An interferometer based phase control system

An interferometer based phase control system for focusing and pointing the solar power satellite (SPS) power beam is discussed. The system is ground based and closed loop. One receiving antenna is required on Earth. A conventional uplink data channel transmits an 8 bit phase error correction back to the SPS for sequential calibration of each power module. Beam pointing resolution is better than 140 meters at the rectenna

A power satellite sonic simulator

A simulator is described which generates and transmits a beam of audible sound energy mathematically similar to the solar power satellite (SPS) power beam. The simulator provides a laboratory means for analysis of ground based closed loop SPS phase control and of ionospheric effects on the SPS microwave power beam

Beat frequency interference pattern characteristics study

The frequency spectra and corresponding beat frequencies created by the relative motions between multiple Solar Power Satellites due to solar wind, lunar gravity, etc. were analyzed. The results were derived mathematically and verified through computer simulation. Frequency spectra plots were computer generated. Detailed computations were made for the seven following locations in the continental US: Houston, Tx.; Seattle, Wa.; Miami, Fl.; Chicago, Il.; New York, NY; Los Angeles, Ca.; and Barberton, Oh

A theoretical study of microwave beam absorption by a rectenna

The rectenna's microwave power beam absorption limit was theoretically confirmed by two mathematical models descriptive of the microwave absorption process; first one model was based on the current sheet equivalency of a large planar array above a reflector and the second model, which was based on the properties of a waveguide with special imaging characteristics, quantified the electromagnetic modes (field configurations) in the immediate vicinity of a Rectenna element spacing which permit total power beam absorption by preventing unwanted modes from propagating (scattering) were derived using these models. Several factors causing unwanted scattering are discussed

Can crack front waves explain the roughness of cracks ?

We review recent theoretical progress on the dynamics of brittle crack fronts and its relationship to the roughness of fracture surfaces. We discuss the possibility that the intermediate scale roughness of cracks, which is characterized by a roughness exponent approximately equal to 0.5, could be caused by the generation, during local instabilities by depinning, of diffusively broadened corrugation waves, which have recently been observed to propagate elastically along moving crack fronts. We find that the theory agrees plausibly with the orders of magnitude observed. Various consequences and limitations, as well as alternative explanations, are discussed. We argue that another mechanism, possibly related to damage cavity coalescence, is needed to account for the observed large scale roughness of cracks that is characterized by a roughness exponent approximately equal to 0.8Comment: 26 pages, 3 .eps figure. Submitted to J. Mech. Phys. Solid

A sonic satellite power system microwave power transmission simulation

A simulator is described which generates and transmits a beam of audible sound energy mathematically similar to the SPS power beam. The simulator provides a laboratory means for analysis of ground based closed loop SPS phase control and of ionospheric effects on the SPS microwave power beam

Sonic simulation of the SPS power beam

A Satellite Power System Microwave Transmission Simulator is described. The simulator generates and transmits a beam audible sound energy which is mathematically similar to the microwave beam which would transmit energy to Earth from a Solar Power Satellite. This allows areas such as power beam formation to be studied in a laboratory environment

Near-IR Variability in Young Stars in Cygnus OB7

We present the first results from a 124 night J, H, K near-infrared monitoring campaign of the dark cloud L 1003 in Cygnus OB7, an active star-forming region. Using 3 seasons of UKIRT observations spanning 1.5 years, we obtained high-quality photometry on 9,200 stars down to J=17 mag, with photometric uncertainty better than 0.04 mag. On the basis of near-infrared excesses from disks, we identify 30 pre-main sequence stars, including 24 which are newly discovered. We analyze those stars and find the NIR excesses are significantly variable. All 9,200 stars were monitored for photometric variability; among the field star population, about 160 exhibited near-infrared variability (1.7% of the sample). Of the 30 YSOs (young stellar objects), 28 of them (93%) are variable at a significant level. 25 of the 30 YSOs have near-infrared excess consistent with simple disk-plus-star classical T Tauri models. Nine of these (36%) drift in color space over the course of these observations and/or since 2MASS observations such that they cross the boundary defining the NIR excess criteria; effectively, they have a transient near-infrared excess. About half of the YSOs have color-space variations parallel to either the classical T Tauri star locus or a hybrid track which includes the dust reddening trajectory. This indicates that the NIR variability in YSOs that possess accretion disks arises from a combination of variable extinction and changes in the inner accretion disk: either in accretion rate, central hole size and/or the inclination of the inner disk. While some variability may be due to stellar rotation, the level of variability on the individual stars can exceed a magnitude. This is a strong empirical suggestion that protoplanetary disks are quite dynamic and exhibit more complex activity on short timescales than is attributable to rotation alone or captured in static disk models.Comment: Accepted by ApJ 35 pages including 10 figures and 3 tables. Figures 2, 5, 6, 7 and 10 have been reduced in resolution for Astro-p

Multidimensional spectroscopy with a single broadband phase-shaped laser pulse

We calculate the frequency-dispersed nonlinear transmission signal of a phase-shaped visible pulse to fourth order in the field. Two phase profiles, a phase-step and phase-pulse, are considered. Two dimensional signals obtained by varying the detected frequency and phase parameters are presented for a three electronic band model system. We demonstrate how two-photon and stimulated Raman resonances can be manipulated by the phase profile and sign, and selected quantum pathways can be suppressed.Comment: 26 pages, 15 figure

Probability distribution of the maximum of a smooth temporal signal

We present an approximate calculation for the distribution of the maximum of a smooth stationary temporal signal X(t). As an application, we compute the persistence exponent associated to the probability that the process remains below a non-zero level M. When X(t) is a Gaussian process, our results are expressed explicitly in terms of the two-time correlation function, f(t)=.Comment: Final version (1 major typo corrected; better introduction). Accepted in Phys. Rev. Let