The development of human-like brain phantom is important for data acquisition in microwave imaging. The characteristics of the phantom should be based on the real human body dielectric properties such as relative permittivity. The development of phantom includes the greymatter and whitematter regions, each with a relative permittivity of 38 and 28 respectively at 10 GHz frequency. Results were compared with the value obtained from the standard library of Computer Simulation Technology (CST) simulation application and the existing research by Fernandez and Gabriel. Our experimental results show a positive outcome, in which the proposed mixture was adequate to represent real human brain for data acquisition.
Wireless communication is a technology that plays an important role in current technology transformation. wireless communication is a method of telecommunication that are available for transmitting large amounts of data, voice and video over long distance using different frequencies. Specifically, Low Noise Amplifier which is located at the first block of receiver system, makes it one of the important element in improving signal transmission. This study was aimed to design a microwave Low Noise Amplifier for Long Term Evolution (LTE) application that will work at 5.8 GHz using high-performance low noise superHEMT transistor FHX76LP manufactured by Eudyna Technologies. The low noise amplifier (LNA) produced gain of 17.2 dB and noise figure (NF) of 0.914 dB. The input reflection (S11) and output return loss (S22) are -17.8 dB and -19.6 dB respectively. The bandwidth of the amplifier recorded is 1.2 GHz. The input sensitivity is compliant with the Long Term Evolution (LTE) standards.
A new technique to pyrolyse biomass in microwave (MW) system is presented in this paper to solve the problem of bio-oil deposition. Pyrolysis of oil palm shell (OPS) biomass was conducted in 800 W and 2.45 GHz frequency MW system using an activated carbon as a MW absorber. The temperature profile, product yield and the properties of the products were found to depend on the stirrer speed and MW absorber percentage. The highest bio-oil yield of 28 wt.% was obtained at 25% MW absorber and 50 rpm stirrer speed. Bio-char showed highest calorific value of the 29.5 MJ/kg at 50% MW absorber and 100 rpm stirrer speed. Bio-oil from this study was rich in phenol with highest detected as 85 area% from the GC-MS results. Thus, OPS bio-oil can become potential alternative to petroleum-based chemicals in various phenolic based applications.
The effect of infrared and microwave alternate thawing (IR + MWT) on frozen pork were compared to fresh, air thawing (AT), infrared thawing (IRT), microwave thawing (MWT). The IR + MWT took only about 11.81 min of the thawing time compared to AT 66.5 min, and the Raman spectroscopy and Low-field nuclear magnetic resonance (LF-NMR) results showed that the IR + MWT maintained better protein secondary structure composition and moisture state compared to MWT and IRT. In terms of thawing losses, IR + MWT had the lowest loss 1.92%. In terms of texture, IR + MWT had the least effect on the post-thawing textural properties and increased the springiness of the meat. Scanning electron microscopy results also showed that there was reduced damage to the muscle structure with IR + MWT. Regarding the odor of the meat after thawing, IR + MWT retained the odor better and was closer to the fresh sample. Therefore, IR + MWT can be used to enhance the thawing rate to protect the quality of the thawed pork.
The objective of this work is to prepare a cost-effective, low reagent consumption and high performance polytetrafluoroethylene (PTFE) vessel that is capable to work in domestic microwave for digesting food and environmental samples. The designed vessel has a relatively thicker wall compared to that of commercial vessels. In this design, eight vessels are placed in an acrylonitrile butadiene styrene (ABS) holder to keep them safe and stable. This vessel needs only 2.0 mL of HNO3 and 1.0 mL H2O2 to digest 100 mg of biological sample. The performance of this design is then evaluated with an ICP-MS instrument in the analysis of the several NIST standard reference material of milk 1849a, rice flour 1568b, spinach leave 1570a and Peach Leaves 1547 in a domestic microwave oven with inverter technology. Outstanding agreement to (SRM) values are observed by using the suggested power to time microwave program, which simulates the reflux action occurring in this closed vessel. Taking into account the high cost of commercial microwave vessels and the volume of chemicals needed for various experiments (8-10 mL), this simple vessel is cost effective and suitable for digesting food and environmental samples.
