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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.
321

Separation of rosin and fatty acids from tall oil by selective chlorination

Crockin, Jerome Monroe January 1940 (has links)
Tall oil is a mixture of rosin acids, fatty acids, and non-acids resulting from acidification of the soaps separating out from the kraft pulp process evaporator liquor. The present uses of tall oil center chiefly around its fatty acid content, but are limited for some purposes because of the rosin content. Separation of these constituents makes each available as such. The rosin, as crystalline abietic acid, has specific possibilities as a raw material. Rosin and fatty acids are separated chiefly by distillation, although chemical means and extraction have been proposed to overcome such objections as corrosion and losses as pitch, incurred in distillation. Chlorination is used as a step in the purification of tall oil, or to produce a sticky chlorinated oil, but no separation based on the use of chlorine appears to have been proposed. It was proposed in this investigation to chlorinate the fatty acid double bonds in hopes that the properties of this product would be such as to permit of a separation. The effects of solvent, light, heat, and catalysts were studied to determine the optimum conditions for such a reaction, and the effect of chlorination upon the rosin and fatty acids, respectively, under specific conditions was determined, It was found that the use of CCl₄ solvent and ultraviolet light accelerate chlorine consumption and promote the addition of chlorine, but do not entirely stifle the substitution reaction. Rosin and fatty acid double bonds are attacked to about an equal extent under these conditions. The chlorinated oil is entirely soluble in most common solvents at room temperature. Petroleum ether insolubles increase slightly over the amount obtained from untreated oil. It is recommended that the range of chlorination conditions be extended to a more complete study of possible results, and that other chemical attacks be investigated. / Master of Science
322

Productivity and quality of tall fescue and switchgrass under two harvest managements and different harvest intensities

Ball, Dale Warren 03 March 2009 (has links)
Tall fescue (Festuca arundinacea Schreb.) often becomes dormant in the hot summer months. Switchgrass (Panicum virgatum L.) has potential to supplement the limited carrying capacity of tall fescue in mid-summer. The objective of this study was to determine the seasonal dry matter distribution and quality of tall fescue and switchgrass as influenced by different harvest managements. Switchgrass and tall fescue were studied on a fine-loamy, mixed, mesic Ultic Hapludalf of the Duffield soil series at Blacksburg, VA during 1987 and 1988. Normal harvest management included harvests taken from the first growth in spring until mid to late August. Delayed management included harvests taken from regrowth after a hay crop in mid-May for tall fescue and early June for switchgrass until mid to late August. Three and four harvest intensities were imposed on tall fescue and switchgrass, respectively. Plots were harvested in 1989 to determine the accumulative influence of treatments. Yield, crude protein, neutral detergent fiber, and invitro dry matter digestibility were measured for each harvest of both species. Digestible yield and protein were calculated for each harvest. Clipping either switchgrass or tall fescue at any harvest intensity reduced potential yield compared to forage not clipped. Accumulated forage resulted in high yields but unsatisfactory quality. Delayed harvest management resulted in higher total yield than normal harvest management because of high hay yields. This study indicated that considerable overlap of forage production of tall fescue and switch grass occurred in late spring but abundant high quality switchgrass was available in midsummer when available tall fescue was low. Switchgrass warrants consideration in southwest Virginia as a solution to the problem of limited cool-season forage in midsummer. / Master of Science
323

Assessing the Effect of Nitrogen Sources, Rates and Time of applications on Yield and Quality of Stockpiled Fescue and Tall Fescue Pastures

