Recovery Scheme Research Articles

An Efficient Tamper Detection and Recovery Scheme for Attacked Speech Signal

An Efficient Tamper Detection and Recovery Scheme for Attacked Speech Signal

Synthesis of green light olefins from direct hydrogenation of CO2. Part I: Techno-economic, decarbonization, and sustainability analyses based on rigorous simulation

BackgroundsConverting CO2 into light olefins through direct hydrogenation is a promising pathway to achieve net-zero emissions. This part aims to present a detailed layout and the analysis results of the process through rigorous simulation. MethodologyThe process encompasses three sections (reaction, CO2 removal, and olefin recovery). Two alternatives for handling the off-gas were proposed, including sending it for additional hydrogen recovery (Scheme 1) or direct combustion (Scheme 2). The minimum required selling price (MRSP), the indirect CO2 emissions per kg of olefins produced (CO2-e), and the carbon efficiency are demonstrated for process evaluation. Significant FindingsScheme 1 demonstrates better economic performance but less decarbonization ability compared to Scheme 2 (i.e. Scheme 1: MRSP = 2327 USD/kg and CO2-e = -2.036 kg/kg; Scheme 2: MRSP = 2366 USD/kg and CO2-e = -2.247 kg/kg). To achieve carbon neutrality, the carbon footprint for the hydrogen feedstock should not exceed 6.92 and 7.08 kg-CO2/kg-H2 for Schemes 1 and 2, respectively. Considering the trade-offs between MRSP and CO2-e, using biomass-based hydrogen is currently the most viable option. Finally, the entire process has a 99.7 % carbon efficiency. In summary, the proposed process is effective in CO2 fixation, with minimal impact on the process economics and sustainability.

Hydrogen assisted cracking using an efficient virtual element scheme

In this paper, a novel virtual element formulation is proposed for phase field modeling of hydrogen assisted cracking (HAC). The multiphysics variational framework is decoupled into three parts which can be solved in a staggered manner, namely, the mechanical, diffusion, and damage sub-problems. The damage and diffusion sub-problems are treated as reaction–diffusion types of equations. The former is subjected to irreversibility constraints while the latter incorporates a transport term to represent the effect of mechanical loading. An efficient super-convergent patch recovery (SPR) scheme is utilized to determine the coefficient of transport term in the hydrogen diffusion equation. Several qualitative and quantitative benchmark problems are considered to validate the proposed framework’s performance. The results show excellent agreement with the corresponding FEM and experimental studies. Meanwhile, without loss of numerical accuracy, the VEM outperforms the FEM with regards to CPU time & memory efficiency and exhibits remarkable versatility in the selection of different element types for simulation. Moreover, this work demonstrates the potential of facilitating the VEM to solve real-scale fracture mechanics problems with multi-physics coupling.

A Triple Self-Embedding Fragile Watermarking Scheme for Image Tamper Detection and Recovery

A Triple Self-Embedding Fragile Watermarking Scheme for Image Tamper Detection and Recovery

A block-based fragile watermarking scheme for digital image authentication and tamper recovery

A block-based fragile watermarking scheme for digital image authentication and tamper recovery

Минералого-геохимические особенности золотосодержащих руд месторождения Пакрут (Центральный Таджикистан) как основа гравитационного обогащения

The mining sector, in particular gold mining, plays an important role in the economy of Tajikistan. Today, the issue of optimizing gold mining mechanisms, increasing its efficiency and expanding the resource base is of topical importance. The depletion of easily accessible gold deposits is stimulating the development of methods for extracting gold from refractory and low-grade ores. One of the promising methods of pre-treatment of such ores is gravity enrichment. The aim of the study is to characterize the Pakrut gold deposit, to determine its mineralogical and chemical composition, and to develop an optimal gravity enrichment scheme for gold recovery. Research objectives are as follows: to study the mineralogical composition and geochemical characteristics of gold-bearing ores, and then to develop a technique for their gravitational enrichment. The object of the study is the gold-bearing ores of the Pakrut deposit (Central Tajikistan). Materials and methods of research: analytical work and enrichment in laboratory conditions were carried out in the chemical laboratory of the Pakrut Joint Venture, the ore enrichment laboratory of the V. I. Nikitin Institute of Chemistry of NANT, the Central Committee of the Main Geological Directorate under the Government of the Republic of Tajikistan. It is found that gold in the Pakrut ores is mainly represented by native gold and electrum. The main gold-bearing minerals are pyrite, arsenopyrite, sphalerite, galena, jamesonite and some vein minerals. The gold content in the ore is about 6 g/t. The granulometric composition of gold is extremely uneven. Most of the gold particles are less than 10 μm in size and are coated with gold-bearing minerals, which hindered their release during grinding. In accordance with the characteristics of the gold deposit, gravity enrichment method has been used to extract the liberated coarse gold. Studies have shown that the gravity separation process is used for the primary processing of ore to recover coarse gold particles. The gold content and recovery in the gravity separation concentrates are 46.58 g/t and 44.59 %, respectively.

