The seamless coalescence of parallelly aligned 2D materials is the primary route toward the synthesis of wafer-scale single crystals (WSSCs) of 2D materials. The epitaxial growth of various 2D ...materials on a single-crystal substrate, which is an essential condition of the seamless coalescence approach, has been extensively explored in previous studies. Here, by using hexagonal boron nitride (hBN) growth on a liquid gold surface as an example, we demonstrate that growth of WSSCs of 2D materials via the seamless coalescence of self-aligned 2D islands on a liquid substrate is possible. Here we show that, in the presence of hydrogen, all the hBN edges tend to be hydrogen terminated and the coalescence of hBN islands occurs only if their crystallographic lattices of neighboring hBN islands are aligned parallelly. The mechanism of hBN self-alignment revealed in this study implies that, under the optimum experimental condition, the seamless coalescence of 2D materials on a liquid substrate is possible and thus provides guidance for synthesizing WSSCs of various 2D materials by using liquid phase substrates.
This article investigates the challenges teachers experience while learning to teach English through drama in an action research project. Through closely examining the fundamental causes, it discerns ...the knowledge constituents crucial for successful learning and implementation of drama for English teaching. Difficulties are identified from three aspects: text selection and interpretation, translation into drama activities, and classroom implementation. Referring to Shulman’s teacher knowledge construct (1986, 1987), the author argues that drama pedagogy for English teaching demands a changed perspective on language regarding its form and meaning and also on drama as both subject and pedagogy. Only then can teachers effectively link language and drama and create a meaningful learning experience.
Alarm systems are commonly deployed in complex industries to monitor the operation status of the production process in real time. Actual alarm systems generally have alarm overloading problems. One ...of the major factors leading to excessive alarms is the presence of many correlated or redundant alarms. Analyzing alarm correlations will not only be beneficial to the detection of and reduction in redundant alarm configurations, but also help to track the propagation of abnormalities among alarm variables. As a special problem in correlated alarm detection, the research on first-out alarm detection is very scarce. A first-out alarm is known as the first alarm that occurs in a series of alarms. Detection of first-out alarms aims at identifying the first alarm occurrence from a large number of alarms, thus ignoring the subsequent correlated alarms to effectively reduce the number of alarms and prevent alarm overloading. Accordingly, this paper proposes a new first-out alarm detection method based on association rule mining and correlation analysis. The contributions lie in the following aspects: (1) An association rule mining approach is presented to extract alarm association rules from historical sequences based on the FP-Growth algorithm and J-Measure; (2) a first-out alarm determination strategy is proposed to determine the first-out alarms and subsequent alarms through correlation analysis in the form of a hypothesis test on conditional probability; and (3) first-out rule screening criteria are proposed to judge whether the rules are redundant or not and then consolidated results of first-out rules are obtained. The effectiveness of the proposed method is tested based on the alarm data generated by a public simulation platform.
Healable, electrically conductive materials are highly desirable and valuable for the development of various modern electronics. But the preparation of a material combining good mechanical ...elasticity, functional properties, and intrinsic self‐healing ability remains a great challenge. Here, we design composites by connecting a polymer network and single‐walled carbon nanotubes (SWCNTs) through host–guest interactions. The resulting materials show bulk electrical conductivity, proximity sensitivity, humidity sensitivity and are able to self‐heal without external stimulus under ambient conditions rapidly. Furthermore, they also possess elasticity comparable to commercial rubbers.
Candidates for smart robotics: Self‐healing conductive composites were prepared by connecting single‐walled carbon nanotubes (SWCNTs) to a polymer network through host–guest interactions (see picture). The poly(2‐hydroxyethyl methacrylate)–SWCNT composite combines bulk electrical conductivity, proximity sensitivity, humidity sensitivity, and autonomic self‐healing properties.
Γ-Z-Source Inverters Poh Chiang Loh; Ding Li; Blaabjerg, F.
IEEE transactions on power electronics,
11/2013, Letnik:
28, Številka:
11
Journal Article
Recenzirano
Voltage-type Γ-Z-source inverters are proposed in this letter. They use a unique Γ-shaped impedance network for boosting their output voltage in addition to their usual voltage-buck behavior. ...Comparing them with other topologies, the proposed inverters use lesser components and a coupled transformer for producing the high-gain and modulation ratio simultaneously. The obtained gain can be tuned by varying the turns ratio γ ΓZ of the transformer within the narrow range of 1 <; γ ΓZ ≤ 2. This leads to lesser winding turns at high gain, as compared to other related topologies. Experimental testing has already proven the validity of the proposed inverters.
