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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.
691

Hydrologic Response Of Meadow Restoration Following The Removal Of Encroached Conifers

Ramirez, Oriana 01 June 2024 (has links) (PDF)
Meadows are important within forest ecosystems because they provide diverse species habitats, facilitate water cycling, help with sediment capture, aid in carbon sequestration, and create natural fire breaks in forested regions. However, fire suppression, poor grazing practices, and climate change have accelerated the encroachment of conifers into historical meadow habitat. This has led to an extensive loss of meadow habitat within the Sierra Nevada and Cascade Mountain Ranges. Therefore, the purpose of this study is to quantify changes in percent soil moisture and groundwater levels following the removal of encroached lodgepole pine (Pinus contorta) in a historic meadow habitat near Lake Almanor, California. A before-after control-intervention (BACI) study design was used, with Marian Meadow (MM) as the control and Rock Creek Meadow (RCM) as the restored meadow. Soil moisture and groundwater level data was collected one year before (water year 2019), and three years after (water years 2020-2023) the removal of lodgepole pine from RCM in the fall of 2020. This data was then analyzed using multiple linear regression and estimated marginal means (EMMs) models. Percent soil moisture increased each year after restoration, with significant increases from pre-restoration values occurring in year 2 and year 3 post-restoration. The overall mean soil moisture content increased from 30.69% (pre-restoration) to 40.42% by the 3rd year post-restoration. Groundwater has had a much more mixed response to restoration, with the 1st year post-restoration seeing a significant decrease in groundwater availability. Years 2 and 3 showed gradual recovery of groundwater levels, although on average they were still less than pre-restoration groundwater levels. This can likely be attributed to moderate drought occurring in the 2020 and 2021 water years. Sources of variability include the 2021 Dixie Fire which burned through both meadows at different severity levels, gaps in the data due to issues with the data loggers, differences in snowmelt timing, and differences in soil attributes. Collectively, however, all these factors converge toward a wetter meadow habitat. Hopefully, the results of this research will help promote a better understanding of how meadow restoration can improve California forestland management.
692

Improving the Reliability of Compartmental Models: Case of Conceptual Hydrologic Rainfall-Runoff Models

Sorooshian, Soroosh, Gupta, Vijai Kumar 08 1900 (has links)
No description available.
693

CALIBRATION OF RAINFALL-RUNOFF MODELS USING GRADIENT-BASED ALGORITHMS AND ANALYTIC DERIVATIVES

Hendrickson, Jene Diane, Sorooshian, Soroosh 05 1900 (has links)
In the past, derivative-based optimization algorithms have not frequently been used to calibrate conceptual rainfall -riff (CRR) models, partially due to difficulties associated with obtaining the required derivatives. This research applies a recently- developed technique of analytically computing derivatives of a CRR model to a complex, widely -used CRR model. The resulting least squares response surface was found to contain numerous discontinuities in the surface and derivatives. However, the surface and its derivatives were found to be everywhere finite, permitting the use of derivative -based optimization algorithms. Finite difference numeric derivatives were computed and found to be virtually identical to analytic derivatives. A comparison was made between gradient (Newton- Raphsoz) and direct (pattern search) optimization algorithms. The pattern search algorithm was found to be more robust. The lower robustness of the Newton-Raphsoi algorithm was thought to be due to discontinuities and a rough texture of the response surface.
694

