Local and global approaches of affinity propagation clustering for large scale data

Recently a new clustering algorithm called 'affinity propagation' (AP) has been proposed, which efficiently clustered sparsely related data by passing messages between data points. However, we want to cluster large scale data where the similarities are not sparse in many cases. This paper presents two variants of AP for grouping large scale data with a dense similarity matrix. The local approach is partition affinity propagation (PAP) and the global method is landmark affinity propagation (LAP). PAP passes messages in the subsets of data first and then merges them as the number of initial step of iterations; it can effectively reduce the number of iterations of clustering. LAP passes messages between the landmark data points first and then clusters non-landmark data points; it is a large global approximation method to speed up clustering. Experiments are conducted on many datasets, such as random data points, manifold subspaces, images of faces and Chinese calligraphy, and the results demonstrate that the two ap-proaches are feasible and practicable.

A sub-grid scale model for Burgers turbulence based on the artificial neural network method

The present study proposes a sub-grid scale model for the one-dimensional Burgers turbulence based on the neuralnetwork and deep learning method.The filtered data of the direct numerical simulation is used to establish thetraining data set,the validation data set,and the test data set.The artificial neural network(ANN)methodand Back Propagation method are employed to train parameters in the ANN.The developed ANN is applied toconstruct the sub-grid scale model for the large eddy simulation of the Burgers turbulence in the one-dimensionalspace.The proposed model well predicts the time correlation and the space correlation of the Burgers turbulence.

Decentralized Stabilization of Large-scale Uncertain Systems with State-Delays——LMIs Approach

This paper deals with the problem of decentralized robustcontrol for a class of interconnected uncertain systemswith state delays.The parameter uncertainties are un-known but norm-bounded.A new sufficient condition isobtained for each subsystem and overall system to be sta-bilizable via linear memoryless state feedback robust de-centralized controllers.The results depend on the size of the delays and are given in terms of linear matrix ine-qualities,so they are less conservative than those of delay-independent.Moreover,matching condition is not a necessary condition.Finally,an example is presented to illustrative the effectiveness of the proposed method.

Utilization Survey of Livestock Manure Resources in Large-scale Farms of Yangzhou

Based on surveying the conditions of large -scale farms and commercial manure in the each county of Yangzhou city, the situations and problems for utilization of livestock manure resources were grasped. After an analysis of the potential value of livestock manure, the suggestion and strategy for utilization of livestock manure resources were proposed based on the actual conditions in Yangzhou city.

Preparation of β-SiC by combustion synthesis in a large-scale reactor

The feasibility of 5 kg β-SiC synthesized in one batch was demonstrated through igniting the mixture of Si, C-black and polytetrafluoroethylene （PTFE） under different nitrogen pressures. The effect of experimental parameters, including the contents of PTFE, nitrogen pressure, preheating, and raw materials distribution forms were investigated. The results show that the products are β-SiC with equiaxed grains. The average grain size is less than 200 nm. The powders loaded loosely promote reaction heat dispersing, resulting in small grains. High purity β-SiC powders are obtained when the PTFE content is as low as 5wt%, which simplifies the process and decreases the cost effectively. The ceramic sintered from the obtained β-SiC powders presents the hardness of 22.20 GPa, the bending strength as high as 715.15 MPa and the fracture toughness of 8.179 MPa·m^1/2, which are higher than those of ceramics fabricated with α-SiC produced by combustion synthesis.

Radio Propagation and Wireless Coverage of LSAA-Based 5G Millimeter-Wave Mobile Communication Systems

Millimeter-wave(mm Wave) communications will be used in fifth-generation(5G) mobile communication systems, but they experience severe path loss and have high sensitivity to physical objects, leading to smaller cell radii and complicated network architectures. A coverage extension scheme using large-scale antenna arrays(LSAAs) has been suggested and theoretically proven to be cost-efficient in combination with ultradense small cell networks. To analyze and optimize the LSAA-based network deployments, a comprehensive survey of recent advances in statistical mmWave channel modeling is first presented in terms of channel parameter estimation, large-scale path loss models, and small-scale cluster models. Next, the measurement and modeling results at two 5G candidate mmWave bands(e.g., 28 GHz and 39 GHz) are reviewed and compared in several outdoor scenarios of interest, where the propagation characteristics make crucial contributions to wireless network designs. Finally, the coverage behaviors of systems employing a large number of antenna arrays are discussed, as well as some implications on future mmWave cellular network designs.

