Journal of University of Chinese Academy of Sciences

DFT mechanistic insight into the modular strategy involved in the palladium-catalyzed synthesis of cyclopentenones from α,β-unsaturated acid chlorides and alkynes

ZHONG Liang, ZHAO Ruihua, WANG Zhixiang

2022, 39 (2): 145-153. DOI: 10.7523/j.ucas.2021.0046

Abstract ( 653 ) PDF (0KB) ( 0 )

Cyclopentenones are important synthetic building blocks and as motifs appear in bioactive molecules and natural products. We applied density functional theory (DFT) calculations to gain insight into the modular strategy involved in the palladium-catalyzed synthesis of cyclopentenone from α,β-unsaturated acid chlorides and alkynes in the presence of hydrosilane. The study unveils that the transformation proceeds via the sequence:the disassembly of α,β-unsaturated acid chloride into vinyl, carbonyl, and Cl fragments with the palladium catalyst; carbon monoxide release; coupling of alkyne with vinyl group; carbon monoxide re-coordination and migratory insertion to form another C-C bond with alkyne, ring-closure via C=C bond insertion, transmetalation with hydrosilane, C, H-reductive elimination to release the product. Different from the mechanism proposed by the experimentalists, the CO group is involved in the reaction via separate liberation and re-coordination in the solvent cage, rather than persistent coordination with palladium. The transmetalation for H/Cl exchange takes place at the late stage and is a bottleneck of the transformation, instead of at early disassembly stage.

Research of dehydration-inducible gene RD in characterization and function

GONG Shufang, CHU Mingyang, YANG Yahan, QIAO Kun, WANG Jin'gang

2022, 39 (2): 154-164. DOI: 10.7523/j.ucas.2020.0054

Abstract ( 528 ) PDF (0KB) ( 0 )

Responsive to dehydration (RD) is a class of genes that regulates dehydration in plants. They are functionally tolerant to plant dehydration, some of which are responsive to abiotic stresses such as low temperature and high salinity. However, they belong to different families, respectively, and have discrepancy in the structure and function. In this paper, the structural composition, conserved motif, regulatory mechanism, and the function in response to biotic and abiotic stress were summarized in different RDs, as well as the different cis-acting elements in the promoter region played a role in response to abiotic stress so as to provide relevant basis for future researches on RD.

Chosen-plaintext attack to linear unitary optical encryption systems

MIAO Dong, MA Rui, SUN Xinkai, SHI Yishi

2022, 39 (2): 165-171. DOI: 10.7523/j.ucas.2020.0025

Abstract ( 372 ) PDF (0KB) ( 0 )

The study of optical encryption algorithm has become an important part of optics research today. Double random phase encoding (DRPE) in 4F system and in Fresnel domain are two typical cryptosystems. In spite of the fact that these two cryptosystems are both linear cryptosystems, the attacks on both systems are usually based on iterative phase retrieve algorithm. These crack algorithms mainly focus on the decipher of the key in the cryptosystem and seldom aim to construct the linear scrambling mapping the whole system stands for. This because one essential nature of these cryptosystems has been neglected for long time, the unitarity. With the condition of unitarity,optical attack theory can be independent from Kerckhoff' s rule and the public knowledge of the cryptosystem become irrelevant to attack algorithm. The complexity of the encryption system will not have any influence on the computation amount and crack result which is not the case in other attack algorithms. Thusly, we proposed a new method of subspace projection optical chosen-plaintext attack based on the linear and unitary nature of DPRE system, and it should fit for any linear unitary optical cryptosystems have been proposed and about to be proposed. We bring Dirac state vector and its representation linear algebra theory into our work for convenience as the Dirac state vector can stands for optical wavefront equally.

