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Search Results: 1 - 10 of 27081 matches for " Gao Q "
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Theoretical Analysis and Numerical Simulation of Resonances and Stability of a Piecewise Linear-Nonlinear Vibration Isolation System
X. Gao,Q. Chen
Shock and Vibration , 2014, DOI: 10.1155/2014/803275
Abstract: A methodology is presented to study the resonance and stability for a single-degree-of-freedom (SDOF) system with a piecewise linear-nonlinear stiffness term (i.e., one piece is linear and the other is weakly nonlinear). Firstly, the exact response of the linear governing equation is obtained, and a modified perturbation method is applied to finding the approximate solution of the weakly nonlinear equation. Then, the primary and 1/2 subharmonic resonances are obtained by imposing continuity conditions and periodicity conditions. Furthermore, Jacobian matrix is derived to investigate the stability of resonance responses. Finally, the results of theoretical study are compared with numerical results, and a good agreement is observed. 1. Introduction Vibration isolation and shock absorbing have always been a hot research topic in engineering practice. A solid and liquid mixture (SALiM) vibration isolator was developed to isolate vibrations and shocks induced by heavy machines [1–3]. The stiffness of the SALiM isolator is piecewise linear-nonlinear in a quasi-static test [3]. That is, the isolator exhibits linear stiffness in some displacement region, beyond which the nonlinear stiffness is observed. Therefore, the elastic restoring force is continuous, but its first-order derivative at the turning point is discontinuous. In the past two decades, the majority of researches focused on the dynamics response, stability, bifurcation, and chaos of piecewise linear systems, such as piecewise bilinear systems or piecewise trilinear systems [4–8]. However, piecewise linear-nonlinear or even nonlinear-nonlinear systems have not received much attention, but many physical systems in fields of aerospace engineering, electric circuit, and so forth appear to be piecewise linear-nonlinear systems [9–12]. For nonsmooth stiffness systems, most approaches finding their steady state responses could be sorted into three groups including harmonic balance method (HBM) and its modified form, increment harmonic balance method (IHBM) [9, 10], classical approximate analytical methods like average method [4, 13–15], and the matching method [6, 7, 11, 16]. For instance, using HBM, Jin et al. investigated the response and stability of an unsymmetrical multiple-degree-of-freedom system with piecewise linear elastic elements [9], and for a more complex oscillator possessing a periodically time-varying and piecewise binonlinear restoring force function HBM is still applicable to its periodic motion [9, 17]. But like all harmonic balance techniques, the accuracy of the results obtained by
The Quantized Characterization of Cooked Rice Hardness and Research on the Automatic Measurement Technology  [PDF]
N. Jiang, Y. Gao, J.P. Zhou, L.Q. Gao, J.H. Zhou, Q.G. Dai
Engineering (ENG) , 2010, DOI: 10.4236/eng.2010.22013
Abstract: The hardness of cooked rice is one of the most important criteria which determine the rice quality. The commonly used near-infrared reflectance (NIR) method is still in argument due to its indirectness and possible error. In this paper, a mechanical method was proposed and its principle, automation, components and operative reliability were evaluated and compared with the NIR method. The results showed that the mechanical testing method can accurately detect the rice quality and were consistent with the NIR testing data. This new mechanical method can be effectively used in rice quality testing and branding with the advantage of simplicity, accuracy and reliability.
Effect of homopolymer poly(vinyl acetate) on compatibility and mechanical properties of poly(propylene carbonate)/poly(lactic acid) blends
J. Gao,Q. Fu,H. Bai,Q. Zhang
eXPRESS Polymer Letters , 2012, DOI: 10.3144/expresspolymlett.2012.92
Abstract: A small amount of homopolymer poly(vinyl acetate) (PVAc) is used to compatibilize the biodegradable blends of poly(propylene carbonate) (PPC) and poly(lactic acid) (PLA). Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) results show that PVAc is selectively localized in the PLA phase and at the interface between PPC and PLA phases. As a result, these interface-localized PVAc layers act as not only a compatibilizer to improve the phase dispersion significantly but also a bridge to increase the interfacial adhesion between PPC and PLA phases dramatically. Both of them are believed to be responsible for the enhancement in mechanical properties. This work provides a simple avenue to fabricate eco-friendly PPC/PLA blends with high performance, and in some cases, reducing the demand for petroleumbased plastics such as polypropylene.
Coherence effects on pion spectrum distribution
Q. H. Zhang,W. Q. Chao,C. S. Gao
Physics , 1997, DOI: 10.1088/0954-3899/23/9/013
Abstract: The effects of two kinds of coherent lengths, the wave packet length of the emitter and the radius of the coherent source, on pion spectrum distribution are studied. It is shown that both coherent lengths can cause abundant pions at low momentum, but the DCC size effects on pion spectrum distribution is more important. So observing abundant pions at low momentum may be taken as a signal of DCC effects.
