Pre-compensation of servo tracking errors through data-based reference trajectory modification

This paper presents a new dynamic error compensation approach with novel data-based closed-loop tuning scheme to enhance tracking accuracy of machine tool feed-drives. Both servo dynamics and friction disturbance induced positioning errors are pre-compensated by modifying the reference trajectory. Velocity and acceleration profiles of reference trajectory are modulated to achieve perfect tracking. Reference position profile is modified based on the pre-sliding friction regime to eliminate quadrant glitches. Optimal error compensation is achieved by a digital trajectory pre-filter whose parameters are tuned automatically by making on-the-fly iterative adjustments. Effectiveness of proposed compensation approach is validated experimentally in multi-axis feed-drive systems.     

Modelling,simulation and identification of an engine air path electromechanical actuator

This paper deals with the modelling and the identification of an electromechanical Diesel engine actuator. The studied Bosch GPA-S actuator is designed for swirl/tumble flaps to control the air amount entering into the cylinder. This study aims to design a complete simulator that reproduces, with sufficient accuracy, the actuator dynamics taking into account the effects of the friction phenomenon. Hence, an overview of the actuator structure and its operation principle is first given. Then, its mathematical model as well as the nonlinearity, related to its behaviour, is discussed. Next, three identification procedures, which allow estimating both the system parameters and the friction model coefficients, are introduced. Finally, simulation results, using MATLAB, and experimental results, using LabVIEW, are presented demonstrating the effectiveness of the proposed techniques.     

A PCR-DGGE method for the identification of histamine-producing bacteria in cheese

Histamine is the biogenic amine (BA) most frequently involved in food poisoning. Cheese is among the foods in which it is most commonly found, and in some of the highest concentrations. Its accumulation in cheese is mainly due to the presence of lactic acid bacteria (LAB) that produce histidine decarboxylase, an enzyme coded by the gene hdcA. This gene has been sequenced in several histamine-producing LAB. This paper reports a new culture-independent method based on PCR-DGGE for detecting and identifying, at the species level, the histaminogenic bacteria present in cheese. Primers were designed based on the hdcA gene sequences available for Gram positive bacteria, and PCR and DGGE optimized in order to differentiate between amplicons corresponding to different histamine-producing species. The proposed method provides a rapid and simple means of detecting and identifying histamine-producing Gram positive bacteria in foods with complex microbial communities, such as cheese.     

Prediction and identification of rotary axes error of non-orthogonal five-axis machine tool

This paper proposes an efficient and automated scheme to predict and identify the position and motion errors of rotary axes on a non-orthogonal five-axis machining centre using the double ball bar (DBB) system. Based on the Denavit-Hartenberg theory, a motion deviations model for the tilting rotary axis B and rotary C of a non-orthogonal five-axis NC machine tool is established, which considers tilting rotary axis B and rotary C static deviations and dynamic deviations that total 24. After analysing the mathematical expression of the motion deviations model, the QC20 double ball bar (DBB) from the Renishaw Company is used to measure and identify the motion errors of rotary axes B and C, and a measurement scheme is designed. With the measured results, the 24 geometric deviations of rotary axes B and C can be identified intuitively and efficiently. This method provides a reference for the error identification of the non-orthogonal five-axis NC machine tool.     

Hybrid model predictive control for flotation plants

Development of control strategies for large-scale processes has led to formulate novel methodologies to consider the global performance of a plant, facilitating the design, validation and evaluation of more complex control strategies. This paper describes a hybrid dynamic simulator for a flotation circuit with one production line composed by one cell and two banks in series, calibrated with industrial data. This simulator allows to represent a real plant behavior, facilitating the process of extracting input–output data. A PieceWise AutoRegresive eXogenous (PWARX) system is obtained from simulated plant by applying identification techniques for different operating conditions. A Hybrid Model Predictive Control (HMPC) methodology based on PWARX models has been developed and evaluated showing a good performance. Simulation results show that the proposed methodology is suitable for modelling the behavior of a flotation process and its control stage by minimizing the tracking error in the final tail grade.     

