bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanowell device for the electrical characterization of metal–molecule–metal junctions
Authors: Majumdar Nabanita , Gergel Nadine , Routenberg David , Bean J. C. , Harriott L. R. , Li B. , Pu L. , Yao Y. , Tour J. M.
Published: August 2005

A nanowell device for the electrical characterization of metal–molecule–metal junctions was built using readily available processing tools and techniques. This device consisted of a nanoscale well, with a gold bottom, filled with a self-assembling monolayer of organic molecules, and capped with titanium and gold. Focused ion beam technology was used to fabricate the well with a width less than the grain size of gold. This nanowell improved the device performance dramatically by reducing the chances of pinhole formation in the self-assembling monolayer on the bottom gold electrode. Unlike some established characterization techniques, including conducting probe atomic force microscopy and scanning tunneling microscopy, the nanowell device has the potential for future circuit integration. The effectiveness of the device was confirmed by testing I–V characteristics of alkanethiols and oligomeric arylthiols. The alkanethiol current was exponentially dependent on chain length with a decay factor (β) that ranged from 0.7to0.75∕Å with the applied voltages of 0.1–1.0V. Additionally, we gained new insight into the electrical behavior of an oligo(phenylene-ethynylene) molecule with a nitro side group. In this work, we present the complete I–V characteristics observed from the nitro molecule showing electrical switching with memory. Unlike previous reports, we did not observe any reversible negative differential resistance. However, the observed switching with memory behavior may have potential applications in logic and memory devices.
Vertically aligned growth of carbon nanotubes with long length and high density
Authors: Lee Kuei-Yi , Honda Shin-ichi , Katayama Mitsuhiro , Miyake Takashi , Himuro Katsuya , Oura Kenjiro , Lee Jung-Goo , Mori Hirotaro , Hirao Takashi
Published: August 2005

Vertically aligned carbon nanotubes (CNTs) with long length and high density were successfully synthesized on SiO2, Ta, and Ti substrates by thermal chemical vapor deposition (CVD). The use of Fe catalyst film supported by an Al buffer layer (Fe∕Al) has a significant influence on the increase of the number density of the aligned CNTs and the decrease of their diameter. The time dependencies of the aligned CNTs growth show that there is a limit to the length of the aligned CNTs formation. The aligned CNTs can be lengthened further using an intermittent growth method. These findings for the aligned CNTs synthesized on SiO2, Ta, and Ti substrates demonstrate that the thermal intermittent CVD with a Fe∕Al multilayer is a versatile method for obtaining vertically aligned CNTs with moderate length, for use in various device applications.
Ordering of quantum dot molecules by self-organization
Authors: van Lippen Twan , Nötzel Richard , Wolter Joachim H.
Published: August 2005

Ordered groups of InAs quantum dots (QDs), lateral QD molecules, are created by self-organized anisotropic strain engineering of a (In,Ga)As/GaAs superlattice (SL) template on GaAs (311)B by molecular beam epitaxy. During stacking the SL template self-organizes into a highly ordered two-dimensional (In,Ga)As and, thus, strain field modulation on a mesoscopic length scale, constituting a Turing pattern in solid state. InAs QDs preferentially grow on top of the SL template nodes due to local strain recognition, forming a lattice of separated groups of closely spaced ordered QDs. The SL template and InAs QD growth conditions like the number of SL periods, growth temperatures, amount and composition of deposited (In,Ga)As, and insertion of Al-containing layers are studied in detail for optimized QD ordering within and among the InAs QD molecules on the SL template nodes, which is evaluated by atomic force microscopy. The average number of InAs QDs within the molecules is controlled by the thickness of the upper GaAs separation layer on the SL template and the (In,Ga)As growth temperature in the SL. The strain correlated growth in SL template formation and QD ordering is directly confirmed by high-resolution x-ray diffraction. Ordered arrays of single InAs QDs on the SL template nodes are realized for an elevated SL template and InAs QD growth temperature together with the insertion of a second InAs QD layer. The InAs QD molecules exhibit strong photoluminescence (PL) emission up to room temperature. Temperature dependent PL measurements exhibit an unusual behavior of the full width at half maximum, indicating carrier redistribution solely within the QD molecules.
Nucleation and growth of InN by high-pressure chemical vapor deposition: Optical monitoring
Authors: Woods Vincent , Senawirante Jayantha , Dietz Nikolaus
Published: August 2005

