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Refrigeration systems running on transcritical CO2 cycle are considered an alternative to phase-down the use of hydrofluorocarbons (HFCs) in response to the Kigali Amendment. Responding to the need to improve the efficiency of CO2 booster systems and to identify optimum system designs, thermodynamic models of three booster systems are proposed with the use of an internal heat exchanger (IHX). Findings from this study suggest that placing the IHX with a low-temperature fluid side at the suction line of high pressure stage compressor and high-temperature fluid side at the outlet of gas cooler represents the most optimal approach in improving the coefficient of performance (COP) of the booster system. When operating in the transcritical conditions, the COP values can be improved by 6.35% at the IHX thermal effectiveness of 0.8 and by 6.48% at the ratio of medium temperature load to low temperature load of 6. Using IHX can significantly reduce the compressor discharge pressure, which can be reduced by 0.55 MPa at the ambient temperature of 40 °C. Furthermore, by adding IHX, the annual performance factor of CO2 system can be improved significantly by 1.68% and the annual total power consumption can be decreased by 6.48% in the tropical climate. It can be concluded that that IHX can improve the COP values of a booster system when operating in the subtropical and tropical regions.

In this work, we designed and synthesized two small molecular acceptors, based on benzotriazole (BTA) as the center core with isopropyl alkyl chain, thienothiophene unit (TT) β-position connected n-hexane alkyl chain as wing, and using different end groups, 2-(3-oxygen generation-2, 3-2H − 1H-indane-1-alkyl)-malononitrile (IC) and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-indane-1-alkylene) (2FIC), named BIT-IC and BIT-2FIC, respectively. The device based on PM6: BIT-IC achieved the PCE of 3.63%, which exhibited inferior performance because the device absorption is not complementary with solar spectrum, leading to the low Jsc of the device. However, the absorption band of the acceptor BIT-2FIC with 2FIC end group can reach 944 nm, and the HOMO energy level is lower than BIT-IC, therefore, the device based on PM6: BIT-2FIC can achieve more efficient exciton dissociation and charge transport, after thermal annealing treatment at 90 °C for 10 min, the device based on PM6: BIT-2FIC can achieve the PCE over 14%.

In recent years, indoor organic photovoltaics (IOPVs) have attracted increasing attention because of their ability to power microelectronic devices and sensors, especially for the internet of things (IoT). In contrast with silicon-based indoor PV, the IOPVs exhibit better performance due to their tunable bandgap via molecular design, which could achieve a better spectrum matched with the lighting sources. Based on the simulated power conversion efficiency (PCE) in theory, the maximum value can achieve over 50 % under the white LED illumination, which is much higher than the practical top PCE of 31 %, indicating there is room further to improve the performance of IOPVs by various optimization methods. Based on these benefits, the recent progress in IOPVs with different methods was summarizes, and light was shed on the remaining challenges for achieving practical applications in the future. In the end, some guidelines for the development of IOPVs were proposed.

As an alternative strategy for H2 production under ambient conditions, solar-driven lignocellulose-to-H2 conversion provides a very attractive approach to store and utilize solar energy sustainably. Exploiting efficient photocatalyst for photocatalytic lignocellulose-to-H2 conversion is of huge significance and remains the key challenge for development of solar H2 generation from lignocellulose. Herein, 2D-2D MoS2 /TiO2 photocatalysts with large 2D nanojunction were constructed for photocatalytic lignocellulose-to-H2 conversion. In this smart structure, the 2D nanojunctions acted as efficient channel for charge transfer from TiO2 to MoS2 to improve charge separation efficiency and thus enhance photocatalytic lignocellulose-to-H2 conversion activity. The 2 % MoS2 /TiO2 photocatalyst showed the highest photocatalytic lignocellulose-to-H2 conversion performance with the maximal H2 generation rate of 201 and 21.4 μmol h-1 g-1 in α-cellulose and poplar wood chip aqueous solution, respectively. The apparent quantum yield at 380 nm reached 1.45 % for 2 % 2D-2D TiO2 /MoS2 photocatalyst in α-cellulose aqueous solution. This work highlights the importance of optimizing the interface structures of photocatalyst for solar-driven lignocellulose-to-H2 conversion.

Recent advances in organic solar cells based on non-fullerene acceptors (NFAs) come with reduced non-radiative voltage losses (ΔVnr). Here we show that, in contrast to the energy-gap-law dependence observed in conventional donor:fullerene blends, the ΔVnr values in state-of-the-art donor:NFA organic solar cells show no correlation with the energies of charge-transfer electronic states at donor:acceptor interfaces. By combining temperature-dependent electroluminescence experiments and dynamic vibronic simulations, we provide a unified description of ΔVnr for both fullerene- and NFA-based devices. We highlight the critical role that the thermal population of local exciton states plays in low-ΔVnr systems. An important finding is that the photoluminescence yield of the pristine materials defines the lower limit of ΔVnr. We also demonstrate that the reduction in ΔVnr (for example

Siloles are one of the most promising building blocks for the construction of functional materials that exhibit potential application in organic photovoltaic. In the present work, two novel organic dyes featuring highly conjugated and planar tetrathienosilole (TTS) as π-bridge have been successfully synthesized and employed in dye-sensitized solar cells (DSSCs) for the first time. For comparison, dye W13 with non-rigidified 2,2′-bithieno[3,2-b]thiophene linker was prepared as well. The effects of π-bridge rigidification upon the optoelectronic properties as well as the charge transfer energetic and kinetic features of these dyes have been systematically researched. It was found that a significant enhanced open-circuit voltage had been displayed for TTS-based sensitizers as the rigidification of π-bridge with tetrahedral silicon atom. Moreover, the energy levels alignment of the dyes could be fine-tuned through modulating the electron-donating groups to optimize the dyes regeneration process. Under AM 1.5G irradiation, the devices fabricated by W15 employing [Co(phen)3]2+/3+ electrolyte achieve the highest power conversion efficiency of 8.10%, which is about 19% higher than that of W13, demonstrating the great potential of TTS spacer for constructing highly efficient organic sensitizers for DSSCs.

