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11.
Norikazu Nakayama Satoru Kijima Satoshi Itoh Toyoharu Ohata Akira Ishibashi Yoshifumi Mori 《Optical Review》1995,2(3):167-170
Green light-emitting diodes (LEDs) were fabricated employing a ZnCdSe/ZnSSe triple quantum-well (TQW) active region surrounded by ZnMgSSe cladding layers grown on an n-type (100) GaAs substrate by molecular beam epitaxy (MBE). A 3.5 mW pure green emission was observed for the surface-emitting LED device at a peak wavelength of 513.3 nm (2.415 eV) with a spectral half-width of 11.7 nm (55 meV) under a 20 mA (4.6 V) direct current at room temperature (25°C). These correspond to an external quantum efficiency of 7.2%, a power conversion efficiency of 3.8%, a luminous current efficiency of 66 lm/A, and a luminous efficiency of 14 lm/W. 相似文献
12.
M.-W. Chu Y. Shingaya T. Nakayama 《Applied Physics A: Materials Science & Processing》2007,86(1):101-106
A combined transmission electron microscopy (TEM) and Raman spectroscopy study has been performed on nanocrystalline Ba0.9Sr0.1TiO3 (BST) crystals and tubes. TEM investigations revealed the existence of 90 deg ferroelastic twins in the materials. Raman spectra showed an obvious shoulder (∼750 cm-1) from the broad band at ∼720 cm-1 that nominally represents the quasimode of E(LO4) and A1(LO3). The intensity of this shoulder increases with the twin population in the nanocrystalline materials, suggesting a correlation between the lattice dynamical characteristics and the long-range ferroelastic strain of the twin wall. The ferroelastic strain is mainly constrained along the c-axis of the BST unit cell, and the effect of this constraint is more pronounced in nanocrystalline materials than in bulks due to a significant wall volume ratio in twinned nano-materials. A1 phonons showing collective ion dynamics along the c-direction could be then hardened by the strain, while E symmetry exhibiting vibrations perpendicular to the c-axis would be less affected. The theoretically predicted giant LO–TO coupling in tetragonal ferroelectric perovskites [18] suggests that the hardening of the softest A1(TO1) mode in A1 symmetry is accompanied by that of the hardest A1(LO3) phonon. Consequently, the shoulder could be ascribed to the ferroelastic strain induced hardening of the quasimode with a considerable contribution from the A1(LO3) phonon. PACS 61.72.Ff; 63.22.+m; 77.80.Bh; 77.80.Dj 相似文献
13.
Hisahiro Nakayama Jiro Kasahara Akiko Matsuo Ikkoh Funaki 《Proceedings of the Combustion Institute》2013,34(2):1939-1947
The propagation of curved detonation waves of gaseous explosives stabilized in rectangular-cross-section curved channels is investigated. Three types of stoichiometric test gases, C2H4 + 3O2, 2H2 + O2, and 2C2H2 + 5O2 + 7Ar, are evaluated. The ratio of the inner radius of the curved channel (ri) to the normal detonation cell width (λ) is an important factor in stabilizing curved detonation waves. The lower boundary of stabilization is around ri/λ = 23, regardless of the test gas. The stabilized curved detonation waves eventually attain a specific curved shape as they propagate through the curved channels. The specific curved shapes of stabilized curved detonation waves are approximately formulated, and the normal detonation velocity (Dn)?curvature (κ) relations are evaluated. The Dn nondimensionalized by the Chapman–Jouguet (CJ) detonation velocity (DCJ) is a function of the κ nondimensionalized by λ. The Dn/DCJ?λκ relation does not depend on the type of test gas. The propagation behavior of the stabilized curved detonation waves is controlled by the Dn/DCJ?λκ relation. Due to this propagation characteristic, the fully-developed, stabilized curved detonation waves propagate through the curved channels while maintaining a specific curved shape with a constant angular velocity. Self-similarity is seen in the front shock shapes of the stabilized curved detonation waves with the same ri/λ, regardless of the curved channel and test gas. 相似文献
14.
15.
