Meshfree simulations of large scale ductile fracture of stiffened ship hull plates during ship stranding

Meccanica - In this work, we have developed a systematic computational methodology to directly simulate the ductile fracture of ship hull structure during ship stranding based on the meshfree...     

4.8 nm Concave {M_(72)}(M=Co,Ni,Fe) metal-organic polyhedra capped by 18 calixarenes

Three 4.8 nm isostructural{M₇₂}(M=Co^Ⅱ for CIAC-128,Ni^Ⅱ for CIAC-129,Fe^Ⅱ for CIAC-130) metal-organic polyhedra(MOPs) are constructed by eighteen M₄-p-tert-butylthiacalix[4]arene (M₄-TC4A) units bridged via sixteen four-connected 5,5′-(1H-1,2,4-triazole-3,5-diyl) diisophthalic acid (H₄TADIPA) linkers.These MOPs are featured with a rarely reported concave coordination cage,which can be simplified as a squeezed double-decker hexagonal prism pressed from the top and bottom hexagonal faces.Furthermore,CIAC-128,CIAC-129 and CIAC-130 are the highest nuclearity discrete clusters of Co,Ni and Fe reported so far.CIAC-128 has higher separation selectivity of C₃H₈ than CH₄ under ambient conditions,and also exhibits separation selectivity for C₂H₆/CH₄,C₂H₂/CH₄,and C₂H₄/CH₄.In addition,CIAC-128 can provide the cavity for the confined synthesis of noble metal nanoclusters such as Pd nanoclusters and the resulting Pd@CIAC-128 hybrids show higher electrocatalytic activity than commercial Pt/C towards hydrogen evolution reaction (HER).     

Dispersion Theory of Polaron in a Parabolic Quantum Dot at Finite Temperatures

By using the dispersion theory instead of the Fröhlich Hamiltonian, the polaron energy in a quantum dot with a parabolic confinement potential is investigated at finite temperatures. It is found that the self-trapping energy of the polaron decreases with the increasing temperature, and the temperature effect is more obvious in quantum dots with weaker confinement.     

Emergent rotational symmetries in disordered magnetic domain patterns

Uniaxial systems often form labyrinthine domains that exhibit short-range order but are macroscopically isotropic and would not be expected to exhibit precise symmetries. However, their underlying frustration results in a multitude of metastable configurations of comparable energy, and driving such a system externally might lead to pattern formation. We find that soft x-ray speckle diffraction patterns of the labyrinthine domains in CoPd/IrMn heterostructures reveal a diverse array of hidden rotational symmetries about the magnetization axis, thereby suggesting an unusual form of emergent order in an otherwise disordered system. These symmetries depend on applied magnetic field, magnetization history, and scattering wave vector. Maps of rotational symmetry exhibit intriguing structures that can be controlled by manipulating the applied magnetic field in concert with the exchange bias condition.     

A ray model for hard parallel noise barriers in high-rise cities

A ray model is developed and validated for prediction of the insertion loss of hard parallel noise barriers placed in an urban environment either in front of a row of tall buildings or in a street canyon. The model is based on the theory of geometrical acoustics for sound diffraction at the edge of a barrier and multiple reflections by the ground, barrier and fa?ade surfaces. It is crucial to include the diffraction and multiple reflection effects in the ray model as they play important roles in determining the overall sound pressure levels for receivers located between the fa?ade and the near-side barrier. Comparisons of the ray model with a wave-based boundary element formulation show reasonably good agreement over a broad frequency range. Results of scale model experimental studies are also presented. It is demonstrated that the ray model agrees tolerably well with the scale model experimental data.     

基于传输线等效法的双腔体屏蔽系数快速算法

传输线等效法（TLM）是一种常用的开孔腔屏蔽系数快速计算方法,在孔缝耦合系数的计算中考虑了孔缝处的场模式,提高了TLM算法在高频段计算屏蔽系数（SE）的准确性。继而将TLM算法推广到开孔双金属腔屏蔽系数的计算,通过将外腔体中任意位置的电压等效为内孔缝处的辐射电压源,计算得到内腔体中任意位置上的屏蔽系数,解决了已有文献中方法的不足。该算法计算结果与CST仿真结果吻合较好。     

Fabrication and characterization of Ge20Sb15S65 chalcogenide glass for photonic crystal fibers

Chalcogenide glasses are known for their high transparency in the mid-infrared (IR) range, which includes two atmospheric windows that lie from 3 to 5 μm and 8 to 12 μm, respectively. Chalcogenide photonic crystal fibers have numerous potential applications in the field of IR, such as spectroscopy, microscopy, astronomy, biology, and sensing. In this paper, Ge₂₀Sb₁₅S₆₅ chalcogenide glass was fabricated and systematically studied. Chalcogenide glass has high transmission property (>70 %), good thermal stability, and good mechanical stability. The glass transition temperature T _g is 296 °C, and no exothermic peak was associated with crystallization up to 500 °C, which indicates its suitability for fiber drawing. As a result of its excellent mechanical properties, preforms with a variety of geometrical patterns were fabricated by using mechanical drilling. The near-field intensity distribution image of the drawn fiber shows a strong light propagation confinement.     

Surface-enhanced Raman scattering from silver nanostructures with different morphologies

Scanning electron microscopy and X-ray diffraction reveal that four different types of crystalline silver nanostructures including nanoparticles, nanowires, nanocubes, and bipyramids are synthesized by a solvothermal method by reducing silver nitrate with ethylene glycol using poly(vinylpyrrolidone) as an adsorption agent and adding different quantities of sodium chloride to the solution. These nanostructures which exhibit different surface plasma resonance properties in the ultraviolet–visible region are shown to be good surface-enhanced Raman scattering (SERS) substrates using rhodamine 6G molecules. Our results demonstrate that the silver nanocubes, bipyramids with sharp corners and edges, and aggregated silver nanoparticles possess better SERS properties than the silver nanowires, indicating that they can serve as high-sensitivity substrates in SERS-based measurements.     

Stability evaluation of Tc-99m radiolabeled GRPr antagonist with amino acid chelators

In order to select a chelator with excellent stability, easier radiolabeling process and low cost, GRPr antagonist RM26 with the amino acid based chelator was radiolabeled with technetium-99m. The stability of the radiolabeled peptides in PBS, serum as well as in the presence of excess cysteine was compared.

     

Preparation of Three Decadeoxyribonucleotides Containing an Uncommon or Modified Base

Three decadeoxyribonucleotides (d-C-C-A-A-I-A-T-T-G-G, d-C-^brC-A-A-G-A-T-T-G-G and d-C-C-A-A-^mG-A-T-T-G-G) involving inosine (I), 5-bromocytidine (^brC) and 6-O-methylguanosine (^mG) were chemically synthesized based on the phosphotriester approach in milligram quantities. The procedures of full protection reaction of these uncommon or modified bases are given in detail. The phosphotriester method was then employed to synthesize all the decamers. It seems the phosphotriester method is applicable to the synthesis of oligodeoxyribonucleotide with these three odd-bases. However, slightly different procedures have to be used while deblocking the fully protected oligodeoxyribonucleotides depending upon the nature of the uncommon or modified base.