995 resultados para variable intensity
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During Integrated Ocean Drilling Program Expedition 302 (Arctic Coring Expedition (ACEX)) a more than 200 m thick sequence of Paleogene organic carbon (OC)-rich (black shale type) sediments was drilled. Here we present new biomarker data determined in ACEX sediment samples to decipher processes controlling OC accumulation and their paleoenvironmental significance during periods of Paleogene global warmth and proposed increased freshwater discharge in the early Cenozoic. Specific source-related biomarkers including n-alkanes, fatty acids, isoprenoids, carotenoids, hopanes/hopenes, hopanoic acids, aromatic terpenoids, and long-chain alkenones show a high variability of components, derived from marine and terrestrial origin. The distribution of hopanoic acid isomers is dominated by compounds with the biological 17beta(H), 21beta(H) configuration indicating a low level of maturity. On the basis of the biomarker data the terrestrial OC supply was significantly enriched during the late Paleocene and part of the earliest Eocene, whereas increased aquatic contributions and euxinic conditions of variable intensity were determined for the Paleocene-Eocene thermal maximum and Eocene thermal maximum 2 events as well as the middle Eocene time interval. Furthermore, samples from the middle Eocene are characterized by the occurrence of long-chain alkenones, high proportions of lycopane, and high ratios (>0.6) of (n-C35 + lycopane)/n-C31. The occurrence of C37-alkenenones, which were first determined toward the end of the Azolla freshwater event, indicates that the OC becomes more marine in origin during the middle Eocene. Preliminary UK'37- based sea surface temperature (SST) values display a longterm temperature decrease of about 15C during the time interval 49-44.5 Ma (25° to 10°C), coinciding with the global benthic d18O cooling trend after the early Eocene climatic optimum. At about 46 Ma, parallel with onset of ice-rafted debris, SST (interpreted as summer temperatures) decreased to values <15°C. For the late early Miocene a SST of 11°-15°C was determined. Most of the middle Eocene ACEX sediments are characterized by a smooth short-chain n-alkane distribution, which may point to natural oil-type hydrocarbons from leakage of petroleum reservoirs or erosion of related source rocks and redeposition.
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Mapping and sediment sampling in reefs of the Pulau Seribu group (southwest Java Sea) shows the existence of ten physiographic zones and subzones represented by seven lithofacies. Reefs in the northern part of the archipelago are smaller, more closely spaced and morphologically sim pler than those in the south. This pattern is attributed to differences in subsidence rate. A th reedimensional model is proposed for the evo lution of these reefs but borehole data are requi red to test this model. Miocene limestones are described in detail from hydrocarbon reservoirs in the Batu Raja Formation of the same area. Brief comparisons a re made with surface outcrops of approximately coeval carbonate developments. The lithofacies developed within these limestones reflect variations in hydrodynam ic regime and basement topography . Ele\le.n diagenetic processes affected the Batu Raja limestones and the dist ribution of these is primarily related to sealevel fluctuations. Early diagenesis was marine and characterised by micritisation and preCipitation of fibrous and bladed cements. Dolomitisat ion occurred in the mixed- water zone and its variable intensity is attributed to the configuration of the carbonate body relative to this zone. Subsequently the limestones were subjected to freshwater phreatic zone diagenesis resulting in dissolution and cementation, and a t a late stage underwent burial compaction. Secondary porosity, which \ar9e1.y determines the suitability of these limestones as hydrocarbon reserVOirs, is a function of the variable intensity of dissolution and cementation, burial compaction, dolomitisation and possibly micrite neomorphism. The sedimentary processes that generated the Batu Raja buildups are inferred f rom comparisons with the Pulau Seribu and other Recent analogues. The contrasting pinnacle form of the Pulau Seribu patch reefs compared with the low relief of the Batu Raja buUdups results from differences in the initial substrate topography and subsequent subsidence rate
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MSC 2010: 05C50, 15A03, 15A06, 65K05, 90C08, 90C35
