Fusion Zone Microstructure Evolution of Al-Alloyed TRIP Steel in Diode Laser Welding

TRansformation Induced Plasticity (TRIP) steels are promising materials to achieve a better combination of formability and strength than conventional steels due to their unique microstructural makeup. Though welding is a vital part of auto body manufacturing, the weldability of TRIP steels has some complex and poorly understood features, which has served to retard the growth of its applications in the automotive industry. In this study, autogeneous welds were carried out on Al-alloyed TRIP steel using a 4 kW diode laser. Both fusion zone solidification behavior and subsequent austenite transformation products were investigated with optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. In terms of solidification behavior, fusion zones solidified with high temperature -ferrite as the primary phase. Fusion zone microstructure at room temperature was composed of ferrite with a skeletal morphology characteristic of solidification, and austenite decomposition products almost all having a lath morphology. Skeletal ferrite covered about 30% fusion zone area. Upper bainite laths separated by retained austenite films comprised most of the transformed microstructure, about 65% of the fused area. Lower bainite with carbide particles dispersed in an aligned way, chunk shaped retained austenite, lath martensite and twinned martensite were also occasionally observed. The Al content was considered to be for a dominant influence on fusion zone microstructure evolution

Managing energy-water-carbon-food nexus for cleaner agricultural greenhouse production : a control system approach

DATA AVAILABILITY : Data will be made available on request.Poverty, food insecurity and climate change are global issues facing humanity, threatening social, economic and environmental sustainability. Greenhouse cultivation provides a potential solution to these challenges. However, some greenhouses operate inefficiently and need to be optimized for more economical and cleaner crop production. In this paper, an economic model predictive control (EMPC) method for a greenhouse is proposed. The goal is to manage the energy-water‑carbon-food nexus for cleaner production and sustainable development. First, an optimization model that minimizes the greenhouse's operating costs, including costs associated with greenhouse heating/cooling, ventilation, irrigation, carbon dioxide (CO2) supply and carbon emissions taking into account both the CO2 equivalent (CO2-eq) emissions caused by electrical energy consumption and the negative emissions caused by crop photosynthesis, is developed and solved. Then, a sensitivity analysis is carried out to study the impact of electricity price, supplied CO2 price and social cost of carbon (SCC) on the optimization results. Finally, a model predictive control (MPC) controller is designed to track the optimal temperature, relative humidity, CO2 concentration and incoming radiation power in presence of system disturbances. Simulation results show that the proposed approach increases the operating costs by R186 (R denotes the South African currency, Rand) but reduces the total cost by R827 and the carbon emissions by 1.16 tons when compared with a baseline method that minimizes operating costs only. The total cost is more sensitive to changes in SCC than that in electricity price and supplied CO2 price. The MPC controller has good tracking performance under different levels of system disturbances. Greenhouse environmental factors are kept within specified ranges suitable for crop growth, which increases crop yields. This study can provide effective guidance for growers' decision-making to achieve sustainable development goals.The Liaoning Province Educational Department and the National Natural Science Foundation of China.http://www.elsevier.com/locate/scitotenvhj2023Electrical, Electronic and Computer Engineerin

Destination Choice of Chinese Rural-Urban Migrant Workers: Jobs, Amenities and Local Spillovers

Using the 2014 China Migrants Dynamic Survey, we analyze rural-urban migrant workers’ destination choices after the global financial crisis, with an emphasis on jobs, amenities, and local spillovers. By using an equilibrium-sorting model, this paper disentangles local spillovers from local attributes in the estimation process. We employ both an artificial instrumental variable and the provincial highway passenger flow in 1979 to tackle the endogeneity issue. After controlling for the network effects of migrants from the same origin, we found a separate and strong preference for co-locating with a large population of migrants, regardless of origin. The results remain robust when we take into account labor supply-driven migration, spatial autocorrelation between provinces, different industry definitions, and regional differences within provinces. Our results imply that due to institutional barriers, the rural migrant community will still be a very important factor in the foreseeable future. In addition, as the ongoing industrial upgrading and transfer policies in China may lead to a westward movement of rural-urban mig

Successful drug-eluting stent implantation in a male patient with dextrocardia: a case report

Situs inversus with dextrocardia is a rare condition, with complete transposition of all the body organs, including the heart. Percutaneous coronary intervention (PCI) in these patients is technically difficult because of the mirror image of organs. Here, we describe a 56-year-old man with coronary heart disease with known situs inversus with dextrocardia and coronary percutaneous intervention was performed for stenosis in the right coronary artery. A drug eluting stent was implanted at this site successfully. This case suggested that the interventional management of such patients follows the same general rules as for non-dextrocardia patients, but the manipulation of the catheter and projection position choices need to be taken into consideration to obtain optimal benefits for the patient

Application of Teager–Kaiser Energy Operator in the Early Fault Diagnosis of Rolling Bearings

