比特切片型算法差分及线性特征的快速构造

比特切片方法由Biham等人于1997年提出,该方法可以高效提升算法的软件实现性能,后来被广泛应用于Serpent、RECTANGLE、TANGRAM等分组算法.本文针对扩散层采用简单行循环移位的RECTANGLE、TANGRAM等比特切片型分组算法,根据算法S盒的性质以及行移位参数,给出了快速判断其是否存在单轮循环差分/线性特征的方法.基于找到的单轮循环差分/线性特征,结合MILP自动化搜索技术,实现了这类算法长轮数差分/线性特征的快速构造.进一步,我们扩展寻找单轮循环特征的思想,利用MILP方法自动化搜索了不超过4轮的循环差分/线性特征,基于此可以更方便构造长轮数差分/线性特征.利用此方法,我们找到了RECTANGLE算法的14轮差分特征和13轮线性特征, TANGRAM128算法的24轮差分特征和23轮线性特征, TANGRAM 256算法的48轮差分特征和44轮线性特征.特别地,我们找到的TANGRAM 256算法的44轮线性特征是目前找到的最长轮数的线性特征.我们的方法只依赖于算法的结构特点和S盒的性质,该研究对采用这种结构的分组算法长轮数差分/线性特征的寻找和相应算法的设计都有重要意义.     

嵌入式数据库评测框架构建研究

嵌入式系统的广泛应用对选择适配的嵌入式数据库提出了要求,为此提出了一种针对嵌入式数据库的评测框架.该框架设计了评测指标和度量方法,反映了嵌入式数据库的多方特征,并以两种最典型的嵌入式数据库 Berkeley DB 和SQLite 为例,从嵌入式特性、设计特性和应用特性3方面对比了两者的异同,验证了该评测方法.     

Determinants of the effectiveness of personal decision support systems

The effectiveness of personal decision support systems is studied in terms of system usage, user characteristics, type of application and system characteristics. A system feature and function analysis was also conducted to determine how various system characteristics are valued by users.     

A case study of user evaluation of information characteristics for systems improvement

This paper reports on a case study of user evaluation of information characteristics as a basis for the improvement of an information system. Branch-managers of a large bank were asked to evaluate the output of the system according to four information characteristics: accuracy, content, frequency, and recency. The findings of this study indicate that the users at the bank had a holistic perception of their information, and that content was a dominant characteristics which spilled over other characteristics. This case study casts doubts about the use of evaluations of users of information characteristics as the only basis for improving existing systems.     

天气系统的混沌特性

运用非线性动力学工具分析天气系统,着重从数据角度描述天气系统的特性,包括重建系统相空间、计算系统吸引子的维数以及Lyapunov指数,从而论证系统的混沌特性．目的在于以混沌动力学为工具。将天气系统作为非线性动力学系统。从实际的天气数据分析天气系统的特性,从数据的角度论证天气系统的混沌特性,并计算系统的混沌参数．     

Effects of dataset characteristics on the performance of feature selection techniques

While extensive research in data mining has been devoted to developing better feature selection techniques, none of this research has examined the intrinsic relationship between dataset characteristics and a feature selection technique’s performance. Thus, our research examines experimentally how dataset characteristics affect both the accuracy and the time complexity of feature selection. To evaluate the performance of various feature selection techniques on datasets of different characteristics, extensive experiments with five feature selection techniques, three types of classification algorithms, seven types of dataset characterization methods and all possible combinations of dataset characteristics are conducted on 128 publicly available datasets. We apply the decision tree method to evaluate the interdependencies between dataset characteristics and performance. The results of the study reveal the intrinsic relationship between dataset characteristics and feature selection techniques’ performance. Additionally, our study contributes to research in data mining by providing a roadmap for future research on feature selection and a significantly wider framework for comparative analysis.     

基于出租车GPS轨迹的城市区域时空交互特征分析

城市大数据为探索城市内部居民出行的行为特征提供数据支撑.本文将以兰州市出租车GPS轨迹数据为基础,结合数据挖掘和可视化技术,研究兰州市城市居民出行规律和城市空间交互特征.首先,分析4个城区居民出行特征和城区间空间交互特征;然后,采用城市栅格方法,统计分析城市栅格空间之间的交通出行量,并采用CLARA聚类算法识别工作日和...     

