A line source on a solid-solid interface—A study of the pseudo-Stoneley wave

1972 ◽  
Vol 62 (4) ◽  
pp. 1017-1027
Author(s):  
C. N. G. Dampney
Keyword(s):  
Closed Form ◽  
Line Source ◽  
Stoneley Wave ◽  
Elastic Media ◽  
Ray Theory ◽  
Interface Waves ◽  
Solid Interface ◽  
Direct Head ◽  
Fresh Insight ◽  
Insight Into

Abstract The displacement caused by a source on an interface between two solid semi-infinite elastic media presents an excellent study in interference between direct, head and interface waves. The solution herein derived provides fresh insight into the nature of pseudo-Stoneley interface waves. As well, the evolution of the head and direct waves is discerned as they move away from the interface. The technique used to solve the problem demonstrates the simplicity of using Sherwood's (1958) method with generalized ray theory. The displacement is simply expressed in a closed form which can be rapidly evaluated and is straightforward to interpret physically.

Propagation of elastic wave motion from an impulsive source along a fluid/solid interface

1959 ◽  
Vol 251 (1000) ◽  
pp. 455-523 ◽  
Keyword(s):  
Rayleigh Wave ◽  
Real Axis ◽  
Wave Velocity ◽  
Transverse Wave ◽  
Line Source ◽  
Interface Problem ◽  
Wave Form ◽  
Stoneley Wave ◽  
The Real ◽  
Solid Interface

Parts I and II of this report compare the experimentally observed pressure response for the impulse excited fluid/solid interface problem with that derived from a corresponding theoretical investigation. In the experiment a pressure wave is generated in the system by a spark and detected with a small barium titanate probe. The output of the probe is displayed on an oscilloscope and photographed. Two cases are investigated: one where the transverse wave velocity is lower than the longitudinal wave velocity of the fluid and the other where the transverse wave velocity is higher. Both of these observed responses are shown to agree even as to details of wave-form, with exact computations made for a delta-excited line source. This comparison is justified by making an approximate calculation for the decaying point source and showing that at these distances it does not differ appreciably from the delta-excited line source. In the case of low transverse wave velocity one finds, besides critically refracted P , direct, and reflected waves, a Stoneley type of interface wave. Although the emphasis in recent years has been towards minimizing the importance of Stoneley waves, the evidence here is that a Stoneley wave can be the largest contributor to a response curve. In the case of high transverse wave velocity the critically refracted P wave is smaller, and the Stoneley wave, though it tends to maintain a rather constant amplitude, becomes compressed in time and arrives very soon after the reflexion. Between the critically refracted P wave and the direct arrivals one finds both experimentally and theoretically a pressure build-up preceding the arrival time that might be expected for a critically refracted transverse wave. In part III this pressure build-up is investigated and found to consist of the superposition of three arrivals. The most prominent of these is a pseudo-Rayleigh wave. The others are the critically refracted transverse wave and the build-up to the later arriving Stoneley wave. Detailed investigation of the pseudo-Rayleigh wave shows it to have the velocity of a true Rayleigh wave which is independent of the existence of the fluid. Furthermore, it has the same retrograde particle motion as the true Rayleigh wave. However, it is radiating into the fluid as it progresses and therefore has many of the properties of a critically refracted arrival when measurements are made in the fluid. Mathematically it differs from the true Rayleigh wave in that its origin is not from a pole on the real axis of the plane of the variable of integration, but rather from a pole which lies on a lower Riemann sheet in the complex plane. In the high transverse wave velocity case this pole is not too far removed from the real axis and the imaginary part of the pole location might be interpreted as a decay factor. The real part, however, yields only approximately the velocity of the pseudo-Rayleigh wave, for the actual velocity as pointed out above is precisely that of the true Rayleigh wave velocity. The migration of this complex pole explains why such a pseudo-Rayleigh wave was not observed in parts I and II in the low transverse velocity case. The problem under discussion is intimately related to the classic work of Horace Lamb On the propagation of tremors over the surface of an elastic solid. One need make only a minor re-interpretation of the source function in order to compare directly the wave-forms (excluding of course the Stoneley wave contribution). Finally, a method is suggested for obtaining the solid rigidity of bottom sediments in watercovered areas from in situ measurements of the pseudo-Rayleigh wave and/or Stoneley wave velocities and arrival times

scholarly journals Closed-form time derivatives of the equations of motion of rigid body systems

