首页 | 官方网站   微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 93 毫秒
1.
It is well known that in the general context the similarity relation is very fuzzy and hard to define. Unfortunately, the intuitive notion of similarity is not a transitive relation: knowing that A is similar to B and that B is similar to C does not necessarily imply similarity between A and C. This is a main obstacle when trying to express formally what a coherent font design is. In this paper we suggest a method to decompose complex letter forms into simpler elements and we suggest a formal transitive definition of a similarity relation between these elements. In the context of digital typography, this definition enables developing an algorithm to recover classes of similar elements within different characters of a given font. This knowledge is further exploited to ensure coherent type processing. For example, a modification (e.g. by a type designer) of a character element is propagated automatically to all the other characters that include a similar element. For the moment, the discussion is limited to the class of stroke fonts.  相似文献   

2.
为了对开关的寿命进行快速准确地测试,设计了开关寿命测试仪。设计过程如下:首先设计了测试仪的硬件,该硬件使用LPC2138CPU芯片采集开关触头对应的开关量,并与TG12864液晶模块接口输出提示信息;其次设计了判断开关好坏算法和识别坏触头算法;最后根据算法给出了测试仪软件的流程图。应用表明,用这种设计方法实现的测试仪工作可靠、容易使用,适合在开关生产行业推广应用。  相似文献   

3.
文中介绍了一种系统级故障诊断模型--通用比较模型,该模型处理器作为自身的比较器,综合经典的PMC模型和Maeng/Malek模型的优点,基于该报多处理器系统的t_可诊断性问题,给出了t_可诊断系统的特征化,证明了一个系统成为t-可诊断系统的新的充分必要条件,其次,证明在通用比较模型中,确定故障顺集的问题等价于求解一个超图的最小横切集(Minimum traversal),该超图是根据多处理器的通信  相似文献   

4.
基于Struts和JDO的信息管理系统   总被引:3,自引:0,他引:3  
饶文碧  范昆鹏 《微机发展》2004,14(10):15-16,20
Struts是广泛应用的Web框架,但它没有提供如何访问数据的方法。JDO是数据访问框架,利用O-R映射来访问数据库,而一般要用JDBC和SQL来访问数据库,较之JDO更加方便和快捷。一个成熟的应用需要两者结合起来才能形成一个完整的方案。这里提出用Struts作为前台和逻辑控制,用JDO作为后台数据访问层来开发B/S架构的信息管理系统的一种方案。  相似文献   

5.
The essence of intelligence is to use certain abilities to obtain knowledge, to use that knowledge, and to operate with that knowledge. New knowledge learned by a human is often related to old existing knowledge, and sometimes we could have more conceptual knowledge based on old knowledge. So, the knowledge in the brain exists in a related structural form, and this structure is dynamic, and therefore is evolvable. Based on the understanding of the real process of learning by a human being, we discuss how to make a model to describe the dynamic structure of knowledge. This model is also a principle of artificial brain design. Most of the knowledge a child learns is from natural language and perception information, and we define this as semantic knowledge. The model to describe the process and structure of knowledge growing in a network form is called a K-net. It is a dynamic network with two main dynamics: one is new knowledge added, and the other is aggregating knowledge existing in the network with some probability. Under these very natural conditions, we found that the network is originally a simple random net, and then some characteristics of a complex network gradually appear when more new knowledge is added and aggregated. A more interesting phenomenon is the appearance of a random hierarchical structure. Does this mean emergence?  相似文献   

6.
在实际应用中有这样一类关系数据库,其中数据项在某个属性上的取值本身又是一个关系。讨论这种混合关系中的函数依赖及其相应的相关规则具有一定的理论意义和实际应用价值。给出这种混合关系的形式定义、混合关系中4种类型的函数依赖关系以及相应的4种类型的相关规则;并给出混合关系到一般关系的转换,通过这个转换说明了混合关系与普通关系的联系及其差别。给出一个实际应用中的例子,来说明混合关系中的函数依赖和相关规则的形式多样性。  相似文献   

7.
The fundamental problem in the design of update strategies for views of database schemata is that of selecting how the view update is to be reflected back to the base schema. This work presents a solution to this problem, based upon the dual philosophies of closed update strategies and order-based database mappings. A closed update strategy is one in which the entire set of updates exhibit natural closure properties, including transitivity and reversibility. The order-based paradigm is a natural one; most database formalisms endow the database states with a natural order structure, under which update by insertion is an increasing operation, and update by deletion is decreasing. Upon augmenting the original constant-complement strategy of Bancilhon and Spyratos – which is an early version of a closed update strategy – with compatible order-based notions, the reflection to the base schema of any update to the view schema which is an insertion, a deletion, or a modification which is realizable as a sequence of insertions and deletions is shown to be unique and independent of the choice of complement. In addition to this uniqueness characterization, the paper also develops a theory which identifies conditions under which a natural, maximal, update strategy exists for a view. This theory is then applied to a ubiquitous example – single-relational schemata constrained by equality-generating dependencies. Within this framework it is shown that for a view defined as a projection of the main relation, the only possibility is that the complement defining the update process is also a projection, and that the reconstruction is based upon functional dependencies.  相似文献   

