Mitigation Of Leakage Research Articles

An adjustable bio-sealing method for rock fracture leakage mitigation

This study proposed a repeated adjustable mixture injection strategy (RAM) based microbial induced carbonate precipitation (MICP) for efficient mitigation of rock fracture leakage. Granite fractures with small apertures were investigated, and bio-sealing experiments were conducted using five different cementation solution (CS) concentrations (0.25−2 M). The results showed that the RAM-based bio-sealing method can seal and bond the small aperture rock fractures with high efficiency and uniform precipitation by adjusting the CS concentration. The RAM-based bio-sealing mechanism is attributed to the following four stages: (1) fixation of bacterial flocs onto the fracture surfaces, (2) precipitation of CaCO3 onto the fracture surfaces, (3) growth of pre-precipitated CaCO3 and adhesion of new-suspended CaCO3, and (4) bridging and clogging processes. The optimal CS concentration of 1 M resulted in a fracture filling rate up to 85%, a transmissivity reduction of 4 orders of magnitude, and a shear strength ranging from 512 kPa to 688 kPa. The bio-sealing effect was found to be influenced by the CS concentration on bacterial attachment, calcium carbonate yield and calcium carbonate bulk density. The CS concentration of 1 M promoted bacterial attachment, and increased calcium carbonate yield as well as calcium carbonate bulk density, while concentrations above 1 M had the opposite effect. The bulk density of calcium carbonate played a crucial role in the sealing and bonding performance of bio-sealed fractures, particularly at comparable filling ratios and bridging areas. The bulk density was regulated by the size of calcium carbonate crystals and was determined by Ca2+ concentration in the CS. This study provides valuable insights into the RAM-based bio-sealing method, highlighting its potential for efficient rock fracture leakage mitigation through precise control of CS concentration and understanding the underlying mechanisms.

Blockchain-Based Swarm Learning for the Mitigation of Gradient Leakage in Federated Learning

Federated Learning (FL) is a machine learning technique, where collaborative and distributed learning is performed, while the private data reside locally on the client. Rather than the data, only gradients are shared among all collaborative nodes with the help of a central server. To ensure the data privacy, the gradients are prone to the deformation, or the representation is perturbed before sharing, ultimately reducing the performance of the model. Recent studies show that the original data can still be recovered using latent space (i.e., gradient leakage problem) by Generative Adversarial Network and different optimization algorithms such as Bayesian and Covariance Matrix Adaptation Evolution Strategy. To address the issues of data privacy and gradient leakage, in this paper, we train deep neural networks by exploiting the blockchain-based Swarm Learning (SL) framework. In the SL scheme, instead of sharing perturbed or noisy gradients to the central server, we share the gradients among authenticated (i.e., blockchain-based smart contract) training nodes. To demonstrate the effectiveness of the SL approach, we evaluate the proposed approach using the standard CIFAR10 and MNIST benchmark datasets and compare it with the other existing methods.

MICRO-POSITIVE PRESSURE AERATION FOR WINDROW COMPOSTING OF MUNICIPAL SOLID WASTE IN CHANDIGARH: AN OPPORTUNITY IN A CARBON CONSCIOUS WORLD FOR COMBATING CLIMATE CHANGE

The present study was a pilot project initiated in Chandigarh to discuss the feasibility andeffectiveness of adept schemes for successful co-composting of green waste and kitchen waste(food and fruit) waste in 64 m2 open covered windrows with bulking grass layer bottom upventilation system generating micro-positive pressure, making windrow piles aerobic, organolepticwith reduced green -house gases (GHGs) emission. The compost temperature profile shows twothermophilic peaks; first in bioreactor (74 oC) and second in charging pit (76.2 oC) after 40 days oninoculation and the high temperature fermentation was maintained for 80days. The high qualityfinal compost has 40oC temperature, 7.6pH, 42% moisture content, 3.36ds/m electrical conductivityand 25 C/N ratio. The main objective of the present study is to analyze and overview theconfiguration technology and analytical parameters to limit the global temperature rise to 1.5 oC,to meet the goals of the Paris agreement to avoid catastrophic impacts of climate change. Theinference of the study is the mitigation of carbon leakage, generating 346.7 carbon credits and 564quintals organic compost worth 25 lakhs to achieve sustainable zero waste future.

