Quasiparticle Dynamics in FeSe Superconductors Studied by Femtosecond Spectroscopy

The ultrafast quasiparticle dynamics in FeSe single crystals were measured by using dual-color transient reflectivity measurements (ΔR/R) from 4.4 to 290 K. In general, the typical ΔR/R of FeSe includes two significant components. One is the relaxation of photoinduced quasiparticles, which has been used to estimate the electron–phonon coupling strength (λ=0.16). The other is the oscillation component due to the acoustic phonon. Moreover, the acoustic phonon’s energy estimated from the period of oscillation in ΔR/R markedly shrinks around 90 K, which is the so-called phonon softening.     

The Use of Fuzzy Logic in the Taguchi Method for the Optimisation of the Submerged Arc Welding Process

The use of fuzzy logic in the Taguchi method to optimise the submerged arc welding process with multiple performance characteristics is reported in this paper. An orthogonal array, the signal-to-noise ratio, multiresponse performance index, and analysis of variance are employed to study the performance characteristics in the submerged arc welding process. The process parameters, namely arc current, arc voltage, welding speed, electrode protrusion, and preheat temperature are optimised with considerations of the performance characteristics, including deposition rate and dilution. Experimental results are provided to confirm the effectiveness of this approach.     

A synchronization scheme using self-pulsating laser diodes inoptical chaotic communication

A synchronization scheme using self-pulsating laser diodes in optical chaotic communication is proposed. Optical chaotic light can be obtained by injecting a sinusoidal electronic signal into a self-pulsating laser diode. To synchronize between two identical chaotic systems with different initial conditions, a drive and response system model is constructed according to Pecora and Carroll's theory. Synchronization can be achieved for optical simplex and duplex transmissions provided that the conditional Lyapunov exponents for the drive and response systems are all negative. This approach offers a key step toward realizing optical chaotic modulation and demodulation     

Do the VOCs that evaporate from a heavily polluted river threaten the health of riparian residents?

To understand the potential threat of volatile organic compounds (VOCs) to the health of residents living close to a heavily polluted river, this study investigated the species and the concentration of VOCs evaporating from a river and surveyed the health condition of the nearby residents. Air samples were taken seasonally at the upstream, midstream, and downstream water surfaces of the river, and at different locations at certain distances from the river. These samples were analyzed qualitatively and quantitatively through gas chromatography and electron capture detector (GC/ECD) for chlorinated organic compounds, and through gas chromatography and flame ionization detector (GC/FID) for ordinary hydrocarbons. The health data obtained from valid health questionnaires of 908 residents were analyzed through Statistical Package for Social Science (SPSS) software. Twenty-six species of VOCs were identified in the environment adjacent the river, many of which are carcinogenic or believed to be carcinogenic to humans. However, results of this study shows that the VOCs evaporating from the polluted river have not been definitively identified as a major factor of cancer in the residents. However, the risk of suffering from certain chronic diseases may increase in residents living less than 225 m away from the river due to the high levels of evaporated VOCs. Residents living less than 225 m away from the river and with nearby specific industries are 3.130 times more at risk of suffering from chronic diseases than those with no nearby specific industries.     

Validation of an improved location-based handover algorithm using GSM measurement data

When a mobile station moves, the path loss and shadow fading contribute to the large-scale variation in the received signal strength. The variation of signal strength caused by shadow fadings is a random process, and handover decision mechanisms based on measurements of signal strength induce the "ping-pong effect." This paper proposes an improved handover algorithm, based on the estimates of location and velocity of the mobile station, to suppress the ping-pong effect in cellular systems. A practical approach based on GSM measurement data is used to estimate the location and velocity of mobile station to identify the correlation among shadowing components. The impact of location errors on handover performance was examined, and the proposed handover algorithm was applied to a real GSM system in urban Taipei city. The results indicate that the number of unnecessary handover can be reduced 18-26 percent by the proposed approach compared to the conventional method, while the signal outage probability remains similar. Besides, the computational complexity of the proposed algorithm is low, and the algorithm does not use a database or lookup table.     

Simplified Procedure for Developing Joint Distribution of amax and Mw for Probabilistic Liquefaction Hazard Analysis

This paper presents an innovative approach for a probabilistic analysis of liquefaction hazard at a given site in a specified exposure time based on the U.S. Geological Survey (USGS) National Seismic Hazard Maps data. The foundation of this new approach is a simplified procedure for obtaining a joint distribution of peak ground surface acceleration (amax) and moment magnitude of earthquake (Mw) at any given locality in the United States based on the USGS website data. The developed joint probability distribution of amax and Mw can be readily combined with the conditional probability of liquefaction (given a pair of amax and Mw) to obtain the total probability of liquefaction at a given site in a specified exposure time. Detailed formulation of the new approach is presented and demonstrated with examples.     

Scanned Probe Oxidation on p-GaAs(100) Surface with an Atomic Force Microscopy

Locally anodic oxidation has been performed to fabricate the nanoscale oxide structures on p-GaAs(100) surface, by using an atomic force microscopy (AFM) with the conventional and carbon nanotube (CNT)-attached probes. The results can be utilized to fabricate the oxide nanodots under ambient conditions in noncontact mode. To investigate the conversion of GaAs to oxides, micro-Auger analysis was employed to analyze the chemical compositions. The growth kinetics and the associated mechanism of the oxide nanodots were studied under DC voltages. With the CNT-attached probe the initial growth rate of oxide nanodots is in the order of ~300 nm/s, which is ~15 times larger than that obtained by using the conventional one. The oxide nanodots cease to grow practically as the electric field strength is reduced to the threshold value of ~2 × 10⁷ V cm⁻¹. In addition, results indicate that the height of oxide nanodots is significantly enhanced with an AC voltage for both types of probes. The influence of the AC voltages on controlling the dynamics of the AFM-induced nanooxidation is discussed.     

Probabilistic Framework for Liquefaction Potential by Shear Wave Velocity

This paper presents a new empirical equation for assessing liquefaction resistance of soils based on shear wave velocity Vs and the results of probabilistic analyses based on this empirical equation. A database consisting of in situ shear wave velocity measurements and field observations of liquefaction∕nonliquefaction in historic earthquakes is analyzed. This database is first used to train and test an artificial neural network to predict the occurrence of liquefaction∕nonliquefaction based on soil and seismic load parameters. The successfully trained and tested neural network is then used to establish the empirical equation. The concept of clean soil equivalence is introduced and used in the development of the empirical equation. The established empirical equation represents a deterministic method for assessing liquefaction resistance of a soil. Based on this newly developed deterministic method, probabilistic analyses of the cases in the database are conducted using the logistic regression approach and the mapping function approach. The results provide a basis for risk-based evaluation of liquefaction evaluation.     

Formal control techniques for power-performance management

These techniques determine when to speed up a processor to reach performance targets and when to slow it down to save energy. They use dynamic voltage and frequency scaling to balance speed and avoid worst case frequency limitations for both multiple-clock-domain and chip multiprocessors.