Towards the prioritization of system test cases

During software development, companies are frequently faced with lack of time and resources, which limits their ability to effectively complete testing efforts. This paper presents a system‐level, value‐driven approach to test case prioritization called the Prioritization of Requirements for Test (PORT). PORT involves analysing and assigning value to each requirement using the following four factors: requirements volatility, customer priority, implementation complexity, and fault proneness. System test cases are prioritized such that the test cases for requirements with higher priority are executed earlier during system test. PORT was applied to four student team projects as well as an industrial case study. The results show that PORT improves the rate of detection of severe failures over random prioritization. Additionally, the results indicate that customer priority was the most important contributor towards improved rate of failure detection. Copyright © 2013 John Wiley & Sons, Ltd.     

Growth of uniform ZnO nanoparticles by a microwave plasma process

ZnO nanoparticle coatings with a controlled size distribution have been grown on quartz substrates by a novel microwave plasma assisted spray (MPAS) technique. This study presents the analysis of structure, photoluminescence, and magnetic properties of particle coatings with two distinctly different mean particle sizes (400 nm and 200 nm). X-ray diffraction patterns show a typical wurtzite structure without any impurity phases for the nanoparticle coatings. SEM and TEM investigations have shown the grown nanoparticles to be spherical and well separated with a narrow size distribution. Nanoparticles are polycrystalline with smaller grain sizes associated with the smaller particle sizes. Photoluminescence (PL) spectra reveal the presence of oxygen vacancy related defects in the 400 nm nanoparticles, which become less pronounced in the 200 nm nanoparticles. The 400 nm nanoparticles are found to exhibit room-temperature ferromagnetism with a clear hysteretic behavior, while the 200 nm nanoparticles are diamagnetic even down to 10 K. These results suggest the oxygen vacancies were the cause for defect-induced ferromagnetism in the 400 nm nanoparticles.     

UVOC-MAC: a MAC protocol for outdoor ultraviolet networks

As an alternative to radio-frequency (RF) communications, optical wireless communications can support high data rates and low power operations while providing good jamming resistance. Our focus in this paper is on deep ultraviolet (UV) outdoor communications (UVOC) where solar blind and non-line-of-sight operations are attractive. Light beams from UV light-emitting diode (LED) arrays serve as information carriers. In an abstract sense, this is similar to directional transmissions in RF; however, the physical (PHY) layer characteristics significantly differ due to atmospheric scattering. First, we perform extensive experiments on a UV testbed towards understanding signal propagation and the impact of the PHY on medium access. We find that UV propagation supports (a) fully duplex communications and (b) multiple data rate transmissions. Next, we propose a novel contention-based media access control (UVOC-MAC) protocol that inherently accounts for the UV PHY layer and fully exploits multi-fold spatial reuse opportunities. Evaluations via both simulations and analysis show that UVOC-MAC effectively mitigates collisions and achieves high throughput. In particular, up to a 4-fold increase in throughput and 50 % reduction in collision are possible compared to a MAC protocol agnostic to the UV PHY properties.     

Biogas generation potential by anaerobic digestion for sustainable energy development in India

The potential of biogas generation from anaerobic digestion of different waste biomass in India has been studied. Renewable energy from biomass is one of the most efficient and effective options among the various other alternative sources of energy currently available. The anaerobic digestion of biomass requires less capital investment and per unit production cost as compared to other renewable energy sources such as hydro, solar and wind. Further, renewable energy from biomass is available as a domestic resource in the rural areas, which is not subject to world price fluctuations or the supply uncertainties as of imported and conventional fuels. In India, energy demand from various sectors is increased substantially and the energy supply is not in pace with the demand which resulted in a deficit of 11,436 MW which is equivalent to 12.6% of peak demand in 2006. The total installed capacity of bioenergy generation till 2007 from solid biomass and waste to energy is about 1227 MW against a potential of 25,700 MW. The bioenergy potential from municipal solid waste, crop residue and agricultural waste, wastewater sludge, animal manure, industrial waste which includes distilleries, dairy plants, pulp and paper, poultry, slaughter houses, sugar industries is estimated. The total potential of biogas from all the above sources excluding wastewater has been estimated to be 40,734 Mm³/year.     

Enhancement of the giant magnetoimpedance effect and its magnetic response in ion-irradiated magnetic amorphous ribbons

The influences of N and Xe ion irradiation on the giant magnetoimpedance (GMI) effect and its magnetic response in Co₆₉Fe_4.5Al_1.5Si₁₀B₁₅ amorphous ribbons were systematically investigated. A large enhancement of the GMI effect and its magnetic response were achieved in N and Xe ion-irradiated amorphous ribbons. At a frequency of 3 MHz, the GMI ratio and magnetic response for an N-ion-irradiated amorphous ribbon respectively reached the highest values of 130% and 13%/Oe, while for a non-irradiated amorphous ribbon they were only about 53% and 8%/Oe. The enhancement of the GMI effect and magnetic response in the ion-irradiated amorphous ribbons resulted from the enhancement of the permeability due to rotational magnetization. Our studies indicate that low energy ion irradiation is useful for improving the magnetic softness, GMI and magnetic response of amorphous alloys, which is of practical importance for the development of high-performance magnetic sensors.     

Adding carbon nanotubes and integrating with AA5052 aluminium alloy core to simultaneously enhance stiffness, strength and failure strain of AZ31 magnesium alloy

New bimetal AZ31-CNT/AA5052 macrocomposite comprising: (a) carbon nanotube (CNT) reinforced magnesium alloy AZ31 shell and (b) aluminium alloy AA5052 millimeter-scale core reinforcement was fabricated using solidification processing followed by hot coextrusion. Microstructural characterisation revealed more rounded intermetallic particle of decreased size, reasonable CNT distribution, and dominant (1 0 −1 1) texture in the longitudinal and transverse directions in the AZ31-CNT nanocomposite shell. Interdiffusion of Mg and Al across the core-shell macrointerface into each other was also significant. Compared to monolithic AZ31, the AZ31-CNT shell had significantly higher hardness (+30%). In tension, the presence of CNT (in the AZ31 shell) and AA5052 core significantly increased stiffness (+39%), ultimate strength (+13%), failure strain (+17%) and work of fracture (+27%) of AZ31, while yield strength (−2%) was marginally decreased. In compression, the presence of CNT (in the AZ31 shell) and AA5052 core significantly increased yield strength (+35%), failure strain (+42%) and work of fracture (+70%) of AZ31, while ultimate strength (+1%) was marginally increased. The effect of joint presence of: (a) CNT (in the AZ31 shell) and (b) AA5052 millimeter-scale core on tensile and compressive properties of AZ31 is investigated in this paper.     

Unique reduced graphene oxide as efficient anode material in Li ion battery

Unique reduced graphene oxide named solar reduced graphene oxide (SRGO) was found to be an excellent anode material in Li ion battery. SRGO exhibited first cycle discharge- and charge-capacities as high as 1480 and 880 mAh \(\hbox {g}^{-1}\), respectively. Moreover, the columbic efficiency was found to be >95% and the specific capacity retention even after 60 cycles was >500 mAh \(\hbox {g}^{-1}\).     

Grain Boundary Diffusion of Oxygen in Alumina Ceramics

The volume and grain boundary diffusion coefficients (D_v and δD_gb) of oxygen at 1673 K in pure and Mg-doped alumina were studied by using a resistive anode encoder of SIMS. The effect of Mg-doping on D_v, was observed clearly. The differences on δD_gb in pure and Mg-doped alumina were about 3 orders and 1 order of magnitude, respectively. The Mg-doping in alumina is useful for homogenizing grain boundary diffusion.