scholarly journals Device for the field measurements of frequency-dependent soil properties in the frequency range of lightning currents

2020 ◽  
Vol 91 (11) ◽  
pp. 114701
Author(s):  
D. Kuklin
Keyword(s):  
Soil Properties ◽  
Field Measurements ◽  
Frequency Range ◽  
Frequency Dependent

scholarly journals Predicting Excavation-Induced Tunnel Response by Process-Based Modelling

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Linlong Mu ◽  
Jianhong Lin ◽  
Zhenhao Shi ◽  
Xingyu Kang
Keyword(s):  
Soil Properties ◽  
Urban Areas ◽  
Field Measurements ◽  
Inverse Modelling ◽  
Machine Learning Techniques ◽  
Interaction Patterns ◽  
Support Structures ◽  
Interaction Processes ◽  
Excavation Support ◽  
Artificial Neural Network Ann

Potential damages to existing tunnels represent a major concern for constructing deep excavations in urban areas. The uncertainty of subsurface conditions and the nonlinear interactions between multiple agents (e.g., soils, excavation support structures, and tunnel structures) make the prediction of the response of tunnel induced by adjacent excavations a rather difficult and complex task. This paper proposes an initiative to solve this problem by using process-based modelling, where information generated from the interaction processes between soils, structures, and excavation activities is utilized to gradually reduce uncertainty related to soil properties and to learn the interaction patterns through machine learning techniques. To illustrate such a concept, this paper presents a simple process-based model consisting of artificial neural network (ANN) module, inverse modelling module, and mechanistic module. The ANN module is trained to learn and recognize the patterns of the complex interactions between excavation deformations, its geometries and support structures, and soil properties. The inverse modelling module enables a gradual reduction of uncertainty associated with soil characterizations by accumulating field observations during the construction processes. Based on the inputs provided by the former two modules, the mechanistic module computes the response of tunnel. The effectiveness of the proposed process-based model is evaluated against high-fidelity numerical simulations and field measurements. These evaluations suggest that the strategy of combining artificial intelligence techniques with information generated during interaction processes can represent a promising approach to solve complex engineering problems in conventional industries.

Frequency dependent resistance calculation of multiple conductors

2017 ◽  
Vol 36 (5) ◽  
pp. 1396-1410
Author(s):  
Tomislav Župan ◽  
Bojan Trkulja
Keyword(s):  
Design Methodology ◽  
Numerical Approach ◽  
Effective Resistance ◽  
Proximity Effects ◽  
The Finite Element Method ◽  
Frequency Range ◽  
Frequency Dependent ◽  
Content Type ◽  
Electromagnetic Devices ◽  
Practical Implications

Purpose The purpose of this paper is to present a method for calculating frequency-dependent resistance when multiple current-carrying conductors are present. Design/methodology/approach Analytical and numerical formulations are presented. Both skin- and proximity-effects are considered in the numerical approach, whereas only skin-effect can be taken into account in analytical equations. The calculation is done using a self-developed integral equation-based field solver. The results are benchmarked using professional software based on the finite element method (FEM). Findings Results from the numerical approach are in agreement with FEM-based software throughout the whole frequency range. Analytical formulations yield unsatisfactory results in higher frequency range. When multiple conductors are mutually relatively close, the proximity-effect has an impact on effective resistance and has to be taken into account. Research limitations/implications The methodology is presented using axially symmetrical conductors. However, the same procedure can be developed for straight conductors as well. Practical implications Presented fast and stable procedure can be used in most electromagnetic devices when frequency-dependent resistance needs to be precisely determined. Originality/value The value of the presented numerical methodology lies in its ability to take both skin- and proximity-effects into account. As conductors are densely packed in most electromagnetic devices, both effects influence the effective resistance. The method can be easily implemented using a self-developed solver and yields satisfactory results.

scholarly journals Operational Amplifiers Revisited for Low Field Magnetic Resonance Relaxation Time Measurement Electronics

Proceedings ◽  
2019 ◽  
Vol 42 (1) ◽  
pp. 1
Author(s):  
Najlaa K. Almazrouei ◽  
Michael I. Newton ◽  
Robert H. Morris
Keyword(s):  
Relaxation Time ◽  
Magnetic Resonance ◽  
Field Measurements ◽  
Time Measurement ◽  
Operational Amplifiers ◽  
Frequency Range ◽  
Sensor Applications ◽  
Low Field ◽  
Front End ◽  
Resonance Relaxation

Advances in permanent magnet technology has seen more reports of sensor applications of low field magnetic resonance. Whilst most are either in the 10–20 MHz range or in the earth’s field, measurements at below 1 MHz are beginning to become more widespread. This range is below the need for careful radio frequency electronics design but above the audio domain and represents an interesting cross over. Many commercial spectrometers do not include the pulse power amplifier, duplexer and preamplifier as these depend on the frequency range used. In this work we demonstrate that, with the current specifications of the humble operational amplifier, the most simple form of an inverting design using only two resistors and decoupling, can effectively provide this ‘front end’ electronics. The low powers used mean crossed Ge diodes provide an excellent duplexer and it is suitable for battery powered applications.

