Underwater Wireless Sensor Network (UWSN) communication at high frequencies is extremely challenging. The intricacies presented by the underwater environment are far more compared to the terrestrial ...environment. The prime reason for such intricacies are the physical characteristics of the underwater environment that have a big impact on electromagnetic (EM) signals. Acoustics signals are by far the most preferred choice for underwater wireless communication. Because high frequency signals have the luxury of large bandwidth (BW) at shorter distances, high frequency EM signals cannot penetrate and propagate deep in underwater environments. The EM properties of water tend to resist their propagation and cause severe attenuation. Accordingly, there are two questions that need to be addressed for underwater environment, first what happens when high frequency EM signals operating at 2.4 GHz are used for communication, and second which factors affect the most to high frequency EM signals. To answer these questions, we present real-time experiments conducted at 2.4 GHz in terrestrial and underwater (fresh water) environments. The obtained results helped in studying the physical characteristics (i.e., EM properties, propagation and absorption loss) of underwater environments. It is observed that high frequency EM signals can propagate in fresh water at a shallow depth only and can be considered for a specific class of applications such as water sports. Furthermore, path loss, velocity of propagation, absorption loss and the rate of signal loss in different underwater environments are also calculated and presented in order to understand why EM signals cannot propagate in sea water and oceanic water environments. An optimal solk6ution for underwater communication in terms of coverage distance, bandwidth and nature of communication is presented, along with possible underwater applications of UWSNs at 2.4 GHz.
As a novel technology to convert low-frequency energy into electric power, the triboelectric nanogenerator is a hot research topic recently. However, the nature of charge carriers and their transfer ...mechanisms still remain poorly understood, especially for the cases of liquid-solid triboelectric nanogenerator. In this paper, charges produced by a triboelectric charging process were designed to provide melt-blown nonwoven fabrics with high filtration efficiency by making full use of the electrostatic attraction filtration mechanism. Influences of water conductivity and drying temperature on the filtration efficiency of melt-blown nonwoven fabrics were investigated. And the corresponding properties such as the surface charge potential and charge stability were analyzed by using the electrostatic voltmeter, bio atomic force microscope and thermally stimulated discharge technique. In addition, metal and inorganic elements in the masterbatch and water before and after triboelectric charging were measured in order to uncover the charge transfer mechanism. Melt-blown nonwoven fabrics with filtration efficiency as high as 96.8% was obtained through the triboelectric charging treatment by using water with the conductivity as low as 1.1 μS/cm for the first time. Negative and positive surface charge density appeared randomly on both sides of melt-blown nonwoven fabrics after the triboelectric charging treatment from the bio atomic force microscope measurement while only one kind of surface charge density can be achieved in the research of TENG, that is, negative or positive. It seems there are both electron and ion transfers during the triboelectric charging process and electron transfer seems to have more important contribution for the generation of charges.
The new application of electrical explosion of wire (EEW) used in petroleum industry is to enhance oil recovery (EOR). Because of the complex environment underground, the effect of underground water ...conductivity on EEW should be considered. This work describes the effect of water conductivities on discharge current, voltage and shock waves. It was found that the effect of water conductivity contains two parts. One is the shunt effect of saline water, which can be considered as a parallel load with the copper wire between the electrodes connected to the discharge circuit. The peak pressure of shock waves are gradually decrease with the increase of water conductivity. The other is the current loss through saline water directly to the ground ends without flowing through the electrodes. The shunt effect is the main factor affecting the wire discharge process. As the charging voltage increased, the energy loss caused by these two parts are all reduced. These indicate that increasing the charging voltage to a certain value will increase the energy efficiency to generate a more powerful shock waves in conductive water.
•Shunting effect and current loss through saline water directly to the ground affect the generation of shock waves.•Shunting effect of saline water can be considered as a parallel load with the wire connected to the discharge circuit.•Increasing the charging voltage will increase the energy efficiency to generate a more powerful shock waves.
