A common assumption in models of water flow from soil to root is that the soil can be described in terms of its representative or effective behavior. Microscale heterogeneity and structure are ...thereby replaced by effective descriptions, and their role in flow processes at the root‐soil interface is neglected. Here the aim was to explore whether a detailed characterization of the microscale heterogeneity at the scale of a single root impacts the relation between flow rate and pressure gradient. Numerical simulations of water flow toward a root surface were carried out in a two‐dimensional domain with a randomized configuration of spatially variable unsaturated hydraulic conductivities and varying boundary conditions, that is, increasing and decreasing root water uptake rates. By employing Matheron's method, the soil hydraulic properties were varied, while the effective hydraulic conductivity (corresponding to the geometric mean) remained unchanged. Results show that domains with a uniform conductivity could not capture important features of water flow and pressure distribution in spatially variable domains. Specifically, increasing heterogeneity at the root‐soil interface allowed to sustain higher root water uptake rates but caused a slower recovery in xylem suction after transpiration ceased. The significance of this is that, under critical conditions, when pressure gradients and flow rates are high, microscale heterogeneity may become an important determinant and should not be neglected in adequate descriptions of water flow from soil to root in dry soil.
Key Points
At the scale of a single root soil heterogeneity impacts the relation between flow rate and pressure head
Here the emergent relation between water flow and pressure head gradient cannot be described by a single effective conductivity
Explicitly accounting for soil heterogeneity might give new insights on water flow in soil‐plant‐atmosphere systems
Hydraulic systems are advanced in function and level as they are used in various industrial fields. Furthermore, condition monitoring using internet of things (IoT) sensors is applied for system ...maintenance and management. In this study, meaningful features were identified through extraction and selection of various features, and classification evaluation metrics were presented through machine learning and deep learning to expand the diagnosis of abnormalities and defects in each component of the hydraulic system. Data collected from IoT sensor data in the time domain were divided into clusters in predefined sections. The shape and density characteristics were extracted by cluster. Among 2335 newly extracted features, related features were selected using correlation coefficients and the Boruta algorithm for each hydraulic component and used for model learning. Linear discriminant analysis (LDA), logistic regression, support vector classifier (SVC), decision tree, random forest, XGBoost, LightGBM, and multi-layer perceptron were used to calculate the true positive rate (TPR) and true negative rate (TNR) for each hydraulic component to detect normal and abnormal conditions. Valve condition, internal pump leakage, and hydraulic accumulator data showed TPR performance of 0.94 or more and a TNR performance of 0.84 or more. This study's findings can help to determine the stable and unstable states of each component of the hydraulic system and form the basis for engineers' judgment.
Hydraulic switching actuators are high-efficiency, fast response, and low-cost solutions for hydraulic control systems. One of the challenging problems is throttling losses during valve transitions. ...Previously, the authors proposed a zero-flowrate switching method to reduce the throttling energy loss of the switching valve, where a hydraulic resonator is applied to make the flowrates through the lines approaching zero before the valves are switched off. The major challenge of this approach is fast switching valves whose transition times are less than 2 ms. In this paper, an improved zero-flowrate switching method is presented. It utilizes the capacity with independent inlet/outlet ports to regulate flowrates through the lines. Models of capacity applied in a simple line with different pressure signals are developed to explore characteristics of the capacity, based on which a complete actuation system is developed. In the complete model, resistance and inductance are optimized to achieve the desired flowrate response. The improved zero-flowrate switching method reduces throttling energy losses by 99.945% compared to a hard switching system. The simulation results demonstrated that the improved zero-flowrate switching method performs as expected in the design condition. A capacity with proper volume is able to regulate flowrates through all the lines to zero, with the help of appropriate resistance and inductance. Compared to the previous zero-flowrate switching method, the novel strategy allows slower switching valves applied in hydraulic actuation systems and achieves better efficiency performance. This research paves a new avenue for reducing throttling energy losses and improves system efficiency in hydraulic switching actuators, as well as most of the hydraulic switch-mode circuits.
The paper deals with the characteristics of three different types of power train hybridization of forest logging machines and with the benefits of reducing environmental impacts by comparing new ...technology with more conventional, older technology. New hybridization options that could be implemented in forestry machines are also discussed. The paper divides a hybrid solution into three classes based on the energy used in the system of hybridization. First is an electro-hybrid system that uses an electric motor and battery or different storage device. The second, a hydraulic hybrid system, is a solution with a hydraulic accumulator, hydraulic motor, and pump. The third system is a combination of the electro-hybrid and hydraulic-hybrid system. The current technical and technological development of hybrid drive systems, as well as their components, has led to significant improvements in drive performance and thus better performance of the new generation of forest vehicles. Improved energy efficiency using hybrid propulsion systems in forest vehicles would result in a significant reduction in greenhouse gas emissions and possibly lower maintenance costs.
This paper proposes a new multi-objective command filtered adaptive control strategy for the active suspension systems with nonlinear hydraulic actuators. Firstly, command filters are designed to ...avoid the influences of the explosion of complexity on hydraulic suspension systems. The output of the command filters replaces the derivatives of virtual control signals to remove the online computational burdens caused by the explosion of complexity in the backstepping technique, which is appropriate for the practical hydraulic suspension systems that the differential coefficients of high-order are difficult to gain. Furthermore, the error compensation signals are designed to eliminate the filtering errors and proved to be bounded. Therefore, the large peaks of the output control forces caused by online computational burdens are eliminated, which means that small control forces can achieve good control results. Then, the ride comfort is improved. The dynamic load ratios and suspension working spaces are proved in small regions, which can guarantee the multi-objective control in nonlinear hydraulic active suspension systems. Finally, the simulation results show the effectiveness of the proposed strategy.
