Internal Water Content Research Articles

Damage Evolution Characteristics of Non-fractured Regions during the Rock Fracture Process of Cracked Chevron Notched Brazilian Disc Specimens with Different Water Contents

To investigate the influence of water content on crack evolution during the fracture process of the red sandstone rock material, the damage and mechanical properties of cracked chevron notched Brazilian disc red sandstone specimens, with different water contents, were experimentally investigated. Using a P-wave velocity meter, the damage information of red sandstone specimens with different water contents, in the non-fractured region, during the pure mode I and II fracture processes, was quantitatively analyzed. The experimental results show that the damage amount of the non-fractured region, during the pure mode I and II fracture processes, increases linearly with an increase in the internal water content of the red sandstone specimens. Thus, the results from this study can provide certain theoretical basis for studying the evolution mechanism of microcracks in the fracture process of CCNBD specimens with the disparate water contents.

Numerical study on the performance of fuel cell with wavy flow field plate

Fuel cell is one of the most promising batteries at present. However, in order to successfully use fuel cell in vehicle, many improvements are still needed. Among them, the flow field plate of fuel cell has an important impact on the performance of fuel cell. In this paper, the influence of the wave channel on the internal pressure, current density, and water content of the fuel cell was studied. After analysis, the influence of the height of flow passage, the number of wave peaks, and wave amplitude on the cathode of the fuel cell was determined. The performance of the fuel cell was successfully improved, and the possible improvement direction of the cathode flow field plate of the fuel cell was further explored.

Fuel cell humidity modeling and control using cathode internal water content

Humidity of proton exchange membrane fuel cell, a critical underlying variable that affects stack efficiency and durability, is quite challenging to be well controlled due to the measuring difficulty and multiple couplings with other variables. For precise humidity description and control, this paper utilizes the internal water content as the feedback signal, whose dynamic model is developed by taking into account various auxiliary couplings. Based on the mechanistic model, the dynamic responses of the internal water content are exhibited and analyzed by manipulating the external current, air compressor voltage and humidifier electrical power, respectively. It is shown that the internal water content is able to better describe the real humidity environment, in contrast with the conventional method using cathode inlet relative humidity. Furthermore, a combined feed-forward and feedback control structure is proposed to maintain the internal humidity as close to the desired as possible. Simulation results show that the proposed control method is able to maintain the fuel cell operating within the safe and efficient region, and the humidification power consumption can be reduced because of the precise and less conservative description on the internal humidity.

Energy and environmental analysis of ultrasound-assisted atmospheric freeze-drying of food

The atmospheric freeze-drying process can be significantly accelerated using power ultrasound. This paper aims to investigate the effects of this technology on the global energy consumption of the process and its environmental impact. Apple, carrot and eggplant were chosen as representative products because of their different internal structure and water content. A mathematical model of an industrial scale plant was developed to simulate in silico the atmospheric ultrasound-assisted freeze-drying process; model parameters were tuned according to the results obtained in a pilot-scale unit. Life Cycle Assessment (LCA) was used to gain an insight into the environmental impact of the process. The results showed that, when ultrasound is applied, the total energy consumption of the whole process can be reduced by up to 70%, while the LCA analysis proved there were reductions of between 58 and 82% depending on the product for every impact category. The moisture removal unit (dehumidifier) has been highlighted as the most critical stage. The internal structure of the product dramatically affects both the energy consumption of the process and, accordingly, the environmental impact.

Ground-penetrating radar investigation for the restoration of Al-Azhar historical minarets

Ground-penetrating radar (GPR) is a modern geophysical tool that was developed for prospecting the ground subsurface. Recently, it has shown great potential for providing valuable information about the integrity of masonry structures. In this study, GPR was used to evaluate the state of bulk mason walls utilised as base foundation for the five historical minarets of Al-Azhar mosque in Cairo, Egypt constructed in different historical periods extending from Mamluk era to Ottoman era. The obtained results provided useful knowledge concerning the composition of the minaret bases and stones arrangement. Also, it showed the existence of multiple anomalies, indicating cavities that are probably caused by migration of fine filling materials downward. Limits of internal water content were clearly identified and salinity inside the wall filling was recognised. Based on these results, a decision was taken to re-inject the fine material lost through time inside the bases, to regain their structural integrity.

