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Calculations of the ground state energy and exchange integrals of crystalline $sup 3$He

Description: Thesis. The variational equation is derived and discussed using Jastrowtype wave functions, which are a product of pair wave functions, as the trail wave function. The various approximations used in simplifying the variational equations so as to obtain a form that is possible to solve numerically are discussed also. A Monte Carlo calculation is described using the wave function obtained. Exchange in /sup 3/He is discussed. (MHR)
Date: July 1, 1973
Creator: Lim, W L
Partner: UNT Libraries Government Documents Department

Specific heat measurements at the spin-reorientation transition in YbFeO$sub 3$

Description: Thesis. The specific heat was measured from 2.55 to 15.7 deg K, first with no external magnetic field, and then with magnetic fields along the c-axis and a-axis of intensity of 1000, 3000, and 5800 Oe. Two specific heat anomalies were observed: a Schottky anomaly caused by the ground state exchange splitting of the Yb/sup 3+/, and spin reorientation of the Fe sublattice. (DLC)
Date: April 30, 1974
Creator: Sjolander, G W
Partner: UNT Libraries Government Documents Department

Coal gasification: Duluth campus heating plant. Grate support system failure

Description: During the seventh run there was a complete failure of the grate support system. Two massive holes and numerous cracks finished the deterioration of the grate holder that had started on the fifth run of the gasification system. The zero ductile casting was quenched with ash water during an emergency loss of blast air with the resulting depressurization of the producer. The cause of the failure was threefold - quenching of the hot cast iron, low ductility in the material used (Meehanite W-1), and high stresses set up in the casting at bolting locations. To correct this problem the grate support system has undergone the following design changes: (1) The structural part of the grate holder will be a plate steel weldment welded directly (instead of bolting) to the ash pan. This will eliminate gasket leaks, give us a more ductile material for transporting the stress from the grate to the rotating ash pan, and give us better thermal conduction of heat (elimination of gasket thermal break) from the grate holder to water in the ash pan. (2) The grinding lobes will be cast iron wearing attachments bolted to the structural steel grate holder. The attachments will be made of a more ductile iron than Meehanite W-1. In the future, when the grinding lobes wear, they can be replaced without removing the entire grate holder.
Date: January 1, 1980
Partner: UNT Libraries Government Documents Department

Contribution of electronically excited states to the radiation chemistry of organic systems. Progress report, September 1, 1978-August 31, 1979

Description: The effect of n-perfluorohexane to quench both the emission and photoionization current of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) in isooctane and in tetramethylsilane has been shown to be consistent with an interaction of perfluorohexane with some relatively long-lived, coherently excited state of TMPD that is generated at the photoionization threshold and which decays either to the emitting state of TMPD or to a geminate ion-pair. The 0/sup 0/ and 90/sup 0/ electron impact spectra of the stable isomers of C/sub 3/, C/sub 4/, and C/sub 5/ saturated hydrocarbons are being determined. Preliminary results show large structural effects on the lowest Rydberg singlet-triplet splittings. Two photon excited emission spectra of decalin, bicyclohexyl, and cyclohexane have been observed in good agreement with previously reported one-photon spectra. A weak emission from propylene has also been detected. From measurement of the photosensitized singlet emission of p-xylene by bicyclohexyl excited at 1740 A, it appears that the bicyclohexyl triplet contributes importantly to the sensitization. Also previously reported deviations from Stern-Volmer behavior in the fast-electron-excited process are found too in the photo-excited process (at 1740 A) and therefore cannot be attributed exclusively to ionic processes. The much larger ratio of excimer to monomer intensity in polystyrene as compared to neat liquid benzene appears to be due mainly to a reduced entropy of dissociation of the excimer when the phenyls are tied to the polymer backbone. Excimers formed therefore from distant phenyl groups may manifest themselves at high quencher concentrations and thus provide a new technique for probing polymer conformation.
Date: January 1, 1979
Creator: Lipsky, S.
Partner: UNT Libraries Government Documents Department

Chemical composition of atmospheric precipitation in Minnesota and North Dakota. Final report, July 1, 1977-Jun 30, 1980

Description: Precipitation chemistry in central North American appears to e controlled by interaction between soil-derived alkaline dust and gaseous NH/sub 3/ from the cultivated prairie and anthropogenic acid aerosols from the urban-industrial Lower Great Lakes-Ohio Valley region. Analyses of major ions and trace metals in precipitation event and snow core samples along a 600-km transect from the North Dakota prairie to the northeastern Minnesota forest indicate that loadings and concentrations of Ca/sup + +/, Mg/sup + +/, P/sub tot/, Al, Fe, M/sub n/, and other soil-derived material decrease with increasing distance from the prairie. Acidity is highest in the east and decreases to the west. Sulfate has natural sources in the west and anthropogenic sources in the east; its concentration was least at sites in the middle of the transect. Acidity increased and inputs of soil-derived elements decreased during winter when snow and freezing temperatures reduced alkaline influxes to the region. Atmospheric inputs of N and P may be beneficial to nutrient-poor ecosystems. However, precipitation in the eastern portions of the region which are highly sensitive to acid inputs, is approaching levels of acidity known to cause adverse effects. Any increase in acid loading will increase this danger.
Date: July 1, 1980
Partner: UNT Libraries Government Documents Department

