The data base

Prior to a discussion of adsorption kinetic rate laws and mechanistic theories, we review the very large amount of data that has been gathered in recent years. We consider first the values reported in the literature for the sticking probabilities at zero coverage, s0, for a variety of gas—metal systems secondly, the variations of s0 with gas temperature, Tg, and surface temperature, Ts and thirdly, the dependence of s on surface coverage. 

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The data base contains provisions for a simple augmentation by up to eight additional compounds or substitution of other compounds for those included. Binary interaction parameters necessary for calculation of fugacities in liquid mixtures are presently available for 180 pairs. 

If values for the binary parameters b., in Equation (20) are available, they can be added to the data base and used in ENTH, which now includes this parameter, however, set to zero. 

In order to describe inherited stress state of weldment the finite element modelling results are used. A series of finite element calculations were conducted to model step-by-step residual stresses as well as its redistribution due to heat treatment and operation [3]. The solutions for the reference weldment geometries are collected in the data base. If necessary (some variants of repair) the modelling is executed for this specific case. 

At present, the data base used for the fit was not specially selected to avoid homologous proteins. Thus, a further improvement can be expected from using data for one of the specially prepared lists of PDB files (cf. Hobohm et al. [9]). We also expect further improvements from replacing the polynomial fits in the potential estimation procedure by piecewise cubic fits though at the moment it is not clear how to select the number of nodes needed to get a good but not overfitting approximation to the density. Finally, we are considering... 

The network model of a database system is an improvement over the hierarchical model. This model was developed in 1969 by the Data Base Task Group (DBTG) of CODASYL (Conference on Data System Languages) [8, because sometimes the re-... 

The values of the orbital exponents ( s or as) and the GTO-to-CGTO eontraetion eoeffieients needed to implement a partieular basis of the kind deseribed above have been tabulated in several journal artieles and in eomputer data bases (in partieular, in the data base eontained in the book Handbook of Gaussian Basis Sets A. Compendium for Ab initio Moleeular Orbital Caleulations, R. Poirer, R. Kari, and I. G. Csizmadia, Elsevier Seienee Publishing Co., Ine., New York, New York (1985)). 

Each of these tools has advantages and limitations. Ab initio methods involve intensive computation and therefore tend to be limited, for practical reasons of computer time, to smaller atoms, molecules, radicals, and ions. Their CPU time needs usually vary with basis set size (M) as at least M correlated methods require time proportional to at least M because they involve transformation of the atomic-orbital-based two-electron integrals to the molecular orbital basis. As computers continue to advance in power and memory size, and as theoretical methods and algorithms continue to improve, ab initio techniques will be applied to larger and more complex species. When dealing with systems in which qualitatively new electronic environments and/or new bonding types arise, or excited electronic states that are unusual, ab initio methods are essential. Semi-empirical or empirical methods would be of little use on systems whose electronic properties have not been included in the data base used to construct the parameters of such models. 

Histogram for data in Tabie 4.12. A normai distribution curve for the data, based onX and s, is superimposed on the histogram. 

Step 4 deals with physical and chemical properties of compounds and mixtures. Accurate physical and chemical properties ate essential to achieve accurate simulation results. Most simulators have a method of maintaining tables of these properties as well as computet routines for calculations for the properties by different methods. At times these features of simulators make them suitable or not suitable for a particular problem. The various simulators differ ia the number of compounds ia the data base number of methods for estimating unknown properties petroleum fractions characterized electrolyte properties handled biochemical materials present abiUty to handle polymers and other complex materials and the soflds, metals, and alloys handled. 

Aside from the fundamentals, the principal compromise to the accuracy of extrapolations and interpolations is the interaction of the model parameters with the database parameters (e.g., tray efficiency and phase eqiiilibria). Compromises in the model development due to the uncertainties in the data base will manifest themselves when the model is used to describe other operating conditions. A model with these interactions may describe the operating conditions upon which it is based but be of little value at operating conditions or equipment constraints different from the foundation. Therefore, it is good practice to test any model predictions against measurements at other operating conditions. 