Literature Pertaining to Water Quality and Quantity in Unsaturated Porous Media

Tyagi, Avdhesh K. 05 1900 (has links)
Introduction: The movement of moisture and the simultaneous transfer of water and solutes in unsaturated porous media are problems of practical interest in ground water hydrology and soil physics. A large fraction of the water falling as rain on the land surfaces of the earth moves through unsaturated zone of soil during the subsequent processes of infiltration, drainage, evaporation, and absorption of soil -water by plant roots. A soil profile is characteristically nonuniform in its properties, nonisothermal, and may be nonrigid. Microorganisms and the roots of higher plants are a part of the system. This region is characterized by cylic fluctuation of water content as water is removed from the soil profile by evaportranspiration and replenished by recharge, irrigation, or rainfall. In unsaturated porous media the problem of movement and retention of water may be approached from (1) the molecular, (2) the microscopic, or (3) the macroscopic standpoint. In the molecular viewpoint theories of the mechanisms of flow and retention in terms of the behavior of water molecules are devised. At microscopic level a theory of flow treating the fluid in pores as a continuum and applying the principles of continuum mechanics to understand the detailed behavior of fluid within the pores is developed. The complicated pore geometry and consequent impossibility of specifying the boundary conditions on flow, preclude any practical progress by this appraoch. Since the behavior of individual molecules and the distributions of fluid velocity and pressure cannot be observed in porous media, a macroscopic theory of flow is needed. In the macroscopic approach, all variables are treated continuous functions of time and space. Velocity, pressure, and other variables are assumed as point functions. Thus, any theory of water transport to be useful must be developed to the point of describing the transfer of water on the macroscopic level. The coefficients of transport such as permeability and diffusivity can be defined microscopically. In many investigations which involve the transport of pesticides and fertilizes along with water , the simultaneous movement of water and solutes is of primary concern. These pollutants when mixed with water move in the unsaturated soil and finally join the region of saturated soil or water table, resulting in the contamination of fresh water existing below the water table. The scope of this report is to review the available literature, that may be categorized into two parts; one, the movement of water in unsaturated soil, and the other, the simultaneous movement of water and solutes in unsaturated soil. The papers, reviewed in this report, pertain to the theoretical study, laboratory study and field study on the two problems. At the end, an appendix appears which lists the references, categorizing the kind of study by various investigators.
695

Fukttillstånd i betongplatta på mark : Ett experimentellt försök att jämföra teori med praktik

Selén, Niklas, Söderström, Tom January 2017 (has links)
When casting the slab in a slab-on-ground structure most of the drying will occur through the surface of the slab, which is in contact with the air. This will create a non-uniform internal moisture distribution. With the top of the slab drying faster it will also have a faster shrinkage due to drying, which in turn leads to stress in the surface layers of the slab as these wants to contract. With the slab wanting to assume a curled geometry, but being restricted by external loads and self-weight, cracks will usually appear in the surface (Lange, Lee & Liu, 2011).  A concrete slab-on-ground does not dehydrate the same way as, for example, floor bellows or wall elements which has the same climate on both sides. The ground beneath a heated building standing on a slab-on-ground structure is warm and moist with a relative moisture close to 100%. After carefully examining moisture damaged slab-on-ground structures it was concluded that the temperature and moisture behavior in this type of structure is more complicated than earlier presumed. In an attempt to broaden the basis of knowledge about humidity conditions under a concrete slab-on-ground structure, measurements were performed on an existing slab.  The Council for Construction Competence (Rådet för ByggKompetens, RBK) sets the industry standard regarding moisture measurement in Sweden. In 2017 the method recommended by RBK for moisture measurement in concrete includes drilling a hole in the slab, sealing it with a plastic pipe and mounting the sensor inside. This is the method that was used for measurements in this paper. Three different measurement locations in the slab along with two sensors mounted at every location was used to gather data.  The results from the measurements show that the relative humidity near the bottom of the slab is close to 100%. The results from the sensors range from 90% to 100% RH with the majority of the results very close to 100% RH. The results discovered in this paper supports the assumption that the ground beneath a slab-on-ground structure is close to 100% RH. / Vid gjutning av en betongplatta på mark sker uttorkning främst genom ovansidan av plattan. De övre skikten av betongen får en snabbare uttorkning än de undre skikten, detta tillsammans med den krympning som sker under uttorkningen skapar spänningar i betongplattan. Fenomenet gör att plattan vill böja upp sig i kanterna men på grund av egentyngd samt laster ovanifrån uttrycker sig spänningarna istället som sprickor på ovansidan (Lange, Lee & Liu, 2011). Uttorkning av en betongplatta på mark skiljer sig från uttorkning av t.ex. väggelement och mellanbjälklag som har samma klimat på bägge sidor. Marken under en uppvärmd byggnad med grundkonstruktionen platta på mark antas vara varm och fuktig med en relativ fukthalt nära 100 %. Efter noggrann undersökning av fuktskadade platta på mark konstruktioner har det visat sig att temperatur- och fuktbeteende i dessa konstruktioner är mer komplicerade än tidigare förmodat. För att bredda underlaget för de fuktförhållanden som råder i underkant av en betongplatta på mark utfördes mätningar i en befintlig betongplatta. Rådet för ByggKompetens, RBK är de som bestämmer branschstandarden inom fuktmätning i Sverige. Från 2017 är den enda metoden för fuktmätning i betong som RBK rekommenderar en metod där ett hål borras i betongplattan, tätas med ett foderrör och en RF-givare monteras inuti. Denna metod användes vid mätningarna i detta arbete. Tre olika mätpunkter med två RF-givare vid varje mätpunkt har använts vid mätningarna. Resultaten från mätningarna visar på att den relativa fuktigheten i betongplattans underkant är nära 100 %. Resultaten från givarna varierade mellan 90 % till 100 % RF där majoriteten av resultaten ligger väldigt nära 100 % RF. I och med dessa resultat styrker denna rapport antagandet om att marken under en platta på mark har en RF på 100 % eller väldigt nära.
696

