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Most paging schemes are considered on a per-user basis, i.e., when an incoming call arrives to a mobile terminal (MT), a paging request (PR) is put in a queue in mobile switching center, and PRs are served in a first-in first-out manner. In this paper, we propose a simplified pipeline probability paging (PPP) scheme, which handles PRs in a pipeline manner with a paging delay constraint under the condition of known knowledge on location probabilities of individual MTs. We then provide a performance evaluation and comparison for blanket paging scheme, sequential probability paging, and PPP in wireless networks. Both analytical models and extensive simulations are adopted to study these schemes. [ABSTRACT FROM AUTHOR]

This paper presents a generalized channel preemption model (GCPM) for multiclass traffic in mobile wireless networks. In the proposed model, a mobile call is identified by four parameters—call type, traffic class, channel requirement, and preemption ratio—in which different classes of traffic can have different priority levels. To effectively reduce dropping probability, high-priority handoff calls are allowed to fully or partially preempt low-priority ongoing calls when the mobile network becomes congested. A fully preempted call can be completely disconnected, whereas a partially preempted call can still communicate with certain degree of quality-of-service degradation. We introduce an analytical model with multidimensional Markov chains. In the model, a cost function, which is expressed as a weighted sum of the ongoing calls to be preempted and the bandwidth reduction rate in the preempted calls, is defined to select candidate calls from a certain traffic class. The statistical result from the model allows us to tune the parameters of the GCPM to support high-priority handoff calls and therefore offers new insights in understanding the tradeoffs in supporting multiclass traffic. [ABSTRACT FROM AUTHOR]

Location management of mobile users is of primary importance in personal communication networks (PCNs), and it is mainly aimed to facilitate the delivery of incoming calls to destination users and to make a more efficient use of network resources. In practical PCNs, the location management algorithms need to keep track of mobile users in a dynamic manner, and it is a design concern to minimize the generated signaling traffic. In this paper, we present the cost analysis for the dynamic movement-based location update scheme. Our model is based on renewal theory arguments, and it is general enough to include a variety of probability distributions for modeling cell residence times (CRTs) in hyperexponentially distributed location area residence times and exponentially distributed intercall times. We compare the location update cost for the dynamic and static schemes. We present numerical results regarding the exponential and circular CRT distributions and discuss the optimal threshold distance for location update that minimizes the cost of the dynamic movement-based scheme. [ABSTRACT FROM AUTHOR]

This paper explores the feasibility of designing an outdoor cellular network based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, which was originally developed for wireless local area networks. Specifically, the performance of the 802.11 radio and medium access control (MAC) protocol in outdoor environments is investigated. For channels typical in cellular networks, we study the radio link power budget and the bit error performance of three kinds of receivers. We also propose a new timing structure for the MAC protocol to handle increased signal propagation delay and analyze its throughput performance in the outdoor network. Our analysis shows that the MAC protocol can handle a cell radius of 6 km without violating the 802.11 standard. However, the link budget reveals that the maximum cell radius in an outdoor 802.11 network ranges from 0.4 to 1.2 km, which is about one third that supported by wideband code-division multiple access and enhanced data rates for global system for mobile communications evolution networks. For a root-mean-square delay spread of 1 μs which. is typical for urban-area cells of this size, our simulation results show that the conventional RAKE receiver can yield a satisfactory performance. Combining these results, we conclude that using ordinary equipment, an 802.11-based cellular network with a cell radius up to 1.2 km is feasible. It is possible to further extend the service range by advanced techniques such as smart antennas. [ABSTRACT FROM AUTHOR]

Mobile positioning has drawn significant attention in recent years. Nonline-of-sight (NLOS) propagation error is the dominant error source in mobile positioning. Most previous research in this area has focused on NLOS identification and mitigation. In this paper, we investigate new positioning algorithms to take advantage of the NLOS propagation paths rather than canceling them. Based on a prior information about the NLOS path, a geometrical approach is proposed to estimate mobile location by using two NLOS paths. On top of this, the least-squares (LS)-based position estimation algorithm is developed to take multiple NLOS paths into account, and its performance in terms of root mean-square error (RMSE) is analyzed. A general LS algorithm considering both LOS and NLOS paths is also derived, and the maximum likelihood-based algorithm is presented to jointly estimate the mobile's and scatterers' positions. The Cramer-Rao lower bound on the RMSE is derived for the benchmark of the performance comparison. The performance of the proposed algorithms is evaluated analytically and is done via computer simulations. Numerical results demonstrate that the derived analytical results closely match the simulated results. [ABSTRACT FROM AUTHOR]

