Experimental Research Articles

Experimental study of taper shape bistable beam for improved vibration energy harvesting

Unwanted vibrations cause discomfort and affect the accuracy of the machinery. Vibrations of low frequency (<30 Hz) are usually inutile. Various researchers focus on harvesting and enhancing energy output through low-frequency vibrations. This paper focuses on improving energy harvesting from low-frequency vibration sources through taper shape (TAP) bistable beam fabricated using thin Piezoelectric Polyvinylidene fluoride (PVDF) film sandwiched between thin copper and aluminium films on both sides. Voltage power output through a PVDF film depends on the film’s strain distribution; hence, in this study, five different beam designs are studied for strain distribution through the ANSYS workbench. Further, an experimental harmonic analysis study for voltage output is performed on rectangular beam (RECT) and TAP beam for both straight and bistable configuration using three different harmonic input conditions, which concluded that the voltage output for the TAP beam is much more than that of the RECT beam, with a much more significant voltage output increase in bistable conditions for all three harmonic input conditions.

An Experimental Study on Vibration Induced by Dynamic Pile Load in an Adjacent Building

An Experimental Study on Vibration Induced by Dynamic Pile Load in an Adjacent Building

In Case You Haven't Heard…

Can bird‐watching improve mental health? A new study has found that people who have nature‐based experiences report better well‐being and lower psychological distress than those who do not, a North Carolina State University news release stated. Bird‐watching in particular yielded promising results, with higher gains in subjective well‐being and more reduction in distress than more generic nature exposure, such as walks. Because bird‐watching is an easily accessible activity, the results are encouraging for college students, who are among those most likely to suffer from mental health problems, the news release indicated. “Bird‐watching is among the most ubiquitous ways that human beings interact with wildlife globally, and college campuses provide a pocket where there's access to that activity even in more urban setting, said Nils Peterson, corresponding author of the study and a professor of forestry and environmental resources at North Carolina State University. The paper, “Birdwatching linked to increased psychological well‐being on college campuses: A pilot‐scale experimental study,” was published in Environmental Psychology.

Progress in Theoretical Modelling of Macroscopic and Microscopic Dynamics of Bolted Joints in Complex Equipment

Bolt connection structure is a common form of connecting large and complex equipment. Its object contact surfaces under normal and tangential loads will appear in the form of slip and adhesion, which affects the service life of mechanical equipment. Bolted connection structures cause changes in stiffness and damping, which have great impacts on the dynamic characteristics. Experimental studies and numerical simulations have difficulty predicting the overall performance of bolts in a timely manner, hence cannot ensure the reliability and safety of complex equipment. In order to improve the overall performance of complex equipment, it is necessary to study the contact theory model of bolt connection structures. Based on the relationship between friction force and velocity in the classical friction model, the mathematical expressions of restoring force and tangential displacement in the kinetic theory model are deduced to predict the stiffness degradation of the bolted structure and to characterise the kinetic properties and laws of the bolted structure. From the perspective of theoretical calculation, it makes up for the situation in which it is difficult to measure the performance of bolts due to the existence of spanning scale and provides theoretical support for the reliability of connecting complex equipment. This paper summarises and analyses the contact theory model of bolt connection structures, ranging from macroscopic to microscopic; describes the static friction model, kinetic friction model, statistical summation contact model, fractal contact model; and analyses the influencing factors of the microscopic contact mechanism. The advantages and disadvantages of the kinetic theoretical models are described, the manifestation of friction and the relationship between tangential force–displacement are discussed, and the key research directions of the kinetic theoretical models of bolted structures in the future are elucidated.

