Search

In this study, a low-cost two-dimensional (2D) trajectory correction mechanism is proposed to address the large trajectory deviation of small-caliber extended-range ammunitions. By controlling the projectile's roll, a single-channel 2D trajectory correction function can be realized. Moreover, based on the ideal trajectory, a five-degree-of-freedom approximate rigid-body trajectory equation is proposed. A high-order system is transformed into two low-order cascading subsystems using fuzzy control and the self-disturbance rejection control theory, which reduces the parameter tuning complexity. The entire control process is divided into three stages which realizes the second-order variable structure control of non-affine nonlinear subsystems. A low-altitude atmospheric disturbance model is established, and as an example, numerical calculations are performed on the control process and projectile impact point dispersion of a 35 mm small-caliber rocket. The results verify the performance of the proposed trajectory correction under atmospheric disturbances. This study provides a control approach for coupled underactuated nonlinear systems and provides guidance for the design of a low-cost 2D trajectory correction controller for small-caliber ammunitions. [ABSTRACT FROM AUTHOR]

The adaptive backstepping method has strong performance in handling control problems with disturbances in previous research. However, it exhibits limitations when applied to time-varying disturbances. This paper proposes an improved adaptive backstepping method based on Discrete Fourier Transform (DFT). By estimating the frequency spectrum of the disturbance and indirectly obtaining its time-domain estimate, the proposed method effectively overcomes the shortcomings of traditional adaptive backstepping. To address the issue of frequency leakage caused by discontinuities in window data, the idea of DFT is improved by using STFT with the addition of the window function and window-shifting operation. Additionally, a projection operator and adaptive reduction of the control objective are employed to mitigate the effects of actuator saturation. Finally, in simulations involving an aircraft subjected to gusts and turbulence, the proposed method is compared with traditional adaptive backstepping and radial basis function (RBF) neural network control methods. Simulation results demonstrate that the proposed method outperforms the others in these experimental scenarios. [ABSTRACT FROM AUTHOR]

Swells can cause coastal hazards. A unique example of such hazards is the Yorimawari‐Nami (YM‐wave) events that have been observed once every few years in Toyama Bay in the Japan Sea. Based on coastal in situ observations and hindcast simulations of ocean waves, the forcing mechanism for the record‐high 2008 YM‐wave event is investigated, focusing on the surface winds and the atmospheric disturbances that drove wind seas and swells in the Japan Sea. Detailed analysis of atmospheric mesoscale data along with cyclone tracking and wave spectral analysis revealed that the 2008 event was forced by an exceptionally persistent northerly wind off the Tohoku and Hokkaido regions associated with two successive extra‐tropical cyclones, passing across the Japan Sea and accompanying a well‐defined upper‐tropospheric cut‐off low. The first cyclone generated the initial northerly wind forcing toward the northwest of Hokkaido Island that was aligned with the direction of southward‐propagating wind seas toward Toyama Bay. This initial fetch caught up with the second cyclone, leading to an extension in the area of a large northerly wind component (>12 ms−1) that lasted longer than 24 hr and extended southward due to the southward extension of the cut‐off low with a propagation speed that matches the wave group velocity, reinforcing the initially generated swell. Plain Language Summary: Due to the frequent passage of storms to the north of Toyama Bay, the surrounding coastal region has been devastated by extreme ocean waves once every several years. Of these extreme waves, one that hit the bay in 2008 was the highest and most destructive. We investigated the factors that contributed to the 2008 wave event being so exceptional compared to previous moderate events associated with similar waves. Matching the wind and wave fields in the Japan Sea in conjunction with cyclone tracking revealed that two successive cyclones passing across the Japan Sea jointly contributed to the generation of the high waves. The first cyclone approaching northern Japan brought northerly winds in its wake that are favorable for generating a wind‐forced ocean wave. As the wave propagated toward Toyama Bay, the second cyclone from the west caught up with the region of initial wind forcing, further extending the area of a large northerly wind component that had continuously provided energy to the propagating wave, further amplifying the wave. While it has been reported that tropical cyclones or polar lows sometimes energize pre‐existing ocean waves, this study suggests that similar mechanisms in midlatitude migratory cyclones can trigger extreme ocean waves. Key Points: Detailed atmospheric forcing in the Japan Sea and the record high ocean wave that eventually hit Toyama Bay in 2008 is investigatedThe 2008 high wave was reinforced by a dynamical fetch‐like mechanism where the moving wind forcing matches the wave propagationA well‐defined cut‐off low in the mid‐troposphere made surface wind forcing persistent and expand southward [ABSTRACT FROM AUTHOR]

