The design and performance of the ZEUS central tracking detector second-level trigger

This paper describes the Second-Level Trigger for the Central Tracking Detector (CTD-SLT) of the ZEUS experiment. The CTD-SLT consists of a network of micro-processors running a track finding algorithm. Operational experience gained during the 1995–1997 HERA data taking periods show that the maximum processing rate approaches 800 Hz, with almost 100% track finding efficiency and adequate p_T and vertex resolution of σ_pT∼0.05 p²_T (p_T in GeV) and σ_z−vtx∼9 cm. The online performance of a highly parallel system with dynamic loading such as the CTD-SLT is characterised by two quantities: the average throughput (speed) and the processing time per event (latency). Detailed understanding of these quantities for the CTD-SLT derived from operational experience, simulations and a simple model is presented.     

Relaxation modulus—complex modulus interconversion for linear viscoelastic materials

This paper is aimed at exploring the interconversion path between the relaxation modulus E(t) and the corresponding complex modulus E ^?(ω) for linear viscoelastic solid materials. In contrast to other approximate methods, the fast Fourier transform (FFT) algorithm is directly applied on the time-dependent part of the viscoelastic response R(t). Firstly, the method foundations are presented. Then, a theoretical example is performed by means of a generalized Maxwell model, where the influence of sampling conditions and eventual experimental error and data dispersion is analyzed. Finally, an application example using experimental data is carried out to assess the method. As a result, the proposed procedure allows obtaining the complex modulus by means of relaxation tests, and vice versa.     

A fast hardware track-finder for the CDF central tracking chamber

We describe the design, construction, and preliminary operation of a hardware track-finder used in the trigger for the Collider Detector at Fermilab (CDF). The track-finder is a 19 stage digital pipeline which uses fast timing information from the central tracking chamber (CTC) to find high momentum tracks. It then transmits information about the tracks to the CDF trigger system for a final decision. The track finder has 8 programmable thresholds between 2.5 and 15 GeV. A search for all high momentum tracks in the central tracking chamber can be completed in an average of 2.5 μs per event. The momentum resolution is δP_t/P_t² = 3.5%, with a high efficiency that is independent of track density.     

A Galerkin multiharmonic procedure for nonlinear multidimensional random vibration

The stationary vector-response of a multidimensional system of nonlinear dynamical equations with random input, is expanded into a finite trigonometric Fourier series on a time interval T (the period). The unknown Fourier coefficients are solutions of a system of nonlinear algebraic equations, obtained by harmonic balance. Let d be the dimension of the problem and M be the number of harmonics. The computational iterative algorithm consists of solving at each step, M-times a 2d-dimensional linear system in place of a linear system with dimension 2Md, via repetitive applications of the Fast Fourier Transform (F.F.T.) procedure to compute at each iteration the Fourier coefficients of the nonlinear terms. The finite Fourier series thus obtained, is called a Galerkin approximation of order M, on the time interval T, of the stationary response process. Good trajectory approximations will be obtained, provided M is large enough. Consistent P.S.D. estimators will be obtained by “smoothing” the square modulus of the computed Fourier coefficients, as in a real time spectral analyser, provided M and T are large enough. The method will be carried out on examples from vehicle dynamics, in Section 4. The results will be compared to the corresponding experimental ones. The mathematical justification of the existence of Galerkin's approximations is given in the Appendix.     

A C++ object-oriented toolkit for track finding with k-dimensional hits

A library is described for the recognition of tracks in a set of hits. The hits are assumed to be k-dimensional points (k-d), with k≥1, of which a subset can be grouped into tracks by using short-range correlations. A connection graph between the hits is created by sorting the hits first in k-d space using one of the developed, fast, k-space containers. The track-finding algorithm considers any connection between two hits as a possible track seed and grows these seeds into longer track segments using a modified depth-first search of the connection graph. All hit-acceptance decisions are called via abstract methods of an acceptance criterion class which isolates the library from the application's hit and track model. An application is tuned for a particular tracking environment by creating a concrete implementation for the hit and track acceptance calculations. The implementer is free to trade tracking time for acceptance complexity (influencing efficiency) depending on the requirements of the particular application. Results for simulated data show that the track finding is both efficient and fast even for high noise environments.     

