Absolute Wall Thickness Measurement of Conducting Plates Using Pulsed Eddy Currents

The method using pulsed eddy currents to determine the thickness of a conduction plate is extended to enable the simultaneous measurement of the plate thickness and material properties. For optimal performance, a probe must be designed depending on the thickness range that should be accessible. The need for a calibration of the material properties of a conducting plate to enable the measurement of its thickness has been removed. All that is needed is a probe with known dimensions and suitable hardware to create a current pulse and measure a transient magnetic induction.

On the functions of astrocyte-mediated neuronal slow inward currents

Slow inward currents are known as neuronal excitatory currents mediated by glutamate release and activation of neuronal extra synaptic N-met hyl-D-aspartate receptors with the contribution of astrocytes.These events are significantly slower than the excitatory postsynaptic currents.Parameters of slow inward currents are determined by seve ral factors including the mechanisms of astrocytic activation and glutamate release,as well as the diffusion pathways from the release site towards the extra synaptic recepto rs.Astrocytes are stimulated by neuronal network activity,which in turn excite neurons,forming an astrocyte-neuron feedback loop.Mostly as a consequence of brain edema,astrocytic swelling can also induce slow inward currents under pathological conditions.There is a growing body of evidence on the roles of slow inward currents on a single neuron or local network level.These events often occur in synchro ny on neurons located in the same astrocytic domain.Besides synchronization of neuronal excitability,slow inward currents also set synaptic strength via eliciting timing-dependent synaptic plasticity.In addition,slow inward currents are also subject to non-synaptic plasticity triggered by long-la sting stimulation of the excitatory inputs.Of note,there might be important regionspecific differences in the roles and actions triggering slow inward currents.In greater networks,the pathophysiological roles of slow inward currents can be better understood than physiological ones.Slow inward currents are identified in the pathophysiological background of autism,as slow inward currents drive early hypersynchrony of the neural networks.Slow inward currents are significant contributors to paroxysmal depolarizational shifts/interictal spikes.These events are related to epilepsy,but also found in Alzheimer's disease,Parkinson's disease,and stroke,leading to the decline of cognitive functions.Events with features overlapping with slow inward currents(excitatory,N-methyl-Daspartate-receptor mediated currents with astrocytic contribution) as ischemic currents and spreading depolarization also have a well-known pathophysiological role in worsening consequences of stroke,traumatic brain injury,or epilepsy.One might assume that slow inward currents occurring with low frequency under physiological conditions might contribute to synaptic plasticity and memory formation.However,to state this,more experimental evidence from greater neuronal networks or the level of the individual is needed.In this review,I aimed to summarize findings on slow inward currents and to speculate on the potential functions of it.

Observation of Arctic surface currents using data from a surface drifting buoy

During the 10th Chinese Arctic scientific expedition carried out in the summer of 2019,the surface current in the high-latitude areas of the Arctic Ocean was observed using a self-developed surface drifting buoy,which was initially deployed in the Chukchi Sea.The buoy traversed the Chukchi Sea,Chukchi Abyssal Plain,Mendeleev Ridge,Makarov Basin,and Canada Basin over a period of 632 d.After returning to the Mendeleev Ridge,it continued to drift toward the pole.Overall,the track of the buoy reflected the characteristics of the transpolar drift and Chukchi Slope Current,as well as the inertial flow,cross-ridge surface flow,and even the surface disorganized flow for some time intervals.The results showed that:(1)the transpolar drift mainly occurs in the Chukchi Abyssal Plain,Mendeleev Ridge,and western Canada Basin to the east of the ridge where sea ice concentration is high,and the average northward flow velocity in the region between 79.41°N and 86.32°N was 5.1 cm/s;(2)the average surface velocity of the Chukchi Slope Current was 13.5 cm/s,and while this current moves westward along the continental slope,it also extends northwestward across the continental slope and flows to the deep sea;and(3)when sea ice concentration was less than 50%,the inertial flow was more significant(the maximum observed inertial flow was 26 cm/s,and the radius of the inertia circle was 3.6 km).