scholarly journals Broadband transmission-line illusions based on transformation electromagnetic

2019 ◽  
Vol 6 ◽  
pp. 23
Author(s):  
Tsutomu Nagayama ◽  
Atsushi Sanada
Keyword(s):  
Transmission Line ◽  
Incident Angle ◽  
Near Field ◽  
Homogeneous Medium ◽  
Field Measurements ◽  
Dielectric Substrate ◽  
Frequency Range ◽  
Microwave Frequencies ◽  
Intrinsic Nature ◽  
Line Technology

We demonstrate broadband transmission-line illusions based on transformation electromagnetics at microwave frequencies by using the distributed full-tensor anisotropic medium. Due to an intrinsic nature of the non-resonant unit cell of the medium, the illusions operate from DC to an upper limit frequency where the homogeneous medium approximation holds. Two-dimensional groove and bump illusion media mimicking scattered waves by an original groove and a bump are designed. Their broadband and incident angle independent operations are confirmed by circuit simulations. The groove illusion medium is implemented on a dielectric substrate with microstrip-line technology, and it is confirmed experimentally by near-field measurements that the illusion medium well mimics scattered waves by the original groove in the broadband frequency range from 2.60 GHz to 4.65 GHz.

Modeling of respiratory system impedances in dogs

1987 ◽  
Vol 62 (2) ◽  
pp. 414-420 ◽  
Author(s):  
A. C. Jackson ◽  
K. R. Lutchen
Keyword(s):  
Respiratory System ◽  
Element Model ◽  
Parameter Estimates ◽  
Frequency Range ◽  
Nonlinear Regression Analysis ◽  
Entire Frequency Range ◽  
Frequency Dependent ◽  
Impedance Data ◽  
Parameter Values ◽  
Gas Compressibility

Mechanical impedances between 4 and 64 Hz of the respiratory system in dogs have been reported (A.C. Jackson et al. J. Appl. Physiol. 57: 34–39, 1984) previously by this laboratory. It was observed that resistance (the real part of impedance) decreased slightly with frequency between 4 and 22 Hz then increased considerably with frequency above 22 Hz. In the current study, these impedance data were analyzed using nonlinear regression analysis incorporating several different lumped linear element models. The five-element model of Eyles and Pimmel (IEEE Trans. Biomed. Eng. 28: 313–317, 1981) could only fit data where resistance decreased with frequency. However, when the model was applied to these data the returned parameter estimates were not physiologically realistic. Over the entire frequency range, a significantly improved fit was obtained with the six-element model of DuBois et al. (J. Appl. Physiol. 8: 587–594, 1956), since it could follow the predominate frequency-dependent characteristic that was the increase in resistance. The resulting parameter estimates suggested that the shunt compliance represents alveolar gas compressibility, the central branch represents airways, and the peripheral branch represents lung and chest wall tissues. This six-element model could not fit, with the same set of parameter values, both the frequency-dependent decrease in Rrs and the frequency-dependent increase in resistance. A nine-element model recently proposed by Peslin et al. (J. Appl. Physiol. 39: 523–534, 1975) was capable of fitting both the frequency-dependent decrease and the frequency-dependent increase in resistance. However, the data only between 4 and 64 Hz was not sufficient to consistently determine unique values for all nine parameters.

scholarly journals Can Soil Electrical Resistivity Measurements Aid the Identification of Forest Areas Prone to Windthrow Disturbance?

Forests ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 234
Author(s):  
Marián Homolák ◽  
Erika Gömöryová ◽  
Viliam Pichler
Keyword(s):  
Electrical Resistivity ◽  
Soil Properties ◽  
Clay Content ◽  
Field Measurements ◽  
Beech Forest ◽  
Root Penetration ◽  
Predictive Tool ◽  
Entire Study ◽  
Resistivity Measurements ◽  
Soil Electrical Resistivity

This study investigates how certain forest soil properties influence the propensity of beech forests to windthrow disturbances. The field measurements of soil electrical resistivity were carried out in an old-growth natural beech forest where the soil has developed from Cainozoic sedimentary rock with mudstone–claystone stratigraphy. In 2014, the forest was hit by a severe windstorm, and dispersed windthrow occurred at certain plots. Apparent electrical resistivity measurements were performed to investigate whether some soil properties could influence the forest trees’ predisposition to windthrow. The increases in the clay content and soil bulk density below 30 cm were associated with weathered claystone and mudstone, which created a physiological barrier for deeper root penetration. The result of the χ 2 test suggested that the windthrown spots were not distributed evenly over the entire study area. They were mainly concentrated over approximately 50% of the area, and their positions coincided with low resistivity values, indicating low soil skeleton content, high clay content and soil moisture. Therefore, electrical resistivity tomography could be considered a useful predictive tool for reducing the risk of natural disturbances by preventive forest management.