Meso/microforming of bulk multi-scaled parts and components by directly using sheet metals is an efficient approach to realizing mass production of meso-/micro-scaled bulk structures with good productivity and low cost. This process is promising with the large-scaled application potentials. In this unique deformation-based meso-/micro-scaled manufacturing, size effect arises due to the size scaling up and down of the extrinsic and intrinsic parameters of materials and forming systems, which further induces different mechanical responses and deformation behaviors in meso/microscale from those in macroscale. In this research, a compound microforming system for a blanking-heading process was developed to produce plug-shaped bulk parts by directly using copper sheets as a case study. Different punch-die clearances and grain sizes of specimen were employed to study the interactive effects of geometry and grain sizes on the microforming process and the micro-formed part. Through numerical simulations and experimental measurements of the final parts, the influences of size effect on microstructural evolution, geometrical precision and surface defects of the meso-/micro-formed parts and the load-stroke relationship were comprehensively investigated. The results reveal that when punch-die clearance equals grain size, the maximum ultimate shear stress of blanking and the highest burr are obtained. The larger grain size and punch-die clearance increase the material loss and reduce the bulge diameter of the produced parts. Three shear bands and three dead metal zones were identified on the cross-section of parts, and various defects including sunken area, pits, crack and surface damage were observed on the surface of the parts. These findings facilitate the production of plug-shaped microparts in the aspects of process monitoring and product qualities control and enrich the understanding of sheet-metal bulk forming in this progressive and compound meso/microforming.

In recent years, China keeps working on restructuring the country’s multimodal transport and highly develops the high-speed rail (HSR) infrastructure to improve transport efficiency. As the economic engine of China, the Yangtze River Delta region keeps leading the HSR development and the transporting modal transformation within the whole country. The fast development of HSR on the one hand highly improves passengers’ travel efficiency and, on the other hand, releases the capacity of conventional rail infrastructures to support regional multimodal freight transport. This study applies a three-level AHP structure and constructs a comprehensive index to evaluate the development of a rail-based multimodal freight transport network including railway, rail-water, and rail-road. The comprehensive index contains 14 quantitative and 8 qualitative indexes, covering the rail-based infrastructures, multimodal transport capability, freight transport performance, and transport sustainability. The comprehensive index is then applied to analyze the rail-based multimodal freight transport for the Yangtze River Delta region. The operational data of 59 freight stations and more than 200 railway links of the Yangtze River Delta were recorded. About 172 valid questionnaires were collected to score the qualitative indexes, and all the quantitative indexes are scored based on the real-life freight data. The results reveal the impacts of HSR development on rail freight transportation and show that Zhejiang has led rail freight transportation while Shanghai mainly leads the waterway freight transportation. Meanwhile, Anhui performs very well on road-rail transportation and Jiangsu has made a great improvement on water-rail transportation.

Hollow core-shell catalytic nanoreactors have received tremendous attention due to their high mass transfer in catalysis applications. Herein, we present a novel type of well-arranged, hollow core-shell nanoreactors featured with a bimetallic porous Zn/Ni-MOF-2 shell and a tiny Au nanoparticle core. The well-designed hollow Au@Zn/Ni-MOF-2 nanoreactors were constructed through the strategy of a facile one step from a rare crystal-structure transformation without any additional template. These nanoreactors exhibit outstanding multifunctional catalysis for a broad range of alcohol oxidation under the green oxidant environment. Moreover, such hollow nanoreactors show excellent recyclability toward the selective alcohol oxidation. These findings might provide a promising platform for a general construct of various metal-organic framework-based hollow core-shell nanostructures and further highly augmented catalytic applications.

Electrode materials with high conductivity and high mass transport rate are highly desirable for a variety of electrochemical energy devices but face a grand challenge to be readily prepared yet. Here, we propose the design and preparation of a nanohybrid of V2O3 nanoparticles embedded in a multichannel carbon nanofiber (V2O3@MCNF) network with high conductivity and high mass transport. We demonstrate the V2O3@MCNF shows superior capability for sodium storage with an excellent capacity of 214.3 mA h g-1 even at 5 A g-1, thanks to its high conductivity for electron transfer and facilitated mass transportation endowed by the one-dimensional conductive multichannel fiber structure. Such favorable structures and properties in V2O3@MCNFs enable them to be applied as high-performance anodes of sodium-ion hybrid capacitors (SIHCs), successfully addressing the critical kinetics imbalance between Faradaic anodes and capacitive cathodes for application of SIHCs, which show impressively high energy/power densities along with impressive cycling performance over 10,000 cycles.

Given a scatterplot with tens of thousands of points or even more, a natural question is which sampling method should be used to create a small but "good" scatterplot for a better abstraction. We present the results of a user study that investigates the influence of different sampling strategies on multi-class scatterplots. The main goal of this study is to understand the capability of sampling methods in preserving the density, outliers, and overall shape of a scatterplot. To this end, we comprehensively review the literature and select seven typical sampling strategies as well as eight representative datasets. We then design four experiments to understand the performance of different strategies in maintaining: 1) region density; 2) class density; 3) outliers; and 4) overall shape in the sampling results. The results show that: 1) random sampling is preferred for preserving region density; 2) blue noise sampling and random sampling have comparable performance with the three multi-class sampling strategies in preserving class density; 3) outlier biased density based sampling, recursive subdivision based sampling, and blue noise sampling perform the best in keeping outliers; and 4) blue noise sampling outperforms the others in maintaining the overall shape of a scatterplot., 9 pages + 2 pages reference, 15 figures, IEEE VIS(VAST) 2020

Molten reduction to release the value metals are the necessary step in the copper slag recovery process. How to effectively choose and utilize the reducing agents has an extremely important significance. In the research, molten reductions with the CO-H2-Ar mixed gases are investigated. De-oxidation amounts and de-oxidation rates maintain stability first and then decrease with the increase of CO/H2 ratios. They are all much higher than those of pure CO or H2 due to the water-gas shift reaction. The magnetite phase decreased gradually with the decrease of CO/H2 ratios, and some pure ferrous phase can generate in the slag as the ratios are less than 1:1. Otherwise, the apparent rate constants, the reaction orders and the activation energies for the various CO/H2 ratios are also measured. The results illustrate that the reaction process will vary with the variety of mixed gas compositions.

