bluuebunny/crossref_metadata_2025 huggingface dataset:
A coupled channel hyperspherical scattering study of the Cl + HCl → ClH + Cl reaction: cumulative and state-selected probabilities, integral cross sections, and product rotational distributions
Authors: Schatz George C. , Sokolovski D. , Connor J.N.L.
Published: May 2006

We present accurate quantum results for the Cl + HCl → ClH + Cl reaction using a coupled channel hyperspherical coordinate method (denoted CCH). A semiempirical extended London–Eyring–Polanyi–Sato potential energy surface is employed. In our calculations, the body-fixed z projection quantum number Ω in the rotational basis set has been truncated at Ωmax = 2, since this is sufficient to give converged results near to, and above, the reaction threshold (total energies E in the range 0.40–0.60 eV). We compare our results with earlier work using the centrifugal sudden hyperspherical (CSH) method, in which only Ω = 0 is included in the basis; other features of the calculations are identical. At E = 0.40 eV, where reactivity is low, the CCH(Ωmax = 2) and CSH(Ω = 0) degeneracy averaged reaction probabilities, integral cross sections and product rotational distributions are mostly in excellent agreement. This agreement deteriorates with increasing E, such that at E = 0.60 eV, the CCH(Ωmax = 2) cumulative reaction probability is approximately twice its CSH(Ω = 0) counterpart. Even at E = 0.40 eV there are some important differences between CCH(Ωmax = 2) and CSH(Ω = 0) concerning mj-resolved reaction probabilities. In addition, there are differences in the relative contributions of "tight bend" and "nearly free-rotor" mechanisms to the reaction probabilities and product rotational distributions, with the "nearly free-rotor" mechanism dominant in all cases.
Interactive design and synthesis of a novel antibacterial agent
Authors: Wolfe Saul , Jin Haolun , Yang Kiyull , Kim Chan-Kyung , McEachern Ernest
Published: May 2006

β-Lactam compounds act on penicillin-recognizing enzymes via acylation of the hydroxyl group of an active site serine. When the resulting acyl enzyme is kinetically stable, as in the case of a penicillin-binding protein (PBP), the biosynthesis of a bacterial cell wall is inhibited, and death of the organism results. The de novo design of an antibacterial agent targeted to a PBP might be possible if the three-dimensional structural requirements of the equilibrium (i.e, fit) and catalytic (i.e. reactivity) steps of the aforementioned enzymatic process could be determined. For a model of the active site of a PBP from Streptomyces R61, the use of molecular mechanics calculations to treat "fit," and ab initio molecular orbital calculations to treat "reactivity," leads to the idea that the carboxyl group (G1) and the amide N-H (G2) of the antibiotic are hydrogen bonded to a lysine amino group and a valine carbonyl group in the enzyme–substrate complex. These two hydrogen bonds place the serine hydroxyl group on the convex face of the antibiotic, in position for attack on the β-lactam ring by a neutral reaction, catalyzed by water, that involves a direct proton transfer to the β-lactam nitrogen. Molecular orbital calculations of structure–reactivity relations associated with this mechanism suggest that C=N is bioisosteric to the β-lactam N-C(=O), comparable to a β-lactam in its reactivity with an alcohol, and that the product RO(C-N)H is formed essentially irreversibly (−ΔE > 10 kcal/mol). Accordingly, structures containing a G1 and a G2 separated by a C=N, and positioned in different ways with respect to this functional group, have been synthesized computationally and examined for their ability to fit to the PBP model. This strategy identified a 2H-5,6-dihydro-1,4-thiazine substituted by hydroxyl and carboxyl groups as a target for chemical synthesis. However, exploratory experiments suggested that the C=N of this compound equilibrates with endocyclic and exocyclic enamine tautomers. This required that the C2 position be substituted, and that the hydroxyl group not be attached to the carbon atom adjacent to the C=N. These conditions are met in a 2,2-dimethyl-3-(2-hydroxypropyl)-1,4-thiazine, which also exhibits the necessary fit to the PBP model. Two epimers of this compound have been synthesized, from D- and L-serine. The compound derived from L-serine is not active. The compound derived from D-serine exhibits antibacterial activity, but is unstable, and binding studies with PBP's have not been performed. It is hoped that these studies can be carried out if modification of the lead structure leads to compounds with improved chemical stability.
Rate constants for cyanate hydrolysis to urea: A Raman study
Authors: Wen Nanping , Brooker Murray H.
Published: May 2006

