Ideal Strength of Nano-Components

2005 ◽  
Vol 482 ◽  
pp. 25-32 ◽  
Author(s):  
Takayuki Kitamura ◽  
Yoshitaka Umeno ◽  
Akihiro Kushima
Keyword(s):  
High Strength ◽  
Perfect Crystal ◽  
The Other ◽  
Ideal Strength ◽  
Structured Materials ◽  
Recent Developments ◽  
Definition Of ◽  
Nano Wires ◽  
External Loads ◽  
The Ideal

The ideal (theoretical) strength was originally defined as the stress or strain at which perfect crystal lattice became mechanically unstable with respect to arbitrary homogeneous infinitesimal deformation. This has been intensely investigated because the ultimate strength without defects is a fundamental mechanical characteristic of materials. In the analyses, the instability criteria have been studied on the basis of elastic constants. Recent developments in computational technology make it possible to analyze the ideal strength on the basis of quantum mechanics. On the other hand, it is well known that the mechanical strength of components is dependent not only on (1) material (atom species), but also on (2) loading condition and (3) structure. Because most studies on the strength in terms of atomic mechanics have focused on the factor (1) (materials), analysis has mainly been conducted on simple crystal consisting of perfect lattices (e.g. fcc and bcc) under simple loading conditions (e.g. tension), though some have explored the properties of bulk materials with defects (e.g. vacancy and grain boundary). Small atomic components (nano-structured components) such as nano-films, nano-wires (tubes) and nano-dots (clusters) possess their own beautiful, defect-free structures, namely ideal structure. Thus, they show characteristic high strength. Moreover, utilizing the structure at the nanometer or micron level is a key technology in the development of electronic devices and elements of micro (nano) electro-mechanical systems (MEMS/NEMS). Therefore, it is important to understand the mechanical properties not only for the sake of scientific interest, but also for engineering usefulness such as design of fabrication/assembly processes and reliability in service. In the other words, the effects of structure (factor (3); e.g. film/wire/dot) have to be understood as the basic properties of atomic components. Thus, the definition of ideal strength should be expanded to include the strength at instability of components with ideal structures under various external loads (factor (2)), which provides fundamental knowledge of nano-structured materials. In this paper, we review works on the strength of ideal nano-structured components in terms of factor (3), mainly under tension.

Recht, Strafrecht und Sozialmoral

1981 ◽  
Vol 3 (2) ◽  
Author(s):  
Klaus Lüderssen
Keyword(s):  
The Other ◽  
Other Hand ◽  
Recent Developments ◽  
Definition Of ◽  
High Degree ◽  
Very High

AbstractIt is shown by means of four examples that the demarcation between law and morals has become problematical. The study of more recent developments in ethics and in law indicates that in both fields the relevance of discourse and consent has grown. Though both law and morals aim at agreement their degree of dependance on it differs. The definition of law and morals suggested in this article is based on this view. Legitimate law consists of norms, which besides fulfilling other conditions have attained a certain degree of consent. On the other hand one can only talk of social morals when a very high degree of consent has been reached. The consequences of this definition are explained by means of the examples presented at the beginning.

What is the Limit of Nanoparticle Strengthening?

MRS Bulletin ◽  
2009 ◽  
Vol 34 (3) ◽  
pp. 173-177 ◽  
Author(s):  
D.C. Chrzan ◽  
J.W. Morris ◽  
Y.N. Osetsky ◽  
R.E. Stoller ◽  
S.J. Zinkle
Keyword(s):  
Nuclear Reactor ◽  
Matrix Material ◽  
Dislocation Motion ◽  
Perfect Crystal ◽  
Atomic Scale ◽  
Ideal Strength ◽  
Deformation Processes ◽  
Precipitate Strengthening ◽  
Transportation Applications ◽  
The Ideal

AbstractThe stress required to deform a perfect crystal to its elastic limit while maintaining perfect periodicity, the so-called ideal strength, sets the gold standard for the strength of a given material. Materials this strong would be of obvious engineering importance, potentially enabling more efficient turbines for energy production, lighter materials for transportation applications, and more reliable materials for nuclear reactor applications. In practice, the strength of engineering materials is often more than two orders of magnitude less than the ideal strength due to easily activated deformation processes involving dislocations. For many materials, precipitate strengthening is a promising approach to impede dislocation motion and thereby improves strength and creep resistance. This observation begs the question: What are the limits of nanoparticle strengthening? Can the ideal strength of a matrix material be reached? To answer these questions, we need a detailed, atomic scale understanding of the interactions between dislocations and obstacles. Fortunately, simulations are beginning to explore this interaction.

