Left ventricular ejection force and impulse: Noninvasive assessment using Doppler ultrasound

Dark matter could meet its nemesis on Earth

Introduction. One of the high points of elementary calculus is the derivation of Kepler's empirically deduced laws of planetary motion from Newton's Law of Gravity and his second law of motion. However, the standard treatment of the subject in calculus books is flawed for at least three reasons that I think are important. First, Newton's Laws are used to derive a differential equation for the displacement vector from the Sun to a planet; say the Earth. Then it is shown that the displacement vector lies in a plane, and if the base point is translated to the origin, the endpoint traces out an ellipse. This is said to confirm Kepler's first law, that the planets orbit the sun in an elliptical path, with the sun at one focus. However, the alert student may notice that the identical argument for the displacement vector in the opposite direction would show that the Sun orbits the Earth in an ellipse, which, it turns out, is very close to a circle with the Earth at the center. That would seem to provide aid and comfort to the Church's rejection of Galileo's claim that his heliocentric view had more validity than their geocentric one. Second, by placing the sun at the origin, the impression is given that either the sun is fixed, or else, that one may choose coordinates attached to a moving body, inertial or not. However, Newton's equations in their usual form hold precisely in inertial coordinates. Furthermore, it is an immediate consequence of Newton's Laws that the center of gravity of the two bodies can serve as the origin of an inertial coordinate system. One then finds that both the Earth and the Sun describe elliptical paths with a focus at the center of gravity of the pair. Third, by considering only the displacement vector, the treatment misses an opportunity to present one of the greatest recent triumphs of Newton's derivation of Kepler's Laws: the discovery of extrasolar planets during the past decade, none of which has been observed directly, but whose existence and orbital parameters have been deduced by detecting and analyzing the motion of the stars that they orbit. Two other considerations make the correct way of treating the subject particularly desirable. First, the current treatment for the displacement vector could be left as is, and only a little algebra is needed to show that the same vector referred to the center of gravity is a constant scalar multiple of the one referred to the sun. Second, it connects with an exciting area of current research in astronomy where the methods of elementary calculus have direct application. The purpose of this note is to spell out the slight modifications to the standard treatment of Kepler's Laws that are needed to obtain the additional and accurate information, and to provide a user's guide to the website http://exoplanets.org where a list of all the extrasolar planets discovered so far is maintained and constantly updated. The Basic Equations. Let r(t) be a (3-dimensional) vector function of the parameter t, and suppose that r(t) satisfies the differential equation

Nonlinear drag force has been a research frontier in complex gas-solid systems. The literature has reported that the commonly-used drag correlations often overestimate drag force and, thus, cause unrealistic homogeneous flow structures in gas-solid fluidized beds of fine particles. For solving this problem, the structure-dependent drag model, derived from energy-minimization multi-scale approach, is used in discrete simulations of fluid catalytic cracking particles in a small riser. The gas phase is dealt with by computational fluid dynamics. Particles are considered as a discrete phase and described by Newton’s second law of motion. Gas-particle phases are coupled according to Newton’s third law of motion. Simulations show that use of structure-dependent drag model results in drag reduction, the effect of which is not so apparent as that in simulations of the two fluid model. The particle clustering tendency, however, is more distinct and leads to more heterogeneous flow structures in riser flow with a much greater amplitude of outlet solid flux fluctuations. Moreover, the behaviors of particle and gas back-mixing can be captured in the present simulations, which was supported by past simulations and experimental data. The simulation time resolution is discussed. The spring constant can be artificially brought down for safe setting of larger time step when modelling the collision process between fine particles with a higher calculation load. To appropriately mimic the continuous decay of van der Waals force may, however, need a much smaller time step. There is also an obvious effect of space resolution on simulations. When using a grid size smaller than 3 times the particle diameter, the simulated clusters turn extraordinarily large, and the effect of gas-solid back-mixing turns insignificant.

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Two-dimensional nonlinear dynamics of an axially moving viscoelastic beam with time-dependent axial speed

Intramolecular (13)C kinetic isotope effects were determined for the dimerization of methacrolein. Trajectory studies accurately predict the isotope effects and support an origin in Newton's second law of motion, with no involvement of zero-point energy or transition state recrossing. Atomic motion reaction coordinate diagrams are introduced as a way to qualitatively understand the selectivity.