Raman spectra of aqueous solutions of potassium cyanate have been obtained at suitable time intervals. It was found that the peaks attributed to cyanate became less intense, while the peaks attributed to urea, carbamate and carbonate, centred at 1003, 1034, and 1065 cm−1, respectively, enhanced greatly with the passage of time. Further Raman spectroscopic studies revealed that the cyanate ion hydrolysed slowly and spontaneously at room temperature. Urea, carbamate, and carbonate were formed even without additional ammonium. Raman intensity measurements were used to monitor species concentrations as a function of time. The results suggested a complicated hydrolysis process: the hydrolysis of cyanate ion to form carbonate and ammonium, a rearrangement type reaction of aqueous cyanate ion with aqueous ammonium to formed urea, and an equilibrium reaction of carbonate and ammonium to form carbamate. The initial hydrolysis of cyanate with pure water was found to be first order with rate constant k1 = (2.67 ± 0.53) × 10−4 min−1 at 22 °C. The reaction of cyanate with aqueous ammonium was found to be second order with rate constant k2 = (4.64 ± 0.93) × 10−4 mol−1•L•min−1. The equilibrium reaction of carbonate and ammonium to form carbamate was very fast. Urea and carbamate were formed in parallel reactions. It was not possible to convert urea to carbamate or carbamate to urea at room temperature.
Preparation of 2- and 4-substituted 3-hydroxy-5-methylfurans and the aluminum and gallium complexes of 3-hydroxy-5-methyl-2-(N-methylformamido)furan
Authors: Lutz T.G. , Clevette D.J. , Hoveyda H.R. , Karunaratne V. , Nordin A. , Sjöberg S. , Winter M. , Orvig C.
Published: May 2006

In model studies designed to study the synthesis of potentially hexadentate chelates based on the linkage of three furan rings to a triamine via amide linkages, new 2- and 4-substituted 3-hydroxy-5-methylfurans have been prepared. Particularly, 3-hydroxy-5-methyl-(N-methylformamido)furan (Hahm) and its Al and Ga complexes (M(ahm)3) have been prepared and thoroughly characterized by a variety of techniques, in the solid state and in solution. Solution equilibrium studies (μ = 0.6 M NaCl, 25 °C) uncovered a complicated set of equilibria in the Al3+/Hahm system; the solution potentiometric data were best explained by the presence of mixed ligand (HL = Hahm, L− = ahm−) hydroxo species [Al3(OH)4L3]2+ and [Al(OH)2L2]−, in addition to the expected [AlLn](3−n)+ (n = 1, 2, 3) species. Further solution studies at HL:M ratios of 3:1 (μ = 0.15 M NaCl, 25 °C) showed that Hahm is a relatively weak complexing agent for both Al and Ga, forming tris-ligand species with overall formation constants of 1019.5 and 1020.6, respectively.
Electronic structure analysis of compounds of interest in drug design: mono- and dicarboxylated pyridines
Authors: Edgecombe Kenneth E. , Weaver Donald F. , Smith Jr. Vedene H.
Published: May 2006

The search for efficacious drug molecules involves, amongst other considerations, identifying compounds that will have activity in the receptor microenvironment through some highly specific microscopic pathway that is governed by molecular interactions. Widespread in the search for compounds with biological activity is the use of quantum pharmacologic structure–activity calculations. In this study, we identify the topological features of ab initio charge densities for a series of carboxylated pyridines. As well, results from conformational and geometric analysis obtained with semi-empirical AM1 and ab initio level geometries are compared. Carboxylated pyridines such as quinolinic and dipicolinic acids, both known to be neuroactive compounds, are logical candidates for a systematic study investigating the suitability of relating topological properties calculated in this manner to biological activity. Future reports will detail the correlation of these properties to biological activity.
Comportement particulier d'arylidènebenzothiazinonedioxydes dans les cycloadditions [3 + 2]. Compétition entre sites dipolarophiliques. Évolution des cycloadduits
Authors: Fathi Toufik , Ciamala Kabula , An Nguyen Dinh , Vebrel Joël
Published: May 2006

The reaction of diphenylnitrilimine with some arylidenebenzothiazinone dioxides leads to a mixture of two products that were isolated by chromatography. Spectroscopic data (infrared, nuclear magnetic resonance) and a radiocrystallographic study illustrate a competition between the two dipolarophilic sites in dipolar cycloaddition.
The synthesis of β-mannopyranosides by intramolecular aglycon delivery: scope and limitations of the existing methodology
Authors: Barresi Frank , Hindsgaul Ole
Published: May 2006

The synthesis of β-mannopyranosides by intramolecular aglycon delivery is shown to proceed with complete stereoselectivity in six separate cases. This strategy has been successfully applied to the synthesis of several disaccharides, including octyl 3,6-di-O-benzyl-4-O-(3,4,6-tri-O-benzyl-β-D-mannopyranosyl)-2-deoxy-2-phthalimido-β-D-glucopyranoside, a precursor of the naturally occurring β-D-Man-(1→4)-β-D-GlcNAc linkage, present in all N-linked glycoproteins. Exclusive formation of the β-mannosidic linkage has been confirmed in all six cases, since independently synthesized α-linked mannopyranoside standards were shown to be absent from the reaction products. The intramolecular stereocontrolled reaction proceeds even in the presence of competing methanol. The extension of this strategy to the synthesis of the core pentasaccharide of N-linked glycoproteins has revealed limitations to the methodology, especially when a block synthesis approach is investigated.
Laser flash photolysis study of the photoenols generated from ortho-benzylbenzophenone in different solvents
Authors: Netto-Ferreira J.C. , Wintgens V. , Scaiano J.C.
Published: May 2006

