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The use of the natural materials instead of conventional materials as electromagnetic absorbers promotes environmental sustainability, cost-effectiveness, and ease of accessibility. Furthermore, these materials may also be designed as absorbers and as reinforcements in building materials in a lightweight form. The absorbing ability of composite materials can be customized based on the chosen fillers. Specifically, magnetic and dielectric fillers can be incorporated to improve the absorption of a composite material compared to traditional materials. This work aims to review recent developments of electromagnetic absorbers enabled by nanocomposites, metamaterial and metasurface-based, as well as green composite alternatives. First, the background concepts of electromagnetic wave absorption and reflection will be presented, followed by the assessment techniques in determining electromagnetic properties of absorbing materials. Next, the state-of-the-art absorbers utilizing different materials will be presented and their performances are compared. This review concludes with a special focus on the future perspective of the potential of metamaterial based nanocellulose composites as ultrathin and broadband electromagnetic absorbers.

The residence of Pulau Pinang and Malaysia generally are worried with the possible health effects due to Base Tower Station (BTS) radiation. Particularly, the residents of Pulau Pinang are utilizing their mobile phones for multiple kind of tasks including communications, browsing the internet and other applications. With the recent advances in mobile communication technologies, the end user demanded a better coverage, great communication services, and faster speed for internet browsing. To fulfill the demand, service provider and communication companies are providing plenty of communication base tower leading to the beliefs of that the tower emitted radiation and cause harmful effect to human health and voiced out and complain to the municipal councils in Malaysia. In this paper, a measurement was conducted to study electromagnetic fields (EMF) radiation level in Pulau Pinang. The measurement is compared with the international standard provided by International Commission of Non-Ionizing Radiation Protection (ICNIRP). Far field measurement of different values of long term evolution (LTE) exposure was demonstrated in radiofrequency (RF) shielded environment. LTE850, LTE1800 and LTE2600 field exposure was compared in term of its’ electrical field and power density that adhere to the standard provided by ICNIRP.

This paper presents the assessment of short-term wireless body area network (WBAN) exposure, which is operated at the industrial, scientific, and medical (ISM) band (2.45 GHz) in the vicinity of the human body. The experiment utilizes two popular textile antenna topologies, a planar monopole and a patch antenna as the radiating sources. The objective of this experiment is to investigate whether the exposure from WBAN may influence the physiological parameters (body temperature, blood pressure, and heart rate) and the well-being of the wearer. Counter-balanced, crossover, and the single-blind method was applied in the experimental setup. $P$ -value is the probability value, under the assumption of no effect or no difference (the null hypothesis) of obtaining a result equal to or more extreme than what was actually observed. If $P , it indicates that $P$ -value will be less than the level of significance. Thus, the null hypothesis (no effect or no difference) can be rejected, and it can be concluded that there exist effects to the respondents. The results showed that there is statistically no significant difference between the active exposure and the Sham (no exposure) which may affect the physiological parameters and well-being of the wearers, with $P>0.05$ , which failed to reject the null hypothesis (no effect).

This paper presents the new design of simple one layer ultrathin metamaterial microwave absorber using coconut coir fibre as the substrate. The metamaterial microwave absorber is composed of a periodic array of square loops and patches with circle cut out printed on a dielectric material which is coconut coir fibre backed by PEC. CST Microwave Studio software is used for the design and simulation over frequency range of X-Band and Ku-Band (8.2–18 GHz). From the simulation result, 90% absorption was achieved in the frequency range of 8.94 – 10.0 GHz (X-Band) with highest absorption of 99.7% at 9.37 GHz. Furthermore, the metamaterial microwave absorber has a total thickness of 1.6 mm which is only approximately 0.04λ at lowest frequency. The result shows that coconut coir fibre from the agricultural waste has a great potential to be developed further in electromagnetic wave applications particularly microwave absorber.

This paper intends to design an Ultra-Wideband (UWB) antenna for future Internet of Things (IoT) applications for off-body Wireless Body Area Networks (WBAN) communication. An antenna based on the Y-shaped patch fed using co-planar waveguide (CPW) line, with a full ground plane is designed. It is implemented on two different substrates, namely a 5mm thick Rogers RO4350B and a 5-mm-thick felt textile. Parametric analysis of antenna is performed by changing its critical dimensions and monitoring parameters such as gain, bandwidth, efficiency, radiation pattern when using both substrates. Besides that, the bending effects towards reflection coefficient and radiation patterns are also studied. The final patch size with the Y-shaped slot is 36 × 40 mm2 for both substrates. The antenna is capable of providing coverage for the bands from 8 to 10 GHz. Finally, the antenna designed on RO4350B substrate outperforms the antenna designed on felt by about four times in terms of bandwidth, with 3.3 GHz (7.7–11 GHz).

