Engineering Structures Research Articles

Increasing the reliability of oil and gas well fastening with polycomponent plugging systems

Purpose. Development of effective composite plugging systems for reliable fastening of oil and gas wells in difficult mining-geological conditions of deposits of Ukraine. Methods. The proposed research is based on an analytical and industrial study of the problems of the well construction and fastening in the conditions of chemogenic deposit occurrence when applying the analysis of geophysical research materials. The research of tamponage solutions and buffer liquids was carried out using standard devices and methods that meet the set of requirements for testing cements and technological systems for well construction. Processing of research results was carried out in MATHSAD and EXCEL. Composite cement CEM V according to the European standard EN 197-1, tamponage cement 1-G, krents - high-basic C2F CaSO4 and low-basic 3(CF) CaSO4 calcium sulfoferites were used for the research. Findings. It was established that the basic plugging material, as well as technological solutions for fastening wells in difficult mining-geological conditions, do not ensure compliance of the well as an engineering structure with operational reliability indicators. As a result, violations in the fastening system are quite often recorded, which require significant time and financial costs for their elimination, and sometimes lead to well liquidation. In order to increase the reliability of fastening wells, it is necessary to use multi-component tamponade systems modified by krents. Calcium sulfoferrite admixtures have been proved to accelerate the kinetics of early strength and contribute to the formation of cement stone with improved characteristics. The need to use effective buffer systems to improve the quality of fastening is substantiated. Originality. On the basis of assessment, systematization and detailed study of geophysical material and features of well fastening under the conditions of exposure to chemogenic sediments, the necessity of using composite plugging material was established. The conducted studies have proved that to ensure reliable fastening of wells in difficult mining-geological conditions, it is necessary to use multicomponent composite plugging material modified by calcium sulfoferites with accelerated kinetics of early strength, which form cement stone with a densely packed structure. Practical implications. Based on the industrial material evaluation and detailed laboratory studies, technological solutions have been developed to increase the reliability of well fastening due to the introduction of multi-component composite plugging material modified by krents and buffer liquids.

Application of Computer-Aided Design Software to the Simulation and Analysis of Composite Material Properties in Housing Engineering Structures

Reinforced polymer composites are widely used in engineering applications due to their excellent mechanical properties, and this paper combines experiments and numerical simulations to fully examine the properties of the composites. The article takes the reinforced concrete structure of civil engineering as the basis for experimental testing on the basic properties of carbon fiber composites in its application. Subsequently, the intrinsic model of reinforced concrete and carbon fiber composites was constructed, and each finite element unit of the member was selected to simulate and finite element analysis the performance of the composites through ABAQUS computer-aided design software. The results show that increasing the diameter of carbon fibers will reduce the number of carbon fibers at the same time, which will reduce the toughness of the composite material, random and chaotic distribution of carbon fibers for the improvement of the compressive properties of concrete can achieve a relatively balanced effect, and the high elastic modulus carbon fibers for the improvement of uniaxial and cyclic compressive properties of concrete play a dominant role. In addition, the oriented elliptical fibers in the long-axis direction have a significant increase in the modulus of elasticity and strength of the material, and this phenomenon will become more and more obvious with the increase of the length-to-diameter ratio. The reasonable structural design may help to improve the performance of composites and enhance their adaptability for engineering applications.

Enhanced solar hydrogen evolution by laminated integration of n+p-SiIP/TiO2/Pt inverted pyramid black Si photocathode

