Effects on two semi-circular wall heaters in a rectangular enclosure containing trapezoidal heated obstacle in presence of MHD

A computational study has been done to illustrate the effects on two semi-circular wall heaters placed in a mixed convection rectangular enclosure containing trapezoidal heated obstacle in presence of magnetic field. The upper wall moves with a velocity in the positive x-direction. Trapezoidal obstacle is located in the middle of the cavity and two semi-circular wall heaters are placed at the bottom wall with fixed distance between them. These two horizontal walls are kept adiabatic except two semi-circular wall heaters. Two vertical walls are kept at low temperature and concentration and the trapezoidal obstacle and two semi-circular walls are kept at high temperature and concentration. Finite element method is used to solve governing equations. The present analysis is performed for parameters such as Hartmann number, Buoyancy ratio and Richardson number. The effects of aforesaid parameters are explored on the fluid flow and temperature at two semi-circular wall heaters. The results show that heat transfer rate along right semi-circular wall heater dominates the left semi-circular wall heater with the increase of both the parameters Hartmann number and Buoyancy ratio

The quest for better outcomes: a randomized controlled trial comparing letrozole versus clomiphene citrate in polycystic ovarian syndrome related infertility

Background: Infertility is a widespread concern, particularly among individuals with polycystic ovarian syndrome (PCOS). Clomiphene citrate (CC) has been a primary treatment for PCOS-related infertility, despite suboptimal pregnancy rates. Letrozole, an aromatase inhibitor, presents an alternative with potential advantages for improving pregnancy outcomes. This study aimed to rigorously compare letrozole and CC in the context of PCOS-related infertility, focusing on Bangladeshi women, adopting incremental dosing protocols, and examining endpoints to contribute valuable insights. Methods: A randomized controlled trial was conducted at a tertiary care center in Bangladesh from July 2021 to June 2023. Participants included women aged 18-35 with anovulatory infertility due to PCOS. They were randomized into two groups: letrozole and CC. Treatments were administered following incremental dosing protocols, and outcomes included endometrial thickness, ovulation rate, mono-follicular development, pregnancy rate, and time to pregnancy. Results: Out of 187 patients assessed for eligibility, 102 were enrolled, with 51 in each group. Demographics were comparable between groups. While endometrial thickness did not significantly differ between the groups, letrozole demonstrated a higher rate of mono-follicular development (72.55% versus 50.98%), a significantly higher pregnancy rate (47.06% versus 23.53%), and a shorter time to pregnancy (9.23 weeks versus 11.7 weeks) compared to CC. Conclusions: This study suggests that letrozole may be a preferred option for ovulation induction in PCOS patients due to its superior pregnancy rates and shorter time to pregnancy compared to CC. However, limitations such as a relatively small sample size and variations in dosages should be considered. Further research is needed to validate these findings and address the evolving needs of patients with PCOS-related infertility

Effects of alternating current voltage amplitude and oxide capacitance on mid-gap interface state defect density extractions in In0.53Ga 0.47As capacitors

This work looks at the effect on mid-gap interface state defect density estimates for In0.53Ga0.47As semiconductor capacitors when different AC voltage amplitudes are selected for a fixed voltage bias step size (100 mV) during room temperature only electrical characterization. Results are presented for Au/Ni/Al2O3/In0.53Ga0.47As/InP metal–oxide–semiconductor capacitors with (1) n-type and p-type semiconductors, (2) different Al2O3 thicknesses, (3) different In0.53Ga0.47As surface passivation concentrations of ammonium sulphide, and (4) different transfer times to the atomic layer deposition chamber after passivation treatment on the semiconductor surface—thereby demonstrating a cross-section of device characteristics. The authors set out to determine the importance of the AC voltage amplitude selection on the interface state defect density extractions and whether this selection has a combined effect with the oxide capacitance. These capacitors are prototypical of the type of gate oxide material stacks that could form equivalent metal–oxide–semiconductor field-effect transistors beyond the 32 nm technology node. The authors do not attempt to achieve the best scaled equivalent oxide thickness in this work, as our focus is on accurately extracting device properties that will allow the investigation and reduction of interface state defect densities at the high-k/III–V semiconductor interface. The operating voltage for future devices will be reduced, potentially leading to an associated reduction in the AC voltage amplitude, which will force a decrease in the signal-to-noise ratio of electrical responses and could therefore result in less accurate impedance measurements. A concern thus arises regarding the accuracy of the electrical property extractions using such impedance measurements for future devices, particularly in relation to the mid-gap interface state defect density estimated from the conductance method and from the combined high–low frequency capacitance–voltage method. The authors apply a fixed voltage step of 100 mV for all voltage sweep measurements at each AC frequency. Each of these measurements is repeated 15 times for the equidistant AC voltage amplitudes between 10 mV and 150 mV. This provides the desired AC voltage amplitude to step size ratios from 1:10 to 3:2. Our results indicate that, although the selection of the oxide capacitance is important both to the success and accuracy of the extraction method, the mid-gap interface state defect density extractions are not overly sensitive to the AC voltage amplitude employed regardless of what oxide capacitance is used in the extractions, particularly in the range from 50% below the voltage sweep step size to 50% above it. Therefore, the use of larger AC voltage amplitudes in this range to achieve a better signal-to-noise ratio during impedance measurements for future low operating voltage devices will not distort the extracted interface state defect density

