大气噪声条件下海上短波通信可通性研究

大气噪声是影响海上短波通信质量的主要因素,研究海上短波通信可通性必须考虑大气噪声影响。介绍短波通信的特点,分析了地波、天波传播的影响因素,归纳出接收场强的计算公式。引入信噪比概念,对大气噪声场强典型值进行计算,设计了一种完整而简洁的海上短波通信接收点信噪比计算流程。可快速、准确的确定可通频段,对提高海上短波通信效率有重要意义。

On Spanning Wide Diameter of Graphs

A t-container Ct(u,v)is a set of t internally disjoint paths between two distinct vertices u and v in a graph G,i.e.,Ct(u,v)={P_(1),P_(2),···,Pt}.Moreover,if V(P_(1))∪V(P_(2))∪···∪V(Pt)=V(G)then Ct(u,v)is called a spanning t-container,denoted by C_(t)^(sc)(u,v).The length of C_(t)^(sc)(u,v)={P_(1),P_(2),···,Pt}is l(C_(t)^(sc)(u,v))=max{l(P_(i))|1≤i≤t}.A graph G is spanning t-connected if there exists a spanning t-container between any two distinct vertices u and v in G.Assume that u and v are two distinct vertices in a spanning t-connected graph G.Let D_(t)^(sc)(u,v)be the collection of all C_(t)^(sc)(u,v)’s.Define the spanning t-wide distance between u and v in G,d_(t)^(sc)(u,v)=min{l(C_(t)^(sc)(u,v))|C_(t)^(sc)(u,v)∈D_(t)^(sc)(u,v)},and the spanning t-wide diameter of G,D_(t)^(sc)(G)=max{d_(t)^(sc)(u,v)|u,v∈V(G)}.In particular,the spanning wide diameter of G is D_(κ)^(sc)(G),whereκis the connectivity of G.In the paper we provide the upper and lower bounds of the spanning wide diameter of a graph,and show that the bounds are best possible.We also determine the exact values of wide diameters of some well known graphs including Harary graphs and generalized Petersen graphs et al..

An efficient reliability evaluation method for industrial wireless sensor networks

Aimed at the difficulties in accurately, comprehensively and systematically evaluating the reliability of industrial wireless sensor networks （WSNs）, a time-evolving state transition-Monte Carlo （TEST-MC） evaluation method and a novel network function value representation method are proposed to evaluate the reliability of the IWSNs. First, the adjacency matrix method is used to characterize three typical topologies of WSNs including the mesh network, tree network and ribbon network. Secondly, the network function value method is used to evaluate the network connectivity, and the TEST-MC evaluation method is used to evaluate network reliability and availability. Finally, the variations in the reliability, connectivity and availability of these three topologies are presented. Simulation results show that the proposed method can quickly analyze the reliability of the networks containing typical WSN topologies, which provides an effective method for the comprehensive and accurate evaluation of the reliability of WSNs.

Bus transit travel time reliability evaluation based on automatic vehicle location data

In order to provide important parameters for schedule designing, decision-making bases for transit operation management and references for passengers traveling by bus, bus transit travel time reliability is analyzed and evaluated based on automatic vehicle location （AVL） data. Based on the statistical analysis of the bus transit travel time, six indices including the coefficient of variance, the width of travel time distribution, the mean commercial speed, the congestion frequency, the planning time index and the buffer time index are proposed. Moreover, a framework for evaluating bus transit travel time reliability is constructed. Finally, a case study on a certain bus route in Suzhou is conducted. Results show that the proposed evaluation index system is simple and intuitive, and it can effectively reflect the efficiency and stability of bus operations. And a distinguishing feature of bus transit travel time reliability is the temporal pattern. It varies across different time periods.

Identification of Traffic Accident Causal Factors Through Dynamic Driving Behavior Analysis

The reliability expression of dynamic driving behavior is derived from the driving shaping behavioural model; and then, in accordance with the combination of computer simulation and mathematical expression of driving reliability, an approach for assessing the effect of driving erroneous actions on the dynamic performance of the driver vehicle system is presented. The analysis of driving erroneous actions in the driver vehicle system has been performed to show that the reliability during perception with variety widely could result in the incidents and/or accidents in traffic system.