Oleanolic acid liposomes with polyethylene glycol modification: promising antitumor drug delivery
Gao D, Tang S, Tong Q
International Journal of Nanomedicine , 2012, DOI: http://dx.doi.org/10.2147/IJN.S31725
Abstract: nolic acid liposomes with polyethylene glycol modification: promising antitumor drug delivery Original Research (2944) Total Article Views Authors: Gao D, Tang S, Tong Q Video abstract presented by Dawei Gao Views: 121 Published Date July 2012 Volume 2012:7 Pages 3517 - 3526 DOI: http://dx.doi.org/10.2147/IJN.S31725 Received: 12 March 2012 Accepted: 10 April 2012 Published: 06 July 2012 Dawei Gao, Shengnan Tang, Qi Tong Applied Chemical Key Laboratory of Hebei Province, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao, China Background: Oleanolic acid is a pentacyclic triterpene present in many fruits and vegetables, and has received much attention on account of its biological properties. However, its poor solubility and low bioavailability limit its use. The objective of this study was to encapsulate oleanolic acid into nanoliposomes using the modified ethanol injection method. Methods: The liposomes contain a hydrophobic oleanolic acid core, an amphiphilic soybean lecithin monolayer, and a protective hydrophilic polyethylene glycol (PEG) coating. During the preparation process, the formulations described were investigated by designing 34 orthogonal experiments as well as considering the effects of different physical characteristics. The four factors were the ratios of drug to soybean phosphatidylcholine (w/w), cholesterol (w/w), PEG-2000 (w/w), and temperature of phosphate-buffered saline at three different levels. We identified the optimized formulation which showed the most satisfactory lipid stability and particle formation. The morphology of the liposomes obtained was determined by transmission electron microscopy and atomic force microscopy. The existence of PEG in the liposome component was validated by Fourier transform infrared spectrum analysis. Results: The PEGylated liposomes dispersed individually and had diameters of around 110–200 nm. Encapsulation efficiency was more than 85%, as calculated by high-performance liquid chromatography and Sephadex gel filtration. Furthermore, when compared with native oleanolic acid, the liposomal formulations showed better stability in vitro. Finally, the cytotoxicity of the oleanolic acid liposomes was evaluated using a microtiter tetrazolium assay. Conclusion: These results suggest that PEGylated liposomes would serve as a potent delivery vehicle for oleanolic acid in future cancer therapy.
Subdomain Precise Integration Method for Periodic Structures
F. Wu,Q. Gao,W. X. Zhong
Shock and Vibration , 2014, DOI: 10.1155/2014/657589
Abstract: A subdomain precise integration method is developed for the dynamical responses of periodic structures comprising many identical structural cells. The proposed method is based on the precise integration method, the subdomain scheme, and the repeatability of the periodic structures. In the proposed method, each structural cell is seen as a super element that is solved using the precise integration method, considering the repeatability of the structural cells. The computational efforts and the memory size of the proposed method are reduced, while high computational accuracy is achieved. Therefore, the proposed method is particularly suitable to solve the dynamical responses of periodic structures. Two numerical examples are presented to demonstrate the accuracy and efficiency of the proposed method through comparison with the Newmark and Runge-Kutta methods. 1. Introduction A periodic structure consists of identical structural cells that are connected together end-to-end to form the entire structure. Precisely because of the repeatability of the periodic structures, these structures exhibit numerous interesting and useful physical properties and are widely applied in many types of engineering, such as railway engineering [1], the pantograph-catenary system [2], and photonic [3, 4] and phononic [5] crystals, among others. Currently, because of the importance of periodic structures, many correlational studies have been reported. In [1], a method based on the symplectic mathematical scheme and Schur decomposition was proposed for the random responses of a vehicle moving on an infinitely long periodic track. In [4], Dobson applied finite element discretization coupled with a preconditioned subspace iteration algorithm to periodic dielectric photonic crystals. In 1993, Kushwaha et al. [5] presented the first full band-structure calculations for periodic, elastic composites. Their work introduced a new field of research on periodic phononic crystals. Zhong and Williams investigated the wave propagation problems of repetitive structures [6, 7] and the localization phenomenon for the high-frequency vibration modes of imperfectly repetitive structures [8] using an analogy between computational structural mechanics theory and optimal control theory. Wang et al. introduced a lumped-mass method to study the propagation of elastic waves in one- [9] and two-dimensional [10] periodic systems. Wang et al. [11] investigated the free and forced vibration of certain periodic structures using the properties of the structural modes of periodic structures. Mead [12] developed
Finite coherent length and multi-pion correlation effects on two-pion interferometry
Q. H. Zhang,X. Q. Li,C. S. Gao,W. Q. Chao
Physics , 1998, DOI: 10.1088/0954-3899/24/1/021
Abstract: The effects of multi-pion correlations and finite coherent length on two-pion interferometry are studied. It was shown that as the pion multiplicity and coherent length become larger, the apparent radius and the apparent coherent parameters derived from two-pion interferometry become smaller. The influence of the coherent length on the effective temperature is discussed.
