Silicon nanoparticles and interstellar extinction

To examine a recently proposed hypothesis that silicon nanoparticles are the source of extended red emission (ERE) in the interstellar medium, we performed a detailed modeling of the mean Galactic extinction in the presence of silicon nanoparticles. For this goal we used the appropriate optical constants of nanosized Si, essentially different from those of bulk Si due to quantum confinement. It was found that a dust mixture of silicon nanoparticles, bare graphite grains, silicate core-organic refractory mantle grains and three-layer silicate-water ice-organic refractory grains works well in explaining the extinction and, in addition, results in the acceptable fractions of UV/visible photons absorbed by silicon nanoparticles: 0.071-0.081. Since these fractions barely agree with the fraction of UV/visible photons needed to excite the observed ERE, we conclude that the intrinsic photon conversion efficiency of the photoluminescence by silicon nanoparticles must be near 100%, if they are the source of the ERE.Comment: Latex2e, uses emulateapj.sty (included), multicol.sty, epsf.sty, 6 pages, 3 figures (8 Postscript files), accepted for publication in ApJ Letters, complete Postscript file is also available at http://physics.technion.ac.il/~zubko/eb.html#SNP

New Interstellar Dust Models Consistent with Extinction, Emission, and Abundance Constraints

We present new interstellar dust models which have been derived by simultaneously fitting the far-ultraviolet to near-infrared extinction, the diffuse infrared (IR) emission and, unlike previous models, the elemental abundance constraints on the dust for different interstellar medium abundances, including solar, F and G star, and B star abundances. The fitting problem is a typical ill-posed inversion problem, in which the grain size distribution is the unknown, which we solve by using the method of regularization. The dust model contains various components: PAHs, bare silicate, graphite, and amorphous carbon particles, as well as composite particles containing silicate, organic refractory material, water ice, and voids. The optical properties of these components were calculated using physical optical constants. As a special case, we reproduce the Li & Draine (2001) results, however their model requires an excessive amount of silicon, magnesium, and iron to be locked up in dust: about 50 ppm (atoms per million of H atoms), significantly more than the upper limit imposed by solar abundances of these elements, about 34, 35, and 28 ppm, respectively. A major conclusion of this paper is that there is no unique interstellar dust model that simultaneously fits the observed extinction, diffuse IR emission, and abundances constraints.Comment: 70 pages, 23 figures, accepted for publication in the Astrophysical Journal Supplemen

Spatial Aspects of Multi-Sensor Data Fusion: Aerosol Optical Thickness

The Goddard Earth Sciences Data and Information Services Center (GES DISC) investigated the applicability and limitations of combining multi-sensor data through data fusion, to increase the usefulness of the multitude of NASA remote sensing data sets, and as part of a larger effort to integrate this capability in the GES-DISC Interactive Online Visualization and Analysis Infrastructure (Giovanni). This initial study focused on merging daily mean Aerosol Optical Thickness (AOT), as measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra and Aqua satellites, to increase spatial coverage and produce complete fields to facilitate comparison with models and station data. The fusion algorithm used the maximum likelihood technique to merge the pixel values where available. The algorithm was applied to two regional AOT subsets (with mostly regular and irregular gaps, respectively) and a set of AOT fields that differed only in the size and location of artificially created gaps. The Cumulative Semivariogram (CSV) was found to be sensitive to the spatial distribution of gap areas and, thus, useful for assessing the sensitivity of the fused data to spatial gaps

Remote Sensing Data Visualization, Fusion and Analysis via Giovanni

We describe Giovanni, the NASA Goddard developed online visualization and analysis tool that allows users explore various phenomena without learning remote sensing data formats and downloading voluminous data. Using MODIS aerosol data as an example, we formulate an approach to the data fusion for Giovanni to further enrich online multi-sensor remote sensing data comparison and analysis

Stress-strain state of the mine massif around the chambers of the second stage of mining

