Performance Engineering Research Articles

Unveiling the temperature-dependent mechanisms of viscoelasticity of sand-enhanced epoxy

The viscoelastic behavior of epoxy is critical for its engineering performance and applications. This work focused on the improvement of its viscoelastic performance by using natural sand particles as fillers. Experiments were carried out to investigate the static and dynamic viscoelastic properties of epoxy with various sand particle contents. Static mechanical tests demonstrated an increase in the elastic modulus, albeit at the cost of reduced strength at a higher sand content due to stress concentrations. Dynamic tests indicated substantially improved storage modulus and damping of epoxy after being filled with sand particles. Moreover, the glass transition temperature of epoxy showed a substantial rise upon the addition of sand particles, signifying an augmentation in its heat resistance. Static viscoelastic characterization revealed an elevation in both room- and high-temperature relaxation moduli upon incorporating sand. By applying time–temperature superposition principles, long-term relaxation curves were obtained, which could provide a reference for engineering design. These viscoelastic investigations offer insights into the underpinning mechanisms governing the performance of sand-reinforced epoxy. This enables the rational design of sand-particle-reinforced epoxy for customized durability, heat resistance and vibration damping.

Enhancing Electrochemical Performance through Swift Functional Group Tuning of MXenes

AbstractChemical manipulation of surface functional groups on two‐dimensional transition metal carbides and/or nitrides (MXenes) provides a wide range of design and application prospects. However, achieving rapid targeted modification of surface groups remains a significant challenge. Herein, we propose a general strategy to swiftly shear and customize surface groups on Ti3C2Tx−MXene via the flash Joule heating (FJH) reaction within 1 s. Successfully, MXenes with 9 target terminations, including VII A (F, Cl, Br, or I), VI A (O, S, or Se), and V A (N or P), either single or multiple, are synthesized, with a surface content of up to about 76 %. The impact of these terminations is systematically analyzed on electrochemical performance, demonstrating that VI A and V A terminations have higher electrochemical activity than VII A. Particularly, N‐, S‐, and O‐terminated MXenes exhibit enhanced specific capacities and undecayed cycling performance. These findings offer valuable insights for the surface engineering design and performance optimization of functional materials.

Frontier model of the environmental inefficiency effects on livestock bioeconomy.

This work was focused on measuring environmental inefficiency in Mexican dairy farms, considering climate change variables related to the emission of greenhouse gases (GHG) and planetary geomagnetic activity. The applied methodology measures the eco-efficiency of Mexican dairy farms using the empirical application of a stochastic frontier model of the bioeconomy. The productive sector of the bioeconomy studied was the eco-intensification of the livestock production system (dairies). The environmental inefficiency effect was assumed to be a distribution-independent truncation of a normal distribution with constant variance, while the mean was a linear environmental function of the observable variable. The results showed that the coefficients of the frontier model were highly significant, highlighting the investment in livestock (50%). The inefficiency model had an impact on climate variation with greenhouse gas emissions CH4 (1.96%). The results of the environmental technical efficiency in geometric average were 81.28%. The producers that reached the border with a technical efficiency equal to 1 are the references for the rest, marking the relative technical efficiency. It was concluded that the coefficients in the model were very significant, showing the level of investment in livestock (50%). The low-performance model estimates the impact of climate change on GHG emissions CH4 (1.96%) explaining the trend of increasing GHG emissions, keeping in view that the management of food and cattle during the study period were affected by summer feeding, which allowed considering the activity of GHG emissions. According to the results, the geometric mean environmental performance of engineering is 81.28%.

Requirement engineering and project performance: mediating effect of communication effectiveness, change readiness, stakeholder engagement and moderating effect of team cohesion

Requirement engineering and project performance: mediating effect of communication effectiveness, change readiness, stakeholder engagement and moderating effect of team cohesion

A novel crimped composite spline joint for pultruded FRP tubes: Conceptual design and tensile properties

