A conventional clinical biopotential measurement system requires the use of wet electrodes that are in contact with skin using conductive gel. Those systems can acquire high-quality signals but may ...not be feasible for a long-term purpose due to the skin irritation and allergic contact dermatitis. The emerging of human-centered monitoring calls for alternative solutions. Recent technological advances enable capacitive measurement of electrophysiological measurement, which can acquire signals through cloth or even with an air gap; however, difficulties still exist. This paper systemically reviews the recent progress in capacitive measurement from electrode design, analog front end to high-level system architecture, aiming to provide comprehensive and practical instructions for entire system design. The current development serves as the solid fundamental, raising new solutions for future improvement. In addition, the challenges and the strategies are highlighted in order to demonstrate a technical guide. Some perspectives based on our experience are also discussed hoping to inspire new idea and technique in this area.
•3D coupled Finite Element Model (FEM) for a vertical geothermal heat exchanger.•Model validation via the experimental data from an in-service GHE.•Sensitivity analysis on the influencing ...factors.•Continuous operation behaviors versus short term transient responses.
This paper conducts sensitivity analyses on factors affecting the performance of vertical geothermal heat pump system, aiming to formulate design and operation strategies to improve its performance. It firstly describes the development of a 3D coupled Finite Element Model (FEM), which is utilized to simulate the steady state and transient behaviors of geothermal heat exchanger (GHE). The model holistically couples the heat exchange processes between pipe fluid flow, grouting backfill material, and adjacent ground associated with GHE. The model is firstly validated by comparison with the experimental data from an in-service GHE. Base on the calibrated model, a series of sensitivity analyses are conducted on the influence of geological, design, and operational factors intermittent operation mode of GHE achieves higher such as the initial ground temperature profile, GHE pipe installation depth, circulation fluid flow velocity, inlet temperature, subsurface water flow velocity, and material thermal properties. It also assess the behaviors of GHE under continuous operation versus intermittent operation modes. The results show that both design parameter (i.e., GHE pipe installation depth) and operational parameters (i.e., circulation fluid flow velocity) have major influence on the GHE performance. For a certain design length of GHE, the GHE performance improves with higher circulation fluid flow velocity until beyond a critical velocity. For GHE working in the heating mode, the heat extraction by GHE increases with decreasing fluid temperature at the inlet. In the geological factor aspect, the thermal conductivity of the ground material plays a very important role on the GHE performance operating in the continuous operation mode, while its specific heat capacity exerts no appreciable influence. However, for intermittent operation mode, both thermal conductivity and specific heat capacity of the ground, particularly the grouting materials, affect the ground thermal energy extraction. The results also showed that the presence of subsurface ground water flow improves the heat exchange of GHE. Operation wise, the GHE achieves higher performance and Coefficient of Performance (COP) under intermittent operation mode than under continuous operation mode. These observations point to ways to improve the performance of GHE from both design and operation aspects.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Thermochromic materials possess the ability to reversibly change the optical properties in response to the environmental temperature. They have the potential to reduce the energy demand in building ...operations by modulating the heat transport through the building envelope, i.e., limiting undesired solar heat gain during the hot seasons and increasing solar heat gain during the cold seasons. This is an advantage over conventional cool roof technology. This study aims to evaluating the performance of adaptive thermochromic roof designed by covering regular building roof with thermochromic (TC) coating. TC coating is prepared by incorporating thermochromic pigment and TiO2 nanoparticle is added to enhance its effectiveness. Optical characterisation shows the temperature-dependent solar reflectance of 18–26% for TC coating and 35–59% for TC/TiO2 coating. EnergyPlus analyses is performed to evaluate impact of thermochromic roof on energy performance of the buildings in seven U.S. geographic locations. The simulation results show that compared to common roof (asphalt shingle), thermochromic roof is effective in reducing the building HVAC load demand, which saves up to 40.9% of total energy consumption, 47.7% of energy cost, and 46.7% of energy associated CO2 emissions for the buildings in San Fran., CA. In comparison with conventional cool roof, thermochromic roof demonstrates benefits in reducing the overall energy use of the buildings, which reduces up to 7.7% of total energy consumption, 3.6% of energy cost, and 28.5% of energy associated CO2 emissions. The effectiveness of thermochromic roof depends upon the geographic regions. This work demonstrates that performance of thermochromic roof systems to improve energy efficiency of buildings across different climatic zones.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Snow melting system based on geothermal heat exchanger pile is an innovative technology that combines geothermal energy with structural foundation. It overcomes the problems of conventional chemical ...based snow melting in mitigating infrastructure corrosion and negative environmental effects. By integrating the underground heat exchanger into pile foundation that support the bridge structure, it effectively reduces the installation cost of geothermal system. This paper analyses the applicability and performance of such snow melting system for different regions. Energy demand for snow removal is firstly determined with ASHRAE criteria. A holistic 3D simulation model is developed to predict the energy extraction rate under different operation conditions. A hypothetical bridge deck (200 m length by 14.8 m (4 lanes) width) is analyzed to assess the feasibility of geothermal heat exchanger pile based snow melting system for 10 cities representing a variety of climatic regions of the United States. The number of pile foundation required for snow melting is used as indication of the technical feasibility. The results show that its feasibility and performance in bridge deck snow removal is dependent upon the geological and snow conditions of a particular region, as well as the design snow removal criteria.
