Search

In the era of big data, the complexity of data is increasing. Problems such as data imbalance and class overlap pose challenges to traditional classifiers. Meanwhile, the importance of imbalanced data has become increasingly prominent, it is necessary to find appropriate methods to enhance classification performance of classifiers on such datasets. In response, this paper proposes a mixed sampling method (ISODF-ENN) based on iterative self-organizing (ISODATA) denoising diffusion algorithm and edited nearest neighbors (ENN) data cleaning algorithm. The algorithm first uses iterative self-organizing clustering algorithm to divide minority class into different sub-clusters, then it uses denoising diffusion algorithm to generate new minority class data for each sub-cluster, and finally it uses ENN algorithm to preprocess majority class data to remove the overlap with the minority class data. Each sub-cluster is oversampled according to sampling ratio, so that the oversampled minority class data also conforms to the distribution of original minority class data. Experimental results on keel datasets demonstrate that the proposed method outperforms other methods in terms of F-value and AUC, effectively addressing the issues of class imbalance and class overlap. [ABSTRACT FROM AUTHOR]

We propose a discontinuous least squares finite element method for solving the Helmholtz equation. The method is based on the L2$$ {L}^2 $$ norm least squares functional with the weak imposition of the continuity across the interior faces as well as the boundary conditions. We minimize the functional over the discontinuous polynomial spaces to seek numerical solutions. The wavenumber explicit error estimates to our method are established. The optimal convergence rate in the energy norm with respect to a fixed wavenumber is attained. The least squares functional can naturally serve as a posteriori estimator in the h‐adaptive procedure. It is convenient to implement the code due to the usage of discontinuous elements. Numerical results in two and three dimensions are presented to verify the error estimates. [ABSTRACT FROM AUTHOR]

For direct formic acid fuel cells (DFAFC), palladium (Pd)-based alloy catalysts with competitive morphology and elemental composition are essential to boost the performance of the formic acid oxidation reaction (FAOR) in the anode zone. Herein, we design and synthesize RuPdx alloy nano-network structures (ANs) via the facile wet-chemical reduction of Pd-Ru cyanogel (Pdx [Ru(CN)6]y·aH2O) as an effective electrocatalyst for the FAOR. The formation of Pd-Ru cyanogel depends on the facile coordination of K2PdCl4 and K3 [Ru(CN)6]. The unique structure of cyanogel ensures the presentation of a three-dimensional mesoporous morphology and the homogeneity of the elemental components. The as-prepared RuPd3 ANs exhibit good electrocatalytic activity and stability for the FAOR. Notably, the RuPd3 ANs achieve a mass-specific activity of 2068.4 mA mg−1 in FAOR, which shows an improvement of approximately 16.9 times compared to Pd black. Such a competitive FAOR performance of RuPd3 ANs can be attributed to the advantages of structure and composition, which facilitate the exposure of more active sites, accelerate mass/electron transfer rates, and promote gas escape from the catalyst layer, as well as enhance chemical stability. [ABSTRACT FROM AUTHOR]

To solve the problem of low accuracy in the traditional FunkSVD recommendation algorithm, an improved FunkSVD algorithm (RM-FS) is proposed. RM-FS is an improvement of the traditional FunkSVD algorithm, using RMSProp, a deep learning optimization algorithm. The RM-FS algorithm can not only solve the problem of reduced accuracy of the traditional FunkSVD algorithm because of iterative oscillations but also alleviate the impact of data sparseness on the accuracy of the algorithm, achieving the effect of improving the accuracy of the traditional algorithm. The experimental results show that the RM-FS algorithm proposed in this paper effectively improves the accuracy of the recommendation algorithm, which is better than the traditional FunkSVD recommendation algorithm and other improved FunkSVD algorithms. [ABSTRACT FROM AUTHOR]

Imbalanced data poses a significant challenge in machine learning, as conventional classification algorithms often prioritize majority class samples, while accurately classifying minority class samples is more crucial. The synthetic minority oversampling technique (SMOTE) represents one of the most renowned methods for handling imbalanced data. However, both SMOTE and its variants have limitations due to their insufficient consideration of data distribution, leading to the generation of incorrect and unnecessary samples. This paper, therefore, introduces a novel oversampling algorithm called data distribution and spectral clustering-based SMOTE (DDSC-SMOTE). This algorithm addresses the shortcomings of SMOTE by introducing three innovative data distribution-based improvement strategies: adaptive allocation of synthetic sample quantities strategy, seed sample adaptive selection strategy, and synthetic sample improvement strategy. First, we use the k-nearest neighbor sample labels and the local outlier factor algorithm to remove noisy and outlier samples. Next, we leverage spectral clustering to identify clusters within the minority class and propose a dual-weight factor that considers inter-cluster and intra-cluster distances to allocate the number of synthetic samples effectively, addressing interclass and intraclass imbalances. Furthermore, we introduce a relative position weight coefficient to determine the probability of selecting seed samples within the subcluster, ensuring that important minority samples have higher chances of being sampled. Finally, we improve the SMOTE sample synthesis formula for safer generation. Extensive comparisons on real datasets from the UCI repository demonstrate that DDSC-SMOTE outperforms seven state-of-the-art oversampling algorithms significantly in terms of G-mean and F1-score, presenting a data distribution-focused solution for addressing imbalanced data challenges. [ABSTRACT FROM AUTHOR]