In response to the growing demand for the global energy supply chain, wind power has become an important research subject among studies in the advancement of renewable energy sources. The major concern is the stochastic volatility of weather conditions that hinder the development of wind power forecasting approaches. To address this issue, the current study proposes a weather prediction method divided into two models for wind speed and atmospheric system forecasting. First, the data-based model incorporated with wavelet transform and recurrent neural networks is employed to predict the wind speed. Second, the physics-informed echo state network was used to learn the chaotic behavior of the atmospheric system. The findings were validated with a case study conducted on wind speed data from Turkmenistan. The results suggest the outperformance of physics-informed model for accurate and reliable forecasting analysis, which indicates the potential for implementation in wind energy analysis. [ABSTRACT FROM AUTHOR]

The Ms 6.2 Zhangbei earthquake occurred at 3:53 (UTC) on 10 January 1998, with its epicenter located at about 150 km northwest of Beijing, China. Over the past 2 decades, many studies have reported that there was a positive thermal infrared (TIR) anomaly appearing along the direction from the Bohai Sea to Zhangbei within 2–3 days preceding the earthquake, which was considered to be caused by the activity of the great Zhangbei-Bohai fault (ZBF) extending across the Bohai Sea to the southeast, while neither the TIR anomaly is convinced nor the mechanism is clear. A collaborative analysis of the atmospheric disturbances several days before, during, and after the earthquake was conducted by using satellite observations and reanalysis datasets with multiple parameters, including sea surface roughness, evaporation rate, atmospheric CO concentration, atmospheric sea salt concentration, and cloud base height above the sea surface, as well as satellite infrared cloud images. Through individual analysis of the change of each parameter and synergic analysis of multiple parameters, particular atmospheric disturbances, including the formation of strip-shaped clouds on January 7 and 9, were revealed over the ZBF and another great fault named Tancheng-Lujiang fault (TLF), which extends across the Bohai Sea to the northeast. After careful investigation and attribution analysis of the spatio-temporal evolutions of the atmospheric disturbances every hour above and around the Bohai Sea from January 7 to 12, we came to the conclusion that the particular strip-shaped clouds were low-level clouds caused by the seismic activity and submarine gas release from TLF but not ZBF and was forced by particular wind field and lowering boundary layer. As an aftereffect of the gas release from TLF and the formation of the localized low-level clouds of higher brightness temperature than that of the land surface, a positive TIR anomaly, thus, appeared above TLF and by chance along ZBF, preceding the Zhangbei earthquake.

Abstract In order to avoid serious safety accidents caused by closed fire zone, based on the continuous monitoring of atmospheric pressure at different monitoring points in multiple mines, the atmospheric pressure fluctuation model and the air leakage model were established and analyzed. The change law with time of oxygen concentration and gas concentration in the fire zone were obtained due to atmospheric disturbances under the influence of different pressure difference, volume and size of fire area, wind resistance, gas emission, sealing moments, etc. so as to evaluate the explosion risk of a closed fire zone. Research showed that the mine atmosphere fluctuates with the atmosphere of ground, and the pressure difference between the inner and outer sides of the enclosed fire zone is affected by the periodic fluctuation of atmosphere, which has about 16-h cosine fluctuation and approximate 8-h fixed value. Compared with the fire zone with poor sealing quality, good sealing fire zone has better resistance to atmospheric disturbance. The reduction of oxygen concentration in the inner side of a well-sealed fire zone mainly depends on the dilution of methane, which is more likely to accumulate and rise rapidly. And the fire zone with poor sealing quality is easy to be interfered. The inner oxygen concentration and gas concentration are easily affected by the absolute gas emission and the air leakage in the fire zone. Fire zone with small wind resistance and small volume is especially obvious. At the initial stage of the closed fire zone it's very possible to happen explosion. The time duration of explosion danger varies under different conditions, and the atmospheric disturbance may lead to repeated explosions in some cases. It's suggested to take some methods to avoid explosions according to the real-time situation, closure time, oxygen concentration and gas concentration of fire zone.

