bluuebunny/crossref_metadata_2025 huggingface dataset:
Real Time Control of Thermal Distortion During Pulsed Laser Welding of Optical Packages
Authors: Jouaneh Musa , Rangwala Sabbir
Published: February 2008

This paper investigates a method to compensate for thermal distortions which occur during pulsed laser welding of optical packages. A control strategy, based on the use of a fast response piezo-actuator to maintain relative alignment between the fiber and the laser in the critical time period after application of the laser pulse and before cooling of the weld nugget is described.
Computer Rigid Disk Surface Assessment With Laser Interferometry Using DDS
Authors: Pandit S. M. , Jordache N. , Joshi G. A.
Published: February 2008

Laser interferometry in conjunction with the data dependent systems (DDS) methodology is first used in this paper to eliminate errors caused by instrumentation and software, and to recover the surface topography of a computer rigid disk used for illustration. The DDS methodology is then applied once more to decompose the surface height profile into a series of exponential and sinusoidal modes. The significant modes are related to the waviness and surface roughness resulting from different manufacturing processes. Surface reconstruction using only the important modes is presented. This provides a visual as well as mathematical description of the resultant effect of each process. The methodology can characterize very complex surface textures, reducing the reliance on complicated and expensive instruments needed for inspection, and replacing them with relatively inexpensive but reliable computation.
Monitoring Rotating Tools Using Laser Diffraction
Authors: Fan Y. , Du R.
Published: February 2008

This paper introduces a new technique for monitoring multiple tooth rotating tools. The technique is based on laser diffraction. A narrow slit is constructed between the cutting edge of a cutter and a sharp straight blade placed parallel to the cutting edge as a reference. A laser beam is projected onto the slit and consequently a diffraction pattern consisting of a number of fringes is created behind the slit. By comparing the fringe spacing variation, cutting edge wear can be obtained. This technique has high resolution and a wide range of measurement. In addition, the measurement can be correlated to the commonly used flank wear measure (VB). The technique can be used for rotating tools such as milling and drilling. Experimental results in end-milling processes show that the technique is repeatable and accurate. With its fast speed, high resolution and reliability, it is expected that the technique has great potential for industrial applications.
A Numerical Study on the Heating of a Cast Iron Slab in a Car-Hearth Furnace
Authors: Jicha Miroslav , Chai John C. , Patankar Suhas V.
Published: February 2008

A numerical study on the transient heating of a cast iron slab in a car-hearth furnace is presented. The influence of the direction of jets issuing from the burners on the velocity and temperature fields during the heating period was investigated. The standard k-ε turbulence model is used in the present study. It is found that the direction of the jets has a significant influence on the temperature distribution in the slab. It is also shown that inclined jets produce a more uniform temperature field and that the time needed for the slab to reach a predetermined temperature can be significantly reduced which results in the reduction of energy consumption.
Analysis of Drill Failure Modes by Multi-sensors on a Robotic End Effector
Authors: Hong Shane Y. , Ni J. , Wu S. M.
Published: February 2008

The characteristics of nine common drill failure modes have been analyzed. To facilitate detecting and diagnosing these failure modes, a multi-sensor approach is developed. Based on the dynamic characteristics of three different measurements including thrust, torque, and lateral vibration, necessary signatures are extracted for the nine failure modes. Experimental tests were conducted to confirm the characteristics of these nine drill failure modes.
Ubiquity of Biological Ice Nucleators in Snowfall
Authors: Christner Brent C. , Morris Cindy E. , Foreman Christine M. , Cai Rongman , Sands David C.
Published: February 2008

Despite the integral role of ice nucleators (IN) in atmospheric processes leading to precipitation, their sources and distributions have not been well established. We examined IN in snowfall from mid- and high-latitude locations and found that the most active were biological in origin. Of the IN larger than 0.2 micrometer that were active at temperatures warmer than -7�C, 69 to 100% were biological, and a substantial fraction were bacteria. Our results indicate that the biosphere is a source of highly active IN and suggest that these biological particles may affect the precipitation cycle and/or their own precipitation during atmospheric transport.
Looking to the Future of Quantum Optics
Authors: Walmsley Ian A.
Published: February 2008

Light has provided both fundamental phenomenology and enabling technology for scientific discovery for many years, and today it continues to play a central role in fundamental explorations and innovative applications. The ability to manipulate light beams and pulses with the quantum degrees of freedom of optical radiation will add to those advances. The future of quantum optics, which encompasses both the generation and manipulation of nonclassical radiation, as well as its interaction with matter, lies in the rich variety of quantum states that is now becoming feasible to prepare, together with the numerous applications in sensing, imaging, metrology, communications, and information processing that such states enable.
Happening Now, Outdoors
Authors: Kokko Hanna
Published: February 2008

How and Why Species Multiply
. The Radiation of Darwin's Finches.
By Peter R. Grant and B. Rosemary Grant
. Princeton University Press, Princeton, NJ, 2008. 272 pp. $35, £19.95. ISBN 9780691133607. Princeton Series in Evolutionary Biology.

