bluuebunny/crossref_metadata_2025 huggingface dataset:
A nine year study of file system and storage benchmarking
Authors: Traeger Avishay , Zadok Erez , Joukov Nikolai , Wright Charles P.
Published: May 2008

Benchmarking is critical when evaluating performance, but is especially difficult for file and storage systems. Complex interactions between I/O devices, caches, kernel daemons, and other OS components result in behavior that is rather difficult to analyze. Moreover, systems have different features and optimizations, so no single benchmark is always suitable. The large variety of workloads that these systems experience in the real world also adds to this difficulty.

In this article we survey 415 file system and storage benchmarks from 106 recent papers. We found that most popular benchmarks are flawed and many research papers do not provide a clear indication of true performance. We provide guidelines that we hope will improve future performance evaluations. To show how some widely used benchmarks can conceal or overemphasize overheads, we conducted a set of experiments. As a specific example, slowing down read operations on ext2 by a factor of 32 resulted in only a 2--5% wall-clock slowdown in a popular compile benchmark. Finally, we discuss future work to improve file system and storage benchmarking.
RFID-based networks
Authors: Vaidya Nitin , Das Samir R.
Published: May 2008

In this article, we outline a research agenda for developing protocols and algorithms for densely populated RFID based systems covering a wide geographic area. This will need multiple readers collaborating to read RFID tag data. We consider cases where the tag data is used for identification, or for sensing environmental parameters. We address performance issues related to 'accuracy' and 'efficiency' in such systems by exploiting 'diversity' and 'redundancy'. We discuss how tag multiplicity can be used to improve accuracy. In a similar fashion, we explore how reader diversity, achieved by using multiple readers with potentially partially overlapping coverage areas, can be exploited to improve accuracy and efficiency. Finally, we show how multiple antennas in a reader can be used to improve accuracy and access rates by utilizing antenna diversity. RFID tag/sensor data can be highly redundant for the purpose of answering a higher level query. For example, often the higher level query needs to compute a statistic or a function on the sensory data obtained by the RFID sensors, and does not need all the individual sensor readings. We outline the need for efficient tag-to-reader communication, and reader-to-reader coordination to effectively compute such functions with low overhead.
Guest editors' introduction
Authors: Penna Paolo , Ravi S. S.
Published: May 2008

We served as the Co-Chairs of the Technical Committee responsible for the Student Poster Session and Research Competition held as part of MobiCom 2007 in Montreal. A total of 29 submissions were received for the poster session and the committee selected 16 of these submissions. Authors of all the accepted submissions were invited to submit their work in the form of an extended abstract of length at most three pages to this special issue. We received abstracts from 13 of the 16 selected submissions.
Deconstructing wireless errors
Authors: Rayanchu Shravan , Agrawal Dheeraj , Saha Sharad , Mishra Arunesh , Banerjee Suman
Published: May 2008

Last few years have seen a tremendous growth of WiFi devices, and with the introduction of smart devices like Zune, iPhone etc., which offer a variety of WiFi-based Internet applications, this trend is only going to accelerate. However, the current throughput/delay characteristics of 802.11 systems are not sufficient to support applications like high definition video streaming, VoIP, online gaming etc. Although, 802.11 theoretically supports data rates up to 54 Mbps, its performance is well below claims.
Pair-wise resistance to traffic analysis in MANETs
Authors: Gray Chase , Byrnes Jason , Nelakuditi Srihari
Published: May 2008

Some of the same features that make MANETs attractive, such as mobility and self-organization, also lead to increased vulnerability to traffic analysis. Data on who is communicating with whom, how often, how much, and when is easily available to any eavesdropper within range of the wireless network. Even if the payload is encrypted, standard MANET protocols transmit enough header and routing information in the clear making traffic analysis relatively easy for attackers. But users of MANETs may want to resist traffic analysis for a variety of reasons, ranging from secrecy for government and industry to simple personal privacy for individuals. Traffic analysis is a threat to secure communication, either by identifying targets for attacks such as denial-of-service or encryption cracking, or by revealing communication relationships.
Alert propagation in mobile ad hoc networks
Authors: He Wenbo , Huang Ying , Nahrstedt Klara , Lee Whay C.
Published: May 2008

Intrusion/misbehavior detection and response are two important components for defending against various attacks in mobile ad hoc networks. Unfortunately, there is a gap between local intrusion/misbehavior detection and network-wide response in such networks. To bridge this gap, alert propagation, aiming to spread alert messages to the whole network upon detection of malicious/abnormal activity, is a viable solution but has been overlooked.
Super-diffusive behavior of mobile nodes from GPS traces
Authors: Kim Sungwon , Lee Chul-Ho , Eun Do Young
Published: May 2008

Mobility is the most important factor in mobile adhoc networks (MANETs) and delay-tolerant networks (DTNs). Mobility models that fail to capture real movement pattern of mobile nodes will result in misleading guidelines on the design of new protocols and their performance evaluations and thus prevent us from making judicious decisions.
On the feasibility of high-power radios in sensor networks
Authors: Sengul Cigdem , Bakht Mehedi , Harris Albert F. , Abdelzaher Tarek , Kravets Robin
Published: May 2008

