Sensitivity analysis of truss structures (virtual distortion method approach)

A new approach to structural sensitivity analysis based on the so-called virtual distortion method is presented. The proposed methodology enables the calculation of derivatives for elastic as well as elasto-plastic structures on the basis of knowledge of current strains, permanent plastic deformations and influence matrix, describing interactions between a chosen member and the entire structure. The analytical basis as well as numerical verification of the concept is demonstrated. Advantages of the proposed approach, in the sense of numerical cost, are summarized in conclusions. © 1998 John Wiley & Sons, Ltd.     

Boosting-based Sequential Output Prediction

Sequence prediction problem has been traditionally identified in the literature with sequence labeling. This approach typically corresponds to the classification of a label sequence associated to observed input sequence. However, another interpretation of sequence prediction may be considered where a label sequence (sequential output) is classified based only on the independent set of attributes. The paper presents a new, based on boosting, ensemble approach, performing such sequential output prediction. The sequential nature of the classified structure is reflected on the applied cost function. The experimental results reported in the paper revealed a high validity and competitiveness of the proposed approach.     

Hyperlink Recommendation Based on Positive and Negative Association Rules

The new HRS method for hyperlink recommendation based on positive and confined negative association rules is presented in the paper. Discovered with the new PANAMA algorithm rules are merged and used in the form of recommendation functions, both to assess the existing hyperlinks and to suggest new ones. Positively and negatively verified and new hyperlinks are presented to the content manager and can considerably facilitate the maintenance of the web site structure and its adjustment to user behaviour. The experiments confirmed the usefulness of the Hyperlink Recommender System (HRS) and in particular, of negative recommendations based on confined negative association rules.

Photoactive epichlorohydrin, 2. Photoinitiated free-radical and promoted cationic polymerization by using polyepichlorohydrin with benzoin terminal groups

The photoinitiated free-radical polymerization of methyl methacrylate (MMA) and the radical-promoted cationic polymerization of cyclohexene oxide (CHO) in the presence of low-molecular-weight polyepichlorohydrin terminated with groups containing benzoin derivatives were studied. Benzoin-terminated polyepichlorohydrin was prepared by Activated Monomer (AM) polymerization. Upon photolysis. polymer-bound alkoxy benzyl radicals were generated, initiating the radical polymerization of MMA. In the case of radical-promoted cationic polymerization of CHO, the cationic initiating species were formed by the oxidation of photochemically generated polymeric radicals by N-ethoxy-2-methylpyridinium hexafluorophosphate.     

Bacterial cell killing properties of silver-loaded polysiloxane microspheres

Cross-linked polysiloxane microspheres containing a large number of SiOH groups were modified by introduction of organic thiol groups, which were further used for the functionalization of the microspheres with silver thiolate groups. The microspheres were characterized by ²⁹Si MAS NMR, ¹³C MAS NMR, SEM, XPS and elemental analysis. They were tested as biocides against selected Gram-positive and Gram-negative bacteria strains and exhibited high bactericidal activity. Separately, linear polysiloxane polymers equipped with organothiol groups and loaded with silver were synthesized. Their antibacterial activity was compared with that of silver thiolate-functionalized microspheres. Different shape of particles and a different form of silver explained somewhat lower activity of polymers.     

Strength of silicon wafers: fracture mechanics approach

This paper describes a model to predict mechanical strength distribution of silicon wafers. A generalized expression, based on a multimodal Weibull distribution, is proposed to describe the strength of a brittle material with surface, edge, and bulk flaws. The specific case of a cast, unpolished photovoltaic (PV) wafer is further analyzed. Assuming that surface microcracks constitute the dominant mechanism of wafer breakage, this model predicts the strength distribution of PV silicon that matches well the experimental results available in the literature.     

A new approach to BER estimation for ISI corrupted baseband transmission systems

This paper derives two new formulae for BER estimation when the transmission system is subject to both intersymbol interference and additive Gaussian noise. The approach undertaken here was oriented to find a simple formula giving close estimation of the true BER, which may be useful for the transmission system designer for rapid evaluation of system performance. The obtained results are compared with commonly used BER estimations. Copyright © 2001 John Wiley & Sons, Ltd.     

Hologram-like transmission of pictures

A new digital representation of pictures is proposed. The main feature of this representation is: Given a string of data Z representing a picture with full resolution, various substrings of Z represent the same picture with appropriately lower resolution. This is analogous to a well-known property of holograms. The new representation is based on a particular picture traversal algorithm and uses overlapping sampling areas. The paper presents the principle of this representation, analyzes its overhead, and provides examples of picture reconstruction. An application of the hologram-like representation to the transmission of pictures with progressive resolution is indicated.     

Refining the macromolecular model – achieving the best agreement with the data from X-ray diffraction experiment

ABSTRACT

Refinement of macromolecular X-ray crystal structures involves using complex software with hundreds of different settings. The complexity of underlying concepts and the sheer amount of instructions may make it difficult for less experienced crystallographers to achieve optimal results in their refinements. This tutorial review offers guidelines for choosing the best settings for the reciprocal-space refinement of macromolecular models and provides practical tips for manual model correction. To help aspiring crystallographers navigate the process, some of the most practically important concepts of protein structure refinement are described. Among the topics covered are the use and purpose of R-free, geometrical restraints, restraints on atomic displacement parameters (ADPs), refinement weights, various parametrizations of ADPs (full anisotropic refinement and TLS), and omit maps. We also give practical tips for manual model correction in Coot, modelling of side-chains with poor or missing density, and ligand identification, fitting, and refinement.