Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Abstraction

  • atom abstraction
  • chart abstraction
  • data abstraction
  • h abstraction
  • h-atom abstraction
  • hydride abstraction
  • hydrogen abstraction
  • hydrogen atom abstraction
  • hydrogen-atom abstraction
  • proton abstraction
  • record abstraction
  • water abstraction

  • Terms modified by Abstraction

  • abstraction form
  • abstraction level
  • abstraction reaction
  • abstraction tool

  • Selected Abstracts

    A Screen Space Quality Method for Data Abstraction

    J. Johansson
    Abstract The rendering of large data sets can result in cluttered displays and non-interactive update rates, leading to time consuming analyses. A straightforward solution is to reduce the number of items, thereby producing an abstraction of the data set. For the visual analysis to remain accurate, the graphical representation of the abstraction must preserve the significant features present in the original data. This paper presents a screen space quality method, based on distance transforms, that measures the visual quality of a data abstraction. This screen space measure is shown to better capture significant visual structures in data, compared with data space measures. The presented method is implemented on the GPU, allowing interactive creation of high quality graphical representations of multivariate data sets containing tens of thousands of items. [source]

    Mechanism of Hydride Abstraction by Cyclopentadienone-Ligated Carbonylmetal Complexes (M = Ru, Fe)

    Megan K. Thorson
    Abstract Cyclopentadienone-ligated ruthenium complexes, such as Shvo's catalyst, are known to oxidize reversibly alcohols to the corresponding carbonyl compounds. The mechanism of this reaction has been the subject of some controversy, but it is generally believed to proceed through concerted transfer of proton and hydride, respectively, to the cyclopentadienone ligand and the ruthenium center. In this paper we further study the hydride transfer process as an example of a coordinatively directed hydride abstraction by adding quantitative understanding to some features of this mechanism that are not well understood. We find that an oxidant as weak as acetone can be used to re-oxidize the intermediate ruthenium hydride without catalyst re-oxidation becoming rate-limiting. Furthermore, C,H cleavage is a significantly electrophilic event, as demonstrated by a Hammett reaction parameter of , = ,0.89. We then describe how the application of our mechanistic insights obtained from the study have enabled us to extend the ligand-directed hydride abstraction strategy to include a rare example of an iron(0) oxidation catalyst.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Asymmetric Abstraction and Allocation: The Israeli-Palestinian Water Pumping Record

    GROUND WATER, Issue 1 2009
    Mark Zeitoun
    The increased attention given to international transboundary aquifers may be nowhere more pressing than on the western bank of the Jordan River. Hydropolitical analysis of six decades of Israeli and Palestinian pumping records reveals how ground water abstraction rates are as asymmetrical as are water allocations. The particular hydrogeology of the region, notably the variability in depth to ground water, variations in ground water quality, and the vulnerability of the aquifer, also affect the outcome. The records confirm previously drawn conclusions of the influence of the agricultural lobby in maintaining a supply-side water management paradigm. Comparison of water consumption rates divulges that water consumed by all sectors of the farming-based Palestinian economy is less than half of Israeli domestic consumption. The overwhelming majority of "reserve" flows from wet years are sold at subsidized rates to the Israeli agricultural sector, while very minor amounts are sold at normal rates to the Palestinian side for drinking water. An apparent coevolution of water resource variability and politics serves to explain increased Israeli pumping prior to negotiations in the early 1990s. The abstraction record from the Western Aquifer Basin discloses that the effective limit set by the terms of the 1995 Oslo II Agreement is regularly violated by the Israeli side, thereby putting the aquifer at risk. The picture that emerges is one of a transboundary water regime that is much more exploitative than cooperative and that risks spoiling the resource as it poisons international relations. [source]

