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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.
51

Influence of fungal diversity and production of cellulolytic enzymes on decay of stored bagasse

Singh, Nashveer 10 February 2009 (has links)
Bagasse is the fibrous derivative of sugar cane, that is grown on a commercial scale in many tropical and sub-tropical countries, where ideal climatic conditions are experienced. The seasonality of sugar cane presents storage problems for bagasse, since this lignocellulosic material is susceptible to degradation by a diverse range of microorganisms, mainly fungi. The decay that is brought about contributes largely to the losses of fibre in a bagasse pile. The surrounding microclimate, and conditions within the pile, needs to be carefully monitored in order to understand the factors that support the fungal populations and biochemical activity. The microclimate at the surface and inside the bagasse pile at a paper mill in Stanger (South Africa) was carefully monitored over a one-year storage period. Significant changes were noted in temperature, pH and moisture content, between the surface and the inside of the pile, as the pile aged. The data were compared to established parameters for bagasse preservation, and it was found that the temperature was lower than expected, thus promoting fungal growth. The pH was much higher (promoting bacteria and actinomycetes) and the moisture content was too low to produce anaerobic conditions. The environmental conditions in the bagasse pile at Stanger, therefore, promoted the proliferation of microbes, and consequently decay. Fungi that were present in the pile, were enumerated in order to investigate the diversity and fungal succession. There was a wider variety of species and higher numbers of fungi at the surface than inside the bagasse pile and the Shannon and Berger-Parker diversity confirmed these observations. Sorensons measure also showed that the types of fungal communities at the surface and inside the pile only started becoming similar toward the latter part of storage. When compared to models for abundance of species, conditions on the surface of the pile allowed maximum niche occupation at the beginning of storage, followed by the establishment of a mature community. The inside of the pile displayed minimal niche pre-emption followed by a state where most fungal species shared the domain. This study indicated that, as the storage time increased, the microbial communities became better established. Bagasse is rich in holocellulose, the basic raw material used for paper-making. Since there were many species of holocellulolytic fungi found growing on the surface and the inside of the bagasse pile, the activity of cellulases and xylanases were determined. These enzymes were found to be active at the surface and inside the pile. However, higher activities of both enzymes were noted inside the bagasse pile than on the surface. The higher levels of activity inside the pile, despite lower fungal numbers, suggested that fungal counts were not a clear indication of biomass or biochemical activity. It appeared that the environment on the inside of the bagasse pile promoted the establishment of specific fungal populations that bring about a high degree of degradation to fibre inside the bagasse pile. / Dissertation (MSc)--University of Pretoria, 2009. / Microbiology and Plant Pathology / unrestricted
52

Annahof / Annahof

Buganská, Petra January 2016 (has links)
Anenský Court has more historical layers. When looking at the half-collapsed brick arch and remnants of walls, we can feel the nostalgia. Concrete silos remind time not so long ago. Today, all overgrown with bushes. What man left, takes nature. Nothing remains constant. As a former farm yard, which currently lacks a feature? The lives of the former inhabitants of Justice are long odžity a nostalgic return to the past times do not provide a basis. Presence is rapidly becoming a thing of the past and nothing remains constant. Ruins ANNAHOF slowly disintegrate, disappear one historic layer. The new layer but has already begun to create. Future is quickly becoming the present and nothing remains constant. Constant change is a fundamental characteristic ANNAHOF, as well as any other place in the world. It gives us the challenge to innovation, as opposed to nostalgia. Adaptation to changing environmental conditions is a prerequisite for survival. In the past, human survival depended entirely on natural conditions - people turned to God to ask for a good harvest. Today, we can predict the weather and the soil fertility is largely influenced. Our survival still depends on the same natural conditions. Instead we wayside chapels and build weather stations and invest in research. In ANNAHOF it decided to propose a station for research into climate change with a visitor's center, which could be felt through microclimates global warming "on your own". The whole house is basically built around four outdoor microclimates., In which it can be accessed. The shape of the building and its position in the field is therefore directly result in the formation of microclimates. The structural system is a wall, even using concrete material. I chose it for its possibilities of shaping and visual quality. Quantity retaining walls, landscaping required for the creation of microclimates is used as efficiently as possible at the same time as the walls of the building. Of the existing structures is to use one concrete silo, and a support pole for measuring towers. Lattice structure of the mast is secured with ropes anchored to the concrete silo. On measuring tower are located automatic measuring devices. The main area of my proposal is a gallery exhibition space. There should be a visitor center acquainted with the problems of climate change and from this space ramps can reach all four outdoor microclimates. The gallery is lit by a skylight above the one hand and also tracked through the window, which runs almost around the perimeter, and that desert light through the supporting structure of steel truss grid in the interior. Operationally in the building blends function research / workplace for scientists and their background and / public / gallery microclimates and facilities for visitors. Both functions can then serve multipurpose hall. The proposal also includes necessary facilities for maintenance of outdoor spaces and buildings, as well as an apartment manager. Překladač Google pro firmy:Translator ToolkitPřekladač webových stránekNástroj pro hledán
53

