4,333 research outputs found
Parylene Accelerometer Utilizing Spiral Beams
This paper reports a Parylene accelerometer utilizing spiral beams. Since Parylene has intrinsic tensile stress, the resonant frequency ω_n of sensor structure is higher than that under no tensile stress. Considering the sensitivity of accelerometer is 1/ω_n^2 , the investigation of ω_n of a suspended structure supported by straight beams is carried out both theoretically and experimentally. As a result, it is proved that comparatively long beams are necessary for realizing the high sensitivity of a Parylene sensor with tensile stress. A spiral beam is effective for not only realizing a long beam in a limited space, but also realizing stress relaxation. Both Parylene accelerometer with straight beams and that with spiral beams are fabricated. Sensitivity of them is characterized, and the effectiveness of utilizing spiral beam is confirmed
Microbiological influences on fracture surfaces of intact mudstone and the implications for geological disposal of radioactive waste
The significance of the potential impacts of microbial activity on the transport properties of host rocks for geological repositories is an area of active research. Most recent work has focused on granitic environments. This paper describes pilot studies investigating changes in transport properties that are produced by microbial activity in sedimentary rock environments in northern Japan. For the first time, these short experiments (39 days maximum) have shown that the denitrifying bacteria, Pseudomonas denitrificans, can survive and thrive when injected into flow-through column experiments containing fractured diatomaceous mudstone and synthetic groundwater under pressurized conditions. Although there were few significant changes in the fluid chemistry, changes in the permeability of the biotic column, which can be explained by the observed biofilm formation, were quantitatively monitored. These same methodologies could also be adapted to obtain information from cores originating from a variety of geological environments including oil reservoirs, aquifers and toxic waste disposal sites to provide an understanding of the impact of microbial activity on the transport of a range of solutes, such as groundwater contaminants and gases (e.g. injected carbon dioxide)
Imaging Simulations of the Sunyaev-Zel'dovich Effect for ALMA
We present imaging simulations of the Sunyaev-Zel'dovich effect of galaxy
clusters for the Atacama Large Millimeter/submillimeter Array (ALMA) including
the Atacama Compact Array (ACA). In its most compact configuration at 90GHz,
ALMA will resolve the intracluster medium with an effective angular resolution
of 5 arcsec. It will provide a unique probe of shock fronts and relativistic
electrons produced during cluster mergers at high redshifts, that are hard to
spatially resolve by current and near-future X-ray detectors. Quality of image
reconstruction is poor with the 12m array alone but improved significantly by
adding ACA; expected sensitivity of the 12m array based on the thermal noise is
not valid for the Sunyaev-Zel'dovich effect mapping unless accompanied by an
ACA observation of at least equal duration. The observations above 100 GHz will
become excessively time-consuming owing to the narrower beam size and the
higher system temperature. On the other hand, significant improvement of the
observing efficiency is expected once Band 1 is implemented in the future.Comment: 16 pages, 12 figures. Accepted for publication in PASJ. Note added in
proof is include
Tongue interface based on surface EMG signals of suprahyoid muscles
The research described herein was undertaken to develop and test a novel tongue interface based on classification of tongue motions from the surface electromyography (EMG) signals of the suprahyoid muscles detected at the underside of the jaw. The EMG signals are measured via 22 active surface electrodes mounted onto a special flexible boomerang-shaped base. Because of the sensor’s shape and flexibility, it can adapt to the underjaw skin contour. Tongue motion classification was achieved using a support vector machine (SVM) algorithm for pattern recognition where the root mean square (RMS) features and cepstrum coefficients (CC) features of the EMG signals were analyzed. The effectiveness of the approach was verified with a test for the classification of six tongue motions conducted with a group of five healthy adult volunteer subjects who had normal motor tongue functions. Results showed that the system classified all six tongue motions with high accuracy of 95.1 ± 1.9 %. The proposed method for control of assistive devices was evaluated using a test in which a computer simulation model of an electric wheelchair was controlled using six tongue motions. This interface system, which weighs only 13.6 g and which has a simple appearance, requires no installation of any sensor into the mouth cavity. Therefore, it does not hinder user activities such as swallowing, chewing, or talking. The number of tongue motions is sufficient for the control of most assistive devices
Slow Switching in Globally Coupled Oscillators: Robustness and Occurrence through Delayed Coupling
The phenomenon of slow switching in populations of globally coupled
oscillators is discussed. This characteristic collective dynamics, which was
first discovered in a particular class of the phase oscillator model, is a
result of the formation of a heteroclinic loop connecting a pair of clustered
states of the population. We argue that the same behavior can arise in a wider
class of oscillator models with the amplitude degree of freedom. We also argue
how such heteroclinic loops arise inevitably and persist robustly in a
homogeneous population of globally coupled oscillators. Although the
heteroclinic loop might seem to arise only exceptionally, we find that it
appears rather easily by introducing the time-delay in the population which
would otherwise exhibit perfect phase synchrony. We argue that the appearance
of the heteroclinic loop induced by the delayed coupling is then characterized
by transcritical and saddle-node bifurcations. Slow switching arises when the
system with a heteroclinic loop is weakly perturbed. This will be demonstrated
with a vector model by applying weak noises. Other types of weak
symmetry-breaking perturbations can also cause slow switching.Comment: 10 pages, 14 figures, RevTex, twocolumn, to appear in Phys. Rev.
