Effects of Accelerated Aging on Physiological and Biochemical Characteristics of Waxy and Non-waxy Wheat Seeds

Experiments were conducted to evaluate the physiological and the biochemical characteristics of waxy wheat seeds under accelerated aging conditions. Five waxy wheat lines, which were Waxy 1, Waxy 4, Waxy 8, Waxy 9, and Waxy 15; and five non-waxy wheat lines： S-39, 04J89, Jan-81, III42-4, and II110 were studied. The seeds were subjected to accelerated aging at 40℃, 45℃, 50℃, 55℃, and 60℃, and 90% relative humidity for 0, 2, 4, 6, and 8 days, respectively. The results showed a gradual increase in conductivity and decrease in germination rate during accelerated aging. SOD, POD and CAT activities increased at lowgrade treatment, but decreased at severe treatment. On the other hand, the soluble protein content decreased at 45 ℃, but successively increased, then decreased 50℃. From the above study, it showed that 90% RH at 55℃ was the best accelerated aging condition for optimum efficiency in a shorter period.

Influence of Accelerated Aging on Detonation Performance of Explosives

To understand the aging effects on detonation performances of explosives,an accelerated aging mechanism and effect of explosives were analyzed.Based on the thermo-gravimetric(TG) curves of explosives under the heat rate of 5,10 and 20 K·min-1,the thermal decomposition activation energy,pre-exponential factor,mechanism function and kinetic equation of the explosives were calculated by Ozawa's equation and decomposition extents.Then,according to the derived kinetic equation,the density,composition and heat of formation of GI-1,PBX-1 and PBX-2 explosive in different decomposition extents were calculated at accelerated aging temperatures of 70 ℃ and 75 ℃,respectively.Furthermore,the detonation parameters of GI-1,PBX-1 and PBX-2 explosives were found out by means of VLWR code.The results show that after accelerated aging,the density are decrease,the detonation velocity and pressure are all decreased slightly.

Effect of Accelerated Ageing on the Dielectric Behaviour of Some Varnish Dry Films

The variation of the dielectric constant e' and the dielectric loss e' of polyesteramide, alkyd polyesteramide and alkyd varnish dry films were measured within the frequency range from 105 to 107 Hz and the temperature range from 20 to 50℃. The varnish films were subjected to accelerated ageing by heating at 110℃ for diferent durations. The efect of the accelerated ageing on e' and e' were measured. The activation energy and the entropy change of dielectric relaxation for the dry films before and after ageing were also calculated. All the results obtained were recorded and discussed in correlation with the molecular structure of the investigated varnishes.

Mechanical properties of thermal aged HTPB composite solid propellant under confining pressure

With the purpose of investigating the effects of confining pressure and aging on the mechanical properties of Hydroxyl-terminated polybutadiene(HTPB)based composite solid propellant,tensile tests of thermal accelerated aged propellant samples under room temperature and different confining pressure conditions were performed through the use of a self-made confining pressure device and conventional testing machine.Afterwards,the maximum tensile stressσmand the corresponding strainεm for the propellant under different test conditions were obtained and analyzed.The results indicate that confining pressure and aging can significantly affect the mechanical properties of HTPB propellant,and the coupled effects are very complex.On the one hand,the stressσmincreases as a whole when confining pressure becomes higher or thermal aging time rises.Besides,this stress is more sensitive to aging with increasing confining pressure.There are almost three regions in the stress increments(σm P-σm0)/σm0and thermal aging time curves for HTPB propellant.The maximum value of the stress increment(σm P-σm0)/σm0for the propellant is about 98%at 7.0 MPa and 170 d.On the other hand,the strainεm decreases with increasing thermal aging time under the whole confining pressure conditions.However,the variation of this strain with confining pressure is more complex at various thermal aging time,which is different from that of unaged solid propellant in previous researches.In addition,this strain is slightly less sensitive to aging as the confining pressure increases.Furthermore,there is also a critical confining pressure in this investigation,whose value is between 0.15 MPa and 4.0 MPa.Beyond this critical pressure,the trends of the stressσmand the corresponding strainεm all change.Moreover,there are some critical thermal aging time for the stress increment(σm P-σm0)/σm0and strain increment(εm P-εm0)/εm0of HTPB propellant in this investigation,which are about at 35,50 and 170 d.Finally,based on the twin-shear strength theory,a new modified nonlinear strength criterion of thermal aged HTPB propellant under confining pressure was proposed.And the whole errors of fitted results are lower than 6%.Therefore,the proposed strength criterion can be selected as a failure criterion for the analysis the failure properties of aged HTPB propellant under different confining pressures,the structural integrity of solid propellant grain and the safety of solid rocket motor during ignition operation after long periods of storage.

