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As an emerging field of research, learning analytics (LA) offers practitioners and researchers information about educational data that is helpful for supporting decisions in management of teaching ...

To investigate the effect of atmospheric corrosion on the fatigue properties of 2024-T4 aluminum alloy structures during the whole corrosion period, atmospheric and accelerated pre-corrosion fatigue tests were carried out. Field exposure tests were carried out for 7, 12, and 20 years. A laboratory accelerated corrosion test method was proposed to simulate the whole atmospheric corrosion period from initial pitting to the subsequent exfoliation corrosion, and the reliability was verified through an analysis of the corrosion morphology, corrosion products, and thickness variation. Pitting and intergranular corrosion occurred after a short exposure to atmospheric corrosion, and intergranular corrosion was the dominant corrosion damage mode. The fatigue cracks initiated at the deepest boundary of intergranular corrosion. The fatigue life decreased dramatically during the initial stage of atmospheric corrosion and then decreased more slowly. Finally, the mechanism through which atmospheric corrosion affected the fatigue properties was analyzed.

Polysaccharide is a key bioactive component of Schisandra chinensis and has significant pharmacological activities. The aim of this study was to evaluate the anti-diabetic effect of acidic polysaccharide from Schisandra chinensis (SCAP). Type 2 diabetic (T2D) rats were developed by giving a high-fat diet (HFD) combined with low-dose streptozotocin (STZ), and administered orally with SCAP (25, 50 mg/kg) for 8 weeks. Fasting blood glucose (FBG), fasting insulin (FINS), triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), malondialdehyde (MDA), and superoxide dismutase (SOD) in the rat's serum were measured. Oral glucose tolerance test (OGTT) and pathological changes of pancreas were observed. Furthermore, expressions of c-Jun N-terminal kinase (JNK), B-cell lymphoma 2-associated X protein (BAX), B-cell lymphoma 2 (Bcl-2), and Cleaved Caspase-3 in pancreatic islet were detected. The results showed that SCAP decreased FBG, TG, TC, LDL-C and MDA levels, increased insulin, HDL-C levels and SOD activity, improved the pathological changes in pancreatic islet. Furthermore, SCAP inhibited the up-regulation of phosphorylated JNK, BAX and Cleaved Caspase-3 proteins, and increased Bcl-2 protein expression. These data indicate that SCAP has a therapeutic effect in T2D rats, and the mechanism may be related to its protection against β-cells apoptosis by regulating apoptosis-related proteins expression to alleviate the injury caused by the oxidative stress.

The study proposes two new measures, time and location entropy, to depict students’ physical spatio-temporal contexts when engaged in an online course. As anytime, anywhere access has been ...

Depolymerization of lignin to low-molecular-weight products plays a vital role in upgrading of lignin into high-value chemicals. One of the problems of lignin depolymerization is the recondensation...

The surface and sectional corrosion behavior of anodized 2024-T4 exposed for 7 and 20 years was investigated. After 7 years of exposure, mild exfoliation corrosion had partially occurred. Pitting and intergranular corrosion (IGC) coexisted in the unexfoliation corrosion area. Due to the continuous formation of corrosion products beneath the surface and their difficulty in being transported through the IGC channel, surface blisters were eventually formed. After 20 years, severe exfoliation corrosion had occurred on the entire surface and cracked corrosion products were partly covered by filamentous corrosion products Al(OH)3. The formation of filamentous corrosion products is the interaction between the ventilated environment, the long-term weathering, and the agglomeration of the Al(OH)3 particles. Interestingly, most of the continuously corroded grain boundaries with severe IGC on the longitudinal section were parallel to the extrusion direction. The grain orientation, high precipitates continuity at grain boundaries and weak restraint of material itself to the expansion of IGC products are the reasons for this phenomenon by EBSD, SEM, TEM and mechanical analyses.

