Experiments and simulations

T. Schlick, E. Bartha, and M. Mandziuk. Biomolecular dynamics at long timesteps Bridging the timescale gap between simulation and experiments tion. Ann. Rev. Biophys. Biom. Structure, 26 181-222, 1997. 

Bond C ], K-B Wong, ] Clarke, A R Ferscht and V Daggett 1997. Characterisation of Residual Structure in the Tliermally Denatured State of Barnase by Simulation and Experiment Description of the Folding Pathway. Proceedings of the National Academy of Sciences USA 94 13409-13413. 

Historically azeotropic distillation processes were developed on an individual basis using experimentation to guide the design. The use of residue curve maps as a vehicle to explain the behavior of entire sequences of heterogeneous azeotropic distillation columns as weU as the individual columns that make up the sequence provides a unifying framework for design. This process can be appHed rapidly, and produces an exceUent starting point for detailed simulations and experiments. 

Fig. 3.1. Mental images of shoek-eompression processes vary eonsiderably depending upon the baekground and experienee of the investigator. The scientifie images are ereated from inputs from theory, numerieal simulation, and experiment. The eritieal nature of the experiment in establishing reality requires unusually eareful study of eritieal aspeets of experimental apparatus.

Here Tq are coordinates in a reference volume Vq and r = potential energy of Ar crystals has been computed [288] as well as lattice constants, thermal expansion coefficients, and isotope effects in other Lennard-Jones solids. In Fig. 4 we show the kinetic and potential energy of an Ar crystal in the canonical ensemble versus temperature for different values of P we note that in the classical hmit (P = 1) the low temperature specific heat does not decrease to zero however, with increasing P values the quantum limit is approached. In Fig. 5 the isotope effect on the lattice constant (at / = 0) in a Lennard-Jones system with parameters suitable for Ne atoms is presented, and a comparison with experimental data is made. Please note that in a classical system no isotope effect can be observed, x "" and the deviations between simulations and experiments are mainly caused by non-optimized potential parameters. 

R. Gonzalez-Cinca, L. Ramirez-Piscina, J. Casademunt, A. Hernandez-Machado, L. Kramer, T. Toth Katona, T. Borzsonyi, A. Buka. Phase field simulations and experiments of faceted growth in liquid crystals. Physica D 99 159, 1996. 

Recently the effect of intrinsic traps on hopping transport in random organic systems was studied both in simulation and experiment [72]. In the computation it has been assumed that the eneigy distribution of the traps features the same Gaussian profile as that of bulk states. 

The DML model, proposed by the present authors, exhibits a good computational efficiency and robustness in different operating conditions, but a careful examination and complete validation are essential for the model to be accepted in engineering applications. The validation presented in this section is made by comparing the results from this model with those published in the literatures, or obtained by other investigators from their simulations and experiments. 

The numerical simulations were performed at the same conditions as in Choo s experiments. It can be found from Fig. 18 that good agreements between the simulation and experiment results are achieved even at the film thickness less than 100 nm. 

SIMULATION AND EXPERIMENT RESULTS FOR ADSORPTION AND DESORPTION IN CANISTER OF AN ORVR SYSTEM... 

The validity of the model is tested against the experiment. A ISOOcc canister, which is produced by UNICK Ltd. in Korea, is used for model validation experiment. In the case of adsorption, 2.4//min butane and 2.4//min N2 as a carrier gas simultaneously enter the canister and 2.1//min air flows into canister with a reverse direction during desorption. These are the same conditions as the products feasibility test of UNICK Ltd. The comparison between the simulation and experiment showed the validity of our model as in Fig. 5. The amount of fuel gas in the canister can be predicted with reasonable accuracy. Thus, the developed model is shown to be effective to simulate the behavior of adsorption/desorption of actual ORVR system. 

The ORVR system is an important subsystem which reduces the contamination of evaporative fuel gas at gas station during the fueling. In this paper, a simulation model of adsoiption and desorption of evaporative fuel gas in canister of ORVR system is developed. From the comparison between the simulations and experiments, the validity of the developed model is verified and the dynamics can be predicted. This PDE model can be used to design the canister of ORVR system effectively for diverse climate and operating conditions. 

Prenosil, J. E. (1976) Multicomponent Steam Distillation A Comparison between Digital Simulation and Experiment. Chem. Eng. J., 12, 59-68. 

Unfortunately, it turns out that the good agreement between simulation and experiment is to some extent fortuituous - attempts aimed at reproducing differences between different polycarbonates (such as TMC-PC and BPA-PC) were less successful [186]. It is clear that the complexity of the chemical structure (Fig. 5.1) makes it very difficult to pin down the precise reasons for the successes and failures of the mapping procedure for this polymer. 

The methodology discussed previously can be applied to the study of colloidal suspensions where a number of different molecular forces and hydrodynamic effects come into play to determine the dynamics. As an illustration, we briefly describe one example of an MPC simulation of a colloidal suspension of claylike particles where comparisons between simulation and experiment have been made [42, 60]. Experiments were carried out on a suspension of AI2O3 particles. For this system electrostatic repulsive and van der Waals attractive forces are important, as are lubrication and contact forces. All of these forces were included in the simulations. A mapping of the MPC simulation parameters onto the space and time scales of the real system is given in Hecht et al. [42], The calculations were carried out with an imposed shear field. 

M. Hecht, J. Harting, M. Bier, J. Reinshagen, and H. J. Herrmann, Shear viscosity of claylike colloids in computer simulations and experiments, Phys. Rev. E 74, 021403 (2006). 

Thompson, Damien Plateau, Pierre Simonson, Thomas, Free-energy simulations and experiments reveal long-range electrostatic interactions and substrate-assisted specificity in an aminoacyl-tRNA synthetase., ChemBioChem Feb 2006, 7, 337-344. 

Fixler, D., Namer, Y., Yishay, Y. and Deutsch, M. (2006). Influence of fluorescence anisotropy on fluorescence intensity and lifetime measurement theory, simulations and experiments. IEEE Trans. Biomed. Eng. 53, 1141-52. 

Dynamics of Poly(oxyethylene) Melts Comparison of 13C Nuclear Magnetic Resonance Spin-Lattice Relaxation and Dielectric Relaxation as Determined from Simulations and Experiments. 

Comparison of Equilibrium and Dynamic Properties of Polymethylene Melts of n-C44Hso Chains from Simulations and Experiments. 

The greatest limitation of QC methods is computational expense. This expense restricts system sizes to a few hundred atoms at most, and hence, it is not possible to examine highly elaborate systems with walls that are several atomic layers thick separated by several lubricant atoms or molecules. Furthermore, the expense of first-principles calculations imposes significant limitations on the time scales that can be examined in MD simulations, which may lead to shear rates that are orders of magnitude greater than those encountered in experiments. One should be aware of these inherent differences between first-principles simulations and experiments when interpreting calculated results. 

The term D is called the fractal index and represents the packing change with distance from the centre of the floe. Computer simulation and experiments allow the value of D to be related to the mechanism of aggregation. Typical values are for ... 

The comparison of simulation and measurement data of an uncoated membrane is shown in Fig. 4.7. The temperature curves, T to T4, were measured with the on-membrane temperature sensors. The graphs of the simulated temperatures are denoted Si to S4. The temperature discrepancy between simulation and experiment was less than 5% for all sensors. The general shape of the temperature distribution was correctly modeled within measurement accuracy. It has to be noted that no additional fitting parameters were used for these simulations. 

---