Making logical copies, or clones, of files and directories is critical to many real-world applications and workflows, including backups, virtual machines, and containers. An ideal clone implementation meets the following performance goals: (1) creating the clone has low latency; (2) reads are fast in all versions (i.e., spatial locality is always maintained, even after modifications); (3) writes are fast in all versions; (4) the overall system is space efficient. Implementing a clone operation that realizes all four properties, which we call a nimble clone , is a long-standing open problem. This article describes nimble clones in B-ϵ-tree File System (BetrFS), an open-source, full-path-indexed, and write-optimized file system. The key observation behind our work is that standard copy-on-write heuristics can be too coarse to be space efficient, or too fine-grained to preserve locality. On the other hand, a write-optimized key-value store, such as a Bε-tree or an log-structured merge-tree (LSM)-tree, can decouple the logical application of updates from the granularity at which data is physically copied. In our write-optimized clone implementation, data sharing among clones is only broken when a clone has changed enough to warrant making a copy, a policy we call copy-on-abundant-write . We demonstrate that the algorithmic work needed to batch and amortize the cost of BetrFS clone operations does not erode the performance advantages of baseline BetrFS; BetrFS performance even improves in a few cases. BetrFS cloning is efficient; for example, when using the clone operation for container creation, BetrFS outperforms a simple recursive copy by up to two orders-of-magnitude and outperforms file systems that have specialized Linux Containers (LXC) backends by 3--4×.

Hollow nanoparticles are of great interest in energy storage and environmental remediation due to their improved mass transfer ability and unique void space for confined pollutants. Herein, fabrication of highly efficient and recyclable hollow porous γ-Fe2O3 nanotubes is reported by direct thermolysis of MIL-88A (Fe) precursors. Metal-organic frameworks (MOFs) that served as the precursors of the hollow γ-Fe2O3 nanotubes were first synthesized by a facile hydrothermal method followed by a one-step annealing process. As a proof-of-concept application, the as-synthesized hollow porous γ-Fe2O3 nanotubes were used in the lithium-ion battery and dye adsorption, respectively. Taking advantage of the hollow porous structure, γ-Fe2O3 nanotubes exhibited excellent lithium-ion batteries performance (1559 mAh g−1 at 100 mA g−1) and corresponding long cycle life (1093 mAh g−1 after 240 cycles at 100 mA g−1). At the same time, maximum methyl orange (MO) uptake capacity for the as-prepared hollow γ-Fe2O3 was calculated to be as high as 63.17 mg g−1. Moreover, this adsorbent also showed good reusability through the application of an external magnetic field, further highlighting the porous structure superiority of these hollow nanotubes. This proposed strategy could be extended to synthesize various hollow metal oxide porous nanoparticles with controllable structure, enhanced energy storage capacity and better environmental remediation performances.

Great progress in organic solar cells (OSCs) has been recently achieved owing to the advent of non-fullerene acceptors (NFAs). Indeed, low-bandgap NFAs ranging from 1.3 to 1.6 eV with broad absorpt...

Design and synthesis of non-noble electrocatalyst with controlled structure and composition for hydrogen evolution reaction (HER) are significant for large-scale water electrolysis. Here, an elegant multi-step templating strategy is developed for the fabrication of vertically aligned CoP@Ni2P nanowire–nanosheet architecture on Ni foam. Cobalt–carbonate hydroxides nanowires grown on Ni foam are first synthesized as the self-template. Afterward, a layer of amorphous Ni(OH)2 nanosheets is grown on the Co-based precursors through a chemical bath process, which is then transformed into the hierarchical CoP@Ni2P nanoarrays by a co-phosphatization treatment. Owing to the synergistic effect of the compositions and the advantages of the hierarchical heterostructures, the resulting hybrid electrocatalyst with dense heterointerfaces is revealed as an excellent HER catalyst, with a low overpotential of 101 mV at the current density of 10 mA cm−2, a relatively small Tafel slope of 79 mV dec−1, and favorable long-term stability of at least 20 h in 1 M KOH.

Sodium–ion hybrid capacitors (SIHCs) hold great promise in large-scale energy storage by compromising the merits of sodium–ion batteries and electrochemical capacitors; however, the mismatch of kinetics and capacity between battery-type anode and capacitive-type cathode is still the Achilles’ heel of this technology. Herein, nanohybrids with Mn single atoms implanted in N, F co-doped ultrathin porous carbon nanosheets (MnSAs/NF-CNs) have been developed as both the anode and cathode of SIHCs. The systematic experimental study coupled with theoretical calculations reveal that N-coordinated Mn atoms (Mn–N4) can act as sites not only for reversible Na+ storage with reduced energy barrier but also for improving the pseudocapacitance, thus making great contribution to accelerating the reaction kinetics of the anode and enhancing the capacity for the cathode in SIHCs. We demonstrate that the Janus-featured MnSAs/NF-CNs endows SIHCs with an impressively high energy/power density (maximum 197 W h kg−1/9350 W kg−1) and ultralong cycling life over 10 000 cycles.

Carbon dots (CDs), possessing unexpected advantages of photostability, biocompatibility and low toxicity, are regarded as novel nanomaterials in fluorescence (FL) imaging. Doping Gd element in CDs makes them have the ability to be used for magnetic resonance (MR) and FL imaging simultaneously. However, CDs reported before exhibit obvious defects like low photoluminescence (PL) quantum yield (QY) or biotoxicity. In this work, we use gadolinium meglumine, a material with relatively low biotoxicity, along with citric acid and diethylenetriamine to synthesize Gd-doped CDs (Gd-CDs) by a one-step hydrothermal method. The prepared Gd-CDs exhibit excitation-independent emission with a PL QY of 78.05% and a longitudinal relaxivity of 7.37 mM-1 S-1, which endows the composite with high-performance in MR/FL imaging. Meanwhile, the FL intensity of Gd-CDs remains stable in the presence of multiple amino acids, which indicates that the FL imaging effect should not be impacted significantly in microenvironments in vivo. In addition to the inconspicuous cytotoxicity, Gd-CDs could be used efficiently for dual-modal molecular imaging to detect diseases such as tumors in the early stages.

