Pressure transducer 3/8-inch in size can be faired into surface

To measure fluid pressure with minimum disturbance to fluid flow, a miniature pressure transducer can be imbedded and faired into the test surface. Incorporated in the design are piezoresistive elements mounted on a diaphragm, which transform pressure strains into an electrical signal

Fast High Resolution Echelle Spectroscopy Of A Laboratory Plasma

An echelle diffraction grating and a multianode photomultiplier tube are paired to construct a high resolution (R=lambda/delta lambda approximate to 2.5x10(4)) spectrograph with fast time response for use from the UV through the visible. This instrument has analyzed the line shape of C III impurity ion emission at 229.687 nm over the lifetime (approximate to 100 mu s) of the hydrogen plasmas produced at SSX. The ion temperature and line of sight average velocity are inferred from the observed thermal broadening and Doppler shift of the line. The time resolution of these measurements is about 1 mu s, sufficient to observe the fastest magnetohydrodynamic activity

Sintering of titanium with yttrium oxide additions for the scavenging of chlorine impurities

Chloride impurities in titanium powders are extremely difficult to remove and present a long-standing problem in titanium powder metallurgy. We show that the detrimental effects of chlorides on the sintering of titanium can be mitigated with trace additions of yttrium oxide, which has a high affinity for the normally volatile species and forms highly stable oxychloride reaction products. Compacts that would otherwise exhibit gross swelling and excessive porosity due to chloride impurities can be now sintered to near full density by liquid phase sintering. The potency of yttrium oxide additions is observable at levels as low as 500 ppm. The scavenging of chlorine by YO appears to be independent of alloy composition and sintering regime. It is effective when used with high-chloride powders such as Kroll sponge fines but ineffective when used with powders containing NaCl impurities or during solid-state sintering. The identification of highly potent chlorine scavengers may enable the future development of chloride-tolerant powder metallurgy (PM) alloys aimed at utilizing low-cost, high-chloride powder feedstocks

High-resolution surface plasmon imaging of gold nanoparticles by energy-filtered transmission electron microscopy

We demonstrate the imaging capabilities of energy-filtered transmission electron microscopy at high-energy resolution in the low-energy-loss region, reporting the direct image of a surface plasmon of an elongated gold nanoparticle at energies around 1 eV. Using complimentary model calculations performed within the boundary element method approach we can assign the observed results to the plasmon eigenmodes of the metallic nanoparticle

Three-Dimensional Magnetohydrodynamics Simulations Of Counter-Helicity Spheromak Merging In The Swarthmore Spheromak Experiment

Recent counter-helicity spheromak merging experiments in the Swarthmore Spheromak Experiment (SSX) have produced a novel compact torus (CT) with unusual features. These include a persistent antisymmetric toroidal magnetic field profile and a slow, nonlinear emergence of the n = 1 tilt mode. Experimental measurements are inconclusive as to whether this unique CT is a fully merged field-reversed configuration (FRC) with strong toroidal field or a partially merged doublet CT configuration with both spheromak- and FRC-like characteristics. In this paper, the SSX merging process is studied in detail using three-dimensional resistive MHD simulations from the Hybrid Magnetohydrodynamics (HYM) code. These simulations show that merging plasmas in the SSX parameter regime only partially reconnect, leaving behind a doublet CT rather than an FRC. Through direct comparisons, we show that the magnetic structure in the simulations is highly consistent with the SSX experimental observations. We also find that the n = 1 tilt mode begins as a fast growing linear mode that evolves into a slower-growing nonlinear mode before being detected experimentally. A simulation parameter scan over resistivity, viscosity, and line-tying shows that these parameters can strongly affect the behavior of both the merging process and the tilt mode. In fact, merging in certain parameter regimes is found to produce a toroidal-field-free FRC rather than a doublet CT. (C) 2011 American Institute of Physics. [doi:10.1063/1.3660533

Band structure analysis of the conduction-band mass anisotropy in 6H and 4H SiC

The band structures of 6H and 4H SiC calculated by means of the FP-LMTO method are used to determine the effective mass tensors for their conduction-band minima. The results are shown to be consistent with recent optically detected cyclotron resonance measurements and predict an unusual band filling dependence for 6H-SiC.Comment: 5 pages including 4 postscript figures incorporated with epsfig figs. available as part 2: sicfig.uu self-extracting file to appear in Phys. Rev. B: Aug. 15 (Rapid Communications

Degree of explanation

Partial explanations are everywhere. That is, explanations citing causes that explain some but not all of an effect are ubiquitous across science, and these in turn rely on the notion of degree of explanation. I argue that current accounts are seriously deficient. In particular, they do not incorporate adequately the way in which a cause’s explanatory importance varies with choice of explanandum. Using influential recent contrastive theories, I develop quantitative definitions that remedy this lacuna, and relate it to existing measures of degree of causation. Among other things, this reveals the precise role here of chance, as well as bearing on the relation between causal explanation and causation itself

Why Compact Tori For Fusion?

A compact torus (CT) has a toroidal magnetic and plasma geometry, but is contained within a simply-connected vacuum vessel such as a cylinder. Spheromaks and field-reversed configurations fall into this category. Compact tori are translatable and have a high engineering beta. The primary benefit of CTs for fusion is the absence of toroidal field and Ohmic Heating coils and the many problems brought on by them. Studying fusion-relevant plasma in simply-connected geometries affords the world fusion program both physics and technology opportunities not found in other configurations. This paper outlines the technology and physics opportunities of compact tori, and presents a cost model based on geometry for comparison with less compact configurations

SQG-Differential Evolution for difficult optimization problems under a tight function evaluation budget

In the context of industrial engineering, it is important to integrate efficient computational optimization methods in the product development process. Some of the most challenging simulation-based engineering design optimization problems are characterized by: a large number of design variables, the absence of analytical gradients, highly non-linear objectives and a limited function evaluation budget. Although a huge variety of different optimization algorithms is available, the development and selection of efficient algorithms for problems with these industrial relevant characteristics, remains a challenge. In this communication, a hybrid variant of Differential Evolution (DE) is introduced which combines aspects of Stochastic Quasi-Gradient (SQG) methods within the framework of DE, in order to improve optimization efficiency on problems with the previously mentioned characteristics. The performance of the resulting derivative-free algorithm is compared with other state-of-the-art DE variants on 25 commonly used benchmark functions, under tight function evaluation budget constraints of 1000 evaluations. The experimental results indicate that the new algorithm performs excellent on the 'difficult' (high dimensional, multi-modal, inseparable) test functions. The operations used in the proposed mutation scheme, are computationally inexpensive, and can be easily implemented in existing differential evolution variants or other population-based optimization algorithms by a few lines of program code as an non-invasive optional setting. Besides the applicability of the presented algorithm by itself, the described concepts can serve as a useful and interesting addition to the algorithmic operators in the frameworks of heuristics and evolutionary optimization and computing