Comparative Study of Dynamic Mathematical Models for Deep-Bar Rotor Induction Machine

ABSTRACT

The paper is concerned with the problem of mathematical modelling of the deep-bar rotor induction machine. Two kinds of models were analysed in this paper. The multiple-rotor circuit modal with constant parameters was presented in which the rotor circuit was replaced by a finite number of R-L sections. The method of determining of section parameters for trapezoidal rotor bars on the basis of Riccati differential equation solution was demonstrated. Then the one-rotor circuit model with parameters changing in function of the motor slip was analysed. The method of the equivalent circuit parameters determining on the base of motor nominal data for any rotor bar shape rectangular or trapezoidal was presented. Proposed models were used for simulation of asynchronous motor transients. Results of the digital simulation and laboratory tests were discussed and presented mathematical models were compared.     

An LC-IT-MS/MS-Based Method to Determine Trichothecenes in Grain Products

The aim of this work was to evaluate the usefulness of the ion trap mass spectrometry coupled to high-performance liquid chromatography for simultaneous determination of selected trichothecenes (nivalenol, deoxynivalenol, fusarenon-X, neosolaniol, 3-acetyl-deoxynivalenol, diacetoxyscirpenol, HT-2 and T-2 toxins) in grain products. These compounds were extracted from the grain products and then cleaned up with the developed, simple and robust procedure using some mixture of neutral alumina, charcoal and diatomaceous earth. Method recovery was 88–125 % depending on combination of the analysed mycotoxins, sample matrix and the fortification level. Method precision expressed by relative standard deviation ranged from 2.6 to 27.4 %. The concentrations of the selected trichothecenes have been determined in 94 samples of cereal-based products. Maize-based next to wheat-based products were the most contaminated with deoxynivalenol, neosolaniol, 3-acetyl-deoxynivalenol, diacetoxyscirpenol and HT-2 toxin. In 83 % of wheat-based products, deoxynivalenol was determined at the average level of 249 μg kg^?1. The highest concentration of deoxynivalenol—2,026 μg kg^?1 (476?±?471 μg kg^?1 on the average)—was found in the maize-based product. Other mycotoxins were found much less frequently: 3-acetyl-deoxynivalenol in only one sample at the concentration of 59 μg kg^?1, neosolaniol, HT-2 toxin and diacetoxyscirpenol in a few samples on average concentrations close to respective limits of quantification.     

Impact of storage at room temperature on the properties of CiP solutions

This work reports the analysis of cleaning solutions used in cleaning in place (CiP) and the changes that occur during storage at room temperature. Tests were performed on different solutions used to clean brewhouse vessels and a mash filter in a local brewery. The solutions were collected from CiP tanks after regeneration and were stored for three months in darkness at room temperature. Over time, the physical, chemical and microbiological parameters of the cleaning solutions were analysed. At the end of the study, the solutions were evaluated in terms of surface wetting and cleaning capability. The results showed that storage of the solutions at room temperature contributed to the agglomeration of particulates into larger conglomerates that may contribute to clarification of cleaning solutions by sedimentation. However, other parameters of the stored CiP solutions did not change. © 2019 The Institute of Brewing & Distilling     

植酸/植酸钠在食品工业上的应用研究进展

植酸/植酸钠广泛存在于谷类、豆类和油料作物等中,应用非常广泛,在食品工业上可用作食品抗氧化剂、抑菌剂、护色剂、螯合剂和保鲜剂等。本文简述了植酸/植酸钠的结构、组成和理化特性,并且综述其在食品工业中的应用与研究进展。重点介绍了植酸/植酸钠在果蔬制品、饮料、发酵食品、酿造酒、油脂和脂肪制品、水产品、肉制品、焙烤制品和面制品等加工中的应用及研究进展。同时探讨了目前植酸/植酸钠在食品工业应用中存在的问题及解决对策,并对其发展趋势进行展望。指出目前高纯度植酸和固体植酸的生产成本较高,将来可以在植酸的色谱层析分离材料上进行改进。同时,为了增加植酸在油溶性食品中的应用范围,可以通过植酸的改性或借助于乳化、微乳化技术制备植酸/植酸钠的乳液和微乳液产品,是将来的发展方向。     

BRACID: a comprehensive approach to learning rules from imbalanced data

In this paper we consider induction of rule-based classifiers from imbalanced data, where one class (a minority class) is under-represented in comparison to the remaining majority classes. The minority class is usually of primary interest. However, most rule-based classifiers are biased towards the majority classes and they have difficulties with correct recognition of the minority class. In this paper we discuss sources of these difficulties related to data characteristics or to an algorithm itself. Among the problems related to the data distribution we focus on the role of small disjuncts, overlapping of classes and presence of noisy examples. Then, we show that standard techniques for induction of rule-based classifiers, such as sequential covering, top-down induction of rules or classification strategies, were created with the assumption of balanced data distribution, and we explain why they are biased towards the majority classes. Some modifications of rule-based classifiers have been already introduced, but they usually concentrate on individual problems. Therefore, we propose a novel algorithm, BRACID, which more comprehensively addresses the issues associated with imbalanced data. Its main characteristics includes a hybrid representation of rules and single examples, bottom-up learning of rules and a local classification strategy using nearest rules. The usefulness of BRACID has been evaluated in experiments on several imbalanced datasets. The results show that BRACID significantly outperforms the well known rule-based classifiers C4.5rules, RIPPER, PART, CN2, MODLEM as well as other related classifiers as RISE or K-NN. Moreover, it is comparable or better than the studied approaches specialized for imbalanced data such as generalizations of rule algorithms or combinations of SMOTE + ENN preprocessing with PART. Finally, it improves the support of minority class rules, leading to better recognition of the minority class examples.     

Current Knowledge about Oxysterols: A Review

For years food consumers have been warned that a cholesterol‐rich diet may result in atherosclerosis. It is also well known that consumption of large amounts of phytosterols decreases concentration of low‐density lipoproteins (LDLs) in blood (LDLs are regarded a key risk factor in development of cardiovascular diseases). However, no scientific evidence has unambiguously proved any direct connection between amount of consumed cholesterol and LDL level in blood. On the other hand, concentration of cholesterol oxidation products, oxysterols, seems to be indeed relevant; for example, they significantly impact appearance of atherosclerotic lesions (plaques). Phytosterols (like sitosterol or campasterol) decrease LDL level in blood, but on the other hand products of their oxidation are toxic. Therefore, it is worth to know influence of phytosterols on living organisms, processes which lead to their formation, and their levels in popular foodstuffs. This paper is an attempt to review literature data on the above aspects, as well as on impact on living organisms of oxidation products of popular sterols.     

Relaxation of magnetoelastic phenomena in electrodeposited nickel-iron films

Cylindrical 5 μm films of Ni-8% Fe alloy electrodeposited onto a substrate wire, with the easy axis of magnetization in a circumferential direction and the hard axis coinciding with the substrate axis, can be used as sensors of tension. The change of the anisotropy field H_k is proportional to the strain produced in the film and can be observed as a change of the current in a measuring circuit. However, at constant load (and strain) a considerable relaxation occurs, which can be represented as an exponential function of time, at least for periods shorter than 10 min. The rate of relaxation is temperature dependent with an apparent activation energy of 0.3 eV. It is suggested that the observed phenomena are due to the migration of defects and to their interaction.