Photoinduced ferroelectric parameter changes in liquid‐crystal systems containing chiral α,β‐unsaturated ketones

Abstract— Photoinduced changes that were revealed for ferroelectric liquid‐crystalline systems with helical supra‐molecular structures induced with chiral α,β‐unsaturated ketones have been summarized. Photoinduced inversion of the spontaneous polarization sign and a concomitant increase in its absolute value and other ferroelectric parameters were observed. The E‐Z photoisomerization of the chiral compounds was determined to be responsible for the discovered effects.     

A wide view auto‐stereoscopic 3D display with an eye‐tracking system for enhanced horizontal viewing position and viewing distance

This paper describes the development of auto‐stereoscopic three‐dimensional (3D) display with an eye‐tracking system for not only the X‐axis (right–left) and Y‐axis (up–down) plane directions but also the Z‐axis (forward–backward) direction. In the past, the eye‐tracking 3D system for the XY‐axes plane directions that we had developed had a narrow 3D viewing space in the Z‐axis direction because of occurrence of 3D crosstalk variation on screen. The 3D crosstalk variation on screen was occurred when the viewer's eye position moved back and forth along the Z‐axis direction. The reason was that the liquid crystal (LC) barrier pitch was fixed and the LC barrier was able to control the only barrier aperture position. To solve this problem, we developed the LC barrier that is able to control the barrier pitch as well as the barrier aperture position in real time, corresponding to the viewer's eye position. As a result, the 3D viewing space has achieved to expand up to 320–1016 mm from the display surface in the Z‐axis direction and within a range of ±267 mm in the X‐axis direction. In terms of the Y‐axis direction, the viewing space is not necessary to be considered, because of a stripe‐shaped parallax barrier.     

Azo‐dye aligning layers for liquid‐crystal cells

Abstract— The photo‐induced alignment of liquid crystal onto a photochemical stable azo‐dye film was studied for liquid‐crystal display (LCD) applications. The photo‐aligning of azo dye takes place due to the pure reorientation of the molecular absorption oscillators perpendicular to the UV‐light polarization. The order parameters S = ?0.4 (80% of the maximum absolute value S_m = ?0.5) was measured at a wavelength of 372 nm from the polarized absorption spectra. The temperature‐stable pretilt angle of 5.3° was obtained by a two‐step exposure of azo‐dye film using normally incident polarized light followed by oblique non‐polarized light. The azimuthal anchoring energy of the photo‐aligned substrate was A_? > 10^?4 J/m², which is of the same magnitude as the anchoring of the rubbed PI layer. The VHR value of the photo‐aligned LC cell was also found to be very high (98–99%) at room temperature and more than 95% at T=80°C. The thermal stability of the photo‐aligned azo‐dye layers is sufficiently high, while UV stability has to be improved, _e.g., by polymerization. The new LCD aligning technology based on photochemical stable azo‐dye layers is envisaged.     

Toward sub‐micron oxide thin‐film transistors for digital holography

High‐performance 2‐μm‐channel oxide thin‐film transistors (TFT) on glass substrate for a 7‐μm‐pixel‐pitch spatial light modulator panel for digital holography applications were fabricated using a two‐step source/drain etching process. It showed a μ_FE of 45.5 cm²/Vs, SS of 0.10 V/dec, and Von of near zero voltage. Furthermore, we succeeded in the demonstration of sub‐micron TFTs, which is an indispensable route to next‐generation spatial light modulation devices with near 1‐μm pixel pitch. The issue of short‐channel transistors for display applications is also introduced. Finally, the digital holographic demonstration results based on the fabricated backplane are presented.     

Separation principle for quasi‐one‐sided Lipschitz nonlinear systems with time delay

In this article, we address the problem of output stabilization for a class of nonlinear time‐delay systems. First, an observer is designed for estimating the state of nonlinear time‐delay systems by means of quasi‐one‐sided Lipschitz condition, which is less conservative than the one‐sided Lipschitz condition. Then, a state feedback controller is designed to stabilize the nonlinear systems in terms of weak quasi‐one‐sided Lipschitz condition. Furthermore, it is shown that the separation principle holds for stabilization of the systems based on the observer‐based controller. Under the quasi‐one‐sided Lipschitz condition, state observer and feedback controller can be designed separately even though the parameter (A,C) of nonlinear time‐delay systems is not detectable and parameter (A,B) is not stabilizable. Finally, a numerical example is provided to verify the efficiency of the main results.     

