Unsteady-state mass transfer from a binary gas bubble with changing volume

Numerical methods are used to investigate the transient mass transfer from a binary gas bubble to an incompressible liquid. The bubble has two components: A – soluble and B – insoluble in the surrounding fluid. The concentration of A inside the bubble is considered spatially uniform but not constant in time. The maximum value of the initial volumetric fraction of A is 0.3. The mathematical model equations were solved numerically in spherical coordinates system. Creeping flow, moderate Re number flow, 10 ? Re ? 100, and potential flow around the bubble were assumed. The computations focused on the influence of the initial fraction of A and Henry number on the mass transfer rate for Pe ? 10⁴.     

THE DISCIPLE–RKF LEARNING AND REASONING AGENT

Over the years we have developed the Disciple theory, methodology, and family of tools for building knowledge-based agents. This approach consists of developing an agent shell that can be taught directly by a subject matter expert in a way that resembles how the expert would teach a human apprentice when solving problems in cooperation. This paper presents the most recent version of the Disciple approach and its implementation in the Disciple–RKF (rapid knowledge formation) system. Disciple–RKF is based on mixed-initiative problem solving , where the expert solves the more creative parts of the problem and the agent solves the more routine ones, integrated teaching and learning , where the agent helps the expert to teach it, by asking relevant questions, and the expert helps the agent to learn, by providing examples, hints, and explanations, and multistrategy learning , where the agent integrates multiple learning strategies, such as learning from examples, learning from explanations, and learning by analogy, to learn from the expert how to solve problems. Disciple–RKF has been applied to build learning and reasoning agents for military center of gravity analysis, which are used in several courses at the US Army War College.     

Climate change and energy policy in Eastern Europe: Two scenarios for the future

The citizens of Poland, Eastern Germany, Czechoslovakia, Hungary, and Romania inhabit perhaps the most polluted environments in the world, largely because of their countries' inefficient use of energy. Energy use is two to three times greater per unit of economic output than in Western Europe. Energy inefficiency also constrains economic growth by diverting capital to unproductive use. As much as 40% of all industrial investment in Poland was consumed in energy production.The emerging democracies of Eastern Europe have embarked on reforms to make their economies more efficient. We assess their potential for energy efficiency and apply end-use analysis in an energy end-use economic model to evaluate future energy use in the region. We assume that Eastern Europe will approach current Western living standards over the next three decades and that this will in turn increase energy consumption. We have found, nevertheless, that Eastern European nations could hold energy demand virtually constant through structural reform and technical energy-efficiency improvement. The six countries in the region could save as much as 3.5 exajoules per year, with savings yielding an economic benefit of $300 million annually.Capturing the energy-efficiency potential in Eastern Europe would require a combination of market forces and policy initiatives. Such optimistic prediction, however, should not be taken at face value. Financial and technical constraints will impede some of the potential gains in energy efficiency in Eastern Europe. Overcoming them will require national leadership and decisive international cooperation.     

The influence of thermal fluctuations on the electronic transport of alkeno-thiolates

In this paper, we investigate the influence of molecular vibrations on the tunneling of electrons through alkeno-thiolates of varying lengths sandwiched in between two gold contacts. The study is confined to the elastic scattering. The vibrational modes are treated quantum-mechanically and the tunneling current is computed as an ensemble average over the distribution of the atomic configurations, obtained by a suitable approximation of the density matrix for the normal mode oscillators. The quantum-mechanical treatment is necessary in order to correctly include the zero-point fluctuations. The calculations show no temperature dependence for the tunneling current in the regime between 270-350 K.     

Intensity parameters of Tm doped Sc2O3 transparent ceramic laser material

This work is focused on spectral investigations of Tm³⁺ doped Sc₂O₃ transparent ceramic as potential material for diode-pumped solid-state laser emitting around 2 μm. In the context of the Judd-Ofelt (J-O) theory a series of spectroscopic parameters such as J-O intensity parameters, oscillator strengths, radiative transitions probabilities, and radiative lifetimes as well as branching ratios are evaluated. The gain cross-sections which lead to an estimation of the probable operating laser wavelength for the ³F₄ → ³H₆ Tm³⁺ laser transition were also calculated.     

Problems of village electrification based on PV systems in Romania: Individual solar home systems for settlements in the Cerna Valley

The autonomous PV systems cover a wide area of the applications that can be developed in the country, in places far from the national grid and with a low demand of electric power. The electrification of homes and farms in rural areas by using PV systems would contribute to improving the inhabitants' social, economic and cultural standard.In Romania, it is estimated that there are about 10,000 homes, farms and schools located in more than 500 settlements which could be electrified by using PV systems. The individual solar home systems would allow each user to adjust his own electricity consumption according to weather variations. A major problem in the development of these systems is the identification of the optimum technical and economic solutions as well as of the main financing sources. The paper aims to present the technical, economic and social problems involved by the implementation of such a project of PV-based electrification in Romania, presenting the particular case of two settlements (Scarisoara and Prisacina) located in the Cerna Valley - the Banat Mountains.     

X-ray absorption fine structure investigations on heat-treated Cr-doped titania thin films

Chromium-doped titanium oxide thin films were investigated in the as-deposited state and after thermal treatment (723 K for 3 h in air). X-ray diffraction data revealed an improvement in film crystallinity induced by the thermal treatment. Extended X-ray absorption fine structure data revealed similar atomic neighboring around Cr atoms in both as-deposited and annealed samples. A lattice contraction of ~ 2% is observed in the annealed samples. The 67% enhancement of the amplitude of the Cr 1 s X-ray absorption fine structure pre-edge peak after thermal treatment, which is a sign of “dipole-forbidden” 1 s → 3 d transitions, suggests strong alteration in the number of Cr 3 d vacancies, in spite of similar Cr local environment in the two kinds of investigated samples. We discuss here the Cr⁺ → Cr⁴⁺ and Cr²⁺ → Cr⁶⁺ changes induced by thermal treatment, and/or the evolution in local structures without inversion center.Refractive index dispersion spectra in the visible wavelength domain allowed us to compute the values of the dispersion energy, the single-oscillator energy and the coordination number of Ti atoms in both as-deposited and annealed samples.     

Nanoparticles from a Gold Complex with Sulfite Ion as Ligand: Preparation and Characterization

Gold colloidal nanoparticles (GNPs) were prepared by reducing a complex of Au⁺. Na₃Au(SO₃)₂ with sodium citrate. The procedure provides control of the dimension of nanoparticles produced, which is a function of reaction time and concentration of reactants. The nanoparticles were separated by centrifugation and their characteristics and dimensions were studied using UV-Vis and IR spectroscopy and transmission electronic microscopy (TEM).