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Long-term decomposition of sugarcane harvest residues in Sao Paulo state, Brazil

Fortes, Cabo; Ocheuze Trivelin, Paulo Cesar; Vitti, Andre Cesar
Fonte: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD Publicador: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.14%
Crop residues returned to the soil are important to preserve fertility and sustainability. This research addressed the long-term decomposition of sugarcane post-harvest residues (trash) under reduced tillage, therefore field renewal was performed with herbicide followed by subsoiling and ratoons were deprived of interrow scarification. The trial was conducted in the northern Sao Paulo State, Brazil during four consecutive crops (2005-2008) where litter bags containing N-15-labeled trash were disposed in the field attempting to simulate two distinct situations: the previous crop trash (PCT) or residues incorporated in the field after tillage, and post-harvest trash (PHT) or the remains of plant-cane harvest. Decomposition rates regarding dry matter (DM), carbon (C), root growth, plant nutrients (N, P, K, Ca, Mg and S), lignin (LIG) cellulose (CEL) and hemicellulose (HCEL) contents were assessed for PCT (2005 ndash;2008) and for PHT (2006-2008). There were significant reductions on DM and C:N ratio due to C losses and root growth within the litter bags over time. The DM from PCT and PHT decreased 96% and 73% after four and three crops, respectively, and the higher nutrients release were found for K, Ca and N. The LIG, CEL and HCEL concentrations in PCT decreased 60%...

Produtividade, crescimento e ciclos econômicos na agricultura brasileira; Productivity, growth and business cycles in Brazilian agriculture

Bragagnolo, Cassiano
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 10/08/2012 PT
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36.1%
Este trabalho é composto por três artigos que visam abordar pontos pouco explorados na literatura de economia agrícola brasileira sobre produtividade total dos fatores (PTF), buscando abordar também o crescimento do setor e seu comportamento nos ciclos econômicos. Após uma breve introdução do tema no primeiro capítulo, analisa-se no segundo capítulo, o crescimento da agricultura brasileira no período 1975 a 2005 por meio de um modelo de fronteira estocástica, com o intuito de decompor a PTF brasileira para cada estado. Os resultados do estudo mostram que o crescimento da PTF foi heterogêneo entre os estados e sugerem que a expansão da agricultura nas regiões Norte e Centro-Oeste foi possível devido à influência do progresso técnico na PTF e que mesmo os estados tradicionais na agricultura apresentaram crescimento da PTF elevado. O segundo artigo, no terceiro capítulo, buscou analisar os impactos dinâmicos dos fatores de produção capital, trabalho e terras no produto agrícola fazendo uso de uma estratégia empírica baseada em um modelo econométrico VAR estrutural para o período compreendido entre 1972 e 2009. Os resultados demonstram que o fator de produção que tem maior influência sobre o produto é o capital. Os resultados indicam...

Temporal Dynamics of Abiotic and Biotic Factors on Leaf Litter of Three Plant Species in Relation to Decomposition Rate along a Subalpine Elevation Gradient

Zhu, Jianxiao; Yang, Wanqin; He, Xinhua
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 19/04/2013 EN
Relevância na Pesquisa
26.42%
Relationships between abiotic (soil temperature and number of freeze-thaw cycles) or biotic factors (chemical elements, microbial biomass, extracellular enzymes, and decomposer communities in litter) and litter decomposition rates were investigated over two years in subalpine forests close to the Qinghai-Tibet Plateau in China. Litterbags with senescent birch, fir, and spruce leaves were placed on the forest floor at 2,704 m, 3,023 m, 3,298 m, and 3,582 m elevation. Results showed that the decomposition rate positively correlated with soil mean temperature during the plant growing season, and with the number of soil freeze-thaw cycles during the winter. Concentrations of soluble nitrogen (N), phosphorus (P) and potassium (K) had positive effects but C:N and lignin:N ratios had negative effects on the decomposition rate (k), especially during the winter. Meanwhile, microbial biomass carbon (MBC), N (MBN), and P (MBP) were positively correlated with k values during the first growing season. These biotic factors accounted for 60.0% and 56.4% of the variation in decomposition rate during the winter and the growing season in the first year, respectively. Specifically, litter chemistry (C, N, P, K, lignin, C:N and lignin:N ratio) independently explained 29.6% and 13.3%...

