180 research outputs found
Improving the Data Warehouse Architecture Using Design Patterns
Data warehousing is an important part of the enterprise information system. Business intelligence (BI) relies on data warehouses to improve business performance. Data quality plays a key role in BI. Source data is extracted, transformed, and loaded (ETL) into the data warehouses periodically. The ETL operations have the most crucial impact on the data quality of the data warehouse. ETL-related data warehouse architectures including structure-oriented layer architectures and enterprise-view data mart architecture were studied in the literature. Existing architectures have the layer and data mart components but do not make use of design patterns; thus, those approaches are inefficient and pose potential problems. This paper relays how to use design patterns to improve data warehouse architectures
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Continuous System Simulation Languages: Design Principles and Implementation Techniques ; CU-CS-034-73
Continuous system simulation languages are very high level programming languages which facilitate modelling and simulation of systems characterized by ordinary and partial differential equations. This paper discusses design principles and implementation techniques for continuous system simulation languages. Following a brief introduction to very high level languages, design principles for continuous system simulation languages are presented. These principles are illustrated by examples from the Continuous System Modelling Program (CSMP) and the Partial Differential Equation Language (PDEL). A typical program in each language in included. Batch and interactive implementation techniques for continuous system simulation languages are discussed. The classical batch implementation technique is to provide a preprocessor which translates the simulation language into an algorithmic language such as FORTRAN or PL/1. The PL/1 preprocessor is described as a useful language for the implementation of very high level language translators. The final section of the paper presents an interactive implementation technique which interfaces a batch program processor to interactive graphics display and updating routines. In this manner, efficient simulation code is interfaced to flexible interaction routines. In addition, the batch processor is preserved intact, thus requiring only one implementation of the language for both batch and interactive applications
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Semantic Models of Parameter Passing ; CU-CS-016-73
This paper presents semantic models of four parameter passing mechanisms utilized in various algebraic programming languages: Call by Value, Copy Restore, Call By Reference, and Call By Name. The correspondence between actual parameter values and formal parameter names is established by use of an environment directory and a denotation component. The environment directory associates each identifier in the program with a unique name, and the denotation component associates unique names with information concerning the value of the identifier denoted by the unique name. The various parameter passing mechanisms are first described informally. A tree structured model of each parameter passing mechanism is then presented. The paper concludes with a discussion of formalizing the models
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Random Entry Searching of Binary Trees ; CU-CS-035-73
A new technique for searching lexically ordered binary trees is analyzed. Searching starts at a randomly selected node, rather than at the root node. Searching progresses in the usual manner until the item of interest is found, or until a leaf node is encountered. Leaf nodes contain pointers to the root of the tree. If the desired item is not found upon first encounter of a leaf node, the tree is reentered at the root, and the usual binary search follows. If the desired item is not found upon second encounter of a leaf node, the item is not in the tree. The average number of probes to retrieve an item of information from a balanced binary tree having 2^k-1 nodes, for integer k, is shown to be bounded above by k+1, as k becomes large. Thus, on the average, this technique requires at most 2 more probes than conventional searching. The maximum number of probes is shown to be 2k-1, as compared to k for conventional proving. However, the maximum number of probes occurs with probability s^-(k+1), as compared to probability 1/2 for conventional searching. Computer simulation and analytical analysis of the random searching strategy are both presented, with complete agreement of results
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The Formal Definition of a Parameter Passing Language ; CU-CS-010-72
The formal definition of the syntax and semantics of A Parameter Passing Language (APPL) is presented. APPL is a simple, nested structure language which permits the communication of parameters between a main program and a subroutine using call by reference, call by value, or call by name. The methodology and techniques of the Vienna Definition Language are used in the formalization of APPL. The syntactic definition of APPL consists of phrase structure grammars for concrete and abstract representations of valid APPL programs. The semantic definition of APPL is in terms of an abstract machine which interprets abstract programs. The machine specification consists of the machine state components and a trasition function that maps states into successor states. The semantics of various parameter passing mechanisms is thus formalized as the sequenceof machine states assumed by the abstract machine during the interpretation of abstract programs
A selected ion flow tube study of the reactions of gas-phase cations with PSCl3
A selected ion flow tube was used to investigate the positive ion chemistry of thiophosphoryl chloride, PSCl. Rate coefficients and ion product branching ratios have been determined at room temperature for reactions with nineteen cations ; HO, CF, CF, NO, NO, SF, SF, CF, O, HO, NO, O, CO, CO, N, N, Ar, F and Ne (in order of increasing recombination energy). Complementary data described in the previous paper have been obtained for this molecule via the observation of threshold photoelectron photoion coincidences. For ions whose recombination energies are in the range 10-22 eV, comparisons are made between the product ion branching rations of PSCl from photoionisation and from ion-molecule reactions. In most instances, the data from the two experiments are well correlated, suggesting that long-range charge transfer is the dominant mechanism for these ion-molecule reactions ; the agreement is particularly good for the atomic ions Ar, F and Ne. Some reactions (e.g. O + PSCl), however, exhibit significant differences; short-range charge transfer must then be occurring following the formation of an ion-molecule complex. For ions whose recombination energies are less than 10 eV (i.e. HO, CF, CF and NO), reactions can only occur via a chemical process in which bonds are broken and formed, because the recombination energy of the cation is less than the ionisation energy of PSCl
Comparison of 4- and 5-beam acoustic Doppler current profiler configurations for measurement of turbulent kinetic energy
Acoustic Doppler current profilers (ADCPs) are commonly used to assess mean currents and turbulence at energetic sites. Since 2014, five-beam ADCP configurations have become more common, but conventional analysis of turbulence properties is still based on the four-beam Janus configuration. We use measurements from a single site to investigate improved estimates of turbulent kinetic energy (TKE) that are made possible by the addition of a fifth vertical beam. We conclude that four-beam estimates of TKE are suitable in most cases, and exhibit lower variance than five-beam estimates, but are more prone to contamination by wave activity
Surface Analysis Insight Note: Observations relating to photoemission peak shapes, oxidation state, and chemistry of titanium oxide films
It is common practice to describe the coordination of metal atoms in a binding configuration with their nearest neighbors in terms of oxidation state, a measure by which the number of electrons redistributed between atoms forming chemical bonds. In XPS terms, change to an oxidation state is commonly inferred by correlating photoemission signal with binding energy. The assumption, when classifying photoemission signals into distinct spectral shapes, is that a distribution of intensities shifted to lower binding energy is evidence of a reduction in oxidation state. In this Insight note, we raise the prospect that changes in photoemission peak shape may occur without obvious changes, determined by XPS in stoichiometry for a material. It is well known that TiO2 measured by XPS yields reproducible Ti 2p photoemission peaks. However, on exposing TiO2 to ion beams, Ti 2p photoemission evolves to complex distributions in intensity, which are particularly difficult to analyze by traditional fitting of bell‐shaped curves to these data. For these reasons, in this Insight note, a thin film of TiO2 deposited on a silicon substrate is chosen for analysis by XPS and linear algebraic techniques. Alterations in spectral shapes created from modified TiO2, which might be interpreted as the change in oxidation state, are assessed in terms of relative proportions of titanium to oxygen. It is found through detailed analysis of spectra that quantification by XPS, using procedures routinely used in practice, is not in accord with the typical interpretations of photoemission shapes. The data processing methods used and results presented in this work are of particular relevance to elucidating fundamental phenomena governing the surface evolution of materials‐enabled energy processes where cyclic/non‐steady usage changes the nature of bonding, especially in the presence of contaminants
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