The Experts below are selected from a list of 171 Experts worldwide ranked by ideXlab platform
Ranjit Kumar Upadhyay - One of the best experts on this subject based on the ideXlab platform.
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Spatiotemporal pattern induced by self and cross-diffusion in a spatial Holling-Tanner model
2012Co-Authors: Ranjit Kumar Upadhyay, Nilesh Kumar ThakurAbstract:In this paper, we have made an attempt to provide a unified framework to understand the complex spatiotemporal patterns induced by self and cross diffusion in a spatial Holling–Tanner model for phytoplankton–zooplankton-fish interaction. The effect of critical wave length which can drive the system to instability is investigated. We have examined the criterion between two cross-Diffusivity (Constant and timevarying) on the stability of the model system and for diffusive instability to occur. Based on these conditions and by performing a series of extensive simulations, we observed the irregular patterns, stationary strips, spots, and strips-spots mixture patterns. Numerical simulation results reveal that the regular strip-spot mixture patterns prevail over the whole domain on increasing the values of self- diffusion coefficients of phytoplankton and zooplankton and the dynamics of the system do not undergo any further changes.
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NONLINEAR NON-EQUILIBRIUM PATTERN FORMATION IN A SPATIAL AQUATIC SYSTEM: EFFECT OF FISH PREDATION
Journal of Biological Systems, 2010Co-Authors: Ranjit Kumar Upadhyay, N. K. Thakur, B. DubeyAbstract:An attempt has been made to introduce the mathematical modeling of nonlinear non-equilibrium spatio-temporal pattern formation in a minimal model of a spatial aquatic system. A hybrid model of the spatio-temporally continuous phytoplankton-zooplankton system with Holling type IV predator response but discrete agents like fish dynamics has been presented. The model has been investigated for plankton patch formation, which is known from natural plankton populations. Fish predation has a significant role in the temporal evolution of spatial pattern of phytoplankton-zooplankton system, which suggests that unstable diffusive system can be made stable by increasing the rate of fish predation and Diffusivity Constant to sufficiently large values.
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Spatiotemporal pattern formation in a diffusive predator-prey system: an analytical approach
Journal of Applied Mathematics and Computing, 2009Co-Authors: Balram Dubey, Nitu Kumari, Ranjit Kumar UpadhyayAbstract:In this paper, we propose and analyse a mathematical model to study the mathematical aspect of reaction diffusion pattern formation mechanism in a predator-prey system. An attempt is made to provide an analytical explanation for understanding plankton patchiness in a minimal model of aquatic ecosystem consisting of phytoplankton, zooplankton, fish and nutrient. The reaction diffusion model system exhibits spatiotemporal chaos causing plankton patchiness in marine system. Our analytical findings, supported by the results of numerical experiments, suggest that an unstable diffusive system can be made stable by increasing Diffusivity Constant to a sufficiently large value. It is also observed that the solution of the system converges to its equilibrium faster in the case of two-dimensional diffusion in comparison to the one-dimensional diffusion. The ideas contained in the present paper may provide a better understanding of the pattern formation in marine ecosystem.
Shihuai Deng - One of the best experts on this subject based on the ideXlab platform.
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Thin-layer drying kinetics and quality changes of sweet sorghum stalk for ethanol production as affected by drying temperature
Industrial Crops and Products, 2011Co-Authors: Fei Shen, Lin Peng, Yanzong Zhang, Xiaohong Zhang, Gang Yang, Hong Peng, Shihuai DengAbstract:Abstract The chopped sweet sorghum stalk was thin-layer-dried for long-term storage and ethanol production. The drying kinetics and the effects of drying temperature on the qualities of sweet sorghum stalk were investigated in this work. The results showed that the drying process could be simulated well by Wang and Singh's model. The Diffusivity Constant ( D 0 ) and active energy ( E a ) were estimated as 4.4 × 10 −5 m 2 /s and 21.4 kJ/(mol K) for drying the chopped fresh stalk. According to the sugar composition, browning degree, and fermentability of the dried stalk obtained at various temperatures, the approximate drying temperature could be suggested as 50–60 °C for application. In this range, the moisture of the chopped fresh stalk could drop below the safe moisture for storage in 7–5.5 h with 12.1–9.7% total sugar loss during the drying process.