Charge carrier scattering is critical to the electrical properties of two-dimensional materials such as graphene, transition metal dichalcogenide monolayers, black phosphorene, and tellurene. Beyond pristine two-dimensional materials, further tailored properties can be achieved by nanoporous patterns such as nano- or atomic-scale pores (antidots) across the material. As one example, structure-dependent electrical/optical properties for graphene antidot lattices (GALs) have been studied in recent years. However, detailed charge carrier scattering mechanism is still not fully understood, which hinders the future improvement and potential applications of such metamaterials. In this paper, the energy sensitivity of charge-carrier scattering and thus the dominant scattering mechanisms are revealed for GALs by analyzing the maximum Seebeck coefficient with a tuned gate voltage and thus shifted Fermi levels. It shows that the scattering from pore-edge-trapped charges is dominant, especially at elevated temperatures. For thermoelectric interests, the gate-voltage-dependent power factor of different GAL samples are measured as high as 509 at 400 K for a GAL with the square pattern. Such a high power factor is improved by more than one order of magnitude from the values for the state-of-the-art bulk thermoelectric materials. With their high thermal conductivities and power factors, these GALs can be well suitable for "active coolers" within electronic devices, where heat generated at the hot spot can be removed with both passive heat conduction and active Peltier cooling.

We report a novel electro-reduction process that can convert CO2 to high-valued fuels with low electrolysis energy. In a designed electrolysis cell, a chemical regenerative catalyst, phosphomolybdic acid (PMo12), was used as an electron-coupled proton carrier, and glycerol, a by-product of biodiesel synthesis, was employed as a reducing agent to provide electrons to PMo12 under photo irradiation. Glycerol was firstly oxidized to value-added products of glyceric acid and acetic acid under the catalysis under PMo12, after an electrical potential was applied, the reduced PMo12 (H PMo12(red)) releases electrons and was re-oxidized to PMo12 on the anode, while CO2 was reduced into valuable hydrocarbons by taking electrons on the cathode. The developed approach has multiple advantages over the conventional CO2 electrolysis, e.g. low electrolysis potential, and a noble metal-free anode due to the low overpotential of H PMo12(red) oxidation on the anode. The electrolysis current densities of 0.23 and 0.29 Acm−2 were achieved under 2.0 V of electrolysis voltage for the Cu and Ag cathode, respectively, which is 2–3 times of conventional electrolysis. The faradaic efficiency for CO2 reduction is 63.53% and 77.75% at 1.9 V, and the energy efficiency is 45.60% and 53.67% for the Cu and Ag electrode, respectively.

Performance prediction is a leading topic in learning analytics research due to its potential to impact all tiers of education. This study proposes a novel predictive modeling method to address the research gaps in existing performance prediction research. The gaps addressed include: the lack of existing research focus on performance prediction rather than identifying key performance factors; the lack of common predictors identified for both K-12 and higher education environments; and the misplaced focus on absolute engagement levels rather than relative engagement levels. Two datasets, one from higher education and the other from a K-12 online school with 13 368 students in more than 300 courses, were applied using the predictive modeling technique. The results showed the newly suggested approach had higher overall accuracy and sensitivity rates than the traditional approach. In addition, two generalizable predictors were identified from instruction-intensive and discussion-intensive courses.

Acupuncture may be beneficial for patients with mild hypertension, but the evidence is not convincing. We aimed to examine the effect of acupuncture on blood pressure (BP) reduction in patients with mild hypertension. We conducted a multicenter, single‐blind, sham‐controlled, randomized trial in eleven hospitals in China. The trial included 428 patients with systolic blood pressure (SBP) from 140 to 159 mm Hg and/or with diastolic blood pressure (DBP) from 90 to 99 mm Hg. The patients were randomly assigned to receive 18 sessions of affected meridian acupuncture (n = 107) or non‐affected meridian acupuncture (n = 107) or sham acupuncture (n = 107) during 6 weeks, or to stay in a waiting‐list control (n = 107). All patients received 24‐hour ambulatory blood pressure monitoring at weeks 6, 9, and 12. We included 415 participants in the intention‐to‐treat analysis. The two acupuncture groups were pooled in the analysis, since they had no difference in all outcomes. SBP decreased at week 6 in acupuncture group vs sham acupuncture vs waiting‐list group (7.2 ± 11.0 mm Hg vs 4.1 ± 11.5 mm Hg vs 4.1 ± 13.2 mm Hg); acupuncture was not superior to sham acupuncture (mean difference 2.7 mm Hg, 95% CI 0.4 to 5.9, adjusted P = 0.103) or waiting‐list control (2.9 mm Hg, 95% CI −0.2 to 6.0, adjusted P = 0.078). However, acupuncture was superior to sham acupuncture (3.3 mm Hg, 95% CI 0.2 to 6.3, adjusted P = 0.035) and waiting‐list control (4.8 mm Hg, 95% CI 1.8 to 7.8, P

