Now showing items 13913-13932 of 14576

    • U.S. smelter acid sales and revenues: The implications of adopting European acid trade and marketing practices

      Virdis, Maria Rosa, 1953- (The University of Arizona., 1989)
      Sulphuric acid obtained as a byproduct of non-ferrous metal ore smelting is often the mandatory result of stringent environmental policies adopted in the industrialized countries to limit sulphur dioxide emissions. For the primary copper industry in the southwestern U.S., improvement of sulphuric acid marketing and distribution economies is a critical factor. In this thesis, through a comparison of the European and U.S. sulphuric acid market structure and organization, both the opportunity and the implications of adopting European acid marketing practices are discussed. A more centralized system of acid distribution, as in the European model, if applied to the U.S. smelter acid market, proves to be potentially beneficial for net revenue enhancement. A rationalization of the logistic aspects could substantially reduce acid transportation costs, allow repayment of at least average variable costs of production and improve southwestern smelter acid competitiveness in the domestic markets.
    • Ultimate flexural strength of flat slabs: with particular attention to membrane action

      Sakolosky, John Joseph, 1941- (The University of Arizona., 1966)
    • Ultimate performance limitations of phase-locked loops

      Paul, William Vincent, 1928- (The University of Arizona., 1961)
    • Ultimate shear strength of footings and flat plates

      Lawrence, Patrick Edward, 1940- (The University of Arizona., 1965)
    • Ultimate strength design of R/C columns by numerical integration method

      Yeung, David Ho-Fung, 1946- (The University of Arizona., 1975)
    • Ultra-compact Integrated Silicon Photonics Balanced Coherent Photodetectors

      Meyer, Jason T. (The University of Arizona., 2016)
      The design, simulation, and initial fabrication of a novel ultra-compact 2x2 silicon multimode-interference device evanescently coupled to a dual germanium metal-semiconductor-metal (MSM) photodetector is presented. For operation at the standard telecom wavelength of 1.5 µm, the simulations demonstrate high-speed operation at 30 GHz, low dark current in the nanoamp range, and external quantum efficiency of 80%. Error analysis was performed for possible tilt error introduced by hybrid integration of the MSM layer on top of the MMI waveguides by use of surface mount technology (SMT) and direct wafer bonding.
    • Ultra-precise measurement of thermal expansion coefficients

      Bradford, James N., 1926- (The University of Arizona., 1969)
    • Ultra-violet light and titanium dioxide catalyzed oxidation of red dye-79

      Adharapurapu, Krishna, 1965- (The University of Arizona., 1991)
      This research focused on the color destruction of red dye-79 in aqueous solution. Red dye-79 is a typical pollutant in the textile industrial wastewater streams. A 50 parts per million (ppm) aqueous solution of this dye was used for all experiments. Although, there are many conventional techniques for the treatment, the research investigated a new methodology, which uses the synthetic ultraviolet radiation (254 nanometers) in combination with an undoped semi-conductor powder titanium dioxide (TiO₂) anatase for the photo-catalytic destruction of inorganics and organic moieties responsible for color in aqueous solution of red dye-79. Also, investigated were the effects of the oxidant hydrogen peroxide (H₂O₂) added externally to enhance the reaction kinetics for color destruction. Ultraviolet absorbance readings at 512 nanometers were employed to quantify the color destruction. The effects of reaction parameters catalyst (TiO₂), oxidant (H₂O₂), alkalinity and, dye concentrations as well as pH, on dye destruction kinetics were also quantified.
    • Ultrafine Bubble-Enhanced Ozonation For Water Treatment

