13474 research outputs found
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Growth and characterization of manganese silicide nanostructures by thermal chemical vapor deposition for magnetic properties and hydrogen evolution reaction / Najwa Hamzan
No full textThe growth of manganese silicide nanorods and nanowires using vapor transport growth was studied in this work. The manganese silicide nanorods and nanowires were grown on SiO2/c-Si and c-Si substrates using a thermal chemical vapor deposition vacuum system. The study starts with substrate temperature's effect on growth and nanorods' structural properties. The manganese silicide nanorods (Mn5Si3) were grown on SiO2/c-Si substrate by varying reaction temperatures at 750 to 1 000 °C. These variations produced different Mn5Si3 nanorods tops, such as flat-tip and diamond tops. Increasing the reaction temperature increased the delivery of Mn vapor to the substrate and resulted in temperature-controlled phase formation. The growth mechanism followed a direct vapor transport process. Next, with the same growth parameters (850 °C and 6.20 mbar), studies on different substrates (SiO2/c-Si and c-Si) have been carried out. In contrast to SiO2/c-Si, which showed the formation of Mn5Si3 nanorods, the Mn4Si7 nanowires with irregular grains were grown on the c-Si substrate. The effect of reaction pressure on the nanowires' growth and structure properties has also been studied. Low pressures (0.03 and 0.12 mbar) showed the formation of high-density nanowires, while at high pressures (0.52 to 6.20 mbar), nanowires with less density and uniformity grew. In the last part of this work, the studies on morphology and structural properties of the nanowires have been done at lowest pressure (0.12 mbar). As Mn powder was spread flat over a c-Si (111) substrate, the nanowires could grow on top of the bottom substrate. Based on EDX the spectra confirmed the formation of MnSi and Mn4Si7 nanowires on top and bottom substrates. The magnetic measurements indicated that the Mn5Si3 nanorods were ferromagnetic. In addition, with the same growth parameters (850 °C and 6.20 mbar), Mn5Si3 nanorods exhibited ferromagnetic solid properties, while Mn4Si7 nanowires showed a weak ferromagnetic property at low temperature (4 K) and paramagnetic at room temperature (300 K). The M-H curves of MnSi nanowires grown on 0.12 mbar reveal ferromagnetic properties at 4 K and paramagnetic at 300 K. As for nanowires grown at different pressures, M-H curve reveals nanowires grown at low pressures (0.03 and 0.12 mbar) exhibit paramagnetic behavior at room temperature and ferromagnetic at 4 K while nanowires at higher pressure (6.20 mbar) show a very weak magnetic hysteresis loop have been observed at 4 K and paramagnetic properties at 300 K. Lastly, the electrochemical hydrogen evolution reaction (HER) of manganese silicide nanowires also been studied. The as-synthesized MnSi nanowire at 0.12 mbar showed the best electrocatalytic performance towards HER with an overpotential of 0.39 V and the smallest Tafel slope of 95 mV dec−1
Micropropagation, agro-environmental studies and pharmacological activities of saffron (Crocus sativus L.) grown in controlled environmental conditions / Asif Khan
No full textSaffron is derived from three stigmatic lobes of Crocus sativus flowers, an autumn-flowering herb that is propagated solely through clonal corm multiplication. Despite its growing market demand and potential value, the saffron yield is low due to its sterile nature and distinctive eco-physiological characteristics. This study aims to explore in vitro cormlet formation, the effect of agro-environmental factors and gamma irradiation on saffron growth indices in Malaysia and its potential nutraceutical importance of different parts of the saffron plant. It was observed that treatment of corms with 70% ethanol followed by washing in 40% clorox and 0.2% HgCl2 ensured clean aseptic viable cultures. MS enriched with BAP (4 mg/l) and IAA (1 mg/l) resulted in maximum buds sprouting response and multiple shoot primordia. Further sub culturing of shoot primordia in BAP (6 mg/l) and IAA (0.5 mg/l) was superior for achieving multiple shoots proliferation. MS supplemented with GA3 (4 mg/l) and 4% sucrose guaranteed highest cormlet number and cormlet weight, whereas GA3 (2 mg/l) and 2% sucrose gave highest root number and root length. In an attempt to assess the response of saffron growth and yield components to temperature, mother corm size, type of fertilizer and planting depth during