At room temperature, the low cycle fatigue tests for smooth specimens of TC25 titanium alloy under various stress ranges are operated at a CSS280I-20w Electro Hydraulic Servo Universal Testing Machine with a microscopic observation system, and the low cycle fatigue lifetimes are measured. Based upon the analysis of stress-strain hysteresis loop of low cycle fatigue of TC25 titanium alloy, a simplified Manson-Coffin formula is derived according to both the experimental characteristics and the stress-strain constitutive model, the fatigue lifetimes are plotted against stress ranges, and a stress-fatigue life curve for TC25 titanium alloy is obtained by the linear regression analysis method. Finally, the fracture surface morphologies of TC25 specimens are investigated using a JSM-6360 Scanning Electron Microscopy, and the fatigue fracture mechanisms of low cycle fatigue are studied. It shows that the plastic deformations are mainly formed at the accelerated fracture stage, and various shear lips can be observed on the fracture surfaces, which demonstrates that the shear stress results in the final rupture of TC25 titanium alloy. During the fracture of low cycle fatigue, the cleavage nucleation leads to the formation of fatigue crack initiation region, the fatigue crack growth exhibits a mixed transgranular and intergranular crack growth mode, and in the final rupture region, the fracture surface of low cycle fatigue of TC25 titanium alloy appears as a typical semi-brittle fracture mode.
The method of oxidative upgrade by nitric acid is used to convert polystyrene plastic into a high-value chemical raw material, benzoic acid. The yield can reach nearly 90% at 180 °C within 3 h, while the purity of the product can reach more than 95%.
The temperature sweep tests at defferent frequencies and heating rates, and frequency sweep tests at various temperatures for the samples of poly(methyl methacrylate) are carried out on a dynamic mechanical thermal spectrometer EPLEXOR® 500N-Gabo. The effects of temperature, frequency and heating rate on dynamic mechanical properties of poly(methyl methacrylate) are investigated. The results indicate that the glass transition temperature of poly(methyl methacrylate) increases with increasing frequency from 1 to 100Hz, and increases with increasing heating rate from 3 to 8°C/min as well. The temperature sweep curves at various heating rates suggest that the storage modulus of poly(methyl methacrylate) is non-sensitive at heating rate 3°C/min or 8°C/min, while heating rate is 5°C/min, there exists a critical temperature, within which the storage modulus versus temperature curves depart from each other, and beyond which the curves overlap one another. The glass transition temperature determined by the peak of loss modulus curve is smaller than that defined by the peak of loss tangent. The frequency sweep curves at a constant temperature show that a drop in storage modulus and a peak in loss tangent appear at a certain critical frequency, and the critical frequency increases with increasing temperature. For amorphous polymer, a competitive mechanism between frequency and temperature is observed. Higher temperature accelerates molecular motion, while higher frequency restrains molecular motion, so that the critical frequency corresponding to the peak of loss tangent shifts toward the direction of high temperature.
LCZ696 is a novel treatment for patients suffering from heart failure that combines the two active pharmaceutical ingredients sacubitril and valsartan in a single chemical compound. While valsartan is an established drug substance, a new manufacturing process suitable for large-scale commercial production had to be developed for sacubitril. The use of chemocatalysis, biocatalysis, and flow chemistry as state-of-the-art technologies allowed to efficiently build up the structure of sacubitril and achieve the defined performance targets.
