Design Change Model for Effective Scheduling Change Propagation Paths

Changes in requirements may result in the increasing of product development project cost and lead time, therefore, it is important to understand how require- ment changes propagate in the design of complex product systems and be able to select best options to guide design. Currently, a most approach for design change is lack of take the multi-disciplinary coupling relationships and the number of parameters into account integrally. A new design change model is presented to systematically analyze and search change propagation paths. Firstly, a PDS-Be- havior-Structure-based design change model is established to describe requirement changes causing the design change propagation in behavior and structure domains. Secondly, a multi-disciplinary oriented behavior matrix is utilized to support change propagation analysis of complex product systems, and the interaction relationships of the matrix elements are used to obtain an initial set of change paths. Finally, a rough set-based propagation space reducing tool is developed to assist in narrowing change propagation paths by computing the importance of the design change parameters. The proposed new design change model and its associated tools have been demonstrated by the scheduling change propagation paths of high speed train＇s bogie to show its feasibility and effectiveness. This model is not only supportive to response quickly to diversified market requirements, but also helpful to satisfy customer require- ments and reduce product development lead time. The proposed new design change model can be applied in a wide range of engineering systems design with improved efficiency.

A method of searching fault propagation paths in mechatronic systems based on MPPS model

In view of the structure and action behavior of mechatronic systems,a method of searching fault propagation paths called maximum-probability path search(MPPS)is proposed,aiming to determine all possible failure propagation paths with their lengths if faults occur.First,the physical structure system,function behavior,and complex network theory are integrated to define a system structural-action network(SSAN).Second,based on the concept of SSAN,two properties of nodes and edges,i.e.,the topological property and reliability property,are combined to define the failure propagation property.Third,the proposed MPPS model provides all fault propagation paths and possible failure rates of nodes on these paths.Finally,numerical experiments have been implemented to show the accuracy and advancement compared with the methods of Function Space Iteration(FSI)and the algorithm of Ant Colony Optimization(ACO).

Comparison on crack propagation under tension at 150℃ of Mg-2Zn-1.5Mn alloy sheets with and without crack notch

Generally,edge crack of rolled magnesium alloy sheets initiates in the RD(rolling direction)-ND(normal direction)plane and then propagate in the RD-TD(transverse direction)plane.Hence,the Mg-2Zn-1.5Mn(ZM21)alloy sheets with and without crack notch were designed to carry out in-situ tensile experiments under 150℃(the same temperature of rolling),with the aim to understand their crack propagation mechanism.The scanning electron microscopy(SEM)and electron backscattered diffraction(EBSD)techniques were utilized to reveal microstructural evolution in real time at designated displacements.The results show that the prismatic slip,basal slip,and extension twining play synergistic role in coordinating strain during the tensile process in ZM21 alloy sheet at 150℃.In both tensile samples with and without crack notch,localized strain is mainly concentrated at relatively fine grain area and the grain boundaries or triple junctions of the grains with large basal Schmid factor(SF)difference,which eventually leads to severe surface roughening and subsequent crack initiation.Compared with the sample without crack notch,the pre-cracked sample exhibits severer deformation at the crack tip due to strain concentration.Strain gradient distribution is observed at the crack tip region in the pre-cracked sample.The crack propagation path of the sample with pre-crack is identified and the underlying mechanism is also discussed.

Environmental Information-Aided Electromagnetic Propagation Testbed for Maritime Communication

Maritime channel modeling can be affected by some key time-varying environmental factors.The ducting effect is one of the thorniest factors since it causes anomalous propagation enhancement and severe co-channel interference.Moreover,the atmospheric attenuation is much more severe in the ocean environment,resulting in shorter coverage distance and more link outage.In this paper,we propose an environmental information-aided electromagnetic propagation testbed.It is based on complex refractivity estimation and improved parabolic equation propagation model,taking into account both ducting effect and atmospheric attenuation.A large-scale temporal and spatial propagation measurement was conducted with meteorological acquisition.We consider practical path loss and ducting conditions to verify the testbed feasibility in these long-distance radio links.The simulation results are in good agreement with the measured data,which further reveal the basic temporal and spatial distribution of ducting effect at 3.5 GHz band.

