随机正交变换法在隐私保持关联规则挖掘中的应用

隐私保护是当前数据挖掘领域中一个十分重要的研究方向。本文针对关联规则挖掘中如何保持隐私的问题,采用一种不依赖具体数据的随机正交变换方法,从而解决了在数据集容量很大的情况下,运算量大的问题,并使用传统隐私保护度评价方法与正交变换的方向隐私保护度相结合的方法评价变换的隐私保护度,进而使得结果更符合实际情况。理论分析和论证表明本文中的方法具有很好的隐私性、高效性和适用性。     

叠加共轭对称训练序列的OFDM系统时频同步方法

针对正交频分复用（OFDM）系统对同步错误率和频率偏移敏感的问题,提出了一种叠加共轭对称训练序列的OFDM系统时间和频率同步方法。该同步方法将快速傅里叶逆变换（IFFT）调制后的序列构成具有共轭对称特性的训练序列,并叠加到OFDM数据符号上;在接收端,利用叠加训练序列和融合循环前缀信息来获取OFDM系统同步信息。理论分析和仿真表明：在信噪比为5 dB时,该同步算法定时同步正确概率已接近100%;在信噪比为4 dB时,频偏估计精度可以达到10-4;该同步算法不仅具有更好的同步性能,而且节省系统的有效带宽以及降低系统的计算法复杂度。     

基于多项式拟合频率重构的物理不可克隆函数优化

近年来硬件安全不断受到挑战,具有不可预测性、随机性等特性的环形振荡器物理不可克隆函数（Ring Oscillator Physical Unclonable Function,RO PUF）可作为硬件安全重要的加密密钥方式,但通常原始RO PUF不满足加密密钥对随机性的要求。因此,提出了基于多项式拟合频率重构的PUF优化方法。首先,实现RO电路的硬宏设计并在现场可编程门阵列(Field Programmable Gate Array,FPGA)上进行实例化,从而获得RO阵列的频率数据;其次,针对原始响应的随机性较差的情况,通过统计分析其分布特征,利用多项式拟合法优化重构RO阵列频率;最后,采用熵密度值评估RO PUF响应的随机性。选用型号为Xilinx Artix 7103的FPGA板进行实验测试评估,结果表明所提方法不仅比原始RO PUF响应的随机性强,而且与随机补丁混合法(Random Patch Mixer,RPM)和基于回归的熵蒸馏法相比也具备更好的随机性。     

墙体参数模糊下穿墙雷达运动目标成像

针对墙参数模糊条件下运动目标成像速度慢、墙参数重建精度差等问题,提出了一种改进拟牛顿-粒子群优化(Limited Broyden Fletcher Goldfarb Shanno-Particle Swarm Optimization,LBFGS-PSO)算法,建立了LBFGS-PSO算法模型,解决了传统拟牛顿算法和粒子群算法计算速度慢、误差较大等问题。该算法与块正交匹配追踪（Block Orthogonal Matching Pursuit,BOMP）算法相结合不仅可以精确重建边墙位置,还能够准确地重建多径效应环境中的运动目标和静止目标,算法的计算速度和精度得到了一定程度的提高。仿真结果和数据分析验证了所提方法的性能。     

The Doctrine of the Mean: Workplace Relationships and Turnover Intention

The present study examines the curvilinear relationships between LMX/TMX and team members' turnover intention simultaneously. That is, members with high LMX, TMX, or both are more likely to have turnover intention. Hypotheses were tested with a sample of 452 nurses, and we adopted the response surface methodology and polynomial regression to test our theoretical model. The hierarchical regression analysis showed that TMX has a U‐shaped relationship with turnover intention but not with LMX. In addition, the results indicate that both the congruence and incongruence of LMX and TMX result in higher turnover intention, but moderate levels of LMX and TMX have the lowest turnover intention. Strengths, limitations, practical implications, and directions for future research are discussed. Copyright © 2018 ASAC. Published by John Wiley & Sons, Ltd.     

