This work aims to evaluate the effects of different particle size, flow rate and modifier ratio on the extraction yield and anthocyanins content of Hibiscus sabdariffa L (Roselle) by using supercritical carbon dioxide (SC-CO2) method. SC-CO2 extraction was carried out at constant pressure and temperature, 10MPa and 70°C respectively with 75% (v/v) ethanol as a modifier. The result shows that 120 minutes was the efficient extraction time at a determination of flow rate. The trend and results for the extraction yield and anthocyanins were varied in all parameters studied. The finding shows that a low flow rate (4 ml/min), smaller particle size (200-355 µm) and high percentage ratio of modifier (10%) could obtain more anthocyanins content. Thus, the manipulation of several parameters in the SC-CO2 extraction process could enhance the selectivity of anthocyanins extraction from the total extract.
Saltwater intrusion has become a crucial issue for water resources management across the globe. Consequently, this issue leads to problems such as encroachment on water intake zone, loss of freshwater vegetation and also disturbance to aquatic life habitat. Undeniably climate change increases the saline water flow into the river system. The meandering rivers are common, and the hydraulics is more complex than straight rivers. An experimental hydraulic investigation was carried out in the Universiti Teknologi Malaysia to elucidate the hydrodynamic interactions between saline water and freshwater in a narrow meandering channel. The spatio-temporal salinity profiles along the river are discussed in this paper. The findings prevailed a typical characteristic of a salt-wedge estuary and indicated the processes of estuarine mixing. As the saltwater flows upstream, the salinity level drops due to the dilution process. Salinity levels and densimetric Froude number were mainly driven by freshwater discharge in the channel. A variation of dilution rate in a narrow meandering channel were up to 78.9% due to strong velocity forces produced by a high freshwater discharge. Furthermore, the flow resistance induced by the channel boundaries and meander planform itself influenced the salinity intrusion profiles along the channel.
Rice is a special crop that requires a thin layer of water to produce, and is produced differently from other crops. The rice sectors in Malaysia continue to be developed in a proactive and progressive manner. Due to its growth process, rice has a different water footprint (WF) compared to other crops. This study improved the calculation of the blue and green WF of rice production and examined the variations of these footprints under the primary granary area of Malaysia. The effects of climate change will, however, make it more difficult to achieve food security and increase rice yields in the future. Therefore, this paper aims to discuss climate change impacts on rice production and food security in Malaysia. Many countries worldwide are becoming increasingly vulnerable to natural disasters due to climate change. Many climate models predict a decline in agricultural productivity due to excessive heat in tropical and subtropical regions, especially in Southeast Asia. Malaysia is no exception. Therefore, the present study examined the impact of climate change on rice yields in Muda Granary, Malaysia. Utilizing literature reviews, we assessed the value of evapotranspiration (ET) in order to calculate the green WF for the area. Climate variables (such as ET), yield, and variance of impact during the main season and off-season were the primary objectives of the study. Precipitation did not show a statistically significant difference between the main and off-seasons from 2011-2015. During the main crop season, the maximum ET was negatively associated with yield, but the minimum ET showed a positive association. In the off-season, green WF levels were higher than those in the main season. These findings indicate that climate change poses a serious threat to rice production, which will in turn affect food security as they are highly interconnected. Thus, it is high time for Malaysia to revamp its paddy and rice intervention strategies by giving due attention to enhancing the adaptive capacity of rice farmers to cope with climate change.
Density currents occur when fluid of one density propagates along a horizontal boundary into fluid of a different density. In dam reservoirs, density currents are the main transport mechanism for the incoming sediments and they play an important role in redistribution of existing sediments. This paper aims to investigate velocity structure in the body of density currents. To this end, laboratory experiments were performed on density currents having various initial conditions and bottom slopes. Then, vertical velocity profiles were recorded in the body of density currents. The velocity structure of the currents was investigated by fitting equations to the wall and jet regions of the measured profiles, and the constants of the equations were yielded with R2 more than 0.80. Temporal and spatial evolution of density currents were also analysed to study the dynamics of the frontal region of the currents. It was observed that the currents having more bottom slope travel at a further distance. It was also found that 400% increase in the initial concentration of the currents can increase their frontal velocity up to 97%.
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