Numerical simulations of multiple scattering of the f−f-mode by flux tubes

We use numerial simulations to study the absorption and phase shift of surface-gravity waves caused by groups of magnetic flux tubes. The dependence of the scattering coefficients with the distance between the tubes and their positions is analyzed for several cases with two or three flux tubes embedded in a quiet Sun atmosphere. The results are compared with those obtained neglecting completely or partially multiple scattering effects. We show that multiple scattering has a significant impact on the absorption measurements and tends to reduce the phase shift. We also consider more general cases of ensembles of randomly distributed flux tubes, and we have evaluated the effects on the scattering measurements of changing the number of tubes included in the bundle and the average distance between flux tubes. We find that for the longest wavelength incoming waves multiple scattering enhances the absorption, and its efficiency increases with the number of flux tubes and the reduction of the distance between them.Comment: Accepted for publication in The Astrophysical Journa

Evaluation of the capability of local helioseismology to discern between monolithic and spaghetti sunspot models

The helioseismic properties of the wave scattering generated by monolithic and spaghetti sunspots are analyzed by means of numerical simulations. In these computations, an incident f or p1 mode travels through the sunspot model, which produces absorption and phase shift of the waves. The scattering is studied by inspecting the wavefield, computing travel-time shifts, and performing Fourier-Hankel analysis. The comparison between the results obtained for both sunspot models reveals that the differences in the absorption coefficient can be detected above noise level. The spaghetti model produces an steep increase of the phase shift with the degree of the mode at short wavelengths, while mode-mixing is more efficient for the monolithic model. These results provide a clue for what to look for in solar observations to discern the constitution of sunspots between the proposed monolithic and spaghetti models.Comment: Accepted for publication in The Astrophysical Journa

The Viability of Distinguishing Between Mandatory and Permissive Subjects of Bargaining in a Cooperative Setting: In Search of Industrial Peace

In July 1985 General Motors entered into an agreement with the United Auto Workers (UAW) setting forth the terms and conditions of a future automobile facility, known as the Saturn Corporation, in Spring Hill, Tennessee. General Motors and the UAW view this project as an unprecedented achievement in union-management partnership. The goal of the Saturn project is to maintain General Motors\u27viability as a domestic enterprise through an agreement to build a new subcompact car in the United States. This partnership between the corporation and the UAW will include employee participation and enhanced job security. Faced with mounting competition from overseas and with uncertain prospects in the United States, General Motors agreed to restructure the workplace in exchange for economic concessions from its employees.\u27 In accordance with a long and productive collective bargaining relationship, General Motors purposefully re-quested the UAW\u27s input and suggestions in the corporation\u27s economic decision to relocate its subcompact facility in Tennessee

Helioseismic holography of simulated sunspots: magnetic and thermal contributions to travel times

Wave propagation through sunspots involves conversion between waves of acoustic and magnetic character. In addition, the thermal structure of sunspots is very different than that of the quiet Sun. As a consequence, the interpretation of local helioseismic measurements of sunspots has long been a challenge. With the aim of understanding these measurements, we carry out numerical simulations of wave propagation through sunspots. Helioseismic holography measurements made from the resulting simulated wavefields show qualitative agreement with observations of real sunspots. We use additional numerical experiments to determine, separately, the influence of the thermal structure of the sunspot and the direct effect of the sunspot magnetic field. We use the ray approximation to show that the travel-time shifts in the thermal (non-magnetic) sunspot model are primarily produced by changes in the wave path due to the Wilson depression rather than variations in the wave speed. This shows that inversions for the subsurface structure of sunspots must account for local changes in the density. In some ranges of horizontal phase speed and frequency there is agreement (within the noise level in the simulations) between the travel times measured in the full magnetic sunspot model and the thermal model. If this conclusion proves to be robust for a wide range of models, it would suggest a path towards inversions for sunspot structure.Comment: Accepted for publication in The Astrophysical Journa

A study of beryllium and beryllium-lithium complexes in single crystal silicon

When beryllium is thermally diffused into silicon, it gives rise to acceptor levels 191 MeV and 145 meV above the valence band. Quenching and annealing studies indicate that the 145-MeV level is due to a more complex beryllium configuration than the 191-MeV level. When lithium is thermally diffused into a beryllium-doped silicon sample, it produces two acceptor levels at 106 MeV and 81 MeV. Quenching and annealing studies indicate that these levels are due to lithium forming a complex with the defects responsible for the 191-MeV and 145-MeV beryllium levels, respectively. Electrical measurements imply that the lithium impurity ions are physically close to the beryllium impurity atoms. The ground state of the 106-MeV beryllium level is split into two levels, presumably by internal strains. Tentative models are proposed

