Water Concentration Distribution Research Articles

Intelligent Devices Harnessing Underwater Superoleophobic and Underoil Superhydrophobic Quartz Sands for the Separation of Diverse Stratified and Emulsified Water-Oil Mixtures.

To achieve the green, sustainable, and controllable recovery of oil-water resources and to address the limited functionality of single superwet materials in oil-water separation, this study reports a multifunctional oil-water separation strategy by compositing the underwater superoleophobic and underoil superhydrophobic materials (HS). The underwater superoleophobic quartz sands with an oil contact angle of 152.68° were prepared by adjusting the particle size. This material demonstrated a water flux of 4688 L m-2 h-1 and a low-density oil and water mixture separation efficiency of 98.6%, which remained above 97.9% over 50 cycles. It was effective in separating oil-in-water emulsions with a separation efficiency of >99%. For HS, quartz sands were modified with dodecyltrimethoxysilane. The optimized HS-4 exhibited superhydrophobic properties with a water contact angle of 157.06°. It achieved an oil flux of 5775 L m-2 h-1 and a water and dichloromethane mixture separation efficiency of 98.4%. Additionally, they exhibited significant potential in the separation of water-in-oil emulsions. Furthermore, by placing the underwater superoleophobic and underoil superhydrophobic units at the bottom of the filter, we achieved cyclic separation of high-density oil and water mixtures, low-density oil and water mixtures, water-in-oil emulsions, and oil-in-water emulsions. The separation efficiency consistently exceeded 96.5% over 10 cycles. In addition, the oil-water separation mechanism of underwater oleophobic and underoil hydrophobic materials was demonstrated by the relative concentration distribution of water and oil with molecular dynamics simulations. This intelligent oil-water separation method marks a significant advancement in the sustainable separation of diverse oil-water mixtures.

Quantitative analysis of sweat evaporation loss in epidermal microfluidic patches.

Sweat analysis is identified as a promising biochemical technique for the non-invasive assessment of human health status. Epidermal microfluidic patches are the predominant sweat sampling and sensing devices. However, the sweat stored inside the patches may suffer from evaporation loss of moisture, which can increase the concentration of biomarkers and cause the biochemical analysis results of sweat to deviate from the actual results. This study focuses on quantitatively analysing the sweat evaporation loss within epidermal microfluidic patches. Analytical models based on the dissolution diffusion mechanism and corresponding partial differential equations for the diffusion process were initially developed. The analytical solution of the equation was derived using the method of separation of variables, and the steady-state concentration distribution of water in the materials of microfluidic patches was calculated when considering the application of epidermal microfluidics. Evaporation losses of sweat through different paths were quantitatively calculated and analysed, including permeation through covers, diffusion along microchannels, and absorption by sidewalls. Then, experiments on the evaporation loss of sweat within microfluidic patches were conducted to validate the theoretical calculations and analytical results. At last, the design of the anti-evaporation structure for microfluidic patches was discussed. This study can provide theoretical and experimental references for the design of water-retention structures in epidermal microfluidic patches, which significantly enhances the overall reliability of sweat biochemical analysis results.

Water concentration and rate of decrease in shiitake cultivation log during fruiting body development, as measured by MRI

Large shiitake mushrooms (Lentinula edodes, pileus > 8 cm in diameter) are difficult to cultivate and account for only 3-5% of the total harvest. This study focused on the water absorption process within a log during the growth of fruiting bodies in order to increase the yield of large shiitake mushrooms. Konara oak logs (Quercus serrata, 85-95 mm in diameter, 290 mm in length) were inoculated with shiitake mycelium plugs and nine months later, young fruiting bodies developed, at which point the log was analyzed using magnetic resonance imaging (MRI) over a period of two weeks. The signal intensity and T1 and T2 relaxation time constants were determined from the acquired images, along with the distribution of water concentration within the entire log. The axial distributions of water concentrations in the log were higher in the 80 mm region around the fruiting body. The rate of decrease in water concentration indicated that water was supplied to the fruiting body from 80 mm axially in the upper half of the sapwood in the log. On the other hand, the water concentration in the heartwood did not decrease and the heartwood did not contribute to the water supply to the fruiting bodies.

