干扰条件下的“北斗”信号解扩重构DOA估计

在干扰条件下,卫星导航抗干扰波束形成算法往往需要卫星信号波达方向（Direction-of-Arrival,DOA）的先验信息。但当存在低信噪比信号或主动干扰源时,常规的DOA估计算法性能急剧下降甚至失效。针对此问题,提出了一种被干扰信号压制的低信噪比“北斗”信号的DOA估计算法。该算法首先通过对接收信号进行子空间投影抑制干扰信号,然后对抑制干扰后的信号进行解扩重构处理,最后通过多重信号分类算法完成对“北斗”信号的DOA估计。仿真结果表明,在干扰信号干信比80 dB条件下,“北斗”信号DOA估计误差在5°以内,为下一步进行波束形成计算提供了高精度的入射角信息。     

MISO窃听系统中的恶意导频干扰检测

在一??个三节点多输入单输出(Multi-Input Single-Output,MISO)窃听系统中,当窃听方在信道估计阶段发送恶意导频信号来干扰信道估计时,合法通信的保密性受到严重威胁。针对该安全问题,提出了基于估计信道协方差和基于接收信干比两种恶意导频干扰检测方案。首先概述基于估计信道协方差的恶意导频干扰检测方案原理,推导该方案下检测概率和虚警概率的解析表达式;其次给出基于接收信干比的恶意导频干扰检测方案机制及其检测概率和虚警概率的具体表达式,并通过理论分析对比得出基于估计信道协方差的检测方案性能较优;最后通过数值仿真对比分析了两种方案的干扰检测性能。     

Q/V频段5G基站对NGSO星座系统地球站的干扰分析

针对Q/V频段5G基站对非静止轨道（Non-geostationary Orbit,NGSO）星座系统地球站的同频干扰问题,提出了一种5G毫米波系统与NGSO星座系统下行链路间的干扰分析方法。结合NGSO星座系统地球站天线指向的时变性,建立了基于时间离散的“拉远式”和“挖洞式”的动态干扰分析模型,并从强度和集总效应两个维度综合评估了系统之间的干扰情况。以OneWeb系统为例,仿真分析了不同保护距离下5G基站对OneWeb地球站的干扰情况。结果表明,在Q/V频段,当保护距离为50 m时,95%的时间内干扰余量不小于15.38 dB,5G基站与NGSO星座系统地球站有兼容共存的空间。     

基于矩阵感知的毫米波MIMO系统信道估计方法

在使用混合波束形成的毫米波大规模多输入多输出系统中，射频链路少于天线数，信道估计非常具有挑战性。当天线阵列缺陷导致未知相位和增益误差时，压缩感知信道估计器的性能会下降。为提高系统鲁棒性，提出了一种新型的基于矩阵感知的信道估计方案。该方案利用毫米波信道的低秩特性，采用凸函数差框架设计信道估计器。理论分析及仿真结果证明，所提方案不受阵列相位和增益误差的影响，与压缩感知方案比较增强了系统的鲁棒性，可获得比矩阵补全方案更好的估计性能。     

无刷直流电机调速系统的最优状态反馈控制研究

本文研究具有量测噪声和负载干扰的无刷直流电动机实时最优速度控制方法。首先建立系统的硬件结构，并推导出系统的数学模型；接着采用卡尔曼滤波器的状态估计；提出了一种基于动态规划的最优反馈控制策略；最后给出了补偿量测噪声和负载干扰的自适应算法。仿照结果表明，提出的方法，在广宽的调速范围内，系统具有较好的静动态性能。验证了提出方法的有效性与可行性。     

SCADA系统干扰与抗干扰研究

所谓干扰就是内部或外部噪声对游有用信号的不良作用。噪声对被测信号存在着严重的干扰,当被测信号很微弱时就会被干扰噪声“淹没”,导致很大的数据采集误差。因此,噪声是数据采集的主要障碍。为了能精确地采集数据,需要消除和抑制系统中的噪声。所以在分析和设计数据采集系统时,必须考虑到可能存在的干扰对系统的影响。SCADA（super Vfsory Control And DataAcquisftion）系统,即数据采集与监视控制系统,由于其应用环境比较恶劣,因此干扰源比较多,从硬件上和软件上采取相应的措施以增强系统的抗干扰能力显得尤其重要,本文结合一个水厂ScADA系统存在的干扰给出实际解决方案。     

DSSS系统中快变化线性调频干扰抑制算法

直接序列扩频(DSSS)系统中用分数傅里叶变换可以抑制线性调频干扰等非平稳干扰,然而快 变化 线性调频干扰有可能在分数傅里叶域上呈现出多个尖峰,不利于干扰的检测。分析了线性调 频干扰对DSSS系统的影响,提出了利用模糊变换和分数傅里叶变换结合抑制线性调频干扰的 算法,通过模糊变换选择延迟时间估计调频斜率,然后在相应的分数傅里叶域滤除干扰,克 服了分数傅里叶变换在估计调频斜率时可能出现的多尖峰问题。仿真表明,此算法可以有效 估计并滤除DSSS中的线性调频干扰。     

