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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.
251

AUTODESBASTE E DIAGRAMA DE MANEJO DA DENSIDADE EM POVOAMENTOS DE Pinus taeda L. / SELF-THINNING AND DENSITY MANAGEMENT DIAGRAM IN Pinus taeda L. STANDS

Schneider, Paulo Sérgio Pigatto 12 August 2008 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / This thesis aims at studying the efficiency of models which express the size-density relationship in even-aged stands of Pinus taeda L., handled in complete and full stock densities. For that, Reineke, Yoda, Zeide and Tang models were tested using data obtained from 50 permanent sample plots placed in stands implanted in spacing of 1.5x1.0 m, 2.5x1.0 m, 1.5x2.0 m, 2.0x2.0 m, 1.5x3.0 m, 2.5x2.0 m, 2.0x3.0 m, 2.5x3.0 m, measured every year until the age of 18 and maintained in full stocks. Results indicated that all of the size-density relationship models presented good statistical precision. However, the no-linear model of Tang was more efficient than the others, presenting excellent coefficient of determination (0.99), low standard error of estimate (0.0948), low coefficient of variation (1.17%), low bias (0.0086) and high efficiency (0,8976), in the estimate of the values of density of trees per hectare for average diameter, and the smallest considered value of the scores of the statistical criteria, equal to 6 points, with good distribution of residues of the number of trees per hectare. The self-tinning occurs in a dimension of average diameter directly proportional to the density of trees per hectare of planting. As bigger is the initial spacing, bigger is the average diameter in the moment of the beginning in the stand the self-thinning. The slope of the size-density and diameter equation varied per planting spacing, not allowing proving the universality of the self-tinning law, with value of this slope is equal -3/2. With help of the size-density model, 5 Indexes of Density of the Stand (IDS) were generated, with variation from the maximum 1400 to the minimum 600, with interval of class of IDS equal to 200, having as reference the standard diameter of 25 cm. The stand s Density Management Diagram (DMD), elaborated for the dendrometric variables average diameter, basal area and volume for hectare by IDS presented good efficiency with low mistake in the estimate of the values of these variables. Real volume and estimate volume per hectare in DMD presented an absolute difference of just -7.39 m3 ha-1 and a relative difference of -1.79 %, showing a great precision of the DMD model. The estimates volume of DMD per hectare, in relation to the real values, presented a value of efficiency equal to 0.99, what indicates a high precision, and a χ 2 value equal to 0.00034, not significant to 0.01% of probability, demonstrating that the real and the estimate values don't differ statistical amongst themselves. / A presente dissertação foi desenvolvida com o objetivo de estudar a eficiência dos modelos que expressam a relação de densidade e diâmetro em povoamentos equiâneos de Pinus taeda L., manejados em densidade completa e altamente estocados. Para isto, foram testados os modelos de Reineke, Yoda, Zeide e Tang, através de dados originados de 50 parcelas permanentes, medidas anualmente até os 18 anos, alocados em povoamentos implantadas em espaçamentos de 1,5x1,0 m, 2,5x1,0 m, 1,5x2,0 m, 2,0x2,0 m, 1,5x3,0 m, 2,5x2,0 m, 2,0x3,0 m, 2,5x3,0 m, e mantidas em densidade completa. Os resultados indicaram que todos os modelos de densidade e diâmetro apresentaram boa precisão estatística, porém o modelo não linear de Tang foi mais eficiente que os demais, tendo apresentado ótimo coeficiente de determinação, igual a 0,99, baixo erro padrão da estimativa igual a 0,0948, baixo coeficiente de variação, igual a 1,17 %, mínima tendência, com valor igual a 0,0086, e elevada eficiência, com valor igual a 0,8976. Na estimativa dos valores de densidade de árvores por hectare por diâmetro médio, e a menor soma de escores dos critérios estatísticos, foi igual a 6 pontos, com boa distribuição dos resíduos do número de árvores por hectare. O autodesbaste ocorre numa dimensão de diâmetro médio diretamente proporcional a densidade de árvores por hectare de plantio. Quanto maior o espaçamento inicial maior é o diâmetro médio no momento do início do autodesbaste da população. O coeficiente angular da equação de densidade e diâmetro variou por espaçamento de plantio, não permitindo comprovar a universalidade da lei do autodesbaste, cujo valor do coeficiente angular é estipulado em -3/2. Com o modelo de densidade e diâmetro foram gerados 5 Índices de Densidade do Povoamento - IDP, que variaram de um valor máximo de 1400 até o mínimo de 600, com intervalo de classe de IDP de 200, tendo com referência o diâmetro padrão de 25 cm. Os Diagramas de Manejo da Densidade - DMD da população, elaborados para as variáveis dendrométricas: diâmetro médio, área basal e volume por hectare, por IDP, apresentaram uma boa eficiência com baixo erro na estimativa dos valores destas variáveis. Os volumes reais por hectare e os estimados no DMD apresentaram uma diferença absoluta de apenas -7,39 m3ha-1 e relativa de -1,79 %, demonstrando elevada precisão do modelo de DMD. As estimativas volumétricas por hectare do DMD em relação aos valores reais, apresentaram valor de eficiência igual a 0,99, o que indica uma alta precisão, e um valor de χ 2 igual a 0,00034, não significativo a 0,01 % de probabilidade, demonstrando que os valores reais e os estimados não diferem estatisticamente entre si.
252

