Search Results (55)

This study focuses on using constant and ramp cyclic processes to evaluate the performance of acrylonitrile–butadiene–styrene (ABS) copolymer with electron beam irradiation cross-linking. The main objective of this study is to compare the effects of both constant and ramp cyclic thermal processes on ABS where the results demonstrated degradation effects on ABS and its irradiated products. Under constant thermal ageing at 100 °C, the impact strength of the samples decreased drastically with increasing irradiation dosage, reaching a minimum value of 54 J/m² at 250 kGy. Tensile strength also showed a significant reduction, with values dropping from 49 MPa to 43 MPa for samples aged for 2 and 8 days, respectively, when dosages exceeded 100 kGy. This degradation is attributed to the chain scission process induced by prolonged thermal ageing and heating effects. In the ramp cyclic thermal ageing condition (Ramp-100), the impact strength followed a trend similar to the constant 100 °C thermal effect but exhibited less severe degradation. The impact strength decreased from 72 J/m² to 58 J/m² for the ramp cyclic effect compared to the greater reduction in the constant 100 °C condition (73 J/m² to 54 J/m²). This difference is likely due to the less harsh, intermittent heating ramp cyclic process compared to the continuous heating, suggesting that intermittent heating mitigated thermal degradation and chain scission mechanisms. Differential Scanning Calorimetry (DSC) analysis verified the effects of irradiation and thermal ageing on thermal properties. For unaged samples, the melting temperature remained low at 106.24 °C. With irradiation dosages of 100 and 200 kGy, the melting temperature increased to 107.76 °C and 111.43 °C, respectively, likely due to enhanced intermolecular bonding from increased cross-linking. Overall, cyclic thermal ageing caused less significant degradation of ABS products compared to constant thermal ageing. This suggests that ABS products have a longer service life in environments with ramp cyclic temperature variations compared to constant temperature conditions, which accelerate degradation. Full article

The structural damage repair of composite material is an important issue that needs to be addressed during the service life of composite materials. To investigate the effects of a scarf structure and scarf angle on the repair quality of composite material, this paper proposes a mixed-scarf (MS) repair structure that combines ramped-scarf (RS) and stepped-scarf (SS) repair structures. The effect of the repair structure on the mechanical properties was analyzed, as well as the quality of the adhesive interface. The results show that at a scarf angle of 10°, the repair efficiency and the quality of adhesive interface are better than that of scarf angles of 20° and 30°. At a scarf angle of 10°, the recovery degree of the flexural strength of the MS repair structure is 79.72%, which is 6.77% and 38.24% higher than that of the RS and SS repair structures, respectively. However, in terms of flexural modulus, regardless of repair structure, the flexural modulus is highest at a scarf angle of 20°. Furthermore, the impact strength of the MS repair structure is approximately 87.60% that of the RS repair structure; additionally, it exhibits an increase of 45.83% compared to the SS repair structure. Overall, the quality of the adhesive interface for the RS and MS repair structures is similar and better than that of the SS repair structure. In conclusion, the MS repair structure is well suited for small-angle scarf repairs, whereas the RS repair structure is more appropriate for large-angle repairs; in contrast, the SS repair structure demonstrates the least effective performance in terms of repair outcomes. Full article

This paper examines the transformative effects of decarbonization on electricity market design, emphasizing the challenges and opportunities posed by the rapid integration of renewable energy sources such as wind and solar. It analyzes the evolution of key wholesale market segments—including day-ahead, real-time, capacity, long-term purchase agreements, ancillary services, and transmission markets—highlighting their critical roles in managing the variability of renewable energy generation through efficient price signals and resource coordination. Variable renewable energy integration introduces significant operational challenges, including overgeneration risks, ramping capacity demands, forecast inaccuracies, and transmission constraints. Addressing these issues requires enhanced market flexibility, dynamic pricing mechanisms, and advanced real-time balancing strategies. This paper assesses these challenges, offering strategies to align generation with demand and optimize market outcomes. As electricity systems evolve, legacy market structures must adapt to incorporate carbon-free resources while maintaining grid reliability and economic sustainability. By exploring case studies such as Chile and California, this paper demonstrates the importance of targeted innovations in market design, regulatory frameworks, and operational technologies. It advocates for a holistic approach to ensure a reliable, affordable, and equitable transition to a decarbonized energy future. Full article

