1 

The Effect of Gamma and Chroma on the Perception of Color Images
We present the results of experiments in which we manipulated color images in the CIELAB space by first applying a scaling factor on chroma (C*). After this we applied a gamma transformation (an exponent relating the input to the output) to the luminance (Y) in XYZ space, while keeping the chromaticity values (x, y) constant. The aim of the experiments was to test the subjective preference for a particular gamma and chroma scaling factor. Two natural images (standard ISO images) were transformed with 4 different values of gamma and 4 different scaling factors for chroma. The images were viewed on a CRT monitor. We found that the preference depends on the gamma, on the chroma scaling factor and on both variables combined. However, increasing or decreasing one or both variables does not improve the preference for the images that are used. The results were not significantly different for the two different images.

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2 

Throughputs in processor sharing models for integrated stream and elastic traffic
We present an analytical study of throughput measures in processor sharing queuing systems with randomly varying service rates, modelling e.g. a communication link in an integrated services network carrying prioritised fixed rate stream traffic and rateadaptive elastic traffic. A number of distinct throughput measures for the elastic traffic are defined, analysed and compared under various system conditions, both by analytical means and simulation. It is concluded that the callaverage throughput, which is most relevant from the user point of view but typically hard to analyse, is very well approximated by the newly proposed socalled expected instantaneous throughput, which is readily obtained from the system's steady state distribution. © 2007 Elsevier Ltd. All rights reserved.

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3 

Sojourntime approximations for a multiserver processor sharing system with priorities
We study mean sojourn times in a multiserver processor sharing system with two priority classes and with general servicetime distributions. For highpriority customers, the mean sojourn time follows directly from classical results on symmetric queues. For lowpriority customers, in the absence of exact results, we propose a simple and explicit approximation for the mean sojourn time. Extensive numerical experiments demonstrate that the approximations are highly accurate for a wide range of parameter settings. © 2003 Elsevier B.V. All rights reserved.

[Abstract]

4 

A Delay Filter for an irUWB FrontEnd
A continuoustime analog delay is designed as a requirement for the autocorrelation function in the quadrature downconversion autocorrelation receiver (QDAR). An eightorder Fade approximation of its transfer function is selected to implement this delay. Subsequently, the orthonormal form is adopted, which is intrinsically semioptimized for dynamic range, has low sensitivity to component mismatch, high sparsity and whose coefficients can be physically implemented. Each coefficient in the statespace description of the orthonormal ladder filter is implemented at circuit level using a novel 2stage gm cell employing negative feedback. Simulation results in IBM's BiCMOS 0.12 μm technology show that this delay filter requires a total current of 70 mA at a 1.6 V power supply. The 1dB compression point of the delay is at 565 mV and the SNR is 47.5 dB. On performing a Monte Carlo simulation it becomes evident that the response of the frequency selective analog delay does not suffer drastically from neither process variations nor component mismatch

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5 

Illposed inverse problem in diffraction optics : Tolerance analysis of diffractive lenses and gratings
A method is proposed for the prediction of deviations of the phase polynomial coefficients of diffractive optical elements from their nominal values due to fabrication errors. This problem represents an illposed inverse problem in diffraction optics. Its solution is based on the regularization technique resulting in an approximate stable (rather than exact but unstable) solution of the inverse problem. The proposed method can become a useful tool, providing optical designers with a possibility of including these deviations into the tolerance analysis of optical devices. © 2006 Optical Society of America.

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6 

Electromagnetic Excitation of a Thin Wire: A travelingWave Approach
An approximate representation for the current along a perfectly conducting straight thin wire is presented. The current is approximated in terms of pulsed waves that travel along the wire with the velocity of the exterior medium. At the ends of the wire, these pulses are partially reflected, with a constant reflection coefficient and delay time. Subsequently, the travelingwave representation for the current is used to derive an approximate expression for the electric field outside the wire that is caused by this current. For voltage excitation, this expression contains only closedform contributions. For planewave excitation, the expression contains a single integral over the initial pulse that must be computed numerically. Although the expression obtained is essentially a farfield approximation, it turns out to be valid from distances of the order of a single wire length. Results for a representative choice of wire dimensions and pulse lengths are presented and discussed

