This paper presents the feasibility and effectiveness of magnetorheological (MR) braces in earthquake hazard mitigation. In doing so, a nondimensional variable, beta, which is the ratio of the yield force of the MR da...
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This paper presents the feasibility and effectiveness of magnetorheological (MR) braces in earthquake hazard mitigation. In doing so, a nondimensional variable, beta, which is the ratio of the yield force of the MR damper to forcing input (the product of a characteristic mass of the building and the seismic acceleration) is used to design the MR damper preventing the locked damper motion that may worsen seismic response of the building. Front this theoretical analysis, the activation gap of the damper as an important design parameter to prevent the locked damper motion is chosen. Based on this analysis, the MR damper is fabricated by modifying the commercial MR damper of Lord Corporation, SD-1000-1. Then, a three-story building with MR braces is constructed and its dynamic equation is theoretically derived. In order to investigate semi-active control methods to MR braces, three different control algorithms are formulated and evaluated both numerically and experimentally. The results show that control of the building with semi-actively controlled MR braces is very effective.
During stretch bending, considerable springback will occur after a tube has been plastically bent. To predict the springback, a simplified two-flange model for stretch bending of a rectangular tube has been developed ...
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During stretch bending, considerable springback will occur after a tube has been plastically bent. To predict the springback, a simplified two-flange model for stretch bending of a rectangular tube has been developed in which the strain history has been considered. A comparison has been made between the springback predicted by this model and experimental data, which shows rough agreement. Based on this model, a real time closed-loop control algorithm is developed.
Mirroring and replication are common techniques for ensuring fault-tolerance and resiliency of client/server applications. Because such mirroring and replication procedures are not usually automated, they tend to be c...
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Mirroring and replication are common techniques for ensuring fault-tolerance and resiliency of client/server applications. Because such mirroring and replication procedures are not usually automated, they tend to be cumberson. In this paper, we present an architecture in which the identification of sites for replicated servers, and the generation of replicas, are both automated. The design is based on a self-configuring mesh of computers and a communication mechanism between nodes that operates on a rooted spanning tree. A query-search component uses Java(TM) language-based query capsules traveling along the branches of the spanning tree, and a caching scheme whereby the query and previous search results are cached at each node for improved efficiency. Furthermore, a security and anonymity component relies on one or more authentication servers and an anonymous communication scheme using link local addresses and indirect communication between the nodes via the spanning tree. The architecture also includes components for resource advertising and for application replication.
We note that the seal can function stably in the fluid friction mode (for thechosen design characteristics of the seal unit) when the axial rigidity of the lifting layer at thecontact of the parr of surfaces of the fa...
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We note that the seal can function stably in the fluid friction mode (for thechosen design characteristics of the seal unit) when the axial rigidity of the lifting layer at thecontact of the parr of surfaces of the face seal ring pair is high. That rigidity is the parameterfor optimizing a seal with a wedge-shaped slot. When designing the unit, the designer must strive tocreate a face seal with the highest attainable lifting layer rigidity in the contact of the facesurfaces of the ring pair.
作者：
Yellin, DMIBM Corp
Div Res Thomas J Watson Res Ctr Yorktown Hts NY 10598 USA
As component-based development matures, more and more applications are built by integrating multiple distributed components. We suggest providing components with multiple implementations, each optimized for a particul...
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As component-based development matures, more and more applications are built by integrating multiple distributed components. We suggest providing components with multiple implementations, each optimized for a particular workload,and augmenting the component run-time environment with a mechanism for switching between implementations. This mechanism monitors the types of requests the component is receiving, and adaptively switches implementations for optimal application performance. Achieving this optimal performance depends on making good choices as to when and how to switch implementations, a problem, we refer to as the adaptive component problem. We first formalize the generic problem and then provide an algorithm, named Delta, for switching implementations in the special case when the component has exactly two implementations. We show that this algorithm is (3 + epsilon)-competitive with respect to the optimal algorithm, where epsilon is a small fraction. We establish a 3-competitve lower bound for the problem, which implies that Delta is close to optimal. We describe the application of these results to the distributed pub/sub problem, and the data structure selection problem.
The problem of minimum time low-thrust transfer between arbitrary elliptic orbits in the central gravitational field is under investigation. The rocket engine is assumed to produce constant in magnitude and controllab...
