基于改进型技术接受模型的物联网服务采纳实证研究

物联网技术的应用已经大量出现在我们的日常生活和企业经济活动中,但仍然局限在相对独立的范围内,网络互连互通和信息共享依然未能实现。本文从行为科学的视角,按照技术接受模型的研究方法,通过问卷调查和结构方程统计分析,对物联网服务采纳进行了实证研究。结果表明:物联网发展的瓶颈依然是核心技术和网络互连标准问题,给消费者提供有用易用的产品和服务是推进其应用的关键,而消费者对物联网环境下的隐私保护和信息安全现已有所关注。     

世界各国的人口出生性别比及其启示

利用联合国《人口年鉴》出生统计专辑汇集的世界各国多年的人口出生数据,对全球不同类型国家近20年来人口出生性别比的统计特征和动态趋势进行描述和概括,以尝试着反映人类人口出生性别比的一般规律及特点,为更客观、准确地认识中国人口出生性别比失常提供背景与基础。     

Fetal movement frequency and the effect of associated perinatal factors: Multicenter study

Background

Decreased fetal movements are associated with adverse perinatal outcomes, including stillbirth. Delayed maternal visits to a health care provider after perceiving decreased fetal movements are frequently observed in stillbirths. Informing pregnant women of the normal range of fetal movement frequency is essential in their earlier visits in order to prevent stillbirth.

基于射频技术的无线识别系统设计

本无线识别系统的设计利用射频技术,阅读器将呼叫信号加载到频率为70MHZ的射频上,以无线方式发给应答器。呼叫信号经过线圈耦合、解调、电压比较器等电路传送到应答器的控制器。控制器对呼叫信号进行分析、确认后,将存储的四位二进制编码通过发送端的调制电路馈送到阅读器,并显示应答器的具体信息。     

高频数据驱动的连续时间模型估计

现代金融经济学中连续时间模型能够更方便地描述重要经济变量的动态过程如股价、汇率和利率等。为连续时间模型提出了一种高频数据驱动的二阶段估计方法,增强了连续时间扩展模型的弹性和可操作性。以Vasicek模型为例给出了该方法的应用实例,首先在第一阶段使用实现波动率方法估计出模型的扩散项参数,然后使用实际数据的稳态分布的前向方程估计漂移项参数。此方法对模型初始设定和优化算法依赖程度低,结果较为稳定可靠。     

Correcting the Errors: Volatility Forecast Evaluation Using High‐Frequency Data and Realized Volatilities

We develop general model‐free adjustment procedures for the calculation of unbiased volatility loss functions based on practically feasible realized volatility benchmarks. The procedures, which exploit recent nonparametric asymptotic distributional results, are both easy‐to‐implement and highly accurate in empirically realistic situations. We also illustrate that properly accounting for the measurement errors in the volatility forecast evaluations reported in the existing literature can result in markedly higher estimates for the true degree of return volatility predictability.     

审美意识:超越有限

艺术的本质在于超越有限 ,即以有限的事物显现无限。艺术表面上离开了有限事物本身 ,实际上却更深入了事物所蕴涵的无限深层内容 ,更接近了事物的真实。艺术品由于超越有限而显现了惟一宇宙的无限内涵 ,故能使鉴赏者具有共通感 ,对鉴赏者具有魅力。艺术品之超越有限物的特点 ,还能使它在不同观赏者那里和在不同时代的人那里不断更新、丰富和深化自身的内容和含义。本文所强调的超越有限 ,不止于超越感性的东西 ,以表现典型概念 ,而且更着重于超越作为感性物与理性物相统一的有限在场者以显现无限的不在场者 ,这不在场者也是感性的东西与理性的东西的统一。     

Why Frequency is Not Well Defined for Engineering Systems with Nonexponential Failure Times

Dr. Yellman proposes to define frequency as “a time‐rate of events of a specified type over a particular time interval.” We review why no definition of frequency, including this one, can satisfy both of two conditions: (1) the definition should agree with the ordinary meaning of frequency, such as that less frequent events are less likely to occur than more frequent events, over any particular time interval for which the frequencies of both are defined; and (2) the definition should be applicable not only to exponentially distributed times between (or until) events, but also to some nonexponential (e.g., uniformly distributed) times. We make the simple point that no definition can satisfy (1) and (2) by showing that any definition that determines which of any two uniformly distributed times has the higher “frequency” (or that determines that they have the same “frequency,” if neither is higher) must assign a higher frequency number to the distribution with the lower probability of occurrence over some time intervals. Dr. Yellman's proposed phrase, “time‐rate of events … over a particular time interval” is profoundly ambiguous in such cases, as the instantaneous failure rates vary over an infinitely wide range (e.g., from one to infinity), making it unclear which value is denoted by the phrase “time‐rate of events.”     

The Realized Laplace Transform of Volatility

We introduce and derive the asymptotic behavior of a new measure constructed from high‐frequency data which we call the realized Laplace transform of volatility. The statistic provides a nonparametric estimate for the empirical Laplace transform function of the latent stochastic volatility process over a given interval of time and is robust to the presence of jumps in the price process. With a long span of data, that is, under joint long‐span and infill asymptotics, the statistic can be used to construct a nonparametric estimate of the volatility Laplace transform as well as of the integrated joint Laplace transform of volatility over different points of time. We derive feasible functional limit theorems for our statistic both under fixed‐span and infill asymptotics as well as under joint long‐span and infill asymptotics which allow us to quantify the precision in estimation under both sampling schemes.     

三维涡流场基于有限元法的电磁位对

介绍了用有限元法解决三维涡流场问题时电磁位对的优选问题,分析了其适应情况和优缺点.对目前基于有限元法的三维涡流场数值分析方法的国内外现状作了综合评述.