Communication Satellite Output Devices

Solid state and vacuum tube output devices for communication satellite

Elemental surface analysis at ambient pressure by electron-induced x-ray fluorescence

The development of a portable surface elemental analysis tool, based on the excitation of characteristic x rays from samples at ambient pressure with a focused electron beam is described. This instrument relies on the use of a thin electron transmissive membrane to isolate the vacuum of the electron source from the ambient atmosphere. The major attributes of this instrument include rapid (several minutes) spectrum acquisition, nondestructive evaluation of elemental composition, no sample preparation, and high-to-medium (several hundreds µm) spatial resolution. The instrument proof-of-principle has been demonstrated in a laboratory setup by obtaining energy dispersive x-ray spectra from metal and mineral samples

Evolution of cracks in selvedge of the coal bed during its stationary working

Purpose. To study rupturing of the coal/rock seam selvedge by natural gas-filled cracks as phenomena that prepare and initiate sudden outbursts of coal, rock, and gas during the steady movement of the face. Methods. The work is based on theoretical studies, including methods of thermodynamics, statistical physics, and asymptotic analysis. Findings. A generalized Griffith’s criterion for the material rupture by a crack is applied to the selvedge part of a gas-saturated coal/rock seam during its stationary unloading. Originality. The kinetic theory describing processes of gas-containing materials destruction is developed using the example of rupturing the selvedge part of a coal/rock seam by natural gas-filled cracks. Practical implications. The criterion for changing the control parameters (reservoir gas pressure, crack dimensions, rock pressure, surface coal/rock energy, elastic modulus) is found at which spontaneous failure of the seam becomes possible. This allows to discuss the possibility of predicting sudden outbursts of coal, rock and gas.Цель. Исследование процессов разрыва краевой части угольного/породного пласта природными газонаполненными трещинами как явлений, подготавливающих и инициирующих внезапные выбросы угля, породы и газа при стационарном подвигании забоя. Методика. Работа выполнена на основе теоретических исследований, включающих методы термодинамики, статистической физики, асимптотического анализа. Результаты. Получен обобщенный критерий Гриффитса разрыва материала трещиной применительно к краевой части газонасыщенного угольного/породного пласта при его стационарной разгрузке. Научная новизна. Развита кинетическая теория процессов разрушения газосодержащих материалов на примере разрыва краевой части угольного/породного пласта природными газонаполненными трещинами. Практическая значимость. Найден критерий изменения управляющих параметров (пластового давления газа, размеров трещин, горного давления, поверхностной энергии угля/породы, модуля упругости), при котором спонтанное разрушение пласта становится возможным. Это позволяет обсуждать возможность прогноза внезапных выбросов угля, породы и газа.Мета. Дослідження процесів розриву крайової частини вугільного/породного пласта природними газонаповненими тріщинами як явищ, що підготовлюють та ініціюють раптові викиди вугілля, породи й газу при стаціонарному посуванні вибою. Методика. Робота виконана на основі теоретичних досліджень, що включають методи термодинаміки, статистичної фізики, асимптотичного аналізу. Результати. Отримано узагальнений критерій Гріффітса розриву матеріалу тріщиною стосовно крайової частини газонасиченого вугільного/породного пласта при його стаціонарному розвантаженні. Наукова новизна. Розвинено кінетичну теорію процесів руйнування матеріалів, що містять газ, на прикладі розриву крайової частини вугільного/породного пласта природними газонаповненими тріщинами. Практична значимість. Знайдено критерій зміни керуючих параметрів (пластового тиску газу, розмірів тріщин, гірського тиску, поверхневої енергії вугілля/породи, модуля пружності), при якому спонтанне руйнування пласта стає можливим. Це дозволяє обговорювати можливість прогнозу раптових викидів вугілля, породи і газу.Работа выполнена в рамках научно-исследовательс-кой темы НАН Украины “Массо-, теплоперенос и физика предвыбросных явлений в газонасыщенном трещиновато-пористом слоистом углепородном массиве”

LHC Z‘Z^` discovery potential for models with continuously distributed mass

We study the Large Hadron Collider (LHC) discovery potential for $Z^`$ models with continuously distributed mass for $\sqrt{s} = 7, 10$ and 14 TeV centre-of-mass energies. One of possible LHC signatures for such models is the existence of broad resonance in Drell-Yan reaction $pp \to Z^` + ... \to l^+l^- + ...$.Comment: 14 pages, some references and formula adde

The Fourth Positive System of Carbon Monoxide in the Hubble Space Telescope Spectra of Comets

