Physics Commons^™

Observation Of A Self-Limiting, Shear-Induced Turbulent Inversion Layer Above Marine Stratocumulus, J. Katzwinkel, H. Siebert, R. A. Shaw

Michigan Tech Publications

High-resolution measurements of thermodynamic, microphysical, and turbulence properties inside a turbulent inversion layer above a marine stratocumulus cloud layer are presented. The measurements are performed with the helicopter-towed measurement payload Airborne Cloud Turbulence Observation System (ACTOS), which allows for sampling with low true air speeds and steep profiles through cloud top. Vertical profiles show that the turbulent inversion layer consists of clear air above the cloud top, with nearly linear profiles of potential temperature, horizontal wind speed, absolute humidity, and concentration of interstitial aerosol. The layer is turbulent, with an energy dissipation rate nearly the same as that in the …

Formation Of Degenerate Band Gaps In Layered Systems, Anton I. Ignatov, Alexander M. Merzlikin, Miguel Levy, Alexey P. Vinogradov

Michigan Tech Publications

In the review, peculiarities of spectra of one-dimensional photonic crystals made of anisotropic and/or magnetooptic materials are considered. The attention is focused on band gaps of a special type—the so called degenerate band gaps which are degenerate with respect to polarization. Mechanisms of formation and properties of these band gaps are analyzed. Peculiarities of spectra of photonic crystals that arise due to the linkage between band gaps are discussed. Particularly, it is shown that formation of a frozen mode is caused by linkage between Brillouin and degenerate band gaps. Also, existence of the optical Borrmann effect at the boundaries of …

Aerosols-Cloud Microphysics-Thermodynamics-Turbulence: Evaluating Supersaturation In A Marine Stratocumulus Cloud, F. Ditas, R. A. Shaw, H. Siebert, M. Simmel, B. Wehner, A. Wiedensohler

Michigan Tech Publications

This work presents a unique combination of aerosol, cloud microphysical, thermodynamic and turbulence variables to characterize supersaturation fluctuations in a turbulent marine stratocumulus (SC) layer. The analysis is based on observations with the helicopter-borne measurement platform ACTOS and a detailed cloud microphysical parcel model following three different approaches: (1) From the comparison of aerosol number size distributions inside and below the SC layer, the number of activated particles is calculated as 435 ± 87 cm -3 and compares well with the observed median droplet number concentration of N̄ d = 464 cm -3. Furthermore, a 50% activation diameter of D …

Arbitrary Super Surface Modes Bounded By Multilayered Metametal, Ruoxi Yang, Xiaoyue Huang, Zhaolin Lu

Michigan Tech Publications

The dispersion of the fundamental super mode confined along the boundary between a multilayer metal-insulator (MMI) stack and a dielectric coating is theoretically analyzed and compared to the dispersion of surface waves on a single metal-insulator (MI) boundary. Based on the classical Kretschmann setup, the MMI system is experimentally tested as an anisotropic material to exhibit plasmonic behavior and a candidate of “metametal” to engineer the preset surface plasmon frequency of conventional metals for optical sensing applications. The conditions to obtain artificial surface plasmon frequency are thoroughly studied, and the tuning of surface plasmon frequency is verified by electromagnetic modeling …

On The Quantization Problem In Curved Space, Benjamin Bernard

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The nonrelativistic quantum mechanics of particles constrained to curved surfaces is studied. There is open debate as to which of several approaches is the correct one. After a review of existing literature and the required mathematics, three approaches are studied and applied to a sphere, spheroid, and triaxial ellipsoid.

The first approach uses differential geometry to reduce the problem from a three dimensional problem to a two-dimensional problem. The second approach uses three dimensions and holds one of the separated wavefunctions and its associated coordinate constant. A third approach constrains the particle in a three-dimensional space between two parallel surfaces …

Analytical Chemical Sensing Using High Resolution Terahertz/Submillimeter Wave Spectroscopy, Benjamin L. Moran

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A highly sensitive and selective Terahertz gas sensor used to analyze a complex mixture of Volatile Organic Compounds (VOCs) has been developed. To best demonstrate analytical capabilities of a THz chemical sensor, we chose to perform analytical quantitative analysis of a certified gas mixture using a prototype gas phase chemical sensor that couples a commercial preconcentration system (Entech 7100A) to a custom high resolution THz spectrometer. A Method TO-14A certified mixture of thirty-nine VOCs was purchased. Twenty-six of the thirty-nine chemicals were identified as suitable for THz spectroscopic detection. The Entech 7100A system is designed and marketed as an inlet …

Characterization Of Ceramic Matrix Composite Materials Using Millimeter-Wave Techniques, Matthew Lee Bischoff

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This thesis describes studies that were carried out on Ceramic Matrix Composite (CMC) materials. These materials were provided by the Air Force Research Laboratory for evaluation in the millimeter-wave frequency region with the goal of developing Non-Destructive Evaluation techniques. This thesis centers on describing the measured reflections from an Oxide/Oxide and SiC/SiNC CMC materials. Models were derived from the Fresnel equations to account for the reflected and transmitted waves in these materials. System models were developed to describe the power coupling of the spectra measured in three separate measurement systems. Using these models the complex index of refraction was determined …

Characterization Of Ceramic Composite Materials Using Terahertz Non-Destructive Evaluation Techniques, Lindsay Owens

