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This study was designed to investigate the relationship between the caloric value and salt tolerance of two varieties of Miscanthus sacchariflorus (Amur silvergrass: M127 and M022). The salt tolerance capacity, photosynthetic characteristics, Na+ and K+ uptake by the roots and aboveground parts, and caloric value of different parts of the aboveground parts were obtained under hydroponic conditions. The results showed that M022 was more tolerant to salt stress than M127 and the former had a higher photosynthetic efficiency as well as a lower aboveground Na+ accumulation, K+ efflux, and larger K+/Na+ ratio. The calorific values of stems, spear leaves, aging leaves, and functional leaves of the two varieties showed a decreasing trend with increasing NaCl concentration. At 270 mM NaCl, the calorific values of the stems, aging leaves, functional leaves, and spear leaves was reduced by 18.10%, 46.73%, 26.11%, and 18.35% for M022 and 41.99%, 39.41%, 34.82%, and 45.09% for M127 compared to the controls, respectively. We observed that the aging leaves of M022 had a faster decline rate in calorific value than those of M127, indicating that the aging leaves of M022 preferentially isolated the harmful Na+ ion, reduced its accumulation in other parts, and increased the K+/Na+ ratio in the corresponding parts, thus inhibiting the decrease in calorific value. Following this result, it can be inferred that M022 inhibited the decline in calorific values during stress by efficiently compartmentalizing the distribution of Na+ and K+. Our results provide a theoretical basis and technical support for the efficient cultivation of salt-tolerant energy plants in saline–alkaline soil. [ABSTRACT FROM AUTHOR]

Populus laurifolia is one of the most valuable tree species in the world and an important silvicultural tree species in the Xinjiang Uygur Autonomous Region, China. In July 2017, an unreported brown leaf spot disease was observed on P. laurifolia in Altay City, Xinjiang. The causal agent of this leaf spot disease was isolated, and Koch's postulates were performed to confirm its pathogenicity. Based on a morphological characterization and phylogenetic analyses, the causal organism was identified to be a fungal species, Coniolariella gamsii. The optimum mycelial growth conditions for C. gamsii are on PLPDA (Populus leaves potato dextrose agar) medium, at 28 °C, in the dark. The sporulation time when using PLPDA medium (12 days) is much less than that for PDA medium (25 days). Pathogenicity tests revealed that C. gamsii can also infect two other Populus species (P. bolleana and P. tomentosa). This is the first report of C. gamsii causing brown leaf spot disease on P. laurifolia, and the optimum culture and sporulation conditions have also been optimized for the first time. This study provides a theoretical basis for the diagnosis of this disease and the monitoring of the disease's occurrence and epidemic status. [ABSTRACT FROM AUTHOR]

Various comorbidities associated with COVID-19 add up in severity of the disease and obviously prolonged the time for viral clearance. This study investigated a novel ultrasensitive MAGLUMI® SARS-CoV-2 Ag chemiluminescent immunoassay assay (MAG-CLIA) for diagnosis and monitoring the infectivity of COVID-19 patients with comorbid conditions during the pandemic of 2022 Shanghai. Analytical performances of the MAG-CLIA were evaluated, including precision, limit of quantitation, linearity and specificity. Nasopharyngeal specimens from 232 hospitalized patients who were SARS-CoV-2 RT-qPCR positive and from 477 healthy donors were included. The longitudinal studies were performed by monitoring antigen concentrations alongside with RT-qPCR results in 14 COVID-19 comorbid participants for up to 22 days. The critical antigen concentration in determining virus infectivity was evaluated at the reference cycle threshold (Ct) of 35. COVID-19 patients were well-identified using an optimal threshold of 0.64 ng/L antigen concentration, with sensitivity and specificity of 95.7% (95% CI: 92.2–97.9%) and 98.3% (95% CI: 96.7–99.3%), respectively, while the Wondfo LFT exhibited those of 34.9% (95% CI: 28.8–41.4%) and 100% (95% CI: 99.23–100%), respectively. The sensitivity of MAG-CLIA remained 91.46% (95% CI: 83.14–95.8%) for the samples with Ct values between 35 and 40. Close dynamic consistence was observed between MAG-CLIA and viral load time series in the longitudinal studies. The critical value of 8.82 ng/L antigen showed adequate sensitivity and specificity in evaluating the infectivity of hospitalized convalescent patients with comorbidities. The MAG-CLIA SARS-CoV-2 Ag detection is an effective and alternative approach for rapid diagnosis and enables us to evaluate the infectivity of hospitalized convalescent patients with comorbidities. [ABSTRACT FROM AUTHOR]

The traditional strategy for isolating cellulose nanomaterials requires various chemicals and a high energy input, while achieving a low product yield owing to lignin removal during pulping and bleaching. Here, we propose a green ethanol pretreatment process with a synergistic effect using ultrasound and FeCl 3 to produce lignocellulose nanofibrils (LCNF) with a high yield (over 67 %) from thermomechanical pulp. Notably, a high-aspect-ratio LCNF with uniformly distributed lignin nanoparticles, a high lignin content, and excellent thermostability (T max > 330 °C) with a typical cellulose I crystalline structure were successfully obtained. In addition, reduced distillation can easily retrieve the FeCl 3 solution and ethanol, reducing reagent waste. In general, FeCl 3 -catalyzed ethanol pretreatment can serve as a sustainable and environmentally friendly approach for converting sustainable lignocelluloses into high value-added nanomaterials. Moreover, the obtained LCNF can be applied in diverse fields. [ABSTRACT FROM AUTHOR]

Herein, the effect of the ordered phases and microstructure of 6.5 wt% Si electrical steel recrystallized and quenched at different cooling rates on its iron loss is investigated. The varied cooling rate barely influences the grain size and the precipitation of Cu but affects the magnetic domain significantly. A higher cooling rate is associated with greater residual stress and hence, leads to an increase in the width of the magnetic domain. In terms of the ordered phases, the quantity of B2 first decreases and then increases with a rising cooling rate while the quantity of D03 decreases. Meanwhile, the size of B2 antiphase domains reduces, while the D03 antiphase domains are either too fine to be observed or absent at higher cooling rates. The increased residual stress, the refinement of B2 antiphase domains, and the associated larger pinning effect on the migration of magnetic domain walls jointly lead to higher hysteresis loss. In addition, the increased width of the magnetic domain results in a larger anomalous loss. Both effects give rise to an overall increase in the iron loss P10/50. [ABSTRACT FROM AUTHOR]

Since the implementation of several pilot production tests were in natural gas hydrate (NGH) reservoirs in terrestrial and marine settings, the study of NGH has entered a new stage of technological development for industrial exploitation. Prior to the industrial exploitation of any given NGH reservoir, the economic feasibility should be examined. The first step of economic evaluation of a NGH reservoir is to know whether its resource amount meets the requirement for industrial exploitation. Unfortunately, few relevant studies have been conducted in this regard. In this study, the net present value (NPV) method is employed to estimate the economic critical resources required for the industrial exploitation of NGHs under different production scenarios. Sensitivity analysis is also performed in order to specify the effects of key factors, such as the number of production wells, gas price, technological improvement and tax incentive, on the economic critical resources. The results indicate that China requires the lowest economic critical resource for a NGH reservoir to be industrially exploited, ranging from 3.62 to 24.02 billion m3 methane. Changes in gas price and tax incentives also play significant roles in affecting the threshold and timeline for the industrial exploitation of NGH. [ABSTRACT FROM AUTHOR]

