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Synthesizing COFs with hybrid linkage coupling with both reversible and irreversible natures remains a challenging issue. Herein, we report the synthesis of two rare COFs constructed by both reversible and irreversible linkages through a liquid–solid two-phase strategy. A systematic study reveals a one-pot, two-step reaction mechanism for the two COFs, the first step being a reversible Schiff base reaction and the second step being an irreversible Knoevenagel reaction. Interestingly, this hybrid linkage COF is found to show an outstanding photoenhanced uranium extraction performance. The results not only provide a general and green approach to develop the linkage chemistry of COFs but also enrich the synthesis toolboxes and application of COFs.

Alcoholic electrolyte mixtures have wide applications in industries. In this study, a series of mixtures composed of ZnCl2and methanol (MeOH) with ZnCl2mol % from 6.7 to 25 were prepared, and their spectral, structural, and thermodynamic properties were studied using infrared (IR) spectroscopy, differential scanning calorimetry (DSC), and density functional theory (DFT) calculations. The DFT-assisted analysis of excess spectra, supported by 2D-correlation spectroscopy, led to the identification of the major constituents of ZnCl2–MeOH mixtures, namely, MeOH monomer, MeOH dimer, and ZnCl2–3MeOH complex, produced after dissociation of MeOH trimer which represents the bulk methanol. The Hirshfeld charge analysis showed that in the competition between the O–H···Cl hydrogen bond (H-bond) and Zn ← O coordination bond to transfer charge in ZnCl2–MeOH complexes, the latter always dominates, making MeOH positively charged. The phase diagram of the binary system showed the presence of V-shaped glass transition temperatures (Tg), characteristic of low-melting mixture solvents (LoMMSs). The present study provides insights into the microscopic properties of the system and sheds light on the understanding of the general principles to prepare deep-eutectic solvents (DESs) or LoMMSs using inorganic salts and alcoholic compounds.

Rational construction of strong electron-transfer materials remains a challenging task. Herein, we show a design rule for the construction of strong electron-transfer materials through covalently integrating electron-donoring Cu(I) clusters and electron-withdrawing triazine monomers together. As expected, Cu-CTF-1 (Cu(I)-triazine framework) was found to enable strong electron transfer up to 0.46|e| from each Cu(I) metal center to each adjacent triazine fragment. This finally leads to good spatial separation in both photogenerated electron–hole pairs and function units for photocatalytic uranium reduction under ambience and no sacrificial agent and to good charge separation of [I+][I5–] for I2immobilization under extremely rigorous conditions. The results have not only opened up a structural design principle to access electron-transfer materials but also solved several challenging tasks in the field of radionuclide capture and CTFs.

ABSTRACT A series tests on concrete and mortar cylinders under cyclic uniaxial loading were carried in this study to investigate the effect of internal stress-induced cracks on their mechanical properties. [...]

The deformation of the track on bridge after the earthquake mainly includes bridge creep and seismic-induced deformation, which poses a serious threat to the running safety of trains. In order to study the influence of the comprehensive deformation on the train-bridge system, a three-dimensional model of train-bridge coupling analysis was established. New point estimation method was used to solve the stochastic problem of initial track irregularity, aiming to study the changes of system motion under different parameters including deformation degrees and train speed. Results show that system motion increases with the increase of track parameters, and the earthquake intensity has the greatest influence on the train the motion, which reaches the peak in 0.4 g. The train speed has the greatest influences on the bridge when the train speed reaches the peak value of 400 km/h, while the impact of bridge creep is the smallest. Conclusion was obtained that the results of random analysis are of more general significance, and that in the vehicle-bridge system considering comprehensive track deformation after earthquake, the damage effect of track deformation induced by earthquake intensity is mainly considered for train, and the impact of train speed shall be mainly considered in bridge design.

Low-cost, green, large-scale, room-temperature, and fast synthesis of covalent organic frameworks (COFs) represents a highly desirable issue, due to both scientific and industrial interests, but remains a big challenge. The disadvantage of the established solvothermal method for COFs is now seriously restricting their practical industrial applications. We report herein aqueous synthesis of ketoenamine- and imine-linked COFs through a two-step dissolution–precipitation (DP) strategy. Impressively, using this DP method, we can prepare five ketoenamine-linked COFs and two imine-linked COFs in an ideal synthetic process with room temperature, 5 min reaction time, and large-scale products for one batch reaction, in the absence of acetic acid. These COFs show impressively high crystallinity and porosity and potential application in iodine and uranyl capture. This ideal synthetic route will pave a powerful methodology for making functional COFs with the value of practical industrial applications.

