bluuebunny/crossref_metadata_2025 huggingface dataset:
A STUDY ON STRAIN RATE EFFECT IN COLLISION ANALYSIS OF ROLLING STOCK
Authors: KIM SEUNG ROK , KOO JEONG SEO
Published: June 2008

In this paper, the strain rate effect of energy absorption members in rolling stock is studied using the virtual testing model (VTM) for Korean high speed train (KHST). The VTM of KHST was simulated for two different strain rate conditions. The VTM is composed of FE models for structures, and nonlinear spring/damper models for dynamic components. To simplify numerical model for the full rake KHST, the first three units consist of full flexible multi-body dynamic models, and the remainder does 1-D spring/damper/mass models. To evaluate the strain rate effect of KHST, the crash simulation was performed under the accident scenario for a collision with a rigid mass of 15 tons at 110kph. The numerical results show that the overall crash response of the train is not largely affected as much as expected, but individual components have some different deformations according to strain rate. The deformation of the front end structure without strain rate effect is larger than that with it. However, the deformation of the rear end structure without strain rate effect is smaller than that with it. Finally, the intrusion of the driver's cabin is overestimated for no strain rate effect when compared to the case with it.
MODELING OF EXTERNAL AND INTERNAL IMPULSES IN CASE OF MULTIPLE COLLISIONS
Authors: CHUNG JAE HEON , YI BYUNG-JU
Published: June 2008

When a robot system collides with environment, not only the contact point but also the joints of the robot system experience impulsive forces or moments. In the real environment, the structure collides with environment at multiple points. However, most previous modeling methods have assumed one point contact to environment. In this work, we propose external and internal impulse models in case of multiple contact. The case of one point contact is compared to the case of multiple points contact through simulation.
IMPACT SIMULATION AND ANALYSIS OF A GLASS CERAMIC SPHERICAL DOME
Authors: LEE JUNG-HEE , KIM JAE-HOON , LEE JE-JUN , LEE YOUNG-SHIN , KOO SONG-HOE , MOON SOON-IL
Published: June 2008

The dome port cover of a ramjet engine is used to seal off the ram air inlet during booster operation. When the ramjet engine undergoes the transition leading to ramjet operation phase, the port cover is fragmented by the ram pressure. Lately, the dome port cover has been made using a MACOR glass-filled ceramic that has high heat resistance and high compression strength, as well as low density. In this study, fracture simulations of a ceramic dome under shock pressure were performed through the finite element method, using the nonlinear code LS-DYNA. The material properties of the simulations were applied to the experimental results of a tensile test for the MACOR glass-filled ceramic. The simulation was carried out on the spherical dome model using various impact pulses. The fracture strength and fracture behavior mode were compared for each case. The type-A spherical dome fractured earlier than the other kinds of domes.
SIMULATION OF HYDRODYNAMIC RAM OF AIRCRAFT FUEL TANK BY BALLISTIC PENETRATION AND DETONATION
Authors: KIM JONG H. , JUN SEUNG M.
Published: June 2008

Airframe survivability and hydrodynamic ram effect of aircraft are investigated. Penetration and internal detonation of a simple tank and ICW(Intermediate Complexity Wing) are simulated by nonlinear explicit calculation. Structural rupture and fluid burst are analytically realized using general coupling of FSI(Fluid-Structure Interaction) and adaptive master-slave contact. Besides, multi-material Eulerian solver and porosity algorithm are employed to model explosive inside fuel and tank bays which are defined in multi-coupling surfaces. Structure and fluid results are animated on the same viewport for enhanced visualization.
SHOCK RESPONSE OF THE CLAMPED DISK IN SMALL FORM FACTOR HARD DISK DRIVE
Authors: GU BIN , SHU DONGWEI , SHI BAOJUN , LU GUOXING
Published: June 2008

As small form factor (one-inch and smaller) hard disk drives are widely used in portable consumer appliances and gadgets, their mechanical robustness is of greater concern. In the previous work, it is found that when the disk is more tightly clamped, it helps to decrease the shock response of the disk and then avoid the head slap. In this paper, the real boundary condition of the disk for a small form factor hard disk drive from Seagate is investigated numerically. The disk is clamped between the clamp and the hub. The shock response of the disk under a half-sine acceleration pulse is simulated by using the finite element method. In the finite element model, both contact between disk and clamp and contact between disk and hub are considered. According to the simulation results, how to decrease the shock response of the disk is suggested.
AXISYMMETRIC SIMULATION OF BULGING PROCESS IN POLYMERIC MATERIALS DURING PROJECTILE IMPACT
Authors: LIM KYUNG-HUN , KIM SEE-JO , SHIN HYUNG-SEOP , CHOI JOON-HONG , KIM JEONG-TAE
Published: June 2008

Combination of different materials used both in the projectile and the sandwich panel is getting more important in designing for maximization of energy absorption during impact. In the present study, we have simulated the bulging process during projectile impact for axisymmetric impact problems. We have discussed the bulging velocity tendency depending on some important geometrical and material parameters such as the yield strength, and tensile limit of the core for several different core thickness and different elapsed time after impact by using the AUTODYN commercial software. From our simulation, we have found that material properties have more dominant effects than the geometric properties on the bulging velocity.
EXPERIMENT STUDY ON MECHANICAL PROPERTIES OF GRANITE UNDER REPEATED LOADING AND UNLOADING
Authors: HU YUN-HUA , LIU QUAN-SHENG
Published: June 2008