Creating an effective composite joint between fiber-reinforced polymers (FRPs) and metallic profiles poses a significant challenge for heavy-loaded and lightweight emergency truss bridges. A novel crimped composite spline joint (CCSJ) was developed to achieve satisfactory engineering performance. Comparative tensile tests were conducted to evaluate the tensile properties and load-carrying mechanism of the CCSJ in comparison to those of joints without splines. Finite element (FE) analysis considering the crimping process and tensile loading was simultaneously executed and calibrated by experiments. Parametric simulation was supplemented to explore the key factors influencing the ultimate bearing capacity. The results indicated that the novel CCSJ features a simple preparation process, high connection efficiency, and large bearing capacity. A 60×6 mm hybrid FRP tube can withstand a maximum tensile load of 804 kN, achieving a connection efficiency of 61.3 % without the need for any secondary processing of the FRP tube. The CCSJ demonstrates a significantly higher connection efficiency of approximately 20 % compared to joints without splines. The ability of the CCSJ to effectively transfer significant axial loads through the interfacial friction effect is attributed to the increase in the interfacial contact area and preloading radial pressure resulting from the incorporation of pre-crimping splines. A typical failure mode involves interfacial slippage, resulting in satisfactory ductile behavior. The ultimate bearing capacity of the CCSJ is positively correlated with the crimping variables, friction coefficient, spline length, and number of splines. The FE model demonstrates sufficient accuracy in predicting the key behavioral indicators of the composite joint.

Improving the performance of CFRP-reinforced concrete cylinders in sulfate-laden environment through nanoclay modification of epoxy resin

The durability of epoxy-concrete interface is a crucial factor for practical application of externally bonded fiber-reinforced polymer (FRP) retrofit systems, particularly when the strengthened structure is subjected to severe environmental conditions. Given the demonstrated potential of nanoclays in enhancing engineering performance of polymers, this work assesses the beneficial effect of organic montmorillonite (OMMT) nano-modification of epoxy resin on the axial compressive properties of FRP-reinforced concrete under a 10 wt% sodium sulfate wet/dry (W/D) cycling environment. Three types of concrete samples were fabricated and tested: plain concrete cylinders, CFRP-reinforced concrete cylinders using unmodified vs. OMMT-modified epoxy resin as the adhesive, respectively. The optimal dosage of OMMT was determined to be 2 wt% through tensile and lap shear tests, as well as microscopic characterization of the fractured cross-section of the molded resin samples. This optimal dosage of OMMT allows the epoxy adhesive to achieve the highest values in the tensile strength (90.4 MPa), lap shear strength (80.0 MPa), Tg (280.5°C) and water contact angle (115.1°). In the fracture section of epoxy resin with a 2 wt% OMMT, multiple microcracks developed and the OMMT nanoplatelets were well dispersed in the epoxy matrix. The laboratory testing program explored various W/D cycle periods. The experimental results indicate that the OMMT-modified epoxy resin significantly improved the mechanical properties and deformation resistance, altered the failure mode, and effectively delayed the strength degradation of the protected concrete. After 150 W/D cycling days, the OMMT-modified CFRP-confined concrete samples maintained their ductility coefficient and axial compressive strength at 3.58 and 123.5 MPa, respectively, 12.6 % and 9.1 % better than the common CFRP-confined samples. Combining these results with the residual axial compressive strength ratio, we propose an improved design model for calculating the axial compressive strength of CFRP-retrofitted concrete structures in sulfate-laden environments. This study demonstrates the beneficial role of OMMT in enhancing the epoxy adhesive and provides insights into the reinforcement of concrete structures by externally bonded CFRP in sulfate-rich environments.

Enhancing empirical software performance engineering research with kernel-level events: A comprehensive system tracing approach