Effects of Freeze-Thaw Cycles on Physical and Mechanical Properties of Glulam Exposed to Outdoor Environment

This paper presents an experimental investigation to identify suitable indices to assess durability of glulam when subjected to freeze-thaw cycles in an exposed enviroenment.In this study,two types of glulam specimens were tested for their performance when subjected to different levels of aging due to freezing and thawing.Effect of aging treatment on various parameters including thickness swelling rate,static bending strength,elastic modulus,shear strength,and peeling rate of adhesive layer were studied.Obtained results showed that freeze-thaw aging treatment did not affect the water-resistance of the specimens as measured by thickness swelling rate and had little effect on the dimensional stability of the material.However,the applied aging treatment weakened the bending resistance of the glulam specimens with more pronounced effects on on low-density wood.On the other hand,bond strength of high-density wood was relatively more affected due to the appliedfreeze-thaw cycles.For highdensity wood,it is suggested that the shear strength of the adhesive layer be taken as an important index to determine the durability of freeze-thaw cycles aging.For low-density wood,on the other hand,the static bending strength can be used as an index to determine the durability of glulam under freeze-thaw cycles aging.

A Study of Estimating the Safe Storage Life, Self-accelerating Decomposition Temperature and Critical Temperature of Thermal Explosion of Double-base Propellant Using Isothermal and Non-isothermal Decomposition Behaviours

A method of estimating the safe storage life （τ）, self-accelerating decomposition temperature （TsADT） and critical temperature of thermal explosion （Tb） of double-base propellant using isothermal and non-isothermal decomposition behaviours is presented. For double-base propellant composed of 56±1wt% of nitrocellulose （NC）, 27±0.5wt% of nitroglycerine （NG）, 8.15±0.15wt% of dinitrotoluene （DNT）, 2.5±0.1wt% of methyl centralite, 5.0±0.15wt% of catalyst and 1.0±0.1wt% of other, the values of r of 49.4 years at 40℃, of TSAOT of 151.35℃ and of Tb of 163.01℃ were obtained.

Experimental Study of Hygrothermal and Ultraviolet Aging on the Flexural Performance of Epoxy Polymer Mortar

This paper studies the effects of hygrothermal environment at different temperatures and ultraviolet(UV)radiation on the bending properties of epoxy polymer mortar(EPM).The microstructure changes of EPM during aging were studied by scanning electron microscopy,and the bending properties of EPM were predicted by the Arrhenius law.The results showed that the bending properties of EPM were greatly affected by the temperature in the hygrothermal aging,but not evidently affected by ultraviolet radiation in UV aging.The prediction of Arrhenius model shows that the EPM will steadily retain 92.8%,89.1%and 79.4%of the original flexural strength after long-term hygrothermal aging at 40∘C,60∘C and 80∘C,respectively.

Thermo-mechanical,Wear and Fracture Behavior of High-density Polyethylene/Hydroxyapatite Nano Composite for Biomedical Applications:Effect of Accelerated Ageing

The objective of this work is to demonstrate how the viscoelastic, thermal, rheological, hardness, wear resistance and fracture behavior of bioinert high-density polyethylene （HDPE） can be changed by the addition of hydroxyapatite （HAP） nano particles. Also the effects of accelerated thermal ageing on the composite properties have been investigated. Different weight fractions of HAP nano particles up to 30 wt% have been incorporated in HDPE matrix by using melt blending in co-rotating intermeshing twin screw extruder. The fracture toughness results showed a remarkable decrease in proportion to the HAP content. The differential scanning calorimetry results indicated that the melting temperature and crystallinity were affected by the addition of HAP nano particles into the matrix. The complex viscosity increased as the percentage of HAP increased due to the restriction of the molecular mobility. The dynamic mechanical analysis results revealed that higher storage modulus （8.3 1011 Pa） could be obtained in the developed HDPE/HAP in 30 wt% compared to neat HDPE （5.1 1011 Pa）. Finally, the hardness and wear resistance of HDPE were improved significantly due to the addition of HAP nano particles. The changes in the HDPE and its nano composite properties due to ageing showed that the HDPE and its nano composites crystallinity increased while the fracture toughness, hardness, wear resistance, storage and loss modulus decreased.