Call admission control (CAC) strongly influences the performance of 3G/4G spread spectrum systems because it determines the number of active users that are admitted to the network, i.e., influences spectral efficiency. A novel air interface CAC algorithm is introduced in this paper. It optimizes the utilization of radio resources and provides real-time adaptation to the radio channel with generalized multiplicative fading. Users are handled as memory-less traffic sources. The suggested CAC method was evaluated for lognormal fading and ON/OFF traffic. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of general packet radio service (GPRS)-wireless local area network (WLAN) mobility gateway (GWMG) for the integration of GPRS and WLANs. The interworking between GPRS and WLANs is achieved by the GWMG that resides on the border of GPRS and WLAN systems. The design goal is to minimize the modifications in GPRS and WLANs as both systems are already widely available. By deploying the GWMG, users can seamlessly roam among the two systems. Unlike other related work, the proposed GWMG could be used when either the GPRS or WLAN is a user's home network. Both mathematical analysis and simulation are developed to analyze the performance. The proposed GWMG has also been implemented in a testbed comprising a commercial GPRS system. The results show that the GWMG could achieve a design goal that will effectively integrate GPRS and WLANs. [ABSTRACT FROM AUTHOR]

Hop timing estimation for noncooperative frequency-hopped (FH) signals is an important problem that feeds into the multiple facets of military communications, from interception of noncooperative communications to interference mitigation. If there is a mismatch between the receiver's observation band and the hop bandwidth of the transmitted signals in an FH system, signals appear to hop in and out of the observation frequency band. This causes model-order variations and high-resolution parametric methods that assume fixed model order may fail. Using an antenna array and capitalizing on the data structure of 2-D frequency mixture (space and time), this paper proposes an expectation-maximization (EM) algorithm for blind hop timing and frequency estimation with possible bandwidth mismatch. The initialization of the EM algorithm is given by the data spectrogram. Simulation results demonstrate that the proposed method performs well even at low-to-moderate signal-to-noise ratio with unknown hop sequences. [ABSTRACT FROM AUTHOR]

In this paper, we consider the high-K-factor Ricean channel, where the channel mean is of arbitrary rank, and the fading channel components are correlated. We propose two suboptimal linear precoding schemes based on the knowledge of the channel mean and covariance at the transmitter. The first precoder is derived from an approximate ergodic capacity expression for the high-K-factor Ricean channels, whereas the second is derived from Jensen's inequality. We compare the capacity obtained to the true ergodic capacity found by using a numerical convex optimization algorithm. We further investigate the impact of the fading channel covariance, the rank of the channel mean, and the K-factor on the precoding schemes and the achievable ergodic capacity limit. [ABSTRACT FROM AUTHOR]

Space-division multiple access (SDMA) and orthogonal frequency-division multiplexing (OFDM) can be combined to design a robust communications system with increased spectral efficiency and system capacity. This combination is one of the most promising candidates for future wireless local area network implementations. However, one drawback of OFDM systems is the high peak-to-average power ratio, which imposes strong requirements on the linearity of power amplifiers (PAs). Such linearity requirements translate into high back-off that results in low power efficiency. In order to improve power efficiency, a PA nonlinearity cancellation (PANC) technique is introduced in this paper. This technique reduces the nonlinear distortion effects on the received signal. The performance of the new technique is evaluated with simulations, which show significant power efficiency improvements. To obtain meaningful results for comparison purposes, we derive a theoretical upper bound on the bit error rate performance of an SDMA-OFDM system subject to PA nonlinearities. In addition, a novel channel estimation technique that combines frequency- and time-domain channel estimation with PANC is also presented. Simulation results show the robustness of the cancellation method also when channel estimation is included. [ABSTRACT FROM AUTHOR]

This paper considers low-complexity coded multiple- input-multiple-output transmission in Rayleigh channels with correlation between antennas at both the transmitter and receiver. We consider statistical beamforming (SB) and spatial multiplexing (SM) with a zero-forcing receiver. We calculate the link-level capacity of both schemes with bit-interleaved coded modulation and derive accurate closed-form approximations to the bit error rate. We then show how the resulting expressions can be used in an adaptive algorithm to select the best combination of code rate, modulation format, and transmission scheme (SB or SM) in order to maximize throughput. Unlike other mode-switching schemes that require empirical lookup tables, this approach applies to any correlation scenario. Numerical studies are used to demonstrate the performance as a function of signal-to-noise ratio and correlation parameters. [ABSTRACT FROM AUTHOR]

Extensive research done in the recent past has proven that power electronic converters and electric propulsion motors are extremely critical components for modem hybrid electric vehicle (HEV) propulsion applications. Therefore, it is essential that both the traction motor and the associated drive operate at their optimal efficiencies throughout the driving schedule. In typical HEV propulsion applications, the traction motor and the drive are used over the entire torque/speed operational range. In view of this fact, this paper aims at modeling the inverter and motor losses/efficiencies over typical city and highway driving schedules. The noteworthy losses within a typical three-phase dc/ac traction inverter, such as the switching and conduction losses for both the insulated-gate bipolar transistors and the antiparallel diodes, are modeled and simulated over the city and highway driving patterns. An induction motor (IM) is used for a medium-sized sport utility vehicle, which was modeled in the ADvanced VehIcle SimulatOR (ADVISOR) software. The significant IM losses that were considered in the study include the stator copper losses, rotor copper losses, and core losses. Thus, the average efficiencies of both the inverter drive and the induction traction motor are evaluated and summarized under city as well as highway driving conditions. Finally, based on the individual-model-based efficiency analysis, the overall traction motor drive system efficiency is estimated. [ABSTRACT FROM AUTHOR]

