bluuebunny/crossref_metadata_2025 huggingface dataset:
MODEL-BASED TESTING OF CONCURRENT PROGRAMS WITH PREDICATE SEQUENCING CONSTRAINTS
Authors: WU PENG , LIN HUIMIN
Published: October 2006

A predicate sequencing constraint logic (PSCL) is proposed to represent test purpose for concurrent program testing. The logic is capable of expressing not only sequencing relationships among input and output events, but also data dependencies between event parameters. A PSCL-based symbolic test generation method is developed to automatically derive symbolic test cases that incorporate given data dependency constraints as verdict conditions. The method works in a syntactic way without referring to concrete program states and the derived test cases allow dynamic test data selection according to the response from the software under test. The advantage of the approach is demonstrated with a case study.
PREPARATION OF TIN OXIDE NANOPARTICLES BY LASER ABLATION IN SOLUTION
Authors: LI MEI , LU QINGHUA , WANG ZONGGUANG
Published: October 2006

Tin oxide nanoparticles with a narrow size distribution were prepared by pulsed laser ablation of a pure tin target both in aqueous solutions and in pure water. Laser beam of 266 nm, 355 nm and 532 nm from an Nd :YAG laser were applied and the wavelength effects on preparation of tin oxide particles were examined. The particle size and phase structure were characterized by using transmission electron microscope (TEM). The observation revealed that the particle size of the nanoparticles was about 2–5 nm. Chemical components of obtained nanoparticles were analyzed by using an energy dispersive X-ray analysis (EDX) and the results demonstrated that the nanoparticles mainly consisted of Sn and O elements. Furthermore, aqueous solutions of sodium dodecyl sulfate (SDS) were used to study the influence of surfactant concentration on the formation of tin oxide nanoparticles. When the surfactant reached critical micelle concentration, relatively stable colloidal suspensions consisting of well-dispersed tin oxide nanoparticles were obtained. UV-vis spectrometer was used to measure the absorption of suspensions of tin oxide nanoparticles.
PREPARING DOUBLE-BASE THERMO-SENSITIVE CERAMICS WITH NANOPOWDERS
Authors: WANG MENG KUI , YANG YU QIANG
Published: October 2006

The preparing process and the properties of thick-film double-based thermo-sensitive material were studied. The preparing steps were as follows: (i) preparing Ba 1-x Sr x TiO 3 micro-powders with chemical co-precipitation method; (ii) adding dispersants and surface active agents into crushing medium powders to prepare Ba 1-x Sr x TiO 3 nanopowders; (iii) preparing V 2 O 3-based micro-powders; (iv) mixing Ba 1-x Sr x TiO 3 nanopowders, V 2 O 3-based micro-powders, donor impurities, acceptor impurities and micro additives according to a certain ratio to make thick-film thermo-sensitive ceramic material. The presintering and sintering temperature of the prepared PTC ceramics were both reduced, which is very meaningful in using cheaper SiC instead of more expensive MoSi 2, prolonging the kiln's life, and lowering the production cost. The samples we prepared did not contain PbO , so they are safe to the environment.
SYNTHESIS AND CHARACTERIZATION OF CdSe/ZnO CORE/SHELL NANOCRYSTALS
Authors: LU QIANG , SHAN GUIYE , BAI YUBAI , AN LIMIN
Published: October 2006

Highly luminescent monodispersed CdSe nanocrystals were prepared from CdO and Se powder in a three-component hexadecylamine-trioctylphosphine oxide-trioctylphosphine (HAD-TOPO-TOP) mixture under high temperature and nitrogen protection. CdSe/ZnO core/shell nanocrystals were produced by adding Zn(Ac) 2 and LiOH into CdSe nanocrystals solution under ultrasonic at low temperature. ZnO shell grows heterogeneously on the CdSe substrate. The structure and fluorescence have been characterized by TEM (transmission electron micrograph), XRD (X-ray diffraction), UV-Vis and PL spectra. It can be found that after the surface passivation with ZnO shell, electrons were confined in the CdSe core due to the wide band-gap effect of ZnO , which resulted in the obvious increasing of the fluorescent intensity.
SYNTHESIS AND CHARACTERIZATION OF Cu NANOPARTICLES PREPARED BY THERMAL DECOMPOSITION OF Cu-OLEATE COMPLEX
Authors: KANG YOUNG SOO , KIM YOUNG HWAN , JO BEONG GI , JEONG JEE HEAN
Published: October 2006

Cu nanoparticles have been synthesized by thermal decomposition of Cu -oleate complex, which was prepared by the reaction with CuCl 2 and sodium oleate in water solution. The monodispersed Cu nanoparticles were produced by controlling temperature (290°C). TEM images of the nanoparticles showed two-dimensional assembly of particles with diameter of 16.2 ± 2.9 nm , demonstrating the uniformity of these nanoparticles. EDX spectrum and XRD peaks of the nanoparticles showed the highly crystalline nature of the Cu structures. The decomposition of Cu -oleate complex was analyzed with TGA and the crystallization of Cu nanoparticles was observed with XRD.
SYNTHESIS AND CHARACTERIZATION OF TITANIUM DIOXIDE DOPED WITH Sc3+ IONS
Authors: KANG YOUNG SOO , ZHANG DONG RI
Published: October 2006

