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1

Entropy production due to conjugate natural convection in a nanofluid-filled enclosure with a stepped wall

Bouchoucha Abd el, Oztop Hakan F., Bessaih Rachid, Abu-Hamdeh Nidal

Engineering Transactions

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2023

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Vol. 71, iss. 2

161-183

EN

The main aim of this paper is to improve the heat transfer in a square cavity with a body at the left wall filled with a Al2O3/water nanofluid for different geometries. Numerous simulation experiments are conducted. A relative temperature is maintained at the vertical and top horizontal walls while the bottom wall is warm. The finite volume approach is considered to resolve the equations governing the thermal transfer flow in the physical domain based on the SIMPLER algorithm. In this study, different values of the following parameters are considered: Rayleigh number (104 ≤ Ra ≤ 105) and solid volume fraction (0 ≤ φ ≤ 0.1) of nanoparticles (NPs). Parameters, such as the Rayleigh (Ra) and Bejan (Be) numbers, thermal conductivity, body’s dimensions, and NPs volume fraction, which directly affect the entropy generation and heat transfer rate, are studied in a particular way. The obtained results show that entropy generation goes ahead with the Ra increase and inverse to the solid volume fraction increase. One can notice that the heat transfer has a proportional relation with φ and Ra.

2

Mixed convection heat transfer in trapezoidal lid-driven cavity with uniformly heated inner circular cylinder

Hussein Asmaa Ali

Archives of Thermodynamics

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2023

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Vol. 44, no 3

99--118

EN

The present work comprises a numerical analysis using the Ansys program to solve the problem of combined free-forced convection around a circular cylinder located in a horizontal lid-driven trapezoidal enclosure. The enclosure is filled with water. The upper moving wall and lower fixed wall are cold at a constant temperature, whereas the inclined walls are adiabatically insulated. The uniformly heated cylinder is located at different positions in the cavity. The study covers three values of Richardson number (0.01, 1, and 10). The results show that the streamlines and isotherms in the enclosure, the Nusselt number and friction factor in the moving wall, hot wall and bottom wall are strongly dependent on the position of the inner hot cylinder. The results are validated with previous work, and the comparison gives good agreement.

3

Four channel optical demultiplexer based on L2 photonic crystal microcavity

Ammari Merzoug, Benmerkhi Ahlem, Bouchemat Mohamed

Optica Applicata

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2022

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Vol. 52, nr 4

613--625

EN

The wavelength demultiplexing is a particularly important function in integrated optics and can be realized using photonic crystals. The aim is to extract accurately the wavelengths in a data flux. In this work, we investigate a new topologies of wavelength demultiplexing based on two-dimensional photonic crystals constituted of dielectric rods spread in a square network. The studied demultiplexer is based on optical filters with optimized parameters in order to extract four different wavelengths in the vicinity of frequencies corresponding to communication windows. It was found that the crosstalk between the structure channels of the demultiplexer are in the range of –19.19 and – 44.1 dB and the channel spacing is equal to 0.96 nm. The simulation results presented in this paper are performed and analyzed using the FDTD method.

4

Model experiments to assess effect of cavities on bearing capacity of two interfering superficial foundations resting on granular soil

Saadi Djamel, Abbeche Khelifa, Boufarh Rafik

Studia Geotechnica et Mechanica

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2020

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Vol. 42, nr 3

222--231

EN

The objective of this paper is to describe the effect of cavities on the bearing capacity of two interfering footings based on granular soil using an exclusively experimental approach with a test model designed in the laboratory. The experimental protocol was carried out based on the variation of several parameters such as the spacing (x) (axis to axis) between the footings, and the distance (H) between the footings and cavities and between the cavities axes (L). The results highlight the effect of cavities and the interference of two strip footings on the bearing capacity factor (q) and efficiency factor (EF). Moreover, the results revealed that, in the case wherein the distance between the footings and the cavity is greater than 3, the cavity impact is eliminated.