Fault detection and diagnosis (FDD) technology plays an important role in maintaining the stable and efficient operation of the chiller system, and screening the most important parameters for FDD is the key step that is far more critical than the selection of diagnosis methods. This study proposes a feature importance ranking method based on random forest (RF) to improve the FDD performance of a chiller while using fewer sensors, which is proved to be effective and efficient. When the product type or sensor configuration changes, the proposed method can be used to rank the feature importance efficiently based on the new fault simulation data, the FDD model using the features that are highly significant to fault indication and diagnosis can be established and the diagnosis performance can be promoted, accordingly. For verification and validation, fault simulation experiments of normal operation, refrigerant leakage and refrigerant overcharge have been carried out on a 200-ton variable-speed screw chiller. The importance of 15 parameters obtained from the experiments is ranked according to their contributions to the diagnosis of the corresponding faults using the proposed RF importance ranking method. Different critical features have also been discussed in terms of FDD performance and expertise knowledge for screw chiller. The optimal feature set for the investigated faults of the chiller is found to have just four parameters: Refrigerant Discharge Temperature (TR_dis), Condenser Water Temperature Difference (TWCD), Evaporator Water Temperature Difference (TWED) and Compressor Power (kW). The overall diagnostic accuracy reaches 99.90%, higher than using all the parameters. Fewer sensors achieve better performance. [ABSTRACT FROM AUTHOR]

Current research on chiller fault detection and diagnosis (FDD) is usually based on the multi-classification method for mixed multiple fault types. The establishment of a multi-classification FDD model requires obtaining extensive test data of normal operation and multiple common faults at different fault levels, so the cost-to-benefit ratio will not be accepted. In addition, because of the information interference between different types of fault data, FDD model is hard to avoid over-fitting or under-fitting, and there may be an intolerable high false alarm rate existing in product application. Therefore, it is difficult to promote FDD in actual chiller product applications. This paper proposes an inverse fault detection and diagnosis (IFDD) strategy, which is based on the characteristics of the target fault (the fault to be concerned) to establish a two-classification fault diagnosis model. Compared with the multi-classification method, the amount of fault test data required by the two-classification methods to realize fault diagnosis can be greatly reduced. With IFDD strategy, the detection and diagnosis are completed simultaneously, while fast calculation speed, high diagnosis accuracy rate and low false alarm rate are achieved. The core of the IFDD strategy is to concentrate resources to capture the characteristics of the target fault, and no longer classify other types of faults and normal operating conditions, so it can avoid the influence of information interference between multiple types of fault data in the fault diagnosis model. In order to verify the feasibility of this strategy, a 200 ton variable-speed screw chiller has been tested on the laboratory, and a database of normal operation, refrigerant leakage, refrigerant overcharge faults, and a new operating condition of insufficient cooling water flow is initially established. Based on the sensors configured by the chiller unit and using the exponentially weighted moving-average (EWMA) control chart for IFDD, the model's fault diagnosis accuracy for the target fault reaches 100%, and no false alarm appears after the transition period. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lignocellulose-based hydrogel-Pd nanoparticles reactor system was synthesized. • Porous LCG/Pd NPs reactor provided a simultaneous adsorption-catalysis strategy. • Catalytic k value of LCG/Pd NPs reactor is 38 times higher than that of Pd NPs. • LCG/Pd NPs reactor exhibited good mechanical strength in separation of catalysts. The separation and reusability of nano-catalysts are paramount for their high-efficiency and low-cost use. Herein, lignocellulose hydrogels (LCG), were fabricated and served as the host matrix for in-situ generated palladium nanoparticles (Pd NPs), creating hydrogel-based Pd NPs reactor systems. The lignocellulose hydrogel-based Pd NPs (LCG/Pd NPs) reactor system possesses the following unique features: (1) lignin present in LCG acts as a "green" reducing agent so that Pd NPs are formed in situ; (2) the in-situ generated Pd NPs are well dispersed in the LCG structure via complexation; (3) the simultaneous adsorption-catalysis process concept is very effective for pollutant remedy: the adsorption of pollutants on the porous LCG effectively increases the pollutant concentration on the reaction sites, where the Pd NPs are co-located, enhancing the catalytic reactions; as a result, a much higher catalytic reaction rate is observed; (4) the LCG/Pd NPs reactor systems are readily reused/recycled after each use. As proof of this concept, the catalytic performance of the LCG/Pd NPs reactor system was demonstrated by the catalytic reduction of toxic heavy metal ions (Cr6+) and organic dye (methyl orange). Results showed that the novel LCG/Pd NPs reactor system exhibited much increased catalytic reduction rates: the pseudo-first-order rate constant (k) is 118 times higher (from 0.018 to 2.129 min−1 at 25 °C) for MO, and 38 times higher (from 0.008 to 0.304 min−1 at 25 °C) for Cr6+, in comparison with the control, under otherwise the same conditions. [ABSTRACT FROM AUTHOR]

The carcass layer inside a flexible marine pipeline is a large-angle spiral structure with a complex cross-section. A carcass resists radial loads and prevents flexible pipelines from collapsing under extreme hydrostatic pressures. The accurate evaluation of the critical collapse pressure of a carcass under external pressure is crucial for the safe design of flexible pipelines. Because of the complex cross-section of the carcass, the internal surface of the carcass slides and contacts adjacent layers under external loads, which complicates the analysis. Therefore, the complex cross-section of the carcass is often simplified into a uniform section with a fixed thickness during analysis. In this study, parametric models of the carcass with different cross-sectional parameters were established, and the radial stiffness of the carcass under symmetric radial compression was calculated numerically. Next, the calculated equivalent radial stiffness was introduced into the analytical model to obtain geometric coefficients with different cross-sectional parameters. Finally, symbolic regression was used to derive a mathematical equation relating the equivalent thickness and critical cross-sectional parameters of the carcass. The results showed that the Minimum error in the buckling eigenvalue between the equivalent models and full carcass layer model was 6.2 %, the error in the critical collapse pressure was 14.5 %. Meanwhile, the influence of different parameters on the critical collapse pressure of the carcass was discussed. [ABSTRACT FROM AUTHOR]

Although natural gas hydrate is taken a potential energy resource, public concerns over environmental risks associated with hydrate exploitation are also growing, especially possible methane leakage to seafloor. However, whether hydrate exploitation can trigger disastrous methane blowout remains not well addressed. Overlying fine-grained sediments with poor seepage capacity are typically assumed to be good seals for methane. Yet, this view may be challenged when considering the geomechanical response of marine sediments, since sediment failure may provide new high-permeability pathways for methane flow. In this research, a new fracture module is supplemented into the Tough + Hydrate simulator to consider hydraulic fracturing of marine sediments. The modified simulator is employed to investigate methane behavior in the exploitation of hydrate reservoirs overlain by fine-grained sediments via the method of depressurization accompanied by warm water injection. Results suggest that overlying fine-grained sediments cannot necessarily seal methane during hydrate exploitation. The direct cause is that water injection elevates pore pressure above the critical stress of marine sediments and generates fractures. The fractured sediments provide pathways for the flow of mobile methane released from hydrate decomposition. Compared with control groups of simulations without the module executed, the results indicate that ignoring the fracturing process may cause significant underestimation of methane leakage when overlying fine-grained sediments exist. In addition, the results of simulations for the Shenhu area suggest that 0.3546–1.5432 Tg/yr may be leaked to the ocean with large-scale commercial hydrate exploitation in this area, contributing little to the global carbon budget. • A new fracture module is supplemented in Tough + Hydrate simulator to consider hydraulic fracturing of marine sediments. • The methane behavior in hydrate exploitation is systematically investigated by the modified simulator. • Overlying fine-grained sediments cannot necessarily prevent methane leakage in hydrate exploitation. [ABSTRACT FROM AUTHOR]

