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Fulltext DC-based smart PV-powered home energy management system based on voltage matching and RF module

Sabry AH, Hasan WZW, Ab Kadir M, Radzi MAM, Shafie S

PLoS One, 2017;12(9):e0185012.
PMID: 28934271 DOI: 10.1371/journal.pone.0185012

The main tool for measuring system efficiency in homes and offices is the energy monitoring of the household appliances' consumption. With the help of GUI through a PC or smart phone, there are various applications that can be developed for energy saving. This work describes the design and prototype implementation of a wireless PV-powered home energy management system under a DC-distribution environment, which allows remote monitoring of appliances' energy consumptions and power rate quality. The system can be managed by a central computer, which obtains the energy data based on XBee RF modules that access the sensor measurements of system components. The proposed integrated prototype framework is characterized by low power consumption due to the lack of components and consists of three layers: XBee-based circuit for processing and communication architecture, solar charge controller, and solar-battery-load matching layers. Six precise analogue channels for data monitoring are considered to cover the energy measurements. Voltage, current and temperature analogue signals were accessed directly from the remote XBee node to be sent in real time with a sampling frequency of 11-123 Hz to capture the possible surge power. The performance shows that the developed prototype proves the DC voltage matching concept and is able to provide accurate and precise results.
Fulltext Field data-based mathematical modeling by Bode equations and vector fitting algorithm for renewable energy applications

Sabry AH, W Hasan WZ, Ab Kadir MZA, Radzi MAM, Shafie S

PLoS One, 2018;13(1):e0191478.
PMID: 29351554 DOI: 10.1371/journal.pone.0191478

The power system always has several variations in its profile due to random load changes or environmental effects such as device switching effects when generating further transients. Thus, an accurate mathematical model is important because most system parameters vary with time. Curve modeling of power generation is a significant tool for evaluating system performance, monitoring and forecasting. Several numerical techniques compete to fit the curves of empirical data such as wind, solar, and demand power rates. This paper proposes a new modified methodology presented as a parametric technique to determine the system's modeling equations based on the Bode plot equations and the vector fitting (VF) algorithm by fitting the experimental data points. The modification is derived from the familiar VF algorithm as a robust numerical method. This development increases the application range of the VF algorithm for modeling not only in the frequency domain but also for all power curves. Four case studies are addressed and compared with several common methods. From the minimal RMSE, the results show clear improvements in data fitting over other methods. The most powerful features of this method is the ability to model irregular or randomly shaped data and to be applied to any algorithms that estimating models using frequency-domain data to provide state-space or transfer function for the model.
Evolution of Vanadium Redox Flow Battery in Electrode

Hossain MH, Abdullah N, Tan KH, Saidur R, Mohd Radzi MA, Shafie S

Chem Rec, 2024 Jan;24(1):e202300092.
PMID: 37144668 DOI: 10.1002/tcr.202300092

The vanadium redox flow battery (VRFB) is a highly regarded technology for large-scale energy storage due to its outstanding features, such as scalability, efficiency, long lifespan, and site independence. This paper provides a comprehensive analysis of its performance in carbon-based electrodes, along with a comprehensive review of the system's principles and mechanisms. It discusses potential applications, recent industrial involvement, and economic factors associated with VRFB technology. The study also covers the latest advancements in VRFB electrodes, including electrode surface modification and electrocatalyst materials, and highlights their effects on the VRFB system's performance. Additionally, the potential of two-dimensional material MXene to enhance electrode performance is evaluated, and the author concludes that MXenes offer significant advantages for use in high-power VRFB at a low cost. Finally, the paper reviews the challenges and future development of VRFB technology.
Fulltext Preparations, Properties, and Applications of Polyaniline and Polyaniline Thin Films-A Review

Beygisangchin M, Abdul Rashid S, Shafie S, Sadrolhosseini AR, Lim HN

Polymers (Basel), 2021 Jun 18;13(12).
PMID: 34207392 DOI: 10.3390/polym13122003

Polyaniline (PANI) is a famous conductive polymer, and it has received tremendous consideration from researchers in the field of nanotechnology for the improvement of sensors, optoelectronic devices, and photonic devices. PANI is doped easily by different acids and dopants because of its easy synthesis and remarkable environmental stability. This review focuses on different preparation processes of PANI thin film by chemical and physical methods. Several features of PANI thin films, such as their magnetic, redox, and antioxidant, anti-corrosion, and electrical and sensing properties, are discussed in this review. PANI is a highly conductive polymer. Given its unique properties, easy synthesis, low cost, and high environmental stability in various applications such as electronics, drugs, and anti-corrosion materials, it has attracted extensive attention. The most important PANI applications are briefly reviewed at the end of this review.
Development, validity and reliability of the short multidimensional positive mental health instrument

Vaingankar JA, Subramaniam M, Abdin E, Picco L, Chua BY, Eng GK, et al.

