Wind Forcing Research Articles

Improve the microstructure and properties of Al0.5CoCrFeNi compositionally complex alloy fabricated by selective laser melting with electropulsing treatment

In order to improve the microstructure of the Al0.5CoCrFeNi compositionally complex alloy (CCA) prepared by selective laser melting (SLM), the electropulsing treatment (EPT) has been used as a post processing in this study. The strengthening and softening mechanism was analyzed by comparing the microstructure of SLM-Al0.5CoCrFeNi CCAs under different EPT parameters. At a 10 s power on time, the substructure size of CCA decreases continuously with increasing voltage. Under 90V/10s EPT, the yield strength increases from 658 ± 10 MPa in the printed state to 748 ± 17 MPa, and the microhardness increases from 265.1 ± 5.6 HV0.1 to 318.9 ± 5.0 HV0.1. At 90V/20s EPT, the cellular substructure disappears, and a large number of uniformly distribute BCC phases precipitates inside the FCC matrix. At 90V/30s EPT, recrystallization occurs and the BCC phase coarsen. Dislocation network is the main factor that affects the strength of SLM-CCA. EPT can change the dislocation network structure to enhance the strength of SLM-CCA. Simultaneously, the EPT effectively promotes the transition from FCC phase to BCC phase in a short time. Joule heat and electronic wind force are the main reasons for changing structure and properties of SLM-Al0.5CoCrFeNi CCA. This work provides a post-processing method named as EPT to effectively control the microstructure in additive manufacturing CCA products.

Extreme waves in the Caribbean Sea: spatial regionalization and long-term analysis

The extreme wave height distribution in the Caribbean Sea is studied using a new method based on the maximum basin-wide aggregate of significant wave height, Hs, values per month. Besides, by means of the Self-Organizing Maps (SOM) technique, we identify coherent geographical regions with similar extreme wave height variability in the Caribbean Sea. Our findings revealed three primary regions: the eastern side with comparatively lower values, the central region with intermediate values, and the western side with the highest extreme wave heights. The study also examines the wind forcing conditions driving the spatial and temporal variability of the extreme waves, highlighting the influence of the low-pressure belt dynamics as well as the role played by the Caribbean Low-Level Jet (CLLJ) index, and the impact of cold fronts and hurricanes on extreme wave heights. Additionally, we explore the relationship between the extreme wave height distribution and climatic indices, such as the Atlantic Multidecadal Oscillation (AMO), the Atlantic Meridional Mode (AMM), the North Atlantic Oscillation (NAO) and the Oceanic Niño (ONI). The results reveal that the spatial distribution of extreme wave heights in the Caribbean Sea is mostly ruled by the influence of the CLLJ, with correlations close to 80%. In addition, significant correlations were observed between the extreme wave heights and the ENSO in the central Caribbean, as well as positive correlations between the extreme wave heights and NAO in the eastern part of the basin, and significant values of correlation with the negative phases of AMO and AMM in the whole basin. We show that, unlike conventional (or broadly used) methods deployed to identify extreme wave height, such as percentile 99th, Hs99, our methodology allows a further assessment of the wind and climate forcing conditions associated with the extreme wave events. Although, we acknowledge that the method here presented has limitations to capture extreme wave height outliers, it has the advantage of being used concomitant with the wind forcing to develop multivariate wave climate analysis at basin scale, and could be extended to a more local scale when studying coastal processes.

Physics-Based Modeling and Fluttering Dynamic Process Simulation for Catkins

Flight simulation of catkins using computer technology helps their prevention and control. However, this is a challenging task due to the complex characteristics, and irregular shapes of catkins, while existing methods mainly focus on rain and snow, which are not suitable for catkins. In this paper, we propose a physics-based algorithm for the dynamic simulation of fluttering catkins. Our approach includes an L-system based 3D modeling method for simulating the natural phenomena of the catkin. We consider the motion of wind, free fall of catkins, and the dynamics of catkins under the joint action of attraction between them, while adhering to the physical motion law of catkins. To provide wind force, we first establish a three-dimensional wind field based on Boltzmann’s equation. We then use the kernel function idea to calculate the attraction force between catkins and finally update the position of the catkin. We incorporate the phenomena of collision and adhesion, attraction, and accumulation of catkins while simulating motion states depending on the adjusted wall height and ground humidity parameters. Our approach overcomes limitations of previous models by achieving good simulation while using relatively less code to simulate various realistic motion states. According to our users’ study, more than 71% of users found the simulation results to be acceptable, authentic, and realistic, confirming the authenticity of our simulation. Our method can generate highly realistic effects, significantly improving efficiency by several orders of magnitude compared to manual modeling. In addition, it can effectively simulate the dynamics of catkins in different scales, providing a decision-making reference for catkin control.