The coexisting free gas within the hydrate stability zone is recognized by laboratory and field studies. The conventional resistivity method fails to obtain hydrate saturation in the sediment with gas hydrate and free gas because both of them are electrical insulators. Hydrate saturation can be obtained from a velocity log based on a certain rock physics model. However, few studies of rock physics have been conducted on gas and hydrate coexistence. In this study, a more realistic distribution of gas bubble size and inclusion aspect ratio was introduced into an effective medium model to elucidate how such coexistence affects velocity and attenuation at a broad-band frequency. The modeling results obtained indicate that such coexistence decreases P-wave velocity at low frequencies, while increases P- and S-wave velocities at high frequencies. The velocity decrease of P-wave at low frequencies is attributed to the overwhelming effect of gas bubble vibration, while it seems not to affect P-wave velocity at high frequencies significantly. Moreover, coexisting gas hydrate and free gas may strengthen P-wave attenuation at the broad-band frequency range. It is found that the damping of oscillating gas bubbles dominates P-wave attenuation at low frequencies, while squirt flow in the porous hydrate is more likely to contribute to P-wave attenuation at high frequencies. Hydrate morphology is also a significant factor affecting P-wave velocity and attenuation at high frequencies. This research reveals that rock physics modeling can provide insight into how to characterize the coexisting gas hydrate and free gas as referring to the acoustic velocity and attenuation at seismic, sonic, and ultrasonic frequencies. • Acoustic properties of coexisting gas hydrate with free gas are investigated. • The coexistence decreases P-wave velocity at low frequencies. • The coexistence strengthens P-wave attenuation at the whole frequency range. • The proposed model considers gas bubble size distribution in the sediments. [ABSTRACT FROM AUTHOR]

Abstract Two ~1000 cm long sediment cores were recovered from the Sea of Marmara, one with the occurrence of gas hydrates in the Western High, and the other without hydrates in the Cinarcik Basin. Differences in mineralogical and chemical compositions have been identified between the two sediment cores. Based on the results of the mineralogical and geochemical analyses, the main sources of the sediments are quite similar for both investigated areas, but the authigenic components are different, particularly iron sulfides and carbonates. Authigenic Fe(II) carbonate are much higher in Core MRS-CS-05 in the Western High, while crystalline Fe(III) phases are more abundant in Core MRS-CS-16 in the Cinarcik Basin. Notably, the enrichments of greigite (Fe 3 S 4), a metastable ferromagnetic iron sulfide mineral and intermediate polysulfide, as well as iron carbonates are identified at 400 cmbsf with the maximum iron content in Core MRS-CS-05. These indicate the presence of a more reducing and acidic environment in the Western High, mainly due to higher organic matter content and seepage of heavy hydrocarbons in the sediments. [ABSTRACT FROM AUTHOR]

The article presents the discussion on developing technology for industrial exploitation of natural gas hydrate. Topcis include hydrate reservoir occurring in fine sediments, techniques as horizontal well being needed for enhancing production rate; and revealing the multiple deep-buried thermogenic source kitchens providing hydrocarbon gas for accumulations of gas hydrate in Qiongdongnan.

The flexible riser top connection with floating production units presents additional tensile armour integrity assessment uncertainties associated to the bend stiffener contact interaction that leads to a non-uniform curvature and contact pressure distribution in a region of large dynamic forces and moments. In this paper, a full-scale 6″ flexible riser and bend stiffener bending-tension experimental campaign is carried out in a horizontal rig. The external tensile armour wires are instrumented with strain gauges for axial strain measurement in several riser cross-sections inside and outside the bend stiffener region. The rig assembly allows the riser rotation in order to measure strains at different circumferential angular positions. The bend stiffener polyurethane hyperelastic mechanical response is obtained by uniaxial tensile tests performed at room temperature. A nonlinear finite element model (FEM), including the riser/bend stiffener contact interaction and interlayer friction mechanisms, is employed to numerically investigate the mechanical behaviour of the flexible riser subjected to the experimental loading conditions. The FEM axial strains on the tensile armour wires are compared with the measured results for pure tension and tension-bending loads. Under axisymmetric loading a relevant experimental axial strain dispersion is observed when compared to the average values. Under tension-bending loading, the interlayer friction coefficient influences on the contact pressure and curvature distribution are initially assessed with the numerical model. The strain gauges located in the cross-sections with highest values of contact pressure and curvature are selected for a detailed numerical-experimental strains comparison. In addition, a parametric study is conducted to calibrate the friction coefficient that yields the minimum mean squared error for all measured data. Generally, good correlations are found between the experimental and numerical results. • Full-scale 6″ flexible riser and bend stiffener bending-tension experimental campaign is carried out. • Relevant experimental axial strain dispersion is observed. • Nonlinear finite element model, including riser/bend stiffener contact and interlayer friction mechanisms, is developed. • A parametric study is conducted to calibrate the friction coefficient that yields the minimum mean squared error. • Generally, good correlations are found between the experimental and numerical results. [ABSTRACT FROM AUTHOR]

The Raman spectra of CO 2 molecules in hydrate cages was studied for structure I CO 2 hydrate and structure II tetrahydrofuran (THF)+CO 2 binary hydrate. The results obtained for sII hydrate indicated that the Fermi dyad peaks of CO 2 in the small cage of THF–CO 2 hydrate are located at 1274 cm −1 and 1380 cm −1 . Numerical fitting of the sI CO 2 hydrate Raman spectrum shows CO 2 Fermi dyad peaks in the small cage are located at 1275 cm −1 and 1382 cm −1 . The unperturbed frequencies of the symmetric stretching v 1 and overtone bending v 2 modes were calculated for CO 2 in various states. It was found that the v 1 frequency does not follow the loose cage–tight cage model for CO 2 in hydrate cages. Explanations are given as to why such a relationship is not expected in terms of the incomplete sampling of the void space of the non-spherical cages by the linear guest molecule and the contribution of H-bonding to the guest–host interactions. [ABSTRACT FROM AUTHOR]

Palladium nanotubes were prepared by using silver nanowires as the template, which were prepared in a modified polyol reduction process. The morphology and structure of silver nanowires and palladium nanotubes were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical experimental data showed that palladium nanotubes displayed high electrocatalytic activity toward the electrooxidation of alcohols, especially for ethanol. The formation mechanism of palladium nanotubes as well as the relationship between their structure and electrocatalytic activity was discussed based on the experimental results. [ABSTRACT FROM AUTHOR]

The huge accumulation of plastic wastes is emerging as a serious threat to the ecological environment and human health. Herein, inspired by the reinforcement principle of lignin-carbohydrate complexes (LCC) in the natural trees, we design a green, highly efficient, and eco-friendly method to prepare cellulose composites with excellent performances. Cationic Guar Gum (CGG) and Lignosulfonate (LS), which are derived from biomass, are employed as raw materials to form LS-CGG complexes (LGC) acted as LCC analogs to improve the performance of the cellulose framework. Based on the principle of electrostatic interactions, a self-assembled and facile infiltrated strategy has been applied in the preparation of the LGC-filter paper complex (LGC-FP), which can be industrial-scale manufactured employing established and mature processes from pulping and papermaking industry. This work provides an eco-friendly, low-cost, and scalable route to prepare bioplastics, which is a promising alternative to address the "white pollution" and reach the carbon neutrality goal to a certain extent. [Display omitted] [ABSTRACT FROM AUTHOR]