A stress-strain state of the rock mass around the chambers of the second stage of mining was analyzed with the help of thermodynamic method. This study is the question of the day as the ore reserves in the chambers of the second stage of mining are, as a rule, extracted being surrounded by the filling mass, and due to this the highest rates of the ore losses and contamination with the filling mass are observed. In connection with this, the study of the stress-strained state of the filling mass and establishment of a method for improving the massif stability presents a great interest today. A calculation scheme for modeling thermodynamic processes in the rock mass around the chambers was developed with the purpose to study the stress field and determine principles of radial stress changing in the filling mass of the surrounding chamber. A chamber in the layer at the depth of 740-840 m was simulated with the following average geotechnical conditions: depth of the extraction chamber, angle of the deposit depression, horizontal thickness of deposit, rock strength in the hanging layer against uniaxial compression, rock strength in the bottom layer against uniaxial compression, and stowing strength against uniaxial compression. The study determined areas with tensile stress in the rocks of the bottom layer, ore mass and filling mass, and their parameters (size, maximum tension) and formulated empirical equations for the dependences between radial tensions and distance to the chambers L of the second stage of mining. The areas of destructive deformation and their dimensions in the stowing mass around the chambers of the second stage of mining at the level 740-840 m were established. Maximum values are defined for the stresses acting in the stowing mass which, exceeding the ultimate strength, cause the mass failure into the space of the chamber of the second stage. In order to prevent the stowing mass failure it is recommended to make a consolidating layer of the solid stowing at the 2/3 height of the chamber in order to resist the high tensile stresses and to ensure the mass stability

Dust Grain-Size Distributions From MRN to MEM

Employing the Maximum Entropy Method algorithm, we fit interstellar extinction measurements which span the wavelength range 0.125-3 micron. We present a uniform set of MEM model fits, all using the same grain materials, optical constants and abundance constraints. In addition, we are taking advantage of improved UV and IR data and better estimates of the gas-to-dust ratio. The model fits cover the entire range of extinction properties that have been seen in the Galaxy and the Magellanic Clouds. The grain models employed for this presentation are the simplistic homogeneous spheres models (i.e., Mathis, Rumpl, & Nordsieck 1977) with two (graphite, silicate) or three (graphite, silicate, amorphous carbon) components. Though such usage is only a first step, the results do provide interesting insight into the use of grain size as a diagnostic of dust environment. We find that the SMC Bar extinction curve cannot be fit using carbon grains alone. This is a challenge to the recent observational result indicating little silicon depletion in the SMC.Comment: 24 pages, 5 figures, accepted for publication in the Astrophysical Journa

Strain gradient induced polarization in SrTiO3 single crystals

Piezoelectricity is inherent only in noncentrosymmetric materials, but a piezoelectric response can also be obtained in centrosymmetric crystals if subjected to inhomogeneous deformation. This phenomenon, known as flexoelectricity, affects the functional properties of insulators, particularly thin films of high permittivity materials. We have measured strain-gradient-induced polarization in single crystals of paraelectric SrTiO$_3$ as a function of temperature and orientation down to and below the 105 K phase transition. Estimates were obtained for all the components of the flexoelectric tensor, and calculations based on these indicate that local polarization around defects in SrTiO$_3$ may exceed the largest ferroelectric polarizations. A sign reversal of the flexoelectric response detected below the phase transition suggests that the ferroelastic domain walls of SrTiO$_3$ may be polar.Comment: 4 pages, 3 figures, 1 tabl

Institutional tool of financial policy : contractual policy

Under the market conditions, the most important role in economic subject belongs to the financial aspect – therefore, effective decisions at the micro-level are predetermined by financial policy, as realization of the strategy in the tactics of finances management is not possible if there’s none. Finances of economic subject are a component of the financial system of the Russian Federation. Together with the state financial policy, which is aimed at overcoming of consequences of the global financial crisis, there is financial policy of separate economic subjects and corporate structures. For the purpose of study of financial policy, the authors deem it expedient to clarify the definition of “policy”. According to M. Weber, policy is “striving for participation in authority or influencing the distribution of authority, be it between states or within a state between groups of people”.peer-reviewe

Experimental and numerical study of pressure intensity in detachable joints of D series pumps