Water content diagnosis for proton exchange membrane fuel cell based on wavelet transformation

The fuel cell reliability and durability are still the main factors limiting the large scale commercialization. To a certain degree, water content, transportation, distribution and state in the fuel cell influence the fuel cell State of Health (SOH). However, it's very difficult to measure water content inside fuel cell directly. The PEMFC system voltage fluctuate during hydrogen purging process, due to the removal of liquid water will affect the reactants transformation. Different internal water content will cause different voltage fluctuations. For this characteristic, The Energy Intensity of Reconstructed Vibrating Voltage (EIV) based on wavelet transformation is proposed and validated in this paper. The boundary value of EIV is determined to be 0.1 through experiments. The results show that the fuel cell voltage drop is reduced to 0.32 V/h from 1.39 V/h by using this method to avoid anode flooding. By several PEMFC system experiment results in test bench, this method can diagnosis the water content in PEMFC properly.

Study of internal multi-parameter distributions of proton exchange membrane fuel cell with segmented cell device and coupled three-dimensional model

Understanding multi-parameter distributions inside the proton exchange membrane fuel cell is critical for the stack design and operation optimization. In this work, in situ measurement and three-dimensional model of internal parameter distributions for fuel cell are studied both experimentally and numerically. A segmented cell device based on printed circuit board with embedded sensors is designed to detect local current, relative humidity and temperature in the single cell simultaneously. Meanwhile, a two-phase flow multi-physical fuel cell model validated by the in situ measurement is built to analyze various internal performances. Quantitative impact of convective gas flow on internal parameter distribution is analyzed to reveal the mechanism of water and heat balance for counter-flow operation. The results show that air flow rate is critical to the parameters distributions including current, relative humidity, reactants concentrations and temperature, but hydrogen flow rate effect is neglected. With parametric sweep modeling, the anode and cathode relative humidity distribution profiles could be respectively described by a linear-approximate piece-wise function, which is helpful to quickly predict and evaluate the internal water content distributions for various fuel cell designs and operations.

Endophytic bacteria of desert cactus (Euphorbia trigonas Mill) confer drought tolerance and induce growth promotion in tomato (Solanum lycopersicum L.)

Endophytic bacteria isolated from cactus were characterized and assessed for their capability to induce drought tolerance and growth promotion in tomato. A total of 191-bacteria representing 13-genera and 18-species were isolated from wild cactus, Euphorbia trigonas. Bacillus (58), Lysinibacillus (36), Enterobacter (29), Stenotrophomonas (18), Lelliottia (12) and Pseudomonas (12) were the most represented genera. 16S rDNA sequence (>1400-bp) comparison placed the bacterial isolates with Bacillus xiamenensis; Bacillus megaterium; Bacillus cereus; Bacillus amyloliquefaciens; Bacillus velezensis; Brevibacillus brevis; Lysinibacillus fusiformis; Enterobacter cloacae; Lelliottia nimipressuralis; Proteus penneri; Sphingobacterium multivorum; Klebsiella pneumoniae; Pseudomonas putida; Pseudomonas aeruginosa; Stenotrophomonas maltophilia; Citrobacter freundii; Chryseobacterium indologenes and Paracoccus sp. Bacillus xiamenensis was identified for the first time as plant endophyte. Upon bacterization, the endophytes triggered germination and growth promotion in tomato as indicated by 118 % and 52 % more root-biomass under drought-free and drought-induced conditions, respectively. Bacillus amyloliquefaciens CBa_RA37 and B. megaterium RR10 displayed broad spectrum endophytism in tomato. Bacterization of tomato with cactus endophyte showed altered oxidative status, stomatal and photosystem II functioning, internal leaf temperature and relative water content suggestive of physiological de-stressing from moisture stress. Activity of oxidative stress enzymes such as guaiacol peroxidase and catalase was also indicative of endophyte assisted de-stressing of tomato. Re-irrigation on 20-days of drought infliction showed 86.9% recovery of B. amyloliquefaciens CBa_RA37 primed tomato when non-primed plantlets succumbed. The cactus endophytic bacterial strain B. amyloliquefaciens CBa_RA37 showed promise for low-cost, efficient and environmentally friendly bio-inoculant technology to mitigate drought in arid zones of Asian and African continents.

