Land subsidence over oilfields in the Yellow River Delta

Subsidence in river deltas is a complex process that has both natural and human causes. Increasing human activities like aquaculture and petroleum extraction are affecting the Yellow River delta, and one consequence is subsidence. The purpose of this study is to measure the surface displacements in the Yellow River delta region and to investigate the corresponding subsidence source. In this paper, the Stanford Method for Persistent Scatterers (StaMPS) package was employed to process Envisat ASAR images collected between 2007 and 2010. Consistent results between two descending tracks show subsidence with a mean rate up to 30 mm/yr in the radar line of sight direction in Gudao Town (oilfield), Gudong oilfield and Xianhe Town of the delta, each of which is within the delta, and also show that subsidence is not uniform across the delta. Field investigation shows a connection between areas of non-uniform subsidence and of petroleum extraction. In a 9 km2 area of the Gudao Oilfield, a poroelastic disk reservoir model is used to model the InSAR derived displacements. In general, good fits between InSAR observations and modeled displacements are seen. The subsidence observed in the vicinity of the oilfield is thus suggested to be caused by fluid extraction

Reinforcement learning control for coordinated manipulation of multi-robots

In this paper, coordination control is investigated for multi-robots to manipulate an object with a common desired trajectory. Both trajectory tracking and control input minimization are considered for each individual robot manipulator, such that possible disagreement between different manipulators can be handled. Reinforcement learning is employed to cope with the problem of unknown dynamics of both robots and the manipulated object. It is rigorously proven that the proposed method guarantees the coordination control of the multi-robots system under study. The validity of the proposed method is verified through simulation studies

Microstructured optical fibres in chalcogenide glass

Chalcogenide glasses offer transmission windows within the far-visible, near- and mid-infrared (IR) range. They exhibit potentially excellent linear and large nonlinear optical properties, photosensitivity and their low phonon energies are conducive to efficient dopant rare earth transitions. These properties enable many potential infrared applications: large-scale optics; fibreoptics; integrated optics; optical imaging; optical data storage and all-optical switching. Two lines of experimental work were followed in this project based on chalcogenide glasses, as below: (1) Antimony was used to replace arsenic, to form the ternary Ge-Sb-Se glass system. Nine compositions of Ge-Sb-Se glasses were synthesised and characterised to reveal their glass forming abilities, thermal properties and optical properties. Glass pairs, with close thermal properties and relatively high refractive index contrast, were developed for fabricating core-clad. structure step index fibre and microstructured optical fibres (MOFs). (2) Fabrication of an all-solid chalcogenide glass microstructured fibre (MOF), which was designed as a mimic of the holey suspended structure silica MOF, was carried out. A cane-drawing technique and a real-time contactless diameter monitor of the chalcogenide canes were developed to improve the precision of the fabrication. Stacking equipment was designed to improve the technique of the chalcogenide preform stacking

A novel method to determine droop coefficients of DC voltage control for VSC-MTDC system

For droop control in voltage source converter based multi-terminal HVDC systems, the determination of droop coefficients is a key issue, which directly affects both power distribution and DC control performances. This paper proposes a novel design of droop coefficients considering the requirements of power distribution, DC voltage control and system stability. Considering the power margins of different converters, the ratio relationship among droop coefficients is established. Converters with larger power margins take bigger portion of power mismatch to avoid overload problem. Furthermore, the integral square error of converters DC voltage is adopted as the DC voltage control performance index, and optimization of droop coefficients to achieve coordinated DC voltage control of steady-state deviation and transient variation, is derived. Finally, the constraint of droop coefficients is established to guarantee the DC system stability after power disturbance. Case studies are conducted on the Nordic 32 system with an embedded 4-terminal DC grid to demonstrate the feasibility and effectiveness of the proposed droop control scheme

Visual landmark sequence-based indoor localization

This paper presents a method that uses common objects as landmarks for smartphone-based indoor localization and navigation. First, a topological map marking relative positions of common objects such as doors, stairs and toilets is generated from floor plan. Second, a computer vision technique employing the latest deep learning technology has been developed for detecting common indoor objects from videos captured by smartphone. Third, second order Hidden Markov model is applied to match detected indoor landmark sequence to topological map. We use videos captured by users holding smartphones and walking through corridors of an office building to evaluate our method. The experiment shows that computer vision technique is able to accurately and reliably detect 10 classes of common indoor objects and that second order hidden Markov model can reliably match the detected landmark sequence with the topological map. This work demonstrates that computer vision and machine learning techniques can play a very useful role in developing smartphone-based indoor positioning applications

Building Cascaded Hierarchical Real Estate Market Based on the Housing Consumption Theory and the Security Theory

The excessively high price not only has adverse impact on the development of the entire national economy, what’s more, it goes against the settlement of livelihood problems and the construction of harmonious society. To solve the current high price’s dilemma, it should combine the local real income levels of China, and perfect market structure according to the effective housing demands, then build up three high, middle and low real estate markets with independent operation, and mutual connection and conversion, in order to control the house prices, realize the basic needs of social housing, and solve the housing problems of urban residents. Key words: Housing theory; Effective demand; Real estate marke