A New Model for Evaluating the Future Options of Integrating Ground Source Heat Pumps in Building Construction

Decision-making for effective infrastructure integration is challenging because the performances of long-lasting objects often depends on conditions which are either outside the control of the designer or difficult to foresee at the design stage. In this paper we examine a new approach to estimating the range of cost-effective solutions for integrating the construction/retrofit of two or more different types of infrastructure. Infrastructure integration has many perceived benefits, but also faces serious new challenges and doubts from practitioners, particularly in sectors with complex construction process, long asset lives, uncertain cost parameters, and slow and unwieldy decision-making, such as is common with civil engineering works. We test all main options in integrating a ground source heat pump (GSHP) system with the construction and retrofit of an archetypal, office building. A new simulation model is developed and parameterized using actual data in the UK. We incorporate unavoidable uncertainties and randomness in how the decisions are triggered, and test the effectiveness of proactive measures to embed future options. The model highlights how sensitive the range of cost-effective solutions is to the setting of renewable energy incentives, discount rates, technical performance and life-cycle asset management of interdependent infrastructure. This points to a clear need for establishing appropriate regulatory standards. We expect this model to find increasing applications in the planning and designing of integrated complexes of buildings, transport facilities, renewable energy supply, water supply and waste management in dense urban areas, which are an increasingly key part of sustainable urban development

Thermodynamics of lattice QCD with 2 flavours of colour-sextet quarks: A model of walking/conformal Technicolor

QCD with two flavours of massless colour-sextet quarks is considered as a model for conformal/walking Technicolor. If this theory possess an infrared fixed point, as indicated by 2-loop perturbation theory, it is a conformal(unparticle) field theory. If, on the other hand, a chiral condensate forms on the weak-coupling side of this would-be fixed point, the theory remains confining. The only difference between such a theory and regular QCD is that there is a range of momentum scales over which the coupling constant runs very slowly (walks). In this first analysis, we simulate the lattice version of QCD with two flavours of staggered quarks at finite temperatures on lattices of temporal extent $N_t=4$ and 6. The deconfinement and chiral-symmetry restoration couplings give us a measure of the scales associated with confinement and chiral-symmetry breaking. We find that, in contrast to what is seen with fundamental quarks, these transition couplings are very different. $\beta=6/g^2$ for each of these transitions increases significantly from $N_t=4$ and $N_t=6$ as expected for the finite temperature transitions of an asymptotically-free theory. This suggests a walking rather than a conformal behaviour, in contrast to what is observed with Wilson quarks. In contrast to what is found for fundamental quarks, the deconfined phase exhibits states in which the Polyakov loop is oriented in the directions of all three cube roots of unity. At very weak coupling the states with complex Polyakov loops undergo a transition to a state with a real, negative Polyakov loop.Comment: 21 pages, 9 figures, Revtex with postscript figures. One extra reference was added; text is unchanged. Corrected typographical erro

Observation of Andreev Surface Bound States in the 3-K phase Region of Sr_2RuO_4

The tunneling spectrum of the superconducting phase with T_c ~ 3.0 K has been measured in the Ru-embedded region of Sr_2RuO_4 using cleaved junctions. A sharp zero-bias conductance peak (ZBCP) has been observed below 3 K. All characteristics of this ZBCP suggest that it originates from Andreev surface bound states, indicating that the pairing in the 3-K phase is also non-s-wave. Below the bulk T_c of Sr_2RuO_4 (~1.5 K), a bell-shaped ZBCP was found. This supports that there is a phase transition in the 3-K phase region near the bulk T_c.Comment: 4 pages, to appear in Phys. Rev. Lett. 87 (2001