The growth of high quality, stoichiometric InN presents a challenge because of the volatility of atomic nitrogen. To overcome the associated difficulties, a high-pressure chemical vapor deposition (HPCVD) system has been developed, which has opened the avenue for achieving stoichiometric single-phase surface compositions for materials such as InN for which thermal decomposition pressures are large at optimum processing temperatures. We report results obtained during InN growth in the pressure range of 2–15bar to achieve the earlier objectives and to obtain insights into the InN nucleation and growth process. Using real-time optical ultraviolet absorption spectroscopy, we characterized the chemistry of the gas-phase precursors as functions of flow, pressure, and temperature. Highly surface sensitive probing on InN nucleation and steady state growth is achieved by principal-angle-reflectance spectroscopy, allowing the characterization of surface chemistry at a submonolayer level. The InN layers grown at lower temperatures exhibit an absorption edge at 1.85eV, which is shifted towards lower energies as the growth temperatures increase. Absorption edges as low as 0.7eV are observed, values reported for molecular beam epitaxy-grown InN material. The real-time optical monitoring techniques employed demonstrated their superiority in optimizing and controlling the growth process, as well as in gaining insight in gas phase and surface chemistry processes during HPCVD.
Growth kinetics and theoretical modeling of selective molecular beam epitaxy for growth of GaAs nanowires on nonplanar (001) and (111)B substrates
Authors: Sato Taketomo , Tamai Isao , Hasegawa Hideki
Published: August 2005

The growth kinetics involved in the selective molecular beam epitaxy growth of GaAs quantum wires (QWRs) on mesa-patterned substrates is investigated in detail experimentally, and an attempt is made to model the growth theoretically, using a phenomenological continuum model. Experimentally, ⟨−110⟩-oriented QWRs were grown on (001) and (113)A substrates, and ⟨−1−12⟩-oriented QWRs were grown on (111)B substrates. From a detailed investigation of the growth profiles, it was found that the lateral wire width is determined by facet boundaries (FBs) within AlGaAs layers separating growth regions on top facets from those on side facets of mesa structures. Evolution of FBs during growth was complicated. For computer simulation, measured growth rates of various facets were fitted into a theoretical formula to determine the dependence of a lifetime of adatoms on the slope angle of the growing surface. The continuum model using the slope angle dependent lifetime reproduced the details of the experimentally observed growth profiles very well for growth on (001), (113)A, and (111)B substrates, including the complex evolution of facet boundaries
Controllable two-dimensional photonic crystal patterns fabricated by nanosphere lithography
Authors: Han Shuo , Hao Zhibiao , Wang Jian , Luo Yi
Published: August 2005

Two-dimensional (2D) photonic crystal patterns have been fabricated by an improved nanosphere lithography method. By introducing an intermediary SiO2 layer between the self-assembled layer and the substrate, this method can be applied to a wide range of materials without much concern for their surface hydrophilicity. The controllability of the photonic crystal patterns has also been investigated. The air-filling factor of the photonic crystal patterns can be easily tailored by thinning the polymer nanospheres in inductively coupled O2 plasma with a controllable etch rate. Large-area ordered 512nm pitch hole array, with vertical and smooth sidewalls, has been successfully formed on a GaAs substrate, indicating the potential application in photonic crystal devices of this method.
Chemical mapping of polymer photoresists by scanning transmission x-ray microscopy
Authors: Muntean Ligia , Planques Romain , Kilcoyne A. L. D. , Leone Stephen R. , Gilles Mary K. , Hinsberg William D.
Published: August 2005

Scanning transmission x-ray microscopy (STXM) is shown to be a powerful imaging technique that provides chemical selectivity and high spatial resolution (∼35nm) for studying chemically amplified photoresists. Samples of poly(4-t-butoxycarbonyloxystyrene) PTBOCST resist, imprinted by deep ultraviolet lithography with a line∕space pattern of 1.10μm∕0.87μm followed by a post-exposure bake, are used to demonstrate STXM imaging capabilities to extract photoresist latent images. Chemical contrast is obtained by measuring the x-ray absorption at an energy of 290.5 eV, corresponding to a carbon K shell electronic transition to the unoccupied π* molecular orbital of the PTBOCST carbonyl group. A quantitative analysis provides the spatial distribution of the fraction of the unexposed and deprotected polymers remaining after the post-exposure bake stage as well as the thickness of both regions. Both chemical and topographical contributions to the total contrast are estimated. Advantages and limitations of STXM in comparison with other imaging techniques with chemical specificity are discussed.
Tailoring of the structural and magnetic properties of MnAs films grown on GaAs—Strain and annealing effects
Authors: Däweritz L. , Herrmann C. , Mohanty J. , Hesjedal T. , Ploog K. H. , Bauer E. , Locatelli A. , Cherifi S. , Belkhou R. , Pavlovska A. , Heun S.
Published: August 2005

