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Articles 1 - 11 of 11
Full-Text Articles in Other Physics
Wide Angle Decentered Lens Beam Steering For Infrared Countermeasures Applications, Jennifer L. Gibson, Bradley D. Duncan, Edward A. Watson, John S. Loomis
Wide Angle Decentered Lens Beam Steering For Infrared Countermeasures Applications, Jennifer L. Gibson, Bradley D. Duncan, Edward A. Watson, John S. Loomis
Electro-Optics and Photonics Faculty Publications
A beam-steering system consisting of three cemented achromatic doublets is presented. Intended for use in IR countermeasure applications, our system is designed to operate over the 2- to 5-μm spectrum with minimum angular dispersion. We show that dispersion can be minimized by using doublet lenses fashioned from AMTIR-1 and germanium. Our system is designed to be compact and lightweight, with no internal foci, while allowing steering to ±22.5 deg. We also maintain a minimum 2-in. clear aperture for all steering angles, and a nominal divergence of 1 mrad. Plane wave and Gaussian beam analyses of our system are presented.
A Simple Design For An Electronic Speckle Pattern Interferometer, Thomas R. Moore
A Simple Design For An Electronic Speckle Pattern Interferometer, Thomas R. Moore
Faculty Publications
An electronic speckle pattern interferometer suitable for use in an undergraduate laboratory is described. This interferometer can be built for a small fraction of the cost of a commercial version and is simple and inexpensive to build and understand. The interferometer is useful for visualizing the normal modes of vibrating objects as well as changes in index of refraction.
Reply To “Comment On Gravitational Slingshot,” By C. L. Cook [Am. J. Phys. 73 (4), 363 (2005)], Asim Gangopadhyaya, Asim Gangopadhyaya, Robert Cacioppo, John J. Dykla
Reply To “Comment On Gravitational Slingshot,” By C. L. Cook [Am. J. Phys. 73 (4), 363 (2005)], Asim Gangopadhyaya, Asim Gangopadhyaya, Robert Cacioppo, John J. Dykla
Physics: Faculty Publications and Other Works
No abstract provided.
Qvd Sensors As Focal Plane Instruments For X-Ray Timing Applications, Kent S. Wood, Armen Gulian, Paul S. Ray
Qvd Sensors As Focal Plane Instruments For X-Ray Timing Applications, Kent S. Wood, Armen Gulian, Paul S. Ray
Mathematics, Physics, and Computer Science Faculty Articles and Research
“QVD” detectors are based on thermoelectric heat‐to‐voltage (Q→V) conversion and digital (V→D) readout. For spectroscopic applications, the theoretical performance limits are competitive with superconducting tunnel junction (STJ) detectors and transition edge sensor (TES) devices. We discuss theoretical and demonstrated timing performance of QVD detectors with different design architectures. Detectors with lanthanum‐cerium hexaboride sensors can be very fast, up to 100 MHz/pixel counting rates. They can serve as focal plane detectors for X‐ray timing, in situations where very large apertures are used to gather X‐ray photons at high event rates. Practical implementation of thermoelectric (QVD) detectors requires cryogenic thermoelectric sensors with …
Interferometric And Holographic Imaging Of Surface-Breaking Cracks, James Lawrence Blackshire, Bradley D. Duncan
Interferometric And Holographic Imaging Of Surface-Breaking Cracks, James Lawrence Blackshire, Bradley D. Duncan
Electro-Optics and Photonics Faculty Publications
Two advanced nondestructive evaluation systems are developed for imaging surface-breaking cracks in aerospace materials. The systems use scanning heterodyne interferometry and frequency-translated holography principles to image ultrasonic displacement fields on material surfaces with high resolution and sensitivity. Surface-breaking cracks are detected and characterized by visualizing near-field ultrasonic scattering processes, which in turn results in local intensification of ultrasonic displacement fields in the immediate vicinity of a crack. The local intensification permits cracks to be easily distinguished from background levels, and creates unique displacement field images that follow the contours and morphology of the cracks with microscopic precision. The interferometric and …
Characterization Of Ultrathin Gate Dielectrics And Multilayer Charge Injection Barriers, Edwin M. Dons
Characterization Of Ultrathin Gate Dielectrics And Multilayer Charge Injection Barriers, Edwin M. Dons
Dissertations
