A Low-Signal-to-Noise-Ratio Sensor Framework Incorporating Improved Nighttime Capabilities in DIRSIG

When designing new remote sensing systems, it is difficult to make apples-to-apples comparisons between designs because of the number of sensor parameters that can affect the final image. Using synthetic imagery and a computer sensor model allows for comparisons to be made between widely different sensor designs or between competing design parameters. Little work has been done in fully modeling low-SNR systems end-to-end for these types of comparisons. Currently DIRSIG has limited capability to accurately model nighttime scenes under new moon conditions or near large cities. An improved DIRSIG scene modeling capability is presented that incorporates all significant sources of nighttime radiance, including new models for urban glow and airglow, both taken from the astronomy community. A low-SNR sensor modeling tool is also presented that accounts for sensor components and noise sources to generate synthetic imagery from a DIRSIG scene. The various sensor parameters that affect SNR are discussed, and example imagery is shown with the new sensor modeling tool. New low-SNR detectors have recently been designed and marketed for remote sensing applications. A comparison of system parameters for a state-of-the-art low-SNR sensor is discussed, and a sample design trade study is presented for a hypothetical scene and sensor

Theorem and Practicum:: Order, Value, Result, Interaction

The Thesis is the last major step toward graduation with a first professional degree, or Bachelor of Architecture (B.Arch.), which traditionally prepares students for practice. As a threshold between directed studios and independent thought, the Thesis provides an opportunity for the student to systematically explore a coherent line of investigation of issues relevant to the field of architecture. The Thesis is an intellectual position laid down or to be advanced. It is the first stage of the dialectic-discussion, that is, discussion and reasoning by dialogue as a method of intellectual investigation. An architectural thesis demands that a student take a position and have something to say that is relevant to the discursive field that it inhabits and/or its wider cultural context. In the field of architecture such intellectual positions have implications that result from a critique and re-examination of the role of architecture as a critical participant in the conditioning of public and private space. Thus, while an undergraduate architectural thesis originates in a determinate intellectual position, it culminates in a designed artifact, but rarely the artifact itself. This paper takes a step in characterizing architectural research, where the interaction of Theorem and Practicum is used not only as a guiding principle in the critical thinking process, but also as a springboard for constructive practices in the built realm. This particular reading is an inquiry into the importance and influence of interaction between Theorem and Practicum, as well as, the importance of which is observed through different modes of cross-pollination occurring in various aspects of architectural discourse and practice. This investigation is explored in four perspectives, labeled ‘order', ‘values', ‘results' and ‘interaction' are categorized according to their relationship to the investigation of Theorem and Practicum. Furthermore, these four attributes permeate and connect the diverse areas of research explored, which in combination provides an argument that rather than questioning: "is doing architecture doing research” as articulated by Jeremy Till, instead asks: "is doing research doing architecture”. Our aim is to expand the pedagogical field where the interaction of Theorem and Practicum is not an isolated act, but one of making

Theorem and Practicum:: Order, Value, Result, Interaction

The Thesis is the last major step toward graduation with a first professional degree, or Bachelor of Architecture (B.Arch.), which traditionally prepares students for practice. As a threshold between directed studios and independent thought, the Thesis provides an opportunity for the student to systematically explore a coherent line of investigation of issues relevant to the field of architecture. The Thesis is an intellectual position laid down or to be advanced. It is the first stage of the dialectic-discussion, that is, discussion and reasoning by dialogue as a method of intellectual investigation. An architectural thesis demands that a student take a position and have something to say that is relevant to the discursive field that it inhabits and/or its wider cultural context. In the field of architecture such intellectual positions have implications that result from a critique and re-examination of the role of architecture as a critical participant in the conditioning of public and private space. Thus, while an undergraduate architectural thesis originates in a determinate intellectual position, it culminates in a designed artifact, but rarely the artifact itself. This paper takes a step in characterizing architectural research, where the interaction of Theorem and Practicum is used not only as a guiding principle in the critical thinking process, but also as a springboard for constructive practices in the built realm. This particular reading is an inquiry into the importance and influence of interaction between Theorem and Practicum, as well as, the importance of which is observed through different modes of cross-pollination occurring in various aspects of architectural discourse and practice. This investigation is explored in four perspectives, labeled ‘order', ‘values', ‘results' and ‘interaction' are categorized according to their relationship to the investigation of Theorem and Practicum. Furthermore, these four attributes permeate and connect the diverse areas of research explored, which in combination provides an argument that rather than questioning: "is doing architecture doing research” as articulated by Jeremy Till, instead asks: "is doing research doing architecture”. Our aim is to expand the pedagogical field where the interaction of Theorem and Practicum is not an isolated act, but one of making

New Insights into the Charge-Transfer-to-Solvent Spectrum of Aqueous Iodide: Surface versus Bulk.

