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Fulltext CFD study on NACA 4415 airfoil implementing spherical and sinusoidal Tubercle Leading Edge

Aftab SMA, Ahmad KA

PLoS One, 2017;12(8):e0183456.
PMID: 28850622 DOI: 10.1371/journal.pone.0183456

The Humpback whale tubercles have been studied for more than a decade. Tubercle Leading Edge (TLE) effectively reduces the separation bubble size and helps in delaying stall. They are very effective in case of low Reynolds number flows. The current Computational Fluid Dynamics (CFD) study is on NACA 4415 airfoil, at a Reynolds number 120,000. Two TLE shapes are tested on NACA 4415 airfoil. The tubercle designs implemented on the airfoil are sinusoidal and spherical. A parametric study is also carried out considering three amplitudes (0.025c, 0.05c and 0.075c), the wavelength (0.25c) is fixed. Structured mesh is utilized to generate grid and Transition SST turbulence model is used to capture the flow physics. Results clearly show spherical tubercles outperform sinusoidal tubercles. Furthermore experimental study considering spherical TLE is carried out at Reynolds number 200,000. The experimental results show that spherical TLE improve performance compared to clean airfoil.

Matched MeSH terms: Computer Simulation*
CHARACTERISATION AND EVALUATION OF AL2O3:C-BASED OPTICALLY STIMULATED LUMINESCENT DOSEMETER SYSTEM FOR DIAGNOSTIC X-RAYS: PERSONAL AND IN VIVO DOSIMETRY

Wong JHD, Bakhsh M, Cheah YY, Jong WL, Khor JS, Ng KH

Radiat Prot Dosimetry, 2019 Dec 31;187(4):451-460.
PMID: 31650160 DOI: 10.1093/rpd/ncz186

This study characterises and evaluates an Al2O3:C-based optically stimulated luminescent dosemeter (OSLD) system, commercially known as the nanoDot™ dosemeter and the InLight® microStar reader, for personal and in vivo dose measurements in diagnostic radiology. The system characteristics, such as dose linearity, reader accuracy, reproducibility, batch homogeneity, energy dependence and signal stability, were explored. The suitability of the nanoDot™ dosemeters was evaluated by measuring the depth dose curve, in vivo dose measurement and image perturbation. The nanoDot™ dosemeters were observed to produce a linear dose with ±2.8% coefficient variation. Significant batch inhomogeneity (8.3%) was observed. A slight energy dependence (±6.1%) was observed between 60 and 140 kVp. The InLight® microStar reader demonstrated good accuracy and a reproducibility of ±2%. The depth dose curve measured using nanoDot™ dosemeters showed slightly lower responses than Monte Carlo simulation results. The total uncertainty for a single dose measurement using this system was 11%, but it could be reduced to 9.2% when energy dependence correction was applied.

Matched MeSH terms: Computer Simulation
Fulltext CORNAS: coverage-dependent RNA-Seq analysis of gene expression data without biological replicates

Low JZB, Khang TF, Tammi MT

BMC Bioinformatics, 2017 12 28;18(Suppl 16):575.
PMID: 29297307 DOI: 10.1186/s12859-017-1974-4

BACKGROUND: In current statistical methods for calling differentially expressed genes in RNA-Seq experiments, the assumption is that an adjusted observed gene count represents an unknown true gene count. This adjustment usually consists of a normalization step to account for heterogeneous sample library sizes, and then the resulting normalized gene counts are used as input for parametric or non-parametric differential gene expression tests. A distribution of true gene counts, each with a different probability, can result in the same observed gene count. Importantly, sequencing coverage information is currently not explicitly incorporated into any of the statistical models used for RNA-Seq analysis.
RESULTS: We developed a fast Bayesian method which uses the sequencing coverage information determined from the concentration of an RNA sample to estimate the posterior distribution of a true gene count. Our method has better or comparable performance compared to NOISeq and GFOLD, according to the results from simulations and experiments with real unreplicated data. We incorporated a previously unused sequencing coverage parameter into a procedure for differential gene expression analysis with RNA-Seq data.
CONCLUSIONS: Our results suggest that our method can be used to overcome analytical bottlenecks in experiments with limited number of replicates and low sequencing coverage. The method is implemented in CORNAS (Coverage-dependent RNA-Seq), and is available at https://github.com/joel-lzb/CORNAS .

