Dislocations in Ceramics

1998 ◽  
Vol 4 (S2) ◽  
pp. 550-551
Author(s):  
C. Barry Carter
Keyword(s):  
Point Defects ◽  
Ceramic Materials ◽  
List Type ◽  
Complex Structures ◽  
Oxide Heterostructures ◽  
Perfect Lattice ◽  
Binary Oxides ◽  
Unit Cells ◽  
Interfacial Dislocations ◽  
Insight Into

Of the four groups of crystal lattice defects, i.e., point defects, dislocations, interfaces and particles, dislocations are often thought to be the least important for ceramic materials. However, they not only give considerable insight into interfaces (they can be thought of as the link between point defects and interfaces), but they are becoming more important as interest grows in epitactic oxide heterostructures.The present paper provides a review of our current understanding of dislocations in ceramics. To simplify the discussion, we can separate the task into the following sections, namely Simple oxides (MgO, ZnO etc.)Simple non-oxides (A1N, GaN, SiC, TiC, etc.)More complex binary oxides (AI2O3, Fe203, etc.)Multicomponent oxides and complex non-oxides (spinels, garnets, S13N4)Interfacial dislocations (misfit, grain boundary, etc.)The features which are most often associated with ceramic materials are their complex structures and large unit cells. For example in bcc garnets, the smallest Burgers vector for a perfect lattice dislocation is ∼0.8nm long.

scholarly journals Ab Initio Study of Ferroelectric Critical Size of SnTe Low-Dimensional Nanostructures

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 732 ◽  
Author(s):  
Takahiro Shimada ◽  
Koichiro Minaguro ◽  
Tao Xu ◽  
Jie Wang ◽  
Takayuki Kitamura
Keyword(s):  
Density Functional ◽  
Critical Size ◽  
Density Functional Theory Calculations ◽  
Cell Width ◽  
Functional Theory ◽  
Unit Cells ◽  
Principle Density Functional Theory ◽  
Low Dimensional ◽  
Insight Into ◽  
Ferroelectric Perovskite

Beyond a ferroelectric critical thickness of several nanometers existed in conventional ferroelectric perovskite oxides, ferroelectricity in ultimately thin dimensions was recently discovered in SnTe monolayers. This discovery suggests the possibility that SnTe can sustain ferroelectricity during further low-dimensional miniaturization. Here, we investigate a ferroelectric critical size of low-dimensional SnTe nanostructures such as nanoribbons (1D) and nanoflakes (0D) using first-principle density-functional theory calculations. We demonstrate that the smallest (one-unit-cell width) SnTe nanoribbon can sustain ferroelectricity and there is no ferroelectric critical size in the SnTe nanoribbons. On the other hand, the SnTe nanoflakes form a vortex of polarization and lose their toroidal ferroelectricity below the surface area of 4 × 4 unit cells (about 25 Å on one side). We also reveal the atomic and electronic mechanism of the absence or presence of critical size in SnTe low-dimensional nanostructures. Our result provides an insight into intrinsic ferroelectric critical size for low-dimensional chalcogenide layered materials.

Large Surface Effect Ship Size Limits

2013 ◽  
Vol 29 (02) ◽  
pp. 84-91
Author(s):  
Stefanos Koullias ◽  
Santiago Balestrini Robinson ◽  
Dimitri N. Mavris
Keyword(s):  
Historical Data ◽  
Surface Effect ◽  
Advanced Materials ◽  
Complex Structures ◽  
First Principle ◽  
Simplified Models ◽  
Surface Effect Ship ◽  
Size Limits ◽  
Technology Level ◽  
Insight Into

The purpose of this study is to obtain insight into surface effect ship (SES) endurance without reliance on historical data as a function of geometry, displacement, and technology level. First-principle models of the resistance, structures, and propulsion system are developed and integrated to predict large SES endurance and to suggest the directions that future large SESs will take. It is found that large SESs are dominated by structural weight, which indicates the need for advanced materials and complex structures, and that advanced propulsion cycles can increase endurance by up to 33%. SES endurance is shown to be a nonlinear discontinuous function of geometry, displacement, and technology level that cannot be predicted by simplified models or assumptions.