Drawing on decades of research in the Galapagos (especially their own work), the authors offer a comprehensive introduction to Darwin's finches and to evolutionary radiations on islands.
Lymphadenopathy Caused byMycobacterium colombiense
Authors: Esparcia Óscar , Navarro Ferran , Quer Miquel , Coll Pere
Published: February 2008

We report the case of a 3-year-old girl with lymphadenopathy caused by the recently described speciesMycobacterium colombiense. M. colombienseis a nonpigmented slow grower that is included in theMycobacterium aviumcomplex. Partial sequencing of the 16S rRNA gene was used for species identification.
Residue L143 of the Foot-and-Mouth Disease Virus Leader Proteinase Is a Determinant of Cleavage Specificity
Authors: Mayer Christina , Neubauer David , Nchinda Aloysius T. , Cencic Regina , Trompf Katja , Skern Tim
Published: February 2008

The foot-and-mouth disease virus (FMDV) leader proteinase (Lpro) self-processes inefficiently at the Lpro/VP4 cleavage site LysLeuLys*GlyAlaGly (* indicates cleaved peptide bond) when the leucine at position P2 is replaced by phenylalanine. Molecular modeling and energy minimization identified the Lproresidue L143 as being responsible for this discrimination. The variant LproL143A self-processed efficiently at the Lpro/VP4 cleavage site containing P2 phenylalanine, whereas the L143M variant did not. LproL143A self-processing at the eIF4GII sequence AspPheGly*ArgGlnThr was improved but showed more-extensive aberrant processing. Residue 143 in Lprois occupied only by leucine and methionine in all sequenced FMDV serotypes, implying that these bulky side chains are one determinant of the restricted specificity of Lpro.
Rubella Virus Capsid Protein Interacts with Poly(A)-Binding Protein and Inhibits Translation
Authors: Ilkow Carolina S. , Mancinelli Valeria , Beatch Martin D. , Hobman Tom C.
Published: February 2008

During virus assembly, the capsid proteins of RNA viruses bind to genomic RNA to form nucleocapsids. However, it is now evident that capsid proteins have additional functions that are unrelated to nucleocapsid formation. Specifically, their interactions with cellular proteins may influence signaling pathways or other events that affect virus replication. Here we report that the rubella virus (RV) capsid protein binds to poly(A)-binding protein (PABP), a host cell protein that enhances translational efficiency by circularizing mRNAs. Infection of cells with RV resulted in marked increases in the levels of PABP, much of which colocalized with capsid in the cytoplasm. Mapping studies revealed that capsid binds to the C-terminal half of PABP, which interestingly is the region that interacts with other translation regulators, including PABP-interacting protein 1 (Paip1) and Paip2. The addition of capsid to in vitro translation reaction mixtures inhibited protein synthesis in a dose-dependent manner; however, the capsid block was alleviated by excess PABP, indicating that inhibition of translation occurs through a stoichiometric mechanism. To our knowledge, this is the first report of a viral protein that inhibits protein translation by sequestration of PABP. We hypothesize that capsid-dependent inhibition of translation may facilitate the switch from viral translation to packaging RNA into nucleocapsids.
REMOVAL OF VIOLATIONS OF THE MASTER WARD IDENTITY IN PERTURBATIVE QFT
Authors: BRENNECKE FERDINAND , DÜTSCH MICHAEL
Published: February 2008

We study the appearance of anomalies of the Master Ward Identity, which is a universal renormalization condition in perturbative QFT. The main insight of the present paper is that any violation of the Master Ward Identity can be expressed as a local interacting field; this is a version of the well-known Quantum Action Principle of Lowenstein and Lam. Proceeding in a proper field formalism by induction on the order in ħ, this knowledge about the structure of possible anomalies as well as techniques of algebraic renormalization are used to remove possible anomalies by finite renormalizations. As an example, the method is applied to prove the Ward identities of the O(N) scalar field model.
SYMMETRIES AND INVARIANTS OF TWISTED QUANTUM ALGEBRAS AND ASSOCIATED POISSON ALGEBRAS
Authors: MOLEV A. I. , RAGOUCY E.
Published: February 2008

We construct an action of the braid group BN on the twisted quantized enveloping algebra [Formula: see text] where the elements of BN act as automorphisms. In the classical limit q → 1, we recover the action of BN on the polynomial functions on the space of upper triangular matrices with ones on the diagonal. The action preserves the Poisson bracket on the space of polynomials which was introduced by Nelson and Regge in their study of quantum gravity and rediscovered in the mathematical literature. Furthermore, we construct a Poisson bracket on the space of polynomials associated with another twisted quantized enveloping algebra [Formula: see text]. We use the Casimir elements of both twisted quantized enveloping algebras to reproduce and construct some well-known and new polynomial invariants of the corresponding Poisson algebras.
DARBOUX TRANSFORMATIONS FOR EFFECTIVE MASS SCHRÖDINGER EQUATIONS WITH ENERGY-DEPENDENT POTENTIALS
Authors: SCHULZE-HALBERG AXEL
Published: February 2008

