Bio-Inspired Artificial Fast-Adaptive and Slow-Adaptive Mechanoreceptors With Synapse-Like Functions

Development of artificial mechanoreceptors capable of sensing and pre-processing external mechanical stimuli is a crucial step toward constructing neuromorphic perception systems that can learn and store information. Here, bio-inspired artificial fast-adaptive (FA) and slow-adaptive (SA) mechanoreceptors with synapse-like functions are demonstrated for tactile perception. These mechanoreceptors integrate self-powered piezoelectric pressure sensors with synaptic electrolyte-gated field-effect transistors (EGFETs) featuring a reduced graphene oxide channel. The FA pressure sensor is based on a piezoelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) thin film, while the SA pressure sensor is enabled by a piezoelectric ionogel with the piezoelectric-ionic coupling effect based on P(VDF-TrFE) and an ionic liquid. Changes in post-synaptic current are achieved through the synaptic effect of the EGFET by regulating the amplitude, number, duration, and frequency of tactile stimuli (pre-synaptic pulses). These devices have great potential to serve as artificial biological mechanoreceptors for future artificial neuromorphic perception systems.     

Double S-Shaped Polarization – Voltage Curve and Negative Capacitance from Al2O3-Hf0.5Zr0.5O2-Al2O3 Triple-Layer Structure

The negative capacitance (NC) effect, recently discovered in a fluorite-based ferroelectric thin film, has attracted great attention as a rescue to overcome the scaling limitations of the conventional memory and logic devices of highly integrated circuits. The NC effect manifesting an S-shaped polarization–voltage (P–V) curve is initially interpreted by a 1-dimensional Landau Ginzburg Devonshire (LGD) model. However, a series of recent studies have found that this effect can also be explained by the inhomogeneous stray field energy (ISE) model. In this study, by extending the ISE model in the ferroelectric (FE)-dielectric (DE) layered structure, an analytical model that considers the influence of the interfacial screening charge distribution is presented. This model showed that the NC effect in the FE-DE heterostructure can be manifested in various forms other than a single S-shaped P–V curve. In particular, a double S-shaped P–V curve is expected from the fully compensated anti-parallel domain structure, confirmed experimentally in the actual Al₂O₃/(Hf_0.5Zr_0.5)O₂/Al₂O₃ triple-layer structure. Furthermore, to reveal the origin of the double S-shaped P–V curve, a multidomain LGD model is presented. It is confirmed that this phenomenon is attributed to the evolution of inhomogeneous stray field energy.     

Synergistic Enhancement of Luminescent and Ferroelectric Properties through Multi-Clipping of Tetraphenylethenes

Synergistically enhancing luminescent and ferroelectric ( SELF ) properties are observed from a tetraphenylethene ( TP ) substituted with clipping groups ( C ), where the C is consisting of a 4-[3,5-bis-(3-decyloxy-styryl)-styryl]-phenyl ( DOS ) unit. The DOS units of TPCn are self-assembled via intermolecular interaction to clip themselves and induce TP aggregation, as evidenced by clip-induced quenching of emission at DOS units ( E _clip ) accompanied by aggregation-induced emission enhancement of TPs ( E _AIE ). TPC4 demonstrates strong photoluminescence in a dilute chloroform solution and large E_AIE in aqueous (>50%) THF solution. TPCn demonstrates SELF properties in film state, with high quantum yields of photoluminescence (>80%) and ferroelectric switching. Due to the introduction of four clips, TPC4 has a higher remnant polarization ( P _r  =  2.27 µC cm⁻²) at room temperature than TPC1. TPC4 is successfully employed in a light-emitting electrochemical cell to achieve over 1290 cd m⁻² under pulsed current conditions. The TPC4 film on a flexible substrate produced a piezoelectric output voltage of up to 0.13 V and a current density of 1.14 nA cm⁻² upon bending. These results indicate that the side chain clipping and TP aggregation resulted in unprecedented flexible SELF properties in a single compound, offering simultaneous enhancement of electroluminescence, mechanical sensitivity, and energy harvesting capacity.     