Device design and process integration of high density nonvolatile memory devices

textThis research focuses on device design and process integration of high density nonvolatile memory devices. Research was carried out to improve scaling of floating gate memories by increasing charge density as well as spin-based memories by reducing critical switching current. This work demonstrates fabrication of CMOS-compatible nonvolatile hybrid memory device using fullerene molecules as a floating gate. Molecules have dimensions of several Angstroms resulting in an electron density of ~10¹³ cm⁻² or higher. In hybrid MOSCAPs, fullerenes were encapsulated between inorganic oxides, i.e. SiO₂ as a tunnel oxide and HfO₂ as a control oxide. Introduction of a high-k material as a control oxide improves capacitive coupling between control gate and floating gate as well as the program/erase efficiency. The MOS capacitors demonstrate nonvolatile memory operation at room temperature. The device data infers that program/erase mechanism in fullerene devices is Fowler-Nordheim tunneling; however, retention is determined by trap-assisted tunneling. The next part of the work focused on spin-transfer-torque (STT) based magnetic memory. Spin-based memory has the unique potential to be the universal memory because of its high density, fast switching, and nonvolatility. This work presents STT switching of perpendicular magnetic anisotropy (PMA) spin-valves with tilted magnetization using point contact measurement. The PMA materials have high coercivity resulting in good retention and tilted magnetization induces precessional switching resulting in a lower switching current density. First, micromagnetic simulations were performed for spin-valves with tilted magnetization and precessional switching was observed to reduce the switching current. Then, spin-valve structures were fabricated by e-beam evaporation. The structure consisted of Co/Pt and Co/Ni layers, where the thickness of the layers was optimized to obtain different amount of tilt in magnetization. Point contact measurements of tilted spin-valves show STT switching, where the switching field of the free layer varies with the magnitude and sign of the applied current. The observed STT effect is stronger in a 45° tilted spin-valve compared to a 12° tilted device presumably due to the tilted spin polarization. However, tilting introduces nonuniform effective field and canting of the domains which affect the STT.Electrical and Computer Engineerin

Capacitance and conductance for an MOS system in inversion, with oxide capacitance and minority carrier lifetime extractions

Experimental observations for the In 0.53 Ga 0.47 As metal-oxide-semiconductor (MOS) system in inversion indicate that the measured capacitance (C) and conductance (G or G m ), are uniquely related through two functions of the alternating current angular frequency (ω). The peak value of the first function (G/ω) is equal to the peak value of the second function (-dC/dlog e (ω) ≡ -ωdC/dω). Moreover, these peak values occur at the same angular frequency (ω m ), that is, the transition frequency. The experimental observations are confirmed by physics-based simulations, and applying the equivalent circuit model for the MOS system in inversion, the functional relationship is also demonstrated mathematically and shown to be generally true for any MOS system in inversion. The functional relationship permits the discrimination between high interface state densities and genuine surface inversion. The two function peak values are found to be equal to C ox 2 /(2(C ox + C D )) where C ox is the oxide capacitance per unit area and C D is the semiconductor depletion capacitance in inversion. The equal peak values of the functions, and their observed symmetry relation about ω m on a logarithmic ω plot, opens a new route to experimentally determining C ox . Finally, knowing ω m permits the extraction of the minority carrier generation lifetime in the bulk of the In 0.53 Ga 0.47 As layer