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Parametric studies of CPW pentagonal Sierpinski gasket fractal patch antenna

Rashid Amier Hafizun Ab., Ahmad Badrul Hisham, Abd Aziz Mohamad Zoinol Abidin, Hassan Nornikman, Mazalan Mazlee

Przegląd Elektrotechniczny

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2023

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R. 99, nr 7

186--191

EN

The parametric study on a dual band CPW Pentagonal Sierpinski gasket fractal patch antenna for WiMAX and WLAN applications is presented in this work. In order to accomplish and advantages of multi-band, broadband, high gain, and low-profile antennas, novel geometries must be developed due to the limits of the conventional antenna design, Sierpinski gasket fractal structure is chosen to improve the antenna performance. The work began with Antenna A as the initiator step with pentagonal patch with CPW technique. Then, it goes with Antenna B was the first iteration stages with pentagonal slot. After that, the work continued by five different parametric studies are chosen in this work to define the effect of different dimensions of the patch antenna. The first and second parametric study works include a different width and length size of the patch antenna at Antenna A. The other three involved in the Antenna B, are including the different dimensions of the CPW / feeding antenna gap, feed line, and lastly the slot width dimension. At 3.5 GHz and 5.8 GHz, the antenna's aimed frequencies are - 31.70 dB and - 22.00 dB, respectively, and these values are feasible for WiMAX and WLAN operation.

PL

W pracy przedstawiono badanie parametryczne dwuzakresowej anteny CPW Pentagonal Sierpińskiego z uszczelką fraktalną dla aplikacji WiMAX i WLAN. Aby osiągnąć i wykorzystać zalety anten wielopasmowych, szerokopasmowych, o dużym zysku i niskoprofilowych, należy opracować nowe geometrie ze względu na ograniczenia konwencjonalnej konstrukcji anteny, wybrano strukturę fraktalną uszczelki Sierpińskiego w celu poprawy wydajności anteny. Pracę rozpoczęto od Anteny A jako kroku inicjującego z pięciokątną łatą techniką CPW. Następnie, z anteną B, były pierwsze etapy iteracji z pięciokątną szczeliną. Następnie w tej pracy wybrano pięć różnych badań parametrycznych, aby określić wpływ różnych wymiarów anteny krosowej. Pierwsze i drugie badania parametryczne obejmują różne wymiary szerokości i długości anteny krosowej na antenie A. Pozostałe trzy prace związane z anteną B obejmują różne wymiary szczeliny CPW/anteny zasilającej, linii zasilającej i wreszcie wymiar szerokości szczeliny. Przy 3,5 GHz i 5,8 GHz docelowe częstotliwości anteny wynoszą odpowiednio -31,70 dB i -22,00 dB i wartości te są możliwe do pracy w sieciach WiMAX i WLAN.

2

Prediction of cavitation inside mini-sac Diesel injector nozzle using computational fluid dynamics

Bansode Vaibhav, Verma Munna, Pandhare Amar, Shinde Sandip

Journal of Mechanical and Energy Engineering

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2022

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Vol. 6, No 1

7--12

EN

The performance of the internal flow of the fuel injector is impeded by several factors. The nozzle is one of the factors, being typically about a millimeter long and a fraction of a millimeter in diameter. Cavitation inside the diesel injector nozzle is associated with local pressure distribution. At flow areas with sharp corners, the pressure may locally drop below vapour pressure. The aim of this study is to assess the impact of turbulence and cavitation models on the prediction of flow in diesel injection nozzle. In the present study, an analysis of an existing 6 hole mini-sac diesel injector nozzle is carried out using a CFD package. The main objective of the research is to design a nozzle to avoid cavitation and to find out the contribution of different parameters through parametric study. Cavitation is a complex phenomenon whose appearance depends on the physical as well as flow properties of the flowing substance. Thus, for a better visualization of cavitation, a 3D CFD simulation of mini-sac injector nozzle is carried out. An analysis of a single nozzle hole of a mini-sac diesel injector nozzle is considered for the analysis, as the flow is uniformly distributed through each nozzle. As the three-dimensional geometry of mini-sac nozzle is complicated, therefore tet/hybrid element with T-Grid meshing scheme is used, for good surface meshing. The analysis is carried out at injection pressure of 5 00 bar. The CFDresults are validated against test data with the maximum deviation for the mass flow rate of 8.67% at full needle lift.

