Accurate detection of objects in 3D point clouds is a central problem in many applications, such as autonomous navigation, housekeeping robots, and augmented/virtual reality. To interface a highly ...sparse LiDAR point cloud with a region proposal network (RPN), most existing efforts have focused on hand-crafted feature representations, for example, a bird's eye view projection. In this work, we remove the need of manual feature engineering for 3D point clouds and propose VoxelNet, a generic 3D detection network that unifies feature extraction and bounding box prediction into a single stage, end-to-end trainable deep network. Specifically, VoxelNet divides a point cloud into equally spaced 3D voxels and transforms a group of points within each voxel into a unified feature representation through the newly introduced voxel feature encoding (VFE) layer. In this way, the point cloud is encoded as a descriptive volumetric representation, which is then connected to a RPN to generate detections. Experiments on the KITTI car detection benchmark show that VoxelNet outperforms the state-of-the-art LiDAR based 3D detection methods by a large margin. Furthermore, our network learns an effective discriminative representation of objects with various geometries, leading to encouraging results in 3D detection of pedestrians and cyclists, based on only LiDAR.
To assess how the current COVID-19 epidemic influenced peoples' utilization of emergency dental services in Beijing, China.
The first-visit patients seeking emergency dental services before or at the ...beginning of the COVID-19 epidemic were retrieved. Their demographic characteristics and the reasons for visiting were recorded and analyzed.
There were 2,537 patients involved in this study. Thirty-eight percent fewer patients visited the dental urgency at the beginning of the COVID-19 epidemic than before. The distribution of dental problems has changed significantly. The proportion of dental and oral infection raised from 51.0% of pre-COVID-19 to 71.9% during COVID-19, and dental trauma decreased from 14.2% to 10.5%. Meanwhile, the non-urgency cases reduced to three-tenths of pre-COVID-19.
Within the limitation of this study, the COVID-19 epidemic had a strong influence on the utilization of emergency dental services.
The past decades have witnessed an increasing interest in developing advanced polymerization techniques subjected to external fields. Various physical modulations, such as temperature, light, ...electricity, magnetic field, ultrasound, and microwave irradiation, are noninvasive means, having superb but distinct abilities to regulate polymerizations in terms of process intensification and spatial and temporal controls. Gas as an emerging regulator plays a distinctive role in controlling polymerization and resembles a physical regulator in some cases. This review provides a systematic overview of seven types of external-field-regulated polymerizations, ranging from chain-growth to step-growth polymerization. A detailed account of the relevant mechanism and kinetics is provided to better understand the role of each external field in polymerization. In addition, given the crucial role of modeling and simulation in mechanisms and kinetics investigation, an overview of model construction and typical numerical methods used in this field as well as highlights of the interaction between experiment and simulation toward kinetics in the existing systems are given. At the end, limitations and future perspectives for this field are critically discussed. This state-of-the-art research progress not only provides the fundamental principles underlying external-field-regulated polymerizations but also stimulates new development of advanced polymerization methods.
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Oily water treatment has become an urgent need in our daily life because of its harmful potential to the ecological system. In recent years, functional materials with superwetting or ...superantiwetting property have experienced a rocketing development due to their applications in various areas, including self-cleaning, anti-icing, printing, water collection, liquid transfer, oil/water separation, and so on. In this regard, recent advances in polymer science hold the promise of fine-tuning the composition and morphology for a targeted design to meet the requirements in specific application fields. This review focused on polymeric materials, especially smart polymers, for controllable oil/water separations. Starting from the fundamental theories and criteria related to the separation mechanisms, different stimuli including pH, solvent, ions, chemicals, temperature, photo, electric, pressure, and dual stimuli for triggering smart oil/water separation processes were summarized. Highlights on polymer types, polymer synthesis approaches, separation materials fabrication method, as well as separation performances were present. Current limitations and future perspective were also given. This review aims to offer deep insights into polymer-based interfacial science and provide guidance for the fabrication of smart polymeric surfaces for oily water separation.
•A newly improved under-load cascading failure model are established.•The method to assess the network robustness and resilience are proposed.•The threshold of key parameter to protect global energy ...and food security is obtained.•There is no positive correlation between network robustness and resilience.•We should pay more attention to the little and countries to handle the risk.
The Russian- Ukraine War has and further influence the global energy and food security. However, the detailed influence degree, key weak points and influence process is still unclear in the current. Therefore, this study established a newly improved under-load cascading failure model with consideration of overload limitation, and used it to evaluate influence of Russian- Ukraine War on the global energy and food security. This study also proposed a method to assess the network structure characteristic including robustness and resilience through model simulation under different scenarios. The main results include: The upper limitation of node load has the dominant function on the global energy and food security, while the influence of lower limitation parameter of node load has limited function. All of the networks have relative consistent recover and anti-damage ability against Russian and Ukraine War and the global panic except barley network. A key phenomenon we should concern is that the largest trade flow amounts are not occurred in the failure nodes. The failure nodes are always the countries with low economic scale and political status. The results tell us that we should further strengthen the importance of enhance production ability and energy types to resist the risk of Russian and Ukraine War. The global international organizations are also required to strengthen the function of balance the global security demand of energy and food between big countries and small countries. We should pay more attention to the little countries in the Africa and Asia to handle the risk.
