Accuracy analysis of time domain maximum likelihood method and sample maximum likelihood method for errors-in-variables and output error identification

For identifying errors-in-variables models, the time domain maximum likelihood (TML) method and the sample maximum likelihood (SML) method are two approaches. Both methods give optimal estimation accuracy but under different assumptions. In the TML method, an important assumption is that the noise-free input signal is modelled as a stationary process with rational spectrum. For SML, the noise-free input needs to be periodic. It is interesting to know which of these assumptions contain more information to boost the estimation performance. In this paper, the estimation accuracy of the two methods is analyzed statistically for both errors-in-variables (EIV) and output error models (OEM). Numerical comparisons between these two estimates are also done under different signal-to-noise ratios (SNRs). The results suggest that TML and SML have similar estimation accuracy at moderate or high SNR for EIV. For OEM identification, these two methods have the same accuracy at any SNR.     

Variance analysis of frequency response function measurements using periodic excitations

The influence of disturbing noise and nonlinear distortions on frequency response function measurements using periodic excitations has been studied in detail in the literature. A variance analysis method has been developed that allows one to detect and quantify the nonlinear distortions and the disturbing noise. In this paper, the variance analysis is generalized to detect and quantify the following nonstationary disturbances: 1) nonsynchronous periodic signals, for example, the 50 Hz mains and its harmonics, and 2) nonstationary behavior of the device under test, for example, phase or frequency modulation.     

Broadband versus stepped sine FRF measurements

In this paper, the required measurement time to measure a transfer function with a specified accuracy is analyzed. The waiting time that is needed to balance the transient induced errors against the noise errors is calculated. This allows one to decide under what conditions broad-band measurements are faster than stepped sine measurements     

Analysis of computational EELS modelling results for MgO-based systems

The ab-initio density functional theory (DFT) code CASTEP was used to model oxygen K edges in various magnesium oxide systems. Firstly, for the bulk material the process of geometry optimisation was carried out. Predicted oxygen K edges were found for a single cell with experimental lattice parameters, and parameters obtained after geometry optimisation, both with single electron core-holes in place. After geometry optimisation, a different predicted result was obtained, although it was qualitatively similar to the result for experimental lattice parameters in some respects. For example, approximately the same sets of peaks are observed, though in different energy positions, and with different relative peak intensities within those sets. Ultimately for the single cell results the experimental lattice parameters generated the predicted result that was in the closest agreement with experiment. It was further observed that a large supercell result (based on the experimental lattice parameters, utilising a core-hole) led to a slightly improved comparison with experiment as compared to the corresponding single cell result, although the latter result, and indeed a ground state calculation also give reasonable agreement with experiment. To rationalise these observations it was necessary to investigate the density of states (DOS) for the MgO cell and its constituent atoms, and it was observed that the conduction bands were of predominantly magnesium character. Furthermore, the core-hole’s introduction had relatively little overall effect on the p DOS prediction for oxygen, though there is a significant localised change close to the Fermi level. This work also considers interface and surface results. The principal aim of the study was to explore the interface of Fe (0 0 1)/MgO (0 0 1), crucial in certain classes of magnetic tunnel junctions (MTJs), which have significant technological applications. An initial step was to consider a MgO (0 0 1) surface. It was verified that a surface could be constructed such that within that surface a theoretical result could be found that matched the bulk result. It was then valid to use this surface as part of an interface with iron. Theoretical results obtained at that interface compare well with experimental results from an epitaxially grown MTJ, and various conclusions are drawn with regard to the nature of the interface.     

Requirements-Level Semantics and Model Checking of Object-Oriented Statecharts

In this paper we define a requirements-level execution semantics for object-oriented statecharts and show how properties of a system specified by these statecharts can be model checked using tool support for model checkers. Our execution semantics is requirements-level because it uses the perfect technology assumption, which abstracts from limitations imposed by an implementation. Statecharts describe object life cycles. Our semantics includes synchronous and asynchronous communication between objects and creation and deletion of objects. Our tool support presents a graphical front-end to model checkers, making these tools usable to people who are not specialists in model checking. The model-checking approach presented in this paper is embedded in an informal but precise method for software requirements and design. We discuss some of our experiences with model checking. Correspondence and offprint requests to: Rik Eshuis, Department of Computer Science, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands. Email: eshuis@cs.utwente.nl     

Noise- and compression-robust biological features for texture classification

Texture classification is an important aspect of many digital image processing applications such as surface inspection, content-based image retrieval, and biomedical image analysis. However, noise and compression artifacts in images cause problems for most texture analysis methods. This paper proposes the use of features based on the human visual system for texture classification using a semisupervised, hierarchical approach. The texture feature consists of responses of cells which are found in the visual cortex of higher primates. Classification experiments on different texture libraries indicate that the proposed features obtain a very high classification near 97%. In contrast to other well-established texture analysis methods, the experiments indicate that the proposed features are more robust to various levels of speckle and Gaussian noise. Furthermore, we show that the classification rate of the textures using the presented biologically inspired features is hardly affected by image compression techniques.     

