A subgridding method for the time-domain finite-difference methodto solve Maxwell's equations

A modification to the time-domain finite-difference method (TDFDM) that uses a variable step size is investigated. The entire computational volume is divided into a coarse grid with a large step size. A fine grid with a small step size is introduced only around discontinuities. The corresponding time increments are related to the spatial increments with the same ratio in order to minimize the numerical dispersion. The fields within the coarse and fine grids are found using the TDFDM, while an interpolation in space and time is utilized to calculate the tangential electric field on the coarse-fine grid boundary. This subgridding decreases the required computer memory and therefore expands the capability of the TDFDM. The technique is shown to be numerically stable and does not entail any extra numerical error. The method is applied to the calculation of waveguides and microstrips     

Iodine-131-metaiodobenzylguanidine dosimetry in cancer therapy: risk versus benefit

In the treatment of neural crest tumors, such as pheochromocytoma, with[131I]MIBG, bone marrow toxicity limits the amount of administered activity and, thus, a therapeutically useful tumor dose. METHODS: We calculated tumor doses in a series of diagnostic studies with [123I]MIBG using accurate quantification of SPECT and planar scintigraphy. By extrapolating diagnostic results to therapeutic activities of [131I]MIBG, we could compare the results with whole-body doses from a series of therapies. RESULTS: The tumor dose was DT = 2.2 mGy MBq(-1) (median value of 27 measurements, range 0.04 < or = DT < or = 20 mGy MBq(-1) and the whole-body dose in a series of 16 patients undergoing 50 therapies was DWB = 0.12 +/- 0.04 mGy MBq(-1) (mean +/- s.d.). The therapeutic ratio varied between 130 to below 10 in some patients. CONCLUSION: The results were compared with published data. We found clearly skewed distribution of tumor doses, with a majority of tumors receiving only a few mGy per MBq administered activity. In some patients, however, doses did reach 20 mGy MBq(-1).     

Modeling time criticality of information

In this paper, we continue the research on formal treatment of attributes of information, based on the computational approach. In this scenario, the usefulness of advisory information is measured by the decrease in complexity of a problem we need to solve. We propose to model the time criticality via usefulness of a piece of information which is received during the computation. As a modeling tool, we use deterministic finite automata.     

Synthesis of new hyperbranched urethane-acrylates and their evaluation in UV-curable coatings

Three series of hyperbranched urethane-acrylates (HB-UA), based on aliphatic hyperbranched polyesters and polyethyleneglycol acrylate, were prepared and evaluated for use in UV-curable coatings. UV-curing kinetics were monitored by FT-IR spectroscopy. The thermal and mechanical properties of UV-cured HB-UA were investigated by means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) and correlated to the mechanical properties of coatings (hardness and flexibility). These new HB-UA's are very reactive and did not show oxygen inhibition. Obtained coatings have good mechanical properties and solvent resistance.     

The determination of molecular weights of polymers from critical concentrations of ternary systems polymer-polymer-solvent

The dependence of the critical concentration of the ternary system polymer-polymer-solvent on the molecular weight can be expressed by the relation where c_c is the critical concentration, M? the appropriate average of the molecular weight of both polymers; A and c_c∞ are constants for the given system. The possibility of determining the molecular weight of one of the polymers from the value c_c and the molecular weight of the known polymer with the aid of equation (1) is discussed.     

Improving practical exact string matching

We present improved variations of the BNDM algorithm for exact string matching. At each alignment our bit-parallel algorithms process a q-gram before testing the state variable. In addition we apply reading a 2-gram in one instruction. Our point of view is practical efficiency of algorithms. Our experiments show that the new variations are faster than earlier algorithms in many cases.     

Method for HDR-like imaging using industrial digital cameras

Dynamic range of the scene can be significantly wider than the dynamic range of an image because of limitations of A/D conversion. In such a situation, numerous details of the scene cannot be adequately shown on the image. Standard industrial digital cameras are equipped with an auto-exposure function that automatically sets both the aperture value and cameras exposure time. When measuring a scene with atypical distribution of light and dark elements, the indicated auto-exposure time may not be optimal. The aim of work was to improve, with minimal cost, the performance of standard industrial digital cameras. We propose a low complexity method for creating HDR-like image using three images captured with different exposure times. The proposed method consists of three algorithms: (1) algorithm for estimating whether the auto-exposure time is optimal, (2) algorithm which determines exposure times for two additional images (one with shorter and another with longer than auto-exposure time), and (3) algorithm for HDR-like imaging based on fusion of three previously obtained images. Method is implemented on FPGA inserted into standard industrial digital camera. Results show that the proposed approach produces high quality HDR-like scene-mapped 8-bit images with minimal computational cost. All improvements may be noticed through the performance evaluation.

     

A novel split-and-merge algorithm for hierarchical clustering of Gaussian mixture models

The paper presents a novel split-and-merge algorithm for hierarchical clustering of Gaussian mixture models, which tends to improve on the local optimal solution determined by the initial constellation. It is initialized by local optimal parameters obtained by using a baseline approach similar to k-means, and it tends to approach more closely to the global optimum of the target clustering function, by iteratively splitting and merging the clusters of Gaussian components obtained as the output of the baseline algorithm. The algorithm is further improved by introducing model selection in order to obtain the best possible trade-off between recognition accuracy and computational load in a Gaussian selection task applied within an actual recognition system. The proposed method is tested both on artificial data and in the framework of Gaussian selection performed within a real continuous speech recognition system, and in both cases an improvement over the baseline method has been observed.     

Simulation model of general human and humanoid motion

In the last decade we have witnessed a rapid growth of Humanoid Robotics, which has already constituted an autonomous research field. Humanoid robots (or simply humanoids) are expected in all situations of humans’ everyday life, “living” and cooperating with us. They will work in services, in homes, and hospitals, and they are even expected to get involved in sports. Hence, they will have to be capable of doing diverse kinds of tasks. This forces the researchers to develop an appropriate mathematical model to support simulation, design, and control of these systems. Another important fact is that today’s, and especially tomorrow’s, humanoid robots will be more and more humanlike in their shape and behavior. A dynamic model developed for an advanced humanoid robot may become a very useful tool for the dynamic analysis of human motion in different tasks (walking, running and jumping, manipulation, various sports, etc.). So, we derive a general model and talk about a human-and-humanoid simulation system. The basic idea is to start from a human/humanoid considered as a free spatial system (“flier”). Particular problems (walking, jumping, etc.) are then considered as different contact tasks – interaction between the flier and various objects (being either single bodies or separate dynamic systems).     

An interpretation of the changes in demographic behaviour at a sub-national level using spatial measures in post-socialist countries: A case study of the Czech Republic and Slovakia

The transformation of fertility and family behaviour in post-socialist countries was quick and the changes were striking. An account of the changes is the subject of dispute and the mechanisms have still not been explained in a fully satisfying manner. Relatively little attention has been paid to the changes in spatial aspects concerning the broadening of changes in family behaviour. The aim of this paper is to answer the question as to whether changes spread stochastically in post-socialist countries or if there are obvious spatial patterns. The study tries to answer the questions whether there are any cores of changes which may be understood as innovations, if there is any spatial clustering and if the extent is hierarchically arranged.