7200-phase generalized Barker sequences

We present 7200-phase generalized Barker sequences with lengths from 19 to 31. Also, we show the number of known M-phase generalized Barker sequences (M=7200), inequivalent under the group of “Barker-preserving transformations”. The autocorrelation values of Barker sequences are also presented     

A low-voltage, low-power CMOS delay element

A low-voltage, low-power CMOS delay element is proposed. With a unit CMOS inverter load, a delay from 2.6 ns to 76.3 ms is achieved in 0.8 μm CMOS technology. Based on a CMOS thyristor concept, the delay value of the proposed element can be varied over a wide range by a control current. The inherent advantage of a CMOS thyristor in low voltage domains enables this delay element to work down to the supply voltage of 1 V while the threshold voltage of the nMOS and pMOS transistors are 840 mV and -770 mV, respectively. The designed delay value is less sensitive to supply voltage and temperature variation than RC-based or CMOS inverter-based delay elements. Temperature compensation and jitter performance in a noisy environment are also discussed     

Analysis and design of aperture-coupled microstrip patch antennasand arrays fed by dielectric image line

This paper presents the analysis and design of aperture-coupled microstrip patch antennas and arrays fed by an dielectric image line. A theory based on the cavity model of the microstrip patch antenna and the change in the modal voltage of the image line at the aperture was developed to analyze the single element aperture-coupled microstrip patch antenna. The theory developed was combined with the array theory to design linear traveling wave arrays at X-band and Ka-band frequencies. The required taper in the excitations of the individual patches of the array was achieved by varying the aperture dimensions. Experiments show very good results for the antennas and the arrays     

Design of power control mechanisms with PCM realization for theuplink of a DS-CDMA cellular mobile radio system

Power control (PC) is an important issue in a direct sequence-code division multiple access (DS-CDMA) cellular mobile radio system. Higher link performance and greater system capacity cannot be achieved unless an appropriate PC mechanism is employed. In previous research, a delta-modulation (DM) realization of strength-based and SIR-based PC mechanisms for uplink communication has been studied by simulation. In order to obtain higher PC trackability, we study a pulse-code-modulation (PCM) realization of the above two PC mechanisms for the uplink of a DS-CDMA cellular mobile radio system. The simulation results presented indicate that the PC mechanisms with PCM realization for the uplink can achieve a lower outage probability and thus higher link performance than the PC mechanisms with DM realization. We also obtain optimal design parameters such as the stepsize and the control mode for the two PCM PC mechanisms. In addition, we compare the two PCM PC mechanisms in terms of their outage probability and stability and find that the strength-based mechanism has a higher outage probability but greater stability than the SIR-based mechanism     

煤矿变频器故障诊断技术探讨

通过对煤矿变频器故障诊断技术进行分析,提出了煤矿变频器的常见故障及诊断技术,以期提升故障诊断水平,满足煤矿企业发展需求.     

ZIF-8衍生柔性多孔炭材料的制备及其电容性能研究

随着柔性可穿戴电子器件的迅速发展,柔性储能电极材料引起众多学者们的广泛关注。金属有机框架结构（MOFs）衍生物具有优异的储能性能,但其本征无柔性的物理特性亟需解决。采用静电纺丝技术将ZIF-8结构单元嵌入纤维结构中,获得高电容性能柔性多孔炭纤维。同时,探究了ZIF-8的嵌入量（CF-ZIF-8-1.2）对柔性多孔炭纤维结构及电容性能的影响。实验结果表明：柔性多孔炭纤维CF-ZIF-8-1.2的比电容可以达到425.5 F?g^-1（电流密度为1 A?g^-1）,并呈现出较小的电荷转移电阻（R_s=0.06 Ω）和接触电阻（R_ct=2.31 Ω）,这主要归因于CF-ZIF-8-1.2具有较大的比表面积（212.83 m²?g^-1）、相对丰富的孔隙结构和丰富的N和O原子共掺杂。随后,进一步将其组装成对称柔性超级电容器（CF-ZIF-8-1.2//CF-ZIF-8-1.2）,其能量密度高达7.6 Wh?kg^-1（功率密度为250 W?kg^-1）,在不同弯曲角度和扭曲下呈现出优异的电容保持率（97%以上）,说明柔性多孔炭纤维电极材料具有优异的柔性和稳定性。因此,CF-ZIF-8-1.2柔性多孔炭纤维材料具有潜在应用前景。     

