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Fulltext Design of a Highly Efficient Wideband Multi-Frequency Ambient RF Energy Harvester

Roy S, Tiang JJ, Roslee MB, Ahmed MT, Kouzani AZ, Mahmud MAP

Sensors (Basel), 2022 Jan 06;22(2).
PMID: 35062383 DOI: 10.3390/s22020424

For low input radio frequency (RF) power from -35 to 5 dBm, a novel quad-band RF energy harvester (RFEH) with an improved impedance matching network (IMN) is proposed to overcome the poor conversion efficiency and limited RF power range of the ambient environment. In this research, an RF spectral survey was performed in the semi-urban region of Malaysia, and using these results, a multi-frequency highly sensitive RF energy harvester was designed to harvest energy from available frequency bands within the 0.8 GHz to 2.6 GHz frequency range. Firstly, a new IMN is implemented to improve the rectifying circuit's efficiency in ambient conditions. Secondly, a self-complementary log-periodic higher bandwidth antenna is proposed. Finally, the design and manufacture of the proposed RF harvester's prototype are carried out and tested to realize its output in the desired frequency bands. For an accumulative -15 dBm input RF power that is uniformly universal across the four radio frequency bands, the harvester's calculated dc rectification efficiency is about 35 percent and reaches 52 percent at -20 dBm. Measurement in an ambient RF setting shows that the proposed harvester is able to harvest dc energy at -20 dBm up to 0.678 V.
Fulltext Reflection and transmission coefficient of yttrium iron garnet filled polyvinylidene fluoride composite using rectangular waveguide at microwave frequencies

Soleimani H, Abbas Z, Yahya N, Shameli K, Soleimani H, Shabanzadeh P

Int J Mol Sci, 2012;13(7):8540-8.
PMID: 22942718 DOI: 10.3390/ijms13078540

The sol-gel method was carried out to synthesize nanosized Yttrium Iron Garnet (YIG). The nanomaterials with ferrite structure were heat-treated at different temperatures from 500 to 1000 °C. The phase identification, morphology and functional groups of the prepared samples were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR), respectively. The YIG ferrite nanopowder was composited with polyvinylidene fluoride (PVDF) by a solution casting method. The magnitudes of reflection and transmission coefficients of PVDF/YIG containing 6, 10 and 13% YIG, respectively, were measured using rectangular waveguide in conjunction with a microwave vector network analyzer (VNA) in X-band frequencies. The results indicate that the presence of YIG in polymer composites causes an increase in reflection coefficient and decrease in transmission coefficient of the polymer.
Fulltext A small and slim coaxial probe for single rice grain moisture sensing

You KY, Mun HK, You LL, Salleh J, Abbas Z

Sensors (Basel), 2013;13(3):3652-63.
PMID: 23493127 DOI: 10.3390/s130303652

A moisture detection of single rice grains using a slim and small open-ended coaxial probe is presented. The coaxial probe is suitable for the nondestructive measurement of moisture values in the rice grains ranging from from 9.5% to 26%. Empirical polynomial models are developed to predict the gravimetric moisture content of rice based on measured reflection coefficients using a vector network analyzer. The relationship between the reflection coefficient and relative permittivity were also created using a regression method and expressed in a polynomial model, whose model coefficients were obtained by fitting the data from Finite Element-based simulation. Besides, the designed single rice grain sample holder and experimental set-up were shown. The measurement of single rice grains in this study is more precise compared to the measurement in conventional bulk rice grains, as the random air gap present in the bulk rice grains is excluded.
Fulltext Complex Permittivity and Electromagnetic Interference Shielding Effectiveness of OPEFB Fiber-Polylactic Acid Filled with Reduced Graphene Oxide