DIRETRIZES PARA DESBASTE DE Pinus taeda L. EM FUNÇÃO DA ALTURA DOMINANTE. / GUIDELINES FOR THINNING OF Pinus taeda L. IN FUNCTION OF THE DOMINANT HEIGHT.

Padoin, Veridiana 26 October 2007 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / The study uses dominant trees to describe the tinning, because they are those that possess larger energy inside of a forest settlement. The main objective of the work is to model and to select models to describe the relationship among the potential number of trees for hectare in function of the dominant height, elaborating a system of curves guides how to aid in the determination of the tinning. The municipal and districts where are located the forests are: Cambará do Sul (RS), São Francisco de Paula (RS), Distrito de Tainhas (RS), Distrito dos Kroeff (RS), Bocaína do Sul (SC), Correia Pinto (SC), Curitibanos (SC), Lages (SC), Otacílio Costa (SC), Ponte Alta do Norte (SC) and Santa Cecília (SC). The units temporary sample random were installed using the Method of modified Prodan, or be, 12 trees were measured by unit sample being the center of the unit the dominant tree of the sample. The units were installed at forests in competition from 5 to 40 meters of dominant height. In those units they were measured: the distance of the 11 trees to the central dominant tree; diameter and the height of the 12 trees; the crown diameter, the length of total crown and the exposed crown length to the light of the 2 dominant trees of the sample. The calculated variables were the number of potential trees for hectare, the Index of relative spacing, the crown percentage and the index of competition of Glover and Hool. The modelling made calculations by the statistical package (Statistical Analysis System) version 8.0 and the adjustment of the equations and covariance analysis for the procedure GLM ( General Lineal Models). The equations that best describes the potential number of trees for hectare were Ln(Np) = 10,31285 - 1,28518*(ln(hdom) with a R²aj 0,68 and CV of 4,76% for the class of S'% of 14-20% and Ln(Np) = 10,36304 - 1,16938*(ln(hdom) with a R²aj 0,34 and CV of 5,24% for the class of S'% of 14-20%. The use of the dominant height as independent variable is efficient to describe the guidelines for tinning in the settlements of Pinus taeda. The model of negative exponential regression adjusts with good precision and low mistake the relationship among the potential number of trees for hectare and the dominant height. The variation of the values of potential frequency for hectare for a given dominant height is strongly reduced with the bedding of the data in classes of Index of relative spacing of Hart Becking larger than 14% and smaller than 14% allowing to elaborate frequency curves for hectare for those two situations. The development of the frequency curves stratified by Index of relative spacing influences in the dimension of the diameter of the trees for a same dominant height. / O estudo utiliza árvores dominantes para descrever o desbaste, pois são aquelas que possuem maior vigor dentro de um povoamento florestal. O principal objetivo do trabalho é modelar e selecionar modelos para descrever a relação entre o número potencial de árvores por hectare em função da altura dominante, elaborando um sistema de curvas guias como auxiliar na determinação do desbaste. Os municípios e distritos onde estão localizadas as florestas são: Cambará do Sul (RS), São Francisco de Paula (RS), Distrito de Tainhas (RS), Distrito dos Kroeff (RS), Bocaína do Sul (SC), Correia Pinto (SC), Curitibanos (SC), Lages (SC), Otacílio Costa (SC), Ponte Alta do Norte (SC) e Santa Cecília (SC). As unidades amostrais temporárias foram instaladas aleatoriamente utilizando o Método de Prodan modificado, ou seja, foram medidas 12 árvores por unidade amostral sendo o centro da unidade a árvore dominante da amostra. As unidades foram instaladas em florestas em competição de 5 a 40 metros de altura dominante. Nessas unidades foram medidas: a distância das 11 árvores até a árvore dominante central; o DAP e a altura das 12 árvores; o diâmetro de copa, o comprimento de copa total e o comprimento de copa exposto à luz das 2 árvores dominantes da amostra. As variáveis calculadas foram o número de árvores potenciais por hectare, o Índice de espaçamento relativo, a percentagem de copa e o índice de concorrência de Glover e Hool. A modelagem foi calculada pelo pacote estatístico SAS (Statistical Analysis System) versão 8.0 e o ajuste das equações e análise de covariância pelo procedimento GLM (General Linear Models). As equações que melhor descrevem o número potencial de árvores por hectare foram Ln(Np) = 10,31285 1,28518*(ln(hdom) com um R²aj de 0,68 e CV de 4,76% para a classe de S % de 14 20% e Ln(Np) = 10,36304 1,16938*(ln(hdom) com um R²aj de 0,34 e CV de 5,24% para a classe de S % de 14 20%. O uso da altura dominante como variável independente é eficiente para descrever as diretrizes para desbaste nos povoamentos de Pinus taeda. O modelo de regressão exponencial negativo ajusta com boa precisão e baixo erro a relação entre o número potencial de árvores por hectare e a altura dominante. A variação dos valores de freqüência potencial por hectare para uma dada altura dominante é fortemente reduzida com a estratificação dos dados em classes de Índice de espaçamento relativo de Hart Becking maior do que 14% e menor do que 14% permitindo elaborar curvas de freqüência por hectare para essas duas situações. O desenvolvimento das curvas de freqüência estratificado por Índice de espaçamento relativo influi na dimensão do diâmetro das árvores para uma mesma altura dominante.
253

