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Search Results: 1 - 10 of 32948 matches for " Guo Xingming "
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The initial boundary value problem of a mixed-typed hemivariational inequality
Guo Xingming
International Journal of Mathematics and Mathematical Sciences , 2001, DOI: 10.1155/s0161171201003994
Abstract: A mixed-typed differential inclusion with a weakly continuous nonlinear term and a nonmonotone discontinuous nonlinear multi-valued term is studied, and the existence and decay of solutions are established.
On weak solution of a hyperbolic differential inclusion with nonmonotone discontinuous nonlinear term
Guo Xingming
International Journal of Mathematics and Mathematical Sciences , 1999, DOI: 10.1155/s0161171299225872
Abstract: In this paper, a hyperbolic differential inclusion with nonmonotone discontinuous and nonlinear term, which the generalized velocity acts as its variable, is studied and the existence and decay of its weak solution are obtained.
Gas-like adhesion of two-dimensional materials onto solid surfaces
Zhengrong Guo,Tienchong Chang,Xingming Guo,Huajian Gao
Physics , 2015,
Abstract: The adhesion of two-dimensional (2D) materials to other surfaces is so far believed to be a solid-solid mechanical contact. Here, we conduct both atomistic simulations and theoretical modeling to show that there exists a reversible conversion of energy between thermal and mechanical work in the attachment/detachment of 2D materials on/off a surface, indicating that 2D materials adhesion is fundamentally like gas adsorption rather than solid adhesion. We reveal that the underlying mechanism of this intriguing gas-like adhesion for 2D materials is the entropy difference between their freestanding and adhered states. Both the theoretical model and atomistic simulations predict that adhesion induced entropy difference increases with increasing adhesion energy and decreasing equilibrium binding distance. The present findings provide a fundamental guidance toward understanding the adhesion of 2D materials, which is important for designing 2D materials based devices and may have general implications for nanoscale efficient energy conversion.
A relative value method for measuring and evaluating cardiac reserve
Shouzhong Xiao, Xingming Guo, Xiaobo Sun, Zifu Xiao
BioMedical Engineering OnLine , 2002, DOI: 10.1186/1475-925x-1-6
Abstract: Tests were carried out on a varied group of volunteers. Four indicators were devised: (1) the increase of the amplitude of the first heart sound after accomplishing different exercise workloads, with respect to the amplitude of the first heart sound (S1)recorded at rest was defined as cardiac contractility change trend (CCCT). When the subjects completed the entire designed exercise workload (7000 J), the resulting CCCT was defined as CCCT(1); when only 1/4 of the designed exercise workload was completed, the result was defined as CCCT(1/4). (2) The ratio of S1 amplitude to S2 amplitude (S1/S2). (3) The ratio of S1 amplitude at tricuspid valve auscultation area to that at mitral auscultation area T1/M1 (4) the ratio of diastolic to systolic duration (D/S). Data were expressed as mean ± SD.CCCT(1/4) was 6.36 ± 3.01 (n = 67), CCCT(1) was 10.36 ± 4.2 (n = 33), S1/S2 was1.89 ± 0.94 (n = 140), T1/M1 was 1.44 ± 0.99 (n = 144), and D/S was 1.68 ± 0.27 (n = 172).Using indicators CCCT(1/4) and CCCT(1) may be beneficial for evaluating cardiac contractility and cardiac reserve mobilization level, S1/S2 for considering the factor for hypotension, T1/M1 for evaluating the right heart load, and D/S for evaluating diastolic cardiac blood perfusion time.Total cardiac reserve involves heart rate reserve, diastole volume reserve, systole volume reserve, coronary reserve [1], metabolic reserve [2], plasma norepinephrine reserve [3], etc. The measurement and evaluation of cardiac reserve is an important indicator of patient health. An ideal method for such an evaluation should be noninvasive, with high benefit/cost ratio, and portable for use at the bedside (for in-patients), in the clinic (for outpatients), in the field (for athletes), or even at home (for healthy or patients with mild disease).Previous studies of cardiac reserve mainly involved chronotropic incompetence, fewer involved inotropic incompetence [3-5]. It is a generally accepted concept that exercise capacity is a more p
Multi-center pragmatic studies evaluating the time indicator of cardiac perfusion reserve  [PDF]
Lin Xiong, Shouzhong Xiao, Qiang Zhou, Xianrong Wu, Zifu Xiao, Xingming Guo, Delin Lu, Wanrong Zhao, Xiaojun Wu, Xiaobo Yan, Yanxia Zhao, Jianming Liu
Journal of Biomedical Science and Engineering (JBiSE) , 2013, DOI: 10.4236/jbise.2013.61001