RESEARCH ON THE FLOW FIELD OF THE PEMFC BIPOLAR PLATE BASED ON THE TREE-LIKE FRACTAL THEORY

Tree-like branching structures occur in both natural and artificial transport systems, which have fascinated multidisciplinary researchers to study and apply the transport mechanisms of tree-like branching structures for decades. In this paper, the flow field of a proton exchange membrane fuel cell (PEMFC) with a Y-shaped tree-like fractal structure was studied utilizing Murray’s law in fractal theory. The polarization curve, gas concentration distribution, water concentration distribution, pressure drop distribution, and current density distribution of the PEMFC are numerically simulated in this research, and the transmission law is analyzed with different channel branching angles [Formula: see text]. The results demonstrate that the optimal branching angle of the designed tree-like fractal flow field is [Formula: see text]. When compared to a parallel flow field under identical conditions, the maximum output power density of the fractal flow field with a branching angle of [Formula: see text] is 26.7% higher. The optimal angle of [Formula: see text] for symmetric branching flow derived from Murray’s law was shown to be applicable to the flow field design of the fuel cell, improving the transport characteristics of the reaction gases and the overall performance of the PEMFC. This research may provide further references for the design of flow fields in fuel cells.

Tomographic Absorption Spectroscopy for H2O Transport in a Laminar Jet with Inverse Concentration Gradient.

We report a tomographic absorption spectroscopy (TAS) study of water vapor transport in a laminar jet issuing into the ambient. The jet was generated using compressed dry air that was straightened by a honeycomb and a smooth contraction nozzle. A TAS scheme using the water vapor in the ambient as absorbing species and the absorption line near 1368.598 nm was proposed to study the H2O transport in the laminar jet with an inverse concentration gradient. One-dimensional tomography was conducted at various heights above the nozzle, and the results were validated by the predictions from computational fluid dynamics (CFD) simulations. Particularly, the variations in the concentration gradient in the shear layer at different heights were captured. The 2D distribution of water concentration in the dry laminar jet was obtained experimentally. The present study shows that TAS has great potential in the research of mass transfer and scalar field of gaseous flows.

Visualization of water concentration distribution in human skin by ultra-multiplex coherent anti-Stokes Raman scattering (CARS) microscopy

Ultra-multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopic imaging was used to visualize the distribution of water concentration in human skin ex vivo. The CARS signal of the OH stretching vibrational mode of water was found to coexist with the signal of intercellular lipids such as ceramides, which were visualized by a sharp vibrational band at 2882 cm−1. Depth-resolved CARS spectroscopic imaging of a skin sample revealed that ceramides were localized in the stratum corneum. These findings demonstrate the powerful potential of CARS spectroscopic imaging for probing pathological changes caused by anomalous water concentration distribution in human skin.

Determination of transport properties and mechanistic modeling of the coupled salt and water transport during osmotic dehydration of salmon induced by dry salting

AbstractA mechanistic forward osmosis model based on nonideal principles and the continuity equation was adapted to the dry salting of salmon. The novelty of this model is that the water loss is coupled to the salt uptake by means of the activity gradient. Consequently, besides the primarily desired predictive purposes, the model also explains why the ion uptake triggers the osmotic dehydration. The determination of the model parameters, as well as the validation of the model was carried out by comparing the results of the simulations with experimental salt and water concentration distributions. The good predictions of the model allow the establishment of a tool to have a better control of the time the salting process must last to meet both organoleptic and safety requirements. Additionally, it is transversally applicable to other food matrices, and by extension, to other engineering situations involving dehydration induced by ion uptake.Practical applicationsAn increasing salt concentration in muscle tissue affects two very important aspects: the water loss (yield) and the water activity (consumer safety). The model presented in this work describes how these three variables are related by means of a physics‐based link. This allows its use to optimize the process. Moreover, as this model can also predict the water activity distribution at any time, it also helps to ensure that every point in the system meets the safety requirements.