Ab Initio DFT Study of Ideal Strength of Crystal and Surfaces in Covalent Systems

2008 ◽  
Vol 1086 ◽  
Author(s):  
Yoshitaka Umeno
Keyword(s):  
Tensile Strength ◽  
Ab Initio ◽  
Normal Stress ◽  
Density Functional ◽  
Level Structure ◽  
High Strength ◽  
Nucleation Site ◽  
Dislocation Nucleation ◽  
Ideal Strength ◽  
The Ideal

AbstractAb initio density functional theory (DFT) calculations were performed to examine various factors which may influence the ideal strength, namely multiaxial loading condition and structure with low symmetry. First, the effect of normal stress on the ideal shear strength (ISS) in covalent crystals, Si, C, Ge and SiC, was evaluated. It was found that the response of ISS to normal stress differs depending on the material, while in metals the trend is unchanged. Obtained ISS as a function of normal stress is useful to understand criteria of dislocation nucleation in a pristine crystal because local lattices at the nucleation site undergo superimposed stress components in experiment. Secondly the ideal tensile strength of silicon surface was evaluated to examine how atomistic-level structure affects the mechanical property. The theoretical tensile strength of Si nanofilms with (100) surface, which is flat with dimer-row structures, shows only 20-30% reduction even though the thickness is down to 1 nm, meaning that the flat surface possesses high strength.

First Principles Study on Ideal Strength of Cu Multi-Shell Nano-Wire

2007 ◽  
Vol 345-346 ◽  
pp. 919-924
Author(s):  
Takayuki Kitamura ◽  
Akihiro Kushima ◽  
Yoshitaka Umeno
Keyword(s):  
First Principles ◽  
Maximum Stress ◽  
Atomic Chain ◽  
Ideal Strength ◽  
Young’S Moduli ◽  
Single Sheet ◽  
The Wire ◽  
Nano Wires ◽  
Insight Into ◽  
The Ideal

The ideal strength of a nano-component, which is the maximum stress of the structure, provides an insight into the mechanical behavior of minute material. We conducted tensile simulations for cylindrical-shaped Cu nano-wires composed of an atomic chain as a core wrapped around by shell(s) with the structure of (111) layers in an fcc crystal. The results are compared with Cu atomic chain and sheet which are components of the nanowire. Young’s moduli and the ideal strengths of the wires are less than a single atomic chain and a sheet. The mechanical strength of the wire is weakened by the following three factors: (A) Change in electron arrangement caused by combining core and shell; (B) Larger interatomic distance (inherent tensile strain) of the outer shell introduced by the mismatch of atomic layers due to the curvature difference; (C) Mismatch between shells due to curvature difference. Factor (A) reduces the bonding strength in the shell(s) that occupy a greater part of the wire. 5-1 wire, which consists of a core and a shell, is weaker than the single atomic chain and the single sheet due to (A) and (B). 10-5-1 wire, consisting of a core and two shells, has less strength than 5-1 wire due to (C) in addition to (A) and (B).

An ab initio study of the ideal tensile and shear strength of single-crystal β–Si3N4

2003 ◽  
Vol 18 (5) ◽  
pp. 1168-1172 ◽  
Author(s):  
Shigenobu Ogata ◽  
Naoto Hirosaki ◽  
Cenk Kocer ◽  
Yoji Shibutani
Keyword(s):  
Shear Strength ◽  
Single Crystal ◽  
Ab Initio ◽  
Density Functional ◽  
Strain Curve ◽  
High Strength ◽  
Indentation Hardness ◽  
Ideal Strength ◽  
Vickers Indentation ◽  
The Ideal

In this study, the ideal tensile and shear strength of single-crystal β–Si3N4 was calculated using an ab initio density functional technique. The stress-strain curve of the silicon nitride polymorph was calculated from simulations of uniaxial strain deformation. In particular, the ideal strength calculated for an applied ∈11 tensile strain was estimated to be approximately 57 GPa. Recently, a good correlation was reported between the shear modulus of high-strength materials and the experimentally determined Vickers indentation hardness value. Using the reported correlation an estimate was made of the Vickers indentation hardness of single-crystal β–Si3N4: approximately 20.4 GPa.

Performative Change

2020 ◽  
Author(s):  
Thomas Duschlbauer
Keyword(s):  
Ludwig Wittgenstein ◽  
Paradigm Shift ◽  
The Other ◽  
Language Games ◽  
Human Beings ◽  
Organisational Theory ◽  
Other Hand ◽  
Recent Developments ◽  
The Relationship ◽  
The Ideal

Due to the phenomena of digitalisation, a new inventory regarding fundamental questions of organisation and communication has taken place, which has ultimately led to a plea for a paradigm shift. For if one follows recent developments in organisational theory and rethinks it radically, the relationship between the means and the purpose—that is, between production and the product and between creation and the artefact—is also reversed. With that relationship seen in this manner, it is not necessarily the organisation and socialisation of human beings that enables them to create artefacts, but it is rather the artefact that may serve to bring people together, enable them to acquire new skills and knowledge, and finally bring organisation to the level that we are now familiar with. Transferred to communication, this would also call into question the ideal of a consensus and, on the other hand, give more prominence to the idea of language games—as first formulated by Ludwig Wittgenstein.