MnAs films were deposited by molecular-beam epitaxy on GaAs(001) and GaAs(111)B surfaces. Imaging of the temperature-dependent magnetic structure by x-ray magnetic circular dichroism photoemission electron microscopy, and the comparison with magnetization measurements by superconducting quantum interference device (SQUID) magnetometry, is used to study the impact of the different strain state of MnAs/GaAs(001) and of MnAs/GaAs(111)B films on the phase transition between ferromagnetic α-MnAs and paramagnetic β-MnAs, the spatial distribution of the two structural and magnetic phases, and the transition temperature. For the isotropically strained MnAs/GaAs(111)B films, the phase coexistence range is much wider than for the anisotropically strained MnAs/GaAs(001) films. The characteristic change of the saturation magnetization with film thickness is found to be a universal property of films with different epitaxial orientation, if at least one MnAs⟨112¯0⟩ direction is in the film plane. For MnAs/GaAs(001) films this variation is related to the striped coexistence of α and β MnAs and the changing intra- and inter-stripe magnetic interaction with film thickness and temperature. The magnetic structure of MnAs/GaAs(111)B is more complex due to the existence of three symmetry-equivalent α-phase domains superimposed by a honeycomb-like network of the coexisting β phase. The magnetic properties (saturation magnetization, domain size) of thin MnAs/GaAs(001) films can be improved by postgrowth annealing. Above a certain film thickness this is inhibited by the complex magnetic structure of the film.
Material and process effects on line-edge-roughness of photoresists probed with a fast stochastic lithography simulator
Authors: Patsis G. P. , Gogolides E.
Published: August 2005

Stochastic simulation of photoresist line-edge roughness (LER) is attempted using a three dimensional (3D) lithography simulator incorporating a fast dissolution algorithm based on a modified critical ionization model. The fast 3D simulation permits detailed evaluation of the material and process effects on LER. In this article the effects of deprotection fraction, critical ionization fraction, photoacid generator concentration, acid diffusion range, and polymerization length on LER are investigated through simulation. It is found that the relation of LER to photoresist polymerization length is greatly affected by the photoacid concentration and diffusion range.
In situ chemical sensing in AlGaN∕GaN high electron mobility transistor metalorganic chemical vapor deposition process for real-time prediction of product crystal quality and advanced process control
Authors: Cho Soon , Rubloff Gary W. , Aumer Michael E. , Thomson Darren B. , Partlow Deborah P. , Parikh Rinku , Adomaitis Raymond A.
Published: August 2005

Gallium nitride and its alloys promise to be key materials for future semiconductor devices aimed at high frequency, high power electronic applications. However, manufacturing for such high performance products is challenged by reproducibility and material quality constraints that are notably higher than those required for optoelectronic applications. To this end, in situ mass spectrometry was implemented in AlGaN∕GaN∕AlN∕SiC metalorganic chemical vapor deposition processes as a real-time process and wafer state metrology tool. Dynamic chemical sensing through the process cycle, carried out downstream from the wafer, revealed generation of methane and ethane reaction byproducts, as well as other residual gas species. Using the methane/ethane ratio, the GaN epilayer crystal quality was shown to be predictable in real time to a precision of 2%–5%. This was verified by postprocess x-ray diffraction using the full-width at half-maximum height of GaN on-axis (002) and off-axis (102) rocking curve peaks as a measure of crystal quality. The methane/ethane ratio may have a fundamental significance in terms of the intrinsic chemistry in that these two byproducts are speculated to reflect two different reaction pathways leading to GaN growth, namely the gas phase adduct formation route and the gas phase thermal decomposition of the precursor, respectively. The fact that lower methane/ethane ratios consistently yield better crystal quality for the GaN films suggests that the gas phase thermal decomposition pathway produces higher quality GaN growth. These results demonstrate that in situ mass spectrometry can be used to predict material quality during crystal growth. In turn, this offers an attractive pathway to advanced process control for GaN-based semiconductor manufacturing.
Structural characterization of strained AlGaN layers in different Al content AlGaN∕GaN heterostructures and its effect on two-dimensional electron transport properties
Authors: Miyoshi Makoto , Egawa Takashi , Ishikawa Hiroyasu
Published: August 2005

Different Al content AlGaN∕GaN two-dimensional-electron-gas (2DEG) structures were grown on 100-mm-diam sapphire substrates by metalorganic vapor phase epitaxy (MOVPE). The structural properties of AlGaN layers, such as alloy composition, layer thickness, tensile strain, in-plane stress, crystal quality, and band gap energy, were investigated in detail mainly by x-ray diffraction and spectroscopic ellipsometry. Correspondingly, the electron transport properties of these epilayers were theoretically as well as experimentally studied, taking into account the structural characterization results. Hall effect measurements showed that 2DEG density linearly increases with increasing Al content and that low-temperature 2DEG mobility largely decreases with the increase of Al content. The calculated results demonstrated that interface roughness scattering is largely enhanced with increasing Al content and has a strong impact on low-temperature 2DEG mobilities in high Al content samples. This is because the roughness of the interface between GaN and AlGaN layers increases with Al content. This calculated result is consistent with the experimental result that the surface of MOVPE-grown samples exhibited poor qualities with increasing Al content. The degradation of the surface and/or interface is associated with the increased strain in AlGaN layers.
Scanning tunneling microscopy investigation of nanostructures produced by Ar+ and He+ bombardment of MoS2 surfaces
Authors: Park J. B. , France C. B. , Parkinson B. A.
Published: August 2005