Qual Life Res, 2014 Jun;23(5):1459-77.
PMID: 24307210 DOI: 10.1007/s11136-013-0589-0

PURPOSE: The 47-item positive mental health (PMH) instrument measures the level of PMH in multiethnic adult Asian populations. This study aimed to (1) develop a short PMH instrument and (2) establish its validity and reliability among the adult Singapore population.
METHODS: Two separate studies were conducted among adult community-dwelling Singapore residents of Chinese, Malay or Indian ethnicity where participants completed self-administered questionnaires. In the first study, secondary data analysis was conducted using confirmatory factor analysis (CFA) to shorten the PMH instrument. In the second study, the newly developed short PMH instrument and other scales were administered to 201 residents to establish its factor structure, validity and reliability.
RESULTS: A 20-item short PMH instrument fulfilling a higher-order six-factor structure was developed following secondary analysis. The mean age of the participants in the second study was 41 years and about 53% were women. One item with poor factor loading was further removed to generate a 19-item version of the PMH instrument. CFA demonstrated a first-order six-factor model of the short PMH instrument. The PMH-19 instrument and its subscales fulfilled criterion validity hypotheses. Internal consistency and test-retest reliability of the PMH-19 instrument were high (Cronbach's α coefficient = 0.87; intraclass correlation coefficient = 0.93, respectively).
CONCLUSIONS: The 19-item PMH instrument is multidimensional, valid and reliable, and most importantly, with its reduced administration time, the short PMH instrument can be used to measure and evaluate PMH in Asian communities.
Fulltext Accuracy of self-reported height, weight and BMI in a multiethnic Asian population

Roystonn K, Abdin E, Sambasivam R, Zhang Y, Chang S, Shafie S, et al.

Ann Acad Med Singap, 2021 04;50(4):306-314.
PMID: 33990818 DOI: 10.47102/annals-acadmedsg.2020183

INTRODUCTION: The study assessed whether self-reported height, weight and derived body mass index (BMI) can provide an accurate measure of anthropometric data in a multiethnic adult population in Singapore.
METHODS: Standardised anthropometric measurements were compared against the self-reported values from 5,132 adult residents in a cross-sectional, epidemiological survey. Discrepancies in self-reports from measurements were examined by comparing overall mean differences. Intraclass correlations, Cohen's kappa and Bland-Altman plots with limits of agreement, and sub-analysis by sex and ethnicity were also explored.
RESULTS: Data were obtained from 5,132 respondents. The mean age of respondents was 43.9 years. Overall, the height was overestimated (0.2cm), while there was an underestimation of weight (0.8kg) and derived BMI (0.4kg/m2). Women had a larger discrepancy in height (0.35cm, 95% confidence interval [CI] 0.22 to 0.49), weight (-0.95kg, 95% CI -1.11 to -0.79) and BMI (-0.49kg/m2, 95% CI -0.57 to -0.41) compared with men. Height reporting bias was highest among Indians (0.28cm, 95% CI 0.12 to 0.44) compared with Chinese and Malays, while weight (-1.32kg, 95% CI -1.53 to -1.11) and derived BMI (-0.57kg/m2, 95% CI -0.67 to -0.47) showed higher degrees of underreporting among Malays compared with Chinese and Indians. Substantially high self-reported versus measured values were obtained for intraclass correlations (0.96-0.99, P<0.001) and kappa (0.74). For BMI categories, good to excellent kappa agreement was observed (0.68-0.81, P<0.0001).
CONCLUSION: Self-reported anthropometric estimates can be used, particularly in large epidemiological studies. However, sufficient care is needed when evaluating data from Indians, Malays and women as there is likely an underestimation of obesity prevalence.
Design of a Sub-Picosecond Jitter with Adjustable-Range CMOS Delay-Locked Loop for High-Speed and Low-Power Applications

Abdulrazzaq BI, Ibrahim OJ, Kawahito S, Sidek RM, Shafie S, Yunus NA, et al.

Sensors (Basel), 2016 Sep 28;16(10).
PMID: 27690040

A Delay-Locked Loop (DLL) with a modified charge pump circuit is proposed for generating high-resolution linear delay steps with sub-picosecond jitter performance and adjustable delay range. The small-signal model of the modified charge pump circuit is analyzed to bring forth the relationship between the DLL's internal control voltage and output time delay. Circuit post-layout simulation shows that a 0.97 ps delay step within a 69 ps delay range with 0.26 ps Root-Mean Square (RMS) jitter performance is achievable using a standard 0.13 µm Complementary Metal-Oxide Semiconductor (CMOS) process. The post-layout simulation results show that the power consumption of the proposed DLL architecture's circuit is 0.1 mW when the DLL is operated at 2 GHz.
A carbon conductive filament-induced robust resistance switching behavior for brain-inspired computing

Yu T, Wang D, Liu M, Lei W, Shafie S, Mohtar MN, et al.