    Effect of Evidence-Based Acute Pain Management Practices on Inpatient Costs

    John M. Brooks
    Objectives. To estimate hospital cost changes associated with a behavioral intervention designed to increase the use of evidence-based acute pain management practices in an inpatient setting and to estimate the direct effect that changes in evidence-based acute pain management practices have on inpatient cost. Data Sources/Study Setting. Data from a randomized "translating research into practice" (TRIP) behavioral intervention designed to increase the use of evidence-based acute pain management practices for patients hospitalized with hip fractures. Study Design. Experimental design and observational "as-treated" and instrumental variable (IV) methods. Data Collection/Extraction Methods. Abstraction from medical records and Uniform Billing 1992 (UB92) discharge abstracts. Principal Findings. The TRIP intervention cost on average $17,714 to implement within a hospital but led to cost savings per inpatient stay of more than $1,500. The intervention increased the cost of nursing services, special operating rooms, and therapy services per inpatient stay, but these costs were more than offset by cost reductions within other cost categories. "As-treated" estimates of the effect of changes in evidence-based acute pain management practices on inpatient cost appear significantly underestimated, whereas IV estimates are statistically significant and are distinct from, but consistent with, estimates associated with the intervention. Conclusions. A hospital treating more that 12 patients with acute hip fractures can expect to lower overall cost by implementing the TRIP intervention. We also demonstrated the advantages of using IV methods over "as-treated" methods to assess the direct effect of practice changes on cost. [source]

    Thiophenol-Mediated 1,5-Hydrogen Atom Abstraction: Easy Access to Mono- and Bicyclic Compounds

    Florent Beaufils
    Abstract A thiophenol-mediated method for cyclization of alkynes is described. The reaction cascade involves the intermolecular addition of a phenylthiyl radical to a terminal triple bond generating an alkenyl radical, followed by a 1,5-hydrogen atom transfer and a 5- exo- trig radical cyclization. This very efficient tin-free procedure allows one to prepare highly functionalized cyclopentane derivatives as well as fused bicyclic and spirocyclic compounds from easily available precursors. During this cyclization process, a phenylthio moiety is incorporated into the final cyclized products. This functionalization is particularly attractive for further transformation of the products. [source]

    Abstraction and Embodiment: Yoko Ono and the Weaving of Global Musical Networks

    Barry Shank
    First page of article [source]

    Neuropsychological Deficits in Sober Alcoholics: Influences of Chronicity and Recent Alcohol Consumption

    ALCOHOLISM, Issue 2 2000
    William W. Beatty
    Background: The relationships between severity of neuropsychological (NP) deficits and quantity and duration of alcoholic drinking remain controversial. Eckardt et al. (1998) proposed that NP deficits can be observed only if chronicity of alcohol abuse equals or exceeds 10 years. In this study we tested the hypothesis of Eckardt et al. and reexamined the relationship of NP performance and alcohol consumption. Methods: One hundred sixty-two alcoholics and 165 controls completed a NP test battery at least 3 weeks after the alcoholics attained sobriety. Chronicity varied from 4 to 9 years for 55 alcoholics and from 10 to 33 years for the remaining 107. Results: Compared to controls, both groups of alcoholics were impaired on the Shipley Vocabulary and Abstraction tests and on two versions of the Digit Symbol test, but there was no difference between the two alcoholic groups on any measure. Regression analyses that controlled for age and education showed that chronicity predicted less than 0.5% of the variance on NP measures. By contrast, a measure of recent alcohol consumption, the Quantity-Frequency Index, contributed significantly (approximately 5% of the variance) to the prediction of alcoholics'NP performance. Conclusions: These data provide weak support for a dose effect relationship between degree of NP impairment and level of alcoholic drinking in the past 6 months but no evidence for an influence of chronicity. [source]

    Cationic Polymerization of 2-Vinylthiophene by Chloroarylmethanes as Surface Initiators on Silica and Consecutive Hydride Abstraction by Acceptors