•Analyses method for geothermal heat exchanger pile in bridge deck snow removal.•Simulation model to predict the energy extraction rates under different conditions.•Assessment framework for technique feasibility of geothermal based deicing system.•Elucidation on the critical role of local geological and snow conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•A case study of in-service geothermal heat pump for residential house.•Real time monitoring data that describes the GHE performance.•Geothermal installation under sedimentary shale rock ...formation.•Strategies to reduce barriers for geothermal installation.
The use of ground-source heat pump system has been widely adopted over the past decades due to its potentials to provide renewable and low carbon footprint energy source for building’s heating and air-conditioning needs. This paper reports the design and post construction monitoring of a vertical ground-coupled heat pump system installed adjacent to a three-floor residential house located in Cleveland, OH, USA. The system operates under the special geological condition with shallow depth outcrop of sedimentary shale rock formation typical of Northeastern Ohio, USA. A comprehensive monitoring program was installed to collect data on the operation and performance of the ground-coupled heat pump system. The data recording was initialized in Oct. 2012 and has been in place ever since. Overall, the monitoring data shows that the ground heat pump achieved very good performance. The coefficient of performance (COP) of ground coupled heat pump system ranges from 3 to 4. The heat pump satisfies most of the house heating requirements, including severe cold winter, during the monitoring period. This case study demonstrates the feasibility of ground-coupled heat pump system in providing Heating Ventilation and Air Conditioning (HVAC) source for residential building for either heating dominant or cooling dominant conditions under sedimentary rock geological conditions. The possible solutions to decrease the initial investment are proposed in the study.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This paper describes an in-vehicle nonintrusive biopotential measurement system for driver health monitoring and fatigue detection. Previous research has found that the physiological signals ...including eye features, electrocardiography (ECG), electroencephalography (EEG) and their secondary parameters such as heart rate and HR variability are good indicators of health state as well as driver fatigue. A conventional biopotential measurement system requires the electrodes to be in contact with human body. This not only interferes with the driver operation, but also is not feasible for long-term monitoring purpose. The driver assistance system in this paper can remotely detect the biopotential signals with no physical contact with human skin. With delicate sensor and electronic design, ECG, EEG, and eye blinking can be measured. Experiments were conducted on a high fidelity driving simulator to validate the system performance. The system was found to be able to detect the ECG/EEG signals through cloth or hair with no contact with skin. Eye blinking activities can also be detected at a distance of 10 cm. Digital signal processing algorithms were developed to decimate the signal noise and extract the physiological features. The extracted features from the vital signals were further analyzed to assess the potential criterion for alertness and drowsiness determination.
