Ducting Research Articles

A development of piezoelectric model as an energy harvester from mechanical vibration

Energy harnessing has gain much interest and become more essential to achieve environment sustainability. By harnessing ambient energy from the environment, it will reduce the electricity energy consumption. Nowadays, vibration energy shows a promising amount of energy generation. This paper presents the modelling for conversion of mechanical vibration into electricity using piezoelectric converter. The model development was based on the piezoelectric model of PI P-876 and the non –adaptive rectifier circuit was employed in order for direct voltage conversion that are much useful for electronic devices nowadays. Several sources of vibration energy literally reviewed such as ducting and piping system which then fed into the piezoelectric model converter in Matlab SIMULINK. As a result, a maximum direct voltage of 0.14 V and 1.96 Watt of energy could be harnessed from ducting system. This power output is sufficient for mini home appliances and low-powered wireless sensor networks in silent mode which can be used in variety of applications.

Meteotsunami (“Marrobbio”) of 25–26 June 2014 on the Southwestern Coast of Sicily, Italy

A major tsunami-like event, locally known as ‘marrobbio’, impacted the southwestern coast of Sicily on 25–26 June 2014. The event was part of a chain of hazardous episodes in the Mediterranean and Black seas during the last week of June 2014 resulting from an anomalous atmospheric system (“tumultuous atmosphere”) propagating eastward over the region. The synoptic patterns and vertical structure of the atmosphere over Sicily at the time of the event indicate that atmospheric wave ducting was responsible for the generation of tsunamigenic air pressure disturbances that produced especially high sea level responses (“meteotsunamis”) at certain sites along the Sicilian coast. The strongest sea level oscillations were observed at Mazara del Vallo, where a 1-m meteotsunami bore, propagating upstream in the Mazaro River, was generated. The combined effects of external resonance (Proudman resonance on the western Sicilian shelf) and internal resonant conditions (bathymetric and topographic characteristics of specific sites) were found to be the key factors that caused the meteotsunami (marrobbio phenomenon) on the coast of Sicily and the meteobore at Mazara del Vallo.

Inferring the atmospheric duct from radar sea clutter using the improved artificial bee colony algorithm

AbstractIn this paper, an orthogonal crossover artificial bee colony (OCABC) algorithm based on orthogonal experimental design is presented and applied to infer the marine atmospheric duct using the refractivity from clutter technique, and the radar sea clutter power is simulated by the commonly used parabolic equation method. In order to test the accuracy of the OCABC algorithm, the measured data and the simulated clutter power with different noise levels are, respectively, utilized to estimate the evaporation duct and surface duct. The estimation results obtained by the proposed algorithm are also compared with those of the comprehensive learning particle swarm optimizer and the artificial bee colony algorithm combined with opposition-based learning and global best search equation. The comparison results demonstrate that the performance of proposed algorithm is better than those of the compared algorithms for the marine atmospheric duct estimation.

Analysis of the Characteristics of Inertia-Gravity Waves during an Orographic Precipitation Event

A numerical experiment was performed using the Weather Research and Forecasting (WRF) model to analyze the generation and propagation of inertia-gravity waves during an orographic rainstorm that occurred in the Sichuan area on 17 August 2014. To examine the spatial and temporal structures of the inertia-gravity waves and identify the wave types, three wavenumber-frequency spectral analysis methods (Fourier analysis, cross-spectral analysis, and wavelet cross-spectrum analysis) were applied. During the storm, inertia-gravity waves appeared at heights of 10–14 km, with periods of 80–100 min and wavelengths of 40–50 km. These waves were generated over a mountain and propagated eastward at an average speed of 15–20 m s−1. Meanwhile, comparison between the reconstructed inertia-gravity waves and accumulated precipitation showed there was a mutual promotion process between them. The Richardson number and Scorer parameter were used to demonstrate that the eastward-moving inertia-gravity waves were trapped in an effective atmospheric ducting zone with favorable reflector and critical level conditions, which were the primary causes of the long lives of the waves. Finally, numerical experiments to test the sensitivity to terrain and diabatic heating were conducted, and the results suggested a cooperative effect of terrain and diabatic heating contributed to the propagation and enhancement of the waves.