Matched MeSH terms: Computer Simulation
Calculation of the release of total organic matter and total mineral using the hydrodynamic equations applied to palm oil mill effluent treatment by cascaded anaerobic ponds

Fulazzaky MA

Bioprocess Biosyst Eng, 2013 Jan;36(1):11-21.
PMID: 22622964 DOI: 10.1007/s00449-012-0756-7

Anaerobic treatment processes to remove organic matter from palm oil mill effluent (POME) have been used widely in Malaysia. Still the amounts of total organic and total mineral released from POME that may cause degradation of the receiving environment need to be verified. This paper proposes the use of the hydrodynamic equations to estimate performance of the cascaded anaerobic ponds (CAP) and to calculate amounts of total organic matter and total mineral released from POME. The CAP efficiencies to remove biochemical oxygen demands, chemical oxygen demands, total solids and volatile solids (VS) as high as 94.5, 93.6, 96.3 and 98.2 %, respectively, are estimated. The amounts of total organic matter and total mineral as high as 538 kg VS/day and 895 kg FS/day, respectively, released from POME to the receiving water are calculated. The implication of the proposed hydrodynamic equations contributes to more versatile environmental assessment techniques, sometimes replacing laboratory analysis.

Matched MeSH terms: Computer Simulation
Carbamoylphosphate synthetase 1 (CPS1) deficiency: clinical, biochemical, and molecular characterization in Malaysian patients

Ali EZ, Khalid MK, Yunus ZM, Yakob Y, Chin CB, Abd Latif K, et al.

Eur J Pediatr, 2016 Mar;175(3):339-46.
PMID: 26440671 DOI: 10.1007/s00431-015-2644-z

Carbamoyl phosphate synthetase 1 (CPS1) deficiency is a rare autosomal recessive disorder of ureagenesis presenting as life-threatening hyperammonemia. In this study, we present the main clinical features and biochemical and molecular data of six Malaysian patients with CPS1 deficiency. All the patients have neonatal-onset symptoms, initially diagnosed as infections before hyperammonemia was recognized. They have typical biochemical findings of hyperglutaminemia, hypocitrullinemia, and low to normal urinary excretion of orotate. One neonate succumbed to the first hyperammonemic decompensation. Five neonatal survivors received long-term treatment consisting of dietary protein restriction and ammonia-scavenging drugs. They have delayed neurocognitive development of varying severity. Genetic analysis revealed eight mutations in CPS1 gene, five of which were not previously reported. Five mutations were missense changes while another three were predicted to create premature stop codons. In silico analyses showed that these new mutations affected different CPS1 enzyme domains and were predicted to interrupt interactions at enzyme active sites, disturb local enzyme conformation, and destabilize assembly of intact enzyme complex.
CONCLUSION: All mutations are private except one mutation; p.Ile1254Phe was found in three unrelated families. Identification of a recurrent p.Ile1254Phe mutation suggests the presence of a common and unique mutation in our population. Our study also expands the mutational spectrum of the CPS1 gene.

Matched MeSH terms: Computer Simulation
Cardiac glycoside cerberin exerts anticancer activity through PI3K/AKT/mTOR signal transduction inhibition

Hossan MS, Chan ZY, Collins HM, Shipton FN, Butler MS, Rahmatullah M, et al.

Cancer Lett, 2019 07 01;453:57-73.
PMID: 30930233 DOI: 10.1016/j.canlet.2019.03.034

Natural products possess a significant role in anticancer therapy and many currently-used anticancer drugs are of natural origin. Cerberin (CR), a cardenolide isolated from the fruit kernel of Cerbera odollam, was found to potently inhibit cancer cell growth (GI50 values 60% bioavailability and rapid absorption; doses of 1-10 mg/kg CR were predicted to maintain efficacious unbound plasma concentrations (>GI50 value). CR's potent and selective anti-tumour activity, and its targeting of key signalling mechanisms pertinent to tumourigenesis support further preclinical evaluation of this cardiac glycoside.

