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Purcell effect of GaAs quantum dots by photonic crystal microcavities

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Chinese Optics Letters 2009年第10期7卷 879-881页

作者： Kazuaki Sakoda Takashi Kuroda NaokiI keda Takaaki Mano Yoshimasa Sugimoto Tetsuyuki Ochiai Keiji Kuroda Shunsuke Ohkouchi Nobuyuki Koguchi Kiyoshi Asakawa National Institute for Materials science Japan graduate school of pure and applied sciences University of Tsukuba NEC Corporation

We fabricate photonic crystal slab microcavities embedded with GaAs quantum dots by electron beam lithography and droplet epitaxy. The Purcell effect of exciton emission of the quantum dots is confirmed by the micro photoluminescence measurement. The resonance wavelengths, widths, and polarization are consistent with numerical simulation results.

关键词： GaAs Purcell effect of GaAs quantum dots by photonic crystal microcavities QDs

Kinetic Alfven Waves Excited by Cometary Newborn Ions with Large Perpendicular Energies

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Plasma science and Technology 2011年第2期13卷 135-139页

作者： George SAMUEL Devi E SAVITHRI Venugopal CHANDU school of pure and applied Physics Mahatma Gandhi University

Stability of the kinetic Alfven wave in a plasma of hydrogen, oxygen and electrons is studied. Each species is modeled by drifting ring distributions in the direction parallel to the magnetic field, while in the perpendicular direction the distribution is simulated with a loss cone type distribution obtained through the subtraction of two Maxwellian distributions with different temperatures. It is found that for frequencies ω＊〈 ωcH with ω＊ and ωcH the Doppler shifted and hydrogen ion gyro-frequencies, respectively, the growth rate of the kinetic Alfven wave increases with the increase in propagation angles and density of oxygen ions. On the other hand, for frequencies ω＊〈 ωco with ωco the oxygen ion gyro-frequency the growth rate is independent of the oxygen ion density.

关键词： kinetic Alfven wave stability multi-ion cometary plasma

Krein Parameters of Fiber-Commutative Coherent Configurations

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Algebra Colloquium 2020年第1期27卷 1-10页

作者： Keiji Ito Akihiro Munemasa Research Center for pure and applied Mathematics Graduate School of Information SciencesTohoku UniversitySendaiJapan

For fiber-commutative coherent configurations,we show that Krein parameters can be defined essentially *** a consequence,the general Krein condition reduces to positive semidefiniteness of finitely many matrices determined by the parameters of a coherent *** mention its implications in the coherent configuration defined by a generalized *** also simplify the absolute bound using the matrices of Krein parameters.

关键词： coherent configuration association scheme Krein parameter Krein condition generalized quadrangle absolute bound

Coexisting Phenomena of Surge and Rotating Stall in an Axial Flow Compressor

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Journal of Thermal science 2013年第6期22卷 547-554页

作者： Takuya ABE Hiroaki MITSUI Yutaka OHTA graduate Student Graduate School of Science and EngineeringWaseda University Department of applied Mechanics and Aerospace Engineering Waseda University

The unsteady inner flow structure of a single-stage axial flow compressor under the coexisting conditions of surge and rotating stall was experimentally investigated via detailed measurements of the unsteady characteristics and the internal flow velocity fluctuations. The main relevant feature of the tested compressor is a shock tube with a capacity tank connected in series to the compressor outlet through slits and a concentric duplex pipe: surge and rotating stall can both be generated by connecting the shock tube. Research attention is focused on the unsteady behavior of a rotating stall during the surge cycle. The size of the rotating stall cell during the recovery process of an irregular surge cycle was experimentally determined by the circumferential flow velocity fluctuations ahead of the rotor blade. The results suggested that the size of the rotating stall cell at the switching point of the performance curve between large and small cycles is considered to be the key parameter in determining the following surge cycle. In addition, the surge cycle is largely influenced by the unsteady behavior of the rotating stall cell.

关键词： Axial flow compressor Surge Rotating stall Coexisting state of surge and rotating stall

The NF-Number of a Simplicial Complex

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Algebra Colloquium 2022年第4期29卷 643-650页

作者： Takayuki Hibi Hasan Mahmood Department of pure and applied Mathematics graduate school of Information science and Technology Osaka University SuitaOsaka 565-0871Japan Department of Mathematics Government College University LahorePakistan

Let△bea simplicial complex on[n].TheNF-complex of△is the simplicial complexδ_(NF)(△)on[n]for which the facet ideal of△is equal to the Stanley-Reisner ideal ofδ_(NF)(△).Furthermore,for each k=2,3,....,we introduce the kth NF-complexδ_(NF)^(k)(△),which is inductively defined asδ_(NF)(k)(△)=δ_(NF)(δ_(NF)^(k-1)(△))by settingδ_(NF)^(1)(△)=δ_(NF)(△).One canδ_(NF)^(0)(△)=△.The NF-number of△is the smallest integer k>0 for whichδ_(NF)^(k)(△)■△.In the present paper we are especilly interested in the NF-number of a finite graph,which can be regraded as a simplicial complex of dimension *** is shown that the NF-number of the finite graph K_(n)■K_(m)on[n+m],which is the disjoint union of the complete graphs K_(n)on[n]and K_(m)on[m]for n≥2 and m≥2 with(n,m)≠(2,2),is equal to n+m+*** a corollary,we find that the NF-number of the complete bipartite graph K_(n,m)on[n+m]is also equal to n+m+2.