Water-sensitive Properties of Shear Strength of Bijie Red Clay under Direct shear Testing

In order to study the water-sensitive properties of Bijie red clay, the basic physical index test and direct shear test of different water content samples were carried out. The relation between shear strength index and water content of red clay was obtained, and the influence of critical water content on strength was analyzed. The testing results show that the shear strength index of Bijie red clay turns around the natural moisture content, because of the cracks generated with water losing. Then the functional relationship between cohesive force, internal friction angle and water content was established. Based on this relationship, it can reflect the quantitative influence of water content on intensity.

BtM, a Low-cost Open-source Datalogger to Estimate the Water Content of Nonvascular Cryptogams.

Communities of nonvascular cryptogams, such as mosses or lichens, are an important part of the Earth's biodiversity, contributing to the regulation of the carbon and nitrogen cycles in many ecosystems. Being poikilohydric organisms, they do not actively control their internal water content and need a humid environment to activate their metabolism. Therefore, studying water relationships of nonvascular cryptogams is crucial to understand both their diversity patterns and their functions in the ecosystems. We present the BtM datalogger, a low-cost open-source platform for the study of the water content of nonvascular cryptogams. The datalogger is designed to measure ambient temperature, humidity, and conductance from up to eight samples simultaneously. We provide a design for a printed circuit board (PCB), a detailed protocol to assemble the components, and the required source code. All this makes the assembly of the BtM datalogger accessible to any research group, even to those without previous specialized knowledge. Therefore, the design presented here has the potential to help popularize the use of this type of device among ecologists and field biologists.

Determination of Internal Density Profiles of Smart Acrylamide-Based Microgels by Small-Angle Neutron Scattering: A Multishell Reverse Monte Carlo Approach.

The internal structure of nanometric microgels in water has been studied as a function of temperature, cross-linker content, and level of deuteration. Small-angle neutron scattering from poly( N-isopropylmethacrylamide) (volume phase transition ≈ 44 °C) microgel particles of radius well below 100 nm in D2O has been measured. The intensities have been analyzed with a combination of polymer chain scattering and form-free radial monomer volume fraction profiles defined over spherical shells, taking polydispersity in size of the particles determined by atomic force microscopy into account. A reverse Monte Carlo optimization using a limited number of parameters was developed to obtain smoothly decaying profiles in agreement with the experimentally scattered intensities. The results are compared to the swelling curve of microgel particles in the temperature range from 15 to 55 °C obtained from photon correlation spectroscopy (PCS). In addition to hydrodynamic radii measured by PCS, our analysis provides direct information about the internal water content and gradients, the strongly varying steepness of the density profile at the particle-water interface, the total spatial extension of the particles, and the visibility of chains. The model has also been applied to a variation of the cross-linker content, N, N'-methylenebisacrylamide, from 5 to 15 mol %, providing insight on the impact of chain architecture and cross-linking on water uptake and on the definition of the polymer-water interface. The model can easily be generalized to arbitrary monomer contents and types, in particular mixtures of hydrogenated and deuterated species, paving the way to detailed studies of monomer distributions inside more complex microgels, in particular core-shell particles.

Variability in obsidian structural water content and its importance in the hydration dating of cultural artifacts

The process of dating ancient obsidian artifacts converts the quantity of surface diffused molecular water to a calendar age using an experimentally derived diffusion coefficient predicted from glass composition. The internal structural water content of rhyolitic obsidian has been identified as a highly influential variable that controls the rate of water diffusion at ambient temperature. We demonstrate through the use of infrared spectroscopy and specific gravity (density) measurements on samples from 34 obsidian sources that total structural water (H2Ot) concentrations between sources can range from 0.07% to 1.66%. Structural water concentration within individual sources may also vary significantly and impact the accuracy of estimated ages for artifact manufacture if not properly monitored. A calibration for the water determination on individual samples by density measurement is developed here and the impact of structural water variation on obsidian chronometric dates is discussed.

Asymptotic analysis for the inlet relative humidity effects on the performance of proton exchange membrane fuel cell

