Beamspace processing is widely applied in Direction‐of‐Arrival (DOA) estimation thanks to dimensional reduction and super‐resolution characterisations. However, the conventional atomic norm ...minimisation (ANM) based methods for beamspace DOA estimation are of high computational complexity for large arrays. To deal with this issue, the proposed method focuses on locating the sources in the mainlobe of the beamspace and encodes such prior information into the ANM problem without frequency‐selective constraints. The proposed method approximates the beamspace array manifold in the mainlobe sector with the truncated sector Fourier series. The theoretical analysis shows that such approximation with the properly designed fitting error relaxation on the boundary yields the low dimensional semidefinite programming (SDP) approximate implementation of the proposed ANM method and guarantees the support recovery inside the mainlobe. Furthermore, the low complexity Burer‐Monteiro factorisation based alternating direction method of multipliers method is proposed to solve the SDP problem. The complexity analysis and simulations show that the proposed method results in significant computational complexity reduction and slightly better performance compared with state‐of‐art benchmarks.
The conventional atomic norm minimisation (ANM) based methods for beamspace Direction‐of‐Arrival (DOA) estimation are of high computational complexity for large arrays. To deal with this issue, the proposed method focuses on locating the sources in the mainlobe of the beamspace and proposes the low complexity ANM based beamspace DOA estimation method.
Recent advances in trajectory replanning have enabled quadrotor to navigate autonomously in unknown environments. However, high-speed navigation still remains a significant challenge. Given very ...limited time, existing methods have no strong guarantee on the feasibility or quality of the solutions. Moreover, most methods do not consider environment perception, which is the key bottleneck to fast flight. In this article, we present RAPTOR, a robust and perception-aware replanning framework to support fast and safe flight, which addresses these issues systematically. A path-guided optimization approach that incorporates multiple topological paths is devised, to ensure finding feasible and high-quality trajectories in very limited time. We also introduce two perception-aware planning approaches to actively observe and avoid unknown obstacles. A risk-aware trajectory refinement ensures that unknown obstacles which may endanger the quadrotor can be observed earlier and avoid in time. The motion of yaw angle is planned to actively explore the surrounding space that is relevant for safe navigation. The proposed methods are tested extensively through benchmark comparisons and challenging indoor and outdoor aggressive flights. We release our implementation as an open-source package 1 for the community.
Fe‐hydrogenase is an efficient biological hydrogenation catalyst. Despite intense research, Fe complexes mimicking the active site of Fe‐hydrogenase have not achieved turnovers in hydrogenation ...reactions. Herein, we describe the design and development of a manganese(I) mimic of Fe‐hydrogenase. This complex exhibits the highest activity and broadest scope in catalytic hydrogenation among known mimics. Thanks to its biomimetic nature, the complex exhibits unique activity in the hydrogenation of compounds analogous to methenyl‐H4MPT+, the natural substrate of Fe‐hydrogenase. This activity enables asymmetric relay hydrogenation of benzoxazinones and benzoxazines, involving the hydrogenation of a chiral hydride transfer agent using our catalyst coupled to Lewis acid‐catalyzed hydride transfer from this agent to the substrates.
The design and development of a manganese(I) mimic of Fe‐hydrogenase is reported. This complex exhibits the highest activity and broadest scope in catalytic hydrogenation among known mimics. Thanks to its biomimetic nature, the complex exhibits unique activity in the hydrogenation of compounds analogous to methenyl‐H4MPT+, the natural substrate of Fe‐hydrogenase.
Room temperature phosphorescence (RTP) materials with long persistent luminescence (LPL) have raised particular attention among researchers for their potential uses in chemical sensing, optical ...recording devices, biological imaging, and security systems applications, due to the long‐lived triplet states. In this study, one‐pot method of reaction of appropriate ratio of crown ether ligand (15‐Crown‐5) and metallic salts (CdX2) is utilized to yield three metal halide‐based complexes (namely 15‐5‐CdCl2, 15‐5‐CdBr2, and 15‐5‐CdI2). In solid state, three complexes exhibit nearly standard white light emission with CIE coordinates of (0.28, 0.32), (0.31, 0.39), (0.30, 0.34) at room temperature under UV radiation of 340 nm. Meanwhile, they display the excitation‐dependent room temperature phosphorescence from blue/cyan to green/yellow, especially, 15‐5‐CdCl2 and 15‐5‐CdBr2 exhibit color‐tunable and visible LPL with time‐resolved luminescence lifetime as high as 1–2 s. Single‐crystal X‐ray diffraction analysis and theoretical calculations reveal that the bright LPL of 15‐5‐CdCl2 and 15‐5‐CdBr2 arise from the crown ether ligand and aggregation state induced by halogen‐bond. The thus obtained LPL provides potentials in lighting and displaying devices, optical recording devices, security systems and so on.
A macrocyclic molecule 15‐crown‐5 with CdX2 was hydrothermally constructed into metal‐organic linker, which was built into 2D metal‐organic frameworks with metal halide chains that play an external heavy atom effect to achieve long persistent luminescence at room temperature. Near white light emission is achieved in a single component, moreover adjustable phosphorescence is realized with longest visual time of 1‐2 s at ambient conditions.
