智能剖竹机上料机械手试验研究

剖竹机传统的手工上料方法非常危险,智能剖竹机能够实现自动上料、智能换刀,应用前景广阔。上料机械手是智能剖竹机的重要部件。上料的成功率和对心率是开发毛竹上料机械手必须考虑的因素。文中通过试验研究一种自主开发的气动毛竹上料机械手的抓取成功率、对心率和抓取动态特性。研究过程中根据直径大小将毛竹毛坯分成60~85,85~110和110~135 mm 3个梯度,开发了大臂长度分别为210,220和230 mm的机械手进行试验,并利用加速度传感器测量抓取动态特性。试验结果表明臂长为220 mm的机械手平均抓取成功率为100%,但臂长为210 mm和230 mm的机械手分别只有96%和98.67%。因此,臂长为220 mm的机械手能可靠地抓取各种直径的毛竹。拟合出机械手抓取响应时间-胚料直径关系曲线与指数函数曲线近似,平均加速度-胚料直径曲线与幂函数曲线近似。

Influence of lateral initial pressure on axisymmetric wave propagation in hollow cylinder based on first power hypo-elastic model

Influence of identical applied initial pressures on the radial surfaces of a hollow cylinder which is compose of materials with first power hypo-elastic constitutive model was investigated.The basic equations of the problem were built up based on the framework of piecewise homogeneous body model with the use of three-dimensional linearized theory of elastic waves in initially stressed bodies(TLTEWISB).With the method proposed previously,this problem was then solved numerically.Moreover,the dispersion group velocity of the lowest order mode with different initial pressures was also studied.It can be concluded that the initial pressure and the geometry parameters will induce considerable changes of different degrees in dispersive relation between phase velocity and wave number in opposite trend(positive in initial pressure and negative in thickness).

Building dynamic thermal simulation of low-order multi-dimensional heat transfer

Multi-dimensional heat transfers modeling is crucial for building simulations of insulated buildings,which are widely used and have multi-dimensional heat transfers characteristics.For this work,state-model-reduction techniques were used to develop a reduced low-order model of multi-dimensional heat transfers.With hot box experiment of hollow block wall,heat flow relative errors between experiment and low-order model predication were less than 8% and the largest errors were less than 3%.Also,frequency responses of five typical walls,each with different thermal masses or insulation modes,the low-order model and the complete model showed that the low-order model results agree very well in the lower excitation frequency band with deviations appearing only at high frequency.Furthermore,low-order model was used on intersection thermal bridge of a floor slab and exterior wall.Results show that errors between the two models are very small.This low-order model could be coupled with most existing simulation software for different thermal mass envelope analyses to make up for differences between the multi-dimensional and one-dimensional models,simultaneously simplifying simulation calculations.

Relativistic Center-of-Mass Vector and Electric Polarizability of a Charged PionMeson

Comparing the relativistic and nonrelativistic frame works, we study the effect of the relativistic center-of-mass vector on the electric polarizability of a compound system.

Origin of symmetry breaking in the seed-mediated growth of bi-metal nano-heterostructures

Seed-mediated growth is the most general way to controllably synthesize bimetal nano-heterostructures. Despite successful instances through trial and error were reported, the way for second metal depositing on the seed. namely whether the symmetry of resulted nano-heterostructure follows the original crystal symmetry of seed metal, remains an unpredictable issue to date. In this work, we propose that the ther- modynamic factor, i.e., the difference of equilibrium electrochemical potentials （corresponding to their Fermi levels） of two metals in the growth solution, plays a key role for the symmetry breaking of bimetal nano-heterostructures during the seed-mediated growth. As a proof-of-principle experiment, by revers- ing the relative position of Fermi levels of the Pd nanocube seeds and the second metal Au with changing the concentration of reductant （L-ascorbic acid） in the growth solution, the structure of as-prepared prod- ucts successfully evolved from centrosymmetric Pd@Au core-shell trisoctabedra to asymmetric Pd-Au hetero-dimers. The idea was further demonstrated by the growth of Ag on the Pd seeds. The present work intends to reveal the origin of symmetry breaking in the seed-mediated growth of nano-heterostructures from the viewpoint of thermodynamics, and these new insights will in turn help to achieve rational con- struction of bimetal nano-heterostructures with soecific functions.

Effects from Periastron Advance of Eccentric Binary Stars

In this paper,we discuss the coefficients of Gravitational waveform due to eccentric binaries periastron advance with evolved eccentricity.For the basic harmonic modes(n ≤ 5),the frequency split and corresponding relative strengths in the spectrum are figured out.Taking the well known binary systems PSRB 1913+16 and PSRB 1534+12 as examples,we study the dominant harmonic and its frequency split caused by periastron advance in the spectra,and give an estimation of detectability for PSRB 1913+16 and PSRB 1534+12,which are the promising targets for space observatories of gravitational wave.