The nano/microstructuring of silicon (Si) via chemical methods has garnered significant attention due to its excellent light-trapping capabilities across a wide spectral range. Current research has predominantly focused on the synthesis of pyramidal-shaped microtextures, which enable two reflections on the surface, while largely overlooking the superior light-trapping potential of inverted pyramid silicon (SiIP) microtextures, which theoretically allow for three reflections. Moreover, there has been limited investigation into the application of inverted pyramid black silicon for solar-driven hydrogen evolution. This study reports the synthesis of uniformly arranged inverted pyramid-textured black silicon using the copper-assisted chemical etching (Cu-ACE) method to enhance the efficiency of solar-driven water splitting for hydrogen production. The formation mechanism and the influence of copper-localized surface plasmon resonance (Cu-LSPR) from Cu nanoparticle (NP) byproducts on photoelectrochemical (PEC) activity were systematically analyzed. To reduce sidewall defects and minimize photogenerated carrier recombination, the surface of the SiIP was treated with tetramethylammonium hydroxide (TMAH). A vertical PN junction was developed through ion implantation to reduce the external bias of the SiIP. Additionally, a uniform TiO₂ antireflective layer was deposited via atomic layer deposition (ALD), reducing the average reflectance of the SiIP-T4 to 5.78 % over the 300–1100 nm wavelength range. MoSₓ and Pt NPs were electrodeposited to improve the fill factor and enhance HER kinetics. With optimized catalyst loading, the n+p-SiIP-T4/TiO₂/Pt 80 mC electrode achieved a photocurrent density of 8.0 mA cm−2 at 0 V vs. RHE, an applied bias photon-to-current efficiency (ABPE) of 0.93 % at 0.24 V vs. RHE, and a double-layer capacitance (Cdl) of 91 μF cm−2. The onset potential (Von) was positively shifted by ∼1.13 V to 0.49 V vs. RHE compared to a SiIP photocathode, and the photocathode operated continuously at 0 V vs. RHE for 27 h in an acidic electrolyte. These results demonstrate that SiIP has significant potential for PEC hydrogen evolution, with further performance optimization achievable through structural and surface engineering.

Self-Templating Engineering of Hollow N-Doped Carbon Microspheres Anchored with Ternary FeCoNi Alloys for Low-Frequency Microwave Absorption.

Rational design and precision fabrication of magnetic-dielectric composites have significant application potential for microwave absorption in the low-frequency range of 2-8GHz. However, the composition and structure engineering of these composites in regulating their magnetic-dielectric balance to achieve high-performance low-frequency microwave absorption remains challenging. Herein, a self-templating engineering strategy is proposed to fabricate hollow N-doped carbon microspheres anchored with ternary FeCoNi alloys. The high-temperature pyrolysis of FeCoNi alloy precursors creates core-shell FeCoNi alloy-graphitic carbon nano-units that are confined in carbon shells. Moreover, the anchored FeCoNi alloys play a critical role in maintaining hollow structural stability. In conjunction with the additional contribution of multiple heterogeneous interfaces, graphitization, and N doping to the regulation of electromagnetic parameters, hollow FeCoNi@NCMs exhibit a minimum reflection loss (RLmin) of -53.5dB and an effective absorption bandwidth (EAB) of 2.48GHz in the low-frequency range of 2-8GHz. Furthermore, a filler loading of 20wt% can also be used to achieve a broader EAB of 5.34GHz with a matching thickness of 1.7mm. In brief, this work opens up new avenues for the self-templating engineering of magnetic-dielectric composites for low-frequency microwave absorption.

Application of Polymer Sheets with Anchor Ribs in the Repair and Reconstruction of Reinforced Concrete Water Supply Storage Structures

The conducted studies have shown that no optimal and effective solution would ensure reliable operation throughout the entire service life of tank structures. The search for effective and innovative technical solutions in this area is a pressing issue. The study aims to determine an effective material for providing secondary protection of a reinforced concrete structure to increase the operational characteristics of tank structures. The conducted experimental studies have shown the possibility of using a polymer sheet with anchor ribs as protection for a reinforced concrete structure. Protection of reinforced concrete structures remains a key aspect of the design and operation of facilities exposed to aggressive media. The conducted studies have shown that there is no optimal and effective solution providing reliable operation during the whole service life of capacitive structures. Search for effective and innovative technical solutions in this area is an urgent task. The research aims to determine an effective material for secondary protection of reinforced concrete structures to increase the operational characteristics of capacitive structures. The performed experimental studies showed the possibility of using polymer sheets with anchor ribs as protection for reinforced concrete structures. The article discusses the use of polymer sheets with rail-shaped anchor ribs for protection of the inner surface of reinforced concrete engineering structures from aggressive influence.

