Thermomechanical investigation of hydroxyl-terminated polybutadiene-based linear polyurethane elastomers

The present work describes the trend of linear polyurethane elastomers for its thermal and mechanical behavior. The linear polyurethane elastomers have been synthesized in two different series by changing the composition of the polymers. Both series have common macrodiol of hydroxyl-terminated polybutadiene and butanediol while they vary in the presence of diisocyanate. One of the series, contain an aromatic diisocyanate, toluene diisocyanate (TDI), and the other consist of 1,6-hexamethylene diisocyanate (HDI) as an aliphatic diisocyanate. For linear structure, ratio of OH and NCO group has been maintained 1.0. The hydrogen bonding index is determined from Fourier transform infrared to calculate the extent of interchain hydrogen bonding which manifest the microphase separation. Young's modulus (5.79 MPa) and tensile strength (1.14 MPa) are recorded for HDI-derived elastomers, while Young's modulus varies from 1.14 to 1.63 MPa for TDI-based elastomers which also resulted in higher thermal stability. Thermogravimetric curves exhibit two-step degradation with the stability of 300 °C. HDI-based polyurethane elastomers show better tensile properties and HDI but poor thermal stability as compared to TDI-based elastomers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47289.     

Insight into the intermolecular interactions in the NF3–HSO system: a computational study

Quantum calculations were carried out in order to investigate the heterodimers of NF₃ with the HSO molecule in the gas phase at the MP2/aug-cc-pVDZ and MP2/aug-cc-pVTZ//MP2/aug-cc-pVDZ computational levels. Ten minima were located on the potential energy surface (PES) of the NF₃–HSO system. Binding energies corrected with basis set superposition error are in the range 3.15–7.85?kJ/mol. The atom in molecules theory was applied to analyze the nature of intermolecular interactions.     

Effect of Sm substitution on the magnetic and electrical properties of Cu-Zn ferrite

Samples of the chemical formula Cu_0.5Zn_0.5Fe_2–x Sm _x O₄ where x = 0.0, 0.02, 0.04, 0.06, 0.08 and 0.1 are studied. X-rays analysis indicated that all investigated samples are formed in a single cubic phase. The lattice parameter is found to increase relative to x = 0.0 except x = 0.02. The grain size is decreased for all samples relative to unsubstituted one except that with x = 0.02. It is noticed that the sample with x = 0.02 has the highest values of initial permeability, magnetization and Curie temperature, T _c. The homogeneity of the samples, the coercive field as well as T _c are found to decrease while the electrical resistivity increases with increasing Sm content.     

Nonparametric waveform estimation using filter banks

This paper presents a nonparametric method for estimating waveforms of event-related signals embedded in additive noise. The signals have transient character with varying shapes and arrival times. The estimation method is based on a series expansion of the signal by a set of basis functions. Using a template that contains a priori information, two sets of basis functions are designed by means of one uniform and one nonuniform bandpass filter bank. Then, signal-dependent basis functions are obtained. When no a priori information about the signal is available, signal-independent basis functions are constituted by the impulse responses of the subfilters. Delayed copies are created for each basis function with which time jitter in arrival time of the signal can be handled. The method gives a robust estimate of the waveform of transient signals having unknown waveforms and arrival times since no model assumptions are needed. One application is discussed through examples and compared with the estimate, which is obtained by the Karhunen-Loeve expansion     

Modular neuron comprises of memristor-based synapse

Design of analog modular neuron based on memristor is proposed here. Since neural networks are built by repetition of basic blocks that are called neurons, using modular neurons is essential for the neural network hardware. In this work modularity of the neuron is achieved through distributed neurons structure. Some major challenges in implementation of synaptic operation are weight programmability, weight multiplication by input signal and nonvolatile weight storage. Introduction of memristor bridge synapse addresses all of these challenges. The proposed neuron is a modular neuron based on distributed neuron structure which it uses the benefits of the memristor bridge synapse for synaptic operations. In order to test appropriate operation of the proposed neuron, it is used in a real-world application of neural network. Off-chip method is used to train the neural network. The results show 86.7 % correct classification and about 0.0695 mean square error for 4-5-3 neural network based on proposed modular neuron.

     

基于可训练机制的联机维吾尔手写字母识别技术研究

在深入研究英文和汉字手写识别的基础上,结合维吾尔文字母的特点,提出一种基于支持向量机机器学习算法的维吾尔文联机手写字母识别方法,系统研究了样本采集、预处理、特征提取和分类等模块。在预处理中,为了消除干扰和噪声及比较中的相似性,采用了平滑滤波和线性归一化处理;考虑到维吾尔文相似字母较多,为了有效提取特征,将结构特征和统计特征相结合,提取了字符的梯度方向特征;分类器采用支持向量机。实验表明,随着训练样本的增加,识别率可以从90.62%提高到96.09%。     

Partial Blockage Detection in Pipelines by Frequency Response Method

A new technique is presented utilizing the frequency response for the detection of partial blockages in a pipeline. In the system frequency response, a partial blockage increases the amplitude of the pressure oscillations at even harmonics. Such an increase in amplitude has an oscillatory pattern, the frequency and amplitude of which may be used to predict the location and size of a partial blockage. In this technique, the pressure transient history at only one location is sufficient, and the history of the transient in the pipe prior to blockage is not needed, which is an advantage over a number of other available techniques, in addition to being simpler to use. It is shown that the technique successfully detects the location of a blockage in a number of simple systems with blockage size as small as 10%. The technique is verified by comparing the computed results with those computed by the method of characteristics and with measurements from simple laboratory setups. A number of practical issues and limitations for field implementations are discussed.     

Optical Investigation of Sm<Superscript>3+</Superscript> Doped in Phosphate Glass

Samarium doped zinc-magnesium-phosphate glasses having composition (60 – x)P₂O₅–10MgO–30ZnO–xSm₂O₃ where x = 0.1, 0.3, 0.6, 1.0 mol % were prepared by melt quenching technique. Archimedes method was used to measure their densitieswhich are lying in the range 2.65–2.91 g/cm³. On the basis of the increasing trend in the density while increasing the content of Sm₂O₃ it can be concluded that the bridging oxygen is converted to non-bridging oxygen The UV-Vis absorption spectroscopy was carried on in the wavelength range 310–900 nm where the absorption spectra consist of six absorption peaks corresponding to the transitions from the ground state ⁶H_5/2 to various excited energy levels. The optical band gaps are calculated to be 3.93–4.41 eV, 3.31–3.73 eV and 0.27–0.29 eV for direct band gap, indirect band gap and Urbach energy, respectively. The physical parameters like oxygen packing density, refractive index, molar refractivity, metallization, and electronic polarizability are also studied. The Differential Scanning Calorimetry (DSC) technique is used to evaluate the thermal stability.