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The structures of Fe78M9B13 (M=Nb, Si, and Zr) melts have been studied by ab initio molecular dynamics simulation. The essential features of the structures are the same in these melts. Prism-type local atomic arrangements dominate around B atoms and icosahedral-like clusters are frequently found around Fe atoms. However, the structures of the three melts differ in the degree of structural distortion caused by introducing M atoms to the prisms. The structural and dynamical properties of these melts change with different M elements, suggesting that they are closely correlated with their glass formation. The degree of complexity of molten structure caused by the interactions among Fe, M, and B may play an important role in their glass forming ability. [ABSTRACT FROM AUTHOR]

The effects of using different interatomic potentials in molecular dynamics (MD) simulations of the formation of He-vacancy clusters within displacement cascades in α-Fe are investigated using two sets of potentials. Simulations of cascades produced by primary knock-on atoms of energy Ep=1–20 keV were performed in α-Fe containing a concentration of substitutional He atoms varying from 1 to 5 at. % at an irradiation temperature of 100 K. Although the effects of interatomic potentials on the nucleation of He-vacancy clusters induced by cascades are relatively small, the number and size of He-vacancy clusters produced are significantly different for the different potentials employed in this study. Thus, these differences may influence the microstructural evolution predicted in damage accumulation models that use the results from MD cascade simulations as input. The observed differences in postcascade configurations can be attributed mainly to the differences in the Fe–Fe and Fe–He potentials. [ABSTRACT FROM AUTHOR]

The key issue in robust M-estimation is to construct the equivalent weights using the residuals of observations for down-weighting the outlying observations. However, the residuals of good observations are also possibly impacted by neighbouring outliers, thus directly down-weighting an observation according to its residual is not theoretically rigorous. Therefore, this paper focuses on the construction of equivalent weights for down-weighting the outlying and doubtful observations by removing the influence of the outlier on the correlated residuals. A down-weighting strategy using the corrected residuals to form the down-weighting factors is proposed. A simulated experiment and a practical experiment are respectively conducted to demonstrate the performances of the proposed down-weighting strategy compared to the direct down-weighting strategy (DDS) and recursive down-weighting strategy (RDS). The results show that the estimated performance of the proposed down-weighting strategy is comparable to that of RDS and the computation efficiency is obviously higher than that of RDS. [ABSTRACT FROM AUTHOR]

Automobile panel moulds are assembled pieces with various surface features, making it difficult to predict the machining properties in ball-end milling process. In this paper, Deform 3D finite element analysis software is used to simulate the ball-end milling of multi-hardness assembled moulds, and to analyse the distribution patterns of milling forces, stress fields and temperature fields in the transition regions of the multi-hardness assembled moulds. Subsequently, milling of sine surface moulds is simulated, and the effects of milling parameters on the thermal performance of sine surfaces are analysed. Finally, the multi-hardness assembling and milling experiment and the sine surface mould milling experiments are conducted to verify the effectiveness of the Deform 3D finite element simulation method. [ABSTRACT FROM AUTHOR]

For simulating freely moving problems, conventional immersed boundary-lattice Boltzmann methods encounter two major difficulties of an extremely large flow domain and the incompressible limit. To remove these two difficulties, this work proposes an immersed boundary-lattice Boltzmann flux solver (IB-LBFS) in the arbitrary Lagragian-Eulerian (ALE) coordinates and establishes a dynamic similarity theory. In the ALE-based IB-LBFS, the flow filed is obtained by using the LBFS on a moving Cartesian mesh, and the no-slip boundary condition is implemented by using the boundary condition-enforced immersed boundary method. The velocity of the Cartesian mesh is set the same as the translational velocity of the freely moving object so that there is no relative motion between the plate center and the mesh. This enables the ALE-based IB-LBFS to study flows with a freely moving object in a large open flow domain. By normalizing the governing equations for the flow domain and the motion of rigid body, six non-dimensional parameters are derived and maintained to be the same in both physical systems and the lattice Boltzmann framework. This similarity algorithm enables the lattice Boltzmann equation-based solver to study a general freely moving problem within the incompressible limit. The proposed solver and dynamic similarity theory have been successfully validated by simulating the flow around an in-line oscillating cylinder, single particle sedimentation, and flows with a freely falling plate. The obtained results agree well with both numerical and experimental data. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Determination of interfacial adhesion energies of thermal barrier coatings is important for understanding failure mechanisms and predicting their lifetime. Combined compression test with a cohesive zone finite element model, it is shown that the interfacial adhesion energy is in the range of 100–130 J/m 2 . Based on the nonlinear delamination theory, the critical interfacial adhesion energy of delamination is 120 J/m 2 and the corresponding loading phase angle is −56°. With the increase of the half-length of the crack, the crack propagation tends to be steady with a steady-state interface energy release rate of 150 J/m 2 , and delamination experiences almost pure mode II. These results obtained from finite element simulations and theoretical analyses are in good agreement with the available values determined by other testing methods reported in the literatures, which confirms the validity of this method. [ABSTRACT FROM AUTHOR]

