SIZE EFFECTS ON THE EFFICIENCY OF NEUTRON SHIELDING IN NANOCOMPOSITES — A FULL-RANGE ANALYSIS

2013 ◽  
Vol 12 (03) ◽  
pp. 1350015 ◽  
Author(s):  
LILY SCHREMPP-KOOPS
Keyword(s):  
Semiclassical Approximation ◽  
Full Range ◽  
Scaling Law ◽  
Filler Particle ◽  
Scale Up ◽  
Characteristic Size ◽  
Range Analysis ◽  
Neutron Shielding ◽  
Aerospace Applications ◽  
Filler Particles

Multiphase composites composed of a continuous hydrogenous (polymeric) phase and of neutron absorbing filler particles are attractive candidate materials for the design of light-weight neutron shields. While the characteristic size of the inclusions is traditionally in the micrometer range, we argue that the shielding performance of the composite is significantly enhanced for decreasing filler particle size. Within a semiclassical approximation scheme we analytically determine the corresponding scaling law valid for inclusions from the nanometer scale up to macroscopic sizes and recover meaningful limiting cases. We find that amongst polymer composites, the physical benchmark for optimized shielding at minimal weight penalty is essentially reached, as soon as the size of the filler particles drops within the nanometer range. We demonstrate that our results are in agreement with recent experimental findings and comment on the emerging potential for aeronautic and aerospace applications.

Plastic Hinge Lengths of Normal and High-Strength Concrete in Flexure

2002 ◽  
Vol 4 (4) ◽  
pp. 189-195 ◽  
Author(s):  
P. Mendis
Keyword(s):  
High Strength Concrete ◽  
Strain Softening ◽  
Plastic Hinge ◽  
Full Range ◽  
High Strength ◽  
Upper And Lower Bounds ◽  
Range Analysis ◽  
Strength Concrete ◽  
Plastic Phase ◽  
Flexural Hinges

Full-range analysis methods are becoming popular in design of reinforced concrete structures. These methods require a knowledge of the behaviour of plastic hinges up to advanced curvatures. Concrete sections characteristically soften beyond the plastic phase. To analyse a strain-softening structure, many researchers have used a finite hinge length. In this paper, existing formulae are re-examined and the effects of different variables on hinge length are discussed. Experimentally measured values are compared with the values predicted by using these formulae. It is shown that the upper and lower bounds suggested by the ACI committee 428 provide reliable estimates of hinge lengths for both normal and high-strength concrete flexural hinges up to 80 MPa.

Universal Properties in Filler-Loaded Rubbers

1994 ◽  
Vol 67 (1) ◽  
pp. 1-16 ◽  
Author(s):  
H. G. Kilian ◽  
M. Strauss ◽  
W. Hamm
Keyword(s):  
Power Law ◽  
Filler Particle ◽  
Simple Extension ◽  
Stress Strain ◽  
Normal Forces ◽  
Matrix Interactions ◽  
Universal Properties ◽  
Filler Particles ◽  
Bridge Distribution ◽  
Interfacial Slippage

Abstract Stress-strain cycles in filler loaded rubbers can be described with the aid of the van der Waals-network model. Reinforcement comes about by drawing pairs of filler particles apart. Reinforcement is observed because the intrinsic strain within the rubber bridge which is located between the filler particles exceeds the macroscopic strain very much, so much that interfacial slippage is enforced. The rubbery intra-cluster bridge distribution is represented by three dominant filler particle distances. One of them describes direct filler-to-filler (FF-) contacts, the critical strength of which is different from the filler-to-matrix (FM-) contacts of the filler-to-filler chains which are located on the whole surface of the filler particles. Formation of clusters is described by a power law. Stress-strain experiments are described with the aid of this model for different filler-matrix combinations (NR, SBR, carbon blacks, silica). Many universal features are observed: The intra-cluster rubber bridges display the same mean thickness when being related to the radius of the primary filler particles. The exponent in the power law is always identical. The deformation mechanisms, including irreversible slippage, do not to depend on the type of strain (simple extension, uniaxial compression). Yet, the Einstein-Smallwood effect turns out to be anisotrop so far as quasipermanent filler-to-matrix interactions seem to be determined by normal forces in the particles surfaces only. Different filler and matrix combinations display different strengths of the FF- and FM-contacts independent of the type of strain.

scholarly journals Axial Compression Behavior of Circular Concrete-Filled High-Strength Thin-Walled Steel Tubular Columns with Out-of-Code D/t Ratios

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Jun-Xin Li ◽  
Jian-Tao Wang ◽  
Qing Sun ◽  
Yan-Ru Wu ◽  
Shi-Ming Zhou ◽  
...  
Keyword(s):  
Axial Compression ◽  
Full Range ◽  
High Strength ◽  
Displacement Curve ◽  
Fe Model ◽  
Range Analysis ◽  
Cross Sectional ◽  
Compression Behavior ◽  
Thin Walled ◽  
Cfst Columns

