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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Electrochemical reactors for PGM recovery

Ferreira, Bronwynne Kim 14 February 2006 (has links)
Master of Science in Engineering - Engineering / The employment of an electrochemical process is an attractive alternative for the treatment of effluents. When dealing with solutions of low metal ion concentrations mass transport limitations are significant and large electrode surfaces are required. The use of a reactor containing a three-dimensional electrode is preferable as the surface area per unit volume is orders of magnitude greater than that of the familiar plate type reactor. A benchscale electrochemical reactor was designed and constructed to incorporate a cylindrical packed bed cathode. The flow of electrolyte is perpendicular to the direction of the flow of the current and the system is operated galvanostatically in a batch recirculation mode. The industrial stream selected for examination contains palladium and copper ions and a small concentration of platinum in a chloride medium containing ammines. The evolution of chlorine gas at the anode by the oxidation of the chloride ions is prevented by the inclusion of a cation exchange membrane and a separate anolyte, namely sulphuric acid, is introduced to the outer anodic chamber. Tests were conducted on both synthetic and industrial solutions and a simplified model which was derived was used to estimate the mass transfer coefficients. The concentrations of the palladium, copper and platinum in the plant effluent were approximately 150, 200 and 10 ppm respectively. The results show that the metal ions can be rapidly reduced to well below 1 ppm in each case. The separation of the palladium and copper ions is shown to occur to a limited degree during electrodeposition, with the extent of separation increasing for lower current densities. Enhanced separation may be possible during the removal of the deposited metals from the cathode either by anodic stripping or chemical treatment. A further method for the recovery of the metals is the combustion of the graphite particles. The high value of palladium, coupled with the significant recoveries shown to be achievable, suggest economic viability in addition to the environmental benefits.

Experimental studies of forward in situ combustion

Alshalabe, Maysoon Ismaeil January 1985 (has links)
Investigation of forward in situ combustion have been carried out in a 7.3 cm diameter tube having a length of 0.869 m. Experiments at pressures up to 50 psig were made to study combustion characteristics and enhanced oil recovery of three different crude oils, namely North Sea Forties (36.6 °API), Maya Isthmus (32.4 °API) and Maya (22.1 °API). Sand packs were prepared with oil saturations in the range 38-44.32%. Close adiabatic control of the combustion tube was achieved for both dry and wet combustion modes. Detailed production history and overall mass balances are presented. Correlation in both graphical and tabular form is given for air-fuel ratio, oxygen utilisation and normalised combustion velocity. In this respect, the results of the present work show good agreement with those of other workers. Normal wet, partial quenched modes of combustion were produced using WARs up to 3.75 m3/Mm3 (STP). The combustion front temperature was not significantly affected by the cooling effect of the injected water. Under partially quenched conditions, high combustion-steam zone temperatures were achieved. For wet combustion, the oxygen utilisation generally improved slightly. Air requirement, air-oil ratio and fuel consumption all decreased with increased water-air ratio and increased with increased clay content. The velocity of the combustion front (normalised with respect to the air flux) increased in a linear manner as the WAR increased. Increasing the clay content, however, gave rise to a decrease in the combustion front velocity. High oil recovery, at 79.37%, was achieved during normal wet combustion of Forties oil. In sand mixtures containing amorphous silica powder, the combustion exhibited virtually 100% oxygen utilisation, with higher carbon burning rates compared with runs using clay addition. These effects are attributed to the nature and magnitude of the surface area of solid additives, which play an important role in the oxidation mechanisms.

Insights into coral recovery based on symbiont state and environmental conditions in the temperate, facultatively symbiotic coral Astrangia poculata

