Masteropgave. / Format: PDF. Bibl.

Thesis (doctoral)--Göteborgs universitet, 2003. / Extra t.p. with thesis statement inserted. Includes bibliographical references.

There are always differences between conceptual design estimates and the performance of a final product. These differences may result in constraint violations, which can have severe financial impacts. Such violations may necessitate downstream changes to recover aircraft performance. The ability to estimate the likelihood and impact of late-stage changes is key to mitigating the overall risk of a design. Reliability methods can treat design uncertainty; however, existing methods do not account for aspects of aircraft design such as sizing processes, the design freeze after conceptual design, and late-stage ``mitigation actions'' taken when a performance constraint is violated. By accounting for these elements, new reliability metrics can be developed. In addition to the probability of compliance, the designer can determine the probability of recovery through mitigation actions, which helps determine the true likelihood that a design can meet the requirements. Hypotheses are developed to fill the identified gaps, resulting in Aircraft Recovery through Mitigation & Optimization under Uncertainty for Reliability. ARMOUR augments reliability methods by integrating aircraft sizing, uncertainty margins, and mitigation actions. ARMOUR is demonstrated on the conceptual design of a large civil transport and is exercised to explore previously obscured relationships. The field of probabilistic aircraft design is enhanced by the concurrent quantification of three elements in one design environment: probability of compliance, probability of recovery after failure, and traditional design criteria. ARMOUR enables the identification of designs which both meets reliability goals and optimizes a traditional performance metric, selecting a design that efficiently meets reliability requirements.

It is doubtless that global warming is enhanced by human activities, and being accelerated in recent years. The building sector is one of the main contributors in carbon emissions over the world, which contributed to over 20%. Hong Kong is a typical metropolis located in the sub-tropical region, whereas financing and servicing are the major industries supporting the development of the city. With these industries, it implies the major carbon emission is from buildings of commercial and residential sectors. A wide range of policies and researches on high efficient / green building design were conducted in the Western countries since the 90s, and there are more in the Asia Pacific since 2000. Among different countries there are many methods in calculating carbon emissions, which are similar in principle and different in the details. It is important to agree a consistenct framework on the calculation of carbon emission and study the performance of different carbon reduction strategies, hence to serve a reference for designers. This study conducted a critical review on the calculation of carbon emission, hence definition of carbon emissions. The review classified different calculation methods by 7 factors, which are the major governors on the results. All methods reviewed in the section were either current standards or methods suggested by scholars. With the critical review, a potential calculation methodology is suggested and will used for the calculation in the later part. A case study was carried out for the identification of the strategies used on two zero carbon buildings and one zero energy building. The study shows these buildings used similar strategies on the emission reduction, including photovoltaics, well insulated fabric, natural lighting, natural ventilation, high efficient lighting system and solar hot water system. A computer simulation was used to analyze the performance of different strategies that could be used on buildings in Hong Kong climate. Commercial buildings and residential buildings are selected as sample buildings for the analysis. A baseline building is setup with typical design. The computer simulation studied the strategies used by other buildings from case study and compares their effect with baseline building. The simulation shows that a zero carbon residential building is possible with sufficient offsetting on the building surface. However, office building cannot be zero carbon by applying the analyzed strategies. The study shows solar hot water is the most effective strategy for residential buildings and day lighting is the most effective strategy for office buildings. / published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Unicellular microalgae are a renewable bioresource that can meet the challenge forfood and energy in a growing world population. Using sunlight, CO2, nutrients,and water, algal cells produce biomass in the form of sugars, proteins and oils, allof which carry commercial value as food, feed and bioenergy. Flue gas CO2 andwastewater nutrients are inexpensive sources of carbon and fertilizers. Microalgaecan mitigate CO2 emissions and reduce nutrients from waste streams whileproducing valuable biomass.My focus was on some of the challenging aspects of cultivating microalgae ascrop: the response of biomass production and quality to seasonality, nutrients andbiological interactions. Approach spans from laboratory experiments to large-scaleoutdoor cultivation, using single microalgal strains and natural communities insouthern (Portugal) and northern (Sweden) Europe.Half of the seasonal variation in algal oil content was due to changes in light andtemperature in outdoor large-scale cultures of a commercial strain (Nannochloropsisoculata). Seasonal changes also influence algal oil composition with more neutrallipids stored in cells during high light and temperature. Nitrogen (N) stress usuallyenhances lipid storage but suppresses biomass production. Our manipulationshowed that N stress produced more lipids while retaining biomass. Thus,projecting annual biomass and oil yields requires accounting for both seasonalchanges and N stress to optimize lipid production in commercial applications.Baltic Sea microalgae proved to be a potential biological solution to reduce CO2emissions from cement flue gas with valuable biomass production. A multi-speciescultivation approach rather than single-species revealed that natural or constructedcommunities of microalgae can produce equivalent biomass quality. Diversecommunities of microalgae can offer resilience and stability due to more efficientresource utilization with less risk of contamination, less work and cost for culturemaintenance.Stable algal biomass production (annual basis) was achieved in outdoor pilot-scale(1600 L) cultivation of Baltic Sea natural communities using cement flue gas as aCO2 source. Results indicate favorable algal oil content at northern Europeanlatitudes compared to southern European latitudes.My thesis establishes the potential of cultivating microalgae as a bioresource inScandinavia, and using a community approach may be one step towardssustainable algal technology.