This paper presents and analyzes a correct and complete translation algorithm that converts a class of propositional linear-time temporal-logic (PTL) formulae to deterministic finite (-trace) automata. The translation algorithm is proposed as a specification interface for finitary control design of discrete-event systems (DESs). While there has been a lot of computer science research that connects PTL formulae to ω-automata, there is relatively little prior work that translates state-based PTL formulae in the context of a finite-state DES model, to event-based finite automata—the formalism on which well-established control synthesis methods exist. The proposed translation allows control requirements to be more easily described and understood in temporal logic, widely recognized as a useful specification language for its intuitively appealing operators that provide the natural-language expressiveness and readability needed to express and ex- plain these requirements. Adding such a translation interface could therefore effectively combine specifiability and readability in temporal logic with prescriptiveness and computability in finite automata. The former temporal-logic features support specification while the latter automata features support the prescription of DES dynamics and algorithmic computations. A practical implementation of the interface has been developed, providing an enabling technology for writing readable control specifications in PTL that it translates for discrete-event control synthesis in deterministic finite automata. Two application examples illustrate the use of the proposed temporal-logic interface. Practical implications of the complexity of the translation algorithm are discussed. [ABSTRACT FROM AUTHOR]

Using a high temperature superconductor, we proposed a model Superconducting Fault Current Limiter (SCFCL) with the high-speed commutation switch. The high-speed commutation switch consists of the parallel coil, the electromagnetic repulsion plate and the vacuum interrupter. In this SCFCL, the current in the superconductor is interrupted within 0.5 cycles. By using this equipment, the current flow time in the superconductor can be easily minimized. We studied resistive type SCFCL with the high-speed commutation switch and use YBCO thin film. For applying to high voltage, it is a problem that the superconductors in series connection don't quench immediately for the Ic variations of the various superconductors. In this paper, we conducted the series connection test using YBCO thin films without a metal layer. The research is aimed at the scalability of small models towards commercial size Fault Current Limiter (FCL). [ABSTRACT FROM AUTHOR]

In this paper, we propose an interframe-space (IFS)-based distributed-fair-queuing (IDFQ) mechanism to provide proportional fairness service for IEEE 802.11 wireless local-area networks (WLANs). IDFQ is designed to emulate self-clocked fair queuing in a distributed manner. It eliminates the backoff process as implemented in existing work and introduces a new mechanism to assign the IFS value to each station. IDFQ is immune from the implementation problem suffered by existing IFS-based mechanisms and is adaptive to the collision state in the system. Moreover, it can be used to eliminate the performance-anomaly problem of 802.11 medium-access control. The performance of IDFQ is validated by ns-2 simulations. The simulation results show that IDFQ supports fairness service for flows in proportion to their weights and outperforms existing mechanisms in terms of fairness and stability, rendering IDFQ an excellent candidate to provide weighted fairness in IEEE 802.11 WLANs. [ABSTRACT FROM AUTHOR]

This paper proposes a joint power and rate assignment (JPRA) algorithm to deal with multirate soft handoffs (SHOs) in mixed-size wideband code division multiple access cellular systems. This JPRA algorithm contains a link proportional power allocation scheme and an evolutionary computing rate assignment method to determine an appropriate allocation of transmission power and service rate for multirate SHOs. It can achieve power balancing among cells better than the conventional site-selection diversity transmission scheme with best effort rate allocation. Simulation results show that the JPRA algorithm can achieve better cell's service coverage and higher system capacity with and without the measurement errors during the active set selection. [ABSTRACT FROM AUTHOR]

This paper presents a new method of digital adaptive predistortion for linearization of power amplifiers (PAs) exhibiting memory effects. The predistorter (PD) device consists of a lookup table (LUT) gain followed by a codebook of filters addressed by the index of the LUT. The adaptation is derived from direct learning for the LUT gains and indirect learning for the filter coefficients. We compared our results with those of two reference methods: a simple LUT system (with direct learning) and a memory polynomial system (with indirect learning). The performances of the new approach lie between those of the two reference methods in terms of adjacent channel power regrowth and error vector magnitude. The LUT is the less complex of the three methods, but it is a memoryless system, and it cannot correct the memory effects in the PA. The memory polynomial PD is more powerful, but its complexity is very high. The new technique, due to the addition of filters to the LUT, has possibilities to compensate not only for the nonlinearity but also for the memory effects in the PA, and it is one order of magnitude less complex than the memory polynomial system. [ABSTRACT FROM AUTHOR]

