Displaying publications 21 - 40 of 306 in total

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  1. Fulltext Air-filled substrate integrated waveguide for smart health applications
    Hidayah Mansor, Razi Abdul-Rahman
    Malaysian Journal of Medicine and Health Sciences, 2020;16(108):23-27.
    MyJurnal
    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.
    Matched MeSH terms: Microwaves
  2. Fulltext Enhanced Handover Decision Algorithm in Heterogeneous Wireless Network
    Abdullah RM, Zukarnain ZA
    Sensors (Basel), 2017 Jul 14;17(7).
    PMID: 28708067 DOI: 10.3390/s17071626
    Transferring a huge amount of data between different network locations over the network links depends on the network's traffic capacity and data rate. Traditionally, a mobile device may be moved to achieve the operations of vertical handover, considering only one criterion, that is the Received Signal Strength (RSS). The use of a single criterion may cause service interruption, an unbalanced network load and an inefficient vertical handover. In this paper, we propose an enhanced vertical handover decision algorithm based on multiple criteria in the heterogeneous wireless network. The algorithm consists of three technology interfaces: Long-Term Evolution (LTE), Worldwide interoperability for Microwave Access (WiMAX) and Wireless Local Area Network (WLAN). It also employs three types of vertical handover decision algorithms: equal priority, mobile priority and network priority. The simulation results illustrate that the three types of decision algorithms outperform the traditional network decision algorithm in terms of handover number probability and the handover failure probability. In addition, it is noticed that the network priority handover decision algorithm produces better results compared to the equal priority and the mobile priority handover decision algorithm. Finally, the simulation results are validated by the analytical model.
    Matched MeSH terms: Microwaves
  3. Microwave steam activation, an innovative pyrolysis approach to convert waste palm shell into highly microporous activated carbon
    Yek PNY, Liew RK, Osman MS, Lee CL, Chuah JH, Park YK, et al.
    J Environ Manage, 2019 Apr 15;236:245-253.
    PMID: 30735943 DOI: 10.1016/j.jenvman.2019.01.010
    Microwave-steam activation (MSA), an innovative pyrolysis approach combining the use of microwave heating and steam activation, was investigated for its potential production of high grade activated carbon (AC) from waste palm shell (WPS) for methylene blue removal. MSA was performed via pyrolytic carbonization of WPS to produce biochar as the first step followed by steam activation of the biochar using microwave heating to form AC. Optimum yield and adsorption efficiency of methylene blue were obtained using response surface methodology involving several key process parameters. The resulting AC was characterized for its porous characteristics, surface morphology, proximate analysis and elemental compositions. MSA provided a high activation temperature above 500 °C with short process time of 15 min and rapid heating rate (≤150 °C/min). The results from optimization showed that one gram of AC produced from steam activation under 10 min of microwave heating at 550 °C can remove up to 38.5 mg of methylene blue. The AC showed a high and uniform surface porosity consisting high fixed carbon (73 wt%), micropore and BET surface area of 763.1 and 570.8 m2/g respectively, hence suggesting the great potential of MSA as a promising approach to produce high grade adsorbent for dye removal.
    Matched MeSH terms: Microwaves
  4. Fulltext Synthesis of magnetic nanocarbon using palm oil as the green precursor via microwave-assisted arc for wastewater treatment
    Zakaria NZJ, Rozali S, Mubarak NM, Khalid M
    Sci Rep, 2022 Nov 04;12(1):18698.
