Path planning among movable obstacles is a practical problem that is in need of a solution. In this paper an efficient heuristic algorithm that uses a generate-and-test paradigm: a good'' candidate path is hypothesized by a global planner and subsequently verified by a local planner. In the process of formalizing the problem, we also present a technique for modeling object interactions through contact. Our algorithm has been tested on a variety of examples, and was able to generate solutions within 10 seconds. 5 figs., 27 refs.

In order to understand the coupling of a charged particle beam to modes in induction cells with gap width -- to -- beampipe radius ratio w/b > 1, the variation of the transverse Z/Q for both axially symmetric and axially asymmetric dipole modes in this regime is investigated. It is found that the gross behavior of the axially symmetric modes when w/b > 1 is at least consistent with the approximate analysis of Briggs, although a thorough comparison has not been undertaken. The axially asymmetric modes are found to be unimportant until w/b approaches 2, and they generally exhibit lower values of Z{perpendicular}/Q than the axially symmetric modes.

Experimental work is being performed by collaborators at LLNL, SLAC, and LBL to investigate relativistic klystrons as a possible rf power source for future high-gradient accelerators. We have learned how to overcome or previously reported problem of high power rf pulse shortening and have achieved peak rf power levels of 330 MW using an 11.4-GHz high-gain tube with multiple output structures. In these experiments the rf pulse is of the same duration as the beam current pulse. In addition, experiments have been performed on two short sections of a high-gradient accelerator using the rf power from a relativistic klystron. An average accelerating gradient of 84 MV/m has been achieved with 80-MW of rf power.

Document issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, Jim Mattox, regarding a legal question submitted for clarification: Whether the Department of Mental Health and Mental Retardation is authorized to contract with the parents of mentally disabled individuals for the provision of community based mental health services (RQ-1912)

Recent studies concerning optimization parameters for e{sup +}e{sup {minus}} super linear colliders use multiple particle bunches for each rf pulse to increase the luminosity and overall efficiency. Requirements for final focusing of the beams severely restrict the bunch to bunch energy variation during the rf pulse. To accurately determine the accelerating fields and energy variation, the dispersion related transient behavior of the rf drive pulse must be considered. A numerical study of dispersion effects on several different accelerating structures is presented.

This report describes research on oil shale. Above ground retorting, process modeling, and shale oil coking kinetics over oxidized recycle shale are discussed. 13 refs., 13 figs., 12 tabs.

A linear, frequency independent model of the rf properties of unbiased, soft ferrite has been implemented in finite-difference, time-domain, electromagnetic simulation code AMOS for the purposes of studying linac induction cavities. The simple model consists of adding a magnetic conductivity term ({sigma}{sub m}H) to Faraday's Law. The value of {sigma}{sub m} that is appropriate for a given ferrite at a particular frequency is obtained via an rf reflection experiment on a very thin ferrite toroid in a shorted coaxial line. It was found that in the frequency range 100 to 1000 MHz, the required value of {sigma}{sub m} varies only slightly (<10%), and so we approximated it as a frequency independent parameter in AMOS. A description of the experimental setup and the technique used to extract the complex {mu} from the measurements is described. The model has been used to study the impedances of the DARHT induction cavity, and comparisons between these experimental measurements and AMOS calculations is presented. Implementation of a frequency dependent version of this model in AMOS is being pursued, and a discussion of this effort is given.

The combustion of chloroethane is modeled as a stirred reactor so that we can study critical emission characteristics of the reactor as a function of residence time. We examine important operating conditions such as pressure, temperature, and equivalence ratio and their influence on destructive efficiency of chloroethane. The model uses a detailed chemical kinetic mechanism that we have developed previously for C{sub 3} hydrocarbons. We have added to this mechanism the chemical kinetic mechanism for C{sub 2} chlorinated hydrocarbons developed by Senkan and coworkers. In the modeling calculations, sensitivity coefficients are determined to find which reaction-rate constants have the largest effect on destructive efficiency. 24 refs., 6 figs., 1 tab.

We have identified the Motorola 2N4014 and 2N5551 and the Raytheon RS3944 as three transistor types that exhibit avalanche characteristics and have long term collector breakdown voltage stability superior to other transistors tested. Stability on all types has been improved by power burnin. An automatic avalanche transistor burnin tester has been constructed to allow power burnin of up to 1008 transistors at a time. The tester is controlled by an IBM Personal Computer (PC) and can be programmed to acquire data, unattended, at any desired rate or period. Data are collected from each run and stored on a floppy disk in ASCII format. The data analysis software, RS/1, was used for analysis and display. Data runs were typically 3 to 4 months long, with readings taken weekly. The transistors were biased into the avalanche or Zener region by individual current sources set to about 20% of the self-avalanche current for each type of transistor. Motorola, Zetex and National transistors were operated at 100 microamperes ({mu}A), and the Raytheon units were operated at 20 {mu}A. The electric field causes migration of material in the high field region at the surface near the collector-base junction, creating the voltage instability. 7 refs., 9 …

OAK B188 Response of Tundra Ecosystems to Elevated Atmospheric CO{sub 2}. Atmospheric CO{sub 2} is expected to double by the end of the next century. Global mean increases in surface air temperature of 1.5-4.5 C are anticipated with larger increases towards the poles predicted. Changes in CO{sub 2} levels and temperature could have major impacts on ecosystem functioning, including primary productivity, species composition, plant-animal interactions, and carbon storage. Until recently, there has been little direct information on the impact of changes in CO{sub 2} and temperature on native ecosystems. The study described here was undertaken to evaluate the effects of a 50 and 100% increase in atmospheric CO{sub 2}, and a 100% increase in atmospheric CO{sub 2} coupled with a 4 C summer air temperature rise on the structure and function of an arctic tussock tundra ecosystem. The arctic contains large stores of carbon as soil organic matter, much frozen in permafrost and currently not reactive or available for oxidation and release into the atmosphere. About 10-27% of the world's terrestrial carbon occurs in arctic and boreal regions, and carbon is accumulating in these regions at the rate of 0.19 GT y{sup -1}. Mean temperature increases of 11 C and …

OAK (B204) Response of Tundra Ecosystems to Elevated Atmospheric CO{sub 2} Part 3 of 3.