A method for topological entity correspondence in a replicated collaborative CAD system

In order to utilize the potential advantages of replicated collaborative CAD system to support natural, free, fast and less-constrained multi-user human-to-human interaction, a local-locking mechanism, which can provide fast modeling response, is adopted as concurrency control mechanism for a replicated on-line collaborative CAD system. A human–human interactive modeling is achieved by immediate local execution of modeling operations and exchange of modeling operations across all collaborative sites real-time. In particular, an approach to achieve topological entity correspondence across collaborative sites during modeling procedure, which is critical to guarantee the correctness and consistency of collaborative modeling result, is proposed. A prototype system based on the ACIS geometric modeling kernel is implemented to verify availability of the proposed solution.     

实时协同中的一致性维护关键技术

实时协同广泛采用数据复制技术来隐藏网络延迟、提高响应速度和改善交互体验。在复制式结构中,用户可以无约束地在不同数据副本上进行操作,这必然会引发一致性维护问题。针对上述问题,根据实时协同应用的特点和需求,总结一致性维护研究面临的技术挑战,通过研究实时协同中操作转换、地址空间转换和WOOT一致性维护的关键技术,讨论Undo和String转换等难点问题,分析这些关键技术在单用户软件向多用户协同软件透明转换、Web2.0环境和移动协同环境中的应用情况。     

A scalable method for testing real-time systems

Real-time systems (RTSs) are used in different domains such as telephone switching systems, air traffic control systems and patient monitoring systems. The behavior of RTSs is time-sensitive; that is, RTSs interact with their environment with input and output events under time constraints. The violation of such time constraints is the main cause of the misbehavior of RTSs, and may result in severe damage to human lives and the environment [Mandrioli, D., Morasca, S., & Morzenti, A. 1995. ACM Transactions on Computer Systems, 13(4), 365–398]. To prevent failures in RTSs, we must verify that the implementation of an RTS is correct before its deployment. Testing is one of the formal techniques that can be used to achieve this goal. It consists of three main phases: test generation, test execution, and test results analysis. This paper presents a test case generation method for RTSs modeled as Timed Input Output Automata (TIOA). The approach is made in two steps. First, the TIOA describing the system being tested is sampled to construct a subautomaton, which is easily testable (i.e., easy to generate test cases from it). Then, the resulting subautomaton is traversed to generate test cases. Our method is scalable in the sense that it generates a small number of test cases even when the specifications are significant. Moreover, the test cases derived by our method are executable (i.e., they can be run on any error-free implementation of the system being tested).

A design of RFTOG model for distributed real-time applications

In this paper, we design the Real-Time Fault-Tolerant Object Group (RFTOG) model that supports the grouping of distributed objects that are required for distributed application. The proposed model basically provides two services. One is the group management service, which supports both consistency maintenance and transparency of the replicated objects with a variety of replication mechanisms. It also provides the load balancing of distributed applications. The other is real-time service in an object group. When the clients request the service to the service object selected through the load balance, this service guarantees the service execution within deadline for the clients’ requests. We develop the Naval Air Defense System (NADS) simulator for verifying the effectiveness of the services proposed by the RFTOG model.     

A string-wise CRDT algorithm for smart and large-scale collaborative editing systems

With the development of big data and cloud computing, real-time collaborative editing systems have to face new challenges. How to support string-wise operations for smart and large-scale collaborations is one of the key issues in next generation of collaborative editing systems, which is both the core topic of collaborative computing area and the fundamental research of many collaborative systems in science and engineering. However, string-wise operations have troubled the existing collaborative editing algorithms, including Operational Transformation (OT) and Commutative Replicated Data Type (CRDT), for many years. This paper proposes a novel and efficient CRDT algorithm that integrates string-wise operations for smart and massive-scale collaborations. Firstly, the proposed algorithm ensures the convergence and maintains operation intentions of collaborative users under an integrated string-wise framework. Secondly, formal proofs are provided to prove both the correctness of the proposed algorithm and the intentions preserving of string-wise operations. Thirdly, the time complexity of the proposed algorithm has been analyzed in theory to be lower than that of the state of the art OT algorithm and CRDT algorithm. Fourthly, experiment evaluations show that the proposed algorithm outperforms the state of the art OT algorithm and CRDT algorithm.     