Cosmological SPH simulations with four million particles: statistical properties of X-ray clusters in a low-density universe
We present results from a series of cosmological SPH (smoothed particle
hydrodynamics) simulations coupled with the P3M
(Particle-Particle-Particle-Mesh) solver for the gravitational force. The
simulations are designed to predict the statistical properties of X-ray
clusters of galaxies as well as to study the formation of galaxies. We have
seven simulation runs with different assumptions on the thermal state of the
intracluster gas. Following the recent work by Pearce et al., we modify our SPH
algorithm so as to phenomenologically incorporate the galaxy formation by
decoupling the cooled gas particles from the hot gas particles. All the
simulations employ 128^3 particles both for dark matter and for gas components,
and thus constitute the largest systematic catalogues of simulated clusters in
the SPH method performed so far. These enable us to compare the analytical
predictions on statistical properties of X-ray clusters against our direct
simulation results in an unbiased manner. We find that the luminosities of the
simulated clusters are quite sensitive to the thermal history and also to the
numerical resolution of the simulations, and thus are not reliable. On the
other hand, the mass-temperature relation for the simulated clusters is fairly
insensitive to the assumptions of the thermal state of the intracluster gas,
robust against the numerical resolution, and in fact agrees well with the
analytic prediction. Therefore the prediction for the X-ray temperature
function of clusters on the basis of the Press-Schechter mass function and the
virial equilibrium is fairly reliable.Comment: Accepted for publication in The Astrophysical Journal. 18 pages with
7 embedded figure
What can we learn from phi_1 and B_d^0 -> pi^+ pi^- ?
We discuss what we can understand from and
decay mode. Using a convention without weak phases and , we
can solve the parameters from the time-depended CP asymmetry. If we can put a
condition the contribution from penguin except for the CKM factor including in
the diagram is small, then we can lead the allowed region of or
by using the convention.Comment: 7 pages, 4 figures, references and comments adde
Local structures of polar wurtzites Zn_{1-x}Mg_{x}O studied by Raman and {67}Zn/{25}Mg NMR spectroscopies and by total neutron scattering
Local compositions and structures of Zn_{1-x}Mg_{x}O alloys have been
investigated by Raman and solid-state {67}Zn/{25}Mg nuclear magnetic resonance
(NMR) spectroscopies, and by neutron pair-distribution-function (PDF) analyses.
The E2(low) and E2(high) Raman modes of Zn_{1-x}Mg_{x}O display Gaussian- and
Lorentzian-type profiles, respectively. At higher Mg substitutions, both modes
become broader, while their peak positions shift in opposite directions. The
evolution of Raman spectra from Zn_{1-x}Mg_{x}O solid solutions are discussed
in terms of lattice deformation associated with the distinct coordination
preferences of Zn and Mg. Solid-state magic-angle-spinning (MAS) NMR studies
suggest that the local electronic environments of {67}Zn in ZnO are only weakly
modified by the 15% substitution of Mg for Zn. {25}Mg MAS spectra of
Zn_{0.85}Mg_{0.15}O show an unusual upfield shift, demonstrating the prominent
shielding ability of Zn in the nearby oxidic coordination sphere. Neutron PDF
analyses of Zn_{0.875}Mg_{0.125}O using a 2x2x1 supercell corresponding to
Zn_{7}MgO_{8} suggest that the mean local geometry of MgO_{4} fragments concurs
with previous density functional theory (DFT)-based structural relaxations of
hexagonal wurtzite MgO. MgO_{4} tetrahedra are markedly compressed along their
c-axes and are smaller in volume than ZnO_{4} units by ~6%. Mg atoms in
Zn_{1-x}Mg_{x}O have a shorter bond to the -axial oxygen atom than to the
three lateral oxygen atoms, which is distinct from the coordination of Zn. The
precise structure, both local and average, of Zn_{0.875}Mg_{0.125}O obtained
from time-of-flight total neutron scattering supports the view that
Mg-substitution in ZnO results in increased total spontaneous polarization.Comment: 12 pages, 14 figures, 2 table
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