Gerhard Ingmar Meijer

Electrical-stress-induced conductivity increase in SrTiO3 films

The charge transport of polycrystalline SrTiO3 films doped with Cr is investigated by means of temperature- and electric-field-dependent current measurements. In particular, the effect of electrical stress on the conduction mechanism is analyzed to understand the forming process of samples exhibiting resistance-switching phenomena. The temperature dependence of the conductivity can be described with the variable-range hopping model. The electrical-stress-induced conductivity increase of SrTiO3:Cr films is accompanied by a change of the temperature dependence corresponding to a significant increase of the density of localized states.

Direct Waste Heat Utilization From Liquid-Cooled Supercomputers

Chip microscale liquid-cooling reduces conductive and convective resistance thereby improving the efficiency of datacenters by allowing coolant temperatures above the free cooling limit in all climates. This eliminates the need for chillers and allows the thermal energy to be re-used in cold climates. Replacing the combustion processes for secondary users with recycled heat from the datacenter effectively eliminates carbon dioxide emission during the winter season and reduces operating cost throughout the year. The energy balance of emission-reduced datacenters is compared with a classical air cooled datacenter, a datacenter with free cooling in a cold climate zone, and a datacenter with chiller-mediated energy re-use. Hot water cooled datacenters reduce the effective energy cost by almost a factor of two compared to a current datacenter and reduce the carbon footprint by an even larger factor. Our energy re-use concept has been demonstrated in terms of cost and energy savings in a 60°C liquid cooled supercomputer. Additional alternative energy re-use schemes in hot climates for desalination and adsorption cooling allow close to full use of datacenter heat in all climates and all seasons. Output temperatures for these applications compared to space heating need to be 10–20°C higher which becomes possible through hotspot adapted cooling that eliminates mixing of fluids with different temperatures. In addition, interlayer cooled chip stacks allow double sided hotspot optimized cooling even closer to the heat source with low flow rates and low pumping power. This improves the large efficiency gain that becomes possible through 3D chip stacking.Copyright

Zero-emission datacenters and 3D chip stacking

Summary form only given. Cloud computing has today become a widespread practice for the provisioning of IT services. Cloud infrastructures provide the means to lease computational resources on demand, typically on a pay per use or subscription model and without the need for significant capital investment into hardware. With enterprises seeking to migrate their services to the cloud to save on deployment costs, cater for rapid growth or generally relieve themselves from the responsibility of maintaining their own computing infrastructures, a diverse range of services is required to help fulfil business processes. In this talk, we discuss some of the challenges involved in deploying and managing an ecosystem of loosely coupled cloud services that may be accessed through and integrate with a wide range of devices and third party applications. In particular, we focus on how projects such as OpenStack are accelerating the evolution towards a federated cloud service ecosystem. We also examine how the portfolio of existing and emerging standards such as OAuth and the Simple Cloud Identity Management framework can be exploited to seamlessly incorporate cloud services into business processes and solve the problem of identity and access management when dealing with applications exploiting services across organisational boundaries.