Ibrahim Lakin I, Abbas Z, Azis RS, Abubakar Alhaji I

Materials (Basel), 2020 Oct 16;13(20).
PMID: 33081082 DOI: 10.3390/ma13204602

This study was aimed at fabricating composites of polylactic acid (PLA) matrix-reinforced oil palm empty fruit bunch (OPEFB) fiber filled with chemically reduced graphene oxide (rGO). A total of 2-8 wt.% rGO/OPEFB/PLA composites were characterized for their complex permittivity using an open-ended coaxial probe (OEC) technique. The shielding efficiency properties were calculated using the measured transmission (S21) and the reflection (S11) coefficient results. All the measurements and calculations were performed in the 8-12 GHz frequency range. The morphological and microstructural study included X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and Fourier transform infrared spectroscopy (FTIR). The results indicated that the incorporation of rGO as filler into the composites enhanced their complex permittivity properties. The composites showed a total shielding efficiency (SET) of about 31.2 dB at a frequency range of 8-12 GHz, which suggests their usefulness for microwave absorption.
Fulltext Enhancement of Complex Permittivity and Attenuation Properties of Recycled Hematite (α-Fe2O3) Using Nanoparticles Prepared via Ball Milling Technique

Mensah EE, Abbas Z, Azis RS, Khamis AM

Materials (Basel), 2019 May 24;12(10).
PMID: 31137736 DOI: 10.3390/ma12101696

The purpose of this study was to synthesize high-quality recycled α-Fe2O3 to improve its complex permittivity properties by reducing the particles to nanosize through high energy ball milling. Complex permittivity and permeability characterizations of the particles were performed using open-ended coaxial and rectangular waveguide techniques and a vector network analyzer. The attenuation characteristics of the particles were analyzed with finite element method (FEM) simulations of the transmission coefficients and electric field distributions using microstrip model geometry. All measurements and simulations were conducted in the 8-12 GHz range. The average nanoparticle sizes obtained after 8, 10 and 12 h of milling were 21.5, 18, and 16.2 nm, respectively, from an initial particle size of 1.73 µm. The real and imaginary parts of permittivity increased with reduced particle size and reached maximum values of 12.111 and 0.467 at 8 GHz, from initial values of 7.617 and 0.175, respectively, when the particle sizes were reduced from 1.73 µm to 16.2 nm. Complex permeability increased with reduced particle size while the enhanced absorption properties exhibited by the nanoparticles in the simulations confirmed their ability to attenuate microwaves in the X-band frequency range.
Integration of statistical and simulation analyses for ternary hybrid nanofluid over a moving surface with melting heat transfer

Rehman AU, Abbas Z, Hussain Z, Hasnain J, Asma M

Nanotechnology, 2024 Apr 09;35(26).
PMID: 38522098 DOI: 10.1088/1361-6528/ad373d

In industrial and engineering fields including lamination, melt-spinning, continuous casting, and fiber spinning, the flow caused by a continually moving surface is significant. Therefore, the problem of ternary hybrid nanofluid flow over a moving surface is studied. This study explores the stability and statistical analyses of the magnetohydrodynamics (MHD) forced flow of the ternary hybrid nanofluid with melting heat transfer phenomena. The impacts of viscous dissipation, Joule heating, and thermal radiation are also included in the flow. Different fluids including ternary hybrid nanofluid, hybrid nanofluids, and nanofluids with base fluid ethylene glycol (EG) are examined and compared, where magnetite (Fe3O4) and silica (SiO2) are taken as the magnetic nanomaterials while silver (Ag) is chosen as the nonmagnetic nanomaterial. The skin friction coefficient and the local Nusselt number are estimated through regression analysis. By employing similarity transformations, the governing partial differential equations are converted into non-linear ordinary differential equations. Then, the least square method is applied to solve the equations analytically. Dual solutions are established in a particular range of moving parameterλ. Due to this, a stability test is implemented to find the stable solution by using the bvp4c function in MATLAB software. It is found that the first solution is the stable one while the second is unstable. The use of ternary hybrid nanomaterials improves the heat transport rate. The increasing values of the Eckert number enlarge the heat passage. The fluid velocity and temperature profiles for nonmagnetic nanomaterials are higher than that of magnetic nanomaterials. The uniqueness and originality of this study stems from the fact that, to the best of the authors' knowledge, it is the first to use this combination technique.
Fulltext Determination of moisture content in oil palm fruits using a five-port reflectometer

