Tool wear is a major cause of accelerated tool failure during the milling of aluminum alloy. The periodically cutting force directly affect the cutting heat and tool wear due to the intermittent ...cutting characteristics of the milling process. The focus of this paper is to analyze the influence of the variation of cutting force on tool wear behavior. The change law of cutting force by cutting parameters was analyzed firstly. Secondly, the variation of the wear land width (VB) of tool flank face by the milling length was analyzed. Thirdly, the wear morphology and the energy dispersive spectrometer (EDS) results of tool rake face and flank face in different cutting parameters were observed by tungsten filament scanning electron microscope. Finally, considering the cutting force effect, the tool wear mechanism during high-speed milling of Aluminum-Alloy Die Castings 12 (ADC12, 12 means aluminum number 12) was analyzed. The cutting force in tangential direction is predominant during high-speed milling aluminum alloy, which decreases gradually with the increase of cutting speed but increases gradually with the feed rising. The adhesion-oxidation wear was main wear mechanism of tool rake face during high-speed milling. While adhesive wear was the main wear mechanism of the tool flank face during high-speed milling. It is found that the formation of adhesive wear is the process from particle adhesion to melting until the formation of adhesive layer, which related to the change of cutting force.
ADC12 aluminum alloy has been widely used in the aerospace, ship, and automotive fields because of its high specific strength, excellent die-casting performance, and wear resistance. Adhesion wear is ...the main wear mechanism of high-speed milling ADC12 aluminum alloy. The most important factor affecting adhesion wear is the tool–chip interface friction, which is directly manifested in the tool–chip interface temperature. Therefore, the temperature variation during the milling of aluminum alloy is analyzed using a temperature field model and infrared temperature measurement technology. Then, the tool wear morphology and the tool wear land width are observed using a scanning electron microscope. Finally, the tool wear mechanism considering the tool–chip interface temperature is discussed. The tool–chip interface temperature is related to the friction angle, tool–chip contact length, and friction force at the rake face, which increases first and then decreases as the cutting speed and feed rate increase. During the formation of the adhesive layer, the tool–chip interface temperature increases, the change rate of the cutting force and the tool wear rate increase, and adhesion, oxidation, and abrasive and delamination wear are generated on the tool surface. With the increase in temperature, the tool wear rate increases, the molten adhesive layer on the tool surface is accompanied by crack propagation, and adhesion wear, oxidation wear, and abrasive wear occur on the tool surface.
Because of the massive work and high cost of milling experiments, finite element analysis technology (FEA) was used to analyze the milling process of ADC12 aluminum alloy. An improved Johnson–Cook ...(J–C) constitutive equation was fitted by a series of dynamic impact tests in different strain rates and temperatures. It found that the flow stress gradually increases as the strain rate rises, but it decreases as the test temperature rises. Compared with the J–C constitutive model, the predicted flow stress by the improved J–C constitutive model was closer to the experimental results when the strain rate was larger than 8000 s−1 and the temperature was higher than 300 °C. A two-dimensional cycloidal cutting simulation model was constructed based on the two J–C constitutive equations which was validated by milling experiments at different cutting speeds. The simulation results based on the improved J–C constitutive equation were closer to the experimental results and showed the cutting force first increased and then decreased, with cutting speed increasing, reaching a maximum at 600 m/min.
Ferrihydrite is one of the most reactive iron (Fe) (oxyhydr)oxides in soils, but the adsorption mechanisms of glyphosate, the most widely used herbicide, on ferrihydrite remain unknown. Here, we ...determined the adsorption mechanisms of glyphosate on pristine and Al-substituted ferrihydrites with aggregated and dispersed states using macroscopic adsorption experiments, zeta potential, phosphorus K-edge X-ray absorption near-edge structure spectroscopy, in situ attenuated total reflectance Fourier transform infrared spectroscopy coupled with two-dimensional correlation spectroscopy, and multivariate curve resolution analyses. Aggregation of ferrihydrite decreases the glyphosate adsorption capacity. The partial substitution of Al in ferrihydrite inhibits glyphosate adsorption on aggregated ferrihydrite due to the decrease of external specific surface area, while it promotes glyphosate adsorption on dispersed ferrihydrite, which is ascribed to the increase of surface positive charge. Glyphosate predominately forms protonated and deprotonated, depending on the sorption pH, monodentate–mononuclear complexes (MMH1/MMH0, 77–90%) on ferrihydrites, besides minor deprotonated bidentate–binuclear complexes (BBH0, 23–10%). Both Al incorporation and a low pH favor the formation of the BB complex. The adsorbed glyphosate preferentially forms the MM complex on ferrihydrite and preferentially bonds with the Al–OH sites on Al-substituted ferrihydrite. These new insights are expected to be useful in predicting the environmental fate of glyphosate in ferrihydrite-rich environments.