Microglia and astrocytes, the two innate cells in CNS, are thought to protect and remodel of synapses for proper maintenance and plasticity of neuronal circuits. The two types of cells are the major ...responders by producing and releasing inflammatory mediators. Isolation of microglia and astrocytes from CNS tissue provides a powerful tool to study basic cell biology and examine the effects of in vivo treatments on microglia and astrocytes immunophenotype and function. The widely used approach of enrichment microglia and astrocytes from CNS was MACS (Magnetic activated cell sorting) and FACS (Fluorescence activated cell sorting). Here we described an optimized protocol of enzymatic dissociation generating single cell suspensions from brain tissue. Then the ability of the two methods to isolate microglia and astrocytes from brain dissociated cells was compared. Both MACS and FACS processing could obtain microglia and astrocytes with high viability (>85%). Microglia sorted by MACS comprises a slight myeloid cells contamination but with a little bit higher efficiency than that sorted by FACS. MACS processing was faster than FACS for either single or multiple samples. ACSA2 can be used to isolate astrocytes from both postnatal and adult brain, and is more suitable for purify astrocytes from newborn. FACS could get purer microglia which is helpful for deep sequencing and other related research. ACSA2 is a good marker of astrocytes.
We report herein an unprecedented highly efficient Guerbet‐type reaction at room temperature (catalytic TON up to >6000). This β‐alkylation of secondary methyl carbinols with primary alcohols has ...significant advantage of delivering higher‐order secondary alcohols in an economical, redox‐neutral fashion. In addition, the first enantioselective Guerbet reaction has also been achieved using a commercially available chiral ruthenium complex to deliver secondary alcohols with moderate yield and up to 92 % ee. In both reactions, the use of a traceless ketone promoter proved to be beneficial for the catalytic efficiency.
A highly efficient Guerbet‐type reaction at room temperature (catalytic TON up to >6000) is reported. This β‐alkylation of secondary methyl carbinols with primary alcohols delivers higher‐order secondary alcohols in an economical, redox‐neutral fashion. This first enantioselective Guerbet reaction has also been achieved using a commercially available chiral ruthenium complex to deliver secondary alcohols with moderate yield and up to 92 % ee.
With the rapid development of science and technology, cloud classroom teaching has gradually become a trend. The cloud-based music teaching aid training system designed in this paper learns to map ...rhythmic and pitch features through music sequence generation technology. The onset detection algorithm of spectral flux detects the onset of the note. The Bezier curve is introduced into the melodic line feature generation algorithm to construct a polynomial function for interpolation between the first and the last endpoints, and the emotion is utilized to guide fractal music creation. Finally, the effectiveness of this auxiliary teaching system in college music teaching has been verified. The results show that the optimal Hamming distance of the system is 0.353 in the music melody generation experiment, which indicates that the system can quickly generate melody lines for students in music teaching and improve their learning efficiency. The system can significantly improve the rationality and efficiency of music skill training, which is worth promoting.
We present herein an unprecedented diastereoconvergent synthesis of vicinal diamines from diols through an economical, redox‐neutral process. Under cooperative ruthenium and Lewis acid catalysis, ...readily available anilines and 1,2‐diols (as a mixture of diastereomers) couple to forge two C−N bonds in an efficient and diastereoselective fashion. By identifying an effective chiral iridium/phosphoric acid co‐catalyzed procedure, the first enantioconvergent double amination of racemic 1,2‐diols has also been achieved, resulting in a practical access to highly valuable enantioenriched vicinal diamines.
Under cooperative ruthenium and Lewis acid catalysis, readily available anilines and 1,2‐diols (as a mixture of diastereomers) couple to forge two C−N bonds in an efficient and diastereoselective fashion. By identifying an effective chiral iridium/phosphoric acid co‐catalyzed procedure, enantioconvergent double amination of racemic 1,2‐diols has also been achieved, resulting in a practical access to highly valuable enantioenriched vicinal diamines.
Deep reinforcement learning (RL) comprehensively uses the psychological mechanisms of "trial and error" and "reward and punishment" in RL as well as powerful feature expression and nonlinear mapping ...in deep learning. Currently, it plays an essential role in the fields of artificial intelligence and machine learning. Since an RL agent needs to constantly interact with its surroundings, the deep Q network (DQN) is inevitably faced with the need to learn numerous network parameters, which results in low learning efficiency. In this paper, a multisource transfer double DQN (MTDDQN) based on actor learning is proposed. The transfer learning technique is integrated with deep RL to make the RL agent collect, summarize, and transfer action knowledge, including policy mimic and feature regression, to the training of related tasks. There exists action overestimation in DQN, i.e., the lower probability limit of action corresponding to the maximum Q value is nonzero. Therefore, the transfer network is trained by using double DQN to eliminate the error accumulation caused by action overestimation. In addition, to avoid negative transfer, i.e., to ensure strong correlations between source and target tasks, a multisource transfer learning mechanism is applied. The Atari2600 game is tested on the arcade learning environment platform to evaluate the feasibility and performance of MTDDQN by comparing it with some mainstream approaches, such as DQN and double DQN. Experiments prove that MTDDQN achieves not only human-like actor learning transfer capability, but also the desired learning efficiency and testing accuracy on target task.
Fe‐hydrogenase, the third type of natural hydrogenase, is capable to heterolytically activate hydrogen molecule and transfer the resulting hydride to an unsaturated substrate, making it a promising ...hydrogenation catalyst. Over the last three decades, fruitful results on this enzyme have been achieved. In this review, we have summarized the major progresses about this enzyme including its structural characterisation, catalytic mechanism, cofactor biosynthesis, mimetic model development as well as artificial enzymes construction. In the meanwhile, challenges and opportunities of this enzyme and its mimetic systems in the application of synthetic chemistry and others are discussed.
Fe‐hydrogenase can heterolytically cleave H2 and transfer the resulting hydride to an unsaturated substrate. Fruitful results have been achieved from studies on enzyme function, structure, catalytic mechanism, cofactor biosynthesis, biomimetic model development and artificial enzyme construction. But application scenarios of this enzyme are still in absence.
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![Current State of [Fe]‐Hydro...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0947-6539/small "Current State of [Fe]‐Hydrogenase and Its Biomimetic Models")