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Articles 1 - 19 of 19
Full-Text Articles in Physics
The Effect Of Cu-Doping On The Magnetic And Transport Properties Of La₀.₇Sr₀.₃Mno₃, M. S. Kim, Jinbo Yang, Qingsheng Cai, X.-D. Zhou, William B. Yelon, Paul Ernest Parris, William Joseph James
The Effect Of Cu-Doping On The Magnetic And Transport Properties Of La₀.₇Sr₀.₃Mno₃, M. S. Kim, Jinbo Yang, Qingsheng Cai, X.-D. Zhou, William B. Yelon, Paul Ernest Parris, William Joseph James
Physics Faculty Research & Creative Works
The effects of Cu-doping on the structural, magnetic, and transport properties of La0.7Sr0.3Mn1xCuxO3 (0<=x<=0.20) have been studied using neutron diffraction, magnetization, and magnetoresistance (MR) measurements. All samples show the rhombohedral structure with the R[overline 3]c space-group from 10 K to room temperature (RT). Neutron diffraction data suggest that some of the Cu ions have a Cu3+ state in these compounds. The substitution of Mn by Cu affects the MnO bond length and Mn-O-Mn bond angle resulting from the minimization of the distortion of the MnO6 octahedron. Resistivity measurements show that a metal to insulator transition occurs for the x>=0.15 samples. The x=0.15 sample shows the highest MR([approximate]80%), which might result from the co-existence of Cu3-Cu2+ and the dilution effect of Cu-doping on the double exchange interaction
Laser Writing Of Semiconductor Nanoparticles And Quantum Dots, Massimo F. Bertino, Raghuveer Reddy Gadipalli, J. Greg Story, C. G. Williams, Guo-Hui Zhang, Chariklia Sotiriou-Leventis, Akira Tokuhiro, Suchi Guha, Nicholas Leventis
Laser Writing Of Semiconductor Nanoparticles And Quantum Dots, Massimo F. Bertino, Raghuveer Reddy Gadipalli, J. Greg Story, C. G. Williams, Guo-Hui Zhang, Chariklia Sotiriou-Leventis, Akira Tokuhiro, Suchi Guha, Nicholas Leventis
Physics Faculty Research & Creative Works
Silica aerogels were patterned with CdS using a photolithographic technique based on local heating with infrared (IR) light. The solvent of silica hydrogels was exchanged with an aqueous solution of the precursors CdNO3 and NH4 OH, all precooled to a temperature of 5°C. Half of the bathing solution was then replaced by a thiourea solution. After thiourea diffused into the hydrogels, the samples were exposed to a focused IR beam from a continuous wave, Nd-YAG laser. The precursors reacted in the spots heated by the IR beam to form CdS nanoparticles. We lithographed features with a diameter of …
How To Establish Successful Cooperative Student Learning Centers For Stem Courses, Ronald James Bieniek, Douglas R. Carroll, Cesar Mendoza, Oran Allan Pringle, Ekkehard Sinn, Kai-Tak Wan, Donald C. Wunsch
How To Establish Successful Cooperative Student Learning Centers For Stem Courses, Ronald James Bieniek, Douglas R. Carroll, Cesar Mendoza, Oran Allan Pringle, Ekkehard Sinn, Kai-Tak Wan, Donald C. Wunsch
Physics Faculty Research & Creative Works
Students learn more if they are actively involved in the learning process, particularly in a cooperative manner. Several UMR faculty have operated course-based learning centers (LCs) as part of the campus-wide Learning Enhancement Across Disciplines (LEAD) Program of student learning assistance and enhancement. LCs are designed to assist large numbers of students in a cost- and time-efficient manner that promotes student engagement without requiring undue amounts of faculty time. Course instructors spend time in the open learning environment of the LC, in lieu of office hours, guiding students to master course material and skills in their evolution from novice to …
Structure And Magnetic Properties Of The Mnbi Low Temperature Phase, Jinbo Yang, William B. Yelon, William Joseph James, Qingsheng Cai, Samit Roy, Naushad Ali
Structure And Magnetic Properties Of The Mnbi Low Temperature Phase, Jinbo Yang, William B. Yelon, William Joseph James, Qingsheng Cai, Samit Roy, Naushad Ali
Physics Faculty Research & Creative Works
High purity MnBi low temperature phase has been prepared and analyzed using magnetic measurements and neutron diffraction. The low-temperature phase of the MnBi alloy has a coercivity μ0iHc of 2.0 T at 400 K, and exhibits a positive temperature coefficient from 0 to at least 400 K. The neutron data refinement indicated that the Mn atom changes its spin direction from c axis above room temperature to nearly perpendicular to the c axis at 50 K. A canted magnetic structure has been observed below 200 K. The anisotropy field increases with increasing temperature which gives rise to …