Sentiment analysis is one of the core tasks in natural language processing, and its main goal is to identify and classify the sentiment tendencies contained in texts. Traditional sentiment analysis methods and shallow models often fail to capture the rich semantic information and contextual relationships in text, while increasing the network depth is prone to problems such as network degradation, which has some limitations in terms of accuracy and performance. Based on this foundation, a sentiment analysis model called BERT-Invos (Bidirectional Encoder Representations from Transformers (BERT)-based stacked involutions) is introduced. The model utilizes the dynamic pre-training language model BERT to encode text, enabling rich semantic features and contextual understanding. In addition, the model employs stacked involutions with varying dimensions to extract features and perceive local information, gradually learning different scales and hierarchical representations of the input text. Furthermore, the proposed method incorporates nonlinear activation functions such as ReLU6 and H-Swish to enhance the model’s expression capability and performance, ultimately delivering classification results. In the experiment, a financial news sentiment dataset was utilized for model validation and comparison against other models. The results revealed that the model achieved an accuracy of 96.34% in sentiment analysis tasks, with precision, recall, and F1 score reaching 96.37%, 96.34%, and 96.34%, respectively. Additionally, the loss value could be minimized to 0.07 with stable convergence, thereby enhancing the accuracy of sentiment classification and reducing loss rates. This improvement facilitates better capturing of local patterns in text and addresses the issue of degradation in deep neural networks. Regarding the deep architecture of the proposed model, future work will focus on further exploring optimization techniques for model compression and deployment. [ABSTRACT FROM AUTHOR]

We propose and analyze a discontinuous least squares finite element method for solving the indefinite time-harmonic Maxwell equations. The scheme is based on the |$L^2$| norm least squares functional with weak imposition of continuity across interior faces. We minimize the functional over the piecewise polynomial spaces to seek numerical solutions. The method is shown to be stable without any constraint on the mesh size. We prove the optimal convergence rate under the energy norm and sub-optimal convergence rate under the |$L^2$| norm. Numerical results in two and three dimensions are presented to verify the error estimates. [ABSTRACT FROM AUTHOR]

Surface functionalization is an effective way to improve the activity of electrocatalysts by adjusting the adsorption and desorption capacity of intermediate species on noble metal surfaces. Herein, density functional theory (DFT) calculations demonstrate that cyanogroup functionalization can effectively reduce the d-band centre (εd) of the Pt (111) plane, thus resulting in a hydrogen evolution reaction (HER) performance improvement. Cyanogroup functionalized Pt ultrafine nanonetworks (CN–Pt UNs, sub-2 nm) are synthesized via a facile one-pot heating method with high yield and abundant defects/grain boundaries as the highly active sites. Owing to the optimized Pt electronic properties and ultrathin network nanostructure, the overpotentials of CN–Pt UNs at 10 mA cm−2 are merely 6 mV and 8 mV in 1 M HClO4 and 1 M KOH, respectively, and are superior to those of commercial 20 wt% Pt/C in a wide pH range. This work offers a new perspective towards the rational design of noble metal catalysts for boosting electrocatalysis by surface cyanogroup functionalization. [ABSTRACT FROM AUTHOR]

It is a difficult and long-term task to develop highly active and stable electrocatalysts to realize efficient hydrogen evolution reaction (HER) in electrochemical water splitting. Herein, we report a facile oil-bath method to fabricate hierarchical Rh2Ir alloy nanodendrites (Rh2Ir NDs) with excellent HER performance in a broad pH range. Due to the unique branched nanostructure and rational Rh2Ir metal proportion, the developed Rh2Ir NDs exhibit superior activity and enhanced stability towards HER in a broad range of pH conditions. To deliver a current density of 10 mA cm−2 in 1 M HClO4 and 1 M KOH, Rh2Ir NDs require overpotentials of only 12 and 9 mV, respectively. This work not only offers a high-performance electrocatalyst for electrochemical water splitting but also provides a new perspective towards the rational synthesis of hierarchical noble-metal nanodendrites. [ABSTRACT FROM AUTHOR]

We propose a high-order discontinuous Galerkin finite element method for solving the H (div) - and H (curl) -elliptic interface problems on unfitted meshes. The vector-valued approximation space is constructed by the patch reconstruction with at most d degrees of freedom per element. The C 2 -smooth interface is allowed to intersect elements in a quite general setup. The patch reconstruction provides the stability near the interface naturally without any additional stabilization strategy. The method is based on the symmetric interior penalty method and the optimal and suboptimal convergence rates under the energy norm and L 2 norm are derived. Numerical examples in both two and three dimensions are presented to demonstrate the accuracy of the method. [ABSTRACT FROM AUTHOR]

Although there have been reports showing the modification effect of carbon nanomaterials on asphalt, there are few studies on whether carbon nanomaterials and polymers can have synergistic modification effects on asphalt. At the same time, the complex composition of asphalt makes it difficult to determine the interface mechanism between the modifier and the asphalt. In this study, graphene oxide (GO) and styrene–butadiene–styrene block copolymer (SBS) were selected as modifiers. A combined experimental and molecular simulation research method was used to study the synergistic modification effect and the interface mechanism between the modifier and the asphalt. The results show that the modification effect of GO/SBS incorporated into asphalt is significantly superior to that of GO or SBS incorporated individually and GO/SBS has a synergistic modification effect. Although the binding strength between SBS and asphalt is weak, the GO surface (GO (0 0 1)) can simultaneously bind with SBS and asphalt, increasing the binding strength of SBS and asphalt as well as promoting the dispersion of SBS in asphalt, so that GO/SBS shows a synergistic modification effect and improves properties such as low-temperature ductility, rheology and storage stability at macroscopic level. Intercalated and exfoliated structure can be formed between GO side (GO (0 1 0)) and asphalt, which improves the anti-aging properties of the asphalt. Physical bonding is the main interface binding for GO/SBS compound-modified asphalt. GO bonds to asphalt or SBS by hydrogen bonds and there are only dispersion forces between SBS and asphalt, resulting in a higher binding strength between GO and asphalt or SBS than between SBS and asphalt. [ABSTRACT FROM AUTHOR]

Ruthenium (Ru) has been theoretically considered a viable alkaline hydrogen evolution reaction electrocatalyst due to its fast water dissociation kinetics. However, its strong affinity to the adsorbed hydroxyl (OHad) blocks the active sites, resulting in unsatisfactory performance during the practical HER process. Here, we first reported a competitive adsorption strategy for the construction of SnO2 nanoparticles doped with Ru single‐atoms supported on carbon (Ru SAs‐SnO2/C) via atomic galvanic replacement. SnO2 was introduced to regulate the strong interaction between Ru and OHad by the competitive adsorption of OHad between Ru and SnO2, which alleviated the poisoning of Ru sites. As a consequence, the Ru SAs‐SnO2/C exhibited a low overpotential at 10 mA cm−2 (10 mV) and a low Tafel slope of 25 mV dec−1. This approach provides a new avenue to modulate the adsorption strength of active sites and intermediates, which paves the way for the development of highly active electrocatalysts. [ABSTRACT FROM AUTHOR]