Nanostructures were fabricated on natural MoS2 crystals by bombardment with low doses of Ar+ and He+ with energies ranging from 100to5keV. The bombarded surfaces were investigated with x-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM) in an ultrahigh vacuum environment. The ion exposures were low enough to ensure that the observed nanostructures can be associated with individual ion impacts. Argon ions (Ar+) with energies of 100eV or less remove very few, if any, sulfur atoms from the surface but STM and XPS studies reveal that the electronic structure of the MoS2 surface is altered. Ar+ with energies greater than 100eV has a higher probability of sputtering sulfur atoms from the surface. The apparent size of the nanostructures in the STM images increased with Ar+ energies up to about 1keV and was dependent on the angle of incidence of the Ar+. Helium ion (He+) sputtering of MoS2 produced similar but smaller nanostructures when compared to Ar+ at the same impinged ion energy. STM images showed bright ring-shaped features were created with He+ energies greater than 500eV. On the basis of XPS and current imaging tunneling spectroscopy investigations, the features are assigned to sulfur atom vacancies. A change in the surface doping type from n to p was observed upon light sputtering of the surface.
Medical ethics: principles, persons, and perspectives: from controversy to conversation
Authors: Boyd K M
Published: August 2005

Medical ethics, principles, persons, and perspectives is discussed under three headings:History,Theory, andPractice. UnderTheory, the author will say something about some different approaches to the study and discussion of ethical issues in medicine—especially those based onprinciples, persons, orperspectives. UnderPractice, the author will discuss how one perspectives based approach,hermeneutics, might help in relation first toeveryday ethical issuesand then topublic controversies. In that context some possible advantages of movingfrom controversytoconversationwill be explored; and that will then be illustrated with reference to a current controversy about the use of human embryos in stem cell therapy research. The paper begins with history, and it begins in the author’s home city of Edinburgh.
Ethical dilemmas in community mental health care
Authors: Liégeois A , Van Audenhove C
Published: August 2005

Ethical dilemmas in community mental health care is the focus of this article. The dilemmas are derived from a discussion of the results of a qualitative research project that took place in five countries of the European Union. The different stakeholders are confronted with the following dilemmas: community careversushospital care (clients); a life with careversusa life without care (informal carers); stimulation of the client toward greater responsibilityversusprotection against such responsibility (professionals); budgetary controlversusfinancial incentives (policy makers), and respect for the clientversusparticular private needs (neighbourhood residents). These dilemmas are interpreted against the background of a value based ethical model. This model offers an integral approach to the dilemmas and can be used to determine policy. The dilemmas are discussed here as the result of conflicting values—namely autonomy and privacy, support and safety, justice and participation, and trust and solidarity.
Attitudes towards and barriers to writing advance directives amongst cancer patients, healthy controls, and medical staff
Authors: Sahm S , Will R , Hommel G
Published: August 2005

Objectives:After years of public discussion too little is still known about willingness to accept the idea of writing an advance directive among various groups of people in EU countries. We investigated knowledge about and willingness to accept such a directive in cancer patients, healthy controls, physicians, and nursing staff in Germany.

Methods:Cancer patients, healthy controls, nursing staff, and physicians (n =  100 in each group) were surveyed by means of a structured questionnaire.

Results:Only 18% and 19% of the patients and healthy controls respectively, and 10% of the medical staff had written an advance directive. However, 50–81% of those surveyed indicated that they wished to write one. This intention was associated with deteriorating health (p < 0.001). Only 29% of the healthy controls and 43% of the patients knew about the possibility of appointing a health care proxy. A majority in all groups believed that advance directives may influence the course of treatment (79–85%), yet half of those surveyed in all groups fear that patients could be pressurised into writing an advance directive, and 38–65% thought that relatives could abuse such documents.

Conclusions:Only a minority of the participants had written an advance directive and knew about the possibility of authorising a health care proxy. Deteriorating health was associated with increasing willingness to make a directive. Despite a majority belief that advance directives may influence treatment at the end of life, other factors limit their employment, such as fear of abuse.
WIGNER–POISSON AND NONLOCAL DRIFT-DIFFUSION MODEL EQUATIONS FOR SEMICONDUCTOR SUPERLATTICES
Authors: BONILLA L. L. , ESCOBEDO R.
Published: August 2005

A Wigner–Poisson kinetic equation describing charge transport in doped semiconductor superlattices is proposed. Electrons are assumed to occupy the lowest miniband, exchange of lateral momentum is ignored and the electron–electron interaction is treated in the Hartree approximation. There are elastic collisions with impurities and inelastic collisions with phonons, imperfections, etc. The latter are described by a modified BGK (Bhatnagar–Gross–Krook) collision model that allows for energy dissipation while yielding charge continuity. In the hyperbolic limit, nonlocal drift-diffusion equations are derived systematically from the kinetic Wigner–Poisson–BGK system by means of the Chapman–Enskog method. The nonlocality of the original quantum kinetic model equations implies that the derived drift-diffusion equations contain spatial averages over one or more superlattice periods. Numerical solutions of the latter equations show self-sustained oscillations of the current through a voltage biased superlattice, in agreement with known experiments.
An experimental study of a simple, distributed edge-coloring algorithm
Authors: Marathe Madhav V. , Panconesi Alessandro , Risinger Larry D.
Published: August 2005