Yee LK, Abbas Z, Jusoh MA, Yeow YK, Meng CE

Sensors (Basel), 2011;11(4):4073-85.
PMID: 22163837 DOI: 10.3390/s110404073

This paper presents the development of a PC-based microwave five-port reflectometer for the determination of moisture content in oil palm fruits. The reflectometer was designed to measure both the magnitude and phase of the reflection coefficient of any passive microwave device. The stand-alone reflectometer consists of a PC, a microwave source, diode detectors and an analog to digital converter. All the measurement and data acquisition were done using Agilent VEE graphical programming software. The relectometer can be used with any reflection based microwave sensor. In this work, the application of the reflectometer as a useful instrument to determine the moisture content in oil palm fruits using monopole and coaxial sensors was demonstrated. Calibration equations between reflection coefficients and moisture content have been established for both sensors. The equation based on phase measurement of monopole sensor was found to be accurate within 5% in predicting moisture content in the fruits when compared to the conventional oven drying method.
Fulltext Theoretical and Numerical Approaches for Determining the Reflection and Transmission Coefficients of OPEFB-PCL Composites at X-Band Frequencies

Ahmad AF, Abbas Z, Obaiys SJ, Ibrahim N, Hashim M, Khaleel H

PLoS One, 2015;10(10):e0140505.
PMID: 26474301 DOI: 10.1371/journal.pone.0140505

Bio-composites of oil palm empty fruit bunch (OPEFB) fibres and polycaprolactones (PCL) with a thickness of 1 mm were prepared and characterized. The composites produced from these materials are low in density, inexpensive, environmentally friendly, and possess good dielectric characteristics. The magnitudes of the reflection and transmission coefficients of OPEFB fibre-reinforced PCL composites with different percentages of filler were measured using a rectangular waveguide in conjunction with a microwave vector network analyzer (VNA) in the X-band frequency range. In contrast to the effective medium theory, which states that polymer-based composites with a high dielectric constant can be obtained by doping a filler with a high dielectric constant into a host material with a low dielectric constant, this paper demonstrates that the use of a low filler percentage (12.2%OPEFB) and a high matrix percentage (87.8%PCL) provides excellent results for the dielectric constant and loss factor, whereas 63.8% filler material with 36.2% host material results in lower values for both the dielectric constant and loss factor. The open-ended probe technique (OEC), connected with the Agilent vector network analyzer (VNA), is used to determine the dielectric properties of the materials under investigation. The comparative approach indicates that the mean relative error of FEM is smaller than that of NRW in terms of the corresponding S21 magnitude. The present calculation of the matrix/filler percentages endorses the exact amounts of substrate utilized in various physics applications.
Fulltext Association of Radiation Doses and Cancer Risks from CT Pulmonary Angiography Examinations in Relation to Body Diameter

Harun HH, Abdul Karim MK, Abbas Z, Abdul Rahman MA, Sabarudin A, Ng KH

Diagnostics (Basel), 2020 Sep 09;10(9).
PMID: 32917029 DOI: 10.3390/diagnostics10090681

In this study, we aimed to estimate the probability of cancer risk induced by CT pulmonary angiography (CTPA) examinations concerning effective body diameter. One hundred patients who underwent CTPA examinations were recruited as subjects from a single institution in Kuala Lumpur. Subjects were categorized based on their effective diameter size, where 19-25, 25-28, and >28 cm categorized as Groups 1, 2, and 3, respectively. The mean value of the body diameter of the subjects was 26.82 ± 3.12 cm, with no significant differences found between male and female subjects. The risk of cancer in breast, lung, and liver organs was 0.009%, 0.007%, and 0.005% respectively. The volume-weighted CT dose index (CTDIvol) was underestimated, whereas the size-specific dose estimates (SSDEs) provided a more accurate description of the radiation dose and the risk of cancer. CTPA examinations are considered safe but it is essential to implement a protocol optimized following the As Low as Reasonably Achievable (ALARA) principle.
Fulltext The Effect of MWCNTs Filler on the Absorbing Properties of OPEFB/PLA Composites Using Microstrip Line at Microwave Frequency

