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Although pervious concrete was first used in the nineteenth century, it has only recently begun to increase in popularity. As urban areas expand, the problems associated with runoff management have become more challenging. The focus on the negative environmental effects associated with pavement runoff has also increased. These two issues have spurred the recent interest in pervious concrete pavements.Pervious concrete, however, has deficiencies which limit its application as pavements. These limitations include low compressive strength, flexural strength, clogging, and other durability issues. The overall purpose of this project was to provide tools to evaluate and improve the durability and strength of pervious concrete such that it may be more confidently employed in urban roadways. The specific objectives of this project were to (a) investigate the effect of mixture design on strength of pervious concrete (including the effect of fibers), (b) evaluate effect of clogging materials on coefficient of permeability, (c) and investigate the use of the dynamic pressurization test to evaluate the durability of pervious concrete, (d) develop a simple model for predicting removal of clogging particles from pervious concrete pavement surface pores. This thesis documents the results of the laboratory testing, and presents recommendations for mixture proportioning. In addition, recommendations are provided for optimizing the balance between compressive strength and permeability.

In this thesis, the author hypothesizes that the use of computationally intensive mathematical operations in password authentication protocols can lead to security vulnerabilities in those protocols. In order to test this hypothesis: 1. A generalized algorithm for cryptanalysis was formulated to perform a clogging attack (a formof denial of service) on protocols that use computationally intensive modular exponentiation to guarantee security. 2. This technique was then applied to cryptanalyze four recent password authentication protocols, to determine their susceptibility to the clogging attack. The protocols analyzed in this thesis differ in their usage of factors (smart cards, memory drives, etc.) or their method of communication (encryption, nonces, timestamps, etc.). Their similarity lies in their use of computationally intensivemodular exponentiation as amediumof authentication. It is concluded that the strengths of all the protocols studied in this thesis can be combined tomake each of the protocols secure from the clogging attack. The conclusion is supported by designing countermeasures for each protocol against the clogging attack.

Permeable pavement structures (PPSs) are one of the significant LID systems that have potential positive effect on the ecosystem. Yet, the performance of permeable pavements is still questionable. Further studies on the hydrological performance of the system need to be addressed for better design criteria and maintenance during the operation. The infiltration through the pavement is a crucial parameter that projects the system performance. Several factors affect its deterioration. The entrapment of suspended materials associated with the infiltrated stormwater through the system is one of the major factors that affect its performance. Factors that promote the entrapment of particles were discussed thoroughly through the literature and are explained in this study. Many previous studies were focused on performing experimental work and developing empirical models to study the hydraulic performance of the system. Yet, prediction models on the infiltration deterioration need to be addressed and theoretical analysis needs to be performed in order to determine the empirical coefficients with defined parameters that were introduced in the previous literature. Furthermore, the sensitivity of the pore and particle size distribution and mass loading rate of the suspended materials on the infiltration rate need to be addressed. The study focuses on investigating performance of PPSs with examining the variation effect of pore and particle size distribution on it. A prediction model was made and simulated using Matlab software, in which pore and particle size means and standard deviations are taken as inputs. Further, the variation in these parameters on infiltration is examined. Critical levels, that infiltration decline would reach, were defined based on the introduced mechanisms from the previous literature. Based on the variation of pore and particle size means and standard deviations, these critical levels were studied through the analysis of the obtained results from the simulated model. / Graduate / 2019-12-10

This thesis describes a laboratory investigation of in-situ treatment of synthetic leachate representative of that generated by a municipal solid waste (MSW) landfill. The overall objective is to evaluate alternative designs and operating procedures for effective leachate collection in conjunction with efforts to accelerate waste stabilization (i.e. leachate recirculation). In the investigation five 15 cm (6) diameter PVC columns were packed with pea gravel and concrete of different sizes; geotextiles were also placed between the packed sections as filter-separators and promoters of bacterial growth. Synthetic leachate was continuously input to the top of the columns and circulated at rates representative of operating field conditions. For each column, effluent was discharged to a nitrification reactor before recirculation. The tests were conducted under anaerobic and unsaturated conditions in the columns. Results indicate about a 97% decrease in COD from the synthetic leachate concentration entering the top of the column, and about 98 % conversion of the ammonia to nitrogen gas. COD depletion and methane production were not significantly inhibited by the denitrification process. Optimum Hydraulic Retention Time (HRT) for the nitrification-denitrification system makes it economically viable for its development at a landfill site. Gas production shows low CO2 values, decreasing the potential of clogging in the Leachate Collection System (LCS) and extending the Landfill Gas (LFG) networks life service by generating a less corrosive environment. The use of concrete as an alternative to the most commonly used natural gravel as leachate collection drains may not be a good option. During the experiment, the leachate that permeated the columns packed with crushed concrete, presented a higher pH than the leachate that permeated the natural stone. At the conclusion of the experiment noticeable weathering was observed when the columns where dismantled. Further studies are recommended until more conclusive evidence as to concrete performance is found. The overall results obtained from the experiment show that in situ passive treatment at landfills is viable.

