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The application of nanocrystalline (NC) materials at high temperatures is challenging due to their poor thermal stability or low creep resistance. Here we report that a thermally stable NC Fe-5 at.% Zr steel produced by High-Pressure-Thermal-Compression sintering exhibits an excellent creep resistance (with a creep rate of 3.92 × 10−8 s−1 at 923 K and under the applied stress of 250 MPa). The excellent creep resistance is ascribed to its highly stable NC structure stabilized by nano-sized precipitates. Mechanical testing suggests that the creep of the NC Fe-5 at.% Zr steel is controlled by dislocation activities rather than diffusion dominated mechanisms.

In this paper, a microsystem integrated with infrared thermography is developed to measure the kinetics of fast exothermic reactions. The hydrolysis of ethyl acetate is chosen as the model reaction to verify the technique. The activation energy of this reaction is successfully obtained, which agrees well with the literature value. Except for the general method of collecting data from several typical points of the infrared radiation (IR) picture, a strategy called image analysis is applied to obtain the temperature profiles along the reactor by collecting data from the whole IR picture. With the image analysis, this system can generate time-series kinetic data in a single experiment, which is usually challenging for a continuous flow system. The reaction enthalpy of classic neutralization reaction and kinetic parameter of hydrolysis are determined again using the image analysis, showing fewer deviations from literature values. The image analysis technique could provide much more reliable and accurate results with higher efficiency.

The objectives of this study were to evaluate the effects of feeding pelleted total mixed ration (PTMR) on growth performance, ruminal fermentation characteristics, and gastrointestinal microflora of fattening lambs. A total of 100 crossbred (Dorper sheep × Small-tail Han Sheep, DH) ram lambs at 120 d age with similar body weight (BW, 34.9 ± 0.5 kg) were randomly allocated to 10 pens. The pens were randomly assigned to 2 treatments with 5 replicates per treatment. Dietary treatments were PTMR and un-pelleted total mixed ration (UPTMR) with the same dietary ingredients and nutritional contents. The average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR) were determined in a 32-d experimental period. Ruminal pH, volatile fatty acid (VFA) concentrations, microbes in the rumen and cecum, and carcass weight were measured at the end of the experiment. Lambs fed PTMR had a greater ADFI (P = 0.002) than these fed UPTMR, greater ADG (P = 0.003) and carcass yield (P = 0.003) than that fed UPTMR. However, no significant difference was observed on FCR (P = 0.259) between the two groups of lambs. Compared with UPTMR treatment, feeding PTMR increased acetate and propionate concentrations, while decreased acetate to propionate ratio in the rumen (P

The cyclic oxidation behaviour at 1050 °C and isothermal oxidation behaviour at 1100 °C of a low-diffusion Pt-modified NiCrAlY coating with Re-base diffusion barrier were investigated, compared with conventional NiCrAlY, Pt-free NiCrAlY with Re-base diffusion barrier and Pt-modified NiCrAlY without Re-base diffusion barrier coatings. The results revealed that Pt-modified NiCrAlY coating with Re-base diffusion barrier exhibited the best oxidation resistance and lowest interdiffusion extent. The role of Re-base diffusion barrier in inhibiting elemental interdiffusion and the contribution of Pt to the growth rate and adhesion of Al2O3 scale, as well as the long-term stability of Re-base diffusion barrier, are discussed.

Changes in riverine suspended and riverbed sediments have environmental, ecological and social implications. Here, we provide a holistic review of water and sediment transport and examine the human impacts on the flux, concentration and size of sediment in the Yangtze River in recent decades. We find that most of the fluvial sediment has been trapped in reservoirs, except for the finest portion. Furthermore, soil-conservation since the 1990s has reduced sediment yield. From 1956-1968 (pre-dam period) to 2013–2015 (post-dams and soil-conservation), the sediment discharge from the sub-basins decreased by 91%; in the main river, the sediment flux decreased by 99% at Xiangjiaba (upper reach), 97% at Yichang (transition between upper and middle reaches), 83% at Hankou (middle reach), and 77% at Datong (tidal limit). Because the water discharge was minimally impacted, the suspended sediment concentration decreased to the same extent as the sediment flux. Active erosion of the riverbed and coarsening of surficial sediments were observed in the middle and lower reaches. Fining of suspended sediments was identified along the river, which was counteracted by downstream erosion. Along the 700-km-long Three Gorges Reservoir, which retained 80% of the sediment from upstream, the riverbed gravel or rock was buried by mud because of sedimentation after impoundment. Along with these temporal variations, the striking spatial patterns of riverine suspended and riverbed sediments that were previously exhibited in this large basin were destroyed or reversed. Therefore, we conclude that the human impacts on sediment in the Yangtze River are strong and systematic.