Mechanistic modelling of the coupled salt and water transport in herring during brining and curing

Salting of fish tissue triggers a water movement to equilibrate the activity gradient. A mechanistic model that can predict the development of salt and water concentration as well as the water activity distributions, was validated by developing an experimental methodology that allows the access to the salt and water concentration distributions at any stage of the process. The model succeeded on offering reasonable predictions, with average RMSEs of 0.019 and 0.033 kg kg−1 for the salt and water concentration distributions, and 0.022 for the water activity; as well as a mathematical framework that is independent of the salting conditions (e.g. brining, curing), which helps to understand why the system behaves the way it does. Additionally, it allows the establishment of a tool to have a better control of the salting time in order to ensure both organoleptic and safety requirements.

Infrared Absorption Imaging of Water Ingress Into the Encapsulation of (Opto-)Electronic Devices

Water ingress into the encapsulation of electronic devices is a serious issue, especially for organic and perovskite-based electronics. In order to guide the development of suitable barrier materials and design, a reliable, fast and non-destructive analysis tool is required. In this work, an imaging setup is presented, which is based on selective infrared (IR) radiation sources and a mid- IR sensitive camera that uses the absorption band of water around 1920 nm and a reference band. This system enables us to monitor the distribution of water concentration inside the packaging of devices and its change over time. Our measurement is capable of detecting the local presence of water down to the mg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> concentration range in a wide variety of encapsulation materials. The new tool allows identifying the pathways of moisture ingress into the encapsulation along with the corresponding diffusion coefficient. Thus, it provides fast and reliable analysis of humidity related failure mechanisms and consequently helps to improve the design of encapsulation materials and processes.

Observing Chemical Reactions by Time-Resolved High-Resolution Neutron Imaging

We developed an operando technique based on time-resolved high-resolution neutron imaging to map the water concentration distribution inside millimeter-sized catalyst beads catalyzing the sorption-...

Measurement of water diffusion coefficient in bio-protective solution

Clinical analytes, which are used for early detection of disease, are rapidly deteriorated. Thus, the preserving the quality of such analytes is highly required. Preservation of clinical analytes with the room-temperature desiccation is an ideal preservation method, although controlling the moisture in a specimen with a glass forming bio protective substance, e.g. trehalose, is essential for the drying process to be successful. In this study, the temporal change of the water concentration distribution in the high concentration aqueous solution of protective agents during the drying process was measured by microscopic infrared spectroscopy using infrared absorption band specific to water. Based on the temporal change of the water concentration distribution, the water self-diffusion coefficient in the high concentration trehalose and ε-poly-L-lysine(PLL) aqueous solution was estimated.

Tomographic imaging of reacting flows in 3D by laser absorption spectroscopy

This paper describes the development of an infrared laser absorption tomography system for the 3D volumetric imaging of chemical species and temperature in reacting flows. The system is based on high-resolution near-infrared tunable diode laser absorption spectroscopy (TDLAS) for the measurement of water vapour above twin, mixed fuel gas burners arranged with an asymmetrical output. Four parallel laser beams pass through the sample region and are rotated rapidly in a plane to produce a wide range of projection angles. A rotation of 180° with 0.5° sampling was achieved in 3.6 s. The effects of changes to the burner fuel flow were monitored in real time for the 2D distributions. The monitoring plane was then moved vertically relative to the burners enabling a stack of 2D images to be produced which were then interpolated to form a 3D volumetric image of the temperature and water concentrations above the burners. The optical transmission of each beam was rapidly scanned around 1392 nm and the spectrum was fitted to find the integrated absorbance of the water transitions and although several are probed in each scan, two of these transitions possess opposite temperature dependencies. The projections of the integrated absorbances at each angle form the sinogram from which the 2D image of integrated absorbance of each line can be reconstructed by the direct Fourier reconstruction based on the Fourier slice theorem. The ratio of the integrated absorbances of the two lines can then be related to temperature alone in a method termed, two-line thermometry. The 2D temperature distribution obtained was validated for pattern and accuracy by thermocouple measurements. With the reconstructed temperature distribution, the temperature-dependent line strengths could be determined and subsequently the concentration distribution of water across the 2D plane whilst variations in burner condition were carried out. These results show that the measurement system based on TDLAS can be used for 2D temporal or 3D volume imaging of temperature and chemical species concentration in reacting flows.

