Subjective Listening Experiments on a Front and Rear Array‐Based WFS System

Wave field synthesis (WFS) has been gathering more and more attention recently due to its ability to perfectly reproduce an original sound field. However, to realize theoretically perfect WFS, a four‐sided loudspeaker array that encloses the listener is required. However, it is difficult to build such a system except in large listening spaces, such as a theater or concert hall. In other words, if the listening space is a home, installing a side loudspeaker array is impractical. If the two side walls located to the left and right of the listener can be omitted, a setup using only front and rear loudspeaker arrays may be a solution. In this letter, we present a subjective listening experiment of sound localization/distance based on a WFS using a front and rear loudspeaker array system which is conducted on two listening points and shows average localization errors of 6.1° and 9.18°, while the average distance errors are –27% (0.5 m) and –29% (0.6 m), respectively.     

A 1.8-V 128-Mb mobile DRAM with double boosting pump, hybrid current sense amplifier, and dual-referenced adjustment scheme for temperature sensor

To verify three important circuit schemes suitable for DRAMs in mobile applications, a 1.8-V 128-Mb SDRAM was implemented with a 0.15-/spl mu/m technology. To achieve an ideal 33% efficiency, the double boosting pump uses two capacitor's series connection at pumping phase, while they are precharged in parallel. The hybrid folded current sense amplifier together with a novel replica inverter connection improved power and speed performances. Also, a dual-referenced adjustment scheme for a temperature sensor was proposed to allow a very high accuracy in tuning. Without loss in productivity, the implemented dual-referenced searching technique achieved tuning error of less than /spl plusmn/2.5/spl deg/C.     

An improved deep submicrometer MOSFET RF nonlinear model with newbreakdown current model and drain-to-substrate nonlinear coupling

An improved deep submicrometer (0.25 μm) MOSFET radio-frequency (RF) large signal model that incorporates a new breakdown current model and drain-to-substrate nonlinear coupling was developed and investigated using various experiments. An accurate breakdown model is required for deep submicrometer MOSFETs due to their relatively low breakdown voltage. For the first time, this RF nonlinear model incorporates the breakdown voltage turnover trend into a continuously differentiable channel current model and a new nonlinear coupling circuit between the drain and the lossy substrate. The robustness of the model is verified with measured pulsed I-V, S-parameters, power characteristics, harmonic distortion, and intermodulation distortion levels at different input and output termination conditions, operating biases, and frequencies     

Automatic Transformation of Membrane‐Type Electronic Devices into Complex 3D Structures via Extrusion Shear Printing and Thermal Relaxation of Acrylonitrile–Butadiene–Styrene Frameworks

This work demonstrates a means of automatic transformation from planar electronic devices to desirable 3D forms. The method uses a spatially designed thermoplastic framework created via extrusion shear printing of acrylonitrile–butadiene–styrene (ABS) on a stress‐free ABS film, which can be laminated to a membrane‐type electronic device layer. Thermal annealing above the glass transition temperature allows stress relaxation in the printed polymer chains, resulting in an overall shape transformation of the framework. In addition, the significant reduction in the Young's modulus and the ability of the polymer chains to reflow in the rubbery state release the stress concentration in the electronic device layer, which can be positioned outside the neutral mechanical plane. Electrical analyses and mechanical simulations of a membrane‐type Au electrode and indium gallium zinc oxide transistor arrays before and after transformation confirm the versatility of this method for developing 3D electronic devices based on planar forms.     

A common-gate switched 0.9-W class-E power amplifier with 41% PAEin 0.25-μm CMOS

A power amplifier for wireless applications has been implemented in a standard 0.25-μm CMOS technology. The power amplifier employs class-E topology to exploit its soft-switching property for high efficiency. The finite dc-feed inductance in the class-E load network allows the load resistance to be larger for the same output power and supply voltage than that for an RF choke. The common-gate switching scheme increases the maximum allowable supply voltage by almost twice from the value for a simple switching scheme. By employing these design techniques, the power amplifier can deliver 0.9-W output power to 50-Ω load at 900 MHz with 41% power-added efficiency (PAE) from a 1.8-V supply without stressing the active devices     

