mechanics

摘要： Purpose This study aimed to investigate if changing the midsole bending stiffness of athletic footwear can affect the onset of lower limb joint work redistribution during a prolonged run.Methods Fifteen trained male runners(10-km time of<44 min)performed 10-km runs at 90%of their individual speed at lactate threshold(i.e.,when change in lactate exceeded 1 mmol/L during an incremental running test)in a control and stiff shoe condition on 2 occasions.Lower limb joint kinematics and kinetics were measured using a motion capture system and a force-instrumented treadmill.Data were acquired every 500 m.Results Prolonged running resulted in a redistribution of positive joint work from distal to proximal joints in both shoe conditions.Compared to the beginning of the run,less positive work was performed at the ankle(approximately 9%;p≤0.001)and more positive work was performed at the knee joint(approximately 17%;p≤0.001)at the end of the run.When running in the stiff shoe condition,the onset of joint work redistribution at the ankle and knee joints occurred at a later point during the run.Conclusion A delayed onset of joint work redistribution in the stiff condition may result in less activated muscle volume,because ankle plantar flexor muscles have shorter muscles fascicles and smaller cross-sectional areas compared to knee extensor muscles.Less active muscle volume could be related to previously reported decreases in metabolic cost when running in stiff footwear.These results contribute to the notion that footwear with increased stiffness likely results in reductions in metabolic cost by delaying joint work redistribution from distal to proximal joints.

摘要： The importance of perturbation theory in many fields is very clear through almost a century or even more. Its importance was exemplified in solving many problems in physics and other applied fields. A great deal of applications arose in dealing with eigenvalue problems especially in quantum mechanics in conjunction with the field of atomic physics. Accordingly, it came to our mind to write a brief review article on the subject. At the beginning, we give some important definitions to do with various eigenvalue problems;then we introduce concepts that have to do with perturbation theory and the techniques used in such a theory, beginning with the algebraic perturbation theory giving a good number of examples from the literature on the use of the theory in solving integral equation, algebraic equations and differential equations. Few applications are then given in applied fields such as classical mechanics, quantum mechanics and fluid mechanics. Finally, a concluding discussion is given which is related to the use of the theory.

摘要： Both biological and engineering approaches have contributed significantly to the recent advance in the field of mechanobiology.Collaborating with biologists,bio-engineers and materials scientists have employed the techniques stemming from the conventional semiconductor industry to rebuild cellular milieus that mimic critical aspects of in vivo conditions and elicit cell/tissue responses in vitro.Such reductionist approaches have help to unveil important mechanosensing mechanism in both cellular and tissue level,including stem cell differentiation and proliferation,tissue expansion,wound healing,and cancer metastasis.In this mini-review,we discuss various microfabrication methods that have been applied to generate specific properties and functions of designer substrates/devices,which disclose cell-microenvironment interactions and the underlying biological mechanisms.In brief,we emphasize on the studies of cell/tissue mechanical responses to substrate adhesiveness,stiffness,topography,and shear flow.Moreover,we comment on the new concepts of measurement and paradigms for investigations of biological mechanotransductions that are yet to emerge due to on-going interdisciplinary efforts in the fields of mechanobiology and microengineering.

摘要： Objective:The objective of this study was to investigate the mechanics of ventricular anchor for heart valve repair or replacement.Methods:Thirteen anchors were designed based on six geometric parameters of the anchor teeth:width,thickness,root length,radius of curvature,tip angle,and tip length.Finite element method was applied to simulate the process of the anchor compressing into a sheath.The Von-Mises strain,peak pulling force,and bite depth were evaluated.An experiment was performed to validate the simulation.Results:The maximum Von-Mises strain was at the contact region of the anchor in a sheath where the teeth were compressed against one another and were distorted.The maximum strain increased with an increase in tooth width,thickness,radius of curvature and tip angle.The peak pulling force increased as tooth thickness and width increased,and radius of curvature decreased.Both the radial and axial bite depths increased with an increase in the tip length at the tip length
3 mm.The radial bite depth increased with an increase in the radius of curvature.Conclusion:1)the maximum strain depends primarily on the tooth width,thickness,radius of curvature and tip angle;2)the peak pulling force depends primarily on the tooth width,thickness,radius of curvature;3)the axial bite depth depends primarily on the tip length at the tip length
3 mm.The radial bite depth depends on the radius of curvature and the tip length at the tip length>3 mm.The study provides guidance for ventricular anchor design.

