Software, computers

Commercially available software for TA apparatus performs a number of tasks (Table 2.3). 

General (DTA, DSC, TG, TMA, DMA) Variation of signal amplitude Signal and temperature calibration Accumulation and storage of data Baseline smoothing Display and calculation of transition temperatures Display of multiple curx es Curve subtraction Derivative TA curve Baseline correction  

DSC Display and calculation of transition enthalpy Heat capacity determination Purity calculation Reaction rate calculation Temperature modulation 

TG Conversion from mass change to % mass change Reaction rate calculation Heating rate control harmonized with mass change 

DMA Thermal expansion coefficient calculation Display of stress-strain curve Display of creep curve Display of stress-relaxation curve Arrhenius plot and associated parameters Calculation and display of master curve Heating rate control harmonized with sample deformation 

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Projection radiography is widely used for pipe inspection and corrosion monitoring. Film digitisation allows a direct access to the local density variations by computer software. Following to a calibration step an interactive estimation of local wall thickness change based on the obtained density variation is possible. The theoretical model is discussed, the limitations of the application range are shown and examples of the practical use are given. The accuracy of this method is compared to results from wall thickness measurements with ultrasonic devices. 

P.C. Jurs, Computer Software Applications in Chemistry, John Wiley Sons, New York, 1996. 

Recent years have witnessed an increase in the number of people using computational chemistry. Many of these newcomers are part-time theoreticians who work on other aspects of chemistry the rest of the time. This increase has been facilitated by the development of computer software that is increasingly easy to use. It is now so easy to do computational chemistry that calculations can be performed with no knowledge of the underlying principles. As a result, many people do not understand even the most basic concepts involved in a calculation. Their work, as a result, is largely unfocused and often third-rate. 

Most chemists want to avoid the paper-and-pencil type of work that theoretical chemistry in its truest form entails. However, keep in mind that it is precisely for this kind of painstaking and exacting research that many Nobel prizes have been awarded. This book will focus almost exclusively on the knowledge needed to effectively use existing computer software for molecular modeling. 

Computational results can be related to thermodynamics. The result of computations might be internal energies, free energies, and so on, depending on the computation done. Likewise, it is possible to compute various contributions to the entropy. One frustration is that computational software does not always make it obvious which energy is being listed due to the dilferences in terminology between computational chemistry and thermodynamics. Some of these differences will be noted at the appropriate point in this book. 

Although equations 5.13 and 5.14 appear formidable, it is only necessary to evaluate four summation terms. In addition, many calculators, spreadsheets, and other computer software packages are capable of performing a linear regression analysis based on this model. To save time and to avoid tedious calculations, learn how to use one of these tools. For illustrative purposes, the necessary calculations are shown in detail in the following example. 

This is a more difficult equation to solve than that for the solubility of Pb(I03)2 in distilled water, and its solution is not immediately obvious. A rigorous solution to equation 6.34 can be found using available computer software packages and spreadsheets. 

Many of the topics covered in analytical chemistry benefit from the availability of appropriate computer software. In preparing this text, however, I made a conscious decision to avoid a presentation tied to a single computer platform or software package. Students and faculty are increasingly experienced in the use of computers, spreadsheets, and data analysis software their use is, I think, best left to the personal choice of each student and instructor. 

The assessment of the contribution of a product to the fire severity and the resulting hazard to people and property combines appropriate product flammabihty data, descriptions of the building and occupants, and computer software that includes the dynamics and chemistry of fires. This type of assessment offers benefits not available from stand-alone test methods quantitative appraisal of the incremental impact on fire safety of changes in a product appraisal of the use of a given material in a number of products and appraisal of the differing impacts of a product in different buildings and occupancies. One method, HAZARD I (11), has been used to determine that several commonly used fire-retardant—polymer systems reduced the overall fire hazard compared to similar nonfire retarded formulations (12). 

There are also laser-scanning confocal microscopes rapidly overtaking the TSM as a means of confocal microscopy. There is also a computer software program that produces a "confocal" image by recogni2ing the shapes of out-of-focus detail, ie, halos, and subtracting these from the in-focus image. 

A fundamental requirement for obtaining a patent is defining an advance, development, or invention which is within those classes of "subject matter" which the law of the United States regards as patentable. Two classes of patentable subject matter, ie, computer software and biotechnology, are the subject of relatively new and evolving law. However, other types of subject matter rest on fairly certain ground as to patentabiUty. Examples of patents directed to various types of subject matter are described in the following. 