    PMID: 36333525 DOI: 10.1038/s41598-022-21982-y
    The presence of metal with microwave irradiation has always invited controversial arguments as the metal will catch on fire easily. But interestingly, researchers found that arc discharge phenomena provide a promising way for molecule cracking to synthesize nanomaterials. This study developed a single-step yet affordable synthesis approach that combines microwave heating and arcing in transforming crude palm oil into magnetic nanocarbon (MNC), which can be considered a new alternative for the palm oil sectors. It involves synthesizing the medium at a partial inert condition with constant coiled stainless steel metal wire (dielectric media) and ferrocene (catalyst). This approach successfully demonstrates heating at a temperature ranging from 190.9 to 472.0 °C with different synthesis times (10-20 min). The produced MNC shows formations of spheres with average sizes of 20.38-31.04 nm, mesoporous structure (SBET: 14.83-151.95 m2/g), and high content of fixed carbon (52.79-71.24wt%), and the ratio of the D and G bands (ID/IG) is 0.98-0.99. The formation of new peaks in the FTIR spectra (522.29-588.48 cm-1) supports the appearance of the FeO compounds from the ferrocene. The magnetometer shows high magnetization saturation (22.32-26.84 emu/g) in ferromagnetic materials. The application of the MNC in wastewater treatment has been demonstrated by evaluating their adsorbent capability with Methylene Blue (MB) adsorption test at a different concentrations varying between 5 and 20 ppm. The MNC produced at synthesis time (20 min) shows the highest adsorption efficiency (10.36 mg/g) compared to others, with 87.79% removal of MB dye. As a result, the value for Langmuir is not promising compared to Freundlich, with R2 being around 0.80, 0.98, and 0.99 for MNC synthesized at 10 min (MNC10), 15 min (MNC15), and 20 min (MNC20), respectively. Hence, the adsorption system is in a heterogeneous condition. The microwave-assisted arcing thereby presents a promising approach to transforming CPO into MNC that could remove the hazardous dye.
    Matched MeSH terms: Microwaves
  5. Simultaneous removal of toxic ammonia and lettuce cultivation in aquaponic system using microwave pyrolysis biochar
    Su MH, Azwar E, Yang Y, Sonne C, Yek PNY, Liew RK, et al.
    J Hazard Mater, 2020 Sep 05;396:122610.
    PMID: 32298865 DOI: 10.1016/j.jhazmat.2020.122610
    This study examined an aquaponic approach of circulating water containing ammonia excretions from African catfish grown in an aquaculture tank for bacterial conversion into nitrates, which then acted as a nutrient substance to cultivate lettuce in hydroponic tank. We found that microwave pyrolysis biochar (450 g) having microporous (1.803 nm) and high BET surface area (419 m2/g) was suitable for use as biological carrier to grow nitrifying bacteria (63 g of biofilm mass) that treated the water quality through removing the ammonia (67%) and total suspended solids (68%), resulting in low concentration of remaining ammonia (0.42 mg/L) and total suspended solid (59.40 mg/L). It also increased the pH (6.8), converted the ammonia into nitrate (29.7 mg/L), and increased the nitrogen uptake by the lettuce (110 mg of nitrogen per plant), resulting in higher growth in lettuce (0.0562 %/day) while maintaining BOD5 level (3.94 mg/L) at acceptable level and 100% of catfish survival rate. Our results demonstrated that microwave pyrolysis biochar can be a promising solution for growing nitrifying bacteria in aquaponic system for simultaneous toxic ammonia remediation and generation of nitrate for growing vegetable in aquaculture industry.
    Matched MeSH terms: Microwaves
  6. Microwave-assisted extractions of active ingredients from plants
    Chan CH, Yusoff R, Ngoh GC, Kung FW
    J Chromatogr A, 2011 Sep 16;1218(37):6213-25.
    PMID: 21820119 DOI: 10.1016/j.chroma.2011.07.040
    Microwave-assisted extraction (MAE) is widely employed in the analysis and the extraction of active compounds from plants. This review summarizes the research done during the last decade on the MAE of active ingredients from plants. Advances and modifications to improve the performance of MAE are presented and discussed in detail. Modified MAE such as vacuum microwave-assisted extraction (VMAE), nitrogen-protected microwave-assisted extraction (NPMAE), ultrasonic microwave-assisted extraction (UMAE), dynamic microwave-assisted extraction (DMAE) and other advancements in MAE are also detailed in this article. In addition, the microwave extraction procedures and the important parameters influencing its performance are also included, together with the advantages and the drawbacks of each MAE techniques.