Today, electromagnetic wave theory is commonly used in many engineering devices. However, such devices produce electromagnetic (EM) radiation, damaging people's health and the impact of other electronic device's operation. Therefore, Microwave Absorber has been widely used in anechoic chamber to measure equipment radiation and prevent unwanted radiation and electromagnetic interference. This research investigates the absorption performance of pyramidal absorbers with a slotted method design. This research used rectangular and triangular slotted on the hollow pyramidal absorber. There are six types of slotted: Design 1, Design 2, and Design 3
which have triangular shapes, and Design 4, Design 5, and Design 6, have rectangular shapes. The pyramidal absorber is produced using CST Microwave Studio Suite. Afterward, the fabrication process is performed using cardboard and coated with Powdered Activated Carbon (PAC). Measurement had been done successfully via far-field measurement using an arch method at 1 GHz to 12 GHz. The slotted pyramidal absorber's absorptivity was taken in each frequency band and was tabulated in figure 10. The result is compared with their maximum absorption in each of the four frequency bands. Comparison based on slot design, triangular and rectangular each had its own advantages at a certain frequency. However, small rectangular slot of Design 1 shows consistent absorption performance at all frequency band.
The adsorption behavior of basic, methylene blue (MB), and reactive, remazol brilliant violet 5R (RBV), dyes from aqueous solution onto Intsia bijuga sawdust-based activated carbon (IBSAC) was executed via batch and column studies. The produced activated carbon was characterized through Brunauer-Emmett-Teller (BET) surface area and pore structural analysis, proximate and ultimate, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Batch studies were performed to investigate the effects of contact time, initial concentration, and solution pH. The equilibrium data for both MB and RBV adsorption better fits Langmuir model with maximum adsorption capacity of 434.78 and 212.77 mg/g, respectively. Kinetic studies for both MB and RBV dyes showed that the adsorption process followed a pseudo-second-order and intraparticle diffusion kinetic models. For column mode, the breakthrough curves were plotted by varying the flow rate, bed height, and initial concentration and the breakthrough data were best correlated with the Yoon-Nelson model compared to Thomas and Adams-Bohart model. The adsorption activity of IBSAC shows good stability even after four consecutive cycles.
This study investigated combination nanocarrier and microwave system for α-tocopherol and γ-tocotrienol delivery against dermatitis, without skin thinning effect of steroids. The vitamin E was formulated into water-rich/water-poor nanoemulsions, and had their droplet size, zeta potential, morphology, therapeutic content, encapsulation efficiency and release, in vitro skin therapeutics/nanoemulsion penetration, retention and permeation profiles, and in vivo pharmacodynamics characteristics examined, with skin pre-treated by precision microwave when applicable. The nanoemulsions had droplet sizes <150 nm and negative zeta potential values. The skin pre-treatment by microwave (1 mW/3985 MHz) promoted therapeutics accumulation in epidermis through enhancing nanoemulsion penetration into skin. The combination nano- and microwave technologies fluidized skin lipid and protein domains with epidermal microstructures being fluidized to a greater extent than dermis, allowing a relatively high epidermal-to-dermal nanoemulsion distribution. Microwave of lower or higher than 3985 MHz brought about lower skin therapeutics/nanoemulsion accumulation due to insufficient lipid/protein domain fluidization or microwave-skin interaction limiting at skin surfaces only. Using water-rich nanoemulsion with higher therapeutic release and skin pre-treatment with 3985 MHz microwave, dermatitis was alleviated in vivo without skin thinning of standard steroid. The use of combination microwave and nanotechnology promotes vitamin delivery and translates to positive dermatitis treatment outcome that warrants future investigation.