Wireless sensor nodes are constrained by limited energy resources. A significant portion of this limited energy is spent in communication, making energy efficiency of the radio a very important factor in increasing the overall lifetime of a sensor node. An ideal radio, in terms of energy efficiency (ignoring issues of transmission range and delay), should satisfy two requirements. First, it should minimize the energy used per bit when transmitting or receiving. Second, its idle time energy consumption should be minimal. Unfortunately, no such "ideal" radio exists. Current sensor radios (e.g., CC2420) meet the second requirement - the energy consumption in the inactive states is very low in comparison to IEEE 802.11 radios, which are comparatively energy-inefficient due to high switching-on cost and idle state energy consumption. On the other hand, IEEE 802.11 radios perform much better when it comes to energy consumption per bit. So the natural question to ask is whether there exists a way to combine the positive features of these two types of radios leading to increased energy conservation. We argue that this objective can indeed be achieved by adding a high-power IEEE 802.11 radio to the mote platform alongside the already existing sensor radio and managing them by an energy-efficient scheme as proposed in this work.
Gender-based feature analysis in campus-wide WLANs
Authors: Kumar Udayan , Yadav Nikhil , Helmy Ahmed
Published: May 2008

Rapid WLAN deployment has led to various research challenges and scenarios. In this paper we come up with a technique to classify users into social groups and then use this information to investigate the usage behavior of these groups. Grouping of users can be done based on diverse parameters like gender, major or other interest groups. In this paper we show the general methodology used to accomplish WLAN user groupings with an example of grouping by gender in a major university campus. The usage patterns of Males and Females are contrasted based on this grouping. Possible applications of this work encompass user profiling; studying gender gaps in social sciences; announcement/advertisement customization to target groups.
A QoS WMN with mobility support
Authors: Bortnikov Edward , Cidon Israel , Keidar Idit , Kol Tal , Vaisman Arkady
Published: May 2008

We present QMesh, a software package that allows utilizing multiple geographically scattered Windows desktops as a wireless mesh network infrastructure with seamless user mobility support. QMesh supports its users through standard protocols, and does not require any client software installation. We optimize the solution's quality of service (QoS) by providing a centralized management infrastructure, which allows an assignment of users to Internet gateways that balances between distance and load considerations. QMesh is implemented as a Windows XP driver, on top of the Mesh Connectivity Layer (MCL) toolkit from Microsoft Research that provides basic routing capabilities. To the best of our knowledge, this is the first mobile mesh solution implemented within the Win32 kernel space.
Location-based media sharing in a MP2P network
Authors: Kotilainen Niko , Kriara Lito , Vandikas Konstantinos , Mastorakis Konstantinos , Papadopouli Maria
Published: May 2008

In both academia and industry, peer-to-peer (p2p) applications have attracted great attention. This paper introduces and implemented a novel location-based multimedia application, the Multimedia Traveling Journal application (PhotoJournal) that employs the p2p paradigm and enables location-based content sharing among mobile users.
Roomba MADNeT
Authors: Reich Joshua , Misra Vishal , Rubenstein Dan
Published: May 2008

We have built a mobile, ad-hoc, delay tolerant, network testbed (MADNeT). Our testbed is geared towards enabling the exploration of highly disconnected networks whose nodes must store and forward information (multi-hop paths are very unlikely), while allowing us to explore connected network scenarios as well. Using our MADNeT, we can emulate a wide range of mobile networking scenarios and execute real-world (albeit somewhat simplified) data collection missions. Our system is built from commercial off-the-shelf (COTS) hardware running a paired-down Linux OS, yielding a relatively inexpensive but fairly flexible mobile network testbed. We have implemented replication-based information diffusion protocols and a distributed opportunistic surveillance application on the testbed as proof-of-concept. Currently, we are refining our software tool-set and instrumenting our nodes to test both our protocols and application.
ParaModel
Authors: Ce Yu , Zhen Xu , Ji-zhou Sun , Xiao-jing Meng , Yan-yan Huang , Hua-bei Wu
Published: May 2008

ParaModel is an extensible system for simplifying the development of parallel applications, by providing a unified user interface for modeling visually while generating different code skeletons according to specific runtime environment automatically. A set of construction blocks and rules is designed to describe parallel applications in form of graph, and parsers for different parallel environments are implemented to translate graph to source code skeletons. ParaModel is implemented basing on Eclipse and compatible with its plug-in architecture. With the help of ParaModel, developers can focus on high level design and obtain code skeletons from visually constructed graphical models.
A parallel dynamic compiler for CIL bytecode
Authors: Campanoni Simone , Agosta Giovanni , Reghizzi Stefano Crespi
Published: May 2008

Multi-core technology is being employed in most recent high-performance architectures. Such architectures need specifically designed multi-threaded software to exploit all the potentialities of their hardware parallelism.

At the same time, object code virtualization technologies are achieving a growing popularity, as they allow higher levels of software portability and reuse.

Thus, a virtual execution environment running on a multi-core processor has to run complex, high-level applications and to exploit as much as possible the underlying parallel hardware. We propose an approach that leverages on CMP features to expose a novel pipeline synchronization model for the internal threads of the dynamic compiler.