Several trial productions of natural gas hydrate (NGH) on onshore and offshore reservoirs have been implemented, signaling the start of the stage of technology development for its industrial exploitation. Several methods for NGH exploitation have been proposed, but none of them has been verified applicable to the commercial exploitation of NGH. The applicability of a technology to NGH exploitation is subject to the evaluation of its economic potential, but unfortunately few relevant studies have been conducted. In this research, each exploitation technology for NGH is evaluated for its economic potential as referring to the break-even production rate with energy return on investment (EROI) analysis. Sensitivity analysis is also performed to specify the effect of each key factor, such as gas production rate, gas-water ratio, efficiency of thermal stimulation, injection-production ratio for the methods of chemical injection or CO 2 replacement, on the standard EROI. The results obtained indicate that depressurization is the most promising method, because on it the lowest critical production rate would be required for commercial exploitation of NGH, ranging from 0.16 to 0.25 million m3/day/well. Comparing with other unconventional oil and gas, the commercial exploitation of NGH still relies on further technological breakthroughs, especially those for the improvement of production rate. [Display omitted] • Economic evaluation of hydrate exploitation technology is conducted on EROI. • The break-even production rate of each production technology is estimated. • Sensitivity analyses of the key factors on standard EROI are carried out. • Depressurization is most promising for the exploitation of natural gas hydrate. • The EROI of hydrate exploitation is compared with other energy resources. [ABSTRACT FROM AUTHOR]

• Please find below the highlights of the manuscript "Flexible Riser Tensile Armour Stress Assessment in the Bend Stiffener Region": • A nonlinear finite element model is developed to account for the effect of the bend stiffener on the flexible riser response. • It is particularly investigated the stresses in the tensile armour wires for extreme and fatigue load cases. • The results are compared with the ones obtained from numerical models assuming no bend stiffener interaction and constant curvature. Comparisons are also performed with analytical models. • It is shown that the contact pressure between the bend stiffener and riser affects the stresses in the tensile armour wires. The flexible riser within the bend stiffener in the top connection is a structurally vulnerable region for extreme and fatigue loads as it is subjected to large dynamic tensile forces and curvatures. This paper presents a nonlinear finite element model (FEM) for the flexible riser with bend stiffener taking into account interlayer friction and riser-bend stiffener contact interaction subjected to combined axisymmetric and bending loads. A case study with typical extreme and fatigue load cases is carried out to assess the curvature variation and bend stiffener contact pressure influence in the riser tensile armours stresses. For the extreme load case, detailed finite element results such as contact pressures and friction, normal and transverse bending stresses are compared with a uniform curvature FEM and available analytical models. A fatigue load case is also performed, where the stress amplitudes and cumulative fatigue damages for the internal tensile armour wires are compared with a uniform curvature FEM and analytical models. From the case study results under extreme loading, it can be observed that the model with bend stiffener interaction predicts larger stresses in comparison to the uniform curvature FEM and analytical models. Under typical fatigue loading conditions, significant differences in the cumulative damage are observed between the models, highlighting the importance of an accurate modeling for lifetime integrity assessment in a region of highly variable riser curvature. [ABSTRACT FROM AUTHOR]

To develop a facile and low-cost nanofibrils process with excellent feedstock adaptability, high-yield lignocellulose nanofibrils (LCNF) are produced directly from wood and non-wood biomass using glycerol solvent via screw extrusion pretreatment. Different LCNFs are obtained from four classical raw materials (polar, pine, bamboo, and wheat straw) in this research, followed by comparing their morphological, thermochemical, and mechanical properties. More than 70 wt% of LCNF could be obtained from low-cost substrates except for LCNF from wheat straw with 62.3 wt% yield. Besides, the morphology property of wood LCNF exhibit more uniform distribution over that of non-wood LCNF due to narrower size distribution. Strikingly, despite of the slightly lower LCNF crystallinity various from 52.4% to 62.6% obtained from four substrates, all the LCNFs separated from wood and non-wood biomass exhibit high thermal stability (T max over 330 °C), which is higher than conventional nanocellulose, indicating that the crystal area could be well maintained during the pretreated process. Moreover, all the LCNF films show excellent tensile strength which is close to nanocellulose materials. Besides, the Young's modulus of wood-based LCNF films is higher than that of non-wood based LCNF films. Overall, LCNF with excellent performance could be achieved from low-cost biomass by our facile process, which provides a feasible route for industrial production of bio-based nanofilms. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Except for those occurring at seafloor, most of natural gas hydrate form in sediments and are subject to the influence of sediment. Among these factors, the particle size effect on hydrate saturation level in sediment have been studied with a series of silica sands with various sizes, and the results obtained clearly indicate that particle size does play an important role in affecting the saturation level of hydrate in sediments. The proton relaxation times of water confined in the same series of silica sands, which were determined with NMR measurement, show logarithmic relationship with particle size. By comprehensive consideration of the results of hydrate saturation and water proton relaxation times, the particle size effect observed is tentatively explained by the water availability for hydrate formation in sediments. [Copyright &y& Elsevier]

Abstract: Collecting and preserving undamaged core samples containing gas hydrates from depth is difficult because of the pressure and temperature changes encountered upon retrieval. Hydrate-bearing core samples were collected at the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well in February 2007. Coring was performed while using a custom oil-based drilling mud, and the cores were retrieved by a wireline. The samples were characterized and subsampled at the surface under ambient winter arctic conditions. Samples thought to be hydrate bearing were preserved either by immersion in liquid nitrogen (LN), or by storage under methane pressure at ambient arctic conditions, and later depressurized and immersed in LN. Eleven core samples from hydrate-bearing zones were scanned using x-ray computed tomography to examine core structure and homogeneity. Features observed include radial fractures, spalling-type fractures, and reduced density near the periphery. These features were induced during sample collection, handling, and preservation. Isotopic analysis of the methane from hydrate in an initially LN-preserved core and a pressure-preserved core indicate that secondary hydrate formation occurred throughout the pressurized core, whereas none occurred in the LN-preserved core, however no hydrate was found near the periphery of the LN-preserved core. To replicate some aspects of the preservation methods, natural and laboratory-made saturated porous media samples were frozen in a variety of ways, with radial fractures observed in some LN-frozen sands, and needle-like ice crystals forming in slowly frozen clay-rich sediments. Suggestions for hydrate-bearing core preservation are presented. [ABSTRACT FROM AUTHOR]

Abstract: Systematic analyses have been carried out on two gas hydrate-bearing sediment core samples, HYPV4, which was preserved by CH4 gas pressurization, and HYLN7, which was preserved in liquid-nitrogen, recovered from the BPXA-DOE-USGS Mount Elbert Stratigraphic Test Well. Gas hydrate in the studied core samples was found by observation to have developed in sediment pores, and the distribution of hydrate saturation in the cores imply that gas hydrate had experienced stepwise dissociation before it was stabilized by either liquid nitrogen or pressurizing gas. The gas hydrates were determined to be structure Type I hydrate with hydration numbers of approximately 6.1 by instrumentation methods such as powder X-ray diffraction, Raman spectroscopy and solid state 13C NMR. The hydrate gas composition was predominantly methane, and isotopic analysis showed that the methane was of thermogenic origin (mean δ 13C=−48.6‰ and δ D =−248‰ for sample HYLN7). Isotopic analysis of methane from sample HYPV4 revealed secondary hydrate formation from the pressurizing methane gas during storage. [ABSTRACT FROM AUTHOR]

The processive motor kinesin-1 moves unidirectionally toward the plus end of microtubules. This process can be visualized by total internal reflection fluorescence microscopy of kinesin bound to a carboxylated quantum dot (Qdot), which acts both as cargo and label. Surprisingly, when kinesin is bound to an anti-HIS Qdot, it shows diffusive movement on microtubules, which decreased in favor of processive runs with increasing salt concentration. This observation implies that kinesin movement on microtubules is governed by its conformation, as it is well established that kinesin undergoes a salt-dependent transition from a folded (inactive) to an extended (active) molecule. A truncated kinesin lacking the last 75 amino acids (kinesin-ΔC) showed both processive and diffusive movement on microtubules. The extent of each behavior depends on the relative amounts of ADP and ATP, with purely diffusive movement occurring in ADP alone. Taken together, these data imply that folded kinesin.ADP can exist in a state that diffuses along the microtubule lattice without expending energy. This mechanism may facilitate the ability of kinesin to pick up cargo, and/or allow the kinesin/cargo complex to stay bound after encountering obstacles. [ABSTRACT FROM AUTHOR]