Similar accuracies have been found for thick, homogeneous, complex specimens when corrections for secondary excitation are also included. With appropriate standards, total accuracies of 2% have been demonstrated. Because the determination of the lighter elements (i.e., 5 < Z< 15) are more sensitive to the uncertainties in the data base items listed above, less accuracy should be expected for these elements. 

To ensure flexibility for possible later additions or changes, the instrumentation has to be selected based on standardized subproducts using national or international norms. These standards are mainly based on the measuring areas and signal types. Typical signals for input and output to the data-based controller (DDC and PTC) are... 

Fig. 6.4. At relatively low pressures the shock speeds observed for stress waves in low density powder compacts are dominated by the crush-up of the powder toward solid density. The figure shows measured wavespeeds for a range of densities and fits to the data based on Herrmann s P-a model on Fe. Note the unusually low wavespeeds compared to solid density (after Herrmann [69H02]).

A sample page is included from many of the data bases. 

The data base contains failure rate data plus some failure mode information for process equipment - pumps, compressors, gas turbines, valves, vessels, heat exchangers etc. 

DATA BOUNDARY The data base contains failure rate data plus some failure... 

Report Cost Free to authorized users of the data base... 

The German Gesellschaft fur Reaktorsicherheit (GRS) has a private arrangement with Rheinische Westalisches Elekrizitatswerke (RWE) to compile reliability data from an operating power plant, Biblis B. The data base contains failure rate, maintenance, and operational event data. External event data (floods, earthquake, fire, etc.) are compiled through a separate utility-sponsored data base. The data base provides information on repair and maintenance, and equipment performance. 

The Swedish Thermal Power Reliability Data System (ATV) is maintained and managed by the Swedish State Power Board at Stockholm, Sweden. Engineering and reliability data have been collected from both nuclear and nonnuclear power generating plants. Nuclear data collection began in 1973. Collection of reliability data began in 1976. Over 30,000 events have been recorded in the data base. 

All data recorded in the data base have been acquired from plant records. Statistical reductions of data for generation of reports or specific end use are available. Data are currently collected from four operating plants (eight units). Time clocks have been installed on components, to record actual exposure time. Event data are available on a broad variety of safety and commercial grade components including pumps, valves, transformers, diesels, filters, tanks (vessels), and heat exchangers. 

Real-time access to the data base is possible through a data base management system. In addition to safety-related system data, data for interfacing (auxiliary) system components are also available. The data base management system provides in-depth flexibility for generation of specific output reports. Although access has been limited to members of the Swedish Utility Consortium and the Swedish Power Board Directorate, a Reliability Data Book is available with generic failure rates based primarily on this data base. 

Three reports have been issued containing IPRDS failure data. Information on pumps, valves, and major components in NPP electrical distribution systems has been encoded and analyzed. All three reports provide introductions to the IPRDS, explain failure data collections, discuss the type of failure data in the data base, and summarize the findings. They all contain comprehensive breakdowns of failure rates by failure modes with the results compared with WASH-1400 and the corresponding LER summaries. Statistical tables and plant-specific data are found in the appendixes. Because the data base was developed from only four nuclear power stations, caution should be used for other than generic application. 

The study performed by Burns and Roe (BSR) shows that valve failures constitute the component category most responsible for the shutdown of PWR and BWR plants. This Investigation, contracted with SNL for DOE, identified the principal types and causes of valve failures that led to plant trips for the period from 12/72 to 12/78. The primary sources of data for the report were searches of the data base, the monthly Gray Books, Nuclear Power Experience publications, as well as discussions with utilities, valve manufacturers, and suppliers. 

