Displaying publications 1 - 20 of 311 in total

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  1. 3,4-Diaminopyrazolo[3,4-d]pyrimidines: a new three-component microwave-assisted synthesis and anti-leukemic properties
    Ng JH, Lim FPL, Tiekink ERT, Dolzhenko AV
    Org Biomol Chem, 2023 Apr 26;21(16):3432-3446.
    PMID: 37039282 DOI: 10.1039/d3ob00350g
    A convenient method for the synthesis of N3,N4-disubstituted 3,4-diaminopyrazolo[3,4-d]pyrimidines was developed using a three-component reaction of 3,5-diaminopyrazole-4-carbonitriles with primary amines and orthoesters. The preparation of 116 examples demonstrated the good scope of the reaction, which tolerated variations in the substrate structure and was particularly efficient under microwave irradiation. The short reaction time and chromatography-free product isolation add practicality to this method. The anti-leukemic activity was assessed in vitro using K562 and Jurkat T cells, and the selectivity of the most active compounds was evaluated using non-cancerous MRC5 cells. The most promising compound inhibited Jurkat T cells with a GI50 value of 0.5 μM and a selectivity index of 65.
    Matched MeSH terms: Microwaves*
  2. Fulltext Electromagnetic Performances Analysis of an Ultra-wideband and Flexible Material Antenna in Microwave Breast Imaging: To Implement A Wearable Medical Bra
    Rahman A, Islam MT, Singh MJ, Kibria S, Akhtaruzzaman M
    Sci Rep, 2016 12 23;6:38906.
    PMID: 28008923 DOI: 10.1038/srep38906
    In this paper, we report a compact and ultra-wide band antenna on a flexible substrate using the 5-(4-(perfluorohexyl)phenyl)thiophene-2-carbaldehyde compound for microwave imaging. In contrast to other microwave based imaging systems, such as an array of 16 antennas, we proposed a bi-static radar based imaging system consisting of two omnidirectional antennas, which reduces complexity and the overall dimension. The proposed compact antennas are 20 × 14 mm2 and designed for operating at frequencies from 4 to 6 GHz. To allow for implantation into a bra, the electromagnetic performances of the antennas must be considered in bending conditions. In comparison with the recently reported flexible antennas, we demonstrated both electromagnetic performance and imaging reconstruction for bending conditions. For the proof of concept, the electromagnetic performances both at flat and bending conditions have been verified using a homogeneous multilayer model of the human breast phantom. Our results demonstrate that the antenna, even at bending conditions, exhibits an excellent omni-directional radiation pattern with an average efficiency above 70% and average gain above 1 dBi, within the operational frequency band. The comprehensive aim of the realized antenna is to design a biodegradable and wearable antenna-based bra for early breast cancer detection in the future.
    Matched MeSH terms: Microwaves*
  3. Fulltext Microwave brain imaging system to detect brain tumor using metamaterial loaded stacked antenna array
    Hossain A, Islam MT, Beng GK, Kashem SBA, Soliman MS, Misran N, et al.
    Sci Rep, 2022 Oct 01;12(1):16478.
    PMID: 36183039 DOI: 10.1038/s41598-022-20944-8
    In this paper, proposes a microwave brain imaging system to detect brain tumors using a metamaterial (MTM) loaded three-dimensional (3D) stacked wideband antenna array. The antenna is comprised of metamaterial-loaded with three substrate layers, including two air gaps. One 1 × 4 MTM array element is used in the top layer and middle layer, and one 3 × 2 MTM array element is used in the bottom layer. The MTM array elements in layers are utilized to enhance the performance concerning antenna's efficiency, bandwidth, realized gain, radiation directionality in free space and near the head model. The antenna is fabricated on cost-effective Rogers RT5880 and RO4350B substrate, and the optimized dimension of the antenna is 50 × 40 × 8.66 mm3. The measured results show that the antenna has a fractional bandwidth of 79.20% (1.37-3.16 GHz), 93% radiation efficiency, 98% high fidelity factor, 6.67 dBi gain, and adequate field penetration in the head tissue with a maximum of 0.0018 W/kg specific absorption rate. In addition, a 3D realistic tissue-mimicking head phantom is fabricated and measured to verify the performance of the antenna. Later, a nine-antenna array-based microwave brain imaging (MBI) system is implemented and investigated by using phantom model. After that, the scattering parameters are collected, analyzed, and then processed by the Iteratively Corrected delay-multiply-and-sum algorithm to detect and reconstruct the brain tumor images. The imaging results demonstrated that the implemented MBI system can successfully detect the target benign and malignant tumors with their locations inside the brain.