Ruthenium (Ru) has been theoretically considered a viable alkaline hydrogen evolution reaction electrocatalyst due to its fast water dissociation kinetics. However, its strong affinity to the adsorbed hydroxyl (OHad) blocks the active sites, resulting in unsatisfactory performance during the practical HER process. Here, we first reported a competitive adsorption strategy for the construction of SnO2 nanoparticles doped with Ru single‐atoms supported on carbon (Ru SAs‐SnO2/C) via atomic galvanic replacement. SnO2 was introduced to regulate the strong interaction between Ru and OHad by the competitive adsorption of OHad between Ru and SnO2, which alleviated the poisoning of Ru sites. As a consequence, the Ru SAs‐SnO2/C exhibited a low overpotential at 10 mA cm−2 (10 mV) and a low Tafel slope of 25 mV dec−1. This approach provides a new avenue to modulate the adsorption strength of active sites and intermediates, which paves the way for the development of highly active electrocatalysts. [ABSTRACT FROM AUTHOR]

Based on the four-component theory of asphalt, molecular models of the saturate, aromatic, resin, and asphaltene were constructed, respectively. The styrene–butadiene–styrene (SBS) polymer was used as the modifier. Using density functional theory (DFT) to study the effect of SBS on the molecular vibration of each component of asphalt, the vibration spectrums and binding energy of the systems composed of SBS and each component molecule of asphalt were calculated. Prepared SBS modified asphalt and measured Fourier transform infrared spectroscopy (FTIR) before and after the experiment. The results show that after SBS was added to asphalt, no chemical reaction occurred, and the system was mainly physical blending. The vibrational peak intensity of SBS and the light components of asphalt (saturate and aromatic) is stronger than that of SBS and the heavy components of asphalt (resin and asphaltene). The interaction strengths of asphalt components and polybutadiene (PB) blocks, polystyrene (PS) blocks of SBS are different. The binding energy of SBS and the saturate is the lowest and the bonding of the system is weakest. The bonding of the systems of SBS and the aromatic, resin, asphaltene is stable, and the stability of these systems are all stronger than that of SBS and the saturate. [ABSTRACT FROM AUTHOR]

To raise photocatalytic efficiency of ZnS nanoparticles (ZnS NPs) under visble light, the novel Ti 3 C 2 Tix (MXene) material was used to modify ZnS NPs through ultrasonic oscillation. Research results showed that ZnS nanoparticles (ZnS NPs) were successfully attached on layered MXene sheet, and the resultant 0.1ZnS NPs/MXene (0.1ZnS/M) sample exhibited very high photocatalytic performance under visible light. The degraded velocity of 0.1ZnS/M sample is about 0.02464 min−1, in which is as 3.2 times as that of pure ZnS (0.0077 min−1). Moreover, 0.1 ZnS/M sample displayed good hydrogen production yield about 212 μmol h−1. The enhanced catalytic performance was attributed to the excellent property of MXene sheets and the effective interaction between ZnS NPs and MXene sheets. • ZnS/MXene (ZnS/M) hybrids were fabricated by ultrasonic oscillation. • ZnS/MX hybrids exhibited high photocatalytic activity under visible-light. • ZnS/M hybrids displayed good photocatalytic hydrogen production ability. • MXene can enhance the photocatalytic activity of ZnS nanonanoparticles. [ABSTRACT FROM AUTHOR]

How to convert heat energy into other forms of usable energy more efficiently is always crucial for our human society. In traditional heat engines, such as the steam engine and the internal combustion engine, high-grade heat energy can be easily converted into mechanical energy, while a large amount of low-grade heat energy is usually wasted owing to its disadvantage in the temperature level. In this work, for the first time, the generation of mechanical energy from both high- and low-temperature steam is implemented by a hydrophilic polymer membrane. When exposed to water vapor with a temperature ranging from 50 to 100 °C, the membrane repeats rolling from one side to another. In nature, this continuously rolling of membrane is powered by the steam, like a miniaturized "steam engine". The differential concentration of water vapor (steam) on the two sides of the membrane generates the asymmetric swelling, the curve, and the rolling of the membrane. In particular, results suggest that this membrane based "steam engine" can be powered by the steam with a relatively very low temperature of 50 °C, which indicates a new approach to make use of both the high- and low-temperature heat energy. [ABSTRACT FROM AUTHOR]

In response to the challenges of intermediate poisoning and the high cost of noble metal catalysts in the hydrogen evolution reaction (HER), we develop a Ru-doped SnO2 catalyst. This Ru–SnO2 catalyst has the characteristics of low Ru loading and a hollow structure, which endow it with good electrocatalytic activity and stability for the HER. [ABSTRACT FROM AUTHOR]

