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The development of porous materials with flexible‐robust characteristics shows some unique advantages to target high performance for gas separation, but remains a daunting challenge to achieve so far. Herein, we report a carboxyl‐based hydrogen‐bonded organic framework (ZJU‐HOF‐8a) with flexible‐robust porosity for efficient purification of natural gas. ZJU‐HOF‐8a features a four‐fold interpenetrated structure with dia topology, wherein abundant supramolecular entanglements are formed between the adjacent subnetworks through weak intermolecular hydrogen bonds. This structural configuration could not only stabilize the whole framework to establish the permanent porosity, but also enable the framework to show some flexibility due to its weak intermolecular interactions (so‐called flexible‐robust framework). The flexible‐robust porosity of ZJU‐HOF‐8a was exclusively confirmed by gas sorption isotherms and single‐crystal X‐ray diffraction studies, showing that the flexible pore pockets can be opened by C3H8 and n‐C4H10 molecules rather by C2H6 and CH4. This leads to notably higher C3H8 and n‐C4H10 uptakes with enhanced selectivities than C2H6 over CH4 under ambient conditions, affording one of the highest n‐C4H10/CH4 selectivities. The gas‐loaded single‐crystal structures coupled with theoretical simulations reveal that the loading of n‐C4H10 can induce an obvious framework expansion along with pore pocket opening to improve n‐C4H10 uptake and selectivity, while not for C2H6 adsorption. This work suggests an effective strategy of designing flexible‐robust HOFs for improving gas separation properties. [ABSTRACT FROM AUTHOR]

Hydrogen-bonded organic frameworks (HOFs) have great potential as sensing platforms for specific molecular recognition due to their designable structures, high solution processability, and easy regeneration. However, the exploration of fluorescent HOFs for chemical sensing in water remains a challenge due to the need to combine excellent photoluminescence performance, high water stability, and specific recognition sites simultaneously. Herein, we report an aggregation-induced emission (AIE) active HOF (termed HOF-TPE-CN) built from a cyano-decorated tetraphenylethylene linker for highly fluorescent sensing of mono-nitrophenol isomers. Owing to the effective AIE effect, HOF-TPE-CN shows a notable enhancement in fluorescence emission, wherein the quantum yield of HOF-TPE-CN was notably increased to 21% compared with that of the TPE-CN ligand in DMF solution (2.89%). Most importantly, this HOF exhibits highly efficient fluorescence quenching toward mono-nitrophenol isomers in water, with a remarkably low detection limit of 0.65 μM. Furthermore, HOF-TPE-CN is more responsive and selective toward mono-nitrophenols compared with a series of homologues. Theoretical calculations combined with X-ray photoelectron spectroscopy revealed that there exist multiple van der Waals and hydrogen-bonding interactions between the trapped nitrophenol molecules and the HOF framework, which form ground-state complexation, resulting in fluorescence quenching by efficient photo-induced electron transfer. [ABSTRACT FROM AUTHOR]

Airborne synthetic aperture radar (SAR) is susceptible to atmospheric disturbance and other factors that cause the position offset error of the antenna phase center and motion error. In close-range detection scenarios, the large elevation angle may make it impossible to directly observe areas near the underlying plane, resulting in observation blind spots. In cases where the illumination elevation angle is extremely large, the influence of range variant envelope error and phase modulations becomes more serious, and traditional two-step motion compensation (MOCO) methods may fail to provide accurate imaging. In addition, conventional phase gradient autofocus (PGA) algorithms suffer from reduced performance in scenes with few strong scattering points. To address these practical challenges, we propose an improved phase-weighted estimation PGA algorithm that analyzes the motion error of UAV SAR under a large elevation angle, providing a solution for high-order range variant motion error. Based on this algorithm, we introduce a combined focusing method that applies a threshold value for selection and optimization. Unlike traditional MOCO methods, our proposed method can more accurately compensate for spatially variant motion error in the case of scenes with few strong scattering points, indicating its wider applicability. The effectiveness of our proposed approach is verified by simulation and real data experimental results. [ABSTRACT FROM AUTHOR]

