Virgin olive oil quality is assessed by chemical as well as sensory analysis. Two of the most important parameters that define the quality of virgin olive oils are the free acidity and the peroxide ...index. These chemical parameters are usually determined by manual titration procedures that must be carried out in a laboratory by trained personnel. In this paper, a portable sensor system to support the quality grade assessment of virgin olive oil is presented. The system is battery operated and characterized by small dimensions, light weight and quick measurement response (about 30 s). The working principle is based on the measurement of the electrical conductance of an emulsion between a chemical reagent and the olive oil sample. Two different chemical reagents have been investigated: (1) a hydro-alcoholic solution (HAS), made of 60% ethanol and 40% distilled water; (2) 100% distilled water (DW). Tests have been carried out on a set of 40 olive oil samples. The results have shown how, for most of the fresh virgin olive oil samples (31 samples out of 40), the free acidity can be estimated with good accuracy from the electrical conductance of the emulsion using HAS as the reagent. In the case of the full set of samples, the emulsion electrical conductance, using HAS as the reagent, is a function of both the sample free acidity as well as the compounds produced by oil oxidation, and a compensation method based on the measured electrical conductance, using DW as the reagent, has been introduced to improve the accuracy in the estimated free acidity. Tests have also been carried out on the full set of samples, using a k-nearest neighbors algorithm, to demonstrate the feasibility of olive oil classification according to the quality grade. The results have shown how measurements carried out using only the HAS reagent provide better classification accuracy than measurements carried out using both the HAS and DW reagents. The proposed system can be a low-cost alternative to standard laboratory analyses to evaluate the quality grade of virgin olive oil.
In this paper, we analyze the methods that are used in The Netherlands to upscale in-situ groundwater measurements in time and in space, and how the selected combinations of upscaling methods affect ...the resulting groundwater characteristic. In The Netherlands, a three-step approach is used to obtain groundwater characteristics for a specific area: (1) in-situ monitoring of the water table depth; (2) temporal upscaling; and (3) spatial interpolation and aggregation. The three-step approach is, however, not standardized, but a combination of the following methods is used: (i) four methods to measure/monitor the phreatic water table; (ii) four methods for temporal aggregation; and (iii) four methods for spatial interpolation and/or aggregation. Over the past sixty years, several combinations of these methods have been used. Our review shows that the use of these different combinations in the approach to measure and interpret water table depths has resulted in significant systematic differences in the corresponding groundwater characteristics and that there are many sources of potential error. Error in the in-situ measurement of the water table depth can be as high as 1 m. Errors in the temporal aggregation are in the range of 10 to 20 cm and for the spatial interpolation between 20 and 50 cm. We show that there has been no systematic assessment of how these errors influence the resulting groundwater characterization. Thus, we cannot answer the question of whether drought stress in The Netherlands is under- or overestimated. Based on these findings we give recommendations for a systematic approach to groundwater characterizations studies that can minimize the impact of errors.
•The system approach to upscale groundwater characteristics in time and space has changed over time.•The selected combinations of upscaling methods affects the resulting groundwater characteristic.•A systematic approach that minimize or avoid the impact of errors in upscaling is not used.•Based on these findings, we cannot conclude whether drought stress is under- or overestimated.
We present data from in situ measurements of the salinity evolution of young sea ice in the Arctic. The measurements were carried out with very high vertical and temporal resolution over the course ...of a few days until the ice had reached a thickness of around 20 cm. The measured bulk salinity profiles show that during ice growth, sea‐ice salinity is continuous across the ice‐ocean interface and that there is no instantaneous loss of salt at the advancing front. Measured salt fluxes emanating from the ice are as high as 90 g m−2 h−1 during the first few hours of new ice formation and are roughly half as large during later stages of the experiments. The bulk salinity within the ice decreases continuously with time from the ocean water salinity to a near–steady state value of around 4 parts per thousand (ppt). These results are interpreted with ideas from mushy layer theory using a Rayleigh number to analyze gravity drainage as the driving mechanism for the observed salt loss. In our experiments, gravity drainage occurs for a critical Rayleigh number of around 10, in close agreement with earlier theoretical and experimental studies.