Lifetime Estimation Based on Surface Degradation and Characterization of HTV Silicone-rubber Based Composites for HVAC and HVDC Transmission

In this paper,six different types of silicone rubberbased composites were investigated for applications in high voltage insulation through multi-stress accelerated aging conducted for a period of 5000 h both under AC and DC voltages.The main goal of this study was lifetime prediction of HTV-SR based composites at a typical multi-stress aging conditions.Several diagnostic techniques such as hydrophobicity assessment,leakage current measurement and FTIR were incorporated to assess the aging.As an outcome of this investigation,all the five hybrid samples were found as quite resistant to aging while the neat sample was comparatively,less resistant to the aging.Overall,among the studied samples,TS2 and TS4 appeared to have shown the highest resistance to aging giving a service life of 43.2 and 42 years,respectively under AC aging.Under DC stress the order of merit of investigated samples was identical to that of AC stress but having marginally less life spans.

锂离子电池加速老化:连接电池老化机制分析与寿命预测的桥梁

储能行业和新能源汽车的爆发式增长要求对锂离子电池的老化行为尤其是电池的寿命行为有更加深入的了解.准确地预测电池在各种工作条件下的使用寿命有助于优化电池的实际运行条件和延长电池的使用寿命,最终达到降低电池生命周期内总成本的目的.加速老化是一种经济高效的产品寿命评价方法,可以在短时间内获得大量的电池老化信息,快速预测锂离子电池在各种工作应力下的寿命特征.然而,基于加速老化进行电池寿命预测的前提是电池老化机理的一致性.本文综述了锂离子电池内各部件的老化机理和应力加速条件下的电池衰退机制以及相应的老化模式,为评价电池老化机理的一致性提供了参考.此外,本文还介绍了一些基于加速老化的电池寿命经验预测模型并为今后锂离子电池的加速老化研究提供了一些建议.

Role ofδ-ferrite in fatigue crack growth of AISI 316 austenitic stainless steel

FF sample(nearly free ofδ-ferrite)and CF sample(containing∼4%δ-ferrite)were prepared from the AISI 316 austenitic stainless steel plate to elucidate the role ofδ-ferrite in the fatigue crack growth under the solution treated and accelerated aged conditions.It is found that the fatigue crack growth resistance of the CF sample is higher than the FF sample under the solution treated condition.However,a significant deterioration of the fatigue crack growth resistance is observed in the CF sample while little variation is found in the FF sample after accelerated aging treatment at 750°C for 10 h.In the solution treated condition,deflected crack growth path is present when the main crack encounters theδ-ferrite in the CF sample due to the differences in the fatigue responses between austenite andδ-ferrite.The measured growth rate of the deflected crack is significantly slower than that of the flat crack of the same length.After the accelerated aging treatment,microcracks are produced at the M_(23)C_(6)/δinterface due to the strain incompatibility between M_(23)C_(6) and retainedδ-ferrite when the decomposedδ-ferrite is subject to plastic deformation in the crack tip plastic zone.The preexisting microcracks in the front of crack tip provide a viable path for crack propagation,resulting in the relatively flat crack path.

Advanced protection against environmental degradation of silver mirror stacks for space application

Protection of silver mirror stacks from environmental degradation before launching is crucial for space applications.Hereby,we report a comparative study of the advanced protection of silver mirror stacks for space telescopes provided by SiO_(2)and Al_(2)O_(3)coatings in conditions of accelerated aging by sulfida-tion.The model silver stack samples were deposited by cathodic magnetron sputtering on a reference silica substrate for optical applications and a surface-pretreated SiC substrate.Accelerated aging was per-formed in dry and more severe wet conditions.Optical micrographic observations,surface and interface analysis by Time-of Flight Secondary Ion Mass Spectrometry(ToF-SIMS)and reflectivity measurements were combined to comparatively study the effects of degradation.The results show a lower kinetics of degradation by accelerated aging of the stacks protected by the alumina coating in comparable test conditions.

Effects of Ultra-drying on Vigor and Physiological characteristics of Hippophae rhamnoides Seeds

Studies of ultra-drying and accelerated aging on Hippophae rhamnoides seeds from the arid and semiarid areas of northwest China were conducted. The results showed that H. rhamnoides seeds had higher desiccation endurance. When seeds were desiccated to 26 g/kg, their germination percentage, vigor indices and enzyme activity could be retained. After 30-day accelerated aging, ultra-dried seeds had better anti-aging ability and storability compared to natural dried seeds, and the best choice for the MC of seed was 34 g/kg. Accordingly, ultra-drying treatment could improve the storability.