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1.
The structure of the nonlinear H∞-filter in the neighborhood of the estimated trajectory is investigated and a bound on the size of the neighborhood that allows this structure is determined, both for finite and infinite horizons. Riccati inequalities that depend on the estimated trajectory are derived for finding the filter gain matrix and an algorithm for calculating the bound on the size of the above neighborhood is presented. Explicit formulas are obtained in the infinite horizon case for the minimum achievable disturbance attenuation level, the size of the neighborhood, and the corresponding filter gain. 相似文献
2.
Alternative measures of pesticide use 总被引:2,自引:0,他引:2
C Barnard S Daberkow M Padgitt ME Smith ND Uri 《Canadian Metallurgical Quarterly》1997,203(3):229-244
tRNA (m5U54)-methyltransferase (RUMT) catalyzes the S-adenosylmethionine-dependent methylation of uridine-54 in the T psi C-loop of all transfer RNAs in E. coli to form the 54-ribosylthymine residue. However, in all tRNA structures, residue 54 is completely buried and the question arises as to how RUMT gains access to the methylation site. A 17-mer RNA hairpin consisting of nucleotides 49-65 of the T psi-loop is a substrate for RUMT. Homonuclear NMR methods in conjunction with restrained molecular dynamics (MD) methods were used to determine the solution structure of the 17-mer T-arm fragment. The loop of the hairpin exhibits enhanced flexibility which renders the conventional NMR average structure less useful compared to the more commonly found situation where a molecule exists in predominantly one major conformation. However, when resorting to softer refinement methods such as MD with time-averaged restraints, the conflicting restraints in the loop can be satisfied much better. The dynamic structure of the T-arm is represented as an ensemble of 10 time-clusters. In all of these, U54 is completely exposed. The flexibility of the T psi-loop in solution in conjunction with extensive binding studies of RUMT with the T psi C-loop and tRNA suggest that the specificity of the RUMT/ tRNA recognition is associated with tRNA tertiary structure elements. For the methylation, RUMT would simply have to break the tertiary interactions between the D- and T-loops, leading to a melting of the T-arm structure and making U54 available for methylation. 相似文献
3.
4.
Noel D. Uri 《Applied Energy》1996,54(4):355-373
This study begins by asking whether fluctuations in the price of crude oil have affected agricultural employment in the USA. After reviewing previous assessments of the issue, the existence of an empirical relationship between agricultural employment and crude-oil price volatility is established using Granger causality. Subsequently, the nature of the relationship is estimated with the results suggesting that at least three full years are required before the measurable impacts of a percentage change in the real price of crude oil on the change in agricultural employment are exhausted. Finally, the structural stability of the functional relationship between the change in agricultural employment and the volatility of the price of crude oil, the percentage changes in expected net farm income, realized technological innovation, and the wage rate are examined. 相似文献
5.
6.
We consider two multicriteria versions of the global minimum cut problem in undirected graphs. In the k-criteria setting,
each edge of the input graph has k non-negative costs associated with it. These costs are measured in separate, non-interchangeable,
units. In the AND-version of the problem, purchasing an edge requires the payment of all the k costs associated with it. In the OR-version, an edge can be purchased by paying any one of the k costs associated with it. Given k bounds b1,b2,. . . ,bk, the basic multicriteria decision problem is whether there exists a cut C of the graph that can be purchased using a budget
of bi units of the ith criterion, for 1 ≤ i ≤ k. We show that the AND-version of the multicriteria global minimum cut problem is
polynomial for any fixed number k of criteria. The OR-version of the problem, on the other hand, is NP-hard even for k = 2,
but can be solved in pseudo-polynomial time for any fixed number k of criteria. It also admits an FPTAS. Further extensions,
some applications, and multicriteria versions of two other optimization problems are also discussed. 相似文献
7.
8.
We discuss the implementation of quantum gate operations in a self-assembled dipolar crystal of polar molecules. Here qubits
are encoded in long-lived spin states of the molecular ground state and stabilized against collisions by repulsive dipole–dipole
interactions. To overcome the single site addressability problem in this high density crystalline phase, we describe a new
approach for implementing controlled single and two-qubit operations based on resonantly enhanced spin–spin interactions mediated
by a localized phonon mode. This local mode is created at a specified lattice position with the help of an additional marker
molecule such that individual qubits can be manipulated by using otherwise global static and microwave fields only. We present
a general strategy for generating state and time dependent dipole moments to implement a universal set of gate operations
for molecular qubits and we analyze the resulting gate fidelities under realistic conditions. Our analysis demonstrates the
experimental feasibility of this approach for scalable quantum computing or digital quantum simulation schemes with polar
molecules. 相似文献
9.
Asaf Shabtai Author Vitae Uri Kanonov Author Vitae Author Vitae 《Journal of Systems and Software》2010,83(8):1524-1537
In this paper, a new approach for detecting previously unencountered malware targeting mobile device is proposed. In the proposed approach, time-stamped security data is continuously monitored within the target mobile device (i.e., smartphones, PDAs) and then processed by the knowledge-based temporal abstraction (KBTA) methodology. Using KBTA, continuously measured data (e.g., the number of sent SMSs) and events (e.g., software installation) are integrated with a mobile device security domain knowledge-base (i.e., an ontology for abstracting meaningful patterns from raw, time-oriented security data), to create higher level, time-oriented concepts and patterns, also known as temporal abstractions. Automatically-generated temporal abstractions are then monitored to detect suspicious temporal patterns and to issue an alert. These patterns are compatible with a set of predefined classes of malware as defined by a security expert (or the owner) employing a set of time and value constraints. The goal is to identify malicious behavior that other defensive technologies (e.g., antivirus or firewall) failed to detect. Since the abstraction derivation process is complex, the KBTA method was adapted for mobile devices that are limited in resources (i.e., CPU, memory, battery). To evaluate the proposed modified KBTA method a lightweight host-based intrusion detection system (HIDS), combined with central management capabilities for Android-based mobile phones, was developed. Evaluation results demonstrated the effectiveness of the new approach in detecting malicious applications on mobile devices (detection rate above 94% in most scenarios) and the feasibility of running such a system on mobile devices (CPU consumption was 3% on average). 相似文献
10.
Uri Zwick 《Algorithmica》2006,46(2):181-192
We present an
-time algorithm for the All Pairs Shortest Paths (APSP) problem for directed graphs with real edge lengths. This slightly
improves previous algorithms for the problem obtained by Fredman, Dobosiewicz, Han, and Takaoka. 相似文献