Nanoparticles of titanium dioxide ( TiO 2) doped with 5 at.% Sc 3+ ions were synthesized using the sol–gel method and calcined at 500°C to obtain better anatase phase. The crystal structures of the doped TiO 2 nanoparticles were characterized by X-ray powder diffraction (XRD), Raman, UV-vis, FT-IR spectroscopy, high resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED). XRD patterns and Raman spectra of TiO 2 + 5 at.% Sc -500°C show the anatase phase and the average particle size of the sample calculated from XRD patterns was determined as 5.9 nm. Well-resolved rings of SAED of TiO 2 doped with Sc 3+ ions are easily indexed to those from XRD pattern. HRTEM shows the well-defined lattice fringes and the lattice spacing measured from HRTEM is 0.33 nm, which is in well agreement with the distance between the (101) planes in anatase TiO 2. Energy-dispersive X-ray (EDX) spectrum of the doped TiO 2 confirms the presence of Sc element in the TiO 2 matrix.
SONOCHEMICAL PREPARATION OF GOLD/IRON OXIDE COMPOSITE MAGNETIC NANOPARTICLES AND SELECTIVE MAGNETIC SEPARATION OF BIOMOLECULES
Authors: MIZUKOSHI YOSHITERU , SEINO SATOSHI , OKITSU KENJI , KINOSHITA TAKUYA , NAKAGAWA TAKASHI , YAMAMOTO TAKAO A.
Published: October 2006

We have successfully prepared Au nanoparticles by the sonochemically reducing Au(III) ions and immobilized them on the surface of magnetic γ- Fe 2 O 3 nanoparticles. Au particles with average diameter of about 10 nm were homogeneously dispersed on the surface of γ- Fe 2 O 3 (average diameter : 26 nm) without aggregation. Au nanoparticles are known to selectively adsorb the molecules having sulfur. Aiming at the uses for magnetic carriers of specific biomolecules, we employed prepared composite nanoparticles for selective separation of biomolecules and estimated their adsorption properties. The composite nanoparticles exhibited a high affinity with glutathione, a tripeptide with mercapto group, so that separation and manipulation of glutathione in aqueous solutions could be performed by applying an external magnetic field. Magnetic separations of amino acids were also investigated. Composite nanoparticles were mixed with amino acid standard solution containing 17 kinds of amino acids and their magnetic separations were carried out by applying an external magnetic field. It was found that adsorption amounts of methionine and cystine, containing internal sulfur were larger than other amino acids. The adsorbed amounts of sulfur containing amino acids increased with relative amount of Au in the composite nanoparticles.
The late Neogene Sahabi rivers of the Sahara and their climatic and environmental implications for the Chad Basin
Authors: GRIFFIN DAVID L.
Published: October 2006

This paper is based on the concept that the drainage system of
c
. 7.5–4.6 Ma is still reflected in the geomorphology of northeastern Chad and adjacent areas of Libya. During the Messinian and early Pliocene a large lake was present in the Chad Basin that is termed Neogene Lake Chad. It fluctuated in size in response to the precessional cycle and at times overflowed to the east, NE or north, giving rise to the Sahabi rivers. The Eosahabi flowed during the drawdown of the Mediterranean (late Messinian) and eroded the Erdi and part of the East Tibesti Valley. The post-rift Miocene deposits of the Chad Basin, some several hundred metres in thickness, record a transgression over an irregular and faulted terrain with the deposition of coarse and fine clastic material. Fluviatile and lacustrine environments are represented. At least part of the Miocene succession belongs to a phase of late Miocene lake development. Fluctuating climate during the Messinian and early Pliocene led to repeated changes in the environment of the Chad and Eosahabi Basins with over 100 climatic cycles developed. This would favour the development of animal species with high adaptability, for example to littoral, riparian, woodland and savanna habitats.
Early dolomitization and recrystallization of carbonate in an evaporite basin: the Middle Devonian Ratner laminite in southern Saskatchewan, Canada
Authors: Fu Qilong , Qing Hairuo , Bergman Katherine M.
Published: October 2006

This study provides an example of early dolomitization of basinal limestone associated with a giant evaporite deposit. The Middle Devonian Ratner carbonate is extensively to completely replaced by microcrystalline to finely crystalline dolomite in the southern and central part of southern Saskatchewan in the Elk Point Basin. In the northern part, however, individual cored intervals of the Ratner laminite are either completely dolomitized or contain no microcrystalline to finely crystalline dolomite. Stratigraphic, petrographical and Sr-isotopic data suggest that the Ratner dolomite has formed penecontemporaneously from dense, evaporitic seawater that percolated downward. The distribution of the Ratner dolomite is highly localized in the northern part of the study area, suggesting that the downward flow of Mg
2+
-rich fluids was restricted by interbedded anhydrite, but where the fluids penetrated, the underlying carbonate deposits were dolomitized. The depletion in
18
O isotope (varying from −4.5 to −6.6‰ PDB), and the coarser and inhomogeneous textures of the Ratner dolomite are considered to be the result of recrystallization, which is interpreted to occur at elevated temperatures related to a thermal anomaly during the Late Devonian and Carboniferous burial.
Age, tectonic setting and regional implications of the Chiang Khong volcanic suite, northern Thailand
Authors: Barr Sandra M. , Macdonald Alan S. , Ounchanum Prayote , Hamilton Michael A.
Published: October 2006

