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Non-destructive diagnosis of power transformer condition is an increasingly important area of research. Power transformer coils are typically insulated with Kraft paper and immersed in mineral oil. There is a clear need to be able to estimate the aged condition of the coil insulation non-destructively. A portable fibre-optic spectroscopic probe system has been developed which can achieve this quickly by determining the degree of polymerization (DP), an indicator of degradation, to an accuracy of 30 DP units. The system can also determine water content to an accuracy of 0.1% w/w, and oil content and condition, very rapidly from the same measurements. The system uses a broadband spectroscopic diffuse reflectance probe operating in the visible and near infrared (NIR) range and interfaced to dedicated multivariate analysis software. Following calibration and measurement trials in the laboratory, the instrument has recently been adapted for use in the field, in which DP predictions have been made from in-situ measurements on the exposed windings of de-tanked transformers. These values have been validated when checked against DP measurements of the same paper taken in parallel using conventional viscometric methods. The system is now being further optimized and is being developed for other applications in the power industry and other industrial areas such as the paper industry and the plastics recycling industry. The system is modular and different probe types can be attached allowing the measurement of a wide variety of solid material surfaces and liquid media. [ABSTRACT FROM AUTHOR]

Presents an overview of the papers selected by the 'IEEE Transactions on Nuclear Science' journal from the European Conference on Radiation and its Effects on Components and Systems in 2000. Information on the conference; Target applications for the conference's workshop; Members of the conference's organizing committee.

The article offers information on the research paper entitled "Recent Advances in Metamaterials and Metasurfaces" from editors Ashwin K. Iyer and Ariel Epstein. It states that the metamaterials research is fueled by fascinating ideas like invisibility cloaks and superlenses which is now sustained by the realization that the ideas are manifestations of a much more tangible and exciting concept that metamaterials afford unprecedented control over electromagnetic waves.

The 39th International Conference on Plasma Science (ICOPS) was held in Edinburgh, Scotland in July 2012. The conference featured a wide range of advances in innovative plasma and beam science and applications, and served as a venue for an international community to meet and discuss their ideas and research results. More than 800 abstracts were received in 35 different topical areas, with more than half the papers originating outside the United State. The conference was attended by over 600 delegates and enjoyed the participation of over 200 registered students. This Special Issue of the IEEE TRANSACTIONS ON PLASMA SCIENCE contains eight refereed papers representing a small collection of some of the most exciting presentations from ICOPS 2012. [ABSTRACT FROM PUBLISHER]

In this article the author cites the five papers presented in the "Institute of Electrical and Electronics Engineers (IEEE) First International Conference on Biometrics: Theory, Applications, and Systems," or BTAS 07, held in Washington, D.C. on September 27-29, 2009. It states that the papers received positive reviews and were revised for the special section of "IEEE Transactions on Systems, Man, and Cybernetics-Part A." Among these papers were authored by Elaine Newton and P. Jonathan Phillips, and Andreas Humm and colleagues from the University of Fribourg in Switzerland.

The article presents information about the recipients of the 2005 H. A. Wheeler Applications Prize Paper Award. The prize was awarded for the paper "Three-Layer Printed Reflectarrays for Contoured Beam Space Applications" by José A. Encinar and J. Agustín Zornoza. Encinar has been with the Applied Electromagnetism and Microwaves Group at UPM, as a Teaching and Research Assistant from 1980 to 1982, as an Assistant Professor from 1983 to 1986, and as Associate Professor from 1986 to 1991. Zornoza worked with the Department of Electromagnetism and Circuit Theory at UPM, initially as collaborator and afterwards as researcher from 1998 to 2004.

Announces the selection of the paper entitled 'Specular Spectroscopic Scatterometry,' by Xinhui Niu, Nickhil Jakatdar, Junwei Bao and Costas J. Spanos, as the best paper published in the 2001 'IEEE Transactions on Semiconductor Manufacturing.' Original date of publication of the winning paper; Highlights of the paper.

The objective of this research was to determine if a relationship could be found between dielectric strength and other properties of electrical insulating materials in the medium of liquid nitrogen on an empirical basis by using variables predicted by basic theory. A simple equation of the form E=A+Blog (ρv /ξr tanδ) to predict the dielectric strength of a solid insulating material in liquid nitrogen medium has been proposed. The equation requires the values of volume resistivity (ρv), relative permittivity (ξr) and loss tangent (tanδ) in the medium of liquid nitrogen, which may be obtained easily by low voltage non-destructive measurements. The values of electric strength calculated using this equation for Crepe paper, Kraft paper, varnished paper, pressboard, presspahn, mica, bakelite and asbestos are quite in agreement with the experimentally measured values. It is expected that the equations obtained will help the designers as a handy tool for quick estimation of breakdown strength of solid dielectrics dipped in liquid nitrogen. [ABSTRACT FROM AUTHOR]

Presents the recipients of the 2000 Outstanding Paper Award of the IEEE Ultrasonics, Ferroelectrics and Frequency Control Society. Timothy Ritter; Xuecang Geng; Patrick D. Lopath.

