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Articles 1 - 21 of 21
Full-Text Articles in Physics
The Role Of Friction In The Static Equilibrium Of A Fixed Ladder: Theoretical Analysis And Experimental Test, Mark P. Silverman
The Role Of Friction In The Static Equilibrium Of A Fixed Ladder: Theoretical Analysis And Experimental Test, Mark P. Silverman
Faculty Scholarship
In a recent publication the author derived and experimentally tested several theoretical models, distinguished by different boundary conditions at the contacts with horizontal and vertical supports, that predicted the forces of reaction on a fixed (i.e. inextensible) ladder. This problem is statically indeterminate since there are 4 forces of reaction and only 3 equations of static equilibrium. The model that predicted the empirical reactions correctly used a law of static friction to complement the equations of static equilibrium. The present paper examines in greater theoretical and experimental detail the role of friction in accounting for the forces of reaction on …
Reaction Forces On A Fixed Ladder In Static Equilibrium: Analysis And Definitive Experimental Test Of The Ladder Problem, Mark P. Silverman
Reaction Forces On A Fixed Ladder In Static Equilibrium: Analysis And Definitive Experimental Test Of The Ladder Problem, Mark P. Silverman
Faculty Scholarship
The development of a theoretical model to predict the four equilibrium forces of reaction on a simple ladder of non-adjustable length leaning against a wall has long remained an unresolved matter. The difficulty is that the problem is statically indeterminate and therefore requires complementary information to obtain a unique solution. This paper reports 1) a comprehensive theoretical analysis of the three fundamental models based on treating the ladder as a single Euler-Bernoulli beam, and 2) a detailed experimental investigation of the forces of reaction as a function of applied load and location of load. In contrast to previous untested proposals …
Bending Of A Tapered Rod: Modern Application And Experimental Test Of Elastica Theory, Mark P. Silverman, Joseph Farrah
Bending Of A Tapered Rod: Modern Application And Experimental Test Of Elastica Theory, Mark P. Silverman, Joseph Farrah
Faculty Scholarship
A tapered rod mounted at one end (base) and subject to a normal force at the other end (tip) is a fundamental structure of continuum mechanics that occurs widely at all size scales from radio towers to fishing rods to micro-electromechanical sensors. Although the bending of a uniform rod is well studied and gives rise to mathematical shapes described by elliptic integrals, no exact closed form solution to the nonlinear differential equations of static equilibrium is known for the deflection of a tapered rod. We report in this paper a comprehensive numerical analysis and experimental test of the exact theory …
Analysis Of Residence Time In The Measurement Of Radon Activity By Passive Diffusion In An Open Volume: A Micro-Statistical Approach, Mark P. Silverman
Analysis Of Residence Time In The Measurement Of Radon Activity By Passive Diffusion In An Open Volume: A Micro-Statistical Approach, Mark P. Silverman
Faculty Scholarship
Residence time in a flow measurement of radioactivity is the time spent by a pre-determined quantity of radioactive sample in the flow cell. In a recent report of the measurement of indoor radon by passive diffusion in an open volume (i.e. no flow cell or control volume), the concept of residence time was generalized to apply to measurement conditions with random, rather than directed, flow. The generalization, leading to a quantity r ∆t , involved use of a) a phenomenological alpha-particle range function to calculate the effective detection volume, and b) a phenomenological description of diffusion by Fick’s law to …
Method To Measure Indoor Radon Concentration In An Open Volume With Geiger-Mueller Counters: Analysis From First Principles, Mark P. Silverman
Method To Measure Indoor Radon Concentration In An Open Volume With Geiger-Mueller Counters: Analysis From First Principles, Mark P. Silverman
Faculty Scholarship
A simple method employing a pair of pancake-style Geiger-Mueller (GM) counters for quantitative measurement of radon activity concentration (activity per unit volume) is described and demonstrated. The use of two GM counters, together with the basic theory derived in this paper, permit the detection of alpha particles from decay of 222Rn and progeny ( 218 Po , 214 Po ) and the conversion of the alpha count rate into a radon concentration. A unique feature of this method, in comparison with standard methodologies to measure radon concentration, is the absence of a fixed control volume. Advantages afforded by the reported …
Method To Measure Indoor Radon Concentration In An Open Volume With Geiger-Mueller Counters: Analysis From First Principles, Mark P. Silverman
Method To Measure Indoor Radon Concentration In An Open Volume With Geiger-Mueller Counters: Analysis From First Principles, Mark P. Silverman
