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Software for Replicating Data Between X.500 and LDAP Directories

X500/LDAP Directory Replication Utility is a computer program for replicating information between X.500 and LDAP directories. [X.500 is an international standard for on-line directory services. LDAP (Lightweight Directory Access Protocol) is a simple directory access protocol.] The utility can be used to replicate an object of any type from X.500 to LDAP or from LDAP to X.500. The program uses the LDAP version 2 protocol, which is capable of working with both X.500 and LDAP directories. The program can provide any or all of the following services: (1) replicate only modified objects; (2) force replication of all objects; (3) replicate individual objects, one level of objects, or a subtree of objects; (4) filter sets of objects to select ones to be replicated; (5) remove and/or modify object classes from objects that are replicated; and (6) select and/or limit attributes that are replicated. The program includes a separate program that is used to remove objects that are no longer required to be replicated.

Posted in: Software, Briefs

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Software Computes Tape-Casting Parameters

Tcast2 is a FORTRAN computer program that accelerates the setup of a process in which a slurry containing metal particles and a polymeric binder is cast, to a thickness regulated by a doctor blade, onto fibers wound on a rotating drum to make a “green” precursor of a metal-matrix/fiber composite tape. Before Tcast2, setup parameters were determined by trial and error in time-consuming multiple iterations of the process. In Tcast2, the fiber architecture in the final composite is expressed in terms of the lateral distance between fibers and the thickness-wise distance between fibers in adjacent plies. The lateral distance is controlled via the manner of winding. The interply spacing is controlled via the characteristics of the slurry and the doctor- blade height. When a new combination of fibers and slurry is first cast and dried to a green tape, the shrinkage from the wet to the green condition and a few other key parameters of the green tape are measured. These parameters are provided as input to Tcast2, which uses them to compute the doctor-blade height and fiber spacings needed to obtain the desired fiber architecture and fiber volume fraction in the final composite.

Posted in: Software, Briefs

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Software for Tracking Costs of Mars Projects

The Mars Cost Tracking Model is a computer program that administers a system set up for tracking the costs of future NASA projects that pertain to Mars. Previously, no such tracking system existed, and documentation was written in a variety of formats and scattered in various places. It was difficult to justify costs or even track the history of costs of a spacecraft mission to Mars. The present software enables users to maintain all cost-model definitions, documentation, and justifications of cost estimates in one computer system that is accessible via the Internet. The software provides sign-off safeguards to ensure the reliability of information entered into the system. This system may eventually be used to track the costs of projects other than only those that pertain to Mars.

Posted in: Software, Briefs

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Improved Piezoelectrically Actuated Microvalve

The improvements are intended to ensure less leakage and true normally-closed operation. Figure 1. The Previous Version of the Valve, like the present version, was opened by applying a voltage that caused the piezoelectric actuator to contract slightly.Efforts are underway to implement an improved design of the device described in “Normally Closed, Piezoelectrically Actuated Microvalve” (NPO-20782), NASA Tech Briefs, Vol. 25, No. 1 (January 2001), page 39. To recapitulate: This valve is being developed as a prototype of valves in microfluidic systems and other microelectromechanical systems (MEMS). The version of the valve reported in the cited previous article (see Figure 1) included a base (which contained a seat, an inlet, and an outlet), a diaphragm, and an actuator. With the exception of the actuator, the parts were micromachined from silicon. The actuator consisted of a stack of piezoelectric disks in a rigid housing. To make the diaphragm apply a large sealing force on the inlet and outlet, the piezoelectric stack was compressed into a slightly contracted condition during assembly of the valve. Application of a voltage across the stack caused the stack to contract into an even more compressed condition, lifting the diaphragm away from the seat, thereby creating a narrow channel between the inlet and outlet.

Posted in: Mechanics, Mechanical Components, Briefs

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Using Laser Diodes to Characterize Force and Pressure Sensors

A proposed method of characterizing microphones and other pressure and force sensors would exploit the temporally varying forces of impingement of amplitude-modulated light beams from inexpensive laser diodes. What makes the method likely to be practical is the surprising fact that these forces, albeit small, are nevertheless large enough to enable quantification of the noise floors, sensitivities, and frequency responses of many modern pressure sensors. The time-averaged force of impingement of a pulsed beam of light on a surface is given by F = SDP/c, where S ranges from 1 for a totally absorptive (black) to 2 for a perfectly reflective surface, D is the pulse duty cycle, P is the peak power of the beam, and c is the speed of light. Hence, if one knows S, D, and P, it may be possible to determine the absolute sensitivity of the sensor. Even if one does not know one or more of these parameters, it should be possible to determine the relative sensitivities of different sensors by measuring their responses to the same modulated beam, or to determine the relative frequency response of a given sensor by measuring its output while sweeping the modulation frequency.

Posted in: Physical Sciences, Briefs

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Tiger Fibers for Enhanced Optical Sensing of Volatiles

Striped polymer coats on optical fibers would induce gratings upon exposure to analytes. Improved fiber-optic transducers, denoted tiger fibers, have been proposed for sensing volatile compounds. Tiger fibers are so named because, as described below, their sensitive portions would be coated with periodically alternating stripes of different polymers, reminiscent of a tiger’s stripes.

Posted in: Physical Sciences, Briefs

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National Nano Engineering Conference

NASA Tech Briefs' 2007 National Nano Engineering Conference (NNEC), November 14-15 at the Marriott Boston Copley Place, is the premier event focused on current and future developments in engineering innovations at the nanoscale, as well as the commercialization of nanotechnology. The event also includes the presentation of the third annual Nano 50® Awards.

Posted in: Blog

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