1 

BLEVE blast by expansioncontrolled evaporation
This report presents a new method to calculate the blast effects originating from an exploding vessel of liquefied gas. Adequate blast calculation requires full knowledge of the blast source characteristics, that is, the release and subsequent evaporation rate of the flashing liquid. Because the conditions that allow explosive evaporation are not entirely clear and the evaporation rate of a flashing liquid is unknown, safe assumptions have been adopted as the starting point in the modeling. The blast effects from a boiling liquid expanding vapor explosion (BLEVE) are numerically computed by imposing the vapor pressure of a flashing liquid as boundary condition for the gas dynamics of expansion. The numerical modeling is quantitatively explored just for liquefied propane. In addition, this paper demonstrates that often an estimate of BLEVE blast effects is possible with very simple acoustic volume source expressions. The modeling shows that the rupture of a pressure vessel containing a liquefied gas in free space develops a blast of significant strength only if the vessel nearly instantaneously disintegrates. Even if a rupture and the consequent release and evaporation of a liquefied gas extend over just a short period of time, the blast effects are minor. © 2005 American Institute of Chemical Engineers.

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2 

Design of a shockinduced combustion experiment in an axisymmetric configuration with hydrogen injection
This work presents a design for a shockinduced combustion experiment using a twoangle cone configuration. Three injector geometries were considered: a cone surface, a dual stage configuration with rectangular gaps (DSRG) and a cylindrical ramp (CR). Four parameters were investigated: the penetration height, the mixing efficiency, the control of premature ignition and the shock wave / boundary layer interaction. The numerical calculations were performed with the Fluent™ code, using the densitybased coupledimplicit solver. The hydrogenoxygen combustion was modeled with a 9 species / 20 reactions Jachimowski mechanism. The CR injector dispersed the hydrogen far from the wall and thus gave the best fiowfield for shockinduced combustion. The reactive portion revealed that combustion can be initiated by the second shock, but under certain conditions, combustion occurs in a subsonic region.

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3 

3D mechanical analysis of complex reservoirs: A novel meshfree approach
Building geomechanical models for induced seismicity in complex reservoirs poses a major challenge, in particular if many faults need to be included. We developed a novel way of calculating induced stress changes and associated seismic moment response for structurally complex reservoirs with tens to hundreds of faults. Our specific target was to improve the predictive capability of stress evolution along multiple faults, and to use the calculations to enhance physicsbased understanding of the reservoir seismicity. Our methodology deploys a meshfree numerical and analytical approach for both the stress calculation and the seismic moment calculation.We introduce a highperformance computational method for highresolution induced Coulomb stress changes along faults, based on a Green?s function for the stress response to a nucleus of strain. One key ingredient is the deployment of an octree representation and calculation scheme for the nuclei of strain, based on the topology and spatial variability of the mesh of the reservoir flow model. Once the induced stress changes are evaluated along multiple faults, we calculate potential seismic moment release in a fault system supposing an initial stress field. The capability of the approach, dubbed as MACRIS (Mechanical Analysis of Complex Reservoirs for Induced Seismicity) is proven through comparisons with finite element models. Computational performance and suitability for probabilistic assessment of seismic hazards are demonstrated though the use of the complex, heavily faulted Gullfaks field. © 2019 The Author(s). Published by Oxford University Press on behalf of The Royal Astronomical Society.

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4 

IR panoramic alerting sensor concepts and applications
During the last decade, protection of military and civilian operational platforms against weapons like guns, grenades, missiles, Unmanned Combat Aerial (and surface) Vehicles (UCAV's) and mines, has been an issue of increased importance due to the improved killprobability of these threats. The standard countermeasure package of armour, guns, decoys, jammers, camouflage nets and smokes is inadequate when not accompanied by a suitable sensor package, primarily consisting of an alerting device, triggering consecutive steps in the countermeasurechain. In this process of alert four different detection techniques are considered: prealert, giving the directions of possible attack, detection of an action of attack, identification of the threat and finally the precise localisation (3D). The design of the alerting device is greatly depending on the platform, on which it will be used, the associated and affordable cost and the nature of the threat. A number of sensor packages, considered, developed and evaluated at TNOFEL is presented for simple, medium size and large and expensive platforms. In recent years the requirements for these sensors have become more and more stringent due to the growing number of scenarios. The attack can practically be from any direction, implying the need for a large Field of Regard (FOR), the attack range can vary considerably and the type of threat can be very diverse, implying great flexibility and dynamic range and rapid response of the sensor. Especially the localisation at short ranges is a challenging issue. Various configurations including advantages and drawbacks are discussed.