Electronic Shooting Simulator Family "STrIzh": Implementation Levels and Free Software Structure

Development of rifle electronic simulators (i.e. for hand weapons and not using ammunition) is an important task, since the production of any type of small arms according to regulatory documents also requires the production of a simulator to instill aiming and firing skills. A family of electronic shooting simulators "STrIzh" of four levels of implementation: initial, basic, professional and special is described. Structural diagrams of different configurations are given, functional purpose and capabilities of each level of simulators are shown. The initial level allows independent assemble the simulator from publicly available elements (laptop, webcam, weapon layouts, IR LEDs), which can contribute to widespread use both in schools and at home, but is low in accuracy and manufacturabili (requires daily calibration). The basic level also allows independent assemble the simulator, and less publicly available elements (laptop, projector, mockup weapons, laser emitters, FHD camera), which allows to be used both in schools and in DOSAAF structures, and has acceptable accuracy and manufacturability (a weekly calibration is enough, but assembling a mock-up weapon with laser emitters requires adjustments). It is recommended to limit the special level to virtual reality simulators, including a helmet with a smartphone and a mockup of a weapon with its smartphone which also contributes to its public availability and widespread use. The simulator software algorithm should fully support all implementation levels with different configurations and include a multimedia shooting training system. Mathematical models of external ballistics of thrown equipment for Kalashnikov assault rifle, Makarov pistol, hand-held anti-tank grenade launcher 7 products are described in detail, taking into account changes in atmospheric factors (temperature, air pressure, wind force) and dispersion of various types of ammunition. The above review of rifle simulators and their experience revealed the main trends of improvement – use of virtual reality and training not only direct shooting skills, but also training in the eligibility of the use of weapons, safe handling of them and even tactical interaction in the group.

Inclination Trend of the Agulhas Return Current Path in Three Decades

The Agulhas Return Current (ARC), as a primary component of the Agulhas system, contributes to water exchange and mass transport between the southern portions of the Indian and Atlantic Ocean basins. In this study, satellite altimeter data and reanalysis datasets, and a new set of criteria for the piecewise definition of the jet axis are used to explore the long-term change of the ARC’s axis position in recent three decades. It is found that the ARC axis exhibits a significant slanting trend with its western part (35–48°E) migrating northward and the eastern part (48–70°E) migrating southward. The meridional movement of the ARC path could be attributed to large-scale wind forcing. The anomalous surface wind stress curl, by Ekman pumping mechanism, leads to positive–negative–positive sea surface height anomalies in the western section and negative–positive–negative anomalies in the eastern section, thus the ARC axis tilts accordingly, in a northwest–southeast direction. Further analysis suggests that this ARC slanting trend is more dependent on the southward shift of the downstream axis and less on the topographic steering upstream. The downstream axis is more likely to interact with the ACC fronts and its migration could dominate the local EKE pattern by changing the background circulation and energy cascade direction. For the headstream west of 35°E, the ARC axis is more subject to topography, thus the EKE change is more dominated by eddy activity processes, including shedding, propagation and merging. This study provides some new insights into the long-term change of ARC and its interaction with the local EKE variability.