Virtual reality research of the dynamic characteristics of soft soil under metro vibration loads based on BP neural networks

In this paper, in order to research the dynamic characteristics of soft soil under metro vibration loads, the mathematical expression of metro vibration loads is obtained. According to the loading form, drainage requirement and vibration frequencies of the actual situation, the corresponding experiment is conducted through indoor dynamic triaxial equipment. Then, the dynamic characteristics of experimental results are analyzed. An empirical formula is proposed to compute the dynamic characteristics of soft soil. Then, the computational results obtained by empirical formula are compared with those of the experimental. They are consistent with each other, and the results show that empirical formula is reliable to compute the dynamic characteristics of soft soil. Then, based on the verified empirical formula, the dynamic characteristics such as the vertical strain and pore water pressure with different CSR are also computed and compared. With the increase in CSR, the dynamic characteristics will be larger when the other parameters are consistent. However, empirical formula can only predict the dynamic characteristics of the simple model. In order to realize virtual reality of the dynamic characteristics of the complex model more accurately, the BP neural network and finite element are adopted, respectively. Then, the computational results are also compared with those of the experimental to verify their reliabilities. In the future, the BP neural network and finite element method can be also used to realize virtual reality of the dynamic characteristics of the more complex model.

     

Quantitative evaluation of display characteristics of AMOLED displays

Abstract— Understanding the display characteristics of OLEDs is not only of general interest but also of technological importance for expanding the application of OLEDs. The display characteristics of AMOLEDs were quantitatively evaluated and compared with LCD or CRT performance. The fast response time and high contrast ratio, which are attractive characteristics of OLEDs, were also retained under low temperature and bright ambient, respectively. Moreover the luminance and color barely changed with viewing angle at any gray‐scale level. The optical design of OLED diodes is important for the emission characteristics, luminance, and color reproducibility.     

基于大用户用电行为分析的错峰管理系统研究与设计

结合当前用电形势和供电企业具体的业务特点,阐述供电企业如何利用大用户用电特征在实现错峰用电方案生成与优化中发挥更大的作用。通过聚类分析的方法研究大用户用电特征及分类,然后根据生成错峰方案所需的条件及流程,构建错峰用电方案生产的算法模型,并以此为基础设计能够有效支撑供电企业实际业务开展的错峰管理系统。     

Colorimetric characterization of LCD and DLP projection displays

Abstract— Successful color‐management of projection systems depends on knowledge of their characteristics. In this study, two typical portable projectors were characterized. The projectors are based on different technologies, liquid‐crystal display (LCD) and digital light‐processing (DLP). Measurements were made with a spectroradiometer. The properties measured were spectral characteristics and the intensity of the primary and white colors, basic colorimetric characteristics, inter‐channel dependency, tone characteristics, color‐tracking characteristics, spatial non‐uniformity, dependency on background, and temporal stability. Based on the characterization results, the possibility of color‐management of the tested projectors is discussed.     

一种面向开源软件特征的开源软件选择方法研究

文章提出一种面向开源软件特征的开源软件选择方法,首先从开源软件的基本特性、评估策略和内在特征三个方面建立其特征,并将特征纳入到开源软件的分类中。其次再根据不同用户的需求的特征与开源软件的分类建立选择机制,使用户需求选择特征与开源软件特征进行对应,从而建立起开源软件选择方法。然后通过该方法来选择面向开源软件开发工具为例进行验证表明,该策略有效且可用性强。     

区块链环境下电商消费者网络多子群混合增长模型构建及特性研究

为探究区块链环境下电商消费者行为的复杂网络特性,在对传统局域网络与BBV增长网络研究的基础上,针对区块链环境下电子商务消费者行为的特性,提出2个方面的创新优化： （1）建立基于声誉的有限信任共识机制; （2）构建基于去中心化特性的消费者社团交互选择的智能合约。将共识机制与智能合约融入多子群混合增长模型中,研究在特定参数下,区块链电商消费者网络在复杂网络结构方面的特性。实证研究表明：即使是在具有去中心化、去信任的区块链电子商务环境下,消费者网络依旧会呈现出节点幂律分布的特点和小世界特性。在多子群混合增长模型中,消费者社团划分明显,消费者之间会出现“富者愈富”的马太效应,但是与传统网络电子商务消费者网络相比,其社团结构则更为松散,具有反垄断的特性。实验表明,在该环境下消费者的消费行为更加自由与透明。     

