scholarly journals Quantized Ultracold Neutrons in Rough Waveguides: GRANIT Experiments and Beyond

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
M. Escobar ◽  
A. E. Meyerovich
Keyword(s):  
Surface Roughness ◽  
Quantum States ◽  
Scaling Relations ◽  
Ultracold Neutrons ◽  
System Parameters ◽  
Neutron Count ◽  
Simple Scaling ◽  
Biased Diffusion ◽  
Rough Boundaries ◽  
Single Constant

We apply our general theory of transport in systems with random rough boundaries to gravitationally quantized ultracold neutrons in rough waveguides as in GRANIT experiments (ILL, Grenoble). We consider waveguides with roughness in both two and one dimensions (2D and 1D). In the biased diffusion approximation the depletion times for the gravitational quantum states can be easily expressed via each other irrespective of the system parameters. The calculation of the exit neutron count reduces to evaluation of a single constant which contains a complicated integral of the correlation function of surface roughness. In the case of 1D roughness (random grating) this constant is calculated analytically for common types of the correlation functions. The results obey simple scaling relations which are slightly different in 1D and 2D. We predict the exit neutron count for the new GRANIT cell.

Supermassive Black Hole feedback in early type galaxies

2020 ◽  
Vol 15 (S359) ◽  
pp. 119-125
Author(s):  
W. Forman ◽  
C. Jones ◽  
A. Bogdan ◽  
R. Kraft ◽  
E. Churazov ◽  
...  
Keyword(s):  
Dark Matter Halo ◽  
Scaling Relations ◽  
Radio Sources ◽  
Early Type ◽  
X Ray ◽  
Galaxy Groups ◽  
Sufficient Energy ◽  
The Galaxy ◽  
Simple Scaling ◽  
Halo Masses

AbstractOptically luminous early type galaxies host X-ray luminous, hot atmospheres. These hot atmospheres, which we refer to as coronae, undergo the same cooling and feedback processes as are commonly found in their more massive cousins, the gas rich atmospheres of galaxy groups and galaxy clusters. In particular, the hot coronae around galaxies radiatively cool and show cavities in X-ray images that are filled with relativistic plasma originating from jets powered by supermassive black holes (SMBH) at the galaxy centers. We discuss the SMBH feedback using an X-ray survey of early type galaxies carried out using Chandra X-ray Observatory observations. Early type galaxies with coronae very commonly have weak X-ray active nuclei and have associated radio sources. Based on the enthalpy of observed cavities in the coronae, there is sufficient energy to “balance” the observed radiative cooling. There are a very few remarkable examples of optically faint galaxies that are 1) unusually X-ray luminous, 2) have large dark matter halo masses, and 3) have large SMBHs (e.g., NGC4342 and NGC4291). These properties suggest that, in some galaxies, star formation may have been truncated at early times, breaking the simple scaling relations.

A soft ring oscillator

2019 ◽  
Vol 4 (31) ◽  
pp. eaaw5496 ◽  
Author(s):  
Daniel J. Preston ◽  
Haihui Joy Jiang ◽  
Vanessa Sanchez ◽  
Philipp Rothemund ◽  
Jeff Rawson ◽  
...  
Keyword(s):  
Constant Pressure ◽  
Particle Separation ◽  
Schmitt Trigger ◽  
Ring Oscillator ◽  
System Level ◽  
Pressure Source ◽  
Pneumatic Actuators ◽  
System Parameters ◽  
Soft Actuators ◽  
Single Constant