scholarly journals Characteristic Constraint Modes for Component Mode Synthesis

1999 ◽  
Author(s):  
Matthew P. Castanier ◽  
Yung-Chang Tan ◽  
Christophe Pierre
Keyword(s):  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Component Mode Synthesis ◽  
Complex Structures ◽  
Cantilever Plate ◽  
Vibration Transmission ◽  
Stiffness Matrices ◽  
Physical Insight ◽  
Insight Into

Abstract In this paper, a technique is presented for improving the efficiency of the Craig-Bampton method of Component Mode Synthesis (CMS). An eigenanalysis is performed on the partitions of the CMS mass and stiffness matrices that correspond to the so-called constraint modes. The resultant eigenvectors are referred to as “characteristic constraint modes,” since they represent the characteristic motion of the interface between the component structures. By truncating the characteristic constraint modes, a CMS model with a highly-reduced number of degrees of freedom may be obtained. An example of a cantilever plate is considered. It is shown that relatively few characteristic constraint modes are needed to yield accurate approximations of the lower natural frequencies. This method also provides physical insight into the mechanisms of vibration transmission in complex structures.

scholarly journals Clinical Characteristics and Outcomes of Diabetic COVID-19 patients in Kuwait

2020 ◽  
Author(s):  
Abdullah Alshukry ◽  
Mohammad Bu Abbas ◽  
Yaseen Ali ◽  
Barrak Alahmad ◽  
Abdullah A. Al-Shammari ◽  
...  
Keyword(s):  
Clinical Characteristics ◽  
Clinical Laboratory ◽  
Fasting Blood Glucose ◽  
List Type ◽  
Laboratory Findings ◽  
Reactive Protein ◽  
Patients With Diabetes ◽  
Laboratory Investigations ◽  
Insight Into ◽  
Variable Clinical Presentation

AbstractBackgroundCOVID-19 has a highly variable clinical presentation, ranging from asymptomatic to severe respiratory symptoms and death. Diabetes seems to be one of the main comorbidities contributing to a worse COVID-19 outcome.ObjectiveIn here we analyze the clinical characteristics and outcomes of diabetic COVID-19 patients.MethodsIn this single-center, retrospective study of 417 consecutive COVID-19 patients, we analyze and compare disease severity, outcome, associated complications, and clinical laboratory findings between diabetic and non-diabetic COVID-19 patients.ResultsCOVID-19 patients with diabetes had more severe outcomes and higher mortality than non-diabetic COVID-19 patients. Diabetic COVID-19 patients had significantly higher prevalence of comorbidities, such as hypertension. Laboratory investigations also highlighted notably higher levels of C-reactive protein in diabetic COVID019 patients and lower estimated glomerular filtration rate. They also showed a higher incidence of complications.ConclusionDiabetes could be a major contributor to worsening outcomes in COVID-19 patients. Understanding the pathophysiology underlining these findings could provide insight into better management and improved outcome of such cases.Highlights of the StudyA significantly higher proportion of Diabetic COVID-19 patients required admission to the ICU.Higher fasting blood glucose was associated with higher risk of COVID-19 associated mortality.Diabetic COVID-19 patients had significantly higher incidence of complications including sepsis, ARDS, cardiac failure and renal failure.

Reality in depression

2011 ◽  
Vol 26 (S2) ◽  
pp. 2065-2065
Author(s):  
J. Cutting
Keyword(s):  
External World ◽  
Depressive Illness ◽  
List Type ◽  
Type Number ◽  
Depressive Realism ◽  
Descriptive Account ◽  
Insight Into

The presentation will cover 3 aspects of reality: 1)Reality as resistance;2)Reality as actuality;3)Reality as correct insight.A brief consideration of the nature of these in normals will be given. A descriptive account of the psychopathology of each aspect will be then discussed, with particular emphasis on: a)undue resistance in depressive illness;b)qualitative differences in actuality, i.e experience of external world and body in schizophrenia;c)so-called “depressive realism” as a more correct insight into ones owen actions than is possessed in normals.

