bluuebunny/crossref_metadata_2025 huggingface dataset:
Buoyancy Driven Flow in Saturated Porous Media
Authors: Sakamoto H. , Kulacki F. A.
Published: June 2007

Measurements are reported of heat transfer coefficients in steady natural convection on a vertical constant flux plate embedded in a saturated porous medium. Results show that heat transfer coefficients can be adequately determined via a Darcy-based model, and our results confirm a correlation proposed by Bejan [Int. J. Heat Mass Transfer. 26(9), 1339–1346 (1983)]. It is speculated that the reason that the Darcy model works well in the present case is that the porous medium has a lower effective Prandtl number near the wall than in the bulk medium. The factors that contribute to this effect include the thinning of the boundary layer near the wall and an increase of effective thermal conductivity.
Noise-enhanced postural stability in subjects with functional ankle instability: Table 1
Authors: Ross Scott E
Published: June 2007

Objective:

To examine the effects of stochastic resonance (SR) stimulation on the postural stability of subjects with functional ankle instability (FAI).

Design:

Experimental research design.

Setting:

Sports medicine research laboratory.

Participants:

12 subjects with FAI who reported a history of recurrent ankle sprains and “giving way” sensations at the ankle.

Interventions:

Subjects performed 20 s single-leg balance tests under SR stimulation at 0.05 mA and 0.01 mA and under control conditions. Testing order was randomised. Stimulators that delivered subsensory stimulation to ankle muscles and ligaments were worn. Subjects were blinded to the test conditions, as SR stimulation was subsensory and stimulators were turned off during the control condition.

Main outcome measures:

Anterior/posterior and medial/lateral centre-of-pressure velocities (COPVs) were combined to form a resultant vector (COPV-R). The COPV-R differences between the optimal SR stimulation and control conditions were analysed. Optimal SR stimulation was defined as the SR stimulation input intensity level (0.05 mA or 0.01 mA) that produced the greatest percentage improvement in postural stability compared with the control condition. Slower velocities indicated enhanced postural stability.

Results:

The optimal input intensity was 0.05 mA for nine subjects and 0.01 mA for the other three. The optimal SR stimulation significantly (p<0.05) improved COPV-R compared with the control condition (6.60 (1.06) vs 7.20 (1.03) cm/s; mean (SD)).

Conclusion:

SR stimulation may enhance signal detection of sensorimotor signals associated with postural stability. This result has clinical relevance as improvements in postural instability associated with FAI may decrease ankle sprain injury.
Epidemiology of knee injuries among adolescents: a systematic review
Authors: Louw Q A , Manilall J , Grimmer K A
Published: June 2007

Background:

Youth sports injury is a public health concern, as it has detrimental effects on the health and well-being of young athletes. The knee joint is reported to be the most common joint injured by young sports participants. The potential loss of ability to participate in regular physical activity after injury is alarming, because physical inactivity is one of the major risk factors associated with systemic disease, disability and/or death worldwide.

Study design:

This paper presents a systematic review of the epidemiological research reporting on the prevalence of knee injuries among active adolescents to ascertain the global scope of the problem.

Results:

The 19 eligible studies for this review were mostly (90%) conducted in developed countries. Global adolescent knee injury prevalence ranges between 10% and 25%, with more recent studies reporting higher percentages. The average methodological appraisal score of the 19 studies was 56%. Females and adolescents appear to be more at an increased risk of sustaining a knee injury compared with males.

Conclusions:

Developing standard injury definitions as well as descriptions of injury causes must be taken into consideration in future injury surveillance research in order to appropriately inform effective knee injury preventative programmes for youth.
Computer-based quantification of the mean Achilles tendon thickness in ultrasound images: effect of tendinosis
Authors: Syha R , Peters M , Birnesser H , Niess A , Hirschmueller A , Dickhuth H-H , Sandrock M
Published: June 2007

Background:

B-mode measurement of the sagital diameter of the Achilles tendon based on a manual tracing (MT) procedure is partly dependent on the subjectivity of the reader. The aim of this study is to establish a standardised automatic procedure to differentiate between normal and chronically degenerated tendons. For this comparison, the tracing results of the tendon boundaries of an automatic identification (AI) process, already established with the detection of intima–media thickness, are compared with computer-assisted MT.

Methods:

The detection of the tendon boundaries was performed in 115 ultrasound images including the cranial border of the calcaneal tuberosity. The measured section (starting point 4 cm away from the anterior boundary of the calcaneal tuberosity) amounted to 3 cm, and was divided into three sub-segments (1 cm each). Intra- and inter-reader/observer variability for mean and maximum Achilles tendon thickness (ATT) with AI and MT were evaluated. A normal group and a group with clinically diagnosed chronic tendon degeneration had mean and maximum ATT readings compared.