IEEE Software editor-in-chief Forrest Shull discusses the software sustainability and his interview with Girish Seshagiri, the CEO of AIS, an organization that offers "firm fixed-price contracting with performance guarantees, including a lifetime warranty on software defects" in government contracts. In addition, he discusses the best paper award at the 21st Annual IEEE International Requirements Engineering Conference and the best research paper award at the Agile Conference. The first Web extra at http://youtu.be/L1XN0R4koRk is an audio interview highlighting IEEE Software editor in chief Forrest Shull's discussion with Girish Seshagiri, the CEO of AIS, about the organization's philosophy of offering "firm fixed-price contracting with performance guarantees, including a lifetime warranty on software defects" in government contracts. The second Web extra at http://youtu.be/iFsZlrhSM9E is the complete audio interview in which IEEE Software editor in chief Forrest Shull's speaks with Girish Seshagiri, the CEO of AIS, about the organization's philosophy of offering "firm fixed-price contracting with performance guarantees, including a lifetime warranty on software defects" in government contracts. [ABSTRACT FROM PUBLISHER]

Growing demand for key-value store applications is building a strong momentum for the commercialization of key-value hard disk drives. To achieve better performance, flash-based solid state drive is the next ideal candidate for commercialization in the foreseeable future. However, the existing fixed-sized management strategies of flash-based devices would potentially result in low storage space utilization when managing variable-sized key-value data. In addition, the low storage space utilization would further lead to the degradation of device performance, due to low invalid data space reclamation efficiency. The space utilization issue motivates this paper to propose a key-value flash translation layer design to improve storage space utilization as well as the performance of the key-value solid state drives. A series of experiments was conducted to evaluate the proposed design, and the experiment results of space utilization and device performance are very encouraging. [ABSTRACT FROM AUTHOR]

All Pairs problems occur in many research fields. The all-pairs problem requires all data elements to be paired with all other data elements. With the advent of new data intensive big data applications and increase in data size, methods to reduce memory foot print and distribute to work equally across compute nodes are needed. In this paper, we propose cyclic quorum sets for all-pairs algorithm computations to reduce memory foot print. We show that the cyclic quorum sets have a unique all-pairs property that allows for minimal data replication. The cyclic quorums set based computing requires only N/\sqrtP size memory, up to 50 percent smaller than the dual N/\sqrtP array implementations proposed earlier, and significantly smaller than solutions requiring all data in each node. Computation can be distributed efficiently and more importantly and are communication-less after initial data distribution, which is a huge advantage in minimizing computation time. Scaling from 16 to 512 cores (1 to 32 compute nodes), our application experiments on a real dataset demonstrated scalability with greater than 150x (super-linear) speedup with less than 1/4th the memory usage per node in our experiments. [ABSTRACT FROM AUTHOR]

The important topic of global climate change builds on a huge collection of scientific research. It is common for agencies releasing climate change information to be served with requests for all supporting materials resulting in a particular conclusion. Capturing and presenting global change provenance, linking to the research papers, data sets, models, analyses, observations, satellites, etc., that support the key research findings in this domain can increase understanding and aid in reproducibility of results and conclusions. The U.S. Global Change Research Program is now coordinating the production of a national climate assessment (NCA) that presents our best understanding of global change. We are now developing a global change information system that will present the content of that report and its provenance, including the scientific support for the findings of the assessment. We are using an approach that will present this information both through a human accessible Web site as well as a machine-readable interface for automated mining of the provenance graph. We plan to use the developing World Wide Web Consortium (W3C) PROV data model and ontology for this system. This paper will describe an overview of the process of developing the NCA and how the provenance trail of the report and each of the technical inputs can be captured and represented using the W3C PROV ontology. This will improve the visibility into the assessment process, increase understanding and possibility of reproducibility, and ultimately increase the credibility and trust of the resulting report. [ABSTRACT FROM AUTHOR]

At present, several papers discuss the accuracy and precision of terrestrial laser scanners (TLSs), but the research continues to focus on the behavior of the TLSs. The purpose of this paper is to propose a method to evaluate the uncertainty of a TLS (FARO Photon 80). A rigid and transportable aluminum structure with 28 black-and-white targets was designed for this purpose. The structure was scanned 12 times at several distances from 2 to 70 m, and the x, y, and z coordinates of the center of the targets were automatically identified. Data were analyzed by means of circular and spherical statistics using R modules programmed in our research group. Analysis reveals that 3-D spatial distribution has a stratified pattern in the Z-axis. Regardless of the scanner status, these results indicate that these analyses should be performed periodically because they can have an impact on some studies. The proposed methodology is robust and simple and can be performed with free software such as the R modules used in this work. [ABSTRACT FROM AUTHOR]

Objective: Reproducibility is the cornerstone of the scientific method. However, currently, many systems biology models cannot easily be reproduced. This paper presents methods that address this problem. Methods: We analyzed the recent Mycoplasma genitalium whole-cell (WC) model to determine the requirements for reproducible modeling. Results: We determined that reproducible modeling requires both repeatable model building and repeatable simulation. Conclusion: New standards and simulation software tools are needed to enhance and verify the reproducibility of modeling. New standards are needed to explicitly document every data source and assumption, and new deterministic parallel simulation tools are needed to quickly simulate large, complex models. Significance: We anticipate that these new standards and software will enable researchers to reproducibly build and simulate more complex models, including WC models. [ABSTRACT FROM PUBLISHER]

