Using optical, TEM, and ultrafast electron diffraction experiments we find that single crystal VO(2) microbeams gently placed on insulating substrates or metal grids exhibit different behaviors, with structural and metal-insulator transitions occurring at the same temperature for insulating substrates, while for metal substrates a new monoclinic metal phase lies between the insulating monoclinic phase and the metallic rutile phase. The structural and electronic phase transitions in these experiments are strongly first order and we discuss their origins in the context of current understanding of multiorbital splitting, strong correlation effects, and structural distortions that act cooperatively in this system.

We present a pedagogical discussion of Similarity Renormalization Group (SRG) methods, in particular the In-Medium SRG (IMSRG) approach for solving the nuclear manybody problem. These methods use continuous unitary transformations to evolve the nuclear Hamiltonian to a desired shape. The IMSRG, in particular, is used to decouple the ground state from all excitations and solve the many-body Schrödinger equation. We discuss the IM-SRG formalism as well as its numerical implementation, and use the method to study the pairing model and infinite neutron matter. We compare our results with those of Coupled cluster theory (Chapter 8), Configuration-Interaction Monte Carlo (Chapter 9), and the SelfConsistent Green's Function approach discussed in Chapter 11. The chapter concludes with an expanded overview of current research directions, and a look ahead at upcoming developments.

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LED with the advantages of high brightness, long-lifetime, energy-saving and environmental protection is widely used in varieties of fields especially the lighting industry. Thermal performance is the key to high power LED lighting integration, which has got broad concern and research. And the thermal management and thermal reliability has been improved quickly in recent years. While, more and more lighting tools will be used outdoors at the temperature of twenty degrees below zero in winter and even lower in very frigid region, the corresponding technical requirements of the LED are not yet fully understood. Aiming at the special issue above, constant and variable temperature loading test with wide range of temperature are designed and implemented in this paper. In the accelerated test, the temperature cycles from 120 above zero to 50 minus degrees, and the performance parameters such as forward voltage and relative light intensity were analyzed, the relationship between the temperature and forward voltage, relative light intensity were developed at the same time. And then, ANSYS software was applied to simulate the extreme cold temperature accelerated aging test.Meanwhile, the stress and strain in extremely cold temperatures were predicted. Ultimately, based on statistical analysis of experimental data, an LED failure mode and the corresponding failure mechanism would be proposed in the condition of extremes low temperature. The technical requirements to prevent failure LED lamps at low temperatures were also reviewed.