The global navigation satellite system (GNSS) struggles to deliver the precision and reliability required for positioning, navigation, and timing (PNT) services in environments with severe interference. Fifth-generation (5G) cellular networks, with their low latency, high bandwidth, and large capacity, offer a robust communication infrastructure, enabling 5G base stations (BSs) to extend coverage into regions where traditional GNSSs face significant challenges. However, frequent multi-sensor faults, including missing alarm thresholds, uncontrolled error accumulation, and delayed warnings, hinder the adaptability of navigation systems to the dynamic multi-source information of complex scenarios. This study introduces an advanced, tightly coupled GNSS/5G/IMU integration framework designed for distributed PNT systems, providing all-source fault detection with weighted, robust adaptive filtering. A weighted, robust adaptive filter (MCC-WRAF), grounded in the maximum correntropy criterion, was developed to suppress fault propagation, relax Gaussian noise constraints, and improve the efficiency of observational weight distribution in multi-source fusion scenarios. Moreover, we derived the intrinsic relationships of filtering innovations within wireless measurement models and proposed a time-sequential, observation-driven full-source FDE and sensor recovery validation strategy. This approach employs a sliding window which expands innovation vectors temporally based on source encoding, enabling real-time validation of isolated faulty sensors and adaptive adjustment of observational data in integrated navigation solutions. Additionally, a covariance-optimal, inflation-based integrity protection mechanism was introduced, offering rigorous evaluations of distributed PNT service availability. The experimental validation was carried out in a typical outdoor scenario, and the results highlight the proposed method’s ability to mitigate undetected fault impacts, improve detection sensitivity, and significantly reduce alarm response times across step, ramp, and multi-fault mixed scenarios. Additionally, the dynamic positioning accuracy of the fusion navigation system improved to 0.83 m ($1\sigma$). Compared with standard Kalman filtering (EKF) and advanced multi-rate Kalman filtering (MRAKF), the proposed algorithm achieved 28.3% and 53.1% improvements in its $1\sigma$ error, respectively, significantly enhancing the accuracy and reliability of the multi-source fusion navigation system. Full article

In order to enhance the development efficiency of thick and complex carbonate reservoirs in the Middle East, a case study was conducted on M oilfield in Iraq. This study focused on reservoir characterization, injection-production modes, well pattern optimization, and other related topics. As a result, key techniques for the high-efficiency development of thick carbonate reservoirs were established. The research findings include the following: (1) the discovery of hidden “low-velocity” features within the thick gypsum-salt layer, which led to the development of a new seismic velocity model; (2) the differential dissolution of grain-supported limestones is controlled by lithofacies and petrophysical properties, resulting in the occurrence of “porphyritic” phenomena in core sections. The genetic mechanism responsible for reversing petrophysical properties in dolostones is attributed to “big hole filling and small hole preservation” caused by dense brine refluxing; (3) fracture evaluation technology based on anisotropy and dipole shear wave long-distance imaging was developed to address challenges associated with quantitatively assessing micro-fractures; (4) through large-scale three-dimensional physical models and numerical simulations, it was revealed that water–oil displacement mechanisms involving “horizontal breakthrough via hyper-permeability” combined with vertical differentiation due to gravity occur in thick and heterogeneous reservoirs under spatial injection-production modes; (5) a relationship model linking economic profit with well pattern density was established for technical service contracts in the Middle East. Additionally, an innovative stepwise conversion composite well patterns approach was introduced for thick reservoirs to meet production ramp-up requirements while delaying water cut rise; (6) a prediction technology for the oilfield development index, considering asphaltene precipitation, has been successfully developed. These research findings provide robust support for the efficient development of the M oilfield in Iraq, while also serving as a valuable reference for similar reservoirs’ development in the Middle East. Full article

