Leakage Effects Research Articles

Performance Analysis and Reliability Optimization of Internal Feedback Hydrostatic Rotary Table Support

AbstractThe internal feedback hydrostatic rotary table is a precision support device, and its performance relies heavily on the oil pad. However, uncertainties in the manufacturing process are often overlooked during the stiffness optimization, affecting the reliability of the optimized results. Accordingly, this paper aims to analyze the influence of structural parameters on the stiffness performance of the internal feedback hydrostatic rotary table and to perform reliability optimization considering the uncertainties. Initially, a theoretical computational model of internal feedback hydrostatic rotary table, accounting for the oil leakage effect, is proposed. The model's accuracy is validated through comparative simulation calculations, and based on this model, the load-bearing performance of the table is further analyzed. Subsequently, focusing on the structural characteristics of the oil pad, a reliability optimization model that considers manufacturing uncertainties is proposed. To improve the optimization efficiency, a Levenberg–Marquardt Backpropagation (LM-BP) neural network is introduced as a surrogate model for theoretical calculations. The oil pad is optimized through a particle swarm optimization algorithm. Ultimately, the optimal structural size parameters of the oil pad are obtained, achieving maximal stiffness under a high level of reliability. Both the stiffness performance and the reliability level of the rotary table are substantially enhanced. The results indicate that the proposed method can significantly improve performance and reliability in practical applications.

Efficacy of MRI data harmonization in the age of machine learning: a multicenter study across 36 datasets

Pooling publicly-available MRI data from multiple sites allows to assemble extensive groups of subjects, increase statistical power, and promote data reuse with machine learning techniques. The harmonization of multicenter data is necessary to reduce the confounding effect associated with non-biological sources of variability in the data. However, when applied to the entire dataset before machine learning, the harmonization leads to data leakage, because information outside the training set may affect model building, and potentially falsely overestimate performance. We propose a 1) measurement of the efficacy of data harmonization; 2) harmonizer transformer, i.e., an implementation of the ComBat harmonization allowing its encapsulation among the preprocessing steps of a machine learning pipeline, avoiding data leakage by design. We tested these tools using brain T1-weighted MRI data from 1740 healthy subjects acquired at 36 sites. After harmonization, the site effect was removed or reduced, and we showed the data leakage effect in predicting individual age from MRI data, highlighting that introducing the harmonizer transformer into a machine learning pipeline allows for avoiding data leakage by design.

Digging Deeper—Evidence on the Effects of Macroprudential Policies from a New Database

AbstractThis paper introduces a comprehensive database of macroprudential policies, which covers 134 countries from January 1990. Using a novel numerical indicator of the tightness of loan‐to‐value (LTV) regulations, we estimate the policy effects of incremental tightening in LTV limits, employing a propensity score–based method to address endogeneity concerns. The results point to economically significant and nonlinear effects on household credit, with a declining per‐unit impact for larger tightening measures. The analysis indicates that policy leakage effects could be a factor behind the nonlinear effects. We finally find that the side effects of macroprudential policies on consumption and output are relatively small.

Application of a Geochemically Informed Leak Detection (GILD) Model to CO2 Injection Sites on the United States Gulf Coast

The Gulf Coast region possesses great potential for CO2 enhanced oil recovery (EOR) and CO2 storage. A geochemically informed leak detection (GILD) model has been applied to CO2 injection sites on the Gulf Coast with considerations of measurement variability. The Jasper aquifer in Montgomery County, Texas, was chosen to demonstrate the method. Based on background data from wells in the area, combinations of mineral and fluid compositions were used to create 23 scenarios for the geochemical model. The output from the geochemical model was used to identify sensitive monitoring species, and response functions were generated for these as a function of the CO2 leakage concentration. The sources of measurement variability for background conditions were characterized from the Jasper aquifer background data, and then normalized using the coefficient of variation of each species across the monitoring wells. Bayesian belief network (BBN) models were constructed, and measurement variability of different levels were added to compare leak detection probabilities. Increasing measurement variability decreased the power to detect a leak of a given size. For a moderately high CO2 concentration of 0.2 mol/kg, the probability of detecting this leakage effect using pH as the monitoring variable in an aquifer with calcite decreases from 98% (no measurement variability) to 61% (medium variability) to 33% (high variability). The loss in power of the sampling protocol with increasing measurement variability is similar in magnitude when Ca2+ or HCO3− is used as the monitoring parameter, but only for aquifers with calcite.