Matched MeSH terms: Computer Simulation
Fulltext Ceiling geometry and daylighting performance of side lit historical museum galleries under tropical overcast sky condition

Sabarinah Sh Ahmad, Noraini Ahmad, Anuar Talib

Pertanika Journal of Science & Technology, 2017;25(107):287-298.
MyJurnal

Safe level of daylighting for artefact conservation in historic buildings is a difficult task to achieve. Previous studies indicated that lighting problems in historic museum galleries were mainly due to unshaded walls that allowed direct sun penetration over the display areas. Ceiling geometry can also affect the daylighting performance significantly, particularly on the interior distribution of light. Malaysia, with hot and humid climate, and tropical sky conditions receives plenty of natural light all year around. The fluxes in natural lighting exposures confirm the need for strategic daylight control programme in the exhibition gallery. The study aims to assess the ceiling geometry contribution for four orientations; North, East, South and West through computer simulations. The research approach was based on comparisons between pitched and flat ceiling simulation output data. Further comparisons were performed with the recommended lighting limits for conservation of artefacts. The comparisons allowed better understanding of light damage issues and highlight the control of daylighting distributions through realistic predictive images and ceiling geometry designs. The results showed that the types of exhibits materials and its placement are affected by the ceiling geometry and constant changes in natural lighting exposure. The study confirms that ceiling geometry can act as a control mechanism with the environment physical features as part of preventive conservation criteria in the exhibition gallery. Thus, a systematic light-monitoring programme in the exhibition gallery is necessary to control illuminance level and cumulative exposure limits, for artefact preservation.

Matched MeSH terms: Computer Simulation
Cellular inhibitory behavior underlying the formation of retinal direction selectivity in the starburst network

Poznanski RR

J Integr Neurosci, 2010 Sep;9(3):299-335.
PMID: 21064220

Optical imaging of dendritic calcium signals provided evidence of starburst amacrine cells exhibiting calcium bias to somatofugal motion. In contrast, it has been impractical to use a dual-patch clamp technique to record membrane potentials from both proximal dendrites and distal varicosities of starburst amacrine cells in order to unequivocally prove that they are directionally sensitive to voltage, as was first suggested almost two decades ago. This paper aims to extend the passive cable model to an active cable model of a starburst amacrine cell that is intrinsically dependent on the electrical properties of starburst amacrine cells, whose various macroscopic currents are described quantitatively. The coupling between voltage and calcium just below the membrane results in a voltage-calcium system of coupled nonlinear Volterra integral equations whose solutions must be integrated into a prescribed model for example, for a synaptic couplet of starburst amacrine cells. Networks of starburst amacrine cells play a fundamental role in the retinal circuitry underlying directional selectivity. It is suggested that the dendritic plexus of starburst amacrine cells provides the substrate for the property of directional selectivity, while directional selectivity is a property of the exclusive layerings and confinement of their interconnections within the sublaminae of the inner plexiform layer involving cone bipolar cells and directionally selective ganglion cells.

Matched MeSH terms: Computer Simulation
Challenging Conventional Paradigms in Applied Sports Biomechanics Research

Glazier PS, Mehdizadeh S

Sports Med, 2019 Feb;49(2):171-176.
PMID: 30511347 DOI: 10.1007/s40279-018-1030-1

This paper evaluates the effectiveness of, and highlights issues with, conventional paradigms in applied sports biomechanics research and comments on their capacity to optimise techniques of individual athletes. In empirical studies, group-based analyses often mask variability between athletes and only permit probabilistic 'in general' or 'on average' statements that may not be applicable to specific athletes. In individual-based analyses, performance parameters typically exhibit a small range and a flat response over iterative performance trials, making establishing associations between performance parameters and the performance criterion problematic. In theoretical studies, computer simulation modelling putatively enables athlete-specific optimum techniques to be identified, but given each athlete's unique intrinsic dynamics, it is far from certain that these optimum techniques will be attainable, particularly under the often intense psychological pressures of competition, irrespective of the volume of practice undertaken. Sports biomechanists and coaching practitioners are advised to be more circumspect with regard to interpreting the results of applied sports biomechanics research and have greater awareness of their assumptions and limitations, as inappropriate interpretation of results may have adverse consequences for performance and injury.

