Solids and Liquids in the NaF–AlF3–Al2O3 System: A High-Temperature NMR Study

Aluminofluoride and oxyfluoride melts are essential in the electrolytic smelting of aluminum, as the precursors of fluoride glasses, and as analogue systems for molten silicates. In these systems, the quantification of the abundances of structural species is crucial in the understanding of both thermodynamic and transport properties. ²⁷Al NMR spectroscopy at high temperatures can provide important constraints on speciation and coordination number in aluminofluoride liquids, as well as structural and dynamical changes in the crystalline fluorides. We present results on a series of solids and liquids in the NaF–AIF₃–Al₂O₃ system. These illustrate the dramatic effects of composition and temperature on liquid structure and suggest that most Al cations are four- or six-coordinated, with a relatively low abundance of five-coordinated sites.     

A 1-17-GHz InGaP-GaAs HBT MMIC analog multiplier and mixer with broad-band input-matching networks

An InGaP-GaAs heterojunction bipolar transistor (HBT) analog multiplier/mixer monolithic microwave integrated circuit (MMIC) is developed that adopts a Gilbert-cell multiplier with broad-band input-matching networks to widen the bandwidth up to 17 GHz. This MMIC was fabricated using a commercially available 6-in InGaP-GaAs HBT MMIC process. It achieved a measured sensitivity of above 1100 V/W for an analog multiplier and a conversion gain of better than 9 dB for a mixer. It also demonstrated a lower corner frequency and noise than that of an InP HBT analog multiplier. The measured low-frequency noise was 10 nV/sqrt(Hz), which is about half of that of an InP HBT analog multiplier with a similar architecture. The corner frequency of the low-frequency noise was roughly estimated to be 15 kHz. The measured performance of this MMIC chip with gain-bandwidth-product (GBP) of 47 GHz rivals that of the reported GaAs-based analog multipliers and mixers. The high GBP result achieved by this chip is attributed to the HBT device performance and the broad-band input-matching network.     

Novel SONOS-Type Nonvolatile Memory Device With Optimal Al Doping in HfAlO Charge-Trapping Layer

Operation properties of polysilicon-oxide-nitride-oxide-silicon-type Flash device with HfAlO charge-trapping layer having various Al contents were investigated in this letter. Satisfactory performance in terms of operation speed, retention, and program/erase endurance of the Flash device is achieved with the optimal Al content of 18%-28% in the HfAlO trapping layer. In addition, high-speed operation can be attained with the combination of channel-hot-electron-injection programming and band-to-band hot hole erasing for NOR architecture applications.     

Characterization of the Ultrathin HfO2 and Hf-Silicate Films Grown by Atomic Layer Deposition

The physical properties of HfO₂ and Hf-silicate layers grown by the atomic layer chemical vapor deposition are characterized as a function of the Hf concentration and the annealing temperature. The peaks of Fourier transform infrared spectra at 960, 900, and 820 cm_-1 originate from Hf-O-Si chemical bonds, revealing that a Hf-silicate interfacial layer began to form at the HfO₂/SiO ₂ interface after post deposition annealing process at 600 degC for 1 min. Moreover, the intensity of the peak at 750 cm^-1 can indicate the degree of crystallization of HfO₂. The formed Hf-silicate layer between HfO² and SiO² is also confirmed by X-ray photoelectron spectroscopy     

Timing Recovery in Digital Subscriber Loops

Tradeoffs in the design of the timing recovery functions in a subscriber loop receiver are analyzed. The techniques considered are applicable to both the echo cancellation (EC) and time compression multiplexing (TCM) methods of full duplex transmission. Emphasis is on those techniques that lend themselves to implementation in MOSLSI technology, where the objective requirement is that timing recovery be implemented on a sampled-data signal (with the minimum possible sampling rate where EC is used). The wave difference method (WDM) for timing recovery appears to be the best candidate. A detailed study of its performance is carried out analytically and by computer simulation for the case of binary and alternate mark-inversion (AMI) line coding. A closed form expression describing the binary jitter performance of the WDM and its continuous time counterpart, the spectral line technique, is used to compare the two techniques. Analytical and simulation results for recovered phase and jitter are presented for various cable pulse responses carefully chosen to represent worst-case or nearly worst-case conditions. Two methods for including frequency detection in the WDM, the quadricorrelator and the rotational detector, are also simulated.     

