Nanjing University

About: Nanjing University is a education organization based out in Nanjing, China. It is known for research contribution in the topics: Catalysis & Adsorption. The organization has 85961 authors who have published 105504 publications receiving 2289036 citations. The organization is also known as: NJU & Nanking University.

DC/DC Conversion Systems Consisting of Multiple Converter Modules: Stability, Control, and Experimental Verifications

Abstract: This paper investigates DC/DC conversion systems constructed from connecting multiple converter modules in series and/or parallel at both the input and output sides. Control strategies aiming at achieving proper sharing of the voltage and/or current at the input or output sides are studied in detail. The relationship between sharing of input voltages/currents and that of output voltages/currents is studied. In particular, the inherent stability of control operations applied at the input side and the output side is analyzed. Based on the analysis, a general control strategy for series-parallel systems, which decouples the output voltage control loop and the sharing control loop, is proposed. Furthermore, three modularization architectures are proposed for input-series-output-parallel (ISOP), input-parallel-output-series (IPOS), and input-series-output-series (ISOS) connected systems. These architectures enjoy full advantages of modularization and no external controller is needed to coordinate the sharing control for the individual modules. Experimental prototypes are built and tested to validate the general control strategy and the proposed modularization architectures.

Standards of medical care for type 2 diabetes in China 2019.

Abstract: The prevalence of diabetes in China has increased rapidly from 0.67% in 1980 to 10.4% in 2013, with the aging of the population and westernization of lifestyle. Since its foundation in 1991, the Chinese Diabetes Society (CDS) has been dedicated to improving academic exchange and the academic level of diabetes research in China. From 2003 to 2014, four versions of Chinese diabetes care guidelines have been published. The guidelines have played an important role in standardizing clinical practice and improving the status quo of diabetes prevention and control in China. Since September 2016, the CDS has invited experts in cardiovascular diseases, psychiatric diseases, nutrition, and traditional Chinese medicine to work with endocrinologists from the CDS to review the new clinical research evidence related to diabetes over the previous 4 years. Over a year of careful revision, this has resulted in the present, new version of guidelines for prevention and care of type 2 diabetes in China. The main contents include epidemiology of type 2 diabetes in China; diagnosis and classification of diabetes; primary, secondary, and tertiary diabetes prevention; diabetes education and management support; blood glucose monitoring; integrated control targets for type 2 diabetes and treatments for hyperglycaemia; medical nutrition therapy; exercise therapy for type 2 diabetes; smoking cessation; pharmacologic therapy for hyperglycaemia; metabolic surgery for type 2 diabetes; prevention and treatment of cardiovascular and cerebrovascular diseases in patients with type 2 diabetes; hypoglycaemia; chronic diabetic complications; special types of diabetes; metabolic syndrome; and diabetes and traditional Chinese medicine.

Second-order topology and multidimensional topological transitions in sonic crystals

Abstract: Topological insulators with unique edge states have revolutionized the understanding of solid-state materials. Recently, higher-order topological insulators (HOTIs), which host both gapped edge states and in-gap corner/hinge states, protected concurrently by band topology, were predicted and observed in experiments, unveiling a new horizon beyond the conventional bulk-edge correspondence. However, the control and manifestation of band topology in a hierarchy of dimensions, which is at the heart of HOTIs, have not yet been witnessed. Here, we propose theoretically and observe experimentally that tunable two-dimensional sonic crystals can be versatile systems to visualize and harness higher-order topology. In our systems, the two-dimensional acoustic bands mimic the quantum spin Hall effect, while the resultant one-dimensional helical edge states are gapped due to broken space-symmetry and carry quantized Zak phases, which then lead to zero-dimensional topological corner states. We demonstrate that topological transitions in the bulk and edges can be triggered independently by tuning the geometry of the sonic crystals. With complementary experiments and theories, our study reveals rich physics in HOTIs, opening a new route towards tunable topological metamaterials where novel applications, such as the topological transfer of acoustic energy among two-, one- and zero-dimensional modes, can be achieved. By tuning the geometry of a two-dimensional sonic crystal, its one-dimensional helical edge states become gapped and zero-dimensional topological corner states emerge. The band topology is thus manifested in a hierarchy of dimensions.

