Realization of In-Plane p-n Junctions with Continuous Lattice of a Homogeneous Material

Non-uniform ion-thinning of heterogenous material structures has constituted a fundamental difficulty in preparation of specimens for transmission electron microscopy (TEM). A variety of corrective procedures have been developed and reported for reducing or eliminating the effect. Some of these techniques are applicable to any non-homogeneous material system and others only to unidirectionalfy heterogeneous samples. Recently, a procedure of the latter type has been developed which is mainly based on a new motion profile for the specimen rotation during ion-milling. This motion profile consists of reversing partial revolutions (RPR) within a fixed sector which is centered around a direction perpendicular to the specimen heterogeneity axis. The ion-milling results obtained through this technique, as studied on a number of thin film cross-sectional TEM (XTEM) specimens, have proved to be superior to those produced via other procedures.XTEM specimens from integrated circuit (IC) devices essentially form a complex unidirectional nonhomogeneous structure. The presence of a variety of mostly lateral features at different levels along the substrate surface (consisting of conductors, semiconductors, and insulators) generally cause non-uniform results if ion-thinned conventionally.

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Numerical Modeling and Safety Design for Lithium-Ion Vehicle Battery Modules Subject to Crush Loading

Energies ◽

10.3390/en14010118 ◽

2020 ◽

Vol 14 (1) ◽

pp. 118

Author(s):

Feng Zhu ◽

Runzhou Zhou ◽

David J. Sypeck

Keyword(s):

Failure Modes ◽

Computational Study ◽

Short Circuit ◽

Computational Cost ◽

Lithium Ion ◽

Simplified Model ◽

Homogeneous Material ◽

Fe Model ◽

Safety Design ◽

Battery Module

In this work, a computational study was carried out to simulate crushing tests on lithium-ion vehicle battery modules. The tests were performed on commercial battery modules subject to wedge cutting at low speeds. Based on loading and boundary conditions in the tests, finite element (FE) models were developed using explicit FEA code LS-DYNA. The model predictions demonstrated a good agreement in terms of structural failure modes and force–displacement responses at both cell and module levels. The model was extended to study additional loading conditions such as indentation by a cylinder and a rectangular block. The effect of other module components such as the cover and cooling plates was analyzed, and the results have the potential for improving battery module safety design. Based on the detailed FE model, to reduce its computational cost, a simplified model was developed by representing the battery module with a homogeneous material law. Then, all three scenarios were simulated, and the results show that this simplified model can reasonably predict the short circuit initiation of the battery module.

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Nonlinear multiscale simulation of instabilities due to growth of an elastic film on a microstructured substrate

Archive of Applied Mechanics ◽

10.1007/s00419-020-01728-w ◽

2020 ◽

Vol 90 (11) ◽

pp. 2397-2412

Author(s):

Iman Valizadeh ◽

Oliver Weeger

Keyword(s):

Deformation Gradient ◽

Multiscale Simulation ◽

Numerical Results ◽

Unit Cell ◽

Homogeneous Material ◽

Two Phase ◽

Biological Phenomena ◽

Elastic Film ◽

Living Tissues ◽

Analytical Approaches

Abstract The objective of this contribution is the numerical investigation of growth-induced instabilities of an elastic film on a microstructured soft substrate. A nonlinear multiscale simulation framework is developed based on the FE2 method, and numerical results are compared against simplified analytical approaches, which are also derived. Living tissues like brain, skin, and airways are often bilayered structures, consisting of a growing film on a substrate. Their modeling is of particular interest in understanding biological phenomena such as brain development and dysfunction. While in similar studies the substrate is assumed as a homogeneous material, this contribution considers the heterogeneity of the substrate and studies the effect of microstructure on the instabilities of a growing film. The computational approach is based on the mechanical modeling of finite deformation growth using a multiplicative decomposition of the deformation gradient into elastic and growth parts. Within the nonlinear, concurrent multiscale finite element framework, on the macroscale a nonlinear eigenvalue analysis is utilized to capture the occurrence of instabilities and corresponding folding patterns. The microstructure of the substrate is considered within the large deformation regime, and various unit cell topologies and parameters are studied to investigate the influence of the microstructure of the substrate on the macroscopic instabilities. Furthermore, an analytical approach is developed based on Airy’s stress function and Hashin–Shtrikman bounds. The wavelengths and critical growth factors from the analytical solution are compared with numerical results. In addition, the folding patterns are examined for two-phase microstructures and the influence of the parameters of the unit cell on the folding pattern is studied.

