基于AMASPGD算法的FSOC系统波前畸变校正及性能分析

为了抑制相干自由空间光通信系统中大气湍流引起光信号波前失真的不利影响,提出了一种基于聚合动量(AM)和自适应矩边界(AdaMod)优化器的增强型随机并行梯度下降(SPGD)算法。仿真结果表明,该优化算法可以显著提高收敛速度和鲁棒性,并有效降低波前畸变的峰谷值和均方根,从而更有效地抑制大气湍流对相干自由空间光通信(FSOC)系统混频效率和误码率的负面影响。

海洋环流模式的并行I/O优化研究

极端气象日益加剧,严重影响人类的生产生活。如何有效应对未来极端环境变化,更关乎国际竞争。因此,发展高精度高分辨率的地球系统模式推动气候变化研究至关重要。随着模式精度和分辨率的不断提高,I/O性能已成为制约模式计算效率和可扩展性的瓶颈。选取典型的海洋环流模式LICOM3作为研究对象,基于天河HPC系统,详细测试和分析了模式的I/O逻辑过程,发现在3K进程规模下I/O可占整体运行时间一半以上,是限制模式计算性能的关键因素。为此,设计并实现了主要输出过程的MPI-IO并行优化方案,显著提升了模式运行效率,基本解决了模式I/O瓶颈。测试结果表明,MPI-IO并行优化方案将输出时间占比从48.58%降到2.44%,将输出带宽提升到6.21 GB/s,约是原程序的14倍。此外,进一步分析了影响并行I/O性能的因素,以期为相关工作提供参考和指导。

GLOBAL RIGIDITY THEOREMS FOR SUBMANIFOLDS WITH PARALLEL MEAN CURVATURE

In this paper,we mainly study the global rigidity theorem of Riemannian submanifolds in space forms.Let Mn(n≥3)be a complete minimal submanifold in the unit sphere Sn+p(1).Forλ∈[0,n2−1/p),there is an explicit positive constant C(n,p,λ),depending only on n,p,λ,such that,if∫MSn/2dM<∞,∫M(S−λ)n/2+dM<C(n,p,λ),then Mn is a totally geodetic sphere,where S denotes the square of the second fundamental form of the submanifold and∫+=max{0,f}.Similar conclusions can be obtained for a complete submanifold with parallel mean curvature in the Euclidean space Rn+p.

Multi-objective Collaborative Optimization for Scheduling Aircraft Landing on Closely Spaced Parallel Runways Based on Genetic Algorithms

A scheduling model of closely spaced parallel runways for arrival aircraft was proposed,with multi-objections of the minimum flight delay cost,the maximum airport capacity,the minimum workload of air traffic controller and the maximum fairness of airlines′scheduling.The time interval between two runways and changes of aircraft landing order were taken as the constraints.Genetic algorithm was used to solve the model,and the model constrained unit delay cost of the aircraft with multiple flight tasks to reduce its delay influence range.Each objective function value or the fitness of particle unsatisfied the constrain condition would be punished.Finally,one domestic airport hub was introduced to verify the algorithm and the model.The results showed that the genetic algorithm presented strong convergence and timeliness for solving constraint multi-objective aircraft landing problem on closely spaced parallel runways,and the optimization results were better than that of actual scheduling.

Actuation Spaces Synthesis of Lower-Mobility Parallel Mechanisms Based on Screw Theory

The lower-mobility parallel mechanism has been widely used in the engineering field due to its numerous excellent characteristics.However,little work has been devoted to the actuator selection and placement that best satisfy the system's functional requirements during concept design.In this study,a unified approach for synthesizing the actuation spaces of both rigid and flexure parallel mechanisms has been presented,and all possible combinations of inputs could be obtained,laying a theoretical foundation for the subsequent optimization of inputs.According to the linear independence of actuation space and constraint space of the lower-mobility parallel mechanism,a general expression of actuation spaces in the format of screw systems is deduced,a unified synthesis process for the lower-mobility parallel mechanism is derived,and the efficiency of the method is validated with two selective examples based on screw theory.This study presents a theoretical framework for the input selection problems of parallel mechanisms,aiming to help designers select and place actuators in a correct and even optimal way after the configuration design.