Faculty Scholarship
A simple method employing a pair of pancake-style Geiger-Mueller (GM) counters for quantitative measurement of radon activity concentration (activity per unit volume) is described and demonstrated. The use of two GM counters, together with the basic theory derived in this paper, permit the detection of alpha particles from decay of 222Rn and progeny ( 218Po , 214 Po ) and the conversion of the alpha count rate into a radon concentration. A unique feature of this method, in comparison with standard methodologies to measure radon concentration, is the absence of a fixed control volume. Advantages afforded by the reported GM …
Search For Anomalies In The Decay Of Radioactive Mn-54 [Post-Print], Mark P. Silverman
Search For Anomalies In The Decay Of Radioactive Mn-54 [Post-Print], Mark P. Silverman
Faculty Scholarship
Recent papers have reported that 54Mn, which decays by electron capture (a weak nuclear interaction) with half-life ~312 days, is influenced by solar activity. Should this actually occur, new physics would be needed to explain it. This paper reports results of an analysis of 54Mn activity measured over a time interval of ~3.6 half-lives. If standard nuclear physics applies, the logarithmic residuals of 54Mn activities should form a stationary set of independent random variables whose statistics are determined solely by a constant decay rate λ and initial mean count μ. Analysis of the time-variation, autocorrelation, and power spectra of …
Effects Of A Periodic Decay Rate On The Statistics Of Radioactive Decay: New Methods To Search For Violations Of The Law Of Radioactive Change, Mark P. Silverman
Effects Of A Periodic Decay Rate On The Statistics Of Radioactive Decay: New Methods To Search For Violations Of The Law Of Radioactive Change, Mark P. Silverman
Faculty Scholarship
It is a long-held tenet of nuclear physics, from the early work of Rutherford and Soddy up to present times that the disintegration of each species of radioactive nuclide occurs randomly at a constant rate unaffected by interactions with the external environment. During the past 15 years or so, reports have been published of some 10 or more unstable nuclides with non-exponential, periodic decay rates claimed to be of geophysical, astrophysical, or cosmological origin. Deviations from standard exponential decay are weak, and the claims are controversial. This paper examines the effects of a periodic decay rate on the statistical distributions …
Simultaneous Observation Of The Quantization And The Interference Pattern Of A Plasmonic Near-Field, L. Piazza, T. T.A. Lummen, Erik Quinonez, Y. Murooka, B. W. Reed, B. Barwick, F. Carbone
Simultaneous Observation Of The Quantization And The Interference Pattern Of A Plasmonic Near-Field, L. Piazza, T. T.A. Lummen, Erik Quinonez, Y. Murooka, B. W. Reed, B. Barwick, F. Carbone
Faculty Scholarship
Surface plasmon polaritons can confine electromagnetic fields in subwavelength spaces and are of interest for photonics, optical data storage devices and biosensing applications. In analogy to photons, they exhibit wave–particle duality, whose different aspects have recently been observed in separate tailored experiments. Here we demonstrate the ability of ultrafast transmission electron microscopy to simultaneously image both the spatial interference and the quantization of such confined plasmonic fields. Our experiments are accomplished by spatiotemporally overlapping electron and light pulses on a single nanowire suspended on a graphene film. The resulting energy exchange between single electrons and the quanta of the photoinduced …
Statistical Analysis Of Subsurface Diffusion Of Solar Energy With Implications For Urban Heat Stress, Mark P. Silverman
Statistical Analysis Of Subsurface Diffusion Of Solar Energy With Implications For Urban Heat Stress, Mark P. Silverman
Faculty Scholarship
Analysis of hourly underground temperature measurements at a medium-size (by population) US city as a function of depth and extending over 5+ years revealed a positive trend exceeding the rate of regional and global warming by an order of magnitude. Measurements at depths greater than ~2 m are unaffected by daily fluctuations and sense only seasonal variability. A comparable trend also emerged from the surface temperature record of the largest US city (New York). Power spectral analysis of deep and shallow subsurface temperature records showed respectively two kinds of power-law behavior: 1) a quasi-continuum of power amplitudes indicative of Brownian …
Design And Implementation Of A Fs-Resolved Transmission Electron Microscope Based On Thermionic Gun Technology [Post-Print], L. Piazza, D. J. Masiel, T. Lagrange, B. W. Reed, Brett Barwick
Design And Implementation Of A Fs-Resolved Transmission Electron Microscope Based On Thermionic Gun Technology [Post-Print], L. Piazza, D. J. Masiel, T. Lagrange, B. W. Reed, Brett Barwick
Faculty Scholarship
