Plasma device feed system Patent

Nonconductive tube as feed system for plasma thrusto

Sandblasting nozzle

A nozzle for use with abrasive and/or corrosive materials is formed of sintered ceramic compositions having high temperature oxidation resistance, high hardness and high abrasion and corrosion resistance. The ceramic may be a binary solid solution of a ceramic oxide and silicon nitride, and preferably a ternary solid solution of a ceramic oxide, silicon nitride and aluminum nitride. The ceramic oxide is selected from a group consisting of Al2O3, Y2O3 and Cr2O3, or mixtures of those compounds. Titanium carbide particles are dispersed in the ceramic mixture before sintering. The nozzles are encased for protection from external forces while in use by a metal or plastic casing

Accuracy analysis of the box-counting algorithm

Accuracy of the box-counting algorithm for numerical computation of the fractal exponents is investigated. To this end several sample mathematical fractal sets are analyzed. It is shown that the standard deviation obtained for the fit of the fractal scaling in the log-log plot strongly underestimates the actual error. The real computational error was found to have power scaling with respect to the number of data points in the sample ($n_{tot}$). For fractals embedded in two-dimensional space the error is larger than for those embedded in one-dimensional space. For fractal functions the error is even larger. Obtained formula can give more realistic estimates for the computed generalized fractal exponents' accuracy.Comment: 3 figure

Black Hole Feedback On The First Galaxies

We study how the first galaxies were assembled under feedback from the accretion onto a central black hole (BH) that is left behind by the first generation of metal-free stars through self-consistent, cosmological simulations. X-ray radiation from the accretion of gas onto BH remnants of Population III (Pop III) stars, or from high-mass X-ray binaries (HMXBs), again involving Pop III stars, influences the mode of second generation star formation. We track the evolution of the black hole accretion rate and the associated X-ray feedback starting with the death of the Pop III progenitor star inside a minihalo and following the subsequent evolution of the black hole as the minihalo grows to become an atomically cooling galaxy. We find that X-ray photoionization heating from a stellar-mass BH is able to quench further star formation in the host halo at all times before the halo enters the atomic cooling phase. X-ray radiation from a HMXB, assuming a luminosity close to the Eddington value, exerts an even stronger, and more diverse, feedback on star formation. It photoheats the gas inside the host halo, but also promotes the formation of molecular hydrogen and cooling of gas in the intergalactic medium and in nearby minihalos, leading to a net increase in the number of stars formed at early times. Our simulations further show that the radiative feedback from the first BHs may strongly suppress early BH growth, thus constraining models for the formation of supermassive BHs.Astronom

Young's Moduli of Cold and Vacuum Plasma Sprayed Metallic Coatings

Monolithic metallic copper alloy and NiCrAlY coatings were fabricated by either the cold spray (CS) or the vacuum plasma spray (VPS) deposition processes. Dynamic elastic modulus property measurements were conducted on these monolithic coating specimens between 300 K and 1273 K using the impulse excitation technique. The Young's moduli decreased almost linearly with increasing temperature at all temperatures except in the case of the CS Cu-23%Cr-5%Al and VPS NiCrAlY, where deviations from linearity were observed above a critical temperature. It was observed that the Young's moduli for VPS Cu-8%Cr were larger than literature data compiled for Cu. The addition of 1%Al to Cu- 8%Cr significantly increased its Young's modulus by 12 to 17% presumably due to a solid solution effect. Comparisons of the Young s moduli data between two different measurements on the same CS Cu- 23%Cr-5%Al specimen revealed that the values measured in the first run were about 10% higher than those in the second run. It is suggested that this observation is due to annealing of the initial cold work microstructure resulting form the cold spray deposition process