REALIZATION OF QUICK-LOOK IMAGING FOR SPACEBORNE SAR BASED ON PARALLEL PROCESSING

Large range cell migration is a severe challenge to imaging algorithm for spaceborne SAR. Based on design of Finite Impulse Response (FIR) filter and Range Doppler (RD) algorithm, a realization of quick-look imaging for large range cell migration is proposed. It realized quick-look imaging of 8 times reduced resolution with parallel processing on memory shared 8 CPU SGI server. According to simulation experiment, this quick-look imaging algorithm with parallel processing can image 16384x16384 SAR raw data within 6 seconds. It reaches the requirement of real-time imaging.

A Generalized State Space Average Model for Parallel DC-to-DC Converters

The high potentiality of integrating renewable energies,such as photovoltaic,into a modern electrical microgrid system,using DC-to-DC converters,raises some issues associated with controller loop design and system stability.The generalized state space average model(GSSAM)concept was consequently introduced to design a DC-to-DC converter controller in order to evaluate DC-to-DC converter performance and to conduct stability studies.This paper presents a GSSAM for parallel DC-to-DC converters,namely:buck,boost,and buck-boost converters.The rationale of this study is that modern electrical systems,such as DC networks,hybrid microgrids,and electric ships,are formed by parallel DC-to-DC converters with separate DC input sources.Therefore,this paper proposes a GSSAM for any number of parallel DC-to-DC converters.The proposed GSSAM is validated and investigated in a time-domain simulation environment,namely a MATLAB/SIMULINK.The study compares the steady-state,transient,and oscillatory performance of the state-space average model with a fully detailed switching model.

Modified overlapped partly parallel decode for AR4JA codes in deep space communication

In this paper, according to the AR4JA codes in deep space communication, two kinds of iterative decoding including partly parallel decoding and overlapped partly parallel decoding are analyzed, and the advantages and disadvantages of them are listed. A modified overlapped partly parallel decoding that not only inherits the advantages of the two algorithms, but also overcomes the shortcomings of the two algorithms is proposed. The simulation results show that the three kinds of decoding have the same decoding performance; modified overlapped partly parallel decoding improves the iterative convergence rate and the throughput of system.

赋Orlicz范数的模函数空间的单调性

模空间是经典Lebesgue和Orlicz空间的推广。在模空间引入Orlicz范数,研究赋Luxemburg范数模空间与赋Orlicz范数模空间的单调性。首先证明了模空间中Luxemburg范数与Orlicz范数是等价的,且赋Orlicz范数模空间是Banach空间,其次证明了赋Orlicz范数模空间是严格单调的,最后给出了赋Luxemburg范数模空间是严格单调的充要条件。

A parallel pipeline connected-component labeling method for on-orbit space target monitoring

The paper designs a peripheral maximum gray differ-ence(PMGD)image segmentation method,a connected-compo-nent labeling(CCL)algorithm based on dynamic run length(DRL),and a real-time implementation streaming processor for DRL-CCL.And it verifies the function and performance in space target monitoring scene by the carrying experiment of Tianzhou-3 cargo spacecraft(TZ-3).The PMGD image segmentation method can segment the image into highly discrete and simple point tar-gets quickly,which reduces the generation of equivalences greatly and improves the real-time performance for DRL-CCL.Through parallel pipeline design,the storage of the streaming processor is optimized by 55%with no need for external me-mory,the logic is optimized by 60%,and the energy efficiency ratio is 12 times than that of the graphics processing unit,62 times than that of the digital signal proccessing,and 147 times than that of personal computers.Analyzing the results of 8756 images completed on-orbit,the speed is up to 5.88 FPS and the target detection rate is 100%.Our algorithm and implementation method meet the requirements of lightweight,high real-time,strong robustness,full-time,and stable operation in space irradia-tion environment.

