大断面煤巷变形破坏规律及控制技术

采用理论分析、FLAC3D数值计算和工程实践等方法,研究分析巷道宽度对巷道围岩变形、塑性区及应力分布的影响规律,提出了巷道临界宽度判定指标：巷道顶板拉破坏深度为1.5 m,顶板拉破坏深度大于1.5 m的巷道维护困难。并提出了超过临界宽度的巷道支护技术为：及时支护、高强高预紧力锚杆、锚索支护和高初撑力的临时支护。研究成果成功应用于王庄煤矿6207综放工作面运输巷。     

A novel wideband and circularly polarized cross‐dipole antenna

In this paper, we present a novel wideband circularly polarized (CP) composite, called cavity‐backed crossed dipole antenna for 2.45 GHz industrial, scientific, and medical (ISM) band wireless communication. To excite the CP radiation effectively, a curved‐delay line providing an orthogonal phase difference among the cross‐dipole elements is attached at corners of the sequentially rotated elements. By choosing a proper radius of the curved‐delay line, a wide input impedance of the antenna can be realized. Unlike conventional cross‐dipole antennas, the proposed cross‐dipole antenna is designed with an open stub added to the radiating arms of the dipole so that both impedance and axial ratio bandwidths are enhanced. The antenna is center‐fed by a 50‐Ω coaxial cable and is placed above a cavity‐backed reflector to obtain a directional CP radiation pattern. With the advantage of being center‐fed, a symmetric CP radiation pattern can be achieved across the entire operating bandwidth. To further improve the directivity and the radiation pattern, a rectangular cavity‐backed reflector is used. Simulated and measured results confirm that the proposed antenna has good CP characteristics. The proposed antenna obtains a broad 3‐dB axial ratio bandwidth of 49% (1.20 GHz, 1.96–3.16 GHz) and an impedance bandwidth of 67.7% (1.66 GHz, 1.69–3.35 GHz) for reflection coefficient (S₁₁) ≦ −10 dB. It also yields an average CP gain of 9.2 dBic across the operating bandwidth and a peak CP gain of 10 dBic. Copyright © 2016 John Wiley & Sons, Ltd.     

飞行器目标RCS计算方法适用性研究

飞行器隐身设计的重要参数是雷达散射截面(Radar Cross Section,RCS),因此RCS的快速精确预估对飞行器隐身设计具有重要意义。目前针对飞行器目标已经发展了很多种RCS的计算方法,分别从目标电尺寸大小、目标类型以及实际分析应用等三个方面对现有的高频近似算法、数值精确算法的适用性进行了详细研究,并分析了各种算法的优缺点,如计算精度、效率、误差等。在目标电尺寸方面主要研究各种方法的计算精度和效率,目标类型方面主要研究飞行器布局、腔体以及不连续特征的计算方法,而实际应用方面则是从多方位散射、多频散射、多站散射三个方面对计算方法进行了分析。研究结果对飞行器隐身设计具有一定参考价值。     

低RCS栅格微带天线研究

研究了栅格微带天线在微带天线RCS减缩中的应用。分析了栅格线宽度、栅格线间距、栅格化方式等参数对天线的谐振频率、增益的影响。设计了一副具有低RCS特性的栅格微带天线,与谐振在同频率的微带贴片天线相比,天线的增益仅降低0. 6dBi,而天线在2~10GHz频带内的平均RCS降低4dBsm。     

带式输送机物料断面系数的分析

对现行物料断面系数Ｋ的３种计算方法进行了分析与讨论，指出３种计算方法的Ｋ不同，主要是由物料在输送带上的有效宽度ｂ的取值不同造成的．找到了物料断面系数Ｋ合理的计算方法．     

高效率E类射频功率放大器

研究了E类RF放大器的电路结构、工作原理、存在问题以及解决的方法--差分和交叉耦合反馈结构,最后给出了E类放大器的实例.由于具有低成本、高集成度、多功用等优点,MOS工艺在射频功率放大方面有很大的发展潜力.在本文中,用0.6 u m CMOS工艺实现了E类放大器的设计.     

镜面反射目标激光雷达截面的估算方法

为了解决镜面反射目标激光雷达截面的工程计算问题,本文从激光雷达截面的定义出发,在具体分析镜面反射目标激光散射特性的基础上,提出了一种简便的适用于镜面反射目标的激光雷达截面的工程估算方法,该方法仅利用目标有效照射面积、散射光束发散角和目标后向反射比就可以估算得到镜面反射目标的激光雷达截面.本文还将该方法应用于两类典型的镜面反射目标,即激光角反射器目标和"猫眼"目标,得到了相应的激光雷达截面估算公式.该法计算结果与实测一致,可用于镜面反射目标激光雷达截面的工程计算.     

Cross‐Layer Resource Allocation Scheme for WLANs with Multipacket Reception

Tailored for wireless local area networks, the present paper proposes a cross‐layer resource allocation scheme for multiple‐input multiple‐output orthogonal frequency‐division multiplexing systems. Our cross‐layer resource allocation scheme consists of three stages. Firstly, the condition of sharing the subchannel by more than one user is studied. Secondly, the subchannel allocation policy which depends on the data packets’ lengths and the admissible combination of users per subchannel is proposed. Finally, the bits and corresponding power are allocated to users based on a greedy algorithm and the data packets’ lengths. The analysis and simulation results demonstrate that our proposed scheme not only achieves significant improvement in system throughput and average packet delay compared with conventional schemes but also has low computational complexity.     

A novel simplified tone reservation combined with cross antenna rotation and inversion to reduce PAPR for MIMO‐OFDM system

In this paper, we first propose a simplified tone reservation (STR) method with low computational complexity which is based on the Fourier series expansion. Then, we analyze how to combine the STR method with the cross antenna rotation and inversion method to reduce the peak‐to‐average power ratio (PAPR) for multi‐input multi‐output orthogonal frequency division multiplexing (MIMO‐OFDM) system. To validate the analytical results, extensive simulations are conducted and the numerical results show the efficiency of the proposed schemes including the PAPR reduction and low computational complexity for MIMO‐OFDM system. Copyright © 2010 John Wiley & Sons, Ltd.     

全程计数激光云高仪原理及实验研究

利用脉冲ＧａＡｌＡｓ二极管激光器进行了云高测量,提出了一种区别于传统的脉冲计数方法－单脉冲全程计数法。