The rich structure of the Fourth Positive System (A-X) of carbon monoxide accounts for many of the spectral features seen in long slit HST-STIS observations of comets 153P/Ikeya-Zhang, C/2001 Q4 (NEAT), and C/2000 WM1 (LINEAR), as well as in the HST-GHRS spectrum of comet C/1996 B2 Hyakutake. A detailed CO fluorescence model is developed to derive the CO abundances in these comets by simultaneously fitting all of the observed A-X bands. The model includes the latest values for the oscillator strengths and state parameters, and accounts for optical depth effects due to line overlap and self-absorption. The model fits yield radial profiles of CO column density that are consistent with a predominantly native source for all the comets observed by STIS. The derived CO abundances relative to water in these comets span a wide range, from 0.44% for C/2000 WM1 (LINEAR), 7.2% for 153P/Ikeya-Zhang, 8.8% for C/2001 Q4 (NEAT) to 20.9% for C/1996 B2 (Hyakutake). The subtraction of the CO spectral features using this model leads to the first identification of a molecular hydrogen line pumped by solar HI Lyman-beta longward of 1200A in the spectrum of comet 153P/Ikeya-Zhang. (Abridged)Comment: 12 pages, 11 figures, ApJ accepte

Distinguishing Solar Flare Types by Differences in Reconnection Regions

Observations show that magnetic reconnection and its slow shocks occur in solar flares. The basic magnetic structures are similar for long duration event (LDE) flares and faster compact impulsive (CI) flares, but the former require less non-thermal electrons than the latter. Slow shocks can produce the required non-thermal electron spectrum for CI flares by Fermi acceleration if electrons are injected with large enough energies to resonate with scattering waves. The dissipation region may provide the injection electrons, so the overall number of non-thermal electrons reaching the footpoints would depend on the size of the dissipation region and its distance from the chromosphere. In this picture, the LDE flares have converging inflows toward a dissipation region that spans a smaller overall length fraction than for CI flares. Bright loop-top X-ray spots in some CI flares can be attributed to particle trapping at fast shocks in the downstream flow, the presence of which is determined by the angle of the inflow field and velocity to the slow shocks.Comment: 15 pages TeX and 2 .eps figures, accepted to Ap.J.Let

Functional renormalization group approach to correlated fermion systems

Numerous correlated electron systems exhibit a strongly scale-dependent behavior. Upon lowering the energy scale, collective phenomena, bound states, and new effective degrees of freedom emerge. Typical examples include (i) competing magnetic, charge, and pairing instabilities in two-dimensional electron systems, (ii) the interplay of electronic excitations and order parameter fluctuations near thermal and quantum phase transitions in metals, (iii) correlation effects such as Luttinger liquid behavior and the Kondo effect showing up in linear and non-equilibrium transport through quantum wires and quantum dots. The functional renormalization group is a flexible and unbiased tool for dealing with such scale-dependent behavior. Its starting point is an exact functional flow equation, which yields the gradual evolution from a microscopic model action to the final effective action as a function of a continuously decreasing energy scale. Expanding in powers of the fields one obtains an exact hierarchy of flow equations for vertex functions. Truncations of this hierarchy have led to powerful new approximation schemes. This review is a comprehensive introduction to the functional renormalization group method for interacting Fermi systems. We present a self-contained derivation of the exact flow equations and describe frequently used truncation schemes. Reviewing selected applications we then show how approximations based on the functional renormalization group can be fruitfully used to improve our understanding of correlated fermion systems.Comment: Review article, final version, 59 pages, 28 figure

Cervical masses in dogs and cats 1. Investigation and management

Abnormalities in the cervical region can be challenging to investigate and manage; however, the area is a common location for disease processes in dogs and cats. The anatomy of this region can make investigations and treatment difficult and a thorough understanding of this is essential before embarking on management and treatment of conditions in this location. Due to the various anatomical structures in the cervical area, there is often a long potential differential diagnoses list for mass lesions in this region. It is important to perform a thorough and logical investigative process in order to manage these masses appropriately. This article discusses investigation and management of cervical masses, while a second article, to be published in a subsequent issue of In Practice, will focus on differential diagnoses

Breakdown of anomalous channeling with ion energy for accurate strain determination in gan-based heterostructures

The influence of the beam energy on the determination of strain state with ion channeling in GaN-based heterostructures (HSs) is addressed. Experimental results show that anomalous channeling may hinder an accurate analysis due to the steering effects at the HS interface, which are more intense at lower ion energies. The experimental angular scans have been well reproduced by Monte Carlo simulations, correlating the steering effects with the close encounter probability at the interface. Consequently, limitations in the determination of the strain state by ion channeling can be overcome by selecting the adequate beam energy

Constraints on Galaxy Bias, Matter Density, and Primordial Non--Gausianity from the PSCz Galaxy Redshift Survey

We compute the bispectrum for the \IRAS PSCz catalog and find that the galaxy distribution displays the characteristic signature of gravity. Assuming Gaussian initial conditions, we obtain galaxy biasing parameters $1/b_1=1.20^{+0.18}_{-0.19}$ and $b_2/b_1^2=-0.42\pm0.19$, with no sign of scale-dependent bias for $k\leq 0.3$ h/Mpc. These results impose stringent constraints on non-Gaussian initial conditions. For dimensional scaling models with $\chi^2_N$ statistics, we find N>49, which implies a constraint on primordial skewness $B_3<0.35$.Comment: 4 pages, 3 embedded figures, uses revtex style file, minor changes to reflect published versio