Grain shape effects on dielectric and electrical properties of rocks

Geophysics ◽  
1984 ◽  
Vol 49 (5) ◽  
pp. 586-587 ◽  
Author(s):  
P. N. Sen
Keyword(s):  
Grain Shape ◽  
Angular Frequency ◽  
Dc Conductivity ◽  
Dielectric Constants ◽  
Water Conductivity ◽  
Depolarization Factor ◽  
The Matrix ◽  
Shape Effects ◽  
Dielectrical Properties ◽  
The Right

Recently there has been a considerable interest in the effect of anisotropy in the grain shape in the electrical and dielectrical properties of rocks and other inhomogeneous media (Sen 1981a, b; Sen et al, 1981; Mendelson and Cohen, 1982; and Kenyon, 1983). In this note I point out that equation (34) of Mendelson and Cohen (MC) is incorrect. The dc limit of MC equation (34) for the conductivity of rock σ, in terms of porosity ϕ and water conductivity [Formula: see text], gives [Formula: see text] or [Formula: see text] where [Formula: see text] L is the depolarization factor along the principal axis of spheroidal grain and 〈 〉 denotes an average over the distribution in L. This value of [Formula: see text] is in disagreement with the correct value of m in equation (28) of MC [equation (6) below]. [When the sign mistakes in equations MC (33)–(34) are corrected, [Formula: see text]. This agrees with equation (6) below for the case when L has a single value and averaging is redundant.] This inconsistency arises from an incorrect replacement of the inverse of an average in MC equation (33) by an average of inverses. The corrected form of MC equation (33) is [Formula: see text] where ε and [Formula: see text] are the dielectric constants of the mixture and of the matrix, respectively. The dielectric constant [Formula: see text] is complex, [Formula: see text] is real, [Formula: see text] is the permittivity of vacuum, σ the conductivity, ω the angular frequency. The last factor in the right‐hand side of the equation was replaced incorrectly by the average of the inverse, which is incorrect in general. Note that in the dc limit equation (4) above gives [Formula: see text] and, by integration, [Formula: see text] where [Formula: see text] is the dc conductivity of water, σ(0) is the dc conductivity of formation, and [Formula: see text]

Chitosan-Bentonite Crosslinked Film As Indicator for Copper (II) Ions Adsorption

2021 ◽  
Author(s):  
Nurul Huda Osman ◽  
Nurul Najiha Mazu ◽  
Josephine Liew Ying Chyi ◽  
Muhammad Mahyiddin Ramli ◽  
Mohammad Abdull Halim Mohd Abdull Majid ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Impedance Spectroscopy ◽  
Adsorption Capacity ◽  
Contact Time ◽  
Dc Conductivity ◽  
Dielectric Constants ◽  
Peak Amplitude ◽  
Electrical Parameters ◽  
Before And After

This paper reports on chitosan/bentonite crosslinked (ChB-ECH) film for removal of Cu (II). The effects of chitosan/bentonite ratio on the removal percentage were studied along with the effect of different Cu (II) concentration and the contact time on the film adsorption capacity, qt. The electrical properties of the film are studied, before and after the adsorption occurred, by using impedance spectroscopy for different parameters such as DC conductivity, the complex dielectric constants (ε’ and ε”) and complex electrical modulas (M’ and M’’). The results showed that the chitosan/bentonite ratio of 3:1 produces highest removal percentage at 29 %, while the contact time of 120 minutes was found to be optimum. An increment in the DC conductivity of the ChB-ECH film’s was observed up to 10-7 S/cm as the removal percentage of film increased. The film with the highest Cu (II) adsorb also showed the highest value for ε’ and ε” while exhibiting non-Derby behavior. Shifting of peak amplitude of the M” towards the higher frequency was also observed as the Cu (II) adsorption in the film increased. The results showed that all the electrical parameters can be utilized to determine the amount of adsorbed copper (II) in chitosan/bentonite film.

scholarly journals Improvement of the Impact Properties of Composite Laminates by Means of Nano-Modification of the Matrix—A Review