Matched MeSH terms: Computer Simulation
Fulltext Characterisation of structure-borne sound source using reception plate method

Putra A, Saari NF, Bakri H, Ramlan R, Dan RM

ScientificWorldJournal, 2013;2013:742853.
PMID: 24324380 DOI: 10.1155/2013/742853

A laboratory-based experiment procedure of reception plate method for structure-borne sound source characterisation is reported in this paper. The method uses the assumption that the input power from the source installed on the plate is equal to the power dissipated by the plate. In this experiment, rectangular plates having high and low mobility relative to that of the source were used as the reception plates and a small electric fan motor was acting as the structure-borne source. The data representing the source characteristics, namely, the free velocity and the source mobility, were obtained and compared with those from direct measurement. Assumptions and constraints employing this method are discussed.

Matched MeSH terms: Computer Simulation
Fulltext Characterization of α-Glucosidase Inhibitors from Psychotria malayana Jack Leaves Extract Using LC-MS-Based Multivariate Data Analysis and In-Silico Molecular Docking

Nipun TS, Khatib A, Ibrahim Z, Ahmed QU, Redzwan IE, Saiman MZ, et al.

Molecules, 2020 Dec 12;25(24).
PMID: 33322801 DOI: 10.3390/molecules25245885

Psychotria malayana Jack has traditionally been used to treat diabetes. Despite its potential, the scientific proof in relation to this plant is still lacking. Thus, the present study aimed to investigate the α-glucosidase inhibitors in P.malayana leaf extracts using a metabolomics approach and to elucidate the ligand-protein interactions through in silico techniques. The plant leaves were extracted with methanol and water at five various ratios (100, 75, 50, 25 and 0% v/v; water-methanol). Each extract was tested for α-glucosidase inhibition, followed by analysis using liquid chromatography tandem to mass spectrometry. The data were further subjected to multivariate data analysis by means of an orthogonal partial least square in order to correlate the chemical profile and the bioactivity. The loading plots revealed that the m/z signals correspond to the activity of α-glucosidase inhibitors, which led to the identification of three putative bioactive compounds, namely 5'-hydroxymethyl-1'-(1, 2, 3, 9-tetrahydro-pyrrolo (2, 1-b) quinazolin-1-yl)-heptan-1'-one (1), α-terpinyl-β-glucoside (2), and machaeridiol-A (3). Molecular docking of the identified inhibitors was performed using Auto Dock Vina software against the crystal structure of Saccharomyces cerevisiae isomaltase (Protein Data Bank code: 3A4A). Four hydrogen bonds were detected in the docked complex, involving several residues, namely ASP352, ARG213, ARG442, GLU277, GLN279, HIE280, and GLU411. Compound 1, 2, and 3 showed binding affinity values of -8.3, -7.6, and -10.0 kcal/mol, respectively, which indicate the good binding ability of the compounds towards the enzyme when compared to that of quercetin, a known α-glucosidase inhibitor. The three identified compounds that showed potential binding affinity towards the enzymatic protein in molecular docking interactions could be the bioactive compounds associated with the traditional use of this plant.

Matched MeSH terms: Computer Simulation
Fulltext ChatGPT's performance before and after teaching in mass casualty incident triage