The Chiang Khong volcanic suite forms the northeastern part of the Tak–Chiang Khong volcanic belt in the Sukhothai terrane of northern Thailand. It consists mainly of subaerial andesitic to rhyolitic tuffaceous rocks. A rhyolitic tuff yielded a Middle Triassic U–Pb (zircon) age of 232.9 ± 0.4 Ma. The suite displays calc-alkalic chemical trends and Nb, P, and Ti depletion characteristic of subduction-related magmatism. Based on petrological similarities, the suite is correlated with the
c
. 240 Ma Lampang volcanic rocks located farther to the SW in the Tak–Chiang Khong belt, and with volcanic rocks of similar age in the Lincang–Jinghong belt in Yunnan, in the western part of the Simao block. These correlations support the placement of the Palaeo-Tethyan suture to the west of the Sukhothai terrane.
Interestingness measures for data mining
Authors: Geng Liqiang , Hamilton Howard J.
Published: October 2006

Interestingness measures play an important role in data mining, regardless of the kind of patterns being mined. These measures are intended for selecting and ranking patterns according to their potential interest to the user. Good measures also allow the time and space costs of the mining process to be reduced. This survey reviews the interestingness measures for rules and summaries, classifies them from several perspectives, compares their properties, identifies their roles in the data mining process, gives strategies for selecting appropriate measures for applications, and identifies opportunities for future research in this area.
Transforming your shadow into colorful visual media
Authors: Minomo Yugo , Kakehi Yasuaki , Iida Makoto , Naemura Takeshi
Published: October 2006

This article proposes a real-time system that transforms shadows on a floor into colorful visual media. This system is based on the effect of complementary colors and multiprojection techniques. By exactly calibrating the system geometrically and photometrically, our system makes it possible to display images such as texture animation, colorful pictures, text, and live videos in shadows without any digitized artifact or latency. Since it can display any image, it is applicable for various purposes such as media art, entertainment, and advertisement.
A practical guide to SQL white-box testing
Authors: Tuya Javier , Suárez-Cabal M. José , de la Riva Claudio
Published: October 2006

SQL is a ubiquitous language used in a wide range of applications for accessing the data stored in relational databases. However, the usual software testing techniques are not designed to address some important features of SQL. We present a set of practical guidelines for designing white-box tests cases that reasonably exercise the way in which an SQL query processes the stored data. These guidelines are illustrated using an example.
Analysis of state-independent importance-sampling measures for the two-node tandem queue
Authors: De Boer Pieter-Tjerk
Published: October 2006

We investigate the simulation of overflow of the total population of a Markovian two-node tandem queue model during a busy cycle, using importance sampling with a state-independent change of measure. We show that the only such change of measure that may possibly result in asymptotically efficient simulation for large overflow levels is exchanging the arrival rate with the smallest service rate. For this change of measure, we classify the model's parameter space into regions of asymptotic efficiency, exponential growth of the relative error, and infinite variance, using both analytical and numerical techniques.
Memory performance
Authors: Bartolini S. , Foglia P. , Giorgi R. , Prete C. A.
Published: October 2006

In this issue of ACM SigArch Newsletter, we present ten papers from MEDEA-2005 Workshop held in conjunction with the IEEE/ACM International Conference on Parallel Architectures and Compilation Techniques (PACT-2004) [1], [2].
Yield enhancement of reconfigurable microfluidics-based biochips using interstitial redundancy
Authors: Su Fei , Chakrabarty Krishnendu
Published: October 2006

Microfluidics-based biochips for biochemical analysis are currently receiving much attention. They automate highly repetitive laboratory procedures by replacing cumbersome equipment with miniaturized and integrated systems. As these microfluidics-based microsystems become more complex, manufacturing yield will have significant influence on production volume and product cost. We propose an interstitial redundancy approach to enhance the yield of biochips that are based on droplet-based digital microfluidics. In this design method, spare cells are placed in the interstitial sites within the microfluidic array, and they replace neighboring faulty cells via local reconfiguration. The proposed design method is evaluated using a set of concurrent real-life bioassays. The defect-tolerant design approach based on space redundancy and local reconfiguration is expected to facilitate yield enhancement of microfluidics-based biochips, especially for the emerging marketplace.
A stochastic model for the evolution of the Web allowing link deletion
Authors: Fenner Trevor , Levene Mark , Loizou George
Published: October 2006

Recently several authors have proposed stochastic evolutionary models for the growth of the Web graph and other networks that give rise to power-law distributions. These models are based on the notion of preferential attachment, leading to the “rich get richer” phenomenon. We present a generalization of the basic model by allowing deletion of individual links and show that it also gives rise to a power-law distribution. We derive the mean-field equations for this stochastic model and show that, by examining a snapshot of the distribution at the steady state of the model, we are able to determine the extent to which link deletion has taken place and estimate the probability of deleting a link. Applying our model to actual Web graph data provides evidence of the extent to which link deletion has occurred. We also discuss a problem that frequently arises in estimating the power-law exponent from empirical data and a few possible methods for dealing with this, indicating our preferred approach. Using this approach our analysis of the data suggests a power-law exponent of approximately 2.15 for the distribution of inlinks in the Web graph, rather than the widely published value of 2.1.
One story, one flow
Authors: Fung Pascale , Ngai Grace
Published: October 2006