Background: Since the greater part of coronary blood flow takes place during the diastolic phase of each cardiac cycle, a time indicator of myocardial perfusion reserve, the ratio of diastolic to systolic duration (D/S ratio), was presented. The objective of this study was to evaluate the accuracy and precision, the biological implication, and the applications of D/S ratio. Methods: Multi-center pragmatic studies evaluating the time indicator of cardiac perfusion reserve were performed. Related experiments, clinical trials, and surveys were conducted at 5 centers. Results: The results showed that the measurement of D/S ratio is both accurate and precise; the mean values of D/S of all of the 3 species studied (human, rabbit, and rat) were greater than 1. These application studies on D/S ratio showed that a close negative correlation existed between D/S ratio and New York Heart Association Functional Classification (NYHA FC) (r = –0.659, p < 0.01); normal persons were mostly distributed at NYHA FC I and at high value of D/S ratio; the patients with cardiovascular disease were mostly at low value of D/S ratio; the difference of D/S between pregnant women with pre-eclampsia and either normal pregnant women or non-pregnant women were significant (p < 0.05); athletes had higher D/S ratio than non-athletes (2.04 ± 0.33 vs 1.82 ± 0.27, p < 0.01). Conclusions: D/S ratio has important biological implication, which is a safe, easy, reliable, and effective indicator, can be used to evaluate fitness levels, served as a pathophysiological marker for screening of cardiovascular disease (CVD), for predicting risk of cardiac events, and for evaluating the severity and prognosis of CVD.

Two kinds of contact problems in decagonal quasicrystalline materials of point group 10mm

Wang Xu Zhang Junqian Guo Xingming,

力学学报 , 2005,
Abstract: By means of the complex variable method, this investigation addresses two kinds of contact problems in decagonal quasicrystalline materials. One kind of contact problem is the frictional contact problem, the other one is the adhesive contact problem. Particularly, the explicit expressions of the analytic functions characterizing the phonon and phason fields as well as the contact stress distribution on the indenter are obtained for a flat indenter on a decagonal quasicrystalline half-space. The results show that 1) the contact stresses exhibit the real power type singularities $ - 1/2\pm \beta$ in the edge of the contact zone for the frictional contact problem with $\beta $ determined by the material constants of the quasicrystal and the static frictional factor; and 2) the contact stresses exhibit the oscillatory singularities $ - 1/2 \pm {\rm i} \v$ in the edge of the contact zone for the adhesive contact problem with $\varepsilon $ determined by the material constants of the quasicrystal.
The Effects of Free Edge Interaction-Induced Knotting on the Buckling of Monolayer Graphene
Hao-Yu Zhang,Jin-Wu Jiang,Tienchong Chang,Xingming Guo,Harold S. Park
Physics , 2015,
Abstract: Edge effects play an important role for many properties of graphene. While most works have focused on the effects from isolated free edges, we present a novel knotting phenomenon induced by the interactions between a pair of free edges in graphene, and investigate its effect on the buckling of monolayer graphene. Upon compression, the buckling of graphene starts gradually in the form of two buckling waves from the warped edges. The collision of these two buckling waves results in the creation of a knot structure in graphene. The knot structure enables the buckled graphene to exhibit two unique post-buckling characteristics. First, it induces a five-fold increase in graphene's mechanical stiffness during the buckling process. Second, the knotted structure enables graphene to exhibit a mechanically stable post-buckling regime over a large (3%) compressive strain regime, which is significantly larger than the critical buckling strain of about 0.5%. The combination of these two effects enables graphene to exhibit an unexpected post-buckling stability that has previously not been reported. We predict that numerical simulations or experiments should observe two distinct stress strain relations for the buckling of identical graphene samples, due to the characteristic randomness in the formation process of the knot structure.
Xingming Chen
Physics , 1995,
Abstract: The global structure of optically thin hot accretion disks with radial advection included has been investigated. We solve the full energy conservation equation explicitly and construct the radial structure of the disk. It is found that advection is a real cooling process and that there are two solutions co-exist for a given mass accretion rate less than a critical limit. One is fully advection cooling dominated and the other is dominated by local radiative cooling. The advection dominated accretion disks are hotter than the local cooling dominated disks; they are most probably in the two-temperature regime and effects such as electron-positron pair production and annihilation may need to be considered to study the microphysics of the hot plasma. However, the global disk structure will not be much affected by the local radiative process.
Xingming Chen
Physics , 1995, DOI: 10.1086/176008
Abstract: Cold optically thick accretion disks with hot coronae and radial advection have been investigated. Within the framework of $\alpha$-viscosity models, we assume that all the mass accretion and angular momentum transport take place in the cold disk, but that a fraction of the gravitational energy released is dissipated in the corona. Both the coronal energy dissipation and the advection heat transport have a stabilization effect on the thermal and viscous instabilities of the disk. If that more than $\sim 95$ percent of the total power is dissipated in the corona, then the locally unstable behavior of the disk is restricted to a relatively narrow spatial region and is found to lie in a small range of mass accretion rates. The global temporal variability of the disk can be very mild or may disappear, and which may be applicable to the low-frequency ($\sim 0.04$~Hz) quasi-periodic oscillations observed in black hole candidates Cyg X--1 and GRO J0422+32.
Instabilities of Advection-Dominated Accretion Flows
Xingming Chen
Physics , 1996,
Abstract: Accretion disk instabilities are briefly reviewed. Some details are given to the short-wavelength thermal instabilities and the convective instabilities. Time-dependent calculations of two-dimensional advection-dominated accretion flows are presented.
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