改进的基于符号数据的协同过滤推荐算法

随着用户和资源种类的不断增加,评价矩阵的稀疏性问题越来越突出,严重影响了推荐系统的推荐质量。奇异值分解(SVD)是一种对数据进行降维处理的方法,符号数据分析(SDA)是一种处理海量数据的全新数据分析思路。提出一种改进的基于符号数据的协同过滤推荐算法,即将奇异值分解和符号数据分析方法结合起来运用到推荐系统中。在EachMovie 数据库集上的实验结果表明该算法在数据稀疏时的推荐质量明显优于传统的推荐算法。     

一种新的BOC(15,2.5)调制信号同步方法

二进制偏移载波(BOC)调制方式由于调制信号自相关函数具有多峰性,在同步阶段易产生捕获模糊性的情况。针对此问题,提出了一种适用于Sine-BOC(15,2.5)调制信号的方法。新方法利用本地设计的一个辅助函数,将辅助函数与BOC调制信号自相关函数作和,按照一定规则构造出无边峰合成相关函数,实现信号的无模糊跟踪。仿真结果表明,该算法能够极大消除相关函数边峰,同时显著提高主峰检测峰值,并且使主峰宽度维持不变。     

智能CAD系统中的关系型图形数据结构

本文阐述了关系型图形数据结构在智能CAD系统中的应用,通过实例说明了如何建立关系型图形数据结构,并指出了其对提高图形设计效率、方便图形修改和支持参数化设计的重要作用。     

MIMO OFDM系统联合时频同步算法

为了解决多输入多输入多输出(Multiple imput multiple output,MIMO)正交频分复用(Orthogonal frequency division multiplexing,OFDM)系统的时间和频率偏移估计问题,提出了一种基于恒幅零自相关(Constant amplitude zero auto correlation,CAZAC)序列的联合时频同步算法。同步前导包括两个相同长度的训练符号。在接收端,分别计算两个本地训练序列与接收信号的互相关,利用CAZAC序列的特性可以检测出所有收发天线对之间的时间偏移和整数频率偏移;然后对接收信号进行整数频偏补偿,利用两个训练符号之间的关系可以估计出小数频率偏移。分析和仿真结果表明,该算法与传统的同步算法相比,不但具有更高的同步概率,而且能够估计出所有收发天线对之间的频率偏移。     

基于CAD的战损模拟装备建模技术

该文认为，研究基于CAD的装备战损模拟技术使战损模拟技术深入发展的必然要求，同时就装备编码信息数据库、CAD平台选择、编码信息在CAD平台中的实现、装备三维实体模型等问题进行了阐述，通过射线分析过程，阐述了如何应用转换后得到的CAD数据。     

Effective real-time scheduling algorithm for cyber physical systems society

CPS (Cyber Physical Systems) tightly couple their cyber factor and physical factor in distributed computing or Grids environments to provide real-time services such as avionics, transportation, manufacturing processes, energy, healthcare, etc. We need to consider not only the cyber space (CPU, network, storage systems, etc.) and the physical space (location, migration, etc.) but also the socio space and mental space for the precise analysis and useful services. In this paper, real-time scheduling algorithms, namely ELST (Effective Least Slack Time First) and H-ELST (Heuristic-Effective Least Slack Time First), are presented for CPS, where servicing node needs to move to serviced node for real-time services. We measure the real-time performance in terms of deadline meet ratio by mathematical analysis and simulations. The results show that our algorithms reduce a deadline miss ratio approximately up to 50% and 20% compared to the conventional real-time scheduling algorithm, FIFO (First In First Out) and LST (Least Slack Time First), respectively.     