Polybutylene succinate (PBS) has become a potential candidate, similar to polypropylene (PP) and acrylonitrile butadiene styrene (ABS), for use as an organic plastic material due to its outstanding mechanical properties as well as high thermal deformation characteristics. A new composition of silica aerogel nanoparticles extracted from rice waste with PBS is proposed for use as a dielectric (εr = 4.5) substrate for microwave applications. A microstrip patch antenna was fabricated on the proposed dielectric substrate for multi-resonant ultra-wideband (UWB) applications. The performance characteristics of the proposed biomaterial-based antenna were investigated in a far-field measurement environment. The results indicate that the proposed biocompatible material-based antenna covered a bandwidth of 9.4 (2.3-11.7) GHz with stop bands from 5.5 GHz to 5.8 GHz and 7.0 GHz to 8.3 GHz. Peak gains of 9.82 dBi, 7.59 dBi, 8.0 dBi and 7.68 dBi were measured at resonant frequencies of 2.7 GHz, 4.6 GHz, 6.3 GHz and 9.5 GHz, respectively.
The influence of microwave irradiation on the drug release properties of freshly prepared and aged alginate, alginate-chitosan and chitosan beads was investigated. The beads were prepared by extrusion method with sulphathiazole as a model drug. The dried beads were subjected to microwave irradiation at 80 W for 10 min, 20 min or three consecutive cycles of 10 and 20 min, respectively. The profiles of drug dissolution, drug content, drug stability, drug polymorphism, drug-polymer interaction, polymer crosslinkage and complexation were determined by dissolution testing, drug content assay, differential scanning calorimetry and Fourier transform infra-red spectroscopy. The chemical stability of drug embedded in beads was unaffected by microwave conditions and length of storage time. The release property of drug was mainly governed by the extent of polymer interaction in beads. The aged alginate beads required intermittent cycles of microwave irradiation to induce drug release retarding effect in contrast to their freshly prepared samples. Unlike the alginate beads, the level of polymer interaction was higher in aged alginate-chitosan beads than the corresponding fresh beads. The drug release retarding property of aged alginate-chitosan beads could be significantly enhanced through subjecting the beads to microwave irradiation for 10 min. No further change in drug release from these beads was observed beyond 30 min of microwave irradiation. Unlike beads containing alginate, the rate and extent of drug released from the aged chitosan beads were higher upon treatment by microwave in spite of the higher degree of polymer interaction shown by the latter on prolonged storage. The observation suggested that the response of polymer matrix to microwave irradiation in induction of drug release retarding property was largely affected by the molecular arrangement of the polymer chains.
Introduction: For “smart health” Internet-of-Things (IoT) applications, substrate integrated waveguide (SIW) is a promising component to construct a wearable microwave device. For its efficacy in wearable devices, minimizing signal losses in terms of return and transition losses in SIW is of paramount importance. To enhance its performance, this paper presents the characterization of air-filled SIW transition losses for the SIW microwave device. Method: To investigate the effect of transition length on losses, the full-wave analysis of an air-filled SIW with different lengths of the taper transition was presented. For the analysis, the linear taper is designed for the Roger RT/Duroid 6002 substrate and utilized in the Ka-band frequencies. Result: From the full-wave analysis results, the length of the tran- sition taper can be reduced considerably while achieving a wide-bandwidth characteristic of return loss better than 20 GHz. The results also show that the transmission loss can be reliably reduced while reducing the size of the SIW component. Conclusion: The findings may contribute to the development of the compact design of wearable micro- wave devices having a comparable performance with the conventional waveguide.
This paper presents the design and development of a planar Aligned-Gap and Centered-Gap Rectangular Multiple Split Ring Resonator (SRR) for microwave sensors that operates at a resonance frequency around 5 GHz. The sensor consists of a microstrip transmission line loaded with two elements of rectangular SRR on both sides. The proposed metamaterial sensors were designed and fabricated on Rogers RT5880 substrate having dielectric constant of 2.2 and thickness of 0.787 mm. The final dimension of the proposed sensor was measured at 35 × 14 mm2. Measured results show good agreement with simulated ones as well as exhibiting high Q-factor for use in sensing application. A remarkably shift of resonance frequency is observed upon introduction of several sample with different dielectric value.
