Total axle load effects on soil compaction

Theoretical and applied research has shown that the pressure at a point in the subsurface soil is a function of both the surface unit pressure and the extent of the area over which it is applied (total load). Thirty years ago, most of the soil compaction from vehicle traffic was in the plow layer and was removed by normal cultural practices. As equipment has increased in size and mass, machine designers have increased tire sizes to keep the soil surface unit pressure relatively constant. However, the increase in total axle loads is believed to have caused an increase in compaction at any given depth in the soil profile, resulting in significant compaction in the subsoil.Two tires of different sizes, a standard agricultural tire and a flotation tire were used to support equal loads. Soil pressures were measured at three depths in the soil profile directly beneath each of the tires. Two soils were used and each was prepared first in a uniform density profile, and then they were prepared with a simulated traffic pan (layer of higher density) at a depth of approximately 30 cm.Results showed that the presence of a traffic pan in the soil profile caused higher soil pressures above the pan and lower pressures below it than was the case for a uniform soil profile. The soil contact surface of the flotation tire was approximately 22% greater than the agricultural tire. The greater contact surface did reduce soil pressures at the soil surface, of course, but the total axle load was still the dominant factor in the 18–50 cm-depth range used in this study.     

Speeding up the FMMR perfect sampling algorithm: A case study revisited

In a previous paper by the second author, two Markov chain Monte Carlo perfect sampling algorithms—one called coupling from the past (CFTP) and the other (FMMR) based on rejection sampling—are compared using as a case study the move‐to‐front (MTF) self‐organizing list chain. Here we revisit that case study and, in particular, exploit the dependence of FMMR on the user‐chosen initial state. We give a stochastic monotonicity result for the running time of FMMR applied to MTF and thus identify the initial state that gives the stochastically smallest running time; by contrast, the initial state used in the previous study gives the stochastically largest running time. By changing from worst choice to best choice of initial state we achieve remarkable speedup of FMMR for MTF; for example, we reduce the running time (as measured in Markov chain steps) from exponential in the length n of the list nearly down to n when the items in the list are requested according to a geometric distribution. For this same example, the running time for CFTP grows exponentially in n. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 2003     

A terahertz polarization insensitive dual band metamaterial absorber

Metamaterial absorbers have attracted considerable attention for applications in the terahertz range. In this Letter, we report the design, fabrication, and characterization of a terahertz dual band metamaterial absorber that shows two distinct absorption peaks with high absorption. By manipulating the periodic patterned structures as well as the dielectric layer thickness of the metal-dielectric-metal structure, significantly high absorption can be obtained at specific resonance frequencies. Finite-difference time-domain modeling is used to design the structure of the absorber. The fabricated devices have been characterized using a Fourier transform IR spectrometer. The experimental results show two distinct absorption peaks at 2.7 and 5.2?THz, which are in good agreement with the simulation. The absorption magnitudes at 2.7 and 5.2?THz are 0.68 and 0.74, respectively.     

Nanosatellites for quantum science and technology

Bringing quantum science and technology to the space frontier offers exciting prospects for both fundamental physics and applications such as long-range secure communication and space-borne quantum probes for inertial sensing with enhanced accuracy and sensitivity. But despite important terrestrial pathfinding precursors on common microgravity platforms and promising proposals to exploit the significant advantages of space quantum missions, large-scale quantum test beds in space are yet to be realised due to the high costs and lead times of traditional ‘Big Space’ satellite development. But the ‘small space’ revolution, spearheaded by the rise of nanosatellites such as CubeSats, is an opportunity to greatly accelerate the progress of quantum space missions by providing easy and affordable access to space and encouraging agile development. We review space quantum science and technology, CubeSats and their rapidly developing capabilities and how they can be used to advance quantum satellite systems.     

Is every approximate trajectory of some process near an exact trajectory of a nearby process?

This paper deals with the problem “Can a noisy orbit be tracked by a real orbit?” In particular, we will study the one-parameter family of tent maps and the one-parameter family of quadratic maps. We writeg _μ for eitherf _μ orF _μ withf _μ (x)=μx forx≦1/2 andf _μ (x)=μ(1?x) forx≧1/2, andF _μ (x)=μx(1?x). For a given μ we will say:g _μ permits increased parameter shadowing if for each δ _x >0 there exists someδ _μ >0 and some δ _f >0 such that every δ _f -pseudog _μ -orbit starting in some invariant interval can be δ _x -shadowed by a realg _α -orbit with α=μ+δ _μ . We show thatg _μ typically permits increased parameter shadowing.     

The work function of hydrothermally synthesized UO2 and the implications for semiconductor device fabrication

The photoelectric work function of nearly stoichiometric (111) and (100) hydrothermally grown UO₂ was measured to be 6.28 ± 0.36 eV and 5.80 ± 0.36 eV, respectively. Candidate metals for electrical contacts are identified for both rectifying and non‐rectifying contacts based on work function, lattice compatibility, and electrical conductivity.     

Manganese(III)-Catalysed Oxidation of Sulphides with Sodium Chlorite in an Aprotic Solvent in the Presence of Alumina

A wide variety of sulphides can be readily converted to the corresponding sulphoxides in good to excellent yields by treatment with a combination of sodium chlorite, (salen)manganese(III) complex, and chromatographic alumina in dichloromethane under mild and neutral conditions.     

Intracavity laser absorption spectroscopy of platinum sulfide in the near infrared

A new electronic transition of PtS with a red degraded band head at 12 460 cm⁻¹ was recorded and analyzed. Gas phase PtS was produced in a platinum-lined hollow cathode with a trace of SF₆ gas, and the spectrum was recorded at near Doppler resolution using intracavity laser absorption spectroscopy. Molecular constants for the newly identified excited state are presented.