Responses of the field-aligned currents in the plasma sheet boundary layer to a geomagnetic storm

Geomagnetic storms can result in large magnetic field disturbances and intense currents in the magnetosphere and even on the ground.As an important medium of momentum and energy transport among the solar wind,magnetosphere,and ionosphere,field-aligned currents(FACs)can also be strengthened in storm times.This study shows the responses of FACs in the plasma sheet boundary layer(PSBL)observed by the Magnetospheric Multiscale(MMS)spacecraft in different phases of a large storm that lasted from May 27,2017,to May 29,2017.Most of the FACs were carried by electrons,and several FACs in the storm time also contained sufficient ion FACs.The FAC magnitudes were larger in the storm than in the quiet period,and those in the main phase were the strongest.In this case,the direction of the FACs in the main phase showed no preference for tailward or earthward,whereas the direction of the FACs in the recovery phase was mostly tailward.The results suggest that the FACs in the PSBL are closely related to the storm and could be driven by activities in the tail region,where the energy transported from the solar wind to the magnetosphere is stored and released as the storm is evolving.Thus,the FACs are an important medium of energy transport between the tail and the ionosphere,and the PSBL is a significant magnetosphere–ionosphere coupling region in the nightside.

Kuroshio Intrusion Combined with Coastal Currents Affects Phytoplankton in the Northern South China Sea Revealed by Lipid Biomarkers

The northern South China Sea(NSCS)is significantly influenced by the Kuroshio intrusion and the coastal currents.Our knowledge on the roles of both currents on phytoplankton spatial variations is still inadequate.Here,we investigated the concentrations of phytoplankton biomarkers and their proportions in surface suspended particles from 47 sites of the NSCS during summer of 2017 and 2019.Brassicasterol/epi-brassicasterol,dinosterol,and C37 alkenones were used as proxies of biomass for diatoms,dinoflagellates,and haptophytes,respectively,and their sum indicating total phytoplankton biomass.A three end-member mixing model was applied to quantitatively assess the influence extent of the Kuroshio intrusion and the coastal currents.Our results showed that the Kuroshio intrusion and the coastal currents contributed equally to the overall surface water masses in the study area;however,the two currents had distinct effects on the spatial distribution of phytoplankton.For phytoplankton biomass,the eutrophic coastal currents were likely to be the main controlling factors,while the impact of the Kuroshio intrusion was weak and stimulated significant increases in phytoplankton biomass only at certain boundary sites.For phytoplankton community structures,the Kuroshio and its intrusion were the main factors,resulting in an increase in the proportions of dinoflagellates and haptophytes.The proportion of diatoms slightly increased due to the influence of the coastal currents.Our study quantifies the effects of the Kuroshio and the coastal currents on phytoplankton in the NSCS in terms of hydrological parameters,providing an important basis for the understanding of ecological functions and biogeochemical cycles in marginal sea-open ocean boundary regions.

An Innovative Approach to Predicting Scour Depth Around Foundations Under Combined Waves and Currents in Large-Scale Tests Based on Small-Scale Tests

This study presents an innovative theoretical approach to predicting the scour depth around a foundation in large-scale model tests based on small-scale model tests under combined waves and currents.In the present approach,the hydrodynamic parameters were designed based on the Froude similitude criteria.To avoid the cohesive behavior,we scaled the sediment size based on the settling velocity similarity,i.e.,the suspended load similarity.Then,a series of different scale model tests was conducted to obtain the scour depth around the pile in combined waves and currents.The fitting formula of scour depth from the small-scale model tests was used to predict the results of large-scale tests.The accuracy of the present approach was validated by comparing the prediction values with experimental data of large-scale tests.Moreover,the correctness and accuracy of the present approach for foundations with complex shapes,e.g.,the tripod foundation,was further checked.The results indicated that the fitting line from small-scale model tests slightly overestimated the experimental data of large-scale model tests,and the errors can be accepted.In general,the present approach was applied to predict the maximum or equilibrium scour depth of the large-scale model tests around single piles and tripods.

