The rapid development of remote sensing technology allows us to get images with high and very high resolution (VHR). VHR imagery scene classification has become an important and challenging problem. ...In this paper, we introduce a framework for VHR scene understanding. First, the pretrained visual geometry group network (VGG-Net) model is proposed as deep feature extractors to extract informative features from the original VHR images. Second, we select the fully connected layers constructed by VGG-Net in which each layer is regarded as separated feature descriptors. And then we combine between them to construct final representation of the VHR image scenes. Third, discriminant correlation analysis (DCA) is adopted as feature fusion strategy to further refine the original features extracting from VGG-Net, which allows a more efficient fusion approach with small cost than the traditional feature fusion strategies. We apply our approach to three challenging data sets: 1) UC MERCED data set that contains 21 different areal scene categories with submeter resolution; 2) WHU-RS data set that contains 19 challenging scene categories with various resolutions; and 3) the Aerial Image data set that has a number of 10 000 images within 30 challenging scene categories with various resolutions. The experimental results demonstrate that our proposed method outperforms the state-of-the-art approaches. Using feature fusion technique achieves a higher accuracy than solely using the raw deep features. Moreover, the proposed method based on DCA fusion produces good informative features to describe the images scene with much lower dimension.
Segmentation of retinal vessels is important for doctors to diagnose some diseases. The segmentation accuracy of retinal vessels can be effectively improved by using deep learning methods. However, ...most of the existing methods are incomplete for shallow feature extraction, and some superficial features are lost, resulting in blurred vessel boundaries and inaccurate segmentation of capillaries in the segmentation results. At the same time, the “layer-by-layer” information fusion between encoder and decoder makes the feature information extracted from the shallow layer of the network cannot be smoothly transferred to the deep layer of the network, resulting in noise in the segmentation features. In this paper, we propose the MFI-Net (Multi-resolution fusion input network) network model to alleviate the above problem to a certain extent. The multi-resolution input module in MFI-Net avoids the loss of coarse-grained feature information in the shallow layer by extracting local and global feature information in different resolutions. We have reconsidered the information fusion method between the encoder and the decoder, and used the information aggregation method to alleviate the information isolation between the shallow and deep layers of the network. MFI-Net is verified on three datasets, DRIVE, CHASE_DB1 and STARE. The experimental results show that our network is at a high level in several metrics, with F1 higher than U-Net by 2.42%, 2.46% and 1.61%, higher than R2U-Net by 1.47%, 2.22% and 0.08%, respectively. Finally, this paper proves the robustness of MFI-Net through experiments and discussions on the stability and generalization ability of MFI-Net.
The ability to control drops and their movements on phobic surfaces is important in printing or patterning, microfluidic devices, and water-repellent materials. These materials are always ...micro-/nanotextured, and a natural limitation of repellency occurs when drops are small enough (as in a dew) to get trapped in the texture. This leads to sticky Wenzel states and destroys the superhydrophobicity of the material. Here, we show that droplets of volume ranging from femtoliter (fL) to microliter (μL) can be self-removed from the legs of water striders. These legs consist of arrays of inclined tapered setae decorated by quasi-helical nanogrooves. The different characteristics of this unique texture are successively exploited as water condenses, starting from self-penetration and sweeping effect along individual cones, to elastic expulsion between flexible setae, followed by removal at the anisotropic leg surface. We envision that this antifogging effect at a very small scale could inspire the design of novel applicable robust water-repellent materials for many practical applications.
Graphene is usually embedded into polymer matrices for the development of thermally conductive composites, preferably forming an interconnected and anisotropic framework. Currently, the directional ...self‐assembly of exfoliated graphene sheets is demonstrated to be the most effective way to synthesize anisotropic graphene frameworks. However, achieving a thermal conductivity enhancement (TCE) over 1500% with per 1 vol% graphene content in polymer matrices remains challenging, due to the high junction thermal resistance between the adjacent graphene sheets within the self‐assembled graphene framework. Here, a multiscale structural modulation strategy for obtaining highly ordered structure of graphene framework and simultaneously reducing the junction thermal resistance is demonstrated. The resultant anisotropic framework contributes to the polymer composites with a record‐high thermal conductivity of 56.8–62.4 W m−1 K−1 at the graphene loading of ≈13.3 vol%, giving an ultrahigh TCE per 1 vol% graphene over 2400%. Furthermore, thermal energy management applications of the composites as phase change materials for solar‐thermal energy conversion and as thermal interface materials for electronic device cooling are demonstrated. The finding provides valuable guidance for designing high‐performance thermally conductive composites and raises their possibility for practical use in thermal energy storage and thermal management of electronics.