Fault Property Identification and Fault Recovery Scheme for Flexible DC Lines Based on Voltage Injection

Fault Property Identification and Fault Recovery Scheme for Flexible DC Lines Based on Voltage Injection

Scenario analysis of the impact of ANSP mergers on traffic distribution and congestion

Economic efficiency gains are one potential advantage that Air Navigation Service Provider (ANSP) mergers might bring to the European Air Traffic Management system. An ANSP merger might also affect the use of airspace and consequently the level of congestion. In this paper, we analyze possible effects of an ANSP merger on traffic distribution i.e., route choices of an airline, congestion levels in different parts of the airspace, and consequences for airline's costs. We analyze four scenarios for an OD-pair market with a monopoly airline and two neighbouring ANSPs. For each scenario, we consider both cases: two ANSPs operate as competing providers and set different unit rates for the airline, and a merged ANSP operates as a monopoly service provider that sets a uniform unit rate for the airline. In all scenarios, we assume that the ANSPs are regulated based on a full cost recovery scheme. The numerical examples show that the different unit rates create an incentive for the airline to take detours in order to avoid the airspace with the higher en-route charge, resulting in additional fuel burn and emissions. Meanwhile, the uniform unit rate incentivizes the airline to choose the shorter route more often, leading to higher congestion levels on the shorter route and higher total congestion cost for the airline. However, in our numerical example, the decrease in the total distance-related cost outweighs the increase in the total congestion cost, leading to higher airline profits. We conclude that an ANSP merger that leads to a uniform unit rate can bring positive effects to airlines even if its potential efficiency gains are not taken into account.

Characteristics and mechanisms of sustainable recovery of perlite from carrageenan residue by green technology and its application in carrageenan extraction

A large amount of carrageenan residue containing perlite is produced in carrageenan process. Management of carrageenan residue is an environmental issue in carrageenan green and clean production. Repeated recovery of perlite from carrageenan residue could reduce resource waste and environmental pollution. However, research on methods, reuse characteristics, and mechanisms of repeatedly recovered perlite remains lacking. In this study, a green recovery scheme was obtained to recover perlite by combining food-grade hydrochloric acid and hydrogen peroxide, and influence of elemental structure changes on gel structure during repeated recovery was investigated. The permeability of recovered perlite (2.61/Darcy) reached reuse standard, showing good economic value. The C–O–C bond of polysaccharide and inner ether galactose ring in carrageenan residue were degraded by hydrogen peroxide and hydrochloric acid. More importantly, gel strength and transparency of carrageenan increased by 42.86% and 16.46% with recycling times, probably due to repeated adsorption and release of K+ from recovered perlite. The C–K bond effectively shielded electrostatic repulsion between carrageenan segments and promotes formation of gel network. The characteristics of carrageenan and recycling times were consistent with gaussian model, y=y0+Awπ/2e−2(x−xc)2w2, with a maximum number of cycles of 4.21. It provides a technical research basis for green and clean carrageenan extraction.

Innovative approaches for deep decarbonization of data centers and building space heating networks: Modeling and comparison of novel waste heat recovery systems for liquid cooling systems