Metal selenides are considered as one of the most promising anode materials for Na‐ion batteries owing to high specific capacity and relatively higher electronic conductivity compared with metal ...sulfides or oxides. However, such anodes still suffer from huge volume change upon repeated Na+ insertion/extraction processes and simultaneously undergo severe shuttle effect of polyselenides, thus leading to poor electrochemical performance. Herein, a facile chemical‐blowing and selenization strategy to fabricate 3D interconnected hybrids built from metal selenides (MSe, M = Mn, Co, Cr, Fe, In, Ni, Zn) nanoparticles encapsulated in in situ formed N‐doped carbon foams (NCFs) is reported. Such hybrids not only provide ultrasmall active nanobuilding blocks (≈15 nm), but also efficiently anchor them inside the conductive NCFs, thus enabling both high‐efficiency utilization of active components and high structural stability. On the other hand, Cu‐driven replacement reaction is utilized for efficiently inhibiting the shuttle effect of polyselenides in ether‐based electrolyte. Benefiting from the combined merits of the unique MSe@NCFs and the utilization of the conversion of metal selenides to copper selenides, the as‐obtained hybrids (MnSe as an example) exhibit superior rate capability (386.6 mAh g−1 up to 8 A g−1) and excellent cycling stability (347.7 mAh g−1 at 4.0 A g−1 after 1200 cycles).
Superior sodium storage performance of metal selenides is realized by constructing 3D interconnected N‐doped carbon foams and simultaneously utilizing Cu‐driven replacement reaction. The former can facilitate rapid electron and ion transport kinetics while the latter can efficiently inhibit the shuttle effect of polyselenides, thus enabling excellent rate capability and cycling stability.
•20 fragrant compounds with OAV > 1 were detected by GC–MS.•Burnt and honey-like odors contributed greatly to the aroma of Chinese-type soy sauce.•GC × GC-TQMS was used in soy sauce analysis, and 414 ...compounds were detected.•85 other fragrant compounds were detected by GC × GC–TQMS.
In this work, a total of 35 important aroma compounds with odor activity values (OAVs) greater than 1 were detected by gas chromatography–mass spectrometry (GC–MS) in traditional Chinese-type soy sauce. Of these, fragrant compounds with aromatic rings (20 compounds) accounted for a large proportion, over 57%. Combining principal component analysis and GC–olfactometry–MS (GC–O–MS), 5-methyl-2-furanmethanethiol (OAV: 284–467), 3-methylbutanal (OAV: 409–938), phenylacetaldehyde (OAV: 47.4–566), 2–phenylethanol (OAV: 7.41–14.3), phenylethyl acetate (OAV: 7.00–18.1) and ethyl phenylacetate (OAV: 12.7–21.3) were confirmed as the typical fragrant compounds among all samples. Furthermore, full two-dimensional gas mass spectrometry (GC × GC–TQMS) was applied and 414 aroma compounds were identified, which included another 85 fragrant compounds with aromatic rings.
Endoscopic resection (ER) has been a standard treatment modality for early gastric cancer with ignorable risks of lymph node metastasis. As for EGCs within expanded indications, endoscopic submucosal ...dissection (ESD) has considerable advantages over endoscopic mucosal resection (EMR) regarding higher rate of en bloc resection, complete resection, but lower risk of local recurrence. Previous meta-analyses comparing ESD with surgery for EGC are scarce and not robust to reach definitive conclusions.
We searched PubMed, Web of Science, EMBASE, Cochrane Library Databases and Google Scholar through July 2019 to identify studies evaluating ESD vs surgery for EGC. Newcastle-Ottawa Quality Assessment Scale was used to assess the quality of enrolled studies. Patient baseline characteristics, procedure-related and prognosis outcomes, and adverse event data were extracted and pooled for analyses by the Review Manager 5.3 software. Grading of Recommendations Assessment, Development and Evaluation guidelines (GRADE) were used to assess the quality of evidence. Trial Sequential Analysis (TSA) was conducted to weaken random error and enhance the reliability of evidence.
