Achieving Very High PV Penetration

This article argues that optimally deployed intermittency solutions could affordably transform solar power generation into the firm power delivery system modern economies require, thereby enabling very high solar penetration and the displacement conventional power generation. The optimal deployment of these high‐penetration enabling solutions imply the existence of a healthy power grid, and therefore imply a central role for utilities and grid operators. This article also argues that a value‐based electricity compensation mechanism, recognizing the multifaceted, penetration‐dependent value and cost of solar energy, and capable of shaping consumption patterns to optimally match resource and demand, would be an effective vehicle to enable high solar penetration and deliver affordable firm power generation

Three-dimensional light-matter interface for collective spin squeezing in atomic ensembles

We study the three-dimensional nature of the quantum interface between an ensemble of cold, trapped atomic spins and a paraxial laser beam, coupled through a dispersive interaction. To achieve strong entanglement between the collective atomic spin and the photons, one must match the spatial mode of the collective radiation of the ensemble with the mode of the laser beam while minimizing the effects of decoherence due to optical pumping. For ensembles coupling to a probe field that varies over the extent of the cloud, the set of atoms that indistinguishably radiates into a desired mode of the field defines an inhomogeneous spin wave. Strong coupling of a spin wave to the probe mode is not characterized by a single parameter, the optical density, but by a collection of different effective atom numbers that characterize the coherence and decoherence of the system. To model the dynamics of the system, we develop a full stochastic master equation, including coherent collective scattering into paraxial modes, decoherence by local inhomogeneous diffuse scattering, and backaction due to continuous measurement of the light entangled with the spin waves. This formalism is used to study the squeezing of a spin wave via continuous quantum nondemolition (QND) measurement. We find that the greatest squeezing occurs in parameter regimes where spatial inhomogeneities are significant, far from the limit in which the interface is well approximated by a one-dimensional, homogeneous model.Comment: 24 pages, 7 figure

Sensor Based Auditory And Haptic Guidance System

A system and method are disclosed that use data provided by a mobile device equipped with sensors to guide a human or machine along a vector path through sensory feedback. The system uses motion and depth sensor information and object recognition to create models of an interior space, which facilitate movement for a person who has never been inside a space before, and to use those models for navigation. The method utilizes interior space maps to identify safe vectors. A realtime algorithm compares the user’s location and direction of movement with the desired path in the model, providing a measure of the deviation. It then plays an auditory and/or haptic signal that focuses the user’s attention to follow a safe path in response to the deviation. Using realtime object recognition sensor data allows the detection of spatial obstacles that are otherwise difficult to navigate using traditional solutions for aiding the visually impaired

Fundamental Solutions in Plane Problem for Anisotropic Elastic Medium Under Moving Oscillating Source

In present article we consider the problems of concentrated point force which is moving with constant velocity and oscillating with cyclic frequency in unbounded homogeneous anisotropic elastic two-dimensional medium. The properties of plane waves and their phase, slowness and ray or group velocity curves for 2D problem in moving coordinate system are described. By using the Fourier integral transform techniques and established the properties of the plane waves, the explicit representation of the elastodynamic Green's tensor is obtained for all types of source motion as a sum of the integrals over the finite interval. The dynamic components of the Green's tensor are extracted. The stationary phase method is applied to derive an asymptotic approximation of the far wave field. The simple formulae for Poynting energy flux vectors for moving and fixed observers are presented too. It is noted that in the far zones the cylindrical waves are separated under kinematics and energy. It is shown that the motion bring some differences in the far field properties. They are modification of the wave propagation zones and their number, fast and slow waves appearance under trans- and superseismic motion and so on.Comment: 19 pages, Proceeding of the Conference "Advanced Problems in Mechanics", Russia, St.Petersburg (Repino), June 22-July 2, 200

Metastable states, quasi-stationary distributions and soft measures

We establish metastability in the sense of Lebowitz and Penrose under practical and simple hypothesis for (families of) Markov chains on finite configuration space in some asymptotic regime, including the case of configuration space size going to infinity. By comparing restricted ensemble and quasi-stationary measures, we study point-wise convergence velocity of Yaglom limits and prove asymptotic exponential exit law. We introduce soft measures as interpolation between restricted ensemble and quasi-stationary measure to prove an asymptotic exponential transition law on a generally different time scale. By using potential theoretic tools, we prove a new general Poincar\'e inequality and give sharp estimates via two-sided variational principles on relaxation time as well as mean exit time and transition time. We also establish local thermalization on a shorter time scale and give mixing time asymptotics up to a constant factor through a two-sided variational principal. All our asymptotics are given with explicit quantitative bounds on the corrective terms.Comment: 41 page

Model-independent determination of the carrier multiplication time constant in CdSe nanocrystals

The experimental determination of the carrier multiplication (CM) time constant is complicated by the fact that this process occurs within the initial few hundreds of femtoseconds after excitation and, in transient-absorption experiments, cannot be separated from the buildup time of the 1p-state population. This work provides an accurate theoretical determination of the electron relaxation lifetime during the last stage of the p-state buildup, in CdSe nanocrystals, in the presence of a single photogenerated hole (no CM) and of a hole plus an additional electron–hole pair (following CM). From the invariance of the 1p buildup time observed experimentally for excitations above and below the CM threshold producing hot carriers with the same average per-exciton excess energy, and the calculated corresponding variations in the electron decay time in the two cases, an estimate is obtained for the carrier multiplication time constant. Unlike previous estimates reported in the literature so far, this result is model-independent, i.e., is obtained without making any assumption on the nature of the mechanism governing carrier multiplication. It is then compared with the time constant calculated, as a function of the excitation energy, assuming an impact-ionization-like process for carrier multiplication (DCM). The two results are in good agreement and show that carrier multiplication can occur on timescales of the order of tens of femtoseconds at energies close to the observed onset. These findings, which are compatible with the fastest lifetime estimated experimentally, confirm the suitability of the impact-ionization model to explain carrier multiplication in CdSe nanocrystals

Using Diffusion-Diffusion Exchange Spectroscopy to observe diffusion exchange in yeast

The permeability of cell membranes varies significantly across both healthy and diseased tissue, and changes in cell membrane permeability can occur during treatment response in tumours. Measurements of cell membrane permeability could therefore be useful for tumour detection and as biomarkers of treatment response in the clinic. As the diffusion of water across the cell membrane is directly dependent on cell membrane permeability, we have investigated the ability of diffusion-diffusion exchange spectroscopy to quantify the diffusion exchange of water in a suspension of yeast, as a first step towards its application in tumours