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Multi-country health surveys: are the analyses misleading?

Masood M, Reidpath DD

Curr Med Res Opin, 2014 May;30(5):857-63.
PMID: 24328497 DOI: 10.1185/03007995.2013.875466

BACKGROUND: The aim of this paper was to review the types of approaches currently utilized in the analysis of multi-country survey data, specifically focusing on design and modeling issues with a focus on analyses of significant multi-country surveys published in 2010.
METHODS: A systematic search strategy was used to identify the 10 multi-country surveys and the articles published from them in 2010. The surveys were selected to reflect diverse topics and foci; and provide an insight into analytic approaches across research themes. The search identified 159 articles appropriate for full text review and data extraction.
RESULTS: The analyses adopted in the multi-country surveys can be broadly classified as: univariate/bivariate analyses, and multivariate/multivariable analyses. Multivariate/multivariable analyses may be further divided into design- and model-based analyses. Of the 159 articles reviewed, 129 articles used model-based analysis, 30 articles used design-based analyses. Similar patterns could be seen in all the individual surveys.
CONCLUSION: While there is general agreement among survey statisticians that complex surveys are most appropriately analyzed using design-based analyses, most researchers continued to use the more common model-based approaches. Recent developments in design-based multi-level analysis may be one approach to include all the survey design characteristics. This is a relatively new area, however, and there remains statistical, as well as applied analytic research required. An important limitation of this study relates to the selection of the surveys used and the choice of year for the analysis, i.e., year 2010 only. There is, however, no strong reason to believe that analytic strategies have changed radically in the past few years, and 2010 provides a credible snapshot of current practice.

Matched MeSH terms: Models, Statistical
Fulltext Coming down from the trees: is terrestrial activity in Bornean orangutans natural or disturbance driven?

Ancrenaz M, Sollmann R, Meijaard E, Hearn AJ, Ross J, Samejima H, et al.

Sci Rep, 2014;4:4024.
PMID: 24526001 DOI: 10.1038/srep04024

The orangutan is the world's largest arboreal mammal, and images of the red ape moving through the tropical forest canopy symbolise its typical arboreal behaviour. Records of terrestrial behaviour are scarce and often associated with habitat disturbance. We conducted a large-scale species-level analysis of ground-based camera-trapping data to evaluate the extent to which Bornean orangutans Pongo pygmaeus come down from the trees to travel terrestrially, and whether they are indeed forced to the ground primarily by anthropogenic forest disturbances. Although the degree of forest disturbance and canopy gap size influenced terrestriality, orangutans were recorded on the ground as frequently in heavily degraded habitats as in primary forests. Furthermore, all age-sex classes were recorded on the ground (flanged males more often). This suggests that terrestrial locomotion is part of the Bornean orangutan's natural behavioural repertoire to a much greater extent than previously thought, and is only modified by habitat disturbance. The capacity of orangutans to come down from the trees may increase their ability to cope with at least smaller-scale forest fragmentation, and to cross moderately open spaces in mosaic landscapes, although the extent of this versatility remains to be investigated.

Matched MeSH terms: Models, Statistical
Age-related rarefaction in retinal vasculature is not linear

Che Azemin MZ, Ab Hamid F, Aminuddin A, Wang JJ, Kawasaki R, Kumar DK

Exp Eye Res, 2013 Nov;116:355-358.
PMID: 24512773 DOI: 10.1016/j.exer.2013.10.010

The fractal dimension is a global measure of complexity and is useful for quantifying anatomical structures, including the retinal vascular network. A previous study found a linear declining trend with aging on the retinal vascular fractal dimension (DF); however, it was limited to the older population (49 years and older). This study aimed to investigate the possible models of the fractal dimension changes from young to old subjects (10-73 years). A total of 215 right-eye retinal samples, including those of 119 (55%) women and 96 (45%) men, were selected. The retinal vessels were segmented using computer-assisted software, and non-vessel fragments were deleted. The fractal dimension was measured based on the log-log plot of the number of grids versus the size. The retinal vascular DF was analyzed to determine changes with increasing age. Finally, the data were fitted to three polynomial models. All three models are statistically significant (Linear: R2 = 0.1270, 213 d.f., p

Matched MeSH terms: Models, Statistical
Fulltext Optimization of extraction time and temperature on antioxidant activity of Schizophyllum commune aqueous extract using response surface methodology

Yim HS, Chye FY, Rao V, Low JY, Matanjun P, How SE, et al.