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Efficient and reliable techniques for power delivery and utilization are needed to account for the increased penetration of renewable energy sources in electric power systems. Such methods are also required for current and future demands of plug-in electric vehicles and high-power electronic loads. Distributed control and optimal power network architectures will lead to viable solutions to the energy management issue with high level of reliability and security. This dissertation is aimed at developing and verifying new techniques for distributed control by deploying DC microgrids, involving distributed renewable generation and energy storage, through the operating AC power system. To achieve the findings of this dissertation, an energy system architecture was developed involving AC and DC networks, both with distributed generations and demands. The various components of the DC microgrid were designed and built including DC-DC converters, voltage source inverters (VSI) and AC-DC rectifiers featuring novel designs developed by the candidate. New control techniques were developed and implemented to maximize the operating range of the power conditioning units used for integrating renewable energy into the DC bus. The control and operation of the DC microgrids in the hybrid AC/DC system involve intelligent energy management. Real-time energy management algorithms were developed and experimentally verified. These algorithms are based on intelligent decision-making elements along with an optimization process. This was aimed at enhancing the overall performance of the power system and mitigating the effect of heavy non-linear loads with variable intensity and duration. The developed algorithms were also used for managing the charging/discharging process of plug-in electric vehicle emulators. The protection of the proposed hybrid AC/DC power system was studied. Fault analysis and protection scheme and coordination, in addition to ideas on how to retrofit currently available protection concepts and devices for AC systems in a DC network, were presented. A study was also conducted on the effect of changing the distribution architecture and distributing the storage assets on the various zones of the network on the system's dynamic security and stability. A practical shipboard power system was studied as an example of a hybrid AC/DC power system involving pulsed loads. Generally, the proposed hybrid AC/DC power system, besides most of the ideas, controls and algorithms presented in this dissertation, were experimentally verified at the Smart Grid Testbed, Energy Systems Research Laboratory. All the developments in this dissertation were experimentally verified at the Smart Grid Testbed.
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Efficient and reliable techniques for power delivery and utilization are needed to account for the increased penetration of renewable energy sources in electric power systems. Such methods are also required for current and future demands of plug-in electric vehicles and high-power electronic loads. Distributed control and optimal power network architectures will lead to viable solutions to the energy management issue with high level of reliability and security. This dissertation is aimed at developing and verifying new techniques for distributed control by deploying DC microgrids, involving distributed renewable generation and energy storage, through the operating AC power system. To achieve the findings of this dissertation, an energy system architecture was developed involving AC and DC networks, both with distributed generations and demands. The various components of the DC microgrid were designed and built including DC-DC converters, voltage source inverters (VSI) and AC-DC rectifiers featuring novel designs developed by the candidate. New control techniques were developed and implemented to maximize the operating range of the power conditioning units used for integrating renewable energy into the DC bus. The control and operation of the DC microgrids in the hybrid AC/DC system involve intelligent energy management. Real-time energy management algorithms were developed and experimentally verified. These algorithms are based on intelligent decision-making elements along with an optimization process. This was aimed at enhancing the overall performance of the power system and mitigating the effect of heavy non-linear loads with variable intensity and duration. The developed algorithms were also used for managing the charging/discharging process of plug-in electric vehicle emulators. The protection of the proposed hybrid AC/DC power system was studied. Fault analysis and protection scheme and coordination, in addition to ideas on how to retrofit currently available protection concepts and devices for AC systems in a DC network, were presented. A study was also conducted on the effect of changing the distribution architecture and distributing the storage assets on the various zones of the network on the system’s dynamic security and stability. A practical shipboard power system was studied as an example of a hybrid AC/DC power system involving pulsed loads. Generally, the proposed hybrid AC/DC power system, besides most of the ideas, controls and algorithms presented in this dissertation, were experimentally verified at the Smart Grid Testbed, Energy Systems Research Laboratory. All the developments in this dissertation were experimentally verified at the Smart Grid Testbed.