The support capacity of built barrier-free facilities often does not align with the actual needs of urban residents, leading to travel obstacles for people with disabilities and posing a threat to the healthy and sustainable development of cities. It is necessary to evaluate the performance of barrier-free facilities from the perspective of demand. However, traditional performance evaluation methods conceal the differences in barrier-free facility performance among different groups of people. Therefore, this paper aims to clarify the barrier-free demand attributes of urban residents under different behavioral states, quantify the differences in residents’ needs based on demand priorities, and establish a human factor performance evaluation model for barrier-free facilities. Eighteen barrier-free needs of Chinese urban residents were identified through text mining. The demand priorities of individuals in various behavioral states for four typical ramps were then calculated using the Kano comprehensive satisfaction coefficient and importance coefficient. Expert evaluations of the facilities’ fulfillment of needs were gathered using the fuzzy Delphi method. Finally, the human factor performance of the facilities was determined based on the demand priority and fulfillment levels. The results show that even barrier-free facilities with high performance exhibit performance inequalities among the population, and this inequality is more obvious in relatively disadvantaged groups. Building a coordinated barrier-free environment with facilities, services, and assistive devices is an effective means to make up for the insufficient performance of barrier-free facilities. This approach not only enhances the support capacity of the environment but also contributes to the sustainable development of urban communities by ensuring equitable access for all residents. Full article

The increasing utilisation of the distribution grid caused by the ramp-up of electromobility and additional electrification can be eased with flexibility through smart and bidirectional charging use cases. Implementing market-oriented, grid-, and system-serving use cases must be tailored to the different national framework conditions, both in technical and regulatory terms. This paper sets out an evaluation methodology for assessing the implementation of smart and bidirectional charging use cases in different countries. Nine use cases are considered, and influencing factors are identified. The evaluation methodology and detailed analysis are applied to Austria, the Czech Republic, Denmark, Finland, France, Germany, Italy, the Netherlands, Spain, and Sweden. In every country, the implementation of vehicle-to-home use cases is possible. Realising market-oriented use cases is feasible in countries with a completed smart meter rollout and availability of tariffs with real-time pricing. Grid-serving and ancillary service use cases depend most on country-specific regulation, which is why no clear trend can be identified. Use cases that require direct remote controllability are the most distant from implementation. The overarching analysis provides orientation for the design of transnational products and research and can serve as a basis for a harmonisation process in regulation. Full article

Most existing coal-fired power plants were designed for sustained operation at full load to maximize efficiency, reliability, and revenue, as well as to operate air pollution control devices at design conditions. Depending on plant type and design, these plants can adjust output within a fixed range in response to plant operating or market conditions. The need for flexibility driven by increased penetration of variable and non-dispatchable power generation, such as wind and solar, is shifting the traditional mission profile of thermoelectric power plants in three ways: more frequent shutdowns when market or grid conditions warrant, more aggressive load ramp rates (rate of output change), and a lower minimum sustainable load, which provides a wider operating range and helps avoid costly plant shutdowns. Recent studies have shown that the flexibility of a coal-fired power plant can be improved by energy storage. The objective of this work was to analyze a set of energy storage options and determine their impact on the flexibility and economics of a representative coal-fired power plant. The effect of three energy storage systems integrated with a coal power plant on plant flexibility and economics was investigated. The results obtained in this project show that energy storage systems integrated with a thermal power plant improve plant flexibility and participation in the energy and ancillary services markets, which improves plant financial performance. The study was funded by the U.S. Department Office of Fossil Energy FE-1 under award number DE-FE0031903. Full article