Irradiation of ortho-benzylbenzophenone leads to the formation of two (E,E and Z,E) out of the possible four photoenols. Laser flash photolysis studies show that the process involves the intermediacy of a short-lived biradical (τ∼50 ns in methanol) that decays concurrently with the formation of the photoenols. The Z,E enol is very short lived and decays by an allowed 1,5-hydrogen shift to regenerate the starting material; its lifetime is < 30 ns, 280 ns, 1.4 µs, and 90 ns, in benzene, acetonitrile, methanol, and trifluoroethanol, respectively. The Z,E enol is stabilized in hydroxylic solvents, although the acidity of trifluoroethanol seems to promote reketonization. E,E Enol lifetimes range from 80 µs (trifluoroethanol) to 47 µs (benzene) and its decay involves cyclization leading to 10-phenylanthrone following oxidation of the appropriate dihydroanthracene formed initially.
PROPERTIES OF WEIGHTED COMPLEX NETWORKS
Authors: XU XIN-JIAN , WU ZHI-XI , WANG YING-HAI
Published: May 2006

We study two kinds of weighted networks, weighted small-world (WSW) and weighted scale-free (WSF). The weight wij of a link between nodes i and j in the network is defined as the product of endpoint node degrees; that is wij =(ki kj)θ. In contrast to adding weights to links when networks are being constructed, we only consider weights depending on the "popularity" of the nodes represented by their connectivity. It was found that both weighted networks have broad distributions on the characterization of the link weight, the vertex strength, and the average shortest path length. Furthermore, as a survey of the model, the epidemic spreading process in both weighted networks was studied based on the standard susceptible-infected (SI) model. The spreading velocity reaches a peak very quickly after the infection outbreaks and an exponential decay was found in the long time propagation.
One-minute column
Authors: Henderson Peter B.
Published: May 2006

The last Math CountS column I wrote six months ago - seems like such a long time. Tony Ralston's editorial "Do We Need ANY Mathematics in Computer Science Curricula?" appeared in that issue of
inroads.
I hope you have read and were able to discuss it with others.
Active and cooperative learning
Authors: McConnell Jeffrey J.
Published: May 2006

Active and cooperative learning provides one way to encourage student involvement with course material. This second article in a series on active and cooperative learning discusses different levels of risk in class exercises and how activities can be designed to minimize that risk. Asking questions and class discussions are ways to enliven the classroom. Ways to use these techniques at various risk levels are presented.
Synopses for query optimization
Authors: Kaushik Raghav , Naughton Jeffrey F. , Ramakrishnan Raghu , Chakravarthy Venkatesan T.
Published: May 2006

Database systems use precomputed synopses of data to estimate the cost of alternative plans during query optimization. A number of alternative synopsis structures have been proposed, but histograms are by far the most commonly used. While histograms have proved to be very effective in (cost estimation for) single-table selections, queries with joins have long been seen as a challenge; under a model where histograms are maintained for individual tables, a celebrated result of Ioannidis and Christodoulakis [1991] observes that errors propagate exponentially with the number of joins in a query.In this article, we make two main contributions. First, we study the space complexity of using synopses for query optimization from a novel information-theoretic perspective. In particular, we offer evidence in support of histograms for single-table selections, including an analysis over data distributions known to be common in practice, and illustrate their limitations for join queries. Second, for a broad class of common queries involving joins (specifically, all queries involving only key-foreign key joins) we show that the strategy of storing a small precomputed sample of the database yields probabilistic guarantees that are almost space-optimal, which is an important property if these samples are to be used as database statistics. This is the first such optimality result, to our knowledge, and suggests that precomputed samples might be an effective way to circumvent the error propagation problem for queries with key-foreign key joins. We support this result empirically through an experimental study that demonstrates the effectiveness of precomputed samples, and also shows the increasing difference in the effectiveness of samples versus multidimensional histograms as the number of joins in the query grows.
A differentiation-enabled Fortran 95 compiler
Authors: Naumann Uwe , Riehme Jan
Published: May 2006

The availability of first derivatives of vector functions is crucial for the robustness and efficiency of a large number of numerical algorithms. An upcoming new version of the differentiation-enabled NAGWare Fortran 95 compiler is described that uses programming language extensions and a semantic code transformation known as
automatic differentiation
to provide Jacobians of numerical programs with machine accuracy. We describe a new user interface as well as the relevant algorithmic details. In particular, we focus on the source transformation approach that generates locally optimal gradient code for single assignments by vertex elimination in the linearized computational graph. Extensive tests show the superiority of this method over the current overloading-based approach. The robustness and convenience of the new compiler-feature is illustrated by various case studies.
More dynamic imperative languages
Authors: Savidis A.
Published: May 2006