Risk of Carbon Leakage and Border Carbon Adjustments under the Korean Emissions Trading Scheme

Purpose – This paper examines South Korea’s potential status as a carbon leakage country, and the level of risk posed by the Korean emissions trading scheme (ETS) for Korean industries. The economic effects of border carbon adjustments (BCAs) to protect energy-intensive Korean industries in the process of achieving the carbon reduction target by 2030 through the Korean ETS are also analyzed. Design/methodology – First, using the Korean Input–Output (IO) table, this paper calculates the balance of emissions embodied in trade (BEET) and the pollution terms of trade (PTT) to determine Korean industries’ carbon leakage status. Analyses of the risk level posed by carbon reduction policy implementation in international trade are conducted for some sectors by applying the EU criteria. Second, using a computable general equilibrium (CGE) model, three BCA scenarios, exemption regulations (EXE), reimbursement (REB), and tariff reduction (TAR) to protect the energy-intensive industries under the Korean ETS are addressed. Compared to the baseline scenario of achieving carbon reduction targets by 2030, the effects of BCAs on welfare, carbon leakage, outputs, and trading are analyzed. Findings – As Korea’s industrial structure has been transitioning from a carbon importing to a carbon leaking country. The results indicate that some industrial sectors could face the risk of losing international competitiveness due to the Korean ETS. South Korea’s industries are basically exposed to risk of carbon leakage because most industries have a trade intensity higher than 30%. This could be interpreted as disproving vulnerability to carbon leakage. Although the petroleum and coal sector is not in carbon leakage, according to BEET and PTT, the Korean ETS exposes this sector to a high risk of carbon leakage. Non-metallic minerals and iron and steel sectors are also exposed to a high risk of carbon leakage due to the increased burden of carbon reduction costs embodied in the Korean ETS, despite relatively low levels of trade intensity. BCAs are demonstrated to have an influential role in protecting energy-intensive industries while achieving the carbon reduction target by 2030. The EXE scenario has the greatest impact on mitigation of welfare losses and carbon leakage, and the TAF scenario causes a disturbance in the international trade market because of the pricing adjustment system. In reality, the EXE scenario, which implies completely exempting energy-intensive industries, could be difficult to implement due to various practical constraints, such as equity and reduction targets and other industries; therefore, the REB scenario presents the most realistic approach and appears to have an effect that could compensate for the burden of economic activities and emissions regulations in these industries. Originality/value – This paper confirms the vulnerability of the Korean industrial the risk of carbon leakage, demonstrating that some industrial sectors could be exposed to losing international competitiveness by implementing carbon reduction policies such as the Korean ETS. The contribution of this paper is the identification of proposed approaches to protect Korean industries in the process of achieving the 2030 reduction target by analyzing the effects of BCA scenarios using a CGE model.

Mitigation of Leakage and Stationary Clutters in Short-Range FMCW Radar With Hybrid Analog and Digital Compensation Technique

In short-range sensing, the frequency-modulated continuous-wave (FMCW) radar is subject to the leakage between the transmitter (Tx) and the receiver (Rx) and the stationary clutter reflections, which are difficult to deal with due to the proximity to the target. The proximity ghost image may not only interfere with the target but also pose limitations on the radar performance, such as the degradation of the signal-to-noise ratio (SNR). This article proposes a novel hybrid analog and digital compensation techniques, which mitigates the leakage and the stationary clutters by compensating with the prestored anti-interference signals in both analog and digital domains at the intermediate-frequency (IF) stage. A novel modulation signal-based synchronization (MBS) technique is developed to align the real-time IF signal with the anti-interference signal during the compensation process. By significantly suppressing both the Tx-Rx leakage and the stationary clutters, the proposed technique greatly improves the signal-to-interference ratio (SIR) of the IF beat signals and makes possible the detection of targets with weak reflections. Moreover, the analog compensation enables the full use of the dynamic range of the analog-to-digital converter (ADC), which will reduce the impact of quantization noise and, thus, improve the SNR. Experiments have been carried out to validate the performance of the proposed technique in leakage compensation, weak target detection, stationary clutter compensation, and gesture sensing. The experimental results show that the SIR and the SNR have been improved by around 38 and 10 dB, respectively.

Mitigation of Leakage in FMCW Radars by Background Subtraction and Whitening

Leakage in frequency-modulated continuous-wave (FMCW) radar with a homodyne receiver induces strong signal components in the lower frequency parts of the radar observations. There, the dynamic range of the observations has been reduced, such that close and weak targets are hard to detect. In this letter, a signal processing method is proposed to mitigate the leakage. First, background subtraction is applied to cancel the leakage. As the cancellation is imperfect, a noisy signal portion remains: the leakage noise. A statistical model is developed to describe the leakage noise as a colored noise process. This model is parameterized from measurements and used to whiten the observations. As a result, the dynamic range is improved, and the close targets become better detectable.

