200 MHz高频晶体振荡器研制

研制了一种200 MHz高频晶体振荡器,概述了产品的组成及工作原理,给出了该高 频晶体振荡器的详细设计方法。仿真与实测结果表明,该晶体振荡器不仅具有优良的相位噪 声,同时也达到了预期的抗振设计要求。     

LDPC码在非相干BFSK系统中的性能分析

通过理论分析和计算机仿真研究了LDPC码在非相干BFSK系统中的性能。首先证明单 输入双输出的非相干BFSK系统满足信道对称条件,然后分别利用离散密度进化（DDE）和高 斯近似（GA）算法给出了LDPC码的性能下界,后者与前者相比性能非常接近而且计算量要小 很多。通过仿真得到几种常用LDPC码的性能并与译码门限以及香农极限进行了比较,在相同 码长条件下,度参数为(3,6)的码字具有最优的性能,并且其译码门限距离香农极限只有 约0.67 dB。     

高速移动OFDM系统信干比的低复杂差分计算

针对高速移动正交频分复用系统,提出了迭代消除子载波干扰的 信干比差分计算方法。该方法把前后两次迭代的子载波干扰进行差分运算,差分运算值的加 权作为干扰,每次迭代消除子载波干扰后的信号作为有用信号,实现信干比的计算。 误差分析和仿真数据表明：采用这种方法计算信干比可以有效估算出系统信干比,同时算法 复杂度较低。     

中继卫星SMA系统前向链路多波束形成技术

提出了一种新的中继卫星前向SMA（S频段多址）系统前向链路中多波束形成方法,即在地面 采用数字移相代替中继星星上模拟移相完成波束形成;指出了需要解决的关键技术问题和解 决方法,通过“星（用户星）-星（中继星）-地”无线联试,验证了地面数字移相的正确性 ,对简化中继星上设备、实现前向链路同时多目标能力具有积极意义。     

Do sunspot numbers cause global temperatures? Evidence from a frequency domain causality test

This article applies the causality test in the frequency domain, developed by Breitung and Candelon (2006), to analyse whether sunspot numbers (used as a partial approximation to solar irradiance) cause global temperatures, using monthly data covering the time period 1880:1–2013:9. While standard time domain Granger causality test fails to reject the null hypothesis that sunspot numbers do not cause global temperatures for both full and sub-samples (identified based on tests of structural breaks), the frequency domain causality test detects predictability for both the full-sample and the last sub-sample at short (2–2.6 months) and long (10.3 months and above) cycle lengths, respectively. Our results highlight the importance of analysing causality using the frequency domain test, which, unlike the time domain Granger causality test, allows us to decompose causality by different time horizons, and hence, could detect predictability at certain cycle lengths even when the time domain causality test might fail to pick up any causality. Further, given the widespread discussion in the literature, those results for the full-sample causality, irrespective of whether it is in time or frequency domains, cannot be relied upon when there are structural breaks present, and one needs to draw inference regarding causality from the sub-samples, we can conclude that there has been an emergence of causality running from sunspot numbers to global temperatures only recently at cycle length of 10.3 months and above.     

How the internet of things technology enhances emergency response operations

The Internet of Things (IoT) is a novel paradigm that connects the pervasive presence around us of a variety of things or objects to the Internet by using wireless/wired technologies to reach desired goals. Since the concept of the IoT was introduced in 2005, we see the deployment of a new generation of networked smart objects with communication, sensory and action capabilities for numerous applications, mainly in global supply chain management, environment monitoring and other non-stress environments. This paper introduces the IoT technology for use in the emergency management community. Considering the information required for supporting three sequential and distinct rhythms in emergency response operations: mobilization rhythm, preliminary situation assessment rhythm, and intervention rhythm, the paper proposes a modified task-technology fit approach that is used to investigate how the IoT technology can be incorporated into the three rhythms and enhance emergency response operations. The findings from our research support our two hypotheses: H1: IoT technology fits the identified information requirements; and H2: IoT technology provides added value to emergency response operations in terms of obtaining efficient cooperation, accurate situational awareness, and complete visibility of resources.     

Spillover across Eurozone credit market sectors and determinants

We examine spillover and its determinants among Eurozone sector level credit markets using time and frequency domain spillover approaches. Based on network theory and connectedness analysis, we identify the sectors that are major transmitters and receivers of spillover during normal and crisis periods. The rolling window analysis shows that short-run spillover among credit market sectors intensifies during global and Eurozone crisis periods. Further, using Bayesian model averaging, we find that overall financial conditions and stock market volatility are the main drivers of total and sector-level spillover. Our findings have important implications for policymakers and investors interested in Euro-area credit risk at the sector level.     

艾滋病疗效的预测模型

文章首先对数据进行预处理,运用K-means聚类方法将患者根据初始特征将其分为3类,通过分析与推测,初步得到了最佳终止停药时期在第10周左右或者是第20-25周。进一步,本文给出应用相对频率作为随机变量落在某个区间的概率的估计值新的方法,从而得到最佳治疗终止时间的概率密度函数的近似拟合函数,并且通过计算得出,最佳治疗终止时间为22或23周;最佳治疗时间段为第21-24周。     

一种基于代价函数的正交频分复用中符号同步与频偏估计算法

本文利用正交频分复用（OFDM）帧结构的特点，引入代价函数，推导出了一种符号同步算法和频偏估计算法，并从理论上分析了在存在频偏的情况下，符号同步可以独立于频偏估计。计算机仿真表明，该算法具有较好的同步和频偏估计性能。     

“Out of sight,out of mind”: Pantry stockpiling and brand-usage frequency

Both researchers and brand managers have suggested that price promotion induced stockpiling can increase a household's usage frequency of a product. Empirical findings, however, contradict this relationship. In reconciling this inconsistency, laboratory results reported in this paper suggest that stockpiling may have the greatest effect on a product's usage frequency when usage-related thoughts about the product are highly salient. These results also suggest that when stockpiling stimulates usage frequency, it can do so by increasing perceptions of a product's versatility. These findings have implications for the advertising versus promotion debate. They suggest that consumer promotions and advertising might play a joint and complementary role in increasing product usage: promotions by encouraging stockpiling, and advertising by building the usage-related salience needed to deplete the stockpiled inventory.The authors are grateful to the Marketing Science Institute and to the Amos Tuck School of Business Administration at Dartmouth College for their financial support of this project. They are additionally grateful to Scott Neslin, Jim Lattin, and Jeff Inman for helpful comments on earlier drafts.