5

Design of the Optimal Geometry of the Moulded Piece Based on Numerical Analyses in Cadmould 3D-F

Mańko Paweł Piotr, Majewski Łukasz

Advances in Science and Technology. Research Journal

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2020

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Vol. 14, no 1

96--106

EN

The subject of the work was the assessment of the possibility of using Cadmould 3D-F® software based on numerical analysis to design complex injection moulding cavities with plasticised polymer feed channels on the example of an element requiring special dimensional accuracy. The overarching goal of the design process was to create the most advantageous geometry of the injection moulding cavity model and the dedicated material supply channels, which will minimize the effect of problems occurring during injection moulding process, such as processing shrinkage, surface collapse, warpage and mouldings deformation. As an additional criterion, the smallest possible degree of complexity of the designed system was adopted for economical reasons and elimination of subsequent production problems resulting from the complex geometry of the designed mould.

6

Integrated 25 GHz and 50 GHz spectral line width dense wavelength division demultiplexer on single photonic crystal chip

Balaji V. R., Murugan M., Robinson S., Nakkeeran R.

Opto-Electronics Review

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2018

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Vol. 26, No. 4

285--295

EN

We propose a new integrated demultiplexer model using the two-dimensional photonic crystal (2D PC) through the hexagonal resonant cavity (HRC) for the International Telecommunication Union (ITU) standard. The integrated model of demultiplexer for both 25 GHz and 50 GHz has been designed for the first time. The demultiplexer consists of bus input waveguide, drop waveguide, Hexagonal Resonant Cavity (HRC), 6 Air Hole Filter (6-AHF), 7 Air Hole Filter (7-AHF). The 7-AHF is used to filter 25GHz wavelength, and the 6-AHF filter is used to filter 50 GHz wavelength. The Q-factor on the designed demultiplexer is flexible based on the idea of increasing the number of air holes between drop waveguide and resonant cavity. The demultiplexer is designed to drop maximum 8 resonant wavelengths. One side of demultiplexer is able to drop 50 GHz ITU standard wavelengths, which are of 1556.3 nm, 1556.7 nm, 1557.1 nm and 1557.5 nm, and further the other facet is able to drop 25 GHz wavelengths, which are of 1551.4 nm, 1551.6 nm, 1551.8 nm, and 1552.0 nm. The proposed demultiplexer may be carried out within the integrated dual system. This system is able to lessen the architecture cost and the size is miniaturized substantially.

7

Modelling of superplastic deformation for metallic alloys using a cavity based approach

Marzbali M. H.

Journal of Achievements in Materials and Manufacturing Engineering

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2017

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Vol. 81, nr 2

61--96

EN

Purpose: In this study, modeling of superplastic deformation characteristic for metallic alloys was investigated using GTN failure criteria in viscoplastic framework. Design/methodology/approach: The proposed model studied the simultaneous effects of cavitation and deformation parameter and considered the effects of strain hardening, static and dynamic recoveries, and hydrostatic stress. This cavity based model was then implemented in a creep subroutine in ABAQUS 6.12 finite element software. Findings: Experimental results of Aluminum 5083 from different studies were used to verify the model and evaluate its reliability. Afterwards, numerical simulations for uniaxial tension were performed, and good agreement between experimental and modeling results was obtained. Research limitations/implications: This study showed that using a viscoplastic framework with a cavity criterion ensures more precise pressure-time algorithm, lower deformation time and better failure predictions. These capabilities provides forming more complex parts and different geometries. Accordingly, applying this model is recommended to predict the behaviour of other metallic superplastic alloys.

8

Finite element analysis of the behaviour of a crack in the orthopedic cement

Benouis A., Boulenouar A., Serier B.

Journal of Theoretical and Applied Mechanics

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2016

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Vol. 54 nr 1

277--284

EN

In this paper, the finite element method is used to analyse the crack behaviour in the orthopedic cement of the total hip replacement by computing the stress intensity factors (SIFs) arround the crack tip. In this work, three cases are studied: crack emanating from a cavity, interaction effect of the crack emanating from a cavity with another cavity and the interaction effect of two cracks emanatingfrom two cavities. The stress intensity factors under mixed mode problems at the crack tip are computed for three zones of prosthesis: proximal, median and distal. The obtained results show that the crack initiated from a micro-cavity in the distal zone of cement can be propagated at the same time by opening and shearing of its lips. It is contrary to that initiated in the proximal zone which cannot be propagated. The mechanical behaviour of cracks in the medial zone depends of the crack initiation position.