An orthogonal test of the component design of aerated concrete was carried out to solve the problems of low strength, easy cracking, and high water absorption of aerated concrete. The influences of cement content, water-binder ratio, foaming agent content, and polypropylene fiber content on the performances of aerated concrete including dry density, compressive strength, and thermal conductivity were investigated. Furthermore, the optimal composition of aerated concrete was determined. The test results showed that the dry density, compressive strength, thermal conductivity, and water absorption of aerated concrete were greatly influenced by the dosage of the foaming agent. Additionally, the water-binder ratio was found to significantly influence the apparent porosity of aerated concrete. Based on the experiment, the optimal combination of components for aerated concrete was 65 wt.% cement and 35% wt.% mineral admixture with a fly ash to slag ratio of 3:1. Meanwhile, the content of water-binder ratio, foaming agent, and polypropylene fibers were 0.4, 4 wt.%, and 0.4 wt.% of the total cementitious material, respectively. Among the mix proportions in this study, aerated concrete prepared by using the above mix proportion had the best performances. Subsequently, the influence of ceramsite content on the strength, dry density, and thermal conductivity of aerated concrete was analyzed. The results showed that the dry density and thermal conductivity of ceramsite aerated concrete increased with the increase of ceramsite content, but the change law of the water absorption was the opposite. Moreover, the compressive strength increased first and then decreased with the increase of ceramsite content, while the apparent porosity was the opposite. The optimal ceramsite content in ceramsite aerated concrete was 20 wt.%.

Constructing ideal adsorbent for the capture of radioactive iodine often requires both high adsorption capacity and fast adsorption kinetics. However, this remains a challenging issue. Herein, we present an effective method to idealize iodine capture with both ultrahigh adsorption capacity and fast adsorption rate through the construction of quinazolinone-anchored covalent organic frameworks (COFs). Post-synthesis modification was employed to functionalize two vinyl free-standing COFs with quinazolinone units through in-situphotocatalytic reductive cyclization between vinyl and 2-aminobenzamide units. The developed material, ECUT-COF-13, exhibits not only I2uptake capacity as high as 10.81 g g−1, exceeding all established adsorbents for such use, but also very fast adsorption rate of 1.4 gh−1, surpassing all previously reported two-dimensional COFs. The outstanding I2capture performance mainly results from an electron-rich mechanism, since anchoring quinazolinone units in COFs will lead to enhanced π-conjugated net and ultrahigh nitrogen content. The results demonstrate not only a new avenue for functionalizing COFs, but also a general electron-rich strategy for COFs.

ABSTRACT The moisture in interior concrete is the primary factor directly influencing the deterioration phenomena of concrete structures. In this study, a method for predicting the moisture of the natural [...]

ABSTRACT Temperature variation in natural environment was conducted in order to predict the action spectrum of temperature under natural environment by substituting the model to the segmented fitting method. A [...]

ABSTRACT A novel protective covering with a layered and staggered structure was proposed to protect concrete against projectile impact. Experimental study was conducted to investigate the ballistic behaviour of the [...]

ABSTRACT In this study, the chloride diffusion coefficient model coupled with environmental factors is proposed to describe chloride ingress into concrete. The S curve model is also presented to fit [...]

ABSTRACT The fatigue performance of corroded reinforced concrete (RC) beams strengthened with carbon fiber-reinforced polymer (CFRP) sheets was examined in experimental and analytical studies. Eleven beams were constructed and tested, [...]

ABSTRACT To approach the rheological testing method based on L-box test for obtaining internal rheological parameters of fresh self-compacting concrete (SCC), an improved L-box without fiber bars and end wall [...]

ABSTRACTTrack irregularity holds strong randomicity, evolvability, and large data sets during the long-term operation of a rail line, possessing a significant influence on the dynamic performance of vehicle-track systems. In this work, methods for simulating track random irregularities are developed by combining the track irregularity probability model (TIPM) and the number theory method and by the Karhunen-Loève expansion (KLE). Furthermore, the vehicle-track interaction model considering the interaction between the vehicle, track, and wheel-rail interaction is constructed at a 3-D space, where the multi-rigid-body dynamics, finite method, and wheel-rail contacts are applied to construct matrix-coupled vehicle-track interaction equations. Finally, a unified random vibration analysis framework for the vehicle-track system is presented. From perspectives of the amplitude, power spectral density, and probabilistic distribution, the accuracy and efficiency of TIPM and KLE models in simulating track random irregularities and revealing system dynamics performance are compared and analysed in detail.