Об’єктом дослідження є відцентровий одноступеневий насос двостороннього входу спірального типу з горизонтальним роз’ємом корпуса. Проблема. У процесі проектування насосів вирішується проблема герметичності горизонтального роз’єму корпуса насоса, що знаходиться під дією високого тиску та температури. При дослідженні герметичності горизонтального роз’єму використовуються чисельні методи розрахунку, що дозволяють оцінювати інтенсивність тиску на поверхнях, що контактують. Роз’ємне з’єднання, що знаходиться під дією зовнішнього навантаження, задовольняє критеріям герметичності, якщо інтенсивність тиску на ущільнювальних поверхнях буде вище значень питомого тиску, встановлених нормативними документами. Однак відсутність можливості експериментального визначення інтенсивності тиску на поверхнях, що контактують, не дозволяло до теперішнього часу оцінити точність результатів, отриманих за допомогою чисельних методів розрахунку. Мета дослідження. З метою верифікації чисельних результатів, отриманих на математичних моделях, було проведено експеримент із використанням спеціальної плівки Prescale, яка фіксує величину контактного тиску на роз’ємі зразка моделі фрагмента фланця. За результатами експерименту проведено аналіз розподілу інтенсивності тиску. Методика реалізації. Для проведення експерименту була розроблена методика визначення інтенсивності тиску на контактуючих поверхнях за запропонованою схемою зразка фрагмента фланця. Результати дослідження. Порівняльний аналіз результатів вирішення контактної задачі на кінцево-елементних моделях фрагмента фланця та ділянки роз’єму корпусу насоса в області напірної порожнини показав гарний збіг результатів. Аналіз результатів, отриманих експериментально на зразку фрагмента фланця, і результатів чисельного розрахунку моделі фрагмента фланця також показав хороший збіг. Висновок. Таким чином отримано експериментальне підтвердження результатів розрахунку інтенсивності тиску в роз’ємних з’єднаннях на математичних моделях.The object of study is a single-stage double-suction axially split volute casing centrifugal pump. Background. In the design process of pumps, the problems associated with ensuring the tightness of the axial joint of a pump casing being under the effect of mechanical and temperature loads, are being solved. During the study of axial joint tightness, numerical calculation methods are used to estimate the pressure intensity on the contacting surfaces. A detachable joint under the external load satisfies the criterions of the tightness if the pressure intensity on the sealing surfaces is higher than values of the specific pressure prescribed by regulations. However, inability to experimentally determine the pressure intensity on the contacting surfaces has so far prevented to assess the accuracy of results obtained by the numerical calculation methods. Objective. In order to verify the numerical results obtained by mathematical models, an experiment was carried out using a special Prescale film that registers the magnitude of the contact pressure on the joint of the specimen model of the flange fragment. Based on the experimental results, an analysis of the pressure intensity distribution was conducted. Methods. To conduct the experiment, there was developed a method for determining the pressure intensity on the contacting surfaces according to the proposed scheme of the specimen of the flange fragment. Results. A comparative analysis of the solving results obtained for the contact problem on the finite-element models of the flange fragment and the zone of the pump casing joint in the discharge chamber area showed a good coincidence of the results. Analysis of results obtained experimentally on the specimen of flange fragment and results of the numerical calculation on the flange fragment model also showed a good agreement. Conclusions. Therefore, results of the calculation of the pressure intensity in the detachable joints on mathematical models have been experimentally confirmed.Объектом исследований является центробежный одноступенчатый насос двустороннего входа спирального типа с горизонтальным разъемом корпуса. Проблема. В процессе проектирования решается проблема герметичности горизонтального разъема корпуса насоса, находящегося под действием высокого давления и температуры. При исследовании герметичности горизонтального разъема используются численные методы расчета, позволяющие оценивать интенсивность давления на контактирующих поверхностях. Разъемное соединение, находящееся под действием внешней нагрузки, удовлетворяет критериям герметичности, если интенсивность давления на уплотняемых поверхностях выше значений удельного давления, установленных нормативными документами. Однако отсутствие возможности экспериментального определения интенсивности давления на контактирующих поверхностях не позволяло до настоящего времени оценить точность результатов, получаемых численными методами расчета. Цель исследования. С целью верификации численных результатов, полученных на математических моделях, был проведен эксперимент с использованием специальной пленки Prescale, фиксирующей величину контактного давления на разъеме образца модели фрагмента фланца. По результатам эксперимента проведен анализ распределения интенсивности давления. Методика реализации. Для проведения эксперимента была разработана методика определения интенсивности давления на контактирующих поверхностях по предложенной схеме образца фрагмента фланца. Результаты исследования. Сопоставительный анализ результатов решения контактной задачи на конечно-элементных моделях фрагмента фланца и участка разъема корпуса насоса в области напорной полости показал хорошее совпадение результатов. Анализ результатов, полученных экспериментально на образце фрагмента фланца, и результатов численного расчета на модели фрагмента фланца также показал хорошее совпадение. Выводы. Таким образом, получено экспериментальное подтверждение результатов расчета интенсивности давления в разъемных соединениях на математических моделях