vSkyConf: Cloud-assisted Multi-party Mobile Video Conferencing

As an important application in the busy world today, mobile video conferencing facilitates virtual face-to-face communication with friends, families and colleagues, via their mobile devices on the move. However, how to provision high-quality, multi-party video conferencing experiences over mobile devices is still an open challenge. The fundamental reason behind is the lack of computation and communication capacities on the mobile devices, to scale to large conferencing sessions. In this paper, we present vSkyConf, a cloud-assisted mobile video conferencing system to fundamentally improve the quality and scale of multi-party mobile video conferencing. By novelly employing a surrogate virtual machine in the cloud for each mobile user, we allow fully scalable communication among the conference participants via their surrogates, rather than directly. The surrogates exchange conferencing streams among each other, transcode the streams to the most appropriate bit rates, and buffer the streams for the most efficient delivery to the mobile recipients. A fully decentralized, optimal algorithm is designed to decide the best paths of streams and the most suitable surrogates for video transcoding along the paths, such that the limited bandwidth is fully utilized to deliver streams of the highest possible quality to the mobile recipients. We also carefully tailor a buffering mechanism on each surrogate to cooperate with optimal stream distribution. We have implemented vSkyConf based on Amazon EC2 and verified the excellent performance of our design, as compared to the widely adopted unicast solutions.Comment: 10 page

The impact of CFO gender on bank loan contracting

Motivated by recent studies that show female CFOs are more risk averse than male CFOs when making various corporate decisions, we examine whether banks take into consideration the gender of CFOs when pricing bank loans. We find that in our sample, firms under the control of female CFOs on average enjoy about 11% lower bank loan price than firms under the control of male CFOs. In addition, loans given to female CFO-led companies have longer maturities and are less likely to be required to provide collateral than loans given to male CFO led companies. Our results are robust to a series of robustness tests, such as a firm and year-fixed effect regression, a Heckman two-stage self selection model, a propensity score match method and a differences-in-differences approach. Overall, our results suggest that banks tend to recognize the role of female CFOs in providing more reliable accounting information ex ante and reducing default risk ex post, and grant firms with female CFOs lower loan price and more favourable contract terms.CFOs; gender; accounting information; bank loans

Realized beta : persistence and predictability

A large literature over several decades reveals both extensive concern with the question of time-varying betas and an emerging consensus that betas are in fact time-varying, leading to the prominence of the conditional CAPM. Set against that background, we assess the dynamics in realized betas, vis-à-vis the dynamics in the underlying realized market variance and individual equity covariances with the market. Working in the recently-popularized framework of realized volatility, we are led to a framework of nonlinear fractional cointegration: although realized variances and covariances are very highly persistent and well approximated as fractionally-integrated, realized betas, which are simple nonlinear functions of those realized variances and covariances, are less persistent and arguably best modeled as stationary I(0) processes. We conclude by drawing implications for asset pricing and portfolio management. JEL Klassifikation: C1, G

A framework for exploring the macroeconomic determinants of systematic risk

We selectively survey, unify and extend the literature on realized volatility of financial asset returns. Rather than focusing exclusively on characterizing the properties of realized volatility, we progress by examining economically interesting functions of realized volatility, namely realized betas for equity portfolios, relating them both to their underlying realized variance and covariance parts and to underlying macroeconomic fundamentals

The Effectiveness of Corporate Boards: Evidence from Bank Loan Contracting

This paper investigates the role of corporate boards in bank loan contracting. We find that when corporate boards are more independent, both price and non-price loan terms (e.g., interest rates, collateral, covenants and performance pricing) are more favorable and syndicated loans comprise more lenders. In addition, board size, board diversity, audit committee structure and other director characteristics also influence bank loan price. However they do not consistently affect all non-price loan terms except for audit committee independence. Moreover, the impact of board independence on bank loans varies with borrower characteristics (e.g., leverage, tangibility and anti-takeover environments) and loan characteristics (e.g., loan types and loan structures). Overall, our study provides strong evidence that banks tend to recognize the benefits of board monitoring in mitigating agency risk and information risk, and reward borrowers with higher quality boards with more favorable loan contract terms.Bank loan contracting, Boards of directors, Corporate governance, Monitoring, SOX

Parkfield earthquake of June 28, 1966: Magnitude and source mechanism

The Parkfield earthquake of June 28, 1966 (04:26:12.4 GMT) is studied using short-period and long-period teleseismic records. It is found that (1) Mb = 5.8 and Ms = 6.4 as compared to Mb = 5.4 and Ms = 5.4 for the foreshock (04:08:54), (2) both the Rayleigh and Love wave radiation patterns conform to those of a double couple at a depth of about 8.6 km, (3) the main shock can be represented by a series of shocks separated in space and time. The near-field strong-motion data support the last conclusion. Based on strong-motion seismograms, and the surficial evidences of the dimensions of the fault, the energy is found to be 10^(21) ergs

