Physical Sciences and Mathematics Commons^™

Single- And Double-Ionization Cross Sections For Angular Scattering Of Fast Protons By Helium, R. (Ronald) E. Olson, J. Ullrich, R. Dörner, H. Schmidt-Böcking

Physics Faculty Research & Creative Works

The angular scattering of H⁺ by He has been investigated for single ionization at energies of 0.5, 1.0, and 3.0 MeV; and for double ionization at 1.0 MeV. The classical-trajectory Monte Carlo method has been used within one- and two-electron models to illustrate the collision dynamics. The angular differential single-ionization cross sections are in good agreement with experiment and display the combined effects of proton scattering from the He nucleus and its electrons. The relative fraction of double ionization, as a function of scattering angle, shows a maximum at 0.9 mrad that is in agreement with the experiments of …

Classical Two-Center Effects In Ejected-Electron Spectra From P+, P-, And He2++He Collisions At Intermediate Energies, C. O. Reinhold, Ronald E. Olson

Physics Faculty Research & Creative Works

Doubly and singly differential cross sections for electron emission have been calculated by means of the classical trajectory Monte Carlo method for the p⁺, p-, and He²⁺+He systems at impact energies of 50 and 100 keV/amu. The calculations for the p⁺ and He²⁺+He systems exhibit the capture to the continuum peak and agree in both shape and magnitude with experimental data. Analysis of the classical trajectories has helped to understand the dynamical formation of this peak. The dependence of the cross sections on the projectile charge (-1, +1, and +2) is analyzed and …

Measured Spectra Of The Hygroscopic Fraction Of Atmospheric Aerosol Particles, Darryl J. Alofs, Donald E. Hagen, Max B. Trueblood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Relation between Dry Diameter (Xo) and Critical Supersaturation (Sc) for Atmospheric Submicron Aerosol Particles is Investigated. the Particles Are Passed through an Electrostatic Aerosol Size Classifier, and Then through an Isothermal Haze Chamber. Results Are Reported in Terms of an Apparent Volume Fraction of Soluble Material, Εv, Defined Such that for Particles Composed Only of Ammonium Sulfate and Water Insoluble Compounds, Εv is the Actual Volume Fraction of Soluble Material. the Probability Distribution of Εv is Found to Be Approximately Gaussian in the Εv Range 0.2 to 1.3. the Mean Εv is 0.5, for Electrostatic Aerosol Classifier Settings of …

Reliable Distributed Sorting Through The Application-Oriented Fault Tolerance Paradigm, Bruce M. Mcmillin, L. M. Ni

Computer Science Faculty Research & Creative Works

The design and implementation of a reliable version of the distributed bitonic sorting algorithm using the application-oriented fault tolerance paradigm on a commercial multicomputer is described. Sorting assertions in general are discussed and the bitonic sort algorithm is introduced. Faulty behavior is discussed and a fault-tolerant parallel bitonic sort developed using this paradigm is presented. The error coverage and the response of the fault-tolerant algorithm to faulty behavior are presented. Both asymptotic complexity and the results of run-time experimental measurements on an Ncube multicomputer are given. The authors demonstrate that the application-oriented fault tolerance paradigm is applicable to problems of …

Morning Increase In Onset Of Ischemic Stroke, John R. Marler, Thomas R. Price, Gregory L. Clark, James E. Muller, Thomas Robertson, Jay P. Mohr, Daniel B. Hìer, Philip A. Wolf, Louis R. Caplan, Mary A. Foulkes

Chemistry Faculty Research & Creative Works

The Time of Onset of Ischemic Stroke Was Determined for 1,167 of 1,273 Patients during the Collection of Data by Four Academic Hospital Centers between June 30, 1983, and June 30, 1986. More Strokes Occurred in Awake Patients from 10:00 Am to Noon Than during Any Other 2-Hour Interval. the Incidence of Stroke Onset Declined Steadily during the Remainder of the Day and Early Evening. the Onset of Stroke is Least Likely to Occur in the Late Evening, Before Midnight. © 1989 American Heart Association, Inc.

