The Impact of moisture and clay content on the unconfined compressive strength of lime treated highly reactive clays

YesThis study aims to provide a thorough evaluation for the changes in the microstructure and evolution of strength of highly reactive clays that were treated with 7 % lime over a period of curing time as a function of the mixing moisture content. Three series of testing were carried out on specimens with 100 %, 85 % and 75 % of bentonite content and prepared with different moisture content of 10, 20, 30 and 40 % above the corresponding optimum moisture content. Specimens of 100 % bentonite were treated with 7 % of lime, compacted to achieve a predetermined dry unit weight and cured at temperatures of 20 OC and 40 OC for up to 28 days whereas the specimens with 85 % and 75 % of bentonite content were prepared by the addition of sand and were cured at 20 oC for up to 7 days. Unconfined Compressive Strength tests and Scanning Electron Microscopy were conducted to observe the strength and the microstructural changes resulting from increasing mixing moisture content. California Bearing Ratio and Resilient Modulus were correspondingly determined based on correlations with the Unconfined Compressive Strength. The failure pattern was also studied to better understand the ultimate behaviour of lime stabilised clays. The results revealed that the strength of treated bentonite increased with the increase in the moisture content up to 30 % above the corresponding optimum moisture content and with increasing the curing time and temperature. Nevertheless, substituting bentonite with sand on the specimen resulted in a significant reduction on the attained strength. Furthermore, the results of California Bearing Ratio and Resilient Modulus showed that values for both parameters are significantly enhanced with lime treatment. The microstructural analysis provided visual evidence to the improved strength in which the pozzolanic reaction was found to be significantly affected by the amount of moisture in the mixture. The results suggested that compacting lime treated expansive clays with moisture content moderately higher than the optimum moisture content would result in a significant enhancement to the attained strength over the period of curing

Prevalence and determinants of anxiety and stress in the general population during COVID-19 pandemic in Iraq: A cross-sectional study

Background The COVID-19 pandemic and its prevention and control measures, such as social distancing, self-isolation, and quarantine, have a negative impact on the population’s mental health. This study aimed to determine the prevalence of anxiety and stress among the general population during the outbreak of COVID-19 and assess their associated factors. Methods We carried out a cross-sectional study in Erbil governorate, Iraqi Kurdistan Region, from July 18 to September 12, 2020. We used an online survey questionnaire to collect data from a sample of Erbil population. The 10-items Perceived Stress Scale and the 7-item Generalized Anxiety Disorder scale were used to measure the levels of stress and anxiety. Results A total of 851 persons responded to the survey. The prevalence of moderate and high perceived stress was 59.6% and 16.6%, respectively. The prevalence of moderate and severe anxiety was 24.7% and 22.7%, respectively. Age, gender, economic level, having contact with COVID-19 patients, and following COVID-19 news were independent variables significantly associated with stress levels. Age, gender, economic level, employment status, having symptoms of COVID-19, having contact with COVID-19 patients, and following COVID-19 news were independent variables significantly associated with anxiety levels. Conclusion A high proportion of people experienced stress and anxiety during the COVID-19 outbreak in Erbil, Iraqi Kurdistan Region. Females, younger age, poor, and unemployed reported significantly higher stress and anxiety levels. There is a need to establish mechanisms at the population level to decrease the stress and anxiety risks and provide mental health coping measures in times of crisis, such as education about positive thinking, stress management programs, and the role of social support

Optimisation of hybrid energy harvesting using finite element method based on vibration excitation

The main objective of this paper is to optimise energy harvesting design of piezoelectric and magnetic based on vibration excitation; an alternate method for predicting the power output of a bimorph cantilever beam using finite element method with harmonic analysis solver. Both power output generated from the electromagnetic and the piezoelectric were combined to form one unit of energy. In addition, the optimum model was analysed using parametric optimisation analysis solver in finite element analysis to produce an optimum power output. The result showed a maximum power output of 56.66 μW from 47.94 Hz, 4.905 m/s2, and 0.18 cm3 generated for resonance frequency with acceleration and volume. The decreasing size of the harvester with a low natural frequency produces a high-power output