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Hydrotalcites of formula Mg6 (Fe,Al)2(OH)16(CO3).4H2O formed by intercalation with the carbonate anion as a function of divalent/trivalent cationic ratio have been successfully synthesised. The XRD patterns show variation in the d-spacing attributed to the size of the cation. Raman and infrared bands in the OH stretching region are assigned to (a) brucite layer OH stretching vibrations (b) water stretching bands and (c) water strongly hydrogen bonded to the carbonate anion. Multiple (CO3)2- symmetric stretching bands suggest that different types of (CO3)2- exist in the hydrotalcite interlayer. Increasing the cation ratio (Mg/Al,Fe) resulted in an increase in the combined intensity of the 2 Raman bands at around 3600 cm-1, attributed to Mg-OH stretching modes, and a shift of the overall band profile to higher wavenumbers. These observations are believed to be a result of the increase in magnesium in the structure. Raman spectroscopy shows a reduction in the symmetry of the carbonate, leading to the conclusion that the anions are bonded to the brucite-like hydroxyl surface and to the water in the interlayer. Water bending modes are identified in the infrared spectra at positions greater than 1630 cm-1, indicating the water is strongly hydrogen bonded to both the interlayer anions and the brucite-like surface.
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A basic understanding of the relationships between rainfall intensity, duration of rainfall and the amount of suspended particles in stormwater runoff generated from road surfaces has been gained mainly from past washoff experiments using rainfall simulators. Simulated rainfall was generally applied at constant intensities, whereas rainfall temporal patterns during actual storms are typically highly variable. This paper discusses a rationale for the application of the constant-intensity washoff concepts to actual storm event runoff. The rationale is tested using suspended particle load data collected at a road site located in Toowoomba, Australia. Agreement between the washoff concepts and measured data is most consistent for intermediate-duration storms (duration <5 h and >1 h). Particle loads resulting from these storm events increase linearly with average rainfall intensity. Above a threshold intensity, there is evidence to suggest a constant or plateau particle load is reached. The inclusion of a peak discharge factor (maximum 6 min rainfall intensity) enhances the ability to predict particle loads.
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We present in this paper, approximate analytical expressions for the intensity of light scattered by a rough surface, whose elevation. xi(x,y) in the z-direction is a zero mean stationary Gaussian random variable. With (x,y) and (x',y') being two points on the surface, we have h.
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The emittance of an extracted ion beam can be estimated to first order by a series of three linear independent profile measurements. This estimation is restricted to the evaluation of an upper limit of the emittance value for a homogeneous, nonfilamented beam. The beam is assumed to be round, respectively elliptical, without any structure of the intensity distribution, no space charge has been assumed for the drifting beam, and the optics is assumed to be linear. Instead of using three different drift sections, a linear focusing element with three different focusing strengths can be used. Plotting the beam radius as function of focusing strength, three independent solutions can be used to calculate the Twiss parameters alpha, beta, and gamma and furthermore the emittance epsilon. Here we describe the measurements which have been performed with the SECRAL ion source at Institute of Modern Physics Lanzhou.
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Consensus HIV-1 genes can decrease the genetic distances between candidate immunogens and field virus strains. To ensure the functionality and optimal presentation of immunologic epitopes, we generated two group-M consensus env genes that contain variable regions either from a wild-type B/C recombinant virus isolate (CON6) or minimal consensus elements (CON-S) in the V1, V2, V4, and V5 regions. C57BL/6 and BALB/c mice were primed twice with CON6, CON-S, and subtype control (92UG37_A and HXB2/Bal_B) DNA and boosted with recombinant vaccinia virus (rVV). Mean antibody titers against 92UG37_A, 89.6_B, 96ZM651_C, CON6, and CON-S Env protein were determined. Both CON6 and CON-S induced higher mean antibody titers against several of the proteins, as compared with the subtype controls. However, no significant differences were found in mean antibody titers in animals immunized with CON6 or CON-S. Cellular immune responses were measured by using five complete Env overlapping peptide sets: subtype A (92UG37_A), subtype B (MN_B, 89.6_B and SF162_B), and subtype C (Chn19_C). The intensity of the induced cellular responses was measured by using pooled Env peptides; T-cell epitopes were identified by using matrix peptide pools and individual peptides. No significant differences in T-cell immune-response intensities were noted between CON6 and CON-S immunized BALB/c and C57BL/6 mice. In BALB/c mice, 10 and eight nonoverlapping T-cell epitopes were identified in CON6 and CON-S, whereas eight epitopes were identified in 92UG37_A and HXB2/BAL_B. In C57BL/6 mice, nine and six nonoverlapping T-cell epitopes were identified after immunization with CON6 and CON-S, respectively, whereas only four and three were identified in 92UG37_A and HXB2/BAL_B, respectively. When combined together from both mouse strains, 18 epitopes were identified. The group M artificial consensus env genes, CON6 and CON-S, were equally immunogenic in breadth and intensity for inducing humoral and cellular immune responses.
