The steric influence of extra-framework cations on framework flexibility: an LTA case study

Abstract The theoretical extent of framework flexibility of Zeolite A (LTA) in response to the steric and geometric effects of different Si/Al compositions and extra-framework cation content has been explored using GASP software. Flexibility windows and compression mechanisms for siliceous LTA and aluminosilicate Na-LTA, Ca-LTA and K-LTA have been modelled. As expected, relatively small cations in the zeolite pores have little effect on the range of flexibility observed. Aluminosilicate LTA, Na-LTA and Ca-LTA frameworks exhibit identical flexibility windows and these frameworks also follow the same compression mechanisms. The introduction of larger K+ ions, however, results in greater steric hindrance. This restricts the flexibility of the framework and alters the compression mechanism to accommodate these larger cations. It is shown that the limits of the flexibility window of Zeolite A are dependent on framework aluminium content and extra-framework cation size.

Download Full-text

Structural properties of garnets under pressure: An ab initio study

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1524/zkri.1999.214.12.808 ◽

1999 ◽

Vol 214 (12) ◽

Cited By ~ 5

Author(s):

E. V. Akhmatskaya ◽

R. H. Nobes ◽

V. Milman ◽

B. Winkler

Keyword(s):

Structural Properties ◽

Density Functional ◽

Applied Pressure ◽

Basis Sets ◽

Geometrical Parameters ◽

Cell Parameters ◽

Unit Cells ◽

Compression Mechanism ◽

End Members ◽

Cation Size

AbstractThe structural properties of end members of the aluminosilicate garnet family (pyrope, grossular, almandine and spessartine) have been investigated as a function of applied pressure. The study has been performed with the density functional theory code CASTEP which uses pseudopotentials and plane-wave basis sets. The geometrical parameters of unit cells containing 80 atoms have been fully optimized. The calculated static geometries (cell parameters, internal coordinates of atoms, bond lengths), bulk moduli and their pressure derivatives are in good agreement with the available experimental data. The results of a systematic study of the effect of the cation size on compressibility are presented. It is suggested that the bending of the Si–O–Al angle between the octahedra and tetrahedra is the main compression mechanism.

Download Full-text

A Review on Research on Critical Analysis on Performance of RCC Structure under various Blast Condition

International Journal for Research in Applied Science and Engineering Technology ◽

10.22214/ijraset.2021.35894 ◽

2021 ◽

Vol 9 (VI) ◽

pp. 3930-3939

Author(s):

Parth Samarth

Keyword(s):

Critical Analysis ◽

Blast Loading ◽

Dynamic Effect ◽

Design Load ◽

Compression Mechanism ◽

The Impact ◽

Is Design ◽

Gain Access ◽

Storey Building

The main aim of this paper is design and implement Critical Analysis on Performance of RCC Structure Under Various Blast Condition. Advance in technology over the past few decades have necessitated the dynamic effect of loading blast such as wind and earthquake loads. The main purpose of this study is to gain access to materials on blast loads that can be designed, to assess vulnerabilities and to provides guidance to designed to economically reduce the impact of explosion on building and provide protection to human and infrastructure. A case study is performed on an RC column subject to blast loading; the effect of force on the deflection over time, the stress rate on the tensile is studies. The compression mechanism is studies by following the alternative path method for minimum design load for building and other structures. The 2-storey building is analyzed and the displacement and blast loading and standoff distance on the floor vehicles are studied by adding X-type brackets and shear wall to make them explosion resistant. Structural, architectural and managerial aspects of the design are also included in the report so that the structures become blast resistant.

Download Full-text

The Genesis and Internal Dynamics of El Salvador's People's Revolutionary Army, 1970–1976

Behavioral and Brain Sciences ◽

10.1017/s0140525x13009850 ◽

2014 ◽

Vol 38 (01) ◽

pp. 102-129

Author(s):

ALBERTO MARTÍN ÁLVAREZ ◽

EUDALD CORTINA ORERO

Keyword(s):

Latin America ◽

El Salvador ◽

Early Years ◽

Left Wing ◽

Internal Dynamics ◽

Internal Coherence ◽

The 1960S

AbstractUsing interviews with former militants and previously unpublished documents, this article traces the genesis and internal dynamics of the Ejército Revolucionario del Pueblo (People's Revolutionary Army, ERP) in El Salvador during the early years of its existence (1970–6). This period was marked by the inability of the ERP to maintain internal coherence or any consensus on revolutionary strategy, which led to a series of splits and internal fights over control of the organisation. The evidence marshalled in this case study sheds new light on the origins of the armed Salvadorean Left and thus contributes to a wider understanding of the processes of formation and internal dynamics of armed left-wing groups that emerged from the 1960s onwards in Latin America.

Download Full-text

Culture and the plasticity of perception

Behavioral and Brain Sciences ◽

10.1017/s0140525x19002887 ◽

2020 ◽

Vol 43 ◽

Author(s):

Michael Lifshitz ◽

T. M. Luhrmann

Keyword(s):

Cultural Context ◽

Sensory Experience ◽

Cultural Learning ◽

The World

Abstract Culture shapes our basic sensory experience of the world. This is particularly striking in the study of religion and psychosis, where we and others have shown that cultural context determines both the structure and content of hallucination-like events. The cultural shaping of hallucinations may provide a rich case-study for linking cultural learning with emerging prediction-based models of perception.

Download Full-text

Dual systems for all: Higher-order, role-based relational reasoning as a uniquely derived feature of human cognition

Behavioral and Brain Sciences ◽

10.1017/s0140525x19000451 ◽

2019 ◽

Vol 42 ◽

Author(s):

Daniel J. Povinelli ◽

Gabrielle C. Glorioso ◽

Shannon L. Kuznar ◽

Mateja Pavlic

Keyword(s):

Temporal Reasoning ◽

Higher Order ◽

Important Case ◽

Human Cognition ◽

Relational Reasoning ◽

Dual Systems ◽

First Order ◽

Reasoning System ◽

Role Based

Abstract Hoerl and McCormack demonstrate that although animals possess a sophisticated temporal updating system, there is no evidence that they also possess a temporal reasoning system. This important case study is directly related to the broader claim that although animals are manifestly capable of first-order (perceptually-based) relational reasoning, they lack the capacity for higher-order, role-based relational reasoning. We argue this distinction applies to all domains of cognition.

Download Full-text

Sociocultural memory development research drives new directions in gadgetry science

Behavioral and Brain Sciences ◽

10.1017/s0140525x19000979 ◽

2019 ◽

Vol 42 ◽

Author(s):

Penny Van Bergen ◽

John Sutton

Keyword(s):

Episodic Memory ◽

Autobiographical Memory ◽

Developmental Psychology ◽

Cross Cultural ◽

Memory Development ◽

Development Research ◽

Cultural Research ◽

New Directions ◽

Cross Cultural Research

Abstract Sociocultural developmental psychology can drive new directions in gadgetry science. We use autobiographical memory, a compound capacity incorporating episodic memory, as a case study. Autobiographical memory emerges late in development, supported by interactions with parents. Intervention research highlights the causal influence of these interactions, whereas cross-cultural research demonstrates culturally determined diversity. Different patterns of inheritance are discussed.

Download Full-text

Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165641 ◽

1996 ◽

Vol 54 ◽

pp. 636-637

Author(s):

D. L. Callahan

Keyword(s):

Plastic Deformation ◽

Aluminum Nitride ◽

Mechanical Response ◽

Three Dimensional ◽

Bright Field Image ◽

Perfectly Plastic ◽

Contrast Analysis ◽

Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

Download Full-text