Pt‐based intermetallics are recognized as effective catalysts for oxygen reduction reaction (ORR) in fuel cells. However, the synthesis of intermetallics often requires prolonged annealing and the effect of different crystal structures on ORR still need to be investigated. Herein, L12‐Pt3Mn and L10‐PtMn intermetallics with Pt‐skin are rapidly synthesized through an emerging periodic carbothermal shock method to investigate their ORR‐activity difference. The formation of L12‐Pt3Mn and L10‐PtMn can be well‐controlled by the Pt/Mn feeding ratio, pulse cycles, and temperature. Electrocatalytic investigations show that L12‐Pt3Mn presents a more positive half‐wave potential (0.91 V vs RHE) and onset potential (1.02 V vs RHE) than those of L10‐PtMn. The mass activity and specific activity of L12‐Pt3Mn are respectively fourfold and threefold greater than those of L10‐PtMn. Theoretical calculations indicate that the L12‐Pt3Mn has a more substantial work function than L10‐PtMn, thereby conferring L12‐Pt3Mn with an increased electron density allocation for catalytic involvement. This electron confinement imparts L12‐Pt3Mn with a Pt d‐band center lower than that of L10‐PtMn, consequently attenuating the adsorption of strongly bonded *O intermediates during the rate‐determining step. This study not only employs a straightforward method for intermetallic preparation but also elucidates the discrepancies in ORR activity across intermetallics with distinct structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • An in-situ processing algorithm is proposed to facilitate the real-time measurement. • A new feature descriptor construction algorithm is developed based on grayscale histogram. • The presented DIC system is capable of inhibiting the error resulting from the vibration of apparatus. This paper developed a real-time and non-destructive 2D fatigue crack propagation tracing method based on an optimized digital image correlation (DIC) approach by introducing an image in-situ processing algorithm and a fatigue crack propagation monitoring algorithm. The in-situ processing algorithm coupled with optimizing the speeded up robust features (SURF) was applied to correct the shifted images during fatigue crack propagation tests, while the fatigue crack propagation monitoring algorithm was developed to detect the true crack tip and measure crack length. By optimizing SURF algorithm, the construction time of feature descriptor for interest point matching was reduced to 0.0066 s, 55 times shorter than the case using traditional SURF. In conjunction with the fatigue crack identification, this enables the real-time measurement of fatigue crack length with the resolution as high as 5.2 μm for a measurement region of 15.85 × 10.57 mm2. Compared to current DIC, the proposed algorithm either enables characterizing the crack tip and crack propagation path, or can be programmed as user-defined subroutine and integrated into commercial DIC software for example MatchID. As a result, the experimental measurements obtained by the proposed approach on the fatigue crack propagation tests of an Aluminium alloy exhibited a good agreement with simulation results based on the extended finite element method (XFEM), indicated its promising industrial prospect. [ABSTRACT FROM AUTHOR]

Highly pure BaSrCoFeO (BSCF) perovskite nanocompound was synthesized via glycine-nitrate process (GNP) and coprecipitation-azeotropic distillation method (ADM), respectively. Compared to ADM, GNP was proved to facilitate the synthesis of BSCF powder with small crystal and particle sizes as well as large surface area. BSCF material was employed as the cathode of solid oxide fuel cell (SOFC) incorporating with SmCeO (SDC) electrolyte. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) tests indicated that the GNP powder-based cathode not only exhibited high electrocatalytic activity but also possessed low oxygen diffusion resistance due to the high porosity. As a result, the cell with GNP powder-based cathode showed a power density of 0.35 W cm when the voltage was 0.7 V at 650 °C. Furthermore, the cathode performance was significantly improved at the high current density condition. [ABSTRACT FROM AUTHOR]

The primary bottleneck in heavy oil production lies in the significant energy consumption and CO 2 emissions associated with steam injection for recovery. To address this challenge, we propose the ISSG-SAGD (in-situ solvent generation enhanced steam assisted gravity drainage) technique. The recovery mechanisms and operational strategies are investigated using a numerical simulation with an Athabasca bitumen reservoir model, affirming the considerable environmental and economic potential of ISSG-SAGD. The results demonstrate that ISSG-SAGD integrates the recovery mechanisms of both SAGP (steam and gas push) and ES-SAGD (expanding solvent SAGD). Moreover, employing cyclic steam injection, maintaining low operating pressure, and initiating ISSG-SAGD at an early stage enable a 33.79 % reduction in steam consumption, a 39 % decrease in average carbon intensity, a 5.40 % increase in oil production, and a 61.28 % rise in net present value compared to conventional SAGD. This study proves that the ISSG-SAGD approach offers a sustainable and efficient alternative for future heavy oil recovery endeavors, addresses the challenges of high energy consumption and carbon emissions, and paves the way towards a green and economically viable future for the heavy oil development. • ISSG-SAGD is a low carbon and high-efficiency heavy oil recovery technique • Utilizing solar power to supply gravity drainage and in-situ cracking • ISSG-SAGD combines SAGP and ES-SAGD mechanisms, increased oil production • ISSG-SAGD lowers carbon emissions and demonstrates higher economic efficiency to SAGD [ABSTRACT FROM AUTHOR]

In a proton-exchange membrane fuel cell, the proton-exchange membrane is located between the oxidant and the fuel, which facilitates proton conduction and prevents the penetration of gas molecules. In this study, sulfonated graphene oxides (SG) were synthesized, and a series of SG/Nafion composite multilayer membranes were prepared using layer-by-layer assembling. This multilayer membrane-structure has an efficient orientation effect on the SG sheets. The thinner the layer is, the more significant is the orientation effect. A statistical angle between the SG sheets and the membrane surface (Θ) is used to represent the orientation of SG sheets, and a correlation between the thickness of the layers and Θ is found. Under various conditions, these multilayer composite membranes improve the gas-barrier properties (H 2 , O 2 , and water vapor) and proton conductivity. The effect of Θ on the gas-barrier properties and proton conductivity of the membranes is discussed. Our results reveal that the SG sheets have excellent gas-barrier properties in the longitudinal direction and good proton conductivity in the lateral direction. Furthermore, based on positron-annihilation lifetime spectroscopy, it is found that the diffusion coefficients of gas molecules in all the SG/Nafion composite membranes are almost identical. In other words, the orientation of the SG sheets changes the gas-barrier properties of the membranes by altering the morphology of the diffusion paths for the gas molecules during the permeation. • SG sheets with certain orientations were incorporated into multilayer PEM. • The orientation of SG sheets is represented by a statistical angle Θ. • The effects of orientation of SG on gas-barrier properties and proton conductivity have been discussed. • The multilayer membranes improve the gas-barrier properties and proton conductivity. [ABSTRACT FROM AUTHOR]

