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Gravitational Force (gravitational + force)
Selected AbstractsAxial symmetric elasticity analysis in non-homogeneous bodies under gravitational load by triple-reciprocity boundary element methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 7 2009Yoshihiro Ochiai Abstract In general, internal cells are required to solve elasticity problems by involving a gravitational load in non-homogeneous bodies with variable mass density when using a conventional boundary element method (BEM). Then, the effect of mesh reduction is not achieved and one of the main merits of the BEM, which is the simplicity of data preparation, is lost. In this study, it is shown that the domain cells can be avoided by using the triple-reciprocity BEM formulation, where the density of domain integral is expressed in terms of other fields that are represented by boundary densities and/or source densities at isolated interior points. Utilizing the rotational symmetry, the triple-reciprocity BEM formulation is developed for axially symmetric elasticity problems in non-homogeneous bodies under gravitational force. A new computer program was developed and applied to solve several test problems. Copyright © 2008 John Wiley & Sons, Ltd. [source] A numerical study of wave structures developed on the free surface of a film flowing on inclined planes and subjected to surface shearINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 7 2006N. H. Shuaib Abstract In this work, we determine the different patterns of possible wave structures that can be observed on a thin film flowing on an inclined plane when at the free surface a shear force (surface traction) is applied. Different wave structures are obtained dependening on the selected combination of downstream and upstream boundary conditions and initial conditions. The resulting initial boundary value problems are solved numerically using the direct BEM numerical solution of the complete two-dimensional Stokes system of equations. In our numerical results, the initial discontinuous shock profiles joining uniform fluid depths are smoothed due to the two-dimensional character of the Stokes formulation, including the effect of the gravitational force as well as the interfacial surface tension force. In this way, physically feasible continuous surface profiles are determined, in which the initial uniform depths are joined by smooth moving wave structures. Numerical solutions have been attained to reproduce the different patterns of possible wave structures previously reported in the literature and extended to identify some other new structures and features defining the behaviour of the surface patterns. Copyright © 2006 John Wiley & Sons, Ltd. [source] Fluid,solid interaction problems with thermal convection using the immersed element-free Galerkin methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 1 2010Claudio M. Pita Abstract In this work, the immersed element-free Galerkin method (IEFGM) is proposed for the solution of fluid,structure interaction (FSI) problems. In this technique, the FSI is represented as a volumetric force in the momentum equations. In IEFGM, a Lagrangian solid domain moves on top of an Eulerian fluid domain that spans over the entire computational region. The fluid domain is modeled using the finite element method and the solid domain is modeled using the element-free Galerkin method. The continuity between the solid and fluid domains is satisfied by means of a local approximation, in the vicinity of the solid domain, of the velocity field and the FSI force. Such an approximation is achieved using the moving least-squares technique. The method was applied to simulate the motion of a deformable disk moving in a viscous fluid due to the action of the gravitational force and the thermal convection of the fluid. An analysis of the main factors affecting the shape and trajectory of the solid body is presented. The method shows a distinct advantage for simulating FSI problems with highly deformable solids. Copyright © 2009 John Wiley & Sons, Ltd. [source] Improving Eulerian two-phase flow finite element approximation with discontinuous gradient pressure shape functionsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2005A. H. Coppola-Owen Abstract In this paper we present a problem we have encountered using a stabilized finite element method on fixed grids for flows with interfaces modelled with the level set approach. We propose a solution based on enriching the pressure shape functions on the elements cut by the interface. The enrichment is used to enable the pressure gradient to be discontinuous at the interface, thus improving the ability to simulate the behaviour of fluids with different density under a gravitational force. The additional shape function used is local to each element and the corresponding degree of freedom can therefore be condensed prior to assembly, making the implementation quite simple on any existing finite element code. Copyright © 2005 John Wiley & Sons, Ltd. [source] Rheological properties and processability of chemically modified poly(ethylene terephthalate- co -ethylene isophthalate)ADVANCES IN POLYMER TECHNOLOGY, Issue 4 2006Masayuki Yamaguchi Abstract Rheological properties and extrusion processability have been evaluated for poly(ethylene terephthalate- co -ethylene isophthalate) (P(ET-EI)) modified by a styrene-acrylate-based copolymer with glycidyl functionality in an extruder. Adding a small amount of the modifier enhances melt elasticity to a great extent. Consequently, modified P(ET-EI) exhibits excellent processability without sagging, that is, downward deformation of extrudates by gravitational force. Considering that molecular weight and its distribution hardly change, which is confirmed by GPC measurements, generation of long-chain branches is responsible for the rheological properties and thus the processability. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 25:236,241, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20078 [source] Chemical Characteristics of Low-Fat Soymilk Prepared by Low-Speed Centrifugal Fractionation of the Raw SoymilkJOURNAL OF FOOD SCIENCE, Issue 5 2010Zhi-Sheng Liu Abstract:, Large oil,protein particles (2 to 60 ,m) were found in raw soymilk (or water extract of soybean), which was prepared in specific conditions. The large particles could be separated by sedimentation by centrifuging raw soymilk for 5 to 30 min at a low gravitational force ranging from 96 to 2410 ×,g. Chemical analysis showed that 80% to 90% of the total lipids and 30% to 40% of the total proteins were located in the precipitated fraction. The supernatant fraction had a dramatically higher protein-to-lipid ratio than the whole soymilk. The ratio of 11S/7S proteins and the ratio of 11S acidic/basic subunits were significantly (P,< 0.05) higher in the precipitate than that either in the whole soymilk or in the supernatant. Besides centrifuging conditions, other factors, including soymilk concentration, grinding method, soybean variety, and soybean storage, also significantly (P,< 0.05) affected the centrifugal fractionation. This study showed that low-speed centrifugation facilitated the separation of oil-protein particles from raw soymilk, and can be used as an innovative method for preparing low-fat soymilk and 11S protein-enriched ingredients. The findings also increased our understanding of the association or aggregation between proteins and lipids in raw soymilk after grinding. Practical Application:, Soymilk has become a popular beverage in the Western world due to its health benefits. Consumer demands for low-fat and organic foods have been increasing in the recent years. Currently, there are no alternative methods for manufacturing low-fat soymilk from whole soybeans. We found that most, if not all, of lipids in the raw soymilk were located in large particles, which could be separated by low-speed centrifugation. This centrifugal fractionation was investigated by varying processing parameters, soybean varieties, and soybean storage conditions. The approach has potential to be used for manufacturing low-fat soymilk. This study also has increased our understanding of the interactions between lipid and protein in raw soymilk. [source] Correlation equation for predicting filter coefficient under unfavorable deposition conditionsAICHE JOURNAL, Issue 5 2008You-Im Chang Abstract A new correlation equation for predicting the filter coefficient under unfavorable deposition conditions is presented. By adopting the triangular network model of using the Brownian dynamic simulation method, as the sum of four individual deposition mechanisms, e.g., the Brownian diffusion, the DLVO interactions, the gravitational force, and the interception, the correlation equation is obtained by regressing against a broad range of parameter values governing particle deposition in deep bed filtration. The new correlation equation is able to describe previous experimental results well, especially for those submicro particles with significant Brownian motion behavior. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] Influences of body posture on duration of oral swallowing in normal young adultsJOURNAL OF ORAL REHABILITATION, Issue 6 2007D. INAGAKI Summary, The primary purpose of this study was to determine whether body posture altered the duration of oral swallowing. To answer this question, we recorded electromyograms (EMGs) from the anterior tongue and suprahyoid (SH) muscles as well as laryngeal movement associated with swallowing in nine normal young subjects. The subjects swallowed a test food after receiving a signal while in four randomly set postures: upright, two inclined (60° and 30° to the horizontal), and supine positions. We measured the durations from the start to the peak and from the peak to the end of the integrated tongue and SH EMGs. We assumed that the duration from the start to the peak of the integrated SH EMG would correspond to the duration of oral swallowing. The average duration from the start to the peak of the integrated SH EMG decreased after moving from the upright to the inclined and supine positions. The decrease in the duration was statistically significant and consistent for three experimental sessions. The duration from the start to the peak of the integrated tongue EMG during swallowing tended to decrease after lying down, but not significantly. The postural changes did not affect the remaining four durations. The decrease in the duration of oral swallowing induced by lying down suggests that the gravitational force placed on the test food facilitates the swallowing reflex. Large variation in the tongue activity during swallowing among the subjects can probably be attributed to the lack of a significant decrease in the duration of the tongue activity. [source] The Tully,Fisher relation and its implications for the halo density profile and self-interacting dark matterMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2000H. J. Mo We show that the Tully,Fisher relation observed for spiral galaxies can be explained in the current scenario of galaxy formation without invoking subtle assumptions, provided that galactic-sized dark haloes have low concentrations which do not change significantly with halo circular velocity. This conclusion does not depend significantly on whether haloes have cuspy or flat profiles in the inner region. In such a system, both the disc and the halo may contribute significantly to the maximum rotation of the disc, and the gravitational interaction between the disc and halo components leads to a tight relation between the disc mass and maximum rotation velocity. The model can therefore be tested by studying the Tully,Fisher zero points for galaxies with different disc mass-to-light ratios. With model parameters (such as the ratio between disc and halo mass, the specific angular momentum of disc material, disc formation time) chosen in plausible ranges, the model can well accommodate the zero-point, slope and scatter of the observed Tully,Fisher relation, as well as the observed large range of disc surface densities and sizes. In particular, the model predicts that low surface brightness disc galaxies obey a Tully,Fisher relation very similar to that of normal discs, if the disc mass-to-light ratio is properly taken into account. About half of the gravitational force at maximum rotation comes from