J. Pagenberg and B. Geissler, Eicense Agreements Patents, Utility Models, Know-How, Computer Software, Cad Heymaims, 1989. 

Mixtures can be identified with the help of computer software that subtracts the spectra of pure compounds from that of the sample. For complex mixtures, fractionation may be needed as part of the analysis. Commercial instmments are available that combine ftir, as a detector, with a separation technique such as gas chromatography (gc), high performance Hquid chromatography (hplc), or supercritical fluid chromatography (96,97). Instmments such as gc/ftir are often termed hyphenated instmments (98). Pyrolyzer (99) and thermogravimetric analysis (tga) instmmentation can also be combined with ftir for monitoring pyrolysis and oxidation processes (100) (see Analytical methods, hyphenated instruments). 

Because of recent advances ia hardware, particularly detector hardware, and computer software, x-ray instmments have become very powerful. Problems that could not be solved several years ago can be solved with the newer iastmmentation. Also the instmments have become much more automatic so that the mote routine problems can be solved much faster than a few years ago. 

X-Ray Spectrometers. An x-ray spectrometer is an instmment that measures the fluorescence spectra of samples. The associated computer software then determines the quaUtative and quantitative elemental composition of the samples from the resulting spectra. 

Control Cont Molecular Arrow Computer Software ... 

Fig. 1. Layers of programming with engineering computation software.

To quantitate proteins from staining, a densitometer aided by computer software is used to evaluate band areas of samples compared to band areas of a standard curve. Amido black, Coomassie Brilliant Blue, and silver stains are all appHcable for use in quantification of proteins. 

Measurements and Audits. The enabling element of continuous improvement is measurement. An old rule of thumb says that increased accuracy in measuring an energy use ultimately yields a reduction in use equal to 10% of the increased closure of the balance. A basic principle of economics is that any thing that is free is used in excess, ie, an unmetered electrical use is bigger than expected by at least 10%. Metering of the cost elements at each unit in a chemical plant provides effective accountabhity. Measurements should be linked via computer software to production as weh as to weather to result in maximum feedback. 

Rigorous error bounds are discussed for linear ordinary differential equations solved with the finite difference method by Isaacson and Keller (Ref. 107). Computer software exists to solve two-point boundary value problems. The IMSL routine DVCPR uses the finite difference method with a variable step size (Ref. 247). Finlayson (Ref. 106) gives FDRXN for reaction problems. 

For further information, see Refs. 90, 175, 255, and 293. For information on computer software, see the Annual CEP Software Direc-toiy (Ref. 8) and other articles (Refs. 7 and 175). 

The use of impedance electrochemical techniques to study corrosion mechanisms and to determine corrosion rates is an emerging technology. Elec trode impedance measurements have not been widely used, largely because of the sophisticated electrical equipment required to make these measurements. Recent advantages in micro-elec tronics and computers has moved this technique almost overnight from being an academic experimental investigation of the concept itself to one of shelf-item commercial hardware and computer software, available to industrial corrosion laboratories. 

The development of the probabilistic design approach, as already touched on, includes elements of probability theory and statistics. The introductory statistical methods discussed in Appendix I provide a useful background for some of the more advanced topics covered next. Wherever possible, the application of the statistical methods is done so through the use of realistic examples, and in some cases with the aid of computer software. 

The choice of variables remaining with the operator, as stated before, is restricted and is usually confined to the selection of the phase system. Preliminary experiments must be carried out to identify the best phase system to be used for the particular analysis under consideration. The best phase system will be that which provides the greatest separation ratio for the critical pair of solutes and, at the same time, ensures a minimum value for the capacity factor of the last eluted solute. Unfortunately, at this time, theories that predict the optimum solvent system that will effect a particular separation are largely empirical and those that are available can be very approximate, to say the least. Nevertheless, there are commercially available experimental routines that help in the selection of the best phase system for LC analyses, the results from which can be evaluated by supporting computer software. The program may then suggest further routines based on the initial results and, by an iterative procedure, eventually provides an optimum phase system as defined by the computer software. 

The determination of the critical GLC is a trial and error computation of GLC s due to various wind speeds, atmospheric stabilities and downwind distances. The maximum value obtained from these procedures is the critical GLC. Because of the number of computations involved, calculations should be performed on the computer. Software simulation is also necessary to calculate GLC s due to multiple stack cases. Wind direction is an additional variable that must be taken into account with multiple stact cases. 

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