Computers Origin

Our laboratory s interest in parallel computing originated with the computational demands of our work in theoretical chemistry and biophysics. We have already discussed some of our researches in parallel computing elsewhere,and we expand and update these discussions here. 

Shenhav, B. and Lancet, D. (2004). Prospects of a computational origin-of-life endeavor. Orig. Life Evol Biosph., 34, 181-94. 

TraPPE Organic Primarily for computing Original Martin, M. G. and Siepmann, J. I. ... 

Figure 6. Measured (Brewer) and computed (original and corrected) global irradiance spectra for Lisbon on l July of 1990 (Z=48.3°, 03=312 Dobson units and Tm> =0.3.

IBM -compatible computer Originally, any personal computer compatible with the IBM line of personal computers. With the launch of IBM s proprietary micro channel architecture in the PS/2 line of computers, which replaced the AT bus, two incompatible standards emerged, and so the term became misleading. Now, it is becoming more common to use the term industry-standard computer when referring to a computer that uses the AT or ISA bus, and the term DOS computer to describe any PC that runs DOS and is based on one of the Intel family of chips. 

The result of the ordering transformation on the common node space is indicated by three vectors at the bottom of figure 3. The three vectors indicate the order in which the operations in the common node space are to be computed. Originally, the inner fc-iterator is the fastest changing iterator and the outer 2-iterator the slowest one. In the optimized result, the fastest movement is along the [50-50-1] direction, followed by the [0,-1,-2] and [1,0,0] directions. This solution corresponds to a diagonal computation of the r [] [] instances. 

The launch velocity of the debris was established as a function of the scaled cover depth and the chamber loading density, based on reports about well doeumented experiments [19-23]. For the calculation of the trajectory of the debris, based on the launch velocity and the ejection angle, the code TRAJ [24—28], a two-dimensional trajectory program for personal computers, originally developed by the U.S. Naval Surface Warfare Center, was used. However, the results from the combination of these two steps did not correspond satisfactorily with observed values. 

It is not clear whether these discrepancies between experiment and theory result from errors of experimental or computational origin. The small-cell problem is a severe test of calculational techniques it is an equally severe test of experimental techniques. 

The use of experimental X-ray vidicons, original technique of X-raying and computer image processing allowed to improve basic parameters of XTVI and to achieve higher defectoscopic sensitivity and greater thickness of X-rayed materials and products. 

The entropically driven disorder-order transition in hard-sphere fluids was originally discovered in computer simulations [58, 59]. The development of colloidal suspensions behaving as hard spheres (i.e., having negligible Hamaker constants, see Section VI-3) provided the means to experimentally verify the transition. Experimental data on the nucleation of hard-sphere colloidal crystals [60] allows one to extract the hard-sphere solid-liquid interfacial tension, 7 = 0.55 0.02k T/o, where a is the hard-sphere diameter [61]. This value agrees well with that found from density functional theory, 7 = 0.6 0.02k r/a 2 [21] (Section IX-2A). 

The original method employed was to scan eitiier the frequency of the exciting oscillator or to scan the applied magnetic field until resonant absorption occiined. Flowever, compared to simultaneous excitation of a wide range of frequencies by a short RF pulse, the scanned approach is a very time-inefficient way of recording the spectrum. Flence, with the advent of computers that could be dedicated to spectrometers and efficient Fourier transfomi (FT) algoritluns, pulsed FT NMR became the nomial mode of operation. 

Static properties of some molecules ([193,277-280]). More recently, pairs of ci s have been studied [281,282] in greater detail. These studies arose originally in connection with a ci between the l A and 2 A states found earlier in computed potential energy surfaces for C2H in symmetry [278]. Similar ci s appear between the potential surfaces of the two lowest excited states A2 and B2 iit H2S or of 82 and A in Al—H2 within C2v symmetry [283]. A further, closely spaced pair of ci s has also been found between the 3 A and 4 A states of the molecule C2H. Here the separation between the twins varies with the assumed C—C separation, and they can be brought into coincidence at some separation [282]. 

An alternative approximation scheme, also proposed by Bom and Oppenheimer [5-7], employed the straightforward perturbation method. To tell the difference between these two different BO approximation, we call the latter the crude BOA (CBOA). A main purpose of this chapter is to study the original BO approximation, which is often referred to as the crude BO approximation and to develop this approximation into a practical method for computing potential energy suifaces of molecules. 

Fig. 2. Distance classes j = 0,1, 2,... (left) are defined for an atom (central dot) by a set of radii Rj+i the right cnrves sketch the temporal evolntion of the tot il force acting on the selected atom originating from cill atoms in distance class j shown are the exact forces (solid line), their exact valnes to be computed within the multiple time step scheme (filled squares), linear force extrapolations (dotted lines), and resulting force estimates (open sqnares).

Acknowledgments. This work was supported by the Petroleum Research Fund of the American Chemical Society (grant 29566-G4), by a K STAR EPSCoR FIRST Award, and by the University of Kansas General Research Fund. The use of the Origin 2000 computer at the Kansas Center for Advanced Scientific Computing is gratefully acknowledged. 

The speed of the method comes from two sources. First, all of the macroscopic cells of the same size have exactly the same internal structure, as they are simply formed of tessellated copies of the original cell, thus each has exactly the same multipole expansion. We need compute a new multipole expansion only once for each level of macroscopic agglomeration. Second, the structure of the periodic copies is fixed we can precompute a single transfer... 

The 3D structure of a raolectile can be derived either from experiment or by computational methods. Regardless of the origin of the 3D model of the molecule under consideration, the user should alway.s be aware of how the data were obtain-... 

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