As the importance of information technology has increased within the business domain, so too has the significance of innovating within those information technologies. The recent proliferation of telecommunications technologies, coupled with conventional information technology, has resulted in a new class of applications with important competitive implications. An important issue for organizations, then, is the causal sequence that leads to more innovative telecommunications adoption. Previous innovation research has shown radical and incremental innovation employing vastly different strategy-structure sequence configurations. Two proposals have been offered on how an organization can effectively innovate incrementally and radically: first, through the use of semi-structures, and second, by utilizing both configurations simultaneously, termed ambidextrous. This paper seeks 1) to determine whether organizations are balancing innovation efforts, and 2) if so, are organizations managing the effort using semi-structures or an ambidextrous approach. The research is conducted within the telecommunications industry by employing theoretical typologies of radical and incremental innovation developed in the literature. Based on a sample of 154 organizations the findings suggest that organizations are indeed using a balanced approach to overall innovativeness by using paradoxical, dual models of innovation simultaneously. Implications for researchers and practitioners are discussed. [ABSTRACT FROM AUTHOR]

Distributed peer-to-peer systems rely on voluntary participation of peers to effectively manage a storage pool. In such systems, data is generally replicated for performance and availability. If the storage associated with replication is not monitored and provisioned, the underlying benefits may not be realized. Resource constraints, performance scalability, and availability present diverse considerations. Availability and performance scalability, in terms of response time, are improved by aggressive replication, whereas resource constraints limit total storage in the network. Identification and elimination of redundant data pose fundamental problems for such systems. In this paper, we present a novel and efficient solution that addresses availability and scalability with respect to management of redundant data. Specifically, we address the problem of duplicate elimination in the context of systems connected over an unstructured peer-to-peer network in which there is no a priori binding between an object and its location. We propose two randomized protocols to solve this problem in a scalable and decentralized fashion that does not compromise the availability requirements of the application. Performance results using both large-scale simulations and a prototype built on PlanetLab demonstrate that our protocols provide high probabilistic guarantees while incurring minimal administrative overheads. [ABSTRACT FROM AUTHOR]

Flooding is one of the most fundamental operations in mobile ad hoc networks. Traditional implementation of flooding suffers from the problems of excessive redundancy of messages, resource contention, and signal collision. This causes high protocol overhead and interference with the existing traffic in the networks. Some efficient flooding algorithms were proposed to avoid these problems. However, these algorithms either perform poorly in reducing redundant transmissions or require each node to maintain 2-hop (or more) neighbors information. In the paper, we study the sufficient and necessary condition of 100 percent deliverability for flooding schemes that are based on only 1-hop neighbors information. We further propose an efficient flooding algorithm that achieves the local optimality in two senses: 1) The number of forwarding nodes in each step is minimal and 2) the time complexity for computing forwarding nodes is the lowest, which is O(nlogn), where n is the number of neighbors of a node. Extensive simulations have been conducted and simulation results have shown the excellent performance of our algorithm. [ABSTRACT FROM AUTHOR]

A number of low degree and, thus, low complexity, Cayley-graph interconnection structures, such as honeycomb and diamond networks, are known to be derivable by systematic pruning of 2D or 3D tori. In this paper, we extend these known pruning schemes via a general algebraic construction based on commutative groups. We show that, under certain conditions, Cayley graphs based on the constructed groups are pruned networks when Cayley graphs of the original commutative groups are κD tori. Thus, our results offer a general mathematical framework for synthesizing and exploring pruned interconnection networks that offer lower node degrees and, thus, smaller VLSI layout and simpler physical packaging. Our constructions also lead to new insights, as well as new concrete results, for previously known interconnection schemes such as honeycomb and diamond networks. [ABSTRACT FROM AUTHOR]

Attack mitigation schemes actively throttle attack traffic generated in Distributed Denial-of-Service (DDoS) attacks. This paper presents Attack Diagnosis (AD), a novel attack mitigation scheme that adopts a divide-and-conquer strategy. AD combines the concepts of Pushback and packet marking, and its architecture is in line with the ideal DDoS attack countermeasure paradigm—attack detection is performed near the victim host and packet filtering is executed close to the attack sources. AD is a reactive defense mechanism that is activated by a victim host after an attack is detected. By instructing its upstream routers to mark packets deterministically, the victim can trace back one attack source and command an AD-enabled router close to the source to filter the attack packets. This process isolates one attacker and throttles it, which is repeated until the attack is mitigated. We also propose an extension to AD called Parallel Attack Diagnosis (PAD) that is capable of throttling traffic coming from a large number of attackers simultaneously. AD and PAD are analyzed and evaluated using the Skitter Internet map, Lumeta's Internet map, and the 6-degree complete tree topology model. Both schemes are shown to be robust against IP spoofing and to incur low false positive ratios. [ABSTRACT FROM AUTHOR]

In this paper, we report the observation of the higher order frequency shift due to the trapping field in a 87Sr optical lattice clock. We show that at the magic wavelength of the lattice, where the first order term cancels, the higher order shift will not constitute a limitation to the fractional accuracy of the clock at a level of 10-is. We also report an accurate frequency measurement of the clock transition. The frequency is determined to be V¹S0–³P0 = 429 228 004 229 879 (5) Hz with a fractional uncertainty that is comparable to state-of-the-art optical clocks with neutral atoms in free fail. [ABSTRACT FROM AUTHOR]

