可编程控制器扫描周期分析及程序设计

可编程控制器通过循环执行控制程序来实现用户要求的控制功能,循环执行控制程序称为扫描周期。分析了可编程控制器的这种工作方式对编程的影响,介绍如何利用扫描周期分析设计程序。     

A unifying framework for analysing common cyclical features in cointegrated time series

A unifying framework in which the coexistence of differing forms of common cyclical features can be tested and imposed upon a cointegrated VAR model is provided. This is achieved by introducing a new notion of common cyclical features, described as the weak form of polynomial serial correlation, which encompasses most of the existing formulations. Statistical inference is based upon reduced-rank regression, and alternative forms of common cyclical features are detected through tests for over-identifying restrictions on the parameters of the new model. Some iterative estimation procedures are then proposed for simultaneously modelling various forms of common features. The concepts and methods of the paper are illustrated via an empirical investigation of the US business cycle indicators.     

基于差分理论的短期负荷预测神经网络模型

电力负荷是受周期性变化以及天气等因素影响的高度非线性系统,而神经网络仅仅对已学习过的模式具有较好的范化能力。为提高神经网络的负荷预测精度,提出先对原始负荷序列进行差分运算以除去其周期性影响,然后依据相似性原理建立RBF神经网络预测模型,仿真实验表明采用该方法短期负荷预测精度有所改善。     

Topology design and kinematic optimization of cyclical 5-DoF parallel manipulator with proper constrained limb

This paper proposes topology design and kinematic optimization of cyclical 5-degree-of-freedom (DoF) parallel manipulator with proper constrained limb. Firstly, a type of cyclical 5-DoF parallel manipulators with proper constrained limb is proposed by analyzing DoF of the proper constrained limb within workspace. Exampled by a cyclical 5-DoF parallel manipulator with the topology 4-UPS&1-RPS, its motion mapping model is formulated. By taking the reciprocal product of a wrench on a twist as the generalized virtual power, the local and global kinematic performance indices are provided. Then, on the basis of the actuated and constrained singularity analysis of the 4-UPS&1-RPS parallel manipulator within the position and pose workspace, the topology design of the manipulator without singularity is carried out, and its reachable and prescribed workspaces are obtained. Finally, by maximizing the global kinematic performance index and subjecting to a set of appropriate constraint conditions, the kinematic optimal design of the 4-UPS&1-RPS parallel manipulator is carried out utilizing the genetic algorithm of MATLAB optimization toolbox.     

远程故障诊断系统通信数据压缩技术研究与验证

根据远程故障诊断的测试数据的网络传输特点,在详细分析和比较了多种数据压缩算法的基础上,针对LZW算法字典列表长度有限、查找时间长等问题,利用加入了动态延伸列表长度、根据压缩比例调整已有的字典内容和哈希函数查找等方法,对LZW算法提出了改进措施;同时,引入MPEG帧间压缩的思想,设计了一种新的"周期性差值压缩方法",将改进的LZW数据压缩算法与"周期性差值压缩方法"相结合,构成了更有效的级联数据压缩方法,有效地提高了数据压缩比率和效率,并且该算法的处理速度能够满足远程故障诊断系统对通信的要求。     

Binary sequences III. Complexity versus homogeneity and symmetry

In this paper complexity and homogeneity/symmetry as introduced in the first two papers of this series are compared with one another. The two classes of measures have similar general properties, but correlate poorly if a representative sample of all possible sequences of a given length is studied. The reason is found to consist mainly in that (1) complexity is sensitive to cyclical permutations of a sequence, whereas homogeneity and symmetry are not; (2) complexity is more sensitive to repetition of individual symbols (“cluster formation”); and (3) complexity is more sensitive to repetitional symbol sequences and inverted symbol sequences than homogeneity and symmetry. Complexity is more versatile in the sense that it easily can be made sensitive to diverse features of order, such as mathematical regularities. Homogeneity and symmetry, on the other hand, are easier to calculate and mathematically more transparent.     