关键词： Stanley-Reisner complex facet ideal simplicial complex vertex cover

Stall Inception Process and Prospects for Active Hub-Flap Control in Three-Stage Axial Flow Compressor

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Journal of Thermal science 2008年第4期17卷 324-330页

作者： Tomoya OKADA Atsushi KAWAJIRI Yutaka OHTA Eisuke OUTA graduate school of science and Engineering Waseda University Department of applied Mechanics and Aerospace Engineering Waseda University

The possibility to apply the active hub-flap control method, which is a proven rotating stall control method for a single-stage compressor, to a 3-stage axial compressor is experimentally discussed, where complex rotating stall inception processes are observed. The research compressor is a 3-stage one and could change the stagger angle settings for rotor blades and stator vanes. Sixteen rotor blade/stator vane configuration patterns were tested by changing stagger angle for the stator vanes. By measurement of surface-pressure fluctuation, stall inception proc- esses are investigated and the measured pressure fluctuation data is used as a predictive signal for rotating stall. The experimental results show that the stall detection system applied to active hub-flap control in a single-stage compressor could be usefully applied to that in a 3-stage compressor with a more complex stall inception process.

关键词： axial flow compressor rotating stall active stall control stall inception stall precursor.

Preparation of PLGA-collagen hybrid scaffolds with controlled pore structures for cartilage tissue engineering

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Progress in Natural science:Materials International 2020年第5期30卷 642-650页

作者： Nur Rofiqoh Eviana Putri Xiuhui Wang Ying Chen Xiaomeng Li Naoki Kawazoe Guoping Chen Research Center for Functional Materials National Institute for Materials Science Department of Materials science and Engineering Graduate School of Pure and Applied Sciences University of Tsukuba Departement of Chemical Engineering Faculty of Engineering Universitas Gadjah Mada

Scaffolds used for cartilage tissue engineering should have high mechanical strength and well-controlled pore structure to provide suitable microenvironments for functional tissue regeneration. In this study, hybrid scaffolds which had open and interconnected pore structure and high mechanical property were prepared by hybridization of PLGA mesh and collagen using ice particulates as porogen templates. Embossing ice particulates template was used to form open pore structures on the scaffold surfaces. Free ice particulates were used to generate interconnected bulk pores in the scaffolds. Hybridization with PLGA mesh provided the scaffolds with high mechanical property. Bovine articular chondrocytes were cultured in the hybrid scaffolds. The unique pore structures facilitated the homogeneous distribution of chondrocytes and cartilaginous matrices throughout the scaffolds. Subcutaneous implantation demonstrated cartilage-like tissue regeneration. The hybrid scaffolds should have a high potential for cartilage tissue engineering.

关键词： Hybrid scaffolds Porous scaffolds PLGA Collagen Cartilage tissue engineering

A note on the entropy of mean curvature flow

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science China Mathematics 2015年第12期58卷 2611-2620页

作者： BAO Chao Key Laboratory of pure and applied Mathematics School of Mathematical SciencesPeking University

The entropy of a hypersurface is given by the supremum over all F-functionals with varying centers and scales, and is invariant under rigid motions and dilations. As a consequence of Huisken's monotonicity formula, entropy is non-increasing under mean curvature flow. We show here that a compact mean convex hypersurface with some low entropy is diffeomorphic to a round sphere. We also prove that a smooth selfshrinker with low entropy is a hyperplane.

关键词： entropy self-shrinker mean curvature flow sphere

Variations in the X-ray eclipse transitions of Cen X-3

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Research in Astronomy and Astrophysics 2010年第11期10卷 1127-1136页

作者： Jincy Devasia Biswajit Paul Marykutty James Kavila Indulekha school of pure & applied Physics Mahatma Gandhi University Raman Research Institute

We report here an investigation of the X-ray eclipse transitions of the high mass X-ray binary pulsar Cen X-3 in different intensity states. The long term light curve of Cen X-3 obtained with RXTE-ASM spanning more than 5000 d shows strong aperiodic flux variations with low and high states. We have investigated the eclipse transitions of Cen X-3 in different intensity states with data obtained from pointed observations with the more sensitive instruments onboard ASCA, BeppoSAX, XMM- Newton, Chandra and RXTE. We found a very clear trend of sharp eclipse transitions in the high state and longer transitions in the low state. This is a confirmation of this feature first observed with the RXTE-ASM but now observed with much better clarity. From the light curves obtained from several missions, it is seen that the eclipse egress in the low state starts earlier by an orbital phase of 0.02 compared to the eclipse egress in the high state indicating that the observed X-rays originate from a much larger region. We have also performed spectral analysis of the post-eclipse part of each observation. From BeppoSAX observations, the out-of-eclipse X-ray flux is found to differ by a factor of -26 during the high and low intensity states while the eclipse count rates differ by a factor of only ~ 4.7. This indicates that in the low state, there is an additional scattering medium which scatters some of the source photons towards the observer even when the neutron star is completely eclipsed. We could also resolve the three iron line components using XMM-Newton observation in the low state. By comparing the iron line equivalent width during the high and low states, it is seen that the width of the iron line is relatively large during the low state which supports the fact that significant reprocessing and scattering of X-rays takes place in the low state.

关键词： stars pulsars individual (Cen X-3) -- (stars:) binaries eclipsing -- X-rays binaries