Performance engineering is a proactive and systematic approach aimed at designing, building, and enhancing software systems to ensure their efficient and reliable operation. It involves observing and measuring the operational behavior of a software system without interference, assessing performance metrics like response times, throughput, and resource utilization. This entails delving into kernel-level events related to performance monitoring, which play a significant role in understanding system behavior and diagnosing performance-related issues. Kernel-level events offer insights into how both the operating system and hardware resources are utilized. This information empowers system administrators, developers, and performance analysts to optimize and troubleshoot the system effectively.A critical aspect of performance analysis is root cause analysis, which involves delving deep into kernel-level events connected to performance monitoring. These events provide valuable insights into the utilization of operating system and hardware resources, equipping system administrators, developers, and performance analysts with tools to effectively troubleshoot and optimize the system. Our study introduces an innovative artifact that captures kernel-level events using Elasticsearch and Kibana, facilitating comprehensive performance analysis under diverse scenarios. By defining both Light-load and Heavy-load scenarios and simulating CPU, I/O, Network, and Memory noise, we offer researchers a realistic environment to explore innovative approaches to system performance enhancement.The artifact comprises both kernel events and system calls, resulting in a cumulative count of 24,263,691 events. The proposed artifact can serve three distinct applications. The first application emphasizes performance analysis by utilizing kernel events for monitoring. The second application targets noise detection and root cause analysis, again using kernel events. Finally, the third application investigates software phase detection through monitoring at the kernel level. These applications demonstrate that through our artifact, researchers can effectively analyze performance, detect and address performance noise, and identify software phases, contributing to the advancement of performance engineering methodologies.All the system configurations, scripts, and traces can be found in the artifact GitHub repository.11URL: https://github.com/mnoferestibrocku/dataset-repo.

Protecting Data at Risk of Unintentional Electromagnetic Emanation: TEMPEST Profiling

Unintentional electromagnetic (EM) emissions often include information about the data processed by electronic devices. Intrusion based on an unintentional EM emission leaves no evidence of an attacker’s activity, while the data owner is unaware that it has been lost. EM attacks can be performed without physically damaging a device that operates regularly. The most typical intrusion activities involve sensitive data exfiltration using various methods that do not require the physical connection of devices to the computer network or communication channels. This research examines EM emissions from computer monitors, wireless keyboards and mice, printers, scanners, conductors, piezoelectric sensors (PES), and radio frequency identification (RFID) devices. The telecommunication electronics material protected from emanating spurious transmissions (TEMPEST) profiling as a performance engineering of the EM footprint is discussed. This study also presents different TEMPEST standards and highlights their importance concerning unintentional EM radiation.

Investigation of sustainable pervious concrete pavement performance using waste travertine aggregate and powder

Travertine cutting generates rubble and waste powder, prompting the need for effective waste utilization. This study aims to develop travertine permeable concrete (TPC) using travertine aggregate and waste powder. An orthogonal test method assessed TPC variations in travertine powder replacement rates, aggregate grading, and void content for porosity, permeability, mechanical strength, and heavy metal adsorption ability. The void content greatly influences the amount of cementitious material and is crucial for TPC performance. To guarantee compliance with the engineering performance for fully pervious pavement, the recommended void content of TPC should not exceed 20 % to have satisfactory compressive strength and permeability. Cement replacement with 5–10 % travertine powder can satisfy engineering requirements, heavy metal adsorption, waste utilization, and CO2 emission reduction. TPC demonstrates much lower removal rates under the rapid method than the immersion method for Cd2+, Cu2+ and Pb2+, mainly due to the difference in contact time. After 25 cycles, the optimized TPC shows less mass and strength loss, demonstrating excellent freeze-thaw resistance. Furthermore, a novel lab-scale rainfall simulation system for travertine permeable concrete pavement (TPCP) was built to assess the water infiltration of TPCP. TPCP can effectively reduce runoff, reaching over 96 % within 1 h for various inflow intensities. After half an hour, the removal rates of Cd2+ and Cu2+ by TPCP were only 41.5 and 79.1 %, respectively, but TPCP achieves exceptional Pb2+ adsorption with a removal rate of over 97 % under the ternary competitive mechanism.

Service Life Design of Reinforced Concrete Maritime Infrastructure: Holistic Approach with Experiences from Chilean Cases

The consideration of the useful life of reinforced concrete in the different stages of a structure's life cycle, as a distinguishing factor in the design process for performance under aggressive environmental conditions, has presented new challenges in construction. This includes the development of new regulations incorporating innovative engineering materials, performance tests and modeling processes to estimate concrete deterioration over time, and construction processes ensuring adequate Quality Control and Quality Assurance (QAQC). As a result, infrastructure projects have been able to exceed their intended lifespan, maintaining serviceability levels for more than 100 years. One such example is the Chacao Bridge project currently under construction in southern Chile. This paper provides an overview of project stages from a holistic approach, focusing on aspects inherent to planning including design and construction processes, control stages for monitoring deterioration levels through regular diagnostics and appropriate monitoring to support ongoing structural health management. Additionally, it presents real case design examples carried out with specific models created for each case.

