In this study, we investigate the connection between planetary equatorial waves, modulated by the Indian Ocean dipole (IOD) and El Ni & ntilde;o Southern Oscillation (ENSO), and the interannual variabilities of th...
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In this study, we investigate the connection between planetary equatorial waves, modulated by the Indian Ocean dipole (IOD) and El Ni & ntilde;o Southern Oscillation (ENSO), and the interannual variabilities of the salinity distribution in the Bay of Bengal (BoB) in October-December (OND), along with its associated dynamics, using satellite and reanalysis datasets. In OND 2010 and 2016 (1994, 1997, 2006, and 2019), positive (negative) sea surface salinity anomalies (SSSAs) were distributed in the eastern equatorial Indian Ocean (EIO) and Andaman Sea. Moreover, the southward movement of negative (positive) SSSAs along the eastern Indian coast was observed. This phenomenon was caused by large-scale anomalous currents associated with zonal wind over the EIO. During OND 2010 and 2016 (1994, 1997, 2006, and 2019), due to anomalous westerlies (easterlies) over the EIO and anomalous downwelling (upwelling) Kelvin waves, the strengthened (weakened) Wyrtki jet and the basin-scale anomalous cyclonic (anticyclonic) circulation in the BoB gave rise to positive (negative) SSSAs within the eastern EIO and Andaman Sea. In addition, the intensified (weakened) eastern Indian coastal currents led to the southward movement of negative (positive) SSSAs. It is worth noting that downwelling Kelvin waves reached the western coast of India during OND 2010 and 2016, while upwelling Kelvin waves were only confined to the eastern coast of India during OND 1994, 1997, 2006, and 2019. Furthermore, westward salinity signals associated with reflected westward Rossby waves could modulate the spatial pattern of salinity. The distribution of salinity anomalies could potentially influence the formation of the barrier layer, thereby impacting the sea surface temperature variability and local convection.
Near-inertial motions contribute most of the velocity shear in the upper *** the Bay of Bengal(BoB),the annual-mean energy flux from the wind to near-inertial motions in the mixed layer in 2013 is dominated by tropica...
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Near-inertial motions contribute most of the velocity shear in the upper *** the Bay of Bengal(BoB),the annual-mean energy flux from the wind to near-inertial motions in the mixed layer in 2013 is dominated by tropical cyclone(TC)***,due to the lack of long-term observations of velocity profiles,our knowledge about interior near-inertial waves(NIWs)as well as their shear features is *** this study,we quantified the contribution of NIWs to shear by integrating the wavenumber-frequency spectra estimated from velocity profiles in the upper layers(40-440 m)of the southern Bo B from April 2013 to May *** is shown that the annual-mean proportion of near-inertial shear out of the total is approximately 50%,and the high contribution is mainly due to the enhancement of the TC processes during which the near-inertial shear accounts for nearly 80%of the *** the steady monsoon seasons,the near-inertial shear is dominant to or at least comparable with the subinertial *** contribution of NIWs to the total shear is lower during the summer monsoon than during the winter monsoon owing to more active mesoscale eddies and higher subinertial shear during the summer *** Doppler shifting of the M_(2)internal tide has little effect on the main results since the proportion of shear from the tidal motions is much lower than that from the near-inertial and subinertial motions.
Based on Soil Moisture and Ocean Salinity (SMOS) data and the Ocean Reanalysis System 5 (ORAS5) dataset, positive salinity anomalies exceeding 2 psu in the northern Bay of Bengal (BoB) and negative salinity anomalies ...
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Based on Soil Moisture and Ocean Salinity (SMOS) data and the Ocean Reanalysis System 5 (ORAS5) dataset, positive salinity anomalies exceeding 2 psu in the northern Bay of Bengal (BoB) and negative salinity anomalies with the peak of the freshening anomalies reaching -2 psu around Sri Lanka were observed in autumn 2010. Here, an analysis of the anomalous salt budget revealed that anomalous horizontal advection contributed most to the variability in salinity in the BoB. With the development of La Nina and negative Indian Ocean dipole (nIOD) in summer and autumn, the strong summer monsoon current and Wyrtki jet combined with the anomalous basin-scale cyclonic circulation led to more high-salinity water entering the northern BoB. In addition, more freshwater was transported southward along the eastern coast of India by east Indian coastal current (EICC) in autumn, resulting in extremely negative salinity anomalies around Sri Lanka and positive salinity anomalies in the northern BoB. Moreover, the freshwater around Sri Lanka was carried farther into the southeastern Arabian Sea by the west Indian coastal current (WICC) in November, which affected the salinity stratification in winter and then influenced the variation of the Arabian Sea Mini Warm Pool (ASMWP) in the following spring. The ASMWP could affect the Indian summer monsoon (ISM) through its influence on the monsoon onset vortex (MOV) over the southeast Arabian Sea (SEAS).
The sea level anomalies(SLAs)pattern in the northwestern Pacific delineated significant differences between La Ni?a events occurring with and without negative Indian Ocean Dipole(IOD)*** the pure La Ni?a events,positi...
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The sea level anomalies(SLAs)pattern in the northwestern Pacific delineated significant differences between La Ni?a events occurring with and without negative Indian Ocean Dipole(IOD)*** the pure La Ni?a events,positive the sea surface level anomalies(SLAs)appear in the northwestern Pacific,but SLAs are weakened and negative SLAs appear in the northwestern Pacific under the contribution of the negative IOD events in 2010/*** negative IOD events can trigger significant westerly wind anomalies in the western tropical Pacific,which lead to the breakdown of the pronounced positive SLAs in the northwestern ***,negative SLAs excited by the positive wind stress curl near the dateline propagated westward in the form of Rossby waves until it approached the western Pacific boundary in mid-2011,which maintained and enhanced the negative phase of SLAs in the northwestern Pacific and eventually,it could significantly influence the bifurcation and transport of the North Equatorial Current(NEC).