Experimental study on critical sand production pressure gradient at different production stages of high temperature and high pressure tight sandstone gas reservoir

AbstractSand production is a common issue in sandstone gas reservoir development, severely impacting the productivity of sandstone gas wells. In order to thoroughly investigate the sand production characteristics of high‐temperature and high‐pressure tight sandstone gas reservoirs, this study focuses on six core samples from tight sandstone gas reservoirs(three samples with fractures), under reservoir conditions (185 MPa, 160°C), sand production experiments were conducted to thoroughly investigate the sand production patterns in sandstone reservoirs under the combined influence of different effective stresses and production pressure differentials. The results indicate: (1) under the simultaneous increase of effective pressure and production pressure differential, sand production near the wellbore (r = 0.1 m) becomes more likely in the reservoir; (2) in actual reservoirs without fractures near the wellbore (r = 0.1 m), sand production phenomena do not occur; (3) reservoirs with fractures near the wellbore (r = 0.1 m) are more prone to sand production, under an effective stress of 90 MPa, with specimens containing fractures exhibiting a 76.48% lower critical sand production pressure gradient compared to those without fractures; (4) when the pore fluid pressure is 95 MPa, the maximum gas production rate for Well X without sand production is 12.4 × 104 m3/d. The experimental results have guiding significance for the rational production of gas wells in this type of reservoir.

Combining Computational Fluid Dynamics and Experimental Data to Understand Fish Schooling Behavior.

Understanding the flow physics behind fish schooling poses significant challenges due to the difficulties in directly measuring hydrodynamic performance and the three-dimensional, chaotic, and complex flow structures generated by collective moving organisms. Numerous previous simulations and experiments have utilized computational, mechanical, or robotic models to represent live fish. And existing studies of live fish schools have contributed significantly to dissecting the complexities of fish schooling. But the scarcity of combined approaches that include both computational and experimental studies, ideally of the same fish schools, has limited our ability to understand the physical factors that are involved in fish collective behavior. This underscores the necessity of developing new approaches to working directly with live fish schools. An integrated method that combines experiments on live fish schools with computational fluid dynamic (CFD) simulations represents an innovative method of studying the hydrodynamics of fish schooling. CFD techniques can deliver accurate performance measurements and high-fidelity flow characteristics for comprehensive analysis. Concurrently, experimental approaches can capture the precise locomotor kinematics of fish and offer additional flow information through particle image velocimetry (PIV) measurements, potentially enhancing the accuracy and efficiency of CFD studies via advanced data assimilation techniques. The flow patterns observed in PIV experiments with fish schools and the complex hydrodynamic interactions revealed by integrated analyses highlight the complexity of fish schooling, prompting a reevaluation of the classic Weihs model of school dynamics. The synergy between CFD models and experimental data grants us comprehensive insights into the flow dynamics of fish schools, facilitating the evaluation of their functional significance and enabling comparative studies of schooling behavior. In addition, we consider the challenges in developing integrated analytical methods and suggest promising directions for future research.

Experimental study on the seepage characteristics of dolomite fracture specimens before and after grouting

Experimental study on the seepage characteristics of dolomite fracture specimens before and after grouting

Influence of coupled water and thermal treatments on the fracture characteristics of a typical sandstone

Understanding the fracture behavior of rock after coupled water and thermal environment is important for many geotechnical projects. This study examines the influence of coupled water and thermal treatments on the fracture toughness and characteristics of a typical sandstone under mode I and mode II loading conditions. Notched deep beam (NDB) specimens were utilized and subjected to soaking treatments at various water temperatures (23 °C, 60 °C, and 99 °C). The experimental results indicate a significant reduction in both mode I and mode II fracture toughness values, with reductions ranging from 15.4% to 13.2% for mode I and 26.1% to 8.9% for mode II respectively. As the water temperatures increase, a slightly rising trend is observed in both mode I and mode II fracture toughness within the examined temperature range. Sandstone specimens displayed typical brittle fracture characteristics at lower soaking temperatures. For mode I specimens, an increase in ductility was evident with higher soaking temperatures, while the ductile behavior is less pronounced in the mode II specimens. Based on the Maximum Tangential Stress (MTS) criterion and the Generalized Maximum Tangential Stress (GMTS) criterion, the predicted values of mode II fracture toughness and the fracture process zone (FPZ) were discussed. The results show that both the GMTS and MTS criteria exhibit inaccuracies in predicting the mode II fracture toughness of sandstone treated at different soaking water temperatures. However, the GMTS criterion, which incorporates T-stress, demonstrates smaller errors compared to the MTS criterion. The study shows that the radius r0 of the fracture process zone is not a constant under both mode I and mode II loading conditions. The calculation of the fracture process zone radius r0 in the GMTS criterion requires further theoretical and experimental study.