Mater Horiz, 2024 Mar 04;11(5):1334-1343.
PMID: 38175571 DOI: 10.1039/d3mh01762a

Memristors have revolutionized the path forward for brain-inspired computing. However, the instability of the nucleation process of conductive filaments based on active metal electrodes leads to the discrete distribution of switching parameters, which hinders the realization of high-performance and low-power devices for neuromorphic computing. In response, a carbon conductive filament-induced robust memristor is demonstrated with variation coefficients as low as 3.9%/-1.18%, a threshold power as low as 10-9 W, and 3 × 106 s retention and 107 cycle endurance behaviors can be maintained. The recognition accuracy for Modified National Institute of Standards and Technology (MNIST) handwriting is as high as 96.87%, attributed to the high linearity of the iterative updating of synaptic weights. The demodulation and storage functions of the American Standard Code for Information Interchange (ASCII) are demonstrated by programmable pulse modulation. Notably, the transmission electron microscopy (TEM) images allow the observation of carbon conductive filament paths formed in the low resistance state. First-principles calculations analyze the energetics of defects involved in the diffusion of carbon atoms into MoTe2 films. This work presents a novel guideline for studying memristor-based neuromorphic computing.
Development of the Chinese, Malay and Tamil translations of the Positive Mental Health Instrument: Cross-cultural adaptation, validity and internal consistency

Vaingankar JA, Abdin E, Chong SA, Sambasivam R, Shafie S, Ong HL, et al.

Transcult Psychiatry, 2021 02;58(1):76-95.
PMID: 33297859 DOI: 10.1177/1363461520976045

This study describes the development and validation of Chinese, Malay and Tamil translations of the Positive Mental Health Instrument (PMHI) in a general population sample in Singapore. Translations were performed using two independent forward translations followed by expert panel discussions and tested for content, construct and language appropriateness using focus group discussions. The final translated tools were field-tested among 220 residents per language using self-administered questionnaires comprising the translated PMHI and other validity measures. Missing data, floor and ceiling effects, confirmatory factor analysis (CFA), internal consistency, item response theory differential item functioning (IRT-DIF) and criterion validity were assessed. A total of 10 PMHI-Chinese items, 26 PMHI-Malay items and six response categories and six PMHI-Tamil items were modified based on expert panel and focus group discussions. PMHI had low missing data and showed negative but acceptable skewness (<2) and kurtosis (<7) for all translations, except for the PMHI-Malay "spirituality" subscale (skewness: -2.8; kurtosis: 12.5). CFA showed that all three PMHI translations fulfilled the original six-factor-higher-order structure (RMSEA = 0.05, CFI = 0.962, TLI = 0.96). Cronbach's alpha coefficients for total PMHI were 0.958, 0.954, 0.945 and 0.949 in the overall sample and the Chinese, Malay and Tamil translations, respectively. The three translations of the PMHI showed expected and significant positive (r = 0.116 to 0.663) and negative correlations (r = -0.137 to -0.574) with established measures. The findings show that the Chinese, Malay and Tamil translations of the PMHI have high internal consistency and validity in this multi-ethnic population.
Hybridization state transition-driven carbon quantum dot (CQD)-based resistive switches for bionic synapses

Yu T, Fang Y, Chen X, Liu M, Wang D, Liu S, et al.

Mater Horiz, 2023 Jun 06;10(6):2181-2190.
PMID: 36994553 DOI: 10.1039/d3mh00117b

As an emerging carbon-based material, carbon quantum dots (CQDs) have shown unstoppable prospects in the field of bionic electronics with their outstanding optoelectronic properties and unique biocompatible characteristics. In this study, a novel CQD-based memristor is proposed for neuromorphic computing. Unlike the models that rely on the formation and rupturing of conductive filaments, it is speculated that the resistance switching mechanism of CQD-based memristors is due to the conductive path caused by the hybridization state transition of the sp2 carbon domain and sp3 carbon domain induced by the reversible electric field. This avoids the drawback of uncontrollable nucleation sites leading to the random formation of conductive filaments in resistive switching. Importantly, it illustrates that the coefficient of variation (CV) of the threshold voltage can be as low as -1.551% and 0.083%, which confirms the remarkable uniform switching characteristics. Interestingly, the Pavlov's dog reflection as an important biological behavior can be demonstrated by the samples. Finally, the accuracy recognition rate of MNIST handwriting can reach up to 96.7%, which is very close to the ideal number (97.8%). A carbon-based memristor based on a new mechanism presented provides new possibilities for the improvement of brain-like computing.