Ambient Micro-Climate and Thermal Comfort Assessment of Davis Wade Stadium during the 2016 Football Season

Collins, Andrew 30 April 2021 (has links)
College football stadiums host anywhere from 15,000 to 115,000 people each Saturday from late summer to early winter and leave fans exposed to ambient conditions. Amplified heat from stadium infrastructure substantially impact attendants’ thermal comfort. In order to assess personal heat exposure and mitigate exposure misclassification, temperature and relative humidity sensors (iButtons) were placed throughout Mississippi State University’s Davis Wade Stadium during the 2016 Football Season. iButton measurements established a micro-climate and compared its readings to the Soil Climate Analysis Network site 1.2 miles north of the stadium. The program RayMan Pro modeled a Physiological Equivalent Temperature (PET) micro-climate to create an individualized heat metric. The results of this study assess stadium occupants’ thermal comfort through Heat Index and PET. Heat-related health outcomes were examined regarding thermal comfort and the stadium micro-climate using data from the stadium’s EMS calls and First Aid stations during game days.
54

Light Coloured Cool Asphalt Pavements

VanderMeulen, John January 2014 (has links)
The black colour of an asphalt pavement causes it to reach very high temperatures throughout the summer months. Asphalt binder is a temperature dependent material, so these high temperatures can result in damage to the road surface. This report explores the use of light coloured surface coatings to decrease the temperature of an asphalt pavement. A field testing method was developed to compare the effect of several surface materials on temperature. To support this field test, a method was developed to characterize the surface colour (albedo) through the use of a simple light meter. As well, the durability of the surface coatings applied to asphalt pavement surfaces was examined using the Wet Track Abrasion Test, and methods for further testing were suggested. A numerical model was developed in Abaqus to predict the temperature effects based on the surface colour and climate conditions. This model can be used to predict the temperature in an asphalt concrete pavement at the surface and throughout the depth of the pavement. Two versions of this model were created: A complete model, which is used when all climate data is available, and a simplified model, which uses estimated values to replace any data that is not available The temperature difference between white and black painted asphalt concrete surfaces was found to be as much as 17C. Using light coloured surfaces with albedo values in the range of 0.2 to 0.3 yielded a temperature decrease of approximately 7 to 10C as compared to a black painted surface. Microclimate effects were found to be significant; wind speed can drastically affect the temperature of a pavement. The use of hydrated lime in conjunction with a polymer modified asphalt surface course yielded good results for both temperature reduction and durability. It should be considered for future work. / Thesis / Master of Applied Science (MASc)
55

EVALUATION OF LAND, SOIL, WATER, AND VEGETATION-RELATED ECOSYSTEM SERVICES AND TRADEOFFS AT UTILITY-SCALE SOLAR PHOTOVOLTAIC FACILITIES