East coast of India is more prone to the cyclones. The major damages caused by the cyclones are due to the effect of storm surges, the temporary rise in sea level due to storm. They pose more risk to ...the coastal population with unexpected flooding. Hence, predicting the surge along the coast is important for providing early warnings to evacuate people living along the coastal villages. This helps to take precautionary measures to minimise the damages caused by the cyclones. This study desires to focus on hazard due to cyclone along the Tamilnadu coast. One of the recent cyclones, cyclone Nivar, is considered for the study. Very Severe Cyclonic Storm Nivar hit Tamilnadu coast in late November 2020. The present numerical model is developed by solving the Shallow Water Equation (SWE) based on an explicit finite element scheme. The study domain is discretized with 9- noded unstructured rectangular grids. The integration over an element is carried out by using two-dimensional Simpson's rule of integration. Solutions at each time is obtained explicitly as the system of equations is uncoupled. The element type along with the integration procedure forms an explicit scheme. When compared with the other implicit finite element schemes-based surge models, the present numerical model is computationally efficient. Thus, early predictions from time to time based on the track of the cyclone is possible due to lesser computational time. The precise cyclone track of Nivar, obtained from National Oceanic and Atmospheric Administration (NOAA), is used to simulate the flow field associated with the storm. The peak surge of about 0.64 m is observed near Marakanam and negative surge is witnessed near Nagapattinam.
Copper and D2 tool steel powders were produced using a drop tube-impulse atomization technique. In order to measure the radiant energy and droplet size of atomised D2 steel droplets, DPV-2000 (Tecnar ...Automation Ltée, St. Hubert Quebec, Canada) was utilised. In-situ velocity and droplet size of the atomised droplets were also measured using shadowgraphy technique (Sizing Master Shadow from LaVision GmbH in Gottingen, Germany). A 3D translation stage was designed, constructed and installed inside the drop tube system. DPV-2000 and shadowgraph were then mounted on the translation stage. The Cu droplets were primarily used to calibrate to particle size and velocity measurements between both instruments. Using this stage, online measurements were conducted at 4 cm, 18 cm and 28 cm distances for D2 droplets below the crucible. Using liquid (fully undercooled) and semi-solid behaviour of droplets, it was possible to estimate the droplet size and temperature at which recalescence ends. These values were then confirmed by the thermal model using experimentally estimated primary phase undercooling values.
Part of the Beringia 2005 expedition covered the North Atlantic Ocean. During this passage, dissolved gaseous mercury (DGHg) in seawater and atmospheric concentrations of total gaseous mercury ...(TGHg), carbon monoxide (CO), and ozone (O
3) were measured continuously at high resolution. In addition, meteorological parameters such as wind speed and water temperature were measured continuously by the ship's meteorological instrumentation. The DGHg concentration was measured using a continuous equilibrium system where the elemental mercury in the sea water was equilibrated with a stream of gas. The DGHg concentration was calculated using DGHg
=
Hg
eq/k
H′ where Hg
eq is the concentration of elemental mercury in the equilibrated air and k
H′ is the dimensionless Henry's law constant. The degree of saturation was determined directly from the measurements S
=
Hg
eq/TGHg. The water sampled had an average DGHg concentration of 58
±
10
fM and the average TGHg concentration was determined to 1.7
±
0.1
ng
m
−
3
. The water sampled was under- and super-saturated with respect to elemental mercury covering a large range of saturation of 70 to 230% resulting in an average degree of saturation of 150
±
30%. Therefore, both evasion and deposition of elemental mercury were observed in the sampled water. In the light of the average flux, 2.1
±
1.8
pmol
m
−2
h
−
1
, it is concluded that mostly evasion occured during the sampling period.
►For the first time, both TGHg and DGHg were measured continuously with a high time resolution along a cruise track in the North Atlantic Ocean. ►The DGHg concentration measured during the expedition ranged from 29 to 90
fM, the average concentration was 58
±
10
fM, and the TGHg concentration ranged from 1.2 to 2.2
ng
m
−
3
with an average of 1.7
±
0.1
ng
m
−
3
. ►The average flux was calculated to 2.1
±
1.8
pmol
m
−2
h
−
1
. Depending on the degree of saturation and wind speed, both deposition (−
3.2
pmol
m
−2
h
−
1
) and evasion (12.6
pmol
m
−2
h
−
1
) of elemental mercury occurred.
