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91.
Ryuya Yokoo Keisuke Goto Jiro Kasahara Venkat Athmanathan James Braun Guillermo Paniagua Terrence R. Meyer Akira Kawasaki Ken Matsuoka Akiko Matsuo Ikkoh Funaki 《Proceedings of the Combustion Institute》2021,38(3):3759-3768
The internal flow structures of detonation wave were experimentally analyzed in an optically accessible hollow rotating detonation combustor with multiple chamber lengths. The cylindrical RDC has a glass chamber wall, 20 mm in diameter, which allowed us to capture the combustion self-luminescence. A chamber 70 mm in length was first tested using C2H4O2 and H2–O2 as propellants. Images with a strong self-luminescence region near the bottom were obtained, confirming the small extent of the region where most of the heat release occurs as found in our previous research. Based on the visualization experiments, we tested RDCs with shorter chamber walls of 40 and 20 mm. The detonation wave was also observed in the shorter chambers, and its velocity was not affected by the difference in chamber length. Thrust performance was also maintained compared to the longer chamber, and the short cylindrical RDC had the same specific impulse tendency as the cylindrical (hollow) or annular 70-mm chamber RDC. Finally, we calculated the pressure distributions of various chamber lengths, and found they were also consistent with the measured pressure at the bottom and exit. We concluded that the short-chamber cylindrical RDC with equal length and diameter maintained thrust performance similar to the longer annular RDC, further expanding the potential of compact RDCs. 相似文献
92.
We derive the low energy effective action for the dilatonic braneworld. In the case of the single-brane model, we find the effective theory is described by the Einstein-scalar theory coupled to the dark radiation. Remarkably, the dark radiation is not conserved in general due to a coupling to the bulk scalar field. The effective action incorporating Kaluza-Klein (KK) corrections is obtained and the role of the AdS/CFT correspondence in the dilatonic braneworld is revealed. In particular, it is shown that CFT matter would not be confined to the braneworld in the presence of the bulk scalar field. The relation between our analysis and the geometrical projection method is also clarified. In the case of the two-brane model, the effective theory reduces to a scalar-tensor theory with a non-trivial coupling between the radion and the bulk scalar field. 相似文献
93.
Yoshikazu Shizuri Jiro Ohtsuka Seiji Kosemura Yukimasa Terada Shosuke Yamamura 《Tetrahedron letters》1984,25(48):5547-5550
Some macrocyclic diterpenes derived from euphohelioscopin A and euphornin have been stereoselectively converted into the jatropholane- and daphnane-type compounds and the known tricyclic compound which has been treated with phCOCl - pyridine to afford euphohelionone, the new type of diterpene isolated from euphorbia helioscopia L. 相似文献
94.
95.
96.
The electrical conductivities of hydrochloric acid and potassium chloride in water have been measured in the concentration range of 3×10
–4
–10
–3
moles-dm
–3
at 0°C up to 3500 bar. The limiting molar conductance (0) for HCl increases with increasing pressure, while 0(KCl) has a maximum around 1700 bar. The excess conductance of hydrogen ion [
0
E
=0(HCl)–0(KCl)] increases with increasing pressure. Its pressure dependence indicates that the reorientation of water molecules, which is the rate-determining step in the proton jump, becomes faster at higher pressure. This anomaly is attributed to the distortion with pressure of the hydrogen bonds in water. 相似文献
97.
Electrical conductivity measurements of Th3P4-type EuLn2S4 (Ln = LaGd) compounds have been made as functions of temperature and sulfur vapor pressure. These compounds are all p-type semiconductors, and their conductivities at room temperature have almost the same values for the specimens from EuLa2S4 to EuNd2S4 but increase on going from EnNd2S4 to EuGd2S4. In addition, the conductivity of EuGd2S4 is sensitive to sulfur vapor pressure and obeys the relationship . The mechanism of electrical transport in these compounds is discussed. 相似文献
98.
A new family of pi-conjugated delocalized biradical compound is developed. The solution of 1,4-bis(2,5-diphenylimidazol-4-ylidene)cyclohexa-2,5-diene shows the ESR signal consisting of a moderately broad unresolved line, Delta H(pp) approximately 1 mT, at room temperature. The presence of the thermal equilibrium between a triplet biradical state and a singlet state is confirmed by the ESR measurements, and the spin concentration is determined as 7.90 x 10(21) spin/mol at 300 K. The spin concentration can also be controlled by modifying the molecular planarity. Moreover, the unrestricted DFT/B3LYP calculations suggest the biradical character of the singlet ground state, and the modulation of the energy gap between the singlet state and the triplet state is investigated from the theoretical point of view. Controlling the equilibrium between a diamagnetic state and a paramagnetic state will provide significant progress in the field of biradical chemistry, and the materials with the biradical character in a ground state will lead to a novel development of molecular-based organic magnets. 相似文献
99.
Preparation of new solid solutions containing divalent europium have been tried in the systems Eu2Nb2O7Sr2Nb2O7 and Eu2Ta2O7Sr2Ta2O7. These solid solutions described as Eu2xSr2(1?x)M2O7 (M = Nb and Ta) exist in a pure orthorhombic phase in a limited region of x from 0 to about 0.5. The compounds with compositions close to Eu2M2O7 exist but techniques have not been found to prepare them in pure form. 相似文献
100.
A simple synthetic method for macrocyclic ketones based on intramolecular alkylation of carbanion, generated from protected cyanohydrin is reported. Subsequent mild treatment with acid and base of the cyclized products leads to macrocyclic ketones in high yields. The reaction is rapid and irreversible, and hence required short reaction time. The method was successfully applied to the syntheses of cyclohexadecanone and trans-2-cyclopentadecenone as a precursor of (±)-muscone and exaltone. 相似文献