Electrical current induced mechanism in microstructure and nano-indention of Al–Zn–Mg–Cu (AZMC) Al alloy thin film

In this study, the microstructural variation and nano-indention of Al-5.7Zn-2.4Mg-1.5Cu (AZMC) thin film was investigated using DC electrical current at a density of 1000 A/cm². The results show that microstructural changes due to the electrical current involved both the solid solubility effect and enhanced diffusion. The electrical current drove the Al atoms and Cu atoms of the matrix from the cathode to the anode. After electrical current testing, precipitation phases (Al₂Cu; CuMgAl₂) had decomposed into the cathode matrix and MgZn phases had grown in the anode zones. Meanwhile, the current also caused the hardness of the thin film to decrease and affected both the texture and dynamic strain mechanism of nano-indention.     

Major elements analysis in bituminous coals under different ambient gases by laser-induced breakdown spectroscopy with PLS modeling

Three major elements, carbon, hydrogen, and nitrogen, in twenty-four bituminous coal samples, were measured by laser-induced breakdown spectroscopy. Argon and helium were applied as ambient gas to enhance the signals and eliminate the interference of nitrogen from surrounding air. The relative standard deviation of the related emission lines and the performance in the partial least squares (PLS) modeling were compared for different ambient environments. The results showed that argon not only improved the intensity, but also reduced signal fluctuation. The PLS model also had the optimal performance in multi-element analysis using argon as ambient gas. The root mean square error of prediction of carbon concentration decreased from 4.25% in air to 3.49% in argon, while the average relative error reduced from 4.96% to 2.98%. Hydrogen line demonstrated similar improvement. Yet, the nitrogen lines were too weak to be detected even in an argon environment which suggested the nitrogen signal measured in air come from the breakdown of nitrogen molecules in the atmosphere.     

Singular solutions of elliptic equations involving nonlinear gradient terms on perturbations of the ball

In this article we obtain positive singular solutions of

(1)$?\mathrm{\Delta }u=|\mathrm{?}u{|}^p\text{ in }\mathrm{\Omega },u=0\text{ on }?\mathrm{\Omega },$

where Ω is a small $C^2$ perturbation of the unit ball in ${\mathbb{R}}^N$. For $\frac{N}{N?1}<p<2$ we prove that if Ω is a sufficiently small $C^2$ perturbation of the unit ball there exists a singular positive weak solution u of (1). In the case of $p>2$ we prove a similar result but now the positive weak solution u is contained in $C^{0,\frac{p?2}{p?1}}(\stackrel{￣}{\mathrm{\Omega }})$ and yet is not in $C^{0,\frac{p?2}{p?1}+\epsilon }(\stackrel{￣}{\mathrm{\Omega }})$ for any $\epsilon >0$.     

具有实时监测能力的光纤光栅传感系统时域地址查询技术

时钟信号控制下的脉冲宽带光源发出的光波,进入4个光栅组成的间距为10m的光栅串。利用受同一时钟信号控制的1×4模拟电子开关,将各传感元的反射光脉冲依次分配至相应的输出信道,实现时域地址查询,并对各传感元位置的待测应变进行实时监测。引入非平衡迈克耳孙干涉解调装置,将来自传感光栅的受待测应变诱导而至的波长漂移信息变为相移信息,定标后便可实现传感信号的解调。1556nm波长时,系统传感灵敏度的实验值为1.658°/με,与理论值1.673°/με基本吻合。     

Rational design of photoelectrodes for photoelectrochemical water splitting and CO2 reduction

Solar energy has promising potential for building sustainable society. Conversion of solar energy into solar fuels plays a crucial role in overcoming the intermittent nature of the renewable energy source. A photoelectrochemical (PEC) cell that employs semiconductor as photoelectrode to split water into hydrogen or fixing carbon dioxide (CO₂) into hydrocarbon fuels provides great potential to achieve zero-carbon-emission society. A proper design of these semiconductor photoelectrodes thus directly influences the performance of the PEC cell. In this review, we investigate the strategies that have been put towards the design of efficient photoelectrodes for PEC water splitting and CO₂ reduction in recent years and provide some future design directions toward next-generation PEC cells for water splitting and CO₂ reduction.     

