Adaptive filtering of evoked potentials with radial-basis-function neural network prefilter

Evoked potentials (EPs) are time-varying signals typically buried in relatively large background noise. To extract the EP more effectively from noise, we had previously developed an approach using an adaptive signal enhancer (ASE) (Chen et al., 1995). ASE requires a proper reference input signal for its optimal performance. Ensemble- and moving window-averages were formerly used with good results. In this paper, we present a new method to provide even more effective reference inputs for the ASE. Specifically, a Gaussian radial basis function neural network (RBFNN) was used to preprocess raw EP signals before serving as the reference input. Since the RBFNN has built-in nonlinear activation functions that enable it to closely fit any function mapping, the output of RBFNN can effectively track the signal variations of EP. Results confirmed the superior performance of ASE with RBFNN over the previous method.     

Application of the hybrid Hopkins–Abbe method in full-chip OPC

The hybrid Hopkins–Abbe method is presented and shown to resolve the problem of the traditional Hopkins theory, namely the requirement for constant mask diffraction efficiencies. Simulation of electromagnetic scattering from the mask that takes into account the oblique angles of incidence from the illumination is performed by application of the domain decomposition method that is extended for offaxis illumination. Examples of 45 nm and 32 nm lines and spaces through pitch and through focus are presented to demonstrate the validity and accuracy of the hybrid Hopkins–Abbe method. The results obtained are in excellent agreement with a rigorous and independent (third party) simulator.     

AC-Boosting Frequency Compensation with Double Pole-Zero Cancellation for Multistage Amplifiers

In this paper, we present an AC-boosting compensation topology with double pole-zero cancellation (ACBC-DPZ) for a multistage amplifier driving a very large capacitive load. The proposed technique modifies the original AC-boosting compensation (ACBC) topology to increase the power-bandwidth efficiency and reduce the size for the output power transistor and compensation capacitor. Simulation results show that the ACBC-DPZ amplifier using a CSM 0.18 μm CMOS process can achieve a unity gain bandwidth of 14 MHz and an average slew rate of 3.88 V/μs at 1500 pF load. The amplifier dissipates 2.55 mW at a 1.8 V supply.     

Temperature profile effects in accelerated thermal cycling of SnPb and Pb-free solder joints

Accelerated thermal cycling (ATC) has been widely used in the microelectronics industry for reliability assessment. ATC testing decreases life cycle test time by one or more of the following means: increasing the heating and cooling rate, decreasing the hold time, or increasing the range of the applied temperature. The relative effect of each of these cycle parameters and the failure mechanisms they induce has been the subject of many studies; however uncertainty remains, particularly regarding the role of the heating and cooling rate. In this research, three conditions with two ramp rates (14 °C/min and 95 °C/min) and two temperature ranges (ΔT = 0–100 °C and −40 to 125 °C) were applied to resistor 2512 and PBGA 256 test vehicles assembled with SnPb and Pb-free solders. The test results showed that the higher ramp rate reduced the testing time while retaining the same failure modes, and that the damage per cycle increased with the temperature difference. For the resistors, the Pb-free solder joints lasted longer than the SnPb joints at the smaller ΔT, but were inferior at the larger ΔT. In contrast, the Pb-free solder joints in the PBGA test vehicles lasted longer than the SnPb solder under both conditions.     

Optimization of photomask design for reducing aberration-induced placement error

In semiconductor manufacturing, the accurate placement of circuit components ensures the proper functioning of microelectronic circuits. This is often subject to photolithography, an optical technique that transfers circuit patterns from photomasks to silicon wafers. Sources of placement error include aberration and misalignment between different levels, and we focus on the former. Aberration is an optical phenomenon that often degrades imaging system performance. Since aberration differs from one imaging system to another, a photomask design that minimizes the aberration-induced placement error is desired. In this paper, we discuss the optimization process of a general one-dimensional mask pattern under a general illumination condition. The constraint is a known population mean of the root mean square aberrations for the imaging systems under consideration. To apply the theory, we search for the optimal parameters for two common mask designs: alternating phase-shifting masks (PSMs) and attenuated PSMs. The theoretical results are compared with those from a Monte Carlo analysis on a large set of imaging systems. These results are indicative to mask manufacturers and circuit designers of increasing manufacturability of circuits.     