J Food Sci Technol, 2013 Apr;50(2):275-83.
PMID: 24425917 DOI: 10.1007/s13197-011-0349-5

Central composite design of response surface methodology (RSM) was employed to optimize the extraction time (X 1 : 99.5-290.5 min) and temperature (X 2 : 30.1-54.9 °C) of Schizophyllum commune aqueous extract with high antioxidant activities and total phenolic content (TPC). Results indicated that the data were adequately fitted into four second-order polynomial models. The extraction time and temperature were found to have significant linear, quadratic and interaction effects on antioxidant activities and TPC. The optimal extraction time and temperature were: 290.5 min and 35.7 °C (DPPH(•) scavenging ability); 180.7 min and 41.7 °C (ABTS(•+) inhibition ability); 185.2 min and 42.4 °C (ferric reducing antioxidant power, FRAP); 290.5 min and 40.3 °C (TPC). These optimum conditions yielded 85.10%; 94.31%; 0.74 mM Fe(2+) equivalent/100 g; 635.76 mg gallic acid equivalent/100 g, respectively. The yields of antioxidant activities and TPC obtained experimentally were close to its predicted values. The establishment of such model provides a good experimental basis employing RSM for optimizing the extraction time and temperature on antioxidants from S. commune aqueous extract.

Matched MeSH terms: Models, Statistical
Classification of speech dysfluencies using LPC based parameterization techniques

Hariharan M, Chee LS, Ai OC, Yaacob S

J Med Syst, 2012 Jun;36(3):1821-30.
PMID: 21249515 DOI: 10.1007/s10916-010-9641-6

The goal of this paper is to discuss and compare three feature extraction methods: Linear Predictive Coefficients (LPC), Linear Prediction Cepstral Coefficients (LPCC) and Weighted Linear Prediction Cepstral Coefficients (WLPCC) for recognizing the stuttered events. Speech samples from the University College London Archive of Stuttered Speech (UCLASS) were used for our analysis. The stuttered events were identified through manual segmentation and were used for feature extraction. Two simple classifiers namely, k-nearest neighbour (kNN) and Linear Discriminant Analysis (LDA) were employed for speech dysfluencies classification. Conventional validation method was used for testing the reliability of the classifier results. The study on the effect of different frame length, percentage of overlapping, value of ã in a first order pre-emphasizer and different order p were discussed. The speech dysfluencies classification accuracy was found to be improved by applying statistical normalization before feature extraction. The experimental investigation elucidated LPC, LPCC and WLPCC features can be used for identifying the stuttered events and WLPCC features slightly outperforms LPCC features and LPC features.

Matched MeSH terms: Models, Statistical
Comparison of the Newtonian and relativistic predicted trajectories for a low-speed periodically delta-kicked system

Lan BL

Chaos, 2006 Sep;16(3):033107.
PMID: 17014212

The dynamics of a periodically delta-kicked Hamiltonian system moving at low speed (i.e., at speed much less than the speed of light) is studied numerically. In particular, the trajectory of the system predicted by Newtonian mechanics is compared with the trajectory predicted by special relativistic mechanics for the same parameters and initial conditions. We find that the Newtonian trajectory, although close to the relativistic trajectory for some time, eventually disagrees completely with the relativistic trajectory, regardless of the nature (chaotic, nonchaotic) of each trajectory. However, the agreement breaks down very fast if either the Newtonian or relativistic trajectory is chaotic, but very much slower if both the Newtonian and relativistic trajectories are nonchaotic. In the former chaotic case, the difference between the Newtonian and relativistic values for both position and momentum grows, on average, exponentially. In the latter nonchaotic case, the difference grows much slower, for example, linearly on average.