Decomposition and nutrient release of leguminous plants in coffee agroforestry systems.

MATOS, E. da S.; MENDONÇA, E. de S.; CARDOSO, I. M.; LIMA, P. C. de; FREESE, D.
Fonte: Revista Brasileira de Ciência do Solo, Campinas, v. 35, p. 141-149, 2011. Publicador: Revista Brasileira de Ciência do Solo, Campinas, v. 35, p. 141-149, 2011.
Tipo: Artigo em periódico indexado (ALICE)
EN
Relevância na Pesquisa
36.18%
Abstract: Leguminous plants used as green manure are an important nutrient source for coffee plantations, especially for soils with low nutrient levels. Field experiments were conducted in the Zona da Mata of Minas Gerais State, Brazil to evaluate the decomposition and nutrient release rates of four leguminous species used as green manures (Arachis pintoi, Calopogonium mucunoides, Stizolobium aterrimum and Stylosanthes guianensis) in a coffee agroforestry system under two different climate conditions. The initial N contents in plant residues varied from 25.7 to 37.0 g kg-1 and P from 2.4 to 3.0 g kg-1. The lignin/N, lignin/polyphenol and (lignin+polyphenol)/N ratios were low in all residues studied. Mass loss rates were highest in the first 15 days, when 25 % of the residues were decomposed. From 15 to 30 days, the decomposition rate decreased on both farms. On the farm in Pedra Dourada (PD), the decomposition constant k increased in the order C. mucunoides < S. aterrimum < S. guianensis < A. pintoi. On the farm in Araponga (ARA), there was no difference in the decomposition rate among leguminous plants. The N release rates varied from 0.0036 to 0.0096 d-1. Around 32 % of the total N content in the plant material was released in the first 15 days. In ARA...

Domain/Multi-Domain Protection and Provisioning in Optical Networks

Do Trung, Kien
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
EN
Relevância na Pesquisa
26.45%
L’évolution récente des commutateurs de sélection de longueurs d’onde (WSS -Wavelength Selective Switch) favorise le développement du multiplexeur optique d’insertionextraction reconfigurable (ROADM - Reconfigurable Optical Add/Drop Multiplexers) à plusieurs degrés sans orientation ni coloration, considéré comme un équipement fort prometteur pour les réseaux maillés du futur relativement au multiplexage en longueur d’onde (WDM -Wavelength Division Multiplexing ). Cependant, leur propriété de commutation asymétrique complique la question de l’acheminement et de l’attribution des longueur d’ondes (RWA - Routing andWavelength Assignment). Or la plupart des algorithmes de RWA existants ne tiennent pas compte de cette propriété d’asymétrie. L’interruption des services causée par des défauts d’équipements sur les chemins optiques (résultat provenant de la résolution du problème RWA) a pour conséquence la perte d’une grande quantité de données. Les recherches deviennent ainsi incontournables afin d’assurer la survie fonctionnelle des réseaux optiques, à savoir, le maintien des services, en particulier en cas de pannes d’équipement. La plupart des publications antérieures portaient particulièrement sur l’utilisation d’un système de protection permettant de garantir le reroutage du trafic en cas d’un défaut d’un lien. Cependant...

