Determination of Phenolic and Flavonoid Contents, Antioxidant Activities and GC-MS Analysis of Clinacanthus Nutans (Acanthaceae) in Different Locations

Clinacanthus nutans is an essential medicinal plant that had been used in various local remedies to treat many illnesses. A study had been conducted to determine the phenolic, flavonoid, antioxidant activities and phytochemical compounds of C. nutans in different locations. C. nutans were harvested from eight locations and the leaves were extracted with 80 % methanol by maceration process. Then, the phytochemical screening using Gas Chromatography-Mass Spectrometry (GC-MS), 2,2 diphenyl-2-picrylhydrazyl hydrate (DPPH) assay method, total phenolic content by Folin Ciocalteu\u27s assay method and total flavonoid content by aluminium chloride (AlCl3) were carried out. The C. nutans extracts showed higher antioxidant activities than phenolic and flavonoid content. The neutral pH sandy clay soil from location KKK (Kuala Ketil, Kedah, Malaysia) had higher antioxidant activities (58.0 %), phenolic (44.1 mg GA.100 g-1) and flavonoid content (30.8 mg QE.100 g-1) compared to other locations. The GC-MS analysis showed the presence of phytochemicals constituents of 20 compounds. The results revealed that environmental factors (light intensity, temperature and soil characteristics) of eight locations were responsible for variations of phenolic, flavonoids, antioxidants and GC-MS analysis in C. nutans. The findings of this study will provide baseline data for future breeding programs for commercial cultivation

Dynamic mechanical properties and morphology characteristics of rubber-toughened poly(lactic acid)

This study investigates the effect of natural rubber (NR), epoxidised natural rubber (ENR), and core-shell rubber (CSR) as toughening agents for poly(lactic acid) (PLA). PLA/rubber blends were prepared by using melt blending method in a twin-screw extruder, with the content of rubbers was fixed at 5 wt. %. All PLA/rubber blends exhibited lower storage modulus compared to neat PLA. Two-stage storage modulus (E’) was also observed, where the first stage occurred at lower temperature corresponded to the glass transition temperature (Tg) of rubber components, whereas the second E’ corresponded to the Tg of PLA. The impact fracture surface of PLA/rubber blends also exhibited phase- separated morphology where the spherical-shaped rubber particles were clearly present in the PLA matrix

Effect of adsorption parameter on the removal of aspirin using tyre waste adsorbent

In recent years, pharmaceutical compound has been detected in small concentration in our surface and ground water. This detection raises a lot of concern as is it reported that pharmaceutical compound can bring adverse effect to the environment even at low concentration. Besides that, there is a growing fear that this compound will eventually end up in human drinking water, thus effecting human health. This prompt a lot of research on the removal method for this particular compound. Adsorption is seen as the most viable option because of its high efficiency, low cost and it is environmentally friendly. In this study, the adsorbent used is carbon black derived from tyre waste via pyrolysis at 800 ºC. The carbon black was treated with 6 M of nitric acid (HNO3) at 90 °C for 0.5 h before being subjected to thermal treatment at 600 °C for 1 h. The response of the adsorption study is the removal of aspirin. There were five adsorption parameters that were varied in this study which are the contact time (until equilibrium), initial pH of aspirin solution (pH 3, pH 7, pH 11), temperature (30, 50, 70 °C), initial concentration (10-100 mg/L) and adsorbent dosage (0.1 g, 0.5 g, 1.0 g). The best removal capacity obtained was 40.40 mg/g of aspirin at pH 3, temperature of 30 °C, 100 mg/L initial concentration and 0.02 g adsorbent dosage

Solid State Switching Control Methods: A Bibliometric Analysis for Future Directions

Recently, the development and controls of solid-state switching have gained significant popularity over the years especially in academic research. The development of control strategies in solid state switching applications to ensure fast switching in a protected distribution system has fueled a great deal of investigation and further developments. Therefore, a critical review and analysis in the field of solid-state switching for distribution systems are provided in this article. The Scopus database is used to compile a list of the most cited published papers in the field of solid-state switching control methods based on the identified criteria. The study explores 120 of the most cited articles emphasizing six keywords such as a solid-state breaker, solid-state transfer switch, static transfer switch, automatic transfer switch, automatic protection switches, and solid-state protection switch. The analysis was conducted using the Scopus database in the fourth week of January 2021. The 120 articles were collected from 24 different journals and 27 different countries. It is reported that 78% of the published papers outline the methodology based on control and test systems whereas 22% of articles are based on review surveys. From that, 73% of articles concentrate on the protection strategy in the system. The main objective of the article is to classify and define the highly cited published articles in the field of solid-state switching control methods as well as to provide direction for future research on fast switching in the distribution system. The analysis also highlights various factors, issues, challenges, and difficulties to identify the existing limitations and research gaps. This review will serve to strengthen the development concepts of solid-state switching control methods towards achieving improved operational performance, energy-saving, economic prosperity, and enhanced power quality. The authors believe that this bibliometric evaluation will allow academic researchers to identify opportunities for growth in the solid-state switching industry

Evaluating Technical Efficiency of Stock Performance using Copula-Based Stochastic Frontier Analysis Approach

This study estimates the technical efficiency for 14 selected Malaysian trading and services companies for 2017 and 2018using the Cobb-Douglas with the Stochastic Frontier production model. In standard stochastic frontier analysis (SSFA), the two-sided error, statistical noise, and one-sided error, inefficiency term are assumed to be independent. The assumption for statistical noise is normally distributed and the inefficiency term is half-normal distributed. In this paper, the copula model is applied to capture the joint distribution of these two error components. The copula model is an alternative method that is able to account for the joint multivariate distribution. Copula functions can be used to capture rank correlation and tail dependence between two error components, thus making the SFA more flexible. Seven copula models from the Archimedean copula family are considered in this study including the copulas with the trigonometric and hyperbolic generator. This study further compares the technical efficiency yielded by copulas with standard SFA, DEA-CCR and DEA-BCC models. The results raise the question of the reliability of SFA based on the standard model. Since the dependence error between statistical noise and inefficiency error cannot be ignored, the copula-based in SFA models can be considered as an alternative suitable tool for measuring efficiency performance

