1,402 research outputs found
The improvement of aluminium casting process control by application of the new CRIMSON process
All The traditional foundry usually not only uses batch melting where the
aluminium alloys are melted and held in a furnace for long time, but also uses
the gravity filling method in both Sand Casting Process (SCP) and Investment
Casting Process (ICP). In the gravity filling operation, the turbulent behaviour
of the liquid metal causes substantial entrainment of the surface oxide films
which are subsequently trapped into the liquid and generate micro cracks and
casting defects. In this paper a new CRIMSON process is introduced which
features instead of gravity filling method, using the single shot up-casting
method to realize the rapid melting and rapid filling mould operations which
reduce the contact time between the melt and environment thus reducing the
possibility of defect generation. Another advantage of the new process is the
drastic reduction of energy consumption due to shortened melting and filling
time. Two types of casting samples from SCP and ICP were compared with the new
process. The commercial software was used to simulate the filling and
solidification processes of the casting samples. The results show that the new
process has a more improved behaviour during filling a mould and solidification
than the two conventional casting processes
Non-monotonic anisotropy in charge conduction induced by antiferrodistortive transition in metallic SrTiO
Cubic SrTiO becomes tetragonal below 105 K. The antiferrodistortive
(AFD) distortion leads to clockwise and counter-clockwise rotation of adjacent
TiO octahedra. This insulator becomes a metal upon the introduction of
extremely low concentration of n-type dopants. However, signatures of the
structural phase transition in charge conduction have remained elusive.
Employing the Montgomery technique, we succeed in resolving the anisotropy of
charge conductivity induced by the AFD transition, in the presence of different
types of dopants. We find that the slight lattice distortion () gives rise to a twenty percent anisotropy in charge conductivity, in
agreement with the expectations of band calculations. Application of uniaxial
strain amplifies the detectable anisotropy by disfavoring one of the three
possible tetragonal domains. In contrast with all other known anisotropic Fermi
liquids, the anisotropy has opposite signs for elastic and inelastic
scattering. Increasing the concentration of dopants leads to a drastic shift in
the temperature of the AFD transition either upward or downward. The latter
result puts strong constraints on any hypothetical role played by the AFD soft
mode in the formation of Cooper pairs and the emergence of superconductivity in
SrTiO.Comment: 6 pages with 5 figure
Experimental realization of three-color entanglement at optical fiber communication and atomic storage wavelengths
Multi-color entangled states of light including low-loss optical fiber
transmission and atomic resonance frequencies are essential resources for
future quantum information network. We present the experimental achievement on
the three-color entanglement generation at 852 nm, 1550 nm and 1440 nm
wavelengths for optical continuous variables. The entanglement generation
system consists of two cascaded non-degenerated optical parametric oscillators
(NOPOs). The flexible selectivity of nonlinear crystals in the two NOPOs and
the tunable property of NOPO provide large freedom for the frequency selection
of three entangled optical beams, so the present system is possible to be
developed as practical devices used for quantum information networks with
atomic storage units and long fiber transmission lines.Comment: 4pages, 4 figure
Examining Users’ Knowledge Change in the Task Completion Process
This paper examines the changes of information searchers’ topic knowledge levels in the process of completing information tasks. Multi-session tasks were used in the study, which enables the convenience of eliciting users’ topic knowledge during their process of completing the whole tasks. The study was a 3-session laboratory experiment with 24 participants, each time working on one subtask in an assigned 3-session general task. The general task was either parallel or dependently structured. Questionnaires were administered before and after each session to elicit users’ perceptions of their knowledge levels, task attributes, and other task features, for both the overall task and the sub-tasks. Our results support the assumption that users’ knowledge generally increases after each search session, but there were exceptions in which a “ceiling” effect was shown. We also found that knowledge was correlated with users’ perceptions of task attributes and accomplishment. In addition, task type was found to affect several aspects of knowledge levels and knowledge change. These findings further our understanding of users’ knowledge in information tasks and are thus helpful for information retrieval research and system design
