Irradiation effects of a 10 MeV neutron beam on a Nd-Fe-B permanent magnet

The effects of irradiation of a Nd-Fe-B permanent magnet by fast neutrons was investigated. The decrease in measured magnetic flux density at the center of the magnets were 0.6%, 6.9%, 25.2% and 47.3% after continuous irradiation of 1.1 kGy, 3.7 kGy, 5.6 kGy and 7.4 kGy, respectively. On the other hand, the decrease due to non-continuous irradiation, in which the magnet was first irradiated at 3.7 kGy, then irradiated again at 3.7 kGy nine months later, was 14% smaller than that of continuous irradiation, even for the same total dose. The temperature coefficient of the magnetization did not change with irradiation. Some radioactive materials, such as ¹⁴⁷Nd, ¹⁵¹Pm, and ⁵⁴Mn, were detected in the magnet after irradiation.     

RPD钻机在云桂铁路某隧道超前预报中的应用

近年来,随着隧道施工地质条件的日益复杂化,如何有效地避免隧道施工中的事故,保障人民生命及财产的安全显得尤为重要。日本"矿研"RPD系列多功能钻机具有长距离超前地质预报、注浆止水、防突以及超前管棚施工等功能特点,极大地保障了隧道的安全施工,满足日益复杂化的施工需要。文章介绍了该钻机的产品功能特性,着重从超前预报功能上介绍了该RPD多功能钻机在云桂铁路某隧道中的应用成果。     

基于路径识别算法的智能车控制系统的设计

介绍了一种基于光电传感器及连续路径识别算法的智能车控制系统。首先对系统设计的总体方案及主芯片MC9S12DG128B进行介绍,然后介绍了具体系统的硬件设计和软件设计,重点对关键的电路和算法的实现进行了详细的阐述。最后给出了实验的调试结果。     

Proton energy determination using activated yttrium foils and ionization chambers for activity assay

Excitation functions of the ⁸⁹Y(p, xn) nuclear reactions were measured up to 18 MeV by the conventional activation method using the stacked-foil technique, and the irradiation of single foils. Activity assays of the irradiated foils were performed via ionization chamber and gamma spectroscopy methods. Activity ratios of the activation products were measured in two different facilities and evaluated for use as a practical and simple method for proton energy determinations. Cross section values measured in this work were compared with published data and with theoretical values as determined by the nuclear reaction model code EMPIRE II. In general, there was a good agreement between the experimental and theoretical values of the cross section data. Activity ratios of the isomeric and ground state of ⁸⁹Zr measured via ionization chamber were found to be useful for proton energy determinations in the energy range from 7 to 15 MeV. Proton energies above 13 MeV were accurately determined using the ^89gZr/⁸⁸Zr and ^89gZr/⁸⁸Y activity ratios measured via gamma spectroscopy.     

Optimal Placement and Sizing of Distributed Generation Using Metaheuristic Algorithm

Power loss and voltage uncertainty are the major issues prevalently faced in the design of distribution systems. But such issues can be resolved through effective usage of networking reconfiguration that has a combination of Distributed Generation (DG) units from distribution networks. In this point of view, optimal placement and sizing of DGs are effective ways to boost the performance of power systems. The optimum allocation of DGs resolves various problems namely, power loss, voltage profile improvement, enhanced reliability, system stability, and performance. Several research works have been conducted to address the distribution system problems in terms of power loss, energy loss, voltage profile, and voltage stability depending upon optimal DG distribution. With this motivation, the current study designs a Chaotic Artificial Flora Optimization based on Optimal Placement and Sizing of DGs (CAFO-OPSDG) to enhance the voltage profiles and mitigate the power loss. Besides, the CAFO algorithm is derived from the incorporation of chaos theory concept into conventional artificial flora optimization AFO algorithm with an aim to enhance the global optimization abilities. The fitness function of CAFO-OPSDG algorithm involves voltage regulation, power loss minimization, and penalty cost. To consider the actual power system scenario, the penalty factor acts as an important element not only to minimize the total power loss but to increase the voltage profiles as well. The experimental validation of the CAFO-OPSDG algorithm was conducted against IEEE 33 Bus system and IEEE 69 Bus system. The outcomes were examined under various test scenarios. The results of the experiment established that the presented CAFO-OPSDG model is effective in terms of reducing the power loss and voltage deviation and boost-up the voltage profile for the specified system.     

Fabrication of microfluidic devices using MeV ion beam Programmable Proximity Aperture Lithography (PPAL)

MeV ion beam lithography is a direct writing technique capable of producing microfluidic patterns and lab-on-chip devices with straight walls in thick resist films. In this technique a small beam spot of MeV ions is scanned over the resist surface to generate a latent image of the pattern. The microstructures in resist polymer can be then revealed using a chemical developer that removes exposed resist, while leaving unexposed resist unaffected. In our system the size of the rectangular beam spot is programmably defined by two L-shaped tantalum blades with well-polished edges. This allows rapid exposure of entire rectangular pattern elements up to 500 × 500 μm in one step. By combining different dimensions of the defining aperture with the sample movements relative to the beam spot, entire fluidic patterns with large reservoirs and narrow flow channels can be written over large areas in short time. Fluidic patterns were written in PMMA using 56 MeV ¹⁴N³⁺ and a 3 MeV ⁴He²⁺ beams from K130 cyclotron and a 1.7 MV Pelletron accelerators, respectively, at the University of Jyväskylä Accelerator Laboratory. The patterns were characterized using SEM, and the factors affecting patterns quality are discussed.     

Measurement of the activation cross section for the (p,xn) reactions in niobium with potential applications as monitor reactions

Excitation functions of the ⁹³Nb(p,n)^93mMo, ⁹³Nb(p,pn)^92mNb and ⁹³Nb(p,αn)⁸⁹Zr nuclear reactions were measured up to 17.4 MeV by the conventional activation method using the stacked-foil technique. Stacks were irradiated at different incident energies on the TR19/9 cyclotron at the Edmonton PET Centre. The potential of the measured excitation functions for use as monitor reactions was evaluated and tested by measuring activity ratios at a different facility. Single Nb foils were irradiated at incident energies in the range from 12 to 19 MeV on the TR19/9 cyclotron at Brookhaven National Laboratory. Results are compared with the published data and with theoretical values as determined by the nuclear reaction model code EMPIRE.     

Solid-phase crystallization kinetics and grain structure during thermal annealing of a-Si:H grown by chemical vapor deposition

Solid-phase crystallization kinetics are examined during thermal annealing of as-deposited hydrogenated amorphous silicon (a-Si:H) thin films deposited by hot-wire chemical vapor deposition (HWCVD) and plasma-enhanced chemical vapor deposition (PECVD). The influence of deposition temperature of HWCVD material on crystallization is also considered. Real-time observation of the crystallization process using in situ transmission electron microscope heating allowed tracking of the crystalline volume fraction and grain number density by image-processing methods. Beyond an initial incubation period, roughly constant grain nucleation rate and growth velocity are observed. Extrapolation from early stages of crystallization allows estimation of the final average grain sizes. PECVD material shows a much lower nucleation rate than does HWCVD material under the same annealing conditions, whereas the grain growth velocities are comparable, leading to dramatically larger grain sizes in PECVD material. X-ray diffraction line widths from PECVD material are broader compared to HWCVD material. The diffraction line broadening is primarily determined by intragranular defect structure, rather than grain size. Low-temperature preannealing reduced the final XRD line widths of HWCVD material, indicating an influence on defect structure or density. Lattice contraction during crystallization of HWCVD material is observed to be independent of the initial hydrogen content.