A simple screen to detect hybrids between native and introduced Phragmites australis in the United States and Canada

In much of the United States and Canada, the common reed consists of both a native subspecies Phragmites australis americanus, and a highly invasive introduced subspecies P. australis australis. DNA testing is generally used to distinguish them definitively and is necessary to detect hybridization. We report a group of single nucleotide polymorphisms and indels in the nuclear NRT2 gene of Phragmites that differentiate North American native and European-introduced populations. All native samples tested were identical in NRT2 sequence over 1564 bases except for two positions. There were nine positions, consisting of seven base substitutions and two indels, at which all introduced samples were fixed for a different allele than the native samples. For the two indels, samples collected from northern Europe were also fixed for the same allele as the introduced samples collected across North America. One of the indels was easily detected by a PCR-RFLP assay and provides a rapid and inexpensive way to screen for hybrids between native and European-introduced populations of Phragmites and thus can facilitate more widespread surveillance for hybrids between native and introduced populations in North America.     

Latent communities of digital publications: The role of editors,followers, and advertisers

This research explores how digital publications may be turned into something more than just a meeting point for people who are seeking information and may become a latent community. The paper proposes that the network of editors, followers, and advertisers of digital publications determine the user sense of community towards the publication. While the pattern of connections among editors and followers reinforces the sense of community, advertisers act as intruders who weaken the feasibility of building a community. Data were collected from followers of digital publications. The dynamics of the sense of community is described as a process in which informational value and identification are essential to nurturing readers’ soft or hard commitment. Findings indicate that the strong ties between editors and followers as well as the diversity positively impacts on informational value and identification, whereas advertising intrusiveness diminishes the informational value.     

Flow pattern identification and measurement techniques in gas-liquid-liquid three-phase flow: A review

The simultaneous flow of gas, oil, and water forms various flow patterns due to the complex interfacial relationships. Three-phase flow patterns are classified as the gas-liquid and liquid-liquid flow patterns. Pressure drop, void fraction, liquid holdup, and phase distribution are important characteristics of the three-phase flow. These characteristics are generally associated with the three-phase flow patterns. Hence, the knowledge about flow patterns can help to predict the overall behavior of the three-phase flow. Studies have been conducted to identify three-phase flow pattern and their characteristics at various superficial velocities of gas, oil, and water. The major purpose of the studies is to gather information about the three-phase co-current flow and use it for improvement of the efficiency of the flow systems. Therefore, the accuracy of the measurement technique is critical. Several types of flow pattern identification and measurement techniques have been developed to improve accuracy and provide high-quality results. In this article, classical and advanced techniques used for the three-phase flow identification and measurement have been reviewed. The survey will help the researchers working in the area of multiphase flow to choose the right technique based on the objectives of the studies.     

关于重大危险源的管理

讨论了重大危险源的种类，辨识的主要内容以及辨识方法；提出了重大危险源管理存在的问题扣管理对策。     

挑檐式结构无底柱阶段崩落采矿法试验研究

崩落采矿法在实际生产过程中矿石损失贫化较难控制，放矿过程中废石漏斗的形成与破裂是造成矿石损失贫化的主要原因。为延缓放矿过程中废石漏斗的形成和到达放矿口的时间，提出了一种挑檐式结构的无底柱阶段崩落采矿法。该方法以阶段为单位，使得每个下分段都超前其上分段一个挑檐距离，在回采巷道工作面形成挑檐结构，回采工作都在其正上方挑檐结构的遮掩下进行。为验证挑檐结构方案的放矿效果，利用多分段放矿模型进行了挑檐结构下放矿和传统结构下放矿2组物理模拟试验，认为在保持矿石回采率80%的情况下，挑檐结构的矿石贫化率可降低5.3个百分点。在弓长岭井下矿-280~+48 m段4-5号穿脉进行了挑檐结构工业性试验，分别对挑檐结构和原结构进行了9个崩矿步距回采的放矿跟班测定。结果表明：挑檐结构与原结构相比，贫化率可降低3.8个百分点，主要原因是挑檐结构可阻挡顶部覆盖岩石，使其向本分段崩落矿石后方移动，而不出现侧漏现象，提高了纯矿石放出量，矿石贫化减小。上述分析进一步表明：挑檐结构方案施工简单，适用于中等稳定以上矿体地下开采。