8.
Discussed in this short paper is a controllability question pertaining to a class of sensitivity problems. More specifically, the possibility is considered of transferring a time-invariant linear system from each initial state to any terminal state in a finite time and in such a way that the terminal condition is insensitive to small parameter variations. Partial controllability, suitably defined, leads to a necessary and sufficient condition for the existence of the solution to such a problem. Terminal output insensitivity is also discussed and a similar result is proved when the output transformation is not affected by some parameter variations.  相似文献   

9.
A method is presented forcomputing the inverse dynamics of a linear non-minimum phasesystem with non-zero initial conditions. The method is also usedto change or correct a trajectory after it is already in motion,and consequently, it will allow for real time control by continuallyupdating the inverse dynamics computation.Frequency domain techniques are used to compute the input functionneeded to produce a desired output trajectory at a particulardegree of freedom. An output profile based on the differencebetween the desired trajectory and either a homogeneous responseor a forced response to a previous forcing function is used tocompute the required input function. The resulting input functionactively damps out initial conditions in the system and makesit track the desired trajectory.The method is applied to a non-collocated single-link flexiblerobot arm. The finite element method using Timoshenko beam theoryis used to discretize the equations of motion. Torque profilesare computed to control the tip displacement for several problems.The first problem is to control the tip to a desired trajectorywhen starting with non-zero initial conditions. The second problemis to change the desired trajectory while the previous desiredtrajectory is already in motion. The third problem is to correctthe trajectory after a disturbance is added to the system. Thefourth problem is to analyze sensitivity to errors in the modeland initial conditions. The last problem is to compare tip responsesfor rigid and flexible link assumptions in the inverse dynamicscomputation.  相似文献   

10.
入侵检测实质上是一个分类的问题,对于提高分类精度是十分重要的.支持向量机(SVM)是一个功能强人的用于解决分类问题的工具.基于支持向量机的入侵检测精度较高,但如何获得更高的精度是一个新的问题.本文利用基于支持向量机和遗传算法(GA)的入侵检测来解决这些问题.我们首先利用遗传算法进行特征选择及优化,然后使用支持向量机模型...  相似文献   

11.
12.
Detection of the presence, size and speed of microdroplets in microfluidic devices is presented using commercially available capacitive sensors which make the droplet based microfluidic systems scalable and inexpensive. Cross-contamination between the droplets is eliminated by introducing a passivation layer between the sensing electrodes and droplets. A simple T-junction generator is used to generate droplets in microchannels. Coplanar electrodes are used to form a capacitance through the microfluidic channel. The change in capacitance due to the presence of a droplet in the sensing area is detected and used to determine the size and speed of the droplet. The design of a single pair of electrodes is used to detect the presence of a droplet and the interdigital finger design is used to detect the size and speed of the droplet. An analytical model is developed to predict the detection signal and guide the experimental optimization of the sensor geometry. The measured droplet information is displayed through a Labview interface in real-time. The use of capacitance sensors to monitor droplet sorting at a T-junction is also presented. The discussions in this paper can be generalized to any droplet detection application and can serve as a guideline in sensor selection.  相似文献   

13.
基于AHP的优化决策模型研究   总被引:1,自引:4,他引:1  
对于传统的AHP求解模型,存在难以识别比较矩阵中的不一致判断的情况。通过构造两阶段线性规划模型,在第一阶段求出一致性求解范围,利用该一致性范围作为第二阶段的限制条件,借助于LINDO或者MATLAB软件求出了最优的优先权矢量,并举例说明应用这个模型的计算过程。最后,通过具体实例对模型的灵敏性进行了分析,给出了不一致性判断的识别方法。  相似文献   

14.
A paradigm is proposed for representing hierarchically specified design data in CAD database systems in which there are alternate expansions of hierarchically specified modules. The paradigm uses an ancestor-based scheme to control which instances of submodules are to be placed in the expansion of each instance of a given module and is formalized using a versioned directed acyclic multigraph (VDAG). The approach is aimed at reducing storage space in engineering design database systems and at providing a means for designers to specify alternate expansions of a module. The VDAG model is defined, and a mechanism by which a VDAG generates an exploded forest of design trees is described. Algorithms are provided to generate a design forest from a given VDAG, determine whether one module is contained by a larger module, extract a version from a VDAG, test whether two VDAGs are equivalent, and try to reduce the size of a VDAG. The problems of module containment and VDAG inequivalence are shown to be NP-complete, and the problem of finding a minimum sized VDAG equivalent to a given VDAG is shown to be NP-hard  相似文献   