AUV-Aided Data Collection Considering Adaptive Ocean Currents for Underwater Wireless Sensor Networks

Autonomous underwater vehicle(AUV)-assisted data collection is an efficient approach to implementing smart ocean.However,the data collection in time-varying ocean currents is plagued by two critical issues:AUV yaw and sensor node movement.We propose an adaptive AUV-assisted data collection strategy for ocean currents to address these issues.First,we consider the energy consumption of an AUV in conjunction with the value of information(VoI)over the sensor nodes and formulate an optimization problem to maximize the VoI-energy ratio.The AUV yaw problem is then solved by deriving the AUV's reachable region in different ocean current environments and the optimal cruising direction to the target nodes.Finally,using the predicted VoI-energy ratio,we sequentially design a distributed path planning algorithm to select the next target node for AUV.The simulation results indicate that the proposed strategy can utilize ocean currents to aid AUV navigation,thereby reducing the AUV's energy consumption and ensuring timely data collection.

Suppression of transmembrane sodium currents on the freshly isolated hippocampal neuron cell with continuous infrared light

Physiotherapeutic effects of infrared lasers have been proved in clinic.These infrared-based regulations of the bioelectrical activities can roughly be classied into enhancement and suppression of action potential(AP),which are described by sodium(Na)and potassium(K)transmembrane current equations,named as Hodgkin and Huxley(HH)-model.The enhancement effect is able to evoke or strengthen the AP when infrared light is applied.Its corresponding mechanism is commonly ascribed to the changes of the cell membrane capacitance,which is transiently increased in response to the infrared radiation.The distinctive feature of the suppression effect is to inhibit or reduce the AP by the designed protocols of infrared radiation.However,its mechanism presents more complexity than that in enhancement cases.HH-model describes how the Na current determines the initial phase of AP.So,the enhancement and suppression of AP can be also ascribed to the regulations of the corresponding Na currents.Here,a continuous infrared light at the wavelength of 980 nm(CIS-980)was employed to stimulate a freshly isolated hippocampal neuron in vitro and a suppression effect on the Na currents of the neuron cell was observed.Both Na and K currents,which are named as whole cell currents,were simultaneously recorded with the cell membrane capacitance current by using a patch clamp combined with infrared irradiation.The results demonstrated that the CIS-980 was able to reversibly increase the capacitance currents,completely suppressed Na currents,but little changed K currents,which forms the steady outward whole cell currents and plays a major role on the AP repolarization.A conrmation experiment was designed and carried out by synchronizing tens of milliseconds of infrared stimulation on the same kinds of hippocampal neuron cells.After the blocked K channel,a reduction of Na current amplitude was still recorded.This proved that infrared suppression of Na current was irrelevant to K channel.A membrane capacitance mediation process was preliminarily proposed to explain the Na channel suppression process.

Ionospheric Currents in the Equatorial and Low Latitudes of Africa

The magnetometer data obtained for 2008 from geomagnetic stations installed across Africa by magnetic data acquisition set (MAGDAS) have been used to study the ionospheric Sq current system in the equatorial and low-latitudes of Africa. The aim of this work is to separate the quiet-day field variations obtained in the equatorial and low latitude regions of Africa into their external and internal field contributions and then to use the paired external and internal coefficients of the SHA to determine the source current and induced currents. The method used involved a spherical harmonic analysis (SHA). This was applied in the separation of the internal and external field/current contribution to the Sq variations. The result shows that the variation in the currents is seen to be a dawn-to-dusk phenomenon with the variation in the external currents different from that of the internal currents both in amplitude and in phase. Furthermore, the seasonal variation in the external current maximizes during the March equinox and minimizes during the December solstice. The maximum current observed in AAB and ILR is due to the Equatorial Electrojet Current present in the AAB and ILR stations. Seasonal variation was observed in the geomagnetic component variations as well as in the currents. This is attributed to the position of the sun with respect to the earth at different months of the year. The equinoctial maximum is observed in external current intensity which occurred mostly during the March Equinox.