Solid waste-based low-carbon autoclaved aerated concrete: Relationship between engineering properties and microstructure

A novel low-carbon autoclaved aerated concrete (AAC) was developed to enhance the high valuable use of solid waste in production, incorporating furnace slag, metro shield sand, and quartz tailings sand as 100 % siliceous raw materials, constituting 60 % of the total weight. In this study, comprehensive analyses were conducted on its engineering properties, including density, compressive, flexural, and splitting tensile strengths, and thermal conductivity. Advanced techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and high-resolution Industrial CT scanner (X-CT) were employed to examine AAC's material composition, hydration products, and pore structure characteristics at the microscale. The results indicated that the addition of 10 % furnace slag resulted in a specific increase of 5.5 % in compressive strength. However, escalating the furnace slag content to 30 % proved detrimental to the toughness and dry shrinkage of AAC. The microstructure analysis indicates that the use of furnace slag can improve the connectivity and roundness of pores and reduce the probability of large pores (>0.01 mm3), which will reduce the risk of damage localization. Furthermore, furnace slag in AAC enhanced sustainability and cost-effectiveness compared to metro shield sand and quartz tailings sand. Based on the TOPSIS model, an optimal AAC mixture, considering engineering performance, economy, and sustainability, was derived by blending the three types of solid wastes.

Electric pulse-tuned piezotronic effect for interface engineering

Investigating interface engineering by piezoelectric, flexoelectric and ferroelectric polarizations in semiconductor devices is important for their applications in electronics, optoelectronics, catalysis and many more. The interface engineering by polarizations strongly depends on the property of interface barrier. However, the fixed value and uncontrollability of interface barrier once it is constructed limit the performance and application scenarios of interface engineering by polarizations. Here, we report a strategy of tuning piezotronic effect (interface barrier and transport controlled by piezoelectric polarization) reversibly and accurately by electric pulse. Our results show that for Ag/HfO2/n-ZnO piezotronic tunneling junction, the interface barrier height can be reversibly tuned as high as 168.11 meV by electric pulse, and the strain (0–1.34‰) modulated current range by piezotronic effect can be switched from 0–18 nA to 44–72 nA. Moreover, piezotronic modification on interface barrier tuned by electric pulse can be up to 148.81 meV under a strain of 1.34‰, which can totally switch the piezotronic performance of the electronics. This study provides opportunities to achieve reversible control of piezotronics, and extend them to a wider range of scenarios and be better suitable for micro/nano-electromechanical systems.

Investigation of Engineering Properties and Solidification Mechanism of Loess by Sodium Silicate Alkali-Activated Coal Gangue Powder

The aim of this study is to investigate the engineering properties and solidification mechanism of loess through the use of alkali-activated coal gangue powder with sodium silicate. Experimental methods and comprehensive analysis were employed to examine the effects of different proportions of alkali-activated coal gangue powder with sodium silicate on the engineering properties of loess, including mass shrinkage, compressibility, and shear strength. Additionally, scanning electron microscopy was utilized to gain in-depth insights into the interaction and solidification mechanism between loess and alkali-activated coal gangue powder. The results show that the sodium silicate alkali-activated gangue powder curing loess has significantly improved the compressive strength and shear strength of the loess. With a ratio of 7 : 2 : 1, the 28 days compressive strength of solidified loess is 1.7 MPa, and the shear strength is 67.92 kPa, which is 1.91 and 2.13 times the 28 days compressive strength and shear strength of unmixed gangue powder and sodium silicate specimens respectively. The hydration–hydrolysis reaction, ion-exchange reaction, and volcanic ash reaction of the gangue powder under an alkaline environment generated hydrides that filled the pores between soil particles, enhanced the interparticle cohesion, and made the internal structure of the specimens denser, improving the engineering performance of loess solidification. The proposed sodium silicate alkali-activated gangue powder curing loess mechanism can provide a theoretical reference for the engineering application of gangue powder and the curing modification of loess.

