Browsing by Subject "deposition"
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Item Beach and Vegetation-Line Changes at Galveston Island, Texas: Erosion, Deposition, and Recovery from Hurricane Alicia(1984) Morton, Robert A.; Paine, Jeffrey G.On August 18, 1983, Hurricane Alicia crossed the Upper Texas Gulf Coast and caused extensive property damage, especially along West Beach of Galveston Island. Aerial photographs taken before and after Alicia, along with field measurements made during the first post-storm year, provide a basis for determining nearshore changes associated with a major storm and for predicting potential beach recovery. Alicia caused substantial landward retreat of both the shoreline and the vegetation line. Retreat of the vegetation line ranged from 20 to 145 ft and averaged 80 ft. Erosion was generally greatest near the Sea Isle and Bay Harbor subdivisions, where storm processes were most intense; beach erosion generally decreased away from San Luis Pass, which is near the site of storm landfall. Because erosion was so severe, surface elevations were lowered as much as 4.5 ft and many Gulf-front houses were undermined and exposed on the beach after the storm. Alicia eroded several million cubic yards of sand from West Beach. About one-tenth of that sand was deposited on the adjacent barrier flat as a washover terrace. Washover penetration was greatest to the east of the storm's eye and along developed shoreline segments. The remaining eroded beach sand was deposited offshore as shoreface bars or as storm deposits on the inner shelf. The shoreface deposits promoted rapid forebeach accretion during the first post-storm year; at the same time, the backbeach elevation remained about 3 ft lower than before the storm, and the natural post-Alicia vegetation line remained essentially unchanged. Recovery of the vegetation line 1 year after the storm was insignificant mainly because the depth of beach erosion exceeded the depth of root penetration, thus eliminating plants from some areas that were densely vegetated before the storm.Item Ceramic Joining by Selective Beam Deposition(1995) Tompkins, J.V.; Birmingham, B.R.; Marcus, H.L.Current methods ofjoining of ceramic components may compromise the strength, chemical resistance, or high temperature properties of the resulting ceramic parts. A new method of joining, Ceramic Joining by Selective Beam Deposition, creates an all-ceramic joint between two or more ceramic components through selective decomposition of a gas precursor. An all-ceramic joint not only preserves the valuable properties of the ceramic materials joined, but may be tailored to match the coefficient of thermal expansion ofthe original material(s). The added material may be the same as one or both of the joined Inaterials, or may be a composite material. This preliminary work explores the effect of scanning speed and precursor pressure on Selective Beam Deposition ofsilicon carbide using tetramethylsilane.Item Dendrimer-Encapsulated Nanoparticles: New Synthetic and Characterization Methods and Catalytic Applications(2011-05) Myers, V. Sue; Weir, Michael G.; Carino, Emily V.; Yancey, David F.; Pande, Surojit; Crooks, Richard M.; Myers, V. Sue; Weir, Michael G.; Carino, Emily V.; Yancey, David F.; Pande, Surojit; Crooks, Richard M.In this article we describe the synthesis, characterization, and applications of dendrimer-encapsulated nanoparticles (DENs). These materials are synthesized using a template approach in which metal ions are extracted into the interior of dendrimers and then subsequently reduced chemically to yield nearly size-monodisperse particles having diameters in the 1-2 nm range. Monometallic, bimetallic (alloy and core@shell), and semiconductor nanoparticles have been prepared by this route. The dendrimer component of these composites serves not only as a template for preparing the nanoparticle replica, but also as a stabilizer for the nanoparticle. In this perspective, we report on progress in the synthesis, characterization, and applications of these materials since our last review in 2005. Significant advances in the synthesis of core@shell DENs, characterization, and applications to homogeneous and heterogeneous catalysis (including electrocatalysis) are emphasized.Item Depositional and Structural Challenges of the Wilcox Lobo Natural Gas Trend, South Texas(1994) Hamlin, H. Scott; Dickerson, Patricia Wood; Hentz, Tucker F.To increase understanding and utilization of gas resources in the Wilcox Lobo play of South Texas, this report reviews current geological knowledge of the Lobo trend. An additional objective of this report is to identify areas where advancements in geological understanding could lead to substantial improvements in efficient development of the Wilcox Lobo trend natural gas resource. According to published accounts, Lobo sandstones formed in a variety of depositional environments in both shallow and deep marine waters. During and after deposition, the Lobo experienced repeated episodes of erosion, faulting, and diagenesis. Thus, accurate prediction of reservoir sandstone attributes is difficult, and this difficulty is cited by operators as a significant challenge to efficiently targeting the remaining gas resource. Knowledge that would aid in the emergence of this resource includes information on sandstone correlation and accurate zone identification, depositional systems and facies interpretations, controls