The assembly of cellulose nanocrystals (CNCs) that produce attractive structural color shows great potential in anti-counterfeiting application, but their processability and recyclability remain unsatisfactory due to the strong hydrogen bonds between CNCs. For the first time, optical anti-counterfeiting patterns are obtained by additive printing of surface-functionalized CNC inks (CNC-DC5700-NPES). The surface-functionalized CNC inks are prepared by sequential modification of CNCs with organosilane (DC5700) and polyoxyethylene ether (NPES), which show good flowability under shearing force and transform into a gel-like phase rapidly after printing, making possible ink-jet printing without additives. The printed patterns are transparent under natural light but show vivid interference color, showing anti-counterfeiting features between crossed polarizers. The texture and optical properties of the printed patterns can be facilely controlled by tuning the printing parameters, such as nozzle diameter, writing angle, and filling width. Moreover, the CNC-DC5700-NPES patterns with a core-shell structure could be collected in various solvents and reprinted after removing solvents. This work provided a new pathway for the preparation of optical anti-counterfeiting patterns from biomass resources.

Three polymer donors named Qx-8F, Qx-10F, and Qx-12F, with similar chemical structures, were synthesized. The energy level of these donors is manipulated by precisely controlling the fluorination sites. We demonstrate that the exciton dissociation efficiency is gradually enhanced from Qx-8F:Y6 to Qx-12F:Y6, leading to improved open circuit voltage VOC and short circuit current density JSC for donors with a higher degree of fluorination. Simultaneously, the trap-assisted recombination or bimolecular recombination intensity is reduced, while the extraction rate is enhanced because of increased charge carrier mobilities, leading to an increase in fill factor for donors with higher amount of fluorine atoms. The optimized device based on Qx-12F with the most fluorine atoms and the non-fullerene acceptor Y6 shows the highest power conversion efficiency of 15.21%, with a VOC of 0.85 V, JSC of 24.55 mA cm−2, and fill factor of 72.88%. It is further demonstrated that the optimized ternary device based on the Qx-12F:PM6:Y6 blend provides a power conversion efficiency of 16.32%.

Researchers are endeavoring to decode the fundamental reasons for the non-fullerene acceptor, Y6, to deliver high-performance in organic solar cells. In this work, we tackle this problem from the molecular packing point of view. By gradually increasing the thermal annealing temperature of Y6, its backbone order in thin films is significantly enhanced and eventually reoriented to the “backbone-on” orientation with the backbone plane standing on the substrate. It displays well-defined Bragg peaks in two-dimensional grazing-incidence wide-angle X-ray scattering patterns for a clear crystal indexing. The 250 °C annealed pure Y6 and binary PM6:Y6 films exhibit square and rectangular diffraction patterns, respectively. It is suggested that both are polymorphs of two-dimensional Y6 packing in its backbone plane, which resulted from its “L” shaped core-group and the biaxial backbone order through the end-group π–π stacking. Interestingly, the square lattice can be restored in the blend PM6:Y6 film by adding a small amount of IDIC. However, on the other hand, a larger portion of IDIC in the ternary blend hinders the long-range crystalline packing of Y6 and correlatedly deteriorates the device performance. This work provides an in-depth understanding of the molecular packing mechanism of Y6 in thin films for the future rational design of high-performance organic photovoltaic molecules with advantageous crystalline packing motifs.

As flowing film gravity concentrators, spiral separators are extensively used in the processing of numerous minerals. Appropriate design of their cross-sectional geometries has been known as an eff...

The versatility and flexibility of organic photoelectric materials endow organic photovoltaic cells fine function modulation and huge commercial potential. In this work, a new noncovalent fused-ring small molecule acceptor (SMA) BID-4F has been synthesized for high-efficient organic solar cells (OSCs). BID-4F consists of a diflurobenzothiadiazole (DFBT) core, ladder-like indacenodithiophene (IDT) spacers, and dicyanoindanone electron-withdrawing end groups, which are supposed to be conformationally interlocked by noncovalent interactions, leading to good molecular planarity. In addition, compact solid state stacking was revealed by UV–vis–NIR absorption spectrum. The optimized PM6:BID-4F based device delivers an eminent power conversion efficiency (PCE) of 12.30% with a high open-circuit voltage (Voc) of 0.92 V and a high fill factor (FF) of 74.3%. Most importantly, the PCE and FF are among one of the highest values reported for the OSCs based on the unfused-ring SMAs. Overall, our work demonstrates that the unfused ring central framework with high molecular planarity through noncovalent interactions provides a good strategy to construct highly efficient SMAs.

Visual analytics for machine learning has recently evolved as one of the most exciting areas in the field of visualization. To better identify which research topics are promising and to learn how to apply relevant techniques in visual analytics, we systematically review 259 papers published in the last ten years together with representative works before 2010. We build a taxonomy, which includes three first-level categories: techniques before model building, techniques during modeling building, and techniques after model building. Each category is further characterized by representative analysis tasks, and each task is exemplified by a set of recent influential works. We also discuss and highlight research challenges and promising potential future research opportunities useful for visual analytics researchers.

The rigid pile composite foundation is widely used in highway projects in soft soil area as it can effectively increase the bearing capacity and stability of the foundation. While the research on the behavior and failure mode of rigid pile composite foundation under embankment is not enough, instability failure of rigid pile composite foundation often occurs in practical projects. This paper presents a centrifuge model test to investigate the load transfer mechanism, settlement characteristic and failure mode of rigid pile composite foundation under embankment. The test results show that: the soil displacement of different region in rigid pile composite foundation was different, obvious vertical displacement occurred in the soil under the center of embankment and the horizontal displacement was very small in this region; both vertical and horizontal displacement occurred in the soil under the shoulder of embankment; and obvious horizontal displacement occurred in the soil under the slope toe of embankment; moreover, ground heave also occurred near the slope toe of embankment. The soil displacement in rigid pile composite foundation had a large influence on the stress characteristic and failure mode of rigid piles, the compressive failure and bending failure would probably occur for the piles under the center and shoulder of the embankment, respectively, and the tension-bending failure would probably occur for the piles under the slope toe of embankment. The different failure modes of piles at different regions should be considered in the design of rigid pile composite foundation under embankment. The test results can be used to improve the design method for rigid pile composite foundation under embankment in practical projects.

