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Resonance Vibrations in Intake and Exhaust Pipes of in-Line Engines 3: The Inlet Process of a Four-Stroke-Cycle Engine

Description: Using a previously developed method, the boundary process of four-stroke-cycle engines are set up. The results deviate considerably from those obtained under the assumption that the velocity fluctuation is proportional to the cylinder piston motion. The deviation is less at the position of resonance frequencies. By the method developed, the effect of the resonance vibrations on the volumetric efficiency can be demonstrated.
Date: October 1940
Creator: Lutz, O.
Partner: UNT Libraries Government Documents Department

Transverse Oscillations in a Cylindrical Combustion Chamber

Description: Note presenting a study of certain features of transverse resonance in an idealized combustion chamber. Modes of weak oscillation are described with average Mach number neglected but with the effect of axial gradient of mean temperature considered. The nature of finite transverse periodic waves is also analyzed.
Date: October 1954
Creator: Moore, Franklin K. & Maslen, Stephen H.
Partner: UNT Libraries Government Documents Department

Nuclear Magnetic Resonance Spectra of Some 1,2,4-triazoles

Description: In the work undertaken here, NMR has been used to ascertain the structure of some 1,2,4-triazoles. The investigation provides information concerning the structure of potentially tautomeric triazoles such as hydroxy- and aminotriazole. Connected with this aspect of triazole chemistry is the larger problem of mesohydric tautomerism. The present study also yields information for a comparison of substituent effects in triazoles, N-heteroaromatic substances and benzene.
Date: January 1967
Creator: Creagh, Linda Truitt
Partner: UNT Libraries

Suppression of probe background signals via B1 field inhomogeneity

Description: A new approach combining a long pulse with the DEPTH sequence (Cory and Ritchey, Journal of Magnetic Resonance, 1988) greatly improves the efficiency for suppressing probe background signals arising from spinning modules. By applying a long initial excitation pulse in the DEPTH sequence, instead of a {pi}/2 pulse, the inhomogeneous B{sub 1} fields outside the coil can dephase the background coherence in the nutation frame. The initial long pulse and the following two consecutive EXORCYCLE {pi} pulses function complementarily and prove most effective in removing background signals from both strong and weak B{sub 1} fields. Experimentally, the length of the long pulse can be optimized around odd multiples of the {pi}/2 pulse, depending on the individual probe design, to preserve signals inside the coil while minimizing those from probe hardware. This method extends the applicability of the DEPTH sequence to probes with small differences in B{sub 1} field strength between the inside and outside of the coil, and can readily combine with well-developed double resonance experiments for quantitative measurement. In general, spin systems with weak internal interactions are required to attain efficient and uniform excitation for powder samples, and the principles to determine the applicability are discussed qualitatively in terms of the relative strength of spin interactions, r.f. power and spinning rate.
Date: January 27, 2011
Creator: Feng, Jian & Reimer, Jeffrey
Partner: UNT Libraries Government Documents Department

Science Drivers and Technical Challenges for Advanced Magnetic Resonance

Description: This report recaps the "Science Drivers and Technical Challenges for Advanced Magnetic Resonance" workshop, held in late 2011. This exploratory workshop's goal was to discuss and address challenges for the next generation of magnetic resonance experimentation. During the workshop, participants from throughout the world outlined the science drivers and instrumentation demands for high-field dynamic nuclear polarization (DNP) and associated magnetic resonance techniques, discussed barriers to their advancement, and deliberated the path forward for significant and impactful advances in the field.
Date: March 7, 2013
Creator: Mueller, Karl T.; Pruski, Marek; Washton, Nancy M. & Lipton, Andrew S.
Partner: UNT Libraries Government Documents Department

Tunneling rate fluctuations induced by nonlinear resonances: A quantitative treatment based on semiclassical arguments

Description: This article discusses tunneling rate fluctuations induced by nonlinear resonances. The authors investigate the tunneling process between two symmetric stable islands of a forced pendulum Hamiltonian in the weak chaos regime.
Date: November 1998
Creator: Bonci, Luca; Farusi, Andrea; Grigolini, Paolo & Roncaglia, Roberto
Partner: UNT College of Arts and Sciences

Cyclotron Resonance Heating of a Deuterium Plasma

Description: Abstract: "The energy gained by a deuterium plasma, from a three megacycle per second radiofrequency field, was studied experimentally. A static magnetic field, in the form of a "mirror", was used. The coil of an rf resonant circuit, placed at the center of the machine produced a time-varying magnetic field parallel to the static field. This, in turn, induced an electrical field, in an azmuthal direction, which acted on the ions. When this was in synchronism with the cyclotron frequency, the ions could pick up energy. At this resonance the light intensity from the plasma increased markedly. This effect was used as evidence for the transfer of energy to the ions."
Date: October 28, 1957
Creator: Chambers, Edmund S.; Lamb, William A. S. & Kippenhan, Dean O.
Partner: UNT Libraries Government Documents Department

