花式纱生产的新概念

介绍了Schlafllorst公司开发的Fancynation花式装置在Autocoro 360转杯纺纱机上的应用。模块化设计的花式装置可适应小批量订货的需求。     

Geopolymer reinforced with E‐glass leno weaves

This study explores the viability of fiberglass‐geopolymer composites as an intermediate temperature structural ceramic composite. E‐glass fibers are cheap, readily available, resistant to heat, electricity and chemical attack. Geopolymers are refractory and can be processed at room temperature. However, pure geopolymers have low tensile strength and fracture toughness, as is typical of ceramics. In this work, tensile and flexure properties of metakaolin‐based sodium and potassium geopolymers reinforced with E‐glass leno weaves were measured and the data was analyzed by Weibull statistics. The average tensile and flexural strengths for sodium geopolymer reinforced with E‐glass leno weaves were 39.3 ± 7.2 MPa and 25.6 ± 4.8 MPa, respectively. For potassium geopolymer reinforced with E‐glass leno weaves, the average tensile and flexural strengths were 40.7 ± 9.9 MPa and 15.9 ± 4.0 MPa, respectively. The composites were heat treated for one hour at two temperatures, 300°C and 550°C and their flexure properties were studied at room temperatures. The average flexural strengths for sodium geopolymer reinforced with E‐glass leno weaves were reduced to 6.6 ± 1.0 MPa after heat treatment at 300°C, and 1.2 ± 0.3 MPa after heat treatment at 550°C, respectively. For potassium geopolymer reinforced with E‐glass leno weaves, the average flexural strengths were 6.1 ± 1.5 MPa and 1.3 ± 0.3 MPa after heat treatment at 300°C and 550°C, respectively. SEM and EDS were performed to observe the fiber‐matrix interface. XRD was done to check if the geopolymer was amorphous as expected.     

Formation of α/β-Si3N4 nanoparticles by carbothermal reduction and nitridation of geopolymers

Silicon nitride (Si₃N₄) particles with various α/β-Si₃N₄ ratios were fabricated from geopolymer (GP)-carbon compositions (M₂O·Al₂O₃·4.5SiO₂·12H₂O+18C), where M is an alkali ion (Na⁺, K⁺ and Cs⁺). They were made by carbothermal reduction and nitridation at 1400°, 1500°, and 1600°C for 2 hours under flowing nitrogen. Characterization of carbothermally reacted GP-carbon compositions was based on XRD, SEM-EDS, HRTEM, and selected area electron diffraction analyses. Depending on the alkaline composition of GP, the carbon content and the reaction temperature, a compositionally variable α/β-Si₃N₄ or SiAlON was achieved. Crystallization of the GPs gradually increased by heat treatment over 1400°C with corresponding weight loss. It was found that NaGP, KGP, and CsGP crystallized into a major phase of α-Si₃N₄, β-Si₃N₄, and SiAlON, respectively. Prolonged heating at 1600°C led to an increase in the α/β-Si₃N₄ ratio in NaGP due to the formation of aluminum nitride, while it led to a decrease in α/β-Si₃N₄ ratio in KGP. In the case of CsGP, SiAlON replaced the pollucite which mainly formed at lower temperatures. Transmission electron microscopy revealed that the needle-like particles were of ~0.5 µm in size and consisting of α/β-Si₃N₄ mixtures.     

Optimal maintenance policies in incomplete repair models

We consider an incomplete repair model, that is, the impact of repair is not minimal as in the homogeneous Poisson process and not “as good as new” as in renewal processes but lies between these boundary cases. The repairs are assumed to impact the failure intensity following a virtual age process of the general form proposed by Kijima. In previous works field data from an industrial setting were used to fit several models. In most cases the estimated rate of occurrence of failures was that of an underlying exponential distribution of the time between failures. In this paper, it is shown that there exist maintenance schedules under which the failure behavior of the failure-repair process becomes a homogeneous Poisson process.     

Modelling of heat transfer in hot strip mill runout table cooling

The need for accurate prediction and control of cooling profiles of steel strips on runout tables has led to the development of a mathematical model that is able to predict coiler temperatures under any given condition with an accuracy of ± 14 °C as well as calculating the entire temperature profile of a steel strip with sufficient accuracy. Comparisons with online strip temperature data at various locations of the runout table, which were obtained by a new experimental procedure, show that the effect of single cooling headers on the thermal response of a steel strip can be predicted. The model takes into account all relevant thermodynamic effects by means of a statistical approach. Heat transfer to the environment, steel thermophysical properties and phase transformation are modelled using B‐splines. Model adaptation is realised by fitting calculated and measured coiler temperatures of approximately 40000 strips with a least square method in order to gain optimal base values for the B‐spline functions. During model development special attention was paid to the model's capability of being re‐adjustable to a large variety of conditions as well as its local behaviour. Therefore, concepts like temperature‐dependent heat transfer coefficients, which are applicable only to one specific plant, have been avoided in favour of a more generalised formulation of the model that helps to gain insight into the physics of the processes involved, i.e. heat transfer of subcooled jet impingement boiling and film boiling. It was found that both cooling water and steel surface temperature have a large influence on heat transfer whereas the influence of strip speed can be neglected.     