We pursue entirely dynamic constructs for imperative object-oriented programming languages by shifting responsibilities from compile-time handling to runtime management. This accounts to the full range of language elements, going beyond statically defined: types, classes, inheritance, and function / operator overloading. The accommodation of the dynamic features in a language named Delta is discussed whose design emphasizes a minimal set of special-purpose language constructs. We demonstrate the way polymorphic higher-order functions, and polymorphic software patterns are directly programmable in a dynamic language context.
News 2.0
Authors: Stanik John
Published: May 2006

IPv6 Gains Government Traction
It Isn’t Your Father’s Realtime Anymore
Authors: Laplante Phillip
Published: May 2006

Isn’t it a shame the way the term realtime has become so misused? I’ve noticed a slow devolution since 1982, when realtime systems became the main focus of my research, teaching, and consulting. Over these past 20-plus years, I have watched my beloved realtime become one of the most overloaded, overused, and overrated terms in the lexicon of computing. Worse, it has been purloined by users outside of the computing community and has been shamelessly exploited by marketing opportunists. Adding to the humiliation, there is not even consistency of spelling: it variously appears as realtime (ACM Queue’s style preference), real-time (the author’s style preference), or real time.
Effective web service load balancing through statistical monitoring
Authors: Porter George , Katz Randy H.
Published: May 2006

Identifying the correlated effects between components to improve response to overload.
Supporting application quality of service in shared resource pools
Authors: Rolia Jerry , Cherkasova Ludmila , Arlitt Martin , Machiraju Vijay
Published: May 2006

Dividing an application's workload demands to better manage resource capacity.
Heterogeneous temporal probabilistic agents
Authors: Dix Jürgen , Kraus Sarit , Subrahmanian V. S.
Published: May 2006

To date, there has been no work on temporal probabilistic agent reasoning on top of heterogeneous legacy databases and software modules. We will define the concept of aheterogeneous temporal probabilistic(HTP) agent. Such agents can be built on top of existing databases, data structures, and software code bases without explicitly accessing the internal code of those systems and can take actions compatible with a policy or operating principles specified by an agent developer. We will develop a formal semantics for such agents through the notion of a feasible temporal probabilistic status interpretation (FTPSI for short). Intuitively, an FTPSI specifies what all an HTP agent is permitted/forbidden/obliged to do at various timest. As changes occur in the environment, the HTP agent must compute a new FTPSI. HTP agents continuously compute FTPSIs in order to determine what they should do and, hence, the problem of computing FTPSIs is very important. We give a sound and complete algorithm to compute FTPSIs for a very large class of HTP agents calledstrictHTP agents. In a given state, many FTPSIs may exist. These represent alternative courses of action that the HTP agent can take. We provide a notion of anoptimalFTPSI that selects an FTPSI optimizing an objective function and give a sound and complete algorithm to compute an optimal FTPSI.
Towards developing a framework for measuring organizational impact of IT- enabled BPR
Authors: Kohli Rajiv , Hoadley Ellen
Published: May 2006

This article reports on a case study of three firms which examined the organizational-level measures and process-level measures that were used to identify the effects of IT-enabled BPR (Business Process Redesign) projects. Firms in three distinct industry sectors provided the context for document review and semi-structured interview studies to identify those measures used to determine whether the firm's project was considered successful and how the firm had made the determination. A theoretical framework is proposed and provisionally confirmed demonstrating the link between IT-payoffs and BPR payoffs and the creation of intermediate assets that were identifiable and measurable. Lessons learned and opportunities for future research are presented.
The data-document distinction revisited
Authors: Blair David C.
Published: May 2006

The Data Retrieval and Document Retrieval models have a number of differences which influence their design, use and management. This paper discusses the most prominent of these differences and shows that they all arise from the more fundamental problem of representational indeterminacy. Representational indeterminacy is a result of the effects of semantic ambiguity and system size. If the differences between the Data Retrieval and Document Retrieval models arise from the same problem then the models are not as distinct as they may have appeared. The Data Retrieval and Document Retrieval models are better seen as examples of information systems with lower and higher levels of representational indeterminacy. The paper concludes with a proposal for an operational definition of representational indeterminacy and a discussion of the role of context and system size in reducing high levels of indeterminacy.
Fitts' law and expanding targets
Authors: McGuffin Michael J. , Balakrishnan Ravin
Published: May 2006