This paper describes two systems recently developed at the National Physical Laboratory (NPL), Teddington, U.K., for the generation and measurement of dc currents in the range 100 fA to 1 nA. Both systems are based on the capacitor charging technique. One system generates known currents, and constitutes a new reference at NPL. The other was designed to meet the traceability requirements of the Ionizing Radiation sections of NPL and combines commercially available instrumentation and standards to produce a reliable stand-alone system for measuring small currents. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the design, implementation, and experimental evaluation of a middleware architecture for enabling Service Level Agreement (SLA)-driven clustering of QoS-aware application servers. Our middleware architecture supports application server technologies with dynamic resource management: Application servers can dynamically change the amount of clustered resources assigned to hosted applications on-demand so as to meet application-level Quality of Service (QoS) requirements. These requirements can include timeliness, availability, and high throughput and are specified in SLAs. A prototype of our architecture has been implemented using the open-source J2EE application server JBoss. The evaluation of this prototype shows that our approach makes possible JBoss' resource usage optimization and allows JBoss to effectively meet the QoS requirements of the applications it hosts, i.e., to honor the SLAs of those applications. [ABSTRACT FROM AUTHOR]

The Capability Maturity Model (CMM) has become a popular methodology for improving software development processes with the goal of developing high-quality software within budget and planned cycle time. Prior research literature, while not exclusively focusing on CMM level 5 projects, has identified a host of factors as determinants of software development effort, quality, and cycle time. In this study, we focus exclusively on CMM level 5 projects from multiple organizations to study the impacts of highly mature processes on effort, quality, and cycle time. Using a linear regression model based on data collected from 37 CMM level 5 projects of four organizations, we find that high levels of process maturity, as indicated by CMM level 5 rating, reduce the effects of most factors that were previously believed to impact software development effort, quality, and cycle time. The only factor found to be significant in determining effort, cycle time, and quality was software size. On the average, the developed models predicted effort and cycle time around 12 percent and defects to about 49 percent of the actuals, across organizations. Overall, the results in this paper indicate that some of the biggest rewards from high levels of process maturity come from the reduction in variance of software development outcomes that were caused by factors other than software size. [ABSTRACT FROM AUTHOR]

Developers of highly configurable performance-intensive software systems often use in-house performance-oriented "regression testing" to ensure that their modifications do not adversely affect their software's performance across its large configuration space. Unfortunately, time and resource constraints can limit in-house testing to a relatively small number of possible configurations, followed by unreliable extrapolation from these results to the entire configuration space. As a result, many performance bottlenecks escape detection until systems are fielded. In our earlier work, we improved the situation outlined above by developing an initial quality assurance process called "main effects screening." This process 1) executes formally designed experiments to identify an appropriate subset of configurations on which to base the performance-oriented regression testing, 2) executes benchmarks on this subset whenever the software changes, and 3) provides tool support for executing these actions on in-the-field and in-house computing resources. Our initial process had several limitations, however, since it was manually configured (which was tedious and error-prone) and relied on strong and untested assumptions for its accuracy (which made its use unacceptably risky in practice), This paper presents a new quality assurance process called "reliable effects screening" that provides three significant improvements to our earlier work. First, it allows developers to economically verify key assumptions during process execution. Second, it integrates several model-driven engineering tools to make process configuration and execution much easier and less error prone. Third, we evaluate this process via several feasibility studies of three large, widely used performance-intensive software frameworks. Our results indicate that reliable effects screening can detect performance degradation in large-scale systems more reliably and with significantly less resources than conventional techniques. [ABSTRACT FROM AUTHOR]

Case studies are evocative narrative descriptions of a specific, real-world activity, event, or problem. Case-based learning is well established in professional education (e.g., law, business, medicine) and rapidly expanding in many other disciplines. We use cases as an instructional resource in our own teaching of usability engineering. In this paper, we analyze the proposition that cases can be a minimalist-information design technique—that is, as a design technique that (1) orients information to facilitate user action, (2) anchors information in activity, (3) prevents, mitigates, and leverages error, and (4) develops user autonomy. We discuss the next steps in a research program on case-based learning and speculate on other applications of cases as minimalist information design. [ABSTRACT FROM AUTHOR]

The Large Hadron Collider at CERN will start data acquisition in 2007. The A Torioidal LHC Apparatus (ATLAS) experiment is preparing for the data handling and analysis via a series of data challenges and production exercises to validate its computing model to provide useful samples of data for detector and physics studies. The ATLAS production system has been successfully used to run production of simulation data at an unprecedented scale. Up to 10 000 jobs were processed by the system on about 100 sites in one day. In this paper, we discuss the experience of performing analysis jobs using this system on the LCG infra-structure. [ABSTRACT FROM AUTHOR]

This paper extends an exponential reliability growth model to determine the optimal number of test cases to be executed for various use case scenarios during the system testing of software. An example demonstrates a practical application of the optimization model for system test planning. [ABSTRACT FROM AUTHOR]

As continuing support of National Public Radio's Tomorrow Radio project, this paper presents results from a consumer study conducted with iBiquity's HD Radio codec. Forty participants judged the quality of the HD codec (HDC) at various bit rates, ranging from 16 kbps to 96 kbps. A range of musical and speech genres were tested. This study provides in-depth information intended to help broadcasters select optimal bit rates when HD Radio's 96 kbps data stream is shared between primary and supplemental channels. [ABSTRACT FROM AUTHOR]