Results:

Using MT, the intra- and inter-reader variability was 3.0% and 6.8%, respectively, using AI the variability was 1.6% and 3.9%, respectively. Mean and maximum ATT were measured systematically lower by AI compared to MT in all regions by 0.4 mm. The AI procedure was most accurate in the second segment. The mean ATT and maximum ATT were correctly detected in 93.9% and 96.6% of the images.

Conclusion:

The AI procedure detected the ATT with a high level of precision in all three segments. The most robust measurement was reached in the second segment. It eliminates most of the inter-/intra-reader variability in ATT measurement using MT. We suggest this new method could be a new gold standard for quantification of chronic disorder in Achilles tendons.
SYMMETRY LIMIT PROPERTIES OF DECAY AMPLITUDES WITH MIRROR MATTER ADMIXTURES
Authors: SÁNCHEZ-COLÓN G. , GARCÍA A.
Published: June 2007

We extend our previous analysis on the symmetry limit properties of nonleptonic and weak radiative decay amplitudes of hyperons in a scheme of mirror matter admixtures in physical hadrons to include the two-body nonleptonic decays of Ω- and the two-photon and two-pion decays of kaons. We show that the so-called parity-conserving amplitudes predicted for all the decays vanish in the strong flavor SU(3) symmetry limit. We also establish the specific conditions under which the corresponding so-called parity-violating amplitudes vanish in the same limit.
Q2DEPENDENCE OF AZIMUTHAL ASYMMETRIES IN SEMIINCLUSIVE DEEP INELASTIC SCATTERING AND IN DRELL–YAN
Authors: DI SALVO ELVIO
Published: June 2007

We study several azimuthal asymmetries in semiinclusive deep inelastic scattering and in Drell–Yan, interpreting them within the formalism of the quark correlator, with a particular reference to T-odd functions. The correlator contains an undetermined energy scale, which we fix on the basis of a simple and rather general argument. We find a different value than the one assumed in previous treatments of T-odd functions. This implies different predictions on the Q2dependence of the above mentioned asymmetries. Our theoretical result on unpolarized Drell–Yan is compared with available data. Predictions on other azimuthal asymmetries could be tested against yields of planned experiments of Drell–Yan and semiinclusive deep inelastic scattering.
ANGULAR POWER SPECTRUM IN MODULAR INVARIANT INFLATION MODEL
Authors: HAYASHI MITSUO J. , HIRAI SHIRO , TAKAMI TOMOYUKI , OKAMEI YUSUKE , TAKAGI KENJI , WATANABE TOMOKI
Published: June 2007

We propose a scalar potential of inflation, motivated by modular invariant supergravity, and compute the angular power spectra of the adiabatic density perturbations that result from this model. The potential consists of three scalar fields, S, Y and T, together with two free parameters. By fitting the parameters to cosmological data at the fixed point T = 1, we find that the potential behaves like the single-field potential of S, which slowly rolls down along the minimized trajectory in Y. We further show that the inflation predictions corresponding to this potential provide a good fit to the recent three-year WMAP data, e.g. the spectral index ns = 0.951.

The TT and TE angular power spectra obtained from our model almost completely coincide with the corresponding results obtained from the ΛCDM model. We conclude that our model is considered to be an adequate theory of inflation that explains the present data, although the theoretical basis of this model should be further explicated.
THE BEHAVIOR OF THE STRANGE QUARK MATTER IN THE FRW UNIVERSES
Authors: YILMAZ IHSAN , KUCUKARSLAN AYSE , OZDER SERHAT
Published: June 2007

In this paper, we study strange quark matter for Friedman–Robertson–Walker (FRW) universes in the context of general relativity. For this purpose we consider quark–gluon plasma as a perfect fluid in the FRW universes. After solving Einstein's field equations, we have analyzed this matter for the different types of universe. Also, we discuss the features of collapsing strange quark matter.
Allocating architected registers through differential encoding
Authors: Zhuang Xiaotong , Pande Santosh
Published: June 2007

Micro-architecture designers are very cautious about expanding the number of architected and exposed registers in the instruction set because increasing the register field adds to the code size, raises the I-cache and memory pressure, and may complicate the processor pipeline. Especially for low-end processors, encoding space could be extremely limited due to area and power considerations. On the other hand, the number of architected registers exposed to the compiler could directly affect the effectiveness of compiler analysis and optimization. For high-performance computers, register pressure can be higher than the available registers in some regions. This could be due to optimizations like aggressive function inlining, software pipelining, etc. The compiler cannot effectively perform compilation and optimization if only a small number of registers are exposed through the ISA. Therefore, it is crucial that more architected registers are available at the compiler's disposal, without expanding the code size significantly.

In this article, we devise a new register encoding scheme, called differential encoding, that allows more registers to be addressed in the operand field of instructions than the direct encoding currently being used. We show that this can be implemented with very low overhead. Based upon differential encoding, we apply it in several ways such that the extra architected registers can benefit the performance. Three schemes are devised to integrate differential encoding with register allocation. We demonstrate that differential register allocation is helpful in improving the performance of both high-end and low-end processors. Moreover, we can combine it with software pipelining to provide more registers and reduce spills.

