Improved extraction of oil from chickpea under ultrasound in a dynamic system

In this work, ultrasound-assisted dynamic extraction (UADE) is proposed. The dynamic approach allows go-and-backward circulation of solvent through the sample subjected to the action of ultrasound. The extraction efficiency of hexane, isopropanol, a hexane–isopropanol mixture as well as the comparison between static extraction and flow-through extraction with or without ultrasound were evaluated. The effects of ultrasonic power, extraction temperature, time and extractant flow rate on the yield of oil from chickpea were also investigated. Results showed that solvent type significantly influenced extraction efficiency, the combination of hexane and isopropanol obtained the highest oil yield. Dynamic system and ultrasonication dramatically enhanced the extraction of oil. Moreover, results indicated that 20 min was sufficient for UADE with lower cost to obtain higher extraction yields (10.45% and 2.06% higher) than those by 4 h conventional solvent extraction (CSE) and 30 min ultrasound-assisted extraction (UAE) for oil. Gas chromatography analysis of chickpea oil indicated that the oil was enriched with polyunsaturated fatty acids and few changes in fatty acid composition occurred in ultrasonicated oil.     

从方法论的角度谈ISO 27001审核

本文将从方法论的视角对ISO 27001审核应关注的内容进行探讨。一、ISO 27001标准简介该标准分为三个部分,分别为引言、正文和附录。引言介绍了建立信息安全管理体系(简称ISMS)的意义和原则;描述了体系建设过程中使用的过程方法和PDCA模型;说明了     

数控机床随机性故障原因分析与对策

数控机床是一种技术复杂的机电一体化设备,在生产上起着关系作用.由于现代数控系统的可靠性越来越高,数控系统本身的故障越来越低,而大量分故障的发生则是非系统本身原因引起的,故针对数控机床随机性故障原因进行了分析,并提出了相应的对策.     

Estimating ultrasonic time of flight using envelope and quasi maximum likelihood method for damage detection and assessment

Time of flight (TOF) is widely used to locate and size faults in ultrasonic non-destructive evaluation (NDE). In this paper, we propose a novel model-based method for ultrasonic echo parameter estimation. The ultrasonic signal is assumed to be composed of an unknown number of Gaussian echoes corrupted by white Gaussian noise. Firstly, the Hilbert transform is used to extract the envelope of the signal. It is shown that the parameter estimation of the signal is improved by using the envelope. To estimate the parameters of the envelope of the signal, quasi maximum likelihood method is used. The number of echoes is estimated using consistent Akaike information criterion. Two measures are used to evaluate the performance of the proposed method: (a) probability of detection of backscattered echoes and (b) the error of estimated time of flights. The proposed method is then compared to the cross-correlation method and the maximum likelihood method which uses the original signal. Simulated and experimental signals are used to evaluate the performance of each method. Both experimental and simulated results show that the proposed method can improve the parameter estimation which ultimately enhances the damage detection and assessment.     

基于门控循环图卷积网络的交通流预测

交通流预测在智能交通系统的建设中起着关键性的作用,然而现有预测方法无法准确地挖掘其潜在的时空相关性,而且大都采用全连接网络进行单步预测。为了进一步挖掘数据的时空特性以及提升长短期预测的精度,提出了一种门控循环图卷积网络（GR-GCN）模型。首先,利用频域上的图卷积结合门控循环单元（GRU）构建一个时空组件（STC）以同时捕获节点的时空相关性,充分地提取数据的时空特征;然后,利用该时空组件构成编码器单元,并将时间序列数据和路网结构数据输入其中;最后,使用门控循环单元作为解码器单元,并按照时间顺序将两者组成一个编码器—解码器（encoder-decoder）结构,依次解码出每个时刻的预测结果。在加利福尼亚交通局（Caltrans）性能评估系统中高速公路数据集PeMSD4和PeMSD8进行了实验。结果表明,所提模型GR-GCN在预测未来15 min、30 min、45 min和60 min的交通流量方面优于大多数现有基准模型,尤其是在长期预测方面。     

数控车床CAD/CAM系统中走刀路线的设计计算分析

本文提出在数控车床CAD／CAM系统中。怎样根据工件形状选择刀具，并且根据工件加工形状。使用的刀具，切削条件等少数数据。计算出加工形态刀尖半径的刀具路线。     

发动机连杆有限元网格划分方法

有限元网格划分是有限元分析的重要部分,基于网格划分的原则,运用专业网格划分软件Hypermesh对发动机连杆进行六面体网格划分,最后对划分有限元网格的方法进行了总结.     

Low temperature synthesis and optical properties of CaTiO3 nanoparticles from Ca(NO3)2·4H2O and TiO2 nanocrystals

Choosing low-melting-point Ca(NO₃)₂·4H₂O and high-reactive-activity TiO₂ nanocrystals as the raw materials, a simple and cost-effective route was developed for the synthesis of CaTiO₃ nanoparticles at 600 °C, which is much lower than that (about 1350 °C) used in the conventional solid state reaction methods. X-ray diffraction, energy dispersive X-ray spectroscopy and field emission scanning electron microscopy revealed the formation of orthorhombic phase CaTiO₃ nanoparticles with oxygen-deficiency at the surface. UV-vis absorption spectrum of the as-obtained CaTiO₃ nanoparticles displayed an absorption peak centered at around 325 nm (3.8 eV), together with a tail at lower energy side. Room temperature photoluminescence spectrum of the as-obtained CaTiO₃ nanoparticles upon laser excitation at 325 nm demonstrated a strong and broad visible light emission ranging from about 527 to 568 nm, which may be originated from the surface states and defect levels.     

A single-machine, single-wafer-processing, multiple-lots-per-carrier scheduling problem to minimize the sum of lot completion times

A high volume/high mix wafer fabrication facility processes customer orders (or lots) that are smaller in size. Because of their small sizes, a number of these lots are transported together in a carrier from one machine to another for processing. This is in contrast to transporting them individually, which would lead to an excessive number of mostly empty carriers, thereby resulting in a situation that would be prone to congestion and delays. At a machine, the wafers contained in a carrier are processed one-at-a-time. The problem that we address in this paper is to configure a given set of identical carriers of known capacity with a given number of lots of various sizes for processing at a machine so that the sum of the completion times of the lots at the machine is minimized. The processing time of a carrier is the sum of the processing times of the wafers in it, and the completion time of each lot in a carrier is the same being equal to the completion time of the carrier. To develop an effective solution methodology, first, we consider carriers of an unlimited capacity. We develop some structural properties for this version of the problem that readily lead to its solution for the case of same-sized lots, and also, that help in devising an effective procedure for its solution when the lots are of different sizes. Then, we consider identical carriers of finite and known capacity and show that the problem is readily solvable if the lots are of the same size. For different-sized lots, we present a branch-and-bound-based method that exploits the structural properties that we develop. For the testbed of data used, the results of our experimental investigation reveal the efficacy of our branch-and-bound method over the direct solution by CPLEX 12.2 of two different mixed integer programming formulations of the problem. The proposed branch-and-bound method has the tendency of solving a problem at the root node itself, while CPLEX 12.2 cannot solve large-sized instances due to excessive memory requirements.