A novel model for measuring carbon dioxide flux on soil surface using an accumulation chamber

Soil surface carbon dioxide (CO2) fluxes hold significant implications for comprehending carbon cycling, global climate change, and ecosystem functioning. Accurate understanding and quantification of this flux are crucial for assessing the carbon dynamics of ecosystems and predicting the impacts of climate change. In this study, we analyzed the variation pattern of CO2 concentration within the accumulated chamber from Fick's law, accounting for diffusion gradient effect and considering leakage effect. We developed a simple model to measure the soil surface CO2 flux, and used the model to calculate the values of CO2 fluxes on a specific soil surface. Comparing the fitting results of the proposed nonlinear model with traditional linear models for the measurement data, we found that the linear model underestimated by at least 18%, even up to 45%. Overall, our research indicates that the proposed model exhibits significant advancement and higher predictive reliability, successfully evaluating soil surface CO2 flux.

Fractional calculus-based modeling and state-of-charge estimation of supercapacitor

Supercapacitors (SCs) are becoming a well-accepted energy storage device in many industrial applications for their high power density and remarkably long life span. The SC-powered systems require an accurate estimation of the state of charge (SOC) to ensure the proper energy management of the system. SOC estimation accuracy is significantly affected by SC leakage current, particularly in low-duty cycle applications like wireless sensor nodes. Considering the memory effect of the electrochemical energy storage systems, the fractional calculus-based SC model accurately characterizes the device’s electrical dynamics. This paper proposes a fractional order (FO) equivalent circuit model of SC considering the leakage effect of the device. The model parameters are experimentally identified, considering the commercially available 5F Maxwell SC cell. Based on the proposed model, a fractional order Extended Kalman Filter (FOEKF) has been designed and implemented to estimate the SOC of the SCs. A state initialization method has been proposed to address the convergence issue of the estimator under unknown initial conditions. The performance of the proposed estimation scheme has been illustrated through simulation and experimental studies. Finally, the performance of the proposed fractional order estimation has been compared with the integer-order approach.

Can marketing counter technology leakage effects in emerging markets

Can marketing counter technology leakage effects in emerging markets

Information sharing strategy for an incumbent retailer in a closed-loop supply chain

This paper considers a closed-loop supply chain with a manufacturer, an incumbent retailer and an entrant retailer. The two retailers order the same products from the common manufacturer and then sell to consumers, and the incumbent retailer possesses private forecast information with respect to the uncertain demand. The incumbent retailer could strategically share its forecast information to make great profits. We find that, when the incumbent retailer shares the information with its upstream manufacturer, the entrant retailer benefits from this information sharing arrangement because of the information leakage effect. However, the incumbent retailer will be motived to share the information with the manufacturer only when the manufacturer is highly efficient in collection investment. To achieve information sharing, the research results show that, the manufacturer and the entrant retailer should pay the incumbent retailer for the demand information if the investment efficiency of the manufacturer meets certain conditions.

Study on the Influence of Urban Water Supply Pipeline Leakage on the Scouring Failure Law of Cohesive Soil Subgrade

Urban water supply pipelines serve as vital lifelines for urban operations. However, the occurrence of underground pipeline leakage, caused by various factors, results in significant water loss and gives rise to safety hazards such as pavement collapse due to the erosive action of leaking water on the overlying soil. To conduct a more comprehensive investigation into the erosion characteristics of the leaking jet on the soil, this study employed a custom-built soil-test system to investigate the erosive effects of leakage from the water supply pipe network on the clay roadbed above. The study considered water flow rate, leakage port size, and leakage angle as influential factors. The experimental results demonstrated that reducing the water flow rate significantly enhances the soil’s erosion resistance. There is a positive correlation between the caliber of pipe leakage, pipe diameter, and the erosion rate of the soil cavity. Under identical conditions, the erosion rate of the specimen increased consistently with an increase in the leakage port angle. The study also investigated and summarized the curve depicting the formation of soil cavities. The aforementioned findings offer valuable insights for the implementation of reinforcement measures using fine-grained cohesive soil backfill in urban water supply pipelines.

(Invited) Heterogeneous Integration of Ultrawide Bandgap III-Nitrides and Diamond