We construct first-order Darboux transformations for stationary Schrödinger equations with position-dependent (effective) mass and energy-dependent potential. We point out characteristic differences to the corresponding Darboux transformation for constant mass.14
TWISTED SEMILOCAL STRINGS WITH TWO HIGGS-DOUBLETS
Authors: BRIHAYE Y. , HONOREZ L.
Published: February 2008

The standard electroweak model is extended by means of a second Brout–Englert–Higgs–doublet. The symmetry breaking potential is chosen in such a way that (i) the Lagrangian possesses a custodial symmetry, (ii) a stationary, axially symmetric ansatz of the bosonic fields consistently reduces the Euler–Lagrange equations to a set of differential equations. The potential involves, in particular, a direct interaction between the two doublets. Magnetic, stationary, axially-symmetric solutions of the classical equations are constructed. Some of them can be assimilated to embedded Nielsen–Olesen strings. From these solutions there are bifurcations and new solutions appear which exhibit the characteristics of the recently constructed twisted semilocal strings. A special emphasis is set on "doubly-twisted" solutions for which the two doublets present different time-dependent phase factors. They are regular and have a finite energy which can be lower than the energy of the embedded twisted solution. Electric-type solutions, such that the fields oscillate asymptotically far from the symmetry-axis, are also reported.
BREAKING OF LINEAR SYMMETRIES AND MICHEL'S THEORY: GRASSMANN MANIFOLDS, AND INVARIANT SUBSPACES
Authors: GAETA GIUSEPPE
Published: February 2008

Michel's theory of symmetry breaking in its original formulation has some difficulty in dealing with problems with a linear symmetry, due to the degeneration in the symmetry type implied by the linearity of group action. Here we propose a fully geometric, approach to the problem, making use of Grassmann manifolds. In this way Michel theory can also be applied to the determination of dynamically invariant manifolds for equivariant nonlinear flows.
REVIEW OF TOP QUARK PHYSICS RESULTS
Authors: KEHOE R. , NARAIN M. , KUMAR A.
Published: February 2008

As the heaviest known fundamental particle, the top quark has taken a central role in the study of fundamental interactions. Production of top quarks in pairs provides an important probe of strong interactions. The top quark mass is a key fundamental parameter which places a valuable constraint on the Higgs boson mass and electroweak symmetry breaking. Observations of the relative rates and kinematics of top quark final states constrain potential new physics. In many cases, the tests available with study of the top quark are both critical and unique. Large increases in data samples from the Fermilab Tevatron have been coupled with major improvements in experimental techniques to produce many new precision measurements of the top quark. The first direct evidence for electroweak production of top quarks has been obtained, with a resulting direct determination of Vtb. Several of the properties of the top quark have been measured. Progress has also been made in obtaining improved limits on potential anomalous production and decay mechanisms. This review presents an overview of recent theoretical and experimental developments in this field. We also provide a brief discussion of the implications for further efforts.
RATE OF PARITY VIOLATION FROM MEASURE CONCENTRATION
Authors: KALOGEROPOULOS NIKOS
Published: February 2008

We present a geometric argument determining the kinematic (phase-space) factor contributing to the relative rate at which degrees of freedom of one chirality come to dominate over degrees of freedom of opposite chirality, in models with parity violation. We rely on the measure concentration of a subset of a Euclidean cube which is controlled by an isoperimetric inequality. We provide an interpretation of this result in terms of ideas of statistical mechanics.
EFFECT OF DEFECT WIRES AND SPLIT RING RESONATORS ON MICROWAVE RESPONSE
Authors: FENG YU , SONG JIAN-PING , WU JIAN
Published: February 2008

The effect of defect introduced in wires and split ring resonators (SRRs) on the pass band and resonant frequency is investigated. The results show that there exists a shift for resonant frequency and a narrow pass band deduced by the introduction of defect into negative refractive index materials, the defect SRR affects the nonlinear microwave response significantly.
ELECTRONS TRAPPED IN AN ANISOTROPIC PARABOLIC POTENTIAL WELL, THOMAS-FERMI APPROACH
Authors: SAÑUDO J. , PACHECO A. F.
Published: February 2008

Using the Thomas-Fermi method, the density distribution of N electrons confined within a three-dimensional anisotropic parabolic potential is studied. This system simulates the structure of the recently built artificial atoms or quantum dots where a bunch of electrons is trapped in a semiconductor material. In the limit of large N, an analytical solution is obtained. Qualitatively speaking, this solution consists of a constant-density interior and a uniform thin skin that covers it. The asymmetry of the external figure is related to that of the confining potential. The radius, density, eccentricity and skin depth of the system are given as a function of N and of the properties of the confining potential and of the matrix material.
STABILITY OF TWO TYPICAL COMPLEX DYNAMICAL NETWORKS
Authors: YUAN WU-JIE , LUO XIAO-SHU , JIANG PIN-QUN , WANG BING-HONG , FANG JIN-QING
Published: February 2008

