•Relevant studies of gas production from natural gas hydrate are reviewed.•The limitations, challenges and some questions of NGH are discussed.•NGH exploitation are mainly carried out from numerical ...simulation, experiments and field tests.•Characteristics of the flow, heat and mass transfer are still not comprehensively recognized.•Environmental impacts and economics are still unclear and await further research.
Natural gas hydrates (NGHs), which extensively exist in sea-floor and permafrost regions, are considered as an alternative energy in the future for the fossil fuels approaching depletion with the gradually increasing energy consumption. Because of the particularity of NGH stabilizing only in the conditions of the high pressure and the low temperature, the exploitation of NGH is distinguished from those of petroleum and natural gas. Researchers over the world are devoting themselves to developing the technologies of NGH exploitation. However, till now, few NGH exploitation technology is identified and employed to exploit commercially NGH. Although there do be two cases of short-term NGH exploitation in Mackenzie Delta (CAN), Alaska North Slope (USA) and Nankai Trough (JAP) in the past 10years. It is mainly because some characteristics of the flow (gas, water, gas-hydrate slurry, quicksand, etc.), the issues of heat and mass transfer, the risk assessment and the economic evaluation are still not comprehensively recognized. Presently, the researches of NGH exploitation are mainly carried out from three aspects, numerical simulation and analysis, experimental simulation and field trial exploitation for the different technologies. In this paper, we comprehensively review the relevant studies of NGHs and propose our comments. We not only represent the achievements for the NGH exploitation researches, but also discuss the limitations and challenges, raise some questions and put forward some suggestions from our points of view.
Isogeometric analysis is an innovative numerical paradigm with the potential to bridge the gap between Computer-Aided Design and Computer-Aided Engineering. However, constructing analysis-suitable ...parameterizations from a given boundary representation remains a critical challenge in the isogeometric design-through-analysis pipeline, particularly for computational domains with complex geometries, such as high-genus cases. To tackle this issue, we propose a multi-patch parameterization method for computational domains grounded in the singular structure of cross-fields. Initially, the vector field functions over the computational domain are solved using the boundary element method. The cross-field is then obtained through the one-to-one mapping between the vector field and the cross-field. Subsequently, we acquire the position information and topological connection relations of singularities and streamlines by analyzing the singular structure of the cross-field. Moreover, we introduce a simple and effective method for computing streamlines. We propose a novel segmentation strategy to divide the computational domain into several quadrilateral NURBS sub-patches. Once the multi-patch structure is established, we develop two methods to construct analysis-suitable multi-patch parameterizations. The first method is a direct generalization of the barrier function-based approach, while the second method yields smoother parameterizations by incorporating the interface control points of sub-patches into the optimization model. Numerical experiments demonstrate the effectiveness and robustness of the proposed method.
Metal-organic frameworks (MOFs) have been widely applied for pollutants removal in water. However, the powdered MOFs are always suffered from aggregation during use and difficult collection after ...use. These problems discount their efficiency and inhibit their reusability. In this work, Zr-based MOF (UiO-66) was successfully imprisoned into a water-stable polyacrylonitrile (PAN) substrate by electrospinning. The containing UiO-66 hybrid membrane was confirmed by instrumental characterizations and its stability was also investigated by ICP-OES analysis. The obtained composite membrane can efficiently remove both arsenite (AsIII) and arsenate (AsV) from water under natural pH conditions. The adsorption kinetic fitted well with pseudo-second-order model and was dominated by chemisorption. Its adsorption isotherm can be described by Langmuir model. The maximal adsorption capacities of the hybrid membrane for As(V) and As(III) were 42.17 mg/g and 32.90 mg/g, respectively. Our results demonstrated that the MOFs-dispersed electrospun nanofiber membrane can greatly inherit the MOFs’ original adsorption properties and exhibits good regenerability without loss of MOFs. Electrospinning is an effective and practical method for the preparation of MOFs hybrid membrane, which makes the composite very easy to be collected after use.
Electrospun MOFs hybrid nanofibers remove arsenic efficiently. Display omitted
●A stable MOFs containing hybrid membrane was prepared by electrospinning.●The membrane exhibited efficient adsorption ability for both As(III) and As(V).●The inherit properties of the contained MOFs can be remained without loss from the fibers.●The hybrid membrane can be easily collected and environment-friendly recycled after use.