Aspects of nutrient cycling in semi arid mallee and mulga communities

Burrows, William Henry
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
EN_AU
Relevância na Pesquisa
26.39%
A study was made of nutrient distribution and fluxes in mallee and mulga ecosystems to obtain an appreciation of the manner in which the woody plants have adapted to their infertile semi arid habitats. Emphasis was placed in utilisation and fluxes of nitrogen and phosphorus within these ecosystems. Pool sizes of total phosphorus, ‘available’ phosphorus and total nitrogen within the communities exhibited remarkable similarities despite wide differences in geographical location and plant assemblages supported. There was a pronounced concentration of organic carbon, total nitrogen and ‘available’ phosphorus in the soil surface horizons. High resilience within mallee communities was demonstrated by comparison of a fifteen year old regrowth community with an adjacent mature (c. 55 year old) stand. There were only small differences between both communities in nitrogen and phosphorus pool size in the vegetation, and in the lignotuber biomass, leaf area index and the amount of leaf litter present on the soil surface. The above ground net primary productivity of the regrowth community (5406 kg/ha/yr) was more than twice that of the mature mallee (2379 kg/ha/yr). The mulga community had high concentrations of nitrogen in both its living and dead tissues compared with mallee. This suggested that the Acacia/ Rhizobium symbiosis was effective but there was apparently no build-up of total nitrogen within the soil profile. There were considerable fluctuations in the pulses of litter and nutrients onto the floors of these woodland ecosystems. However litter fall from Eucalyptus spp. exhibited a distinct summer maximum whereas litter fall in mulga appeared to be largely independent of season and rainfall. Withdrawal of nitrogen and phosphorus prior to leaf abscission indicated conservation in the use of these elements. There were striking similarities in the breakdown and decomposition rates of mallee and mulga leaves...

Strukturen, thermischer Abbau und mögliche Anwendungen von Oxidnitraten; Structures, thermal decomposition and possible applications of oxide nitrates

Dill, Simone
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
36.14%
Die vorliegende Arbeit beschäftigt sich mit der Synthese und Charakterisierung von bekannten und neuen Oxidnitraten, deren Zersetzungsprodukten und der potentiellen Anwendungen der Oxidnitrate als Precursoren und NOx-Speicher. In Kapitel 3 wurde die thermische Zersetzung von Sr(NO3)2 und Ba(NO3)2, welches in NOx-Speicherkatalysatoren in der Automobilindustrie verwendet wird, untersucht. Um eventuell auftretende Zwischenstufen, bei denen es sich auch um Oxidnitrate handeln könnte, zu isolieren, wurden die Nitrate von Barium und Strontium nur kurz über ihren Schmelzpunkt erhitzt und wieder abgekühlt. Beim Abkühlen der jeweiligen Nitratschmelzen an Luft trat eine neue, unbekannte Phase auf. Dabei handelte es sich um die Verbindungen Sr2(OH)3NO3 bzw. Ba2(OH)3NO3. Die Strukturen dieser Verbindungen wurden anhand von Röntgen-Einkristall- und Pulverdaten bestimmt und verfeinert. In den hexagonalen Kristallstrukturen (P6`2m) dieser Hydroxidnitrate sind die Erdalkalimetallionen von den Hydroxidionen in Form von trigonalen Prismen umgeben. Diese Prismen sind über die trigonalen Flächen entlang der c-Richtung und über Kanten in der ab-Ebene verknüpft. Sie bilden sechseckige Röhren, in denen sich die Nitratgruppen befinden. Die Bildung und Zersetzung von Sr2(OH)3NO3 wurde mit Hilfe von DTA/TG-Messungen untersucht...

Efficient VLSI Architectures for Recursive Vandermonde QR Decomposition in Broadband OFDM Pre-distortion

Guo, Yuanbin; Guo, Yuanbin
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Conference paper
ENG
Relevância na Pesquisa
35.97%
Conference Paper; The Vandermonde system is used in OFDM predistortion to enhance the power efficiency dramatically. In this paper, we study efficient FPGA architectures of a recursive algorithm for the Cholesky and QR factorization of the Vandermonde system. We identify the key bottlenecks of the algorithm for the real-time constraints and resource consumption. Several architecture/resource tradeoffs are studied to find the commonalities in the architectures for a best partitioning. Hardware resources are reused according to the algorithmic parallelism and data dependency to achieve the best timing/area performance in hardware. The architectures are implemented in Xilinx FPGA and tested in Aptix real-time hardware platform with 11348 cycles at 25ns clock rate.

