Force impulse

The need to integrate the fast forces analytically can be avoided by approximating it by a sequence of suitably weighted impulses but more closely spaced in time than the slow force impulses ... 

B, E, BE, force impulse selection experiments, high-energy ... 

Drop Weight or Impact Vibration Testing (IVT) IVT is a special form of forced vibration testing in which only a short force impulse acts on the structure. Figure 2 shows the system developed at the K.U. Leuven. Traffic on the bridge has only to be closed for a short time. IVT is a good compromise between AVT and FVT. 

In the lefthand circuit diagram, a piezo actuator is connected as a load. The coil (choke) protects it from rectangular switching voltages, but not from force impulses due to high peaks that can occur in the triangular current-... 

It has been demonstrated by [196] that a sequence of force impulses applied to a structure can be selected in such a way that the power spectral density of the displacement at a particular point within the structure matches the spectral density produced by earthquake ground motions as closely as desired. This result naturally suggests the possibility of using the force pulses to counteract or reduce displacements produced by earthquakes. 

Comparison of o for heavy and light particle impact 147 7.5. Dynamic correlation the forced impulse method 192... 

A way to proceed is to write down how we might perform a completely correlated calculation and see which of these ideas falls out. We shall follow this scheme and discover the Forced Impulse Method. If we wish to introduce dynamic correlation we can in principle diagonafize the many-electron... 

If the collision is truly fast enough then we may consider the interval to be extended to (1l, -1l). But unlike the analytical approximation schemes discussed before we can drive this method to convergence by stringing together consecutive short intervals, each in length. We force the impulse-like approximation to be true by choosing to be short enough hence the name of the procedure, the forced impulse method (FIM). It defines a crude time step T, ... 

Both nutrients and waste products diffuse through the liquid material. Approximately 70% of cormective tissue is composed of water, of which the ground substance is primarily responsible. Hyaluronic acid, a component of ground substance, is very hydrophilic. This aspect gives the fascia a colloid-like capacity. Intermittent or low-force impulses can create wave-like fluid mechanics that are distributed and then dissipate. Drag is the amount of resistance to morion as determined by internal molecular resistance. 

Nightingale K, Soo M, Nightingale R, Trahey G (2002) Acoustic radiation force impulse imaging in vivo demonstration of clinical feasibility. Ultrasound Med Biol 28 227-235. 

It can be seen that the elementary body s momentum change is a product of the force acting on the body and the time of its action. The product dt is called the elementary force impulse. 

Force impulse—newton X second (a force impulse produced by a force of 1 N for 1 sec)... 

In LN, the bonded interactions are treated by the approximate linearization, and the local nonbonded interactions, as well as the nonlocal interactions, are treated by constant extrapolation over longer intervals Atm and At, respectively). We define the integers fci,fc2 > 1 by their relation to the different timesteps as Atm — At and At = 2 Atm- This extrapolation as used in LN contrasts the modern impulse MTS methods which only add the contribution of the slow forces at the time of their evaluation. The impulse treatment makes the methods symplectic, but limits the outermost timestep due to resonance (see figures comparing LN to impulse-MTS behavior as the outer timestep is increased in [88]). In fact, the early versions of MTS methods for MD relied on extrapolation and were abandoned because of a notable energy drift. This drift is avoided by the phenomenological, stochastic terms in LN. 

A. Sandu and T. Schlick. Further analysis of impulse and extrapolation force splitting in molecular dynamics. J. Comp. Phys., 1998. Submitted... 

The derivation of the mollified impulse method in [7] suggests that the same integrator be used for the auxiliary problem as that used for integrating the reduced primary problem M d fdt )X = F X) between impulses. Of eourse, Ax(x) is also needed. For the partitionings + j/aiow typically used in MD, this would lead unfortunately to a matrix Ax(x) with a great many nonzeros. However, it is probably important to take into account only the fastest components of [7]. Hence, it would seem sufficient to use only the fastest forces jjj averaging calculation. 

The procedure Merge transforms the internal displacement coordinates and momenta, the coordinates and velocities of centers of masses, and directional unit vectors of the molecules back to the Cartesian coordinates and momenta. Evolve with Hr = Hr(q) means only a shift of all momenta for a corresponding impulse of force (SISM requires only one force evaluation per integration step). 

Enef Delivery Requirements Specific impulse or force... 

There are two types of impulse printers (Eig. 19). A piezoelectric ink jet propels a drop by flexing one or more walls of the firing chamber to decrease rapidly the volume of the firing chamber. This causes a pressure pulse and forces out a drop of ink. The flexing wall is either a piezoelectric crystal or a diaphragm driven by a piezoelectric incorporated into the firing chamber (Eig. 19a). Thermal impulse ink jets also propel one drop at a time, but these use rapid bubble formation to force part of the ink in a firing chamber out the orifice (Eig. 19b). 

Piezoelecttic impulse ink-jet printers ate especially sensitive to bubbles in the ink. A bubble in the firing chamber absorbs some of the comptessional force from the flexing of the chamber wall and reduces drop volume and drop velocity, thereby affecting print quaHty. Because of the limited range of motion of the crystal, bubbles ate not readily ejected, and the loss of print quaHty owing to their presence is persistent. 

Swift, H.F., Preonas, D.D., Dueweke, P.W., and Bertke, R.S., Response of Materials to Impulsive Loading, Air Force Materials Laboratory Technical Report No. AFML-TR-70-135, Wright-Paterson AFB, OH, 76 pp.. May 1970. 

Herrman, W. and Nunziato, J.W., Nonlinear Constitutive Equations, in Dynamic Response of Materials to Intense Impulsive Loading (edited by Chou, P.C. and Hopkins, A.K.), Air Force Materials Laboratory, Wright-Paterson AFB, 1973, Chap. 5. 

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