In order to study the inlet relative humidity (RH) effects on the performance of proton exchange membrane fuel cell (PEMFC), the inlet humidification efficiency (IHE) model is proposed. The total water content of PEMFC is consisted of two parts including the internal electro-migration water content and the external water content of the humidified gas. The dynamic inlet humidification efficiency is derived. The current density of PEMFC is calculated by the incorporating parameters including inlet humidification efficiency and water content of the humidified gas in the IHE model. Firstly, the schedule diagram of calculation is given and the geometric model is established according to actual size of PEMFC. The computational meshes are partitioned by using the software (Gambit). The IHE model is imported into the computational fluid dynamics software (Fluent). Secondly, the experimental system is established and experiments have been done at the operating temperature of 70 °C and at 40% RH, 55% RH, 70% RH, 85% RH and 100% RH, respectively. Finally, the contours of H2O molar concentrations (both in anode channels and cathode channels), membrane water content (MWC) and polarization curves of the IHE model, the Fluent model and experimental are compared and analyzed at above experimental conditions. The results show that the species distribution uniformities of the IHE model such as H2O molar concentrations (both in anode channels and cathode channels) and MWC are the best when the PEMFC at 100% RH. When the operating temperature is 70 °C (40% RH and 350mA/cm2), the accuracy of the IHE model is improved by 79% compared with the Fluent model. When the operating temperature is 70 °C (40% RH and 350mA/cm2), the inlet humidification efficiency reaches 57%.

Effect of internal water content on carbonation progress in cement-treated sand and effect of carbonation on compressive strength

This study investigates the effect of internal water content in cement-treated sand on carbonation progress and the effect of carbonation on compressive strength. To alter the internal water content, specimens were cured under three conditions: sealed, drying, and water sprayed. The carbonation coefficient, which was determined by a phenolphthalein spray test, decreased as the internal water content increased because of water sprayed. However, a thermal analysis revealed that the amounts of portlandite consumed and calcium carbonate generated by carbonation exhibited dissimilar trends: the amount of generated calcium carbonate was the maximum when there was a small increase in water content by water sprayed. Further increments in water content significantly lowered the amount of generated calcium carbonate. The measured compressive strength increased linearly with the amount of calcium carbonate. This implies that the amount of calcium carbonate is a good indicator of the effect of carbonation on the strength development of cement-treated sand and that both these quantities are affected by the internal water content.

Proton spectroscopy of the thalamus in a homogeneous sample of patients with easy-to-control juvenile myoclonic epilepsy.

ObjectiveJuvenile myoclonic epilepsy (JME) is a subtype of genetically determined generalized epilepsy that does not present abnormalities on conventional magnetic resonance imaging. The aim of this study was to identify metabolic alterations in the thalamus in a clinically homogeneous sample of patients with easy-to-control JME, using short-echo time proton magnetic resonance spectroscopy (MRS).Materials and MethodsWe performed single-voxel (2 cm × 2 cm × 2 cm), short-echo time (TE = 35 ms) proton MRS of the thalamus in 21 patients with JME and in 14 healthy age-matched controls. We quantified N-acetylaspartate (NAA), total NAA, creatine (Cr), choline, and myo-inositol (MI), as well as the sum of glutamate and glutamine signals, all scaled to internal water content, and we calculated metabolite ratios using Cr as a reference. Values of p < 0.05 were considered significant.ResultsThe MI level and the MI/Cr ratio were significantly lower in the thalami of patients diagnosed with JME than in those of the controls. Other metabolites and their ratios did not differ significantly between the two groups.ConclusionIn our sample of 21 JME patients, we identified lower levels of MI in the thalamus. No significant abnormalities were observed in the concentrations or ratios of other metabolites.

Poly High Internal Phase Emulsion for the Immobilization of Chemical Warfare Agents.

We report a facile method for the absorption (characterized by the weight/weight swelling degree, Q) of a variety of chemical warfare agents (CWAs); including sulfur mustard (HD) (Q = 40) and V-series (VM, VX, i-Bu-VX, n-Bu-VX) of nerve agents (Q ≥ 45) and a simulant, methyl benzoate (Q = 55), through the use of a poly(styrene-co-vinyl benzyl chloride-co-divinylbenzene) lightly cross-linked poly high internal phase emulsion (polyHIPE). By varying the vinyl benzyl chloride (VBC) content and the volume of the internal phase of the precursor emulsion it is demonstrated that absorption is facilitated both by the swelling of the polymer and the uptake of liquid in the pores. In particular the sample prepared from a 95% internal emulsion water content showed rapid swelling (<5 min to total absorption) and the ability to swell both from a monolithic state and from a compressed state, making these systems ideal practical candidates for the rapid immobilization of CWAs.

