• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 14
  • 8
  • 5
  • 5
  • 3
  • 2
  • 1
  • 1
  • Tagged with
  • 51
  • 12
  • 9
  • 8
  • 6
  • 6
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 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.
1

Ecophysiological studies on four species of tropical trees

Ramos-Prado, J. M. January 1987 (has links)
No description available.
2

Simulations of moist convection using the quasi-elastic equations

Bopape, M.M. (Mary-Jane Morongwa) January 2013 (has links)
Cloud Resolving Models use microphysics parameterisation schemes for the simulation of clouds. The thesis reports on the introduction of two single-moment Bulk Microphysics Parameterisation (BMP) schemes in the Nonhydrostatic - coordinate Model (NSM). The rst BMP is known as the PURDUE-LIN scheme, and can be used with ve (excluding graupel) or six (including graupel) classes of the water substance. The second scheme was developed using the PURDUELIN scheme as a starting point, and is known as SBU-YLIN. Graupel and snow share a category and processes in the latter scheme. Simulations of two hours in length are made, with convection initiated through inserting a warm thermal into a cooler environment, using a six-class and ve-class PURDUE-LIN and the SBU-YLIN BMPs. The simulations are performed at various horizontal resolutions of 500 m, 1 km and 2 km. The six-class PURDUE-LIN scheme simulates more rainfall than the ve-class PURDUE-LIN and the SBU-YLIN schemes. The SBU-YLIN scheme generally rains the least, looses the least water vapour to hydrometeors and warms up the least. The PURDUE-LIN schemes simulate two convective cells in a no shear environment. The maximum updrafts associated with the rst cell (triggered by the warm perturbation) are similar in all the simulations. The second cell is triggered by a cold pool. While the cold pool is stronger in the six-class PURDUE-LIN scheme simulations, the updrafts in the second cell are stronger in the ve-class PURDUE-LIN simulation. The SBU-YLIN scheme generally simulates just one cell because of a weak cold pool. Simulations were also made for three di erent periods dominated by suppressed convection with deep convection at the beginning and end of the three periods, forced with large scale tendencies observed during the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE). The NSM is able to capture di erences in the suppressed and deep convection periods. Qualitatively, the simulations provide new insight into the interplay between cloud microphysics and cloud dynamics, and points out the potential for better describing the uncertainty range associated with projections of future climate change, through the improvement and stochastic application of cloud microphysics schemes. / Thesis (PhD)--University of Pretoria, 2013. / gm2013 / Geography, Geoinformatics and Meteorology / unrestricted
3

Modelling the impact of Southeast Asian deforestation on climate and the atmospheric circulation

Wan Hassan, Wan Azli January 1999 (has links)
No description available.
4

Winter Waterbird Use and Food Resources of Aquaculture Lands in Mississippi

Feaga, James Stephen 17 May 2014 (has links)
The conversion of wetland systems to aquaculture provides alternate aquatic habitats for a variety of waterbirds. In response to the 2010 British Petroleum oil spill, the National Resource Conservation Service (NRCS) enacted the Migratory Bird Habitat Initiative (MBHI) through which NRCS partnered with landowners to provide additional wetlands and associated foraging habitat for migrating waterbirds. During winters 2011–2013, I estimated abundances of waterbirds, seeds, and invertebrates in six production and idled aquaculture facilities in the Mississippi Alluvial Valley. Wintering waterbirds exhibited similar densities on production (i.e., ~22 birds/ha) and idled (i.e., ~20 birds/ha) MBHI sites. My results suggest production and idled MBHI aquaculture impoundments produced suitable conditions for waterbirds in terms of food and habitat. I recommend future programs strive to enroll properties that promote an increased diversity of habitats in terms of vegetation structure, available forage, and varying water depth, with the aim of maximizing waterbird diversity.
5

Upprättande av mall för fuktsäkerhetsbeskrivning : Genom granskning av projekt ur fuktsäkerhetssynpunkt / Establishing of a Moist-safety description : By reviewing projects from a moist-safety point of view

