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Terbium ions were installed on nodes of a two-dimensional Zr-based MOF, and the material was applied for photoluminescence nitrite detection.

Three topologically distinct zirconium-based metal-organic frameworks (Zr-MOFs) constructed from redox-innocent linkers, MOF-808, defective UiO-66, and CAU-24, are synthesized, and the spatially dispersed redox-active manganese sites are post-synthetically immobilized on the hexa-zirconium nodes of these Zr-MOFs. The crystallinity, morphology, porosity, manganese loading, and bulk electrical conductivity of each material are studied. The redox-hopping-based electrochemical reaction between the installed Mn(III) and Mn(IV) occurring within the thin films of these MOFs in aqueous electrolytes is investigated, in the presence of various concentrations of Na

Cobalt sulphide nanoparticles solely confined within the nanopores of a water-stable Zr-based MOF are synthesized by a two-step approach.

Based on water quality monitoring data and land use data, Dongjiang River source watershed water quality variation characteristics from 2017 to 2019 and the relationships between the landscape pattern of the Dongjiang River source watershed and water quality were analyzed using spatial analysis, correlation analysis, and redundancy analysis. The results showed that:① the water quality of the Dongjiang River source watershed improved overall, but the total nitrogen pollution was still severe. As of 2019, the annual average concentration of total nitrogen in all sampling points exceeded the type Ⅲ water quality standard. ② At the landscape level, water quality was positively correlated with landscape shape index, number of patches, and Shannon's diversity index but negatively correlated with largest patch index and aggregation index. Considering the land use type, construction land was the primary source of total nitrogen and total phosphorus. Landscape shape index and number of forest patches were positively correlated with NH

The flat-joint model, which constructs round particles as polygons, can suppress rotation after breakage between particles and simulate more larger compression and tension ratios than the linear parallel-bond model. The flat-joint contact model was chosen for this study to calibrate the rock for 3D experiments. In the unit experiments, the triaxial unit was loaded with flexible boundaries, and the influence of each microscopic parameter on the significance magnitude of the macroscopic parameters (modulus of elasticity E, Poisson’s ratio ν, uniaxial compressive strength UCS, crack initiation strength σci, internal friction angle φ and uniaxial tensile strength TS) was analysed by ANOVA (Analysis of Variance) in an orthogonal experimental design. Among them, Eƒ, kƒ has a significant effect on E; Cƒ and kƒ have a significant effect on ν; Cƒ, σƒ and kƒ have a significant effect on UCS; Cƒ; σƒ and Eƒ have a significant effect on TS; Rsd has a significant effect on σci; and φf, Eƒ, kƒ, μƒ, and σƒ have a significant effect on φ. Regressions were then carried out to establish the equations for calculating the macroscopic parameters of the rock material so that the three-dimensional microscopic parameters of the PFC can be quantitatively analysed and calculated. The correctness of the establishment of the macroscopic equations was verified by comparing the numerical and damage patterns of uniaxial compression, Brazilian splitting, and triaxial experiments with those of numerical simulation units in the chamber.

Electrochemical conversion of acrylonitrile (AN) to produce adiponitrile (ADN), the raw material for the production of Nylon 66, has become a crucial process owing to the increasing market demand of Nylon 66. Although the metallic Pb or Cd electrodes are commonly used for this reaction, the use of electrocatalysts or electrodes modified with catalysts has been barely investigated. In this study, nanoporous and electrically conductive metal-organic framework (MOF)-derived materials composed of Pb, PbO, and carbon are synthesized by carbonizing a Pb-based MOF through thermal treatments, and these MOF-derived materials are served as electrocatalysts for the electrosynthesis of ADN. The crystallinity, morphology, elemental composition, porosity, electrical conductivity, and electrochemically active surface area of each MOF-derived material are investigated. Mass-transport-corrected Tafel analysis is used to probe the enhanced kinetics for the electrochemical reduction of AN occurring at the electrode modified with the MOF-derived material. Electrolytic experiments at various applied potentials are conducted to quantify the production rate and Faradaic efficiency toward ADN, and the result shows that the MOF-derived materials can act as electrocatalysts to initiate the electrochemical reduction of AN to produce ADN at a reduced overpotential. The optimal MOF-derived electrocatalyst can achieve a Faradaic efficiency of 67% toward ADN at an applied potential of -0.85 V versus reversible hydrogen electrode─a much lower overpotential compared to that typically required for this reaction without the use of catalysts. Findings here shed light on the design and development of advanced electrocatalysts to boost the performances for the electrosynthesis of ADN.