Návrh nástroje pro tváření kuželových prolisů v austenitickém nerezovém plechu / A design of the die for creation of conic press in the austhenitic inox

Šlosr, Michal January 2012 (has links)
The thesis deals with a design of the tool that creates the conic press in the austhenitic inox 17 240 (X5CrNi18-10). In the first part are described the possible production technologies with a focus of non rigid tool. For the realization is chosen the Guerin process. The rigid tool is replaced by non rigid tool (rubber / polyurethane). In a final part is performed an evaluation of the influence of non rigid tool, lubricants and venting.
254

A High-Performance Parallel Thinning Approach Using a Non-cubic Grid Structure

Brunner, David, Brunnett, Guido, Strand, Robin 14 September 2006 (has links)
In the past years the so-called body-centered cubic grid (bcc) has been examined and proved to be superior over Cartesian lattices for certain applications. Our work deals with parallel thinning on these bcc grids. We introduce conditions which are sufficient for retaining topology and suggest additional conditions to influence the shape of the resulting skeleton. We further developed an algorithm to extract curve skeletons out of 3d objects in parallel which we also present here. We show in our results that the developed thinning approach on bcc grids is extremely efficient.
255

En vänlig grönskas rika dräkt : En undersökning av tillgänglig rönn, asp, sälg och ek efter röjning / The rich costume of a friendly green : a study of available rowan/mountain ash, aspen, sallow and oak after pre-commercial thinning

Hjälte, Kenny, Larsson, Björn January 2020 (has links)
Röjningsinstruktioner och virkesinköpare anser att rönn, asp, sälg/salix och ek (RASE) ska sparas i ungskogsröjningar för att det ska finnas annat foder åt skogslevande vilt än produktionsskog. Dessutom är ett vanligt råd till skogsägare av virkesköparna att satsa på foderskapande åtgärder för att avleda hjortdjuren. Undersökningen av ungskogsröjning visar dock att teori och praktik inte går ihop, där få stammar av RASE sparas och det är troligare att björk sparas. Enstaka RASE kan sparas i lucka där de inte kan konkurrera med en huvudstam av det planterade trädslaget. En alternativ skogsskötsel, som Öster Malma-modellen, ser blandskog som en mer ekonomiskt stabilt skogsbestånd och det bidrar samtidigt med mer lövskog än traditionell skötsel som sköter bestånd utifrån monokulturer. Forskning har även visat att foderkonkurrens mellan hjortdjuren kan göra att älg betar mer tall än bärris. En kunskapsbaserad viltförvaltning som omfamnar fler arter än en skulle kunna vara en del av lösningen.
256

Laser Scanning Confocal Ophthalmoscopy and Polarimetry of Human Immunodeficiency Virus Patients Without Retinopathy, Under Antiretroviral Therapy