the disc component for normal discs, while the disc contribution is lower for galaxies with a lower surface density. The halo profile required by the Tully,Fisher relation is as concentrated as that required by the observed rotation curves of faint discs, but less concentrated than that given by current simulations of cold dark matter (CDM) models. We discuss the implication of such profiles for structure formation in the Universe and for the properties of dark matter. Our results cannot be explained by some of the recent proposals for resolving the conflict between conventional CDM models and the observed rotation-curve shapes of faint galaxies. If dark matter self-interaction (either scattering or annihilation) is responsible for the shallow profile, the observed Tully,Fisher relation requires the interaction cross-section ,X to satisfy ,,X|v|,/mX,10,16 cm3 s,1 GeV,1, where mX is the mass of a dark matter particle. [source] Gravity and the quantum vacuum inertia hypothesisANNALEN DER PHYSIK, Issue 8 2005A. Rueda Abstract In previous work it has been shown that the electromagnetic quantum vacuum, or electromagnetic zero-point field, makes a contribution to the inertial reaction force on an accelerated object. We show that the result for inertial mass can be extended to passive gravitational mass. As a consequence the weak equivalence principle, which equates inertial to passive gravitational mass, appears to be explainable. This in turn leads to a straightforward derivation of the classical Newtonian gravitational force. We call the inertia and gravitation connection with the vacuum fields the quantum vacuum inertia hypothesis. To date only the electromagnetic field has been considered. It remains to extend the hypothesis to the effects of the vacuum fields of the other interactions. We propose an idealized experiment involving a cavity resonator which, in principle, would test the hypothesis for the simple case in which only electromagnetic interactions are involved. This test also suggests a basis for the free parameter ,(,) which we have previously defined to parametrize the interaction between charge and the electromagnetic zero-point field contributing to the inertial mass of a particle or object. [source] Experimental study of rill bank collapseEARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2007Jovan R. Stefanovic Abstract Rill bank collapse is an important component in the adjustment of channel morphology to changes in discharge and sediment flux. Sediment inputs from bank collapse cause abrupt changes in flow resistance, flow patterns and downstream sediment concentrations. Generally, bank retreat involves gradual lateral erosion, caused by flow shear stress, and sudden bank collapse, triggered by complex interactions between channel flow and bank and soil water conditions. Collapse occurs when bank height exceeds the critical height where gravitational forces overcome soil shear strength. An experimental study examined conditions for collapse in eroding rill channels. Experiments with and without a deep water table were carried out on a meandering rill channel in a loamy sand and sandy loam in a laboratory flume under simulated rainfall and controlled runon. Different discharges were used to initiate knickpoint and rill incision. Soil water dynamics were monitored using microstandpipes, tensiometers and time domain reflectometer probes (TDR probes). Bank collapse occurred with newly developed or rising pre-existing water tables near rill banks, associated with knickpoint migration. Knickpoint scour increased effective bank height, caused positive pore water pressure in the bank toe and reduced negative pore pressures in the unsaturated zone to near zero. Matric tension in unsaturated parts of the bank and a surface seal on the ,interrill' zone behind the bank enhanced stability, while increased effective bank height and positive pore water pressure at the bank toe caused instability. With soil water contents >35 per cent (sandy loam) and >23 per cent (loamy sand), critical bank heights were 0·11,0·12 m and 0·06,0·07 m, respectively. Bank toe undercutting at the outside of the rill bends also triggered instability. Bank displacement was quite different on the two soils. On the loamy sand, the failed block slid to the channel bed, revealing only the upper half of the failure plane, while on the sandy loam the failed block toppled forwards, exposing the failure plane for the complete bank height. This study has shown that it is possible to predict location, frequency and magnitude of the rill bank collapse, providing a basis for incorporation into predictive models for hillslope soil loss or rill network development. Copyright © 2006 John Wiley & Sons, Ltd. [source] The molecular chaperone HSP47 rapidly senses gravitational changes in myoblastsGENES TO CELLS, Issue 11 2006Asami Oguro Skeletal muscle unloading induced by spaceflight or bed rest leads to muscle atrophy. It is unclear how muscle atrophy is caused and how muscles respond to microgravity. We addressed the response of collagen and its chaperone system to gravitational forces. We show here that expression of HSP47, a collagen-specific molecular chaperone, responds to gravitational changes, including microgravity and hypergravity in vitro and in vivo. By using the method hindlimb suspension of rats, which mimics microgravity conditions, we demonstrated that the expression of Hsp47 mRNA decreased within 1 day and the mRNA levels of collagen types I and IV were subsequently reduced. In contrast, hypergravity stimulated HSP47 expression. HSP47 and collagen types I and IV were localized intracellularly in the endoplasmic reticulum and/or Golgi apparatus of myoblasts, as expected. Intriguingly, Hsp47 mRNA levels in cultured myoblasts increased significantly with hypergravity treatment at 40G for 2 h, and decreased with microgravity treatment at almost 0G for 1,2 h. Collagen mRNA levels were also altered, although changes were slower and less pronounced compared with those for HSP47. The gravity-regulated HSP47 may play a role in the maintenance of the extracellular matrix by modulating collagen production at the primary stage of adaptation. [source] | ||||||||||||||||