Objective: Only reproducible results are of significance to science. The lack of suitable standards and appropriate support of standards in software tools has led to numerous publications with irreproducible results. Our objectives are to identify the key challenges of reproducible research and to highlight existing solutions. Results: In this paper, we summarize problems concerning reproducibility in systems biology and systems medicine. We focus on initiatives, standards, and software tools that aim to improve the reproducibility of simulation studies. Conclusions: The long-term success of systems biology and systems medicine depends on trustworthy models and simulations. This requires openness to ensure reusability and transparency to enable reproducibility of results in these fields. [ABSTRACT FROM PUBLISHER]

This paper deals with the Bayesian signal denoising problem, assuming a prior based on a sparse representation modeling over a unitary dictionary. It is well known that the maximum a posteriori probability (MAP) estimator in such a case has a closed-form solution based on a simple shrinkage. The focus in this paper is on the better performing and less familiar minimum-mean-squared-error (MMSE) estimator. We show that this estimator also leads to a simple formula, in the form of a plain recursive expression for evaluating the contribution of every atom in the solution. An extension of the model to real-world signals is also offered, considering heteroscedastic nonzero entries in the representation, and allowing varying probabilities for the chosen atoms and the overall cardinality of the sparse representation. The MAP and MMSE estimators are redeveloped for this extended model, again resulting in closed-form simple algorithms. Finally, the superiority of the MMSE estimator is demonstrated both on synthetically generated signals and on real-world signals (image patches). [ABSTRACT FROM AUTHOR]

In this paper, we introduce a new class of transform method--the arithmetic cosine transform (ACT). We provide the central mathematical properties of the ACT, necessary in designing efficient and accurate implementations of the new transform method. The key mathematical tools used in the paper come from analytic number theory, in particular the properties of the Riemann zeta function. Additionally, we demonstrate that an exact signal interpolation is achievable for any block-length. Approximate calculations were also considered. The numerical examples provided show the potential of the ACT for various digital signal processing applications. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the net sidelobe power reduction of noncontiguous orthogonal frequency-division-multiplexing (NC-OFDM) signals using an approach combining cancellation carriers (CCs) and modulated filter banks (MFBs). NC-OFDM can enable high-speed dynamic spectrum access (DSA) networks via transmission over several disjoint separate frequency bands. However, OFDM generally produces a substantial amount of out-of-band (OOB) interference that can potentially disrupt communications in adjacent wireless channels. One solution is to apply a filter bank, which is an array of bandpass filters that serves to isolate different frequency components of a signal. In this paper, we propose a combined OFDM sidelobe-suppression approach consisting of MFBs and the existing CC technique to achieve OOB radiation reduction. The simulation results show a significant net reduction of sidelobe power after using these two techniques. Furthermore, an algorithm has been developed to determine the number of OFDM data carriers (DCs) that can be transmitted in a given spectrum space. [ABSTRACT FROM AUTHOR]

In this paper, we propose an analysis of frequency rendezvous techniques employing three different scanning rules by combining analytical results with computer simulations. Frequency rendezvous is a critical step in bootstrapping a wireless network that does not possess centralized control. Current techniques for enabling frequency rendezvous in decentralized dynamic spectrum access (DSA) networks either require preexisting infrastructure or use one of several simplifying assumptions regarding the architecture, such as the use of regularly spaced frequency channels for communications. Our approach is designed to be operated in a purely decentralized wireless networking environment, where no centralized control is present, and the spectrum possesses no predefined channels. This is accomplished via a combination of receiver pilot tones, a tone-scanning protocol, and a transmitter/receiver handshaking process. To realize a shortest search time for the target receiver, an efficient scanning rule should be employed. In this paper, three scanning rules, i.e., frequency sequence scanning, pilot tone strength scanning, and cluster scanning, are analyzed using mathematical derivations. To validate our theoretical result, we test the three scanning rules with computer simulations. [ABSTRACT FROM AUTHOR]

In this paper, quality-of-service (QoS) provisioning for voice service in cognitive radio networks is considered. As voice traffic is sensitive to delay, the presence of primary users and the requirement that secondary users should not interfere with them pose many challenges for QoS support in cognitive radio networks. Two cognitive medium-access control (MAC) schemes are proposed in this paper for secondary voice users to access the available channel. One is the contention-based scheme, and the other is the contention-free scheme. An analytical model is developed to obtain the voice-service capacity (i.e., the maximum number of secondary voice users that can be supported with QoS guarantee) of the two proposed schemes, taking into account the impact of the primary users' activity. Both independent and correlated channel busy/idle state models for primary activity are considered. The analytical model is validated by simulations. The analytical results will be useful to support voice service in cognitive radio networks. [ABSTRACT FROM AUTHOR]

