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New construction of hybrid and aperiodic ordered PBG cavity

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Science China(Physics,Mechanics & Astronomy) 2011年第S2期54卷 207-209页

作者： ZHAO JingXiong WU CongFeng FAN Hao LI Bo DONG Sai National Synchrotron Radiation Laboratory University of Science and Technology of ChinaHefei 230022China

The band gap of a photonic crystal (PhC) cavity intrinsically avoids HOM problems. In this paper, we present a new PBG structure based on the possible advantage of using hybrid structures and aperiodic lattices. This novel hybrid and aperiodically ordered cavity was designed for apparently higher Q-factor (more than 10300) and achieving large accelerating field gradient. The HOMs in the cavity are able to be absorbed efficiently.

关键词： PBG hybrid aperiodic high Q-factor

New construction of hybrid and aperiodic ordered PBG cavity

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New construction of hybrid and aperiodic ordered PBG cavity

Switching-based stabilization of aperiodic sampled-data Boolean control networks with all subsystems unstable

第一届中国粒子加速器会议

作者： ZHAO JingXiong WU CongFeng FAN Hao LI Bo DONG Sai National Synchrotron Radiation Laboratory University of Science and Technology of China

The band gap of a photonic crystal(PhC) cavity intrinsically avoids HOM *** this paper,we present a new PBG structure based on the possible advantage of using hybrid structures and aperiodic *** novel hybrid and aperiodically ordered cavity was designed for apparently higher Q-factor(more than 10300) and achieving large accelerating field gradient. The HOMs in the cavity are able to be absorbed efficiently.

关键词： PBG hybrid aperiodic high Q-factor

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Frontiers of Information Technology & Electronic Engineering 2020年第2期21卷 260-267页

作者： Liang-jie SUN Jian-quan LU Wai-Ki CHING School of Mathematics Southeast UniversttyNanjing 210096China Department of Mathematics The University of Hong KongHong KongChina

We aim to further study the global stability of Boolean control networks(BCNs)under aperiodic sampleddata control(ASDC).According to our previous work,it is known that a BCN under ASDC can be transformed into a switched Boolean network(SBN),and further global stability of the BCN under ASDC can be obtained by studying the global stability of the transformed ***,since the major idea of our previous work is to use stable subsystems to offset the state divergence caused by unstable subsystems,the SBN considered has at least one stable *** central thought in this paper is that switching behavior also has good stabilization;i.e.,the SBN can also be stable with appropriate switching laws designed,even if all subsystems are *** is completely different from that in our previous ***,for this case,the dwell time(DT)should be limited within a pair of upper and lower *** means of the discretized Lyapunov function and DT,a sufficient condition for global stability is ***,the above results are demonstrated by a biological example.

关键词： aperiodic sampled-data control Boolean control networks Unstable subsystem Discretized Lyapunov function Dwell time

aperiodic Checkpoint Placement Algorithms—Survey and Comparison

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Journal of Software Engineering and Applications 2013年第4期6卷 41-53页

作者： Shunsuke Hiroyama Tadashi Dohi Hiroyuki Okamura Department of Information Engineering Hiroshima University Hiroshima Japan

In this article we summarize some aperiodic checkpoint placement algorithms for a software system over infinite and finite operation time horizons, and compare them in terms of computational accuracy. The underlying problem is formulated as the maximization of steady-state system availability and is to determine the optimal aperiodic checkpoint sequence. We present two exact computation algorithms in both forward and backward manners and two approximate ones;constant hazard approximation and fluid approximation, toward this end. In numerical examples with Weibull system failure time distribution, it is shown that the combined algorithm with the fluid approximation can calculate effectively the exact solutions on the optimal aperiodic checkpoint sequence.