Thanks to compilation latency masking effect of the pipeline organization, our dynamic compiler, ILDJIT, is able to achieve significant speedups (26% on average) with respect to the baseline, when the underlying hardware exposes at least two cores.
An automated refactoring tool for dataflow visual programming language
Authors: Sui Yang Yi , Lin Jun , Zhang Xiao Tuo
Published: May 2008

Refactoring tools are extremely important to prevent errors and reduce consumed time. But these tools only support text-based languages, especially in Object Oriented languages. In order to accommodate the situation that Dataflow Visual Programming Languages (DFVPLs) are more and more popular, an automated refactoring tool for DFVPL was proposed. DFVPL was divided into two layers---visual layer and dataflow layer. Two layers mutually evolved, which ensured correctness of visual elements and dataflow semantic during refactoring. Some algorithms like middle graph generation; terminal auto-generation and terminal auto-modification were proposed to implement the changes of two layers. This tool has been proved correct and efficient by some refactoring instances. In addition, we discussed some famous DFVPL like LabVIEW to expose lacking of automated refactoring tool forced refactoring by hand to be time-consuming and error-prone.
Data management projects at Google
Authors: Cafarella Michael , Chang Edward , Fikes Andrew , Halevy Alon , Hsieh Wilson , Lerner Alberto , Madhavan Jayant , Muthukrishnan S.
Published: May 2008

This article describes some of the ongoing research projects related to structured data management at Google today. The organization of Google encourages research scientists to work closely with engineering teams. As a result, the research projects tend to be motivated by real needs faced by Google's products and services, and solutions are put into production and tested rapidly. In addition, because of the sheer scale at which Google operates, the engineering challenges faced by Google's services often require research innovations.
The repeatability experiment of SIGMOD 2008
Authors: Manolescu I. , Afanasiev L. , Arion A. , Dittrich J. , Manegold S. , Polyzotis N. , Schnaitter K. , Senellart P. , Zoupanos S. , Shasha D.
Published: May 2008

SIGMOD 2008 was the first database conference that offered to test submitters' programs against their data to verify the experiments published. This paper discusses the rationale for this effort, the community's reaction, our experiences, and advice for future similar efforts.
Report from the Third International Workshop on Computer Vision Meets Databases (CVDB 2007)
Authors: Amsaleg Laurent , Jónsson Björn pór , Oria Vincent
Published: May 2008

This report summarizes the presentations and discussions of the Third International Workshop on Computer Vision meets Databases, or CVDB 2007, which was held in Beijing, China, on June 10, 2007. The workshop was colocated with the 2007 ACM SIGMOD/PODS conferences and attended by twenty-five participants.
Databases and Web 2.0 panel at VLDB 2007
Authors: Amer-Yahia Sihem , Markl Volker , Halevy Alon , Doan AnHai , Alonso Gustavo , Kossmann Donald , Weikum Gerhard
Published: May 2008

Web 2.0 refers to a set of technologies that enables indviduals to create and share content on the Web. The types of content that are shared on Web 2.0 are quite varied and include photos and videos (e.g., Flickr, YouTube), encyclopedic knowledge (e.g., Wikipedia), the blogosphere, social book-marking and even structured data (e.g., Swivel, Many-eyes). One of the important distinguishing features of Web 2.0 is the creation of
communities
of users. Online communities such as LinkedIn, Friendster, Facebook, MySpace and Orkut attract millions of users who build networks of their contacts and utilize them for social and professional purposes. In a nutshell, Web 2.0 offers
an architecture of participation and democracy
that encourages users to add value to the application as they use it.
Characterization of Core-Shell Type Cathode Material in Li-ion Cells
Authors: Amiruddin Shabab , Li Bing , Sun Yang Kook , Prakash J.
Published: May 2008

Novel cathode material having a shell and core structure has been developed for Lithium Ion batteries. This study essentially involves the electrochemical performance and thermal stability of core-shell material and verifies the effects of the shell and core separately. It was observed that the capacity obtained of the shell was about 145mAh/g and that of core was about 190 mAh/g. The overall capacity of the core-shell composite electrode was 175 mAh/g. Electrochemical impedance spectroscopy was used to explain the possible interfacial phenomena occurring within the material during lithium intercalation-deintercalation processes. Thermal studies were also investigated using Differential Scanning Calorimeter (DSC).
Electrochemical and Thermal Studies of LiFePO4 Cathode in Lithium-Ion Cells
Authors: Joachin Humberto , Kaun Thomas D. , Zaghib K. , Prakash J.
Published: May 2008

The carbon-coated LiFePO4 Li-ion cathode material was studied for its electrochemical and thermal performance. This electrode exhibited a reversible capacity corresponding to more than 90% of the theoretical capacity, when cycled between 2.5 V and 4.0 V. The material also showed good capacity retention at high powers implying that the carbon coating improves the electronic conductivity and hence the cycling of this material. Thermal studies were also investigated by Differential Scanning Calorimeter (DSC) and Accelerating Rate Calorimeter (ARC) and compared with the commonly used lithium metal oxide cathodes with layered structure.
Electrochemical Performance of Various Electrodes for Lithium -Ion Batteries Deposited by the Condensation-Solidification Method
Authors: Kylyvnyk Kostyantyn Y. , Kalynushkin Yevgen P. , Novak Peter J.
Published: May 2008

High-Pressure Deposition Solidification (HDS) proprietary method was proposed for the production of nanostructured coatings. HDS method has the ability to embed active powder materials (both cathode and anode) into the metal substrate, resulting in the formation of thin and thick electrodes with high electrochemical performance. HDS electrodes based on LiMn2O4 spinel, MnO2, Si, SiO, Li4Ti5O12, and LiCoO2 were prepared and electrochemical testing of HDS electrodes was conducted. All the above-mentioned active materials after deposition had particle size less than 200 nm and reproduced the electrochemical properties of initial materials. Mostly, HDS LiMn2O4 electrodes were described, and they showed good repeatability, cycleability (800 cycles), low charge- transfer resistance and as a result good C-rate performance. As an example of application of HDS electrodes, prototype of thin battery with thickness of approximately 50 µm and capacity of 0.15 mAh/cm2 was proposed.
Chemical Vapor Deposition of Nanocarbon-Supported Platinum and Palladium Catalysts for Oxygen Reduction
Authors: Vijayaraghavan Ganesh , Stevenson Keith J.
Published: May 2008

