Comparison of reflectivity and wind profiles measured on 46.8 MHz and 430 MHz at the Arecibo Observatory

Comparisons of troposphere and stratosphere radar experiments at ultrahigh frequency (UHF) and very high frequency (VHF) were done at the Arecibo Observatory in April 1980 with the 430 MHz and 46.8 MHz radar. The velocity profiles measured on both frequencies with the Doppler beam swinging mode were compared. In general, the velocity profiles were equivalent. The VHF profile, however, shows more fluctuations with height than the UHF profile, although the latter was recorded with 150 m resolution instead of 300 m resolution on VHF

The first operation and results of the Chung-Li VHF radar

The Chung-Li Very High Frequency (VHF) radar is used in the dual-mode operations, applying Doppler beam-swinging as well as the spaced-antenna-drift method. The design of the VHF radar is examined. Results of performance tests are discussed

How far have we achieved by systemic therapy for recurrent/metastatic nasopharyngeal carcinoma?

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Investigations of the lower and middle atmosphere at the Arecibo Observatory and a description of the new VHF radar project

The atmospheric science research at the Arecibo Observatory is performed by means of (active) radar methods and (passive) optical methods. The active methods utilize the 430 NHz radar, the S-band radar on 2380 MHz, and a recently constructed Very High Frequency (VHF) radar. The passive methods include measurements of the mesopause temperature by observing the rotational emissions from OH-bands. The VHF radar design is discussed

Lightning discharge identification system

A system for differentiating between cloud to cloud and cloud to ground lightning discharges is described which includes an electric field antenna that senses the rate of charge of an electric field produced by a lightning discharge. When the signal produced by the electric field exceeds a predetermined threshold, it is fed to a coincidence detector. A VHF antenna is also provided and generates a video signal responsive to a cloud to cloud lightning discharge, and this signal is fed through a level sensor, an inverter, to the coincidence detector simultaneously with the signal from the field detector. When signals from the electric field antenna and the VHF antenna appear at the coincidence detector simultaneously, such indicates that there is a cloud to cloud lightning discharge; whereas, when there is not a signal produced on the VHF antenna simultaneously with a signal produced by the field sensor, then a strike indicator connected to the coincidence detector indicates a cloud to ground lightning discharge

The aftermath of LUX-Lung 7 study—what have we learnt from it?

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Parametric Nanomechanical Amplification at Very High Frequency

Parametric resonance and amplification are important in both fundamental physics and technological applications. Here we report very high frequency (VHF) parametric resonators and mechanical-domain amplifiers based on nanoelectromechanical systems (NEMS). Compound mechanical nanostructures patterned by multilayer, top-down nanofabrication are read out by a novel scheme that parametrically modulates longitudinal stress in doubly clamped beam NEMS resonators. Parametric pumping and signal amplification are demonstrated for VHF resonators up to ~ 130 MHz and provide useful enhancement of both resonance signal amplitude and quality factor. We find that Joule heating and reduced thermal conductance in these nanostructures ultimately impose an upper limit to device performance. We develop a theoretical model to account for both the parametric response and nonequilibrium thermal transport in these composite nanostructures. The results closely conform to our experimental observations, elucidate the frequency and threshold-voltage scaling in parametric VHF NEMS resonators and sensors, and establish the ultimate sensitivity limits of this approach

The proposed flatland radar

A flexible very high frequency (VHF) stratosphere-troposphere (ST) radar configured for meteorological research is to be constructed near Urbana, Illinois. Measurement of small vertical velocities associated with synoptic-scale meteorology can be performed. A large Doppler microwave radar (CHILL) is located a few km from the site of the proposed ST radar. Since the microwave radar can measure the location and velocity of hydrometeors and the VHF ST radar can measure clear (or cloudy) air velocities, simultaneous observations by these two radars of stratiform or convective weather systems would provide valuable meteorological information

Vertical transport in the atmosphere: Measurement capabilities and requirements of VHF radars, part 1.6A

Mass exchange, mixing on transport in the atmosphere involves reversible processes, i.e., any kind of organized motions such as wave and large scale flows, and nonreversible processes, i.e., molecular and turbulent diffusion. Without evaluating in detail the relative efficiency of these processes, an attempt is made to summarize those phenomena which can be qualitatively (and eventually also quantitatively) observed with VHF radars. Only mixing in the vertical direction is considered, since this appears to be the essential part of transport processes to which VHF radars can contribute better understanding. Mixing processes in the troposphere are discussed. Possible contributions of VHF radars to the study the mass exchange processes between the troposphere and stratosphere are studied. Transport in the middle atmosphere is briefly summarized, since it is in principle similar to transport in the lower atmosphere