An extended exponential-polynomial-closure (EPC) method is presented in this paper for solving the non-stationary nonzero mean probabilistic solutions of nonlinear stochastic oscillators under both additive and multiplicative Gaussian white noise excitations. The main idea is to propose an exponential function of polynomial with time-variant coefficients which represents the non-stationary probability density function (PDF) of the responses of the nonlinear stochastic oscillator and to introduce a proper weighted function to solve the well-known Fokker–Planck–Kolmogorov (FPK) equation which governs the non-stationary probabilistic solutions of nonlinear stochastic oscillator. The numerical analysis illustrates that the extended EPC method is valid and efficient for achieving the non-stationary nonzero mean PDFs of the responses for the system with strong nonlinearity by comparing the results obtained by extended EPC method, equivalent linearization method and Monte Carlo simulation method. The PDFs of the responses are asymmetric about the nonzero mean values due to the existence of even nonlinearities.

ZnO plays a very important role in many catalytic processes involving H2, yet the details on their interactions and H2activation mechanism are still missing, owing to the lack of a characterization method that provides resolution at the atomic scale and follows the fate of oxide surface species. Here, we apply 17O solid-state NMR spectroscopy in combination with DFT calculations to unravel the surface structure of ZnO nanorods and explore the H2activation process. We show that six different types of oxygen ions in the surface and subsurface of ZnO can be distinguished. H2undergoes heterolytic dissociation on three-coordinated surface zinc and oxygen ions, while the formed hydride species migrate to nearby oxygen species, generating a second hydroxyl site. When oxygen vacancies are present, homolytic dissociation of H2occurs and zinc hydride species form from the vacancies. Reaction mechanisms on oxide surfaces can be explored in a similar manner.

ABSTRACT When concrete elements are partially exposed to sulfate rich environment, the upper part of concrete in contact with air will be deteriorated more severely than the underground part. Fly [...]

ABSTRACT When concrete elements are partially immersed in the sulfate environment, researchers always attribute 'salt weathering', 'salt crystallization' or ''physical attack' to the failure of concrete. However, there were few [...]

This study investigated the bonding strength between various cement-based grouting materials (CBGM) and high-strength bolts, the flexural and compressive strength variation of different CBGM with curing age, and the failure characteristics of flexural, compressive and bonding strengths. Moreover, the morphological characteristics of bond-slip curves and their similarities and differences were discussed as well. Based on the mechanical property and safety analysis, a calculation model of the critical anchorage length of high-strength bolt in CBGM was proposed. The results indicate that the flexural and compressive strengths increase with the increase of curing age. The strength growth rate is faster at the initial stage of 3 days, which implies that the CBGM has a significant high-early strength characteristic. Depending on the diameter and type of high-strength bolts employed, the bonding strength of specimens can be divided into two failure forms, i.e., splitting and slipping pull-out. The specimens with threaded bolts easily take place a splitting failure form, but the specimens with plain round bolts tend to be destroyed with a slipping pull-out failure form. The ascending section of bond-slip curve is well fitted with the same stage of CEB-FIP 2010. However, a linear relationship can be employed to characterize the bonding strength between CBGM and high-strength bolt. The bond failure capacity is also linear correlation with the strength of CBGM.

Different crumb rubber (CR) particle sizes affect asphalt performance differently. To improve the performance of CR in SBS/CR composite modified asphalt (SBS/CRMA) and to study the enhancement of SBS/CRMA performance with varying ratios of composite CR particle sizes. This study employed three different configurations of SBS/CRMA composite ratios. Several tests and analyses were conducted, Brookfield viscosity measurements, conventional performance tests, storage stability, high- and low-temperature rheology, LAS, Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM) analysis. The results indicated that, in the composite CR particle size ratio, a finer particle size of CR demonstrated more significant benefits in improving the high- and low-temperature performance of asphalt. However, with aging, the role of a coarse particle size of CR gradually became more prominent. Furthermore, compared to a single CR mesh SBS/CRMA, the 3 S + 5R-6:2:2 composite CR particle size ratio of SBS/CRMA exhibited superior high- and low-temperature deformation and fatigue resistance. Considering the microscopic analysis, it can be observed that the fine particle size of CR exhibited superior compatibility and anti-aging performance compared to the coarse particle size. In the composite CR particle size ratio, adjusting the proportion of coarse and fine CR particle size will improve the performance of SBS/CRMA significantly. Contrary to common belief, it was not necessarily true that a higher ratio of coarse CR particles leads to a better modification effect in SBS/CRMA. On the other hand, the composite CR particle size ratio proved significantly advantageous, thereby providing valuable guidance for enhancing the performance of SBS/CRMA.