Geological hazards when justifying the regulations of urban development

Relevance. Territorial planning of cities determines the reduction or prevention of possible or existing losses of the population, economic facilities and the environment from technoprirodnye hazards of different genesis. The effectiveness of planning regulations for urban development depends on the degree of validity of identification and forecasts of the occurrence and evolution of hazardous natural and technogenic processes in time and space. This, in its turn, is determined by the reliability of our ideas about the patterns of their formation and regional distribution. Aim. To identify geological hazards and propose the main engineering and geological constraints in urban planning on the example of Gomel. Objects. Natural and technical system "geological environment – technogenic impacts – hazardous natural and technoprirodnye processes". Methods. Systematic approach to the analysis of patterns of formation of hazardous natural and technoprirodic processes in the city; numerical modeling of geofiltration and geomigration processes based on the geofiltration model "GOMEL". Results. The most characteristic dangerous natural and technoprirodnye processes have been established on the example of the city of Gomel. Priority areas for the introduction of planning restrictions: tectonic situation; man-made flooding, were identified. Soil conditions are considered separately as one of the factors effecting the precipitation of natural and artificial bases under the influence of loads from civil and industrial buildings and structures. The authors have revealed the presence of disjunctive, as well as plicative in the form of flexures, age-varying and multi-scale dislocations forming the block structure of the upper part of the earth's crust of the city. It is shown that from the point of view of the stability of engineering structures, the absolute values of the velocities of long-period unidirectional block displacements are dangerous during long-term operation of structures located in interblock active zones. At the same time, short-period multidirectional movements in the active geodynamic zones of the articulation of blocks cause a change in the slope and bending of the foundations of structures. The paper introduces the engineering-geological features of the most common surface deposits: the terrigenous gray-colored formation of the Paleogene; glacial, periglacial and extraglacial formations of anthropogenic origin and their facies-genetic complexes. The authors identified the potential natural and technological hazards associated with the marked deposits. The paper demonstrates the causes and mechanisms of the formation of technogenic flooding of the city, as well as the genesis of the decrease in the deformation properties of moraine sandy loam with a technogenic increase in humidity. It is concluded that when establishing land use regulations for a city, as a rule, general measures cannot be taken, both for its entire territory and for certain stages of construction activity. The paper introduces the corresponding restrictions on the use of subsoil.

Application of MS Excel and FastTest PlugIn to automatically evaluate the students' performance in structural engineering courses

AbstractBackgroundIn recent years, the method of assessment in universities has been rapidly changing, shifting from entirely in‐person evaluations to a blended evaluation approach (b‐Learning).PurposeTo effectively implement this type of assessment, it is necessary to create numerous similar problems with different data sets. In structural engineering courses, this entails a significant amount of work for the lecturers. Therefore, this work introduces a novel teaching and evaluation strategy leveraging technology to automate tasks, aiming to enhance student monitoring and alleviate lecturer workload.MethodThe digital platform Moodle has been used combined with the FastTest PlugIn to create computer coding to develop different problems. These problems, maintaining consistent structures but varying data, served both instructional and evaluative purposes in two structural engineering courses. As a novelty, these problems are automatically evaluated and created following the coding routine created. Some drawbacks have been identified while applying the method. Scientifically validated quizzes have been used to assess the efficacy of the method in engaging students and enhancing their confidence and satisfaction.ResultsFindings suggest that while initial setup requires additional time, the investment pays off in the grading efficiency, benefiting educators and students alike. The method has facilitated the creation of additional exercises for practice, and the inclusion of automatically corrected diagrams was appreciated by students. The results have indicated that this method has improved the motivation, attention, and confidence among students, leading to significant enhancements in academic performance, up to 40%.ConclusionsThis methodology has achieved positive responses from students. Hence, it is concluded that the time invested in developing structural engineering problems using MS Excel and the FastTest PlugIn in Moodle is worthwhile, as it motivates students to improve their academic performance. Furthermore, as the main outcome, it is shown that the time invested by the lecturer in developing the problems is amortized in subsequent academic years since the problems are graded automatically. For courses with many students, it is amortized sooner.

