Experimental insight into the evolutionary mechanism of solid-to-hollow hydrogel.

We for the first time disclose the evolutionary mechanism of solid-to-hollow sodium alginate (SA) hydrogel in an aqueous solution of Cu2+, H2O2 and Tris-HCl elements, where the oxidative degradation and gas bubble assistance result in the hollow structures. This provides a promising concept or method basis for the preparation of hollow hydrogels with sophisticated geometries.

Humidity-Driven Soft Actuator Built up Layer-by-Layer and Theoretical Insight into Its Mechanism of Energy Conversion.

An improved protocol is proposed for preparation of a humidity-sensitive soft actuator through the layer-by-layer assembling of weight-ratio-variable composites of sodium alginate (SA) and poly(vinyl alcohol) (PVA) into laminated structures. The design induces nonuniform hygroscopicity in the thickness direction and gives rise to strong interfacial interaction between layers, making the actuator have directional motility. A mathematical model reveals that the directional motion is driven by the chemical potential of humidity, and its energy conversion efficiency from humidity to mechanical work reaches 81.

A spectrum matching method for accurate frequency estimation of real sinusoids.

It is well-known that incoherent sampling is detrimental for frequency estimation of a real sinusoid, and the estimation errors get worse when the signal lengths are very short. In this paper, a spectrum matching based frequency estimator is proposed as well as evaluated against other four two-step methods developed to suppress the effect of incoherent sampling. The spectral interference introduced by incoherent sampling is eliminated via a spectrum matching process including modulation and spectral analysis.

Antifreezing Heat-Resistant Hollow Hydrogel Tubes.

Hollow hydrogel tubes that are capable of maintaining their flexibility and structural stability in extreme temperature conditions have potential for use in biomedical scaffolds, carriers, and soft robotics over a wide temperature range. However, the preparation of hollow hydrogel tubes still remains challenging because it normally requires templates or complex devices and it is hard to endow the hollow tubes with antifreezing heat-resistant capabilities. We report a protocol that does not require a template or complex devices, in which sodium alginate film strips are immersed in an aqueous mixture of CaCO, CaCl, NaHCO, and HCl, which results in the manufacture of hollow tubes in 30 min.

A modulation based phase difference estimator for real sinusoids to compensate for incoherent sampling.

Phase difference estimation is a fundamental problem in numerous applications. However, incoherent sampling (IS) is an inevitable factor which degrades the precision of many correlations or Fourier transform-based approaches. In this paper, IS and the spectral superposition of real signals are both considered.

A phase match based frequency estimation method for sinusoidal signals.

Accurate frequency estimation affects the ranging precision of linear frequency modulated continuous wave (LFMCW) radars significantly. To improve the ranging precision of LFMCW radars, a phase match based frequency estimation method is proposed. To obtain frequency estimation, linear prediction property, autocorrelation, and cross correlation of sinusoidal signals are utilized.

A new phase difference measurement algorithm for extreme frequency signals based on discrete time Fourier transform with negative frequency contribution.

For the ultralow frequency signals or adjacent Nyquist frequency signals, which widely exist in vibration engineering domain, the traditional discrete time Fourier transform (DTFT) algorithms show poor performance for phase difference measurement. To improve the accuracy of phase difference measurement for these extreme frequency signals, the phase difference measurement error of DTFT algorithm is analyzed, which indicates that the negative frequency contribution is the main cause of the bias. By considering the negative frequency contribution, a new phase difference measurement algorithm for extreme frequency signals is proposed based on DTFT, and the new formulas for phase difference calculation with different windows are derived in detail.

A novel time varying signal processing method for Coriolis mass flowmeter.

The precision of frequency tracking method and phase difference calculation method affects the measurement precision of Coriolis Mass Flowmeter directly. To improve the accuracy of the mass flowrate, a novel signal processing method for Coriolis Mass Flowmeter is proposed for this time varying signal, which is comprised of a modified adaptive lattice notch filter and a revised sliding recursive discrete-time Fourier transform algorithm. The method cannot only track the change of frequency continuously, but also ensure the calculation accuracy when measuring phase difference.