Structural and electronic properties of carbon nanotubes under hydrostatic pressures

We studied the structural and electronic properties of carbon nanotubes under hydrostatic pressures based on molecular dynamics simulations and first principles band structure calculations. It is found that carbon nanotubes experience a hard-to-soft transition as external pressure increases. The bulk modulus of soft phase is two orders of magnitude smaller than that of hard phase. The band structure calculations show that band gap of (10, 0) nanotube increases with the increase of pressure at low pressures. Above a critical pressure (5.70GPa), band gap of (10, 0) nanotube drops rapidly and becomes zero at 6.62GPa. Moreover, the calculated charge density shows that a large pressure can induce an {sp}²-to-{sp}³ bonding transition, which is confirmed by recent experiments on deformed carbon nanotubes.     

不圆度对圆环和圆管静水压力下临界荷载的影响

采用最小二乘法求解曲率半径对称波动变化的非理想圆环在均匀静水压力作用下的平面内稳定性问题,分别求得了反对称屈曲和对称屈曲的临界荷载系数。当不圆度参数β=0．4时,反对称屈曲的临界荷载系数降低67．71％。用最小相对误差拟合法得到了精度较高的临界荷载系数拟合公式,其最大相对误差仅为土0．76％。采用平面应变假设,推广得到...     

Release of charges under external fields of PbLa（Zr,Sn,Ti）O3 ceramic

This paper investigates the pyroelectric of poled antiferroelectric (AFE) ceramic Pb 0.97 La 0.02 (Zr 0.69 Sn 0.196 Ti 0.114)O 3 and its remnant polarization dependence of hydrostatic pressure.The results show that the bound charges of poled sample can be released in short time by temperature field or pressure field.The released charge abruptly forms a large pulse current.The phenomena of released charge under external fields result in the ferroelectric-AFE phase transition induced by temperature or hydrostatic pressure.     

Secure authentication scheme for 10 Gbit/s Ethernet passive optical networks

With the development of access network, 10G EPON has gained more and more attention. As its topology structure is point-to-multi-point and the downstream data is broadcasted, it will suffer from eavesdropping and masquerading attack. To eliminate these safety threats, this paper proposes an integrated security scheme including a bilateral authentication method and an encryption algorithm combined with one-way hash function. The authentication method can verify OLT and ONU during the registration process, preventing illegal users joining the network, and safely establish a secret key used for encrypting as well. The proposed scheme's security is based on the computational Diffie–Hellman assumption and the target collision resistant hash functions. The simulation results indicate that this mechanism is more suitable for practical use.     

超高压和热杀菌对草莓浊汁及清汁品质的影响

研究超高压(常温下,550MPa,处理5min)、热处理(中心温度90℃,处理1min)及高温短时杀菌(110℃,处理8.6s)对草莓浊汁和清汁品质的影响。结果表明:(1)经超高压处理后,草莓浊汁的黏度、果胶含量和浊度无显著变化,悬浮稳定性显著增加;而热处理和高温短时杀菌处理后,浊汁的黏度和果胶含量显著减小,浊度增大,悬浮稳定性降低,但高温短时杀菌组好于热处理组;(2)草莓浊汁和清汁经超高压处理后Vc分别损失11.09%和13.59%,而热烫结合超高压处理后分别损失7.75%和10.73%;热处理和高温短时杀菌组浊汁和清汁中Vc的损失率高于超高压组,分别为28.86%~38.89%和20.38%~29.02%;(3)超高压处理对草莓浊汁和清汁的单体花色苷、聚合色度及总酚含量、DPPH和FRAP抗氧化活性没有显著影响;热处理和高温短时杀菌处理后草莓浊汁中的花色苷总量分别损失了3.89%~4.63%和7.46%~8.02%,而清汁中分别损失了5.97%~6.02%和8.09%~9.20%;聚合色度和聚合色度百分比增加,总酚含量无显著变化,抗氧化活性显著降低;(4)超高压处理对草莓浊汁和清汁的亮度L*、红值a*、黄值b*、彩度C*及色调角hab均没有显著影响;而热处理和高温短时杀菌处理使L*值和a*值均显著减小。     

X‐ray reflectivity measurements of liquid/solid interfaces under high hydrostatic pressure conditions

A high‐pressure cell for in situ X‐ray reflectivity measurements of liquid/solid interfaces at hydrostatic pressures up to 500 MPa (5 kbar), a pressure regime that is particularly important for the study of protein unfolding, is presented. The original set‐up of this hydrostatic high‐pressure cell is discussed and its unique properties are demonstrated by the investigation of pressure‐induced adsorption of the protein lysozyme onto hydrophobic silicon wafers. The presented results emphasize the enormous potential of X‐ray reflectivity studies under high hydrostatic pressure conditions for the in situ investigation of adsorption phenomena in biological systems.     

Melting of icosahedral nickel clusters under hydrostatic pressure

The thermal stabilities and melting behavior of icosahedral nickel clusters under hydrostatic pressure have been studied by constant‐pressure molecular dynamics simulation. The potential energy and Lindemann index are calculated. The overall melting temperature exhibits a strong dependence on pressure. The Lindemann index of solid structure before melting varies slowly and is almost independent of pressure. However, after the clusters melt completely, the Lindemann index at the overall melting point strongly depends on pressure. The overall melting temperature is found to be increasing nonlinearly with increasing pressure, while the volume change during melting decreases linearly with increasing pressure. Under a high pressure and temperature environment, similar angular distributions were found between liquid and solid structures, indicating the existence of a converging local structure. © 2014 Wiley Periodicals, Inc.     

Effects of hydrostatic pressure on the donor impurity in a cylindrical quantum dot with Morse confining potential

The effects of hydrostatic pressure and size quantization on the binding energies of a hydrogen-like donor impurity in cylindrical GaAs quantum dot (QD) with Morse confining potential are studied using the variational method and effective-mass approximation. In the cylindrical QD, the effect of hydrostatic pressure on the binding energy of electron has been investigated and it has been found that the application of the hydrostatic pressure leads to the blue shift. The dependence of the absorption edge on geometrical parameters of cylindrical QD is obtained. Selection rules are revealed for transitions between levels with different quantum numbers. It is shown that for the radial quantum number, transitions are allowed between the levels with the same quantum numbers, and any transitions between different levels are allowed for the principal quantum number.     

Nonthermal pasteurization of beer by high pressure processing: modelling the inactivation of saccharomyces cerevisiae ascospores in different alcohol beers

The industrial production of beer ends with a process of thermal pasteurization. In this research, the nonthermal pasteurization of beer by high pressure processing (HPP) was carried out. First, the effect of alcohol content on Saccharomyces cerevisiae ascospore inactivation at 400?MPa was studied. The number of ascospores in 0.0%, 4.8%, and 7.0% alc/vol beers for 10?min processing time decreased by 3.1, 4.9, and ≥?6.0 log, respectively. The Weibull model fitted the ascospore inactivation by HPP in 0.0%, 4.8%, and 7.0% alc/vol beers. At 400?MPa, 7.2?s could ensure the minimum pasteurization of beers and for 600?MPa 5?s were enough for ≥?7 log reductions. The overall flavour of HPP vs. untreated beers was evaluated for a lager and an ale, with no significant differences between the untreated and HPP beers. Thus, nonthermal HPP is a feasible technology to pasteurize beer with different alcohol contents without heat.