Byggföretagens hantering av fuktsäkerhetsprojektering – med fokus på projektörer / The Management of Moisture Safety Design by the Construction Companies   – with focus on the Planners

Aghaie Azghandi, Mohammed Ali, Ahmad, Omar January 2019 (has links)
Fuktskador uppstår vanligtvis på grund av felaktig planering, projektering och utförande under hela byggprocessen. Dessa felaktigheter resulterar i stora åtgärdskostnader som kan minimeras eller till och med elimineras om fuktsäkerhetsarbetet är väl genomförd. Projekteringsskedet är ett viktigt skede, där en noggrann och korrekt genomförd fuktsäkerhetsprojektering är av stor betydelse för det försatta fuktsäkerhetsarbetet under byggprocessen. Projektörernas roll i detta skede är att utföra en fuktsäkerhetsprojektering utifrån de ställda kraven från byggherren.  Syftet med detta examensarbete är att ta reda på projektörernas val av metod vid genomförandet av fuktsäkerhetsprojektering och granska om behovet av eventuell kompetensutveckling, inom fukt, bland projektörerna är nödvändig.     De två metoder som har använts för att uppnå syftet i detta examensarbete är intervjuer och litteraturstudier.  Målgruppen i detta examensarbete är byggföretagen i Sverige. Det som granskas är hur de hanterar fuktsäkerhetsarbetet i projekteringsskedet, med fokus på hur fuktsäkerhetsprojekteringen utförs. Av de aktörer som medverkar i projekteringsskedet riktas all fokus på projektörerna.   Tre av fem projektörer är missnöjda med den egna fuktkompetensen vilket överensstämmer med de fuktsakkunnigas uppfattning om projektörernas fuktkompetens. Under intervjuerna har flera fuktsakkunniga påpekat behovet av ökat fuktkompetens bland projektörerna. Den bristande fuktkompetensen leder till att projektörerna inte kan beakta eller upptäcka eventuella fuktrisker vid fuktsäkerhetsprojekteringen. Metod som 80 % av projektörerna tillämpar vid fuktsäkerhetsprojektering är ByggaF metoden. Projektörerna kunskap om ByggaF är fortfarande låg enligt de fuktsakkunniga och av den anledningen kan projektörerna inte tillämpa ByggaF metoden i sin helhet. Kompetens och erfarenhet är de viktigaste faktorerna som en projektör måste ha med sig, för att kunna beakta och upptäcka vad som är fel krävs det kunskap samt erfarenhet om vad som är rätt.        Utifrån responsen från både byggnadsnämnden och deltagarna, framgår det att en granskning av dokumentationen gällande fuktsäkerhetsarbetet inte, alltid, begärs in av byggnadsnämnden.    Slutsatsen är att projektörer måste införskaffa sig kompetens inom fukt och ByggaF metoden. / Moisture damage usually occurs due to incorrect planning, design and execution throughout the construction process. These inaccuracies result in large cost of action that can be minimized or even eliminated if the moisture safety work is done properly. The design phase is an important stage and a properly implemented moisture safety design can be of great importance for the moisture safety work during the construction process. The planners’ role at this stage is to carry out a moisture safety work based on the requirements of the developer. The purpose of this exam is to find out the choice of method made by the planners’ in the implementation of moisture safety design and to review the need of competence development among the planners’ about moisture.    The two methods that have been used to achieve the purpose of this exam are interviews and literature studies. The target group in this exam is the construction companies in Sweden. The way of how the companies handle of moisture safety design is being reviewed in the design stage.  Of all involved actors in the design phase, the focus is on the planners'. Three out of five planners' are dissatisfied with their own moisture competence, which is in line with the opinion of the experts' of moisture about the planners' competence.   During the interviews, several experts' of moisture have pointed out the need for increased moisture competence among the planners'. The lack competence means that the planners' cannot consider or detect possible moisture risks during the moisture safety design. The method that is used by 80% of the planners' during moisture safety design is the ByggaF method. The planners' knowledge of ByggaF is still low according to the experts' of moisture and for this reason the planners' cannot apply entirely the ByggaF method. The tools that planners' need to have with them is knowledge and experience. In order to discover what is wrong, you need to have both the knowledge and experience about what is right.  Based on the response from both the building committee and the participants, a review of the documentation regarding the moisture safety work is not always requested by the building committee.  The conclusion is that projectors must acquire competence in both moisture and the ByggaF method.
697