Recently, there has been renewed interest in techniques for facilitating the selection of user interface widgets or other on-screen targets with a pointing device. We report research into using
target expansion
for facilitating selection. Widgets that expand or grow in response to the user's focus of attention allow for a reduced initial size which can help optimize screen space use and may be easier to select than targets that do not expand. However, selection performance could plausibly suffer from a decreased initial widget size. We describe an experiment in which users select a single, isolated target button that expands just before it is selected. Our results show that users benefit from target expansion even if the target only begins expanding after 90% of the distance to the target has been travelled. Furthermore, our results suggest that, for sufficiently large
ID
values, users are able to take approximately full advantage of the expanded target size. For interfaces with multiple expanding widgets, however, subtle problems arise due to the collisions or overlap that may occur between adjacent expanding widgets. We give a detailed examination of the issues involved in both untiled and tiled multiple expanding targets and present various design strategies for improving their performance.
Experiences creating three implementations of the repast agent modeling toolkit
Authors: North Michael J. , Collier Nicholson T. , Vos Jerry R.
Published: May 2006

Many agent-based modeling and simulation researchers and practitioners have called for varying levels of simulation interoperability ranging from shared software architectures to common agent communications languages. These calls have been at least partially answered by several specifications and technologies. In fact, Tanenbaum [1988] has remarked that the “nice thing about standards is that there are so many to choose from.” Tanenbaum goes on to say that “if you do not like any of them, you can just wait for next year's model.” This article does not seek to introduce next year's model. Rather, the goal is to contribute to the larger simulation community the authors' accumulated experiences from developing several implementations of an agent-based simulation toolkit. As such, this article focuses on the implementation of simulation architectures rather than agent communications languages. It is hoped that ongoing architecture standards efforts will benefit from this new knowledge and use it to produce architecture standards with increased robustness.
Approximation algorithms for 2-stage stochastic optimization problems
Authors: Swamy Chaitanya , Shmoys David B.
Published: May 2006

Uncertainty is a facet of many decision environments and might arise for various reasons, such as unpredictable information revealed in the future, or inherent fluctuations caused by noise. Stochastic optimization provides a means to handle uncertainty by modeling it by a probability distribution over possible realizations of the actual data, called scenarios. The field of stochastic optimization, or stochastic programming, has its roots in the work of Dantzig [4] and Beale [1] in the 1950s, and has since increasingly found application in a wide variety of areas, including transportation models, logistics, financial instruments, and network design. An important and widely-used model in stochastic programming is the2-stage recourse model: first, given only distributional information about (some of) the data, one commits on initial (first-stage) actions. Then, once the actual data is realized according to the distribution, further recourse actions can be taken (in thesecond stage) to augment the earlier solution and satisfy the revealed requirements. The aim is to choose the initial actions so as to minimize the expected total cost incurred. The recourse actions typically entail making decisions in rapid reaction to the observed scenario, and are therefore more costly than decisions made ahead of time. Thus there is a trade-off between committing initially, having only imprecise information while incurring a lower cost, and deferring decisions to the second-stage, when we know the input precisely but the costs are higher. Many applications can be modeled this way, and much of the textbook of Birge and Louveaux [2] is devoted to models and algorithms for this class of problems. A commonly cited example involves a setting where a company has to decide where to set up facilities to serve client demands. Typically the demand pattern is not known precisely at the outset, but one might be able to obtain, through simulation models or surveys, statistical information about the demands. This motivates the following 2-step decision process: in the first-stage, given only distributional information about the demands (and deterministic data for the facility opening costs), one must decide which facilities to open initially; once the client demands are realized according to this distribution, we can extend the solution by opening more facilities, incurring a recourse cost, and we have to assign the realized demands to open facilities. This is the2-stage stochastic uncapacitated facility locationproblem. The recourse costs are usually higher than the original ones (because opening a facility later would involve deploying resources with a small lead time); these costs could be different for the different facilities, and could even depend on the realized scenario.
A Bayesian method for probable surface reconstruction and decimation
Authors: Diebel James R. , Thrun Sebastian , Brünig Michael
Published: May 2006

We present a Bayesian technique for the reconstruction and subsequent decimation of 3D surface models from noisy sensor data. The method uses oriented probabilistic models of the measurement noise and combines them with feature-enhancing prior probabilities over 3D surfaces. When applied to surface reconstruction, the method simultaneously smooths noisy regions while enhancing features such as corners. When applied to surface decimation, it finds models that closely approximate the original mesh when rendered. The method is applied in the context of computer animation where it finds decimations that minimize the visual error even under nonrigid deformations.
Salient geometric features for partial shape matching and similarity
Authors: Gal Ran , Cohen-Or Daniel
Published: May 2006

