Uncertainty analysis technique for OMEGA Dante measurements

The Dante is an 18 channel x-ray filtered diode array which records the spectrally and temporally resolved radiation flux from various targets (e.g., hohlraums, etc.) at x-ray energies between 50 eV and 10 keV. It is a main diagnostic installed on the OMEGA laser facility at the Laboratory for Laser Energetics, University of Rochester. The absolute flux is determined from the photometric calibration of the x-ray diodes, filters and mirrors, and an unfold algorithm. Understanding the errors on this absolute measurement is critical for understanding hohlraum energetic physics. We present a new method for quantifying the uncertainties on the determined flux using a Monte Carlo parameter variation technique. This technique combines the uncertainties in both the unfold algorithm and the error from the absolute calibration of each channel into a one sigma Gaussian error function. One thousand test voltage sets are created using these error functions and processed by the unfold algorithm to produce individual spectra and fluxes. Statistical methods are applied to the resultant set of fluxes to estimate error bars on the measurements.     

Design and testing of a hybrid polymeric electrostrictive/piezoelectric beam with bang–bang control

Electrostrictive materials, hard ceramics and soft polymers, have been used as precision actuators in many engineering applications. This study is to examine bang–bang control performance of a hybrid Plexiglas beam laminated with polymeric electrostrictive (RTV 270) actuator and piezoelectric polyvinylidene fluoride (PVDF) sensor layers using both analytical and experimental techniques. Material characteristics are calibrated via static testing first; a hybrid beam model is then fabricated and an experiment set-up, consisting of a bang–bang controller, high-voltage amplifier, data acquisition system and the hybrid beam system, is designed to evaluate vibration control characteristics (i.e., damping ratio estimation) of the hybrid beam subjected to various control conditions. Due to the quadratic behaviour of electrostrictive materials, the controller activates the electrostrictive actuator only in upward motion of the beam, with reference to signals generated from the piezoelectric sensor. Base on constitutive equations and dynamic/control characteristics, a mathematic hybrid beam model is also derived from the electrostrictive thin shell theory and its dynamic responses, based on the finite difference discretization, are simulated to predict damping ratios resulting from control forces induced by the electrostrictive actuators. Dynamic responses (with and without control) of the physical beam model are measured and compared with simulation results. Favourable comparison suggests that the mathematical model describes the experimental model very well and its application to other advanced structures can be proceeded.     

A spherical crystal imager for OMEGA EP

A narrowband x ray imager for the Cu K(α) line at ~8 keV using a spherically bent quartz crystal has been implemented on the OMEGA EP laser at the University of Rochester. The quartz crystal is cut along the 2131 (211) planes for a 2d spacing of 0.3082 nm, resulting in a Bragg angle of 88.7°, very close to normal incidence. An optical system is used to remotely align the spherical crystal without breaking the vacuum of the target chamber. The images show a high signal-to-background ratio of typically >100:1 with laser energies ≥1 kJ at a 10-ps pulse duration and a spatial resolution of less than 10 μm.     

Gamma spectroscopy at high counting rates with large volume germanium detectors

The energy resolution and the throughput rate of a quasi-trapezoidal filter, based on a modified version of the DL-RC circuit, have been studied as a function of the counting rate up to ∼10⁵ counts per second.The performance of the modified DL-RC circuit is compared with that of a semi-Gaussian active filter and that of a quasi-trapezoidal gated integrator.     

Source characterization and modeling development for monoenergetic-proton radiography experiments on OMEGA

A monoenergetic proton source has been characterized and a modeling tool developed for proton radiography experiments at the OMEGA [T. R. Boehly et al., Opt. Comm. 133, 495 (1997)] laser facility. Multiple diagnostics were fielded to measure global isotropy levels in proton fluence and images of the proton source itself provided information on local uniformity relevant to proton radiography experiments. Global fluence uniformity was assessed by multiple yield diagnostics and deviations were calculated to be ～16% and ～26% of the mean for DD and D(3)He fusion protons, respectively. From individual fluence images, it was found that the angular frequencies of ?50 rad(-1) contributed less than a few percent to local nonuniformity levels. A model was constructed using the Geant4 [S. Agostinelli et al., Nuc. Inst. Meth. A 506, 250 (2003)] framework to simulate proton radiography experiments. The simulation implements realistic source parameters and various target geometries. The model was benchmarked with the radiographs of cold-matter targets to within experimental accuracy. To validate the use of this code, the cold-matter approximation for the scattering of fusion protons in plasma is discussed using a typical laser-foil experiment as an example case. It is shown that an analytic cold-matter approximation is accurate to within ?10% of the analytic plasma model in the example scenario.     