The Coupling of the Carbon and Nitrogen Cycles in Agriculture: Crop Ecosystem Oxidative Ratio and the Effects of Fertilization on Biofuel Feedstock Quality

Gallagher, Morgan Elizabeth
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
36.15%
Agriculture significantly impacts the global carbon (C) and nitrogen (N) cycles through land use change, soil C loss, greenhouse gas emissions, and increased fixed-N availability. Agriculture occupies a third of the terrestrial biosphere, making understanding its impacts on the C and N cycles critical. I used a novel analytical tool (solid-state 13 C nuclear magnetic resonance spectroscopy) to characterize properties of the C and N cycles in agriculture, including biochemical responses to N fertilizer and agriculture gas fluxes. A central component of the C cycle is the rapid exchange of carbon dioxide (CO 2 ) and oxygen (O 2 ) between the terrestrial biosphere and the atmosphere. Gas flux O 2 /CO 2 ratios (oxidative ratio-OR) vary depending on ecosystem type, plant species, and nutrient status. It is necessary to constrain OR to assess the uptake of anthropogenic CO 2 by the terrestrial biosphere and ocean. I measured the OR of the top three crops in the United States (soybean, corn, and wheat) and found significant variability. I additionally tested the effect of N fertilizer application on corn ecosystem OR and on the difference between respiration and photosynthesis OR and observed no detectable changes. Conversely, soil organic matter OR is different from gas flux OR values...

Terms of trade cycles in extreme land abundant countries, 1870-2009. Spectral analysis

Arrufat, José Luis; Martín Díaz Cafferata, Alberto; Viceconte, José Antonio
Fonte: Universidad de Alcalá. Instituto Universitario de Análisis Económico y Social Publicador: Universidad de Alcalá. Instituto Universitario de Análisis Económico y Social
Tipo: Trabalho em Andamento Formato: application/pdf
ENG
Relevância na Pesquisa
36.1%
Spectral analysis is applied to the empirical identification of terms of trade cycles, in the secular evolution, 1870-2009, of a group of extreme-land-abundant countries: Argentina, Australia, Canada, New Zealand, and Uruguay. Estimates of the power density spectrum functions produce statistically significant spectral peaks associated with long-run cycle periods between 24 and 56 years, with a mode of about 28 years for all five countries, and the variance decomposition shows that these long-run cycles account for a very substantial fraction, between 68% and 83%, of the TOT total variance. These results are very robust to changes in the choice of truncation lag, as well as to the type of spectral window (Parzen and Bartlett) used in the estimations.; Mediante aplicación del análisis espectral se descompone el ciclo empírico de los términos de intercambio en ciclos teóricos periódicos, para un grupo de países que denominamos “de extrema abundancia de tierra”. Para Argentina, Australia, Nueva Zelanda y Uruguay en el período 1870-2009 las funciones de densidad espectral identifican picos correspondientes a ciclos de largo plazo de sus términos de intercambio de entre 24 y 56 años, con una media de 28 años. La descomposición de la varianza indica que tales movimientos cíclicos de largo plazo explican una fracción sustancial de entre el 68% y el 83% de la varianza total. Los resultados estadísticos son robustos a la elección de los parámetros y del tipo de ventana espectral...

