Optical properties of Si0.8Ge0.2/Si multiple quantum wells

The optical property was studied on the Si_0.8Ge_0.2/Si strained multiple quantum well (MQW) structure grown using ultra-high vacuum chemical vapor deposition (UHV-CVD). Three peaks are observed in Raman spectrum, which are located at about 510, 410, and 300 cm⁻¹, corresponding to the vibration of Si–Si, Si–Ge, and Ge–Ge phonons, respectively. The photoluminescence (PL) spectrum originates from the radiative recombinations both from the Si substrate and the Si_0.8Ge_0.2/Si MQW. For Si_0.8Ge_0.2/Si strained MQW, the transition peaks related to the MQW region observed in the photocurrent (PC) spectrum were preliminarily assigned to electron–heavy hole (e–hh) and electron–light hole (e–lh) fundamental excitonic transitions.     

Effects of focused ion beam milling on the compressive behavior of directionally solidified micropillars and the nanoindentation response of an electropolished surface

Focused ion beam (FIB) milling is the typical method used to fabricate micropillars to study small-scale plasticity and size effects in uniaxial compression. However, FIB milling can introduce defects into the milled pillars. To investigate the effects of FIB damage on mechanical behavior, we tested Mo-alloy micropillars that were FIB milled following directional solidification, and compared their compressive response to pillars that were not FIB milled. We also FIB milled at glancing incidence a Mo-alloy single-crystal surface, and compared its nanoindentation response to an electropolished surface of the same crystal. Implications for the interpretation of data obtained from FIB-milled micropillars are discussed.     

Load-adaptive, low switching-noise output buffer

An output buffer is described which employs built-in load monitoring in order to bound the transition time over a wide range of load conditions. The adaptive control of driving current enables the switching-noise to be kept to a minimum value. The experimental chip, which was designed to bound the fall time within 6 ns for loading capacitance up to 100 pF, revealed a reduced switching-noise level, 15-35% of a conventional buffer     

A new polarization-insensitive 1.55-μm InGaAsP-InGaAsPmultiquantum-well electroabsorption modulator using astrain-compensating layer

In a conventional polarization-insensitive multiquantum-well electroabsorption modulator, it is normal to apply tensile and compressive strain on the well and the barrier, respectively. But the main disadvantages of such a structure are a low conduction band offset (0.04-0.06 eV), a high heavy-hole band offset (0.20-0.24 eV), and a relatively large well thickness (110-120 Å). We propose a new method of overcoming these disadvantages by placing a tensile strain on both the well and the barrier and compensating for them with a compressive strained intrinsic layer     

Digital signal processing applied to the detection of partialdischarge: an overview

This article is the first of a four-part series by the authors that treats various aspects of digital signal processing applied to partial discharge detection. It is shown that manufacturers and users of high-voltage apparatus are interested in on-site, off-line and on-line analysis of partial discharge to identify and locate defects in insulation systems     

Preparation of silica-layered multi-walled carbon nanotubes activated by grafting of poly(4-vinylpyridine)

Herein, uniformly silica coated carbon nanotubes (CNTs) were fabricated by step reactions with minimized damage of CNTs during oxidation process. First, hydroxyl groups were generated on the surface of CNTs using KMnO₄ in conjunction with tetrapropyl ammonium bromide (TPABr) as a phase transfer catalyst, followed by the grafting of a vinyl group carrying silane coupling agent, methacryloxypropyl trimethoxy silane (MPTMS). Utilizing terminal vinyl groups in in-situ solution polymerization, poly(4-vinylpyrridine) (P4VP) brush was grown from the CNTs which promotes the acid–base interaction between CNTs and tetraethylorthosilicate (TEOS). By means of well-known ammonia catalyzed sol–gel reaction of TEOS in the presence of P4VP-functionalized CNTs, uniformly silica-coated CNTs were obtained. The thickness of the silica layer could be readily controlled by the amounts of reactants. After calcination of silica-coated CNTs, only outer silica remained which resulted in silica nanotubes.     

A semi-empirical atomic potential for the Fe-Cr binary system

Asemi-empirical atomic potential, the second nearest-neighbor MEAM, has been applied to obtain an atomic potential for the Fe-Cr system, based on the previously developed potentials for pure Fe and Cr. The procedure for the determination of potential parameter values and the performance of the assessed alloy potential were also presented. It was shown that the potential describes the basic thermodynamic property and alloy behavior in the bcc solid solution successfully, as well as many physical properties of pure Fe and Cr. The limit in the applicability of the present potential is also discussed.     

Detection of PD utilizing digital signal processing methods. Part3: Open-loop noise reduction

The paper shows that open-loop noise reduction techniques can be effective in separating partial discharge (PD) signals from noise. Wavelet-based denoising through the use of thresholding of wavelet coefficients provides near optimal noise reduction for many classes of signals including PD signals in noise. The effectiveness of wavelet transform-based noise reduction depends on selection of an appropriate wavelet basis function as well as on careful selection of threshold function and levels     

Cure rate of DGEBA/MDA/GN/HQ system by differential scanning calorimetry analysis

To compare investigations of the cure kinetics of DGEBA/MDA/GN/HQ system by different methods, the fractional life method, Kissinger equation, Barrett method and integral method were used. From the fractional life method, reaction orders were between 0.77 and 0.93 but had no correlation with cure temperature, and from the Kissinger equation, the activation energy was 11.08 kcal mol⁻¹ and pre-exponential factor was 2.78×10³ s⁻¹. For the second-order reaction by the Barrett method and integral method, the activation energy was 20 kcal mol⁻¹ and the pre-exponential factor was 8.5×10⁸ s⁻¹. By comparison of the Barrett model with experimental data, it was found that the Barrett model was useful for predicting the cure time at a given temperature.     

PGF2 alpha causes bronchoconstriction and pulmonary vasoconstriction via thromboxane receptors in rat lung

OBJECTIVE: The present study set out to determine general levels of distress, anxiety and depression in an obstetric-gynaecology inpatient population and to ascertain levels of patient satisfaction with services. METHOD: 200 English-speaking consecutive admissions to the hospital filled out a package of questionnaires consisting of a demographic data form, the 30-item General Health Questionnaire, the Speilberger State-Trait Anxiety Inventory, the Inventory to Diagnose Depression and a Patient Satisfaction with Services Questionnaire. 134 packages were fully completed. RESULTS: The most significant findings were: first, that high levels of anxiety prevailed, with approximately 1/3 of patients at or above the 75th percentile for anxiety levels; and second, that those patients born in non-English speaking countries were significantly more dissatisfied with their care. CONCLUSIONS: The results of this study suggest that there is a need for increased awareness of and further research into the psychological needs of obstetric-gynaecology patients.