• Journal of Magnetics
• /
• v.18 no.3
• /
• pp.255-259
• /
• 2013

In this paper a new coupling method for efficient and simple analysis of single phase induction motor is presented. The circuit representation of both the stator winding and each conducting rotor loop (composed of rotor bar and end ring segment) is used in conjunction with the distribution of magnetic flux linkage instead of inductance matrix. The flux linkage is calculated using air-gap flux density distributions driven by unit currents in the stator windings and rotor bars. The field distribution of one turn of a coil is calculated by FEM and the result is used to calculate total flux linkage by employing a coordinate transformation. The numerical results give good agreement with prior literature. The method is particularly effective in analyzing the effect of the number of rotor bars.

• Bulletin of the Korean Chemical Society
• /
• v.10 no.4
• /
• pp.335-339
• /
• 1989

Cholesteryl methyl ether$(CH_3OC_{27}H_{45})$ crystallizes in the monoclinic space group $P2_1$with a = 11.740 (8), b = 7.576 (5), c = 15.492 (10)${\AA},\; {\beta}\;= 110.39 (5)^{\circ}$, Z = 2, Dc = 1.03 g/$cm^3$ and Do = 0.96 g/$cm^3$. The intensities were collected on a Nonius CAD-4 diffractometer with Nb-filtered Mo-$K_{\alpha}$ radiation. The structure was solved by direct methods and refined by full matrix least-squares methods. The final R factor was 0.085 for 1479 observed reflections. Compared with other cholesterol derivatives, the cholesteryl ring and tail region of the molecule are normal. The molecular long axes are parallel to the [101] axis and molecules are packed together in a similar way to those in cholesteryl cliloride and bromide.

• Bulletin of the Korean Chemical Society
• /
• v.5 no.4
• /
• pp.158-162
• /
• 1984

The crystal structure of chloramphenicol base, $C_9H_{l2}N_2O_4$, the deacylated base of antibiotic chloramphenicol, has been determined by X-ray diffraction techniques using diffractometer data obtained by the ${\omega}-2{\theta}$ scan technique with CuK${\alpha}$ radiation from a crystal with space group symmetry $P2_12_12_1$ and unit cell parameters a = 22.322(6), b = 7.535(6), c = 5.781(5) ${\AA}$. The structure was solved by direct methods and refined by full-matrix least-squares to a final R = 0.051 for the 573 observed reflections. The overall conformation of the base is quite different from those of the chloramphenicol congeners which are similar despite the presence of many rotatable single bonds. The propane chain in the base is bent with respect to the phenyl ring, while it is extended in the chloramphenicol congeners. There is no intramolecular hydrogen bond between the hydroxyl groups of the propanediol moiety. All of the molecules in the crystal lattice are connected by a three-dimensional hydrogen bonding network.

• Bulletin of the Korean Mathematical Society
• /
• v.60 no.2
• /
• pp.475-484
• /
• 2023

Let R be a commutative ring with identity. In this paper, we characterize the prime submodules of a free R-module F of finite rank with at most n generators, when R is a GCD domain. Also, we show that if R is a Bézout domain, then every prime submodule with n generators is the row space of a prime matrix. Finally, we study the existence of primary decomposition of a submodule of F over a Bézout domain and characterize the minimal primary decomposition of this submodule.

• Kyungpook Mathematical Journal
• /
• v.64 no.2
• /
• pp.197-204
• /
• 2024

Let R = 𝕂[x] be a univariate polynomial ring over an algebraically closed field 𝕂 of characteristic zero. Let A ∈ M_m,m(R) be an m×m matrix over R with non-zero determinate det(A) ∈ R. In this paper, utilizing linear-algebraic techniques, we investigate the relationship between a basis for the syzygy module of f₁, . . . , f_m and a basis for the syzygy module of g₁, . . . , g_m, where [g₁, . . . , g_m] = [f₁, . . . , f_m]A.

• Analytical Science and Technology
• /
• v.24 no.2
• /
• pp.135-141
• /
• 2011

MMPs (Matrix metalloproteinases) are enzymes playing an important role to turnover and remodel main protein compositions of extracellular matrix. MMP-2 and MMP-9 of MMPs having a catalytic domain which is apart from a hemopexin-like domain part, are different from the other MMPs pertaining fibronectinlike domain close to hemopexin-like domain. It was reported that the development of MMP-9 restrainer can prevent the transfer of liver cancer. In this study, MMP-9 restrainers were extracted and purified from Hovenia dulcis Thunberg. The each fractionary part was examined to investigate the inhibitory effect on MMPs. Three compounds, compound A and B eluted with ethyl acetate (EA) and compound C with methanol, were identified by $^1H$ and $^{13}C$ NMR, GC/MS, and FT-IR. Compound A is considered as a kind of catechine type compound having a benzene ring substituted by hydroxyl and methoxyl groups. Compound B and C are nobiletin type compound pertaining a carbonyl group. Compound A, B and C showed 76%, 66% and 71% of inhibition effect on MMP-9 at 1.0% concentration, respectively. Compound A showed the best inhibition effect on MMP-9.

