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Search Results: 1 - 10 of 166486 matches for " W. Q. Chen "
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Structural Health Monitoring Using High-Frequency Electromechanical Impedance Signatures
Wei Yan,W. Q. Chen
Advances in Civil Engineering , 2010, DOI: 10.1155/2010/429148
Abstract: An overview of recent advances in electromechanical impedance- (EMI-) based structural health monitoring is presented in this paper. The basic principle of the EMI method is to use high-frequency excitation to sense the local area of a structure. Changes in impedance indicate changes in the structure, which in turn indicate that damages appear. An accurate EMI model based on the method of reverberation-ray matrix is introduced to correlate changes in the signatures to physical parameters of structures for damage detection. Comparison with other numerical results and experimental data validates the present model. A brief remark of the feasibility of implementing the EMI method is considered and the effects of some physical parameters on EMI technique are also discussed. 1. Introduction Over the last decades, structural health monitoring (SHM) has been recognized as a useful tool for improving the safety and reliability of structures and to thereby reduce their operational cost [1]. Many SHM techniques thus have been developed in the literature [2–4] to quantify and locate the damages in the structures, based on either the global or the local interrogation of the structures [5]. Although these SHM methods have their specific advantages for detecting damages in the structures, the existent drawbacks may limit their applications on some aspects. For example, in global dynamic techniques, it is well known that the structure is subjected to low-frequency excitations and only the first few mode shapes and their corresponding natural frequencies can be accurately extracted. Because localized damages find it hard to alter global parameters such as natural frequency, curvature mode shape, and mode shape data, only large damages can be detected. Meanwhile, signals obtained using these methods are more prone to contamination by ambient vibration noise at low frequencies less than 100?Hz particularly [5]. Other typical local techniques, such as ultrasonic techniques, acoustic emission, and impact echo testing, require expensive and sophisticated hardware as well as well-trained professional operators [6]. On the other hand, electromechanical impedance (EMI) based structural health monitoring has shown promising successes in monitoring and finding minor changes in structural integrity [5–9]. A key aspect of EMI method is the use of PZT patches as collocated sensors and actuators. To apply PZT as an actuator-sensor simultaneously, a PZT patch bonded to a structure is driven by a fixed alternating electric field. A surface charge is generated in response to an applied
New evidents of tectonic uplift and trasform of movement style along Allao Shan-Red River fault zone
W. J. Chen,Q. Li
Chinese Science Bulletin , 1998, DOI: 10.1007/BF02891395
Abstract:
The rapid cooling of gangdese batholith(GB) and it“s tectonic implication
Q. Li,W. J. Chen
Chinese Science Bulletin , 1998, DOI: 10.1007/BF02891491
Abstract:
Therapeutic Outcome of Botulinum Toxin Type A for Patients with Low Bladder Compliance Secondary to Spinal Cord Injury  [PDF]
H. Chen, M. P. Huang, T. H. Huang, C. H. Jiang, J. W. Zeng, L. L. Zhou, Q. L. Liu, Q. Q. Li, X. Y. Yang
Open Journal of Urology (OJU) , 2017, DOI: 10.4236/oju.2017.711024
Abstract: Objective: To evaluate the efficacy and safety of botulinum toxin type A (BTX-A) in treating patients with low bladder compliance (BC) secondary to spinal cord injury (SCI). Methods: From 2011 to 2016, we retrospected patients who received BTX-A injections for LBC secondary to SCI. The primary outcomes were urodynamic parameters including maximum detrusor pressure (Pdetmax), bladder compliance (BC). Related adverse events were recorded. Results: 72 SCI patients were selected (62 males, 10 females, age range 18 - 52 years; mean age 28.5 years). 12 weeks after BTX-A injection, Pdetmax decreased from 51.02 cmH2O to 28.31 cmH2O. BC increased from 3.64 ml/cmH2O to 10.08 ml/cmH2O. 12 patients had mild transient haematuria for 1 - 2 days. Conclusion: Intradetrusor BTX-A injection was effective and safe for patients with low BC secondary to SCI.
Metallogenetic chronology and its tectonic significance of magmatogenic copper-nickel deposits in North Xinjiang
H. Q. Li,F. W. Chen
Chinese Science Bulletin , 1998, DOI: 10.1007/BF02891489
Abstract:
The utilization of BSA-modified chip on the investigation of ligand/protein interaction with surface plasma resonance
L Chen, Q Wang, W Hou
African Journal of Biotechnology , 2009,
Abstract: The kinetic behavior of glutathione (GSH)/ glutathione-S-transferase (GST) was investigated using surface plasmon resonance (SPR). Here, an alkanethiol-modified chip incorporated with bovine serum albumin (BSA) was employed. Subsequently, GSH was anchored on BSA surface only in the experimental channel and the without-active BSA surface was designed as the reference channel to improve the quality of the binding data and prevent a number of experimental artifacts to complicate the final biosensor analysis. Our results demonstrated that the BSA-modified chip was effective not only in binding the target proteins but also in suppressing the nonspecific binding (NSB) of proteins.