Yarber, Elizabeth Lee 15 July 2009 (has links)
In Virginia, tall fescue [(Schedonorus phoenix (Scop.) Holub,) formally known as Festuca arundinacea L.] can be found on more than 4 million ac of hay and pastureland. Two separate experiments were conducted at three different geographical locations over two growing seasons. The objective of Experiment 1 was to evaluate the influence of N sources and rates on yield and nutritive value of stockpiled tall fescue. Experiment 2 examined the effect of split spring and fall N applications at various rates on yield and nutritive value of tall fescue pastures. The first experiment was conducted at three locations (Blacksburg, Blackstone, and Steeles Tavern, VA) while the second experiment was conducted only at the Blacksburg and Steeles Tavern locations. In Experiment 1, the N sources included ammonium nitrate, ammonium sulfate, urea, urea + Agrotain®, Environmentally Smart N® (ESN), Nutrisphere (NSN), Nitamin® (Blackstone only), pelleted biosolids (Blackstone only), and broiler litter (Steeles Tavern only) applied at 0, 28, 56, 84, and 112 kg plant available N (PAN) ha-1. Plots were harvested in mid-December (Blacksburg and Steeles Tavern) and late January (Blackstone). The yield of the stockpiled tall fescue in 2006 ranged from 1,300 to 2,900, 1,700 to 3,000, and 2,600 to 3,300 kg DM ha-1 for the Blacksburg, Steeles Tavern and Blackstone locations, respectively. In 2007, however, the yield response to N rate and sources was significantly less than that of 2006 due to low rainfall. At the Blacksburg location, ammonium sulfate and ESN resulted in higher CP concentrations, ranging from 11-14% and 12-20% for 2006 and 2007 growing seasons, respectively. Similar variation (12-20%) was observed for the Steeles Tavern location in 2006. In general, the ADF and NDF content decreased as N rate increased from 0-112 kg ha1. Although the source and rate that resulted in high yield and nutritive value varied across location and years, N rates and sources improved the quality and yield of stockpiled fescue. Experiment 2 utilized urea which was applied in the fall at the rates of 0, 45, 90 or 135 kg N ha-1. followed by spring application of 0, 45, 90 or 135 kg N ha-1. A total of 16 treatment combinations per replication were used. Yields ranged from 1,900 to 3,600 kg DM ha-1 and 700 to 2,500 kg DM ha-1 in 2007 and 2008, respectively. At the Steeles Tavern location, yields ranged from 3,100 to 5,700 kg DM ha-1 and 2,500 to 5,100 kg DM ha-1, in 2007 and 2008, respectively. In both years CP increased with increasing N fertilization. On a dry matter basis, CP values ranged from 14 to 23% for both years. Treatments did not affect on NDF and ADF values. Split fall/spring N applications did not maximize yield of cool-season grass pastures in these experiments. / Master of Science
324

Laboratory test methods for the determination of the corrosion of metals in tallol at high temperatures

Markwood, Ira M. January 1942 (has links)
An investigation of the factors affecting the corrosion rates of metals in hot tallol was undertaken to answer questions raised by previous investigators. The items studied were as follows: 1. The change in composition of tallol on heating was determined by heating tallol at 300° C. for 48 hours, and analyzing samples withdrawn at frequent time intervals. 2. The effect of change in composition of tallol was studied by determining the corrosion rate of steel in fresh tallol at 300° C., and in tallol which had been subjected to heating for 48 hours at 300° C. 3. The effect on the corrosive properties of the tallol of removing volatile components, of which a large proportion was water, was studied by determining the corrosion rates of aluminum, steel, nickel and copper at 300° C. when condensable volatile matter was returned to the system, and when it was allowed to escape. 4. The effect of water in the tallol was studied by determining the corrosion rate of steel in tallol at 300° C. for 48 hours, during which time water and other volatile products were allowed to escape, then adding water and repeating the corrosion test for five hours. From the results obtained in this investigation, it was decided that the most satisfactory correlation with plant data would probably be obtained by operating the test with fresh tallol at 300° C and replacing it every eighteen hours, allowing volatile components to escape from the vessel during the test periods. Separate tests must be made on those metals affected by ions of other metals, as shown by Keister(15) and Maguire(19). / M.S.
325

Horizontal natural frequency in a 10 story building : A comparison between CLT and concrete using estimate calculations / Horisontell egenfrekvens i ett 10-våningshus : En jämförelse mellan KL-trä och betong med hjälp av överslagsberäkningar

