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Author

David J. Daniels

Bio: David J. Daniels is an academic researcher. The author has contributed to research in topics: Radar & Ground-penetrating radar. The author has an hindex of 2, co-authored 2 publications receiving 1702 citations.

Papers
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Book ChapterDOI
15 Apr 2005
TL;DR: The ground penetrating radar (GPR) is a nondestructive measurement technique which uses electromagnetic waves to locate targets or interfaces buried within a visually opaque substance or Earth material.
Abstract: Ground penetrating radar (GPR) is a nondestructive measurement technique, which uses electromagnetic waves to locate targets or interfaces buried within a visually opaque substance or Earth material. GPR is also termed ground probing, surface penetrating (SPR), or subsurface radar. A GPR transmits a regular sequence of low-power packets of electromagnetic energy into the material or ground, and receives and detects the weak reflected signal from the buried target. The buried target can be a conductor, a dielectric, or combinations of both. There are now a number of commercially available equipments, and the technique is gradually developing in scope and capability. GPR has also been used successfully to provide forensic information in the course of criminal investigations, detect buried mines, survey roads, detect utilities, measure geophysical strata, and in other applications. Keywords: ground penetrating radar; ground probing radar; surface penetrating radar; subsurface radar; electromagnetic waves

1,082 citations

DatasetDOI
TL;DR: A non-destructive technique using electromagnetic waves to locate objects or interfaces buried in the ground has been proposed in this article, which can be used to locate buried objects and interfaces.
Abstract: A nondestructive technique using electromagnetic waves to locate objects or interfaces buried benea…

626 citations

Journal ArticleDOI
TL;DR: In this article, the authors consider the impact of the antenna on the system performance of the radar and show that the clutter performance of antenna can be the prime metric of system detection rather than the noise figure, given the self-clutter often exceeds the latter.
Abstract: The performance of very short-range radar systems such as ground penetrating radar for anti-personnel landmine detection is critically dependent on the impulse characteristics of the antennas that are used. Typically, a pair of individual antennas is used in the radar, one for transmit and one for receive. These antennas are usually closely spaced for reasons of both portability and close in detectability. A variety of design techniques are used to achieve their wideband performance in terms of return loss, isolation, radiation patterns, polarization, and impulse formation. Not only the antenna elements, but their surrounds, form the overall antenna structure and this ensemble becomes integral to the antenna performance and design process. Both the antenna and the surrounding structure can create late time signals or time sidelobes, which are in effect a form of self-generated clutter. Minimising the duration of the antenna impulse response assists in reducing self-generated clutter and achieving optimum radar performance. This paper considers the impact of the antenna on the system performance of the radar and shows that the clutter performance of the antenna can be the prime metric of system detection rather than the noise figure, given the self-clutter often exceeds the latter.

4 citations

12 Sep 2022
TL;DR: In this article , the effects of bowtie antenna alignment for potato detection from the side of the ridge were investigated for crop monitoring and assessment in agriculture, and the best detection sensitivity can be achieved by aligning the antenna's long axis with the scanning direction and stacking the antennas in the short axis direction.
Abstract: Ground penetrating radar (GPR) is an emerging technology for crop monitoring and assessment in agriculture. The performance of GPR is directly related to its antenna radiation patterns. In this paper, the effects of bowtie antenna alignment is investigated for potato detection from the side of the ridge. Bowtie antenna shows different patterns in its E-plane and H-plane. This difference result in distinct performance with different antenna alignments. Simulation results suggest that the best detection sensitivity can be achieved by aligning the bowtie antenna’s long axis with the scanning direction and stacking the antennas in the short axis direction.

