基于轮廓和方位角的单线激光雷达旋转扫描快速空间构网

传统点云构网算法(泊松算法、Delaunay三角剖分算法、Graph Cut算法等)能够处理多种激光雷达获取的点云数据,通用性较强,但都需要去噪、降采样、法向量提取等预处理,其实,在已知扫描轮廓和方位角信息的情况下,可以充分利用已知信息进行直接构网。针对上述情况,提出了一种基于点云初始信息的单线激光雷达旋转扫描快速空间构网方法,该方法利用激光雷达旋转扫描形成的轮廓信息以及轮廓中每个点的方位角信息,将两条相邻轮廓上的点云按照方位角顺序进行构网,当某方位角点缺失时两条轮廓同时跳过该点,与下一个点构网,再将所有轮廓按照轮廓顺序依次构网并对缺失点产生的破面进行修补。实验结果表明所提方法在纸箱、房间及长廊中均能表现出较好的三维重建效果,平均误差SD(Standard Deviation)相比于传统方法更小,提高了三维重建的准确性,构网速度和鲁棒性也显著增加。

法国创新历史对我国创新型国家创建的启示

法国是一个具有创新传统的国度,目前是世界第五经济和科技大国。本文对法国200多年来在科技创新方面取得的成就和经验教训作了系统的分析。法国经历过两个创新辉煌时代,使其在核能、航空、航天、高速铁路和农业等方面今天仍是处于世界领先地位;不过法国在以信息技术为核心的第四次科技革命浪潮中丧失了机会,2004年初法国爆发的全国范围的科技人员抗议浪潮暴露了科研体制上存在的问题;目前政府正在努力采取措施,冀望解决创新中存在的问题,进一步加强法国企业竞争力、重新推动法国经济增长。今天,增强自主创新能力,建设创新型国家是中国立足国情、面向未来的重大选择。我们从法国200多年丰富的创新史看到,没有哪个国家能不依靠自主创新而立于不败之地的,即使她已经拥有了雄厚的科技和经济基础。法国的科技和经济管理体制在很多方面与我国类似,其成功经验和失败教训对我们都具有现实的指导意义。

INTERNET TRAFFIC DATA FLOW FORECAST BY RBF NEURAL NETWORK BASED ON PHASE SPACE RECONSTRUCTION

Characteristics of the Internet traffic data flow are studied based on the chaos theory. A phase space that is isometric with the network dynamic system is reconstructed by using the single variable time series of a network flow. Some parameters, such as the correlative dimension and the Lyapunov exponent are calculated, and the chaos characteristic is proved to exist in Internet traffic data flows. A neural network model is construct- ed based on radial basis function （RBF） to forecast actual Internet traffic data flow. Simulation results show that, compared with other forecasts of the forward-feedback neural network, the forecast of the RBF neural network based on the chaos theory has faster learning capacity and higher forecasting accuracy.

FAST台址区岩堆的岩土工程治理对策研究

FAST项目属国家重大科技基础设施之一,台址区岩堆为影响开挖的主要灾害,必须对其进行治理,本文在分析岩堆特征的基础上,根据岩堆稳定性的不同情况,分别提出其防治方案,同时对不稳定岩堆提出空间格构网壳的治理对策。

Short-term traffic flow prediction with PSR-XGBoostconsidering chaotic characteristics

To improve the level of active traffic management,a short-term traffic flow prediction model is proposed by combining phase space reconstruction(PSR)and extreme gradient boosting(XGBoost)algorithms.Firstly,the traditional data preprocessing method is improved.The new method uses hierarchical clustering to determine the traffic flow state and fills in missing and abnormal data according to different traffic flow states.Secondly,one-dimensional data are mapped into a multidimensional data matrix through PSR,and the time series complex network is used to verify the data reconstruction effect.Finally,the multidimensional data matrix is inputted into the XGBoost model to predict future traffic flow parameters.The experimental results show that the mean square error,average absolute error,and average absolute percentage error of the prediction results of the PSR-XGBoost model are 5.399%,1.632%,and 6.278%,respectively,and the required running time is 17.35 s.Compared with mathematical-statistical models and other machine learning models,the PSR-XGBoost model has clear advantages in multiple predictive indicators,proving its feasibility and superiority in short-term traffic flow prediction.

