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  • Wiley  (71)
  • American Association for the Advancement of Science
  • 2010-2014  (71)
  • 1955-1959  (4)
  • 1
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    Effect of Hydrothermally Carbonized Char Application on Trace Gas Emissions from Two Sandy Soil Horizons (2014)
    Wiley
    Details
    Publikationsdatum: 2014-09-01
    Print ISSN: 0047-2425
    Digitale ISSN: 1537-2537
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Publiziert von Wiley
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
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    Development of Electrical Discharge Machinable ZTA Ceramics with 24 vol% of TiC,TiN,TiCN,TiB2 and WC as Electrically Conductive Phase (2012)
    Wiley
    Details
    Publikationsdatum: 2012-04-15
    Beschreibung: In order to develop ED-machinable ceramics with high strength, toughness and wear resistance, ZTA was chosen as matrix material. A dispersion of 24 vol% electrically conductive phase ( TiC , TiN , TiCN , TiB 2 and WC ) was added. These composites were hot pressed for 1 h at 60 MPa and temperatures ranging from 1475°C to 1550°C. Mechanical and electrical properties were investigated. The influence of the electrically conductive phase on the surface quality after EDM was analyzed. The mechanical properties and machining quality were found to depend significantly on the type of conductive phase added. Machining of a complex shaped ZTA- TiC component was demonstrated.
    Print ISSN: 1546-542X
    Digitale ISSN: 1744-7402
    Thema: Maschinenbau
    Publiziert von Wiley
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  • 3
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    Analysis of a Compliant Mechanism for Positioning in the cm-Range (2012)
    Wiley
    Details
    Publikationsdatum: 2012-04-18
    Beschreibung: The kinematics and kinetics of a compliant mechanism are analyzed quasi-statically. The mechanism consists of a parallelkinematic (Biglide type) with the particular feature, that its revolute joints are implemented by flexure hinges. In the considered example the flexure hinges are uniform beams similar to leaf springs. The preliminary considerations with a rigid body system and by linear theory of elasticity result in an initial geometry. In order to predict the large displacement behavior more precisely the theory of Elastica is used. An optimization method is applied to solve the mechanism's state of deformation. It was found that some aspects can be approximated by a pseudo rigid body system, while others, namely the rotation, cannot be rendered. The decreased stiffness in the highly deformed operating state appears as key problem. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Digitale ISSN: 1617-7061
    Thema: Mathematik , Physik , Technik allgemein
    Publiziert von Wiley
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  • 4
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    Nitrogen fluxes during the initial stage of willows and poplars in short-rotation coppices (2012)
    Wiley
    Details
    Publikationsdatum: 2012-05-04
    Beschreibung: Among energy crops, short-rotation coppices (SRC) are recommended to provide renewable energy. Compared to annual crops, willows and poplars are regarded as plants with low requirements for nutrients, herbicides, pesticides, and soil maintenance. However, only little is known about N-fertilizer effects on SRC and the few studies are even inconsistent. Therefore, we studied the effects of N on yields of willows and poplars in a field experiment. The effects of N fertilization on nitrate leaching and nitrous oxide emissions from the loamy-sand soil were also measured. Cuttings of willows ( Salix viminalis clone Inger) and poplars ( Populus maximovizcii × P. nigra clone max 4) were planted on farmland in 2008. The experiment was arranged in a random block design with three levels of N fertilizer (0, 50, and 75 kg N ha –1 y –1 ). After 2 y, the trees were harvested for the first time. Fertilization did not affect the yields of willows or poplars. However, the application of 75 kg N ha –1 y –1 caused an average increase of N leaching in the willow and poplar plots of 25 kg N ha –1 y –1 and 40 kg N ha –1 y –1 , respectively. Emissions of N 2 O were increased by a maximum of only 0.2 kg N ha –1 y –1 . Further, the N fertilizer stimulated the growth of the weed biomass in case of the willow plots by 46% and of the weed N content by 52% ( r = 0.53). In conclusion, in the first 2 y, SRC could be produced in a more effective and environmentally friendly manner without mineral fertilizer.