Technical aspect of the operation of accelerometers as composition of a system for monitoring engineering structures of a cable-stayed bridge over the Petrovsky canal in the construction of the Western Speed Diameter highway in Saint Petersburg

Aim. This study analyzes the current monitoring system for the engineering structures of a cable-stayed bridge across the Petrovsky Canal, part of the Western High-Speed Diameter highway in St. Petersburg, focusing on emergency situations where accelerometers on pylons record values that exceed limits. Methods and Materials. The study utilizes statistical data from existing monitoring system databases. The tasks, set within the framework of the study, are accomplished by applying theoretical scientific methods including analytical techniques, mathematical statistics, and induction. Results. The analysis presents an overview of the current system used for monitoring engineering structures and highlights issues related to emergency situations in which accelerometer readings exceed threshold values. This study proposes a method for assessing the reliability of the monitoring system by classifying the data obtained from the accelerometer into two groups. The research identifies the need for further investigations to understand the root causes of these issues. Conclusion. Тhe results can assist in the design and installation of monitoring systems of the engineering structures for cable-stayed bridges, as well as for modernization and optimization of existing monitoring systems to improve the quality of structural technical condition assessments.

Reliability analysis and uncertainty evaluation for assessing low velocity car impacted cosmetic damage of prototyped RC bridge pier

Crashworthiness of low velocity vehicles with reinforced concrete (RC) bridge pier has become widespread scenario that warrants a continuous threat on the structural viability. Even, low velocity small car collisions creates a short duration quasi-static to dynamic effect in different damage levels from low and cosmetic to collapse, depending on energy dissipation, not generally considered in design practices, making the piers susceptible to various level of damage. Bridge piers do not always collapse upon impact, and some are kept in service without pertinent health examinations that warrant serviceability. Unfortunately, little attention has been provided to keep the post impact low to medium distressed piers in service. Medium to higher damage need a complete replacement, whereas the low to cosmetic damage needs an additional meticulous investigation. This study is an attempt to assess cosmetic damage and residual capacities of RC pier via pendulum impacts to replicate low velocity car crash scenarios. To investigate post impact performance, experimental results are captured and transformed into realistic crash scenarios. Deterministic analysis via dynamic increase factor (DIF) approach to evaluate damage index (λ) and probabilistic method via resistance reduction method (RRM) to capture the uncertainties are performed in determining residual and reduced capacity of the representative pier. To identify damage incurred from collision and identify the probability of failure (Pf), a limit state (LS) equation has been developed comprising impact load and resistance and utilized as a model to estimate reliability index (β). Both the models used are able to precisely capture reduced capacities providing a good agreement between the shear and the axial capacity which control primary resistance of the impact loads and principal serviceability respectively. This study will provide an aid to forensic structural engineers.

The Correlation Between Academic Performance in CELE-Related Subjects and CELE Performance Among Bachelor of Science in Civil Engineering Students at Nueva Ecija University of Science and Technology

This study investigated the relationship between academic performance in CELE-related subjects and CELE performance among Bachelor of Science in Civil Engineering (BSCE) students at Nueva Ecija University of Science and Technology (NEUST). A quantitative research design employing correlation analysis was utilized. The sample consisted of 322 random BSCE students who had taken CELE in the last five exam dates. The results revealed a significant positive correlation between students' performance in their Mathematics, Surveying, and Transportation Engineering (MSTE) and Structural Engineering and Construction (SEC) subjects during their BSCE program and their corresponding achievements on the PRC board exam. However, no significant correlation emerged between students' performance in their Hydraulics and Geotechnical Engineering (HGE) subjects during their BSCE program and their performance on the corresponding section of the PRC board exam. Additionally, the results indicated a significant positive correlation between students' weighted GPAs during their BSCE program and their performance on the PRC board exam.These findings suggest that strong academic performance in CELE-related subjects is associated with success on the CELE, highlighting the importance of a well-aligned curriculum and educational strategies. However, further research is needed to explore causative factors and provide a more comprehensive understanding of the dynamics influencing CELE performance.

Seismic Vulnerability Assessment of Historic Centers with Two Fast Methods Based on CARTIS Survey Methodology and Fragility Curves

After an earthquake, legislation tends to permit the rapid demolition of damaged buildings, including the built heritage, for safety reasons, as was the case for many small historic centers after the 2016 earthquake in central Italy. A balance should, of course, be struck between safety and preservation. There must be a willingness to engage in continuous interaction with the various bodies involved in post-earthquake management, particularly in the preventive phase of the complex activities regarding the issues of the seismic vulnerability of historic built. The widespread historical built heritage in Italy requires fast and reliable assessment procedures that allow a large-scale evaluation of the vulnerability of historical buildings before a seismic event. To this end, a proposal is presented here for the inverse use of the protocol for the seismic vulnerability survey of historic centers by means of a system called CARTIS form, coordinated since 2015 by the Italian consortium of Seismic and Structural Engineering Laboratories (ReLUIS). This rapid assessment is compared with an equally fast method for constructing fragility curves, based only on the information available in the ReLUIS–CARTIS database, defining the relationship between the probability of reaching a level of loss of structural safety or a vulnerability index as a function of the seismic acceleration PGA and the ground orography. The methodology outlined could be considered to be progress in cultural heritage diagnostics on a large scale, considering cultural heritage to be the diffuse historical residential masonry buildings that form the historic centers.