作业时间测定的可信度分析

作业时间测定是制定标准作业时间的重要途径之一。针对作业时间测定得到的数据的可信度问题．提出了一种分析方法，从而保证了通过作业时间测定得到的数据的可靠性。     

工作流时间性能分析方法

工作流性能分析是对工作流进行评价和优化的基础,时间则是反映工作流性能的一个重要方面。工作流管理系统中通常有属于不同工作流的多个实例同时运行,从而在不同工作流的多个实例之间造成资源竞争。对此,从资源的角度出发,利用排队论提出了一种通用的工作流时间性能分析方法,其中采用工作流实例平均响应时间作为工作流时间性能的分析与评价的指标。最后,通过实例说明了该方法的可行性和有效性,并提出了未来的研究方向。     

The coincidence counting technique for orders of magnitude background reduction in data obtained with the magnetic recoil spectrometer at OMEGA and the NIF

A magnetic recoil spectrometer (MRS) has been built and successfully used at OMEGA for measurements of down-scattered neutrons (DS-n), from which an areal density in both warm-capsule and cryogenic-DT implosions have been inferred. Another MRS is currently being commissioned on the National Ignition Facility (NIF) for diagnosing low-yield tritium-hydrogen-deuterium implosions and high-yield DT implosions. As CR-39 detectors are used in the MRS, the principal sources of background are neutron-induced tracks and intrinsic tracks (defects in the CR-39). The coincidence counting technique was developed to reduce these types of background tracks to the required level for the DS-n measurements at OMEGA and the NIF. Using this technique, it has been demonstrated that the number of background tracks is reduced by a couple of orders of magnitude, which exceeds the requirement for the DS-n measurements at both facilities.     

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A Model Gamma Tomograph and the Visualization of Objects in Gamma Rays

It is shown that the features of the detection of simultaneous photon pairs make it possible to visualize a macroscopic object in scattered -rays.     

Autoradiography: its methodology at the present time

The autoradiographic methods used in biological and medical research are reviewed from an historical viewpoint. It is pointed out that early methodological research was directed at the selection of suitable detector substances for radiation (nuclear emulsions) and at the preparation and application of suitable layers of these detectors to biological samples. On the other hand, later research was more concentrated on aspects of the preparation of the biological components of the specimens. In particular, the retention of biochemicals in the tissue sample was studied in detail. Research in the quantification of the emulsion response to α and β radiation paved the way for certain quantitative applications of autoradiography. This has been followed by the derivation of models for the measurement of image spread and the evolution of image analysis methods which allow refined determinations of the specific radioactivity of fine structures taking into account losses and gains of silver grains by image spread. The sum of all these advances is a methodology capable of localizing and quantifying radioactivity and hence marking chemical processes from an organism and organ level down almost to the present limits of anatomical delineation.     

体感诱发EEG的混沌时间序列分析

电刺激左腿足三里穴,采用单极导联法记录,C3、CA、F3、F4、13、T4的脑电图信号,在对原始脑电信号进行去噪处理后,进行混沌时间序列分析.使用小数据量法和G-P算法分别计算EEG时间序列的最大Lyapunov指数和关联维数.结果显示各个状态下脑电时间序列的最大Lyapunov指数均大于零,说明脑电信号可能是混沌的.比较刺激前、刺激时以及刺激后的脑电时间序列的关联维变化,可以发现刺激左腿足三里穴可以引起大脑右侧脑电信号的关联维数显著增加,尤其是额叶和颞叶部分,说明该脑区在刺激时出现比较明显的激活,为大脑认知功能研究提供了理论依据.     

New Neutron, Gamma and X-Ray Detectors

New detectors intended to record absorbed doses of neutron, gamma and X-radiation in a range of 0–1500 Mrad are described. One of these detectors is based on dibutylphthalate (DP), another is based on epoxy resin, and a 5-40 detector is a mixture of dibutylphthalate and epoxy resin. Experimental methods of detector calibration and for the interpretation of measured absorbed doses are given for these detectors. All three detectors cover a measured dose range of 0–30000 Mrad. The measurement accuracy is ±10% and, in fact, does not depend on the radiation dose rate within 20–2000 rad/s at temperatures of 20–80°C. The detectors can be applied in the atomic industry, radiation biotechnology, medicine (for object radicidation), the food industry for radiation handling of foodstuffs, radiation processing of paper (for example, mail radiation processing), etc.     