Engineering Transition Metal Layers for Long Lasting Anionic Redox in Layered Sodium Manganese Oxide

Oxygen-redox-based-layered cathode materials are of great importance in realizing high-energy-density sodium-ion batteries (SIBs) that can satisfy the demands of next-generation energy storage technologies. However, Mn-based-layered materials (P2-type Na-poor Na_y[A_xMn_1−x]O₂, where A = alkali ions) still suffer from poor reversibility during oxygen-redox reactions and low conductivity. In this work, the dual Li and Co replacement is investigated in P2-type-layered Na_xMnO₂. Experimentally and theoretically, it is demonstrated that the efficacy of the dual Li and Co replacement in Na_0.6[Li_0.15Co_0.15Mn_0.7]O₂ is that it improves the structural and cycling stability despite the reversible Li migration from the transition metal layer during de-/sodiation. Operando X-ray diffraction and ex situ neutron diffraction analysis prove that the material maintains a P2-type structure during the entire range of Na⁺ extraction and insertion with a small volume change of ≈4.3%. In Na_0.6[Li_0.15Co_0.15Mn_0.7]O₂, the reversible electrochemical activity of Co³⁺/Co⁴⁺, Mn³⁺/Mn⁴⁺, and O^2-/(O₂)^n- redox is identified as a reliable mechanism for the remarkable stable electrochemical performance. From a broader perspective, this study highlights a possible design roadmap for developing cathode materials with optimized cationic and anionic activities and excellent structural stabilities for SIBs.     

Implementation of mmWave long-range backhaul for UAV-BS

Uncrewed aerial vehicles (UAVs) have become a vital element in nonterrestrial networks, especially with respect to 5G communication systems and beyond. The use of UAVs in support of 4G/5G base station (uncrewed aerial vehicle base station [UAV-BS]) has proven to be a practical solution for extending cellular network services to areas where conventional infrastructures are unavailable. In this study, we introduce a UAV-BS system that utilizes a high-capacity wireless backhaul operating in millimeter-wave frequency bands. This system can achieve a maximum throughput of 1.3 Gbps while delivering data at a rate of 300 Mbps, even at distances of 10 km. We also present the details of our testbed implementation alongside the performance results obtained from field tests.     

Encapsulation of lead-free Sn/Zn/Bi solder alloy particles by coating with wax powder for improving oxidation resistance

An encapsulation treatment of lead-free Sn/Zn/Bi solder powder was investigated for improving the oxidation resistance. Sn-8mass%Zn-3mass%Bi alloy particles were coated with a wax (12-hydroxystearic acid) powder by means of a dry mechanical treatment method using a ball mill. In order to determine the optimum operating conditions of the ball mill in the wax-coating treatments, the compressive energy required for deforming a single Sn/Zn/Bi alloy particle was measured with an unconfined compression tester and the mechanical energy applied to the alloy particles in the ball mill was estimated using the results of the compression test. The optimum operating conditions were determined based on both the applied energy and the flowability of solder pastes, and the wax-coated alloy particles maintaining the spherical shape were obtained under the conditions. The wettability test and the solder balling test for the solder pastes containing the wax-coated alloy particles stored at room temperature in air were carried out to evaluate the oxidation resistance performance. The wax-coated alloy particles had an excellent wettability compared with the original alloy particles, and the oxidation resistance of the Sn/Zn/Bi solder powder was improved by the encapsulation treatment.     

Textural and microstructural transformation of Cu damascene interconnects after annealing

Influence of annealing on the textural and microstructural transformation of Cu interconnects having various line widths is investigated. Two types of annealing steps have been considered here: room temperature over 6 months and 200°C for 10 min. The texture was determined by x-ray diffraction (XRD) of various cross-sectional profiles after electropolishing, and the surface, microstructure, and grain boundary character distribution (GBCD) of Cu interconnects were characterized using electron backscattered diffraction (EBSD) techniques. In order to analyze a relationship between the stress distribution and textural evolution in the samples, microstresses were calculated with decreasing line widths at 200°C using finite element modeling (FEM). In this investigation, it was found that the inhomogeneity of stress distribution in Cu interconnects is an important factor, which is necessary for understanding textural transformation after annealing. A new interpretation of textural evolution in damascene interconnects lines after annealing is suggested, based on the state of stress and the growth mechanisms of Cu electrodeposits.     