Different combinations of low impact development (LID) technologies can be applied for control of urban non-point source pollution. There are currently few evaluations of urban non-point source pollution and pollution load reduction based on a combination of porous asphalt and bio-retention. Taking Shenzhen International Low Carbon City as an example, road-deposited sediments were collected prior to and after rainfall events. Runoff was monitored under six typical rainfall events, from porous asphalt and the inlet/outlet of bio-retention. Through analysis of changes in the process of "build-up-wash-off-transport" of pollutant loads, the average build-up of road-deposited sediments in the study area was found to be (15.80±3.79) g·m-2; the mass percentage of road-deposited sediments (size>250 μm) was approximately 65.14%. The average wash-off percentage of six different intensity rainfall events was 17.15%, and road-deposited sediments (size<105 μm) were carried by 62.71%-74.94%. The average pollution loads of surface runoff pollutants SS, TN, and TP were 2.02, 0.025, and 0.0013 g·m-2, respectively. The removal rates of SS, TN, and TP through porous asphalt under infiltration and filtration were 70.26%, 46.29%, and 19.27%, respectively. The secondary purification removal rates of runoff water in bio-retention were 85.25%, 20.22%, and 70.27%, respectively. Pollutant loads into Dingshan River totaled 0.08, 0.011, and 0.0003 g·m-2, representing 4.05%, 43.47%, and 24.39% of runoff. The combination thus had a significant effect on runoff purification. Through quantitative research on the formation of non-point source pollution, this paper provides a scientific basis for estimating pollution loads of urban non-point source pollution and evaluating the performance of LID projects. It makes suggestions for the popularization and application of LID and sponge city design in China.
The fatigue crack initiation life at various stress ratios for GH4133B superalloy specimen with different circular notch radios are studied at ambient temperature and atmospheric pressure utilizing the fracture mechanics method. It is shown that a controlling parameter Δ K I / ρ 0.5 can be adopted to characterize the fatigue crack initiation life, and the effect of notch radius on fatigue crack initiation life increases with increasing control parameter, while the fatigue crack initiation life firstly increases and then decreases with increasing stress ratio. The fatigue fracture surfaces of circular notched compact tension specimens of GH4133B superalloy for fatigue crack initiation tests at various stress ratios are investigated using a scanning electron microscopy, and the fracture surface morphologies in the fatigue source region are analyzed. It is found that the separation between carbide inclusion on the surface or subsurface and matrix, or the separation between nickel-rich second phase particle and matrix, or the interaction between persistent slip bands and inclusion, mainly results in the fatigue crack initiation.
Abstract With intensified global warming, accurate quantification of hydrological processes in seasonally frozen regions, particularly with irrigated overwinter crops, is necessary to develop management strategies that promote groundwater conservation. By incorporating a physically based freeze‐thaw cycle module into the Soil and Water Assessment Tool (SWAT‐FT) model, variations of surface hydrology and groundwater dynamics were systematically assessed in North China Plain under three Shared Socioeconomic Pathways during 2041–2070 and 2071–2100 periods between the conventional and improved SWAT models. Compared to the conventional SWAT model, the SWAT‐FT model predicted an increase in soil water content, decrease in irrigation, and an increase in percolation during the growing season of winter wheat. These discrepancies resulted in a 5% higher decline rates of shallow groundwater levels simulated by the SWAT model compared to the SWAT‐FT. Additionally, the SWAT‐FT model projected that the average decline rates of shallow groundwater levels were approximately 0.90 ± 0.16 m yr −1 (SSP1‐2.6), 0.60 ± 0.46 m yr −1 (SSP2‐4.5), and −0.17 ± 0.53 m yr −1 (SSP5‐8.5), respectively, during 2071–2100 compared to the historical period. The SWAT‐FT simulations indicated that the decline rates in shallow groundwater levels were projected to either decrease slowly or potentially increase by the end of the 21st century under the SSP5‐8.5 scenario, potentially achieving equilibrium between shallow groundwater extraction and replenishment. Our study emphasized the importance of considering the freeze‐thaw processes to evaluate groundwater variations more accurately in response to climate change effects in temperate regions with an overwinter crop.
Abstract Mesoporous silica has been functionalized with vanadium pentoxide (V 2 O 5 ) and cerium oxide (CeO 2 ). It was then immobilized with biocatalyst horseradish (HRP) to realize highly sensitive detection of H 2 O 2 . The electrode was characterized with SEM, cyclic voltammetry, and impedance measurements. A well‐defined peak for HRP reduction was noticed at about −0.31 V with an apparent heterogeneous electron transfer rate constant of 1.01 s −1 . The catalytic reduction of H 2 O 2 was achieved. The Michaelis constant was calculated to be 0.018 mM. On this electrode, H 2 O 2 was detectable in the range of 20 to 180 µM and the detection limit was 3.0 µM.
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