Effect of Sr substitution on structural,dielectric, magnetic and magnetoelectric properties of rapid liquid sintered BiFe0.8Ti0.2O3 ceramics

Structural, dielectric, magnetic and magnetoelectric properties of polycrystalline Sr doped BiFe_0.8Ti_0.2O₃ ceramics [Bi_1?xSr_x(Fe_0.8Ti_0.2)O₃; x = 0.05, 0.10 and 0.15)] were studied. All the samples were prepared by rapid liquid phase sintering method. Rietveld refinement of X-ray diffraction patterns of all samples confirmed that the samples crystallize in a rhombohedral structure and showed change in Fe–O–Fe bond angle and Fe–O bond length which in turn enhanced magnetization from 0.33 to 0.73 emu/g with the increase in Sr concentration from x = 0.05 to 0.15. The dielectric constant and dielectric loss were observed to increase with the increase in temperature from 30 to 500 °C. An anomalous peak has been observed in dielectric constant versus temperature plot around 300 °C for all the samples, which is close to the magnetic transition temperature of BiFeO₃. The composition-dependent magnetic properties with the expected Fe²⁺/Fe³⁺ ratio fluctuations were correlated by X-ray photoelectron spectroscopy. Magnetic and electric hysteresis loops showed a systematic increase in magnetization and polarization as a result of Sr doping in BiFe_0.8Ti_0.2O₃ ceramics. The value of magnetocapacitance at 10 kHz was observed as 0.95, 1.23 and 1.73 for x = 0.05, 0.10, 0.15 respectively in Bi_1?xSr_xFe_0.80Ti_0.20O₃ ceramics.     

Comparison of Measured Soft X-Ray Yield Versus Pressure for NX1 and NX2 Plasma Focus Devices Against Computed Values Using Lee Model Code

The soft X-ray yield versus pressure curves of NX1 and NX2 plasma focus machines have been measured and published for different pressures and electrode configurations. In this work, the numerical experiments are carried out, using Lee model code. The Lee model code is configured for each of these devices NX1 and NX2 by fitting computed total discharge current waveform against a measured total discharge current waveform. The computed soft X-ray yield versus pressure curves are compared with the laboratory measured soft X-ray yield versus pressure data. The comparison shows agreement between computation and measurement of several important features of the yield versus pressure curves.     

GOX-functionalized nanodiamond films for electrochemical biosensor

The importance of nanodiamond in biological and technological applications has been recognized recently, and applied in drug delivery, biochip, sensors and biosensors. Under this investigation, nanodiamond (ND) and nitrogen doped nanodiamond (NND) were deposited on n-type silicon films, and later functionalized with enzyme Glucose oxidase (GOX). The GOX functionalized doped and undoped ND films were characterized using combination of several techniques; i.e. FTIR spectroscopy, Raman spectroscopy, atomic force microscopy (AFM) and electrochemical techniques. ND/GOX and NND/GOX thin films on n-type silicon have been found to provide sensitive glucose sensor. GOX has been chosen as a model enzyme system to functionalize with ND at molecular level to understand the glucose biosensor.     

Short-period segmented-in-series solid oxide fuel cells on flattened tube supports

Segmented-in-series solid oxide fuel cells (SIS-SOFCs) were prepared on flattened-tube partially stabilized zirconia supports. The distinguishing characteristic of these cells was the short repeat period, 2.4 mm, and small active cell length, 1.3 mm, compared to ≈10 mm in previous SIS-SOFCs. The support tubes, formed by gelcasting, were bisque fired and then screen printing was used to sequentially deposit Ni-YSZ anodes, YSZ electrolytes, and Pt-YSZ composite interconnects. After high-temperature co-firing, LSM–YSZ and LSM cathode layers were screen printed and fired. Each flattened tube side had 12–16 individual cells. For testing, the open tube ends were sealed and humidified hydrogen flowed inside of the tubes; air was flowed over the outside of the tubes. Maximum total power at 800 °C was ≈8 W and maximum power density was ≈0.7 W cm⁻², calculated using cell active area. Good stability was observed during a ≈650 h steady-state test. Excellent stability was also observed over ≈20 redox cycles.     