Choi, Chong Seok, 0000-0002-6860-2038 05 1900 (has links)
Solar photovoltaics are a low-emission electricity source, but utility-scale development of ground-mounted PV may displace natural or agricultural land and compromise the land’s ability to provide ecosystem services. Co-locating solar photovoltaics with vegetation (sometimes referred to as “agrivoltaics”) could provide a sustainable solution to meet growing food and energy demands while minimizing the land-use impacts of solar energy. Pilot-scale experiments and modeling studies have shown potential for microclimatic alterations by the solar photovoltaics (PV) and the soil-vegetation components of a co-located system to benefit each other. One predicted co-benefit is cooling of PV modules caused by diversion of sensible heat to latent heat for evapotranspiration in the understory vegetation during the growing season. Field experiments that validate the theorized co-benefits within a utility-scale co-located system are less common. Since a large percentage of current and future land use conversions for utility-scale solar energy developments are estimated to occur on farmlands, validation of co-benefits in utility-scale co-located systems are critical for determining the outcome of co-location in a wide range of physical conditions and optimizing the system design for the environmental co-benefits. In the first study of its kind and scale, three years (2019 – 2021) of microclimate and soil data at three vegetated utility-scale solar plants in Minnesota were tied to the power output data from the corresponding period to examine the influence of ground cover on the PV performance and that of the arrays on the underlying soil and vegetation. Soil moisture, soil temperature, air temperature, relative humidity, wind direction/speed were recorded at a 15-minute interval at three treatments: PV arrays with a vegetated ground cover (“veg PV”), PV arrays with a bare ground cover (“bare PV”), and a nearby open space with the same vegetation as that in veg PV (control). Solar irradiance and cumulative precipitation were also recorded in the control. While air temperature and relative humidity were not significantly different between the veg PV and the bare PV, soil moisture was lowest in the bare PV treatment and comparable between the veg PV and the control. Soil moisture also varied spatially along the transect perpendicular to the array, though the spatial distribution was not consistent between the treatments and different facilities. Soil temperature was the lowest in the veg PV and the highest in the control, implying that the partial shade from the solar array keeps the underlying soils cooler. Cooler soil temperature in PV arrays could be a buffer for plants during periods of drought, which implies that co-located systems could be implemented in ecosystem restoration projects for climate resilience. In addition to the microclimate variables, panel temperature was also recorded at veg PV and bare PV treatments and electricity generation data from the corresponding treatments during the study period was provided by the operators of the facilities. Neither vegetation-driven panel cooling nor the increased power output was observed in the veg PV: the bare PV had higher output and panel temperatures than the veg PV in the early mornings, which may imply that the observed difference in output may be due to shading of the panels in the veg PV treatment by the co-located vegetation. The differential of total daily production (bare PV – veg PV) was positive on most days, though the mode in a frequency distribution of the differential was centered around a very small positive value. The lack of panel-cooling in the veg PV was determined to be due to the short rainfall interval (1-2 days) during the study period. Because of the frequent rainfalls, evaporation in the bare PV treatment and evapotranspiration process in the veg PV treatment remained in an energy-limited stage, and the water would evaporate more rapidly from the bare soil that is more exposed to sunlight and wind. In a drier environment with infrequent rainfalls, evaporation and evapotranspiration would be moisture-limited most of the times, and plants may be able to transpire water from deeper in the soil over a longer period of time to cool the overlying panels, given enough irrigation. The lack of panel cooling in our field sites implies that such environmental co-benefits are likely to be climate dependent, which indicates the need for further study of the influence of the vegetation on the PV operation and vice-versa at large-scale solar facilities in varying climate zones. Soil samples were also collected for grain size analysis using laser diffraction and nutrient analysis using standard combustion methods. In the sandy soils at the Chisago facility, the bare PV treatment had significantly less clay portion than the veg PV treatment and the control. On the other hand, the clay percentages did not significantly differ among the three treatments in the other two facilities with higher background clay contents (Atwater and Eastwood). The loss in total carbon, nitrogen, and soil cations was also the most pronounced in the bare PV in a facility with the sandy soil. Maintenance of vegetation or re-vegetation while minimizing land grading may protect the soil’s ability to store carbon and nutrients, and that effect may be magnified in coarse-textured soils or ones whose carbon and nutrient storage capacity is otherwise compromised. Overall, the field investigation found that the occurrence of some of the environmental co-benefits of co-locating PV with vegetation depended on the climate and soil, prompting a need for case-by-case consideration of these variables to identify which of the co-benefits will be achievable. Extensive solar PV development to meet energy demand and decarbonize the energy grid will significantly impact the landscape. Co-location offers an opportunity to mitigate the potential negative impacts of utility-scale solar energy, while still meeting sustainable development goals. A system dynamics model is developed to compare the regional land occupation, water usage, carbon emissions, and change in soil carbon storage resulting from solar development using two different development strategies: traditional, in which the land is graded and vegetation is removed, and co-location, in which land grading is minimized and the soil is re-vegetated with native vegetation. The model is applied in two water-sensitive semi-arid regions with high technical potential for solar energy where agriculture is an important element of the local economy. First, Rajasthan, India is undergoing rapid expansion of solar PV to address the growing energy demand while meeting sustainable energy development goals in a developing economy. The results show that at the current growth rate of solar energy in Rajasthan, solar energy will grow to more than 500 GW by 2070 and will occupy a land area equivalent to 20% to 95% of the unused land suitable for solar. Second, the Central Valley of California has a mature power system in a mature economy seeking to decarbonize. The results show that the overall capacity of California’s solar energy in 2070 will be less than a fifth of Rajasthan’s and occupy at most 10% of California’s unused land suitable for solar. Consequently, soil carbon loss due to future solar capacity additions under conventional development strategy will be similarly smaller in California than in Rajasthan. Together, the results show that the opportunity for the mitigation of the negative impacts of energy development may be greater in younger economies with a developing grid network. / Geoscience
56