Sliding‐mode control of a three‐degrees‐of‐freedom nanopositioner

This paper presents the sliding‐mode control of a three‐degrees‐of‐freedom nanopositioner (Z, θ_x, θ_y). This nanopositioner is actuated by piezoelectric actuators. Capacitive gap sensors are used for position feedback. In order to design the feedback controller, the open‐loop characteristics of this nanopositioner are investigated. Based on the results of the investigation, each pair of piezoelectric actuators and corresponding gap sensors is treated as an independent system and modeled as a first‐order linear model coupled with hysteresis. When the model is identified and the hysteresis nonlinearity is linearized, a linear system model with uncertainty is used to design the controller. When designing the controller, the sliding‐mode disturbance (uncertainty) estimation and compensation scheme is used. The structure of the proposed controller is similar to that of a proportional integral derivative controller. Thus, it can be easily implemented. Experimental results show that 3‐nm tracking resolution can be obtained. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

H∞ finite‐horizon filtering for complex networks with state saturations: The weighted try‐once‐discard protocol

This paper addresses the finite‐horizon H_∞ filtering problem for a kind of discrete state‐saturated time‐varying complex networks subjected to the weighted try‐once‐discard (WTOD) protocol. Under the WTOD protocol, only the measurement signal from one sensor node is allowed to be transmitted to the filter at each time point, where such a node is selected based on a certain quadratic selection principle. The main purpose of this paper is to design an H_∞ filter that guarantees the disturbance attenuation level on a given finite time‐horizon for the underlying complex network subject to both state saturations and WTOD protocols. By using the convex hull approach, sufficient conditions are first obtained to ensure the existence for the desired filter to achieve the H_∞ performance specification by means of a few recursive matrix inequalities. Then, based on the obtained results, the filter parameters are designed, which cope effectively with both state saturations and communication protocols. Finally, a numerical simulation is employed to demonstrate the validity of the developed filter algorithm.     

Z‐uncertain probabilistic linguistic variables and its application in emergency decision making for treatment of COVID‐19 patients

Probabilistic linguistic term sets (PLTSs) have many applications in the field of group decision making (GDM) because it includes both linguistic evaluation and probabilistic distribution when expressing preference information. However, the difference of information credibility in PLTSs is ignored, resulting in an inaccurate representation of decision information and unreasonable probability calculation. In this paper, we first consider the credibility of the information and propose the concept of Z‐uncertain probabilistic linguistic variables (Z‐UPLVs). Subsequently, the operational rules, normalization, distance and similarity measures, and comparison method of Z‐UPLVs are introduced. Then, a probability calculation method based on credibility, an extended TOPSIS method, and some operators are proposed, which can be applied to emergency decision making in the Z‐uncertain probabilistic linguistic (Z‐UPL) environment. Finally, an emergency decision‐making case of COVID‐19 patients and comparative analysis illustrate the necessity and effectiveness of this method.     

Development of a liquid crystal with fine‐pitch light‐source display (LFD) using an organic light‐emitting diode (OLED)

Abstract— A novel display system, refered to as an LFD (liquid crystal with fine‐pitch light‐source display) is proposed. In an LFD, an auxiliary light source patterned with a fine pitch is attached to a reflective liquid‐crystal display (LCD), and a light shield is formed on the observer's side of the light source. A vertical‐alignment LCD (VA‐LCD) is attached as the reflective LCD, and an organic light‐emitting diode (OLED) is attached as the fine‐pitch light source. An LFD can produce bright, high‐contrast images under any ambient light. A test sample was built and its display characteristics confirmed.     

The new route for realization of 1‐μm‐pixel‐pitch high‐resolution displays

A new pixel structure for the realization of a 1‐μm‐pixel‐pitch display was developed. This structure, named vertically stacked thin‐film transistor (VST), was based on the conventional back‐channel etched thin‐film transistor (TFT), but all the layers except the horizontal gate line were vertically stacked on the embedded data line, enabling the implementation of high‐resolution display panels. The VST device with a channel length of 1 μm showed a high field effect mobility of more than 50 cm²/Vs and low subthreshold slope of 78 mV per decade. It also shows a high uniform electrical characteristic over the entire 6‐in. wafer. The development of a new pixel architecture is expected to enable the implementation of 1‐μm‐pixel‐pitch high‐resolution displays such as spatial light modulators for digital holograms.     