Liquid phase charge-transfer-to-solvent (CTTS) transitions are important, as they serve as photochemical routes to solvated electrons. In this work, broadband deep-ultraviolet electronic sum frequency generation (DUV-ESFG) and two-photon absorption (2PA) spectroscopic techniques were used to assign and compare the nature of the aqueous iodide CTTS excitations at the air/water interface and in bulk solution. In the one-photon absorption (1PA) spectrum, excitation to the 6s Rydberg-like orbital (5p → 6s) gives rise to a pair of spin-orbit split iodine states, 2P3/2 and 2P1/2. In the 2PA spectra, the lower-energy 2P3/2 peak is absent and the observed 2PA peak, which is ∼0.14 eV blue-shifted relative to the upper 2P1/2 CTTS peak seen in 1PA, arises from 5p → 6p electronic promotion. The band observed in the ESFG spectrum is attributed to mixing of excited states involving 5p → 6p and 5p → 6s promotions caused by both vibronic coupling and the external electric field generated by asymmetric interfacial solvation

Science and Technology Progress at the Sydney University Stellar Interferometer

This paper presents an overview of recent progress at the Sydney University Stellar Interferometer (SUSI). Development of the third-generation PAVO beam combiner has continued. The MUSCA beam combiner for high-precision differential astrometry using visible light phase referencing is under active development and will be the subject of a separate paper. Because SUSI was one of the pioneering interferometric instruments, some of its original systems are old and have become difficult to maintain. We are undertaking a campaign of modernization of systems: (1) an upgrade of the Optical Path Length Compensator IR laser metrology counter electronics from a custom system which uses an obsolete single-board computer to a modern one based on an FPGA interfaced to a Linux computer - in addition to improving maintainability, this upgrade should allow smoother motion and higher carriage speeds; (2) the replacement of the aged single-board computer local controllers for the siderostats and the longitudinal dispersion compensator has been completed; (3) the large beam reducing telescope has been replaced with a pair of smaller units with separate accessible foci. Examples of scientific results are also included.Comment: 10 pages, 9 Figure

The hydration structure of dissolved carbon dioxide from X-ray absorption spectroscopy

Abstract The dissolution of carbon dioxide in water and its subsequent hydrolysis reactions comprise one of the most central processes in all of science, yet it remains incompletely understood despite enormous effort. We report the detailed characterization of dissolved CO2 gas through the combination of X-ray spectroscopy and first principles theory. The molecule acts as a hydrophobe in water with an average hydrogen bond number of 0.56. The carbon atom interacts weakly with a single water at a distance of >2.67 Å and the carbonyl oxygens serve as weak hydrogen bond acceptors, thus locally enhancing the tetrahedral water hydrogen bonding structure

Tectonic memoirs: the epistemological parameters of tectonic theories of architecture

The purpose of architectural theory is to provide a paradigm, or episteme, from which one can address contemporary design issues within the broader cultural context. It comprises any written system of architecture and may be either partial or comprehensive, but it must encompass a framework of cognitive categories that inevitably provide criteria for judgment. If not explicitly stated, it nevertheless implies an epistemology, a substructure for architectural knowledge. Previous studies of tectonics have tended to treat it as an autonomous architectural discourse, focusing on an individual writer and theory, or on a thematic concern such as the relationship between ontology and representation. This study approaches tectonics differently, relating it to the broader shifts within the discourses of architecture and philosophy, thereby sanctioning a more synergistic, as opposed to autonomous, examination. In exploring the epistemological parameters of tectonics theories in the West it isolates three major periods in its development: Classical Tectonics- derived from ancient philosophy, Rational Tectonics- emerging from the epistemology of science and Poetic Tectonics- developed out of concerns raised by the German Counter- Enlightenment and the Romantic Movement. At each stage in its development tectonics has served to provide key principles that collectively constitute its ground. The study reveals that Poetic Tectonics was a reaction against the duality of mind and abstract rationalism- so central to Cartesian thought and the epistemology of science- and its impact on architectural thought. In response Poetic Tectonics while accepting the key principles of Rational Tectonics sought to redirect it along the philosophical lines of the 2 German Enlightenment and Romanticism while also re-presencing the ethical substructure of Classical Tectonics. This study recognizes that through the course of time, the epistemology upon which cultures are formed have and will continue to change and as they do new tectonic theories will need to be negotiated; rendering tectonics in a continual state of 'becoming'. If there is to be a conclusion it lies in the fact that in its historical persistence and continuity tectonics represents a tradition within Western architecture on par with the likes of the Vitruvian, Organic and Functionalist.Ph.D.Committee Chair: Lewcock, Ron; Committee Member: Dimitropoulos, Harris; Committee Member: Dowling, Elizabeth; Committee Member: Harries, Karsten; Committee Member: Verene, Donal

