Bamboo structures have a good performance like wooden structures. The flexural performance of glued laminated bamboo beams for bamboo structures were studied through ten large-scale beams tested. The study investigated the failure modes of bamboo beams, flexural capacity, cross-sectional stiffness and strain distribution. In test, four kinds of typical failure modes of bamboo beams include brittle fracture of the bottom fiber, compressive buckling failure at the top of the bamboo strips layers, stratified fracture and oblique tear of the bottom fiber. The control condition of the design load was the cross-sectional stiffness rather than the flexural strength according to the experimental results. The flexural elastic modulus of 10GPa is suggested to check deformation of bamboo beams in the design. The plane-section assumption of cross-sectional strain distribution along the height is verified for bamboo beams.
The objective of this study was to determine the effect of close-up diets with increased ratios of neutral detergent fiber (NDF) to non-fibrous carbohydrates (NFC) on feeding behavior in transition cows. Thirty-nine dry cows were blocked, assigned randomly to three groups and fed diets with a low (1.07, LF), medium (1.41, MF) or high (2.08, HF) NDF:NFC ratio from 21 d prior to the expected day of calving. After parturition, all cows were fed the same diet for a further 35 d. The average DMI decreased as the ratio of NDF:NFC increased at -3 weeks (Wk) and -2 Wk and increased at +5 Wk plessthan 0.05). The average daily feeding time was lower and the average feeding rate was higher (plessthan 0.05) for LF cows compared with MF and HF cows during prepartum. In conclusion, a prepartum diet with increased ratios of NDF:NFC decreased the DMI and feeding rate, increased daily feeding times and visits prepartum and was beneficial in increasing DMI postpartum.
The calculation of local stress and strain mostly adopts approximate Neuber method in engineering. The elastoplastic finite element method (EFEM) is more exact. The Taylor-expansion stochastic finite element method (SFEM) was used to deduce the iterative formulas of ESFEM under cyclic loading. The random responses of local multiaxial stress and strain were calculated. The structure material has some new random characteristics under fatigue loading, such as the randomness of the stress-strain response and the stress-life or strain-life relation. The stress-strain relation and its randomness are reflected in the elastoplastic matrix of ESFEM. The partial derivative formula of elastoplastic matrix was deduced and analyzed. The numerical method was used to calculate the partial derivative formula of elastoplastic matrix with respect to stress. For the complicated cyclic loading, the aeolotropism and Bauschinger effect resulted from plastic deformation were reflected by the kinematic hardening model. The usage of yield-stress increment could solve the plastic hysteresis problems in EFEM including cycle-hardening or cycle-softening phenomenon.
Energy management strategy is important to keep microgrid stable. In this paper, energy management strategy of Wind-PV-ES hybrid microgrid is proposed. Due to the power output of wind and PV are unknown quantities, the key point of Wind-PV-ES hybrid energy management lies in the energy management of storage battery. The flow charts of energy management strategy are given in detail and Wind-PV-ES microgrid model is built with DigSILENT/PowerFactory. Then the transition state simulation as to the micro-grid mode switching process is carried out. The result shows that the proposed energy management strategy could keep connected bus voltage and micro-grid frequency stable in grid-connected mode, islanding mode and during micro-grid mode switching.
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