Field and modelling investigations of eight failed or removed dams have been undertaken to examine the upstream effects of low head dam decommissioning on channel morphology. Failed or decommissioned sites were selected such that no upstream interventions or channel mitigation had been applied since the time of decommissioning resulting in a physically-based analog consistent with the passive dam removal restoration approach. Field surveys of the sites, which failed between 2 years and 70 years ago, included longitudinal profiles, cross-sections and bed material pavement sampling on each riffle, run, and headcut. Findings demonstrate that vertical disturbances typically in the form of headcuts frequently extend well beyond the backwater limits of most reservoirs. Although in most cases, critical velocity and shear stress thresholds were exceeded, the localized increases in friction slope where headcuts occurred demonstrated that the velocities associated with larger flows exceeded critical thresholds more often than critical shear stress thresholds. Findings show that if the grain size distributions of the underlying alluvial geologic units are close to that of critical velocity thresholds, when headcuts are initiated (with their resulting increase in friction slope), they can result in continued channel degradation upstream of impoundment regions.

Field and modelling investigations of eight failed or removed dams have been undertaken to examine the upstream effects of low head dam decommissioning on channel morphology. Failed or decommissioned sites were selected such that no upstream interventions or channel mitigation had been applied since the time of decommissioning resulting in a physically-based analog consistent with the passive dam removal restoration approach. Field surveys of the sites, which failed between 2 years and 70 years ago, included longitudinal profiles, cross-sections and bed material pavement sampling on each riffle, run, and headcut. Findings demonstrate that vertical disturbances typically in the form of headcuts frequently extend well beyond the backwater limits of most reservoirs. Although in most cases, critical velocity and shear stress thresholds were exceeded, the localized increases in friction slope where headcuts occurred demonstrated that the velocities associated with larger flows exceeded critical thresholds more often than critical shear stress thresholds. Findings show that if the grain size distributions of the underlying alluvial geologic units are close to that of critical velocity thresholds, when headcuts are initiated (with their resulting increase in friction slope), they can result in continued channel degradation upstream of impoundment regions.

Most watermark-removal methods treat watermarks as noise and apply denoising approaches to remove them. However, denoising methods remove not only this watermark energy, but also some of the energy of the original image. A trade-off therefore exists: if not enough of the watermark energy is removed, then the watermark will still be detected, but if too much is removed, the image quality will be noticeably poor. To solve this problem, the relationship among the energies of the original image, the watermark and the watermarked image is initially determined using stochastic models. Then, the energy of the watermark is estimated using just-noticeable-distortion (JND). Finally, the watermark energy is removed from the watermarked image based on the energy distribution of its Eigen-images. The experimental results show that the proposed approach yields a mean peak signal-to-noise ratio (PSNR) of the predicted images that is 2.2dB higher than that obtained using the adaptive Wiener filter, and a mean normalized correlation (NC) value of the extracted watermarks that is 0.27 lower than that obtained using the adaptive Wiener filter. In removing watermark energy from 100 randomly selected watermarked images in which watermarks were embedded using the ¡¥Broken Arrows (BA)¡¦ algorithm proposed for the second Breaking Our Watermarking System (BOWS-2) contest, the mean PSNR of 100 predicted images is 24.1dB and the proposed approach successfully removed watermarks from 90 of these images. This result exceeds the minimum requirement of PSNR 20dB for the BOWS-2 contest. Clearly, the proposed approach is a very effective watermark-removal approach for removing watermarks.

Perchlorate is known to adversely affect the thyroid gland functions including iodide take up, thus perchlorate should be removed from drinking water. Bituminous coal-based activated carbon (AC) has been used for perchlorate removal in past years. Virgin carbon and carbon modified by oxidation with HNO3, NaOH and H2O2 were examined in this study for their ability to remove perchlorate by reduction or adsorption mechanisms. Surface functional groups formed on the modified AC (MAC) were examined with diffuse reflectance infrared spectrometry. Inhibition of perchlorate removal onto MAC by various anions ( - Cl , - 3 NO , and - 2 4 SO ) and solution pH (4.5, 7.2 and 10.5) were examined to characterize the MACs before an electrochemical reaction was performed. Surface functional groups were increased by oxidation. Groups that were found on the carbon include, but are not limited to lactone, quinine, carboxylate, and nitrogenoxygen groups. The effect of pH on removal of perchlorate by MAC was greatly affected by the change in the zero point charge (ZPC) induced on the carbon by modification. Virgin carbon also experienced difficulty in removing perchlorate when solution pH was above the ZPC. Anion inhibition varied with the modification process. - 3 NO inhibited perchlorate removal only by the virgin carbon. The other anions showed no major effects on the removal efficiency of perchlorate by the carbons. Electrochemical processes did not show favorable results in removal of perchlorate. The dominant mechanism of perchlorate removal during desorption tests was adsorption onto the carbon surfaces via ion exchange.