In this paper, the design and implementation of a femtosecond-resolved ultrafast transmission electron microscope is presented, based on a thermionic gun geometry. Utilizing an additional magnetic lens between the electron acceleration and the nominal condenser lens system, a larger percentage of the electrons created at the cathode are delivered to the specimen without degrading temporal, spatial and energy resolution significantly, while at the same time maintaining the femtosecond temporal resolution. Using the photon-induced near field electron microscopy effect (PINEM) on silver nanowires the cross-correlation between the light and electron pulses was measured, showing the impact of the gun settings and …
Femtosecond Photoelectron Point Projection Microscope, Erik Quinonez, Jonathan Handali, Brett Barwick
Femtosecond Photoelectron Point Projection Microscope, Erik Quinonez, Jonathan Handali, Brett Barwick
Faculty Scholarship
By utilizing a nanometer ultrafast electron source in a point projection microscope we demonstrate that images of nanoparticles with spatial resolutions of the order of 100 nanometers can be obtained. The duration of the emission process of the photoemitted electrons used to make images is shown to be of the order of 100 fs using an autocorrelation technique. The compact geometry of this photoelectron point projection microscope does not preclude its use as a simple ultrafast electron microscope, and we use simple analytic models to estimate temporal resolutions that can be expected when using it as a pump-probe ultrafast electron …
Fragmentation Of Explosively Metastable Glass [Post-Print], Mark P. Silverman, Wayne Strange, J. Bower, L. Ikejimba
Fragmentation Of Explosively Metastable Glass [Post-Print], Mark P. Silverman, Wayne Strange, J. Bower, L. Ikejimba
Faculty Scholarship
An unusual form of glass with bulbous head and thin tail, known as Rupert's drops, can withstand high impact or pressure applied to the head, but explodes instantly into small particles when the tail is broken. The mechanism is not well understood. To examine this, we performed macro- and microstatistical analyses of a sample of 500 g of fragments of exploded Rupert's drops to determine the mass and particle distributions and associated fractal dimensions. To our knowledge, this is the first such statistical study of the fragmentation of a metastable material with large internal energy. The resulting fractal dimensionD …
Quantum Stabilization Of General-Relativistic Variable-Density Degenerate Stars, David Cox, Ronald Mallett, Mark P. Silverman
Quantum Stabilization Of General-Relativistic Variable-Density Degenerate Stars, David Cox, Ronald Mallett, Mark P. Silverman
Faculty Scholarship
Research by one of the authors suggested that the critical mass of constant-density neutron stars will be greater than eight solar masses when the majority of their neutrons group into bosons that form a Bose-Einstein condensate, provided the bosons interact with each other and have scattering lengths on the order of a picometer. That analysis was able to use Newtonian theory for the condensate with scattering lengths on this order, but general relativity provides a more fundamental analysis. In this paper, we determine the equilibrium states of a static, spherically-symmetric variable-density mixture of a degenerate gas of noninteracting neutrons and …
Search For Patterns In Sequences Of Single-Photon Polarization Measurements, David Branning, Adam Katcher, Wayne Strange, Mark P. Silverman
Search For Patterns In Sequences Of Single-Photon Polarization Measurements, David Branning, Adam Katcher, Wayne Strange, Mark P. Silverman
Faculty Scholarship
Sequences of random binary numbers created from polarization measurements of single photons were subjected to a comprehensive runs analysis. Photon pairs from a spontaneous parametric downconversion source were detected in coincidence, with one photon acting as a trigger while the other was analyzed for horizontal or vertical polarization. The resulting sequences of polarization measurements were tested for runs of consecutive vertical or horizontal outcomes against a theory of nonoverlapping runs, without numerical unbiasing. The sequences produced no statistically significant discrepancies with the predicted numbers of runs, even with multiphoton events retained.
Note: Scalable Multiphoton Coincidence-Counting Electronics, David Branning, Sarthak Khanal, Young Ho Shin, Brandon A. Clary, Mark Beck
Note: Scalable Multiphoton Coincidence-Counting Electronics, David Branning, Sarthak Khanal, Young Ho Shin, Brandon A. Clary, Mark Beck
Faculty Scholarship
We present a multichannel coincidence-counting module for use in quantum optics experiments. The circuit takes up to four transistor–transistor logic pulse inputs and counts either twofold, threefold, or fourfold coincidences, within a user-selected coincidence-time window as short as 12 ns. The module can accurately count eight sets of multichannel coincidences, for input rates of up to 84 MHz. Due to their low cost and small size, multiple modules can easily be combined to count arbitrary M-order coincidences among N inputs.
