3,535 research outputs found
Limit cycle oscillation of missile control fin with structural non-linearity
No full textNon-linear aeroelastic characteristics of a deployable missile control fin with structural non-linearity are investigated. A deployable missile control fin is modelled as a two-dimensional typical section model. Doublet-point method is used for the calculation of supersonic unsteady aerodynamic forces, and aerodynamic forces are approximated by using the minimum-state approximation. For non-linear flutter analysis structural non-linearity is represented by an asymmetric bilinear spring and is linearized by using the describing function method. The linear and non-linear flutter analyses indicate that the flutter characteristics are significantly dependent on the frequency ratio. From the non-linear flutter analysis, various types of limit cycle oscillations are observed in a wide range of air speeds below or above the linear divergent flutter boundary. The non-linear flutter characteristics and the non-linear aeroelastic responses are investigated. (C) 2003 Elsevier Ltd. All rights reserved.This research was supported by Agency for Defense Development (ADD) and the Ministry of
Science and Technology (National Research Laboratory Program) in the Republic of Korea. This
support is gratefully acknowledged
An enhanced role model for alleviating the role-binding anomaly
No full textRoles and role models have received much attention as useful concepts for developing highly reusable and dynamically evolvable systems. Role models belong to the category of collaboration-based development techniques. but most of the existing approaches to role models do not explicitly incorporate the core principle of collaboration-based developments as an essential property of their primary design goals. Consequently, the existing approaches still suffer from a problematic phenomenon that the structural and behavioral constraints defined in a role system can be violated during the role-binding stage. We call such a problematic phenomenon the role-binding anomaly. In order to alleviate the role-binding anomaly, we propose an enhanced role model, in which all role instances and core objects can exist by themselves, namely., they can be developed, executed, and tested independently. Roles and core classes can be bound to each other at the instance level. In addition, the role system describes and encapsulates the behavior for dynamic reconfigurations among role instances. The enhanced role model is designed so as to be meaningful with respect to software engineering principles, rather than dynamic evolution. It also facilitates role model implementation using general programming languages (i.e. not supporting dynamic specialization) such as Java. To illustrate how the proposed role model makes such benefits, we develop a set of Java classes necessary for implementing the enhanced role model in the form of a Java package role, and present a simplified automatic teller machine system as an example application. Copyright (C) 2002 John Wiley Sons, Ltd
An aspect-oriented framework for developing component-based software with the collaboration-based architectural style
No full textComponent-based development (CBD) technique for software has emerged to fulfill the demand on the reuse of existing artifacts. In comparison to traditional object-oriented techniques, CBD can provide more advanced abstraction concepts such as subsystem-level reusability, gross structure abstraction, and global control flow abstraction. Unfortunately, existing software development techniques are not mature enough to make it come true that components developed in the third party can be used in a highly flexible way. It is notable that there are certain kinds of software requirements, such as non-functional requirements, that must be implemented cross-cutting multiple classes, largely losing the modularity in object-oriented design and implementation code. Therefore, it is not easy that components are reused without consideration of their low-level implementation details. In this article, we propose Aspect-Oriented Development Framework (AODF) in which functional behaviors are encapsulated in each component and connector, and particular non-functional requirements are flexibly tuned separately in the course of software composition. To support the modularity for non-functional requirements in component-based software systems, we devise Aspectual Composition Rules (ACR) and Aspectual Collaborative Composition Rule (ACCR). Note that AODF makes component-based software built to provide both supports of modularity and manageability of non-functional requirements such as synchronization, performance, physical distribution, fault tolerance, atomic transaction, and so on. With the Collaboration-Based architectural style, AODF explicitly enables to deal with nonfunctional requirements at the intra-component and inter-component levels. (C) 2003 Elsevier B.V. All rights reserved
An approach to specifying concurrent, distributed, and autonomous object behaviors using a high-level meta-object protocol
No full textTo develop distributed applications requires to consider not only functional requirements but also nonfunctional requirements such as distributions, synchronizations, and scheduling policies. Specifying such non-functional requirements is necessary for supporting on-line capabilities of Autonomous Decentralized Systems (ADS). However, the existing design notations and methods do not address such needs sufficiently enough to develop ADS applications systematically using object-oriented technique. Ln this paper, we propose an object-oriented design-level support for specifying concurrent, distributed, and autonomous object behaviors in developing dynamic distributed applications. We develop a high-level meta-object protocol called diMOP to deal with object distributions, method synchronizations, and method scheduling policies. In addition, we develop Class Diagram Supporting diMOP (CDSM) and Dynamically Configurable Object Statemachine (DCOS) for specifying non-functional behaviors and dynamic configuration behaviors, by extending the ordinary class diagram and state diagram of UML. A development environment called diMOPer is implemented to support our approach
Improved selectivity of oxide semiconductor type gas sensor using compensating element