Since the invention of the first integrated circuit, the semiconductor industry has distinguished itself by a phenomenally rapid pace of improvements in device performance. This trend of ever smaller and faster devices is a result of the ability to exponentially reduce feature sizes of integrated circuits, a trend commonly known as "scaling". A reduction of overall feature sizes requires a simultaneous reduction in the thickness of the gate dielectric, SiO2, of a MOSFET. Gate oxides in the ultrathin regime (<35 A) feature a large direct tunneling leakage current. The presence of this leakage current requires a reevaluation of standard characterization techniques as well as a reevaluation of the continued usefulness of SiO2 as the gate dielectric of choice for future applications. On the other hand, a thorough understanding of …
Understanding The Origin Of The Recovery Of Superconductivity In Halogenated Ybco Single Crystal : Atomic Structure Study, Lamine Mohamed Kollakoye Dieng
Understanding The Origin Of The Recovery Of Superconductivity In Halogenated Ybco Single Crystal : Atomic Structure Study, Lamine Mohamed Kollakoye Dieng
Dissertations
The recovery of superconductivity in underdoped YBa2Cu3O6+y (YBCO) by exposure to bromine, iodine, chlorine and fluorine is a long-standing problem which has not been clearly resolved. The key question concerns the role of these halogens in the lattice. In order to shed light to this problem, we have performed multiple-edge x-ray absorption fine structure (XAFS) measurements about the Y K, Ba L3, I L3, Cu K and Br K-edges at room temperature on brominated (non-brominated) and iodinated (non-iodinated) YBCO single crystals. Our XAFS results at the Br K (brominated) and I …
High Resolution Solar Observations In The Context Of Space Weather Prediction, Guo Yang
High Resolution Solar Observations In The Context Of Space Weather Prediction, Guo Yang
Dissertations
Space weather has a great impact on the Earth and human life. It is important to study and monitor active regions on the solar surface and ultimately to predict space weather based on the Sun's activity. In this study, a system that uses the full power of speckle masking imaging by parallel processing to obtain high-spatial resolution images of the solar surface in near real-time has been developed and built. The application of this system greatly improves the ability to monitor the evolution of solar active regions and to predict the adverse effects of space weather. The data obtained by …
Statistical Study Of Solar Radio Bursts, Gelu-Marius Nita
Statistical Study Of Solar Radio Bursts, Gelu-Marius Nita
Dissertations
The peak flux distribution of 40 years of solar radio burst data recorded by NOAA, as a function of frequency and time over a wide range of frequencies, was investigated to quantify the potential impact of radio bursts on wireless systems. Tables of fit parameters, which can be used to find burst occurrence rates in a number of frequency ranges, are presented. The typical power-law index of number density distribution, -1.8, is similar to that found in many hard X-ray studies. Significant changes were found in power-law index with frequency. The results may be useful for designers of current and …
Tem Study Of Crystalline Structures Of Cr–N Thin Films, Xingzhong Li, J. Zhang, David J. Sellmyer
Tem Study Of Crystalline Structures Of Cr–N Thin Films, Xingzhong Li, J. Zhang, David J. Sellmyer
Nebraska Center for Materials and Nanoscience: Faculty Publications
Cr–N films were grown on Si (001) substrates by reactive magnetron sputtering under an N2/Ar atmosphere at room temperature. The composition of the films, expressed as Cr1–xNx, can be varied by changing the N2/Ar pressure ratio during the synthesis process. Crystalline states of Cr–N films have been studied using electron diffraction. It is well known that two intermediate phases, Cr2N (hexagonal) and CrN (cubic), exist in the Cr–N system, and small variations around the ideal stoichiometry are tolerated. The present study shows that cubic CrN with vacancies rather than hexagonal Cr2 …
Rectification Of Thermal Fluctuations In Ideal Gases, Alejandro Garcia, P. Meurs, C. Van De Broeck
Rectification Of Thermal Fluctuations In Ideal Gases, Alejandro Garcia, P. Meurs, C. Van De Broeck
Faculty Publications
We calculate the systematic average speed of the adiabatic piston and a thermal Brownian motor, introduced by C. Van den Broeck, R. Kawai and P. Meurs [Phys. Rev. Lett. 93, 090601 (2004)], by an expansion of the Boltzmann equation and compare with the exact numerical solution.