When being constructed, complex dynamical networks can lose stability in the sense of Lyapunov (i. s. L.) due to positive feedback. Thus, there is much important worthiness in the theory and applications of complex dynamical networks to study the stability. In this paper, according to dissipative system criteria, we give the stability condition in general complex dynamical networks, especially, in NW small-world and BA scale-free networks. The results of theoretical analysis and numerical simulation show that the stability i. s. L. depends on the maximal connectivity of the network. Finally, we show a numerical example to verify our theoretical results.
SLOW AND FAST LIGHTS WITH MOVING AND STATIONARY REFRACTIVE INDEX GRATINGS IN SOLIDS AT ROOM TEMPERATURE
Authors: ZHANG GUOQUAN , BO FANG , GAO FENG , DONG RONG , TU YANFEI , XU JINGJUN
Published: February 2008

We reviewed the recent progress on slow and fast lights in solids at room temperature based on moving and stationary refractive index gratings. A dispersive photorefractive phase coupling associated with moving gratings results in slow and fast lights. In principle, such phase-coupling-induced slow and fast lights can be observed in any nonlinear wave mixing process with a dispersive phase coupling effect. The slow and fast lights in the stationary gratings are also discussed. One advantage of the stationary gratings is the possibility to engineer the dispersion slope of the grating through designing the grating structure and parameters. As an example, we show that the dispersion slope of the gratings is enhanced significantly by stratifying a series of identical volume index gratings with homogeneous optical buffer layers sandwiched between every two neighboring grating layers. The slow and fast lights, therefore, can be controlled more effectively in such specifically designed grating structures than in the homogeneous gratings. Another advantage is the high transparency of the slow and fast lights with appropriate grating structure and parameters. Issues such as the pulse broadening effect and the pulse distortion are addressed. The slow and fast light techniques have many important potential applications such as optical delay lines and optical buffers.
Equilibrium in the balance? Implications for landscape evolution from dryland environments
Authors: Bracken Louise J. , Wainwright John
Published: February 2008

Equilibrium is a central concept in geomorphology. Despite the widespread use of the term, there is a great deal of variability in the ways equilibrium is portrayed and informs practice. Thus, there is confusion concerning the precise meanings and usage of the concept. In this chapter we draw on examples from dryland environments to investigate the practical implications of applying and testing the concept of equilibrium. Issues that we cover include the importance of scale and spatial variability, time, the assumption of constant environmental feedbacks and nonlinearities. The evaluation demonstrates that there are a range of problems inherent with using ideas of geomorphological equilibrium explicitly or implicitly to structure research in drylands. Many of these problems also apply to other environments.
Inferring bedload transport from stratigraphic successions: examples from Cenozoic and Pleistocene rivers, south central Pyrenees, Spain
Authors: Jones Stuart J. , Frostick Lynne E.
Published: February 2008

Geologists and geomorphologists have long been concerned with rates of sediment transfer as bedload in gravel-bed rivers, especially as rates of sediment transfer are important factors controlling river aggradation and incision. Bedload transport equations, originally derived for Holocene streams, have been used widely in modern gravel-bed river systems. However, palaeohydraulic reconstructions have received less attention and are generally dismissed as inaccurate since most are estimated to be at least an order of magnitude out. This study focuses on deriving stream power, bedload transport rates and efficiency estimates for Oligo–Miocene and Plio–Pleistocene gravel-bed river deposits from the south central Pyrenees, Spain. The basic data used in the palaeohydraulic calculations are estimates of palaeoslope, palaeovelocity, palaeodepth and the volume of sediment accreted in yearly flood events on gravel bars. Analyses of data from these ancient river systems yield more accurate estimates of relative stream power, bedload transport rates and efficiency parameters. This study illustrates the need for understanding the palaeohydraulics of river systems in order to characterize ancient rivers. Gravel-bed rivers with low sediment supply and high bedload transport rates incise. Conversely, when sediment supply is abundant, bedload transport rates and efficiency are low and the river system aggrades.
Evaluation of methods for approximating shapes used to synthesize 3D solid textures
Authors: Jagnow Robert , Dorsey Julie , Rushmeier Holly
Published: February 2008

In modern computer graphics applications, textures play an important role in conveying the appearance of real-world materials. But while surface appearance can often be effectively captured with a photograph, it is difficult to use example imagery to synthesize fully three-dimensional (3D) solid textures that are perceptually similar to their inputs. Specifically, this research focuses on human perception of 3D solid textures composed of aggregate particles in a binding matrix. Holding constant an established algorithm for approximating particledistributions, we examine the problem of estimating particleshape. We consider four methods for approximating plausible particle shapes—including two methods of our own contribution. We compare the performance of these methods under a variety of input conditions using automated, perceptually motivated metrics, as well as a psychophysical experiment. In the course of assessing the relative performance of the four algorithms, we also evaluate the reliability of the automated metrics in predicting the results of the experiment.
Automata-based assertion-checker synthesis of PSL properties
Authors: Boulé Marc , Zilic Zeljko
Published: February 2008