In this work, a simple distribution function-based gas-kinetic scheme for simulation of viscous flows is presented. The work applies the finite volume method to discretize the governing differential equations, and inviscid and viscous fluxes at the cell interface are evaluated simultaneously by local reconstruction of solution for the continuous Boltzmann equation. Differently from the conventional gas-kinetic scheme [13-15], in the present work, the Maxwellian distribution function is simplified by a simple distribution function, and integrals in the infinity domain of phase space are reduced to integrals around a circle. As a consequence, the computational efficiency is greatly improved. Since the simple distribution function is defined on the circle, for simplicity, it is termed as circular function hereafter. The present work is the extension of our previous work [20], where the circular function-based gas-kinetic scheme is presented to simulate inviscid flows. Only the equilibrium distribution function is considered in [20]. To solve viscous flows, the non-equilibrium part of density distribution function has to be considered. One of major contributions in this work is to present a simple way to compute the non-equilibrium part of the distribution function. It can be calculated by the difference of equilibrium distribution functions at the cell interface and its surrounding point. As a result, the formulations for computing the conservative flow variables and fluxes at the cell interface can be given explicitly. The present solver can simulate both incompressible and compressible viscous flows. To validate the proposed new gas-kinetic scheme, several incompressible and compressible viscous flows are simulated. Numerical results showed that the circular function-based gas-kinetic scheme can provide accurate numerical results with the same computational cost as that needed by conventional Navier-Stokes solver. [ABSTRACT FROM AUTHOR]

An ultrasonic backscattering model is developed for textured polycrystalline materials with orthotropic or trigonal grains of ellipsoidal shape. The model allows us to simulate realistic microstructures and orthotropic macroscopic material textures resulting from thermomechanical processing for a broad variety of material symmetries. The 3-D texture is described by a modified Gaussian orientation distribution function (ODF) of the crystallographic orientation of the grains along the macroscopic texture direction. The preferred texture directions are arbitrary relative to the axes of the ellipsoidal grains. The averaged elastic covariance and the directional anisotropy of the backscattering coefficient are obtained for a wave propagation direction arbitrary relative to the texture and grain elongation directions. One particular application of this analysis is the backscattering solution for cubic crystallites with common textures such as Cube, Goss, Brass and Copper. In our analysis, in the texture-defined coordinates the matrix of elastic constants for cubic crystallites takes the form of orthotropic or trigonal symmetry. Numerical results are presented, discussed and compared to the experimental data available in the literature illustrating the dependence of the backscattering coefficient on texture and grain shape. [ABSTRACT FROM AUTHOR]

A recently constructed cyclotron magnet at the Institute of Modern Physics of Chinese Academy of Sciences (IMPCAS) will be used as the injector of Heavy Ion Therapy Facility in Lanzhou (HITFiL). The diameter of the magnet is 2.92 m and its height is 1.52 m. The total weight of the magnet is 70 tons. The isochronous magnetic field for \q/m = 5/12 is achieved by appropriate pole edge profile. The paper discusses the various design and fabrication aspects of the magnet. The paper also presents the field measurement results and its comparison with simulation. [ABSTRACT FROM PUBLISHER]

