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To improve hydrogen production performance of self-heating methanol steam reforming (MSR) microreactor, novel nickel foam with multiple microchannels was proposed as combustion reaction support. A wall temperature comparison of the methanol combustion microreactors with nickel foam catalyst support and particles catalyst support in the combustion reaction process was performed. According to the numerical simulation result of combustion reaction of nickel foam, the shape and size of multiple microchannels of nickel foam were determined. The laser processing was then used to fabricate the multiple microchannels of nickel foam. The experimental results show that the methanol combustion microreactor with nickel foam loaded with Pt catalyst exhibits similar wall temperature distribution with the methanol combustion microreactor with Pt/γ-Al2O3 particles reaction support. Compared with the nickel foam without a microchannel, the maximum temperature difference (ΔTmax) and the maximum temperature of nickel foam with multiple microchannels were decreased, respectively, by 57.8% and 33.8 °C when 1.1 mL/min methanol flow rate was used. Hydrogen production performance of the self-heating MSR microreactor using the nickel foam with multiple microchannels increased by about 21% when 430 °C reforming temperature and 4 mL/h methanol–water mixture flow rate were performed.

Concrete CT test is an effective method used to analyze micro-structural damage evolution of concrete under loading condition. In the CT images of different stress states in the same section, gray value changes in the original number matrix of CT image are the key to investigate microscopic damage evolution of concrete. However, the slight changes in the gray value of CT images before peak stress cannot be intuitively observed with the naked eye. This study mainly aims to develop a coupled method based on statistical method and X-ray CT to extract indicators of such subtle changes. Different cross-sectional CT images of concrete at different stress stages were obtained by uniaxial static compression CT test. The theory of the grey level co-occurrence matrices (GLCM) was then adopted to analyze micro-damage evolution and crack properties. That is, the GLCM of the CT images were calculated, and four statistical features including contrast, energy, correlation, and homogeneity were extracted, which can be extended into quantitative analysis of micro-damage hidden in the CT images of concrete. Results exhibited that the damage growth area, concentrating between the 45th and 225th concrete cross-section, could be predicted by the distribution of four statistical features (i.e., contrast, energy, correlation and homogeneity) at the fourth scan, and it is consistent with the crack location in the fifth scan. The contrast, energy and homogeneity follow the Gaussian distribution under five scan stages, and the correlation follows the Laplace distribution. In addition, the changes of bandwidth in color heat map illustrating the GLCM before and after specimen failure show that the bandwidth is positively correlated with micro-structural damage of concrete specimen.

To replace the traditional electric heating mode and increase methanol steam reforming reaction performance in hydrogen production, methanol catalytic combustion was proposed as heat-supply mode for methanol steam reforming microreactor. In this study, the methanol catalytic combustion microreactor and self-thermal methanol steam reforming microreactor for hydrogen production were developed. Furthermore, the catalytic combustion reaction supports with different structures were designed. It was found that the developed self-thermal methanol steam reforming microreactor had better reaction performance. Compared with A-type, the △Tmax of C-type porous reaction support was decreased by 24.4 °C under 1.3 mL/min methanol injection rate. Moreover, methanol conversion and H2 flow rate of the self-thermal methanol steam reforming microreactor with C-type porous reaction support were increased by 15.2% under 10 mL/h methanol-water mixture injection rate and 340 °C self-thermal temperature. Meanwhile, the CO selectivity was decreased by 4.1%. This work provides a new structural design of the self-thermal methanol steam reforming microreactor for hydrogen production for the fuel cell.

In this study, a multivariate analysis of light-weight aggregate concrete embedded by microencapsulated phase change material (MPCM-LWAC) was performed by assessing the effect of water-cement ratio (0.5,0.55, and 0.6), MPCM content (0%, 2.5%, 5.0%, 7.5%, and 10%), curing time (3 d, 7 d, 14 d, and 28 d), as well as MPCM state (liquid and solid state) on the compressive strength , splitting tensile strength , and elasticity modulus. In order to understand the mechanism of the strength change, porosity, SEM images and adiabatic temperature rise of MPCM-LWAC were measured. Results shown that porosity of MPCM-LWAC is linearly proportional to the water-cement ratio, while with the increase of MPCM content, the growth rate of porosity of MPCM-LWAC with the larger water-cement ratio grow more slowly than that of MPCM-LWAC with the lower water-cement ratio, which is contrary to the changes of compressive and splitting tensile strength of MPCM-LWAC. The growth rate of compressive and splitting tensile strength at each age reduces with increasing amount of MPCM, which attributes to the delay in the hardening time of the cement. When MPCM-LWAC samples are subjected to temperature greater than the melting temperature of MPCM, the mechanical behaviors of MPCM-LWAC slightly reduced. The addition of MPCM to LWAC resulted in a linear reduction in elastic modulus . In addition, SEM images showed that no phase change material leakage was found in the damaged specimens.