Experimental research on influence mechanism of loading rates on rock pressure stimulated currents

The study of pressure stimulated current(PSC)changes of rocks is significant to monitor dynamic disasters in mines and rock masses.The existing studies focus on change laws and mechanism of currents generated under the loading of rocks.An electrical and mechanics test system was established in this paper to explore the impacts of loading rates on PSCs.The results indicated that PSC curves of different rocks had different change laws under low/high loading rates.When the loading rate was relatively low,PSC curves firstly changed gently and then increased exponentially.Under high loading rates,PSC curves experienced the rapid increase stage,gentle increase stage and sudden change stage.The compressive strength could greatly affect the peak PSC in case of rock failure.The loading rate was a key factor in average PSC.Under low loading rates,the variations of PSCs conformed to the damage charge model of fracture mechanics,while they did not at the fracture moment.Under high loading rates,the PSCs at low stress didn’t fit the model due to the stress impact effects.The experimental results could provide theoretical basis for the influence of loading rates on PSCs.

Vertical structure of tidal currents in the Xuliujing Section of Changjiang River Estuary

Three long-term fixed acoustic Doppler current profilers were first used for investigating the vertical structure of tidal currents in Xuliujing Section of Changjiang River Estuary.Moreover,three different periods(spring,summer and fall)were also considered for investigating seasonal variations.The semi-diurnal tides were the most energetic,with along-channel speed of up to 80 cm/s for M_(2)constituent,which dominates at all stations with percent energy up to 65%–75%during seasons.The shape of tidal ellipses of the most energetic semi-diurnal constituent M_(2)showed obvious polarization of the flow paralleling to the riverbank,with the minor semi-axis being generally less than 20%of the major one.The maximum velocity of mean current is appeared in top layers at all the three stations,and the velocity decreased with the depth.The seasonal variations of direction are also observed,which is probably caused by complex local topography since the erosion and deposition in riverbed.Observed vertical variation of four parameters of M_(2)ellipses,agreed well with the optimally fit frictional solutions in top and middle layers.However,there was an obvious difference between frictional model and observed data in the lower water column.Discrepancies are probably on account of stratification,which strengthens in summer and fall due to the freshening influence of the Changjiang River Estuary outflow.

Rashba spin-orbit coupling induced rectified currents in monolayer graphene with exchange field and sublattice potential

We investigate the effect of Rashba spin-orbit coupling(RSOC)on photoconductivities of rectified currents in monolayer graphene with exchange field and sublattice potential.The system shows that the photoconductivities of resonant shift and injection current contributions are nonzero,while the photoconductivities of non-resonant shift current contribution are zero.We find that the RSOC induces a warping term,which leads to the nonzero rectified currents.Moreover,the photoconductivities of resonant injection(shift)current contribution are(not)related to the relaxation rate.The similar behavior can be found in other Dirac materials,and our findings provide a way to tune the nonlinear transport properties of Dirac materials.

The failure propagation of weakly stable sediment:A reason for the formation of high-velocity turbidity currents in submarine canyons

The long-distance movement of turbidity currents in submarine canyons can transport large amounts of sediment to deep-sea plains.Previous studies show obvious differences in the turbidity current velocities derived from the multiple cables damage events ranging from 5.9 to 28.0 m/s and those of field observations between 0.15 and 7.2 m/s.Therefore,questions remain regarding whether a turbid fluid in an undersea environment can flow through a submarine canyon for a long distance at a high speed.A new model based on weakly stable sediment is proposed(proposed failure propagation model for weakly stable sediments,WS S-PFP model for short)to explain the high-speed and long-range motion of turbidity currents in submarine canyons through the combination of laboratory tests and numerical analogs.The model is based on two mechanisms:1)the original turbidity current triggers the destabilization of the weakly stable sediment bed and promotes the destabilization and transport of the soft sediment in the downstream direction and 2)the excitation wave that forms when the original turbidity current moves into the canyon leads to the destabilization and transport of the weakly stable sediment in the downstream direction.The proposed model will provide dynamic process interpretation for the study of deep-sea deposition,pollutant transport,and optical cable damage.