Matched MeSH terms: Models, Statistical
Process optimization and performance evaluation on sequential ionic liquid dissolution-solid acid saccharification of sago waste

Lee KM, Ngoh GC, Chua AS

Bioresour Technol, 2013 Feb;130:1-7.
PMID: 23280179 DOI: 10.1016/j.biortech.2012.11.124

The production of reducing sugars from sago waste via sequential ionic liquid dissolution-solid acid saccharification was optimized in this study. Ionic liquid dissolution of sago waste with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was conducted prior to the solid acid saccharification with Amberlyst 15 (A15). The effect of time, temperature and substrate loading during dissolution reaction; and the effect of time, temperature and catalyst loading during saccharification reaction were examined by applying central composite design (CCD) separately. Both dissolution and saccharification reactions were respectively modeled into quadratic polynomial equations with good predictive accuracies. A high reducing sugars yield of 98.3% was obtained under the optimized conditions, i.e. dissolution at 1.75h, 160°C, 1.5% substrate loading, and saccharification at 0.5h, 130°C, 4% catalyst loading. From comparison studies of different saccharification schemes, the sequential ionic liquid dissolution-solid acid saccharification has proven to be a potential method in reducing sugars production from the lignocellulosic biomass.

Matched MeSH terms: Models, Statistical
Fulltext Complex Network Theory Applied to the Growth of Kuala Lumpur's Public Urban Rail Transit Network

Ding R, Ujang N, Hamid HB, Wu J

PLoS One, 2015;10(10):e0139961.
PMID: 26448645 DOI: 10.1371/journal.pone.0139961

Recently, the number of studies involving complex network applications in transportation has increased steadily as scholars from various fields analyze traffic networks. Nonetheless, research on rail network growth is relatively rare. This research examines the evolution of the Public Urban Rail Transit Networks of Kuala Lumpur (PURTNoKL) based on complex network theory and covers both the topological structure of the rail system and future trends in network growth. In addition, network performance when facing different attack strategies is also assessed. Three topological network characteristics are considered: connections, clustering and centrality. In PURTNoKL, we found that the total number of nodes and edges exhibit a linear relationship and that the average degree stays within the interval [2.0488, 2.6774] with heavy-tailed distributions. The evolutionary process shows that the cumulative probability distribution (CPD) of degree and the average shortest path length show good fit with exponential distribution and normal distribution, respectively. Moreover, PURTNoKL exhibits clear cluster characteristics; most of the nodes have a 2-core value, and the CPDs of the centrality's closeness and betweenness follow a normal distribution function and an exponential distribution, respectively. Finally, we discuss four different types of network growth styles and the line extension process, which reveal that the rail network's growth is likely based on the nodes with the biggest lengths of the shortest path and that network protection should emphasize those nodes with the largest degrees and the highest betweenness values. This research may enhance the networkability of the rail system and better shape the future growth of public rail networks.

Matched MeSH terms: Models, Statistical
Fulltext A Microwave Ring-Resonator Sensor for Non-Invasive Assessment of Meat Aging

Jilnai MT, Wen WP, Cheong LY, ur Rehman MZ

Sensors (Basel), 2016;16(1).
PMID: 26805828 DOI: 10.3390/s16010052

The assessment of moisture loss from meat during the aging period is a critical issue for the meat industry. In this article, a non-invasive microwave ring-resonator sensor is presented to evaluate the moisture content, or more precisely water holding capacity (WHC) of broiler meat over a four-week period. The developed sensor has shown significant changes in its resonance frequency and return loss due to reduction in WHC in the studied duration. The obtained results are also confirmed by physical measurements. Further, these results are evaluated using the Fricke model, which provides a good fit for electric circuit components in biological tissue. Significant changes were observed in membrane integrity, where the corresponding capacitance decreases 30% in the early aging (0D-7D) period. Similarly, the losses associated with intracellular and extracellular fluids exhibit changed up to 42% and 53%, respectively. Ultimately, empirical polynomial models are developed to predict the electrical component values for a better understanding of aging effects. The measured and calculated values are found to be in good agreement.