Eriksson, Jennifer January 2018 (has links)
Tall slender buildings are easily set in motion by wind and earthquakes but by estimating the buildings horizontal natural frequencies in the design phase, these motions can be kept within acceptable boundaries. There are many parameters that decides the natural frequency of a building and it can therefore be difficult to calculate it. There are a few ways though to estimate horizontal natural frequencies of tall buildings and two methods have been tested in this report. Both methods give the frequency of a clamped-free cantilever but one of them requires a single degree of freedom system whilst the other handles a multi degree of freedom system. The methods are called SDOF method and MDOF method in this report. A fictional building was created for this project to be the reference object in the comparison between the two methods SDOF and MDOF. The walls and floors of the building was designed with the support of both an acoustic engineer and a structural engineer to create a realistic building. A building’s natural frequency is dependent of the self-weight, stiffness and height of the building and it was therefore important to design these components with care. The fictional building is called House 1 and is a 10 story, almost square building about 20 m wide and broad and 30 m high. This report does not only compare the natural frequencies obtained from the two different calculation methods, but it also shows the difference in frequency in timber and concrete structures. Shear walls constitutes the horizontal stabilization system of the fictional building and both a CLT core and a concrete core is designed and compared. It is only the walls that comes in two different versions, the floorings consist of CLT boards for both structures tested. The horizontal natural frequencies of House 1 were about 2 Hz and 3 Hz for the CLT version and concrete version respectively. It was expected to get frequencies within that range considering the height of House 1. The CLT core having a lower frequency than the concrete core was also expected since concrete is a stiffer material than wood. To be able to make a fair comparison between the SDOF method and the MDOF method, House 1 was designed with the same dimensions and stiffness on all floors because the SDOF method requires that. The results from the two methods are almost identical with only 0.3 Hz and 0.4 Hz difference for the concrete and CLT respectively. For a shear wall structure with a consistent stiffness, weight and dimension, any of the two methods can be used to estimate the horizontal natural frequency. However, it is not realistic for a building of 30 m or higher, to have the same dimensions on the load bearing structure on all floors which makes the MDOF method more accurate in more cases than the SDOF method. / Höga slanka byggnader kan sättas i svajande rörelser av vind och jordbävningar, men genom att uppskatta byggnadernas horisontella egenfrekvenser i den tidiga konstruktionsfasen kan dessa rörelser hållas inom acceptabla gränser. Det är många parametrar som bestämmer byggnadens egenfrekvens och det kan därför vara svårt att beräkna den. Det finns dock några sätt att uppskatta horisontella egenfrekvenser hos höga byggnader och två metoder har testats i denna rapport. Båda metoderna ger frekvensen av en fast inspänd konsolbalk men en av dem kräver ett enfrihetsgradsystem medan den andra kan hantera ett system med flera frihetsgrader. Metoderna kallas SDOF-metoden och MDOF-metoden i denna rapport. En fiktiv byggnad skapades i detta projekt för att vara referensobjekt i jämförelsen mellan de två metoderna SDOF och MDOF. Byggnadens väggar och golv konstruerades med stöd av både en akustiker och en konstruktör för att skapa en realistisk byggnad. Byggnadens egenfrekvens är beroende av byggnadens egenvikt, styvhet och höjd och det var därför viktigt att utforma dessa komponenter med omsorg. Den fiktiva byggnaden kallas House 1 och är en 10 vånings-, nästan fyrkantig byggnad ca 20 m lång och bred och 30 m hög. Denna rapport jämför inte bara egenfrekvenserna erhållna från de två olika beräkningsmetoderna, den visar även skillnaden i frekvens i trä- och betongkonstruktioner. Skjuvväggar utgör det horisontella stabiliseringssystemet för den fiktiva byggnaden och både en KL-kärna och en betongkärna har utformats och jämförts. Det är bara väggarna som skiljer de två olika versionerna åt, bjälklagen består av KL-skivor i båda fallen. De horisontella egenfrekvenserna hos House 1 var ca 2 Hz och 3 Hz för KL-version respektive betongversion. Frekvenser inom detta område var väntade med tanke på höjden av House 1. Att KL-kärnan skulle ha en lägre frekvens än betongkärnan förväntades också eftersom betong är ett styvare material än trä. För att kunna göra en rättvis jämförelse mellan SDOF-metoden och MDOF-metoden, var House 1 utformad med samma dimension och styvhet på alla våningsplan eftersom SDOF-metoden kräver det. Resultaten från de två metoderna är nästan identiska med endast 0,3 Hz och 0,4 Hz skillnad för betong respektive KL. För en skjuvväggskonstruktion med en kontinuerlig styvhet, vikt och dimension kan båda de två metoderna användas för att uppskatta den horisontella egenfrekvensen. Det är dock inte realistiskt för en byggnad på 30 m eller högre att ha samma dimensioner på den lastbärande konstruktionen på alla våningar vilket gör MDOF-metoden mer korrekt i fler fall än SDOF-metoden.
326

Symbols in Clay : A Study of Early Bronze IV Potter's Marks from the Amman-Zarqa Region in Transjordan