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Genetics of symbiosis and nitrogen fixation in legumes

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1969.0030 ◽

1969 ◽

Vol 172 (1029) ◽

pp. 417-437 ◽

Cited By ~ 38

Keyword(s):

Nitrogen Fixation ◽

Bacterial Strain ◽

Host Plants ◽

Strain Differences ◽

Homogeneous Material ◽

Developmental Sequence ◽

Bacterial Strains ◽

Nodule Bacteria ◽

Microbial Genetics ◽

Nodular Tissue

Soon after the isolation of nodule bacteria in 1888, differences were recognized in the ability of bacterial strains to form nodules on particular host plants and in the nitrogen-fixing ability of the nodules so formed. These and other symbiotic heterogeneities were attributed, sometimes correctly, to bacterial strain differences, not then thought to be open to formal genetic analysis. The realization that the host plant was an essential component of this variability came only gradually, stimulated by observations of host varietal differences and by the demand for reliable and homogeneous material for experimental work. Only within the last two decades has host variability been studied by plant breeding, and bacterial strain differences by some of the methods of microbial genetics. This review, except for a brief reference to earlier work of some historic interest, will consider only genetic problems open to investigation by these methods. The developmental sequence in all legume nodules is broadly similar. The initial infection phases are followed by the induction of the nodule, the invasion of part of the nodular tissue and culminate in bacteroid formation and nitrogen fixation; the genetics of symbiosis will be considered in this context.

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Majorana zero modes in impurity-assisted vortex of LiFeAs superconductor

Nature Communications ◽

10.1038/s41467-021-24372-6 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Lingyuan Kong ◽

Lu Cao ◽

Shiyu Zhu ◽

Michał Papaj ◽

Guangyang Dai ◽

...

Keyword(s):

Quantum Computation ◽

Zero Mode ◽

Scanning Tunneling ◽

Homogeneous Material ◽

Dirac Fermions ◽

Tunneling Microscopy ◽

Zero Modes ◽

Topological Quantum ◽

One Step ◽

Topological Quantum Computation

AbstractThe iron-based superconductor is emerging as a promising platform for Majorana zero mode, which can be used to implement topological quantum computation. One of the most significant advances of this platform is the appearance of large vortex level spacing that strongly protects Majorana zero mode from other low-lying quasiparticles. Despite the advantages in the context of physics research, the inhomogeneity of various aspects hampers the practical construction of topological qubits in the compounds studied so far. Here we show that the stoichiometric superconductor LiFeAs is a good candidate to overcome this obstacle. By using scanning tunneling microscopy, we discover that the Majorana zero modes, which are absent on the natural clean surface, can appear in vortices influenced by native impurities. Our detailed analysis reveals a new mechanism for the emergence of those Majorana zero modes, i.e. native tuning of bulk Dirac fermions. The discovery of Majorana zero modes in this homogeneous material, with a promise of tunability, offers an ideal material platform for manipulating and braiding Majorana zero modes, pushing one step forward towards topological quantum computation.

