Reachable Set and Robust Mixed Performance of Uncertain Discrete Systems with Interval Time-Varying Delay and Linear Fractional Perturbations

In this paper, the mixed performance and reachable set of uncertain discrete systems with slow variation interval time-varying delay are considered. The original uncertain discrete systems with interval time-varying delay are first transformed into a switched system. Then, the proposed improved results are used to guarantee the stability and reachable set of the uncertain system with slow variation interval time-varying delay. The mixed performance (H2/H∞) can be derived in the same formulation simultaneously. The design scheme of robust switched control is also developed in this paper. The gains of the controller can be designed and switched to achieve stabilization and mixed performance of the system according to the delay value. Some comparisons with published results are made to show the main contribution of the proposed approach. Finally, some numerical examples are illustrated to show the main results.

A Zero-Cross Detection Algorithm for Cavity-Length Interrogation of Fiber-Optic Fabry–Perot Sensors

A zero-cross detection algorithm was proposed for the cavity-length interrogation of fiber-optic Fabry–Perot (FP) sensors. The method can avoid the inaccuracy of peak determination in the conventional peak-to-peak method for the cavity-length interrogation of fiber-optic FP sensors caused by the slow variation of the spectral power density in peak neighboring regions. Both simulations and experiments were carried out to investigate the feasibility and performance of the zero-cross detection algorithm. Fiber-optic FP sensors with cavity lengths in the range of 150–1000 μm were successfully interrogated with a maximum error of 0.083 μm.

Flow Through Microchannels With Textured Walls: A Theory for Moderately Slow Variations

A microchannel with topographical texture on one or more of its walls is often employed to achieve objectives such as mixing, pumping and bio-molecular detection in microfluidics. Flow through a microchannel with sinusoidal ridges on one of its walls, when the ridges are oriented in the direction of flow, is studied. The classical infinitely-slow-variation or lubrication analysis is extended through a systematic scaling and perturbation procedure for applicability to moderately slow variations. Finite element simulations are used to assess the relative strengths and weaknesses of moderately and infinitely slow-variation theories as well as a small-amplitude theory from the literature based on the domain perturbation technique. Depending on the wavelength of patterning, the hydraulic permeability can either decrease or increase with pattern amplitude with a transitional behavior from an initial decrease to subsequent increase is observed at certain wavelengths.

Photometry of the δ Scuti Star DG Leo: Preliminary Results

New uvby photoelectric photometry has been acquired for the triple star DG Leo at two different observatories equipped with analogous instrumentation. A preliminary period analysis indicates the presence of at least 3 close δ Scuti frequencies (10-12 c/d, 3-6 mmag) and a slow variation. This slow variation fits quite well with half the orbital period of the spectroscopic binary; the noise level in the amplitude spectrum is only 3–4 mmag (after prewhitening).