Second generation and perceptual wavelet based noise estimation

peer-reviewedThe implementation of three noise estimation algorithms using two different signal decomposition methods: a second-generation wavelet transform and a perceptual wavelet packet transform are described in this paper. The algorithms, which do not require the use of a speech activity detector or signal statistics learning histograms, are: a smoothing-based adaptive technique, a minimum variance tracking-based technique and a quantile-based technique. The paper also proposes a new, robust noise estimation technique, which combines a quantile-based algorithm with smoothing-based algorithm. The performance of the latter technique is then evaluated and compared to those of the above three noise estimation methods under various noise conditions. Reported results demonstrate that all four algorithms are capable of tracking both stationary and non-stationary noise adequately but with varying degree of accuracyPUBLISHEDpeer-reviewe

Mechanical Activation of a Waste Material Used AS Cement Replacement in Soft Soil Stabilisation

Waste materials, sometimes called by-product materials have been increasingly used as replacement materials to reduce the usage of cement in different construction projects. In the field of soil stabilisation, waste materials such as pulverised fuel ash (PFA), biomass fly ash (BFA), sewage sludge ash (SSA), etc.; have been used since the 1960s. In this study, a particular type of a waste material (WM) was used in soft soil stabilisation as a cement replacement combined with the effect of mechanical activation, using grinding, to enhance the performance. The stabilised soil in this study was an intermediate plasticity silty clayey soil with medium organic matter content. The experimental investigations were conducted to find the optimum content of WM by determining the Atterberg limits and the unconfined compressive strength (UCS) of soil samples containing (0, 3, 6, 9, 12, and 15%) of WM by the dry weight of soil. The UCS test was carried out on specimens exposed to different curing periods (zero, 7, 14, and 28 days). Moreover, the optimum percentage of the WM was subject to different periods of grinding (10, 20, 30, 40mins) using a mortar and pestle grinder to determine the effect of grinding and its optimum time by conducting UCS tests. The results indicated that the WM used in this study improved the physical properties of the soft soil where the index of plasticity (IP) was decreased significantly from 21 to 13.10 with 15% of WM. Meanwhile, the results of UCS test indicated that 12% of WM was the optimum and this percentage developed the UCS value from 202kPa to 700kPa for 28 days of curing. In terms of the time of grinding, the results revealed that 10 minutes of grinding was the best for mechanical activation for the WM used in this study

The Utilisation of Two Types of Fly Ashes Used as Cement Replacement in Soft Soil Stabilisation

This study represents the results of an experimental work using two types of fly ashes as a cement replacement in soft soil stabilisation. The fly ashes (FA1 and FA2) used in this study are by-products resulting from an incineration processes between 800 and 1200 ˚C. The stabilised soil in this study was an intermediate plasticity silty clayey soil with medium organic matter content. The experimental works were initially conducted on soil treated with different percentages of FA1 (0, 3, 6, 9, 12, and 15%) to identify the optimum FA1 content. Then FA1 was chemically activated by FA2 which has high alkalinity by blending the optimum content of FA1 with different portions of FA2. The improvement levels were evaluated dependent on the results obtained from consistency limits and compaction tests along with the results of unconfined compressive strength (UCS) tests which were conducted on specimens of soil treated with FA1 and FA2 and exposed to different periods of curing (zero, 7, 14, and 28 days). The results indicated that the FA1 and FA2 used in this study effectively improved the physical and geotechnical properties of the soft soil where the index of plasticity (IP) was decreased significantly from 21 to 13.17 with 12% of FA1; however, there was a slight increase in IP with the use of FA2. Meanwhile, 12% of FA1 was identified as the optimum percentage improving the UCS of stabilised soil significantly. Furthermore, FA2 was found effective as a chemical activator to FA1 where the UCS was improved significantly after using FA2

Assessing the Potential of a Waste Material for Cement Replacement and the Effect of Its Finennes in Soft Soil Stabilisation

This paper represents the results of experimental work to investigate the suitability of a waste material (WM) for soft soil stabilisation. In addition, the effect of particle size distribution (PSD) of the waste material on its performance as a soil stabiliser was investigated. The WM used in this study is produced from the incineration processes in domestic energy power plant and it is available in two different grades of fineness (coarse waste material (CWM) and fine waste material (FWM)). An intermediate plasticity silty clayey soil with medium organic matter content has been used in this study. The suitability of the CWM and FWM to improve the physical and engineering properties of the selected soil was evaluated dependant on the results obtained from the consistency limits, compaction characteristics (optimum moisture content (OMC) and maximum dry density (MDD)); along with the unconfined compressive strength test (UCS). Different percentages of CWM were added to the soft soil (3, 6, 9, 12 and 15%) to produce various admixtures. Then the UCS test was carried out on specimens under different curing periods (zero, 7, 14, and 28 days) to find the optimum percentage of CWM. The optimum and other two percentages (either side of the optimum content) were used for FWM to evaluate the effect of the fineness of the WM on UCS of the stabilised soil. Results indicated that both types of the WM used in this study improved the physical properties of the soft soil where the index of plasticity (IP) was decreased significantly. IP was decreased from 21 to 13.64 and 13.10 with 12% of CWM and 15% of FWM respectively. The results of the unconfined compressive strength test indicated that 12% of CWM was the optimum and this percentage developed the UCS value from 202kPa to 500kPa for 28 days cured samples, which is equal, approximately 2.5 times the UCS value for untreated soil. Moreover, this percentage provided 1.4 times the value of UCS for stabilized soil-CWA by using FWM which recorded just under 700kPa after 28 days curing