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The problem of minimum time low-thrust transfer between arbitrary elliptic orbits in the central gravitational field is under investigation. The rocket engine is assumed to produce constant in magnitude and controllable in direction thrust, which is essentially smaller than the gravity force. Approximate solution is obtained with the use of the averaging method. Averaged optimal motion equations are written in analytical form. Using both known and the new first integrals allows to reduce the order of the differential system of optimal motion equations down to fourth. The analytical solutions are obtained for a number of maneuvers. Since any transfer between elliptic orbits can be presented as a combination of those, allowing analytical solution, rapid estimation of the characteristic velocity requirements is possible. Control algorithms more simple for practical realization are proposed, and their efficiency is compared with that of the optimal control. (C) 2002 Elsevier Science Ltd. All rights reserved.
A new adaptive integral backstepping control algorithm for motion control systems is proposed. The design approach is non-conventional in that it only implicitly incorporates error states into a design Lyapunov functi...
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A new adaptive integral backstepping control algorithm for motion control systems is proposed. The design approach is non-conventional in that it only implicitly incorporates error states into a design Lyapunov function and computes time derivative of the Lyapunov function symbolically to the point of getting parameter estimate update laws on which desirable structures are imposed. The closed-loop error system turns out to be linear and time-varying and can be reformulated as a linear-non-linear cascade system. Uniform exponential stability or absolute stability can be achieved. The design is robust against system parameter variations. The effectiveness and robustness of the control algorithm are verified by numerical examples. Copyright (C) 2002 John Wiley Sons, Ltd.
Most adaptive problems of interest are non-linear, however, the application of non-linear, or pole-zero filter to these problems have been restricted due to the poor convergence properties of adaptive pole-zero algori...
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Most adaptive problems of interest are non-linear, however, the application of non-linear, or pole-zero filter to these problems have been restricted due to the poor convergence properties of adaptive pole-zero algorithms that often result in an unstable solution. Here, we present a stable pole-zero filter model for such applications. In a given example, this filter resulted in significant, up to 4 times reduction in computations and up to 7 time reduction in memory bandwidth when compared to a linear filter for the same problem. The above algorithm has been used for echo cancellation and demonstrated in a directory assistance system that has been deployed in carrier networks and also for channel equalization in a V.17 modem(1).
The seismic response of a single-story steel building frame with a smart base isolation system is evaluated. The isolation system consists of sliding bearings combined with an adaptive fluid damper. The damping capaci...
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The seismic response of a single-story steel building frame with a smart base isolation system is evaluated. The isolation system consists of sliding bearings combined with an adaptive fluid damper. The damping capacity of the fluid damper can be modulated in real time based on feedback from the earthquake ground motion and superstructure response. The adaptive capabilities of the fluid damper enable the isolation system displacement to be controlled while simultaneously limiting the interstory drift response of the superstructure. This paper concentrates on the development of analytical models of the smart isolation system and control algorithms for operation of the system. In general, the results from numerical simulations demonstrate that, for disparate earthquake ground motions, the smart isolation system is capable of simultaneously limiting both the response of the isolation system and the superstructure.
In this paper we present an algorithm for segmenting or locating the endpoints of speech in a continuous signal stream. The proposed algorithm is based on non-linear likelihood-based projections derived from a Bayesia...
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In this paper we present an algorithm for segmenting or locating the endpoints of speech in a continuous signal stream. The proposed algorithm is based on non-linear likelihood-based projections derived from a Bayesian classifier. It-utilizes class distributions in a speech/non-speech classifier to project the signal into a 2-dimensional space where, in the ideal case, optimal classification can be performed with a simple linear discriminant. The projection results in the transformation of diffuse, nebulous classes in high-dimensional space into compact clusters in the low-dimensional space that can be easily separated by simple clustering mechanisms. In this space, decision boundaries for optimal classification can be more easily identified using simple clustering criteria. The segmentation algorithm proposed utilizes this property to determine and update optimal classification thresholds continuously for the signal being segmented. The performance of the proposed algorithm has been evaluated on data recorded under extremely diverse environmental noise conditions. The experiments show that the algorithm performs comparably to manual segmentations even under these diverse conditions. (C) 2002 Elsevier Science Ltd. All rights reserved.
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