Operational Storm Surge Forecasting at the National Hurricane Center: The Case for Probabilistic Guidance and the Evaluation of Improved Storm Size Forecasts Used to Define the Wind Forcing

Abstract The primary source of guidance used by the Storm Surge Unit (SSU) at the National Hurricane Center (NHC) for issuing storm surge watches and warnings is the Probabilistic Tropical Storm Surge model (P-Surge). P-Surge is an ensemble of Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model forecasts that is generated based on historical error distributions from NHC official forecasts. A probabilistic framework is used for operational storm surge forecasting to account for uncertainty related to the tropical cyclone track and wind forcing. Previous studies have shown that the size of a storm’s wind field is an important factor that can affect storm surge. A simple radius of maximum wind (RMW) prediction scheme was developed to forecast RMW based on NHC forecast parameters. Verification results indicate this scheme is an improvement over the RMW forecasts used by previous versions of P-Surge. To test the impact of the updated RMW forecasts in P-Surge, retrospective cases were selected from 25 storms from 2008 to 2020 that had an adequate number of observations. Evaluation of P-Surge forecasts using these improved RMW forecasts shows that the probability of detection is higher for most probability of exceedance thresholds. In addition, the forecast reliability is improved, and there is an increase in the number of high probability forecasts for extreme events at longer lead times. The improved RMW forecasts were recently incorporated into the operational version of P-Surge (v2.9), and serve as an important step toward extending the lead time of skillful and reliable storm surge forecasts.

Residual design life-based evaluation of structural retrofitting on high-rise reinforced concrete buildings

The deteriorating structural performance of aging high-rise reinforced concrete (RC) buildings has brought increasing attention to the necessity of retrofitting in developed regions. In this context, the present paper introduces a novel approach by reversing the conventional service life-based structural design procedure. The proposed approach establishes a residual design life evaluation framework, enabling a comprehensive assessment of the performances of existing RC buildings both before and after retrofitting. This assessment framework takes into account various load scenarios, including wind and earthquake forces, etc., and yields an intuitive index based on design codes, termed "residual design life", which serves as valuable information for decision-makers. To exemplify the framework's application, a case study involving a high-rise RC building is presented. Initially, the influence of the adopted design codes on the residual life of the aging building is investigated. Subsequently, three commonly employed structural-level retrofit methods, namely steel bracing, RC wall addition, and exoskeleton, are examined. The findings reveal that the residual design life of the existing building decreases as the adopted design code transitions from an outdated version to the current one. However, the implementation of structural-level retrofit interventions proves highly effective in enhancing the building's residual life, particularly when failure is primarily governed by column capacities and storey drift. Nonetheless, it should be noted that certain structural-level interventions may increase the load on adjacent beams, potentially leading to a negative impact on the building's residual life when the condition of the beams becomes the predominant factor. Furthermore, the obtained residual life of the retrofitted building could be used to assist in conducting life-cycle analysis and further investigations and contribute to the understanding regarding structural performance and safety in the built environment.

Investigating the influence of 3D building models on pedestrian wind comfort through wind computational fluid dynamics analysis

Wind flow plays a crucial role in determining pedestrian comfortability in the surrounding environment. However, the shape and detailing of buildings, as well as the angle of the wind, can manipulate the wind flow patterns and velocity. Different urbanized areas have different building shapes and detailing, which can lead to diverse wind flow patterns and velocities, affecting pedestrian wind comfort (PWC). This study utilized wind Computational Fluid Dynamics (CFD) technique to investigate the influence of building models on wind velocity and its impact on PWC. The CFD simulation integrated with a 3D urbanized building model provided wind velocity values throughout the study area, which were used to analyze wind comfort at 1.75m elevation based on Beaufort wind force criteria. The study found that diverse effects due to different building detailing were observed, leading to multiple flow patterns and changes in wind velocity. The downstream building recorded a lower velocity value than the upstream building mainly because of wind flow separation from the building frontal. Wind comfort levels were represented using the Beaufort wind force scale (BWS), and all values fell in level 2 and 3, indicating good wind comfort level because of the BWS ≤ 3. This study highlights the significance of building models in determining wind flow patterns and velocity, which ultimately impacts PWC. Despite the study area involving multiple buildings with different shapes and detailing, the wind comfort levels were found to be suitable for pedestrians.