2021 ◽  
Author(s):  
Andreas Müller ◽  
Shivesh Kumar
Keyword(s):  
Rigid Body ◽  
Closed Form ◽  
Multibody Systems ◽  
Equations Of Motion ◽  
Alternative Formulation ◽  
Dynamics Of Rigid Body ◽  
Control Forces ◽  
And Control ◽  
Derivatives Of ◽  
Insight Into

AbstractDerivatives of equations of motion (EOM) describing the dynamics of rigid body systems are becoming increasingly relevant for the robotics community and find many applications in design and control of robotic systems. Controlling robots, and multibody systems comprising elastic components in particular, not only requires smooth trajectories but also the time derivatives of the control forces/torques, hence of the EOM. This paper presents the time derivatives of the EOM in closed form up to second-order as an alternative formulation to the existing recursive algorithms for this purpose, which provides a direct insight into the structure of the derivatives. The Lie group formulation for rigid body systems is used giving rise to very compact and easily parameterized equations.

Stanlake Samkange’s Insufferable Zimbabwe: Distanciating Trauma from the Novel to Philosophy

2021 ◽  
Vol 8 (2) ◽  
pp. 158-176
Author(s):  
Jeanne-Marie Jackson
Keyword(s):  
Trauma Theory ◽  
The Novel ◽  
African Context ◽  
Independence Era ◽  
The Relationship ◽  
Fresh Insight ◽  
Insight Into

This article theorizes the Zimbabwean writer Stanlake Samkange’s turn from the novel to philosophy as an effort to circumvent the representational pressure exerted by African cultural traumatization. In breaking with the novel form to coauthor a philosophical treatise called Hunhuism or Ubuntuism in the same year as Zimbabwe achieves independence (1980), Samkange advances a comportment-based, deontological alternative to the psychic or subjective model of personhood that anchors trauma theory. Revisiting the progression from his most achieved novel, The Mourned One, to Hunhuism or Ubuntuism thus offers fresh insight into the range of options available to independence-era writers for representing the relationship between African individuality and collectivity. At the same time, it suggests a complementary and overlooked relationship between novelistic and philosophical forms in an African context.

scholarly journals Molecular architecture of the endocytic TPLATE complex

2021 ◽  
Vol 7 (9) ◽  
pp. eabe7999
Author(s):  
Klaas Yperman ◽  
Jie Wang ◽  
Dominique Eeckhout ◽  
Joanna Winkler ◽  
Lam Dai Vu ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Structural Approach ◽  
Eukaryotic Cells ◽  
Molecular Architecture ◽  
Membrane Proteome ◽  
Complex Assembly ◽  
Membrane Interaction ◽  
Structural Insight ◽  
Fresh Insight ◽  
Insight Into

Eukaryotic cells rely on endocytosis to regulate their plasma membrane proteome and lipidome. Most eukaryotic groups, except fungi and animals, have retained the evolutionary ancient TSET complex as an endocytic regulator. Unlike other coatomer complexes, structural insight into TSET is lacking. Here, we reveal the molecular architecture of plant TSET [TPLATE complex (TPC)] using an integrative structural approach. We identify crucial roles for specific TSET subunits in complex assembly and membrane interaction. Our data therefore generate fresh insight into the differences between the hexameric TSET in Dictyostelium and the octameric TPC in plants. Structural elucidation of this ancient adaptor complex represents the missing piece in the coatomer puzzle and vastly advances our functional as well as evolutionary insight into the process of endocytosis.

scholarly journals Metachronal waves in magnetic micro-robotic paddles for artificial cilia