Ibrahim Lakin I, Abbas Z, Azis RS, Ibrahim NA, Abd Rahman MA

Materials (Basel), 2020 Oct 14;13(20).
PMID: 33066690 DOI: 10.3390/ma13204581

Oil palm empty fruit bunch (OPEFB) fiber/polylactic acid (PLA)-based composites filled with 6-22 wt.% multi-walled carbon nanotubes (MWCNTs) were prepared using a melt blend method. The composites were analyzed using X-ray diffraction (XRD), Fourier transforms infrared (FTIR), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) of the MWCNTs. The composites were characterized for complex permittivity using the coaxial probe at 8-12 GHz range and the transmission/reflection coefficients were measured through micro strip line. The dielectric permittivity measurements carried out at X-band frequency revealed that 22 wt.% MWCNTs nanocomposite display higher dielectric constant (ε') and dielectric loss (ε″) values of 4.23 and 0.65, respectively. A maximum absorption loss of 15.2 dB was obtained for the 22 wt.% nanocomposites at 11.75 GHz. This result suggests that PLA/OPEFB/MWCNTs composites are a promising cheap and lightweight material for the effective microwave absorption in the X-band frequency range.
Fulltext An acceleration of microwave-assisted transesterification of palm oil-based methyl ester into trimethylolpropane ester

Aziz NAM, Yunus R, Hamid HA, Ghassan AAK, Omar R, Rashid U, et al.

Sci Rep, 2020 11 12;10(1):19652.
PMID: 33184363 DOI: 10.1038/s41598-020-76775-y

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.
Complex permittivity and power loss characteristics of α-Fe2O3/polycaprolactone (PCL) nanocomposites: effect of recycled α-Fe2O3 nanofiller

Mensah EE, Abbas Z, Azis RS, Ibrahim NA, Khamis AM, Abdalhadi DM

Heliyon, 2020 Dec;6(12):e05595.
PMID: 33305050 DOI: 10.1016/j.heliyon.2020.e05595

The development of microwave absorbing materials based on recycled hematite (α-Fe2O3) nanoparticles and polycaprolactone (PCL) was the main focus of this study. α-Fe2O3 was recycled from mill scale and reduced to nanoparticles through high energy ball milling in order to improve its complex permittivity properties. Different compositions (5% wt., 10% wt., 15% wt. and 20% wt.) of the recycled α-Fe2O3 nanoparticles were melt-blended with PCL using a twin screw extruder to fabricate recycled α-Fe2O3/PCL nanocomposites. The samples were characterized for their microstructural properties through X - ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The complex permittivity and microwave absorption properties were respectively measured using the open ended coaxial (OEC) probe and a microstrip in connection with a vector network analyzer in the 1-4 GHz frequency range. An average α-Fe2O3 nanoparticle size of 16.2 nm was obtained with a maximum imaginary (ε") part of permittivity value of 0.54 at 4 GHz. The complex permittivity and power loss values of the nanocomposites increased with recycled α-Fe2O3 nanofiller content. At 2.4 GHz, the power loss (dB) values obtained for all the nanocomposites were between 13.3 dB and 14.4 dB and at 3.4 GHz, a maximum value of 16.37 dB was achieved for the 20 % wt. nanocomposite. The recycled α-Fe2O3/PCL nanocomposites have the potential for use in noise reduction applications in the 1-4 GHz range.
Fulltext Computational and Experimental Approaches for Determining Scattering Parameters of OPEFB/PLA Composites to Calculate the Absorption and Attenuation Values at Microwave Frequencies

