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Search Results: 1 - 10 of 15493 matches for " Yongsheng Ren "
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Oscillation Theorems for Second-Order Damped Nonlinear Differential Equations
Hui-Zeng Qin,Yongsheng Ren
International Journal of Differential Equations , 2009, DOI: 10.1155/2009/714357
Abstract: We present new oscillation criteria for the differential equation of the form [()()]
Modeling and Dynamical Behavior of Rotating Composite Shafts with SMA Wires
Yongsheng Ren,Qiyi Dai,Ruijun An,Youfeng Zhu
Shock and Vibration , 2014, DOI: 10.1155/2014/765875
Abstract: A dynamical model is developed for the rotating composite shaft with shape-memory alloy (SMA) wires embedded in. The rotating shaft is represented as a thin-walled composite of circular cross-section with SMA wires embedded parallel to shaft’s longitudinal axis. A thermomechanical constitutive equation of SMA proposed by Brinson is employed and the recovery stress of the constrained SMA wires is derived. The equations of motion are derived based on the variational-asymptotical method (VAM) and Hamilton’s principle. The partial differential equations of motion are reduced to the ordinary differential equations of motion by using the Galerkin method. The model incorporates the transverse shear, rotary inertia, and anisotropy of composite material. Numerical results of natural frequencies and critical speeds are obtained. It is shown that the natural frequencies of the nonrotating shaft and the critical rotating speed increase as SMA wire fraction and initial strain increase and the increase in natural frequencies becomes more significant as SMA wire fraction increases. The initial strain of SMA wires appears to have marginal effect on dynamical behaviors of the shaft. The actuation performance of SMA wires is found to be closely related to the ply-angle. 1. Introduction Composite materials have found the increased applications for replacement of the conventional metallic materials in the rotating flexible shaft employed for drive shafts of helicopters, steam, and gas turbines. This is likely attributed to high stiffness and strength/weight ratios of composite shaft compared with its metallic counterparts. The development trend in design of light-weight composite shafts is towards higher operating speeds, which gives rise to the problems of high vibration amplitude and stability. Seeking the solution of these problems has caused great research effort [1] in the dynamic of composite rotor. A review on the literature in this area has shown that composite shafts have high whirling resistance capability and are less susceptible to dynamic instability associated with metallic shafts [2]. Several attempts to develop mathematical models of spinning composite shafts are reported in the literature. These models include the shaft models based on shell theories [3], or beam theories combined with the strain—displacement relations of the shell theories [4], or a thin-walled beam theory [5]. Song et al. [5] developed the composite thin-walled shaft model based on a thin-walled beam theory of Rehfield [6]. This model was used to investigate the natural frequencies and
Vibration and Instability of Rotating Composite Thin-Walled Shafts with Internal Damping
Ren Yongsheng,Zhang Xingqi,Liu Yanghang,Chen Xiulong
Shock and Vibration , 2014, DOI: 10.1155/2014/123271
Abstract: The dynamical analysis of a rotating thin-walled composite shaft with internal damping is carried out analytically. The equations of motion are derived using the thin-walled composite beam theory and the principle of virtual work. The internal damping of shafts is introduced by adopting the multiscale damping analysis method. Galerkin’s method is used to discretize and solve the governing equations. Numerical study shows the effect of design parameters on the natural frequencies, critical rotating speeds, and instability thresholds of shafts. 1. Introduction The rotating composite material shafts are being used as structural elements in many application areas involving the rotating machinery systems. This is likely to contribute to the high strength to weight ratio, lower vibration level, and longer service life of composite materials. A significant weight saving can be achieved by the use of composite materials. Also by appropriate design of the composite layup configuration, orientation, and number of plies the improved performance of the shaft system can be obtained. Furthermore, the use of composite would permit the use of longer shafts in the supercritical range than what is possible with conventional metallic shafts. In the last few years, there exist numerous researches related to predicting critical speeds and natural frequencies of composite shaft. Zinberg and Symonds [1] investigated the critical speeds of rotating anisotropic cylindrical shafts based on an equivalent modulus beam theory (EMBT), and dos Reis et al. [2] evaluated the shaft of Zinberg and Symonds [1] by the finite element method. Kim and Bert [3] adopted the thin- and thick-shell theories of first-order approximation to derive the motion equations of the rotating composite thin-walled shafts. They used this model to obtain a closed form solution for a simply supported drive shaft and to analyze the critical speeds of composite shafts. Singh and Gupta [4] developed two composite spinning shaft models employing EMBT and layerwise beam theory (LBT), respectively. It was shown that a discrepancy exists between the critical speeds obtained from both models for the unsymmetric laminated composite shaft. Chang et al. [5] presented a simple spinning composite shaft model based on a first-order shear deformable beam theory. The finite element method is used here to find the approximate solution of the system. The model was used to analyze the critical speeds, frequencies, mode shapes, and transient response of a particular composite shaft system. Gubran and Gupta [6] presented a modified
Removal of Methyl Violet from aqueous solutions using poly (acrylic acid-co-acrylamide)/attapulgite composite
Removal of Methyl Violet from aqueous solutions using poly (acrylic acid.co-acrylamide)/attapulgite composite

Yongsheng Wang,Li Zeng,Xuefeng Ren,Hai Song,Aiqin Wang,
Yongsheng Wang
,Li Zeng,Xuefeng Ren,Hai Song,Aiqin Wang

环境科学学报(英文版) , 2010,
Abstract: The adsorption of Methyl Violet (MV) cationic dye from aqueous solution was carried out by using crosslinked poly (acrylic acid-co-acrylamide)/attapulgite (Poly(AA-co-AM)/ATP) composite as adsorbent. The factors influencing adsorption capacity of the composite such as pH, concentration of the dye, temperature, contact time, adsorbent dosage, ionic strength and surfactant were systematically investigated. The equilibrium data fitted very well to the Langmuir isotherm and the maximum adsorption capacity reach...
