A New Method Modifying Single Miller Feedforward Frequency Compensation to Drive Large Capacitive Loads: Putting an Attenuator in the Path

A new method to compensate three-stage amplifier to drive large capacitive loads is proposed in this paper. Gain Bandwidth Product is increased due to use an attenuator in the path of miller compensation capacitor. Analysis demonstrates that the gain bandwidth product will be improved significantly without using large compensation capacitor. Using a feedforward path is deployed to control a left half plane zero which is able to cancel out first non-dominant pole. A three stage amplifier is simulated in a 0.18 μm CMOS technology. The purpose of the design is to compensate three-stage amplifier loading 1000 pF capacitive load. The simulated amplifier with a 1000 pF capacitive load is performed in 3.3 MHz gain bandwidth product, and phase margin of 50. The compensation capacitor is reduced extremely compared to conventional nested miller compensation methods. Since transconductance of each stage is not distinct, and it is close to one another; as a result, this method is suitable low power design methodology.     

Special all-round fillet weld for anchor rods of base-plate T-stub connections

The eccentricity between connected steel parts and the anchor rods in base-plate T-stub connections makes base plates the weaker components in tension and compression. Additionally, the oversized holes in base plates lead to irregular placement of anchor rods, resulting in an unsymmetrical shear behavior. Thus, this paper aims to develop a special all-round fillet weld to connect the anchor rods beneath the base plate concentrically to the steel part, removing the base plate from the load-transferring chain. Accordingly, design criteria were first developed based on Eurocode's directional method considering all the potential failure modes. Next, results were validated by conducting experimental work. The digital image correlation technique (DIC) was also used to capture the strain distribution developed over the tested specimen till failure. Consequently, numerical analysis was carried out to investigate the fracture strength and the fracture angle and compare the special fillet weld with its equivalent standard one, which has the same weld volume. The results indicated that the proposed design criteria produced safe strength prediction for the developed special all-round fillet weld. Furthermore, the results revealed that using a special all-round fillet weld instead of the equivalent standard one can increase the strength by about 8% and improve the ductility of the weld. However, it decreases the stiffness of the weld by about 21%. The fracture surface occurred at $15°$ from the face of the anchor rod, which produced a higher strength than the predicted tensile strength calculated according to the theoretical throat plane.     

Efficient repairing effect of PEG based tri-block copolymer on mechanically damaged PC12 cells and isolated spinal cord

Membrane sealing effects of polymersomes made of tri-block copolymer, PEG-co-FA/SC-co-PEG, (PFSP) were studied on isolated spinal cord strips, PC12 cell lines and artificial bilayer following mechanical impact implemented by aneurism clip, sonication and electric shock, respectively. The homogeneity and size of PFSP, membrane permeability and cell viability were assessed by dynamic light scattering, LDH release and MTT assays. According to the results, the biocompatible, physico-chemical, size, surface charge and amphipathic nature of PFSP polymersome makes it an ideal macromolecule to rapidly reseal damaged membranes of cells in injured spinal cord as well as in culture medium. Compound action potentials recorded from intentionally damaged spinal cord strips incubated with PFSP showed restoration of neural excitability by 82.24 % and conduction velocity by 96.72 % after 5 min that monitored in real time. Thus, they triggered efficient instant and sustained sealing of membrane and reactivation of temporarily inactivated axons. Treatment of ultrasonically damaged PC12 cells by PFSP caused efficient cell membrane repair and led to their increased viability. The optimum effects of PFSP on stabilization and impermeabilizing of the lipid bilayer occurred at the same concentrations applied to the damaged cells and spinal cord fibers and was approved by restoration of membrane conductance and calcein release manifested by NanoDrop technique. The unique physico-chemical characteristics of novel polymersomes introduced here, make them capable to reorganize membrane lipid molecules, reseal the breaches and restore the hydrophobic insulation in spinal cord damaged cells. Thus, they might be considered in the clinical treatment of SCI at early stages.     

Particle Detachment from Rough Surfaces in Turbulent Flows: An Analytical Expression for Resuspension Fraction

The critical shear velocity for resuspension of micrometer size particles from rough surfaces was studied. The random variation of surface roughness was accounted for. The recently developed Monte Carlo simulations accounted for the statistical variations of physical parameters that control the particle resuspension process. A sensitivity analysis showed that the surface roughness and its random variation was the key factor affecting the particle resuspension from rough surfaces. The theory of probabilistic transformation was used and an analytical expression for evaluating the resuspension fraction of particles of different sizes from rough surfaces versus the shear velocity was developed. The resuspension fractions as predicted by the analytical model were evaluated for several particles sizes for a range of turbulent flow shear velocities. The resulting resuspension fractions were compared with those obtained from the Monte Carlo simulations as well as the available experimental data. It was found that the predictions of the new analytical equation were in good agreement with the Monte Carlo simulation results and the experimental data, especially for smaller size particles. This new analytical expression could be used as a simple empirical equation for estimating flow-induced resuspension of particles from rough surfaces.     