Cited by
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Journal ArticleDOI
TL;DR: The goal of this paper is to provide a comprehensive review of wireless sub-THz and THz communications and report on the reported advantages and challenges of using sub-terahertz andTHz waves as a means to transmit data wirelessly.
Abstract: According to Edholm’s law, the demand for point-to-point bandwidth in wireless short-range communications has doubled every 18 months over the last 25 years It can be predicted that data rates of around 5–10 Gb/s will be required in ten years In order to achieve 10 Gb/s data rates, the carrier frequencies need to be increased beyond 100 GHz Over the past ten years, several groups have considered the prospects of using sub-terahertz (THz) and THz waves (100–2000 GHz) as a means to transmit data wirelessly Some of the reported advantages of THz communications links are inherently higher bandwidth compared to millimeter wave links, less susceptibility to scintillation effects than infrared wireless links, and the ability to use THz links for secure communications Our goal of this paper is to provide a comprehensive review of wireless sub-THz and THz communications

991 citations

Journal ArticleDOI
TL;DR: In this article, the authors review advances in sensor technology, particularly emerging geophysical methods and distributed sensors, aimed at bridging this gap and offer a vision for future research, listing many of the current scientific and technical challenges.
Abstract: At the watershed scale, soil moisture is the major control for rainfall–runoff response, especially where saturation excess runoff processes dominate. From the ecological point of view, the pools of soil moisture are fundamental ecosystem resources providing the transpirable water for plants. In drylands particularly, soil moisture is one of the major controls on the structure, function, and diversity in ecosystems. In terms of the global hydrological cycle, the overall quantity of soil moisture is small, ∼0.05%; however, its importance to the global energy balance and the distribution of precipitation far outweighs its physical amount. In soils it governs microbial activity that affects important biogeochemical processes such as nitrification and CO2 production via respiration. During the past 20 years, technology has advanced considerably, with the development of different electrical sensors for determining soil moisture at a point. However, modeling of watersheds requires areal averages. As a result, point measurements and modeling grid cell data requirements are generally incommensurate. We review advances in sensor technology, particularly emerging geophysical methods and distributed sensors, aimed at bridging this gap. We consider some of the data analysis methods for upscaling from a point to give an areal average. Finally, we conclude by offering a vision for future research, listing many of the current scientific and technical challenges.

877 citations

Journal ArticleDOI
TL;DR: A comprehensive review of methods to measure soil water content with ground penetrating radar (GPR) is presented in this article, where the authors distinguish four methods: reflected wave velocity, ground wave velocity and surface reflection coefficient.
Abstract: We present a comprehensive review of methods to measure soil water content with ground penetrating radar (GPR) We distinguish four methodologies: soil water content determined from reflected wave velocity, soil water content determined from ground wave velocity, soil water content determined from transmitted wave velocity between boreholes, and soil water content determined from the surface reflection coefficient For each of these four methodologies, we discuss the basic principles, illustrate the quality of the data with field examples, discuss the possibilities and limitations, and identify areas where future research is required We hope that this review will further stimulate the community to consider ground penetrating radar as one of the possible tools to measure soil water content

759 citations

Journal ArticleDOI
TL;DR: A review of the current understanding of phenomena involved in gas hydrate formation and the physical properties of hydrate-bearing sediments can be found in this paper, where the magnitudes and interdependencies of these properties are critically important for predicting and quantifying macroscale responses of hydrates to changes in mechanical, thermal, or chemical boundary conditions.
Abstract: [1] Methane gas hydrates, crystalline inclusion compounds formed from methane and water, are found in marine continental margin and permafrost sediments worldwide. This article reviews the current understanding of phenomena involved in gas hydrate formation and the physical properties of hydrate-bearing sediments. Formation phenomena include pore-scale habit, solubility, spatial variability, and host sediment aggregate properties. Physical properties include thermal properties, permeability, electrical conductivity and permittivity, small-strain elastic P and S wave velocities, shear strength, and volume changes resulting from hydrate dissociation. The magnitudes and interdependencies of these properties are critically important for predicting and quantifying macroscale responses of hydrate-bearing sediments to changes in mechanical, thermal, or chemical boundary conditions. These predictions are vital for mitigating borehole, local, and regional slope stability hazards; optimizing recovery techniques for extracting methane from hydrate-bearing sediments or sequestering carbon dioxide in gas hydrate; and evaluating the role of gas hydrate in the global carbon cycle.

745 citations

Journal ArticleDOI
TL;DR: In this article, a literature based review aims to compile the available knowledge on the methods used to estimate soil moisture at the landscape level, compare and evaluate the available methods on the basis of common parameters such as resource efficiency, accuracy of results and spatial coverage and identify the method that will be most useful for forested landscapes in developing countries.

335 citations