Compressive MIMO Beamforming of Data Collected in a Refractive Environment

AbstractThe phenomenon of ducting is caused by abnormal atmospheric refractivity patterns and is known to allow electromagnetic waves to propagate over the horizon with unusually low propagation loss. It is unknown what effect ducting has on multiple input multiple output (MIMO) channels, particularly its effect on multipath propagation in MIMO channels. A high‐accuracy angle‐of‐arrival and angle‐of‐departure estimation technique for MIMO communications, which we will refer to as compressive MIMO beamforming, was tested on simulated data then applied to experimental data taken from an over the horizon MIMO test bed located in a known ducting hot spot in Southern California. The multipath channel was estimated from the receiver data recorded over a period of 18 days, and an analysis was performed on the recorded data. The goal is to observe the evolution of the MIMO multipath channel as atmospheric ducts form and dissipate to gain some understanding of the behavior of channels in a refractive environment. This work is motivated by the idea that some multipath characteristics of MIMO channels within atmospheric ducts could yield important information about the duct.

Heat stress alleviation for dairy cows housed in an open-sided barn by cooling fan and perforated air ducting (PAD) system

Curtain-sided barns with circulation fans above stall are commonly used to house dairy cows in China. Many farms equipped with circulation fans are unable to provide appropriate cooling, especially for the naturally ventilated shed, which can result in decreasing feed intake and milk production. For alleviating heat stress and improving animal comfort, a system consisting of an air cooler and a 30 m perforated air duct (PAD) was integrated to evenly distribute cooling air. The air was cooled by underground water and delivered to targeted zones above stall bed. The system was evaluated in an open sided dairy barn in Tianjin, China. For the stalls equipped with PAD system, air velocity reached above 1.1 m/s at 0.5 m height plane of the stall space, and was more uniformly distributed. Compared to the stalls equipped with circulation fans, the PAD system lowered air temperature by 1.5°C, and increased relative humidity by 8.1%. On average, Temperature Humidity Index (THI) and Equivalent Temperature Index (ETI) were decreased by 0.5 and 0.6, respectively. After a 15 days’ operation of the system, rectal temperatures of the treated dairy cows were significantly lowered. The results also showed that the cows under PADs had a higher milk production. These findings suggest the PAD can be an effective cooling alternative for naturally ventilated dairy barns to alleviate heat stress. Keywords: dairy cow, heat stress, perforated air duct, cooling fan, naturally-ventilated barn DOI: 10.25165/j.ijabe.20171006.3135 Citation: Xie L N, Wang C Y, Ding L Y, Gui Z Y, Zhang L, Shi Z X, et al. Heat stress alleviation for dairy cows housed in an open-sided barn by cooling fan and perforated air ducting (PAD) system. Int J Agric & Biol Eng, 2017; 10(6): 1–10.

Infrasound phenomenology, propagation, and detection

Infrasound is generally understood to refer to acoustic disturbances in the atmosphere in frequency bands below the threshold of human hearing, but above the frequencies at which internal gravity waves propagate. The infrasonic band is nominally taken to be 0.05 Hz up to about 20 Hz. Infrasonic signals tend to be generated by large, violent events and propagate efficiently in sound ducts formed by wind jets and temperature gradients in the middle and upper atmosphere. Infrasonic signals can be detected at very large distances from the source, sometimes even globally. This tutorial will present an overview of the generation of infrasound by both natural and anthropomorphic sources and of the subsequent propagation and detection of infrasonic signals. Two particular sources will be discussed in detail: the signal generated by a large explosion and the so-called microbarom signal generated by colliding ocean waves. Signal propagation through the atmosphere will then be discussed. Available open source infrasound propagation packages and their use will be introduced, the significant atmospheric sound ducts will be identified, and the difficulties inherent in modeling propagation through a dynamic atmosphere will be emphasized. The current state and availability of atmospheric specification will be touched upon. Finally, the use of array processing for the extraction of infrasonic signals from the pressure fluctuations inherent to a turbulent atmosphere will be discussed.

