Using solidification parameters to predict porosity distributions in alloy castings

Quality criteria used in the computer-aided design and analysis of casting processes typically relate geometric, thermal, or solidification parameters to structural features such as centerline shrinkage and microporosity. Quality criteria for the prediction of porosity in castings have been used successfully in steel, but the application of criteria functions to nonferrous alloys has been less successful. Recent work suggests that the dominating mechanism that determines the amount and distribution of porosity in castings is strongly dependent on the solidification mode of the alloy and the solidification conditions. Accordingly, casting processes and alloy types are divided into four groups, and a different set of criteria functions are obtained for each group.     

Managing supply systems with partial information on shipment locations

This paper studies a supply system for a retailer who orders a single product from one manufacturer. Orders filled by the manufacturer pass through multiple transportation stages before reaching the retailer. Each stage represents either a physical location or a step in the delivery process. The lead time for a new order depends on the location of shipments against prior orders in transit. Shipments are not allowed to cross over in time. Thus, the movement of each shipment depends on the movements of shipments ahead of it and the resulting congestion. The retailer is able to track shipments as they move through the transportation channel. The retailer adopts an ordering policy that minimises the sum of his one-period holding and shortage costs, using available status information of shipments already in transit. The case where practical constraints prevent the retailer from obtaining a complete status of shipments at all stages in the transportation channel is considered. The methodology developed evaluates the value of partial shipment tracking information, and uses it to determine the optimal placement of a limited number of tracking devices. The methodology can also be used to evaluate the cost–benefit of placing additional tracking devices in the supply system.     

Formation of Zinc–Antimony-Based Spinel Phases

Formation of spinel phases in ZnO–Sb₂O₃and ZnO–Sb₂O₃–Bi₂O₃systems is studied by the use of X-ray diffraction. The formation of nonstoichiometric Zn_2.33Sb_0.67O₄phase is observed in both the systems at ∼900°C. However, in these systems, at higher temperatures ( T ≥ 1100°C), formation of the inverse spinel phase Zn₇Sb₂O₁₂is observed. The study has been extended to understand the effect of CrO₃doping on the stability of the different spinel phases in the previously mentioned systems. Interestingly, in both the systems, samples doped with CrO₃, displayed the presence of Zn_2.33Sb_0.67O₄phase <1200°C, indicating the stabilization of the spinel phase by CrO₃.     

Optical,electrical, mechanical,and thermal properties and non-isothermal decomposition behavior of poly(vinyl alcohol)–ZnO nanocomposites

Iranian Polymer Journal - Poly(vinyl alcohol) (PVA) nanocomposites incorporated with ZnO nanofiller were prepared and examined to study the influence of nanofiller on their properties. All the...