scholarly journals Theoretical and Experimental Studies on the Signal Propagation in Soil for Wireless Underground Sensor Networks

Sensors ◽  
2020 ◽  
Vol 20 (9) ◽  
pp. 2580
Author(s):  
Hongwei Huang ◽  
Jingkang Shi ◽  
Fei Wang ◽  
Dongming Zhang ◽  
Dongmei Zhang
Keyword(s):  
Sensor Networks ◽  
Near Field ◽  
Path Loss ◽  
Far Field ◽  
Stage Model ◽  
Field Region ◽  
Experiment Data ◽  
Two Stage ◽  
Proposed Model ◽  
Wireless Underground Sensor Networks

Wireless Underground Sensor Networks (WUSNs), an important part of Internet of things (IoT), have many promising applications in various scenarios. Signal transmission in natural soil undergoes path loss due to absorption, radiation, reflection and scattering. The variability and dynamic of soil conditions and complexity of signal attenuation behavior make the accurate estimation of signal path loss challenging. Two existing propagation models for predicting path loss are reviewed and compared. Friis model does not consider the reflection loss and is only applicable in the far field region. The Fresnel model, only applicable in the near field region, has not considered the radiating loss and wavelength change loss. A new two stage model is proposed based on the field characteristics of antenna and considers four sources of path loss. The two stage model has a different coefficient m in the near field and far field regions. The far field distance of small size antenna is determined by three criteria: 2 D2/λ, 5 D, 1.6 λ in the proposed model. The proposed two stage model has a better agreement with the field experiment data compared to Friis and Fresnel models. The coefficient m is dependent on the soil types for the proposed model in near field region. It is observed from experiment data that the m value is in the range of 0~0.20 for sandy soils and 0.433~0.837 for clayey silt.

scholarly journals Experimental observation of asymmetrical microwave jets and far-field distribution generated by a dual-material system

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
B. Varghese ◽  
O. Shramkova ◽  
P. Minard ◽  
L. Blondé ◽  
V. Drazic ◽  
...  
Keyword(s):  
Near Field ◽  
Microwave Frequency ◽  
Far Field ◽  
Material System ◽  
Field Region ◽  
Edge Diffraction ◽  
Jet Behavior ◽  
Electric Field Profile ◽  
Dual Material ◽  
Plane Wave Diffraction

AbstractIn this paper, we report the experimental and numerical investigation of plane wave diffraction by an all-dielectric dual-material cuboid. Edge diffraction by a cuboid leads to the generation of a narrow, high intensity beam in the near-field region called a photonic jet. We examine the dependence of the jet behavior and orientation on the materials and dimensions of constitutive parts in the microwave frequency domain. The possibility to shift and deviate the resultant microwave jet in the near-field region of such a structure depending on the size of constitutive parts is demonstrated numerically. Experimentally, we observe a shift in the spatial position of the jet. The experimental asymmetric electric field profile observed in the far-field region is attributed to the input of multiple edge waves generated by the dual-material cuboid. The presented results may be scaled at different frequency bands such as optical frequencies for designing nanostructures enabling the focusing and deviation functionality and creation of new optical devices which would satisfy the needs of emerging nanophotonic applications.

scholarly journals Two-Stage Fuzzy Portfolio Selection Problem with Transaction Costs

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Yanju Chen ◽  
Ye Wang
Keyword(s):  
Transaction Costs ◽  
Portfolio Selection ◽  
Optimal Solution ◽  
Single Stage ◽  
Selection Problem ◽  
Stage Model ◽  
Two Stage ◽  
Portfolio Selection Problem ◽  
Fuzzy Portfolio Selection ◽  
Proposed Model

This paper studies a two-period portfolio selection problem. The problem is formulated as a two-stage fuzzy portfolio selection model with transaction costs, in which the future returns of risky security are characterized by possibility distributions. The objective of the proposed model is to achieve the maximum utility in terms of the expected value and variance of the final wealth. Given the first-stage decision vector and a realization of fuzzy return, the optimal value expression of the second-stage programming problem is derived. As a result, the proposed two-stage model is equivalent to a single-stage model, and the analytical optimal solution of the two-stage model is obtained, which helps us to discuss the properties of the optimal solution. Finally, some numerical experiments are performed to demonstrate the new modeling idea and the effectiveness. The computational results provided by the proposed model show that the more risk-averse investor will invest more wealth in the risk-free security. They also show that the optimal invested amount in risky security increases as the risk-free return decreases and the optimal utility increases as the risk-free return increases, whereas the optimal utility increases as the transaction costs decrease. In most instances the utilities provided by the proposed two-stage model are larger than those provided by the single-stage model.

