To “Volumetric wavefield recording and wave equation inversion for near‐surface material properties” (A. Curtis and J. O. A. Robertsson, GEOPHYSICS, 67, 1602–1611).

Geophysics ◽  
2003 ◽  
Vol 68 (2) ◽  
pp. 760-760 ◽  
Author(s):  
Andrew Curtis ◽  
Johan O. A. Robertsson
Keyword(s):  
Wave Equation ◽  
Material Properties ◽  
Surface Material ◽  
Near Surface

Nanomechanical Properties of Aluminum 390-T6 Rough Surfaces Undergoing Tribological Testing

2004 ◽  
Vol 126 (3) ◽  
pp. 573-582 ◽  
Author(s):  
Shaun R. Pergande ◽  
Andreas A. Polycarpou ◽  
Thomas F. Conry
Keyword(s):  
Surface Roughness ◽  
Material Properties ◽  
Bulk Material ◽  
Normal Load ◽  
Effective Elastic Modulus ◽  
Surface Microstructure ◽  
Surface Material ◽  
Surface Layers ◽  
Near Surface ◽  
Nanomechanical Properties

The nanoindentation technique was used to quantify nano-scale changes in material properties (effective elastic modulus and hardness) of Al390-T6 samples that have undergone tribological testing under a protocol in a high-pressure tribometer where the applied normal load was step-wise increased until failure by scuffing occurred. The test was highly repeatable, so additional tests were run to three intermediate fractions of the total-time-to-scuffing-failure, which provided data on the progressive wear of the surfaces preparatory to reaching the scuffed condition. The samples were engineering surfaces with significant surface roughness, nonhomogeneous surface microstructure and unknown, nonuniform surface layers. This study demonstrated that nanomechanical techniques can be extended to characterize the material properties of rough engineering surfaces. For the samples subjected to tribological testing, the material at the surface, and to approximately 60 nm below the surface, exhibited significantly higher hardness than the bulk material. Also, progressive wear of the surfaces resulted in a corresponding weakening of the near-surface material below the surface to a depth of 60 nm, while the hardness of material below the 60 nm depth remained relatively unchanged. The hardness data for the scuffed samples showed a large amount of scatter in the data, indicating that the surface is not homogeneous and that the protective surface layer is removed, at least at some points on the surface.

Volumetric wavefield recording and wave equation inversion for near‐surface material properties

Geophysics ◽  
2002 ◽  
Vol 67 (5) ◽  
pp. 1602-1611 ◽  
Author(s):  
Andrew Curtis ◽  
Johan O. A. Robertsson
Keyword(s):  
Wave Equation ◽  
Material Properties ◽  
Surface Condition ◽  
Elastic Wave Equation ◽  
Wave Type ◽  
Near Surface ◽  
The Earth ◽  
Spatial Derivatives ◽  
Seismic Wavefield ◽  
Derivatives Of

“Volumetric recording” of the seismic wavefield implies that the local receiver group or array approximately encloses a volume of the earth. We show how volumetric recording can be used to measure several spatial derivatives of the wavefield. By making use of the full elastic wave equation, the free surface condition on elastic wavefields, and derivative centering techniques analagous to Lax‐Wendroff corrections used in synthetic finite‐difference modeling, these derivative estimates can be inverted for P‐ and S‐velocities in the near surface directly beneath the receiver group. The quantities estimated are the effective velocities of the P‐ and S‐components experienced by the wavefield at any point in time. Hence, the velocity estimates may vary with both wave type and wavelength. The estimates may be useful to aid statics estimation and are exactly the effective velocities required for separation of the wavefield into P‐ and S‐, and up‐ and down‐going components.

scholarly journals Impact of Enzymatic Degradation on the Material Properties of Poly(Ethylene Terephthalate)

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3885
Author(s):  
Teresa Menzel ◽  
Sebastian Weigert ◽  
Andreas Gagsteiger ◽  
Yannik Eich ◽  
Sebastian Sittl ◽  
...  
Keyword(s):  
Material Properties ◽  
Enzymatic Degradation ◽  
Ethylene Terephthalate ◽  
Compact Tension ◽  
Time Dependent ◽  
Material Failure ◽  
Near Surface ◽  
Poly Ethylene Terephthalate ◽  
Poly Ethylene ◽  
The Impact

With macroscopic litter and its degradation into secondary microplastic as a major source of environmental pollution, one key challenge is understanding the pathways from macro- to microplastic by abiotic and biotic environmental impact. So far, little is known about the impact of biota on material properties. This study focuses on recycled, bottle-grade poly(ethylene terephthalate) (r-PET) and the degrading enzyme PETase from Ideonella sakaiensis. Compact tension (CT) specimens were incubated in an enzymatic solution and thermally and mechanically characterized. A time-dependent study up to 96 h revealed the formation of steadily growing colloidal structures. After 96 h incubation, high amounts of BHET dimer were found in a near-surface layer, affecting crack propagation and leading to faster material failure. The results of this pilot study show that enzymatic activity accelerates embrittlement and favors fragmentation. We conclude that PET-degrading enzymes must be viewed as a potentially relevant acceleration factor in macroplastic degradation.

Formation and paleontologic recognition of structures caused by marine annelids

Paleobiology ◽  
1977 ◽  
Vol 3 (4) ◽  
pp. 389-403 ◽  
Author(s):  
Thomas E. Ronan
Keyword(s):  
Function Analysis ◽  
Structural Complexity ◽  
Soft Sediment ◽  
Water Interface ◽  
Surface Material ◽  
Near Surface ◽  
Sedimentary Structures ◽  
Biogenic Structures ◽  
Sediment Mixing ◽  
Feeding Function

Laboratory and field collected sediments were x-rayed to document the array of biogenic sedimentary structures produced by the burrowing and feeding behavior of six species of marine intertidal annelid (Glycera robusta, Nephtys caecoides, Pectinaria californiensis, Notomastus magnus, Eupolymnia crescentis, and Cirriformia spirabrancha). Polychaete burrows were found to vary greatly in structural complexity with both errant (N. magnus) and relatively sessile forms (C. spirabrancha) producing a variety of biogenic structures. Sediment mixing by the tentacle-feeding polychaete C. spirabrancha was observed by sequentially x-raying an experimental field enclosure stratified with an opaque substance. The experiment demonstrates that tentacle-feeding polychaetes can influence the topography of the sediment-water interface and transport substantial amounts of near surface material downward.Criteria by which fossil biogenic sedimentary structures, presumably produced by soft-bodied organisms, can be assigned a feeding function have been advanced by Walker (1972). Some of the assumptions inherent in feeding function analysis were applied, with varying degrees of success, to the biogenic structures of modern soft-sediment polychaetes.

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