The overload method is difficult to be promoted in slope stability analysis for its disunity of loading forms and directions. Based on the traditional overload method and the Strength Reduction Method (SRM) in which the limit equilibrium state of the slope was reached by reducing sliding resisting force without changing the sliding force, a new way to reach the limit equilibrium state of the slope was developed by increasing sliding force without changing resisting force. Referring the loading forms in Gravity Increase Method (GIM) and sliding direction determination in Vector Sum Method (VSM), the theoretical relationship was built between overload coefficient and safety factor of Vector Sum Method (VSM) and the unified overload method based on overall potential sliding direction was proposed. The loading forms and directions were unified by this method, respectively. Sliding surface could be determined while solving the safety factor and the developing direction of overload method in slope stability analysis application was indicated. Three representative slopes with fixed sliding surfaces and two slopes with unknown sliding surfaces were taken as examples to compare results from Limit Equilibrium Method (LEM), Strength Reduction Method (SRM), Vector Sum Method (VSM), Gravity Increase Method (GIM) and overloading method along the horizontal direction with each other. The safety factor resulted from the method proposed in this paper was close to the one from Vector Sum Method (VSM) and the location of sliding surface was close to the one from Strength Reduction Method (SRM). Thus the reliability of the method was testified.

Employing glutathione (HSG) as a protecting ligand, we have synthesized water-soluble and biocompatible Ag14(SG)12 nanoclusters (Ag14 NCs) of which the composition and structure are determined via high-resolution mass spectrometry, fingerprint spectroscopy and DFT calculations. Natural bond orbital (NBO) analysis on a basis of first-principles theoretical calculations demonstrates the donor–acceptor orbital overlaps and charge-transfer interactions between silver and the ligand HSG. Further, it is interestingly found that the fluorescence of Ag14 NCs can be largely enhanced at the presence of lysozyme distinguishing from other proteases which we have tested, revealing the feasibility of Ag14 NCs as chemosensing to identify lysozyme. Also found is that, the fluorescence on-state of the obtained Ag14NCs-Lys can be exclusively switched off at the addition of Hg2+ ions with an ultralow detection limit of ∼16.2 nM. This interesting finding reveals Ag14 NCs a versatile chemosensor to identify lysozyme from proteases and to detect mercury ions from various cations.

Here we report a successful synthesis of water-soluble 13-atoms gold clusters under the monolayer protection of binary thiolates, glutathione and penicillamine, under a molecular formula of Au 13 (SG) 5 (PA) 7 . This monolayer-protected cluster (MPC) finds decent stability and is demonstrated to possess an icosahedral geometry pertaining to structural accommodation in contrast to a planar bare Au 13 of local minima energy. Natural bond orbital (NBO) analysis depicts the interaction patterns between gold and the ligands, enlightening to understand the origin of enhanced stability of the Au 13 MPCs. Further, the water-soluble Au 13 MPCs are found to be a decent candidate for chemosensing and bioimaging.

Extraction of effective and discriminative meso-scale damage evolution information from concrete CT test results is great significance because it is critical to predicting and understanding the complex meso-scale damage behavior of concrete material highly linking to their complex meso-scale structures. This research mainly focused on the following three aspects: (1) Concrete CT tests were performed to obtain real-time scanning CT images of concrete specimen under dynamic compression loads. The meso-scale damage information contained in CT images was extracted for investigating the meso-scale damage evolution characteristics, (2) A new zoning method for concrete meso-scale damage was proposed by analyzing the change characteristics of CT number in CT images with different stress stages. Meso-scale damage was divided into visible and invisible meso-scale damage by using the new zoning method. Moreover, visible and invisible meso-scale damage were respectively defined as the meso-scale damage outside the transition region (MD-OTR) and meso-scale damage inside the transition region (MD-ITR), and (3) Changes of MD-OTR during dynamic compression loading were elucidated by using crack morphologic parameters, such as porosity, crack length, crack density, and crack tortuosity. The evolution characteristics of MD-ITR were investigated by analyzing the statistical feature parameters including contrast, energy, and homogeneity. Results shown that the corresponding porosity gradually increased at the middle-upper part of the specimen and it remained constant at the middle-lower part with increased dynamic compression load. Length, tortuosity, and density of crack presented a Gaussian distribution along the direction of the specimen height after specimen failure. In addition, contrast, energy, and homogeneity revealed different evolution rules at different specimen heights. For example, contrast increased linearly with the increase of dynamic load at H = 20 and 60 mm, but it firstly decreased and then increased at of H = 40 and 80 mm. Noteworthy, statistical feature parameters were more sensitive to stress changes before peak strength than the porosity, which is due to porosity depending heavily on the binary images of CT images ignoring the MD-ITR.

