In this paper, a low parasitic inductance SiC power module with double-sided cooling is designed and compared with a baseline double-sided cooled module. With the unique 3D layout utilizing vertical ...interconnection, the power loop inductance is effectively reduced without sacrificing the thermal performance. Both simulations and experiments are carried out to validate the design. Q3D simulation results show a power loop inductance of 1.63 nH, verified by the experiment, indicating more than 60% reduction of power loop inductance compared with the baseline module. With 0Ω external gate resistance turn-off at 600V, the voltage overshoot is less than 9% of the bus voltage at a load of 44.6A.
A look at the development, preparation and other issues related to supermolecular polymers is presented. The authors discuss supramolecular polymers with branch-like and hyperbranch-like topology and ...application of supramolecular polymers.
The process of self-assembly spontaneously creates well-defined structures from various chemical building blocks. Self-assembly can include different levels of complexity: it can be as simple as the ...dimerization of two small building blocks driven by hydrogen bonding or as complicated as a cell membrane, a remarkable supramolecular architecture created by a bilayer of phospholipids embedded with functional proteins. The study of self-assembly in simple systems provides a fundamental understanding of the driving forces and cooperativity behind these processes. Once the rules are understood, these guidelines can facilitate the research of highly complex self-assembly processes. Among the various components for self-assembly, an amphiphilic molecule, which contains both hydrophilic and hydrophobic parts, forms one of the most powerful building blocks. When amphiphiles are dispersed in water, the hydrophilic component of the amphiphile preferentially interacts with the aqueous phase while the hydrophobic portion tends to reside in the air or in the nonpolar solvent. Therefore, the amphiphiles aggregate to form different molecular assemblies based on the repelling and coordinating forces between the hydrophilic and hydrophobic parts of the component molecules and the surrounding medium. In contrast to conventional amphiphiles, supra-amphiphiles are constructed on the basis of noncovalent interactions or dynamic covalent bonds. In supra-amphiphiles, the functional groups can be attached to the amphiphiles by noncovalent synthesis, greatly speeding their construction. The building blocks for supra-amphiphiles can be either small organic molecules or polymers. Advances in the development of supra-amphiphiles will not only enrich the family of conventional amphiphiles that are based on covalent bonds but will also provide a new kind of building block for the preparation of complex self-assemblies. When polymers are used to construct supra-amphiphiles, the resulting molecules are known as superamphiphiles. This Account will focus on the use of amphiphiles and supra-amphiphiles for self-assembly at different levels of complexity. We introduce strategies for the fabrication of robust assemblies through self-assembly of amphiphiles. We describe the supramolecular approach for the molecular design of amphiphiles through the enhancement of intermolecular interaction among the amphiphiles. In addition, we describe polymerization under mild conditions to stabilize the assemblies formed by self-assembly of amphiphiles. Finally, we highlight self-assembly methods driven by noncovalent interactions or dynamic covalent bonds for the fabrication of supra-amphiphiles with various topologies. Further self-assembly of supra-amphiphiles provides new building blocks for complex structures, and the dynamic nature of the supra-amphiphiles endows the assemblies with stimuli-responsive functions.
Supramolecular materials held together by noncovalent interactions, such as hydrogen bonding, host–guest interactions, and electrostatic interactions, have great potential in material science. The ...unique reversibility and adaptivity of noncovalent intreractions have brought about fascinating new functions that are not available by their covalent counterparts and have greatly enriched the realm of functional materials. This review article aims to highlight the very recent and important progresses in the area of functional supramoleuclar materials, focusing on adaptive mechanical materials, smart sensors with enhanced selectivity, soft luminescent and electronic nanomaterials, and biomimetic and biomedical materials with tailored structures and functions. We cannot write a complete account of all the interesting work in this area in one article, but we hope that it can in a way reflect the current situation and future trends in this prosperously developing area of functional supramolecular materials.