Parallel Structure of Topological Space in Shakespeare’s Cymbeline

Topology is a newly branch of mathematics,dealing with the non-qualitative properties of members within a solid topological space.In a broad sense,space is considered as an arena to exemplify the power relations,and power relationship becomes a dominant property within a topological space in a holistic way.Recently,topology has been allied with literary criticism,arising as a transdisciplinary approach.In Shakespeare’s Cymbeline,three physical places-namely chamber,cave and battlefield-function as three individual topological places due to the commonality of power relationship within each place.At first,Innogen,the female protagonist who is enclosed in her chamber,becomes an object of supervision and scrutiny by triplex authorities,thus female body gains a metaphorical meaning within the topological boundary.Later,she changes costumes and enters the cave,embodying as the other in terms of power relations,where gender awareness becomes blurred.Finally,Innogen moves to the battlefield,gets access to the court,a public topological space symbolizing male authority,and launches an equal dialogue with men,thus constructing a brave female image.From chamber to the battlefield,Innogen’s self-saving trip set up a parallel structure of topological space and a token for the subversiveness of hierarchy social order dominated by royalty,paternity and the absolute authority of husband in early Renaissance.

A Time-Space Optimal Parallel Sorting on a Hypercube

In this paper we discuss a parallel sorting algorithm on a hypercube. Its time complexity is O(n logn/p) +O(n). Here, P is the number of processors available and n, the amount of items to be sorted. Take the problem of time-space optimization into consideration, when P≤ O(log n), this algorithm is both timespace optimal and cost optimization. But this means only speedup is O(P) and it is not linear speedup. Therefore, we further discuss relevant parallel efficiency problems.

DISTRIBUTION OF REACHABLE WORKSPACE AREAS IN PHYSICAL MODEL OF THE SOLUTION SPACE OF 2-DOF PARALLEL PLANAR MANIPULATORS

The expressions for calculating the values of the workspace areas of 2-DOF parallel planar manipulators (PPM) is derived. By the aid of computer, the values are calculated and plotted on the physical model of the solution space of the 2-DOF PPMs,so the workspaee-area-property atlas is obtained. The atlas delineates the relationship between the workspace areas and the link lengths of the 2-DOF PPMs all-sidedly. It is very useful for designers overalI to understand and know welI the relationship.

基于S-O-R理论的新型公共阅读空间用户流失行为分析——来自大众点评网用户评论

文章以大众点评网站中新型公共阅读空间的评论数据为对象,以S-O-R模型为理论基础,利用Python爬取其“中评”与“差评”的评论数据,运用内容分析法归纳得出新型公共阅读空间用户流失行为的主要因素,并构建新型公共阅读空间用户流失行为模型。在此基础上,提出提高新型公共阅读空间服务效能的相关建议,为提高新型阅读空间的服务质量,降低用户流失率提供参考。

Homing Strategy for a 4RRR Parallel Kinematic Machine

Returning home is the most important process of a parallel kinematic machine （PKM） with incremental encoders.Currently,most corresponding articles focus on the accuracy of homing process,and there lacks the investigation of the operation＇s safety.For a 4RRR PKM,all servoaxes would be independently driven to their zero positions at the same time based on the traditional homing mode,and that can bring serious interfere of the kinematic chains.This paper systemically investigates this 4RRR PKM＇s safety of homing process.A homing strategy usually contains three parts which are the home switches＇ locations,the platform＇s initial moving space,and each links＇ homing direction,and all of them can influence the safety of homing operation.For the purpose of evaluating and describing the safety of the homing strategy,some important parameters are introduced as follows：Safely homing ratio （SHR） is used to evaluate the probability of a machine＇s successfully returning home from an initial moving space;Synchronal rotational angle （SRA） is the four links＇ largest synchronal rotational angle with given directions from a given pose.Whether a machine can safely return home from a given pose can be judged by comparing the SRA with all four home switches＇ mounting angles.By meshing the initial moving space and checking the safeties of returning home from all the initial poses on the nodes,the SHR of this initial moving space can be calculate.For the sake of convenience,the platform＇s initial moving space should be as large as possible,and in this 4RRR PKM,a square zone in the center of the workspace with a giving initial rotation range is selected as the platform＇s initial moving space.The forward direction is selected as each link＇s homing direction according to custom,and the platform＇s initial rotational angle is selected as larger than 0° based on this 4RRR PKM＇s kinematic characteristics.The platform＇s initial moving space can be defined only by the side length of the initial moving square.By setting a probable searching step and calculating the SHR of the initial moving square,an optimal procedure of searching for the largest side length of the platform＇s initial moving square is proposed.The homing strategy proposed is based on a systemic research on the safety of homing process for PKM,and the two new indexes SHR and SRA can clearly describe the safety of homing operation.The homing operation based on this strategy is fast and safe,and the method can also be used in other PKMs with the situation of serious components＇ interference.