Gan RK, Uddin H, Gan AZ, Yew YY, González PA

Sci Rep, 2023 Nov 21;13(1):20350.
PMID: 37989755 DOI: 10.1038/s41598-023-46986-0

Since its initial launching, ChatGPT has gained significant attention from the media, with many claiming that ChatGPT's arrival is a transformative milestone in the advancement of the AI revolution. Our aim was to assess the performance of ChatGPT before and after teaching the triage of mass casualty incidents by utilizing a validated questionnaire specifically designed for such scenarios. In addition, we compared the triage performance between ChatGPT and medical students. Our cross-sectional study employed a mixed-methods analysis to assess the performance of ChatGPT in mass casualty incident triage, pre- and post-teaching of Simple Triage And Rapid Treatment (START) triage. After teaching the START triage algorithm, ChatGPT scored an overall triage accuracy of 80%, with only 20% of cases being over-triaged. The mean accuracy of medical students on the same questionnaire yielded 64.3%. Qualitative analysis on pre-determined themes on 'walking-wounded', 'respiration', 'perfusion', and 'mental status' on ChatGPT showed similar performance in pre- and post-teaching of START triage. Additional themes on 'disclaimer', 'prediction', 'management plan', and 'assumption' were identified during the thematic analysis. ChatGPT exhibited promising results in effectively responding to mass casualty incident questionnaires. Nevertheless, additional research is necessary to ensure its safety and efficacy before clinical implementation.

Matched MeSH terms: Computer Simulation
Fulltext Classification-based deep neural network vs mixture density network models for insulin sensitivity prediction problem

Benyó B, Paláncz B, Szlávecz Á, Szabó B, Kovács K, Chase JG

Comput Methods Programs Biomed, 2023 Oct;240:107633.
PMID: 37343375 DOI: 10.1016/j.cmpb.2023.107633

Model-based glycemic control (GC) protocols are used to treat stress-induced hyperglycaemia in intensive care units (ICUs). The STAR (Stochastic-TARgeted) glycemic control protocol - used in clinical practice in several ICUs in New Zealand, Hungary, Belgium, and Malaysia - is a model-based GC protocol using a patient-specific, model-based insulin sensitivity to describe the patient's actual state. Two neural network based methods are defined in this study to predict the patient's insulin sensitivity parameter: a classification deep neural network and a Mixture Density Network based method. Treatment data from three different patient cohorts are used to train the network models. Accuracy of neural network predictions are compared with the current model- based predictions used to guide care. The prediction accuracy was found to be the same or better than the reference. The authors suggest that these methods may be a promising alternative in model-based clinical treatment for patient state prediction. Still, more research is needed to validate these findings, including in-silico simulations and clinical validation trials.

Matched MeSH terms: Computer Simulation
Fulltext Combating obesity through healthy eating behavior: a call for system dynamics optimization

Abidin NZ, Mamat M, Dangerfield B, Zulkepli JH, Baten MA, Wibowo A

PLoS One, 2014;9(12):e114135.
PMID: 25502170 DOI: 10.1371/journal.pone.0114135

Poor eating behavior has been identified as one of the core contributory factors of the childhood obesity epidemic. The consequences of obesity on numerous aspects of life are thoroughly explored in the existing literature. For instance, evidence shows that obesity is linked to incidences of diseases such as heart disease, type-2 diabetes, and some cancers, as well as psychosocial problems. To respond to the increasing trends in the UK, in 2008 the government set a target to reverse the prevalence of obesity (POB) back to 2000 levels by 2020. This paper will outline the application of system dynamics (SD) optimization to simulate the effect of changes in the eating behavior of British children (aged 2 to 15 years) on weight and obesity. This study also will identify how long it will take to achieve the government's target. This paper proposed a simulation model called Intervention Childhood Obesity Dynamics (ICOD) by focusing the interrelations between various strands of knowledge in one complex human weight regulation system. The model offers distinct insights into the dynamics by capturing the complex interdependencies from the causal loop and feedback structure, with the intention to better understand how eating behaviors influence children's weight, body mass index (BMI), and POB measurement. This study proposed a set of equations that are revised from the original (baseline) equations. The new functions are constructed using a RAMP function of linear decrement in portion size and number of meal variables from 2013 until 2020 in order to achieve the 2020 desired target. Findings from the optimization analysis revealed that the 2020 target won't be achieved until 2026 at the earliest, six years late. Thus, the model suggested that a longer period may be needed to significantly reduce obesity in this population.