Simulation of Radio Path Strength for Multipath Propagation in Land Mobile Communications

Based on the characteristics of the radio propagation in land mobile communications environment, a theoretical model for the reflecting(scattering) number of each radio path is derived firstly. This model can be used to predict the variation of radio path strength, which is important for practical mobile communications engineering. Using this model, a method for simulating radio path strength is developed, with numerical results presented.

Path loss modelling and comparison based on the radio propagation measurement at 3.5GHz

Wideband IMT-Advanced mobile communication systems tend to operate in the high frequency bands due to a relatively large capacity available. Thus, Measurement and modelling methods of radio propaga- tion eharaeteristics are proposed for the field test of Chinese 4th generation （4G） trial system. The mea- surement system is established for 3.5GHz based on the sophistieated measurement instruments and the virtual instrument teehnology. The characteristic parameters of radio propagation sueh as path loss （PL） exponent and shadow fading standard deviation are extracted from measurement data, which result in the path loss model finally. The comparisons with other existing international models results validate our mea- surement in terms of path loss model. Based on the analysis of the existing extension model assumed for the microwave frequency at 3.5GHz, we find that the Stanford University Interim （SUI） model fits very well with the measurement result in the hotspot scenario, while the COST 231 model is closer to the mea- surement result in the suburban scenario. This result provides a measurement-based channel referenee for the development of the future IMT-Advanced systems in China.

Effect of Space Charge on the Propagation Path of Air Gap Discharge

The existence of space charge may be addressed as one of the reasons that could cause shielding failure of transmission lines. In order to study the effect of space charge on discharge propagation path, a new experimental system, including mainly DC high voltage generator, impulse voltage generator as well as rod-plane electrode, has been established. The space charge was generated around the rod by means of pre-applying DC high voltage, and the air gap dis- charge experiments were conducted with and without pre-applying DC high voltage, respectively. Meanwhile, high speed cameras worked simultaneously from the front and lateral side to record the discharge propagation path so as to obtain the curvature. After statistical analysis, it is shown that the curvature increases in the middle and lower portions of the propagation path when the effect of space charge is taken into account.

Analysis and Modeling of Propagation in Tunnel at 3.7 and 28 GHz

In present-day society,train tunnels are extensively used as a means of transportation.Therefore,to ensure safety,streamlined train operations,and uninterrupted internet access inside train tunnels,reliable wave propagation modeling is required.We have experimented and measured wave propagation models in a 1674 m long straight train tunnel in South Korea.The measured path loss and the received signal strength were modeled with the Close-In(CI),Floating intercept(FI),CI model with a frequency-weighted path loss exponent(CIF),and alpha-beta-gamma(ABG)models,where the model parameters were determined using minimum mean square error(MMSE)methods.The measured and the CI,FI,CIF,and ABG modelderived path loss was plotted in graphs,and the model closest to the measured path loss was identified through investigation.Based on the measured results,it was observed that every model had a comparatively lower(n<2)path loss exponent(PLE)inside the tunnel.We also determined the path loss component’s possible deviation(shadow factor)through a Gaussian distribution considering zero mean and standard deviation calculations of random error variables.The FI model outperformed all the examined models as it yielded a path loss closer to the measured datasets,as well as a minimum standard deviation of the shadow factor.

An Integrated Approach to Oscillation Propagation Identification and Source Locating in Process Multi-loop Systems

An integrated method for identifying the propagation of multi-loop process oscillations and their source location is proposed in this paper. Oscillatory process loop variables are automatically selected based on the component-related ratio index and a mixing matrix, both of which are obtained in data preprocessing by spectral independent component analysis. The complex causality among oscillatory process variables is then revealed by Granger causality test and is visualized in the form of causality diagram. The simplification of causal connectivity in the diagram is performed according to the understanding of process knowledge and the final simplest causality diagram, which represents the main oscillation propagation paths, is achieved by the automated cutting-off thresh-old search, with which less significant causality pathways are filtered out. The source of the oscillation disturbance can be identified intuitively through the final causality diagram. Both simulated and real plant data tests are presented to demonstrate the effectiveness and feasibility of the proposed method.

A Study of Propagation in Shenzhen City

Surveying the propagation path loss behavior of Shenzhen city and from the data recorded we can obtain the city’s path loss slopes, which can be comparatively regarded as the reliable bases of system design.