Our results show that differential encoding significantly reduces the number of spills and speeds-up program execution. For a low-end configuration, we achieve over 14% speedup while keeping code size almost unaffected. For a high-end VLIW in-order machine, it can significantly speed-up loops with high register pressure (about 80% speedup) and the overall speedup is about 15%. Moreover, our scheme can be applied in an adaptive manner, making its overhead much smaller.
A provenly correct translation of Fickle into Java
Authors: Ancona D. , Anderson C. , Damiani F. , Drossopoulou S. , Giannini P. , Zucca E.
Published: June 2007

We present a translation from
Fickle
, a small object-oriented language allowing objects to change their class at runtime, into Java. The translation is provenly correct in the sense that it preserves the static and dynamic semantics. Moreover, it is compatible with separate compilation, since the translation of a Fickle class does not depend on the implementation of used classes. Based on the formal system, we have developed an implementation.

The translation turned out to be a more subtle problem than we expected. In this article, we discuss four possible approaches we considered for the design of the translation and to justify our choice, we present formally the translation and proof of preservation of the static and dynamic semantics, and discuss the prototype implementation. Moreover, we outline an alternative translation based on generics that avoids most of the casts (but not all) needed in the previous translation.

The language Fickle has undergone and is still undergoing several phases of development. In this article we are discussing the translation of Fickle
II
.
Foundations of incremental aspect model-checking
Authors: Krishnamurthi Shriram , Fisler Kathi
Published: June 2007

Programs are increasingly organized around features, which are encapsulated using aspects and other linguistic mechanisms. Despite their growing popularity amongst developers, there is a dearth of techniques for computer-aided verification of programs that employ these mechanisms. We present the theoretical underpinnings for applying model checking to programs (expressed as state machines) written using these mechanisms. The analysis is incremental, examining only components that change rather than verifying the entire system every time one part of it changes. Our technique assumes that the set of pointcut designators is known statically, but the actual advice can vary. It handles both static and dynamic pointcut designators. We present the algorithm, prove it sound, and address several subtleties that arise, including cascading advice application and problems of circular reasoning.
An empirical study of static program slice size
Authors: Binkley David , Gold Nicolas , Harman Mark
Published: June 2007

This article presents results from a study of all slices from 43 programs, ranging up to 136,000 lines of code in size. The study investigates the effect of five aspects that affect slice size. Three slicing algorithms are used to study two algorithmic aspects: calling-context treatment and slice granularity. The remaining three aspects affect the upstream dependencies considered by the slicer. These include collapsing structure fields, removal of dead code, and the influence of points-to analysis.

The results show that for the most precise slicer, the average slice contains just under one-third of the program. Furthermore, ignoring calling context causes a 50% increase in slice size, and while (coarse-grained) function-level slices are 33% larger than corresponding statement-level slices, they may be useful predictors of the (finer-grained) statement-level slice size. Finally, upstream analyses have an order of magnitude less influence on slice size.
A characterization of regular expressions under bisimulation
Authors: Baeten J. C. M. , Corradini F. , Grabmayer C. A.
Published: June 2007

We solve an open question of Milner [1984]. We define a set of so-called well-behaved finite automata that, modulo bisimulation equivalence, corresponds exactly to the set of regular expressions, and we show how to determine whether a given finite automaton is in this set. As an application, we consider the star height problem.
The rational numbers as an abstract data type
Authors: Bergstra J. A. , Tucker J. V.
Published: June 2007

We give an equational specification of the field operations on the rational numbers under initial algebra semantics using just total field operations and 12 equations. A consequence of this specification is that 0
−1
= 0, an interesting equation consistent with the ring axioms and many properties of division. The existence of an equational specification of the rationals
without hidden functions
was an open question. We also give an axiomatic examination of the divisibility operator, from which some interesting new axioms emerge along with equational specifications of algebras of rationals, including one with the modulus function. Finally, we state some open problems, including: Does there exist an equational specification of the field operations on the rationals without hidden functions that is a complete term rewriting system?
Efficient importance sampling heuristics for the simulation of population overflow in Jackson networks
Authors: Nicola Victor F. , Zaburnenko Tatiana S.
Published: June 2007

In this article, we propose state-dependent importance sampling heuristics to estimate the probability of population overflow in Jackson queueing networks. These heuristics capture state-dependence along the boundaries (when one or more queues are empty), which is crucial for the asymptotic efficiency of the change of measure. The approach does not require difficult (and often intractable) mathematical analysis and is not limited by storage and computational requirements involved in adaptive importance sampling methodologies, particularly for a large state space. Experimental results on tandem, parallel, feed-forward, and feedback networks with a moderate number of nodes suggest that the proposed heuristics may yield asymptotically efficient estimators, possibly with bounded relative error, when applied to queueing networks wherein no other state-independent importance sampling techniques are known to be efficient. The heuristics are robust and remain effective for larger networks. Moreover, insights drawn from the basic networks considered in this article help understand sample path behavior along the boundaries, conditional on reaching the rare event of interest. This is key to the application of the methodology to networks of more general topologies. It is hoped that empirical findings and insights in this paper will encourage more research on related practical and theoretical issues.
Sound and complete elimination of singleton kinds
Authors: Crary Karl
Published: June 2007