Fahad Ahmad A, Aziz SHA, Abbas Z, Mohammad Abdalhadi D, Khamis AM, Aliyu US

Polymers (Basel), 2020 Aug 26;12(9).
PMID: 32858790 DOI: 10.3390/polym12091919

This article describes attenuation and absorption measurements using the microstrip transmission line technique connected with a microwave vector network analyzer (Agilent 8750B). The magnitudes of the reflection (S11) and transmission (S21) coefficients obtained from the microstrip transmission line were used to determine the attenuation and absorption of oil palm empty fruit bunch/polylactic acid (OPEFB/PLA) composites in a frequency range between 0.20 GHz and 12 GHz at room temperature. The main structure of semi-flexible substrates (OPEFF/PLA) was fabricated using different fiber loading content extracted from oil palm empty fruit bunch (OPEFB) trees hosted in polylactic acid (PLA) using the Brabender blending machine, which ensured mixture homogeneity. The commercial software package, Computer Simulation Technology Microwave Studio (CSTMWS), was used to investigate the microstrip line technique performance by simulating and determine the S11 and S21 for microwave substrate materials. Results showed that the materials' transmission, reflection, attenuation, and absorption properties could be controlled by changing the percentage of OPEFB filler in the composites. The highest absorption loss was calculated for the highest percentage of filler (70%) OPEFB at 12 GHz to be 0.763 dB, while the lowest absorption loss was calculated for the lowest percentage of filler 30% OPEFB at 12 GHz to be 0.407 dB. Finally, the simulated and measured results were in excellent agreement, but the environmental conditions slightly altered the results. From the results it is observed that the value of the dielectric constant (εr') and loss factor (εr″) is higher for the OPEFB/PLA composites with a higher content of OPEFB filler. The dielectric constant increased from 2.746 dB to 3.486 dB, while the loss factor increased from 0.090 dB to 0.5941 dB at the highest percentage of 70% OPEFB filler. The dielectric properties obtained from the open-ended coaxial probe were required as input to FEM to calculate the S11 and S21 of the samples.
Fulltext Effects of Recycled Fe2O3 Nanofiller on the Structural, Thermal, Mechanical, Dielectric, and Magnetic Properties of PTFE Matrix

Khamis AM, Abbas Z, Azis RS, Mensah EE, Alhaji IA

Polymers (Basel), 2021 Jul 16;13(14).
PMID: 34301089 DOI: 10.3390/polym13142332

The purpose of this study was to improve the dielectric, magnetic, and thermal properties of polytetrafluoroethylene (PTFE) composites using recycled Fe2O3 (rFe2O3) nanofiller. Hematite (Fe2O3) was recycled from mill scale waste and the particle size was reduced to 11.3 nm after 6 h of high-energy ball milling. Different compositions (5-25 wt %) of rFe2O3 nanoparticles were incorporated as a filler in the PTFE matrix through a hydraulic pressing and sintering method in order to fabricate rFe2O3-PTFE nanocomposites. The microstructure properties of rFe2O3 nanoparticles and the nanocomposites were characterized through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). The thermal expansion coefficients (CTEs) of the PTFE matrix and nanocomposites were determined using a dilatometer apparatus. The complex permittivity and permeability were measured using rectangular waveguide connected to vector network analyzer (VNA) in the frequency range 8.2-12.4 GHz. The CTE of PTFE matrix decreased from 65.28×10-6/°C to 39.84×10-6/°C when the filler loading increased to 25 wt %. The real (ε') and imaginary (ε″) parts of permittivity increased with the rFe2O3 loading and reached maximum values of 3.1 and 0.23 at 8 GHz when the filler loading was increased from 5 to 25 wt %. A maximum complex permeability of 1.1-j0.07 was also achieved by 25 wt % nanocomposite at 10 GHz.
Fulltext Complex Permittivity and Microwave Absorption Properties of OPEFB Fiber-Polycaprolactone Composites Filled with Recycled Hematite (α-Fe2O3) Nanoparticles

Mensah EE, Abbas Z, Azis RS, Ibrahim NA, Khamis AM

Polymers (Basel), 2019 May 24;11(5).
PMID: 31137695 DOI: 10.3390/polym11050918

Recycled hematite (α-Fe2O3) nanoparticles with enhanced complex permittivity properties have been incorporated as a filler in a polycaprolactone (PCL) matrix reinforced with oil palm empty fruit bunch (OPEFB) fiber for microwave absorption applications. The complex permittivity values were improved by reducing the particle sizes to the nano scale via high-energy ball milling for 12 h. A total of 5-20 wt.% recycled α-Fe2O3/OPEFB/PCL nanocomposites were examined for their complex permittivity and microwave absorption properties via the open ended coaxial (OEC) technique and the transmission/reflection line measurement using a microstrip connected to a two-port vector network analyzer. The microstructural analysis of the samples included X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FTIR). At 1 GHz, the real (ε') and imaginary (ε″) parts of complex permittivity of recycled α-Fe2O3 particles, respectively, increased from 7.88 to 12.75 and 0.14 to 0.40 when the particle size was reduced from 1.73 μm to 16.2 nm. A minimum reflection loss of -24.2 dB was achieved by the 20 wt.% nanocomposite at 2.4 GHz. Recycled α-Fe2O3 nanoparticles are effective fillers for microwave absorbing polymer-based composites in 1-4 GHz range applications.
Effect of iterative reconstruction algorithm levels on noise index and figure-of-merit in CT pulmonary angiography examinations