Li-based batteries are intrinsically unsafe because of their use of flammable organic electrolyte. Great efforts are being made to develop solid electrolytes or safer alternative battery chemistries, among which Zn-based batteries stand out for their high energy density and good compatibility with aqueous electrolyte. Theoretically, Zn-air batteries have very high volumetric energy density, which is ∼85% of that of Li-S batteries. However, Zn anodes have poor cycling performance because of their passivation (insulating discharge product ZnO) and dissolution (soluble zinc species in alkaline electrolytes) problems. In this work, we overcome these problems by modifying Zn anode with graphene oxide (Zn@GO) by a facile solution casting method. The GO layers on the Zn surface can deliver electrons across insulating ZnO, slow down the Zn intermediates from dissolving into the electrolyte, and thereby enhance the utilization and rechargeability of Zn anodes. As a result, the Zn@GO anode containing only 1.92 wt% GO showed improved cycling performance compared to that of the unmodified Zn mesh. The accumulated areal discharge capacity of the Zn@GO anode is 128% of that of the unmodified Zn mesh. The Zn@GO anode reported here can potentially be paired with oxygen cathode to form safe high-energy rechargeable batteries, and be used in large scale applications, ranging from electric vehicles, to grid-scale energy storage. The surface modification method reported here can also potentially be applied to other high-capacity electrodes that undergo passivation or dissolution issues.

Zirconium pentatelluride (ZrTe5) has recently attracted renewed interest owing to many of its newly discovered extraordinary physical properties, such as 2D and 3D topological-insulator behavior, p...

Vapor compression heat pump is of great significance to space thermal control. It can effectively regulate the temperature of electronic devices to ensure proper operation. Weightlessness is a significant factor affecting the operation. Weightlessness test of vapor compression heat pump was conducted to investigate the weightless effect on its performance. Weightlessness test was achieved by free fall on a platform 60 m above the ground. The tests of continuous weightlessness and single stroke of weightlessness were presented and analyzed. The results showed that the weightlessness decreased the evaporative heat transfer performance and enhanced the condensation heat transfer performance. It is then advisable to increase heat transfer area of the evaporator in the design of future vapor compression heat pumps, and the design of condensers could still be based on the routine method adopted in ground applications. This part of experimental data for space application of vapor compression heat pump is expected to be of great significance.

An efficiency-oriented innovation analysis will enhance the understanding of the operational quality related to the transformation process of limited innovation investments for improving innovation outputs. The purpose of this study was to measure the static-dynamic efficiency of agricultural science, technology, and innovation (ASTI) and identify the efficiency determinants across the Group of Twenty (G20) countries. First, the static comprehensive efficiency of ASTI was measured employing the Data Envelopment Analysis (DEA)-BCC model, and some of the binding constraints to higher efficiency were investigated. Then, we applied the DEA-Malmquist index model to calculate the efficiency change of ASTI in certain periods and decomposed the sources of efficiency change. Finally, the G20 countries were classified into four-level clusters based on the rankings of efficiency measurement and capability evaluation of ASTI to locate the type of ASTI level and identify the type change in both the efficiency and capability. The empirical results indicate the following. (1) The efficiency range of the G20 developing countries was relatively larger than the G20 developed countries. The G20 developed countries showed a fluctuating downward trend, while the G20 developing countries showed an upward trend from the perspective of efficient proportion. The R&amp, D expenditure redundancy and the agricultural journal papers deficiency were the main binding constraints to the higher efficiency of ASTI. (2) The total factor productivity change (TFPC) of ASTI showed an alternating trend of “decline–growth–continuous decline–growth recovery”, where the G20 developed countries experienced “growth–decline–growth” and the G20 developing countries underwent a fluctuating upward trend. The TFPC of ASTI in most G20 countries was primarily due to technological change. (3) The G20 developed countries usually had advantages in capacity, while the G20 developing countries performed better in efficiency.