Rolling bearings are key components that support the rotation of motor shafts, operating with a quite high failure rate among all the motor components. Early bearing fault diagnosis has great significance to the operation security of motors. The main contribution of this paper is to illustrate Gaussian white noise in bearing vibration signals seriously masks the weak fault characteristics in the diagnosis based on the Teager–Kaiser energy operator envelope, and to propose improved TKEO taking both accuracy and calculation speed into account. Improved TKEO can attenuate noise in consideration of computational efficiency while preserving information about the possible fault. The proposed method can be characterized as follows: a series of band-pass filters were set up to extract several component signals from the original vibration signals; then a denoised target signal including fault information was reconstructed by weighted summation of these component signals; finally, the Fourier spectrum of TKEO energy of the resulting target signal was used for bearing fault diagnosis. The improved TKEO was applied to a vibration signal dataset of run-to-failure rolling bearings and compared with two advanced diagnosis methods. The experimental results verify the effectiveness and superiority of the proposed method in early bearing fault detection

Three-dimensional meteorological drought characteristics and associated risk in China

Drought as a hazardous natural disaster has been widely studied based on various drought indices. However, the characteristics of droughts have not been robustly explored considering its dual nature in space and time across China in the past few decades. Here, we characterized meteorological drought events from a three-dimensional perspective for the 1961–2018 period in the mainland of China, and attributed the variation of drought intensity to its influencing factors. We further assessed associated drought risk with socioeconomic data for the 2002–2018 period. We found that drought events with high intensity, large area, and long duration are mainly distributed in western and northern China, especially in Inner Mongolia, Xinjiang, Tibet, and Qinghai. The drought intensity and affected area anomalies present a six-phase pattern of ‘negative-positive-negative-positive-negative-positive’ during 1961–2018. The intensity of drought events showed a decreasing trend but the affected area and duration showed an increasing trend in 2009–2018. Over the decades, the centers of high drought intensity and long duration tend to move eastward and northeastward, respectively. The PET variations contributes larger than precipitation variations to drought intensity variations in the arid regions while being opposite in the humid southern regions. Drought risk assessment further indicates that high drought risk areas are concentrated in northern China, including Inner Mongolia, Xinjiang, Gansu, Sichuan, Hebei, and Heilongjiang. Increasing trends in drought risk for the 2002–2018 period are detected in Inner Mongolia, Xinjiang, Sichuan, Henan, Gansu, Hunan, Shanxi, Qinghai. Our findings provide scientific guidance for policymakers to develop adaptive disaster prevention measures

Multimodality molecular imaging to monitor transplanted stem cells for the treatment of ischemic heart disease.

PURPOSE: Non-invasive techniques to monitor the survival and migration of transplanted stem cells in real-time is crucial for the success of stem cell therapy. The aim of this study was to explore multimodality molecular imaging to monitor transplanted stem cells with a triple-fused reporter gene [TGF; herpes simplex virus type 1 thymidine kinase (HSV1-tk), enhanced green fluorescence protein (eGFP), and firefly luciferase (FLuc)] in acute myocardial infarction rat models. METHODS: Rat myocardial infarction was established by ligating the left anterior descending coronary artery. A recombinant adenovirus carrying TGF (Ad5-TGF) was constructed. After transfection with Ad5-TGF, 5 × 10(6) bone marrow mesenchymal stem cells (BMSCs) were transplanted into the anterior wall of the left ventricle (n = 14). Untransfected BMSCs were as controls (n = 8). MicroPET/CT, fluorescence and bioluminescence imaging were performed. Continuous images were obtained at day 2, 3 and 7 after transplantation with all three imaging modalities and additional images were performed with bioluminescence imaging until day 15 after transplantation. RESULTS: High signals in the heart area were observed using microPET/CT, fluorescence and bioluminescence imaging of infarcted rats injected with Ad5-TGF-transfected BMSCs, whereas no signals were observed in controls. Semi-quantitative analysis showed the gradual decrease of signals in all three imaging modalities with time. Immunohistochemistry assays confirmed the location of the TGF protein expression was the same as the site of stem cell-specific marker expression, suggesting that TGF tracked the stem cells in situ. CONCLUSIONS: We demonstrated that TGF could be used as a reporter gene to monitor stem cells in a myocardial infarction model by multimodality molecular imaging

Nitrogen removal performance and microbial community changes in subsurface wastewater infiltration systems (SWISs) at low temperature with different bioaugmentation strategies

Poor nitrogen removal efficiency (mainly nitrate, NO3 −-N) at low temperatures strongly limits application of subsurface wastewater infiltration systems (SWISs). Seven psychrophilic strains (heterotrophic nitrifying bacteria and aerobic denitrifying bacteria) were isolated and added to SWISs to investigate the effect of embedding and direct-dosing bioaugmentation strategies on sewage treatment performance at low temperature. Both bioaugmentation strategies improved ammonium (NH4 +-N) removal efficiencies, and the embedding strategy also exhibited satisfactory NO3 −-N and total nitrogen (TN) removal efficiencies. Pyrosequencing results of the bacterial 16S rRNA gene indicated that the embedding strategy significantly decreased the indigenous soil microbial diversity (p <.05) and altered the bacterial community structure, significantly increasing the relative abundance of Clostridia, which have good nitrate-reducing activity