• Journal of the Korean Chemical Society
• /
• v.25 no.6
• /
• pp.343-350
• /
• 1981

The crystal and molecular structure of P-aminobenzaldehyde cyclohexylthiosemicarbazone, C14H20N4S, has been determined from 2712 integrated intensities measured on a computer controlled four circle diffractometer with monochromated $CuK_{\alpha}$, X-ray radiation. The crystals are monoclinic, space group C2/c with eight molecules in a unit cell of dimensions, a = 12.488(2), b = 12.276(4), c = 19.997(6)${\AA}$ and ${\beta}=103.55(3)^{\circ}$. The structure was solved by Patterson and Fourier method and refined by a full-matrix least squares method to a final R value of 0.058 for all reflections. The C(8)-S bond is trans to N(2)-N(3) and C(8)-N(1) is cis to N(2)-N(3) bond. The cyclohexane ring has chair conformation and makes an angle of $40.7^{\circ}$ with the benzene ring. The molecules are linked by N(2)H…S hydrogen bonds into dimer-like units which are held together by $N-H{\ldots}N$ hydrogen bonds. Sulfur accepts second rather weak hydrogen bond from N(4). An intramolecular hydrogen bond exists between N(1) and N(3) atoms.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.9
• /
• pp.2787-2790
• /
• 2014

Quercetin is a major dietary flavonoid found in onions, apples, tea, and red wine, and potentially has beneficial effects on disease prevention. We carried out this study to investigate the effect of quercetin on UVB-induced matrix metalloproteinase-1 (MMP-1) expression in human keratinocyte HaCaT cells and to further understand the mechanisms of its action. The anti-inflammatory activity of quercetin was investigated and quercetin significantly suppressed the NO production in LPS-stimulated RAW264.7 mouse macrophages. Post treatment of quercetin decreased UV irradiation-induced phosphorylation of JNK, p38 MAPK, and ERK by 91%, 21%, and 17%, respectively. MMP-1 is mainly responsible for the degradation of dermal collagen during the aging process of human skin and quercetin suppressed the UVB-induced MMP-1 by 94%. Binding studies revealed that quercetin binds to p38 with high binding affinity ($1.85{\times}10^6M^{-1}$). The binding model showed that the 4'-hydroxy groups of the B-ring of quercetin participated in hydrogen bonding interactions with the side chains of Lys53, Glu71, and Asp168 and the 5-hydroxy group of the A-ring formed a hydrogen bond with the backbone amide of Met109. The major finding of this study shows that quercetin inhibits phosphorylation of JNK, p38 MAPK, and ERK pathway leading to the prevention of MMP-1 expression in human keratinocyte HaCaT cells. Therefore, our findings suggested the potentials of quercetin as a skin anti-photoaging agent.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.3
• /
• pp.301-306
• /
• 2009

In this study a 3-component rotating balance, which is designed to measure the thrust (Fz) and two moment components (Mx, My) simultaneously for a rotor test jig, is designed and its performance is validated experimentally. The low voltage signal from the strain gages mounted on the balance is amplified with a rotating amplifier, which is then fed through a slip-ring unit into the data acquisition system. In order to validate the accuracy of the calibration matrix obtained from a static calibration test, an additional reaction type balance is used to measure the thrust from a model rotor simultaneously, and shows very good result. Finally, the expanded uncertainty value, which is obtained from ISO method is estimated to be $2.82\times10^{-1}$, and the balance turns out to be reliable.

• Bulletin of the Korean Chemical Society
• /
• v.10 no.6
• /
• pp.582-585
• /
• 1989

Two crystal structures of dehydrated $Sr^{2+}\;and\;Tl^+$ exchanged zeolite A, $Sr_xTl_{12-2x}-A$ (x = 1.6 and 5.45), have been determined by single-crystal X-ray diffraction techniques. Their structures were solved and refined in the cubic space group Pm3m at $21(1)^{\circ}C.$ Both crystals were ion exchanged in flowing streams of mixed $Sr(NO_3)_2\;and\;TlNO_3$ aqueous solution, followed by dehydration at $360^{\circ}C\; and\; 2${\times}$10^{-6}$ Torr for 2 days. Full-matrix least-squares refinements of the dehydrated $Sr_{1.6}Tl_{8.8}-A (a = 12.214(2){\AA})\; and\;Sr_{5.45}Tl{1.1}-A (a=12.291(2){\AA})$ have converged to final error indices, $R_1=0.055\; and\;R_2=0.061$ with 286 reflections, and R1 = 0.072 and R2 = 0.090 with 217 reflections, respectively, for which$\;I\;{>}\;3{\sigma}(I)$. In both structures, all Sr(II) ions are coordinated by three framework oxygens; Sr(II) to O(3) distances are $2.21(2){\AA}\;for\;Sr_{1.6}Tl_{8.8}-A \;and\;2.31(1){\AA} \;for\;Sr_{5.45}Tl_{1.1}-A,$and Tl(I) to O(3) distances are $2.657(6){\AA}\;for\;Sr_{1.6}Tl_{8.8}-A\;and\;2.845(8){\AA}\;for\;Sr_{5.45}Tl_{1.1}-A,$ respectively. In each structure, the angle subtended at Sr(II), O(3)-Sr(II)-O(3) is $118.7(4)^{\circ}\;for\; Sr_{1.6}Tl_{8.8}-A \;and\;120.0(4)^{\circ}\;for\;Sr_{5.45}Tl_{1.1}-A.\;Sr^{2+}$ ions prefer to 6-ring sites and $Tl^+$ ions to 8-ring sites when total number of ions per unit cell is more than 8.