Abstract: Atomistic simulations of the nucleation of He clusters and bubbles in bcc iron at 800K have been carried out using the newly developed Fe–Fe interatomic potential, along with Ackland potential for the Fe–Fe interactions. Microstructure changes were analyzed in detail. We found that a He cluster with four He atoms is able to push out an iron interstitial from the cluster, creating a Frenkel pair. Small He clusters and self-interstitial atom (SIA) can migrate in the matrix, but He-vacancy (He-V) clusters are immobile. Most SIAs form <111> clusters, and only the dislocation loops with a Burgers vector of b =1/2<111> appear in the simulations. SIA clusters (or loops) are attached to He-V clusters for He implantation up to 1372appm, while the He-V cluster–loop complexes with more than one He-V cluster are formed at the He concentration of 2057appm and larger. [Copyright &y& Elsevier]

Abstract: The microstructure features of a representative Zr48Cu45Al7 bulk metallic glass (BMG) were investigated via a series of simulations and calculations coupled with the synchrotron radiation-based experiments. It was revealed that bond shortening occurs in the atomic pairs, due to the strong interaction between the Al dopant atoms and their neighbors. The bond shortening leads to the atomic and cluster level dense packing in the local structures, which should be the structural mechanism of the high glass-forming ability in Al-microalloyed BMGs. This work not only reveals the atomic and cluster level microstructures in this class of glass materials, but also has implications for developing other BMGs with relatively large critical sizes. [Copyright &y& Elsevier]

Abstract: This study investigates the performance of hybrid renewable microgeneration systems in load sharing application between a detached residential house and a small office building. Two renewable energy systems are investigated: a ground source heat pump (GSHP) system and a hybrid GSHP/fuel cell (FC) system. The renewable systems performance is compared to a conventional system that utilizes boiler and chiller to meet the thermal loads of the two buildings. Models are developed for the three selected systems and then simulated in TRNSYS-17 environment over one full year under Ottawa, Canada weather conditions. The simulation results showed that, by implementing a single GSHP system able to meet both heating and cooling loads of the buildings, an overall energy saving of 39% can be achieved mainly due to the introduction of a significant renewable component. The integrated hybrid GSHP–FC system results an overall energy saving of 24%. However, the hybrid GSHP–FC system generates additional electricity and based on the energy pricing structure can lead to more significant cost savings. Additionally, the GSHP–FC microgeneration system''s capability to generate both heat and power at the point of use is considered more attractive for new and remote community applications and for inclusion in the “smart” grid applications. [Copyright &y& Elsevier]

In this paper, a novel G-shaped defected microstrip structure (DMS) is presented. Compared with the conventional DMS, the proposed G-shaped DMS exhibits lower resonant frequency and wider stopband. A lowpass filter with 3 dB cutoff frequency at 3.17 GHz using four pairs of parallel cascaded G-shaped DMS units is designed and fabricated. The measured results show that the transition band is only 0.09 GHz and the stopband over 25 dB attenuation covers 3.4 GHz to 10 GHz. The measured and simulated results are in good agreement. [ABSTRACT FROM AUTHOR]

A broadband circularly polarized patch antenna with high gain and wide axial ratio beamwidths is proposed for ultra-high- frequency (UHF) RF identification (RFID) applications in this paper. The antenna is composed of a square patch, a feed network printed on the bottom side of the substrates and an antenna radome. The CP radiation of the proposed antenna is excited by four cylinder probes which transmit four signals that have equal amplitude with quadrature phase difference (0°, 90°, 180°, and 270°) generated from the feed network. To obtain an optimum peak gain and a broad CP bandwidth, 100 Ω isolation resistor is omitted in the feed network for obtaining high radiation efficiency, and the effects of varying the feed positions and dimensions of the various parameters on the antenna performances are respectively investigated. Simulation results are compared with the measurements, and a good agreement is obtained. The measured results show that the proposed antenna can provide broad impendence bandwidth of 19.7% (815-993MHz) (reflection coefficient less than -15 dB), a maximum gain of 9.65 dBi, and a 3-dB axial ratio (AR) bandwidth of about 11% (860-960MHz). The results indicate that the proposed antenna is an excellent candidate for UHF RFID reader system. At last, read performance of the proposed antenna array in RFID systems is presented, which verify the superior features of the proposed antenna in practical RFID system applications. [ABSTRACT FROM AUTHOR]