    Matched MeSH terms: Microwaves*
  4. Microwave processing of oil palm wastes for bioenergy production and circular economy: Recent advancements, challenges, and future prospects
    Foong SY, Chan YH, Lock SSM, Chin BLF, Yiin CL, Cheah KW, et al.
    Bioresour Technol, 2023 Feb;369:128478.
    PMID: 36513306 DOI: 10.1016/j.biortech.2022.128478
    The valorization and conversion of biomass into various value-added products and bioenergy play an important role in the realization of sustainable circular bioeconomy and net zero carbon emission goals. To that end, microwave technology has been perceived as a promising solution to process and manage oil palm waste due to its unique and efficient heating mechanism. This review presents an in-depth analysis focusing on microwave-assisted torrefaction, gasification, pyrolysis and advanced pyrolysis of various oil palm wastes. In particular, the products from these thermochemical conversion processes are energy-dense biochar (that could be used as solid fuel, adsorbents for contaminants removal and bio-fertilizer), phenolic-rich bio-oil, and H2-rich syngas. However, several challenges, including (1) the lack of detailed study on life cycle assessment and techno-economic analysis, (2) limited insights on the specific foreknowledge of microwave interaction with the oil palm wastes for continuous operation, and (3) effects of tunable parameters and catalyst's behavior/influence on the products' selectivity and overall process's efficiency, remain to be addressed in the context of large-scale biomass valorization via microwave technology.
    Matched MeSH terms: Microwaves*
  5. Fulltext UWB Antenna with Enhanced Directivity for Applications in Microwave Medical Imaging
    Awan D, Bashir S, Khan S, Al-Bawri SS, Dalarsson M
    Sensors (Basel), 2024 Feb 18;24(4).
    PMID: 38400473 DOI: 10.3390/s24041315
    Microwave medical imaging (MMI) is experiencing a surge in research interest, with antenna performance emerging as a key area for improvement. This work addresses this need by enhancing the directivity of a compact UWB antenna using a Yagi-Uda-inspired reflector antenna. The proposed reflector-loaded antenna (RLA) exhibited significant gain and directivity improvements compared to a non-directional reference antenna. When analyzed for MMI applications, the RLA showed a maximum increase of 4 dBi in the realized gain and of 14.26 dB in the transmitted field strength within a human breast model. Moreover, it preserved the shape of time-domain input signals with a high correlation factor of 94.86%. To further validate our approach, another non-directional antenna with proven head imaging capabilities was modified with a reflector, achieving similar directivity enhancements. The combined results demonstrate the feasibility of RLAs for improved performance in MMI systems.
    Matched MeSH terms: Microwaves*
  6. Fulltext Metamaterial sensor based on rectangular enclosed adjacent triple circle split ring resonator with good quality factor for microwave sensing application
    Islam MR, Islam MT, M MS, Bais B, Almalki SHA, Alsaif H, et al.
    Sci Rep, 2022 Apr 26;12(1):6792.