Assertion-based verification with languages such as PSL is gaining in importance. From assertions, one can generate hardware assertion checkers for use in emulation, simulation acceleration and silicon debug. We present techniques for checker generation of the complete set of PSL
properties
, including all variants of operators, both strong and weak. A full automata-based approach allows an entire assertion to be represented by a single automaton, hence allowing optimizations that can not be done in a modular approach where subcircuits are created only for individual operators. For this purpose, automata algorithms are developed for the base cases, and a complete set of rewrite rules is derived for other operators. Automata splitting is introduced for an efficient implementation of the eventually! operator.
A tool for automatic detection of deadlock in wormhole networks on chip
Authors: Taktak Sami , Desbarbieux Jean-Lou , Encrenaz Emmanuelle
Published: February 2008

We present an extension of Duato's necessary and sufficient condition a routing function must satisfy in order to be deadlock-free, to support environment constraints inducing
extra-dependencies
between messages. We also present an original algorithm to automatically check the deadlock-freeness of a network with a given routing function. A prototype tool has been developed and automatic deadlock checking of large scale networks with various routing functions have been successfully achieved. We provide comparative results with standard approach, highlighting the benefits of our method.
SoCDAL
Authors: Ahn Yongjin , Han Keesung , Lee Ganghee , Song Hyunjik , Yoo Junhee , Choi Kiyoung , Feng Xingguang
Published: February 2008

Time-to-market pressure and the ever-growing design complexity of multiprocessor system-on-chips have demanded an efficient design environment that enables fast exploration of large design space. In this article, we introduce a new design environment, called SoCDAL, for accelerating multiprocessor system-on-chip design through fast design-space exploration targeting real-time multimedia systems. SoCDAL is a set of mostly automated tools covering system specification, hardware/software estimation, application-to-architecture mapping, simulation model generation, and system verification through simulation. For system specification, the process network model has been widely used for system specification because of its modeling capability. However, it is hard to use for real-time systems design, since its behavior cannot be estimated statically. We introduce a new approach which enables analyzing a process network model statically with some restrictions. For the hardware/software estimation, we analyze codes statically. Application-to-architecture mapping process implements a novel algorithm to support an arbitrary number of processors, with performance evaluation by static scheduling considering communication behavior. Mapping results are used to generate simulation models automatically at several transaction levels to be pipelined to a commercial tool. We show the effectiveness of our approaches by some experimental results with multimedia applications such as JPEG, H.263, and H.264 encoders, as well as an H.264 decoder.
A fuel-cell-battery hybrid for portable embedded systems
Authors: Lee Kyungsoo , Chang Naehyuck , Zhuo Jianli , Chakrabarti Chaitali , Kadri Sudheendra , Vrudhula Sarma
Published: February 2008

This article presents our work on the development of a fuel cell (FC) and battery hybrid (FC-Bh) system for use in portable microelectronic systems. We describe the design and control of the hybrid system, as well as a dynamic power management (DPM)-based energy management policy that extends its operational lifetime. The FC is of the proton exchange membrane (PEM) type, operates at room temperature, and has an energy density which is 4--6 times that of a Li-ion battery. The FC cannot respond to sudden changes in the load, and so a system powered solely by the FC is not economical. An FC-Bh power source, on the other hand, can provide the high energy density of the FC and the high power density of a battery.

In this work we first describe the prototype FC-Bh system that we have built. Such a prototype helps to characterize the performance of a hybrid power source, and also helps explore new energy management strategies for embedded systems powered by hybrid sources. Next we describe a Matlab/Simulink-based FC-Bh system simulator which serves as an alternate experimental platform and that enables quick evaluation of system-level control policies. Finally, we present an optimization framework that explicitly considers the characteristics of the FC-Bh system and is aimed at minimizing the fuel consumption. This optimization framework is applied on top of a prediction-based DPM policy and is used to derive a new fuel-efficient DPM scheme. The proposed scheme demonstrates up to 32% system lifetime extension compared to a competing scheme when run on a real trace-based MPEG encoding example.
Incorporating feature hierarchy and boosting to achieve more effective classifier training and concept-oriented video summarization and skimming
Authors: Luo Hangzai , Gao Yuli , Xue Xiangyang , Peng Jinye , Fan Jianping
Published: February 2008

For online medical education purposes, we have developed a novel scheme to incorporate the results of semantic video classification to select the most representative video shots for generating concept-oriented summarization and skimming ofsurgery education videos. First, salient objects are used as the video patterns for feature extraction to achieve a good representation of the intermediate video semantics. The salient objects are defined as the salient video compounds that can be used to characterize the most significant perceptual properties of the corresponding real world physical objects in a video, and thus the appearances of such salient objects can be used to predict the appearances of the relevant semantic video concepts in a specific video domain. Second, a novelmulti-modal boostingalgorithm is developed to achieve more reliable video classifier training by incorporating feature hierarchy and boosting to dramatically reduce both the training cost and the size of training samples, thus it can significantly speed up SVM (support vector machine) classifier training. In addition, the unlabeled samples are integrated to reduce the human efforts on labeling large amount of training samples. Finally, the results of semantic video classification are incorporated to enable concept-oriented video summarization and skimming. Experimental results in a specific domain ofsurgery education videosare provided.
Hierarchical video patching with optimal server bandwidth
Authors: Hlavacs Helmut , Buchinger Shelley
Published: February 2008

