短时分数阶傅里叶变换对调频信号的时频分辨能力

调频信号的检测和参数估计一直是信号处理领域的研究热点之一。为深入挖掘短时分数阶傅里叶变换对调频信号的时频分析优势,从短时分数阶傅里叶变换的定义出发,推导了其时频分辨能力与信号参数的关系,并与短时傅里叶变换进行了对比分析。结论表明,短时傅里叶变换时频分辨能力与信号频率变化率有关,而短时分数阶傅里叶变换几乎不受调频率变化率影响。最后,通过对比仿真实验证明,对于频率变化率较小的信号,两者时频分辨效果差别不明显,对于频率变化率较大的信号,短时分数阶傅里叶变换的时频分辨效果更好。     

数字化短波调制解调器设计

为了实现高速、可靠、易于实现的数字化短波通信,提出了一种基于通用计算机的调制解调器设计方案。为了实现高可靠性的数字短波信号传输,搭建了用户端到用户端的转换平台设计,其中,模拟短波电台提供系统收发天线,使用计算机声卡实现数字信号与音频之间的数模/模数互转,使用计算机处理器（CPU）调制解调。根据短波通信功率受限的特点,使用恒包络调制——高斯最小频移键控（GMSK）作为调制方式。为了实现快速准确的时间同步,设计了一种多训练序列分段插入的帧结构方案。计算机仿真和实测结果表明,该调制解调器在信噪比15 dB下可达到10-5的误比特率,实现可靠短波通信。     

An exploratory look at supermarket shopping paths

We present analyses of an extraordinary new dataset that reveals the path taken by individual shoppers in an actual grocery store, as provided by RFID (radio frequency identification) tags located on their shopping carts. The analysis is performed using a multivariate clustering algorithm not yet seen in the marketing literature that is able to handle data sets with unique (and numerous) spatial constraints. This allows us to take into account physical impediments (such as the location of aisles and other inaccessible areas of the store) to ensure that we only report feasible centroid paths. We also recognize that time spent in the store plays an important role, leading to different cluster configurations for short, medium, and long trips. The resulting three sets of clusters identify a total of 14 “canonical path types” that are typical of grocery store travel, and we carefully describe (and cross-validate) each set of clusters. These results dispel certain myths about shopper travel behavior that common intuition perpetuates, including behavior related to aisles, end-cap displays, and the “racetrack.” We briefly relate these results to previous research (using much more limited datasets) covering travel behavior in retail stores and other related settings.     

梯形弯折线单极子天线的谐振特性

基于矩量法数值方法，研究了由梯形弯折线构成的单极子天线的谐振特性。着重于分析在天线高度和宽度都有明确尺寸要求条件下，天线输入参数与梯形弯折线弯折次数的关系以及与弯折角的关系。结果表明，弯折角的改变对天线谐振特性具有很强的调节作用，恰当地选择弯折角可以有效地改变天线的谐振频率与带宽，提高天线的辐射能力和匹配性能。     

A cross-cultural study of switching barriers and propensity to stay with service providers

This study examines the important and often underestimated role that switching barriers play in the propensity to stay with service providers. Three service types (with different structural characteristics) were studied across two diverse cultures—Australia (Western, individualistic culture) and Thailand (Eastern, collectivist culture). Six potential switching barriers are examined: search costs; loss of social bonds; setup costs; functional risk; attractiveness of alternatives; and loss of special treatment benefits. The results from a series of multiple regression analyses show switching costs capture a substantial amount of the explained variance in the dependent variable, propensity to stay with a focal service provider. Furthermore we demonstrate using interaction terms that these switching costs appear to be universal across west-east cultures. However, significant variations were found across industries. Next, using a hierarchical regression procedure, we add a satisfaction variable into each model. The incremental gain in R² is significant in each industry. Nonetheless the significant impact of switching barriers gives rise to the identification of a new type of service loyalty, which we term “captive loyalty.”     

模糊群决策方法在中间商选择中的应用研究

企业在选择中间商时往往面临着候选伙伴评价指标信息获取的困难,为了使决策科学合理,采用群决策方法集成各领域不同专家的信息,通过语言变量把专家的主观判断转化为对应模糊数,建立相应的数学模型,并计算出用模糊数表示的候选者综合评价值。     

浅析庞巴迪CRJ-200飞机高频通信系统的故障

本文对庞巴迪CRJ-200飞机运行中出现的高频通信系统故障进行分析,介绍了根据故障现象,依据维护手册并结合以往经验,快速判明故障原因,排除故障的方法。对故障进行了分析和经验总结。     

基于全面预算管理的火电企业成本控制研究

本文探究了火电企业的成本构成,总结了火电企业全面预算管理成本核算的方法,分析研究了成本核算的途径,提出了成本控制的指标,研究了控制成本的措施,找到了解决问题的途径。对企业节能降耗,降低经营风险,加强计划性成本开支,实施积极的财务费用、生产费用、煤炭资金等成本控制,进行全面的预算管理,提高企业效益意义重大。     

红外碳硫仪测定土壤中碳含量的探讨

目前,传统土壤中碳的测定常采用重量法、容量法、气量法等手段,这些方法存在装置复杂、操作繁琐、效率低下、不易掌握等诸多问题,不能满足大批量地质土壤样品的分析。本文探讨通过采用高频红外碳硫分析仪代替传统手段对土壤中碳、有机碳和无机碳进行测定的可行性及优越性,并分析测定过程中进一步提高测定准确度、提升操作效率、提升实验室经济效益的方法手段。     

基于GIS空间分析的泉州市居民点分布特征研究

从泉州市居民地图斑提取居民点分布图,构建居民点空间分布的泰森多边形,统计泉州市8个县市居民点分布的泰森多边形面积的变异系数（CV值）,结合人口密度图分析泉州市居民点的空间分布特征,进一步研究高程、坡度、道路3个因素对泉州市居民点空间分布的影响。研究结果显示,石狮市居民点呈随机分布模式,其它7个县市居民点均呈集群分布模式,总体上属于集群分布;居民点趋于分布在高程低,坡度平缓,距离道路较近,交通运输便利的地带。