Magnetic And Mössbauer Studies On Oxygen Deficient Perovskite, La₀.₆Sr₀.₄Feo3-Δ, Jinbo Yang, William B. Yelon, William Joseph James, X.-D. Zhou, Yixiang Xie, Harlan U. Anderson, Zili Chu
Magnetic And Mössbauer Studies On Oxygen Deficient Perovskite, La₀.₆Sr₀.₄Feo3-Δ, Jinbo Yang, William B. Yelon, William Joseph James, X.-D. Zhou, Yixiang Xie, Harlan U. Anderson, Zili Chu
Physics Faculty Research & Creative Works
Samples of La0.6Sr0.4Fe3-δ with varying oxygen vacancy contents were prepared by heating them in different gas flows. Magnetization measurement showed that samples with low oxygen vacancies have a magnetic ordering temperature in the range of 300-325 K while those with 9%-12% oxygen vacancies have a magnetic ordering temperature of 800 K and higher. Mössbauer spectra at 300 K exhibit paramagnetic or weak magnetic characteristics for the N2, O2, and air-quenched samples, whereas an average hyperfine field of 52 T is found for the CO/CO2 reduced samples. The heat treatment in …
Effect Of Oxygen Vacancies On The Magnetic Structure Of The La₀.₆Sr₀.₄Feo3-Δ Perovskite: A Neutron Diffraction Study, Zili Chu, William B. Yelon, Jinbo Yang, William Joseph James, Harlan U. Anderson, Yixiang Xie, Satish K. Malik
Effect Of Oxygen Vacancies On The Magnetic Structure Of The La₀.₆Sr₀.₄Feo3-Δ Perovskite: A Neutron Diffraction Study, Zili Chu, William B. Yelon, Jinbo Yang, William Joseph James, Harlan U. Anderson, Yixiang Xie, Satish K. Malik
Physics Faculty Research & Creative Works
Magnetic interactions in perovskite compounds of the type La1-xSrxMO3-δ (M=3d transition such as Mn and Fe) are presumed to arise through a super exchange between 3d electrons of the magnetic ions via oxygen orbitals. The magnetic structure of La0.6Sr0.4FeO3-δ has been studied with neutron diffraction. Oxygen vacancies were created by annealing samples under various gases including N2, air and mixtures of CO/CO2. All La0.6Sr0.4FeO3-δ compounds maintain the rhombohedral structure (space group R3̄c). The air- or oxygen-annealed samples have almost no oxygen …
X-Ray Absorption, Neutron Diffraction, And Mössbauer Effect Studies Of Mnzn-Ferrite Processed Through High-Energy Ball Milling, D. J. Fatemi, V. G. Harris, Mingxing Chen, Satish K. Malik, William B. Yelon, Gary J. Long, Amitabh Mohan
X-Ray Absorption, Neutron Diffraction, And Mössbauer Effect Studies Of Mnzn-Ferrite Processed Through High-Energy Ball Milling, D. J. Fatemi, V. G. Harris, Mingxing Chen, Satish K. Malik, William B. Yelon, Gary J. Long, Amitabh Mohan
Physics Faculty Research & Creative Works
MnZn-ferrite has been prepared via high-energy ball milling of elemental oxides MnO, ZnO, and α-Fe2O3. Neutron diffraction measurements suggest a high density of vacancies in a spinel structure. The spinel phase appears to comprise 99.8 wt % of the material in the sample milled for 40 h, with the remainder attributable to unreacted α-Fe2O3. The x-ray absorption near-edge structure was analyzed to provide an understanding of the charge state of the constituent Fe ions. This analysis reveals about 2/3 of Fe cations to be trivalent, increasing to about 3/4 after a 5 …
Diffraction In The Binary Encounter Electron Peak Observed In Collisions Of 0.6 Mev Amu⁻¹ I7+, I23+ And Au11+ Projectiles With He And Ar, W. Wolff, J. L. Shinpaugh, H. E. Wolff, Ronald E. Olson, Jee-Ching Wang, S. Lencinas, D. Piscevic, R. Herrmann, H. Schmidt-Böcking
Diffraction In The Binary Encounter Electron Peak Observed In Collisions Of 0.6 Mev Amu⁻¹ I7+, I23+ And Au11+ Projectiles With He And Ar, W. Wolff, J. L. Shinpaugh, H. E. Wolff, Ronald E. Olson, Jee-Ching Wang, S. Lencinas, D. Piscevic, R. Herrmann, H. Schmidt-Böcking
Physics Faculty Research & Creative Works
Relative double differential cross sections for electron emission from collisions of 0.6 MeV amu-1I7+and I23+ projectiles with Ar and Au11+projectiles with He were measured for electron energies from 100 eV to 2000 eV and for angles from 0° to 50°. Experimentally observed sudden shifts of the position of the binary encounter peak were interpreted as resulting from quantum interference in the scattering of target electrons from the partially stripped projectile ion. To this end calculations for the elastic scattering of free electrons initially at rest in the laboratory reference frame from the screened …
Effects Of Sample Orientation On The Corrosion Of Zinc In Ammonium Sulfate And Sodium Hydroxide Solutions, D. Abayarathna, Edward Boyd Hale, Thomas J. O'Keefe, Y. M. Wang, D. Radovic