A comprehensive and comprehensible summary of existing deep neural networks (DNNs) helps practitioners understand the behaviour and evolution of DNNs, offers insights for architecture optimization, and sheds light on the working mechanisms of DNNs. However, this summary is hard to obtain because of the complexity and diversity of DNN architectures. To address this issue, we develop DNN Genealogy, an interactive visualization tool, to offer a visual summary of representative DNNs and their evolutionary relationships. DNN Genealogy enables users to learn DNNs from multiple aspects, including architecture, performance, and evolutionary relationships. Central to this tool is a systematic analysis and visualization of 66 representative DNNs based on our analysis of 140 papers. A directed acyclic graph is used to illustrate the evolutionary relationships among these DNNs and highlight the representative DNNs. A focus + context visualization is developed to orient users during their exploration. A set of network glyphs is used in the graph to facilitate the understanding and comparing of DNNs in the context of the evolution. Case studies demonstrate that DNN Genealogy provides helpful guidance in understanding, applying, and optimizing DNNs. DNN Genealogy is extensible and will continue to be updated to reflect future advances in DNNs.

In this work, Mg/Al layered double hydroxides embedded phosphorylated cellulose microspheres (Mg/Al LDH@PCMs) were prepared first with solid-phase phosphorylation on CMs then in situ nano-assembly between Mg2+, Al3+ and phosphate groups. Hence the synthesis degree of Mg/Al LDH was enhanced. The obtained Mg/Al LDH@PCMs were characterized by scanning electron microscopy (SEM), specific surface area test (BET), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), ζ potential, X-ray electron energy (XPS). The novel in situ nano-assembly method provided improved Mg/Al LDH load without compromising the porous structure of CMs, making Mg/Al LDH@PCMs suitable for water treatment. The Mg/Al LDH@PCMs adsorbed tetracycline hydrochloride (TC) with a kinetic pattern of pseudo second-order kinetic model, while isothermally fitted with the Freundlich isotherm model. The maximum theory adsorption capacity of Mg/Al LDH@PCMs qm was 25.107 mg g−1 with the Gibbs free energy ∆G = 7.523 kJ mol−1 under 298 K. The TC removal mechanism was deeply investigated via characterization results and also the batch experimental results, it was inferred that electrostatic attraction between LDH particles and the anion species mainly dominated the adsorption process. These properties make Mg/Al LDH@PCMs have a wide application prospect in the water purification field.

A relatively simple, but very effective method via magnetron sputtering process was used in the surface doping of the electrode plates. Molybdenum nano-particles coated electrodes were studied in the paper. The flower-like deposits appeared on the electrode plate surface, and Ni4Mo could be in-situ formed with the coating process. The hydrogen ab/desorption rates were accelerated at the beginning and dropped subsequently. The max discharge capacity and retention rate after twenty cycles of the St 5min sample reached about 370mAh/g and 92%, respectively. Comparing to the typical hydrogen storage alloys, they were much closed to the A2B7-type and have surpassed the most AB3-type Co-containing alloys. The activation energies and enthalpies of the various electrodes during the ab/dehydrogenation process were also discussed in details.

Power conversion efficiencies (PCEs) of solution-processed organic solar cells (OSCs) have recently reached 17.4% (certified) for single-junction devices. Crucial to this advancement is the development of non-fullerene acceptors (NFAs) since 2015. The recent A-DAD-A NFAs have attracted widespread attention because of their ladder-type electron-deficient-core-based central fused ring with improved transport properties and optimum energy levels. With the synergistic effect of electron-deficient-core and specific molecular geometry, the A-DADA molecules could achieve low voltage losses and high current generation at the same time, reaching new regimes of device physics and photophysics. This perspective will discuss the voltage losses in state-of-the-art A-DAD-A NFA-based OSCs and propose new molecular design strategies to achieve PCEs over 20% in OSCs based on these new acceptors by further decreasing their total voltage losses. Funding Agencies|National Natural Science Foundation of China (NSFC)National Natural Science Foundation of China (NSFC) [21875286]; National Key Research & Development Projects of China [2017YFA0206600]; Science Fund for Distinguished Young Scholars of Hunan ProvinceNational Natural Science Foundation of China (NSFC)National Science Fund for Distinguished Young Scholars [2017JJ1029]; Swedish Research Council VRSwedish Research Council [2018-06048]; Swedish Energy Agency EnergimyndighetenSwedish Energy Agency [2016-010174]; Stiftelsen For Strategisk Forskning through a Future Research Leader program [FFL18-0322]; NSERCNatural Sciences and Engineering Research Council of Canada

Materials under space confinement can alter their physical and chemical properties, paving the way for new science and novel applications. Nanoparticles can enforce spatial constraints on the polym...

The amount of time-series data that is generated has exploded due to the growing popularity of Internet of Things (IoT) devices and applications. These applications require efficient management of the time-series data on both the edge and cloud side that support high throughput ingestion, low latency query and advanced time series analysis. In this demonstration, we present Apache IoTDB managing time-series data to enable new classes of IoT applications. IoTDB has both edge and cloud versions, provides an optimized columnar file format for efficient time-series data storage, and time-series database with high ingestion rate, low latency queries and data analysis support. It is specially optimized for time-series oriented operations like aggregations query, down-sampling and sub-sequence similarity search. An edge-to-cloud time-series data management application is chosen to demonstrate how IoTDB handles time-series data in real-time and supports advanced analytics by integrating with Hadoop and Spark. An end-to-end IoT data management solution is shown by integrating IoTDB with PLC4x, Calcite, and Grafana.

A major challenge for organic solar cell (OSC) research is how to minimize the tradeoff between voltage loss and charge generation. In early 2019, we reported a non-fullerene acceptor (named Y6) that can simultaneously achieve high external quantum efficiency and low voltage loss for OSC. Here, we use a combination of experimental and theoretical modeling to reveal the structure-property-performance relationships of this state-of-the-art OSC system. We find that the distinctive π–π molecular packing of Y6 not only exists in molecular single crystals but also in thin films. Importantly, such molecular packing leads to (i) the formation of delocalized and emissive excitons that enable small non-radiative voltage loss, and (ii) delocalization of electron wavefunctions at donor/acceptor interfaces that significantly reduces the Coulomb attraction between interfacial electron-hole pairs. These properties are critical in enabling highly efficient charge generation in OSC systems with negligible donor-acceptor energy offset., Y6, as a non-fullerene acceptor for organic solar cells, has attracted intensive attention because of the low voltage loss and high charge generation efficiency. Here, Zhang et al. find that the delocalization of exciton and electron wavefunction due to strong π-π packing of Y6 is the key for the high performance.