Origin and evolution of the surface desalinated layer of the Kara Sea during the ice-free period

This work focuses on the freshwater contribution (water from the Ob’ and Yenisei rivers and ice meltwater) to the surface layer of the Kara Sea according to 2015–2020 expedition data. Salinity and hydrochemical data (total alkalinity and silicates) were used to calculate the proportion of freshwater in the desalinated layer of the Kara Sea. The ratio of the water fractions with the linear mixing of several sources was considered. Our results showed that riverine sources varied greatly, and the total contributions of the Ob’ and Yenisei runoff ranged from 10 to 60%, while the contribution of ice meltwater did not exceed 25%. The relationship between the period of seasonal ice retreat in the Kara Sea and its proportion in the surface desalinated layer was revealed. The interannual variability in freshwater source composition varied greatly from the southwestern to the eastern part of the sea owing to wind forcing and seasonality in river discharge.

An Innovative and Environmentally Friendly System for Moving and Stabilising a Floating Dock in Position during Docking Operations

The study is aimed at designing a system which ensures dock mobility (moving from the quay to the dock trench) and stabilises the dock in position during docking operations. A number of requirements and design criteria have been defined for the dock moving system, the most important of them being its capability to support docking operations at a maximum wind force of 5 °B, and environmental friendliness (zero exhaust fumes or other pollutants). As part of the research, concepts for various dock moving systems have been developed, including calculations of technical and operational parameters. Each concept has been analysed for meeting the defined requirements and design criteria. Ultimately, a system which meets all of the requirements and criteria and is completely environmentally friendly has been selected for construction. The authors discuss the entire process of creating system concepts, parameter calculations, and assessment of fulfilment of the requirements and design criteria. The principle of operation and the design of the system have been explained. The dock is powered by electricity stored in batteries and generated from renewable energy sources.

The effect of electric current on dislocation activity in pure aluminum: A 3D discrete dislocation dynamics study

Introducing electric current into metals and alloys to improve their ductility and to reduce the hardening tendency has been widely adopted. Nevertheless, how the electricity affects the plastic deformation of those materials remains a critical issue with controversial opinions. To clarify the material plastic deformation subjected to electric current, or the so-called electroplastic behavior, an in-depth understanding of the dislocation evolution during that process is vital. From that motivation, three-dimensional dislocation dynamics simulations were carried out to explore the dislocation behavior during the uniaxial tensile deformation of pure aluminum with the introduction of electric current. The scattering process between electrons and dislocations was first captured by a physical model. The electron wind force and local heat effect were quantitatively analyzed by figuring out the momentum and the energy transferred during the interaction of electrons and dislocations respectively. The dislocation density evolution, the activation of different slip systems and the dislocation distribution were further analyzed based on the simulations. The dislocation density in the [111] direction is revealed to increase more significantly than [101] and [001] directions with the introduction of electric current. The results show that the current can reduce the flow stress by promoting the activation of the difficult-to-move dislocations. The activation effect reduces the dislocation tangling tendency and leads to more uniform dislocation distribution. Therefore, a reduction of the flow stress can be observed in EAT comparing to TAT, via the discrete dislocation dynamics simulations even though the dislocation densities are similar. The simulation results are also confirmed by the EAT and TAT experiment results and TEM observations.

Ecological and sediment dynamics response to typhoons passing from the east and west sides of the Changjiang (Yangtze River) Estuary and its adjacent sea area