One heavy crude oil from Liaohe Basin, NE China and its oxidized counterparts at 200 and 400 °C have been characterized geochemically by negative-ion electrospray ionization Orbitrap mass spectrometry to investigate the variation of acid and neutral nitrogen compounds during in-situ combustion. The heteroatom compounds of acid and neutral nitrogen detected in the samples are mainly N 1 , N 1 O 1 , N 1 O 2 , O 1 , O 2 , O 3 and O 4 classes, dominated by N 1 , O 1 and O 2. The N 1 class predominated by carbazole and benzocarbazole with double bond equivalents (DBE) 9 and 12, is relatively stable and resistant to oxidation, while the N 1 O 1 and N 1 O 2 classes vary without a clear trend during oxidation. The O 1 class is generally low in raw sample and the 200 °C oxidized oil but increases sharply in the 400 °C oxidized oil. The O 2 class is peaked in the 200 °C oxidized oil but its relative concentration declines drastically in the 400 °C oxidized oil. The O 1 and O 2 class compounds show a similar DBE and carbon number (CN) distribution trend with increasing temperatures. Lower DBE and CN compounds are enriched in the 400 °C oxidized oil after alkyl side chain cleavage, where small proportion of high DBE compounds derived from aromatization and condensation has also been observed. The relative abundance of O 1 and O 2 species with specific DBE values and carbon number ranges are sensitive to in-situ thermal upgrading and ratios of DBE1/DBE4-O 1 and DBE1/DBE3-O 2 endure the potential as geochemical proxies to monitor the degree of oil upgrading. [ABSTRACT FROM AUTHOR]

Most heavy oils or tar sands are formed by microbial biodegradation and show a compositional gradient toward the base of oil column. However, a reversed pseudo-gradient has been observed from the fourth member of the Shahejie Formation in Shuguang oilfield, Liaohe Basin, NE China, on the basis of bulk and molecular compositions in a series core extracts from well K037. The bulk compositions show systematic depletion of saturated hydrocarbons and enrichment of polars (resins + asphaltenes) toward the top of the oil column. Molecular compositions illustrate that these extracts have similar source input, depositional environment and thermal maturity, and their compositional differences are mainly caused by varying degrees of biodegradation. Biodegradation removes all n -alkanes, most isoprenoid alkanes, partial alkylnaphthalenes and alkylphenanthrenes at the top of oil column, whereas only n -alkanes are affected at the bottom. Reservoir temperature has no crucial impact on biodegradation levels as the whole oil column in the temperature range of 41–44 °C is ideal for microbial activities. The studied reservoir is not a continuous oil column, which is separated by a few barriers and baffles. The occurrence of locally high-water saturation layers caused multiple small gradients in the mid and lower part of oil column with a normal biodegradation gradient in the lowermost compartmentalized interval. The overall reversed compositional pseudo-gradient is controlled by a generally upward coarsening sedimentary sequence and the existence of top water situated at a lithology change boundary from coarse sandstones and conglomerates to fine grained sandstones. This study provides a new perspective to assess the reservoir fluid heterogeneity and sheds the light on sweet spots identification for heavy oil exploration and development. • Oils in the studied reservoir have suffered light to moderate biodegradation influence. • A reversed compositional pseudo-gradient showing most biodegradation at top of oil column. • Oil-water-contact situation exert dominant controls on levels of biodegradation. • Top water results in the occurrence of reversed biodegradation pseudo-gradient. • Coarsing upward lithology plays important role in overall biodegradation intensity. [ABSTRACT FROM AUTHOR]

In order to decrease the agglomeration of carbon nanotubes (CNTs) and enhance the interaction between CNTs and epoxy asphalt (EA), CNTs were modified by epoxy resin (ER) after treated with mixture acid, and then CNTs-EA was synthesized via mechanical stirring method. Experimental results confirmed that ER was decorated on the surface of CNTs. Moreover, the softening point and anti-ultraviolet aging of matrix asphalt were significantly improved by introducing modified CNTs, which increased about 48.7% for softening point and the variety ratio of UV aging (UAI) value was close to 1. The enhancement is mainly attributed to the excellent property of CNTs and the effective synergistic effect between CNTs and ER. [ABSTRACT FROM AUTHOR]

• GO improved high temperature stability and heat aging resistance of the asphalt. • The bonding of GO to asphalt resin molecules is the most stable. • GO is stably dispersed in asphalt by hydrogen bonding and aromatic ring stacking. Preparation of graphene oxide (GO) by oxidative dispersion, using GO as an asphalt modifier, graphene oxide modified asphalt was prepared by high temperature melting method. The effect of GO incorporation on the basic physical properties of asphalt was investigated, and the X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were used to analyze the microstructure characteristic of GO and modified asphalt. In order to reveal the bonding mechanism between GO and asphalt, a calculation model of asphalt molecules and GO molecules was constructed. Each of constructed asphalt molecules and GO molecules were placed in the primitive cells to obtain systems of asphalt with GO. Density functional theory (DFT) was used to calculate the molecular charge density, the electron density difference, the binding energy and the number of charges transferred between asphalt and GO. The results shown that the GO improved high temperature stability and heat aging resistance of the asphalt, but unable improve the crack resistance of the asphalt. GO was stably dispersed in asphalt, GO modified asphalt by forming an intercalation structure, which improves the high temperature stability of the asphalt. However, the effect of GO on asphalt was based on the physical modification, which unable crosslink each other in the asphalt, as a result, the crack resistance of the modified asphalt unable be improved. Density functional calculation results show that the bonding of resin with GO was the most stable, followed by those for aromatic with GO, and those for saturate with GO was the weakest, GO can hinder the movement of saturate and inhibit the volatilization of saturate, thereby improving the high temperature stability and heat aging resistance of asphalt. GO molecules can form hydrogen bonds with asphalt molecules, and it can also form aromatic ring stacks with aromatic and resin molecules, these non-bond interactions were the key to the stable dispersion of GO in asphalt. [ABSTRACT FROM AUTHOR]