Immunoferritin localization of intracellular antigens in positively stained frozen sections

1978 ◽  
Vol 36 (2) ◽  
pp. 168-169
Author(s):  
K. T. Tokuyasu
Keyword(s):  
Surface Tension ◽  
Water Surface ◽  
Thin Layers ◽  
The Other ◽  
Positive Staining ◽  
Frozen Sections ◽  
The Past ◽  
Ultrathin Frozen Sections ◽  
Definition Of

During the past investigations of immunoferritin localization of intracellular antigens in ultrathin frozen sections, we found that the degree of negative staining required to delineate u1trastructural details was often too dense for the recognition of ferritin particles. The quality of positive staining of ultrathin frozen sections, on the other hand, has generally been far inferior to that attainable in conventional plastic embedded sections, particularly in the definition of membranes. As we discussed before, a main cause of this difficulty seemed to be the vulnerability of frozen sections to the damaging effects of air-water surface tension at the time of drying of the sections.Indeed, we found that the quality of positive staining is greatly improved when positively stained frozen sections are protected against the effects of surface tension by embedding them in thin layers of mechanically stable materials at the time of drying (unpublished).

NEUROTIC SYMPTOMATICS RELATED TO PERSONAL CHARACTERISTICS IN YOUTH

2019 ◽  
pp. 2014-2019
Author(s):  
Milen Dimov
Keyword(s):  
Personal Characteristics ◽  
The Self ◽  
The Other ◽  
Social Responsiveness ◽  
Training Process ◽  
Self Assessment ◽  
School Year ◽  
Real Behavior ◽  
Low Levels ◽  
The Ideal

The present study traces the dynamics of personal characteristics in youth and the manifested neurotic symptoms in the training process. These facts are the reason for the low levels of school results in the context of the existing theoretical statements of the problem and the empirical research conducted among the trained teenagers. We suggest that the indicators of neurotic symptomatology in youth – aggression, anxiety, and neuroticism, are the most demonstrated, compared to the other studied indicators of neurotic symptomatology. Studies have proved that there is a difference in the act of neurotic symptoms when tested in different situations, both in terms of expression and content. At the beginning of the school year, neurotic symptoms, more demonstrated in some aspects of aggressiveness, while at the end of school year, psychotism is more demonstrated. The presented summarized results indicate that at the beginning of the school year, neurotic symptoms are strongly associated with aggression. There is a tendency towards a lower level of social responsiveness, both in the self-assessment of real behavior and in the ideal “I”-image of students in the last year of their studies. The neurotic symptomatology, more demonstrated due to specific conditions in the life of young people and in relation to the characteristics of age.

KONSTRUKSI ISLAM DALAM KEKUASAAN NEGARA

1970 ◽  
Vol 6 (2) ◽  
Author(s):  
Nurul Aini Musyarofah
Keyword(s):  
Islamic Law ◽  
Social Condition ◽  
The Other ◽  
Good Society ◽  
Ideal Form ◽  
Other Hand ◽  
Islamic Politics ◽  
The Relationship ◽  
The Ideal

The relationship between Islam and state raises a controversy that includes two main groups;formalists and substantialists. Both of them intend to achieve a good social condition which is inaccordance with Islamic politics. The ideal form of good society to be achieved is principallydescribed in the main source of Islamic law, Al Qur’an and As Sunnah, as follows. A form of goodsociety should supprot equality and justice, egalitarianism, and democracy in its social community.The next problem is what the needed methods and instruments to achieve the ideal Islamic politicsare. In this case, the debate on the formalization and substance of Islamic teaching is related to therunning formal political institution.Each group claims itself to be the most representative to the ideal Islam that often leads to anescalating conflict. On the other hand thr arguments of both groups does not reach the wholeMuslims. As a result, the discourse of Islam and state seems to be elitist and political. As a result,Both groups suspect each other each other and try to utilize the controversy on the relationshipbetween Islam and state to get their own benefit which has no relation with the actualization ofIslamic teaching.

Comparative Area Studies

2018 ◽  
Author(s):  
Dirk Berg-Schlosser
Keyword(s):  
Cold War ◽  
Ivory Coast ◽  
Qualitative Comparative Analysis ◽  
The Other ◽  
Area Studies ◽  
International Context ◽  
Recent Developments ◽  
Cross Area Studies ◽  
The Cold War ◽  
Analytical Approaches

Area studies have undergone significant changes over the last two decades. They have been transformed from mostly descriptive accounts in the international context of the Cold War to theory-oriented and methodological analytical approaches. More recent comparative methods such as “Qualitative Comparative Analysis” (QCA) and related approaches, which are particularly suitable for medium N studies, have significantly contributed to this development. This essay discusses the epistemological background of this approach as well as recent developments. It provides two examples of current “cross area studies,” one concerned with successful democratic transformations across four regions (Africa, Eastern Europe, Latin America, and East Asia), the other with political participation in marginalized settlements in four countries (Brazil, Chile, Ivory Coast, Kenya) in a multilevel analysis. The conclusion points to the theoretical promises of this approach and its practical-political relevance.

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