The hydrodynamic environment of the Changjiang (Yangtze River) Estuary and its adjacent sea area frequently experiences the influence of typhoon activities during the summer season. However, the differences in responses to typhoons with different trajectories are still poorly understood. Using buoy observations with synchronous satellite images, we investigated the sediment dynamics response to Typhoon Danas and Lekima, which passed through the Changjiang Estuary and its adjacent sea area from the east and west sides, respectively. The results indicated that wind forcings disrupted the semidiurnal cycles of ocean currents, leading to southeastward or northwestward residual currents during typhoons Danas and Lekima, respectively. The residual current velocity was typically below 150 mm/s under calm conditions but exceeded 200 mm/s, reaching up to 600 mm/s during typhoon conditions. Typhoon Danas (Lekima) generated onshore (offshore) Ekman transport in the surface layer, resulting in coastal downwelling (upwelling) and bottom offshore (onshore) currents due to the Ekman pumping (suction) effect. Typhoon Danas shifted the Changjiang Diluted Water from northeastward to southeastward, triggering the post-typhoon phytoplankton bloom, while Typhoon Lekima strengthened and even drove the detachment of the Changjiang Diluted Water. These findings suggest the need for different preventive strategies based on the trajectory of each typhoon, considering the potential land damage caused by west-side typhoons and the occurrence of post-typhoon Harmful Algal Blooms resulting from east-side typhoons. Additionally, sediment transport primarily occurred in the bottom layer, governed by the combined effect of tidal currents and typhoon-driven bottom currents. Typhoon Danas, located on the east side of the Changjiang Estuary, led to offshore (positive cross-shore) sediment flux and southwestward (negative along-shore) sediment flux. Conversely, Typhoon Lekima, situated on the west side, caused onshore (negative cross-shore) sediment flux and northeastward (positive along-shore) sediment flux. These findings suggest that existing sediment records may underestimate the frequency and intensity of historical typhoon activities.

Microstructural modification and mechanical improvement of ultrafine-grained Ti alloy through electron wind force: An innovative approach

This study focuses on the effect of high-density pulsed electric current (HDPEC) on the microstructure and mechanical properties of ultrafine-grained (UFG) Ti–6Al–7Nb (mass%) alloy. After the UFG Ti alloy prepared by high-pressure torsion (HPT), the samples exhibit high tensile yield strengths of 1200 MPa with total elongation of ∼20 %. Interestingly, an unusual improved elongation of ∼33 % with a yield strength of 1100 MPa was obtained in samples processed by HPT plus HDPEC. Quantitative evaluation shows that the improved ductility is attributed to the decreasing of dislocation density. The electron wind force played an important role to promote the movement of dislocation easier with the assistance of local Joule heating during HDPEC processing. It is shown that the bimodal structure with a low dislocation density leads to the high strength and high ductility. It indicated that HDPEC give an effective method to improve the ductility in UFG alloys.

A meridional dipole mode in the Indian Ocean subsurface ocean heat content and its multidecadal variability

The dominant mode of the Indian Ocean variability can be impacted by changes in the background state (multidecadal timescale) of the subsurface heat content. The multidecadal variability of subsurface ocean heat content (sub-OHC) in the Indian Ocean is examined using four reanalysis products from 1958 to 2017. The analysis reveals a meridional basin-wide dipole mode in the subsurface OHC until the late 1980s, followed by the mode embedded in the uniform basin-wide patterns. These patterns are also observed in the trends of thermocline and sea surface height. The observed patterns in the Indian Ocean are explained by two distinct mechanisms. Firstly, the multidecadal variability of dipole patterns over the Indian Ocean is influenced by local wind forcing. Wind stress trends and Ekman pumping velocity trends favor downwelling (upwelling) in the off-equatorial southern Indian Ocean region, leading to thermocline depth deepening (shallowing) during 1958–1975 and 1976–1987, respectively. Secondly, the combined effect of heat transport from the western Pacific through Indonesian Through Flow and local wind forcing accounts for the basin-wide cooling and warming trends observed during 1988–2000, and 2001–2014, respectively.

Localized engineering of grain boundary morphology by electro-nano-pulsing processing

We report a novel electro-nano-pulsing (ENP) processing method to achieve localized engineering of grain boundary (GB) morphology in polycrystalline metallic materials. ENP is extraordinarily capable of generating intense nanopulse electric current with a current density greater than a few to several hundreds of 1010A/m2 and a pulse duration on the order of a few 100ns. Such a level of current density is ∼3–5 magnitudes higher than that is usually achieved during the Spark Plasma Sintering process. Using the Nichrome-80 superalloy as a model material, we observed a variety of GB roughening phenomena at multiple length scales, resulting in the generation of diverse forms of atomistic facets, nanoscale serrations, and nanoscale step-like GB morphologies after the ENP processing. We think that the excessive GB heat localization and electron wind force or stress are the main factors contributing to the GB morphological changes during the ENP processing. The ENP processing provides a new unique grain boundary engineering strategy to manipulate the GBs with the changes localized at the GB region, without altering its adjacent grains.