Magnetic measurements at room temperature have been used to monitor the production of the superconducting coils of the Large Hadron Collider main dipoles. They have made it possible to identify several assembly errors, e.g. cases of bad gluing of the coil layers, bad conductor positioning, missing pole shims and other problems related to faulty procedures. This paper reviews the experience accumulated so far considering almost 1000 dipoles. After a short outline of the method used to pin out field anomalies and deduce realistic deformation of the coil, an exhaustive list of the cases met during the production is given. A discussion follows on the findings after decollaring as compared to the predictions, including the still open cases. [ABSTRACT FROM AUTHOR]

A permanent magnet quadrupole (PMQ) is one of the candidates for the final focus lens in a linear collider. An over 120 T/m strong variable permanent magnet quadrupole is achieved by the introduction of saturated iron and a ‘double ring structure’. A fabricated PMQ achieved 24 T integrated gradient with ϕ20 mm bore diameter, ϕ100 mm magnet diameter and 20 cm pole length. The strength of the PMQ is adjustable in 1.4 T steps, due to its ‘double ring structure’: the PMQ is split into two nested rings; the outer ring is sliced along the beam line into four parts and is rotated to change the strength. This paper describes the variable PMQ from fabrication to recent adjustments. [ABSTRACT FROM AUTHOR]

For the LHC dipoles [1], mandatory electrical integrity tests are performed to qualify the cold mass (CM) at four production stages: individual pole, collared coil, CM before end cover welding and final CM. A description of the measurement equipment and its recent development are presented. After passing the demands set out in the specification, the results of the tests are transmitted to CERN where they are further analyzed. The paper presents the most important results of these measurements. We also report a review of the electrical nonconformities encountered e.g. inter-turn shorts and quench heater failure, their diagnostic and the cures. [ABSTRACT FROM AUTHOR]

The detailed shape of the 15 m long superconducting LHC dipole cold mass is of high importance as it determines three key parameters: the beam aperture, nominally of the order of 10 beam standard deviations; the connectivity of the beam- and technical lines between magnets; the transverse position of nonlinear correctors mounted on the dipole ends. An offset of the latter produces unwanted beam dynamics perturbations. The tolerances are in the order of mm over the length of the magnet. The natural flexibility of the dipole and its mechanical structure allow deformations during handling and transportation which exceed the tolerances. This paper presents the observed deformations of the geometry during handling and various operations at CERN, deformations which are interpreted thanks to a simple mechanical model. These observations have led to a strategy of dipole geometry control at CERN, based on adjustment of the position of its central support (the dipole is supported at three positions, horizontally and vertically) to recover individually or statistically their original shape as manufactured. The implementation of this strategy is discussed, with the goal of finding a compromise between conflicting requirements: quality of the dipole geometry, available resources for corrective actions and magnet installation strategy whereby the geometry tolerances depend on the final magnet position in the machine. [ABSTRACT FROM AUTHOR]

During the construction of the LHC main dipoles, 12 cases of short circuits between the cables of the superconducting coils have been detected. Some of them appeared only under the press, making impossible their localization after disassembly. In this paper we describe a method to locate electrical shorts through the use of room temperature magnetic measurements. An example case is discussed in detail to illustrate the features of the approach, and a statistic of the cases met during the production of more that 70% of the dipole total quantity is presented. [ABSTRACT FROM AUTHOR]

The main superconducting dipoles for the LHC are being stored outdoors for periods from a few weeks to several years after conditioning with dry nitrogen gas. Such a storage before installation in the 27 km circumference tunnel may affect not only the mechanical and cryogenic functionality of the cryodipoles but also their quench and field performance. A dedicated task force was established to study all aspects of long term behavior of the stored cryodipoles, with particular emphasis on electrical and vacuum integrity, quench training behavior, magnetic field quality, performance of the thermal insulation, mechanical stability of magnet shape and of the interface between cold mass and cryostat, degradation of materials and welds. In particular, one specifically selected cryodipole stored outdoors for more than one year, was re-tested at cold. In addition, various tests have been carried out on the cryodipole assembly and on the most critical subcomponents to study aspects such as the hygrothermal behavior of the supporting system and the possible oxidation of the Multi Layer Insulation reflective films. This paper summarizes the main investigations carried out and their results. [ABSTRACT FROM AUTHOR]

In order to keep the electro-magnetic forces and to minimize conductor movements, the superconducting coils of the main Large Hadron Collider dipoles are held in place by means of austenitic steel collars. Two suppliers provide the collars necessary for the whole LHC production, which has now reached more than 800 collared coils. In this paper we first assess if the different collar suppliers origin a noticeable difference in the magnetic field quality measured at room temperature. We then analyze the measurements of the collar dimensions carried out at the manufacturers, comparing them to the geometrical tolerances. Finally we use a magneto-static model to evaluate the expected spread in the field components induced by the actual collar dimensions. These spreads are compared to the magnetic measurements at room temperature over the magnet production in order to identify if the collars, rather than other components or assembly process, can account for the measured magnetic field effects. It has been found that in one over the three Cold Mass Assemblers the driving mechanism of the magnetic field harmonics b2 and a3 is the collar shape. [ABSTRACT FROM AUTHOR]