Matched MeSH terms: Models, Statistical
The effects of drainage basin geomorphometry on minimum low flow discharge: the study of small watershed in Kelang River Valley in Peninsular Malaysia

Yunus AJ, Nakagoshi N, Salleh KO

J Environ Sci (China), 2003 Mar;15(2):249-62.
PMID: 12765268

This study investigate the relationships between geomorphometric properties and the minimum low flow discharge of undisturbed drainage basins in the Taman Bukit Cahaya Seri Alam Forest Reserve, Peninsular Malaysia. The drainage basins selected were third-order basins so as to facilitate a common base for sampling and performing an unbiased statistical analyses. Three levels of relationships were observed in the study. Significant relationships existed between the geomorphometric properties as shown by the correlation network analysis; secondly, individual geomorphometric properties were observed to influence minimum flow discharge; and finally, the multiple regression model set up showed that minimum flow discharge (Q min) was dependent of basin area (AU), stream length (LS), maximum relief (Hmax), average relief (HAV) and stream frequency (SF). These findings further enforced other studies of this nature that drainage basins were dynamic and functional entities whose operations were governed by complex interrelationships occurring within the basins. Changes to any of the geomorphometric properties would influence their role as basin regulators thus influencing a change in basin response. In the case of the basin's minimum low flow, a change in any of the properties considered in the regression model influenced the "time to peak" of flow. A shorter time period would mean higher discharge, which is generally considered the prerequisite to flooding. This research also conclude that the role of geomorphometric properties to control the water supply within the stream through out the year even though during the drought and less precipitations months. Drainage basins are sensitive entities and any deteriorations involve will generate reciprocals and response to the water supply as well as the habitat within the areas.

Matched MeSH terms: Models, Statistical
Fulltext Developing an index based on GIS and statistical analysis for family support of substance abuser in Terengganu

Juahir, H., Fazillah, A., Kamarudin, M.K.A., Toriman, E., Mohamad, N., Fairuz, A., et al.

Malaysian Journal of Applied Sciences, 2018;2(2):45-54.
MyJurnal

Family support has a strong impact on individuals and there is no exception in substance abuse
recovery process. Family support manages to play a positive role in substance abuse problems. The
present study deals with the developing model of family support substance abuser with the
combination method of Geographic Information System (GIS) and statistical models. The data used
for this study was collected from seven districts in Terengganu with a constant number of
respondents. 35 respondents for each district were involved in this study. It was then processed using
factor analysis (FA) to develop index of family support. By using the developed indices, GIS tool was
used to plot the distribution map of family support indices according to each form of family support.
The result indicated that the highest index for all form of family support abuser was located in Besut
district. High level of family support is essential as an effort for rehabilitation process of substance
abusers.

Matched MeSH terms: Models, Statistical
Fulltext Optimisation of biomass, exopolysaccharide and intracellular polysaccharide production from the mycelium of an identified Ganoderma lucidum strain QRS 5120 using response surface methodology