Kalman filter tracking in a Cherenkov neutrino telescope

The reconstruction of tracks in underwater Cherenkov neutrino telescopes is strongly complicated due to large background counting rate originates from ⁴⁰K beta decay and to the electromagnetic showers accompanying high energy muons together with the effects of light propagation in the water, in particular the photon scattering. These two effects lead to a non-linear problem with a non-Gaussian measurement noise. A method for track reconstruction based on Kalman filter approach in this situation is presented. We use Gaussian Sum Filter algorithm to take into account non-Gaussian process noise. While usual Kalman filter estimators based on linear least-square method are optimal in case all observations are Gaussian distributed, the Gaussian Sum Filter offers a better treatment of non-Gaussian process noise and/or measurement errors when these are modeled by Gaussian mixtures. As an example of the application, the results of muon track reconstruction in NEMO underwater neutrino telescope are presented as well as the comparison of its capability with other standard track reconstruction methods.     

远程水声扩频通信时变多普勒估计与码片同步联合处理算法

在低信噪比的远程浅海水声移动通信中,传统多普勒估计算法难以有效跟踪时变多普勒因子,针对该问题提出了一种基于时频联合搜索的新的时变多普勒跟踪算法。利用正交支路扩频码的扩频增益和互相关特性,结合迭代处理技术,搜索扩频码符号在不同码片相位下的多普勒频谱峰值,选择具有最大峰值的频谱对应的多普勒因子和码片相位,对信号进行多普勒补偿和码片同步。蒙特卡洛仿真表明,该算法能够在信噪比为-18 dB的情况下有效地对10 m.s~(-1)以内产生的时变多普勒进行逐符号跟踪补偿。算法经过海试测试,在远程浅海移动通信中成功完成了多普勒跟踪估计,通信误码率达到10~(-3)。     

Linear models for non-Gaussian processes and applications to linear random vibration

Linear models are finite sums of specified deterministic, continuous functions of time with random coefficients. It is shown that linear models provide (i) accurate approximations for real-valued non-Gaussian processes with continuous samples defined on bounded time intervals, (ii) simple solutions for linear random vibration problems with non-Gaussian input, and (iii) efficient techniques for selecting optimal designs from collections of proposed alternatives. Theoretical arguments and numerical examples are presented to establish properties of linear models, illustrate the construction of linear models, solve linear random vibration with non-Gaussian input, and propose an approach for optimal design of linear dynamic systems. It is shown that the proposed linear model provides an efficient tool for analyzing linear systems in non-Gaussian environment.     

Coupling of physical and modal components for analysis of moving non-linear dynamic systems on general beam structures

A general, well-structured and efficient method is advanced for the solution of-a large class of dynamic interaction problems including a non-linear dynamic system running at a prescribed time-dependent speed on a linear track or guideway. The method uses an extended state-space vector approach in conjunction with a complex modal superposition. It allows for the analysis of structures containing both physical and modal components. The physical components studied here are vehicles modelled as linear or non-linear discrete mass–spring–damper systems. The modal component studied is a linear continuous model of a track structure containing beam elements which can be generally damped and which can be embedded in a three-parameter damped Winkler-type foundation. The complex modal parameters of the track structure are solved for. Algebraic equations are established which impose constraints on the transverse forces and accelerations at the interfaces between the moving dynamic systems and the track. An irregularity function modelling a given non-straight profile of the non-loaded track or a non-circular periphery of the wheels is also accounted for. Loss of contact and recovered contact between a vehicle and the track can be treated. The system of coupled first-order differential equations governing the motion of the vehicles and the track and the set of algebraic constraint equations are together compactly expressed in one unified matrix format. A time-variant initial-value problem is thereby formulated such that its solution can be found in a straightforward way by use of standard time-stepping methods implemented in existing subroutine libraries. Examples for verification and application of the proposed method are given. The present study should be of particular value in railway engineering.     

