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Abstract: We present a new method for estimating the frontier of a sample. The estimator is based on a local polynomial regression on the power-transformed data. We assume that the exponent of the transformation goes to infinity while the bandwidth goes to zero. We give conditions on these two parameters for obtaining almost complete convergence. The asymptotic conditional bias and variance of the estimator are provided and its good performance is illustrated for some finite sample situations. [Copyright &y& Elsevier]

Abstract: When we think of mobility in technical terms, we think of topics such as bandwidth, resource management, location, and wireless networks. When we think of mobility in social or cultural terms, a different set of topics come into view: pilgrimage and religious practice, globalization and economic disparities, migration and cultural identity, daily commutes and the suburbanization of cities. In this paper, we examine the links between these two aspects of mobility. Drawing on non-technological examples of cultural encounters with space, we argue that mobile information technologies do not just operate in space, but they are tools that serve to structure the spaces through which they move. We use recent projects to illustrate how three concerns with mobility and space—legibility, literacy, and legitimacy—open up new avenues for design exploration and analysis. [Copyright &y& Elsevier]

Abstract: Fiber Bragg gratings (FBGs) with random fluctuations are investigated theoretically by using the coupled-mode theory. The fluctuation of the period causes interference inside the grating, which makes some light with wavelength inside the reflection bandwidth transmit through the grating and thus split the reflection spectrum. Simulation results show that low-frequency disturbed random fluctuation easily forms interference because the coupling wavelength in different position of the grating is different, while small high-frequency disturbed random fluctuation has almost no influence on the reflection spectrum and large high-frequency disturbed random fluctuation makes the grating incontinuous, which results in the interference. At the same time, a numerical method based on the fourth-order Runge–Kutta formula is developed to solve the coupled equations directly. By using this method, a grating with complex index modulation does not need to be treated as a superposition of a set of uniform grating with sinusoidal index modulation through the Fourier transform. [Copyright &y& Elsevier]

Abstract: We present an all-fiber bandpass operation by using an absorptive core mode blocker self-aligned between two long-period fiber gratings (LPFGs). The first LPFG converts the core mode into the cladding modes at resonant wavelengths, and the second LPFG operates in reverse direction. The core mode blocker attenuates the nonresonant core mode from the first LPFG but passes the resonant cladding modes to the second LPFG. This bandpass filter exhibits a passband of 20-nm bandwidth at a center wavelength of 1542 nm with nonresonant light suppression greater than 15 dB. Thermal tuning coefficient is found to be −0.51 nm/°C for the temperature range from 10 to 70 °C. [Copyright &y& Elsevier]

Abstract: In this publication, we introduce a version of the rotational resonance width experiment with a homogeneously broadened matching condition. The increase in the bandwidth is achieved by the reduction of the proton decoupling power during mixing, which results in the reduction of zero-quantum relaxation, and broadens the rotational resonance condition. We show that one can achieve recoupling of the carbonyl-aliphatic side chain dipolar interactions band selectively, while avoiding the recoupling of strongly interacting C′–Cα and C′–Cβ spin pairs. The attenuation of the multi-spin effects in the presence of short zero-quantum relaxation enables a two-spin approximation to be employed for the analysis of the experimental data. The systematic error introduced by this approximation is estimated by comparing the results with a three-spin simulation. The experiment is demonstrated in [U–13C,15N]N-acetyl-l-Val-l-Leu dipeptide, where 11 distances, ranging from 2.5 to 6Å, were measured. [Copyright &y& Elsevier]

Abstract: In this paper, we propose a methodology to synthesize facial expressions from photographs for devices with limited processing power, network bandwidth and display area, which is referred as “LLL” environment. The facial images are reduced to small-sized face alive icons (FAI). Expressions are decomposed into the expression-unrelated facial features and the expression-related expressional features. As a result, the common features can be identified and reused across expressions using a discrete model constructed from the statistical analysis on training dataset. Semantic synthesis rules are introduced to reveal the inner relations of expressions. Verified by the experimental prototype system and usability study, the approach can produce acceptable facial expression images utilizing much less computing, network and storage resource than the traditional approaches. [Copyright &y& Elsevier]