2018 ◽  
Vol 8 (12) ◽  
pp. 2406 ◽  
Author(s):  
Hamed Saghafi ◽  
Mohamad Fotouhi ◽  
Giangiacomo Minak
Keyword(s):  
Composite Laminates ◽  
Cost Effective ◽  
Careful Consideration ◽  
Impact Performance ◽  
Compression After Impact ◽  
The Matrix ◽  
The Right ◽  
2D And 3D ◽  
The Impact ◽  
Selection Of

This paper reviews recent works on the application of nanofibers and nanoparticle reinforcements to enhance the interlaminar fracture toughness, to reduce the impact induced damage and to improve the compression after impact performance of fiber reinforced composites with brittle thermosetting resins. The nanofibers have been mainly used as mats embedded between plies of laminated composites, whereas the nanoparticles have been used in 0D, 1D, 2D, and 3D dimensional patterns to reinforce the matrix and consequently the composite. The reinforcement mechanisms are presented, and a comparison is done between the different papers in the literature. This review shows that in order to have an efficient reinforcement effect, careful consideration is required in the manufacturing, materials selection and reinforcement content and percentage. The selection of the right parameters can provide a tough and impact resistant composite with cost effective reinforcements.

The inflammatory macrophage: a story of Jekyll and Hyde

2002 ◽  
Vol 104 (1) ◽  
pp. 27-38 ◽  
Author(s):  
Jeremy S. DUFFIELD
Keyword(s):  
Apoptotic Cells ◽  
Tissue Healing ◽  
Immune Mediated ◽  
Selective Depletion ◽  
The Matrix ◽  
Matrix Components ◽  
The Right ◽  
Extracellular Structures ◽  
Two Populations ◽  
Inflammatory Macrophage

Recent investigations have highlighted new roles for the macrophage (Mϕ) in the biology of inflammation. Selective depletion of Mϕs from inflamed sites has confirmed their predominant role in immune-mediated damage. The components of this injury have been dissected. Mϕs mediate death of stromal, parenchymal and other immune cells by engaging the death programme, resulting in apoptosis. In addition, Mϕs induce destruction of matrix and extracellular structures both directly and indirectly by inducing stromal cells to release matrix metalloproteinases. However, there is another side to the inflammatory Mϕ. Evidence is provided that Mϕs at the same sites possess the ability to aid cell proliferation, secrete and stabilize new matrix components and induce resident cells to secrete matrix components themselves. Mϕ phagocytosis of apoptotic cells brings about a change from the cell-killing matrix-degrading cell to the matrix-generating cell-proliferating tissue-healing cell. Just as both Mϕ types are necessary at the inflamed site, the right balance of these two populations is required for healing and resolution. Evidence of excessive inflammation as a manifestation of impaired phagocytosis of apoptotic cells emphasizes that defects in the transition from one Mϕ type to another may account for the uncontrolled excessive inflammation seen in disease. Recent insights into the mechanisms by which apoptotic cells signal the change of function to the Mϕ offer the prospect of novel targets for manipulation of Mϕs in the inflamed tissue.

The Role of Average Health Status

2016 ◽  
pp. 884-899
Author(s):  
Jordan Panayotov
Keyword(s):  
Health Status ◽  
Population Health ◽  
Gold Standard ◽  
Health Impact ◽  
Local Context ◽  
Policy Options ◽  
The Matrix ◽  
The Right ◽  
No Gold Standard ◽  
Average Health

Economic, social and environmental policies, programs and projects have impact on health. Health in All Policies (HiAP) aims to improve population health by taking into account these impacts. HiAP needs appropriate tools for assessing impacts on population health. When making choices between policy options, decision-makers rely on predictions from Health Impact Assessment. Currently there is no gold standard for establishing and assessing validity of predictions. This paper distinguishes between two levels of causal pathways regarding health impacts – specific and conditional, and proposes the Average Health Status – Health Inequalities Matrix as gold standard. The Matrix facilitates making the right choices at any level and local context, thus is useful for researchers, policy-makers and practitioners for designing, analysing and evaluating all kinds of policies. By allowing quick, reliable and inexpensive appraisal of different policy options the matrix makes feasible taking into account the impacts on population health and paves the way for institutionalizing of HiAP.