Opening segments of the IP2 PRA data analysis section describe the definitions of terms and concepts employed, the assumptions made, and limitations recognized during the data base construction. A set of 39 plant-specific component failure mode summaries established the basis for component service hour determinations, the number of failures, and the test data source for each failure mode given for each component. Generic data from WASH-1400, IEEE Std 500, and the LER data summaries on valves, pumps, and diesels were combined with plant-specific failure data to produce "updated" failure information. All the IP2 specialized component hardware failure data, both generic and updated, are contained in Table 1.5.1-4 (IP3 1.6.1-4). This table contains (by system, component, and failure mode) plant-specific data on the number of failures and service hours or demands. For some components, it was determined that specifications of the system was warranted because of its impact on the data values. 

The performance data for plug versus mix reactor were obtained. The data were collected as the inverse of qx vs inverse of substrate concentration. Table E.1.1 shows the data based on obtained kinetic data. From the data plotted in Figure E.1.1, we can minimise the volume of the chemostat. A CSTR works better than a plug flow reactor for the production of biomass. Maximum qx is obtained with a substrate concentration in the leaving stream of 12g m 3. 

The concept of the Polymat database was based on the following criteria (1) the data-base is neutral, independent of raw-material manufacturers (2) anyone can use the database (3) all the products on. the European market should, if possible, be included (4) since testing is carried out in accordance with a variety of different international standards, the relevant standard, as well as the testing conditions, is registered (5) during the search, all properties should be capable of being linked with one another as desired and (6) the sources used for the database are the technical data sheets and additional information supplied by raw-material manufacturers, and various lectures, publications, and measured data from different institutes. 

Estimates of urban NOx emissions and trends are generally limited to those provided by the developed countries which have the detailed emission Inventories. As In the case of other pollutants, the USA contributes the most on a per-country basis to the global NOx emissions per year. Because of the Inaccuracy of the data base used. It Is difficult to discern trends In these emissions. However, with new control technologies being Implemented for both stationary and mobile sources, downward trends In the developed countries may be more prevalent In the future years. Unfortunately, the opposite trend Is likely to occur In the developing countries. 

The uncertainties associated with the data base of an individual river basin are compounded when the intent is to provide a global perspective. This point is made in a recent bound volume of UNEP data in which a number of data interpretation limitations are sited. Quality of data varies from one individual reporting entity to another and the precision of the data is usually not possible to ascertain. Thus direct comparisons between data from one country, or even one laboratory to the next are not always possible. Since uncertainties associated with the data (variability, accuracy, precision, etc.) are often not specified, the significance of the data may be difficult to determine and no valid interpretation of the data may therefore be possible. It comes as no surprise that these and similar data from other data bases are often, if not usually, inadequate to establish cause and effect relationships. 

Figure 3.2. Average carbon isotopic ratios for all human, herbivore, carnivore, and omnivore bone samples from the European Holocene in the data base A Uncorrected ratios (Cu) B climate-corrected ratios (Cc). Only countries with more than 10 samples are included. For a description of the climatic correction procedure see text. 

Simulated spectra can be created by another option in the main menu of the program. Probabilities (P1-P4) are prompted from the user, depending on the model, if vaiues other than those stored with the data base are desired and a single linewidth is entered. Equation 1 and 2 are then used to simulate a spectrum which can be saved, compared to the experimental spectrum (including overlaying spectra, spectral subtractions, additions, etc.) or plotted. 

Due to its modularity, the software comes in many parts (shown in Fig. 9). The Chemkin package is composed of four important pieces the Interpreter, the Thermodynamic Data Base, the Linking File, and the Gas-Phase Subroutine Library. The Interpreter is a program that first reads the user s symbolic description of the reaction mechanism. It then extracts thermodynamic information for the species involved from the Thermodynamic Data Base. The user may add to or modify the information in the data base by input to the Interpreter. In addition to printed output, the Interpreter writes a Linking File, which contains all the pertinent information on the elements, species, and reactions in the mechanism. 

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