Wyniki wyszukiwania - BazTech

1

Energetic efficiency of mixing in a periodically reoriented Dean flow

Rożeń Antoni, Kopytowski Janusz

Chemical and Process Engineering

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2021

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Vol. 42, nr 4

391–-410

EN

The energetic efficiency of mixing is studied numerically in a continuous flow mixer constructed from a sequence of alternately twisted pipe bends. Counter-rotating vortices present in the curved channels and known as Dean vortices narrow the distribution of the residence time of fluid elements and accelerate the generation of a new material surface without obstructing the main flow and increasing the risk of fouling or flow stoppage. Cyclic twisting of the pipe curvature allows for quick reorientation of Dean vortices. The reorientation induces chaotic advection in a stable three-dimensional flow and speeds up mixing. The effect of computational domain discretisation for the low and medium Reynolds numbers (20 < Re < 2000º on the head loss, primary and secondary flow, residence time distribution, and the energetic efficiency of generation of the inter material surface is determined. The energetic efficiency is calculated in the time space, a standard approach in modelling reactive micromixing, and at the reactor exit. The maximum energetic efficiency is determined for Re = 600 : 700. It is also found that the initial orientation of the material surface to the pipe curvature has a significant impact on the energetic efficiency of mixing.

2

Advanced time-frequency representation in voice signal analysis

Mika Dariusz, Józwik Jerzy

Advances in Science and Technology. Research Journal

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2018

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Vol. 12, no 1

251--259

EN

The most commonly used time-frequency representation of the analysis in voice signal is spectrogram. This representation belongs in general to Cohen’s class, the class of time-frequency energy distributions. From the standpoint of properties of the resolution, spectrogram representation is not optimal. In Cohen class representations are known which have a better resolution properties. All of them are created by smoothing the Wigner-Ville’a distribution characterized by the best resolution, however, the biggest harmful interference. The used smoothing functions decide about a compromise between the properties of resolution and eliminating harmful interference term. Another class of time-frequency energy distributions is the affine class of distributions. From the point of view of readability of analysis of the best properties are known so called Redistribution of energy caused by the use of a general methodology referred to as reassignment to any time-frequency representation. Reassigned distributions efficiently combine a reduction of the interference terms provided by a well adapted smoothing kernel and an increased concentration of the signal components.

3

Stratigraphic absorption compensation based on multiscale shearlet transform

Liu C., Wang D., Sun J., Li Y., Yang F.

Acta Geophysica

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2018

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Vol. 66, no. 4

575--584

EN

Seismic waves propagating through viscoelastic media experience stratigraphic absorption and attenuation effects, which directly affect the imaging resolution in seismic exploration. Without stratigraphic absorption, the ratio of deep reflection energy to shallow reflection energy (attenuation ratio) is invariable at different frequencies. If a seismogram is decomposed into different frequency bands, these signals will show similar time–energy distributions. Therefore, the attenuation ratios should be similar across different frequency bands, except for frequency-variable weights. Nevertheless, the frequencyvariable weights for different frequency bands can be obtained by benchmarking against the time–energy distributions of low-frequency information because the loss of low-frequency information is relatively insignificant. In this light, we obtained frequency-variable weights for different frequencies and established a stratal absorption compensation (SAC) model. The anisotropic basis of the shearlet enables nearly optimal representation of curved-shape seismic signals, and shearlets at different scales can represent signals for different frequency bands. Then, we combined the SAC model with the shearlet transform and established the new compensation method. As the signal and noise have different distributions in the shearlet domain, we selectively compensated the signals using a thresholding algorithm. Hence, it was possible to avoid noise enhancement. This is the prominent advantage of the proposed method over other compensation methods.

4

Analiza i symulacje czasowych protokołów zabezpieczających

Szymoniak S.

Studia Informatica

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2017

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Vol. 38, nr 2

55--66

PL

W pracy zawarto opis problemu weryfikacji czasowych protokołów zabezpieczających przy uwzględnieniu opóźnień w sieci. Za pomocą specjalnie skon-struowanego modelu formalnego, który stał się podstawą do implementacji narzędzia, możliwe jest obliczanie czasu poprawnego wykonania protokołu. Narzędzie umożli-wia przeprowadzenie badań czasowych protokołów zabezpieczających, w tym prze-prowadzenie symulacji.

EN

This paper contains a description of the problem of timed security pro-tocols verification, taking into account delays in the network. Using a specially con-structed formal model, which became the basis for the implementation of the special tool, it is possible to calculate the correct time of execution protocol. The tool enables testing timed security protocols, including simulations.

