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Open Access Publications from the University of California

Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UC Merced Electronic Theses and Dissertations (2010)

This dissertation presents a series of studies on the analysis and control of time-delayed dynamical systems. We first review the discrete methods of semidiscretization and digital control approach. Then we introduce a new method of continuous time approximation (CTA) for the response of linear and nonlinear dynamical systems with time delay. We investigate the accuracy of temporal responses as well as the spectral properties of the CTA method, and present several variants of the CTA method with improved accuracy. Finally, we apply the CTA method to control problems of time-delayed systems including optimal control, supervisory control and sliding mode control of uncertain systems. The CTA method creates a set of state equations for the delayed portion of the response leading to a high and finite dimensional state space formulation of the time-delayed system. The resulting state equations are in the standard state space form, making all the existing solution methods and control design tools for linear and nonlinear dynamical systems amenable to time-delayed systems. The CTA method can handle multiple independent time delays in a natural way. The work in this dissertation indicates that the CTA method is a promising method for analysis and control design of complex nonlinear time-delayed dynamical systems.

    • Article
    • Peer Reviewed
    Advanced Light Source (2016)
    We investigate the interaction between charges and spin order of the defect complex V6 in silicon. The first-principles calculations predict spin resolved band splitting incurred by a neutral V6 yet with no net spin. Therefore, any shift of Fermi level can trigger the spin polarization. Both s and p states contribute local moments in the positively charged V6. The ferromagnetic coupling is only obtained between a positively charged V6 and a neutral one. In silicon after neutron irradiation, magnetism is achieved even at room temperature. The 3s∗3p∗ hybrid states of V6 are probably responsible for the observed long-range magnetic order. Our results unravel the role of charged V6 in inducing magnetism and will be useful in understanding and further manipulating the intrinsic properties of defect complexes in silicon and other semiconductors.
      Cover page: Vacancy defect complexes in silicon: Charges and spin order
      • Article
      • Peer Reviewed
      LBL Publications (2023)
      Finger millet is a key food security crop widely grown in eastern Africa, India and Nepal. Long considered a 'poor man's crop', finger millet has regained attention over the past decade for its climate resilience and the nutritional qualities of its grain. To bring finger millet breeding into the 21st century, here we present the assembly and annotation of a chromosome-scale reference genome. We show that this ~1.3 million years old allotetraploid has a high level of homoeologous gene retention and lacks subgenome dominance. Population structure is mainly driven by the differential presence of large wild segments in the pericentromeric regions of several chromosomes. Trait mapping, followed by variant analysis of gene candidates, reveals that loss of purple coloration of anthers and stigma is associated with loss-of-function mutations in the finger millet orthologs of the maize R1/B1 and Arabidopsis GL3/EGL3 anthocyanin regulatory genes. Proanthocyanidin production in seed is not affected by these gene knockouts.
        Cover page: Genome analyses reveal population structure and a purple stigma color gene candidate in finger milletCreative Commons 'BY' version 4.0 license
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