Background radiation in the LiDAR detection field of view is complex and variable, and the background noise generated can easily cause false alarms in the receiver, which affects the effective detection of the system. Through the analysis of the influence of background radiation noise of LiDAR on the detection performance, an adaptive suppression method of LiDAR background noise is proposed. This method realizes the rapid suppression of background noise in the instantaneous field of view through an adaptive threshold adjustment of current steering architecture with a back-end digital-to-analog converter (DAC) correction based on the principle of constant false alarm rate (CFAR) control. Aiming at the problem of accurate noise detection and quantification in a very short time, a dynamic comparator is used to replace the traditional continuous comparator. While detecting the number of noise pulses, the measurement of the pulse duration of noise is realized, which improves the accuracy of short-time noise detection. In order to verify the actual effect of the adaptive method, experiments were carried out based on the team's self-developed LiDAR. The experimental results show that the measured noise ratio of the adaptive mode by using this method is the lowest. Even at 12 a.m., the noise ratio of the point cloud obtained by the adaptive mode is 0.012%, compared with 0.08% obtained by the traditional mode, which proves that this method has a good ability to suppress background noise. The proportion of noise reduction of the adaptive mode is more than 80% compared with the traditional mode. It achieves noise suppression through hardware at each detection, and each adjustment can be completed within a single period of pulse detection. Therefore, it has great advantages in real-time detection compared with the back-end software noise reduction processing method, and it is suitable for the application of LiDAR in the complex background environment. [ABSTRACT FROM AUTHOR]

The automotive synthetic aperture radar (SAR) can obtain two-dimensional (2-D) high-resolution images and has good robustness compared with the other sensors. Generally, the 2-D high-resolution always conflicts with the real-time requirement in conventional SAR imaging. This article suggests an automotive video SAR (ViSAR) imaging technique based on sub-aperture spectrum fusion to address this issue. Firstly, the scene space variation problem caused by close observation distance in automotive SAR is analyzed. Moreover, the sub-aperture implementation method, frame rate and resolution of automotive ViSAR are also introduced. Then, the improved Range Doppler algorithm (RDA) is used to focus the sub-aperture data. Finally, a sub-aperture stitching strategy is proposed to obtain a high-resolution frame image. Compared with the available ViSAR imaging method, the proposed method is more efficient, performs better, and is more appropriate for automotive ViSAR. The simulation results and actual data of the automotive SAR validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Gas separation is a crucial process for the production of many highly valuable chemical feedstocks in the petrochemical industry. Traditional separation technologies, including cryogenic distillation, chemisorption, and solvent extraction, are energy-intensive or environmentally unfriendly. The development of new separation technologies with low energy consumption and high efficiency is of significant importance for adapting to the increasing industrial demands. Adsorptive gas separation based on solid porous adsorbents has made much progress over the past few decades, benefiting from low cost, high efficiency, and environment friendliness. In this regard, porous metal–organic frameworks (MOFs), as a novel class of crystalline porous materials featuring adjustable structures and finely tunable pore metrics, have shown great promise to address various gas separation challenges. Furthermore, the highly crystalline nature of MOFs endows this kind of material with a unique advantage, providing an in-depth understanding of the structure–property relationship, which is crucial and meaningful to guide the design of separating materials for gas separation. Herein, we summarize the main advancements achieved in the last five years of developing MOFs as physisorbents for various critical gas separations, including but not limited to the separation of light hydrocarbons, C2H2/CO2, and Xe/Kr, and CO2 capture, and the separation mechanisms are also highlighted in each section. Finally, some challenges and perspectives in the design of MOFs for gas separation and industrial applications are outlined. [ABSTRACT FROM AUTHOR]