Determinants Of Early Recurrence Of Cerebral Infarction: The Stroke Data Bank, R. L. Sacco, M. A. Foulkes, J. P. Mohr, P. A. Wolf, D. (Daniel) B. Hier, T. R. Price

Chemistry Faculty Research & Creative Works

We Studied 1,273 Patients with Ischemic Cerebral Infarction Who Were Entered into the Stroke Data Bank, a Prospective, Observational Study Involving Four University Hospitals and the Biometry and Field Studies Branch of the National Institute of Neurological Disorders and Stroke. Forty Patients Had Non-Iatrogenic Recurrent Stroke within 30 Days after the Index Cerebral Infarction. using Life Tables, the 30-Day Cumulative± SE Risk of Early Recurrence for All Infarctions Was 3.3±0.4%. the Risk of Early Recurrence Was Greatest for Atherothrombotic Infarction (7.9±2.2%, Eight of 113 Patients) and Least for Lacunar Infarction (2.2±1.2%, Eight of 337 Patients). Both Cardioembolic Infarction (4.3±0.9%, 10 …

Predictors Of Survival In Clinically Diagnosed Alzheimer's Disease And Multi-Infarct Dementia, Daniel B. Hier, Joshua D. Warach, Philip B. Gorelick, Joseph Thomas

Chemistry Faculty Research & Creative Works

No abstract provided.

Expectations For Associative-Commutative Unification Speedups In A Multicomputer Environment, Ralph W. Wilkerson, Bruce M. Mcmillin

Computer Science Faculty Research & Creative Works

An essential element of automated deduction systems is unification algorithms which identify general substitutions and when applied to two expressions, make them identical. However, functions which are associative and commutative, such as the usual addition and multiplication functions, often arise in term rewriting systems, program verification, the theory of abstract data types and logic programming. The introduction to the associative and commutative equality axioms together with standard unification brings with it problems of termination and unreasonably large search spaces. One way around these problems is to remove the troublesome axioms from the system and to employ a unification algorithm which …

A Definition Optimization Technique Used In A Code Translation Algorithm, David M. Dejean, George Winston Zobrist

Computer Science Faculty Research & Creative Works

Data flow analysis is used to optimize variable definitions in a program that translates microprocessor object code to a higher order language. © 1989, ACM. All rights reserved.

Reversibility Of Ct And Mr Findings In Neuro-Behçet Disease, Dushyant V. Patel, Michael J. Neuman, Daniel B. Hier

Chemistry Faculty Research & Creative Works

A Woman with Neuro-Behçet Disease Characterized by Recurrent Attacks of Meningoencephalitis is Reported. during an Attack of Brain Stem Dysfunction Characterized by Dysarthria, Diplopia, and Ataxia, the Postcontrast CT Showed an Enhancing Lesion of the Upper Brain Stem. during a Subsequent Attack Characterized by Subcortical Dementia and Amnesia, Magnetic Resonance (MR) Showed Abnormal Signal Intensity in the Hypothalamus and Upper Brain Stem. Upon Remission of Her Symptoms, Follow-Up Contrast Enhanced CT and MR Were Entirely Normal. Magnetic Resonance is Especially Useful in Localizing Acute Inflammatory Lesions in Behçet Disease. This Case Suggests that Abnormal MR and CT Findings in Neuro-Behçet …

Fault Diagnosis Using First Order Logic Tools, Ralph W. Wilkerson, Barbara A. Smith

Computer Science Faculty Research & Creative Works

An automated circuit diagnostic tool implementing R. Reiter's theory of diagnosis (1987) based on deep knowledge (i.e. knowledge based on certain design information) and using first-order logic as the representation language is discussed. In this approach, the automated diagnostician uses a description of the system structure and observations describing its performance to determine if any faults are apparent. If there is evidence that the system is faulty, the diagnostician uses the system description and observations to ascertain which component(s) would explain the behavior. In particular, Reiter's method finds all combinations of components which explain this behavior.

Large-Angle Scattering In Positron-Helium And Positron-Krypton Collisions, D. R. Schultz, C. O. Reinhold, Ronald E. Olson

Physics Faculty Research & Creative Works

We have calculated differential cross sections as a function of the projectile scattering angle for positron-helium and positron-krypton collisions using the classical-trajectory Monte Carlo technique. These intermediate- velocity collisions have been simulated by various independent-electron and n-electron models, using both screened Coulomb and quantum model potentials to approximate the effects of electron-electron interactions. These several models all indicate that scattering of positrons to large angles in ionizing collisions persists to high impact velocities. In a previous work [Phys. Rev. A 38, 1866 (1988)] we proposed that the recent experiments that have measured the total cross section for positronium formation could …

Personal Computing For The Visually Impaired, Bruce M. Mcmillin, P. Y. Mcmillin

Computer Science Faculty Research & Creative Works

The problem of providing feedback from the computer to a visually impaired user is examined. The use of traditional tactile input and output (Braille) is described. The limitations of voice output are discussed, and difficulties posed by complicated screen formats and screen review are considered.