Manufacturing an array of high-quality metallic pattern layers on a dielectric substrate remains a major challenge in the development of flexible and 3-D frequency selective surfaces (FSS). This paper proposes an improved fabrication solution for the 3-D FSS based on water transfer printing (WTP) technology. The main advantages of the proposed solution are its ability to transform complicated 2-D planar FSS patterns into 3-D structures while improving both manufacturing quality and production costs. WTP technology makes use of water surface tension to keep the thin metallic patterns of the proposed FSS floating flat with the absence of a solid planar substrate. This feature enables these metallic FSS patterns to be transferred onto 3-D structures through a dipping process. To test the effectiveness of the proposed technique, the FSS was designed using computer simulation software Microwave Studio to obtain the numerical performance of the FSS structure. The WTP technology was then used to fabricate the proposed FSS prototype before its performance was tested experimentally. The measurement results agreed well with the numerical results, indicating the proposed manufacturing solution would support the development of complicated 3-D electronics devices, such as conformal antenna arrays and metamaterials.
A new, metamaterial-based electromagnetic cloaking operation is proposed in this study. The metamaterial exhibits a sharp transmittance in the C-band of the microwave spectrum with negative effective property of permittivity at that frequency. Two metal arms were placed on an FR-4 substrate to construct a double-split-square shape structure. The size of the resonator was maintained to achieve the effective medium property of the metamaterial. Full wave numerical simulation was performed to extract the reflection and transmission coefficients for the unit cell. Later on, a single layer square-shaped cloak was designed using the proposed metamaterial unit cell. The cloak hides a metal cylinder electromagnetically, where the material exhibits epsilon-near-zero (ENZ) property. Cloaking operation was demonstrated adopting the scattering-reduction technique. The measured result was provided to validate the characteristics of the metamaterial and the cloak. Some object size- and shape-based analyses were performed with the cloak, and a common cloaking region was revealed over more than 900 MHz in the C-band for the different objects.
An Ultrawideband (UWB) octagonal ring-shaped parasitic resonator-based patch antenna for microwave imaging applications is presented in this study, which is constructed with a diamond-shaped radiating patch, three octagonal, rectangular slotted ring-shaped parasitic resonator elements, and partial slotting ground plane. The main goals of uses of parasitic ring-shaped elements are improving antenna performance. In the prototype, various kinds of slots on the ground plane were investigated, and especially rectangular slots and irregular zigzag slots are applied to enhance bandwidth, gain, efficiency, and radiation directivity. The optimized size of the antenna is 29 × 24 × 1.5 mm3 by using the FR-4 substrate. The overall results illustrate that the antenna has a bandwidth of 8.7 GHz (2.80 ̶ 11.50 GHz) for the reflection coefficient S11 < -10 dB with directional radiation pattern. The maximum gain of the proposed prototype is more than 5.7 dBi, and the average efficiency over the radiating bandwidth is 75%. Different design modifications are performed to attain the most favorable outcome of the proposed antenna. However, the prototype of the proposed antenna is designed and simulated in the 3D simulator CST Microwave Studio 2018 and then effectively fabricated and measured. The investigation throughout the study of the numerical as well as experimental data explicit that the proposed antenna is appropriate for the Ultrawideband-based microwave-imaging fields.
Microwave-assisted synthesis is known to accelerate the transesterification process and address the issues associated with the conventional thermal process, such as the processing time and the energy input requirement. Herein, the effect of microwave irradiation on the transesterification of palm oil methyl ester (PME) with trimethylolpropane (TMP) was evaluated. The reaction system was investigated through five process parameters, which were reaction temperature, catalyst, time, molar ratio of TMP to PME and vacuum pressure. The yield of TMP triester at 66.9 wt.% and undesirable fatty soap at 17.4% were obtained at 130 °C, 10 mbar, sodium methoxide solution at 0.6 wt.%, 10 min reaction time and molar ratio of TMP to PME at 1:4. The transesterification of palm oil-based methyl ester to trimethylolpropane ester was 3.1 folds faster in the presence of microwave irradiation. The total energy requirement was markedly reduced as compared to the conventional heating method. The findings indicate that microwave-assisted transesterification could probably be an answer to the quest for a cheaper biodegradable biolubricant.