The dual‐assembled graphene framework (DAGF), which combines a highly oriented graphene structure along the vertical direction and a low junction thermal resistance between the graphene building blocks, exhibits excellent performance in improving the thermal conductivity of polymers. The resultant composites have a record‐high thermal conductivity of 56.8–62.4 W m−1 K−1(≈13.3 vol%), significantly outperforming previously reported results.
In recent years, air pollution events have occurred frequently in China during the winter. Most studies have focused on the physical and chemical composition of polluted air. Some studies have ...examined the bacterial bioaerosols both indoors and outdoors. But few studies have focused on the relationship between air pollution and bacteria, especially pathogenic bacteria. Airborne PM samples with different diameters and different air quality index values were collected in Hangzhou, China from December 2014 to January 2015. High-throughput sequencing of 16S rRNA was used to categorize the airborne bacteria. Based on the NCBI database, the “Human Pathogen Database” was established, which is related to human health. Among all the PM samples, the diversity and concentration of total bacteria were lowest in the moderately or heavily polluted air. However, in the PM2.5 and PM10 samples, the relative abundances of pathogenic bacteria were highest in the heavily and moderately polluted air respectively. Considering the PM samples with different particle sizes, the diversities of total bacteria and the proportion of pathogenic bacteria in the PM10 samples were different from those in the PM2.5 and TSP samples. The composition of PM samples with different sizes range may be responsible for the variances. The relative humidity, carbon monoxide and ozone concentrations were the main factors, which affected the diversity of total bacteria and the proportion of pathogenic bacteria. Among the different environmental samples, the compositions of the total bacteria were very similar in all the airborne PM samples, but different from those in the water, surface soil, and ground dust samples. Which may be attributed to that the long-distance transport of the airflow may influence the composition of the airborne bacteria. This study of the pathogenic bacteria in airborne PM samples can provide a reference for environmental and public health researchers.
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•Total bacteria and pathogenic bacteria in airborne particulate matter were studied.•Air quality levels had a influence on total bacteria and pathogenic bacteria.•Particle sizes effected the distribution of total bacteria and pathogenic bacteria.•Relative humidity, carbon monoxide and ozone were the main factors.•The potential source environments of total bacteria were investigated.
Different concentrations and sizes of particulate matter, and various environmental factors were related to the variance of total bacteria and pathogenic bacteria.
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•The BTX production by Org-CaO/NZSM-5 is almost twice as that by conventional CaO/ZSM-5.•The proportion of aromatics and BTX with Org-CaO/NZSM-5 were up to 93% and 54%.•Org-CaO ...contributed to BTX formation during dual catalytic pyrolysis.•NZSM-5 promoted the conversion of bulky molecules into naphthalenes.
Catalytic pyrolysis of biomass wastes is a promising way to produce aromatics. Based on the conventional CaO/ZSM-5 system, this study aims to improve the aromatics yields by developing an upgraded system which combined nanosized ZSM-5 with CaO from organic calcium precursors (Org-CaO/NZSM-5). The results showed that the aromatics proportion in bio-oil from pyrolysis of Jatropha de-oiled cake with Org-CaO/NZSM-5 increased to 93%. The corresponding yield of BTX (benzene, toluene and xylene) and naphthalene was around 70% which was almost twice than that with conventional CaO/ZSM-5. Org-CaO showed better thermal cracking ability and deoxygenation with more hydrocarbons intermediates and higher H/Ceff of vapors, contributing to enhanced formation of BTX over NZSM-5. NZSM-5 contained much more mesopores and acid sites on external surface, promoting higher conversion of bulky molecules into naphthalenes. Compared with peanut shell, corncob and bagasse pyrolysis, Jatropha de-oiled cake pyrolysis produced much higher aromatics with Org-CaO/NZSM-5.
•A new type of heat exchanger design with four inlets and outlet is proposed.•The performance of the novel heat sink is studied by numerically and experimentally.•The effect of geometric parameters ...on the cooling ability is studied numerically.•The CFD results well agree with the numerical results.•The fatigue life of heat exchanger is analyzed and the numerical correlation of fatigue life is achieved.