Biomimetic Quasi‐Skin‐Capillary Structure Engineering of Ionic‐Electronic Conducting Full‐Chain Networks for Stable Zinc Powder Anodes

Biomimetic Quasi‐Skin‐Capillary Structure Engineering of Ionic‐Electronic Conducting Full‐Chain Networks for Stable Zinc Powder Anodes

Achieving high thermal conductivity and strong bending strength diamond/aluminum composite via nanoscale multi-interface phase structure engineering

Diamond/aluminum composites, as a new generation of thermal management materials, are caught in the dilemma between inhibiting the formation of Al4C3 and improving the performance. Herein, we proposed a strategy for nanoscale multi-interface phase structure engineering, utilizing a combination of magnetron sputtering and vacuum heat treatment to obtain diamond particles with nanoscale TiC-Ti layers. Prolonging the vacuum heating time increases the content of TiC, but results in significant differences in the morphology and coverage of TiC formed on the diamond(100) and (111) facets. First-principles calculations reveal that the work of adhesion and C-Ti reaction tendency of diamond(100)/Ti are stronger than those of diamond(111)/Ti, clarifying the difference in interfacial properties between diamond/Ti and diamond/TiC. Diamond-TiC-Ti configuration obtained in advance contributes to fabricating the composite with diamond-TiC-Al(Al3Ti) structure, and the multi-interface phase structure is beneficial to improve the interface bonding, adjust the acoustic mismatch, and inhibit the formation of Al4C3. (800 °C 0.5 h)@Ti-coated diamond(100 μm)/aluminum composite with the multi-interface phase exhibits excellent thermal conductivity(646 W m−1 K−1) and outstanding bending strength(358 MPa), exceeding 90 % of the theoretical prediction of the differential effective medium model. The performance of (800 °C 0.5 h)@Ti-coated diamond/aluminum composite is about 30 % higher than that of traditional Ti-coated diamond/aluminum composite. The TiC layer formed by increasing the heat treatment time is thicker and discontinuous, leading to a decrease in the thermal conductivity of the composite and a weakening effect of Al4C3 inhibition. We clarified the formation mechanism of interface structure related to diamond orientation by multi-scale characterization. Based on the thermal conductivity prediction models, the interface structures corresponding to different diamond orientations were considered, and the predicted values showed good consistency with the experimental results. By interface modification engineering, we overcome the dilemma of introducing modified layer to inhibit Al-C reaction while leading to additional interface thermal resistance, providing insights into the interfacial thermal transport mechanism.

Mechanical behaviors and seismic performance of a novel rotary amplification friction damper (RAFD): Experimental and analytical studies

Friction dampers are widely used energy dissipators for the seismic fortification of engineering structures, due to their efficiency, reliability, and cost-effectiveness. Since the friction force is proportional to the normal load applied on the sliding interfaces for given friction materials, increasing the applied normal load is always the only approach to enhance the energy dissipation capacity of friction dampers. However, a large applied normal load may result in serious wear problems at the interfaces, which in turn affects the functionality of the damper. To address the above issue, a novel rotary amplification friction damper (RAFD) is proposed in the present study, which can realize several times amplified friction force for a given normal load due to the adopted amplification system. The conceptual design and working mechanism of the proposed RAFD are first introduced. Subsequently, a damper prototype was manufactured and experimental studies were carried out to examine the behaviors of RAFD. Then, a nonlinear mechanical model considering the gap between the gear and rack is developed based on the experimental results. Finally, an analytical model of a single-degree-of-freedom (SDOF) system equipped with RAFD is established to investigate the control performance of RAFD in reducing the structural seismic responses and evaluate the influences of various parameters including gap and earthquake types (far-field and near-field ground motions). The analytical and experimental results demonstrate that the proposed RAFD showcases superior seismic control effectiveness compared to the traditional friction damper; the presence of a gap would reduce the control effectiveness of RAFD to some extent, while earthquake types have minimal impact.

