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We report a simple and novel scheme to achieve the reconfigurable frequency mixing based on a filter-free photonic microwave in-phase/quadrature (I/Q) modulator. With proper photodetection configuration, four microwave frequency mixing functions are expediently reconfigured in our system: single-ended mixing, balanced mixing, I/Q mixing and image-reject mixing. The employed crucial optical modulator is a dual-polarization dual-parallel Mach–Zehnder modulator (DPol-DPMZM) driven by in-phase and quadrature intermediate frequency (IF) and local oscillator (LO) signals. The generation and switching of frequency down- and up-conversion and different mixing functions depend on the main direct current (DC) biases of the two sub-DPMZMs, instead of using additional optical hybrid, wavelength division multiplexer (WDM) or two pairs of cascaded polarization controller (PC) and polarization beam splitter (PBS) in previous reports. Our demonstrated experiment shows that the reconfigurable frequency mixer has high mixing spur suppression, frequency tunability, and image rejection ratio (IRR) of over 35 dB. The proposed simple and multifunctional structure may bring a broad potential application in radar and communication systems.

Creep tests of T92/Super304H joints were performed at 923 K under the stress of 85–165 MPa. Microstructure evolution was characterized by light microscopy, scanning electron microcopy and transmission electron microscopy to probe the relationship between creep performance deterioration and microstructure evolution. Results showed that for all the creep tests, failure occurred at fine-grained heat-affected zone of T92, and the joints have lower creep strength than the base metal T92. However, as the stress increased from 85 to 165 MPa, the creep fracture changed from a mixed mode, i.e., intergranular fracture in the center part and transgranular fracture in the edge part to total transgranular fracture. The longer the creep life, the greater is the proportion of the intergranular fracture. The M23C6coarsened and the Laves phase precipitated along grain boundaries during long-term creep. Vacancies nucleate and propagate at the interface between coarse M23C6, Laves phase and matrix. Finally, cracks forming along grain boundaries are responsible for intergranular fracture.

Objective To compare the growth of preterm infants fed standard protein-fortified human milk with that containing human milk fortifier (HMF) with a higher-than-standard protein content.Methods Published articles reporting randomized controlled trials and prospective observational intervention studies listed on the PubMed®, Embase®, CINAHL and Cochrane Library databases were searched using the keywords ‘fortifier’, ‘human milk’, ‘breastfeeding’, ‘breast milk’ and ‘human milk fortifier’. The mean difference with 95% confidence intervals was used to compare the effect of HMF with a higher-than-standard protein content on infant growth characteristics.Results Five studies with 352 infants with birth weight ≤1750 g and a gestational age ≤34 weeks who were fed human milk were included in this meta-analysis. Infants in the experimental groups given human milk with higher-than-standard protein fortifier achieved significantly greater weight and length at the end of the study, and greater weight gain, length gain, and head circumference gain, compared with control groups fed human milk with the standard HMF.Conclusions HMF with a higher-than-standard protein content can improve preterm infant growth compared with standard HMF.

In PWM controlled variable rate spraying system, spraying quantities were regulated by fast switching solenoid valves. However, hydraulic impacts were generated by these fast switching solenoid valves in pipe system, which affected stabilities of spraying quantities and atomization characteristics. In order to study pressure changing regularities when solenoid valves operated, then to design a pressure controller to improve spraying qualities in PWM controlled variable rate spraying system, Fluent was used to simulate pressure characteristics in the pipe system and pressure curves were drawn under the following 3 working conditions, solenoid valve opening, closing, and switching continuously with 5 Hz frequency and 50% duty ratio. Related experiments were carried out to test real pressure signals in the pipe based on a PWM controlled variable rate spraying system. Relative errors between simulation results and experiment results were below 10%. Thus, this simulation model of PWM controlled variable rate spraying system in Fluent was reliable to simulate pressure characteristics in the pipe in other common working conditions, and which contributed to design pressure controller and to optimize the whole PWM controlled variable rate spraying system.

In this paper, a design method that teaching and playback of motion trajectory based on the double-pole angles rotation parallel mechanical arm is introduced. Take writing as example, each stroke of the word can be fitted by the line and then the beginning and the end of the segment can be used as the teaching points. Using Siemens S7-200PLC’s counter to record the data of the encoder on the teaching point, completing the teaching. When playback, plc reads the data of the teaching points recorded and controls the input pulse of motors, uses the linear interpolation to complete playback of writing. The parallel manipulator’s structure is simple, it can easily be controlled and has rich working space and low cost.