14 research outputs found
Enhanced durability of concrete with palm oil fuel ash in a marine environment
No full textThis research aimed to enhance the durability of concrete at a marine site by using ground palm oil fuel ash (GPOFA). Portland cement type I had been replaced by GPOFA at various replacement levels of 0–50% by weight of binder, with three different strength grades. Cubical concrete specimens with embedded steel bars at various covering depths were cast to determine chloride ingression and steel corrosion. After curing for 28 days, the concrete specimens were placed in a marine environment. The compressive strength, total and free chloride ingress, and embedded steel corrosion of the specimens were determined after subjecting them to tidal zone conditions for 7 years. The results show that the concrete specimens containing GPOFA at replacement levels of 15–35% by weight of binder provided the best durability performances at the marine site, with lower compressive strength loss and higher chloride and steel corrosion resistances than ordinary Portland cement concrete. This indicates that GPOFA in a replacement levels of 15–35% by weight of binder, with a maximum W/B ratio of 0.45, can be used efficiently in concrete to enhance the service life of marine concrete structures
Chloride Penetration and Steel Corrosion of Concrete Containing Palm Oil Fuel Ash under 5-year Exposure in Marine Environment
No full textInfluence of Palm Oil Fuel Ash and W/B Ratios on Compressive Strength, Water Permeability, and Chloride Resistance of Concrete
Get PDFThis research studies the effects of W/B ratios and palm oil fuel ash (POFA) on compressive strength, water permeability, and chloride resistance of concrete. POFA was ground until the particles retained on sieve number 325 were less than 5% by weight. POFA was used to partially replace OPC at rates of 15, 25, and 35% by weight of binder. The water to binder (W/B) ratios of concrete were 0.40 and 0.50. The compressive strength, water permeability, and chloride resistance of concrete were investigated up to 90 days. The results showed that POFA concrete with W/B ratio of 0.40 had the compressive strengths ranging from 45.8 to 55.9 MPa or 82–94% of OPC concrete at 90 days, while POFA concrete with W/B ratio of 0.50 had the compressive strengths of 33.9–41.9 MPa or 81–94% of OPC concrete. Furthermore, the compressive strength of concrete incorporation of ground POFA at 15% was the same as OPC concrete. The water permeability coefficient and the chloride ion penetration of POFA concrete were lower than OPC concrete when both types of concrete had the same compressive strengths. The findings also indicated that water permeability and chloride ion penetration of POFA concrete were significantly reduced compared to OPC concrete
Investigation on the strength, chloride migration, and water permeability of eco-friendly concretes from industrial by-product materials
No full textTemporal patterns in sheep fetal heart rate variability correlate to systemic cytokine inflammatory response: A methodological exploration of monitoring potential using complex signals bioinformatics
No full textFetal inflammation is associated with increased risk for postnatal organ injuries. No means of early detection exist. We hypothesized that systemic fetal inflammation leads to distinct alterations of fetal heart rate variability (fHRV). We tested this hypothesis deploying a novel series of approaches from complex signals bioinformatics. In chronically instrumented near-term fetal sheep, we induced an inflammatory response with lipopolysaccharide (LPS) injected intravenously (n = 10) observing it over 54 hours; seven additional fetuses served as controls. Fifty-one fHRV measures were determined continuously every 5 minutes using Continuous Individualized Multi-organ Variability Analysis (CIMVA). CIMVA creates an fHRV measures matrix across five signal-analytical domains, thus describing complementary properties of fHRV. We implemented, validated and tested methodology to obtain a subset of CIMVA fHRV measures that matched best the temporal profile of the inflammatory cytokine IL-6. In the LPS group, IL-6 peaked at 3 hours. For the LPS, but not control group, a sharp increase in standardized difference in variability with respect to baseline levels was observed between 3 h and 6 h abating to baseline levels, thus tracking closely the IL-6 inflammatory profile. We derived fHRV inflammatory index (FII) consisting of 15 fHRV measures reflecting the fetal inflammatory response with prediction accuracy of 90%. Hierarchical clustering validated the selection of 14 out of 15 fHRV measures comprising FII. We developed methodology to identify a distinctive subset of fHRV measures that tracks inflammation over time. The broader potential of this bioinformatics approach is discussed to detect physiological responses encoded in HRV measures
A comparative study of green composites based on tapioca starch and celluloses
