筛分法和激光粒度法联合测定陆源碎屑岩粒度

用筛分法和激光粒度法联合测定陆源碎屑岩粒度,对激光粒度法的分析数据进行了校正,以保证两种方法的分析数据配套衔接。通过对比不同地质年代沉积岩的岩心校正前后概率累积频率曲线,校正后的曲线能更好地表征碎屑岩粒度的分布。对影响马尔文Mastersizer 2000激光粒度仪背景测量的进样器搅拌转速A、泵速B、超声强度C三个因子进行L9(34)正交优化设计,筛选出最优的测量条件是A取600r/min,B取2000r/min,可使背景测量稳定,并得出它们对背景测量影响程度可用B>A>误差>C表示。用仪器自带的9个标准物质校正了粒度标准曲线,粒度标准曲线与仪器标准曲线的加权残差小,在0.795%～2.934%之间。该方法相对标准偏差在0.24%～0.33%之间,适用于各种地质年代陆源碎屑岩的粒度分析。     

低截止频率多倍频程高增益对跖Vivaldi天线北大核心CSCD

针对传统对跖Vivaldi天线的最低截止工作频率较高、增益较低和方向性较差的问题,文中设计了一种新型超宽带对跖Vivaldi天线。融合运用辐射极板开矩形斜槽、加载吸收电阻和寄生矩形贴片等一系列电磁调控措施,扩展了天线的低频工作带宽;采取在天线极板间加载椭圆寄生贴片的技术方式大幅提高了天线的方向性和辐射增益。最后给出了天线的设计流程,从电场分布和表面电流分布的角度揭示了天线的微观工作机制。仿真和实测结果表明:天线的工作频带为0.85~16 GHz(近20倍频程),相对带宽达180%,在3 GHz以上频段增益均超过10 dBi,并且具有较好的端射方向性,在超宽带无线通信、雷达探测、电子对抗和遥感遥测等领域具有广泛的应用前景。     

Advances in radio frequency pasteurisation equipment for liquid foods: a review

Radiofrequency (RF) heating is an alternative emerging technology to conventional thermal methods; it has been employed for food pasteurisation, providing fast and volumetric heating. However, non-uniformity in the heating pattern has been reported. RF pasteurisation has been studied in different liquid foods. This review provides information about the RF heating mechanism and equipment used to pasteurise liquid food to control deteriorative or pathogen micro-organisms and the effect of the RF treatment on the quality of liquid foods. Developing an effective RF pasteurisation for liquid foods requires knowing the food dielectric properties, which determine the heating uniformity, temperature distribution and heating rate. The efficiency of continuous RF heating systems could depend on the fluid rate, resident time and absorbed power. RF heating can pasteurise liquid food, decrease microbial population and preserve the product's nutritional and physicochemical quality.     

Fourier transform ion cyclotron resonance mass spectrometry at the true cyclotron frequency

Ion cyclotron resonance (ICR) cells provide stability and coherence of ion oscillations in crossed electric and magnetic fields over extended periods of time. Using the Fourier transform enables precise measurements of ion oscillation frequencies. These precisely measured frequencies are converted into highly accurate mass-to-charge ratios of the analyte ions by calibration procedures. In terms of resolution and mass accuracy, Fourier transform ICR mass spectrometry (FT-ICR MS) offers the highest performance of any MS technology. This is reflected in its wide range of applications. However, in the most challenging MS application, for example, imaging, enhancements in the mass accuracy of fluctuating ion fluxes are required to continue advancing the field. One approach is to shift the ion signal power into the peak corresponding to the true cyclotron frequency instead of the reduced cyclotron frequency peak. The benefits of measuring the true cyclotron frequency include increased tolerance to electric fields within the ICR cell, which enhances frequency measurement precision. As a result, many attempts to implement this mode of FT-ICR MS operation have occurred. Examples of true cyclotron frequency measurements include detection of magnetron inter-harmonics of the reduced cyclotron frequency (i.e., the sidebands), trapping field-free (i.e., screened) ICR cells, and hyperbolic ICR cells with quadrupolar ion detection. More recently, ICR cells with spatially distributed ion clouds have demonstrated attractive performance characteristics for true cyclotron frequency ion detection. Here, we review the corresponding developments in FT-ICR MS over the past 40 years.     

一种基于业务区分的随机接入方案

通过对移动通信系统关键技术的发展趋势和网络实时业务服务质量（QoS）需求的分析,提出了一种适用于时分－正交频分多址接入系统（TD-OFDMA）的简单高效的随机接入方案。在该方案中,网络终端利用特有的优先随机接入信道（FRRACH）对不同时延特性的业务采用不同的随机接入机制,从而有效地避免分组碰撞,保障实时业务的QoS需求。理论分析和仿真结果表明,该方案在成功接入概率、接入时延以及资源利用率等方面的性能较目前常用的随机接入方案有着较大的改善。     

隔爆兼本安型全数字变频绞车调速系统改造与实践

针对隔爆兼本安型全数字变频绞车调速系统改造的实践,介绍应用AFE技术实现变频器四象限运行的原理和特点,分析"双线控制"提高控制系统的安全性和可靠性的技术措施,为井下绞车变频改造提供技术支持。     

利用浓缩因子区划矿井富水性

电阻率浓缩因子是相邻多个极距视电阻率之和与其中最小值之比，是在电阻率差异较小，无法解释时的一种数据处理方法，该方法突出有用异常、压制干扰性能较强。论文以郭二庄煤矿下架煤层涌水为例，研究了浓缩因子的求取方法和分区原则，利用浓缩因子将其底部奥陶系地下水富水性划分为三个区，并论证其划分的可靠性。     

系统理论与频率分析法在水资源评价中的应用

频率分析法适用于具有长系列的泉水流量观测资料的泉域的水资源评价。当泉水流量观测系列较短而降水系列较长时,可采用系统理论分析法延长泉水流量系列。该文在对系统理论和频率分析法进行介绍的基础上,对陕西省神木县考考赖沟水源地水资源进行了评价。     

地下汽车库通风排烟系统的节能设计

分析了变频技术对风机调节的影响，指出地下汽车库通风排烟系统采用定风量设计不利于系统节能，该系统宜采用变风量设计，同时介绍了变频技术在地下汽车库通风排烟系统中的应用。     

矿井移动通信技术难题及解决方案探讨

介绍了我国煤矿井下移动通信现状,分析了技术上的难题-巷道对无线传输的影响、弱信号接收和井下环境噪声干扰,提出了解决途径。同时指出,陆地移动通信技术解决方案完全可以解决井下移动通信难题。