A Room-Temperature Reactive-Template Route to Mesoporous ZnGa2O4 with Improved Photocatalytic Activity in Reduction of CO2

Abstract: Mesoporous materials are of scientific and technological interest due to their potential applications in various areas. Over the past two decades, significant effort has been devoted to the synthesis of mesoporous materials. For instance, mesoporous silica and phosphate metal oxides have been synthesized and applied widely in many industrial processes. However, little progress has been made in the synthesis of mesoporous metal oxides containing more than one type of metal. To date, a limited number of routes including evaporation-induced self-assembly (EISA) and nonaqueous solvent methods have been developed to synthesize multimetallic mesoporous materials such as Pb3Nb4O13, [3] Bi20TiO32, [4] SrTiO3, MgTa2O6, CoxTi1 xO2 x, [5] and Ce1 xZrxO2. [6] In these routes, introducing surfactant molecules or a template is a general method used to construct the mesostructures. Challenges in using the template method to synthesize multimetallic mesoporous materials are uncontrolled phase separation in the multicomponent reactions and poor thermal and chemical stability of the resulting mesoporous structure. Maintaining the complete mesostructure during removal of the template by heating or chemical treatment is a key process for obtaining the expected mesostructures, and increases the uncertainty in a given synthetic route. In addition, to obtain a crystalline mesoporous material, high-temperature heat treatment is usually required for crystallization of the product. However, this process probably induces collapse of mesostructures. Recently, we developed a synthetic route to mesoporous multimetal oxides that uses the inorganic starting reactants directly as pore makers which aid in building the mesoporous structures of multimetal oxides and improve the thermal stability of the resulting mesostructure. However, in these reported synthetic routes, postcrystallization and introducing or removing an exotemplate are usually needed. In recent years, a route that does not require template removal, which was named “reactive hard templating”, was developed to synthesize porous TiN/carbon composite materials. In this route, the template consists of nanostructures of porous graphitic C3N4, which thermally decomposes completely during formation of porous TiN. This route provides a means to overcome the problems associated with synthesizing multimetal mesoporous materials. A simplified soft-chemistry route based on a reactive template is expected to allow synthesis to proceed at room temperature without requiring the introduction or removal of a template. Here we report a novel direct method for preparing mesoporous ZnGa2O4 with a wormhole framework by an ion-exchange reaction at room temperature involving a mesoporous NaGaO2 colloid precursor. The method does not require any additional processes and can be extended to prepare other porous materials, such as CoGa2O4 and NiGa2O4. The X-ray diffraction (XRD) pattern of NaGaO2 powder, which can be indexed as the orthorhombic phase (JCPDS 762151), is presented in Figure 1. Scanning electron microscopy (SEM) revealed that the powder particles are irregular in shape with little agglomeration, and most of the particles are larger than 500 nm in diameter (see Supporting Information). The as-prepared NaGaO2 powder can be dispersed in water to form a suspension. When the NaGaO2 suspension is illuminated with a 532 nm laser, a Tyndall effect is observed, that is, the suspension behaves as a colloid (see Supporting Information). Multimodal measurements of particle size distribution by dynamic light scattering show that the NaGaO2 colloidal particles exhibit two peak distributions: 20 % of the particles have an average size of 70 nm, and 80 % an average size of 335 nm. Most particulate or macroscopic materials in contact with a liquid acquire an electric charge on their surfaces. The zeta potential is an important and useful indicator of this charge that can be used to predict the stability of colloidal suspensions. The zeta potential of NaGaO2 colloidal particles is 21.57 mV (pH 6). This is lower than the critical zeta potential of 30 mV for maintaining colloid stability in an aqueous system, that is, the colloidal particles are slightly [*] S. C. Yan, J. Gao, M. Yang, X. X. Fan, L. J. Wan, Prof. Y. Zhou, Prof. Z. G. Zou Ecomaterials and Renewable Energy Research Center National Laboratory of Solid State Microstructures, Nanjing University, 22 Hankou Road, Nanjing 210093 (China) E-mail: zgzou@nju.edu.cn

Syntheses, Structures, and Physical Properties of Three Novel Metal−Organic Frameworks Constructed from Aromatic Polycarboxylate Acids and Flexible Imidazole-Based Synthons

Abstract: Three novel interesting coordination polymers, [Cd3(SIP)2(bbi)5·3H2O]n (1), [Co3(SIP)2(bix)4(2H2O)·2H2O]n (2), and [Cd(2,5-pydc)2(bix)1.5·H2O]n (3) (SIP = 5-sulfoisophthalic acid monosodium salt; bbi = 1,1‘-(1,4-butanediyl)bis(imidazole); bix = 1,4-bis(imidazol-1-ylmethyl)-benzene; 2,5-pydc = pyridine-2,5-dicarboxylic acid), have been isolated under hydrothermal conditions and structurally characterized. Polymer 1 has a 3D complicated framework comprised of an infinite 1D ladder-like chain and 2D layer structure. Polymer 2 features a 3D hydrated framework with uncoordinated water molecules trapped in the pores. Polymer 3 is a 2D infinite layer framework, which is further interconnected by hydrogen-bond interactions to lead to a 3D supramolecular architecture. Compounds 1 and 3 exhibit medium-strong fluorescent emissions in the solid state at room temperature and could be significant in the field of photoactive materials.