This thesis describes a laboratory investigation of in-situ treatment of synthetic leachate representative of that generated by a municipal solid waste (MSW) landfill. The overall objective is to evaluate alternative designs and operating procedures for effective leachate collection in conjunction with efforts to accelerate waste stabilization (i.e. leachate recirculation). In the investigation five 15 cm (6) diameter PVC columns were packed with pea gravel and concrete of different sizes; geotextiles were also placed between the packed sections as filter-separators and promoters of bacterial growth. Synthetic leachate was continuously input to the top of the columns and circulated at rates representative of operating field conditions. For each column, effluent was discharged to a nitrification reactor before recirculation. The tests were conducted under anaerobic and unsaturated conditions in the columns. Results indicate about a 97% decrease in COD from the synthetic leachate concentration entering the top of the column, and about 98 % conversion of the ammonia to nitrogen gas. COD depletion and methane production were not significantly inhibited by the denitrification process. Optimum Hydraulic Retention Time (HRT) for the nitrification-denitrification system makes it economically viable for its development at a landfill site. Gas production shows low CO2 values, decreasing the potential of clogging in the Leachate Collection System (LCS) and extending the Landfill Gas (LFG) networks life service by generating a less corrosive environment. The use of concrete as an alternative to the most commonly used natural gravel as leachate collection drains may not be a good option. During the experiment, the leachate that permeated the columns packed with crushed concrete, presented a higher pH than the leachate that permeated the natural stone. At the conclusion of the experiment noticeable weathering was observed when the columns where dismantled. Further studies are recommended until more conclusive evidence as to concrete performance is found. The overall results obtained from the experiment show that in situ passive treatment at landfills is viable.

A sports field construction method that uses a geotextile to support the root zone atop a synthetic drainage structure is an alternative to the common design that uses gravel drainage material to support the root zone. A study was conducted to address the concern that fine particles in the root zone may migrate under the influence of percolating water, clog geotextile pores, and restrict the amount of water drained from a sports field. In test columns, six root zone mixtures with different particle size distributions were combined with ten geotextiles with different opening sizes to produce 60 replicated treatments. Water flow through the root zone mixture-geotextile combinations in the test columns was evaluated over a six-month period. Change in permeability was assessed by monitoring the temporal distribution of drainage from a 25-mm pulse of water applied to 300-mm deep root zone mixture in the test column. Particles in drainage water were analyzed for size distribution. The study revealed that drainage rates were affected more by drainage trough the root zone mixture than through the geotextile. The amount and particle size distribution of particles in drainage water were influenced more by root zone mixture than by geotextile. It appeared that in the establishment phase of a sports field that fine particles in the root zone may present more of a problem to clogging of the root zone pores than clogging of the geotextile pores.

abstract: The Santa Cruz River, in southern Arizona, receives steady inputs of nutrient-enriched treated wastewater (effluent). Previous studies have documented reduced infiltration of surface water in the river. This disruption of hydrologic connectivity, or clogging, can have consequences for groundwater recharge, flows of wastewater in unwanted locations, and potentially even survivorship of floodplain riparian vegetation. Clogging can result from biotic processes (microbial or algal growth), abiotic processes (siltation of interstitial spaces), or both. Little is known about clogging in rivers and the environmental factors that regulate their dynamics, so natural field experiments along the Santa Cruz and San Pedro Rivers were used to answer: 1) Are there spatial patterns of hydraulic conductivity in the riverbed downstream from the effluent point-source? 2) Is there temporal variability in hydraulic conductivity and microbial abundance associated with flooding? 3) Are there environmental variables, such as nutrients or stream flow, related to differences in hydraulic conductivity and microbial abundance? To address these questions, a series of sites at increasing distance from two municipal effluent discharge points with differing water quality were selected on the Santa Cruz River and compared with non-effluent control reaches of the San Pedro River. Physical, chemical, and biological parameters were monitored over one year to capture seasonal changes and flood cycles. / Dissertation/Thesis / M.S. Biology 2012