A direct scheme for the synthesis of carbon nanotube (CNT) supported Pt and Pd catalysts is reported. Pt and Pd nanocatalysts deposited on nitrogen doped CNTs (NCNTs) were prepared via metal organic chemical vapor deposition (MOCVD) using thermally labile metal organic precursors. These materials were characterized by a host of techniques including TEM, XPS, TGA and voltammetry. The MOCVD based synthetic route offers several advantages including the circumvention of a majority of processing steps that are normally required to disperse and activate such catalysts on carbon supports. The low temperature dispersion and loading of catalysts also allows for study of the synergistic role of the carbon support on the oxygen reduction reaction (ORR). The activity of NCNT supported Pt catalysts for ORR was comparable to Pt/ Vulcan catalysts. Results from preliminary experiments and prospects for extending the MOCVD synthesis route for preparing viable carbon supported catalysts for ORR are discussed.
Some Observations on the Oxygen Reduction Reaction (ORR) At Platinum Catalysts based on Post Year 2000 Reports
Authors: Gottesfeld Shimshon
Published: May 2008

This paper examines theoretical and experimental ORR work performed post year 2000, with the targets of reviewing new insights and new advances and addressing remaining apparent disagreements on proper reading and interpretation of new theoretical and experimental results. It is argued that the description of the ORR rate at a Pt , or Pt alloy catalyst in a fuel cell cathode, has to be relevant to the actual nature of the catalyst surface in the fuel cell-relevant potential range, i.e., a Pt surface with potential dependent coverage by chemisorbed oxygen which blocks metal sites required for the ORR. A way to achieve this goal, is to express the pre-exponential factor in the rate expression in terms of the cathode potential vs. E0Pt-OH2/ Pt-OH , while the exponential factor remains a function of over-potential vs. E0H2O/O2 . It is further suggested, that the surface couple Pt-OH2 / Pt-OH, can be described as redox mediator for the ORR process at a Pt catalyst with a partly oxidized surface and, consequently, ignition of the ORR process at Pt may critically depend on the potential difference E- E0Pt-OH2/Pt-OH .
Direct Mechanism of OH Radicals Formation in PEM Fuel Cells
Authors: Atrazhev Vadim , Timokhina Elena , Burlatsky Sergey F. , Sultanov Vadim , Madden Thomas , Gummalla Mallika
Published: May 2008

The generation of hydroxyl and/or peroxyl (•OOH) radicals on fuel cell catalysts has direct consequences for the durability of the polymer electrolyte membrane. Whether radical generation occurs from hydrogen peroxide decomposition vs. direct generation on the Pt catalyst surface is of key interest. Ab initio calculations were performed with Gaussian software employing both cluster models of a platinum surface, as well as single / double Pt atom ensembles. Although complete four-electron reduction to water on Pt is desired, hydrogen peroxide is also formed at potentials below 0.6 Vrhe. In this work, we show that the main pathway of H2O2 formation on platinum involves the •OH free radical as an intermediate. •OH radicals may be released from the Pt surface either by dissociation of the adsorbed OOH intermediate at high potentials or by dissociation of one-site adsorbed peroxide intermediate at low potentials. Adsorptio n of hydrogen peroxide transported to the Pt surface to achieve this state, though possible, is unfavored. These results indicate that the direct formation of hydroxyl radicals on Pt surfaces is possible under certain conditions and need not proceed through a peroxide intermediate.
Preparation of Pt/Electro-conductive polymer Loaded Carbon Composite for Improvement of Electrode Durability for Fuel Cells
Authors: Mizuhata Minoru , Oga Masako , Miyachi Yoshikazu , Deki Shigehito
Published: May 2008

The platinum nanoparticles/Electroconductive polymer; e. g., polypyrrole(PPy) and polyaniline(PANi) composite loaded on carbon was synthesized successfully by following process; oxidation of carbon, ion-exchange of H+ and platinum ion, and the polymerization of pyrrole using the platinum ion dispersed on carbon as oxidant in the previous study. The thin layer of polypyrrole suppresses the ionization to platinum ion and distribute into electrolyte under operational condition of fuel cells. The catalytic activity and the size of the platinum particles of synthesized composite had less change than the conventional electrocatalyst, platinum nanoparticles/carbon composite (Pt/C), during the durability test, multiple scanning of the cyclic voltammetry. The catalytic activity for the Pt/PPy/C was held during the durability examination up to 12500 cycles between -0.2-1.0 V vs Ag/AgCl without a coagulation and crystal growth of the platinum particles.
Oxygen Reduction on PtFe/C Electrocatalysts Prepared in Microemulsions
Authors: Malheiro Arthur R. , Perez Joelma , Villullas Hebe D.
Published: May 2008

