A compact dual-polarized 8.51-GHz rectenna for high-voltage (50 V)actuator applications

This paper describes a dual-polarized rectenna capable of producing a 50-V output voltage that can be used for driving mechanical actuators. This study demonstrates a circuit topology that allows the output of multiple rectenna elements to be combined in order to step up the output voltage. In this paper, an independent rectifying circuit is used for each of two orthogonal polarizations. By proper combination, the output voltage is doubled over that of the single polarization case. Such panels are being explored for use on the next-generation space telescope to eliminate wiring between actuators and provide for true mechanical isolation     

Using Hands‐On Design Challenges in a Product Development Master's Degree Program

A design challenge has been developed as the first experience in a new Master's degree program in product development, offered by a consortium of schools: the Massachusetts Institute of Technology, the Rochester Institute of Technology, and the University of Detroit Mercy. The program admits experienced technical specialists who have been identified by their employers as future leaders of product development. The program begins with a brief, intense design challenge that exposes the students to a multi‐disciplinary problem and initiates reflection on systems architecture and organizational processes. The unique requirements of hands‐on design challenges for graduate education in product development are discussed from a constructionist viewpoint. Implementation details of the design challenge are presented and the results from the first two years are analyzed. Students in the program rate the design challenge as a very good introduction to the program and agree that the exercise provides material for discussion of system architecture and organizational processes.     

Mispredicting and misremembering: Patients with renal failure overestimate improvements in quality of life after a kidney transplant.

Objective: People tend to overestimate the impact that future events will have on their quality of life. In the case of a medical treatment like kidney transplant, this should result in biased predictions--overestimates of how much the transplant will benefit quality of life. The authors surveyed kidney transplant patients, both before and after transplant, to test whether they would overestimate the benefits of a successful transplant for their quality of life. Design: The authors interviewed 307 patients on a waiting list for cadaveric renal or renal-pancreatic transplant, and 195 patients one year after a successful transplant. A sub sample of patients were interviewed both before and after transplant. Main Outcome Measures: The survey included measures of quality of life, both in terms of an overall estimate (0-100), and across sub domains, including health, employment, and travel. Results: Cross-sectional results suggested that overall quality of life improved after transplant, but the predictions of pretransplant patients overestimated the magnitude of the improvement (p     

Performance of waveguide-based two-dimensional photonic-crystalmirrors studied with Fabry-Perot resonators

As a step toward the use of photonic crystals in optoelectronic devices, we present a thorough study of 2-D photonic-crystal mirrors etched into a GaAs-AlGaAs planar waveguide. Fabry-Perot resonators are fabricated to deduce the reflectivity, transmission, losses, as well as the penetration lengths of these mirrors. The guided photoluminescence of InAs quantum dots embedded in GaAs is used to obtain the transmission spectra of these cavities. The varying thickness between the mirrors allows a scan across the whole bandgap spectral range. Quality factors (up to 200) and peak transmissions (up to 0.3) are measured showing that mirrors of four rows of holes have 88% reflectivity, 6% transmission and 6% losses. Losses are also related to a two-dimensional transfer matrix method calculation including a recently introduced scheme to account for losses     

The CLAS forward electromagnetic calorimeter

The CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab utilizes six iron-free superconducting coils to provide an approximately toroidal magnetic field. The six sectors are instrumented individually to form six independent spectrometers. The forward region (8°<θ<45°) of each sector is equipped with a lead–scintillator electromagnetic sampling calorimeter (EC), 16 radiation lengths thick, using a novel triangular geometry with stereo readout. With its good energy and position resolution, the EC is used to provide the primary electron trigger for CLAS. It is also used to reject pions, reconstruct π° and η decays and detect neutrons. This paper treats the design, construction and performance of the calorimeter.     

Planning for Civil Engineering Applications of Information Technology

Providers of civil engineering infrastructure face increasing pressure to apply information technology. Unfortunately, technology's rapid evolution renders it easy to acquire expensive equipment that quickly becomes obsolete. In response, this paper outlines a systems analysis planning approach that focuses on the long-term goals of engineering managers. Using the case study method, the strengths and weaknesses of a relatively new technology, the World Wide Web, are mapped to the goals of a key civil infrastructure user, a transit provider. Six strategic areas are identified where the Web can have a high impact on the delivery of transit services: attracting greater advertising revenue, improving the image of the service, improving services for existing patrons, attracting other market segments, educating customers, and facilitating electronic commerce. The value of this goal-oriented planning application is that uncommon but practical transit initiatives are identified, several of which would have been undiscovered had a more traditional technology-oriented approach been employed. The significance of this approach is that one makes better investments rather than simply better justifications for existing projects.     

Hysteresis and Related Error Mechanisms in the NIST Watt Balance Experiment

The NIST watt balance experiment is being completely rebuilt after its 1998 determination of the Planck constant. That measurement yielded a result with an approximately 1×10⁻⁷ relative standard uncertainty. Because the goal of the new incarnation of the experiment is a ten-fold decrease in uncertainty, it has been necessary to reexamine many sources of systematic error. Hysteresis effects account for a substantial portion of the projected uncertainty budget. They arise from mechanical, magnetic, and thermal sources. The new experiment incorporates several improvements in the apparatus to address these issues, including stiffer components for transferring the mass standard on and off the balance, better servo control of the balance, better pivot materials, and the incorporation of erasing techniques into the mass transfer servo system. We have carried out a series of tests of hysteresis sources on a separate system, and apply their results to the watt apparatus. The studies presented here suggest that our improvements can be expected to reduce hysteresis signals by at least a factor of 10—perhaps as much as a factor of 50—over the 1998 experiment.     

THE MANUFACTURE AND PHYSICAL PROPERTIES OF DRY PRESS BRICK

The process of manufacture of dry press brick is described and physical differences between dry press and stiff mud brick are enumerated. The advantages of the dry press process are summed up as follows: (1) they are uniform in size and shape; (2) they have small spalling loss; (3) they have good fusion resistance; (4) their heat conductivity is less than brick made by other processes; and (5) they have a low rate of manufacturing costs.