the first two years, it was shown that lower temperature of 18 °C, bigger sized of planted corms and cattle manure application were the most favorable conditions for the entire reproductive and vegetative attributes of saffron irrespective of planting depth. Likewise, different doses of γ-rays (0, 10, 20, 30, and 40 Gy) was evaluated for their potential effect on morpho-agronomic characteristics of saffron and the results indicated that 10 Gy treatment stimulatively effected on various vegetative attributes, whereas radiation at 20 Gy was the most optimal dose for the reproductive traits of saffron. Also, one of the 20 Gy plants showed four irregular dark petals, tetrafid stigma, and two stamens compared with six normal-sized petals, trifid stigma, and three stamens in control. Conversely, higher doses of 30 Gy and 40 Gy were lethal by showing deleterious effects in terms of saffron growth indices. Saffron parts i.e corm, leaf, petal and stigma obtained were further evaluated for their toxicity and pharmacological activities in mice. During the 14 days oral toxicity study, none of the saffron ethanolic extracts at a dose of 2000 mg/kg body weight showed any mortality and abnormality in all selected parameters in mice of both sexes as compared with their respective control groups. Stigma and petal ethanolic extracts showed significant enhancement behavior in carrageenan induced hind paw edema assay and hot plate analgesic assay as well as antidepressant test and anticoagulant test in mice. However, leaf and corm ethanolic extracts displayed mild activity. Likewise, SEE followed by PEE exhibited antihyperglycemic effect and showed strong hypolipidemic response in STZ-induced diabetic mice. The SEE and PEE treatment to diabetic mice also significantly restored the level of serum glucose, kidney and liver biomarkers towards the normal control which validate its use as an antidiabetic drug in folk medicine
The application of Quranic values among teachers of Islamic education to their students at the secondary stage in Kuwait / Ahmed Alanazi
No full textThis study aimed to reveal the extent to which Islamic education teachers apply the Qur’anic values to their students at the secondary stage in the State of Kuwait. The researcher used the descriptive survey method. The study sample consisted of 82 individuals. The questionnaire consists of three domains: 1) the Qur’anic values related to the relationship of man to Allah, 2) the Qur’anic values related to the relationship of man to himself, and 3) the Qur’anic values related to the relationship of man to others. The validity of the tool was confirmed by presenting it to a group of experts. It was applied to the sample, and the most important results of the study was that secondary school teachers apply the Qur’anic values in general education schools and in private (bilingual) schools in the State of Kuwait in a large extent on the basis of Qur’anic values related to the relationship of human to Allah and man to others, while achieved a medium degree on the basis of values related to the relationship of human, The results also revealed that there were no statistically significant differences between the average responses of the sample members to the type of schools, or the educational department, while there were statistically significant differences between the average responses of the sample members attributable to job experience in favor of higher job experience. The researcher recommended working hard on the development of teacher training programmes, the aim of which is to train teachers on the teaching methods of Quranic values and to master their practical application, and the need to include in the teacher's manual multiple strategies aimed at developing the teaching skills of Quranic values as well as developing educational supervision and improving its programmes by including Koranic values in all training and qualification programmes for the teacher of Islamic education before and during service
Optimisation of emulsified liquid culture system for bacterial poly-3-hydroxyalkanoate production / Aishat Abdulwaheed
