A tightly coupled and hierarchical multiprocessor architecture

The Erlangen General Purpose Array (EGPA) consists of a grid-like array of memory-coupled processor-modules. Above the array there is a hierarchy of processors for supervising and for data transports. An experimental pilot pyramid was realized. For a broad spectrum of applications the measured efficiency of the 4 worker-processors of the pilot pyramid ranged between 80 and 100%.     

Sorptivity and acid resistance of ambient-cured geopolymer mortars containing nano-silica

This study investigated the effects of nano-silica on flowability, strength development, sorptivity and acid resistance properties of fly ash geopolymer mortars cured at 20 °C. The changes in mass, compressive strength and microstructure of the specimens after immersion in acid solutions for different durations were determined. The microstructures were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis. It was found that addition of nano-silica in geopolymer mortars based on fly ash alone or fly ash blended with 15% GGBFS or 10% OPC improved the compactness of microstructure by reducing porosity. Thus, the nano-silica reduced sorptivity and increased compressive strength of the mixes. The average mass loss after 90 days of immersion in acid solutions reduced from 6.0% to 1.9% by addition of 2% nano-silica. Similarly, significant reduction in strength loss after immersion in acid solution was observed in the specimens by using nano-silica.     

Optimizing a microgrid photovoltaic-fuel cell energy system at the highest renewable fraction

The current research examined the usage of fuel cells as an energy storage unit to increase renewable energy self-consumption in microgrid energy system applications. The studied model is comprised of photovoltaic modules and a fuel cell that serves as the energy storage unit. The study was conducted in 2020, utilizing real-time weather and electrical load data with a one-minute temporal resolution. The daily average energy consumption for the analyzed household was 10.1 kWh, with a peak power output of 5.3 kW, and the yearly energy consumption was 3755 kWh. The investigated photovoltaic system has a capacity of 2.7 kWp (6 modules at 0.45 kWp/module), and the fuel cell capacity is in the range of 0–3 kW in order to obtain optimal integration with the photovoltaic system to get maximum renewable energy fraction utilization. The findings indicate that using fuel cells powered by hydrogen generated by renewable energy systems can significantly increase self-consumption and self-sufficiency. The annual results showed that the use of 2.5 kW fuel cells can increase renewable fraction utilization from 0.622 to 0.918 with a 2.5 kW fuel cell, and energy self-consumption can reach 3338.2 kWh/year, an increase of 98.4%, and energy self-sufficiency can reach 3218.8 kWh/year, an increase of 94.41%. The results obtained demonstrate that the proposed photovoltaic fuel cell energy system provides a viable option to run semi-autonomous or fully autonomous applications in a self-sustaining medium at a percentage of 95%. Furthermore, the economic aspect is analysed for the optimal system configuration.     

Modernizing the chemical engineering curriculum via a student-centered framework that promotes technical,professional, and technology expertise skills: The case of unit operations

The development of a comprehensive set of skills, including technical, professional, and technology expertise, is critical to succeeding in the increasingly competitive global job marketplace. We proposed to develop such skills in our junior students (third year) via a flipped-classroom approach, a PO-PBL problem, and interactive e-learning tools. The intervention was implemented in the core course of Unit Operations and led to an increase in the students’ perception of the development of teamwork and people-related skills. Despite the benefits of promoting student learning, our intervention revealed that we still need to conduct work to approach more robust peer-to-peer interactions and connectedness. In this regard, students showed a marked tendency to have superficial discussions, which reflected their inability to develop superior emotional connections with peers. This is critical to promote complex thinking and ideation as well as continued engagement with the course contents and will be the focus of our future work.     

Experiment research on mix design and early mechanical performance of alkali-activated slag using response surface methodology (RSM)

To enhance the quality of alkali-activated slag (AAS) materials, scientific and efficient mix design method is preferred. This paper presents an optimization of AAS materials using Response Surface Methodology (RSM). Three factors related to early strength such as modulus (n), concentration of alkali activator (CAA) and liquid–solid ratio (LSR) were investigated. Specimens with different mix ratios were prepared based on RSM design. The early mechanical performance was assessed, after 2 or 3 h of curing. Then response surface models were established and the effect law of each factor was systemically analyzed. The result shows that both n and CAA have a significant effect on the early strength, while LSR affects slightly. By adjusting the mix design parameters, the early performance of AAS can be effectively improved. This study verifies that RSM is efficient in the preparation of AAS and it can control the early strength of AAS accurately.     

