Big Data Dreams and Reality in Shenzhen: An Investigation of Smart City Implementation in China

Chinese cities are increasingly using digital technologies to address urban problems and govern society. However, little is known about how this digital transition has been implemented. This study explores the introduction of digital governance in Shenzhen, one of China's most advanced smart cities. We show that, at the local level, the successful implementation of digital systems faces numerous hurdles in long-standing data management and bureaucratic practices that are at least as challenging as the technical problems. Furthermore, the study finds that the digital systems in Shenzhen entail a creeping centralisation of data that potentially turns lower administrative government units into mere users of the city-level smart platforms rather than being in control of their own data resources. Smart city development and big data ambitions thereby imply shifting stakeholder relations at the local level and also pull non-governmental stakeholders, such as information technology companies and research institutions, closer to new data flows and smart governance systems. The findings add to the discussion of big data-driven smart systems and their implications for governance processes in an authoritarian context

Flavors in an expanding plasma

We consider the effect of an expanding plasma on probe matter by determining time-dependent D7 embeddings in the holographic dual of an expanding viscous plasma. We calculate the chiral condensate and meson spectra including contributions of viscosity. The chiral condensate essentially confirms the expectation from the static black hole. For the meson spectra we propose a scheme that is in agreement with the adiabatic approximation. New contributions arise for the vector mesons at the order of the viscosity terms.Comment: 15 pages, 7 figures; v2: accepted for publ. in Phys. Rev. D; revised mass definition agrees with adiabatic approximatio

25 years QUENCH program. Main results of the QUENCH bundle tests

In the framework of the QUENCH program at KIT, over the past 22 years, 21 bundle tests were performed under severe accident conditions with different cladding materials. Additionally, 7 QUENCH-LOCA bundle tests with fresh and pre-hydrogenated different cladding materials (Zry-4, M5®, opt. ZIRLO™) were performed according to a temperature/time-scenario typical for a LBLOCA in a German PWR. Main purposes of severe accident tests were hydrogen source term, as well as investigation of phenomena on melt relocation, debris, and aerosol formation. Concerning the hydrogen source term, six parameters, enhancing hydrogen production during reflood, have been identified: 1) low reflood flow rates < 1 g/s/rod; 2) breakaway effect with weakness and spallation of protective oxide layer; 3) steam starvation; 4) nitride formation by air ingress with formation of very porous oxide layer during following reflood; 5) high temperatures with melt relocation outside claddings and intensive melt oxidation; 6) eutectic interactions between B4C, stainless steel and Zircaloy-4 leading to low melting point. Post-test tensile experiments performed in the framework of the QUENCH-LOCA program evidenced fracture at hydrogen bands (formed during secondary hydriding) for claddings with local hydrogen concentrations >1500 wppm

25 years QUENCH program. Highlights of separate-effects tests

The main objective of the QUENCH program at KIT is the investigation of the hydrogen source term and materials interactions during LOCA and the early phase of severe accidents including reflood. Bundle experiments as well as separate-effects tests are conducted to provide data for the development of models and the validation of severe fuel damage code systems. In the framework of the QUENCH jubilee session highlights of 25 years separate-effects tests were presented in this talk. The focus of the QUENCH SETs are clearly on high-temperature (> 600°C) oxidation and materials interactions of zirconium alloys (cladding), absorber materials, and structure materials in well-defined atmospheres. In this context, hydrogen release and uptake by the Zr alloy cladding materials was investigated as well. More recent experiments concentrated on the high-temperature behavior of new ATF cladding materials. The main takeaways from this presentation were: • Zirconium oxidation at high temperatures is a source of significant release of hydrogen and heat affecting nuclear accident progression. • Oxidation is not always of parabolic kinetics and may be strongly dependent on experimental boundary conditions. • Eutectic interactions may lead to melt formation far below the melting points of the individual materials. These melts may slowly relocate and severely oxidize. • ATF claddings could strongly decrease the risk of temperature escalation and hydrogen detonation during BDB accidents as well as significantly increase the coping time for AMMs. • Most experimental results were used to improve models, especially in cooperation with IBRAE, GRS, and IRSN as well as internally by H. Steiner and M. Große