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5 

Green's function of an infinite slot printed between two homogeneous dielectrics  Part II: Uniform asymptotic solution
This second part of a twopaper sequence deals with the uniform asymptotic description of the Green's function of an infinite slot printed between two different homogeneous dielectric media. Starting from the magnetic current derived in Part I, the dyadic green's function is first formulated in integral form in both spectral and spatial domains; next, the asymptotic solution for the vector potential is evaluated asymptotically. The asymptotic rayfield is structured in three contributions: a spherical wave radiated by the source (space wave), a conical leaky wave, and a lateral wave. These contributions are first introduced by the stationary phase method applied to the spacedomain radiation integral. From this approach it is seen that the lateral wave contribution is negligible in actual configurations. Next, a rigorous uniform asymptotic evaluation of the radiated field is formulated in the spectral domain by using a steepest descent path deformation which accounts for the vicinity of the pole to the saddle point. Through this rigorous asymptotics, the domain of existence of the leakywave is found to be limited by a conical shadow boundary which deviates from that defined by the stationary phase regime. Along this conical shadow boundary, phase matching occurs between space and leaky wave, which facilitates the transition mechanism between the two wave types. This transition occurs inside a conical transition region with elliptical cross section. The interference between space and leaky waves from the near to the far zone are discussed by means of illustrative examples, which also confirm the accuracy of the asymptotics.

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6 

Performance modelling and evaluation of wireless multiaccess networks
In support of the ongoing research and development activity in the design and performance assessment of radio access network integration schemes, we present novel resource sharing models for the efficient simulation of multiaccess networks involving GSM/EDGE, UMTS/HSDPA and 802.11Abased WLAN systems. The applicability of the proposed models in determining call and system level performance measures is demonstrated by means of a limited set of illustrative numerical experiments revealing the significant performance gains when integrating distinct access networks with a rather simple Radio Access selection scheme. © SpringerVerlag Berlin Heidelberg 2007.

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7 

Increasing the robustness of a preconditioned filteredX LMS algorithm
This letter presents a robustification of the preconditioned FilteredX LMS algorithm proposed by Elliott et al.. The method optimizes the average performance for probabilistic uncertainty in the secondary path and relaxes the SPR condition for global convergence. It also prevents large amplification in the preconditioning filters due to secondary path zeros on and/or close to the unit circle, which may yield overactuation in practical applications.

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8 

Convergence analysis of the FilteredU LMS algorithm for active noise control in case perfect cancellation is not possible
The FilteredU LMS algorithm, proposed by Eriksson for active noise control applications, adapts the coefficients of an infiniteimpulse response controller. Conditions for global convergence of the FilteredU LMS algorithm were presented by Wang and Ren (Signal Processing, 73 (1999) 3) and Mosquera and PérezGonzález (Signal Processing, 80 (2000) 5) for the case where perfect noise cancellation is achievable, which means only measurement noise remains. This paper shows that the assumption of perfect cancellation is not necessary. In real situations perfect cancellation is often not achievable due to delays and nonminimum phase zeros. The conclusion is derived by analysis of the structure of the Wiener optimal solution. This also leads to the suggestion of preconditioning filters in the FilteredU LMS updating. The preconditioning has shown considerable increase of the convergence rate in a realistic simulation study.

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9 

Predictions of flow and heat transfer in multiple impinging jets with an ellipticblending secondmoment closure
We present numerical computations of flow and heat transfer in multiple jets impinging normally on a flat heated surface, obtained with a new secondmoment turbulence closure combined with an elliptic blending model of nonviscous wall blocking effect. This model provides the mean velocity and turbulent stress fields in very good agreement with PIV measurements. The exploration of several simpler closures for the passive thermal field, conducted in parallel, confirmed that the major prerequisite for the accurate prediction of the temperature field and heat transfer is to compute accurately the velocity and stress fields. If this is achieved, the conventional anisotropic eddydiffusivity model can suffice even in complex flows. We demonstrate this in multipleimpinging jets where such a model combination provided the distribution of Nusselt number over the solid plate in good agreement with experiments. Extension of the elliptic blending concept to full secondmoment treatment of the heat flux and its truncation to a quasilinear algebraic model is also briefly discussed.