Collective Fluorescence Enhancement In Nanoparticle Clusters

Many nanoscale systems are known to emit light intermittently under continuous illumination. In the fluorescence of single semiconductor nanoparticles, the distributions of bright and dark periods (\u27on\u27 and \u27off\u27 times) follow Levy statistics. Although fluorescence from single-quantum dots and from macroscopic quantum dot ensembles has been studied, there has been little study of fluorescence from small ensembles. Here we show that blinking nanorods (NRs) interact with each other in a cluster, and the interactions affect the blinking statistics. The on-times in the fluorescence of a NR cluster increase dramatically; in a cluster with N NRs, the maximum on-time increases by a factor of N or more compared with the combined signal from N well-separated NRs. Our study emphasizes the use of statistical properties in identifying the collective dynamics. The scaling of this interaction-induced increase of on-times with number of NRs reveals a novel collective effect at the nanoscale

Aerodynamic test results of bicycle helmets in different configurations: Towards a responsive design

© IMechE 2019. Within the sport of cycling, aerodynamic efficiency is a fundamental criterion for equipment such as bicycle frames, wheels, clothing and helmets. Emerging technologies continually challenge the rules governing the sport as designers, engineers, sports scientists and athletes attempt to gain the edge on their competition. This study compares three-dimensional (3D) printed bicycle helmet prototypes with three commercially available helmets via aerodynamic testing in a wind tunnel. One 3D printed helmet featured a mechanical mechanism allowing two states of ventilation closure to be examined for aerodynamic efficiency, while the other featured electronically adjustable ventilation openings tested at five different states of ventilation closure. Data were collected using an anthropometrically accurate mannequin sitting atop a bicycle in a road-cycling position. The results found that the mechanically controlled prototype offered a 4.1% increase in overall drag experienced by the mannequin with ventilation in the open position compared to the closed position. The electronic prototype showed an increase in drag as ventilation openings increased through the five states, with an overall difference in drag of 3.7% between closed and the maximum opening. These experimental findings indicate that the responsive helmet prototypes can significantly affect the drag force on a cyclist between their closed and open positions and, when understood as being adaptable using sensors and automated controls, may provide new opportunities to modify athlete performance throughout varying stages of training and competition

I\u27m Only Sixteen

I\u27m only sixteen, \u27tis a nice little age,I would not be younger or older,Already I\u27ve conn\u27d over Love\u27s mystic page,And warm\u27d when I should have grown colder.I would like to be married,But wedlock, they say, Has troubles which I\u27ve never seen,So, I\u27d rather not barter my freedom away,For I\u27ve only just enter\u27d sixteen. I hate an old maid yet I don\u27t wish to wedUntil I have jilted my dozens;And the beaux who had been by my glances misled,I\u27d give to my young country cousins. Make hay while the sun shines, so wisely they say,Mine\u27s bright, and my pasture is green;I\u27ll think of November though blooming in May,For I\u27ve only just enterd sixteen. I\u27ve done with young fops they are playthings at best,And please while around you they flutter;The schoolgirls are getting to be quite a pest,And I warmly detest bread and butter.I can smile on a man if he\u27s not quite too old,Has whiskers is noble in mien;And i would not object to the music of gold,For I\u27ve only just enter\u27d sixteen

Universal and Excavatable Controlled Low Strength Material Using High Loss on Ignition Fly Ash and Limestone Screenings†

Limestone screenings and high loss on ignition (LOI) fly ash are by-products that are stockpiling because of their unintentional production and the negative effects when utilized in portland cement concretes. The research objective was to investigate whether these by-products could produce controlled low strength materials (CLSMs) meeting the three types of Tennessee Department of Transportation (TDOT) 204.06 flowable fill specifications. TDOT defines these CLSMs as the following: general use, excavatable, and early strength. Each type is required to have an inverted slump flow of not less than 15 inches (38.1 cm) while meeting ASTM International D6024 at 24 hours. Because of trench unavailability, a 10-psi minimum compressive strength requirement was substituted for the ASTM D6024 ball drop. Early strength flowable fills must meet ASTM D6024 at 6 hours and provide a 30-psi minimum compressive strength at 24 hours. Excavatable flowable fills (EFFs) must also provide a 30-psi minimum at 28 days and a 140-psi maximum at 98 days. A universal flowable fill was produced without portland cement (PC), but by using an 11.1% LOI fly ash, class C fly ash, and limestone screenings. The EFF was produced using 92% high LOI fly ash and 7% PC by weight of the cementing materials. The results indicated that high LOI fly ash and limestone screenings can be combined to produce an excavatable CLSM satisfying TDOT CLSM requirements, and an universal CLSM can be produced that satisfies the requirements for general use, excavatable, and early strength TDOT CLSMs