Mechanoresponsive polymers have garnered significant attention in recent years, due to their great potential application in stress/strain sensing and damage warning. Several reviews of ...mechanochemistry have been published recently. In this review, we mainly focus on the most established mechanophore, spiropyran (SP), from an engineering perspective. We present a workflow for SP mechanochemistry, applications in various polymeric systems and impacting factors, as well as characterization techniques. Current limitations and future research directions are briefly highlighted in the end. This review aims to offer deep insight into polymer mechanochemistry and provide approaches to study other mechanophores using the example of SP mechanochemistry in polymers.
In this study we systematically reviewed 1203 research papers published between 2008 and 2018 in China and recorded related data on eight kinds of soil heavy metals (Cr, Pb, Cd, Hg, As, Cu, Zn, and ...Ni). Based on that, the pollution levels, ecological risk and health risk caused by soil heavy metals were evaluated and the pollution hot spots and potential driving factors of different heavy metals in different provinces were also identified. Results indicated accumulation of heavy metals in soils of most provinces in China compared with background values. Consistent with previous findings, the most prevalent polluted heavy metals were Cd and Hg. Polluted regions are mainly located in central, southern and southwestern China. Hunan, Guangxi, Yunnan, and Guangdong provinces were the most polluted provinces. For the potential health risk caused by heavy metals pollution, children are more likely confront with non-carcinogenic risk than adults and seniors. And children in Hunan and Guangxi province were experiencing relatively larger non-carcinogenic risk. In addition, children in part of provinces were undergoing potentially carcinogenic risks due to soil heavy metals exposure. Furthermore, in our study the 31 provinces in mainland China were divided into six subsets according to corresponding potential driving factors for heavy metal accumulation. Our study provide more comprehensive and updated information for contributing to better soil management, soil remediation, and soil contamination control in China.
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•Cd and Hg were the most polluted heavy metals in soil across China.•The ER values for Cd in 30 provinces varied from moderate to very high risk.•Hunan, Guangxi, Yunnan and Guangdong were confirmed as priority control provinces.•Children are undergo larger health risk than adults and seniors in China.•Controlling factors of heavy metals accumulation in different provinces were mapped.
To investigate the characteristics and risk factors of perioperative hypertension during dental implant surgeries with bone augmentation.
A retrospective cohort study was conducted. Seven hundred and ...twenty-eight cases underwent dental implant placement and bone augmentation in Peking University School and Hospital of Stomatology from September 2021 to August 2022 were recruited in this study according to the inclusion and exclusion criteria. They were divided into different groups according to the exposure factors which were gender, age, surgical time, and surgical approach. The correlation between perioperative hypertension and the exposure factors was analyzed.
The average systolic blood pressure variability was 9.93%±6.63% (maximum 50.41%), the average diastolic blood pressure variability was 12.45%±8.79% (maximum 68.75%), and the average mean arterial pressure variability was 10.02%±6.61% (maximum 49.48%). The incidence rate of perioperative hypertension was 26.77%. Male, age ≥ 60 years, and surgical tim
A detailed heterogeneous model considering the thermodynamic incompatibility was developed to simulate polyurethane/poly(methyl methacrylate) (PU/PMMA) interpenetrating polymer network (IPN) ...formation. The Gibbs free energy was calculated to predict the phase separation point and a two‐film theory was used to quantify the mass transfer between the PU‐rich phase and the PMMA‐rich phase. Compared with the homogeneous model, the cross‐linking density of PMMA increases rapidly during the network formation, because the monomer dispersion in two phases improves the possibility of free radical cross‐linking reaction, whereas the cross‐linking density of PU is unaffected. Simulations show that the partitioning of monomer significantly affects the PMMA network structure. The phase separation is strongly dependent on the onset of MMA polymerization. The proposed model allows visualizing of the IPN formation process and provides direction for reducing the extent of phase separation. Moreover, the structural information derived from the simulations can be further related to the properties.
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•Novel S-CQDs/hollow tubular g-C3N4 photocatalyst was successfully fabricated.•HTCN-C(2) exhibited excellent photocatalytic activity for Escherichia coli photodestruction.•The changes ...of Escherichia coli morphology and inside contents were verified by SEM images.•h+, O2− and OH radicals participate in the photocatalytic degradation process.•Cycle experiments revealed the outstanding photo-stability and reusability.
Microbial contamination and antibiotic pollutions diffusely exist in wastewater system, and contaminated water poses a threat to public health. Therefore, there is a need to effectively remove biohazard and antibiotic contamination from wastewater systems. In this paper, sulfur doped carbon quantum dots (S-CQDs)/hollow tubular g-C3N4 photocatalyst (HTCN-C), prepared via ultrasonic assisted synthesis strategy, was regarded as an efficient catalyst for the degradation of antibiotic (tetracycline) and destruction of a typical Gram-negative bacterium (Escherichia coli) in imitated wastewater system. The unique structures of hollow tubular g-C3N4 and loading of modified carbon quantum dots enhanced electron transfer and charge separation, leading to a significant improvement in photocatalytic efficiency. Benefiting from these merits, the optimized catalysts (HTCN-C(2)) exhibited superior performance with a reaction rate of 0.0293 min−1 for tetracycline (TC) degradation and 99.99% destruction of Escherichia coli under visible-light irradiation. Moreover, the characterization of UV–Vis diffuse reflectance spectra, photoluminescence technique, transient photocurrent responses and electrochemical impedance spectroscopy also verified the good optical and electrochemical properties of resultant samples. Our current work indicates that HTCN-C has great potential in degradation of antibiotic and destruction of bacterium for practical wastewater treatment.
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