Measuring Housing Affordability: Looking Beyond the Median

We draw a distinction between the concepts of purchase affordability (whether a household is able to borrow enough funds to purchase a house) and repayment affordability (the burden imposed on a household of repaying the mortgage). We operationalize this distinction in the context of a new methodology for constructing affordability measures that draws on the value-at-risk concept and takes account of the whole distribution of household income and house prices rather than just the median. Empirically we find that the distinction between purchase and repayment affordability can be pronounced. In the Sydney prime mortgage market over the period 1996 to 2006, repayment affordability deteriorated very significantly while purchase affordability remained quite stable. This difference can be attributed to the loosening of credit constraints in the mortgage market which it seems has carried through primarily into higher house prices. We also consider how median house-price-to-income ratio measures of affordability can be extended to take account of the whole distribution of income and house prices. We propose a new quantile based measure which indicates that the housing affordability problem may be systematically worse than suggested by standard median measures.Housing affordability; Affordability at risk; Affordable limit; Mortgage market; Price-to-income ratio

A continuum model for coupled stress and fluid flow in discrete fracture networks

Acknowledgments This work is a partial result of support from the US Department of Energy under project DOE-DE-343 EE0002761. This support is gratefully acknowledged. We also acknowledge the data from the University of Oklahoma and University of Texas at Austin.Peer reviewedPublisher PD

Fault zone exploitation in geothermal reservoirs: Production optimization, permeability evolution and induced seismicity

 This study employs a coupled thermal-hydrological-mechanical model to investigate the permeability evolution and fault reactivation of a critically stressed fault in geothermal reservoir. The fracture permeability sensitivity analysis for permeabilities of the fault damage zone that hydro-mechanical processes have dominating control on permeability evolution and the associated timing of slip on the fault plane for high fracture permeability. The mode of thermal sweep in the reservoir is dominated by advection, as the high fracture permeability permitted higher velocity of fluid flow. For the condition of low fracture permeability, heat transfer process has pronounced control on permeability evolution and timing of slip due to heat conduction process. With reduction in fluid flow and hydromechanical effects, heat transfer in the reservoir is dominated by heat conduction, as the temperature difference between the fault zone and the country rock becomes negligible. For the intermediate fracture permeabilities, the induced thermal unloading due to conduction could prompt the onset of failure. Changing the locations of the injection well along the fault zone shows that shear failure on the fault/fracture plane occurs earlier for lower stress state and vice versa. The evolutions of production rate and power generation are also influenced by the stress state at the injection and production wells. The elevated pore pressures in the fault zone due to fluid injection causes distributed seismicity on the fault/fracture planes which all have moment magnitudes that are below 2.5.Cited as: Anyim, K., Gan, Q. Fault zone exploitation in geothermal reservoirs: Production optimization, permeability evolution and induced seismicity. Advances in Geo-Energy Research, 2020, 4(1): 1-12, doi: 10.26804/ager.2020.01.0

Unconventional Superconducting Symmetry in a Checkerboard Antiferromagnet

We use a renormalized mean field theory to study the Gutzwiller projected BCS states of the extended Hubbard model in the large $U$ limit, or the $t$-$t'$-$J$-$J'$ model on a two-dimensional checkerboard lattice. At small $t'/t$, the frustration due to the diagonal terms of $t'$ and $J'$ does not alter the $d_{x^2-y^2}$-wave pairing symmetry, and the negative (positive) $t'/t$ enhances (suppresses) the pairing order parameter. At large $t'/t$, the ground state has an extended s-wave symmetry. At the intermediate $t'/t$, the ground state is $d+id$ or $d+is$-wave with time reversal symmetry broken.Comment: 6 pages, 6 figure

Synthesis of Cyclic Polymers by Ring Expansion and Ring Opening Metathesis Polymerization