OBJECTIVE: To study the clinical features of children with recurrent medulloblastoma (MB) and treatment regimens. METHODS: A retrospective analysis was performed on 101 children with recurrent MB who were admitted to the hospital from August 1, 2011 to July 31, 2017. The children were followed up to July 31, 2020. The Kaplan-Meier method was used for survival analysis. The Cox regression model was used for multivariate regression analysis. RESULTS: Of the 101 children, 95 underwent remission induction therapy, among whom 51 had response, resulting in a response rate of 54%. The median overall survival (OS) time after recurrence was 13 months, and the 1-, 3-, and 5-year OS rates were 50.5%±5.0%, 19.8%±4.0%, and 10%±3.3% respectively. There was no significant difference in the 5-year OS rate between the children with different ages (< 3 years or 3-18 years), sexes, pathological types, or Change stages, between the children with or without radiotherapy before recurrence or re-irradiation after recurrence, and between the children with different times to recurrence (< 12 months or ≥ 12 months after surgery) (P > 0.05). There were significant differences in the 5-year OS rate between the children with or without reoperation after recurrence and between the children with different recurrence sites (P < 0.05). The children with reoperation after recurrence had a significantly longer survival time than those without reoperation (P=0.007), and the risk of death in children undergoing reoperation after recurrence was 0.389 times (95% confidence interval:0.196-0.774) that in children who did not undergo such reoperation. CONCLUSIONS: As for the recurrence of MB, although remission induction therapy again can achieve remission, such children still have a short survival time. Only reoperation can significantly prolong survival time, and therefore, early reoperation can be considered to improve the outcome of children with recurrent MB.

We propose a novel scalable Web portal called LSOMP (Large Scale Ordinance Mining Portal) to analyze ordinances and their tweets (of the order of thousands and millions). It entails commonsense knowledge (CSK) and natural language processing (NLP), disseminating ordinance-tweet mining results via interactive graphics and Question Answering (QA).

Skid Steering vehicles are being widely used due to their robust mechanical structure and high maneuverability. Moving object tracking for unmanned skid-steered vehicle (USSV) is a challenging task that requires delicate actions to ensure a smooth trajectory and accurate response between ego vehicle and the moving object. However, inevitable slipping and sliding of the tire that makes the vehicle difficult to control and accurate model of USSV are hard to describe. This paper proposes a real-time moving object tracking system with continuous actions for USSV base on a reinforcement learning algorithm named Twin Delay Deterministic Policy Gradient (TD3). The capacity of the replay buffer, which is critical in the training process, changes softly as the training episodes increases. We added two control group models with a fixed capacity of replay buffer and trained the RL agent from scratch in the gazebo environment. By observing the training and validation results, we can conclude that our RL model performs well for moving target tracking, and the model with soft updated replay buffer has high efficiency in the training process and high accuracy in the evaluation process.

The integration of renewables into electrical grids calls for novel control schemes, which usually are model based. Classically, for power systems parameter estimation and optimization-based control are often decoupled, which may lead to increased cost of system operation during the estimation procedures. The present work proposes a method for simultaneously minimizing grid operation cost and estimating line parameters. To this end, we rely on methods from optimal design of experiments. This approach leads to a substantial reduction in cost for optimal estimation and in higher accuracy in the parameters compared with standard combination of optimal power flow and maximum-likelihood estimation. We illustrate the performance of the proposed method on simple benchmark system.

With the development of e-commerce, a large number of hotel reviews have been produced. According to the short text features of hotel reviews, sentiment classification method based on emotion dictionary needs a lot of emotional database resources, while machine learning method needs complex artificial design features and feature extraction process. In this paper, long short term memory is proposed. The text classification algorithm is used to analyze the sentiment tendency. Firstly, word2vec and word segmentation technology are used to process the short comment text into the LSTM network, and dropout algorithm is added to prevent over fitting to get the final classification model, Using the unique characteristics of short-term memory of LSTM network, it has achieved a good effect on sentiment classification of hotel reviews, with an accuracy rate of more than 95%.