Plasma Polymerization By Magnetron Glow Discharge. I. Effect Of Magnetic Field On Breakdown Of Monomers In Low Pressure, K. Sato, Y. Iriyama, D. L. Cho, H. Yasuda

Chemistry Faculty Research & Creative Works

The breakdown voltage Vb of glow discharge of an organic monomer generally decreases as the system pressure decreases; however, below a certain threshold pressure, the breakdown voltage increases with decreasing system pressure. In the pressure range below 100 mTorr, the breakdown voltage generally increases as a linear function of 1 /p, where p is the system pressure of the reactor. In this region, glow discharge without magnetic enhancement often yields unstable discharge, which is associated with a very steep slope of a line in the Vh vs /p plot. The similar plots for glow discharges of non-polymer-forming gases, such as …

Exciton Diffusion At Finite Frequency: Luminescence Observables For Anisotropic Percolating Solids, Paul Ernest Parris

Physics Faculty Research & Creative Works

A study is made of the luminescence intensities associated with exciton diffusion and trapping on a three-dimensional anisotropic percolating lattice. The calculation is based upon a relationship that exists between the frequency dependent diffusion tensor at frequencies comparable to the inverse excitation lifetime, and luminescence observables such as the host and trap luminescence intensities for conditions of constant illumination. The present approach allows the study of crossover behavior in percolative systems that are of intermediate transport dimensionality 2 < d_t < 3. Our results suggest that curvature seen in luminescence observables near the transition need not always be a direct reflection of the critical indices associated with classical isotropic percolation. We have identified three possible sources of deviation from the classical behavior: (1) the radiative time scale of the luminescence measurements, (2) the functional dependence of the luminescence yields on the diffusion tensor, and (3) the demands of dimensional crossover in the critical region arising from the anisotropy of the medium.

Impedance Controlled Connector Interface, Stephen L. Clark

Mathematics and Statistics Faculty Research & Creative Works

A connector interface for electrically mating a multi-row connector with a printed circuit board is defined by a flex circuit in the form of laminated polyimide layers having conductive traces for each interconnect pair with connection fields at the opposite ends of the traces for electrical connection to the terminal pins on the connector and the conductive pads or pins on the circuit board. The conductive traces are all of equal length to provide equal resistance and impedance paths for each of the circuit interconnects.

Polymerization Of Methane, Ashok K. Sharma, H. Yasuda

Chemistry Faculty Research & Creative Works

Plasma polymerization of methane in a magnetically enhanced capacitively coupled bell jar reactor operating at a frequency of 10 kHz is reported. Dependence of polymer deposition rate on monomer feed rate (F), composite power parameter (W/FM), electrode temperature, and electrode cleanliness have been examined. Such functional properties as wettability, adhesion, and thermal stability of the polymer are found to depend on the composite power parameter (W/FM) of the plasma. The permeability studies indicate highly crosslinked nature of the polymer. ESCA studies reveal code position of electrode material with the polymer under high W/FM conditions, potential applications of plasma polymer of …

Strong Continuum-Continuum Couplings In The Direct Ionization Of Ar And He Atoms By 6-Mev/U U38+ And Th38+ Projectiles, D. Schneider, D. Dewitt, A. S. Schlachter, Ronald E. Olson, W. G. Graham, J. R. Mowat, R. (Robert) D. Dubois, D. H. Loyd, V. Montemayor, G. Schiwietz

Physics Faculty Research & Creative Works

Doubly differential cross sections have been measured as a function of the electron energy and observation angle for electron emission following collisions of 6-MeV/u U³⁸⁺ and Th³⁸⁺ on He and Ar. The electron-emission data show an enhancement at forward angles and a decrease at backward angles with respect to scaled-cross-section results based on the Born approximation. Comparison with classical-trajectory Monte Carlo calculations suggests that the deviation from the Born approximation can be explained by continuum-continuum couplings. By comparing with previously published data, we found that the forward enhancement as well as the backward decrease follow a q/vp (q,vp …