This study proposes a novel non-inverting buck–boost converter topology with extra-wide operational zones under both continuous current mode (CCM) and discontinuous current mode (DCM), by introducing a four-mode modulation (4MM) strategy. The proposed 4MM method is able to eliminate the operation dead zone, thus extending the operation zones of the buck–boost converter to contain boost mode, extended boost mode, extended buck mode, and buck mode. Rigorous analyses and design principles are presented in detail to demonstrate the four-mode function through CCM and DCM operational investigations and illustrations. Theoretical analyses and parameter design are verified by software simulation and hardware experimentation in this study, which validates the proposed 4MM method and the functionality of the proposed 4MM-based buck–boost converter. They clearly indicate the superiority of the proposed 4MM-based four-switch non-inverting buck–boost converter over its conventional counterparts, posing wide applicability in industrial practices.

Since the world-record power conversion efficiency of 15.7% was achieved for organic solar cells (OSCs) in 2019, the newly developed non-fullerene acceptor (NFA) Y6 with an A-DA′D-A structure (A denotes an electron-accepting moiety, D denotes an electron-donating moiety) has attracted increasing attention. Subsequently, many new A-DA′D-A NFAs have been designed and synthesized, and the A-DA′D-A NFAs have played a significant role in the development of high-performance non-fullerene organic solar cells (NF-OSCs). Compared with the classical A-D-A-type acceptors, A-DA′D-A NFAs contain an electron-deficient core (such as benzothiadiazole (BT), benzotriazole (BTA), quinoxaline (Qx), or their derivatives) in the ladder-type fused rings to fine-tune the energy levels, broaden light absorption and achieve higher electron mobility of the NFAs. This review emphasizes the recent progress on these emerging A-DA′D-A (including Y-series) NFAs. The synthetic methods of DA′D-fused rings are introduced. The relationships between the chemical structure of the A-DA′D-A NFAs and the photovoltaic performance of the corresponding OSCs are summarized and discussed. Finally, issues and prospects for further improving photovoltaic performance of the OSCs are also proposed.

Semitransparent organic solar cells (ST-OSCs) have drawn great attention due to their wide application, such as smart windows, greenhouses and building integrated photovoltaics. The ternary strategy is often considered an useful way to enhance device performance due to improve the attracting or retracting morphology. Here, non-fullerene small molecule (Y8) with electron-deficient core as the center unit and a novel PBDTTT-type low-bandgap polymer (PCE10) were chosen to fabricate ST-OSCs according to the principle of more closely matched energy levels. With the introduction of indene-C60bisadduct (ICBA) as third component, opaque organic solar cells with a power conversion efficiency (PCE) of 12.86% and ST-OSCs with a PCE of 10.46% were obtained by using spin coating after optimization. The average visible transmittance of ST-OSCs is up to 26.56%. By the blade coating technique, 9.52% PCE is achieved for ST-OSCs, which is the highest value reported to date. These results show that it's higher efficiency to improve the performance of ST-OSCs through ternary strategy. And the blade coating technique has a promising application prospect for mass manufacturing ST-OSCs.

The intermittency of renewable energy sources, i.e., photovoltaic cells and wind power causes problems such as unreliability, harmonic pollution, unpredictability and inefficiency, which pose a great challenge for constructing a reliable modern microgrid. To address these problems, in this paper, we propose a novel structure of microgrid, where sensitive loads, non-sensitive loads and the concept of “load follows demand” are adopted and incorporated. Within the designed microgrid, energy storage systems (ESSs) are coupled with the non-sensitive loads to achieve the supply/demand balance. In addition, a particle swarm optimization (PSO)-based collective load control is employed in this study to create pure resistiveness and piecewise constant active power features in the microgrid, in order to resolve harmonics and unpredictability problems. The proposed microgrid experimental platform is established based on real-time (RT)-lab and dSPACE in a hardware-in-the-loop (HIL) environment, where the efficacy of the proposed microgrid structure is verified in both islanded mode and grid-connected mode, which is able to achieve nearly 100% utilization rate of the intermittent solar energy, piecewise constant power and unity power factor. The proposed microgrid structure and established testing environment also have the potential to be scaled up to multi-microgrid power systems for advanced and wider applicability.

The aim of this paper was to investigate the extraction, purification and characterization of sulphated polysaccharide (BQPS) from Bellamya quadrata and its stabilization roles on atherosclerotic plaque. Firstly, crude polysaccharide (CBQP) from Bellamya quadrata was extracted by protease enzyme assisted extraction. Moreover, its optimal parameters were obtained by the response surface method as follows: the ratio of water to raw material of 24:1, enzyme dosage of 285 U/g, enzymolysis pH value of 4.7 and temperature of 67 °C. Secondly, CBQP was further purified to obtain the target polysaccharide BQPS by Q Sepharose Fast Flow and Sephacryl S-400 gel column chromatography. Then, the characterization of BQPS revealed that it possessed a total polysaccharide content of 91.88 ± 1.23%, sulfuric acid group content of 9.12 ± 1.59% and molecular weight of 91.1 kDa. BQPS was only consisted of glucose without any proteins. Finally, BQPS was confirmed to have a significant stabilizing effect on atherosclerotic plaque and its mechanism was related to the selective promotion of autophagy with the precisely right strength.

Summary Generally, it is important to fine-tune the energy levels of donor and acceptor materials in the field of polymer solar cell (PSCs) to achieve a minimal highest occupied molecular orbital (HOMO) energy offset, which yet is still sufficient for charge separation. Based on the high-performance small-molecule acceptor (SMA) of BTP-4F, we modified the end groups of BTP-4F from IC-2F to CPTCN-Cl. It was found that when both end groups were substituted by CPTCN-Cl, the energy level upshift was too large that caused unfavorable energetic alignment, thus poor device performance. By using the strategy of asymmetric end groups, we were able to achieve near optimal energy level match, resulting in higher open-circuit voltage (VOC) and power conversion efficiency (PCE) compared with those given by the PM6:BTP-4F system. Our strategy can be useful and potentially applied to other material systems for maximizing efficiency of non-fullerene PSCs.