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7 

On the availability of a koutofN system given limited spares and repair capacity under a condition based maintenance strategy
This paper considers a koutofN system with identical, repairable components. Maintenance is initiated when the number of failed components exceeds some critical level. After a possible setup time, all failed components are replaced by spares. A multiserver repair shop repairs the failed components. The system availability depends on the spare part stock level, the maintenance policy and the repair capacity. We present a mathematical model supporting the tradeoff between these three parameters. We present both an exact and an approximate approach to analyse our model. In some numerical experiments, we provide insight on the impact of repair capacity, number of spares and preventive maintenance policy on the availability. © 2003 Elsevier Ltd. All rights reserved.

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8 

Soft sensing for gaslift wells
This paper considers the use of extended Kalman Filtering as a softsensing technique for gaslift wells. This technique is deployed for the estimation of dynamic variables that are not directly measured. Possible applications are the estimation of flow rates from pressure measurements or the estimation of parameters of a driftflux model. By means of simulation examples different configurations of sensor systems are analyzed. The estimation of driftflux model parameters is demonstrated on real data from a laboratory setup.

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9 

Steadystate hydrazinium nitroformate (HNF) combustion modeling
Two simplified modeling approaches are used to model the combustion of hydrazinium nitroformate (HNF), N2H5·C(NO2)3. The condensed phase is treated by highactivationenergy asymptotics. The gas phase is treated by two limit cases: the classical highactivationenergy approximation and the recently introduced lowactivationenergy approach. This results in simplification of the gasphase energy equation, making an (approximate) analytical solution possible. The results of both models are compared with experimental results of HNF combustion. It is shown that the lowactivationenergy approach yields better agreement with experimental observations, for example, regression rate and temperature sensitivity, than the highactivationenergy approach.

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10 

Detection of small targets in a marine environment using laser radar
Small maritime targets, e.g., periscope tubes, jet skies, swimmers and small boats, are potential threats for naval ships under many conditions, but are difficult to detect with current radar systems due to their limited radar cross section and the presence of sea clutter. On the other hand, applications of lidar systems have shown that the reflections from small targets are significantly stronger than reflections from the sea surface. As a result, dedicated lidar systems are potential tools for the detection of small maritime targets. A geometric approach is used to compare the diffuse reflection properties of cylinders and spheres with flat surfaces, which is used to estimate the maximum detectable range of such objects for a given lidar system. Experimental results using lasers operating at 1.06 μm and 1.57 μm confirm this theory and are discussed. Small buoys near Scheveningen harbor could be detected under adverse weather over more than 9 km. Extrapolation of these results indicates that small targets can be detected out to ranges of approximately 20 km.

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11 

Robust Fusion of Irregularly Sampled Data Using Adaptive Normalized Convolution
We present a novel algorithm for image fusion from irregularly sampled data. The method is based on the framework of normalized convolution (NC), in which the local signal is approximated through a projection onto a subspace. The use of polynomial basis functions in this paper makes NC equivalent to a local Taylor series expansion. Unlike the traditional framework, however, the window function of adaptive NC is adapted to local linear structures. This leads to more samples of the same modality being gathered for the analysis, which in turn improves signaltonoise ratio and reduces diffusion across discontinuities. A robust signal certainty is also adapted to the sample intensities to minimize the influence of outliers. Excellent fusion capability of adaptive NC is demonstrated through an application of superresolution image reconstruction.

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12 

Stochastic electromagnetic radiation of complex sources
The emission of electromagnetic radiation by localized complex electric charge and current distributions is studied. A statistical formalism in terms of general dynamical multipole fields is developed. The appearing coefficients are treated as stochastic variables. Hereby as much as possible a priori physical knowledge is exploited. First results of simulated statistical electromagnetic fields as a function of position are presented. Sampling this field at one point approximates its resulting probability density. © 2007 The American Physical Society.