Formation conditions and exploration direction of large natural gas reservoirs in the oil-prone Bohai Bay Basin, East China

The Bohai Bay Basin is a typical oil-prone basin, in which natural gas geological reserves have a small proportion. In this basin, the gas source rock is largely medium-deep lake mudstone with oil-prone type Ⅱ2-Ⅱ1 kerogens, and natural gas preservation conditions are poor due to active late tectonic movements. The formation conditions of large natural gas fields in the Bohai Bay Basin have been elusive. Based on the exploration results of Bohai Bay Basin and comparison with large gas fields in China and abroad, the formation conditions of conventional large-scale natural gas reservoirs in the Bohai Bay Basin were examined from accumulation dynamics, structure and sedimentation. The results show that the formation conditions of conventional large natural gas reservoirs in Bohai Bay Basin mainly include one core element and two key elements. The core factor is the strong sealing of Paleogene "quilt-like" overpressure mudstone. The two key factors include the rapid maturation and high-intensity gas generation of source rock in the late stage and large scale reservoir. On this basis, large-scale nature gas accumulation models in the Bohai Bay Basin have been worked out, including regional overpressure mudstone enriching model, local overpressure mudstone depleting model, sand-rich sedimentary subsag depleting model and late strongly-developed fault depleting model. It is found that Bozhong sag, northern Liaozhong sag and Banqiao sag have favorable conditions for the formation of large-scale natural gas reservoirs, and are worth exploring. The study results have important guidance for exploration of large scale natural gas reservoirs in the Bohai Bay Basin.

多用户大规模LDPC-SM-MIMO联合分层消息传递检测

对于多用户大规模空间调制多输入多输出(Spatial Modulation Multiple Input Multiple Output,SM-MIMO)系统,消息传递检测(Message Passing Detection,MPD)是常用的检测算法,但其复杂度较高。针对该问题,引入基于分层消息传递机制的分层MPD(Layered MPD,LMPD)算法以加快算法收敛速度,降低算法复杂度。进一步,将低密度奇偶校验码(Low-density Parity-check,LDPC)与SM-MIMO系统相结合,提出联合LMPD-BP(Joint LMPD Belief Propagation,JLMPD-BP)算法,LMPD算法可利用BP算法反馈的概率信息,提升系统检测性能。理论分析与仿真结果表明:与传统MPD算法相比,LMPD算法在不损失误码率性能的前提下可加快算法收敛速度,当信噪比(Signal-to-Noise Ratio,SNR)为4 dB时,MPD算法需3次迭代才能达到收敛,而LMPD算法仅需2次迭代即可收敛;同时,通过与LDPC码结合,JLMPD-BP算法极大地降低了系统误码率,如在迭代次数为(2,2,2)、SNR=2 dB时,与迭代次数为(4,4,0)的LMPD-BP算法相比,JLMPD-BP算法的误码率由10-2降至5×10-3。

Okumura-Hata传播预测模型的可视化仿真研究

对大尺度传播预测模型的可视化计算问题进行了研究。应用先进仿真技术 ,通过对图形建模涉及的多种资源如算法、参数及结果数据等进行可视化处理 ,构造出Okumura- Hata传播预测模型的可视化计算环境。与基于传统高级程序设计语言 (如C、Fortran)的数值预测方法相比 ,该方法不仅实现了 Okumura- Hata模型的图形建模和可视化预测 ,而且无需算法编程及调试 ,为蜂窝和陆地移动无线通信路径损耗预测提供一个全面的图形化解决方案。