No full textThe objective of this study was to compare the properties of green composites based on tapioca starch (TS) and celluloses isolated from empty fruit bunches (EFB) and commercial celluloses from cotton linter (supplied by Sigma). Empty fruit bunches (EFB) acted as the main source to obtain the cellulose by using a chemical approach whereas the commercial cellulose from Sigma was used as reference. The TS/cellulose composite films were prepared using cellulose in varying proportions as filler into TS matrix by a casting method. The amount of celluloses added into the tapioca starch were 5, 10, 15, 20 and 25 phr (as per dry mass of TS). The celluloses were characterized using Fourier transform infrared (FTTR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). While the green composite films were analyzed in terms of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), SEM and tensile properties. FTTR analysis confirmed the removal of non-cellulosic materials such as hemicelluloses and lignin from raw EFB after the chemical treatment. XRD diffractograms revealed that the crystallinity of celluloses EFB increased from 43.1 % of raw EFB to 52.1 %. SEM images showed the fibrillar structure of cellulose isolated from EFB. The TGA and derivative thermogravimetric (DTG) curves of green composite films showed no significant effect on the thermal stability. Melting temperature of TS/cellulose EFB higher than neat TS while TS/cellulose Sigma lower than neat TS. The green composite films with 15 phr cellulose from EFB filler loading provided the best tensile properties in term of its strength and modulus. However, in term of elongation at break, the percentage elongation decreased with the increased of the amount of filler loading. SEM images of the films demonstrated a good interaction between cellulose filler and TS matrix especially with the addition of 15 phr of cellulose from EFB. © 2017 Author(s)
Extraction of microcrystalline cellulose from rice straw and its effect on polyvinyl alcohol biocomposites film
No full textModeling long-range dependent Gaussian processes with application in continuous-time financial models
Get PDFThis paper considers a class of nonstationary Gaussian processes with possible long-range dependence (LRD) and intermittency. The author proposes a new estimation method to simultaneously estimate both the LRD and intermittency parameter. An application of the proposed estimation method to a continuous-time financial model is discussed.continuous-time model; diffusion process; long-range dependent process; parameter estimation; stochastic volatility
Analysis of click-evoked otoacoustic emissions by concentration of frequency and time: Preliminary results from normal hearing and Ménière’s disease ears
No full text© 2018 Author(s). The presence of click-evoked (CE) otoacoustic emissions (OAEs) has been clinically accepted as an indicator of normal cochlear processing of sounds. For treatment and diagnostic purposes, however, clinicians do not typically pay attention to the detailed spectrum and waveform of CEOAEs. A possible reason is due to the lack of noise-robust signal processing tools to estimate physiologically meaningful time-frequency properties of CEOAEs, such as the latency of spectral components. In this on-going study, we applied a modern tool called concentration of frequency and time (ConceFT, [1]) to analyze CEOAE waveforms. Randomly combined orthogonal functions are used as windowing functions for time-frequency analysis. The resulting spectrograms are subject to nonlinear time-frequency reassignment so as to enhance the concentration of time-varying sinusoidal components. The results after reassignment could be further averaged across the random choice of windows. CEOAE waveforms are acquired by a linear averaging paradigm, and longitudinal data are currently being collected from patients with Ménière's disease (MD) and a control group of normal hearing subjects. When CEOAE is present, the ConceFT plots show traces of decreasing but fluctuating instantaneous frequency against time. For comparison purposes, same processing methods are also applied to analyze CEOAE data from cochlear mechanics simulation
Data-Driven optimal shrinkage of singular values under high-dimensional noise with separable covariance structure with application
Get PDFWe develop a data-driven optimal shrinkage algorithm for matrix denoising in
the presence of high-dimensional noise with a separable covariance structure;
that is, the noise is colored and dependent across samples. The algorithm,
coined {\em extended OptShrink} (eOptShrink) depends on the asymptotic behavior
of singular values and singular vectors of the random matrix associated with
the noisy data. Based on the developed theory, including the sticking property
of non-outlier singular values and delocalization of the non-outlier singular
vectors associated with weak signals with a convergence rate, and the spectral
behavior of outlier singular values and vectors, we develop three estimators,
each of these has its own interest. First, we design a novel rank estimator,
based on which we provide an estimator for the spectral distribution of the
pure noise matrix, and hence the optimal shrinker called eOptShrink. In this
algorithm we do not need to estimate the separable covariance structure of the
noise. A theoretical guarantee of these estimators with a convergence rate is
given. On the application side, in addition to a series of numerical
simulations with a comparison with various state-of-the-art optimal shrinkage
algorithms, we apply eOptShrink to extract maternal and fetal
electrocardiograms from the single channel trans-abdominal maternal
electrocardiogram.Comment: arXiv admin note: text overlap with arXiv:1905.13060 by other author