    PMID: 35474227 DOI: 10.1038/s41598-022-10729-4
    In this article, a novel shaped metamaterial sensor is presented for the recognition of various oils, fluids, and chemicals using microwave frequency. The performance of the designed sensor structure has been studied both theoretically and experimentally, and it works well. A new sample holder for convenient operation is created and located just behind the designed structure. The results of this study performed better than those of prior liquids sensing studies. Various designs were explored using the Genetic Algorithm (GA), and it is embedded in the Computer Simulation Technology (CST) microwave studio, to optimize the optimal dimensions of the resonator. The suggested metamaterial sensor has a good-quality factor and sensitivity in both frequency shifting and amplitude changing. The resonance frequency shifted to 100 MHz between olive and corn oils, 70 MHz between sunflower and palm oils, 80 MHz between clean and waste brake fluids, and 90 MHz between benzene and carbon-tetrachloride chemicals. The quality factor of the sensor is 135, sensitivity is 0.56, and the figure of merit is 76 which expresses its efficient performance. Furthermore, the proposed sensor can sensitively distinguish different liquids by using the frequency shifting property. The study was carried out in three stages: dielectric constant (DK) measurement with the N1500A dielectric measurement kit, simulation of the structure, and experimental test study with the vector network analyzer. Since the recommended sensor has high sensitivity, good quality factor, and excellent performance, hence it can be used in chemical, oil, and microfluidic industries for detecting various liquid samples.
    Matched MeSH terms: Microwaves*
  7. Analisis pengurangan kadar penyerapan spesifik dalam kepala manusia menggunakan bahan ferit dan metabahan
    Norbahiah Misran, Mohammad Tariqul Islam, Mohammad Rashed Iqbal Faruque, Nurul Hafizah Mohd Hanafi, Farizah Ansarudin, Mohd Faisal Ibrahim
    Sains Malaysiana, 2012;41:779-785.
    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.
    Matched MeSH terms: Microwaves
  8. Enhancing silkworm protein yield, extraction efficiency, structure, functionality, and antioxidant activity using ultrasound-, microwave-, and freeze-thaw-assisted methods
    Phuangjit U, Klinkesorn U, Tan CP, Katekhong W
    J Sci Food Agric, 2024 Jan 15;104(1):383-390.
    PMID: 37595024 DOI: 10.1002/jsfa.12929
    BACKGROUND: Silkworm protein applications are limited in the food industry because of their low emulsifying and foaming properties. This study investigated the effect of ultrasound-assisted extraction (UAE) for 15 and 30 min, microwave-assisted extraction (MAE) for 1 and 2 min, and freeze-thaw-assisted extraction (FTAE) for one and three cycles on the yield, extraction efficiency, functional properties, and antioxidant activities of proteins from silkworm pupae. Relationships of protein structure and functionality were also examined.

    RESULTS: UAE for 15 and 30 min and MAE for 1 and 2 min significantly increased protein yield and extraction efficiency compared to the control. Both UAE and MAE processes, especially MAE for 2 min, greatly improved the emulsifying and foaming properties of extracted proteins. FTAE one and three cycles did not increase the protein yield and extraction efficiency but showed enhanced functional properties, especially foaming. All samples showed changes in protein structure, such as increased exposed sulfhydryl (SH) contents, denaturation temperatures, and enthalpy. Only MAE samples had low-molecular-weight proteins based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. UAE and FTAE samples had significantly higher antioxidant activities, while the MAE process showed the opposite.

    CONCLUSION: UAE and MAE processes improved the yield and functionality of extracted silkworm proteins, while MAE negatively impacted protein antioxidant activities. © 2023 Society of Chemical Industry.

    Matched MeSH terms: Microwaves
  9. Fulltext Design and realization of a planar ultrawideband antenna with notch band at 3.5 GHz
    Azim R, Islam MT, Misran N, Yatim B, Arshad H
    ScientificWorldJournal, 2014;2014:563830.
    PMID: 25133245 DOI: 10.1155/2014/563830
    A small antenna with single notch band at 3.5 GHz is designed for ultrawideband (UWB) communication applications. The fabricated antenna comprises a radiating monopole element and a perfectly conducting ground plane with a wide slot. To achieve a notch band at 3.5 GHz, a parasitic element has been inserted in the same plane of the substrate along with the radiating patch. Experimental results shows that, by properly adjusting the position of the parasitic element, the designed antenna can achieve an ultrawide operating band of 3.04 to 11 GHz with a notched band operating at 3.31-3.84 GHz. Moreover, the proposed antenna achieved a good gain except at the notched band and exhibits symmetric radiation patterns throughout the operating band. The prototype of the proposed antenna possesses a very compact size and uses simple structures to attain the stop band characteristic with an aim to lessen the interference between UWB and worldwide interoperability for microwave access (WiMAX) band.
