Modulation stabilization of Bloch oscillations of two-component Bose-Einstein condensates in optical lattices

We study the Bloch oscillations (BOs) of two-component Bose-Einstein condensates (BECs) trapped in spin-dependent optical lattices. Based on the derived equations of motion of the wave packet in the basis of localized wave functions of the lattice sites, the damping effect induced by the intercomponent and intracomponent interactions to the BOs is explored analytically and numerically. We also show that such damping of the BOs can be suppressed entirely if all the atom-atom interactions are modulated synchronously and harmonically in time with suitable frequency via the Feshbach resonance. When the intercomponent and the intracomponent interactions have inverse signs, we find that the long-living BOs and even the revival of the BOs can be achieved via only statically modulating the configuration of optical lattices. The results provide a valuable guidance for achieving long-living BOs in the two-component BEC system by the Feshbach resonances and manipulating the configuration of the optical lattices.Comment: 13 pages in IOP preprint style, 5 figure

Cost of photovoltaic energy systems as determined by balance-of-system costs

The effect of the balance-of-system (BOS), i.e., the total system less the modules, on photo-voltaic energy system costs is discussed for multikilowatt, flat-plate systems. Present BOS costs are in the range of 10 to 16 dollars per peak watt (1978 dollars). BOS costs represent approximately 50% of total system cost. The possibility of future BOS cost reduction is examined. It is concluded that, given the nature of BOS costs and the lack of comprehensive national effort focussed on cost reduction, it is unlikely that BOS costs will decline greatly in the next several years. This prognosis is contrasted with the expectations of the Department of Energy National Photovoltaic Program goals and pending legislation in the Congress which require a BOS cost reduction of an order of magnitude or more by the mid-1980s

Background-oriented schlieren (BOS) for scramjet inlet-isolator investigation

Background-oriented Schlieren (BOS) technique is a recently invented non-intrusive flow diagnostic method which has yet to be fully explored in its capabilities. In this paper, BOS technique has been applied for investigating the general flow field characteristics inside a generic scramjet inlet-isolator with Mach 5 flow. The difficulty in finding the delicate balance between measurement sensitivity and measurement area image focusing has been demonstrated. The differences between direct cross-correlation (DCC) and Fast Fourier Transform (FFT) raw data processing algorithm have also been demonstrated. As an exploratory study of BOS capability, this paper found that BOS is simple yet robust enough to be used to visualize complex flow in a scramjet inlet in hypersonic flow. However, in this case its quantitative data can be strongly affected by 3-dimensionality thus obscuring the density value with significant errors

Polychromatic Optical Bloch Oscillations

Bloch oscillations (BOs) of polychromatic beams in circularly-curved optical waveguide arrays are smeared out owing to the dependence of the BO spatial period on wavelength. Here it is shown that restoring of the self-imaging property of the array and approximate BOs over relatively broad spectral ranges can be achieved by insertion of suitable lumped phase slips uniformly applied across the array.Comment: 3 pages, 4 figure

Bloch Oscillations of Einstein-Podolsky-Rosen States

Bloch Oscillations (BOs) of quantum particles manifest themselves as periodic spreading and re-localization of the associated wave functions when traversing lattice potentials subject to external gradient forces. Albeit BOs are deeply rooted into the very foundations of quantum mechanics, all experimental observations of this phenomenon so far have only contemplated dynamics of one or two particles initially prepared in separable local states, which is well described by classical wave physics. Evidently, a more general description of genuinely quantum BOs will be achieved upon excitation of a Bloch-oscillator lattice system by nonlocal states, that is, containing correlations in contradiction with local realism. Here we report the first experimental observation of BOs of two-particle Einstein-Podolsky-Rosen states (EPR), whose associated N-particle wave functions are nonlocal by nature. The time evolution of two-photon EPR states in Bloch-oscillators, whether symmetric, antisymmetric or partially symmetric, reveals unexpected transitions from particle antibunching to bunching. Consequently, the initial state can be tailored to produce spatial correlations akin to bosons, fermions or anyons. These results pave the way for a wider class of photonic quantum simulators.Comment: 21 pages, 6 figure

Reconceptualising temporality in young lives: exploring young people’s current and future livelihoods in AIDS-affected southern Africa

In recent years, anxieties have been expressed that the impacts of southern Africa's AIDS pandemic on young people today will damage their future livelihood prospects. Geographers have been remarkably reluctant to explore young people's future livelihoods, inspired by a concern to view young people as human beings, worthy of study in their own right rather than mere human becomings, of interest only as ‘adults in the making’. Yet there is growing acknowledgement that young people, like older people, are always both ‘being and becoming’. The connections between current and future lives merit much greater attention, both because experiences and actions in childhood and youth undoubtedly shape the futures of individuals and wider society, but also because young people's thoughts and actions are so often geared to the future, and this future orientation shapes their present worlds. This paper reports on research that set out to explore links between the impacts of AIDS and young people's livelihood prospects. Intensive case study research was undertaken, combining participatory methods and life history interviews with young people aged 10–24 in two villages, one in southern Malawi and the other in the mountains of Lesotho. By theorising a temporal dimension to de Haan and Zoomers’ concept of livelihood trajectories, the paper focuses on the ways in which young people respond to both the immediate sustenance requirements of themselves and their households and their need to accrue assets for future livelihoods. Some young people's trajectories appear to be disturbed by the influence of AIDS, but with no systematic patterns. Beyond addressing empirical questions concerning the impacts of AIDS, the paper contributes to our understanding of how livelihoods are produced and to the conceptualisation of youth transitions as produced through the iteration of present and future

Photonic Bloch oscillations of correlated particles

A photonic realization of Bloch oscillations (BOs) of two correlated electrons that move on a one-dimensional periodic lattice, based on spatial light transport in a square waveguide array with a defect line, is theoretically proposed. The signature of correlated BOs, such as frequency doubling of the oscillation frequency induced by particle interaction, can be simply visualized by monitoring the spatial path followed by an optical beam that excites the array near the defect line.Comment: 4 page

Inspection gage for boss Patent

Gage for quality control of sealing surfaces of threaded bos

Machine learning-based prediction of a BOS reactor performance from operating parameters

A machine learning-based analysis was applied to process data obtained from a Basic Oxygen Steelmaking (BOS) pilot plant. The first purpose was to identify correlations between operating parameters and reactor performance, defined as rate of decarburization (dc/dt). Correlation analysis showed, as expected a strong positive correlation between the rate of decarburization (dc/dt) and total oxygen flow. On the other hand, the decarburization rate exhibited a negative correlation with lance height. Less obviously, the decarburization rate, also showed a positive correlation with temperature of the waste gas and CO2 content in the waste gas. The second purpose was to train the pilot-plant dataset and develop a neural network based regression to predict the decarburization rate. This was used to predict the decarburization rate in a BOS furnace in an actual manufacturing plant based on lance height and total oxygen flow. The performance was satisfactory with a coefficient of determination of 0.98, confirming that the trained model can adequately predict the variation in the decarburization rate (dc/dt) within BOS reactors. View Full-Tex