Elite Social Movements and the State: A Case Study of the Committee on the Present Danger

http://deepblue.lib.umich.edu/bitstream/2027.42/51183/1/416.pd

Variational description of the dimensional cross-over in the array of coupled one-dimensional conductors

Variational wave function is proposed to describe electronic properties of an array of one-dimensional conductors coupled by transverse hopping and interaction. For weak or intermediate in-chain interaction the wave function has the following structure: Tomonaga-Luttinger bosons with momentum higher then some variational quantity \tilde\Lambda are in their ground state while other bosons (with |k|<\tilde\Lambda) form kinks -- fermion-like excitations of the Tomonaga-Luttinger boson field. Nature of the ground state for this quasiparticles can be determined by solving three dimensional effective hamiltonian. Since the anisotropy of the effective hamiltonian is small the use of the mean field theory is justified. For repulsive interaction possible phases are density wave and p-wave superconductivity. Our method allows us to calculate the low-energy part of different electronic Green's functions. In order to do that it is enough to apply standard perturbation theory technique to the effective hamiltonian. When the in-chain interaction is strong \tilde\Lambda vanishes and no fermionic excitation is present in the system. In this regime the dynamics is described by transversally coupled Tomonaga-Luttinger bosons

Modelling and evaluation of a biomethane truck for transport performance and cost

This article compares a conventional diesel-fuelled heavy goods vehicle with one that runs on compressed gas (CG): either Compressed Natural Gas (CNG) or biomethane. It includes an evaluation of the transport performance, carbon emissions, and total costs. 41 CG trucks were trialled by a supermarket, delivering goods from their distribution centre. One of the vehicles was instrumented with a gas flow meter, which measured the gas consumption, and a smartphone based data logger, which collected data from the truck's Fleet Management System (FMS) interface. Similarly, a baseline diesel truck was instrumented. Based on the measurements that were collected in-service, fuel consumption models were developed and validated. Using the validated models, the CG and diesel trucks were compared for their transport performance, costs and carbon emissions. In addition, the vehicles were evaluated using telematics data and refuelling data from a year of transport operations for all 41 CG trucks and 9 diesel trucks. The results show that for a tonne.km of in-service (mostly long haul) transport work, compared to the diesel trucks, the CG trucks spend on average 22% more energy and their fuel cost is 30% lower for biomethane. When running on CNG, their equivalent carbon emissions is 10% lower than the baseline diesel, and when running on biomethane, their equivalent carbon emissions is 78% lower. Compared to long haul, the benefits are lower for regional operations, and are the lowest for city centre operations where using CNG, the CG truck's equivalent carbon emissions is higher than the diesel truck

Catalyst nanoparticle growth dynamics and their influence on product morphology in a CVD process for continuous carbon nanotube synthesis

Extrapolating the properties of individual CNTs into macro-scale CNT materials using a continuous and cost effective process offers enormous potential for a variety of applications. The floating catalyst chemical vapor deposition (FCCVD) method discussed in this paper bridges the gap between generating nano- and macro-scale CNT material and has already been adopted by industry for exploitation. A deep understanding of the phenomena occurring within the FCCVD reactor is thereby key to producing the desired CNT product and successfully scaling up the process further. This paper correlates information on decomposition of reactants, axial catalyst nanoparticle dynamics and the morphology of the resultant CNTs and shows how these are strongly related to the temperature and chemical availability within the reactor. For the first time, in-situ measurements of catalyst particle size distributions coupled with reactant decomposition profiles and a detailed axial SEM study of formed CNT materials reveal specific domains that have important implications for scale-up. A novel observation is the formation, disappearance and reformation of catalyst nanoparticles along the reactor axis, caused by their evaporation and re-condensation and mapping of different CNT morphologies as a result of this process.The authors thank Qflo Ltd for providing funding towards this research, C. Hoecker additionally thanks Churchill College Cambridge for financial support, M. Bajada gratefully acknowledges financial support through the 'Master it! Scholarship Scheme'.This is the accepted manuscript. The final version is available at http://dx.doi.org/10.1016/j.carbon.2015.09.05

