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101.
ABSTRACTThe measurement of acoustic emission (AE) signals during injection molding of polypropylene with new and damaged mold is presented. The damaged injection mold was fitted with a steel insert with cracks induced by laser surface heat treatment. Two resonant piezoelectric AE sensors were attached to the mold via AE waveguides. To improve the mold integrity prediction with smaller defects, AE signal frequency characteristics and a measure of AE signal amplitude probability distribution are implemented. A 5-dimensional feature vector with real-valued explanatory variables is proposed, providing the defining points in an appropriate multidimensional space to characterize the state of injection molding tool. Feature vectors are classified with neural network pattern recognition. The results confirm that presented AE technique offers characterizing the integrity of molds also with resonant sensors. 相似文献
102.
Zoran H. Peric Milan R. Dincic Dragan B. Denic Aleksandar V. Jocic 《Wireless Personal Communications》2011,59(4):625-641
The aim of this paper is to improve the G.711 standard, which is widely used, especially in the public switched telephone
network (PSTN). Two solutions are proposed. The first solution uses only lossless coder, achieving a bit-rate decrease of
0.82 bits/sample, compared to the G.711 codec. The second solution uses forward adaptation and a lossless coder, further decreasing
the bit-rate (by 1.25 bits/sample) and achieving higher average signal-to-quantization noise ratio (SQNR) in comparison with the G.711 codec. Also, the second solution is more robust than the G.711 codec, which means that it has
near constant SQNR for a wide range of input signal power. That is very important for signals whose input power varies with time, such as speech
and video signals. Our solutions are compatible with the G.711 codec, they have little additional complexity and delay and
therefore can be applied in real-time systems, such as PSTN or VoIP. They can also be used in many other systems, such as
WiMax and OFDM, as a replacement or improvement of the G.711 codec. Standardization process of the G.711.1 standard (which
is a wide-band extension of the G.711 standard) is largely present. Our solutions fulfill all the requirements for that new
standard; therefore they can be implemented in its low-frequency part. 相似文献
103.
The aim of this study was to determine ochratoxin A (OTA) concentrations in the raw materials and cooked meat products made from pigs sub-chronically exposed to OTA. The treated animal group (n = 5) was administered with 300 μg OTA/kg of feed for 30 days, whereas the control group (n = 5) was left untreated. OTA concentrations were quantified using immunoassay (ELISA) and high performance liquid chromatography with fluorescence detection (HPLC-FD). OTA concentration was the highest in the kidney, followed by the lungs, liver, blood, spleen, heart, and adipose tissue. As for the final meat products, the highest average OTA concentration was detected in black pudding sausages (14.02 ± 2.75 μg/kg), then in liver sausages (13.77 ± 3.92 μg/kg), while the lowest was found in pâté (9.33 ± 2.66 μg/kg). The results pointed out that a sub-chronic pig exposure leads to the accumulation of OTA in raw materials and consequently in meat products, whose level of contamination is directly dependent on OTA contents in raw materials used for their production. 相似文献
104.
In this paper a cylindrical model of human body exposed to the extremely low frequency (ELF) electromagnetic field is presented. The analysis is based on the solution of the simplified integral equation for thick wires. The numerical solution of the integral equations is performed by the Galerkin–Bubnov variant of the boundary element method. Several numerical results for the ELF exposures are presented. 相似文献
105.
Jelena Svorcan Slobodan Stupar Dragan Komarov Ognjen Peković Ivan Kostić 《Journal of Mechanical Science and Technology》2013,27(8):2367-2373
Small-scale vertical axis wind turbines are regarded today as an attractive source of green energy, still insufficiently implemented and tested. This paper presents a fast design methodology of such a VAWT, in terms of choosing its main parameters: airfoil, rotor diameter and solidity. For obtaining generated power of each considered geometrical model at different undisturbed wind velocities and rotor angular velocities two models were used — momentum and vortex-wake model, combined with experimentally measured airfoil data (airfoil lift and drag coefficients). Even though the former model is simpler, it is the most utilized model, known to provide good results in stationary working regimes. Both models still present fairly accurate and fast tools for computation and optimization, particularly useful in the phase of conceptual design. In this research, the use of the momentum model resulted in determination of the maximal power coefficient, optimal- and minimal freestream velocity for every considered VAWT model. From these output parameters, a selection of the optimal geometric model was done, and a more detailed transient analysis and flow representation around the selected solution was obtained by the vortex-wake model. The results obtained by the two used computational models coincide satisfactorily. 相似文献
106.
107.
Yang Xiang Ruoming Jin David Fuhry Feodor F. Dragan 《Data mining and knowledge discovery》2011,23(2):215-251
Transactional data are ubiquitous. Several methods, including frequent itemset mining and co-clustering, have been proposed to analyze transactional databases. In this work, we propose a new research problem to succinctly summarize transactional databases. Solving this problem requires linking the high level structure of the database to a potentially huge number of frequent itemsets. We formulate this problem as a set covering problem using overlapped hyperrectangles (a concept generally regarded as tile according to some existing papers); we then prove that this problem and its several variations are NP-hard, and we further reveal its relationship with the compact representation of a directed bipartite graph. We develop an approximation algorithm Hyper which can achieve a logarithmic approximation ratio in polynomial time. We propose a pruning strategy that can significantly speed up the processing of our algorithm, and we also propose an efficient algorithm Hyper+ to further summarize the set of hyperrectangles by allowing false positive conditions. Additionally, we show that hyperrectangles generated by our algorithms can be properly visualized. A detailed study using both real and synthetic datasets shows the effectiveness and efficiency of our approaches in summarizing transactional databases. 相似文献
108.
Andreas Kuczynski Dragan Stokic Uwe Kirchhoff 《The International Journal of Advanced Manufacturing Technology》2006,29(3-4):398-407
The effective generation, sharing and re-use of innovation knowledge play an increasingly crucial role in the competitiveness
of industrial enterprises allowing the companies to offer new solutions based on rapidly exploited innovations. As the innovation
knowledge is by its nature very unstructured and manifold in its definition, solutions for effective exchange and sharing
of such knowledge within collaboration networks of extended enterprises are still missing. This paper presents a set of new
methods and IT tools to support efficient and smooth exchange of innovation knowledge in extended and networked enterprises.
The methods and tools are based on so-called hybrid approach in definition of ontologies needed as a basis for knowledge sharing
within a network of companies. The developed tools enable efficient set-up, harmonisation and maintenance of generic, shared
ontologies. The solutions are tested within a large manufacturing enterprise involving several subsidiaries. 相似文献
109.
Structure and mechanical properties of a Nb/Ti microalloyed steel, thermomechanically rolled on a strip-production facility, are evaluated. Small (0.02%) titanium addition to niobium-containing steel is found to increase precipitation while reducing grain-refining potential of niobium. This effect increases with increasing finish-rolling temperature, and is also reflected in an increased charpy energy transition temperature. A reduced tendency for precipitation in a nitrogen-free austenite together with the short interpass times in the finishing train, is assumed to reduce the tendency for pancaking, which is prerequisite for an effective grain refining. 相似文献
110.
Dragan D. Djakovic 《Computer Languages, Systems and Structures》1988,13(3-4):143-147
At the Center for Multidisciplinary Studies, University of Belgrade, Yugoslavia, a high level language for easily manipulating fuzzy set operations was developed. In this paper, after a brief introduction to the theory of fuzzy sets, some features and possibilities are described from the user point of view, and an application in picture enhancement is shown. The language presented was written in BASIC, thus any microcomputer, for personal/home use, should be able to execute RASP. 相似文献