We conduct an experimental analysis of a distributed randomized algorithm for edge coloring simple undirected graphs. The algorithm is extremely simple yet, according to the probabilistic analysis, it computes nearly optimal colorings very quickly [Grable and Panconesi 1997]. We test the algorithm on a number of random as well as nonrandom graph families.The test cases were chosen based on two objectives: (i) to provide insights into the worst-case behavior (in terms of time and quality) of the algorithm and (ii) to test the performance of the algorithm with instances that are likely to arise in practice. Our main results include the following:(1) The empirical results obtained compare very well with the recent empirical results reported by other researchers [Durand et al. 1994, 1998; Jain and Werth 1995].(2) The empirical results confirm the bounds on the running time and the solution quality as claimed in the theoretical paper. Our results show that for certain classes of graphs the algorithm is likely to perform much better than the analysis suggests.(3) The results demonstrate that the algorithm might be well suited (from a theoretical as well as practical standpoint) for edge coloring graphs quickly and efficiently in a distributed setting.Based on our empirical study, we propose a simple modification of the original algorithm with substantially improved performance in practice.
File sharing activities over BT Networks
Authors: Kwok Sai Ho
Published: August 2005

Pirated movies are available for sale at low prices in many online stores such as eBay and MovieGoods. But a new way of distributing pirated movies based on Peer-to-Peer (P2P) networks, in particular BitTorrent (BT), which can cause even greater financial losses to the movie industry, has surged in popularity. The financial losses to the movie industry due to P2P can be more severe and long-lasting because (1) distributing the digital form of pirated movies is much easier; (2) copyright holders or movie publishers can do very little to prevent distribution over P2P networks, and they usually respond passively; and (3) pirated movies exist even before their official release since the Telesync (TS) version of movies shot in the cinema can be easily produced. For the movie industry to come up with an effective anti-piracy strategy to combat BT networks, it is necessary to understand the sharing activity of pirated movies in BT. This article presents data collected from two representative BT discussion groups to explain the file-sharing patterns of pirated movies over BT networks and to analyze their impact on other movies in the same series. "The Lord of The Rings" was chosen for our study. We were amazed at the speed that this unreleased Hollywood movie became available for download in BT. So our study is intended to generate insights as to when BT users began to show interest in the movie, to think about downloading it, to actually download and play the movie, and finally to leave BT undetected. This article concludes with suggestions on the design of an anti-piracy strategy.
Statistics and secret leakage
Authors: Coron Jean-Sebastien , Naccache David , Kocher Paul
Published: August 2005

In addition to its usual complexity assumptions, cryptography silently assumes that information can be physically protected in a single location. As one can easily imagine, real-life devices are not ideal and information may leak through different physical channels.This paper gives a rigorous definition of leakage immunity and presents several leakage detection tests. In these tests, failure
confirms
the probable existence of secret-correlated emanations and indicates how likely the leakage is. Success
does not refute
the existence of emanations but indicates that significant emanations were not detected
on the strength of the evidence presented
, which of course, leaves the door open to reconsider the situation if further evidence comes to hand at a later date.
Security on FPGAs
Authors: Wollinger Thomas , Guajardo Jorge , Paar Christof
Published: August 2005

In the last decade, it has become apparent that embedded systems are integral parts of our every day lives. The wireless nature of many embedded applications as well as their omnipresence has made the need for security and privacy preserving mechanisms particularly important. Thus, as field programmable gate arrays (FPGAs) become integral parts of embedded systems, it is imperative to consider their security as a whole. This contribution provides a state-of-the-art description of security issues on FPGAs, both from the system and implementation perspectives. We discuss the advantages of reconfigurable hardware for cryptographic applications, show potential security problems of FPGAs, and provide a list of open research problems. Moreover, we summarize both public and symmetric-key algorithm implementations on FPGAs.
Towards fault-tolerant cryptographic computations over finite fields
Authors: Reyhani-Masoleh Arash , Hasan M. Anwar
Published: August 2005

Cryptographic schemes, such as authentication, confidentiality, and integrity, rely on computations in very large finite fields, whose hardware realization may require millions of logic gates. In a straightforward design, even a single fault in such a complex circuit is likely to yield an incorrect result and may be exploited by an attacker to break the cryptosystem. In this regard, we consider computing over finite fields in presence of certain faults in multiplier circuits. Our work reported here deals with errors caused by such faults in polynomial basis multipliers over finite fields of characteristic two and presents a scheme to correct single errors. Towards this, pertinent theoretical results are derived, and both bit-parallel and bit-serial fault tolerant multipliers are proposed.
LiSP
Authors: Park Taejoon , Shin Kang G.
Published: August 2005