Multimode-diode-pumped gas (alkali-vapor) laser

Description: We report the first demonstration of a multimode-diode-pumped gas laser--Rb vapor operating on the 795 nm resonance transition. Peak output of {approx}1 Watt was obtained using a volume-Bragg-grating stabilized pump diode array. The laser's output radiance exceeded the pump radiance by a factor greater than 2000. Power scaling (by pumping with larger diode arrays) is therefore possible.
Date: August 22, 2005
Creator: Page, R H; Beach, R J & Kanz, V K
Partner: UNT Libraries Government Documents Department

New mechanism of plasmons specific for spin-polarized nanoparticles

Description: This article experimentally shows that Co nanoparticles with a single-domain crystal structure support a plasmon resonance at approximately 280 nm with better quality than gold nanoparticle resonance in the visible. The magnetic nature of these nanoparticles suggests a new type of these plasmons.
Date: March 27, 2018
Creator: Bhatta, Hari L.; Aliev, Abil E. & Drachev, Vladimir P.
Partner: UNT College of Arts and Sciences

Raman and NMR Relaxation Studies of Molecular Dynamics in Liquids

Description: Raman vibrational bands are sensitive to fluctuations in the molecular environment. Variations in the bandwidth and peak position can then be utilized to monitor molecular forces and interactions present in condense phases. Nuclear Magnetic Resonance (NMR) provides a convenient probe for the study of molecular reorientation in liquids since nuclear spin relaxation times are dependent on the details of molecular motion. Presented here is the solvent study of the Raman bandwidths and frequency displacements of the mode of the compounds CH3MCI3 (M = C, Si, Ge, Sn) in a number of solvents of widely varying molecular structure. Also, a detailed isotope dilution study of the modes in CH2CI2/CD2CI2 mixtures is presented. In this set of experiments, I observed broadening of the v1 mode of CH2C12 upon dilution,which is the first experimental observation of such behavior. The temperature-dependent carbon-13 relaxation times and nuclear Overhauser enhancements in neat dichloromethane were measured. In this study we found that the molecular reorientation of this molecule was highly anisotropic, but could be well characterized assuming quasi-symmetric top behavior. In addition, in order to gain a more complete understanding of the reorientational dynamics in dichloromethane, we analyzed the 13-C NMR relaxation of CH2CI2 both in "inert" solvents of differing viscosities and in interactive solvents of varying Lewis basicities. Various theoretical models were also applied in order to characterize dichloromethane1s reorientational dynamics.
Date: August 1987
Creator: Rodriguez, Arturo A. (Arturo Angel)
Partner: UNT Libraries

Magnetic Resonance Facility (Fact Sheet)

Description: This fact sheet provides information about Magnetic Resonance Facility capabilities and applications at NREL's National Bioenergy Center. Liquid and solid-state analysis capability for a variety of biomass, photovoltaic, and materials characterization applications across NREL. NREL scientists analyze solid and liquid samples on three nuclear magnetic resonance (NMR) spectrometers as well as an electron paramagnetic resonance (EPR) spectrometer.
Date: March 1, 2012
Partner: UNT Libraries Government Documents Department

Least Squares Magnetic-Field Optimization for Portable Nuclear Magnetic Resonance Magnet Design

Description: Single-sided and mobile nuclear magnetic resonance (NMR) sensors have the advantages of portability, low cost, and low power consumption compared to conventional high-field NMR and magnetic resonance imaging (MRI) systems. We present fast, flexible, and easy-to-implement target field algorithms for mobile NMR and MRI magnet design. The optimization finds a global optimum ina cost function that minimizes the error in the target magnetic field in the sense of least squares. When the technique is tested on a ring array of permanent-magnet elements, the solution matches the classical dipole Halbach solution. For a single-sided handheld NMR sensor, the algorithm yields a 640 G field homogeneous to 16 100 ppm across a 1.9 cc volume located 1.5 cm above the top of the magnets and homogeneous to 32 200 ppm over a 7.6 cc volume. This regime is adequate for MRI applications. We demonstrate that the homogeneous region can be continuously moved away from the sensor by rotating magnet rod elements, opening the way for NMR sensors with adjustable"sensitive volumes."
Date: March 27, 2008
Creator: Paulsen, Jeffrey L; Franck, John; Demas, Vasiliki & Bouchard, Louis-S.
Partner: UNT Libraries Government Documents Department

