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Open Access Publications from the University of California

Scholarly Works (206 results)

  • Article
  • Peer Reviewed
Proceedings of the Annual Meeting of the Cognitive Science Society, Volume 18 (1996)
    Cover page: A Computer Simulation Of Emotion Based Development and Processing
    • Article
    • Peer Reviewed
    UC Santa Cruz Previously Published Works (2018)
    State-feedback optimal control and cost evaluation problems for constrained difference inclusions are considered. Sufficient conditions, in the form of Lyapunov-like inequalities, are provided to derive an upper bound on the cost associated with the solution to a constrained difference inclusion with respect to a given cost functional. Under additional sufficient conditions, we determine the cost exactly without computing solutions. The proposed approach is extended to study an optimal control problem for discrete-time systems with constraints. In this setting, sufficient conditions for closed-loop optimality are given in terms of a constrained steady-state-like Hamilton-Jacobi-Bellman equation. Applications and examples of the proposed results are presented.
      Cover page: On the Optimality of Lyapunov-based Feedback Laws for Constrained Difference Inclusions
      • Article
      • Peer Reviewed
      UC Santa Cruz Previously Published Works (2019)
      We formulate an optimal control problem for hybrid systems with inputs and propose conditions for the design of state-feedback laws solving the optimal control problem. The optimal control problem has the flavor of an infinite horizon problem, but it also allows solutions to have a bounded domain of definition, which is possible in hybrid systems with deadlocks. Design conditions for optimal feedback laws are obtained by relating a quite general hybrid cost functional to a Lyapunov like function. These conditions guarantee closed-loop optimality and are given by constrained steady-state-like Hamilton-Jacobi-Bellman-type equations. Applications and examples of the proposed results are presented.
        Cover page: Certifying Optimality in Hybrid Control Systems via Lyapunov-like Conditions ⁎ ⁎ Research by R. G. Sanfelice has been partially supported by the National Science Foundation under Grant no. ECS-1710621 and Grant no. CNS-1544396, by the Air Force Office of Scientific Research under Grant no. FA9550-16-1-0015, Grant no. FA9550-19-1-0053, and Grant no. FA9550-19-1-0169, and by CITRIS and the Banatao Institute at the University of California. Research by Francesco Ferrante is funded in part by ANR via project HANDY, number ANR-18-CE40-0010.
        • Article
        • Peer Reviewed
        UC Santa Cruz Previously Published Works (2017)
        This paper deals with robust minimum-time control of a class of asymptotically null-controllable with bounded input planar systems. A hybrid controller is proposed to robustly achieve global finite time stability of a set of points wherein the plant state is zero. The resulting controller provides time optimal response from initial conditions in a certain subset of the state space, and finite time convergence elsewhere. Finally, the effectiveness of the proposed methods is demonstrated in a numerical example.
          Cover page: Hybrid Robust Minimum-time Control for a Class of Non-Exponentially Unstable Planar Systems
          • Article
          • Peer Reviewed
          UC Santa Cruz Previously Published Works (2018)
          Cost evaluation problems for hybrid inclusions are studied. Sufficient conditions, in the form of Lyapunov-like inequalities, are provided to derive an upper bound on the cost associated with the solution to a hybrid inclusion with respect to a hybrid cost functional. Under additional sufficient conditions, we determine the cost exactly without computing solutions. Constructive results are proposed to solve cost evaluation problems in some relevant applications. Numerical examples are presented.
            Cover page: Cost Evaluation for Hybrid Inclusions: A Lyapunov Approach
            • Article
            • Peer Reviewed
            UC Santa Cruz Previously Published Works (2018)
            Regional stability analysis of linear systems with multi-rate samplers and actuator saturation is studied. A hybrid controller is used to perform a fusion of measurements sampled at different times. In between sampling events, the controller behaves as a copy of the plant. When a new measurement is available, the controller state undergoes a jump. The resulting system is analyzed in a hybrid system framework. Sufficient conditions in the form of matrix inequalities are given to determine estimates of the basin of attraction of the closed-loop system. Finally, the effectiveness of the proposed methodology is shown in an example.
              Cover page: Hybrid Regional Stabilization of Linear Systems with Actuator Saturation and Multi-Rate Samplers
              • Article
              • Peer Reviewed
              UCLA Previously Published Works (2006)