    Print ISSN: 1436-8730
    Digitale ISSN: 1522-2624
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Publiziert von Wiley
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  • 5
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    The Role of Interannual Climate Variability in Controlling Solifluction Processes, Endalen, Svalbard (2011)
    Wiley
    Details
    Publikationsdatum: 2011-05-18
    Beschreibung: ABSTRACT A continuous record is presented of active layer processes at Endalen, Svalbard, over the period 2005–08. The monitored slope has a gradient of around 7° and in 2005, active layer depth was 94 cm, but this increased by around 14 cm over the next three years. The presence of an ice-rich transient layer proved highly significant in determining the timing and profiles of solifluction movement. Frost heaving was 4.2 cm in 2005–06, 6.6 cm in 2006–07 and 3.2 cm in 2007–08, but thaw settlement exceeded frost heave in each year, giving a net total ground surface lowering of 6.2 cm. In winter, segregation ice was concentrated within the upper and lower active layer, leaving the central parts ice-poor. During the summers of 2006 and 2008, thawing of the transient layer was associated with artesian pore pressures at 90 cm depth and basal soil shearing, but in 2007, when the thaw front failed to reach the ice rich basal zone, pore pressures during thaw were sub-hydrostatic and no basal shearing was observed. Solifluction shear strain during thaw settlement resulted in downslope surface displacements of 2.3 cm in 2005–06, 1.2 cm in 2006–07 and 1 cm in 2007–08. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 1045-6740
    Digitale ISSN: 1099-1530
    Thema: Geographie , Geologie und Paläontologie
    Publiziert von Wiley
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  • 6
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    Initiation of deep convection at marginal instability in an ensemble of mesoscale models: a case-study from COPS (2011)
    Wiley
    Details
    Publikationsdatum: 2011-01-07
    Beschreibung: The present study investigates the initiation of precipitating deep convection in an ensemble of convection-resolving mesoscale models. Results of eight different model runs from five non-hydrostatic models are compared for a case of the Convective and Orographically-induced Precipitation Study (COPS). An isolated convective cell initiated east of the Black Forest crest in southwest Germany, although convective available potential energy was only moderate and convective inhibition was high. Measurements revealed that, due to the absence of synoptic forcing, convection was initiated by local processes related to the orography. In particular, the lifting by low-level convergence in the planetary boundary layer is assumed to be the dominant process on that day. The models used different configurations as well as different initial and boundary conditions. By comparing the different model performance with each other and with measurements, the processes which need to be well represented to initiate convection at the right place and time are discussed. Besides an accurate specification of the thermodynamic and kinematic fields, the results highlight the role of boundary-layer convergence features for quantitative precipitation forecasts in mountainous terrain. Copyright © 2010 Royal Meteorological Society
    Print ISSN: 0035-9009
    Digitale ISSN: 1477-870X
    Thema: Geographie , Physik
    Publiziert von Wiley
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  • 7
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    Development of Electrical Discharge Machinable ZTA Ceramics with 24 vol% of TiC,TiN,TiCN,TiB2 and WC as Electrically Conductive Phase (2012)
    Wiley
    Details
    Publikationsdatum: 2012-03-14
    Beschreibung: In order to develop ED-machinable ceramics with high strength, toughness and wear resistance, ZTA was chosen as matrix material. A dispersion of 24 vol% electrically conductive phase ( TiC , TiN , TiCN , TiB 2 and WC ) was added. These composites were hot pressed for 1 h at 60 MPa and temperatures ranging from 1475°C to 1550°C. Mechanical and electrical properties were investigated. The influence of the electrically conductive phase on the surface quality after EDM was analyzed. The mechanical properties and machining quality were found to depend significantly on the type of conductive phase added. Machining of a complex shaped ZTA- TiC component was demonstrated.