    Susanne Höhne
    Abstract Summary: 2-Vinylthiophene (2-VT) has been cationically polymerized using chloroarylmethane derivatives as the surface polymerization initiator on silica. By applying this procedure a soluble fraction of poly(vinylthiophene) (PVT) and PVT/silica composites can be simultaneously synthesized. The mass balance of the products (soluble fraction and hybrid particle fraction) depends significantly on temperature and 2-VT/silica ratio. The hydride abstraction reaction of PVT both in solution and immobilized on silica particle surface has been studied using 2,3-dichloro-5,6-dicyano-1,4-quinone (DDQ), tetrachloro-1,4-quinone (chloranile,=,ClA) and triphenylmethylium as reagents. The transformation process of PVT towards conjugated polymers has been studied with UV-vis spectroscopy and ESR spectroscopy. Cyclic voltammetry shows that chloranil is complexated with the formed polymer. Radical formation increases with increasing degree of conversion. The soluble fraction of the conjugated PVT sections formed is capable of reacting with each other as evidenced by GPC data. Structure of PVT/silica and resulting hybrid materials have been investigated by solid state 13C {1H} CP MAS NMR-spectroscopy showing a reaction of methine and methylene hydrogen atoms after treatment with DDQ or chloranil as hydride acceptors. For all poly-(2-vinylthiophene)/hydride acceptor systems studied, chloranil has been found to be the best reagent for the transformation of PVT towards conjugated polymers. Transformation of PVT in poly(2-ethinylthiophene) (PET) and PVT-PET copolymers. [source]

    Features as an Abstraction for Designer Convenience in the Design of Ships

    Joshua D. Summers
    ABSTRACT This paper reports on a research effort involving design of a class of ships , nuclear submarines. It focuses on the use of features as a means of design abstraction, and it is found that a principal motivation for the use of features in this design environment is the convenience of the early stage submarine designer. To support this argument, a review of feature research is presented. Experiments in the development of feature catalogs are described, and implementation through two generations of feature-based submarine CAD systems are discussed. The architecture of the feature-based submarine CAD systems includes the use of Microsoft Foundation Classes (MFC), the ACIS geometric modeler, and user interfaces which store/recall hierarchical submarine feature information easily. Strong connections to object-oriented programming and object-oriented databases are recognized. Conclusions are drawn regarding the use of features for ship designer convenience and regarding support provided by hierarchical, parameterized features for other means of design automation. [source]

    The Ladder of Abstraction: A Framework for the Systematic Classification of Democratic Regime Types

    POLITICS, Issue 2 2003
    Siobhan Daly
    This article argues that classificatory problems such as parochialism, misclassification, degreeism and conceptual stretching underpin the classification of democratic regime types. This is due to the safeguarding of the parliamentary/presidential dichotomy as a framework for the classification and comparison of democratic types of regime. Drawing upon Giovanni Sartori's ladder of abstraction, types of democratic regime are classified as part of a hierarchy of concepts. This approach enables scholars to avoid classificatory pitfalls as it facilitates the methodological expansion of the conceptual framework for the classification of democratic regime types. Therefore, democratic regime types are more conducive to systematic comparative research. [source]

    ChemInform Abstract: Cyclodimerization of an Oxoboryl Complex Induced by trans Ligand Abstraction.

    CHEMINFORM, Issue 43 2010
    Holger Braunschweig
    Abstract The abstraction of Br from (I) induces instant cyclodimerization to the ionic compound (III). [source]

    Dimethyl Phosphite Mediated Hydrogen Atom Abstraction: A Tin-Free Procedure for the Preparation of Cyclopentane Derivatives.

    CHEMINFORM, Issue 51 2005
    Florent Beaufils
    No abstract is available for this article. [source]

    Hydrogen-Atom Abstraction from Methane by Stoichiometric Vanadium,Silicon Heteronuclear Oxide Cluster Cations

