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排序方式: 共有420条查询结果,搜索用时 15 毫秒
1.
Theodore Karoubalis Kostas Adaos George Ph. Alexiou Nick Kanopoulos 《International Journal of Circuit Theory and Applications》1995,23(6):587-598
This paper describes an efficient technique for the design of fault-secure VLSI circuits based on differential cascode voltage switch (DCVS) logic. We propose a new synthesis method for constructing DCVS circuits with a near-optimal transistor count based on binary decision diagrams (BDDs). the time and memory resources required are very low, making the technique practical even for PC-based synthesis tools. This method is the basis for a CAD tool that allows automatic synthesis of fault-secure circuits based on the DCVS technology. We finally present an improved design and implementation of a 2's complement serial/parallel multiplier as an application of the proposed technique and algorithm. 相似文献
2.
The paper deals with methods facilitating the preparation of oncospheres of the cestode, Hymenolepis diminuta, for experimental studies. Described in detail are procedures for the infection of the definitive hosts with the oncospheres; collection and artificial hatching of oncospheres; purification of hexacanths; preparation of extracts from the hexacanths; and preparation of hexacanths for electronmicroscopic studies. 相似文献
3.
4.
George Caridakis Stylianos Asteriadis Kostas Karpouzis 《Personal and Ubiquitous Computing》2014,18(1):37-46
Present work deals with the incorporation of non-manual cues in automatic sign language recognition. More specifically, eye gaze, head pose, and facial expressions are discussed in relation to their grammatical and syntactic function and means of including them in the recognition phase are investigated. Computer vision issues related to extracting facial features, eye gaze, and head pose cues are presented and classification approaches for incorporating these non-manual cues into the overall Sign Language recognition architecture are introduced. 相似文献
5.
Kostas Tzoumas Amol Deshpande Christian S. Jensen 《The VLDB Journal The International Journal on Very Large Data Bases》2013,22(1):3-27
Query optimizers rely on statistical models that succinctly describe the underlying data. Models are used to derive cardinality estimates for intermediate relations, which in turn guide the optimizer to choose the best query execution plan. The quality of the resulting plan is highly dependent on the accuracy of the statistical model that represents the data. It is well known that small errors in the model estimates propagate exponentially through joins, and may result in the choice of a highly sub-optimal query execution plan. Most commercial query optimizers make the attribute value independence assumption: all attributes are assumed to be statistically independent. This reduces the statistical model of the data to a collection of one-dimensional synopses (typically in the form of histograms), and it permits the optimizer to estimate the selectivity of a predicate conjunction as the product of the selectivities of the constituent predicates. However, this independence assumption is more often than not wrong, and is considered to be the most common cause of sub-optimal query execution plans chosen by modern query optimizers. We take a step towards a principled and practical approach to performing cardinality estimation without making the independence assumption. By carefully using concepts from the field of graphical models, we are able to factor the joint probability distribution over all the attributes in the database into small, usually two-dimensional distributions, without a significant loss in estimation accuracy. We show how to efficiently construct such a graphical model from the database using only two-way join queries, and we show how to perform selectivity estimation in a highly efficient manner. We integrate our algorithms into the PostgreSQL DBMS. Experimental results indicate that estimation errors can be greatly reduced, leading to orders of magnitude more efficient query execution plans in many cases. Optimization time is kept in the range of tens of milliseconds, making this a practical approach for industrial-strength query optimizers. 相似文献
6.
George Nikolakopoulos Kostas Alexis 《International Journal of Control, Automation and Systems》2013,11(2):389-397
In this article, a switching networked attitude controller for an unmanned quadrotor over a wireless sensor network is presented. To deal with the network induced time varying delays, the quadrotor is being modeled as a switching time varying linear system, while the applied switching output feedback control scheme, is calculated based on Linear Matrix Inequalities, and is able to guarantee the stability of the quadrotor under arbitrary changes in the time delays. 相似文献
7.
Theodore Pachidis John Lygouras Kostas Tarchanidis 《Journal of Intelligent and Robotic Systems》2008,51(4):385-420
In this paper, first HumanPT architecture for low cost robotic applications is presented. HumanPT architecture differs than
other architectures because it is implemented on existing robotic systems (robot robotic controller) and exploits the minimum
communication facilities for real-time control that these systems provide. It is based on well-known communication methods
like serial communication (USB, RS232, IEEE-1394) and windows sockets (server–client model) and permits an important number
of different type of components like actuators, sensors and particularly vision systems to be connected in a robotic system.
The operating system (OS) used is Microsoft Windows, the most widely spread OS. The proposed architecture exploits features
of this OS that is not a real-time one, to ensure – in case that the robotic system provide such a facility – control and
real time communication with the robotic system controller and to integrate by means of sensors and actuators an important
number of robotic tasks and procedures. As implementation of this architecture, HumanPT robotic application and experimental results concerning its performance and its implementation in real tasks are provided.