Industry demands for power switching, amplification and photonic applications are continually pushing the limits of semiconductor device technologies leading to increasing applied voltages and, thus, higher electric fields while simultaneously requiring reduction in the size, weight and power consumption. In addition, recent heightened interest in higher temperature (and other extreme environment) applications, while simultaneously maintaining high-voltage and high-power performance, has inexorably led to ultrawide bandgap (UWBG) semiconductor materials. This interest in UWBG materials stems from superior properties that include high material hardness, breakdown strength to withstand large electric fields and mitigation of power dissipation during device switching, deliver high current density while operating at higher junction and ambient temperature. Among these materials are boron nitride in its hexagonal and cubic phases, gallium oxide, diamond, and aluminum gallium nitride. The versatile alloys of wurtzite AlxGa1-xN have long been demonstrated across the full composition range. The variation in Eg with AlGaN composition, along with select WBG and UWBG materials, is shown in Figure 1 versus (in-plane for non-cubic) lattice constant.Premier WBG materials to date for electronics and photonics are SiC (Eg = 3.3 eV) and GaN (Eg = 3.4 eV). The latter has been successfully applied to high-power transistors and near ultraviolet photonics. In both electronics and photonics applications, the polarization fields of the wurtzite crystal structure, generally grown along (0001) direction, produce design challenges. In photonics, for example, the fields and band alignment couple to spatially separate electrically injected electrons and holes to reduce wavefunction overlap in quantum wells. In electronics, the internal fields have contributed to difficulties in the design of logic and bipolar transistor devices based on these materials. Despite this, the inherent polarization field and band offsets were successfully employed in the design of high electron-mobility transistors (HEMTs). The inherent AlGaN/GaN HEMT band offset produces a high electron concentration at the interface that spontaneously forms a two-dimensional electron gas (2DEG). Because charge flow in these devices is restricted to the 2DEG, current crowding results in intense self-heating. The local heating decreases electrical conductivity to produce a runaway scenario for elevating the Joule heating. Dissipating this heat, therefore, is the principal limiting factor in operating at power higher than 40 W/mm.The various temperature dependences of semiconductor device parameters are the principal drivers in the operation of semiconductor devices. The physics has inextricably led to UWBGs for future high temperature applications, > 300 °C, due to their lower intrinsic carrier density and thus the effects of leakage are orders of magnitudes less than Si-based devices. Furthermore, AlGaN and diamond offer superior high temperature mechanical stability due to their structural hardness and chemical inertness. Thermal management is essential for achieving higher power densities. Diamond is highly attractive for many applications due to its high hardness, transparency, chemical inertness, promising semiconductor properties, and its high thermal conductivity (κ) to 2500 W/m·K in natural material. Factors related to the consequences of self-heating in devices have motivated extensive research to improve the properties of diamond and produce better approaches to determine the thermal properties. Laboratory-grown diamond films exhibit significantly poorer κ than natural diamond and, when integrated with other electronic materials, a low thermal boundary conductance (TBC in W/m2·K) that inhibits heat transfer between materials. The former originates from the ubiquitous polycrystalline nature of chemical vapor deposition (CVD) diamond and the presence of non-diamond carbon (NDC) in the layer. The low TBC stems from fundamental barriers to phonon propagation between two materials and from practical issues of poor diamond quality in the initial growth regime. Continued research is needed to improve κ in the polycrystalline diamond and mitigate the negative impact of the initial diamond layer on TBC.The current status of hetero-integration of UWBG AlGaN and diamond will be reviewed. Particular emphasis is given to high Al content AlGaN for near-bandgap matching with diamond. Patterned diamond grown using hot-filament CVD to realize unique three-dimensional lateral device structures in a self-aligned, as-grown fabrication process is employed. Engineering the AlGaN-diamond bandgap alignment is noteworthy at the nonpolar AlGaN – diamond interface including diamond surface terminations that produce either negative or positive electron affinity. The review will focus on improvements in material properties, especially the interfaces, that are critical to both charge and heat transport for UWBG device structures. Figure 1

Duct flow with leakage

The effect of wall leakage on the traditional duct flow equations based of the balance of mass, momentum and mechanical energy applied on a duct section is considered. Application of the momentum balance produces a Bernoulli equation type form, where the multiplier 1/2 in the dynamic pressure is however replaced by the value 1. Some relevant literature references are discussed. As an application, a nozzle duct flow problem is treated.

Carbon leakage or carbon reduction? Carbon emission effect of the production relocation of metal smelting industry in China

AbstractThe metal smelting industry (MSI) is one of the major carbon emission sectors in China, and it is of great significance to clarify the mechanism and truth of the carbon effect of production relocation (PR) of MSI for reducing national carbon emissions. Based on this thinking and previous studies, we proposed two concepts of relative carbon emission effect (RCE) and absolute carbon emission effect (ACE) of PR, then developed models to explore the impact of PR of MSI (PRM) on national carbon emission between 30 provincial administrative units in China from 2007 to 2017. The study demonstrates that the PRM and its ACE and RCE is divergent across provinces and regions. Overall, the PRM is beneficial to national carbon reduction under both relative and absolute scenarios. Specifically, the transfer‐in PRM of most provinces in central regions is beneficial to national carbon reduction, while the transfer‐out PRM of many provinces in coastal areas has worst carbon leakage effect.