Small low-cost sensor devices with limited resources are being used widely to build a self-organizing wireless network for various applications, such as situation monitoring and asset surveillance. Making such a sensor network secure is crucial to their intended applications, yet challenging due to the severe resource constraints in each sensor device. We present a
lightweight security protocol
(LiSP) that makes a tradeoff between security and resource consumption via efficient rekeying. The heart of the protocol is the novel rekeying mechanism that offers (1) efficient key broadcast without requiring retransmission/ACKs, (2) authentication for each key-disclosure without incurring additional overhead, (3) the ability of detecting/recovering lost keys, (4) seamless key refreshment without disrupting ongoing data encryption/decryption, and (5) robustness to inter-node clock skews. Furthermore, these benefits are preserved in conventional contention-based medium access control protocols that do not support reliable broadcast. Our performance evaluation shows that LiSP reduces resource consumption significantly, while requiring only three hash computations, on average, and a storage space for eight keys.
Affective usability evaluation for an interactive music television channel
Authors: Chorianopoulos Konstantinos , Spinellis Diomidis
Published: August 2005

Computer-mediated television brings new requirements for user interface design and evaluation, since interactive television applications are deployed in a relaxed domestic setting and aim to gratify the need for entertainment. Digital video recorders, the generation of custom computer graphics on each digital set-top box, and the introduction of new advertising formats are important issues for research and practice. We explore the employment of an animated character and the dynamic insertion of advertising in the design of an intuitive user interface for interactive music-video television. We found that the animated character and the skippable videoclip feature seamlessly enhanced consumer satisfaction, as shown by affective usability questionnaires.
Creating emotion in games
Authors: Freeman David
Published: August 2005

Why put emotion into games? The answers are art and money. Sure, it's an unholy alliance, but so are pineapple and pizza, windmills and tiny golf courses, the military and intelligence, and canned fruit and gelatin molds. Don't get me wrong. I think of myself as an artist first and a businessman second. But game companies that don't make a profit aren't game companies for very long. There are at least nine reasons that putting emotion in games can lead to greater profits, and it's worth taking a few minutes to mention them.
High resolution live streaming with the HYDRA architecture
Authors: Zimmermann Roger , Pawar Moses , Desai Dwipal A. , Qin Min , Zhu Hong
Published: August 2005

Digital continuous media (CM) are now well established as an integral part of many applications. With highdefinition (HD) displays becoming increasingly common and large network bandwidth available, high-quality video streaming has become feasible, and novel, innovative applications possible. However, the majority of existing systems for HD-quality streaming are based on offline content and use elaborate buffering techniques that introduce long latencies. Therefore, these solutions are ill-equipped for interactive real-time applications. Also, due to the massive amount of data required to transmit such streams, simultaneously achieving low latency and keeping the bandwidth low are contradictory requirements. Our HYDRA project (Highperformance Data Recording Architecture) focuses on the acquisition, transmission, storage, and rendering of high-resolution media such as H-quality video and multiple channels of audio. HYDRA consists of multiple components to achieve its overall functionality. Here we elaborate on the live-streaming capabilities of HYDRA that enable media streaming across an IP-based network with commodity equipment.
The implementation and evaluation of dynamic code decompression using DISE
Authors: Corliss Marc L. , Lewis E. Christopher , Roth Amir
Published: August 2005

Code compression coupled with dynamic decompression is an important technique for both embedded and general-purpose microprocessors.
Postfetch decompression
, in which decompression is performed after the compressed instructions have been fetched, allows the instruction cache to store compressed code but requires a highly efficient decompression implementation. We propose implementing postfetch decompression using a new hardware facility called
dynamic instruction stream editing
(DISE). DISE provides a programmable decoder---similar in structure to those in many IA-32 processors---that is used to add functionality to an application by injecting custom code snippets into its fetched instruction stream. We present a DISE-based implementation of postfetch decompression and show that it naturally supports customized program-specific decompression dictionaries, enables parameterized decompression allowing similar-but-not-identical instruction sequences to share dictionary entries, and uses no decompression-specific hardware. We present extensive experimental results showing the virtue of this approach and evaluating the factors that impact its efficacy. We also present implementation-neutral results that give insight into the characteristics of any postfetch decompression technique. Our experiments not only demonstrate significant reduction in code size (up to 35%) but also significant improvements in performance (up to 20%) and energy (up to 10%).
Agents-based modeling for a peer-to-peer MMOG architecture
Authors: El Rhalibi Abdennour , Merabti Madjid
Published: August 2005

Massively Multiplayer Online Games (MMOGs) are becoming a very important part of computer entertainment business. With the recent development of broadband technologies, the increase in the number of players is putting a strong pressure on this type of application. Commonly used clients/server systems don't cope well with scalability, limiting the number of players who can interact with each other, are not robust enough, and might be subject to bottlenecks due to their centralized infrastructure. These systems also force developers to invest enormous amounts of money in hardware and time to design complex software systems. To solve these problems we propose a fully distributed, peer-to-peer architecture for MMOGs.We discuss the issues surrounding MMOGs, the limitations in terms of network infrastructure and the lack of a simulation environment to study and evaluate network architectures and protocols. We use a peer-to-peer (P2P) based architecture and protocol to provide a more scalable, flexible, and robust technology solution than do currently used infrastructures. We conducted the design and implementation of a modular MMOG, called "Time-Prisoners," using a P2P protocol developed in Java and JXTA. The characteristics of P2P overlays enabled us to organize dynamically, and in transparent way for the users, the group of players according to their locations in the virtual world, and allowed the design of a scalable mechanism to distribute the game state to the players and to maintain a consistent world in case of node failures.
Converging CSP specifications and C++ programming via selective formalism
Authors: Gardner William B.
Published: August 2005