Simulations of shock generation and propagation in laser-plasmas

AbstractWe analyze the results of a recent experiment performed at the PALS laboratory and concerning ablation pressure at 0.44 µm laser wavelength measured at irradiance up to 2 × 1014 W/cm2. Using the code "ATLANT," we have performed two-dimensional (2D) hydrodynamics simulations. Results show that 2D effects did not affect the experiment and also give evidence of the phenomenon of delocalized absorption of laser light

Stabilisation of soft soil using binary blending of high calcium fly ash and palm oil fuel ash

Lime and/or Ordinary Portland cement (OPC) are the traditional binders used in soft soil stabilisation. However, their manufacture has a negative impact on the environment. This paper reports the results of experimental work for the optimisation of a binary blended cementitious binder (BBCB) using two types of fly ash as an alternative for use in soft soil stabilisation. The optimum content of the high calcium fly ash (HCFA) was initially determined along with the effect of grinding activation on the performance of HCFA. Subsequently, the effect of palm oil fuel ash (POFA) pozzolanic reactivity on the engineering properties of soft soil, stabilised with HCFA, was investigated by producing different binary mixtures of HCFA and POFA. Based on the Atterberg limits and unconfined compressive strength (UCS) tests, the combination of POFA with HCFA results in a considerably lower plasticity index (PI) and higher compressive strength than those obtained from the soil treated with HCFA alone. Substantial changes in the microstructure and binders of the stabilised soil over curing time were evidenced by SEM imaging and XRD analysis. A solid and coherent structure was achieved after treatment with BBCB as evidenced by the formation of C-S-H, portlandite and ettringite as well as secondary calcite

Development of a New Ternary Blended Cementitious Binder Produced from Waste Materials for use in Soft Soil Stabilisation

Soil stabilisation using traditional binders such as Ordinary Portland Cement (OPC), has a serious negative environmental impact, specifically carbon dioxide (CO2) emissions as a result of the manufacture of OPC. Because of this, the use of sustainable binders has become a critical issue to help reduce cement production through the use of by-product materials. This research seeks to develop a new ternary blended cementitious binder (TBCB) to replace cement for soft soil stabilisation. Different ternary mixtures containing wastes i.e., high calcium fly ash (HCFA), palm oil fuel ash (POFA) and rice husk ash (RHA) along with flue gas desulphurisation (FGD) gypsum used as a sulphate activator and grinding agent, were examined. The results illustrate that ternary mixtures improved the engineering and mechanical properties of stabilised soil. The results indicated that the plasticity index (PI) was reduced from 20.2 to 13.0 and the unconfined compressive strength (UCS) increased after 28 days of curing from 202kPa to 944kPa using the optimum non-FGD activated mixture. FGD contributed significantly by increasing the UCS to 1464kPa at 180 days of curing, which surpassed that for the reference cement (1450kPa), and by improving the soil consistency limits; where the PI decreased to 11.7 using TBCB compared with 14.5 for the soil treated with the reference cement. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis revealed substantial changes in the diffraction patterns and microstructure components of the TBCB paste over the curing period, confirming the formation of cementitious products. A solid, coherent and compacted structure was achieved after treatment with TBCB as evidenced by the formation of C-S-H, CH and ettringite

Is self-reported depression, HIV status, COVID-19 health risk profile and SARS-CoV-2 exposure associated with difficulty in adhering to COVID-19 prevention measures among residents in West Africa?

Background: The aim of this study was to determine whether self-reported depression, coronavirus disease of 2019 (COVID-19) health risk profile, HIV status, and SARS-CoV-2 exposure were associated with the use of COVID-19 prevention measures.Methods: This survey collected data electronically between June 29 and December 31, 2020 from a convenient sample of 5050 adults 18 years and above living in 12 West African countries. The dependent variables were: social distancing, working remotely, difficulty obtaining face masks and difficulty washing hands often. The independent variables were self-reported depression, having a health risk for COVID-19 (high, moderate and little/no risk), living with HIV and COVID-19 status (SARS-CoV-2 positive tests, having COVID-19 symptoms but not getting tested, having a close friend who tested positive for SARS-CoV-2 and knowing someone who died from COVID-19). Four binary logistic regression models were developed to model the associations between the dependent and independent variables, adjusting for socio-demographic variables (age, gender, educational status, employment status and living status).Results: There were 2412 (47.8%) male participants and the mean (standard deviation) age was 36.94 (11.47) years. Respondents who reported depression had higher odds of working remotely (AOR: 1.341), and having difficulty obtaining face masks (AOR: 1.923;) and washing hands often (AOR: 1.263). People living with HIV had significantly lower odds of having difficulty washing hands often (AOR: 0.483). Respondents with moderate health risk for COVID-19 had significantly higher odds of social distancing (AOR: 1.144) and those with high health risk had difficulty obtaining face masks (AOR: 1.910). Respondents who had a close friend who tested positive for SARS-CoV-2 (AOR: 1.132) and knew someone who died of COVID-19 (AOR: 1.094) had significantly higher odds of social distancing. Those who tested positive for SARS-CoV-2 had significantly lower odds of social distancing (AOR: 0.629) and working remotely (AOR: 0.713). Those who had symptoms of COVID-19 but did not get tested had significantly lower odds of social distancing (AOR: 0.783) but significantly higher odds of working remotely (AOR: 1.277).Conclusions: The study signifies a disparity in the access to and use of COVID-19 preventative measures that is allied to the health and COVID-19 status of residents in West Africa. Present findings point to risk compensation behaviours in explaining this outcome.</p