Proton exchange membranes, such as the widely used Nafion membranes, are essential components in industrial proton-exchange membrane fuel cells. In this study, multilayer sulfonated carbon-nanotubes/Nafion composite membranes with high performances have been prepared using layer-by-layer assembly. The membranes consist of a certain number of equally thick sulfonated carbon-nanotubes/Nafion layers. The thickness of the layers varies from 40 μ m to 0.5 μ m. This study indicates that the multilayered structure in composite membranes, especially in membranes with ultrathin layers (< 1 μ m), encourages the alignment of the sulfonated carbon-nanotubes and the proton-conducting pathways in the lateral direction (parallel to the membrane interface). The multilayered structure also improves the dispersion of sulfonated carbon-nanotubes, which leads to a uniformly-distributed proton-conducting network. Therefore, the multilayer composite membranes are excellent proton conductors in the lateral direction at different temperatures. In addition, due to the formation of a hydrophilic interface between the layers, the composite membranes show a higher water-retention capacity. Furthermore, the lateral-aligned sulfonated carbon-nanotubes lead to significantly improved mechanical properties of the multilayer composite membranes, which results in a better electrochemical stability and a long-term performance stability of membranes. ● Lateral-aligned Su-CNTs/Nafion composite membranes with multilayered structure were prepared. ● Multilayered structure encourages the lateral alignment of the Su-CNTs and proton-conducting pathways. ● Lateral-aligned Su-CNTs show anisotropic reinforcement on membranes. ● Lateral-aligned Su-CNTs result in significantly improved mechanical properties of membranes. ● Lateral-aligned Su-CNTs/Nafion composite membranes show enhanced long-term performance stability. [ABSTRACT FROM AUTHOR]

Although the role of cathepsin C (Cat C) in inflammation is gradually being elucidated, its function in periapical periodontitis, which is one of the most common infectious diseases worldwide, has not been studied. This study evaluated a surgically-induced model of periapical periodontitis in cathepsin C (Cat C) knock-down (KD) mice, which was constructed with a tetracycline operator, to evaluate the role of Cat C in the pathogenesis and progression of periapical periodontitis. Our results showed, for the first time, that there was a statistically significant increase in the expression of Cat C as periapical periodontitis progressed; this increase started from 1 week after surgery and reached a peak at 3 weeks after surgery, before gradually decreasing. The volume of periapical bone resorption in Cat C KD mice was significantly smaller than that in wild-type mice at 3 and 4 weeks after surgery (P <0.05). Inflammatory cell infiltration into the apical tissues of wild-type mice was also significantly higher than that of Cat C KD mice. The expression of receptor activator of nuclear factor-κB ligand (RANKL) in wild-type mice was also higher than that in Cat C KD mice. The difference in the number of osteoclasts in the apical area between the two groups was statistically significant after 2 weeks. Correlation analysis showed that there was a significant correlation between Cat C and RANKL expression (r = 0.835). Therefore, our data indicated that Cat C promoted the apical inflammation and bone destruction in mice. [ABSTRACT FROM AUTHOR]

Abstract In order to enhance the interaction between GO/TiO 2 nanostructure and SiO 2 microsphere, graphene oxide/WO 3 quantum dots/TiO 2 @SiO 2 (GOWTS) microspheres were prepared by using urchin-like SiO 2 microsphere as template, and were characterized with X-ray diffractometer (XRD), nitrogen adsorption analyzer, scanning electron microscope (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscope (XPS), respectively. Furthermore, the photocatalytic activity was tested by degrading Rhodamine b (RhB) solution. The resultant GOWTS microsphere possesses very good photocatalytic performance under UV light or nature solar light, in which the decomposition rate of Rhodamine B (RhB) reached 100% within 60 min under nature solar light without stirring. The degradation rate constant of GOWTS is about 3 times of GOTS. Moreover, the GOWTS microspheres display very good photocatalytic stability, indicating a potential industrial application in sewage treatment. Highlights • Graphene oxide/WO 3 quantum dots/TiO 2 @SiO 2 microspheres (GOWTS) were prepared. • The urchin-like SiO 2 microsphere was prepared and used as template. • The SiO 2 microsphere was decorated by graphene oxide/WO 3 quantum dots/TiO 2 hybrids. • GOWTS microspheres possess very good photocatalytic performance under nature solar light. [ABSTRACT FROM AUTHOR]

To improve the photocatalytic activity and electrochemical performance, WO 3 quantum dots (WO 3 QDs) were used to modify GO/TiO 2 (GOT) composites by sol-gel method, and the resultant GO/WO 3 /TiO 2 (GOWT) composites were characterized. Experimental results show that WO 3 QDs can enhance photocatalytic activity of GOT composite under visible light, in which its degraded efficiency for Rhodamine B (RhB) is about three times as that of GOT composite. Furthermore, GOWT composite possess excellent electrochemical performance. The enhanced photocatalytic activity is attributed to the special band gap structure and excellent electrochemical properties of WO 3 QDs. [ABSTRACT FROM AUTHOR]

Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3- δ (BSCF)/Gd 0.2 Ce 0.8 O 1.9 (GDC) dual-gradient cathodes for solid oxide fuel cells (SOFCs) were prepared via a spraying-sintering route, using corn starch as a pore-forming agent. The X-ray diffraction (XRD) analysis results revealed that the BSCF and GDC showed good chemical compatibility even at 1200 °C. The scanning electron microscopy (SEM) results indicated that a graded pore structure, in addition to a gradient composition, can be obtained by regulating the dosage of the pore-forming agent. Consequently, the dual-gradient cathode possessed a low polarization resistance of 0.25 Ω cm 2 at 750 °C, when the pore-forming agent contents were graded at 5 wt%, 10 wt%, and 15 wt% from the inner sub-layer to the outer sub-layer, respectively. This comparative study indicated that high levels of porosity are beneficial for oxygen transport; however, the variation in the porosity of the adjoining sub-layers should be tailored to guarantee the provision of continuous conductive paths for charge carriers. [ABSTRACT FROM AUTHOR]