Abstract: In this paper, we address the issue of efficiently streaming a set of heterogenous videos under the constraint of service latency over a scalable multimedia systems. We propose a novel strategy, referred to as window-assisted video partitioning (WAVP), for rendering cost-effective multimedia services. The objective is to minimize the service cost and maximize the number of requests that can be successfully served under resources constraints (cache capacity and link bandwidth). We formulate the problem of video partitioning as an optimization of both bandwidth resources and cache space, and derive the optimal schedule window for different video portions under consideration of time constraints, the popularities and the sizes of the video portions. In WAVP, video are partitioned into multiple portions and delivered according to by adaptive schedule windows. We prove that WAVP strategy not only optimize the service cost but also be able to serve requests under the time constraints without causing too much delay. We conduct mathematical analysis and derive certain performance bounds that quantify the overall performance of the strategy. It shows that the service cost can be optimized by adjusting the schedule window and resources utilization can be improved as video streams are partitioned into multiple portions. We evaluate the performance under several influencing parameters such as available bandwidth, cache capacity, and partition gradients. Simulation results show that our proposed method can not only significantly reduce the service cost under tight time constraints and with low partition overhead, but also balance the utilization of network resources to achieve high acceptance ratio with low average service cost. [Copyright &y& Elsevier]

Abstract: The achievable bandwidth of common linear-phase RF pulses is limited by the maximum feasible B 1 amplitude of the MR system. It has been shown previously, that this limitation can be circumvented by overlaying a quadratic phase in the frequency domain, which spreads the power across the pulse duration. Quadratic-phase RF pulses are near optimal in terms of achieving minimal B 1max. In this work, it is demonstrated that further B 1max reduction can be achieved by combining quadratic with higher-order polynomial-phase functions. RF pulses with a phase response up to tenth order were designed using the Shinnar-Le Roux transformation, yielding considerable increases in bandwidth and selectivity as compared to pure quadratic-phase pulses. These benefits are studied for a range of pulse specifications and demonstrated experimentally. For B 1max =20μT and a pulse duration of 2.1ms, it was possible to increase the bandwidth from 3.1kHz for linear and 3.8kHz for a quadratic to 9.9kHz for a polynomial-phase pulse. [Copyright &y& Elsevier]

Abstract: In this paper, we use the kernel method to estimate sliced average variance estimation (SAVE) and prove that this estimator is both asymptotically normal and root consistent. We use this kernel estimator to provide more insight about the differences between slicing estimation and other sophisticated local smoothing methods. Finally, we suggest a Bayes information criterion (BIC) to estimate the dimensionality of SAVE. Examples and real data are presented for illustrating our method. [Copyright &y& Elsevier]

Abstract: Two new formulations of a symmetric WENO method for the direct numerical simulation of compressible turbulence are presented. The schemes are designed to maximize order of accuracy and bandwidth, while minimizing dissipation. The formulations and the corresponding coefficients are introduced. Numerical solutions to canonical flow problems are used to determine the dissipation and bandwidth properties of the numerical schemes. In addition, the suitability and accuracy of the bandwidth-optimized schemes for direct numerical simulations of turbulent flows is assessed in decaying isotropic turbulence and supersonic turbulent boundary layers. [Copyright &y& Elsevier]

Abstract: TCP over bandwidth asymmetric networks such as Cable TV and Asymmetric Digital Subscriber Loop (ADSL) exhibits different characteristics from TCP on symmetric links. A number of techniques have been proposed to address this problem. However, previous research has been largely focused on bulk transfers. This paper investigates the effects of bandwidth asymmetry on Web-like short-lived transfers. Two prediction models, one given in a closed form and the other in a recursive form, are presented for TCP transfers without and with ACK Filtering (AF), a representative optimizing technique for TCP transfers over bandwidth asymmetric links. Ns-2 based experiments show that these models can predict TCP transfer latency with a high degree of accuracy. [Copyright &y& Elsevier]

Abstract: This paper presents a kernel smoothing method for multinomial regression. A class of estimators of the regression functions is constructed by minimizing a localized power-divergence measure. These estimators include the bandwidth and a single parameter originating in the power-divergence measure as smoothing parameters. An asymptotic theory for the estimators is developed and the bias-adjusted estimators are obtained. A data-based algorithm for selecting the smoothing parameters is also proposed. Simulation results reveal that the proposed algorithm works efficiently. [Copyright &y& Elsevier]