Abstract: The paper considers the construction of a confidence band for the trend function of a stationary time series. An explicit formula is derived based on polynomial splines and . The performance of the confidence band is illustrated by simulation studies. The proposed method is applied to the analysis of the annual yields of wheat in the United States. [Copyright &y& Elsevier]

This study mainly focuses on the asymptotical performance of two-way amplify-and-forward network coding opportunistic relaying (TWOR-AFNC) where the nodes have the same transmission powers, and there is (no) direct link between two sources, that is, TWOR-AFNC-Dir and TWOR-AFNC-Nodir. Firstly, based on the max-min criterion, the authors obtain the closed-form expressions to the probability density function (PDF), the cumulative distribution function (CDF) and the moment-generating function (MGF) of the equivalent end-to-end signal-to-noise ratio (SNR). These results are given with very simple analytical expressions by defining an auxiliary variable ωeq-k(θ), 2≤θ≤3. Secondly, the comparison analyses of the outage probability and symbol error probability (SEP) between the two systems are presented. The comparison analysis shows that the derived results are the tight lower bound when θ=2, and are the upper bound when θ=3. Finally, to obtain the exact estimation of the performance, the authors obtain the optimisation values of θ. The results show that the optimisation values of θ are a little greater than 2 in lower SNR, whereas are equal to 2 in high SNR. Moreover, the feasible SNR regime for θ=2 is expanding with the increasing of the asymmetry between relay channels. Besides of this, the authors also present the closed-form expressions to CDF and PDF when the nodes have different transmission powers. The results indicate that the closed-form expressions to CDF and PDF are similar for the two cases where the nodes transmission powers are same or different. [ABSTRACT FROM AUTHOR]

The article considers the Yule-Walker estimator of the autoregressive coefficient based on the observed time series that contains an unknown trend function and an autoregressive error term. The trend function is estimated by means of B-splines and then subtracted from the observations. The Yule-Walker estimator is obtained from the residual sequence. Asymptotic properties of this estimator are derived. The performance of the estimator is illustrated by simulation studies and real data analysis. [ABSTRACT FROM AUTHOR]

Partial transmit sequence (PTS) is one of the most well-known peak-to-average power ratio (PAPR) reduction techniques proposed for orthogonal frequency-division multiplexing (OFDM) systems. The main drawbacks of the conventional PTS (C-PTS) are high computational complexity and transmission of several side information bits. A new PTS with simple detector is proposed in this paper to deal with these drawbacks of C-PTS. The candidates can be generated through cyclically shifting each sub-block sequence in time domain and combining them in a recursive manner. At the receiver, by utilizing the natural diversity of phase constellation for different candidates, the detector can successfully recover the original signal without side information. Numerical simulation shows that the proposed scheme performs very well in terms of PAPR. The probability of detection failure of the side information demonstrates that the detector could work without any side information with high reliability. The proposed scheme achieves almost the same bit error rate (BER) performance as the C-PTS with perfect side information, under both additive white Gaussian noise (AWGN) channel and Rayleigh fading channel. [ABSTRACT FROM AUTHOR]

A maximum mean squared error optimal relay beamformer is proposed here for two-way single-antenna distributed relaying systems. A constrained optimisation problem with respect to the relay beamforming vector is first formulated. It is then shown that the design problem of such a relay beamformer supporting both downlink and uplink transmissions simultaneously can be converted to convex optimisation when full channel state information (CSI) is available at the relays. By employing the Lagrangian multiplier method, a closed-form solution for the relaying vector is obtained. The proposed relay beamforming method is also extended to the situation where only the statistics of the CSI are available. A simulation study is conducted to confirm the merit of the proposed two-way relaying scheme. [ABSTRACT FROM AUTHOR]

PROB is an animation and model checking tool, which supports integrated event- and state-based specifications combining B and CSP. We present an initial strategy for implementing the combined specification model as a concurrent Java program. Our Java implementation for the combined B and CSP model uses a similar approach to that of JCSP. The restricted operational semantics for the integrated B and CSP model in PROB is defined. Then a new Java package, JCSProB, is developed for implementing the semantics. The new package supports external choice with multi-way synchronization, and introduces an improved multi-threading implementation from JCSP. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The effects of He-vacancy (He-V) clusters on the mobility of an a/2〈111〉{110} edge dislocation in α-Fe are investigated by atomic simulation with empirical potentials at 0K. A number of small He n V m (n/m 0–4) clusters initially placed at the same position on the slip plane are comparatively studied. The results show that the interaction of He-V clusters with edge dislocations depends on not only the helium-to-vacancy (He/V) ratio, but also the cluster size. The small He-V clusters with low He/V ratios have a small effect on the dislocation mobility, but the larger clusters with higher He/V ratios significantly increase the critical resolved shear stress for dislocation glide. One of interesting results is that the He-V clusters almost stay at their original positions, and do not move along with the dislocation. [Copyright &y& Elsevier]