Forage Production and Nutritive Value in a Temperate Appalachian Silvopasture

Buergler, Alicia Lenore 24 May 2004 (has links)
Integrating trees into pasture may be an effective management tool to improve water, nutrient, and light allocation and increase total system productivity in Appalachia. We tested this hypothesis in a silvopasture near Blacksburg, VA. In 1995, black walnut and honey locust trees were planted within plots (r=3) of predominantly tall fescue pasture. Across a 12% slope, trees were planted to create treatments of low, medium, and high tree densities at shoulder, mid, and toe slope positions within plots of honey locust and black walnut. Sampling sites (n=54) under tree density and slope position combinations were harvested May to October at 35-d intervals in 2002 and 2003 for determination of yield and nutritive value characteristics. Soil surface temperature, forage canopy temperature, soil moisture, and photosynthetically active radiation were measured to determine forage responses to field treatments as functions of resource allocation. Tree density had the greatest effect on forage production and nutritive value. Across both years, yields were 16% greater (P=0.0006) at medium density (6130 kg/ha) compared to forage mass at low (5280 kg/ha)) and high density (4970 kg/ha, SE=130). Increasing tree density did not affect (P>0.2) ADF, CP, P, K, and Mg levels, but reduced (P<0.001) NDF and TNC, and increased (P<0.0001) ADL and Ca. Elevated soil surface and forage canopy temperatures limited forage production and nutritive value at low density, while low light levels were the limiting factor at high density. Moderating forage microclimate with appropriately spaced trees is an effective way to improve forage production in temperate pastures. / Master of Science
57

Creating Shade in Arid Climates: A Welcoming Landscape Based on Zoroastrian Beliefs for the Towers of Silence