Abstract: Pipeline blockage by gas hydrate is a serious problem in petroleum industry. Recently, low-dosage inhibitors have been developed. In particular, poly(-vinylcaprolactam) (PVCap) is a stronger inhibitor than poly(-vinylpyrrolidone) (PVP). In this study, PVCap was also found to have stronger inhibition activity compared to PVP, but it was less effective during reformation of hydrate. To understand the mechanism, the adsorption of PVCap and PVP on silica, a common nucleating agent, was examined using quartz crystal microbalance with dissipation factor observation function. The results reveal that PVP forms a loose film on silica whereas PVCap forms a relatively more rigid and compact film. However, most of the PVCap film could be rinsed off. These results help explain the different inhibition activities of PVCap and PVP. [Copyright &y& Elsevier]

Abstract: Experiments with a set of electrolyte solutions have been carried out to investigate the effects of pore water composition changes on the stability conditions of methane hydrate in marine sediments. The results reveal that (1) SO42− and Cl− concentration changes can affect hydrate stability slightly, (2) the changes in both the type and the concentration of cations, which occur in normal diagenetic processes, do not exert a significant influence on the methane hydrate stability conditions, and (3) the shift of hydrate stability in pore water can be expressed as a function of the Cl− concentration only. Based on the results above, an empirical equation ΔT (K)=0.00206 Cl− (mmol/dm3) has been obtained for estimating the shift in the equilibrium temperature of methane hydrate in pore water at a given pressure. [Copyright &y& Elsevier]

Using the force sensor of an atomic force microscope, motor forces of the human immunodeficiency virus-1 reverse transcriptase were measured during active replication of a short DNA transcript. At low load forces the polymerase is mechanically slowed, whereas at high force (∼15 piconewton) it stalls. From recordings of es- timated polymerase turnover velocity versus load force, an approximate force-velocity curve has been constructed. The shape of the curve suggests that load force strongly inhibits the rate-limiting step of the polymerase turnover cycle and that the combined effect of load on all steps involves an effective motion of about 1.6 nm. Earlier results from pre-steady-state kinetics experiments have identified the rate-limiting step as the closing of the fingers domain to form a tight catalytic com- plex. Together these findings indicate that the closing of the fingers domain is a major force-generating step for human immunodeficiency virus reverse transcriptase and, by extension, for all DNA polymerase machines. [ABSTRACT FROM AUTHOR]

The calculation of stress components in tensile armour wires of flexible pipes subjected to combined tension and bending is challenging given the intrinsic geometrical and physical nonlinearities. Mechanical loading simulation in finite element models yields heterogeneous curvature distribution, directly impacting stress evaluation. Addition of two auxiliary thermal layers internally and externally subjected to radial and longitudinal thermal expansions simulates equivalent axisymmetric loading, achieving relatively uniform curvature distribution. Calculation of equivalent thermal loads and expansion coefficients involves time consuming trial and error processes by running several finite element models. Therefore, a theoretical formulation that takes into consideration thermal sheaths with orthotropic thermal expansion coefficients and respective thermal loads is developed. A three-dimensional finite element model is also developed for direct application of axisymmetric mechanical or equivalent thermal loadings. A 6″ flexible pipe is employed in a case study to compare the finite element model results within themselves and with the analytical mechanical and thermal models. The analytical results are shown to be rigorously identical. The finite element models present small differences when compared to the analytical results allowing combined application of thermal and bending loading that results in constant curvature away from the boundaries. • Theoretical formulation considering thermal sheaths and loads with orthotropic thermal expansion coefficients is developed. • Three-dimensional finite element model simulates the flexible pipe axisymmetric response and equivalent thermal loading. • Detailed finite element model results are compared within themselves and with the analytical mechanical and thermal models. • Nearly constant curvature is observed when the flexible pipe is subjected to combined thermal and bending loads. [ABSTRACT FROM AUTHOR]

Flexible pipes are key equipment for offshore oil and gas production systems, conveying fluids between the platform and subsea wells. The structural arrangement of unbonded flexible pipes is quite complex, encompassing several layers with polymeric, metallic and textile materials. Different topologies and a large amount of intricate nonlinear contact interactions between and within their components, especially because of the relative stick-slip mechanism during bending, makes numerical analysis challenging. This paper presents an alternative three-dimensional nonlinear finite element model that describes the response of flexible pipes subjected to combined axisymmetric and bending loads. To simulate the response of a flexible pipe under axial tension or compression combined with uniform curvature, an equivalent thermal loading is employed on the external sheath, which is modelled as an orthotropic thermal expansion material with temperature-independent mechanical properties. To assess the feasibility of the proposed model, the bending moment versus curvature of the finite element solution is compared with experimental results obtained in literature and good agreements are found between them. Detailed finite element results such as contact pressures, armour wire slip displacements and friction, normal and transverse bending stresses are also shown and compared with available analytical models. • Alternative three-dimensional finite element model describes the response of flexible pipes subject to combined axisymmetric and bending loads. • To simulate the response of a flexible pipe under axial tension or compression and uniform curvature, an equivalent thermal loading is employed. • The bending moment versus curvature of the finite element model is compared with experimental results obtained in literature. • Contact pressures, armour wire slips and friction, normal and transverse bending stresses are shown and results compared with analytical models. [ABSTRACT FROM AUTHOR]

With the implementation of the production tests in permafrost and offshore regions in Canada, US, Japan, and China, the study of natural gas hydrate has progressed into the stage of technology development for industrial exploitation. The depressurization method is considered as a better strategy to produce gas from hydrate reservoirs based on production tests and laboratory experiments. Multi‐well production is proposed to improve gas production efficiency, to meet the requirement for industrial production. For evaluating the applicability of multi‐well production to hydrate exploitation, a 2D model is established, with numerical simulations of the performance of the multi‐well pattern carried out. To understand the dissociation behavior of gas hydrate, the pressure and temperature distributions in the hydrate reservoir are specified, and the change in permeability of reservoir sediments is investigated. The results obtained indicate that multi‐well production can improve the well connectivity, accelerate hydrate dissociation, enhance gas production rate and reduce water production as compared with single‐well production. [ABSTRACT FROM AUTHOR]

Metal–organic framework (MOF)-based derivatives are attracting increased interest in various research fields. In this study, nano-cellulose MOF-derived carbon-doped CuO/Fe3O4 nanocomposites were successfully synthesized via direct calcination of magnetic Cu-BTC MOF (HKUST-1)/Fe3O4/cellulose microfibril (CMF) composites in air. The morphology, structure, and porous properties of carbon-doped CuO/Fe3O4 nanocomposites were characterized using SEM, TEM, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM). The results show that the as-prepared nanocomposite catalyst is composed of Fe3O4, CuO, and carbon. Compared to the CuO/Fe3O4 catalyst from HKUST-1/Fe3O4 composite and CuO from HKUST-1, this carbon-doped CuO/Fe3O4 nanocomposite catalyst shows better catalytic efficiency in reduction reactions of 4-nitrophenol (4-NP), methylene blue (MB), and methyl orange (MO) in the presence of NaBH4. The enhanced catalytic performance of carbon-doped CuO/Fe3O4 is attributed to effects of carbon preventing the aggregation of CuO/Fe3O4 and providing high surface-to-volume ratio and chemical stability. Moreover, this nanocomposite catalyst is readily recoverable using an external magnet due to its superparamagnetic behavior. The recyclability/reuse of carbon-doped CuO/Fe3O4 was also investigated. [ABSTRACT FROM AUTHOR]