This article introduces a method for partial matching of surfaces represented by triangular meshes. Our method matches surface regions that are numerically and topologically dissimilar, but approximately similar regions. We introduce novel local surface descriptors which efficiently represent the geometry of local regions of the surface. The descriptors are defined independently of the underlying triangulation, and form a compatible representation that allows matching of surfaces with different triangulations. To cope with the combinatorial complexity of partial matching of large meshes, we introduce the abstraction of salient geometric features and present a method to construct them. A salient geometric feature is a compound high-level feature of nontrivial local shapes. We show that a relatively small number of such salient geometric features characterizes the surface well for various similarity applications. Matching salient geometric features is based on indexing rotation-invariant features and a voting scheme accelerated by geometric hashing. We demonstrate the effectiveness of our method with a number of applications, such as computing self-similarity, alignments, and subparts similarity.
Human-KV Interaction
Authors: Neville-Neil George
Published: May 2006

Welcome to another installment of Kode Vicious, the monthly forum for Queue’s resident kode maven and occasional rabble-rouser. KV likes to hear your tales from the coding trenches, preferably those ending with a focused question about programming. KV also has a tried-and-true arsenal of techniques for dealing with interpersonal relationships so feel free to enlist his help with those characters as well.
Best Practice (BPM)
Authors: Miers Derek
Published: May 2006

Just as BPM (business process management) technology is markedly different from conventional approaches to application support, the methodology of BPM development is markedly different from traditional software implementation techniques. With CPI (continuous process improvement) as the core discipline of BPM, the models that drive work through the company evolve constantly. Indeed, recent studies suggest that companies fine-tune their BPM-based applications at least once a quarter (and sometimes as often as eight times per year). The point is that there is no such thing as a "finished" process; it takes multiple iterations to produce highly effective solutions. Every working BPM-based process is just a starting point for the future. Moreover, with multiple processes that could benefit from BPM-style automated support, the issue becomes how to support dozens or even hundreds of engagements per year.
The costs and limits of availability for replicated services
Authors: Yu Haifeng , Vahdat Amin
Published: May 2006

As raw system performance continues to improve at exponential rates, the utility of many services is increasingly limited by availability rather than performance. A key approach to improving availability involves replicating the service across multiple, wide-area sites. However, replication introduces well-known trade-offs between service consistency and availability. Thus, this article explores the benefits of dynamically trading consistency for availability using a
continuous consistency model
. In this model, applications specify a maximum deviation from strong consistency on a per-replica basis. In this article, we: i) evaluate the availability of a prototype replication system running across the Internet as a function of consistency level, consistency protocol, and failure characteristics, ii) demonstrate that simple optimizations to existing consistency protocols result in significant availability improvements (more than an order of magnitude in some scenarios), iii) use our experience with these optimizations to prove tight upper bound on the availability of services, and iv) show that maximizing availability typically entails remaining as close to strong consistency as possible during times of good connectivity, resulting in a communication versus availability trade-off.
Why students with an apparent aptitude for computer science don't choose to major in computer science
Authors: Carter Lori
Published: May 2006

The statistics show that the number of Computer Science majors is dropping across the United States. Possible reasons include a reduced number of jobs in the field, an incorrect perception of what Computer Scientists do, and the students' disinterest due to a lack of familiarity with the subject. The reasons may be different for males and females. This paper reports on a study in which 836 high school calculus and pre-calculus students were surveyed to try to determine why students with an apparent aptitude for CS did not pursue a major in Computer Science. The results supported some of the hypotheses for declining enrollment, and rejected others. The top reasons for rejecting the major were the same for both genders, but the reasons for choosing the major differed.
Engagement theory
Authors: Miliszewska Iwona , Horwood John
Published: May 2006

A Computer Science degree is offered by Victoria University both locally in Australia and transnationally in Hong Kong. The degree includes a compulsory final year Project subject. The Project, a team effort, involves the design and implementation of a real-life computer application for an external client. Academics responsible for the degree consider Project and its three components of group context, project-based problems, and outside focus essential to transforming computing students into competent graduates. Do Project students support this view? This paper reports on a comparative study of the students' perceptions of the project experience and the relative importance of its three components. The paper discusses the results of the study with respect to the different locales, Melbourne and Hong Kong, and concludes by considering the implications of the study on the Project model.

Erratum
:

This paper is slightly edited from: Miliszewska, I., & Horwood, J. (2004). Engagement Theory: A Framework for Supporting Cultural Differences in Transnational Education, Proceedings of the HERDSA Conference, Miri, Malaysia, July 2004, (electronic proceedings).