The data usage surge drives greater data center demand, amplifying global CO2 emissions. Mitigating climate change necessitates reducing data center CO2 emissions. Reusing waste heat from data centers offers a potential energy efficiency boost and environmental impact reduction. This study utilizes liquid cooling technology to raise waste heat temperature for building space heating and introduces the concept of ‘data furnaces,’ where data centers directly supply waste heat to heat buildings on-site, reducing district heating consumption and lowering CO2 emissions. Efficiently designing a heat recovery heat exchanger system that accounts for both heat rejection and cooling sides of a liquid cooling system is crucial for achieving complete heat recovery without using heat pump, a commonly overlooked aspect in existing literature. To address this issue, we propose two heat exchanger schemes: connecting the building space heating network to the secondary side (Scheme 1) and the primary side (Scheme 2) of the cooling distribution unit. Implementing these innovations leads to the elimination of dependence on a heat pump, substantially cutting energy and CO2 emissions. Using TRNSYS software, we develop, model, and compare waste heat recovery schemes to curb district heating consumption and CO2 emissions. To demonstrate broad implications of the proposed approaches for energy efficiency and sustainability in the data centers and building space heating networks, a showcase study examines constant 25 kW waste heat from a direct-to-chip liquid-cooled rack in an office building with 285.7 MWh annual space heating demand. A novel waste heat recovery rate relationship graph is created to assist system design, uncovering an unexpected result in Scheme 2: waste heat recovery decreases as outdoor temperature falls. In contrast, Scheme 1 maintains a stable waste heat recovery rate around 25 kW, regardless of outdoor temperature fluctuations. As a result, Scheme 1 reuses 155.2 MWh of waste heat annually compared to 138 MWh for Scheme 2. Schemes 1 and 2 yield annual electricity savings of 2290.5 kWh and 905.2 kWh, respectively, for the cooling system. Both schemes achieve profitability within a year through a 25-year life cycle analysis (LCC) and substantially reduce CO2 emissions, with Scheme 1 saving 291,996 kgCO2 and Scheme 2 saving 258,192 kgCO2. The study addresses critical gaps in existing literature by emphasizes LCC. The proposed heat exchanger designs represent pioneering solutions for optimizing waste heat recovery, particularly in challenging climates. New findings offer substantial benefits to both liquid-cooled and air-cooled facilities, making significant contributions to achieve carbon neutrality in data center operations.

Multi-objective optimization of supercritical CO2 Brayton cycles for coal-fired power generation with two waste heat recovery schemes

The efficiency of supercritical CO2 (sCO2) Brayton cycle (SCBC) based coal-fired power generation can be enhanced by harnessing the waste heat from sCO2 cooling and flue gas, which currently remains largely untapped. In this paper, we propose two types of design roadmap for utilizing this waste heat. The first method involves using an organic Rankine cycle (ORC) to generate additional power, while the second method utilizes LiBr/H2O absorption refrigeration cycle (ARC) to further cool down compressor inlet sCO2, and thereby reduces its compression power consumption. An energy-economic-environmental multi-criteria models are formulated to access performance of the aforementioned designs and compare them with a standalone sCO2 Brayton recompression cycle system (Standalone). The non-dominated sorting genetic algorithm II is applied to carry out the multi-objective optimization of the three systems. The results show that the SCBC-ARC system achieves the maximum thermal efficiency (ηth) and minimum environmental impact load (EIL), while SCBC-ORC system achieves the minimum levelized cost of electricity (LCOE). We also find that minimizing LCOE conflicts with maximizing ηth and minimizing EIL, respectively. The relationship between maximizing ηth and minimizing EIL is consistent, suggesting that increasing efficiency will alleviate environmental impact of the systems. We also identify and discuss balanced designs for the systems, and our results show that the ηth of SCBC-ORC and SCBC-ARC is 1.40% and 1.70% higher than the Standalone, respectively, the LCOE is 0.56% lower and 3.66% higher than Standalone, respectively, and EIL is 1.16% and 1.59% lower than the Standalone, respectively.

Allocating Indivisible Goods to Strategic Agents: Pure Nash Equilibria and Fairness

We consider the problem of fairly allocating a set of indivisible goods to a set of strategic agents with additive valuation functions. We assume no monetary transfers, and therefore, a mechanism in our setting is an algorithm that takes as input the reported—rather than the true—values of the agents. Our main goal is to explore whether there exist mechanisms that have pure Nash equilibria for every instance and, at the same time, provide fairness guarantees for the allocations that correspond to these equilibria. We focus on two relaxations of envy-freeness, namely, envy-freeness up to one good (EF1) and envy-freeness up to any good (EFX), and we positively answer the preceding question. In particular, we study two algorithms that are known to produce such allocations in the nonstrategic setting: round-robin (EF1 allocations for any number of agents) and a cut-and-choose algorithm of Plaut and Roughgarden (EFX allocations for two agents). For round-robin, we show that all of its pure Nash equilibria induce allocations that are EF1 with respect to the underlying true values, whereas for the algorithm of Plaut and Roughgarden, we show that the corresponding allocations not only are EFX, but also satisfy maximin share fairness, something that is not true for this algorithm in the nonstrategic setting! Further, we show that a weaker version of the latter result holds for any mechanism for two agents that always has pure Nash equilibria, which all induce EFX allocations. Funding: This work was supported by the Horizon 2020 European Research Council Advanced “Algorithmic and Mechanism Design Research in Online Markets” [Grant 788893], the Ministero dell’Università e della Ricerca Research project of national interest (PRIN) “Algorithms, Games, and Digital Markets,” the Future Artificial Intelligence Research project funded by the NextGenerationEU program within the National Recovery and Resilience Plan (PNRR-PE-AI) scheme [M4C2, investment 1.3, line on Artificial Intelligence], the National Recovery and Resilience Plan-Ministero dell’Università e della Ricerca (PNRR-MUR) project IR0000013-SoBigData.it, the Nederlandse Organisatie voor Wetenschappelijk Onderzoek Veni Project [Grant VI.Veni.192.153], and the National Recovery and Resilience Plan Greece 2.0 funded by the European Union under the NextGenerationEU Program [Grant MIS 5154714].

