675 research outputs found
Incremental costs and optimization of in-core fuel management of nuclear power plants
"Issued: February 1973."Also issued as an Sc. D. thesis by the first author and supervised by the second and third authors, MIT, Dept. of Nuclear Engineering, 1973Includes bibliographical references (pages 250-251)This thesis is concerned with development of methods for optimizing the energy production and refuelling decision for nuclear power plants in an electric utility system containing both nuclear and fossil-fuelled stations. The objective is to minimize the revenue requirements for refuelling the power plants during the planning horizon; the decision variables are the energy generation, reload enrichment and batch fraction for each reactor cycle; the constraints are that the customer's load demand, as well as various other operational and engineering requirements be satisfied. This problem can be decomposed into two sub-problems. The first sub-problem is concerned with scheduling energy between nuclear reactors which have been fuelled in an optimal fashion. The second sub-problem is concerned with optimizing the fuelling of nuclear reactors given an optimized energy schedule.These two sub-problems when solved iteratively and interactively, would yield an optimal solution to the original problem. The problem of optimal energy scheduling between nuclear reactors can be formulated as a linear program. The incremental cost of energy is required as input to the linear program. Three methods of calculating incremental cost are considered: the Rigorous Method, based on the definition of partial derivativesis accurate but time consuring; the Inventory Value Method and the Linearization Method, based respectively on equations of inventory evaluation and linearization, are less accurate, but efficient. The latter two methods are recommended for the early stages of optimization. The problem of optimizing the fuelling of nuclear reactors has been solved for two cases: the special case of steady state operation, and the general case of nonsteady- state operation. The steady-state case has been solved by simple graphic techniques.The results indicate that reactors should be refuelled with as small a batch fraction as allowed by burnup constraints. The non-steady case has been solved by polynomial approximation, in which the objective function as well as the constraints are approximated by a sum of polynomials. The results indicate that the final selection of an optimal solution from a set of sub-optimal solutions is primarily based on engineering considerations, and not on economics considerations
Point cloud hand-object segmentation using multimodal imaging with thermal and color data for safe robotic object handover
This paper presents an application of neural networks operating on multimodal 3D data (3D point cloud, RGB, thermal) to effectively and precisely segment human hands and objects held in hand to realize a safe human–robot object handover. We discuss the problems encountered in building a multimodal sensor system, while the focus is on the calibration and alignment of a set of cameras including RGB, thermal, and NIR cameras. We propose the use of a copper–plastic chessboard calibration target with an internal active light source (near-infrared and visible light). By brief heating, the calibration target could be simultaneously and legibly captured by all cameras. Based on the multimodal dataset captured by our sensor system, PointNet, PointNet++, and RandLA-Net are utilized to verify the effectiveness of applying multimodal point cloud data for hand–object segmentation. These networks were trained on various data modes (XYZ, XYZ-T, XYZ-RGB, and XYZ-RGB-T). The experimental results show a significant improvement in the segmentation performance of XYZ-RGB-T (mean Intersection over Union: 82.8% by RandLA-Net) compared with the other three modes (77.3% by XYZ-RGB, 35.7% by XYZ-T, 35.7% by XYZ), in which it is worth mentioning that the Intersection over Union for the single class of hand achieves 92.6%
How Integrated is Integrated Reporting? From a Malaysian Perspective
The lack of coherence, transparency and accountability in traditional financial reporting, led the International Integrated Reporting Council (IIRC) to developed Integrated Reporting (IR) in 2010. This study draws the attention towards the top 50 public listed companies listed in Malaysian Stock Exchange as per asset size, and their fulfilment towards voluntary IR disclosures. This study was also conducted to examine the organisational characteristics that foster the IR initiative. A comparison was made with ISO 26000, GRI G4 and IR framework against the annual reports. This study was qualitative and descriptive in nature. The findings revealed that although there were traces of the fulfilment of all requirements with regard to ISO 26000, GRI and IR respectively, there were much to be done to encourage PLCs to incorporate such reporting guidelines. It was also found that, government-linked companies have greater fulfilment of these requirements
Gelsolin induces colorectal tumor cell invasion via modulation of the urokinase-type plasminogen activator cascade
Gelsolin is a cytoskeletal protein which participates in actin filament dynamics and promotes cell motility and plasticity. Although initially regarded as a tumor suppressor, gelsolin expression in certain tumors correlates with poor prognosis and therapy-resistance. In vitro, gelsolin has anti-apoptotic and pro-migratory functions and is critical for invasion of some types of tumor cells. We found that gelsolin was highly expressed at tumor borders infiltrating into adjacent liver tissues, as examined by immunohistochemistry. Although gelsolin contributes to lamellipodia formation in migrating cells, the mechanisms by which it induces tumor invasion are unclear. Gelsolin’s influence on the invasive activity of colorectal cancer cells was investigated using overexpression and small interfering RNA knockdown. We show that gelsolin is required for invasion of colorectal cancer cells through matrigel. Microarray analysis and quantitative PCR indicate that gelsolin overexpression induces the upregulation of invasion-promoting genes in colorectal cancer cells, including the matrix-degrading urokinase-type plasminogen activator (uPA). Conversely, gelsolin knockdown reduces uPA levels, as well as uPA secretion. The enhanced invasiveness of gelsolin-overexpressing cells was attenuated by treatment with function-blocking antibodies to either uPA or its receptor uPAR, indicating that uPA/uPAR activity is crucial for gelsolin-dependent invasion. In summary, our data reveals novel functions of gelsolin in colorectal tumor cell invasion through its modulation of the uPA/uPAR cascade, with potentially important roles in colorectal tumor dissemination to metastatic sites
Can Barrier to Relative Sliding of Carbon Nanotube Walls Be Measured?