Transistor Doping Experiments on Superconducting CaCuO2 and C60 Interpreted on a Bond Ordering Model

The curve shape of T _c vs. holes injected by fields (transistor doping) of CaCuO₂ and C₆₀ are interpreted on a charge or bond ordering [BO] model. For CaCuO₂ both the magnitude of optimal T _c (89 K vs. a calculated 83 K) and the linear portions around a “sharp” T _c peak at h ～ 0.17 = 1/6 are in accord with a universal algorithm for cuprates, in which T _c scales linearly with radical bond density to an optimal BO. These linear regions extrapolate to h = 0 and 1/3 respectively. Small trends to electronic freezing are observed at h = 1/8. A second linear region extends from h ～ 1/12 to 1/16 with 4 times the slope of the first linear region, indicating a second mode of BO filling. A surprisingly similar behavior is observed for transistor doped C₆₀ type materials with characteristic sequence of BO dictated hole concentrations for T _c onset, rise, a linear region extrapolating to T _c = 0 at h = 0, indications for electronic freezing, a sharp peak and linear decrease thereafter. This suggests that a common phenomenology obtains for all high T _c materials, representing generally an ordering phenomenon of doped covalent radical bonds.     

Construction and decoding of matrix-product codes from nested codes

We consider matrix-product codes ${[C_1\cdots C_s] \cdot A}$ , where ${C_1, \ldots , C_s}$ are nested linear codes and matrix A has full rank. We compute their minimum distance and provide a decoding algorithm when A is a non-singular by columns matrix. The decoding algorithm decodes up to half of the minimum distance.     

Linear m-gap-consecutive k-out-of-r-from-n:F systems

This paper proposes a new model that generalizes the linear consecutive k-out-of-r-from-n system. In this model the system consists of n linearly ordered statistically independent identical elements and fails if the gap between any pair of groups of r consecutive elements containing at least k failed elements is less than m elements. An algorithm for system reliability evaluation is suggested, which is based on an extended universal moment generating function. Examples of system reliability evaluation are presented.     

An algorithm for discrete Chebyshev linear approximation with linear constraints

We describe a dual linear programming algorithm for solving the discrete Chebyshev (or l_∞) approximation problem subject to any type of linear constraints. The numerical results provided here indicate that the present algorithm is an efficient extension of the Barrodale and Phillips Chebyshev algorithm, to which it reduces in the absence of constraints.     

The role of hole mobility in scintillator proportionality

Time-dependent radial diffusion and drift are modeled in the high carrier concentration gradient characteristic of electron tracks in scintillators and other radiation detector materials. As expected, the lower mobility carrier (typically the hole) controls the ambipolar diffusion. Carrier separation when electron and hole mobilities are unequal produces a built-in radial electric field near the track analogous to an n-intrinsic semiconductor junction. The diffusion is shown to have significant effects on both the low dE/dx and high dE/dx ends of electron light-yield curves and their respective contributions to nonproportionality. In CsI:Tl, it is shown that electron confinement toward the end of the track accentuates high-order quenching such as Auger recombination or dipole-dipole transfer, while in HPGe extremely rapid (<1 fs) dilution of carrier concentration by radial diffusion renders Auger quenching negligible. Separation of geminate carriers is accentuated in the beginning of the track if electron and hole mobilities are widely unequal as in CsI:Tl, leading to bimolecular recombination of trapped carriers by slower thermal hopping routes as the favored channel at low dE/dx.     

