System reliability estimation using simulation combined with network reductions

This paper proposes a dynamic Monte Carlo sampling method, called the conditional minimal cut set (COMICS) algorithm, where all arcs are not simulated at each trial and all minimal cut sets need not be given in advance. The proposed algorithm repeats simulating a minimal cut set composed of the arcs which originate from the (new) source node and reducing the network on the basis of the states of simulated arcs until the s-t connectedness is confirmed. We develop the importance sampling estimator, the total hazard estimator and the hazard importance sampling estimator which are all based on the proposed algorithm, and compare the performance of these simulation estimators. It is found that these estimators can significantly reduce the variance of the raw simulation estimator and the usual importance sampling estimator.     

Estimation of joint length distribution using window sampling

One of the most difficult procedures in statistical joint modeling is the determination of the joint length distribution. In this study, a window sampling method was adopted to estimate the trace length distribution for the Poisson disc joint model. Four kinds of equations were derived for estimating the trace length distribution from contained or dissecting trace length distributions in a rectangular or circular window. The equations were tested for accuracy through Monte Carlo simulation and their efficiencies for estimating the trace length distribution were compared. This new technique using window sampling was compared with the method using a semi-trace or complete trace length distribution from scanline sampling. A numerical technique for determining the diameter distribution from the trace length distribution was also suggested. To check the validity of this numerical method, it was applied to solving four example cases and their results were compared with theoretical solutions.     

PVT-aware leakage reduction for on-die caches with improved read stability

Effectiveness of previous SRAM leakage reduction techniques vary significantly as the leakage variation gets worse with process and temperature fluctuation. This paper proposes a simple circuit technique that adaptively trades off overhead energy for maximum leakage savings under severe leakage variations. The proposed run-time leakage reduction technique for on-die SRAM caches considers architectural access behavior to determine how often the SRAM blocks should enter a sleep mode. A self-decay circuit generates a periodic sleep pulse with an adaptive pulse period, which puts the SRAM array into a sleep mode more frequently at high leakage conditions (fast process, high temperature) and vice versa. An 0.18-/spl mu/m 1.8-V 16-kbyte SRAM testchip shows 94.2% reduction in SRAM cell leakage at a performance penalty less than 2%. Measurement results also indicate that our proposed memory cell improves SRAM static noise margin by 25%.     

Optimal Dual-$V_{T}$ Design in Sub-100-nm PD/SOI and Double-Gate Technologies

Dual-threshold-voltage (V_T) CMOS is an effective way to reduce leakage power in high-performance very-large-scale-integration circuits. In this paper, we explore the technology design space for dual-threshold-voltage transistor design in deep-sub-100-nm technology nodes. We propose a technique of achieving high-V_T (HVT) devices using thicker gate-sidewall offset spacers to increase the channel length without increasing the printed-gate length. The effectiveness of all the dual-V_T technology options-increasing channel doping, increasing gate length, and proposed technique of increasing spacer thickness-is analyzed at transistor and basic logic gate level. Results on 65-nm partially depleted silicon-on-insulator and double-gate technologies indicate that the proposed technique yields lower dynamic power consumption and lower performance penalty compared with longer gate length and high body-doping devices. Our proposed technique, however, incurs extra fabrication mask similar to achieving HVT by increasing body doping.     

Electrochemical Impedance Spectroscopic Analysis of Sensitization-Based Solar Cells

Electrochemical impedance spectroscopy (EIS) is a very powerful tool for elucidation of charge transfer and transport processes in sensitization-based solar cells (e.g., dye-sensitized solar cells [DSSCs], quantum dot-sensitized solar cells [QDSSCs], and perovskite solar cells [PSCs]). EIS measures the electrochemical response to small amplitude AC signals over a wide range of frequencies. Analysis of the EIS response provides information about the corresponding parameters of the cells. Here, we review the fundamentals of EIS, charge transport kinetic processes, and equivalent circuit models of sensitization-based solar cells and use these concepts to explain the EIS spectra of DSSCs, QDSSCs, and PSCs. This review will be very useful for understanding the fundamental charge transfer and transport processes in different sensitization-based solar cells and the use of an equivalent circuit model to interpret the observed charge transfer and reactions.     

Empirical millimeter-wave wideband propagation characteristics of high-speed train environments

Owing to the difficulties associated with conducting millimeter-wave (mmWave) field measurements, especially in high-speed train (HST) environments, most propagation channels for mmWave HST have been studied using methods based on simulation rather than measurement. In this study, considering a linear cell layout in which base stations are installed along a railway, measurements were performed at 28 GHz with a speed up to 170 km/h in two prevalent HST scenarios: viaduct and tunnel scenarios. By observing the channel impulse responses, we could identify single- and double-bounced multipath components (MPCs) caused by railway static structures such as overhead line equipment. These MPCs affect the delay spread and Doppler characteristics significantly. Moreover, we observed distinct path loss behaviors for the two scenarios, although both are considered line-of-sight (LoS) scenarios. In the tunnel scenario, the path loss exponent (PLE) is 1.3 owing to the waveguide effect, which indicates that the path loss is almost constant with respect to distance. However, the LoS PLE in the viaduct scenario is 2.46, which is slightly higher than the free-space loss.     

Immobilization of horseradish peroxidase onto a gold-nanoparticle-adsorbed poly(thionine) film for the construction of a hydrogen peroxide biosensor

An amperometric hydrogen peroxide (H2O2) biosensor was developed based on the immobilization of horseradish peroxidase (HRP) onto a gold-nanoparticle (GNP)-adsorbed conducting poly(thionine) (PTH) film. The modification process was characterized by scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The effects of experimental parameters such as the concentration of the mediator (hydroquinone, HQ), the pH of the solution, and the working potential were investigated for optimum analytical performance. In the presence of the mediator, the immobilized HRP showed excellent electrocatalytic activity towards the reduction of H2O2. The linear dynamic range of 5-150 microM with the regression coefficient of 0.999 was obtained. The detection limit was calculated to be 1.5 microM based on a signal-to-noise ratio of 3. The reproducibility, repeatability, and stability of the biosensor were studied, with satisfactory results. The biosensor performance was evaluated with respect to the possible interferences and the application of the biosensor to real-sample analysis.     

Estimation of a joint diameter distribution by an implicit scheme and interpolation technique

A new technique to estimate the diameter distribution of a joint set from the contained trace length distribution is suggested. This technique obtains the diameter distribution directly from the sample histogram of the contained trace lengths without using any information about the trace length distribution of an infinite window. Compared with the previous method of Song and Lee [Estimation of joint length distribution using window sampling. Int J Rock Mech Mining Sci 2001; 38: 519–28], it is more accurate for small-size joint samples. To obtain more accurate estimates, we adopt an interpolation technique of B-spline to smooth out the sampled contained trace length distribution. The effect of the B-spline as a function of three kinds of predefined diameter distributions is examined by Monte Carlo simulations.