Thermodynamics of lattice QCD with 2 sextet quarks on N_t=8 lattices

We continue our lattice simulations of QCD with 2 flavours of colour-sextet quarks as a model for conformal or walking technicolor. A 2-loop perturbative calculation of the $\beta$-function which describes the evolution of this theory's running coupling constant predicts that it has a second zero at a finite coupling. This non-trivial zero would be an infrared stable fixed point, in which case the theory with massless quarks would be a conformal field theory. However, if the interaction between quarks and antiquarks becomes strong enough that a chiral condensate forms before this IR fixed point is reached, the theory is QCD-like with spontaneously broken chiral symmetry and confinement. However, the presence of the nearby IR fixed point means that there is a range of couplings for which the running coupling evolves very slowly, i.e. it 'walks'. We are simulating the lattice version of this theory with staggered quarks at finite temperature studying the changes in couplings at the deconfinement and chiral-symmetry restoring transitions as the temporal extent ($N_t$) of the lattice, measured in lattice units, is increased. Our earlier results on lattices with $N_t=4,6$ show both transitions move to weaker couplings as $N_t$ increases consistent with walking behaviour. In this paper we extend these calculations to $N_t=8$. Although both transition again move to weaker couplings the change in the coupling at the chiral transition from $N_t=6$ to $N_t=8$ is appreciably smaller than that from $N_t=4$ to $N_t=6$. This indicates that at $N_t=4,6$ we are seeing strong coupling effects and that we will need results from $N_t > 8$ to determine if the chiral-transition coupling approaches zero as $N_t \rightarrow \infty$, as needed for the theory to walk.Comment: 21 pages Latex(Revtex4) source with 4 postscript figures. v2: added 1 reference. V3: version accepted for publication, section 3 restructured and interpretation clarified. Section 4 future plans for zero temperature simulations clarifie

Global Models of Planet Formation and Evolution

Despite the increase in observational data on exoplanets, the processes that lead to the formation of planets are still not well understood. But thanks to the high number of known exoplanets, it is now possible to look at them as a population that puts statistical constraints on theoretical models. A method that uses these constraints is planetary population synthesis. Its key element is a global model of planet formation and evolution that directly predicts observable planetary properties based on properties of the natal protoplanetary disk. To do so, global models build on many specialized models that address one specific physical process. We thoroughly review the physics of the sub-models included in global formation models. The sub-models can be classified as models describing the protoplanetary disk (gas and solids), the (proto)planet (solid core, gaseous envelope, and atmosphere), and finally the interactions (migration and N-body interaction). We compare the approaches in different global models and identify physical processes that require improved descriptions in future. We then address important results of population synthesis like the planetary mass function or the mass-radius relation. In these results, the global effects of physical mechanisms occurring during planet formation and evolution become apparent, and specialized models describing them can be put to the observational test. Due to their nature as meta models, global models depend on the development of the field of planet formation theory as a whole. Because there are important uncertainties in this theory, it is likely that global models will in future undergo significant modifications. Despite this, they can already now yield many testable predictions. With future global models addressing the geophysical characteristics, it should eventually become possible to make predictions about the habitability of planets.Comment: 30 pages, 16 figures. Accepted for publication in the International Journal of Astrobiology (Cambridge University Press

Thermal transport in the hidden-order state of URu2_{2}Si2_{2}

We present a study of thermal conductivity in the normal state of the heavy-fermion superconductor URu$_{2}$Si$_{2}$. Ordering at 18K leads to a steep increase in thermal conductivity and (in contrast with all other cases of magnetic ordering in heavy-fermion compounds) to an enhancement of the Lorenz number. By linking this observation to several other previously reported features, we conclude that most of the carriers disappear in the ordered state and this leads to a drastic increase in both phononic and electronic mean-free-path.Comment: 5 pages including 4 figure

Trend-Breaking Influences of Built Form on Travel in UK Cities Evidence from New Quantifications of Within- and Between-Built-Form Variations

Using a consistent time series of 11 years (1,137,259 sample trips, 2002 to 2012) and all main variables from the UK National Travel Survey, this paper develops a novel structural equation model (SEM) with random intercepts to gain new insights into the influences of built-form characteristics on travel behavior. With simultaneous modeling of car ownership as an endogenous variable in determining influences on travel outcomes and allowing SEM intercepts to vary across built-form categories, one controls for car ownership endogeneity while measuring within- and between-built-form variations through incorporating random intercepts in the model. The new models unambiguously decompose the self-selection and spatial sorting of household effects from the influence of the built-form characteristics. This research further investigates trend-breaking influences by generating pre-2007 and post-2007 model outputs with a multi-time-period structure. The new quantifications are built on more-robust statistical theories than hitherto and, thus, imply significant implications on how to interpret the effect of recent transformations in UK inner cities. The method can also be used to produce a regular and timely update on any shifts in the influences on travel and provide feedback for land use planning and integrated built-form and transport interventions.Kaveh Jahanshahi acknowledges the support of an Engineering and Physical Sciences Research Council doctoral training grant, and Ying Jin acknowledges funding support from the Engineering and Physical Sciences Research Council Centre for Smart Infrastructure and Construction at Cambridge University

Propagating waves in an extremal black string

We investigate the black string in the context of the string theories. It is shown that the graviton is the only propagating mode in the (2+1)--dimensional extremal black string background. Both the dilation and axion turn out to be non-propagating modes.Comment: Minor corrections, 11 pages in ReVTeX, no figure