Hepatocyte culture in a radial-flow bioreactor with plasma polypyrrole coated scaffolds

We have designed and evaluated a radial-flow bioreactor for three-dimensional liver carcinoma cell culture on a new porous coated scaffold.We designed a culture chamber where a radial flow of culture medi-um was continuously delivered through it.Once this system was established,flow was simulated using flow dy-namics software based on numeric methods to solve Navier-Stockes flow equations.Perfusion within cell culture scaffolds was simulated using a flow velocity of 7 mL/min and found that cell culture medium was distributed unhindered in the bioreactor chamber.Afterwards,the bioreactor was built according to the simulated design and was tested with liver carcinoma cells(HepG2)cultured over an L-polylactic acid scaffold whose surface was modified with iodine-doped polypyrrole.The bioreactor was tested under non-flow and in radial flow condi-tions.Cell density under radial flow conditions was almost double than that under static conditions and both total protein and albumin output was also increased under radial flow conditions.

Transient Behavior of a System Composed of Conductive Thin Wire Structures Excited by Harmonic and Lightning Type Signals

The transient response of a system of independent electrodes buried in a semi-infinite conducting medium is studied. Using a simple and versatile numerical scheme written by the authors and based on the Electric Field Integral Equation (EFIE), the effect caused by harmonic signals ranging on frequency from Hz to hundred of MHz, and also by lightning type driving signal striking at a remote point far from the conductors, is extensively studied. The value of the scalar potential appearing on the electrodes as a function of the frequency of the applied signal is one of the variables investigated. Other features such as the input impedance at the injection point of the signal and the Ground Potential Rise (GPR) over the electrode system are also discussed.

Corrosion and tribocorrosion behavior of Ti6Al4V/xTiN composites for biomedical applications

The corrosion and tribocorrosion behavior of Ti6Al4V/xTiN(x=0,5,10 and 15,vol.%)composites fabricated by solid-state sintering and their relationship with the microstructure and microhardness were investigated.Simulated body conditions such as a temperature of 37℃ and a simulated body fluid were used.The main results demonstrated a microstructural change caused by theα-Ti stabilization due to solid-solution of nitrogen(N)into the titanium(Ti)lattice,producing a maximum hardening effect up to 109%for the Ti64 matrix by using 15 vol.%TiN.Corrosion potentials of composites changed to more noble values with the TiN particle addition,while corrosion current density of samples increased as an effect of the remaining porosity,decreasing the corrosion resistance of materials.However,changes to a less passive behavior were observed for samples with 15 vol.%TiN.The non-passive behavior of composites resulted in the reduction of the potential drops during rubbing in tribocorrosion tests.Besides,an improvement of up to 88%of the wear rate of composites was seen from the solid-solution hardening.The results allowed to understand the relationship between composition and sintering parameters with the improved tribocorrosion performance of materials.

Detection of DC series arc in more electric aircraft power system based on optical spectrometry

Series arcing faults have been recognised as a hazardous phenomenon in the power system of more electric aircraft(MEA),especially with the increasing voltage level and power supply.Instead of the electrical method,the optical method can be used as an approach to detect arc fault with the advantages of fast response and immunity to electromagnetic interference.It is the basis of optical arc detection to determine the distribution spectrum range of direct current(DC)arc fault.Aiming at series arc optical detection in the MEA DC system,a DC series arc test platform was established to measure the series arc spectrum.The spectrum was disassembled though empirical mode decomposition to extract characteristic wavelengths of arc light and denoised by means of wavelet decomposition and reconstruction(wavelet transformation)to reduce equipment noise.To resolve the baseline drift,the baseline of the arc spectrum measured was calculated and corrected based on Savitzky−Golay.The experimental results indicate that there are several series arc characteristic spectra of the MEA DC system,including 309.3 and 324.5 nm in the ultraviolet range.Moreover,the arc spectrum with different metals,copper and aluminium,were contrasted,indicating the arc spectral behaviour is related to the melting/boiling point and chemical properties of the anode material.The measurement of the series arc spectrum makes it more effective to apply optical detection in the MEA discharging faults diagnosis.

A new technique for separation of partial discharge sources and electromagnetic noise in radiofrequency measurements using energy ratios of different antennas

One of the main tools for monitoring the condition of high voltage equipment is the measurement of partial discharges(PD).The electromagnetic(EM)radiation originated from this degradation phenomenon can be captured by various types of ultra‐high fre-quency(UHF)antennas carefully designed and optimised for specific frequency bands.However,the presence of environmental noise may limit the use of this technique.Different types of monopole antennas normally used in UHF PD measurement have been evaluated in order to validate the performance of a novel separation technique of EM sources.Accordingly,a new separation technique based on the energy ratio of the captured signals was developed,considering noise interferences.The results revealed that the new technique allows an adequate separation,even when three sources act simultaneously.

Robust Disturbance Rejection Based Control with Extended-state Resonant Observer for Sway Reduction in Uncertain Tower-cranes

In this paper, the problem of load transportation and robust mitigation of payload oscillations in uncertain tower-cranes is addressed. This problem is tackled through a control scheme based on the philosophy of active-disturbance-rejection. Here, a general disturbance model built with two dominant components: polynomial and harmonic, is stated. Then, a disturbance observer is formulated through state-vector augmentation of the tower-crane model. Thus, better performance of estimations for system states and disturbances is achieved. The control law is then formulated to actively reject the disturbances but also to accommodate the closed-loop system dynamics even under system uncertainty. The proposed control schema is validated via experimentation using a small-scale tower-crane,and compared with other relevant active disturbance rejection control(ADRC)-based techniques. The experimental results show that the proposed control scheme is robust under parametric uncertainty of the system, and provides improved attenuation of payload oscillations even under system uncertainty.