Deformation rules and acoustic emission characteristics of granite under repeated loading-unloading are studied using the MTS Mechanics Testing System and Disp. acoustic emission instrument. It's found that the axial stiffness of granite as well as Poisson's ratio increases with the development of the plastic strain while the change trend of lateral stiffness is negative. For brittle rocks, strain is produced by three mechanisms: elastic deformation, axial micro-cracking and compaction. The peak AE rate is increasing with the plastic strain, which indicates that using the axial plastic strain as the internal damage variable to represent rock damage is reasonable.
OBSERVATION OF METAL JET IN EXTREMELY HIGH IMPULSIVE PRESSURE GENERATOR
Authors: KIRA AKIO , HOKAMOTO KAZUYUKI , UJIMOTO YASUHIRO , KAI SHOICHIRO , FUJITA MASAHIRO
Published: June 2008

A new technique has been developed to generate an extremely high impulsive pressure by using an explosive. A metal jet, typically observed in explosive welding is used in this technique. The behavior of metal jet is crucial to the design of pressure generator. The experimental observation was made by the collision of metal jet on a metal block surface. Many craters formed by the collision of metal jets on the surface of the metal block were observed. The craters were overlapped and distributed in a wide range. The diameter of the largest crater was 0.5 mm. The quantity of the discharged metal jets was found to be a function of the quantity of explosive. The total area of the craters is considered as proportional to the quantity of the discharged metal jets and the experimental conditions for the formation of large craters was investigated.
MODELING OF SERRATED CHIP FORMATION IN HIGH SPEED ORTHOGONAL MACHINING
Authors: PARK HYUNG WOOK , RHIM SUNG-HAN , OH SOO-IK
Published: June 2008

Modeling of serrated chip formation is important to provide guidance for further development of this process and predict the quality of machined parts. The simulation of serrated chip formation is hard to achieve due to the lack of a proper material model which represents real phenomenon within a narrow adiabatic shear band. In the present study, a material constitutive law containing strain hardening and thermal softening was proposed to predict adiabatic shear localization within serrated chips. The outcomes of FEM simulation show the capability to predict serrated chip formation. The effective strain distributions and the forces are computed within this study.
SHOCK COMPACTION OF Gd-DOPED CERIA CERAMICS
Authors: KIM HA NEUL , KIM DO KYUNG , CHANG SOON NAM , THADHANI NARESH N.
Published: June 2008

Gd -doped ceria nano powder(~5 nm) was shock-loaded by a plate impact experiment using a single stage light gas gun. A computational model was used to simulate the shock state (pressure and density changes along time) of the sample in two dimensional Eulerian code. The predicted density of compacted sample from the simulation was about 90%. To reveal the effect of shock compaction on sintering behavior, the recovered sample was heat-treated and the microstructure was compared with that of a conventionally compacted and heat-treated sample.
MEASUREMENT OF PRESSURE RESPONSES IN A PHYSICAL MODEL OF A HUMAN HEAD WITH HIGH SHAPE FIDELITY BASED ON CT/MRI DATA
Authors: MIYAZAKI YUSUKE , TACHIYA HIROSHI , ANATA KENJI , HOJO AKIHIRO
Published: June 2008

This study discusses a head injury mechanism in case of a human head subjected to impact, from results of impact experiments by using a physical model of a human head with high-shape fidelity. The physical model was constructed by using rapid prototyping technology from the three-dimensional CAD data, which obtained from CT/MRI images of a subject's head. As results of the experiments, positive pressure responses occurred at the impacted site, whereas negative pressure responses occurred at opposite the impacted site. Moreover, the absolute maximum value of pressure occurring at the frontal region of the intracranial space of the head model resulted in same or higher than that at the occipital site in each case that the impact force was imposed on frontal or occipital region. This result has not been showed in other study using simple shape physical models. And, the result corresponds with clinical evidences that brain contusion mainly occurs at the frontal part in each impact direction. Thus, physical model with accurate skull shape is needed to clarify the mechanism of brain contusion.
FABRICATION OF TRICALCIUM PHOSPHATE COMPACTS BY UNDERWATER-SHOCK CONSOLIDATION
Authors: CHIBA AKIRA , MORIZONO YASUHIRO
Published: June 2008

The present study is to fabricate dense tricalcium phosphate (TCP) compacts by our newly developed underwater-shock consolidation technique and to investigate the characteristics of the compacts. By adding Al 2 O 3 powder to β-TCP powder, the biocomposites were fabricated to improve the fracture toughness. Sound compacts of α- and β-TCP powders and β-TCP/ Al 2 O 3 biocomposite powder were fabricated without any cracks and tears. The relative densities of α- and β-TCP compacts were about 85% in as-compacted state and more 94% after annealing at 1373K for 7.2ks. Compressive strengths of α- and β-TCP compacts are 160 and 140MPa after annealing at 1373K for 7.2ks, respectively. Compressive strength and fracture toughness of β-TCP/ Al 2 O 3 biocomposites after annealed at 1373K for 7.2ks were 188MPa and 2.54MPa·m1/2, which are comparable to values of human bone, respectively.
LOAD TRANSMISSION THROUGH ARTIFICIAL HIP JOINTS DUE TO STRESS WAVE LOADING
Authors: TANABE Y. , UCHIYAMA T. , YAMAOKA H. , OHASHI H.
Published: June 2008