Matched MeSH terms: Computer Simulation
Combination of phenolic profiles, pharmacological properties and in silico studies to provide new insights on Silene salsuginea from Turkey

Zengin G, Rodrigues MJ, Abdallah HH, Custodio L, Stefanucci A, Aumeeruddy MZ, et al.

Comput Biol Chem, 2018 Dec;77:178-186.
PMID: 30336375 DOI: 10.1016/j.compbiolchem.2018.10.005

The genus Silene is renowned in Turkey for its traditional use as food and medicine. Currently, there are 138 species of Silene in Turkey, amongst which have been several studies for possible pharmacological potential and application in food industry. However, there is currently a paucity of data on Silene salsuginea Hub.-Mor. This study endeavours to access its antioxidant, enzyme inhibitory, and anti-inflammatory properties. Besides, reversed-phase high-performance liquid chromatography-diode array detector (RP-HPLC-DAD) was used to detect phenolic compounds, and molecular docking was performed to provide new insights for tested enzymes and phenolics. High amounts of apigenin (534 μg/g extract), ferulic acid (452 μg/g extract), p-coumaric acid (408 μg/g extract), and quercetin (336 μg/g extract) were detected in the methanol extract while rutin (506 μg/g extract) was most abundant in the aqueous extract. As for their biological properties, the methanol extract exhibited the best antioxidant effect in the DPPH and CUPRAC assays, and also the highest inhibition against tyrosinase. The aqueous extract was the least active enzyme inhibitor but showed the highest antioxidant efficacy in the ABTS, FRAP, and metal chelating assays. At a concentration of 15.6 μg/mL, the methanol extract resulted in a moderate decrease (25.1%) of NO production in lipopolysaccharide-stimulated cells. Among the phenolic compounds, epicatechin, (+)-catechin, and kaempferol showed the highest binding affinity towards the studied enzymes in silico. It can be concluded that extracts of S. salsuginea are a potential source of functional food ingredients but need further analytical experiments to explore its complexity of chemical compounds and pharmacological properties as well as using in vivo toxicity models to establish its maximum tolerated dose.

Matched MeSH terms: Computer Simulation
Fulltext Combining In Silico and In Vitro Studies to Evaluate the Acetylcholinesterase Inhibitory Profile of Different Accessions and the Biomarker Triterpenes of Centella asiatica

Jusril NA, Muhamad Juhari ANN, Abu Bakar SI, Md Saad WM, Adenan MI

Molecules, 2020 Jul 24;25(15).
PMID: 32721993 DOI: 10.3390/molecules25153353

Alzheimer's disease (AD) is a neurodegenerative disease and the most cause of dementia in elderly adults. Acetylcholinesterase (AChE) is an important beneficial target for AD to control cholinergic signaling deficit. Centella asiatica (CA) has proven to be rich with active ingredients for memory enhancement. In the present study, the chemical profiling of three accession extracts of CA namely SECA-K017, SECA-K018, and, SECA-K019 were performed using high-performance liquid chromatography (HPLC). Four biomarker triterpene compounds were detected in all CA accessions. Quantitative analysis reveals that madecassoside was the highest triterpene in all the CA accessions. The biomarker compounds and the ethanolic extracts of three accessions were investigated for their acetylcholinesterase (AChE) inhibitory activity using Ellman's spectrophotometer method. The inhibitory activity of the triterpenes and accession extracts was compared with the standard AChE inhibitor eserine. The results from the in vitro study showed that the triterpene compounds exhibited an AChE inhibitory activity with the half-maximal inhibitory concentration (IC50) values between 15.05 ± 0.05 and 59.13 ± 0.18 µg/mL. Asiatic acid was found to possess strong AChE inhibitory activity followed by madecassic acid. Among the CA accession extracts, SECA-K017 and SECA-K018 demonstrated a moderate AChE inhibitory activity with an IC50 value of 481.5 ± 0.13 and 763.5 ± 0.16 µg/mL, respectively from the in silico docking studies, it is observed that asiatic acid and madecassic acid showed very good interactions with the active sites and fulfilled docking parameters against AChE. The present study suggested that asiatic acid and madecassic acid in the CA accessions could be responsible for the AChE inhibitory action and could be used as markers to guide further studies on CA as potential natural products for the treatment of AD.

