812 research outputs found
Design and fabrication of robust broadband extreme ultraviolet multilayers
The random layer thickness variations can induce a great deformation of the
experimental reflection of broadband extreme ultraviolet multilayer. In order
to reduce this influence of random layer thickness fluctuations, the
multiobjective genetic algorithm has been improved and used in the robust
design of multilayer with a broad angular bandpass. The robust multilayer with
a lower sensitivity to random thickness errors have been obtained and the
corresponding multilayer mirrors were fabricated. The experimental results of
robust Mo/Si multilayer with a wide angular band were presented and analyzed,
and the advantage of robust multilayer design was demonstrated
Data Arrangement With Rotation Transformation for Fully Polarimetric Synthetic Aperture Radar
This letter proposes a data arrangement for fully polarimetric synthetic aperture radar (PolSAR). It is an essential novel method in the use of the rotation transformation in data interpretation. The key point of the proposal is employing a single pixel-based and selective rotation transformation for each pixel before the speckle filtering. The experimental results with ALOS2-PALSAR2 data show that the proposed data arrangement has much higher performance in recognizing double-bounce scattering in the man-made target area. At the same time, it is effective in avoiding the overestimation of double-bounce and/or surface scattering in natural target areas
Formation of episodic jets and associated flares from black hole accretion systems
Episodic ejections of blobs (episodic jets) are widely observed in black hole
sources and usually associated with flares. In this paper, by performing and
analyzing three dimensional general relativity magnetohydrodynamical numerical
simulations of accretion flows, we investigate their physical mechanisms. We
find that magnetic reconnection occurs in the accretion flow, likely due to the
turbulent motion and differential rotation of the accretion flow, resulting in
flares and formation of flux ropes. Flux ropes formed inside of 10-15
gravitational radii are found to mainly stay within the accretion flow, while
flux ropes formed beyond this radius are ejected outward by magnetic forces and
form the episodic jets. These results confirm the basic scenario proposed in
Yuan et al.(2009). Moreover, our simulations find that the predicted velocity
of the ejected blobs is in good consistency with observations of Sgr A*, M81,
and M87. The whole processes are found to occur quasi-periodically, with the
period being the orbital time at the radius where the flux rope is formed. The
predicted period of flares and ejections is consistent with those found from
the light curves or image of Sgr A*, M87, and PKS 1510-089. The possible
applications to protostellar accretion systems are discussed.Comment: 16 pages, 13 figures; accepted for publication in Ap
Vulnerability and Resilience of Social Engagement: Equilibrium Theory
Social networks of engagement sometimes dramatically collapse. A widely
adopted paradigm to understand this catastrophe dynamics is the threshold model
but previous work only considered the irreversible K-core pruning process and
the resulting kinetic activity patterns. Here we study the network alliance
problem as a simplified model of social engagement by equilibrium statistical
mechanics. Our theory reveals that the surviving kinetic alliances are
out-of-equilibrium and atypical configurations which may become highly
vulnerable to single-node-triggered cascading failures as they relax towards
equilibrium. Our theory predicts that if the fraction of active nodes is beyond
a certain critical value, the equilibrium (typical) alliance configurations
could be protected from cascading failures by a simple least-effort local
intervention strategy. We confirm these results by extensive Monte Carlo
simulations.Comment: Revised with modified title, supplementary technical details
included, to be published in Europhysics Letters (EPL
Psychological Stress Alters Ultrastructure and Energy Metabolism of Masticatory Muscle in Rats
To investigate the effects of psychological stress on the
masticatory muscles of rats, a communication box was applied to
induce the psychological stress (PS) in rats. The successful
establishment of psychological stimulation was confirmed by
elevated serum levels of adrenocorticotropic hormone (ACTH) and
changed behaviors in the elevated plusmaze apparatus. The energy
metabolism of the bilateral masseter muscles was tested via
chemocolorimetric analysis, whereas muscle ultrastructure was
assessed by electron microscopy. In comparison to the control
group, the PS group showed evidence of swollen mitochondria with
cristae loss and reduced matrix density in the masticatory muscles
after three weeks of stimulation; after five weeks of stimulation,
severe vacuolar changes to the mitochondria were observed.
Increased vascular permeability of the masticatory muscle
capillaries was found in the five-week PS rats. In addition, there
was decreased activity of Na+-K+ATPase and Ca2+-ATPase and a
simultaneous increase in the activity of lactate dehydrogenase and
lactic acid in the masticatory muscles of PS rats. Together, these
results indicate that psychological stress induces alterations in
the ultrastructure and energy metabolism of masticatory muscles in
rats
The global warming hiatus: Slowdown or redistribution?
Global mean surface temperatures (GMST) exhibited a smaller rate of warming during 1998-2013, compared to the warming in the latter half of the 20th Century. Although, not a "true" hiatus in the strict definition of the word, this has been termed the "global warming hiatus" by IPCC (2013). There have been other periods that have also been defined as the "hiatus" depending on the analysis. There are a number of uncertainties and knowledge gaps regarding the "hiatus." This report reviews these issues and also posits insights from a collective set of diverse information that helps us understand what we do and do not know. One salient insight is that the GMST phenomenon is a surface characteristic that does not represent a slowdown in warming of the climate system but rather is an energy redistribution within the oceans. Improved understanding of the ocean distribution and redistribution of heat will help better monitor Earth's energy budget and its consequences. A review of recent scientific publications on the "hiatus" shows the difficulty and complexities in pinpointing the oceanic sink of the "missing heat" from the atmosphere and the upper layer of the oceans, which defines the "hiatus." Advances in "hiatus" research and outlooks (recommendations) are given in this report
Study on coupling effect between the time-varying gear backlash and the different time-varying mesh parameters on the gear system
The vibration excitation of the rolling mill mainly comes from the gearbox in the process of rolling strip, and the meshing excitation is the main excitation factor of the gearbox. And the gear backlash plays an important role in the meshing excitation. However, the backlash is inevitable in the process of designing the gear system. Therefore, it is important to select the appropriate gear backlash to reduce the vibration amplitude of the gearbox, to improve the rolling speed and the quality of the steel strip. So, in this paper, the effect of the different variation amplitudes for the time-varying gear backlash (TVGB) on the vibration characteristics of the gear system under various mesh parameters is studied. A new formulation for calculating nonlinear damping and time varying meshing stiffness is applied in this coupling model. The results show that increasing of the load torque, the damping ratio, the system parameter or decreasing the directional rotation radius variation or kinematic transmission error caused the effects of variation amplitudes for the (TVGB) on the dynamic characteristics of the gear system to decrease. Test data from a gearbox experimental table verifies the accuracy of the model. The model is shown to be capable of simulating the mutually coupled effect between the backlash and the different parameters on the gear system. So, the new coupled model can be used as guide to select the appropriate gear backlash values for the rolling mill under different operating conditions
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