Wulff Krabbenhöft, Rikke January 2010 (has links)
The present work examines the taxonomy and function of potters’ marks applied to pottery in the Amman-Zarqa region during the last phase of the Early Bronze Age, the so-called EB IV ca. 2350/2300–2000 BC. The study is anchored in a small data set gathered from 12 archaeological sites, in which 24 different mark types have been identified. These mark types - together with their associated vessel classes, circumstances of deposition, and geographical distribution - comprise the background against which previous suggestions regarding potters’ marks are evaluated. Evidence from ethno-archaeological sources concerning traditional potters’ rationales for marking vessels today is also included as part of the interpretive framework. The mode and scale of production is discussed on the basis of the ceramic evidence, the size and character of settlements located within the region, and the socio-economic setting of the EB IV period in general.
327

The impact of zoning on housing prices in Hong Kong

Han, Qinchun., 韓秦春. January 1997 (has links)
published_or_final_version / Real Estate and Construction / Doctoral / Doctor of Philosophy
328

Tillväxt och blandskogseffekt i återplanterade objekt : Tecken på spatial inverkan på blandskogseffekt i unga trädbestånd / Growth and mixed-specie effect in replanted areas : Signs of spatial effect on mixed-stands in young populations of trees

Sundström, Alice Ulrika January 2017 (has links)
2001 skedde ett kraftigt utbrott av Gremeniella abietina (Lagerb.) M. Morelet i området Bergvik, Dalarna. Skogsägarna var tvungna att avverka kraftigt i deras tallbestånd som respons på detta. I de objekt som återplanterades planterades det nya artsammansättningar än vad som planterats tidigare, gran och blandbestånd av gran och tall. I denna studie jämfördes och inventerades medelhöjderna på de återplanterade objektens träd för att skatta arternas framgång i de olika ståndorterna. Gran verkade vara mest lämpat eftersom den växte signifikant bättre än vad tillväxtekvationerna hade förutspått. Det påträffades även en positiv blandskogseffekt på trädens medelhöjd i provytorna. Provytor med högre antal arter, hade gran och tall med högre medelhöjd än artfattigare provytor. Provytor med tre arter, björk gran och tall hade högre tillväxt än provytor med endast tall och gran. Graden av inblandning i hela objektet hade inte någon signifikant effekt på medelhöjden. Detta tyder på att den spatiella artsammansättningen har större betydelse för de positiva effekterna av blandskog än artsammansättningen inom ståndorten i sin helhet. Detta antas vara på grund av nisch-komplementering och facilitering, möjligtvis via mykorrhiza interaktion. En annan möjlig förklaring är den minskade intra-specifika konkurrensen när individer av samma art är planterade med större avstånd sinsemellan. Troligtvis beror det på en nischuppdelning som tillåter de olika trädarterna att utnyttja markens tillgångar effektivare. Detta indikerar att småskalig artsammansättning är av vikt för tillväxten hos gran och tall. / In 2001 there was a serious outbreak of Gremmeniella abietina (Lagerb.) M. Morelet in the municipality of Bergvik in Dalarna, Sweden. The forest owners were forced to effectively cut their Pine stands in an attempt to halt the onslaught of the fungus. In the areas where new trees were planted after the cuttings, different compositions of species were implemented. Instead of only Pine (Pinus sylvestris), most of the new plantations consisted of spruce (Picea abies) or mixtures of the two species. In this study the average height of these replanted trees was measured to assess the success that the different species had in the different replanted areas. Spruce seemed to be the species that was best adapted to the local area because it grew significantly higher then what had been predicted. A positive effect of mixed-stands was also observed. The sample areas with three species, pine, spruce and birch (Betula pendula) had a higher average height then the sample areas that contained less species. The degree of mixture in the plantation as a whole had no significant effect on tree height. This implies that the spatial composition of species is of bigger importance then the quota of different species in the whole plantation. This could be explained by niche-complementation and by facilitation, probably via interactions between mykorrhiza. Intra-specific competition is another possible explanation for the greater height in sample areas with more species.  Most likely because a decrease in intra-specific competition allows a division of niches and therefore permits the resources in the soil to be utilized more efficiently. The implication of this being that small-scale specie composition is of importance.
329

Análise não-linear das estruturas de contraventamento de edifícios em concreto armado / Non-linear analysis of reinforced concrete buildings bracing structures