高速铁路GSM-R系统电波传播场景分类与路径损耗指数的求解

基于电波传播的机理,结合高速铁路电波传播的特点,对高速铁路电波传播衰落影响因素进行分析,对高速铁路电波传播场景进行划分。利用最小平方差估计算法,提出大尺度传播模型路径损耗指数n、均方差的数学求解方法。将联调联试取得的实测数据按照典型的传播场景划分整理,统计出各典型地形场景电波传播路径损耗指数n、均方差和接收电平初值。

拉萨裸裂尻鱼规模化人工繁殖技术研究

为探索拉萨裸裂尻鱼人工规模化繁殖技术,于2021年3月获得8批拉萨裸裂尻鱼亲本,统计亲本体长、体重及繁殖力;再采用DOM和LHRH-A2组合对拉萨裸裂尻鱼进行人工催产,统计催产率、效应时间、产卵量、受精率和孵化率。结果表明:52尾亲本体长(37.97±2.01)cm,体重(764.38±113.79)g,绝对繁殖力(21667±2864)粒,相对繁殖力(45.56±11.67)粒/g;随着体长、体重增加,拉萨裸裂尻鱼绝对繁殖力呈线性增加,相对繁殖力呈线性降低。测量356尾拉萨裸裂尻鱼,体长(34~38)cm占比最高,为68.28%,体重(500~800)g占比最高,为72.47%;各体长及体重百分比呈正态分布。人工催产8批拉萨裸裂尻鱼雌鱼,共计522尾,总催产率92.27%,催产效应时间为(48~72)h;雄鱼催产效应时间为(24~72)h,催产率为100%。8批卵累计634.2万粒,平均受精率90.57%,平均孵化率70.30%。因此,采用DOM和LHRH-A2组合对拉萨裸裂尻鱼进行催产,可获得较好的催产率、受精率和孵化率。

基于实测数据的LTE-A大尺度传播模型校正

随着城市的迅速发展,密集城区的地貌环境趋向多元化和复杂化,导致传播模型校正的准确性降低、难度增加。为了提高密集城区模型校准的准确性,得到与本地传播环境相匹配的传播模型,采用环境适应分段校正法,对LTE-A系统的实际路测数据进行传播模型校正,校正结果表明,在地貌环境复杂的密集城区进行大尺度传播模型分段校正时,预测数据的误差降低了5dB,这说明分段校正后的传播模型准确性大幅提高,能够有效反映当地的传播环境。

Saint-Venant and Navier-Stokes Models for Tsunami Simulations

Into the frame of the French TANDEM project (Tsunamis in the Atlantic and the English ChaNnel: Definition of the Effects through numerical Modelling) Principia has been working on the development and qualification of two in-house CFD software: the 2D EOLE-SV (Saint-Venant) model for simulation of large scale tsunami propagation from the source up to coastal scale and the 3D EOLE-NS (Navier-Stokes) model dedicated to tsunami coastal impact modelling. This paper presents a large range of test cases carried out into the frame of the project and dedicated to the validation of numerical codes in various tsunami wave conditions. The main aspects of phenomena such as wave generation, propagation and coastal impact are investigated on academic situations. A real case simulation is concerned as well, the devastating 2011 Tohoku event which is compared with in-situ data.

大型音乐节活动中人员不安全行为传播的干预研究

近年来国内外大型音乐节活动中拥挤踩踏事故频繁发生,造成巨大的人员伤亡和财产损失。基于元胞自动机理论和SEIR模型,构建新的人员不安全行为传播模型,将事故致因2-4模型中安全意识、安全氛围和安全习惯的概念引入模型中,通过数值模拟方法研究大型音乐节活动中人员不安全行为的传播现象,并探讨安全培训对人员不安全行为传播过程的影响。结果表明:通过开展安全培训后,个体的安全意识越高,不安全行为的传播范围越小;个体的安全氛围越好,人群中潜伏者和传播者的数量越少,对人员不安全行为传播过程的影响也越小;个体的安全习惯越好,人员不安全行为传播过程结束的时间越早,说明通过安全培训可以有效约束人员不安全行为的传播。