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Matthew T. Bryan ◽  
Elizabeth L. Martin ◽  
Aleksandra Pac ◽  
Andrew D. Gilbert ◽  
Feodor Y. Ogrin
Keyword(s):  
Large Scale ◽  
Point Of Care ◽  
Hydrodynamic Response ◽  
Flow Speeds ◽  
Break Time ◽  
Large Scale Manufacture ◽  
Fresh Insight ◽  
Metachronal Waves ◽  
Insight Into ◽  
Phase Differences

AbstractBiological cilia generate fluid movement within viscosity-dominated environments using beating motions that break time-reversal symmetry. This creates a metachronal wave, which enhances flow efficiency. Artificially mimicking this behaviour could improve microfluidic point-of-care devices, since viscosity-dominated fluid dynamics impede fluid flow and mixing of reagents, limiting potential for multiplexing diagnostic tests. However, current biomimicry schemes require either variation in the hydrodynamic response across a cilia array or a complex magnetic anisotropy configuration to synchronise the actuation sequence with the driving field. Here, we show that simple modifications to the structural design introduce phase differences between individual actuators, leading to the spontaneous formation of metachronal waves. This generates flow speeds of up to 16 μm/s as far as 675 μm above the actuator plane. By introducing metachronal waves through lithographic structuring, large scale manufacture becomes feasible. Additionally, by demonstrating that metachronal waves emerge from non-uniformity in internal structural mechanics, we offer fresh insight into the mechanics of cilia coordination.

A Fresh Insight into Film Morphology Measurement Techniques for Advanced Ulsi Manufacturing

1993 ◽  
Vol 309 ◽  
Author(s):  
Seshadri Ramaswami
Keyword(s):  
Grain Size ◽  
Integrated Circuit ◽  
Measurement Techniques ◽  
Film Morphology ◽  
Integrated Circuit Fabrication ◽  
Circuit Fabrication ◽  
Non Destructive ◽  
Fresh Insight ◽  
Insight Into

AbstractA laser based non-destructive technique has been used to study the morphology of sputterdeposited aluminum alloy films. The data emanating from the Therma-wave Imager that makes use of this principle, has been correlated with reflectivity, grain size and micro-roughness of the film. In addition, through the use of a case study, this paper demonstrates the utility of this application as an in-line monitor in an integrated circuit fabrication line.

An Annotated Edition of Chaucer Belonging to Stephan Batman

The Library ◽  
2021 ◽  
Vol 22 (2) ◽  
pp. 217-224
Author(s):  
Conor Leahy
Keyword(s):  
Sixteenth Century ◽  
Reading Practices ◽  
Line Drawings ◽  
Annotated Edition ◽  
Medieval Chronicles ◽  
Fresh Insight ◽  
Insight Into

Abstract This article introduces a copy of The Woorkes of Geffrey Chaucer (1561) formerly belonging to the writer, cleric, limner, and book-collector Stephan Batman (c. 1542–1584). The volume is currently held at the Guildhall Library (SR 2.3.3), and contains Batman’s annotations and manicules throughout the text. It also features a 28-line poem in Batman’s hand, a short booklist of medieval chronicles, and five line drawings. The book thus offers a fresh insight into the reading practices of one of the most industrious English antiquaries of the sixteenth century, and sheds new light on Chaucer’s sixteenth-century reception.

Zakir Naik and His Audiences: A Case Study of Srinagar, Kashmir

2018 ◽  
Vol 7 (2) ◽  
pp. 203-222
Author(s):  
Raoof Mir
Keyword(s):  
Social Media ◽  
Cultural Studies ◽  
Jammu And Kashmir ◽  
Or Groups ◽  
Indian State ◽  
Fresh Insight ◽  
Insight Into ◽  
Religious Worldviews

Most literature on Mumbai-based Muslim tele-Islamicist Zakir Naik offers an organizational, biographical and ideological profile. This approach has concealed the symbolic significance attached to Naik by his audiences. This paper attempts to explore not only who and what Naik is, but how and where he is located. By incorporating ethnographic and cultural studies approaches, this paper offers fresh insight into Naik and his methods of communicating religion. Taking Srinagar, a city in the Indian state of Jammu and Kashmir, as an ethnographic site, this paper explores how Muslim individuals or groups interpret Naik in relation to their religious worldviews. The articulation of Islam by Zakir Naik through media platforms such as television and social media has contributed to a religious trend in Kashmir, in which people have discovered new ways to think about themselves and to participate in discourses about religion that would have been unthinkable a few decades ago.