Calcium chloride is widely used in various fields of society because of its good chemical stability and non‐toxic properties. As an inorganic salt with low ductility at low temperature, it is never used to prepare bulk materials but is usually used to prepare energy storage materials. The work in this paper presents the first synthesis of a moldable calcium chloride ceramic‐like material (flexural strength up to 32 MPa) using calcium chloride. The process results in occurring ion‐dipole interactions between calcium chloride and glycerol by means of direct heating and forms supramolecular structure. Due to the presence of dynamic and reversible non‐covalent bonds, the bonds break upon heating bringing good flowability; the re‐established bonds upon cooling allow the formation of rigid materials. The preparation is also a green and recyclable process, as the molded material can be reshaped by heating. Such a brilliant moldable property reveals the potential of this new approach for the design and production of calcium chloride materials with adjustable shapes. [ABSTRACT FROM AUTHOR]

In this study, we developed a novel method to prepare chemical fibers by plasticizing cotton with 1-allyl-3-methylimidazolium chloride (AMIMCl) under high temperature and pressure. Cotton was homogeneously mixed with AMIMCl by kneading in a certain mass proportion. It would be a sheet after hot-pressing and this process could be repeated several times. The morphologies of chemical fibers showed that cotton was successfully plasticized by AMIMCl with the crystallinity of the chemical fibers increased by about 15%. Differential scanning calorimetry (DSC) showed that the glass transition temperature (T g) occurred in chemical fibers and we could further verify cotton was plasticized by AMIMCl. This simple and green method will be helpful to modify and broaden the application field of cotton. [ABSTRACT FROM AUTHOR]

Abstract Structure type, gas composition and cage occupancy are important gas hydrate characteristics which play an important role in calculating gas hydrate stability and estimating the amount of global hydrate-bound methane. China conducted the Fourth gas hydrate drilling campaign (GMGS4) in the Shenhu Sea Area (SSA) of the South China Sea in 2016, during which comprehensive Logging-While-Drilling (LWD) data and natural gas hydrate samples were obtained. The LWD data shows high electrical resistivity and high sound velocity at various depth, indicating the occurrence of gas hydrate in this area. Coexistence of structure I (sI) and structure II (sII) gas hydrates in the South China Sea was confirmed for the first time by using Raman spectra analysis. The methane cage occupancies of large cages and small cages in sI hydrate are 0.95 and 0.96, respectively. The hydration number of sI hydrate is 6.03. Gas composition analysis shows that methane (>98.7%) is the dominate gas, with small amount of heavier hydrocarbon gases (ethane: 0.006%–0.976%, propane: 0.033%–0.216%, isobutane: 0.004%–0.047%) and other non-hydrocarbon gases (carbon dioxide: <0.008%). Gas composition (C 1 /(C 2 +C 3): 84–2333) and isotope composition (δ13C: −50.9‰∼-46.46‰, δD: −177.69‰∼-148.90‰) indicate hydrate-bound gas is dominated by thermogenic source, mixed with certain amount of biogenic source. Existence of sII hydrate potentially deepen the base of sI gas hydrate stability zone in the marine sediment. Coexistence of sI and sII gas hydrates increases the complexity of the gas-water-hydrate system which need to be considered when studying the gas hydrate distribution, estimating the amount of global natural hydrate-bound gases and modeling the gas production. Highlight • sII gas hydrate is discovered for the first time in the South China Sea. • Gas composition and isotope composition indicate hydrate-bound gas is mainly thermogenic origin. • LWD data shows that high saturation gas hydrate of SC-W01 is mainly distributed between 151 and 173 mbsf. [ABSTRACT FROM AUTHOR]

The wettability of a reservoir rock is an important property affecting the states of fluids in pores that are constructed with minerals of various types. However, the mineral grains are usually micro-sized so that the traditional optical contact angle method is hard to be applied to study their wettabilities. Although some measurements have been carried out for the contact angles of liquids on mineral surfaces, those previous studies were mainly on flat artificial mineral surfaces. To understand the wettabilities of water on rough natural mineral surfaces, the contact angles of micro-sized water droplets on relatively rough quartz surfaces in a natural sand rock were measured with an atomic force microscopy (AFM). The results obtained show that the droplets were asymmetrical so that the contact angles, which were around 27.8–50.3°, were different along the triple-phase contact lines, probably due to surface roughness, heterogeneity, atomic arrangement, etc. As compared with previous studies, surface pretreatment and droplet size were regarded as the two key factors that caused the substantial difference in contact angles of water on quartz between the current and previous researches, which might imply that the present results could better describe the wettability of a natural reservoir rock. [ABSTRACT FROM AUTHOR]

The anaerobic oxidation of methane, a key geochemical process that is involved in the cycling of sulfate and iron (oxyhydr)oxides in marine sediments, results in the formation of iron sulfides. Although ferrimagnetic iron sulfides have been identified in seepage systems, the link between iron migration and sediment magnetic properties remains poorly understood. Here, we investigate two cores from the Sea of Marmara to evaluate biogeochemical iron cycling and iron sulfide mineralogy in gas hydrate-bearing sediments. Magnetic analyses indicate the presence of greigite and pyrrhotite in a core from a hydrate-rich site with a high hydrocarbon flux, which contrasts with a lack of these minerals in a core characterized by only mild seepage. This is supported by the results of rock magnetic and scanning electron microscope analyses of the sediments. The presence of authigenic greigite is critical for assessing local redox records and together with the occurrence of monoclinic pyrrhotite may suggest specific diagenetic processes in gas hydrate environments. Our analysis demonstrates the usefulness of these ferrimagnetic minerals, with a high saturation isothermal remanent magnetization to magnetic susceptibility ratio (SIRM/χ > 15 kAm−1) and a high index of hysteresis parameters (D JH > 0.2) indicative of magnetic mineralogy changes, for evaluating variability in the intensity of seepage fluxes and for estimating gas hydrate distributions. • Two sediment cores with a similar original terrigenous source have contrasting magnetic properties. • A reducing and strong flux environment caused iron-driven AOM and formation of authigenic magnetic minerals in the sediments. • Greigite and monoclinic pyrrhotite are identified as the major magnetic minerals formed in hydrate-bearing sediments. [ABSTRACT FROM AUTHOR]

[Display omitted] • A gel-based ZnO-Cu catalyst with high activity and recyclability is prepared. • The coagulating bath plays an important role in the network structure of CCG. • The network structure of CCG affects the morphologies of ZnO-Cu nanoparticles. • Flower-like structure improves the surface reactivity of the ZnO-Cu/CCG catalyst. • ZnO-Cu/CCG can be reused over 50 cycles without evident loss of catalytic efficiency. The recyclability of heterogeneous catalysts directly affects their utilization efficiency, use cost, sustainability, and environmental issues. Herein, the flower-like ZnO-Cu nanoparticles with high interfacial reactivity were in-situ synthesized in the porous cellulose gel to obtain the ZnO-Cu/cellulose composite gel (ZnO-Cu/CCG) catalyst, which possesses superior recycling and reusing stability thanks to the bulk nature of the gel. The ZnO-Cu/CCG catalysts with tunable sheet-like and flower-like ZnO were fabricated by the dissolution of cellulose into zinc chloride (ZnCl 2) solvent and regeneration using different coagulating baths (water, ethanol, or isopropanol). The CCG prepared from isopropanol coagulation exhibited the highest specific surface area (291.6 m2/g) and porosity (92.3%). The various network structures of CCG provided different nucleation sites and growing spaces for controllable preparation of ZnO with tunable morphology. The complete removal of methyl orange (MO), Congo red (CR), and methylene blue (MB) required only 80 sec, 3 min, and 5 min, using flower-like ZnO-Cu/CCG catalysts prepared by isopropanol coagulating bath, the pseudo-first-order rate constant (k) is 2.8170 min−1, 1.1330 min−1, and 0.8506 min−1, respectively, much higher than that of the ZnO-Cu powders. Furthermore, the catalytic reusability of ZnO-Cu/CCG can be investigated over 50 successive cycles, in which the catalytic efficiency did not decrease appreciably. [ABSTRACT FROM AUTHOR]