Methodology for assessment of cognitive skills in virtual environments

The client briefing of the proposed building design is usually in the form of drawingsand artistic impressions being presented to the client. However, very few clients areable to read a technical drawing and the artist impressions are limited and do not aidthe client to visualise all aspects of the proposed building. During the client briefingprocess the client needs to have the experiential quality described, to be able to fullyunderstand the design of the proposed building. Generally, humans perceive anddirectly experience architectural space by building qualities like texture, form, colour,light, scale, movement. A full-scale model of the proposed building would fullyafford the experimental qualities. In reality it would be impractical and not costeffective. However, VR technology allows the creation of an inclusion of space inuser's mind, through a minimum of means, but achieves a maximum impact, andaffords all the experiential qualities offered by a physical model.A virtual model with a high degree of detail which can be explored by the designerand his clients will therefore be of significant help. However, to give clients the bestpossible impression of the proposed design it is important to understand howdimensions of those designed spaces are perceived. Therefore, a study was carried outfocusing on fundamental investigations into the perception of basic architecturaldimensions in order to assess the potential usefulness of VR technology inarchitecture and the client briefing process. In two experiments, subjects were required to estimate egocentric and exocentricdimensions in Virtual Environments and Real World Setting (RWS). The influence ofstimuli orientation was also investigated. In estimating all dimensions a magnitudeestimation procedure was employed using a modified free-modulus technique. Allparticipants were pre-tested. Psychometric and visual tests were used for choosing anexperimental group with a fair degree of homogenity. Two independent subject groupswere used. In addition to dimension estimations recall of simple layout and feeling ofspace were investigated when evaluating the virtual interface.The general null hypothesis assumed that people perceive space in VE as well as inthe real world. It has been shown that the results are statistically significant andtherefore one was able to reject the general hypothesis. Overall participantsunderestimated the dimensions in both experiments by approximately 20%. Resultsand limitations of the study are discussed. The results of the experiments wouldindicate that VR technology can be used for simulations of architectural spacesbecause despite underestimations of dimensions it still performed relatively well ifone compares it with results of experiments in the Real World Settings

Resolving the high redshift Lyman-alpha forest in smoothed particle hydrodynamics simulations

We use a large set of cosmological smoothed particle hydrodynamics (SPH) simulations to examine the effect of mass resolution and box size on synthetic Lya forest spectra at 2 \leq z \leq 5. The mass resolution requirements for the convergence of the mean Lya flux and flux power spectrum at z=5 are significantly stricter than at lower redshift. This is because transmission in the high redshift Lya forest is primarily due to underdense regions in the intergalactic medium (IGM), and these are less well resolved compared to the moderately overdense regions which dominate the Lya forest opacity at z~2-3. We further find that the gas density distribution in our simulations differs significantly from previous results in the literature at large overdensities (\Delta>10). We conclude that studies of the Lya forest at z=5 using SPH simulations require a gas particle mass of M_gas \leq 2x10^5 M_sol/h, which is >8 times the value required at z=2. A box size of at least 40 Mpc/h is preferable at all redshifts.Comment: 5 pages, 5 figures, 2 tables, accepted by MNRA

Proposing Thematic Mapping for Integrated Risk Communication: A study of British & Japanese perspectives in flood-prone communities

Modern flood risk communication continues to lack the input of different stakeholder levels and as a result, there has been an insufficiency to construct communication that is inclusive of all stakeholders. There is also still an absence of consideration of context-specific information that helps to shape the communication crafting process. This study sought to establish the above through the creation of a thematic map (a visual display based on themes), merging top-down and bottom-up approaches to create a clearer picture of important factors for risk communication within the specific contexts being observed. The research team conducted 16 semi-structured interviews and focus groups with 4 different types of stakeholders at 2 rural sites in the UK and 2 rural sites in Japan. The results outlined five key themes that underpin integrated risk communication, establishing the thematic map – Individual Circumstances, Community Structure, Impact Scale, Response Capacity, and Social Barriers. These findings are important in beginning to help conceptualise how current DRR efforts can be enhanced and in presenting an integrated approach to risk communication that helps to reduce unnecessary complexity and inaccessibility. However, further replications of the study are needed at other sites across the world to test the robustness and adaptability of this kind of modelling