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Light transmission through a single subwavelength aperture in a silver film is examined with a novel input configuration comprising an annular laser beam of variable diameter that is prism-coupled to the back face of the silver. Transmission peaks driven by excitation of the back-face surface plasmon mode or by the aperture resonance itself are separately observed. For both cases, comparison of films with and without a front-face, circular grating implies significantly more efficient coupling from the aperture fields to the front-face surface plasmon than directly to free radiation. (c) 2007 Optical Society of America.
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Purpose: The aim of this work was to determine if volumetric modulated arc therapy (VMAT) plans, created for constant dose-rate (cdrVMAT) delivery are a viable alternative to step and shoot five-field intensity modulated radiation therapy (IMRT). Materials and methods: The cdrVMAT plans, inverse planned on a treatment planning system with no solution to account for couch top or rails, were created for delivery on a linear accelerator with no variable dose rate control system. A series of five-field IMRT and cdrVMAT plans were created using dual partial arcs (gantry rotating between 260° and 100°) with 4° control points for ten prostate patients with the average rectal constraint incrementally increased. Pareto fronts were compared for the planning target volume homogeneity and average rectal dose between the two techniques for each patient. Also investigated were tumour control probability and normal tissue complication probability values for each technique. The delivery parameters [monitor units (MU) and time] and delivery accuracy of the IMRT and VMAT plans were also compared. Results: Pareto fronts showed that the dual partial arc plans were superior to the five-field IMRT plans, particularly for the clinically acceptable plans where average rectal doses were less for rotational plans (p = 0·009) with no statistical difference in target homogeneity. The cdrVMAT plans had significantly more MU (p = 0·005) but the average delivery time was significantly less than the IMRT plans by 42%. All clinically acceptable cdrVMAT plans were accurate in their delivery (gamma 99·2 ± 1·1%, 3%3 mm criteria). Conclusions Accurate delivery of dual partial arc cdrVMAT avoiding the couch top and rails has been demonstrated.
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En 1992, la Cour suprême du Canada souligne l'importance de faire la distinction entre l'obligation principale de conseil qui est l'objet principal du contrat et l'obligation d'information qui est accessoire. L'obligation principale de conseil est reconnue à l'égard des professionnels des professions dites libérales à l'époque, comme les avocats et notaires dans un contrat de mandat. Par contre, l'évolution jurisprudentielle récente démontre que l'obligation de conseil ne se limite plus à l'objet principal du contrat, et que la notion de «professionnel» n'a plus le sens restrictif d'autrefois. Au Québec, l'obligation principale de conseil est reconnue dans un premier temps à l'égard des professionnels soumis au Code des professions, notamment avocats et notaires. On reconnaît aussi une telle obligation accessoire de conseil à l'égard d'autres personnes qui, bien qu'elles ne soient pas des «professionnels» au sens du Code des professions, exercent tout de même des activités de nature professionnelle. C'est le cas, par exemple, des courtiers en valeurs mobilières, des courtiers en assurances ou des institutions financières. D'ailleurs, une controverse semble régner dans le domaine bancaire sur l'étendue de l'obligation de conseil et d'information des institutions financières envers un client dans le cadre d'un contrat de prestation de services. Plus particulièrement, les tribunaux semblent partagés sur la reconnaissance ou non d'une obligation de conseil de la banque dans le cadre d'un emprunt. Certaines décisions sont à l'effet que seule une obligation d'information s'impose alors que d'autres préconisent le conseil. Afin d'élucider la confusion qui règne présentement en jurisprudence dans le domaine bancaire ainsi que dans le contrat de services et d'entreprise en général, il faut faire une étude jumelée de l'évolution de l'obligation de conseil accessoire et de l'obligation de conseil principale. Notre étude porte sur l'évolution jurisprudentielle qui tend vers une théorisation dans le contrat de services ou d'entreprise, de l'obligation de conseil qui devient alors une variante ou une intensité de l'obligation accessoire d'information. Par le fait même, on constate qu'une obligation de conseil principale semble également s'étendre à une catégorie plus large de professionnels. Dans ce cas, l'obligation de conseil est similaire, dans son fondement, au devoir de conseil du «professionnel» traditionnel, au sens du Code des professions. On constate alors que l'obligation principale de conseil n'est plus restreinte aux professionnels au sens classique du terme.