The empowerment expectation–perception gap: An examination of three alternative models

Previous empowerment research has focused on subordinate perceptions of empowering leadership and its outcomes. Met‐expectations theory suggests that subordinate expectations of leader behaviours are essential in forming their a posteriori evaluations. To address the lack of investigation of individual expectations in the empowerment literature, in this study, we explore how subordinates' empowerment expectations and perceptions combine to influence their job satisfaction and psychological empowerment based on three alternative, theoretically derived met‐expectation models, namely, the disconfirmation model, the ideal‐point model, and the experiences‐only model. The results of a 2‐stage study of 114 respondents indicate that employees are more satisfied with their work when perceived empowerment exceeds expectations. However, both empowerment perceptions and expectations positively contribute to higher psychological empowerment. We then discuss implications and directions for future research.     

The short‐time behavior of VIX‐implied volatilities in a multifactor stochastic volatility framework

We consider a modeling setup where the volatility index (VIX) dynamics are explicitly computable as a smooth transformation of a purely diffusive, multidimensional Markov process. The framework is general enough to embed many popular stochastic volatility models. We develop closed‐form expansions and sharp error bounds for VIX futures, options, and implied volatilities. In particular, we derive exact asymptotic results for VIX‐implied volatilities, and their sensitivities, in the joint limit of short time‐to‐maturity and small log‐moneyness. The expansions obtained are explicit based on elementary functions and they neatly uncover how the VIX skew depends on the specific choice of the volatility and the vol‐of‐vol processes. Our results are based on perturbation techniques applied to the infinitesimal generator of the underlying process. This methodology has previously been adopted to derive approximations of equity (SPX) options. However, the generalizations needed to cover the case of VIX options are by no means straightforward as the dynamics of the underlying VIX futures are not explicitly known. To illustrate the accuracy of our technique, we provide numerical implementations for a selection of model specifications.     

基于正交试验的“十三五”中国能源强度情景预测与分析

基于1990—2014年相关数据,利用多元回归法构建了中国能源强度预测模型,分析了能源价格、产业结构、能源结构、人口总数4个因素对中国能源强度的影响。将正交试验法与情景分析法相结合,对"十三五"期间中国的能源强度发展进行情景预测及相关路径规划。结果表明:4个因素对中国能源强度均具有显著影响,其中人口总数增加和能源结构优化对中国能源强度的降低具有抑制作用,产业结构调整和能源价格上升对能源强度的降低具有促进作用。对2016—2020年中国能源强度的发展路径进行情景预测,其中2020年中国能源强度最低可降至0.477吨标准煤/万元。最后,提出合理的政策建议。     

基于Fluent的波节管内流体流动与传热特性研究

为了深入研究影响波节管传热效果的主要因素,应用CFD软件Fluent对波节管内流体的流动和传热特性进行数值模拟,分别研究了不同入口流速v(0.3,0.5,0.7和0.9 m/s)、波峰直径D_1(28,30,32,34和36 mm)、弧形段长S_1(34,23,17,13和10 mm)下波节管内流体的流动与传热特性。结果表明,不同型号波节管的努塞尔数(Nu)、流体压力损失以及综合性能随着入口流速的增加而增加;随着波峰直径D_1(弧形段长S_1)的增大,波节管的Nu先增大后减小,最后趋于一个相对稳定的值。当波节管的波峰直径D_1=34 mm时,波节管的传热性能最好,流体压力损失最大,综合性能最好;弧形段长S_1=23 mm时,波节管的换热性能最佳,流体压力损失最大,综合性能最好。通过参数正交分析可知,影响波节管传热效果的因素由强到弱依次为入口流速v、波峰直径D_1、弧形段长S_1。研究成果可为工程实际中提高波节管传热性能提供理论指导。     

绞股蓝荷叶复配茶包研发

以荷叶和绞股蓝为主要原料,对荷叶与绞股蓝复配比例、过筛目数、水的添加量和冲泡时间4个因素进行单因素试验,并根据单因素试验结果,设计L9(34)正交试验.结果表明,绞股蓝荷叶复配茶包最佳工艺配方为:荷叶添加量与绞股蓝添加量的比例为1:4、过筛目数为70μm、水添加量为150 mL、冲泡时间为7 min,此条件下的荷叶绞股...