This article presents a multidocument, multilingual, theme-based summarization system based on modeling text cohesion (story flow). Conventional extractive summarization systems which pick out salient sentences to include in a summary often disregard any flow or sequence that might exist between these sentences. We argue that such inherent text cohesion exists and is (1) specific to a particular story and (2) specific to a particular language. Documents within the same story, and in the same language, share a common story flow, and this flow differs across stories, and across languages. We propose using Hidden Markov Models (HMMs) as story models. An unsupervised segmental K-means method is used to iteratively cluster multiple documents into different topics (stories) and learn the parameters of parallel Hidden Markov Story Models (HMSM), one for each story. We compare story models within and across stories and within and across languages (English and Chinese). The experimental results support our “one story, one flow” and “one language, one flow” hypotheses. We also propose a Naïve Bayes classifier for document summarization. The performance of our summarizer is superior to conventional methods that do not incorporate text cohesion information. Our HMSM method also provides a simple way to compile a single metasummary for multiple documents from individual summaries via state labeled sentences.
Ensemble-level Power Management for Dense Blade Servers
Authors: Ranganathan Parthasarathy , Leech Phil , Irwin David , Chase Jeffrey
Published: October 2006

One of the key challenges for high-density servers (e.g., blades) is the increased costs in addressing the power and heat density associated with compaction. Prior approaches have mainly focused on reducing the heat generated at the level of an individual server. In contrast, this work proposes power efficiencies at a larger scale by leveraging statistical properties of concurrent resource usage across a collection of systems ("ensemble"). Specifically, we discuss an implementation of this approach at the blade enclosure level to monitor and manage the power across the individual blades in a chassis. Our approach requires low-cost hardware modifications and relatively simple software support. We evaluate our architecture through both prototyping and simulation. For workloads representing 132 servers from nine different enterprise deployments, we show significant power budget reductions at performances comparable to conventional systems.
Techniques for Multicore Thermal Management
Authors: Donald James , Martonosi Margaret
Published: October 2006

Power density continues to increase exponentially with each new technology generation, posing a major challenge for thermal management in modern processors. Much past work has examined microarchitectural policies for reducing total chip power, but these techniques alone are insufficient if not aimed at mitigating individual hotspots. The industry's current trend has been toward multicore architectures, which provide additional opportunities for dynamic thermal management. This paper explores various thermal management techniques that exploit the distributed nature of multicore processors. We classify these techniques in terms of core throttling policy, whether that policy is applied locally to a core or to the processor as a whole, and process migration policies. We use Turandot and a HotSpot-based thermal simulator to simulate a variety of workloads under thermal duress on a 4-core PowerPCTMprocessor. Using benchmarks from the SPEC 2000 suite we characterize workloads in terms of instruction throughput as well as their effective duty cycles. Among a variety of options we find that distributed controltheoretic DVFS alone improves throughput by 2.5X under our test conditions. Our final design involves a PI-based core thermal controller and an outer control loop to decide process migrations. This policy avoids all thermal emergencies and yields an average of 2.6X speedup over the baseline across all workloads.
SODA
Authors: Lin Yuan , Lee Hyunseok , Woh Mark , Harel Yoav , Mahlke Scott , Mudge Trevor , Chakrabarti Chaitali , Flautner Krisztian
Published: October 2006

The physical layer of most wireless protocols is traditionally implemented in custom hardware to satisfy the heavy computational requirements while keeping power consumption to a minimum. These implementations are time consuming to design and difficult to verify. A programmable hardware platform capable of supporting software implementations of the physical layer, or software defined radio, has a number of advantages. These include support for multiple protocols, faster time-to-market, higher chip volumes, and support for late implementation changes. The challenge is to achieve this without sacrificing power. In this paper, we present a design study for a fully programmable architecture, SODA, that supports software defined radio a high-end signal processing application. Our design achieves high performance, energy efficiency, and programmability through a combination of features that include single-instruction multiple- data (SIMD) parallelism, and hardware optimized for 16bit computations. The basic processing element is an asymmetric processor consisting of a scalar and SIMD pipeline, and a set of distributed scratchpad memories that are fully managed in software. Results show that a four processor design is capable of meeting the throughput requirements of theW-CDMA and 802.11a protocols, while operating within the strict power constraints of a mobile terminal.
Balanced Cache
Authors: Zhang Chuanjun
Published: October 2006