Power Series Expansion of Propagator for Path Integral and Its Applications

In this paper we obtain a propagator of path integral for a harmonic oscillator and a driven harmonic oscillator by using the power series expansion. It is shown that our result for the harmonic oscillator is more exact than the previous one obtained with other approximation methods. By using the same method, we obtain a propagator of path integral for the driven harmonic oscillator, which does not have any exact expansion. The more exact propagators may improve the path integral results for these systems.

Phase Space Path Integral Method for Problem of Obtaining Propagator of a Particle with a Force Quadratic in Velocity

This article uses the phase space path integral method to find the propagator for a particle with a force quadratic in velocity. Two specific canonical transformations has been used for this purpose.

Propagation Characterization and Analysis for 5G mmWave Through Field Experiments

The 5G network has been intensively investigated to realize the ongoing early deployment stage as an effort to match the exponential growth of the number of connected users and their increasing demands for high throughput,bandwidth with Quality of Service(QoS),and low latency.Given that most of the spectrums below 6 GHz are nearly used up,it is not feasible to employ the traditional spectrum,which is currently in use.Therefore,a promising and highly feasible effort to satisfy this insufficient frequency spectrum is to acquire new frequency bands for next-generation mobile communications.Toward this end,the primary effort has been focused on utilizing the millimeter-wave(mmWave)as the most promising candidate for the frequency spectrum.However,though the mmWave frequency band can fulfill the desired bandwidth requirements,it has been demonstrated to endure several issues like scattering,atmospheric absorption,fading,and especially penetration losses compared to the existing sub-6 GHz frequency band.Then,it is fundamental to optimize the mmWave band propagation channel to facilitate the practical 5G implementation for the network operators.Therefore,this study intends to investigate the outdoor channel characteristics of 26,28,36,and 38 GHz frequency bands for the communication infrastructure at the building to the ground floor in both Line of Sight(LOS)and Non-Line of Sight(NLOS)environments.The experimental campaign has studied the propagation path loss models such as Floating-Intercept(FI)and Close-In(CI)for the building to ground floor environment in LOS and NLOS scenarios.The findings obtained from the field experiments clearly show that the CI propagation model delivers much better performance in comparison with the FI model,thanks to its simple setup,accuracy,and precise function.

Numerical simulation of crack propagation by manifold method

In this paper, by means of the maximum circle tensile stress on curve of constant ω and stress intensity factors by a path independent contour integral method, trajectories of maxed mode crack propagation are simulated through numerical manifold method. The crack propagation is traced dynamically by modifying the neighboring connection between the crack-top and nodes within elements in the calculating process. This method has the advantages such as less modified area, easiness of programming, high realizability and so on. Then a single sharp nicked specimen is used to verified the numerical result. It is shown that the provided method is reasonable and effective.

基于ABAQUS平台考虑T应力的Ⅰ型裂纹扩展模拟开发

工程结构在制造工艺过程中或使用期间会产生裂纹,对结构断裂路径的预测和研究是防治工程安全问题发生的重要手段。在考虑裂纹尖端应力场常数项T应力的基础上对传统的最大周向应力准则(Maximum tangential stress criterion,MTS)和最小应变能密度因子准则(Minimum strain energy density criterion,SED)进行修正,采用Python语言对ABAQUS的前、后处理和有限元计算模块进行二次开发,通过计算最优解的粒子群算法(Particle swarm optimization,PSO)将修正后的准则编入裂纹自动扩展程序脚本中。利用上述二次开发程序对初始纯Ⅰ型裂纹的扩展路径进行模拟,结果表明:采用ABAQUS脚本程序模拟结果与相关文献实验结果吻合,表明了程序的有效性,进而实现考虑T应力的多种断裂准则对裂纹扩展路径的预测;当T应力值处于一定范围内时,修正的MTS准则无法预测裂纹发生的偏转现象,扩展路径呈直线,此时可采用修正的SED准则进行预测。

融媒体视域下黄炎培劳动教育思想传播的三重维度

黄炎培劳动教育思想是其职业教育思想的重要组成部分。从理论逻辑看,黄炎培劳动教育思想内容丰富,蕴含着“手脑并用、尊重劳动、注重培养劳动者素质”等核心要义,对新时代劳动教育具有重要的启示。从现实逻辑看,融媒体的发展给黄炎培劳动教育思想的传播和利用带来了新的挑战和机遇,其呈现出传播主体多元化、传播内容大众化、传播场域虚拟化的时代特征。从实践逻辑看,通过打造传播矩阵、创新传播方式、优化传播生态等实践理路,提升黄炎培劳动教育思想传播的广度、深度、效度和温度。

