Investigations on the properties of composite coatings electro co-deposited on AZ80 Mg alloy using triangular waveform pulse current

In this research, boron carbide (B4C) and titanium carbide (TiC) nanoparticles were deposited along with Nickel on AZ80 magnesium alloy substrates. Triangular waveform pulse current was used for depositing the coatings on the substrate. The objective of this research is to investigate the microstructural evolution of the coatings in response to the current density, duty cycle and the concentration of reinforcements in the bath. The influence of process parameters were also assessed in terms of the microhardness and specific wear rate. To enhance the surface properties of AZ80 magnesium alloy, a three component layer was successfully applied via electro co-deposition technique for the first time. The magnesium alloy substrates were cleaned and pretreated as per ASTM B480−88. The pretreated samples were coated at three levels of current density viz. 1.5 A/dm2, 2 A/dm2 and 2.5 A/dm2, and the duty cycle was varied between 30%, 40% and 50%. The concentrations of reinforcements in the bath were kept at 0 g/L, 0.5 g/L and 1 g/L. The samples were coated according to Taguchi L9 orthogonal array with two replications. The microstructural studies conducted using scanning electron microscope (SEM) revealed the defects, grain refinement and homogeneous distribution of reinforcements in the Ni matrix. The deposition and orientation of reinforcements in preferred planes were investigated with XRD. Vickers microhardness tests conducted as per ASTM E384-17 revealed that the sample coated with 2.5 A/dm2current density, 30 % duty cycle, 1 g/L B4C and 0.5 g/L TiC produced the coatings with the highest hardness of 412.56 Hv. The results of the pin on disc wear tests conducted according to ASTM G99 were in agreement with the hardness results and the corresponding microstructure. The sample with the maximum microhardness exhibited the minimum specific wear rate of 2.1 E-08 mm3/Nm. The ability of triangular pulse current waveform to deposit hybrid composite coatings on AZ80 magnesium alloy and enhance its surface properties has been confirmed by the results of this research.

Personalized physiologic flow waveforms improve wave reflection estimates compared to triangular flow waveforms in adults

Central aortic pressure waveforms contain valuable prognostic information in addition to central systolic pressure. Using pressure-flow relations, wave separation analysis can be used to decompose aortic pressure waveforms into forward- (Pf) and backward-travelling (Pb) components. Reflection magnitude, the ratio of pressure amplitudes (RM=Pb/Pf), is a predictor of heart failure and all-cause mortality. Aortic flow can be measured via Doppler echocardiography or estimated using a triangular flow waveform; however, the latter may underestimate the flow waveform convexity and overestimate Pb and RM. We sought to determine the accuracy of a personalized synthetic physiologic flow waveform, compared to triangular and measured flow waveforms, for estimating wave reflection indices in 49 healthy young (27±6 yrs) and 29 older adults (66±6 yrs; 20 healthy, 9 CKD). Aortic pressure and measured flow waveforms were acquired via radial tonometry and echocardiography, respectively. Triangular and physiologic flow waveforms were constructed from aortic pressure waveforms. Compared to the measured flow waveform, the triangular waveform underestimated Pf in older, but not young, adults and overestimated Pb and RM in both groups. The physiologic waveform was equivalent to measured flow in deriving all wave reflection indices and yielded smaller mean absolute biases than the triangular waveform in all instances (p<0.05). Lastly, central pulse pressure was associated with triangular, but not physiologic, mean biases for Pb and RM independent of age or central arterial stiffness (p<0.05). These findings support the use of personalized physiologic flow waveforms as a more robust alternative to triangular flow waveforms when true flow cannot be measured.

A Photonic-Assisted Generation of Triangular Waveform With Frequency Octupling

A new photonic approach for generating a triangular waveform with octupled-frequency is presented. The core principle is the frequency outupling technique based on two cascaded dual-parallel Mach-Zehnder modulators (DP-MZMs). A dual-electrode MZM (De-MZM) and a single mode fiber (SMF) are subsequently applied to manipulate the signal spectrum to satisfy the characteristics of that of a triangular waveform. By applying a 2-GHz radio frequency (RF) signal, a full-duty-cycle triangular waveform with repetition rate of 16-GHz is obtained. The high frequency multiplying factor shows great potential in generating a cost-effective waveform. Additionally, the phase imbalance of hybrid coupler and bias drift of MZM have been considered in our simulation, which further verify the feasibility and stability of our proposal.

A novel multilevel inverter with reduced switch count

<p><span>This paper presents a multilevel inverter with reduced number of switches to produce a five level output. PWM technique (pulse width modulation) has been used to trigger the MLI switches. It gives reduced harmonic. This proposed topology is connected with R-load and RL-load. Four signals are generated for switching on the multilevel inverter (MLI) switches by comparing four level triangular waveform with sine wave. In this proposed topology two switches are reduced from the conventional Cascaded five level inverter. The simulation analysis has been done by MATLAB/SIMULINK.</span></p>