Analysis on Influencing Elements of Enterprise Logistics Risk Early Warning: Based on Manufacturing Industries in Beijing Area  [PDF]
Yongsheng Liu, Rong Yu
American Journal of Industrial and Business Management (AJIBM) , 2013, DOI: 10.4236/ajibm.2013.34045
Abstract:

Enterprise logistics risk early warning is an essential part of enterprise logistics risk management, which has been increasingly drawing the attentions of both practical and academic world. However, enterprise logistics risk early warning hasn’t been radically put into practice yet. Therefore, the factors hinder the proceeding of enterprise logistics risk early warning become the key to starting the engine of enterprise logistics risk early warning. In this paper, review of researches on enterprise logistics risk early warning is provided, a questionnaire has been designed according to both exterior and internal factors influencing enterprise logistics risk early warning and a survey on manufacturing industries in Beijing area has been carried out, logistics risk early warning status and influencing elements have been analyzed based on previous survey and advices proposed are concluded to provide valuable references.

Dual effects of TGF-β on ERα-mediated estrogenic transcriptional activity in breast cancer
Yongsheng Ren, Liyu Wu, Andra R Frost, William Grizzle, Xu Cao, Mei Wan
Molecular Cancer , 2009, DOI: 10.1186/1476-4598-8-111
Abstract: Effect of TGF-β on ERα-mediated gene transcription was investigated in breast cancer cell lines using transient transfection, real-time PCR, sequential DNA precipitation, and small interfering RNA assays. The expression of Smads on both human breast cancer cell lines and ERα-positive human breast cancer tissue was evaluated by immunofluorescence and immunohistochemical assays.A complex of Smad3/4 mediates TGF-β inhibition of ERα-mediated estrogenic activity of gene transcription in breast cancer cells, and Smad4 is essential and sufficient for such repression. Either overexpression of Smad3 or inhibition of Smad4 leads to the "switch" of TGF-β from a repressor to an activator. Down-regulation and abnormal cellular distribution of Smad4 were associated with some ERα-positive infiltrating human breast carcinoma. There appears a dynamic change of Smad4 expression from benign breast ductal tissue to infiltrating ductal carcinoma.These results suggest that aberrant expression of Smad4 or disruption of Smad4 activity lead to the loss of TGF-β suppression of ERα transactivity in breast cancer cells.Estrogens act as mitogens to promote cell proliferation in both normal breast tissue and breast carcinomas through their binding to estrogen receptors (ER). The ERα is a transcriptional activator and regulates gene transcription either by directly binding to the estrogen-responsive element (ERE) or by interacting with other transcription factors [1,2]. Gene amplification or overexpression of ERα was found in some breast cancer [3,4]. Approximately 70% of breast cancers are ERα positive and estrogen dependent. ERα has become an important prognostic marker and a therapeutic target in breast cancer [5,6].In contrast to estrogens, which induce proliferation of breast cancer cells, transforming growth factor-β (TGF-β) inhibits the growth of human breast cancer cells in culture [7,8]. TGF-β is the prototypic inhibitor of cell cycle progression and appears to directly antagonize the ef
Impact of Snow Storms on Habitat and Death of Yunnan Snub-Nosed Monkeys in the Baimaxueshan Nature Reserve, Yunnan, China
Dayong Li,Baoping Ren,Jie Hu,Yongsheng Shen,Xinming He,Ali Krzton,Ming Li
ISRN Zoology , 2012, DOI: 10.5402/2012/813584