基于长短期神经网络的遥测参数趋势预测

时间序列分析的主要目的是根据已有的历史数据对未来进行预测。传统的时间序列预测主要依靠基于模型的方法，比如季节性差分整合移动平均自回归模型（SARIMA）和指数平滑法（EXP）等。此类方法的参数选择严重依赖于专家经验，适用性并不广泛。针对周期性遥测参数，采用长短期记忆网络（LSTM），学习长时序依赖关系并给出多步预测值。试验通过将预测问题转化为监督学习问题建立半实时仿真环境，并重点研究了观测窗口、预测窗口、网络结构等对性能指标的影响。对比LSTM、SARIMA、EXP，结果表明LSTM具备优异的线性拟合能力和良好的非线性关系映射能力。LSTM预测方法摆脱了传统方法受制于专家经验和模型精度低等问题，为开展实时遥测参数预测奠定了基础。     

Counterbalancing Exploitative Knowledge Search during Environmental Dynamism: Reinforcing New Ideas for Existing Products

Established firms face the challenge of counterbalancing their predominant focus on exploitation with exploration. This paper explores how these firms can reinforce new exploratory ideas for existing products, especially during periods of environmental dynamism. The study is based on an action research study at a new product development (NPD) department at an international manufacturing firm operating in a cyclical market. The results show that increased environmental dynamism opens new opportunities for counterbalancing exploitative approaches by building exploratory skills. The action contributed specifically to breaking with old traditions in the NPD organization, and resulted in actionable knowledge in terms of an ideation approach. However, the study also shows that fast industry cycles that do not match the remote returns of exploratory knowledge searches diminish the possibility to sustain exploratory knowledge searches in organizations. The paper identifies important problems related to the long‐time horizon of exploration and the cyclical nature of industries.     

数据块前向相容标记码的测试数据压缩方法

提出一种类似于字典索引的编码压缩方法,将与参考数据块相容的测试数据块用"1"标记来压缩测试数据,解压体系结构只需要一个有限状态机和一个与数据块等长的循环扫描移位寄存器.与在Golomb码和FDR码中所需要的与测试向量等长的循环扫描移位寄存器相比,该方法的硬件开销较小.实验结果表明,该方法可以有效地压缩测试数据,且效果优于Golomb码和FDR码.     

S模式数据链CRC校验实现方法

介绍了一种基于FPGA的S模式地空数据链循环冗余校验(CRC)实现方法。在掌握S模式数据链上、下行信息传输格式的基础上,根据循环码编码原理搭建校验电路,在QuartusII 8.1环境下进行逻辑设计。对发送端和接收端信息进行仿真验证,达到了预期效果。     

Work routinization and implications for ergonomic exposure assessment

Jobs in many modern settings, including manufacturing, service, agriculture and construction, are variable in their content and timing. This prompts the need for exposure assessment methods that do not assume regular work cycles. A scheme is presented for classifying levels of routinization to inform development of an appropriate exposure assessment strategy for a given occupational setting. Five levels of routinization have been defined based on the tasks of which the job is composed: 1) a single scheduled task with a regular work cycle; 2) multiple cyclical tasks; 3) a mix of cyclical and non-cyclical tasks; 4) one non-cyclical task; 5) multiple non-cyclical tasks. This classification, based primarily on job observation, is illustrated through data from a study of automobile manufacturing workers (n = 1200), from which self-assessed exposures to physical and psychosocial stressors were also obtained. In this cohort, decision latitude was greater with higher routinization level (p < 0.0001), and the least routinized jobs showed the lowest self-reported exposure to physical ergonomic stressors. The job analysis checklist developed for non-routinized jobs is presented, and limitations of the task analysis method utilized in the study are discussed. A work sampling approach to job analysis is recommended as the most efficient way to obtain a comparable unbiased exposure estimate across all routinization levels.     

