scholarly journals Carbon storage change and δ13C transitions of peat columns in a partially forestry-drained boreal bog

2019 ◽  
Vol 447 (1-2) ◽  
pp. 365-378 ◽  
Author(s):  
Hannu Nykänen ◽  
Antti J. Rissanen ◽  
Jukka Turunen ◽  
Teemu Tahvanainen ◽  
Heikki Simola
Keyword(s):  
Surface Layer ◽  
Bulk Density ◽  
Carbon Storage ◽  
Thin Surface Layer ◽  
Stratigraphic Correlation ◽  
Humification Index ◽  
Ash Layer ◽  
Peat Profile ◽  
Storage Change ◽  
Isotope Analyses

Abstract Background and aims In forestry-drained peatlands, drying leads to changes in C cycling which could affect peat δ13C. Furthermore, the δ13C profile of the entire peat column may reveal effects of earlier climatic periods. Methods We measured peat δ13C and C inventories in adjacent peat profiles, two collected from undrained and two from the drained side of a bog that was partially ditch-drained 37 years earlier. The cores were sliced into 10-cm subsamples for analyses; matching of the profiles based on surface levelling, peat stratigraphic correlation and a horizontal ash layer found in both profiles. Results Surface subsidence of 30 cm was observed in the dried site and the uppermost 160 cm in the undrained site contained an excess of 5.9 kg m−2 of C compared with the corresponding strata of the ditch-drained site. The δ13C values increased but markedly only in the thin surface layer of the drained site, indicating low δ13C of the missing C (ca. –30‰). In the deeper strata, dating to Mid-Holocene, high dry bulk density, C%, N%, humification index and low C/N ratio were connected to low δ13C of peat. Conclusions Drainage of 37 years increased δ13C values in the upper peat profile of the drained bog and led to the selective loss of 13C depleted C. Results indicate that C balance studies can be aided by C isotope analyses. Low δ13C values in the peat profile indicate the existence of a wet fen stage during the moist and warm period during Mid-Holocene.

Application of a convolutional neural network in permeability prediction: A case study in the Jacksonburg-Stringtown oil field, West Virginia, USA

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. B363-B373 ◽  
Author(s):  
Zhi Zhong ◽  
Timothy R. Carr ◽  
Xinming Wu ◽  
Guochang Wang
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Regression Model ◽  
Bulk Density ◽  
Carbon Storage ◽  
Oil Field ◽  
Well Logs ◽  
Storage Site ◽  
Core Samples ◽  
Permeability Prediction

Permeability is a critical parameter for understanding subsurface fluid flow behavior, managing reservoirs, enhancing hydrocarbon recovery, and sequestering carbon dioxide. In general, permeability is measured in the laboratory based on subsurface core samples, calculated from well logs or estimated from well tests. However, laboratory measurements and well tests are expensive, time-consuming, and usually limited to a few core samples or wells in a hydrocarbon field or carbon storage site. Machine-learning techniques are good options for generating a rapid, robust, and cost-effective permeability prediction model because of their strengths to recognize the potential interrelationships between input and output variables. Convolutional neural networks (CNN), as a good pattern recognition algorithm, are widely used in image processing, natural language processing, and speech recognition, but are rarely used with regression problems and even less often in reservoir characterization. We have developed a CNN regression model to estimate the permeability in the Jacksonburg-Stringtown oil field, West Virginia, which is a potential carbon storage site and enhanced oil recovery operations field. We also evaluate the concept of the geologic feature image, which is converted from geophysical well logs. Five variables, including two commonly available conventional well logs (the gamma rays [GRs] and bulk density) and three well-log-derived variables (the slopes of the GR and bulk density curves, and shale content), are used to generate a geologic feature image. The CNN treats the geologic feature image as the input and the permeability as the desired output. In addition, the permeability predicted using traditional backpropagation artificial neural networks, which are optimized by genetic algorithms and particle swarm optimization, is compared with the permeability estimated using our CNN. Our results indicate that the CNN regression model provides more accurate permeability predictions than the traditional neural network.

Features of Wear of Abrasive Grains Depending on Microcuttings Speed of Steels

2016 ◽  
Vol 674 ◽  
pp. 189-194 ◽  
Author(s):  
Margarita A. Skotnikova ◽  
Galina V. Tsvetkova ◽  
Nikolay A. Krylov ◽  
Evgeniy K. Ivanov ◽  
Viktoriy V. Medvedeva ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Surface Layer ◽  
Thin Surface Layer ◽  
Abrasive Grains ◽  
Microscopy Method ◽  
Scanning Electron Microscopy Method ◽  
Electron Microscopy Method ◽  
Scanning Electron ◽  
Alloy Titanium

In this article by the example of two abrasive materials from oxide of aluminum and nitride of boron, the processes developing in a thin surface layer between a grain of abrasive and the material, processed by microcutting with speeds of 40 and 160 m/s, the preforms from armko-iron, steels R18, 45, H18N10T and alloy titanium VT6 are investigated, using the scanning electron microscopy method.

