Pulse Phase Difference Research Articles

Study of the High-Efficiency Ejecting-Explosion EDM of SiCp/Al Composite.

SiCp/Al composites have excellent physical properties and are widely used in aerospace and other fields. Because of their poor machinability, they are often machined by non-traditional machining methods such as electrical discharge machining (EDM). In the process of EDM, due to the "shielding" effect of the reinforced particles of SiC, the local ejection force is low during the processing process, and it is difficult to throw the reinforced particles smoothly, which ultimately leads to a low material removal rate and poor surface quality. In this paper, a high-low-voltage composite ejecting-explosion EDM power supply is developed to explore the explosive effect of reinforced particles in the ejecting-explosion EDM process and the unique process law of the explosion process. The experiment platform uses self-developed CNC machining machine tools based on an ejecting-explosive EDM power supply, and the influence of a detonation-increasing wave on the processing of SiCp/Al composites with different volume fractions was studied by changing four factors: the open-circuit voltage difference, pulse current difference, pulse phase difference, and pulse width difference of the back wave behind the step front. The material removal rate and surface roughness were measured. The research results showed that the material removal rate could be increased to 164.63%, and the material surface roughness could be increased to 30.03% by adjusting the high and low pulse current difference from 1 A to 8 A. When the voltage difference between high and low wave (HLW) pulses increases from 40 V to 120 V, the material removal rate can be increased to 150.39%, and the material surface roughness can be increased to 20.49%. The material removal rate increases with the increase in pulse phase difference and open-circuit voltage difference. With the increase in peak current difference and pulse width difference, the material removal rate becomes faster at first and then slower. The surface roughness of materials increases with the growth of open-circuit voltage difference, peak current difference, pulse width difference, and pulse phase difference.

Mixing performance enhancement and parametric investigation of swirl-inlets split-and-recombine micromixer with pulsatile flow

The current study develops a pulsatile flow micromixing model, and investigates the performance of swirl-inlets split-and-recombine micromixer. A three-dimensional transient flow numerical model solving Navier-Stokes and diffusion equation is prepared to model the species mixing in a microchannel. The effect of pulsatile flow parameters, i.e., Strouhal number, amplitude ratio, and phase difference, on mixing performance is investigated along with the nature and extent of performance enhancement. A significant improvement in the mixing index is observed with the application of pulsatile flow. The pulse phase difference was found to be the more effective parameter to enhance the mixing index compared to Strouhal number and amplitude ratios investigated in the present study.

Effects of pulse phase difference on metal transfer process and weld formation in the integrated circular triple-electrode GMAW

The pulse synergic control on three arcs in the integrated circular triple-electrode GMAW was proposed to reduce arc interference. The research focused on the effects of pulse phase difference on metal transfer process and weld formation. In the aspect of metal transfer mode, it was found that one droplet per pulse accounted for a higher proportion at pulse phase difference of 120°, followed by pulse phase difference of 180°. However, complete one droplet per pulse hardly occurred at pulse phase difference of 0°, and short-circuiting transfer and one droplet multiple pulses became main transfer mode. In the aspect of weld formation, there were no distinct differences among weld widths and weld reinforcements under three pulse phase differences of 0°, 120°, and 180°. Nevertheless, the weld depths under three pulse phase differences successively varied from minimum to maximum. Moreover, the special cross-section appearance of “twin peaks” was formed at pulse phase difference of 120°. There were two main reasons for this phenomenon, i.e., arc force and droplet impact.

Azimuth and Elevation Estimation With Rotating Long-Baseline Interferometers

The performance of most multi-channel 2-D direction-of-arrival (DOA) estimation array systems are very sensitive to various model imperfections, while static single-channel interferometers can only realize 1-D direction estimation, and they have to trade off between the DOA estimation precision and the non-ambiguity scope. This paper establishes a system framework for 2-D DOA estimation with a phase-only rotating long-baseline interferometer (RLBI), whose baseline is much longer than the signal wavelength. The RLBI collects interleaved pulse phase-difference measurements of multiple emitters when it is rotating with a uniform angular speed, and the measurements are then exploited to estimate the number and 2-D directions of these emitters. Deep insights are given into the DOA estimation properties of the RLBI system, and the spatial sparsity of the emitters is exploited to propose a source number and 2-D DOA estimation method, named Direction estimation via Spectral orthogonal Matching Pursuit and DeSoMP for short. DeSoMP is implemented based on a spectral data vector obtained via particular transformations from the original phase measurements and do not need to de-interleave the phase measurements of different emitters beforehand. The feasibility of the established RLBI system framework and the performance of the proposed method are demonstrated with simulations.