基于接地弹簧及配点法的系统动态特性分析

核电设备和部件的动态特性包括其固有频率和相应模态。对于动态特性受支承条件影响的核电设备,将之简化为带接地弹簧的质量一弹簧系统．并分析接地弹簧刚度的变化对该系统动态特性的影响。在此基础上,从带罚数的有限元配点法出发,推导接地弹簧的有限元等价形式,证明接地弹簧刚度与罚数的等价性,并由此等价性,阐明支承条件在施加设备边界条件过程中所起的作用。     

基于握力特征量的授权机制手柄传感器研制

利用力学特征量来进行人身份的识别是一种极有应用前景的新型认证技术,它是一种全新的利用人的行为所产生的动态力学特征量的多模识别方案,本文主要研究了合理的力学特征量的传感、采集方法,探索了传感器及特征采集系统设计和实施,为进一步力学特征信号的时变特征,特征描述方案的研究打好了硬件平台基础.     

基于LMS的超声换能器温度补偿仿真

针对超声波测风、测距等领域中温度变化引起超声波传感器的传输特性变化,从而影响测量精度的问题,提出通过仿真实验研究超声换能器等效电路中各参数随温度变化对传输特性的影响情况,并得出其主要影响的因素.然后根据自适应算法的特性,尝试使用最小均方误差算法(LMS)自适应滤波算法对超声波传感器的传输特性进行补偿.仿真实验结果表明:...     

低通滤波器的计算机自动设计

针对集中参数低通滤波器的传统人工设计费工、元件数目不甚节省、其特性不甚理想的状况 ,直接从工程预给的特性要求出发 ,由计算机按步骤自动准确给出能满足工程要求的集中参数低通滤波器的元件数值及其特性 ,且可根据仿真扫描的衰减特性曲线随时修改 ,直到特性满意。结果直观 ,所得元件数目节省且特性理想     

Multisim电路仿真软件在门电路特性分析中的应用

利用Multisim电路仿真软件的仿真功能,结合实例演示了门电路的基本逻辑功能,测试了输入负载特性、输入输出特性、电路的延迟性能,测试出电路的一些典型参数。对于门电路的基本特性有了直观的感性的认识,对学习门电路的基本特性及其基本概念得以加深理解。     

高温超导磁体与普通磁体的实验研究

本文从黑箱建模的角度出发,分析高温超导磁悬浮系统和常导磁悬浮系统在稳态悬浮时的动态特性。此外,通过对比实验,还比较了磁悬浮系统稳态悬浮时高温超导磁体与普通磁体的电磁特性异同。研究结果表明,虽然高温超导磁悬浮系统和常导磁悬浮系统动态特性的传递函数模型不同,但从控制的角度看,它们的电磁特性并无明显区别。在系统的工作频段内,高温超导磁体线圈自感应给其电磁特性带来的影响可以忽略。     

无耦合PCNN频域特性分析

脉冲耦合神经网络（PCNN）模型具有脉冲调制和耦合连接特性,广泛应用于数字图像处理领域。然而现有PCNN模型的研究都是从时域或图像本身包含信息角度分析参数与模型特性之间的关系,无法全面解释参数对模型特性的影响。从PCNN模型的迭代方程出发,利用离散系统频域分析方法从频域角度对无耦合PCNN模型进行分析,揭示无耦合PCNN模型的动态门限子系统具有低通特性,并确定网络参数a_E的选取范围,同时通过对脉冲发放时刻公式进行推导,得到参数v_E的选取范围。采用傅里叶变换方法分析单个神经元的脉冲发放频率特性和动态门限衰减频率特性,解释无耦合PCNN模型的参数对频域特性的影响。仿真实验结果验证了该理论分析结论的正确性,从频域角度理解无耦合PCNN模型的参数与模型特性之间的关系,为挖掘PCNN模型特性提供一种新的方法。