A distributed laxity-based priority scheduling scheme for time-sensitive traffic in mobile ad hoc networks

Characteristics of Mobile Ad hoc Networks such as shared broadcast channel, bandwidth and battery power limitations, highly dynamic topology, and location dependent errors, make provisioning of quality of service (QoS) in such networks very difficult. The Medium Access Control (MAC) layer plays a very important role as far as QoS is concerned. The MAC layer is responsible for selecting the next packet to be transmitted and the timing of its transmission. We have proposed a new MAC layer protocol that includes a laxity-based priority scheduling scheme and an associated back-off scheme, for supporting time-sensitive traffic. In the proposed scheduling scheme, we select the next packet to be transmitted, based on its priority value which takes into consideration the uniform laxity budget of the packet, the current packet delivery ratio of the flow to which the packet belongs, and the packet delivery ratio desired by the user. The back-off mechanism devised by us grants a node access to the channel, based on the rank of its highest priority packet in comparison to other such packets queued at nodes in the neighborhood of the current node. We have studied the performance of our protocol that combines a packet scheduling scheme and a channel access scheme through simulation experiments, and the simulation results show that our protocol exhibits a significant improvement in packet delivery ratio under bounded end-to-end delay requirements, compared to the existing 802.11 DCF and the Distributed Priority Scheduling scheme proposed recently in [ACM Wireless Networks Journal 8 (5) (2002) 455–466; Proceedings of ACM MOBICOM '01, July 2001, pp. 200–209].     

CO2 laser processing for reducing core loss of cold-rolled grain-oriented silicon steel

Non-contact processing technique involving the use of CW and pulsed CO₂ laser irradiation has been used for reducing the core loss of cold-rolled grain-oriented silicon steel. Laser scribing perpendicular to the rolling direction resulted in a refinement of domain wall spacing which subsequently reduced the loss of silicon steel. It was found that laser irradiation was more effective in a specimen with higher magnetic induction (Hi-B) and the loss was reduced by more than 10% under optimum conditions of the laser irradiation and the scribing speed. Since laser processing is a non-contact technique, it can be easily applied to the production line of the silicon steel.     

Effect of gender and left ventricular dysfunction on the incidence of hypotension induced by dobutamine stress echocardiography

BACKGROUND: Of patients who undergo dobutamine stress echocardiography (DSE), 14% to 38% experience hypotension that sometimes requires termination of the test before an adequate cardiac work-load is reached. The mechanisms of hypotension reportedly are related to peripheral vasodilation, a decrease in cardiac output, and left ventricular (LV) cavity obliteration. DSE is performed increasingly in women and in patients with LV dysfunction. However, the impact of gender and LV dysfunction on DSE-induced hypotension has not been elucidated. METHODS AND RESULTS: Clinical, hemodynamic, and echocardiographic characteristics were studied in 412 patients undergoing DSE, 82 patients with an LV ejection fraction of 40% or less, and 147 women. Hypotension, defined as a decrease in systolic blood pressure of at least 20 mm Hg, occurred in 117 (28%) patients. Hypotension was more common in women than men (36% vs 24%, P = .01). Hypotension was also more common in older adults (P = .004), persons taking diuretics (P = .025) or angiotensin-converting enzyme inhibitors (P = .01), and persons with higher baseline blood pressures (P < .0001). Hypotension was not related to the use of beta blockers, calcium channel blockers, digoxin, nitrates, LV dimensions, or ejection fraction. CONCLUSIONS: The incidence of DSE-induced hypotension is related to gender but not to the level of LV systolic function. It also is associated significantly with higher age, and use of angiotensin-converting enzyme inhibitors or diuretics.     

A realistic defect oriented testability methodology for analog circuits

Owing to the non-binary nature of their operation, analog circuits are influenced by process defects in a different manner compared to digital circuits. This calls for a careful investigation into the occurrence of defects in analog circuits, their modeling related aspects and their detection strategies. In this article, we demonstrate with the help of a real CMOS circuit that simple test stimuli, like DC, transient and AC, can detect most of the modeled process defects. Silicon devices tested with the proposed test methodology demonstrate the effectiveness of the method. Subsequently, the proposed test method is implemented in production test environment along with the conventional test for a comparative study. This test methodology is structured and simpler, therefore results in substantial test cost reduction.