Multiple parameters (brightness temperature, soil moisture, surface latent heat flux, surface air temperature and carbon monoxide) before and after the 2015 Nepal M7.8 Gorkha main earthquake and M7.3 Dolakha aftershock were analysed using satellite observation data. The thermal anomalies from optical and microwave data appear about two months prior to the 2015 Gorkha earthquake. Some of the parameters show anomalous changes at different altitudes about 20 days prior to the main earthquake event and 10 days prior to the strong aftershock. Our results show that pre-earthquake anomalous signals propagate from the in situ to the top of atmosphere, and the anomalies in the atmosphere often observed prior to an impending earthquake. The changes on the land surface and corresponding changes in meteorological and atmospheric parameters show existence of strong coupling during the seismogenic period, although the transfer mechanism of seismic/electromagnetic is still has to be investigated and understood.

In order to avoid serious safety accidents caused by closed fire zone, based on the continuous monitoring of atmospheric pressure at different monitoring points in multiple mines, the atmospheric pressure fluctuation model and the air leakage model were established and analyzed. The change law with time of oxygen concentration and gas concentration in the fire zone were obtained due to atmospheric disturbances under the influence of different pressure difference, volume and size of fire area, wind resistance, gas emission, sealing moments, etc. so as to evaluate the explosion risk of a closed fire zone. Research showed that the mine atmosphere fluctuates with the atmosphere of ground, and the pressure difference between the inner and outer sides of the enclosed fire zone is affected by the periodic fluctuation of atmosphere, which has about 16-h cosine fluctuation and approximate 8-h fixed value. Compared with the fire zone with poor sealing quality, good sealing fire zone has better resistance to atmospheric disturbance. The reduction of oxygen concentration in the inner side of a well-sealed fire zone mainly depends on the dilution of methane, which is more likely to accumulate and rise rapidly. And the fire zone with poor sealing quality is easy to be interfered. The inner oxygen concentration and gas concentration are easily affected by the absolute gas emission and the air leakage in the fire zone. Fire zone with small wind resistance and small volume is especially obvious. At the initial stage of the closed fire zone it's very possible to happen explosion. The time duration of explosion danger varies under different conditions, and the atmospheric disturbance may lead to repeated explosions in some cases. It's suggested to take some methods to avoid explosions according to the real-time situation, closure time, oxygen concentration and gas concentration of fire zone. [ABSTRACT FROM AUTHOR]

GB-InSAR, with high time-spatial resolution and high accuracy, shows great potential in landslide monitoring. However, the accuracy of GB-InSAR is usually reduced by the atmospheric disturbance and temporal decorrelation. PS-InSAR technology can solve those problems well and get accurate deformation information, so it has been widely adopted in space-borne SAR. For the atmospheric correction, PS-InSAR assumes that the atmospheric phase is only strongly correlated in the space domain. But for GB-InSAR, atmospheric phase shows correlation in both the time and space domains, because of the short time interval. Therefore, the calculation of linear velocity will be affected by the atmospheric disturbance when the PS-InSAR technology is applied to the GB-SAR data. To solve this problem, a PS-InSAR strategy for GB-SAR data considering the atmospheric disturbance in the time domain is proposed. The proposed method uses the differential interferograms interfered by nearby SLCs to ensure the high coherence of interferometric phase and reduces the impact of atmospheric disturbance. The coherence is used for PS selection besides the amplitude deviation index, which can increase the density of PS points. Furthermore, a method for atmospheric correction based on the wrapped phase is presented. Thus, the linear velocity is computed based on the interferogram without most atmospheric disturbance. The validation using the data of the open pit in Malanzhuang, Hebei, China, shows that the proposed method can get a deformation monitoring accuracy of sub-millimeter. [ABSTRACT FROM AUTHOR]