Cyclic polymers are topologically interesting and envisioned as a lubricant material. However, scalable synthesis of pure cyclic polymers remains elusive. The most straightforward way is to recover a used catalyst after the synthesis of cyclic polymers and reuse it. Unfortunately, this is demanding because of the catalyst’s vulnerability and inseparability from polymers, which reduce the practicality of the process. In Chapter 1 we describe a continuous circular process, where polymerization, polymer separation, and catalyst recovery happen in situ, to dispense a pure cyclic polymer after bulk ring-expansion metathesis polymerization of cyclopentene. This process is enabled by introducing silica-supported ruthenium catalysts and newly designed glassware. Different depolymerization kinetics of the cyclic polymer from its linear analogue are also discussed. This process minimizes manual labour, maximizes the security of vulnerable catalysts and guarantees the purity of cyclic polymers, thereby showcasing a prototype of a scalable access to cyclic polymers with increased turnovers (≥415,000) of precious catalysts. α-Oxygenated Z-olefins are ubiquitous in biologically active molecules and serve as versatile handles for organic synthesis, but their syntheses are often tedious and less selective. In Chapter 2 we report the efficient Z-selective metathesis of various terminal acrylates and allyl alcohols, which enables facile and selective construction of high value-added α-oxygenated Z-olefins from readily available feedstock chemicals. These challenging metathesis transformations are enabled by novel cyclometalated Ru-carbene-nitrate complexes bearing bulky-yet-flexible side arms, whose assembly was unlocked by new organometallic syntheses. Efficient separation of macrocyclic polyolefins from reaction mixtures of ring-opening metathesis polymerization is crucial for their application in materials science, drug delivery, and for the mechanistic study of the reaction mechanism. In Chapter 3, we present a facile method for obtaining topologically pure macrocyclic fractions by modifying chain ends using enyne metathesis chemistry and introducing polar functional groups into linear polymer chains through the addition of polar monomers. Nonpolar cyclic polyolefins are then readily separated using silica gel chromatography. The purity of the cyclic fractions was verified using multiple techniques, including gel permeation chromatography, nuclear magnetic resonance spectroscopy, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. We investigate the reaction factors affecting the yield and molecular weight of macrocycles during ring-opening metathesis polymerization of cyclooctadiene and discuss macrocycle formation in the ring-opening metathesis polymerization of cyclooctene, cyclopentene, and norbornene. Our work offers crucial insights into the synthesis and separation of macrocycles.</p

Feasibility investigation of energy regenerative hybrid vehicle suspension system

A conventional vehicle suspension system contains passive elements, namely a viscous damper and a spring. The damper converts vibration energy into heat energy-due to the viscous friction of fluid in the device, and is finally dissipated to the external environment. Other than damper configuration, the amount of energy dissipated largely depends on the road roughness, the vehicle velocity and the vehicle mass. Under common operating conditions, this energy may be considered insignificant. On the other hand, over rough urban roads, the energy may be higher and thus presents a potential to tap the energy. For this, a hybrid linear motor/generator may be adapted to replace existing damper in the vehicle suspension system. With an appropriate controller, the device may be alternated between damping and generating device to provide damping as well as extracting energy. The energy even small may help in improving the efficiency of vehicle, especially electric and hybrid vehicle systems. With such device, it is also possible to vary the damping in a nonlinear and adaptive manner to accommodate the conflicting requirement between high speed operation and control of resonance. This investigation examines the feasibility of a hybrid suspension damper namely, linear motor/generator in providing adequate damping for isolation of vibration while generate energy from relative motion between sprung and unsprung masses. The study utilizes a simplified quarter vehicle model with linear spring and the proposed damping/generating device to illustrate its performance. The performances are evaluated in terms of acceleration transmissibility, rattle space, power spectral density (PSD) of acceleration response, and Dynamic Load Coefficient (DLC) to quantity the resulting pavement loads

Influence of permeability anisotropy on heat transfer and permeability evolution in geothermal reservoir

Acknowledgments The author would like to thank Dr. Quan Gan’s supervision, family’s support, and Prof. Cai’s valuable suggestions in completing this work, as part of the MSc degree requirements in Reservoir Engineering programme in the University of Aberdeen.Peer reviewedPublisher PD

Evolution of permeability in sand injectite systems

The author would like to thank the financial support from the Laboratory of Coal Resources and Safe Mining (China University of Mining and Technology), the grant No. SKLCRSM16KFC01. We would also appreciate the discussion and data support from Qinghua Lei at Imperial College London, Antonio Grippa at the University of Aberdeen, and Valeri Mourzenko at the Institut Pprime CNRS.Peer reviewedPostprin