Groupage et protection du trafic dynamique dans les réseaux WDM

Metnani, Ammar
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
Relevância na Pesquisa
26.42%
Avec les nouvelles technologies des réseaux optiques, une quantité de données de plus en plus grande peut être transportée par une seule longueur d'onde. Cette quantité peut atteindre jusqu’à 40 gigabits par seconde (Gbps). Les flots de données individuels quant à eux demandent beaucoup moins de bande passante. Le groupage de trafic est une technique qui permet l'utilisation efficace de la bande passante offerte par une longueur d'onde. Elle consiste à assembler plusieurs flots de données de bas débit en une seule entité de données qui peut être transporté sur une longueur d'onde. La technique demultiplexage en longueurs d'onde (Wavelength Division Multiplexing WDM) permet de transporter plusieurs longueurs d'onde sur une même fibre. L'utilisation des deux techniques : WDM et groupage de trafic, permet de transporter une quantité de données de l'ordre de terabits par seconde (Tbps) sur une même fibre optique. La protection du trafic dans les réseaux optiques devient alors une opération très vitale pour ces réseaux, puisqu'une seule panne peut perturber des milliers d'utilisateurs et engendre des pertes importantes jusqu'à plusieurs millions de dollars à l'opérateur et aux utilisateurs du réseau. La technique de protection consiste à réserver une capacité supplémentaire pour acheminer le trafic en cas de panne dans le réseau. Cette thèse porte sur l'étude des techniques de groupage et de protection du trafic en utilisant les p-cycles dans les réseaux optiques dans un contexte de trafic dynamique. La majorité des travaux existants considère un trafic statique où l'état du réseau ainsi que le trafic sont donnés au début et ne changent pas. En plus...

Time Reversibility of Stationary Regular Finite State Markov Chains

McCAUSLAND, William
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Artigo de Revista Científica Formato: 242508 bytes; application/pdf
Relevância na Pesquisa
26.45%
We propose an alternate parameterization of stationary regular finite-state Markov chains, and a decomposition of the parameter into time reversible and time irreversible parts. We demonstrate some useful properties of the decomposition, and propose an index for a certain type of time irreversibility. Two empirical examples illustrate the use of the proposed parameter, decomposition and index. One involves observed states; the other, latent states.; Nous proposons une paramétrisation alternative des chaînes markoviennes stationnaires et régulières à états finis, ainsi qu'une décomposition du paramètre en une partie réversible et une partie irréversible. Nous démontrons certaines propriétés utiles de cette décomposition et proposons une mesure pour un type particulier d'irreversibilité temporelle. Deux exemples empiriques illustrent l'utilisation du paramêtre proposé, sa décomposition et la mesure. Le premier traite d'états observables, alors que le second traite d'états latents.

Latin american growth cycles. Empirical evidence 1960-2000

Pineda, José; Cerro, Ana María
Fonte: Universidad de Chile. Facultad de Economía y Negocios Publicador: Universidad de Chile. Facultad de Economía y Negocios
Tipo: Artículo de revista
EN
Relevância na Pesquisa
36.05%
This paper measures and explains to what extent Latin American countries’ growth cycles experienced co-movement in the last forty years, using different methodologies. We find that short lasting cycles showed a great dispersion among cyclical correlation, while long lasting ones displayed considerable co-movement. From the structural VAR approach, the results imply a very low degree of co-movement among the shocks affecting these economies. There exist important differences regarding the speed of adjustment and the excess volatility of demand shocks. Processes of integration among Latin-American countries need more policy coordination prior to any attempt to go further in an economic integration process.

The Matlab Vectorization Paradigm

Gaspar, Miguel; Martins-Ferreira, N.
Fonte: CDRSP-IPLeiria Publicador: CDRSP-IPLeiria
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
Relevância na Pesquisa
35.97%
We give two examples of application of a vectorized programming paradigm: binary addition and cycle decomposition of directed graphs.

Zero cycles with modulus and zero cycles on singular varieties

Binda, Federico; Krishna, Amalendu
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/12/2015
Relevância na Pesquisa
26.33%
Given a smooth variety $X$ and an effective Cartier divisor $D \subset X$, we show that the cohomological Chow group of 0-cycles on the double of $X$ along $D$ has (under some conditions) a canonical decomposition in terms of the Chow group of 0-cycles ${\rm CH}_0(X)$ and the Chow group of 0-cycles with modulus ${\rm CH}_0(X|D)$ on $X$. When $X$ is projective, we construct an Albanese variety with modulus and show that this is the universal regular quotient of ${\rm CH}_0(X|D)$. As a consequence of the above decomposition, we prove the Roitman torsion theorem for the 0-cycles with modulus. We show that, if $X$ is affine, ${\rm CH}_0(X|D)$ is torsion-free and that there is an injective cycle class map ${\rm CH}_0(X|D) \hookrightarrow K_0(X,D)$, where $K_0(X,D)$ denotes the relative $K_0$-group for the inclusion $D\subset X$. For a smooth affine surface $X$, this is strengthened to show that $K_0(X,D)$ is an extension of ${\rm CH}_1(X|D)$ by ${\rm CH}_0(X|D)$. We derive from this Bloch's formula for 0-cycles with modulus on surfaces.; Comment: 51 pages