Since wear of the polyethylene (Ultra High Molecular Weight Polyethylene or UHMWPE) acetabular cup is considered to be the main cause of loosening of the artificial hip joint, the cross-linked UHMWPE with high durability to wear has been developed. This paper deals with impact load transmission through the complex of an artificial hip joint consisting of a UHMWPE acetabular cup (or liner), a metallic femoral head and stem. Impact compressive tests on the complex were performed using the split-Hopkinson pressure bar apparatus. To investigate the effects of material (conventional or cross-linked UHMWPE), size and setting angle of the liner, and test temperature on force transmission, the impact load transmission ratio (ILTR) was experimentally determined. The ILTR decreased with an increase of the setting angle independent of material and size of the liner, and test temperature. The ILTR values at 37°C were larger than those at 24 °C and 60°C. The ILTR also appeared to be affected by the type of material as well as size of the liner.
THE EFFECT OF POLYAMIDE PARTICLES ON THE PROCESSIBILITY OF SELECTIVE LASER SINTERING
Authors: LIM BYUNG-SEOK , KIM HYUNG-IL , KIM DONG-SOO , BANG YOUNG-KIL
Published: June 2008

Polyamide powders were prepared as the laser sintering materials for the three-dimensional duplication equipment of selective laser sintering process. Though polyamide powders had a similar chemical structure, there were big differences in thermal properties, particle size and distribution, and shape. These variations had a close relation with the processibility of laser sintering. As far as the particle shape approached a spherical shape, the processibility of laser sintering was improved. The particle size distribution also played an important role in the precision of fabrication.
ON A THEORY OF CHERN CLASSES FOR SUPER VECTOR BUNDLES
Authors: VARSAIE S.
Published: June 2008

In this paper, a theory of characteristic classes for super vector bundles over [Formula: see text] is studied. Some properties of even and odd Chern classes, constructed in this theory, are established. At last, the relevance of the theory to supergeometry is discussed.
New occurrence of
Mawsonia
(Sarcopterygii: Actinistia) from the Early Cretaceous of the Sanfranciscana Basin, Minas Gerais, southeastern Brazil
Authors: de Carvalho Marise S. S. , Maisey John G.
Published: June 2008

The Cretaceous actinistian
Mawsonia
is represented by more than 360 dissociated, but well-preserved, bones obtained from the Areado Group in the Sanfranciscana Basin of Minas Gerais, Brazil. These are among the oldest records of
Mawsonia
(Berriasian, Lower Neocomian) and include previously undescribed or poorly known skeletal elements (e.g. splenial, dentary, autopalatine, zygals). The new material is referred to the type species,
M. gigas
. Morphological variation in the sample blurs some of the distinctions formerly drawn between nominal species of
Mawsonia
, and species level diversity in the genus is difficult to establish.
Mawsonia ubangiensis
,
M. libyca
, and
M. brasiliensis
are considered to be junior subjective synonyms of
M. gigas. Mawsonia gigas
probably appeared prior to the separation of S America and Africa and became widespread throughout much of western Gondwana (including parts of Africa), even surviving briefly on both continents following their separation.
Mawsonia tegamensis
is a morphologically distinctive Late Cretaceous African species with no evident fossil record in Brazil and which probably arose by vicariant speciation following isolation of a local
Mawsonia
population during the later stages of rifting between Northern Africa and the rest of Western Gondwana. Similarities between
Axelrodichthys
,
Lualabaea
(here regarded as Early Cretaceous in age) and recently described fossils from Morocco, Niger, and Madagascar suggest the presence of a second endemic Cretaceous mawsoniid lineage in northeastern Brazil and Africa.
Predictive data grouping
Authors: Essary David , Amer Ahmed
Published: May 2008

We demonstrate that predictive grouping is an effective mechanism for reducing disk arm movement, thereby simultaneously reducing energy consumption and data access latency. We further demonstrate that predictive grouping has untapped dramatic potential to further improve access performance and limit energy consumption. Data retrieval latencies are considered a major bottleneck, and with growing volumes of data and increased storage needs it is only growing in significance. Data storage infrastructure is therefore a growing consumer of energy at data-center scales, while the individual disk is already a significant concern for mobile computing (accounting for almost a third of a mobile system's energy demands). While improving responsiveness of storage subsystems and hence reducing latencies in data retrieval is often considered contradictory with efforts to reduce disk energy consumption, we demonstrate that predictive data grouping has the potential to simultaneously work towards both these goals. Predictive data grouping has advantages in its applicability compared to both prior approaches to reducing latencies and to reducing energy usage. For latencies, grouping can be performed opportunistically, thereby avoiding the serious performance penalties that can be incurred with prior applications of access prediction (such as predictive prefetching of data). For energy, we show how predictive grouping can even save energy use for an individual disk that is never idle.