Chronology and origin of the Jinwozi gold deposit in Eastern Xinjiang
F. W. Chen,H. Q. Li
Chinese Science Bulletin , 1998, DOI: 10.1007/BF02891389
Abstract:
Spin dynamics in a doped-Mott-insulator superconductor
W. Q. Chen,Z. Y. Weng
Physics , 2004, DOI: 10.1103/PhysRevB.71.134516
Abstract: We present a systematic study of spin dynamics in a superconducting ground state, which itself is a doped-Mott-insulator and can correctly reduce to an antiferromagnetic (AF) state at half-filling with an AF long-range order (AFLRO). Such a doped Mott insulator is described by a mean-field theory based on the phase string formulation of the t-J model. We show that the spin wave excitation in the AFLRO state at half-filling evolves into a resonancelike peak at a finite energy in the superconducting state, which is located around the AF wave vectors. The width of such a resonancelike peak in momentum space decides a spin correlation length scale which is inversely proportional to the square root of doping concentration, while the energy of the resonancelike peak scales linearly with the doping concentration at low doping. An important prediction of the theory is that, while the total spin sum rule is satisfied at different doping concentrations, the weight of the resonancelike peak does not vanish, but is continuously saturated to the weight of the AFLRO at zero-doping limit. Besides the low-energy resonancelike peak, we also show that the high-energy excitations still track the spin wave dispersion in momentum space, contributing to a significant portion of the total spin sum rule. The fluctuational effect beyond the mean-field theory is also examined, which is related to the broadening of the resonancelike peak in energy space. In particular, we discuss the incommensurability of the spin dynamics by pointing out that its visibility is strongly tied to the low-energy fluctuations below the resonancelike peak. We finally investigate the interlayer coupling effect on the spin dynamics as a function of doping, by considering a bilayer system.
Wobbling geometry in simple triaxial rotor
W. X. Shi,Q. B. Chen
Physics , 2014, DOI: 10.1088/1674-1137/39/5/054105
Abstract: The spectroscopy properties and angular momentum geometry for the wobbling motion of a simple triaxial rotor are investigated within the triaxial rotor model up to spin $I=40\hbar$. The obtained exact solutions of energy spectra and reduced quadrupole transition probabilities are compared to the approximate analytic solutions by harmonic approximation formula and Holstein-Primakoff formula. It is found that the low lying wobbling bands can be well described by the analytic formulas. The evolution of the angular momentum geometry as well as the $K$-distribution with respect to the rotation and the wobbling phonon excitation are studied in detail. It is demonstrated that with the increasing of wobbling phonon number, the triaxial rotor changes its wobbling motions along the axis with the largest moment of inertia to the axis with the smallest moment of inertia. In this process, a specific evolutionary track that can be used to depict the motion of a triaxial rotating nuclei is proposed.
Gauss-Green theorem for weakly differentiable vector fields, sets of finite perimeter, and balance laws
G. Q. Chen,M. Torres,W. Ziemer
Mathematics , 2007,
Abstract: We analyze a class of weakly differentiable vector fields (\FF \colon \rn \to \rn) with the property that (\FF\in L^{\infty}) and (\div \FF) is a Radon measure. The primary focus of our investigation is to introduce a suitable notion of the normal trace of any divergence-measure field $\FF$ over the boundary of an arbitrary set of finite perimeter, which ensures the validity of the Gauss-Green theorem. To achieve this, we establish a fundamental approximation theorem which states that, given a Radon measure $\mu$ that is absolutely continuous with respect to $\mathcal{H}^{N-1}$ on $\rn$, any set of finite perimeter can be approximated by a family of sets with smooth boundary essentially from the measure-theoretic interior of the set with respect to the measure $\|\mu\|$. With this approximation theorem, we derive the normal trace of $\FF$ on the boundary of any set of finite perimeter, (E), as the limit of the normal traces of $\FF$ on the boundaries of the approximate sets with smooth boundary, so that the Gauss-Green theorem for $\FF$ holds on (E). With these results, we analyze the Cauchy fluxes that are bounded by a Radon measure over any oriented surface (i.e. an $(N-1)$-dimensional surface that is a part of the boundary of a set of finite perimeter) and thereby develop a general mathematical formulation of the physical principle of balance law through the Cauchy flux. Finally, we apply this framework to the derivation of systems of balance laws with measure-valued source terms from the formulation of balance law. This framework also allows the recovery of Cauchy entropy fluxes through the Lax entropy inequality for entropy solutions of hyperbolic conservation laws.
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