Maksutov spectrograph Patent

Maksutov spectrograph for low light level researc

Apparatus for photographing meteors

Apparatus for photographing meteors in a selected area of the sky is described. A photomultiplier is pointed in the direction of the area. When a meteor passes through the area the signal output of the photomultiplier increases. Means are provided that activate a camera, pointed at the area, in response to an increased signal from the photomultiplier. Hence, the camera photographs the selected are only while meteors are likely to be passing through the area

NASA-LRC faint meteor spectra

A brief description is given of the instrumentation, the facilities, and the patrol technique used by the NASA faint meteor spectra patrol. A classification of 500 meteor spectra obtained in the first 2-1/2 years of the patrol is reported. The general characteristics of typical spectra are discussed and preliminary conclusions drawn. Examples of unusual spectra are briefly described

Spectral analysis of a high-velocity meteor

A spectrogram of a fast optical meteor was reduced and analyzed, and 60 features were identified in the spectrum. Air and ionized elements in this meteor radiate throughout the spectrum from 3000 A to 6800 A. A mass of 9 mg and an effective radiation temperature of approximately 5700 K were computed for the meteor. Weight ratios of Ca:Fe, and Mg:Fe, and Na:Fe were computed. A plasma particle velocity distribution for meteors was derived, and the average collision speed obtained from this distribution was compared with the relative collision speed of a Fe-N2 gas mixture at 5700 K

Spectral analysis of four meteors

Four meteor spectra are analyzed for chemical composition and radiative processes. The chemical compositions of the Taurid, Geminid, and Perseid meteors were found to be similar to that of a typical stony meteorite. The chemical composition of the sporadic meteor was found to be similar to that of a nickel iron meteorite. The radiation from optical meteors was found to be similar to that of a low temperature gas, except that strong, anomalous ionic radiation is superposed on the neutral radiation in bright, fast meteors

Photographic observations of a low-density iron artificial meteoroid

Photographic observations of low density iron artificial meteoroi

Simulation of the influence of hydrophones used for the characterization of pressure field distribution in low frequency, high power ultrasonic reactor vessels

This paper describes the use of a finite element (FE) modeling approach to investigate the influence of different hydrophone designs in laboratory scale reactor vessels. In addition to conventional PVDF membrane and piezoceramic hydrophone, the performance of a conceptual array hydrophone, comprising a 2D matrix of PVDF array elements, will be simulated. The FE modeling concentrates on two issues: the disturbance to the field through the introduction of each hydrophone configuration; and their suitability and response to measuring non-linear effects. To simplify the model the ultrasonic transducer is not directly represented. Here, a pressure loading function is used as the excitation technique, with a sawtooth waveform applied for the simulation of the non-linear detection capability of each hydrophone configuration. The results from the simulation programme demonstrate that the dynamics of the reactor vessel are critical to optimize the performance of the ultrasonic system. In addition, the introduction of a hydrophone alters the wave propagation, and hence the field distribution beyond a given probe location. Nevertheless, the spatial pressure distribution at the active area remains reasonably accurate if within the useable bandwidth of the device. Accordingly, the broadband nature of the membrane device is suited to operation in both the linear and non-linear regimes, with the PVDF array membrane device offering a fast, convenient measurement of the pressure field distribution for industrial applications

Investigating the influence of the constituent materials on the performance of periodic piezoelectric composite arrays

This paper describes a theoretical investigation into the influence of the constituent materials on periodic composite array transducer performance. A finite element (FE) model, configured in PZFlex, is used to analyze the performance of a wedge coupled array transducer operating into a steel component. Here, the improvements offered by new single crystal piezoelectric materials are compared to standard PZT‐based configurations. In addition, new passive polymer materials, possessing low longitudinal loss and high shear loss, are evaluated for their potential to significantly reduce inter‐element mechanical cross talk. The FE results illustrate the potential for the next generation of array transducers incorporating these new materials and this is highlighted in the A‐scan predictions from simulated defects