5

On the Motivation and Foundation of Natural Time Analysis: Useful Remarks

Varotsos A., Sarlis N. V., Skordas E. S.

Acta Geophysica

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2016

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Vol. 64, no. 4

841--852

EN

Since its introduction in 2001, natural time analysis has been applied to diverse fields with remarkable results. Its validity has not been doubted by any publication to date. Here, we indicate that frequently asked questions on the motivation and the foundation of natural time analysis are directly answered if one takes into account the following two key points that we have considered as widely accepted when natural time analysis was proposed: first, the aspects on the energy of a system forwarded by Max Planck in his Treatise on Thermodynamics; second, the theorem on the characteristic functions of probability distributions which Gauss called Ein Schönes Theorem der Wahrscheinlichkeitsrechnung (beautiful theorem of probability calculus). The case of the time series of earthquakes and of the precursory Seismic Electric Signals are discussed as typical examples.

6

Cykl realizacji zamówienia w łańcuchu dostaw branży motoryzacyjnej - analiza opóźnień

Kramarz M.

Prace Naukowe Politechniki Warszawskiej. Transport

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2008

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z. 64

77-86

PL

Czas w logistycznej obsłudze klienta odnoszony jest przede wszystkim do okresu trwania cyklu realizacji zamówienia. Przyjmuje się, że klienci oczekują jak najkrótszego czasu dostawy, a firmy starają się; spełnić oczekiwania klientów. Do identyfikacji procesów i ich analizy posłużono się techniką mapowania. W celu wyeliminowania problemów i opóźnień w obszarze produkcji przeprowadzono dokładną analizę procesów wytwarzanie za pomocą metody Mapowania Strumienia Wartości.

EN

Polish companies have to meet requirements concerning the service of clients. For that reason, maintaining high quality of services provided, they should also try to decrease the time of order realization. Nowadays, flexibility of a company's logistic system is essential, since it requires from companies the capacity to quickly and efficiently adjust to changing demand and the ability to quickly change the products offered for the market. The cycle of order realization goes through all links of a supply chain, thus it is one of the most fundamental criterion in assessing its efficiency. For the analysis of order realization cycle, one should recall the values influencing the creation of added value. The group of operations not adding the value should be reduced, factors adding the value need to be temporarily restricted only in the limit of maintaining the required level of client service, without worsening the service quality.

7

Metody sprzętowej implementacji kryptografii odpornej na kryptoanalizę

Strachacki M., Piotrowski R.

Zeszyty Naukowe Wydziału ETI Politechniki Gdańskiej. Technologie Informacyjne

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2007

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T. 14

601-608

PL

W pracy zaprezentowano problematykę kryptoanalizy implementacji sprzętowych bazującej na informacji z kanału bocznego. Opisano rodzaje ataków pasywnych ze szczególnym uwzględnieniem analizy czasowej i analizy poboru mocy. Przedstawiono podstawowe metody zapobiegania atakom. Zaproponowano metodę projektowania wykorzystującą wyrównywanie mocy w asynchronicznych układach kombinacyjnych oraz w układach synchronicznych. Dokonano implementacji algorytmu AES w układzie FPGA Xilinx Spartan II-E w wersji standardowej i zmodyfikowanej. Osiągnięte wyniki symulacji wykazały, że zaproponowana metoda projektowania skutecznie uniemożliwia wykonanie analizy mocy DPA.

EN

The paper presents cryptoanalysis issues of hardware implementations based on side channel information. Kinds of passive attacks are described, especially considering timing analysis and power analysis. Basic countermea-sures against known attacks are shown. New design method based on both asynchronous and synchronous power equalization is proposed. Algorithm AES is chosen for implementation on FPGA Xilinx Spartan II-E device using standard and modified design methodology. Simulation results show that proposed design methodology efficiently prevents from carring out differential power analysis.

8

Zastosowanie programu Pertmaster Professional +Risk do analizy czasu harmonogramu robót inżynierskich

Połoński M., Bogusz W.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2005

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Vol. 14, No. 1

234--243

EN

Basic messages were given to the chance to apply the Pertmaster Professional +Risk application for the subject in the article for the construction of network schedules and leading the analysis of the time. System requirements of the application, introducing data about activities, defining the relation between activities were characterized in paper. Possibilities were given to the presentation of the schedule in the form of the Gantt and the network chart. The edition of the calendar of the project or activities and dates restrictions were characterized. They took note of the chance to setting dependencies between task and of introducing delays between activities. The method of leading the analysis of the time and the chance to provide documentation for effects of counts carried out was characterized in the more far-away part.