Benthic suspension feeders play essential roles in the functioning of marine ecosystems. By filtering large volumes of water, removing plankton and detritus, and excreting particulate and dissolved ...compounds, they serve as important agents for benthic-pelagic coupling. Accurately measuring the compounds removed and excreted by suspension feeders (such as sponges, ascidians, polychaetes, bivalves) is crucial for the study of their physiology, metabolism, and feeding ecology, and is fundamental to determine the ecological relevance of the nutrient fluxes mediated by these organisms. However, the assessment of the rate by which suspension feeders process particulate and dissolved compounds in nature is restricted by the limitations of the currently available methodologies. Our goal was to develop a simple, reliable, and non-intrusive method that would allow clean and controlled water sampling from a specific point, such as the excurrent aperture of benthic suspension feeders, in situ. Our method allows simultaneous sampling of inhaled and exhaled water of the studied organism by using minute tubes installed on a custom-built manipulator device and carefully positioned inside the exhalant orifice of the sampled organism. Piercing a septum on the collecting vessel with a syringe needle attached to the distal end of each tube allows the external pressure to slowly force the sampled water into the vessel through the sampling tube. The slow and controlled sampling rate allows integrating the inherent patchiness in the water while ensuring contamination free sampling. We provide recommendations for the most suitable filtering devices, collection vessel, and storing procedures for the analyses of different particulate and dissolved compounds. The VacuSIP system offers a reliable method for the quantification of undisturbed suspension feeder metabolism in natural conditions that is cheap and easy to learn and apply to assess the physiology and functional role of filter feeders in different ecosystems.
Overheating in the residential buildings has been identified as a major challenge in terms of public health especially in an urban context. Increased duration and frequency of heatwaves associated ...with climate change will increase the severity of overheating. However to date overheating has not been adequately addressed by the building regulations. In a case study retrofit high rise apartment block in Leeds, UK major overheating has been identified through and in-depth building performance evaluation (BPE) study. The study was extended with transient dynamic modelling of top floor apartments to explore the effectiveness of 18 fabric and practices scenarios based on actual BPE findings. The results show 10-30% difference in overheating severity was caused by a performance gap in relation to the building fabric. What's more they indicate that in the given climatic conditions of summer 2013 overheating might have been avoided if shading was introduced and mechanical extract ventilation used as designed. This points towards the need of focusing more attention on overheating prevention at design and handover stages.
Data from Argo floats equipped with Iridium communications are used to obtain a global map of the total amplitude (or variance) of the semidiurnal internal tide at 1,000 dbar. The results are ...confirmed by a comparison with data from an historical collection of moored instruments. The obtained amplitude is in turn compared with the High‐Resolution Empirical Tide (HRET) model, based on satellite altimetry. While HRET only contains the stationary component, with a fixed phase difference to the astronomical tide, the present results capture the total amplitude, including the nonstationary component. We estimate the global average ratio of total (Argo) to stationary (HRET) semidiurnal internal tide variance to be 6.5, and the amplitude ratio to be 3.6. Our estimate of the stationary fraction of the semidiurnal internal tide is subject to significant uncertainties. In particular, HRET is thought to mainly represent baroclinic mode‐1 waves, while Argo data contain contributions from all modes.
Plain Language Summary
Internal tides are internal waves generated by the barotropic tide. As they propagate they are affected by the eddying general circulation. This causes the waves to decorrelate: their phase shifts and is no longer locked to the phase of the generating force. Satellite altimetry can only measure the stationary wavefield, that is, the component phase locked to the exactly known astronomical forcing. The total amplitude is therefore poorly known. Here, we describe the total internal tide field using a global collection of autonomous floats recording data as they freely drift at 1,000 m below the surface. By comparing these data to a satellite altimetry product we find that the nonstationary fraction of the semidiurnal internal tide is significantly larger than commonly thought. Quantifying the nonstationary internal tides is crucial for a better understanding of the abyssal circulation, and therefore of the global climate system.
Key Points
Time series from Argo floats are analyzed in the time domain to produce a global map of the total semidiurnal internal tide variance
The results are validated by a comparison with an historical collection of moorings
A comparison with satellite altimetry shows that 85% of the variance of the internal semidiurnal tide becomes decorrelated in 400 hr
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