We introduce a quantum key distribution protocol using mean multi-kings’ problem. Using this protocol, a sender can share a bit sequence as a secret key with receivers. We consider a relation between information gain by an eavesdropper and disturbance contained in legitimate users’ information. In BB84 protocol, such relation is known as the so-called information disturbance theorem. We focus on a setting that the sender and two receivers try to share bit sequences and the eavesdropper tries to extract information by interacting legitimate users’ systems and an ancilla system. We derive trade-off inequalities between distinguishability of quantum states corresponding to the bit sequence for the eavesdropper and error probability of the bit sequence shared with the legitimate users. Our inequalities show that eavesdropper’s extracting information regarding the secret keys inevitably induces disturbing the states and increasing the error probability. 相似文献
16.
K. Tshoo Y. Satou H. Bhang S. Choi T. Nakamura S. Deguchi Y. Kawada Y. Kondo N. Kobayashi Y. Nakayama K. N. Tanaka N. Tanaka N. Aoi M. Ishihara T. Motobayashi H. Otsu H. Sakurai S. Takeuchi Y. Togano K. Yoneda Z. H. Li F. Delaunay J. Gibelin F. M. Marques N. A. Orr T. Honda M. Matsushita T. Kobayashi Y. Miyashita T. Sumikama K. Yoshinaga S. Shimoura D. Sohler T. Zheng Z.X. Cao 《Few-Body Systems》2013,54(1-4):459-463
The unbound excited states of the most neutron-rich dripline oxygen isotope, 24O, have been investigated by using the 24O(p,p′)24O* reaction at the beam energy of 62 MeV/nucleon in inverse kinematics. The first and second unbound excited states of 24O have been observed at ${E_{\rm x}= 4.63_{-0.14}^{+0.30}}$ MeV and ${E_{\rm x}= 5.13_{-0.24}^{+0.19}}$ MeV (preliminary) along with the evidence for another higher lying state at around 7.3 MeV. The quadrupole deformation parameter ${\beta_{2^+}}$ was deduced to be ${0.15_{-0.03}^{+0.08}}$ (preliminary) for the first time. The systematics of the ${\beta_{2^+}}$ and the ${E_{\rm x}(2_1^+)}$ in the Z = 8 isotopes shows the N = 16 spherical shell closure in 24O. 相似文献
17.
18.
Takanari Yasui Takeshi Ohtsuka Tetsu Suzuki Shigeki Okajima Kazuya Nakayama Mitsuru Tomioka Katsuhiro Kamimura Takeo Namekata Hiroaki Minamide Hiromasa Ito 《International Journal of Infrared and Millimeter Waves》2006,27(2):199-210
A new, wide-band, high-speed and high-sensitivity THz detector has been developed. The prototype detector consists of a parabolic
cylindrical mirror, a long wire antenna and a Schottky barrier diode. Direct detection measurements have shown a stable sensitivity
of 150 ± 50 V/W for 1–2 THz without any adjustments. The long wire antenna was fixed at the focus of parabolic cylindrical
mirror then it has been realized less operation steps, easy coupling to the external THz signals and a dramatic enhancement
in the practicality of this system. The optically polished mirror and frosted surface one showed comparable sensitivities,
thus easy polishing and less cost mirror fabrication can be applied for this system. The radiation pattern showed a maximum
radiation angle of approximately 23° with its dominant main lobe, which was attributed to the wire antenna character and confirmed
good agreements with classical antenna theory. 相似文献
19.
Takeo MoroiKazunori Nakayama 《Physics letters. [Part B]》2011,703(2):160-166
Thermal inflation is an attractive solution to the cosmological moduli problem. However, domain walls may be formed after thermal inflation and some mechanisms are needed to eliminate the domain wall before it dominates the Universe. We point out that gravitational waves produced by the dynamics of domain walls may be observed by the pulsar timing experiments and future space-borne gravitational wave detectors, which provides a probe into the period of thermal inflation. We also show that the QCD instanton effect can effectively eliminate the domain walls with producing observable amount of gravitational waves. 相似文献
20.