Investigation of the Surface Properties of Aqueous Solutions

Understanding the structure and composition of the air-water interfaces is of utmost important to many areas of scientific study. Aqueous interfaces are ubiquitous in nature and as such, are intimately involved in chemical processes ranging from those affecting atmospheric aerosols to those governing cellular structuring. The current state of the atmosphere in relation to climate change is of utmost importance, and surface sensitive spectroscopies are only now beginning to shed light on the chemical mechanisms involved. An understanding of how ions adsorb to the water surface will be invaluable in predicting and combatting the environmental chemistry which is central to climate change. Despite the importance of the air-water interface, it remains incompletely understood – particularly in the case of those solutions which contain ions and/or biomolecules – due to the experimental challenges involved in probing it. However, recent experimental and theoretical results have established the existence of certain anions that are preferentially adsorbed to the air-water interface. In this dissertation, I discuss my development of a broadband deep-UV sum frequency generation (DUV-SFG) spectroscopy experiment which was used to explicitly measure the adsorption of ions at the air-water interface. I also use a Raman thermometry experiment that, while it is not a surface specific probe, is a surface sensitive probe and so interfacial information can be drawn from those experiments. In Chapter 2 I describe broadband DUV-SFG studies of the aqueous iodide ion wherein the first full interfacial charge-transfer-to-solvent (CTTS) spectrum of an ion was measured. Interestingly, the spectrum is redshifted by ~8 nm relative to the bulk spectrum as well as significant line narrowing – 17% for the J = 1/2 peak and 66% for the J = 3/2 peak. These results may indicate very interesting dynamics at the air-water interface as well as reporting on the hydration structure of those ions at the water surface. A recent publication indicated that sodium nitrite adsorbs strongly to the interface as a contact ion pair, wherein the Gibbs free energy of adsorption to the air-water interface was found to be -17.8 kJ/mol. In Chapter 3 I describe broadband DUV-SFG studies on the aqueous sodium nitrite system in an attempt to confirm or deny the contact ion pairing hypothesis. It was found that despite elaborate attempts to purify the salt prior to studying it in solution, there was always a significant degree of hydrocarbon contamination. This contamination likely resulted in the previous study’s misinterpretation of large SHG intensity as nitrite adsorption to the air-water interface. Interestingly, the broadband SFG experiment was found to be a good method for confirming sample purity by examining the nonresonant signal collected.Clearly the development of nonlinear optical spectroscopies has greatly advanced the field of interfacial science, but there is still much to be learned. In Chapter 4 I describe what I feel are the most important future steps toward furthering our understanding of interfaces. I have outlined several experimental techniques that need to be developed or refined, as well as indicated the next steps for theoreticians. This chapter does not encompass all of what can or should be done, but it is a good starting point.Nonlinear optical spectroscopies are incredibly powerful due to their interfacial specificity, but they are also quite difficult to utilize because they are naturally a low signal method and are very susceptible to contamination. In Chapter 5 I describe the use of Raman thermometry to study the evaporation rate of water from aqueous HCl droplets. By definition, evaporation is a process that occurs at the interface, and so despite Raman spectroscopy not being a surface specific probe, this experimental technique allows us to draw conclusions about interfacial properties. The kinetics and energetics of cloud droplet and aerosol formation in the atmosphere are highly governed by the evaporation and condensation rates of water, yet the magnitude and mechanism of evaporation remains incompletely characterized. Of particular import (and controversy) is the nature of interfacial water pH and its effect on the evaporation rate and environmental reactivity. Raman thermometry measurements of freely evaporating micro-droplets were used to determine evaporation coefficients () for two different hydrochloric acid solutions, both which result in a significant deviation from γwater. With a 95% confidence level, it is found that the evaporation coefficient for 1.0 M HCl is 0.24 ± 0.04 – a ~60% decrease relative to pure water, and for 0.1 M HCl is 0.91 ± 0.08 – a ~45% increase relative to pure water. These results suggest a large perturbation in the surface structure induced by hydronium at the water surface