Physical and Adsorptive Characterization of Precipitated Magnesium Silicate from Rice Hull Ash Silica

Precipitation of magnesium silicate from sodium silicate and MgCl₂ and MgSO₄ solutions was investigated at four different reactant feed rates and two temperatures (25 °C and 50 °C). Sodium silicate solutions were produced from rice hull ash silica. The final product was characterized by scanning electron microscopy, X‐ray diffraction, thermogravimetric analysis/differential thermal analysis, crystal size distribution, and filtration rate measurements. Physical characteristics of the studied magnesium silicates were determined by the Brauner‐Emmett‐Teller method and their adsorption capacities were compared to commercial magnesium silicate (Florisil). The adsorption was spontaneous and endothermic. The best fit of the kinetic results was achieved by a pseudo‐second‐order equation. The equilibrium data were found to be well represented by the Freundlich isotherm equation.     

Capacitated production and subcontracting in a serial supply chain

This paper extends a series of recent results regarding the polynomial solvability of single and two-echelon deterministic lot sizing models. In particular, we consider a two-echelon supply chain in which production, inventory, transportation, backlogging, and subcontracting decisions are integrated. We allow for arbitrary concave cost functions and for stationary production and subcontracting capacities. We develop dynamic programming algorithms for various problems in this class that run in polynomial time in the planning horizon of the problem.     

Experimental investigation of green brick shrinkage behavior with Bigot’s curves

The objective of this work is to define the convenient drying parameters such that the energy consumption in the brick drying process is minimized. This is an experimental study where the challenge lies in the mechanical resistance of the dried bricks which must satisfy the quality standards despite the reduction of energy consumption and the drying time. Firstly, we run multiple drying process tests and gather experimental data, and then discover the most suitable drying conditions. Secondly, the overall drying rate is improved using a Bigot’s curve analysis on the most suitable drying conditions. The results show that the drying rate increases significantly in conjunction with shorter drying time and lower energy consumption.     

Utilization of statistical process control (SPC) in emergent software organizations: Pitfalls and suggestions

Common wisdom in the domain of software engineering tells us that companies should be mature enough to apply Statistical Process Control (SPC) techniques. Since reaching high maturity levels (in CMM or similar models such as ISO 15504) usually takes 5–10 years, should software companies wait years to utilize Statistical Process Control techniques? To answer this question, we performed a case study of the application of SPC techniques using existing measurement data in an emergent software organization. Specifically, defect density, rework percentage and inspection performance metrics are analyzed. This paper provides a practical insight on the usability of SPC for the selected metrics in the specific processes and describes our observations on the difficulties and the benefits of applying SPC to an emergent software organization.     

Effect of impurities on the microhardness of borax decahydrate

Microhardness of borax decahydrate single crystals grown from pure and impure borax solutions was measured. It was found that the microhardness of borax decahydrate crystals showed clear load dependence. The results obtained from Meyer Law indicated that Meyer index was found to be less than 2. The microhardness measurements were also evaluated according to the PSR (proportional specimen resistance) model to analyze normal ISE and measured microhardness values were converted to load-independent microhardness. The variation of these load independent microhardness values with different types and concentrations of impurities was determined and found that the microhardness of borax decahydrate crystals was strongly affected by ionic impurities. Based on microhardness measurements it was observed that radial and lateral cracks occurred during the measurements. The dependence of these crack lengths on applied load and fracture toughness was investigated by some empirical equations. Crystal surface stresses were evaluated using an empirical equation and it was determined that tensile stresses were effective on the microhardness of borax decahydrate crystals.     

Multi-objective integrated acyclic crew rostering and vehicle assignment problem in public bus transportation

In this study, we try to solve a real planning problem faced in public bus transportation. It is a multi-objective integrated crew rostering and vehicle assignment problem. We model this problem as a multi-objective set partitioning problem. Most of the time, crew rostering problem with a single-objective function is considered, and the output may not satisfy some transport companies. To minimize the cost and maximize the fairness of the workload among the drivers, we define many criteria. Although crew rostering problem and its integrated versions appear in the literature, it is the first time these two problems are integrated. We propose a new multi-objective tabu search algorithm to obtain near Pareto-optimal solutions. The algorithm works with a set of solutions using parallel search. We test our algorithm for the case with ten objectives and define a method to choose solutions from the approximated efficient frontier to present to the user. We discuss the performance of our meta-heuristic approach.