    Print ISSN: 1546-542X
    Digitale ISSN: 1744-7402
    Thema: Maschinenbau
    Publiziert von Wiley
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
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    Influence of Particle Size and Single-Tube Diameter on Thermal Behavior of Fischer-Tropsch Reactors. Part II. Eggshell Catalysts and Optimal Reactor Performance (2011)
    Wiley
    Details
    Publikationsdatum: 2011-12-31
    Beschreibung: The optimal combination of particle and tube size for simulation of a single tube of a wall-cooled multitubular Fischer-Tropsch (FT) reactor with cobalt as catalyst was determined. The maximum size of the tubes, realized without temperature runaway, enhances with increasing particle size until an optimal value is reached, thereby improving the production rate of liquid fuels per tube. Reasons for this are that heat transfer to the cooled tube wall for a given tube size is considerably enhanced by increasing the particle size and that the influence of pore diffusion on the effective rate of FT synthesis gets stronger with rising particle size, which reduces the temperature sensitivity of the reactor and decreases the danger of a temperature runaway. The simulations indicate that the use of FT eggshell catalysts is not an option for fixed-bed reactors. The temperature sensitivity of the reactor is strongly enhanced, which decreases the maximum tube size and with that the productivity per tube. All these effects are valid in general for wall-cooled fixed-bed reactors. Respective criteria are presented. With cobalt as catalyst, the optimal combination of particle size and tube size for simulation of a single tube of a wall-cooled multitubular Fischer-Tropsch reactor was established. The maximum size of the tubes, realized without temperature runaway, is improved with increasing particle size until an optimal value is reached, thereby improving the production rate of liquid fuels per tube.
    Print ISSN: 0930-7516
    Digitale ISSN: 1521-4125
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Publiziert von Wiley
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  • 9
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    Influence of Particle Size and Single-Tube Diameter on Thermal Behavior of Fischer-Tropsch Reactors. Part I. Particle Size Variation for Constant Tube Size and Vice Versa (2011)
    Wiley
    Details
    Publikationsdatum: 2011-12-31
    Beschreibung: Simulation of a single tube of a wall-cooled multitubular Fischer-Tropsch (FT) reactor with a cobalt catalyst indicates that the reactor performance is improved by enlarging the catalyst particle diameter. This aspect is studied for variation of the particle size for a fixed tube diameter and vice versa. For a syngas conversion per pass of about 30 % as target and a typical industrially used single-tube diameter of 40 mm, a particle size of 〉 3 mm is appropriate with regard to a high production rate of higher hydrocarbons. For a particle diameter of 〈 3 mm, a temperature runaway can only be avoided by rather low cooling temperatures, and the target conversion cannot be reached. In addition, the pressure drop then gets rather high. The reasons for this behavior are: (i) the heat transfer to the cooled tube wall for a given tube size is considerably enhanced by increasing the particle size; (ii) the influence of pore diffusion on the effective rate gets stronger with rising particle size which decreases the danger of temperature runaway. Detailed simulation of the influence of the catalyst particle size on the behavior of a multitubular Fischer-Tropsch reactor with regard to syngas conversion and production rate of hydrocarbons per tube in a wall-cooled single tube with cobalt as catalyst indicates that the reactor performance is improved by enlarging the catalyst particle diameter. Reasons for this unexpected behavior are evaluated.
    Print ISSN: 0930-7516
    Digitale ISSN: 1521-4125
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Publiziert von Wiley
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  • 10
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    Interception of atmospheric fluxes by Arctic sea ice: Evidence from cosmogenic 7Be (2011)
    Wiley
    Details
    Publikationsdatum: 2011-12-28
    Beschreibung: The natural cosmogenic radionuclide 7Be (T1/2 = 53.4 d) is supplied to the surface ocean from the atmosphere and, in the Arctic Ocean, can be used as a tracer of the efficiency with which sea ice intercepts the atmospheric fluxes of chemical species and of the importance of ice as a transport mechanism for particulate matter and chemical species. Analyses of 7Be in samples of surface water, surface sea ice, water beneath the ice, sea ice sediments, and precipitation from the Eurasian Basin of the Arctic Ocean show that the fraction of sea ice coverage determines the amount of 7Be in the surface water. When sea ice coverage is 80%, the water column inventory drops to 58 ± 20 Bq m−2. The 7Be inventory in sea ice is 39 ± 23 Bq m−2, and mass balance calculations show that sea ice can intercept 30 ± 18% of the atmospheric flux of 7Be during the studied period. We suggest that other atmospherically transported contaminants should be similarly intercepted. 7Be in the ice also can be used to estimate that the annual transport and release of sediment to the ablation area of the Fram Strait is ∼500 g m−2, a value comparable to previously measured fluxes in sediment traps deployed in the area.
    Print ISSN: 0148-0227
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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