    Dr. Xun-Lei Ding
    Abstract Vanadium,silicon heteronuclear oxide cluster cations were prepared by laser ablation of a V/Si mixed sample in an O2 background. Reactions of the heteronuclear oxide cations with methane in a fast-flow reactor were studied with a time-of-flight (TOF) mass spectrometer to detect the cluster distribution before and after the reactions. Hydrogen abstraction reactions were identified over stoichiometric cluster cations [(V2O5)n(SiO2)m]+ (n=1, m=1,4; n=2, m=1), and the estimated first-order rate constants for the reactions were close to that of the homonuclear oxide cluster V4O10+ with methane. Density functional calculations were performed to study the structural, bonding, electronic, and reactivity properties of these stoichiometric oxide clusters. Terminal-oxygen-centered radicals (Ot.) were found in all of the stable isomers. These Ot. radicals are active sites of the clusters in reaction with CH4. The Ot. radicals in [V2O5(SiO2)1,4]+ clusters are bonded with Si rather than V atoms. All the hydrogen abstraction reactions are favorable both thermodynamically and kinetically. This work reveals the unique properties of metal/nonmetal heteronuclear oxide clusters, and may provide new insights into CH4 activation on silica-supported vanadium oxide catalysts. [source]

    Competitive Hydrogen-Atom Abstraction versus Oxygen-Atom and Electron Transfers in Gas-Phase Reactions of [X4O10].+ (X=P, V) with C2H4

    Nicolas Dietl Dipl.-Chem.
    Why so different? The comparison of the reaction of "bare" [P4O10].+ and [V4O10].+ with ethene by mass-spectrometric and computational studies permits insight into mechanistic aspects of the competition between CH bond activation and oxygen-atom and electron transfers. Whereas [P4O10].+ reacts by homolytic CH bond cleavage and electron transfer, the isostructural [V4O10].+ shows only oxygen-atom transfer (see picture). [source]

    Generation of Cationic [Zr-{tert -Butyl Enolate}] Reactive Species: Methyl Abstraction versus Hydride Abstraction

    Bing Lian Dr.
    Abstract Treatment of the neutral methyl,Zr,enolate [Cp2Zr(Me){O(tBuO)CCMe2}] (1) with one equivalent of B(C6F5)3 or [HNMe2Ph][B(C6F5)4] as a methyl abstractor in THF at 0,°C leads to the selective formation of the free ion pair complex [Cp2Zr(THF){O(tBuO)CCMe2}]+,[anion], (2) (anion=MeB(C6F5)3,, B(C6F5)4,), which is relevant to the controlled polymerization of methacrylates. Cation 2 rapidly decomposes at 20,°C in THF with release of one equivalent of isobutene to form the cationic Zr,carboxylate species [Cp2Zr(THF)(O2CiPr)]+ (3), through a proposed intramolecular proton transfer process from the tert -butoxy group to the enolate. The reaction of 1 with one equivalent of B(C6F5)3 or [HNMe2Ph][B(C6F5)4] in CH2Cl2 leads to the direct, rapid formation of the dimeric ,-isobutyrato,Zr dicationic species [{Cp2Zr[,-(O2CiPr)]}2]2+ (4), which gives 3 upon dissolution in THF. Contrastingly, when [Ph3C][B(C6F5)4] is used to generate the cationic Zr,enolate species from 1 in CD2Cl2, a 15:85 mixture of dicationic complexes 4 and [{Cp2Zr[, -(O2CC(Me)CH2)]}2]2+[B(C6F5)4] (5 -[B(C6F5)4]2) is obtained quantitatively. The formation of 5 is proposed to arise from initial hydride abstraction from a methyl enolate group by Ph3C+, as supported by the parallel production of Ph3CH, and subsequent elimination of methane and isobutene. In addition to standard spectroscopic and analytical characterizations for the isolated complexes 2,5, complexes 4 and 5 have also been structurally characterized by X-ray diffraction studies. [source]

    Reviving Inert Knowledge: Analogical Abstraction Supports Relational Retrieval of Past Events

    Dedre Gentner
    Abstract We present five experiments and simulation studies to establish late analogical abstraction as a new psychological phenomenon: Schema abstraction from analogical examples can revive otherwise inert knowledge. We find that comparing two analogous examples of negotiations at recall time promotes retrieving analogical matches stored in memory,a notoriously elusive effect. Another innovation in this research is that we show parallel effects for real-life autobiographical memory (Experiments 1,3) and for a controlled memory set (Experiments 4 and 5). Simulation studies show that a unified model based on schema abstraction can capture backward (retrieval) effects as well as forward (transfer) effects. [source]

