Contrast mechanisms in polarization-sensitive Mueller-matrix optical coherence tomography and application in burn imaging

We investigate the various contrast mechanisms provided by polarization-sensitive (PS) Mueller-matrix optical coherence tomography (OCT). Our PS multichannel Mueller-matrix OCT is the first, to our knowledge, to offer simultaneously comprehensive polarization-contrast mechanisms, including the amplitude of birefringence, the orientation of birefringence, and the diattenuation in addition to the polarization-independent intensity contrast, all of which can be extracted from the measured Jones or the equivalent Mueller matrix. Theoretical analysis shows that when diattenuation is negligible, the round-trip Jones matrix represents a linear retarder, which is the foundation of conventional PS-OCT, and can be calculated with a single incident polarization state, although the one-way Jones matrix generally represents an elliptical retarder; otherwise, two incident polarization states are needed. The experimental results obtained from rat skin samples, which conform well with the histology, show that Mueller OCT provides complementary structural and functional information on biological samples and reveal that polarization contrast is more sensitive to thermal degeneration of biological tissue than amplitude-based contrast. Thus, Mueller OCT has significant potential for application in the noninvasive assessment of burn depth.     

Host Mobility Using an Internet Indirection Infrastructure

We propose the Robust Overlay Architecture for Mobility (ROAM) to provide seamless mobility for Internet hosts. ROAM is built on top of the Internet Indirection Infrastructure (i3). With i3, instead of explicitly sending a packet to a destination, each packet is associated with an identifier. This identifier defines an indirection point in i3, and is used by the receiver to obtain the packet. ROAM takes advantage of end-host ability to control the placement of indirection points in i3 to provide efficient routing, fast handoff, and preserve location privacy for mobile hosts. In addition, ROAM allows end hosts to move simultaneously, and is as robust as the underlying IP network to node failure. We have developed a user-level prototype system on Linux that provides transparent mobility without modifying applications or the TCP/IP protocol stack. Simulation results show that ROAM's latency can be as low as 0.25–40% of Mobile IP. Experimental results show that with soft handoff the TCP throughput decreases only by 6% when there are as many as 0.25 handoffs per second. Shelley Zhuang received the B.S. degree in computer engineering and computer science from the University of Missouri-Columbia in 1999, and is now pursuing her Ph.D. degree in computer science at University of California-Berkeley. She has interned at NASA Goddard Space Flight Center, Microsoft, and DaimlerChrysler Research and Technology North America. Her research interest include overlay networking, content distribution networks, streaming media, multicast routing, wireless communications, and network security. Kevin Lai is currently a Scientist at HP Labs. He received his A.B. in Computer Science from U.C.Berkeley and his Ph.D. in Computer Science from Stanford University. Previously he was a post-doctoral scholar in the School of Information Management and Systems (SIMS) and EECS Department at U.C. Berkeley. He has worked on operating systems, mobility, ad hoc networking, network measurement, and incentive systems Ion Stoica received his PhD from the Carnegie Mellon University in 2000. He is an Assistant Professor in the EECS Department at University of California at Berkeley, where he does research on resource management, scalable solutions for end-to-end quality of service, and peer-to-peer network technologies in the Internet. Stoica is the recipient of a Sloan Foundation Fellowship (2003, a National Science Foundation CAREER Award (2002), the ACM doctoral dissertation award (2001), and an Okawa Foundation Fellowship (2001). He is a member of ACM. Randy Howard Katz received his undergraduate degree from Cornell University, and his M.S. and Ph.D. degrees from the University of California, Berkeley. He joined the faculty at Berkeley in 1983, where he is now the United Microelectronics Corporation Distinguished Professor in Electrical Engineering and Computer Science. He is a Fellow of the ACM and the IEEE, and a member of the National Academy of Engineering. He has published over 200 refereed technical papers, book chapters, and books. His hardware design textbook, Contemporary Logic Design, has sold over 85,000 copies worldwide, and has been in use at over 200 colleges and universities. He has supervised 35 M.S. theses and 21 Ph.D. dissertations, and leads a research team of over a dozen graduate students, technical staff, and industrial visitors. He has won numerous awards, including seven best paper awards, one “test of time" paper award, one paper selected for a 50 year retrospective on IEEE communications publications, three best presentation awards, the Outstanding Alumni Award of the Computer Science Division, the CRA Outstanding Service Award, the Berkeley Distinguished Teaching Award, the Air Force Exceptional Civilian Service Decoration, the IEEE Reynolds Johnson Information Storage Award, the ASEE Frederic E. Terman Award, and the ACM Karl V. Karlstrom Outstanding Educator Award. With colleagues at Berkeley, he developed Redundant Arrays of Inexpensive Disks (RAID), a $ 25 billion per year industry sector today. While on leave for government service in 1993–1994, he established whitehouse.gov and connected the White House to the Internet. His current research interests are Internet Services Architecture, Mobile Internet, and the technologies underlying the convergence of telecommunications and packet networks. Prior research interests have included: database management, VLSI CAD, and high performance multiprocessor and storage architectures. Scott Shenker received his degrees, in theoretical physics, from Brown University (Sc. B.) and the University of Chicago (Ph. D.). After a postdoctoral year at Cornell's physics department in 1983, he joined Xerox's Palo Alto Research Center. He left PARC in 1999 to head up a newly established Internet research group at the International Computer Science Institute (ICSI) in Berkeley. Scott's research over the past 15 years has spanned the range from computer performance modeling and computer networks to game theory and economics. Most of his recent work has focused on the Internet architecture and related issues.     