Neural networks for detecting cyclic behavior in autocorrelated process

In quality control area, cyclic behavior is one of the signals indicating an out-of-control situation in a manufacturing process. Neural network (NN)-based approaches have been proposed to detect the cyclical pattern in the data set collected from process. However, virtually all such proposed methods assume that the process data is independent and identically distributed when the process is under control. In other words, data from a manufacturing process is assumed uncorrelated. In this paper, a NN-based model for detecting the cyclical pattern in an autocorrelated process is proposed. After collecting the process data, this data set is preprocessed using the same information needed to calculate the fractal dimension of the data. It is then fed to a trained feedforward NN with a scaled conjugate gradient backpropagation training algorithm. An output of the model is the state of the process, i.e., whether the process is in-control or out-of-control with a particular cycle period. Such information can assist users of a manufacturing process to identify and remove the underlying causes of the out-of-control state. Our approach is thus suitable for automated manufacturing environment as a supplementary tool to traditional control charts. A Monte Carlo simulation was carried out to study performance of our proposed model. The results showed that the neural-based approach can quickly detect the cyclical pattern with better than 90% accuracy when the signal-to-noise ratio is greater than or equal 2.00. It performs well not only on autocorrelated data for a wide range of autoregressive coefficients, but also on uncorrelated data.     

Mutual influences between message volume and emotion intensity on emerging infectious diseases: An investigation with microblog data

The dynamic interdependence between microblog volume and emotions expressed in message content has been largely underexplored. To understand the public’s reaction to emerging infectious diseases, we draw upon theories in psychology and social media, and propose that there is a cyclical relationship between message volume and the intensity of emotions (positive or negative) in which they influence each other positively over time. Furthermore, negative and positive emotions mutually suppress each other, yet are autocorrelated, respectively. Relying on more than 560,000 microblogs collected from Sina Weibo between February 2013 and June 2013 on the outbreak of avian influenza in China, we used vector autoregression to test the research model. We find a cyclical relationship between microblog volume and the intensity of negative emotions (fear in particular, a subcategory of negative emotions). Microblog volume positively contributes to positive emotions. While the intensity of negative emotions, and that of positive emotions is autocorrelated, respectively, surprisingly our results suggest that negative emotion intensity positively affects positive emotion intensity. We further rely on impulse response functions to illustrate how the impacts of a variable on another change over time, and generalized forecast error variance decomposition to understand the importance of each variable contributing to the others. Theoretical and practical implications of the study are discussed.     

Timing analysis of PL programs

This paper studies the worst case execution time (WCET) of PL programs which specify cyclic computing applications. The structure of a PL program differs from that of a sequential program. A PL program contains declarative information about the data to be operated on and about the periodic processes. The WCET of a PL program is defined as WCET for each period of the cyclical application. The processes of a cyclical application may run in different execution modes depending on the context. Not every combination of modes is feasible. Two methods are provided to calculate the WCET of a PL program while taking the unfeasibility constraints into account. One method uses the Integer Linear Programming technique and the other uses heuristic search-based technique. Timing analysis for multiple-period PL programs is also studied. The calculated WCET can be used to validate the timing constraints of the system or to help to decide the sampling rates of the system.     

关于烟气在线监测装置SO2周期性异常的分析与处理

本文针对目前电厂脱硫烟气连续排放监测系统（CEMS）中SO2数据周期性波动,通过对历史数据曲线分析排查,发现取样探头温控仪故障导致取样探头加热器无法加热,烟气中水分遇冷凝结在管壁,管壁中的水分平时吸收烟气中的SO2,导致测量值偏低,待水珠汇聚变大流入下面带加热的取样管中后,水中溶解SO2的集中释放,导致数据在短期急剧上升,蒸发释放完后回归到原来的水平,形成这样一个周期性吸收和集中释放的过程。可见烟气取样管道温度保护环节在烟气测量中的作用非常重要。     

A checklist for evaluating ergonomic risk factors resulting from awkward postures of the legs, trunk and neck

A one-page checklist for determining the presence of ergonomic risk factors associateed with awkward postures of the lower extremities, trunk and neck was developed and evaluated as part of a joint labor-management ergonomics intervention program. This checklist was used by plant personnel at four work sites to assess the postural requirements on 335 cyclical (i.e., work-cycle duration less than five minutes) manufacturing and warehouse jobs. In addition, results generated by the checklist were compared to the results of ergonomic analyses performed by persons with advanced training in occupational ergonomics.