    Humor, Abstraction, and Disbelief

    Elena Hoicka
    Abstract We investigated humor as a context for learning about abstraction and disbelief. More specifically, we investigated how parents support humor understanding during book sharing with their toddlers. In Study 1, a corpus analysis revealed that in books aimed at 1-to 2-year-olds, humor is found more often than other forms of doing the wrong thing including mistakes, pretense, lying, false beliefs, and metaphors. In Study 2, 20 parents read a book containing humorous and non-humorous pages to their 19-to 26-month-olds. Parents used a significantly higher percentage of high abstraction extra-textual utterances (ETUs) when reading the humorous pages. In Study 3, 41 parents read either a humorous or non-humorous book to their 18-to 24-month-olds. Parents reading the humorous book made significantly more ETUs coded for a specific form of high abstraction: those encouraging disbelief of prior utterances. Sharing humorous books thus increases toddlers' exposure to high abstraction and belief-based language. [source]

    Emergence explained: Abstractions: Getting epiphenomena to do real work,

    COMPLEXITY, Issue 1 2006
    Russ Abbott
    First page of article [source]

    Situation agents: agent-based externalized steering logic

    Matthew Schuerman
    Abstract We present a simple and intuitive method for encapsulating part of agents' steering and coordinating abilities into a new class of agents, called situation agents. Situation agents have all the abilities of typical agents. In addition, they can influence the steering decisions of any agent, including other situation agents, within their sphere of influence. Encapsulating steering logic into moving agents is a powerful abstraction which provides more flexibility and efficiency than traditional informed environment approaches, and works with many of the current steering methodologies. We demonstrate our proposed approach in a number of challenging scenarios. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Towards closing the analysis gap: Visual generation of decision supporting schemes from raw data

    T. May
    Abstract The derivation, manipulation and verification of analytical models from raw data is a process which requires a transformation of information across different levels of abstraction. We introduce a concept for the coupling of data classification and interactive visualization in order to make this transformation visible and steerable for the human user. Data classification techniques generate mappings that formally group data items into categories. Interactive visualization includes the user into an iterative refinement process. The user identifies and selects interesting patterns to define these categories. The following step is the transformation of a visible pattern into the formal definition of a classifier. In the last step the classifier is transformed back into a pattern that is blended with the original data in the same visual display. Our approach allows in intuitive assessment of a formal classifier and its model, the detection of outliers and the handling of noisy data using visual pattern-matching. We instantiated the concept using decision trees for classification and KVMaps as the visualization technique. The generation of a classifier from visual patterns and its verification is transformed from a cognitive to a mostly pre-cognitive task. [source]

    A Screen Space Quality Method for Data Abstraction

    J. Johansson
    Abstract The rendering of large data sets can result in cluttered displays and non-interactive update rates, leading to time consuming analyses. A straightforward solution is to reduce the number of items, thereby producing an abstraction of the data set. For the visual analysis to remain accurate, the graphical representation of the abstraction must preserve the significant features present in the original data. This paper presents a screen space quality method, based on distance transforms, that measures the visual quality of a data abstraction. This screen space measure is shown to better capture significant visual structures in data, compared with data space measures. The presented method is implemented on the GPU, allowing interactive creation of high quality graphical representations of multivariate data sets containing tens of thousands of items. [source]

    Adaptive structured parallelism for distributed heterogeneous architectures: a methodological approach with pipelines and farms