scholarly journals Model for Evaluating Outsourcing Logistics Companies in the COVID-19 Pandemic

Logistics ◽  
2021 ◽  
Vol 5 (3) ◽  
pp. 64
Author(s):  
Cheng-An Tsai ◽  
Tien-Hwa Ho ◽  
Jyh-Shyan Lin ◽  
Chien-Chih Tu ◽  
Che-Wei Chang
Keyword(s):  
Hierarchical Structure ◽  
Manufacturing Industry ◽  
Stage Model ◽  
Two Stage ◽  
Analytic Hierarchy ◽  
Modified Delphi ◽  
Proposed Model ◽  
The Hierarchical Structure ◽  
Outsourcing Logistics ◽  
Hierarchy Process

The COVID-19 pandemic has severely affected the world’s manufacturing industry, particularly in terms of the continued increase in logistics costs that has led to an increase in business operating costs. This study proposes a two-stage model for evaluating the most appropriate outsourcing logistics companies for a manufacturing factory. In the first stage, a modified Delphi method was used to recruit experienced experts to determine criteria for evaluating outsourcing logistics vendors and establish a hierarchical structure. In the second stage, the analytic hierarchy process (AHP) was used to evaluate suitable logistics companies based on the hierarchical structure. Finally, a case study was conducted to demonstrate the suitability of the two-stage model for evaluating outsourcing logistics companies for reducing logistics costs while maintaining service quality. The proposed model can be used as a basis for evaluating outsourcing logistics companies.

scholarly journals Bessel-like light beams formed by the two-component scheme consisting of an axicon and a spherical lens

2020 ◽  
Vol 56 (3) ◽  
pp. 373-383
Author(s):  
N. A. Khilo ◽  
P. I. Ropot ◽  
P. K. Petrov ◽  
V. N. Belyi
Keyword(s):  
Light Field ◽  
Near Field ◽  
Cone Angle ◽  
Longitudinal Component ◽  
Optical Scheme ◽  
Far Field ◽  
Field Region ◽  
Spherical Lens ◽  
Bessel Beams ◽  
Remote Probing

The combination in an optical scheme of rather different elements such as axicons and spherical lenses allows forming light fields that differ by a variety of properties. The simplest example of such a scheme consists of an axicon and a spherical lens spatially separated from it. Though this scheme was investigated earlier, the region of so-called secondary focusing located behind the well-known annular focus has not been studied yet. In this paper, the analytical and numerical analysis of a light field in the region of secondary focusing is conducted. The boundaries of this region are determined, and the longitudinal and transverse distribution of the light intensity is calculated. It is shown that the near field region of secondary focusing is formed in the regime of abrupt autofocusing of the annular field. It is established that in a general case the transverse intensity distribution in the far field region is a superposition of an annular field and an oscillating axialtype field. The distance between the axicon and the lens is determined when the annular component of the field practically disappears. It is shown that in this case the light field in the region of the secondary focusing is a locally Bessel light beam. The peculiarity of this beam is that its cone angle depends on the longitudinal component, namely, decreases in inverse proportion while the distance z increases. The important feature of such z-dependent Bessel beams is the absence of their transformation into annular fields, as it occurs for ordinary Bessel or Bessel-Gaussian beams in the far field region. This opens the prospect for application of z-dependent Bessel beams for optical communication in free space and remote probing, which is why such beams are perspective for application in different systems of remote probing.