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10 

ProblemMatched Basis Functions for Microstrip Coupled Slot Arrays Based on Transmission Line Green's Functions (TLGF)
Problem matched basis functions are proposed for the method of moments analysis of printed slot coupled microstrips. The appropriate equivalent currents of the integral equation kernel are represented in terms of two sets of entire domain basis functions. These functions synthesize on one hand the resonant behavior of slots, microstrips or dipoles and on the other hand the field in proximity of the feeding source and of the discontinuities. In order to define these basis functions, canonical geometries are identified, whose Green's functions have been found in semianalytical form. The accuracy and the effectiveness of the method in terms of convergence rate and number of unknowns is demonstrated by comparison with a standard fine meshing fullwave analysis. The method is extremely convenient for large arrays, where the subwavelength details should be treated together with large global dimensions. Since the proposed solution is independent of the dimensions of these details, it provides dramatic reduction of the number of unknowns and improvement of condition number.

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11 

Element failure correction for a large monopulse phased array antenna with active amplitude weighting
Recently a new method is introduced to synthesize low sidelobe patterns for planar array antennas with a periodic element arrangement. The method makes use of the property that for a planar array with periodic spacing of the elements, an inverse Fourier transform relationship exists between the array factor and the element excitations. This property is used in an iterative way to derive the array element excitations from the prescribed array factor. The same method is also able to partially compensate the degradation of the sidelobe and gain performance of array patterns due to element failures. Numerical examples of arrayfailure correction using this method are given for ultralow sidelobe sum and difference patterns of a 5800element circular array where the failed elements are randomly dispersed across the aperture. The tapers in this array are created exclusively by active weighting in the transmit/receive (T/R) modules using variable gain control. © 2007 IEEE.

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12 

Observable parameters from multipath bottom reverberation in shallow water
Multipath ocean reverberation originating from the seabed in shallow isovelocity water, with particular attention to its information content in the cylindrical spreading and mode stripping regions, is considered. The reverberation is evaluated using Weston's flux integral method, both analytically with various simplifying approximations and numerically with all but one of these approximations rescinded. The functional form of the analytical solution is used to infer which physical seabed parameters can be extracted from measurements of reverberation. Coarse and finegrained sediments (sand and clay) are both considered. The main purpose of the numerical solutions is to check the accuracy of the analytical approximations; they also serve as a convenient surrogate for measured reverberation. © 2007 Acoustical Society of America.

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13 

The deflation accelerated schwarz method for CFD
Accurate simulation of glass melting furnaces requires the solution of very large linear algebraic systems of equations. To solve these equations efficiently a Schwarz domain decomposition (multiblock) method can be used. However, it can be observed that the convergence of the Schwarz method deteriorates when a large number of subdomains is used. This is due to small eigenvalues arising from the domain decomposition which slow down the convergence. Recently, a deflation approach was proposed to solve this problem using constant approximate eigenvectors. This paper generalizes this view to piecewise linear vectors and results for two CFD problems are presented. It can be observed that the number of iterations and wall clock time decrease considerably. The reason for this is that the norm of the initial residual is much smaller and the rate of convergence is higher.

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14 

A multiple timescale model for TCP bandwidth sharing under user heterogeneity
Building on the vast body of existing TCP models, we develop a novel versatile model that explicitly captures user heterogeneity, and takes into consideration dynamics at both the packet level and the flow level. It is described how the resulting multiple timescale model can be numerically evaluated. Validation is done by using NS2 simulations as a benchmark. In extensive numerical experiments, we study the impact of heterogeneity in the roundtrip times on userlevel characteristics such as throughputs and flow transmission times, thus quantifying the resulting bias. In particular, we investigate to what extent this bias is affected by the networks' 'packetlevel parameters', such as buffer sizes. We conclude by extending the singlelink model in a straightforward way to the general network setting. © IFIP International Federation for Information Processing 2005.

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15 

Calculating traffic noise reduction at long distance using diffracting elements
A series of resonators alongside a road or railway can be used to diffract noise upwards to create a zone of noise reduction behind the elements. The company 4Silence developed the socalled Whisstone, a concrete block with 18 resonators of different depths designed to operate in a broad frequency range. Several measurements at short distance, up to 15 meters, have proven that a noise reduction up to 4 dB(A) can be achieved. To determine the noise reduction at long distances calculations are necessary, due to the uncertainties of ground and meteorological effects. In this paper a comparison between measurements and numerical results (FEM) at short distance is presented. The positive results of this comparison allow the numerical method to be applied at larger ranges, up to 600 meters, taking a downwind condition into account. To this end the FEM method is coupled to a Green's function parabolic equation method (GFPE). The calculations for long distances show noise reductions up to 5 dB in octave bands and 3 dB(A) for the broadband level. These results can be used to account for the diffracting elements in standard noise calculation models used in practice, such as the Dutch national standard model or Cnossos. © INTERNOISE 2018  47th International Congress and Exposition on Noise Control Engineering: Impact of Noise Control Engineering. All rights reserved.