Mitigating the impact of controller failures on QoS robustness for software-defined wide area networks

Emerging cloud services and applications pose different Quality of Service (QoS) requirements for the network, where Software-Defined Wide Area Networks (SD-WANs) play a crucial role in QoS provisioning by introducing network programmability into network flows to enable dynamic flow routing and ensure low data transmission latency for these applications. However, controller failures may happen in SD-WANs, and all programmable flows that the failed controller previously controlled will become offline and lose the network programmability, resulting in the degradation of QoS. Existing control recovery solutions propose to remap offline switches/flows to available active controllers but cannot promise good recovery performance due to the following two problems: (1) the recovery performance suffers from either coarse-grained remapping granularity or introducing extra processing delays, and (2) QoS robustness cannot be guaranteed in the design of recovery solution. To this end, we propose Predator, a QoS-aware network programmability recovery scheme that utilizes the P4 Runtime enabled by existing P4 switches to achieve fine-grained per-flow remapping without introducing extra delays. Specifically, our proposed Predator categorizes flows based on their QoS requirements and smartly recovers offline flows based on their priorities to guarantee the QoS robustness for high-priority flows. Simulation results under real-world topology demonstrate that our proposed Predator can improve the recovered network programmability of high-priority flows by up to 505.5%, and substantially reduce the communication overhead of high-priority flows, compared with baselines.

Energy management and performance analysis of an off-grid integrated hydrogen energy utilization system

In integrated hydrogen energy utilization systems, due to the low efficiency of hydrogen/electricity conversion, coordination of energy management and efficient waste heat recovery is required to optimize performance. To address this challenge, this paper presents a comprehensive and sophisticated modeling and energy management strategy to enhance the off-grid energy utilization rate while prolonging the main components’ lifetime. The developed model incorporates multiphase flow and heat transport balance for electricity and heat production, enabling a highly accurate representation of real-world behaviors of the system. The proposed off-grid operation strategy is complemented by a designed heat recovery scheme, ensuring the use of energy resources and waste heat. In addition, the proposed energy management strategy monitors the real-time status of each subsystem, actively reducing the number of harmful start-stop cycles of the hydrogen production system, thereby mitigating short-term power impacts and delaying its aging. Specifically, the voltage degradation of the reduction cell is reduced from 4.67 mV to 4.48 mV, the energy utilization rate is increased from 47.6 % to 53.9 %, and the energy efficiency of fuel cells significantly increases from 53.6 % to 78.1 %.

Development of a Testing System for High-efficiency Power Recovery Bag Accumulators

Currently, most of the bladder-type accumulator test benches used have problems such as large installed capacity, severe energy loss, and incomplete testing functions. This article focuses on the research of the testing requirements and power recovery issues of bladder-type accumulators. A new type of hydraulic schematic and electrical control system for power recovery bladder type accumulator testing based on mechanical compensation with dual output shaft motor transmission, differential charging and discharging of dual accumulators, and parallel addition of oil replenishing accumulators has been designed. A measurement and control software based on the LabVIEW platform has been developed. The experimental results show that the system’s power recovery efficiency can reach 60.5% by adopting a scheme of mechanical compensation type power recovery, differential charging and discharging of energy accumulator group, and parallel addition of oil replenishing energy accumulator. The testing system can accurately, efficiently, and conveniently complete various performance tests of hydraulic bladder accumulators.

Self-Healing Secure Blockchain Framework in Microgrids

Blockchain has recently been depicted as a secure protocol for information exchange in cyber-physical microgrids. However, it is still found vulnerable to consensus manipulation attacks. These stealth attacks are often difficult to detect as they use kernel-level access to mask their actions. In this paper, we firstly build a trusted and secured peer-to-peer network mechanism for physical DC microgrids’ validation of transactions over Distributed Ledger. Secondly, we leverage from a physics-informed approach for detecting malware-infected nodes and then recovering from stealth attacks using a self-healing recovery scheme augmented into the microgrid Blockchain network. This scheme allows compromised nodes to adapt to a reconstructed trustworthy signal in a multi-hop manner using corresponding measurements from the reliable nodes in the network. Additionally, recognizing the possible threat of denial-of-service attacks and random time delays (where information sharing via communication channels is blocked), we also integrate a model-free predictive controller with the proposed system that can locally reconstruct an expected version of the attacked/delayed signals. This supplements the capabilities of Blockchain, enabling it to detect and mitigate consensus manipulation attempts, and network latencies.