Herein, SiO2-photonic crystal/TiO2 composite film (STF) with multilayer structure was designed and fabricated via self-assembly method and spin coating method. The micro-morphology and optical properties of the STF were characterized by scanning electron microscope (SEM) and UV/Vis/NIR spectrophotometer respectively. The photocatalytic activity of the STF was tested via the degradation rate of rhodamine B. The characterization results indicate that the STF has a regular ordered structure when the amount of ammonia is 3 mL and the concentration of SiO2 suspension is 1%, and SiO2 can be effectively combined with TiO2, so the STF has the best photocatalytic performance. The double-layer SiO2-photonic crystal/TiO2 composite film (DSTF) was further prepared and compared with the single-layer SiO2-photonic crystal/TiO2 composite film (SSTF). The photocatalytic properties of the DSTF are better than that of the SSTF. Finally, the mechanism of STF with enhanced photocatalytic performance is discussed, indicating that photonic crystal can effectively enhance the utilization of light which are near the wavelength of the center band gap, and then improve the photocatalytic performance of the photocatalyst.

In the long-distance shield tunneling process, the shield tail brush needs to be replaced after wear failure, especially in cross-river and cross-sea tunnel projects. Taking the shield tail brush replacement project of Qingchun Road tunnel in Hangzhou, China as the research background, a three-dimensional sequential thermo-mechanical coupled numerical simulation was carried out to study the shield tail brush replacement with liquid nitrogen freezing by ABAQUS software. The development of temperature fields and displacement fields of soil, and the deformations of the tunnel sections along the longitudinal direction induced by freezing were obtained. The numerical model was further validated by site measurement. In addition, the effects of the frozen wall thickness, buried depth, excavation radius, and coefficients of linear thermal expansion of soils on the frost heave were studied.

This paper investigates a controllable fluke's regulation effect on the gliding motion of a self-propelled robotic dolphin in both theory and practice. In theory, based on a dynamic model, the gliding equilibria is first analyzed. Through deriving the explicit expressions of the pitch angle, gliding angle, and velocities, we explore how the deflection angle of the controllable fluke changes the gliding performance. Then, aided by these theoretical analyses, a pitch control strategy relying on the fluke is constructed. In simulations, the robotic dolphin is able to track a given pitch angle during gliding, directly through adopting this control strategy to regulate the fluke's deflection angle. Furthermore, extensive gliding experiments in different fluke's deflection angles are carried out. From the statistical data, we further explore the remarkable effects of the controllable fluke on the gliding performance in practice. Besides, the other pitch control experiment is also executed to validate the effectiveness of the proposed control approach. The results of this paper shed light on improving the gliding performance of the robotic dolphin in future mechanical design and gliding control.

Astrocytes are key stromal components in glioblastoma (GBM) and have complex interactions with the GBM cells (GBC) promoting the survival, progression and therapy resistance of GBM. In this study, we first demonstrated the existence of a reciprocal activation loop mediated by the STAT3/IL-6 signaling between GBC and astrocytes. This loop of reciprocity was found to be initiated by the constitutive activity of STAT3 and downstream expression of IL-6 in the GBC. GBC-derived IL-6 activated STAT3 and thereby upregulated IL-6 expression in the astrocytes. Astrocyte-derived IL-6 acted back on the GBC causing further activation of STAT3 and leading to enhanced downstream events that promote proliferation, migration, invasion and apoptosis resistance of the GBC. Next, we showed that doxorubicin-polyglycerol-nanodiamond conjugates (Nano-DOX), which could be delivered via GBM-associated macrophages, suppressed STAT3 activity in the GBC reducing their IL-6 output to the astrocytes and thereby abolished the astrocytes' feedback activation of the GBC. Moreover, Nano-DOX also suppressed stimulated activation of STAT3 and IL-6 induced by temozolomide, a first-line anti-GBM chemotherapy, resistance to which critically involves STAT3 activation. In conclusion, Nano-DOX could disrupt the STAT3/IL-6-mediated reciprocal activation loop between the GBC and astrocytes. Nano-DOX also provides a novel approach to therapeutic modulation of the GBM microenvironment.

Exploiting an appropriate strategy to prepare fine crystal quality black phosphorus nanosheet (BPNS) catalyst is a major challenge for its practical application in catalysis. Herein, we address this challenge by developing a rapid electrochemical expansion strategy for scale preparation of fine crystal quality BPNSs from bulk black phosphorus, which was demonstrated to be an active cocatalyst for photocatalytic nitrogen fixation in the presence of CdS as a photocatalyst. The transient photocurrent and charge density studies show that the BPNSs can efficiently accelerate charge separation of CdS, leading to the enhanced photocatalytic activities of BPNS/CdS nanocomposites for nitrogen fixation. The 1.5% BPNS/CdS photocatalyst exhibits the highest photocatalytic activity for nitrogen fixation with an NH3 evolution rate of 57.64 μmol·L-1·h-1. This study not only affords a rapid and simple strategy for scale synthesis of fine crystal quality BPNSs but also provides new insights into the design and development of black phosphorus-based materials as low-cost metal-free cocatalysts for photocatalytic nitrogen fixation.

Rational structure design of carbon nanomaterials including modulation of interlayer spacing and control of order degree, has been adopted to improve their electrochemical properties for high performance lithium-ion batteries (LIBs). Here, we construct three-dimensional (3D) architectures composed of intercrossed 1D graphitized-carbon nanotubes (g-CNTs) via a simple template synthesis. The g-CNT with high aspect ratio, can be viewed as a thin graphitized carbon sheet rolled up into a large hollow nanotube (average diameter: 222 nm). Its thin tube wall (3–4 nm) with multi-layered structure and relatively large interlayer spacing (3.73 nm) in short range can conduct fast diffusion of lithium ions (Li+), accommodate increased volume expansion and facilitate reversible Li+ intercalation/extraction. Particularly, heteroatoms like N and O are also doped in C patterns and would provide more active insertion or adsorption sites. Thus, the porous architectures are enabled to serve as freestanding anodes for LIBs, exhibiting a high specific capacity of ∼624 mA h/g at current density of 100 mA/g, stable long-term cycle stability, as well as good rate capability. Due to their larger tube cavity and 3D structures, our g-CNT architectures are further exploited as conductive frameworks to dual-load MnO2 nanoflowers, and would speed up the development of next-generation rechargeable LIBs.