Predictive data grouping with effective replication results in a reduction of the overall mechanical movement required to retrieve data. We have built upon our detailed measurements of disk power consumption, and have estimated both the energy expended by a hard disk for its mechanical components, and that needed to move the disk arm. We have further compared, via simulation, three models of predictive grouping of on-disk data, including an optimal arrangement of data that is guaranteed to minimize disk arm movement. These experiments have allowed us to measure the limits of performance improvement achievable with optimal data grouping and replication strategies on a single device, and have further allowed us to demonstrate the potential of such schemes to reduce energy consumption of mechanical components by up to 70%.
A new approach to dynamic self-tuning of database buffers
Authors: Tran Dinh Nguyen , Huynh Phung Chinh , Tay Y. C. , Tung Anthony K. H.
Published: May 2008

Current businesses rely heavily on efficient access to their databases. Manual tuning of these database systems by performance experts is increasingly infeasible: For small companies, hiring an expert may be too expensive; for large enterprises, even an expert may not fully understand the interaction between a large system and its multiple changing workloads. This trend has led major vendors to offer tools that automatically and dynamically tune a database system.

Many database tuning knobs concern the buffer pool for caching data and disk pages. Specifically, these knobs control the buffer allocation and thus the cache miss probability, which has direct impact on performance.

Previous methods for automatic buffer tuning are based on simulation, black-box control, gradient descent, and empirical equations. This article presents a new approach, using calculations with an analytically-derived equation that relates miss probability to buffer allocation; this equation fits four buffer replacement policies, as well as twelve datasets from mainframes running commercial databases in large corporations.

The equation identifies a buffer-size limit that is useful for buffer tuning and powering down idle buffers. It can also replace simulation in predicting I/O costs. Experiments with PostgreSQL illustrate how the equation can help optimize online buffer partitioning, ensure fairness in buffer reclamation, and dynamically retune the allocation when workloads change. It is also used, in conjunction with DB2's interface for retrieving miss data, for tuning DB2 buffer allocation to achieve targets for differentiated service.
THAT'S ENTERTAINMENTHCI impact and uncitedness
Authors: Hopson John
Published: May 2008

For this issue it's my pleasure to introduce John Hopson, who is one of the rising stars in the user research department at Microsoft Game Studios. John's column is a thoughtful and personal reflection on the purpose and our practice of applied research. I hope you all enjoy it as much as I did. ---Dennis Wixon
Pattern-based design of a service-oriented middleware for remote object federations
Authors: Zdun Uwe
Published: May 2008

Service-oriented middleware architectures should enable the rapid realization of loosely coupled services. Unfortunately, existing technologies used for service-oriented middleware architectures, such as Web services, P2P systems, coordination and cooperation technologies, and spontaneous networking, do not fully support all requirements in the realm of loosely coupled business services yet. Typical problems that arise in many business domains are for instance missing central control, complex cooperation models, complex lookup models, or issues regarding dynamic deployment. We used a pattern-based approach to identify the well working solutions in the different technologies for loosely coupled services. Then we reused this design knowledge in our concept for a service-oriented middleware. This concept is centered around a controlled environment, called a federation. Each remote object (a peer service) is controlled in one or more federations, but within this environment peers can collaborate in a simple-to-use, loosely coupled, and ad hoc style of communication. A semantic lookup service is used to let the peers publish rich metadata about themselves to their fellow peers.
A Hybrid Technique for English-Chinese Cross Language Information Retrieval
Authors: Zhou Dong , Truran Mark , Brailsford Tim , Ashman Helen
Published: May 2008

In this article we describe a hybrid technique for dictionary-based query translation suitable for English-Chinese cross language information retrieval. This technique marries a graph-based model for the resolution of candidate term ambiguity with a pattern-based method for the translation of out-of-vocabulary (OOV) terms. We evaluate the performance of this hybrid technique in an experiment using several NTCIR test collections. Experimental results indicate a substantial increase in retrieval effectiveness over various baseline systems incorporating machine- and dictionary-based translation.
Automatically Acquiring Causal Expression Patterns from Relation-annotated Corpora to Improve Question Answering for why-Questions
Authors: Higashinaka Ryuichiro , Isozaki Hideki
Published: May 2008

This article describes our approach for answering why-questions that we initially introduced at NTCIR-6 QAC-4. The approach automatically acquires causal expression patterns from relation-annotated corpora by abstracting text spans annotated with a causal relation and by mining syntactic patterns that are useful for distinguishing sentences annotated with a causal relation from those annotated with other relations. We use these automatically acquired causal expression patterns to create features to represent answer candidates, and use these features together with other possible features related to causality to train an answer candidate ranker that maximizes the QA performance with regards to the corpus of why-questions and answers. NAZEQA, a Japanese why-QA system based on our approach, clearly outperforms baselines with a Mean Reciprocal Rank (top-5) of 0.223 when sentences are used as answers and with a MRR (top-5) of 0.326 when paragraphs are used as answers, making it presumably the best-performing fully implemented why-QA system. Experimental results also verified the usefulness of the automatically acquired causal expression patterns.
Reducing Abstraction in High School Computer Science Education
Authors: Sakhnini Victoria , Hazzan Orit
Published: May 2008

The research presented in this article deals with the difficulties and mental processes involved in the definition, implementation, and use of abstract data types encountered by 12
th
grade advanced-level computer science students. Research findings are interpreted within the theoretical framework of
reducing abstraction
[Hazzan 1999]. The article describes the research setting and findings and concludes with some pedagogical implementations.
An energy-efficient fault-tolerant monitoring system for sensor networks
Authors: Liu Changlei , Cao Guohong
Published: May 2008