Based on Eisenberg et al.'s model of prosocial motivations, the present study examined what motivates preschoolers to display instrumental helping and how various motivations develop during the preschool years. The participants were 477 preschoolers aged 3–5 years assigned to one of five groups. In each experimental group, the experimenter emphasized an altruistic or egoistic helping motivation, namely, empathic concern, moral rules, praise or rewards. In the control group, no helping motivations were emphasized. Their instrumental helping was then measured by sorting cards for a sick child to play a game. The results show that each helping motivation had a positive effect on instrumental helping. Most of the motivational effects were similar across age, but the motivational effect of empathic concern increased obviously at the age of 5 years. Therefore, the present study reveals that both altruistic and egoistic motivations motivate preschoolers to help others. Most of the motivations develop steadily during the preschool years, but empathic concern as an altruistic motivation increases greatly at the end of the preschool years. The present study thus confirms the diversity of preschoolers' helping motivations with Eisenberg et al.'s model of prosocial motivations.

The shaping of the waveform of a two- or three-color driving laser pulse is essential for generating an ultrashort isolated attosecond pulse (IAP) from high-order harmonic generation, which can be implemented in two different ways, i.e., direct coherent synthesizing of electric fields with appropriate parameters (wavelength, intensity, carrier envelope phase, time delay), and superposition of fields undergoing a spectral phase shaping in frequency space view, which additionally results in a chirp and pulse-width broadening. In this work, we perform a comparative study on the IAP generation with these two schemes by virtue of a genetic algorithm, and two very meaningful conclusions are clarified. First, weighing the advantages and disadvantages of the two methods, the width and strength of IAPs optimized from two schemes are basically the same. More optimization parameters in the second method of laser shaping do not show an advantage in shortening width or enhancing the intensity of the IAP compared with the first one. Second, in each case, one can get the shortest IAP when the carrier envelope phases for each spectral component are not required to be precisely controlled. This study provides useful theoretical guidance for generating a shorter IAP with multicolor gating in the experiment.

As a result of mutations in the upstream components of the Wnt/β-catenin signaling pathway, this cascade is abnormally activated in colon cancer. Hence, identifying the activation mechanism of this pathway is an urgent need for the treatment of colon cancer. Here, we found an increase in ADCK1 (AarF domain-containing kinase 1) expression in clinical specimens of colon cancer and animal models. Upregulation of ADCK1 expression promoted the colony formation and infiltration of cancer cells. Downregulation of ADCK1 expression inhibited the colony formation and infiltration of cancer cells, in vivo tumorigenesis, migration, and organoid formation. Molecular mechanistic studies demonstrated that ADCK1 interacted with TCF4 (T-cell factor 4) to activate the β-catenin/TCF signaling pathway. In conclusion, our research revealed the functions of ADCK1 in the development of colon cancer and provided potential therapeutic targets.

First-principles calculations are carried out by DFT within the CASTEP plane wave code to investigate the mechanical properties and electronic structure of N and Al doped TiC. The results show that the co-doping of nitrogen and aluminum narrows the lattice constant and nitrogen could enhance the stability of TiC, however, aluminum makes the compound unstable. The calculated elastic constants and elastic moduli reveal that aluminum reduces the elastic constants, bulk modulus B, shear modulus G and Young's modulus E, but nitrogen can enhance them. The results of B/G and C12–C44 indicate that aluminum could significantly increase the ductility of TiC. Meanwhile, the electronic structure calculations reveal that strong p–d covalent bonds exist among C-p, N-p, Ti-d and Al-p states and Al-doping causes DOS peak transfer to a higher energy level and increases the DOS above the Fermi level. The hardness is estimated by a semi-empirical model that is based on the Mulliken overlap population and bond length. The addition of Al sharply reduces the hardness of the TiC-based alloys due to the weakest bond taking a determinative role in the hardness of materials, which is the C–Al bond in those compounds.