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13 

Analysis of congestion periods of an m/m/∞queue
A ccongestion period of an m/m/ ∞queue is a period during which the number of customers in the system is continuously above level c. Interesting quantities related to a ccongestion period are, besides its duration Dc, the total area Ac above c, and the number of arrived customers Nc. In the literature Laplace transforms for these quantities have been derived, as well as explicit formulae for their means. Explicit expressions for higher moments and covariances (between Dc, Nc and Ac), however, have not been found so far. This paper presents recursive relations through which all moments and covariances can be obtained. Up to a starting condition, we explicitly solve these equations; for instance, we write E Dc2 explicitly in terms of E D02. We then find formulae for these starting conditions (which directly relate to the busy period in the m/m/ ∞ queue). Finally, a cintercongestion period is defined as the period during which the number of customers is continuously below level c. Also for this situation a recursive scheme allows us to explicitly compute higher moments and covariances. Additionally we present the Laplace transform of a socalled intercongestion triple of the three performance quantities. It is also shown that expressions for the quantities of a cintercongestion period can be used in an approximation for the ccongestion period. This is especially useful as the expressions for the cintercongestion period are numerically more stable than those for the ccongestion period. © 2007 Elsevier Ltd. All rights reserved.

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14 

Influence of turbulent grazing flow on the impedance of an opening
In this paper, the impedance of a rectangular opening submitted to a turbulent grazing flow is investigated experimentally. The opening is located in a flat plate where a turbulent boundary layer flow develops. The impedance is measured with a twomicrophone measuring pipe installed below the opening. The opening has a rectangular shape of large aspect ratio. With the long side oriented perpendicular to the flow. The results, the contribution due to the flow of the acoustic resistance and length correction, are nondimensionalized and compared with equivalent values computed with a vortexsheet model.

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15 

Auditory distance perception in humans : A summary of past and present research
Although auditory distance perception is a critical component of spatial hearing, it has received substantially less scienti.c attention than the directional aspects of auditory localization. Here we summarize current knowledge on auditory distance perception, with special emphasis on recent research results. The summary will be structured around three central questions. 1. How accurately can humans estimate the distances of stationary sound sources? We show that this psychophysical relationship is well approximated by a compressive power function, which suggests that listeners systematically underestimate distances to faraway sound sources. 2. What determines perceived sound source distance? We examine the various acoustical and nonacoustical factors thought to contribute to source distance percepts, and summarize the psychophysical literature relevant to each factor. 3. What are the neural correlates to perceived sound source distance? Recent evidence points to the role of areas within right temporal cortex in auditory distance perception, as well as in other spatial tasks in different sensory modalities.

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16 

Conspicuity and identifiability : efficient calibration tools for synthetic imagery
We argue that visual conspicuity and identifiability are two efficient taskrelated measures that can be deployed to calibrate synthetic imagery that is intended to be used for human visual search and detection tasks. The conspicuity of a target is operationally defined as the region around the center of the visual field where the target is capable to attract visual attention. Visual conspicuity predicts human visual search performance in realistic and military relevant complex scenario's. Conspicuity can easily and quickly be measured either in the field (in complex environments) or in the lab. This eliminates the need for costly and time consuming visual search experiments. The agreement between field and lab measurements implies that conspicuity can be used to validate synthetic imagery. Target identifiability is operationally defined as the amount of Gaussian blur that is required to reduce the target signature to its identification threshold. It is an efficient metric that can be used to gain insight into human identification performance without having to resort to elaborate and costly experiments. Identifiability is directly related to PIDperformance, and is therefore well suited forcomparing synthetic and realistic imagery. We conclude that synthetic imagery can be calibrated for human visual search and detection tasks by setting the conspicuity and identifiability of targets equal to those of their real world counterparts.

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17 

Correction of the effects induced by the continuous motion in airborne FMCW SAR
The combination of Frequency Modulated Continuous Wave (FMCW) technology and Synthetic Aperture Radar (SAR) leads to lightweight, costeffective imaging sensors of high resolution. In FMCW SAR applications the conventional stopandgo approximation used in pulse radar algorithms can be not valid anymore, therefore the motion within the sweep needs to be taken into account. Analytical development of the FMCW SAR signal model, starting from the deramped signal and without using the stopandgo approximation, is presented in this paper. The model is then applied to spotlight and single transmitter/multiple receiver Digital Beam Forming (DBF) operational mode, where the effect of the motion during the transmission and reception of the pulse, if not compensated for, can become seriously degrading for the SAR image quality. The derivation is then verified by processing real FMCW SAR data collected with the demonstrator system built at the Delft University of Technology. © 2006 IEEE.