Seismic behaviors of CFT-column frame-four-corner bolted connected buckling-restrained steel plate shear walls using ALC/RAC panels

A Frame-Buckling Restrained Steel Plate Shear Walls (BRSPSWs) system has been designed, featuring a steel plate connected to frame elements, to withstand lateral loads like seismic or wind forces. This system incorporates recycled aggregate concrete (RAC) to create concrete-filled and concrete panels, promoting eco-friendly and sustainable construction materials. Two single-span, two-floor specimens were tested under cyclic quasi-static load. A four-corner bolted connection was used to connect the steel plate to the square concrete-filled steel tubes (CFTs) column and H-section beam, minimizing the potential deformation of the frame elements produced by the tension field of the steel plate after high-order bucking. The steel plate was sandwiched using either autoclaved lightweight concrete (ALC) or RAC panels. The study analyzed failure modes, load-displacement responses, and characteristic capacities. Test results inferred that BRSPSWs exhibited favorable cyclic behavior, with similar failure modes observed using both ALC and RAC panels. The buckling of steel plates was reduced, and the type of restrained panels had a negligible impact on buckling. Consequently, ALC panels can effectively replace RAC panels. Furthermore, bearing capacities and yield stiffness were primarily determined by the bolted connection forms. A finite element (FE) modeling was developed using ABAQUS software and validated against test results. This FE modeling method successfully simulated failure modes and load-displacement curves. Parametric analyses were conducted and revealed that bearing capacity and yield stiffness positively correlated with steel plate thickness, bolt diameter, and the number of bolts but negatively correlated with the axial compression ratio. In contrast, the panel thickness and span length had a minor impact due to shear deformation in the bolted connection. Based on the test results and parametric studies, an equation for the yield-bearing capacity of BRSPSWs was proposed and verified.

Design and evaluation of an efficient high-precision ocean surface wave model with a multiscale grid system (MSG_Wav1.0)

Abstract. Ocean surface waves induced by wind forcing and topographic effects are a crucial physical process at the air–sea interface, which significantly affect typhoon development, ocean mixing, etc. Higher-resolution wave modeling can simulate more accurate wave states but requires a huge number of computational resources, making it difficult for Earth system models to include ocean waves as a fast-response physical process. Given that high-resolution Earth system models are in demand, efficient high-precision wave simulation is necessary and urgent. Based on the wave dispersion relation, we design a new wave modeling framework using a multiscale grid system. It has the fewest number of fine grids and reasonable grid spacing in deep-water areas. We compare the performance of wave simulation using different spatial propagation schemes, reveal the different reasons for wave simulation differences in the westerly zone and the active tropical cyclone region, and quantify the matching of spatial resolutions between wave models and wind forcing. A series of numerical experiments show that this new modeling framework can more precisely simulate wave states in shallow-water areas without losing accuracy in the deep ocean while costing a fraction of the price of traditional simulations with uniform fine-gridding space. With affordable computational expenses, the new ocean surface wave modeling can be implemented into high-resolution Earth system models, which may significantly improve the simulation of the atmospheric planetary boundary layer and upper-ocean mixing.

An “objective” definition of potential vorticity. Generalized evolution equation and application to the study of coastal upwelling instability