As a kind of renewable energy, wind energy is getting more and more attention with its advantage of rich, clean and environmentally sustainable. Stochastic volatility is the inherent property of wind energy and the essential factor hindering the development of wind power prediction research. In this paper, by considering the actual movement rule of wind energy described by Lorenz system, the Lorenz system and the wavelet decomposition were combined to improve the wind speed prediction models of BP, RBF, and Elman neural network for the first time, and a wind speed prediction model with the Lorenz system based on wavelet decomposition was established. The model has been compared with three traditional numerical prediction methods, proving that Lorenz disturbance model can get better prediction accuracy and can grasp the actual movement of wind more accurately. The research of this paper can make up for the neglect of the atmospheric system in the field of wind speed prediction, which is helpful to the large-scale development and utilization of wind energy resources. [ABSTRACT FROM AUTHOR]

Multiple parameters (brightness temperature, soil moisture, surface latent heat flux, surface air temperature and carbon monoxide) before and after the 2015 Nepal M7.8 Gorkha main earthquake and M7.3 Dolakha aftershock were analysed using satellite observation data. The thermal anomalies from optical and microwave data appear about two months prior to the 2015 Gorkha earthquake. Some of the parameters show anomalous changes at different altitudes about 20 days prior to the main earthquake event and 10 days prior to the strong aftershock. Our results show that pre-earthquake anomalous signals propagate from the in situ to the top of atmosphere, and the anomalies in the atmosphere often observed prior to an impending earthquake. The changes on the land surface and corresponding changes in meteorological and atmospheric parameters show existence of strong coupling during the seismogenic period, although the transfer mechanism of seismic/electromagnetic is still has to be investigated and understood. [ABSTRACT FROM AUTHOR]

This paper considers the effect of nonlinear atmospheric disturbances on wind power prediction. A Lorenz system is introduced as an atmospheric disturbance model. Three new improved wind forecasting models combined with a Lorenz comprehensive disturbance are put forward in this study. Firstly, we define the form of the Lorenz disturbance variable and the wind speed perturbation formula. Then, different artificial neural network models are used to verify the new idea and obtain better wind speed predictions. Finally we separately use the original and improved wind speed series to predict the related wind power. This proves that the corrected wind speed provides higher precision wind power predictions. This research presents a totally new direction in the wind prediction field and has profound theoretical research value and practical guiding significance.

Thirty infrasound sensors have been operated over Japan since 2015. We developed the irregular array data processing in order to detect and estimate the parameters of the arrival source waves by using infrasound data related to the sequence of the volcanic eruption at Mt. Shinmoedake in March 2018. We found that the apparent velocity at the ground was equal to the acoustic velocity at particular reflection levels. The results were confirmed through a comparison of the findings of the apparent velocity with a wave propagation simulation on the basis of the azimuth, infrasound time arrivals, and the state of the atmospheric background using global atmospheric models. In addition, simple ideas for estimating horizontal wind speeds at certain atmospheric altitudes based on infrasound observation data and their validation and comparison were presented. The calculated upper wind speed and wind observed by radiosonde measurements were found to have a qualitative agreement. Propagation modeling for these events estimated celerities in the propagation direction to the sensors that were consistent with the tropospheric and stratospheric ducting. This study could inspire writers, in particular, and readers, in general, to take advantage of the benefits of infrasound wave remote-sensing for the study of the Earth’s atmospheric dynamics.