A new non-fullerene electron acceptor with A-DA'D-A structure, namely, Y9, featuring a ladder-type heptacyclic fused ring (3-undecyl-thieno [2′,':4,5]thieno[3,2-b]pyrrole units with benzotriazole) as a core unit, is designed and synthesized. The new acceptor exhibits a broad and efficient absorption and extends into the near-infrared (NIR) region with a low optical bandgap of 1.36 eV. Efficient organic solar cells (OSCs) are fabricated with the wide bandgap polymer PBDB-T as polymer donor, showing high power conversion efficiency (PCE) of 13.26%. These results demonstrate that Y9 is a promising NIR non-fullerene acceptor for high-performance OSCs.

In the present work, the hybridization of subnanometer-scale metal oxide cluster SiW₁₂O₄₀⁴– (STA) with poly(ethylene oxide) (PEO) and PEO-block-poly(propylene oxide)-block-PEO was investigated. A new crystalline phase was formed in the hybrid nanocomposites, which is attributed to the inclusion of PEO in the lattices of STA, that is, inclusion crystallization. The crystal lattice and dimensions of STA/PEO inclusion crystals are determined to be an orthorhombic unit cell with a = 1.52 nm, b = 2.74 nm, c = 2.52 nm, and α = β = γ = 90°. Remarkably, hybrid nanosheets with large size and high shape asymmetries can be formed by lamellar inclusion crystals. The dependence of proton conductivities of STA nanocomposites on crystalline structures was examined, and it was found that the formation of hybrid nanosheets could enhance proton conductivities of STA nanocomposites. This work provides new insight into the development of cluster-based nanocomposites with controlled morphology and optimized performance.

Tar measurement and calculation is crucial for understanding the in-situ tar elimination and hydrogen-rich syngas production during the biomass gasification process. In this study, the method of evaluating tar production was proposed and studied on a two-stage fixed-bed reactor. Two different groups of oxidized and reduced oxygen carriers were investigated for comparison. The collected tar was tested on a gas chromatography–mass spectrometry (GC-MS) system. The types of the tar were all belonged to aromatic hydrocarbons. The H2 composition in the syngas was over 34% in three reduced-OC conditions. The carbon percentage identified by the GC-MS was at the range of 93.75–95.05 wt%. The average carbon from the char combustion period was 2.85 mmol. The tar yield in the three oxidized-OC conditions was 43 ± 22 mg/g, 53 ± 11 mg/g, and 62 ± 8 mg/g, respectively. The result indicated that the reduced OC had a catalytic effect for increasing the H2 composition in syngas. On the other hand, the oxidized OC influenced the reactions by providing with lattice oxygen. The evaluation of the produced tar was beneficial for a further understanding of the mechanism for producing the H2-rich syngas.

For many large and complex computer models, there usually exist a large number of unknown parameters. To improve the computer model's predictive performance for more reliable and confident decision making, two important issues have to be addressed. The first is to calibrate the computer model and the second is to select the most influential set of parameters. However, these two issues are often addressed independently, which may waste computational effort. In this article, a Gaussian process-based Bayesian method is first proposed to simultaneously calibrate and select parameters in stochastic computer models. The whole procedure can be conducted more efficient by sharing the data information between these two steps. To further ease the computational burden, an approximation approach based on a weighted normal approximation is proposed to evaluate the posteriors in the proposed Bayesian method. A sequential approximation procedure is further proposed to improve the approximation accuracy by allocating the sequential design points more appropriately. The efficiency and accuracy of the proposed approaches are compared in a building energy model and a pandemic influenza simulation model.

Energy loss within organic solar cells (OSCs) is undesirable as it reduces cell efficiency1–4. In particular, non-radiative recombination loss3 and energetic disorder5, which are closely related to the tail states below the band edge and the overall photon energy loss, need to be minimized to improve cell performance. Here, we report how the use of a small-molecule acceptor with torsion-free molecular conformation can achieve a very low degree of energetic disorder and mitigate energy loss in OSCs. The resulting single-junction OSC has an energy loss due to non-radiative recombination of just 0.17 eV and a high power conversion efficiency of up to 16.54% (certified as 15.89% by the National Renewable Energy Laboratory). The findings take studies of organic photovoltaics deeper into a new regime, beyond the limits of energetic disorder and large energy offset for charge generation. An organic solar cell designed with minimal energetic disorder exhibits very low energy loss due to non-radiative recombination and highly efficient operation.

In comparison with symmetric small molecule acceptors (SMAs), their asymmetric counterparts have received much less attention. Organic solar cells (OSCs) based on asymmetric non-fullerene SMAs previously reported show relatively low power conversion efficiency (PCE < 15%) and lower short circuit current densities (Jsc < 20 mA cm−2), although they exhibit a larger dipole moment and stronger intermolecular interactions. Here we report a new asymmetric A–D1A′D2–A type SMA, namely Y22, containing an asymmetric hexacyclic fused donor–acceptor–donor (DA′D) type central framework and end-capped with two electron-deficient 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile moieties. Y22 shows good solubility and a broad near-infrared absorption. The effects of the asymmetric structure on the physicochemical and photovoltaic performance were systematically investigated. Y22-based OSCs were fabricated by using PM6, QX2 and J71 as polymer donors, all exhibiting high PCEs over 10%. Notably, the optimal PM6:Y22-based device shows a high PCE of 15.4% and a high Jsc of 24.37 mA cm−2, which is among the best values reported for asymmetric SMA based OSCs, attributed to the fine nanofiber morphology after thermal annealing and solvent addition. This work demonstrates that the asymmetric fused structure with an electron-deficient-core is a promising building block to build high performance SMAs towards efficient photovoltaic applications.