No full textThe use of polyhydroxyalkanoates (PHAs) as a polymer in various industries, including packaging and medicine, is receiving significant attention due to their biodegradability and biocompatibility. However, the high cost of production from carbon sources remains a major obstacle to the widespread use of PHAs as alternative polymers. Consequently, there has been a search for cost-effective substrates that can yield high productivity. One such substrate is cooking oil, which serves as an energy and carbon source. However, using an immiscible substrate like oil presents unique challenges because the fermentation liquid consists of a heterogeneous multiphase system that makes it difficult for bacterial to grow. Therefore, this study aimed to optimize the PHA production using the Box-Behnken method with oil, inoculums, and surfactants as the variables. The amount of PHA produced was comparable to the control experiments using a pure, single-type fatty acid as the sole carbon and energy substrate. The addition of surfactant (Tween-80) to the mixture of liquid medium and oil facilitated the emulsification of the immiscible substrates, thereby promoting bacterial growth. The optimal conditions for PHA production were determined as follows: biomass of 0.375 ml, oil of 1.25 g, and surfactant of 0.125 ml per 100 ml of medium. Furthermore, the molecular weight and chemical characteristics of the extracted PHA were analyzed. The study demonstrated the effectiveness of surfactants in achieving favourable cellular growth while simultaneously enhancing PHA production
Forest waste biochar enhances growth and antioxidant defence in Sonneratia caseolaris seedlings grown under salinity stress / Nur Sa’adah Abdul Halim
No full textMangrove forests are well inundated by seawater that is particularly high in salinity which limits propagule germination, seedling growth, survival rate and reproduction of mangrove trees. Continual loss of mangroves will bring detrimental impacts on the ecosystem and humans. Therefore, mangrove conservation is now a priority, and this involves enormous efforts to rehabilitate the forest. Recently, biochar, which is a product from thermal degradation of organic biomass under low- oxygen condition known as pyrolysis process has a great ability in adsorbing salt ions has received numerous applications. Application of biochar as a soil amendment can assist to mitigate the adverse impacts of salinity stress. Thus, this study was aimed to elucidate the effect of forestry waste biomass biochar on Sonneratia caseolaris under salinity stress in mangrove nursery by optimizing the production of biochar from different sources of forestry waste biomass and, to determine the effects of biochar application as soil amendments on plant growth, soil properties and nutrient uptake as well as the antioxidant defense mechanism in plants. Biochar was produced from forestry sources of Gigantochloa levis, Melaleuca cajuputi, Bruguiera parviflora and Sonneratia caseolaris. The materials were pyrolyzed at 300 ℃, 450 ℃ and 600 ℃ for 2 hours. Proximate analysis and ultimate analyses were done followed with physical and chemical analyses of the biochar before undergoing the sodium adsorption study. From the study, the fixed carbon was observed to increase from 11.75% to 70.62% (Bruguiera parviflora) and 9.04% to 72.92% (Gigantochloa levis) upon carbonization of the raw materials. These values correlated with the increasing C content of the samples, which also resulted in lower H/C value. It was found that biochar aromaticity and stability increased with increasing temperature. Additionally, Field Emission Scanning Electron Microscopy (FESEM) elucidated that higher pyrolysis temperature increased the porosity and surface area. The pH was observed to increase from 4.51 to 9.83. (B. parviflora) and 5.36 to 7.98 (G. levis). In Langmuir isotherm, biochar can adsorb exchangeable Na content up to 121.95 mg/g and (B. parviflora) and 49.15 mg/g (G. levis). These two biochar types were further studied at different application in incubation study for 35 days and application as soil amendment in Sonneratia caseolaris seedlings through a six-month study period at Kampung Sijangkang Mangrove Recreational Park, Telok Panglima Garang, Selangor. Five treatments were evaluated in this study: control (T1), 10% of B. parviflora biochar (T2), 20% of B. parviflora biochar (T3), 10% of G. levis biochar (T4), and 20% of G. levis biochar (T5). From the incubation study, both B. parviflora biochar and G. levis biochar can significantly increase the pH value of mangrove soil, while significantly reducing the EC of mangrove soil. Meanwhile, these two biochars can also significantly increase the SOM of mangrove soil. On the other hand, mangrove soil SAR has a strong positive correlation with Na+ content, a negative correlation with Ca2+ content, and almost no relationship with Mg2+ content. In nursery study, application