HumanPT robotic application, developed in Visual C++, is an integrated, but simultaneously an open-source software that can be adapted
in different types of robotic systems. An important number of robotic tasks or procedures including sensors and particularly
vision systems can be generated and executed. Small enterprises by means of the proposed architecture and the open source
software can be automated at low cost enhancing in this way their production. 相似文献
8.
Estimation of behavioral user state based on eye gaze and head pose—application in an e-learning environment 总被引:1,自引:1,他引:0
Stylianos Asteriadis Paraskevi Tzouveli Kostas Karpouzis Stefanos Kollias 《Multimedia Tools and Applications》2009,41(3):469-493
Most e-learning environments which utilize user feedback or profiles, collect such information based on questionnaires, resulting
very often in incomplete answers, and sometimes deliberate misleading input. In this work, we present a mechanism which compiles
feedback related to the behavioral state of the user (e.g. level of interest) in the context of reading an electronic document;
this is achieved using a non-intrusive scheme, which uses a simple web camera to detect and track the head, eye and hand movements
and provides an estimation of the level of interest and engagement with the use of a neuro-fuzzy network initialized from
evidence from the idea of Theory of Mind and trained from expert-annotated data. The user does not need to interact with the
proposed system, and can act as if she was not monitored at all. The proposed scheme is tested in an e-learning environment,
in order to adapt the presentation of the content to the user profile and current behavioral state. Experiments show that
the proposed system detects reading- and attention-related user states very effectively, in a testbed where children’s reading
performance is tracked.
相似文献
Stefanos KolliasEmail: |
9.
This paper investigates the effect of microwave curing on the bond strength of steel reinforcement in concrete repair. Pull-out tests on plain mild steel reinforcement bars embedded in four repair materials in 100 mm cube specimens were performed to determine the interfacial bond strength. The porosity and pore structure of the matrix at the steel interface, which influence the bond strength, were also determined. Test results show that microwave curing significantly reduces the bond strength of plain steel reinforcement. The reduction relative to normally cured (20 °C, 60% RH) specimens is between 21 and 40% with low density repair materials and about 10% for normal density cementitious mortars. The corresponding compressive strength of the matrix also recorded similar reduction and microwave curing resulted in increased porosity at the interface transition zone of the steel reinforcement. A unique relationship exists between bond strength and both compressive strength and porosity of all matrix materials. Microwave curing reduced shrinkage but despite the wide variation in the shrinkage of the repair mortars, its effect on the bond strength was small. The paper provides clear correlations between the three parameters (compressive strength, bond strength and porosity), which are common to both the microwave and conventionally cured mortars. Therefore, bond-compressive strength relationships used in the design of reinforced concrete structures will be also valid for microwave cured elements. 相似文献
10.
Kostas N. Oikonomou 《Formal Methods in System Design》1996,8(3):195-220
Anabstraction A of an fsmM consists in partitioning its states, inputs, and outputs into groups, thus turning it into a non-deterministic fsmM
A. For fixed sets of states, inputs, and outputs, and abstraction generally maps a number of machinesM defined on these sets into the sameM
A. We would like to find anoptimal abstractionA
* which minimizes this number, while lumping the states, inputs, and outputs into a specified number of classes. We extend
these ideas to an fsmM operating in a random environment, and show that the abstraction results in a probabilistic fsm
. Thinking of changes inM's output map as resulting in machinesM≠MM, we want to find anA
* that minimizes the number ofMM which are such that the transition probabilities of their abstracted version
are identical to those of the specification machine
. SuchMM arise from statistically-undetectable output faults inM. Abstractions are directly applicable to the monitoring of a complex system by an observer for deviations from correct behavior
(faults). Complex systems are usually accessible through restricted interfaces, which do not allow the observer to distinguish
among all states, inputs, and outputs, thus rendering some faulty transitions undetectable. An optimal interface design will
minimize the number of such undetectable faults.
Assuming that only single-transition output faults occur inM, we show that each of the classes into which the abstraction lumps the outputs contributes a number of undetectable output
faults. We then show that the problem of partitioning the outputs into a given number of classes that minimizes the maximum
of these numbers is NP-complete. However, we give (a) an approximate minimization algorithm, running in time linear in the
number of classes and quadratic in the number ofM's outputs, and (b) a lower bound on the minimum, computable in the same amount of time. The concept of optimal abstractions
is illustrated by numerical results on combinational logic circuits that perform arithmetical operations. The results shed
light on the trade-off between model simplification and the ability to detect erroneous behaviors in complex systems. 相似文献