Finite element model based on a unit with cracks in the rotor of the exciter is set up. Andthen critical speed is calculated that compared to actual measured value to verify the rationality of themodel. Lastly response characteristics of the three-bearings supporting structure are studied when thefirst critical speed of the exciter with cracks is closed to the working speed. And the reliability ofconclusions is further verified by case analysis.

The macroscopic mechanical properties of granite collected from the Fujian Province, China were measured using uniaxial compression and three-point bending after the granite was exposed to high temperatures. The stress-strain relationship was measured and mechanical properties were calculated. The microstructure and content of minerals are detected. The failure mechanisms and the mechanical characteristics of the granite are explained in terms of the microstructure and the minerals present. Where after the Universal Distinct Element Code (UDEC) was used to numerically simulate the mechanical behavior of granite specimens under uniaxial compressive loading after the granite was exposed to different high temperatures. The model parameters were calculated based on previous experiments. The effects of heat treatment on granite was investigated numerically. The model predictions were compared with experimental results and an acceptable agreement was achieved. A modified failure criterion was developed and a corresponding fish function was written to investigate the development of shear and tensile cracking during loading. It was found that initial cracking is in the form of shear cracks which increase rapidly in number until the model reached the unstable fracture developing stage. The number of tensile cracks increases slowly as the axial stress increases from the crack initiation stress (CIS) to the unstable fracture developing stage. Once the specimen enters into unstable fracture developing stage, there is a transition between the type of failure recorded in the model where the shear cracks change to tensile cracks.

With cooling tests on polypropylene fiber reinforced concrete and plain concrete that were initially subjected to different heating temperatures, the change of mechanical properties including mass loss, uniaxial compressive strength and microstructure were analyzed. The results show that the compressive strength of concrete tend to decrease with an increase in temperature. After experiencing high temperatures, the internal fibers of the polypropylene fiber reinforced concrete melted and left a large number of voids in it, thereby deteriorating the mechanical properties of concrete.

The mechanical properties of heated granite subjected to two different cooling ways, namely cooled in the water (fast-cooling) and cooled in the air (slow-cooling) at room temperature, were studied respectively. The effects of the heating temperatures and cooling ways on the failure mode and failure mechanism of heated granite were analyzed. The tested results indicated that the longitudinal wave velocity, uni-axial compressive strength, and initial elastic modulus of heated granite decreased with the increasing heating temperature, especially for those subjected to the fast-cooling way compared to those subjected to slow-cooling way. To the contrary, the peak strain increased as the heating temperature increases, and the peak strain was bigger for the slow-cooling way than for the fast-cooling way. The analysis of the experimental results indicated that the water cooling accelerated the deterioration of the internal structure of heated granite and resulted in undesired mechanical properties.

An integrated system is proposed of base station module, key module and tire modules, in order to overcome the independence of tire pressure monitor system, remote keyless entry and immobilization of engine. Tire modules or key module communicate base station module with UHF frequency signal of 434MHZ. The transponder PCF7961 in key module and PJF7992 in base station module authenticate mutually with LF frequency signal of 125KHZ. The result is shown that the system can improve the security and controllability of cars, compress system redundancy, reduce produce costs and optimize the skeleton network.

This paper describes a hot model test of natural draft wet cooling towers (NDWCTs) to investigate the effect of cross walls on the thermal performance of NDWCTs under crosswind conditions. The hot model test can simulate the actual operation of a prototype tower by operating a model tower at steady state conditions while varying the temperature and flow rate of the incoming hot water along with the crosswind velocity. Cross walls of two shapes at different setting angles were installed in the rain zone and tested under various operating conditions. The results show that crosswinds degrade the NDWCT performance below a critical crosswind velocity Vcr, but improve the performance above Vcr. Increasing water flow rate and inlet water temperature can raise Vcr. Installing cross walls can improve the NDWCT performance. At low crosswind velocities, the solid wall leads to better NDWCT performance than the porous wall. However, the opposite effect is obtained at high crosswind velocities. At all crosswind velocities, the cross wall at a setting angle of 0° results in higher performance than that at 45°, regardless of cross wall shapes. Moreover, the cross wall at 45° degrades the NDWCT performance under high crosswind conditions.

A new approach of installing air deflectors around tower inlet circumferentially was proposed to optimize the inlet airflow and reduce the adverse effect of crosswinds on the thermal performance of natural draft wet cooling towers (NDWCT). And inlet airflow uniformity coefficient was defined to analyze the uniformity of circumferential inlet airflow quantitatively. Then the effect of air deflectors on the NDWCT performance was investigated experimentally. By contrast between inlet air flow rate and cooling efficiency, it has been found that crosswinds not only decrease the inlet air flow rate, but also reduce the uniformity of inlet airflow, which reduce NDWCT performance jointly. After installing air deflectors, the inlet air flow rate and uniformity coefficient increase, the uniformity of heat and mass transfer increases correspondingly, which improve the cooling performance. In addition, analysis on Lewis factor demonstrates that the inlet airflow optimization has more enhancement of heat transfer than mass transfer, but leads to more water evaporation loss.