    Matched MeSH terms: Microwaves*
  7. Continuous microwave flow synthesis of mesoporous hydroxyapatite
    Akram M, Alshemary AZ, Goh YF, Wan Ibrahim WA, Lintang HO, Hussain R
    Mater Sci Eng C Mater Biol Appl, 2015 Nov 1;56:356-62.
    PMID: 26249601 DOI: 10.1016/j.msec.2015.06.040
    We have successfully used continuous microwave flow synthesis (CMFS) technique for the template free synthesis of mesoporous hydroxyapatite. The continuous microwave flow reactor consisted of a modified 2.45GHz household microwave, peristaltic pumps and a Teflon coil. This cost effective and efficient system was exploited to produce semi-crystalline phase pure nano-sized hydroxyapatite. Effect of microwave power, retention time and the concentration of reactants on the phase purity, degree of crystallinity and surface area of the final product was studied in detail. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to study the phase purity and composition of the product, while transmission electron microscopy (TEM) was used to study the effect of process parameters on the morphology of hydroxyapatite. The TEM analysis confirmed the formation of spherical particles at low microwave power; however the morphology of the particles changed to mesoporous needle and rod-like structure upon exposing the reaction mixture to higher microwave power and longer retention time inside the microwave. The in-vitro ion dissolution behavior of the as synthesized hydroxyapatite was studied by determining the amount of Ca(2+) ion released in SBF solution.
    Matched MeSH terms: Microwaves*
  8. Microwave-stimulated fixation for electron microscopy using a domestic microwave oven
    Ng KH, Gan SK
    Malays J Pathol, 1990 Jun;12(1):27-33.
    PMID: 2090887
    We investigated microwave-stimulated fixation of tissues for transmission electron microscopy using a domestic microwave oven operating at a frequency of 2.45 GHz with an output power of 500W. Microwave-stimulated fixation, in 4% glutaraldehyde, of fresh rat kidney, liver, heart and brain tissues was compared to conventional fixation. Human renal biopsies were similarly studied. Electron microscopy showed excellent ultrastructural preservation comparable to that obtained by conventional fixation. The optimal temperature range for microwave-stimulated fixation was found to lie between 50 degrees C and 55 degrees C. Our results indicate that microwave-stimulated fixation is a rapid and reproducible technique and can be effectively applied to routine diagnostic pathology.
    Matched MeSH terms: Microwaves*
  9. Extraction of bioactives from Orthosiphon stamineus using microwave and ultrasound-assisted techniques: Process optimization and scale up
    Chan CH, See TY, Yusoff R, Ngoh GC, Kow KW
    Food Chem, 2017 Apr 15;221:1382-1387.
    PMID: 27979103 DOI: 10.1016/j.foodchem.2016.11.016
    This work demonstrated the optimization and scale up of microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE) of bioactive compounds from Orthosiphon stamineus using energy-based parameters such as absorbed power density and absorbed energy density (APD-AED) and response surface methodology (RSM). The intensive optimum conditions of MAE obtained at 80% EtOH, 50mL/g, APD of 0.35W/mL, AED of 250J/mL can be used to determine the optimum conditions of the scale-dependent parameters i.e. microwave power and treatment time at various extraction scales (100-300mL solvent loading). The yields of the up scaled conditions were consistent with less than 8% discrepancy and they were about 91-98% of the Soxhlet extraction yield. By adapting APD-AED method in the case of UAE, the intensive optimum conditions of the extraction, i.e. 70% EtOH, 30mL/g, APD of 0.22W/mL, AED of 450J/mL are able to achieve similar scale up results.
    Matched MeSH terms: Microwaves/therapeutic use*
  10. Evaluation of direct transesterification of microalgae using microwave irradiation
    Teo CL, Idris A
    Bioresour Technol, 2014 Dec;174:281-6.