15.
This paper studies the Semantic Network Language Generation (SNLG), which is used to generate natural language from the information represented as Semantic Networks (SN). After a brief analysis of the challenges faced by SNLG, a Semantic Network Serialization Grammar (SNSG) is proposed to generate natural language from semantic networks. The SNSG is constituted by four components: (a) a semantic pattern approach to serializing a trivial semantic star into a language stream. (b) a transformative generation to serialize a trivial semantic tree by serializing semantic star recursively. (c) a procedure of trivialization to convert any complicated semantic star or semantic tree into composition of trivial semantic tree. (d) a mechanism of semantic pattern priority and semantic pattern network to guarantee a sentence generated from a semantic tree to be well formed. Based on the SNSG, a new approach of the content planning for SNLG is proposed to improve the content integrity. For discourse planning, a trivialization time splitting method is presented to make well-formed sentence, and a splitting time aggregation method is proposed to improve the readability of sentence. Finally a fully semantized Semantic Wiki system, the Natural Wiki, is developed to verify and demonstrate the theory and techniques addressed in this paper.  相似文献   

16.
二进神经网络中汉明球的逻辑意义及一般判别方法   总被引:3,自引:0,他引:3  
剖析二进神经元的逻辑意义对二进神经网络的规则提取是十分重要的,在布尔空间中,汉明球是一种线性可分的空间结构,如何从汉明球中提取出具有清晰逻辑意义的规则是二进神经网络研究的一个问题,通过对MofN规则表达形式的扩展,分析了汉明球的逻辑意义,提出了表达汉明球逻辑意义的LEM规则和GEM规则方法,并且讨论了汉明球和汉明补球的等价性,另一个重要的结果是证明了二进神经元和汉明球等价的充要条件,从而建立了判别汉明球的一般方法。  相似文献   

17.
In this paper, an approach to decision making is described. It combines a knowledge acquisition technique, a multi-attribute decision making technique, a validation technique and a machine learning algorithm. The suggested system is an extension of a previous decision support system based on the fuzzy repertory table technique. The aim is to increase its efficiency when dealing with a great amount of alternatives and criteria. The solution is based on a mechanism to divide the original problem into several simpler sub-problems. Moreover, a case study is presented to illustrate how the proposed system is used to design a Product Search Assistant. It will be integrated into a multi-agent architecture developed to give support to an e-marketplace.  相似文献   

18.
The notion of steady-state invertibility of a system is introduced, which is concerned about the problem of being able to find an input so that the output of a stable system is asymptotically equal to a specified output of a certain class of functions. Necessary and sufficient conditions are found for a linear time-invariant system to be steady-state invertible. Application of these results is then made to find necessary and sufficient conditions for a feedforward controller to exist for a general linear time-invariant system, so that asymptotic tracking, in the presence of a general class of measurable disturbances occurs. Explicit feedforward controllers which will accomplish this are obtained. Properties of the steady-state invertibility condition are then obtained; in particular, it is shown that a system is "almost always" steady-state invertible if the number of plant inputs is not less than the number of outputs; if the number of plant inputs is less than the number of outputs, then a system is "almost never" steady-state invertible. It is then shown that a system which is minimum phase and which has at least the same number of inputs as outputs is always steady-state invertible.  相似文献   

19.
Abstract The p-center problem is one of choosing p facilities from a set of candidates to satisfy the demands of n clients in order to minimize the maximum cost between a client and the facility to which it is assigned. In this article, PBS, a population based meta-heuristic for the p-center problem, is described. PBS is a genetic algorithm based meta-heuristic that uses phenotype crossover and directed mutation operators to generate new starting points for a local search. For larger p-center instances, PBS is able to effectively utilize a number of computer processors. It is shown empirically that PBS has comparable performance to state-of-the-art exact and approximate algorithms for a range of p-center benchmark instances.  相似文献   

20.
This paper presents an adaptive algorithm designed for batch feed bioprocess control, The proposed algorithm is based on a non-linear ‘grey box’ model, which is adapted on-line to the process behaviour by the estimation of a key parameter. Stability and convergence analysis of this algorithm is presented, and from this, a practical tuning method is given. The proposed algorithm is compared to a standard adaptive generalized predictive controller approach, and is shown to exhibit similar performance while being easier to use. A real application of this adaptive algorithm to a batch feed lysine process is presented. Good results are obtained, which show that this control scheme is a worthwhile alternative for batch feed bioprocess control.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号