Intelligent identification of tunnel water leakage based on super-resolution reconstruction and triple attention

To effectively solve the issues of poor anti-environmental interference and inaccurate defect boundary segmentation in tunnel water leakage intelligent identification methods, an intelligent segmentation method based on super-resolution reconstruction and triple attention is proposed in this paper, named TR-Unet. In TR-Unet, the Real-ERSGAN super-resolution reconstruction algorithm is used to perform resolution enhancement on water leakage images to strengthen the edge details of the defect regions. Then triple attention mechanism is established by fusing channel attention, spatial attention, and self-attention, and is introduced into the encoder of the Unet network, thus enhancing the model's resistance to environmental interference. The results show that the mIoU and mPA of the TR-Unet are 84.31% and 88.95%, respectively, which are higher than the other compared models. In addition, TR-Unet has better segmentation effect of water leakage, which mainly reflected in less false recognition and better edge details.

Modeling non-linear ion transport phenomena in ion-selective membranes: Three simplified models

In electromembrane processes employing the ion concentration polarization phenomenon, such as electrodialysis (ED), ion concentration polarization (ICP) desalination, and reverse electrodialysis, the ion-selective membrane (ISM) has been modeled with an assumption of an ideal ISM permits only the passage of counter-ions with all the co-ions blocked. However, in the works that study the effects of co-ion flux on the response of system, this assumption has been questioned about the adequate answer to the simulation of the characteristic properties of the membrane. In this work, we evaluate the three models which are used widely in modeling ISM including surface-charged, space-charged and nanochannel array model. The results show that the nanochannel array and space-charged models, the alternative model for the model ISM in the case of the studies which consider the effects of co-ion leakage on the performance of the system, sufficiently mimic the key characteristic of the membrane. Their current–voltage response (I-V) curve conforms to a typical one, yet they differ due to the varying co-ion fluxes. The nanochannel array model, which is the direct model of the actual ISM, closely mimics the seed electroconvection vortices near the membrane, which does not appear in the surface-charged and space-charged model. This model is computationally expensive because of resolving the nonlinearity of the variables near the entrance of nanochannels, so it is not the appropriate model to employ in a study that considers the micrometer or millimeter order scale system. Finally, the space-charged model is more appropriate to mimic the ISM but requires more careful consideration of the simplification condition. By investigating the volume charge density of the membrane in the space-charged model, we suggest a value that brings the most similar I-V curve to that of the nanochannel array model.

Investigation of transitional flow in a transonic compressor rotor with hub leakage using large eddy simulation

The hub leakage flow has been acknowledged as an important factor for performance deficiency of axial-flow compressors. Meanwhile, the laminar-turbulent transition in compressors is highly sensitive to the upstream flow state and significantly affects the flow loss. In the present work, quasi-wall-resolved large eddy simulation of a transonic axial-flow compressor rotor at the near-peak-efficiency point is carried out to investigate the effects of hub leakage as well as its absolute tangential velocity on the compressor performance and the laminar-turbulent transition in the blade passage. It is confirmed that the hub leakage with an absolute tangential velocity of 0.5 wheel speed can result in the near-hub total pressure deficit. With the hub leakage taken into account, the predicted total pressure ratio and adiabatic efficiency agree well with the experimental data. The simulation results indicate that increasing the absolute tangential velocity of hub leakage would intensify the near-hub vortices, elevate the endwall turbulence level, increase the near-hub flow loss, and cause a remarkable total pressure ratio drop. This work promotes the understanding of complex flow mechanisms in axial-flow compressors in the presence of hub leakage.

Deriving the Terrestrial Water Storage Anomaly From GRACE Spherical Harmonic Coefficients Using a Convolutional Neural Network

AbstractTerrestrial water storage anomaly (TWSA), derived from Gravity Recovery and Climate Experiment (GRACE) satellites, has been widely used in hydrology studies. The inversion is commonly achieved by truncating and filtering spherical harmonic coefficients (SHC), whereby the result is characterized by leakage error and low resolution. It remains unclear whether machine learning methods can help resolve this challenging issue. In this study, we present a convolutional neural network (CNN) approach to correct TWSA from GRACE SHC by leveraging the knowledge of the leakage effect determined from global hydrological models (GHMs) and land surface models (LSMs). The CNN approach is implemented in three representative regions in China, that is, the human‐impacted Haihe River Basin, the nature‐impacted Yangtze River Basin and the model‐limited Tibetan Plateau. The results show the following: (a) The recovery performance of CNN at the basin scale is better than that at the grid scale, and the grid‐scale recovery is significantly influenced by the spatial heterogeneity of TWSA and the input GHM/LSMs; (b) The more accurate the GHM/LSMs used for training, the better the recovery performance of CNN; and (c) The trained model retains comparable performance in deriving the TWSA time series from GRACE SHC when compared to that derived from other methods (i.e., scaling factor and mass concentration solutions) with average r = 0.90 and RMSE = 21.50 mm. This study highlights the potential of machine learning to supplement conventional correction methods when deriving the TWSA from GRACE SHC by utilizing signal restoration knowledge learned from multiple accurate GHMs/LSMs.