Practical CNT‐FED structure for high‐luminance character displays

Abstract— A high‐luminance CNT‐FED character display using a simple line rib structure was constructed. The display panel had 48 × 480 dots and the subpixel pitch was 1 mm. The greatest benefit of a display using CNT technology is high luminance performance with low‐power consumption. The luminance of the green‐color dot wasca. 10,000 cd/m² under 1/1 6 duty‐cycle driving at a 6‐kV anode voltage. The high luminance of the display panel can provide good visibility when installed even in outdoor locations, and the power consumption was ca. 4 W at the character displaying module. This, a CNT‐FED for character displays also has potential multifunctionality, which could be battery driven. It should be useful for public displays even under emergency no‐power conditions. In this work, a practical structure and process technologies for making ribs with reasonable cost were developed. The newly introduced 2‐mm‐tall line ribs as spacers were formed by using innovative production processes; i.e., the rib paste was pushed out of a multi‐slit nozzle, and the rib shape was formed by UV‐light irradiation. The developed panel structure and manufacturing processes also had the advantages of size flexibility and high production yield.     

Input‐to‐state exponents and related ISS for delayed discrete‐time systems with application to impulsive effects

This paper aims to investigate the input‐to‐state exponents (IS‐e) and the related input‐to‐state stability (ISS) for delayed discrete‐time systems (DDSs). By using the method of variation of parameters and introducing notions of uniform and weak uniform M‐matrix, the estimates for 3 kinds of IS‐e are derived for time‐varying DDSs. The exponential ISS conditions with parts suitable for infinite delays are thus established, by which the difference from the time‐invariant case is shown. The exponential stability of a time‐varying DDS with zero external input cannot guarantee its ISS. Moreover, based on the IS‐e estimates for DDSs, the exponential ISS under events criteria for DDSs with impulsive effects are obtained. The results are then applied in 1 example to test synchronization in the sense of ISS for a delayed discrete‐time network, where the impulsive control is designed to stabilize such an asynchronous network to the synchronization.     

Polynomial filtering for nonlinear stochastic systems with state‐ and disturbance‐dependent noises

This article is concerned with the polynomial filtering problem for a class of nonlinear stochastic systems governed by the Itô differential equation. The system under investigation involves polynomial nonlinearities, unknown‐but‐bounded disturbances, and state‐ and disturbance‐dependent noises ((x,d)‐dependent noises for short). By expanding the polynomial nonlinear functions in Taylor series around the state estimate, a new polynomial filter design method is developed with hope to reduce the conservatism of the existing results. In virtue of stochastic analysis and inequality technique, sufficient conditions in terms of parameter‐dependent linear matrix inequalities (PDLMIs) are derived to guarantee that the estimation error system is input‐to‐state stable in probability. Moreover, the desired polynomial matrix can be obtained by solving the PDLMIs via the sum‐of‐squares approach. The effectiveness and applicability of the proposed method are illustrated by two numerical examples with one concerning the permanent magnet synchronous motor.     

A 1‐to‐n way single‐ended‐to‐balanced substrate integrated waveguide filtering power splitter

An approach to 1‐to‐n (n = 3, 4…) way single‐ended‐to‐balanced filtering power splitter (SETBFPS) is proposed. The properly placed balanced ports with 0.5λ_g (λ_g is the substrate integrated waveguide [SIW] guided wavelength at f₀) space make the TE32nd 103 and TE32nd 105 modes of n 32nd‐mode SIW multimode resonators form differential‐mode (DM) passband of the SETBFPS. Compared with the state‐of‐art single‐ended‐to‐balanced power splitters, the proposed approach has all the functions of 1‐to‐n way, filtering, and common‐mode (CM) suppression. A 1‐to‐3 way prototype is exemplified at 3.5 GHz with the minimum insertion loss (IL) of 0.09 dB, a fractional bandwidth (FBW) for a 15‐dB return loss of 35%, and a FBW for 15‐dB CM suppression of 52%. Low IL and wide bandwidth can be observed.     

A new unified input‐to‐state stability criterion for impulsive stochastic delay systems with Markovian switching

In this paper, the problems of the input‐to‐state stability (ISS), the integral input‐to‐state stability (iISS), the stochastic input‐to‐state stability (SISS) and the e^λt(λ>0)‐weighted input‐to‐state stability (e^λt‐ISS) are investigated for nonlinear time‐varying impulsive stochastic delay systems with Markovian switching. We propose one unified criterion for the stabilizing impulse and the destabilizing impulse to guarantee the ISS, iISS, SISS and e^λt‐ISS for such systems. We verify that when the upper bound of the average impulsive interval is given, the stabilizing impulsive effect can stabilize the systems without ISS. We also show that the destabilizing impulsive signal with a given lower bound of the average impulsive interval can preserve the ISS of the systems. In addition, one criterion for guaranteeing the ISS of nonlinear time‐varying stochastic hybrid systems under no impulsive effect is derived. Two examples including one coupled dynamic systems model subject to external random perturbation of the continuous input and impulsive input disturbances are provided to illustrate the effectiveness of the theoretic results developed.     

