|Vcb|, |Vub|, and Hqet at Cleo

I report results from the CLEO collaboration on semileptonic B decays, highlighting measurements of the Cabibbo-Kobayashi-Maskawa matrix elements Vcb and Vub. I describe the techniques used to obtain the recent improvements in precision for these measurements, including the use of the b -> s gamma photon spectrum to reduce hadronic uncertainties in semileptonic B decays. I also report new measurements of Vcb using the inclusive semileptonic branching fraction BF(B -> X e nu) and of Vub through study of the q^2 dependence of B -> pi l nu and B -> rho l nu.Comment: 3 pages, 3 figures, uses svjour.cls, submitted to Proceedings of EPS 200

The grid array antenna

Attention is called to the grid array as a possible useful antenna design for UHF clear air radars. This type of antenna integrates radiating elements and the feed network into a single structure so that a fairly large array can be driven from a single feed point. Figures are given which demonstrate the basic principle of the grid array, which are adapted from Conti et al. (1981). Conductors are arranged above a ground plane in a repeating, staggered array of connected rectangles. Each rectangular element is approximately one by one-half wavelength in size. The currents on the conductors at resonance is indicated. The grid array illustrated can be expanded in both vertical and horizontal directions about the feed point by adding additional rectangular conductors. The design eliminates the feed network and would provide a thin, panel-like antenna that could be easily built and transported

Design considerations for high-power VHF radar transceivers: Phase matching long coaxial cables using a cable radar

The Poker Flat 49.92-MHz MST radar uses 64 phase-controlled transmitters in individual shelters distributed throughout the antenna array. Phase control is accomplished by sampling the transmitted pulse at the directional coupler of each transmitter and sending the sample pulse back to a phase-control unit. This method requires phase matching 64 long (256 meter) coaxial cables (RG-213) to within several electrical degrees. Tests with a time domain reflectometer showed that attenuation of high frequency components in the long RG-213 cable rounded the leading edge of the reflected pulse so that the cables could only be measured to within 50 cm (about 45 deg at 49.92 MHz). Another measurement technique using a vector voltmeter to compare forward and reflected phase required a directional coupler with unattainable directivity. Several other techniques were also found lacking, primarily because of loss in the long RG-213 cables. At this point it was realized that what was needed was a simple version of the phase-coherent clear-air radar, i.e., a cable radar. The design and operation of this cable are described

Design considerations for high-power VHF radar transceivers: Distributed versus single large transmitter

The factors which enter into the choice of using a single large transmitter versus a number of smaller units in clear-air radar systems are examined. Feedline economics, ease of repair and spare part costs, operating strategy, vulnerability to catastrophic failure, and phase control requirements are considered

Low-altitude coverage of ST radars

Clear air ST (stratosphere troposphere) radars are now widely used for atmospheric research and wind profiling. Most attention to date has been directed toward extending the altitude coverage as high as possible. It is also desirable to extend the coverage as low as possible. Any improvement in the low altitude coverage of existing wind profiling radars would be useful. The approximate lower limits of some existing ST radars are listed and what set these limits are briefly examined

Recent CLEO CKM Results

I report B physics results from the CLEO collaboration, highlighting measurements of the Cabibbo-Kobayashi-Maskawa matrix elements |Vcb| and |Vub|. I report a recent measurement of |Vub| through study of the q^2 dependence of B -> pi l nu and B -> rho l nu. I also describe new measurements of the inclusive semileptonic branching fraction BF(B -> X e nu) and of moments of the hadronic invariant mass spectrum in B -> X l nu, with impact on |Vcb|.Comment: 5 pages, 4 figures, submitted to Proceedings of Beauty 200

Review of specific antenna configurations: An estimate of cost and performance versus frequency for a simple (10 Lambda)-2 clear-air radar antenna array

The building of operational clear air radar wind profilers is discussed. The choice of operating frequency and antenna configuration for these profilers is examined. The cost and performance of a (10 lambda) 2 antenna array versus operating frequency over the range 30 to 400 MHz is compared. To simplify the comparison the array beam will be fixed and the array will be uniformly fed. Yagi and coaxial collinear (COCO) cable antennas are compared, although other configurations may be competitive. It is assumed that the array is driven by a typical 50 kW peak power, 1 kW average, power transmitter located at the array edge when calculating feedline power handling requirements and when system performance is compared. For this comparison an array aperture of (10 lambda) 2 was chosen since a one way beam width of 5 deg or less is desirable to limit beam spreading effects

The NOAA TOGA antenna array

The Aeronomy Laboratory recently installed a 100 x 100 meter array antenna with limited beam steering on Christmas Island as a part of the TOGA (Tropical Ocean and Global Atmosphere) program. The array and the associated beam steering and indicating hardware are described

The Scholarly Conversation Project

This is a project assignment. Learning objective: Students will understand how serial publications are presented in databases and how to read them chronologically