Flow pattern measurement in a full scale silo containing iron ore

The flow pattern in a silo is important because it affects both the recovery of solids and the pressures on the silo wall during discharge. Wherever mass flow is not achieved, the boundary of the flow channel has significant implications for both the functional and structural design of the silo. Many techniques have been used for the study of flow patterns in model silos, but most cannot be used at full scale, and very few quality measurements at full scale have ever been made. This paper outlines a full scale experimental study in which the patterns of solids flow and the flow channel boundaries are reliably quantified.The full scale silo was specially designed, constructed and instrumented to exhibit funnel flow and to make observations of the solids flow pattern and the silo wall pressures. It had three outlets: one concentric, one fully eccentric and one in between. Three materials were used: iron ore pellets, slag fines and crushed basalt. This paper describes experiments involving iron ore pellets. The silo was seeded with radio frequency tags whose residence times were measured by detecting them on exit during discharge. The residence time data were studied to deduce the discharge flow pattern. This paper presents the results of three different flow pattern interpretation techniques: the best of them (mass-time relationships) is shown to give a very clear identification of the solids flow pattern and the flow channel boundary.     

表面活性剂在卜特兰水泥表面上的吸附行为(英文)

实验探索了脂肪醇聚氧乙烯醚硫酸盐 (AES)、氯化十六烷基吡啶 (CPC)、β -萘磺酸聚合物 (NS)以及烷基酚聚氧乙烯醚 (TX -10 )等四种不同类型的表面活性剂在普通硅酸盐水泥表面的吸附行为。研究表明 ,AES在水泥颗粒表面的吸附是一种快吸附 ,属于LS型 ;CPC在水泥颗粒表面的吸附过程则是一种慢吸附 ,受动力学因素所控制 ;NS的吸附量与其浓度成线性关系 :TX -10则基本上不被吸附。结果显示 ,被吸附的三种表面活性剂都是疏水基朝向水相 ,增加了水泥颗粒的疏水性。然而AES随着添加量的增大 ,由于吸附胶束的形成 ,使水泥颗粒表面经由亲水 -疏水 -亲水的变化过程。从表面电荷的变化来看 ,AES、NS的添加均使水泥表面Zeta电位有所增加 ,而CPC却使得水泥颗粒表面从带负电变到带正电。文中所提出的改进Stern双电层模型能很好地说明几种表面活性剂在水泥颗粒表面的吸附特性     

Proton exchange membranes prepared by simultaneous radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) films. II. Properties of sulfonated membranes

Proton exchange membranes were prepared by radiation‐induced grafting of styrene onto commercial poly(tetrafluoroethylene‐co‐hexafluoropropylene) films using a simultaneous irradiation technique followed by a sulfonation reaction. The resulting membranes were characterized by measuring their physicochemical properties such as water uptake, ion exchange capacity, hydration number, and proton conductivity as a function of the degree of grafting. The thermal properties (melting and glass transition temperatures) and thermal stability of the membrane were also investigated using differential scanning calorimetry and thermal gravimetric analysis, respectively. Membranes having degrees of grafting of 16% and above showed proton conductivity of the magnitude of 10⁻² Ω⁻¹ cm⁻¹ at room temperature, as well as thermal stability at up to 290°C under an oxygen atmosphere. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2443–2453, 2000     

Part II. Properties of the grafted and sulfonated membranes

The physical and chemical properties of polystyrene grafted and sulfonated polytetrafluoroethylene (PTFE‐graft‐PSSA) membranes prepared by radiation‐induced grafting of styrene onto commercial PTFE films using simultaneous irradiation technique followed by a sulfonation reaction are evaluated. The investigated properties include water uptake, ion exchange capacity, hydration number and ionic conductivity. All properties are correlated with the amount of grafted polystyrene (degree of grafting). The thermal stability of the membrane evaluated by thermal gravimetric analysis (TGA) is compared with that of original and grafted PTFE films. The membrane surface structural properties are analysed by electron spectroscopy for chemical analysis (ESCA). Membranes having degrees of grafting of 18 % and above show a good combination of physical and chemical properties that allow them to be proposed for use as proton conducting membranes, provided that they have sufficient chemical and mechanical stability. © 2000 Society of Chemical Industry     

Hierarchical Indexing Structure for Efficient Similarity Search in Video Retrieval