Najafi Ashtiani, Azadeh 13 December 2019 (has links)
This study develops a landscape design, which demonstrates how to change the microclimate in a historical public space (Towers of silence, in city of Yazd, designated as World Heritage Site, in the heart of Iran). The arid historic city of Yazd is getting hotter. The increasing temperatures make it more and more difficult to use the public space. Towers of silence inherited from Zoroastrianism are stone cylindrical structures located on top of the hills within infertile land located south east of the city of Yazd. This historic site brings visitors from around the world every year but the microclimate of the site it is not welcoming. The current layout does not provide information about the rich culture it entailed, and visitors are not able to understand the meaning that is behind these structures. This design aims to improve the current conditions of these magnificent towers and utilize techniques like historical plan analysis, comparative analysis and experimental design study. Using landscape architecture to address the climate issue the proposed design translates Zoroastrian's beliefs to visitors as well as creating a more hospitable environment. / Master of Landscape Architecture / All around the world people must deal with climate change and the effects of extreme weather. City of Yazd in the heart of Iran is not immune to such changes and has traditionally faced a harsh desert like climate. This study focuses on improving the climate surrounding a unique and magnificent historic site in city of Yazd called the Silent Towers (a designated UNESCO World Heritage Site). The design uses material and natural elements that are local to the site (stone, plants and trees) and infuse Zoroastrian and ancient Persian beliefs to bring about a more pleasant conditions (reducing the heat) for the visitors to this site. The outcome of merging tradition and natural elements to mitigate extreme temperatures brings about a layout that is inviting to visitors and hospitable to the local population without changing any of the values or the integrity of the main attraction: The Towers of Silence.
58

Gopher tortoise nest-site selection at burrows and the influence of nest environment on hatching success