CSP (communicating sequential processes) is a useful algebraic notation for creating a hierarchical behavioral specification for concurrent systems, due to its formal interprocess synchronization and communication semantics. CSP specifications are amenable to simulation and formal verification by model-checking tools. A translator has been created to synthesize C++ code from CSP for execution with an object-oriented framework called CSP++, thereby making CSP specifications directly executable. To overcome the drawback that CSP is neither a full-featured nor popular programming language, an approach called “selective formalism” allows the use of CSP to be limited to specifying the control portion of a system, while the rest of its functionality is supplied in the form of C++ modules. These are activated through association with abstract events in the CSP specification. This is a new means of bringing convergence between a formal method and a popular programming language. It is believed that this methodology can be extended to hardware/software codesign for embedded systems.
The dilemma of credibility vs. speed
Authors: Prekeges James
Published: August 2005

CoRRs implicitly constrained but officially open acceptance policy for submitted papers raises concerns about both censorship and credibility. To avoid refereeing incoming papers yet still help readers assess their merits, CoRR could use coordinated public comments and ratings in the manner of some online auctions and booksellers.
A computing research repository
Authors: van Loon A. J.
Published: August 2005

The Computing Research Repository (CoRR) described by Halpern is potentially a powerful tool for researchers in computing science.In its current form, however, shortcomings exist that restrict its value and that,in the long term,might strongly undermine its usefulness.Important aspects that have insufficiently been taken care of are (1) the quality and consequently the reliability of the material stored, (2) the still restricted submission of material,which implies that other sources have to be consulted by researchers as well, (3) the still unsound financial basis of the project, and (4) the confusion that may easily arise when a preliminary version is stored in the CoRR, while a different final version is published in a journal.
Readability formulas in the new millennium
Authors: Schriver Karen A.
Published: August 2005

While readability formulas were intended as a quick benchmark for indexing readabilty, they are inherently unreliable: they depend on criterion (calibration) passages too short to reflect cohesiveness, too varied to support between-formula comparisons, and too text-oriented to account for the effects of lists, enumerated sequences,and tables on text comprehension. But readability formulas did spark decades of research on what comprehension really involoves.
A new string-pattern matching algorithm using partitioning and hashing efficiently
Authors: Kim Sun
Published: August 2005

In this paper, we present a new string-pattern matching algorithm that partitions the text into segments of the input pattern length and searches for pattern occurrences using a simple hashing scheme. Unlike the well known Boyer-Moore style algorithm, our algorithm does not compute variable shift length, thus providing a conceptually simpler way to search for patterns. Empirical evaluation shows that our algorithm runs significantly faster than Sunday's and Horspool's extensions of the Boyer-Moore algorithm. The notion of the non-occurrence heuristic used in our algorithm, together with a text partitioning scheme, leads to a simplified scheme for searching for pattern occurrences, thus yielding better run time performance.
Matrix multiplication
Authors: Eiron N. , Rodeh M. , Steinwarts I.
Published: August 2005

Modern machines present two challenges to algorithm engineers and compiler writers: They have superscalar, super-pipelined structure, and they have elaborate memory subsystems specifically designed to reduce latency and increase bandwidth. Matrix multiplication is a classical benchmark for experimenting with techniques used to exploit machine architecture and to overcome the limitations of contemporary memory subsystems.This research aims at advancing the state of the art of algorithm engineering by balancing instruction level parallelism, two levels of data tiling, copying to provably avoid any cache conflicts, and prefetching in parallel to computational operations, in order to fully exploit the memory bandwidth. Measurements on IBM's RS/6000 43P workstation show that the resultant matrix multiplication algorithm outperforms IBM's ESSL by 6.8-31.8%, is less sensitive to the size of the input data, and scales better.In this paper we introduce a cache aware algorithm for matrix multiplication. We also suggest generic guidelines that may be applied to compute intensive algorithm to efficiently utilize the data cache. We believe that some of our concepts may be embodied in compilers.
Fast and flexible string matching by combining bit-parallelism and suffix automata
Authors: Navarro Gonzalo , Raffinot Mathieu
Published: August 2005