Pants Decomposition of the Punctured Plane

Poon, Sheung-Hung; Thite, Shripad
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/02/2006
Relevância na Pesquisa
26.34%
A pants decomposition of an orientable surface S is a collection of simple cycles that partition S into pants, i.e., surfaces of genus zero with three boundary cycles. Given a set P of n points in the plane, we consider the problem of computing a pants decomposition of the surface S which is the plane minus P, of minimum total length. We give a polynomial-time approximation scheme using Mitchell's guillotine rectilinear subdivisions. We give a quartic-time algorithm to compute the shortest pants decomposition of S when the cycles are restricted to be axis-aligned boxes, and a quadratic-time algorithm when all the points lie on a line; both exact algorithms use dynamic programming with Yao's speedup.; Comment: 5 pages, 1 grayscale figure

Proof of the $1$-factorization and Hamilton Decomposition Conjectures

Csaba, Béla; Kühn, Daniela; Lo, Allan; Osthus, Deryk; Treglown, Andrew
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.34%
In this paper we prove the following results (via a unified approach) for all sufficiently large $n$: (i) [$1$-factorization conjecture] Suppose that $n$ is even and $D\geq 2\lceil n/4\rceil -1$. Then every $D$-regular graph $G$ on $n$ vertices has a decomposition into perfect matchings. Equivalently, $\chi'(G)=D$. (ii) [Hamilton decomposition conjecture] Suppose that $D \ge \lfloor n/2 \rfloor $. Then every $D$-regular graph $G$ on $n$ vertices has a decomposition into Hamilton cycles and at most one perfect matching. (iii) [Optimal packings of Hamilton cycles] Suppose that $G$ is a graph on $n$ vertices with minimum degree $\delta\ge n/2$. Then $G$ contains at least ${\rm reg}_{\rm even}(n,\delta)/2 \ge (n-2)/8$ edge-disjoint Hamilton cycles. Here $\text{reg}_{\text{even}}(n,\delta)$ denotes the degree of the largest even-regular spanning subgraph one can guarantee in a graph on $n$ vertices with minimum degree $\delta$. (i) was first explicitly stated by Chetwynd and Hilton. (ii) and the special case $\delta= \lceil n/2 \rceil$ of (iii) answer questions of Nash-Williams from 1970. All of the above bounds are best possible.; Comment: We originally split the proof into four papers [arXiv:1401.4159,arXiv:1401.4164, arXiv:1401.4178...

Proof of the 1-factorization and Hamilton decomposition conjectures II: the bipartite case

Csaba, Béla; Kühn, Daniela; Lo, Allan; Osthus, Deryk; Treglown, Andrew
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.34%
In a sequence of four papers, we prove the following results (via a unified approach) for all sufficiently large $n$: (i) [1-factorization conjecture] Suppose that $n$ is even and $D \geq 2\lceil n/4\rceil -1$. Then every $D$-regular graph $G$ on $n$ vertices has a decomposition into perfect matchings. Equivalently, $\chi'(G)=D$. (ii) [Hamilton decomposition conjecture] Suppose that $D \ge \lfloor n/2 \rfloor $. Then every $D$-regular graph $G$ on $n$ vertices has a decomposition into Hamilton cycles and at most one perfect matching. (iii) [Optimal packings of Hamilton cycles] Suppose that $G$ is a graph on $n$ vertices with minimum degree $\delta\ge n/2$. Then $G$ contains at least ${\rm reg}_{\rm even}(n,\delta)/2 \ge (n-2)/8$ edge-disjoint Hamilton cycles. Here ${\rm reg}_{\rm even}(n,\delta)$ denotes the degree of the largest even-regular spanning subgraph one can guarantee in a graph on $n$ vertices with minimum degree $\delta$. According to Dirac, (i) was first raised in the 1950s. (ii) and the special case $\delta= \lceil n/2 \rceil$ of (iii) answer questions of Nash-Williams from 1970. All of the above bounds are best possible. In the current paper, we prove the above results for the case when $G$ is close to a complete balanced bipartite graph.; Comment: We originally split the proof into four papers...

