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Symplectic perturbation series methodology for non-conservative linear Hamiltonian system with damping

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Acta Mechanica Sinica 2021年第6期37卷 983-996,I0002页

作者： Zhiping Qiu Haijun xia Institute of Solid Mechanics School of Aeronautic Science and EngineeringBeihang UniversityBeijing100083China

In this paper,the symplectic perturbation series methodology of the non-conservative linear Hamiltonian system is presented for the structural dynamic response with ***,the linear Hamiltonian system is briefly introduced and its conservation law is proved based on the properties of the exterior *** the symplectic perturbation series methodology is proposed to deal with the non-conservative linear Hamiltonian system and its conservation law is further *** structural dynamic response problem with eternal load and damping is transformed as the non-conservative linear Hamiltonian system and the symplectic difference schemes for the non-conservative linear Hamiltonian system are *** applicability and validity of the proposed method are demonstrated by three engineering *** results demonstrate that the presented methodology is better than the traditional Runge–Kutta algorithm in the prediction of long-time structural dynamic response under the same time step.

关键词： Symplectic perturbation series methodology Non-conservative Hamiltonian system Structural dynamic response Symplectic difference scheme

Global Optimization of a Class of Nonconvex Quadratically Constrained Quadratic Programming Problems

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Acta Mathematica Sinica,English Series 2011年第9期27卷 1803-1812页

作者： Yong xia LMIB of the Ministry of Education School of Mathematics and Systems Science Beihang University Beijing 100191 P. R. China

In this paper we study a Class of nonconvex quadratically constrained quadratic programming problems generalized from relaxations of quadratic assignment problems. We show that each problem is polynomially solved. Strong duality holds if a redundant constraint is introduced. As an application, a new lower bound is proposed for the quadratic assignment problem.

关键词： Nonconvex programming quadratically constrained quadratic programming quadratic assignment problem polynomial solvability strong duality

Pseudo Asymptotically Periodic Solutions for Volterra Difference Equations of Convolution Type

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Chinese Annals of Mathematics,Series B 2019年第4期40卷 501-514页

作者： Zhinan xia Department of Applied Mathematics Zhejiang University of Technology

In this paper, the author studies the existence and uniqueness of discrete pseudo asymptotically periodic solutions for nonlinear Volterra difference equations of convolution type, where the nonlinear perturbation is considered as Lipschitz condition or non-Lipschitz case, respectively. The results are a consequence of application of different fixed point theorems, namely, the contraction mapping principle, the Leray-Schauder alternative theorem and Matkowski’s fixed point technique.

关键词： Pseudo asymptotically periodic function Volterra difference equations Contraction mapping principle Leray-Schauder alternative theorem

Application of probabilistic risk assessment at a coking plant site contaminated by polycyclic aromatic hydrocarbons

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Frontiers of Environmental Science & Engineering 2014年第3期8卷 441-450页

作者： Tianxiang xia Beijing Municipal Research Institute of Environmental Protection Beijing 100037 China Beijing Key Laboratory for Risk Modeling and Remediation of Contaminated Sites Beijing 100037 China

Application of Probabilistic Risk Assessment （PRA） and Deterministic Risk Assessment （DRA） at a coking plant site was compared. By DRA, Hazard Quotient （HQ） following exposure to Naphthalene （Nap） and Incremental Life Cancer Risk （ILCR） following exposure to Benzo（a）pyrene （Bap） were 1.87 and 2.12 × 104. PRA revealed valuable information regarding the possible distribution of risk, and risk estimates of DRA located at the 99.59th and 99.76th percentiles in the risk outputs of PRA, which indicated that DRA overestimated the risk. Cleanup levels corresponding acceptable HQ level of 1 and ILCR level of 104 were also calculated for both DRA and PRA. Nap and Bap cleanup levels were 192.85 and ***-1 by DRA, which would result in only 0.25% and 0.06% of the exposed population to have a risk higher than the acceptable risk, according to the outputs of PRA. The application of PRA on cleanup levels derivation would lift the cleanup levels 1.9 times for Nap and 2.4 times for Bap than which derived by DRA. For this coking plant site, the remediation scale and cost will be reduced in a large portion once the method of PRA is used. Sensitivity analysis was done by calculating the contribution to variance for each exposure parameter and it was found that contaminant concentration in the soil （Cs）, exposure duration （ED）, total hours spent outdoor per day （ETout）, soil ingestion rate （IRs）, the air breathing rate （IRa） and bodyweight （BW） were the most important parameters for risk and cleanup levels calculations.

关键词： Probabilistic Risk Assessment (PRA) a coking plant risk cleanup level sensitivity analysis polycyclic aromatic hydrocarbons (PAHs)

Sharp spectral gap for the Finsler p-Laplacian

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Science China Mathematics 2019年第8期62卷 1615-1644页

作者： Qiaoling xia School of Mathematical Sciences Zhejiang University

In this paper, we give a sharp lower bound for the first(nonzero) p-eigenvalue on a compact Finsler manifold M without boundary or with convex boundary if the weighted Ricci curvature RicciNis bounded from below by a constant K in terms of the diameter d of a manifold, dimension, K, p and N. In particular, if RicciNπis non-negative, then the first p-eigenvalue is bounded from below by(p-1)(~πp/d)p, and the equality holds if and only if M is either a circle or a segment.

