Development of a Numerical Model to Predict the Dielectric Properties of Heterogeneous Asphalt Concrete

Ground-penetrating radar (GPR) has been used for asphalt concrete (AC) pavement density prediction for the past two decades. Recently, it has been considered as a method for pavement quality control and quality assurance. A numerical method to estimate asphalt pavement specific gravity from its dielectric properties was developed and validated. A three-phase numerical model considering aggregate, binder, and air void components was developed using an AC mixture generation algorithm. A take-and-add algorithm was used to generate the uneven air-void distribution in the three-phase model. The proposed three-phase model is capable of correlating pavement density and bulk and component dielectric properties. The model was validated using field data. Two methods were used to calculate the dielectric constant of the AC mixture, including reflection amplitude and two-way travel time methods. These were simulated and compared when vertical and longitudinal heterogeneity existed within the AC pavement layers. Results indicate that the reflection amplitude method is more sensitive to surface thin layers than the two-way travel time methods. Effect of air-void content, asphalt content, aggregate gradation, and aggregate dielectric constants on the GPR measurements were studied using the numerical model.

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Effect of Moisture Content on Calculated Dielectric Properties of Asphalt Concrete Pavements from Ground-Penetrating Radar Measurements

Remote Sensing ◽

10.3390/rs14010034 ◽

2021 ◽

Vol 14 (1) ◽

pp. 34

Author(s):

Qingqing Cao ◽

Imad L. Al-Qadi

Keyword(s):

Dielectric Properties ◽

Numerical Model ◽

Moisture Content ◽

Ground Penetrating Radar ◽

Asphalt Concrete ◽

Concrete Pavements ◽

Proposed Model ◽

Moisture Variation ◽

Ground Penetrating ◽

Non Destructive

Moisture presence in asphalt concrete (AC) pavement is a major cause of damage to the pavement. In recent decades, an increasing need exists for non-destructive detection and monitoring of the moisture content in AC pavement. This paper provides a simulated approach to quantify the effect of internal moisture content on AC pavement dielectric properties using ground-penetrating radar (GPR). A heterogeneous numerical model was developed to simulate AC pavement with internal moisture at various saturation levels. The numerical model was validated using GPR surveys on cold-in-place recycling treated pavements. An empirical formula was derived from the simulation to correlate the dielectric constant with the moisture content for non-dry AC pavement. The results validated the proposed model and, hence, demonstrated the ability of GPR to monitor moisture variation in AC pavements.

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Influence of Al Particle Size and Lead Zirconate Titanate (PZT) Volume Fraction on the Dielectric Properties of PZT-Epoxy-Aluminum Composites

Journal of Engineering Materials and Technology ◽

10.1115/1.4004812 ◽

2011 ◽

Vol 133 (4) ◽

Cited By ~ 13

Author(s):

S. Banerjee ◽

K. A. Cook-Chennault

Keyword(s):

Dielectric Properties ◽

Lead Zirconate Titanate ◽

Volume Fraction ◽

Lead Zirconate ◽

Dielectric Constants ◽

Aluminum Composites ◽

Aluminum Particles ◽

Volume Fractions ◽

Zirconate Titanate ◽

Three Phase

Two-phase PZT-epoxy piezoelectric composites and three phase PZT-epoxy-Al composites were fabricated using a poling voltage of 0.2 kV/mm. The influence of aluminum inclusion size (nano and micron) and (lead zirconate titanate) PZT volume fraction on the dielectric properties of the three phase PZT-epoxy-aluminum composites were experimentally investigated. In general, dielectric and piezoelectric properties of the PZT-epoxy matrix were improved with the addition of aluminum particles. Composites that were comprised of micron scale aluminum inclusions demonstrated higher piezoelectric d33-strain-coefficients, and higher dielectric loss compared to composites that were comprised of nanosize aluminum inclusions. Specifically, composites comprised of micron sized aluminum particles and PZT volume fractions of 20%, 30%, and 40% had dielectric constants equal to 405.7, 661.4, and 727.8 (pC/N), respectively, while composites comprised of nanosize aluminum particles with the same PZT volume fractions, had dielectric constants equal to 233.28, 568.81, and 657.41 (pC/N), respectively. The electromechanical properties of the composites are influenced by several factors: inclusion agglomeration, contact resistance between particles, and air voids. These composites may be useful for several applications: structural health monitoring, energy harvesting, and acoustic liners.

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Transport of organochlorine pesticides in soil columns enhanced by dissolved organic carbon

Water Science & Technology ◽

10.2166/wst.1997.0270 ◽

1997 ◽

Vol 35 (7) ◽

pp. 139-145 ◽

Cited By ~ 10

Author(s):

Jiann-Yuan Ding ◽

Shian-Chee Wu

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Organochlorine Pesticides ◽

Transport Model ◽

Phase Model ◽

Soil Columns ◽

Two Phase ◽

Three Phase ◽

Phase Transport ◽

Remediation Of Soil

The objective of this study is to quantify the effects of humic acid solution infiltration on the transport of organochlorine pesticides (OCPs) in soil columns using a three-phase transport model. From experimental results, it is found that the dissolved organic carbon enhances the transport of OCPs in the soil columns. In the OCPs-only column, the concentration profiles of OCPs can be simulated well using a two-phase transport model with numerical method or analytical solution. In the OCPs-DOC column, the migrations of aldrin, DDT and its daughter compounds are faster than those in the OCPs-only column. The simulation with the three-phase model is more accurate than that with the two-phase model. In addition, significant decrease of the fluid pore velocities of the OCPs-DOC column was found. When DOC leachate is applied for remediation of soil or groundwater pollution, the decrease of mean pore velocities will be a crucial affecting factor.