of 20% of B. parviflora biochar (T3) were observed to give the highest plant height, stem diameter, biomass dry weight, root fresh weight, length of entire plant, length of primary root, and also possess low ROS (H2O2, OH-, MDA) and DPPH meanwhile high in (chlorophyll a, carotenoid, CAT, APX, DHAR, and FRAP potential) which signifies a good impact for the growth of the seedlings. These demonstrate the potential of the treatment as soil amendments to not only improve soil properties, but also improve Sonneratia caseolaris plants’ tolerance towards salinity stress. Other than that, numerus metabolites with antioxidant potential were induced in T3 compared to other treatments, which were shown to elicit notable responses in terms of metabolite production. To sum up, B. parviflora biochar gave the best quality of biochar and can improve the growth of mangrove plant seedlings where it can adsorb salinity, improve root growth and development, as well as scavenging the ROS, v
improve enzymatic and non-enzymatic activities, which help to protect the seedlings from oxidative and salinity stress. In conclusion, this research demonstrates the positive impacts of biochar application as soil amendment on the growth performance, physiological features, and biochemical properties of Sonneratia caseolaris when cultivated in high salinity mangrove area
A-share market prediction and trading strategies / Lu Tianfeng
No full textAs a significant financial instrument, stocks have consistently attracted investors seeking profitable opportunities. Yet, forecasting stock prices remains challenging due to intricate market dynamics characterized by noise, nonlinearity, and temporal variability. Recent global crises ranging from pandemics to geopolitical tensions have heightened market volatility, underscoring the need for more robust predictive models. The rapid development of artificial intelligence and machine learning techniques, with their enhanced capacity to model complex nonlinear relationships, has rendered them increasingly essential in stock price prediction tasks. This study integrates Particle Swarm Optimization (PSO) with Long Short-Term Memory (LSTM) neural networks to improve predictive accuracy in the Chinese A-share market. Through a PSO-driven hyperparameter tuning process, we refine the LSTM architecture, enabling it to better capture intricate temporal dependencies and market patterns. Empirical results show that the PSO-LSTM model outperforms traditional LSTM, MLP neural networks, and conventional benchmark models in terms of key accuracy metrics (MSE, MAE, RMSE, MAPE, an
Adjacency preserving maps on classical spaces of tensors / Lau Jin Ting
No full textWe define tensor rank, symmetric rank and exterior rank of tensor, symmetric tensors and multivectors, respectively. A pair of tensors, symmetric tensors or multivectors is adjacent if the rank of their difference is one. A map on tensor spaces, symmetric spaces or exterior spaces is strong adjacency preserving provided it preserves adjacent pairs in both directions. In this thesis, we characterize strong adjacency preserving maps on tensor spaces of order at least three, and classify surjective strong adjacency preserving maps on symmetric spaces and exterior spaces. Our strategy is to extract properties of rank one tensors, symmetric rank one tensors and exterior rank one multivectors, and reduce surjective strong adjacency preserving maps to certain maps on affine spaces or projective spaces. Additive maps on exterior spaces that preserve decomposable multivectors are closely related to strong adjacency preserving maps. We characterize this class of additive maps by reducing them to linear maps through the field extensions approach, and deduce the structure of such additive maps from the linear maps
Implementation of solid waste management policy in Malaysia / Mohd Fazli Abdul Aziz
No full textUnprecedented population growth, rising community living standards, and urbanisation have significantly contributed to the increase of solid waste generation in Malaysia. Improper solid waste management has negatively affected the environment and public health. Despite strategies to improve the country’s waste management system, Malaysia still struggles to translate policy decisions into actionable activities. Hence, this research examines the challenges in implementing a solid waste management policy in Malaysia. It analyses the possible gaps in the implementation process that hinder the policy from achieving its intended outcomes.
