Dynamics of fracture in dissipative systems

Dynamics of fracture in two-dimensional systems is studied with a dissipative network model by including the local relaxation of the force field via Maxwellian viscoelasticity. In addition to disorder the fundamentals of crack formation and propagation depend on the strength of dissipation compared to the loading rate. We investigate the dynamics of a single crack and the role of stress reduction at the crack tip when dissipation is increased. As a consequence, the crack starts to propagate slowly and it reaches terminal velocity later. If the relaxation of local forces is strong enough compared with crack velocity, crack arrest takes place. For a disordered system, the presence of strong dissipation in local dynamics is reflected as ductility and as an increase in the damage, accumulated during the fracture process.Peer reviewe

Dissipative dynamic fracture of disordered systems

Breakdown of two-dimensional disordered systems is studied with a time-dependent network model. The dependence of fracture process on the local relaxation of the force field is included within the framework of Maxwellian viscoelasticity. The dynamics and characteristics of crack formation and propagation are shown to depend on disorder and relative time scales of dissipation and loading. Brittle behavior is encountered in the adiabatic limit of slow straining. At finite strain rates, the development of damage shows ductile behavior with increasing dissipation. Nucleation of cracks in various dynamical situations is discussed.Peer reviewe

Multiplexed readout of kinetic inductance bolometer arrays

Kinetic inductance bolometer (KIB) technology is a candidate for passive sub-millimeter wave and terahertz imaging systems. Its benefits include scalability into large 2D arrays and operation with intermediate cryogenics in the temperature range of 5 -- 10 K. We have previously demonstrated the scalability in terms of device fabrication, optics integration, and cryogenics. In this article, we address the last missing ingredient, the readout. The concept, serial addressed frequency excitation (SAFE), is an alternative to full frequency-division multiplexing at microwave frequencies conventionally used to read out kinetic inductance detectors. We introduce the concept, and analyze the criteria of the multiplexed readout avoiding the degradation of the signal-to-noise ratio in the presence of a thermal anti-alias filter inherent to thermal detectors. We present a practical scalable realization of a readout system integrated into a prototype imager with 8712 detectors. This is used for demonstrating the noise properties of the readout. Furthermore, we present practical detection experiments with a stand-off laboratory-scale imager.Comment: 7 pages, 6 figure

Protecting cattle feedyard workers in the Central States region: Exploring state, regional, and national data on fatal and nonfatal injuries in agriculture and the beef production sector

Working in agriculture can be dangerous. Despite ongoing efforts of Extension, animal production worker safety has not been adequately addressed. We present state, regional, and national counts and rates on fatal and nonfatal injuries in agriculture and animal production using publicly available data from the Bureau of Labor Statistics. We found that animal production had a high number of fatal injuries and a higher rate of nonfatal injuries than the average within agriculture. More needs to be done to protect livestock workers from injury. Extension professionals can play a key role in increasing safety knowledge and changing behaviors

Long-Lived Double-Barred Galaxies From Pseudo-Bulges

A large fraction of barred galaxies host secondary bars that are embedded in their large-scale primary counterparts. These are common also in gas poor early-type barred galaxies. The evolution of such double-barred galaxies is still not well understood, partly because of a lack of realistic $N$-body models with which to study them. Here we report a new mechanism for generating such systems, namely the presence of rotating pseudo-bulges. We demonstate with high mass and force resolution collisionless $N$-body simulations that long-lived secondary bars can form spontaneously without requiring gas, contrary to previous claims. We find that secondary bars rotate faster than primary ones. The rotation is not, however, rigid: the secondary bars pulsate, with their amplitude and pattern speed oscillating as they rotate through the primary bars. This self-consistent study supports previous work based on orbital analysis in the potential of two rigidly rotating bars. The pulsating nature of secondary bars may have important implications for understanding the central region of double-barred galaxies.Comment: Paper submitted to ApJ

From path dependence to policy mixes for Nordic electric mobility: lessons for accelerating future transport transitions?

We examine the problem of how to accelerate policies related to electric vehicles (EVs) in the Nordic countries Denmark, Finland, Norway and Sweden. These four Nordic countries represent an interesting collection of cases by virtue of having common decarbonization targets extending to the transport sector, interlinked electric energy systems and a joint electricity market largely based on low-carbon energy while they are open societies bent on innovation, making them well adaptable to a transition toward electric mobility. Our analytical framework drawing from transition research, lock-in and path dependency and institutionalism enables us to discern technological, institutional and behavioral mechanisms which can have both constraining and enabling effects vis-à-vis this transition by means of shaping national socio-technical systems and regimes. On this basis, we also discuss how to develop policies accelerating the transition. We find that the incumbent industries can shape policy choice through the lock-in into institutional inter-dependencies. The accumulation of social and material features, and vested interests of actors, for its part can maintain regime level inertia, impeding the transition. Yet, technological lock-in can also enable EVs, by means of learning effects from technologically interrelated wind energy projects and available infrastructure in buildings that support the EV charging needs. Overall, the complexity of path-dependent mechanisms embedded in the dominant regimes, together with the diversity of emerging policy mixes, demands attention both on the technologies and broader socio-technical systems in order to properly assess the prospects of transition toward electric mobility