Temporal Floorplanning Using Solution Space Smoothing Based on 3D-BSSG Structure

We develop a 3D bounded slice-surface grid （3D-BSSG） structure for representation and introduce the solution space smoothing technique to search for the optimal solution. Experiment results demonstrate that a 3D-BSSG structure based algorithm is very effective and efficient.

STUDY ON THE OPTIMUM PATTERN OF DAQIN G URBAN SPATIAL STRUCTURE

Daqing is a mining city that was set up on wetland by exploiting and processing petroleum.This paper points out that net-group urban system is the optimization mode for Daqin g urban spatial structure through an alyzing and appraising the present situation,c haracteristics,advantages and dis advantages of Daqing spatial structure.And the best way of optimizing Daqing urban spatial structure is to adopt sustainable development strategy,establish th e coordinated grade structure of urban system,con struct developed towns net system,p refect the function structure of the towns at all levels,make full use of resources an d strengthen environmental protection.Spatial structure of Daqing must be according-ly adjusted in order to adapt to the tr ansformation of future economy types and functions.Based on the foundation of keep-ing net group,the development shoul d be from disperse to moderate centra lization in order to give prominence to the multi-function of the central city.Constr ucting ruralizing city should be the future goal of Daqing City.

Spatial Structural Pattern and Vulnerability of China-Japan-Korea Shipping Network

The economies of China-Japan-Korea （CJK） are complementary, with their proximity resulting in the three countries having a high degree of interdependence with respect to trade. Currently, trade among these countries relies mainly on port-centered shipping. The development of the shipping network is integral for in-depth integration of CJK trade. This paper analyzes the overall characteristics, centrality, spatial structure, and vulnerability of the CJK shipping network using the methods of complex network analysis, blocking flow theory, and interruption and deletion of hub ports. The main findings are as follows： 1） The CJK shipping network has a small average path length and clustering coefficient, and its degree distribution follows a power-law distribution, which make the network present obvious characteristics of a Barabasi-Albert scale-free. 2） The characteristics of the multi-center point of the CJK shipping network can alleviate traffic pressure. At the same time, the network shows a clear hierarchy in the port transportation system, with cargo transport relying mainly on the ‘hub port-hub port＇ connection. 3） The CJK shipping network is relatively stable. Compared with ports in Japan and Korea, the main hub ports in China have a greater impact on the stability of the shipping network, in particular those ports of the central coastal region, including Shanghai, Ningbo, and Lianyungang.

On the Motivation and Reasons of Popularity of Parody in Network Language From the Perspective of Conceptual Integration Theory

The Conceptual Integration Theory was first formally put forward in 1997 by Fauconnier and Turner. According to it, there is a conceptual blending network comprised of four mental spaces： Input space Ⅰ, Input space Ⅱ, generic space, and blended space. In the process of blending, common information or structures from input spaces are projected to the ＂generic space＂. Meanwhile, through partially cross-space mapping, those structures are selectively projected to the ＂blended space＂. By means of composition, completion, and elaboration, consequently ＂emergent structure＂ comes into being from the development of blending. This theory instantly became a fresh power in cognitive research field. With the rapid development of network technology and the popularization of the internet, network language makes tremendous progresses and spreads quickly, which reflects the social and cultural development. The uniqueness and effectiveness of network language creation, to a great extent, relies on various rhetorical devices, among which parody is frequently used and plays an important role. In recent years, studies about network language somehow concentrate a lot on the construction, word transformation, and features of network vocabulary, and cognitive analysis on the mechanism of parody in network language is rather limited and requires further exploration. This paper tends to probe into the motivation and the reasons ofparody＇s popularity in network language through some examples in light of Conceptual Integration Theory in hope of a better comprehension, appreciation, and application of parody in network language

OpenFIow-Based Control Architecture for the Mobile FreeSpace Optical Networks

Mobile free space optical networks have aroused much attention due to the ability of providing high speed connectivity over long distance using the wireless laser links,while requiring relatively high available bandwidth resource and less energy consumption.However,maintaining the network with laserlinks is quite challenging due to a number of issues,such as the link fragility,the difficulty in pointingand tracking of the link,which also raises the great difficulty in the control of the network.In this paper,we present the methodology for the deployment of the mobile freespace optical networks based on our proposed OpenFlow-based control architecture.In addition,a new routing scheme is proposed and demonstrated on the testbed based on this control architecture.Delivery ratio,average delivery delay and time complexity are given to verify the performance of the OpenFlow-based control architecture.