Singleton kinds provide an elegant device for expressing type equality information resulting from modern module languages, but they can complicate the metatheory of languages in which they appear. I present a translation from a language with singleton kinds to one without, and prove this translation to be sound and complete. This translation is useful for type-preserving compilers generating typed target languages. The proof of soundness and completeness is done by normalizing type equivalence derivations using Stone and Harper's type equivalence decision procedure.
Where fail-safe default logics fail
Authors: Liberatore Paolo
Published: June 2007

Reiter's original definition of default logic allows for the application of a default that contradicts one previously applied. We call this condition
failure
. The possibility of generating failures has been in the past considered a
semantical
problem, and variants have been proposed to solve it. We show that it is instead a
computational
feature that is needed to encode some domains into default logic.
Logical definability and query languages over ranked and unranked trees
Authors: Benedikt Michael , Libkin Leonid , Neven Frank
Published: June 2007

We study relations on trees defined by first-order constraints over a vocabulary that includes the
tree extension relation T
≺
T
′ (holding if and only if every branch of
T
extends to a branch of
T
′), unary node-tests, and a binary relation checking whether the domains of two trees are equal. We consider both ranked and unranked trees. These are trees with and without a restriction on the number of children of nodes. We adopt the model-theoretic approach to tree relations and study relations definable over the structure consisting of the set of all trees and the aforementioned predicates. We relate definability of sets and relations of trees to computability by tree automata. We show that some natural restrictions correspond to familiar logics in the more classical setting where every tree is a structure over a fixed vocabulary, and to logics studied in the context of XML pattern languages. We then look at relational calculi over collections of trees, and obtain quantifier-restriction results that give us bounds on the expressive power and complexity. As unrestricted relational calculi can express problems that are complete for each level of the polynomial hierarchy, we look at their restrictions, corresponding to the restricted logics over the family of all unranked trees, and find several calculi with low (NC
1
) data complexity which still express properties important for database and document applications. We also give normal forms for safe queries in the calculus.
On unification for bounded distributive lattices
Authors: Sofronie-Stokkermans Viorica
Published: June 2007

We give a method for deciding unifiability in the variety of bounded distributive lattices. For this, we reduce the problem of deciding whether a unification problem S has a solution to the problem of checking the satisfiability of a set Φ
S
of ground clauses. This is achieved by using a structure-preserving translation to clause form. The satisfiability check can then be performed by either a resolution-based theorem prover or a SAT checker. We apply the method to unification with free constants and to unification with linear constant restrictions, and show that, in fact, it yields a decision procedure for the positive theory of the variety of bounded distributive lattices. We also consider the problem of unification over (i.e., in an algebraic extension of) the free lattice. Complexity issues are also addressed.
The arithmetical complexity of dimension and randomness
Authors: Hitchcock John M. , Lutz Jack H. , Terwijn Sebastiaan A.
Published: June 2007

Constructive dimension and constructive strong dimension are effectivizations of the Hausdorff and packing dimensions, respectively. Each infinite binary sequence
A
is assigned a dimension dim(
A
) ∈ [0,1] and a strong dimension Dim(
A
) ∈ [0,1].

Let DIM
α
and DIM
α
str
be the classes of all sequences of dimension α and of strong dimension α, respectively. We show that DIM
0
is properly Π
0
2
, and that for all Δ
0
2
-computable α ∈ (0, 1], DIM
α
is properly Π
0
3
.

To classify the strong dimension classes, we use a more powerful effective Borel hierarchy where a coenumerable predicate is used rather than an enumerable predicate in the definition of the Σ
0
1
level. For all Δ
0
2
-computable α ∈ [0, 1), we show that DIM
α
str
is properly in the Π
0
3
level of this hierarchy. We show that DIM
1
str
is properly in the Π
0
2
level of this hierarchy.

We also prove that the class of Schnorr random sequences and the class of computably random sequences are properly Π
0
3
.
Transfer-based statistical translation of Taiwanese sign language using PCFG
Authors: Wu Chung-Hsien , Su Hung-Yu , Chiu Yu-Hsien , Lin Chia-Hung
Published: June 2007