    PMID: 25463809 DOI: 10.1016/j.biortech.2014.10.035
    Nannochloropsis sp. wet biomass was directly transesterified under microwave (MW) irradiation in the presence of methanol and various alkali and acid catalyst. Two different types of direct transesterification (DT) were used; one step and two step transesterification. The biodiesel yield obtained from the MWDT was compared with that obtained using conventional method (lipid extraction followed by transesterification) and water bath heating DT method. Findings revealed that MWDT efficiencies were higher compared to water bath heating DT by at least 14.34% and can achieve a maximum of 43.37% with proper selection of catalysts. The use of combined catalyst (NaOH and H2SO4) increased the yield obtained by 2.3-folds (water bath heating DT) and 2.87-folds (MWDT) compared with the one step single alkaline catalyst respectively. The property of biodiesel produced by MWDT has high lubricating property, good cetane number and short carbon chain FAME's compared with water bath heating DT.
    Matched MeSH terms: Microwaves*
  11. Microwave-enhanced CO2 gasification of oil palm shell char
    Lahijani P, Zainal ZA, Mohamed AR, Mohammadi M
    Bioresour Technol, 2014 Apr;158:193-200.
    PMID: 24607454 DOI: 10.1016/j.biortech.2014.02.015
    CO2 gasification of oil palm shell (OPS) char to produce CO through the Boudouard reaction (C + CO2 ↔ 2CO) was investigated under microwave irradiation. A microwave heating system was developed to carry out the CO2 gasification in a packed bed of OPS char. The influence of char particle size, temperature and gas flow rate on CO2 conversion and CO evolution was considered. It was attempted to improve the reactivity of OPS char in gasification reaction through incorporation of Fe catalyst into the char skeleton. Very promising results were achieved in our experiments, where a CO2 conversion of 99% could be maintained during 60 min microwave-induced gasification of iron-catalyzed char. When similar gasification experiments were performed in conventional electric furnace, the superior performance of microwave over thermal driven reaction was elucidated. The activation energies of 36.0, 74.2 and 247.2 kJ/mol were obtained for catalytic and non-catalytic microwave and thermal heating, respectively.
    Matched MeSH terms: Microwaves*
  12. Fulltext A Negative Index Metamaterial-Inspired UWB Antenna with an Integration of Complementary SRR and CLS Unit Cells for Microwave Imaging Sensor Applications
    Islam MT, Islam MM, Samsuzzaman M, Faruque MR, Misran N
    Sensors (Basel), 2015 May 20;15(5):11601-27.
    PMID: 26007721 DOI: 10.3390/s150511601
    This paper presents a negative index metamaterial incorporated UWB antenna with an integration of complementary SRR (split-ring resonator) and CLS (capacitive loaded strip) unit cells for microwave imaging sensor applications. This metamaterial UWB antenna sensor consists of four unit cells along one axis, where each unit cell incorporates a complementary SRR and CLS pair. This integration enables a design layout that allows both a negative value of permittivity and a negative value of permeability simultaneous, resulting in a durable negative index to enhance the antenna sensor performance for microwave imaging sensor applications. The proposed MTM antenna sensor was designed and fabricated on an FR4 substrate having a thickness of 1.6 mm and a dielectric constant of 4.6. The electrical dimensions of this antenna sensor are 0.20 λ × 0.29 λ at a lower frequency of 3.1 GHz. This antenna sensor achieves a 131.5% bandwidth (VSWR < 2) covering the frequency bands from 3.1 GHz to more than 15 GHz with a maximum gain of 6.57 dBi. High fidelity factor and gain, smooth surface-current distribution and nearly omni-directional radiation patterns with low cross-polarization confirm that the proposed negative index UWB antenna is a promising entrant in the field of microwave imaging sensors.
    Matched MeSH terms: Microwaves*
  13. Fulltext Antioxidant Activity, and Volatile and Phytosterol Contents of Strobilanthes crispus Dehydrated Using Conventional and Vacuum Microwave Drying Methods
    Chua LYW, Chua BL, Figiel A, Chong CH, Wojdyło A, Szumny A, et al.