Mechanical behavior of rock-like specimens with 3D nonpenetrating and nonpersistent rough joints under uniaxial compression: experimental study

Mechanical behavior of rock-like specimens with 3D nonpenetrating and nonpersistent rough joints under uniaxial compression: experimental study

Effects of Maitland mobilization technique on upper extremity function in stroke survivors with spasticity: An experimental study.

The recovery of upper limb function is of great significance for stroke patients to regain their self-care ability, yet it is still a difficult point in clinical practice of neurological rehabilitation. This study aimed to investigate the effect of Maitland joint mobilization technique on the recovery of upper extremity function in patients with spasticity after stroke. From August to December 2023, 71 patients with upper extremity flexor spasm after stroke were recruited and randomly divided into experimental group (n = 35) and control group (n = 36). The control group was given conventional rehabilitation treatment, while the experimental group was treated with Maitland mobilization technique treatment of upper extremity joints on the basis of the control group. The experiment lasted for 8 weeks. Participants of the 2 groups were observed for Fugl-Meyer motor assessment-upper extremity (FMA-UE), box and block test (BBT) and Brunnstrom stage, modified Ashworth scale (MAS), and functional independence measure (FIM) at pre- and post-8 weeks study. There was no significant difference in gender distribution, hemiplegic side, diagnosis, past history, age, duration, body mass index, and mini-mental state examination between the 2 groups (P > .05). After 8 weeks of intervention, both groups showed significant improvement in FMA-UE, Brunnstrom stage, BBT, FIM, and MAS of the shoulder (P < .05); however, there was no significant change in MAS of the elbow, wrist, and finger joints (P > .05). The posttreatment values showed a significant improvement in FMA-UE, BBT, and FIM in the experimental group compared to the control group. Comparing the changes in pretreatment and posttreatment, FMA-UE, BBT, and FIM in the experimental group were significantly improved compared with those in the control group (P < .05). Maitland joint mobilization can improve the motor function of upper extremity and the spasticity of shoulder joint complex in patients with stroke.

Functionalization of chlorogenic acid extracted from honeysuckle and preparation of highly efficient anti-aging NR composites: Experimental and molecular simulation study

In this study, chlorogenic acid (CA) was extracted as a natural antioxidant from honeysuckle by ultrasonic method. The CA was quantitatively analyzed by high performance liquid chromatography (HPLC). And the extracted CA was successfully loaded into treated carbon nanotubes (CNTs) by immersion method. An effective strategy to improve the anti-aging property of natural rubber (NR) was proposed by the collaborative use of CNTs-loaded CA (CNTs-CA) and free CA that enabling the NR matrix to maintain a comparatively high concentration of antioxidants for a long period of time. The experiment results showed that the loaded CA was 2.25 times more resistant to migration than that of the free CA after three days of aging. Encapsulation of antioxidant into CNTs inhibited the antioxidant blooming. And the addition of CNTs-CA significantly enhanced the mechanical characteristics of NR. Furthermore, molecular dynamics (MD) simulations elucidated the migration process of the antioxidant in the NR system at the molecular level. The migration kinetics analysis was carried out by MD simulation, and the results showed that the CNTs-CA has more significant migration resistance than free CA. It can be concluded from the calculation results of the binding energy (Ebinding) that the Ebinding of loaded CA and NR was more than three times that of the free CA and NR. In summary, the proposed synergy NR/CA/CNTs-CA system resolved the issue of easy migration and blooming of the antioxidant. Overall, through such efforts, it has become possible to prepare environmentally friendly materials that are durable and resistant to aging.