According to the assumption of small strains and total strain decomposition of cast iron, the expressions of the inelastic principal strain rate and relative energy dissipation rate of cast iron are derived, and the parameters of the tensile and compressive damage ratio of cast iron in the inelastic phase are proposed. Based on the least energy consumption principle, combined with the above expressions and parameters, the damage ratio strength criterion for cast iron under biaxial stress states is established. The damage ratio variable expression of the cast iron damage ratio strength criterion considering the effect of Lode angle is proposed. Furthermore, the values of the damage ratio variable are verified by the experimental stress–strain curves of cast iron under uniaxial stress states. By comparing the predicted values to 104 experimental data points of cast iron specimens, the failure envelopes of the proposed criterion can represent the failure behavior of cast iron under biaxial loading conditions. To facilitate the practical application in engineering, the further simplified expression of the four-parameter damage ratio strength criterion for cast iron under biaxial stress states is suggested and those empirical parameters are recommended. Compared with some main strength criteria, the simplified criterion is in better agreement with the experimental results under every stress state.

Background Emerging evidence suggests that circular RNAs (circRNAs) were aberrantly expressed in the patients of non-small cell lung cancer (NSCLC). This study aims to evaluate the diagnostic value of potential serum biomarker in circRNAs.Methods Serum circRNAs were extracted and purified by RNA isolated kit and identified by quantitative real time-polymerase chain reaction (qRT-PCR) assay. We then performed a receiver operating characteristic (ROC) curve to estimate the diagnostic efficacy. The relationship between circRNA and clinic characteristics of patients was analyzed by SPSS 25.0. Univariate and multivariate analyses were also used to evaluate its diagnostic capability. The mechanism of circFOXP1 was further excavated by bioinformatics analysis.Results By performing qRT-PCR assay, we identified that circFOXP1 (hsa_circ_0008234) and conventional tumor markers (carcinoembryonic antigen (CEA) and cytokeratin fragment 21–1 (CYFRA21-1)) were all significantly overexpressed in the serum of patients with NSCLC when compared with healthy controls (P< 0.05). While the ROC curves analysis demonstrated that area under the curve of circFOXP1 was obviously superior to CEA and CYFRA21-1, which exerted more diagnostic advantage. Univariate and multivariate analyses revealed that serum circFOXP1 was an independent diagnostic molecule, and was significantly correlated with T stage and lymphatic metastasis in NSCLC (P< 0.05). Mechanistically, circFOXP1 might target hsa-miR-370-3p and hsa-miR-18a-5p, and be involved in vascular endothelial growth factor signaling pathways to regulate proliferative and metastasis processes.Conclusion Our results highlight the preferable diagnostic potential of serum circFOXP1 in NSCLC.

The mix proportion, phase diagram components and mechanical properties of ultra-high performance mortar (UHPM) based on simplex-centroid design method were investigated. The effects of material components, sand/binder ratio (S/B) and water/binder ratio (W/B) on the strength and fluidity of UHPM were studied. Simultaneously, the relationship between water reducer dosage and slump flow of UHPM was investigated as well as the mix proportion design and performance prediction. The results showed that the simplex-centroid design method can be used to determine the relationship between influence factors and performance of UHPM. The differences of strength phase diagram for different mix proportion of UHPM were manifested in central position of minimum strength, strength contours and gradient, and position of maximum strength. There has a quadratic function relationship between water reducer dosage, slump flow and W/B. The slump flow of UHPM increases with the increase of water reducer dosage. The UHPM can be prepared based on simplex-centroid experimental design method.