Modeling for Action of Recovering from Erroneous Driving Condition Based on Revised Decision Tree

Driving behavior modeling is very important in the research area of road traffic systems safety analysis. The characteristics of action of recovering from erroneous driving condition underlying road traffic accident or incident scenarios is quantitatively analyzed, the model of action of recovering from erroneous driving condition is set up according to the identification of erroneous driving condition and the measurement of correction from erroneous driving condition. And then, the probability of action of recovering from erroneous driving condition has been measured based on a revised decision tree. The measure process uses a combination of test data and subjective judgments of driving behavior. It can provide a very helpful theoretical basis for the further analysis of driving behavior in road traffic system.

领潮头 挹绝艳——试析《西行漫记》文化通约性的独特方法

本文基于《西行漫记》在国际上产生“轰动效应”的现象,认为该著提出了跨文化交往中的“文化可通约性”法则,并对其具体方法——“零点思维的精神集萃法”作了简要的分析.

An indoor positioning system for mobile target tracking based on VLC and IMU fusion

An indoor positioning system( IPS) is designed to realize positioning and tracking of mobile targets,by taking advantages of both the visible light communication( VLC) and inertial measurement unit( IMU). The platform of the IPS is designed,which consists of the light-emitting diode( LED)based transmitter,the receiver and the positioning server. To reduce the impact caused by measurement errors,both inertial sensing data and the received signal strength( RSS) from the VLC are calibrated. Then,a practical propagation model is established to obtain the distance between the transmitter and the receiver from the RSS measurements. Furthermore,a hybrid positioning algorithm is proposed by using the adaptive Kalman filter( AKF) and the weighted least squares( WLS)trilateration to estimate the positions of the mobile targets.Experimental results show that the developed IPS using the proposed hybrid positioning algorithm can extend the localization area of VLC,mitigate the IMU drifts and improve the positioning accuracy of mobile targets.

Reliability of Substation Protection System Based on IEC61850

Although the new technology of protection and automation system of substation based on IEC61850 standard has developed rapidly in China,reliability measures depending on this technology need to be further researched.By taking advantage of convenient information sharing,two kinds of new schemes,shared backup protection unit(SBPU)and signal backup(SB),have been proposed to solve the failure problem of protective devices and current/voltage transducers respectively,and the working principle of these two schemes are also described.Furthermore,the key technologies of on-line diagnosis of protective devices'failure and on-line status diagnosis of optical or electronic current/voltage transducers to realize the two schemes are proposed.

A novel MAC mechanism to resolve 802.11 performance anomaly

In the 802.11b networks, the guarantee of an equal long-run channel access probability causes performance anomaly in a multi-rate wireless cell. Much interest has been involved in this issue and many effective mechanisms have been proposed. The usual MAC layer solutions include the initial contention window adaptation, the maximum transfer unit size adaptation and the packet bursting. In this paper, we propose a novel approach which introduces a new parameter called the transmission prob- ability pt to the legacy protocol. By adjusting pt according to the transmission rate, the proposed scheme can solve the performance anomaly problem cleanly. Throughput analysis and performance evaluation show that our scheme achieves significant im- provement in the aggregate throughput and the fairness.

Development of control strategy of variable speed limits for improving traffic operations at freeway bottlenecks

A control strategy of variable speed limits(VSL)was developed to reduce the travel time at freeway recurrent bottleneck areas.The proposed control strategy particularly focused on preventing the capacity drop and increasing the discharge flow.A cell transmission model(CTM)was developed to evaluate the effects of the proposed VSL control strategy on the traffic operations.The results show that the total travel time is reduced by 25.5% and the delay is reduced by 56.1%.The average travel speed is increased by 34.3% and the queue length is reduced by 31.0%.The traffic operation is improved by the proposed VSL control strategy.The way to use the proposed VSL control strategy in different types of freeway bottlenecks was also discussed by considering different traffic flow characteristics.It is concluded that the VSL control strategy is effective for merge bottlenecks but is less effective for diverge bottlenecks.