Video patching is a way for transporting true video-on-demand, that is, instantaneous without any delay, from a video server to several clients. Instead of sending a unique stream to each newly arriving client, clients share as many multicast transmissions as possible, and are serviced only those parts of the video that they have missed.

We present a novel video patching scheme using hierarchies of patches. Our scheme minimizes the bandwidth needed by the video server, and may result in the fact that clients receive several streams in parallel. We show analytically that for Poisson arrival our algorithm achieves the optimal possible server bandwidth for all schemes where clients share multicast transmissions.

We also show, how our approach can be combined with batching. This combination requires less server bandwidth than all fixed start point periodic broadcast algorithms.
Just say 'A Class Defines a Data Type'
Authors: Hu Chenglie
Published: February 2008

When teaching computer programming to novices, forget "objects early," "objects later," and "back to basics."
The contribution of critical IS research
Authors: Stahl Bernd Carsten , Brooke Carole
Published: February 2008

Solving ongoing external problems may require looking inward first.
Promoting personal responsibility for internet safety
Authors: LaRose Robert , Rifon Nora J. , Enbody Richard
Published: February 2008

Online safety is everyone's responsibility---a concept much easier to preach than to practice.
Mitigating DoS attacks against broadcast authentication in wireless sensor networks
Authors: Ning Peng , Liu An , Du Wenliang
Published: February 2008

Broadcast authentication is a critical security service in wireless sensor networks. There are two general approaches for broadcast authentication in wireless sensor networks: digital signatures and μTESLA-based techniques. However, both signature-based and μTESLA-based broadcast authentication are vulnerable to Denial of Services (DoS) attacks: An attacker can inject bogus broadcast packets to force sensor nodes to perform expensive signature verifications (in case of signature-based broadcast authentication) or packet forwarding (in case of μTESLA-based broadcast authentication), thus exhausting their limited battery power. This paper presents an efficient mechanism called
message-specific puzzle
to mitigate such DoS attacks. In addition to signature-based or μTESLA-based broadcast authentication, this approach adds a weak authenticator in each broadcast packet, which can be efficiently verified by a regular sensor node, but takes a computationally powerful attacker a substantial amount of time to forge. Upon receiving a broadcast packet, each sensor node first verifies the weak authenticator, and performs the expensive signature verification (in signature-based broadcast authentication) or packet forwarding (in μTESLA-based broadcast authentication) only when the weak authenticator is valid. A weak authenticator cannot be precomputed without a non-reusable (or short-lived) key disclosed only in a valid packet. Even if an attacker has intensive computational resources to forge one or more weak authenticators, it is difficult to reuse these forged weak authenticators. Thus, this weak authentication mechanism substantially increases the difficulty of launching successful DoS attacks against signature-based or μTESLA-based broadcast authentication. A limitation of this approach is that it requires a powerful sender and introduces sender-side delay. This article also reports an implementation of the proposed techniques on TinyOS, as well as initial experimental evaluation in a network of MICAz motes.
On the Existence of Unconditionally Privacy-Preserving Auction Protocols
Authors: Brandt Felix , Sandholm Tuomas
Published: February 2008

We investigate whether it is possible to preserve privacy in sealed-bid auctions to a maximal extent. In particular, this paper focuses on unconditional full privacy, i.e., privacy that relies neither on trusted third parties (like auctioneers), nor on computational intractability assumptions (like the hardness of factoring). These constraints imply a scenario in which bidders exchange messages according to some predefined protocol in order to jointly determine the auction outcome without revealing any additional information. It turns out that the first-price sealed-bid auction can be emulated by an unconditionally fully private protocol. However, the protocol's round complexity is exponential in the bid size, and there is no more efficient protocol. On the other hand, we prove the impossibility of privately emulating the second-price sealed-bid auction for more than two bidders. This impossibility holds even when relaxing various privacy constraints such as allowing the revelation of all but one losing bid (while maintaining anonymity) or allowing the revelation of the second highest bidder's identity.
Energy-aware cosynthesis of real-time multimedia applications on MPSoCs using heterogeneous scheduling policies
Authors: Kim Minyoung , Banerjee Sudarshan , Dutt Nikil , Venkatasubramanian Nalini
Published: February 2008