on fault pattern variability, and, to a lesser extent, recognition of diagenetic patterns and faults and fractures that are below seismic resolution. Geologic challenges of the Lobo trend are opportunities for targeting increasingly smaller and more difficult-to-detect compartments with advanced technology.Item Depositional Architecture of the Quaternary BlackWater Draw and Tertiary Ogallala Formations, Texas Panhandle and Eastern New Mexico(1985) Gustavson, Thomas C.; Holliday, Vance T.Deposition of basal fluvial sediments of the Ogallala Formation was controlled by topography on the middle Tertiary erosional surface. Paleovalley-fill sequences consist of gravelly and sandy-braided stream deposits overlain by eolian sediments deposited as sand sheets and loess. The change from fluvial to eolian sedimentation may have resulted from diversion of Ogallala streams to form the Pecos and Canadian Rivers. Paleostream divides on the middle Tertiary erosional surface are overlain primarily by eolian sediments. Source areas for eolian sediments may initially have been Ogallala braided streams, and later the floodplains of the newly formed Pecos and Canadian Rivers. Ground-water calcretes are extensively developed in the fluvial portion of Ogallala sediments. Pedogenic calcretes, consisting of nodular, laminated, brecciated and recemented, or pisolitic calcium carbonate occur primarily in the eolian portions of the Ogallala Formation. The geomorphic processes of eolian deposition, deflation, and pedogenesis have operated on the Southern High Plains from Ogallala time to the present, as evidenced by the distribution of coarse eolian deposits, which make up both the upper part of the Ogallala Formation and all of the Blackwater Draw Formation. The distinctive reddish sediments of the Blackwater Draw Formation contain as many as six well-developed buried soils that resemble each other, as well as the surface soils, in lithology and morphology. Although the Blackwater Draw Formation was originally assigned an Illinoian age, pedologic similarities of soils beneath ash deposits dated as 1.4 million years (Guaje ash) and 0.6 million years (Lava Creek "B") in Crosby and Swisher Counties, respectively, to paleosols at a thick section in Lubbock County, suggest that pedogenic processes have operated throughout the Quaternary. It is hypothesized that, at least from near the end of the Pleistocene, eolian sediments aggraded contemporaneously with lacustrine facies in a mosaic of laterally restricted lenses of eolian and playa sediments. Pulses of deposition were separated by relatively long periods of either landscape stability, during which soil development occurred, or deflation, which stripped surface horizons from newly formed soils. Modern processes appear to be analogous to those that operated much earlier, suggesting that on the Southern High Plains, the present is indeed the key to the past.Item Digitally-Driven Micro Surface Patterning by Hybrid Manufacturing(University of Texas at Austin, 2018) Smith, Matthew A.A.; Fry, Nicholas R.; Kay, Robert W.; Harris, Russell A.Aerosol Jet printing is a versatile direct-write method allowing selective deposition and alteration of surface chemistry on a variety of substrates, making it suitable for incorporation in a range of hybrid manufacturing processes. The digitally controlled nature of the presented hybrid manufacturing process enables rapid turnaround of designs, and improvements in flexibility and complexity compared to established methods. The apparatus and instrumentation that has been created at the University of Leeds enables specific processing conditions that result in deposition of features with critical dimensions smaller than 20µm. In this study the analysis of the effect of process variables on deposition geometries is presented. The features were assessed by a combination of optical microscopy and white light interferometry. Using in-process machine vision, topographical compensation, and alignment capability the deposition of material into micropatterned features in poly(dimethylsiloxane) (PDMS) was demonstrated. High-value applications of this technology for surface functionalisation include electronics and bio-engineering.Item Geologic History, Depostional Envirnoment, Processes, and Hydology of Galveston Island, Texas(1997) Garner, L. E.Galveston Island is a very young geologic feature compared to the Earth's age of approximately 4.5 billion years. Estimates suggest that Galveston Island and other Texas barrier islands began forming as submerged bars no more than 4,500 to 5,500 years ago, based on radiocarbon dating of shells (Fisk, 1959). The following descriptions of development history, present shoreline conditions, and processes and environments have been modified from various sources including LeBlanc and Hodgson (1959), Bernard and others (1970), Fisher and others (1972), Morton (1974), McGowen and others (1977), Weise and White (1980), and Paine and Barton (1989). The origin of barrier islands has been the subject of debate, with different processes or combinations of processes shaping and modifying them. These processes depend on variables such as sediment source, type, and supply, rate and direction of relative sea-level changes, basin shape, continental shelf slope, currents, waves, and tides. Three of the most discussed theories of barrier-island origin include development from an offshore shoal