High performance single stage operation of the LBL ECR and the design of an advanced ECR ion source

Description: A new mode of operation using only the second stage of the LBL ECR has been developed. This single stage mode produces charge states and currents equal to or better than the traditional two stage operation of the LBL ECR for a variety of gases such as nitrogen, oxygen, and argon. The critical parameter for this mode appears to be conditioning the plasma chamber walls with a coating of SiO/sub 2/. Various models to explain this effect will be discussed along with implications for ECR ion source design. A new Advanced ECR ion source which will operate at 14 GHz is being designed for the 88-Inch Cyclotron. Construction is scheduled to begin in the fall of 1988 and test operation should begin in the fall of 1989. The design includes hollow core copper wire solenoids, iron yoke, a Nd-Fe-B sextupole, radial pumping, and access to the plasma chamber. 8 refs., 4 figs., 1 tab.
Date: September 1, 1988
Creator: Lyneis, C.M.
Partner: UNT Libraries Government Documents Department

Temperature Dependence of the Absolute Third-order Rate Constant for the Reaction between Na + O₂ + N₂ over the Range 571 - 1016 K Studied by Time-resolved Atomic Resonance Absorption Spectroscopy

Description: Article on temperature dependence of the absolute third-order rate constant for the reaction between Na + O₂ + N₂ over the range 571-1016 K studied by time-resolved atomic resonance absorption spectroscopy.
Date: 1985
Creator: Husain, David; Marshall, Paul & Plane, John M. C.
Partner: UNT College of Arts and Sciences

Laboratory measurements of resonant contributions to Fe XXIV line emission

Description: A number of X-ray astronomy satellites are scheduled for launch in the next few years. The Advanced X-ray Astrophysics Facility (AXAF) is scheduled for launch in 1998, and the X-Ray Multi-mirror Mission (XMM) and Astro-E in 1999. These satellites will carry spectrometers with resolving powers in the Fe L-shell emission region over an order of magnitude greater than the spectrometers aboard A CA. Interpreting AXAF, XMM, Astro-E spectra will require atomic data at an accuracy significantly greater than the data presently used in the standard emission codes. To address some of the existing and upcoming needs of X-ray astrophysics, we have continued our studies of Fe XXIV line emission. In this work, we measured Fe XXIV 3{yields}2 line emission at energies around threshold, using EBIT to examine the resonance contributions to the line emissivity. Here we present relative cross sections, at electron energies between 700 and 1500 eV, for producing line emission at wavelength A = 11.18 of the Fe XXIV 3d{sub 5/2}{yields}2P{sub 3} transition. Various processes can contribute to line emission observed from a collisional plasma. Direct excitation (DE) is the most important one at energies above the EIE threshold. Below threshold, Dielectronic recombination (DR) produces high n satellites which cannot be resolved from the EIE line. Resonant excitation (RE) can populate the same levels as DE via dielectronic capture followed by autoionization to the level of interest.
Date: October 27, 1997
Creator: Gu, M.F.; Beiersdorfer, P.; Brown, G.V.; Kahn, S.M.; Liedahl, D.A.; Reed, K.J. et al.
Partner: UNT Libraries Government Documents Department

The Proton Nuclear Magnetic Resonance Spectra of Pyridines

Description: Report discussing the proton NMR spectra of 32 pyridines in two solvents, carbon tetrachloride and bezene-d6, are presented. The chemical-shift and differential-shift values are correlated with the substitutent position and with the solvent media. The ring protons and the protons on alkyl substituents are tabulated. The paramagnetic shift of the protons adjacent to the nitrogen is discussed, and a proposed structure for the pyridine-benzene complex that is consistent with the observed anomalous paramagnetic shift is presented. The utility of the data in the identification of pyridine compounds found in shale-oil naphtha is demonstrated.
Date: 1971
Creator: McDonald, F. R.; Decora, A. W. & Cook, G. L.
Partner: UNT Libraries Government Documents Department


Description: In the AGS spin resonances due to coupling may account for as much as a 50 percent loss in polarization at a reduced acceleration rate. The major source of coupling in the AGS is the solenoidal snake. In the past some preliminary work was done to understand this phenomena, and a method to overcome these resonances was attempted. However in the polarized proton run of 2002 we sought to study more thoroughly the response of these coupled spin resonances to the strength of the solenoidal snake, skew quadrupoles and vertical and horizontal betatron tune separation. In this paper we present our results and compare them with those predicted by a modified DEPOL program.
Date: June 2, 2002
Partner: UNT Libraries Government Documents Department