The Wu-Luo River located in the Ping-Tong County of southern Taiwan has long been polluted by untreated domestic and partially treated poultry wastewaters and is among the most polluted rivers in Taiwan. A full-scale constructed wetland (CW) has been in operation since January of 2005 for cleaning a part of the polluted river water. The purpose of this study was to investigate the specifications of the CW and its performance for removing both organic and inorganic pollutants form the influent water. Results indicate that during the investigation period of April 2006 to February 2007, the CW had channel widths of 86-112 m (average 100 m) and a zone-type length of 1,600 m. It occupied a total area of 18 hectares in which around 9 hectares were wetted by the introduced river water. Around 4.7 hectares of the CW was flooded by the river water and 1.9 hectares were occupied by emergent and floating plants such as cattail, water lettuce, reed, water celery, and bara grass. A total water volume of around 6,800 m3 was estimated. In the period, 10,000-20,000 m3/day (CMD) (average 10,800 CMD) of the polluted river water was introduced to the CW and a hydraulic retention time (HRT) of 0.63 day was estimated for the flowing water in the through the water body. Results also indicated that the influent water has the following qualities (unit in mg/L except pH and number in parentheses indicates the average value): total COD (CODt) 10-121 (52), BOD 6-36 (21), suspended solids (SS) 10-165 (70), pH 5.4-8.1 (7.4), ammonia-N 2-22 V (13), nitrate-N 0-9.4 (2.5), nitrite-N 0-1.8 (0.2), total-N (TN) 9.9-41.3 (22.6), phosphate-P 0-3.1 (0.9), total-P (TP) 1.2-36.7 (5.2), Cu 0.022-0.60 (0.071), and Zn 0.01-0.36 (0.13). It was found that water sampled from nearly the middle point of the CW got better clarification results than that from the effluent end. Pollutant removal efficacies were 60, 60, and 67%, respectively, for CODt, BOD, and SS at the middle point, while 56, 54, and 45%, respectively, for CODt, BOD, and SS at the effluent end. Organics, N, and P released from rotten plants were responsible for the poor water qualities at the end. The CW had only a TN removal efficacy of around 18% and no TP removal effect.

The effects of work¡¦s surface wavelength on the ultimate surface roughness are considered in this study. Both the experimental and theoretical studies will be done in this study. In the experimental study, the relationships between ultimate surface roughness and various operating parameters will be examined. In the theoretical study, a mathematical model relating the machining rate and various machining parameters are proposed. In the mathematical model, qualitative and quantitative properties of machining rate under various surface geometric condition are obtained by the aid of computer simulation. For the experimental study, a series of experiments will be done to investigate the effects of various factors on the ultimate surface roughness of different work¡¦s surface wavelength.The factors may include the the tool speed, the tool¡¦s surface irregularity, and the particle density of slurry. The comouter simulation indicates that the removal rate is non-linear proportional to tool speed and normal load. Besides, results also showed that the difference of removal rate between peak and valley of surface profile always decreases as the work¡¦s surface wavelength increases. The experimental study confirmed that the relationship between ultimate roughness and wavelength does exist in the specific range of work¡¦s surface wavelength . The model appears to be consistent with currently available experimental data.

Artificial wetland treatment system is an economical water purification system which has high potential in water purification ecology method. Many countries utilized this natural treatment system to solve their waste problems (for example, wastewater and solid waste) and well results were found with proven efficient. Recently, Taiwan has started developing the natural treatment system utilizing the self-purifying function of the natural surrounding by using the physical, chemical and biological reactions in soil, plants and microorganisms, to reduce the concentrations of pollutants produced by wastes. Eventually, all the pollutants can be eliminated to the harmless level to the environment and its organisms. For better understanding the feasibility of artificial wetlands, we study the performance of artificial wetland system with its raw wastewater produced from its community household wastewater at Liao-Luo Village. Artificial wetland system is a natural purification system, no additional chemicals are needed. In addition, it can be easily operated and maintained, and can be used to treat wastewater with simple pollutants in school. Wetlands not only can be utilized to treat wastewater, but also for can be used for educational purposes. The investigation periods in this work is from May 2008 to Dec.2008. The average of removal efficiency were as follows: BOD (52%), E-colis (79%), NH3 (74%). Total N (61%) and Total P (72%). In comparison with related literatures, we operated with higher removal due to the facts containing the lower organic loading and longer water retention time to decompose pollutants in solution. To keep the Liao-Luo Village wetland¡¦s wastewater treatment function, periodical maintenance is performed. Besides moving grass and removing garbage, proper vegetables are planted in each treatment area are needed.