Spatio-temporal change of ecological land in lake-basin of Yangtze River system

CHEN Zhongyuan, GAO Yongnian

2022, 39 (2): 172-184. DOI: 10.7523/j.ucas.2021.0045

Abstract ( 613 ) PDF (0KB) ( 0 )

The area of lake type watershed (LTW) accounts for more than 30% of the Yangtze River basin, and the change of its ecological land plays an important role in regulating the water ecological environment of the Yangtze River. Based on the land use data of 229 LTWs in the Yangtze River system from 1980 to 2015, the temporal and spatial change characteristic of ecological land in recent decades was analyzed by using the methods of ecological land area and its proportion, improved comprehensive dynamic degree, transfer matrix, and spatial operation. The results showed that the change of ecological land use in the LTWs presented a three-stage trend of "first gradually increasing, then fluctuating and stable, and finally rapidly decreasing"; Woodland and grassland showed a downward trend, while wetland showed an upward trend; The comprehensive dynamic degree of ecological land in the LTWs presented a state of "wave-like vibration". From the perspective of lake size classification, the total area of ecological land in the four types of LTW was quite different. The watershed ecological land corresponding to small lakes was the least, followed by large and medium-sized lakes, while the watershed ecological land area of super large lakes was the largest. Although the ecological land change trend in different types of LTWs was first rising and then declining, the corresponding turning points appeared in different years. From the perspective of different regions of the Yangtze River system, compared with 1980, the ecological land of the LTW in the source, middle, and lower regions increased in 2015, while the ecological land of the LTW in the upper regions decreased; The transfer amount within ecological land was the least, and the transfer amount between ecological land and non-ecological land and the transfer amount within nonecological land accounted for more than 42% of the total transfer amount. The transfer of ecological land was the most complex and intense in the middle region, followed by the lower region, the source region and the upper region were relatively gentle and simple. Before 2000, the main reasons for the change of ecological land were cutting trees, developing agriculture and animal husbandry and reclaiming land from lakes. After 2000, the main reasons were returning farmland to forests and building reservoirs. The increase of construction land, i. e., urban expansion, was one of the main reasons for the decrease of ecological land for most LTWs from 2010 to 2015.

Potential absorption distance for Rb⁺ by Stipa purpurea and Leontopodium nanum in an alpine steppe

KONG Qian, NIU Haishan

2022, 39 (2): 185-192. DOI: 10.7523/j.ucas.2020.0039

Abstract ( 432 ) PDF (0KB) ( 0 )

Micro-patches are basic spatial units of steppe vegetation, which cause redistribution of soil nutrients during the formation and break of the patches. To what extent the resources in inter-patch bare ground could be utilized by plants is of an important issue to be answered. In this study, we injected rare elemental tracer Rb⁺ into the soil at different distances from the vegetation patch. By measuring the amount and distance of Rb⁺ being absorbed by vegetation micro-patches, we found that:1) the average potential absorption distance of Rb⁺ by the dominant species Stipa purpurea is 5.6 cm, which almost equals the average interval of 5.7 cm among patches; 2) the average potential absorption distance by companion species Leontopodium nanum is 34.2 cm, which is much larger than that of S. purpurea and average interval among patches; 3) the total amount of Rb⁺ absorption is significantly positively correlated (P<0.001) with the biomass/size of the micro-patches in both species. These results indicate that the nutrient resources in the bare soil are accessible to adjacent plant patches and that large patches have higher utilization potential and broader foraging area than small ones.

Ab initio simulations of NO adsorption on hematite (0001) surface: PBE versus PBE+U

WU Cuixia, SUN Tao, FABRIS Stefano, DU Lin

2022, 39 (2): 193-200. DOI: 10.7523/j.ucas.2020.0041

Abstract ( 543 ) PDF (0KB) ( 5 )

NO_x(x=1,2) are major air-pollutants detrimental to human health and much effort has been devoted to find efficient photocatalysts capable of removing NO_x from air (de-NO_x). Recent experiments indicate that hematite (α-Fe₂O₃) is a promising de-NO_x photocatalyst. However some key features of the NO adsorption on the hematite surface remain unclear, hindering further comprehension of the photocatalytic process. Here we study the adsorption of NO on the hematite (0001) surface using the PBE+U method with a dispersion correction (vdw) in the framework of density functional theory (DFT). We find the addition of a Hubbard U term in the DFT Hamiltonian strongly affects the adsorption properties, with the adsorption energy (-0.64eV) decreased by 50% with respect to those of PBE (-1.31eV). This decrease is attributed to two factors:(i) the U term shifts the energy of Fe 3d orbitals away from the valence band maximum, making them chemically less active; (ii) the NO molecule has an unpaired π^* electron and is more sensitive to the electronic structure of the substrate. In contrast to the inclusion of U, the dispersion correction causes little change to the adsorption properties except increases the adsorption energy by about -0.18eV. We use the Langmuir formula to calculate the thermal equilibrium coverage of NO on the hematite (0001) surface and find predictions made with the PBE+U vdw are more consistent with experiments. These results highlight the importance of strong electronic correlations in describing the hematite surface reactions, and may serve as a starting point to unravel the complete photocatalytic mechanism.