PtFe/C nanocatalysts of different compositions and nearly constant particle size were prepared by a microemulsion method. Crystallite sizes and degree of alloying were determined by X-ray diffraction. Particle size and distribution were characterized by transmission electron microscopy and average composition was determined by energy dispersive X-ray analysis. Measurements of electrocatalytic activity for oxygen reduction were done using the rotating disk electrode technique in O2 saturated 0.5 mol L-1 sulfuric acid solutions, at room temperature. For all catalysts oxygen reduction begins at ~ 0.90V. Tafel plots show slopes of c.a. 60 and 120 mV dec-1 in the regions of low and high overpotentials, respectively. The best results for the ORR were obtained for the PtFe/C catalyst of composition Pt:Fe 70:30. This catalyst was also found to exhibit the largest methanol tolerance.
Effects of Cobalt Phthalocyanine on Pt/C as the Cathodic Catalyst in DMFC
Authors: Lu Yuhao , Reddy Ramana G.
Published: May 2008

The CoPc-Pt/C system exhibits unique electrocatalytic behavior as cathodic catalyst in direct methanol fuel cells (DMFC). In this work electrochemical behavior of CoPc-Pt/C was studied with emphasis on effects of cobalt phthalocyanine (CoPc) on platinum/carbon. Physical properties and structural change of CoPc-Pt/C and CoPc were investigated using TGA, EDAX, IR, XRD and XPS. Electrochemical techniques were conducted to obtain electrochemical performance of catalysts. All results indicated that CoPc interacts with platinum and modifies the surface of the platinum. The interaction synergizes the electrocatalytic activity of CoPc-Pt/C catalyst for oxygen reduction reaction (ORR). The modification of CoPc prevents platinum from the absorption of methanol and intermediate compounds produced by methanol oxidation reaction (MOR), which improves the resistance of catalysts for methanol poisoning. The presence of metallic cobalt in catalyst increases t he electrocatalytic activity for MOR, however metallic cobalt does not improve resistance of catalyst for methanol poisoning.
Performance and Durability of Chalcogenide-Modified Ruthenium Catalysts for Oxygen Reduction: Hydrogen-Air MEA and RRDE Studies
Authors: Johnston Christina M. , Choi Jong-Ho , Babu Panakkatu , Wieckowski Andrzej , Zelenay P.
Published: May 2008

The ORR performance of a Se/Ru catalyst has been evaluated by RRDE measurements and in fuel cell tests. The catalyst was prepared by adding aqueous SeO2 to metallic Ru black, then bubbling H2 through the mixture. The Tafel slope (80{plus minus}5 mV decade-1 at low overpotential) and activation energy (25{plus minus}3 kJ mol-1 at 0.40 V overpotential) indicate that this Se/Ru catalyst behaves mechanistically in a similar way to pure noble metal catalysts (e.g., Pt and Ru). In comparison to other Se/Ru catalysts, the sample shows higher activity, presumably due to the greater number of Ru sites uncovered by Se available for reaction with oxygen, as estimated by CO stripping. Fuel cell tests demonstrate that Se/Ru is superior to Ru black at low current densities, thanks to the inhibiting effect of Se on the oxidation of Ru to inactive species. The stability of Se under aqueous and fuel cell conditions is also discussed.
Structural Investigation of Carbon Supported Ru-Se Based Catalysts using Anomalous Small Angle X-Ray Scattering
Authors: Haas Sylvio , Hoell Armin , Zehl Gerald , Dorbandt Iris , Bogdanoff Peter , Fiechter Sebastian
Published: May 2008

Selenium modified ruthenium nano-particles are of interest as methanol tolerant electro-catalysts replacing the rare and expensive platinum at the cathode side of low-temperature Direct Methanol Fuel Cells. Recently, it has been found that both the activity and the oxidation resistance of ruthenium can be improved significantly by selenium. The structure and chemical composition of that RuSe(x)O(y) electro-catalyst were analyzed by Anomalous Small Angle X-ray Scattering (ASAXS). ASAXS represents a powerful tool that yields not only averaged structural parameters, but also useful data on the chemical composition on the sub-nanometer scale. Comprehensive ASAXS measurements using X-ray energies near below the Se-K- and Ru-K- absorption edges have been performed in addition to XRD, EXAFS, XPS and TEM studies of these catalysts. The results obtained allowed to deduce a structural model. A cluster like distribution of sub-nanometer sized selenium on the surface of carbon black supported ruthenium nano-particles has been proven.
A Kinetic Study of Oxygen Reduction Reaction on Palladium-Nickel Alloy Surfaces
Authors: Li Bing , Amiruddin Shabab , Prakash J.
Published: May 2008

Polycrystalline Palladium-nickel alloy was successfully electrodeposited on gold disk of a rotating ring-disk electrode (RRDE) and on gold foils. The structure and morphology of the deposits were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical measurements of cyclic voltammetry (CV) and RRDE measurement were also carried out to characterize the Pd-Ni alloy and the oxygen reduction reaction (ORR) on this alloy. The number of electrons transferred in a potential range of 0.36V to 0.04V was calculated to be between 2.1 to 3.3, and Tafel slope obtained was about 110mV/dec on this smooth polycrystalline Pd- Ni alloy surface. The tolerance of this alloy towards methanol oxidation was also investigated.
Nanostructured Halide Modified Carbon Electrodes for Symmetric and Asymmetric Electrochemical Supercapacitors
Authors: Barpanda Prabeer , Fanchini Giovanni , Amatucci Glenn G G.
Published: May 2008

Pristine and high-energy milled activated carbon was chemically modified by vapor phase iodine reaction. Besides significant modification of the physical properties, moderate degrees of iodation results in about 200-500% increase in the volumetric capacity of activated carbons by an increase in the non-Faradaic performance and the development of a Faradaic reaction around 3.1 V. Examining variety of physical and electrochemical properties of iodated carbons, halide modification is proposed as a novel way to produce carbon electrodes for symmetric and asymmetric supercapacitors.
Novel Binderless Nanostructured Carbon Nanotubes-Carbon Aerogel Composites for Electrochemical Double Layer Capacitors
Authors: Bordjiba Tarik , Mohamedi Mohamed , Dao LÊ H.
Published: May 2008