Matched MeSH terms: Computer Simulation
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.

Matched MeSH terms: Computer Simulation
Fulltext Comparative analysis and FPGA realization of different control synchronization approaches for chaos-based secured communication systems

Bonny T, Al Nassan W, Sambas A

PLoS One, 2024;19(1):e0291714.
PMID: 38261569 DOI: 10.1371/journal.pone.0291714

Synchronization of the chaotic systems has attracted much attention in recent years due to its vital applications in secured communication systems. In this paper, an implementation and comparative analysis of two different control approaches for synchronization between two identical four-dimensional hyperchaotic systems is presented. The two control approaches are the Adaptive nonlinear controller and the linear optimal quadratic regulator LQR. To demonstrate the effectiveness of each controller, the numerical simulation is presented using Matlab/Simulink and the control law is derived. The performance of the proposed controllers is compared based on four factors; response time, squared error integration, energy applied from the controller, and cost function. To measure the robustness of the control approaches, the performance factors are compared when there is a change in system parameters and a variation in the initial conditions. Then the proposed synchronization methods are implemented on the FPGA platform to demonstrate the utilized resources on Field Programmable Gate Array (FPGA) hardware platform and the operation speed. Finally, to generalize the results of the comparison, the study is implemented for the synchronization of another secured communication system consisting of two identical three-dimensional chaotic. The experimental results show that the LQR method is more effective than the Adaptive controller based on the performance factors we propose. Moreover, the LQR is much simpler to implement on hardware and requires fewer resources on the FPGA.

Matched MeSH terms: Computer Simulation
Comparative analysis of realistic CT-scan and simplified human airway models in airflow simulation

Johari NH, Osman K, Helmi NH, Abdul Kadir MA

Comput Methods Biomech Biomed Engin, 2015;18(1):48-56.
PMID: 23521065 DOI: 10.1080/10255842.2013.776548

Efforts to model the human upper respiratory system have undergone many phases. Geometrical proximity to the realistic shape has been the subject of many research projects. In this study, three different geometries of the trachea and main bronchus were modelled, which were reconstructed from computed tomography (CT) scan images. The geometrical variations were named realistic, simplified and oversimplified. Realistic refers to the lifelike image taken from digital imaging and communications in medicine format CT scan images, simplified refers to the reconstructed image based on natural images without realistic details pertaining to the rough surfaces, and oversimplified describes the straight wall geometry of the airway. The characteristics of steady state flows with different flow rates were investigated, simulating three varied physical activities and passing through each model. The results agree with previous studies where simplified models are sufficient for providing comparable results for airflow in human airways. This work further suggests that, under most exercise conditions, the idealised oversimplified model is not favourable for simulating either airflow regimes or airflow with particle depositions. However, in terms of immediate analysis for the prediction of abnormalities of various dimensions of human airways, the oversimplified techniques may be used.

Matched MeSH terms: Computer Simulation*
Fulltext Comparative study of popular objective functions for damping power system oscillations in multimachine system

Islam NN, Hannan MA, Shareef H, Mohamed A, Salam MA

ScientificWorldJournal, 2014;2014:549094.
PMID: 24977210 DOI: 10.1155/2014/549094

Power oscillation damping controller is designed in linearized model with heuristic optimization techniques. Selection of the objective function is very crucial for damping controller design by optimization algorithms. In this research, comparative analysis has been carried out to evaluate the effectiveness of popular objective functions used in power system oscillation damping. Two-stage lead-lag damping controller by means of power system stabilizers is optimized using differential search algorithm for different objective functions. Linearized model simulations are performed to compare the dominant mode's performance and then the nonlinear model is continued to evaluate the damping performance over power system oscillations. All the simulations are conducted in two-area four-machine power system to bring a detailed analysis. Investigated results proved that multiobjective D-shaped function is an effective objective function in terms of moving unstable and lightly damped electromechanical modes into stable region. Thus, D-shape function ultimately improves overall system damping and concurrently enhances power system reliability.

Matched MeSH terms: Computer Simulation

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