This article presents a transfer-based statistical model for Chinese to Taiwanese sign-language (TSL) translation. Two sets of probabilistic context-free grammars (PCFGs) are derived from a Chinese Treebank and a bilingual parallel corpus. In this approach, a three-stage translation model is proposed. First, the input Chinese sentence is parsed into possible phrase structure trees (PSTs) based on the Chinese PCFGs. Second, the Chinese PSTs are then transferred into TSL PSTs according to the transfer probabilities between the context-free grammar (CFG) rules of Chinese and TSL derived from the bilingual parallel corpus. Finally, the TSL PSTs are used to generate the possible translation results. The Viterbi algorithm is adopted to obtain the best translation result via the three-stage translation. For evaluation, three objective evaluation metrics including AER, Top-N, and BLUE and one subjective evaluation metric using MOS were used. Experimental results show that the proposed approach outperforms the IBM Model 3 in the task of Chinese to sign-language translation.
Predictive technology model for nano-CMOS design exploration
Authors: Zhao Wei , Cao Yu
Published: June 2007

A predictive MOSFET model is critical for early circuit design research. In this work, a new generation of Predictive Technology Model (PTM) is developed, covering emerging physical effects and alternative structures, such as the double-gate device (i.e., FinFET). Based on physical models and early stage silicon data, PTM of bulk and double-gate devices are successfully generated from 130nm to 32nm technology nodes, with effective channel length down to 13nm. By tuning only ten primary parameters, PTM can be easily customized to cover a wide range of process uncertainties. The accuracy of PTM predictions is comprehensively verified with published silicon data: the error of the current is below 10% for both NMOS and PMOS. Furthermore, the new PTM correctly captures process sensitivities in the nanometer regime. PTM is available online at http://www.eas.asu.edu/~ptm.
Simulation of random cell displacements in QCA
Authors: Schulhof Gabriel , Walus Konrad , Jullien Graham A.
Published: June 2007

We analyze the behavior of quantum-dot cellular automata (QCA) building blocks in the presence of random cell displacements. The QCA cells are modeled using the coherence vector description and simulated using QCADesigner. We evaluate various fundamental circuits: the wire, the inverter, the majority gate, and the two-wire crossing approaches: the coplanar crossover and the multilayer crossover. Our results show that different building blocks have different displacement tolerances. The coplanar crossover and inverter perform the weakest. The wire is the most robust. We have found displacement tolerances to be a function of circuit layout and geometry rather than cell size.
Designing CMOS/molecular memories while considering device parameter variations
Authors: Rose Garrett S. , Yao Yuxing , Tour James M. , Cabe Adam C. , Gergel-Hackett Nadine , Majumdar Nabanita , Bean John C. , Harriott Lloyd R. , Stan Mircea R.
Published: June 2007

In recent years, many advances have been made in the development of molecular scale devices. Experimental data shows that these devices have potential for use in both memory and logic. This article describes the challenges faced in building crossbar array-based molecular memory and develops a methodology to optimize molecular scale architectures based on experimental device data taken at room temperature. In particular, issues in reading and writing such as memory using CMOS are discussed, and a solution is introduced for easily reading device conductivity states (typically characterized by very small currents). Additionally, a metric is derived to determine the voltages for writing to the crossbar array. The proposed memory design is also simulated with consideration to device parameter variations. Thus, the results presented here shed light on important design choices to be made at multiple abstraction levels, from devices to architectures. Simulation results, incorporating experimental device data, are presented using Cadence Spectre.
Automatic classification of Web queries using very large unlabeled query logs
Authors: Beitzel Steven M. , Jensen Eric C. , Lewis David D. , Chowdhury Abdur , Frieder Ophir
Published: June 2007

Accurate topical classification of user queries allows for increased effectiveness and efficiency in general-purpose Web search systems. Such classification becomes critical if the system must route queries to a subset of topic-specific and resource-constrained back-end databases. Successful query classification poses a challenging problem, as Web queries are short, thus providing few features. This feature sparseness, coupled with the constantly changing distribution and vocabulary of queries, hinders traditional text classification. We attack this problem by combining multiple classifiers, including exact lookup and partial matching in databases of manually classified frequent queries, linear models trained by supervised learning, and a novel approach based on mining selectional preferences from a large unlabeled query log. Our approach classifies queries without using external sources of information, such as online Web directories or the contents of retrieved pages, making it viable for use in demanding operational environments, such as large-scale Web search services. We evaluate our approach using a large sample of queries from an operational Web search engine and show that our combined method increases recall by nearly 40% over the best single method while maintaining adequate precision. Additionally, we compare our results to those from the 2005 KDD Cup and find that we perform competitively despite our operational restrictions. This suggests it is possible to topically classify a significant portion of the query stream without requiring external sources of information, allowing for deployment in operationally restricted environments.
PRISM interaction for enhancing control in immersive virtual environments
Authors: Frees Scott , Kessler G. Drew , Kay Edwin
Published: June 2007

When directly manipulating 3D objects in an immersive environment we cannot normally achieve the accuracy and control that we have in the real world. This reduced accuracy stems from hand instability. We present PRISM, which dynamically adjusts the C/D ratio between the hand and the controlled object to provide increased control when moving slowly and direct, unconstrained interaction when moving rapidly. We describe PRISM object translation and rotation and present user studies demonstrating their effectiveness. In addition, we describe a PRISM-enhanced version of ray casting which is shown to increase the speed and accuracy of object selection.
Design parameters of rating scales for web sites
Authors: Van Schaik Paul , Ling Jonathan
Published: June 2007