Raise boring is an important method to construct underground shafts of mines and other underground infrastructures by drilling down the pilot hole and then reaming up to the desired diameter. As a typical cyber-physic...
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Raise boring is an important method to construct underground shafts of mines and other underground infrastructures by drilling down the pilot hole and then reaming up to the desired diameter. As a typical cyber-physical system, the raise boring construction project is full of high heterogeneity, complexity and intrinsic uncertainty. Currently, its decision making loop is mainly based on the document-based system engineering and expertise experience. Regarding the intrinsic invisibility and uncertain risks in the underground engineering, especially for the remotely underground constructions on the extraterrestrial planets, it is absolutely required to shift the document-based and experience-dependent decision making paradigm into a digital and smart way. To this end, a systematic framework of the digital twin-driven process planning system for the raise boring method was conceived and presented. Then following the principles of open architecture, modularization and extensibility, a five-dimension architecture of digital twinning was built comprehensively that contained physical entity, digital representation, service entity, cross-systems entity and connection entity. Furthermore, a digital twin-driven decision making prototype system for the raise boring process was developed by the hybrid modeling of data-based model, visual geometric models, domain knowledge-based model and physics-based model. System verification indicated that the presented system had great potentials to facilitate the already very complicated process planning via the planning recommendation, visual simulation and models fusion. Finally, the contributions, novelty and limitations of this endeavour to extend the current digital twin practice were discussed.
In this paper, internal solitary waves (ISWs) in the northern South China Sea (NSCS) are investigated with respect to their propagation and evolution processes in different months. To achieve that, environmental param...
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In this paper, internal solitary waves (ISWs) in the northern South China Sea (NSCS) are investigated with respect to their propagation and evolution processes in different months. To achieve that, environmental parameters associated with ISW are first calculated using climatological datasets derived from the Simple Ocean Data Assimilation 3.3.1 (SODA3.3.1) reanalysis. The environmental parameters are significantly distinct from month to month, especially the quadratic nonlinearity coefficient alpha. It is negative in the deep basin and turns positive on the shallow continental shelf. A clear dividing line that alpha equals to zero can be found along the shelf from northeast to southwest from January to February and from October to December. The dividing line is interrupted starting from March and is mostly constrained on the northeast shelf, and from May to September only limited areas can positive alpha be found. Further simulations based on the variable extended Korteweg-de Vires (veKdV) model indicate that the polarity conversion process of ISWs therefore exhibits significant seasonality. It can be concluded from the simulation results that near the 200-m isobath on the continental shelf the elevation waves are more likely to appear from November to March owing to the positive values of alpha. The large-scale background current exhibits little effect on the deformation and polarity conversion of ISW in the NSCS although it prominently affects the environmental parameters around the shelf currents from Luzon strait.
This article addresses the grid-connected single-phase photovoltaic (PV) inverter control. A long-horizon finite-set model predictive control (MPC) strategy is proposed to control the voltage source inverter. To achie...
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This article addresses the grid-connected single-phase photovoltaic (PV) inverter control. A long-horizon finite-set model predictive control (MPC) strategy is proposed to control the voltage source inverter. To achieve this, a multi-step implementation approach and a control sequence rearrangement method are designed to reduce the sampling frequency and switching frequency. The optimization problem for the finite-set MPC is further simplified to reduce the computational complexity of the optimization procedure. Moreover, a multi-step delay compensation method is developed to compensate for the computational delay of the control algorithm. Finally, the proposed control method is implemented in a grid-connected PV inverter and simulation test results demonstrate its effectiveness under different load and generation conditions.
Most of the existing localization schemes necessitate a priori statistical characteristic of measurement noise, which may be unrealistic in practical applications. This article addresses the problem of indoor localiza...
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Most of the existing localization schemes necessitate a priori statistical characteristic of measurement noise, which may be unrealistic in practical applications. This article addresses the problem of indoor localization by implementing distributed set-membership filtering based on a received signal strength indicator (RSSI) under unknown-but-bounded process and measurement noises. First, the transmit power and the path-loss exponent are estimated by a novel least-squares curve fitting (LSCF) method in RSSI-based localization. Since the localization process of trilateration is susceptible to inaccuracy caused by the noise-affected distance measurements, a convex optimization method is then developed to obtain the state ellipsoid estimation under the unknown-but-bounded noises. Third, a recursive algorithm is established to compute the global ellipsoid that guarantees to locate the true target at every time step. Finally, experimental validation is presented to demonstrate the accuracy and effectiveness of the proposed set-membership filtering method for indoor localization.
This paper addresses the cyber-security issue of microgrid energy management system, where cyber-attacks, appearing in communication networks, corrupt the transmitted data and falsify the state estimates. This can pot...
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This paper addresses the cyber-security issue of microgrid energy management system, where cyber-attacks, appearing in communication networks, corrupt the transmitted data and falsify the state estimates. This can potentially threaten the physical system and lead to severe physical consequences. Therefore, it is of great significance to detect, locate and tolerate cyber-attacks. To this end, set-membership estimation is employed to detect the occurrence and locate the position of DoS attacks. The model predictive control technique is utilised to schedule the energy management by using the forecasts of photovoltaic generation and load demand. It is shown that the cyber-attack localisation and the desired tolerant control performance against attacks can be both achieved. Simulation results are provided to demonstrate the effectiveness of the proposed strategy.
Drill rods are core components to transmit the power in drilling machines such as raise bore machine, petroleum drilling rig and geological exploration rigs. Owing to its importance and high cost, it is very essential...
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