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INTRACELLULAR FORMS OF POX VIRUSES AS SHOWN BY THE ELECTRON MICROSCOPE (VACCINIA, ECTROMELIA, MOLLUSCUM CONTAGIOSUM)

Journal of Experimental Medicine ◽

10.1084/jem.98.2.157 ◽

1953 ◽

Vol 98 (2) ◽

pp. 157-172 ◽

Cited By ~ 83

Author(s):

William H. Gaylord ◽

Joseph L. Melnick

Keyword(s):

Electron Microscope ◽

Hollow Spheres ◽

Molluscum Contagiosum ◽

Dense Granule ◽

Homogeneous Material ◽

Dense Matrix ◽

Thin Sections ◽

Virus Particles ◽

Typical Inclusion ◽

Mature Virus

The intracellular development of three pox viruses has been studied with the electron microscope using thin sections of infected tissue. Cells infected with vaccinia, ectromelia, and molluscum contagiosum viruses all form developmental bodies preliminary to the production of mature virus. Developmental bodies, believed to be virus precursors, are round to oval, slightly larger than mature virus particles, less dense to electrons, and have a more varied morphology. It is suggested as a working hypothesis that the process of maturation of a virus particle takes place as follows. In the earliest form the developmental bodies appear as hollow spheres, imbedded in a very dense cytoplasmic mass constituting an inclusion body, or in a less dense matrix near the nucleus in cells without typical inclusion bodies. The spheres become filled with a homogeneous material of low electron density. A small, dense granule appears in each developmental body and grows in size at the expense of the low density material. Following growth of the granule, particles are found with the dimensions of mature virus and having complex internal structure resembling bars or dumbells. Mature virus is ovoid and very dense to electrons. An "empty" interior may be found within its thick walls.

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Forces on a Circular Hole Located in Functionally Graded Material

Materials Science Forum ◽

10.4028/www.scientific.net/msf.704-705.631 ◽

2011 ◽

Vol 704-705 ◽

pp. 631-635

Author(s):

Xian Feng Wang ◽

Feng Xing ◽

Norio Hasebe

Keyword(s):

Circular Hole ◽

Constant Term ◽

Complex Stress ◽

Functionally Graded ◽

Homogeneous Material ◽

Dimensional Problem ◽

Stress Components ◽

Graded Material ◽

Stress Functions ◽

Stress Function Method

The complex stress function method is used in this study to formulate the 2-dimensional problem for nonhomogeneous materials. The Young’s modulus E varies linearly with the coordinate x and the Poisson’s ratio of the material is assumed constant and. The stress components and the boundary conditions are expressed in terms of two complex stress functions in explicit forms. It is noted that the constant term in stress functions has an influence on the stress components, which is different from the homogeneous material case. Subsequently, the problem of a nonhomogeneous plane containing a circular hole subjected to a uniform internal pressure is studied.

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A Crack Model of a Bone Cement Interface

Journal of Biomechanical Engineering ◽

10.1115/1.3138488 ◽

1984 ◽

Vol 106 (3) ◽

pp. 235-243 ◽

Cited By ~ 9

Author(s):

J. P. Clech ◽

L. M. Keer ◽

J. L. Lewis

Keyword(s):

Bone Cement ◽

Cohesive Zone ◽

Edge Crack ◽

Crack Problem ◽

Bimaterial Interface ◽

Fracture Mechanisms ◽

Homogeneous Material ◽

Crack Model ◽

Cement Interface ◽

Crack Faces

This paper is concerned with the fracture mechanics of a bone-cement interface that includes a cohesive zone effect on the crack faces. This accounts for the experimentally observed strengthening mechanism due to the mechanical interlock between the crack faces. Edge crack models are developed where the cohesive zone is simulated by a continuous or a discrete distribution of linear or nonlinear springs. It is shown that the solution obtained by assuming a homogeneous material is fairly close to the exact solution for the bimaterial interface edge crack problem. On the basis of that approximation, the analysis is conducted for the problem of two interacting edge cracks, one at the interface, and the other one in the cement. The small crack that was observed to initiate in the cement, close to the bone-cement interface, does not affect much the mode I stress-intensity factor at the tip of the interface crack. However it may grow, leading to a catastrophic breakdown of the cement. The analysis and following discussion point out an interdependency between bone-cement interface strength and cement strength not previously appreciated. The suggested crack models provide a framework for quantifying the fracture mechanisms at the bone-cement interface.

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