Near well-bore sealing in the Bečej CO2 reservoir: Field tests of a silicate based sealant

A silica gel was applied in a porous gas reservoir, with the purpose of testing mitigation and remediation of CO2 leakage from geological storage reservoirs. The gel has a high strength and a very low water-like viscosity, that extends its applicability to small pore diameters and low permeability media. The gel was prepared and applied on-site with oilfield equipment. Mixing was upscaled from laboratory- to field-scale, including one unsuccessful attempt. Environmental concerns and additional health and safety requirements were modest as the formulation was composed only of the non-toxic commercial silica-based product Betol K28 T, acetic acid and fresh water. A well was selected and prepared in the Bečej natural CO2 field in Serbia, the well and reservoir were prepared and the gel was placed into a 600 m deep CO2- and CH4-bearing sandstone layer. The reservoir was selectively sealed to the gas cap through a fast, CO2-selective gelation, while the hydraulic pathways of the liquid-filled part of the reservoir remained open. In the regions where no CO2 was present the gelation reaction was slower and the kinetic was temperature-accelerated. A numerical model was used to simulate the impact of the pre-injection operational procedures and to quantify the impact on the temperature-dependent gelation time. The workflow aligns the needs of a research project with the interests and practical priorities of an operating company.

Windowing Design and Performance Assessment for Mitigation of Spectrum Leakage

This paper investigates the windowing design and performance assessment for mitigation of spectral leakage. A pretreatment method to reduce the spectral leakage is developed. In addition to selecting appropriate window functions, the Welch method is introduced. Windowing is implemented by multiplying the input signal with a windowing function. The periodogram technique based on Welch method is capable of providing good resolution if data length samples are selected optimally. Windowing amplitude modulates the input signal so that the spectral leakage is evened out. Thus, windowing reduces the amplitude of the samples at the beginning and end of the window, altering leakage. The influence of various window functions on the Fourier transform spectrum of the signals was discussed, and the characteristics and functions of various window functions were explained. In addition, we compared the differences in the influence of different data lengths on spectral resolution and noise levels caused by the traditional power spectrum estimation and various window-function-based Welch power spectrum estimations.

Assessment, Mitigation, and Control of Potential Gas Leakage in Existing Buildings Not Designed for Gas Installation in Indonesia

Operational activities of gas pipelines are associated with potential hazards and risks that can potentially lead to pipeline failure, including failure of the gas distribution pipeline in existing buildings. Unfortunately, few studies on risk analysis of the gas distribution pipeline in existing buildings have been published. Therefore, this study was conducted to provide a reference for analyzing the risk of pipeline leakage caused by small-scale leakage, large-scale gas release, and gas pipeline rupture in existing buildings in Indonesia not designed for gas installation. The study was performed using the event tree analysis method. The methodology of this study was initiated by identifying the scenario of the case of small-scale leakage, large-scale gas release, or gas pipeline rupture. Then, pivotal events were identified, an event tree diagram was constructed, the event failure of each pivotal event was determined, and the probability value of the outcome risk was calculated. The risk was evaluated in terms of fire, casualties, and gas released. The results of this study showed the highest risk in each scenario which can result in fire, severe casualties, and light poisoning. The highest risk in the small-scale leak scenario had a probability value of 1.5 × 10−3. In the large-scale gas release scenario, the highest risk had a probability value to incur a fireball, severe casualties, and light gas poisoning of 6.0 × 10−4. In the gas pipeline rupture scenario, the highest risk had a probability value of fireball, severe casualties, and light poisoning of 7.0 × 10−4. The probability value of each risk was reduced by the installation of a gas detector and water sprinkler as a barrier.