This paper systematically investigated the axial compression behavior of circular concrete-filled high-strength thin-walled steel tubular (CFHTST) columns with out-of-code diameter-to-thickness (D/t) ratios. The axial compression test was first conducted to examine the failure mode, load-displacement curves, and composite mechanism effect. The finite element (FE) model was thereafter established to perform full-range analysis on the load versus displacement curve as well as the interaction behavior, where the parametric study was performed to investigate the influences of the material strengths and geometric sizes. Subsequently, the applicability of typical design methods was evaluated, and a revised equation for determining strain εscy corresponding to ultimate strength was established to assess the plastic deformation capacity of CFHTST columns. Finally, a theoretical model for calculating axial bearing capacity was derived based on unified twin-shear strength theory by considering the influence of intermediate principal stress. The research results indicate that a relatively high confine effect can be guaranteed for CFHTST columns under out-of-code D/t ratios, given that the ratio Nu/Nnom between the measured capacity (Nu) and nominal cross-sectional capacity (Nnom) mainly distributes within 1.179∼1.292; the full-range analysis reflects that the axial load-deformation curve can be distinguished by four various loading stages; the scope b = 0.3∼0.55 of intermediate stress coefficient is generally suggested for predicting axial strength of circular CFST columns within an error of ±5%. The abovementioned study can provide the meaningful design reference for the analysis and application of CFHTST columns.

scholarly journals Where do we go with HIV pre-exposure prophylaxis in Indonesia?

2017 ◽  
Vol 5 (2) ◽  
pp. 77
Author(s):  
I Nyoman Sutarsa
Keyword(s):  
Full Range ◽  
Scale Up ◽  
Public Health Intervention ◽  
People Living With Hiv ◽  
Mortality And Morbidity ◽  
Preventative Measures ◽  
Treatment Measures ◽  
Exposure Prophylaxis ◽  
Living With Hiv ◽  
Current Systems

Mantled by discrimination and exclusion, HIV/AIDS became a major epidemic of present-day globalization. Access to antiretroviral therapy (ART) and numerous preventative measures have resulted in reduced mortality and morbidity rates.1 However, the burden of disease associated with HIV infection remains tremendous. Total number of people living with HIV in 2016 were 36.7 million. PrEP is an effective additional prevention strategy at trial settings. Decision to adopt PrEP as a public health intervention must be made based on the need and capacity of current systems. Instead of allocating substantial resources for PrEP, the limited resources could be wisely allocated to scale-up the existing prevention strategies including access to ART, as well as to ensure equality of access of people to full-range of HIV prevention and treatment measures.

scholarly journals Numerical Behaviour of Composite K-Joints Subjected to Combined Loading and Corrosive Environment

2018 ◽  
Author(s):  
Chao Hou ◽  
Shameer Saleh ◽  
Lin-Hai Han ◽  
You-Xing Hua
Keyword(s):  
Failure Modes ◽  
Full Range ◽  
Steel Tube ◽  
Combined Loading ◽  
Truss Structures ◽  
Mechanism Analysis ◽  
Corrosive Environment ◽  
Range Analysis ◽  
Element Analysis ◽  
Fea Model

Concrete filled steel tubular (CFST) truss structures have been adopted in various infrastructures worldwide for past several decades. Application of CFST truss is more prevalent especially in areas where harsh marine condition with chloride corrosion limits the design life of structures. Design of joints is one of the most complicated issues in CFST truss structures; and it becomes more critical when corrosion causes section loss in the outer steel tube. Improved designs in terms of economy and durability need to be suggested based on rational research on composite K-joints in corrosive environment, whilst such research is very limited up until now. This paper thus attempts to study the behaviour of circular concrete filled steel tubular (CFST) K-joints under combined effect of long-term loading and corrosion. A finite element analysis (FEA) model is presented and verified against existing test results. The model is then utilized to perform mechanism analysis of CFST K-joints under varying loading and corrosion situations. Failure modes, detailed propagation of yield and stress distribution between the core concrete in chord and the tubular steel is investigated, based on which a favourable mode of failure is suggested in terms of maximum joint capacity. Finally, a full range analysis of the load-deformation characteristics is carried out for various corrosion situations, with the corresponding joint strength as well as ductility predicted.

scholarly journals Pseudo-Ductility, Morphology and Fractography Resulting from the Synergistic Effect of CaCO3 and Bentonite in HDPE Polymer Nano Composite

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3333
Author(s):  
Tauseef Ahmed ◽  
Hamdan H. Ya ◽  
Rehan Khan ◽  
Abdul Munir Hidayat Syah Lubis ◽  
Shuhaimi Mahadzir
Keyword(s):  
Synergistic Effect ◽  
Filler Particle ◽  
Stress Transfer ◽  
Polymeric Materials ◽  
High Strength ◽  
Type I ◽  
Nano Composite ◽  
Rigid Particles ◽  
Rigid Filler ◽  
Filler Particles

Polymeric materials such as High density polyethylene(HDPE) are ductile in nature, having very low strength. In order to improve strength by non-treated rigid fillers, polymeric materials become extremely brittle. Therefore, this work focuses on achieving pseudo-ductility (high strength and ductility) by using a combination of rigid filler particles (CaCO3 and bentonite) instead of a single non-treated rigid filler particle. The results of all tensile-tested (D638 type i) samples signify that the microstructural features and surface properties of rigid nano fillers can render the required pseudo-ductility. The maximum value of tensile strength achieved is 120% of the virgin HDPE, and the value of elongation is retained by 100%. Furthermore, the morphological and fractographic analysis revealed that surfactants are not always going to obtain polymer–filler bonding, but the synergistic effect of filler particles can carry out sufficient bonding for stress transfer. Moreover, pseudo-ductility was achieved by a combination of rigid fillers (bentonite and CaCO3) when the content of bentonite dominated as compared to CaCO3. Thus, the achievement of pseudo-ductility by the synergistic effect of rigid particles is the significance of this study. Secondly, this combination of filler particles acted as an alternative for the application of surfactant and compatibilizer so that adverse effect on mechanical properties can be avoided.

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