The state of the art and challenges of marine communications

To implement the Maritime Silk Road in the 21st century and to meet the demands of increasing maritime activity, a seamless, effective, and reliable communications coverage of relevant sea areas is necessary. In this review, we first outline state of the art marine communications networks in China and then analyze and compare several major marine communications networks, including marine radio communications, satellite communications, and shore-based mobile communications networks. Next, based on the geometric characteristics of numerous islands and reefs, a novel system architecture of marine communications networks is proposed, and the main technical challenges precluding its implementation are described, including channel modeling of marine communications, atmospheric duct effect, microwave scattering effect, and unified and effective network resource management. This work will benefit policy makers, scientific researchers, and engineers, by providing a global overview and enabling them to grasp the trends in marine communications, and thus is likely to promote the construction and development of marine communications in China.

Parameter dependence of acoustic quantities in a nonlinear internal wave duct

Parameter dependence of acoustic quantities in a nonlinear internal wave duct BJD, Matt Milone, YTL Ocean features with 3-D spatial variability in shallow water can significantly affect acoustic propagation. One example is a curved front modeled with a discontinuous sound speed change over a sloping shelf [Lin and Lynch, JASA-EL (2012)], which has an extension to a continuous sound-speed change. An approach using normal modes and perturbation approximations yields convenient formulas that show how acoustic quantities depend on environmental parameters [DeCourcy et al., ASA, Salt Lake City (2016)]. Another common 3-D example is nonlinear internal waves, with wave fronts that pairwise can produce acoustic ducting, radiating, and scattering effects often observed in field data. The previous approach is applied to this feature, using a well model with two sound-speed jumps for such a duct [Lin et al., (2013)]. Approximate formulas for acoustic wavenumbers and phase speeds are determined in order to estimate sensitivity to changes in environmental parameters. All mode types will be considered (whispering gallery, fully bouncing, and leaky), highlighting differences from those in the single-front example. [Work supported by ONR Grants N00014-14-1-0372 and N00014-11-1-0701.]

Estimating Range-Dependent Evaporation Duct Height

AbstractThe refractivity from clutter (RFC) technique has been proved to be an effective way to estimate atmospheric duct structure. An important issue for RFC is how to make the estimate more robust, especially in range-dependent ducting conditions. Traditionally, statistical inversion methods need a large number of forward propagation model runs to obtain an acceptable result. Especially when the parameter search space is multidimensional, these methods are prone to being trapped into local optimal solutions. Recently published results (Zhao and Huang) indicate that the adjoint parabolic equation (PE) method holds promise for real-time estimation of one-dimensional refractive index structure from radar sea clutter returns. This paper is aimed at extending the adjoint PE method to range-dependent evaporation duct cases, with a log-linear relationship describing duct structures. Numerical simulations are used to test the performance of this method and the results are compared with that retrieved using a genetic algorithm. Both noise-free and 3-dB additive Gaussian noise clutter simulations are considered, as well as linearly and nonlinearly varying duct height with range.