The Bi 2 WO 6 /graphene oxide (BWO/GO) nanoflake hybrids were prepared by cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal method. Compared with the pure BWO catalysts, the resultant BWO/GO nanohybrids exhibited higher adsorptive ability and visible-light photocatalytic activity for rhodamine B (RhB) under Xe lamp irradiation. Furthermore, it has a high circulative stability and antibacterial ability. This work will provide some supports for the potential applications of BWO/GO nanohybrids in photocatalysis and antibacterial materials under common environment. [ABSTRACT FROM AUTHOR]

Mesoporous carbon is constructed by monolithic polyaromatic mesophase deriving from the hexane insoluble of coal-tar pitch. This carbon material exhibits spherical morphology and layered crystallite, and thereby can be graphitized at 900 °C without destroying the mesoporous structure. Electrochemical measurements indicate that graphitic mesoporous carbon (GMC) support not only improves the activity of Pt electrocatalyst to oxygen reduction reaction (ORR), but also shows higher corrosion resistance than commercial XC-72 carbon black in the acid cathode environment. [ABSTRACT FROM AUTHOR]

Graphene/ZnO-Bi2O3nanoplates (GZB) were prepared by means of the low temperature hydrothermal method, and their photocatalytic activity for degradating rhodamine B (RhB) was studied. Experimental results show that the ZnO-Bi2O3nanoparticles were supported on graphene sheet under the assist of cetyltrimethylammonium bromide (CTAB). Furthermore, the resultant GZB nanoplates exhibited very strong adsorption capacity and high photocatalytic activity, in which the first absorbed ability comes up to about 74.62% within 30 min. Moreover, 90% RhB in solution can be degraded within 100 min under visible light after the sample reach the maximum adsorption. [ABSTRACT FROM PUBLISHER]

Water debinding technique was applied in preparing injection molded large-sized parts. The results showed that the origin of cracking and blistering defects was the swelling from polyethylene glycols of folded chain crystal. The combination of polyethylene glycols with molecular weight 600 and 4000 could ensure both debinding quality and green body strength. It was shown that higher than 20% of insoluble backbone binder was sufficient to resist the stress from swelling. For the compact with length sale of 3.14 mm (the ratio of volume to surface area), approximately 65% of polyethylene glycols were leached after 22 h at 40°C. [ABSTRACT FROM AUTHOR]

Abstract: Monoclinic BiVO4 nanorods and nanoplates were synthesized via the CTAB/water/n-butanol/n-octane microemulsion-mediated hydrothermal process. The physical and photophysical properties of the as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, and UV–vis diffuse reflectance spectroscopy (UV–vis). It was found that the ratio of H2O to CTAB in microemulsion played a key role in the morphology evolution of the products. The possible formation mechanism of BiVO4 nanostructure with various morphologies was briefly discussed. The Raman results indicated that the symmetry distortions in the local structure of the synthesized BiVO4 were affected by the morphology of the products. The bandgaps (E g) of BiVO4 nanorods and nanoplates are 2.45 and 2.38eV, respectively. The synthesized BiVO4 nanoplates showed superior photocatalytic activity compared with BiVO4 nanorods due to their higher degree of structural distortion, larger surface area, and thinness. [Copyright &y& Elsevier]

Abstract: Novel Fe doped mesoporous TiO2 microspheres were fabricated by an ultrasonic–hydrothermal method when tetrabutyl titanate was used as a precursor and octadecylamine was used as a structure-directing agent. The mesoporous materials were characterized by XRD, SEM, TEM, N2 adsorption–desorption measurements, XPS, FL, and UV–vis. The results suggest that both ultrasonic treatment and hydrothermal procedure are critical for the fabrication of Fe doped mesoporous TiO2 microspheres with a combination of regular morphology, large specific surface area, high crystallinity, and high thermal stability. Low-angle XRD and TEM images indicate that the disordered wormhole-like mesostructure of Fe doped TiO2 microspheres with diameters of about 300−400nm is actually formed by the agglomerization of nanoparticles with an average size of about 10nm. The photocatalytic activity of Fe doped mesoporous TiO2 microspheres was evaluated by the photodegradation of methyl orange. A small amount of Fe3+ can obviously enhance their photocatalytic activity. The optimal atomic ratio of Fe to Ti for photocatalytic activity is about 0.5at%. [Copyright &y& Elsevier]

Abstract: H2S is generally very low in fresh water lacustrine origin oil and gas deposits, while unusual high amounts of H2S in thermal recovery pilot areas may be formed in situ during steam injection process. Present paper shows such kind of case study from the Liaohe Basin, NE China, where abundant heavy oil accumulated in the Eogene sandstone reservoirs with burial depth shallower than 1000m. Qi 40 Block is one of pilot areas where steam injection was applied for heavy oil recovery. Almost no H2S can be detected in initial gas production, while up to 3% of H2S occurs in associated gas after thermal recovery. We proposed that most of H2S were derived from the TSR (thermochemical sulfate reduction) during thermal recovery, even though minor amount of H2S from thermal decomposition of organosulfur compound (TDS) within oil cannot be ruled out. Heavy oils in the Liaohe Basin contain very low amount of sulfur (generally <0.3%), which cannot generate decent amount of H2S during thermal decomposition of heavy oil. However, the formation water in Eogene Shahejie Formation is rich in sulfate ions (SO4 2−), which can provide reactant for TSR reaction triggered by thermal stress from injected steam. Geochemical data including sulfur isotope of H2S, oil, sulfate, and natural gas, support the conclusion that the abundant H2S from the steam drive pilots of the Liaohe Basin are mainly originated from TSR effect under high temperature during the thermal recovery process. The observed δ 34S variations lend support to the conclusion that in situ thermochemical sulfate reduction can occur during thermal recovery process. The intensity of TSR and amount of H2S occurring in pilot areas is controlled by methods of steam injection, temperature and times of treatment. [Copyright &y& Elsevier]

