• Journal of applied mathematics & informatics
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• v.16 no.1_2
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• pp.453-459
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• 2004

A left-invariant flat Riemannian connection on a Lie group makes its Lie algebra a left symmetric algebra compatible with an inner product. The left symmetric algebra is decomposed into trivial ideal and a subalgebra of e(l). Using this result, the Lie group is embedded isomorphically into the direct product of O(l) $\times$ $R^{k}$ for some nonnegative integers l and k.

• Journal of the Chungcheong Mathematical Society
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• v.13 no.1
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• pp.1-11
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• 2000

The non-commutative torus $A_{\omega}=C^*(\mathbb{Z}^n,{\omega})$ may be realized as the $C^*$-algebra of sections of a locally trivial $C^*$-algebra bundle over $\widehat{S_{\omega}}$ with fibres $C^*(\mathbb{Z}^n/S_{\omega},{\omega}_1)$ for some totally skew multiplier ${\omega}_1$ on $\mathbb{Z}^n/S_{\omega}$. It is shown that $A_{\omega}{\otimes}M_l(\mathbb{C})$ has the trivial bundle structure if and only if $\mathbb{Z}^n/S_{\omega}$ is torsion-free.

• Bulletin of the Korean Chemical Society
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• v.15 no.5
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• pp.379-386
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• 1994

Reactions of 1',2-bis(diphenylphosphino)-l-(N,N-dimethylaminomethyl)ferrocene (FcNPP) with $M(CO)_6$ (M=Cr, Mo, W) in the presence of TMNO (Trimethylamine oxide) in a stoichiometric ratio of 1 : 1.5 : 3.5 produced a series of Gp 6 metal carbonyl derivatives with a variety of coordination modes: M(CO)$_4({\eta}^2$-FcNPP-P,P) (M=Cr, Mo, W), $M(CO)_5({\eta}^1-FcNPP-P) (M=Mo, W)\;,\; M_2(CO)_9({\eta}^1\;,\;{\eta}^2-FcNPP-P,P,N) (M=Cr, Mo)\;,\;M_2(CO)_{10}({\eta}^1\;,\;{\eta}^1-FcNPP-P,P) (M=Cr, Mo, W)\;, and\;W(CO)_4({\eta}^2-FcNPP(O)-P,N)$. All these complexes were characterized by microanalytical and spectroscopic techniques. In one case, the structure of W(CO)$_4({\eta}^2$-FcNPP(O)-P,N) was determined by X-ray crystallography. Crystals are monocinic, space group P$2_{1/C}$, with a=10.147(2), b=19.902(3), c=19.821(4) ${\AA},\;{\beta}=96.88(2)^{\circ},\;V=3974(l){\AA}^3$, Z=4, and $D_{calc}=1.64 g cm^{-3}$. The geometry around the central tungsten metal is a distorted octahedron, with the nitrogen and phosphorus atoms being cis to each other. Some of these complexes exhibited catalytic activities in the allylic oxidation and epoxidation of cholesterly acetate. Other oxidation products were also formed with the different chemical yields and product distribution depending upon the ligand and the central metal.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.537-541
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• 2004

A high efficiency ZVS PWM asymmetrical half bridge converter for a plasma display panel (PDP) sustaining power module is proposed in this paper. To achieve the ZVS of power switches for the wide fond range, n small additional inductor $L_{lkg}$, which also acts as an output filter inductor, is serially inserted to the transformer primary side. Then, to solve the problem related to ringing in the secondary rectifier caused by $L_{lkg}$, the proposed circuit employs a structure without the output filter inductor, which helps the voltages across rectifier diodes to be clamped at the output voltage. Therefore, no dissipative RC (resistor capacitor) snubber for rectifier diodes is needed and n high efficiency as well as low noise output voltage can be realized. In addition, since it has no large output inductor filter, it features a simpler structure, lower cost, less mass, and lighter weight. Moreover, since all energy stored in $L_{lkg}$ is transferred to the output side, the circulating energy problem can be effectively solved. The operational principle, theoretical analysis, and design considerations are presented. To confirm the operation, validity, and features of the proposed circuit, experimental results from a 425W, 385Vdc/170Vdc prototype are presented.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.1
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• pp.63-73
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• 2004