The enhancement of microwave absorbing properties in nickel zinc ferrite (Ni0.5Zn0.5Fe2O4) via multiwall carbon nanotubes (MWCNT) growth is studied in this research work. Ni0.5Zn0.5Fe2O4 was initially synthesized by mechanical alloying followed by sintering at 1200 °C and the microstructural, electromagnetic and microwave characteristics have been scrutinized thoroughly. The sintered powder was then used as a catalyst to grow MWCNT derived from chemical vapor deposition (CVD) method. The sample was mixed with epoxy resin and a hardener for preparation of composites. The composite of multi-walled carbon nanotubes/Ni0.5Zn0.5Fe2O4 shown a maximum reflection loss (RL) of -19.34 dB at the frequency and bandwidth of 8.46 GHz and 1.24 GHz for an absorber thickness of 3 mm for losses less than -10 dB. This acquired result indicates that multi-walled carbon nanotubes/Ni0.5Zn0.5Fe2O4 could be used as a microwave absorber application in X-band.
Kertas ini membincangkan kaedah untuk mengurangkan kesan interaksi gelombang elektromagnet dengan kepala manusia menggunakan bahan ferit dan metabahan. Pengukuran pengurangan bagi Kadar Penyerapan Spesifik (SAR) menggunakan bahan ferit dan metabahan telah dilaksana dengan kaedah domain-masa perbezaan-terhingga (FDTD) model Lossy-Drude melalui perisian CST Microwave Studio. Metabahan dibentuk dengan menyusun penyalun cincin terpisah (SRRs) secara berkala. Nilai SAR diukur pada beberapa nilai jarak antara model kepala dengan telefon, kelebaran, ketebalan dan ketinggian bahan ferit dan metabahan. Hasil kajian menunjukkan bahawa nilai SAR1g telah berkurang kepada 1.043 W/kg dengan menggunakan bahan ferit dan 1.161 W/kg dengan menggunakan metabahan. Bagi SAR10g, nilai SAR menurun kepada 0.676 W/kg menggunakan bahan ferit dan 0.737 W/kg dengan menggunakan metabahan. Keputusan bagi nilai SAR dalam kepala manusia dengan kehadiran SRR yang membentuk metabahan telah dianalisis untuk menentusahkan kesan bagi pengurangan SAR ini. Keputusan analisis ini boleh memberikan maklumat yang dapat membantu dalam reka bentuk peralatan komunikasi tanpa wayar bagi mematuhi peraturan keselamatan.
A radio frequency (RF) resonator using glass-reinforced epoxy material for C and X band is proposed in this paper. Microstrip line technology for RF over glass-reinforced epoxy material is analyzed. Coupling mechanism over RF material and parasitic coupling performance is explained utilizing even and odd mode impedance with relevant equivalent circuit. Babinet's principle is deployed to explicate the circular slot ground plane of the proposed resonator. The resonator is designed over four materials from different backgrounds which are glass-reinforced epoxy, polyester, gallium arsenide (GaAs), and rogers RO 4350B. Parametric studies and optimization algorithm are applied over the geometry of the microstrip resonator to achieve dual band response for C and X band. Resonator behaviors for different materials are concluded and compared for the same structure. The final design is fabricated over glass-reinforced epoxy material. The fabricated resonator shows a maximum directivity of 5.65 dBi and 6.62 dBi at 5.84 GHz and 8.16 GHz, respectively. The lowest resonance response is less than -20 dB for C band and -34 dB for X band. The resonator is prototyped using LPKF (S63) drilling machine to study the material behavior.
The aim of this paper is to investigate the effects of the distances between the human head and internal cellular device antenna on the specific absorption rate (SAR). This paper also analyzes the effects of inclination angles between user head and mobile terminal antenna on SAR values. The effects of the metal-glass casing of mobile phone on the SAR values were observed in the vicinity of the human head model. Moreover, the return losses were investigated in all cases to mark antenna performance. This analysis was performed by adopting finite-difference time-domain (FDTD) method on Computer Simulation Technology (CST) Microwave Studio. The results indicate that by increasing the distance between the user head and antenna, SAR values are decreased. But the increase in inclination angle does not reduce SAR values in all cases. Additionally, this investigation provides some useful indication for future design of low SAR mobile terminal antenna.