Transfer-Learning-Enhanced Regression Generative Adversarial Networks for Optimal eVTOL Takeoff Trajectory Prediction

Electric vertical takeoff and landing (eVTOL) aircraft represent a crucial aviation technology to transform future transportation systems. The unique characteristics of eVTOL aircraft include reduced noise, low pollutant emission, efficient operating cost, and flexible maneuverability, which in the meantime pose critical challenges to advanced power retention techniques. Thus, optimal takeoff trajectory design is essential due to immense power demands during eVTOL takeoffs. Conventional design optimizations, however, adopt high-fidelity simulation models in an iterative manner resulting in a computationally intensive mechanism. In this work, we implement a surrogate-enabled inverse mapping optimization architecture, i.e., directly predicting optimal designs from design requirements (including flight conditions and design constraints). A trained inverse mapping surrogate performs real-time optimal eVTOL takeoff trajectory predictions with no need for running optimizations; however, one training sample requires one design optimization in this inverse mapping setup. The excessive training cost of inverse mapping and the characteristics of optimal eVTOL takeoff trajectories necessitate the development of the regression generative adversarial network (regGAN) surrogate. We propose to further enhance regGAN predictive performance through the transfer learning (TL) technique, creating a scheme termed regGAN-TL. In particular, the proposed regGAN-TL scheme leverages the generative adversarial network (GAN) architecture consisting of a generator network and a discriminator network, with a combined loss of the mean squared error (MSE) and binary cross-entropy (BC) losses, for regression tasks. In this work, the generator employs design requirements as input and produces optimal takeoff trajectory profiles, while the discriminator differentiates the generated profiles and real optimal profiles in the training set. The combined loss facilitates the generator training in the dual aspects: the MSE loss targets minimum differences between generated profiles and training counterparts, while the BC loss drives the generated profiles to share analogous patterns with the training set. We demonstrated the utility of regGAN-TL on optimal takeoff trajectory designs for the Airbus A3 Vahana and compared its performance against representative surrogates, including the multi-output Gaussian process, the conditional GAN, and the vanilla regGAN. Results showed that regGAN-TL reached the 99.5% generalization accuracy threshold with only 200 training samples while the best reference surrogate required 400 samples. The 50% reduction in training expense and reduced standard deviations of generalization accuracy achieved by regGAN-TL confirmed its outstanding predictive performance and broad engineering application potential.

Engineering, Emulators, Digital Twins, and Performance Engineering

Developments in digital twins are driven by the availability of sensor technologies, big data, first principles knowledge, and advanced analytics. In this paper, we discuss these changes at a conceptual level, presenting a shift from nominal engineering, aiming at design optimisation, to performance engineering, aiming at adaptable monitoring diagnostic, prognostic, and prescriptive capabilities. A key element introduced here is the role of emulators in this transformation. Emulators, also called surrogate models or metamodels, provide monitoring and diagnostic capabilities. In particular, we focus on an optimisation goal combining optimised and robust performance derived from stochastic emulators. We demonstrate the methodology using two open-source examples and show how emulators can be used to complement finite element and computational fluid dynamic models in digital twin frameworks. The case studies consist of a mechanical system and a biological production process.

Study of the engineering performance of pipes buried in the soil

This paper investigates the response of a flexible buried pipe to traffic load using laboratory experiments and numerical analysis. A series of laboratory tests and numerical simulations were performed to examine the effect of surface pressure, loading width, pipe type, pipe thickness, and burial depth on model response. In the experiments, a load was applied to the surface of a tank in which a pipe was buried. To gain a better understanding of the pipe's behavior, numerical simulations were performed using the finite element method; PLAXIS 2-D software. The results show that there is a good agreement between numerical and experimental test results. Furthermore, experimental and numerical analysis show that increasing burial depth reduces pipe deflection, increases soil surface settlement, and decreases pipe pressure, whereas increasing surface pressure increases all of the above parameters. Finally, equations were developed based on all numerical and experimental results to predict maximum stress on the pipe crown.