In this work, we report an electrochemical characterization of novel binderless monolithic nanocomposites based on multi wall carbon nanotubes (MWNTs) coated with carbon aerogel (CAG). These interesting architectures became possible trough application of a newly developed technique in our laboratory that is based on coating carbon nanotubes (MWNTs) directly grown on an electrically conductive carbon paper (MFCP) with CAG. The electrochemical properties of these nanocomposites electrodes were studied by cyclic voltammetry and galvanostatic charge-discharge in 5 M KOH. Remarkable high specific capacitance of 524 F/g was demonstrated by these novel nanocomposites.
A Study of Amorphous Carbon Coated Graphite for Lithium Ion Battery Anode Material
Authors: Amiruddin Shabab , Joachin Humberto , Li Bing , Prakash J.
Published: May 2008

Amorphous carbon coated natural graphite (modified graphite, MG) was studied for its thermal and electrochemical performance as a lithium ion anode material. This electrode exhibited a reversible capacity of 94% when compared with the theoretical capacity. MG showed a comparable electrochemical performance when compared with mesocarbon microbeads (MCMB). The morphology was studied using scanning electron microscopy and transmission electron microscopy. Thermal studies were also investigated using Differential Scanning Calorimeter.
Various Carbon Metal Nanocomposites for Lithium Ion Batteries and Direct Methanol Fuel Cells
Authors: Zhao Zhengwei , Guo Zaiping , Liu Huakun , Duo Shixue
Published: May 2008

In this review, the recent activities in our laboratory for the synthesis of metal carbon nanocomposites are presented. Different types of carbon (carbon nanotube-CNT, mesoporous carbon-MC, carbon aerogel-CA) metal nanocomposites (Sn, Ni/CNT, Sn/MC, Pt/ CNT, Pt/ MC, Pt/ CA) were synthesized by various methods as novel electrodes and electrocatalysts for lithium ion batteries and direct methanol fuel cells. The physical and electrochemical properties of these nanocomposites were characterized by XRD, SEM, TEM, CV, charge/discharge measurements, etc. These novel carbon supported metal nanocomposites exhibit great potential to substitute the current used anodes materials for lithium ion batteries or electrocatalysts for direct methanol fuel cells.
Electrocatalytic Activity of Pt-Sb Alloys in Oxidation of Formic Acid and Metanol
Authors: Matsui Hiroshi , Saitou Kimiaki , Kashu Kensuke
Published: May 2008

A series of platinum-antimony intermetallic compounds were prepared by a quenching and annealing method under argon gas atmosphere. The crystal structure was well confirmed by the powder X ray diffraction method. The surface of the prepared compounds was characterized by a cyclic voltametry in a sulfuric acid solution, and the catalytic activity of the intermetallic compounds was determined in the solution containing 0.1 M these substances, taking into account the surface characterization. The intermetallic compound of PtSb in formic acid oxidation was the most active in the prepared compounds, while PtSb2 was quite inactive. An increase in the platinum composition from 50 mol % resulted in strengthened characteristics of platinum metal. The catalytic activity of PtSb and PtSb2 was explained in terms of atom arrangement. Regarding the methanol oxidation, higher catalytic activity than that of platinum metal was not obtained.
Synthesis and Electrochemical Performance of Manganese Oxide
Authors: Kuratani Kentaro , Tatsumi Kuniaki , Kuriyama Nobuhiro
Published: May 2008

Manganese oxides with various nanostructures have successfully been synthesized by means of surfactant-assisted hydrothermal method. The morphological and structural changes of the manganese oxides had simultaneously been achieved during hydrothermal reaction under the presence of surfactant. After reaction for 72 hours, the manganese oxide nanorods with 2 x 4 tunnel structure were obtained by using the layer-structured manganese oxide as a starting material. Cyclic voltammogram of thus obtained manganese oxides showed rectangular curve, which is characteristic of capacitive behavior. The layer-structured manganese oxides showed high specific capacitance compared with the 2 x 4 tunnel-structured manganese oxides, indicates that layer-structured manganese oxides are preferable to the tunnel-structured manganese oxides for applying to the electrochemical capacitor.
Novel Chalcogenide-Based Materials for Oxygen Reduction Reaction
Authors: Delacôte C. , Johnston Christina M. , Zelenay P. , Alonso-Vante Nicolas
Published: May 2008

Partial replacement of Ru in chalcogenide nanoparticles (RuxSey) by a less noble metal, such as Fe, was studied by electrochemical and materials-characterization techniques. The synthesis of the nanoparticles consisting of Ru, Fe, and Se was performed using two different chemical routes, which led either to a combination of RuxSey with oxidized iron or a true alloying of iron with the RuxSey bulk. The physical-chemical properties of the different types of three-component system were subsequently examined. The electrochemical performance in oxygen reduction reaction (ORR) in acidic medium (0.5 M H2SO4) was evaluated relative to the iron-free catalyst. The results demonstrate that the reaction mechanism (four-electron charge transfer) is not perturbed at the modified metal center, even when Ru is replaced by 50 at.% of Fe.
Heteropolyacids as Co-Catalysts with Platinum on the Anode of a Direct Methanol Fuel Cell
Authors: Ferrell Jack R. , Kuo Mei Chen , Turner John A. A. , Herring Andrew M.
Published: May 2008

