This paper presents a study of in-process waiting times on a linear walking worker assembly line in a real buffer-constrained flowshop environment using the simulation method. The in-process waiting time can lead to production loss and in-process inventory; it can also affect the throughput time for completion of a product assembled in a sequential flowline-based manufacturing system. The aim of this research is to investigate the varying magnitude of the total in-process waiting time for individual walking workers who may have to wait to carry out operations at a station due to blocking on the line ahead. The results were obtained by varying a number of system parameters embedded in a simulation model created using Witness® with the key input/output data being manipulated by a series of MS Excel-spreadsheets. The main finding of this work is that the in-process waiting time (which affects the expected throughput time) can be determined and it is adjustable by the strategic application of walking workers on a linear assembly line, even if the system behaviour is random.
A description of the anisotropy of elastic and nonlinear acoustic properties of dense (95% of theoretical), highly textured, sinter-forged, ceramic Bi~Sr2CaCu208+~(Bi-2:2:1:2)high-T, superconductors is provided from measurements of the velocities of longitudinal and shear ultrasonic waves as functions of temperature and hydrostatic pressure. A high proportion of the grains are aligned preferentially with the c axis along the forging direction in this material, while it is essentially isotropic in the plane normal to the forging axis. A complete set of the elastic stiffness tensor components has been determined as a function of temperature from 10 to 290 K, treating this material as if it had cylindrical symmetry. The results are used to compute the orientation dependences of the Young's modulus and Poisson's ratio which are compared with those estimated for single crystal Bi-2:2:1:2.The main finding is a marked anisotropy of the elastic stiffness moduli and their dependences on pressure. The elastic and nonlinear acoustic properties of the textured and single-crystal Bi-2:2:1:2comply with the behavior expected for a layerlike material with rather weak interlayer binding forces: C» ) C33 the linear compressibility and thermal expansion along to the c axis, i.e. , normal to the layers, being substantially larger than in the ab plane. The hydrostatic pressure derivative (BC33/BP)p -p(=21.3) of the elastic stiffness tensor component, which corresponds to a longitudinal wave propagated along the c axis, is larger than that (BC»/BP)p=o(=15. 1), for such a wave propagated in the ab plane. The anisotropies of the linear compression and the acoustic mode Griineisen parameters are also typical of a layerlike material.
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