University of Electro-Communications

About: University of Electro-Communications is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Laser & Robot. The organization has 8041 authors who have published 16950 publications receiving 235832 citations. The organization is also known as: UEC & Denki-Tsūshin Daigaku.

Load-based covert channels between Xen virtual machines

Abstract: Multiple virtual machines on a single virtual machine monitor are isolated from each other. A malicious user on one virtual machine usually cannot relay secret data to other virtual machines without using explicit communication media such as shared files or a network. However, this isolation is threatened by communication in which CPU load is used as a covert channel. Unfortunately, this threat has not been fully understood or evaluated. In this study, we quantitatively evaluate the threat of CPU-based covert channels between virtual machines on the Xen hypervisor. We have developed CCCV, a system that creates a covert channel and communicates data secretly using CPU loads. CCCV consists of two user processes, a sender and a receiver. The sender runs on one virtual machine, and the receiver runs on another virtual machine on the same hypervisor. We measured the bandwidth and communication accuracy of the covert channel. CCCV communicated 64-bit data with a 100% success rate in an ideal environment, and with a success rate of over 90% in an environment where Web servers are processing requests on other virtual machines.

Irregular sampling theorems for wavelet subspaces

Abstract: From the Paley-Wiener 1/4-theorem, the finite energy signal f(t) can be reconstructed from its irregularly sampled values f(k+/spl delta//sub /spl kappa//) if f(t) is band-limited and sup/sub /spl kappa//|/spl delta//sub /spl kappa//|<1/4. We consider the signals in wavelet subspaces and wish to recover the signals from its irregular samples by using scaling functions. Then the method of estimating the upper bound of sup/sub /spl kappa//|/spl delta//sub /spl kappa//| such that the irregularly sampled signals can be recovered is very important. Following the work done by Liu and Walter (see J. Fourier Anal. Appl., vol.2, no.2, p.181-9, 1995), we present an algorithm which can estimate a proper upper bound of sup/sub /spl kappa//|/spl delta//sub /spl kappa//|. Compared to Paley-Wiener 1/4-theorem, this theorem can relax the upper bound for sampling in some wavelet subspaces.

A SUBSTELLAR-MASS PROTOSTAR AND ITS OUTFLOW OF IRAS 15398–3359 REVEALED BY SUBARCSECOND-RESOLUTION OBSERVATIONS of H2CO AND CCH

Abstract: Subarcsecond (0.''5) images of H{sub 2}CO and CCH line emission have been obtained in the 0.8 mm band toward the low-mass protostar IRAS 15398–3359 in the Lupus 1 cloud as one of the Cycle 0 projects of the Atacama Large Millimeter/Submillimeter Array. We have detected a compact component concentrated in the vicinity of the protostar and a well-collimated outflow cavity extending along the northeast-southwest axis. The inclination angle of the outflow is found to be about 20°, or almost edge-on, based on the kinematic structure of the outflow cavity. This is in contrast to previous suggestions of a more pole-on geometry. The centrally concentrated component is interpreted by use of a model of the infalling rotating envelope with the estimated inclination angle and the mass of the protostar is estimated to be less than 0.09 M {sub ☉}. Higher spatial resolution data are needed to infer the presence of a rotationally supported disk for this source, hinted at by a weak high-velocity H{sub 2}CO emission associated with the protostar.

Near-Forward Rescattering Photoelectron Holography in Strong-Field Ionization: Extraction of the Phase of the Scattering Amplitude.

Abstract: We revisit the concept of near-forward rescattering strong-field photoelectron holography introduced by Y. Huismans et al. [Science 331, 61 (2011)]. The recently developed adiabatic theory is used to show how the phase of the scattering amplitude for near-forward rescattering of an ionized electron by the parent ion is encoded in and can be read out from the corresponding interference pattern in photoelectron momentum distributions (PEMDs) produced in the ionization of atoms and molecules by intense laser pulses. A procedure to extract the phase is proposed. Its application to PEMDs obtained by solving the time-dependent Schr\"odinger equation for a model atom yields results in good agreement with scattering calculations. This establishes a novel general approach to extracting structural information from strong-field observables capable of providing time-resolved imaging of ultrafast processes.