Kicker magnets are installed in the extraction section of the RCS (Rapid Cycling Synchrotron) in J-PARC (Japan Proton Accelerator Research Complex) facility. They extract a 3 GeV proton beam and inject it into a downstream beam transport line at a repetition rate of 25 Hz. The power supply is mainly composed of the charging unit, the pulse forming network, and thyratrons as switching device. The maximum charging voltage is 80 kV. The kicker magnet is a distributed (transmission line) twin-C type. The circuit parameters are designed to have the 10 characteristic impedance. The magnets are installed in vacuum chambers to prevent voltage breakdown. In order to accept 1 MW beam power, strict conditions are imposed on the kicker system. In the first part of this paper, we give an outline of the RCS extraction kicker system. Next, we report the specifications and performance of the power source and magnet. In addition, we report the measurements of the vacuum performance and magnetic field. [ABSTRACT FROM AUTHOR]

Most microscale electric and magnetic machines studied in the last decade lack the power density to support many practical applications. This paper introduces a design for a magnetic induction machine that offers power densities in excess of 200 MW/m³ and efficiencies of up to 50%, while providing more than 10 W of mechanical power. This is a substantial performance increase in MEMS electromagnetic machines studied to date. [ABSTRACT FROM AUTHOR]

This paper presents the design, fabrication, and characterization of laminated, magnetic induction machines intended for high-speed, high-temperature, high-power-density, silicon-based microengine power generation systems. Innovative fabrication techniques were used to embed electroplated materials (Cu, Ni80Fe20, Co65Fe18Ni17) within bulk-micromachined and fusion-bonded silicon to form the machine structures. The induction machines were characterized in motoring mode using tethered rotors, and exhibited a maximum measured torque of 2.5 μN·m. [ABSTRACT FROM AUTHOR]

A novel device with microchannels for flowing cells and twin microcantilever arrays for measuring the electrical impedance of a single cell is proposed. The fabrication process is demonstrated and the twin microcantilever arrays have been successfully fabricated. In our research, we measured the electrical impedance for normal and abnormal red blood cell over the frequency range from 1 Hz to 10 MHz. From the electrical impedance experiment of normal and abnormal red blood cell, it was examined that the electrical impedance between normal and abnormal red blood cells was significantly different in magnitude and phase shift. In this paper, we show that the normal cell can be taken apart from the abnormal cell by electrical impedance measurement. Therefore, it is expected that the applicability of this technology can be used in cellular studies such as cell sorting, counting or membrane biophysical characterization. [ABSTRACT FROM AUTHOR]

In Beyond Third Generation (B3G) wireless communications, multiple overlays of wireless access networks may cooperate to allow a user access to novel services, the future demands of which will significantly increase the load on location management systems within the networks. In this paper, we introduce the reader to our novel proposals for providing efficient Mobile Terminal (MT) Location Discovery and Paging across an inter-worked network consisting a Digital Video Broadcast (DVB) network and Universal Mobile Telecommunication System (UMTS) network. We further present numerical and simulation analyzes of our scheme. The numerical and simulation results allow broadcast and cellular network operators to configure their inter-worked system to reduce location management and paging costs whilst controlling average latency. Our .results demonstrate that our UMTS LA plus DVB paging schemes offer promise for efficient MT discovery in an inter-network environment that includes uni-directional broadcast network such as DVB; under realistic scenarios we achieve a minimum 4 times reduction in paging cost across the inter-network compared with independent paging systems. Furthermore, we briefly introduce further aspects of research that must be addressed in order to fully evaluate our proposals. [ABSTRACT FROM AUTHOR]

The interaction of solid particles with various surfaces has been experiencing growing interest in many areas of nanotechnology, colloidal science, and biology. In this paper the interactions of solid particles with the sur- face of piezoelectric thickness shear mode (TSM) sensors have been studied. A mechanical model has been presented to evaluate the effect of particle loading on the behavior of a TSM sensor. The main sources contributing to the interaction, such as Van der Waals force, friction force, and electrostatic force, are discussed. Experiments have been designed for 10-100 ,μm particles on the 5-MHz and 10-MHz TSM sensors. It has been shown that the resonant frequencies of the TSM sensors might increase or decrease depending on the interaction conditions, The results have shown that the TSM sensor technique could provide the information on the mass/size of a particle and the binding energy between a particle and the sensor surface. This technique may find its applications in characterizing the properties of an interaction between particles and various surfaces. [ABSTRACT FROM AUTHOR]