Experimental and numerical analysis of L-shaped concrete-filled steel tube stub columns

This paper reports experimental and numerical studies on the cross-sectional compression resistance and behaviour of a novel L-shaped concrete-filled steel tube system. The novel composite system is proposed to eliminate concave corners and enhance the confinement of the outer steel tube to the concrete infill. A testing programme was firstly conducted, including nine tensile steel coupon tests, six compressive concrete cube tests and ten stub column tests. Upon testing, all the ten L-shaped concrete-filled steel tube stub column specimens were found to fail by local buckling. Finite-element models were then developed in the finite-element analysis software ABAQUS and validated against test results. The validated models were then employed to perform parametric studies to obtain an additional set of 48 numerical data. Test and numerical results were used to perform a design analysis, in which the suitability of the design rules in the European code EN 1994–1-1, the American specification ANSI/AISC 360 and the Chinese code GB 50936 for the developed L-shaped concrete-filled steel tube stub column system was assessed. The analysis results reveal that both EN 1994–1-1 and GB 50936 yield unsafe compression resistance predictions for the studied L-shaped concrete-filled steel tube stub columns, owing to the improper consideration of the contributions of the outer steel tube and the concrete infill to the overall capacity, while ANSI/AISC 360 offers safe design with high accuracy. The research findings are expected to contribute to the safe and wide use of the proposed novel L-shaped concrete-filled steel tube system in structural engineering and also to the further development of the current international design standards.

Mix proportion design and life cycle assessment of ultra-high-performance lightweight concrete with hollow microspheres

Achieving high strength and low weight in cement-based composites remains a critical objective in material and structure engineering. This study presents the development of an ultra-high-performance lightweight concrete (UHPLC) composite with a density not exceeding 1950 kg/m³ and a compressive strength of at least 100 MPa. The UHPLC mix design was optimized using the central composite design (CCD) response surface methodology, and a life cycle assessment (LCA) was conducted for the first time on UHPLC from cradle to gate. The interactions between cement content, hollow microspheres, and their effects on workability, mechanical properties, and durability were analyzed. The results show that using the CCD response surface method for designing UHPLC mix proportions is feasible, allowing effective optimization for various objectives, such as balancing both strength and density, highlighting low density, or emphasizing ultra-high strength. the designed UHPLC exhibits mechanical and durability properties comparable to or better than UHPC. LCA results show higher energy consumption and environmental impact for UHPLC in the cradle-to-gate stage, mainly due to the microsphere production phase. Monte Carlo uncertainty analysis reveals that ADP, HTP, POCP, and EP are most sensitive to microsphere content, while GWP and AP are more affected by cement content. The optimized UHPLCs in this study can be selected depending on specific technical or environmental scenarios. Introducing HMs into the UHPC system for UHPLC production shows excellent performance, making it a promising material for advanced structural applications.

Evaluating the Effectiveness of Fiber Reinforced Polymer (FRP) in Structural Strengthening: A Meta-analysis

This study aims to evaluate the effectiveness of Fiber Reinforced Polymer in strengthening structures. This research is a type of meta-analysis research. The data source comes from 9 studies sourced from google scholar, DOAJ, ProQuest and Fronteins published in 2023-2024. Data selection techniques through the PRISMA method in 2020. The data analysis in this study is to calculate the effect size value with the help of the STATA application. The results of this study concluded that the application of Fiber Reinforced Polymer had a positive effect on the strengthening of the structure with an effect size value = 0.813 with a high effect size category. This finding explains that the application of fiber reinforced polymer is effective in strengthening concrete structures in civil engineering.