A more energy efficient and sustainable method of desalinating water is needed due to increasing water shortages and contamination of current freshwater sources. Capacitive deionization (CDI), a new emerging technology, is a type of electric desalination that uses an applied voltage to pull the salt ions out of the salty solution and store the ions in porous carbon electrodes. CDI uses less applied energy than more commonly used methods of desalination like reverse osmosis and multi-flash distillation and has the added advantage of energy recovery. This report details experiments conducted to analyze the effect of different separation distances between the electrodes on salt ion adsorption for a high concentration solution under various flow rates and a 1 V voltage potential difference. The testing was performed in the Multiscale Thermal-Fluids Laboratory at The University of Texas at Austin using a uniquely fabricated CDI cell. Voltage, elapsed time, and electrical conductivity measurements were taken during the testing. Electrical conductivity was used to signify salinity of the solution. Two different separation distances were created by placing either one 2mm mesh between the electrodes or by using two 2 mm meshes between the electrodes. The results did not agree with the expectation that the one-mesh tests would adsorb twice the amount of salt ions as the two-mesh tests because of the differences in the electric field between the two types of tests. This is believed to be due to the high concentration tested. Future testing should include repeating these tests to verify the results and performing the tests for lower concentrations to see if they followed the expectation. / text

Ozone (O₃) and oxides of nitrogen (NO[subscript x]) are ubiquitous pollutants in many urban areas around the world. Though they mostly originate outdoors, human inhalation exposure to these pollutants largely occurs indoors, because of the large fraction of our time spent inside buildings. Exposure to O₃ and nitrogen dioxide (NO₂) has been associated with decreased respiratory function, onset of asthma, and cardiovascular events. Through laboratory testing, field exposure and modeling, this study evaluates the feasibility and long-term efficiency of using passive removal materials (PRMs) both indoors and outdoors for removal of O₃ and NO[subscript x]. Three photocatalytic coatings used outdoors and four indoor building materials were tested for their capacity to remove NO[subscript x] and O₃. Since materials outdoors experience a wider range of environmental conditions than indoors, their effects on NO[subscript x] removal by photocatalytic coatings were evaluated through full factorial experiments representative of summertime outdoor conditions in Southeast Texas. Photocatalytic coatings were also exposed to real outdoor environments for a year to assess their long-term viability. Indoor materials were exposed to real indoor environments for a six-month period and tested monthly for their capacity to remove O₃. Carbonyl emissions from these materials before and after exposure to O₃ were also tested at regular intervals during the six-month period. Finally, removal capacity of NO and NO₂ by new indoor building materials was tested as well. For outdoor PRMs, results suggest that the effect of certain environmental parameters (contact time, relative humidity, temperature) on NO[subscript x] removal effectiveness are consistent across different photocatalytic coatings, while other effects are coating specific. The type of semiconductor used and resistance to wear of the coating are important factors in its ability to retain removal efficacy over time. For indoor PRMs, two of the four materials tested, an activated carbon mat and perlite-based ceiling tiles, exhibited consistent O₃ removal effectiveness over time with low carbonyl emissions, both before and after ozonation. All materials except for activated carbon mat had higher post-ozonation than pre-ozonation emissions. Post-ozonation emissions were dominated by nonanal. Simulation of the use of indoor and outdoor PRMs on a model building through multi-zone/CFD modeling showed that indoor PRMs alone could lead to concentration reductions up to 18 % for O₃ and 23 % for NO₂ in rooms of the model building selected. Addition of PRMs on the outside of the building led to small reductions in pollutant concentrations in the air infiltrating into the building, leading to negligible changes in indoor concentrations. / text

Neutrino oscillation experiments have shown de nite evidence for non-zero neutrino masses. However, these experiments only tell us about neutrino mass di erences, and nothing about the absolute masses themselves. The observation of neutrinoless double-beta (0 ) decay, a hypothetical nuclear transition, would provide the rst absolute mass scale measurement of the neutrino outside of cosmology. This decay would imply the neutrino to be a Majorana particle, the rst fermion of its kind. 0 decay would also be the rst observation of lepton number violation. The Enriched Xenon Observatory (EXO) is currently searching for 0 decay in 136Xe with a half-life greater than 1025 years. EXO-200 is the rst experiment of the EXO physics program, which has observed twoneutrino double beta decay (2 ) in 136Xe for the rst time, with a half-life of 2:165 0:075 1021 years [1]. This is the longest measured half-life to date. EXO is now designing a 5-tonne scale detector, nEXO, to be sensitive to the inverted-scale hierarchy. Despite the careful selection of radiopure substances for the detector, the existence of trace levels of 222Rn is inevitable. One of the daughters of 222Rn, 214Bi, can emit photons at the Q-value for 0 decay, making it a critical background. This dissertation investigates the method of Rn removal from gaseous Xe through the use of a Cu wool trap.