6,032 research outputs found
Restoring Voice to the Mute Clay: Sumer and the Magoffin Collection Cuneiform Tablets
This thesis contains a history of Sumer from the earliest known periods through the fall of the Third Dynasty of Ur, a detailed investigation into the lives and careers of Sumerian scribes, a history of modern Mesopotamian archaeology, and the results of eighteen months\u27 research into the cuneiform tablet component of the Magoffin Collection at the Columbia Museum of Art. It finds that the latter documents are Sumerian in origin, with most published during the late twenty-first and early twentieth centuries BCE, based on assessments from cuneiform specialists at institutions across the United States. It includes the first full translation of a Magoffin tablet since their donation to the Columbia Museum, prepared by Dr. Robert Englund of UCLA
Understanding Extrudate Swell: From Theoretical Rheology to Practical Processing
This thesis focusses on the measurement and prediction of extrudate (or die) swell of molten polymers. The overall aim of this work is to understand extrudate swell for complex, industrially relevant systems. This is performed by first understanding the causes of swelling for well defined, monodisperse polymers at a molecular level. The systems are then gradually built up in complexity from bidisperse to very polydisperse and/or branched samples. At each stage predictions for extrudate swell are obtained using the \textit{flowSolve} fluid dynamics package combined with a molecular constitutive equation and are compared to extrusion experiments using a novel Multi-Pass-Rheometer setup.
The effects of both molecular weight and temperature can be ignored when shear rates are scaled by Rouse Weissenberg number as extrudate swell is a chain stretch controlled phenomenon. For monodisperse systems theoretical predictions using the Rolie-Poly constitutive equation match experimental results up to a =7 above which simulations over-predict swelling ratios. This is justified in this work using reduction of monomeric friction at high deformation rates.
Extrudate swell of polydisperse polystyrenes is successfully predicted up to high Weissenberg numbers using the Rolie-Double-Poly equation when combined with monomeric friction reduction. A slight under-prediction is seen at low Weissenberg number where the chain stretch times of long polymer chains are increased by dilution with shorter chains. Qualitatively correct but quantitatively poor predictions are obtained for highly polydisperse polyethylenes where the low shear extrudate swell is under-predicted.
Branched polymers behave differently experimentally to linear samples, exhibiting extrudate swell below the Rouse time of the polymer backbone. A small amount of branching increases swelling ratios versus the linear case but moderate increases in branching above this point have little effect on the experimentally observed swelling ratios. Significantly branched polyethylenes swell more than this, especially at high shear rates. There is a similar trend in simulated results using the XPP model but only a partial agreement between simulated and experimental extrudate swell is observed
Theoretical Methods in the Non-Equilibrium Quantum Mechanics of Many Bodies
A toolbox of theoretical methods pertinent to the study of non-equilibrium many-body quantum mechanics is presented with an eye to specific applications in cold atoms systems and solids. We discuss the generalization from unitary quantum mechanics to the non-unitary framework of open quantum systems. Theoretical techniques include the Keldysh close-time-path integral and its associated correlation functions, the quantum kinetic equation, and numerical integration of equations of motion both unitary and non-unitary. We explore how the relaxation of the assumption of equilibrium yields a whole new array of sometimes counterintuitive effects. We treat such examples as the non-equilibrium enhancement of BCS superfluidity by driving, bistability and coherent population transfer in Feshbach coupled fermions, and the dynamic stimulation of quantum coherence in bosons confined to a lattice. These systems are considered with an eye to enhancing some useful quantum properties and making them available in wider parameter regimes
Texas Oil and Gas Case Law Update
As the Texas economy enjoys the impact of robust oil and gas exploration and development spurred on by the shale drilling boom, Texas courts continue to experience similarly swollen dockets of oil and gas disputes. The Texas Supreme Court remained active in the energy sector in the 2011-2012 term with significant opinions affecting the areas of pipeline condemnation, exploration and production industry contracts, and lessor-lessee relations. Texas intermediate appellate courts also issued dozens of opinions touching various aspects of the industry from title and conveyancing disputes to lease operating issues. The following update will address the significant Texas Supreme Court opinions from the 2011-2012 term as well as selected cases from the intermediate appellate courts
A low cost scheme for high precision dual-wavelength laser metrology
A novel method capable of delivering relative optical path length metrology
with nanometer precision is demonstrated. Unlike conventional dual-wavelength
metrology which employs heterodyne detection, the method developed in this work
utilizes direct detection of interference fringes of two He-Ne lasers as well
as a less precise stepper motor open-loop position control system to perform
its measurement. Although the method may be applicable to a variety of
circumstances, the specific application where this metrology is essential is in
an astrometric optical long baseline stellar interferometer dedicated to
precise measurement of stellar positions. In our example application of this
metrology to a narrow-angle astrometric interferometer, measurement of
nanometer precision could be achieved without frequency-stabilized lasers
although the use of such lasers would extend the range of optical path length
the metrology can accurately measure. Implementation of the method requires
very little additional optics or electronics, thus minimizing cost and effort
of implementation. Furthermore, the optical path traversed by the metrology
lasers is identical with that of the starlight or science beams, even down to
using the same photodetectors, thereby minimizing the non-common-path between