This paper proposed a two layered 2 × 1 Koch Curve patch array antenna design with suspended air gap technique for Wireless Local Area Network (WLAN) application of 2.4 GHz resonant frequency. This proposed patch antenna is using two FR-4 substrate layers with dielectric constant, e r = 4.4 and the electrical conductivity tangent loss, tanΔ = 0.019. It is using the suspended air gap technique between two layers for enhancement effect of antenna gain from 4.89 dB to 5.18 dB. At the upper part of substrate, it consists a two feeding networks that connected the two patch of Koch Curve array patch. Beside antenna gain, this technique also improves the bandwidth and return loss of the antenna. It also contains a Koch Curve array structure at the patch part and have a full ground of copper at the back. This Koch Curve is design based on the basic equilateral triangle with three iteration steps. For the first iteration step, it be made up of the equilateral triangular shaped while the second iteration are added with mirror design of equilateral triangular to create a six segment of star-shaped. For the third iteration step, the equilateral triangle with the length base on previous iteration step is constructed on top of the side line of the base triangle. This third iteration step of the Koch Curve effect the reduction size of the patch antenna from 100 mm × 100mm to only 90mm × 60 mm. The return loss performance at resonant frequency 2.4 GHz is −32.735 dB.

Nowadays, the world has rapidly evolved in the communication system in term of speed and information capacity. Thus, a bow-tie antenna is the suggestion to use because of its exhibits low profile and lightweight. However, the bow-tie patch antenna, inherently have narrow bandwidths and in general are half wavelength structures operating at the fundamental resonant mode. To cater this problem, a slotted bow-tie antenna is designed for wireless applications with consist techniques a pair of polygon-shaped branches structure is implemented on each arm of the bow-tie slot antenna characteristics. The co-planar waveguide is applied to this antenna to effect the wider bandwidth to the antenna. This proposed CPW slotted bow-tie antenna is using FR-4 substrate with dielectric constant, e r = 4.4 and the electrical conductivity tangent loss, tan Δ = 0.019 with substrate dimension of 52.4 mm length × 22.3 mm width. Several parametric studies are done to make sure the suitable dimension for best antenna performance. In this case, several different dimensions of three part are consider to study, such as the microstrip line width (W ml ), height of feedline (H fl ), and the length of branch, L br . The basic antenna without polygon-shaped branches can offer a wider frequency band operation at 2.293 GHz–2.541 GHz with bandwidth of 248 MHz effect by the co-planar waveguide technique. After the addition of the polygon-shaped branches structure to the bow-tie part, its effect a band-notch effect at the 2.46 GHz, while creating a new resonant frequency at two different part at 2.394 GHz and 2.511GHz with resonant frequency of −18.585dB and 19.555dB, respectively.

With the higher speed growth and wide use of wireless telecommunication technology in recent years, the demand for miniature size, low profile, broadband and high gain antennas have increased so rapidly. The slots at the patch antenna is one of the technique can be used to cater this problem. This works proposed a stacked patch antenna with double U-slots structure technique at the patch antenna for Wireless LAN application. This proposed stacked patch antenna is designed on FR-4 substrate with dielectric constant of 4.4 and substrate thickness of 1.6mm with an air gap between the substrate and ground. Firstly, a basic patch antenna had been design. Then, a 65mm × 65mm stacked patch of copper plate was used as the ground plane under-shape patch. By integrating the stacked patch with air gap and the double U-slots techniques, the proposed designed offer an improvement in term of the gain and wide bandwidth of the antenna. A parametric study is of the patch width, patch length and length slot are determined to realize the antenna design. The results show the gain values increased from 7.189 dB to 7.358dB at resonant frequency of 2.4 GHz with a return loss of −14.739 dB. The increment of the length of slot effects the increase value of the return loss of the antenna. Compare with the basic antenna with 100 MHz of bandwidth, the performance for this proposed antenna is 120 MHz with the operating frequency range from 2.34 GHz to 2.46 GHz.

This project proposed a single linear-polarized and a single circular-polarized patch antenna are design for WLAN applications at 2.4 GHz. This antenna is using FR-4 substrate with permittivity, e r = 4.4 and the electrical conductivity tangent loss, tan Δ = 0.019. Three design antennas with same dimension size but with different feed line configuration had been consider as Design A, Design B and Design C. Design A and C have a better measured return loss of − 25.38 dB and − 24.384 dB, respectively. Beside that the Design B shows the performance of − 15.976 dB only.