The effects of design parameters of rating scales on the perceived quality of interaction with web sites were investigated, using four scales (Disorientation, Perceived ease of use, Perceived usefulness and Flow). Overall, the scales exhibited good psychometric properties. In Experiment 1, psychometric results generally converged between two response formats (visual analogue scale and Likert scale). However, in Experiment 2, presentation of one questionnaire item per page was better than all items presented on a single page and direct interaction (using radio buttons) was better than indirect interaction (using a drop-down box). Practical implications and a framework for measurement are presented.
The exact channel density and compound design for generic universal switch blocks
Authors: Fan Hongbing , Liu Jiping , Wu Yu-Liang , Cheung Chak-Chung
Published: June 2007

A switch block of
k
sides
W
terminals on each side is said to be universal (a (
k
,
W
)-USB) if it is routable for every set of 2-pin nets of channel density at most
W
. The generic optimum universal switch block design problem is to design a (
k
,
W
)-USB with the minimum number of switches for every pair of (
k
,
W
). This problem was first proposed and solved for
k
=4 in Chang et al. [1996], and then solved for even
W
or for
k
≤6 in Shuy et al. [2000] and Fan et al. [2002b]. No optimum (
k
,
W
)-USB is known for
k
≥7 and odd
W
≥3. But it is already known that when
W
is a large odd number, a near-optimum (
k
,
W
)-USB can be obtained by a disjoint union of (
W
−
f
2
(
k
))/2 copies of the optimum (
k
, 2)-USB and a noncompound (
k
,
f
2
(
k
))-USB, where the value of
f
2
(
k
) is unknown for
k
≥8. In this article, we show that
f
2
(
k
) =
k
+3−
i
/3, where 1≤
i
≤6 and
i
≡
k
(mod 6), and present an explicit design for the noncompound (
k
,
f
2
(
k
))-USB. Combining these two results we obtain the exact designs of (
k
,
W
)-USBs for all
k
≥7 and odd
W
≥3. The new (
k
,
W
)-USB designs also yield an efficient detailed routing algorithm.
A narrative-based abstraction framework for story-oriented video
Authors: Jung Byunghee , Song Junehwa , Lee Yoonjoon
Published: June 2007

This article proposes a novel video abstraction framework for online review services of story-oriented videos such as dramas. Among the many genres of TV programs, a drama is one of the most popularly watched on the Web. The abstracts generated by the proposed framework not only give a summary of a video but also effectively help viewers understand the overall story. In addition, our method is duration-flexible. We get clues about human understanding of a story from scenario writing rules and editorial techniques that are popularly used in the process of video production to explicitly express a narrative, and propose a new video abstraction model, called a
Narrative Abstraction Model
. The model effectively captures the narrative structure embedded in a story-oriented video and articulates the progress of the story in a weighted directed graph, called a
Narrative Structure Graph (NSG)
. The model provides a basis for a flexible framework for abstract generation using the NSG as the intermediary representation of a video. Different abstracts can be appropriately generated based upon different user requirements. To show the effectiveness of the proposed model and method, we developed a video abstraction system realizing the framework, and successfully applied it to large volumes of TV dramas. The evaluation results show that the proposed framework is a feasible solution for online review services.
Introduction
Authors: Wise David S.
Published: June 2007

Tracing the early days of ACM---its landmark accomplishments, its challenges, its goals---in celebration of its first 60 years.
Sources for ACM history
Authors: Haigh Thomas , Kaplan Elisabeth , Seib Carrie
Published: June 2007

ACM has developed a rich and varied history over its first six decades. Preserving that history in an open and plentiful archive is key to helping future historians tell the ACM story.
A history of the history of programming languages
Authors: Bergin Thomas J. (Tim)
Published: June 2007

"If I have seen further it is by standing on the shoulders of giants."
---Isaac Newton, in a letter to Robert Hooke, Feb. 15, 1676
Accessing the deep web
Authors: He Bin , Patel Mitesh , Zhang Zhen , Chang Kevin Chen-Chuan
Published: June 2007

Attempting to locate and quantify material on the Web that is hidden from typical search techniques.
Modeling multi-agent systems
Authors: da Silva Viviane Torres , de Lucena Carlos J.P.
Published: June 2007

Emerging from a paradigm different from objects, the modeling of agents requires its own conceptual frameworks, modeling languages, and methodologies.
Does personality matter?
Authors: Da Cunha Alessandra Devito , Greathead David
Published: June 2007

Developing a better understanding of the mental processes leading to success or failure in code review.
Saturn
Authors: Xie Yichen , Aiken Alex
Published: June 2007

This article presents Saturn, a general framework for building precise and scalable static error detection systems. Saturn exploits recent advances in Boolean satisfiability (SAT) solvers and is path sensitive, precise down to the bit level, and models pointers and heap data. Our approach is also highly scalable, which we achieve using two techniques. First, for each program function, several optimizations compress the size of the Boolean formulas that model the control flow and data flow and the heap locations accessed by a function. Second, summaries in the spirit of type signatures are computed for each function, allowing interprocedural analysis without a dramatic increase in the size of the Boolean constraints to be solved.