In this work, polarization and electrochemical impedance spectroscopy experiments were performed on a direct methanol fuel cell (DMFC). Two heteropoly acids, phosphomolybdic acid (PMA) and phosphotungstic acid (PTA), were incorporated into the anode catalyst layer in combination with Pt/C. Both PTA-Pt and PMA-Pt showed higher performance than the Pt control at 30 psig of backpressure. Anodic polarizations were also performed, and Tafel slopes were extracted from the data. An equivalent circuit model which incorporated constant phase elements (CPEs) was used to model the impedance data. From the impedance model it was found that the incorporation of HPAs into the catalyst layer resulted in a reduction in the resistance to charge transfer, Rct. This shows that these two heteropoly acids do act as co-catalysts with platinum for methanol electrooxidation. However, the performance seen here is below that of PtRu catalysts.
Tantalum Compounds as New Non-Platinum Cathode for PEFC
Authors: Ishihara Akimitsu , Shibata Yohei , Mitsushima Shigenori , Kamiya Nobuyuki , Ota Ken-Ichiro
Published: May 2008

A partially oxidized TaC0.52N0.48 has been investigated as new cathodes for polymer electrolyte fuel cells. The working electrodes were prepared with two methods. First, the working electrode was prepared with an electrophoretic deposition of TaC0.52N0.48 on a Ti substrate. Then, the specimen was heat- treated under 0.25% oxygen to proceed to a partial oxidation. Second, the TaC0.52N0.48 was partially oxidized with heat- treatment under 0.25% oxygen, and then, mixed with carbon black to obtain a sufficient electrical contact. In both case, the catalytic activity for the oxygen reduction reaction (ORR) significantly depended on the oxidation state of the TaC0.52N0.48. The onset potential for the ORR had maximum value of 0.83 V in 0.1 mol dm-3 at 30oC. The XRD analysis showed that the specimens, which had a definite catalytic activity, had both TaCxNy and Ta2O5 peaks. This result indicated that the appropriate oxidation of TaC0.52N0.48 was essenti al to enhance the ORR activity.
Pulsing for Enhanced CO Mitigation: Single Cell Performance
Authors: Saunders James , Glenn Bradley , Myers Jeffrey , Cucksey Chad , Mukerjee Sanjeev , Boggs Christopher , Urian R. C.
Published: May 2008

Improved CO tolerance in PEM fuel cells was achieved by periodically varying the anodic overvoltage to convert CO to CO2 directly on the anode. The conversion was controlled by a feedback control algorithm, which used current pulsing and time- varying flow rate parameters as the control variables. Single cell performance data was obtained with 1 and 3 percent CO in a synthetic reformate mixture at 50 C using conventional catalysts and a Nafion 115 membrane. Favorable comparisons are made to 20 ppm CO in H2 for conventional operation and to representative DMFC performance. Durability remains a challenge, but preliminary data with less degradation is presented.
Effects of Pressure Modulation on Porous Gas Electrodes
Authors: Villa Marco , Lorenzi M. , Nelli P. , Kohnke H-J , Zangari Giovanni
Published: May 2008

We explore experimentally the coupling between cell voltages at constant current and pressure differentials applied at the gas/electrolyte compartments of a reversible alkaline fuel-cell electrolyzer system. In the fuel cell mode, higher pressure on the gas side improves the efficiency until gas bubbles evolve into the electrolyte; instead, above a well defined value of overpressure on the electrolyte, the fuel cell voltage drops to zero, as expected. In the electrolyzer mode, an overpressure on the electrolyte decreases the power requirements, mostly due a drop in the overpotential of the H2 electrode. The response of anode and cathode voltages to pressure step consists of a fast component and slow training or relaxation effects.
Characterization of Thin-Film Electrodes on Proton-Conducting Glass Membranes for Micro DMFC Applications
Authors: Mustain William E. , Kim Hyea , Prakash Shruti , Stark Johanna , Osborn Tyler , Kohl Paul
Published: May 2008

Thin film electrodes for a low power direct methanol fuel cell (DMFC) were prepared by incorporating carbon-supported Pt nanoparticles (Pt/C) into a silicon dioxide glass matrix. Scanning electron micrographs (SEM) indicate that the Pt/C was well dispersed. The catalyst islands were interconnected into a conductive sheet by electrolessly depositing platinum from an aqueous plating bath. The Pt/C - SiO2 glass composite thin- film electrodes showed high methanol oxidation peak currents of approximately 180 mA/cm2 in 0.5 M H2SO4, 0.5 M methanol electrolyte. The composite electrode was also applied to the anode of a 1 cm2 passive DMFC and compared to an equivalent passive DMFC with a traditional Nafion®-based Pt anode electrode with 10 M MeOH at room temperature. The new composite electrode DMFC showed a 50 mV higher open circuit voltage than the Nafion electrode cell and the current density was also modestly improved.
Anodic Aluminum Oxide Templated Channel Electrodes via Atomic Layer Deposition
Authors: Martinson Alex B. , Elam Jeff , Hupp Joseph T. T. , Pellin Michael
Published: May 2008

