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.
Besides the relatively high redox potential of the adopted S super(2-)/Sn super(2-) polysulfide redox couple electrolyte, the parasitic charge recombination process is another significant factor that ...limits the open-circuit voltage and consequent power conversion efficiency (PCE) of quantum dot sensitized solar cells (QDSCs). Herein, we report a facile method to modify the polysulfide electrolyte with the addition of polyethylene glycol (PEG) additives to suppress the charge recombination occurring at the TiO sub(2)/QDs/electrolyte interfaces. Impedance spectroscopy and open circuit voltage decay (OCVD) measurements reveal that the PEG additive in the polysulfide electrolyte reduces interfacial recombination when compared with the conventional polysulfide electrolyte in the absence of the PEG additive. A dramatic enhancement of PCE from 5.80% to 6.74% was observed with the introduction of 15 wt% PEG in the polysulfide electrolyte in CdSe based QDSCs. Moreover, the PEG additive also improves the photovoltaic performance stability of the resultant cells.
The aim of this article is to explore the impact of housing investment on household entrepreneurship. Using survey data from China and employing a Probit model, we examine three aspects of housing ...status and innovatively subdivide household entrepreneurship into agricultural entrepreneurship and business entrepreneurship. The results show that households with higher housing investment are less likely to become agricultural entrepreneurs, but more likely to start a new business. Households with full-owned housing enjoy a higher likelihood to become business entrepreneurs. However, other ownerships have no relation with the choice of entrepreneurship. More housing loans discourage entrepreneurial activities. One exception is that bank loan raises the chance of being agricultural entrepreneurs. Households who build their own houses have a higher agricultural entrepreneurship. Buying market price houses encourages households to be business entrepreneurs. Low-price house and inherited house prevent households from being business entrepreneurs.
The use of doxorubicin (DOX) as an anthraquinone antineoplastic agent is limited due to its cardiotoxicity. Our previous study suggested that low-dose radiation (LDR) could mitigate the ...cardiotoxicity induced by DOX via suppressing oxidative stress and cell apoptosis. However, the molecular targets and protective mechanism of LDR are not understood. In the present study, we sought to investigate the mechanisms underlying LDR’s cardioprotection. Balb/c mice were randomly divided into four groups: Control group (no treatment), DOX group, LDR group (75 mGy), and LDR-72 h-DOX group (LDR pretreatment followed by intraperitoneal injection of DOX). Electron microscopy, PCR, and Western blot analyses indicated that LDR pretreatment mitigated changes in mitochondrial morphology caused by DOX, upregulated activity of mitochondrial complexes, and restored ATP levels in cardiomyocytes that were decreased by DOX. Whole genome microarray and PCR analyses showed that mitochondrial-related genes were altered by LDR pretreatment. Thus, our study showed that LDR can protect cardiomyocytes against DOX through improving mitochondrial function and increasing ATP production. This research could inform DOX chemotherapy strategies and provide new insight into the molecule mechanisms underlying the cardioprotective effects of LDR.
Due to the relatively high density of conventional non-sintered lightweight aggregate(NLA), a low-density core-shell NLA(CNLA) was developed. Moreover, two types of porous lightweight aggregate ...concrete (PLAC) for wallboard were designed, using both foam and lightweight aggregates. The effects of LA on lightweight concrete workability, compressive strength, dry shrinkage, and thermal conductivity were studied and compared. The bulk density of CNLA can be lowered to 500 kg/m
3
, and its cylinder crushing strength is 1.6 MPa. PLACs also have compressive strengths ranging from 7.8 to 11.8 MPa, as well as thermal conductivity coefficients ranging from 0.193 to 0.219 W/(m·K
−1
). The CNLA bonds better to the paste matrix at the interface transition zone, and CNLA concrete has a superior pore structure than SLA concrete, resulting in a 20% improvement in fluidity, a 10% increase in strength, a 6% reduction in heat conductivity, and an 11% decrease in drying shrinkage.
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.
Using a prefectural level data, we shed the light on the knowledge spillovers within three mega-economic zones (MEZs) in China by adopting spatial econometric methods. We first examine the spillovers ...within all regions, and then the spillovers within the MEZs, and finally the spillovers from core cities. The results show that there are pronounced spillovers between cities in China, which is stronger between cities with high techno-proximity. Moreover, spillovers within the MEZs are found to be stronger but unequal. Spillovers between cities in the Pearl River Delta are the greatest among the MEZs, while the spillovers within Jing-jin-ji are the lowest. Eventually, Shenzhen outperforms Shanghai and Beijing in knowledge spillovers, whereas Beijing may even adversely affect the innovation of neighbors.
An artificial microbial community consisted of Ketogulonicigenium vulgare and Bacillus megaterium has been used in industry to produce 2-keto-gulonic acid (2-KGA), the precursor of vitamin C. During ...the mix culture fermentation process, sporulation and cell lysis of B. megaterium can be observed. In order to investigate how these phenomena correlate with 2-KGA production, and to explore how two species interact with each other during the fermentation process, an integrated time-series proteomic and metabolomic analysis was applied to the system. The study quantitatively identified approximate 100 metabolites and 258 proteins. Principal Component Analysis of all the metabolites identified showed that glutamic acid, 5-oxo-proline, L-sorbose, 2-KGA, 2, 6-dipicolinic acid and tyrosine were potential biomarkers to distinguish the different time-series samples. Interestingly, most of these metabolites were closely correlated with the sporulation process of B. megaterium. Together with several sporulation-relevant proteins identified, the results pointed to the possibility that Bacillus sporulation process might be important part of the microbial interaction. After sporulation, cell lysis of B. megaterium was observed in the co-culture system. The proteomic results showed that proteins combating against intracellular reactive oxygen stress (ROS), and proteins involved in pentose phosphate pathway, L-sorbose pathway, tricarboxylic acid cycle and amino acids metabolism were up-regulated when the cell lysis of B. megaterium occurred. The cell lysis might supply purine substrates needed for K. vulgare growth. These discoveries showed B. megaterium provided key elements necessary for K. vulgare to grow better and produce more 2-KGA. The study represents the first attempt to decipher 2-KGA-producing microbial communities using quantitative systems biology analysis.
Aiming at the organophosphorus pesticide residues in tea, a method integrating solid-phase microextraction and liquid chromatography-mass spectrometry was investigated for the detection of ...organophosphorus pesticide residues in tea. Firstly, the conditions in the process were optimized; then the method was established to analyze the organophosphorus pesticides in tea; finally, the method feasibility was verified by using actual sample determination. In terms of the results, the standard curve correlation coefficients of the solid-phase microextraction and liquid chromatography-mass spectrometry methods used in the study were greater than 0.99, while the average recoveries ranged from 72 to 109% with the relative standard deviations (RSDs) of less than 9.0%. This indicates that the method has a good linear range, low detection limit and high recovery. In the application validation in real samples, the concentrations of organophosphorus pesticide residues in tea were within the safe range. The method was validated to be suitable for the monitoring and control of organophosphorus pesticide residues in tea with low cost and simplified sample preparation.
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.
PDF