[Abstract]

18 

TimeEvolving Acoustic Propagation Modeling in a Complex Ocean Environment
article 
2013

Author: 
Colin, M.E.G.G.
·
Duda, T.F.
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Raa, L.A. te
·
Zon, T. van
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Haley Jr., P.J., P. F. J.
·
Lermusiaux, P.F.J.
·
Leslie, W.G.
·
Mirabito, C.
·
Lam, F.P.A.
·
Newhall, A.E.
·
Lin, Y.T.
·
Lynch, J.F.

Keywords: 
Marine · Acoustic wave propagation modeling · Propagation loss · Approximation theory · Naval Operations · Ocean waves · Oceanographic techniques · Parabolic equations · Shallow water · Defence Research · Defence, Safety and Security · Physics & Electronics · AS  Acoustics & Sonar · TS  Technical Sciences

During naval operations, sonar performance estimates often need to be computed insitu with limited environmental information. This calls for the use of fast acoustic propagation models. Many naval operations are carried out in challenging and dynamic environments. This makes acoustic propagation and sonar performance behavior particularly complex and variable, and complicates prediction. Using data from a field experiment, we have investigated the accuracy with which acoustic propagation loss (PL) can be predicted, using only limited modeling capabilities. Environmental input parameters came from various sources that may be available in a typical naval operation. The outer continental shelf shallowwater experimental area featured internal tides, packets of nonlinear internal waves, and a meandering water mass front. For a moored source/receiver pair separated by 19.6 km, the acoustic propagation loss for 800 Hz pulses was computed using the peak amplitude. The variations in sound speed translated into considerable PL variability of order 15 dB. Acoustic loss modeling was carried out using a datadriven regional ocean model as well as measured sound speed profile data for comparison. The acoustic model used a twodimensional parabolic approximation (vertical and radial outward wavenumbers only). The variance of modeled propagation loss was less than that measured. The effect of the internal tides and subtidal features was reasonably well modeled; these made use of measured sound speed data. The effects of nonlinear waves were not well modeled, consistent with their known threedimensional effects but also with the lack of measurements to initialize and constrain them

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19 

Sojourn time approximations in queueing networks with feedback
This paper is motivated by the responsetime analysis of distributed information systems, where transactions are handled by a sequence of frontend server and backend server actions. We study sojourn times in an open queueing network with a single Processor Sharing (PS) node and an arbitrary number of M multiserver FirstComeFirstServed (FCFS) nodes. Customers arrive at the PS according to a Poisson process. After departing from the PS node a customer jumps to FCFS node k with probability pk, and departs from the system with probability 1  p, where p = ∑k  1M pk(0 < p < 1). After receiving service at a FCFS node, a customer jumps back to the PS node. For this model, we focus on the mean and the variability of the sojourn time of an arbitrary customer in the system. The model is a productform network, which immediately leads to a closedform expression for the mean sojourn times. The variance of the sojourn times, however, does not admit an exact expression; the complexity is caused by the possibility of overtaking. To this end, we propose a new methodology for deriving closedform approximations for the variance of sojourn times in queueing networks with feedback. Numerical results from extensive experimentation with simulations demonstrates that the approximations are highly accurate for a wide range of parameter values. © 2005 Elsevier B.V. All rights reserved.

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20 

Phase Controlled 2.63.5 GHz FractionalN PLL IC
This paper describes a fractionalN PLL IC with absolute phase control utilizing an onchip loopfilter. The frequency range is 2.6 to 3.5 GHz, which covers one of the bands for future lowband 5G telecommunication systems. For phasedarray operation a compact formfactor is needed as the space available for the complete frontend is limited by the wavelength. The onchip loopfilter allows to obtain the compact form factor required. The absolute phasecontrol allows for phasedarray operation. The chip has been implemented in a mathbf{0.25}mumathbf{m} BiCMOS process. Â© 2018 European Microwave Association.

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