Burmester, Elizabeth 02 February 2018 (has links)
Coral reefs are declining globally, calling for better ways to quantify coral health and predict resilience to future stress. The relationship between bleaching and fitness is key, as is reserve capacity to deal with physical trauma. This dissertation is an integrative study of the coral-algal symbiosis, holobiont performance under varied environmental conditions, and interactions between holobiont and environment on coral colony health and ability to recover from routine partial damage. I utilize the facultatively symbiotic, temperate coral Astrangia poculata as a natural model to explore the dynamics of colony health, performance, and the influence of environmental and nutritional stress under stable aposymbiotic and symbiotic states. Unlike most tropical hermatypic corals that rely heavily upon photosynthetic symbionts for energy, A. poculata can (1) flexibly use both heterotrophic and autotrophic nutritional pathways and (2) exist in naturally occurring, stable, and measurable aposymbiotic and symbiotic states. I begin by describing the impacts of environmentally relevant (winter, summer, and above range) temperatures on small-scale wound healing and recovery. Next, I explore the effects of nutritional and symbiotic states by comparing wound recovery, total colony health, host behavior, and symbiont performance in fed and starved colonies. Finally, I generate a novel reference transcriptome for A. poculata, and use computational approaches to characterize variation in gene expression between the symbiotic and aposymbiotic states. This analysis reveals that regardless of temperature, and with or without the potential for heterotrophic nutritional sources, a relationship with Symbiodinium enhances wound recovery and resilience to stress. Compromised healing ability and tissue cover at low temperatures suggest that in temperate stony corals, recovery and survival are more impacted by winter conditions than by exposure to high summer temperatures. Differential expression analysis revealed predictable enhancements to photosynthesis-related gene expression in symbiotic colonies. Together these results illuminate the complex interactions among symbiotic state, stress, recovery, and performance. We propose that studies like ours that examine the effects of combined stressors, as opposed to a monotonic focus on coral bleaching per se, are essential to clinical diagnosis and stewardship for coral reefs subjected to intense, cumulative human impacts.

Making Disaster Zones into “Scenic Sites,” Homelands into “Gardens,” and Peasants into “Grateful Survivors”: The Chinese State in Qiang Village Earthquake Recovery

January 2016 (has links)
acase@tulane.edu / 1 / Qiaoyun Zhang

Analysis and modelling of membrane heat exchanger in HVAC energy recovery systems.

Nasif, Mohammad Shakir, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW January 2008 (has links)
The performance of membrane heat exchangers for HVAC total energy recovery systems was evaluated through experimentation and detailed system modelling. The operating principle of the membrane heat exchanger (enthalpy heat exchanger) is based on passing ambient hot and humid supply air over one side of a porous membrane heat exchanger surface and cold and less humid room exhaust air on the other side of the transfer surface. Due to the gradient in temperature and vapour pressure, both heat and moisture are transferred across the membrane surface causing a decrease in temperature and humidity of the supply air before it enters the evaporator unit of the conventional air conditioner. Hence both sensible and latent energy are recovered. In this study, both experimental and numerical investigations were undertaken and mathematical models were developed to predict the performance of the latent heat recovery heat exchangers for use with conventional air conditioning systems. The membrane moisture transfer resistance was determined by a laboratory-scale permeability measurements. It was found that the membrane heat exchanger performance is significantly influenced by the heat exchanger flow profile and shape, heat and moisture transfer material characteristics, air velocity and air moisture content. Improvement of membrane heat exchanger performance requires an in depth study on flow, temperature and moisture distribution in the heat exchanger flow paths. Thus, a commercial CFD package FLUENT is used to model the membrane heat exchanger. However, software of this type cannot model moisture diffusion through the porous transfer boundary. Therefore, two user defined function codes have been introduced to model the moisture transfer in latent energy heat exchangers. The annual energy consumption of an air conditioner coupled with a membrane heat exchanger is also studied and compared with a conventional air conditioning cycle using the HPRate software. Energy analysis shows that in hot and humid climates where the latent load is high, an air conditioning system coupled with a membrane heat exchanger consumes less energy than a conventional air conditioning system. The membrane heat exchanger dehumidifies the air before it enters the air conditioning system, resulting in a decrease in energy consumption in comparison with conventional air conditioning system.