This paper presents a new system for measuring water conductivity as a function of electrophysical property (admittance). The system is cheap and its manufacturing is easy. In addition, it does not ...require any sort of electrolysis and calibration. The system consists of four electrodes made of silver (Ag 92.5 g to Cu 7.5 g) fixed in a plastic tube filled by water which allows the use of two and four electrode setups. The admittance (reciprocal of impedance) was measured for different water sources (distilled, rainfall, mineral, river and tap water) using different frequencies between 50 Hz and 100 kHz. These measurements were taken twice, first with four electrodes and then with two electrodes of two modes (inner and outer electrodes). The results showed good correlation between the measured admittance and the conductivity of all the water sources and the best correlation was found at low frequencies between 50 Hz and 20 kHz. The highest efficiency can be achieved by using the four electrode system which allows circumventing the effect of the electrode impedance. This result makes the system efficient compared to traditional conductivity meters which usually require high frequencies for good operation.
•Miniaturised, real-time, multi-parameter and cost-effective soil sensor for measurements in mini plugs.•Electrical impedance detection at two frequencies for sensing two soil parameters, water ...content and water conductivity.•Easy and efficient calibration method of the sensor.•Good correlation between the sensor’s readings and the traditional soil testing.
Obtaining more data for the research/studies of plants growing may be easier realized when suitable non-destructive detection methods are available. We are here presenting the development of a miniaturised, low-power, real-time, multi-parameter and cost-effective sensor for measurements in mini plugs (growth of seedling). The detection technique is based on measurement of electrical impedance at two frequencies for sensing two soil parameters, water content and water conductivity (dependent on e.g. total ions concentration). Electrical models were developed and comply with data at two frequencies. An easy and efficient calibration method for the sensor is established by using known liquids’ properties instead of various soil types. The measurements show a good correlation between the sensor’s readings and the traditional soil testing. This soil sensor can easily send data wirelessly allowing for spot checks of substrate moisture levels throughout a greenhouse/field, and/or enable sensors to be buried inside the soil/substrate for long-term consecutive measurements.
Study on the microscopic structure of saline-alkali soil can reveal the change of its permeability more deeply. In this paper, the relationship between permeability and microstructure of ...saline-alkali soil with different dry densities and water content in the floodplain of southwestern Shandong Province was studied through freeze-thaw cycles. A comprehensive analysis of soil samples was conducted using particle-size distribution, X-ray diffraction, freeze-thaw cycles test, saturated hydraulic conductivity test and mercury intrusion porosimetry. The poor microstructure of soil is the main factor that leads to the category of micro-permeable soil. The porosity of the local soil was only 6.19-11.51%, and ultra-micropores (< 0.05 μm) and micropores (0.05-2 μm) dominated the pore size distribution. Soil saturated water conductivity was closely related to its microscopic pore size distribution. As the F-T cycles progressed, soil permeability became stronger, with the reason the pore size distribution curve began to shift to the small pores (2-10 μm) and mesopores (10-20 μm), and this effect was the most severe when the freeze-thaw cycle was 15 times. High water content could promote the effects of freeze-thaw cycles on soil permeability and pore size distribution, while the increase of dry density could inhibit these effects. The results of this study provide a theoretical basis for the remediation of saline-alkali soil in the flooded area of Southwest Shandong.
•IAA affected maize root hydraulic, mainly decreasing root hydraulic conductivity (Lo).•Aquaporins are likely involved in the IAA-dependent inhibition of Lo.•IAA differentially regulated apoplastic ...water flow in AM and non-AM plants.•Other phytohormones contributed to the IAA-dependent effects on root hydraulics.
Drought stress is one of the most devastating abiotic stresses, compromising crop growth, reproductive success and yield. The arbuscular mycorrhizal (AM) symbiosis has been demonstrated to be beneficial in helping the plant to bear with water deficit. In plants, development and stress responses are largely regulated by a complex hormonal crosstalk. Auxins play significant roles in plant growth and development, in responses to different abiotic stresses or in the establishment and functioning of the AM symbiosis. Despite these important functions, the role of indole-3acetic acid (IAA) as a regulator of root water transport and stress response is not well understood. In this study, the effect of exogenous application of IAA on the regulation of root radial water transport in AM plants was analyzed under well-watered and drought stress conditions. Exogenous IAA application affected root hydraulic parameters, mainly osmotic root hydraulic conductivity (Lo), which was decreased in both AM and non-AM plants under water deficit conditions. Under drought, the relative apoplastic water flow was differentially regulated by IAA application in non-AM and AM plants. The effect of IAA on the internal cell component of root water conductivity suggests that aquaporins are involved in the IAA-dependent inhibition of this water pathway.