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16 

Offline motion simulation framework: Optimizing motion simulator trajectories and parameters
This paper presents a method to simultaneously compute optimal simulator motions and simulator parameters for a predefined set of vehicle motions. The optimization can be performed with a model of human motion perception or sensory dynamics taken into account. The simulator dynamics, sensory dynamics, and optimality criterion are provided by the user. The dynamical models are defined by implicit index1 differentialalgebraic equations (DAE). The direct collocation method is used to find the numerical solution of the optimization problem. The possible applications of the method include calculating optimal simulator motion for scenarios when the future motion is perfectly known (e.g., comfort studies with autonomous vehicles), optimizing simulator design, and evaluating the maximum possible cueing fidelity for a given simulator. To demonstrate the method, we calculated optimal trajectories for a set of typical car maneuvers for the CyberMotion Simulator at the MaxPlanck Institute for Biological Cybernetics. We also optimize the configurable cabin position of the simulator and assess the corresponding motion fidelity improvement. The software implementation of the method is publicly available. © 2019 Elsevier Ltd

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17 

Numerical study of beam cleanup by stimulated Raman scattering
One can use stimulated Raman scattering to obtain a neardiffractionlimited Stokes beam from a multimode

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18 

The initial conditions of observed star clusters  I. Method description and validation
We have coupled a fast, parametrized star cluster evolution code to a Markov Chain Monte Carlo code to determine the distribution of probable initial conditions of observed star clusters, that may serve as a starting point for future Nbody calculations. In this paper, we validate our method by applying it to a set of star clusters which have been studied in detail numerically with Nbody simulations and Monte Carlo methods: the Galactic globular clusters M4, 47 Tucanae, NGC 6397, M22, ω Centauri, Palomar 14 and Palomar 4, the Galactic open cluster M67, and the M31 globular cluster G1. For each cluster, we derive a distribution of initial conditions that, after evolution up to the cluster's current age, evolves to the currently observed conditions. We find that there is a connection between the morphology of the distribution of initial conditions and the dynamical age of a cluster and that a degeneracy in the initial halfmass radius towards small radii is present for clusters that have undergone a core collapse during their evolution. We find that the results of our method are in agreement with Nbody and Monte Carlo studies for the majority of clusters. We conclude that our method is able to find reliable posteriors for the determined initial mass and halfmass radius for observed star clusters, and thus forms an suitable starting point for modelling an observed cluster's evolution. © 2015 The Authors.

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19 

Mitigation of surface contamination from resist outgassing in EUV lithography
Contamination of optics and mask is one of the possible show stoppers for Extreme Ultraviolet Lithography. One of the important sources of hydrocarbon contamination is the outgassing of photoresist coated wafers. Due to the vacuum conditions, these hydrocarbons can freely travel to coat the first optical component they encounter. This leads to unacceptably short life times which should be increased with 5 orders of magnitude. A new gas lock system is presented to prevent this type of contamination and which eliminates the need for a window between the optics and the wafer. Experimental results are in agreement with numerical calculations and an analytical model. Based on agreement between the experiments and the models, it is predicted that in realistic EUV tools this method can give 5 orders of magnitude debris suppression at 15 mbar·1/s flow with 5% absorption of EUV.

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20 

An integral quadratic constraint approach to the robust performance estimation problem of guidance loops
The problem of evaluating the performance of an uncertain guidance loop system is considered, when the uncertainty is described in terms of an integral quadratic constraint. The idea of the approach proposed in this paper is to determine the set of all possible state vector values at the end of the flight that are compatible with the model uncertainty and determine the upper and lower bound for the miss distance by solving two optimization problems on this set. The main theoretical result of the paper shows that this is a quadric that can be determined by the solving a differential Riccati equation and a set of coupled linear differential equations. Unfortunately, numerical experiments showed that the method is practically unusable for realistic models of guidance loops. A single integral quadratic constraint is a poor representation of the usual model uncertainties, meaning that the results are certainly too conservative. In addition, the optimization problem turns out to be badly conditioned in all cases of interest for homing guidance loop analysis. This is illustrated using a contrived numerical example based on a relatively wellbehaved linear timeinvariant system. Although in its present form, the approach taken in this paper did not achieve the results that were hoped for, the ideas advanced here, and some of the technical results are interesting in themselves and may be useful in future research on this theme.

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