Abstract: High interprocess communication latency is detrimental to parallel and grid computing. Over the years, the network bandwidth has increased rapidly while the end-to-end latency has not decreased much. This is because the latency is dominated by the protocol software execution time in the kernel instead of the raw transmission time over the link. In this paper, we perform an anatomical analysis of the complete communication path between a sender and a receiver through measurements. We present an in-depth evaluation of various components of the UDP protocol over Fast Ethernet. Virtual Interface Architecture (VIA) protocol has been recently proposed to overcome the software overhead of the TCP/UDP/IP protocol. We analyze M-VIA, a modular VIA implementation for Linux over Ethernet, and compare its performance with UDP. The aim of our experiments is to present the protocol overheads in details rather than to suggest new techniques to reduce overheads. [Copyright &y& Elsevier]

Abstract: Network contention hotspots can limit network throughput for parallel disk I/O, even when the interconnection network appears to be sufficiently provisioned. We studied I/O hotspots in mesh networks as a function of the spatial layout of an application''s compute nodes relative to the I/O nodes. Our analytical modeling and dynamic simulations show that when I/O nodes are configured on one side of a two-dimensional mesh, realizable I/O throughput is at best bounded by four times the network bandwidth per link. Maximal performance depends on the spatial layout of jobs, and cannot be further improved by adding I/O nodes. Applying these results, we devised a new parallel layout allocation strategy (PLAS) which minimizes I/O hotspots, and approaches the theoretical best case for parallel I/O throughput. Our I/O performance analysis and processor allocation strategy are applicable to a wide range of contemporary and emerging high-performance computing systems. [Copyright &y& Elsevier]

Abstract: For robust real-time transmission of scalable image and video data over packet-loss networks, a commonly used approach is FEC-based multiple description coding, which protects a scalable bitstream with a fixed number of packets of equal length. In this paper, by considering the problem of applying this approach of multicasting a source to a collection of clients with heterogeneous bandwidths, we propose a novel technique that changes packet length but fixes packet number. In one scenario where different clients access the server via separate links, we study the sensitivity of an optimal solution to the change of packet length, and propose a local search procedure which refines the already computed optimal solutions for other bandwidths. Compared to the scheme that computes an optimal solution individually for each bandwidth, this procedure can achieve comparable performance, however with quite lower time complexity, thus can be used in real-time applications. In another scenario where many clients share a bottleneck link, we present an embedded packetization framework for layered multiple description coding, in which even simple methods with low complexities can achieve good performance. We also propose a local search algorithm to optimize the weighted average performance in case of two layers, and a fast heuristic algorithm which can achieve very good performance tradeoff among all clients in case of more than two layers. [Copyright &y& Elsevier]

Abstract: SmartSpectra is a smart multispectral system for industrial, environmental, and commercial applications where the use of spectral information beyond the visible range is needed. The SmartSpectra system provides six spectral bands in the range 400–1000nm. The bands are configurable in terms of central wavelength and bandwidth by using electronic tunable filters. SmartSpectra consists of a multispectral sensor and the software that controls the system and simplifies the acquisition process. A first prototype called Autonomous Tunable Filter System is already available. This paper describes the SmartSpectra system, demonstrates its performance in the estimation of chlorophyll in plant leaves, and discusses its implications in real-time applications. [Copyright &y& Elsevier]

Abstract: We propose a new method for tuning the dispersion of a linearly chirped fiber Bragg grating with fixed center wavelength and bandwidth. We polished one side of the grating and attached it to a cantilever metal beam. By contacting an index matching block to the polished face of the grating, we could shorten the effective grating length through which light can propagate in the core of fiber. Decrease of grating length results in reflection bandwidth narrowing. However, by bending the grating attached on the cantilever beam, we could restore the bandwidth. Because the grating is shortened without bandwidth narrowing, the amount of dispersion is decreased. By using this method, we tuned chromatic dispersion of the linearly chirped fiber Bragg grating from −687.24 to for 0.75 nm fixed bandwidth without center wavelength shift. [Copyright &y& Elsevier]