A Closed Form Solution for Flow During the Vacuum Assisted Resin Transfer Molding Process

1999 ◽  
Vol 122 (3) ◽  
pp. 463-475 ◽  
Author(s):  
K-T. Hsiao ◽  
R. Mathur ◽  
S. G. Advani ◽  
J. W. Gillespie, ◽  
B. K. Fink
Keyword(s):  
Closed Form ◽  
Scaling Laws ◽  
Resin Transfer Molding ◽  
Closed Form Solution ◽  
Form Solution ◽  
Flow Front ◽  
Molding Process ◽  
Transfer Molding ◽  
Front Region ◽  
Insight Into

A closed form solution to the flow of resin in vacuum assisted resin transfer molding process (VARTM) has been derived. VARTM is used extensively for affordable manufacturing of large composite structures. During the VARTM process, a highly permeable distribution medium is incorporated into the preform as a surface layer. During infusion, the resin flows preferentially across the surface and simultaneously through the preform giving rise to a complex flow front. The analytical solution presented here provides insight into the scaling laws governing fill times and resin inlet placement as a function of the properties of the preform, distribution media and resin. The formulation assumes that the flow is fully developed and is divided into two regimes: a saturated region with no crossflow and a flow front region where the resin is infiltrating into the preform from the distribution medium. The flow front region moves with a uniform velocity. The law of conservation of mass and Darcy’s Law for flow through porous media are applied in each region. The resulting equations are nondimensionalized and are solved to yield the flow front shape and the development of the saturated region. It is found that the flow front is parabolic in shape and the length of the saturated region is proportional to the square root of the time elapsed. The results thus obtained are compared to data from full scale simulations and an error analysis of the solution was carried out. It was found that the time to fill is determined with a high degree of accuracy while the error in estimating the flow front length, d, increases with a dimensionless parameter ε=K2xxh22/K2yyd2. The solution allows greater insight into the process physics, enables parametric and optimization studies and can reduce the computational cost of full-scale 3-dimensional simulations. A parametric study is conducted to establish the sensitivity of flow front velocity to the distribution media/preform thickness ratio and permeabilities and preform porosity. The results provide insight into the scaling laws for manufacturing of large scale structures by VARTM. [S1087-1357(00)02002-5]

Manipulation of the immune response in parasitic infections

Parasitology ◽  
1984 ◽  
Vol 88 (4) ◽  
pp. 665-675
Author(s):  
J.G. Howard
Keyword(s):  
Immune Response ◽  
Inbred Mouse ◽  
Lymphocyte Subset ◽  
Mouse Strains ◽  
Parasitic Infections ◽  
Research Experience ◽  
Relevant Research ◽  
Fresh Insight ◽  
Insight Into

The following brief survey considers various manoeuvres which can be applied to manipulate the immune response to parasitic infectionsin vivo. The examples quoted largely concern malaria, babesiosis, schistosomiasis and leishmaniasis, predominantly in inbred mouse strains. Since my own relevant research experience has been restricted to leishmaniasis, this will receive undue emphasis, although it does illustrate particularly well points I wish to stress. The types of intervention described do not all provide the precision of interpretation with which they are sometimes credited. Thus, effects of immunosuppression or T-cell depletion alone can usually only implicate the specific immune response (in its broad sense) in shaping the natural history and outcome of an infection or in underlying the effect of prophylactic immunization. Nevertheless, more precise delineation of lymphocyte subset involvement can be obtained by cell replacement studies in some of these models or by exclusion of antibody. The outcomes of these approaches have been (or are) predictable in most cases. More fascinating, however, are the various instances which will be stressed where totally unpredicted and contrary observations have been made which led (or may lead) to fresh insight into the disease. These serendipitous findings illustrate at the same time the value of applying the manoeuvres, even though they imply that the logical immunologist cannot yet always outsmart the parasite by design.

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