Background: Glial Maturation Factor Beta (GMFB) is a highly conserved brain-enriched protein implicated in immunoregulation, neuroplasticity and apoptosis, processes central to neural injury and repair following cerebral ischaemia. Therefore, we examined if changes in neurocellular GMFB expression and release can be used to assess brain injury following ischaemia. Methods and Results: Immunofluorescence staining, Western blotting, immunohistochemistry and ELISA were used to measure GMFB in cultured neurons and astrocytes, rat brain tissues and plasma samples from stroke model rats and stroke patients, while cell viability assays, TTC staining and micro- PET were used to assess neural cell death and infarct severity. Immunofluorescence and immunohistochemistry revealed GMFB expression mainly in astrocyte and neuronal nuclei but also in neuronal axons and dendrites. Free GMFB concentration increased progressively in the culture medium during hypoxia-hypoglycaemia treatment. Plasma GMFB concentration increased in rats subjected to middle cerebral artery occlusion (MCAO, a model of stroke-reperfusion) and in stroke patients. Plasma GMFB in MCAO model rats was strongly correlated with infarct size (R2=0.9582). Plasma GMFB concentration was also markedly elevated in stroke patients within 24 h of onset and remained elevated for more than one week. Conversely, plasma GMFB elevations were not significant in myocardial infarct patients and stroke patients without infarction. Conclusion: GMFB has the prerequisite stability, expression specificity and response dynamics to serve as a reliable indicator of ischaemic injury in animal models and stroke patients. Plasma GMFB may be a convenient non-invasive adjunct to neuroimaging for stroke diagnosis and prognosis.

To investigate the composite performance of the track slab and the self-compacting concrete filling layer in the China Railway Track System III slab track structure, six segmental specimens comprising either one or a pair of sleepers were fabricated by dividing a full-scale slab track structure. Fatigue tests in the transverse bending perpendicular to the rail were conducted on four slab track specimens supported on rubber plates simulating the subgrade, to a maximum of five million applied load cycles. It was observed in the fatigue tests that longitudinal cracks first appeared on the top surface of the track slab at the mid-span of the specimen. Splitting cracks appeared later from the anchorage ends of the transverse prestressed tendons to the top surface of track slab. Delamination of the track slab–filling layer interface developed with increasing number of cycles. Static three-point bending tests were also conducted on both fatigue-damaged and control composite plate specimens to evaluate the effect of fatigue damage on the composite performance of the track slab and the filling layer. In the static tests, significant deformation developed in the fatigue-damaged specimens from the start of loading, and the fatigue damage and interface delamination adversely affected the composite action of the track slab and the filling layer. Static loads corresponding to new cracking of the fatigue-damaged composite plates were reduced by 20–30%, and the load corresponding to the initial interlayer slip reduced by 25–62% compared with the control specimens. The interfacial bond strength between the track slab and the filling layer is the first line of defense against the interlayer slip, and the dowel action of the interlayer connection reinforcement is the second line of defense. Roughening by multitooth chiseling on the track slab and an increase in the ratio of interlayer connection reinforcements are both effective ways to enhance the composite action of the track slab and the filling layer.

Sensitive and selective detection of copper ions (Cu2+) using fluorometric methods is of growing significance due to their widespread industrial use, which poses severe environmental and health risks. Here, we reported a porphyrin-based luminescent metal-organic framework (labelling LMOF), Al-TCPP, which exhibits dual emission peaks at 467 and 646 nm upon excitation by a single wavelength. When exposed to Cu2+ions, the fluorescence peak at 646 nm reduces while the intensity of the 467 nm remains steady. This intriguing property enables the construction of a ratio-metric fluorescence sensor that utilizes an internal standard, significantly enhancing Cu2+sensing accuracy. Our study establishes a linear relationship (y = 0.0454x + 0.3081) between the fluorescence intensity ratio I467/I646and the Cu2+concentration, with a high correlation coefficient R2= 0.9943. Impressively, the present Al-TCPP achieves a low limit of detection (LOD) of 5.28 nM, one of the lowest reported values for Cu2+detection. The mechanism underlying this phenomenon involves charge transfer from TCPP ligands in Al-TCPP to Cu2+ions, as revealed by solid-state NMR and X-ray photoelectron spectroscopy analysis. Utilizing Al-TCPP, we successfully developed test strips for the practical Cu2+detection. Furthermore, the present Al-TCPP has also effectively applied to determine low Cu2+content in various samples, including water, tea and serum. This study demonstrates the versatility and practical applicability of present Al-TCPP LMOF for selective detection of Cu2+ions in diverse environments.