A high proportion of renewable energy access makes the net load of the power system volatile and uncertain, increasing the demand for the ramping capacity of the power system. Traditional electricity spot markets compensate for the power imbalances caused by an insufficient ramping capacity through traditional flexibility services such as ancillary services and interconnection power. However, conventional flexibility services may lead to frequency deviations in the power system, increased response costs, spikes in electricity prices, and dramatic price volatility in the traditional spot market. To solve the above problems, this paper proposes an FRP and convex electricity spot market joint clearing (FCESMJC) market mechanism. The FCESMJC model can more accurately represent the relationship between electrical power output and the price of electricity and reduces the number of spikes in electricity prices. In addition, a novel FRP pricing method is proposed to compensate FRP market participants for their FRP costs more reasonably. Additionally, the difference in system performance is provided by comparing the energy prices, pricing method, clearing prices, and system costs in the FCESMJC method and the traditional electricity spot market. The FCESMJC system reduces the total system cost by 18.6% compared with the electricity spot market. Numerical experiments are simulated on the IEEE 14-bus test system to validate the superiority of the proposed model. Full article

In recent years, energy challenges such as grid congestion and imbalances have emerged from conventional electric grids. Furthermore, the unpredictable nature of these systems poses many challenges in meeting various users’ demands. The Battery Energy Storage System is a potential key for grid instability with improved power quality. The present study investigates the global trend towards integrating battery technology as an energy storage system with renewable energy production and utility grid systems. An extensive review of battery systems such as Lithium-Ion, Lead–Acid, Zinc–Bromide, Nickel–Cadmium, Sodium–Sulphur, and the Vanadium redox flow battery is conducted. Furthermore, a comparative analysis of their working principles, control strategies, optimizations, and technical characteristics is presented. The review findings show that Lead–Acid, Lithium-Ion, Sodium-based, and flow redox batteries have seen increased breakthroughs in the energy storage market. Furthermore, the use of the BESS as an ancillary service and control technique enhances the performance of microgrids and utility grid systems. These control techniques provide potential solutions such as peak load shaving, the smoothing of photovoltaic ramp rates, voltage fluctuation reduction, a large grid, power supply backup, microgrids, renewable energy sources time shift, spinning reserve for industrial consumers, and frequency regulation. Conclusively, a cost summary of the various battery technologies is presented. Full article

Driven by the rapid escalation of its utilization, as well as ramping commercialization, Internet of Things (IoT) devices increasingly face security threats. Apart from denial of service, privacy, and safety concerns, compromised devices can be used as enablers for committing a variety of crime and e-crime. Despite ongoing research and study, there remains a significant gap in the thorough analysis of security challenges, feasible solutions, and open secure problems for IoT. To bridge this gap, we provide a comprehensive overview of the state of the art in IoT security with a critical investigation-based approach. This includes a detailed analysis of vulnerabilities in IoT-based systems and potential attacks. We present a holistic review of the security properties required to be adopted by IoT devices, applications, and services to mitigate IoT vulnerabilities and, thus, successful attacks. Moreover, we identify challenges to the design of security protocols for IoT systems in which constituent devices vary markedly in capability (such as storage, computation speed, hardware architecture, and communication interfaces). Next, we review existing research and feasible solutions for IoT security. We highlight a set of open problems not yet addressed among existing security solutions. We provide a set of new perspectives for future research on such issues including secure service discovery, on-device credential security, and network anomaly detection. We also provide directions for designing a forensic investigation framework for IoT infrastructures to inspect relevant criminal cases, execute a cyber forensic process, and determine the facts about a given incident. This framework offers a means to better capture information on successful attacks as part of a feedback mechanism to thwart future vulnerabilities and threats. This systematic holistic review will both inform on current challenges in IoT security and ideally motivate their future resolution. Full article