Ultrasonic imaging of bioflims in water is difficult due to the very low contrast in acoustic impedance between the biofilm and water. In this paper, biofilms ex- posed to moist air are scanned through the substrate in order to obtain echoes from the bioflim/air interface. A 50 MHz scanning system was used to scan 1 mm X 1 mm areas of biofilms in a 10 μm grid pattern. Two fast Fourier transform (FFT) based methods for enhancement of the film thickness measurement resolution are compared. Using these techniques, the surface topography of biofilms with thickness less than the acoustic wavelength can be imaged. [ABSTRACT FROM AUTHOR]

In this paper, the Kirk effect has been analyzed for silicon-based bipolar transistors (BJTs). with a nonuniform collector profile. We show that, for any arbitrary collector doping profile, the Kirk effect starts when the electron concentration equals the average doping concentration in the depletion region. We present a basic guideline for determining the collector current density at the onset of Kirk effect (JK) for any collector doping profile and simple expressions for JK and the electrical field in the collector drift region for the case of a linearly graded collector drift region. These analytical expressions are verified with device simulations. The Kirk effect for this kind of transistor is substantially different from that presented previously for transistors having a uniform collector drift region. For example, the possibility of the onset of the Kirk effect in a partially depleted collector occurs, while in a uniform collector profile the effect can only occur in a fully depleted collector. Our expressions can be used to do approximate analytical calculations for optimizing future BJTs. [ABSTRACT FROM AUTHOR]

This paper analyzes solutions to improve the program/erase (PIE) window for nanocrystal (NC) memory cells, by means of the model presented in our previous work [1]. The limited threshold voltage (VT) window typically observed in the Fowler-Nordheim (FN) programming regime for NC memories was shown to be a direct consequence of the lack of any conduction and c mismatch between the tunnel and the interpoly-oxide at steady-state. This condition can be avoided when tunnel oxide conduction is due to direct tunneling, but to assure sufficiently short PIE times very thin oxides are required, sacrificing cell nonvolatility. The use of alternative materials for interpoly dielectric, gate and NC is investigated. Finally, barrier engineering is presented as a valid way to improve the available VT window. [ABSTRACT FROM AUTHOR]

A novel modified Schottky barrier p-channel FinFET (MSB FinFET) has been successfully demonstrated previously. In this paper, the detailed process conditions, especially the formation of MSB junctions, has been presented. Device characteristics as well as the geometry effect are also discussed extensively. In the MSB FinFETs fabricated by the two-step silicidation and implant-to-silicide techniques (ITS), an ultrashort and defect-free source/drain extension (SDE) could be formed at a temperature as low as 600 ° C, resulting in excellent electrical characteristics. The ultrashort SDE could effectively thin out the SB width between source/channel during on-state or broaden and elevate it between drain/channel during off-state. A leakage mechanism of MSB FinFETs similar to the conventional ones was identified by the activation energy analysis. Strong fin width dependence of the electrical characteristics was also found in the proposed devices. When the fin width becomes larger than the silicide grain size, the multigrain structure results in a rough front edge of the MSB junction, which in turn degrades the short-channel device performance. This result indicates that the MSB device is suitable for use as FinFET. The low thermal budget of the MSB FinFET relaxes the thermal stability issue for metal gate/high-ic dielectric integration. It is considered that the proposed MSB FinFET is a very promising nanodevice. [ABSTRACT FROM AUTHOR]

In this paper, we report on parasitic bipolar conduction occurring in floating-body effect based capacitor-less DRAMs. A way to include these effects into a previously developed model is presented. The enhanced model is then compared with electrical data realized on triple-well nMOSFET devices within the 26 °C-100 ° C temperature range. [ABSTRACT FROM AUTHOR]

We outlined a simple model to account for the surface roughness (SR)-induced enhanced threshold voltage (VTH) shifts that were recently observed in ultrathin-body MOSFETs fabricated on (100) Si surface, The phenomena of enhanced VTH shifts can be modeled by accounting for the fluctuation of quantization energy in the ultrathin body (UTB) MOSFETs due to SR up to a second-order approximation. Our model is then used to examine the enhanced VTH shift phenomena in other novel surface orientations for Si and Ge and its impact on gate work- function design. We also performed a calculation of the SR-limited hole mobility (μH,SR) of p-MOSFETs with an ultrathin Si and Ge active layer thickness, TBody < 10 nm. Calculation of the electronic band structures is done within the effective mass framework via the Luttinger Kohn Hamiltonian, and the mobility is calculated using an isotropic approximation for the relaxation time calculation, while retaining the full anisotropy of the valence subband structure. For both Si and Ge, the dependence of PR,SR. on the surface orientation, channel orientation, and TBody are explored. It was found that a (110) surface yields the highest μH,SR The increasing quantization mass mz for (110) surface renders its μH,SR less susceptible with the decrease of TBody. In contrast, (100) surface exhibits smallest μH,SR. due to its smallest mz. The SR parameters i.e., autocorrelation length (L) and root-mean-square (Δrms) used in this paper is obtained from the available experimental result of Si(100) UTB MOSFETs [1], by adjusting these SR parameters to obtain a theoretical fit with experimental data on SR-limited mobility and VTH shifts. This set of SR parameters is then employed for all orientations of both Si and Ge devices. [ABSTRACT FROM AUTHOR]