The solar temperature field and its temperature effects on the straddle monorail tourist transportation system (SMTTS) significantly affect its mechanical performance. To investigate the distribution law of the daylight temperature field of the unpaved steel beams, the daylight temperature fields of box-type and I-sectional steel beams in different regions were measured and simulated. With the simulation results, the vertical temperature gradient curves of the unpaved steel girders were determined. Afterward, with the historical meteorological data as variables, the parameters of the extreme value model of generalized extreme value (GEV) distribution were obtained, and the representative values of temperature differences in China, based on the recurrence period, were analyzed. By analyzing the temperature difference values in 34 cities in China, an empirical prediction formula for the representative temperature difference value with three parameters was proposed, and the temperature gradient partition was established. The results indicated that the vertical temperature gradients of closed-section steel box girders are about 2–3 °C greater than that of open-section I-beams. Moreover, there are apparent geographical differences in the temperature difference values of steel girders.

To investigate the fatigue and freeze-thaw properties of the geotextile isolation layer in CRTS III ballastless track, a new type of disc multi-point load distribution device was manufactured. The experimental study was carried out on the geotextile isolation layer subjected to the fatigue load and freeze-thaw cycles. The results showed that the mechanical properties of the geotextile isolation layers were affected by the harsh environment and cyclic load. With the increase of fatigue loading cycles, the dynamic stiffness of the geotextile isolation layers increased and tended to be stable, and the nonlinear performance of the geotextile isolation layer gradually weakened. The freeze-thaw cycle greatly influenced the dynamic stiffness of the geotextile isolation layer compared with the fatigue loadings, and the freeze-thaw cycle action could accelerate the elastic loss of the geotextile isolation layer. Under the fatigue load and freeze-thaw cycles, the tensile strength of the geotextile isolation layer decreased and caused damage to the geotextile isolation layers, which should be paid attention to in long-term service.

Solvent effect plays an important role in manipulating the chemical reactivity, equilibrium constant, and reaction rate. Such effect is observed in heterogeneous catalysis, especially for the acidic zeolite catalyst with molecularly size pores (≤1 nm). Nevertheless, it is a great challenge to systematically investigate the intermolecular interaction and the mechanism of solvent effect on the catalytic performance inside the acidic zeolite nanocages. Here, we used the state-of-the-art solid-state NMR (SSNMR) experimental techniques combined with multiscale theoretical simulations to quantitatively investigate the solvent effect on the reactant electronic property and reaction activity. In particular, a series of 13C CP/MAS solid-state NMR experiments with acetone probe for H-ZSM-5 zeolite were performed via changing the coadsorption amount of nitromethane solvent. It is found that the solvent effect accounts for the enhancement of the apparent Brønsted acidic strength of zeolite catalysts, and thus promotes the catalytic reactivity. Furthermore, multiscale theoretical simulations for coabsorption configurations and electronic properties were employed to elucidate the mechanism of solvent effect on the zeolite catalysis. Therefore, so far for the first time the quantitative relationship between solvent effect and the catalytic performance inside the H-ZSM-5 zeolites has been established, and the mechanism of solvent effect in nanocage of zeolites was systematically elucidated.

The last two to three decades have seen significant advances in the mechanics of unsaturated soils. It is now widely recognized that the fundamental principles in soil mechanics must cover both saturated and unsaturated soils. Nevertheless, there is still a great deal of uncertainties in the geotechnical community about how soil mechanics principles well-established for saturated soils can be extended to unsaturated soils. There is even wide skepticism about the necessity of such extension in engineering practice. This paper discusses some common pitfalls related to the fundamental principles that govern the volume change, shear strength and hydromechanical behaviour of unsaturated soils. It also attempts to address the issue of engineering relevance of unsaturated soil mechanics.

An isolated structure often possesses distinct non-proportional damping characteristics. However, traditional seismic calculation theory and methods are derived based on the assumption that damping is proportional. Based on this drawback, a new, more efficient stochastic calculation method, an improvement on the pseudo-excitation method, is introduced. This method is then applied to the seismic analysis of an isolated structure. By comparing it with the forced decoupling, matrix inversion and iteration methods, it is shown that the presented method can produce accurate results while increasing the efficiency of the stochastic analysis. Moreover, the calculation process of the seismic response of an isolated structure is convergent. Based on the results of the example presented in this paper, the given method is applicable to the seismic analysis of an isolated structure and can be utilized in practice.An isolated structure often possesses distinct non-proportional damping characteristics. However, traditional seismic calculation theory and methods are derived based on the assumption that damping is proportional. Based on this drawback, a new, more efficient stochastic calculation method, an improvement on the pseudo-excitation method, is introduced. This method is then applied to the seismic analysis of an isolated structure. By comparing it with the forced decoupling, matrix inversion and iteration methods, it is shown that the presented method can produce accurate results while increasing the efficiency of the stochastic analysis. Moreover, the calculation process of the seismic response of an isolated structure is convergent. Based on the results of the example presented in this paper, the given method is applicable to the seismic analysis of an isolated structure and can be utilized in practice.