OBJECTIVE: To study the clinical effect of surgery combined with chemotherapy and radiotherapy in children with central primitive neuroectodermal tumor (cPNET), as well as the risks factors for poor prognosis. METHODS: A retrospective analysis was performed for the clinical data of 42 children who were diagnosed with cPNET from June 2012 to September 2018. RESULTS: The 42 children had a median overall survival (OS) time of 2.0 years and a median event-free survival (EFS) time of 1.3 years; the 1-, 3-, and 5-year OS rates were 76.2%±6.6%, 41.4%±8.7%, 37.3%±8.8% respectively, and the 1-, 3-, and 5-year EFS rates were 64.3%±7.4%, 32.7%±8.0%, 28.0%±8.1% respectively. The univariate analysis showed that there were significant differences in the OS and EFS rates among the children with different patterns of surgical resection, chemotherapy cycles, and risk grades (P < 0.05), and there was also a significant difference in the OS rate between the children receiving radiotherapy and those not receiving radiotherapy (P < 0.05). The multivariate Cox regression analysis showed that chemotherapy cycles and risk grade were independent influencing factors for EFS and OS rates (P < 0.05). The EFS and OS rates increased with the increase in chemotherapy cycles and the reduction in risk grade. CONCLUSIONS: Multimodality therapy with surgery, chemotherapy, and radiotherapy is an effective method for the treatment of cPNET in children. Early diagnosis and treatment and adherence to chemotherapy for as long as possible may improve EFS and OS rates.

Lignin is the largest source of renewable aromatic compounds, making the recovery of aromatic compounds from this material a significant scientific goal. Recently, many studies have reported on lignin depolymerization and upgrading strategies. Electrochemical approaches are considered to be low cost, reagent free, and environmentally friendly, and can be carried out under mild reaction conditions. In this Review, different electrochemical lignin conversion strategies, including electrooxidation, electroreduction, hybrid electro-oxidation and reduction, and combinations of electrochemical and other processes (e. g., biological, solar) for lignin depolymerization and upgrading are discussed in detail. In addition to lignin conversion, electrochemical lignin fractionation from biomass and black liquor is also briefly discussed. Finally, the outlook and challenges for electrochemical lignin conversion are presented.

Professor

In practical propagation environments, different massive MIMO users can have correlated angles in spatial paths. In this paper, we study the effect of angle correlation on inter-user channel correlation via a combination of measurement and analysis. We show three key results. First, we collect a massive MIMO channel dataset for examining the inter-user channel correlation in a real-world propagation environment; the dataset is now open-access. We observed channel correlation higher than $0.48$ for all close-by users. Additionally, over $30$ % of far-away users, even when they are tens of wavelengths apart, have inter-user channel correlation that is at least twice higher than the correlation in the i.i.d. Rayleigh fading channel. Second, we compute the inter-user channel correlation in closed-form as a function of inter-user angle correlation, the number of base-station antennas, and base-station inter-antenna spacing. Our analysis shows that inter-user angle correlation increases the inter-user channel correlation. Inter-user channel correlation reduces with a larger base-station array aperture, i.e., more antennas and larger inter-antenna spacing. Third, we explain the measurements with numerical experiments to show that inter-user angle correlation can result in significant inter-user channel correlation in practical massive MIMO channels., accepted to be published by IEEE Transactions on Vehicular Technology

The implementation of aberration-corrected electron beam lithography (AC-EBL) in a 200 keV scanning transmission electron microscope (STEM) is a novel technique that could be used for the fabrication of quantum devices based on 2D atomic crystals with single nanometer critical dimensions, allowing to observe more robust quantum effects. In this work we study electron beam sculpturing of nanostructures on suspended graphene field effect transistors using AC-EBL, focusing on the in situ characterization of the impact of electron beam exposure on device electronic transport quality. When AC-EBL is performed on a graphene channel (local exposure) or on the outside vicinity of a graphene channel (non-local exposure), the charge transport characteristics of graphene can be significantly affected due to charge doping and scattering. While the detrimental effect of non-local exposure can be largely removed by vigorous annealing, local-exposure induced damage is irreversible and cannot be fixed by annealing. We discuss the possible causes of the observed exposure effects. Our results provide guidance to the future development of high-energy electron beam lithography for nanomaterial device fabrication.

Recently, the layered transition metal dichalcogenide 1T′-MoTe2 has generated considerable interest due to their superconducting and non-trivial topological properties. Here, we present a systematic study on 1T′-MoTe2 single-crystal and exfoliated thin-flakes by means of electrical transport, scanning tunnelling microscope (STM) measurements and band structure calculations. For a bulk sample, it exhibits large magneto-resistance (MR) and Shubnikov–de Hass oscillations in ρxx and a series of Hall plateaus in ρxy at low temperatures. Meanwhile, the MoTe2 thin films were intensively investigated with thickness dependence. For samples, without encapsulation, an apparent transition from the intrinsic metallic to insulating state is observed by reducing thickness. In such thin films, we also observed a suppression of the MR and weak anti-localization (WAL) effects. We attributed these effects to disorders originated from the extrinsic surface chemical reaction, which is consistent with the density functional theory (DFT) calculations and in-situ STM results. In contrast to samples without encapsulated protection, we discovered an interesting superconducting transition for those samples with hexagonal Boron Nitride (h-BN) film protection. Our results indicate that the metallic or superconducting behavior is its intrinsic state, and the insulating behavior is likely caused by surface oxidation in few layer 1T’-MoTe2 flakes.