基于BP神经网络的大规模在线教育学习者满意度测评模型构建

为提升大规模在线教育学习者满意度测评效果,降低测评冗余值,构建了一种基于反向传播(Back Propagation,BP)神经网络的大规模在线教育学习者满意度测评模型。首先选取满意度测评指标,设定测评模型的路径系数图,其次估计路径系数图块结构参数,分析结构变量与观测变量间的关系,最后通过设计BP设计网络的结构并进行学习训练,实现大规模在线教育学习者满意度测评模型的构建。试验结果证明,构建模型能够取得更低的测评冗余值。

面向毫米波大规模极化敏感阵列的多径信号二维快速测向算法

作为B5G/6G的可能发展方向之一,毫米波大规模敏感阵列拥有诸多潜在的优势,如能提供高分辨率的二维波达角(2D-DOA)估计、可以实现极化保密通信等。关注极化敏感阵列中的相干源2D-DOA估计问题,提出了一种基于矩阵重排的快速估计方法。首先利用矩阵重排解决矩阵秩亏问题,再利用传播算子(PM)进行高效测向,并给出了算法相关性能的理论分析,包括计算复杂度、可辨识性和Cramer-Rao界。最后,通过仿真结果验证了所提算法的有效性。

AN ADAPTIVE CONTROL STRATEGY FOR PROPER MESH DISTRI-BUTION IN LARGE EDDY SIMULATION

The Filtering Grid Scale （FGS） of sub-grid scale models does not match with the theoretical Proper FGS （PFGS） because of the improper mesh. Therefore, proper Large Eddy Simulation （LES） Mesh is very decisive for better results and more economical cost. In this work, the purpose is to provide an adaptive control strategy for proper LES mesh with turbulence theory and CFD methods. A new expression of PFGS is proposed on the basis of -5/3 law of inertial sub-range and the proper mesh of LES can be built directly from the adjustment of RANS mesh. A benchmark of the backward facing step flow at Re = 5147 is provided for application and verification. There are three kinds of mesh sizes, including the RANS mesh, LAM （LES of adaptive-control mesh）, LFM （LES of fine mesh）, employed here. The grid number of LAM is smaller than those of LFM evidently, and the results of LAM are in a good agreement with those of DNS and experiments. It is revealed that the results of LAM are very close to those of LFM. The conclusions provide positive evidences for the novel strategy.

大规模风电接入电网谐波影响分析

随着可再生能源的快速发展,风电已成新能源体系的重要组成部分,大规模风电接入电网也逐步投入使用。然而,风力发电机的非线性特性和电力电子设备的广泛应用可能会引入谐波问题,对电网和电力设备运行的稳定性造成影响。通过对大规模风电接入电网的谐波影响进行详细分析,包括谐波发生机理、谐波传播路径、谐波功率流计算以及谐波滤波技术等方面的内容,为风电场的谐波管理和电网的谐波抑制提供理论与实践指导。

东亚季风涌对我国东部大尺度降水过程的影响分析

将NECP/NCAR资料中850 hPa纬向风分量进行30~60天带通滤波,用大气季节内振荡(ISO)来表征东亚夏季风涌的活动特征。研究表明,长江中下游地区和淮河流域分别出现涝年时,都伴有很显著的季风涌向北传播的特征。季风涌的北传实质就是季风中来自热带地区ISO的向北传播。季风涌北传过程中,得到来自东西两侧纬向传播的ISO补充。纬向传播的ISO在110°E^120°E附近汇合后增强自热带地区向北传的季风涌,使得季风涌在经向上可以继续向北传播,并对我国东部地区夏季大尺度降水过程产生一定的影响。纬向补充的ISO特征差异对我国东部大尺度降水位置会产生一定的差异。

泥鳅规模化人工催产与孵化的研究

于2009年5月17日至6月5日,在浙江省湖州市进行了5次泥鳅人工繁殖试验。结果表明:累计催产种鳅314 kg,约21 980尾,获受精卵2 340万粒,得泥鳅水花苗1 850万尾。其催产率为68.3%～95.5%,平均值为84.2%;孵化率为56.8%～93.3%,平均值为81.21%。对种鳅筛选、抓捕器具、催产激素剂种配伍、产卵水流及水温等影响泥鳅人工繁殖因素进行了探索和试验,为泥鳅规模化繁殖提供参考。