Three-dimensional porous structure CoP/N-doped carbon nanospheres as anode for enhanced lithium storage performance

Transition metal phosphides (TMPs) with high theoretical capacities and safe operating voltage are recognized as prospective anode materials for lithium-ion batteries (LIBs). While, the huge volume expansion and low conductivity of TMPs still restrict their applications. Engineering nanostructured composites consisting of TMPs and conductive carbon-based materials is of great importance to improve electrochemical performance. Herein, a novel and facile pyrolysis-oxidation-phosphidation approach is designed to fabricate porous nanospheres composing of CoP nanoparticles and N-doped carbon substrate. The abundant pores in CoP/N-C provide ample active sites for lithium storage and facilitate Li+ transport. The introduction of N-doped carbon substrate enhances the electrical conductivity, allowing CoP to maintain its structure during cycling. The CoP/N-C anode achieves remarkable cycle performance, maintaining an extremely stable cycle life over 2000 cycles at 5 A g−1. More importantly, the full cell consisting of CoP/N-C and LiFePO4 also exhibits a prominent cycling durability with a capacity retention of 96.5 % at 0.1 A g−1 after 150 cycles. This work proposes a simple and feasible structural engineering strategy, which can provide a new way for optimizing the electrochemical performance of conversion-type anode materials.

Study on the Protective Effect of Viscous Buffering Device under Explosive Load

In recent years, with the complex and changeable international situation, local wars and conflicts abroad have occurred frequently, which seriously threaten the safety of human life and property. Against this background, high-precision and high-intensity strikes against key targets such as enemy command posts and ordnance reserves have become the norm in modern warfare. As the undercard of national security, the security and protection capabilities of underground military facilities are of great importance. Underground structures not only play the role of emergency evacuation of personnel to avoid air and missile attacks, but also the core of the combat command system, where key facilities such as military underground factories and warehouses are located. The security of these facilities has a direct bearing on the outcome of a war and even the fate of a country. In view of this, taking effective measures to improve the explosion resistance, durability and survivability of underground protective structures has become an important research topic in the field of military engineering in various countries. Under the action of the explosion of conventional weapons at a certain distance, the underground protective structures can be damaged due to insufficient resistance. The powerful shock wave generated by the explosion, with its huge kinetic energy and impact force, will cause a large vibration acceleration ring inside the structure, which is very easy to cause casualties and equipment damage within the structure, thus posing a serious threat to the safety of underground engineering. In order to improve the anti-explosion performance of the protective structure under the action of blast impact load, the underground protection engineering structure has been continuously upgraded and optimized, among which the layered protective structure has been widely used because of its relatively excellent protection effect. The layered protective structure realizes a relatively effective protection system through a well-designed camouflage layer, a bullet shielding layer, a dispersed layer and a main structure. However, although significant progress has been made in the optimization of three-layer materials, the defects such as the unstable state of the dispersed layer and the possibility of reducing the overall protection performance with time or external conditions are still an urgent problem to be solved. This system is designed to replace or partially replace the traditional dispersed layer, which is not only designed to effectively absorb and dissipate the blast wave energy transmitted by the bomb shielding layer, but also fundamentally solve the problem of the reduction of protection effect caused by the change of the state of the dispersed layer. In this study, the simulation technology will be used to deeply explore the structural dynamic response of the protective structure after the addition of buffer energy dissipation device under the blast impact load, and the key factors affecting the protection effect will be systematically analyzed, the simulation parameters will be accurately set, and the protection effect under different parameter combinations will be simulated, so as to find an optimal parameter configuration scheme. This study not only helps to deepen the understanding of the anti-explosion performance of underground protection structures, but also provides valuable theoretical basis and practical guidance for the design and construction of underground protection projects in the future.

Linear equivalence for motion amplification devices in earthquake engineering

AbstractMotion amplification devices utilized to amplify the motion of dampers can effectively improve the energy dissipation performance of dampers to reduce seismic responses of engineering structures. This study systematically develops a linear equivalence theory for motion amplification devices based on the proposed equivalent Maxwell model. This equivalent model accurately predicts the supplemental damping effect provided by motion amplification devices without approximation. Also, the equivalent model is capable of quantifying the amplification effect of motion amplification devices by means of deriving the analytical expressions of the equivalent damping and stiffness coefficients, which reveal that motion amplification devices simultaneously enhance the original damping and stiffness coefficients by , where is the proposed rigidity motion amplification factor. The representative value of member stiffness is developed to comprehensively evaluate the supporting stiffness of motion amplification devices. All the achieved results strongly support that the proposed linear equivalence theory provides a generic paradigm to explain, measure and compare different types of motion amplification devices in terms of their supplemental damping effects, and hence helps researchers and engineers gain valuable insight into the dynamic properties of motion amplification devices.