In this paper, a mathematical model for the beacon-enabled mode of the IEEE 802.15.4 medium-access control (MAC) protocol is provided. A personal area network (PAN) composed of multiple nodes, which transmit data to a PAN coordinator through direct links or multiple hops, is considered. The application is query based: Upon reception of the beacon transmitted by the PAN coordinator, each node tries to transmit its packet using the superframe structure defined by the IEEE 802.15.4 protocol. Those nodes that do not succeed in accessing the channel discard the packet; at the next superframe, a new packet is generated. The aim of the paper is to develop a flexible mathematical tool able to study beacon-enabled 802.15.4 networks organized in different topologies. Both the contention access period (CAP) and the contention-free period defined by the standard are considered. The slotted carrier-sense multiple access with collision avoidance (CSMA/CA) algorithm used in the CAP portion of the superframe is analytically modeled. The model describes the probability of packet successful reception and access delay statistics. Moreover, both star and tree-based topologies are dealt with; a suitable comparison between these topologies is provided. The model is a useful tool for the design of MAC parameters and to select the better topology. The mathematical model is validated through simulation results. The model differs from those previously published by other authors in the literature as it precisely follows the MAC procedure defined by the standard in the context of the application scenario described. [ABSTRACT FROM AUTHOR]

Inherent timing variables and constraints in communication protocols require new extended finite-state machine (EFSM) models to formally represent their behavior, particularly for test generation purposes. However, infeasible paths due to the conflicts among the timing condition and action variables in the timed EFSM models with the activation and expiration of concurrent timers complicate the test generation process. In a test measurement laboratory, such timers, if not properly taken into account by formal methods at the test generation step, can generate false results by failing correct implementations or, worse, passing faulty implementations. This paper analyzes the fault detection capability of the timed EFSM models introduced in our earlier work in the presence of multiple timing faults. It is proven that, for a class of timing faults, test sequences generated from our models can detect multiple occurrences of pairwise combinations of such faults. A simplified version of the Session Initiation Protocol (SIP) registration process, which is widely used by Voice over IP (VoIP) telephones, has been used as a working example throughout this paper. [ABSTRACT FROM AUTHOR]

In this paper, we consider the problem of associating estimated direction-of-arrival (DOA) angles of multiple targets using two uniform linear arrays (ULAs) of sensors. It is categorized as a multisource information aggregation problem, in which we devise our algorithm in the following two steps: 1) Estimate two sets of DOA angles from two ULAs, respectively, and 2) associate estimated DOA angles with the targets. Note, however, that the primary focus of this paper is the second step, i.e., association of DOA angles with the corresponding targets, whereas for the first step, we use the well-known improved polynomial rooting method. Generally speaking, if there are q targets, we have q! possible association pairs, among which, there is only one set corresponding to the correct association. Since target signals must be correlated in the observations of two ULAs, we can determine how to associate the DOA angles computed from step 1 by evaluating the covariance matrix of the data received at the two ULAs. The algorithm is effective, robust, and accurate in classifying the DOA angles into the correct association. [ABSTRACT FROM AUTHOR]

In this paper, the analysis of biomedical. data characterizing motor activities of the limbs is carried out with the aim of extracting useful information for evaluating the state of subjects affected by Parkinson's disease. Initially, a simple and inexpensive system that measures the force of the palmar grip has been presented; then, a suitable software protocol that is able to record, manage, and interpret the acquired data has been realized. Afterward, a first analysis in the time domain has led to the identification of some biomedical parameters characterizing motor activities of the limbs; the study of these parameters and the analysis of the correlations between the acquired data have permitted the development of suitable models describing the time behavior of the palmar grip. In this paper, the authors propose a more detailed study that evaluates the filtering, phase noise effects, and performance of different methods used to estimate the characteristic parameters of the palmar grip. [ABSTRACT FROM AUTHOR]

This paper presents a method of determining electromotive force and battery internal resistance as time functions, which are depicted as functions of state of charge (SOC) because Soc = f(t). The model is based on battery discharge and charge characteristics under different constant currents that are tested by a laboratory experiment. This paper further presents the method of determining the battery soc according to a battery modeling result. The influence of temperature on battery performance is analyzed according to laboratory-tested data, and the theoretical background for calculating the SOC is obtained. The algorithm of battery SOC indication is depicted in detail. The algorithm of the battery SOC "online" indication considering the influence of temperature can be easily used in practice by a microprocessor. An NiMH battery is used in this paper to depict the modeling method. In fact, the method can also be used for different types of contemporary batteries, as well as Li-ion batteries, if the required test data are available. [ABSTRACT FROM AUTHOR]

We study the embedding of Hamiltonian cycle in the Crossed Cube, which is a prominent variant of the classical hypercube, obtained by crossing some straight links of a hypercube, and has been attracting much research interest in literatures since its proposal. We will show that due to the loss of link-topology regularity, generating Hamiltonian cycles in a crossed cube is a more complicated procedure than in its original counterpart. The paper studies how the crossed links affect an otherwise succinct process to generate a host of well-structured Hamiltonian cycles traversing all nodes. The condition for generating these Hamiltonian cycles in a crossed cube is proposed. An algorithm is presented that works out a Hamiltonian cycle for a given link permutation. The useful properties revealed and the algorithm proposed in this paper can find their way when system designers evaluate a candidate network's competence and suitability, balancing regularity and other performance criteria, in choosing an interconnection network. [ABSTRACT FROM AUTHOR]