Research on the Dynamic Response of Submerged Floating Tunnels to Wave Currents and Traffic Load

Submerged floating tunnel(SFTs)are typically subjected to complex external environmental and internal loads such as wave currents and traffic load.In this study,this problem is investigated through a finite element method able to account for fluid-structure interaction.The obtained results show that increasing the number of vehicles per unit length enhances the transverse vibrational displacements of the SFT cross sections.Under ultimate traffic load condition,one-way and two-way syntropic distributions can promote the dynamic responses of SFTs whereas two-way reverse distributions have the opposite effect.

Currents in the Luzon Strait during the spring of 2002: observation and computation by modified inverse model

On the basis of the current measurements at 200,500 and 800 m from moored current meters with the time series data from March 17 to April 15 at the mooring station (20°49′57″N, 120°48′ 12″E) and the hydrographic data obtained in the Luzon Strait during the spring of 2002 cruise, the circulation in the investigated area is computed by using the modified inverse method. The major observed results are as follows: (1) the average velocity and the flow direction in the observing days are (47.4 cm/s, 346°) at the 200 m level. The average velocity in the observing days is (20.3 cm/s, 350? at the 500 m level. These mean that the Kuroshio intrudes into the South Chin Sea to flow northwestward through the Luzon Strait at 200 and 500 m levels. (2) The average velocity in the observing days is (1.2 cm/s, 35°) at the 800 m level, i. e., its direction is northeastward. This means that the flow condition at the 800 m level very differs from mat at the 200 and 500 m levels. (3) There is the high density and cold water (HDCW) in the middle of western part of in the investigated region, and its center is located near the hydrological station 3 at Section A. (4) There is the lower density and warm water (LDWW) in the southeastern part of investigated region. (5) The currents in April 2002 are stronger than those in March 2002.The major computed results are as follows: (1) The northwestward and southeastward VTs through Section B are 32.48×106 m3/s (inclusive of VT of anticyclonic eddy) and 3.34×106m3/s, respectively. The net northwestward VT through Section B in the investigated area is about 29.14×106 m3/s. (2) The eastern and western VTs through Section A are about 16.71×106 and 8.57×106 m3/s, respectively. Thus, the net eastward VT through Section A is about 8.14×106 m3/s. (3) The net northward VT through Section M is about 24.68×106 m3/s. (4) After about 24.68×106 m3/s flows through Section M, most of it, about 16.54×106 m3/s, flows northward through the eastern part of Section C and then flows northward into the region east Taiwan Island. The other part of it, about 8.14×106 m3/s, branches out from the main Kuroshio and then flows meanderingly through the western part of Section C. Thus, the Kuroshio has the two cores of current at Section C. (5) The direction of the computed current near the mooring station M agrees with the direction of the current measurements at 200 and 500 m from moored current meters, i.e., their directions both are northwestward. (6) About 3.34×106 m3/s of the South Chin Sea water probably flows slowly from the northwest to the southeast in the layer below 550 m at the western part of Section B.

Thermoelectric Currents of Earth’s Core Generate the Earth’s Magnetic Field

The geotemperature gradient is considered as taking main part in generating the Earth’s magnetic field. It is shown that geotemperature gradient functions as a generator of both nuclear and mantle thermoelectrical currents thanks to the great temperature difference between the core and the mantle. The movement of those currents is close to the radial direction towards the Earth’s crust. However, the nuclear thermocurrents movement tends to cyclically change into opposite one. If the mantle and core thermocurrents move oppositely, the Earth’s crust cools down globally and ice age comes, but if they move unidirectionally then global warming comes. The calculation show that the Earth’s surface can warm up to not more than 10°C. The latter, considering how human factor affects the warming of Earth, is incomparably great. There are calculations that show power of the Earth’s thermocurrents being enough to generate and maintain the Earth’s magnetic field, its modern dynamics and the poles inversion.