Turbulence anisotropy with higher-order moments in flow through passive grid under rigid boundary influence

2020 ◽  
pp. 095440622096973
Author(s):  
Pankaj Kumar Raushan ◽  
Santosh Kumar Singh ◽  
Koustuv Debnath
Keyword(s):  
Reynolds Stress ◽  
Isotropic Turbulence ◽  
Near Field ◽  
Far Field ◽  
Field Region ◽  
Rigid Boundary ◽  
Third Order ◽  
Solidity Ratio ◽  
Eigen Values ◽  
Flow Through

The investigation presents the estimate of the degree of deviation from the isotropic turbulence in terms of Reynolds stress tensor for grid generated turbulence under the influence of bottom boundary. The turbulence triangle, Eigen values, and the invariant functions are presented at near and far field regions of the grids with different solidity ratio. In addition, the work also deals with the analysis based on third-order moments of the velocity fluctuations and the ratio of momentum flux to the turbulent kinetic energy in the frequency domain. The Reynolds stress anisotropy exposes that the anisotropic invariant maps possess a closed looping trend in the near field region and an open looping trend in the far-field region of the grid. Further, to describe the physical behaviour of the velocity time-series of random fluctuating components in the stream-wise directions, the probability distribution function are estimated and interpreted.

scholarly journals Near-Field to Far-Field RCS Prediction on Arbitrary Scanning Surfaces Based on Spherical Wave Expansion

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7199
Author(s):  
Woobin Kim ◽  
Hyeong-Rae Im ◽  
Yeong-Hoon Noh ◽  
Ic-Pyo Hong ◽  
Hyun-Sung Tae ◽  
...  
Keyword(s):  
Near Field ◽  
Linear Equations ◽  
Spherical Wave ◽  
Scattered Wave ◽  
Far Field ◽  
Field Region ◽  
System Of Linear Equations ◽  
Wave Expansion ◽  
Field Transformation ◽  
Spherical Wave Expansion

Near-field to far-field transformation (NFFFT) is a frequently-used method in antenna and radar cross section (RCS) measurements for various applications. For weapon systems, most measurements are captured in the near-field area in an anechoic chamber, considering the security requirements for the design process and high spatial costs of far-field measurements. As the theoretical RCS value is the power ratio of the scattered wave to the incident wave in the far-field region, a scattered wave measured in the near-field region needs to be converted into field values in the far-field region. Therefore, this paper proposes a near-field to far-field transformation algorithm based on spherical wave expansion for application in near-field RCS measurement systems. If the distance and angular coordinates of each measurement point are known, the spherical wave functions in an orthogonal relationship can be calculated. If each weight is assumed to be unknown, a system of linear equations as numerous as the number of samples measured in the near electric field can be generated. In this system of linear equations, each weight value can be calculated using the iterative least squares QR-factorization method. Based on this theory, the validity of the proposed NFFFT is verified for several scatterer types, frequencies and measurement distances.

scholarly journals JOINT AZIMUTH-ELEVATION/(-RANGE) ESTIMATION OF MIXED NEAR-FIELD AND FAR-FIELD SOURCES USING TWO-STAGE SEPARATED STEERING VECTOR-BASED ALGORITHM

2011 ◽  
Vol 113 ◽  
pp. 17-46 ◽  
Author(s):  
Junli Liang ◽  
Ding Liu ◽  
Xianju Zeng ◽  
Wenyi Wang ◽  
Jiulong Zhang ◽  
...  
Keyword(s):  
Near Field ◽  
Far Field ◽  
Range Estimation ◽  
Two Stage ◽  
Steering Vector ◽  
Elevation Range

scholarly journals Different Designs of Dual-Focus Perforated Transmitarray Antenna in Near/Far-Field Region

2016 ◽  
Vol 4 (3) ◽  
pp. 25 ◽  
Author(s):  
H. Abd El-Azem Malhat ◽  
S. Zainud-Deen ◽  
W. Hassan
Keyword(s):  
Phase Distribution ◽  
Near Field ◽  
Far Field ◽  
Field Region ◽  
Radiation Characteristics ◽  
Array Configuration ◽  
Unit Cells ◽  
Single Structure ◽  
Single Sheet ◽  
Single Focus

Designs of the single-focus and multi-focused transmitarray antennas for the near-field (NF) or/and far-field (FF) applications have been introduced. Perforated dielectric single sheet is used for transmitarray design for simple configuration. Single-focus transmitarray for the far-field and the near-field are obtained. The radiation characteristics of 13×13 unit-cells transmitarray in the near-field and the far-field region have been investigated. A single structure multi-focus transmitarray is designed using the chess-board arrangement of the unit-cells elements. Multi-focus transmitarray for FF/FF, FF/NF, and NF/NF have been designed and investigated. The phase distribution and the corresponding holes radii for the first quadrant of the multi-focus transmitarray are presented. The radiation characteristics of different array configuration have been investigated and analyzed using full-wave simulator CST Microwave Studio.

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