    Matched MeSH terms: Microwaves*
  10. Fulltext Gain enhancement of a multiband resonator using defected ground surface on epoxy woven glass material
    Alam MS, Islam MT, Arshad H
    ScientificWorldJournal, 2014;2014:159468.
    PMID: 24883354 DOI: 10.1155/2014/159468
    A multiband microstrip resonator is proposed in this study which is realized through a rectangular radiator with embedded symmetrical rectangular slots in it and a defected ground surface. The study is presented with detailed parametric analyses to understand the effect of various design parameters. The design and analyses are performed using the FIT based full-wave electromagnetic simulator CST microwave studio suite. With selected parameter values, the resonator showed a peak gain of 5.85 dBi at 5.2 GHz, 6.2 dBi at 8.3 GHz, 3.9 dBi at 9.5 GHz, 5.9 dBi at 12.2 GHz, and 4.7 dBi at 14.6 GHz. Meanwhile, the main lobe magnitude and the 3 dB angular beam width are 6.2 dBi and 86°, 5.9 dBi and 53.7°, 8.5 dBi and 43.9°, 8.6 dBi and 42.1°, and 4.7 dBi and 30.1°, respectively, at the resonant frequencies. The overall resonator has a compact dimension of 0.52λ  × 0.52λ  × 0.027λ at the lower resonant frequency. For practical validation, a lab prototype was built on a 1.6 mm thick epoxide woven glass fabric dielectric material which is measured using a vector network analyzer and within an anechoic chamber. The comparison between the simulated and measured results showed a very good understanding, which implies the practical suitability of the proposed multiband resonator design.
    Matched MeSH terms: Microwaves*
  11. Microwave assisted synthesis and characterization of magnesium substituted calcium phosphate bioceramics
    Khan NI, Ijaz K, Zahid M, Khan AS, Abdul Kadir MR, Hussain R, et al.
    Mater Sci Eng C Mater Biol Appl, 2015 Nov 1;56:286-93.
    PMID: 26249592 DOI: 10.1016/j.msec.2015.05.025
    Hydroxyapatite is used extensively in hard tissue repair due to its biocompatibility and similarity to biological apatite, the mineral component of bone. It differs subtly in composition from biological apatite which contains other ions such as magnesium, zinc, carbonate and silicon (believed to play biological roles). Traditional methods of hydroxyapatite synthesis are time consuming and require strict reaction parameter control. This paper outlines synthesis of magnesium substituted hydroxyapatite using simple microwave irradiation of precipitated suspensions. Microwave irradiation resulted in a drastic decrease in ageing times of amorphous apatitic phases. Time taken to synthesize hydroxyapatite (which remained stable upon heat treatment at 900°C for 1h) reduced twelve folds (to 2h) as compared to traditionally required times. The effects of increasing magnesium concentration in the precursors on particle size, surface area, phase-purity, agglomeration and thermal stability, were observed using scanning electron microscopy, BET surface area analysis, X-ray diffraction and photo acoustic Fourier transform infra-red spectroscopy. Porous agglomerates were obtained after a brief heat-treatment (1h) at 900°C.
    Matched MeSH terms: Microwaves*
  12. Microwave ovens: mapping the electrical field distribution
    Ng KH
    Med Lab Sci, 1991 Jul;48(3):189-92.
    PMID: 1787775
    Uniformity of electric field intensity of microwaves within the microwave oven cavity is necessary to ensure even load-heating, and is particularly important in pathology procedures where small volume irradiation is carried out. A simple and rapid method for mapping electric field distribution, using reversible thermographic paint, is described. Spatial heating patterns for various positions, and the effects of introducing dummy loads to modify heating distributions, have been obtained for a dedicated microwave processor, and comparison made with a domestic microwave oven.
