An LMI-Based Fuzzy State Feedback Control with Multi-Objectives

This paper proposes a systematic design methodology for the Takagi-Sugeno (TS) model based fuzzy state feedback control system with multi-objectives. In this investigation, the objectives are set to be guaranteed stability and pre-specified transient performance, and this scheme is applied to a nonlinear magnetic bearing system. More significantly, in the proposed methodology, the control design problems that consider both stability and desired transient performance are reduced to the standard LMI problems. Therefore, solving these LMI constraints directly (not trial and error) lead to a fuzzy state-feedback controller such that the resulting fuzzy control system meets the above two objectives. Simulation and experimentation results show that the proposed LMI-based design methodology yields not only maximized stability boundary but also the desired transient responses.     

Modified Notch Filter-based Instantaneous Phasor Estimation for High-speed Distance Protection

A novel method for estimating the instantaneous phasor of a fault current signal is proposed for high-speed distance protection immune to a DC-offset. The method uses a modified notch filter in order to eliminate the fundamental frequency component from the fault current signal. Since the output of the modified notch filter is the delayed DC-offset, delay compensation results in the same waveform as the original DC-offset. Subtracting the obtained DC-offset from the fault current signal yields a sinusoidal waveform, which becomes the real part of the instantaneous phasor. The imaginary part of the instantaneous phasor is based on the first difference of the fault current signal. Since a DC-offset also appears in the first difference, the DC-offset is removed from the first difference using the results of the delay compensation. The performance of the proposed method was evaluated for a–phase to ground faults on a 345 kV 100 km overhead transmission line. The Electromagnetic Transient Program was used to generate fault current signals for different fault locations and fault inception angles. The performance evaluation showed that the proposed method can estimate the instantaneous phasor of a fault current signal with high speed and high accuracy. The paper concludes by describing the hardware implementation of the proposed method on a prototype unit based on a digital signal processor.     

Fault location algorithm for cross-bonded cables using the singularity of the sheath impedance matrix

This paper proposes a fault location algorithm for cross-bonded cables. The algorithm uses nonlinear equations that describe the voltage drops between both ends of core conductors and sheaths in terms of the phase voltages and currents of both the local and remote ends. Arranging these equations about the sheath currents yields a sheath impedance matrix, which is singular independently of the fault distance. Due to this singularity, the equations have no solution or an infinite number of solutions. The proposed algorithm finds the condition for which a solution to the equations exists. Since the equation of the condition is linear and explicit, the fault location can be found easily. Test results indicate that the algorithm accurately estimates the fault distance regardless of fault impedance, fault type, and fault section.     

Optimization of Fiber Bragg Gratings Using a Hybrid Optimization Algorithm

A new hybrid optimization algorithm is proposed for the design of a fiber Bragg grating (FBG) with complex characteristics. The hybrid algorithm is a two-tier search that employs a global optimization algorithm (i.e., the staged continuous tabu search (SCTS) algorithm) and a local optimization method (i.e., the quasi-Newton method). First, the SCTS global optimization algorithm is used to find a "promising" FBG structure that has a spectral response as close as possible to the targeted spectral response. Then, a local optimization method, namely, the quasi- Newton method, is applied to further optimize the promising FBG structure obtained from the SCTS algorithm to arrive at a targeted spectral response. To demonstrate the effectiveness of the method, the design and fabrication of an optical bandpass filter are presented.     

A 2.4-GHz Low-Power Low-IF Receiver and Direct-Conversion Transmitter in 0.18-μm CMOS for IEEE 802.15.4 WPAN Applications

In this paper, a low-power low-IF receiver and a direct-conversion transmitter (DCT) suitable for the IEEE standard 802.15.4 radio system at the 2.4-GHz band are presented in 0.18-mum deep n-well CMOS technology. By using vertical NPN (V-NPN) bipolar junction transistors in the baseband analog circuits of the low-IF receiver, the image rejection performance is improved and the power consumption is reduced. In addition, by applying the V-NPN current mirrored technique in a DCT, the carrier leakage is reduced and the linearity performance is improved. The receiver has 10 dB of noise figure, -15 dBm of third-order input intercept point, and 35 dBc of image rejection. The transmitter has more than -2 dBm of transmit output power, -35 dBc of local oscillator leakage, and -46 dBc of the transmit third harmonic component. The receiver and transmitter dissipate 6 and 9 mA from a 1.8-V supply, respectively     

A Low-Power Unified Arithmetic Unit for Programmable Handheld 3-D Graphics Systems

