Under a capacity constrained multi-product manufacturing system, the products are usually prepared and produced in lots. As a lot-sizing strategy is critical for effective production and high productivity, this encourages practical and research interest in the strategic batch sizing decision for a minimum procedure time in an order-to-delivery (OTD) operating environment. While the lot-sizing plan can be formed by studying the manufacturing parameters of the established bottleneck procedure, for a multi-stage manufacturing system, the bottleneck is not fixed and fluctuates with the production rate or batch size. This paper proposes a lot-sizing strategy to determine the optimal lot-size for each class of products taking bottleneck drifting into consideration. A queuing network analyser (QNA) method is employed to deal with the non-linear mixed integer programming model targeting at the total flow time minimization of the system. A practical case is presented and solved using the proposed method, and the results are validated with Flexsim, a simulation model.
Ultrasonic spectroscopy is becoming a promising particle measurement technique for the characterization of emulsions and suspensions over a wide range of particle size and concentration especially in the petrochemical, pharmaceutical, adhesives, food and other industries. Compared with other competitive methods like laser diffraction, dynamic light scattering and image analysis, the approach of ultrasonic attenuation spectroscopy possesses significant superiority in the highly-concentrated particulate twophase flow measurement even in the optical opaque medium, due to the high penetrability of ultrasonic waves through medium, as well as in situ non-invasive measurement and low cost but endurable apparatus. Typically, the overall process by which the particle size distribution of a suspension is measured using ultrasonic attenuation spectroscopy can be divided into two parts: the measurement of frequency-dependent ultrasonic attenuation in two-phase system, and the inversion calculation based on the prediction of mathematical model. The modeling process relies on the fundamental relationship between attenuation spectrum and physical properties, where viscosity could be a critical and complex property because its quantity can influence the ultrasonic attenuation seriously and ultimately the inversion calculation of the resultant particle size distribution. In this paper, a variable viscosity experimental system has been established through changing the concentration of aqueous glycerol solutions or the temperature of glycerol solutions. For the sample of micron-sized glass beads, a series of experiments have been carried out to obtain the attenuation spectrum, which were predicted and interpreted using the ECAH (Epstein, Carhart, Allegra and Hawley) model simultaneously. Hence, the particle size distribution of the glass beads can be retrieved through the inversion calculation.
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