With the rapid increase in both centralized video archives and distributed WWW video resources, content-based video retrieval is gaining its importance. To support such applications efficiently, content-based video indexing must be addressed. Typically, each video is represented by a sequence of frames. Due to the high dimensionality of frame representation and the large number of frames, video indexing introduces an additional degree of complexity. In this paper, we address the problem of content-based video indexing and propose an efficient solution, called the ordered VA-file (OVA-file) based on the VA-file. OVA-file is a hierarchical structure and has two novel features: 1) partitioning the whole file into slices such that only a small number of slices are accessed and checked during k nearest neighbor (kNN) search and 2) efficient handling of insertions of new vectors into the OVA-file, such that the average distance between the new vectors and those approximations near that position is minimized. To facilitate a search, we present an efficient approximate kNN algorithm named ordered VA-LOW (OVA-LOW) based on the proposed OVA-file. OVA-LOW first chooses possible OVA-slices by ranking the distances between their corresponding centers and the query vector, and then visits all approximations in the selected OVA-slices to work out approximate kNN. The number of possible OVA-slices is controlled by a user-defined parameter delta. By adjusting delta, OVA-LOW provides a trade-off between the query cost and the result quality. Query by video clip consisting of multiple frames is also discussed. Extensive experimental studies using real video data sets were conducted and the results showed that our methods can yield a significant speed-up over an existing VA-file-based method and (distance with high query result quality. Furthermore, by incorporating temporal correlation of video content, our methods achieved much more efficient performance     

Embossed Bragg Gratings Based on Organically Modified Silane Waveguides in InP

Considering the large variety of applications for optical glass waveguide gratings, the effective production method of embossing for micropatterning, and the unique advantages of InP-based materials, we expect that hybridization of embossed optical glass waveguide gratings and InP substrates will inevitably lead to new applications in integrated optics. We present our preliminary results of research toward the development of solgel-derived glass waveguide gratings made by embossing on InP. Theoretically, the dependence of the stop-band FWHM and transmission contrast of the grating filter on the grating length, and the relationship between the Bragg grating's reflective wavelength and the dopant concentration in the solgel waveguide, are obtained. Experimentally, using organically modified silane, we solve the problem of mismatching of SiO(2) and InP, and successfully fabricate an embossed glass grating with a second-order Bragg reflection wavelength of 1580 nm and a FWHM of 0.7 nm fabricated upon a solgel waveguide on an InP substrate.     

Delta-modulated buck-type PWM converter

A delta-modulated, current-source, three-phase pulsewidth modulation (PWM) rectifier is described. The rectifier is intended to be used in conjunction with controlled current inverters. An outer proportional feedback loop regulates the unidirectional output current flowing through the DC link. An inner feedback loop maintains near sinusoidal waveform currents at unity or leading power factor from the utility power supply. The inner loop controls the current indirectly by delta modulation of the voltage across the AC terminals of the converter. The converter has been conceived as the circuit dual of the hysteresis current-controlled boost-type rectifier. Experimental results from a laboratory model are presented     

Faceless identification based on temporal strips

This paper first presents a novel approach for modelling facial features, Local Directional Texture (LDT), which exploits the unique directional information in image textures for the problem of face recognition. A variant of LDT with privacy-preserving temporal strips (TS) is then considered to achieve faceless recognition with a higher degree of privacy while maintaining high accuracy. The TS uses two strips of pixel blocks from the temporal planes, XT and YT, for face recognition. By removing the reliance on spatial context (i.e., XY plane) for this task, the proposed method withholds facial appearance information from public view, where only one-dimensional temporal information that varies across time are extracted for recognition. Thus, privacy is assured, yet without impeding the facial recognition task which is vital for many security applications such as street surveillance and perimeter access control. To validate the reliability of the proposed method, experiments were carried out using the Honda/UCSD, CK+, CAS(ME)² and CASME II databases. The proposed method achieved a recognition rate of 98.26% in the standard video-based face recognition database, Honda/UCSD. It also offers a 81.92% reduction in the dimension length required for storing the extracted features, in contrast to the conventional LBP-TOP.

     

在电子测试技术工程教育中,使用NI LabVIEW和NI ELVIS进行IC参数测试

1引言 将NILabVIEW、NI教学实验室虚拟仪器套件II（NIELVISII）与易于使用、自定义的即插即用IC测试板结合,创建了一个用户界面友好且可编程配置的IC直流参数测试平台,为高等教育提供了测试中小规模集成电路芯片直流参数的动手实践平台。