The spatial proximities of acid sites in dealuminated H–MOR and H–ZSM-5 zeolites have been comprehensively studied by two-dimensional 1H and 27Al double-quantum magic-angle spinning (DQ-MAS) NMR spectroscopy. 1H DQ-MAS NMR revealed the detailed spatial proximities among Brønsted and Lewis acid sites, while 27Al DQ-MAS NMR probed the detailed spatial proximities among various aluminum species in the dealuminated zeolites. It was found that all of the extra-framework aluminum species (EFAL, Lewis acid sites) are always in close proximity to the framework aluminum (Brønsted acid sites) in both H–MOR and H–ZSM-5 zeolites. The result from 13C CP/MAS NMR of adsorbed acetone demonstrated that the spatial proximities between Brønsted and Lewis acid sites lead to a synergy effect that can remarkably enhance the Brønsted acid strength of the dealuminated zeolites. On the basis of these experimental results, we proposed a model to describe the Brønsted/Lewis acid synergy in the dealuminated zeolites.

The validity of using 31P NMR of adsorbed trimethylphosphine (TMP) as a probe molecule for discerning the types (Brønsted vs Lewis) and strengths of acid sites in solid acid catalysts have been studied by density functional theory (DFT) calculations. Brønsted acid sites with varied acidic strengths covering from weak, strong, to superacid, mimicked by 8T zeolite cluster models having different Si−H bond lengths and hence proton affinities, were examined together with Lewis acid systems having different metallic centers, e.g., BClnF3−n(n= 0−3), AlClnF3−n(n= 0−3), and TiClnF4−n(n= 0−4) and their mixed halides. The theoretical 31P chemical shifts predicted for the hydrogen-bonded TMP···H complex and the TMPH+adducts were −61 ± 1 and −3 ± 1 ppm, respectively, in good agreement with the experimental data. For the TMP−Lewis acid complex, a linear correlation between the calculated 31P chemical shifts and corresponding binding energies was observed for the B-, Al-, and Ti-containing Lewis acids, respectively, indicating the feasibility of using the 31P chemical shift of adsorbed TMP as a scale for Lewis acidic strength.

A zeolite dealumination mechanismis proposed on the basis of sensitivity‐enhanced 27Al DQ‐MAS NMR spectra (see picture), which revealed for the first time the detailed evolution of extra‐framework aluminum (EFAL) species and the spatial proximities of various aluminum species in dealuminated HY zeolites. Three types of EFAL species in close proximity to framework aluminum were identified.

The ultra-high performance concrete (UHPC) was prepared by using the limestone coarse aggregate and ordinary Portland cement. The effects of sand ratio, water to cement ratio (W/C), cementitious materials, type and content of fiber, dosage of water reducer and defoamer on the mechanical and rheological properties of the UHPC were investigated. The correlations among influence factors and performances of UHPC were discussed. Moreover, the internal relationship between loading rate and elasticity modulus of UHPC was also studied. The results indicate that the compressive strength of UHPC first increases and then decreases with the increase of sand ratio, and a maximum compressive strength of UHPC was found at the sand ratio of 41%. The water reducer content of fresh UHPC first decreases and then increases with the increase of sand ratio. The compressive strength of UHPC first increases and then decreases with the increase of W/C, which also increases with the increase of cementitious materials. The elasticity modulus of UHPC decreases with increase of sand ratio and cementitious materials content, and the compressive strength and elasticity modulus of UHPC cured for 28 d increase with the increase of defoamer dosage. The slump flow of fresh UHPC first increases and then decreases with the increase of water reducer dosage. An optimum fiber content of UHPC can enhance the tensile strength and adhesive property, which can play the restraining deformation and toughening effect.