9

Application of Electrical Resistivity Imaging for Engineering Site Investigation. A Case Study on Prospective Hospital Site, Varamin, Iran

Amini A., Ramazi H.

Acta Geophysica

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2016

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Vol. 64, no. 6

2200--2213

EN

The article addresses the application of electrical resistivity imaging for engineering site investigation in Pishva Hospital, Varamin, Iran. Some aqueduct shafts exist in the study area backfilled by loose materials. The goals of this study are to detect probable aqueduct tunnels and their depth, investigate filling quality in the shafts as well as connection(s) between them. Therefore, three profiles were surveyed by dipoledipole electrode array. Also, to investigate the potentially anomalous areas more accurately, five additional resistivity profiles were measured by a Combined Resistivity Sounding-Profiling array (CRSP). According to the results of 2-D inversion modelling, a main aqueduct tunnel was detected beneath the central part of the site. Finally, the resistivity pattern of the detected aqueduct system passing the investigated area was provided using the obtained results.

10

Safety problem of cavity under open pit bench

Liu X., Li X., Gong F., Liu K.

Archives of Mining Sciences

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2015

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Vol. 60, no. 2

565--580

EN

Some open pits in China are severely threatened by hidden cavities under benches which are always inaccessible and unmapped. The first thing to be well considered is safe and precise cavity detection, as the conventional detection methods cannot output a clear cavity vision, a three-dimensional laser measurement system is employed to perform detection, which is deployed from the surface through boreholes. The results from the scanner demonstrated very well the detailed level of information that can be collected In a cavity using this method, with the cavities’ layout under various benches being fully mapped. As detected cavities are always in horizontal and vaulted roof shape, two different theoretical calculation methods are proposed to analyze the cap rock stability for different roof shape. And also, the three-dimensional solid model generated through scanned laser data is used for stability numerical simulation by converting the data format into the one that recognized in corresponding software. Furthermore, acoustic emission technique is adopted to carry out long term real time rupture monitoring in cap rock, and four kinds of typical monitoring results are discussed which represent the rupture behavior in cap rock of unstable cavity, stable cavity, cavity with large working drill above and cavity beside explosion site. Thus, a complete safety evaluation system for such cavity will be established to ensure safe operation above.

PL

W wielu kopalniach odkrywkowych na terenie Chin powstało zagrożenie wskutek istnienia ukrytych pustek pod warstwami wybierania (ławami), część z nich jest trudno dostępna, a niektóre nie są nawet naniesione na mapach. Najważniejszą kwestią jest więc bezpieczna i dokładna lokalizacja pustek. Ponieważ konwencjonalne metody wykrywania nie są w stanie ujawnić dokładnego obrazu pustek, zastosowano trójwymiarowy laserowy system detekcji pustek, zakładany z powierzchni poprzez wywiercone otwory. Odczyty ze skanera ujawniły dokładne zarysy pustek. Z pomocą tej metody można dokładnie obrazować układy pustek pod warstwami wybierania (ławami). Ponieważ stropy w wykrywanych pustkach są zawsze poziome lub sklepione, zaproponowano dwie teoretyczne metody obliczania stabilność stropu dla różnych jego kształtów. Ponadto, na podstawie danych ze skanera wygenerowano model bryły trójwymiarowej, który wykorzystany został do numerycznych badań stabilności stropu poprzez przekształcenie formatu danych na format rozpoznawalny w zastosowanym oprogramowaniu. Zastosowano także techniki pomiary emisji akustycznej w długofalowym monitorowaniu spękań stropu w czasie rzeczywistym, przeanalizowano cztery rodzaje uzyskanych wyników opisujących zachowanie stropu w przypadku pustek niestabilnych, stabilnych, pustek ponad którymi wykonano otwory znacznych rozmiarów oraz pustek w pobliżu miejsc prowadzenia prac strzałowych. Opracowano w ten sposób pełny system oceny stabilności pustek zapewniający bezpieczne prowadzenie prac ponad nimi.

