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排序方式: 共有151条查询结果,搜索用时 156 毫秒
1.
Takeshi Nishii Fumiaki Miyamae Makoto Yoshizuka Hiroto Kaku Mitsuyo Horikawa Makoto Inai Tetsuto Tsunoda 《Tetrahedron: Asymmetry》2012,23(10):739-741
Excess lithium hexamethyldisilazide (LHMDS) with LiCl prompted the asymmetric aza-Claisen rearrangement of carboxamide and retarded the decomposition of its amide enolate. The addition of these two reagents was a key step that led to the total synthesis of (+)-α-cuparenone with a stereogenic quaternary center. 相似文献
2.
Susumu Kuwamura Yuuki Yoshinoya Noriaki Miura Fumiaki Tsumuraya Makoto Sakamoto Naoshi Baba 《Optical Review》2011,18(1):19-26
A bispectral method for astronomical speckle imaging utilizes an average speckle bispectrum of an object to derive its Fourier
phase. There has been, however, a problem in conventional bispectral algorithm owing to difficulty in processing bispectral
data in a four-dimensional (4D) space. In this paper, we propose an implementation to overcome this problem, where a one-dimensional
(1D) object projection is reconstructed from a two-dimensional (2D) average bispectrum of speckle projections, and object
projections so obtained at various angles are then tomographically combined into a 2D object image. In this tomographic approach,
processes are separable into those for individual projection angles, implying that bispectral data required to be stored at
a time are from 4D to 2D and computation time can be substantially reduced by parallelizing angle-by-angle processes. We have
performed experiments using simulated and observed data, and have demonstrated the feasibility of the present approach with
an achievable accuracy comparable to that of a conventional approach. 相似文献
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6.
Masashi?BanEmail author Sachiko?Kitajima Fumiaki?Shibata 《International Journal of Theoretical Physics》2012,51(8):2419-2426
The time-evolution of the trace distance between two qubit states in the presence of an initial correlation with an environment is investigated by means of the exactly solvable model of qubit and environmental system, where there is at most one excitation in the whole system, It is found that the trace distance can exceed its initial value during the time-evolution under certain conditions if the qubit is initially entangled with the environment. Furthermore the Bures distance between two qubit states is investigated. It is seen that the time-evolution of the Bures distance is quite different from that of the trace distance. 相似文献
7.
Fumiaki Ishii Toshio Ohga Akihiro Tsutsumi Hiroji Ohigashi 《Journal of Polymer Science.Polymer Physics》2002,40(10):1026-1037
The heterogeneous higher order structure and molecular motion in a single crystalline film of a vinylidene fluoride (VDF) and trifluoroethylene (TrFE) copolymer with 73 mol % VDF was investigated with the 1H–13C cross‐polarization/magic‐angle spinning NMR technique. A transient oscillation was observed in plots of the 13C peak intensity versus the contact time for the CH2, CHF, and CF2 groups. On the basis of the extended cross‐relaxation theory of spin diffusion, we determined that the oscillation behavior was caused by the TrFE‐rich segments in the chain and that the crystal consisted of VDF‐rich and TrFE‐rich domains. The former had TrFE‐rich segments in VDF and TrFE fractions of 0.24 and 0.27, respectively, and the latter had VDF‐rich segments in a VDF fraction of 0.49. The spin–lattice relaxation time T1ρH in the rotating frame for each group was minimal in the three temperature regions of β, αb, and αc (↑) on heating and in the two temperature regions of α1D and αc (↓) on cooling. The αc (↑) and αc (↓) processes depended on the first‐order ferroelectric phase‐transition regions on heating and cooling, respectively. The motional modes for the other processes were confirmed by the T1ρH minimum behavior of the VDF and TrFE groups in the TrFE‐rich domain and the VDF‐rich segments in the VDF‐rich domain. The β and αb processes were attributed to the flip–flop motion of the TrFE‐rich segments and the competitive motion of the TrFE‐ and VDF‐rich segments in the ferroelectric phase, respectively. The α1D process was due to the one‐dimensional diffusion motion of the conformational defects along the chain in the paraelectric phase, accompanied by the trans and gauche transformation of the VDF conformers of ttg+tg? and g+tg?tt. The effect of the competitive motion of the TrFE‐rich segment on the thermal stability of the VDF‐rich segment in the chain near the Curie temperature was examined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1026–1037, 2002 相似文献
8.
The first total synthesis of a cyclic depsipeptide possessing the 3-amino-6-hydroxy-2-piperidone (Ahp) unit was successfully achieved in a convergent manner by the oxidative construction of the Ahp unit at the later stage of the synthesis. This synthetic work provides data indicating that the structure of the target Ahp-depsipeptide, micropeptin T-20, should be re-examined. 相似文献
9.
Direct numerical simulations with a C3-chemistry model have been performed to investigate the transient behavior and internal structure of flames propagating in an axisymmetric fuel jet of methane, ethane, ethylene, acetylene, or propane in normal earth gravity (1g) and zero gravity (0g). The fuel issued from a 3-mm-i.d. tube into quasi-quiescent air for a fixed mixing time of 0.3 s before it was ignited along the centerline where the fuel–air mixture was at stoichiometry. The edge of the flame formed a vigorously burning peak reactivity spot, i.e., reaction kernel, and propagated through a flammable mixture layer, leaving behind a trailing diffusion flame. The reaction kernel broadened laterally across the flammable mixture layer and possessed characteristics of premixed flames in the direction of propagation and unique flame structure in the transverse direction. The reaction kernel grew wings on both fuel and air sides to form a triple-flame-like structure, particularly for ethylene and acetylene, whereas for alkanes, the fuel-rich wing tended to merge with the main diffusion flame zone, particularly methane. The topology of edge diffusion flames depend on the properties of fuels, particularly the rich flammability limit, and the mechanistic oxidation pathways. The transit velocity of edge diffusion flames, determined from a time series of calculated temperature field, equaled to the measured laminar flame speed of the stoichiometric fuel–air mixtures, available in the literature, independent of the gravity level. 相似文献
10.
A regularly preemptive model D,MAP/D
1,D
2/1 is studied. Priority customers have constant inter-arrival times and constant service times. On the other hand, ordinary customers' arrivals follow a Markovian Arrival Process (MAP) with constant service times. Although this model can be formulated by using the piecewise Markov process, there remain some difficult problems on numerical calculations. In order to solve these problems, a novel approximation model MAP/MR/1 with Markov renewal services is proposed. These two queueing processes become different due to the existence of idle periods. Thus, a MAP/MR/1 queue with a general boundary condition is introduced. It is a model with the exceptional first service in each busy period. In particular, two special models are studied: one is a warm-up queue and the other is a cool-down queue. It can be proved that the waiting time of ordinary customers for the regular preemption model is stochastically smaller than the waiting time of the former model. On the other hand, it is stochastically larger than the waiting time of the latter model. 相似文献