Analysis and prediction of 100 km-scale atmospheric duct interference in TD-LTE networks

Atmospheric ducts are horizontal layers that occur under certain weather conditions in the lower atmosphere. Radio signals guided in atmospheric ducts tend to experience less attenuation and spread much farther, i.e, hundreds of kilometers. In a large-scale deployed TD-LTE (Time Division Long Term Evolution) network, atmospheric ducts cause faraway downlink wireless signals to propagate beyond the designed protection distance and interfere with local uplink signals, thus resulting in a large outage probability. In this paper, we analyze the characteristics of ADI atmospheric duct interference (Atmospheric Duct Interference) by the use of real network-side big data from the current operated TD-LTE network owned by China Mobile. The analysis results yield the time varying and directional characteristics of ADI. In addition, we proposed an SVM (Support Vector Machine)-classifier based spacial prediction method of ADI by machine learning over combination of real network-side big data and real meteorological data. Furthermore, an implementation of ADMM (Alternating Direction Methods of Multipliers) framework is proposed to implement a distributed SVM prediction scheme, which reduces data exchange among different regions/cities, maintains similar prediction accuracy and is thus of a more practical use to operators.

STUDY THE EFFECT OF THE ENVIRONMENTAL PARAMETERS ON THE PERFORMANCE OF A PROTOTYPE FOR ASPHALT SOLAR COLLECTOR USING AIR AS A WORKING FLUID

Diminution of fossil fuel inspires researches to look for renewable energy sources. Heat island and road accidents resulted from tires explosion due to excessive asphalt heat (reach to 70 oC) were another problems. These problems oriented researchers to use asphalt as a heat collector. They found by using asphalt as a heat collector it will gain energy, reduce heat island and reduce road accidents as well. Recently researchers started to use some applications of asphalt solar collector (ASC). Majority of these applications used to heat and cool water. In this research, the first ASC prototype was built outside the laboratory and using atmospheric air as a working fluid. The environmental parameters such as ambient temperature, variation of solar day time, asphalt surface temperature is considered. This prototype consisted of buried pipes under asphalt layers with two opening ends. One end is connected to atmospheric air duct and the other ends connected to Unplasticized Poly Vinyl Chloride (UPVC) chimney. It has been found compatibility with the laboratory study in the strong effect of the chimney height on the air flow velocity through the ASC. Also it can be concluded that the ASC prototype performance for producing energy depends on prototype components in terms of chimney height, asphalt temperature and the environmental / atmospheric conditions in terms of ambient air temperature, and ambient wind speed. Key words: Asphalt collector, solar energy, energy harvesting, and air velocity.

Estimating refractivity from propagation loss in turbulent media

AbstractThis paper estimates lower atmospheric refractivity (M‐profile) given an electromagnetic (EM) propagation loss (PL) measurement. Specifically, height‐independent PL measurements over a range of 10–80 km are used to infer information about the existence and potential parameters of atmospheric ducts in the lowest 1 km of the atmosphere. The main improvement made on previous refractivity estimations is inclusion of range‐dependent fluctuations due to turbulence in the forward propagation model. Using this framework, the maximum likelihood (ML) estimate of atmospheric refractivity has good accuracy, and with prior information about ducting the maximum a priori (MAP) refractivity estimate can be found. Monte Carlo methods are used to estimate the mean and covariance of PL, which are fed into a Gaussian likelihood function for evaluation of estimated refractivity probability. Comparisons were made between inversions performed on propagation loss data simulated by a wide angle parabolic equation (PE) propagation model with added homogeneous and inhomogeneous turbulence. It was found that the turbulence models produce significantly different results, suggesting that accurate modeling of turbulence is key.

Path-Loss and Correlation Analysis for Space and Polarization Diversity in Surface Ducts

Atmospheric ducts that are caused by the rapid decrease in the refractive index of the lower atmosphere can trap the propagating signals. The trapping effect of atmospheric ducts provides significant received power enhancements and enables signals to reach beyond-line-of-sight distances. Although wave propagation in atmospheric ducts are well studied, there is no work that provides fading and correlation analysis for atmospheric ducts. Therefore, the main motivation of this communication is to develop a large-scale path-loss model, estimate the distribution of fading, and analyze fading correlation for space and polarization diversity systems in the presence of surface ducts. Lastly, the achievable data rate results are presented to show the performance improvement with space and polarization diversity techniques.