Engineering the electronic band structure of material systems enables the unprecedented exploration of new physical properties that are absent in natural or as-synthetic materials. Half metallicity, ...an intriguing physical property arising from the metallic nature of electrons with singular spin polarization and insulating for oppositely polarized electrons, holds a great potential for a 100% spin-polarized current for high-efficiency spintronics. Conventionally synthesized thin films hardly sustain half metallicity inherited from their 3D counterparts. A fundamental challenge, in systems of reduced dimensions, is the almost inevitable spin-mixed edge or surface states in proximity to the Fermi level. Here, we predict electric field-induced half metallicity in bilayer A-type antiferromagnetic van der Waals crystals (i.e., intralayer ferromagnetism and interlayer antiferromagnetism), by employing density functional theory calculations on vanadium diselenide. Electric fields lift energy levels of the constituent layers in opposite directions, leading to the gradual closure of the gap of singular spin-polarized states and the opening of the gap of the others. We show that a vertical electrical field is a generic and effective way to achieve half metallicity in A-type antiferromagnetic bilayers and realize the spin field effect transistor. The electric field-induced half metallicity represents an appealing route to realize 2D half metals and opens opportunities for nanoscale highly efficient antiferromagnetic spintronics for information processing and storage.
Surgery is one of the main effective strategies for the treatment of solid tumors, but high postoperative recurrence is also the main cause of death in current cancer therapy. The prevention of ...postoperative hepatocellular carcinoma (HCC) recurrence is a clinical problem that needs to be solved urgently. At present, there are still some problems to be solved, such as, how to achieve free drugs to target the site of surgical resection; develop a strategy for the simultaneous administration of multiple drugs to inhibit postoperative recurrence; and provide the appropriate animal model that mimics the process of postoperative HCC recurrence. In this study, we used a facile and reproducible method to successfully prepare amphiphilic Janus nanoparticles (JNPs). In order to improve targeting of the JNPs to residual HCC cells after surgery, we modified the side of gold nanorods (GNRs) with lactobionic acid (LA), thus creating LA-JNPs. This provided an active and targeted co-delivery system for hydrophilic and hydrophobic drugs in separate rooms, thus avoiding mutual effects. Next, we established two models to simulate postoperative HCC recurrence: a subcutaneous postoperative recurrence model based on patient-derived tumor xenograft (PDX) tissues and a postoperative recurrence model of orthotopic HCC. By applying these models, the enhanced permeability and retention effect (EPR) based tumor targeting and LA based active targeting can jointly promote the enrichment and uptake of JNPs at tumor site. LA-JNPs represented an efficient targeting system for the co-delivery of Sorafenib/Doxorubicin with an optimized anti-recurrence effect and significantly improved the survival of mice during treatment for postoperative recurrence.
The realization of multiferroic materials offers the possibility of multifunctional electronic device design. However, the coupling between the multiferroicity and piezoelectricity in Janus materials ...is rarely reported. In this study, we propose a mechanism for manipulating valley physics by magnetization reversing and ferroelectric switching in multiferroic and piezoelectric material. The ferromagnetic VSiGeP4 monolayer exhibits a large valley polarization up to 100 meV, which can be effectively operated by reversing magnetization. Interestingly, the antiferromagnetic VSiGeP4 bilayers with AB and BA stacking configurations allow the coexistence of valley polarization and ferroelectricity, supporting the proposed strategy for manipulating valley physics via ferroelectric switching and interlayer sliding. In addition, the VSiGeP4 monolayer contains remarkable tunable piezoelectricity regulated by electron correlation U. This study proposes a feasible idea for regulating valley polarization and a general design idea for multifunctional devices with multiferroic and piezoelectric properties, facilitating the miniaturization and integration of nanodevices.
The health risks and toxicity of heavy metals (HMs) in PM2.5 are not only associated with their total amounts, but also with their species and bioaccessibility. In this study, the speciation ...(fractions) and bioaccessibility of HMs (Pb, Cd, Cr, Cu and Zn) as well as their correlations in fine particulate matter (PM2.5) samples from four seasons were studied. A sequential extraction procedure was applied to divide the studied HMs into four fractions: acid-soluble fraction (F1), reducible fraction (F2), oxidative fraction (F3) and residual fraction (F4). The simulated body fluids (gastrointestinal and lung phases) were used for in vitro tests in order to evaluate the bioaccessibility of HMs. The distribution of HMs in PM2.5 was season and element dependent. It was found that Zn was the most abundant element among the five measured metals and followed by Pb, Cu, Cr and Cd. The total contents of each HM in different seasons were in the following order: winter > autumn > spring > summer. The studied HMs were mainly concentrated in acid-soluble fraction (F1) with high bioaccessibility (p < 0.05) except for Cr. Zn, Pb and Cu possessed the highest bioaccessibility in summer while Cd and Cr were the highest in winter. In vitro tests indicated that HMs in PM2.5 were much more accessible to gastrointestinal fluids rather than lung phase (Gamble's solution). A significant correlation was found between the results from the optimized BCR sequential extraction and solubility bioaccessibility research consortium (SBRC). The fractions extracted by SBRC were consistent with the first two fractions extracted by the sequential extraction method.