This is a revised and extended version of: Miliszewska, I., Horwood J., & McGill, A. (2003). Transnational Education through Engagement: Students Perspective, Proceedings of the Informing Science and IT Education Conference IS2003, Pori, Finland, June 2003, 165-173.
Visual programming and the blind
Authors: Siegfried Robert M.
Published: May 2006

The proliferation of graphical user interfaces has had a dramatic impact on the ability to work as a programmer. It is particularly difficult for the blind to create forms for visual programming applications, such as Visual Basic. A scripting language is introduced that enables the blind to create Visual Basic forms without needing to specify a great deal of detail and without needing the "point and click" approach that they cannot use. Related issues of accommodating the blind in a computer science course are also discussed.
Teaching graphs to visually impaired students using an active auditory interface
Authors: Cohen Robert F. , Meacham Arthur , Skaff Joelle
Published: May 2006

We present our ongoing research in the communication of graphs and relational information to blind computer science students. We have developed a system called exPLoring graphs at UMB (PLUMB) that displays a drawn graph on a tablet PC and uses auditory cues to help a blind user navigate the graph. Beyond Computer Science education, this work has applications to assist blind individuals in navigation, map manipulation and other applications that require graph visualization.
Teaching requirements engineering to an unsuspecting audience
Authors: Callele David , Makaroff Dwight
Published: May 2006

One of a Software Engineer's most important skills is the ability to define the scope of the problem and ascertain the requirements from general and vague specifications. Teaching this skill is known to be difficult and is made more complex because students are conditioned to expect that this portion of programming projects is already complete. This paper reports on experience in teaching a second year computer science class which exposed the need for requirements engineering and gave students an opportunity to engage in the activity. We found that the student response was bimodal, and while some students met the challenge, more felt betrayed by the experience. We conclude that students gained the requisite knowledge using this approach but that a less traumatic approach may produce better results.
An interactive codesign environment for domain-specific coprocessors
Authors: Schaumont Patrick , Ching Doris , Verbauwhede Ingrid
Published: May 2006

Energy-efficient embedded systems rely on domain-specific coprocessors for dedicated tasks such as baseband processing, video coding, or encryption. We present a language and design environment called GEZEL that can be used for the design, verification and implementation of such coprocessor-based systems.The GEZEL environment creates a platform simulator by combining a hardware simulation kernel with one or more instruction-set simulators. The hardware part of the platform is programmed in GEZEL, a deterministic, cycle-true and implementation-oriented hardware description language. GEZEL designs are scripted, allowing the hardware configuration of the platform simulator to be changed quickly without going through lengthy recompiles. For this reason, we call the environment interactive. We present the execution ladder as an optimization framework to balance interactivity against simulation speed.We demonstrate our approach using several designs including an AES encryption coprocessor and a Viterbi decoding coprocessor. We discuss the advantages of our approach as opposed to more conventional approaches using SystemC and Verilog/VHDL.
ILP models for simultaneous energy and transient power minimization during behavioral synthesis
Authors: Mohanty Saraju P. , Ranganathan N. , Chappidi Sunil K.
Published: May 2006

In low-power design for battery-driven portable applications, the reduction of peak power, peak power differential, cycle difference power, average power and energy are equally important. These are different forms of dynamic power dissipation of a CMOS circuit, which is predominant compared to static power dissipation for higher switching activity. The peak power, the cycle difference power, and the peak power differential drive the transient characteristic of a CMOS circuit. In this article, we propose an ILP-based framework for the reduction of energy and transient power through datapath scheduling during behavioral synthesis. A new metric called “modified cycle power function” (CPF*) is defined that captures the above power characteristics and facilitates integer linear programming formulations. The ILP-based datapath scheduling schemes with CPF* as objective function are developed assuming three modes of datapath operation, such as, single supply voltage and single frequency (SVSF), multiple supply voltages and dynamic frequency clocking (MVDFC), and multiple supply voltages and multicycling (MVMC). We conducted experiments on selected high-level synthesis benchmark circuits for various resource constraints and estimated power, energy and energy delay product for each of them. Experimental results show that significant reductions in power, energy and energy delay product can be obtained.
UML-B
Authors: Snook Colin , Butler Michael
Published: May 2006

The emergence of the UML as a de facto standard for object-oriented modeling has been mirrored by the success of the B method as a practically useful formal modeling technique. The two notations have much to offer each other. The UML provides an accessible visualization of models facilitating communication of ideas but lacks formal precise semantics. B, on the other hand, has the precision to support animation and rigorous verification but requires significant effort in training to overcome the mathematical barrier that many practitioners perceive. We utilize a derivation of the B notation as an action and constraint language for the UML and define the semantics of UML entities via a translation into B. Through the UML-B profile we provide specializations of UML entities to support model refinement. The result is a formally precise variant of UML that can be used for refinement based, object-oriented behavioral modeling. The design of UML-B has been guided by industrial applications.
Detection of video sequences using compact signatures
Authors: Zobel Justin , Hoad Timothy C.
Published: May 2006