This paper introduces a space-time decision feedback equalizer whose coefficients are recursively renewed on the basis of the modified affine projection algorithm (APA). Despite its effectiveness against a rank-deficiency problem, the complexity of the conventional APA utilizing the sample matrix inversion is considerable. Furthermore, the shift invariance property could not be exploited in the case of a space-time decision-directed equalizer (STDE) application. To overcome such challenges, this paper introduces an APA employing a hyperplane projection scheme to reduce computational complexity without any degradation in its convergence characteristic and tracking capability. The performance of the proposed equalization methodology is verified by showing its superior bit error rate behaviors, fast convergence property, and reduced computational complexity by performing adaptive STDE under the single-input-multiple-output wireless multipath fading channel. [ABSTRACT FROM AUTHOR]

This paper investigates the hidden-node phenomenon (HN) in IEEE 802.11 wireless networks. HN occurs when nodes outside the carrier-sensing range of each other are nevertheless close enough to interfere with each other. As a result, the carrier- sensing mechanism may fail to prevent packet collisions. HN can cause many performance problems, including throughput degradation, unfair throughput distribution among flows, and through-put instability. The contributions of this paper are threefold. 1) This is a first attempt to identify a set of conditions-which we called Hidden-node-Free Design (HFD)—that completely remove HN in 802.11 wireless networks. 2) We derive variations of HFD for large-scale cellular WiFi networks consisting of many wireless LAN cells. These HFDs are not only HN-free, but they also reduce exposed nodes at the same time so that the network capacity is improved. 3) We investigate the problem of frequency-channel assignment to adjacent cells. We find that with HFD, careful assignment in which adjacent cells use different frequency channels does not improve the overall network capacity (in unit of bits per second per frequency channel). Indeed, given f frequency channels, a simple scheme with f overlaid cellular WiFi networks in which each cell uses all f frequencies yields near-optimal performance. [ABSTRACT FROM AUTHOR]

Due to its spectral efficiency and robustness over multipath channels, orthogonal frequency-division multiplexing (OFDM) has served as one of the major modulation schemes for high-speed communication systems. In the future, wireless OFDM systems are expected to operate at high carrier frequencies, high speed, and high throughput for mobile reception, where fast time-varying fading channels are encountered. Channel variation destroys the orthogonality among the subcarriers and leads to intercarrier interference (ICI). ICI poses a significant limitation on wireless OFDM systems. The aim of this paper is to find an efficient method of providing reliable communications using OFDM in fast time-varying fading channels. It is observed that ICI power arises from a few adjacent subcarriers. This observation motivates us to design low-complexity Q-tap ICI equalizers. To employ these equalizers, channel state information is also required. In this paper, we also design a pilot-aided minimum mean square error (MMSE) channel estimation scheme for a time-varying wide-sense stationary uncorrelated scatters channel model. The MMSE channel estimator utilizes the statistical channel properties to achieve computational efficiency. Simulation results show that our proposed low-complexity ICI suppression scheme, which incorporates the Q-tap equalizer with the MMSE channel estimator, can significantly improve the performance of OFDM systems in fast time-varying fading channels. [ABSTRACT FROM AUTHOR]

This paper introduces a linear space—time precoding scheme for downlink transmission in a multiple-transmit single-receive antenna code-division multiple-access (CDMA) system. The proposed scheme relies on using space-time spreading sequences that are constructed from the time-domain user signatures combined with spatial channel information that corresponds to multiple transmit antennas. Numerical results show that the proposed scheme significantly reduces the multiple-access interference in both flat- and multipath-fading channels. At the same time, it achieves the maximum possible diversity order that is offered by the combination of multiple transmit antennas and multipath fading. To further improve the performance in overloaded CDMA systems, the proposed linear precoding method is combined with a nonlinear operation known as vector perturbation (based on applying modulo operation to minimize the transmit energy). Throughout the paper, we assume that 1) the channel state information is known at the transmitter, 2) the modulation is binary phase-shift keying, and 3) the receivers are simply based on linear filters that are matched to the time-domain user signatures. We use a recent work of Reynolds et a!. as a baseline for comparison. Numerical results show that our proposed method outperforms that of Reynolds et al. in both flat and multipath channels. [ABSTRACT FROM AUTHOR]

Output-time prediction is a critical task to a wafer fab. To further enhance the accuracy of wafer-lot output-time prediction, the concept of input classification is applied to Chen's fuzzy backpropagation network (FBPN) approach in this paper by preclassifying wafer lots with the fuzzy c-means (FCM) classifier before predicting the output times. In this way, similar wafer lots are clustered in the same category. The data of wafer lots of different categories are then learned with different FBPNs but with the same topology. After learning, these FBPNs form an FBPN ensemble that can be applied in predicting the output time of a new lot. The output of the FBPN ensemble determines the cycle/output time forecast and is obtained by aggregating the outputs of the component FBPNs. Production simulation is applied in this paper to generate test data. According to experimental results, the prediction accuracy of the hybrid FCM-FBPN approach was significantly better than those of many existing approaches. [ABSTRACT FROM AUTHOR]