This review article aims to highlight the very recent and important progress in the area of functional supramolecular materials, focusing on their extraordinary functions arising from the reversible and adaptive noncovalent interactions. It mainly includes adaptive mechanical materials, smart sensors with enhanced selectivity, soft luminescent and electronic nanomaterials, and biomimetic and biomedical materials with tailored structures and functions.
To examine the clinical characteristics and identify independent risk factors for in-hospital mortality of 2019 novel coronavirus (COVID-19) pneumonia.
A total of 156 patients diagnosed with COVID-19 ...pneumonia at the Central Hospital of Wuhan from January 29, 2020, to March 20, 2020, and 20 healthy individuals were enrolled in this single-centered retrospective study. The epidemiological parameters, clinical presentations, underlying diseases, laboratory test results, and disease outcomes were collected and analyzed.
The median age of all enrolled patients was 66 years. At least one underlying disease was identified in 101 COVID-19 patients, with hypertension being the most common one, followed by cardiovascular disease and diabetes. The most common symptoms identified upon admission were fever, cough, dyspnea, and fatigue. Compared to survival cases, patients who died during hospitalization had higher plasma levels of D-dimer, creatinine, creatine kinase, lactate dehydrogenase, lactate, and lower percentage of lymphocytes (LYM %), platelet count and albumin levels. Most enrolled patients received antibiotics and anti-viral treatment. In addition, 60 patients received corticosteroids, and 51 received intravenous immunoglobulin infusion. Forty-four patients received noninvasive ventilation and 19 received invasive ventilation. Respiratory failure was the most frequently observed complication (106 67.9%), followed by sepsis (103 66.0%), acute respiratory distress syndrome (ARDS) (67 42.9%), and septic shock (50 32.1%). Multivariable regression suggested that advanced age (OR odds ratio = 1.098, 95% CI confidence interval: 1.006-1.199, P = 0.037), shorter duration from onset to admission (OR = 0.853, 95% CI: 0.750-0.969, P = 0.015) and elevated lactate level upon admission (OR = 2.689, 95% CI: 1.044-6.926, P = 0.040) were independent risk factors for in-hospital mortality for COVID-19 infection. Meanwhile, increased LYM (%) at admission (OR = 0.787, 95% CI: 0.686-0.903, P = 0.001) indicated a better prognosis.
In this study, we discovered that age, duration from onset to admission, LYM (%), and lactate level upon admission were independent factors that affecting the in-hospital mortality rate.
Developing efficient but nonprecious bifunctional electrocatalysts for overall water splitting in basic media has been the subject of intensive research focus with the increasing demand for clean and ...regenerated energy. Herein, we report on the synthesis of a novel hierarchical hybrid electrode, NiFe-layered double hydroxide molecularly ultrathin sheets grown on NiCo2O4 nanowire arrays assembled from thin platelets with nickel foam as the scaffold support, in which the catalytic metal sites are more accessible and active and most importantly strong chemical coupling exists at the interface, enabling superior catalytic power toward both oxygen evolution reaction (OER) and additionally hydrogen evolution reaction (HER) in the same alkaline KOH electrolyte. The behavior ranks top-class compared with documented non-noble HER and OER electrocatalysts and even comparable to state-of-the-art noble-metal electrocatalysts, Pt and RuO2. When fabricated as an integrated alkaline water electrolyzer, the designed electrode can deliver a current density of 10 mA cm–2 at a fairly low cell voltage of 1.60 V, promising the material as efficient bifunctional catalysts toward whole cell water splitting.