In this paper, a novel direct solar steam generation method is proposed that realizes highly efficient vapour generation. The strategy was inspired by the evaporation of sweat from the human skin and ...the transpiration of plants in biological systems. A micro-porous structured broadband absorption paper-based carbon nanotube (CNT) film was prepared by a facile vacuum filtration process, and was utilized as both the solar harvesting surface and steam generation skin. The excellent optical absorptivity and water conductivity of CNTs make great contributions to the solar steam generation. The heat and mass transfer properties on the direct solar steam generation performance of CNT films was investigated. The evaporation rate and temperature distribution of the steam generation system were experimentally studied to evaluate the evaporation performance. The results demonstrate that the bio-inspired solar heating of CNT films has significant advantages for enhancing direct solar steam generation compared to those of direct volumetric solar heating. Through this research, it was found that the localized photo-heating of floating CNT films at the water-air interface and the fast capillary flow through the porous structures of the films enhanced the solar steam generation process. This bio-inspired direct solar steam generation method using carbon nanotube films has great potential in a variety of industrial applications, including electrical power generation, freshwater distillation, and solar hygiene systems.
Display omitted
•A novel bio-inspired direct solar steam generation method was proposed.•Porous and broadband absorption CNT films were prepared via a facile method.•Heat and steam flow through the micro-porous CNT films were studied.•Broadband absorption CNT films improved the efficiency of solar steam by up to 400%.
Understanding how environmental conditions and plant functional variation are mutually related is critical to improving our comprehension of plant adaptations. In this context, our knowledge of the ...interlinks between plant functional, spectral and genetic traits and environmental filters is still very limited, especially for wetland species. To gain new insights on this topic, a multidimensional dataset, centred on the widespread macrophyte species Nuphar lutea, was assembled by collecting data on functional traits (including spectral traits), genetic metrics and environmental determinants from 28 plots spanning north‐central Italy. A strong environmental filter acts on all traits (morphological, biochemical, spectral and the genetic diversity metrics) resulting in significant local control over trait patterns, exemplified by the discrimination value of water electrical conductivity. This is further reinforced by the key contribution of sediment variables in explaining traits variation. Site‐specific environmental conditions were reflected in different patterns of genetic diversity, suggesting a long‐term effect of environmental filters on genotypes as well. High water conductivity – in our study sites indicative of long‐term hydrogeological settings – is linked to more acquisitive behaviour in N. lutea and a progressive reduction in its genetic diversity, while high nutrients availability in sediments promotes higher leaf traits performance. This study better explores how high variability in leaf traits reinforces current genetic and mechanistic knowledge about competitive strategies in the key aquatic plant N. lutea, by testing the effectiveness of a novel integrative approach to assess multiple sources of plant functional variation.
Abstract
An experiment was carried out to study the effect of soil organic carbon (SOC) and soil texture on the distance of the wetting front, cumulative water infiltration (I), infiltration rate ...(IR), saturated water conductivity (Ks), and water holding capacity (WHC). Three levels ( 0, 10, 20, and 30 g OC kg-1 ) from organic carbon (OC) were mixed with different soil materials sandy, loam, and clay texture soils. Field capacity (FC) and permanent wilting point (PWP) were estimated. Soil materials were placed in transparent plastic columns(12 cm soil column ), and water infiltration(I) was measured as a function of time, the distance of the wetting front and Ks. Results showed that advance wetting front as a function of time for soil column was 6 minutes and with no differences between OC levels for sandy soils, while it ranged between 90 minutes (0% OC) - 130 minutes (3% OC) for loam soils, and between 470 minutes (0 %OC) and 590 minutes (1%OC) for clay soils, at the same time cumulative water infiltration(I) increases at the beginning of infiltration and decreases with time and levels of OC. The highest infiltration values were in sandy soils, giving data of 0.05 and 0.12 cm min-1, with no significant differences with OC rates. IR values decreased when OC increased in loam soils, and IR increased exponentially in clay soils with increasing OC levels. The values of Ks decrease with increasing OC for sandy and loam soils, and increase when OC increases above 3% for clay soils. FC and WP values were increased for sandy, loam and clay soils when OC was increased. The AW values decreased for both sandy and clay soils compared to loam soils. It can be concluded that AW can be estimated from FC values regardless of texture and OC by the linear function: AW=0.51(FC)+0.005.
PDF