In this letter, we report on the design, fabrication, measurement, and analysis of a tunable low-frequency and broadband radar absorber applied in the frequency range of 1-12 GHz. Numerical ...simulations indicate that absorbers based on the resistor-loaded frequency selective surface (FSS) can be resistively tuned to give a broadband absorption of exceeding -10 dB between 1 and 12 GHz. Moreover, superior absorbing performance can be achieved by introducing capacitance paralleled with resistance. Measurement results show that the radar absorber, by way of configuration with active FSS (AFSS) controlled by p-i-n diodes, can be tuned to provide a continuously variable reflectivity level of less than -10 dB from 2 to 11.3 GHz with varied bias voltages. Furthermore, experimental results have good agreement with simulations.
Nowadays, hydrogel-based sensors have drawn great attention owing to the growing demand for wearable devices. However, tailoring the property of the hydrogel sensor through a facile approach remains ...a great challenge. In this work, inspired by natural plants, a stretchable, adhesive and conductive hydrogel was prepared via the coordination between gallic acid (GA) and Zn2+ and chemical cross-linking. The dynamic crosslinking provided greater structural integrity for the polyvinyl alcohol / polyacrylamide (PVA/PAM) double network, endowing the hydrogel with high mechanical performance (0.25 MPa at 910% tensile strain, and 1.21 MPa at 70% compressive strain). Meanwhile, the presence of GA enabled the hydrogel with excellent repeatable adhesive performance, which greatly solved the problem of signal loss caused by poor adhesion. Moreover, the addition of ZnCl2 enhanced the ionic conductivity and gauge factor of the hydrogel. Besides, the conductive hydrogel exhibited successively stable changes of resistance signals under different external stimuli (5–500% strains and 80–200 mm/min rates) and superior durability (over 500 cycles). The hydrogel-based wearable sensors demonstrated excellent sensing performance in detecting various human motions. The multifunctional PVA/PAM/GA-Zn2+ hydrogel has significant applications in soft robots and healthcare monitoring as the flexible strain sensor.
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•The hydrogel was prepared via the coordination and chemical cross-linking.•The prepared hydrogel has excellent mechanical properties performance.•Plant-derived GA makes the hydrogels have good adhesion properties.•the hydrogel exhibited successively stable changes of resistance signals
Conductive hydrogels are gaining significant attention as promising candidates for the fabrication materials for flexible electronics. Nevertheless, improving the tensile properties, hysteresis, ...durability, adhesion, and electrochemical properties of these hydrogels remains challenging. This work reports the development of a novel semi‐interpenetrating network poly(ionic liquid) hydrogel named PATV, via the in situ polymerization of acrylamide, N‐Tris(hydroxymethyl)methyl acrylamide, and 1‐vinyl‐3‐butylimidazolium tetrafluoroborate. The density functional theory calculations reveal that the poly(ionic liquid) in the hydrogel network acts as physical cross–linking points to construct hydrogen‐bond networks. Furthermore, the hydrogen‐bond networks dissipate energy efficiently and quickly, and thus stress concentration and hysteresis are avoided. The prepared hydrogel has a low hysteresis (9%), high tensile properties (900%), fast response (180 ms), high sensitivity (gauge factor = 10.4, pressure sensitivity = 0.14 kPa−1), and wide sensing range (tensile range: 1–600%, compression range: 0.1–20 kPa). A multifunctional sensor designed based on the designed hydrogel enables real‐time, rapid, and stable response‐ability for the detection of human movement, facial expression recognition, pronunciation, pulse, handwriting, and Morse code encryption. Furthermore, the assembled triboelectric nanogenerator displays an excellent energy harvesting capability, thus highlighting its potential application in self‐powered flexible wearable electronic devices.
A semi‐interpenetrating poly(ionic liquid) network‐driven low hysteresis and transparent hydrogel as a self‐powered multifunctional sensor is reported in this work. The multifunctional sensor enables the real‐time, rapid, and stable response ability of different types of human movement. Furthermore, the assembled triboelectric nanogenerator displays an excellent energy harvesting capability.