Strain History and Polar Decomposition

1996 ◽  
Author(s):  
Gerhard Oertel
Keyword(s):  
Polar Decomposition ◽  
Transformation Matrix ◽  
Strain History ◽  
Transformation Matrices ◽  
Before And After ◽  
The Matrix ◽  
Principal Stretches ◽  
Principal Directions ◽  
The Right ◽  
Asymmetric Transformation

The effect of two consecutive strains (only two states enter into the calculation of a strain, the states before and after, independently of the actual strain path) can be calculated by premultiplying the transformation matrix of the first strain (its stretch tensor) with that of the second. Unless the two strains are coaxial (their principal directions coincide), however, the resulting cumulative transformation matrix represents not only a strain but also a rigid-body rotation; in that case the matrix is asymmetric. The method of polar decomposition allows one to interpret the combined transformation as if it had come about either by a strain followed by a rotation (right polar decomposition) or by a rotation followed by a strain (left polar decomposition). Let 𝔸 and 𝔹 be two stretch tensors, or transformation matrices, representing each a strain without rotation; and let the strain 𝔹 follow the strain 𝔸. Then the combined transformation matrix 𝔽 is: . . . 𝔹𝔸 = 𝔽 = ℝ𝕌= 𝕍ℝ, (8.1) . . . where 𝔽 results from premultiplication of the earlier stretch 𝔸 with the later 𝔹, where ℝ𝕌 is the “right” and 𝕍ℝ the “left” decomposition of 𝔽, where 𝕌 and 𝕍 are two distinct stretch tensors, and where ℝ is the transformation matrix for a rotation (elements of rotation matrices are indicated by the symbol aij elsewhere in this book). 𝔽 is asymmetric and ℝ differs from the identity matrix (δij) except when 𝔸 and 𝔹 are coaxial. 𝕌 and 𝕍 have the same principal stretches and differ by orientation only. In Problems 120 to 122, false approaches in the search for an appropriate decomposition of an asymmetric transformation were recognized by yielding impossible values for a rotation. Application of eq. (8.1) makes such a trial-and-error approach unnecessary.

scholarly journals Functional Polymer Hybrid Nanocomposites Based on Polyolefins: A Review

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1475
Author(s):  
Sandra Paszkiewicz ◽  
Krzysztof Pypeć ◽  
Izabela Irska ◽  
Elzbieta Piesowicz
Keyword(s):  
Uniform Distribution ◽  
Hybrid Nanocomposites ◽  
Entire Volume ◽  
Polymer Hybrid ◽  
Engineering Plastics ◽  
The Matrix ◽  
The Right ◽  
Performance Results ◽  
Relationship Of ◽  
Structure Properties

For the last twenty years, polymer hybrid nanocomposites have enjoyed unflagging interest from numerous scientific groups and R&D departments, as they provide notable enhancement of properties, even at low nanofillers’ content. Their performance results from many factors, the most important of which is the uniform distribution in the entire volume of the matrix, that still is very challenging, but is the right choice of two types of nanoparticles that can lead to an increase of dispersion stability and even more uniform distribution of fillers. The incorporation of two types of nanofillers, especially when they differ in aspect ratio or chemical nature, allows to additively reduce the price of the final composite by replacing the more expensive filler with the cheaper one, or even synergistically improving the properties, e.g., mechanical, thermal, and barrier, etc., that can extend their usage in the industry. Despite numerous review papers on nanocomposites, there is no review on how the introduction of a hybrid system of nanofillers affects the properties of polyolefins, which are the most commonly used engineering plastics. This review deeply focuses on the structure–properties relationship of polyolefins-based hybrid nanocomposites, especially based on two types of polyethylenes (low-density polyethylenes (LDPE) and high-density polyethylenes (HDPE)) and polypropylene.

scholarly journals Structural Organization of Themagnetic Part of Smart Material Based on Nanoparticles of Iron or Magnetite in Pores of Mcm-41 Mesoporous Silica for Target Drug Delivery