Multiple-Ionization Collision Dynamics, R. (Ronald) E. Olson, J. Ullrich, H. Schmidt-Böcking

Physics Faculty Research & Creative Works

The 1.4-MeV/u U³²⁺+Ne collision system is studied in detail in order to elucidate the dynamics of multiple ionization in energetic, heavy-ion atom collisions. Differential cross sections versus recoil-ion charge state, calculated by the n-body classical-trajectory Monte Carlo method, are presented for the and cphi angle dependences of the projectile, recoil ion, and ejected electrons. The calculations show a high degree of ejected-electron asymmetry towards the projectile side of the target nucleus which strongly effects the transverse-momentum balance between the heavy particles. Experimental and calculated cross sections differential in the recoil-ion charge state and transverse momentum are found to …

N, L Distributions For Electron-Capture From H(1s) By C⁶⁺And O8+, Ronald E. Olson, D. R. Schultz

Physics Faculty Research & Creative Works

Total cross sections for electron-capture from the ground state of hydrogen by C⁶⁺(40, 50, 60, 80, 100 and 120 keV/u) and O⁸⁺(40, 50, 60, 80, 100, 120 and 140keV/u) have been calculated using the classical-trajectory Monte Carlo (CTMC) technique. We tabulate these cross sections as a function of projectile energy for (i) capture to all product states, (ii) capture to product n-levels, and (iii) capture to product n, l-levels. The results of these calculations agree with and extend previous CTMC n, ldistribution results. © 1989 IOP Publishing Ltd.

Safe Computing, Bruce M. Mcmillin, T. L. Casavant

Computer Science Faculty Research & Creative Works

So-called worms, viruses, and Trojan horses that attack computer systems are defined. The vehicle that allows these attacks to occur, namely, the open computer internetwork, is examined. The problem of providing protection against attack in an internetwork environment is discussed. The need for professional responsibility on the part of the scientific and engineering community in enforcing strong ethical practices and neither tolerating nor condoning such practices is stressed.

Automated Translation Of Digital Logic Equations Into Optimized Vhdl Code, John Evan Stark

Masters Theses

"It was desired to develop an algorithm for the automated translation of' finite slate machines from state table form to optimized VHDL form. To do this, algorithms arc needed for reducing the state machine to simplest form, making state assignments, producing minimal logic equations to represent the state machine, and producing VHDL code which describes the intended circuit. Various such algorithms were examined and a prototype program written to perform this translation"--Abstract, page ii.

Geology And Petrochemistry Of The Mount Chase Massive Sulfide Prospect, Penobscot County, Maine, Michael V. Scully

Masters Theses

"The Mount Chase massive sulfide prospect of northern Penobscot County, Maine was discovered in 1979 by Getty Mining Company. The deposit occurs within a sequence of lower paleozoic metavolcanic and metasedimentary rocks. The footwall units consist of rhyolitic flows, quartz-feldspar crystal tuff, and altered tuffaceous volcanic breccias. These rocks lie unconformably upon intensely folded sediments which are tentatively correlated with the Grand Pitch Formation of probable Cambrian age. The footwall volcanoclastic rocks exhibit a narrow zone of intense chloritic alteration immediately below the massive sulfide horizon, and a broader zone of sericitic alteration below that. A zone of stringer mineralization …

Symbolic Automation And Numerical Synthesis For Robot Kinematics, Jen Sriwattanathamma, Chung You Ho

Computer Science Technical Reports

This research analyzes three topics in robot arm kinematics. First, the direct kinematics which determines the Cartesian position and orientation of the end effector for the specified values of joint parameters is analyzed. Second, the differential motions concerning the differential relationships between the command variables in position and orientation of the end effector and the joint-controlled variables are studied. Finally, the inverse kinematics which determines the joint variables for a specified Cartesian position and orientation of the end effector is considered.