Recovery after intracerebral hemorrhage

Auriat, Angela Michelle 11 1900 (has links)
There are two types of stroke: ischemic and hemorrhagic. Intracerebral hemorrhage (ICH) accounts for about 15% of all strokes and is often severe. Currently no treatments are available to reduce injury, but rehabilitation may improve recovery. Most studies focus on ischemia, putting little emphasis on understanding recovery after hemorrhage. In chapter 2, we evaluated exercise prior to and/or following ICH. Similar protocols improve recovery after ischemic stroke, and we hypothesized that the treatment would also reduce deficits after hemorrhagic injury. However, exercise was not beneficial for ICH and increased intensity of treatment worsened functional outcome. In chapter 3 we assessed amphetamine and/or rehabilitation after ICH, an intervention also shown to improve recovery after ischemia. The rehabilitation consisted of environmental enrichment (EE) with modest amounts of training on beam and skilled reaching. Rehabilitation but not amphetamine partially improved recovery. Skilled reaching was not improved by rehabilitation so we decided to combine EE with more reach training. In chapter 4, we found that two weeks of rehabilitation (EE and skilled reaching), started one week after ICH significantly reduced lesion volume, and improved recovery on walking and skilled reaching tests. We were particularly interested in the mechanisms contributing to the reduction in lesion volume after ICH, and attempted to identify these. In chapter 5, we used the same rehabilitation intervention as in chapter 4 to determine if treatment alters dendritic complexity, spine density, or cell proliferation. Unfortunately, the reduction in lesion volume from chapter 4 was not replicated. But we were able to identify several plastic changes. Dendritic complexity was increased in neurons of the forelimb motor cortex ipsilateral to injury. Dendritic complexity of neurons in the peri-hematoma region and corresponding area in the uninjured hemisphere were also increased. In contrast, rehabilitation did not alter spine density or cell proliferation. In summary, we found that treatments that work for ischemic stroke do not necessarily work for hemorrhagic injury. Some methods of rehabilitation are able to reduce functional deficits and in some cases lesion volume after ICH. These rehabilitation effects are likely due to enhanced plasticity and not cell genesis.

Modeling single family housing recovery after Hurricane Andrew in Miami-Dade County, FL

Zhang, Yang 02 June 2009 (has links)
This research seeks to improve the current state of knowledge about housing recovery following a major natural disaster through examining single family housing recovery following Hurricane Andrew, a category 5 hurricane, which impacted southern sections of Miami-Dade County in 1992. This inquiry focused on two questions: (1) what is the recovery process for single family housing in a disaster impact area, and (2) how does the housing recovery process vary across households and neighborhoods? To answer these questions, the 1992-96 tax appraisal values for Miami-Dade County were used to measure housing damage and recovery after the storm. Hierarchical Linear Modeling (HLM) was used to quantitatively model this recovery process and identify the major factors in play. With regard to the first question, our findings suggested that Hurricane Andrew caused extensive housing damage in the impact area, rendering an average loss to households of 50.4% of pre-disaster home value. Two years after the storm (1994), the average home value returned to its pre-disaster level. In the subsequent two years (1995-96), the average home value continued growing, representing a 7.6% and 14.9% gain, respectively, over the pre-disaster average. Regarding the second question, our analysis found that the housing recovery process varied significantly across households and neighborhoods. Owner-occupied homes recovered more rapidly than rental units. Household income had a positive effect on housing recovery. Our analysis also suggested that post-disaster home sales had a significant negative effect on housing recovery. Neighborhood race/ethnicity composition affected the housing recovery process. Homes in minority populated neighborhoods (both Hispanic and non-Hispanic Black) recovered more slowly than homes in majority populated areas (non-Hispanic White). When considering Cuban- Hispanics and non-Cuban Hispanics as two separate groups, neighborhoods with a higher concentration of Cuban-Hispanics, while having no clear advantage at the beginning of the recovery period, recovered more rapidly than other minority populated areas. Previous studies suggested that the long-term impact of natural disasters at the aggregated level is minimal, and yet our results showed that the housing impact of Hurricane Andrew lasted at least more than four years. In fact, housing inequality in the impact area increased markedly during the recovery process due to the unequal nature of housing recovery.