An improved distribution network reconfiguration method based on minimum spanning tree algorithm and heuristic rules

This paper presents an improved distribution network reconfiguration method with the goal to minimize active power loss. The proposed method combines the minimum spanning tree (MST) algorithm and improved heuristic rules. It consists of three procedures. The first procedure calculates the branch (edge) weights with bus (vertex) voltages, and then carries out preliminary optimization with MST algorithm to get a local optimal solution. The second procedure gets alternative optimal solution based on the improved heuristic rules. Then during the third procedure, the optimal solution can generally be obtained through correcting the results. The algorithm does not rely on the initial network topology. The local optimal solution, solved by MST algorithm, provides a favorable initial condition for the subsequent optimization procedures. Further with the improved heuristic rules, the amount of the candidate switches can be significantly reduced. Two typical test systems, 33-bus system and 69-bus system, and a real 210-bus MV utility distribution system verified the feasibility and effectiveness of the proposed method. The method has higher efficiency and can be used to the large distribution systems.     

Rotation friction pressing riveting of AZ31 magnesium alloy sheet

A kind of joining method for magnesium alloys, rotation friction pressing riveting (RFPR), is proposed in this paper. In RFPR operation, a rivet with a plug rotating at high speed is brought to contact with the riveted sheets, generating frictional heat between the rivet and riveted sheets, which softens the sheet materials and enables the rivet to be drilled into the sheets under reduced force. When fully inserted, the rivet is stopped rotating, and the plug is immediately pressed into the shank of the rivet by a punch. The expansive deformation of the rivet shank occurs under the action of the plug, thereby forming a mechanical interlock between the rivet and the sheets to fasten the sheets together. The studies show that RFPR of AZ31 magnesium alloy sheet can be carried out at ambient temperature, and provides the joints with superior shear strength and fatigue property when compared with self-piercing riveting (SPR). The effects of the operating parameters of RFPR process on the quality of the joints were investigated in the study. The results shows that while the rivet rotation speed little affects the shear strength of RFPR joints, the punch pressure has a significant influence on the mechanical properties of the RFPR joints. A numerical analysis was also performed to understand the effect of the punch pressure on the interlock between the rivet and the sheets, and the stress and strain distribution inside the sheet materials around the rivet. The results show that the interlock increased with the punch pressure and there is residual compressive stress inside the sheet materials, which seems to explain the good fatigue property of RFPR joints observed.     

Polyaniline by new miniemulsion polymerization and the effect of reducing agent on conductivity

A new stable miniemulsion of aniline was prepared using sodium dodecyl sulphate (SDS) as the surfactant and cetyl alcohol as the cosurfactant. The oxidative polymerization reaction was initiated by ammonium peroxy disulphate (APS). At the end of the polymerization reaction polyaniline (PAni) formed was treated with stannous chloride (SnCl₂) and finally doped with p-toluene sulphonic acid (PTSA). The monomer to oxidant and polymer to dopant mole ratio were optimized. Maximum conductivity is obtained with monomer to oxidant mole ratio1:1 and polymer to dopant mole ratio 1:0.5. There is a decrease in particle size and increase in the solubility in miniemulsion process. Dramatic increase in the conductivity is due to the treatment with SnCl_2. Part of the pernigraniline (PNB) form of PAni formed was reduced by SnCl₂ to emeraldine base (EB) form having higher conductivity. Plausible reduction mechanism with SnCl₂ is proposed. The conduction mechanism is explained using EPR measurement. The reason for difference in conductivity of different forms of PAni is explained with the help of polaron formation and hole theory.     

Effect of self-support friction stir welding on microstructure and microhardness of 6082-T6 aluminum alloy joint

In this paper, 5-mm-thick 6082-T6 aluminum alloy was joined by means of self-support friction stir welding (SSFSW). Here we report the grain structure and second phase particles in various regions including the welding nugget zone (WNZ), thermo-mechanically affected zone (TMAZ), and heat affected zone (HAZ). In the upper part of the joint, microhardness in the TMAZ in proximity of the UWNZ was the highest (average 89.4 HV) due to the severe plastic deformation. The similar result was also found in the lower part of the SSFSW joint. The microstructural development in each region was a strong function of the local thermo-mechanical cycle experienced during welding. Some coarse equiaxed grains which were produced in incomplete dynamic recrystallization process and dissolution of some precipitates have been observed in TMAZ. The HAZ retained the same grain structure as the base material, however, the grain size decreased with increasing distance of the weld centerline.