Modified Adsorption Capacity to Space Molecular Pollutant of Zeolite via Interface Engineering with Atomic Layer Deposition

When spacecraft operate in space,most organic materials will release small molecular hydrocarbons and large molecular organic gases due to gas evolution effect under high vacuum conditions.These gases can deposit on the surface of spacecraft,adversely affecting its performance.Adsorption becomes the first choice for removing such organic pollutants in the space environment.Zeolite material has a stable and dense porous structure,and has been widely used in the field of pollution adsorption.In this work,Al2O3 was deposited on the surfaces of 5A zeolite for the first time by atomic layer deposition(ALD)technology.As a result,the adsorption performance of Al2O3 coated 5A zeolite(zeolite@Al2O3)was significantly modified.The corresponding adsorption process was clarified via adsorption kinetics study.

Optimal design of the link lengths for a planar parallel manipulator

This paper addresses geometry design of a new kind of 2-DOF parallel manipulator actuated horizontally by linear actua- tors. The first step of the optimum design involves developing a non-dimensional structure of the planar 2-DOF parallel manipulator. The global conditioning index, global velocity index, global stiffness index and global payload index of the 2-DOF parallel manipu- lators are investigated, and the geometrical parameters without dimension are determined with respect to the specification on per- formances. Finally, based on the optimum non-dimensional result, the optimum dimensional parameters are achieved which is suit- able for the desired workspace. The optimum methodology of this paper is convenient and can be extended to other parallel mecha-

Lower Bounds and a Nearly Fastest General Parallel Branch-and-Bound Algorithm

In this paper, it is supposed that the B&B algorithm finds the first optimal solution after h nodes have been expanded and m active nodes have been created in the state-space tree. Then the lower bound Ω(m+h log h) of the running time for the general sequential B&B algorithm and the lower bound Ω(m/p+h log p) for the general parallel best-first B&B algorithm in PRAM-CREW are proposed, where p is the number of processors available. Moreover, the lower bound Ω(M/p+H+(H/p) log (H/p)) is presented for the parallel algorithms on distributed memory system, where M and H represent total number of the active nodes and that of the expanded nodes processed by p processors, respectively. In addition, a nearly fastest general parallel best-first B&B algorithm is put forward. The parallel algorithm is the fastest one as p = max{hε, r}, where ε = 1/ rootlogh, and r is the largest branch number of the nodes in the state-space tree.

PIC-MF-based Iterative Receiver for Multiuser Space Frequency Block Coding Systems

A novel low-complexity iterative receiver for multiuser space frequency block coding (SFBC) system was proposed in this paper. Unlike the conventional linear minimum mean square error (MMSE) detector, which requires matrix inversion at each iteration, the soft-in soft-out (SISO) detector is simply a parallel interference cancellation (PIC)-matched filter (MF) operation. The probability density function (PDF) of PIC-MF detector output is approximated as Gaussian, whose variance is calculated with a priori information fed back from the channel decoder. With this approximation, the log likelihood ratios (LLRs) of transmitted bits are under-estimated. Then the LLRs are multiplied by a constant factor to achieve a performance gain. The constant factor is optimized according to extrinsic information transfer (EXIT) chart of the SISO detector. Simulation results show that the proposed iterative receiver can significantly improve the system performance and converge to the matched filter bound (MFB) with low computational complexity at high signal-to-noise ratios (SNRs).

Space Group of Aquaimidazolemaleatozinc, [(H_2O)(C_3H_4N_2)(O_2CCH=CHCO_2Zn)]_n

The space group of [(H2O)(C3H4N2)(O2CCH=CHCO2Zn)]n, which was originally described in the acentric Pc space group (Liu et al., Chin. J. Struct. Chem. 2004, 23, 160～163), is re-described in the centric P21/c space group.