A LiDAR data visualized management and analysis system for power line inspection application based on B/S architecture

LIANG Lei, XI Xiaohuan, WANG Cheng, WANG Jinliang, HUANG Youju

2022, 39 (2): 201-207. DOI: 10.7523/j.ucas.2020.0044

Abstract ( 525 ) PDF (0KB) ( 36 )

LiDAR, being an active remote sensing technology, can obtain 3D information of surface feature and has extensive applications in power line fields, such as construction line selection, digital management, safety inspection, etc. However, the software visualized management ability is a serious limitation of its widespread use. In this paper, we built the overall and functional design of a LiDAR data visualized management and analysis system based on B/S architecture, focusing on electric power line inspection application requirements. WebGL was applied to develop this system and points cloud data were stored and indexed by an improved modifiable nested octree, and rendered by Levels of Detail and other technologies. A lot of practical function and tools, such as interaction in 3D scene, managing data of power line features, editing point cloud attribute, 3D measurement, clipping, profile map and points cloud filtering were all achieved. The research results show that LiDAR electric power line inspection in web browser is applicable and effective, and has prospective application in future.

A multichannel SAR-GMTI method based on low-rank and one-dimensional sparse matrix decomposition

ZHENG Huimin, ZHENG Mingjie, ZHANG Zhenning, SHEN Xiaotian

2022, 39 (2): 208-216. DOI: 10.7523/j.ucas.2020.0003

Abstract ( 378 ) PDF (0KB) ( 0 )

After being regrouped and processed, the data of the multichannel SAR-GMTI (synthetic aperture radar-ground moving target indicator) system can be considered as a joint matrix composed of three matrices, namely, a low-rank matrix of ground clutter, a sparse matrix of moving targets, and an entry-wise matrix of noise component. The existing GMTI method based on matrix decomposition can cause error by the impact of the strong clutter or slow-moving targets. Moreover, the weighted parameters in the optimization model are not redefined according to the actual application. To solve these problems, an adaptive weighted parameter and matrix decomposition model are designed in this paper, and a new multi-channel SAR-GMTI method based on low-rank and one-dimensional sparse matrix decomposition is proposed to improve the accuracy of matrix decomposition. The results based on the simulation data and the real data from Gaofen-3 SAR satellite demonstrate that the proposed method can accurately extract moving targets without clutter and noise components, and can obtain better performance in slow-moving target detection and strong clutter suppression too.

Ground target tracking and approaching based on multi-rotor drone and kernel correlation filtered visual detection

WANG He, BU Zhiyong, TAN Chong

2022, 39 (2): 217-223. DOI: 10.7523/j.ucas.2020.0002

Abstract ( 370 ) PDF (0KB) ( 0 )

Currently, ground target tracking and approaching based on drone is one of the hot spots for research in the military and civilian sectors. Aiming at the problems of relative motion and guidance control in the tracking and approaching of ground targets based on UAV platform, DJI multi-rotor aircraft platform was selected to design a ground station system based on Android. The system uses an improved kernel correlation filtering visual detection algorithm to complete ground target tracking and position locking. It uses the distance between the drone and the target as a scale factor to achieve multiscale tracking, and integrates FHOG + Lab + LBP features to represent the target to increase the tracker.Robustness. Proportional guidance law is used to control the multi-rotor aircraft to complete the target tracking and approaching tasks. The experimental surface improved algorithm has improved success rate and accuracy compared with the original algorithm. At the same time, the use of proportional guidance can control the multi-rotor drone to complete the tracking and approaching tasks.

