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Digitale Medien

Switchable fiber coupling using variable-focal-length microlenses (2001)

Smith, P. J. ; Taylor, C. M. ; McCabe, E. M.

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 72 (2001), S. 3132-3134

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ISSN: 1089-7623

Quelle: AIP Digital Archive

Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: An array of microlenses, with focal lengths that can be electrically varied, can control the coupling of light into a single mode fiber using an applied voltage. We have examined this technology with a view to the design of a confocal microlens/image-fiber endoscope. Maximum coupling to the fiber was found to occur over a voltage range of ∼1 V and over an axial range of 1 cm. Contrast ratios between minimum and maximum coupling of up to 30 dB were demonstrated. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1380391

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2

Digitale Medien

Experimental and numerical investigations of a hydrogen-assisted laser-induced materials transfer procedure (2000)

Toet, D. ; Smith, P. M. ; Sigmon, T. W.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 87 (2000), S. 3537-3546

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We present investigations of the mechanisms of a laser-induced transfer technique, which can be used for the spatially selective deposition of materials such as Si. This transfer is effected by irradiating the backside of a hydrogenated amorphous silicon film, deposited on a transparent substrate with an excimer laser pulse. The resulting release and accumulation of hydrogen at the film/substrate interface propels the silicon onto an adjacent receptor wafer. Time-resolved infrared transmission measurements indicate that the amorphous film is melted by the laser pulse and breaks into droplets during ejection. These droplets travel towards the receptor substrate and coalesce upon arrival. The transfer velocity increases as a function of fluence, the rate of increase dropping noticeably around the full melt threshold of the film. At this fluence, the transfer velocity reaches values of around 1000 m/s for typical films. Atomic force microscopy reveals that films transferred below the full melt threshold only partially cover the receptor substrate, while uniform, well-adhering films, which can be smoothed by subsequent laser irradiation, are obtained above it. Transfer of hydrogen-free Si films, on the other hand, does not occur until much higher fluences. The dynamics of the process have been simulated using a semiquantitative numerical model. In this model, hydrogen released from the melt front is instantaneously accumulated at the interface with an initial kinetic energy given by the melting temperature of Si and the enthalpy of solution. The resulting pressure accelerates the Si film, the dynamics of which are modeled using Newtonian mechanics, and the gas cools adiabatically as its kinetic energy is converted to the film's momentum. The results of the calculations are in good agreement with the experimental data. © 2000 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.372378

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3

Digitale Medien

Spatially selective materials deposition by hydrogen-assisted laser-induced transfer (2000)

Toet, D. ; Smith, P. M. ; Sigmon, T. W.

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 77 (2000), S. 307-309

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Si and Al lines were deposited on glass substrates using a transfer technique based on the explosive release of hydrogen from a hydrogenated amorphous Si film melted by a laser pulse. The Si lines have a minimum width of 4.5 μm and are well defined, while the Al lines are wider and less uniform. Analysis of time-resolved infrared transmission signals reveals that the lines do not break into droplets upon ejection, in contrast to the behavior of unpatterned films. This difference is attributed to the escape of hydrogen through the sides of the molten lines into the adjacent material. © 2000 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.126959

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4

Digitale Medien

Soils as carbon sinks: the global context (2004)

Smith, P.

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 20 (2004), S. 0

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ISSN: 1475-2743

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract. Soil carbon sequestration could meet at most about one-third of the current yearly increase in atmospheric CO2-carbon, but the duration of the effect would be limited, with significant impacts lasting only 20–50 years. Coupled with this limited duration, increases in population and per-capita energy demand mean that soil carbon sequestration could play only a minor role in closing the difference between predicted and target carbon emissions by 2100. However, if atmospheric CO2 concentrations are to be stabilized at reasonable levels (450–650 ppm), drastic reductions in carbon emissions will be required over the next 20–30 years. Given this, carbon sequestration should form a central role in any portfolio of measures to reduce atmospheric CO2 concentrations over this crucial period, while new energy technologies are developed and implemented. International agreements, such as the Kyoto Protocol, encourage soil carbon sequestration and could be used to formulate soil carbon sequestration polices. Such policies need to take account of other environmental impacts as well as political, economic and societal needs, so that they form part of a raft of measures encouraging sustainable development. Of the carbon sequestration options available, those of a ‘win–win’ nature, that is, those that increase carbon stocks at the same time as improving other aspects of the environment, and those that protect or enhance existing stocks (‘no regrets’ implementation) show the greatest promise in meeting these goals.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1475-2743.2004.tb00361.x

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Digitale Medien

Meeting the UK's climate change commitments: options for carbon mitigation on agricultural land (2000)

