Modeling of a Cantilever-Based Near-Field Scanning Microwave Microscope

We present a detailed modeling and characterization of our scalable microwave nanoprobe, which is a micro-fabricated cantilever-based scanning microwave probe with separated excitation and sensing electrodes. Using finite-element analysis, the tip-sample interaction is modeled as small impedance changes between the tip electrode and the ground at our working frequencies near 1GHz. The equivalent lumped elements of the cantilever can be determined by transmission line simulation of the matching network, which routes the cantilever signals to 50 Ohm feed lines. In the microwave electronics, the background common-mode signal is cancelled before the amplifier stage so that high sensitivity (below 1 atto-Farad capacitance changes) is obtained. Experimental characterization of the microwave probes was performed on ion-implanted Si wafers and patterned semiconductor samples. Pure electrical or topographical signals can be realized using different reflection modes of the probe.Comment: 7 figure

On-line load balancing

AbstractThe setup for our problem consists of n servers that must complete a set of tasks. Each task can be handled only by a subset of the servers, requires a different level of service, and once assigned cannot be reassigned. We make the natural assumption that the level of service is known at arrival time, but that the duration of service is not. The on-line load balancing problem is to assign each task to an appropriate server in such a way that the maximum load on the servers is minimized. In this paper we derive matching upper and lower bounds for the competitive ratio of the on-line greedy algorithm for this problem, namely, [(3n)23/2](1+o(1)), and derive a lower bound, Ω(n12), for any other deterministic or randomized on-line algorithm

Global Ultrasound Elastography Using Convolutional Neural Network

Displacement estimation is very important in ultrasound elastography and failing to estimate displacement correctly results in failure in generating strain images. As conventional ultrasound elastography techniques suffer from decorrelation noise, they are prone to fail in estimating displacement between echo signals obtained during tissue distortions. This study proposes a novel elastography technique which addresses the decorrelation in estimating displacement field. We call our method GLUENet (GLobal Ultrasound Elastography Network) which uses deep Convolutional Neural Network (CNN) to get a coarse time-delay estimation between two ultrasound images. This displacement is later used for formulating a nonlinear cost function which incorporates similarity of RF data intensity and prior information of estimated displacement. By optimizing this cost function, we calculate the finer displacement by exploiting all the information of all the samples of RF data simultaneously. The Contrast to Noise Ratio (CNR) and Signal to Noise Ratio (SNR) of the strain images from our technique is very much close to that of strain images from GLUE. While most elastography algorithms are sensitive to parameter tuning, our robust algorithm is substantially less sensitive to parameter tuning.Comment: 4 pages, 4 figures; added acknowledgment section, submission type late

Expression and response surface optimization of the recovery and purification of recombinant D-galactose dehydrogenase from Pseudomonas fluorescens

The enzyme D-galactose dehydrogenase (GalDH) has been used in diagnostic kits to screen blood serum of neonates for galactosemia. It is also a significant tool for the measurement of β-D-galactose, α-D-galactose and lactose as well. In this study, response surface methodology (RSM) was used to identify the suitable conditions for recovery of recombinant GalDH from Pseudomonas fluorescens in aqueous two-phase systems (ATPS). The identified GalDH gene was amplified by PCR and confirmed by further cloning and sequencing. E. coli BL-21 (DE3) containing the GalDH gene on a plasmid (pET28aGDH) was used to express and purify the recombinant enzyme. The polyethylene glycol (PEG) and ammonium sulfate concentrations and pH value were selected as variables to analyze purification of GalDH. To build mathematical models, RSM with a central composite design was applied based on the conditions for the highest separation. The recombinant GalDH enzyme was expressed after induction with IPTG. It showed NAD+-dependent dehydrogenase activity towards D-Galactose. According to the RSM modeling, an optimal ATPS was composed of PEG-2000 14.0 (w/w) and ammonium sulfate 12.0 (w/w) at pH 7.5. Under these conditions, GalDH preferentially concentrated in the top PEG-rich phase. The enzyme activity, purification factor (PF) and recovery (R) were 1400 U/ml, 60.0 and 270.0, respectively. The PEG and salt concentrations were found to have significant effect on the recovery of enzyme. Briefly, our data showed that RSM could be an appropriate tool to define the best ATPS for recombinant P. fluorescens GalDH recovery. © 2015 National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved

System-level investigation of multi-MW direct-drive wind power PM vernier generators

