Search

The U.S. Department of Energy has established an unmanned aerospace vehicle (UAV) measurement program. The purpose of this paper is to describe the evolution of the program since its inception, review the progress of the program, summarize the measurement capabilities developed under the program, illustrate key results from the various UAV campaigns carried out to date, and provide a sense of the future direction of the program. The Atmospheric Radiation Measurement (ARM)–UAV program has demonstrated how measurements from unmanned aircraft platforms operating under the various constraints imposed by different science experiments can contribute to our understanding of cloud and radiative processes. The program was first introduced in 1991 and has evolved in the form of four phases of activity each culminating in one or more flight campaigns. A total of 8 flight campaigns produced over 140 h of science flights using three different UAV platforms. The UAV platforms and their capabilities are describ...

New techniques for extruding aluminum directly over paper insulated cable core at low temperature and pressure are described. Pistons operate from opposite ends of a cylinder to force the aluminum through a circular orifice between a die and core-tube located on an axis perpendicular to that of the pistons and midway between them. The inter-relation of extrusion temperature, pressure and rate, as well as the quality of the sheath produced, are found to be dependent on the die and core-tube design. Special lubrication and press charging techniques are discussed.

THE seriousness of the present tin scarcity has stimulated large consumers of this vital metal to develop drastic conservation measures in order to extend the available supplies to cover the emergency period. By devising new soldering methods and alloys the Bell System has contributed a substantial share in the tin conservation effort. Fortunately, the changes, as far as can now be determined, have not introduced weakness into the soldered joints. Some of the new procedures now used were already in the process of development at the onset of the emergency, while others were devised under its stress. In some instances, the newly developed solders were found to be more difficult to use than the alloys previously available, and would not have been introduced under normal conditions. One major change made that previously had been under consideration will result in large tin savings. Unless service difficulties are encountered, this modification gives promise to remain after the emergency has passed. The change involves a reduction in the amount of solder placed on a wiped joint between the cable sheath and the sleeve. Instead of the customary full size wiped joint a wipe of fillet proportions is formed. Through this change, a solder saving of over 60% per joint can be realized.

SOME fourteen or more wiped joints occur in every mile of lead-sheathed telephone cable, and in making these joints from one to two million pounds of solder are used per year. To join cables a lead sleeve of sufficient diameter to accommodate the bundle of spliced wires is slid in place at the junction, the ends of the sleeve are beaten to conform to the circumference of the cable, and an air-tight and mechanically strong joint formed at each end of the sleeve by molding a solidifying mass of solder into the desired shape. This last step is called the wiping operation.

This paper presents results of experiments to measure the current extracted through the foil of an electron beam diode by observing the heating of the foil. Generally anode current density is measured with a dosimeter film, often of dubious linearity, or with Faraday cups which give a current density versus time map at isolated points or with an array of calorimeters. For the present measurements a fast scanning infrared camera is used to measure the temperature rise of the foil after a pulse. The measurement takes 600 ?s for a single line scan or 16 ms for a full raster scan. Resolution is comparable to that of dosimeter film, the IR camera is easily calibrated to produce accurate temperature plots, and because of the fast scan this system is ideally suited to observing small scale structure in the beam current density for repetitive pulses up to several hundred Hertz pulse repetition rates.

Recent investigations, conducted at the Bell Telephone Laboratories and elsewhere, have demonstrated that the lead-antimony alloys almost universally employed in storage cell construction are far from ideal for the purpose from the elect rochemical standpoint. It has been shown that in the course of normal operation of the present type cell, antimony is leached out of the positive electrode, passes through the solution and deposits on the negative. where it promotes “localaction” and self-discharge. Also, it has been demonst rated that stibine is generated in perce ptible amounts by the present type battery on over-charge.

Commercially available mechanical, video, and electronic high-speed imaging systems are compared as part of an attempt to answer the question, will electronic cameras replace film cameras for high-speed recording? Of special interest is the relationship between spatial resolution and frame rate. Equally important is the compatibility of the imaging systems for recording different types of experiments and tests. The resolution of a number of systems that represent various classes of framing cameras has been compared at their maximum framing rate. Included are several classes of mechanically advanced framing cameras, electronic streak cameras operated in a framing mode, and high-speed video systems. Likewise, the resolution of various classes of streak and image motion cameras has been compared at their maximum temporal resolution. The results: at frame rates up to 25 Mf/s, mechanical cameras can record from 10 to 100 times more data per frame and several times as many frames per run as existing electronic cameras, and from 100 to 1000 times more data per frame than existing video cameras. Video systems are limited in resolution and speed but provide instant access to data. Electronic cameras provide faster frame and streak rates than mechanical cameras (up to 600 Mf/s) but are limited in resolution. Neither of these "electronic" technologies is expected to replace mechanical technologies for frame rates up to a few million frames per second. Future development of new electronic technologies using CCD arrays, however, may result in devices that are more competitive with conventional film techniques.

Five bleaching techniques for Agfa Gevaert Scientia 10E75 high-resolution plates were evaluated to determine resultant diffraction efficiency and SNR for identically recorded single-exposure holograms. We determined the optimum recording conditions for both single- and multiple-exposure bleached holograms using a cupric bromide bleach, judged to be the "best bleach." Data are presented for diffraction efficiency, SNR, and resolution of diffuse and focused-image holograms for both single- and multiple-exposure holograms, using a 1951 Air Force resolution chart as the object. Bleaching improved the diffraction efficiency of both types of holograms by up to 3 orders of magnitude. The SNR of diffuse holograms is degraded by bleaching, but that of the focused-image holograms is improved, while the resolution of both types is not affected by bleaching. Bleached multiple-exposure holograms are similar in response to single-exposure holograms except that their diffraction efficiencies are lower. The diffraction efficiency of bleached holograms decreases with age.

The holographic characteristics of Agfa-Gevaert Scientia 10E75 have been examined for multiple exposures. They include not only diffraction efficiency, but SNR and resolution as functions of number of exposures, time of development, and/or input modulation (rho'). The maximum diffraction efficiency, occurring at a density of 0.7, was observed to increase with increasing development time and decrease as the number of exposures increased. An approximately 10% decrease in maximum diffraction efficiency was observed for each successive reconstructed image of a multiple exposure hologram. Reconstructed noise was found to be fairly well represented by grain-noise considerations only for the region 0.1rho'0.4. Elsewhere noise is considerably different from grain-noise predictions. The SNR, at a density of 0.7, was observed to increase from 50 to 85 as the number of exposures increased from one to four. For postexposure or preexposure holograms the maximum signal-to-noise and resolution peaked near an input moduation of 0.4.

Two reprocessing techniques have been investigated that are capable of correcting the effects of nonoptimum optical density of photographic amplitude holograms recorded on Agfa-Gevaert type 10E75 plates. In some cases a reprocessed hologram will exhibit a diffraction efficiency even higher than that obtainable from a hologram exposed and processed to the optimum density. The SNR of the reprocessed holograms is much higher than that of the same holograms bleached with cupric bromide. In some cases the SNR approaches the optimum value for a properly exposed amplitude hologram. Subjective image quality and resolution of reprocessed hologram reconstructions appear to be no different than for normal single-development holograms. Repeated reprocessing is feasible and in some cases desirable as a means of increasing diffraction efficiency.