Noninvasive technique for the diagnosis of patent ductus arteriosus in premature infants by analyzing pulse wave phases on photoplethysmography signals measured in the right hand and the left foot.

ObjectiveTo evaluate the impact of patent ductus arteriosus (PDA) on the pulse phase difference (PPD) between the left foot (postductal region) and the right hand (preductal region).Materials and MethodsPPD was determined from arterial photoplethysmography signals (pulse waves) measured by infrared sensors routinely used for pulse oximetry in 56 premature infants less than 32 weeks gestation. Only infants with significant PDA (sPDA) diagnosed by echocardiography were treated with ibuprofen (for 3 days). Patients were classified according to whether or not they responded (Success/Failure) to this treatment. The Control group was composed of infants in whom ductus had already closed spontaneously at the time of the first echocardiography. The 3 groups were compared in terms of PPD at the beginning (T1) and at the end (T2) of the study. For patients in the Failure (n = 17) and Success groups (n = 18), T1 corresponded to the first day of treatment and T2 to the day after completion of the course of ibuprofen. In the Control group (n = 21), T1 corresponded to 1 to 3 days of life (DOL), and T2 to 4–6 DOL.ResultsCompared to the Control group, PPD was higher in the Failure (at T1 and T2) and Success (at T1) groups characterized by sPDA. After ibuprofen therapy, PPD in the Success group decreased to about the level observed in the Control group. The area under the ROC curve of PPD for the diagnosis of sPDA was 0.98 (95% CI 0.96–1); for an optimal cut-off of PPD ≥1.65 deg/cm, the sensitivity was 94.2% and the specificity was 98.3%.ConclusionIn this study, PPD was correlated with ductus arteriosus status evaluated by echocardiography, indicating involvement of the ductal shunt in the mechanism of redistribution in systemic vascular territories. PPD can be considered for the diagnosis of hemodynamically significant PDA.

An all-digital PLL for frequency multiplication by 4 to 1022 with seven-cycle lock time

An all-digital phase-locked loop (PLL) circuit in which resolution in the phase detector and digitally controlled oscillator (DCO) exactly matches the gate-delay time is presented. The pulse delay circuit is connected in a ring shape with 32 inverters (2/sup 5/ inverters). With the inverter gate-delay time as the time base, the pulse phase difference is detected simultaneously with the generation of the output clock. In this system, the phase detector and oscillator share a single ring-delay-line (RDL). This means the resolution is the same at all times, making a high-speed response possible. In a prototype integrated circuit (IC) using 0.65-/spl mu/m CMOS, the generation of a frequency multiplication clock was achieved with four reference clocks, and that of a phase-locked clock with seven reference clocks, for a high-speed response. The cell size was 1.08 /spl times/ 1.08 mm/sup 2/, and the output clock frequency had a wide range of 50 kHz/spl sim/60 MHz. The multiplication range of the clock frequency was also a very wide 4/spl sim/1022, and a high level of precision was achieved with a clock jitter standard deviation of 234 ps. This digital PLL can withstand a broad range of operating environments, from -30/spl deg/C/spl sim/140/spl deg/C, and is suitable for making a programmable clock generator on a chip.

High-resolution n.m.r. in solids with strong homonuclear dipolar broadening: combined multiple-pulse decoupling and magic angle spinning

The theory of homonuclear decoupling combined with magic angle spinning is developed in the average Hamiltonian formalism. A description of pulse sequences used to tune for pulse width, pulse phase difference, and to minimize phase transient impurities is given. Resolution of n.m.r. spectra of 1 H in crystalline, partly crystalline and amorphous solids under various pulse sequences with and without magic angle spinning are illustrated. Sources of residual broadening are discussed.