To solve the problems of heat dissipation and improve the reliability of high heat flux electronic devices, a new W-type mini microchannel heat exchanger is proposed. Firstly, the effect of the inlet and outlet positions on the flow and thermal behaviors are discussed. Secondly, two traditional heat sinks are introduced to compare the cooling ability with the new exchanger. The results shows that the temperature difference of W-type heat exchanger is 10.4 K, which is lower than that of the two traditional channels. Thirdly, the effect of width for the intermediate channel and inlet annular channel length on heat transfer characteristics are analyzed. The results indicate that when the width of the intermediate channel is 4 mm and the channel length is 15.5 mm, the temperature uniformity of the heat exchanger is the best with appropriate pressure drop. On this basis, the experimental test is carried out to verify the numerical results. It is found that the maximum Nusselt number and pressure drop errors between numerical and experimental tests are 8.01% and 5.06%, respectively, which verifies the correctness of the numerical results. In addition, the strength of the heat exchanger is checked, and the maximum working stress is 249.76 MPa indicating that the strength of the heat exchanger meets the using requirements. Finally, the influence of ambient temperature on the fatigue life of heat exchanger is analyzed. The results show that the fatigue life presents a trapezoidal trend with the change of ambient temperature. Moreover, the numerical correlation of fatigue life is achieved.
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CaO is a traditional desulfurizer used in coal combustion, and it is also a widely applied chemical conditioner in sewage sludge dewatering. In this study, the feasibility of ...co-combustion of CaO-conditioned sludge (Sc-CaO) and coal was discussed, including combustion characteristics and gas pollutants emission. The results show that adding 30% Sc-CaO into co-combustion strengthened the procedure of devolatilization and volatiles combustion (220–380°C). But the main combustion performance (430–600°C) was still similar to that of coal. Conditioner CaO could capture almost all the SO2 during sludge mono-combustion and 15.8–48.4% of SO2 during co-combustion. Meanwhile, conditioner CaO also contributed to N2O catalytic reduction and mitigated the NO increase caused by the co-effect of raw sludge and coal at 900°C. Compared with physical additive CaO, conditioner CaO distributed evenly in sludge matrix and partially bonded to carbon, which was benefit to SO2 adsorption and N2O reduction. At the same time, the increase of NO was more mild than that caused by physical additive CaO. This study shows that co-combustion of Sc-CaO and coal is a suitable and promising technology for clean disposal of sewage sludge.
Abstract Background Percutaneous endoscopic lumbar discectomy (PELD) has been widely used for treating lumbar disc herniation (LDH). Recurrence after PELD has been reported, but few studies have ...focused on the risk factors responsible for PELD recurrence. Methods From March 2005 to March 2016, 116 patients suffering from recurrent herniation after successful PELD were enrolled in this retrospective study. Kaplan-Meier methods and Cox regression analysis were employed to identify the significant risk factors predicting PELD recurrence. Results Univariate analysis showed that age (≥ 50 years old), obesity (body mass index BMI ≥ 25), no smoking history, decreased reflexes, the learning curve of the surgeon (< 200 cases), the treatment period (2005.03-2010.09), Modic change, migrated herniation, and a central herniation are potential risk factors for PELD recurrence. Multivariate analysis suggested that age (≥ 50 years old), obesity (BMI ≥ 25), the learning curve of the surgeon (< 200 cases), the treatment period (2005.03-2010.09) and a central location of herniation are independent significant risk factors for PELD recurrence. Conclusions Obesity (BMI ≥ 25) was the most robust risk factor responsible for PELD recurrence. Age (≥ 50 years old), the learning curve of the surgeon (< 200 cases), the treatment period (2005.03-2010.09) and a central location of herniation were also closely associated with recurrent herniation after successful PELD.
Microorganisms are ubiquitous in the atmosphere, where they can disperse for a long distance. However, it remains poorly understood how these airborne microorganisms vary and which factors influence ...the microbial distribution in different anthropogenic activity regions. To explore the regional differences of bacteria and fungi in airborne particles, PM2.5 and PM10 samples were collected in the urban and rural areas of Hangzhou. The bacterial and fungal communities in the urban atmosphere was more similar to each other than those in the rural atmosphere. Analyses conducted by the concentration weighted trajectory model demonstrated that the local environment contributed more to the similarity of airborne bacteria and fungi compared with the atmospheric transport. The concentrations of local air pollutants (PM2.5, PM10, NO2, SO2 and CO) were positively correlated with the similarity of the bacterial and fungal communities. Additionally, the concentrations of these air pollutants in the urban site were about 1.5 times than those in the rural site. This implicated that anthropogenic activity, which is the essential cause of air pollutants, influenced the similarity of airborne bacteria and fungi in the urban area. This work ascertains the outdoor bacterial and fungal distribution in the urban and the rural atmosphere and provides a prospective model for studying the contributing factors of airborne bacteria and fungi.
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•Airborne microorganisms were more similar in more urbanized site.•Atmospheric transport made contribution to the source of bacteria and fungi.•Local environment made a greater contribution to the source of bacteria and fungi.•Air pollutants were positively correlated with the similarity of bacteria and fungi.
Exploring the distribution difference and influence factors of airborne bacteria and fungi in urban and rural areas shed light on the relationships between airborne microorganisms and air pollutants.
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