Simulation of Fluid Flow During Direct Synthesis of H2_{2}O2_{2} in a Microstructured Membrane Reactor

A microstructured membrane reactor has been developed to overcome the safety and productivity challenge of the direct synthesis of hydrogen peroxide. A single membrane is employed for separate, continuous dosage of the gaseous reactants hydrogen and oxygen to the solid catalyst present in the aqueous solvent. Using a custom OpenFOAM® model, the impact of catalyst‐coated static mixers with different mixer geometries is studied. It is demonstrated that the custom fluid guiding elements outperform the investigated commercial static mixer under the flow conditions relevant to this application

Investigation of mass transport processes in a microstructured membrane reactor for the direct synthesis of hydrogen peroxide

Microstructured membrane reactors present a promising approach to master the productivity and safety challenges during the direct synthesis of hydrogen peroxide. However, various mass transport processes occur in this complex system. In order to gain a deeper understanding of these processes, the saturation and desaturation behaviour of the liquid reaction medium with the gaseous reactants is investigated experimentally to examine possible cross-contamination. Moreover, the employed PDMS membrane’s permeances to hydrogen and oxygen are researched at different pressures, by using a variable-pressure/constant-volume setup for the behaviour at ambient pressure and a constant-pressure/variable-volume setup for the behaviour at elevated pressures. A mathematical model in MATLAB is applied to simulate the results. It is shown that a certain desaturation of the gasses through the membrane occurs, and the results are underlined by the modelled ones using a solution-diffusion model in MATLAB. Thus a constant flushing of the gas channels of the reactor is required for safety reasons. Moreover, the measured permeance values indicate that the species transport is mainly limited by the diffusion in the liquid phase and not the membrane resistance

Making Password Authenticated Key Exchange Suitable For Resource-Constrained Industrial Control Devices

Connectivity becomes increasingly important also for small embedded systems such as typically found in industrial control installations. More and more use-cases require secure remote user access increasingly incorporating handheld based human machine interfaces, using wireless links such as Bluetooth. Correspondingly secure operator authentication becomes of utmost importance. Unfortunately, often passwords with all their well-known pitfalls remain the only practical mechanism. We present an assessment of the security requirements for the industrial setting, illustrating that offline attacks on passwords-based authentication protocols should be considered a significant threat. Correspondingly use of a Password Authenticated Key Exchange protocol becomes desirable. We review the signif-icant challenges faced for implementations on resource-constrained devices. We explore the design space and shown how we succeeded in tailoring a partic-ular variant of the Password Authenticated Connection Establishment (PACE) protocol, such that acceptable user interface responsiveness was reached even for the constrained setting of an ARM Cortex-M0+ based Bluetooth low-energy transceiver running from a power budget of 1.5 mW without notable energy buffers for covering power peak transients

Hyper-precarious lives : Migrants, work and forced labour in the Global North

This paper unpacks the contested inter-connections between neoliberal work and welfare regimes, asylum and immigration controls, and the exploitation of migrant workers. The concept of precarity is explored as a way of understanding intensifying and insecure post-Fordist work in late capitalism. Migrants are centrally implicated in highly precarious work experiences at the bottom end of labour markets in Global North countries, including becoming trapped in forced labour. Building on existing research on the working experiences of migrants in the Global North, the main part of the article considers three questions. First, what is precarity and how does the concept relate to working lives? Second, how might we understand the causes of extreme forms of migrant labour exploitation in precarious lifeworlds? Third, how can we adequately theorize these particular experiences using the conceptual tools of forced labour, slavery, unfreedom and precarity? We use the concept of ‘hyper-precarity’ alongside notions of a ‘continuum of unfreedom’ as a way of furthering human geographical inquiry into the intersections between various terrains of social action and conceptual debate concerning migrants’ precarious working experiences

FourQ on Embedded Devices with Strong Countermeasures Against Side-Channel Attacks

This work deals with the energy-efficient, high-speed and high-security implementation of elliptic curve scalar multiplication, elliptic curve Diffie-Hellman (ECDH) key exchange and elliptic curve digital signatures on embedded devices using FourQ and incorporating strong countermeasures to thwart a wide variety of side-channel attacks. First, we set new speed records for constant-time curve-based scalar multiplication, DH key exchange and digital signatures at the 128-bit security level with implementations targeting 8, 16 and 32-bit microcontrollers. For example, our software computes a static ECDH shared secret in 6.9 million cycles (or 0.86 seconds @8MHz) on a low-power 8-bit AVR microcontroller which, compared to the fastest Curve25519 and genus-2 Kummer implementations on the same platform, offers 2x and 1.4x speedups, respectively. Similarly, it computes the same operation in 496 thousand cycles on a 32-bit ARM Cortex-M4 microcontroller, achieving a factor-2.9 speedup when compared to the fastest Curve25519 implementation targeting the same platform. A similar speed performance is observed in the case of digital signatures. Second, we engineer a set of side-channel countermeasures taking advantage of FourQ\u27s rich arithmetic and propose a secure implementation that offers protection against a wide range of sophisticated side-channel attacks, including differential power analysis (DPA). Despite the use of strong countermeasures, the experimental results show that our FourQ software is still efficient enough to outperform implementations of Curve25519 that only protect against timing attacks. Finally, we perform a differential power analysis evaluation of our software running on an ARM Cortex-M4, and report that no leakage was detected with up to 10 million traces. These results demonstrate the potential of deploying FourQ on low-power applications such as protocols for the Internet of Things