Analysis of an output error identification algorithm

An output error-based algorithm proposed by Landau and recently analysed by Dugard and Landau is shown to have a certain robustness property. Specifically it is proved that the parameters of the system transfer function can be estimated consistently with that algorithm even if the noise is not correctly modelled. This fact was noticed empirically by Dugard and Landau but a theoretical analysis was not provided.     

Optimal instrumental-variable methods for identification of multivariable linear systems

The identification of multivariable linear systems using instrumental-variable (IV) methods is discussed. The emphasis is on accuracy properties. The IV estimates of multi-input-multi-output system parameters are proved to be asymptotically Gaussian distributed under weak conditions. An explicit expression for the covariance matrix of the parameter estimates is given. It is then shown how this matrix can be optimized by appropriately choosing the IV variant. The optimal accuracy so obtained is for some model structures equal to that corresponding to a prediction error method.     

Comments on "A Bayesian comparison of different classes of dynamic model using empirical data"

ln this note the method proposed in the above paper for structure determination of time series is numerically compared with other well-known methods: the F-test, Akaike's criteria, and the test of residual whiteness.     

Space-Time Diversity Using Orthogonal and Amicable Orthogonal Designs

In this paper we consider the utilization of multiple transmitterand receiver antennas for space-time diversity. The optimalSNR scheme, which also provides the best diversity, is outlined.This scheme however involves a reduction in the data rate. Coding schemes are then presentedwhich not only achieve the optimal SNR but also mitigate the reductionof data rate. The proposed schemes are based on the theory of Orthogonal Designsand Amicable Orthogonal Designs.     

Amplitude estimation of sinusoidal signals: survey, new results,and an application

This paper considers the problem of amplitude estimation of sinusoidal signals from observations corrupted by colored noise. A relatively large number of amplitude estimators, which encompass least squares (LS) and weighted least squares (WLS) methods, are described. Additionally, filterbank approaches, which are widely used for spectral analysis, are extended to amplitude estimation; more exactly, we consider the matched-filterbank (MAFI) approach and show that by appropriately designing the prefilters, the MAFI approach to amplitude estimation includes the WLS approach. The amplitude estimation techniques discussed in this paper do not model the observation noise, and yet, they are all asymptotically statistically efficient. It is, however, their different finite-sample properties that are of particular interest to this study. Numerical examples are provided to illustrate the differences among the various amplitude estimators. Although amplitude estimation applications are numerous, we focus herein on the problem of system identification using sinusoidal probing signals for which we provide a computationally simple and statistically accurate solution     

Approximate maximum likelihood estimators for array processing inmultiplicative noise environments

We consider the problem of localizing a source by means of a sensor array when the received signal is corrupted by multiplicative noise. This scenario is encountered, for example, in communications, owing to the presence of local scatterers in the vicinity of the mobile or due to wavefronts that propagate through random inhomogeneous media. Since the exact maximum likelihood (ML) estimator is computationally intensive, two approximate solutions are proposed, originating from the analysis of the high and low signal to-noise ratio (SNR) cases, respectively. First, starting with the no additive noise case, a very simple approximate ML (AML₁) estimator is derived. The performance of the AML₁ estimator in the presence of additive noise is studied, and a theoretical expression for its asymptotic variance is derived. Its performance is shown to be close to the Cramer-Rao bound (CRB) for moderate to high SNR. Next, the low SNR case is considered, and the corresponding AML₂ solution is derived. It is shown that the approximate ML criterion can be concentrated with respect to both the multiplicative and additive noise powers, leaving out a two-dimensional (2-D) minimization problem instead of a four-dimensional (4-D) problem required by the exact ML. Numerical results illustrate the performance of the estimators and confirm the validity of the theoretical analysis     

Computationally efficient two-dimensional Capon spectrum analysis

We present a computationally efficient algorithm for computing the 2-D Capon (1969) spectral estimator. The implementation is based on the fact that the 2-D data covariance matrix will have a Toeplitz-block-Toeplitz structure, with the result that the inverse covariance matrix can be expressed in closed form by using a special case of the Gohberg-Heinig (1974) formula that is a function of strictly the forward 2-D prediction matrix polynomials. Furthermore, we present a novel method, based on a 2-D lattice algorithm, to compute the needed forward prediction matrix polynomials and discuss the difference in the so-obtained 2-D spectral estimate as compared with the one obtained by using the prediction matrix polynomials given by the Whittle-Wiggins-Robinson (1963, 1965) algorithm. Numerical simulations illustrate the improved resolution as well as the clear computational gain in comparison to both the well-known classical implementation and the method published by Liu et al.(see IEEE Trans. Aerosp. Electron. Syst., vol.34, p.1314-19, 1998)     

A mobile detector for measurements of the atmospheric muon flux in underground sites

Muons comprise an important contribution of the natural radiation dose in air (approx. 30 nSv/h of a total dose rate of 65-130 nSv/h), as well as in underground sites even when the flux and relative contribution are significantly reduced. The flux of muons observed underground can be used as an estimator for the depth in mwe (meter water equivalent) of the underground site. The water equivalent depth is important information to devise physics experiments feasible for a specific site. A mobile detector for performing measurements of the muon flux was developed in IFIN-HH, Bucharest. Consisting of two scintillator plates (approx. 0.9 m²) which measure in coincidence, the detector is installed on a van which facilitates measurements at different locations at the surface or underground. The detector was used to determine muon fluxes at different sites in Romania. In particular, data were taken and the values of meter water equivalents were assessed for several locations at the salt mine in Slanic-Prahova, Romania. The measurements have been performed in two different galleries of the Slanic mine at different depths. In order to test the stability of the method, also measurements of the muon flux at the surface at different elevations were performed. The results were compared with predictions of Monte-Carlo simulations using the CORSIKA and MUSIC codes.