Surface mounted permanent magnet Vernier (SPM-V) machines are known for their high torque density but relatively poor power factor compared to conventional SPM machines. The high torque density feature of the SPM-V machines is desirable for direct-drive offshore wind power applications as it leads to reduced generator size, mass and cost. However, their poor power factor can negatively affect the converter cost and efficiency. This paper compares the system-level performance, including generator active and structural components and converter, between the SPM-V and the conventional SPM generator systems. Four different power ratings, i.e. 0.5MW, 3MW, 5MW and 10MW, have been considered to study the trend of system-level performance with increasing power rating. The study shows that the SPM-V generators can be lighter and cheaper than their conventional SPM counterparts. However, after the consideration of converter cost and efficiency, the conventional SPM generator exhibited slightly better overall performance. Nonetheless, with the development of novel Vernier topologies and reduction in converter costs in the future due to emerging technologies, the Vernier generators can still be competitive for direct-drive offshore wind power applications

Understanding Hydrogen Adsorption in MIL-47-M (M = V and Fe) through Density Functional Theory

The present paper aims to investigate the role of open metal site metal-organic frameworks (MOFs) on hydrogen adsorptivity using periodic boundary condition (PBC) density functional theory (DFT). Hence, MIL-47-M (M = V and Fe) were selected and one hydrogen molecule adsorptivity was calculated in different orientations on them. Four different chemical sites were identified in every cluster section of these MOFs, and molecular hydrogen adsorption was studied in these sites. In these MOFs, V has fewer electrons than Fe in its valence layer. Results demonstrated that when dihedral angle of M-O-H-H is 0, the binding energy of hydrogen adsorption is higher than that in other orientations in both MILs (-26.16 and -19

Proposal for a modernized iranian notifiable infectious diseases surveillance system: Comparison with usa and Australia Proposition en vue de la modernisation du système iranien de surveillance des maladies infectieuses à déclaration obligatoire: Comparaison avec les �tats-Unis et l'Australie

This article reports on a comparative study of the national notifiable infectious diseases surveillance systems currently employed in the United States of America, Australia and the Islamic Republic of Iran, with the aim of developing a modified system specific to the needs of the Iranian health system. Features of the surveillance systems examined in each country included: official data gathering structures; types of data collected; case definition and classification criteria; data collection processes; data analysis methods; disease classification systems; data dissemination and distribution methods; data quality control; and confidentiality procedures and guidelines. After consolidating the data, a model for an Iranian notifiable infectious diseases surveillance system was developed and was tested by the Delphi method in 3 stages

In-depth investigation of inter-turn short-circuit faults of surface-mounted permanent magnet machines with series-parallel coil connections

A general analytical model is developed in a concise block matrix form for surface-mounted permanent magnet (SPM) machines with series-parallel coil connections under inter-turn short circuit (ITSC) fault. In the model, branch currents are used as state variables and inductances of different series-parallel coil connections are calculated using an analytical method, namely winding function approach (WFA) together with slot permeance method. Based on the characteristics of the calculated inductances and the developed fault model, the multiphase Clarke transformation has been proposed to simplify the fault model. In the process of model simplification, the healthy machine model using branch currents as state variables have been proven to be equivalent to that using 3-phase currents as state variables. The proposed fault models of a 3kW 96-slot 32-pole SPM machine with different series-parallel coil connections have been built in Matlab/Simulink and validated by time-stepping 2D FE simulations. Simulation results show that different series-parallel coil connections have little influence on the amplitude of the ITSC current. Finally, a small scale 24-slot 8-pole SPM machine prototype has been built to further validate the accuracy of the proposed fault model

Modelling and analysis of inter-turn short-circuit faults for large-power SPM wind generators

This paper proposes a general analytical model for large-power surface-mounted permanent magnet (SPM) wind generators under inter-turn short-circuit (ITSC) faults. In the model, branch currents rather than phase currents are used as state variables to describe the electromagnetic behavior of the faulty machine. In addition, it is found that the multiphase Clarke transformation can be used to simplify the proposed fault model with the inductances calculated analytically or numerically using finite element analysis. With the latter, both linear and nonlinear inductances can be obtained, and the non-linear inductances are used for the fault modelling of large power rating machines due to larger electrical loading and heavier magnetic saturation. With the developed fault model, studies of scaling effects (different power ratings such as 3 kW, 500 kW and 3 MW) and the influence of fault location on the electromagnetic performance of SPM generators with series-parallel coil connections have been carried out. The simulation results show that large-power SPM wind generators are vulnerable to ITSC faults when a relatively small number of turns are short-circuited and a single-turn short-circuit fault at the top of the slot is found to be the worst case