The energy of impact must decay and be transmitted after a bullet is shot through a ballistic-resistant cloth with a laminate structure. A rigid net structure transmits the impact stress to reduce the breakage of the material in the direction perpendicular to the fabric after the impacting of a projectile. This work combines the rigid net structure of stainless steel mesh with two layers a needle-punched polyamide nonwoven fabric to create a sandwich-like laminate structure. A compound fabric that is composed of a stainless steel mesh and polyamide nonwoven fabrics is placed in multi-layer Kevlar fabrics, and the buffer effect is measured by performing a dropping weight impact test and a bullet-shooting test. The specifications of the stainless steel mesh and the order of placement of the compound fabrics are varied to show the effect of these parameters on the energy of fracture propagation and the buffer effect of the multi-layered Kevlar compound fabric that includes a layer of compound fabric that is made of stainless steel mesh and polyamide nonwoven fabrics. In this study, the compound fabric replaces several layers of Kevlar unidirectional fabric, to be used to reduce the cost of bulletproof vests without reducing ballistic resistance.

The gray prediction theory has already been widely applied to solving all kinds of social, scientific and technical problems. It is also used for the prediction of engineering mechanical and material scientific problems. But the traditional gray prediction model is applicable only for equidistant time sequences. In order to extend the scope of application, an improved gray prediction model is put forward. By weighted summation, the new developed gray prediction model can also be applied to the situation of non-equidistant time sequence. The improved gray prediction model is used for the prediction of creep fracture time of rocks and gypsum. The deduced results are proven to be very accurate. The research work of the current paper opens many opportunities for further thoughts of the prediction of many other engineering mechanical problems.

The mechanism and criterion of crack initiation and propagation of rocks were investigated by many researchers. And the creep behaviour of rocks was also theoretically and experimentally studied by some scientists and engineers.The characteristics of crack initiation and propagation of rocks under creep condition, however, are very important for rock engineering and still not paid enough attention by researchers. In this paper, the criterion and mechanism ofcrack initiation and propagation under creep condition were investigated using specimens collected from sandstone rock formations outcropping in the Emei Mountain, the Sichuan Province of China. Cuboid specimens under three point bendingwere used in this investigation. All specimens were classified into four sorts and used for Mode-I fracture or creep fracture tests. The experimental result shows that due to creep deformation,rock crack will inevitably initiate and propagate under a load of K I, which is less than fracture toughness K ICbut not less than a constant (marked as K IC2). K IC2indicates the ability of rock to resist crack initiation and propagation under creep conditions and is less than fracture toughness K IC, defined as creep fracture toughness in this paper.K IC2 should be considered as an important parameter on design and computation of rock engineering. The microstructural mechanism for crack initiation and propagation of rock materials undercreep condition was introduced based on competitive model between softening effect and hardening effect, and the validity of test result was explained. The test result was also verified in rheological theory. When K Iis more than K IC2 but less than K IC, rock crack will initiate and propagate after a time interval of sustained loading under creep condition.In order to find the relation between duration of sustained loading, which can lead to crack initiation and propagation, and the initial stress intensity factor K I, an unequal-interval time sequence forecasting andpredicting model was introduced, and the relation was obtained for homogeneous and isotropic fine-grained red sandstone. Finally a modified fracture toughness formula was given, in which the influence of fracture process zone(FPZ) was fully considered.

Based on the traditional theory of fracture, time-dependence of rock fracture is taken into account and the creep fracture criteria are given. The effect of the microcrack zone on fracture toughness is analyzed. Finally, a model for time prediction of rheological fracture is derived and its feasibility is proven.

Based on the developed three-dimensional computation model of natural draft wet cooling towers, the effect of crosswind on circumferential distribution of air radial pressure gradient and velocity at tower air inlet was studied, and the effect of crosswind on total air inflow rate, transverse mass flow rate, vertical mass flow rate and water temperature drops of the three zones (i.e. spray zone, filling zone and rain zone) were also analyzed. Analysis of crosswind effect on air flow field in heat and mass transfer zone indicates that the induced longitudinal eddy causes reduction of effective ventilation area in filling zone. Results showed that crosswind destroys the uniform air inflow, reducing the total air inflow mass rate and the effective ventilation area of filling zone, resulting in cooling performance deterioration of natural draft wet cooling towers.Copyright © 2011 by ASME