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Investigation of two-dimensional nonstationary processes of outflow a gas-saturated liquid from axisymmetric vessels

Proceedings of the Mavlyutov Institute of Mechanics ◽

10.21662/uim2012.1.008 ◽

2012 ◽

Vol 9 (1) ◽

pp. 47-52

Author(s):

R.Kh. Bolotnova ◽

V.A. Buzina

Keyword(s):

Comparative Analysis ◽

Numerical Model ◽

Liquid Mixture ◽

Phase Model ◽

Test Problems ◽

Two Dimensional ◽

Nonstationary Processes ◽

Saturated Liquid ◽

Two Phase ◽

One Dimensional

The two-dimensional and two-phase model of the gas-liquid mixture is constructed. The validity of numerical model realization is justified by using a comparative analysis of test problems solution with one-dimensional calculations. The regularities of gas-saturated liquid outflow from axisymmetric vessels for different geometries are established.

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Autocratisation by Term Limits Manipulation in Sub-Saharan Africa

Africa Spectrum ◽

10.1177/0002039720964218 ◽

2020 ◽

Vol 55 (3) ◽

pp. 228-250 ◽

Cited By ~ 1

Author(s):

Andrea Cassani

Keyword(s):

Comparative Studies ◽

Political Competition ◽

Chief Executive ◽

Term Limits ◽

Sub Saharan Africa ◽

Phase Model ◽

Econometric Modelling ◽

Three Phase ◽

Sub Saharan ◽

Personal Rule

Besides the introduction of multi-party elections, the sub-Saharan wave of democratic reforms of the 1990s encompassed the introduction of limits to the number of terms that a chief executive can serve. Executive term limits (ETLs) are key for democracy to advance in a continent with a legacy of personal rule. However, the manipulation of ETLs has become a recurring mode of autocratisation, through which African aspiring over-stayers weaken executive constraints, taint political competition, and limit citizens’ possibility to choose who governs. This article presents a three-phase model of autocratisation by ETL manipulation and, using new data, offers one of the first regional comparative studies of ETL manipulation in sub-Saharan Africa that rests on econometric modelling. The analysis leads to revisiting some previous findings on the drivers of ETL manipulation and highlights the relevance of other previously underestimated factors that may either discourage a leader from challenging ETLs or prevent their successful manipulation.

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Dielectric Properties of Wood-Polymer Composites: Effects of Frequency, Fiber Nature, Proportion, and Chemical Composition

Journal of Composites Science ◽

10.3390/jcs5060141 ◽

2021 ◽

Vol 5 (6) ◽

pp. 141

Author(s):

Imen Elloumi ◽

Ahmed Koubaa ◽

Wassim Kharrat ◽

Chedly Bradai ◽

Ahmed Elloumi

Keyword(s):

Dielectric Properties ◽

Polymer Composites ◽

Wide Frequency Range ◽

Dielectric Constants ◽

Cellulose Content ◽

Wood Fibers ◽

Low Frequencies ◽

Wood Polymer ◽

Wood Polymer Composites ◽

New Applications

The characterization of the dielectric properties of wood–polymer composites (WPCs) is essential to understand their interaction with electromagnetic fields and evaluate their potential use for new applications. Thus, dielectric spectroscopy monitored the evolution of the dielectric properties of WPCs over a wide frequency range of 1 MHz to 1 GHz. WPCs were prepared using mixtures of different proportions (40%, 50%, and 60%) of wood and bark fibers from various species, high-density polyethylene, and maleated polyethylene (3%) by a two-step process, extrusion and compression molding. Results indicated that wood fibers modify the resistivity of polyethylene at low frequencies but have no effect at microwave frequencies. Increasing the fiber content increases the composites’ dielectric properties. The fibers’ cellulose content explains the variation in the dielectric properties of composites reinforced with fibers from different wood species. Indeed, composites with high cellulose content show higher dielectric constants.

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Crystallization and dielectric properties of SrO–BaO–Nb2O5–GeO2 tungsten–bronze glass–ceramics

Journal of Materials Research ◽

10.1557/jmr.2001.0282 ◽

2001 ◽

Vol 16 (7) ◽

pp. 2057-2063 ◽

Cited By ~ 10

Author(s):

Jiin-Jyh Shyu ◽

Hsin-Wei Peng

Keyword(s):

Heat Treatment ◽

Dielectric Properties ◽

Tungsten Bronze ◽

Glass Ceramics ◽

Dielectric Behavior ◽

Dendritic Morphology ◽

Dielectric Constants ◽

Two Stage ◽

Tetragonal Tungsten Bronze ◽

Stage Heat Treatment

The crystallization and dielectric properties of SrO–BaO–Nb2O5–GeO2 glass–ceramics were investigated. One- and two-stage heat-treatment methods were used to convert the parent glass to glass–ceramics. Strontium barium niobate (SBN) with a tetragonal tungsten-bronze structure formed as the major crystalline phase. When the crystallizing temperature/time was increased, the secondary crystalline BaGe2O5 phase coexisted with SBN. BaGe2O5 formed as a surface layer grown from the surface into the interior of the sample. The dendritic morphology of SBN crystals was examined. The glass–ceramics crystallized by two-stage heat treatment have higher dielectric constants than those crystallized by one-stage heat treatment. The highest dielectric constant that was obtained in the present glass–ceramics was 320. The glass–ceramics showed relaxor-type dielectric behavior.

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