Brain ischemic preconditioning protects against ischemic injury and preserves the blood-brain barrier via oxidative signaling and Nrf2 activation

Brain ischemic preconditioning (IPC) with mild ischemic episodes is well known to protect the brain against subsequent ischemic challenges. However, the underlying mechanisms are poorly understood. Here we demonstrate the critical role of the master redox transcription factor, nuclear factor (erythroid-derived 2)-like 2 (Nrf2), in IPC-mediated neuroprotection and blood-brain barrier (BBB) preservation. We report that IPC causes generation of endogenous lipid electrophiles, including 4-hydroxy-2-nonenal (4-HNE), which release Nrf2 from inhibition by Keap1 (via Keap1-C288) and inhibition by glycogen synthase kinase 3β (via GSK3β-C199). Nrf2 then induces expression of its target genes, including a new target, cadherin 5, a key component of adherens junctions of the BBB. These effects culminate in mitigation of BBB leakage and of neurological deficits after stroke. Collectively, these studies are the first to demonstrate that IPC protects the BBB against ischemic injury by generation of endogenous electrophiles and activation of the Nrf2 pathway through inhibition of Keap1- and GSK3β-dependent Nrf2 degradation.

Real-Time Mitigation of Short-Range Leakage in Automotive FMCW Radar Transceivers

Frequency-modulated continuous wave radar systems suffer from permanent leakage of the transmit signal into the receive path. Besides leakage within the radar device itself, an unwanted object placed in front of the antennas causes so-called short-range (SR) leakage. In an automotive application, for instance, it originates from signal reflections of the car’s own bumper. Particularly the residual phase noise of the downconverted SR leakage signal causes a severe degradation of the achievable sensitivity. In an earlier work, we proposed an SR leakage cancellation concept that is feasible for integration in a monolithic microwave integrated circuit. In this brief, we present a hardware prototype that holistically proves our concept with discrete components. The fundamental theory and properties of the concept are proven with measurements. Further, we propose a digital design for real-time operation of the cancellation algorithm on a field programmable gate array. Ultimately, by employing measurements with a bumper mounted in front of the antennas, we show that the leakage canceller significantly improves the sensitivity of the radar.

MiReCOL: Remediation of Shallow Leakage from a CO2 Storage Site

Within the EU-funded project MiReCOL (Remediation and Mitigation of CO2 Leakage; project number 608608), a comprehensive review was undertaken of techniques available for the remediation of leakage of CO2 to the near surface environment, here defined as the depth range of typical remediation techniques used by the pollution clean-up industry. The review drew from existing relevant fields of experience such as the remediation of groundwater pollution; the remediation of industrial waste; CO2-EOR, natural gas storage sites; the geothermal energy industry; the construction of dams (as barriers to subsurface fluid flow); pilot scale CCS projects and natural analogues.

Mitigation of spectral leakage for single carrier, block-processing cognitive radio receivers

Cognitive Radio (CR) is a multiuser, wireless communication concept that allows for a dynamic and adaptive assignment of spectral resources. The coexistence of multiple users, often transmitting at significantly different power levels, makes CR receivers vulnerable to spectral leakage caused by components’ nonlinearities and time-truncation of the processed signal records. In this work we propose a method for mitigating the latter with an adaptive choice of the length of the processing block size. With simulations we show that a significant leakage reduction that leads to receiver dynamic range improvement of around 10dB can be achieved with the proposed method.

Finding a Balance between Accuracy and Effort For Modeling Biomineralization

Microbially induced calcite precipitation (MICP) is a technology aiming at the mitigation of potential leakage from underground gas storage sites. A numerical model for MICP was previously developed and validated. The model complexity leads to high computation times, prohibiting at the moment the use of the model for designing field-scale MICP applications. This study investigates savings of the computational time by well-chosen model simplifications. Additionally, this approach is motivated by the high uncertainty of relevant input-parameters. Excessively detailed equations are unnecessary burdens to the MICP model, whose reliability is influenced by the input-parameter uncertainty.

First Field Example of Remediation of Unwanted Migration from a Natural CO2 Reservoir: The Bečej Field, Serbia

The Bečej field, discovered in 1951 by the Petroleum Industry of Serbia (NIS), is one of the largest natural CO2 fields in Europe. Uncontrolled migration of CO2 out of the main reservoir, leading to subsurface seepage and surface leakage, was caused by the Bč-5 well blowout in 1968. Remediation measures were deployed in 2007 to reduce and prevent further leakage of CO2 from the Bečej natural CO2 field. To the best of our knowledge, this is the first field application of remediation measures deployed to remedy leakage from a natural CO2 reservoir – a natural analogue for an engineered geological storage site. Experiences and lessons learned from the Bečej field case are studied within the MiReCOL project (Mitigation and Remediation of CO2 Leakage). The project aims at developing a handbook of corrective measures, which can be considered in the event of significant irregularities and leakage from a CO2 storage site. We performed a comprehensive geological characterization of the Bečej field and interpreted the most recently collected monitoring data to assess the effectiveness of the remediation measures taken in 2007. A static model was constructed that comprises the main CO2 reservoir (Upper Cretaceous and Badennian) and several aquifers in the overburden (Pontian and Pliocene). Eight small hydrocarbon reservoirs are defined above the main CO2 pool at depths ranging from 450 to 900 m, suggesting that the Bečej CO2 field is a natural leaking system. The monitoring data indicate that the remediation measures were effective and have practically stopped the decline of reservoir pressure.