Belt or network?The spatial structure and shaping mechanism of the Great Wall cultural belt in Beijing

The relationship between cross-regional cultural landscapes does not currently receive enough attention in cultural landscape conservation. Cultural landscapes in China are faced with the crisis of fragmentation and islanding, which makes it necessary to strengthen the idea of integrated conservation. The Great Wall cultural belt in Beijing is a cross-regional linear cultural landscape in the northwest mountainous area of Beijing. With the Great Wall as a link connecting the surrounding natural, social, and cultural resources to form a banded structure, it has the typical and practical significance of integrated conservation. Based on the theory of the cultural landscape security pattern and its ‘node – setting – connection' model, this research studies the spatial structure and shaping mechanism of the Great Wall cultural belt in Beijing from the perspective of tourist flow, using Flickr geo-tagged photos and Wikiloc tracks. The results identify the core nodes and intermediate nodes of the Great Wall cultural belt in Beijing and show that it has a multicore, multi-group hierarchical nesting structure differing from the geographic space, which has groups following the evolution orbit of ‘linear string – circumnuclear star – complete network.' To explain the differences between the cultural association network(CAN) and the geospatial network(GSN), we find that the cultural associations between nodes rely on geophysical channels, including heritage corridors and traffic passages, as physical carriers, but the nodes' attraction and their setting elements, containing natural geography environments, settlements, administrative divisions, etc., change the channel resistance, so CAN and GSN present different characteristics. From the perspective of systematic and spatial network thoughts, this study has made an attempt to adopt new analysis and research methods to achieve the integrated conservation and inheritance of linear cultural landscapes in mountainous areas.

Effects of Dimers on Cooperation in the Spatial Prisoner's Dilemma Game

We investigate the evolutionary prisoner＇s dilemma game in structured populations by introducing dimers, which are defined as that two players in each dimer always hold a same strategy. We find that influences of dimets on cooperation depend on the type of dimers and the population structure. For those dimers in which players interact with each other, the cooperation level increases with the number of dimers though the cooperation improvement level depends on the type of network structures. On the other hand, the dimers, in which there are not mutual interactions, will not do any good to the cooperation level in a single community, but interestingly, will improve the cooperation level in a population with two communities. We explore the relationship between dimers and self-interactions and find that the effects of dimers are similar to that of self-interactions. Also, we find that the dimers, which are established over two communities in a multi-community network, act as one type of interaction through which information between communities is communicated by the requirement that two players in a dimer hold a same strategy.

Exploring relations between city regions based on mobile phone data

City regions often have great diversity in form and function. To better understand the role of each region, the relations between city regions need to be carefully studied. In this work, the human mobility relations between regions of Shanghai based on mobile phone data is explored. By formulating the regions as nodes in a network and the commuting between each pair of regions as link weights, the distribution of nodes degree, and spatial structures of communities in this relation network are studied. Statistics show that regions locate in urban centers and traffic hubs have significantly larger degrees. Moreover, two kinds of spatial structures of communities are found. In most communities, nodes are spatially neighboring. However, in the communities that cover traffic hubs, nodes often locate along corridors.

Spatial Analysis of Commuting Mode Choice in Guangzhou, China

Metropolitan cities in China are commonly confronted with unresolved traffic congestion issues, primarily due to rapidly increasing traffic demand. Group disparity between commuting mode choice and its spatial distribution on road networks has enabled us to examine the factors that give rise to the discrepancies and the fundamental spatial causes of traffic congestion. In recent years, mi- cro-perspective, individual, and behavior-based spatial analysis have mushroomed and been facilitated with effective tools such as tem- poral geographic information systems （T-GIS）. It is difficult to study the interrelations between transport and space on the basis of commuting mode choice since the mode choice data are invisible in a specific space such as a particular road network. Therefore, in the field of transport, the classical origin destination （OD） four-stage model （FSM） is usually employed to calculate data when studying commuting mode choice. Based on the relative principles of T-GIS and the platform of ArcGIS, this paper considers Guangzhou as a case study and develops a spatio-temporal tool to examine the daily activities of residents. Meanwhile, the traffic volume distribution in rush hours, which was analyzed according to commuting modes and how they were reflected in the road network, was scrutinized with data extracted from travel diaries. Moreover, efforts were made to explain the relationship between traffic demand and urban spatial structure. Based on the investigation, this research indicates that traffic volumes in divergent groups and on the road networks is driven by： l） the socio-economie characteristics of travelers; 2） a jobs-housing imbalance under suburbanization; 3） differences in the spatial supply of transport modes; 4） the remains of the Danwei （work unit） system and market development in China; and 5） the transition of urban spatial structure and other factors.

