视距传播中地面起伏对传播中值衰减的影响

电波在以视距传播方式进行传播时,在低空大气层中还要受到地面的影响。文中具体分析了视距传播下几种传播模型中地面起伏对电波传播衰减中值的影响,并进行了相应的计算,最后给出相应地面起伏度与传播衰减中值之间的关系。     

用于高动态目标探测雷达的相位编码脉冲压缩技术

为避免多普勒频移对相位编码信号脉冲压缩处理的影响,提出了利用已知脉冲编码序列对回波信号进行逐符号共轭点乘的脉冲压缩方法,将对齐的回波信号转换为单频信号,并利用傅里叶变换实现信号能量的积累。理论分析与计算机仿真表明,多普勒频移对脉冲压缩性能无影响。该方法适合于应用到对高动态目标进行探测的雷达系统中。     

干涉自相关与光谱联合测量超短脉冲啁啾

提出了联合测量超短激光脉冲混合啁啾量值的方法,这种方法是基于干涉自相关包络宽度及超短激光脉冲光谱宽度随啁啾量值的变化而变化.通过对干涉自相关信号包络宽度及超短激光脉冲光谱宽度的理论分析,得到干涉自相关包络宽度及超短激光脉冲光谱宽度与啁啾量值之间的对应关系,获得联合测量混合啁啾量值的方法.采用干涉自相关二次谐波检测系统对加浓染料激光器输出的脉冲进行测量,利用该方法测量出被测超短激光脉冲的线性啁啾值及平方啁啾值.根据干涉自相关包络信号及超短激光脉冲光谱,分别独立测量超短激光脉冲混合啁啾值,从而实现了对超短激光脉冲啁啾值的确定性测量.     

AWGN信道下TH-PPM UWB通信系统性能分析与仿真

首先介绍了TH—PPM UWB信号，然后从理论上对加性高斯白噪声（AWGN）信道下系统的性能进行了分析，包括误码率分析和系统容量分析，最后对系统的误码率和接入用户数进行了仿真比较。结果表明，重复码长度、脉冲重复时间和用户数目的选取对系统的误码率都有较大的影响，同时，系统容量与输出信噪比和数据传输速率有关并趋于定值。     

卷丹百合组培快繁技术的研究

以卷丹百合珠芽为实验材料,以MS为基本培养基,对其组培快繁进行了研究,结果表明,适宜的小鳞茎诱导培养基为MS 1.0mg/LNAA 0.5mg/L6-BA 0.1mg/LKT;适宜的增殖培养基为MS 2mg/LNAA 0.5mg/L6-BA 0.1mg/LKT;适宜的生根培养基为1/2MS 0.2mg/LIBA;诱导和快繁适宜的条件为光照16h/d,温度(25±1)℃。     

一种新型调宽功放电路

本文给出一种新型调宽功率放大电路并从理论上进行详细分析。     

移动通信无线覆盖均匀性分析

本文分析了移动通信系统中电波传播对覆盖均匀性的影响。通过典型路径传播损耗和移动通信系统同频干扰的分析，给出了衡量覆盖均匀性的性能指标。计算机模拟表明了覆盖均匀性与覆盖模式的关系。     

Introducing errors in progress ratios determined from experience curves

Progress ratios (PRs) derived from historical data in experience curves are used for forecasting development of many technologies as a means to model endogenous technical change in for instance climate–economy models. These forecasts are highly sensitive to uncertainties in the progress ratio. As a progress ratio is determined from fitting data, a coefficient of determination R² is frequently used to show the quality of the fit and accuracy of PR. Although this is instructive, we recommend using the error σ_PR in PR, which can be directly determined from fitting the data. In this paper we illustrate this approach for three renewable energy technologies, i.e., wind energy, bio-ethanol, and photovoltaics.     

双通道跟踪接收机对地校相技术

为了解决新建地面测控站的无塔标校技术难题,提出了一种抛物面天线近场对地校 相新方法,在径向距离大于0.3倍远场距离的条件下可实现对地校相功能,通过外场专题试 验研究进行了验证,对靶场测控系统的工程建设具有较高的参考价值。     

An Exploratory analysis of flight delay propagation in China

Delay propagation is the flight departure delay caused by the arrival delay of pre-segment flight. Chinese airline market has suffered very poor on-time performance (OTP) in recent years. It is, however, unclear whether delay propagation prevails as one major source for such problem. This study first aims to empirically quantify delay propagation in the Chinese airline market. Specifically, we shed light on heterogenous levels of delay propagations across different airports and airlines. Then, the distinct delay propagation patterns in China are also discussed and compared with other developed airline markets (e.g., the US and Europe). Our estimation is based on OTP data for over 12 million Chinese flights covering the 2015–2017 period. Specifically, it is found that 10 min arrival delay of pre-segment flight within 1 hr before the departure lead to an average of 7.49 mins delay propagation for subsequent departure flight. Arrival delay of earlier pre-segments (1–2 and 2–3 hr before the departure) leads to much less delay propagation, due to longer ground buffer. Chinese airlines arrange longer ground and flight buffer than that of the US airlines to prevent the delay propagation from accumulating along the subsequent flights in a day. Thus, unlike the US market, delay propagation is not the major reason for poor OTP in China. In addition, delay propagation is less prevailing at the Chinese hub airport. This is because China has relied on point-to-point network, which does not require sophisticated schedule coordination. And the local passengers at these Chinese hub airports have higher time value such that the Chinese airlines also try to improve OTP at these hub airports to better serve these lucrative but time-sensitive local passengers. Unlike the European LCCs, Spring Airlines, the largest low-cost carrier (LCC) in China, outperforms major full-service carriers (FSCs) in controlling delay propagation. This finding may also apply to other Northeast Asian LCCs sharing common operational characteristics as Spring Airlines. Last, we find that airlines purposely tolerate moderate departure delays of up to 15 min, which is the threshold that defines delays, no matter whether the pre-segment flight arrives late or on-time. The relevant policy and managerial implications are also discussed.