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Pulse excitation method for measurement of high frequency magnetic properties of large cores (abstract) : 37th Annual conference on magnetism and magnetic materials (1993)

Hikosaka, Tomoyuki ; Miyamoto, Masahiro ; Yamada, Mamoru ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 73 (1993), S. 6875-6875

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: It is very important to obtain saturated magnetic properties from reverse saturation (full B-H curve) of ferromagnetic cores to design magnetic switches which are used in high power pulse generators. The magnetic switch is excited in the high frequency range (∼MHz). But, it is extremely difficult to measure full B-H curve of large toroidal cores of which diameter is some hundreds of mm, using the conventional ac excitation method at high frequency. The main reason is poor output ability of power source for core excitation. Therefore we have developed pulse excitation method to get high frequency magnetic properties. The measurement circuit has two sections. One is excitation part composed by charge transfer circuit. The others is reset part for adjustment initial point on direct B-H curve. The sample core is excited by sinusoidal voltage pulse expressed as 1−cos(2π ft). Excitation frequency f is decided by the constants of the elements of the charge transfer circuit. The change of magnetic flux density ΔB and magnetic field H are calculated, respectively, by measuring the induced voltage of search coil and magnetizing current. ΔB-H characteristics from reverse saturation of four different kinds of large cores were measured in frequency range from 50 kHz to 1 MHz. Core loss increases in proportion to Nth powers of the frequency, where the index N depends on each of cores. N is about 0.5 in case of winding ribbon cores, such as Fe-based amorphous, Co-based amorphous, and Finemet, but N is about 0.2 in case of the Ni-Zn ferrite.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.352468

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Digitale Medien

Synthesis and properties of aromatic polyimides derived from 2,7-triptycenediamine (1996)

Akutsu, Fumihiko ; Saito, Go ; Miyamoto, Masahiro ; [weitere]

Weinheim : Wiley-Blackwell

Macromolecular Chemistry and Physics 197 (1996), S. 2239-2245

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ISSN: 1022-1352

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Novel aromatic polyimides were synthesized from 9,10-dihydro-9,10-o-benzenoanthracene-1,5-diamine (2,7-triptycenediamine) and aromatic tetracarboxylic dianhydrides. The polymerization was carried out in a two-step procedure including ring-opening poly-addition giving polyamic acids, followed by thermal cyclodehydration. The polyamic acids have high inherent viscosities (0.97-1.95 dL/g in 1-methyl-2-pyrrolidone). The polyimides show high glass transition temperatures (392-409°C), high decomposition temperatures at 5% weight loss (516-566°C), and high weight residues (64-69% at 800°C). All polyimides are amorphous. The polyimide from the diamine with 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride (4,4′-sulfonyldiphthalic anhydride) is soluble in pyridine, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide and conc. sulfuric acid at 60°C, and shows high thermal stability. The introduction of 2,7-triptycenediyl structure into the polyimide backbone has the effect of improving the solubility and maintaining the high thermal stability.

Zusätzliches Material: 3 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/macp.1996.021970715

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Digitale Medien

Construction of α-phosphonolactams via rhodium (II)-catalyzed intramolecular C—H insertion reactionsDedicated to Prof. Shigeru Oae on the occasion of his seventy-fifth birthday. (1995)

Okada, Yoshiharu ; Minami, Toru ; Miyamoto, Masahiro ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Heteroatom Chemistry 6 (1995), S. 195-210

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ISSN: 1042-7163

Schlagwort(e): Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The Rh(II)-catalyzed intramolecular C—H insertion reactions of N,N-dialkyl-α-diazo-α-(diethylphosphono)acetamides 2a,f-j in CHCl3 or ClCH2CH2Cl were found to give monocyclic and bicyclic α-phosphono-β-lactams, 3a and 3f-j, in 43-67% yields via regiospecific α-C—H insertion of the N-alkyl groups. Similar treatment of N-benzyl-N-isopropyl-α-diazo-α-(diethylphosphono)acetamide (2b) and the corresponding N-isobutyl-N-methylacetamide 2d in ClCH2CH2Cl afforded mixtures of β-lactams 3b (35%) and and 3b′ (16%), β-lactam 3d (47%), and γ-lactam 4d (10%), respectively, each of which is formed by the competitive C—H insertion reaction between benzylic and isopropyl α-C—H bonds and between methyl α-C—H and methine β-C—H bonds, respectively. For the formation of β-lactams, the selectivity in the rhodium-mediated C—H insertion in ClCH2CH2Cl follows the order methyl 〉 methine 〉 benzylic α-C—H bond on N-substituents. The N,N-dibutyl-α-diazo homologue 2c and Nα[α-diazo-α-(diethylphosphono)acetyl]-2-methylindoline (2k) exclusively produced γ-lactams 4c (67%) and 4k (81%) via insertion into the methylene β-C—H and methyl β-C—H bonds. tert-Butyl N-[α-diazo-α-(dibenzylphosphono)acetyl]-piperidine-2-carboxylate (2m) on similar treatment, followed by deprotection of the benzyl ester afforded the 7-phosphono carbacepham 6 in 32% overall yield. Similar Rh(II)-catalyzed cyclization of N-methyl-N[4-benzyloxy-α-(diethylphosphono)-phenyl(diethyl-phosphono)methyl]-α-diazo-acetamide (2n) led to 1-[4′-benzylphenyl(diethylphosphono)methyl] -3-(diethyl-phosphono)azetidin-2-one (3n) in 78% yicld. The phosphono group at C-7 of 3f was converted into the acetylamino group via a four-step reaction. Application of chiral rhodium(II) carboxylates 12a-c to the insertion reactions of 2b,c produced α-phosphono-β-and γ-lactams, 3b and 4c, in 6-24% ee and 25-29% ee, respectively.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hc.520060304

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