Short‐Time Linear Quadratic Form Technique for Estimating Fast‐Varying Parameters in Feedback Loops

The precision of a closed‐loop controller system designed for an uncertain plant depends strongly upon the maximum extent to which it is possible to track the trend of time‐varying parameters of the plant. The aim of this study is to describe a new parameter estimation algorithm that is able to follow fast‐varying parameters in closed‐loop systems. The short‐time linear quadratic form (STLQF) estimation algorithm introduced in this paper is a technique for tracking time‐varying parameters based on short‐time analysis of the regressing variables in order to minimize locally a linear quadratic form cost function. The established cost function produces a linear combination of errors with several delays. To meet this objective, mathematical development of the STLQF estimation algorithm is described. To implement the STLQF algorithm, the algorithm is applied to a planar mobile robot with fast‐varying parameters of inertia and viscous and coulomb frictions. Next, performance of the proposed algorithm is assessed against noise effects and variation in the type of parameters.     

Electromagnetic MEMS microspeaker for portable electronic devices

This work presents the conception, the microfabrication, and the electroacoustic characterization of a new electromagnetic microspeaker based on silicon. The objectives are to get improved sound quality compared to that of conventional microspeakers, while keeping the electroacoustic efficiency as high as possible. An optimized stiffening silicon microstructure let the sound radiator be extremely light and rigid. The mobile part is suspended to the fixed part by silicon suspension springs, which enable large out-of-plane displacement. The acoustic radiator is actuated by an electromagnetic motor, composed of a fixed permanent magnet and a planar coil located on top of the silicon radiator. The piston-like motion of the radiator favored by this structure is very beneficial for the sound quality. Electro–mechano–acoustic characterization of the microfabricated microspeaker showed that the radiator surface could run out-of-plane with displacements higher than ±400 μm, with no mechanical and electrical failure. For an electrical power of 0.5 W, the microspeaker was capable to generate a sound pressure level of 80 dB at 10 cm, from 330 Hz up to 20 kHz frequency. The efficiency reaches 3 × 10^?5, that is to say three times more than typical efficiency of conventional microspeakers. Moreover, as characterization results showed, the existence of very few structural modes and the low electroacoustic distortions evidence the high sound quality of the microspeaker.     

Investigating shrinkage and moisture diffusivity of melon seed in a microwave assisted thin layer fluidized bed dryer

This work aimed to investigate the drying behavior of melon seed during combined fluidized bed-microwave drying system. Three drying air temperatures (40, 55 and 70 °C), three microwave powers (270, 450 and 630 W) and three air velocities (0.8, 1.5 and 2.3 m/s) were tested. Five mathematical models were selected to fit the experimental data for drying kinetics, and the results revealed that the Aghbashloo et al. model exhibited, in all cases, the best performance in fitting the experimental data (R² varying from 0.99088 to 0.99998; χ² from 0.00000 to 0.00185 and RMSE from 0.02289 to 0.82316). Calculated values of moisture diffusivity for dried melon seed varied from a minimum of 6.51 × 10?10 to a maximum of 6.59 × 10?9 m²/s under the tested drying conditions. Moisture diffusivity values increased as air temperature and microwave power was increased. Shrinkage values were calculated and found to vary in the range from 46.99 to 15.09 %.     

Integrated all-optical infrared switchable plasmonic quantum cascade laser

We report a type of infrared switchable plasmonic quantum cascade laser, in which far field light in the midwave infrared (MWIR, 6.1 μm) is modulated by a near field interaction of light in the telecommunications wavelength (1.55 μm). To achieve this all-optical switch, we used cross-polarized bowtie antennas and a centrally located germanium nanoslab. The bowtie antenna squeezes the short wavelength light into the gap region, where the germanium is placed. The perturbation of refractive index of the germanium due to the free carrier absorption produced by short wavelength light changes the optical response of the antenna and the entire laser intensity at 6.1 μm significantly. This device shows a viable method to modulate the far field of a laser through a near field interaction.