Comparative study on the enhancement of thermo-mechanical properties of carbon fiber and glass fiber reinforced epoxy composites

This work is the part of a study on the enhancement of thermo-mechanical properties of Epoxy by incorporating carbon and glass fiber and preparing epoxy composites and are rarely used before. The composite/laminates of Carbon fiber/Epoxy (CFE) and Glass fiber/Epoxy (GFE) having 1.5 mm thickness were prepared by hand layup vacuum bagging technique. The fiber-epoxy ratios for preparation of CFE and GFE were 40:60, 50:50 and 60:40 by weight percent. Thermal properties of the composites were investigated using Differential Scanning Calorimetry (DSC), while mechanical properties were examined using Universal testing machine (UTM) in terms of tensile strength and Young's modulus. The tensile strength of CFE were enhanced to 844.44%, 951.11% and 1122.22% by incorporation of carbon fiber having 40, 50 and 60 wt%, respectively. While the increase of 156.66%, 171.10% and 197.77% in tensile strength of GFE was noticed when 40, 50 and 60 wt% of glass fiber was incorporated. The glass transition temperature (Tg) increased from 71 °C of neat epoxy to 110 °C for both the epoxy composites. Overall, the properties of CFE were found to be much superior to that of GFE

Determination of optimum CO2 water alternating gas (CO2-WAG) ratio in Sumatera Light Oilfield

The CO2 Water Alternating Gas (CO2-WAG) injection method, allows the oil to first expand and become better able to flow because of the CO2, and then the water increases the pressure in the reservoir to flush this newly freed oil to production wells. This study is in Sarolangun District, Jambi Province which is prospect of CO2 injection tertiary recovery project due to its abundant CO2 reserve. The success of CO2-WAG injection can be determined by investigating ratios between CO2 and water. The goal of this study is to determine optimum CO2-WAG injection ratio in Sumatera Light Oilfield. This study is done through a numerical simulation of immiscible CO2-WAG which is conducted under three scenarios of ratio using both CMG WINPROP and GEM simulator. The CO2/water ratios are varied from 1:1, 2:1 and 1:2. The study results show that the CO2/water 1:2 is the best CO2-WAG injection ratio that gives highest additional oil recovery factor of 35.24%. Additional recovery factor given by CO2/water ratio 2:1 and 1:1 is 1.49% and 19.52% respectively. Based on this study, the effect of CO2-WAG ratio to oil productivity is depending of amount of water injected. Lower initial oil viscosity lead to an insignificant effect of CO2. Proper CO2-WAG injection ratio will give an optimum oil recovery. This works will have a great use in the CO2-Enhanced Oil Recovery (EOR) application

Synthesis and application of rice husk silica nanoparticles for chemical enhanced oil recovery

Silica (SiO2) nanoparticles were synthesized from rice husk (RH) via wet milling method and evaluated for enhanced oil recovery (EOR) applications. Physical properties of RH-SiO2 nanoparticles (RH-SNP) with its size distribution were explored through field emission scanning electron microscopy (FESEM) and dynamic light scattering (DLS). Stability, functional groups and purity of RH-SNP were determined by zeta potential, Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD), respectively. Effect of RH-SNP on the precipitation and thermal degradation of oilfield polyacrylamide (HPAM) was studied using Brookfield RST rheometer. Interfacial tension (IFT) properties of RH-SiO2 polymeric nanofluid (RH-SPNF) at interface of oil and water (O/W) were investigated using Easy-Dyne KRUSS tensiometer. Subsequently, oil displacement efficiency of RH-SPNF was determined and compared with oilfield HPAM at reservoir conditions using Fars EOR high-pressure high-temperature (HPHT) core flooding equipment. The wet milling method was effective in producing RH-SNP of size ranges 43.9-59.5 nm with a purity of 98% through the mechanism of nucleation, Brownian motion and coalescence. Rheological results show that RH-SNP inhibited the precipitation and thermal degradation of oilfield HPAM. IFT of RH-SPNF showed a monotonic tendency as temperature increased. HPAM and RH-SPNF flooding showed an incremental oil recovery of approximately 10% and 24%, respectively. Emulsion generated using RH-SPNF shows higher stability and resistance to coalescence. Finally, mobility ratio of water flooding approaches unity faster, compared to HPAM and RH-SPNF. Overall, the low energy utilization, use of low-cost and benign raw material make RH-SNP and the extraction method an appropriate substitute to commercially available SiO2 nanoparticles

Rubber seed shell based activated carbon by physical activation for phenol removal

This work was aimed at evaluating the characteristics of activated carbons derived from rubber seed shell through physical activation using CO2 for phenol removal. Two activated carbons were obtained at different retention times of 30 min (AC1) and 90 min (AC2) at fixed temperature of 900 °C. Activated carbons were characterized for specific surface area, surface functional groups and morphology. The values of specific surface area were recorded as 852 m 2 /g and 606 m 2 /g for AC2 and AC1. AC2 shows a higher phenol removal capacity of 302 mg/g than AC1 (112 mg/g) that is directly related to the specific surface area of activated carbons. The equilibrium data fitted well to the Langmuir isotherm, suggesting monolayer coverage of phenol molecules on the homogeneous surface of activated carbons. The kinetics data obeyed pseudo-first-order model, indicating the external diffusion as the rate-limiting step in adsorption