3

Bio inspired salamander robot with Pneu-Net Soft actuators – design and walking gait analysis

Natarajan Elango, Chia Kwang Y., Faudzi Ahmad Athif Mohd, Lim Wei Hong, Ang Chun Kit, Jafaari Ali

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2021

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Vol. 69, nr 3

art. no. e137055

EN

The research was attempted to mimic the locomotion of the salamander, which is found to be one of the main animals from an evolutionary point of view. The design of the limb and body was started with the parametric studies of pneumatic network (Pneu-Net). Pneu-Net is a pneumatically operated soft actuator that bends when compressed fluid is passed inside the chamber. Finite Element Analysis software, ANSYS, was used to evaluate the height of the chamber, number of chambers and the gap between chambers for both limb and body of the soft mechanism. The parameters were decided based on the force generated by the soft actuators. The assembly of the salamander robot was then exported to MATLAB for simulating the locomotion of the robot in a physical environment. Sine-based controller was used to simulate the robot model and the fastest locomotion of the salamander robot was identified at 1 Hz frequency, 0.3 second of signal delay for limb actuator and negative π phase difference for every contralateral side of the limbs. Shin-Etsu KE-1603, a hyper elastic material, was used to build the salamander robot and a series of experiments were conducted to record the bending angle, the respective generated force in soft actuators and the gait speed of the robot. The developed salamander robot was able to walk at 0.06774 m/s, following an almost identical pattern to the simulation.

4

Detailed micro-modeling of partially grouted reinforced masonry shear walls: extended validation and parametric study

Calderón Sebastián, Sandoval Cristián, Milani Gabriele, Arnau Oriol

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

114--137

EN

Partially grouted reinforced masonry (PG-RM) shear walls have been widely used as structural elements in low- and medium-rise earthquake-resistant buildings. Nonetheless, assessing its shear strength represents a complex task mainly because the partial grouting provides a non-constant cross section, which results in heterogeneous stress–strain patterns. Consequently, refined modeling techniques are needed to reproduce local failure mechanisms taking place in these walls, which significantly influence the global response. In response to this issue, a detailed micro-modeling approach based on the finite element method was proposed in previous studies by the authors. Although the numerical strategy provided accurate results, further validation is required. Therefore, in this study, the experimental results of seven PG-RM shear walls of multi-perforated clay bricks with bed-joint reinforcement are employed as validation cases. These seven walls presented variations in five design parameters. The validated numerical model was then employed to perform a parametric study to assess the influence of the wall aspect ratio, axial pre-compression stress, and horizontal reinforcement ratio on the in-plane lateral behavior of PG-RM shear walls. The obtained results show that the three studied design parameters modified the crack patterns of the walls. Besides, increasing the axial pre-compression stress or reducing the aspect ratio resulted in higher walls’ shear strength. Additionally, decreasing the horizontal reinforcement ratio or increasing the aspect ratio generated a higher story-drift ratio at maximum lateral force. Finally, it was corroborated that the positive effect of the axial pre-compression stress on the walls’ shear strength decreases inversely proportional to the aspect ratio.

5

Ultimate shear response of ultra-high-performance steel fibre-reinforced concrete elements

Tibea C., Bompa Dan V.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 2

280--295

EN

This paper examines the experimental performance of ultra-high-performance steel fibre-reinforced concrete (UHPSFRC) beams subjected to loads at relatively low shear span-to-depth ratios. The results and observations from six tests provide a detailed insight into the ultimate response including shear strength and failure mode of structural elements incorporating various fibre contents. The test results showed that a higher fibre content results in an increase in ultimate capacity and some enhancement in terms of ductility. Detailed nonlinear numerical validations and sensitivity studies were also undertaken in order to obtain further insights into the response of UHPSFRC beams, with particular focus on the influence of the shear span-to-depth ratio, fibre content and flexural reinforcement ratio. The parametric investigations showed that a reduction in shear span-to-depth ratio results in an increase in the member capacity, whilst a reduction in the flexural reinforcement ratio produces a lower ultimate capacity and a relatively more flexible response. The test results combined with those from numerical simulations enabled the development of a series of design expressions to estimate the shear strength of such members. Validations were performed against the results in this paper, as well as against a collated database from previous experimental studies.

6

Mathematical modelling of a cut-and-cover construction

Kunc K.

Zeszyty Naukowe. Budownictwo / Politechnika Śląska

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2003

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z. 98

73-78

EN

Firstly, the replacement of the soil by two different kinds of plasticity models (Mohr-Coulomb model and Hardening-Soil model) is conducted. Secondly, the response of the numerical models without and with compaction process is analysed. Finally, several parametric studies are performed by means of the numerical model with the closest results to the field measurements to investigate the influence of the soil properties, on which the cut-and-cover construction is build, on lining displacements.

PL

Po pierwsze, zastąpiono grunt dwoma różnymi modelami sprężystości (modele Mohra-Coulomba i ze wzmocnieniem). Po drugie, przeanalizowano reakcję modeli numerycznych z zastosowaniem procesu zagęszczania i bez niego. Przeprowadzono wreszcie szereg badań parametrycznych za pomocą modelu numerycznego, dającego wyniki najbliższe do badań terenowych, w celu zbadania wpływu własności gruntu, na którym prowadzona jest budowa metodą odkrywkową, na przemieszczenia obudowy.