1,721,615 research outputs found
Wei Shuzi wen chao.
No full text[魏禧撰] ; 王均卿選本.書名據封面.[Wei Xi zhuan] ; Wang Junqing xuan ben.Detailed notes in vernacular field only
Cross-type optical separation of elastic oblate capsules in a uniform flow
No full textThe dynamic behavior of an elastic capsule with an initially oblate spheroidal shape during cross-type optical separation was numerically investigated. The penalty immersed boundary method was adopted for the fluid-membrane interaction, and the optical force calculation was conducted by using the ray optics method including the ray-surface intersection algorithm. The oblate elastic capsule of b/a = 0.5 with different surface Young's moduli and different initial inclination angles was considered. The oblate capsule with higher surface Young's moduli was less deformed, and was more migrated for each initial inclination angle. Unlike the oblate rigid particle, the initially inclined capsules with moderate inclination angles were similarly migrated since the oblate elastic capsule was deformed during rotation near the laser beam axis. The oblate capsules can be separated according to the surface Young's modulus, except for nearly non-inclined capsules. As the fluid velocity decreased, the migration distance increased. The maximum deformation parameter was insensitive to the fluid velocity. Furthermore, a new dimensionless number (S-ec) was introduced to predict the migration distance of the oblate elastic capsule
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
SIMULATION OF SPERM SWIMMING IN AMBIENT FLUID
No full textSperm swimming in a viscous fluid is simulated numerically by the immersed boundary method. The sperm is modeled by an elliptical head attached by a line flagellum in the present work. Both the familiar travelling-wave and the asymmetric parabola flagellum beatings are simulated. First, the simulation is validated by comparing the sperm swimming speed and the rate of working with the theoretical perturbation solutions. Then, a sperm swimming in a channel is discussed in detail. The traveling-wave beating drives the sperm to move forward, while the asymmetric beating leads the sperm to change its swimming direction. When the channel half height is less than the wavelength, the wall effect on the sperm motion becomes significant, which can be expressed by a function only of the ratio of the channel half height to the wavelength. A sperm offset from the channel centerline moves toward the near wall. The relationships of the swimming speed, the angular velocity and the rate of working with the beating parameters are also obtained
Global Gevrey hypoellipticity for the twisted Laplacian on forms
No full textWe study in this paper the global hypoellipticity property in the Gevrey category for the generalized twisted Laplacian on forms. Different from the 0-form case, where the twisted Laplacian is a scalar operator, this is a system of differential operators when acting on forms, each component operator being elliptic locally and degenerate globally. We obtain here the global hypoellipticity in anisotropic Gevrey space
Simulation of Energy Harvesting Eel by the Immersed Boundary Method
No full textIn the present study, we carry out numerical simulations of energy harvesting eel by using the immersed boundary method. Eel is modeled by a flexible filament and is placed behind a circular cylinder. We perform systematic simulations in order to explore the effects of Reynolds number. The instantaneous eel motion is analyzed under different conditions and surrounding vortical structures are identified. The flapping frequency of eel has been compared with that in case of plate alone as well as filament alone. As increasing Reynolds number, we can see that the flexible filament flaps passively by obtaining the Strouhal number of cylinder alone and filament with cylinder
Modeling and simulation of the mechanical response of biopolymer networks / y Wei Xi
No full textThe mechanical response of live cells is largely determined by the cytoskeleton, a network composed of different types of biopolymers. In addition to maintain structural integrity and stability of cells, cytoskeleton also plays important roles in the processes like intracellular transport, cell division and locomotion. Although extensive effort has been spent in the past few decades trying to study the nonlinear and viscoelastic properties of bio-filament networks both experimentally and theoretically, fundamental questions such as how thermal fluctuations of biopolymers and the deformability as well as the association/dissociation kinetics of crosslinking molecules, “gluing” individual filaments together, dictate the bulk response of a network remain unsettled.
To address these important issues, a computational framework for analyzing the mechanical behavior of biopolymer networks was developed in this thesis on the basis of continuum mechanics. Specifically, a combined finite element-Langevin dynamics(FEM-LD)method was first established to capture the influence of thermal undulations of biopolymers. The validity of this new approach was verified by comparing its results with a variety of theoretical predications. In addition, strategies for the implementation of this method in simulating the dynamic response of realistic filamentous networks have also been developed. Interestingly, it was found that entropic effect will be important when the macroscopic strain level is below ~1%,beyond which the network response will be dominated by filament elasticity.
After that, formulations taking into account the deformability and failure of crosslinking molecules, along with large deflections of individual filaments, were added to the model. It was shown that the stress-strain relationship of random biopolymer networks typically undergoes linear increase –strain hardening –stress serration –total fracture transitions due to the interplay between the bending and stretching of individual filaments and the deformation and breakage of cross-linkers. Furthermore, the network fracture energy was found to reach its minimum when the crosslinking molecules possess intermediate rotational stiffness, reflecting the fact that most of the strain energy will be stored in the distorted filaments with rigid cross-linkers while the imposed deformation will be “evenly” distributed among significantly more crosslinking molecules with high rotational compliance.
Finally, the influence of binding/unbinding kinetics of cross-linkers on the rheological response biopolymer networks was examined and three distinct regimes were identified. At high driving frequencies, the bulk network response will be governed by the mechanics of individual filaments, leading to a 3/4 exponent scaling behavior, while stress relaxation induced by the unbinding of crosslinking molecules will dominate the process at intermediate frequencies. In comparison, the collective effect of multiple dissociation of cross-linkers will result in a power-law rheology behavior (with an exponent of ~0.5) when the driving frequency is very low, in broad agreement with experimental observations.published_or_final_versionMechanical EngineeringDoctoralDoctor of Philosoph
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