Finite element analysis of hybrid energy harvesting of piezoelectric and electromagnetic

Harvesting energy from ambient vibrations is a highly required method because of the wide range of available sources that produce vibration energy application from industrial machinery to human motion application. In this paper, the implementation of harvesting energy from two technologies to form a hybrid energy harvester system was analyzed. These two technologies involve the piezoelectric harvesting energy and the electromagnetic harvesting energy. A finite element model was developed using the Ansys software with the harmonic analysis solver to analyze and examine hybrid harvesting energy system. Both power output generated from the magnet and the piezoelectric is then combined to form one unit of energy. Further, it was found that the result shows the system generate the maximum power output of 14.85 μW from 100 Hz, 4.905 m/s2, and 0.6 cm3 for resonance frequency, acceleration, and the volume respectively from the optimal energy harvester design. Normalized Power Density (NPD) result of 10.29 kgs/m3 comparable with other literature also can be used in energy harvesting system for vibration application

Emerging chitosan and cellulose green materials for ion exchange membrane fuel cell: a review

Polymer electrolyte fuel cell is an attractive type of fuel cell, which has proved to be an interesting area for further investigation. This is due to several advantages such as minimal risk of electrolyte leakage, short warm-up time (due to moderate operating temperature) and high power density. Over the last decades, a substantial progress has been made to improve the performance and durability of the cell while working on strategies to reduce its cost of fabrication. These objectives are achieved through the development of a natural biopolymer-based ion exchange membrane. Chitosan and cellulose have demonstrated an outstanding potential due to their excellent thermal and mechanical properties, good water retention ability, low reactants permeability, biodegradability and renewability. These characteristics are essential for a high-performance membrane. Therefore, several modifications for chitosan and cellulose were studied to further improve its properties and enhance its performance. Hence, this paper aims to comprehensively review the current development of membrane fabrication which utilizes green materials like chitosan and cellulose. Besides that, the influence of these materials toward improving the membrane properties and performance for ion exchange membrane fuel cell applications are also reviewed. We hope that this perspective will be able to provide useful interpretations for the development of the next generation of polymer electrolyte membrane in fuel cell applications

Improvement in properties of nanocrystalline cellulose/poly (vinylidene fluoride) nanocomposite membrane for direct methanol fuel cell application

Improving methanol resistance and dimensional stability are the main challenges in polymer electrolyte membranes for direct methanol fuel cell application. In this study, nanocrystalline cellulose (NCC) was initially synthesized and then blended together with poly (vinylidene fluoride) (NCC/PVDF) and the resultant dope solution was used for the fabrication of membranes via solution casting method. The physical characteristics of the membranes were evaluated using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). Crystallinity differences between all the membranes were confirmed by x-ray diffraction (XRD). Results revealed that the swelling ratio at 80° C and methanol permeability of NCC-3/PVDF were as low as 15.19% and 2.69 × 10-9 cm2/s, respectively compared to Nafion 117 (18.25% and 2.74 ×10-6 cm2/s). It was found that blending hydrophilic NCC with hydrophobic PVDF could profoundly influence the physical properties of the membrane. High crystallinity structure of NCC/PVDF membrane significantly improved the dimensional stability and reduce methanol permeation rate. Although the proton conductivity of NCC-3/PVDF (7.57 ×10-2 mS cm-1) is low, its selectivity (28.141 ×103 Scm-3s) was higher than that of Nafion 117 (0.074 ×103 Scm-3s) due to improvements in methanol barrier. The alternative membrane prepared from NCC and PVDF successfully overcame the weaknesses of Nafion 117, hence exhibiting its potential for DMFC application

Analysis of sociodemographic and clinical characteristics of the respondents on stress level by regression analysis.

Analysis of sociodemographic and clinical characteristics of the respondents on stress level by regression analysis.</p

Factors associated with self-perceived stress and anxiety in the sample.

Factors associated with self-perceived stress and anxiety in the sample.</p

Prevalence of different degrees of stress and anxiety among the participants.

Prevalence of different degrees of stress and anxiety among the participants.</p

Sociodemographic and clinical characteristics of the respondents.

Sociodemographic and clinical characteristics of the respondents.</p