              Background and objectives: This study attempts to assess the intensity and quality of pain and health-related quality of life in patients with sacroiliac syndrome and to compare those constructs to patients with lumbar radiculopathy. Methods: A retrospective review of patient records with the diagnosis of sacroiliac syndrome or lumbar radiculopathy was performed. Patients with sacroiliac syndrome were age and gender matched to patients with lumbar radiculopathy. Data from the McGill Pain Questionnaire, visual numerical pain scores, and SF-36 health-related quality of life measure (version 2) were compared between groups. Results: The age of patients with a traumatic etiology for sacroiliac syndrome was lower than those with previous back surgery and "idiopathic" etiologies (P < .02). Duration of pain in patients with "idiopathic" etiology was longer in comparison to those with previous back surgery (P < .005). No statistical difference occurred between patients with sacroiliac syndrome and lumbar radiculopathy with respect to McGill pain scores, visual numerical pain scores, and SF-36 health-related quality of life measure. Conclusions: The results of this study suggest the following: (1) no true difference exists in the health-related quality of life or pain scores/descriptors between patients with SI syndrome or lumbar radiculopathy, or (2) the presence of comorbid spinal conditions confounds the ability of the SF-36 to detect disparities in health-related quality of life among differing etiologies of low-back pain, despite the use of rigorous diagnostic criteria, and/or (3) other factors besides the diagnostic categories of low-back pain (e.g., functional capability, psychological stress) may be primary determinants of health-related quality of life. To our knowledge, no other study has attempted to use the SF-36 to detect differences in health-related quality of life among patients with different spinal diagnoses.

                Cover page: Health-related quality of life in sacroiliac syndrome: A comparison to lumbosacral radiculopathy
                • Article
                • Peer Reviewed
                Technical Reports (1999)
                This paper investigates the idle time associated with a parallel computation, that is, the time that processors are idle because they are either waiting for data from other processors or waiting to synchronize with other processors. We study doubly-nested loops corresponding to parallelogram- or trapezoidal-shaped iteration spaces that have been parallelized by the well-known tiling transformation. We introduce the notion of rise r, which relates the shape of the iteration space to that of the tiles. For parallelogram-shaped iteration spaces, we show that when r -2, the idle time is linear in P, the number of processors, but when r -1, it is quadratic in P. In the context of hierarchical tiling, where multiple levels of tiling are used, a good choice of rise can lead to less idle time and better performance. While idle time is not the only cost that should be considered in evaluating a tiling strategy, current architectural trends (of deeper memory hierarchies and multiple levels of parallelism) suggest it has increasing importance.

                Pre-2018 CSE ID: CS1999-0617

                  Cover page: Determining the idle time of a tiling
                  • Article
                  • Peer Reviewed
                  Technical Reports (2001)
                  Predicated Execution can be used to alleviate the costs associated with frequently mispredicted branches. This is accomplished by trading the cost of a mispredicted branch for execution of both paths following the conditional branch. In this paper we concentrate on using predicated execution to aggressively reduce a program's branch misprediction rate. We examine an aggressive region formation algorithm focused on removing hard-to-predict branches. This region formation algorithm allows the inclusion of unbiased, but predictable, branches within a region. This was essential in order to predicate the hard-to-predict branches for the programs we examined. The branches left in the predicated region will now need to be predicted during fetch with greater frequency. Using a traditional branch prediction architecture, these region-based branches can end up having a similar miss rate to the hard-to-predict branches that were removed. We propose the Predicate Update Branch Predictor architecture to aid the prediction of these region-based branches. Region-based branches are heavily correlated with the outcome of the predicate with which they are guarded. A branch predicated on false should always predict that the branch should not be taken. Our predicate update predictor updates the global history with the result of the predicate defining instruction. This allows the region branches guarded by those predicates to benefit from this correlation history when making their prediction. For codes predicated with our hard-to-predict region formation algorithm, our results show that a Predicate Update Branch Predictor reduces the mispredict rate from an average of 7% to 5% for the benchmarks we studied.

                  Pre-2018 CSE ID: CS2001-0677

                    Cover page: Predicting Region Branches Using Predicate Update Branch Prediction
                    • Article
                    • Peer Reviewed
                    UC Santa Cruz Previously Published Works (2018)
                      Cover page: Hybrid Regional Stabilization of Linear Systems with Actuator Saturation and Multi-Rate Samplers.
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