Protection of the vehicle cab environment against bacteria, fungi and endotoxins in composting facilities

Microbial quality of air inside vehicle cabs is a major occupational health risk management issue in composting facilities. Large differences and discrepancies in protection factors between vehicles and between biological agents have been reported. This study aimed at estimating the mean protection efficiency of the vehicle cab environment against bioaerosols with higher precision. In-cab measurement results were also analysed to ascertain whether or not these protection systems reduce workers’ exposure to tolerable levels.Five front-end loaders, one mobile mixer and two agricultural tractors pulling windrow turners were investigated. Four vehicles were fitted with a pressurisation and high efficiency particulate air (HEPA) filtration system. The four others were only equipped with pleated paper filter without pressurisation. Bacteria, fungi and endotoxins were measured in 72 pairs of air samples, simultaneously collected inside the cab and on the outside of the cab with a CIP 10-M sampler.A front-end loader, purchased a few weeks previously, fitted with a pressurisation and high efficiency particulate air (HEPA) filtration system, and with a clean cab, exhibited a mean protection efficiency of between 99.47% CI 95% [98.58–99.97%] and 99.91% [99.78–99.98%] depending on the biological agent. It is likely that the lower protection efficiency demonstrated in other vehicles was caused by penetration through the only moderately efficient filters, by the absence of pressurisation, by leakage in the filter-sealing system, and by re-suspension of particles which accumulated in dirty cabs. Mean protection efficiency in regards to bacteria and endotoxins ranged between 92.64% [81.87–97.89%] and 98.61% [97.41–99.38%], and between 92.68% [88.11–96.08%] and 98.43% [97.44–99.22%], respectively. The mean protection efficiency was the lowest when confronted with fungal spores, from 59.76% [4.19–90.75%] to 94.71% [91.07–97.37%]. The probability that in-cab exposure to fungi exceeded the benchmark value for short-term respiratory effects suggests that front-end loaders and mobile mixers in composting facilities should be fitted with a pressurisation and HEPA filtration system, regardless of whether or not the facility is indoors or outdoors. Regarding the tractors, exposure inside the cabs was not significantly reduced. However, in this study, there was a less than 0.01% risk of exceeding the bench mark value associated with fungi related short-term respiratory effects during an 1-h per day windrow turning operation.Pressurisation and a HEPA filtration system can provide safe working conditions inside loaders and mobile mixer with regard to airborne bacteria, fungi and endotoxins in composting facilities. However, regular thorough cleaning of the vehicle cab, as well as overalls and shoes cleaning, and mitigation of leakage in the filter-sealing system are necessary to achieve high levels of protection efficiency.

Mitigation of UWB Signals Spectral Leakage to the GPS L1 Band via Filtering After Clipping in the UWB Transmitter

Ultra-wideband (UWB) has recently attracted much attention as an indoor short-range high-speed wireless communication. However, the high peak-to-average power ratio (PAPR) limits its capacity due to distortion caused by nonlinear components such as high-power amplifiers. Hence it is necessary to reduce the PAPR of UWB signals. Deliberate clipping is a simple technique for PAPR reduction. But PAPR reduction of UWB signals by clipping may cause spectral leakage. The spectral power leakage to outside frequency bands causes interference with the other systems operating in the vicinity of UWB. Global Positioning System (GPS) has a pivotal role in so many critical systems upon which the public depends for its safety and well-being, and thus it is necessary to assess the interference to the GPS band due to UWB signals spectral leakage. Therefore, in this paper, the interference to the GPS caused by spectral leakage of clipped direct-sequence UWB (DS-UWB) signals and multiband orthogonal frequency division multiplexing UWB (MB-OFDM UWB) signals is assessed, and the effect of filtering after clipping on the spectral leakage is evaluated using power spectral density (PSD) and bit-error rate (BER) as performance measures.