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

Iridium-based nanomaterials for electrochemical water splitting

3D and 4D printing in dentistry and maxillofacial surgery: Printing techniques, materials, and applications.

https://publikationen.bibliothek.kit.edu/1000096569/37128217

Formation of the third bodies of steel sliding against brass under lubricated conditions

To investigate the improvement in vibration fatigue and the strengthening mechanism of laser shock peening, a nanosecond laser was used to strengthen the 2024-T351 aluminium alloy. Accordingly, the microstructure, residual stress, nanohardness and surface roughness of the treated alloy were measured. Subsequently, the vibration fatigue damage and fatigue life were evaluated, and the vibration fracture morphology was observed. The results showed that the grains in the peened surface were refined. A residual stress of −141 MPa and a nanohardness of 3.1 GPa were obtained by laser shock peening. Based on the relationship between the peened microstructure and fracture morphology, it was deduced that an increase in the grain boundaries led to a lower crack initiation rate and a higher crack initiation life. The compressive residual stress decreased the crack growth rate and increased the crack growth life. Therefore, laser shock peening increases the total vibration fatigue life by about 63.5%.

Gradient microstructure and vibration fatigue properties of 2024-T351 aluminium alloy treated by laser shock peening

Studies on viscosity reduction and structural change of crude oil treated with acoustic cavitation

The effects of titanium ion implantation on the stress corrosion cracking (SCC) behaviour of 304 austenitic stainless steel were studied. Slow strain rate tests (SSRTs) were conducted on 304 steel ...

Inhibition of stress corrosion cracking in 304 stainless steel through titanium ion implantation

This paper is concerned with the effect of laser shock peening on micro-hardness and microstructure of brass. In order to study the plastic deformation behaviors of brass, laser shock peening with 1, 2, and 3 impacts at pulse energy of 6.5 J were performed in this experiment respectively. The micro-hardness distribution in the near-surface layer is performed by hardness tester, and the microstructure in the surface layer is determined by X-ray diffraction and transmission electron microscopy. The results indicate that higher surface micro-hardness of brass after laser shock peening impacts is induced comparing with untreated brass. Additionally, increasing the impact times of laser shock peening, the surface micro-hardness improves correspondingly. Combined with transmission electron microscopy analysis, the determinate factors for variation of surface micro-hardness owes to the twins spacing and grain refinement induced by laser shock peening. The formation and interaction of surface mechanical twins are accompanied by improving in surface strain and strain rate. The equiaxed grains with an average size of 70–100 nm are generated in the top surface layer after 3 laser shock peening impacts. Furthermore, the grain refinement mechanism in the top surface layer subjected to laser shock peening is summarized as follows: (i) parallel mechanical twins are generated due to the effect of strain deformations induced by laser shock peening; (ii) mechanical twins are subdivided into secondary twins with the formation of dense dislocation tangles at the mechanical twins boundaries; (iii) twins interaction in different directions refine the grain into nano-scale equiaxed grains.

Lin Liu

Papers

Formation of the third bodies of steel sliding against brass under lubricated conditions

Gradient microstructure and vibration fatigue properties of 2024-T351 aluminium alloy treated by laser shock peening

Studies on viscosity reduction and structural change of crude oil treated with acoustic cavitation

Inhibition of stress corrosion cracking in 304 stainless steel through titanium ion implantation

Characterization and analysis on micro-hardness and microstructure evolution of brass subjected to laser shock peening