With the rapid development of high-resolution synthetic aperture radar (SAR) systems, the technique that utilizes multiple two-dimensional (2-D) SAR images with different view angles to extract three-dimensional (3-D) coordinates of targets has gained wide concern in recent years. Unlike the traditional multi-channel SAR utilized for 3-D coordinate extraction, the single-channel curvilinear SAR (CLSAR) has the advantages of large variation of view angle, requiring fewer acquisition data, and lower device cost. However, due to the complex aerodynamic configuration and flight characteristics, important issues should be considered, including the mathematical model establishment, imaging geometry analysis, and high-precision extraction model design. In this paper, to address these challenges, a 3-D vector model of CLSAR was presented and the imaging geometries under different view angles were analyzed. Then, a novel 3-D coordinate extraction approach based on radargrammetry was proposed, in which the unique property of the SAR system, called cylindrical symmetry, was utilized to establish a novel extraction model. Compared with the conventional approach, the proposed one has fewer constraints on the trajectory of radar platform, requires fewer model parameters, and can obtain higher extraction accuracy without the assistance of extra ground control points (GCPs). Numerical results using simulated data demonstrated the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Brucellosis is a chronic infectious disease caused by brucellae or other bacteria directly invading human body. Brucellosis presents the aggregation characteristics and periodic law of infectious diseases in temporal and spatial distribution. Taking major European countries as an example, this study established the temporal and spatial distribution sequence of brucellosis, analyzed the temporal and spatial distribution characteristics of brucellosis, and quantitatively predicted its epidemic law by using different traditional or machine learning models. This paper indicates that the epidemic of brucellosis in major European countries has statistical periodic characteristics, and in the same cycle, brucellosis has the characteristics of piecewise trend. Through the comparison of the prediction results of the three models, it is found that the prediction effect of long short-term memory and convolutional long short-term memory models is better than autoregressive integrated moving average model. The first mock exam using Conv layer and data vectorizations predicted that the convolutional long short-term memory model outperformed the traditional long short-term memory model. Compared with the monthly scale, the prediction of the trend stage of brucellosis can achieve better results under the single model prediction. These findings will help understand the development trend and liquidity characteristics of brucellosis, provide corresponding scientific basis and decision support for potential risk assessment and brucellosis epidemic prevention and control, and reduce the loss of life and property. [ABSTRACT FROM AUTHOR]

For unmanned aerial vehicle (UAV) synthetic aperture radar (SAR) imaging, motion errors cannot be obtained accurately when high precision motion sensors are not equipped on the platform. This means that traditional data-based motion compensation (MOCO) cannot be directly implemented due to large measurement errors. In addition, classic autofocusing techniques, such as phase gradient autofocus (PGA) or map-drift algorithm (MDA), do not perform well with spatially variant errors, greatly affecting the imaging qualities, especially for high-resolution and large-swath cases. In this study, an improved spatially variant MOCO approach based on an MDA is developed to effectively eliminate the spatially variant errors. Based on the coarse and precise MDA chirp rate error estimation, motion errors are optimally acquired by the random sample consensus (RANSAC) iteration. Two-dimensional (2D) mapping is used to decouple the spatially variant residual errors into two linear independent dimensions so that the chirp-z transform (CZT) can be performed for echo data correction. Unlike traditional approaches, the spatially variant components can be compensated without any measured motion information, which indicates that the proposed approach can be applied to the common UAV SAR system with significant measurement errors. Simulations and real data experiments were used to evaluate the performance of the proposed method. The simulation results show that the proposed algorithm is able to effectively minimize spatially variant errors and generate much better imaging results. [ABSTRACT FROM AUTHOR]

A facile approach to the fully substituted cyclopentenones involving an unprecedented benzofuran-ring-opening is described. The cleavage of a benzofuran endocyclic C2–O bond proceeded smoothly in the absence of any transition metal catalyst or highly reactive organometallic reagent. Such benzofuran-ring-opening is delicately incorporated into an acid-catalyzed cascade process, orchestrating a novel synthetic strategy for complex cyclopentenones with excellent yields and diastereoselectivities. [ABSTRACT FROM AUTHOR]