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•BCR sequential extraction and in vitro test were used to study HMs in PM2.5.•Pb, Cd, Cu and Zn in PM2.5 were mainly existed in F1 with high bioaccessibility.•Bioaccessibility and speciation of HMs in PM2.5 varied with different seasons.•Correlation was found between BCR sequential extraction and SBRC method.
High bioaccessibility of HMs in PM2.5 and the significant correlation of SBRC/BCR sequential extraction were discovered.
Gas hydrate has great application potential in gas separation, energy storage, seawater desalination,
etc.
However, the intensity of mass and heat transfer is not enough to meet the needs of ...efficient hydrate synthesis. Nanoparticles, different from other liquid chemical additives, are considered as effective additives to promote hydrate formation due to their rich specific surface area and excellent thermal conductivity. This work summarizes the effect of the nanoparticles on the thermodynamics and kinetics of hydrate formation. And also, this work probes into the mechanism of the effect of the nanoparticles on the formation of hydrate as well as provides some suggestions for future research. It is found that it's difficult for nanoparticles to effectively promote the formation of the gas hydrate without the use of surfactants, because the adhesion characteristics of the nanoparticles make them easily agglomerate or even agglomerate in solution. In addition, at present, the research on the influence of nanoparticles on the formation and decomposition of natural gas hydrate is still very fragmented, and the micro mechanism of the influence is not clear, which requires more systematic and specific research in the future. At the same time, the development of nanoparticles that can promote the formation of natural gas hydrate should also become the focus of future research.
The use of nanoparticles and their effects on thermodynamics and kinetics during the hydrate formation process is summarized. For their application in drilling fluid and cement slurry, it is found nanoparticles must be used in conjunction with surfactants to be effective.
With continuing improvements in the efficiencies of the flue gas pollution control devices, a greater proportion of mercury emitted from coal fired power plants is in the recovered byproducts, such ...as fly ash and desulfurization gypsum. The leaching ability and bioavailability of mercury are related with its speciation and finally determine the total emission of mercury from power plants. Therefore, it is important to understand the speciation of mercury in the byproducts. In this study, mercury in the gypsum samples from eleven power plants in Hebei Province, China was determined in five sequential extracts representing fractionation of mercury species, namely water soluble fraction (WS, F1), ion-exchangeable fraction (IE, F2), acid soluble fraction (AS, F3), elemental fraction (EF, F4) and sulfide fraction (SF, F5). The leaching ability and the distribution of mercury in the various fractions from different power plants were examined. The results showed that mercury was dominantly in elemental fraction, and the leaching ability as well as the fraction distribution of mercury varied with samples from different power plants. The rapid release and releasable mercury in gypsum which shouldn’t be overlooked were taken into account for the estimation of mercury emission from coal fired power plants. Three models, including Mass Balance model (MB), Emission modification factors model (EMF) and Flue calculation model (FC), were also employed to estimate the possible mercury emission from flue gas in these studied power plants. A comparison of the results from the different models indicated variability among the different models. The mercury re-emission from gypsum to the environment is needed to address the important issue of further improvement of these models for estimation of mercury emission.
The cocrystal formation of indomethacin (IMC) and saccharin (SAC) by mechanical cogrinding or thermal treatment was investigated. The formation mechanism and stability of IMC–SAC cocrystal prepared ...by cogrinding process were explored. Typical IMC–SAC cocrystal was also prepared by solvent evaporation method. All the samples were identified and characterized by using differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) microspectroscopy with curve-fitting analysis. The physical stability of different IMC–SAC ground mixtures before and after storage for 7 months was examined. The results demonstrate that the stepwise measurements were carried out at specific intervals over a continuous cogrinding process showing a continuous growth in the cocrystal formation between IMC and SAC. The main IR spectral shifts from 3371 to 3,347cm−1 and 1693 to 1682cm−1 for IMC, as well as from 3094 to 3136cm−1 and 1718 to 1735cm−1 for SAC suggested that the OH and NH groups in both chemical structures were taken part in a hydrogen bonding, leading to the formation of IMC–SAC cocrystal. A melting at 184°C for the 30-min IMC–SAC ground mixture was almost the same as the melting at 184°C for the solvent-evaporated IMC–SAC cocrystal. The 30-min IMC–SAC ground mixture was also confirmed to have similar components and contents to that of the solvent-evaporated IMC–SAC cocrystal by using a curve-fitting analysis from IR spectra. The thermal-induced IMC–SAC cocrystal formation was also found to be dependent on the temperature treated. Different IMC–SAC ground mixtures after storage at 25°C/40% RH condition for 7 months had an improved tendency of IMC–SAC cocrystallization.
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