Xylem hydraulic characteristics govern plant water transport, affecting both drought resistance and photosynthetic gas exchange. Therefore, they play critical roles in determining the adaptation of ...different species to environments with various water regimes. Here, we tested the hypothesis that variation in xylem traits associated with a trade‐off between hydraulic efficiency and safety against drought‐induced embolism contributes to niche differentiation of tree species along a sharp water availability gradient on the slope of a unique river valley located in a semi‐humid area. We found that tree species showed clear niche differentiation with decreasing water availability from the bottom towards the top of the valley. Tree species occupying different positions, in terms of vertical distribution distance from the bottom of the valley, showed a strong trade‐off between xylem water transport efficiency and safety, as evidenced by variations in xylem structural traits at both the tissue and pit levels. This optimized their xylem hydraulics in their respective water regimes. Thus, the trade‐off between hydraulic efficiency and safety contributes to clear niche differentiation and, thereby, to the coexistence of tree species in the valley with heterogeneous water availability.
Xylem embolism resistance has been identified as a key trait with a causal relation to drought-induced tree mortality, but not much is known about its intra-specific trait variability (ITV) in ...dependence on environmental variation. We measured xylem safety and efficiency in 300 European beech (F
agus sylvatica
L.) trees across 30 sites in Central Europe, covering a precipitation reduction from 886 to 522 mm year
−1
. A broad range of variables that might affect embolism resistance in mature trees, including climatic and soil water availability, competition, and branch age, were examined. The average
P
50
value varied by up to 1 MPa between sites. Neither climatic aridity nor structural variables had a significant influence on
P
50
. However,
P
50
was less negative for trees with a higher soil water storage capacity, and positively related to branch age, while specific conductivity (
K
s
) was not significantly associated with either of these variables. The greatest part of the ITV for xylem safety and efficiency was attributed to random variability within populations. We conclude that the influence of site water availability on
P
50
and
K
s
is low in European beech, and that the high degree of within-population variability for
P
50
, partly due to variation in branch age, hampers the identification of a clear environmental signal.
Turbines based on oscillating foils possess obvious advantages in shallow waters. In this study, a hydraulic system was designed for the semi-passive oscillating foil, which is more suitable for ...practical applications than the traditional spring-damper system. Co-simulations using software Fluent® and AMESim™ were carried out to examine the performance of the hydraulic system. Based on the results of the spring-damper system, three typical cases were analyzed for each variable to study the effects of kinematic and mechanical parameters. The results demonstrated that the oscillating foil based on the hydraulic system could achieve a regular heaving response. However, a significant feature of the developed system is that the foil stops briefly at the endpoint of the heaving motion. The kinematic parameter had a significant effect on both the hydrodynamic characteristics and the heaving response. Maximum energy is harvested at reduced frequency f ∗ = 0.10, while the maximum efficiency occurred at f ∗ = 0.125. The mechanical parameters, including the spring, cylinder radius, and rotary load, affected the hydrodynamic characteristics slightly. However, the parameters of the cylinder and the rotary load had a significant impact on the heaving response and the power output performance. The results also indicated that the unstable heaving response should be avoided, as it would decrease the energy harvesting efficiency.
•The hydraulic system was applied to a semi-passive oscillating foil turbine.•Co-simulations using Fluent and AMESim were conducted to study such system.•The foil stops briefly at the endpoint of the heaving motion for the novel system.•Kinematic parameters have a more obvious impact on the hydrodynamic behavior.•Mechanical parameters affect the power output performance more significantly.
•Self-potential data can be jointly inverted with head data.•The two types of data have complementary sensitivity map.•The reconstruction of the hydraulic conductivity and specific storage is ...improved.•The low-cost of the self-potential method makes it attractive for pumping tests.
Transient hydraulic tomography is used to image the heterogeneous hydraulic conductivity and specific storage fields of shallow aquifers using time series of hydraulic head data. Such ill-posed and non-unique inverse problem can be regularized using some spatial geostatistical characteristic of the two fields. In addition to hydraulic heads changes, the flow of water, during pumping tests, generates an electrical field of electrokinetic nature. These electrical field fluctuations can be passively recorded at the ground surface using a network of non-polarizing electrodes connected to a high impedance (> 10MOhm) and sensitive (0.1mV) voltmeter, a method known in geophysics as the self-potential method. We perform a joint inversion of the self-potential and hydraulic head data to image the hydraulic conductivity and specific storage fields. We work on a 3D synthetic confined aquifer and we use the adjoint state method to compute the sensitivities of the hydraulic parameters to the hydraulic head and self-potential data in both steady-state and transient conditions. The inverse problem is solved using the geostatistical quasi-linear algorithm framework of Kitanidis. When the number of piezometers is small, the record of the transient self-potential signals provides useful information to characterize the hydraulic conductivity and specific storage fields. These results show that the self-potential method reveals the heterogeneities of some areas of the aquifer, which could not been captured by the tomography based on the hydraulic heads alone. In our analysis, the improvement on the hydraulic conductivity and specific storage estimations were based on perfect knowledge of electrical resistivity field. This implies that electrical resistivity will need to be jointly inverted with the hydraulic parameters in future studies and the impact of its uncertainty assessed with respect to the final tomograms of the hydraulic parameters.
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