    Matched MeSH terms: Microwaves*
  13. Optimisation of microwave-assisted extraction and functional elucidation of bioactive compounds from Cola nitida pod
    Olalere OA, Gan CY, Akintomiwa OE, Adeyi O, Adeyi A
    Phytochem Anal, 2021 Sep;32(5):850-858.
    PMID: 33583076 DOI: 10.1002/pca.3030
    INTRODUCTION: The quality characteristics and stability of phenolic by-products from Cola nitida wastes are critical factors for drug formulation and food nutraceutical applications.

    OBJECTIVES: In this study, the effect of electromagnetic-based microwave-reflux extraction on the total phenolic content, antioxidant capacity, morphological characteristics, physisorption and chromatographic phenolic profiles were successfully investigated. These physicochemical analyses are often employed in the standardisation of dried herbal and food nutraceutical products.

    MATERIAL AND METHODS: In this study, the electromagnetic-based extraction process was optimised using the Box-Behnken design. The oleoresin bio-products were subsequently characterised to determine the total phenolic content, morphological and microstructural degradation. These analyses were conducted to elucidate the effect of the microwave heating on the C. nitida pod powder.

    RESULTS: From the predicted response, the optimal percentage yield was achieved at 26.20% under 5.39 min of irradiation time, 440 W microwave power and oven temperature of 55°C. Moreover, the rapid estimation of the phenolic content and antioxidant capacity were recorded at 124.84 ± 0.064 mg gallic acid equivalent (GAE)/g dry weight (d.w.) and 6.93 ± 0.34 μg/mL, respectively. The physicochemical characterisation results from the Fourier-transform infrared spectroscopy, field emission scanning electron microscopy and physisorption analyses showed remarkable changes in the micro-surface area (13.66%) characteristics.

    CONCLUSION: The recorded optimal conditions established a basis for future scale-up of microwave extraction parameters with a potential for maximum yield. The physiochemical characterisation revealed the functional characteristics of C. nitida and their tolerance to microwave heating.

    Matched MeSH terms: Microwaves*
  14. Microwave plasma technology for sustainable energy production and the electromagnetic interaction within the plasma system: A review
    Zamri AA, Ong MY, Nomanbhay S, Show PL
    Environ Res, 2021 06;197:111204.
    PMID: 33894238 DOI: 10.1016/j.envres.2021.111204
    The composition of carbon dioxide (CO2) is increasing day by day in the Earth's atmosphere. Worldwide energy demand is now increasing, and this has led to an increase in the percentage of global carbon emission. Moreover, this phenomenon can occur from the careless use of heating systems, generators and especially transportation, therefore, the release of these gases will continue to be widespread if there is no solution. Interaction within the microwave plasma-based gasification system of synthetic natural gas (syngas) production is presented in this paper. Consequently, this reduces the high concentrations of methane and carbon dioxide emission in our atmosphere. Syngas is very useful products that can be used as a source of energy such as fuel production and fuel source. The overview and basic theory about gasification process and microwave plasma technology are provided. Modelling of the microwave plasma system particularly on its application of system electromagnetic field inside waveguide of plasma reactor to produce microwave plasma and how it was calculated are presented in this paper. To recapitulate, the global challenges on the rising of greenhouse gases volume can be regulated with microwave plasma technology and its important aspects have been underlined.
    Matched MeSH terms: Microwaves*
  15. Microwave assisted acid hydrolysis for bioethanol fuel production from sago pith waste
    Thangavelu SK, Rajkumar T, Pandi DK, Ahmed AS, Ani FN
    Waste Manag, 2019 Mar 01;86:80-86.