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Several methods were used to estimate Vs30 from site profiles with borehole depths of about 20 m for the strong-motion stations located in Southwest China. The methods implemented include extrapolation (constant and gradient), Geomatrix Site Classification correlation with shear-wave velocity, and remote sensing (terrain and topography). The gradient extrapolation is the preferred choice of this study for sites with shear-wave velocity profile data. However, it is noted that the coefficients derived from the California data set are not applicable to sites in Southwest China. Due to the scarcity of borehole profiles data with depth of more than 30 m in Southwest China, 73 Kiknet profiles were used to generate new coefficients for gradient extrapolation. Fortunately, these coefficients provide a reasonable estimate of Vs30 for sites in Southwest China. This study showed Vs30 could be estimated by the time-average shear-wave velocity (average slowness) of only 10 meters of depth. Furthermore, a median Vs30 estimate based upon Geomatrix Classification is derived from the results of the gradient extrapolation using a regional calibration of the Geomatrix Classification with Vs30. The results of this study can be applied to assign Vs30 to the sites without borehole data in Southwest China
Concentrating Membrane Proteins Using Asymmetric Traps and AC Electric Fields
Membrane proteins are key components of the plasma membrane and are responsible for control of chemical ionic gradients, metabolite and nutrient transfer, and signal transduction between the interior of cells and the external environment. Of the genes in the human genome, 30% code for membrane proteins (Krogh et al. J. Mol. Biol.2001, 305, 567). Furthermore, many FDA-approved drugs target such proteins (Overington et al. Nat. Rev. Drug Discovery2006, 5, 993). However, the structure-function relationships of these are notably sparse because of difficulties in their purification and handling outside of their membranous environment. Methods that permit the manipulation of membrane components while they are still in the membrane would find widespread application in separation, purification, and eventual structure-function determination of these species (Poo et al. Nature1977, 265, 602). Here we show that asymmetrically patterned supported lipid bilayers in combination with AC electric fields can lead to efficient manipulation of charged components. We demonstrate the concentration and trapping of such components through the use of a “nested trap” and show that this method is capable of yielding an approximately 30-fold increase in the average protein concentration. Upon removal of the field, the material remains trapped for several hours as a result of topographically restricted diffusion. Our results indicate that this method can be used for concentrating and trapping charged membrane components while they are still within their membranous environment. We anticipate that our approach could find widespread application in the manipulation and study of membrane proteins
Live Imaging of Glial Cell Migration in the Drosophila Eye Imaginal Disc
Glial cells of both vertebrate and invertebrate organisms must migrate to final target regions in order to ensheath and support associated neurons. While recent progress has been made to describe the live migration of glial cells in the developing pupal wing (1), studies of Drosophila glial cell migration have typically involved the examination of fixed tissue. Live microscopic analysis of motile cells offers the ability to examine cellular behavior throughout the migratory process, including determining the rate of and changes in direction of growth. Paired with use of genetic tools, live imaging can be used to determine more precise roles for specific genes in the process of development. Previous work by Silies et al. (2) has described the migration of glia originating from the optic stalk, a structure that connects the developing eye and brain, into the eye imaginal disc in fixed tissue. Here we outline a protocol for examining the live migration of glial cells into the Drosophila eye imaginal disc. We take advantage of a Drosophila line that expresses GFP in developing glia to follow glial cell progression in wild type and in mutant animals
Dependence of quantum correlations of twin beams on pump finesse of optical parametric oscillator
The dependence of quantum correlation of twin beams on the pump finesse of an
optical parametric oscillator is studied with a semi-classical analysis. It is
found that the phase-sum correlation of the output signal and idler beams from
an optical parametric oscillator operating above threshold depends on the
finesse of the pump field when the spurious pump phase noise generated inside
the optical cavity and the excess noise of the input pump field are involved in
the Langevin equations. The theoretical calculations can explain the previously
experimental results, quantitatively.Comment: 27 pages, 8 figure
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