Demystifying operator 4.0 through an integrative framework

PurposeDespite increased interest in the Operator 4.0 concept, there has been scarce attention on practice-oriented frameworks that can assist firms in reaping the potential benefits of technologies within the I4.0 framework. The purpose of this paper is to provide an integrative framework on how to engage Operator 4.0 effectively.Design/methodology/approachFollowing meta-synthesis logic and integrative conceptual analysis, this study synthesizes and integrates experimental case studies on Operator 4.0 solutions. The analysis is conducted on 24 cases retrieved from peer-reviewed articles.FindingsThe analysis revealed several factors that determine the type and extent of benefits that can be realized within a human-cyber-physical system. However, enhancing these capabilities is not straightforward, as several factors can inhibit the realization of these capabilities. Firstly, the benefits vary depending on the type of Operator 4.0. Secondly, the interoperability of the introduced I4.0 solution with the existing systems is crucial. Thirdly, the adaptability of the solution to serve multiple purposes is crucial, as it tends to increase technology acceptance.Research limitations/implicationsThe studies reviewed in this research were based on experimental cases, with limited implementation of the solutions they proposed. As such, their implications when implemented on a larger scale are tentative.Originality/valueThe present study has synthesized existing experimental cases and developed an integrative framework to guide the implementation of Operator 4.0. By gathering primary insights from these experiments, we have clarified when and how Operator 4.0 and the required interactions can lead to successful implementation.

Incorporation of Ag in Co9S8-Ni3S2 for Predominantly Enhanced Electrocatalytic Activities for Oxygen Evolution Reaction: A Combined Experimental and DFT Study.

Electrodeposition of abundant metals to fabricate efficient and durable electrodes play a viable role in advancing renewable electrochemical energy technologies. Herein, we deposit Co9S8-Ag-Ni3S2@NF onto nickel foam (NF) to form Co9S8-Ag-Ni3S2@NF as a highly efficient electrode for oxygen evolution reaction (OER). The electrochemical investigation verifies that the Co9S8-Ag-Ni3S2@NF electrode exhibits superior electrocatalytic activity toward OER because of its nanoflowers' open-pore morphology, reduced overpotential (η10 = 125 mV), smaller charge transfer resistance, long-term stability, and a synergistic effect between various components, which allows the reactants to be more easily absorbed and subsequently converted into gaseous products during the water electrolysis process. DFT calculation also reveals that the introduction of Ag (222) surface into the Co9S8 (440)-Ni3S2 (120) system increases the electronic density of states per unit cell of a system and significantly reduces the energy barriers of intermediates for OER, leading to enhanced electrocatalytic activity for OER. This study showcases the innovation of employing trimetallic nanomaterials immobilized on a conductive, continuous porous three-dimensional network formed on a nickel foam (NF) substrate as a highly efficient catalyst for OER.

Assessment of the potential structure and nucleation efficacy of multi-component heterogeneous substrate

In recent years, nucleation of multi-component heterogeneous interface structures has attracted increasing attention due to their excellent grain refinement and anti-poisoning capabilities in Al-Si alloy. In this research, a general methodology was proposed to predict the surface structure and meanwhile evaluate the grain refinement efficacy of the multi-component boride nucleants based on a comprehensive experimental and theoretical study of a novel Al-Si alloy refiner, i.e., Al-3.5Nb-1V-1B. By using high-resolution electron microscopy, the (Nb, V)B2 particle with a characteristic “core-shell” surface structure was observed, attributed to V adsorption driven by interfacial energy minimization, validated by ab initio calculations. A general interfacial energy-based model was then proposed which predicts the multi-component boride substrate structure, well consistent with the experimental findings. The nucleation potency of different substrates was analyzed in atomic scale and only if the interfacial atomic vibration was considered together with the nucleation-influencing factors (i.e., the lattice mismatch and the anti Si-poisoning effect), the predicted nucleation potency order can agree well with the experimental results. A thermodynamics-kinetics combined analytic model was summarized by coupling the lattice mismatch parameter, the interfacial Si adsorption energy and the interfacial atomic vibration amplitude, which accurately evaluates the multi-component boride grain refiners for the Al-Si alloys.