Effects Of Sample Orientation On The Corrosion Of Zinc In Ammonium Sulfate And Sodium Hydroxide Solutions, D. Abayarathna, Edward Boyd Hale, Thomas J. O'Keefe, Y. M. Wang, D. Radovic
Physics Faculty Research & Creative Works
The corrosion and electrochemical properties of three zinc single crystal surfaces with different orientations have been investigated. In near-neutral 1 M (NH4)2SO4, the corrosion rates on all three surfaces were found to be similar. However, the SEM morphologies of the corresponding corroded surfaces were markedly different from each other, but consistent with preferential attack of {1120} surfaces. In alkaline 0.5 N NaOH solution, the three sample orientations showed significantly different reactivities, with the (1120) surface exhibiting the highest reactivity and corrosion rate. Here, passivation ultimately occurred and the difference in the corrosion performance of …
Condensation Coefficient Measurement For Water In The Umr Cloud Simulation Chamber, Donald E. Hagen, John L. Schmitt, Max B. Trueblood, John C. Carstens, Daniel R. White, Darryl J. Alofs
Condensation Coefficient Measurement For Water In The Umr Cloud Simulation Chamber, Donald E. Hagen, John L. Schmitt, Max B. Trueblood, John C. Carstens, Daniel R. White, Darryl J. Alofs
Physics Faculty Research & Creative Works
A systematic series of condensation coefficient measurements of water have been made using the University of Missouri-Rolla cooled-wall expansion chamber which simulates the thermodynamics of cloud. This coefficient is seen to decrease from a value near unity, at the outset of simulation, to a value in the neighborhood of 0.01 toward the end of a simulation. Final values of this coefficient are sufficiently low as to contribute significantly to the broadening of the drop-size distribution in cloud.
University Of Missouri--Rolla Cloud Simulation Facility: Proto Ii Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred Raymond Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker
University Of Missouri--Rolla Cloud Simulation Facility: Proto Ii Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred Raymond Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker
Physics Faculty Research & Creative Works
The Graduate Center for Cloud Physics Research at UMR has developed a cloud simulation facility to study phenomena occurring in terrestrial clouds and fogs. The facility consists of a pair of precision cooled-wall expansion chambers along with extensive supporting equipment. The smaller of these chambers, described in this article, is fully operational, and is capable of simulating a broad range of in-cloud thermodynamic conditions. It is currently being used to study water drop growth and evaporation for drops nucleated (activated) on well-characterized aerosol particles. Measurements have been made not only for continuous expansions (simulated updraft) but also for cyclic conditions, …
Measurement Of The Condensation Coefficient Of Water In The Umr Simulation Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred R. Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker
Measurement Of The Condensation Coefficient Of Water In The Umr Simulation Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred R. Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker
Physics Faculty Research & Creative Works
The UMR Cloud Simulation Facility is described. The facility is designed to provide a controlled environment simulating the conditions of natural atmospheric processes. It consists of two cooled-wall expansion cloud chambers and peripheral instrumentation for generation and characterization of aerosols used for cloud formation studies. Results of initial studies of the growth of warm cloud droplets and inferred measurements of the condensation coefficient are described.
Non-Linear Oscillation, Automodulation And Anelasticity, Tetsuro Suzuki, Manfred Wuttig
Non-Linear Oscillation, Automodulation And Anelasticity, Tetsuro Suzuki, Manfred Wuttig
Physics Faculty Research & Creative Works
The auto modulation observed in the course of internal friction is discussed as a special example of the universal nature of non-linear oscillations. Universal features of non-linear oscillations are the requirement of energy supply or negative damping and the period doubling route to chaos. The negative damping responsible for the auto modulation is described in terms of the soliton model for twinning deformation. © 1984 The Japan Society of Applied Physics.