Because sensors are often deployed in harsh and/or adversarial environments, the sensors or the communication links may fail and hence endanger the mission of the sensor network. Although using more redundant sensors can tolerate some sensor failures, in most cases, only limited sensors are awake to extend the network life time. Therefore, sensor status (such as liveness, density estimation, residue energy, etc.) has to be closely monitored and made known to the sink, which can promptly react to the sensor status changes.
TraNS
Authors: Piórkowski M. , Raya M. , Lugo A. Lezama , Papadimitratos P. , Grossglauser M. , Hubaux J.-P.
Published: May 2008

Realistic simulation is a necessary tool for the proper evaluation of newly developed protocols for Vehicular Ad Hoc Networks (VANETs). Several recent efforts focus on achieving this goal. Yet, to this date, none of the proposed solutions fulfil all the requirements of the VANET environment. This is so mainly because road traffic and communication network simulators evolve in disjoint research communities. We are developing TraNS, an open-source simulation environment, as a step towards bridging this gap. This short paper describes the TraNS architecture and our ongoing development efforts.
A call to arms
Authors: Walsh Chris , Doci Arta , Camp Tracy
Published: May 2008

The choice of a mobility model has a significant impact on the performance of mobile network simulations. In order to accurately evaluate performance, it is important to mimic the environment in which the mobile network will be deployed. Thus, using realistic mobility models for simulation environments are preferred to synthetic models. Historically, however, unrealistic movement models have been mostly used due to their simplicity and mathematical tractability. Recently, a few mobility models have been derived from real user traces; these models, however, have not yet been adopted by the mobile research community for evaluation of protocol performance. We have implemented a realistic university campus-based pedestrian mobility model (RealMobGen) for use with the NS-2 network simulator. We offer RealMobGen to anyone interested.
Heterogeneous multi-channel wireless networks
Authors: Bhandari Vartika , Vaidya Nitin H.
Published: May 2008

We consider multi-channel wireless networks where nodes may be equipped with heterogeneous radios, each potentially capable of operation on a limited portion of the total available spectrum. Moreover even the channels may not all be identical; they may have potentially different propagation characteristics, and may support different sets of transmission rates. Much prior research on multi-channel networks has assumed identical channels and radio capabilities. However heterogeneity of channels and radios introduces a host of new issues that must be handled. In recent theoretical work we considered asymptotic transport capacity of multi-channel networks of single-radio nodes subject to switching constraints. This constitutes a class of instances involving heterogeneous radios, albeit identical channels. We leverage some of the insights obtained from our theoretical results, and now consider a more general model involving heterogeneity of radios and channels. We identify the key issues that differentiate heterogeneous multi-channel wireless networks, and describe a design framework for routing and channel assignment.
Exploiting environmental properties for wireless localization
Authors: Chen Shu , Chen Yingying , Trappe Wade
Published: May 2008

Wireless sensor networks are usually deployed to monitor environmental fields. In this work, we take a different viewpoint by dual-using the wireless sensor networks beyond their original purpose and exploit the general spatial information fields associated with wireless networks to assist position verification and refine conventional localization results. We developed the Flex - EP algorithm. And further our experimental evaluation results provide strong evidence that our approach can achieve the similar performance as traditional localization algorithms, without requiring the deployment of a localization infrastructure.
Profile-cast
Authors: Hsu Wei-jen , Dutta Debojyoti , Helmy Ahmed
Published: May 2008

In this paper we propose a new communication paradigm called profile-casting where destination nodes are identified by their (inferred) properties, not by node IDs. As an example case study, we use the mobility profile to show a design of profile-casting protocol based on the similarity in user mobility processes. The similarity-based protocol has good potential in both overhead reduction and delivery ratio improvement compared with simple message delivery protocols, such as flooding or random transmission. It is also flexible to operate at various points of the overhead-performance tradeoff.
Guest editor introduction
Authors: Banerjee Suman
Published: May 2008

Building complete systems and demonstrating that our research idea really works is always exciting. The goal of the ACM Mobicom 2007 Research Demonstrations was to foster this spirit of system building and prototyping. This year we introduced a new dimension to the research demonstration event --- the Student Demo Competition. This competition was open to any demonstration in which the lead participant was a student. The event generated quite a bit of excitement as the number of eligible student demonstration submissions was about 20 out of a total of 24 demos. This created a very exciting event on the day of the demo event, September 11, 2007. I would like to congratulate all the different participants of this event for a spectacular show.
WARP
Authors: Khattab Ahmed , Camp Joseph , Hunter Chris , Murphy Patrick , Sabharwal Ashutosh , Knightly Edward W.
Published: May 2008

The flexible interface between the medium access layer and the custom physical layer of the Rice University Wireless Open-Access Research Platform (WARP) provides a high performance research tool for clean-slate cross layer designs. As we target a community platform, we have implemented various basic PHY and MAC technologies over WARP. Moreover, we are implementing cross-layer schemes such as rate adaptation and crosslayer MIMO MAC protocols. In this demo, we demonstrate the flexibility of the interaction between the the WARP PHY and MAC layers by showing the capability to instantaneously change the modulation scheme, disabling/enabling MAC features such as carrier sensing or RTS/CTS 4-way handshake, and different multi-rate schemes.
UNAGI
Authors: Kohmura Naoya , Mitsuhashi Hikaru , Watanabe Masahiro , Bandai Masaki , Obana Sadao , Watanabe Takashi
Published: May 2008

