NOTICEThis report was prepared as an account of vork sponsored by the United States Government. Neither the United States nor the United States Deyartment of Energy, nor any of their employees, aor a q of their contractors, subcontractors, or their employees, makes any warranty, e-rpress or implied, or assumes any legal liaSility or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disciosed, or represents that its use would not infringe privately owned zights. FOREWORDThis report was prepared under Contract No. SUMMARYThe optical analysis of a solar concentrator is usually carried out by means of computer ray tracing, a microscopic method that provides an enormous amount of detailed information but obscures functional relationships. This paper describes a macroscopic approach that yields all the parameters needed for the optical design of line focus parabolic troughs in closed analytical form, requiring only minimal computation.The goal of the optical analysis developed in this report is to determine the flux a t the receiver as a function of concentrator configuration, receiver size, width of sun, and optical errors (e.g., tracking, reflector contour). All causes of image spreading are quantified as angular standard deviation. Ray tracing with a real reflector and a real sun is shown to be equivalent to convoluting the angular acceptance function of a perfect concentrator with an effective radiation source. This effective source, in turn, is obtained by convoluting the distribution function of optical errors with the angular profile of the sun. The problem is reduced to two dimensions by projecting the threedimensional motion of the sun on the plane normal to the tracking axis. In this frame the apparent width of the sun increases as l/cos 8 with incidence angle 8.A formula is derived for the optimal geometric concentration ratio, maximizing net power output as a function of all relevant variables (all-day average insolation, optical errors, effective transmittance-absorptance, heat loss, and concentrator configuration). Graphical solution of this equation consists of finding the intersection between a universal curve and a straight line representing a critical intensity ratio.In the last section, which is written as a self-contained users guide, the results are summarized and illustrated by specific examples. LIST OF FIGURES NOMENCLATUREThe optimization procedure proposed in this paper is based on typical all-day average values of insolation. All-day averages are designated by angular brackets < >* A subscript tc under the bracket indicates that the average is taken over an operating period from tc hours before until tc hours after solar noon. Subscripts I I and i designate angular variables measured parallel or transverse to the tracking axis.%un ( ' ) Angular profile of sun (w/m2 rad) for line focus geometryEffective source (W/m rad) = convolution of solar profile BSun(8) and distribution

On May 3, 2004, NIST conducted a workshop to identify information needs for emergency responders during building emergencies. The workshop brought together emergency responders with the goals of sharing the vision of how the availability of building information can impact emergency response, and to gain from attendees guidance on what specific building information would be of greatest benefit to public safety officials, as well as how best to present it, and with what security measures. Prior to the workshop, NIST prepared a draft white paper detailing information needs of first responders at different times for different emergencies. During the workshop, the draft white paper served as a starting point for discussion with fire, police, and emergency medical responders. Based on workshop input, the white paper was both confirmed and extended. The revised paper is incorporated into this report.

This paper describes initial research using the Virtual Reality Modeling Language (VRML97) in construction industry applications. The modeling of steel structures and construction equipment as objects for inclusion in construction-site world models was studied. The ultimate goal is to provide three-dimensional web-based technologies for managing, accessing, and viewing construction project information.

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The Building Tactical Information project begins the process of developing technology and standards to realize the vision of making real-time building information accessible to emergency responders to enable safer and more efficient emergency response. This project addresses both the information needs of the fire, police and emergency medical services and the technology needed for moving building data out to emergency responders. A workshop was held to gather information on first responders' building information needs, and presentation standards have been examined based on emergency responder needs while enroute to an incident and on-scene. A technology data path is proposed that will allow information collection and transport to the emergency responder. A security analysis addresses the security concerns of the information transfer. A demonstration of the technology, with a decision support system transmitting real-time building information to first responders, was held at NIST and forms the basis for a documentary video.