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The characterization of defects such as rust, voids, etc. on materials and the analysis and prediction of strain and stress induced breakdown are well known applications of non-destructive evaluation (NDE) techniques. THz radiation has been suggested as an effective NDE tool for use in the field of ceramics and ceramic matrix composite materials (CMC), via THz spectroscopy and imaging. The goal of this research is to monitor the progression of thermal and mechanical damage applied to the CMC materials using terahertz spectroscopic imaging in order to create a predictive model that will correlate THz imaging data of these materials to …

Terahertz Time Domain Spectroscopy And Fresnel Coefficient Based Predictive Model, Justin C. Wheatcroft

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An optical material parameter predictive model that accounts for sample to air interfaces was developed. The model predicts how a terahertz time-domain spectroscopy time domain pulse will be affected as it passes through a given thickness of a material. The model assumes a homogenous, linear, isotropic dielectric or semiconductor. The inputs to the model are the real and imaginary refractive indices across the desired frequency band. Different dielectric material's optical parameters were taken from the literature and the predicted time domain pulses were shown. It was also shown that the refractive index and absorption coefficient for samples that were optically …

Photorefractive Thin Films And Polymers For Use In Organic-Inorganic Hybrid Cells, Steven Harris Buller

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Two classes of materials were investigated as possible replacements for the bulk photorefractive windows in inorganic-organic hybrid cells: thin films and polymers. Each material was fabricated and subsequently characterized using two different methods due to their different stages of development. The thin films were characterized by X-ray diffraction while the polymers were characterized by two-beam coupling. Thin films of strontium barium niobate and potassium niobate were grown, using pulsed laser deposition, on four different substrates. It was found that it was possible to grow a thin film of potassium niobate in the correct orientation to replace a bulk photorefractive window. …

Radio-Frequency Heating Of Magnetic Nanoparticles, Mohammud Zafrullah Jagoo

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In the present study, a power supply capable of converting a direct current into an alternating current was built. The frequency of oscillation of the output current could be varied from 174.8 kHz to 726.0 kHz by setting a set of capacitors in resonance. To this power supply is attached a 20-turns copper coil in the shape of a spiral. Because of the high heat generated in the coil, the latter has to be permanently water-cooled. A vacuum pump removes the air between the sample holder and the coil. A fiber optic temperature sensor with an accuracy of 0.001 K …

The Mechanisms Of Luminescence From Zno Under Electron Irradiation, Devin Marlinjames Todd

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Zinc Oxide has been utilized for centuries in a wide range of applications including medical, food, and materials. It is now that ZnO draws much attention to its potential as a high frequency semiconductor and UV laser. As a result, there has been much investigation into the properties of ZnO and many papers have been published in the area. Despite this fact, there is still much that is unknown about its electronic defect structure. This research investigates the broad region of the Zinc Oxide luminescence spectrum known as the green band, which lies roughly between 480 - 580 nm or …

Comparing Us And Chinese High-School Physics Teaching In Terms Of The Use Of Inquiry, Lingbo Qian

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Inquiry based teaching has been widespread in the United States as well as in China in the last two decades. It was implemented by many teachers and shown to be effective in both countries. This study examines the extent to which inquiry-based teaching in high-school physics is practiced in US and China through the use of lesson observations and a survey. Nineteen lessons taught by 19 teachers (9 US and 10 Chinese) were observed (N=19). Results show that both US and Chinese teachers know well about the inquiry-based teaching. However, in practice, little inquiry-based teaching was observed in the two …

Dielectric Constant Measurements Using Atomic Force Microscopy System, Hembathanthirige Yasas Dhanapala

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A new technique to obtain local dielectric constant of thin films was developed using atomic force microscopy system. This technique, in addition to other characterization methods such as AFM imaging and X-Ray diffraction, was used to study, as an example, dielectric constant of thin films of 0.3BiScO3 - 0.7BaTiO3. The thin films were fabricated by using pulsed laser deposition technique under following temperature of the substrate: 6500C, 7000C and 7500C. At each temperature, two different oxygen pressures were used in deposition chamber: 50 mTorr and 100 mTorr. Our goal was to find optimal growth conditions with the highest dielectric constant …

Characterization Of Structured Nanomaterials Using Terahertz Frequency Radiation, Andrew John Niklas

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Measurements that use terahertz frequency radiation to characterize materials are beneficial for scientists trying to determine the physical parameters that govern the interaction of electromagnetic waves and matter at those frequencies. Results will be presented of time domain terahertz spectroscopy measurements taken in forward and backward scattering directions from vertically aligned arrays of multi-walled carbon nanotubes and thin films of perforated copper. The intent of this research is to both corroborate results from independent research groups conducting similar experiments and to further increase understanding in the scientific community with respect to carbon nanotube reflection phenomena at terahertz frequencies.

Electronic And Structural Properties Of Silicene And Graphene Layered Structures, Patrick B. Benasutti

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Graphene is a two-dimensional nanomaterial with useful and novel properties, but it is a material that does not integrate well with the current silicon microchip infrastructure. Silicene could solve this problem, as it is made of silicon yet retains the novel properties that make graphene desirable. This thesis will outline density functional calculations of a newly proposed structure involving the combination of these two materials. The structure includes silicene layered on graphene in such a manner that it composes a superlattice. It will be examined using the ab-initio density functional theory software Quantum Espresso.

This superlattice structure is proposed to …