Irrationality in Scientific Development？

The paper discusses several wide-spread misunderstandings of Kuhn＇s theory of scientific development, most prominently the ascription that he conceives of scientific development as irrational. The core of this ascription is an assessment of incommensurability as implying the lack of any rational possibility of theory comparison. This is supposed to be due to Gestalt switches and a quasi-religious element of conversion in theory change. Accordingly, scientific revolutions cannot be a serious matter for philosophical analysis; they furthermore foreclose any scientific progress. It is shown that such images of Kuhn＇s theory rest on deep misunderstandings that are partly due to Kuhn＇s writing style.

Interpreting Kuhn＇s Incommensurability-Thesis： Its Different Meanings and Epistemological Consequences

Kuhn＇s incommensurability-thesis is crucial for consequences for the pursuit of epistemology. A interpreting his views on the development of science and their commemoration of the 50th anniversary of the publication of the original version of Kuhn＇s epoch-making book The Structure of Scientific Revolutions （henceforth： SSR） should thus provide a thorough reflection on this thesis. However, this thesis is not easy to interpret. It is not only complex in itself but has also undergone a historical development--in Kuhn＇s own hands and in those of his interpreters. In this article, I sort out the different interpretations of it, in particular, in Part A. In Part B, I demonstrate their epistemological consequences. Under closer scrutiny, Kuhn＇s incommensurability-thesis contains several sub-theses Different senses of ＂incommensurability＂ thus need to be distinguished. However, the way in which those distinctions are drawn in Kuhn-scholarship differs. In paragraph I of Part A, I provide an overview of the reception of the incommensurability-thesis in Kuhn-scholarship. In Paragraph II, I trace its development in Kuhn＇s later writings： given its importance and contested nature, Kuhn later clarifies his original thesis. Those later clarifications＇ main function consists in domesticating the most radically relativistic aspects his original incommensurability-thesis had, at least, in the eyes of his interpreters. The upshot of Part A （Paragraphs I and II） is to provide a coherent interpretation of Kuhn＇s incommensurability-thesis. To that end, I distinguish in line with much of Kuhn-scholarship a semantic from a methodological sense of incommensurability. In part B, the question is raised： What sort of epistemological consequences follow from both senses of incommensurability？ In particular, what consequences follow for the issues of reference, subjectivity （objectivity）, pluralism, and realism？ The underlying question is to what extent Kuhnian incommensurability caters to a relativistic understanding of those issues. This question is answered in Paragraph Ill with the help of the analyses of a currently leading Kuhn-scholar, C. H. Sankey. His answers are taken as a vantage point for my concluding evaluation of the consequences of Kuhnian incommensurability in Paragraph IV.

Political Reasoning and the Typology of Arguments in the Context of Political Philosophy

The main purpose of this article is to present the initial phase of the project in the field of argumentation theory and political philosophy. Project concerns studies of different types of rationality in the context of the argumentation. Background consideration is the problem of incommensurability and incompatibility types of rationality in political and ideological disputes. The first step is the establishment of a category of argumentative potential as a criterion for the typology of argument, which will build a map of argumentation, which will provide a starting point for a discussion. Apart from demonstrating the disproportion of discourses, the conclusion of the argument is to prove the local character of rationality.

