Development of MgO:TiO2 thin films for gas sensor applications

In this study, structural, morphological and optical properties, and gas sensor performance of magnesium oxide (MgO) doped titanium dioxide (TiO₂) thin films were investigated in detail. Gas sensor metallic patterns were fabricated on Si substrate using traditional photolithographic technique. MgO doped TiO₂ thin films were deposited on formed Pt electrode surface by confocal sputtering (co-sputtering) system as the active layer. Thin film characterizations were realized by using secondary ion mass spectroscopy (SIMS), atomic force microscope (AFM) and UV–Vis Spectrometer (UV–Vis). Gas sensing measurements were performed by gas sensing test system against methane gas at working temperature of 300?°C. To evaluate deposition and thermal annealing effects on the sensing performance, sensors were tested under gas. The sensitivity and response/recovery time of gas sensors were measured in 1000?ppm. MgO doped TiO₂ based sensor at substrate temperature of 100?°C has high sensitivity and short response/recovery time.     

Low-dose esterified estrogen therapy: effects on bone, plasma estradiol concentrations, endometrium, and lipid levels. Estratab/Osteoporosis Study Group

BACKGROUND: Prospective studies have shown that doses equivalent to conjugated equine estrogens of 0.625 mg/d or higher are needed to produce a significant increase in bone mineral density of the lumbar spine. OBJECTIVES: To determine the effects of unopposed esterified estrogens on bone mineral density, lipid levels, and endometrial tissue structure, and to relate these effects to changes in plasma estradiol levels. METHODS: Four hundred six postmenopausal women were given calcium, 1000 mg/d, and randomly assigned to receive continuous esterified estrogens (0.3, 0.625, or 1.25 mg/d) or placebo for 24 months. Bone mineral density measurements and endometrial and laboratory assessments were conducted every 6 months; plasma estradiol concentrations were measured after 12, 18, and 24 months. RESULTS: All doses of esterified estrogens produced significant increases in bone mineral density of the lumbar spine compared with baseline and with placebo at 6, 12, 18, and 24 months. Mean plasma estradiol levels increased with esterified estrogens dose, and individual subject bone mineral density changes appeared related to plasma estradiol concentrations. Clinically relevant rates of endometrial hyperplasia were noted only in the groups receiving 0.625 and 1.25 mg of esterified estrogens daily. Lipid changes were dose related and apparent in all groups. CONCLUSIONS: Esterified estrogens at doses from 0.3 to 1.25 mg/d, administered unopposed by progestin, produce a continuum of positive changes on bone and lipids. Plasma estradiol concentrations increased with esterified estrogens dose and were related to positive bone mineral densities. The 0.3-mg dose resulted in positive bone and lipid changes without inducing endometrial hyperplasia.     

Application of reaching law approach to the position control of a vector controlled induction motor drive

In this paper, a new position control method based on the reaching law control (RLC) approach is proposed for the robust position control of electrical drive systems. The main aim of this study is to investigate the robustness of the RLC approach under inertial-frictional variations and external disturbances and to address the application problems of the RLC approach for position control systems. New components are added to the controller in order to improve the robustness. The control method is applied to a vector-controlled induction motor drive system. It is shown in the paper that the practical constraints such as torque limitation, and the demand of high control performance, i.e., high bandwidth, result in undesirable overshoots. The performance of the control method is shown by simulation and experimental results.List of symbols X, X _k Continuous and discrete-time state vectors - x ₁, x ₂ State variables (the shaft position and speed of the rotor) - , _re Position and reference angles (rad) - Angular velocity (rad/s) - A,A _n State variable matrix with true and nominal parameters - B,B _n Control input matrix, with true and nominal parameters - u,u _max Control signal, and its maximum value - A,B Uncertain parts of the state matrix and the control input matrix - Equivalent terms of A, B uncertainties referred to matching condition - C Gain vector of switching function - s _k Switching function - q A constant used in the reaching law - A constant used in the reaching law - A constant used in the chattering reduction approach - T sampling period - J,J _n True and nominal inertia coefficient (kg m²) - B,B _n True and nominal friction coefficient (kg m²/s) - J,B The uncertain parts of the inertia and friction coefficients - T _e Produced (electrical) torque (control signal) (Nm) - Load torque (Nm) - Equivalent term of A referred to matching condition and scalar component - Equivalent term of B referred to matching condition - All uncertainties and disturbances referred to matching condition - J₀,B₀ The variation ratios of the inertia and friction coefficients - G State variable matrix in discrete-time model - H Control input matrix in discrete-time model - Slope of the sliding line (surface) - a Mechanical time constant - v _sd, v _sq Stator voltages in d-q axis (V) - i _sd, i _sq Stator currents in d-q axis (A) - L _s, L _R Stator and rotor self inductances (H) - L _m Mutual inductance (H) - Leakage factor - _e, _sl Stator and slip angular velocity (rad/s) - _r Rotor time constant - P Number of poles