Isolating LCDs at end-of-life using active disassembly technology: A feasibility study

The European Union draft Waste Electrical and Electronic Equipment (WEEE) directive calls for the removal and separate treatment of liquid crystal displays (LCD). This aspect of the legislation will potentially have an important impact upon the future `End of Life' (EoL) processing of much WEEE. Active Disassembly using Smart Materials (ADSM) has been proven to have applicability in self-dismantling, nondestructive and rapid disassembly of small electronic products. This paper investigates the technical feasibility of removing LCD screens from IT communication products using ASDM technology. In this paper an option is suggested to cleanly separate LCD screens from printed circuit boards, utilizing an LCD bracket made from `shape memory polymer'. The case study products employed are Nokia Japanese J-Phones. Demonstration experiments with initial results are presented, and future developments discussed. SMB glass transformation temperatures (Tg) and time efficiency in disassembly are considered

Investigations of generic self disassembly using shape memory alloys

Industrial recycling is a practice of growing importance while impending `Take Back' European legislation and economic pressures are increasing. Landfill sites are becoming exhausted and the industry could benefit from a novel approach to recycling pre and post consumer waste. Cost constraints limit the number of different products that can be recycled. Recyclers are working on broadening the range of reusable components from this waste stream, but the proposed approach would significantly increase the volume of recyclable material used in manufacturing new products. This alternative could potentially reduce recycling cost per product in the event of mandatory recycling as a wide variety of consumer electronics could be actively or self disassembled on the same generic dismantling line. The use of Shape Memory Alloy (SMA) actuators in a wide variety of consumer electronic products in the same dismantling facility was tested. The candidate products had undergone a multi-stage hierarchical temperature regime on their macro and subassembly disassemblies and results reported. Two forms of SMA actuators were employed in the designs of actuators; these were one-way Nickel-Titanium (NiTi) and two-way Copper-Zinc-Aluminum (CuZnAl) actuators

Extended density matrix model applied to tall barrier quantum cascade lasers

Quantum cascade lasers (QCLs) are promising sources of terahertz (THz) radiation that have applications such as security and medical screening. While optical output power has recently exceeded 1 W, their highest operating temperature is currently limited to ~200 K due to mechanisms such as thermal back filling and non-radiative phonon emission between lasing states. Another possible cause of performance degradation is parasitic leakage currents over barriers into continuum states as subband electron temperatures increase with lattice temperature. Novel designs with new injection schemes remain an intensive research area and new efforts are being made assuming that barrier heights no longer need to be constant. A possible advantage of this is using tall barriers to reduce the leakage current, and in this work we present a theoretical study of recent experimental evidence supporting this. Interface roughness (IFR) scattering scales with the conduction band discontinuity squared and the calculations also assume a typical correlation length Λ and root mean roughness value Δ which are related to growth quality of the individual sample. We take typical values of Λ=60 Å and Δ=3 Å for these parameters. The QCL gain and current output characteristics are calculated using an extended density matrix solver which models transport through the injection barrier coherently. We obtain similar current and gain values at resonance for both structures, indicating that the experimentally observed reduction in current density could be accredited to the reduction of parasitic current leakage. Additionally, this work attempted a similar design with all AlAs barriers which did not lase and it was conjectured that this was due to excessive IFR scattering as well as increased susceptibility to monolayer fluctuations with thinner layers. Our model, which accounts for the lifetime broadening in the gain calculation, confirms that modifying the IFR parameters to Λ=100 Å and Δ=1 Å (i.e. unrealistically sharp interfaces) leads to a significant improvement in performance as shown in Figure 1. We extend this work by proposing designs which aim to balance leakage current reduction and excessive scattering to achieve higher operating temperatures

Open-source bandstructure models of interdiffusion, impurity and exciton states for the QWWAD v1.4 simulation suite

The vast majority of high-quality software for simulating semiconductor nanostructures (e.g., [1]) is supplied under a proprietary license and its source code cannot be studied, modified or redistributed by its users. The open-source project, Quantum Wells, Wires and Dots (QWWAD) [2] is a free, non-commercial community-focused resource, which accompanies the new 4th edition of the eponymous textbook [3]. Previously described features in QWWAD include numerical Schrodinger/Poisson solvers in generic 1D potentials [e.g., Fig. 1(a)], quasi-analytical and empirical pseudopotential calculations of the band-structure in quantum wires and dots, and scattering calculations for interactions with impurities, phonons, interface roughness, alloy disorder and carrier–carrier processes. We describe new tools, included in the latest release (QWWAD v1.4), for modelling the perturbed quantum-confined states within 2D heterostructures resulting from interdiffusion, impurities and excitonic contribution

Ligand-based virtual screening using binary kernel discrimination

This paper discusses the use of a machine-learning technique called binary kernel discrimination (BKD) for virtual screening in drug- and pesticide-discovery programmes. BKD is compared with several other ligand-based tools for virtual screening in databases of 2D structures represented by fragment bit-strings, and is shown to provide an effective, and reasonably efficient, way of prioritising compounds for biological screening

Influence of barrier height on interface roughness scattering and coherent transport in AlGaAs quantum cascade lasers

Quantum cascade lasers (QCLs) are promising sources of terahertz (THz) radiation that have applications such as security and medical screening. While optical output power has recently exceeded 1 W, their highest operating temperature is currently limited to ~200 K due to mechanisms such as thermal back filling and non-radiative phonon emission between lasing states. Another possible cause of performance degradation is parasitic leakage currents over barriers into continuum states as subband electron temperatures increase with lattice temperature. Novel designs with new injection schemes remain an intensive research area and new efforts are being made assuming that barrier heights no longer need to be constant. A possible advantage of this is using tall barriers to reduce the leakage current, and in this work we present a theoretical study of the effects of increased barrier heights on transport between states in the structure. Similar to previous efforts, we initially restrict the modification of barrier height to the injection barrier; these are typically the thickest in THz QCLs and allow the reduced barrier widths necessary for AlAs barriers to remain above 1 ML