Abstract: Natural disasters such as snow storms have far-reaching effects on variations in the habitat structure and ecological aspects of non-human primates. Yunnan snub-nosed monkeys (Rhinopithecus bieti) inhabit high-altitude forest and endure harsh winters. The effect of heavy snow-storms (January 19 to February 6, 2008) on two large groups of R. bieti (Gehuaqing group and Xiangguqing group) inhabiting Samage Forest in the Baimaxueshan Nature Reserve were assessed. Data on habitat damage were collected between March and May 2008 via field line sampling. The snow storms destroyed 237 big trees in the Samage Forest. The destroyed trees were mostly located along the mountain ridge and valley including Abies georgei, Tsuga dumosa, Pinus yunnanensis and Cyclobalanopsis oxyodon. These trees were important for R. bieti as they provide a dietary source of lichen that is a critical winter fallback food for this primate species, and consequently food availability for R. bieti was reduced. Our results also showed that two juveniles in the Gehuaqing group and three juveniles in the Xiangguqing group were found deceased following the storms. The fact indicates that R. bieti is well adapted to high altitude and strongly seasonal habitat might explain its resilience to heavy snow storms. 1. Introduction Natural disasters have far-reaching impacts on vegetative biomass, forest structure, food supply, wild animal population demography, and activity in forest ecosystems [1, 2]. For example, significant losses of tree and shrub species diversity and richness occurred in Wolong National Nature Reserve following the 8.0 magnitude earthquake in 2008 [3]. Earthquakes have also instigated abnormal behaviors and increased activity in nonhuman primates [4]. Fujimoto and Hanamura [5] reported that wild chimpanzees (Pan troglodytes schweinfurthii) displayed scream vocalizations, climbed trees, and stopped grooming and feeding during a high intensity earthquake. Disaster events can also seriously threaten primate populations and social group structure due to their habitat destruction [6, 7]. For instance, 26% of chacma baboons (Papio ursinus) died or disappeared after almost 150 days of drought in the Kuiseb River canyon, Namibia [8]. Dittus [9] also reported that group size of toque macaques (Macaca sinica) declined by 15% because of severe drought. Pavelka et al. [6] found that a population of black howlers (Alouatta pigra) decreased by 88% during the three and a half years after Hurricane Iris hit southern Belize. One group of golden snub-nosed monkeys (Rhinopithecus roxellana
An Energy-Efficient MAC Protocol for Ad Hoc Networks  [PDF]
Yongsheng SHI, T. Aaron GULLIVER
Wireless Sensor Network (WSN) , 2009, DOI: 10.4236/wsn.2009.15049
Abstract: A mobile ad hoc network (MANET) is a collection of nodes equipped with wireless communications and a networking capability without central network control. Nodes in a MANET are free to move and organize themselves in an arbitrary fashion. Energy-efficient design is a significant challenge due to the characteristics of MANETs such as distributed control, constantly changing network topology, and mobile users with limited power supply. The IEEE 802.11 MAC protocol includes a power saving mechanism, but it has many limitations. A new energy-efficient MAC protocol (EE-MAC) is proposed in this paper. It is shown that EE-MAC performs better than IEEE 802.11 power saving mode and exceeds IEEE 802.11 with respect to balancing network throughput and energy savings.
Geometric properties of composition operators belonging to Schatten classes
Yongsheng Zhu
International Journal of Mathematics and Mathematical Sciences , 2001, DOI: 10.1155/s0161171201003726
Abstract: We investigate the connection between the geometry of the image domain of an analytic function mapping the unit disk into itself and the membership of the composition operator induced by this function in the Schatten classes. The purpose is to provide solutions to Lotto's conjectures and show a new compact composition operator which is not in any of the Schatten classes.
D+ to mu+nu and fD+ from 281 pb-1 at Psi(3770) from CLEO-c
Yongsheng Gao
Physics , 2005,
Abstract: We report improved measurements of branching fraction and decay constant fD+ in D+ to mu+nu using 281 pb-1 of data taken on the Psi(3770) resonance with the CLEO-c detector. We extract a relatively precise value for the decay constant of the D+ meson by measuring Br(D+ to mu+nu) = (4.40+-0.66+0.09-0.12)x10^-4 and find fD+ = (222.6+-16.7+2.8-3.4) MeV. We also set 90% confidence upper limit on Br(D+ to e+nu) < 2.4x10^-5 which limits contributions from non-Standard Model physics.
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