Lawson, Garrett Richard 09 August 2024 (has links)
Nesting and early life is a period of high mortality for many turtle species, so understanding how turtles select nest sites, and how those nest sites impact hatching success, may be important for successful species conservation. In this research, my objective was to 1) understand how the environment around potential nest sites (canopy, understory, and soil) influences gopher tortoise nest-site selection at burrows and 2) how that nest environment both directly (nest microclimate: temperature and moisture) and indirectly (nest characteristics: nest depth, distance from burrow, canopy and understory cover, percent clay in soil, and lay date) affects hatching success in naturally incubated tortoise nests. In the summers of 2022 and 2023, I conducted repeated searches at burrows to locate nests at the Jones Center at Ichauway and the Greenwood Ecological Reserve in southwestern Georgia. I collected soil samples, measured canopy and ground cover at gopher tortoise nest locations (n=132) and an equal number of comparison non-nest burrows. At nest sites, I also monitored temperature and moisture throughout incubation. To evaluate nest-site selection, I compared burrows with and without nests using multiple logistic regression to create a suite of five biologically relevant candidate models and compared models with Akaike's Information Criterion adjusted for small sample sizes. The top three models identified canopy cover and understory vegetation cover as the only significant predictors of nest presence at burrows, with tortoises in the sites nesting at burrows with lower understory and canopy cover. Furthermore, there was an interaction between the understory vegetation and canopy cover effects, where the effect of understory cover decreased as canopy cover increased. This suggests that the vegetation effect may be primarily driven by an avoidance of shade, whereby nests laid in burrows with high canopy cover were so shaded that understory vegetation had a weaker influence on nest-site selection. When tortoises nested in burrows with lower canopy cover, which was far more common than high canopy cover at our sites, they also avoided understory vegetation so that nest sites were least shaded. These results suggest that maintaining habitats with very open overstories may be most important for allowing gopher tortoises access to preferred nest sites. To quantify the direct and indirect effects of nest environment on hatching success, I built a structural equation model (SEM) in a Bayesian framework in which hatching success was affected by nest temperature and moisture, which were themselves affected by nest site characteristics. I found that nest microclimate could be predicted moderately well from characteristics of the nest environment (R2=0.25-0.49), with lay date influencing both temperature and moisture, vegetation affecting temperature, nest position influencing moisture and temperature variability, and percent clay in soil influencing moisture. Hatching success was highest at lower mean temperatures and moistures and at intermediate levels of temperature and moisture variability, but the ability of this model to predict hatching success was low (R2=0.10). I observed very high hatching success (87.5%) and, thus, eggs were generally receiving the conditions they needed to successfully develop and there was not much variation in hatching success to explain. This framework may be useful for investigating environmental causes of lower hatching success at less robust tortoise populations that may be experiencing low rates of natural hatching success. / Master of Science / Many turtle species experience high rates of mortality in early life, so understanding how turtles select areas to nest, and how those places impact hatching success, may be important for successful species conservation. In this research, my objective was to 1) understand how the environment around potential nest locations (vegetation and soil) influences where gopher tortoise place nests at burrows and 2) how the conditions of that nest location both directly and indirectly affect hatching success in natural gopher tortoise (Gopherus polyphemus) nests. In the summers of 2022 and 2023, I conducted repeated searches at burrows to locate nests at the Jones Center at Ichauway and the Greenwood Ecological Reserve in southwestern Georgia. I collected soil samples, measured canopy and vegetative ground cover at gopher tortoise nest locations and an equal number of burrows without nests. At nest sites, I also monitored temperature and moisture throughout incubation. To evaluate how tortoises chose nest locations, I created models to compare tortoise burrows with nests to burrows that were available for nesting, but where no nest was placed. The top three models identified canopy cover and understory vegetation cover as the only significant predictors of nest presence at burrows, with tortoises in my sites nesting at burrows with lower understory and canopy cover. Furthermore, there was an interaction between the understory vegetation and canopy cover effects, where the effect of understory cover decreased as canopy cover increased. This suggests that the vegetation effect may be primarily driven by an avoidance of shade, whereby nests laid in burrows with high canopy cover were so shaded that understory vegetation had a weaker influence on nest-site selection. When tortoises nested in burrows with lower canopy cover, which was far more common than high canopy cover at my sites, they also avoided understory vegetation so that nest sites were least shaded. These results suggest that maintaining habitats with open overstories may be most important for allowing gopher tortoises access to preferred nest sites. To quantify the direct and indirect effects of nest environment on hatching success, I built a structural equation model (SEM) in which hatching success was predicted by nest temperature and moisture, which were themselves predicted by nest-site characteristics. This allowed me to evaluate both the direct effects of nest temperature and soil and the indirect pathways by which nest environment may be influencing hatching success. I found that nest temperature and moisture could be predicted moderately well from characteristics of the nest environment (R2=0.25-0.49), with the date the nest was laid influencing both temperature and moisture, vegetation around the nest affecting temperature, nest position influencing moisture and temperature variability, and percent clay in soil influencing moisture. Hatching success was highest at lower mean temperatures and moistures and at intermediate levels of temperature and moisture variability, but the ability of this model to predict hatching success was low (R2=0.10). I observed very high hatching success (87.5%) and, thus, eggs were generally receiving the conditions they needed to successfully develop and there was not much variation in hatching success to explain. This framework may be useful for investigating environmental causes of lower hatching success at less robust tortoise populations that may be experiencing low rates of natural hatching success.
59

