Interference checking approach with tolerance based on assembly dimension chain

CAD model with nominal dimension is implemented in interference checking of assembly simulation of aircraft complex parts at present,which causes inadequate availability.In order to address this challenging issue,interference checking method with tolerance based on assembly dimension chain was proposed.Worst case and maximum error probability of tolerance of composing loop were used,and CAD models were respectively re-constructed and inserted into simulation system.Before dynamic interference checking,engineering semantic interference condition was set to assembly requirements.Finally,the interface checking result was a basis for reasonability of assembly process and tolerance.A prototype system was developed based on the above research.     

A new approach for predicting and collaborative evaluating the cutting force in face milling based on gene expression programming

Cutting force is one of the fundamental elements that can provide valuable insight in the investigation of cutter breakage, tool wear, machine tool chatter, and surface finish in face milling. Analyzing the relationship between process factors and cutting force is helpful to set the process parameters of the future cutting operation and further improve production quality and efficiency. Since cutting force is impacted by the inherent uncertainties in the machining process, how to predict the cutting force presents a significant challenge. In the meantime, face milling is a complex process involving multiple experts with different domain knowledge, collaborative evaluation of the cutting force model should be conducted to effectively evaluate the constructed predictive model. Gene Expression Programming (GEP) combines the advantages of the Genetic Algorithm (GA) and Genetic Programming (GP), and has been successfully applied in function mining and formula finding. In this paper, a new approach to predict the face milling cutting force based on GEP is proposed. At the basis of defining a GEP environment for the cutting force prediction, an explicit predictive model has been constructed. To verify the effectiveness of the proposed approach, a case study has been conducted. The comparisons between the proposed approach and some previous works show that the constructed model fits very well with the experimental data and can predict the cutting force with a high accuracy. Moreover, in order to better apply the constructed predictive models in actual face milling process, a collaborative model evaluation method is proposed to provide a distributed environment for geographical distributed experts to evaluate the constructed predictive model collaboratively, and four kinds of collaboration mode are discussed.     

A Lie-Backlund approach to equivalence and flatness of nonlinearsystems

A new system equivalence relation, using the framework of differential geometry of jets and prolongations of infinite order, is studied. In this setting, two systems are said to be equivalent if any variable of one system may be expressed as a function of the variables of the other system and of a finite number of their time derivatives. This is a Lie-Backlund isomorphism. The authors prove that, although the state dimension is not preserved, the number of input channels is kept fixed. They also prove that a Lie-Backlund isomorphism can be realized by an endogenous feedback. The differentially flat nonlinear systems introduced by the authors (1992) via differential algebraic techniques, are generalized and the new notion of orbitally flat systems is defined. They correspond to systems which are equivalent to a trivial one, with time preservation or not. The endogenous linearizing feedback is explicitly computed in the case of the VTOL aircraft to track given reference trajectories with stability     

A new optimization model to support a bottom-up approach to facility design

The facility layout problem is typically solved in what is referred to as a “top-down approach” of block layout design followed by detailed layout determination. However, a number of research efforts recently have challenged this approach, producing a reformulated bottom-up approach to the facility layout problem. In this paper we consider the bottom-up approach, applying a tighter formulation than prior efforts and investigating the solvability limits of the new model. Empirical testing of the new bottom-up layout model indicates that although this model produces more usable output, as judged by industry experts, it is approximately three times harder to solve. Valid inequalities and special cases are identified to help improve the formulation's solvability.     

基于入侵容忍的数据库安全体系模型

本文提出了一种基于入侵容忍的数据库安全体系模型。在数据库受到入侵的情况下,该模型从事务处理的角度出发,结合入侵检测和入侵容忍技术,把对关键数据的操作及可疑事务都进行隔离,运用多阶段控制技术来阻止破坏扩散,同时事务合并与多阶段控制技术相结合,进一步减少入侵可能对系统造成的破坏。从而保证系统在被入侵时,为合法用户提供不间断服务。     

A topology control algorithm based on D-region fault tolerance

In a wireless network, node failure due to either natural disasters or human intervention can cause network partitioning and other communication problems. For this reason, a wireless network should be fault tolerant. At present, most researchers use k-connectivity to measure fault tolerance, which requires the network to be connected after the failure of any up to k-1 nodes. However, wireless network node failures are usually spatially related, and particularly in military applications, nodes from the same limited area can fail together. As a metric of fault-tolerance, k-connectivity fails to capture the spatial relativity of faults and hardly satisfies the fault tolerance requirements of a wireless network design. In this paper, a new metric of fault-tolerance, termed D-region fault tolerance, is introduced to measure wireless network fault tolerance. A D-region fault tolerant network means that even after all the nodes have failed in a circular region with diameter D, it still remains connected. Based on D-region fault tolerance, we propose two fault-tolerant topology control algorithms--the global region fault tolerance algorithm (GRFT) and the localized region fault tolerance algorithm (LRFT). It is theoretically proven that both algorithms are able to generate a network with D-region fault tolerance. Simulation results indicate that with the same fault tolerance capabilities, networks based on both GRFT and LRFT algorithms have a lower transmission radius and lower logical degree.     

A statistical approach to the generation of a database for evaluating OCR software

In this paper we consider a statistical approach to augment a limited database of groundtruth documents for use in evaluation of optical character recognition software. A modified moving-blocks bootstrap procedure is used to construct surrogate documents for this purpose which prove to serve effectively and, in some regards, indistinguishably from groundtruth. The proposed method is validated through a rigorous statistical procedure. Received: March 30, 2000 / Revised: September 14, 2001     

乙烯装置节能技术的模糊层次综合评价

针对国内乙烯能耗偏高,各项节能技术发展水平参差不齐,同时缺乏对各项节能技术统一评价方法的现状,本文通过对乙烯装置节能技术影响因素的分析,构建了涵盖技术性、节能性与经济性的综合评价指标体系.采用层次分析法与模糊评价法相集成的方式,建立了用于节能技术评价的模糊综合评价指标体系.针对有一定推广潜力的11项乙烯装置的节能技术进行了模糊综合评价,并利用综合指标值与评价集合相结合评价各项技术.评价结果显示,多项技术在不同方面具有优势,综合评价可使对技术的选择,从“最优化”向“提高满意度”方向转变,从而更好地为乙烯企业选择先进适用的节能技术提供决策支持依据.     

A group decision support approach to evaluating journals

One of the most important decisions made in academic institutions, research organizations, and government agencies is the grading or ranking of journals for their academic values. Current methods for evaluating journals use either a subjective (e.g., experts’ judgments on journals) or objective approach (e.g., impact factors of journals), or an informal mix of the two. This paper presents a formal procedure that integrates objective and subjective judgments to provide a comprehensive method. The procedure is based on a fuzzy set approach that deals with the imprecise and missing information inherent in the evaluation process. The system was tested in Hong Kong in an assessment of faculty research productivity. Similar assessments exist in the UK, Singapore, and other countries. The proposed model can also be used for similar decisions that involve subjective and objective information.     

A unified approach to pattern recognition

The paper is an outline of a new approach to pattern recognition developed by the author. A fuller introduction to the approach will appear soon.⁽¹⁾ Within the proposed framework the two principal approaches to pattern recognition—vector and syntactic—are unified.