Experimental Study on Using Synthetic Images as a Portion of Training Dataset for Object Recognition in Construction Site

The application of Artificial Intelligence (AI) across various industries necessitates the acquisition of relevant environmental data and the implementation of AI recognition learning based on this data. However, the data available in real-world environments are limited and difficult to obtain. Construction sites represent dynamic and hazardous environments with a significant workforce, making data acquisition challenging and labor-intensive. To address these issues, this experimental study explored the potential of generating synthetic data to overcome the challenges of obtaining data from hazardous construction sites. Additionally, this research investigated the feasibility of hybrid dataset in securing construction-site data by creating synthetic data for scaffolding, which has a high incidence of falls but low object recognition rates due to its linear object characteristics. We generated a dataset by superimposing scaffolding objects, from which the backgrounds were removed, onto various construction site background images. Using this dataset, we produced a hybrid dataset to assess the feasibility of synthetic data for construction sites and to evaluate improvements in object recognition performance. By finding the optimal composition ratio with real data and conducting model training, the highest accuracy was achieved at an 8:2 ratio, with a construction object recognition accuracy of 0.886. Therefore, this study aims to reduce the risk and labor associated with direct data collection at construction sites through a hybrid dataset, achieving data generation at a low cost and high efficiency. By generating synthetic data to find the optimal ratio and constructing a hybrid dataset, this research demonstrates the potential to address the problems of data scarcity and data quality on construction sites. The improvement in recognition accuracy of the construction safety management system is anticipated, suggesting that the creation of synthetic data for constructing a hybrid dataset can reduce construction safety-accident issues.

Rotational and Vibrational Temperatures of Transient Atmospheric Glow Plasma

Abstract Plasma ignition can significantly improve the efficiency and performance of combustion devices through the enhancement of combustibility limits. Investigating plasma development for fundamental experimental flame conditions (i.e., spherical flame experiments) can provide insight into how plasma thermalizes the combustible mixture and, therefore a better understanding of flame development in future experimental studies. This study observed an ignition system designed to produce spherical flames in quiescent gas inside a constant-volume combustion chamber. Rotational and vibrational temperature measurements of dry atmospheric air glow plasma are reported. Measurements were taken for a transient discharge with currents less than 0.5 A. The electrode wire geometry and discharge variation resulted in an ellipsoid-shaped kernel and plasma region with an abnormal glow discharge. The measured temperatures were compared to the conductive thermal kernel boundary observed with Schlieren imaging. Maximum rotational and vibrational temperatures of 3000K and 10000K, respectively, were observed near the anode electrode for a 0.5 A current. The temperature decreased with the axial distance from the anode, while a constant temperature was observed in the radial direction. Lower currents resulted in a smaller temperature, with minimum measured rotational and vibrational temperatures of 1500K and 5000K, respectively. The results were compared with available experimental literature and the variation observed was a result of the transient nature, which resulted in hysteresis in temperature vs discharge current measurements.

Experimental study of the effect of different pulse charging patterns on lithium-ion battery charging

This study aims to experimentally investigate the impact of different pulse charging patterns on the charging time and performance of lithium-ion batteries at room temperature. Experimental results indicate that most pulse charging protocols have a positive impact on shortening the total charging time compared to the CC-CV charging method with the same input charge capacity. This effect is observed not only in LFP batteries but also in NMC batteries. Three pulse charging patterns are studied: constant current charge (C–C), charge rest (C–R), and charge discharge (C-D). The C-D mode results in the shortest charging time and the smallest cell internal resistance. Compared to the 1C CC-CV baseline, the pulse C-D mode reduces the charging time by approximately 6.8 %, decreases the average pulse internal resistance by about 17.5 %, and increases the remaining discharge capacity ratio by 3.76 % after 800 cycles. Additionally, a pseudo-2D physics model is used to study the internal effects on the battery using the pulse C-D mode. The results show that using the pulse charging method (C-D) results in a more even distribution of electrolyte salt concentration and electrode particle lithium concentration across the cell, thereby improving battery performance.