Here, a novel and low cost redox flow fuel cell that directly converts raw biomass to electricity at low temperature without utilizing any noble metal catalyst is reported. In this cell, Fe3+ ion, which has strong oxidizing power and is chemical stable, was directly utilized as an oxidant for biomass in anolyte. The reduced Fe2+ acted as charge carriers, transferring the electrons to the anode of the cell and being converted back to Fe3+ simultaneously. The degradation chemistry of the biomass from the oxidation reaction and the apparent oxidation kinetics were investigated using glucose as the biomass model compound. The results showed that glucose was decomposed to small organic molecules and even CO2, and the reaction rate was significantly affected by temperature and content of reactant. The apparent activation energy of the redox reaction is 127.85 kJ·mol−1 based on the linear relation equation at the initial stage of the reaction. And the preference conditions of the redox reaction are 100–110 °C, 0.2–0.5 mol·L−1 glucose and the mol ratio of C6H12O6/FeCl3 from 1:10 to 1:12. Meantime, a high potential (VO2)2SO4 solution was synthesized as catholyte which was regenerated by O2 in the present of small amount of HNO3. The power density and discharge current density of the biomass redox flow fuel cell could reach 125.7 mW·cm−2 and 314.2 mA·cm−2, respectively, which was about 755 times higher than the reported microbial fuel cell by utilizing glucose as substrate. This work provides a promising way for converting abundant natural biomasses, such as crop straws and bagasse, into electricity at low temperature (80–110 °C).

The integration of renewables into electrical grids calls for the development of tailored control schemes which in turn require reliable grid models. In many cases, the grid topology is known but the actual parameters are not exactly known. This paper proposes a new approach for online parameter estimation in power systems based on optimal experimental design using multiple measurement snapshots. In contrast to conventional approaches, our method computes optimal excitations extracting the maximum information in each estimation step to accelerate convergence. The performance of the proposed method is illustrated with a case study.

Accessing the nonradiative near-field electromagnetic interactions with high in-plane momentum (q) is the key to achieve super resolution imaging far beyond the diffraction limit. At far-infrared and terahertz (THz) wavelengths (e.g., 300 μm = 1 terahertz = 4 meV), the study of high q response and nanoscale near-field imaging is still a nascent research field. In this work, we report on THz nanoimaging of exfoliated single and multilayer graphene flakes by using a state-of-the-art scattering-type near-field optical microscope (s-SNOM). We experimentally demonstrated that the single layer graphene is close to a perfect near-field reflector at ambient environment, comparable to that of the noble metal films at the same frequency range. Further modeling and analysis considering the nonlocal graphene conductivity indicate that the high near-field reflectivity of graphene is a rather universal behavior: graphene operates as a perfect high-q reflector at room temperature. Our work uncovers the unique high-q THz...

A high saturation velocity semiconductor is appealing for applications in electronics and optoelectronics. Thin-film black phosphorus (BP), an emerging layered semiconductor, shows a high carrier mobility and strong mid-infrared photoresponse at room temperature. Here, we report the observation of high intrinsic saturation velocity in 7 to 11 nm thick BP for both electrons and holes as a function of charge-carrier density, temperature, and crystalline direction. We distinguish a drift velocity transition point due to the competition between the electron-impurity and electron–phonon scatterings. We further achieve a room-temperature saturation velocity of 1.2 (1.0) × 107 cm s–1 for hole (electron) carriers at a critical electric field of 14 (13) kV cm–1, indicating an intrinsic current-gain cutoff frequency ∼20 GHz·μm for radio frequency applications. Moreover, the current density is as high as 580 μA μm–1 at a low electric field of 10 kV cm–1. Our studies demonstrate that thin-film BP outperforms silicon ...