Digital image correlation methods were used for further studies of the viscoelastic Poisson's ratio of solid propellants. The Poisson's ratio and the Young's relaxation modulus of solid propellants were separately determined in a single stress relaxation test. In addition, the effects of temperature, longitudinal strain, preload and storage time on the Poisson's ratio of solid propellants were discussed. The Poisson's ratio master curve and the Young's relaxation modulus master curve were constructed based on the time‐temperature equivalence principle. The obtained results showed that the Poisson's ratio of solid propellants is a monotone non‐decreasing function of time, the instantaneous Poisson's ratio increased from 0.3899 to 0.4858 and the time of the equilibrium Poisson's ratio occurred late when the temperature was varied from −30 °C to 70 °C. The Poisson's ratio increased with temperature and longitudinal strain, decreased with preload and storage time, while the amplitude Poisson's ratio increased with preload, decreases with longitudinal strain and storage time. The time of the equilibrium Poisson's ratio occurred in advance with the increase of longitudinal strain, preload and storage time.

Objectives Patients with psychiatric disorders have an increased risk of cardiovascular pathologies. A bidirectional feedback model between the brain and heart exists widely in both psychotic and nonpsychotic disorders. The aim of this study was to compare heart rate variability (HRV) and pulse wave velocity (PWV) functions between patients with psychotic and nonpsychotic disorders and to investigate whether subgroups defined by HRV and PWV features improve the transdiagnostic psychopathology of psychiatric classification. Methods In total, 3448 consecutive patients who visited psychiatric or psychological health services with psychotic (N = 1839) and nonpsychotic disorders (N = 1609) and were drug-free for at least 2 weeks were selected. HRV and PWV indicators were measured via finger photoplethysmography during a 5-minute period of rest. Canonical variates were generated through HRV and PWV indicators by canonical correlation analysis (CCA). Results All HRV indicators but none of the PWV indicators were significantly reduced in the psychotic group relative to those in the nonpsychotic group. After adjusting for age, gender, and body mass index, many indices of HRV were significantly reduced in the psychotic group compared with those in the nonpsychotic group. CCA analysis revealed 2 subgroups defined by distinct and relatively homogeneous patterns along HRV and PWV dimensions and comprising 19.0% (subgroup 1, n = 655) and 80.9% (subgroup 2, n = 2781) of the sample, each with distinctive features of HRV and PWV functions. Conclusions HRV functions are significantly impaired among psychiatric patients, especially in those with psychosis. Our results highlight important subgroups of psychiatric patients that have distinct features of HRV and PWV which transcend current diagnostic boundaries.

The viscoelastic Poisson's ratio of solid propellant seriously affects the analytical accuracy of the structural integrity of the solid rocket motor. Based on the digital image correlation (DIC) method, a stress relaxation test and a uniaxial constant tensile rate test were carried out to measure the viscoelastic Poisson's ratio of the composite solid propellant according to the stress characteristics of solidification cooling and ignition pressurization conditions. The effects of time, temperature, longitudinal strain as well as tensile rate on the viscoelastic Poisson's ratio of propellant were studied. In this paper, the main curves of the temperature and strain rate of the propellant Poisson's ratio at the reference temperature of 25 °C and the main curves of temperature and longitudinal strain at the reference time of 10000 s were established. The research shows that the viscoelastic Poisson's ratio of composite solid propellants increased with increasing temperature, longitudinal strain and tensile rate. Under the solidification cooling condition, the Poisson's ratio of the solid propellant does not change significantly with time. At this point, the Poisson's ratio can be regarded as a constant, but the appropriate value must be selected according to the operating temperature and initial deformation of the solid rocket motor. In the uniaxial constant tensile rate test, when the stretching rate reached 500 mm/min, Poisson's ratio of the propellant gradually approached a certain constant value. Considering that the loading rate of the propellant is generally above 0.5 s−1 under the ignition pressurization condition, the strain rate is large, the Poisson's ratio of the propellant can be taken as a constant. Relevant methods and conclusions can provide a reference for structural analysis and storage life prediction of solid rocket motors.

The evaluation of basic mechanical properties are shown to be of importance for the solid composite propellant development and application. The numerical analysis approach termed the three-phase Voronoi cell finite element method, was proposed to evaluate of the interfacial transition zone effect. Numerical results showed that the performance of the effective modulus could be essentially enhanced by increasing the zone thickness. The module of the composite with the inhomogeneous zone was higher than that of the composite with the homogeneous one. The effect of different zones on volume fractions and matrix moduli was also calculated. The Voronoi method can also be helpful for analyzing the characteristic properties of other three-phase composites.