    Molecules, 2019 04 09;24(7).
    PMID: 30970652 DOI: 10.3390/molecules24071397
    The preservation of active constituents in fresh herbs is affected by drying methods. An effective drying method for Strobilanthes crispus which is increasingly marketed as an important herbal tea remains to be reported. This study evaluated the effects of conventional and new drying technologies, namely vacuum microwave drying methods, on the antioxidant activity and yield of essential oil volatiles and phytosterols. These drying methods included convective drying (CD) at 40 °C, 50 °C, and 60 °C; vacuum microwave drying (VMD) at 6, 9, and 12 W/g; convective pre-drying and vacuum microwave finish drying (CPD-VMFD) at 50 °C and 9 W/g; and freeze-drying (FD). GC–MS revealed 33 volatiles, and 2-hexen-1-ol, 2-hexenal, 1-octen-3-ol, linalool, and benzaldehyde were major constituents. The compounds β-sitosterol and α-linolenic acid were the most abundant phytosterol and fatty acid, respectively, in fresh S. crispus. The highest phenolic content was achieved with CD at 60 °C. The highest antioxidant activity was obtained with CD at 40 °C and VMD at 9 W/g. On the contrary, the highest total volatiles and phytosterols were detected with CD at 50 °C and VMD at 9 W/g, respectively. This study showed that CD and VMD were effective in producing highly bioactive S. crispus. A suitable drying parameter level, irrespective of the drying method used, was an important influencing factor.
    Matched MeSH terms: Microwaves*
  14. Sequential ultrasound-microwave assisted acid extraction (UMAE) of pectin from pomelo peels
    Liew SQ, Ngoh GC, Yusoff R, Teoh WH
    Int J Biol Macromol, 2016 Dec;93(Pt A):426-435.
    PMID: 27565298 DOI: 10.1016/j.ijbiomac.2016.08.065
    This study aims to optimize sequential ultrasound-microwave assisted extraction (UMAE) on pomelo peel using citric acid. The effects of pH, sonication time, microwave power and irradiation time on the yield and the degree of esterification (DE) of pectin were investigated. Under optimized conditions of pH 1.80, 27.52min sonication followed by 6.40min microwave irradiation at 643.44W, the yield and the DE value of pectin obtained was respectively at 38.00% and 56.88%. Based upon optimized UMAE condition, the pectin from microwave-ultrasound assisted extraction (MUAE), ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE) were studied. The yield of pectin adopting the UMAE was higher than all other techniques in the order of UMAE>MUAE>MAE>UAE. The pectin's galacturonic acid content obtained from combined extraction technique is higher than that obtained from sole extraction technique and the pectin gel produced from various techniques exhibited a pseudoplastic behaviour. The morphological structures of pectin extracted from MUAE and MAE closely resemble each other. The extracted pectin from UMAE with smaller and more regular surface differs greatly from that of UAE. This has substantiated the highest pectin yield of 36.33% from UMAE and further signified their compatibility and potentiality in pectin extraction.
    Matched MeSH terms: Microwaves*
  15. Fulltext Microwave bio-sensor based on symmetrical split ring resonator with spurline filters for therapeutic goods detection
    Alahnomi RA, Zakaria Z, Ruslan E, Ab Rashid SR, Mohd Bahar AA, Shaaban A
    PLoS One, 2017;12(9):e0185122.
