Comments on 'Cramer?Rao lower bound for tracking multiple targets'

In a recent paper, Ristic et al., 2004, proposed a simple and exact derivation of the theoretical Cramer-Rao lower bound (CRLB) for tracking multiple targets using intensity maps as measurements. Although the formulation and the theoretical derivations presented in their work are indeed correct, the analysis of the proposed bound and the conclusions that follow are wrong. Here, a correct analysis is presented with the key observation that [as opposed to the claim made in the work of Ristic et al. (2004)], the proposed CRLB reflects the interaction between the targets, even if their motion is independent. The multi-target CRLB is also compared with the error performance of a multi-target state maximum likelihood estimator; a remarkable agreement is observed for high signal-to-noise ratio     

A formula for frequency responses of distributed systems with one spatial variable

We develop a method for the exact determination of frequency responses for a class of infinite dimensional systems. In particular, we consider distributed systems in which a spatial independent variable belongs to a finite interval, and in which the inputs and outputs are spatially distributed over the same interval. We show that an explicit formula for the Hilbert–Schmidt norm of the operator-valued frequency response can be obtained whenever the underlying operators are represented by a forced two point boundary value state-space realizations (TPBVSR). This formula involves finite dimensional computations with matrices whose dimension is at most four times larger than the order of the underlying differential operator. Two examples are provided to illustrate the procedure.     

Push-pull polarization conversion using novel asymmetric coupled quantum-well structures

A novel type of polarization conversion modulator, employing multiple repetitions of two novel InGaAlAs-InAlAs asymmetric coupled quantum-well structures, is proposed. The novelty of the proposed design is that, via the electrorefraction effect, it allows for a change in the TM mode's effective refractive index, which is opposite in sign to the change in the TE mode's effective refractive index. Numerical simulations based on the effective-mass envelope-function approximation show that the modulator provides not only an electrorefractive response similar to other quantum-well modulators but can also provide a low-chirp push-pull polarization modulation.     

A simple solution for the wavenumber of off-axis modes in Y-cut Ti:LiNbO3waveguides

A general dispersion equation for off-axis modes inY-cut Ti:LiNbO3waveguides is derived. The complex wavenumber of the leaky modes is found by a simple numerical procedure.     

Chemical composition and antimicrobial activity of Vitex agnus-castus L. fruits and leaves essential oils

The following study deals with the chemical composition, antimicrobial activity of essential oils of Vitex agnus-castus L. and their main constituents in vitro and in vivo. The main compounds in the oil of unripe fruits were sabinene (17.8%) and 1,8-cineole (17.5%), while in the oil of the ripe fruits dominant compounds were 1,8-cineole (16.3%) and sabinene (13.4%). The leaves oil contained an abundance of 1,8-cineole (22.0%), as well. All of the oils tested were rich sources of α-pinene (12.2%, 9.4% and 9.4%, respectively). Antimicrobial activity was tested using bacterial and fungal strains by the microdilution method. Using the same technique 1,8-cineole and α-pinene showed very high antimicrobial potency as well. As 1,8-cineole was the predominant constituent of the oils, we have chosen to test it further in an in vivo experiment. Randomly chosen apples were treated with 1,8-cineol solution and infected with Aspergillus niger in order to provoke Aspergillus rot in apples. Disease incidence was recorded.     

Measurement-based modification of NURBS surfaces

A frequent requirement in computer aided design and manufacture is to update or refine an existing CAD model using measured data. Least squares surface fitting is known to suffer from stability problems, caused by an insufficient measurement density in some regions. This is particularly evident in situations involving local surface updating and when knot insertion is applied for local surface refinement. This paper presents a new method to update the CAD model consisting of NURBS surfaces, trimmed or untrimmed, based on a set of unorganised measured points in three-dimensional space. The proposed method overcomes the fundamental problem of singular or ill-conditioned matrices resulting from incomplete data sets. This was achieved by introducing additional fitting criteria in the minimisation functional, which constrain the fitted surface in the regions with insufficient number of data points. Two main benefits were realised by this approach. First, local surface updating can be performed by treating the surface as a whole, without the need to specially identify the regions with insufficient data, nor to re-measure those regions. Second, the quality of the unmeasured regions may be controlled to suit specific needs. The results were found to be highly encouraging and the method was found to be especially useful in situations involving knot insertion and large surface deformations.     

Synthesis and rheological study of some maleic acid polyamides

The contributions of the cis and trans configurations of the main chain double bonds to the transition temperatures and rheological properties were determined for four well-defined polymaleamides, which were prepared by the room temperature ring-opening, step-growth polymerization reactions of N,N′-bisisomaleimide monomers with bifunctional primary diamines. The polymaleamides were glassy solids, which could be thermally isomerized into related polyfumaramides. The glass transition temperatures of the polyfumaramides, as determined by mechanical spectrometry, are systematically and markedly higher than those of the polymaleamides from which they were derived.     

pMOS dosimeter with two-layer gate oxide operated at zero andnegative bias

The linearity of threshold voltage shift, during irradiation of thick gate oxide pMOS transistors, operated at zero and negative bias, is investigated. It is found that the threshold voltage shift is not linear in the `zero bias regime'. The linearity increases with an increase in the absolute value of the negative gate voltage     

Development of a profile gauging sensor

A non-contact inspection system that can automatically assess the quality of complex engineering components such as turbine blades, has been identified by the aeroengine industry as a requirement in automating the process of proof inspection. This requirement led Rolls-Royce plc. and Imperial College to investigate non-contact measurement techniques and to devise an automated system based on such technology. The system in its final form, will provide an integrated CAD/CAM-based concept that will enable design and manufacture data relating to complex three-dimensional objects to be compared and assessed.     

Electrocatalysis for hydrogen electrode reactions in the light of fermi dynamics and structural bonding FACTORS-I. individual electrocatalytic properties of transition metals

The Brewer valence-bond theory for bonding in metals and intermetallic phases has been employed, together with Fermi dynamics, to correlate with the electrocatalytic properties of both individual and composite transition metal catalysts for the hydrogen electrode reactions (HELR). It has been inferred that the electrocatalytic activity of both individual transition metals and their intermetallic phases and alloys for both hydrogen evolution (HER) and its oxidation (HOR), primarily correlates with the electronic density of states and obeys typical laws of catalysis reflected in the first place in the existence of volcano plots along the Periodic Table. Since the bonding effectiveness of both individual and intermetallic hypo-hyper-d-electronic transition metal composite electrocatalysts correlates in a straightforward manner with their electrocatalytic activity, such evidence strongly suggests Fermi energy, as a typical elementary binding energy, which otherwise stays in the linear relation with cohesive energy, this forms the basis in investigation and correlation of electrocatalytic activity. Due to the fact that the Fermi wave-vector represents the individual and collective (alloys and intermetallic phases) bulk property of the available electronic number density (or its concentration, n, i.e., k_F = (3π²n) ), and in a straightforward manner correlates with the electronic density of states at the Fermi level, and thereby defines all metallic properties of a metal (and intermetallics) as “a solid with a Fermi surface”, including electrocatalytic features, it has been taken as the main parameter to correlate with the exchange current density in the hydrogen electrode reactions.