多层介质频率选择表面的等效电路分析方法

基于数值仿真计算和微波网络理论,提出了一种多层介质中频率选择表面（FSS）等效电路的分析方法。该方法物理过程直观,计算量小,适用于二维任意形状FSS等效电路的精确求解。以方形贴片型FSS为例验证了等效电路模型的准确性,并分析了多层介质对其等效电路参数的影响规律。最后,基于滤波器理论与FSS等效电路模型设计了双层带通型FSS,计算结果表明全波仿真结果与理论计算结果基本一致,为多层FSS的综合设计提供了一种精确设计方法。     

跳频信号的归一化多普勒频差最大似然估计

针对双站定位涉及的跳频信号多普勒频差估计问题,提出了归一化的频差最大似然估计算法,利用两个定位站接收到的跳频脉冲串信号,构建一个关于基准跳频频率多普勒频差的似然函数,通过网格搜索得到使似然函数最大的多普勒频差估计,既解决了跳频信号在不同跳频频率上多普勒频差不一致的问题,又充分利用在不同频率的脉冲串信号提高了多普勒频差估计精度。通过仿真对算法的性能进行了评估,结果表明,与基于子空间的算法比较,在脉冲数达到240个时,所提算法执行效率提升30%以上。     

Empirical Evidence of the Leverage Effect in a Stochastic Volatility Model: A Realized Volatility Approach

Increasing attention has been focused on the analysis of the realized volatility, which can be treated as a proxy for the true volatility. In this paper, we study the potential use of the realized volatility as a proxy in a stochastic volatility model estimation. We estimate the leveraged stochastic volatility model using the realized volatility computed from five popular methods across six sampling-frequency transaction data (from 1-min to 60- min) based on the trust region method. Availability of the realized volatility allows us to estimate the model parameters via the MLE and thus avoids computational challenge in the high dimensional integration. Six stock indices are considered in the empirical investigation. We discover some consistent findings and interesting patterns from the empirical results. In general, the significant leverage effect is consistently detected at each sampling frequency and the volatility persistence becomes weaker at the lower sampling frequency.     

Are high–frequency traders informed?

Are high–frequency traders (HFTs) informed? To address this question, we examine HFTs' activity in the call auction environment, where speed-related trading is limited and signal processing capacity becomes more relevant. To model the call market, we consider the Kyle (1989) rational expectations framework for strategic trading. The test we propose for detecting informed HFTs in this market assesses potential deviations of the informativeness of HFTs' aggregate (net) demand, from the informativeness of the aggregate demand submitted by the rest of the traders. Data from the Euronext Paris preopening phase indicate that informed HFTs are present in the market just before the opening. Our results provide useful guidance for the assessment of the influence of HFTs’ quotes on price quality, an important issue for market regulators and policy makers.     

地区创业氛围及其作用机理——一个族群水平的创业分析架构

创业氛围是一个地区所有族群成员关于创业的心智能力、价值观念和习俗惯例的集体和外在的表现。创业氛围是内生的,它是由创业活动衍生的创业学习、心理体验和社会互动的结果。创业氛围通过提升创业平均收益率和改变族群成员创业风险偏好,来提高创业惯例复制频率,进而提高地区创业活动水平。创业氛围与创业活动之间存在一个以知识累积和报酬激励为动力的正反馈演化路径。中西部地区促进创业活动的关键是,着力培育创业氛围并实现其临界突破。     

基于交易成本的消费者网络购物意愿的实证研究

首先对网络购物中的交易成本相关研究进行文献综述,在此基础上,建立网络购物中消费者交易成本影响因素的相关研究假设,运用PLS—SEM模型的研究方法,采用问卷调研获取的数据,对消费者网络购物意愿进行了实证分析。研究表明,购买频率和不确定性显著地影响交易成本,不确定的影响作用较大,并最终对购买意愿产生影响。     

Consumers' perception of and attitudes towards organic food in Galicia (Northern Spain)

Although the organic sector is still relatively small, the demand for organic food is increasing throughout the world. The characterization of consumers' perception of and attitudes towards organic food is important to enable the development of marketing policies aimed at attracting conventional consumers to the sector. Consumers' behaviour studies must be conducted specifically for different regions and countries as perceptions and attitudes vary across the world. In the present study, a questionnaire was designed for administration to consumers in Galicia (Northern Spain). The questionnaire was administered to 830 consumers in 200 establishments to obtain data about the consumers' perception of and attitudes towards organic food. The survey results showed that one‐third of responders consume organic food and that the typical profile of a consumer of organic food is a middle‐aged, medium‐high class, university‐educated female living in a large village, who shops in supermarkets and preferably consume vegetables, fruits and eggs. Most people who declared that they consume organic products confuse these with home and locally produced food, indicating the potential for growth of the organic sector by providing such consumers with appropriate information. Most consumers (including conventional consumers) have a good opinion of organic food and consider that it is better for health, is of better quality than conventional food and avoid pesticide residues. However, price continues to be a barrier to the consumption of organic produce. Most respondents stated that they would consume more organic food if the price was only between 10% and 30% higher than the conventional equivalent. Finally, organic consumers in Galicia showed positive attitudes towards using local breeds in organic agriculture, both for producing food and for ecotourism and educational activities. Such activities could contribute to conserving breed biodiversity and adding value to organic farming.     

RFID在物流管理中的战略价值与挑战

射频识别是物流行业中的数据采集技术之一．能为物流和供应链管理提供大量准确和实时数据．为提高供应链敏捷性、透明度提供潜在的解决方案。但RFID技术的大规模应用取决于RFID系统能否与企业内外物流信息系统有效集成,企业能否分析数量巨大的数据,以及是否顺利实施和RFID技术采纳相关的组织流程和文化的重新设计。     

The differences in hotel selection among various types of travellers: A comparative analysis with a useful bounded rationality behavioural decision support model

This study aims to investigate the hotel selection differences among different types of travellers through online hotel reviews. Specifically, the study performs a detailed examination of the differences in hotel key factors, criterion importance and selection results among five types of travellers, namely, business, couples, families, friends and solo. Using a sample of 194,885 online reviews on TripAdvisor.com, this study identifies the hotel key factors and criterion importance by employing the term frequency-inverse document frequency algorithm and Word2Vec algorithm. Additionally, a bounded rationality behavioural decision support model with picture fuzzy information is proposed to address hotel selection problems for different traveller types. Our results suggest that different types of travellers present differences in hotel key factors, criterion importance and selection results. However, families and friends have similar hotel selection results. This study can serve as a reference for hotel managers in understanding traveller preferences and for tourism website optimisation.     

Vivid-memory formation through experiential value in the context of the international industrial exhibition

This study empirically tests the relationships between experiential value, vividness, storytelling intentions, and patronage intentions in the industrial exhibitions, and examines the moderating effect of mementos. A total of 211 respondents were recruited from visitors to the international game exhibition. According to the results, (1) three dimensions of experiential value (service excellence, playfulness, and aesthetics) had positive effects on vividness, (2) vividness positively influenced storytelling and patronage intentions, (3) storytelling intentions increased patronage intentions, and (4) mementos had a significant moderating effect on the relationship between vividness and storytelling intentions but not on the relationship between vividness and patronage intentions.