This paper describes a protocol testbed system called UNAGI/ESPAR for ad hoc networks, which enables the evaluation of communication protocols with a gain-controlled antenna. It incorporates ESPAR as a practical smart antenna, IEEE802.15.4/ZigBee, GPS and gyro modules to allow easy installation of different protocols. Some experimental results are also shown.
Wireless ad hoc podcasting
Authors: Lenders Vincent , May Martin , Karlsson Gunnar , Wacha Clemens
Published: May 2008

Podcasting has become a very popular and successful Internet service in a short time. This success illustrates the interest for participatory broadcasting, in its actual form however, podcasting is only available with fixed infrastructure support to retrieve publicized episodes. We aim at releasing this limitation and present herein our podcasting system architecture together with a prototype implementation based on opportunistic wireless networking that allows us to extend podcasting to ad hoc domains.
Distributed databases and peer-to-peer databases
Authors: Bonifati Angela , Chrysanthis Panos K. , Ouksel Aris M. , Sattler Kai-Uwe
Published: May 2008

The need for large-scale data sharing between autonomous and possibly heterogeneous decentralized systems on the Web gave rise to the concept of P2P database systems. Decentralized databases are, however, not new. Whereas a definition for a P2P database system can be readily provided, a comparison with the more established decentralized models, commonly referred to as distributed, federated and multi-databases, is more likely to provide a better insight to this new P2P data management technology. Thus, in the paper, by distinguishing between db-centric and P2P-centric features, we examine features common to these database systems as well as other ad-hoc features that solely characterize P2P databases. We also provide a non-exhaustive taxonomy of the most prominent research efforts toward the realization of full-fledged P2P databases.
Report on the First International Workshop on Mining Graphs and Complex Structures (MGCS'07)
Authors: Holder Lawrence B. , Yan Xifeng
Published: May 2008

The fast accumulation of graph data is witnessed in a wide range of scientific and commercial domains. Typical graph data include chemical compounds, circuits, biological networks, computer networks, 2D/3D models, XML, RDF and workflows. Graph is regarded as a critical data type for knowledge discovery in bioinformatics, chemical informatics, computer vision, informational retrieval, computer security, semantic web, social science, etc., just to name a few. Unfortunately, due to the lack of graph management and mining tools, it is hard, if not impossible, for users to search and analyze any reasonably large collection of graphs. There is an imminent need for scalable methods for mining and search in graphs and other complex structures.
Report on the Sixth ACM Workshop on Privacy in the Electronic Society (WPES 2007)
Authors: Lee Adam J. , Yu Ting
Published: May 2008

The world is transforming into an electronic society where almost every aspect of our lives is increasingly computerized and interconnected. Such a transformation has profoundly changed the scope, the scale and the level of automation for information collection, storage, analysis and dissemination. It, on the one hand, has and continues to enable new and better services. On the other hand, it inevitably increases the degree of privacy concerns.
Report on the Tenth ACM International Workshop on Data Warehousing and OLAP (DOLAP'07)
Authors: Pedersen Torben Bach , Song Il-Yeol
Published: May 2008

This paper presents an overview of DOLAP'07, the 10th ACM International Workshop on Data Warehousing and OLAP, held on November 9, 2007 in Lisbon, Portugal in conjunction with CIKM'07, the ACM 16th Conference on Information and Knowledge Management.
Cathodic Electrodeposition of Mixed Rhenium-Molybdenum Oxides
Authors: Hahn Benjamin P. , Stevenson Keith J.
Published: May 2008

The electrochemical deposition of molybdenum-rhenium oxides, MoxRe1-xO3, from acidic peroxo-polymolybdo-perrhenate solutions is described. The presence of perrhenate in the deposition solution is observed to accelerate the electrodeposition rate of MoxRe1-xO3 in comparison to that seen for MoO3. Cyclic voltammetry, spectroelectrochemistry, and electrochemical quartz crystal microbalance (EQCM) experiments are used to understand the electrodeposition mechanism.
Electrochemical Behaviour of Platinum Nanoparticles Supported on Polypyrrole (PPy)/C Composite
Authors: Mokrane Souad , Makhloufi Laid , Alonso-Vante Nicolas
Published: May 2008

We report on the synthesis of composites Polypyrrole/Carbon (PPy/C) to be used as matrix-support of platinum nanoparticles prepared by carbonyl chemical route. The composite materials with different PPy loading were characterized by physical chemical methods, such as elemental analysis, infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The catalysts: 20 wt. % Pt/composites were used as substrates for the oxygen reduction reaction in acid medium. For the same catalyst loading (50 µg cm-2), it was observed that the nature of the composite strongly influences the electrochemical activity of nanoparticulated platinum.
Proton Transfer and Storage Behavior in Nanoparticles of Hydrous Ruthenium Oxide
Authors: Zheng Jim P.
Published: May 2008