Abstract: We investigate the issue of stalling in the LogP model. In particular, we introduce a novel quantitative characterization of stalling, referred to as -stalling, which intuitively captures the realistic assumption that once the network''s capacity constraint is violated, it takes some time (at most ) for this information to propagate to the processors involved. We prove a lower bound that shows that LogP under -stalling is strictly more powerful than the stall-free version of the model where only strictly stall-free computations are permitted. On the other hand, we show that -stalling LogP with can be simulated with at most logarithmic slowdown by a BSP machine with similar bandwidth and latency values, thus extending the equivalence (up to logarithmic factors) between stall-free LogP and BSP argued in Bilardi et al. (Algorithmica 24 (1999) 405) and Ramachandran et al. (J. Parallel Distributed Comput. 63 (2003) 1175) to the more powerful -stalling LogP. [Copyright &y& Elsevier]

Within statistical energy analysis (SEA), the coupling loss factor (CLF) is a statistical quantity defined in terms of the average behaviour of an ensemble of similar systems. Thus, the ‘effective’ CLF for a given realization may differ from the ensemble average. The effective CLF of two coupled plates with low modal density and low modal overlap fluctuates significantly compared with the ensemble average CLF. Accordingly, the CLF is the main parameter expected to determine the confidence intervals in the SEA prediction. The aim of the present paper is to quantify the variability of the effective CLF for the case of two finite rectangular plates. Extensive parameter investigations have been performed by using the dynamic stiffness method (DSM) and a ‘numerical’ power injection method (PIM) using the SEA power balance equations. The effects of frequency bandwidth and the number of modes in a band were separated by using frequency averages at a series of constant bandwidths rather than one-third octave averages, while the modal overlap is made independent of frequency by setting the damping loss factor to be inversely proportional to frequency. Finally, an improved empirical model for the variability of the CLF is derived, from these numerical results, in terms of the modal overlap factor and the number of modes in a frequency band. This model can subsequently be used to evaluate the uncertainty of the CLF of such a system. [Copyright &y& Elsevier]

Currently, bandwidth limitations pose a major challenge for delivering high-quality multimedia information over the Internet to users. In this research, we aim to provide a better compression of presentation videos (e.g., lectures). The approach is based on the idea that people tend to pay more attention to the face and gesturing hands, and therefore these regions are given more resolution than the remaining image. Our method first detects and tracks the face and hand regions using color-based segmentation and Kalman filtering. Next, different classes of natural hand gesture are recognized from the hand trajectories by identifying gesture holds, position/velocity changes, and repetitive movements. The detected face/hand regions and gesture events in the video are then encoded at higher resolution than the remaining lower-resolution background. We present results of the tracking and gesture recognition approach, and evaluate and compare videos compressed with the proposed method to uniform compression. [Copyright &y& Elsevier]

Abstract: The server allocation with bounded simultaneous requests problem arises in isolated infostations, where mobile users going through the coverage area require immediate high-bit rate communications such as web surfing, file transferring, voice messaging, email and fax. Given a set of service requests, each characterized by a temporal interval and a category, an integer k, and an integer for each category c, the problem consists in assigning a server to each request in such a way that at most k mutually simultaneous requests are assigned to the same server at the same time, out of which at most are of category c, and the minimum number of servers is used. Since this problem is computationally intractable, a 2-approximation on-line algorithm is exhibited which asymptotically gives a -approximation, where . Generalizations of the problem are considered, where each request r is also characterized by a bandwidth rate , and the sum of the bandwidth rates of the simultaneous requests assigned to the same server at the same time is bounded, and where each request is characterized also by a gender bandwidth. Such generalizations contain bin-packing, multiprocessor task scheduling, and interval graph coloring as special cases, and they admit on-line algorithms providing constant approximations. [Copyright &y& Elsevier]

Asymptotic modal analysis (AMA) has been shown to be a useful approximation and valid limiting case for classical modal analysis (CMA) when the number of resonant modes in a frequency bandwidth becomes sufficiently large and the cross-correlation between resonant modes is neglected. For CMA the neglect of these cross-correlations is usually justified if the damping is small and the resonant modal frequencies are well separated. In this paper it is shown that the cross-correlations may be neglected in the AMA limit even when the damping is not small. There is a rare exception to this, i.e., when two or more identical resonant frequencies occur. But this exceptional case is easily treated by including the cross-correlations for only such modes that have the same frequencies. [Copyright &y& Elsevier]