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951.
952.
953.
Fundamentals of rotating detonations 总被引:17,自引:0,他引:17
A rotating detonation propagating at nearly Chapman–Jouguet velocity is numerically stabilized on a two-dimensional simple
chemistry flow model. Under purely axial injection of a combustible mixture from the head end of a toroidal section of coaxial
cylinders, the rotating detonation is proven to give no average angular momentum at any cross section, giving an axial flow.
The detonation wavelet connected with an oblique shock wave ensuing to the downstream has a feature of unconfined detonation,
causing a deficit in its propagation velocity. Due to Kelvin–Helmholtz instability existing on the interface of an injected
combustible, unburnt gas pockets are formed to enter the junction between the detonation and oblique shock waves, generating
strong explosions propagating to both directions. Calculated specific impulse is as high as 4,700 s.
相似文献
954.
955.
T. Omata H. Fujiwara S. Otsuka-Yao-Matsuo N. Ono 《Applied Physics A: Materials Science & Processing》2000,71(6):609-614
Indium tin oxide (ITO) and Er3+-doped ITO powders were prepared by a conventional ceramic method. The density of ITO powders and optical absorption spectra
of Er3+ ions in Er3+-doped ITO were measured as a function of the SnO2 doping level. The results obtained were discussed in terms of the trapping center for immobile electrons in ITO. Observed
densities of ITO powders were in good agreement with those calculated from their lattice parameters, assuming that the immobile
electrons were trapped at the excess interstitial oxygen. The optical absorption spectra of Er3+-doped ITO indicated that some In3+ ions in ITO were surrounded by 7 and/or 8 oxygen ions; the increase in the coordination number of In3+ from 6 in In2O3 to 7 and/or 8 in ITO must be caused by the introduction of excess interstitial oxygen into the quasi-anion site in the C-typerare-earth
lattice upon SnO2 doping. It was concluded that the immobile electrons in ITO are trapped at the excess interstitial oxygen, and that the mechanism
of conduction carrier generation and compensation upon SnO2 doping into In2O3 can be expressed by the defect equation, 2SnO2?2SnIn·+2(1-z)e′+zOi
′′+3OO
×+(1-z)/2O2.
Received: 26 November 1999 / Accepted: 20 April 2000 / Published online: 13 September 2000 相似文献
956.
Fuminori Saito Naoki Suzuki Yoshiko Itoh Akira Goto Ichiro Fujiwara Toshikazu Kurihara Ren Iwata Yasuyuki Nagashima Toshio Hyodo 《Radiation Physics and Chemistry》2000,58(5-6):755-757
A system which supplies an intense 18F (half life 110 min) positron source produced by an AVF cyclotron through 18O(p,n)18F reaction has been constructed. Produced 18F is transferred to a low background experiment hall through a capillary. It is electro-deposited on a graphite rod and used for a source of a slow positron beam. In the meantime the next batch of target 18O water is loaded and proton irradiation proceeds. This system makes it possible to perform continuous positron beam experiments using the 18F positron source. 相似文献
957.
Dr. Susumu Tsuda Yoshitsugu Komai Prof. Dr. Shin-ichi Fujiwara Prof. Dr. Yutaka Nishiyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(6):1966-1969
A [c2]daisy chain rotaxane with two diarylacetylene cores was efficiently synthesized in 53 % yield by capping a C2-symmetric pseudo[2]rotaxane composed of two diarylacetylene-substituted permethylated α-cyclodextrins (PM α-CDs) with aniline stoppers. The maximum absorption wavelength of the [c2]daisy chain rotaxane remained almost unchanged in various solvents, unlike that of the stoppered monomer, indicating that the two independent diarylacetylene cores were insulated from the external environment by the PM α-CDs. Furthermore, the [c2]daisy chain rotaxane exhibited fluorescence emission derived from both diarylacetylene monomers and the excimer, which implies that the [c2]daisy chain structure can undergo contraction and extension. This is the first demonstration of a system in which excimer formation between two π-conjugated molecules within an isolated space can be controlled by the unique motion of a [c2]daisy chain rotaxane. 相似文献
958.