Fuktsäkert byggande : Sjönära bostäder i Östra Hamnen i Västerås

Hyytiä, Nanna January 2007 (has links)
<p>Housing construction very close to the lake Mälaren has become very popular today. One potential problem with these houses is the influence of the sea climate. Unprotected buildings are affected by strong winds and precipitation. So for that reason, it is very important to make an accurate climate investigation and use it for decision-making during the planning of the new settlement.</p><p>It is very important with a good moisture protection regarding pelting rain, that is the combination of wind and rain. This is more important for buildings close to a lake, as this location normally means a higher exposure to wind. The location of the main bodies of the houses has an effect on the wind force between the houses. Some house parts are affected more than other, for instance curtain walls, bays, balconies and so on. These are problematic because of water and moisture that are moving in into joints and cavities in connections.</p><p>Bigger efforts than climate investigations are needed to get rid of the moisture problem.</p><p>The different actors that are involved in the construction project need to cooperate and focus on potential moisture problems during the complete construction process, not only during the production phase. It is also important that the construction workers have the knowledge on how to construct buildings that are moisture safe in practice.</p><p>According to investigations made, it appears that many of the moisture damages in buildings originate from the production phase because of incorrect construction components that are moisture-sensitive. But approximately 50% of the moisture problems derive from the planning process. The reasons are mainly lack of easily available tools, (for instance descriptions of moisture protection), insufficient knowledge, lack of time and lack of interest. These early mistakes results in later problems during the production phase. It is of great importance that the project members have good communication with the building contractors. They need to inform them on how to calculate dry times for different construction components and what type of inspections that shall be performed.</p>
698