摘要： The quantum object is in general considered as displaying both wave and particle nature. By particle is understood an item localized in a very small volume of the space, and which cannot be simultaneously in two disjoint regions of the space. By wave, to the contrary, is understood a distributed item, occupying in some cases two or more disjoint regions of the space. The quantum formalism did not explain until today the so-called “collapse” of the wave-function, i.e. the shrinking of the wave-function to one small region of the space, when a macroscopic object is encountered. This seems to happen in “which-way” experiments. A very appealing explanation for this behavior is the idea of a particle, localized in some limited part of the wave-function. The present article challenges the concept of particle. It proves in the base of a variant of the Tan, Walls and Collett experiment, that this concept leads to a situation in which the particle has to be simultaneously in two places distant from one another—situation that contradicts the very definition of a particle. Another argument is based on a modified version of the Afshar experiment, showing that the concept of particle is problematic. The concept of particle makes additional difficulties when the wave-function passes through fields. An unexpected possibility to solve these difficulties seems to arise from the cavity quantum electrodynamics studies done recently by S. Savasta and his collaborators. It involves virtual particles. One of these studies is briefly described here. Though, experimental results are needed, so that it is too soon to conclude whether it speaks in favor, or against the concept of particle.

摘要： Modern but not entirely coordinated foundations of quantum physics are described in the book “The Quantum Challenge”. The difficulties and philosophical problems of this area of science are discussed. Discussions of many great scientists who paved the foundations of the physics of micro-world are described. These discussions are still urgent. The diversity of interpretations of the wave function, light interference, uncertainty principle, complementarity and completeness of micro-world description are stressed in this book. Difficulties and problems of quantum mechanics described in this book allowed the author of the present communication to propose a new approach based on the infinitely small metrics The difference of infinitesimals in two geometries allows one to explain W. Heisenberg’s uncertainty principle. Interconnection of the images in these geometries is possible with the help of Weierstrass integral transform. This approach allows one to describe the interference of light behind the screen with slits as a sum of the corpuscular component (Weierstrass transform) and the wave component (Fourier transform).

摘要： The incompatibility of Orthodox Quantum Mechanics with philosophical realism poses a serious challenge to scientists upholding such a philosophical doctrine. The desire to find a solution to this and other conceptual problems that quantum mechanics confronts has motivated many authors to propose alternative versions to Orthodox Quantum Mechanics. One of them is the Spontaneous Projection Approach, a theory grounded on philosophical realism. It has been introduced in previous papers and, with a few exceptions, it yields experimental predictions coincident with those of Orthodox Quantum Mechanics. One of these exceptions is analyzed in detail. The difference in predictions becomes apparent in a suggested experiment which could put both theories to the test.

摘要： The goal is to define Quantum Gravity Value by combination between our new concept about physics energy behaviour [1] and Einstein relativity’s Theory [2]. Our theory is based on the existence of a relationship between energy and vacuum! So it can be considered that the energy is a function of the vacuum ratio (v). Therefore, we can say that vacuum ratio constitutes a part of space-time. With simple mathematical formula, we can easily obtain the equation of the Energy Vacuum. This gives us the distribution of the energy Vacuum (E) into two parts are inversely proportional from our vacuum energy diagram, the effective energy that the sole responsible for Curvature of space-time fabric, and the lost energy that the responsible of the Gravitational waves [3]. From these equations, we can find that the relationship with Energy and Vacuum ratio is linear which are compatible with Quantum Mechanics laws and Maintains the energy conservation principle. It is also observed that the equations obtained through our theory are Combining relativity and Quantum Mechanics into one continuum. If we take the equations of our theory, we can easily obtain from Curvature of Space-Time Fabric, the Gravity value equation which equals to the square root of energy multiply times the square of the vacuum ratio. On other hand, a curvature matrix and a Time Dilation’s Circle are proposed, which gives us a new method to facilitate the calculations of the parameters involved in the Space-Time Curvature.

摘要： Finding that in the formula of expansion of a function into a series of wave-like functions ?the coefficients are its Fourier transforms, if existed, we deduce mathematically all the principles and hypothesis that illustrated physicists utilized to build quantum mechanics a century ago, beginning with the duality particle-wave principle of Planck and including the Schrödinger equations. By the way, we find a simple Fourier transform relation between Dirac momentum and position bras and a useful permutation relation between operators in phase and Hilbert spaces. Moreover, from the found particle-wave duality formula we prove and obtain again essentially by mathematical analysis all the laws of wave optics concerning reflections, refractions, polarizations, diffractions by one or many identical 3D objects with various forms and dimensions.

摘要： More than a century ago, M. Sagnac realized an experiment with light rays, whose results according to him invalidated the theory of Relativity and validated the hypothesis of the Aether. This hypothesis of the ether was not retained by the scientific community, and relativistic explanations were given to the results of the Sagnac experiment. But these relativistic explanations remain open to criticism because they are various and because the prediction may differ depending on whether the observer’s frame of reference is at rest or in motion. The neo-Newtonian mechanics proposes a new explanation which leads to demonstrate the formula with P the light path. In order to verify this new interpretation, it is proposed to do again the Sagnac experiment with a slightly different light path, a square-shaped path. The results should be at least 30% lower than those predicted by the theory of Relativity. In which case, the relativistic explanation would be questioned.