11

Effects of Interaction between Two Cavities on the Bone Cement Damage of the Total Hip Prothesis

Sahli A., Benbarek S., Bouiadjra B., Mokhtar B. M.

Mechanics and Mechanical Engineering

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2014

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Vol. 18, nr 2

107--120

EN

In orthopedic surgery and more particularly in total hip arthroplasty, the fixation of implants is usually done with surgical cement consisting essentially of polymer (PMMA). Fractures and loosening appear after a high stress gradient. The origin of this phenomenon is the presence of micro–cavity located in the volume of PMMA. The aim of this study is to investigate the effect of the interaction between two cavities on the cement damage where the external conditions (loads and geometric forms) can cause the fracture of the cement and therefore aseptic loosening of the prosthesis. A numerical model is generated using finite element method to analyze the damage of orthopedic cement around the microcavity and estimate the length of the crack emanating from microcavity for each position of the human body. Result show that the damaged area is influenced by the cavity shape (only elliptical cavity shape can initiate damage). The most dangerous cavity position is located in the middle of the cement socket, on the axis of the loading. The distance between two cavities has an effect if it is less than 100 μm. One can estimate the initiation of a crack of maximum length of 16μm.

12

Analiza możliwości wykorzystania magazynów ciekłego propanu, lokowanych w strefie kawern wysadów solnych, do produkcji energii

Pająk L., Gonet A., Śliwa T., Knez D.

Wiertnictwo, Nafta, Gaz

|

2010

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T. 27, z. 4

657-667

PL

Artykuł przedstawia zagadnienia magazynowania płynów w kawernach wytworzonych w wysadach solnych. Wykorzystanie ciepła z wysadów solnych jest koncepcją przyszłościową. W pracy poruszono zagadnienia połączenia pozyskiwania ciepła z magazynowaniem propanu. Przeanalizowano możliwości wykorzystania kawern magazynowych z ciekłym propanem do pozyskiwania ciepła oraz w systemach chłodzenia. Artykuł zawiera analizę możliwości produkcji energii elektrycznej w analizowanym przypadku.

EN

Paper presents fluids storage problems in cavities made in salt domes. Using heat from salt domes is future concept. This work raise a problem of combination propane storage and heat extraction. There are analyzed possibilities of using storage cavities with liquid propane to heating and air conditioning systems. Paper discuss usability of electric energy production in analyzed case.

13

Nesting sites of the Great Spotted Woodpecker Dendrocopos major L. in Poland : analysis of nest cards

Hebda G.

Polish Journal of Ecology

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2009

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Vol. 57, nr 1

149-158

EN

Analysis of 531 nest cards (Polish Nest Record Scheme) of the Great Spotted Woodpecker, obtained in the years 1970-2003 is presented here. The data is derived from almost the whole of Poland, except for the Białowieża National Park. From the material processed for the purpose of this study, the Great Spotted Woodpeckers appear to nest in various types of wooded habitats, especially in forests and they are very flexible in their choice of nesting sites, both in terms of age of tree stands and intensity of human penetration. As a rule, woodpeckers breed mostly in holes made in deciduous trees (oak, birch, and alder). More than 95% of nests were excavated in tree trunks, primarily in dead or weakened trees. Woodpeckers excavated their nest in the range of 0.5-19 m above the ground, with more than 75% of them found in the narrower range from 1-7 m. The height of cavity above the ground did not depend on tree species or vegetation type and was also weakly correlated with the height of tree stands. The openings of cavities showed no statistically significant differences in their geographical orientation. Although the information about woodpecker nests, gathered in the Nest Record Scheme does contain certain errors (such as "habitat preferences" of observers), the obtained results provided a better insight into the nesting ecology of this species in Poland.

14

Indirect method of measuring changes of EM field in RF-gun cavity for XFEL accelerator

Poźniak K., Stanisławski T., Zabołotny W., Koehler W., Stephan F., Simrock S.

