scholarly journals Design and SAR assessment of three compact 5G antenna arrays

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. Lak ◽  
Z. Adelpour ◽  
H. Oraizi ◽  
N. Parhizgar
Keyword(s):  
Antenna Arrays ◽  
Millimeter Waves ◽  
Reasonable Agreement ◽  
Specific Absorption Rate ◽  
Human Head ◽  
Head Model ◽  
Measurement Results ◽  
Exposure Source ◽  
Simulation Results ◽  
The Brain

AbstractIn this paper three different multi stub antenna arrays at 27–29.5 GHz are designed. The proposed antenna arrays consist of eight single elements. The structure of feeding parts is the same but the radiation elements are different. The feeding network for array is an eight way Wilkinson power divider (WPD). To guarantee the simulation results, one of the proposed structures is fabricated and measured (namely the characteristics of S11, E-, and H-plane patterns) which shows acceptable consistency with measurement results. The simulation results by CST and HFSS show reasonable agreement for reflection coefficient and radiation patterns in the E- and H- planes. The overall size of the proposed antenna in maximum case is 29.5 mm × 52 mm ×  0.38 mm  (2.8 $${{\varvec{\lambda}}}_{0}$$ λ 0 × 4.86$${{\varvec{\lambda}}}_{0}$$ λ 0 × 0.036$${{\varvec{\lambda}}}_{0}$$ λ 0 ). Moreover, for Specific Absorption Rate (SAR) estimation, a three-layer spherical human head model (skin, skull, and the brain) is placed next to the arrays as the exposure source. The simulation results show that the performance of proposed antennas as low-SAR sources makes them ideal candidates for the safe usage and lack of impact of millimeter waves (mmW) on the human health. In all three cases of SAR simulations the value of SAR1g and SAR10g are below the standard limitations.

scholarly journals Evaluation of 8-Channel Radiative Antenna Arrays for Human Head Imaging at 10.5 Tesla

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6000
Author(s):  
Myung Kyun Woo ◽  
Lance DelaBarre ◽  
Matt Thomas Waks ◽  
Young Woo Park ◽  
Russell Luke Lagore ◽  
...  
Keyword(s):  
Antenna Array ◽  
Antenna Arrays ◽  
Specific Absorption Rate ◽  
Human Head ◽  
Dipole Antenna ◽  
Monopole Antenna ◽  
Human Model ◽  
Head Model ◽  
Coaxial Feed ◽  
Substantial Drop

For human head magnetic resonance imaging at 10.5 tesla (T), we built an 8-channel transceiver dipole antenna array and evaluated the influence of coaxial feed cables. The influence of coaxial feed cables was evaluated in simulation and compared against a physically constructed array in terms of transmit magnetic field (B1+) and specific absorption rate (SAR) efficiency. A substantial drop (23.1% in simulation and 20.7% in experiment) in B1+ efficiency was observed with a tight coaxial feed cable setup. For the investigation of the feed location, the center-fed dipole antenna array was compared to two 8-channel end-fed arrays: monopole and sleeve antenna arrays. The simulation results with a phantom indicate that these arrays achieved ~24% higher SAR efficiency compared to the dipole antenna array. For a human head model, we observed 30.8% lower SAR efficiency with the 8-channel monopole antenna array compared to the phantom. Importantly, our simulation with the human model indicates that the sleeve antenna arrays can achieve 23.8% and 21% higher SAR efficiency compared to the dipole and monopole antenna arrays, respectively. Finally, we obtained high-resolution human cadaver images at 10.5 T with the 8-channel sleeve antenna array.

Biomechanical Analysis of the Sensitivity of Brain Tissue Responses to FE Head Models in the Study of Impact-Induced TBI

2020 ◽  
Author(s):  
Hesam S. Moghaddam ◽  
Asghar Rezaei ◽  
Mariusz Ziejewski ◽  
Ghodrat Karami
Keyword(s):  
Shear Stress ◽  
Mesh Size ◽  
Human Head ◽  
Biomechanical Analysis ◽  
Head Model ◽  
Tissue Responses ◽  
Stress Prediction ◽  
Brain Material ◽  
The Brain

Abstract A numerical investigation is conducted on the injury-related biomechanical parameters of the human head under blunt impacts. The objective of this research is twofold; first to understand the role of the employed finite element (FE) head model — with its specific components, shape, size, material properties, and mesh size — in predicting tissue responses of the brain, and second to investigate the fidelity of pressure response in validating FE head models. Accordingly, two independently established and validated FE head models are impacted in two directions under two impact severities and their predicted responses in terms of intracranial pressure (ICP) and shear stress are compared. The coup-counter ICP peak values are less sensitive to head model, mesh size, and the brain material. In all cases, maximum ICPs occur on the outer surface, vanishing linearly toward the center of the brain. Hence, it is concluded that different head models may simply reproduce the results of ICP variations due to impact. Shear stress prediction, however, is mainly affected by the head model, direction and severity of impact, and the brain material.