Wireless local area networks are currently evolving to support adequate degrees of service differentiation. Work is in progress to define an enhanced version of the IEEE 802.11 distributed coordination function, which is capable of supporting quality of service for multimedia traffic at the medium access control layer. In this paper, we aim at gaining insight into one mechanism to differentiate among traffic categories, i.e., differentiating the minimum contention window sizes according to the priority of different traffic categories. The contribution of this paper is the analysis of the optimal operation point where maximum throughput can be achieved. Through the analysis, we answer some fundamental questions about the existence and uniqueness of the optimal operation point, about the maximum system throughput, about the existence of simple rules to decide if the system operates under the optimal state or not, and about procedures to lead the system to the optimal operation point. The other contribution is the proposal of a simple adaptive scheme that makes the system operate under the optimal operation point and, at the same time, achieve target service differentiation between different traffic flows. The results that are obtained in this paper are relevant to both theoretical research and implementations of real systems. [ABSTRACT FROM AUTHOR]

Universal mobile-telecommunication system supports IP multimedia services through the IP multimedia core-network subsystem (IMS). This paper proposes a prepaid application server (PAS) to handle both the prepaid calls and messaging services in the IMS. When both voice and messaging are simultaneously offered, a potential problem is that the delivery of a message during a call may result in force-termination of that call due to credit depletion. To address this issue, we describe a strategy to determine if a prepaid message can be sent out during a call session. We propose an analytic model to investigate the performance of this strategy. This paper provides guidelines to select appropriate input parameters for the PAS. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the behavior of flooding-based packet forwarding in a densely populated mobile ad hoc network. Specifically, we develop the probability distribution of hop count distance for a source-destination pair in the network, given that all nodes are roaming. The behavior of packet forwarding in such an environment is analogous to the ripples radiating from the source when one drops a stone into a pond. Due to node mobility, the number of hops traversed by each packet is not simply equal to the number of ripples from source to destination. In this paper, node mobility is represented as a growing circle centered at the destination node. The moving behavior of intermediate nodes can be ignored in a flooding-based ad hoc network with high node density since there is always a node available in the transmission direction to forward packets. The analytical model is validated via simulations. We further demonstrate that based on the proposed analytical model, one can estimate the flooding cost and search latency of target location discovery commonly used in most existing on-demand ad hoc routing protocols, and learn the impact of different flooding schemes on target discovery. [ABSTRACT FROM AUTHOR]

This paper presents a nonlinear sliding-mode-type controller for slip regulation in a braking event for an electromagnetic brake-by-wire (BBW)-system-equipped automobile. The electromagnetic BBW system under consideration consists of a set of eddy current brakes (ECBs) attached to the automobile wheels. The antilock-braking controller modifies the brake torque command generated by a supervisory controller which, in turn, is based on the driver's command sensed via brake pedal sensors. The modified brake torque command is then generated by a closed-loop actuator control algorithm to control the ECB system. It is shown in this paper that the proposed antilock-braking control system is stable in the sense of Lyapunov. Experunental results are presented for a test vehicle equipped with an eddy-current-based BBW system. Experimental results show that the proposed antilock brake control algorithm provides very good slip regulation in a braking event on low friction-coefficient surfaces (wet jennite) when compared with that of a braking event without the proposed antilock-braking control. Experimental results also indicate that the proposed antilock-braking control system provides a smooth stop for the vehicle. [ABSTRACT FROM AUTHOR]

In recent years, edge computing has emerged as a popular mechanism to deliver dynamic Web content to clients. However, many existing edge cache networks have not been able to harness the full potential of edge computing technology. In this paper, we argue and experimentally demonstrate that cooperation among the individual edge caches coupled with scalable server- driven document consistency mechanisms can significantly enhance the capabilities and performance of edge cache networks in delivering fresh dynamic content. However, designing large-scale cooperative edge cache networks presents many research challenges. Toward addressing these challenges, this paper presents cooperative edge cache grid (cooperative EC grid, for short)—a large-scale cooperative edge cache network for efficiently delivering highly dynamic Web content with varying server update frequencies. The design of the cooperative EC grid focuses on the scalability and reliability of dynamic content delivery in addition to cache hit rates, and it incorporates several novel features. We introduce the concept of cache clouds as a generic framework of cooperation in large-scale edge cache networks. The architectural design of the cache clouds includes dynamic hashing-based document lookup and update protocols, which dynamically balance lookup and update loads among the caches in the cloud. We also present cooperative techniques for making the document lookup and update protocols resilient to the failures of individual caches. This paper reports a series of simulation-based experiments which show that the overheads of cooperation in the cooperative EC grid are very low, and our architecture and techniques enhance the performance of the cooperative edge networks. [ABSTRACT FROM AUTHOR]