Modeling of Unburned Carbon in Pulverized Coal-Fired Supercritical Steam Generators

ABSTRACT In coal-fired boilers, one of the most important metrics for optimizing combustion is the proportion of unburned carbon (UC) in the ash. In most Indian power plants, it is still assessed offline through manual sample collection and laboratory analysis. The laborious processes of sample collection, preparation, analysis, and reporting require at least five to eight hours of work. The delayed results may not be useful to optimize combustion in the boiler furnace, as the boiler operating conditions may be completely different from the conditions when the samples were collected. Instead, the use of prediction algorithms may bring timely corrective action if the UC goes high. The present experimental study is taken up to obtain a correlation between UC and corresponding relevant boiler operational parameters and on the residence time of coal particles in the boiler furnace. Multiple regression analysis is performed using ANOVA tools. One hundred and ninety-four sets of coal, ash samples and boiler operating parameters are collected from 07 supercritical units. Coal proximate, coal fineness and ash UC analysis are carried out. The analyzed results and collected boiler operational data are statistically analyzed using Microsoft Excel’s ANOVA tool to understand the dependent behavior of UC on the boiler operational parameters and fired coal characteristics. The empirical equations are proposed for the prediction of UC in bottom and fly ash for supercritical boilers. Additionally, fresh 20 sets of coal, ash samples, and related operating data are gathered for the validation of the proposed empirical equations. For additionally collected samples, the predicted results are compared with the offline measured laboratory results. The maximum deviation between the predicted and laboratory results are within the range of ± 0.40% and ± 0.24% for bottom and fly ash samples, respectively.

Intratubular Penetration Depth of Ultrasound Activated Bioceramic Sealant Cements at the Dentin-Radicular Cement Interface

To evaluate the intratubular penetration depth of ultrasound-activated bioceramic sealant cements into root dentin, specifically at the dentin-cement interface. This in vitro experimental study was conducted with samples that were randomly divided based on the type of sealer used and whether ultrasound activation was applied prior to obturation. This resulted in four experimental groups (n=40). Groups A1 and B1 utilized the Eighteeth Ultra X ultrasonic activator with a blue tip #20 featuring a 2% taper at low power for activation, while groups A2 and B2 did not employ any form of activation. The symbol (+) denotes groups with ultrasonic activation, while (-) represents groups without ultrasonic activation. In the middle third, it was observed that BioC Sealer (+) had a mean sealing value of 0.66±0.17, while MTA Fillapex (+) showed a mean value of 0.38±0.07. It was found that BioC Sealer (-) had a mean sealing value of 0.24±0.04 in the middle third, while MTA Fillapex (-) showed a mean value of 0.16±0.04. These differences were not statistically significant (p=0.569). In the apical third, the BioC Sealer (-) presented a mean sealing value of 0.44±0.17, while the MTA Fillapex (-) obtained a mean value of 0.30±0.04. However, this difference did not reach statistical significance (p=0.0745), suggesting that both materials can provide a similar seal in the apical third. The results suggest that both BioC Sealer and MTA Fillapex provide a comparable seal in the middle and apical thirds of the root canal system, however, this was not statistically significant. This indicates their potential efficacy in both endodontic sealing procedures.

Numerical and experimental study of new fully prefabricated ballastless track

Reducing the workload of cast-in-place construction of ballastless tracks can effectively reduce diseases. This study designed the limiting structures of the prefabricated slabs and base plates. A new fully prefabricated ballastless track was proposed. And the track limiting capacity tests and fatigue tests were carried out to verify its service performance. Results indicated that it is necessary to insert two limiting steel bars into the grouting holes for slab limitation, and double piles with a diameter of 0.2 m for base plate limitation. The field tests demonstrated it could withstand large loads from freight trains, and the limiting capabilities of limiting structures were satisfactory. The track structure showed no fatigue damage after 3 million fatigue load cycles. This research can provide insights for low-damage and high-efficiency construction of ballastless tracks for new lines.