Application of a Computational Micro-Electro-Mechanical Model for the Prediction of Self-Heating of Ferroelectric Ceramic Materials

Aerospace ◽  
2003 ◽  
Author(s):  
Lisa Mauck Weiland
Keyword(s):  
Ceramic Materials ◽  
Ferroelectric Ceramic ◽  
Ferroelectric Materials ◽  
Material Behavior ◽  
Combined Loading ◽  
Self Heating ◽  
Heating Effects ◽  
Rate Effects ◽  
Polycrystalline Model ◽  
Insight Into

Application of ferroelectric materials in devices subject to high fields and a range of drive frequencies is becoming increasingly common. As a result, self-heating of these devices is of concern. An energy based polycrystalline model including thermal and rate effects has been developed. The model has been developed from the thermodynamics of piezoelectrics, and includes elastic, dielectric, and piezoelectric anisotropy. It captures ferroelectric and ferroelastic switching under combined loading. In the current work the model is expanded to include self-heating effects. Model results are compared to experimental data. Results from the model give insight into material behavior.

scholarly journals A Molecular Dynamics Simulation of the Tensile Behavior of Y-Branched-CNT/SiC Nanocomposite

2019 ◽  
Vol 804 ◽  
pp. 7-10
Author(s):  
Guo Bin Zheng ◽  
Hideaki Sano ◽  
Osamu Nakagoe ◽  
Shuji Tanabe
Keyword(s):  
Molecular Dynamics ◽  
Simulation Method ◽  
Ceramic Materials ◽  
Nanocomposite Materials ◽  
Dynamics Simulation ◽  
Uniaxial Tensile ◽  
Direct Knowledge ◽  
Uniaxial Tensile Stress ◽  
Dynamics Method ◽  
Insight Into

The purpose of incorporating CNTs into ceramic materials is to enhance the toughness of ceramic materials, in which the interface plays a key role. Due to the nanoscale of nanocomposites, however, it is not easy to acquire a direct knowledge of the interface behavior. In this research, we simulated the dynamics of CNT/SiC and branched CNT/SiC under uniaxial tensile stress using molecular dynamics method (LAMMPS). The simulation method using molecular dynamics provide an insight into designing an effectively toughened ceramic nanocomposite materials.

scholarly journals Latvijas minerālās izejvielas eko-keramikas izstrādei

2018 ◽  
Vol 35 ◽  
pp. 62-85
Author(s):  
Gaida Sedmale ◽  
Māris Rundāns ◽  
Mārtiņs Randers ◽  
Ingunda Šperberga ◽  
Andris Cimmers
Keyword(s):  
High Temperature ◽  
Ceramic Material ◽  
Gas Phase ◽  
Phase Formation ◽  
Raw Materials ◽  
Ceramic Materials ◽  
Firing Process ◽  
Mineral Raw Materials ◽  
Technological Processes ◽  
Insight Into

Darbā dots ieskats par iespējām izmantot Latvijas minerālās izejvielas kā bāzi vai  piedevu  keramikas  materiālu  (eko-materiālu)  izstrādei ar dažādu pielietošanas aspektu, to skaitā parādīt iespēju šo materiālu ieguves tehnoloģisko procesu optimizēšanai virzībā uz to apdedzināšanas temperatūras samazināšanu, līdz ar to reducējot kaitīgu gāzveida izmešu nonākšanu vidē. Parādīti darbu rezultāti laika periodā no 2007. g. līdz 2017. g. Tiek apskatīti un analizēti sekojoši pētījumi:neapstrādāta māla pielietošana atkritumu deponēšanas vietu noblīvēšanai;daļēji dehidratizēta māla pielietošana Cr3+, Cr6+, Zn2+ un Cu+ jonu sorbcijai, kas veidojas galvanisko procesu notekūdeņos; poru saturošas augsttemperatūras keramikas izstrāde no jauktiem izejvielu maisījumiem, kas nodrošina pietiekamu gāzveida fāzes izveidošanos keramikas apdedzināšanas procesā, veidojot poras, lai pielietotu par filtrēšanas/attīrīšanas materiālu;illīta māla piedevu izmantošana, lai pazeminātu augsttemperatūras blīvas keramikas saķepināšanas/apdedzināšanas temperatūru, iegūstot ilgspējīgu mehāniski un termiski izturīgu produktu; kā arī tehnoloģiskie procesi, kas nodrošina porainas, siltumu izolējošas keramikas materiāla ieguvi pie pazeminātām temperatūrām (ģeopolimēru metode).Mineral Raw Materials of Latvia for Development of Eco-CeramicsThe paper gives an insight into the possibilities to use Latvian mineral raw materials as a base or additives for the development of ceramic materials (eco- materials) with different application aspects, including showing the possibility of optimizing the technological processes of these materials towards the reduction of their firing temperature, thereby reducing the release of harmful gaseous effluents into the environment.The results of the works that are reported in the period were obtained from  2007 to 2017. The following studies are reviewed and analyzed: the use of untreated clay for the sealing of waste deposits; the use of partly dehydrated clay for sorption of Cr3+,6+, Zn2+ and Cu2+, which have formed in galvanic processes; the development of porous high temperature ceramics from mixes  of mineral raw materials and synthetic additives that provide a sufficient gas phase  formation in the firing process and consecutively to form pores in obtained ceramic material; the use of illite clay additives to reduce the temperature of sintering of high temperature dense mechanical and thermally durable ceramics, as well as technological processes that ensure the production of porous, heat-insulating ceramic materials at reduced temperatures (geopolymer method).