      Hung, Isaac (The University of Arizona., 2016)
      Ultrafine bubbles, often referred to as nanobubbles, have been used in various applications from environmental remediation to medicine. Even though the technology to generate ultrafine bubbles has been around for many years, the full potential of its applications has not been completely studied. This project seeks to study the use of ultrafine bubble technology for water treatment in combination with ozone gas. A factorial design experiment was chosen to test the effects of ultrafine bubbles on the concentration of an indicator organism, E. coli, in water as well as their effects on ozone gas being injected into water. Ozone gas or nitrogen gas was injected into water contaminated with E. coli as either ultrafine bubbles or fine bubbles as treatments for up to 60 minutes. Ultrafine bubbles were found to not have any significant effect on the concentration of E. coli in water. However, ultrafine bubbles did provide benefits when used in conjunction with ozone gas that regular, fine bubbles did not provide. The benefits included allowing the concentration of dissolved ozone in the water to decrease at a slower rate as well as allowing more ozone to dissolve into water at a higher rate than conventional methods of bubbling in ozone. While in this particular set of experiments the concentration of dissolved ozone in water didn't surpass 2 mg/L, which didn't allow for rapid disinfection and treatment of water, it is believed that with a more powerful ozone generator better results can be achieved. This project demonstrates the benefits and potential of injecting ozone gas as ultrafine bubbles into water as a way to effectively and efficiently disinfect and treat water.

      McIntosh, Michael Philip. (The University of Arizona., 1982)
    • Ultrasonic transducer modeling in homogeneous and nonhomogeneous media

      Lee, Joon Pyo (The University of Arizona., 2001)
      Ultrasonic transducer modeling is important and fundamental research for nondestructive testing of materials. Traditionally, in most nondestructive evaluation applications, the ultrasonic transducers are modeled as point sources generating spherical wave fronts, line sources generating cylindrical wave fronts, or planar surfaces generating plane wave fronts. In reality, the transducer front face has finite dimensions; it is neither point source nor planar source. This study shows how the ultrasonic field in the neighborhood of a transducer with finite dimension varies in homogeneous and nonhomogeneous media. In this thesis, the pressure variation in front of a transducer face is computed for the following three situations: (1) the transducer is immersed in a homogeneous fluid; (2) the transducer is near a fluid-fluid interface; and (3) the transducer is near a fluid-solid interface using Distributed Point Source Method For the nonhomogeneous fluid medium, both normal incidence and oblique incidence cases have been studied.
    • An ultrasound phased array system for intracavitary hyperthermia

      Buchanan, Mark Thomas, 1967- (The University of Arizona., 1992)
      Intracavitary ultrasound hyperthermia applicators have the potential to better heat certain tumor sites, especially in the pelvic region, than external techniques. To allow deep, controlled heating, an intracavitary phased array has been developed. The hardware required to drive the array was also developed; including amplifiers, phase shifters, power meters and matching circuits. The entire system is computer controlled and capable of driving up to 64 individual ultrasound transducers. This system was used to conduct acoustic field measurements and in vivo perfused kidney experiments with the phased arrays. These results show that these arrays focus as predicted, and are capable of controlling the heating field by electrically controlling the position of the focus.

      Takessian, Alex. (The University of Arizona., 1983)
    • Ultrastructure changes induced by Scutellonema brachyurum in roots of potato

      Schuerger, Andrew Conrad (The University of Arizona., 1981)
    • The ultrastructure of retinal development in the chicken

      Miller, Mahlon Frederick, 1940- (The University of Arizona., 1965)
    • Ultraviolet and ultrasound disinfection of a recycle irrigation water

      Hardcastle, Clavin Hunter,1959- (The University of Arizona., 1987)
      Disinfection of an irrigation recycle water is evaluated by an investigation divided into three phases. Phase I experiments investigates disinfection by ultraviolet light alone; Phase II examines ultrasound disinfection; and Phase III investigates combined effects of ultrasound and ultraviolet light. Phase III also evaluates unit process sequencing in order to optimize disinfection performance. Ultraviolet light produced an average microorganism inactivation of 85.4% following one minute of UV irradiation. The response became asymptotic at this point. Cell viability, measured by ATP concentration, was not reduced below 10% until 15 minutes of UV treatment. Ultrasonic treatment resulted in microorganism survivals ranging fram 66.4% (60 W/1 and 30 minutes of treatment) to 25.1% (350 W/1 and 30 minutes of treatment). Combined treatment processes produced comparable results to UV only disinfection schemes. Overall, a satisfactory level of disinfection was not attained using UV light or ultrasound. The lack of disinfection response was attributable to the presence of interfering water constituents.