Periodic actuation of multiple soft, pneumatic actuators requires coordinated function of multiple, separate components. This work demonstrates a soft, pneumatic ring oscillator that induces temporally coordinated periodic motion in soft actuators using a single, constant-pressure source, without hard valves or electronic controls. The fundamental unit of this ring oscillator is a soft, pneumatic inverter (an inverting Schmitt trigger) that switches between its two states (“on” and “off”) using two instabilities in elastomeric structures: buckling of internal tubing and snap-through of a hemispherical membrane. An odd number of these inverters connected in a loop produces the same number of periodically oscillating outputs, resulting from a third, system-level instability; the frequency of oscillation depends on three system parameters that can be adjusted. These oscillatory output pressures enable several applications, including undulating and rolling motions in soft robots, size-based particle separation, pneumatic mechanotherapy, and metering of fluids. The soft ring oscillator eliminates the need for hard valves and electronic controls in these applications.

scholarly journals Breaking Simple Scaling Relations through Metal–Oxide Interactions: Understanding Room-Temperature Activation of Methane on M/CeO2 (M = Pt, Ni, or Co) Interfaces

2020 ◽  
Vol 11 (21) ◽  
pp. 9131-9137
Author(s):  
Pablo G. Lustemberg ◽  
Feng Zhang ◽  
Ramón A. Gutiérrez ◽  
Pedro J. Ramírez ◽  
Sanjaya D. Senanayake ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Room Temperature ◽  
Scaling Relations ◽  
Simple Scaling ◽  
Temperature Activation

Comparative Analysis of the Process Mechanics in Micro-Electrical Discharge Machining (EDM) and Reverse Micro-EDM

2011 ◽  
Author(s):  
Sachin Mastud ◽  
Ramesh K. Singh ◽  
Johnson Samuel ◽  
Suhas S. Joshi
Keyword(s):  
Surface Roughness ◽  
Electrical Discharge ◽  
Erosion Rate ◽  
Electrical Discharge Machining ◽  
Process Analysis ◽  
System Parameters ◽  
Erosion Rates ◽  
Micro Electrical Discharge Machining ◽  
Material Erosion ◽  
Process Mechanics

The objective of this paper is to study the time-evolution of the process mechanics for micro-electrical discharge machining (MEDM) and reverse-micro-electrical discharge machining (R-MEDM), as a function of key system parameters, viz., voltage, capacitance, and threshold of the spark circuit. Full factorial experiments have been performed to quantify the aforementioned system parameters on the MEDM and R-MEDM processes. The process monitoring voltage and current signals, material erosion rate and the surface roughness values are the machining responses of interest. The voltage and current (V-I) signals reveal information about the material erosion rate and the extent of debris-interference associated with the corresponding process. Analysis of the V-I signals shows that R-MEDM is more stable than MEDM and can therefore be operated at aggressive conditions of capacitance and voltage. R-MEDM also results in higher material erosion rates but the resulting surface has a higher surface roughness value than that generated by MEDM. A debris deposition mechanism is proposed for R-MEDM that suggests debris entrapment and subsequent welding to the machined feature to be the reason for the increased surface roughness.

scholarly journals Breaking Simple Scaling Relations Through Metal-Oxide Interactions: Understanding Room Temperature Activation of Methane on M-CeO2 (M= Pt, Ni or Co) Interfaces

2020 ◽  
Author(s):  
Pablo Lustemberg ◽  
Feng Zhang ◽  
Ramón A. Gutiérrez ◽  
Pedro J. Ramírez ◽  
Sanjaya D. Senanayake ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Ambient Pressure ◽  
Scaling Relations ◽  
Time Resolved ◽  
X Ray ◽  
Metal Support ◽  
Simple Scaling

The clean activation of methane at low temperatures remains an eminent challenge and a field of competitive research. In particular, on late transition metal surfaces such as Pt(111) or Ni(111), elevated temperatures are necessary to activate the hydrocarbon molecule, but a massive deposition of carbon makes the metal surface useless for catalytic activity. However, on very low-loaded M/CeO2 (M= Pt, Ni, or Co) surfaces, the dissociation of methane occurs at room temperature, which is unexpected considering simple linear scaling relationships. This intriguing phenomenon has been studied using a combination of experimental techniques (ambient-pressure X-ray photoelectron spectroscopy, time-resolved X-ray diffraction and X-ray absorption spectroscopy) and density functional theory-based calculations. The experimental and theoretical studies show that the size and morphology of the supported nanoparticles together with strong metal-support interactions are behind the deviations from the scaling relations. These findings point toward a possible strategy to circumvent scaling relations, producing active and stable catalysts which can be employed for methane activation and conversion. <br>