Design of clock data recovery IC for high speed data communication systems

Li, Jinghua 2008 December 1900 (has links)
Demand for low cost Serializer and De-serializer (SerDes) integrated circuits has increased due to the widespread use of Synchronous Optical Network (SONET)/Gigabit Ethernet network and chip-to-chip interfaces such as PCI-Express (PCIe), Serial ATA(SATA) and Fibre channel standard applications. Among all these applications, clock data recovery (CDR) is one of the key design components. With the increasing demand for higher bandwidth and high integration, Complementary metal-oxidesemiconductor (CMOS) implementation is now a design trend for the predominant products. In this research work, a fully integrated 10Gb/s (OC-192) CDR architecture in standard 0.18 μ m CMOS is developed. The proposed architecture integrates the typically large off-chip filter capacitor by using two feed-forward paths configuration to generate the required zero and poles and satisfies SONET jitter requirements with a total power dissipation (including the buffers) of 290mW. The chip exceeds SONET OC-192 jitter tolerance mask, and high frequency jitter tolerance is over 0.31 UIpp by applying PRBS data with a pattern length of 231-1.The implementation is the first fully integrated 10Gb/s CDR IC which meets/exceeds the SONET standard in the literature. The second proposed CDR architecture includes an adaptive bang-bang control algorithm. For 6MHz sinusoidal jitter modulation, the new architecture reduces the tracking error to 11.4ps peak-to-peak, versus that of 19.7ps of the conventional bangbang CDR. The main contribution of the proposed architecture is that it optimizes the loop dynamics by adjusting the bang-bang bandwidth adaptively to minimize the steady state jitter of the CDR, which leads to an improved jitter tolerance performance. According to simulation, the jitter performance is improved by more than 0.04UI,which alleviates the stringent 0.1UI peak to peak jitter requirements in the PCIe/Fibre channel/Sonet Standard.

Study on the Recovery and Treatment of the Food-Waste

Yang, Hung-wen 28 August 2006 (has links)
According to the statistics of ¡§Annual Report of Environment Protection in Taiwan, the Republic of China¡¨ published by the Executive Yuan, the percentage of food waste and organic garbage amount to about 20-30% of ordinary family garbage, where the food waste is about 10-15% of ordinary family garbage.To recycle the wastes, an effective method of collecting and processing food waste in order to achieve the goal of garbage reduction depends on the cooperation of civilians. The food waste collected will be processed through composting, hog-feeding, or anaerobic decomposition. The composting treatment can be divided into anaerobic and aerobic methods. Aerobic composting process is to make use of turning, forced blowing or suction of air in order to supply oxygen. Major process is based on aerobic decomposition to cause the stabilization of organic material. As the reaction speed is fast, the processing time can be drastically reduced and is thus called ¡§high-speed composting process¡¨. Presently there are already many researches in the method of processing food waste that could complete composting products within the shortest time. The result of this study shows if the collection, transportation, treatment, and recycling processes can be properly planned and promoted, the civilians tend to cooperate and the amount of waste recycling can be significantly increased. In addition, by controlling living condition of fungi including moisture content, temperature, PH value, and volatile solid through evaluating primers of superior fungi, the investigation of the food waste processing efficiency and its influence shows there is a trend of significant reduction in the amount of volatile solid material with time.This indicates the phenomena of food waste being decomposed by fungi. The estimation of decomposing speed for food waste is in the range of 2.08¡Ñ10-4 ~ 1.00¡Ñ10-2 kg/hr and the average speed is 2.87¡Ñ10-3 kg of food waste per hr-kg of fungi. The efficiency of treatment is about 50% of the result of original Japanese plants.

Drain water heat recovery in a residential building

Gavilán del Amo, Asier, Alonso Lopez, Ana January 2015 (has links)
Numerous of energy saving measures have been carried out in the Swedishhousing stock since the energy crisis in the 70’s. Additionally, there have been manylow-energy housing projects. However, so far few of these have been followed up aftersome years in operation concerning the energy use. That the energy use stays on a lowlevel is important from a sustainable perspective. The objectives of this study are find a system capable of reduce energy demandand minimize the environmental impact, make the minimum investment with themaximum results and maintain the actual infrastructure of the building. This report looks into the potential for saving energy and money with greywastewater. This potential depends on both the quantity available and whether thequality fits the requirement of the heating load. To recover heat from waste water inresidential buildings is hard to achieve in quality because of its low temperature range.Nevertheless, efforts to recycle this waste energy could result in significant energysavings. To implement this system the method used is to gather all the information aboutthis system, compare all the options available and calculate how much energy can besaved and how much time is the payback. The building studied is on Maskinisten Brynäs in Gävle with 23 apartments onfive different floors and a total living area of 400 m2 in each floor. In the case building used in this report the 60% of the total water used is hotwater. Installing a heat recovery system can be saved up to 23% of the energy used forheating water. This energy can be used for the preheating of the hot water. In this report is given two different solutions to save energy with this systems,the first one is to use a heat exchanger only in the drain of the showers saving up to7.045 MWh or using a centralized heat exchanger saving up to 23.16 MWh. After analysing the results the best option is to use the centralized heatexchanger system, it can be saved more energy and the total investment is lower thanusing a heat exchanger in each shower.

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