WiMAX (Worldwide Interoperability for Microwave Access) is a part of wireless communication standards based on the IEEE 802.16 set of standards. In this work, a co-planar waveguide (CPW) patch antenna with octagonal-shaped ring had been design for WiMAX application of 3.5 GHz. This proposed CPW antenna is using FR-4 substrate with dielectric constant, e r = 4.4 and the electrical conductivity tangent loss, tan Δ = 0.019. There are three stages of the antenna design that consist the Design A — basic rectangular patch antenna, the Design B — rectangular patch antenna with octagonal-shaped ring while the last stage is Design C rectangular patch antenna with octagonal-shaped ring with CPW effect. A parametric study of CPW length, LCPW had been done to make sure the best return loss performance and the location of the resonant frequency near to WiMAX frequency range. In this case, nine different dimensions of LCPW that considers is from 11 mm to 19 mm. It shows that the LCPW = 18 mm shows the resonant frequency of T 3.528dB. The CPW patch antenna with octagonal-shaped ring effect a wider bandwidth and create two resonant frequencies. It shows that the proposed antenna covers from the 2.282 GHz to 4.216 GHz, with bandwidth of 1.978 GHz, improve from Design A and Design B of 0.11 GHz and 0.73 GHz, respectively. Two resonant frequencies are located at 2.59 GHz and 3.528 GHz with return loss of −23.89 dB and −34.78 dB, respectively. The antenna gain of Design C is improve to 2.92 dB, after the addition of the CPW technique.

The human body characteristics with different dimensions and tissue properties are one of the major factors in influencing the on-body radio propagation channel characteristics. A broadband textile monopole antenna operating at 2.45 GHz is evaluated to validate its performance on different subjects’ characteristics. The results show that the textile monopole antenna is sufficiently robust against the variations introduced by the body up to 0.9 and 0.2% changes in the antenna’s impedance matching level and resonant frequency shift when evaluated 10 mm from the body.

SiO2 nanostructure is synthesized by the Sol-Gel method and thin films are prepared using dip coating technique. The effect of laser densification is studied. X-ray Diffraction (XRD), Fourier Transformation Infrared Spectrometer (FTIR), and Field Emission Scanning Electron Microscopy (FESEM) are used to analyze the samples. The results show that the silica nanoparticles are successfully synthesized by the sol-gel method after laser densification. XRD patterns show that cristobalite structure is observed from diode laser (410 nm) rather than diode laser (532 nm). FESEM images showed that the shape of nano silica is spherical and the particles size is in nano range (? 100 nm). It is concluded that the spherical nanocrystal structure of silica thin films is successfully densified by Doide laser (410 nm).

Introduction: Previous studies from other countries that have investigated the level of knowledge of bronchial asthma and competence of primary care physicians in management issues concluded that there is a substantial variation among general practitioners in both their knowledge and management practices. There is no such study conducted in Qatar; therefore, we have conducted assessment for PHC physicians for further educational interventions that improve their quality of care for asthmatic patients. Subjects and Methods: It is a cross sectional observational study. Our target population was the PHC physicians working in PHC centers affiliated to Hamad Medical Corporation in Qatar. Of the 21 centers present in Qatar; we selected 3 urban and 3 rural centers randomly. The total number of physicians who attended the evaluation setting was 55 (30 urban and 25 rural physicians). The evaluation format was of three groups of questions to collect data for evaluation of knowledge and practice. Previously validated 30 MCQ questions were used to evaluate knowledge and 2 written problems were used to evaluate the practice. 50% and 60% were the cut of point to pass the evaluation for knowledge and practice respectively. Epi-Info statistical package was usedfor data entry and statistical analysis. Results: the percentage of physicians who passed the knowledge evaluation was 44% of the total number ofphysicians while 37% only of them passed the practice assessment. Age (p = 0.04), nationality (p = 0.003), specialty (p = 0.00), last certificate (p = 0.00), and No of years since graduation (p = 0.00) were significant variables in passing the knowledge test while age (p = 0.018), specialty (p = 0.00), and last certificate (p = 0.00) were significant variables in passing practice test. Regarding source of information about asthma, 96.7% of urban physicians reported that their main source is conferences and meetings while 84% of rural physicians using textbooks as their main source of information (p = 0.02). 80% of urban physicians versus 48% of rural doctors felt that they need more knowledge and training in asthma diagnosis and management (p = 0.00) while 73.3% of urban physicians recommended more CME seminars to improve their asthma practice and 64% of rural physicians recommended standard guidelines (p = 0.04). Conclusion: this study addresses areas of weakness that might be a stimulus to design a tailored educational interventions in order to improve the PHC physician's knowledge and practice of asthma.