Nonlinear Anelasticity Of Magnesium, Alexander Aning, Tetsuro Suzuki, Manfred Wuttig
Nonlinear Anelasticity Of Magnesium, Alexander Aning, Tetsuro Suzuki, Manfred Wuttig
Physics Faculty Research & Creative Works
An approximate solution of the equation of motion of a nonlinear anelastic reed at or near resonance is presented. The steady state solution reproduces the well-known nonlinear resonances. The solution also predicts the existence of auto modulations, i.e., self-excited modulations of the amplitude and phase at constant power of excitation of the reed. Numerical examples of such auto modulations are presented for an antisymmetric deformation potential. Experimental studies of finite amplitude oscillations of a magnesium reed vibrating at 72 and 431 Hz at room temperature confirm the existence of auto modulations. The experimental results can be semi quantitatively described in …
Phaseautomodulation In Magnesium, Alexander Aning, Tetsuro Suzuki, Manfred Wuttig
Phaseautomodulation In Magnesium, Alexander Aning, Tetsuro Suzuki, Manfred Wuttig
Physics Faculty Research & Creative Works
No abstract provided.
Measurement Of The Wear Properties Of Metallic Solids With A Falex Lubricant Testing Machine, Edward Boyd Hale, Chun-Ping John Meng, Ronald A. Kohser
Measurement Of The Wear Properties Of Metallic Solids With A Falex Lubricant Testing Machine, Edward Boyd Hale, Chun-Ping John Meng, Ronald A. Kohser
Physics Faculty Research & Creative Works
A modified Falex Lubricant Testing Machine has been used to determine wear properties of metallic solids. In particular, wear mass loss, wear volume loss, wear rates, and other parameters have been determined for a basic steel, as heat treated and after ion implantation. Wear rate improvements of more than an order of magnitude were found in a nickel-chrome steel (SAE 3135) implanted with 2.5x1017 N+2/cm2. Wear tests were conducted with a cylinder-in-groove geometry in a mild lubricating oil with loads greater than 540 N, which corresponded to pressures which exceeded 108N/m2 …
Two-Step Photoionization Of Potassium Atoms, Kaare J. Nygaard, Robert J. Corbin, James A. Jones
Two-Step Photoionization Of Potassium Atoms, Kaare J. Nygaard, Robert J. Corbin, James A. Jones
Physics Faculty Research & Creative Works
The cross section for photoionization of potassium atoms in the 4P2 states has been measured in a triple-crossed-beam experiment. © 1978 The American Physical Society.
Photoionization Of The 6p32,122 Fine-Structure Levels In Cesium, Kaare J. Nygaard, Robert E. Hebner, James A. Jones, Robert J. Corbin
Photoionization Of The 6p32,122 Fine-Structure Levels In Cesium, Kaare J. Nygaard, Robert E. Hebner, James A. Jones, Robert J. Corbin
Physics Faculty Research & Creative Works
The relative photoionization cross sections for cesium atoms selectively excited to the 6P32,122 states have been measured in a triple-crossed-beam experiment. A cesium discharge lamp produced resonant wavelengths of 8521 and 8944 for the excitation process. A Hg-Xe lamp combined with a grating monochromator was used for the actual ionization in the wavelength region from 2500 to 5000. Background counts due to photoionization of ground-state cesium atoms and dimers as well as various surface effects were discriminated against by chopping the excitation light source. The data are compared with results from radiative-recombination measurements in which the fine-structure levels are not …
Analogy Between Spinodal Decomposition And Martensitic Transformation, Tetsuro Suzuki, Manfred Wuttig
Analogy Between Spinodal Decomposition And Martensitic Transformation, Tetsuro Suzuki, Manfred Wuttig
Physics Faculty Research & Creative Works
The translation of the theory developed for the spinodal decomposition of a supercooled alloy to the language appropriate for the martensitic transformation is carried out. In the spinodal theory, the stability of the alloy with respect to the composition fluctuation is examined, while in the present theory the stability of the crystal with respect to the shear displacement fluctuation, the transverse phonon, is studied. The analogy to the spinodal theory requires the revival of the strain gradient energy term or the couple stress term, the presence of which has been a subject of controversies for a long time since Laval. …