scholarly journals Feasibility Study on Measuring the Particulate Matter Level in the Atmosphere by Means of Yagi–Uda-Like Antennas

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3225 ◽  
Author(s):  
Aarón A. Salas-Sánchez ◽  
Julian Rauch ◽  
M. Elena López-Martín ◽  
J. Antonio Rodríguez-González ◽  
Giorgio Franceschetti ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Simulated Annealing ◽  
Method Of Moments ◽  
Surrounding Medium ◽  
Measurement Procedure ◽  
Characteristic Parameters ◽  
Trade Off ◽  
Promising Solution ◽  
Moderate Length ◽  
Concentration Levels

In this work, the application of a technique for monitoring changes of the dielectric constant of the atmosphere caused by the presence of pollution is discussed. The method is based on changes in the reflection coefficient of the device induced by these dielectric constant variations of the surrounding medium. To that end, several Yagi–Uda-like antenna designs with different size limitations were simulated by using a Method-of-Moments software and optimized by means of a simulated annealing strategy. It has been found that the larger the optimal elements of the array are allowed to be, the higher the sensitivity reached. Thus, in a trade-off between sensitivity and moderate length (regarding flexibility purposes), the most promising solution has been built. This prototype has been experimentally tested in presence of an artificial aerosol made of PAO (polyalphaolefin) oil and black carbon inclusions of a size of 0.2 μm. As a result, potentials for developing a measurement procedure by means of changes in the characteristic parameters of the antenna led by different concentration levels of suspended particles in the surrounding medium are shown. In this manner, a local mapping of polluted levels could be developed in an easy, real-time, and flexible procedure.

Preliminary First Principles Study Of Hf and Zr Aluminates as Replacement High-k Dielectrics

2001 ◽  
Vol 670 ◽  
Author(s):  
Michael Haverty ◽  
Atsushi Kawamoto ◽  
Gyuchang Jun ◽  
Kyeongjae Cho ◽  
Robert Dutton
Keyword(s):  
Density Functional Theory ◽  
Dielectric Constant ◽  
Bulk Density ◽  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Conduction Band Edge ◽  
Functional Theory ◽  
Trade Off ◽  
High K

ABSTRACTBulk Density Functional Theory calculations were performed on Hf and Zr substitutions for Al in κ-alumina. The lowest energy configuration found was an octahedrally coordinated Zr site. Zr dissolution was favorable with an enthalpy of -2eV/unit cell for forming Al1.875Zr0.125O3 from pure Zr and κ-alumina. Hf and Zr substitution for Al atoms introduced empty d-states below the conduction band edge reducing the Eg of pure κ-alumina (7.5eV) to 6.4-5.9eV. The edge of the valence band however remained fixed by the O p-state character. The substitution of Hf and Zr into the alumina structure may lead to a higher dielectric constant, but will also reduce Eg and result in a trade off in tunneling currents in devices.

Multi-Objective Hydraulic Optimization on Intake Duct of Water-Jet Propulsion Using NSGA-II

2019 ◽  
Author(s):  
Rui Zhu ◽  
Puyu Cao ◽  
Yang Wang ◽  
Chao Ning
Keyword(s):  
Pareto Front ◽  
Water Jet ◽  
Outlet Section ◽  
Characteristic Parameters ◽  
Upper Lip ◽  
Nsga Ii ◽  
Lower Lip ◽  
Trade Off ◽  
Jet Propulsion ◽  
Multi Objective

Abstract Flow distortions occur at the outlet section of the intake duct owing to its shape properties, which is a component of water-jet propulsion. Since the noticeable influence of intake’s flow characteristics upon propulsive efficiency, it’s necessary to focus on intake duct redesign. In this paper, a systematic methodology for reducing flow distortions and power losses within the intake duct through a shape optimization process was obtained. In addition, the mechanism of flow distortions was also developed. The flush type inlet applied in the marine vessel with the speed of 30 knots was chosen as research project. Four characteristic parameters were set as optimization variables depending on the geometrical relationship of thirteen characteristic parameters referred to the duct longitudinal midsection, which were the ramp angle α, the radius of the upper lip R3, the radius of the lower lip R4 and the lip height h respectively. Subsequently, a sample space was built by Latin Hypercube Sampling (LHS) and the parameters were normalized in the range of 0 to 1. With the commercial software CFX, the numerical simulation was accomplished driven by SST k-ω turbulence model. Multi-objective optimization based on the Non-Dominated Sorting Genetic Algorithm II (NSGA-II) was utilized to minimize the non-uniformity at outlet section and maximize the minimal pressure at lip simultaneously. Moreover, the Radial Basis Function (RBF) neural network was employed to approximate the functional relationship between variables and objectives, which could be applied in the NSGA-II to get the Pareto Front. The minimum non-uniformity point and the trade-off point (The point both satisfies the minimum non-uniformity and the maximum minimal pressure at lip strategically) were selected from the Pareto Front. With regard to the characteristic parameters of the trade-off point, the ramp angle, the radius of the upper lip, the radius of the lower lip and the lip height are 31.91°, 11.42 mm, 400.97 mm and 55.43 mm respectively. Meanwhile, the characteristic parameters of the minimum non-uniformity point are 30.22°, 25.59 mm, 166.65 mm and 89.90 mm respectively. Ultimately, the duct outflow characteristics of prototype and optimization are compared. In terms of the trade-off point, the minimal pressure at lip increases 66.40% to −24488.93 Pa and the non-uniformity has a drop of 4.56% to 0.1571. The non-uniformity of the minimum point is 0.1481 which is reduced by 10.02%. Through the optimization of duct shape, the secondary flow (Dean vortices) is suppressed effectively. This paper is expected to provide a better comprehension of the flow field within the intake duct of water-jet propulsion.