Wigenstam, Frida January 2011 (has links)
During the 1990’s a large number of building projects were revealed where lack of moist safety precautions during the construction process had led to extensive moisture damage. Also resent implemented studies have shown that the problems with moisture damages have rather increased than decreased during the past few years. Moist is considered to be one of the main factors to cause unhealth due to deficiencies in the indoor-environment and does also cause unnecessary expenses and a reduction of the confidence in the construction industry. In this Bachelor of Science thesis three projects have been reviewed to examine how moistsafety has been observed during the construction process. Main focus has been to identify the building components that are the most exposed to moist, and to examine how they have been taken into account during the period of design and construction. The objective of the review has been to get an overview of the moist-safety precautions taken by the municipality of Karlstad, in order to develop guidelines for future projects. The information that the review has given has been used to establish a template that can be used to create a “Moist-safetydescription”. / Under 1990-talet uppdagades ett stort antal byggprojekt där bristande fuktsäkerhetsåtgärder under byggprocessen lett till omfattande fuktskador. Även nyligen utförda undersökningar visar att problemen med fuktskador snarare ökat än minskat under senare år. Fukt anses vara en av de främsta faktorerna som orsakar besvär på grund av brister i inomhusmiljön och orsakar dessutom onödiga kostnader och minskat förtroende för byggbranschen. I examensarbetet har tre projekt granskats för att undersöka hur arbetet med fuktsäkerhet har fungerat under byggprocessen. Fokus har lagts på att identifiera fuktkritiska byggnadsdelar och kontrollera hur dessa har beaktats främst under projekterings- och byggskede. Målet med granskningen har varit att få en överblick över Karlstad kommuns arbete med fuktsäkerhet för att kunna skapa riktlinjer inför framtida projekt. Den information som granskningen gett har använts som underlag för upprättandet av en mall för en Fuktsäkerhetsbeskrivning.
6

Effects of management and hydrology on vegetation, winter waterbird use, and water quality on wetlands reserve program lands, Mississippi

Fleming, Kathryn Sarah 01 May 2010 (has links)
No evaluations of plant and wildlife communities in Wetlands Reserve Program wetlands have been conducted in the Mississippi Alluvial Valley. Therefore, I evaluated active and passive moist-soil management (MTYPE) and early and late draw-down on plant communities, waterbird use, and water quality on 18 WRP lands, Mississippi, 2007-2009. Active-early sites had greater waterfowl Vegetative Forage Quality (VFQI), percentage occurrence of grass, plant diversity, and structural composition than passively managed sites (P < 0.10). I modeled variation in densities of wintering waterbirds; the best model included VFQI*MTYPE and decreased % woody vegetation (wi ≥ 0.79). Additionally, waterbird densities varied positively with active-late management (R2 ≤ 0.27), as did duck species richness with flooded area (R2 = 0.66). I compared water quality parameters among managed wetlands and drainage ditches but did not detect differences due to variability. Therefore, wetland restoration on WRP lands should focus on active management and maximizing wetland area.
7

Ecosystem Services of Moist-Soil Wetlands: Water Quality Benefits and Crayfish Harvest, Economics and Consumer Acceptance