The effect of cholesterol, desmosterol, stigmasterol, sitosterol, ergosterol, and androsterol on the phase behavior of aqueous dispersions of dipalmitoylphosphatidylcholine (DPPC) was studied to understand the role of the side chain in the formation of ordered phases of the type observed in membrane rafts. Thermotropic changes in the structure of mixed dispersions and transition enthalpies were examined by synchrotron X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The observations indicated that cholesterol was more efficient than phytosterols (stigmasterol and sitosterol) or ergosterol in its interaction with DPPC to form the liquid ordered phase ( Lo). The Loinduced by cholesterol or desmosterol was stable over a wide temperature range, whereas, the liquid ordered phase containing phytosterols or ergosterol was profoundly dependent on temperature, which should be distinguished as Lo βand Lo α, representing the phases below and above the main transition temperature. The characteristics in forming ordered structures of cholesterol and other sterols imply that the evolution may have selected cholesterol as the most efficient sterol for animals to form rafts in their cell membranes.

Benesi-Hildebrand (B-H) method is a widely used approach for determining the stoichiometry and equilibrium constants of nonbonded interactions, particularly 1:1 and 1:2 interactions. Using computer simulation, it was shown that, under certain conditions, the approach could generate inappropriate stoichiometric conclusions for 1:2 interactions. This problem could occur in the cases of both weak and strong interactions, where the 1:1 B-H plots showed a linear feature and the 1:2 B-H plots showed a nonlinear feature. In addition, effect of the initial concentrations on the accurate evaluation of equilibrium constants of 1:1 interactions was investigated. It was found that the minimum safe concentration ratio r0between ligand and central species was 100. However, for weak nonbonding interactions, for example K<25 L·mol –1( CP0=4×10 –4mol·L –1), the ratio r0has no limitation. Two conditions proposed in literatures for the safe application of the B-H method were examined. It was found that the inequation, 1/( KC0P)≥10, was a condition to secure CB/ C0B>91%. The other inequation, KC0B>0.1, was not found to be the safe condition to validate the B-H method.

A new unified strength criterion in the principal stress space has been proposed for use with normal strength concrete (NC) and high strength concrete (HSC) in compression-compression-tension, compression-tension-tension, triaxial tension, and biaxial stress states. The study covers concrete with strengths ranging from 20 to 130 MPa. The conception of damage Poisson’s ratio is defined and the expression for damage Poisson’s ratio is determined basically. The failure mechanism of concrete is illustrated, which points out that damage Poisson’s ratio is the key to determining the failure of concrete. Furthermore, for the concrete under biaxial stress conditions, the unified strength criterion is simplified and a simplified strength criterion in the form of curves is also proposed. The strength criterion is physically meaningful and easy to calculate, which can be applied to analytic solution and numerical solution of concrete structures.

Experimental results for eleven continuous composite beams of steel and concrete are presented in this paper, which includes laws of deflection and slip between the concrete and steel. Governing differential equations of slip and deflection for simply supported composite beams with different boundary conditions and different loads are established, and a set of numerical expressions for slip and deflection of continuous composite beams are established by the superposition method as well. The deflection and slip of seventeen continuous composite beams are calculated by the numerical expressions. The calculated results show good agreement with the experimental results. The numerical results show that the slip of continuous composite beams increases and approaches the slip of sandwich panels without shear connectors. At the same time, the degree of shear connection influences deflection to a certain extent. The degree of shear connection influences deflections little at full shear connection and the increment of deflection caused by slip is less than 5% when the degree of shear connection is between 60 to 100%. When the degree of shear connection is between 80 to 140%, the strain in the lower flange of the steel beam at the internal-support is influenced little.

In this work, a novel and practical method is developed to depict the track slab damage and residual strain evolution, where the concrete damage constitutive relation of track slabs is considered within the train–track–bridge dynamics framework. A three-step strain method is presented to judge the load/unloading, compression/tension status of track slab elements ergodically, so that the damage condition and residual strain of track slabs can be determined. To improve the computational accuracy and efficiency, the combination of the matrix augment method and iterative solution algorithm is elucidated in detail. To validate the present model, the solutions among incremental solution, iterative solution, and non-iterative solution are firstly illustrated, and then experimental studies are performed to declare the effectiveness of this model in characterising strain/stress relation of concrete no matter in compression state or in tension state, and finally, other model results are also introduced to prove the effectiveness of this model. In the numerical studies, the damage distributions of track slabs in the longitudinal and lateral direction are presented, where the influence of track irregularities and track slab positions on the bridge is clarified, besides, the evolution of the damage and residual strain of a track slab subject to a moving train is revealed.

The strong n-π* electronic transition was awakened through a microwave sintering route, which realizes a 6-fold enhancement in photocatalytic H2generation under visible light exposure.

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