Wyniki wyszukiwania - Biblioteka Nauki

1

A study of critical point instability of micro and nano beams under a distributed variable-pressure force in the framework of the inhomogeneous non-linear nonlocal theory

100%

Rahimi Z. , Rezazadeh G. , Sumelka W. , Yang X.-J.

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tom Vol. 69, nr 6

413--433

EN

Fractional derivative models (FDMs) result from introduction of fractional derivatives (FDs) into the governing equations of the differential operator type of linear solid materials. FDMs are more general than those of integer derivative models (IDMs) so they are more fixable to describe physical phenomena. In this paper the inhomogeneous nonlocal theory has been introduced based on conformable fractional derivatives (CFD) to study the critical point instability of micro/nano beams under a distributed variable-pressure force. The phase of distributed variable-pressure force is used for electrostatic force, electromagnetic force and so on. This model has two free parameters: i) parameter to control the order of inhomogeneity in constitutive relations that gives a general form to the model, and ii) a nonlocal parameter to consider size dependence effects in micron and sub-micron scales. As a case study the theory has been used to model micro cantilever (C-F) and doubly-clamped (C-C) silicon beams under a distributed uniform electrostatic force in the presence of von-Karman nonlinearity and their static critical point (static pull-in instability), moreover, effects of different inhomogeneity have been shown on the pull-in instability.

2

Elevated active contour with global image energy based on electrostatic force

75%

Bołdak C.

Zeszyty Naukowe Politechniki Białostockiej. Informatyka

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2010

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tom Z. 6

5-21

EN

In this article a new modification of the well known segmentation technique, namely active contour - snake, was proposed. This modification consists in a new formulation of its external force based on the electrostatics. However the base idea of giving electric charges to the image and the snake has been already presented in several works, none of them clearly adressed the problem where the charged snake took place of a charged pixel. In this situation the electrostatic force is not defined, since the distance between charges is zero. The snake proposed in this work evolves on a plane elevated above the image, what never allows this distance to become zero. The method was implemented and verified on real microscopic images of oocytes, proving its superiority on the classic snake.

PL

W artykule tym zaprezentowana jest nowa modyfikacja techniki segmentacji znanej pod nazwą aktywnego konturu - węża. Polega ona na nowym sformułowaniu siły zewnętrznej opartej na sile elektrostatycznej. W istniejących pracach, w których obraz i kontur posiadały ładunek elektryczny, omijano problem konturu zajmującego pozycję naładowanego piksela. W takiej sytuacji siła elektrostatyczna jest niezdefiniowana, gdyż odległość między ładunkami jest zerowa. Proponowany w tej pracy kontur operuje na płaszczyźnie wyniesionej ponad obraz, co sprawia, że odległość ta nigdy nie spada do zera. Metoda została zaimplementowana i zweryfikowana na rzeczywistych obrazach mikroskopowych oocytów, gdzie wykazała swoją wyższość nad klasyczną techniką węża.

3

Computer modelling and simulation as a research and proposal method of some selected physical-technical systems

75%

Bernat M. , Cimbala R.

International Journal of Applied Mechanics and Engineering

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2008

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tom Vol. 13, no 1

263-271

EN

The article deals with the application of the research method of mathematical modelling and simulation at solving some issues in the area of electrostatic technology. It focuses on the process of electrostatic separation and sorting. The author emphasises the necessity of taking into account the existence and effects of gradient force acting in the process. The presented computer models may be applied both by profect and design engineers using the most advanced computer-aided design of electrostatic technologies, f.e. in these areas where computer simulation is highly required such as in prognosing and diagnosing critical operating states.

4

Zinc ion adsorption on carbon nanotubes in an aqueous solution

75%

Ansari A. , Mehrabian M. A. , Hashemipour H.

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tom Vol. 14, nr 3

29-37

EN

The literature devoted to numerical investigation of adsorption of heavy metal ions on carbon nanotubes is scarce. In this paper molecular dynamics is used to simulate the adsorption process and to investigate the effect of the infl uencing parameters on the rate of adsorption. The predictions of the molecular dynamics simulation show that the adsorption process is improved with increasing the temperature, pH of solution, the mass of nanotubes, and surface modifi cation of CNT using hydroxyl and carboxyl functional groups. The results predicted by the model are compared with the experimental results available in the literature; the close agreement validates the accuracy of the predictions. This study reveals that the water layers around the carbon nanotubes and the interaction energies play important roles in the adsorption process. The study also shows that electrostatic force controls the attraction of zinc ions on the nanotube sidewall.

5

Numerical calculation of electrostatic forces in Micro Electro Mechanical Systems (MEMS)

75%

Greiff M. , Bala U. , Freitag J. , Mathis W.

Przegląd Elektrotechniczny

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2007

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tom R. 83, nr 11

18-20

EN

Since the forces are one of the main parts of the interface between mechanical and electrical part, their calculation plays an important role in the simulation of micro electro mechanical systems (MEMS). In this paper an approach for the numerical calculation of electrostatic forces in MEMS is presented and applied to an electrostatic force microscope (EFM).

PL

Siła jest głównym elementem "łączącym" obwody mechaniczne i elektryczne. Jej obliczanie odgrywa ważną rolę w symulacji mikroukładów elektro-mechanicznych (MEMS). W artykule przedstawiono numeryczne obliczenia sił elektrostatycznych w systemach MEMS na przykładzie mikroskopu EFM.

