The preparation and microwave properties of Ba3ZnZCo2-ZFe24O41/SiO2 microcrystalline glass ceramics by citrate sol-gel process

A series of Ba₃Zn_ZCo_2-ZFe₂₄O₄₁/SiO₂ microcrystalline glass ceramics with Z=0.0,0.4,0.8 and 1.2 were prepared by citrate sol-gel process. The result showed that Ba₃Zn_ZCo_2-ZFe₂₄O₄₁ hexferrite crystallites could be obtained by this process at 1200 °C in the system of BaO-Fe₂O₃-CoO-ZnO-SiO₂. The complex dielectric constant and complex permeability of Ba₃Zn_ZCo_2-ZFe₂₄O₄₁/SiO₂ microcrystalline glass ceramics calcined at different temperature were measured in the range of 200MHz-6 GHz by transmission/reflection coaxial line method. The complex dielectric constant and dielectric loss exhibited insignificant variety in the whole range of measuring frequencies for all samples. The real part of the permeability decreased as the measuring frequency increasing, and calcining temperature had a clear influence on the value of μ′ for Ba₃Zn_ZCo_2-ZFe₂₄O₄₁/SiO₂ microcrystalline glass ceramics, and so did the content of Zn²⁺ and Co²⁺. The natural resonance phenomenon was observed in μ′′ spectra for all the Ba₃Zn_ZCo_2-ZFe₂₄O₄₁/SiO₂ microcrystalline glass ceramics. The substitution of Zn²⁺ ion and annealing temperature closely affect the resonance frequency, the more the Zn²⁺ ion, the higher the annealing temperature and the lower the resonance frequency. Received: 23 July 2001 / Accepted: 24 July 2001     

C语言与汇编语言的接口技术在DSP芯片中的应用

对于DSP芯片的控制程序的开发,采用C语言和汇编语言混合编程具有较高的效率。该文阐述了两种语言的接口方式和接口协议,并给出了采用这种接口技术实现混合编程在DSP芯片TM320C24x中的几种典型应用实例。     

页岩气水平井生产套管变形机理及工程应对方案——以昭通国家级页岩气示范区黄金坝区块为例

针对四川盆地周缘昭通国家级页岩气示范区黄金坝区块2口页岩气水平井套管严重变形的情况,基于24臂井径套管变形测量、裸眼井径、电阻率电测、钻时及气测录井、固井CBL/VDL及CBL成像等资料,分析引起套管变形位置附近地层的地质与工程特征,利用三维成像分析软件分析24臂井径测量数据并进行三维成像,得到了变形套管的形态特征。研究结果表明:(1)极严重套管变形井段发生在构造裂缝发育区;(2)套管变形形态为上下方向为主的"S"形弯曲;(3)极严重套管变形呈现明显的遭受岩石高角度滑移挤压而横向剪切变形特征。据此提出建议:(1)该区应重点防范由岩石沿裂缝面滑移引起的剪切套管变形,利用产层段构造等值线图,设计井眼轨迹避开地下局部高陡构造的"脊部"或"谷底"位置;(2)利用产层段蚂蚁体分布图预测的裂缝带分布信息,使井眼轨迹沿裂缝带走向钻进;(3)推荐采用免钻磨大通径桥塞或全通径无限级完井工艺技术,避开压裂后常规桥塞钻磨工序,以确保压裂后的各级压裂层都能投产。     

The sources of the urban wage premium by worker skills: Spatial sorting or agglomeration economies?

We estimate the respective importance of spatial sorting and agglomeration economies in explaining the urban wage premium for workers with different sets of skills. Sorting is the main source of the wage premium. Agglomeration economies are in general small, but are larger for workers with skills associated with non‐routine job tasks. They also appear to involve human capital accumulation, as evidenced by the change in the wage of workers moving away from denser regions. For workers with routine jobs, agglomeration economies are virtually non‐existent. Our results provide further evidence of spatial density bringing about productivity advantages primarily in contexts when problem‐solving and interaction with others are important.     

一种高分辨率数据采集系统的设计

针对石油测井采集信号的特点,设计了一种高分辨率24位数据采集系统。给出了单片机和A/D转换器的接口电路,设计上位机控制软件。该采集系统采样最大频率为32ksps,可超前采集1s,采集数据以二进制文件形式保存。     

Anisotropic and tensile flow behaviors of Mg alloy AZ31B thin sheet in H24 condition at elevated temperatures

In this work, a series of experiments was performed to explore the effects of anisotropy, strain rate, and temperature on microstructure change and associated mechanical response of a rolled AZ31B-H24 Mg alloy sheet under tension. Tensile tests were carried out on specimens in the 0, 45, and 90° to the rolling direction, using initial strain rates in the range of 4 × 10⁻³ to 1 × 10⁻¹ s⁻¹ at temperatures of 250 and 370 °C. Results showed that variations in flow behavior under tension could be related to the changes in microstructure resulting from applied tensile conditions. Resultant microstructures, such as degree of dynamic recrystallization, grain growth, and shape of the grain, were associated with temperature, strain rate, and tensile loading direction. The initial texture influenced the variations in changes in microstructure and mechanical properties upon testing in different directions. The specimens upon testing in the 45° to the rolling direction yielded higher m-value, lower strength, and greater elongation to failure under all test conditions.     

基于nRF24L01的2.4GHz无线通信系统设计

提出一种基于NORDIC公司生产的2.4 GHz无线收发芯片nRF24L01的短距离无线数据传输系统设计方法。介绍了系统的实现方案和硬件选型,该系统以ATmega8L为控制核心,PTR6000为无线传输模块;详细描述了硬件电路和软件程序设计方法,其中软件设计包括单片机主程序设计和PTR6000通信程序设计等;在硬件和软件设计的基础上,通过实验仿真验证了系统的正确性和可靠性,为系统实际应用提供了依据,最终达到了设计的要求。     

基于nRF24L01的钢丝绳无损检测系统

提出一种基于nRF24L01的钢丝绳无损检测系统设计方法,利用该系统对在线钢丝绳进行无损检测,检测结果采用nRF24L01进行无线传输,克服了有线传输的应用弊端,解决了钢丝绳恶劣的工作环境和其无损检测有线传输方式的矛盾,提高了检测精度。可以保证在役钢丝绳的安全可靠,避免钢丝绳更换的盲目性,做到按照钢丝绳的运行状态进行预知维修。并重点讲述了系统的硬件和软件设计,给出了详细的结论。     

高空温度动态采集系统设计

在采集不同高度的温度时,在不同高度安置无线网络传感器成本高,无线传感器的电源替换比较困难,为解决此问题,采用了简易螺旋直升机,内置由AT89C51单片机、DS1820数字芯片,可实时采集不同高度的温度。使用JF24D-B无线传输模块将信号送至ARM7控制系统。监控端通过无线信号接收并解析,在μClinux下进行进程调度和数据处理,并通过Python完成数据图表的实时显示,便于用户查看当前温度做出正确决策。