Using Nonadditive Fuzzy Integral to Assess Performances of Organizational Transformation Via Communities of Practice

Organizational transformations have been widely adopted by firms who wish to improve their competitive advantage to be better prepared to face external challenges. This research has chosen Communities of Practice (CoPs) as the subject of discussion for an assessment model to reform organizations that undertake CoPs for collective knowledge to enhance their core competencies. Given the interrelationships between criteria, this research uses the nonadditive fuzzy integral to develop a framework for the CoPs performance assessment. The purposes of this paper are to identify the key dimensions/criteria in the CoPs, to use fuzzy logic method to analyze the relative importance of each criterion, and to rank the criteria so that proper resources can be allocated while managing the CoPs. Through interviews with experts, four strategy alternatives and 16 criteria along four dimensions are generated. A survey of the CoPs practitioners is then conducted to compare the results of each criterion. The results will not only help organizations that intend to initiate changes via the CoPs activities to decide the ranking of their appraisal criteria, but it can also assist them in guiding the behavior of their staff while effectively monitoring and improving the performances of the CoPs     

A novel method to measure acoustic speed of bone tissue

Acoustic speed is an important parameter that can be used to characterize bone tissue for evaluation of osteoporosis. Traditional approaches for measuring acoustic speed require knowledge of either the specimen thickness, which is sometimes difficult to obtain from biological tissues, or the reference fluid velocity that, moreover, is an unknown parameter for internal tissue in in vivo measurement. In this paper, a new method is proposed to measure acoustic speed from dual reflected ultrasound signals. This technique utilizes two transducers placed on the same side of the test object; one for transmitter and receiver, and the other one for receiver only. The acoustic speed of the test object is based on the information of time-of-flight from the signals received by both transducers and the separation distance between the transducer pair. The technique developed here not only eliminates the requirement of knowledge of specimen thickness, but also shows a feasibility for clinical applications. The results of different porcine and bovine bone samples measured in vitro by this technique are in good agreement with those measured by other published methods. In vivo measurement results of 10 healthy young volunteers' tibias are also reported.     

1.3 mu m semiconductor laser power amplifier

The performance of a 3.4-Gb/s system using a low-power 1.318- mu m distributed-feedback (DFB) laser transmitter and a traveling-wave semiconductor laser power amplifier is studied. The -14.5-dBm, input from a directly modulated DFB laser is boosted to +10.3 dBm, of which +4.8 dBm is coupled into the transmission fiber. The penalty, caused by amplifier noise and pattern effects due to gain saturation, is less than 0.5 dB.<>     

Cellular thiols as a determinant of responsiveness to menadione in cardiomyocytes

The role of intracellular thiols in menadione-mediated toxicity was studied in neonatal rat cardiomyocytes. The sensitivity of cardiomyocytes to menadione was greater than that of skeletal muscle cells and 3T3 fibroblasts. Before cell degeneration, menadione induced marked depletion of intracellular thiols and an increase of oxidized glutathione. The sensitivity of these cells to menadione correlated with the level of depletion of intracellular thiols. After incubation of cardiomyocytes with menadione, glutathione reductase activity was inhibited and lipid peroxidation was increased. Both dicumarol (an inhibitor of DT-diaphorase) and diethyldithiocarbamate (an inhibitor of superoxide dismutase) enhanced the capacity of menadione to induce cellular damage and to cause depletion of intracellular glutathione. Decreasing intracellular glutathione by pretreatment of cells with N-ethylmaleimide or buthionine sulphoximine also increased menadione-induced cell degeneration. Preincubation with cysteine or dithiothreitol suppressed the capacity of menadione to damage the cells. Menadione-induced lipid peroxidation was also suppressed by the same treatment. These results show that the oxidative stress induced by menadione in cardiomyocytes results in the depletion of glutathione and protein thiols. Both DT-diaphorase and superoxide dismutase can protect cells from the toxicity of menadione. Cellular thiols are determinants of the responsiveness to menadione.