6

Sterowanie i pomiar planarnych aktuatorów elektrostatycznych

63%

Palczyńska A. , Ekwińska M. , Janus P. , Grabiec P. , Gotszalk T.

Przegląd Elektrotechniczny

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2012

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tom R. 88, nr 10b

95-97

PL

W niniejszym artykule zostały opisane badania dwóch typów planarnych aktuatorów elektrostatycznych. Przedstawiono zasadę działania aktuatorów z uwzględnieniem zjawiska przyciągania elektrod. Zaprezentowano obliczenia podstawowych parametrów mechanicznych takich jak stałe sprężystości i częstotliwości rezonansowe. Porównano ponadto charakterystyki uzyskane dwiema metodami – z zastosowaniem interferometru światłowodowego, a także światłowodowego czujnika zbliżeniowego. Omówiono wady i zalety wymienionych metod w odniesieniu do badanych aktuatorów.

EN

In this article investigations of two types of planar electrostatic actuators are described. The principle of actuator operation is explained. The basic parameters of the analysed system are calculated, including spring constant and resonant frequency. The characteristics measured with Fabry-Perot interferometer and fiber proximity sensor system are compared. The advantages and disadvantages of measurements planar electrostatic actuators with these two methods are described.

7

Modelling of coalescence in turbulent liquid/liquid dispersions considering droplet charge

63%

Kamp J. , Nachtigall S. , Maaß S. , Kraume M.

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2012

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tom R. 109, z. 1-M

113--124

EN

Drop size distributions in liquid/liquid systems within a turbulent flow, being an integral part of many technical applications, can be simulated solving population balance equations. Experimental investigations in stirred toluene/water systems at constant ionic strength of 0.1 mol/L showed that with pH values higher than 11, coalescence is hindered considerably due to electrostatic effects. Within this work, two designated models are used to simulate the transient drop size distributions in a stirred tank, showing that the influence of droplet charge due to a change in pH value or ion concentration cannot be predicted satisfactorily by existing models. This finding motivates a new modelling approach implementing the DLVO theory into the population balance framework.

PL

Nierównomierne rozmieszczenie w przepływie turbulentnym w układach między płynami, stanowiących integralną część wielu urządzeń technicznych, można symulować przez rozwiązywanie równań równowagi populacji. Badania doświadczalne w zakresie mieszanych układów toluen/woda przy stałej sile jonowej 0,1 mol/L pokazały, że przy wartościach pH przekraczających 11 koalescencja jest znacznie utrudniona ze względu na efekty elektrostatyczne. W pracy niniejszej wykorzystano dwa przydzielone modele symulujące nierównomierne rozmieszczenie przejściowe w mieszanym zbiorniku. Za pomocą istniejących modeli nie można wiarygodnie prognozować wpływu ładunku kropelki po zmianie wartości pH lub stężenia jonu. Odkrycie to stanowi motywację dla nowej taktyki realizowania teorii DLVO w zakresie równowagi populacji.

8

A review on active techniques in microchannel heat sink for miniaturization problem in electronic industry

51%

Bhandari P. , Singh J. , Kumar K. , Ranakoti L.

Acta Innovations

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2022

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tom no. 45

45--54

EN

With continuous miniaturization of modern electronic components, the need of better cooling devices also keeps on increasing. The improper thermal management of these devices not only hampers the efficiency but can also cause permanent damage. Among various techniques, microchannel heat sink has shown most favourable performance. To further enhance the performance, two techniques i.e., active and passive are used. In passive technique, no external power source is required like heat sink design alteration and working fluid modification. External power source is necessary for heat transfer augmentation in the microchannel heat sink when using the active approach. Due to compact size of microchannel, active techniques are not used more often. However, the present work highlights the different active technique used in microchannel i.e., Electrostatic forces, flow pulsation, magnetic field, acoustic effects, and vibration active techniques. Above mentioned techniques have been analysed in detail.

9

Analysis of Mechanical Traces Left Probably by Ball Lightning

51%

Polak W.

Advances in Science and Technology. Research Journal

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2021

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tom Vol. 15, no 4

182--191

EN

A possible ball lightning (BL) incident, reported in a local TV as a thunderbolt which during heavy storm entered the room through one of windows and left it through the other, is analyzed. Precise reports, concerning the course of the incident and caused damages, were collected over the next few days in talks with seven eyewitnesses. To verify the reports, photographic documentation, pieces of the window panes, front-window meshes and other fragments of damaged objects were collected simultaneously on the scene. Reconstruction of the glass panes in the laboratory and analysis of Wallner lines existing on surfaces of radial cracks of the panes enabled to identify the direction of force causing the pane breakage. Since the forces turned out to be external for both windows, it excludes the reported movement of BL through the room. From the analysis of traces, the object which destroyed the window pane from the outside should have the following properties differing from those of an ordinary stone: it should be able to break the mesh mechanically on a small circular area, then becoming a larger and softer object be able to push the glass pane forcefully and violently. BL may be responsible for the damages if a solid-like non-hot BL core, capable to explode, is assumed. It is postulated that the BL core is composed of positively-charged crystalline nanoparticles of covalently-bonded nitrogen ions N+ and electron gas inside.