scholarly journals Subjectivity in Construction: Situating Desire and Pleasure in Heterosexual Relationships

2015 ◽  
Vol 2 (4) ◽  
Author(s):  
Pankhuri Chandra ◽  
Dr. Anuradha Sharma
Keyword(s):  
Discourse Analysis ◽  
Young People ◽  
Research Work ◽  
External World ◽  
Sexual Life ◽  
Complex Structures ◽  
Heterosexual Relationships ◽  
Men And Women ◽  
Qualitative Technique ◽  
Insight Into

The present research work Subjectivity in Construction of heterosexual relationships is an attempt to understand the gender positions taken up by men and women with regard to desire and pleasure in heterosexuals. This requires an insight into the developing sexual selves of the participants. Using the qualitative technique of discourse analysis, the focus was to cultivate an image of the sexual life of these young people such that one is able to see how the elements in the construction of their sexuality have coalesced resulting in the current positions. It became evident through an analysis of the narratives, that women were very much creatures of desire and pleasure who thought about their sexual nature, their needs and fantasies. They had no qualms in admitting and accepting the same to not just themselves but also to the external world. Among the men, it was seen that men were not uni-dimensional, single-minded and self-centered with regard to sex. Intimacy and emotionality were very much part of their sexual repertoire. Thus, the focus here has not been to complete the jigsaw but to understand how these pieces have come to be a part of this puzzle, being completely aware that the results would only be an entry point to understanding how these complex structures come about.

scholarly journals Causally informed activity flow models provide mechanistic insight into the emergence of cognitive processes from brain network interactions

2021 ◽  
Author(s):  
Ruben Sanchez-Romero ◽  
Takuya Ito ◽  
Ravi D. Mill ◽  
Stephen José Hanson ◽  
Michael W. Cole
Keyword(s):  
Functional Connectivity ◽  
Effective Connectivity ◽  
Pearson Correlation ◽  
Explanatory Power ◽  
Memory Task ◽  
Brain Regions ◽  
Brain Network ◽  
List Type ◽  
Flow Models ◽  
Insight Into

AbstractBrain activity flow models estimate the movement of task-evoked activity over brain connections to help explain the emergence of task-related functionality. Activity flow estimates have been shown to accurately predict task-evoked brain activations across a wide variety of brain regions and task conditions. However, these predictions have had limited explanatory power, given known issues with causal interpretations of the standard functional connectivity measures used to parameterize activity flow models. We show here that functional/effective connectivity (FC) measures grounded in causal principles facilitate mechanistic interpretation of activity flow models. Starting from Pearson correlation (the current field standard), we progress from FC measures with poor to excellent causal grounding, demonstrating a continuum of causal validity using simulations and empirical fMRI data. Finally, we apply a causal FC method to a dorsolateral prefrontal cortex region, demonstrating causal network mechanisms contributing to its strong activation during a 2-back (relative to a 0-back) working memory task. Together, these results reveal the promise of parameterizing activity flow models using causal FC methods to identify network mechanisms underlying cognitive computations in the human brain.Highlights-Activity flow models provide insight into how cognitive neural effects emerge from brain network interactions.-Functional connectivity methods grounded in causal principles facilitate mechanistic interpretations of task activity flow models.-Mechanistic activity flow models accurately predict task-evoked neural effects across a wide variety of brain regions and cognitive tasks.

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