Part I: Lower limit of the total energy of earthquakes and partitioning of energy among seismic waves. Part II: Reflected waves and crustal structures

Part I: The basic formulae for estimating the energy in the seismic waves are derived. The formulae take into account the radiation pattern of the source, the compensation for the non-elastic absorption of the waves, the velocity-density structure of the earth, the effects of the crustal structure under the receiver and the response of the recording instruments. Operations are performed in the frequency domain. Estimation of the seismic energy of an earthquake is closely related to the determination of the source mechanism and the radiation pattern of the source. We have determined the surface wave radiation pattern of a shallow shock and the P wave radiation pattern of an intermediate shock to show the correspondence between the fault-plane solutions and the fault mechanisms derived from radiation pattern. We have obtained the energies of the two earthquakes mentioned above as well as 7 other earthquakes with known fault-plane solutions and/or radiation patterns. The "total" seismic energies for these earthquakes (magnitudes between 6 1/2 and 7 1/2) using the present procedures are at least an order of magnitude higher than those arrived at from the current magnitude-energy formula. The S wave energies are approximately an order higher than that of the P waves. The surface wave energies for the shallow shocks are three orders of magnitude less than the body wave energies. Thus, the S wave seems to be the main seismic wave energy carrier. Energies in the lower order spheroidal oscillations (ℓ = 2, 15) for the 1964 Alaskan earthquake have been calculated from Isabella strain data and Berkeley ultra-long period pendulum seismometer data. The sum of the energies is 1023 ergs. Part II: Haskell's formulation for reflection of the body waves at the base of a solid crust is extended to include overlying liquid layers. Normalized displacement and the phase shift at the base of the crust as a function of angle of incidence and frequency are calculated for two continental models and an oceanic model. Complex reflection coefficients are inverse-Fourier transformed numerically to the time domain to show the change of pulse shape upon reflection. These time traces show that the water layer of the oceanic model causes the main difference between continental and oceanic reflections. Sample seismograms from a deep shock were compared to the theoretical records; they are found to be consistent. PP waves from a deep earthquake recorded at Tonto Forest Seismic Array were processed to display the details of an oceanic PP wave.</p

Progress in compilation of the 1:2,000,000-scale topographic map

The application of special photogrammetric techniques has enabled the systematic mapping of Mars' topography at a scale of 1:2,000,000, using high-altitude Viking Orbiter pictures. In fiscal 86, compilation was completed of the 24 subquadrangles that make up the quadrangles MC-12, MC-13, MC-14, MC-15, MC-20, and MC-21. This work completes compilation of the 60 topographic maps covering the equatorial belt (lat. + or - 30 deg). The remaining 80 subquadrangles of Mars are planned to be completed within 3 years (27, 27 and 26 subquadrangles, in fiscal 87, 88, and 89, respectively). Elevations on all topographic maps are relative to the Mars topographic datum. The maps have a contour interval of 1 km and a precision of + or - 1 km. The equatorial-belt maps are Mercator projections having true scale at lat. + or - 27.476 deg. These maps provide more precise information than do those previously available and they will help in understanding the geologic processes that have shaped the Martian surface

Online VNF Scaling in Datacenters

Network Function Virtualization (NFV) is a promising technology that promises to significantly reduce the operational costs of network services by deploying virtualized network functions (VNFs) to commodity servers in place of dedicated hardware middleboxes. The VNFs are typically running on virtual machine instances in a cloud infrastructure, where the virtualization technology enables dynamic provisioning of VNF instances, to process the fluctuating traffic that needs to go through the network functions in a network service. In this paper, we target dynamic provisioning of enterprise network services - expressed as one or multiple service chains - in cloud datacenters, and design efficient online algorithms without requiring any information on future traffic rates. The key is to decide the number of instances of each VNF type to provision at each time, taking into consideration the server resource capacities and traffic rates between adjacent VNFs in a service chain. In the case of a single service chain, we discover an elegant structure of the problem and design an efficient randomized algorithm achieving a e/(e-1) competitive ratio. For multiple concurrent service chains, an online heuristic algorithm is proposed, which is O(1)-competitive. We demonstrate the effectiveness of our algorithms using solid theoretical analysis and trace-driven simulations.Comment: 9 pages, 4 figure