First observations of elevated ducts associated with intermittent turbulence in the stable boundary layer over Bosten Lake, China

AbstractNocturnal radiative cooling is a main driver for atmospheric duct formation. Within this atmospheric process, the impacts of intermittent turbulence on ducting have seldom been studied. In this paper, we reported two confusing ducting events observed in the early morning in August 2014 over Bosten Lake, China, when a stable boundary layer (SBL) still survived, by using tethered high‐resolution GPS radiosondes. Elevated ducts with strong humidity inversions were observed during the balloon ascents but were absent during observations made upon the balloon descents several minutes later. This phenomenon was initially hypothesized to be attributable to turbulence motions in the SBL, and the connection between the turbulence event and the radar duct was examined by the statistical Thorpe method. Turbulence patches were detected from the ascent profiles but not from the descent profiles. The possible reasons for the duct formation and elimination were discussed in detail. The turbulent transport of moisture in the SBL and the advection due to airflows coming from the lake are the most probable reasons for duct formation. In one case, the downward transport of moisture by turbulence mixing within a Kelvin‐Helmholtz billow at the top of the low‐level jet resulted in duct elimination. In another case, the passage of density currents originating from the lake may have caused the elimination of the duct. Few studies have attempted to associate intermittent turbulence with radar ducts; thus, this work represents a pioneering study into the connection between turbulent events and atmospheric ducts in a SBL.

Anomalous propagation conditions over eastern Pacific Ocean derived from MAGIC data

AbstractThis study characterizes the evaporation and elevated ducts, the most common types of ducts observed over the ocean, along a track of around 4000 km between the California coast and Hawaii. We analyzed 1 year (2012–2013) of ship‐based measurements made during the Marine Atmospheric Radiation Measurement GPCI (GEWEX cloud system study Pacific Cross‐Section Intercomparison) Investigation of Clouds (MAGIC) campaign. During this period, the ship made multiple transects between Southern California and Hawaii. While the ship‐based in situ measurements and the radiosonde data served as the primary data source, a marine atmospheric surface layer model adapted from the Coupled Ocean‐Atmosphere Response Experiment 3.0 surface flux scheme is used to diagnose evaporative duct properties. Calculated mean evaporation duct heights based on shipboard measurements were found to increase steadily from 7 m offshore California to about 15 m near Hawaii. Overall 78% of duct heights are below 20 m. On average the evaporation duct strength is between ≈ 25 and 35 M units near Hawaii and about 15 M units near the California coast. A gradual transition from stratocumulus (Sc) dominated offshore California to trade wind regime with cumulus (Cu) clouds takes place along MAGIC track. The measured marine atmospheric boundary layer (MABL) height and the capping inversion characteristics are significantly different in the two regimes with MABL decoupling occurring in the longitude range between 125°W and 140°W along the track. The characteristics of the elevated ducts, obtained from the rawinsonde sounding profiles, are also different in the two regions west and east of the MABL decoupling region. Approximately 70–80% of the elevated ducts occur below 1.5 km east of the decoupling region, whereas almost equal percentage of ducts forms at heights above 1.5 km on the west side.

The interaction between infrasonic waves and gravity wave perturbations: Application to observations using UTTR Rocket Motor Fuel Elimination Events

AbstractInfrasonic waves propagate at long ranges through atmospheric ducts resulting from the stratification of atmospheric properties. In order to study the infrasonic wave propagation, we resort to atmospheric specification combining Numerical Weather Prediction and climatological models. However, these models do not describe small‐scale variability such as perturbations associated to the presence of internal gravity waves. These waves play an important role in the atmospheric dynamic by transferring momentum to the mean flow at critical levels and at wave‐breaking altitudes. In this study we intend to describe the interaction of infrasonic waves with internal gravity waves in order to understand the extended wave trains observed in broadband infrasound signals. We use a numerical model for the propagation of internal waves to generate realistic perturbations of the background atmospheric states. By using a linear full‐wave model of infrasound propagation, our goal is to ultimately relate infrasound characteristics to internal waves properties. We apply those numerical models to different atmospheric mean states including gravity wave perturbations and compare the simulations to infrasound signals recorded from rocket motor fuel elimination events at the Utah Test and Training Range (UTTR). Our results, based on an intensive simulation of infrasound waveforms, show that combining atmospheric background with gravity wave propagation model is relevant to explain, to first order, the behavior of the infrasound field at the distance of the first stratospheric arc. In particular we obtain a better match between pulse duration and peak‐to‐peak amplitude along the stratospheric arc. Such study supports the use of gravity wave simulation in conjunction with infrasound modeling in order to improve gravity wave parameterization in Numerical Weather Forecasting.