Real-time multimedia applications are increasingly being mapped onto MPSoC (multiprocessor system-on-chip) platforms containing hardware--software IPs (intellectual property), along with a library of common scheduling policies such as EDF, RM. The choice of a scheduling policy for each IP is a key decision that greatly affects the design's ability to meet real-time constraints, and also directly affects the energy consumed by the design. We present a cosynthesis framework for design space exploration that considers heterogeneous scheduling while mapping multimedia applications onto such MPSoCs. In our approach, we select a suitable scheduling policy for each IP such that system energy is minimized—our framework also includes energy-reduction techniques utilizing dynamic power management. Experimental results on a realistic multimode multimedia terminal application demonstrate that our approach enables us to select design points with up to 60.5% reduced energy for a given area constraint, while meeting all real-time requirements. More importantly, our approach generates a tradeoff space between energy and cost allowing designers to comparatively evaluate multiple system level mappings.
Semantics-preserving multitask implementation of synchronous programs
Authors: Caspi Paul , Scaife Norman , Sofronis Christos , Tripakis Stavros
Published: February 2008

We study the implementation of a synchronous program as a set of multiple tasks running on the same computer, and scheduled by a real-time operating system using some preemptive scheduling policy, such as fixed priority or earliest-deadline first. Multitask implementations are necessary, for instance, in multiperiodic applications, when the worst-case execution time of the program is larger than its smallest period. In this case, a single-task implementation violates the schedulability assumption and, therefore, the synchrony hypothesis does not hold. We are aiming at semantics-preserving implementations, where, for a given input sequence, the output sequence produced by the implementation is the same as that produced by the original synchronous program, and this under all possible executions of the implementation. Straightforward implementation techniques are not semantics-preserving. We present an intertask communication protocol, called DBP, that is semantics-preserving and memory-optimal. DBP guarantees semantical preservation under all possible triggering patterns of the synchronous program: thus, it is applicable not only to time-, but also event-triggered applications. DBP works under both fixed priority and earliest-deadline first scheduling. DBP is a nonblocking protocol based on the use of intermediate buffers and manipulations of write-to/read-from pointers to these buffers: these manipulations happen upon arrivals, rather than executions of tasks, which is a distinguishing feature of DBP. DBP is memory-optimal in the sense that it uses as few buffers as needed, for any given triggering pattern. In the worst case, DBP requires, at most,
N
+ 2 buffers for each writer, where
N
is the number of readers for this writer.
Secure routing based on distributed key sharing in large-scale sensor networks
Authors: Park Taejoon , Shin Kang G.
Published: February 2008

Sensor networks, usually built with a large number of small, low-cost sensor nodes, are characterized by their large-scale and unattended deployment, necessitating “secur ” communications between nearby, as well as remote, sensor nodes for their intended applications and services. Key setup/sharing is crucial to the protection of such applications/services from attacks, but existing (public-key, cluster-based, or pairwise) solutions become too expensive (hence, inefficient) when the underlying applications/services require communications between distant sensor nodes. To remedy this inefficiency, we propose a novel
distributed key-sharing
scheme, in which each participating sensor node shares unique keys with a small number of other sensor nodes—called
distributed key servers
(DKSs)—chosen according to their geographic distance and communication direction. Using DKSs, we develop two secure routing protocols: (1)
secure geographic forwarding
that delivers packets by using a chain of DKS lookups, each secured with its own key and forwarded geographically; and (2)
key establishment
that creates a secure session between two distant sensor nodes based solely on symmetric-ciphers. These protocols enable low-cost, low-power sensors to provide high-level security at a very low cost.
A controlled experiment on white-box database testing
Authors: Tuya Javier , Dolado Javier , Suarez-Cabal Ma Jose , de la Riva Claudio
Published: February 2008

Controlled experiments are a powerful way to assess and compare the effectiveness of different techniques. In this paper we present the experimental results of the evaluation of the effectiveness of a structural test coverage criterion developed for SQL queries when used by a tester to guide the selection of database test cases. We describe a controlled experiment designed for comparing this criterion with other conventional criteria such as equivalence partitioning and boundary value analysis. The results show that 1) the use of the structural coverage allows the tester to develop more effective test cases, 2) the effectiveness is higher when considering the kind of faults that are more specifically related to SQL than other kinds of faults, and 3) the results give us some insight into how to improve the coverage criterion.
The book review column
Authors: Gasarch William
Published: February 2008

In this column we review the following books.

1.
The Access Principle
by John Willinsky. Review by Scott Aaronson. The book is about how journals should be more available on-line and other issues about journals. I invited Scott Aaronson to do a review but also told him he could make it into an opinion piece on the issue. He has done so. At the end I have a rebuttal- sort of.

2.
A Century of Scientific Publishing: A collection of essays
Edited by Fredriksson. Review by William Gasarch. This is a colletion of essays about how scientific information has been published and distributed over the last century. Can the past be helpful in understanding and dealing with our current problems?

3.
Mathematics of Physics and Engineering
by Edward K. Blum and Sergey V. Lototsky. Review by Frederic Green. This is a textbook for a 1-semester course in physics that covers much of the interplay of math and physics.