Fracture analysis of composites by time independent moving-crack orthotropic XFEM

Time-independent orthotropic enrichment functions are introduced for dynamic propagation analysis of moving cracks in composites by the extended finite element method (XFEM). The proposed enrichment functions are derived from the analytical solutions for a moving/propagating crack in orthotropic media, and can be considered as a new extension to the available XFEM techniques for dynamic analysis of stationary and moving cracks in orthotropic materials. They are included within the framework of partition of unity and XFEM to enhance the accuracy of basic FEM solution near a moving crack tip in orthotropic media. The method allows for analysis of the whole crack propagation pattern on an unaltered finite element mesh, which is independently defined from the existence of any predefined crack or its propagation path. A combination of dynamic crack initiation toughness and crack orientation along the maximum circumferential stress is used to design a relatively simple and efficient formulation. Dynamic stress intensity factors (DSIFs) are evaluated by means of the domain separation integral method and the dynamic energy release rate. The time dependent XFEM equations are constructed by discretizing the standard weak formulation of the governing elastodynamics equation. They are solved by the unconditionally stable Newmark time integration scheme. A number of benchmark and test problems are simulated and the results are compared with the available reference results to illustrate the accuracy and efficiency of the proposed scheme.     

Stochastic analysis of Poisson impact series using discrete form,spectrum analysis and time correlation

A stochastic model based on Poisson impact series is developed from a random pulse train model. Using the discrete form of the expectation function, first- and second-order time correlation functions are generated. Then, the force and power spectral density functions are generated by the Fourier transform of the first- and second-order correlation functions, respectively. Experimental force and power spectra are compared with those from the developed model and an existing model using single, multiple and ensemble averaged impact samples. Overlapping and consistent matching occur in most of the regions in these comparisons. The effects of noise and pulse shape deviation are discussed. It is shown theoretically and experimentally that the signal-to-noise ratio increases with the impaction rate. Using ensemble averages of a 100 samples, the impact magnitude and its arrival time is validated to be Gaussian and Uniformly distributed. The signal-to-error ratio increases with the number of ensemble averages. The established model is utilised to carry out modal tests of a space truss. Comparing modal parameters, such as mode shapes, natural frequencies, and damping ratios, consistent matching is observed with those obtained from the random noise test.     

Finite element analysis of transient dynamic viscoelastic problems in time domain

In this paper, the simplified and stable finite element method is presented for the time domain analysis of the transient dynamic viscoelastic problems, for which the weak form is obtained by applying the Galerkin's method to the equations of motion in time integral which do not contain the inertia terms explicitly, but the inertia effect is taken into account, and discretized spatially to obtain the semidiscrete equations in time integral. In the temporal approximation, only the time interpolation functions are used for approximating the dependent variables on the divided time axis, while the time integration schemes such as the Newmark and Houbolt methods are not necessary in contrary to the conventional approach. To show the validity and applicability, two-dimensional examples are given and solved for the displacements and stresses, especially for the dynamic stress concentrations by the wave diffraction, which are discussed in detail at the aspect of the viscoelastic damping. To the authors' knowledge, no previous results except for the test example exist in the literature.     

模糊时态工作流网的建模和时间可能性分析

现有的工作流模型中很少考虑时间不确定性,以及资源和变迁的有效时间约束问题。为此,通过对模糊时间Petri网的各个元素中引入时间约束,提出了一种工作流模型,即模糊时态工作流网,给出了该工作流网中各种时态元素的计算方法,并讨论了利用该网对工作流中的时态现象进行时间建模和时间可能性分析的方法。最后,用一个实例解释了这些方法的使用。模糊时态工作流网可以对带有时间不确定性和时间约束的工作流模型中的时态信息进行建模,并对一些典型的时间约束进行时间可能性分析。     

Signal-to-noise analysis of biomedical photoacoustic measurements in time and frequency domains

Sensitivity analysis of photoacoustic measurements is conducted using estimates of the signal-to-noise ratio (SNR) achieved under two different modes of optical excitation. The standard pulsed time-domain photoacoustic imaging is compared to the frequency-domain counterpart with a modulated optical source. The feasibility of high-SNR continuous wave depth-resolved photoacoustics with frequency-swept (chirp) modulation pattern has been demonstrated. Utilization of chirped modulation waveforms achieves dramatic SNR increase of the periodic signals and preserves axial resolution comparable to the time-domain method. Estimates of the signal-to-noise ratio were obtained using typical parameters of piezoelectric transducers and optical properties of tissue.     

实时环境下的对弈机器人控制系统设计与分析

介绍了一种能够实现与人进行中国象棋对弈的对弈机器人及其控制系统的设计,并对实时环境下的软件开发进行了详细说明和分析。经实际运行证明,该机器人作为国内利用开放式控制器开发成功的第一台对弈机器人,具有较高的开放性、智能性、可靠性和实用性。