Cu-based amorphous alloy plates with good mechanical properties have tremendous potential applications as structural materials. However, there is a lack of effective methods for preparing such plates. In this work, 0.53-mm-thick Cu47Zr45Al8 (at.%) and 0.25-mm-thick Cu64Zr36 (at.%) amorphous-alloy plates were prepared continuously by twin-roll strip casting, and their mechanical properties were investigated through both experiments and in-situ observations. The Cu-based amorphous-alloy plates prepared by strip casting were found to have good surface quality and shape; these plates did not exhibit tensile plasticity, but showed excellent bending and compression plasticity at room temperature. Such plasticity is achieved through the formation and evolution of multiple shear bands. Overall, the present study proves the feasibility of continuous preparation of amorphous Cu-based alloy plates with good plasticity by twin-roll strip casting and serves as a guide for this process in the future.

A single-phase (Ni,Pt)Al coating was removed by soft chemical stripping method successfully after preceding oxidation at 1100 °C for 300 h, and a fresh one was refurbished subsequently. Oxidation behaviour of the refurbished (Ni,Pt)Al coating was studied in comparison with the virgin one at 1100 °C. The results show that the refurbished coating exhibited superior isothermal and cyclic oxidation resistance than the virgin one in terms of oxidation rate and surface rumpling. The effects of surface roughness and residual elements in the refurbished coating on oxidation rate, surface rumpling and interdiffusion behaviour were discussed.

Nitration of acetyl guaiacol, one typical aromatic nitration, is highly exothermic and extremely fast. Better control and high efficiency can be achieved in the microreactor due to its enhanced mixing and heat transfer rates. In this study, nitration of acetyl guaiacol was carried out in a microreactor using nitric acid-acetic acid as nitrating agent. The nitration kinetics was first investigated, and a kinetic model was established and revealed good prediction of experimental results at higher temperatures. Effects of molar ratio of nitric acid-acetyl guaiacol, residence time, temperature, and nitric acid concentration on the reaction were studied in detail. Under optimized condition, 90.7% yield of desired product, 5-nitroguaiacol, was achieved with 40% of nitric acid concentration, nitric acid-acetyl guaiacol molar ratio of 2.6, reaction temperature of 120 °C, and residence time of 2 min. Compared to traditional batch reactor, microreactor showed the advantages of higher yield and selectivity, much shorter reaction time, and less use of nitric acid.

Beckmann rearrangement of cyclohexanone oxime is an important step to produce caprolactam. Many researches have been devoted to it by using new organic catalysts or new reactors such as microreactor to improve the process efficiency. In this paper, the process was assessed by an inherently safer design (ISD) methodology based on risk approach to evaluate the safety effects of new organic catalysts and microreactors. The results show that organocatalyzed Beckmann rearrangement in continuous stirred tank reactors is unacceptable from the view of inherently safer concept due to the large amount of use of organic solvent and the large reactor volume. However, the application of microreactors could significantly increase the safety of both traditional and organocatalyzed Beckmann rearrangement processes with making inventories much smaller. The hazard conflicts that would be transferred to other parts of the process due to the application of microreactors were also evaluated by the Likelihood Index of Hazard Conflicts (LIHCs). The high value of LIHC because of microreactors indicates that some factors need to be paid more attention at the early design stage.

Fe-based amorphous alloys are characteristic of high saturation magnetization, low coercivity, and low core loss, which holds a grand promise for several engineering applications, such as soft magnetic, corrosion-resistant and wear-resistant coatings. However, poor amorphous forming ability (AFA) and size limit remain the main obstacles in applications. This study aims to address those scientific-technical challenges through a twin-roll strip casting method to yield two cost-effective Fe-based amorphous alloy (Fe73Mo4B5Si5P8C5 and Fe80Al2B5P9C4) ribbons with ca. 200-μm thickness and promising soft magnetic functions. Their crystallization behavior, thermal stability, magnetic properties, and mechanical performance for melt-spun and annealed alloys were studied systematically. Results demonstrate that Fe73Mo4B5Si5P8C5 and Fe80Al2B5P9C4 present good thermal stability, a large temperature interval between Tg and Tx1(61.7 °C for Fe73Mo4B5Si5P8C5 and 43.1 °C for Fe80Al2B5P9C4) infers that both the alloys have good processability. Meanwhile, Fe80Al2B5P9C4 amorphous alloy subjected to annealing at 450 °C for 300 s exhibited high saturation magnetization greater than 1.5 T, low coercivity of 5.3 A/m and high hardness of 989 Hv, which were attributed to the utterly amorphous structure and superior thermal stability achieved by twin-roll strip casting. Integrating the favorable mechanical, magnetic characteristics and high manufacturability of ultra-thick Fe73Mo4B5Si5P8C5 and Fe80Al2B5P9C4 amorphous alloys indicates that twin-roll strip casting is a sound solution to tackle the poor AFA and size limit in production of amorphous ribbons.