SiO 2 is a sustainable structural material, but it cannot be easily shaped while maintaining its mechanical properties. Herein, we demonstrate the synthesis of directional rod-shaped nano-SiO 2 via a facile method based on a modified physical and precipitation procedure and endow it with thermoplastic material properties. Scanning electron microscopy and particle size analyses showed that the average length-to-diameter ratio of the prepared rod-shaped nano-SiO 2 was 5.607. After co-mingling the nano-SiO 2 with a small amount of water-soluble polyacrylic acid (PAA), the resulting composite material was hot-press moulded or injection-moulded at a moderate temperature of 170–180 °C. Moreover, the composite material could be moulded repeatedly. The composites have a good elongation at break (29.94%) and tensile strength (10–20 MPa) as well as an excellent flexural strength (212.5 MPa), transparency (76.62%), and flame retardancy. Such an excellent combination of mechanical and thermoplastic properties reveals the potential of this new approach for the design and production of nanosized silica materials with adjustable shapes. [Display omitted] [ABSTRACT FROM AUTHOR]

Cellulose, as a renewable biopolymer, was acknowledged as a promising alternative for petroleum polymer. However, the poor thermoplasticity of cellulose caused a limitation in its full development. Herein, a solvent-free and simple strategy was proposed for the preparation of thermoplastic bio-materials from microcrystalline cellulose (MCC). Kraft lignin (KL) was employed as a plasticizer in this work. It was demonstrated that MCC-based materials with great thermoplasticity and mechanical properties could be successfully prepared by reactive extrusion. The obtained MCC-based material ML8G (with 50 wt% KL adding) possessed great thermostability and thermoplastic properties with an obvious glass transition temperature (T g) at 106 °C. In addition, the bending strength, flexural modulus and storage modulus of the MCC-based material were improved to 20.44 MPa, 3139.47 MPa and 5.81 GPa respectively. Furthermore, the obtained MCC-based material exhibited good water stability and biodegradability. The comprehensive results confirmed the feasibility of MCC-based materials plasticized with KL through reactive extrusion. Overall, this work was a promising development in the field of bio-plastic utilization of natural products from a green source. • Thermoplastic MCC-based materials were successfully prepared with Kraft lignin (KL) as a plasticizer and reinforcement. • The preparation strategy was simple and highly-efficient with reactive extrusion. • There was not any harmful solvents involved throughout the process. • The KL content should be controlled to ensure the mechanical properties of MCC-based materials. [ABSTRACT FROM AUTHOR]

In this work, a molecular dynamics simulation was conducted to study the microscopic mechanism of how nitrogen bubbles affect the formation of THF hydrates at the molecular level. The results obtained reveal that the nitrogen bubble can promote the formation of THF hydrates. In the system with a nitrogen bubble, more THF-filled cages were generated, and the crystal structure was more orderly. The promotion of nitrogen bubbles on hydrate crystallization comes from the dissolution of nitrogen molecules. Some of dissolved nitrogen molecules can be enclosed in small hydrate cages near the nitrogen bubble, which can serve as stable sites for hydrate crystal growth, resulting in the fact that THF-filled cages connected with N2-filled cages are much more stable and have a long lifetime. The results in this work can help to understand the promotion effect of micro- and nano-air bubbles on the crystallization of THF hydrates. [ABSTRACT FROM AUTHOR]

As an integral component of the S-lay, the overboarding chute plays a pivotal role in supporting the weight of the umbilical. In the context of deepwater S-lay operations, the contact force between the umbilical and overboarding chute experiences significant amplification, potentially leading to structural failure of umbilical. In this study, a dynamic substructure experiment using a six-degree-of-freedom platform was conducted to simulate the intricate contact between umbilical and overboarding chute during the deepwater S-lay process. A comprehensive finite element model (FEM) for the deepwater S-lay system was established to examine the contact forces acting on the umbilical by employing Orcaflex. The observed discrepancies between the experimentally acquired contact force data at the selected measurement points and their numerical counterparts were minimal, confirming the efficacy of the finite element model. The results revealed that the contact force of the umbilical undergoes an evident stress concentration phenomenon throughout the deepwater S-lay process. This study investigates the implications of the umbilical bending stiffness, bending radius, and normal stiffness of the overboarding chute on the contact force in deepwater S-lay operations. The results obtained in this study provide a robust foundation for optimizing laying parameters in the design of deepwater S-lay systems. • Combined experimental and numerical methods are proposed to study the contact force between the umbilical and over-boarding chute in deepwater S-lay. • The stress concentration phenomenon of the contact force is found to be strongly related to the water depth of laying and the curvature of the umbilical. • The influence of different parameters is studied. These parameters include the bending stiffness of the umbilical, bending radius and the normal stiffness of the chute on the distribution of contact force. [ABSTRACT FROM AUTHOR]

• Non-amide kinetic hydrate inhibitors are reviewed systematically. • The inhibition performance of non-amide KHIs is related to their chemical structures. • Several non-amide KHIs are with great potential for commercial development. • The inhibition mechanisms of non-amide KHIs are discussed. Kinetic hydrate inhibitors (KHIs) have been used for several decades to solve the hydrate formation problem in oil and gas flowlines. Traditional KHIs are amide-based polymers, e.g., poly(N-vinyl pyrrolidone) (PVP) and poly(N-vinyl caprolactam) (PVCap). With the requirement of high performance, well fluid compatibility, and biodegradable KHIs in oil and gas production and transportation assurance field, more and more non-amide KHI categories have been developed. According to the functional groups, synthetic non-amide KHIs can be classified into amine-based KHIs, amine oxide-based KHIs, phosphonate-based KHIs, sulfonate-based KHIs, hydroxyl-based KHIs, acrylate-based KHIs, urethane-based KHIs, etc. Some natural non-amide polymers, e.g., polysaccharides, are also found with inhibition effect. The inhibition performance of the non-amide polymers is related to their chemical structures. Different functional groups in the polymers have different effects on their inhibition performance. However, the inhibition performance of a polymer largely depends on the type and size of the hydrophobic groups connected to the functional groups. Some of the non-amide KHIs with suitable hydrophobic groups show better inhibition performance and higher cloud point (T Cl) in brines than some of the well-known commercial amide-containing KHIs, which provides a great potential for further development for field applications. In addition, aspects of the KHI inhibition mechanism related to the amphiphilic groups in the polymers and their hydrogen-bonding ability are discussed. [ABSTRACT FROM AUTHOR]