We have experimentally validated our approach by conducting two case studies involving a Linux lock checker and a memory leak checker. Results from the experiments show that our system scales well, parallelizes well, and finds more errors with fewer false positives than previous static error detection systems.
Combinators for bidirectional tree transformations
Authors: Foster J. Nathan , Greenwald Michael B. , Moore Jonathan T. , Pierce Benjamin C. , Schmitt Alan
Published: June 2007

We propose a novel approach to the
view-update problem
for tree-structured data: a domain-specific programming language in which all expressions denote bidirectional transformations on trees. In one direction, these transformations---dubbed
lenses
---map a concrete tree into a simplified abstract view; in the other, they map a modified abstract view, together with the original concrete tree, to a correspondingly modified concrete tree. Our design emphasizes both robustness and ease of use, guaranteeing strong well-behavedness and totality properties for well-typed lenses.

We begin by identifying a natural space of well-behaved bidirectional transformations over arbitrary structures, studying definedness and continuity in this setting. We then instantiate this semantic framework in the form of a collection of
lens combinators
that can be assembled to describe bidirectional transformations on trees. These combinators include familiar constructs from functional programming (composition, mapping, projection, conditionals, recursion) together with some novel primitives for manipulating trees (splitting, pruning, merging, etc.). We illustrate the expressiveness of these combinators by developing a number of bidirectional list-processing transformations as derived forms. An extended example shows how our combinators can be used to define a lens that translates between a native HTML representation of browser bookmarks and a generic abstract bookmark format.
Selective code transformation for dual instruction set processors
Authors: Lee Sheayun , Lee Jaejin , Park Chang Yun , Min Sang Lyul
Published: June 2007

Embedded systems are often constrained in terms of both code size and execution time, because of a limited amount of available memory and real-time nature of applications. A dual instruction set processor, which supports a reduced instruction set (16 bits/instruction), in addition to a full instruction set (32 bits/instruction), allows an opportunity for a tradeoff between these two design criteria. Specifically, while the reduced instruction set can be used to reduce code size by providing smaller instructions, a program compiled into the reduced instruction set typically runs slower than the same program compiled into the full instruction set. Motivated by this observation, we propose a code generation technique that exploits this tradeoff relationship by selectively using the two instruction sets for different sections in the program. The proposed technique, called selective code transformation, not only provides a mechanism to enable a flexible tradeoff between a program's code size and its execution time, but also facilitates program optimization toward enhancing its worst case performance. The results from our experiments show that our proposed technique can be effectively used to fine-tune an application program on a spectrum of code size and execution performance, which, in turn, enables a system-wide optimization on memory space and execution speed involving multiple applications.
ASIP architecture exploration for efficient IPSec encryption
Authors: Scharwaechter Hanno , Kammler David , Wieferink Andreas , Hohenauer Manuel , Karuri Kingshuk , Ceng Jianjiang , Leupers Rainer , Ascheid Gerd , Meyr Heinrich
Published: June 2007

Application-Specific Instruction-Set Processors (ASIPs) are becoming increasingly popular in the world of customized, application-driven
System-on-Chip
(SoC) designs. Efficient ASIP design requires an iterative architecture exploration loop---gradual refinement of the processor architecture starting from an initial template. To accomplish this task, design automation tools are used to detect bottlenecks in embedded applications, to implement application-specific processor instructions, and to automatically generate the required software tools (such as instruction-set simulator, C-compiler, assembler, and profiler), as well as to synthesize the hardware. This paper describes an architecture exploration loop for an ASIP coprocessor that implements common encryption functionality used in symmetric block cipher algorithms for internet protocol security (IPSec). The coprocessor is accessed via shared memory and, as a consequence, our approach is easily adaptable to arbitrary main processor architectures. This paper presents the extended version of our case study that has been already published on the SCOPES conference in 2004. In both papers, a MIPS architecture is used as the main processor and Blowfish as encryption algorithm.
Classifying interprocess communication in process network representation of nested-loop programs
Authors: Turjan Alexandru , Kienhuis Bart , Deprettere Ed
Published: June 2007