Supramolecular polymers are made of monomers that are held together by noncovalent interactions. This is the reason for the wide range of novel properties, such as reversibility and responses to ...stimuli, exhibited by supramolecular polymers. A range of supramolecular polymerization methods have been developed leading to a number of novel supramolecular materials. However, standard techniques for the characterization of supramolecular polymers have yet to be established. The dynamic nature of supramolecular polymers makes them difficult to be fully characterized using conventional polymer techniques. This tutorial review summarizes various methods for characterizing supramolecular polymers, including theoretical estimation, size exclusion chromatography, viscometry, light scattering, vapor pressure osmometry, mass spectrometry, NMR spectroscopy, scanning probe microscopy, electron microscopy, and atomic force microscopy-based single molecule force spectroscopy. Each of these methods has its own particular advantages and disadvantages. Most of the methods are used to characterize the supramolecular polymer chain itself. However, some of the methods can be used to study the self-assembled state formed by supramolecular polymers. The characterization of a supramolecular polymer cannot be realized with a single method; a convincing conclusion relies on the combination of several different techniques.
The coal-based energy consumption structure will significantly increase carbon emissions. Along with the rise in per-capita income, this energy consumption structure will reduce economy sustainable ...growth. The measure of sustainable economic growth is to use the DEA-SBM super efficiency model of unexpected output and calculate the green total factor productivity (GTFP). The proportion of coal consumption in energy consumption represents the structure of energy consumption . The panel data in this paper are from the records of various provinces and cities in China from 2005 to 2017 (except Tibet). In the results of the mixed panel regression, the impact of energy consumption structure on sustainable economic growth is not significantly positive, and after controlling for time and provinces, the overall impact of energy consumption structure on sustainable economic growth is positive, and significant at the 5% level, and its impact on carbon dioxide emissions is significant at the 1% level. It means that the coal-based energy consumption structure is a significant factor in increasing carbon emissions. Due to the heterogeneity of various provinces, the energy consumption structure of developed provinces and cities will significantly reduce sustainable economic growth at the 1% level, while it will increase significantly at the 5% level in less developed provinces and cities, which has uncertain impact on moderately developed provinces and cities. For developed provinces, reducing the proportion of coal consumption, improving the energy consumption structure can bring about the improvement of GTFP, that is, to promote sustainable economic growth. For other provinces, strategies to change the structure of energy consumption should be put forward according to the stage of economic development. Using the mediating effect model, it is found that both developed and underdeveloped provinces contribute to sustainable economic growth through carbon dioxide emissions. Therefore, controlling carbon dioxide emissions is very important for sustainable economic growth.
With the development of intelligent device and social media, the data bulk on Internet has grown with high speed. As an important aspect of image processing, object detection has become one of the ...international popular research fields. In recent years, the powerful ability with feature learning and transfer learning of Convolutional Neural Network (CNN) has received growing interest within the computer vision community, thus making a series of important breakthroughs in object detection. So it is a significant survey that how to apply CNN to object detection for better performance. First the paper introduced the basic concept and architecture of CNN. Secondly the methods that how to solve the existing problems of conventional object detection are surveyed, mainly analyzing the detection algorithm based on region proposal and based on regression. Thirdly it mentioned some means which improve the performance of object detection. Then the paper introduced some public datasets of object detection and the concept of evaluation criterion. Finally, it combed the current research achievements and thoughts of object detection, summarizing the important progress and discussing the future directions.
To reduce the steady-state torque ripples for permanent-magnet synchronous motor drives with predictive torque control (PTC), this paper proposes a modified PTC algorithm based on the extended ...control set (ECS-PTC). In the proposed algorithm, more candidate voltage vectors are extended to the control set, which forms the ECS, and then, the torque control precision could be improved and the torque ripples will be reduced. More attractive thing is that a new voltage vector synthesis method is deigned in ECS-PTC, and the corresponding predictive model and cascaded predictive algorithm are set up on the basis of this method. With the help of them, the optimal vector can be selected from ECS in a shorter control period of time, and its amplitude is also optimized at the same time to achieve high-precision control effects for torque and flux. In addition, the three-phase duty ratios of the output vector can be determined in ECS-PTC directly, without the help of space vector pulse width modulation. The experimental results show that ECS-PTC has excellent dynamic torque performance, and it also has more stable torque control performance and better execution efficiency at the same time.
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