Influence of temperature control limits on passively cooled computing system performance
Passively-cooled electronic systems such as tablet computers and cell phones commonly are thermally limited by the allowable touch temperature of their surfaces. These systems typically cannot cool maximum processor power in steady state and simultaneously meet surface temperature restrictions. The primary surface temperature control method for thin mobile devices is to limit power, typically resulting in lower computing performance. Improved thermal designs allow higher power dissipation and therefore increased computing performance. Thermal and mechanical design engineers typically operate in terms of temperature for a given power, and this is not usually translated to computing performance. It can be difficult to justify a better thermal design if it is not quantified in its utility to the user. This paper quantifies the tradeoffs between thermal solution performance/temperature control limits and computing performance for two tablet computers and one cell phone that all use the same type of SoC processor.
Package level thermal analysis of backside power delivery network (BS-PDN) configurations
This paper presents a thermal modeling analysis of the impact of the introduction of a backside power delivery network (BS-PDN) and assesses the trade-off between the beneficial and detrimental thermal consequences of this BS-PDN. In the BS-PDN concept, the power delivery network is moved to the backside of the chip, which enables enhanced system performance, increased chip-area utilization and reduced fine metal pitch BEOL complexity. The connectivity between the backside metals of the PDN and the transistors is provided by means of micro or nano through-Si vias, which requires an extreme thinning of the Si substrate. The potential self-heating issue due to this substrate thinning is the main thermal concern for the backside PDN concept. This paper focuses on the thermal modeling study for a TSV-last BS-PDN concept, for which the TSVs through the Si substrate are processed in the last step, after the processing of the front-end and power rails. A unit cell thermal finite element model of the via-last BS-PDN test case is used with size dependent thermal properties, derived from dedicated nanoscale Monte Carlo simulations. The simulation studies assess the thermal impact of the Si substrate thickness, the backside metals, and the density of the µTSVs.
Parboiled rice effluent: A wastewater niche for microalgae and cyanobacteria with growth coupled to comprehensive remediation and phosphorus biofertilization
Abstract The potential of microalgae and cyanobacteria for bioremediation of wastewater by nutrient uptake combined with simultaneous biomass production is a well recognized perception of today's world. The present study illustrates the treatment of a highly polluted wastewater generated during parboiling of paddy in rice mill industries, widely operational in developing countries where rice is the staple food crop, with the help of microalgal and cyanobacterial isolates capable of growing at high rates in parboiled rice mill effluent (RME). This endeavor leads to comprehensive bioremediation of the said effluent and subsequent use of the harvested biomass as slow release phosphorus biofertilizers and the treated effluent for crop irrigation. The RME-acclimatized algal consortium demonstrated highest growth in terms of fresh weight and greatest remediation efficiency at the end of 36 days' treatment of RME, with 93.9% phosphorus and 100% ammonia-nitrogen removal, 98.7%, 91.6% and 93.5% reduction in biological oxygen demand, chemical oxygen demand and total dissolved solid, respectively, and an increment of 186 ± 0.3 mg L − 1 dissolved oxygen, bringing down the pollutants level well below the discharge limits suggested by Central Pollution Control Board, India. Additionally, microalgae in the consortium aggregated in clumps spontaneously in presence of the filaments of Phormidium sp. facilitating easy harvest. The RME-acclimatized algal consortium demonstrated highest accumulation of polyphosphate (poly-P) (0.76 ± 0.01% of dry weight) as well as highest release of phosphorus in non-sterile soil emphasizing the essential role of soil phosphorus solubilizing organisms to leach soluble phosphorus from the insoluble poly-P present in the biomass. The rice seedlings watered with treated RME also showed improved growth effect on shoot height and leaf width. The study results establish the suitability of RME as an excellent growth media for microalgae and cyanobacteria.