A simple analytical model has been presented for the study of the optical bistability using a $GaAs-Al_{0.32}Ga_{0.68}As$ multiple quantum well (MQW) p-i-n diode structure. The calculation of the optical absorption is based on a semi-emperical model which is accurately valid for a range of wells between 5 and 20 nm and the electric field F< 200kV/cm . The electric field dependent analytical expression for the responsivity is presented. An attempt has been made to derive the analytical relationship between the incident optical power ( $(P_{in})$ ) and the voltage V across the device when the diode is reverse biased by a power supply in series with a load resistor. The relationship between $P_{in}$ and $P_{out}$ (i.e. transmitted optical power) is also presented. Numerical results are presented for a typical case of well size $L_Z=10.5nm,\;barrier\;size\;L_B=9.5nm$ optical wave length l = 851.7nm and electric field F? 100kV/cm. It has been shown that for the values of $P_{in}$ within certain range, the device changes its state in such a way that corresponding to every value of $P_{in}$ , two stable states and one unstable state of V as well as of $P_{out}$ are obtained which shows the optically controlled bistable nature of the device.

• Bulletin of the Korean Chemical Society
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• v.17 no.12
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• pp.1127-1131
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• 1996

[FeⅡ2(N-Et-HPTB)Cl2]BPh4(1), where N-Et-HPTB is the anion of N,N,N',N'-tetrakis(N-ethyl-2-benzimidazolylmethyl)-2-hydroxy-l,3-diaminopropane, has been synthesized to model dioxygen binding to the diferrous centers of proteins. 1 has a singly bridged structure with a μ-alkoxo of N-Et-HPTB and contains two five-coordinate iron(Ⅱ) centers with two chloride ligands as exogenous ligands. 1 exhibits an electronic spectrum with a λmax at 336 nm in acetone. 1 in acetone exhibits no EPR signal at 4 K, indicating diiron(Ⅱ) centers are antiferromagnetically coupled. Exposure of acetone solution of 1 to O2 at -90 ℃ affords an intense blue color intermediate showing a broad band at 586 nm. This absorption maximum of the dioxygen adduct(1/O2) was found in the same region of μ-l,2-peroxo diiron(Ⅲ) intermediates in the related complexes with pendant pyridine or benzimidazole ligand systems. However, this blue intermediate exhibits EPR signals at g = 1.93, 1.76, and 1.59 at 4 K. These g values are characteristic of S = 1/2 system derived from an antiferromagnetically coupled high-spin Fe(Ⅱ)Fe(Ⅲ) units. 1 is the unique example of a (μ-alkoxo)diferrous complex which can bind dioxygen and form a metastable mixed-valence intermediate. At ambient temperature, most of 1/O2 intermediate decays to form a diamagnetic species. It suggests that the dacay reaction of the intermediate might be bimolecular, implying the formation of mixed-valence tetranuclear species in transition state.

• Speech Sciences
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• v.8 no.3
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• pp.15-30
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• 2001

Lateralization, the change of a coronal nasal into a lateral in an l-n sequence, has been considered to be prosodically unrestricted, e.g. an utterance-span rule, in Korean (Han 1993, Park 1990). However, aerodynamic data of the nasal do not corroborate their claims. In the paper, I look at how lateralization can best be characterized. Specifically, I ask whether its domain is best treated via a syntax-based (Nespor & Vogel 1986, Selkirk 1984) or an intonation-based approach (Pierrehumbert 1980, Jun 1993) to prosodic structure. Based on nasal airflow data as a means of monitoring velum activity coincident with a nasal stop in an l-n sequence, combined with pitch tracks to define an accentual phrase, I argue that lateralization is neither an utterance-span rule nor a syntax-based rule. Sentences recorded with a potential environment for lateralization show that lateralization occurs within an accentural phrase but is blocked between accentual phrase boundaries. When intonation-based and syntax-based models disagree about phrase boundaries, lateralization only occurs where the intonation-based model predicts it will. This indicates that lateralization is best defined as an accentual pheonomenon, being sensitive to the accentual phrase. This finding lends further support to an intonation-based model for Korean prosodic structure (Jun 1993).