Modular mutagenesis of a TEM-barrel enzyme: the crystal structure of a chimeric E.coli TIM having the eighth {beta}{alpha}-unit replaced by the equivalent unit of chicken TIM

Abstract The crystal structure of a hybrid Escherichia coli triosephosphateisomerase (TIM) has been determined at 2.8 Å resolution.The hybrid TIM (ETIM8CHI) was constructed by replacing the eighthß-unit of E.coli TIM with the equivalent unit of chickenTIM. This replacement involves 10 sequence changes. One of thechanges concerns the mutation of a buried alanine (Ala232 instrand 8) into a phenylalanine. The ETIM8CHI structure showsthat the A232F sequence change can be incorporated by a side-chainrotation of Phe224 (in helix 7). No cavities or strained dihedralsare observed in ETIM8CHI in the region near position 232, whichis in agreement with the observation that ETIM8CHI and E.coliTIM have similar stabilities. The largest CA (C-alpha atom)movements, 3 Å, are seen for the C-terminal end of helix8 (associated with the outward rotation of Phe224) and for theresidues in the loop after helix 1 (associated with sequencechanges in helix 8). From the structure it is not clear whythe k_cat of ETIM8CHI is 10 times lower than in wild type E.coliTIM     

The canonical expression of the drama product manufacturing processes

As the broadcast industry is evolving toward IT-based facilities, the production workflows and their associated production metadata should similarly take advantage of IT commodities. This paper presents a manufacturing system for the production of drama television and motion picture programmes, constructed using IT-based technologies in a file-based media environment. This drama production facility implements a production workflow based on common industrial manufacturing processes and extensively models the individual aspects of the drama production process. We aim to show that the different processes contained in this manufacturing workflow can be expressed in terms of elementary building blocks, the canonical processes of media production. By identifying recurring and canonical functionality, process implementations can be simplified and input and output from different processes can be coordinated for better integration with external systems.     

Silhouette-based multi-sensor smoke detection

Fire is one of the leading hazards affecting everyday life around the world. The sooner the fire is detected, the better the chances are for survival. Today’s fire alarm systems, such as video-based smoke detectors, however, still pose many problems. In order to accomplish more accurate video-based smoke detection and to reduce false alarms, this paper proposes a multi-sensor smoke detector which takes advantage of the different kinds of information represented by visual and thermal imaging sensors. The detector analyzes the silhouette coverage of moving objects in visual and long-wave infrared registered (~aligned) images. The registration is performed using a contour mapping algorithm which detects the rotation, scale and translation between moving objects in the multi-spectral images. The geometric parameters found at this stage are then further used to coarsely map the silhouette images and coverage between them is calculated. Since smoke is invisible in long-wave infrared its silhouette will, contrarily to ordinary moving objects, only be detected in visual images. As such, the coverage of thermal and visual silhouettes will start to decrease in case of smoke. Due to the dynamic character of the smoke, the visual silhouette will also show a high degree of disorder. By focusing on both silhouette behaviors, the system is able to accurately detect the smoke. Experiments on smoke and non-smoke multi-sensor sequences indicate that the automated smoke detection algorithm is able to coarsely map the multi-sensor images. Furthermore, using the low-cost silhouette analysis, a fast warning, with a low number of false alarms, can be given.     

Decoder-driven mode decision in a block-based distributed video codec

Distributed Video Coding (DVC) is a video coding paradigm in which the computational complexity is shifted from the encoder to the decoder. DVC is based on information theoretic results suggesting that, under ideal conditions, the same rate-distortion performance can be achieved as for traditional video codecs. In practice however, there is still a significant performance gap between the two coding architectures. One of the main reasons for this gap is the lack of multiple coding modes in current DVC solutions. In this paper, we propose a block-based distributed video codec that supports three coding modes: Wyner–Ziv, skip, and intra. The mode decision process is entirely decoder-driven. Skip blocks are selected based on the estimated accuracy of the side information. The choice between intra and Wyner–Ziv coding modes is made on a rate-distortion basis, by selecting the coding mode with the lowest rate while assuring equal distortion for both modes. Experimental results illustrate that the proposed block-based architecture has some advantages over classical bitplane-based approaches. Introducing skip and intra coded blocks yields average bitrate gains of up to 33.7% over our basic configuration supporting Wyner–Ziv mode only, and up to 29.7% over the reference bitplane-based DISCOVER codec.