In this paper, we propose a form for potential vorticity (PV), rescaled using the Lorenz’s rearranged density profile, the novelty being that we here take into account its time evolution. We argue this rescaled PV is more representative of the dynamics, in particular to evaluate the respective impact of mixing and friction on the generation of geostrophic circulation. The impact of mixing at global scale, which only modifies the global stratification at rest, is taken into account in the evolution equation of this “objective” definition of PV, in the sense that it scales the PV changes with respect to its effect on the circulation. Numerically, we show that all terms can be calculated coherently using a single computation cell.We illustrate our purpose by studying the instability of coastal upwelling currents, using a numerical model at high resolution. The configuration is a periodic flat channel on the f-plane with vertical walls at the southern and northern boundaries. A constant wind is applied over a fluid at rest with an initial linear stratification. An upwelling current forms at the northern coast. After a few days, instabilities develop and vortices eventually emerge with surface intensified cyclones and subsurface anticyclones. We show that these instabilities and eddies are associated with (rescaled) PV anomalies, triggered by mixing and friction.We describe rescaled PV budgets in a layer bounded between the surface and an isopycnal level. Eulerian and Lagrangian diagnostics allow to analyze irreversible PV production terms, distinguishing the influence of advection, friction (associated with wind stress) and mixing. We find that friction plays the main role, generating negative PV anomalies, while mixing acts to dampen this negative PV production. The association of this negative PV anomaly with the outcropping front leads to the baroclinic destabilization of the upwelling front, creating subsurface anticyclonic vortices and surface intensified cyclonic vortices. Varying the strength of the wind forcing shows that mixing is the most sensitive process, with a net effect that is strongly reduced or even reversed with moderate to weak winds.When the dynamics is fully turbulent, with filaments and vortices of small sizes, the PV production by mixing and friction is enhanced but the Lagrangian diagnostics are more difficult to analyze, since fluctuations at grid scale become significant and numerical effects – associated with imperfections of the numerical schemes – spoil the PV budget calculation.

Kinematic Motion Modelling from Differential Inductive Oscillation Sensing for a Servomechanism and Electromechanical Devices and Applications

This paper presents mathematical modeling approach of an inductive sensor producing oscillating output of a given frequency representing displacement of a core moving in and out of a coil of known geometrical dimensions. The technique is hence used in characterizing the speed, acceleration and frequency of the proposed differential inductive transducer. This model uses a double coil arrangement with a freely movable iron core. This is made to oscillate freely thereby producing the proposed output for characterization of oscillating parameters. The application of this work finds utility in generating small amplitude signals from tiny force winds for the purpose of acquiring impulsive electrical signal from sources such as machine vibrations. Using an inductive coil sensing technique in a differential manner, physical parameters of speed, acceleration and displacement are translated into a signal with proportionate output frequency change. The results shown can be used for characterizing the materials and hence sensor with high sensitivity, linearity and responsiveness in harsh environmental condition is obtained.

Hydrography, inorganic nutrients and chlorophyll a linked to sea ice cover in the Atlantic Water inflow region north of Svalbard

Changes in the inflow of Atlantic Water (AW) and its properties to the Arctic Ocean bring more warm water, contribute to sea ice decline, promote borealisation of marine ecosystems, and affect biological and particularly primary productivity in the Eurasian Arctic Ocean. One of the two branches of AW inflow follows the shelf break north of Svalbard, where it dominates oceanographic conditions, bringing in heat, salt, nutrients and organisms. However, the interplay with sea ice and Polar Surface Water (PSW) determines the supply of nutrients to the euphotic layer especially northeast of Svalbard where AW subducts below PSW. In an effort to build up a time series monitoring the key characteristics of the AW inflow, repeat sampling of hydrography, macronutrients (nitrate, phosphate and silicate), and chlorophyll a (chl a) was undertaken along a transect across the AW inflow at 31°E, 81.5°N since 2012 — first during late summer and in later years during early winter. Such time series are scarce but invaluable for investigating the range of variability in hydrography and nutrient concentrations. We investigate linkages between late summer hydrographic conditions and nutrient concentrations along the transect and the preceding seasonal dynamics of surface chl a and sea ice cover in the region north of Svalbard. We find large interannual variability in hydrography, nutrients and chl a, indicating varying levels of nutrient drawdown by primary producers over summer. Sea ice conditions varied considerably between the years, impacting upper ocean stratification, light availability and potential wind-driven mixing, with a strong potential for steering chl a concentration over the productive season. Early winter measurements show variable efficiency of nutrient re-supply through vertical mixing when stratification was low, related to autumn wind forcing and sea ice conditions. While this re-supply elevates nutrient levels sufficiently for primary production, it likely happens too late in the season when light levels are already low, limiting the potential for autumn blooms. Such multidisciplinary observations provide insight into the interplay between physical, chemical and biological drivers in the marine environment and are key to understanding ongoing and future changes, especially at this entrance to the central Arctic Ocean.