    Horacio González-Vélez
    Abstract Algorithmic skeletons abstract commonly used patterns of parallel computation, communication, and interaction. Based on the algorithmic skeleton concept, structured parallelism provides a high-level parallel programming technique that allows the conceptual description of parallel programs while fostering platform independence and algorithm abstraction. This work presents a methodology to improve skeletal parallel programming in heterogeneous distributed systems by introducing adaptivity through resource awareness. As we hypothesise that a skeletal program should be able to adapt to the dynamic resource conditions over time using its structural forecasting information, we have developed adaptive structured parallelism (ASPARA). ASPARA is a generic methodology to incorporate structural information at compilation into a parallel program, which will help it to adapt at execution. ASPARA comprises four phases: programming, compilation, calibration, and execution. We illustrate the feasibility of this approach and its associated performance improvements using independent case studies based on two algorithmic skeletons,the task farm and the pipeline,evaluated in a non-dedicated heterogeneous multi-cluster system. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    The effect of uncontrolled concurrency on model checking

    Donna M. Carter
    Abstract Correctness of concurrent software is usually checked by techniques such as peer code reviews or code walkthroughs and testing. These techniques, however, are subject to human error, and thus do not achieve an in-depth verification of correctness. Model-checking techniques, which can systematically identify and verify every state that a system can enter, are a powerful alternative method for verifying concurrent systems. However, the usefulness of model checking is limited because the number of states for concurrent models grows exponentially with the number of processes in the system. This is often referred to as the ,state explosion problem.' Some processes are a central part of the software operation and must be included in the model. However, we have found that some exponential complexity results due to uncontrolled concurrency introduced by the programmer rather than due to the intrinsic characteristics of the software being modeled. We have performed tests on multimedia synchronization to show the effect of abstraction as well as uncontrolled concurrency using the Promela/SPIN model checker. We begin with a sequential model not expected to have exponential complexity but that results in exponential complexity. In this paper, we provide alternative designs and explain how uncontrolled concurrency can be removed from the code. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    A framework for performance analysis of Co-Array Fortran

    Bernd Mohr
    Abstract Co-Array Fortran (CAF) is a parallel programming extension to Fortran that provides a straightforward mechanism for representing distributed memory communication and, in particular, one-sided communication. Although this integration of communication primitives with the language improves programmer productivity, this new level of abstraction makes the analysis of CAF performance mode difficult. This situation is due, in part, to a lack of tools for the analysis of CAF applications. In this paper, we present an extension to the KOJAK toolkit based on a source-to-source translator that supports performance instrumentation, data collection, trace generation, and performance visualization of CAF applications. We illustrate this approach with a performance visualization of a CAF version of the Halo kernel benchmark using the VAMPIR event trace visualization tool. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    On the modelling of publish/subscribe communication systems

    R. Baldoni
    Abstract This paper presents a formal framework of a distributed computation based on a publish/subscribe system. The framework abstracts the system through two delays, namely the subscription/unsubscription delay and the diffusion delay. This abstraction allows one to model concurrent execution of publication and subscription operations without waiting for the stability of the system state and to define a Liveness property which gives the conditions for the presence of a notification event in the global history of the system. This formal framework allows us to analytically define a measure of the effectiveness of a publish/subscribe system, which reflects the percentage of notifications guaranteed by the system to subscribers. A simulation study confirms the validity of the analytical measurements. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Security Maintenance Mediation: a technology for preventing unintended security breaches

    Roger (Buzz) KingArticle first published online: 4 DEC 200
    Abstract Web-resident information is becoming ,smarter', in the sense that emerging technology will support the annotation of it with ontological terms, which will be used to locate and reuse information. This will pose a great security risk in the form of unintended breaches (as distinct from deliberate invasions). Web-resident information will be far more readily available and relevant, thus causing inadvertent releases of secure information to potentially cause it to be diffusely spread across the Internet. Then as this information is iteratively transformed and integrated with other information, it will become irretrievable and potentially used in a myriad of unpredictable ways. The problem is that ontological annotations, while making information more understandable in its original form, do not provide a means for easily capturing the complex semantics of information that has been transformed via abstraction, aggregation, and integration. This demands the development of a semantically rich way of specifying ,views' of Web information, to which security controls can be attached. Also needed is a way for users of secure information to easily and voluntarily blend,and thereby propagate,security controls as information is transformed. Information mediators designed by collaborative teams of experts are proposed as the vehicle for wrapping information, so that at each step of reuse, high-level views and their corresponding integrity controls can be made easily accessible to trusted users who will then be able to ensure their proper maintenance. Copyright © 2004 John Wiley & Sons, Ltd. [source]