Numerical study of pollutant movement in waves and wave-induced long-shore currents in surf zone

Water waves, wave-induced long-shore currents and movement of pollutants in waves and currents have been numerically studied based on the hyperbolic mild-slope equation, the shallow water equation , as well as the pollutant movement equation, and the numerical results have also been validated by experimental data. It is shown that the long-shore current velocity and wave set-up increase with the increasing incident wave amplitude and slope steepness of the shore plane ; the wave set-up increases with the in- creasing incident wave period;and the pollutant morement proceeds more quiekly with the increasing incident wave amplitude and slope steepness of the shore palane. In surf zones, the long-shore currents induced by the inclined incident waves have effectively affected the pollutant movement.

Evaluation of Mid-Depth Currents of NCEP Reanalysis Data in the Tropical Pacific Using ARGO Float Position Information

The global project of the Array for Real-time Geostrophic Oceanography （ARGO） provides a unique opportunity to observe the absolute velocity in mid-depths of the world oceans. A total of 1597 velocity vectors at 1000 （2000） db in the tropical Pacific derived from the ARGO float position information during the period November 2001 to October 2004 are used to evaluate the intermediate currents of the National Centers for Environmental Prediction reanalysis. To derive reliable velocity information from ARGO float trajectory points, a rigorous quality control scheme is applied, and by virtue of a correction method for reducing the drift error on the surface in obtaining the velocity vectors, their relative errors are less than 25%. Based on the comparisons from the quantitative velocity vectors and from the space-time average currents, some substantial discrepancies are revealed. The first is that the velocities of the reanalysis at mid-depths except near the equator are underestimated relative to the observed velocities by the floats. The average speed difference between NCEP and ARGO values ranges from about -2.3cm s^-1 to -1.8 cm s^-1. The second is that the velocity difference between the ocean model and the observations at 2000 dB seems smaller than that at 1000 dB. The third is that the zonal flow in the reanalysis is too dominant so that some eddies could not be simulated, such as the cyclonic eddy to the east of 160°E between 20°N and 30°N at 2000 dB. In addition, it is noticeable that many floats parking at 1000 dB cannot acquire credible mid-depth velocities due to the time information of their end of ascent （start of descent） on the surface in the trajectory files. Thus, relying on default times of parking, descent and ascent in the metadata files gravely confines their application to measuring mid-depth currents.

Spatial-temporal variability of submesoscale currents in the South China Sea

Spatial and seasonal variabilities of submesoscale currents in the northeastern South China Sea are investigated by employing a numerical simulation with a horizontal resolution of 1km. The results suggest that submesoscale currents are widespread in the surface mixed layer mainly due to the mixed layer instabilities and frontogenesis. In horizontal, submesoscale currents are generally more active in the north than those in the south, since that active eddies, especially cyclonic eddies, mainly occur in the northern area. Specifically, submesoscale currents are highly intensified in the east of Dongsha Island and south of Taiwan Island. In temporal sense, submesoscale currents are more active in winter than those in summer, since the mixed layer is thicker and more unstable in the winter. The parameterization developed by Fox-Kemper et al. is examined in terms of vertical velocity, and the results suggest that it could reproduce the vertical velocity if mixed layer instability dominates there. This study improves our understanding of the submesoscale dynamics in the South China Sea.

Equivalent Currents on an Anisotropic MaterialBacked by a Metal Surface and Their Relation

Based on a first-order state-vector differential equation representation of Maxwell's equations, an analytical formulation is derived for the equivalent currents on an anisotropic material backed by a metal surface, and the relation between two currents is also considered. These expressions are degenerated into the common forms for some simple cases. This effort will provide the theoretical preparation for the approximate calculation of electromagnetic scattering from a conducting object coated by an anisotropic material.