The study demonstrates how the outcome of solid waste management policy is dependent upon the attempted implementation of the policy influenced by the prevailing political scenario, socio-economic conditions, cultural background, and the structure and availability of requisite resources. It also shows how policy is developed and implemented (or not implemented) from the combined influences of several stakeholders in the decision-making arena.
To understand policy, one needs to understand the interaction between different stakeholders and how they affect and are affected by the policy process. In light of this, semi-structured interviews and focus group discussions are employed as the main research instrument. Examination of practices and experiences of those involved in solid waste management policy implementation have shed some light on the current practices and issues of solid waste management. Additionally, field observations and analysis of written documents are employed to illustrate Malaysia’s solid waste management policy implementation.
The result indicates that six factors have influenced solid waste management policy implementation in Malaysia: (a) political system, (b) institutional capacity, (c) inter-governmental relationship, (4) policy clarity, (5) cultural and socio-economic conditions, and (6) the role of local governments. In the developing countries context generally, but specifically in Malaysia, the policy process takes place within the complex socio-cultural, highly centralised, and hierarchical setting of a state-bureaucratic network, which has shaped the development and implementation of policy
Properties enhancement of ternary blended geopolymer mortar with fibres / Adel Kassem Farag Gaddafi
No full textThis thesis presents a comprehensive examination of two distinct aspects of construction materials: the development of ambient-cured geopolymer mortar and the enhancement of its ductility through fiber reinforcement. The investigation encompasses various properties and attributes critical to the understanding and application of these materials. First, the study focused on the development of ambient-cured geopolymer as a potential ordinary Portland cement (OPC) substitute. Ternary geopolymer mixes were examined for their workability, density, ultra-sonic velocity (UPV), compressive strength, X-ray diffraction (XRD) analysis, and scanning electron microscope (SEM) analysis. The study explored various proportions of ground granulated blast furnace slag (GGBS) at 10%, 20%, and 30% by weight as replacements in a fly ash (FA)-based mixes. The mixes included palm oil waste materials, such as palm oil fuel ash (POFA), ecoprocessed pozzolan (EPP) and palm oil clinker sand (POC) sand. The UPV values increased with higher GGBS content but were adversely affected by voids in POC sand. Compressive strength improved over time with inclusion 30% GGBS replacement exhibit a remarkable 60% after 28 days. XRD analysis confirmed the existence of amorphous geopolymers. SEM analysis showed GGBS reduced voids, leading to denser microstructures. In parallel, the study investigates the development of fiber-reinforced geopolymer mortar. Geopolymers, a subset of ceramic materials, exhibit a brittle nature. The experimental work involved the study of polypropylene (PP) and micro steel (MS) fibers added to fiber-reinforced geopolymer mortar (FRGM) at volume fractions of 0.5%, 1%, and 1.5%. The investigation assessed a range of hardened properties, including compressive strength, splitting tensile strength, modulus of elasticity (MoE), and UPV. The research assessed load-deflection response and compressive stress-strain behavior, focusing on toughness and ductility. The bonding between the fibers and the mortar matrix was examined using field emission scanning electron microscopy (FESEM). The addition of 0.5% PP fibers and up to 1.5% MS fibers marginally improved compressive strength by up to 25% and MoE by up to 14%, with corresponding increments in splitting tensile strengths enhanced by 27% and 177%, respectively. The incorporation of 1.5% fiber volume into the non-fibrous mix resulted in an average improvement of 50 N.m and 13 N.m in flexural toughness (T150) for MS and PP mixes, respectively. The equivalent flexural strength ratio for 0.5%, 1%, and 1.5% MS and PP composites ranged from 180% to 240% and 47% to 89%, indicating an improvement in the material's ductility and overall performance in bending applications. The gradual increase in MS fiber volume significantly enhances compressive toughness in mining sand geopolymer mortars, with mixes containing 