一种针对直扩系统的高效干扰方案

扫频干扰是针对直扩系统的一种常用干扰手段,但传统扫频干扰对频率信息未加利用 ,存在干扰效率低下的问题,为此提出了一种基于载频估计的区间扫频干扰方法,通过接收 机对直扩信号进行载频估计,干扰机利用估计的载频确定干扰区间,并在其中进行扫频干扰 。通过分析及仿真验证,证明了这种方法减小了扫频范围,相比传统的扫频干扰能够有效 提高干扰效率,同时相比单/多音等形式的干扰降低了对载频估计的要求。     

同步轨道卫星四站时差统计定轨精度分析

基于卫星通信信号的多站时差测轨是一种重要的新型无源测轨方法,分析其定轨精度对系统 应用具有重要意义。介绍了四站时 差测轨原理与系统组成,提出了基于四站时差测量数据的自校准统计定轨策略,采用计算机 仿真了同步轨道卫星的统计定轨精度。仿真结果表明：当无系统误差时,24 h观测数据统计定轨位置误差约为11 m,预报1周位置误差约100 m;当存在系统 误差时,可用自校准方法同步估计系统误差,系统误差估计精度约为4 m,位置误差约 为120 m,预报1周的位置误差约为200 m。     

UFMC系统在多径衰落信道中的干扰消除

通用滤波多载波(UFMC)是5G通信系统中的关键技术，能够降低带外泄露。但是在多径衰落信道下UFMC系统会受到符号间干扰（ISI）和多普勒效应产生的载波频率偏差的影响，从而使系统的性能下降。为了消除系统中的干扰，提出了一种迭代最大似然算法。该方法主要通过迭代最大似然算法（ML）计算出载波频率偏差，把估计出的结果作为初始值并运用迭代的方法得到最终的载波频率偏差，当达到收敛区间时，迭代结束；最后利用相位旋转的概念补偿载波频率偏差并运用最小二乘算法更新信道响应信息，减少该系统干扰。仿真结果表明，在信噪比大于10 dB时，随着信噪比的增大，算法能够有效地抑制系统中的干扰，提高UFMC系统的性能。     

运用多层中间商模型解析“贴牌生产”微利与大商企发展问题

"贴牌"(生产或销售)是当今国内外相当普遍的经济现象,关于贴牌生产(或贴牌销售)利弊的争论在学术界已相当广泛,争论的焦点是利益分配。为使我国赢得在贴牌生产中因销售环节丢失的大部分利润,必须高度重视销售流通环节,同时着力培育中国自己的"商业航母",尤为重要。     

试论经济增加值(EVA)方法的应用及其局限性

经济增加值(EVA)是指公司税后经营利润扣除债务和股权成本后的利润余额。EVA强调的是一种“经济收益”,与传统会计上描述的利润是有区别的。EVA的简单公式:EVA=税后利润-(加权平均资本成本WACC)×(负债+股东投资)或EVA=调整后的收入-资金的机会成本。EVA对企业管理体系、激励制度、评价指标、理念体系、企业文化等方面将可以起到十分重要的作用。EVA有局限性。     

自驾车旅游研究的新视角:旅游网络论坛的主帖分类研究

随着互联网的普及,自驾车旅游与旅游网络论坛产生了密切的联系。确立主帖的分类体系为询问帖、分享帖、活动帖、资讯帖是4个主要类型,体现出旅游者信息行为、旅游体验分享行为和社区交往行为。“行车路线”、“寻找同行”、“图文游记”是会员最关注的话题。网络论坛具备了单向传媒、口碑传播和专家意见多种信息渠道的功能,灵活性强,能够满足游客个性化的需求。     

“神秘湘西”旅游品牌核心价值的构建理念

随着"神秘湘西"旅游品牌吸引力的逐渐增强,及湘西各景点纷繁杂乱、各自为阵的问题不断凸现,关于如何打造作为地域总品牌的"神秘湘西"的品牌核心价值,并把各个设计理念不统一的景点收敛在一个统一的品牌内涵和定位中,从而进一步提升湘西旅游品牌的魅力和竞争力,日益成为当前湘西旅游产业进一步发展亟待解决的紧迫问题。所以要从湘西历史文化根籁中,寻找出"巫傩化的民俗风情"这一品牌核心理念,并把它作为构建湘西旅游品牌核心价值的总理念。     

外商直接投资、经济集聚与绿色经济效率——理论分析与中国经验

现有关于FDI如何影响绿色发展的文献往往忽略经济集聚的作用,文章构建"FDI-经济集聚-绿色经济效率"的逻辑框架,并基于2004~2018年城市面板数据进行验证。研究发现:(1)FDI对绿色经济效率扮演着双重角色,其既通过产业结构产生负面效应,又通过经济集聚与节能减排技术发挥正面效应;(2)FDI总体上有利于提升绿色经济效率,这得益于经济集聚在削弱FDI产业结构效应的同时,强化其节能减排技术效应;(3)无论是全国还是东部地区,当经济集聚适度时,FDI与经济集聚能形成协同效应,从而促进绿色经济效率;当经济集聚超过临界值,全国与东部地区呈现拥挤效应,而中西部地区呈现集聚效应,由此致使FDI对绿色经济效率的影响效果存在显著的区域差异。     