社会主义核心价值观图像化传播:困境与优化

从古至今,图像都是人们认识世界和表达情感的基本方式,更是传播价值观的重要载体。而社会主义核心价值观图像化传播则是培育和践行社会主义核心价值观的重要举措。但当下在推动社会主义核心价值观图像化传播时却出现价值观内容传递失真、过度娱乐化以及各价值要素的关联性断裂的困境。因此围绕挖掘社会主义核心价值观图像化传播资源、完善社会主义核心价值观图像化传播监管、提升社会主义核心价值观图像化传播质量以及增强对社会主义核心价值观图像的识图能力等方面,系统探寻社会主义核心价值观图像化传播的优化路径。

超越教育场域进入学术场域——近现代应用写作生成场域和传播路径对当代应用写作学科建设的影响

近现代过渡时期,由于学科生成场域的特殊性,学界缺乏对关键词“应用文”的学理性分析和对学科基础理论问题的系统研究,导致学科建设先天不足,没有完成应有的学科建树。进入现代,张鸿来、张须、陈子展、胡怀琛等同时代的一大批教育工作者有意识地改变这种状况,编写出版教材,发展和丰富了刘半农的应用“文字”说,使现代应用文概念在教育场域初步成型、学科体系初步生成。他们的研究与南京国民政府多次组织修订国语课程标准相辅相成,使得应用文在教育场域的传播路径发生变化,位阶有所提高,共同促进了教育场域对学科建设的引领作用。然而,开展当代学科建设,还需要反思刘半农的应用“文字”说的局限,防止学科建设的衰变;更需要超越教育场域,进入学术场域,并通过应用文基础理论研究和学科发展史研究等方面的突破性成果,提升学科发展水平,反哺教育场域和应用场域。

随机轮载下钢桥面顶板与纵肋焊缝疲劳裂纹扩展特性研究

车辆轮迹横向分布是钢桥面板焊缝处产生随机应力谱的一项关键因素,加之焊接缺陷形态的随机性,诱发钢桥面板疲劳裂纹随机扩展行为。为了研究钢桥面顶板焊缝处疲劳裂纹的随机扩展特性,基于断裂力学理论与扩展有限元方法分析了轮迹横向分布对钢桥面板顶板焊根和焊趾等效应力强度因子的影响规律,揭示了轮迹横向分布离散度、初始裂纹深度和初始裂纹形态比对焊缝处疲劳裂纹随机扩展路径分布的影响规律。结果表明:轮载中心处于U肋正上方中心和焊缝中心位置分别为顶板焊趾和焊根的最不利横向加载工况;车辆轮迹横向分布对顶板焊根和顶板焊趾疲劳裂纹前缘应力强度因子影响差异显著,顶板焊根最大等效应力强度因子为85.99 MPa·mm^(1/2),比顶板焊趾增加了6.72%;轮迹横向分布离散度和初始裂纹深度与钢桥面板焊缝处疲劳裂纹随机扩展路径分布离散程度成正相关,初始裂纹形态比与其成负相关;焊缝细节初始裂纹深度越大,车辆荷载对其横向影响范围越大;焊缝细节初始裂纹形态比越大,车辆荷载对其横向影响范围变化不明显。

新与旧:以数字平台为载体的戏剧文化传播路径研究

戏剧作为中华优秀传统文化之一,内含充沛的生命力,但原始单一的舞台剧场表演形式限制了戏剧文化的推广与传播,戏剧传播“失活”现象频发。现如今,随着数字技术的开发与拓展,各式数字平台崛起给传统戏剧文化的传播渠道和形式注入新鲜血液。本文立足于探索我国戏剧文化传播现状,发现戏剧文化传播内生与外源困境,从传者及受者两方面分析数字平台的传播优势,并对以数字平台为载体的新兴戏剧文化传播方式进行探讨与研究,用以创新传播路径,拓展传统戏剧边界、推动戏剧文化产业发展以及焕发传统戏剧的文化传播自信。