Water Absorption in Polymer Composites Reinforced with Vegetable Fiber Using Langmuir-Type Model: An Exact Mathematical Treatment

This work presents a theoretical study of the anomalous behavior of moisture transient diffusion in vegetable fiber-reinforced composites materials using Langmuir-type model. For obtain the analytical solution was used the Laplace transform technique. Results of the absorption kinetics and concentration distribution of water (free and trapped water molecules) within the material along the process are presented and analyzed. Predicted results compared to experimental data of average moisture content have shown that the model was effective for description of the phenomenon, allowing a better understanding about the effects of moisture migration mechanisms.

Water Concentration Analysis by Raman Spectroscopy to Determine the Location of the Tumor Border in Oral Cancer Surgery.

Adequate resection of oral cavity squamous cell carcinoma (OCSCC) means complete tumor removal with a clear margin of more than 5 mm. For OCSCC, 85% of the surgical resections appear inadequate. Raman spectroscopy is an objective and fast tool that can provide real-time information about the molecular composition of tissue and has the potential to provide an objective and fast intraoperative assessment of the entire resection surface. A previous study demonstrated that OCSCC can be discriminated from healthy surrounding tissue based on the higher water concentration in tumor. In this study, we investigated how the water concentration changes across the tumor border toward the healthy surrounding tissue on freshly excised specimens from the oral cavity. Experiments were performed on tissue sections from 20 patients undergoing surgery for OCSCC. A transition from a high to a lower water concentration, from tumor (76% ± 8% of water) toward healthy surrounding tissue (54% ± 24% of water), takes place over a distance of about 4 to 6 mm across the tumor border. This was accompanied by an increase of the heterogeneity of the water concentration in the surrounding healthy tissue. The water concentration distributions between the regions were significantly different (P < 0.0001). This new finding highlights the potential of Raman spectroscopy for objective intraoperative assessment of the resection margins. Cancer Res; 76(20); 5945-53. ©2016 AACR.

The apparent counter diffusion coefficient of water absorbing on zeolite particles in the case of the water moving through macro-size pores in a column packed with zeolite particles

The oxygen concentration discharged from a compact adsorption-type oxygen concentrator decreases when water attaches to the zeolite particles used as a nitrogen adsorbent. In order to estimate the expansion of the water adsorption region in the zeolite column, it is necessary to measure the water diffusion occurring in a zeolite column after stopping PSA (Pressure Swing Adsorption) operations. Li-X type zeolite particles (molecular sieve OXYSIV-700) with particle diameters in the range of approximately 0.4–0.5mm were used as a nitrogen adsorbent column of length 157mm and of inner diameter 33mm. By comparing the water concentration distributions obtained from MR (Magnetic Resonance) images and the distributions calculated by analytical solution of a one-dimensional diffusion equation under transient conditions, the counter diffusion coefficient of water absorbing on zeolite particles in the column was determined. The apparent diffusion coefficient of water absorbing on the zeolite particles moving into the zeolite column with macroscale pores was determined to be 1.25±0.15×10−11m2/s.

Direct Comparison of Disaccharide Interaction with Lipid Membranes at Reduced Hydrations.

Understanding sugar-lipid interactions during desiccation and freezing is an important step in the elucidation of cryo- and anhydro-protection mechanisms. We determine sucrose, trehalose, and water concentration distributions in intra-bilayer volumes between opposing dioleoylphosphatidylcholine bilayers over a range of reduced hydrations and sugar concentrations. Stacked lipid bilayers at reduced hydration provide a suitable system to mimic environmental dehydration effects, as well as a suitable system for direct probing of sugar locations by neutron membrane diffraction. Sugar distributions show that sucrose and trehalose both behave as typical uncharged solutes, largely excluded from the lipid bilayers regardless of sugar identity, and with no correlation between sugar distribution and the lipid headgroup position as the hydration is changed. These results are discussed in terms of current opinions about cryo- and anhydro-protection mechanisms.