This dissertation presents a methodology for incorporating the artificial intelligence types of knowledge into automating solutions for the direct …

A Parallel Implementation Of Stickel's Ac Unification Algorithm In A Message-Passing Environment, David John Kleikamp, Ralph W. Wilkerson

Computer Science Technical Reports

Unification algorithms are an essential component of automated reasoning and term rewriting systems. Unification finds a set of substitutions or unifiers that, when applied to variables in two or more terms, make those terms identical or equivalent. Most systems use Robinson's unification algorithm or some variant of it. However, terms containing functions exhibiting properties such as associativity and commutativity may be made equivalent without appearing identical. Systems employing Robinson's unification algorithm must use some mechanism separate from the unification algorithm to reason with such functions. Often this is done by incorporating the properties into a rule base and generating equivalent …

A System For The Diagnosis Of Faults Using A First Principles Approach, Barbara A. Smith, Ralph W. Wilkerson

Computer Science Technical Reports

One of the primary areas of application of Artificial Intelligence is diagnosis. Diagnosis from first principles is a diagnostic technique which uses knowledge of the designed structure and function of a device to determine the possible causes of the malfunction.

This work builds on the foundation of a theory of diagnosis by implementing and extending the theory. A correction to the algorithm which defines the theory is presented. The theory is extended for multiple sets of observations of the system and measurement data.

A fundamental problem in diagnosis is selecting the measurement which will be of the most benefit in …

Spin-Polarized ³He Nuclear Targets And Metastable 4he Atoms By Optical Pumping With A Tunable, Nd:Yap Laser, C. L. Bohler, Laird D. Schearer, M. Leduc, P. J. Nacher, L. Zachorowski, R. G. Milner, R. D. Mckeown, C. E. Woodward

Physics Faculty Research & Creative Works

Several Nd:YAP lasers were constructed which could be broadly tuned in the 1083-nm region which includes the helium ²³S-²³P transition, using a Lyot filter and thin, uncoated etalons within the laser cavity. 1 W of power could be extracted at 1083 nm through a 1% transmitting output coupler. This laser beam was used to optically pump metastable ⁴He and ³He ²³S helium atoms in a weak discharge cell, spin polarizing the metastable ensemble. In a ³He cell the polarization is transferred to the nuclear spin system. A ³He target cell at 0.3 …

Nd:Lna Laser Optical Pumping Of ⁴He: Application To Space Magnetometers, R. E. Slocum, Laird D. Schearer, P. Tin, R. Marquedant

Physics Faculty Research & Creative Works

We have observed Hanle signals and n=0, p=1 parametric resonances of ₂₃S¹ metastable helium atoms in a discharge cell by optically pumping the helium atoms with a tunable Nd:LNA laser. These resonances were used to construct a sensitive magnetometer for the measurement of very small magnetic fields. Since magnetometer sensitivity is proportional to the slope of the parametric resonance signal (signal amplitude divided by linewidth), the slopes for single-line laser pumping were compared with similar quantities obtained from conventional helium lamp pumping. Laser pumping yielded 45 times greater slopes with comparable power requirements, thus establishing the potential for …

The Ipe-Pc Integrated Programming Environment, Nurcan Coskun, Thomas J. Sager

Computer Science Technical Reports

An Integrated Programming Environment, IPE-PC, that supports pseudo-code development has been designed and implemented. This environment is based on a Pascal-like language which is designed according to the requirements of a language-based environment. The nucleus of IPE-PC is a language-based editor which represents programs as graphs internally. The same representation is used in every mode of the environment (i.e., editing, compilation, execution, debugging and translation). The system provides facilities to take advantage of both top-down and bottom-up programming. Stepwise refinement has been supported by providing comment structures that can be transformed into procedures. Bottom-up programming is supported because it is …

Magnetism And Superconductivity In (Er₀.₁₆Ho₀.₈₄)Rh₄B₄, Oran Allan Pringle, Herbert A. Mook, Steven E. Lambert, M. Brian Maple

Physics Faculty Research & Creative Works

The superconducting and ferromagnetic phase boundaries in the (Er_1-xHox)Rh₄B₄ mixed ternary alloy system meet in a multicritical point at x_cr ≈ 0.9. For xcr, the compounds first become superconducting as the temperature is lowered, and then lose superconductivity in a transition to ferromagnetism. The coexistence of superconductivity and ferromagnetism for alloys near the erbium-rich end of the phase diagram is well established. It has also been suggested that ferromagnetism and superconductivity coexist in alloys with x just below x_cr. We have carried out neutron-diffraction, ac magnetic susceptibility, and heat-capacity …