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White or Guinea yam (Dioscorea rotundata), grown for its underground tubers, is an important food in West Africa. Progress in yam breeding is constrained by variable flowering behaviour, making hybridization difficult. Yam clones may be dioecious, monoecious or hermaphrodite with variable sex ratios. The proportion of plants that flower and the flowering intensity also vary with season and location. The objective of the present work was to investigate whether variation in flowering behaviour was related to factors determining rate of development (photoperiod and temperature through sowing date, location and year) or growth (cumulative solar radiation and temperature). Sex ratios, the proportion of plants that had flower buds and open flowers, and the number of flowers or spikes was recorded in one male (TDr 131) and one female (TDr 99-9) clone of white yam grown in the field in Nigeria at three locations and at different sowing dates. Clone TDr 131 was uniformly male flowering, while clone TDr 99-9 exhibited a number of sex types with gynoecious, monoecious and trimonoecious plants observed. The proportion of flowering plants was low in both clones, averaging 0.34 in clone TDr 131 and 0.13 in clone TDr 99-9. Day of vine emergence had a significant and contrasting effect on the proportion of flowering plants and on flowering intensity in the two clones. In clone TDr 131, the proportion of flowering plants and flowering intensity declined with later vine emergence at all locations (r=0.43-0.53, P<0.05), whereas in clone TDr 99-9 the proportion of flowering plants increased with later emergence (r=0.46, P<0.01). In clone TDr 131, this response was strongly associated with warmer temperatures (r=0.49-0.50; P<0.05) and greater cumulative radiation (r=0.85-0.93; P<0.001) between vine emergence and flowering, rather than photoperiod at vine emergence. This suggests that flowering behaviour in the male clone TDr 131 is strongly influenced by factors that affect growth rather than development. Clone TDr 99-9, on the other hand, exhibited no clear relations between flowering and growth or developmental factors, though the proportion of flowering plants and flowering intensity was greatest at planting dates close to the longest day and at temperatures of 25-26 degrees C. This might suggest that flowering behaviour in clone TDr 99-9 is controlled by photothermal responses.
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Brazilian Campos grasslands are rich in species and the maintenance of its diversity and physiognomy is dependent on disturbance (e.g. fire and grazing) Nevertheless, studies about fire intensity and severity are inexistent. The present paper describes fire parameters, using 14 experimental burn plots in southern Brazil (30 degrees 02` to 30 degrees 04`S, and 51 degrees 06` to 51 degrees 09`W. 311masl). Two sites under different fire histories were chosen: frequently burned and excluded since six years. Experimental burning was performed during summer (2006-2007), when most burning takes place in these grasslands. The following parameters were measured: air temperature and moisture, vegetation height, wind speed, fuel (fine, coarse), fuel moisture, fire temperatures (soil level and at 50cm), ash, residuals, flame freight, fire duration: burning efficiency and fire intensity were later calculated. Fuel load varied from 0.39 to 1.44kg.m(-2). and correlated positively with both fire temperature and fire intensity. Fire temperatures ranged 47 to 537.5 degrees C. being higher in the excluded site Fire intensity was low compared to grassland elsewhere (36 5-319.5kW.m(-1)), differing significantly between sties Fine fuel was the variable that best explained fire intensity. The results on fire intensity and severity in Campos grasslands can be considered a pilot study, since plots were very small. However the data provided can help other researchers to get permission for experimentation using larger plots The results provide support for further studies about the effects of fire on grassland vegetation and for studies involving fire models and fire risk prediction