Coded caching in hierarchical network with centralized and decentralized strategy

WANG Ke, CHEN Jiahui, WU Youlong

2022, 39 (2): 224-231. DOI: 10.7523/j.ucas.2020.0017

Abstract ( 342 ) PDF (0KB) ( 0 )

For a hierarchical network consisting of a server, multiple relays and multiple users, this paper studies on how to utilize cache at user and relay nodes to reduce the transmission delay. We propose novel coded caching schemes for the centralized and decentralized settings respectively. Our centralized scheme achieves better performance but requiring a fixing number of users, and our decentralized scheme supports flexible network change with only small loss of performance. Both schemes combine the traditional caching technology with network coding, and exploit the relays' cache resource to assist the transmission between the server and users. Moreover, our schemes allow parallel transmission between the server and relay, and achieve multicast gain by using coding during the delivery phase. The simulation results show that compared to the previous scheme, our schemes can greatly reduce the transmission delay without increasing the caching size.

Data fusion algorithm of wireless sensor network based on BP neural network optimized by improved grey wolf optimizer

CAO Ke, TAN Chong, LIU Hong, ZHENG Min

2022, 39 (2): 232-239. DOI: 10.7523/j.ucas.2020.0004

Abstract ( 558 ) PDF (0KB) ( 0 )

In order to improve the accuracy of the fusion data in wireless sensor network, reduce the energy consumption, and extend the network lifetime, data fusion algorithm of wireless sensor network based on improved grey wolf optimizer to optimize BP neural network (IGWOBPDA) is proposed in this paper. Firstly to balance the global and local search capabilties, the improved considering the actual energy consumption and clustering of the wireless sensor network's transmitting nodes, a clustering scheme based on node residual energy parameters and node density parameters is proposed,which adjusts the weighting factors to adapt to the actual situation of the network data fusion transmission process. Compared with BPNDA algorithm and GAPSOBP algorithm, simulation results show that IGWOBPDA algorithm has better data fusion accuracy and convergence in different data sets, which can effectively reduce the amount of data transmission and node energy consumption, extend network survival time, and maintain stability under different network scales. control parameter and the method of dynamic weight update position is proposed in the paper, which aims at the problems that the initial value of BP neural network in wireless sensor network data fusion algorithm is sensitive and the result can easily be the local optimal solution. Secondly,

A new joint model for extracting overlapping relations based on deep learning

ZHAO Minjun, ZHAO Yawei, ZHAO Yajie, LUO Gang

2022, 39 (2): 240-251. DOI: 10.7523/j.ucas.2020.0026

Abstract ( 872 ) PDF (0KB) ( 0 )

With the rapid developments of Internet technologies and popularization of Internet among daily activities, we are surrounded by all kinds of information every moment. Hence, to mine valuable information from massive data has always been a hotspot of research at home and abroad. In this environment, relationship extraction is an important subtask of information extraction, which purpose is to identify the relationship between entities from the text, so as to mine the structured information in the text, that is, fact triplet. In the text, entity overlapping and relationship overlapping are very common phenomena, but the existing joint extraction model cannot effectively solve such problems, so the paper proposes a new joint extraction model, which regards the relationship extraction task as consisting of entity recognition and relationship recognition of two subtasks. The two subtasks are identified using sequence labeling method and multi-classification method, respectively. In the joint extraction process, in order to fully mine the semantic information of the text, the part of speech (POS) and syntactic dependency (Deprel) features were added to the input layer of the model. Attention mechanism is also introduced in the model, which can eliminate the problem of long-distance dependence as sentence length increases. Finally, the paper conducts relationship extraction experiments on the NYT dataset and the WebNLG dataset. The experimental results show that the model proposed in the paper can effectively solve the problem of overlapping relationships and obtain the best extraction effect.