关键词： Checkpoint Placement aperiodic Policy Availability Models Computation Algorithms Comparison

Flow-structure interaction of an inverted flag in a water tunnel

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Science China(Physics,Mechanics & Astronomy) 2019年第12期62卷 57-67页

作者： YaoWei Hu JiangSheng Wang JinJun Wang Christian Breitsamter Key Laboratory of Fluid Mechanics(Beihang University) Ministry of EducationBeijing 100191China Lehrstuhl fur Aerodynamik und Stromungsmechanik Technische Universitat MiinchenGarching 85748Germany

Herein, the dynamics and flow fields of an inverted flag are studied using hydrogen bubble flow visualization and particle image velocimetry technologies at different height-to-length ratios and flow velocities in a water tunnel. Results show that the heightto-length ratio of the inverted flag at which the critical flow velocity remains nearly constant is approximately 1.4. Moreover, a nonperiodic flapping phenomenon is observed under various height-to-length ratios. This phenomenon may be attributed to the existence of multiple equilibrium solutions to the self-excited vibration system, thus engendering chaos in the system comprising an inverted flag and surrounding fluid. Other indications that the system has entered chaos include multiple frequencies, nonoverlapping phase diagram, and positive Lyapunov exponent. Further discussion of the flow fields around the inverted flag reveals that the large-amplitude oscillation is due to the flow separation, while the flapping instability is a static divergence instability. In the large flapping mode, the starting leading-edge vortex(LEV) is wrapped by Kelvin-Helmholtz instabilities,which are arranged at almost uniform spacing along a circular path. In addition, the variation in position, circulation, and radius of the starting LEV are discussed in detail.

关键词： inverted flag modes aperiodic flapping LEV

A New Effective and Efficient Measure of PAPR in OFDM

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International Journal of Communications, Network and System Sciences 2010年第9期3卷 755-766页

作者： Ibrahim M. Hussain Imran A. Tasadduq Abdul Rahim Ahmad 不详

In multi-carrier wireless OFDM communication systems, a major issue is related to high peaks in transmitted signals, resulting in such problems as power inefficiency. In this regard, a common practice is to transmit the signal that has the lowest Peak to Average Power Ratio (PAPR). Consequently, some efficient and accurate method of estimating the PAPR of a signal is required. Previous literature in this area suggests a strong relationship between PAPR and Power Variance (PV). As such, PV has been advocated as a good measure of PAPR. However, contrary to what is suggested in the literature, our research shows that often low values of PV do not correspond to low values of PAPR. Hence, PV does not provide a sound scientific basis for comparing and estimating PAPR in OFDM signals. In this paper a novel, effective, and efficient measure of high peaks in OFDM signals is proposed, which is less complex than PAPR. The proposed measure, termed as Partial Power Variance (PPV), exploits the relationship among PAPR, aperiodic Autocorrelation Co-efficient (AAC), and Power Variance (PV) of the transmitted signal. Our results demonstrate that, in comparison to PV, Partial Power Variance is a more efficient as well as a more effective measure of PAPR. In addition, we demonstrate that the computational complexity of PPV is far less than that of PAPR.

关键词： aperiodic Autocorrelation Co-Efficient OFDM PAPR Power Variance Partial Power Variance

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Quasicrystals

Open Journal of Physical Chemistry 2012年第1期2卷 7-14页

作者： Feridoun Samavat Mohammad Hossein Tavakoli Safdar Habibi Babak Jaleh Parisa Taravati Ahmad Department of Physics Bu-Ali Sina University Hamedan Iran

Quasicrystals are material with perfect long-range order, but with no three-dimensional translation periodicity. They are typically binary and ternary metallic alloys. Quasicrystals have characteristic physical properties. Some resemble those of periodic crystals while others have similar properties to amorphous alloys. Many of their mechanical physical prop- erties are quite unusual by the standards of common metals. The peculiar physical properties of quasicrystals certainly give rise to the hope that they may become of some practical importance in the future. Some of these properties are surface related. This provides the main motivation for surface scientists to study this material. In this paper;quasicrystals, types of them, physical properties, surface science and potential applications of them have been discussed.

关键词： Quasicrstals Icosahedral Quasicrystals Polygonal Quasicrystals aperiodic Intermetallics