    An analysis of VI Architecture primitives in support of parallel and distributed communication

    Andrew Begel
    Abstract We present the results of a detailed study of the Virtual Interface (VI) paradigm as a communication foundation for a distributed computing environment. Using Active Messages and the Split-C global memory model, we analyze the inherent costs of using VI primitives to implement these high-level communication abstractions. We demonstrate a minimum mapping cost (i.e. the host processing required to map one abstraction to a lower abstraction) of 5.4 ,s for both Active Messages and Split-C using four-way 550 MHz Pentium III SMPs and the Myrinet network. We break down this cost to the use of individual VI primitives in supporting flow control, buffer management and event processing and identify the completion queue as the source of the highest overhead. Bulk transfer performance plateaus at 44 Mbytes/s for both implementations are due to the addition of fragmentation requirements. Based on this analysis, we present the implications for the VI successor, Infiniband. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Viability of Auction-Based Revenue Management in Sequential Markets

    DECISION SCIENCES, Issue 2 2005
    Tim Baker
    ABSTRACT The Internet is providing an opportunity to revenue management practitioners to exploit the potential of auctions as a new price distribution channel. We develop a stochastic model for a high-level abstraction of a revenue management system (RMS) that allows us to understand the potential of incorporating auctions in revenue management in the presence of forecast errors associated with key parameters. Our abstraction is for an environment where two market segments book in sequence and revenue management approaches consider auctions in none, one, or both segments. Key insights from our robust results are (i) limited auctions are best employed closest to the final sale date, (ii) counterbalancing forecast errors associated with overall traffic intensity and the proportion of customer arrivals in a segment is more important if an auction is adopted in that segment, and (iii) it is critically important not to err on the side of overestimating market willingness to pay. [source]

    Optimal Design of the Online Auction Channel: Analytical, Empirical, and Computational Insights,

    DECISION SCIENCES, Issue 4 2002
    Ravi Bapna
    ABSTRACT The focus of this study is on business-to-consumer (B2C) online auctions made possible by the advent of electronic commerce over an open-source, ubiquitous Internet Protocol (IP) computer network. This work presents an analytical model that characterizes the revenue generation process for a popular B2C online auction, namely, Yankee auctions. Such auctions sell multiple identical units of a good to multiple buyers using an ascending and open auction mechanism. The methodologies used to validate the analytical model range from empirical analysis to simulation. A key contribution of this study is the design of a partitioning scheme of the discrete valuation space of the bidders such that equilibrium points with higher revenue structures become identifiable and feasible. Our analysis indicates that the auctioneers are, most of the time, far away from the optimal choice of key control factors such as the bid increment, resulting in substantial losses in a market with already tight margins. With this in mind, we put forward a portfolio of tools, varying in their level of abstraction and information intensity requirements, which help auctioneers maximize their revenues. [source]

    Active Learning through Modeling: Introduction to Software Development in the Business Curriculum,

    Boris Roussev
    ABSTRACT Modern software practices call for the active involvement of business people in the software process. Therefore, programming has become an indispensable part of the information systems component of the core curriculum at business schools. In this paper, we present a model-based approach to teaching introduction to programming to general business students. The theoretical underpinnings of the new approach are metaphor, abstraction, modeling, Bloom's classification of cognitive skills, and active learning. We employ models to introduce the basic programming constructs and their semantics. To this end, we use statecharts to model object's state and the environment model of evaluation as a virtual machine interpreting the programs written in JavaScript. The adoption of this approach helps learners build a sound mental model of the notion of computation process. Scholastic performance, student evaluations, our experiential observations, and a multiple regression statistical test prove that the proposed ideas improve the course significantly. [source]