Abstract: The gravitational effects of the atmosphere and subsurface water are significant obstacles to observing gravity variations on the sub‐μGal (1 μGal = 10 nm/s2) scale. The goal of this study is to detect changes in gravity that are caused by mass redistributions deep underground related to seismological phenomena by reducing environmental gravity effects using multiple gravimeters belowground and aboveground, which we term a “vertical gravimeter array.” Based on an evaluation of the responses to atmospheric effects and rainfall events identified in observations made with individual relative gravimeters, the vertical gravimeter array succeeds in stacking the target signals from deep underground and in reducing errors due to rainfall or free groundwater and atmospheric effects. To enable accurate interpretation, we introduce a physical approach that is based on attraction and loading deformation effects for atmospheric reduction using state‐of‐the‐art gridded weather data products. Changes in the water levels of confined groundwater can be regarded as a signal from deep underground, and a response coefficient of approximately −15 μGal/m was obtained. In addition, the response coefficient of the free groundwater level was determined to be approximately 5 μGal/m. Such array observations are expected to contribute to monitoring crustal activity and hydrological studies. [ABSTRACT FROM AUTHOR]

Atmospheric disturbance has a great influence on the measurement accuracy of Ground-Based SAR; thus the selection of a suitable atmospheric correction method is related to the reliability and accuracy of measurement results. A whole scene atmospheric correction method using the PS atmospheric correction network is proposed, and applied in a experiment monitoring a high-risk slope under construction. The effectiveness of the meteorological correction method proposed in this paper was verified by a comparison with the results of conventional atmospheric correction method and surveying robot. [ABSTRACT FROM AUTHOR]

Kim, H.; Kim, M.-S.; Lee, H.-J.; Woo, S.-B., and Kim, Y.-K. 2016. Seasonal Characteristics and Mechanisms of Meteo-tsunamis on the West Coast of Korean Peninsula. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1147 - 1151. Coconut Creek (Florida), ISSN 0749-0208. A meteo-tsunami is produced by atmospheric disturbances, such as pressure jumps, and the seasonal frequency changes of meteo-tsunamis might be dependent on the seasonal synoptic weather features. Therefore, an analysis of the synoptic atmospheric mechanism for the cause of meteo-tsunamis is important for predicting the meteo-tsunamis precisely and reducing the sudden damage. As the west coast of the Korean peninsula is a region with frequent meteo-tsunamis, the outcome of an analysis of the tidal level observation data at 1-min intervals shows that meteo-tsunami have occurred 92 times (3-SD(exceeding the 3 times of standard deviation): 28 times, 2-SD: 64 times) over the last 12 years (2002-2013). Meteo-tsunamis occur every season but have the greatest frequency in the spring (MAM; 53.3%) and winter (DJF; 26.1%). In particular, strong meteo-tsunamis in excess of 3-SD have occurred in spring (53.6%) and winter (28.6%). Climatologically, low pressure systems often passes through the Korean peninsula located in the mid-latitudes during spring. In this season, the potential instability of the atmosphere is increased on the Yellow sea. On contrast, the Siberian high pressure system periodically extends to the Korean peninsula during winter. This can cause atmospheric dynamic instability from the boundary between the land and sea. [ABSTRACT FROM AUTHOR]

Atmospheric disturbance is a complex nonlinear process. The Lorenz system was seen as a classical model to reveal essential characteristics of nonlinear systems. It has further improved people's understanding of the evolution of the climate system. Different from traditional studies working on improving the numerical methods for wind prediction, dynamic characteristics of the atmospheric system are fully considered here. This paper proposed the concept of the Lorenz Comprehensive Disturbance Flow (LCDF) and defined the perturbation formula for wind prediction. The Lorenz disturbance has significant influence on wind forecasting, which is proved by using wind data from the Sotavento wind farm. That is to say, the change process of atmospheric motion around the wind farm is more ideally described based on the Lorenz system. This research has important theoretical value in developing nonlinear systems and plays a great role on wind prediction and wind resource exploitation. [ABSTRACT FROM AUTHOR]