    PMID: 30902242 DOI: 10.1016/j.wasman.2019.01.035
    Microwave assisted acid hydrolysis (H2SO4 and HCl with >0.5 mol/L) to produce bioethanol from sago pith waste (SPW) was studied. The energy consumption for microwave hydrolysis at different energy inputs and acid concentration were calculated. The overall energy consumption for bioethanol fuel production from SPW was assessed. A maximum of 88% glucose yield and 80% ethanol yield (3.1 g ethanol per 10 g SPW) were obtained using 1.0 mol/L H2SO4. Microwave hydrolysis using 1.0 mol/L H2SO4 consumed the minimum energy of 8.1 kJ to produce 1 g glucose from SPW when energy input was fixed at 54 kJ (900 W for 1 min). In general, 1 g glucose can produce 16 kJ. The overall energy consumption for fuel grade bioethanol production from SPW was 31.77 kJ per g ethanol, which was slightly higher than the lower heating values of ethanol (26.74 kJ/g ethanol).
    Matched MeSH terms: Microwaves*
  16. Enhanced fuel characteristics and physical chemistry of microwave hydrochar for sustainable fuel pellet production via co-densification
    Kang K, Nanda S, Lam SS, Zhang T, Huo L, Zhao L
    Environ Res, 2020 07;186:109480.
    PMID: 32302869 DOI: 10.1016/j.envres.2020.109480
    Microwave assisted hydrothermal treatment (MHTC) was compared with torrefaction in terms of carbonization efficiency and physicochemical characteristics of char products. The utilization of produced char was optimized for composite solid biofuel production. The results show that MHTC significantly improved the binding capability of the microwave hydrochar (MHC) particles during co-densification with unprocessed biomass and coal. One possible contributor to the improved binding is the pseudo lignin formed during the MHTC, which led to a better interlocking of the feedstock particles and promoted the solid bridge formation. Composite pellet prepared with 80 wt% of torrefaction char (TC-120), 10 wt% of microwave hydrochar (MHC-30), and 10 wt% of Coal-04 showed a higher heating value of 24.54 MJ/kg and energy density of 26.43 GJ/m3, which is significantly higher than that of the raw cotton stalk pellet (16.77 MJ/kg and 18.76 GJ/m3, respectively), showing great promise as a solid biofuel. The moisture resistance and oxidation reactivity are also significantly improved. The results demonstrate that MHCs provides dual functionalities in acting as binder and fuel promoter in the production of composite biofuel. This study can provide new insight into the unique functions of MHC during fuel application, which demonstrates the great potential of applying MHTC in energy recovery from lignocellulosic biomass.
    Matched MeSH terms: Microwaves*
  17. Biodiesel synthesized from waste cooking oil in a continuous microwave assisted reactor reduced PM and NOx emissions
    Mohd Ali MA, Gimbun J, Lau KL, Cheng CK, Vo DN, Lam SS, et al.
    Environ Res, 2020 06;185:109452.
    PMID: 32259725 DOI: 10.1016/j.envres.2020.109452
    A synergistic effect of the activated limestone-based catalyst (LBC) and microwave irradiation on the transesterification of waste cooking oil (WCO) was screened using a two-level factorial design and response surface methodology. The catalyst was prepared using a wet-impregnation method and was characterised for its surface element, surface morphology, surface area and porosity. The reaction was performed in a purpose-built continuous microwave assisted reactor (CMAR), while the conversion and yield of biodiesel were measured using a gas chromatography. The results showed that the catalyst loading, methanol to oil molar ratio and the reaction time significantly affect the WCO conversion. The optimum conversion of oil to biodiesel up to 96.65% was achieved at catalyst loading of 5.47 wt%, methanol to oil molar ratio of 12.21:1 and the reaction time of 55.26 min. The application of CMAR in this work reduced the transesterification time by about 77% compared to the reaction time needed for a conventional reactor. The biodiesel produced in this work met the specification of American Society for Testing and Materials (ASTM D6751). Engine test results shows the biodiesel has a lower NOx and particulate matters emissions compared to petrodiesel.
    Matched MeSH terms: Microwaves*
  18. Fulltext Experimental tissue mimicking human head phantom for estimation of stroke using IC-CF-DMAS algorithm in microwave based imaging system
    Islam MS, Islam MT, Almutairi AF
    Sci Rep, 2021 11 10;11(1):22015.