4.
Research Problems in Discrete Geometry
by Brass, Moser, Pach. Review by William Gasarch. This is a collection of research problems in discrete geometry, together with their history, context, and (lots of) references. Problems deal with points and lines in the plane, convex polygons, and many other geometrical objects.
Logical concepts in cryptography
Authors: Kramer Simon
Published: February 2008

The thesis is about a breadth-first exploration of logical concepts in cryptography and their linguistic abstraction and model-theoretic combination in a comprehensive logical system, called CPL (for
Cryptographic Protocol Logic
). We focus on two fundamental aspects of cryptography. Namely, the security of
communication
(as opposed to security of
storage
) and cryptographic
protocols
(as opposed to cryptographic
operators
). The logical concepts explored are the following. Primary concepts: the
modal
concepts of belief, knowledge, norms, provability, space, and time. Secondary concepts: belief with error control, individual and propositional knowledge, confidentiality norms, truth-functional and relevant (in particular, intuitionistic) implication, multiple and complex truth values, and program types. The distinguishing feature of CPL is that it unifies and refines a variety of existing approaches. This feature is the result of our
wholistic conception
of property-based (modal logics) and model-based (process algebra) formalisms. We illustrate the expressiveness of CPL on representative
requirements engineering
case studies. Further, we extend (core) CPL (qualitative time) with
rational-valued time
, i.e., time stamps, timed keys, and potentially drifting local clocks, to tCPL (quantitative time). Our extension is conservative and provides further evidence for Lamport's claim that adding real time to an untimed formalism is really simple. Furthermore, we sketch an extension of (core) CPL with a notion of
probabilistic polynomial-time
(PP) computation. We illustrate the expressiveness of this extended logic (ppCPL) on tentative formalisation case studies of fundamental and applied concepts.
Fundamental concepts:
(1) one-way function, (2) hard-core predicate, (3) computational indistinguishability, (4) (
n
-party) interactive proof, and (5) (
n
-prover) zero-knowledge.
Applied concepts:
(1) security of encryption schemes, (2) unforgeability of signature schemes, (3) attacks on encryption schemes, (4) attacks on signature schemes, and (5) breaks of signature schemes. In the light of logic, adding PP to a formalism for cryptographic protocols is perhaps also simple and can be achieved with an Ockham's razor extension of an existing core logic, namely CPL.
A MetaL for C and Pascal
Authors: Nair Achuth Sankar S. , Chandra Vinod
Published: February 2008

In this work, we have tried to combine Pascal and C language to form a meta-frame work. This metaplatform also provides data structure flexibility to the programmers. By this, one can declare a data structure in Pascal and can use it in C language segments, and vice versa. This meta-language provides a simple, flexible, extensible, and a formal framework for expressing transformational schemes. It also automates the cumbersome and error-prone part of the program transformation. Our aim is to make meta-programming less error-prone, by providing a type system to facilitate the construction of correct meta- frame.
Findings from "A Methodological Review of the Computer Science Education Research: 2000--2005"
Authors: Randolph Justus J.
Published: February 2008

A summary of the findings and recommendations from an ACM SIGCSE Special Projects grant to conduct a large-scale methodological review of the computer science education literature are presented here.
The computing ontology
Authors: Cassel Lillian N. , Davies Gordon , Fone William , Hacquebard Anneke , Impagliazzo John , LeBlanc Richard , Little Joyce Currie , McGettrick Andrew , Pedrona Michela
Published: February 2008

Working Group 3 at ITiCSE 2007 continued the ongoing work of the Ontology of Computing project. The working group brought several new people into the project and addressed areas of the ontology of particular interest to these participants. In particular, the group worked on the Ontology sections related to History of Computing, Computing Security and Social and Ethical issues. With the intention of applying the ontology to the support of curriculum development in mind, the group also reviewed and discussed proposed means of presenting a visual representation of the ontology. There was also some work on the present structure of the ontology and future possibilities.
A combination of approaches to solve task "How Many Ratings" of the KDD CUP 2007
Authors: Sueiras Jorge , Vélez Daniel , Flórez José Luis
Published: February 2008

This paper presents a solution to the KDD CUP 2007 task "How Many Ratings?". The combination of three different approaches is used to produce a final solution which improves the results obtained by each of these procedures by itself.
DDDM2007
Authors: Cao Longbing , Zhang Chengqi , Zhao Yanchang , Yu Philip S. , Williams Graham
Published: February 2008

Real-world data mining generally must consider and involve domain and business oriented factors such as human knowledge, constraints and business expectations. This encourages the development of a domain driven methodology to strengthen data-centered pattern mining. This report presents a review of the ACM SIGKDD Workshop on Domain Driven Data Mining (DDDM2007), held in conjunction with the Thirteenth ACM SIGKDD International Conference on Knowledge Discovery and Data Mining (KDD07), which was held in San Jose, USA on 12 August, 2007. The aims and objectives of this workshop were to provide a premier forum for sharing innovative findings, knowledge, insights, experiences and lessons in tackling challenges met in domain driven, actionable knowledge discovery in the real world.