Nanorod‐form ZnO‐homojunction ultraviolet light‐emitting diodes

Abstract— Ultraviolet (UV) light‐emitting diodes based on ZnO‐homojunction nanorods is reported. p‐type doping can be obtained from intrinsic (or close to) ZnO by introducing acceptors, such as P or As, using ion implantation followed by appropriate thermal annealing and dopant activation. Our approach provides a possible solution to p‐type doping of ZnO and ZnO‐homojunction light‐emitting diodes. It is interesting to note that this solution is offered in the form of nanorods.     

Asymmetric dual‐band linear‐to‐circular converter by bi‐layered chiral metamaterial

In this article, we present a dual‐band linear‐to‐circular transparent converter by bi‐layered chiral metamaterial (CMM) with an inverted “G” array in microwave region. The proposed metasurface consists of three layers which are the upper layer of the metasurface with a periodic regular metallic inverted “G” and wire array, the dielectric layer, and the bottom layer operating as chiral symmetric structure of the upper. The simulation results show that the transmitted right‐circular polarized wave with the axial ratio of 3 dB or less is in the range of 8.6‐10.9 GHz and the left‐circular polarized wave is within 18.1‐22.5 GHz when y‐polarized forward wave is normally incident. Specifically, the polarization conversion transmission can be maintained at over 85% at angle of incidence up to 40°. Therefore, the proposed CMM device is useful for the development of the integrated polarization manipulation devices.     

A 4‐bit ultra‐wideband complementary metal‐oxide‐semiconductor attenuator with low root‐mean‐square amplitude error

This article presents the 4‐bit ultra‐wideband complementary metal‐oxide‐semiconductor (CMOS) attenuator in a standard 0.18‐μm CMOS process. This design adopts switched bridge‐T type topologies for each attenuation bit. Based on insertion losses and input P_1‐dB considerations, the circuit performances can be optimized by the proper bit ordering arrangement. Therefore, the bit ordering 0.5‐4‐2‐1 dB is employed in the 4‐bit attenuator. Moreover, series inductors are added between each bit to further improve the input and output return losses. Measured results demonstrate that the attenuation range of the circuit is 7.5 dB with 0.5 dB step and the root‐mean‐square (RMS) amplitude error is between 0.11 and 0.13 dB from 3.1 to 10.8 GHz. The differences between simulated and measured RMS amplitude errors are less than 0.2 dB, which demonstrates the good agreement and feasibility of the design concept. The measured input P_1‐dB is 15 dBm at 5 GHz and the chip area is 1.12 mm² including all testing pads.     

Leader‐Following Consensus of Multi‐Agent System with Diffusion

This paper is concerned with the leader‐following consensus problem for multi‐agent systems consisting of one stationary leader and multiple cooperative followers, where the controlling effect of each follower depends on its own state. It is noted that the influence of diffusion among followers is taken into account and the system is modeled by reaction‐diffusion equations. With the assumption of the followers' initial states, a linear control protocol is designed. Based on algebraic graph theory, the method of energy estimates, and Sobolev embedding theorem, the sufficient conditions guaranteeing the leader‐following consensus under the proposed control protocol are provided. Numerical examples illustrate the effectiveness of the theoretical results.     

New approach to H ∞ filtering of two‐dimensional T‐S fuzzy systems

This paper is concerned with the H _∞ filtering problem for two‐dimensional T‐S fuzzy systems. Sufficient conditions for the solvability of this problem are obtained by using basis‐dependent Lyapunov functions. By considering the measured output as an independent variable with respect to the state variable and the disturbance input, a new method for designing two‐dimensional H _∞ filters is presented. Moreover, it has been shown that the proposed method is equivalent to the conventional one. Therefore, the proposed method does not lead to any conservativeness that may be caused by separately considering the measured output, the state variable, and the disturbance input. In converting the parameterized linear matrix inequalities (PLMI) into LMI constraints, attention is focused on the reduction of the number of LMI‐based conditions. On the basis of the proposed theorem, the number of LMI‐based conditions is reduced to r³ from r³(r + 1)² ∕ 4 by the conventional method. Thus, the computational advantage is obvious for fuzzy systems with large number of fuzzy rules. Simulation results have demonstrated the effectiveness of the proposed method. Copyright © 2012 John Wiley & Sons, Ltd.