In vitro assembly of an archaeal D-L-N RNA polymerase subunit complex reveals a eukaryote-like structural arrangement

Archaeal RNA polymerases (RNAPs) resemble the eukaryotic nuclear RNAPs in complexity, and many of their subunits display a high degree of sequence similarity to their eukaryotic counterparts. Here we describe specific protein-protein contacts present between individual recombinant RNAP subunits from the archaeon Methanococcus jannaschii. Subunits D and L interact specifically with each other in two-hybrid assays. D also interacts under the same conditions with the RPB11 and AC19 subunits from the yeast Saccharomyces cerevisiae, suggesting that essential elements of the binding surface between these proteins have been conserved across the archaeal/eukaryotic evolutionary domain boundary. Interactions between L and RPB3 or AC40 were, however, not detectable. Recombinant D and L subunits associate under in vitro conditions and copurify with each other during size-exclusion chromatography. Addition of an another recombinant subunit (N) to the D-L complex results in the formation of a triple complex. This D-L-N complex resembles the RPB3-RPB11-RPB10 or AC40-AC19-RPB10 complexes in eukaryotic RNAPIIand RNAPI/RNAPIII, respectively. Our data provide evidence for a close similarity in the quaternary arrangement of a subset of archaeal and eukaryotic RNA polymerase subunits and the conservation of the protein-protein contacts formed between them.     

gTybalt—a free computer algebra system

This article documents the free computer algebra system “gTybalt”. The program is build on top of other packages, among others GiNaC, TeXmacs and Root. It offers the possibility of interactive symbolic calculations within the C++ programming language. Mathematical formulae are visualized using fonts.

Program summary

Title of program: gTybaltVersion: 1.0.0Catalogue identifier: ADSIProgram summary URL:http://cpc.cs.qub.ac.uk.summaries/ADSIProgram obtained from: CPC Program Library, Queen's University of Belfast, N. IrelandLicense: GNU Public LicenseComputers: allOperating system: GNU/LinuxProgram language: C++Distribution format: tar gzip fileNo. of bytes in distributed program, including test data, etc.: 499583Memory required to execute: 64 MB recommendedOther programs called: see Appendix AExternal files needed: noneKeywords: Symbolic calculations, Computer algebraNature of the physical problem: Symbolic calculations occur nowadays in all areas of science. gTybalt is a free computer algebra system based on the C++ language.Method of solution: gTybalt is a “bazaar”-style program, it relies on existing, freely-available packages for specific sub-tasks.Restrictions on complexity of the problem: gTybalt does not try to cover every domain of mathematics. Some desirable algorithms, like symbolic integration are not implemented. It can however easily be extended in new directions. Apart from that, standard restrictions due to the available hardware apply.Typical running time: Depending on the complexity of the problem.     

A homotopy approach for nonlinear control synthesis

In this paper, the authors propose a control method for nonlinear systems which relies on the homotopy method for solving nonlinear equations and tangent linearized control systems. They present a mathematically rigorous treatment of the theoretical foundations, including a constructive proof of the exponential error decay for the controlled system which contains an explicit control design instruction. For illustration, this design instruction is applied to an example system. The behavior of the controlled system is examined by numerical simulations. To demonstrate the advantages and drawbacks of the proposed method they include a short comparison with two usual nonlinear control techniques by means of the considered example system     

Chemical stability, microstructure and mechanical behavior of LaPO4-containing ceramics

The use of LaPO₄ as a weak interface in composites for high temperature applications was investigated using tape-cast laminates and fiber model systems. Three laminates were fabricated with LaPO₄ as one component and Al₂O₃, Y₃Al₅O₁₂ or LaAl₁₁O₁₈ as the other. The chemical compatibility between the different components of the laminates, as well as the mechanical responses to flexural deformation and the propagation of indentation cracks, were examined. Two fiber model systems (Al₂O₃ fiber/LaPO₄ coating/Al₂O₃ matrix and Y₃Al₅O₁₂ fiber/LaPO₄ coating/Al₂O₃ matrix) were studied by fiber pushout tests to measure the interfacial shear strengths. The interfacial shear strengths were calculated by the linear and shear-lag approaches for different embedded fiber lengths. The results suggest that Y₃Al₅O₁₂ fiber-reinforced composites with LaPO₄ coatings have potential as high temperature materials in oxidizing environments.     

On-line spectroscopic measurements of wood chips before a continuous digester

A VIS spectrometer was evaluated during 25 days of on-line operation. The spectrometer was installed above a conveyor belt carrying softwood chips to a continuous digester that was charged with 100 tonnes chips/h. We found that VIS spectroscopy can be used on-line both to predict chip properties and to monitor a continuous digester. Prediction models for pine, bark and dry content were made using partial least square (PLS) regression models. The prediction models were based on data from a designed experiment that was performed in the lab before the on-line installation. Spectral information taken from the VIS range can be used for monitoring the digester, as the information correlates well to process variables. For 3 days, an NIR spectrometer, calibrated via a designed experiment to make the same predictions as did the VIS spectrometer, was also installed at the conveyor belt. The VIS and NIR predictions proved to be similar.