or submerged sandbar, development by spit accretion resulting from longshore drift, and development by drowning of the area landward of mainland beach sand ridges (Wanless, 1974). One possible explanation for the origin of Galveston Island is that it developed from offshore shoals, with later growth aided by spit accretion. The offshore shoals might have originally been mainland beach ridges submerged during a rise in sea level. All three processes may have played a role in the island's origin, with different segments of the island undergoing different processes at varying rates during their development.Item Geology of the Lower Cretaceous Travis Peak Formation, East Texas: Depositional History, Diagenesis Structure and Reservoir Engineering Implications(1990) Dutton, Shirley P.; Laubach, Stephen E. (Stephen Ernest), 1955-Â ; Tye, Robert S.; Baumgardner, Jr., Robert W.; Herrington, Karen L.This report summarizes stratigraphic, petrographic, and structural studies of the Lower Cretaceous Travis Peak Formation, a low-permeability gas sandstone in East Texas, and presents reservoir engineering implications. Depositional systems in this region were interpreted from logs and cores and include (1) a braided- to meandering-fluvial system that forms the majority of the Travis Peak section; (2) deltaic deposits interbedded with the distal part of the fluvial system; (3) paralic deposits that overlie and interfinger with the deltaic and fluvial deposits near the top of the Travis Peak; and (4) shelf deposits present at the downdip extent of the formation. Petrographic studies indicate the sandstones are quartzarenites and subarkoses. Cementation by quartz, dolomite, ankerite, illite, chlorite, and reservoir bitumen have reduced porosity to less than 8 percent and permeability to less than 0.1 md throughout most of the formation. Structurally deeper sandstones are more intensely quartz cemented than are shallower sandstones and contain abundant, open natural fractures. Borehole breakouts and drilling-induced fractures in core can be used to predict horizontal stress directions and the direction of hydraulic fracture propagation. Hydraulic fractures propagate in directions subparallel to the east-northeast strike of the natural fractures; thus, hydraulically induced fractures may not intersect many natural fractures.Item Historical Shoreline Changes in the Galveston Bay and San Antonio Bay Systems, Texas Gulf Coast(1983) Morton, Robert A.; Paine, Jeffrey G.; White, William Allen, 1939-Changes in shoreline position and stability in the Galveston and San Antonio Bay systems since the late 1800s were documented using historical monitoring techniques. This is accomplished by comparing shorelines from topographic charts (dated 1850 to 1860) and aerial photographs (taken in 1929-37, 1956-57, 1974, and 1982), measuring the magnitude (distance) of shoreline movement at specific sites, and calculating the rates of change for particular time periods (late 1800s to 1930s, 1930s to 1982, and late 1800s to 1982). Geological interpretations of the maps and photographs are used in conjunction with meteorological data and historical records to explain the important trends revealed in the tabulated shoreline data. Unprotected sediments forming the margins of these bays are subjected to natural coastal processes and modified by human activities that together cause shoreline movement. These unstabilized shorelines include high, nearly vertical clay bluffs, moderate slopes composed mainly of sand, saltwater marshes, sand and shell beaches, and newly formed areas filled by dredged material. Composition of the shoreline material and orientation of the shoreline with respect to prevailing wind directions and wave fetch largely determine the response and consequent movement of the shoreline. In some areas, property owners have attempted to stabilize the shoreline and prevent further movement by building seawalls and bulkheads and using riprap to dissipate wave energy. Factors contributing to shoreline changes include (1) regional and worldwide climate, (2) local changes in relative sea-level position, (3) local alterations in sediment supply, (4) storm frequency and intensity, and (5) human activities. Historical data compiled for these various factors indicate that warming temperatures, rising sea level, decreasing sediment supply, recurring severe storms, and ongoing human activities all favor continued erosion of most unprotected bay shorelines.Item Letter to Alfred C. Lane from H.B. Stenzel on 1939-05-29(1939-05-29) Stenzel, H.B.Item Letter to Bob H. Slaughter from H.B. Stenzel on 1969-06-16(1969-06-16) Stenzel, Henryk B.Item Letter to Donald W. Kohls from H.B. Stenzel on 1965-10-21(1965-10-21) Stenzel, H.B.Item Letter to H.B. Stenzel from Dan E. Feray on 1948-05-11(1948-05-11) Feray, Dan E.Item Letter to H.B. Stenzel from Harbans S. Puri on 1948-05-14(1948-05-14) Puri, Harbans S.Item Letter to H.B. Stenzel from John Emery Adams on 1931-06-12(1931-06-12) Adams, John EmeryItem Letter to H.B. Stenzel from K.J. Hsu on 1959-06-04(1959-06-04) Hsu, K.J.Item Letter to H.B. Stenzel from Le Brun N. Smith on 1960-07-13(1960-07-13) Smith, Le Brun N.Item Letter to H.B. Stenzel from Leo W. Hough on 1964-04-29(1964-04-29) Hough, Leo W.Item Letter to H.B. Stenzel from Leon Bromberg on 1959-05-19(1959-05-19) Bromberg, LeonItem Letter to H.B. Stenzel from R.C. Allison on 1963-01-24(1963-01-24) Allison, Richard C.