Alford, Amy Brooke 13 December 2014 (has links)
I estimated yield, population metrics, production costs, and evaluated consumer acceptability and nutritive content of crayfish (Procambarus clarkii, P. zonangulus) harvested from moist-soil wetlands in the Lower Mississippi Alluvial Valley (MAV) during springs 2009-2011. I also compared nutrient and sediment concentrations and loads exported from moist-soil wetlands and nearest agriculture fields in the MAV during winters 2010-2012. Daily yield of crayfish from moist-soil wetlands was 2.4 kg (wet) ha-1 (SE = 0.50; 95% CI = 1.3-3.4). When graded by size, yield of large crayfish (> 30 g) from wetlands dominated by P. clarkii was four times greater (P < 0.05) than yield of large crayfish from wetlands dominated by P. zonangulus. Crayfish harvesting costs (2013 US dollars [$]) ranged from $405.69 ha-1 to $917.88 ha-1 and breakeven selling prices ranged from $3.74 kg-1 to $8.49 kg-1. Consumer acceptability, proximate composition, and total fatty acid content of P. clarkii did not differ (0.73 > P > 0.11) between crayfish harvested from moist-soil wetlands and rice-crayfish culture fields in Louisiana. Although selling prices likely will not compete with prices for crayfish harvested from Louisiana rice fields ($2.75 kg-1; 2012 US$), harvesting crayfish from moist-soil wetlands may enhance recreational opportunities while increasing awareness of ecosystem benefits of these wetlands. Although concentrations (mg L-1) of soluble reactive phosphorus (SRP) in runoff from moist-soil wetlands and adjoining croplands did not differ (P = 0.95), concentrations of total and particulate phosphorus, nitrate-nitrogen, and total suspended solids were 42, 52, 86, and 89% lower (P < 0.03) in runoff from moist-soil wetlands. However, the load (kg ha-1) of SRP from moist-soil wetlands was six times (P = 0.08) greater than load from croplands. Estimated loading rate of total phosphorus from moistsoil wetlands (2.36 kg ha-1 year-1) was greater than the rate reported by regulatory agencies in Mississippi (1 kg ha-1 year-1), but field replication is needed to verify these results. Nearly 80% of the total loads exported from moist-soil wetlands occurred during < 30% runoff events. Retention of runoff from storm events may reduce phosphorus loss from moist-soil wetlands while not interfering with conservation objectives.
8

Conservation Of Waste Rice And Estimates Of Moist-Soil Seed Abundance For Wintering Waterfowl In The Mississippi Alluvial Valley

Kross, Jennifer 13 May 2006 (has links)
Waste rice in harvested fields and natural seeds in moist-soil wetlands are important foods for waterfowl in the Mississippi Alluvial Valley (MAV). Waste rice declines significantly between harvest and late autumn. I conducted experiments in 19 rice fields in Arkansas and Mississippi during autumns 2003 and 2004 to evaluate the ability of common post-harvest practices to conserve waste rice between harvest and late autumn. Greatest mean abundance of waste rice in late autumn occurred in standing stubble (x&95 = 105 kg/ha; CL = 72.84, 150.16 kg/ha) followed by burned (x&95 = 72 kg/ha; 49.57, 105.81 kg/ha), mowed (x&95 = 67 kg/ha; 46.65, 97.42 kg/ha), rolled (x&95 = 51 kg/ha; 35.54, 73.076 kg/ha), and disked stubble (x&95 = 48 kg/ha; 33.26, 68.41 kg/ha). I recommend leaving stubble or burning fields to create interspersion of stubble and water after flooding. Additionally, I estimated abundance of moist-soil seed in 72 management units on public lands throughout the MAV for autumns 2002-2004. Mean seed abundance was 496 kg/ha (SE = 62). I recommend increased active management of moist-soil wetlands to mitigate decreased availability of waste rice in the MAV.
9

Numerical study on the self-aggregation of moist convection in radiative-convective equilibrium / 放射対流平衡下における湿潤対流の自己集合化に関する数値的研究

Yanase, Tomoro 23 March 2022 (has links)
京都大学 / 新制・課程博士 / 博士(理学) / 甲第23712号 / 理博第4802号 / 新制||理||1687(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 竹見 哲也, 准教授 重 尚一, 教授 榎本 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM
10

UTTORKNING AV HÅLDÄCKSELEMENT - En studie som jämför uttorkningsmöjligheterna för olika betongblandningar / DEHYDRATION OF HOLLOW CORE SLAB - A study comparing the drying possibilities for different concrete mixes

