Object-oriented implementation of 3D DC adaptive finite-element method

In this paper, we introduced a clear object-oriented framework to implement the complicated adaptive procedure with C ++ programming language. In this framework, it consisted of the unstructured mesh generation, a-posterior error estimating, adaptive strategy, and the postprocessing. Unlike the procedure-oriented framework, which is commonly used in DC resistivity modeling with FORTRAN language, the object-oriented one, which is famous for its characteristic of encapsulation, could be used for a class of problems that would be executed by only making some changes on the user interface. To validate its flexibility, two synthetic DC examples were tested her

Highly sensitive twist sensor based on partially silver coated hollow core fiber structure

Interferometer based on multiple beam interferences inside a hollow core fiber (HCF) structure (also known as an anti-resonant reflecting optical waveguide) has been attracting interest of many researchers due to its periodic transmission spectrum containing high quality factor spectral dips. Functionalized HCF structures have been demonstrated for a wide range of applications in humidity, magnetic field and bio-sensing. Here, we report a new application of the HCF based structure with a partial silver coating layer for sensing of twist. It is configured by fusion splicing a section of 4.5-mm long HCF between two standard single mode fibers (SMFs), followed by a sputter-coating of a very thin layer of silver on one side of the HCF surface. It is found that the spectral response of the partially silver coated HCF structure is very sensitive to the changes of input light polarization. An increase in sensitivity of the fiber structure to twist after deposition of the silver coating when twist is applied to both the SMF and HCF sections is demonstrated by comparison with an uncoated HCF fiber structure. Experimental results show that twisting of the HCF section results in much greater changes in a selected dip’s strength compared to that in the case of twisting the SMF section of the structure. The proposed HCF fiber sensors with 4.5 nm and 6.7 nm-thick silver layers show the highest sensitivities of 0.647 dB/°and 0.717 dB/° in the twist angles range of up to 10°. To the best of our knowledge, this is the highest twist sensitivity reported for intensity modulation based fiber sensors. Moreover, the proposed sensor offers excellent measurement repeatability

Fabrication and Sensing Applications of Special Microstructured Optical Fibers

This chapter presents the fabrication of the special microstructured optical fibers (MOFs) and the development of sensing applications based on the fabricated fibers. Particularly, several types of MOFs including birefringent and photosensitive fibers will be introduced. To fabricate the special MOFs, the stack-and-draw technique is employed to introduce asymmetrical stress distribution in the fibers. The microstructure of MOFs includes conventional hexagonal assembles, large-air hole structures, as well as suspended microfibers. The birefringence of MOFs can reach up to 10−2 by designing the air hole structure properly. Fiber Bragg gratings as well as Sagnac interferometers are developed based on the fabricated special MOFs to conduct sensing measurement. Various sensing applications based on MOFs are introduced

Optimization method and application research of dewatering design for complicated foundation pits

The groundwater control system of complex deep foundation pit engineering is designed based on experience and analysis of items such as dewatering, anti-inrushing, water-recharging, etc. Three-dimensional numerical simulation methods are used to optimize the design. By repeatedly adjusting the design items and simulating the working system, a safer, more reasonable and economical design scheme can be confirmed by comparing the analysed results

Revealing the spatio-temporal coupling coordination characteristics and influencing factors of carbon emissions from urban use and ecosystem service values in China at the municipal scale

In the context of the “dual-carbon” goal, studying the complex relationship between carbon emissions and ecosystem service values brought about by land-use change is of great significance in promoting regional low-carbon optimization, territorial spatial governance, and the achievement of the goal of carbon peaking and carbon neutrality. This study takes 286 cities in China as the research object, and based on the data of China’s land use and ecosystem service value (ESV) from 2012 to 2022, adopts geo-spatial analysis techniques such as spatial autocorrelation and geographically-weighted regression models to study the spatial and temporal characteristics, the degree of coupling coordination, and the influencing factors of China’s municipal total land use carbon emissions and ESV. The results show that (1) China’s total land-use carbon emissions have exhibited an overall increasing trend from 2012 to 2022. The total ESV has shown a downward trend characterized by an inverted “N” shape. (2) The coupling coordination effect between land-use carbon emissions and ESV in China generally shows a mirrored “L” growth shape. (3) There is a significant spatial negative correlation between land-use carbon emissions and ESV, primarily manifested as “high-high,” “high-low,” and “low-low” clustering characteristics. (4) Three socio-economic factors—local fiscal general budget expenditure, energy utilization efficiency, and total population—positively influence the coupling coordination of land-use carbon emissions and ESV. Strictly controlling the local fiscal general budget expenditure, energy utilization efficiency, and total population can effectively promote China's green, low-carbon development and ecological security