Testing Quantum Randomness In Single-Photon Polarization Measurements With The Nist Test Suite, David Branning, Matthew Bermudez
Testing Quantum Randomness In Single-Photon Polarization Measurements With The Nist Test Suite, David Branning, Matthew Bermudez
Faculty Scholarship
A binary sequence was constructed from 1.7×107 polarization measurements of single photons from a spontaneous parametric downconversion source, under pumping conditions similar to those used in optical quantum cryptography. To search for correlations in the polarization measurement outcomes, we subjected the sequence to a suite of tests developed at the National Institute of Standards and Technology (NIST) for the assessment of algorithmic random-number generators. The bias of the sequence was low enough to allow all fifteen tests to be applied directly to the polarization outcomes without using any numerical unbiasing procedures. No statistically significant deviations from randomness were observed, …
Search For Correlated Fluctuations In The B+ Decay Of Na-22, Mark P. Silverman, Wayne Strange
Search For Correlated Fluctuations In The B+ Decay Of Na-22, Mark P. Silverman, Wayne Strange
Faculty Scholarship
Claims for a “cosmogenic” force that correlates otherwise independent stochastic processes have been made for at least 10 years, based on visual inspection of histograms whose shapes were interpreted as suggestive of recurrent patterns. Building on our earlier work to test nuclear alpha, beta, and electron-capture decay processes for non-randomness, we searched for correlations in the time series of e+e- annihilations deriving from the decay of 22Na. Coincident gamma photons were counted within narrow time and energy windows over a period of 167 hours leading to a time series of more than 1 million events. Statistical …
Stress Evolution In Nanocrystalline Diamond Films Produced By Chemical Vapor Deposition, Hao Li, Brian W. Sheldon, Abhishek Kothari, Zhigang Ban, Barbara L. Walden
Stress Evolution In Nanocrystalline Diamond Films Produced By Chemical Vapor Deposition, Hao Li, Brian W. Sheldon, Abhishek Kothari, Zhigang Ban, Barbara L. Walden
Faculty Scholarship
Nanocrystalline diamond films were grown on silicon substrates by microwave plasma enhanced chemical vapor deposition with 1% methane, 2%–10% hydrogen, and argon. High resolution transmission electron microscope images and selected area electron diffraction patterns confirm that the films consist of 10–20 nm sized diamond grains. The residual and intrinsic stresses were investigated using wafer curvature. Intrinsic stresses were always tensile, with higher H2 concentrations generally leading to higher stresses. Annealing the films in a hydrogen plasma significantly increased these stresses. These hydrogen induced changes also appear to alter stress levels and stress gradients during the growth process itself. Raman …
Chemistry-Induced Intrinsic Stress Variations During The Chemical Vapor Deposition Of Polycrystalline Diamond, Ashok Rajamani, Brian W. Sheldon, Sumit Nijhawan, Alan Schwartzman, Janet Rankin, Barbara L. Walden, Laura Riester
Chemistry-Induced Intrinsic Stress Variations During The Chemical Vapor Deposition Of Polycrystalline Diamond, Ashok Rajamani, Brian W. Sheldon, Sumit Nijhawan, Alan Schwartzman, Janet Rankin, Barbara L. Walden, Laura Riester
Faculty Scholarship
Intrinsic tensile stresses in polycrystalline films are often attributed to the coalescence of neighboring grains during the early stages of film growth, where the energy decrease associated with converting two free surfaces into a grain boundary provides the driving force for creating tensile stress. Several recent models have analyzed this energy trade off to establish relationships between the stress and the surface∕interfacial energy driving force, the elastic properties of the film, and the grain size. To investigate these predictions, experiments were conducted with diamond films produced by chemical vapor deposition. A multistep processing procedure was used to produce films with …
Experimental Tests For Randomness Of Quantum Decay Examined As A Markov Process [Post-Print], Mark P. Silverman, Wayne Strange
Experimental Tests For Randomness Of Quantum Decay Examined As A Markov Process [Post-Print], Mark P. Silverman, Wayne Strange
Faculty Scholarship
The number of decays from four distinct nuclear disintegration processes were recorded over a long succession of counting intervals, converted into sequences of binary outcomes based on parity, and examined as a discrete two-state Markov process. The difference in single-step transition probabilities was found to be null to within an uncertainty of order 10−3, supporting the proposition that quantum particles decay at random unaffected by their past history.