Kuhn and Taxonomies of History

This paper introduces the idea that if theories of history generate different taxonomies of history they too are incommensurable. I argue this is unavoidable for Kuhn given what he says about incommensurability and 1 investigate the consequences in relation to reflexivity, justification, and paradox for Kuhn＇s account of science. I want to do this on two levels, firstly looking at different possibilities for characterising individual paradigms. I will look at some examples from ancient and early modem astronomy as here it is clearest that paradigms can be characterised in different ways and that this has important consequences. I will argue in particular that Kuhn＇s characterisation of the paradigm for astronomy which emerges from antiquity （geocentrism） is favourable to his general account of the history of science, but that there is a very plausible and extremely damaging alternative. I argue that these differing characterisations generate differing, incommensurable taxonomies of the history of astronomy, with attendant ＂local holism,＂ untranslatability of key terms and issues of theory choice. If so, Kuhn then has problems with generating an adequate decision making protocol for choosing between the two paradigm characterisations. That is problematic in itself, but I also argue this problem is systemic and affects the evidence needed for Kuhn to justify his general account of the history of science. I also want to investigate the implications of differing taxonomies of the history of science at a more abstract level. Kuhn＇s general theory of the history of science generates a taxonomy of the history of science, as do other theories such as those of Popper and of gradualism. If so, the incommensurability involved here, again with attendant ＂local holism,＂ untranslatability of key terms and issues of theory choice, leads to issues of paradox and justification for Kuhn＇s general account of the history of science. With this broader understanding of taxonomic issues, some important Kuhn statements about scientific theories become self-referential, again generating problems of paradox and justification.

Incommensurability in Second Language Acquisition Approaches

Researchers in the field of Second Language Acquisition （SLA） have been taking different routes. Some researchers make linguistic-cognitive issues their inquire object and pursue objectivity with quantitative research methods. Other researchers regard the social context of activity as an essential characteristic of learning and teaching. These groups of researchers make use of qualitative research methods like case study, grounded theory, narrative inquiry, and ethnography. There are many other routes that SLA researchers have taken, but the two just mentioned are perhaps the most predominant ones and the ones that are most easily contrasted. The present paper explores the disparity between the different research paths from the perspective of philosophy of science echoing the notion of incommensurability. In this paper the author argues that the differences between different SLA perspectives are not only commensurable but wholesome for the development of SLA.

Kuhnian Understanding of Incommensurability and Implications of Paradigmatic Conception of Knowledge in International Relations

In international relations theory （maybe more than in any other discipline of social sciences）, the paradigmatic construction of Thomas Kuhn and his model of incommensurability might be applied to the theoretical interpretation of phenomena; and it is one of the cornerstones of the methodological toolkit for the interpretation in this field. The paper explores the reason why Kuhn＇s understanding of incommensurability seems to be necessary for the conception of knowledge in international relations： the concept of incommensurability can be considered typical as it is meant to indicate a conflict, of one form or another, between theories. And the discipline of international relations is more than a perfect ground for considering this concept when one is having in mind the high degree of polarized debate among rivalry theoretical schools （for interpreting and describing the identical phenomena） that is present from the very beginning of the discipline. Recalling the Kuhnian conception of science in paradigmatic view with an aim for understanding--international relations theory, the paper analyzes furthermore his rejection of the traditional dichotomy between “objectivisn”and ＂subjectivism.＂

Operation reliability for on-ramp junction of urban freeway

A disorder situation of traffic operation always appears in on-ramp junction area of urban freeway,because the operation action for vehicles presents the weaving condition,especially for different vehicle types.Based on the analysis on the cellular automata theory,and combining with on-site survey data,several key parameters were defined,namely,cellular length,cellular speed,cellular acceleration,updating time interval.In addition,cellular acceleration rule,cellular deceleration rule,random rule,lane-changing rule and other micro-simulation rules were set,and cellular automaton micro-simulation model was set up.Further-more,a micro-simulation module was developed for traffic operation actions of on-ramp junction with Matlab toolbox.Finally,a simulation experiment for traffic operation reliability was done with this micro-simulation module,and the situation of change for on-ramp junction area was obtained under the conditions of different mainline design speed,acceleration lane length,vehicle generation probability and lane-changing probability.The results show that operation reliability for on-ramp junction is determined by the parameters of the probability of vehicle generation and the length of acceleration lane,especially for on-ramp.

Dynamic Single/Dual-channel Filter with Tunable Fiber Bragg Gratings

The shift mechanism of Bragg wavelength with stress variation for a fiber grating is investigated in detail. The influence of strain change on reflection and bandpass is theoretically analyzed. By applying stress, the dynamic single/dual channel filter with tunable fiber Bragg gratings is achieved.