Harun HH, Karim MKA, Abbas Z, Sabarudin A, Muniandy SC, Ibahim MJ

J Xray Sci Technol, 2020;28(5):893-903.
PMID: 32741801 DOI: 10.3233/XST-200699

PURPOSE: To evaluate the influence of iterative reconstruction (IR) levels on Computed Tomography (CT) image quality and to establish Figure of Merit (FOM) value for CT Pulmonary Angiography (CTPA) examinations.
METHODS: Images of 31 adult patients who underwent CTPA examinations in our institution from March to April 2019 were retrospectively collected. Other data, such as scanning parameters, radiation dose and body habitus information from the subjects were also recorded. Six different levels of IR were applied to the volume data of the subjects. Five circles of the region of interest (ROI) were drawn in five different arteries namely, pulmonary trunk, right pulmonary artery, left pulmonary artery, ascending aorta and descending aorta. The mean Signal-to-noise ratio (SNR) was obtained, and the FOM was calculated in a fraction of the SNR2 divided by volume-weighted CT dose index (CTDIvol) and SNR2 divided by the size-specific dose estimates (SSDE).
RESULTS: Overall, we observed that the mean value of CTDIvol and SSDE were 13.79±7.72 mGy and 17.25±8.92 mGy, respectively. Notably, SNR values significantly increase with increase of the IR level (p
Fulltext Development of a predictive model for estimating the specific heat capacity of metallic oxides/ethylene glycol-based nanofluids using support vector regression

Alade IO, Abd Rahman MA, Bagudu A, Abbas Z, Yaakob Y, Saleh TA

Heliyon, 2019 Jun;5(6):e01882.
PMID: 31304407 DOI: 10.1016/j.heliyon.2019.e01882

The specific heat capacity of nanofluids ( C P n f ) is a fundamental thermophysical property that measures the heat storage capacity of the nanofluids. C P n f is usually determined through experimental measurement. As it is known, experimental procedures are characterised with some complexities, which include, the challenge of preparing stable nanofluids and relatively long periods to conduct experiments. So far, two correlations have been developed to estimate the C P n f . The accuracies of these models are still subject to further improvement for many nanofluid compositions. This study presents a four-input support vector regression (SVR) model hybridized with a Bayesian algorithm to predict the specific heat capacity of metallic oxides/ethylene glycol-based nanofluids. The bayesian algorithm was used to obtain the optimum SVR hyperparameters. 189 experimental data collected from published literature was used for the model development. The proposed model exhibits low average absolute relative deviation (AARD) and a high correlation coefficient (r) of 0.40 and 99.53 %, respectively. In addition, we analysed the accuracies of the existing analytical models on the considered nanofluid compositions. The model based on the thermal equilibrium between the nanoparticles and base fluid (model II) show good agreement with experimental results while the model based on simple mixing rule (model I) overestimated the specific heat capacity of the nanofluids. To further validate the superiority of the proposed technique over the existing analytical models, we compared various statistical errors for the three models. The AARD for the BSVR, model II, and model I are 0.40, 0.82 and 4.97, respectively. This clearly shows that the model developed has much better prediction accuracy than existing models in predicting the specific heat capacity of metallic oxides/ethylene glycol-based nanofluids. We believe the presented model will be important in the design of nanofluid-based applications due to its improved accuracy.
Hepatitis B and hepatitis C in southeast and southern Asia: challenges for governments

Wait S, Kell E, Hamid S, Muljono DH, Sollano J, Mohamed R, et al.