聚合物驱效果影响因素关联性及适应性分析

聚合物驱是一项复杂而且具有多目标性的系统工程,对聚合物驱影响因素进行排序对聚合物驱的实施调整有一定指导意义。将聚合物驱看成灰色系统,用灰色关联分析的方法分析各种影响因素对聚合物驱效果的关联度,确定出影响措施效果的主要因素。统计了河南油田8个已注聚区块的开发效果,选取了渗透率变异系数,地层温度等9个因素作为主要影响因素,经灰色关联分析得出,该油田聚合物驱效果影响因素影响程度从大到小排序:注入速度＞地层温度＞渗透率变异系数＞地层水矿化度＞注入孔隙体积＞段塞尺寸＞地层渗透率＞原油黏度＞聚驱前含水。建立了典型模型,针对主控因素对聚合物驱的适应性进行了分析,结果表明,随着注入速度的增加,聚合物驱提高采收率幅度降低;聚合物工作黏度对开发效果的影响曲线呈明显的二段式分布;渗透率变异系数在0.7附近时聚合物驱效果最佳。     

添加剂对润滑脂抗磨极压性能的影响

对比考察了聚异丁烯、氟化镧、醋酸钙和硫代氨基甲酸盐对锂钙基脂、复合锂基脂和复合锂钙基脂抗磨极压性能的影响,结果显示：聚异丁烯对润滑脂的抗磨极压性基本无影响,氟化镧、醋酸钙和硫代氨基甲酸盐都可提高润滑脂的抗磨极压性,其中二烷基二硫代氨基甲酸钼的效果最好。用XPS对醋酸钙提高润滑脂抗磨极压性的原因进行了分析,从分析结果推测是在摩擦表面形成了CaCO3、CaO表面膜。     

混合泥质砂岩双电层电导率理论模型

基于层状泥质与分散泥质砂岩并联导电理论,以及悬浮于电解液中三维周期排列带电球体导电理论,建立了分散泥质和层状泥质同时存在的混合泥质砂岩通用双电层电导率理论模型.分析了模型影响的因素.结果表明,随总含水饱和度的增大,分散枯土阳离子交换容量、胶结指数对混合泥质砂岩电导率与总含水饱和度关系曲线的影响增大;而饱和度指数对混合泥质砂岩电导率与总含水饱和度的关系曲线的影响在总含水饱和度较大时随总含水饱和度的增大而减小.通过2组分散泥质砂岩岩样和1组混合泥质砂岩岩样实验测量数据计算,表明该模型既适用于分散泥质砂岩地层解释,又适用于层状泥质砂岩地层解释,同时还适用于含有分散泥质和层状泥质的混合泥质砂岩地层解释.     

榆林气田含油含醇污水预处理工艺改造效果评价

污水预处理直接关系到后续处理能否正常运行。榆林天然气处理厂污水预处理系统自投产以来经常出现过滤器、换热器堵塞,无法加入药剂等现象,致使污水处理效果不理想。为此,通过深入分析该厂含油含醇污水预处理工艺存在的问题,进行了工艺改造,优化了工艺流程和加药方案,变原来的两级沉降两级除油为三级沉降三级除油,并在加药流程前增加蒸气混合加热器,使预处理药剂絮凝反应效果达到最佳。改造取得了满意的效果,预处理后的含醇污水油含量降至20 mg/L,铁离子含量降至0.5～1.0 mg/L,悬浮杂质浓度小于5 mg/L,含油含醇污水透光率在95%以上,既可以满足甲醇回收装置的进料要求,又有效缓解了后续设备、管线堵塞的问题,达到了预期目标。