With the development of the electricity spot market, pumped-storage power stations are faced with the problem of realizing flexible adjustment capabilities and limited profit margins under the current two-part electricity price system. At the same time, the penetration rate of new energy has increased. Its uncertainty has brought great pressure to the operation of the power system. The ramp market and its market mechanism have emerged as the times require. To this end, this article proposes a bidding strategy for pumped-storage power stations to participate in multi-level markets such as the ramp market. Considering the demand calculation of ramping services, a two-layer model of pumped storage’s participation in multiple markets is constructed. The upper level makes trading decisions with the goal of maximizing pumped-storage revenue; the lower level aims to minimize the total social cost and jointly clears the primary and auxiliary markets. The income from pumped storage participating in the main energy and ramp-up auxiliary markets at the same time is significantly higher than the income from the two-part electricity price system. Its flexible adjustment ability can be quantified, reducing dependence on capacity electricity charges and providing a theoretical reference for cost recovery and profitability of future pumped-storage power stations. Full article

The aim of this study was to explore the outcomes of pelvic reconstruction with a rectus abdominis myocutaneous (RAM) or rectus abdominis myoperitoneal (RAMP) flap following radical surgery for gynecologic malignancy. This is a retrospective case series of all pelvic reconstructions with RAM or RAMP flap performed in a gynecologic oncology service between 1998 and 2023. Reconstructions with other flaps were excluded. A total of 28 patients were included. Most patients had vulvar cancer (n = 15, 53.6%) and the majority had disease recurrence (n = 20, 71.4%). Exenteration was the most common procedure, being carried out in 20 (71.4%) patients. Pelvic reconstruction was carried out with a RAM flap in 24 (85.7%) cases and a RAMP flap in 4 (14.3%) cases. Flap-specific complications included cellulitis (14.3%), partial breakdown (17.9%), and necrosis (17.9%). Donor site complications included surgical site infection and necrosis occurring in seven (25.0%) and three (10.7%) patients, respectively. Neovaginal reconstruction was performed in 14 patients. Out of those, two (14.3%) had neovaginal stenosis and three (21.4%) had rectovaginal fistula. In total, 50% of patients were disease-free at the time of the last follow up. In conclusion, pelvic reconstruction with RAM/RAMP flaps, at the time of radical surgery for gynecologic cancer, is an uncommon procedure. In our case series, we had a significant complication rate with the most common being infection and necrosis. The development of a team approach, with input from services including Gynecologic Oncology and Plastic Surgery should be developed to decrease post-operative complications and improve patient outcomes. Full article

This paper highlights the importance of accurately modeling the operational constraints of Combined-Cycle Gas Turbines (CCGTs) within a unit-commitment framework. In practice, in Colombia, when given an initial dispatch by the Independent System Operator, CCGT plants are operated according to the results of heuristic simulation codes. Such heuristics often omit technical operating constraints, including hot, warm, or cold startup ramps; the minimum operation hours required for a gas turbine to start a steam turbine; the relationship between the dispatched number of steam and gas turbines; the load distribution among gas turbines; and supplementary fires. Most unit-commitment models in the literature represent standard technical constraints like startup, shutdown, up/down ramps, and in some cases, supplementary fires. However, they typically overlook other real-life CCGT operating constraints, which were considered in this work. These constraints are crucial in integrated energy systems to avoid equipment damage, which can potentially put CCGT plants out of service and ultimately lead to lower operating costs. Full article

Identifying the bottleneck segments and developing targeted traffic control strategies can facilitate the mitigation of highway traffic congestion. In this study, we proposed a new method for identifying the bottleneck segment in a large highway network based on the percolation theory. A targeted on-ramp control approach was further developed by identifying the major vehicle sources of the bottleneck segment. We found that the identified bottleneck segment played a crucial role in maintaining the functional connectivity of the highway network in terms of meeting the required level of service. The targeted on-ramp control approach can more effectively enhance the service level of the highway network. Full article