Dimensional instability of cement bonded particleboard: Modelling CBPB as a composite of two materials

Copyright @ Springer Verlag. This is a post print version of the article. The official published version can be obtained from the link below.Previous papers have quantitatively indicated that the total movement of cement bonded particleboard (CBPB) is equal to the sum of the movement of its components. This paper examined the efficacy of the law of mixtures when applied to the movement of a wood-cement composite under internal swelling or shrinkage stresses. Abundant data generated in companion papers were first manipulated to develop the universal formulae for predicting the movement of components. In conjunction with previous numerical results from image analysis of the structure of CBPB, and the orientated elasticity and stress algorithms, the models for theoretically predicting mass and dimensional changes of CBPB were derived. Validation studies were conducted and these demonstrated an excellent agreement of the theoretical predictions with experimental data for both mass and dimensional changes of CBPB due to internal swelling or shrinkage stresses during adsorption and desorption. The success also implied that CBPB can be treated as a composite and its properties can be well derived by the law of mixtures even though CBPB is an unusual type of composite having a very high volume fraction of wood chips, but a very high mass fraction of cement paste

Dimensional instability of cement bonded particleboard - Part 2: Behaviour and its prediction under cyclic changes in RH

This is a post print version of the article. The official published version can be obtained from the link below.This paper examines the dimensional instability of cement bonded particleboard (CBPB) and discusses the behaviour of CBPB during cyclic changes in relative humidities (RH). The results indicated that the changes of CBPB in both mass and dimensions reflected the changes in RH; in a cycle 90–65–35–65–90%RH the change of per percentage change in RH was 1.0:1.3:1.3:2.5 for mass, 1:2:2:1 for length and 1.3:1.1:1.0:1.0 for thickness. The changes were closely related to the structure of CBPB and the nature of the cement paste and wood chips. Thickness change was double that of the length change between 65 and 35%RH and triple that between 65 and 90%RH. The rate of change in mass was much higher than that in dimensions. The hysteresis loops were dissimilar to those of other wood and wood-based materials, with the loops of mass change closed between 65 and 90%RH, while the loops for dimensional changes were open. A set of the former loops moved upward and the latter moved downward with increasing number of cycles, corresponding to an accumulated increase in mass, but decrease in dimensions. The models developed for CBPB under constant and a single changing RH were successfully applied to changes under cyclic RH. The sorption behaviour and dimensional movement of CBPB has been shown to be influenced not only by RH, but also by its intermediate history, with the maximum values for change within every phase of sorption, in both mass and dimensions, being higher for the cycling between 35–90%RH than the cycling regime 35–65–90%RH. The ratios of dimensional changes to mass change of CBPB were greater under the latter regime than under the former regime.Partly Financial Support from the British Council

Space-efficient Feature Maps for String Alignment Kernels

String kernels are attractive data analysis tools for analyzing string data. Among them, alignment kernels are known for their high prediction accuracies in string classifications when tested in combination with SVM in various applications. However, alignment kernels have a crucial drawback in that they scale poorly due to their quadratic computation complexity in the number of input strings, which limits large-scale applications in practice. We address this need by presenting the first approximation for string alignment kernels, which we call space-efficient feature maps for edit distance with moves (SFMEDM), by leveraging a metric embedding named edit sensitive parsing (ESP) and feature maps (FMs) of random Fourier features (RFFs) for large-scale string analyses. The original FMs for RFFs consume a huge amount of memory proportional to the dimension d of input vectors and the dimension D of output vectors, which prohibits its large-scale applications. We present novel space-efficient feature maps (SFMs) of RFFs for a space reduction from O(dD) of the original FMs to O(d) of SFMs with a theoretical guarantee with respect to concentration bounds. We experimentally test SFMEDM on its ability to learn SVM for large-scale string classifications with various massive string data, and we demonstrate the superior performance of SFMEDM with respect to prediction accuracy, scalability and computation efficiency.Comment: Full version for ICDM'19 pape

Mechanisms of enhanced heterogeneous nucleation during solidification in binary Al-Mg alloys

This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2012 ElsevierThe mechanisms involved in the grain refinement of Al–Mg alloys through varying the Mg content and applying intensive melt shearing were investigated. It was found that the oxide formed in Al–Mg alloys under normal melting conditions is MgAl2O4, which displays an equiaxed and faceted morphology with {1 1 1} planes exposed as its natural surfaces. Depending on the Mg content, MgAl2O4 particles exist either as oxide films in dilute Al–Mg alloys (Mg 1 wt.%). Such MgAl2O4 particles can act as potent sites for nucleation of α-Al grains, which is evidenced by the well-defined cube-on-cube orientation relationship between MgAl2O4 and α-Al. Enhanced heterogeneous nucleation in Al–Mg alloys can be attributed to the high potency of MgAl2O4 particles with a lattice misfit of 1.4% and the increased number density of MgAl2O4 particles due to either natural dispersion by the increased Mg content or forced dispersion through intensive melt shearing. It was also found that intensive melt shearing leads to significant grain refinement of dilute Al–Mg alloys by effective dispersion of the MgAl2O4 particles entrapped in oxide films, but it has marginal effect on the grain refinement of concentrated Al–Mg alloys, where MgAl2O4 particles have been naturally dispersed into individual particles by the increased Mg content.This study is funded from the EPSRC Grant EP/H026177/1

PENGARUH PENAMBAHAN LIAT DAN BIOCHAR SEKAM PADI PADA PENGOLAHAN MINIMUM TERHADAP DISTRIBUSI PORI TANAH PSAMMENT DAN PERTUMBUHAN SERTA HASIL TANAMAN JAGUNG (Zea Mays L.)

