表面纳米化吸能薄壁多胞结构的数值模拟与设计

采用局部表面纳米化技术和数值模拟方法,对金属薄壁多胞结构的吸能问题开展有限元数值分析和优化设计.结果 显示,局部表面纳米化布局可诱导结构的屈曲变形,并能大幅度提高结构的能量吸收.优化结果还发现,在多胞外壁呈交错矩形格状表面纳米化格局和内附加结构呈均布框架式矩形格状表面纳米化布局情况下,结构屈曲变形稳定且吸能效果最优.该研究为吸能结构的设计提供了依据.     

关于ut= div(|▽u|p-2▽u)方程解的梯度H?lder连续性的一个注记

对文献［１－３］中的结果：u_t= div(|▽u|^p-2▽u)在ΩＴ＝Ω×（０，Ｔ）上弱解的空间梯度是Ｈ?ｌｄｅｒ连续的做一个补充．在这个注记里，讨论了条件ｐ＞ｍａｘ｛１，２Ｎ/Ｎ＋２｝是怎样由ｕ的性质所决定的．属于L^N_loc(Ω_T)空间解的梯度是Ｈ?ｌｄｅｒ连续的条件仅仅是ｐ＞１．     

Theoretical Studies of O(1D)+HD (v=0, j=0, 1, 2, 3)→OD(H)+H(D) Reaction

利用准经典轨线计算方法在DK势能面上对O+HD进行了计算,获得了产物的反应截面和分支比OD/OH. 计算结果表明,当碰撞能由4.6 kJ/mol增加到46.0 kJ/mol时,产物的反应截面随着碰撞能的增加明显减小;产物的平均分支比随着转动量子数的增加逐渐减小.     

Influence of O2 Flux on Compositions and Properties of ITO Films Deposited at Room Temperature by Direct-Current Pulse Magnetron Sputtering

Indium tin oxide （ITO） films were deposited on glass substrates at room temperature by dc pulse magnetron sputtering. Varying 02 flux, ITO films with different properties are obtained. Both x-ray diffractometer and x-ray photoelectron spectrometer are used to study the change of crystalline structures and bonding structures of ITO films, respectively. Electrical properties are measured by four-point probe measurements. The results indicate that the chemical structures and compositions of ITO films strongly depend on the O2 flux. With increasing O2 flux, ITO films display better crystallization, which could decrease the resistivity of films. On the contrary, ITO films contain less O vacancies with increasing O2 flux, which could worsen the conductive properties of films. Without any heat treatment onto the samples, the resistivity of the ITO film could reach 6.0 × 10^-4 Ω·cm, with the optimal deposition parameter of 0.2 scem O2 flux.     

Formation of carbon nanotubes in water by the electric-arc technique

A simplified arc discharge apparatus was used for growing carbon nanotubes, required only water (solution) in a glass container with no need for vacuum, water-cooled chamber. Carbon nanotubes with highest purity (20%) and highest yield (7 mg/min) were obtained when using salt solution as the medium. Resonance Raman spectrum of multi-walled carbon nanotubes (MWNTs) presented in as-grown materials was measured and RBM peaks originating from very thin core nanotubes were observed. The results show that high-quality MWNTs can be effectively prepared in water-arcing process.     

Delayed extraction experiments using a repulsive potential before ion extraction: evidence of clusters as ion precursors in UV-MALDI. Part I: dynamical effects with the matrix 2,5-dihydroxybenzoic acid

Delayed extraction experiments were undertaken to precise the dynamical effects involved in the ion formation in ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI). Careful examination of the ion time-of-flight variation with the extraction delay time were performed with a repulsive potential before ion extraction. Depending on the mass of the ion (matrix 2,5-dihydroxybenzoic acid and peptides) and on the repulsing potential, some deviations from the linear relationship between the ion time-of-flight and the delay time were observed. Simulations of the ion time-of-flight clearly show that ions are not directly produced on the target surface but originate from the gas-phase decomposition of higher mass precursors. The size of the precursor, composed of the analyte surrounded by matrix molecules, increases with that of the analyte. Complete desolvation of the cluster-precursor could be likely induced by the high electric field transient during the pulse extraction. The existence of clusters as precursor of the ion production in MALDI highlights a new global frame to explain the analyte protonation in UV-MALDI.     