Besada, Eulogio, Shechtman, Diana, Black, Greg, Hardigan, Patrick C. 01 March 2007 (has links)
PURPOSE. Confocal laser scanning ophthalmoscopy (HRT; Heidelberg retinal tomograph II) and scanning laser polarimetry (GDx-variable corneal compensator [VCC]) were used to investigate whether early indicators of retinal nerve fiber layer (RNFL) thickness loss could be observed in patients infected with the human immunodeficiency virus (HIV) that had no associated retinopathy or optic neuropathy and were concomitantly receiving antiretroviral medications. METHODS. HRT and GDx-VCC parameters obtained from a group of 13 HIV-positive subjects (n = 26 eyes) on antiretroviral therapy examined with HRT, with a subgroup of six subjects (n = 12 eyes) examined with both HRT and GDx-VCC, were compared with those of a matched HIV-negative control cohort (13 subjects, n = 26 eyes) examined with HRT, with a subgroup of five subjects (n = 10 eyes) examined with both HRT and GDx-VCC. We employed generalized estimating equations for statistical analysis. RESULTS. Reduced mean values for the HRT height variation contour (p < 0.045) and HRT mean RNFL thickness (p < 0.023) were observed in HIV-positive subjects controlling for age, sex, and race. A significantly reduced mean value corresponding to the GDx-VCC superior maximum (p < 0.014) and inferior maximum (p < 0.016) were also observed for the HIV-positive cohort analyzed controlling for age, sex, and race. CONCLUSION. HRT and GDx-VCC indicators of RNFL thickness appear to be significantly reduced in HIV-positive subjects without retinopathy or optic nerve disease using antiretroviral medication, suggesting RNFL loss occurs in this population of HIV-positive patients. The lack of correlation between CD4 counts, viral load, number of antiretroviral medications used, or years from diagnosis of HIV and RNFL thinning, suggests that possibly other factors associated with HIV infection may contribute to the apparent RNFL thickness loss.
257

Behavior of Copper Contamination for Ultra-Thinning of 300 mm Silicon Wafer down to <5 μm

Mizushima, Yoriko, Kim, Youngsuk, Nakamura, Tomoji, Sugie, Ryuichi, Ohba, Takayuki 22 July 2016 (has links)
Bumpless interconnects and ultra-thinning of 300 mm wafers for three-dimensional (3D) stacking technology has been studied [1, 2]. In our previous studies, wafer thinning effect using device wafers less than 10 μm was investigated [3, 4]. There was no change for the retention time before and after thinning even at 4 μm in thickness of DRAM wafer [5]. In this study, the behavior of Cu contamination on an ultra-thin Si stacked structure was investigated. Thinned Si wafers were intentionally contaminated with Cu on the backside and 250 °C of heating was carried out during the adhesive bonding and de-bonding processing. An approximately 200 nm thick damaged layer was formed at the backside of the Si wafer after thinning process and Cu particle precipitates ranged at 20 nm were observed by cross-sectional transmission electron microscopy (X-TEM). With secondary ion mass spectrometry (SIMS) and EDX analyses, Cu diffusion was not detected in the Si substrate, suggesting that the damaged layer prevents Cu diffusion from the backside.
258

Betongoptimering av bärande innerskivor isandwichelement : Vad innebär minskad betongvolym för de direkta utsläppenav växthusgaser?