Dye-sensitized solar cells (DSSCs) utilize high surface area metal oxide sintered particle networks to absorb molecular dyes and transport injected charge carriers. While this sintered particle architecture allows liquid electrolyte DSSCs to achieve efficiencies up to 11%, slow charge transport through the semiconductor network limits the amount of modification that can be made to the electrolyte and dye without adversely affecting the efficiency. The functionalization of anodic aluminum oxide membranes with thin films of transparent, semiconducting oxides via atomic layer deposition may allow for significantly faster charge transport. We demonstrate the fabrication of ZnO thin films within and upon commercially available anodic aluminum oxide membranes via atomic layer deposition.
Variability Reduction in Interaural Time Difference Tuning in the Barn Owl
Authors: Fischer Brian J. , Konishi Masakazu
Published: May 2008

The interaural time difference (ITD) is the primary auditory cue used by the barn owl for localization in the horizontal direction. ITD is initially computed by circuits consisting of axonal delay lines from one of the cochlear nuclei and coincidence detector neurons in the nucleus laminaris (NL). NL projects directly to the anterior part of the dorsal lateral lemniscal nucleus (LLDa), and this area projects to the core of the central nucleus of the inferior colliculus (ICcc) in the midbrain. To show the selectivity of an NL neuron for ITD requires averaging of responses over several stimulus presentations for each ITD. In contrast, ICcc neurons detect their preferred ITD in a single burst of stimulus. We recorded extracellularly the responses of LLDa neurons to ITD in anesthetized barn owls and show that this ability is already present in LLDa, raising the possibility that ICcc inherits its noise reduction property from LLDa.
Serial analysis of the vascular endothelial transcriptome under static and shear stress conditions
Authors: Chu Tian Jiao , Peters David G.
Published: May 2008

We have utilized serial analysis of gene expression (SAGE) to analyze the response of human coronary artery endothelial cells (HCAECs) to laminar shear stress (LSS). Primary cultures of HCAECs were exposed to 15 dyn/cm2LSS for 24 h in a parallel plate flow chamber and compared with identical same passage cells cultured under static conditions. The expression levels of a number of functional categories of genes were reduced by shear stress including those encoding proteins involved in cell proliferation (CDC10, CDC20, CDC23, CCND1, CCNB1), angiogenesis (ANGPTL4, CTGF, CYR61, ENG, EPAS1, EGFR, LGALS3, PGK1, and SPARC), extracellular matrix and cell-matrix adhesion (EFEMP1, LOXL2, P4HB, FBN1, FN1, ITGA5, ITGAE, ITGAV, ILK, LAMR1) and ATP synthesis (ATP5G3, ATP5J2, ATP5L, ATP5D). We also observed an increase in the LSS-responsive expression of genes encoding stress response proteins, including HMOX1, which is significant since HMOX1 may have anti-inflammatory and vasodilatory vascular effects. The autosomal dominant polycystic kidney disease (ADPKD) genes PKD1 and PKD2 were also elevated by LSS. ADPKD is associated with vascular malfunction, including the impairment of vasoreactive processes. To our knowledge, this is the first SAGE-based analysis of the shear stress-responsive endothelial cell transcriptome. These immortal data provide a resource for further analyses of the molecular mechanisms underlying the biological response to LSS and contribute to the expanding collection of publicly available SAGE data.
Synchrotron X-ray powder diffraction study of the tetragonal-cubic phase transition in nanostructured ZrO2-Sc2O3 solid solutions
Authors: Abdala Paula M. , Lamas Diego G. , Fernández de Rapp Mária E. , Walsöe de Reca Noemí E. , Craievich Aldo F. , Fantini Márcia C. A.
Published: May 2008

The transition between tetragonal and cubic phases in nanostructured ZrO2-Sc2O3 solid solutions by high-temperature X-ray powder diffraction using synchrotron radiation is presented. ZrO2-8 and 11 mol% Sc2O3 nanopowders that exhibit the t′- and t″-forms of the tetragonal phase, respectively, were synthesized by a stoichiometric nitrate-lysine gel-combustion route. The average crystallite size treated at 900°C was about 25 nm for both compositions. Our results showed that t′-t″ and t″-cubic transitions take place for the 8 and 11 mol% Sc2O3 samples, respectively.
Applications of the Rietveld method to quantify the crystalline phases of Portland cement clinker doped with nickel and chromium
Authors: Ferreira Andréa Vidal , Righi Ariete , Araújo Fernando Gabriel Silva , Espinosa Denise Crocce Romano , Tenório Jorge Alberto Soares
Published: May 2008

The effects of chromium or nickel oxide additions on the composition of Portland clinker were investigated by X-ray powder diffraction associated with pattern analysis by the Rietveld method. The co-processing of industrial waste in Portland cement plants is an alternative solution to the problem of final disposal of hazardous waste. Industrial waste containing chromium or nickel is hazardous and is difficult to dispose of. It was observed that in concentrations up to 1% in mass, the chromium or nickel oxide additions do not cause significant alterations in Portland clinker composition.
Frontiers between crystal structure prediction and determination by powder diffractometry
Authors: Le Bail Armel
Published: May 2008

The fuzzy frontiers between structure determination by powder diffractometry and crystal structure prediction are discussed. The application of a search-match program combined with a database of more than 60 000 predicted powder diffraction patterns is demonstrated. Immediate structure solution (before indexing) is shown to be possible by this method if the discrepancies between the predicted crystal structure cell parameters and the actual ones are <1%. Incomplete chemistry of the hypothetical models (missing interstitial cations, water molecules, etc.) is not necessarily a barrier to a successful identification (in spite of inducing large intensity errors), provided the search-match is made with chemical restrictions on the elements present in both the virtual and experimental compounds.