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Fulltext Sidelobe reduction and capacity improvement of open-loop collaborative beamforming in wireless sensor networks

Jayaprakasam S, Abdul Rahim SK, Leow CY, Ting TO

PLoS One, 2017;12(5):e0175510.
PMID: 28464000 DOI: 10.1371/journal.pone.0175510

Collaborative beamforming (CBF) with a finite number of collaborating nodes (CNs) produces sidelobes that are highly dependent on the collaborating nodes' locations. The sidelobes cause interference and affect the communication rate of unintended receivers located within the transmission range. Nulling is not possible in an open-loop CBF since the collaborating nodes are unable to receive feedback from the receivers. Hence, the overall sidelobe reduction is required to avoid interference in the directions of the unintended receivers. However, the impact of sidelobe reduction on the capacity improvement at the unintended receiver has never been reported in previous works. In this paper, the effect of peak sidelobe (PSL) reduction in CBF on the capacity of an unintended receiver is analyzed. Three meta-heuristic optimization methods are applied to perform PSL minimization, namely genetic algorithm (GA), particle swarm algorithm (PSO) and a simplified version of the PSO called the weightless swarm algorithm (WSA). An average reduction of 20 dB in PSL alongside 162% capacity improvement is achieved in the worst case scenario with the WSA optimization. It is discovered that the PSL minimization in the CBF provides capacity improvement at an unintended receiver only if the CBF cluster is small and dense.
Fulltext Compact circularly polarized truncated square ring slot antenna with suppressed higher resonances

Sabran MI, Abdul Rahim SK, Leow CY, Soh PJ, Chew BW, Vandenbosch GA

PLoS One, 2017;12(2):e0172162.
PMID: 28192504 DOI: 10.1371/journal.pone.0172162

This paper presents a compact circularly polarized (CP) antenna with an integrated higher order harmonic rejection filter. The proposed design operates within the ISM band of 2.32 GHz- 2.63 GHz and is suitable for example for wireless power transfer applications. Asymmetrical truncated edges on a square ring create a defected ground structure to excite the CP property, simultaneously realizing compactness. It offers a 50.5% reduced patch area compared to a conventional design. Novel stubs and slot shapes are integrated in the transmission line to reduce higher (up to the third) order harmonics. The proposed prototype yields a -10 dB reflection coefficient (S11) impedance bandwidth of 12.53%, a 3 dB axial ratio bandwidth of 3.27%, and a gain of 5.64 dBi. Measurements also show good agreement with simulations.
A Review on Microdialysis Calibration Methods: the Theory and Current Related Efforts

Kho CM, Enche Ab Rahim SK, Ahmad ZA, Abdullah NS

Mol Neurobiol, 2017 07;54(5):3506-3527.
PMID: 27189617 DOI: 10.1007/s12035-016-9929-8

Microdialysis is a sampling technique first introduced in the late 1950s. Although this technique was originally designed to study endogenous compounds in animal brain, it is later modified to be used in other organs. Additionally, microdialysis is not only able to collect unbound concentration of compounds from tissue sites; this technique can also be used to deliver exogenous compounds to a designated area. Due to its versatility, microdialysis technique is widely employed in a number of areas, including biomedical research. However, for most in vivo studies, the concentration of substance obtained directly from the microdialysis technique does not accurately describe the concentration of the substance on-site. In order to relate the results collected from microdialysis to the actual in vivo condition, a calibration method is required. To date, various microdialysis calibration methods have been reported, with each method being capable to provide valuable insights of the technique itself and its applications. This paper aims to provide a critical review on various calibration methods used in microdialysis applications, inclusive of a detailed description of the microdialysis technique itself to start with. It is expected that this article shall review in detail, the various calibration methods employed, present examples of work related to each calibration method including clinical efforts, plus the advantages and disadvantages of each of the methods.
Fulltext Two-Stage Design Method for Enhanced Inductive Energy Transmission with Q-Constrained Planar Square Loops

Eteng AA, Abdul Rahim SK, Leow CY, Chew BW, Vandenbosch GA

PLoS One, 2016;11(2):e0148808.
PMID: 26890878 DOI: 10.1371/journal.pone.0148808

Q-factor constraints are usually imposed on conductor loops employed as proximity range High Frequency Radio Frequency Identification (HF-RFID) reader antennas to ensure adequate data bandwidth. However, pairing such low Q-factor loops in inductive energy transmission links restricts the link transmission performance. The contribution of this paper is to assess the improvement that is reached with a two-stage design method, concerning the transmission performance of a planar square loop relative to an initial design, without compromise to a Q-factor constraint. The first stage of the synthesis flow is analytical in approach, and determines the number and spacing of turns by which coupling between similar paired square loops can be enhanced with low deviation from the Q-factor limit presented by an initial design. The second stage applies full-wave electromagnetic simulations to determine more appropriate turn spacing and widths to match the Q-factor constraint, and achieve improved coupling relative to the initial design. Evaluating the design method in a test scenario yielded a more than 5% increase in link transmission efficiency, as well as an improvement in the link fractional bandwidth by more than 3%, without violating the loop Q-factor limit. These transmission performance enhancements are indicative of a potential for modifying proximity HF-RFID reader antennas for efficient inductive energy transfer and data telemetry links.
Facilitators and barriers for using artificial intelligence in cancer pain assessment: a qualitative study

Tashtoush N, Zawiah M, Sulaiman SAS, Amran FA, Rahim SK, Harun SN

Support Care Cancer, 2025 Aug 04;33(8):751.
PMID: 40759777 DOI: 10.1007/s00520-025-09800-3

