二维多孔数控钻床加工路径的生成及优化

印刷电路板 PCB的加工是二维多孔数控钻的典型。实践表明加工同一零件不同的走刀路径其长度相差极大。为提高生产率 ,应使刀具的走刀路径尽量短 ,这其实是大型的 TSP问题。本文提出了几种路径的生成方法 ,分析了各自的适用场合。并用实例验证所提出的路径生成方法可极大地提高实际钻孔的加工效率。     

Annular ring slot antenna design with reconfigurable polarization

A microstrip‐fed conventional annular ring slot (ARS) antenna with linear polarization (LP) is initially studied. To generate two orthogonal degenerate modes for circular polarization (CP) radiations, two identical meandering perturbation slots (MPS) are symmetrically loaded into the ARS. By further incorporating a PIN diode switch across each MPS, the proposed antenna can switch between left‐hand CP (LHCP), right‐hand CP (RHCP), and LP. All three polarizations have shown good impedance bandwidth and broad CP bandwidth that can satisfy the wireless local area network (WLAN) 2.4‐GHz operating band (2400–2480 MHz). Furthermore, desirable gains of 1.8–2.0 dBi and 2.40–2.84 dBic are also exhibited at LP and LHCP/RHCP, respectively. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:110–120, 2016.     

High performance VLSI CORDIC algorithms,architecture and chip design

Abstract

CORDIC is a rotation based computation kernel algorithm which has been found to be very attractive for problems which require intensive, frequent evaluations of elementary functions. This paper addresses the implementation issues in the design of a VLSI CORDIC processor for digital signal processing and numerical linear algebra computations. The first part of this paper will discuss various design considerations for practical CORDIC algorithms. In particular, we have established criteria for the selection of nearly optimal shift sequences which are crucial to the performance of the CORDIC computation. The various design considerations of a CORDIC processor are discussed. Finally, the architecture of a prototype CORDIC processor data path chip is described.     

Changes in bioactive compounds and antioxidant activity during convective drying of murta (Ugni molinae T.) berries

Murta (Ugni molinae T.) berries were air‐dried at five temperatures (40, 50, 60, 70 and 80 °C), and the changes in β‐carotene, phenolic acids, total phenolic and flavonoid contents and antioxidant capacities (DPPH and ORAC) were investigated. The berries showed a high content of β‐carotene, which decreased during drying temperature between 40 °C and 80 °C. Free and bound phenolic acids were also determined, showing gallic acid to be the prevalent phenolic acid. Total phenolic and flavonoid contents in the dried berries showed a higher decrease at lower temperature due to longer drying time. The radical‐scavenging activity also showed higher antioxidant activity at higher drying temperatures (70–80 °C) than at lower drying temperatures (40–50 °C). Total phenolic content (TPC) and flavonoids showed good correlation with antioxidant capacity. Murta berries proved to be an excellent source of antioxidants and bioactive compounds and are therefore a potential ingredient for new functional food products.     

The effect of polyethylene crystallinity and polarity on thermal stability and controlled release of essential oils in antimicrobial films

Antimicrobial packaging can preserve and increase shelf life of free preservatives food products. Active materials present in the packaging material can migrate, in a controlled manner, to the food surface, avoiding bacterial and fungal proliferation and keeping the food product edible for longer periods of time. Essential oils (EO) are natural antimicrobial agents that can be released to the headspace with no direct contact between the package and the food. To minimize loses of EO during high heat melt processing, a three stages process was implemented and tested. Antimicrobial films were prepared by melt mixing a variety of polyethylene copolymers in the presence of organo‐modified montmorillonite nano clay (NC) and thymol, an EO present in oregano and thyme. A controlled EO desorption from films can be achieved by changing the polymer crystallinity and polarity. As the crystallinity increased, the thermal stability of the EO during the extrusion process improved. The addition of NC affects the structure and homogeneity of the crystals. The combination of high polymer crystallinity and chemical affinity between EO and NC increased the thermal stability of the EO during film processing, enabling to control the desorption rate. The effect of multilayer structure based on varied densities and polarities was also studied. Increasing the polarity of the outer layers in multilayered film reduced the EO desorption rate as a result of chemical interactions between the polymer and the EO. The final antimicrobial activity of the films was also found to be dependent on the EO partitioning. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40309.     

Effect of Rehydration Temperature on Functional Properties,Antioxidant Capacity and Structural Characteristics of Apple (Granny Smith) Slices in Relation to Mass Transfer Kinetics

Apple slices dried at 60C were rehydrated at 20, 40 and 60C to analyze the influence of processing temperature on quality attributes and rehydration kinetics. Diffusion coefficient increased with process temperature from 1.36 to 2.37 × 10^?9 m²/s. The Weibull model obtained the best fit quality for the experimental data based on statistical test, chi square. Color was not recovered during rehydration and the results indicated that the use of low temperatures is more adequate. Water‐holding capacity decreased, while rehydration ratio increased with increasing rehydration temperature, indicating structural modifications. Increasing rehydration temperatures led to a reduction in the glass transition temperature and hardness values of samples. The radical‐scavenging activity showed higher antioxidant activity at higher rehydration temperatures rather than at lower temperatures. It was found that rehydration temperature modifies the cell structure and antioxidant capacity of final product.     

基于GPRS的有杆泵井集群自动量油系统研究

将GPRS通信方式与功图法量油技术结合到一起,提出了基于GPRS的有杆泵抽油井集群自动量油系统,并详细介绍了功图法量油的主要原理、系统的软、硬件平台及各层主要硬件的具体选型。实验结果表明,该系统一方面采用GPRS通信方式,对油井工况数据进行远程实时传输,实现了油井产量的实时测控、计算,提高了油井量油计产精度;另一方面利用批处理技术,实现了油井产量的集群计算处理。该系统的研究成功对实时监控油井产量波动、防止影响油井安全稳定生产因素的出现、提高油井管理的自动化水平具有重大意义。     

平面机械系统运动学的分析方法

本文介绍一种机械系统运动学分析的通用方法。文中根据多刚体系统运动学的原理,建立了受约束机械系统的运动约束方程、速度方程及加速度方程,还详细推导了以铰接副及滑动副连接的两邻接刚体的雅可比矩阵和加速度方程右边项,以求进一步说明本方法。文后还给出了实例。     

软件体系结构风格的实例研究

软件体系结构研究领域中，风格的研究与应用是一个重要的领域。本文讨论了软件体系结构的概念和风格，在此基础上特别对CORBA，基于Web的分布式系统结构，领域专家系统，基于商业背景的可重用软件体系结构等内容进行了讨论，并给出了它们相关风格。     

攀枝花钒钛磁铁矿的综合利用与深度加工

针对攀枝花钒钛磁铁矿的特殊性，探讨了攀钢冶炼过程中ＴｉＯ２的流向和分布情况，论述了钛系列精细化工产品深度开发的重要性，对攀枝花钛化工的发展方向提出了具体建议．认为，研制高纯ＴｉＯ２微粉和超微粉、钛酸酯偶联剂、ＴｉＣｌ２催化剂、钛系列彩色颜料、无机钛酸盐等多品种，作为大宗化工产品钛白颜料及钛冶金产品的补充，对进一步提高攀枝花钒钛磁铁矿的综合利用，具有十分重要意义．