Level one cache normally resides on a processor's critical path, which determines the clock frequency. Directmapped caches exhibit fast access time but poor hit rates compared with same sized set-associative caches due to nonuniform accesses to the cache sets, which generate more conflict misses in some sets while other sets are underutilized. We propose a technique to reduce the miss rate of direct mapped caches through balancing the accesses to cache sets. We increase the decoder length and thus reduce the accesses to heavily used sets without dynamically detecting the cache set usage information. We introduce a replacement policy to direct-mapped cache design and increase the access to the underutilized cache sets with the help of programmable decoders. On average, the proposed balanced cache, or BCache, achieves 64.5% and 37.8% miss rate reductions on all 26 SPEC2K benchmarks for the instruction and data caches, respectively. This translates into an average IPC improvement of 5.9%. The B-Cache consumes 10.5% more power per access but exhibits 2% total memory access related energy saving due to the miss rate reductions and hence the reduction to applications' execution time. Compared with previous techniques that aim at reducing the miss rate of direct-mapped caches, our technique requires only one cycle to access all cache hits and has the same access time of a direct-mapped cache.
Chisel
Authors: Hasan Jahangir , Cadambi Srihari , Jakkula Venkatta , Chakradhar Srimat
Published: October 2006

Longest Prefix Matching (LPM) is a fundamental part of various network processing tasks. Previously proposed approaches for LPM result in prohibitive cost and power dissipation (TCAMs) or in large memory requirements and long lookup latencies (tries), when considering future line-rates, table sizes and key lengths (e.g., IPv6). Hash-based approaches appear to be an excellent candidate for LPM with the possibility of low power, compact storage, and O(1) latencies. However, there are two key problems that hinder their practical deployment as LPM solutions. First, naïve hash tables incur collisions and resolve them using chaining, adversely affecting worst-case lookup-rate guarantees that routers must provide. Second, hash functions cannot directly operate on wildcard bits, a requirement for LPM, and current solutions require either considerably complex hardware or large storage space. In this paper we propose a novel architecture which successfully addresses for the first time, both key problems in hash based LPM  making the following contributions: (1) We architect an LPM solution based upon a recently-proposed, collision-free hashing scheme called Bloomier filter, by eliminating its false positives in a storage efficient way. (2) We propose a novel scheme called prefix collapsing, which provides support for wildcard bits with small additional storage and reduced hardware complexity. (3) We exploit prefix collapsing and key characteristics found in real update traces to support fast and incremental updates, a feature generally not available in collision-free hashing schemes.
Interconnection Networks for Scalable Quantum Computers
Authors: Isailovic Nemanja , Patel Yatish , Whitney Mark , Kubiatowicz John
Published: October 2006

We show that the problem of communication in a quantum computer reduces to constructing reliable quantum channels by distributing high-fidelity EPR pairs. We develop analytical models of the latency, bandwidth, error rate and resource utilization of such channels, and show that 100s of qubits must be distributed to accommodate a single data communication. Next, we show that a grid of teleportation nodes forms a good substrate on which to distribute EPR pairs. We also explore the control requirements for such a network. Finally, we propose a specific routing architecture and simulate the Quantum Fourier Transform to demonstrate the impact of resource contention.
Learning-Based SMT Processor Resource Distribution via Hill-Climbing
Authors: Choi Seungryul , Yeung Donald
Published: October 2006

The key to high performance in Simultaneous Multithreaded (SMT) processors lies in optimizing the distribution of shared resources to active threads. Existing resource distribution techniques optimize performance only indirectly. They infer potential performance bottlenecks by observing indicators, like instruction occupancy or cache miss counts, and take actions to try to alleviate them. While the corrective actions are designed to improve performance, their actual performance impact is not known since end performance is never monitored. Consequently, potential performance gains are lost whenever the corrective actions do not effectively address the actual bottlenecks occurring in the pipeline. We propose a different approach to SMT resource distribution that optimizes end performance directly. Our approach observes the impact that resource distribution decisions have on performance at runtime, and feeds this information back to the resource distribution mechanisms to improve future decisions. By evaluating many different resource distributions, our approach tries to learn the best distribution over time. Because we perform learning on-line, learning time is crucial. We develop a hill-climbing algorithm that efficiently learns the best distribution of resources by following the performance gradient within the resource distribution space. This paper conducts an in-depth investigation of learningbased SMT resource distribution. First, we compare existing resource distribution techniques to an ideal learning-based technique that performs learning off-line. This limit study shows learning-based techniques can provide up to 19.2% gain over ICOUNT, 18.0% gain over FLUSH, and 7.6% gain over DCRA across 21 multithreaded workloads. Then, we present an on-line learning algorithm based on hill-climbing. Our evaluation shows hill-climbing provides a 12.4% gain over ICOUNT, 11.3% gain over FLUSH, and 2.4% gain over DCRA across a larger set of 42 multiprogrammed workloads.
Cooperative Caching for Chip Multiprocessors
Authors: Chang Jichuan , Sohi Gurindar S.
Published: October 2006