Bubble size distributions (BSDs) near a reference electrode (RE) in aqueous glycerol solutions of an electrolyte NaCl have been investigated under various gas superficial velocities (Us). BSD and voltage reading of the solution were measured by using a high-speed digital camera and a pH/voltage meter, respectively. The results show that bubble size (b) increases with liquid viscosity (μc) and Us. Self-similarity is seen and can be described by the log-normal form of the continuous number frequency distribution. The result shows that b controls the voltage reading in each solution. As b increases, the voltage increases because of gas bubbles interrupting their electrolyte paths in the solutions. An analysis of bubble rising velocity reveals that Stokes' Law should be used cautiously to describe the system. The fundamental equation for bubble formation was developed via Newton's second law of motion and shown to be the function of three dimensionless groupsWeber number, Bond number, and Capillary number. Af...

The equation F = ma, shorthand for Newtion's second law of motion, is the 1 + 1 = 2 of classical mechanics. The equation seems obvious and straightforward. It appears simply to translate an ordinary experience into measurable terms: push something and it moves.

In pattern recognition, clustering is a powerful technique that can be used to find the identical group of objects from a given dataset. It has proven its importance in various domains such as bioinformatics, machine learning, pattern recognition, document clustering and so on. But, in clustering, it is difficult to determine the optimal cluster centers in a given set of data. So, in this paper, a new method called magnetic charged system search (MCSS) is applied to determine the optimal cluster centers. This method based on the behavior of charged particles. The proposed method employs the electric force and magnetic force to initiate the local search while Newton second law of motion is employed for global search. The performance of the proposed algorithm is tested on several datasets which are taken from UCI repository and compared with the other existing methods like K-Means, GA, PSO, ACO and CSS. The experimental results prove the applicability of the proposed method in clustering domain.

Inkjet printers are being developed to enable printing on surfaces other than paper, such as building walls, the ground, and clothes. The challenge for printers that print on surfaces other than paper is the formation of a liquid film after the ink has landed on the surface. On uneven surfaces other than paper, the droplets are affected by gravity and their shape is distorted, resulting in a reduction in image quality. To improve these problems, it is necessary to understand how high viscosity ink used in printing spread on the substrate. In this paper, it is examined whether the droplet motion model based on Newton’s second law of motion can explain the motion of highly viscous droplets. The results show that it is necessary to consider models that take into account changes in droplet shape and velocity over time and dynamic changes when the Reynolds number is large, and to establish a method for estimating Boc when the receding contact angle does not move.

Newton’s second law of motion is a fundamental principle in classical mechanics that forms the cornerstone of dynamic analysis in rock mechanics.

In this paper, the transverse vibration of an initially stressed viscoelastic moving string is considered. The string material is assumed to obey the fractional differentiation constitutive law. The governing equation is obtained by Newtonian second law of motion and reduced to a set of nonlinear differential integral equations by using Galerkin’s method. The differential integral equation system that contains fractional derivatives is then truncated to a finite dimensional one and solved numerically by using Runge-Kutta method and some other numerical manipulations. Finally, the numerical results are analyzed. The effects of elastic and viscoelastic parameters on the moving string and the variations of the nonlinear vibration with the changing of transport velocity and some other terms are investigated by numerical experiments.

Newton’s Second Law of Motion

Influencing Cyber Laboratory Conceptual Change Through Laboratory Learning

The Rapid Evaluation of Potential Fields in Particle Systems presents a group of algorithms for the computation of the potential and force fields in large-scale systems of particles that are likely to revolutionize a whole class of computer applications in science and engineering. In many areas of scientific computing, from studying the evolution of galaxies, to simulating the behavior of plasmas and fluids, to modelling chemical systems, a numerical scheme is used to follow the trajectories of a collection of particles moving in accordance with Newton's second law of motion in a field generated by the whole ensemble. Extending the earlier work of Rokhlin, Greengard has developed general, numerically stable methods for evaluating all pairwise interactions in linear time, a great improvement over the quadratic time required by the naive approach, and significantly better than any other proposed alternative. The "Rokhlin-Greengard" algorithm promises to make previously prohibitive simulations feasible, with speedups of three to four orders of magnitude in a system of a million particles. Moreover, the algorithm is well-suited for vector and parallel machines, and should make full use of their capabilities. The author presents his work with great clarity, and demonstrates the superiority of his methods both by mathematical analysis and by the results of numerical experiments. The Rapid Evaluation of Potential Fields in Particle Systems is a 1987 ACM Distinguished Dissertation.