Towards structural web services discovery

A syntactic and structural matching mechanism for service discovery was put forward, which tries to exploit the underlying semantics of web services to enhance tbe traditional syntactic service discovery. We commit WSDL （Web Service Description Language） as service description language. The syntactic matching mechanism is based on the textual similarity among WSDL documents using VSM （ Vector Space Model）. The structural information is extracted from WSDL document tree or the invocation sequence of a series of services which can be viewed as the problem of graph isomorphism. Then we combine the syntactic and structural similarity linearly to calculate the service similarity. Finally we provide a novel web services discovery framework named SG^＊ to find the exact services meeting the users＇ goals based on service similarity.

Cooperative Dynamics in Lattice-Embedded Scale-Free Networks

We investigate cooperative behaviors of lattice-embedded scale-free networking agents in the prisoner'sdilemma game model by employing two initial strategy distribution mechanisms,which are specific distribution to themost connected sites (hubs) and random distribution.Our study indicates that the game dynamics crucially dependson the underlying spatial network structure with different strategy distribution mechanism.The cooperators' specificdistribution contributes to an enhanced level of cooperation in the system compared with random one,and cooperationis robust to cooperators' specific distribution but fragile to defectors' specific distribution.Especially,unlike the specificcase,increasing heterogeneity of network does not always favor the emergence of cooperation under random mechanism.Furthermore,we study the geographical effects and find that the graphically constrained network structure tends toimprove the evolution of cooperation in random case and in specific one for a large temptation to defect.

An Overview of General Theory of Security

Cyber security lacks comprehensive theoretical guidance. General security theory, as a set of basic security theory concepts, is intended to guide cyber security and all the other security work. The general theory of security aims to unify the main branches of cyber security and establish a unified basic theory. This paper proposal an overview on the general theory of security, which is devoted to constructing a comprehensive model of network security. The hierarchical structure of the meridian-collateral tree is described. Shannon information theory is employed to build a cyberspace security model. Some central concepts of security, i.e., the attack and defense, are discussed and several general theorems on security are presented.

A Neural Network based Method for Detection of Weak Underwater Signals

Detection of weak underwater signals is an area of general interest in marine engineering.A weak signal detection scheme was developed; it combined nonlinear dynamical reconstruction techniques, radial basis function (RBF) neural networks and an extended Kalman filter (EKF).In this method chaos theory was used to model background noise.Noise was predicted by phase space reconstruction techniques and RBF neural networks in a synergistic manner.In the absence of a signal, prediction error stayed low and became relatively large when the input contained a signal.EKF was used to improve the convergence rate of the RBF neural network.Application of the scheme to different experimental data sets showed that the algorithm can detect signals hidden in strong noise even when the signal-to-noise ratio (SNR) is less than -40d B.

Persistent variation in spatial behavior affects the structure and function of interaction networks

The function of a network is affected by its structure. For example, the presence of highly interactive individuals, or hubs, influences the extent and rate of information spread across a network. In a network of interactions, the duration over which individual variation in interactions persists may affect how the network operates. Individuals may persist in their behavior over time and across situations, often referred to as personality. Colonies of social insects are an example of a biological system in which the structure of the coordinated networks of interacting workers may greatly influence information flow within the colony, and therefore its collective behavior. Here I investigate the effects of persistence in walking patterns on interaction networks us- ing computer simulations that are parameterized using observed behavior of harvester ants. I examine how the duration of persis- tence in spatial behavior influences network structure. Furthermore, I explore how spatial features of the environment affect the relationship between persistent behavior and network structure. I show that as persistence increases, the skewness of the weighted degree distribution of the interaction network increases. However, this relationship holds only when ants are confined in a space with boundaries, but not when physical barriers are absent. These findings suggest that the influence of animal personalities on network structure and function depends on the environment in which the animals reside [Current Zoology 61 （1）： 98-106, 2015].