    PMID: 28934301 DOI: 10.1371/journal.pone.0185122
    A novel symmetrical split ring resonator (SSRR) based microwave sensor with spurline filters for detecting and characterizing the properties of solid materials has been developed. Due to the weak perturbation in the interaction of material under test (MUT) and planar microwave sensor, spurline filters were embedded to the SSRR microwave sensor which effectively enhanced Q-factor with suppressing the undesired harmonic frequency. The spurline filter structures force the presented sensor to resonate at a fundamental frequency of 2.2 GHz with the capabilities of suppressing rejected harmonic frequency and miniaturization in circuit size. A wide bandwidth rejection is achieved by using double spurlines filters with high Q-factor achievement (up to 652.94) compared to single spurline filter. The new SSRR sensor with spurline filters displayed desired properties such as high sensitivity, accuracy, and performance with a 1.3% typical percentage error in the measurement results. Furthermore, the sensor has been successfully applied for detecting and characterizing solid materials (such as Roger 5880, Roger 4350, and FR4) and evidently demonstrated that it can suppress the harmonic frequency effectively. This novel design with harmonic suppression is useful for various applications such as food industry (meat, fruit, vegetables), biological medicine (derived from proteins and other substances produced by the body), and Therapeutic goods (antiseptics, vitamins, anti-psychotics, and other medicines).
    Matched MeSH terms: Microwaves*
  16. Catalytic microwave pyrolysis of oil palm fiber (OPF) for the biochar production
    Hossain MA, Ganesan PB, Sandaran SC, Rozali SB, Krishnasamy S
    Environ Sci Pollut Res Int, 2017 Dec;24(34):26521-26533.
    PMID: 28948458 DOI: 10.1007/s11356-017-0241-6
    Microwave pyrolysis of oil palm fiber (OPF) with three types of Na-based catalysts was experimentally investigated to produce biochar. Sodium hydroxide (NaOH), sodium chloride (NaCl), and sodium carbonate (Na2CO3) with purity 99.9% were selected for this investigation. Microwave muffle reactor (Model: HAMiab-C1500) with a microwave power controller including a microwave generator was used to perform the microwave pyrolysis. OPF particles were used after removing foreign materials, impurities, and dust. Microwave power ranges from 400 to 900 W, temperature ranges from 450 to 700 °C, and N2 flow rates ranges from 200 to -1200 cm3/min were used along with all three Na-based catalysts for this investigation. Lower microwave power, temperature, and N2 flow rate have been found favorable for higher yield of biochar. NaOH is to be found as the more suitable catalyst than NaCl and Na2CO3 to produce biochar. A maximum biochar yield (51.42 wt%) has been found by using the catalysts NaOH at N2 flow rate of 200 cm3/min. One sample of the biochar (maximum yield without catalysts) was selected for further characterization via thermo gravimetric analysis (TGA), scanning electron microscopy (SEM), BET surface area, Fourier transform infrared spectroscopy (FTIR), and ultimate and proximate analysis. SEM and BET surface area analysis showed the presence of some pores in the biochar. High percentage of carbon (60.24 wt%) was also recorded in the sample biochar. The pores and high percentage of carbon of biochar have significant impact on soil fertilization by increasing the carbon sequestration in the soil. It assists to slow down the decomposition rate of nutrients from soil and therefore enhances the soil quality.
    Matched MeSH terms: Microwaves*
  17. A comparative study of microwave oven-assisted tissue processing and conventional method of tissue processing on turnaround laboratory time and morphological quality of tissue sections
    FinNie O, Aye SA, Krishnappa P, Ravindran R
    Med J Malaysia, 2023 Mar;78(2):202-206.
    PMID: 36988531
    INTRODUCTION: The purpose of tissue processing is to fix the tissue in a solid medium toenable thin sections. Conventional method of tissue processing is the standardized method of tissue processing which has been used for more than 10 decades. However, the conventional method is time-consuming, and the overall turnaround time for the histopathology report is at least two days. The objective of this study is to identify the protocol for tissue processing procedure using domestic microwave oven. To determine the tissue processing time when using domestic microwave oven. To compare the morphological quality of tissue slides made by domestic microwave oven and conventional method using automated tissue processor.

    MATRIALS AND METHODS: The conventional protocol and three microwave protocols of tissue processing were used in this study. A pilot study was done prior to the real run to determine the baseline timing for microwave protocol. The baseline timing was fixed at 2 minutes,30 minutes,5 minutes and 25 minutes. The processing time of the microwave protocol was adjusted from 62 minutes to 70 minutes to 77 minutes by increasing the dehydration and wax impregnation time while the time for tissue fixation and clearing remain the same throughout all the microwave protocols.