Applying likelihood on Hopfield neural network for radar tracking

Abstract

The multiple‐target tracking (MTT) algorithm plays an important role in radar systems. Data association is the most important technique to solve the tracking problems associating dense measurements with existing tracks. A new approach applying Likelihood to measurements and existing tracks in a radar system based on Neural Network computation is investigated in this paper. The proposed algorithm will solve both the data association and the target tracking problems simultaneously. With this approach, the matching between radar measurements and existing target tracks can achieve global relevance. Computer simulation results indicate the ability of this algorithm to keep track of targets under various conditions.     

Reconstructing the flight kinematics of swarming and mating in wild mosquitoes

We describe a novel tracking system for reconstructing three-dimensional tracks of individual mosquitoes in wild swarms and present the results of validating the system by filming swarms and mating events of the malaria mosquito Anopheles gambiae in Mali. The tracking system is designed to address noisy, low frame-rate (25 frames per second) video streams from a stereo camera system. Because flying A. gambiae move at 1–4 m s⁻¹, they appear as faded streaks in the images or sometimes do not appear at all. We provide an adaptive algorithm to search for missing streaks and a likelihood function that uses streak endpoints to extract velocity information. A modified multi-hypothesis tracker probabilistically addresses occlusions and a particle filter estimates the trajectories. The output of the tracking algorithm is a set of track segments with an average length of 0.6–1 s. The segments are verified and combined under human supervision to create individual tracks up to the duration of the video (90 s). We evaluate tracking performance using an established metric for multi-target tracking and validate the accuracy using independent stereo measurements of a single swarm. Three-dimensional reconstructions of A. gambiae swarming and mating events are presented.     

快速运动目标的Mean shift跟踪算法

针对Mean shift本身的理论缺陷,提出Mean shift和卡尔曼滤波器相结合的快速目标跟踪算法。利用卡尔曼滤波器来获得每帧Mean shift算法的起始位置,然后再利用Mean shift算法得到跟踪位置。在目标出现大比例阻挡情况时,利用卡尔曼残差的计算来关闭和打开卡尔曼滤波器,此时,目标位置的线性预测替代了卡尔曼的作用。试验证明,本算法可以实现对快速运动目标的跟踪,对阻挡也有很好的鲁棒性。     

Nonlinear calibration curves in secondary ion mass spectrometry for quantitative analysis of gesi heterostructures with nanoclusters

For the first time in the practice of secondary ion mass spectrometry, we obtained a nonlinear calibration curve for the ratio of the cluster and elementary secondary ions of germanium Ge₂/Ge without secondary ions of silicon, which enables the quantification of germanium in Ge _x Si_1–x heterostructures in the entire range of 0 < x ≤ 1. We developed a method for quantitative lateral analysis based on the plotting of a lateral map of x. An algorithm to identify and analyze the lateral heterogeneity of x in Ge _x Si_1–x heterostructures with 3D clusters by comparing the results of depth profiling analysis, obtained using linear and nonlinear calibration curves, is developed, and concentration x in the self-assembled nanoislands is determined.     

Calibration factors for determination of relativistic particle induced fission rates in U, U, Th, Pb and Au foils

Calibration factors w, for determination of fission rate in metallic foils of ^natU, ²³⁵U, ²³²Th, ^natPb and ¹⁹⁷Au were determined for foils in contact with synthetic mica track detectors. Proton-induced fission at proton energies of 0.7 GeV and 1.5 GeV were used. Using our experimental results as well as those of the other authors, w for different foil-mica systems were determined. Two methods were used to calculate w, relative to the calibration factor for uranium-mica system, which has been obtained in a standard neutron field of energy 14.7 MeV. One of these methods requires the knowledge of the mean range of the fission fragments in the foils of interest and other method needs information on the values of the fission cross-sections at the required energies as well as the density of the tracks recorded in the track detectors in contact with the foil surfaces. The obtained w-values were compared with Monte Carlo calculations and good agreements were found. It is shown that a calibration factor obtained at low energy neutron induced fissions in uranium isotopes deviates only by less than 10% from those obtained at relativistic proton induced fissions.