Causal-based optimization of micro-perforated treatments

Enhancing the low-frequency performance of compact acoustical micro-perforated treatments is a challenging task that requires global optimization studies performed on numerical or theoretical models. However, for a given geometry, there always exists a lower frequency bound below which the treatment will exhibit poor dissipation performance. In this study, it is shown how this lower frequency bound is related to the total integrated dissipated power through a causal-based criterion. Examples are shown for the cases of a rigidly-backed micro-perforate under plane wave incidence and for a locally-reacting micro-perforated resonant silencer mounted in a duct. Such criterion provides the ultimate bandwidth-to-length ratio that can be achieved by the acoustical treatments for a given target dissipation value. One can also deduce the optimal values of individual parameters such as the hole diameters or the wall porosity that leads to a suitable balance between leakage and dissipation effects. The causal-based optimized treatments are validated against simulated or measured impedance tube data.

Impedance measurements on reflective surfaces: effect of nodes

The ISO 13472-2 standardizes the in-situ measurement of normal-incidence acoustic absorption of road pavements. The standard describes the use of the two-microphone method with an impedance tube specially configured for sealing against pavement surfaces. The method is of interest to the tire-pavement noise and vehicle pass-by noise communities. For roads constructed of dense graded asphalt, for example, pass-by noise test tracks conforming to ISO 10844, the pavement is a highly reflective surface. Under this measurement condition, the acoustic field within the tube develops nodes at one or the other microphone positions at characteristic frequencies. These nodes present as sharp peaks and valleys in the two-microphone transfer function. Such narrow bandwidth features are susceptible to measurement error, in particular, signal processing leakage as evidenced by significant drops in the coherence function at the frequencies of the nodes. In this paper we study the nature of the nodes and the effect they have on the two-microphone transfer function and coherence function. We further investigate how different formulations of the transfer function affect the overall 1/3rd octave band accuracy. The effect of the number of averages on both coherence and leakage error is assessed. The potential to solve this leakage effect by switching microphones to other positions is evaluated in relation to a procedure with two fixed microphones. It was concluded that although shifting microphone positions does have advantages in terms of preventing leakage, the mandatory application of a reference measurement reduces the overall error. Finally, recommendations for improving the procedure in ISO 13472-2 are formulated.

A coordination failure between EU climate policies exemplified by the North Sea energy island

ABSTRACT We highlight a coordination problem between the EU Emissions Trading System (ETS) and the EU's offshore renewable energy strategy. We exemplify this coordination failure by analyzing carbon leakage effects associated with Denmark's planned North Sea energy island. The Danish energy island project will not start production before 2033, implying a long interval between project announcement and production. Using a dynamic model of the EU ETS, we show that the large time gap between announcement and production likely results in a ‘Green Paradox’, where the energy island increases aggregate EU ETS emissions. The mechanism leading to the emission increase is complicated and works through the Market Stability Reserve (MSR). The estimated 2050 leakage rate is 145 percent in our main scenario and not below 100 percent in any alternative scenario. We discuss how to improve the climate benefits of the energy island or similar large-scale renewable energy projects. This includes possible revisions to the EU ETS and the role of Power-to-X technologies.

CARBON TAX AND ITS EFFECT ON THE ECONOMY, TAXES AND ENVIRONMENT

This research discusses theoretically the relationship between carbon tax with economy, tax and environment. This research is a legal research with analytical descriptive nature, namely research that analyzes secondary data on issues related to carbon taxes as an instrument for reducing carbon dioxide emissions. According to secondary data, this research is aimed at discovering aspects of carbon tax design, collection of carbon taxes, and state management of carbon tax revenues. Carbon taxes are an effective and efficient instrument to support the reduction of carbon dioxide emissions. To be implemented, a carbon tax must be feasible. Eligibility requires public acceptance. On the other hand, a carbon tax can create a lot of controversy. The main argument against carbon taxes is that carbon taxes do not always guarantee emission reductions. In addition, there are also concerns over the unintended effects of competitiveness, carbon leakage, and fears of unintended distributional impacts, which could be barriers to implementation.