Automatic radio telemetry recording of fish temperature and depth

Description: Radio frequency fish transmitters capable of relaying temperature or pressure information and a multichannel recording system were developed and used successfully in the field. Both transmitters operated on pulse rate variation with either temperature or depth. Design considerations for temperature and pressure dependant pulse rates are discussed, including power supply variation, sensitivity ranges, drift, size, power consumption and temperature variation. The receiving-recording system is described, including a 16 channel programmable scanning receiver and a pulse decoder.
Date: January 1, 1979
Creator: Ross, M J; Kuechle, V B; Reichle, R A & Siniff, D B
Partner: UNT Libraries Government Documents Department

Nuclear structure studies with pions and heavy ions. Progress report, June 1, 1979-May 31, 1980. [Univ. of Minnesota, June 1, 1979-May 31, 1980]

Description: The elastic and inelastic scattering of ..pi../sup +/ and ..pi../sup -/ by /sup 13/C, /sup 16/O, and /sup 17/O was studied at pion energies close to the (3,3) resonance. Data were taken at the Los Alamos Meson Physics Facility. Large asymmetries were observed, two of which are consistent with pure neutron and pure proton excitations. Transitions to strongly excited states of /sup 13/C are in strikingly good agreement with theoretical predictions of Lee and Kurath. In sharp contrast, strong disagreements are found for the weakly excited states. The asymmetries for /sup 16/O + ..pi../sup + -/ were interpreted as due to isospin mixing between the excited states. High-resolution data for (t,t') and (/sup 3/He,/sup 3/He') on /sup 13/C were taken to supplement the pion work. Asymmetries were found for the relative cross sections for some states. In studies of the heavy-ion-nucleus potential the effect of potential resonances on the elastic scattering of /sup 16/O + /sup 28/Si was found to be small. A close similarity between the elastic exchange amplitude at 180/sup 0/ and the effect of the parity dependence on the elastic amplitude was found. Fits to the new data at 40 and 41.226 MeV required the use of a composite absorptive potential. The surface derivative part of this potential can be deduced from a coupled-channels calculation. 17 figures.
Date: March 1, 1980
Creator: Dehnhard, D.
Partner: UNT Libraries Government Documents Department

Initial study of thermal energy storage in unconfined aquifers. [UCATES]

Description: Convective heat transport in unconfined aquifers is modeled in a semi-analytic way. The transient groundwater flow is modeled by superposition of analytic functions, whereby changes in the aquifer storage are represented by a network of triangles, each with a linearly varying sink distribution. This analytic formulation incorporates the nonlinearity of the differential equation for unconfined flow and eliminates numerical dispersion in modeling heat convection. The thermal losses through the aquifer base and vadose zone are modeled rather crudely. Only vertical heat conduction is considered in these boundaries, whereby a linearly varying temperature is assumed at all times. The latter assumption appears reasonable for thin aquifer boundaries. However, assuming such thin aquifer boundaries may lead to an overestimation of the thermal losses when the aquifer base is regarded as infinitely thick in reality. The approach is implemented in the computer program UCATES, which serves as a first step toward the development of a comprehensive screening tool for ATES systems in unconfined aquifers. In its present form, the program is capable of predicting the relative effects of regional flow on the efficiency of ATES systems. However, only after a more realistic heatloss mechanism is incorporated in UCATES will reliable predictions of absolute ATES efficiencies be possible.
Date: April 1, 1986
Creator: Haitjema, H.M. & Strack, O.D.L.
Partner: UNT Libraries Government Documents Department

Energy transfer and utilization in biological systems. Final report, September 1, 1967--September 15, 1976. [Fluorescence studies of photosynthesis]

Description: In fluorescence studies of the photosynthetic process it was shown that the photosynthetic rate and light loss via chlorophyll fluorescence are strictly complementary. The exciplex state of matter responsible for most photochemistry was discovered and a wide variety of information about the state gained from studies of indole exciplexes. In addition to the nature of the bonding, degree of stability and general excited state behavior of indole exciplexes, their ability to lose electrons in a highly temperature-dependent quenching process was established. Time resolved emission spectroscopy demonstrated that local-movement relaxation in the interior of globular proteins occurs more rapidly than 10/sup -9/ sec. Subsequent studies show this to be an important and general time cut-off in the conformational fluctuations which support protein function. Although a chlorophyll-chlorophyll exciplex was produced, its relevance to the System II trapping center was not established. Only recently has the exciplex nature of both System I and System II trapping centers been exposed by others.
Date: March 1, 1978
Creator: Lumry, R.W.
Partner: UNT Libraries Government Documents Department