Interwall interaction energies, as well as barriers to relative sliding of
the walls along the nanotube axis, are first calculated for pairs of both
armchair or both zigzag adjacent walls of carbon nanotubes with a wide range of
radiuses. It is found that for the pairs with the radius of the outer wall
greater than 5 nm both the interwall interaction energy and barriers to the
relative sliding per one atom of the outer wall only slightly depends on the
wall radius. A wide set of the measurable physical quantities determined by
these barriers are estimated as a function of the wall radius: shear strengths
and diffusion coefficients for relative sliding of the walls along the axis, as
well as frequencies of relative axial oscillations of the walls. For
nonreversible telescopic extension of the walls, maximum overlap of the walls
for which threshold static friction forces are greater than capillary forces is
estimated. Possibility of experimental verification of the calculated barriers
by measurements of the estimated physical quantities is discussed.Comment: 16 pages, 8 figure
Consequences of local gauge symmetry in empirical tight-binding theory
A method for incorporating electromagnetic fields into empirical
tight-binding theory is derived from the principle of local gauge symmetry.
Gauge invariance is shown to be incompatible with empirical tight-binding
theory unless a representation exists in which the coordinate operator is
diagonal. The present approach takes this basis as fundamental and uses group
theory to construct symmetrized linear combinations of discrete coordinate
eigenkets. This produces orthogonal atomic-like "orbitals" that may be used as
a tight-binding basis. The coordinate matrix in the latter basis includes
intra-atomic matrix elements between different orbitals on the same atom.
Lattice gauge theory is then used to define discrete electromagnetic fields and
their interaction with electrons. Local gauge symmetry is shown to impose
strong restrictions limiting the range of the Hamiltonian in the coordinate
basis. The theory is applied to the semiconductors Ge and Si, for which it is
shown that a basis of 15 orbitals per atom provides a satisfactory description
of the valence bands and the lowest conduction bands. Calculations of the
dielectric function demonstrate that this model yields an accurate joint
density of states, but underestimates the oscillator strength by about 20% in
comparison to a nonlocal empirical pseudopotential calculation.Comment: 23 pages, 7 figures, RevTeX4; submitted to Phys. Rev.
Over-expression of severe acute respiratory syndrome coronavirus 3b protein induces both apoptosis and necrosis in Vero E6 cells
The genome of the severe acute respiratory syndrome coronavirus encodes for eight accessory viral proteins with no known homologues in other
coronaviruses. One of these is the 3b protein, which is encoded by the second open reading frame in subgenomic RNA 3 and contains 154 amino
acids. Here, a detailed time-course study was performed to compare the apoptosis and necrosis profiles induced by full-length 3b, a 3b mutant
that was deleted by 30 amino acids from the C terminus (3b 124-154) and the classical apoptosis inducer, Bax. Our results showed that Vero E6
cells transfected with a construct for expressing 3b underwent necrosis as early as 6 h after transfection and underwent simultaneous necrosis and
apoptosis at later time-points. At all the time-points analysed, the apoptosis induced by the expression of 3b was less than the level induced by Bax
but the level of necrosis was comparable. The 3b 124-154 mutant behaves in a similar manner indicating that the localization of the 3b protein
does not seems to be important for the cell-death pathways since full-length 3b is localized predominantly to the nucleolus, while the mutant is
found to be concentrated in the peri-nuclear regions. To our knowledge, this is the first report of the induction of necrosis by a SARS-CoV protein.IS
Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector
The inclusive and dijet production cross-sections have been measured for jets
containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass
energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The
measurements use data corresponding to an integrated luminosity of 34 pb^-1.
The b-jets are identified using either a lifetime-based method, where secondary
decay vertices of b-hadrons in jets are reconstructed using information from
the tracking detectors, or a muon-based method where the presence of a muon is
used to identify semileptonic decays of b-hadrons inside jets. The inclusive
b-jet cross-section is measured as a function of transverse momentum in the
range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet
cross-section is measured as a function of the dijet invariant mass in the
range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets
and the angular variable chi in two dijet mass regions. The results are
compared with next-to-leading-order QCD predictions. Good agreement is observed
between the measured cross-sections and the predictions obtained using POWHEG +
Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet
cross-section. However, it does not reproduce the measured inclusive
cross-section well, particularly for central b-jets with large transverse
momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final
version published in European Physical Journal
Standalone vertex finding in the ATLAS muon spectrometer
A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at √s = 7 TeV collected with the ATLAS detector at the LHC during 2011
Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC
Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H →γ γ, H → Z Z∗ →4l and H →W W∗ →lνlν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV, corresponding to an integrated luminosity of about 25 fb−1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson
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