The Photo-Oxidation of Polypropylene Monofilaments

1977 ◽  
Vol 47 (6) ◽  
pp. 423-428 ◽  
Author(s):  
A. Garton ◽  
D. J. Carlsson ◽  
P. Z. Sturgeon ◽  
D. M. Wiles
Keyword(s):  
Mechanical Properties ◽  
Surface Layer ◽  
Uv Irradiation ◽  
Oxidation Product ◽  
Uv Exposure ◽  
Thin Surface Layer ◽  
Elongation At Break ◽  
Photo Oxidation ◽  
Oriented Samples ◽  
Oriented Polypropylene

The elongation-at-break of highly-oriented polypropylene monofilaments is much less affected by photo-oxidation build-up than undrawn or partially-oriented filaments. This appears to result from the very poor lateral cohesion of the fibril bundles in the highly-oriented filament, limiting restructuring and cracking to a thin surface layer. For less-oriented samples photo-oxidation-induced restructuring of the surface layer results in deep cracks that can propagate under stress, greatly embrittling the sample. Areas of filaments cold drawn by, for example, bending or stretching deteriorate very rapidly on uv irradiation as a result of strain-induced chromophore formation, and fracture occurs first at these points. Oxidation-product levels (either hydroperoxide or carbonyl) are shown to be an unreliable index of the extent of deterioration of mechanical properties resulting from uv exposure.

Effect of Weather, Age, and Cyclic Pressurizations on Structural Performance of Acrylic Plastic Spherical Shells Under External Pressure Loading

1982 ◽  
Vol 104 (2) ◽  
pp. 190-200
Author(s):  
J. D. Stachiw ◽  
R. B. Dolan
Keyword(s):  
Surface Layer ◽  
Critical Pressure ◽  
External Pressure ◽  
Thin Surface Layer ◽  
Ambient Atmosphere ◽  
Plastic Shell ◽  
Spherical Shells ◽  
Acrylic Plastic ◽  
Operational Life ◽  
Physical And Chemical

Weathering, aging, and cyclic application of stresses to acrylic plastic degrades its physical properties. The rate of degradation must be known if the useful life of load-carrying acrylic structures is to be predicted with accuracy. Physical and chemical tests conducted by the authors on thick spherical shells indicate that the weathering affects only a thin surface layer of material, which after 10 years is still less than 0.020 in. thick. Similarly, pollutants in the ambient atmosphere of the pressure chamber affect the surface layer of the spherical shell facing the interior of the chamber. The physical and chemical properties of the thin surface layer affected by weathering differed significantly from those in the middle of 2.5-in.-thick Plexiglas G plate; the decrease in properties was: 40 percent in tensile elongation, 34 percent in flexure strength, 21 percent in tensile strength, and 79 percent in molecular weight. Since the interior body of the thick plastic shell is not affected by weathering or chemical attack and the affected surface layers are very thin, the ability of the shell to carry compressive loads is not significantly diminished after 10 years of service. Only an 11 percent decrease of critical pressure was observed in spherical shells with thickness of 1 in. subjected to 10 years of weathering and 2000 pressure cycles of 8 hour duration each to 30 percent of its original critical pressure. Based on the preceding data it appears safe to extend the operational life from 10 to 20 years of all acrylic plastic spherical shells with bearing surfaces normal to spherical surface designed on the basis of ANSI/ASME PVHO-1 Safety Standard for external pressure service.

Scattering of a Love Wave by the Edge of a Thin Surface Layer

1975 ◽  
Vol 42 (4) ◽  
pp. 842-846 ◽  
Author(s):  
D. A. Simons
Keyword(s):  
Boundary Condition ◽  
Surface Layer ◽  
Reflection Coefficient ◽  
Scattered Field ◽  
Love Wave ◽  
Thin Surface Layer ◽  
Antiplane Strain ◽  
Power Flux ◽  
Power Reflection Coefficient

The antiplane strain problem of the scattering of an incident Love wave by the edge of a thin surface layer is solved. The effect of the layer is represented by a boundary condition applied at the surface of the substrate. In addition, the condition of vanishing traction on the edge of the layer is explicitly enforced. At large distances from the layer’s edge the scattered field is found to consist of a reflected Love wave and a radiated wave. The power flux identity for the problem is derived, and values of the power reflection coefficient are computed. The power flux identity is verified numerically, and the discrepancy which would arise from a failure to satisfy the condition of vanishing traction on the layer’s edge is evaluated.

Abnormal Structural Strength of Topocomposites

2012 ◽  
Vol 560-561 ◽  
pp. 338-343 ◽  
Author(s):  
Nikolay A. Voronin
Keyword(s):  
Surface Layer ◽  
Bearing Capacity ◽  
Half Space ◽  
Contact Interaction ◽  
Solid Body ◽  
Mechanical Characteristics ◽  
Structural Strength ◽  
Layered Material ◽  
Thin Surface Layer ◽  
Layer Coating

The mechanics of contact interaction of rigid spherical indenter with two-layer elastic - plastic half-space, simulating a surface of a solid body with a thin surface layer is considered. Analytical dependences of critical indentation and bearing capacity on mechanical characteristics of materials of a base and a coating, and as well as that for thickness of top layer (coating) in all region of possible thickness are received and analyzed. Existence of regions of the abnormal structural strength allowing the surface layered material to identify unequivocally as a topocomposite is shown. Theoretical dependences were verified by a final elements method.

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