Objective: This study was to evaluate the risk factors of survival in patients with columnar cell variant (CCV) and encapsulated variant (ECV). Materials and methods: The Surveillance, Epidemiology, and End Results database (19882013) was used to compare the characteristics of CCV and ECV with those of classic papillary thyroid carcinoma (PTC). Survival was analyzed by the Kaplan-Meier method, the log-rank test, and Cox multivariate regression. Multivariate logistic regression was used to further analyze lymph node metastases and distant metastasis. There were 765 CCV, 529 ECV, and 39,035 PTC patients. ECV tumors were similar to PTC in terms of overall survival, disease-specific survival, age, sex, and distant metastasis. Results: Compared with PTC, CCV tumors tended to be larger, with a higher incidence rate among males and in patients ≥65 years of age. CCV was associated with higher rates of extrathyroidal extension, multifocality, lymph node examinations, and lymph node and distant metastases (p<0.0001). Significant differences were found in 10-year overall survival (97.14% vs 89.15%, p<0.0001) and disease-specific survival (99.08% vs 93.07%, p<0.0001) between PTC and CCV In CCV, distant metastasis (hazard ratio 5.125, p<0.0001) and lymph nodal metastasis (hazard ratio 2.152, p=0.032) predicted a poor prognosis. After adjustment, distant metastasis was independently associated with age >65 years, and lymph nodal metastasis was independently associated with female sex (odds ratio [OR] 0.341 [0.234-0.496]), extrathyroidal extension (OR 2.453 [1.368-4.397]), multifocality (OR 2.168 [1.318-3.569]), size >20 mm, ≤40 mm (OR 1.851 [1.170-2.928]), and size >40 mm (OR 1.847 [1.088-3.136]). Conclusion: ECV appears to have a similar prognosis to PTC, while CCV has a worse prognosis than classic PTC. Treatment with external beam radiotherapy and radioactive implants should be conducted carefully in patients with CCV. [ABSTRACT FROM AUTHOR]

A thin layer of a highly porous metal-organic framework material, ZIF-8, is fabricated uniformly on the surface of nanostructured transition metal oxides (ZnO nanoflakes and MnO2 nanorods) to boost the transfer of lithium ions. The novel design and uniform microstructure of the MOF-coated TMOs (ZIF-8@TMOs) exhibit dramatically enhanced rate and cycling performance comparing to their pristine counterparts. The capacities of ZIF-8@ZnO (nanoflakes) and ZIF-8@MnO2 (nanorods) are 28 % and 31 % higher that of the pristine ones at the same current density. The nanorods of ZIF-8@MnO2 show a capacity of 1067 mAh g−1 after 500 cycles at 1 Ag−1 and without any fading. To further improve the conductivity and capacity, the ZIF-8-coated materials are pyrolyzed at 700 °C in an N2 atmosphere (ZIF-8@TMO-700 N). After pyrolysis, a much higher capacity improvement is achieved: ZIF-8@ZnO-700 N and ZIF-8@MnO2-700 N have 54 % and 69 % capacity increases compared with the pristine TMOs, and at 1 Ag−1, the capacity of ZIF-8@MnO2-700 N is 1060 mAh g−1 after cycling for 300 cycles. [ABSTRACT FROM AUTHOR]

Segmented planar image detector for electro-optical reconnaissance (SPIDER) is a new type of lightweight and high-resolution computational imaging system that has applications in fields such as remote sensing terrain exploration, high precision military detection, and remote environmental monitoring. Currently, the lens combination methods used in the SPIDER system misses a large amount of the spatial-frequency information detected by each spoke's lens array. The SPIDER imaging principle was analyzed with a particular focus on understanding the effect of the lenslets combination method on image quality. To optimize the quality of reconstructed images, we have proposed a pseudo two-layer parity configuration. To compare the quality of image restoration using the pseudo two-layer parity combination methods with previously existing methods, the entire imaging process was numerically simulated and the peak signal-to-noise ratio of each reconstructed image was estimated. The simulation demonstrated that the reconstructed image obtained using the pseudo two-layer parity combination was more similar to the original image and exhibited a higher image quality than the images reconstructed using other methods. These results indicate that the optical structure of the SPIDER system can be optimized by implementing the pseudo two-layer parity aperture combination method and this provides theoretical support for the further development of the SPIDER system. [ABSTRACT FROM AUTHOR]