Wan Ramli Wan Daud - One of the best experts on this subject based on the ideXlab platform.
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Drying kinetics and product quality of dried Chempedak
Journal of Food Engineering, 2008Co-Authors: Chien Hwa Chong, Chung Lim Law, Michael Cloke, Ching Lik Hii, Luqman Chuah Abdullah, Wan Ramli Wan DaudAbstract:The objective of this study was to investigate the drying kinetics of chempedak (Artocarpus integer) at different drying temperatures (50 °C, 60 °C, 70 °C) and slab dimensions. The drying data were fitted to the different semi-theoretical models based on moisture ratio (MR) to predict the drying kinetics. A logarithmic model was found to be the best fit in this study for all the drying temperatures tested. Effective diffusivities were estimated from Fick’s 2nd law and the Arrhenius equation was used to determine the Diffusivity Constant (Do) and activation energy (Ea). The texture and color of dried product were altered significantly during drying. The total color change (ΔE), hardness and chewiness were found to be increased with elevated temperature; meanwhile, springiness and cohesiveness of dried chempedak were relatively Constant.
Fei Shen - One of the best experts on this subject based on the ideXlab platform.
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Thin-layer drying kinetics and quality changes of sweet sorghum stalk for ethanol production as affected by drying temperature
Industrial Crops and Products, 2011Co-Authors: Fei Shen, Lin Peng, Yanzong Zhang, Xiaohong Zhang, Gang Yang, Hong Peng, Shihuai DengAbstract:Abstract The chopped sweet sorghum stalk was thin-layer-dried for long-term storage and ethanol production. The drying kinetics and the effects of drying temperature on the qualities of sweet sorghum stalk were investigated in this work. The results showed that the drying process could be simulated well by Wang and Singh's model. The Diffusivity Constant ( D 0 ) and active energy ( E a ) were estimated as 4.4 × 10 −5 m 2 /s and 21.4 kJ/(mol K) for drying the chopped fresh stalk. According to the sugar composition, browning degree, and fermentability of the dried stalk obtained at various temperatures, the approximate drying temperature could be suggested as 50–60 °C for application. In this range, the moisture of the chopped fresh stalk could drop below the safe moisture for storage in 7–5.5 h with 12.1–9.7% total sugar loss during the drying process.
Megat Mohamad Hamdan Megat Ahmad - One of the best experts on this subject based on the ideXlab platform.
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moisture absorption behavior of sugar palm fiber reinforced epoxy composites
Materials & Design, 2008Co-Authors: Zulkiflle Leman, A M Saifol, Md Abdul Maleque, S M Sapuan, Megat Mohamad Hamdan Megat AhmadAbstract:Abstract In engineering practice, moisture absorption test is generally used for quality control purposes and to measure the degradation of the quality for the composite materials. The objectives of this study are to investigate the value of Fickian Diffusivity Constant, moisture equilibrium content and correction factor for the natural fiber composites. Tests were carried out on composite plates, which was a combination of sugar palm fiber and epoxy resins and two different fiber compositions have been chosen which were 10% and 20% by weight. Pure epoxy plates have been used for the control measures. The specimens were oven dried for 60 h in an air-circulating oven operated with 108 °C before being immersed in the Constant temperature water bath, which the distilled water was set at 40 °C for the moisture absorption behavior test for 33 days. From this study, plates with 20% fiber loading possessed the highest amount of moisture prior to the moisture absorption behavior test, which is 0.93%. In moisture absorption behavior test, the corrected value of Fickian Diffusivity Constant for the 20% fiber loading is 3.76 × 10 −7 mm 2 /s, which is the highest among other composites. It is shown that, for composite plates that contain higher fiber composition, the moisture absorption rate is even higher.