scholarly journals Modeling the hydrophysical soil properties and comparative analysis for three systems of functions

2020 ◽  
Vol 175 ◽  
pp. 09016
Author(s):  
Vitaly Terleev ◽  
Roman Ginevsky ◽  
Viktor Lazarev ◽  
Aleksandr Nikonorov ◽  
Alexander Topaj ◽  
...  
Keyword(s):  
Porous Medium ◽  
Soil Moisture ◽  
Comparative Analysis ◽  
Hydraulic Conductivity ◽  
Soil Properties ◽  
Water Retention ◽  
Field Measurements ◽  
Practical Significance ◽  
Water Retention Capacity ◽  
Retention Capacity

A functional description of the hydrophysical properties of the soil as a capillary-porous medium is presented. The described functions of water retention capacity and hydraulic conductivity of the soil have common parameters, which are interpreted within the framework of physical and statistical concepts. The practical significance of the proposed functions lies in the fact that the volume of labor-intensive field measurements necessary, for example, for modeling the dynamics of soil moisture, is significantly reduced. To identify the parameters of these functions, it is sufficient to use data only on the water retention capacity of the soil. The parameters identified in this way can be used to predict the ratio of the hydraulic conductivity of the soil to the moisture filtration coefficient. The presented system of the hydrophysical functions of the soil is compared with world analogues using literature data on soils of different texture.

Analysis of Process Interactions in Dynamic System Using Frequency Dependent RGA

2011 ◽  
Vol 403-408 ◽  
pp. 895-899
Author(s):  
Amit Jain ◽  
B.V. Babu
Keyword(s):  
Transfer Function ◽  
Process Model ◽  
Transfer Function Model ◽  
Control Loop ◽  
Frequency Range ◽  
Function Model ◽  
Frequency Dependent ◽  
Relative Gain ◽  
Relative Gain Array ◽  
Correct Pairing

A frequency dependent approach to defining a dynamic relative gain array (DRGA) is discussed. The approach assumes the availability of a dynamic transfer function based process model for control loop pairing analysis. Two examples are considered: one in which the traditional RGA (based on steady-state gain matrix) gives the correct pairing recommendation and the other in which the traditional RGA suggests wrong pairings particularly in the frequency range of interest. The calculations pertaining to analysis of control loop pairing is performed using MATLAB (version 7.0.1). An inaccurate indication of the amount of interaction present is discussed. The first example uses 2x2 transfer function model [1] and the second one uses 3x3 transfer function model [2].

scholarly journals PENGUKURAN NILAI DIELEKTRIK MATERIAL CALCIUM COPPER TITANAT ( CaCu3Ti4O12) MENGGUNAKAN SPEKTROSKOPI IMPEDANSI TERKOMPUTERISASI

2017 ◽  
Vol 6 (1) ◽  
pp. 26
Author(s):  
Widodo Budi Kurniawan
Keyword(s):  
Dielectric Constant ◽  
Impedance Spectroscopy ◽  
Ceramic Materials ◽  
Complex Dielectric Constant ◽  
Frequency Range ◽  
Frequency Dependent ◽  
Calcium Copper Titanate ◽  
Ccto Sample

Telah dilakukan pengukuran tetapan dielektrik kompleks dan besarnya impedansi kapasitor pada material keramik Calcium Copper Titanate dengan struktur material CaCu3Ti4O12 (CCTO) dengan kemurnian 99 % menggunakan metode spektroskopi impedansi terkomputerisasi dalam rentang frekuensi 5 kHz – 120 kHz. Tetapan dielektrik maksimum terukur pada sampel yang disintering dengan suhu 7000C yaitu 745 pada frekuensi 5 kHz dan besarnya impedansi kapasitor maksimum terjadi pada sampel CCTO non sintering yaitu 150434 Ω. Hasil penelitian menunjukkan adanya pengaruh frekuensi terhadap tetapan dielektrik kompleks dan impedansi kapasitor dari material yang diteliti. Kata kunci : spektroskopi impedansi, CaCu3Ti4O12, tetapan dielektrik kompleks dan impedansi kapasitor.   MEASUREMENT OF THE DIELECTRIC CONSTANT CALCIUM COPPER TITANATE (CaCu3Ti4O12) MATERIALS USING COMPUTERIZED IMPEDANCE SPECTROSCOPY  ABSTRACT The measurement of the complex dielectric constant and the magnitude of the capacitor impedances of the ceramic materials Calcium Copper Titanate CaCu3Ti4O12 (CCTO) with purity of 99% has been done by using the method of computerized impedance spectroscopy in the frequency range 5 kHz - 120 kHz. The highest dielectric constant of the material was found to be 745 at 5 kHz in the sample sintered 7000C and the highest impedance of capacitor occured in CCTO sample non sintered that is 150434Ω. The results showed that complex dielectric constant and impedance of the capacitor of the material under study was frequency dependent. Keywords : impedance spectroscopy, CaCu3Ti4O12,complex dielectric constant and impedance of capacitor

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