No full textThe selectivity of SnO2 gas sensor for a hydrocarbon gas like i-C4H10 has been improved through the serial connection of a compensating element which is sensitive to the interfering gas. The devices were fabricated in 2 mm x 2 mm through the screen-printing technique. The sensing material, made of SnO2, was doped with Sb2O5 and treated with Pt catalyst to detect a hydrocarbon gas. The compensating material was composed of Sb2O5-doped SnO2 with Pd catalyst to detect interfering gas such as ethanol. The amount of resistance change in each material upon exposure to gas is differed depending on the kind of gas to be exposed, giving rise to an improvement in the selectivity of the device. (C) 2001 Elsevier Science B.V. All rights reserved.The authors wish to acknowledge the financial support of the Korean Research Foundation offered in the 1998 program year
Tactics based approach for integrating non-functional requirements in object-oriented analysis and design
No full textNon-Functional Requirements (NFRs) are rarely treated as "first-class" elements in software development as Functional Requirements (FRs) are. Often NFRs are stated informally and incorporated in the final software as an after-thought. We leverage existing research work for the treatment of NFRs to propose an approach that enables to systematically analyze and design NFRs in parallel with FRs. Our approach premises on the importance of focusing on tactics (the specific mechanisms used to fulfill NFRs) as opposed to focusing on NFRs themselves. The advantages of our approach include filling the gap between NFRs elicitation and NFRs implementation, systematically treating NFRs through grouping of tactics so that tactics in the same group can be addressed uniformly, remedying some shortcomings in existing work (by prioritizing NFRs and analyzing tradeoff among NFRs), and integration of FRs and NFRs by treating them as first-class entities. (C) 2009 Elsevier Inc. All rights reserved.This research was supported by the Ministry of Information and Communication
(MIC), Korea, under the Information Technology Research Center (ITRC) support
program supervised by the Institute of Information Technology Advancement (IITA)
(IITA-2008-(C1090-0801-0032))
Flutter analysis of a wraparound fin projectile considering rolling motion
No full textThe aeroelastic stabilities of curved fins (or wraparound fins) in rolling motion are investigated in the supersonic flow region. Because of their inherent roll, wraparound fins are subjected to both aerodynamic and centrifugal forces. The aerodynamic force is computed by solving Euler equations in a body-fixed rotating coordinate frame. The normal mode analyses of the spinning structure are performed by using a multipurpose finite element code. For the consistent analysis a nondimensionalized aeroelastic equation considering the rolling motion is derived and aeroelastic parameters, such as velocity index and mass ratio, are devised. From the flutter analyses for wraparound fins, it is observed that the flutter characteristics with roll are very different from those without roll. It indicates that the consideration of the rolling motion must be made to predict the flutter stability accurately. Because of the geometric asymmetry of the wraparound fin, the flutter characteristics in each roll directions are different from each other. Flutter analyses indicate that there exists a more stable roll direction for flutter.This researchwas supportedby Agencyfor DefenseDevelopment
in the Republic of Korea. This support is gratefully acknowledged
Effects of structural nonlinearity on subsonic aeroelastic characteristics of an aircraft wing with control surface
No full textThe nonlinear aeroelastic characteristics of an aircraft wing with a control surface are investigated. A doublet-hybrid method is used for the calculation of subsonic unsteady aerodynamic forces and the minimum-state approximation is used for the approximation of aerodynamic forces. A free vibration analysis is performed using the finite element and the fictitious mass methods. The structural nonlinearity in the control surface hinge is represented by both free-play and a bilinear nonlinearity. These nonlinearities are linearized using the describing function method. From the nonlinear flutter analysis, various types of limit cycle oscillations and periodic motions are observed in a wide range of air speeds below the linear flutter boundary. The effects of structural nonlinearities on aeroelastic characteristics are investigated. (C) 2004 Elsevier Ltd. All rights reserved.This research was supported by Agency for Defense Development (ADD) and the Ministry of Science and
Technology (National Research Laboratory Program) in the Republic of Korea. This support is gratefully
acknowledged. And also, the authors appreciate the review and comments of Mr Christopher O. Johnston of Virginia
Tech about this paper and express special thanks to the associate Editor Dr Earl H. Dowell and reviewers for many
valuable comments and suggestions
A known-signal detector based on ranks in weakly dependent noise
No full textLocally optimum rank detection of known signals under a weakly dependent noise model is considered in this paper. The weakly dependent noise model is known to be useful for modeling inter-user interference, which is important in the synthesis and analysis of mobile communication systems. For good weak-signal detection performance under any specified noise probability density function, the locally optimum detector is derived based on signs and ranks of the observation. It is also shown that the locally optimum rank detector has the same asymptotic performance as the locally optimum rank detector which uses the actual values of the observations.Ministry of Information and Communication (MIC) under grant from the University Basic Research Fun
Aspect-Oriented Design (AOD) technique for developing distributed object-oriented systems over the Internet
No full textWhile software development techniques for identifying specifying, and analyzing functional requirements of software systems are quite mature, existing traditional design methods are not mature enough to capture non-functional requirements such as concurrency, performance, fault tolerance, distribution, and persistence of a software application. Very recently, Aspect-Oriented Programming (AOP) approach has been introduced to provide an implementation-level programming framework for separately developing basic functionalities and non-functionalities of a software application. However, this is just an implementation-level approach. There are still needs for supporting AOP concepts at the design level, and for providing the traceability between the design model and the implementation model. In this paper, we propose an approach called Aspect-Oriented Design (AOD), which supports the concept of AOP at design level, for developing distributed object systems over the Internet. We also demonstrate the usability of the proposed approach with Multi-media Video Conference Systems (MVCS) example
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