Nonlinear Dissipation Heat Devices in Finite-Time Thermodynamics: An Analysis of the Trade-Off Optimization

2017 ◽  
Vol 42 (3) ◽  
Author(s):  
Can-can Lu ◽  
Long Bai
Keyword(s):  
Input Power ◽  
Coefficient Of Performance ◽  
Efficiency Coefficient ◽  
Nonlinear Dissipation ◽  
Characteristic Parameters ◽  
Trade Off ◽  
Heat Engines ◽  
Low Dissipation ◽  
Order Case ◽  
Quadratic Order

Abstract:The nonlinear dissipation heat devices are proposed by means of generalizing the low-dissipation heat devices to the quadratic order case. The dimensionless formulas of the output (input) power and the efficiency (coefficient of performance) for the nonlinear dissipation heat engines (refrigerators) are derived in terms of characteristic parameters for heat devices and the dimensional analysis. Based on the trade-off criterion, the optimal performance of the nonlinear dissipation heat devices is discussed in depth, and some system-specific properties for the nonlinear dissipation heat devices under the trade-off optimization are also uncovered. Our results may provide practical insight for designing actual heat engines and refrigerators.

scholarly journals Identification of Shaft Centerline Orbit for Wind Power Units Based on Hopfield Neural Network Improved by Simulated Annealing

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Kun Ren ◽  
Jihong Qu
Keyword(s):  
Neural Network ◽  
Simulated Annealing ◽  
Wind Power ◽  
Hopfield Neural Network ◽  
Affine Invariant ◽  
Characteristic Parameters ◽  
Invariant Moments ◽  
The Status ◽  
Identification Model ◽  
Better Than

In the maintenance system of wind power units, shaft centerline orbit is an important feature to diagnosis the status of the unit. This paper presents the diagnosis of the orbit as follows: acquire characters of orbit by the affine invariant moments, take this as the characteristic parameters of neural networks to construct the identification model, utilize Simulated Annealing (SA) Algorithm to optimize the weights matrix of Hopfield neural network, and then some typical faults were selected as examples to identify. Experiment’s results show that SA-Hopfield identification model performed better than the previous methods.

Properties Development During Curing of Low Dielectric-Constant Spin-On Glasses

1998 ◽  
Vol 511 ◽  
Author(s):  
Robert F. Cook ◽  
Eric G. Liniger ◽  
David P. Klaus ◽  
Eva E. Simonyi ◽  
Stephan A. Cohen
Keyword(s):  
Dielectric Constant ◽  
Mechanical Stability ◽  
Low Dielectric Constant ◽  
Thermal Expansion Mismatch ◽  
Curing Time ◽  
Semiconductor Wafer ◽  
Trade Off ◽  
Low Dielectric ◽  
Semiconductor Wafer Fabrication ◽  
Critical Aspects

ABSTRACTVariations in the electrical and mechanical properties of silsesquioxane spin-on glass thin films are examined as a function of curing time and temperature. Particular attention is paid to the trade-off between producing low dielectric constant films, suitable for advanced microelectronic interconnection structures, and mechanically stable films, able to withstand semiconductor wafer fabrication processes. Two critical aspects of the mechanical stability of spin-on glasses are shown to be: the positive thermal expansion mismatch with silicon–leading to tensile film stresses; and reactivity with water–leading to susceptibility to stress-corrosion cracking.

scholarly journals The dynamics of recovery and growth: how defoliation affects stored resources

2014 ◽  
Vol 281 (1783) ◽  
pp. 20133355 ◽  
Author(s):  
R. R. L. Atkinson ◽  
M. M. Burrell ◽  
K. E. Rose ◽  
C. P. Osborne ◽  
M. Rees
Keyword(s):  
Growth Rate ◽  
Life History ◽  
Principal Axis ◽  
Ecological Strategy ◽  
Fast Recovery ◽  
Trade Off ◽  
Carbohydrate Concentration ◽  
Total Carbohydrates ◽  
And Storage ◽  
Concentration Levels

Growth rate varies widely among species and the trade-off between growth rate and storage or maintenance traits is a principal axis of variation between species. Many plant species have substantial root stores, but very little is known about how growth rate modifies responses of these stores to defoliation and other stresses. Species with different growth rates are predicted to respond in distinct ways, because of variation in the pre-defoliation allocation to storage. Here, we quantified the dynamics of stored carbohydrates in seven species with varying growth rate, following defoliation in a pot experiment. For faster growing species, there was significant reduction in carbohydrate concentration following defoliation, followed by relatively fast recovery, whereas for slower growing species, carbohydrate concentration levels remained relatively invariant across treatments. Results for total carbohydrates mirrored those for concentration, but were not as significant. Our findings were consistent with the idea that faster growing species respond more rapidly than slower growers to defoliation, through changes in carbohydrate pool concentrations. Growth rate as an indicator of life-history and ecological strategy may therefore be key to understanding post-defoliation recovery and storage strategies.

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