The most important features of a string matching algorithm are its efficiency and its flexibility. Efficiency has traditionally received more attention, while flexibility in the search pattern is becoming a more and more important issue. Most classical string matching algorithms are aimed at quickly finding an exact pattern in a text, being Knuth-Morris-Pratt (KMP) and the Boyer-Moore (BM) family the most famous ones. A recent development uses deterministic "suffix automata" to design new optimal string matching algorithms, e.g. BDM and TurboBDM. Flexibility has been addressed quite separately by the use of "bit-parallelism", which simulates automata in their nondeterministic form by using bits and exploiting the intrinsic parallelism inside the computer word, e.g. the Shift-Or algorithm. Those algorithms are extended to handle classes of characters and errors in the pattern and/or in the text, their drawback being their inability to skip text characters. In this paper we merge bit-parallelism and suffix automata, so that a nondeterministic suffix automaton is simulated using bit-parallelism. The resulting algorithm, called BNDM, obtains the best from both worlds. It is much simpler to implement than BDM and nearly as simple as Shift-Or. It inherits from Shift-Or the ability to handle flexible patterns and from BDM the ability to skip characters. BNDM is 30%-40% faster than BDM and up to 7 times faster than Shift-Or. When compared to the fastest existing algorithms on exact patterns (which belong to the BM family), BNDM is from 20% slower to 3 times faster, depending on the alphabet size. With respect to flexible pattern searching, BNDM is by far the fastest technique to deal with classes of characters and is competitive to search allowing errors. In particular, BNDM seems very adequate for computational biology applications, since it is the fastest algorithm to search on DNA sequences and flexible searching is an important problem in that area. As a theoretical development related to flexible pattern matching, we introduce a new automaton to recognize suffixes of patterns with classes of characters. To the best of our knowledge, this automaton has not been studied before.
Computing the nxm shortest path efficiently
Authors: Shibuya Tetsuo
Published: August 2005

Computation of all the shortest paths between multiple sources and multiple destinations on various networks is required in many problems, such as the traveling salesperson problem (TSP) and the vehicle routing problem (VRP). This paper proposes new algorithms that compute the set of shortest paths efficiently by using the A* algorithm. The efficiency and properties of these algorithms are examined by using the results of experiments on an actual road network.
Analysing cache effects in distribution sorting
Authors: Rahman Naila , Raman Rajeev
Published: August 2005

We study cache effects in distribution sorting algorithms for sorting keys drawn independently at random from a uniform distribution ('uniform keys'). We note that the performance of a recently-published distribution sorting algorithm, Flashsort1, which sorts n uniform floating-point keys in O(n) expected time, does not scale well with the input size due to poor cache utilisation. We present an approximate analysis for distribution sorting uniform keys which, as validated by simulation results, predicts the expected cache misses of Flashsort1 quite well. Using this analysis, we design a multiple-pass variant of Flashsort1 which outperforms Flashsort1 and comparison-based algorithms on uniform floating-point keys for moderate to large values of n. Using experimental results we also show that the integer distribution sorting algorithm MSB radix sort performs well on both uniform integer and uniform floating-point keys.
Performance engineering case study
Authors: Bojesen Jesper , Katajainen Jyrki , Spork Maz
Published: August 2005

The behaviour of three methods for constructing a binary heap on a computer with a hierarchical memory is studied. The methods considered are the original one proposed by Williams [1964], in which elements are repeatedly inserted into a single heap; the improvement by Floyd [1964], in which small heaps are repeatedly merged to bigger heaps; and a recent method proposed, e.g., by Fadel et al. [1999] in which a heap is built layerwise. Both the worst-case number of instructions and that of cache misses are analysed. It is well-known that Floyd's method has the best instruction count. Let N denote the size of the heap to be constructed, B the number of elements that fit into a cache line, and let c and d be some positive constants. Our analysis shows that, under reasonable assumptions, repeated insertion and layerwise construction both incur at most cN/B cache misses, whereas repeated merging, as programmed by Floyd, can incur more than (dN log2 B)/B cache misses. However, for our memory-tuned versions of repeated insertion and repeated merging the number of cache misses incurred is close to the optimal bound N/B. In addition to these theoretical findings, we communicate many practical experiences which we hope to be valuable for others doing experimental algorithmic work.
Metaphor in theory and practice
Authors: Hamilton Anne
Published: August 2005

The use of metaphors is pervasive in all forms of discourse. This paper is concerned with providing a brief review of the development of metaphor theory,illustrated with some examples of supportive empirical research.These include a canonical study of the way concepts of instruction and education are influenced, a study into the effects of human-computer interface metaphors on computer systems users,and a study designed to assess the impacts of metaphor use on attitudes to internet commerce, particularly on attitudes to the roles played by information technology (IT). The paper provides some contextual background to assist consideration of the effects of metaphors on attitudes and beliefs.In practice, metaphor use may be intentional,unconscious,or a mixture of both, but in any case metaphors can be shown to play powerful roles in the social construction of human reality.
Halasz's "seven issues" in context
Authors: Furuta Richard
Published: August 2005

Frank Halasz's "Seven issues" paper first received widespread distribution in the July 1988
Communications of the ACM.
It appeared at a time when hypertext and hypermedia systems were receiving widespread attention. In this retrospective, I discuss the role of this paper in supporting and encouraging the broadening of the interests of the research community and its relevance in today's World-Wide-Web-centered milieu.