Sensor networks have emerged as a promising technology with various applications, where power efficiency is one of the critical requirements. The recent IEEE 802.15.4 standard offers a promising platform for wireless sensor networks. Since each node can act as a coordinator or a device in the IEEE 802.15.4 standard, 802.15.4-based sensor networks have various possible network topologies. To reduce power consumption, in this paper, we try to construct network topologies with a small number of coordinators while still maintaining network connectivity. By reducing the number of coordinators, the average duty cycle is reduced and the battery life is prolonged. Three topology control algorithms are proposed in this paper. Self-pruning (SP) is the simplest one with O(1) running time and provides the shortest path to the sink node. Ordinal pruning (OP) can significantly improve SP in terms of power saving with O(n) running time. Layered pruning (LP) is a trade off between the first two pruning algorithms with O(√n) running time and has a slightly higher power consumption than OP. Furthermore, all three algorithms are independent of the physical radio propagation characteristics. Extensive simulations have been performed to verify the effectiveness of the proposed topology control schemes. [ABSTRACT FROM AUTHOR]

This paper is concerned with a particular family of regular 4-connected graphs, called chordal rings. Chordal rings are a variation of ring networks. By adding two extra links (or chords) at each vertex in a ring network, the reliability and fault-tolerance of the network are enhanced. Two spanning trees on a graph are said to be independent if they are rooted at the same vertex, say, r, and for each vertex v ≠ r, the two paths from r to v, one path in each tree, are internally disjoint. A set of spanning trees on a given graph is said to be independent if they are pairwise independent. Iwasaki et al. [9] proposed a linear time algorithm for finding four independent spanning trees on a chordal ring. In this paper, we give a new linear time algorithm to generate four independent spanning trees with a reduced height in each tree. Moreover, a complete analysis of our improvements on the heights of independent spanning trees is also provided. [ABSTRACT FROM AUTHOR]

This paper explores the factors influencing perceptions of data warehousing process maturity. Data warehousing, like software development, is a process, which can be expressed in terms of components such as artifacts and workflows. In software engineering, the Capability Maturity Model (CMM) was developed to define different levels of software process maturity. We draw upon the concepts underlying CMM to define different maturity levels for a data warehousing process (DWP). Based on the literature in software development and maturity, we identify a set of features for characterizing the levels of data warehousing process maturity and conduct an exploratory field study to empirically examine if those indeed are factors influencing perceptions of maturity. Our focus in this paper is on managerial perceptions of DWP. The results of this exploratory study indicate that several factors—data quality, alignment of architecture, change management, organizational readiness, and data warehouse size—have an impact on DWP maturity, as perceived by IT professionals. From a practical standpoint, the results provide useful pointers, both managerial and technological, to organizations aspiring to elevate their data warehousing processes to more mature levels. This paper also opens up several areas for future research, including instrument development for assessing DWP maturity. [ABSTRACT FROM AUTHOR]

One of the challenging problems for software developers is guaranteeing that a system as built is consistent with its architectural design. In this paper, we describe a technique that uses runtime observations about an executing system to construct an architectural view of the system. In this technique, we develop mappings that exploit regularities in system implementation and architectural style. These mappings describe how low-level system events can be interpreted as more abstract architectural operations and are formally defined using Colored Petri Nets. In this paper, we describe a system, called DiscoTect, that uses these mappings and we introduce the DiscoSTEP mapping language and its formal definition. Two case studies showing the application of DiscoTect suggest that the tool is practical to apply to legacy systems and can dynamically verify conformance to a preexisting architectural specification. [ABSTRACT FROM AUTHOR]

This paper presents the influence of current distribution on AC transport current loss in multi-strand high-temperature superconductor (HTS) tapes. The current-distribution-dependent-AC loss is analyzed by introducing a current distribution parameter. We calculated AC loss of multi-strand HTS tapes numerically and performed AC loss measurements as well. Though the effect of current distribution on AC transport current loss is relatively insignificant for a low applied transport current, the effect of nonuniform current distribution seriously increases AC loss for a high applied transport current. The AC loss measurement method used in this paper is also confirmed by comparison with numerical results: the experimental and computational results showed good agreement for various current distribution parameters. [ABSTRACT FROM AUTHOR]

Due to its many advantages such as the improved power quality, high energy efficiency and controllability, etc. the variable speed wind turbine using a doubly fed induction generator (DFIG) is becoming a popular concept and thus the modeling of the DFIG based wind turbine becomes an interesting research topic. Fundamental frequency models have been presented but these models are often complex with significant numerical overhead as the power converter block consisting of power control, rotor side and grid side converter control and DC link are often simulated in detail. This paper develops a simple DFIG wind turbine model in which the power converter is simulated as a controlled voltage source, regulating the rotor current to meet the command of real and reactive power production. This model has the form of traditional generator model and hence is easy to integrate into the power system simulation tool such as PSSIE. As an example, the interaction between the Arklow Bank Wind Farm and the Irish National Grid was simulated using the proposed model. The model performance and accuracy was also compared with the detailed model developed by DIgSILENT. Considering the simplification adopted for the model development, the limitation and applicability of the model were also discussed in this paper. [ABSTRACT FROM AUTHOR]

