Measuring the Efficiency of Residential Real Estate Brokerage Firms

This article measures overall, allocative, technical, pure technical and scale efficiency levels for a sample of residential real estate brokerage firms using data envelopment analysis, a linear-programming technique. The results suggest that real estate brokerage firms operate inefficiently. Inefficiencies are primarily a function of sub-optimal input allocations and the failure to operate at constant returns to scale rather than from poor input utilization. Regression analysis is employed to determine which firm and/or market characteristics affect efficiency levels. The results show that increasing firm size increases efficiency while choosing to franchise, adding an additional multiple listing service and increasing operating leverage decreases firm performance.

Self-Consistent Model of Magnetospheric Electric Field, Ring Current, Plasmasphere, and Electromagnetic Ion Cyclotron Waves: Initial Results

Further development of our self-consistent model of interacting ring current (RC) ions and electromagnetic ion cyclotron (EMIC) waves is presented. This model incorporates large scale magnetosphere-ionosphere coupling and treats self-consistently not only EMIC waves and RC ions, but also the magnetospheric electric field, RC, and plasmasphere. Initial simulations indicate that the region beyond geostationary orbit should be included in the simulation of the magnetosphere-ionosphere coupling. Additionally, a self-consistent description, based on first principles, of the ionospheric conductance is required. These initial simulations further show that in order to model the EMIC wave distribution and wave spectral properties accurately, the plasmasphere should also be simulated self-consistently, since its fine structure requires as much care as that of the RC. Finally, an effect of the finite time needed to reestablish a new potential pattern throughout the ionosphere and to communicate between the ionosphere and the equatorial magnetosphere cannot be ignored

Turning mobile phones into a mobile quiz platform to challenge players' knowledge: An experience report

In the past few years, many new mobile technologies including the 3G, WiFi or mobileTV have created unprecedented learning opportunities on mobile devices. Furthermore, such technologies continuously fuel the rapid growth of new fields of research like the edutainment for educational entertainment. In a recent project awarded by the Hong Kong Wireless Development Center, we have developed a mobile quiz game system on 3G mobile phone networks in China, Hong Kong or other countries to facilitate learning anytime and anywhere. Our developed mobile quiz system is so generic that it can be readily extended to any wireless network. In this paper, we discuss about the design and possible uses of our quiz system in mobile learning, and also share the relevant experience in system development with the evaluation strategies carefully examined. After all, our work shed light on many interesting directions for future exploration. © 2008 IEEE.published_or_final_versionThe 8th IEEE International Conference on Advanced Learning Technologies (ICALT 2008), Santander, Cantabria, Spain, 1-5 July 2008. In Proceedings of the 8th ICALT, 2008, p. 943-94

Anisotropic diffusion in continuum relaxation of stepped crystal surfaces

We study the continuum limit in 2+1 dimensions of nanoscale anisotropic diffusion processes on crystal surfaces relaxing to become flat below roughening. Our main result is a continuum law for the surface flux in terms of a new continuum-scale tensor mobility. The starting point is the Burton, Cabrera and Frank (BCF) theory, which offers a discrete scheme for atomic steps whose motion drives surface evolution. Our derivation is based on the separation of local space variables into fast and slow. The model includes: (i) anisotropic diffusion of adsorbed atoms (adatoms) on terraces separating steps; (ii) diffusion of atoms along step edges; and (iii) attachment-detachment of atoms at step edges. We derive a parabolic fourth-order, fully nonlinear partial differential equation (PDE) for the continuum surface height profile. An ingredient of this PDE is the surface mobility for the adatom flux, which is a nontrivial extension of the tensor mobility for isotropic terrace diffusion derived previously by Margetis and Kohn. Approximate, separable solutions of the PDE are discussed.Comment: 14 pages, 1 figur

Global, collisional model of high‐energy photoelectrons

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95539/1/grl8976.pd

Quantum geometry of 3-dimensional lattices

We study geometric consistency relations between angles on 3-dimensional (3D) circular quadrilateral lattices -- lattices whose faces are planar quadrilaterals inscribable into a circle. We show that these relations generate canonical transformations of a remarkable ``ultra-local'' Poisson bracket algebra defined on discrete 2D surfaces consisting of circular quadrilaterals. Quantization of this structure leads to new solutions of the tetrahedron equation (the 3D analog of the Yang-Baxter equation). These solutions generate an infinite number of non-trivial solutions of the Yang-Baxter equation and also define integrable 3D models of statistical mechanics and quantum field theory. The latter can be thought of as describing quantum fluctuations of lattice geometry. The classical geometry of the 3D circular lattices arises as a stationary configuration giving the leading contribution to the partition function in the quasi-classical limit.Comment: 27 pages, 10 figures. Minor corrections, references adde

A bounce‐averaged kinetic model of the ring current ion population

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94668/1/grl7966.pd

Ground State Hyperfine Structure of Muonic Helium Atom

On the basis of the perturbation theory in the fine structure constant $\alpha$ and the ratio of the electron to muon masses we calculate one-loop vacuum polarization and electron vertex corrections and the nuclear structure corrections to the hyperfine splitting of the ground state of muonic helium atom $(\mu e ^4_2He)$. We obtain total result for the ground state hyperfine splitting $\Delta \nu^{hfs}=4465.526$ MHz which improves the previous calculation of Lakdawala and Mohr due to the account of new corrections. The remaining difference between the theoretical result and experimental value of the hyperfine splitting equal to 0.522 MHz lies in the range of theoretical error and requires the subsequent investigation of higher order corrections.Comment: Talk presented at the scientific session-conference of Nuclear Physics Department RAS "Physics of fundamental interactions", 25-30 November 2007, ITEP, Moscow, 18 pages, 5 figure

Transport of photoelectrons in the nightside magnetosphere

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95682/1/jgra16120.pd