Supramani S, Ahmad R, Ilham Z, Annuar MSM, Klaus A, Wan-Mohtar WAAQI

AIMS Microbiol, 2019;5(1):19-38.
PMID: 31384700 DOI: 10.3934/microbiol.2019.1.19

Wild-cultivated medicinal mushroom Ganoderma lucidum was morphologically identified and sequenced using phylogenetic software. In submerged-liquid fermentation (SLF), biomass, exopolysaccharide (EPS) and intracellular polysaccharide (IPS) production of the identified G.lucidum was optimised based on initial pH, starting glucose concentration and agitation rate parameters using response surface methodology (RSM). Molecularly, the G. lucidum strain QRS 5120 generated 637 base pairs, which was commensurate with related Ganoderma species. In RSM, by applying central composite design (CCD), a polynomial model was fitted to the experimental data and was found to be significant in all parameters investigated. The strongest effect (p < 0.0001) was observed for initial pH for biomass, EPS and IPS production, while agitation showed a significant value (p < 0.005) for biomass. By applying the optimized conditions, the model was validated and generated 5.12 g/L of biomass (initial pH 4.01, 32.09 g/L of glucose and 102 rpm), 2.49 g/L EPS (initial pH 4, 24.25 g/L of glucose and 110 rpm) and 1.52 g/L of IPS (and initial pH 4, 40.43 g/L of glucose, 103 rpm) in 500 mL shake flask fermentation. The optimized parameters can be upscaled for efficient biomass, EPS and IPS production using G. lucidum.

Matched MeSH terms: Models, Statistical
Dual-response quadratic model for optimisation of electricity generation and chlorophenol degradation by electro-degradative Bacillus subtilis in microbial fuel cell system

Hassan H, Jin B, Dai S

Environ Technol, 2021 Apr 01.
PMID: 33749543 DOI: 10.1080/09593330.2021.1907451

The interactions within microbial, chemical and electronic elements in microbial fuel cell (MFC) system can be crucial for its bio-electrochemical activities and overall performance. Therefore, this study explored polynomial models by response surface methodology (RSM) to better understand interactions among anode pH, cathode pH and inoculum size for optimising MFC system for generation of electricity and degradation of 2,4-dichlorophenol. A statistical central composite design by RSM was used to develop the quadratic model designs. The optimised parameters were determined and evaluated by statistical results and the best MFC systematic outcomes in terms of current generation and chlorophenol degradation. Statistical results revealed that the optimum current density of 106 mA/m2 could be achieved at anode pH 7.5, cathode pH 6.3-6.6 and 21-28% for inoculum size. Anode-cathode pHs interaction was found to positively influence the current generation through extracellular electron transfer mechanism. The phenolic degradation was found to have lower response using these three parameter interactions. Only inoculum size-cathode pH interaction appeared to be significant where the optimum predicted phenolic degradation could be attained at pH 7.6 for cathode pH and 29.6% for inoculum size.

Matched MeSH terms: Models, Statistical
Fulltext Optimization of spray drying parameters for pink guava powder using RSM

Islam Shishir MR, Taip FS, Aziz NA, Talib RA, Hossain Sarker MS

Food Sci Biotechnol, 2016;25(2):461-468.
PMID: 30263292 DOI: 10.1007/s10068-016-0064-0

The optimization of pink guava was executed using central composite face-centred design to optimize the spray drying parameters of inlet temperature, maltodextrin concentration (MDC) and feed flow (FF). The experimental results were significantly (p<0.01) fitted into second-order polynomial models to describe and predict the response quality in terms of the final moisture, particle size and lycopene with R2 of 0.9749, 0.9616, and 0.9505, respectively. The final moisture content significantly (p<0.01) decreased with increasing inlet temperature and MDC, whereas the particle size increased. In contrast, the lycopene content significantly (p<0.01) decreased with the higher temperature and increased with increasing MDC. However, according to multiple response optimization, the optimum conditions of 150°C inlet temperature, 17.12% (w/v) MDC and 350 mL/h FF-predicted 3.10% moisture content, 11.23 μm particle size and 58.71 mg/100 g lycopene content. The experimental observation satisfied the predicted model within the acceptable range of the responses.