Facile Synthesis of Red/NIR AIE Luminogens with Simple Structures,Bright Emissions,and High Photostabilities,and Their Applications for Specific Imaging of Lipid Droplets and Image‐Guided Photodynamic Therapy

Red/near‐infrared (NIR) fluorescent molecules with aggregation‐induced emission (AIE) characteristics are of great interest in bioimaging and therapeutic applications. However, their complicated synthetic approaches remain the major barrier to implementing these applications. Herein, a one‐pot synthetic strategy to prepare a series of red/NIR‐emissive AIE luminogens (AIEgens) by fine‐tuning their molecular structures and substituents is reported. The obtained AIEgens possess simple structures, good solubilities, large Stokes shifts, and bright emissions, which enable their applications toward in vitro and in vivo imaging without any pre‐encapsulation or ‐modification steps. Excellent targeting specificities to lipid droplets (LDs), remarkable photostabilities, high brightness, and low working concentrations in cell imaging application make them remarkably impressive and superior to commercially available LD‐specific dyes. Interestingly, these AIEgens can efficiently generate reactive oxygen species upon visible light irradiation, endowing their effective application for photodynamic ablation of cancer cells. This study, thus, not only demonstrates a facile synthesis of red/NIR AIEgens for dual applications in simultaneous imaging and therapy, but also offers an ideal architecture for the construction of AIEgens with long emission wavelengths.     

Potential pitfalls of smart city development: A study on parking mobile applications (apps) in Hong Kong

Smart cities are built upon information and communication technologies (ICTs) to enable a broad range of advanced services. Through a comprehensive literature review, this study identified four pitfalls brought by the pervasive application of ICT, including information insecurity, privacy leakage, information islands, and digital divide. Therefore, a questionnaire survey together with 27 interviews was conducted in Hong Kong to investigate how the public perceived these pitfalls within the context of mobile apps providing real-time parking information which form a major part of smart mobility. System insecurity and privacy leakage were found to arouse worries among the app-users while their awareness of protecting personal data was found to have room for improvement. Islands of real-time parking information occur as a result of the lack of collaboration among private carpark operators. Digital divide existed widely among the disadvantaged groups and the problem cannot be solved by mere provision of ICT facilities. Overall, technologies alone cannot make a city smart or smarter. It is the suitable way in which ICTs are used to serve all citizens that matters.     

Outage Probability with Correlated Lognormal Interferers using Log Shifted Gamma Approximation

The computation of outage probability in cellular radio system has been extensively studied. The Signal-to-Interference-plus-Noise Ratio (SINR) distribution involves the sum of lognormal distributions due to dominant effect of shadowing in both the signal and interference components. Since no closed-form expression can be found for the sum of lognormal distributions, many approximation methods and bounds were proposed in the past. In this paper, Log Shifted Gamma (LSG) approximation is proposed to calculate the sum of correlated lognormal random variables (RVs), hence the outage probability, accurately with a wide range of dB spreads, number of interferers M, correlation coefficients r among interference components, and noise power N. Overall, LSG approximation shows consistent accuracy due to its flexibility over the classical lognormal approximation, especially with small correlation coefficients r and/or large dB spreads.     

Fast ping‐pong arbitration for input–output queued packet switches

Input–output queued switches have been widely considered as the most feasible solution for large capacity packet switches and IP routers. In this paper, we propose a ping‐pong arbitration scheme (PPA) for output contention resolution in input–output queued switches. The challenge is to develop a high speed and cost‐effective arbitration scheme in order to maximize the switch throughput and delay performance for supporting multimedia services with various quality‐of‐service (QoS) requirements. The basic idea is to divide the inputs into groups and apply arbitration recursively. Our recursive arbiter is hierarchically structured, consisting of multiple small‐size arbiters at each layer. The arbitration time of an n‐input switch is proportional to log₄?n/2? when we group every two inputs or every two input groups at each layer. We present a 256×256 terabit crossbar multicast packet switch using the PPA. The design shows that our scheme can reduce the arbitration time of the 256×256 switch to 11 gates delay, demonstrating the arbitration is no longer the bottleneck limiting the switch capacity. The priority handling in arbitration is also addressed. Copyright © 2001 John Wiley & Sons, Ltd.     

Far-infrared microbolometer detectors

The bismuth microbolometer is a simple, easily made detector suitable for use throughout the far-infrared, which has been integrated with a variety of planar antennas. The general thermal properties of these devices and some of the constraints on bolometer materials are discussed. The fabrication and performance of several different types of microbolometers and microthermocouples are described.