Abstract: The effects of different Fe–He interatomic potentials on primary damage formation in Fe-1%He are investigated using molecular dynamics (MD) methods. Simulations of cascades produced by primary knock-on atoms (PKA) of energy E p =0.5–10keV were performed at an irradiation temperature of 100K. It is found that the Fe–He potentials have significant effects on the point defect creation and the formation of Fe–He interstitial clusters, whereas small effects on the formation of He–vacancy clusters. [Copyright &y& Elsevier]

The Shanghai Synchrotron Radiation Facility (SSRF) is a third-generation synchrotron radiation light source and will come into commission in April 2009. The project Shanghai Laser Electron Gamma Source (SLEGS), which is a high intensity γ-ray beamline based on Laser Compton Scattering (LCS) between relativistic electron bunches and a laser, has been proposed at the SSRF. According to our simulations, the SLEGS is expected to generate a polarized γ-ray beam of up to 22 MeV and 109-10 photons/s if using 3.5 GeV, 200-300 mA relativistic electrons and a 500 W CO2 polarized laser. Here we describe the status and the application prospects of SLEGS and its developed prototype. [ABSTRACT FROM AUTHOR]

The determination methods of the major model parameters are explained in this article, and the upstream weighted multi-cell balance method is adopted to solve the numerical models established. The author also analyzes and discusses the simulated calculation results, which show that, except for very few points in the loosening zone, where the relative calculation error is comparatively high resulting from the low oxygen concentration, the relative calculation error of other points falls between 8% and 19%. Therefore, the calculation value and the experiment value take on a good conformity. The simulated results indicate that the calculation value of the oxygen concentration is a little bit lower than the experiment one. On top of that, with the prolonging of gasification time, in a high temperature zone the change gradient of oxygen concentration for experimental value is bigger than that of the calculation value. The oxygen concentration is in direct proportion to its distance from the flame working face, i.e., the longer its distance is, the higher the oxygen concentration is; otherwise, the lower the oxygen concentration is. [ABSTRACT FROM AUTHOR]

By using the time domain sequence superposition (TDSS) technique, in this paper, we propose a low complexity selected mapping (LC-SLM) scheme for the peak-to-average power ratio (PAPR) reduction of the orthogonal frequency division multiplexing (OFDM) system. Unlike the conventional selected mapping (SLM) scheme which needs several inverse fast Fourier transform (IFFT) operations for an OFDM signal, the proposed scheme requires to implement two IFFT operations only. Thus, it can remarkably reduce the computational complexity. Simulation results show that the proposed scheme can achieve similar PAPR performance as the conventional SLM scheme. [ABSTRACT FROM AUTHOR]

The conditions for the optimal non-reciprocal operation of longitudinally magnetised ferrite-coupled line (FCL) are obtained for the first time from the scattering-matrix treatment, and the necessary conditions for the multicomponent reciprocal network joint with a FCL section to be a circulator are specified. Using these optimal conditions, the minimum length of the FCL is also found. A self-biasing circulator with the minimum length of FCL at millimetre-wave frequency is reported and its scattering characteristics are simulated and discussed. [ABSTRACT FROM AUTHOR]