Design of Low Quality Heat Recovery and Utilization System for Fixed Discharge of Coal-fired Boilers

In order to optimize the energy structure, increase the proportion of clean heat sources, and solve the problem of high energy consumption for heating, a waste heat recovery scheme is planned to be designed, which mainly recovers the waste heat of the 700MW boilers in the thermal power plant, which can be used to heat the condensed water of the steam turbine in summer., It can be used to heat the circulating water in the heating network in winter to achieve the goal of recovering heat and reducing energy consumption. In the design process, a lithium bromide absorption heat pump is used as the main system for low-quality heat recovery, and steam is used as a driving heat source to release heat in the generator to heat a dilute solution of lithium bromide to generate refrigerant vapor, thereby achieving high efficiency, energy saving and economic benefits. the goal of. At the same time, two booster pumps (one for transport and one for standby) are added to the condensate pipeline at the inlet of the low-low temperature economizer system to achieve the purpose of boosting the condensate. This design plan adheres to the concept of energy saving and environmental protection, and proposes a technical transformation route for low-quality heat recovery and utilization projects to achieve the goals of reducing production costs and increasing corporate benefits.

Research on hydraulic braking energy recovery system of heavy vehicles

The carbon emission of a heavy-duty diesel vehicle is almost equal to the sum of 100 small cars. In the global environment where energy conservation and emission reduction are advocated, the pollution caused by heavy vehicles is non-negligible. A hydraulic brake energy recovery and regeneration system can store the braking energy, convert the energy into kinetic energy and output it to the vehicle transmission system when starting or accelerating, thereby reducing energy consumption and achieving the role of energy conservation and emission reduction. Firstly, this paper mainly summarizes several vehicle energy recovery technology schemes and determines the hydraulic braking energy recovery scheme after a comprehensive comparison. Secondly, the overall structure of the hydraulic brake energy recovery and regeneration system is designed, and the working mode is analyzed. Finally, according to the working characteristics of the main components in the system, the mathematical model is established, the key parameters are simulated and studied, and the appropriate selection and matching scheme is provided.

The Synergetic Economic Evaluation of PSC Cost Recovery and Gross Split Schemes on Field A

In month of August, year 2021, there was an alteration in the production-sharing contract for this field. The contract previously used was Production Sharing Contract (PSC) Cost Recovery, which changed to PSC Gross Split. This contract comparison aims to synergetically evaluate the comparison of the two economic models and also to determine a more efficient and appropriate scheme to be applied to field A, as well as to analyze the parameters that can affect the economic indicators of field A. The results of the economic analysis that has been carried out show that the PSC Gross Split scheme is better than the PSC Cost Recovery scheme. For PSC Cost Recovery, the Net Present Value (NPV) obtained for 30 wells is equal to 13,848,000 US$, the average Interest Rate of Return (IRR) is 118%, the average Pay Out Time (POT) is 1.43 years, the Contractor Take is 20,740,000 US$, and the Government Take is 176,587,000 US$. Whereas for PSC Gross Split, the NPV obtained for 30 wells was US$ 37,906,000, the average IRR was 245%, the average POT was 1.30 years, the Contractor Take was US$ 52,544,000, and the Government Take was 136,402,000 US$. The sensitivity analysis that has been carried out shows that the parameters of the amount of oil production and the price of oil have a significant effect on both schemes.

Achieving Crash Fault Tolerance In Autonomous Vehicle Autopilot Software Stacks Through Safety-Critical Module Rejuvenation

Autonomous driving vehicles (ADV), have been in recent years, victims of their own success. Through their use of increasingly sophisticated sensor modalities and deep learning capabilities, ADVs have not only learned how to probe their chaotic environment with higher granularity coupled with smooth trajectory execution but also inherited all the vulnerabilities that were hiding behind these new features. Ensuring the safety of ADVs is crucial since a simple fault along their underlying autopilot software stack can lead to catastrophic accidents with the loss of human lives. Therefore we propose a crash-fault tolerant scheme that can be triggered whenever a crash fault of the safety critical submodules of the autopilot software stack is detected, which executes an emergency trajectory and effectively steers the car into a safe spot where the autopilot can be rejuvenated. We implement and evaluate the efficacy of this recovery scheme in the Apollo ADV software stack in conjunction with the SVL simulator. Keywords: autonomous driving vehicles, rejuvenation, crash fault tolerance, simplex architecture, apollo software stack.