Dynamic force

Gotsmann B, Anczykowski B, Seidel C and Fuchs H 1999 Determination of tip-sample interaction forces from measured dynamic force spectroscopy curves Appl. Surf. Sc/. 140 314... 

GiessibI F J 1997 Forces and frequency shifts in atomic-resolution dynamic-force microscopy Phys. Rev. B 56 16 010... 

Bammerlin M, Luthi R, Meyer E, Baratoff A, Lu J, Guggisberg M, Gerber Ch, Howald L and Gutherodt H-J 1997 True atomic resolution on the surface of an insulator via ultrahigh vacuum dynamic force microscopy Probe Microsc. 1 3... 

VER occurs as a result of fluctuating forces exerted by the bath on the system at the system s oscillation frequency O [5]. Fluctuating dynamical forces are characterized by a force-force correlation function. The Fourier transfonn of this force correlation function at Q, denoted n(n), characterizes the quantum mechanical frequency-dependent friction exerted on the system by the bath [5, 8]. 

The breaker will interrupt only during a transient state (Figure 13.20) by which time the d.c. component responsible for the dynamic forces, has subsided. 

F, = maximum dynamic force that may develop on a fault... 

A molecular dynamics force field is a convenient compilation of these data (see Chapter 2). The data may be used in a much simplified fonn (e.g., in the case of metric matrix distance geometry, all data are converted into lower and upper bounds on interatomic distances, which all have the same weight). Similar to the use of energy parameters in X-ray crystallography, the parameters need not reflect the dynamic behavior of the molecule. The force constants are chosen to avoid distortions of the molecule when experimental restraints are applied. Thus, the force constants on bond angle and planarity are a factor of 10-100 higher than in standard molecular dynamics force fields. Likewise, a detailed description of electrostatic and van der Waals interactions is not necessary and may not even be beneficial in calculating NMR strucmres. 

The determination of the first bending critical speed is well established however, there is also concern with regard to the rotor support system s sensitivity to exciting forces. These come from unbalance and/or gas dynamic forces arising during operation in service. Operation with dirty corrosive gas will soon cause rotor unbalance. The rotor dynamics verification test is concerned with synchronous excitaticm, namely unbalance. The test must also verify that the separation margins are to specification. 

Another potential problem is due to rotor instability caused by gas dynamic forces. The frequency of this occurrence is non-synchronous. This has been described as aerodynamic forces set up within an impeller when the rotational axis is not coincident with the geometric axis. The verification of a compressor train requires a test at full pressure and speed. Aerodynamic cross-coupling, the interaction of the rotor mechanically with the gas flow in the compressor, can be predicted. A caution flag should be raised at this point because the full-pressure full-speed tests as normally conducted are not Class IASME performance tests. This means the staging probably is mismatched and can lead to other problems [22], It might also be appropriate to caution the reader this test is expensive. 

Another velocity finally appears in a system where a liquid is in contact with an interface. The interface energy 7 then works as a static driving force. This can trigger a current which is damped by a dynamic force, the viscous friction, in the case of density difference between crystal and liquid. Taking the ratio... 

After a fragment has attained a certain initial velocity, the forces acting upon it during flight are those of gravity and fluid dynamics. Fluid-dynamic forces are subdivided into drag and lift components. The effects of these forces depend on the fragment s shape and direction of motion relative to the wind. 

Overstressed piston rods due to unbalanced or dynamic forces. 

Centrifugal pumps, as do most other mechanical equipment, generate dynamic forces that must be absorbed by their foundation. The foundation should have a mass that is at least five times that of the installed pump and driver. In addition, the pump assembly must be properly affixed... 

Gravity, applied forces, and atmospheric pressure are examples of static factors that apply equally to fluids at rest or in motion. Inertia and friction are dynamic forces that apply only to fluids in motion. The mathematical sum of gravity, applied forces, and atmospheric pressure is the static pressure obtained at any one point in a fluid system at a given point in time. Static pressure exists in addition to any dynamic factors that may also be present at the same time. 