Evaluation of Specific Absorption Rate due to Medical Implant in Near-Field Exposure

2013 ◽  
Vol 64 (3) ◽  
Author(s):  
Nazirah Othman ◽  
Noor Asmawati Samsuri ◽  
Norfatin Akma Ellias
Keyword(s):  
Intramedullary Nail ◽  
Specific Absorption Rate ◽  
Near Field ◽  
Dipole Antenna ◽  
Medical Implants ◽  
Field Exposure ◽  
Maximum Enhancement ◽  
Medical Implant ◽  
Measurement Results ◽  
Simulation Results

This paper presents the effects of conductive medical implant on energy absorbed by the human body and the testicular area when exposed to near field electromagnetic radiation. A dipole antenna is used as the radiating source and it is placed in front of the trousers pocket. Two types of medical implants are used in this study: intramedullary nail and bone plate. Numerical simulations are performed by means of CST Microwave Studio. Results are discussed in terms of changes in SAR values due to the presence of conductive medical implant at 0.4, 0.9, 1.8 and 2.4 GHz. The results have indicated that the conductive intramedullary nail that is located inside the femur significantly increases the SAR. Maximum enhancement in SAR is found when the length of the intramedullary nail is approximately one wavelength of the respective frequency tested. The measurement results indicate good agreements with the simulation results at 2.4 GHz.

Relaxation Time Effect on the Human Head Using the Thermal Wave Model

2012 ◽  
Author(s):  
Toni K. Tullius ◽  
Yildiz Bayazitoglu
Keyword(s):  
Relaxation Time ◽  
Wave Model ◽  
Human Head ◽  
The Body ◽  
Bioheat Transfer ◽  
Time Dependent ◽  
Head Model ◽  
Transfer Model ◽  
The Waves ◽  
The Brain

The most common electronics used by the vast majority of the world’s population emit low radio frequencies and they may be harmful to both skin and brain tissue. The bio-heat transfer model is numerically solved to predict the time dependent temperature distribution of micro waves as it emits to the brain caused by everyday electronics in order to understand the effects the waves have on our organs. A time dependent finite difference technique is used to model a multilayer system depicting this external heat source passing through skin, bone, and into the brain. This model accounts for the extra heat generated within the body from the chemical reactions of the tissue, whereas pervious work took this heat sources to be negligible. A relaxation time is also included in the bioheat transfer model in order to account for the response time the tissue takes caused by the perturbation. Most studies neglect this parameter. Parameters for the adult and child head model are compared. The manuscript is aimed to understand the potential threats on the human body caused by everyday use of the technologies such as Ipods, cellular phones, bluetooth’s, etc.

scholarly journals Analysis of Specific Absorption Rate on Six Layer Human Head Model

2020 ◽  
Author(s):  
Anand Swaminathan ◽  
Ramprakash A ◽  
Dhejonithan K
Keyword(s):  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Mass Density ◽  
Human Head ◽  
Federal Communications Commission ◽  
Head Model ◽  
Health Issues ◽  
Specific Absorption ◽  
Proposed Model ◽  
The Impact

Despite numerous advantages, mobile phones cause serious health issues to people due to electromagnetic radiation. Various head models already exist to study the impact of radiation on a human head. The accuracy of the measurement of power absorbed by different layers of a head should be high. A new head model with six layers is proposed in this paper. Parameters such as dielectric constant, conductivity and mass density of different tissue layers skin, fat, bone, Dura, cerebrospinal fluid (CSF), and brain are extracted from the Federal Communications Commission (FCC) database. To study the impact of radiation in the proposed model, standard planar inverted F-antennas (PIFA) capable to radiate at 1.7 GHz and 2.4 GHz are used. Simulations are performed using ANSYS Electromagnetics Suite. The analysis shows that the specific absorption rate (SAR) in the brain layer decreased in the proposed model when compared to the existing model.

