Competition and subsidies in the deregulated US local telephone industry

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/115904/1/rand12109.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/115904/2/rand12109-sup-0001-SupMat.pd

Stability of Phase-modulated Quantum Key Distribution System

Phase drift and random fluctuation of interference visibility in double unbalanced M-Z QKD system are observed and distinguished. It has been found that the interference visibilities are influenced deeply by the disturbance of transmission fiber. Theory analysis shows that the fluctuation is derived from the envioronmental disturbance on polarization characteristic of fiber, especially including transmission fiber. Finally, stability conditions of one-way anti-disturbed M-Z QKD system are given out, which provides a theoretical guide in pragmatic anti-disturbed QKD.Comment: 9 pages, 3 figue

Estimating the Option Value of Waiting: A Dynamic Entry Game of the U.S. Local Telephone Competition

We estimate a dynamic oligopoly entry game in the early U.S. local telephone market. We observe the identities of potential entrants into local markets and therefore the waiting time of each potential entrant before it commits actual entry. To capture the feature of the data, we allow firms to be heterogeneous long-run players who have option value of waiting. We find that firm-level heterogeneity in entry costs plays a significant role in determining a firm's entry behavior into a local market. Our model can be used to conduct counterfactual simulations to understand the effectiveness of subsidy policies with different focuses

Intrinsic-Stabilization Uni-Directional Quantum Key Distribution Between Beijing and Tianjin

Quantum key distribution provides unconditional security for communication. Unfortunately, current experiment schemes are not suitable for long-distance fiber transmission because of instability or backscattering. We present a uni-directional intrinsic-stabilization scheme that is based on Michelson-Faraday interferometers, in which reflectors are replaced with 90 degree Faraday mirrors. With the scheme, key exchange from Beijing to Tianjin over 125 kilometers with an average error rate is below 6% has been achieved and its limited distance exceeds 150 kilometers. Experimental result shows the system is insensitive to environment and can run over day and night without any break even in the noise workshop.Comment: 7 pages,4 figure

Investigation on risk prediction of pedestrian head injury by real-world accidents

Head injury is the most common and fatal injury in car-pedestrian accidents. Due to the lack of human test data, real-world accident data is useful for the research on the mechanism and tolerance of head injuries. The objective of the present work is to investigate pedestrian head-brain injuries through real car-pedestrian accidents and evaluate the existed injury criteria. Seven car-to-pedestrian accidents in China were selected from the IVAC (Investigation of Vehicle Accident in Changsha) database. Accident reconstructions using multi-body models were conducted to determine the kinematic parameters associated with the injury and were used to measure head injury criteria. Kinematic parameters were input into a finite element model to run simulations on the head-brain and car interface to determine levels of brain tissue stress, strain, and brain tissue injury criteria. A binary logistic regression model was used to determine the probability of head injury risk associated with AIS3+ injuries (Abbreviated Injury Scale). The results showed that head injury criteria using kinematic parameters can effectively predict injury risk of a pedestrians’ head skull. Regarding brain injuries, physical parameters like coup/countercoup pressure are more effective predictors. The results of this study can be used as the background knowledge for pedestrian friendly car design

High-quality mesoporous graphene particles as high-energy and fast-charging anodes for lithium-ion batteries.

The application of graphene for electrochemical energy storage has received tremendous attention; however, challenges remain in synthesis and other aspects. Here we report the synthesis of high-quality, nitrogen-doped, mesoporous graphene particles through chemical vapor deposition with magnesium-oxide particles as the catalyst and template. Such particles possess excellent structural and electrochemical stability, electronic and ionic conductivity, enabling their use as high-performance anodes with high reversible capacity, outstanding rate performance (e.g., 1,138 mA h g-1 at 0.2 C or 440 mA h g-1 at 60 C with a mass loading of 1 mg cm-2), and excellent cycling stability (e.g., >99% capacity retention for 500 cycles at 2 C with a mass loading of 1 mg cm-2). Interestingly, thick electrodes could be fabricated with high areal capacity and current density (e.g., 6.1 mA h cm-2 at 0.9 mA cm-2), providing an intriguing class of materials for lithium-ion batteries with high energy and power performance

Time-dependent density-functional theory for open systems

By introducing the self-energy density functionals for the dissipative interactions between the reduced system and its environment, we develop a time-dependent density-functional theory formalism based on an equation of motion for the Kohn-Sham reduced single-electron density matrix of the reduced system. Two approximate schemes are proposed for the self-energy density functionals, the complete second order approximation and the wide-band limit approximation. A numerical method based on the wide-band limit approximation is subsequently developed and implemented to simulate the steady and transient current through various realistic molecular devices. Simulation results are presented and discussed.Comment: 16 pages, 12 figure

Equivalent electric circuit of a carbon nanotube based molecular conductor

We apply our first-principles method to simulate the transient electrical response through carbon nanotube based conductors under time-dependent bias voltages, and report the dynamic conductance for a specific system. We find that the electrical response of the carbon nanotube device can be mapped onto an equivalent classical electric circuit. This is confirmed by studying the electric response of a simple model system and its equivalent circuit.Comment: 10 pages, 4 figure