This paper presents CMP Cooperative Caching, a unified framework to manage a CMP's aggregate on-chip cache resources. Cooperative caching combines the strengths of private and shared cache organizations by forming an aggregate "shared" cache through cooperation among private caches. Locally active data are attracted to the private caches by their accessing processors to reduce remote on-chip references, while globally active data are cooperatively identified and kept in the aggregate cache to reduce off-chip accesses. Examples of cooperation include cache-to-cache transfers of clean data, replication-aware data replacement, and global replacement of inactive data. These policies can be implemented by modifying an existing cache replacement policy and cache coherence protocol, or by the new implementation of a directory-based protocol presented in this paper. Our evaluation using full-system simulation shows that cooperative caching achieves an off-chip miss rate similar to that of a shared cache, and a local cache hit rate similar to that of using private caches. Cooperative caching performs robustly over a range of system/cache sizes and memory latencies. For an 8-core CMP with 1MB L2 cache per core, the best cooperative caching scheme improves the performance of multithreaded commercial workloads by 5-11% compared with a shared cache and 4-38% compared with private caches. For a 4-core CMP running multiprogrammed SPEC2000 workloads, cooperative caching is on average 11% and 6% faster than shared and private cache organizations, respectively.
Area-Performance Trade-offs in Tiled Dataflow Architectures
Authors: Swanson Steven , Putnam Andrew , Mercaldi Martha , Michelson Ken , Petersen Andrew , Schwerin Andrew , Oskin Mark , Eggers Susan J.
Published: October 2006

Tiled architectures, such as RAW, SmartMemories, TRIPS, and WaveScalar, promise to address several issues facing conventional processors, including complexity, wire-delay, and performance. The basic premise of these architectures is that larger, higher-performance implementations can be constructed by replicating the basic tile across the chip. This paper explores the area-performance trade-offs when designing one such tiled architecture, WaveScalar. We use a synthesizable RTL model and cycle-level simulator to perform an area/performance pareto analysis of over 200 WaveScalar processor designs ranging in size from 19mm2 to 378mm2 and having a 22 FO4 cycle time. We demonstrate that, for multi-threaded workloads, WaveScalar performance scales almost ideally from 19 to 101mm2 when optimized for area efficiency and from 44 to 202mm2when optimized for peak performance. Our analysis reveals that WaveScalar's hierarchical interconnect plays an important role in overall scalability, and that WaveScalar achieves the same (or higher) performance in substantially less area than either an aggressive out-of-order superscalar or Sun's Niagara CMP processor.
Distributed Arithmetic on a Quantum Multicomputer
Authors: Van Meter Rodney , Nemoto Kae , Munro W. J. , Itoh Kohei M.
Published: October 2006

We evaluate the performance of quantum arithmetic algorithms run on a distributed quantum computer (a quantum multicomputer). We vary the node capacity and I/O capabilities, and the network topology. The tradeoff of choosing between gates executed remotely, through "teleported gates" on entangled pairs of qubits (telegate), versus exchanging the relevant qubits via quantum teleportation, then executing the algorithm using local gates (teledata), is examined. We show that the teledata approach performs better, and that carry-ripple adders perform well when the teleportation block is decomposed so that the key quantum operations can be parallelized. A node size of only a few logical qubits performs adequately provided that the nodes have two transceiver qubits. A linear network topology performs acceptably for a broad range of system sizes and performance parameters. We therefore recommend pursuing small, high-I/O bandwidth nodes and a simple network. Such a machine will run Shor's algorithm for factoring large numbers efficiently.
An Integrated Framework for Dependable and Revivable Architectures Using Multicore Processors
Authors: Shi Weidong , Lee Hsien-Hsin S. , `Falk Laura , Ghosh Mrinmoy
Published: October 2006

This paper presents a high-availability system architecture called INDRA an INtegrated framework for Dependable and Revivable Architecture that enhances a multicore processor (or CMP) with novel security and fault recovery mechanisms. INDRA represents the first effort to create remote attack immune, self-healing network services using the emerging multicore processors. By exploring the property of a tightly-coupled multicore system, INDRA pioneers several concepts. It creates a hardware insulation, establishes finegrained fault monitoring, exploits monitoring/backup concurrency, and facilitates fast recovery services with minimal performance impact. In addition, INDRA's fault/exploit monitoring is implemented in software rather than in hardware logic, thereby providing better flexibility and upgradability. To provide efficient service recovery and thus improve service availability, we propose a novel delta state backup and recovery on-demand mechanism in INDRA that substantially outperforms conventional checkpointing schemes. We demonstrate and evaluate INDRA's capability and performance using real network services and a cycle-level architecture simulator. As indicated by our performance results, INDRA is highly effective in establishing a more dependable system with high service availability using emerging multicore processors.
This side up!
Authors: Epstein Leah , van Stee Rob
Published: October 2006

We consider two- and three-dimensional bin-packing problems where 90° rotations are allowed. We improve all known asymptotic performance bounds for these problems. In particular, we show how to combine ideas from strip packing and two-dimensional bin packing to give a new algorithm for the three-dimensional strip packing problem where boxes can only be rotated sideways. We propose to call this problem “This side up”. Our algorithm has an asymptotic performance bound of 9/4.
Wireless laptops in the classroom (and the Sesame Street syndrome)
Authors: Adams Dennis
Published: October 2006

Give instructors the option of turning off wireless Web access to accommodate their students' learning styles, in some cases to save them from themselves.
Distributed usage control
Authors: Pretschner Alexander , Hilty Manuel , Basin David
Published: October 2006