Abstract: Cubic aluminum nitride has been obtained in carbothermal reduction reaction at 1700–1800 °C under a flowing nitrogen stream. The as-synthesized products were characterized by XRD, SAD and IR spectrum. The results indicated the product was consisted of wurtzite hexagonal AlN, cubic AlN and corundum. It is speculated that the nucleation and growth of cubic AlN result from the transition of cubic AlON, since intermediate AlON in carbothermal reduction has the same cubic symmetry as cubic AlN. Cubic AlN are unstable metastable phase and are easily transformed into stable hexagonal AlN via crystalline transition with increasing reaction temperature or reaction time. The formation mechanism of cubic AlN is also discussed. [Copyright &y& Elsevier]

Asphalt, as an indispensable binder in road paving, plays an important role in transportation development. However, the mechanism of action between the modifier and asphalt cannot be fully explained by the existing test methods. This paper combines molecular simulations with experiments to provide a research and analysis tool to evaluate the "structure−performance" relationship of asphalt. From the trend of experimental results, the optimal content of Nano-Fe2O3 is 1% to 3%. The AFM micrograph of the asphalt material shows that at 3%, the Nano-Fe2O3 can be effectively dispersed in the asphalt and the unique " bee structures " of the asphalt can be adsorbed around the modifier. Molecular dynamics studies and results show that when Nano-Fe2O3 are incorporated into the asphalt and have a strong adsorption force on the colloidal structure of asphalt, the " bee structures " can be adsorbed around the Nano-Fe2O3. In the range of 208–543 K, the sol-gel structure of asphalt in the Nano-Fe2O3/asphalt composite system is gradually disrupted. [ABSTRACT FROM AUTHOR]

Previous studies on high-pour-point (PPT) oil have focused on the effects of temperature. There has been no systematic investigation of the pressure-sensitivity of crude oil, the deposition composition change of solid phases, and the effects of asphaltene deposition on wax precipitation. In the development of a high-PPT oil field, experiments using dead oil instead of live oil will exaggerate the effect of wax precipitation. In this paper, the wax appearance temperature (WAT), PPT, and asphaltene deposition pressure were obtained by the laser transmittance method. Subsequently, a new set of experimental devices and methods were developed to analyze the solid-phase components in live oil under various conditions. Finally, the viscosity of crude oil at various shear rates was measured with a capillary viscometer, and the wax network structure was evaluated. The experimental results showed that the WAT and PPT decrease with decreased pressure, and their fast decreasing ranges were 12–18 MPa and 15–18 MPa, respectively. The oil pressure-sensitivity not only includes the influence of wax; the appearance of the platform stage and trough pattern phenomenon proves that there is also the influence of asphaltenes. The main component of the deposition is C 27+ , and the amount of wax precipitated can reach 2.72%. For crude oil with a pressure lower than 15.83 MPa, the amount of asphaltene deposition reaches 0.04% at temperatures above WAT. Asphaltene can inhibit the aggregation and growth of wax crystal molecules, leading to a decrease in WAT and an increase in the viscosity at temperatures above WAT; however, the inhibition may be advanced or delayed with decreased pressure. Asphaltene also enhanced the strength of the wax crystal network structure, leading to an increase in the viscosity of crude oil at the critical shear stress under low pressure. When wax precipitation is dominant, there is a positive correlation between asphaltene deposition and wax, and the growth rate of wax is higher than that of nucleation in the early stage. This study improves the understanding of the effect of pressure on the physical properties of high-PTT live oil, provides reliable parameters for numerical simulations and the adjustment of the injection scheme, and lays the foundation for future evaluation experiments on wax removal chemicals. • A new experimental device and method are developed to analyze solid-phase components. • The pressure-sensitivity of high-pour-point oil includes the influence of wax and asphaltene. • The inhibition of asphaltene on wax precipitation may be advanced or delayed with the decrease of pressure. [ABSTRACT FROM AUTHOR]

• 1D in-situ combustion (ISC) simulation has performed on core from heavy oil reservoir. • Concentrations of saturated and aromatic hydrocarbons behavior regularly in ISC zones. • Molecular parameters based on degree of isomerization are insensitive to ISC process. • Geochemical proxies derived from degree of thermal cracking can monitor ISC process. • Occurrence of anthracene and benzo[a]anthracene is supplementary evidence of ISC. 1-D combustion tube in-situ combustion (ISC) simulation experiment has been performed on a natural bitumen bearing core. Five ISC zones were distinguished on the basis of the temperature filed and oil saturation analysis of the experiment. A suite of six oil sand residues at different locations after ISC simulation (initial, oil bank, condensation, coking, combustion zone and burned zone, respectively) were obtained for further analysis by using gas chromatography-mass spectrometry to assess the ISC impact and possible proxies monitoring the ISC process. Compounds in the saturated and aromatic hydrocarbon fractions change systematically with increasing temperatures. The concentrations of various compound classes increase generally from the initial zone to the combustion zone, then decrease drastically in the burned zone. However, different compounds show distinct behaviors during ISC and several geochemical proxies were temporary proposed. The amount of light molecular weighted n -alkanes increases significantly, while isoprenoids and heavy molecular weighted n -alkanes show the same trend but less dramatic changes. The ratios of n -C 17 /pristane (Pr) and n -C 18 /pyhtane (Ph) and ∑ n -C 20 −/∑ n -C 20 + increase continuously from the initial zone to the combustion zone and clearly reflect ISC impact. A similar proxy can be derived from the ratio of summed n -alkanes to summed pentacyclic terpanes (∑ n -alkanes/∑PTs), which increase more perceptibly due to easy decomposition of biomarkers. In the aromatic fraction, the most sensitive proxy to monitor ISC is derived from degree of alkylation of aromatic homologues. Non-substituted compounds especially naphthalene and phenanthrene increase constantly from the initial zone to the burned zone accompanied by the depletion of highly alkylated counterparts. Some newly formed compounds such as 2-methylanthracene and benz[a]anthracene are defined combustion evidence. However, commonly used maturity parameters based on relative stability of different isomers show no significant variation and cannot serve as valid ISC proxies. [ABSTRACT FROM AUTHOR]