Chun‐Kai Chen Hui‐Ching Hsieh Chien‐Chung Shih Chien‐Hsin Wu Mao‐Chun Fu Tomoya Higashihara Ru‐Jong Jeng Wen‐Chang Chen 《Journal of polymer science. Part A, Polymer chemistry》2019,57(10):1113-1121
With the rapid advances in organic memory, organic field‐effect transistor (OFET) memory has been recognition of the value over the past few years. Although the functional polymer with the Donor‐Acceptor (D‐A) structure has been widely investigated, little research has been carried out to clarify the relationships among D‐A structure of the polymer, capability of charge‐transfer, and memory performance. Here, we report the nonvolatile memory characteristics of pentacene‐based OFET memory using random copolyimides, poly[4,4′‐diaminotriphenylamine‐hexafluoroisopropylidenediphthalimide‐co‐4‐(N,N‐bis(p‐aminophenyl)amino)‐4′‐nitroazobenzene‐hexafluoroisopropylidenediphthalimide) (PI(TPA‐6FDA‐DACx)), with feeding ratios of DAC to TPA set as x (where x = 0,10, 30,50,70,100). The OFET memory performance based on the molar ratio of DAC to TPA equal to 30:70 represents the best results with the proper charge mobility, on/off current ratio, and memory window. Intriguingly, the memory performance can be enhanced by introducing more D‐A monomer in polymer electrets, yet the concomitant inferior growth of pentacene decreases the charge mobility, attributed to the intrinsically destructive arrangement of polymer backbone. Our conclusion points out the importance of polymer arrangement and capability of charge‐transfer to the OFET performance and memory characteristics. The comparable results can also be applied for advanced OFET memory devices. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1113–1121 相似文献
959.
Nóra Taricska Dániel Horváth Dr. Dóra K. Menyhárd Hanna Ákontz-Kiss Masahiro Noji Dr. Masatomo So Prof. Dr. Yuji Goto Prof. Dr. Toshimichi Fujiwara Prof. Dr. András Perczel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(9):1968-1978
The amyloid formation of the folded segment of a variant of Exenatide (a marketed drug for type-2 diabetes mellitus) was studied by electronic circular dichroism (ECD) and NMR spectroscopy. We found that the optimum temperature for E5 protein amyloidosis coincides with body temperature and requires well below physiological salt concentration. Decomposition of the ECD spectra and its barycentric representation on the folded-unfolded-amyloid potential energy surface allowed us to monitor the full range of molecular transformation of amyloidogenesis. We identified points of no return (e.g.; T=37 °C, pH 4.1, cE5=250 μm , cNaCl=50 mm , t>4–6 h) that will inevitably gravitate into the amyloid state. The strong B-type far ultraviolet (FUV)-ECD spectra and an unexpectedly strong near ultraviolet (NUV)-ECD signal (Θ≈275–285 nm) indicate that the amyloid phase of E5 is built from monomers of quasi-elongated backbone structure (φ≈−145°, ψ≈+145°) with strong interstrand Tyr↔Trp interaction. Misfolded intermediates and the buildup of “toxic” early-stage oligomers leading to self-association were identified and monitored as a function of time. Results indicate that the amyloid transition is triggered by subtle misfolding of the α-helix, exposing aromatic and hydrophobic side chains that may provide the first centers for an intermolecular reorganization. These initial clusters provide the spatial closeness and sufficient time for a transition to the β-structured amyloid nucleus, thus the process follows a nucleated growth mechanism. 相似文献
960.
Norihiko Sasaki Jennifer Yuan Dr. Tomoya Fukui Prof. Masayuki Takeuchi Prof. Kazunori Sugiyasu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(35):7840-7846
Recent developments in kinetically controlled supramolecular polymerization permit control of the size (i.e., length and area) of self-assembled nanostructures. However, control of molecular self-assembly at a level comparable with organic synthetic chemistry and the achievement of structural complexity at a hierarchy larger than the molecular level remain challenging. This study focuses on controlling the aspect ratio of supramolecular nanosheets. A systematic understanding of the relationship between the monomer structure and the self-assembly energy landscape has derived a new monomer capable of forming supramolecular nanosheets. With this monomer in hand, the aspect ratio of a supramolecular nanosheet is demonstrated that it can be controlled by modulating intermolecular interactions in two dimensions. 相似文献