Existing and novel laboratory techniques and equipment are used to produce comprehensive information on the liquefaction mitigation provided by granular drainage columnar inclusions in loose sand. Extensive use is made of bender-element testing techniques and the frequency dependence of such measurements is examined. Phase-sensitive detection is proposed as a new method to obtain the frequency response of the element data. The applicability of this technique is extended to provide a convenient and accurate method for determination of the time-of-flight of a shear-wave in sand. This technique is employed to measure the load share between sand and columnar components during triaxial testing. A novel low cost, high loading frequency, triaxial testing system is developed and preliminary testing is carried out on both pure sand samples and composite columnar samples. The testing programme examines aspects of liquefaction mitigation due to the rigidity of the columnar inclusions and due to the increased permeability of the columns. The laboratory results are verified by the application of existing analytical models. The equipment and techniques are used to investigate the feasibility of using recycled aggregates in place of stone backfill.

Context and rationale – This work originates from policy priorities established within Defra to manage exotic animal diseases (EAD); specifically to understand the causes of low probability events, and to establish contingencies to manage outbreak incidents. Outbreaks of exotic animal diseases, e.g. FMD, CSF and HPAI, can cause economic and social impacts of catastrophic proportions. The UK’s government develops and implements policies and controls to prevent EAD and thus minimise these impacts. Control policies to achieve this are designed to address the vulnerabilities within the control systems. However, data are limited for both the introduction of an EAD as well as its resurgence following the disposal of infected carcasses, i.e. the pre-outbreak and post-outbreak phases of an EAD event. These lack of data compromises the development of policy interventions to improve protection. To overcome these data limitations, predictive models are used to predict system vulnerabilities. Cont/d.