Pinto, Rivelli da Silva 16 April 2002 (has links)
Neste trabalho são discutidos os aspectos inerentes à análise não-linear física (NLF) e geométrica (NLG) das estruturas de contraventamento em concreto armado. O estudo proposto tem como base a análise estrutural de pórticos planos de concreto armado, desenvolvendo-se uma ferramenta rigorosa capaz de analisar essas estruturas de forma elaborada e consistente. Com essa ferramenta serão avaliadas as reduções de inércia que ocorrem em pórticos planos de concreto armado, submetidos a diferentes condições de carregamento e a diferentes taxas de armadura, contribuindo para o estabelecimento de estimativas confiáveis dos efeitos da NLF nessas estruturas. Estes resultados, combinados com os parâmetros de estabilidade &#945 e &#947z - capazes de estimar com bastante precisão os efeitos devidos à NLG - permitem o estabelecimento de métodos simplificados para a análise não-linear física e geométrica das estruturas de contraventamento de edifícios em concreto armado, de grande utilidade para os projetistas. / In this work the inherent aspects to the physical nonlinear analysis (PNL) and geometric nonlinear analysis (GNL) of reinforced concrete bracing structures are argued. The considered study is based in the structural analysis of in reinforced concrete plane frames, developing a rigorous tool capable to analyze these structures of elaborated and consistent form. Using this tool, inertia reductions that occurs in reinforced concrete plane frames, submitted the different loading conditions and the different levels of reinforcement will be evaluated, contributing for the establishment of trustworthy estimates to the effects of PNL in these structures. These results, matched with the stability parameters &#945 e &#947z - capable to estimate with sufficient accuracy the effects of GNL - allow the establishment of simplified methods for physical and geometrical non-linear analysis of reinforced concrete buildings bracing structures, of great utility for the designers.
330

Tillväxt på gran och tall efter dikesrensning i Jönköpings län / Growth of Norway spruce and Scots pine trees after ditch cleansing in Jönköping county

Johansson, Ingvor Laila January 2019 (has links)
Detta arbete är utfört som ett examensarbete åt Skogsstyrelsen som en uppföljning på samråd för dikesrensning utförda på distrikt Jönköping från hösten 2004 till 2009. Följande saker har studerats: Hur uppfattades samrådet? Hur utfördes rensningen? Är markägaren nöjd med resultatet? Har skogen svarat på rensningen genom ökad tillväxt och i så fall hur snart och hur mycket? Har markfloran förändrats? Syns några andra positiva eller negativa effekter efter rensningen?Arbetet har utförts i två steg dels i form av en markägarintervju på 7 olika fastigheter och sedan som fältinventering med datainsamling. Utifrån det första besöket valdes 10 bestånd ut för inventering på 4 fastigheter, 2 tall och 8 granbestånd med totalt 136 träd, 27 tallar och 109 granar. 122 träd borrades för årsringsanalys 27 tallar och 95 granar. Borrkärnorna analyserades i WinDENDROs tillväxtprogram, sammanfattningar gjordes i Microsoft Excel och variansanalys i SAS statistikprogram.Träd närmast diket visade i genomsnitt en högre radiell tillväxt efter dikesrensningen än träd som stod längre ifrån diket. Alla markägare kunde se en förbättrad tillväxt efter rensningen och 4 av 7 kunde se en klar förbättring. 6 av 10 bestånd hade 4-7 år efter rensning fortfarande 20-50 % björn-och vit mossor i bottenskiktet. Två hade stora problem med kraftig grästillväxt men ingen hade sett några andra negativa effekter på markfloran. / The work was carried out for the Swedish Forest Agency as a follow-up on consultation for cleansing ditches in the district of Jönköping from autumn 2004 to 2009.The following things were studied: How was the consultation and results of cleansing perceived? How was the cleansing carried out? Has the forest responded to the cleansing through increased growth and if so how soon and how much? Has the ground flora changed? Were there any other positive or negative effects after the cleaning? Interviews were carried out with the property owners and the forest inventoried in the field.The work has been carried out in two stages, partly in the form of a market interview of 7 different properties and then as a field inviting with data collection. Based on the first visit, 10 stocks were selected for inventory of 4 properties, 2 pine (Pinus sylvestris) and 8 spruces (Picea abies) stands with a total of 136 trees, 27 pines and 109 spruces were measured. 122 trees were drilled for growth ring analysis 27 pines and 95 spruces. The drill cores were analyzed in WinDENDRO's growth ring program, summaries were made in Microsoft Excel and variance analysis was performed in SAS's statistical program.Trees that were closest to the ditch showed on average a higher radial growth after cleaning than before compared to trees that were farther from the ditch.6 out of 10 stands had after 4-7 years of cleansing still 20-50% bear- and white moss in the bottom layer. All landowners could see an improved profitability after cleaning and four out of seven could noticeably see better growth. Two had problems with troubling grass growth, but no one had seen any other positive or negative effects on the ground flora.

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