Do attitudes matter? An investigation into students’ attitudes toward engineering and learning performances through engineering-focused STEM curricula

Do attitudes matter? An investigation into students’ attitudes toward engineering and learning performances through engineering-focused STEM curricula

Treatment of waste marine clay by alkaline-activated ground granulated blast-furnace slag and municipal solid waste incineration bottom ash

The construction of coastal areas generates a substantial volume of waste marine clay (WMC), which poses environmental and safety challenges during the stockpiling process. The improved preparation of WMC as roadbed materials emerges as a crucial pathway for resource utilization. However, the engineering performance and durability of roadbed materials prepared from WMC have always been a concern for scholars and engineers. This study employs alkali-activated ground granulated blast-furnace slag (GGBFS) and municipal solid waste incineration bottom ash (MSWIBA) to solidify WMC for preparation of the roadbed materials. The results showed that the combined utilization of alkali-activated GGBFS and MSWIBA to improve WMC can meet the environmental and mechanical requirements of roadbed materials. The incorporation of 5-20% MSWIBA could improve the water stability coefficient and California bearing ratio to more than 85% and 80%, respectively. The durability of roadbed material was significantly improved by addition of MSWIBA. After 12 dry–wet cycles, the strength of the material without MSWIBA and with 5% MSWIBA was 0 and 2.87 MPa, respectively. Following analysis of engineering properties and durability, the optimal dosage of MSWIBA was determined to be 5%. The enhanced durability can be attributed to the optimization of material gradation and pore structure achieved through the incorporation of a small quantity of MSWIBA. The carbon emission and normalized global warming potentials of roadbed material treated by MSWIBA and GGBFS were much lower than that of cementitious binders such as ordinary Portland cement. These findings indicate that MSWIBA has the potential to substitute natural aggregates like sand and gravel, effectively improving the durability of roadbed materials and promoting the safe and efficient recycling of solid waste resources.

Epi‐Endocytic Performance Engineering through Nanomaterials Co‐Challenging: A Study of Mechanism and Implication in Radiotherapy

AbstractWhile the influence of size on nanomaterial uptake has been extensively explored, it remains elusive how cells simultaneously respond to multiple, size‐varying particles due to the lack of a proper quantitative assay. In this study, a strategy named “metal‐doping engineering” is developed, and constructed a library of multi‐elemental alloys (MEAs) features precisely controlled size and dopant dosage for quantification with mass spectra. Next a comprehensive study of cellular uptake behaviors is conducted when treated with dual‐, triple‐, and quadra‐, size‐differing nanoparticles. Specifically, the exposure to triple‐, and quadra‐, size‐differing MEAs resulted in an unprecedented, enhanced uptake of counterpart in the middle size as 10/20 nm. Further efforts including RNA‐sequencing and photo‐affinity labeling‐assisted proteomics are devoted to uncovering the underlying mechanism, wherein the role of nonconical endocytic pathways in fast‐endophilin‐mediated endocytosis is uncovered. Given the capacity of MEAs as chaperones to facilitate the uptake of one featuring a predetermined size promoted to propose a straightforward, “bystander nanomaterials”‐assisted drug delivery strategy, whose superior dosage‐reduced radio‐sensitization performance and anti‐tumoral outcome are confirmed in vivo.

New and Sustainable Coal Char-Based Paving Blocks for Roadway Applications

Paving blocks are widely used in engineering construction for durable pavement surfaces characterized by their interlocking capability to enhance structural integrity. This study explores the potential use of char as a byproduct from coal pyrolysis and an alternative raw material to natural aggregates in developing paving blocks, aiming to reduce the associated environmental issues associated with the uncontrolled and excessive mining of natural resources. This study finds the paving blocks made from char to have the required engineering properties as mentioned by ASTM standard C936. Trass and trass-lime are added as supplementary cementitious materials (SCMs) to enhance the performance of char-based paving blocks. The incorporation of SCMs as a cement replacement also aims to reduce the carbon footprint arising from increased cement use. The compressive strength increased from 55.7 MPa to 65.71 MPa at 12.5% cement replacement with trass-lime. The water absorption is reduced to 4.63% from 4.95%. Beneficial effects towards freeze–thaw durability and abrasion resistance are also observed on trass-lime-incorporated paving blocks. This study signifies the remarkable potential use of coal-derived char and SCMs in developing light, high-strength, and durable paving blocks, showcasing their competitive engineering performance. These new char-based paving blocks will contribute towards a more sustainable construction environment and advance the current construction and engineering practices.