Sample configuration

This method needs a highly specialized sample configuration and the sample has to be a very sharp point... 

MD, one needs to use multiple time step methods to ensure proper handling of the sprmg vibrations, and there is a possible physical bottleneck in the transfer of energy between the spring system and the other degrees of freedom which must be handled properly [199]. In MC, one needs to use special methods to sample configuration space efficiently [200, 201]. 

Thus, unlike molecular dynamics or Langevin dynamics, which calculate ensemble averages by calculating averages over time, Monte Carlo calculations evaluate ensemble averages directly by sampling configurations from the statistical ensemble. 

Simulations need a substantial number of timesteps to sample configurational states such that desired properties are represented well enough to either con —100 ps. For systems of >100 atoms, mn for 500—2,000 ps if computing resources permit. 

From a constitutive relation of the form t = t(D, ri) (here t is stress not time) it can be readily shown that, since there is no change in electric displacement in an open-circuit, thick-sample configuration, there are no secondary stresses due to electromechanical coupling. Nevertheless, the wavespeed is that of a piezoelectrically stiffened wave. 

Resistivity. Control of the resistivity of the mud and mud filtrate while drilling may be desirable to permit better evaluation of formation characteristics from electric logs. The determination of resistivity is essentially the measurement of the resistance to electrical current flow through a known sample configuration. Measured resistance is converted to resistivity by use of a cell constant. The cell constant is fixed by the configuration of the sample in the cell and is determined by calibration with standard solutions of known resistivity. The resistivity is expressed in ohm-meters. 

Often, differences in test measurements and samples configurations make comparisons difficult. The ASTM has a standard that defines the methods for stabilizing materials measurement, thus allowing relative... 

Let us leave, for a moment, the domain of discrete torsion angles and consider torsion-angle moves in a torsion continuum. Much effort has been directed to the development of efficient phase-space sampling methods for MC [17,23,37,128-138]. The simplest off-lattice move - being a pivotal move [128,131] of a single torsion angle at a time - hardly samples configuration... 

Studies of relatively slow segregation in closed sample configurations, such as the rotating drum, are perhaps the easiest granular experiments to perform by MRI. Measurements can be made with the sample stopped the process can continue to evolve between the measurements. As mentioned above, MRI is much easier to perform on stationary systems as opposed to systems undergoing motion. 

Figure 7-2. Properties of CAII active site in the COHH state (zinc-bound hydroxide and protonated His 64). (a) Superposition of a few key residues from two stochastic boundary SCC-DFTB/MM simulations with the X-ray structure [87] (colored based on atom-types) the two sets of simulations did not have any cut-off for the electrostatic interactions between SCC-DFTB and MM atoms but used different treatments for the electrostatic interactions among MM atoms group-based extended electrostatics (in yellow) and atom-based force-shift cut-off (in green). Extended electrostatics simulations sampled configurations with the protonated His 64 too close to the zinc moiety while force-shift simulations consistently sampled the out configuration of His 64 in multiple trajectories, (b) Statistics for productive water-bridges (only from two and four shown here) between the zinc bound water and His 64 with different electrostatics protocols...

Table VI. Effect of Sample Configuration on the Minimum Ignition Temperature (in Oxygen) of Cottonwood Chars...

In order to overcome the problems that can occur in sampling configurations of the unbound ligands when using a multiple topology model, we consider two types of restraining potentials. For simplicity, both restraining potentials disappear at the bound states... 

In principle, MC algorithms can be tuned for particular systems and can thus be more efficient than MD for obtaining equilibrium distributions. An interesting idea is to use MC simulations to obtain accurate initial guesses for subsequent MD simulations. Already as early as 1993, Venable and co-workers [68] used a scheme for efficiently sampling configurations of individual lipids in a mean field. These configurations were then used to develop the initial conditions for the molecular dynamic simulations. 

Table 1. Sample configuration of dynamic Hg isotope analysis in three sequences. Faraday cups are labeled L for low masses, H for high masses and Ax for the axial collector. The axial cup is the reference so its efficiency is assumed to be unity.

Atomistic computer simulations are a statistical mechanical tool to sample configurations from the phase space of the physical system of interest. The system is uniquely treated by specifying the interactions between the particles (which are usually described as being pointlike), the masses of all the particles, and the boundary conditions. The interactions are calculated either on-the-fly by an electronic structure calculation (see Section 2.2.3) or from potential functions, which have been parametrized before the simulation by fitting to the results of electronic structure calculations or a set of experimental data. In the first case, one frequently speaks of AIMD (see Section 2.2.3), although the motion of the nuclei is still treated classically. 

Figure 6.2 Common sampling configurations for spectral process analyzer systems.

Raman spectroscopy s flexible and minimally intrusive sampling configurations reduce sample pretreatment demands. Sampling interfaces can be engineered for almost any environment, but these requirements must be clearly defined before probes are built. No probe can be made to survive all environments so there may be some design trade-offs. In a noncontact system, the laser usually comes to a focus several inches... 

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