19,229 research outputs found
Finite element analysis of stress distribution and the effects of geometry in a laser-generated single-stage ceramic tile grout seal using ANSYS
Optimisation of the geometry (curvature of the vitrified enamel layer) of a laser-generated single-stage ceramic tile grout seal has carried out with a finite element (FE) model. The overall load bearing capacities and load-displacement plots of three selected geometries were determined experimentally by the indentation technique. Simultaneously, a FE model was developed utilising the commercial ANSYS package to simulate the indentation. Although the load-displacement plots generated by the FE model consistently displayed stiffer identities than the experimentally obtained results, there was reasonably close agreement between the two sets of results. Stress distribution profiles of the three FE models at failure loads were analysed and correlated so as to draw an implication on the prediction of a catastrophic failure through an analysis of FE-generated stress distribution profiles. It was observed that although increased curvatures of the vitrified enamel layer do enhance the overall load-bearing capacity of the single-stage ceramic tile grout seal and bring about a lower nominal stress, there is a higher build up in stress concentration at the apex that would inevitably reduce the load-bearing capacity of the enamel glaze. Consequently, the optimum geometry of the vitrified enamel layer was determined to be flat
Comment on "Quantum Decoherence in Disordered Mesoscopic Systems"
In a recent paper, Phys. Rev. Lett. 81, 1074 (1998), Golubev and Zaikin (GZ)
found that ``zero-point fluctuations of electrons'' contribute to the dephasing
rate extracted from the magnetoresistance. As a result, the dephasing rate
remains finite at zero temperature. GZ claimed that their results ``agree well
with the experimental data''. We point out that the GZ results are incompatible
with (i) conventional perturbation theory of the effects of interaction on weak
localization (WL), and (ii) with the available experimental data. More detailed
criticism of GZ findings can be found in cond-mat/9808053.Comment: 1 page, no figure
Minimum-error discrimination between symmetric mixed quantum states
We provide a solution of finding optimal measurement strategy for
distinguishing between symmetric mixed quantum states. It is assumed that the
matrix elements of at least one of the symmetric quantum states are all real
and nonnegative in the basis of the eigenstates of the symmetry operator.Comment: 10 page
Characteristics of Cavity-Stabilized Flames in a Supersonic Flow
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77050/1/AIAA-15095-553.pd
Polymers grafted to porous membranes
We study a single flexible chain molecule grafted to a membrane which has
pores of size slightly larger than the monomer size. On both sides of the
membrane there is the same solvent. When this solvent is good, i.e. when the
polymer is described by a self avoiding walk, it can fairly easily penetrate
the membrane, so that the average number of membrane crossings tends, for chain
length , to a positive constant. The average numbers of monomers on
either side of the membrane diverges in this limit, although their ratio
becomes infinite. For a poor solvent, in contrast, the entire polymer is
located, for large , on one side of the membrane. For good and for theta
solvents (ideal polymers) we find scaling laws, whose exponents can in the
latter case be easily understood from the behaviour of random walks.Comment: 4 pages, 6 figure
Renminbi Internationalisation: Precedents and Implications
While it is commonly assumed that there are no known precedents against which to benchmark the internationalisation of the Renminbi (RMB), this paper argues that the PRCs own development experience provides a useful perspective on the internationalisation debate. In particular it indicates that lessons can be learnt from both the successes and the shortcomings of efforts to internationalise the RMB in the 1970s. During this period state-owned banks in Hong Kong played a central role in mobilising finance for foreign trade. Access to Hong Kongās developed financial institutions allowed the PRC to maximise receipts from foreign trade as well as minimise the risks of undue swings in capital flows. The paper shows that although China no longer faces foreign exchange scarcity, economic reforms have not yet resolved vulnerabilities in Chinaās financial institutions and as such Hong Kongās role in mitigating the risk of undue capital swings remains
Microwave Components with MEMS Switches
RF MEMS switches with metal-metal contacts are being developed for microwave applications where broadband, high linearity performance is required. These switches provide less than 0.2 dB insertion loss through 40 GHz. This paper describes the integration of these switches into selected microwave components such as reconfigurable antenna elements, tunable filters, switched delay lines, and SPDT switches. Microwave and millimeter wave measured results from these circuits are presented
Robust paramagnetism in Bi2-xMxRu2O7 (M=Mn,Fe,Co,Ni,Cu) pyrochlore
We report physical property characterization of Bi2-xMxRu2O7 pyrochlores,
including magnetic suseptibility, resistivity, and Seebeck coefficients. The
solid solution exists up to x=0.5 for (M=Cu,Ni,Co) and up to x=0.1 for
(M=Fe,Mn). None of the doped materials exhibit ferromagnetism or any localized
ruthenium moment behavior. Instead we find the Ru-O and Bi-O sublattices to be
essentially independent, with any magnetism resulting from the unpaired
transition metal dopant spins. Cobalt substitution for bismuth results in
localized Co{2+}, and low temperature spin-glass transitions in several cases.
Nickel moments on the pyrochlore lattice display properties intermediate to
localized and itinerant. Finally, copper doping results in only an enhancement
of the Pauli metallic density of states.Comment: submitted, Phys. Rev.
Mapping CH_4 : CO_2 ratios in Los Angeles with CLARS-FTS from Mount Wilson, California
The Los Angeles megacity, which is home to more than 40% of the population in California, is the second largest megacity in the United States and an intense source of anthropogenic greenhouse gases (GHGs). Quantifying GHG emissions from the megacity and monitoring their spatiotemporal trends are essential to be able to understand the effectiveness of emission control policies. Here we measure carbon dioxide (CO_2) and methane (CH_4) across the Los Angeles megacity using a novel approach ā ground-based remote sensing from a mountaintop site. A Fourier transform spectrometer (FTS) with agile pointing optics, located on Mount Wilson at 1.67 km above sea level, measures reflected near-infrared sunlight from 29 different surface targets on Mount Wilson and in the Los Angeles megacity to retrieve the slant column abundances of CO_2, CH_4 and other trace gases above and below Mount Wilson. This technique provides persistent space- and time-resolved observations of path-averaged dry-air GHG concentrations, XGHG, in the Los Angeles megacity and simulates observations from a geostationary satellite. In this study, we combined high-sensitivity measurements from the FTS and the panorama from Mount Wilson to characterize anthropogenic CH_4 emissions in the megacity using tracerātracer correlations. During the period between September 2011 and October 2013, the observed XCH_4 : XCO_2 excess ratio, assigned to anthropogenic activities, varied from 5.4 to 7.3 ppb CH_4 (ppm CO_2)^(ā1), with an average of 6.4 Ā± 0.5 ppb CH_4 (ppm CO_2)^(ā1) compared to the value of 4.6 Ā± 0.9 ppb CH_4 (ppm CO_2)^(ā1) expected from the California Air Resources Board (CARB) bottom-up emission inventory. Persistent elevated XCH_4 : XCO_2 excess ratios were observed in Pasadena and in the eastern Los Angeles megacity. Using the FTS observations on Mount Wilson and the bottom-up CO_2 emission inventory, we derived a top-down CH_4 emission of 0.39 Ā± 0.06 Tg CH_4 year^(ā1) in the Los Angeles megacity. This is 18ā61% larger than the state government's bottom-up CH_4 emission inventory and consistent with previous studies
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