Reducing Encoder Bit-Rate Variation in MPEG Video

A shortcoming of current video transmission using the MPEG standard is that its encoder produces a variable bit rate (VBR). Due to this, the encoder output has to be buffered and released over the network at a constant rate. This buffering of the encoder output introduces an additional delay between the encoding and decoding phases of the video transmission. To remedy this problem, we present a strategy to distribute the load produced by the encoder as evenly as possible, i.e., try to have a constant bit rate (CBR). This is done by treating the slices in each frame separately while compressing them and then mixing the different kinds of slices that are sent over the network. The resulting load variation is much more uniform, reducing the buffering delay and making future bandwidth requirement estimates more accurate.This material is based upon work supported in part by the National Science Foundation under Award No. IRI-9526004, by the Texas Advanced Research Program under Grant No. 3652270, and by a grant from the University of Houston Institute of Space Systems Operations. Rajat Agarwal is now with Lucent Technologies. This paper is an extended version of a shorter paper presented at IEEE ICMCS 1999.Albert Mo Kim Cheng received the B.A. with Highest Honors in Computer Science at age 19, graduating Phi Beta Kappa, the M.S. in Computer Science with a minor in Electrical Engineering at age 21, and the Ph.D. in Computer Science at age 25, all from The University of Texas at Austin, where he held a GTE Foundation Doctoral Fellowship. Dr. Cheng is currently a tenured Associate Professor in the Department of Computer Science at the University of Houston, where he is the founding Director of the Real-Time Systems Laboratory. He has served as a technical consultant for several organizations, including IBM, and was also a visiting faculty in the Departments of Computer Science at Rice University (2000) and at the City University of Hong Kong (1995).He is the author/co-author of over seventy refereed publications in IEEE Transactions on Software Engineering, IEEE Transactions on Knowledge and Data Engineering, Real-Time Systems Symposium, Real-Time and Embedded Technology and Applications Symposium, and other leading conferences. One of his recent work presents a timing analysis of the NASA X-38 Space Station Crew Return Vehicle Avionics, which contains a fault-tolerant distributed system.Dr. Cheng has received numerous awards, including the National Science Foundation Research Initiation Award (now known as the NSF CAREER award). He has been invited to present seminars and tutorials at over 30 conferences, and has given invited seminars/keynotes at over 20 universities and organizations, most recently at ICEIS, Ecole Superieure de l Ouest (ESEO), Angers, France, April 2003. His next invited keynote speech will be at the 1st Intl. Conf. on Informatics in Control, Automation and Robotics (ICINCO), Setubal, Portugal, August 2004.He is an Associate Editor of the IEEE Transactions on Software Engineering (1998-2003), a Guest Co-Editor of two IEEE TSE Special Issues on Software and Performance (Nov. and Dec. 2000), an Associate Editor of the International Journal of Computer and Information Science, the work-in-progress program chair of the 2001 IEEE-CS Real-Time Technology and Applications Symposium, the work-in-progress session chair of the 2003 IEEE-CS Real-Time Systems Symposium, and the invited special panel chair for the software engineering for multimedia session at the 1999 IEEE-CS International Conference on Multimedia Computing Systems (ICMCS). Currently, he is a member of the program committees of RTSS, RTAS, ICEIS, ICECCS, RTAS, LCN, COMPSAC, ICCCN, AIA, DBA, PDCN, SE, and ICINCO. Dr. Cheng is an Honorary Member of the Institute for Systems and Technologies of Information, Control and Communication (INSTICC). He is a Senior Member of the IEEE.Dr. Cheng is the author of several book chapters on E-commerce/Enterprise Information Systems, and an article entitled Embedded OS, in the upcoming Encyclopedia of Computer Science and Engineering (John Wiley & Sons). He is the author of the new senior/graduate-level textbook entitled Real-Time Systems: Scheduling, Analysis, and Verification (John Wiley & Sons). cheng@cs.uh.eduRajat Agarwal received the M.S. in Computer Science from the University of Houston. He is currently a Member of the Technical Staff at Lucent Technologies. His research interest is in real-time multimedia systems.     

A four-channel 3.125-Gb/s/ch CMOS serial-link transceiver with a mixed-mode adaptive equalizer

This work presents a quad-channel serial-link transceiver providing a maximum full duplex raw data rate of 12.5Gb/s for a single 10-Gbit eXtended Attachment Unit Interface (XAUI) in a standard 0.18-/spl mu/m CMOS technology. To achieve low bit-error rate (BER) and high-speed operation, a mixed-mode least-mean-square (LMS) adaptive equalizer and a low-jitter delay-immune clock data recovery (CDR) circuit are used. The transceiver achieves BER lower than <4.5/spl times/10/sup -15/ while its transmitted data and recovered clock have a low jitter of 46 and 64 ps in peak-to-peak, respectively. The chip consumes 178 mW per each channel at 3.125-Gb/s/ch full duplex (TX/RX simultaneous) data rate from 1.8-V power supply.     

Fabrication of electrically controllable microlens array using liquid crystals

Electrically controllable liquid-crystal (LC) microlens arrays have been fabricated using the process of anisotropic phase separation of the LC from its solution in a ultraviolet curable prepolymer. The focal length of nematic LC-based microlens arrays can be changed in milliseconds with an applied electric field. The ferroelectric LC microlens array exhibits the memory effect and modulates the transmitted light within a few microseconds, i.e., /spl sim/1000 times faster than the nematic LC-based microlens. Having no internal substructures to scatter light, these devices offer high efficiency and high light throughput that is different from polymer-dispersed devices.