This paper aims at studying the band gap phenomena of three-dimensional phononic crystals using the finite difference time domain (FDTD) method and a PC cluster system. In the paper, Bloch's theorem is applied to the wave equation and to the boundary conditions of the periodic `structure. We calculate the variations of displacements and take discrete Fourier transform to acquire the resonances of the structures. Then, the dispersion relations of the bulk acoustic wave can be obtained and the band gaps are predicted accordingly. On the other hand, because of larger data calculation in three-dimensional phononic crystals, we introduce the PC cluster system and parallel FDTD programs written with respect to the architecture of a PC cluster system. Finally, we discuss the numerical calculation of two-dimensional and three-dimensional phononic crystals consisting of steel/epoxy and draw conclusions regarding the band gap phenomena between these phononic crystals. [ABSTRACT FROM AUTHOR]

This paper briefly summarizes software reuse research, discusses major research contributions and unsolved problems, provides pointers to key publications, and introduces four papers selected from The Eighth International Conference on Software Reuse (ICSR8). [ABSTRACT FROM AUTHOR]

A concise review is given of the progress made in the field of partial discharges (PD) at dc voltage. Although ample reference will be made to work of other authors in this field, the paper will concentrate on the progress that was made at Delft University of Technology over a period of 14 years in three Ph.D. projects. In the first project, a start was made with the analysis of the physics of partial discharges at dc voltage and different types of PD were characterized based on parameters like time interval between PD and PD magnitude. In a second project, PD analysis was applied to IIVDC apparatus and different means of classification of PD at dc volt- age were proposed. In the third project, PD analysis was applied to HVDC mass- impregnated cables and test specifications were proposed. In this paper the work performed in the above three Ph.D. projects is summarized with ample reference to papers of other workers in this field. Attention is given to the mechanism of PD at dc voltage as compared to ac voltage and techniques for measurement and analysis of dc PD patterns. Examples of practical application of dc PD testing are given. Finally, some thoughts on future work are presented. [ABSTRACT FROM AUTHOR]

This paper focuses on the multiport characterization of antennas. In particular, special attention is given to the cavity backed annular patch antenna (CABAPA) for multipolarization operations. We will show that the reflection coefficient is not the best representative parameter to determine the frequency response of the multiport antenna and its radiation performance. Therefore, we seek a new generalized parameter that conveys the frequency response of multiport antennas. The total active reflection coefficient (TARC) is introduced as the square root of the sum of all incident powers at the ports minus radiated power, divided by the sum of all incident powers at the ports. The TARC is a function of frequency and is a real number between zero and one. With this definition we can characterize the multiport antenna's frequency bandwidth and radiation performance. In this paper, a method for calculating the TARC is detailed for different port excitations directly from the scattering matrix of the antenna and independent of the feeding network. First, the CABAPA is analyzed by the method of moments. Next, the corresponding scattering matrix is employed to calculate the TARC for different polarizations. The calculated results, when compared to the measured results, show good agreement. The measured -10 dB TARC bandwidth of the CABAPA is 30 % compared with 68% as measured using only the s11. [ABSTRACT FROM AUTHOR]

The numerical simulation of long-distance, over-terrain propagation of electromagnetic waves has received considers able attention due to its strong impact on radar and communication technology. One highly desirable feature of the methods currently used in these simulations is numerical efficiency, which is typically achieved by approximating the actual three-dimensional (3-D) propagation medium by a two-dimensional (2-D) medium. In this medium, the atmospheric variations are confined to the range/altitude (x/z) propagation plane while terrain variations are confined to the range direction (one-dimensional terrain). With an additional, paraxial assumption, these models arrive at an extremely efficient, scalar parabolic wave equation (PWE) that can be solved with marching techniques. A significant drawback, how- ever, is that the 2-D approximation discards propagation effects associated with the lateral variations of the 2-D terrain-namely lateral diffraction, lateral scattering and depolarization. These effects may have substantial impact on clutter modeling in radar detection and imaging. In this paper, the propagation effects associated with lateral terrain variations are examined via 3DVPWE , a full 3-D numerical model based on the vector PWE. A notional urban terrain configuration, as well as a realistic digital-map terrain example is considered. The 3DVPWE results are then compared to results from 2-D PWE model to assess the performance of this commonly used approximation. The main emphasis of the paper will be placed on lateral diffraction and scattering. The examination of depolarization effects will be deferred to a future publication. [ABSTRACT FROM AUTHOR]

In the first half of this paper, an efficient method to calculate transmission and reflection characteristics of wire-grids consisting of periodic arrays of cylindrical conductors for arbitrary directions of incidence is presented by extending exact theory of wire-grids proposed by Yasumoto et al. In the latter half of this paper, an approximate calculation method for wire-grids with slight random irregularity in their spacings between wires is proposed by treating the irregularity as a small perturbation to the theory for regular grids. A comparison with preliminary measurements for actual wire-grids in millimeter- and submillimeter-wave regions demonstrated that this method is effectively applicable to wire-grids whose irregularity is not too much. [ABSTRACT FROM AUTHOR]