We report the synthesis of penicillamine-protected Ag20 nanoclusters (NCs), with properties of high monodispersity, red fluorescence and water solubility. Full characterization of the Ag20 NCs is addressed, along with first-principles optimization calculations, revealing the chemical composition and structure of the as-prepared Ag NCs within a molecular formula [Ag20(DPA)18-H]−. Moreover, natural bond orbital (NBO) analysis demonstrates the charge-transfer interactions between the ligand and Ag atoms, and helps in understanding the origins of fluorescence of Ag20 NCs related to the ligand-to-metal charge transfer (LMCT) mechanism. Further, fluorescence chemosensing of the Ag20 NCs is demonstrated for tracing copper ions with high sensitivity and selectivity in aqueous solution.

To study the change of concrete internal structure before and after stress, the meso-mechanical experiment of concrete was conducted using CT technology and a portable dynamic loading device. And CT images of the concrete internal structure change under uniaxial compression condition were obtained. For establishing the relationship between the micro-structure and macro-mechanics of concrete, an improved differential box counting (IDBC) method was proposed to calculate the fractal dimension of the CT images, which could describe the entire damage process of concrete. By comparing the fractal dimension calculated by the two methods, it can be seen that the fitting error of the fractal dimension obtained by the IDBC method is reduced by nearly 50% compared with that obtained by the DBC method. Afterward, the damage variable expression was established on the basis of the fractal dimension. The research results indicated that the damage variable established in this research can describe the damage process of concrete well. That is, the damage variable equaled to 0 during the first scan, and before reaching the peak stress, the damage variable showed a trend of increasing first and then decreasing. After the concrete specimen has completely fractured, the damage variable reached a maximum of one. Furthermore, through extracting the area of CT image cracks region at different stress stages, the relationship between the area of cracks region and the stress was studied. It appeared that the CT technology and fractal theory are promising methods to analyze the evolution of the concrete damage process under static uniaxial compression.

A comparative study on the meso-scale damage evolution of concrete specimens was conducted through coupling concrete CT test and digital image analysis technology to investigate the deterioration properties of concrete material under static and dynamic tensile loading. The content of this research program mainly includes: (1) use of concrete CT test to acquire CT images containing the information of meso-scale damage evolution in concrete specimens under static and dynamic tensile loading modes; (2) use of digital image analysis technology to extract quantitative indications for assessing the differences of the initial meso-scale defects distribution and the differences of meso-scale damage evolution in concrete specimens under two different loading modes; (3) use of representative concrete cross-sectional CT images to analyze the differences of local meso-scale damage evolution and predict the fracture location of specimens; and (4) use of the air voids fraction to calculate the degree of meso-scale damage for investigating the differences in the spatial distribution of meso-scale damage under different deformation levels. Results showed that the meso-scale defects of heterogeneous concrete specimen could be identified on the basis of the relative grayscale values of CT images and could be characterized by quantitative indicators, such as aggregate fraction, mortar fraction, air voids fraction, and the mean and variance of the CT number. A comparison of the meso-scale damage evolution in concrete specimens under two different loading modes showed that the specimen subjected to dynamic tensile loading was first compacted, then expanded, and finally destroyed. By contrast, the specimen subjected to static tensile loading gradually failed as the load increased, and without exhibiting compaction. Moreover, the analysis of local meso-scale damage evolution contributed to predicting the fracture location of concrete specimens. The changes of degree of meso-scale damage clearly showed that the meso-scale damage is continuously distributed along the height of specimens, and its increment in each cross section is different under the same deformation condition. These proposed indicators are effective in analyzing the changes in the meso-scale damage of concrete. Among them, the air voids fraction and aggregate fraction are positively correlated with the CT number variance and CT number mean, respectively.

To solve the problems presented by the rational determination of the reduction mode in the traditional strength reduction method and to overcome the difficulty in determining double safety factors from the existing double reduction factors method, a nonproportional relationship between the cohesion reduction factor and the internal friction angle reduction factor is established for a case in which the strength parameter distribution obeys the linear attenuation assumption. By introducing this correlation into the traditional strength reduction finite element method, the nonproportional correlative reduction finite element method for slope strength parameters is proposed. To verify the reliability of the proposed method, the nonproportional correlation is introduced into Bishop’s slice method, yielding the nonproportional double safety factors of Bishop’s slice method. For the whole safety storage of the slope based on the double safety factors, a comprehensive safety factor with the contribution of the shear strength parameter to the sliding resistance force as weight is proposed. Finally, in combination with an example and a comparative analysis of the slope sliding surface positions and the comprehensive safety factors for three different types of reduction modes with two types of methods, the rationality and reliability of this method were validated.

Development of Raman spectroscopy, profiting from surface-enhanced Raman scattering and tip-enhanced Raman scattering techniques, has inspired extensive research interest for trace analysis and dynamic measurements up to single-molecule level. For another, Raman spectroscopy has also been recognized of significance in solving some important issues relating to molecule aggregates in chemistry and biology, owing to the capability of non-destructive detection and high-resolution fingerprints by which molecules and their aggregates can be identified. Herein, we summarize the recent progress of Raman spectroscopy in probing single molecules and molecular aggregates and block out a future prospective of Raman spectroscopy applied in cluster science. Copyright © 2015 John Wiley & Sons, Ltd.