A comparative study of using spatial-temporal graph convolutional networks for predicting availability in bike sharing schemes

Accurately forecasting transportation demand is crucial for efficient urban traffic guidance, control and management. One solution to enhance the level of prediction accuracy is to leverage graph convolutional networks (GCN), a neural network based modelling approach with the ability to process data contained in graph based structures. As a powerful extension of GCN, a spatial-temporal graph convolutional network (ST-GCN) aims to capture the relationship of data contained in the graphical nodes across both spatial and temporal dimensions, which presents a novel deep learning paradigm for the analysis of complex time-series data that also involves spatial information as present in transportation use cases. In this paper, we present an Attention-based ST-GCN (AST-GCN) for predicting the number of available bikes in bike-sharing systems in cities, where the attention-based mechanism is introduced to further improve the performance of an ST-GCN. Furthermore, we also discuss the impacts of different modelling methods of adjacency matrices on the proposed architecture. Our experimental results are presented using two real-world datasets, Dublinbikes and NYC-Citi Bike, to illustrate the efficacy of our proposed model which outperforms the majority of existing approaches

Highly Sensitive Twist Sensor Based on Partially Silver Coated Hollow Core Fiber Structure

Interferometer based on multiple beam interferences inside a hollow core fiber (HCF) structure (also known as an antiresonant reflecting optical waveguide) has been attracting interest of many researchers due to its periodic transmission spectrum containing high quality factor spectral dips. Functionalized HCF structures have been demonstrated for a wide range of applications in humidity, magnetic field, and biosensing. Here, we report a new application of the HCF-based structure with a partial silver coating layer for sensing of twist. It is configured by a fusion splicing a section of 4.5-mm long HCF between two standard single mode fibers (SMFs), followed by a sputter-coating of a very thin layer of silver on one side of the HCF surface. It is found that the spectral response of the partially silver coated HCF structure is very sensitive to the changes of input light polarization. An increase in sensitivity of the fiber structure to twist after deposition of the silver coating when the twist is applied to both the SMF and HCF sections is demonstrated by comparison with an uncoated HCF fiber structure. Experimental results show that twisting of the HCF section results in much greater changes in a selected dip\u27s strength compared to that in the case of twisting the SMF section of the structure. The proposed HCF fiber sensors with 4.5-nm and 6.7 nm-thick silver layers show the highest sensitivities of 0.647 dB/°and 0.717 dB/° in the twist angles range of up to 10°. To the best of our knowledge, this is the highest twist sensitivity reported for intensity modulation-based fiber sensors. Moreover, the proposed sensor offers excellent measurement repeatability

Ultrasensitive cascaded in-line Fabry-Perot refractometers based on a C-shaped fiber and the Vernier effect.

peer reviewedWe propose and experimentally demonstrate a fiber refractometer based on a C-shaped fiber and the Vernier effect. The sensor is fabricated by cascading a single mode fiber (SMF) pigtail together with a C-shaped fiber segment and another SMF segment. Thus, the C-shaped fiber would constitute an open cavity (sensing cavity) in which test analytes could be filled, while the SMF segment would constitute another reference cavity. Due to the similar optical path length of these two cavities, the Vernier effect would be activated, thus forming spectral envelops in the reflection spectrum of the sensor. Variations in the refractive index (RI) of analytes would result in the shifts of the spectral envelops. Both theoretical calculations and experiments are carried out in the characterization of the sensor measuring liquid and gaseous analytes. The experimental sensitivity of the sensor is found to be ∼37238 nm/RIU for gas RI measurement. The proposed sensor features the advantages such as ease of fabrication, extremely high sensitivity, capability of sensing of both gaseous and liquid analytes, small footprint, and good mechanical strength. Compared to other existing Vernier effect-based fiber refractometers typically fabricated using PCFs, the proposed sensor would allow analytes to have much easier and quicker access to the sensor probe

An intelligent multi-speed advisory system using improved whale optimisation algorithm

An intelligent speed advisory system can be used to recommend speed for vehicles travelling in a given road network in cities. In this paper, we extend our previous work where a distributed speed advisory system has been devised to recommend an optimal consensus speed for a fleet of Internal Combustion Engine Vehicles (ICEVs) in a highway scenario. In particular, we propose a novel optimisation framework where the exact format of each vehicle’s cost function can be implicit, and our algorithm can be used to recommend multiple consensus speeds for vehicles travelling on different lanes in an urban highway scenario. Our studies show that the proposed scheme based on an improved whale optimisation algorithm can effectively reduce CO2 emission generated from ICEVs while providing different recommended speed options for groups of vehicles