    PMID: 34759284 DOI: 10.1038/s41598-021-01486-x
    This paper presents the preparation and measurement of tissue-mimicking head phantom and its validation with the iteratively corrected coherence factor delay-multiply-and-sum (IC-CF-DMAS) algorithm for brain stroke detection. The phantom elements are fabricated by using different chemical mixtures that imitate the electrical properties of real head tissues (CSF, dura, gray matter, white matter, and blood/stroke) over the frequency band of 1-4 GHz. The electrical properties are measured using the open-ended dielectric coaxial probe connected to a vector network analyzer. Individual phantom elements are placed step by step in a three-dimensional skull. The IC-CF-DMAS image reconstruction algorithm is later applied to the phantom to evaluate the effectiveness of detecting stroke. The phantom elements are preserved and measured multiple times in a week to validate the overall performance over time. The electrical properties of the developed phantom emulate the similar properties of real head tissue. Moreover, the system can also effectively detect the stroke from the developed phantom. The experimental results demonstrate that the developed tissue-mimicking head phantom is time-stable, and it shows a good agreement with the theoretical results in detecting and reconstructing the stroke images that could be used in investigating as a supplement to the real head tissue.
    Matched MeSH terms: Microwaves*
  19. Microwave induced plasma for solid fuels and waste processing: A review on affecting factors and performance criteria
    Ho GS, Faizal HM, Ani FN
    Waste Manag, 2017 Nov;69:423-430.
    PMID: 28811144 DOI: 10.1016/j.wasman.2017.08.015
    High temperature thermal plasma has a major drawback which consumes high energy. Therefore, non-thermal plasma which uses comparatively lower energy, for instance, microwave plasma is more attractive to be applied in gasification process. Microwave-induced plasma gasification also carries the advantages in terms of simplicity, compactness, lightweight, uniform heating and the ability to operate under atmospheric pressure that gains attention from researchers. The present paper synthesizes the current knowledge available for microwave plasma gasification on solid fuels and waste, specifically on affecting parameters and their performance. The review starts with a brief outline on microwave plasma setup in general, and followed by the effect of various operating parameters on resulting output. Operating parameters including fuel characteristics, fuel injection position, microwave power, addition of steam, oxygen/fuel ratio and plasma working gas flow rate are discussed along with several performance criteria such as resulting syngas composition, efficiency, carbon conversion, and hydrogen production rate. Based on the present review, fuel retention time is found to be the key parameter that influences the gasification performance. Therefore, emphasis on retention time is necessary in order to improve the performance of microwave plasma gasification of solid fuels and wastes.
    Matched MeSH terms: Microwaves*
  20. Fulltext Prospects and Challenges of Microwave-Combined Technology for Biodiesel and Biolubricant Production through a Transesterification: A Review
    Mohamad Aziz NA, Yunus R, Kania D, Abd Hamid H
    Molecules, 2021 Feb 03;26(4).
    PMID: 33546303 DOI: 10.3390/molecules26040788
    Biodiesels and biolubricants are synthetic esters produced mainly via a transesterification of other esters from bio-based resources, such as plant-based oils or animal fats. Microwave heating has been used to enhance transesterification reaction by converting an electrical energy into a radiation, becoming part of the internal energy acquired by reactant molecules. This method leads to major energy savings and reduces the reaction time by at least 60% compared to a conventional heating via conduction and convection. However, the application of microwave heating technology alone still suffers from non-homogeneous electromagnetic field distribution, thermally unstable rising temperatures, and insufficient depth of microwave penetration, which reduces the mass transfer efficiency. The strategy of integrating multiple technologies for biodiesel and biolubricant production has gained a great deal of interest in applied chemistry. This review presents an advanced transesterification process that combines microwave heating with other technologies, namely an acoustic cavitation, a vacuum, ionic solvent, and a supercritical/subcritical approach to solve the limitations of the stand-alone microwave-assisted transesterification. The combined technologies allow for the improvement in the overall product yield and energy efficiency. This review provides insights into the broader prospects of microwave heating in the production of bio-based products.
    Matched MeSH terms: Microwaves*
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