Disruption in the automotive industry: A Cambrian moment

The automotive industry is experiencing a moment of innovation. With electronics gaining importance, the need to find sustainable solutions and the rampant availability of sharing platforms, the dynamics of this sector is witnessing a paradigm shift. A host of startups is colonizing every niche of what seems to be the new architecture: shared and self-driven electric vehicles. Old incumbents and emerging startups are interacting to control key technologies and the user interfaces of the future. The mechanical machine is being converted into a computer. The connected car is creating a new ecosystem for entrepreneurial opportunities. This study analyzes a set of 156 venture-backed startups: the nature of the firms, their founders’ profiles, their origins, their technological capabilities, and their investors. Our findings and conclusions are: (1) a phase of instability and vibrancy is beginning wherein multiple emerging firms compete to impose their standards, (2) the competitive battle is conducted in the digital arena, (3) disruption is led by outsiders with entrepreneurial experience and deep knowledge of digital technologies, and (4) a final winning dominant design may emerge. Entrepreneurial outsiders and outsiders coming from consumer electronics, electrical companies, and/or digital platforms have a window of opportunity to enter this new market.     

时变信道下ADF协作车载通信误码率分析

智能车载协作系统中车辆快速移动使得无线通信信道具有时变特性，为有效评估系统的误码性能，给出了符合车载时变信道的一阶自回归（AR1）模型，提出了一种基于AR1模型的自适应解码转发（ADF）协作误码率分析方法。该方法通过AR1模型的多普勒频偏相关系数来刻画时变信道特性,根据中继译码结果自适应选择是否协作转发，提升了智能交通系统的可靠性。此外，利用矩生成函数（MGF）推导出ADF协作下多进制正交幅度调制（M-QAM）信号误码率封闭表达式，并分析了车载移动速度和信道状态信息(CSI)估计精度对误码性能的影响。数值仿真结果表明，车载系统能通过增加CSI估计精度，有效地减少车载快速移动引起的误码平顶值。该方法相对于放大转发（AF）协作通信方式，平均误码性能提高约8.7 dB。     

进出口贸易与中国制造业要素重置——基于动态面板数据的实证分析

在使用2000-2009年企业层面的数据测度中国制造业的要素重置效应的基础上,运用动态面板数据的系统广义矩方法检验了进出口贸易对制造业要素重置的影响作用。结果表明进出口贸易对中国制造业的要素重置综合效应存在显著的促进作用,从分解来看,进出口贸易对退出效应和在位企业要素重置效应均有显著的正向作用;进一步研究发现,进出口贸易仅对劳动力密集型行业的进入效应存在显著的正向影响,而对资本密集型行业的进入效应作用不明显。     

逐次定数截尾下Weibull分布参数的逆矩估计

基于逐次定数截尾样本下,讨论了两参数Weibull分布的参数估计,得到了两参数的逆矩估计.并利用模拟方法与极大似然估计作比较,模拟结果表明逆矩估计优于极大似然估计。     

样本数据缺失情形下泊松过程的强度估计和检验

文章讨论了样本数据缺失情形下泊松过程的强度估计和检验问题。用极大似然估计、矩估计法和最小二乘估计法对强度进行估计,分别得出了极大似然估计强度的迭代方法,矩估计值及最小二乘估计值。证明了矩估计值和最小二乘估计值的无偏性和相合性,导出了其统计量的极限分布。最后,对两个Poisson过程的差异进行了假设检验同时给出渐近置信区间。     

弯曲梁上剪力、弯矩和分布载荷间微分关系

学习梁的弯曲变形必然要分析梁横截面上的内力,最基本的方法是采用截面法进行逐段进行截取分析求出其剪力和弯矩,但是这种方法非常复杂和繁琐。根据多年的教学、研究和分析,找出了一个求解弯曲梁界面剪力图和弯矩图的方法,可以省去繁琐的截面法求解过程,不用列剪力方程和弯矩方程快速画出剪力图和弯矩图。     

中欧标准关于钢结构地震作用的对比

对比了中欧抗震标准中有关钢结构抗震设计的若干条文,包括抗震设防目标、场地分类、抗震设计反应谱及抗弯框架结构的设计地震作用。结果表明:在对场地条件以及地震作用的计算方法进行一定换算的基础上,对于D类场地下不超过50 m的工字形截面抗弯框架结构,欧洲抗震标准中柱的设计地震作用基本上要高于GB 50011—2010,梁的设计地震作用基本上要比GB 50011—2010低10%~40%。     

Stability of characterizations of normal distributions based on the conditional expected values of the sample skewness and the sample kurtosis

Characterizations of normal distributions given by Nguyen and Dinh (1998) based on conditional expected values of the sample skewness and the sample kurtosis, given the sample mean and the sample variance, are shown to be stable. Received: September 1998     

Pricing and hedging contingent claims using variance and higher order moment swaps

This paper suggests perfect hedging strategies of contingent claims under stochastic volatility and random jumps of the underlying asset price. This is done by enlarging the market with appropriate swaps whose pay-offs depend on higher order sample moments of the asset price process. Using European options and variance swaps, as well as barrier options written on the S&P 500 index, the paper provides clear cut evidence that hedging strategies employing variance and higher order moment swaps considerably improves upon the performance of traditional delta hedging strategies. Inclusion of the third-order moment swap improves upon the performance of variance swap-based strategies to hedge against random jumps. This result is more profound for short-term out-of-the money put options.     

现浇混凝土空心楼盖体系受弯研究

现浇混凝土空心无梁楼盖有两个突出的特点:一是在板内预埋有高强薄壁管,从而形成空心,减轻结构自重;二是在框架柱之间设有暗扁梁,以增强结构整体刚度,提高结构整体抗震性能。本文以现浇混凝土空心无梁楼盖两个突出的特点为基础,对其基本力学性能进行研究分析,探讨合理的计算方法。