A novel method for pulmonary embolism detection in CTA images

In this paper, we propose a new computer-aided detection (CAD) – based method to detect pulmonary embolism (PE) in computed tomography angiography images (CTAI). Since lung vessel segmentation is the main objective to provide high sensitivity in PE detection, this method performs accurate lung vessel segmentation. To concatenate clogged vessels due to PEs, the starting region of PEs and some reference points (RPs) are determined. These RPs are detected according to the fixed anatomical structures. After lung vessel tree is segmented, the region, intensity, and size of PEs are used to distinguish them. We used the data sets that have heart disease or abnormal tissues because of lung disease except PE in this work. According to the results, 428 of 450 PEs, labeled by the radiologists from 33 patients, have been detected. The sensitivity of the developed system is 95.1% at 14.4 false positive per data set (FP/ds). With this performance, the proposed CAD system is found quite useful to use as a second reader by the radiologists.     

RFID-enabled real-time manufacturing execution system for mass-customization production

Mass-customization production (MCP) companies must fight with shop-floor uncertainty and complexity caused by wide variety of product components. The research is motivated by a typical MCP company that has experienced inefficient scheduling due to paper-based identification and manual data collection. This paper presents an RFID-enabled real-time manufacturing execution system (RT-MES). RFID devices are deployed systematically on the shop-floor to track and trace manufacturing objects and collect real-time production data. Disturbances are identified and controlled within RT-MES. Planning and scheduling decisions are more practically and precisely made and executed. Online facilities are provided to visualize and manage real-time dynamics of shop-floor WIP (work-in-progress) items. A case study is reported in a collaborating company which manufactures large-scale and heavy-duty machineries. The efficiency and effectiveness of the proposed RT-MES are evaluated with real-life industrial data for shop-floor production management in terms of workers, machines and materials.     

基于1DCNN的二阶段OFDM系统定时同步方法

针对存在多径干扰的正交频分复用系统的定时同步准确性低的问题,提出基于一维卷积神经网络（1-D CNN）的二阶段OFDM系统定时同步方法。在第一阶段,利用经典互相关方法实现路径特征初始抽取,捕获可分辨路径上的定时辅助同步点;基于定时辅助同步点构建1-D CNN网络学习第二阶段中的定时偏移;最后,结合两阶段处理,获得系统最终的定时同步偏移估计。相比于基于压缩感知的定时同步方法和基于极限学习机的定时同步方法,所研究的二阶段OFDM系统定时同步方法提高了定时同步准确性,并有效地降低计算复杂度与处理延迟。     

A novel two-stage evolutionary optimization method for multiyear expansion planning of distribution systems in presence of distributed generation

In this paper, a new approach for multiyear expansion planning of distribution systems (MEPDS) is presented. The proposed MEPDS model optimally specifies the expansion schedule of distribution systems including reinforcement scheme of distribution feeders as well as sizing and location of distributed generations (DGs) during a certain planning horizon. Moreover, it can determine the optimal timing (i.e. year) of each investment/reinforcement. The objective function of the proposed MEPDS model minimizes the total investment, operation and emission costs while satisfying various technical and operational constraints. In order to solve the presented MEPDS model as a complicated multi-dimensional optimization problem, a new two-stage solution approach composed of binary modified imperialist competitive algorithm (BMICA) and Improved Shark Smell Optimization (ISSO), i.e. BMICA + ISSO, is presented. The performance of the suggested MEPDS model and also two-stage solution approach of BMICA + ISSO is verified by applying them on two distribution systems including a classic 34-bus and a real-world 94-bus distribution system as well as a well-known benchmark function. Additionally, the achieved results of BMICA + ISSO are compared with the obtained results of other two-stage solution methods.     

A non-preemptive scheduling algorithm for soft real-time systems

Real-time systems are often designed using preemptive scheduling and worst-case execution time estimates to guarantee the execution of high priority tasks. There is, however, an interest in exploring non-preemptive scheduling models for real-time systems, particularly for soft real-time multimedia applications. In this paper, we propose a new algorithm that uses multiple scheduling strategies for efficient non-preemptive scheduling of tasks. Our goal is to improve the success ratio of the well-known Earliest Deadline First (EDF) approach when the load on the system is very high and to improve the overall performance in both underloaded and overloaded conditions. Our approach, known as group-EDF (gEDF) is based on dynamic grouping of tasks with deadlines that are very close to each other, and using Shortest Job First (SJF) technique to schedule tasks within the group. We will present results comparing gEDF with other real-time algorithms including, EDF, Best-effort, and Guarantee, by using randomly generated tasks with varying execution times, release times, deadlines and tolerance to missing deadlines, under varying workloads. We believe that grouping tasks dynamically with similar deadlines and utilizing a secondary criteria, such as minimizing the total execution time (or other metrics such as power or resource availability) for scheduling tasks within a group, can lead to new and more efficient real-time scheduling algorithms.     