A novel user pairing scheme for millimeter wave non-orthogonal multiple-access networks

LU Xiaolin, ZHOU Yong

2022, 39 (2): 252-259. DOI: 10.7523/j.ucas.2020.0016

Abstract ( 306 ) PDF (0KB) ( 0 )

For the features of high-speed and multiple-requirements of multiple users in 5G millimeter wave networks, in order to further enhance the downlink non-orthogonal multiple-access transmission in millimeter wave networks, a novel user pairing scheme based on angle and distance is proposed in this paper. This scheme fully considers the high directional beam-forming of the antenna array and the randomness of the user. The base station will choose to enable the nonorthogonal multiple access scheme based on the instantaneous spatial angle difference and the distance information between the paired users. Using methods from stochastic geometry, we derive the ergodic sum rate of the proposed scheme. Simulation results show that this scheme outperforms four other common user pairing schemes, and there is an optimal value of the distance threshold that maximizes the ergodic sum rate.

Optimal computing node placement in fog-enabled networks

LI Xuanfeng, LUO Xiliang

2022, 39 (2): 260-266. DOI: 10.7523/j.ucas.2020.0028

Abstract ( 381 ) PDF (0KB) ( 0 )

Fog computing is a promising solution to enable computation-intensive and latencycritical applications in Internet of Things (IoT). Considering that the placement of computing nodes (CNs) directly affect the task offloading performance, this paper addresses the optimal CN placement problem in a fog-enabled network. By jointly considering the communication and computing abilities of CNs, the problem is formulated as a p-center problem, which is NP-hard. To solve such a problem, we first give a lower bound on the number of required CNs and then propose two efficient heuristic algorithms to place the CNs with low complexity. Numerical results verify the advantages of the proposed algorithms.

Online task offloading in mobile edge computing

LIU Ting, LUO Xiliang

2022, 39 (2): 267-274. DOI: 10.7523/j.ucas.2020.0012

Abstract ( 381 ) PDF (0KB) ( 0 )

To reduce the costs of task processing, task offloading is put forward as a promising technology in mobile edge computing. In this paper, in order to lessen the burden of long-term tasks of the moving user, we utilize Markov decision process to formulate the task offloading problem as a stochastic programming problem, when taking the user mobility and system dynamics into account. According to the system information state, the problem can be categorized as the one with fully known system information and the other one with limited system information. We provide the optimal and learning-based task offloading algorithms under these two kinds of systems respectively. Furthermore, two learning-based algorithms, one with optimality and another with faster convergence rate, are proposed. The performance is verified in simulations.

On the efficiency of user-level parallel file systems

DENG Tongliang, CHEN Chen, YIN Shu

2022, 39 (2): 275-282. DOI: 10.7523/j.ucas.2020.0027

Abstract ( 651 ) PDF (0KB) ( 6 )

A common and easier way to deploy parallel filesystem is using the user-space file system framework (FUSE). However, it serves as an I/O interposition layer which crosses user and kernel space that may introduce significant overhead due to the user-kernel mode switches, context switches and additional memory copies. This paper designs a method based on dynamic linking techniques to bypass FUSE, and implements the interposition layer in user space. This method is implemented and evaluated in parallel log-structured file system which is a popular parallel file system for checkpointing. The experiments and evaluation show that it can improve 131% of the read performance when the transfer block size is large, and improve 5 times write performance at small transfer block size and guarantee no significant write performance downgrade in other scenarios.

An all-digital multiphase delay-locked loop with phase-blender structure

SUN Haoxin, HONG Qinzhi, GUAN Wu, LIANG Liping

2022, 39 (2): 283-288. DOI: 10.7523/j.ucas.2020.0010

Abstract ( 405 ) PDF (0KB) ( 6 )

The conventional multiphase DLL may suffer from the problem of large power and area, designed in a full-custom design flow that is labor intensive and cost lots of hours. An all-digital DLL is proposed to generate multiphase clock signals. The proposed DLL is designed in a cell-based design flow using SMIC 55 nm CMOS technology. In this paper, the phase-blender structure is used to generate multiphase output signals, the phase-blender structure can also be extended to multiple cascaded stages for more outputs. Compared to the traditional multiphase DLL, the proposed design is area efficient and the power consumption is low. Designed in the cell-based design flow, the paper saves a lot of hours in the design phase. Post-layout simulation results reveal that the proposed DLL operates at 860 MHz-1. 04 GHz with 21 outputs. The design occupies 0. 001 7 mm² area and the average resolution is 13 ps. Power consumption is 2. 66 mW at the supply voltage of 1.2 V.

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