双栅低能电子积分谱仪的实验研究

结合电子中微子质量测量研制高分辨率β谱仪的需要,我们开展了低能电子减速积分谱仪的实验研究。减速积分谱仪已出现多年了。五十年代哈密顿,六十年代卡德维尔,以及七十年代的赫契托等都曾作过减速栅型谱仪的工作。他们所用都是双层球栅分析栅网。赫契托用了每毫米四线的32°张角的球面栅,透射率达20%,对于200—1400eV的电子分辨率为0.06%。但前人所研究谱仪都是能量极低(2 keV以下)、尺寸较小的。为了适应中微子质量测量的要求,我们在较高能区作了实验研究。     

Digital-sampling systems in high-resolution and wide dynamic-range energy measurements: Comparison with peak sensing ADCs

The use of fast digital sampling techniques in Nuclear Physics experiments as a replacement of the standard analog signal processing methods is discussed for applications needing high-resolution signal amplitude measurements. This is for example the case of a solid-state detector with a charge-sensitive preamplifier, processed using fast digital sampling methods. Under very general assumptions, an expression for the achievable resolution and dynamic range of the system is reported, valid for any detector/digitizer/digital-filter combination, taking into account the detector noise and the ADC properties, namely the Effective Number of Bits (ENOB) and the sampling frequency. The system properties are summarized using the parameter PSENOB, i.e. the “Peak-Sensing-Equivalent Number of Bits”. These results can be used to predict the attainable performances in various applications, possibly requiring a resolution/dynamic-range trade-off. Numerical examples for some representative cases in γ-ray spectroscopy and charged particle experiments are reported, demonstrating that the equivalent performances of a 15 bit peak-sensing ADC are feasible with today-available sampling ADCs. For ease of presentation, other non-trivial effects as baseline- and non-linearity-related issues as well as experimental tests of the proposed approach are presented in a companion paper [L. Bardelli, G. Poggi, Digital sampling-systems in high-resolution and wide dynamic-range energy measurements: finite time window, baseline effects, and experimental tests, this issue].     

A kinematically compatible framework for cooperative payload transport by nonholonomic mobile manipulators

In this paper, we examine the development of a kinematically compatible control framework for a modular system of wheeled mobile manipulators that can team up to cooperatively transport a common payload. Each individually autonomous mobile manipulator consists of a differentially-driven Wheeled Mobile Robot (WMR) with a mounted two degree-of-freedom (d.o.f) revolute-jointed, planar and passive manipulator arm. The composite wheeled vehicle, formed by placing a payload at the end-effectors of two (or more) such mobile manipulators, has the capability to accommodate, detect and correct both instantaneous and finite relative configuration errors. The kinematically-compatible motion-planning/control framework developed here is intended to facilitate maintenance of all kinematic (holonomic and nonholonomic) constraints within such systems. Given an arbitrary end-effector trajectory, each individual mobile-manipulator's bi-level hierarchical controller first generates a kinematically-feasible desired trajectory for the WMR base, which is then tracked by a suitable lower-level posture stabilizing controller. Two variants of system-level cooperative control schemes—leader-follower and decentralized control—are then created based on the individual mobile-manipulator control scheme. Both methods are evaluated within an implementation framework that emphasizes both virtual prototyping (VP) and hardware-in-the-loop (HIL) experimentation. Simulation and experimental results of an example of a two-module system are used to highlight the capabilities of a real-time local sensor-based controller for accommodation, detection and corection of relative formation errors.     

高分辨^13C NMR在聚合物辐射化学中的应用

综述了高分辨~(13)C核磁共振谱(~(13)C NMR)在聚合物辐射化学研究中的应用。重点介绍了用固体高分辨~(13)C NMR研究聚合物辐射交联结构途径和应用范围。     

基于傅氏变换特点的一种速度分析新方法

本文基于速度分析原理和傅里叶变换特点，假设相邻地震道来自地下同一反射界面的反射波波形基本不变，提出一种新的速度分析方法。该法首先要求沿着ｔ０时间和叠加速度决策的双曲延迟数据中提取向量序列，进行快速傅氏变换，将时间域数据转换到频率域。     

Horizons for new semiconducting materials*

The properties of existing semiconductors limit performance in a whole range of devices and leave many interesting potential applications (e.g. for lighting, power generation or air-conditioning) possible in principle but technologically impracticable. Better properties, then, could be valuable. They could be obtained in two ways, by discovering new materials (a long-range option apt for academic investigation) or by modifying existing materials either chemically (e.g. by forming solid solutions, perhaps of highly unconventional type) and/or physically (e.g. by low dimensional confinement effects). These options are reviewed and some of their implications explored.     

Gandalf

We give a brief overview of the first-order classical logic component in the Gandalf family of resolution-based automated theorem provers for classical and intuitionistic logics. The main strength of the described version is a sophisticated algorithm for nonunit subsumption.     

DRASTIC IMPROVEMENT OF THE RESOLUTION OF AEROSOL SIZE SPECTROMETERS VIA AERODYNAMIC FOCUSING: THE CASE OF VARIABLE-PRESSURE IMPACTORS*

Due to their finite inertia, particles carried in a gas follow trajectories that differ from fluid streamlines. They may thus be size-segregrated, though only with the modest resolving power allowed by the dependence of their trajectories on the fluid streamline Ψin which they are initially seeded. This limitation is greatly reduced in the present work via aerodynamic focusing, a phenomenon discovered by Israel and Friedlander and briefly reviewed here. McM urry and his colleagues have recently shown that passage through a succession of coaxial converging nozzles brings virtually into the axis of symmetry (Ψ= 0) all particles within a relatively wide size range. Considerable gains in instrument resolution may thus be achieved by inserting a series of focusing nozzles right upstream of an aerosol size spectrometer. This general principle is demonstrated here for the case of variable-pressure impactors, which are ideally suited for coupling to the focusing lenses. The resolution improvements found are impressive, particularly in the viscous and compressible regimes.     

Some evidence for conflict resolution in impression formation.

This experiment is designed to reveal, in a S's "first impressions" of a purportedly living stimulus person, tendencies to resolve a conflict experimentally created in that stimulus person. In the condition of strong conflict, the person is simultaneously a member of groups characterized by an upper socioeconomic orientation and the Communist party. In the weak stimulus condition, the stimulus person is a member of the same socioeconomic groups and the Socialist party. In the control situation, there are no incompatible memberships. The majority of S's under both stimulus conditions attempt to resolve the stimulus person's conflict; however, a greater proportion of the S's, under the strong condition, fail to attempt a resolution. The direction of conflict resolution is more equally distributed in the strong condition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analytical electron microscopy of aluminium alloys

X-ray microanalysis and electron energy loss spectroscopy of thin foils constitute the important techniques of high resolution chemical analysis using the electron microscope. The technique of x-ray microanalysis is discussed in this paper with particular emphasis on the study of aluminium alloys using a dedicated scanning transmission electron microscope (stem). The principle of determining chemical composition from observed x-ray peak intensities including the absorption of x-rays and beam broadening in thin foils are considered. The accuracy of peak intensity measurement and detection limits in x-ray microanalysis are illustrated with reference to Al-Mn alloys. The Cliff-Lorimer (k) factors for manganese, iron and copper with respect to aluminium were obtained from standard samples. Identification of phases in 1100 and 1200 aluminium and 3008 (Al-Mn-Zr) alloy were carried out from measured intensities of x-ray peaks. The experimental results emphasize the value of developing techniques for extracting the particles from the aluminium matrix. The transition phases formed in Al-6%Zn-3%Mg and Al-4% Cu were investigated by micro-diffraction and x-ray microanalysis.