At very low frequencies the movement of the panel will be controlled by the stiffness, as inertia is a dynamic force and cannot come into effect until the panel has measurable velocity. Stiffness controls the performance of the panel at low frequencies until resonance occurs. As the driving frequency increases, the resonance zone is passed and we enter the mass-controlled area. The increase in the sound-reduction index with frequency is approximately linear at this point, and can be represented by Figure 42.8. 

Rotating machines subject to imbalance caused by turbulent or unbalanced media flow include pumps, fans, and compressors. A good machine design for these units incorporates the dynamic forces of the gas or liquid in stabilizing the rotating element. The combination of these forces and the stiffness of the rotor-support system (i.e., bearing and bearing pedestals) determine the vibration level. Rotor-support stiffness is important... 

While steady-state data provide a snapshot of the machine, dynamic or real-time data provide a motion picture. This approach provides a better picture of the dynamics of both the machine-train and its vibration profile. Data acquired using steady-state methods would suggest that vibration profiles and amplitudes are constant. However, this is not tme. All dynamic forces, including mnning speed, vary constantly in all machine-trains. When real-time data acquisition methods are used, these variations are captured and displayed for analysis. 

To minimize effects of friction and other lateral forces in the topography measurements in contact-modes AFMs and to measure topography of the soft surface, AFMs can be operated in so-called tapping mode [53,54]. It is also referred to as intermittent-contact or the more general term Dynamic Force Mode" (DFM). A stiff cantilever is oscillated closer to the sample than in the noncontact mode. Part of the oscillation extends into the repulsive regime, so the tip intermittently touches or taps" the surface. Very stiff cantilevers are typically used, as tips can get stuck" in the water contamination layer. The advantage of tapping the surface is improved lateral resolution on soft samples. Lateral forces... 

Bubble size at departure. At departure from a heated surface, the bubble size may theoretically be obtained from a dynamic force balance on the bubble. This should include allowance for surface forces, buoyancy, liquid inertia due to bubble growth, viscous forces, and forces due to the liquid convection around the bubble. For a horizontally heated surface, the maximum static bubble size can be determined analytically as a function of contact angle, surface tension, and... 

For saturated pool boiling on vertical surfaces, the Weber number (a ratio of dynamic force to the stabilizing force) alone determines the stability of a rising bubble ... 

Odorico, M., Teulon, J.-M., Bessou, T., Vidaud, C., Bellanger, L., Chen, S.-W., Qucmcncur, fi., Parot, P., and Pellequer, J.-L. (2007) Energy landscape of chelated uranyl Antibody interactions by dynamic force spectroscopy. Biophys. J. 93, 645-654. 

Dynamic Force Spectroscopy A Fokker-Planck Approach. 

Perhaps the most commonly overlooked, aspect of using SDOF approximations is the determination of the dynamic reactions for the actual member. The spring force r) in the SDOF system is not equal to the support reaction. In order to determine the dynamic reactions, the distribution of the inertia force within the member must be considered (Biggs 1964, Chapter 5). The basic approach as illustrated in Figure 6.8 is to express the dynamic forces acting on the member, or a segment of the member, in terms of the displacement and acceleration at the control point. This displacement, y(t) is determined in the solution of the time history analysis of the equivalent SDOF system,... 

For elastic behavior, an applied static force is half that of an applied dynamic force of infinitely long duration. 

The pore size distributions of the molded monoliths are quite different from those observed for classical macroporous beads. An example of pore size distribution curves is shown in Fig. 3. An extensive study of the types of pores obtained during polymerization both in suspension and in an unstirred mold has revealed that, in contrast to common wisdom, there are some important differences between the suspension polymerization used for the preparation of beads and the bulk-like polymerization process utilized for the preparation of molded monoliths. In the case of polymerization in an unstirred mold the most important differences are the lack of interfacial tension between the aqueous and organic phases, and the absence of dynamic forces that are typical of stirred dispersions [60]. 

Among the several olfactometers available on the market, our institute in 1976 ordered an olfactometer developed by Dr.Dravniek at IIT, Chicago (1), based upon the dynamic forced triangle principle. 

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