The management of peat swamp forests in Malaysia contends with two major issues: forest fires and the effects of abandoned forest-logging drainage systems or canals. Forest fire occurs during low rainfall season relat...The management of peat swamp forests in Malaysia contends with two major issues: forest fires and the effects of abandoned forest-logging drainage systems or canals. Forest fire occurs during low rainfall season related to the local people activities. The drainage networks change the hydrological function of the intact forest ecosystem. A key function of the hydrological system in the undisturbed forest is to absorb water during rainfall season, thus delaying downstream runoff and preventing flash floods. The objective of the project described here is to restore the hydrological function of peat swamp forest (PSF) at Ayer Hitam North Forest Reserve (AHNFR) in Muar, Johor, Malaysia. The oil palm plantations, especially in the southern part of the area affect the forest reserve. Water flows out of the forest reserve through the drainage system constructed for managing these plantations. In 2016 and 2017, two water block structures or check dams were constructed near the boundaries of the forest reserve to hold the water and raise the groundwater level in the forest reserve. The implementation of the check dams at the two locations has conserved the groundwater level and subsequently, about 1.2 million m<sup>3</sup> of water was saved annually from leaving the forest reserve from each of the check dam. This project is also part of the Coca-Cola Company’s sustainability commitment for water strategy with the global that is to replenish 100% of the equivalent volume of water consumed in their products and production by 2020. Replenishment is the key sustainability commitment for the Company.展开更多
By coupling the standard and the conservative level set methods, an improved conservative level set method is proposed to capture the free surface smoothly with excellent mass conservation properties. The improvement ...By coupling the standard and the conservative level set methods, an improved conservative level set method is proposed to capture the free surface smoothly with excellent mass conservation properties. The improvement lies in the fact that the surface normal is computed from a signed distance function instead of the Heaviside function. Comparing with the conservative level set method, the inevitable numerical discretization errors to point the surface normal in arbitrary directions could be eliminated, and the instability of the numerical solution could be improved efficiently. The advantage is clear in the straightforward combination of the standard level set and the conservative level set and a little effort is taken in coding compared with other coupled methods. The present method is validated with several well-known benchmark problems, including the 2-D Zalesak＇s disk rotating, the 3-D sphere stretching in deformation vortex and the dam break flow simulation. The results are shown to be in good agreement with the published experimental data and numerical results.展开更多
Transient stability assessment(TSA) is of great importance in power systems. For a given contingency, one of the most widely-used transient stability indices is the critical clearing time(CCT), which is a function of ...Transient stability assessment(TSA) is of great importance in power systems. For a given contingency, one of the most widely-used transient stability indices is the critical clearing time(CCT), which is a function of the pre-fault power flow.TSA can be regarded as the fitting of this function with the prefault power flow as the input and the CCT as the output. In this paper, a data-driven TSA model is proposed to estimate the CCT. The model is based on Mahalanobis-kernel regression,which employs the Mahalanobis distance in the kernel regression method to formulate a better regressor. A distance metric learning approach is developed to determine the problem-specific distance for TSA, which describes the dissimilarity between two power flow scenarios. The proposed model is more accurate compared to other data-driven methods, and its accuracy can be further improved by supplementing more training samples.Moreover, the model provides the probability density function of the CCT, and different estimations of CCT at different conservativeness levels. Test results verify the validity and the merits of the method.展开更多
A numerical model is proposed for the simulation of impulse waves generated by landslides. The fluid-like landslide is modeled as a generalized non-Newtonian visco-plastic fluid. The conservative level set method is e...A numerical model is proposed for the simulation of impulse waves generated by landslides. The fluid-like landslide is modeled as a generalized non-Newtonian visco-plastic fluid. The conservative level set method is extended to the n-phase flow and applied to capture the interfaces of air, water and landslide. Numerical results show an excellent performance of the current model to capture the whole process of the landslide and the impulse wave generation.展开更多
文摘The management of peat swamp forests in Malaysia contends with two major issues: forest fires and the effects of abandoned forest-logging drainage systems or canals. Forest fire occurs during low rainfall season related to the local people activities. The drainage networks change the hydrological function of the intact forest ecosystem. A key function of the hydrological system in the undisturbed forest is to absorb water during rainfall season, thus delaying downstream runoff and preventing flash floods. The objective of the project described here is to restore the hydrological function of peat swamp forest (PSF) at Ayer Hitam North Forest Reserve (AHNFR) in Muar, Johor, Malaysia. The oil palm plantations, especially in the southern part of the area affect the forest reserve. Water flows out of the forest reserve through the drainage system constructed for managing these plantations. In 2016 and 2017, two water block structures or check dams were constructed near the boundaries of the forest reserve to hold the water and raise the groundwater level in the forest reserve. The implementation of the check dams at the two locations has conserved the groundwater level and subsequently, about 1.2 million m<sup>3</sup> of water was saved annually from leaving the forest reserve from each of the check dam. This project is also part of the Coca-Cola Company’s sustainability commitment for water strategy with the global that is to replenish 100% of the equivalent volume of water consumed in their products and production by 2020. Replenishment is the key sustainability commitment for the Company.
基金supported by the National Natural Science Foundation of China(Grant No.51279050)the National High Technology Research and Development Program of China(863 Program,Grant No.2012BAK10B04)the Non-profit Industry Financial Program of Ministry of Water Resources of China(Grant No.201301058)
文摘By coupling the standard and the conservative level set methods, an improved conservative level set method is proposed to capture the free surface smoothly with excellent mass conservation properties. The improvement lies in the fact that the surface normal is computed from a signed distance function instead of the Heaviside function. Comparing with the conservative level set method, the inevitable numerical discretization errors to point the surface normal in arbitrary directions could be eliminated, and the instability of the numerical solution could be improved efficiently. The advantage is clear in the straightforward combination of the standard level set and the conservative level set and a little effort is taken in coding compared with other coupled methods. The present method is validated with several well-known benchmark problems, including the 2-D Zalesak＇s disk rotating, the 3-D sphere stretching in deformation vortex and the dam break flow simulation. The results are shown to be in good agreement with the published experimental data and numerical results.
基金supported by National Key R&D Program of China (No.2018YFB0904500)State Grid Corporation of China。
文摘Transient stability assessment(TSA) is of great importance in power systems. For a given contingency, one of the most widely-used transient stability indices is the critical clearing time(CCT), which is a function of the pre-fault power flow.TSA can be regarded as the fitting of this function with the prefault power flow as the input and the CCT as the output. In this paper, a data-driven TSA model is proposed to estimate the CCT. The model is based on Mahalanobis-kernel regression,which employs the Mahalanobis distance in the kernel regression method to formulate a better regressor. A distance metric learning approach is developed to determine the problem-specific distance for TSA, which describes the dissimilarity between two power flow scenarios. The proposed model is more accurate compared to other data-driven methods, and its accuracy can be further improved by supplementing more training samples.Moreover, the model provides the probability density function of the CCT, and different estimations of CCT at different conservativeness levels. Test results verify the validity and the merits of the method.
基金supported by the National Natural Science Foundation of China(Grant No.51279050)the National High Technology Research Development Program of China(863 Pro-gram,Grant No.2012AA112507)the Non-profit Industry Financial Program of Ministry of Water Resources of China(Grant No.201301058)
文摘A numerical model is proposed for the simulation of impulse waves generated by landslides. The fluid-like landslide is modeled as a generalized non-Newtonian visco-plastic fluid. The conservative level set method is extended to the n-phase flow and applied to capture the interfaces of air, water and landslide. Numerical results show an excellent performance of the current model to capture the whole process of the landslide and the impulse wave generation.