中西治税理念比较及借鉴——兼议我国公共财政框架下“公共税收”治税理念的确立

我国与西方国家的治税理念是截然不同的,主要表现在“国家本位观”与“纳税人本位观”以及“人治”观与“法治”观的差异上。在我国社会主义市场经济的初步建立和发展的背景下,在构建成的公共财政基本框架下,借鉴西方国家的治税理念,应确立以“社会公众的税收”理念为灵魂,以“保护纳税人权利、服务纳税人”和“税收法治”的理念为本质特征的我国自己的“公共税收”治税理念。     

低压电力线载波通信的接口电路设计

中国加入WTO后纺织业面临的竞争环境发生变化,面对国外反倾销等其他非关税壁垒的加强,研究浙江纺织业如何通过规范竞争秩序等措施,避免被国外反倾销,对具有比较优势的浙江纺织业具有重要意义。     

The political market for immigration restrictions: Model and test

This paper addresses the important question of whether public investment spending on economic infrastructure enhances economic growth in Mexico. It estimates a Cobb-Douglas production function that includes public infrastructure capital. Using cointegration analysis, the paper estimates a vector error correction model (VECM) for the 1995?–?99 period. The results suggest that there is a long-term stable relationship among the variables included in the VECM. The evidence also indicates that both public infrastructure spending and private capital formation have a positive and highly significant effect on the rate of output growth. Finally, the impulse response functions (IRF) and the variance decompositions (VDC) of the endogenous variables in the VECM suggest that the response of private capital to public infrastructure is positive while the reverse causation is not affirmed. From a policy standpoint, the findings call into question stabilization policies that disproportionately reduce public infrastructure to meet targeted reductions in the fiscal deficit (JEL, O1, O47, O54).     

Investing in Socially Responsible Companies is a must for Public Pension Funds – Because there is no Better Alternative

>With assets of over US$1.0 trillion and growing, public pension funds in the United States have become a major force in the private sector through their holding of equity positions in large publicly traded corporations. More recently, these funds have been expanding their investment strategy by considering a corporations long-term risks on issues such as environmental protection, sustainability, and good corporate citizenship, and how these factors impact a companys long-term performance. Conventional wisdom argues that the fiduciary responsibility of the pension funds trustees must be solely focused on their beneficiaries and, therefore, their investment criteria must be based strictly on narrowly defined financial measures. It is also asserted that well-established financial measurements of corporate performance already include long-term risk assessment through discounted present value of future flow of earnings. Consequently, all other criteria are contrary to the best interest of the pension funds beneficiaries. In this paper, we assert that, contrary to conventional wisdom, pension funds, and for that matter other mutual funds, must be concerned with the long-term survival and growth of corporations. These measures are generally referred to socially responsible investing (SRI) and when applied to corporations, it is termed socially responsible corporate conduct (SRCC). We demonstrate that current measurement of future risk assessment invariably understates, and quite often completely overlooks, these long-term risks because of the inherent bias towards short-run on the part of financial intermediaries whose compensation depends greatly on short-term results. Furthermore, there is ample evidence to suggest that these intermediaries have been engaging in self-serving practices and thus failing in their duties to serve their clients, i.e. pension funds, best interests. Because of their large holdings in the total market as well as individual companies, these funds cannot easily divest from poorly performing companies without destabilizing the companies stock and overall markets. Hence, they must opt for a strategy of emphasizing investment criteria that encourage companies to take into account long-term aspects of their operations in terms of their impact on environment, sustainability, and community welfare, to name a few. We argue that an exclusionary, and even a primary, focus on short-term financial criteria is no longer a viable option. It also calls for the pension funds to encourage greater transparency and accountability of the entire corporate sector through improved corporate governance. Thus socially responsible investing practices are not merely discretionary and desirable activities; they are a necessary imperative, which both the corporations and public pension funds, and other large institutional holders, will ignore at serious peril to themselves. Finally, the paper considers some of the recent developments where corporations have been responding to these challenges and how their actions might be strengthened through greater disclosure and transparency of corporate activities. It also makes recommendations for the pension funds to support further research in creating new measurement standards that further refine the concept of socially responsible investing as a necessary ingredient of long-term corporate survival and growth in the context of a changing economic, environmental and socio-political dynamic.     

Distributed group support: The effects of voting Tools on group perceptions of media richness

Decision groups distributed both temporally and geographically encounter a multitude of coordination problems. This experiment used a set of GDSS Tools called List and Vote, and alternative interaction management procedures, as mechanisms for coordinating distributed groups using a computer conferencing system and for structuring group processes. The study examined media richness using a modification of the adjective-pairs developed by Zmud, Lind, and Young (1990). The Tools significantly improved subjective perceptions of media richness. The attempted manipulation of the presence or absence of sequential procedures for the most part was not effective in creating significant differences in group perception of media richness.