Interchain coherence of coupled Luttinger liquids at all orders in perturbation theory

We analyze the problem of Luttinger liquids coupled via a single-particle hopping \tp and introduce a systematic diagrammatic expansion in powers of \tp. An analysis of the scaling of the diagrams at each order allows us to determine the power-law behavior versus \tp of the interchain hopping and of the Fermi surface warp. In particular, for strong interactions, we find that the exponents are dominated by higher-order diagrams producing an enhanced coherence and a failure of linear-response theory. Our results are valid at any finite order in \tp for the self-energy.Comment: 4 pages, 3 ps figures. Accepted for publication in Phys. Rev. Let

Dimensional crossover and metal-insulator transition in quasi-two-dimensional disordered conductors

We study the metal-insulator transition (MIT) in weakly coupled disordered planes on the basis of a Non-Linear Sigma Model (NL$\sigma$M). Using two different methods, a renormalization group (RG) approach and an auxiliary field method, we calculate the crossover length between a 2D regime at small length scales and a 3D regime at larger length scales. The 3D regime is described by an anisotropic 3D NL$\sigma$M with renormalized coupling constants. We obtain the critical value of the single particle interplane hopping which separates the metallic and insulating phases. We also show that a strong parallel magnetic field favors the localized phase and derive the phase diagram.Comment: 16 pages (RevTex), 4 poscript figure

Vanadium Dioxide Cathodes for High-Rate Photo-Rechargeable Zinc-Ion Batteries

Photovoltaics are an important source of renewable energy, but due the intermittent nature of insolation, solar cells usually need to be connected to rechargeable batteries, electrochemical capacitors or other energy storage devices, which adds to the complexity and cost of these systems. In this work, we report a cathode design for photo-rechargeable zinc-ion batteries (photo-ZIBs) that is inherently capable of harvesting sunlight to recharge without the need for external solar cells. The proposed photocathodes comprising a composite of vanadium dioxide nanorods and reduced graphene oxide, are engineered to provide the necessary charge separation and storage for photocharging under illumination. The photo-ZIBs achieve gravimetric capacities of ~ 282 mAh g-1 in the dark and ~ 315 mAh g-1 under illumination, at 200 mA g-1, demonstrating the use of light not only to charge the deceives, but additionally to enhance their capacity. The photo-ZIBs also demonstrate enhanced high-rate capabilities under illumination, as well as a capacity retention of ∼ 90% over 1000 cycles. The proposed photo-ZIBs demonstrate a promising new technology for addressing energy poverty, due to their high performance and inherent cost-efficiency and safety.Newton International Fellowship-Royal Society (UK) grant NIF∖R1∖181656 ERC Consolidator grant MIGHTY - 866005 EPSRC Graphene CDT EP/L016087/

Spin Gap and Superconductivity in Weakly Coupled Ladders: Interladder One-particle vs. Two-particle Crossover

Effects of the interladder one-particle hopping, $t_{\perp}$, on the low-energy asymptotics of a weakly coupled Hubbard ladder system have been studied, based on the perturbative renormalization-group approach. We found that for finite intraladder Hubbard repulsion, $U$, there exists a crossover value of the interladder one-particle hopping, $t_{\perp c}$. For $0<t_{\perp}<t_{\perp c}$, the spin gap metal (SGM) phase of the isolated ladder transits at a finite transition temperature, $T_{c}$, to the d-wave superconducting (SCd) phase via a two-particle crossover. In the temperature region, $T<T_{c}$, interladder coherent Josephson tunneling of the Cooper pairs occurs, while the interladder coherent one-particle process is strongly suppressed. For $t_{\perp c}<t_{\perp}$, around a crossover temperature, $T_{cross}$, the system crosses over to the two-dimensional (2D) phase via a one-particle crossover. In the temperature region, $T<T_{cross}$, the interladdercoherent band motion occurs.Comment: 4 pages, 5 eps figures, uses jpsj.st