OBJECTIVES: This study qualitatively explored healthcare providers' perception regarding the use of modern technology, specifically artificial intelligence (AI), in the assessment and management of cancer pain. It also aimed to identify barriers to adopting AI-based solutions in clinical settings.
METHODS: In-depth interviews were conducted with a purposive sample of healthcare professionals between July and October 2023. Participants included physicians and nurses shared their insights into how AI technology could support their practices in managing cancer pain while also highlighting the challenges and barriers to its incorporation. The collected data were analyzed using thematic analysis to identify key themes and sub-themes.
RESULTS: A total of 13 healthcare providers participated, comprising seven males (54%) and six females (46%), with a mean age of 36 ± 4 years. Their professional experience ranged from 3 to 16 years. The analysis revealed two primary themes: (1) facilitators for AI adoption in cancer pain management and (2) barriers to AI integration. Under the first theme, sub-themes included positive attitudes toward AI adoption, the potential for enhancing clinical efficiency, anticipated future advancements in AI, and support for training and implementation. Barriers included concerns about the reliability and technical limitations of AI, financial and resource constraints, resistance to change and preference for traditional methods, risks of miscommunication and misunderstanding, and dependency on developers' expertise for AI validation.
CONCLUSIONS: The findings indicate that while healthcare professionals generally perceive AI as a valuable tool in cancer pain management, successful implementation requires addressing concerns regarding trust, training, and resource availability. Ensuring adequate training and development confidence in AI's reliability are essential steps for integrating AI into routine clinical practice.
Fulltext Plant-based calcium silicate from rice husk ash: A green adsorbent for free fatty acid recovery from waste frying oil

Zainal ZS, Hoo P, Ahmad AL, Abdullah AZ, Ng Q, Shuit S, et al.

Heliyon, 2024 Feb 29;10(4):e26591.
PMID: 38404855 DOI: 10.1016/j.heliyon.2024.e26591

Driven by the urgent need for a solution to tackle the surge of rice husk (RH) and waste frying oil (WFO) waste accumulation at a global scale, this report highlights the use of calcium silicates (CS) extracted from acid-pre-treated rice husk ash (RHA) for free fatty acid (FFA) removal from WFO as conventional RHA shows limited FFA adsorption performance. A novel alkaline earth silicate extraction method from acid-pre-treated RHA was outlined. The structural and behavioural attributes of the synthesised CS were identified through BET, SEM-EDS, and XRD analyses and compared to those of RHA. Notable morphology and structural modification were determined, including reducing specific surface areas, mitigating from amorphous to crystalline structure with regular geometric forms, and detecting Si-O-Ca functional groups exclusive to CS adsorbents. A comparison study showed superior lauric acid (LA) adsorption performance by CS absorbents over acid-pre-treated RHA, with a significant increase from 0.0831 ± 0.0004 mmol LA/g to 2.5808 ± 0.0011 mmol LA/g after 60 min. Recognised as the best-performing CS adsorbent, CS-1.0 was used for further investigations on the effect of dosage, LA concentration, and temperature for efficient LA adsorption, with up to 100% LA removal and 5.6712 ± 0.0016 mmol LA/g adsorption capacity. The adsorption isotherm and kinetic studies showed LA adsorption onto CS-1.0 followed Freundlich isotherm with KF = 0.0598 mmol(1-1/n) L(1/n) g-1 & Qe,cal = 3.1696 mmol g-1 and intraparticle diffusion model with kid = 0.1250 mmol g-1 min0.5 & Ci = 0.9625 mmol g-1, indicating rapid initial adsorption and involvement of carboxylate end of LA and the calcium ions on the CS-1.0 in the rate-limiting step. The high equilibrium adsorption capacity and LA adsorption rate indicated that the proposed CS-1.0 adsorbent has excellent potential to recover FFA from WFO effectively.
Broadband near unity absorption meta-structure for solar thermophotovoltaic systems and optical window applications

Soliman MM, Islam MT, Alam T, Misran N, Abdul Rahim SK, Alzamil A, et al.

Nanoscale, 2023 Aug 10;15(31):12972-12994.
PMID: 37477438 DOI: 10.1039/d3nr01941a

Developing a meta-structure with near-unity absorbance in the visible and infrared spectra for solar energy harvesting, photodetection, thermal imaging, photo-trapping, and optical communications is a long-term research challenge. This research presents a four-layered (insulator-metal-insulator-metal) meta-structure unit cell that showed a peak absorbance of 99.99% at 288-300 nm and the average absorbance of 99.18% over the 250-2000 nm wavelength range in TE and TM modes, respectively. The symmetric pattern of the resonator layer shows polarization insensitivity with an average absorption of 99.18% in both TE and TM modes. Furthermore, the proposed design shows a wide incident angle stability up to ≤60 degrees in both TE and TM modes. The proposed structure also exhibits negative index properties at 288-300 nm and 1000-2000 nm, respectively. The negative index properties of the proposed design generate an anti-parallel surface current flow in the ground and resonator layers, which induces magnetic and electric field resonance and increases absorption. The performance of the proposed design is further validated by the interference theory model and a zero value for the polarization conversion ratio (PCR). The electric field E, magnetic field H, and current distribution are analyzed to explain the absorption mechanism of the proposed meta-structure unit cell. It also exhibits the highest photo-thermal conversion efficiency of 99.11%, demonstrating the viability of the proposed design as a solar absorber. The proposed design promises potentially valuable applications such as solar energy harvesting, photodetection, thermal imaging, photo-trapping, and optical communications because of its decent performance.