Using a server-side architecture to connect specialized enforcement mechanisms with usage control requirements and policies.
Legal programming
Authors: Subirana Brian , Bain Malcolm
Published: October 2006

Using a process modeling-based approach to address privacy and related legal issues arising in an RFID-based augmented reality shopping situation.
Can self-organizing P2P file distribution provide QoS guarantees?
Authors: Bindal Ruchir , Cao Pei
Published: October 2006

In this paper, we examine the factors that contribute to the variability in download time of a self-organizing P2P file distribution application such as BitTorrent. We conducted a series of side-by-side live experiments, involving two clients running on the same machine downloading the same file at the same time. We found that the download latency varied significantly, sometimes by a factor of 2. Surprisingly, the main contributing factor isn't the network bandwidths of the set of neighbors that a client is given. Rather, it has to do with the frequency of turn-overs in "close" neighbors, i.e. those that are in a stable data-exchange relationship with the client. Analysis of the log data shows that a client obtains over 90% of the file from a small set of close neighbors, and if a close neighbor leaves the network, it takes the client a long time,
over half an hour
, to find another one. This suggests that self-organizing P2P file distributions indeed need external help in order to provide QoS guarantees, but such guarantees are achievable with proper enhancements to the P2P network.
MINIX 3
Authors: Herder Jorrit N. , Bos Herbert , Gras Ben , Homburg Philip , Tanenbaum Andrew S.
Published: October 2006

Different kinds of people use computers now than several decades ago, but operating systems have not fully kept pace with this change. It is true that we have point-and-click GUIs now instead of command line interfaces, but the expectation of the average user is different from what it used to be, because the user is different. Thirty or 40 years ago, when operating systems began to solidify into their current form, almost all computer users were programmers, scientists, engineers, or similar professionals doing heavy-duty computation, and they cared a great deal about speed. Few teenagers and even fewer grandmothers spent hours a day behind their terminal. Early users expected the computer to crash often; reboots came as naturally as waiting for the neighborhood TV repairman to come replace the picture tube on their home TVs. All that has changed and operating systems need to change with the times.
Analyzing the MAC-level behavior of wireless networks in the wild
Authors: Mahajan Ratul , Rodrig Maya , Wetherall David , Zahorjan John
Published: October 2006

We present Wit, a non-intrusive tool that builds on passive monitoring to analyze the detailed MAC-level behavior of operational wireless networks. Wit uses three processing steps to construct an enhanced trace of system activity. First, a robust merging procedure combines the necessarily incomplete views from multiple, independent monitors into a single, more complete trace of wireless activity. Next, a novel inference engine based on formal language methods reconstructs packets that were not captured by any monitor and determines whether each packet was received by its destination. Finally, Wit derives network performance measures from this enhanced trace; we show how to estimate the number of stations competing for the medium. We assess Wit with a mix of real traces and simulation tests. We find that merging and inference both significantly enhance the originally captured trace. We apply Wit to multi-monitor traces from a live network to show how it facilitates 802.11 MAC analyses that would otherwise be difficult or rely on less accurate heuristics.
The impact and implications of the growth in residential user-to-user traffic
Authors: Cho Kenjiro , Fukuda Kensuke , Esaki Hiroshi , Kato Akira
Published: October 2006

It has been reported worldwide that peer-to-peer traffic is taking up a significant portion of backbone networks. In particular, it is prominent in Japan because of the high penetration rate of fiber-based broadband access. In this paper, we first report aggregated traffic measurements collected over 21 months from seven ISPs covering 42% of the Japanese backbone traffic. The backbone is dominated by symmetric residential traffic which increased 37%in 2005. We further investigate residential per-customer trafficc in one of the ISPs by comparing DSL and fiber users, heavy-hitters and normal users, and geographic traffic matrices. The results reveal that a small segment of users dictate the overall behavior; 4% of heavy-hitters account for 75% of the inbound volume, and the fiber users account for 86%of the inbound volume. About 63%of the total residential volume is user-to-user traffic. The dominant applications exhibit poor locality and communicate with a wide range and number of peers. The distribution of heavy-hitters is heavy-tailed without a clear boundary between heavy-hitters and normal users, which suggests that users start playing with peer-to-peer applications, become heavy-hitters, and eventually shift from DSL to fiber. We provide conclusive empirical evidence from a large and diverse set of commercial backbone data that the emergence of new attractive applications has drastically affected traffic usage and capacity engineering requirements.
Towards unbiased end-to-end network diagnosis
Authors: Zhao Yao , Chen Yan , Bindel David
Published: October 2006

Internet fault diagnosis is extremely important for end users, overlay network service providers (like Akamai [1]) and even Internet service providers (ISPs). However, because link-level properties cannot be uniquely determined from end-to-end measurements, the accuracy of existing statistical diagnosis approaches is subject to uncertainty from statistical assumptions about the network. In this paper, we propose a novel
Least-biased End-to-end Network Diagnosis
(in short, LEND) system for inferring link-level properties like loss rate. We define a
minimal identifiable link sequence
(MILS) as a link sequence of minimal length whose properties can be uniquely identified from end-to-end measurements. We also design efficient algorithms to find all the MILSes and infer their loss rates for diagnosis. Our LEND system works for any network topology and for both directed and undirected properties, and incrementally adapts to network topology and property changes. It gives highly accurate estimates of the loss rates of MILSes, as indicated by both extensive simulations and Internet experiments. Furthermore, we demonstrate that such diagnosis can be achieved with fine granularity and in near real-time even for reasonably large overlay networks. Finally, LEND can supplement existing statistical inference approaches and provide smooth tradeoff between diagnosis accuracy and granularity.
Detecting evasion attacks at high speeds without reassembly
Authors: Varghese George , Fingerhut J. Andrew , Bonomi Flavio
Published: October 2006