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第17131号 / 工博第3621号 / 新制||工||1550(附属図書館) / 29870 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査）教授 松岡 俊文, 教授 大津 宏康, 准教授 水戸 義忠 / 学位規則第4条第1項該当

O processo de lingotamento contínuo de produtos planos de aço tem sido alvo de incessantes estudos devido a sua importância na produção de bobinas laminadas a partir de placas, para um grupo muito diversificado de clientes, dentre os quais, destacam-se as indústrias automobilística e de eletrodomésticos (\"linha branca\"), que têm se mostrado muito exigentes. No entanto, por tratar-se de aços desoxidados ao alumínio, é comum a ocorrência de formação de um depósito de óxido de alumínio (alumina), no interior do tubo submerso do processo de lingotamento contínuo, o que diminui seu diâmetro interno, levando à restrição de passagem do aço líquido pelo seu interior, provocando a perda de produtividade devido à necessidade de se reduzir a velocidade de lingotamento e até mesmo a contaminação do aço com inclusões de alumina, principalmente naqueles seqüenciais com um elevado tempo de lingotamento, próximo de dez horas. Para tanto, desenvolveu-se um tubo com um material interno anti-clogging que na literatura é chamado de C-less, para minimizar e/ou evitar a deposição de alumina e com uma linha de escória reforçada com uma camada de zircônia (ZrO2) mais espessa e mais nobre, para resistir ao ataque da escória. O objetivo desta dissertação foi comparar tubos de diferentes fornecedores, avaliando as principais variáveis que têm influência direta na sua performance: perfil de aquecimento, taxa de erosão na linha de escória, índice de obstrução e parâmetros físico-químicos através da correlação dos materiais antes e após uso (post-mortem). Os resultados encontrados mostraram uma melhor performance dos tubos do fornecedor \"M\", que apresentaram menores taxas de desgaste e, conseqüentemente, maior potencial de vida (maior tempo de lingotamento) após análise da linha de escória, que pode ser atribuída a uma melhor distribuição dos grãos de zircônia na matriz (maior homogeneidade), além de apresentarem grãos mais finos e desta forma, reduzindo os espaços \"vazios\" na matriz, propícios ao ataque da escória por meio de um desequilíbrio químico entre esta escória líquida e o refratário. Além disto, seu material anti-clogging e projeto de distribuição do mesmo na peça, propiciaram um melhor resultado em relação à obstrução pela deposição de alumina ao longo do corpo do tubo submerso. / The continuous casting process of steel plane products has been objective of incessant studies due to its importance in the production of laminated coils starting from slabs, for a very diversified group of customers, among all the automobile industries and of appliances (\"home appliances\"), that have been showing very demanding. However, for being low carbon aluminum killed steels, is common the occurrence of aluminum oxide (alumina) deposit formation, inside of submerged nozzle in continuous casting process, what decreases its internal diameter, taking to the restriction of passage of the liquid steel for its interior, provoking the productivity loss due to the need of being reduced the casting speed and even the contamination of the steel with alumina inclusions, mainly in those sequential with a high casting time, close of ten hours. For so much, a submerged nozzle was developed with a internal anti-clogging material that it is called C-less in the literature, to minimize and/or to avoid the alumina building up and with a slag reinforced line with a zirconium layer (ZrO2) thicker and more noble, slag attack resist to. The dissertation objective was compare submerged nozzles from different suppliers, evaluating the main variables that have direct influence in its performance: heating profile, slag line erosion rate, clogging index and physical-chemical parameters through the materials correlation before and after use (post-mortem). The results showed submerged nozzle\'s better performance from supplier \"M\", that presented smaller waste rates and, consequently, last longer live (larger time of casting) after analysis of the slag line, that can be attributed to a better distribution of the zirconium grains in the head office (larger homogeneity), besides they present finer grains and this way, reducing the empty \" spaces \" in the head office, favorable to slag attack by means of a chemical unbalance between this liquid slag and the refractory. Besides, its anti-clogging material and project distribution in the same piece, they propitiated a better result in relation to the clogging for the alumina building up along the body of the submerged nozzle.