Jet Propulsion Laboratory

About: Jet Propulsion Laboratory is a facility organization based out in La Cañada Flintridge, California, United States. It is known for research contribution in the topics: Mars Exploration Program & Telescope. The organization has 8801 authors who have published 14333 publications receiving 548163 citations. The organization is also known as: JPL & NASA JPL.

Monolithic Schottky-collector resonant tunnel diode oscillator arrays to 650 GHz

Abstract: We report monolithic array oscillators incorporating Schottky-collector resonant tunnel diodes (SRTD's). In the SRTD, a 0.1-/spl mu/m width Schottky collector contact provides a greatly reduced device series resistance, resulting in an estimated 2.2 THz maximum frequency of oscillation. A 64-element oscillator array oscillated at 650 GHz while a 16-element array produced 28 /spl mu/W at 290 GHz.

Quantum Technology: The Second Quantum Revolution

Abstract: We are currently in the midst of a second quantum revolution. The first quantum revolution gave us new rules that govern physical reality. The second quantum revolution will take these rules and use them to develop new technologies. In this review we discuss the principles upon which quantum technology is based and the tools required to develop it. We discuss a number of examples of research programs that could deliver quantum technologies in coming decades including; quantum information technology, quantum electromechanical systems, coherent quantum electronics, quantum optics and coherent matter technology.

Novel Horn Designs for Ultrasonic/Sonic Cleaning Welding, Soldering, Cutting and Drilling

Abstract: A variety of Industrial applications exist where power ultrasonic elements such as the ultrasonic horn are used. These included the Automotive, Instruments, Foods, Medical, Textiles and Material Joining and Fabrication Industries. In many of these devices the ultrasonic horn is the key component. The standard transducer used in these devices consists of three main parts, the backing, the piezoelectric elements and the horn. Standard horn designs have changed very little since their inception. There are four common types of standard horns. They are; constant, linear, exponential and stepped, which refer to the degree to which the area changes from the base to the tip. A magnification in the strain occurs in the horn that in general is a function of the ratio of diameters. In addition the device is generally driven at resonance to further amplify the strain. The resonance amplification is in general determined by the mechanical Q (attenuation) of the horn material and radiation damping. The horn length primarily determines the resonance frequency. For a 22 kHz resonance frequency a stepped horn of titanium has a length of approximately 8 cm. Although these standard horns are found in many current industrial designs they suffer from some key limitations. In many applications it would be useful to reduce the resonance frequency however this would require device lengths of the order of fractions of meters which may be impractical. In addition, manufacturing a horn requires the turning down of the stock material (eg. Titanium) from the larger outer diameter to the horn tip diameter, which is both time consuming and wasteful. In this paper we will present a variety of novel horn designs, which overcome some of the limitations discussed above. One particular design that has been found to overcome these limitations is the folded horn. In this design the horn elements are folded which reduce the overall length of the resonator (physical length) but maintain or increase the acoustic length. In addition initial experiments indicate that the tip displacement can be further adjusted by phasing the bending displacements and the extensional displacements. The experimental results for a variety of these and other novel horn designs will be presented and compared to the results predicted by theory.

Cracking the MJO nut

Abstract: [1] The Madden-Julian oscillation poses great challenges to our understanding and prediction of tropical convection and the large-scale circulation. Several internationally coordinated activities were recently formed to meet the challenges from the perspectives of numerical simulations, prediction, diagnostics, and virtual and actual field campaigns. This article provides a brief description of these activities and their connections, with the motivation in part to encourage the next generation of physical scientists to help solve the grand challenging problem of the Madden-Julian oscillation.

Low simulated radiation limit for runaway greenhouse climates

Abstract: Terrestrial planet atmospheres must be in long-term radiation balance, with solar radiation absorbed matched by thermal radiation emitted. For hot moist atmospheres, however, there is an upper limit on the thermal emission which is decoupled from the surface temperature. If net absorbed solar radiation exceeds this limit the planet will heat uncontrollably, the so-called \runaway greenhouse". Here we show that a runaway greenhouse induced steam atmosphere may be a stable state for a planet with the same amount of incident solar radiation as Earth has today, contrary to previous results. We have calculated the clear-sky radiation limits at line-by-line spectral resolution for the first time. The thermal radiation limit is lower than previously reported (282 W/sq m rather than 310W/sq m) and much more solar radiation would be absorbed (294W/sq m rather than 222W/sq m). Avoiding a runaway greenhouse under the present solar constant requires that the atmosphere is subsaturated with water, and that cloud albedo forcing exceeds cloud greenhouse forcing. Greenhouse warming could in theory trigger a runaway greenhouse but palaeoclimate comparisons suggest that foreseeable increases in greenhouse gases will be insufficient to do this.