Moving boundary problem for a one-dimensional crawling nematode sperm cell model

This paper is a continuation of the authors’ investigation of the crawling nematode sperm cell model proposed by Mogilner and Verzi in 2003 (J. Stat. Phys. 110 (2003) 1169). In the earlier papers (J. Math. Biol. 49 (2004) 310 and J. Math. 8 (2004) 399), the first and last authors and Juliet Lee proved the existence of traveling wave solutions for the nematode sperm cell model. In this paper, we prove local existence of solutions to the same model and global existence under certain additional assumption on the initial data. Finally, we also provide numerical evidence that the traveling wave solutions found in (J. Math. Biol., accepted for publication) is globally asymptotically stable.     

Simultaneous construction of the polymer backbone and side chains by three‐component polycondensation: The synthesis of polyurethanes with allyl side chains from dialdehydes,alkylene N,N′‐bis(trimethylsilyl) carbamates,and allyltrimethylsilane

Polyurethanes with allyl side chains were synthesized by the simultaneous acid‐catalyzed reaction of dialdehydes ( 1 ), alkylene N,N′‐bis(trimethylsilyl) carbamates ( 4 ), and allyltrimethylsilane ( 5 ). When 5 was added to a mixture of 1 , 4 , and the catalyst, a low molecular weight polymer was formed, as well as a large amount of an insoluble gel. However, when a mixture of 1 , 4 , and 5 was added to the catalyst, the formation of gel was depressed, and the desired polyurethanes, consisting of 1 , 4 , and 5 in a molar ratio of 1/1/2, were obtained in good yields. This polyurethane synthesis is unusual in that it concurrently constructs both the polymer backbone and the functional side chains from three starting compounds. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1236–1242, 2002     

Electronic spectroscopy of highly polar aromatics. X. Luminescence of the fluorobenzonitriles

The absorption and emission spectra of the three isomeric fluorobenzonitriles have been investigated. Quantum yields and decay lifetimes are reported for both fluorescence and phosphorescence processes. Kinetic parameters for energy-depletive processes have been generated and it is shown that this weakly polar subset of D-?-A molecules exhibits most of the characteristics which are peculiar to highly polar isomeric D-?-A triads.     

Mild alpha-halogenation reactions of 1,3-dicarbonyl compounds catalyzed by Lewis acids

Lewis acid Mg(ClO4)2, combined with NBS, in CH3CN or EtOAc provided mild and fast bromination of 1,3-dicarbonyl compounds. In particular, this protocol could be applied to the alpha-monobromination of alpha-unsubstituted beta-keto esters. Similar Lewis acid catalysis was also extended to the alpha-chlorination and iodination of 1,3-dicarbonyl compounds with NCS and NIS, respectively.     

SIMS study of plumes generated from laser ablation of polymers

Plumes generated by ablation of polymer targets using a third-harmonic Nd:YAG laser under different atmospheres (air, N₂ and He) were deposited on a H-terminated silicon substrate. The chemical composition and distribution of deposited ablation debris were measured using time-of-flight secondary-ion mass spectrometry. Mass-resolved images show that the size and shape of the plume is dependent on the laser pulse energy and atmosphere in which the plume expanded. In air and nitrogen, plumes are hemispherical with distinct borders. In He they are mushroom-shaped without sharp borders. Since all experiments were carried out at atmospheric pressure, these differences can be related to the reactivity and molecular weight of the gas. Nitrogen-containing compounds (NCCs) and oxygen-containing compounds (OCCs) were found in plumes ablated in air but not in N₂ and He environments. We suggest that the formation of NCCs and OCCs is due to the interaction of the hot plume with air, initiating thermal dissociation of O₂ and oxygen-assisted dissociation of N₂. PACS 52.25.Kn