Anomalous propagation conditions of electromagnetic wave observed over Bosten Lake, China in July and August, 2014

Atmospheric duct is a common phenomenon over large bodies of water, and it can significantly affect the performance of many radio systems. In this paper, a two-month (in July and August, 2014) sounding experiment in ducting conditions over Bosten Lake was carried out at a littoral station (41.89° N, 87.22° E) with high resolution GPS radiosondes, and atmospheric ducts were observed for the first time in this area. During the two months, surface and surface-based ducts occurred frequently over the Lake. Strong diurnal variations in ducting characteristics were noticed in clear days. Ducting occurrence was found at its lowest in the early morning and at its highest (nearly 100%) in the afternoon. Duct strength was found increasing from early morning to forenoon, and reaching its maximum in the afternoon. But contrarily, duct altitude experienced a decrease in a clear day. Then the meteorological reasons for the variations were discussed in detail, turbulent bursting was a possible reason for the duct formation in the early morning and the prevailing lake-breeze front was the main reason in the afternoon. The propagation of electromagnetic wave in a ducting environment was also investigated. A ray-tracing framework based on Runge–Kutta method was proposed to assess the performance of radio systems, and the precise critical angle and grazing angle derived from the ray-tracing equations were provided. Finally, numerical investigations on the radar performance in the observed ducting environments have been carried out with high accuracy, which demonstrated that atmospheric ducts had made great impacts on the performance of radio systems. The range/height errors for radar measurement induced by refraction have also been presented, too, which shows that the height errors were very large for trapped rays when the total range was long enough.

Investigation on the Inversion of the Atmospheric Duct Using the Artificial Bee Colony Algorithm Based on Opposition-Based Learning

The artificial bee colony (ABC) algorithm is a recently introduced optimization method in the research field of swarm intelligence. This paper presents an improved ABC algorithm named as OGABC based on opposition-based learning (OBL) and global best search equation to overcome the shortcomings of the slow convergence rate and sinking into local optima in the process of inversion of atmospheric duct. Taking the inversion of the surface duct using refractivity from clutter (RFC) technique as an example to validate the performance of the proposed OGABC, the inversion results are compared with those of the modified invasive weed optimization (MIWO) and ABC. The radar sea clutter power calculated by parabolic equation method using the simulated and measured refractivity profile is utilized to carry out the inversion of the surface duct, respectively. The comparative investigation results indicate that the performance of OGABC is superior to that of MIWO and ABC in terms of stability, accuracy, and convergence rate during the process of inversion.

Beyond-Line-of-Sight Ducting Channels: Coherence Bandwidth, Coherence Time and Rain Attenuation

Atmospheric ducts trap the propagating signals by refraction. In this way, the propagating signals in the duct can propagate through beyond-line-of-sight distances (b-LoS). Although atmospheric ducts are promising candidate for b-LoS communication especially for military applications, channel characteristics of the ducting channel have not been completely modeled. In this letter, coherence time and coherence bandwidth of ducting channels are analyzed for the first time in the literature. In addition, a slant-path rain attenuation model is proposed to determine rain attenuation in ducting links for the first time. At the end, simulation results are presented for the distribution of rain loss and spectral efficiency of the system.