Abstract: Multiple-interactions of displacement cascades with He–vacancy (He–V) clusters are investigated using molecular dynamics simulations. The effects of a single displacement cascade on the stability of a He–V cluster depend on the He-to-vacancy (He/V) ratio and the primary knock-on atom (PKA) energy. Initial He–V clusters consist of 10 and 20 vacancies with He/V ratios ranging from 0.2 to 3 and the PKA energy, E p, varying from 2keV to 10keV. The size of He–V clusters was found to generally increase with increasing He/V ratios for the same PKA energy, but the stability of He–V clusters decreases with increasing PKA energy. The results are compared with those for voids impacted by collisional cascades. During multiple 5keV, cascade events, the final size of He–V clusters depends on only the initial He/V ratios. It is of interest to notice that the number of vacancies in a He–V cluster is determined by the first cascade event, while subsequent cascade overlap has a significant effect on its stability. These results are discussed in terms of the internal pressure of He–V clusters, the mobility of He atoms, the number of vacancies produced by cascades and the He/V ratio. [Copyright &y& Elsevier]

Abstract: Time series often contain unknown trend functions and unobservable error terms. As is known, Yule–Walker estimators are asymptotically efficient for autoregressive time series. The focus of this article is the Yule–Walker estimators for time series with trends. A nonparametric detrending procedure is proposed. It is concluded that the asymptotic properties of the Yule–Walker estimators of autoregressive coefficients are not altered by the detrending procedure. The results of the simulation studies and real data application corroborate the asymptotic theory. [Copyright &y& Elsevier]

Abstract: Laminar flame speeds and extinction strain rates of premixed C5–C12 n-alkane flames were determined at atmospheric pressure and elevated unburned mixture temperatures, over a wide range of equivalence ratios. Experiments were performed in the counterflow configuration and flow velocities were measured using Laser Doppler Velocimetry. The laminar flame speeds were obtained using a non-linear extrapolation technique utilizing numerical simulations of the counterflow experiments with detailed descriptions of chemical kinetics and molecular transport. Compared to linearly extrapolated values, the laminar flame speeds obtained using non-linear extrapolations were found to be 1–4cm/s lower depending on the equivalence ratio. It was determined that the laminar flame speeds of all n-alkane/air mixtures considered in this investigation are similar to each other and sensitive largely to the H2/CO and C1–C4 hydrocarbon kinetics. Additionally, the resistance to extinction decreases as the fuel molecular weight increases. Simulations of the experiments were performed using the recently developed JetSurF 0.2 reaction model consisting of 194 species and 1459 reactions. The laminar flame speeds were predicted with good accuracy for all the n-alkane-air mixtures considered. The experimental extinction strain rates are well predicted by the model for fuel-lean mixtures. For stoichiometric and fuel-rich mixtures, the predicted extinction strain rates are approximately 10% lower than the experimental values. Insights into the physical and chemical processes that control the response of n-alkane flames are provided through detailed sensitivity analyses on both reaction rates and binary diffusion coefficients. [Copyright &y& Elsevier]

Pointing error is one of the most critical performance indices of space-borne optical imager and is of great significance for optical imaging and target tracking. In order to correct the pointing error of an optical imager and make it meet the design requirement, first of all, the mathematical model of the relation of pointing error and assembly errors of mechanical components is established, acquiring the analytical expressions of pitch angle and azimuth angle of the 2-DOFs pointing mechanism. Then, the mathematical model of transformation matrix calibration of coordinate systems is set up and the calculation formulas of transformation matrix and angular deviation are provided. Moreover, the simulation model of pointing error is built based on Monte-Carlo method given that the distribution of each assembly error satisfies normal assumption, together with the distribution of pointing error before and after assembly error correction. Finally, the correction test of pointing error is accomplished and test results before and after correction are compared, demonstrating that the maximum of compensated value is 26″ and the minimum is 6″ and the pointing accuracy has increased by 64% in average. After correction, the total pointing error of imager is no more than 20″ which meets the system performance requirement. [ABSTRACT FROM AUTHOR]

Abstract: An upgrade project is under way to further improve the brightness of the Advanced Light Source at Berkeley Lab by reducing its horizontal emittance from 6.3 to 2.2nm (effective emittance in the straights from 6.4 to 2.5nm). This will result in a brightness increase by a factor of three for bend magnet beamlines and at least a factor of two for insertion device beamlines and will keep the ALS competitive with newer sources. This paper presents an overview of the upgrade project with emphasis on the nonlinear beam dynamics simulations. It also discusses in a more general way the techniques used at LBNL for finding optimum lattices (e.g. the ones with maximum brightness) and optimizing the particle dynamics, thereby increasing beam lifetime and stability. [Copyright &y& Elsevier]