Hf and/or Y doped (Ni,Pt)Al coatings were prepared to investigate their initial oxidation behavior and cyclic oxidation performance at 1150 °C. Finer grain sizes were observed in Hf and/or Y doped (Ni,Pt)Al coatings in as-received state, wherein the best oxidation resistance was achieved in the co-doped coating. In oxidation, Hf and Y were observed synchronously segregating at grain boundaries of alumina scale, which more effectively retarded the phase transformations of θ-Al2O3 to α-Al2O3 for the oxide scale and from β to γ′ for the coating. Mechanisms responsible for the merits of Hf-Y co-doping in (Ni,Pt)Al coating are discussed.

In this paper, a microsystem integrated with infrared camera is developed to measure the reaction enthalpy of fast exothermic reactions. The microsystem is composed of a micromixer and a coiled capillary, which are all placed in a vacuum box to form an adiabatic environment. The fast exothermic reactions are started in the micromixer and then the temperature profiles of the capillary are measured via the infrared transparent window by the infrared camera. The reaction enthalpy can be determined from the temperature rise of the capillary. Two reactions which are homogeneous and heterogeneous respectively are performed with this method. The results show that the data obtained are in good agreement with the values reported in literature with the relative experimental errors less than 5%. Compared with the traditional calorimeter, the microsystem can provide a quick, safe and non-intrusive method to obtain the temperature profiles of the fast exothermic reactions.

Daylily or Hemerocallis spp. (Xanthorrhoeaceae) is one of the most economically important flowering crops in the world. Ploidy level of 149 genotypes both local to China and introduced from the United States and New Zealand were assessed with an outcome of 79 diploids, 22 triploids and 48 tetraploids. A large proportion of introduced cultivars were tetraploid (42%), half were diploid and the rest, 8%, were triploid. Most Chinese cultivars were diploid; only one was tetraploid. Among the 29 wild genotypes collected from the Taihang Mountain range, 13 (45%) were triploid and 16 (55%) were diploid; no tetraploids were identified. For the 31 genotypes with known ploidy, 22 matched previous counts with the rest showing a lower ploidy. As different ploidy is common in daylily, we suggest that ploidy levels should be assessed in breeding programmes for specific breeding purposes. Karyotypes of three diploid, three triploid and two tetraploid genotypes were constructed and they were assigned to ‘3A’, ‘2B’ and ‘3B...

Metallic foam is a typical porous material with heterogeneous mesostructure. The complex influences of the porous structure on the mechanical properties of metallic foam are not well known yet and this remains a crucial problem in the ability to predict and optimize the mechanical properties of foam materials. Here we explored the three dimensional Voronoi structure to model the meso-structure of metallic foam. The average pore size was controlled by the number of seeding points used to construct the Voronoi structure and the porosity was controlled by calibrating the cell wall thickness. In addition, the concept of pore irregularity was introduced to try to further quantify the description of the heterogeneous structure. The correlation between the pore irregularity variation and the plastic response variation suggests inclusion of the measurable meso-structural parameter would improve the constitutive modeling of foam materials. The plastic and the cracking behavior of pores at the mesoscale under large compressive deformation and tensile deformation were studied and the excellent compressibility of metallic foams can be attributed to the formation of multiple plastic bands while the poor stretchability is due to that only one damaged plastic band can be formed.

cited By 4; International audience; In the current study, jump stress creep and stress relaxation experiments were performed to Zr65Cu18Ni7Al10 metallic glass below the transition temperatures Tg. The viscoplasticity effect and transition between the Newtonian and non-Newtonian flow are investigated. The activation energy of creep is obtained from two theoretical methods. It is found that the activation volume of creep is more than that of stress relaxation, which is mainly caused by different organizational behaviors. © 2015 Elsevier Ltd. All rights reserved.

A new method for analyzing the reliability of mechanism is proposed. The proposed method suggests the use of two response surface functions to evaluate the reliability probability. Structural reliability can be calculated through the analysis of the maximum stress and the maximum deformation of crank-rocker mechanism to establish its limit states equations respectively and then ganged sample these response surfaces that is double response surface, structural reliability can be calculated. Aiming at analyzing reliability of mechanical system with multiple components which have multiple failure modes, this method can realize the whole reliability analysis under the consideration of the correlation of these failure modes. The example result indicates that calculation velocity of this method is high; precision of this method is exact. It can be used in other researches and projects.