Вплив нерівномірності розподілу щільності зрошування у порожнистому скрубері на ефективність очистки димових газів від твердих частинок

Вплив нерівномірності розподілу щільності зрошування у порожнистому скрубері на ефективність очистки димових газів від твердих частинок

A study of numerical analysis for PEMFC using a multiphysics program and statistical method

This study utilizes a numerical analysis of the PEMFC unit cell in which the electrode area is 25 cm2. The calculation is carried out by a multiphysics program called COMSOL. Water concentration distribution, hydrogen concentration distribution, and transport phenomena were calculated simultaneously. The resulting data from COMSOL are qualitatively expressed as images in many cases. However, a statistical method was proposed to analyze image data quantitatively and more precisely. The resulting data describing the water distribution and hydrogen concentration were exported and shown to have a normal distribution. The data were clearly identified using maximum, minimum, average, variance, skewness, and kurtosis values. The voltage ranges, where two kurtoses are approximately −1 for data of both the anode hydrogen concentration (AHC) and cathode water concentration (CWC), are similar to the voltage range of the ohmic loss section of PEMFC. In conclusion, the operating reference voltage of PEMFC was selected using the statistical analysis values of the AHC and CWC.

Water concentration distribution in coatings during accelerated weathering protocols

The long outdoor service life of painted metal and wood objects, often measured in decades, requires the use of accelerated weathering protocols to predict the long-term efficacy and performance of new barrier protective coating candidates. The mechanism of damage imposed on a coating system in accelerated weathering tests must have parity with the damage mechanisms occurring within the system as it undergoes natural, in-service weathering. Similarly, the physical conditions involved in the accelerated exposure regime, including water distribution as it is defined both temporally and spatially, must show equivalency to the natural exposure regime. An added complication in accurately accelerating coating damage is that the wet and dry cycles of accelerated weathering and corrosion test protocols are often performed at different and elevated temperatures from in-service exposure, which results in altered bulk transport and diffusion rates of water during each phase of the weathering or corrosion protocol, when compared to those rates experienced in field or in-service conditions. In this study, Fick’s law of diffusion is applied to coating surfaces exposed to surface water concentrations at cyclical intervals for a set of two-stage accelerated weathering protocols. The governing equations are solved using Laplace transforms followed by time rescaling to account for the variation in temperature, which impacts the diffusion coefficient between the wet and dry portions of several accelerated weathering protocols. This serves to predict the asymptotic average water concentration within the coating as well as at the coating–metal interface, based on the diffusion and temperature parameters of the coating and the parameters of the accelerated weathering protocol, including the duration of each imposed wet or dry stage. The analytic solution to Fick’s second law also allows the water concentration at the substrate–coating interface to be predicted based on Arrhenius parameters of the diffusion process. This resultant average time of wetness and water concentration variance at the coating–substrate interface can be used to more directly compare corrosion and adhesion loss between various accelerated weathering protocols and natural weathering conditions. The numerical average and range of water concentration as a function of coating depth can then be used to interpret coating damage distribution with depth, and enable more insightful comparison of the results of various accelerated weathering protocols. The simulations indicate that good barrier systems may actually exhibit increased barrier properties in accelerated protocols as compared to systems with mediocre or poor barrier performance as determined by global diffusion coefficients. The good barrier coating imparts substantially less exposure challenge to the interface than the mediocre or poor barrier coatings in accelerated weathering protocols. Therefore, in industry-standard tests, the observed performance gain of good barrier coating systems over poor systems may be unduly exaggerated. However, the overall exposure challenge to the interface of a good barrier coating is likely to be larger in service or field conditions due to the much extended time of wet exposure. Thus, laboratory-accelerated weathering cycles that do not consider the impact of temporal and spatial diffusion could potentially misrepresent the quality of a coating, in most cases overestimating the performance of coatings with good baseline barrier protection for adhesion or corrosion protection. In other words, the accelerated weathering protocols do not equally challenge the interface of different coatings operating in the same in-service conditions.

Simulation and analysis of water concentration in the proton exchange membrane

Water content in proton exchange membranes (PEM) has an important effect on PEM fuel cells. The water concentration gradient map was simulated by using COMSOL multiphysics, and this figure was calculated and analysed to get the water concentration distribution in PEM. The results show that water concentration in the membrane shows inverse parabolic increase along the direction of gas flow. The trend of water concentration on the cathode surface is the same as on the anode surface, both of them increase along the direction of gas flow, but the value on the cathode side is higher than that on the anode side. The change rate of water concentration on the membrane increases along the direction of gas flow. The water concentration on the middle position of the membrane is the lowest throughout the membrane, even lower than inlet along the thickness direction, which can lead to water shortages.