New embedded signal-processing architectures are emerging that are composed of loosely coupled heterogeneous components like CPUs or DSPs, specialized IP cores, reconfigurable units, or memories. We believe that these architectures should be programmed using the process network model of computation. To ease the mapping of applications, we are developing the Compaan compiler that automatically derives a process network (PN) description from an application written in Matlab or C. In this paper, we investigate a particular problem in nested loop programs, which is about classifying the interprocess communication in the PN representation of the nested loop program. The global memory arrays present in the code have to be replaced by a distributed communication structure used for communicating data between the network processes. We show that four types of communication exist, each exhibiting different requirements when realizing them in hardware or software. We first present two compile time tests that are based on integer linear programming to decide the type of the communication. In the second part of this paper, we present alternative classification techniques that have polynomial complexity. However, in some cases, those techniques do not give a definitive answer and the ILP tests have to be applied. All present tests are combined in a hybrid classification scheme that correctly classifies the interprocess communication. In only 5% of the cases to classify, we have to rely on integer linear programming while, in the remaining 95%, the alternative techniques presented in this paper are able to correctly classify each case. The hybrid classification scheme has become an important part of our Compaan compiler.
Batch zero-knowledge proof and verification and its applications
Authors: Peng Kun , Boyd Colin , Dawson Ed
Published: June 2007

The batch verification technique of Bellare et al. is extended to verification of several frequently employed zero-knowledge proofs. The new techniques are correct, sound, efficient, and can be widely applied. Specific applications are discussed in detail, including batch ZK proof and verification of validity of encryption (or reencryption) and batch ZK proof and verification of validity of decryption. Considerable efficiency improvements are gained in these two applications without compromising security. As a result, efficiency of the practical cryptographic systems (such as mix networks) based on these two applications is dramatically improved.
Specification and verification of security requirements in a programming model for decentralized CSCW systems
Authors: Ahmed Tanvir , Tripathi Anand R.
Published: June 2007

We present, in this paper, a role-based model for programming distributed CSCW systems. This model supports specification of dynamic security and coordination requirements in such systems. We also present here a model-checking methodology for verifying the security properties of a design expressed in this model. The verification methodology presented here is used to ensure correctness and consistency of a design specification. It is also used to ensure that sensitive security requirements cannot be violated when policy enforcement functions are distributed among the participants. Several aspect-specific verification models are developed to check security properties, such as task-flow constraints, information flow, confidentiality, and assignment of administrative privileges.
Requirements for scalable access control and security management architectures
Authors: Keromytis Angelos D. , Smith Jonathan M.
Published: June 2007

Maximizing local autonomy by delegating functionality to end nodes when possible (the end-to-end design principle) has led to a scalable Internet. Scalability and the capacity for distributed control have unfortunately not extended well to resource access-control policies and mechanisms. Yet management of security is becoming an increasingly challenging problem in no small part due to scaling up of measures such as number of users, protocols, applications, network elements, topological constraints, and functionality expectations.

In this article, we discuss scalability challenges for traditional access-control mechanisms at the architectural level and present a set of fundamental requirements for authorization services in large-scale networks. We show why existing mechanisms fail to meet these requirements and investigate the current design options for a scalable access-control architecture.

We argue that the key design options to achieve scalability are the choice of the representation of access control policy, the distribution mechanism for policy, and the choice of the access-rights revocation scheme. Although these ideas have been considered in the past, current access-control systems in use continue to use simpler but restrictive architectural models. With this article, we hope to influence the design of future access-control systems towards more decentralized and scalable mechanisms.
Optimal design of english auctions with discrete bid levels
Authors: David Esther , Rogers Alex , Jennings Nicholas R. , Schiff Jeremy , Kraus Sarit , Rothkopf Michael H.
Published: June 2007

This article considers a canonical auction protocol that forms the basis of nearly all current online auctions. Such
discrete bid
auctions require that the bidders submit bids at predetermined discrete bid levels, and thus, there exists a minimal increment by which the bid price may be raised. In contrast, the academic literature of optimal auction design deals almost solely with continuous bid auctions. As a result, there is little practical guidance as to how an auctioneer, seeking to maximize its revenue, should determine the number and value of these discrete bid levels, and it is this omission that is addressed here. To this end, a model of an ascending price English auction with discrete bid levels is considered. An expression for the expected revenue of this auction is derived and used to determine numerical and analytical solutions for the optimal bid levels in the case of uniform and exponential bidder's valuation distributions. Finally, in order to develop an intuitive understanding of how these optimal bid levels are distributed, the limiting case where the number of discrete bid levels is large is considered, and an analytical expression for their distribution is derived.
Phase changes in random point quadtrees
Authors: Chern Hua-Huai , Fuchs Michael , Hwang Hsien-Kuei
Published: June 2007

We show that a wide class of linear cost measures (such as the number of leaves) in random
d
-dimensional point quadtrees undergo a change in limit laws: If the dimension
d
= 1, …, 8, then the limit law is normal; if
d
≥ 9 then there is no convergence to a fixed limit law. Stronger approximation results such as convergence rates and local limit theorems are also derived for the number of leaves, additional phase changes being unveiled. Our approach is new and very general, and also applicable to other classes of search trees. A brief discussion of Devroye's grid trees (covering
m
-ary search trees and quadtrees as special cases) is given. We also propose an efficient numerical procedure for computing the constants involved to high precision.