0.5%, 1%, and 1.5% fibers showing up to 2.67 times improvement. Remarkably, when entirely replacing mining sand with POC sand, it demonstrates outstanding improvements in stress-strain graph results. The POC sand mixes demonstrated substantial strain enhancements. The plain mix showed a strain at failure of 0.001687 mm/mm, which increased by 84%, 185%,\ and 197% with the addition of 0.5%, 1%, and 1.5% fibers, respectively. Moreover, 1.5% MS fiber addition resulted in a 562% improvement in compressive toughness compared to the plain POC sand mix. In elevated exposure, the 1.5% MS mix exhibited significant performance increases: 42%, 69%, and 100% improvements at 200°C, 400°C, and 600°C, respectively, compared to the non-fibrous control mix. In conclusion, this research presents vital insights into the development of ambient-cured fiber-reinforced geopolymer and the enhancement of its ductility through fiber reinforcement. These materials offer the potential for sustainable and environmentally friendly applications in construction and infrastructure projects
Fatigue behavior analysis and life prediction of CFRP-strengthened reinforced concrete structures / Zou Chuanlong
No full textInfrastructures are frequently vulnerable to sustained cyclic loads and structural vibration. The accumulated cyclic stresses will induce fatigue in the structures and contribute to their inadequate service lifespan. Consequently, analyzing the present structural health status by the structural stiffness measurement is crucial. Meanwhile, a significant issue in structural health monitoring is identifying fatigue damage in concrete structures that have been retrofitted with Carbon Fiber Reinforced Polymer (CFRP). Although the finite element (FE) method has significantly contributed to modeling the damage mechanisms of concrete, reinforcement, and CFRP, further research is still needed in this area. For instance, reinforced concrete (RC) slabs reinforced with externally bonded CFRP (EB-CFRP) technology, and RC beams strengthened with side-bonded CFRP (SB-CFRP) technology due to narrow soffit constraints, must be evaluated and predicted for high-cyclic fatigue and progressive damage. Therefore, this study aims to investigate the fatigue performance and dynamic progressive damage behavior of strengthened RC structures under high-cyclic fatigue loadings using nonlinear FE analysis. Initially, a new model was recommended for predicting the concrete's residual strength of unstrengthened RC slabs. The accuracy of the suggested model and the FE simulation was validated by comparing the predicted natural frequencies, mode shapes, residual strength, and crack characteristics of specimens with the experimental results. Then, a novel model for determining the dynamic stiffness of RC slabs was developed for strengthened RC structures such as the RC slabs with EB-CFRP and RC beams with SB-CFRP. Finally, this research developed a cyclic-dependent CFRP concrete interface degradation model that could be utilized to analyze the dynamics of fatigue RC structures and find damage in structures that have prestressed EB-CFRP reinforcement. Results showed that the cumulative degradation of the natural frequency, stiffness, and damage development of steel rebars and concrete increased as the fatigue loading cycle increased, indicating that the dynamic response and fatigue damage for RC slabs in the later stages of high-cyclic fatigue loading were more severe. Validation of the dynamic stiffness model demonstrated its capability in predicting the stiffness of fatigued and damaged RC slabs. It was discovered that prestressed EB-CFRP-strengthened RC slabs can significantly affect the vibration response of specimens. When the prestressing and fatigue loads were high, the prestressing altered the damage distribution at the CFRP concrete interface, leading to debonding of the CFRP near the ends of the RC slabs. Fatigue failure modes in non-prestressed and low-prestressed SB-CFRP-strengthened beams primarily involve rebar rupture, while high prestress levels lead to CFRP delamination. Properly placed end U-shaped wrapping effectively reduces CFRP-concrete interface damage caused by highly prestressed SB-CFRP, extending the structure's service life. In addition, a simple model is proposed to predict the fatigue life of externally bonded CFRP reinforced structures, considering combined load and prestress levels. The results provide practical insights for analyzing the dynamic behavior of existing structures by considering the nonlinear progressive damage and may improve the efficiency of structural damage detection