Ptacek and Newsham [14] showed how to evade signature detection at Intrusion Prevention Systems (IPS) using TCP and IP Fragmentation. These attacks are implemented in tools like FragRoute, and are institutionalized in IPS product tests. The classic defense is for the IPS to reassemble TCP and IP packets,and to consistently normalize the output stream. Current IPS standards require keeping state for 1 million connections. Both the state and processing requirements of reassembly and normalization are barriers to scalability for an IPS at speeds higher than 10 Gbps.In this paper, we suggest breaking with this paradigm using an approach we call Split-Detect. We focus on the simplest form of signature, an exact string match, and start by splitting the signature into pieces. By doing so the attacker is either forced to include at least one piece completely in a packet, or to display potentially abnormal behavior (e.g., several small TCP fragments or out-of-order packets) that cause the attacker's flow to be diverted to a slow path. We prove that under certain assumptions this scheme can detect all byte-string evasions. We also show using real traces that the processing and storage requirements of this scheme can be 10% of that required by a conventional IPS, allowing reasonable cost implementations at 20 Gbps. While the changes required by Split-Detect may be a barrier to adoption, this paper exposes the assumptions that must be changed to avoid normalization and reassembly in the fast path.
Teaching programming and language concepts using LEGOs®
Authors: Hood Cynthia S. , Hood Dennis J.
Published: October 2006

In this paper we describe an innovative method for using LEGO® bricks to teach programming and other computing concepts. LEGO® bricks are used to express a special purpose language to build creations out of LEGOs®. Using this language, students can execute and create programs. Both fundamental and more advanced concepts can be taught. The use of LEGOs® increases the tactile and kinesthetic aspects of the learning experience and helps to make abstract concepts more concrete. We have used this method to teach a variety of concepts to college freshmen, K-12 teachers, and K-12 students.
Is it really an algorithm
Authors: Haberman Bruria , Averbuch Haim , Ginat David
Published: October 2006

The notion of an algorithm is fundamental in computer science. Yet, it is not always fully conceived by novices. This paper focuses on a particular facet of algorithm conception - the relationship between an algorithmic problem, its analysis, and its desired algorithmic solution. The paper displays evidence that novices demonstrate cognitive obstacles regarding the notion of an algorithm, which relate to a process-object duality phenomena [13] and inadequate classroom norms of communication.
From objects-first to design-first with multimedia and intelligent tutoring
Authors: Moritz Sally H. , Wei Fang , Parvez Shahida M. , Blank Glenn D.
Published: October 2006

"Objects-first" is an increasingly popular strategy for teaching object-oriented programming by introducing the concepts of objects, classes, and instances before procedural elements of a programming language. Still, this approach emphasizes coding rather than other critical aspects of software development, notably problem-solving and design. We propose a "design-first" curriculum, which subsumes an objects-first approach into lessons that also introduce object-oriented analysis and design, using elements of UML before implementing any code. We also present CIMEL ITS, an intelligent tutoring system that uses the design-first approach to help students of various learning styles in a CS1 course. It interfaces with an IDE we have chosen specifically to support the design-first curriculum, and CIMEL, multimedia courseware which has been shown to be effective in helping students learn object-oriented programming concepts.
Iconic programming for flowcharts, java, turing, etc
Authors: Chen Stephen , Morris Stephen
Published: October 2006

One of the largest barriers to learning programming is the precise and complex syntax required to write programs. This barrier is a key impediment to the integration of programming into the core curriculum of general high school science courses - there is not enough time to learn both syntax and programming in a three-week course module. The newly developed "Iconic Programmer" allows executable programs to be written through mouse clicks and menus, includes symbol by symbol translation into Java and Turing, and comes complete with a three-week lesson plan suitable to new programmers. To date, the new tool has been used effectively with full-semester, introductory programming courses at both the university and high school level.
Teaching software engineering through game design
Authors: Claypool Kajal , Claypool Mark
Published: October 2006

Many projects currently used in Software Engineering curricula lack both the "fun factor" needed to engage students, as well as the practical realism of engineering projects that include other computer science disciplines such as Software Engineering, Networks, or Human Computer Interaction. This paper reports on our endeavor to enhance interest and retention in an existing Software Engineering curriculum through the use of computer game-based projects. Specifically, a set of game-centric, project-based modules have been developed that enable students to: (1) actively participate in the different phases of the software lifecycle taking a single project from requirement elicitation to testing and maintenance; (2) expose students to real issues in project and team management over the course of a 2-semester project; and at the same time (3) introduce students to the different aspects of computer game design. Preliminary results suggest the merits of our approach, showing improved class participation and performance.