There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

https://hal.archives-ouvertes.fr/hal-02417326/document

Materials for electrochemical capacitors

Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

Developing high-performance anode materials for potassium-ion batteries is significantly urgent. We here demonstrate Sb2S3 nanoparticles (∼20 nm) homogeneously dispersed in porous S,N-codoped graphene framework (Sb2S3-SNG) as a self-supported anode material for potassium-ion batteries. The rational structure design of integrating Sb2S3 nanoparticles with S,N-codoped graphene contributes to high reactivity, strong affinity, good electric conductivity, and robust stability of the composite, enabling superior K-storage performance. Moreover, the self-supported architecture significantly decreases the inactive weight of the battery, resulting in a high energy density of a Sb2S3-SNG/KVPO4F-C full cell to ∼166.3 W h kg−1.

Robust self-supported anode by integrating Sb 2 S 3 nanoparticles with S,N-codoped graphene to enhance K-storage performance

Perovskite alkaline niobates, especially of one-dimensional morphology, have many important industrial applications. Wirelike Nb2O5 and ANbO3 (A = K, Na, (Na,K)) were fabricated by a topochemical method based on the molten salt synthesis. First, the precursor KNb3O8 with wire structure was prepared under the condition of molten salt KCl environment at 800 °C for 3 h. Then, rodlike H3ONb3O8 and Nb2O5 were obtained from the wirelike KNb3O8 precursor. Finally, the rodlike ANbO3 (A = K, Na, (Na,K)) were achieved with the intermediate oxide Nb2O5. The wirelike structure of the final product can be achieved when using wirelike Nb2O5 precursor only. The structural evolution was investigated among protonic niobate, niobium oxide, and niobates. The mechanism of these shape transitions was elucidated in the view of structure recombining and atomic diffusing. The (Na,K)NbO3 ceramic sintered from the as-prepared rodlike particles under pressureless condition in the air performed with high piezoelectricity (d33 = 140 ...

http://ylsong.iccas.ac.cn/documents/25353/0d736593-312d-4d0b-9932-c864dde8cc78

Wire Structure and Morphology Transformation of Niobium Oxide and Niobates by Molten Salt Synthesis

Chaotropic Anion and Fast-Kinetics Cathode Enabling Low-Temperature Aqueous Zn Batteries

Paper-like free-standing polypyrrole and polypyrrole-liFePO4 composite films for flexible and bendable rechargeable battery

Silicon/disordered carbon (Si-DC) nanocomposites have been synthesized by high-energy ballmilling of Si-sucrose and silicon-polyvinyl alcohol followed by pyrolysis under argon flow. The exact disordered carbon content in the as-prepared Si-DC nanocomposites was determined by thermogravimetric analysis for the first time. Based on the thermogravimetric analysis, X-ray diffraction, Raman, and cyclic voltammetric results, we believe that carbon distribution on the Si particles in Si-DC nanocomposite using PVA as the carbon source is more uniform and has higher efficiency than that using sucrose as the carbon source, under the same preparation conditions. The carbon content and the starting polymers significantly affect the electrochemical performance of the Si-DC nanocomposites. The optimized Si-DC nanocomposite anode demonstrated a reversible capacity of 754 mAh/g within 20 cycles.

/pdf/silicon-disordered-carbon-nanocomposites-for-lithium-ion-b84agowl28.pdf

Jun Chen

Papers

Robust self-supported anode by integrating Sb 2 S 3 nanoparticles with S,N-codoped graphene to enhance K-storage performance

Wire Structure and Morphology Transformation of Niobium Oxide and Niobates by Molten Salt Synthesis

Chaotropic Anion and Fast-Kinetics Cathode Enabling Low-Temperature Aqueous Zn Batteries

Paper-like free-standing polypyrrole and polypyrrole-liFePO4 composite films for flexible and bendable rechargeable battery

Silicon/Disordered Carbon Nanocomposites for Lithium-Ion Battery Anodes