A comparison of analytical results for 20 K LOX/hydrogen instabilities

Test data from NASA Lewis' Effect of Thrust Per Element on Combustion Stability Characteristics of Hydrogen-Oxygen Rocket Engines test program are used to validate two recently released stability analysis tools. The first tool is a design methodology called ROCCID (ROCket Combustor Interactive Design). ROCCID is an interactive design and analysis methodology that uses existing performance and combustion stability analysis codes. The second tool is HICCIP (High frequency Injection Coupled Combustion Instability Program). HICCIP is a recently developed combustion stability analysis model. Using a matrix of models, results from analytic comparisons with 20 K LOX/H2 experimental data are presented

In-Plane Magnetolumnescence of Modulation-Doped GaAs/AlGaAs Coupled Double Quantum Wells

In-plane magnetic field photoluminescence spectra from a series of GaAs/AlGaAs coupled double quantum wells show distinctive doublet structures related to the symmetric and antisymmetric states. The magnetic field behavior of the upper transition from the antisymmetric state strongly depends on sample mobility. In lower mobility samples, the transition energy shows an $\cal N$-type kink with fields (namely a maximum followed by a minimum), whereas higher mobility samples have a linear dependence. The former is due to a homogeneous broadening of electron and hole states and the results are in good agreement with theoretical calculations.Comment: 3 pages, 4 figures, submitted to Appl. Phys. Let

A Method to Measure the Beta-Beating in a 90 Degrees Phase Advance Lattice

A method to compute the beta-beating in an accelerator, using as input the measurement of the phase advance of a betatron oscillation between three BPMs (beam position monitors), had been developed in the past. The beauty of this method is that the result does not depend on the BPM relative errors on the measurement of the oscillation amplitude. Unfortunately, this method is not applicable when the phase advance between two of the three BPMs is (close to) 180 degrees. In this latter case the measurement of the amplitude of the beam oscillation should be combined with the phase advance measurement to get a complete picture of the beta-beating. Detecting and filtering BPMs with large gain errors requires some care. A method dealing with these aspects has been developed. Examples obtained by applying the method to real data from LEP and SPS are shown

Multiturn Measurements at the CERN SPS

The CERN SPS multiturn facility, based on the new beam orbit measurement system MOPOS, enables the User to acquire the position of the beam at each beam position monitor (BPM) over a number of consecutive turns. When the multiturn acquisition is synchronised with a perturbation imposed on the beam (for instance a fast kick), useful information about the optics of the SPS and the dynamic behaviour of the beam can be extracted from the data. A measurement of the amplitude and phase of the betatron oscillation at each BPM can be used to compare the theoretical optics functions with the real ones, and possibly to detect localised errors. Differences between two such measurements can be used to study the dependence on a variable parameter (e.g. beam intensity, beam energy, etc) and therefore indirectly measure quantities, like the impedance, distributed along the ring. Finally, due to 90 degrees phase advance lattice, plotting the positions measured at two consecutive BPMs against each other gives information about the behaviour of the beam in the transverse phase space. Results of measurements performed at the CERN SPS are presente

Giant supercurrent states in a superconductor-InAs/GaSb-superconductor junction

Superconductivity in topological materials has attracted a great deal of interest in both electron physics and material sciences since the theoretical predictions that Majorana fermions can be realized in topological superconductors [1-4]. Topological superconductivity could be realized in a type II, band-inverted, InAs/GaSb quantum well if it is in proximity to a conventional superconductor. Here we report observations of the proximity effect induced giant supercurrent states in an InAs/GaSb bilayer system that is sandwiched between two superconducting tantalum electrodes to form a superconductor-InAs/GaSb-superconductor junction. Electron transport results show that the supercurrent states can be preserved in a surprisingly large temperature-magnetic field (T-H) parameter space. In addition, the evolution of differential resistance in T and H reveals an interesting superconducting gap structure

Proton extraction from a high-energy beam with bent crystals

Extraction with a bent crystal seems to be the only feasible option for providing the possibility for a fixed-target facility at future high-energy hadron colliders such as the LHC. If the extraction set-up is carefully designed and integrated with the beam cleaning system, a crystal could be used in a parasitic mode, i.e. without disturbing the collider experiments and using only particles that would be lost otherwise. Crystal assisted extraction has been studied at the CERN SPS. Different crystal designs and beam excitation methods have been used. Extraction efficiencies above 15% have been measured. The existence and importance of multi-pass extraction has been demonstrated with a crystal that does not allow single-pass extraction. The energy dependence of crystal extraction has been measured at three beam energies, and found to be in very good agreement with expectations. It has also been shown that the procedure for setting up extraction with a crystal is fast and easy, and that the extracted beam is very stable. During the measurements at the SPS, significant progress has been made in the understanding of the extraction process

Influence of Sowing, Nitrogen Nutrition and Weather Conditions on Stand Structure and Yield of Spring Barley

The processes of stand structure and yield formation of spring barley were studied under different weather conditions and crop management. The multifactorial small-plot trials focused on the combined effect of variety, sowing density and nitrogen nutrition were carried out in two years with contrast weather conditions for yield formation (2011 and 2013). Evaluation of the above-ground biomass and the segmentation of tillers into three groups was conducted in four growth stages (BBCH 25, 31, 39 and 75). The performed analyses confirmed that for effective use of inputs and high yield, it is important to create a sufficient number of strong tillers at the beginning of vegetation. In year with low proportion of strong tillers at the end of tillering (2013), the differentiation of tillers is delayed and their productivity decreases. In this year therefore, yield formation is shifted from the number of spikes to the number of grains in a spike. The comparison of barley genotypes revealed that high yield plasticity can be obtained especially in the variety Bojos, which is able to compensate effectively the changes in spike number by increased grain number in a spike. This variety is also able to create a high proportion of strong tillers even under unfavourable conditions. This knowledge could help to improve the breeding and management strategy in spring barley for the expected weather conditions in the near future, especially higher temperatures in early spring

Why lose weight? Reasons for seeking weight loss by overweight but otherwise healthy men

OBJECTIVE: To identify the reasons for seeking weight loss in overweight or obese but otherwise healthy men. DESIGN: Interviews, prior to intervention, with subjects who had volunteered to participate in a work-site-based weight loss study. SUBJECTS: Ninety-one overweight=obese male workers. Mean age 41, range 18 – 55 y, mean body mass index (BMI) 31.0, range 26.2 – 41.6 kg=m2. MEASUREMENTS: Anthropometric measurements; body weight and height. Body mass index calculated. A short interview using open questions to determine the individuals reason for seeking weight loss. RESULTS: The message that weight loss is beneficial to health for the overweight was recognized by all subjects regardless of BMI, and was reported as the main factor for attempting weight loss. Improved fitness and effects on appearance and well-being were reported half as often as the primary reason for weight loss. CONCLUSION: Overweight lay members of the public have accepted the health education message that weight loss can improve health. Overweight but otherwise healthy men who responded, of their own accord, to an electronic mail message offering help to lose weight did not regard obesity and overweight as primarily a cosmetic issue. This is still, however, important, especially to younger people