In rural Bangladesh, the drinking water supply is mostly dependent upon manually operated hand pumped tubewells, installed by the local community. The presence of natural arsenic (As) in groundwater and its wide scale occurrence has drastically reduced the safe water access across the country and put tens of millions of people under health risk. Despite significant progress in understanding the source and distribution of As and its mobilization through sediment-water interactions, there has been limited success in mitigation since the problem was discovered in the country’s water supply in 1993. This study evaluated the viability of other kinds of alternative safe drinking water options and found tubewells are the most suitable due to simplicity and technical suitability, a wide acceptance by society and above all low cost for installation, operation and maintenance. During planning and decision making in the process of tubewell installation, depth of the tubewell is a key parameter as it is related to groundwater quality and cost of installation. The shallow wells (usually &lt; 80m) are mostly at risk of As contamination. One mitigation option are deep wells drilled countrywide to depths of around 250 m. Compared to safe water demand, the number of deep wells is still very low, as the installation cost is beyond affordability of the local community, especially for the poor and disadvantaged section of the society. Using depth-specific piezometers (n=82) installed in 15 locations spread over the 410 km2 area of Matlab (an As-hot spot) in southeastern Bangladesh, groundwater monitoring was done over a 3 year period (pre- and post-monsoon for 2009-2011 period). Measurements were performed for hydrogeological characterization of shallow, intermediate deep and deep aquifer systems to determine the possibility of targeting safe aquifers at different depths as the source of a sustainable drinking water supply. In all monitoring piezometers, As was found consistently within a narrow band of oscillation probably due to seasonal effects. Hydrogeochemically, high-As shallow groundwaters derived from black sands are associated with elevated DOC, HCO3, Fe, NH4-N and PO4-P and with a relatively low concentration of Mn and SO4. Opposite to this, shallow aquifers composed of red and off-white sediments providing As-safe groundwater are associated with low DOC, HCO3, Fe, NH4-N and PO4-P and relatively higher Mn and SO4. Groundwaters sampled from intermediate deep and deep piezometers which were found to be low in As, are characterized by much lower DOC, HCO3, NH4-N and PO4-P compared to the shallow aquifers. Shallow groundwaters are mostly Ca-Mg-HCO3 type and intermediate deep and deep aquifers’ groundwaters are mostly Na-Ca-Mg-Cl-HCO3 to Na-Cl-HCO3 type. A sediment color tool was also developed on the basis of local driller’s color perception of sediments (Black, White, Off-white and Red), As concentration of tubewell waters and respective color of aquifer sediments. A total of 2240 sediment samples were collected at intervals of 1.5 m up to a depth of 100 m from all 15 nest locations. All samples were assigned with a Munsell color and code, which eventually led to identify 60 color varieties. The process continued in order to narrow the color choices to four as perceived and used by the local drillers for identification of the targeted As-safe aquifers. Munsell color codes assigned to these sediments render them distinctive from each other which reduces the risk for misinterpretation of the sediment colors. During the process of color grouping, a participatory approach was considered taking the opinions of local drillers, technicians, and geologists into account. In addition to the monitoring wells installed in the piezometer nests, results from 87 other existing drinking water supply tubewells were also considered for this study. A total of 39 wells installed in red sands at shallow depths producing As-safe water providing strong evidence that red sediments are associated with As-safe water. Average and median values were found to be less than the WHO guideline value of 10 μg/L. Observations for off-white sediments were also quite similar. Targeting off-white sands could be limited due to uncertainty of proper identification of color, specifically when day-light is a factor. Elevated Mn in red and off-white sands is a concern in the safe water issue and emphasizes the necessity of a better understanding of the health impact of Mn. White sediments in shallow aquifers are relatively uncommon and seemed to be less important for well installations. Arsenic concentrations in more than 90% of the shallow wells installed in black sands are high with an average of 239 μg/L from 66 wells installed in black sediments. It is thereby recommended that black sands in shallow aquifers must be avoided. This sediment color tool shows the potential for enhancing the ability of local tubewell drillers for the installation of As-safe shallow drinking water tubewells. Considering the long-term goal of the drinking water safety plan to provide As-safe and low-Mn drinking water supply, this study also pioneered hydrogeological exploration of the intermediate deep aquifer (IDA) through drilling up to a depth of 120 m. Clusters of tubewells installed through site optimization around the monitoring piezometer showed a similar hydrochemical buffer and proved IDA as a potential source for As-safe and low-Mn groundwater. Bangladesh drinking water standard for As (50 µg/L) was exceeded in only 3 wells (1%) and 240 wells (99%) were found to be safe. More than 91% (n=222) of the wells were found to comply with the WHO guideline value of 10 µg/L. For Mn, 89% (n=217) of the wells show the concentration within or below the previous WHO guideline value of 0.4 mg/L, with a mean and median value of 0.18 and 0.07 mg/L respectively. The aquifer explored in the Matlab area shows a clear pattern of low As and low Mn. The availability of similar sand aquifers elsewhere at this depth range could be a new horizon for tapping safe drinking water at about half the cost of deep tubewell installation. All findings made this study a comprehensive approach and strategy for replication towards As mitigation and scaling-up safe water access in other areas of Bangladesh and elsewhere having a similar hydrogeological environment. / <p>QC 20151211</p> / Sida-SASMIT project (Sida Contribution 75000854).

Green buildings are increasingly in demand yet current green building practices often do not consider hazard mitigation. High-performance buildings that can withstand hazards, protect residents, and do not need to be rebuilt following a disaster are truly sustainable buildings. This report focuses on current hazard mitigation and disaster resilience standards for wildfires and earthquakes through an in-depth analysis of case studies and best practices for these hazards. The U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) framework is the ideal vehicle to incorporate hazard mitigation methods into official green building certification. Language for a new LEED Hazard Mitigation and Resilience credit area is established using guidelines for hazard mitigation for wildfires and earthquakes. / text

In wireless communication systems, receivers have generally been designed under the assumption that the additive noise in system is Gaussian. Wireless receivers, however, are affected by radio frequency interference (RFI) generated from various sources such as other wireless users, switching electronics, and computational platforms. RFI is well modeled using non-Gaussian impulsive statistics and can severely degrade the communication performance of wireless receivers designed under the assumption of additive Gaussian noise. Methods to avoid, cancel, or reduce RFI have been an active area of research over the past three decades. In practice, RFI cannot be completely avoided or canceled at the receiver. This dissertation derives the statistics of the residual RFI and utilizes them to analyze and improve the communication performance of wireless receivers. The primary contributions of this dissertation are to (i) derive instantaneous statistics of co-channel interference in a field of Poisson and Poisson-Poisson clustered interferers, (ii) characterize throughput, delay, and reliability of decentralized wireless networks with temporal correlation, and (iii) design pre-filters to mitigate RFI in wireless receivers. / text