From the perspective of Fracture Mechanics, concrete/rebar bonding failure process in reinforced concrete (RC) structures means the decreasing of the crack closure force imposed by rebar in RC beams, which will result in crack propagation, and eventually structural damage. In this paper the crack-arresting mechanism of the concrete/rebar bonding stress in RC beams was analyzed, which was employed to reveal the degradation mechanism of RC beams induced by concrete/rebar bonding failure; and bending tests of RC beams were presented where effects of concrete/rebar bonding failure on bending performance of RC beams had been investigated. The concrete/rebar bonding failure was obtained by wrapping the rebar with different length of plastic film during casting. The results shows effective concrete/rebar bonding is the key to provide crack closure force, which can prevent functional degradation of RC beams.

In this study, p-type ZnO films with excellent electrical properties were prepared by ultrasonic spray pyrolysis (USP) combining with a N–Al codoping technique. The influence of the substrate temperature and annealing temperature on electrical properties of ZnO films was investigated. The growth and doping process of ZnO films was explored by thermogravimetry, differential scanning calorimetry and mass spectrum (TG–DSC–MS) measurements. It is suggested that the variation of electrical properties of ZnO films with the substrate temperature and annealing temperature results from the removal of H element out of the films.

Chroma and turbidity of flowing water were measured by using a colorimetric method that requires no conventional spectrophotometer, colorimeter or turbidimeter. A dual-wavelength light-source and a BDJ (buried double p–n junction) optical wavelength sensor were employed in the measurement. The intensity–insensitive photocurrent ratio of the two p–n junctions in the sensor is monotonously related to chroma and turbidity of water. The potential applications of this method of monitoring water chroma and turbidity, two important physics indexes to describe the quality of water, have been demonstrated. The results show that this simple method is sensitive and accurate, and not affected by fluctuation of flowing water.

The crystal structures and electronic properties of hydrides LaNi4.5Al0.5H6−xHey ( x = 0 , 0.5 , 1.0 ) have been investigated by means of the density functional theory using the full-potential linearized augmented plane wave (FLAPW) method with the generalized gradient approximation (GGA). The calculated data indicate that the micro-arrangement of hydrogen atoms in LaNi4.5Al0.5H6 is the same as that of hydride LaNi5H6, which is consistent with the experimental results in terms of the equilibrium desorption isotherms. And we found that once the first He atom locates in the tetrahedral interstitial sites (6m site) near Al atom for LaNi4.5Al0.5H5.5He0.5, then it is difficult for the second He atom to locate in the 6m site again. Therefore, the second He atom would prefer to occupy the middle plane site (6m\ast site) apart from Al atom for LaNi4.5Al0.5H5He. To study the interaction among La, Ni, Al, H and He atoms, the figures referring to the densities of states and contour maps of the electron densities on two different planes are analysed.

The thermal-mechanical process of V-N microalloyed N80 casing was simulated using Gleeble-3500 simulator in the laboratory scale, and the complex effects of the nitrogen addition and reheating temperature for on-line normalization on the final microstructure and mechanical properties were examined by optical and transmission electron microscope as well as mechanical testing. It is indicated that the enhanced nitrogen resulted in a high degree of grain refinement in the final microstructures. An increase in reheating temperature brought elevated strength at an expense of toughness. Improved combination of yielding strength in 650 MPa and toughness in 48J at −20°C can be obtained in 33Mn2V steel with nitrogen content of 140ppm at reheating temperature of around 930°C. The results can be used as a reference to determine a reasonable scheme suitable for the on-line normalizing process of nitrogen enhanced V microalloyed seamless oil casings.

There thermal cycles for the cyclic heat treatment of a bainitic steel were simulated under the different heating rate ranged from 2°C/s to 100°C/s and 1000°C/s followed by subsequent rapid cooling using a Gleeble3500 thermal-mechanical simulator equipped with the self-designed quench system. The microstructural change of the starting material imposed by the different thermal cycles was observed by optical and transmission electron microscope (TEM). The results indicate that a high degree of superheating for the reverse bainitic α→γ transformation was realized as a result of extremely rapid heating (1000°C/s) up to an elevated austenitisation temperature (1250°C), which prevent restoration of the initial coarse-grained austenite and lead to a significant refinement of austenite grain. An ultrafine-grained structure with enhanced mechanical properties then formed during the subsequent rapid γ→α reaction on cooling. The results indicate a novel microstructure refinement route for the bainitic steels.