A low-power, area-efficient four-way 32-bit multifunction arithmetic unit has been developed for programmable shaders for handheld 3D graphics systems. It adopts the logarithmic number system (LNS) at the arithmetic core for the single-cycle throughput and the small-size low-power unification of various complicated arithmetic operations such as power, logarithm, trigonometric functions, vector-SIMD multiplication, division, square root and vector dot product. 24-region and 16-region piecewise linear logarithmic and antilogarithmic converters are proposed with 0.8% and 0.02% maximum conversion error, respectively. All the supported operations are implemented with less than 6.3% operation error and unified into a single arithmetic platform with maximum four-cycle latency and single-cycle throughput. A 93 K gate test chip is fabricated using one-poly five-metal 0.18-mum CMOS technology. It operates at 210 MHz with maximum power consumption of 15.3 mW at 1.8 V.     

A hybrid PET‐MRI: An integrated molecular‐genetic imaging system with HRRT‐PET and 7.0‐T MRI

A PET‐MRI fusion system is developed for molecular‐genetic imaging. The purpose of the system is to obtain images of the in‐vivo human brain using two high‐end imaging devices, an advanced PET and an ultrahigh‐field MRI. These are the HRRT‐PET, a high‐resolution research tomograph dedicated to brain imaging on the molecular level, and the 7.0‐T MRI, an ultrahigh field version used for morphological imaging. HRRT‐PET delivers high‐resolution molecular imaging with a resolution down to 2.5 mm FWHM, which is currently the highest spatial resolution available for the observation of the human brain's molecular activities, including enzymes and receptors, which are manipulated genetically, such as reporter genes and probes. The 7.0‐T MRI began to reveal submillimeter resolution images of the cortical as well as deep brain areas, down to 250 μm, which allows us to visualize the fine details of the cortical and brainstem areas, including the line of Gennari in the visual cortex and the corticospinal tracts in the pontine area. The current PET‐MRI fusion imaging system produces the highest quality images of molecular and genetic activities of the human brain in vivo. It is starting to provide many answers to the key questions about the neurological diseases. Some of these start providing answers to many cognitive neuroscience problems with clear molecular and genetic bases. There is great potential in the PET‐MRI for early diagnosis of cancers as well as other neurological diseases, which we were previously unable to diagnose, such as microscopic molecular changes that occur in Parkinson's and Alzheimer's diseases. © 2007 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 17, 252–265, 2007     

Operational Analysis of a Quantum Dot Optically Gated Field-Effect Transistor as a Single-Photon Detector

We report on the operation of a novel single-photon detector, where a layer of self-assembled quantum dots (QDs) is used as an optically addressable floating gate in a GaAs/Al_0.2Ga_0.8As delta-doped field-effect transistor. Photogenerated holes charge the QDs, and subsequently, change the amount of current flowing through the channel by screening the internal gate field. The photoconductive gain associated with this process makes the structure extremely sensitive to light of the appropriate wavelength. We investigate the charge storage and resulting persistent photoconductivity by performing time-resolved measurements of the channel current and of the photoluminescence emitted from the QDs under laser illumination. In addition, we characterize the response of the detector, and investigate sources of photogenerated signals by using the Poisson statistics of laser light. The device exhibits time-gated, single-shot, single-photon sensitivity at a temperature of 4 K. It also exhibits a linear response, and detects photons absorbed in its dedicated absorption layer with an internal quantum efficiency (IQE) of up to (68 plusmn18)%. Given the noise of the detection system, the device is shown to operate with an IQE of (53 plusmn 11)% and dark counts of 0.003 counts per shot for a particular discriminator level.     

The Orientations of Large Aspect‐Ratio Coiled‐Coil Proteins Attached to Gold Nanostructures

Methods for patterning biomolecules on a substrate at the single molecule level have been studied as a route to sensors with single‐molecular sensitivity or as a way to probe biological phenomena at the single‐molecule level. However, the arrangement and orientation of single biomolecules on substrates has been less investigated. Here, the arrangement and orientation of two rod‐like coiled‐coil proteins, cortexillin and tropomyosin, around patterned gold nanostructures is examined. The high aspect ratio of the coiled coils makes it possible to study their orientations and to pursue a strategy of protein orientation via two‐point attachment. The proteins are anchored to the surfaces using thiol groups, and the number of cysteine residues in tropomyosin is varied to test how this variation affects the structure and arrangement of the surface‐attached proteins. Molecular dynamics studies are used to interpret the observed positional distributions. Based on initial studies of protein attachment to gold post structures, two 31‐nm‐long tropomyosin molecules are aligned between the two sidewalls of a trench with a width of 68 nm. Because the approach presented in this study uses one of twenty natural amino acids, this method provides a convenient way to pattern biomolecules on substrates using standard chemistry.