Penelitian mengenai pengaruh penambahan liat dan biochar sekam padi pada pengolahan tanah minimum terhadap distribusi pori tanah Psamment dan pertumbuhan serta hasil tanaman jagung (Zea mays L.) ini dilaksanakan di Nagari Katapiang, Kecamatan Batang Anai, Kabupaten Padang Pariaman, dan di laboratorium Fisika Tanah, Jurusan Tanah, Fakultas Pertanian, Universitas Andalas pada bulan Agustus 2019 sampai Januari 2020. Penelitian ini dilakukan dengan menggunakan Rancangan Acak Kelompok (RAK) dengan 4 jenis perlakuan dan 3 kelompok. Perlakuan-perlakuan tersebut adalah A (Pengolahan tanah minimum tanpa liat dan biochar sekam padi), B (Pengolahan tanah minimum + Liat/Ultisol 20ton/ha), C (Pengolahan tanah minimum + biochar sekam padi 20 ton/ha), dan D (Pengolahan tanah minimum + liat/Ultisol 20 ton/ha dan biochar sekam padi 20 ton/ha). Hasil penelitian ini dianalisis berdasarkan tabel kriteria, analisis sidik ragam, dan uji Duncan’s New Multiple Range Test (DNMRT) pada taraf 5 %. Dari penelitian ini disimpulkan bahwa pemberian liat dan biochar sekam padi dapat memperbaiki sifat fisika tanah Psamment. Pemberian liat 20 ton/ha dan biochar sekam padi 20 ton/ha mampu menurunkan bobot volume tanah Psamment dari 1,40 g/cm3 (kontrol) menjadi 0,84 g/cm3, meningkatkan total ruang pori dari 42,86 % (kontrol) menjadi 65,10 %, merubah persentase distribusi pori dengan meningkatkan pori drainase cepat (31,63 % vol menjadi 41,00 % vol), menurunkan pori drainase lambat (5,80 % vol menjadi 4,53 %vol), dan meningkatkan pori air tersedia (6,00 % vol menjadi 7,50% vol). Penambahan liat dan biochar sekam padi pada tanah Psamment juga meningkatkan pertumbuhan tinggi tanaman jagung (236,2 cm) 8 minggu setelah tanam dibanding kontrol (211,59 cm), dan meningkatkan hasil tanaman jagung berupa bobot tongkol (20,58 ton/ha) dibanding kontrol (13,27 ton/ha). Kata kunci: Psamment, liat, biochar, sekam padi

Entanglement sudden birth of two trapped ions interacting with a time-dependent laser field

We explore and develop the mathematics of the two multi-level ions. In particular, we describe some new features of quantum entanglement in two three-level trapped ions confined in a one-dimensional harmonic potential, allowing the instantaneous position of the center-of-mass motion of the ions to be explicitly time-dependent. By solving the exact dynamics of the system, we show how survivability of the quantum entanglement is determined by a specific choice of the initial state settings.Comment: 13 pages, 4 figure

Formation of Supermassive Black Holes

Evidence shows that massive black holes reside in most local galaxies. Studies have also established a number of relations between the MBH mass and properties of the host galaxy such as bulge mass and velocity dispersion. These results suggest that central MBHs, while much less massive than the host (~ 0.1%), are linked to the evolution of galactic structure. In hierarchical cosmologies, a single big galaxy today can be traced back to the stage when it was split up in hundreds of smaller components. Did MBH seeds form with the same efficiency in small proto-galaxies, or did their formation had to await the buildup of substantial galaxies with deeper potential wells? I briefly review here some of the physical processes that are conducive to the evolution of the massive black hole population. I will discuss black hole formation processes for `seed' black holes that are likely to place at early cosmic epochs, and possible observational tests of these scenarios.Comment: To appear in The Astronomy and Astrophysics Review. The final publication is available at http://www.springerlink.co

Microstructural evolution under low shear rates during Rheo processing of LM25 alloy

© ASM InternationalMicrostructural features of LM25 alloy processed by two different routes: (1) conventional casting, and(2)shear casting based on inclined heated surface are studied. The microstructures of the primary phase for the shear-cast samples show rosette or ellipsoidal morphologies. Heat transfer of contacting melt with the inclined tube surface and shear stress exerted on the layers of the melt as result of gravitational force are crucial parameters for the microstructural evolution. Compared to those produced by conventional casting, shear-cast samples have a much improved tensile strength and ductility due to globular microstructure

Optimising low acoustic impedance back-fill material wave barrier dimensions to shield structures from ground borne high speed rail vibrations

Ground borne vibrations generated due to high speed train passage can cause undesirable effects on the nearby environment. One approach to mitigate vibration levels is to use “wave barriers”, however their installation cost may be very high. In an attempt to minimize construction costs, numerical modelling and physical experiments are performed to determine guidelines for the optimisation of trench dimensions. Substantial savings are found to be achievable through carefully chosen barrier dimensions. Firstly, for the purposes of testing a numerical model that can be used by railway wave barrier designers, a geophysical investigation is undertaken on a high speed railway line outside Edinburgh, Scotland. The testing schedule consists of vibration measurements adjacent to the line and a multi-channel analysis of surface waves technique to determine the underlying soil properties. An outline is then presented describing a newly developed three dimensional finite element railway model using commercially available software. The resulting model is modified to replicate the track and soil properties at the test site and then it is shown that the model results exhibit a strong correlation in comparison to those collected during the experimental stage. The numerical model is then used to assess the ability of a range of wave barrier configurations to protect nearby sites from railway vibration. It is found that depth and length have a strong influence on the mitigation of vibration levels but the effect of trench width is negligible. Lastly, for a specific example it is shown that cost savings of 95% are achievable if trench dimensions are carefully planned. All of the analyses require that the ratio of the acoustic impedance of soil compared to wave barrier backfill material must be greater than eight