A model of proton transfer and storage in amorphous RuO2.xH2O was proposed to explain the relationship between the specific capacitance and the structure and water content in RuO2.xH2O materials. The morphologies and crystalline structures of RuO2.xH2O annealed at different temperatures were investigated using electrochemical (EC) methods, transmission electron microscope (TEM) and selected area electron diffraction (SAED) techniques, respectively. From EC measurements, it was found that the specific capacitance increased with increasing annealing temperature, and reached the maximum value at a critical temperature, at which the crystalline RuO2.xH2O started to be formed. It was also found from EC measurement that proton conductivity is low for RuO2.xH2O at steady-state. From the SAED patterns, the structure disorder brought about by proton insertion was obtained from a sample annealed at the critical temperature. From 1H nuclear magnetic reso nance (NMR) spectroscopy, it was demonstrated that the activation energy of proton in RuO2.xH2O samples is directly associated with the proton transport and storage ability of these materials.
Self-Limiting Electropolymerization of o-Aminophenol on Ultraporous Carbon Nanoarchitectures for Electrochemical Capacitor Applications
Authors: Fischer Anne E. , Saunders Matthew P. , Lytle Justin C. , Rolison Debra R. , Long Jeffrey
Published: May 2008

Electropolymerization of o-aminophenol at planar glassy carbon and ultraporous carbon nanofoam electrodes in buffered aqueous electrolytes produces an ultrathin coating of poly(o- aminophenol), POAP. Poly(o-aminophenol) is not electroactive at the deposition pH of 4.7, and thus the electrodeposited POAP film rapidly passivates the electrode surface against further monomer oxidation. The self-limiting nature of the deposition process allows ultrathin coatings to be deposited onto and within ultraporous electrode structures without occluding the through-connected pore network of the nanofoam. When transferred to acidic aqueous electrolytes, POAP protonates and becomes electroactive. The charge-storage capacity for the resulting composite POAP-coated carbon is higher than that for bare carbon because of the added faradaic electrochemical reactions from the polymer coating.
Oxidation of Metallic Mn Thin Films Prepared in Butylmethylpyrrolidinium Bis(trifluoromethylsulfony)imide Ionic Liquid and the Pseudo-Capacitive Performance of the Anodized Oxides
Authors: Chang Jeng-Kuei , Huang Chiung-Hui , Tsai Wen-Ta , Sun I-Wen , Chen Po-Yu
Published: May 2008

Metallic Manganese (Mn) thin films were successfully prepared by electrodeposition in butylmethylpyrrolidinium bis (trifluoromethylsulfony)imide (BMP-NTf2) ionic liquid, which has a very wide potential window extending over the reduction potential of Mn. Potentiostatic, galvanostatic, and cyclic voltammetric methods were performed to anodize the Mn films in Na2SO4 solution. The surface morphology and crystal structure of the obtained oxides were examined by a scanning electron microscope and X-ray diffractometer, respectively. Moreover, their chemical states were also analyzed with an X-ray photoelectron spectroscopy. It was clearly confirmed that the anodization methods could affect the material characteristics of the Mn oxides and therefore their pseudo-capacitive performance. The Mn oxide anodized by the cyclic voltammetric method showed a promising specific capacitance of 355 F/g (measured in 0.1 M Na2SO4 solution at a potential scan rate o f 25 mV/s). Its capacitance retained ratio after 500 charge- discharge cycles was as high as 94 %.
Monolithic Carbon-based Nanocomposites with Hierarchical Porosity: Novel Anode Materials for Li Ion Batteries
Authors: Wang Zhiyong , Li Fan , Ergang Nicholas S. , Stein Andreas
Published: May 2008

This study compares the effects of meso- and macroporosity and the influence of nanocomposite structure on textural, electronic, and mechanical properties of monolithic carbon samples. Glassy carbon monoliths with three-dimensionally ordered macropores and walls containing mesopores (3DOM/m C) were synthesized by nanocasting from monolithic silica with hierarchical pore structure. Subsequent introduction of more graphitic, nitrogen-doped carbon into the mesopores by chemical vapor deposition produced a monolithic 3DOM/m carbon-graphitic carbon nanocomposite material (3DOM/m C/C). The materials were characterized in detail by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen- adsorption measurements, depth-sensing indentation, and electrochemical measurements.
Ethanol Electrooxidation on Pt-Sn Catalysts Deposited by Pulsed Laser Ablation
Authors: Bommersbach Pascale , Mohamedi Mohamed , Guay Daniel
Published: May 2008

Pt3Sn catalysts were prepared from pure Pt and Sn targets by crossed beam pulsed laser deposition. The deposition was performed either under vacuum or in the presence of a He background pressure (1, 2, 3, 4 and 5 Torr). The pressure in the deposition chamber influences the surface structure and the morphology of the catalytic nanoparticles, as determined from scanning electron microscopy. Cyclic voltammogram curves reveal that Pt3Sn catalysts deposited under He lower the onset oxidation potential of ethanol compared to Pt3Sn electrodes synthesized under vacuum. This effect is particularly evident for Pt3Sn elaborated at 2 Torr He which provides a high current density value close to 20 mA.cm-2 at 0.7 V vs. RHE. Chronoamperometric measurements conducted at + 0.5 V vs. RHE also demonstrated that Pt3Sn deposited at 2 Torr He is the most active electrocatalyst after 1 hour of electrolysis.
Electrochemical Characterization of the n = 2 Ruddlesden-Popper Sr3FeMO6+δ (M = Fe, Co, Ni) Phases by Electrochemical Impedance Spectroscopy
Authors: Mogni Liliana , Prado Fernando , Caneiro Alberto
Published: May 2008