Short range radars can provide robust information about their surroundings under atmospheric disturbances, such as dust, rain, and snow, conditions under which most other sensing technologies fail. However, this information is corrupted by received power noise, resulting in false alarms, missed detections, and range/bearing uncertainty. The reduction of radar image noise, for human interpretation, as well as the optimal, automatic detection of objects, has been a focus of radar processing algorithms for many years. This paper combines the qualities of the well established binary integration detection method, which manipulates multiple images to improve detection within a static scene, and the noise reduction method of power spectral subtraction. The binary integration method is able to process multiple radar images to provide probability of detection estimates, which accompany each power value received by the radar. The spectral subtraction method then utilizes these probabilities of detection to form an adaptive estimate of the received noise power. This noise power is subtracted from the received power signals, to yield reduced noise radar images. These are compared with state-of-the-art noise reduction methods based on the Wiener filter and wavelet denoising techniques. The presented method exhibits a lower computational complexity than the benchmark approaches and achieves a higher reduction in the noise level. All of the methods are applied to real radar data obtained from a 94-GHz millimetre wave FMCW 2D scanning radar and to synthetic aperture radar data obtained from a publicly available data set. [ABSTRACT FROM PUBLISHER]

Abstract: The paper overviews meteotsunami events documented in the Adriatic Sea in the last several decades, by using available eyewitness reports, documented literature, and atmospheric sounding and meteorological reanalysis data available on the web. The source of all documented Adriatic meteotsunamis was examined by assessing the underlying synoptic conditions. It is found that travelling atmospheric disturbances which generate the Adriatic meteotsunamis generally appear under atmospheric conditions documented also for the Balearic meteotsunamis (rissagas). These atmospheric disturbances are commonly generated by a flow over the mountain ridges (Apennines), and keep their energy through the wave-duct mechanism while propagating over a long distance below the unstable layer in the mid-troposphere. However, the Adriatic meteotsunamis may also be generated by a moving convective storm or gravity wave system coupled in the wave-CISK (Conditional Instability of the Second Kind) manner, not documented at other world meteotsunami hot spots. The travelling atmospheric disturbance is resonantly pumping the energy through the Proudman resonance over the wide Adriatic shelf, but other resonances (Greenspan, shelf) are also presumably influencing the strength of the meteotsunami waves, especially in the middle Adriatic, full of elongated islands and with a sloping bathymetry. The generated long ocean waves are hitting funnel-shaped bays or harbours of large amplification factors, resulting in meteotsunami waves with heights up to 6m at the very end of bays or harbours. Within models the mechanism is fairly well understood, but it is extremely difficult to reproduce these events (and presently almost impossible to forecast) as the meteotsunami generating process is highly variable at both temporal and spatial scales. The final part of the paper discusses the possibilities for further research of the Adriatic meteotsunamis, and meteotsunamis in general, including the basis of a meteotsunami warning system which should be able to capture potentially dangerous travelling atmospheric disturbances in real-time. [Copyright &y& Elsevier]

This letter studies the impact of the use of permanent scatterers (PS) on the distribution of the perpendicular baselines in long-term satellite interferometric synthetic aperture radar surveys. This letter also evaluates the relation between the radar center frequency and the dispersion of the estimates of the elevations of the PS as a function of noise and of the time jitter due to atmospheric disturbances. [ABSTRACT FROM PUBLISHER]

Copyright of Annals of Telecommunications is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thirty infrasound sensors have been operated over Japan since 2015. We developed the irregular array data processing in order to detect and estimate the parameters of the arrival source waves by using infrasound data related to the sequence of the volcanic eruption at Mt. Shinmoedake in March 2018. We found that the apparent velocity at the ground was equal to the acoustic velocity at particular reflection levels. The results were confirmed through a comparison of the findings of the apparent velocity with a wave propagation simulation on the basis of the azimuth, infrasound time arrivals, and the state of the atmospheric background using global atmospheric models. In addition, simple ideas for estimating horizontal wind speeds at certain atmospheric altitudes based on infrasound observation data and their validation and comparison were presented. The calculated upper wind speed and wind observed by radiosonde measurements were found to have a qualitative agreement. Propagation modeling for these events estimated celerities in the propagation direction to the sensors that were consistent with the tropospheric and stratospheric ducting. This study could inspire writers, in particular, and readers, in general, to take advantage of the benefits of infrasound wave remote-sensing for the study of the Earth's atmospheric dynamics. [ABSTRACT FROM AUTHOR]