Elektronika : konstrukcje, technologie, zastosowania

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2009

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Vol. 50, nr 8

193-199

EN

In the article a RF-Gun control system is described. Difficulties caused by the impossibility to observe the field gradient are mentioned. Next calibration and measurement procedure is discussed. A mathematical model, which provides a way to calculate the desired signal from observed ones is developed and analyzed. This model is supported by both measurements and simulations discussed in the final part of the article.

PL

Artykuł opisuje system sterowania działem elektronowym. Uwzględniono w nim problemy wynikające z niemożności bezpośredniego pomiaru gradientu pola we wnęce. Przedyskutowano procedurę kalibracji i pomiaru. Opracowano i przeanalizowano model matematyczny pozwalający estymować szukany parametr na podstawie sygnałów dostępnych do pomiaru. Poprawność modelu została potwierdzona pomiarami i symulacjami przedstawionymi w końcowej części artykułu.

15

Ośmiokanałowy zintegrowany system sterowania modułem akceleratora X-FEL/TESLA

Giergusiewicz W., Poźniak K., Romaniuk R. S.

Elektronika : konstrukcje, technologie, zastosowania

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2005

|

Vol. 46, nr 7

51-55

PL

Przedstawiono projekt, konstrukcję i wstępne pomiary właściwości ośmiokanałowego modułu elektronicznego przeznaczonego do budowy systemu sterowania akceleratora TESLA (DESY). Moduł, nazywany w pracy SIMCON 3 (cavity simulator and controller), składa się z dużego układu FPGA (Virtexll-4000 firmy Xilinx), ośmiu szybkich przetworników A/C i czterech C/A firmy Analog Devices. Moduł wykonano jako 16-warstwową płytę drukowaną usytuowaną na uniwersalnej platformie LLRF. Jest pierwszym tego typu rozwiązaniem dla techniki akceleratorowej, w którym uzyskano latencję algorytmu sterowania DSP poniżej 250 ns. Przy optymalizacji systemu transmisji danych możliwa jest redukcja latencji systemu LLRF do 500 ns.

EN

The paper describes design, construction and initial measurements of eight channel electronic device predicted for building of the control system for TESLA accelerator (DESY). The device, referred in the paper to sa the SIMCON3 (from cavity simulator and controller) consists of 16 layer PCB, a large FPGA chip (Virtexll-4000 firmy Xilinx), eight ADC and four DAC (Analog Devices). The proposed device is the first of this kind for accelerator technology in which there was achieved DSP latency below 200 ns. With the optimized data transmission system the overall LLRF system latency can be as low as 500 ns.

16

The dynamics of an ideal fluid flow into an inclined cavity of a paraboloid form

Filip D., Trimbitas R., Pop I.

International Journal of Applied Mechanics and Engineering

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2001

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Vol. 6, no 4

947-968

EN

The present paper is a theoretical study of the motion of an inclined cavity of a paraboloid form filled with an ideal and incompressible fluid. The cavity is placed in the gravity field and its roto-translation motion is unknown. We look for determining the translation and rotation velocities of the cavity, the velocity potential of the fluid particles as well as the form of the fluid free surface. To this end, we shall use both the analytical and numerical methods. Numerical examples are presented in tables and graphs to elucidate the accuracy and efficiency of the proposed method.

17

Recent sinkholes in an area of intensive karst development in northern Lithuania

Bucevičiūtė S., Mikulėnas V.

Geological Quarterly

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2000

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Vol. 44, Nr 4

371-375

EN

The karst of northern Lithuania is developed in gypsiferous layers of the Pasvalys and Nemunelis beds of the Tatula Formation of the Upper Devonian (Frasnian) stage. The new sinkholes formed during the last ten years in around Birzai and Pasvalys indicate recent karst activity. 84 recent sinkholes appeared around the villages of Karajimiskis, Mantagailiskis in the Birzai district from 1995 to 1999. The three biggest sinkholes occur in Pasvalys. Karst processes and phenomena are particularly dangerous in urban areas. The sudden appearance of sinkholes and ground subsidence have often caused building damage. New sinkholes indicate a very sensitive engineering geological environment.