The performance of a variety of geostructures, such as compacted clay liners, earth dams, and pavement embankments, is compromised by soil cracking. Experiments are set up to monitor the drying ...process of a clay layer under controlled temperature and humidity conditions. The gravimetric water content and images are captured automatically. Volumetric shrinkage of the bentonite sample as well as the crack patterns are determined from images. The monitored volumetric strain development is used to implement the discrete element method (DEM) to simulate the drying shrinkage and desiccation cracking. Model parameters are calibrated through unconfined compression tests on clay specimens at different water contents. This simplified calibration procedure allows characterization of the soil behaviors in the mesoscale and bypass the complex physicochemical processes involved. The initiation and propagation of cracks from the DEM model agree well with the phenomena observed in the laboratory experiments. The influence of boundary constraint and sample thickness on the crack patterns is analyzed, which includes the use of hydrophobic coating to diminish the boundary constraint. Major features of desiccation cracking can be replicated with the computational procedures. Boundary constraint, including surface roughness and strength of boundary layer, is found to significantly influence the final crack patterns.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A fluid–solid interaction model has been implemented by coupling two numerical methods — computational fluid dynamics (CFD) and discrete element method (DEM) — that capture the mesoscale behaviors of ...the fluid–solid system. The model is first validated by comparing the results of simulations with two types of experiments: free settling of a single sphere in water and formation of angle of repose of particles under water, which show its capability in modeling the behaviors of both particle phase and fluid phase. The verified model is then used to study factors affecting the soil erodibility, where case studies are designed for soil particles deposited inside a pipe and subsequently subjected to water flow–induced surface erosion. Influencing factors for soil erodibility, including particle diameter and interparticle bond, are analyzed. For cohesionless soils without bond strength, the critical shear stress is found to be linearly related to particle size; while for soils with bond strength, simulation results show that interparticle bonding largely decelerates the erosion process and causes a much lower erosion rate. To further the understanding of soil surface erosion under turbulent flow, the “k–ε” turbulence model has been successfully implemented for the fluid phase. Comparison between the laminar model and the turbulence model shows turbulence significantly accelerates the erosion process.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Water distribution networks (WDNs) are critical infrastructure for communities. The dramatic expansion of the WDNs associated with urbanization makes them more vulnerable to high‐consequence hazards ...such as earthquakes, which requires strategies to ensure their resilience. The resilience of a WDN is related to its ability to recover its service after disastrous events. Sound decisions on the repair sequence play a crucial role to ensure a resilient WDN recovery. This paper introduces the development of a graph convolutional neural network‐integrated deep reinforcement learning (GCN‐DRL) model to support optimal repair decisions to improve WDN resilience after earthquakes. A WDN resilience evaluation framework is first developed, which integrates the dynamic evolution of WDN performance indicators during the post‐earthquake recovery process. The WDN performance indicator considers the relative importance of the service nodes and the extent of post‐earthquake water needs that are satisfied. In this GCN‐DRL model framework, the GCN encodes the information of the WDN. The topology and performance of service nodes (i.e., the degree of water that needs satisfaction) are inputs to the GCN; the outputs of GCN are the reward values (Q‐values) corresponding to each repair action, which are fed into the DRL process to select the optimal repair sequence from a large action space to achieve highest system resilience. The GCN‐DRL model is demonstrated on a testbed WDN subjected to three earthquake damage scenarios. The performance of the repair decisions by the GCN‐DRL model is compared with those by four conventional decision methods. The results show that the recovery sequence by the GCN‐DRL model achieved the highest system resilience index values and the fastest recovery of system performance. Besides, by using transfer learning based on a pre‐trained model, the GCN‐DRL model achieved high computational efficiency in determining the optimal repair sequences under new damage scenarios. This novel GCN‐DRL model features robustness and universality to support optimal repair decisions to ensure resilient WDN recovery from earthquake damages.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Shale gas is becoming an important energy source worldwide. The geomechanical properties of shale rocks can have a major impact on the efficiency of shale gas exploration. This paper studied the ...mineralogical and mechanical characteristics of a typical gas shale in Ohio, USA. Scanning electron microscope (SEM) with energy dispersive X-ray (EDX) analyses was employed to measure the microstructure and material composition of the shale rock. The anisotropic behaviors of shale rock, including compressive and tensile strengths, were experimentally measured. The characteristics of shale rock were also studied by nondestructive wave speed measurements. The shale demonstrated strong anisotropic behaviors with the tensile strengths perpendicular to the bedding plane around 300–360 times of that parallel to bedding plane. Results of ultrasonic tests indicated that both compression and shear wave velocities show strong anisotropic patterns. The compression wave speed was the smallest in the direction perpendicular to the bedding plane; while the shear wave speed was the smallest in the direction parallel to the bedding plane. The ratio of wave speed anisotropy is around 1.3–1.4 for compression wave; the ratio of shear wave speed anisotropy is larger and more diverse compared with the compression wave anisotropy. This might be related to the larger variability in the frictional adhesive strength along bedding plane than the compressive adhesive strength.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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