Proof of the 1-factorization and Hamilton decomposition conjectures III: approximate decompositions

Csaba, Béla; Kühn, Daniela; Lo, Allan; Osthus, Deryk; Treglown, Andrew
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.37%
In a sequence of four papers, we prove the following results (via a unified approach) for all sufficiently large $n$: (i) [1-factorization conjecture] Suppose that $n$ is even and $D\geq 2\lceil n/4\rceil -1$. Then every $D$-regular graph $G$ on $n$ vertices has a decomposition into perfect matchings. Equivalently, $\chi'(G)=D$. (ii) [Hamilton decomposition conjecture] Suppose that $D \ge \lfloor n/2 \rfloor $. Then every $D$-regular graph $G$ on $n$ vertices has a decomposition into Hamilton cycles and at most one perfect matching. (iii) We prove an optimal result on the number of edge-disjoint Hamilton cycles in a graph of given minimum degree. According to Dirac, (i) was first raised in the 1950s. (ii) and (iii) answer questions of Nash-Williams from 1970. The above bounds are best possible. In the current paper, we show the following: suppose that $G$ is close to a complete balanced bipartite graph or to the union of two cliques of equal size. If we are given a suitable set of path systems which cover a set of `exceptional' vertices and edges of $G$, then we can extend these path systems into an approximate decomposition of $G$ into Hamilton cycles (or perfect matchings if appropriate).; Comment: We originally split the proof into four papers...

Assessing a sustainable sugarcane production system in Tucumán, Argentina: Part 1: Dynamics of sugarcane harvest residue (trash) decomposition

Digonzelli,Patricia A.; Romero,Eduardo R.; Alonso,Luis; Fernández de Ullivarri,Juan; Rojas Quinteros,Hugo; Scandaliaris,Jorge; Fajre,Sofia
Fonte: Revista industrial y agrícola de Tucumán Publicador: Revista industrial y agrícola de Tucumán
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2011 EN
Relevância na Pesquisa
36.37%
The elimination of burning practices in sugarcane harvest has led to more sustainable productive systems, with lower impact on the environment and on communities. The present paper is part of a study in which two sugarcane management systems were compared: (a) one with sugarcane harvest residue kept on the ground (trash blanketing); and (b) one without trash blanketing (burnt residue). Cultivar LCP 85-384 was planted in macro-plots in a commercial field in Albarracín, Tucumán, Argentina. A split-plot experimental design with three replications was used. Each plot had five 30 m-long rows. Two crop cycles (2006/2007 and 2007/2008), i.e. second and third ratoon, were evaluated. From the end of harvest onwards, residue amount (dry matter/ha) and residue C/N relationship were determined periodically. At the beginning and at the end of each crop cycle, residue P and K contents were assessed. Residue left after harvest amounted to 12 and 16 tons of dry matter per hectare in the first and second evaluated crop cycles, respectively, but decreased significantly throughout these periods. Residue C/N relationship was over 100 in both crop cycles (117 and 101, respectively), but decreased significantly in their course. Reductions in both sugarcane residue and C/N relationship were correlated with days after harvest and accumulated thermal time (∑ mean daily air temperature). Trash initial C concentration was similar in both crop cycles and amounted to approximately 45%...