• Bulletin of the Korean Chemical Society
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• v.15 no.6
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• pp.432-436
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• 1994

Monomeric rhodium and iridium-diaryltetrazene complexes $Cp^*$M(RNN=NNR)($Cp^*$=1,2,3,4,5-pentamethylcyclope ntadienyl; M=Rh, Ir; R=Ph, 4-tolyl) have been synthesized from [$Cp^*MCl_2]_2$(M=Rh, Ir) and 2 equiv. of $[Li(THF)_x]_2(RN_4$R) in benzene. We have determined the crystal structure of (${\eta}^5$-pentamethylcyclopentadienyl)diphenyltetrazene iridium by using graphite-monochromated Mo-$K_a$ radiation. The compound was crystallized in the monoclinic space group $P2_{1/c}$ with a=13.781(3), b=9.035(l), c=17.699(3) ${\AA}$, and ${\beta}=111.93(l)^{\circ}$. An X-ray crystal structure of complex 1 showed a short N(2)-N(3) distance ($1.265 {\AA}$) consistent with the valence tautomer A with Ir(III) rather than Ir(I). All complexes are highly colored and decompose on irradiation at 254 nm. Electrochemical studies show that complex 1 displays a quasi-reversible reduction.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1244-1248
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• 1998

Ozonolysis reactions of cyclic olefins 1a-c and norbomene In in the presence of trifluoroactophenone 6 provided the corresponding cross-ozonides 7a-c and 7n. Further reactions of ozonides 7a-c and 7n with the independently prepared carbonyl oxide 11 gave diozonides of structure l0a-c and 10n. The ozonolysis of 1methylcyclopentene 12a and 1-methylcyclohexene 12b in the presence of trifluoroactophenone 6 provided exclusively ozonide 15 and 16 derived from capture of carbonyl oxide 13. All of the new ozonides have been isolated as pure substances and characterized by their 1H NMR and 13C NMR spectra.

• Journal of the Korean Chemical Society
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• v.20 no.1
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• pp.19-34
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• 1976

The crystal structure of sodium sulfisoxazole hexahydrate, $C_{11}H_{12}N_3O_3SNa{\cdot}6H_2O$,has been determined by X-ray diffraction method. The compound crystallizes in the monoclinic space group $$P2_1}c$$ with a = 15.68(3), b = 7.70(2), c = 17.94(4)${\AA}$, ${\beta}$ = $118(2)^{\circ}$ and Z = 4. A total of 1717 observed reflections were collected by the Weissenberg method with $CuK{\alpha}$ radiation. Structure was solved by heavy atom method and refined by block-diagonal least-squares methods to the R value of 0.14. The conformational angle formed by the S-C(l) bond with that of N(2)-C(7), when the projection in taken along the S-N(2), is $73^{\circ}.$ The benzene ring is planar and makes an angle of $60^{\circ}$ with the plane of the isoxazole ring, which is also planar. The sodium atom has a distorted octahedral coordination of N(l) and five oxygen atoms from hydrate molecules. Sodium sulfisoxazole hexahydrate shows fourteen different hydrogen bondings in the crystal. These are six $O-H{\cdots}O-H bonds, three $O-H{\cdots}O$ bonds, two $O-N{\cdots}N,$ one $N-H{\cdots}O,O-H{\cdots}N,N-H{\cdots}O-H$ bond, with the distances in the range of 2.71 to $3.04{\AA}.$.