Photosynthesis and growth characteristics of Parthenocissus quinquefolia were measured under differing soil water availability within a pot. Decreased soil moisture significantly reduced the leaf relative water content (RWC) and the above- and below-ground biomass. However, more biomass was allocated to the root than to the leaf. Net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) were also significantly decreased but water use efficiency (WUE) was increased. Midday depressions in PN and gs were not evident for the well-irrigated plants. With the lower water availability, midday reductions in PN and gs were much more marked and the duration of the depression was longer. Additionally, the PN-irradiance response curves also indicated that water supply affected photosynthesis capacity. The growth and photosynthetic response of P. quinquefolia to water supply indicated that this species could resilient to water availabilities and adapt to Hunshandak conditions very well.

Boron nitride (BN) nanocrystals with explosion (E) phase were prepared by a novel laser-assisted materials fabrication, i.e., pulsed-laser-induced liquid (acetone)/solid (hexagonal boron nitride bulk) interfacial reaction at normal temperature and pressure. Typical diameters of these synthesized quasi-spherical BN nanocrystals were in the range of 30 to 80 nm. Transmission electron microscopy, x-ray diffraction, and Fourier transformed infrared spectroscopy were used to identify the morphologies and structures of the synthesized nanocrystals. Additionally, we proposed the formation mechanism of cubic-BN and E-BN nanocrystals upon pulsed-laser-induced liquid/solid interfacial reaction, in which both liquid and solid were simultaneously involved.

Cubic nitride boron (c-BN) films have been prepared on polished single crystal Si(1 1 1) surface at room temperature (25 °C) by radio frequency plasma enhanced pulsed laser deposition (RF-PEPLD), assisted with substrate negative bias. Components, structure and surface morphology of the deposited films were identified by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The growth mechanism of c-BN phase upon RF-PEPLD is discussed in detail, and the experimental evidence indicates that two deposition parameters, i.e., RF plasma power and substrate negative bias, played the key roles in the growth of the resulted c-BN films at room temperature.

Cubic boron nitride (c-BN) nanocrystals have been synthesized by pulsed laser induced liquid–solid interfacial reaction. It is shown that the diameters of the prepared quasi-spherical c-BN nanocrystals vary from 30 to 80 nm via transmission electron microscopy (TEM). The 2 θ values of the X-ray diffraction (XRD) peaks of the resultant c-BN nanocrystals are 43.16°, 74.16°, 90.08° and 136.1°, respectively, corresponding to the (1 1 1), (2 2 0), (3 1 1) and (3 3 1) crystalline planes of a c-BN phase. Fourier transform infrared (FTIR) spectroscopy has also been used to characterize the structure of boron nitride. The formation of c-BN nanocrystals upon pulsed laser ablation at the liquid–solid interface is discussed in detail.

Diamond nanocrystals with cubic and hexagonal structures have been prepared by pulsed laser induced liquid–solid (acetone1–graphite) interfacial reaction (PLIIR) at normal temperature and pressure. The structure and morphology of the resulted diamond nanocrystals were characterized by transmission electron microscopy (TEM). The Raman spectroscopy analysis of the obtained diamond nanocrystals showed that three diamond Raman lines, i.e., 1307, 1100, and 623 cm −1 were observed. Interestingly, the Raman line at 1100 cm −1 was identified to be original from nano-diamond. In addition, a new Raman line at 926 cm −1 due to diamond was observed in the Raman spectra (RS).

The cardiovascular activities of crude water extract (WE) of Andrographis paniculata (Burm. f.) Nees (Acanthaceae), its three semi-purified ethyl acetate (FA), n-butanol (FB) and aqueous (FC) fractions, as well as andrographolide, a major plant constituent, were elucidated in anaesthetized Sprague-Dawley (SD) rats for the very first time. FA and andrographolide, which possesses multiple pharmacological activities, elicited no drop in mean arterial blood pressure (MAP), while WE, FB and FC produced a significant fall in MAP in a dose-dependent manner without significant decrease in heart rate. The ED50 values for WE, FB and FC were 11.4, 5.0 and 8.6 mg/kg-respectively. These suggested that the hypotensive substance(s) of the crude water extract was concentrated in FB. Pharmacological antagonist studies were consequently only tested in FB (5 mg/kg). The hypotensive action of FB was not mediated through effects on the beta-adrenoceptor, muscarinic cholinergic receptor and angiotensin-converting enzyme, for it was not affected by propranolol, atropine and captapril, respectively. However, it seems to work via alpha-adrenoceptors, autonomic ganglion and histaminergic receptors, since the hypotensive effect of FB was negated or attenuated in the presence of phentolamine, hexamethonium as well as pyrilamine and cimetidine.