Lancet Gastroenterol Hepatol, 2016 11;1(3):248-255.
PMID: 28404097 DOI: 10.1016/S2468-1253(16)30031-0

In 2015, the Coalition to Eradicate Viral Hepatitis in Asia Pacific gathered leading hepatitis experts from Bangladesh, India, Indonesia, Malaysia, Pakistan, the Philippines, and Thailand to discuss common challenges to the burden posed by hepatitis B virus (HBV) and hepatitis C virus (HCV), to learn from each other's experience, and identify sustainable approaches. In this report, we summarise these discussions. Countries differ in their policy responses to HBV and HCV; however, substantial systemic, cultural, and financial barriers to achievement of elimination of these infections persist in all countries. Common challenges to elimination include limited availability of reliable epidemiological data; insufficient public awareness of risk factors and modes of transmission, leading to underdiagnosis; high rates of transmission through infected blood products, including in medical settings; limited access to care for people who inject drugs; prevailing stigma and discrimination against people infected with viral hepatitis; and financial barriers to treatment and care. Despite these challenges, promising examples of effective programmes, public-private initiatives, and other innovative approaches are evident in all countries we studied in Asia Pacific. The draft WHO Global Health Sector Strategy on Viral Hepatitis 2016-21 provides a solid framework upon which governments can build their local strategies towards viral hepatitis. However, greater recognition by national governments and the international community of the urgency to comprehensively tackle both HBV and HCV are still needed. In all countries, strategic plans and policy goals need to be translated into resources and concrete actions, with national governments at the helm, to enable a sustainable response to the rising burden of hepatitis B and C in all countries.
Fulltext In-situ preparation of CoFe2O4 nanoparticles on eggshell membrane-activated carbon for microwave absorption

Soleimani H, Yusuf JY, Chuan LK, Soleimani H, Bin Sabar ML, Öchsner A, et al.

Heliyon, 2023 Mar;9(3):e13256.
PMID: 36851968 DOI: 10.1016/j.heliyon.2023.e13256

This study explores the potential of using cobalt ferrite (CF) nanoparticles grown in situ on eggshell membranes (ESM) to mitigate the increasing problem of electromagnetic interference (EMI). A simple carbonization process was adopted to synthesize CF nanoparticles on ESM. The study further examines the composites' surface morphology and chemical composition and evaluates their microwave absorption performance (MAP) at X-band frequency. Results showed that the composite of CF and ESM - CESM@CF, exhibited a strong RL peak value of -39.03 mm with an optimal thickness of 1.5 mm. The combination of CF and ESM demonstrates excellent impedance matching and EM wave attenuation. The presence of numerous interfaces, conduction loss from the morphology, interfacial polarisation, and dual influence from both CF and ESM contribute to the high MAP of the composite. CESM@CF composite is projected as an excellent biomass-based nano-composite for EM wave absorption applications.
Fulltext Chemically Reduced Graphene Oxide-Reinforced Poly(Lactic Acid)/Poly(Ethylene Glycol) Nanocomposites: Preparation, Characterization, and Applications in Electromagnetic Interference Shielding

Ahmad AF, Aziz SA, Abbas Z, Obaiys SJ, Matori KA, Zaid MHM, et al.

Polymers (Basel), 2019 Apr 11;11(4).
PMID: 30978935 DOI: 10.3390/polym11040661

In this study, a nanocomposite of reduced graphene oxide (RGO) nanofiller-reinforcement poly(lactic acid) (PLA)/poly(ethylene glycol) (PEG) matrix was prepared via the melt blending method. The flexibility of PLA was improved by blending the polymer with a PEG plasticizer as a second polymer. To enhance the electromagnetic interference shielding properties of the nanocomposite, different RGO wt % were combined with the PLA/PEG blend. Using Fourier-transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM) and X-ray diffraction, the structural, microstructure, and morphological properties of the polymer and the RGO/PLA/PEG nanocomposites were examined. These studies showed that the RGO addition did not considerably affect the crystallinity of the resulting nanomaterials. Thermal analysis (TGA) reveals that the addition of RGO highly improved the thermal stability of PLA/PEG nanocomposites. The dielectric properties and electromagnetic interference shielding effectiveness of the synthesized nanocomposites were calculated and showed a higher SE total value than the target value (20 dB). On the other hand, the results showed an increased power loss by increasing the frequency and conversely decreased with an increased percentage of filler.

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