Smith, P. ; Powlson, D.S. ; Smith, J.U. ; [weitere]

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 16 (2000), S. 0

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ISSN: 1475-2743

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract. Under the Kyoto Protocol, the European Union is committed to an 8% reduction in CO2 emissions, compared to baseline (1990) levels, during the first commitment period (2008–2012). However, within the overall EU agreement, the UK is committed to a 12.5% reduction. In this paper, we estimate the carbon mitigation potential of various agricultural land-management strategies (Kyoto Article 3.4) and examine the consequences of UK and European policy options on the potential for carbon mitigation.We show that integrated agricultural land management strategies have considerable potential for carbon mitigation. Our figures suggest the following potentials (Tg yr−1) for each scenario: animal manure, 3.7; sewage sludge, 0.3; cereal straw incorporation, 1.9; no-till farming, 3.5; agricultural extensification, 3.3; natural woodland regeneration, 3.2 and bioenergy crop production, 4.1. A realistic land-use scenario combining a number of these individual management options has a mitigation potential of 10.4 Tg C yr−1 (equivalent to about 6.6% of 1990 UK CO2-carbon emissions). An important resource for carbon mitigation in agriculture is the surplus arable land, but in order to fully exploit it, policies governing the use of surplus arable land would need to be changed. Of all options examined, bioenergy crops show the greatest potential. Bioenergy crop production also shows an indefinite mitigation potential compared to other options where the potential is infinite.The UK will not attempt to meet its climate change commitments solely through changes in agricultural land-use, but since all sources of carbon mitigation will be important in meeting these commitments, agricultural options should be taken very seriously.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1475-2743.2000.tb00162.x

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6

Digitale Medien

Using dynamic simulation models and the ‘Dot-to-Dot’ method to determine the optimum sampling times in field trials (2002)

Smith, J.U. ; Smith, P. ; Coleman, K. ; [weitere]

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 18 (2002), S. 0

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ISSN: 1475-2743

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract. Dynamic simulation models are increasingly used in environmental and agricultural science. Here we present a method that allows models to be used to determine optimum timing of sampling for field trials. The model is used to decide when to concentrate sampling effort before the field trial begins. The model chosen to design sampling strategy should include an appropriately sensitive description of all processes that influence measurements significantly. The simulation is run, using predicted weather data, to generate the full time series before the trial begins. Every point in the simulation is considered initially to be a potential sampling point. The potential error due to not including a measurement at each point is calculated using the ‘dot-to-dot’ method of b10Smith et al. (2002) by omitting simulated values consecutively. The calculated potential error provides a measure of the priority that should be given to sampling at each point. Where the error introduced by omitting the simulated value exceeds an acceptable error, the value at the last discernible time step should be measured so that all statistically significant changes in the system can be observed. The output from the calculation is a plan of sampling times needed to capture all statistically significant events that are likely to occur over the course of the trial.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1475-2743.2002.tb00254.x

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7

Digitale Medien

Managing field margins for biodiversity and carbon sequestration: a Great Britain case study (2004)

Falloon, P. ; Powlson, D. ; Smith, P.

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 20 (2004), S. 0

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ISSN: 1475-2743

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract. Field margins are a valuable resource in the farmed landscape, providing numerous environmental benefits. We present a preliminary analysis of the carbon mitigation potential of different field margin management options for Great Britain, calculated using data from long-term experiments and literature estimates. The carbon sequestration potential of the individual options investigated here varies from 0.1 to 2.4% of 1990 UK CO2-C emissions, or 0.7–20% of the Quantified Emission Limitation Reduction Commitment (QELRC). The scenarios investigated covered three possible margin widths and options for the management of margins at each width (viz. grass strips, hedgerows and tree strips). Scenarios involving margin widths of 2, 6 or 20 m would require approximately 2.3, 6.7 or 21.3% of the total arable area of Great Britain, respectively. Scenarios including tree strips offered the greatest potential for carbon sequestration, since large amounts would be accumulated in above-ground biomass in addition to that in soil. We also accounted for the possible impacts of changed land management on trace gas fluxes, which indicated that any scenario involving a change from arable to grass strip, hedgerow or tree strip would significantly reduce N2O emissions, and thus further increase carbon mitigation potential. There would also be considerable potential for including the scenarios investigated here with other strategies for the alternative management of UK arable land to identify optimal combinations. We assumed that it would take 50–100 years for soil carbon to reach a new equilibrium following a land use change. More detailed analyses need to be conducted to include environmental benefits, socioeconomic factors and the full system carbon balance.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1475-2743.2004.tb00364.x

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8

Digitale Medien

Monitoring and verification of soil carbon changes under Article 3.4 of the Kyoto Protocol (2004)

Smith, P.

