Studying the electronic and phononic structure of penta-graphane

In this paper, we theoretically consider a two dimensional nanomaterial which is a form of hydrogenated penta-graphene; we call it penta-graphane. This structure is obtained by adding hydrogen atoms to the sp² bonded carbon atoms of penta-graphene. We investigate the thermodynamic and mechanical stability of penta-graphane. We also study the electronic and phononic structure of penta-graphane. Firstly, we use density functional theory with the revised Perdew–Burke–Ernzerhof approximation to compute the band structure. Then one–shot GW (G₀W₀) approach for estimating accurate band gap is applied. The indirect band gap of penta-graphane is 5.78 eV, which is close to the band gap of diamond. Therefore, this new structure is a good electrical insulator. We also investigate the structural stability of penta-graphane by computing the phonon structure. Finally, we calculate its specific heat capacity from the phonon density of states. Penta-graphane has a high specific heat capacity, and can potentially be used for storing and transferring energy.     

On the Impact of Performance Faults in Modern Microprocessors

Modern microprocessors incorporate a variety of architectural features, such as branch prediction and speculative execution, which are not critical to the correctness of their operation yet are essential towards improving performance. Accordingly, while faults in the corresponding hardware may not necessarily affect functional correctness, they may, nevertheless, adversely impact performance. In this paper, we investigate quantitatively the performance impact of such faults using a superscalar, dynamically-scheduled, out-of-order, Alpha-like microprocessor, on which we execute SPEC2000 integer benchmarks. We provide extensive fault simulation-based experimental results that elucidate the various aspects of performance faults and we discuss how this information may guide the inclusion of additional hardware for performance loss recovery and yield enhancement.     

A low-overhead and reliable switch architecture for Network-on-Chips

This paper proposes and evaluates Low-overhead, Reliable Switch (LRS) architecture to enhance the reliability of Network-on-Chips (NoCs). The proposed switch architecture exploits information and hardware redundancies to eliminate retransmission of faulty flits. The LRS architecture creates a redundant copy of each newly received flit and stores the redundant flit in a duplicated flit buffer that is associated with the incoming channel of the flit. Flit buffers in the LRS are equipped with information redundancy to detect probable bit flip errors. When an error is detected in a flit buffer, its duplicated buffer is used to recover the correct value of the flit. In this way, the propagation of the erroneous flits in NoC is prevented without any need to credit signals and, retransmission buffers. Using an HDL-based NoC simulator, the LRS is compared to two other widely used reliability enhancement methods: the Switch-to-Switch (S2S) and the End-to-End (E2E) methods. The simulation results show that the LRS consumes less power and provides higher performance compared to those of the E2E and S2S methods. More importantly, unlike the E2E and the S2S methods, the LRS has constant overheads, which makes it applicable in all working conditions. To validate the comparison, an analytical performance and reliability model is developed for the LRS, S2S and E2E methods. The results of the model match those obtained from the simulations while the proposed model is significantly faster.     

Statistical analysis of dimensional changes in thermomechanical tube-spinning process

Tube-spinning process is an effective method for manufacturing long thin-wall tubes with precision dimensions and desired mechanical property. The main objectives of this research deal with the influences of major process parameters of thermomechanical tube-spinning process such as preform thickness, thickness reduction, mandrel rotational speed, feed rate of rollers, solution treatment time, and aging treatment time on internal diameter growth and wall thickness changes for manufacturing of 2024 aluminum spun tubes using design of experiments. Experimental results are analyzed by analysis of variance and empirical models of internal diameter growth and wall thickness changes are developed. It is found that lower thickness reduction with thinner preform thickness, higher feed rate of rollers, slower mandrel rotational speed, and lower solution treatment time have advantages for obtaining smaller internal diameter growth and wall thickness changes.     

Comparative effect of probiotic and paraprobiotic addition on rheological and sensory properties of yoghurt

Yoghurt was produced using killed cells of Lactobacillus acidophilus ATCCSD 5221 and Bifidobacterium animalis subsp. lactis BB‐12. The rheological and sensory properties of the yoghurt were investigated at the end of the fermentation. The results revealed that the samples made with killed cells gave the lowest storage modulus, loss modulus, stress crossover point and loss tangent. The frequency‐sweep of yoghurt samples containing paraprobiotics added before fermentation showed the highest correlation coefficient. In the case of sensory assessment, significant differences were indicated among treatments. Adding killed cells of B. animalis subsp. lactis BB‐12 before fermentation produced yoghurt with the highest total score, whereas samples containing killed cells of L. acidophilus ATCCSD 5221 and B. animalis subsp. lactis BB‐12 added before fermentation exhibited the lowest total score.     

Investigation of effective parameters on surface roughness in thermomechanical tube spinning process

Tube spinning process is recognized as an effective process for fabricating of thin wall cylindrical parts, with precision tolerances, high surface quality and desired mechanical property. In this research, the influences of major parameters of thermomechanical tube spinning process such as preform thickness, percentage of thickness reduction, mandrel rotational speed, feed rate of rollers, solution treatment time and aging treatment time on surface roughness for fabricating of 2024 aluminum spun tubes using design of experiments are studied. Experimental data are analyzed by analysis of variance (Anova) and empirical models of surface roughnesses are developed. It is found that deeper percentage of thickness reduction with thicker preform thickness, slower feed rate of rollers and mandrel rotational speed and higher solution treatment time and aging treatment time are advantageous for obtaining smoother surface.