A novel on-line OCID method and its application to input-constrained active fault-tolerant tracker design for unknown nonlinear systems

ABSTRACT

The existing off-line observer/controller identification (OCID) method for linear systems is newly extended in this paper for off-line/on-line identification of known/unknown highly nonlinear systems, and a new input-constrained active fault-tolerant tracker is developed, based on the identified linear models. The advantages of the proposed extended on-line OCID method for linear/nonlinear systems are briefly described as follows: (i) Implement novel servo-control-oriented off-line OCID methods in observer and controller canonical forms for highly nonlinear systems; (ii) Is able to overcome the discontinuity induced by the singular value decomposition (SVD) that should be carried out at each sampling instant; (iii) It directly realises the identified parameters in the observer/controller canonical forms; this simplifies the identification process; (iv) Can be practically implemented for the on-line control of an unknown nonlinear system which was constituted by an unknown open-loop plant, an existing but unknown controller and/or an unknown observer; and (v) Can be utilised to develop a new active fault-tolerant controller to compensate the immovable existing controller of the practical operating system. Finally, the servo-control-oriented off-line OCID method for the highly nonlinear PUMA 560 manipulator is shown in the illustrative examples to demonstrate the superiority of the proposed method.     

A solution of multidisciplinary collaborative simulation for complex engineering systems in a distributed heterogeneous environment

This paper presents an integrated approach to multidisciplinary collaborative simulation for complex engineering systems. The formulized paradigm of multidisciplinary collaborative simulation for com- plex engineering systems is principally analyzed. An IEEE HLA and web services based framework is proposed to provide a heterogeneous, distributed and collaborative running environment where multidisciplinary modeling, running management and post-processing of collaborative simulation are undertaken. The mecha...     

A real-time personalized route recommendation system for self-drive tourists based on vehicle to vehicle communication

Recently, traffic jams and long queuing problems in tourist hot spots is growing with the increasing number of self-drive tourists. Some recommendation systems have been developed in attempt to relieve these problems. However, all these systems lack information pertaining to real-time traffic as well as the ability of personalization. In this research, we have developed a novel route recommendation system to provide self-drive tourists with real-time personalized route recommendations. This will help to reduce the traffic jams and queuing time in tourist hot spots. It will also help to personalize visiting routes based on the user’s specific preferences. Ultimately, based on the evaluation results given by experienced self-drive tourists, we have shown that the proposed system not only saves total visiting time, but also meets their specific visiting preferences.     

A novel reduced-basis method with upper and lower bounds for real-time computation of linear elasticity problems

This paper presents a novel reduced-basis method for analyzing problems of linear elasticity in a systematical, rapid and reliable fashion for solutions with both upper and lower bounds to the exact solution in the form of energy norm or compliance output. The lower bound of the solution output is obtained form the well-known reduced-basis method based on the Galerkin projection used in the finite element method, which is termed as GP_RBM. For the upper bound, a new reduced-basis approach is developed by the combination of the reduced-basis method and a smoothed Galerkin projection used in the linearly conforming point interpolation method, and it is thus termed as SGP_RBM. To examine the present SGP_RBM, we first conduct a theoretical study on the very important upper bound property. Reduced-basis models for both GP_RBM and SGP_RBM are constructed with the aid of an asymptotic error estimation and greedy adaptive procedure. The GP_RBM and the newly proposed SGP_RBM are applied to analyze a cantilever beam with an oblique crack to verify the proposed RBM technique in terms of accuracy, convergence, bound properties and computational savings. Both theoretical analysis and numerical results have demonstrated that the present method is a very efficient method for real-time solutions providing exact output bounds.