Computation of Blast-Induced Traumatic Brain Injury

2009 ◽  
Author(s):  
M. S. Chafi ◽  
G. Karami ◽  
M. Ziejewski
Keyword(s):  
Experimental Data ◽  
Wave Propagation ◽  
Blast Wave ◽  
Human Head ◽  
Propagation Model ◽  
Head Model ◽  
Brain Response ◽  
Brain Responses ◽  
The Impact ◽  
The Brain

In this paper, an integrated numerical approach is introduced to determine the human brain responses when the head is exposed to blast explosions. The procedure is based on a 3D non-linear finite element method (FEM) that implements a simultaneous conduction of explosive detonation, shock wave propagation, and blast-brain interaction of the confronting human head. Due to the fact that there is no reported experimental data on blast-head interactions, several important checkpoints should be made before trusting the brain responses resulting from the blast modeling. These checkpoints include; a) a validated human head FEM subjected to impact loading; b) a validated air-free blast propagation model; and c) the verified blast waves-solid interactions. The simulations presented in this paper satisfy the above-mentioned requirements and checkpoints. The head model employed here has been validated again impact loadings. In this respect, Chafi et al. [1] have examined the head model against the brain intracranial pressure, and brain’s strains under different impact loadings of cadaveric experimental tests of Hardy et al. [2]. In another report, Chafi et al. [3] has examined the air-blast and blast-object simulations using Arbitrary Lagrangian Eulerian (ALE) multi-material and Fluid-Solid Interaction (FSI) formulations. The predicted results of blast propagation matched very well with those of experimental data proving that this computational solid-fluid algorithm is able to accurately predict the blast wave propagation in the medium and the response of the structure to blast loading. Various aspects of blast wave propagations in air as well as when barriers such as solid walls are encountered have been studied. With the head model included, different scenarios have been assumed to capture an appropriate picture of the brain response at a constant stand-off distance of nearly 80cm (2.62 feet) from the explosion core. The impact of brain response due to severity of the blast under different amounts of the explosive material, TNT (0.0838, 0.205, and 0.5lb) is examined. The accuracy of the modeling can provide the information to design protection facilities for human head for the hostile environments.

Development and validation of a new finite element human head model

2018 ◽  
Vol 35 (1) ◽  
pp. 477-496 ◽  
Author(s):  
Fábio A.O. Fernandes ◽  
Dmitri Tchepel ◽  
Ricardo J. Alves de Sousa ◽  
Mariusz Ptak
Keyword(s):  
Finite Element ◽  
Design Methodology ◽  
Human Head ◽  
Design Tool ◽  
Head Model ◽  
Accident Reconstruction ◽  
Research Groups ◽  
Content Type ◽  
Development And Validation ◽  
The Brain

Purpose Currently, there are some finite element head models developed by research groups all around the world. Nevertheless, the majority are not geometrically accurate. One of the problems is the brain geometry, which usually resembles a sphere. This may raise problems when reconstructing any event that involves brain kinematics, such as accidents, affecting the correct evaluation of resulting injuries. Thus, the purpose of this study is to develop a new finite element head model more accurate than the existing ones. Design/methodology/approach In this work, a new and geometrically detailed finite element brain model is proposed. Special attention was given to sulci and gyri modelling, making this model more geometrically accurate than currently available ones. In addition, these brain features are important to predict specific injuries such as brain contusions, which usually involve the crowns of gyri. Findings The model was validated against experimental data from impact tests on cadavers, comparing the intracranial pressure at frontal, parietal, occipital and posterior fossa regions. Originality/value As this model is validated, it can be now used in accident reconstruction and injury evaluation and even as a design tool for protective head gear.

scholarly journals Development of a Finite Element Head Model for the Study of Impact Head Injury

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Bin Yang ◽  
Kwong-Ming Tse ◽  
Ning Chen ◽  
Long-Bin Tan ◽  
Qing-Qian Zheng ◽  
...  
Keyword(s):  
Finite Element ◽  
Brain Injuries ◽  
Current Knowledge ◽  
Human Head ◽  
Von Mises Stress ◽  
Head Model ◽  
Fe Model ◽  
Prediction And Prevention ◽  
Von Mises ◽  
The Brain

This study is aimed at developing a high quality, validated finite element (FE) human head model for traumatic brain injuries (TBI) prediction and prevention during vehicle collisions. The geometry of the FE model was based on computed tomography (CT) and magnetic resonance imaging (MRI) scans of a volunteer close to the anthropometry of a 50th percentile male. The material and structural properties were selected based on a synthesis of current knowledge of the constitutive models for each tissue. The cerebrospinal fluid (CSF) was simulated explicitly as a hydrostatic fluid by using a surface-based fluid modeling method. The model was validated in the loading condition observed in frontal impact vehicle collision. These validations include the intracranial pressure (ICP), brain motion, impact force and intracranial acceleration response, maximum von Mises stress in the brain, and maximum principal stress in the skull. Overall results obtained in the validation indicated improved biofidelity relative to previous FE models, and the change in the maximum von Mises in the brain is mainly caused by the improvement of the CSF simulation. The model may be used for improving the current injury criteria of the brain and anthropometric test devices.

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