Mokyklos bendruomenės mikroklimatas / The school community microclimate

Čepulienė, Gintarė 29 June 2009 (has links)
Gintarė Čepulienė. Magistro darbo tema – Mokyklos bendruomenės mikroklimatas. Mokslinis vadovas Doc. dr. V. Senkus. Darbo tikslas - išnagrinėti mokyklos bendruomenę mikroklimato ir bendradarbiavimo aspektais. Darbo hipotezės : · Mokyklos mikroklimatą didele dalimi lemia pedagogų - moksleivių santykiai ir bendradarbiavimas. · Klasės auklėtojas imasi tarpininko vaidmens ir tokiu būdu padeda mokiniams spręsti iškilusias problemas. · Moksleivių bendruomenės vienijančioji grandis yra moksleivių savivaldos institucija, kurioje lavinami moksleivių tikslingos veiklos gebėjimai, įtvirtinama asmeninė atsakomybė. · Bendradarbiavimą mokykloje lemia mokyklos vadovo, kuris yra ir mokyklos bendruomenės vadovas, bendruomenės organizavimo stilius. Tyrimo objektas - mokyklos bendruomenės mikroklimatas. Tyrimo problema - išnagrinėti mokyklos bendruomenę mikroklimato ir bendradarbiavimo aspektais. Tyrimo metu naudota: - literatūros šaltinių analizė ir anketinė apklausa. Duomenų analizės metodas – statistinis – aprašomasis. Informacija grupuojama, pateikiama lentelėse, vaizduojama diagramomis, grafikais. Atliktas kiekybinis tyrimas. Apklausoje dalyvavo Šviesos vid. m-klos (10 -12 kl.) moksleiviai , atrinkti atsitiktiniu būdu pasirenkant klases. Anketas užpildė (39) pedagogai, tarp kurių buvo (23) mokytojai ir (16) klasės auklėtojų. Jų tarpe (36) moterys ir (3) vyrai . ( 60 anketų) užpildė mokinių tėvai . Mokiniai užpildė ( 108 ) anketas. / Gintare Čepulienė. Master's thesis topic - the school community microclimate. Supervisor Assoc. dr. V. Senk. The purpose of the work is to analyze microclimate and collaboration of school society. Hypothesis: · Most of all, schools microclimate is determined by teachers and students relations and collaboration. · Preceptor is intermediator between students; in that case he helps students to solve problems. · Students’ self-government institution is the rally link of students society, where students are educated in purposive activity ability, strengthened personal responsibility. · School collaboration depends of school heads society organization style. The object of investigation is the microclimate of schools society. Investigation problem is to analyze microclimate and collaboration of school society. The study used - analysis of literature and the questionnaire survey. The method of data analysis is statistical - descriptive. The information is grouped, binged in tables, images and graphs. The quantitative study is done. “Šviesos” secondary school (10-12 class) students where the participants of survey, the participants where selected randomly choosing classes. Completed the questionnaires (39) teachers, among which were (23) and teachers (16)-class educators. Among them (36) and women (3) men. (60 questionnaires) completed the parents of pupils.
60

Macro and microclimate effects on cover zone properties of field cured concrete

Al-Kindy, Adil January 1998 (has links)
Three sets of concrete blocks were cast to investigate the effects of natural exposure conditions, at the macro and microclimate scale, and field curing on the performance and durability of OPC and OPCjGGBS concretes. These are termed the Loughborough winter series, the Loughborough summer series and the Muscat summer series. Three concrete mixes were investigated in the two Loughborough series (30 and 50 MPa OPC concrete mixes and a 30 MPa OPCjGGBS concrete mix) and two in the Muscat weather series (the two 30 MPa concretes). A group of specimens were cast with each mix consisting of 600 x 500 x 150mm concrete blocks plus control cubes and prisms. The samples were cured in-situ and exposed to a range of curing methods and microclimates. Surface zone properties (up to 50mm depth) were evaluated by air permeability, sorptivity, carbonation, thermogravimetry (TG) and mercury intrusion porosimetry (MIP) tests, conducted after 3 and 12 months of site exposure. The results revealed distinct variations due to macroclimate, microclimate, curing, concrete type and age. The air permeability, sorptivity and carbonation of the concrete exposed under moderate and rainy conditions of a Loughborough summer season were lower than identical concrete cast and cured during a very cold and dry Loughborough winter season. Further, the sorptivity of concrete subjected to the hot and dry climatic conditions of Muscat was significantly higher than companion samples subjected to the temperate Loughborough climate. Significant variations in properties were observed within the two sides of the same concrete element, each subjected to a different microclimate. The air permeability, sorptivity, carbonation and porosity were reduced with increased hessian curing duration. However, premature drying of wet hessian during curing had an adverse effect on concrete quality as this produced concrete of higher permeability and carbonation than non-cured concrete. The application of controlled permeability formwork was effective in improving the concrete's sub-surface properties. The curing affected zone (CAZ) extended to approximately 20mm below the surface of the concrete that was exposed to the Loughborough winter and summer climate, and 40-50mm for the concrete exposed to the Muscat climate, with notable variation in properties due to climate and curing. The TG and MlP results provided insights into the mechanisms associated with the variations in the three concrete's properties due to natural field exposure.

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