scholarly journals Seismic performance

2019 ◽  
Vol 622 ◽  
pp. A76 ◽  
Author(s):  
B. Mosser ◽  
E. Michel ◽  
R. Samadi ◽  
A. Miglio ◽  
G. R. Davies ◽  
...  
Keyword(s):  
Information Content ◽  
Seismic Performance ◽  
Scaling Relations ◽  
Fundamental Properties ◽  
Evolved Stars ◽  
Simple Scaling ◽  
Observational Noise ◽  
Stellar Properties ◽  
Seismic Index ◽  
Intrinsic Scatter

Context. Asteroseismology is a unique tool that can be used to study the interior of stars and hence deliver unique information for the studiy of stellar physics, stellar evolution, and Galactic archaeology. Aims. We aim to develop a simple model of the information content of asteroseismology and to characterize the ability and precision with which fundamental properties of stars can be estimated for different space missions. Methods. We defined and calibrated metrics of the seismic performance. The metrics, expressed by a seismic index ℰ defined by simple scaling relations, are calculated for an ensemble of stars. We studied the relations between the properties of mission observations, fundamental stellar properties, and the performance index. We also defined thresholds for asteroseismic detection and measurement of different stellar properties. Results. We find two regimes of asteroseismic performance: the first where the signal strength is dominated by stellar properties and not by observational noise; and the second where observational properties dominate. Typically, for evolved stars, stellar properties provide the dominant terms in estimating the information content, while main sequence stars fall in the regime where the observational properties, especially stellar magnitude, dominate. We estimate scaling relations to predict ℰ with an intrinsic scatter of around 21%. Incidentally, the metrics allow us to distinguish stars burning either hydrogen or helium. Conclusions. Our predictions will help identify the nature of the cohort of existing and future asteroseismic observations. In addition, the predicted performance for PLATO will help define optimal observing strategies for defined scientific goals.

scholarly journals Fast compression of magnetic flux inside an imploding cylinder driven by laser beams

1990 ◽  
Vol 8 (3) ◽  
pp. 477-484 ◽  
Author(s):  
W. H. Choe
Keyword(s):  
Magnetic Flux ◽  
Shell Model ◽  
Thin Shell ◽  
Pulse Generator ◽  
Laser Beams ◽  
Scaling Relations ◽  
Magnetic Pulse ◽  
Simple Scaling

A method for the compression of magnetic flux inside a cylindrical liner imploded by laser beams is analyzed using a thin shell model. Simple scaling relations are derived for a number of key parameters. The potential of this scheme, as a fast-rising magnetic pulse generator, is explored based on the scalings obtained.

QUANTUM STATES OF NEUTRONS IN THE EARTH'S GRAVITATIONAL FIELD: CONSTRAINTS FOR QUASI-ELASTIC REFLECTIONS IN THE RANGE ΔE~10-12–10-9eV

2005 ◽  
Vol 14 (03n04) ◽  
pp. 511-519 ◽  
Author(s):  
V. V. NESVIZHEVSKY
Keyword(s):  
Quantum Mechanics ◽  
Gravitational Field ◽  
Energy Range ◽  
Quantum States ◽  
Ultracold Neutrons ◽  
Neutron Spectrometry ◽  
Earth’S Gravitational Field ◽  
Elastic Process

A restrictive constraint for any quasi-elastic process was obtained in the previously inaccessible energy range ΔE~10-12–3·10-10 eV for reflections of ultracold neutrons from surfaces in the experiment on neutron quantum states in the earth's gravitational field. This could be useful for precision neutron spectrometry experiments and for the verification of extensions of quantum mechanics.

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