Digital representations are widely used for audiovisual content, enabling the creation of large online repositories of video, allowing access such as video on demand. However, the ease of copying and distribution of digital video makes piracy a growing concern for content owners. We investigate methods for identifying coderivative video content---that is, video clips that are derived from the same original source. By using dynamic programming to identify regions of similarity in video signatures, it is possible to efficiently and accurately identify coderivatives, even when these regions constitute only a small section of the clip being searched. We propose four new methods for producing compact video signatures, based on the way in which the video changes over time. The intuition is that such properties are likely to be preserved even when the video is badly degraded. We demonstrate that these signatures are insensitive to dramatic changes in video bitrate and resolution, two parameters that are often altered when reencoding. In the presence of mild degradations, our methods can accurately identify copies of clips that are as short as 5 s within a dataset 140 min long. These methods are much faster than previously proposed techniques; using a more compact signature, this query can be completed in a few milliseconds.
HCI and cognitive disabilities
Authors: Lewis Clayton
Published: May 2006

Considering different user groups is a central principle of user-centered design. In this Connections column, Clayton Lewis discusses aspects of the cognitively disabled as an important group of users.

            ---Manfred Tscheligi
Voices across the digital divide
Authors: Jones Matt
Published: May 2006

In this Under Development column, Matt Jones reports on an exciting new initiative funded by the UK government to create a design repository for researchers working on HCI projects in the developing world.

        ---Gary Marsden
Adaptive web information extraction
Authors: Gregg Dawn G. , Walczak Steven
Published: May 2006

The Amorphic system works to extract Web information for use in business intelligence applications.
How UML is used
Authors: Dobing Brian , Parsons Jeffrey
Published: May 2006

Many UML projects are not Use Case driven.
Revisiting my campaign statement
Authors: Patterson David A.
Published: May 2006

Two years ago I entered the race for ACM President with my campaign statement. In the second-to-last President's Letter of my term, I thought I would revisit what I said we would do and reflect on what we did.
Improved results for data migration and open shop scheduling
Authors: Gandhi Rajiv , Halldórsson Magnús M. , Kortsarz Guy , Shachnai Hadas
Published: May 2006

The
data migration
problem is to compute an efficient plan for moving data stored on devices in a network from one configuration to another. We consider this problem with the objective of minimizing the sum of completion times of all storage devices. It is modeled by a transfer graph, where vertices represent the storage devices, and the edges indicate the data transfers required between pairs of devices. Each vertex has a nonnegative weight, and each edge has a release time and a processing time. A vertex completes when all the edges incident on it complete; the constraint is that two edges incident on the same vertex cannot be processed simultaneously. The objective is to minimize the sum of weighted completion times of all vertices. Kim (
Journal of Algorithms, 55:42--57, 2005
) gave a 9-approximation algorithm for the problem when edges have arbitrary processing times and are released at time zero. We improve Kim's result by giving a 5.06-approximation algorithm. We also address the
open shop scheduling
problem,
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, and show that it is a special case of the data migration problem. Queyranne and Sviridenko (
Journal of Scheduling, 5:287-305, 2002
) gave a 5.83-approximation algorithm for the nonpreemptive version of the open shop problem. They state as an obvious open question whether there exists an algorithm for open shop scheduling that gives a performance guarantee better than 5.83. Our 5.06 algorithm for data migration proves the existence of such an algorithm. Crucial to our improved result is a property of the linear programming relaxation for the problem. Similar linear programs have been used for various other scheduling problems. Our technique may be useful in obtaining improved results for these problems as well.
Content-based multimedia information retrieval
Authors: Lew Michael S. , Sebe Nicu , Djeraba Chabane , Jain Ramesh
Published: May 2006

Extending beyond the boundaries of science, art, and culture, content-based multimedia information retrieval provides new paradigms and methods for searching through the myriad variety of media all over the world. This survey reviews 100+ recent articles on content-based multimedia information retrieval and discusses their role in current research directions which include browsing and search paradigms, user studies, affective computing, learning, semantic queries, new features and media types, high performance indexing, and evaluation techniques. Based on the current state of the art, we discuss the major challenges for the future.
What’s on Your Hard Drive?
Authors: O'Hanlon Charlene
Published: May 2006

So along with those parkas and snow blowers, why not pack away some of your less-than-satisfactory dev tools and take a look at this month’s WOYHD.
A Conversation with Chuck McManis
Authors: O'Hanlon Charlene
Published: May 2006

When thinking about purpose-built systems, it’s easy to focus on the high-visibility consumer products: the iPods, the TiVos. Lying in the shadows of the corporate data center, however, are a number of less-glamorous devices built primarily to do one specific thing: and do it well and reliably.
Java in a Teacup
Authors: Johnson Stephen
Published: May 2006

Few technology sectors evolve as fast as the wireless industry. As the market and devices mature, the need (and potential) for mobile applications grows. More and more mobile devices are delivered with the Java platform installed, enabling a large base of Java programmers to try their hand at embedded programming. Unfortunately, not all Java mobile devices are created equal, presenting many challenges to the new J2ME (Java 2 Platform, Micro Edition) programmer. Using a sample game application, this article illustrates some of the challenges associated with J2ME and Bluetooth programming.