2018 ◽  
Vol 57 (2) ◽  
pp. 175-182
Author(s):  
E.G. Zemtsova ◽  
A.N. Ponomareva ◽  
A.Y. Arbenin ◽  
V.M. Smirnov
Keyword(s):  
Drug Delivery ◽  
Mesoporous Silica ◽  
Smart Material ◽  
The Body ◽  
Superparamagnetic Nanoparticles ◽  
Target Drug Delivery ◽  
Target Drug ◽  
The Matrix ◽  
The Right ◽  
Mcm 41

Abstract The important stage of the development of smart material for the target drug delivery is the construction of the magnetic part of this material, including mesoporous silica and magnetic nanoparticles (Fe3O4or Fe0). Such a systemwill allow carry outmagnetic decapsulation (excretion) of drug from smart material using the magnetic field of a given value in the right place of the body. The paper considers the features of synthesis mesoporous silica MCM-41 with various pore diameter (33-51 Å) and synthesis of superparamagnetic nanoparticles of magnetite or metallic iron in the pores of mesoporous silica. The dependence of magnetic properties of nanocomposites MCM-41/Fe0 and MCM-41/Fe3O4 from the pore diameters of MCM-41 templates is studied. It was found that the matrix has a decisive influence on the content of iron or magnetite nanoparticles. The saturation magnetization of the material increases with increasing pore size of the mesoporous matrix. Nanocomposites MCM-41/Fe0 and MCM-41/Fe3O4 exhibit superparamagnetism, that allows them to be used as a magnetic material for targeted drug delivery.

Fractal Geometry and Properties of Doped BaTiO3 Ceramics

2010 ◽  
Vol 67 ◽  
pp. 42-48 ◽  
Author(s):  
V.V. Mitic ◽  
V.B. Pavlovic ◽  
L. Kocic ◽  
V. Paunovic ◽  
L. Zivkovic
Keyword(s):  
Fractal Dimension ◽  
Solid State ◽  
Fractal Geometry ◽  
Grain Shape ◽  
Grain Structure ◽  
Fractal Method ◽  
Ceramic Structure ◽  
New Approach ◽  
Fractal Modeling ◽  
Dielectrical Properties

Taking into account that the complex grain structure is difficult to describe by using traditional analytical methods, in this study, in order to establish ceramic grain shapes of sintered BaTiO3, new approach on correlation between microstructure and properties of doped BaTiO3 ceramics based on fractal geometry has been developed. BaTiO3 ceramics doped with various dopants (MnCO3, Er2O3, Yb2O3) were prepared using conventional solid state procedure, and were sintered at 1350oC for four hours. The microstructure of sintered specimens was investigated by SEM-5300. Using method of fractal modeling a reconstruction of microstructure configurations, like grains shapes, or intergranular contacts has been successfully done. Furthermore, the area of grains surface was calculated using fractal correction that expresses the irregularity of grains surface through fractal dimension. The presented results, indicate that fractal method for ceramics structure analysis provides a new approach for describing, predicting and modeling the grain shape and relations between the BaTiO3-ceramic structure and dielectrical properties.

scholarly journals Research of the Robust Stability of Control Systems Using a New Approach to the Lyapunov Functions Construction

2015 ◽  
Vol 9 (11) ◽  
pp. 176 ◽  
Author(s):  
Gulzhan Uskenbayeva
Keyword(s):  
Robust Stability ◽  
Lyapunov Functions ◽  
Closed Loop ◽  
Time Derivative ◽  
State Equation ◽  
The State ◽  
New Approach ◽  
Vector Lyapunov Functions ◽  
The Matrix ◽  
The Right

<p class="22">We investigate a new approach to the construction of vector Lyapunov functions. An approach to the construction of Lyapunov functions as vector functions is developed based on a geometrical interpretation of the second method of Lyapunov. The negative of the gradient is determined from the components of the time derivative of the state vector (i.e., the right-hand side of the state equation). The region of stability of a closed-loop linear, stationary system with uncertain parameters is governed by inequalities in the matrix elements of the closed-loop system. This study developed a method for analysing the robust stability of SISO and MIMO linear systems in canonical forms.</p>

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