The poor dispersibility and re-dispersibility of cellulose nanofibrils (CNFs) in various solvents and polymers have been recognized as the key factors limiting their potential applications. TEMPO oxidation, as the most common surface modification, can greatly improve the dispersion and re-dispersion of CNFs. However, the diameter of TEMPO-oxidized cellulose nanofibers (TOCNFs) has not been regulated in most researches, which was an important factor determining the dispersion and re-dispersion of TOCNFs. Herein, this work explored the effect of carboxyl groups on dispersion and re-dispersion of TOCNFs with uniform diameter in various solvents. Notably, fractal dimension was innovatively introduced to characterize the distribution of TOCNFs diameter. The fractal dimension and statistic diameter of TCONFs with different carboxyl group contents are ~1.56 and ~22 nm, demonstrating that the diameter of TOCNFs has been regulated in the same range. When the carboxyl group content is up to 1.58 mmol/g, the dispersion and re-dispersion of TOCNFs suspension in water and different organic solvents are the most uniform and stable. In a word, this work explores the dispersion and re-dispersion of TOCNFs with the uniform diameter and different carboxyl group contents, which can provide the theoretical guidance for various potential applications of nanofibrils in polymer matrix composites. • Effect of carboxyl groups on dispersion of TOCNFs with uniform diameter was revealed. • Fractal technology was innovatively introduced to analyze the diameter of TOCNFs. • The size uniformization of TOCNFs was achieved by grinding treatment (fractal dimension was ~1.56 and diameter was ~22 nm). • TOCNFs with carboxyl group content of 1.58 mmol/g exhibited the best dispersibility and stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Simple preparation method, low cost and wide application range. • Excellent strength, the pore structure remains unchanged under high temperature. • Excellent thermal stability, excellent heat-shielding performance and adsorptive property. Carbon aerogels have expanded the trend of the catalytic, adsorption, super capacitor field, and so on. Unfortunately, the real-world applications of porous carbon materials are limited because of the high cost, complicated preparation process and poor mechanical properties. Herein, we report an extremely simple and novel method to prepare carbon aerogels. Based on the principles of two-step curing including acid curing and heat curing, we develop a elastic Phenol-formaldehyde resin gel (PFRG) with high strength (18.9 MPa) from Phenol-formaldehyde resin (PFR) by controlling the loss of solvent in the process. Due to the robust network of RFRG, the Phenol-formaldehyde resin carbon aerogels (PFRCAs) can be directly procured through a tube furnace. The obtained PFRCAs possess macroporous/microporous hierarchical structure with high mechanical strength of 11.2 MPa and low thermal conductivity (0.0381 Wm/K). These results show that the proposed method can be promoted as a universal and promising method for preparing aerogel with thermosetting resin, which has driven a wider industrial utilization of aerogel and thermosetting resin. [ABSTRACT FROM AUTHOR]

The adsorption of glycine, cysteine and glutamic acid by gibbsite and montmorillonite was studied as a function of amino acid concentration and solution pH. Zeta potential measurements, X-ray diffraction (XRD), and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopic analysis were performed to deduce the mechanism(s) of adsorption and to observe changes in the basic structure of the minerals after interaction with amino acids. The ATR-FTIR analysis revealed that both NH 3 + and COO− groups of amino acids were very vital for interactions with the surface of gibbsite and montmorillonite. XRD analysis revealed that the formation of mineral-amino acid composites decreased the d 001 value of montmorillonite from 17.95 to 14.2 (glycine), 15.49 (cysteine), and 15.22 Å (glutamic acid). This observation suggests that amino acid adsorption induced structural stress on montmorillonite and expanded its interlayer space. Also, the adsorption of glycine and cysteine to gibbsite and montmorillonite increased their zeta potentials at pH 5.0 while glutamic acid decreased the zeta potentials. Thus, amino acid-induced increase/decrease in the surface positive/negative charge of the minerals indicates that chemical bonds were formed between glycine, cysteine, glutamic acid and the minerals. The findings of this study can serve as a reference for studies related to understanding the bonding interactions and distribution of different amino acids in soils. • More amino acids were adsorbed by gibbsite than by montmorillonite. • Amino acids adsorbed mainly through their amino and carboxylate groups. • Adsorption of amino acids to montmorillonite induced expansive phase formation. [ABSTRACT FROM AUTHOR]

Understanding the engineering properties of hydrate-bearing sands (HBS) is the key to assessing the safety during the exploitation of natural gas hydrates. The formation and presence of hydrates in pore spaces are complicated, yet the HBS specimens with different hydrate morphologies have not been precisely tested due to the difficulty in controlling the hydrate formation in the laboratory. In this study, the discrete element method (DEM) is used to create HBS models containing pore-filling, cementing, load-bearing, grain-coating, and patchy hydrates. A series of HBS specimens with different hydrate morphologies and hydrate saturations ranging from 0 to 40% are tested by simulating biaxial compression tests. The numerical results show that the shear strength is slightly but the secant modulus is significantly influenced by the hydrate morphology. The shear strength and secant modulus of HBS increase with hydrate saturation regardless of the hydrate morphology. Further relationships are established between the micro mechanical analyses of the evolution of bonds and contact-type-related contributions and the macro mechanical properties of HBS. These DEM results can provide lower and upper limits for HBS, which are beneficial for further understanding the mechanical responses of HBS with complex hydrate morphologies. [ABSTRACT FROM AUTHOR]

Rock-Eval pyrolysis and the biomarker composition of organic matter were systematically studied in hydrate-bearing sediments from the Shenhu area, South China Sea. The n-alkane distribution patterns revealed that the organic matter in the sediments appeared to originate from mixed sources of marine autochthonous input, terrestrial higher plants, and ancient reworked organic matter. The low total organic carbon contents (average < 0.5%) and the low hydrogen index (HI, <80 mg HC/g TOC) suggested the poor hydrocarbon-generation potential of the deposited organic matter at a surrounding temperature of <20 °C in unconsolidated sediments. The abnormally high production index and the fossil-originated unresolved complex mixture (UCM) accompanied by sterane and hopane of high maturity indicated the contribution of deep hydrocarbon reservoirs. Preliminary oil-to-source correlation for the extracts implied that the allochthonous hydrocarbons in the W01B and W02B sediments might have originated from the terrestrial source rocks of mature Enping and Wenchang formations, while those of W03B seem to be derived from more reduced and immature marine source rocks such as the Zhuhai formation. The results of the organic extracts supported the previous identification of source rocks based on the isotopic composition of C2+ hydrate-bound gases. The biomarker of methanogens, squalane, was recognized in the sediments of this study, possibly suggesting the generation of secondary microbial gases which are coupled with the biodegradation of the deep allochthonous hydrocarbons. [ABSTRACT FROM AUTHOR]

In recent years, natural gas hydrate has attracted increasing attention worldwide as a potential alternative energy source due to its attributes of wide distribution, large reserves, and low carbon. Since the acoustic characteristics of hydrate‐bearing reservoirs clearly differ from those of adjacent formations, an acoustic approach, using seismic and acoustic logging, is one of the most direct, effective and widely used methods among the identification and characterization techniques for hydrate reservoir exploration. This review of research on the influence of hydrate (content and distribution) on the acoustic properties (velocity and attenuation) of sediments in the past two decades includes experimental studies based on different hydrate formation methods and measurements, as well as rock physics models. The main problems in current research are also pointed out and future prospects discussed. [ABSTRACT FROM AUTHOR]

Natural gas hydrate contains a specific amount of heavy hydrocarbons, such as ethane, propane, etc., aside from the primary guest gas of methane. Although the coexistence of two or even three hydrate structures has been discovered at several hydrate sites, the requisite formation mechanism is still not well understood. In‐situ observation of the formation process of mixed methane‐propane hydrate in a confined space was conducted using confocal Raman imaging microscopy. The Raman imaging results reveal that sI methane hydrate and sII mixed methane‐propane hydrate are formed and coexist in the reaction system. In the confined space, the sI hydrate originates from the dissolved gas in water, while the sII hydrate is formed from free gas. The results obtained can help explain the coexistence of sI and sII hydrates found in natural hydrate samples, as well as providing insights into a possible dynamic scenario of hydrate reservoirs in geological history. [ABSTRACT FROM AUTHOR]