Changing profiles of bound water content and distribution in the activated sludge treatment by NaCl addition and pH modification

Currently the dewatering of activated sludge from wastewater treatment plants is a problem not well solved. Extracellular polymeric substances (EPS), including loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS), are highly hydrated biopolymers and play important roles in sludge dewatering. In the present work, two types of treatments, i.e., salt addition and pH modification, were proposed to evaluate the effects of bound water content and its distribution on the dewatering performance of activated sludge. Results show that the bound water content in activated sludge was deeply related to the floc structures and EPS compositions. Both salt addition and acid treatment altered the flocculated matrix and increased the contents of LB-EPS, resulting in the release of trapped water and reduction in sludge volume. In addition, the chemical treatments also affected the distribution of bound water. The internal water content increased upon the dose of NaCl, leading to a decreased water content trapped in EPS. Hence, salt addition caused a slower filtration rate, but did not effectively decrease the total water content, although the EPS were decomposed. Under acidic conditions, cell lysis helped to release the intracellular water and further enhance the sludge dewatering performance. In contrast, conditioning with low-dosage alkali increased the bound water content and deteriorated the sludge dewaterability. Therefore, an in-depth investigation into the mechanisms is useful to optimize the activated sludge dewatering process.

Modified hydrogels based on poly(2-hydroxyethyl methacrylate) (pHEMA) with higher surface wettability and mechanical properties

Soft contact lenses made with poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels modified with various comonomers such as N-vinyl pyrrolidone, methacrylic acid, glycidyl methacrylate, and glycerol monomethacrylate were prepared to investigate the effect of adding the comonomer on the water content, surface wettability, and tensile modulus. These polymers were synthesized by the free radical polymerization of 2-hydroxyethyl methacrylate (HEMA) with the comonomers in the presence of divinyl benzene used as the crosslinker and azobisisobutyronitrile as the initiator. The chemical structure and transmittance of the hydrogels were analyzed by FTIR and UV/Vis spectrophotometers. The surface wettability and tensile modulus were also studied by measuring the contact angle and tensile modulus with a universal testing machine (UTM). Regarding the properties of water in the hydrogels, the ratio between free to bound water was investigated using differential scanning calorimetry (DSC). As the concentration of crosslinker in the hydrogels increases, the tensile strength also increases, whereas the internal water content and contact angle decrease. The effect of the comonomer composition of the hydrogels was also investigated to optimize the various properties of these comonomers for soft contact lenses.

Modeling and analysis of internal water transfer behavior of PEM fuel cell of large surface area

The PEM fuel cell has been widely used in the area of transportation and power station. The surface area of a fuel cell is enlarged to provide high enough power but the problem of analysis of internal water content behavior follows tightly. Many scholars have investigated the mathematical models of a small fuel cell and validated them through experiment. Besides, the introduction of AC impedance technique helps find relationship between water content and membrane resistance. Based on their research, an approach is put forward in this paper to model and analyze the internal water content behavior in a fuel cell of large surface area. For large surface area, three special cases are studied according to the actual operating states at cathode outlet. The first case applies to a fuel cell with no saturated water vapor at both outlets while in the second and third case, the fuel cell is divided into an electrochemical reaction zone and no reaction zone owing to emerging liquid water. The indicators of model are the water content profile inside membrane and the total membrane resistance. The simulation results show that the net water transfer coefficient has significant influence on the performance of the membrane and the constituents of anode side are easy to be varied. In addition, when the fuel cell is operated in counter-flow mode with emerging liquid water, the only back diffusion of water from cathode to anode helps improve the state of the membrane.

Cryopreservation of Coffea arabica L. Zygotic Embryos by Vitrification

As a consequence of the difficulty in conventional coffee seed storage, biotechnological alternatives such as cryopreservation have been investigated. The objective of this study was to develop a protocol for the cryopreservation of Coffea arabica L. (cv. ‘Catuaí Vermelho’ - IAC 144) zygotic embryos by vitrification. For the cryopreservation study, the embryos were immersed in Plant Vitrification Solution 2 at different times (0, 10, 25, 50, 100, and 250 min) and two temperatures (0 and 25 °C). Subsequently, the best thawing time was determined in a water bath (1, 3, 5 minutes or directly in Recovery Solution). An anatomical study was conducted on non-stored and stored embryos, with or without the use of Plant Vitrification Solution 2. The immersion in cryoprotectant solution for 100 min at 0 °C allows embryo cryopreservation. Embryos can be directly thawed in Recovery Solution after storage in liquid nitrogen. It was observed that Plant Vitrification Solution 2 reduced internal water content in the cells, allowing subsequent embryo growth resumption.