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Browsing by Author Wang, Y.

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A robust data‐worth analysis framework for soil moisture flow by hybridizing sequential data assimilation and machine learning

Authors: Wang, Y.; Advisor: -; Participants: Shi, L.; Lin, L.; Holzman, M.; Carmona, F.; Zhang, Q. (2020)

As the collection of soil moisture data is often costly, it is essential to implement data‐worth analysis in advance to obtain a cost‐effective data collection scheme. In previous data‐worth analysis, the model structural error is often neglected. In this paper, we propose a robust data‐worth analysis framework based on a hybrid data assimilation method. By constructing Gaussian process (GP) error model, this study attempts to alleviate biased data‐worth assessments caused by unknown model structural errors, and to excavate complementary values of multisource data without resorting to multiple governing equations. The results demonstrated that this proposed framework effectively ident...

Finger Flow Development in Layered Water‐Repellent Soils

Authors: Wang, Y.; Advisor: -; Participants: Li, Y.; Wang, X.; Chau, H.W. (2018)

The results showed: (i) the temporal variations of cumulative infiltration (CI) decreased with the increase of the WR level so that CI was generally larger when the top layer was sandy loam rather than clay loam and therefore the top layer soil texture controlled CI more than the sublayer; (ii) for the wettable treatments, finger flow was clearly and uniformly generated in layered soils with a sublayer of heavy gravel rather than sand, but for WR layered treatments, fingers developed irregularly with the WR levels and finger length, width, and velocity varied with the WR levels; (iii) there were good power function or linear correlations between CI and cumulative wetting area, and bet...

Influence of climate change and human activity on water resources in arid region of Northwest China: An overview

Authors: Qin, D.; Wang, Y.; Advisor: -; Participants: - (2017)

This study reviews the latest progress in research on climate change and water resources in the arid region of Northwest China, analyzes the cause of water resource changes within the region from the perspective of climate change and human activities, and summarizes future likely changes in water resources and associated adaptation strategies. Recommendations for future studies are suggested that include characteristics of changes in extreme weather events and their impacts on water resources, projections of future climate and water resource changes, climate change attribution, the selection of adaptation strategies relating to climate change and social economic activities, and use of...

Map based segmentation of airborne laser scanner data

Authors: Wang, Y.; Advisor: -; Participants: - (2016)

The task of segmenting point clouds is to group points that belong to the same (part of an) object. In this project we make use of an existing topographic map as a kind of background layer to segment point clouds acquired by airborne laser scanning systems. This map is an object based representation into polygons which are labelled into topographic classes like buildings, roads, terrain, water and vegetation. We implemented a point-in-polygon operation which is succeeded by a relabeling step at locations of roof overhangs. Next, the topographic class of the object is used to correctly process the point cloud into meaningful segments. The type of segmentation, e.g. planar or smooth seg...

Map based segmentation of airborne laser scanner data

Authors: Wang, Y.; Advisor: -; Participants: - (2016)

Policy Analysis of Agricultural Water Fee Collection in China

Authors: Chen, S.; Wang, Y.; Advisor: -; Participants: - (2013)

The low collection rate of agricultural irrigation water fee is a common problem facing many developing countries, which has also troubled China since the 2000s. In different areas of China, there are two problem-solving strategies: raising water collection rate or exempting water fee. In this paper, we analyze the dilemma of China's agricultural water fee collection from both practical and theoretical perspective. We argue that China will not follow up one single model in agricultural water fee collection and each local government should explore appropriate policy in line with their own situation.

Water Movement and Finger Flow Characterization in Homogeneous Water‐Repellent Soils

Authors: Wang, Y.; Advisor: -; Participants: Wang, X.; Chau, H.W.; Si, B.; Yao, N.; Li, Y. (2018)

Soil water repellency (SWR) is a widespread property in soils around the world. It influences soil water movement and causes unstable flow. The mechanics of finger flow occurrence in water‐repellent soils are not clearly understood. Slab chamber infiltration experiments consisting of increasing SWR persistence in clay and sandy loam soils were conducted to compare wetting front advancement and mechanics of finger flow development. The temporal variation curves of cumulative infiltration (CI) decreased with an increase in SWR persistence. For wettable soils, the wetting front advanced regularly with time, but for water‐repellent soils, it became unstable and finger flow occurred as the...