Phase evolution of an aluminized steel by oxidation treatment

Effects of temperature and time on the microstructure and phase evolution for different thermal treatments were investigated with respect to the measurement of intermetallic layer thickness, phase identification and microhardness distribution in the aluminized zone of a steel substrate. The intermetallic phases present in the aluminized region after hot dip aluminizing is mainly Fe₂Al₅. The thickness of the intermetallic layers increases with increasing oxidation temperature and time. In the oxidation treatments of the aluminized steel in air, the initial Fe₂Al₅ phase remains at the temperature below 950 °C in 2-h, and the Fe₂Al₅ phase is completely transformed into low iron content Fe-Al intermetallics due to oxidation at 950 °C for 4 h. However, the Fe₂Al₅ phase remains in the outer layer of the aluminized samples diffusion-treated in vacuum regardless of diffusion time. The microhardness values of the Al₂O₃ and the intermetallic Fe₂Al₅, FeAl₂, FeAl and Fe₃Al phases are HV1150, HV1010, HV810, HV650 and HV320, respectively. The oxide layer formed on the steel substrate has an extremely fast adherence to the steel substrate and excellent properties of thermal shock resistance, high temperature oxidation resistance and anti-liquid aluminum corrosion.     

Further Ramanujan-like series containing harmonic numbers and squared binomial coefficients

The Ramanujan Journal - The Gauss summation theorem and an extended $$_3F_2$$ -series of Watson and Whipple type are examined by means of power series expansions. Numerous Ramanujan-like series...     

A periodic DFT study on adsorption of small molecules(CH4,CO,H2O,H2S,NH3)on the WO3(001) surface-supported Au

Gas molecules(such as CH4,CO,H2O,H2S,NH_3)adsorption on the pure and Au-doped WO3(001)surface have been studied by Density functional theory calculations with generalized gradient approximation.Based on the the calculation of adsorption energy,we found the most stable adsorption site for gas molecules by comparing the adsorption energies of different gas molecules on the WO3(001)surface.We have also compared the adsorption energy of five different gas molecules on the WO3(001)surface,our calculation results show that when the five kinds of gases are adsorbed on the pure WO3(001)surface,the order of the surface adsorption energy is CO>H2S>CH4>H2O>NH3.And the results show that NH3 is the most easily adsorbed gas among the other four gases adsorbed on the surface of pure WO3(001)surface.We also calculated the five different gases on the Au-doped WO3(001)surface.The order of adsorption energy was found to be different from the previous calculation:CO>CH4>H2S>H2O>NH3.These results provide a new route for the potential applications of Au-doped WO3 in gas molecules adsorption.     

Heat capacities and thermodynamic functions of d-ribose and d-mannose

The heat capacities of d-ribose and d-mannose have been studied over the temperature range from 1.9 to 440 K for the first time using a combination of Quantum Design Physical Property Measurement System and a differential scanning calorimeter. The purity, crystal phase and thermal stability of these two compounds have been characterized using HPLC, XRD and TG–DTA techniques, respectively. The heat capacities of d-Mannose have been found to be larger than those of d-ribose due to its larger molecular weight, and the solid–liquid transition due to the sample melting has also been detected in the heat capacity curve. The heat capacities of these two compounds have been fitted to a series of theoretical models and empirical equations in the entire experimental temperature region, and the corresponding thermodynamic functions have been derived based on the curve fitting in the temperature range from 0 to 440 K. Moreover, the phase transition enthalpy and melting temperature of these two compounds have also been determined from the heat flows obtained in DSC measurements.