1,592 research outputs found
Quantifying the effect of end support restraints on vibration serviceability of mass timber floor systems: Testing
Design of mass timber floor systems is commonly governed by vibration serviceability due to high stiffness-to-weight ratio and low inherent damping of timber. Research and design practice have shown that static deflection under a concentrated load and fundamental natural frequency can be effective and robust indicators for vibration performance of mass timber floors. These design parameters are normally calculated by assuming simply supported conditions in existing design methods. However, such an assumption deviates from actual floor supports, especially in platform-framed buildings, and in-situ end support restraints have been widely recognized as a significant factor affecting the vibration performance. The purpose of the study is to quantify the influence of end support restraints on vibration serviceability of mass timber floors in platform construction through a comprehensive experimental program and analytical treatment. This paper is the first part and focus specifically on the experimental work on cross-laminated timber (CLT) panels. In particular, extensive laboratory tests have been conducted on different CLT floor panels with various end support restraints induced by top loads, self-tapping screws and steel angle brackets. The fundamental natural frequency and mid-span deflection under a concentrated load were measured for each end support configuration. The rotational restraint stiffness was determined by comparing results of restrained supports to those of simple supports and represented as end fixity factors. The analysis of test results shows that the CLT floor-to-wall connection exhibited inherent non-linear behaviour and such characteristic was more significant for higher top loads. Compared with screws and brackets, the top loads dominated the partially restrained effect but such dominance gradually diminished for lower-level top loads. In addition, support wall thickness notably impacts the support restraint. It was then suggested that the clear span could be used to determine deflection and frequency in the design, but further investigation is needed
Dynamical Properties of a Growing Surface on a Random Substrate
The dynamics of the discrete Gaussian model for the surface of a crystal
deposited on a disordered substrate is investigated by Monte Carlo simulations.
The mobility of the growing surface was studied as a function of a small
driving force and temperature . A continuous transition is found from
high-temperature phase characterized by linear response to a low-temperature
phase with nonlinear, temperature dependent response. In the simulated regime
of driving force the numerical results are in general agreement with recent
dynamic renormalization group predictions.Comment: 10 pages, latex, 3 figures, to appear in Phys. Rev. E (RC
Soliton Staircases and Standing Strain Waves in Confined Colloidal Crystals
We show by computer simulation of a two-dimensional crystal confined by
corrugated walls that confinement can be used to impose a controllable
mesoscopic superstructure of predominantly mechanical elastic character. Due to
an interplay of the particle density of the system and the width D of the
confining channel, "soliton staircases" can be created along both parallel
confining boundaries, that give rise to standing strain waves in the entire
crystal. The periodicity of these waves is of the same order as D. This
mechanism should be useful for structure formation in the self-assembly of
various nanoscopic materials.Comment: 22 pages, 5 figure
Towards Efficient Sequential Pattern Mining in Temporal Uncertain Databases
Uncertain sequence databases are widely used to model data with inaccurate or imprecise timestamps in many real world applications. In this paper, we use uniform distributions to model uncertain timestamps and adopt possible world semantics to interpret temporal uncertain database. We design an incremental approach to manage temporal uncertainty efficiently, which is integrated into the classic pattern-growth SPM algorithm to mine uncertain sequential patterns. Extensive experiments prove that our algorithm performs well in both efficiency and scalability
Identification of Log Characteristics in Computed Tomography Images Using Back-Propagation Neural Networks with the Resilient Back-Propagation Training Algorithm and Textural Analysis: Preliminary Results
This research addressed the feasibility of identifying internal log characteristics in computed tomography (CT) images of sugar maple and black spruce logs by means of back-propagation (BP) neural networks with a resilient BP training algorithm. Five CT images were randomly sampled from each log. Three of the images were used to develop the corresponding classifier, and the remaining two images were used for validation. The image features that were used in the classifier were gray-level values, textual, and distance features. The important part of the classifier topology, ie the hidden node number, was determined based on the performance indicators: overall accuracy, mean square error, training iteration number, and training time. For the training images, the classifiers produced class accuracies for heartwood, sapwood, bark, and knots of 99.3, 100, 96.7, and 97.9%, respectively, for the sugar maple log; and 99.7, 95.3, 98.4, and 93.2%, respectively, for the black spruce log. Overall accuracies were 98.5% for sugar maple and 96.6% for black spruce, respectively. High overall accuracies were also achieved with the validation images of both species. The results also suggest that using textural information as the inputs can improve the classification accuracy. Moreover, the resilient BP training algorithm made BP artificial neural networks converge faster compared with the steepest gradient descent with momentum algorithm. This study indicates that the developed BP neural networks may be applicable to identify the internal log characteristics in the CT images of sugar maple and black spruce logs
Entangled Husimi distribution and Complex Wavelet transformation
Based on the proceding Letter [Int. J. Theor. Phys. 48, 1539 (2009)], we
expand the relation between wavelet transformation and Husimi distribution
function to the entangled case. We find that the optical complex wavelet
transformation can be used to study the entangled Husimi distribution function
in phase space theory of quantum optics. We prove that the entangled Husimi
distribution function of a two-mode quantum state |phi> is just the modulus
square of the complex wavelet transform of exp{-(|eta|^2)/2} with phi(eta)being
the mother wavelet up to a Gaussian function.Comment: 7 page
Symmetric-Asymmetric transition in mixtures of Bose-Einstein condensates
We propose a new kind of quantum phase transition in phase separated mixtures
of Bose-Einstein condensates. In this transition, the distribution of the two
components changes from a symmetric to an asymmetric shape. We discuss the
nature of the phase transition, the role of interface tension and the phase
diagram. The symmetric to asymmetric transition is the simplest quantum phase
transition that one can imagine. Careful study of this problem should provide
us new insight into this burgeoning field of discovery.Comment: 6 pages, 3 eps figure
Kinetic Roughening in Surfaces of Crystals Growing on Disordered Substrates
Substrate disorder effects on the scaling properties of growing crystalline
surfaces in solidification or epitaxial deposition processes are investigated.
Within the harmonic approach there is a phase transition into a low-temperature
(low-noise) superrough phase with a continuously varying dynamic exponent z>2
and a non-linear response. In the presence of the KPZ nonlinearity the disorder
causes the lattice efects to decay on large scales with an intermediate
crossover behavior. The mobility of the rough surface hes a complex dependence
on the temperature and the other physical parameters.Comment: 13 pages, 2 figures (not included). Submitted to Phys. Rev. Letts.
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Synthesis of hexahydrofuro[3,2-c]quinoline, a martinelline type analogue and investigation of its biological activity
2015-2016 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Co-ordination between Rashba spin-orbital interaction and space charge effect and enhanced spin injection into semiconductors
We consider the effect of the Rashba spin-orbital interaction and space
charge in a ferromagnet-insulator/semiconductor/insulator-ferromagnet junction
where the spin current is severely affected by the doping, band structure and
charge screening in the semiconductor. In diffusion region, if the the
resistance of the tunneling barriers is comparable to the semiconductor
resistance, the magnetoresistance of this junction can be greatly enhanced
under appropriate doping by the co-ordination between the Rashba effect and
screened Coulomb interaction in the nonequilibrium transport processes within
Hartree approximation.Comment: 4 pages, 3 figure
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