metrology and science channels.Comment: 17 pages, 4 figures, accepted for publication in Applied Optic
G-band FMCW Doppler radar for sea clutter and target characterisation
Funding: UK Engineering and Physical Sciences Research Council under grant EP/S032851/1.Marine autonomy is a field receiving a high degree of interest for its many potential applications in terms of commerce, crew safety, and the military. A successful autonomous vessel depends on a sophisticated degree of situational awareness facilitated by sensors. We are investigating sub-THz radar sensors for this purpose, with the primary goal being the characterization of sea clutter and targets in terms of both amplitude and Doppler statistics at frequencies spanning 24 to 350 GHz, where presently there is a lack of data. Sub-THz frequencies are of particular interest due to improved range and Doppler resolutions, and reduced sensor size, factors expected to be critical in enabling anomaly detection in the dynamic marine environment. As part of this work, a new 207 GHz frequency modulated continuous wave (FMCW) radar is being developed for the collection of clutter and target phenomenology data. The architecture uses a direct digital synthesis (DDS) generated chirp which is upconverted onto a low phase noise microwave LO then frequency multiplied by 24 to the carrier frequency. Twin Gaussian optics lens antennas (GOLAs) are used for transmit and receive with beamwidths of 2° , with adjustable linear polarization. The radar head is gimbal mounted for raster scanning RCS maps or for use in staring mode Doppler measurements. A chirp bandwidth of 4 GHz enables range bins of a few centimeters and high speed chirps enable a maximum unambiguous velocity of ±5 m/s.Publisher PD
Giant Change in Electrical Resistivity Induced by Moderate Pressure in Pt(bqd)2 – First Candidate Material for an Organic Piezoelectronic Transistor (OPET)
The piezoelectronic transistor (PET) has been proposed to overcome the voltage and clock speed limitations of conventional field-effect transistors (FET). In a PET, voltage is transduced to stress, which leads to an insulator-metal transition in a piezo-resistive (PR) element. Although the simulated switching speeds are promising, the viable candidates proposed so far for the PR layer are rare earth compounds that require several GPa of pressure (P) to metalize, necessitating breakthroughs in transduction mechanism scaling and processing. Here, a PR candidate that metalizes in the 0–300 MPa range – the transition metal complex platinum benzoquinonedioximato (Pt(bqd)2) is demonstrated. Such electrical sensitivity to the application of P arises when the material is grown as a thin film with the preferred needle orientation perpendicular to the substrate. As evidence, a combination of hydrostatic and uniaxial pressure studies is provided. The former studies are produced on the compressed powder pellet in a specially developed piston-cylinder cell (P-C cell) under variable temperatures (T) and P. The latter is via thin film deposition and uniaxial resistivity (ρ) measurements and these revealed the high potential of this material for the PET concept.</p
Doppler characteristics of sea clutter at K-band and W-band : results from the St Andrews and Coniston water trials
Funding: UK Engineering and Physical Sciences Research Council under grant EP/S032851/1.This study reports on the experimental results from two field trials conducted by the University of St Andrews, focusing exclusively here on Doppler data. The first trial was at the Bruce Embankment in St Andrews, UK (winter 2020) and the second one was at Coniston Water in the Lake District, UK (autumn 2022). A 24 GHz K-band radar and a 94 GHz W-band radar were used in both trials to collect sea clutter data for phenomenology studies. As very few sea clutter data and analysis of these are available in the literature at these high frequencies, the results are expected to be of general interest within this field of study. The data collection at both trials was done for low grazing angles in the littoral zone. The datasets are quite varied in terms of wave direction, polarization and wind speed. The Doppler signatures and corresponding statistical parameters for these various conditions are reported here. The spectral analysis of different wave types (burst, whitecap, rough surface scattering) along with the combined spectra are also discussed. It is anticipated that these empirical results will be the precursor for improving upon the frequency ranges of existing sea clutter Doppler models
Telemedicine coverage for post-operative ICU patients.
Introduction There is an increased demand for intensive care unit (ICU) beds. We sought to determine if we could create a safe surge capacity model to increase ICU capacity by treating ICU patients in the post-anaesthesia care unit (PACU) utilizing a collaborative model between an ICU service and a telemedicine service during peak ICU bed demand. Methods We evaluated patients managed by the surgical critical care service in the surgical intensive care unit (SICU) compared to patients managed in the virtual intensive care unit (VICU) located within the PACU. A retrospective review of all patients seen by the surgical critical care service from January 1st 2008 to July 31st 2011 was conducted at an urban, academic, tertiary centre and level 1 trauma centre. Results Compared to the SICU group ( n = 6652), patients in the VICU group ( n = 1037) were slightly older (median age 60 (IQR 47-69) versus 58 (IQR 44-70) years, p = 0.002) and had lower acute physiology and chronic health evaluation (APACHE) II scores (median 10 (IQR 7-14) versus 15 (IQR 11-21), p \u3c 0.001). The average amount of time patients spent in the VICU was 13.7 + /-9.6 hours. In the VICU group, 750 (72%) of patients were able to be transferred directly to the floor; 287 (28%) required subsequent admission to the surgical intensive care unit. All patients in the VICU group were alive upon transfer out of the PACU while mortality in the surgical intensive unit cohort was 5.5%. Discussion A collaborative care model between a surgical critical care service and a telemedicine ICU service may safely provide surge capacity during peak periods of ICU bed demand. The specific patient populations for which this approach is most appropriate merits further investigation
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