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 20 (2004), S. 0

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ISSN: 1475-2743

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract. The Marrakech Accords allow biospheric carbon sinks and sources to be included in attempts to meet emission reduction targets for the first commitment period of the Kyoto Protocol. Forest management, cropland management, grazing land management and re-vegetation are allowable activities under Article 3.4 of the Kyoto Protocol. Soil carbon sinks and sources can therefore be included under these activities. The Kyoto Protocol states that sinks and sources of carbon should be accounted for ‘taking into account uncertainties, transparency in reporting, verifiability’. At its most stringent, verifiability would entail the sampling of each geo-referenced piece of land subject to an Article 3.4 activity at the beginning and end of a commitment period, using a sampling regime that gives adequate statistical power. Soil and vegetation samples and records would be archived and the data from each piece of land aggregated to produce a national figure. Separate methods would be required to deliver a second set of independent verification data. Such an undertaking at the national level would be prohibitively expensive. At its least stringent, verifiability would entail the reporting of areas under a given practice (without geo-referencing) and the use of default values for a carbon stock change for each practice, to infer a change for all areas under that practice. A definition of verifiability between these extremes would allow simple methods, such as those derived from IPCC default values for CO2 fluxes from soil, to be used for estimating changes in soil carbon. These may enable low-level verifiability to be achieved by most parties by the beginning of the first commitment period (2008–2012).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1475-2743.2004.tb00367.x

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9

Digitale Medien

Accounting for changes in soil carbon under the Kyoto Protocol: need for improved long-term data sets to reduce uncertainty in model projections (2003)

Falloon, P. ; Smith, P.

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 19 (2003), S. 0

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ISSN: 1475-2743

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract. Soils can be used as a biospheric sink for carbon under Article 3.4 of the Kyoto Protocol and parties are able to use agricultural soil carbon sinks to contribute towards carbon emission reduction targets. This should be done ‘taking into account uncertainties, transparency in reporting, and verifiability’. Models are often tested against data sets of long-term changes in soil organic carbon (SOC), but most data sets have only mean SOC values available at each sample date, with no estimates of error about the mean. We show that when using data sets that do not include estimates of error about the mean, it is not possible to reduce the error (root mean squared error) between modelled and measured values below 6.8–8.5%, even with site-specific model calibration. Equivalent errors for model runs using regional default input values are 12–34%. Using error as an indicator of the certainty that can be attached to model projections, we show that a significant reduction in uncertainty is needed for Kyoto accounting. Uncertainties for modelling during the first Kyoto Commitment Period could be reduced by better replication of soil measurements at benchmark sites. This would allow model error to be separated from measurement error, which would allow more comprehensive model testing and, ultimately, more certainty to be attached to model predictions.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1475-2743.2003.tb00313.x

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10

Digitale Medien

Revised estimates of the carbon mitigation potential of UK agricultural land (2000)

Smith, P. ; Milne, R. ; Powlson, D.S. ; [weitere]

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 16 (2000), S. 0

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ISSN: 1475-2743

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract. The soil sequestration components of recent estimates of the carbon mitigation potential of UK agricultural land were calculated on the basis of a percentage change to the soil carbon stock present in the soil. Recent data suggest that the carbon stock of soil in UK arable land has been overestimated, meaning that potential soil carbon sequestration rates were also overestimated. Here, we present a new estimate of the carbon stock in UK arable land, and present revised estimates for the carbon mitigation potential of UK agricultural land. The stock of soil organic carbon in UK arable land (0–30 cm) is estimated to be 562 Tg, about half of the previous estimate. Consequently, the soil carbon sequestration component of each mitigation option is reduced by about half of previously published values. Since above-ground carbon accumulation and fossil fuel carbon savings remain unchanged by these new soil carbon data, options with a significant non-soil carbon mitigation component are reduced by less than those resulting from soil carbon sequestration alone. The best single mitigation option (bioenergy crop production on surplus arable land) accounts for 3.5 Tg C yr−1, (2.2% of the UK's 1990 CO2-carbon emissions), whilst an optimal combined land-use mitigation option accounts for 6.1 Tg C yr−1 (3.9% of the UK's 1990 CO2-carbon emissions). These revised figures suggest that through manipulation of arable land, the UK could, at best, meet 49% of its contribution to the EU's overall Kyoto CO2-carbon emission reduction target (8% of 1990 emissions), and 31% of the greater target accepted by the UK (12.5%). Even these reduced estimates show a significant carbon mitigation potential for UK arable land.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1475-2743.2000.tb00214.x

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