UBET to the analysis of ring rolling which produces rings having more complex cross-sectional configuration, an element of triangular cross-section has been introduced and the corresponding kinematically admissible velocity field has been derived while considering the material flow between neighboring elements. The theoretical perdictions in roll torque and profile formation show good agreement with the experiments. The effect of process parameters such as feed rate and taper angle of the roll groove has been discussed.

• Communications of the Korean Mathematical Society
• /
• v.39 no.3
• /
• pp.563-574
• /
• 2024

Given a sequence of point blow-ups of smooth n-dimensional projective varieties Z_i defined over an algebraically closed field $k,\,Z_s\,{\overset{{\pi}_s}{\longrightarrow}}\,Z_{s-1}\,{\overset{{\pi}_{s-1}}{\longrightarrow}}\,{\cdots}\,{\overset{{\pi}_2}{\longrightarrow}}\,Z_1\,{\overset{{\pi}_1}{\longrightarrow}}\,Z_0$, with Z₀ ≅ ℙⁿ, we give two presentations of the Chow ring A^•(Z_s) of its sky. The first one uses the classes of the total transforms of the exceptional components as generators and the second one uses the classes of the strict transforms ones. We prove that the skies of two sequences of point blow-ups of the same length have isomorphic Chow rings. Finally we give a characterization of the final divisors of a sequence of point blow-ups in terms of some relations defined over the Chow group of zero-cycles A₀(Z_s) of its sky.