Johansson, Gutstav, Johansson, Rickard January 2019 (has links)
Håldäcksbjälklag är ett fördelaktigt bjälklagsalternativ på grund av dess många fördelar så som reducerad vikt och snabbt montage. Däremot har bland annat korta byggtider medfört att betongblandningar med lågt vct och hög andel cement efterfrågats av Strängbetongs kunder för att reducera risken för fuktproblematik, då en snabb uttorkning eftersträvas. Med en allt strängare och ambitiösare miljömålsättning har ett behov för att reducera andelen cement uppkommit. Vid en minskad cementmängd ökar således betongens vct vilket leder till en miljövänligare framställning samtidigt som en ekonomisk vinning erhålls. Syftet med undersökningen är därför att undersöka om olika betongblandningar med ett högre vct kan ersätta den nuvarande betongblandningen och samtidigt uppfylla förekommande uttorkningskrav. Detta skulle innebära fördelar för såväl producenterna som för beställarna. Betongen som undersökts i utredningen är av jordfuktig karaktär och är enbart avsedd för håldäckstillverkning. Uttorkningsprocessen som studeras motsvarar uttorkningen från tillverkning fram till montage. Fyra olika betongblandningar fördelade på tolv kuber kommer att undersökas i tre olika klimat och enbart uttorkningsmässiga skillnader mellan kuberna kommer att jämföras. Undersökningen baseras på mätdata som grundar på mätningar utförda av en auktoriserad fuktkonsult via Rådet för byggkompetens, RBK. Betongrecepten i utredningen har framtagits av Cementa. Litteraturstudier används även för att styrka påståenden och underlag som framkommer i rapporten. Resultatet från studien visar att de kuber som förvarats i inomhusklimatet och i klimatrummet har en linjär uttorkningsutveckling, till skillnad från kuberna som är placerade i utomhusklimatet som har en olinjär uttorkningsutveckling. I inomhusklimatet och i klimatrummet har kuberna med högre vct torkat ut mer än betongblandningarna med lägre vct (0,40 och 0,45), däremot är skillnaden i uttorkning minimal i kuberna som har förvarats utomhus. Den fastställda slutsatsen i undersökningen är att mer djupgående och längre mätstudier behövs för att säkerställa hur betonguttorkningen förändras i ett senare skede av uttorkningsprocessen. / Hollow-deck joists are an advantageous flooring alternative because of its many advantages such as reduced weight and rapid assembly. However, among other things, short construction times have meant that concrete mixes with low w/c ratio and high proportion of cement have been requested by Strängbetongs customers in order to reduce the risk of moisture problems, when a rapid drying out pursued. With an increasingly stringent and ambitious environmental goal, a need to reduce the proportion of cement has arisen. With a reduced amount of cement, the w/c ratio of the concrete increases, which leads to a more environmentally friendly production, while at the same time an economic gain is obtained. The purpose of the study is therefore to investigate whether different concrete mixes with a higher w/c ratio can replace the current concrete mix and at the same time meet existing drying requirements. This would mean benefits for both the producers and orderers. The concrete that has been investigated in the investigation is of a soil-moist nature and is only intended for hole-deck production. The drying process that is studied corresponds to the dehydration from production to assembly. Four different concrete mixes divided into twelve cubes will be investigated in three different climates and only dehydration differences between the cubes will be compared. The survey is based on measurement data that are based on measurements performed by an authorized moisture consultant at Rådet för byggkompetens, RBK. The concrete recipes in the investigation have been developed by Cementa. Literature studies are also used to substantiate claims and supporting documents that appear in the report. The results from the study show that the cubes stored in the indoor climate and in the climate room have a linear dehydration development, unlike the cubes located in the outdoor climate that has a nonlinear dehydration development. In the indoor climate and in the climate room, the cubes with higher w/c ratio have dried out more than the concrete mixtures with lower w/c ratio (0,40 and 0,45), however, the difference in dehydration is minimal in the cubes that have been stored outdoors. The established conclusion in the study is that more in-depth and longer measurement studies are needed to ensure how concrete dehydration changes at a later stage of the drying process.

Page generated in 0.0374 seconds