Porous Bulk Metallic Glass Fabricated by Powder Consolidation  [PDF]
Z.Y. Suo, S.W. Liu, L. Zhang, H. L. Gao, H. Y. Zhang, K. Q. Qiu
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2008, DOI: 10.4236/jmmce.2008.72008
Abstract: A synthesis method for the production of porous bulk metallic glass (BMG) is introduced. This method utilizes the superplastic forming ability of amorphous powder in the supercooled liquid (SCL) state and intenerating salt mixture as a placeholder to produce BMG foam by using a hot die pressing method. Scanning electron microscope (SEM), x-ray diffraction (XRD) and differential scanning calorimetry (DSC) were employed to characterize the morphologies of foaming structure, the crystallization and percentage of amorphous phase of the as-produced porous BMG. The results suggest that the formation of porous structure by superplastic forming process is feasible. Good bonding effect was observed between amorphous powder particles. None of crystalline phases was formed during hot pressing, and less than 3.5% percent of residual salt was enclosed in the foam. In order to remove any residual salt particles, salt preform with three-dimensional network and good connectivity is necessary.
Transition Dependency: A Gene-Gene Interaction Measure for Times Series Microarray Data
Xin Gao, Daniel Q Pu, Peter X-K Song
EURASIP Journal on Bioinformatics and Systems Biology , 2009, DOI: 10.1155/2009/535869
Abstract: Biological processes in the cell such as biochemical interactions and regulatory activities involve complicated dependency relationships among genes. It is one of the most fundamental aims in biology to build up appropriate models for inferring such dependency relationships. Time series microarray data consist of trajectories of gene expression profiles at multiple time points, which provide an innovative platform for biologists to investigate the dynamic nature of gene dependencies. Such gene-gene dependencies are attributed to some physical interactions among encoded proteins or between an encoded protein and genes, or through coregulation of some common transcription factors. Although from the microarray data, we cannot directly learn about how these physical interactions work, we can still make inference whether or not there is a dependency relationship between two genes' transcriptional changes via some mathematical models. The notion of gene-gene interaction in this article refers to such dependency relationship in the expression levels.Many methods have been proposed to detect gene-gene interactions using microarray data [1–3]. A traditional approach is to cluster genes using pairwise Pearson or Spearman correlations as a distance measure [4–6]. Pearson correlation captures linear dependencies and depends on normality assumption. Spearman correlation measures the concordance in the ranks of data and is invariant to any monotonic transformations on the data. As it does not rely on any normality or linearity assumptions, it is often used as a robust statistic to identify the coexpression patterns in genes. When applied on a pair of time series data, calculating both Pearson and Spearman correlations implicitly assumes that all the paired measurements across different time points are independent replications. This calculation is too simplistic to adequately describe the complex relationship between two time series, in which the dependency may be beyond a linear
Preparation and antidiabetic activity of polysaccharide from Portulaca oleracea L.
F Li, Q Li, D Gao, Y Peng, C Feng
African Journal of Biotechnology , 2009,
Abstract: Extraction parameters of polysaccharide from Portulaca oleracea L. (POP) and antidiabetic activity of POP on alloxan induced diabetic mice were studied. Better extraction parameters of POP were obtained by the single factor test, as follows: extraction temperature 95°C, extraction time 5 h, and ratio of solvent to raw material 40. POP treatment (200, 400 mg/ kg body weight) for 28 days resulted in a significant decrease in the concentration of fasting blood glucose (FBG), total cholesterol (TC) and triglyceride (TG) in diabetes mellitus mice. Furthermore, POP significantly increased the concentration of high-density lipoprotein cholesterol (HDLc) and serum insulin level in diabetes mellitus mice. Our data demonstrated POP at the dose of 400 mg/kg body weight (bw) exhibited optimal effect. The above results suggest that polysaccharide extracted from P. oleracea L. can control blood glucose and modulate the metabolism of glucose and blood lipid in diabetes mellitus mice.
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