Matched MeSH terms: Models, Statistical
Optimization and modelling of enzymatic polymerization of ε-caprolactone to polycaprolactone using Candida Antartica Lipase B with response surface methodology and artificial neural network

Pakalapati H, Tariq MA, Arumugasamy SK

Enzyme Microb Technol, 2019 Mar;122:7-18.
PMID: 30638510 DOI: 10.1016/j.enzmictec.2018.12.001

Recently enzymatic catalysts have replaced organic and organometallic catalysts in the synthesis of bio-resorbable polymers. Enzymatic polymerization is considered as an alternative to conventional polymerization as they are less toxic, environmental friendly and can operate under mild conditions. In this research, the enzymatic ring-opening polymerization (e-ROP) of e-caprolactone (e-CL) using Candida Antartica Lipase B (CALB) as catalyst to produce the Polycaprolactone. Two modelling techniques namely response surface methodology (RSM) and artificial neural network (ANN) have been used in this work. RSM is used to optimize the parameters and to develop a model of the process. ANN is used to develop the model to predict the results obtained from the experiment. The parameters involved are time, reaction temperature, mixing speed and enzyme-solvent ratio. The experimental result is Polydispersity index (PDI) of the polymer. The experimental data obtained was adequately fitted into second-order polynomial models. Simulation was done using artificial neural network model developed with Mean absolute error (MAD) value of 1.65 in comparison with MAD value of 7.4 for RSM. The Regression value (R2) values of RSM and ANN were found to be 0.96 and 0.93 respectively. The predictive models were validated experimentally and were found to be in agreement with the experimental values.

Matched MeSH terms: Models, Statistical
Fulltext Classification of community-acquired outbreaks for the global transmission of COVID-19: Machine learning and statistical model analysis

Wang WC, Lin TY, Chiu SY, Chen CN, Sarakarn P, Ibrahim M, et al.

J Formos Med Assoc, 2021 Jun;120 Suppl 1:S26-S37.
PMID: 34083090 DOI: 10.1016/j.jfma.2021.05.010

BACKGROUND: As Coronavirus disease 2019 (COVID-19) pandemic led to the unprecedent large-scale repeated surges of epidemics worldwide since the end of 2019, data-driven analysis to look into the duration and case load of each episode of outbreak worldwide has been motivated.
METHODS: Using open data repository with daily infected, recovered and death cases in the period between March 2020 and April 2021, a descriptive analysis was performed. The susceptible-exposed-infected-recovery model was used to estimate the effective productive number (Rt). The duration taken from Rt > 1 to Rt

Matched MeSH terms: Models, Statistical
Fulltext Statistical model for dynamically-changing correlation matrices with application to brain connectivity

Huang SG, Samdin SB, Ting CM, Ombao H, Chung MK

J Neurosci Methods, 2020 02 01;331:108480.
PMID: 31760059 DOI: 10.1016/j.jneumeth.2019.108480

BACKGROUND: Recent studies have indicated that functional connectivity is dynamic even during rest. A common approach to modeling the dynamic functional connectivity in whole-brain resting-state fMRI is to compute the correlation between anatomical regions via sliding time windows. However, the direct use of the sample correlation matrices is not reliable due to the image acquisition and processing noises in resting-sate fMRI.
NEW METHOD: To overcome these limitations, we propose a new statistical model that smooths out the noise by exploiting the geometric structure of correlation matrices. The dynamic correlation matrix is modeled as a linear combination of symmetric positive-definite matrices combined with cosine series representation. The resulting smoothed dynamic correlation matrices are clustered into disjoint brain connectivity states using the k-means clustering algorithm.
RESULTS: The proposed model preserves the geometric structure of underlying physiological dynamic correlation, eliminates unwanted noise in connectivity and obtains more accurate state spaces. The difference in the estimated dynamic connectivity states between males and females is identified.
COMPARISON WITH EXISTING METHODS: We demonstrate that the proposed statistical model has less rapid state changes caused by noise and improves the accuracy in identifying and discriminating different states.
CONCLUSIONS: We propose a new regression model on dynamically changing correlation matrices that provides better performance over existing windowed correlation and is more reliable for the modeling of dynamic connectivity.