Disclosing the Role of Defect-Engineered Metal–Organic Frameworks in Mixed Matrix Membranes for Efficient CO2 Separation: A Joint Experimental-Computational Exploration

Incorporation of defects in metal–organic frameworks (MOFs) offers new opportunities for manipulating their microporosity and functionalities. The so-called “defect engineering” has great potential to tailor the mass transport properties in MOF/polymer mixed matrix membranes (MMMs) for challenging separation applications, for example, CO₂ capture. This study first investigates the impact of MOF defects on the membrane properties of the resultant MOF/polymer MMMs for CO₂ separation. Highly porous defect-engineered UiO-66 nanoparticles are successfully synthesized and incorporated into a CO₂-philic crosslinked poly(ethylene glycol) diacrylate (PEGDA) matrix. A thorough joint experimental/simulation characterization reveals that defect-engineered UiO-66/PEGDA MMMs exhibit nearly identical filler–matrix interfacial properties regardless of the defect concentrations of their parental UiO-66 filler. In addition, non-equilibrium molecular dynamics simulations in tandem with gas transport studies disclose that the defects in MOFs provide the MMMs with ultrafast transport pathways mainly governed by diffusivity selectivity. Ultimately, MMMs containing the most defective UiO-66 show the most enhanced CO₂/N₂ separation performance—CO₂ permeability = 470 Barrer (four times higher than pure PEGDA) and maintains CO₂/N₂ selectivity = 41—which overcomes the trade-off limitation in pure polymers. The results emphasize that defect engineering in MOFs would mark a new milestone for the future development of optimized MMMs.     

LMS adaptive filters using distributed arithmetic for high throughput

We present a new hardware adaptive filter architecture for very high throughput LMS adaptive filters using distributed arithmetic (DA). DA uses bit-serial operations and look-up tables (LUTs) to implement high throughput filters that use only about one cycle per bit of resolution regardless of filter length. However, building adaptive DA filters requires recalculating the LUTs for each adaptation which can negate any performance advantages of DA filtering. By using an auxiliary LUT with special addressing, the efficiency and throughput of DA adaptive filters can be of the same order as fixed DA filters. In this paper, we discuss a new hardware adaptive filter structure for very high throughput LMS adaptive filters. We describe the development of DA adaptive filters and show that practical implementations of DA adaptive filters have very high throughput relative to multiply and accumulate architectures. We also show that DA adaptive filters have a potential area and power consumption advantage over digital signal processing microprocessor architectures.     

Photomultiplication-Type Organic Photodetectors with High EQE-Bandwidth Product by Introducing a Perovskite Quantum Dot Interlayer

A photomultiplication (PM)-type organic photodetector (OPD) that exploits the ionic motion in CsPbI₃ perovskite quantum dots (QDs) is demonstrated. The device uses a QD monolayer as a PM-inducing interlayer and a donor–acceptor bulk heterojunction (BHJ) layer as a photoactive layer. When the device is illuminated, negative ions in the CsPbI₃ QD migrate and accumulate near the interface between the QDs and the electrode; these processes induce hole injection from the electrode and yield the PM phenomenon with an external quantum efficiency (EQE) >2000% at a 3 V applied bias. It is confirmed that the ionic motion of the CsPbI₃ QDs can induce a shift in the work function of the QD/electrode interface and that the dynamics of ionic motion determines the response speed of the device. The PM OPD showed a large EQE-bandwidth product >10⁶ Hz with a −3 dB frequency of 125 kHz at 3 V, which is one of the highest response speeds reported for a PM OPD. The PM-inducing strategy that exploits ionic motion of the interlayer is a potential approach to achieving high-efficiency PM OPDs.     

On surface recombination velocity and output intensity limit of pulsed semiconductor lasers

Relationships obtained by F. Kappeler et al. (1982) are utilized to assess the effect of facet passivation on the output intensity limit in terms of surface recombination velocity. The results show a trend that the output intensity limit increases in an exponential manner with decreasing recombination velocity once the velocity is reduced by a factor of 2 from that for an unpassivated laser. They also indicate that the output intensity is not likely to be limited by nonradiative recombination at the facet when the recombination velocity is reduced by a factor of 4.<>