关键词： Finsler p-Laplacian first eigenvalue weighted Ricci curvature gradient comparison

A conducted emission mitigation method for software-defined radios through vector signal cancellation

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Chinese Journal of Aeronautics 2023年第9期36卷 289-298页

作者： Siyu xia Qi WU School of Electronics and Information Engineering Beihang UniversityBeijing 100191China

Recently,Software-Defined Radio(SDR)has gained great popularity owing to its attractive merits,such as flexible signals configuration in multiple ***,commercial SDR equipment also has large spurious emissions in the Transmitting(Tx)*** paper presents a cascaded model for the Conducted Emission(CE)properties of a general SDR platform,which captures all the key components with high *** on a deeper understanding of the CE properties,a mitigation method is proposed for suppressing the spurious emissions of an SDR Tx *** method is based on an efficient vector signal cancellation scheme,in which multiple SDR channels are adopted to suppress the second-and third-order harmonic signals simultaneously.A hardware prototype with dual SDR channels is built and measured for *** results show that the suppression level of the third-order harmonic signal is 24 dB on average in the frequency range of 100 MHz to 3000 *** theoretic limit of the suppression level is related to the magnitude and phase errors,and the suppression level may be further improved by calibrating each SDR channel.

关键词： Cancellation Conducted Emission(CE) Harmonic suppression SDR Spurious emission

Gold nanocages as multifunctional materials for nanomedicine

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Frontiers of physics 2014年第3期9卷 378-384页

作者： xiaohu xia The Wallace H. Coulter Department of Biomedical Engineering Georgia Institute of Technology and Emory University Medical School Atlanta GA 30332 USA School of Chemistry and Biochemistry School of Chemical and Biomolecular Engineering Georgia Institute of Technology Atlanta GA 30332 USA

Featured by tunable localized surface plasmon resonance peaks in the near-infrared region and hollow interiors, Au nanocages represent a novel class of multifunctional nanomat, erials that have gained considerable attention in recent vears. This short review summarizes our recent work on the capabilities of An nanocages in nanomedicine. We start with a brief description of the synthesis of Au nanocages and highlight our recent protocols for the scaled-up production of An ***. We then use a numer of examples to illustrate how Au nanocages can contribute to nanomedicine with respect to both diagnosis and therapy.

关键词： gold nanocage nanomedicine diagnosis therapy

Generalization of quasi-Koszul algebras

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Applied Mathematics(A Journal of Chinese Universities) 2010年第1期25卷 117-126页

作者： xia qi Department of Mathematics Zhejiang University Hangzhou 310027 China

In this paper, we generalize two kinds of graded algebras, δ-Koszul algebras and Kp algebras, to the non-graded cases. The trivial modules of δ-Koszul algebras have pure resolutions, while those of Kp algebras admit non-pure resolutions. We provide necessary and sufficient conditions for a notherian semiperfect algebra either to be a quasi-δ-Koszul algebra or to be a quasi-Kp algebra.

关键词： Quasi-Koszul algebra Yoneda-Ext algebra semiperfect algebra.

Efficient production of hydrogen peroxide in microbial reverse-electrodialysis cells coupled with thermolytic solutions

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Frontiers of Environmental Science & Engineering 2023年第9期17卷 137-146页

作者： Xi Luo Ao Li Xue xia Peng Liang xia Huang College of Life and Environmental Sciences Minzu University of ChinaBeijing 100081China State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing 100084China Yangtze Ecology and Environment Co. Ltd.Wuhan 430062China

H_(2)O_(2) was produced at an appreciable rate in microbial reverse-electrodialysis cells(MRCs)coupled with thermolytic solutions,which can simultaneously capture waste heat as electrical *** determine the optimal cathode and membrane stack configurations for H_(2)O_(2) production,different catalysts,catalyst loadings and numbers of membrane cell pairs were *** black(CB)outperformed activated carbon(AC)for H_(2)O_(2) production,although AC showed higher catalytic activity for oxygen *** optimum CB loading was 10 mg/cm^(2) in terms of both the H_(2)O_(2) production rate and power *** optimum number of cell pairs was determined to be three based on a tradeoff between H_(2)O_(2) production and capital costs.A H_(2)O_(2) production rate as high as 0.99±0.10 mmol/(L·h)was achieved with 10 mg/cm^(2) CB loading and 3 cell pairs,where the H_(2)O_(2) recovery efficiency was 52±2%and the maximum power density was 780±37 mW/m^(2).Increasing the number of cell pairs to five resulted in an increase in maximum power density(980±21 mW/m^(2))but showed limited effects on H_(2)O_(2) *** results indicated that MRCs can be an efficient method for sustainable H_(2)O_(2) production.

关键词： Microbial reverse-electrodialysis cell Hydrogen peroxide production Ammonium bicarbonate Electrolysis cell Optimization