Fuktsäkert byggande : Sjönära bostäder i Östra Hamnen i Västerås

Hyytiä, Nanna January 2007 (has links)
Housing construction very close to the lake Mälaren has become very popular today. One potential problem with these houses is the influence of the sea climate. Unprotected buildings are affected by strong winds and precipitation. So for that reason, it is very important to make an accurate climate investigation and use it for decision-making during the planning of the new settlement. It is very important with a good moisture protection regarding pelting rain, that is the combination of wind and rain. This is more important for buildings close to a lake, as this location normally means a higher exposure to wind. The location of the main bodies of the houses has an effect on the wind force between the houses. Some house parts are affected more than other, for instance curtain walls, bays, balconies and so on. These are problematic because of water and moisture that are moving in into joints and cavities in connections. Bigger efforts than climate investigations are needed to get rid of the moisture problem. The different actors that are involved in the construction project need to cooperate and focus on potential moisture problems during the complete construction process, not only during the production phase. It is also important that the construction workers have the knowledge on how to construct buildings that are moisture safe in practice. According to investigations made, it appears that many of the moisture damages in buildings originate from the production phase because of incorrect construction components that are moisture-sensitive. But approximately 50% of the moisture problems derive from the planning process. The reasons are mainly lack of easily available tools, (for instance descriptions of moisture protection), insufficient knowledge, lack of time and lack of interest. These early mistakes results in later problems during the production phase. It is of great importance that the project members have good communication with the building contractors. They need to inform them on how to calculate dry times for different construction components and what type of inspections that shall be performed.
699

Impact of moisture on long term performance of insulating products based on stone wool

Vrána, Tomás January 2007 (has links)
<p>Demands for energy have been increasing in the whole world. According to higher consumption, the price of energy rises yearly too. This evokes usage of insulating products in a wider range. By adding insulation, we lower the amount of energy needed to heat our homes, resulting in fewer associated greenhouse gas emissions and a lower monthly heating bill. Savings depend on insulation thicknesses and on conditions, in which the insulant is kept. Mineral insulation based on stone wool is also a member of building insulants that defends buildings and constructions against temperature changes of the ambient. However, even when we use modern technologies and building techniques to reduce high energy losses, we can never provide unimpeachable protection of stone wool from damage. During a construction process on a building site or at fast climate changes, it often happens that stone wool is exposed to rain precipitaions or other climate effets. This brings water to the insulating structure. Besides the loss of insulating qualities, the stone wool is left permanently wet. Even the fibres of stone wool are inorganic, they still can be attacked by degradation processes due to organic agents fixing fibres together. Analysis of damaged flat-roof constructions using stone wool and verification of material properties is a starting point of this licentiate thesis.</p><p>The attached paper section can be divided into two parts:</p><p>In-situ practice that notes troubles with insulating materials based on stone wool with inbuilt moisture on a building site</p><p>Laboratory measurement that observe material properties of stone wool under varying conditions</p>
700

Påföljder av inbyggd fukt i konstruktionselement av korslimmat trä / Effects of built in moisture in cross-laminated construction elements

Albertsson, Nils, Gustavsson, Isak January 2023 (has links)
In spring 2023, two engineering students from Jönköping University collaborated with GBJ Bygg Jönköping to investigate the impact of moisture on cross-laminated timber (CLT) and its drying process. The study aimed to identify potential issues, damages, and propose mitigation methods. Through measurements and investigations, this study generated in-depth knowledge of moisture effects on CLT, ensuring proper material handling to avoid long-term negative consequences.The methodology involved quantitative investigations to obtain credible results. Experiments simulated the application of wet macadam on a CLT floor slab in a natural environment to measure time to reach an acceptable moisture content. Collaboration with GBJ Bygg provided access to information, materials, and simulation facilities. Two tests were conducted: immediate construction after placing washed macadam and a 9-day drying period before reconstruction. Results showed that direct macadam application led to high timber moisture content, while drying according to industry recommendations resulted in low moisture content without negative consequences. The drying process varied depending on reconstruction timing, and methods like extending macadam drying time were proposed to reduce damages and shorten the drying period.The discussion of results demonstrated data relevance with limited room for misinterpretation. However, the study's time frame limited complete results, and the lack of prior research on timber drying affected connections to previous studies. The clearest answer came from the 9-day drying test, showing a decrease in moisture content. Some measured values deviated, possibly due to measurement errors. Facility climate and construction execution posed potential error sources. Despite limitations, the experiment effectively addressed the study's purpose and research questions.

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