Workers were observed using awkward postures for most of the jobs in the survey. Awkward postures of the lower extrimities were relatively uncommon, occuring in 25 percent or less of the jobs. Awkward postures of the trunk and neck were common, occuring in more than 70 percent of the jobs. Results generated by the checklist were generally in agreement with results generated by the experienced ergonomists; however, the checklist was found to be more sensitive in identifying the presence of awkward postures.

The checklist was found to be an effective rapid-screening instrument for identifying cyclical jobs that expose workers to potentially harmful postures. However, the checklist methodology did not include sufficient documentation of work methods to identify the specific job attributes associated with these exposures. Furthermore, the checklist was not used to evaluate non-cyclical jobs (e.g., maintenance and skilled trades).     

On application of input data partitioning to Bayesian weighted averaging of biomedical signals

Averaging in the time domain may be used for noise attenuation in case of biomedical signals with a quasi‐cyclical character. Traditional arithmetic averaging technique assumes the constancy of the noise power cycle‐wise, however, most types of noise are not stationary and the variability of noise power is observed. It constitutes a motivation for using methods of weighted averaging, in particular Bayesian weighted averaging. This paper presents the computational study of Bayesian weighted averaging with traditional (sharp) and fuzzy partition of the input data in the presence of non‐stationary noise. There is presented the known empirical Bayesian weighted averaging method (EBWA), with the parameter p describing the probabilistic model, and its modification NBWA which eliminates the parameter. Both methods can be extended by partitioning of the input data. The performance of presented methods is experimentally evaluated for an analytical signal as well as a real ECG signal and compared with traditional arithmetic averaging method. However, the methods can be applied to any signal with a quasi‐cyclical character. The aim of the paper is to show the influence of the type of partition as well as the number of parts on the quality of the averaged signal.     

Analyzing an inventory system with multiple reorder points and periodic replenishment

This paper investigates multiple reorder point, periodic replenishment systems similar to those utilized on board some U.S. naval vessels for Selected Item Management (SIM). This inventory system is of interest since it involves both regular and priority replenishment, three reorder points, and cyclical restocking of regular orders. A simulation model is developed to study the impact of demand distribution, cycle time, priority order leadtime, and the quantity of units ordered on the performance of the system. It is found that the frequency of service and days without shortages performance measures can be maximized by setting the reorder points at equal intervals between the zero level and the high level. Also, a power approximation model is presented that estimates the high level that will lead to a desired percent days without shortage percentage.     

用锁相式采样法抑制周期性干扰噪声

本文介绍一种对周期性干扰噪声有较强抑制能力的锁相式采样法,论述了该方法的理论依据,并给出了实用锁相控制电路.该电路可以很方便地嵌入通常的数据采集系统.     

Simulating Weyl points and nodal loops in an optical superlattice

We propose a scheme to simulate Weyl points and nodal loops with ultracold atoms in an optical lattice that is subjected to realizable synthetic magnetic field and synthetic dimension. We show that a Hofstadter-like Hamiltonian with a cyclically parameterized on-site energy term can be realized in a tunable two-dimensional optical superlattice, based on the laser-assisted atomic tunneling method. This model effectively describes a three-dimensional periodic lattice system under magnetic fluxes, where a synthetic dimension is encoded by a cyclical phase of the optical lattice potential. For different atomic hopping configurations, the single-particle bands are demonstrated to, respectively, exhibit Weyl points and nodal loops in the extended three-dimensional Brillouin zone. Furthermore, we illustrate that the mimicked Weyl points and nodal loops can be experimentally detected by measuring the atomic transfer fraction in Bloch–Zener oscillations.