    RESULTS: The group 2 microwave protocol produced the sections that is closely comparable to group 1 conventional protocol. The morphological quality of histopathology slides is best observed when the processing time of microwave protocol is 62 minutes.

    CONCLUSION: The most appropriate microwave protocol for tissue processing is group 2 as the morphological quality of histopathology slides are more superior than that of group 1 with an overall percentage of 80% of satisfactory slides in group 2 and 76.68% in group 1.

    Matched MeSH terms: Microwaves*
  18. Fulltext An Aligned-Gap and Centered-Gap Rectangular Multiple Split Ring Resonator for dielectric sensing applications
    Rusni IM, Ismail A, Alhawari AR, Hamidon MN, Yusof NA
    Sensors (Basel), 2014 Jul 21;14(7):13134-48.
    PMID: 25051036 DOI: 10.3390/s140713134
    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.
    Matched MeSH terms: Microwaves
  19. Fulltext Experimental Breast Phantom Imaging with Metamaterial-Inspired Nine-Antenna Sensor Array
    Islam MT, Samsuzzaman M, Islam MT, Kibria S
    Sensors (Basel), 2018 Dec 14;18(12).
    PMID: 30558191 DOI: 10.3390/s18124427
    An experimental system for early screening of a breast tumor is presented in this article. The proposed microwave imaging (MI) system consists of a moveable array of nine improved negative-index metamaterial (MTM)-loaded ultrawideband (UWB) antenna sensor with incorporation of a corresponding SRR (split-ring resonator) and CLS (capacitively loaded strip) structure, in a circular array, the stepper motor-based array-mounting stand, the adjustable phantom hanging platform, an RF switching system to control the receivers, and a personal computer-based signal processing and image reconstruction unit using MATLAB. The improved antenna comprises of four-unit cells along one axis, where an individual unit cell integrates a balancing SRR and CLS pair, which makes the antenna radiation omnidirectional over the operating frequencies. The electrical dimensions of this proposed antenna are 0.28λ × 0.20λ × 0.016λ, measured at the lowest operating frequency of 2.97 GHz as the operating bandwidth of this is in between 2.97⁻15 GHz (134.82% bandwidth), with stable directional radiation pattern. SP8T 8 port switch is used to enable the eight receiver antennas to sequentially send a 3⁻8.0 GHz microwave signal to capture the backscattered signal by MATLAB software. A low-cost realistic homogeneous breast phantom with tumor material is developed and measured to test the capability of the imaging system to detect the breast tumors. A post-processing delay-multiply-and-sum (DMAS) algorithm is used to process the recorded backscatter signal to get an image of the breast phantom, and to accurately identify the existence and located area of multiple breast tumor tissues.
    Matched MeSH terms: Microwaves
  20. Cold-pressed rapeseed (Brassica napus) oil: Chemistry and functionality
    Chew SC
    Food Res Int, 2020 05;131:108997.
    PMID: 32247493 DOI: 10.1016/j.foodres.2020.108997
    Rapeseed oil is the second most abundant produced edible oil in the world with low erucic acid and low glucosinolate. Thus, the quality of rapeseed oil had attracted global attention. Cold-pressed rapeseed oil appeared to be a preferred choice than refined oil as no solvent and less processing involved in the cold-pressing. The methods of cold-pressing and microwave pre-treatment on the extraction yield and bioactive compounds of rapeseed oil have been reviewed in this paper. Cold-pressed rapeseed oil offers health benefits due to its preserved fatty acid profile and bioactive compounds. High phenolic compounds, tocopherols, phytosterols, and carotenoids contents in the cold-pressed rapeseed oil offer health benefits like regulating blood lipid profile, insulin sensitivity, and glycemic control, as well as offer antioxidant and cytotoxic activity. Besides using as edible oil, cold-pressed rapeseed oil find applications in animal feed, chemical, and fuel.
    Matched MeSH terms: Microwaves
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