SECS—simulation and evaluation

Plan Representation in SECS. The SECS Simulation and Evaluation of Chemical Synthesis program explicitly represents its plans(2) as a list structure of goal instructions with logical connectives. A goal instruction can specify one of the following ... 

Wipke, W. T. Braun, H. Smith, G. Choplin, F. Sieber, W. "SECS — Simulation and Evaluation of Chemical Synthesis Strategy and Planning American Chemical Society Vol. 61,... 

Wipke, W. T., Brown, H., Smith, G., Choplin, F., Seber, W. SECS-Simulation and evaluation of chemical synthesis strategy and planning , ACS 61, 1977... 

Corey EJ, Wipke WT, Cramer RD, Howe WJ (1972) Computer-assisted synthetic analysis. Facile man-machine communication of chemical structure by interactive computer graphics, J Am Chem Soc 94/2 421 Wipke WT, Braun H, Smith G, Choplin F, SieberW (1977) SECS — Simulation and evaluation of chemical synthesis Strategy and planning, in Computer-assisted organic synthesis, Wipke WT, Howe WJ ed, ACS Symposium Series, p 98... 

SECS—Simulation and Evaluation of Chemical Synthesis Strategy and Planning... 

W. T. Wipke, H. Braun, G. Smith, F. Choplin, and W. Sieber. in SECS - Simulation and Evaluation of Chemical Synthesis in Computer Assisted Organic Synthesis, eds. W. T, Wipke... 

The evolution of molecular graphics (7) is described in an earlier ACS Symposium Series book (77) which acts as an interesting precursor to this present volume. Chemical reaction systems such as LHASA (Logic and Heuristics Applied to Synthetic Analysis) 18) and SECS (Simulation and Evaluation of Chemical Synthesis) (79) had long used graphics but it was some time before the first in-house, proprietary system appeared, attracting much interest in the chemical and pharmaceutical industries. This was Upjohn s Compound Information System, COUSIN 20-21). 

Simulation and Evaluation of Chemical Synthesis (SECS) was developed by Wipke and uses heuristic methods similar to LHASA but puts special emphasis on stereochemistry, topology, and energy minimization [112]. 

Wipke, W.T., Ouchi, G.I., and Krishnan, S., Simulation and Evaluation of Chemical Synthesis — SECS — Application of Artificial Intelligence Techniques, Artif. IntelL, 11, 173, 1978. 

For a synthesizer, we are reimplementing the Simulation and Evaluation of Chemical Synthesis (SECS) program on our IBM computer in collaboration with Professor Wipke, Once the program is running at Merck, we will instruct the chemists in program operation, and then ask them to code and test transforms. 

The Standard Molecular Data (SMD) format is designed to provide such an integration tool on the basis of a file format. It has been developed in the course of the CASP project (Computer Assisted Synthesis Planning) which is run by a consortium of seven German and Swiss Chemical Companies (BASF, Bayer, Ciba-Geigy, Hoechst, E Merck, Hoffmann La Roche and Sandoz). The basis of this development was the Molfile format of the earlier SECS program (4) (Simulation and Evaluation of Chemical Synthesis). 

The outline of the paper is as follows. In Sec. 1, the expression used to fit the VESUVIO data is derived. Sec. 2 describes the way in which the instrument resolution is incorporated into the data analysis. Sec. 3 describes the Monte Carlo (MC) procedure, used to test the fitting programs. In Secs. 4 to 6 the influence of instrumental effects on the results are evaluated, using MC simulations and also by comparing data taken under different experimental conditions. Sec. 4 considers the effects of the correction for the incident beam intensity. Sec. 5 considers the systematic errors generated by approximations made to incorporate the instrument resolution in the fitting programs. Sec. 6 discusses effects dependent on sample size, such as attenuation, multiple scat-... 

The principles of the Monte Carlo approach are briefly described in Sec. 5.3. It should be mentioned that a true Monte Carlo simulation does not involve any energy minimization step. Each randomly generated conformation is evaluated by applying the Metropolis criterion and is rejected or accepted without any further minimization. Furthermore, no time-dependent movements or conformational changes are investigated as is the case in MD simulations. 

Spontaneous nucleation of the type just described has been observed recently in computer simulation studies, and details of the nucleating structures have been reported,but the dependence of on T has not been studied (indeed this would be prohibitively costly at the moment). The nucleation rates in the simulation experiments can be approximately evaluated and are enormous, as is appropriate for argon and liquid metals. For instance, the observation of one nucleus forming in a sample of 5(X) atoms of a substance of atomic volume 40 cmVmol in a run of 1(X) psec implies a nucleation rate of 10 /cm sec. 

Although it was a simulation related to the cutting process, the brittle-ductile transition can be commonly evaluated by the critical depth of cut d<--Inamura et al. have developed a new simulation technique called renormalized molecular dynamics, which is able to deal with the dynamical phenomenon scaled from nanometer to micrometer. In the simulation, a defectless monocrystalline silicon was cut at the speed of 20 m/sec, the depth of cut of 1 pm, and in an absolute vacuum environment. 

To increase the applicability of state-based methods, several approaches have been developed in order to automatically generate these models from high-level input specifications (see Sec. 2). All these approaches convert one specific type of input to one specific type of state-based model. In order to be more flexible, we suggest to use an intermediate model representation, which can be generated from different kind of application-specific input, and from which different type of state-based models can be generated. Hence, different types of analytical solvers or simulators readily available can be applied for quantitative evaluation. 

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