Matched MeSH terms: Models, Statistical
Fulltext Transverse cerebellar diameter as a sonographic parameter for estimating gestational age: an experience from Yemeni population

Muneera A. S. Yahya, Husni A. Al- Goshae, Hameed M. Aklan, Maha Abdul-aziz, Abdullah A. Al-Mikhlafy

Malaysian Journal of Medicine and Health Sciences, 2020;16(107):23-27.
MyJurnal

Introduction: Estimation of gestational age (GA) is clinically crucial for managing pregnancy and assessing the foetal anatomy, growth and development. Transverse cerebellar diameter (TCD) has been reported as an accurate tool for dating the pregnancy. This study aimed to determine the accuracy of foetal TCD for dating the pregnancy and to con- struct a reference chart for GA of Yemeni foetuses. Methods: We conducted this prospective cross-sectional study among 400 Yemeni pregnant women between 18 and 40 weeks of gestation provided that they were with known last menstrual period and singleton normal pregnancies. Sonographic TCDs were measured for each foetus. The mean TCD was measured for gestational weeks separately, and a polynomial regression model was then used to predict the GA by TCD. Results: There was a robust correlation between GA and TCD (r = 0.995, p

Matched MeSH terms: Models, Statistical
Fulltext Optimisation of sterilisation process for oil palm fresh fruit bunch at different ripeness

Junaidah, M.J., Norizzah, A.R., Zaliha, O., Mohamad, S.

International Food Research Journal, 2015;22(1):275-282.
MyJurnal

The optimisation of fresh fruit bunch (FFB) sterilisation process was studied using different degree of FFB ripeness (i.e. under-ripe, ripe, overripe) and loose fruits. This study was carried out with the application of Response Surface Methodology (RSM), based on the interrelation between process temperature (X1; 100 to 120oC) and time (X2; 20 to 80 min) used for FFB sterilisation process on Free Fatty Acid, FFA (Y1,underripe FFB; Y2,ripe FFB; Y3,Overripe FFB; and Y4,loose fruits). Thirteen experimental runs were conducted per degree of ripeness using laboratory scale steriliser with varying sterilisation temperature and time, as generated by Central Composite Rotatable Design (CCRD). Raw experimental data trend showed substantial FFA increment with the increment of FFB maturity. Four polynomial models were found appropriate to predict the responses within experimental regions. Analysis regarding factor influences on each response was performed using Analysis of Variance (ANOVA) and graphical analysis. For under-ripe and ripe FFB, the temperature exerted higher and significant (p

Matched MeSH terms: Models, Statistical
Fulltext The influence of lightning induced voltage on the distribution power line polymer insulators

Izadi M, Abd Rahman MS, Ab-Kadir MZ, Gomes C, Jasni J, Hajikhani M

PLoS One, 2017;12(2):e0172118.
PMID: 28234930 DOI: 10.1371/journal.pone.0172118

Protection of medium voltage (MV) overhead lines against the indirect effects of lightning is an important issue in Malaysia and other tropical countries. Protection of these lines against the indirect effects of lightning is a major concern and can be improved by several ways. The choice of insulator to be used for instance, between the glass, ceramic or polymer, can help to improve the line performance from the perspective of increasing the breakdown strength. In this paper, the electrical performance of a 10 kV polymer insulator under different conditions for impulse, weather and insulator angle with respect to a cross-arm were studied (both experimental and modelling) and the results were discussed accordingly. Results show that the weather and insulator angle (with respect to the cross-arm) are surprisingly influenced the values of breakdown voltage and leakage current for both negative and positive impulses. Therefore, in order to select a proper protection system for MV lines against lightning induced voltage, consideration of the local information concerning the weather and also the insulator angles with respect to the cross-arm are very useful for line stability and performance.

Matched MeSH terms: Models, Statistical

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