The electrochemical characterization of the porous Sr3FeMO6+d (M = Fe, Co, Ni) electrode materials has been performed by EIS under pure O2 atmosphere and temperatures between 500 and 800 ºC. Thick films of porous Sr3FeMO6+d were deposited on a dense Ce0.9Gd0.1O2-x electrolyte disc by spray deposition and heat treated at 1000 ºC during 1 h. XRD and SEM were used to evaluate the structure and microstructure of the cells before and after the EIS measurements. Data of the Area Specific Resistance (ASR), defined by ASR = Z'(ω→0)-Z'(ωHF), associated with the overall oxygen reduction reaction, were obtained for the three compositions (Sr3Fe2O6+d, Sr3FeCoO6+d, Sr3FeNiO6+dγ). The ASR values are quite similar for the Sr3FeNiO6+d and Sr3FeCoO6+d compositions, and they are higher than those of Sr3Fe2O6+d. The activation energy (Ea) corresponding to the ASR for the Sr3FeNiO6+dγ material (1.3 eV) is high er than those of Sr3FeCoO6+d and Sr3Fe2O6+d, (0.9-1.0 eV).
Electrochemical Charging of Ultra-Thin Films of Conducting Polymer Supported Carbon Nanotubes and Particles: Application to Supercapacitors
Authors: Kulesza Pawel J. , Skunik Magdalena , Baranowska Beata , Chojak Malgorzata , Miecznikowski Krzysztof
Published: May 2008

Modification of multi-walled carbon nanotubes with ultra-thin films of oxocyanoruthenium structures resulted in their improved capacitive characteristics, as evident from increased specific capacitances and energy densities determined using diagnostic charging-discharging electrochemical experiments (involving cyclic voltammetry, galvanostatic and AC impedance methods). The largest specific capacitance (123 F g-1) was found when the oxocyanoruthenium modified carbon nanotubes were further covered or linked with conducting polymer, namely poly (3,4-ethylenedioxythiophene) or PEDOT, structures. Among important issues are high stability of both inorganic and organic components, attractive electrostatic interactions between negatively charged oxocyanoruthenate and positively charged PEDOT, fast redox transitions of oxocyanoruthenium and high dynamics of charge propagation in PEDOT species, as well as ability to improve distribution of charge by mul ti-walled carbon nanotubes.
Superior Capacitive Performance of Aligned Carbon Nanotubes in Ionic Liquids
Authors: Lu Wen , Qu Liangti , Dai Liming , Henry Kent
Published: May 2008

Electrodes and electrolytes are two essential components of a supercapacitor and play important roles in determining the performance for the supercapacitor. In the present work, we investigated the electrochemical and capacitive behavior of aligned carbon nanotube electrodes in ionic liquid electrolytes to study the feasibility to develop high performance supercapacitors from these two components. Synthesis procedure of the carbon nanotubes and composition of the ionic liquids have been studied to achieve a high capacitance and fast charge/discharge process for the carbon nanotube electrode in the ionic liquid electrolyte.
Characteristics of Pulse Deposited CdZnSe Films
Authors: Murali K. R. , Balasubramanian M.
Published: May 2008

CdZnSe films were pulse deposited using aqueous solutions of AR grade cadmium sulphate, zinc sulphate and selenium di oxide.To get different compositions of the ternary films, concentrations of Cadmium and zinc sulphate were varied. The films exhibited hexagonal structure after heat treatment. The band gap of the films varied in the range of 1.72 - 2.70 eV as the composition of the films changed from CdSe to ZnSe side.XPS studeis also confirmed the formation of CdZnSe. I-V characteristics of the films were studied. Laser Raman studies indicated LO and TO modes depending on the composition of the films.
Micro- and Mesoporous Carbon Based Electrode Materials for Electrical Double Layer Capacitors
Authors: Janes Alar , Lust Enn
Published: May 2008

Micro- and mesoporous carbons are attractive electrode materials with the unique porous structure, narrow pore size distribution and possibility to fine-tune the pore size for electrodes of electrical double layer capacitors (EDLC), commonly called supercapacitors. The excellent adsorptivity of carbide-derived carbon (CDC) has been demonstrated but these materials are quite expensive and the main aim of this work was to establish conditions for the preparation of nanoporous carbon electrodes, based on less expensive raw materials, synthesis and activation (i.e. with H2O vapor) methods.
Electrochemical Behavior of Nickel in Acidic Sulfate Electrolytes
Authors: Zangari Giovanni , Villa Marco
Published: May 2008

The electrochemical behaviour of Nickel in sulphuric acid electrolytes was studied by various electrochemical means. Under cathodic polarization, Nickel forms metastable hydrides under cathodic charging; the successive egress of hydrogen is controlled by solid state diffusion of hydrogen atoms. The nature of these hydrides evolves with electrochemical aging of the samples, as judged by their electrochemical signature. The nature of the (hydro)oxides formed during anodic polarization also evolves with aging. Anodic polarization and investigation of electrochemical oscillations in the transpassive region show that defect states which constitute preferred dissolution sites assume a wider energy range with increasing aging, indicating a high degree of inhomogeneity of the surface. The catalytic activity of Nickel increases after aging under both cathodic and anodic conditions, due to the formation of an inhomogeneous surface.