A digital-based image analysis system has been developed for the experimental determination of size, spatial distribution and two components of velocity for particles suspended in any clear fluid flow. A volumetric measurement directly provides number density and consequently particle flow. A peculiarity of the developed system is its suitability for relatively large particles (some mm in diameter), which can hardly be measured with other systems. Double exposed particle images, in the same frame, provide the starting point for image processing. The system includes a procedure for the classification of the particles in the image, the separation of the partially overlapped particles and the selection of those that are found in the control volume. These parameters serve as a basis for the velocity determination through a particle-tracking algorithm (PTV), which is based on iteratively estimating the match probability as a measure of the likelihood of pairing. The depth of the control volume is obtained with a new technique, based on the loss of focus of the particles in the image, combined by diffuse illumination, provided by twin short pulse argon spark discharge lamps. The system has been extensively checked using calibrated micro-balls and sprays that simulate rain.

An effective way of improving the reliability of a system is the allocation of active redundancy. Let 1 X , 2 X be independent lifetimes of the components 1 C and 2 C , respectively, which form a series system. Let denoteX is the lifetime of a redundancy (say S ) independent of 1 X and 2 X . That is C is preferred to 2 C for redundancy. In this paper we use the same criterion of Singh and Misra (1994) and we investigate the allocation of one active redundancy when it differs depending on the component with which it is to be allocated. We find sufficient conditions for the optimization which depend on the components and redundancies probability distributions. We also compare the allocation of two active redundancies (say 1 S and 2 S ) in two different ways, that is, 1 S with 1 C and 2 S with 2 C and viceversa. For this case the hazard rate order plays an important role. We obtain results for the allocation of more than two active redundancies to a kout-of-n systems. Note: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accesible. Keywords

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a b s t r a c tThis paper studies coordination in a three-echelon supply chain and examines the impact of sub-supply chain coordination (sub-coordination). Our analysis is based on the price-only contracts that are commonly used in practice. The model is of the newsvendor type. We consider the following cases: no coordination between any members of the supply chain (decentralized), coordination between only two members (sub-supply chain coordination) and coordination of the whole supply chain as a benchmark. We explicitly analyze the order quantity and contracting decisions for a decentralized three-echelon supply chain. We compare supply chain efficiency when there is upstream coordination and when there is downstream coordination and show that the former is more efficient than or as efficient as the latter. In our setting, the difference between upstream and downstream sub-supply chain coordination is equivalent to the shortage cost transfer. We find that both the supplier and the retailer would prefer to act alone rather than to coordinate with the manufacturer when sub-supply chain coordination is suggested. This contradiction may partly explain the popularity of price-only contracts in practice.