Contribution of electronically excited states to the radiation chemistry of organic systems. Progress report, September 1, 1976--August 31, 1977

Description: The fluorescence of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) has been studied in the solvents n-hexane, methylcyclohexane, cyclohexane, isooctane, and tetramethylsilane for excitation energies below and above the photoionization threshold. Evidence is obtained for the existence, as a major intermediate in the photoionization process of a coherent but spatially diffuse excited state of TMPD. Electron impact spectra of NH/sub 3/ at low energies and 90/sup 0/ scattering angle has failed to reveal any evidence for a low-lying valence triplet. For simple saturated hydrocarbons, large angle electron-impact spectra also fail to reveal any evidence for low-lying valence triplet states. Therefore if valence-shell transitions exist at all in these molecules they must be imbedded at significantly higher energies in the absorption manifold. The fluorescence of the A ..-->.. X transition in ammonia-d/sub 3/ has been studied in the presence of saturated hydrocarbon perturbers up to densities of approximately 6 M. Essentially no change in fluorescence quantum yield is observed. This eliminates inelastic processes as contributing importantly to pressure broadening and to shifting of the A reverse arrow X transition. The pressure broadening and pressure shifting of the first 10 vibrational peaks in the A reverse arrow X (n/sub N/ ..-->.. 3s Rydberg) absorption of NH/sub 3/ has been studied using He, Ne, Ar, N/sub 2/, CH/sub 4/, CF/sub 4/ and SF/sub 6/ gases up to pressures of approximately 100 atm. Both blue and red shifts are observed depending on the nature of the perturber. A dependence of the magnitude of the shift on vibrational level is observed and attributed to important variations of the electronic wavefunction of the upper state with position of the nuclei.
Date: January 1, 1977
Creator: Lipsky, S.
Partner: UNT Libraries Government Documents Department

Grid-connected integrated community energy system. Phase II, Stage 2, final report. Preliminary design pyrolysis facility. [Andco-Torrax system]

Description: The University of Minnesota is studying and planning a grid connected integrated community energy system to include disposal of wastes from health centers and utilizing the heat generated. The University of Minnesota has purchased the so called Southeast Generating Station from the Northern States Power Company. This plant contains two coal-fired boilers that will be retrofitted to burn low-sulfur Montana coal. Building modifications and additions will be made to support the components of the Andco-Torrax system and integrate the system with the rest of the plant. The Andco-Torrax system is a new high-temperature refuse-conversion process known technically as slagging pyrolysis. Although the pyrolysis of solid waste is a relatively new innovation, pyrolysis processes have been used for years by industry. This report covers the preliminary design and operation of the system. (MCW)
Date: March 22, 1978
Partner: UNT Libraries Government Documents Department

Polarization in inclusive lambda production

Description: At high energies the reaction p + N ..-->.. ..lambda../sup 0/ + X yields ..lambda../sup 0/s which are strongly polarized. The behavior of this polarization should give information about quark production mechanisms. The inclusive ..lambda../sup 0/ polarization is also compared with anti ..lambda../sup 0/, and proton polarization in the fragmentation region of the incident proton at Fermilab energies.
Date: January 1, 1981
Creator: Heller, K.
Partner: UNT Libraries Government Documents Department

Grid-connected integrated community energy system. Phase II, Stage 2, final report. Executive summary

Description: The University of Minnesota Grid-ICES was divided into four identifiable programs in order to study the feasibility of each of the parts of the ICES independently. The total program involves cogeneration, fuel conversion, fuel substitution, and energy conservation by system change. This Phase II report substantiates the theory that the Basic Grid ICES is not only energy-effective, but it will become cost effective as unit operating costs adjust to supply and demand in the 1980's. The Basic Program involves the cogeneration of steam and electricity. The University of Minnesota has been following an orderly process of converting its Central Heating Plant from gas-oil to 100% coal since 1973. The first step in the transition is complete. The University is presently 100% on coal, and will begin the second step, the test burning of low Btu Western coal during the spring, summer, and fall, and high Btu Eastern coal during the high thermal winter period. The final step to 100% Western coal is planned to be completed by 1980. In conjunction with the final step a retired Northern States Power generating plant has been purchased and is in the process of being retrofitted for topping the existing plant steam output during the winter months. The Basic Plan of ICES involves the add-on work and expense of installing additional boiler capacity at Southeast Steam and non-condensing electric generating capability. This will permit the simultaneous generation of electricity and heat dependent upon the thermal requirements of the heating and cooling system in University buildings. This volume presents an overview of the Community and the ICES. (MCW)
Date: March 22, 1978
Partner: UNT Libraries Government Documents Department