Olander, Maja January 2022 (has links)
Under 2019 stod Bygg- och fastighetssektorn för 21 procent avSveriges totala utsläpp av växthusgaser. Sett till ett intervall från1993 fram till 2019 har det totala utsläppet av växthusgaserminskat. Det beror på att utsläppen vid uppvärmning reducerats.Studeras enbart utsläppen vid renovering och byggnation harutsläppen ökat nämnvärt under samma intervall. För att brytadenna trend av ökade växthusgaser vid renovering och byggnationkrävs det att Bygg- och fastighetssektorn reagerar och utvecklaralternativa lösningar. Ett alternativ till att minska utsläpp är attdimensionera slankare konstruktioner som kräver mindre material.Betongkonstruktioner utgör en betydande andel av utsläpp avväxthusgaser. Betongindustrins dåliga utgångspunkt ger ettslagkraftigt initialläge i att klimatförbättra kommandekonstruktioner. Denna studie har utförts åt Attacus Stomsystemmed syftet att undersöka hur ett pelar-balksystem medförtunningar för bärande innerskivor i sandwichelement påverkarde direkta utsläppen av växthusgaser. Studien har studerat ettfiktivt väggelement som utsätts för 5, 10, 15 och 20 våningars last.Efter dimensionering av väggarnas pelar-balksystem undersöktesfem leverantörers EPD:er i fas A1-A3 för massivväggar. GWPvärdetsom användes i studien är ett medelvärde från de olikaproducenterna. I resultatet presenteras utsläppet i kg CO2e från entraditionell innerskivas betong med tillhörande armering ochisolering kontra pelar-balksystem med ökad armering ochisolering. Resultatet påvisar att ett pelar-balksystem till och med 10våningars last ger en reduktion av växthusgaser. Därefter ökarklimatpåverkan jämfört mot traditionell innerskiva. För 5 våningarär reduktionen 8 procent och knappt 2 procent för 10 våningarslast. Slutsatsen är att pelar-balksystem är fördelaktigt att applicera iverkligheten om byggnaden inte överstiger 10 våningar. / In 2019, construction and the real estate sector accounted forapproximately 21 percent of Sweden´s total domestic greenhousegas emissions. Seen in an interval from 1993 until 2019, the totalemissions of greenhouse gases have decreased. This is because theemissions from heating have been reduced. If only the emissionsfrom renovation and construction are studied, the emissions haveincreased significantly during the same period. To break this trendof increased greenhouse gases during renovation and construction,it´s necessary for the construction and real estate sector to react anddevelop alternative solutions. An alternative to reducing emissionsis to dimension leaner constructions that require less material.Concrete structures constitutes a significant proportion ofgreenhouse gas emissions. The concrete industry´s poor startingpoint provides a strong initial position in improving futureconstructions. This study was carried out on behalf of AttacusStomsystem with the purpose of investigating how a column-beamsystem with thinners for load-bearing inner boards insandwichelements affect the direct emissions of greenhouse gases.The study investigated a fictitious sandwichelement. Thesandwichelement is exposed to loads from 5, 10, 15 and 20 floors.After dimension the column-beam system, the EPD of fivesuppliers in phase A1-A3 for solid walls was examined. The GWPvalue used in the study is an average value from the differentproducers. The result presents the emission in kg CO2e from theconcrete of a traditional inner boards with associatedreinforcement an insulation versus the column-beam system. Theresults show that at column-beam system up to and including aload of 10 storeys provides a reduction of greenhouse gases.Thereafter, the climate impact increases in line with the traditionalinner board. For 5 storeys, the reduction is 8 percent and just under2 percent for 10 storey loads. The conclusion is that column-beamsystem are advantageous to apply in reality if the building doesn´texceed 10 floors. / <p>2022-07-01</p>
259

Digitalt optimeringsverktyg i den operativa verksamheten : En analys av ett beslutsstöd för att minimera uppkomsten av körskador / Digital decision support tool in operational planning : Analysis on how to minimize the risk of ruttingdamages by using a decision support tool.

Warg, Maria January 2023 (has links)
Skogen brukas allt intensivare och större och tyngre maskiner vid skogliga operationer innebär förhöjd risk för körskador. En körskada kan innebära stora ekonomiska förluster likväl som allvarlig påverkan på miljö och sociala värden. Den skogliga branschen jobbar kontinuerligt för att utveckla nya mer hållbara metoder. Ett sätt är att använda sig av digitala beslutsstöd vid planeringstillfället. Timbertrail är ett sådant som tar hänsyn till en trakts beskaffenhet för att hitta bästa avlägg och basväg. Studien visade på att beslutsstödet i teorin hänvisar till bättre bärighet och minskad risk för körskador. Den kan vara ett bra hjälpmedel vid planering men att den skogliga operationen till sist är beroende av att alla inblandade också tar ett personligt ansvar för att minimera risken för körskador.
260

Effects Of Prescribed Burning And Herbicide (Imazapyr) On The Abundance And Diversity Of Selected Invertebrate Communities In Thinned Pine Plantations Of Mississippi

Iglay, Raymond Bruce 15 December 2007 (has links)
Prescribed fire and herbicides are 2 silviculture tools used by forest managers to control hardwood competition in pine (Pinus spp.) forests. I tested effects of prescribed burning and herbicides on selected invertebrate communities, including carabid beetles, and compared 2 invertebrate sampling approaches in thinned, intensively managed pine stands in Kemper County, Mississippi. I used 6 replicate stands containing 4, 10-ha treatment plots each that were randomly assigned treatments of burn only, herbicide only, burn/herbicide, and control. I suction-sampled invertebrate communities and pitfall trapped carabid beetles to examine treatment responses. Direct effects of burning and overall vegetation response influenced communities most but responses were limited. Sampling inefficiencies may have obscured treatment effects and managers and researchers are advised to consider all available methods when integrating invertebrate research. Information on forest management effects is still lacking but future research incorporating invertebrate sampling will support a better understanding of management impacts on ecosystems.

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