Estimation of quantities, metal concentrations in components and management of waste rechargeable lighting devices in Nigeria

Rechargeable lighting devices are used in Nigeria as alternative source of lighting due to epileptic power supply. They contain printed wiring board, battery and plastic casings containing heavy metals. This waste category is often neglected and disposed of with household garbage with concomitant deleterious consequences on environment. We estimated quantities, disposal methods and concentrations of selected metals in some components of 34 waste rechargeable lighting devices in Nigeria. Estimated quantities and disposal methods were carried out through online survey. Leached metals were prepared and analyzed using standard methods. Approximately 6000 tons/year of waste rechargeable lighting devices were estimated. An average life span of 9 months and 4 rechargeable lighting devices were estimated to be used per household in Nigeria. The commonest disposal method was with household garbage. Lead and copper contents on the boards and Pb in battery electrodes were far higher than permissible limits. All metals determined in plastic casings were within permissible limits. High lead and copper contents in some components makes waste rechargeable lighting devices to be regarded as hazardous materials and should be handled with care at disposal.

Optimal Dummy Pattern Design Method for PWB Warpage Control Using the Human-Based Genetic Algorithm

In this work, a method that minimizes printed wiring board (PWB) warpage by dummy pattern design is proposed. This work suggests that dummy patterns are placed on a preset discretized location in the PWB to reduce the warpage. On each discretized candidate area, the dummy pattern can be set or unset. The warpage is numerically simulated based on direct modeling of the as-is PWB patterns to evaluate the warpage alongside the dummy pattern design set. The optimal pattern that minimizes warpage is determined using the human-based genetic algorithm where the objective function is evaluated by the structural simulation. The optimization method is realized in a spreadsheet that allows scripting language with which the input and output files of the simulation tool can be modified and read. Two different cases have been tested and the results show that the method can determine the optimal dummy patterns. The measured and simulated deflections agree well with each other. Moreover, it has been shown that certain dummy pattern designs that should reduce the warpage can be sought by the optimization.