Totally 18 retrospective studies, involving 5993 patients, were included. ESD benefits were 128.38 min shorter operation duration 95%CI: (−204.68, −52.09), P = 0.001, 7.13 days shorter hospital stay 95%CI: (−7.98, −6.28), P < 0.00001, lower risk of procedure-related death OR = 0.21, 95%CI: (0.07, 0.68), P = 0.009, lower risk of overall complication OR = 0.47, 95%CI: (0.34, 0.63), P < 0.00001. ESD was also associated with lower costs and better quality of life. However, ESD had lower rate of en bloc resection OR = 0.07, 95%CI: (0.03, 0.21), P < 0.00001, histologically complete resection OR = 0.07, 95%CI: (0.03, 0.14), P < 0.00001, curative resection OR = 0.06, 95%CI: (0.01, 0.27), P = 0.002, and higher rate of local recurrence OR = 5.42, 95%CI: (2.91, 10.11), P < 0.00001, metachronous cancer OR = 10.84, 95%CI: (6.43, 18.26), P < 0.00001, synchronous cancer OR = 6.59, 95%CI: (1.96, 22.1), P = 0.002. ESD also led to lower disease-free survival HR = 4.58, 95%CI: (2.79, 7.52), P < 0.00001 and recurrence-free survival HR = 1.99, 95%CI: (1.38, 2.87), P = 0.0002. No significant differences in overall survival (OS) and disease-specific survival (DSS) between ESD and surgery were observed.
ESD offers a method of less expensive, less trauma, faster recovery and better quality of life compared to surgery for EGC. However, ESD is associated with higher risk of recurrence without compromising OS and DSS. Strict and careful surveillance after ESD is needed. Recurrent EGCs following ESD can usually be detected in early stage and successfully managed by repeated ESD. Accordingly, ESD technique provides an alternative to surgical resection for highly selected EGC patients.
•The meta-analyses of the same topic are scarce and not robust to reach definitive conclusions.•ESD offers a method of less expensive, less trauma and faster recovery than surgery for EGC.•Due to higher risk of recurrence following ESD pathway, strict and careful surveillance is needed.•ESD technique provides an alternative to surgical resection for highly selected EGC patients.
Sodium ion batteries attract increasing attention for large-scale energy storage as a promising alternative to the lithium counterparts in view of low cost and abundant sodium source. However, the ...large ion radius of Na brings about a series of challenging thermodynamic and kinetic difficulties to the electrodes for sodium-storage, including low reversible capacity and low ion transport, as well as large volume change. To mitigate or even overcome the kinetic problems, we develop a self-assembly route to a novel architecture consisting of nanosized porous NASICON-type NaTi2(PO4)3 particles embedded in microsized 3D graphene network. Such architecture synergistically combines the advantages of a 3D graphene network and of 0D porous nanoparticles. It greatly increases the electron/ion transport kinetics and assures the electrode structure integrity, leading to attractive electrochemical performance as reflected by a high rate-capability (112 mAh g–1 at 1C, 105 mAh g–1 at 5C, 96 mAh g–1 at 10C, 67 mAh g–1 at 50C), a long cycle-life (capacity retention of 80% after 1000 cycles at 10C), and a high initial Coulombic efficiency (>79%). This nanostructure design provides a promising pathway for developing high performance NASICON-type materials for sodium storage.
The dissolution and controlled release of poorly water soluble drugs have been challenging during the past half century. Food ingredients are often exploited to implement some strategies to conceive ...new drug delivery systems as potential solutions. In this study, Janus zein–PVP medicated nanofibers were fabricated through side-by-side electrospinning and by using zein as a key filament-forming matrix and a drug carrier. Ferulic acid (FA), as a poorly water-soluble model drug, was loaded on both sides of the Janus fibers. The side-by-side electrospinning process was performed for a smooth and robust preparation. SEM and TEM revealed that the resultant Janus fibers had linear morphology without beads-on-a-string phenomena, smooth surface, and obvious side-by-side structure. The FA was present in the fibers in an amorphous state due to its fine compatibility with zein and PVP. In vitro dissolution tests verified that the Janus fibers manipulated the release of FA in a two-stage manner. The controlled release mechanism of the Janus fibers was proposed. On the basis of the application of zein, a process–structure–performance relationship, which should be useful for developing many new functional materials from biological macromolecules, was disclosed.
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•Zein is utilized to create medicated Janus structure•A modified side-by-side electrospinning is implemented to treat zein•The Janus fibers can provide a two-stage controlled release of ferulic acid•A clear process-nanostructure-performance relationship is exhibited
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