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•FeN4-doped carbon nanotubes by ball milling and pyrolysis of ZIF-8 and MIL-101.•D2-FeN4 the main active site in PMS activation.•1O2 the major active species in the degradation of ...organic pollutants.•Minor contributions from •OH and SO4∙- radicals to pollutant degradation.
Development of low-cost, high-performance catalysts for the effective degradation of organic dyes is of both fundamental and technological significance for environmental remediation. Herein, FeN4-doped carbon nanotubes exhibit a remarkable catalytic activity towards the degradation of acid orange 7 (AO7) in the presence of peroxymonosulfate (PMS). This is accounted for by the abundant well-dispersed FeN4 sites and appropriate adsorption energy. Radical quenching experiments and electron paramagnetic resonance measurements suggest that singlet oxygen is the main reactive oxygen species. 57Fe Mossbauer spectroscopy measurements show that the FeN4 moieties contain multiple spin states, and in conjunction with density functional theory calculations, confirm that FeN4 with a low/medium spin state serves as the key sites for PMS activation and hence AO7 degradation. Results from this study highlight the critical role of spin states in FeN4 in the generation of singlet oxygen for effective degradation of organic pollutants.
Several international centers have used and reported pediatric-inspired regimens for adolescent and adult patients with Philadelphia chromosome-negative acute lymphoblastic leukemia (Ph- ALL). ...However, there is a lack of prospective data on the Chinese population. Herein, we performed a prospective study with a pediatric-inspired regimen (IH-2014 regimen) in treating adolescent and adult Ph- ALL patients in our center. From 2014 to 2021, a total of 415 patients aged between 14 and 65 years (median age, 27) were included in this study. After a median follow-up of 40.8 months, the 5-year overall survival, disease-free survival, and event-free survival rates were 53.8%, 51.1% and 45.0%, respectively. The regimen was generally well tolerated and safe, and the overall chemotherapy-related mortality was 3.6%. Age ≥ 40 years and persistent detectable minimal residual disease (MRD) post-induction were independent prognostic factors. Traditional risk factors for adult patients combined with MRD post-induction exhibit predictive significance for survival and relapse, which is helpful in the selection of subsequent treatment. Patients with high risk factors who can achieve deep MRD response after induction do not derive benefit from allogeneic hematopoietic stem cell transplantation.
Objective. To investigate the risk factors of systemic inflammatory response syndrome (SIRS) induced by flexible ureteroscope combined with Holmium laser lithotripsy. Patients and Methods. The ...clinical data from 216 consecutive patients who had undergone flexible ureteroscope combined with Holmium laser lithotripsy between August 2015 and May 2019 were retrospectively analyzed. To identify the risk factors of systemic inflammatory response syndrome induced by flexible ureteroscope combined with Holmium laser lithotripsy, the cases were divided into two groups according to whether they developed postoperative SIRS: SIRS group (21 cases) and non-SIRS group (195 cases). Age, gender, body mass index, stone size, surgery time, stone location, hydronephrosis, urine culture, hospital stay, stone-free rate, ureteral access sheath, and diabetes mellitus were collected. Univariate analysis was performed to calculate the potential factors. In order to determine the independence of the various factors, factors that potentially contributed to SIRS were compared between the SIRS group and the non-SIRS group. Furthermore, multivariate logistic regression analysis was used to identify the risk factors of systemic inflammatory response syndrome induced by flexible ureteroscopic lithotripsy. Results. All patients were successfully treated with flexible ureteroscopic lithotripsy. The incidence of SIRS after flexible ureteroscopic lithotripsy was 9.7%. The univariate analysis demonstrated the potential risk factors of systemic inflammatory response syndrome induced by flexible ureteroscopic lithotripsy were stone size (p=0.002), surgery time (p=0.01), urine culture (p≤0.001), and ureteral access sheath (p=0.001). Multivariable logistic regression analysis showed that stone size (p=0.002, OR=1.618; 95% CI, 0.452-0.844), surgery time (p≤0.001, OR=1.025; 95% CI, 1.016-1.034), urine culture (p≤0.001, OR=25.795; 95% CI, 22.131-30.065), and ureteral access sheath (p≤0.001, OR=6.101; 95% CI, 5.109-7.284) were independent risk factors for SIRS induced by flexible ureteroscopic lithotripsy. Conclusions. Stone size, surgery time, urine culture, and ureteral access sheath are independent risk factors for SIRS induced by flexible ureteroscopic lithotripsy. Patients with these high-risk factors should be carefully evaluated to reduce systemic inflammatory response syndrome.
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