Single Load Research Articles

Impact of Heavy Vehicle Axle Overload and Axle Configuration on Road Damage in Afghanistan

Aim: This study aimed to determine the percentage of heavy vehicles, overloaded vehicles, and heaviest vehicle that leads to deterioration of asphalt roads. Furthermore, the study aimed to assess the impact of ESALs and axle configuration on asphalt thickness and subgrade.
 Methods: This research used quantitative truck traffic data collected for three months in the Laghman WIM (Weigh in Motion) station located on the Kabul Torkham National Highway. Observed axle loads and GVW (Gross Vehicle Weight) data collected from April/ 10/2022, up to June/7/2022 average daily truck traffic of 73895 was estimated axle loads converted to the standard axle ESALs (Equivalent Single Axle Loads).
 Results: The percentage of heavy overweight vehicles is 13% while the heaviest vehicle is T2-Bedford truck vehicles at 20.17%. The T2 Bedford truck percentage was 42.17% in overall volume; this truck was overloaded 20.17%, compared to the general trend of Ministry of Public Works (MoPW), the T3 Hino truck contribution was 1.24% in total volume and 18.64% was overloaded, the ST112 semi-trailer contributed 3.02% in total volume, and 8.52% were overloaded. The ST113 5-axle and TT123 6-axle trailers percentile in entire volume was 9.6 % and 40.85% whereas, the overloading degree for these heavy vehicles was 2.29% and 6.72% respectively.
 Conclusion: Overloading percentage is 13% while, T2 Truck is the heaviest vehicle The variation of ESALs and axle configuration on asphalt thickness and subgrade modulus illustrates the higher thickness of asphalt decreases the damage to asphalt roads.
 Recommendations: Afghanistan Weigh-in-Motion stations need professional employees, internet facilities, electricity, and proper databases to record the data. By applying tight legislation and fines overloading will be minimized. Researchers may also research heavy vehicle tires' impact on road damage. Furthermore, it needs to determine the level of fatigue cracking and rutting failures by overloading.

Low-Power Single Bitline Load Sense Amplifier for DRAM

With the significant growth in modern computing systems, dynamic random access memory (DRAM) has become a power/performance/energy bottleneck in data-intensive applications. Both the power management mechanism and downscaling method face decreasing performance or difficulties in the smaller footprint of the DRAM capacitor. Since optimizing the circuit of sense amplifier (SA) is an efficient method to reduce energy consumption, we propose two single bitline load sense amplifier (SBLSA) circuits, i.e., a redundant voltage discharged SBLSA (RVD-SBLSA) circuit and a bit aware SBLSA (BA-SBLSA) circuit, to improve conventional and single bitline write (SBW) circuits. The RVD-SBLSA circuit utilizes a clamp diode to discharge redundant voltage over VDD/2 with an additional working stage. The BA-SBLSA circuit abandons the single bitline load (SBL) circuit during read and write ‘1’ operations. The RVD-SBLSA circuit can offer the lowest total energy consumption, and the BA-SBLSA circuit can make a better balance between energy consumption and latency. Through the simulation results, the proposed circuits can efficiently reduce energy consumption or balance energy consumption and latency and show huge potentials in very large-scale integrated circuits.

Coupled stability of offshore wind monopile foundations and submarine slopes under periodic loads

Long-term cyclic loading on offshore wind monopiles will lead to a decrease in the mechanical properties of the seabed near the monopile's foundation, therefore, causing instability of the submarine slope and the monopile foundation. To capture the accumulation strain caused by high cycle numbers and plastic deformation of seabed sands, the high cycle accumulation (HCA) model is complied with Mohr-Coulomb constitutive models. The shear strength reduction (SSR) method is used to obtain the safety factor of submarine slopes. The coupled numerical model simulates a 6 MW offshore monopile foundation with a single periodic lateral load applied on the monopile at the sea level, which represents concentrated wind and wave loads in storm conditions. The results show that the plastic zones begin to form at the monopile foundation, then extends towards the slope toe and slope top, and eventually across the entire slope, leading to slope instability. In this process, the safety factor of the slope is significantly reduced with each stage of the process. It was found that both the sharp changes of load amplitude and large average load also decreases the safety factors. Moreover, at the beginning of the monopile installation, the safety factor will increase by nearly 10%, but it will drop by nearly 30% due to long-term periodic lateral loads. Therefore, these have important implications for the installation of monopile foundations for offshore wind turbines (OWTs) since the slopes we consider are within the range of slopes at planned sites for OWTs. An increase in monopile diameter and embedded depth can enhance the overall slope stability. However, an increase in embedded depth could potentially instigate more extensive seabed landslides despite enhancing overall stability.

Point-of-care testing for C-reactive protein in a sequential microfluidic device

Point-of-care testing (POCT) devices are currently available for the detection of various important diseases owing to their easy-to-use, portable, and user-friendly nature. However, the multistep regent manipulation still impedes the performance of the device for end-users. To address this issue, we present a novel sequential flow-through microfluidic device that incorporates dual flow behaviors (fast-flow/delayed) into a single device for assessing the risk of cardiovascular disease (CVDs) using C-reactive protein (CRP) as the model analyte. The device features a fast-flow channel for automated washing of unbound CRP antigens and a delayed channel for flow of a redox reagent for electrochemical analysis. It requires only a single buffer loading, resulting in a total analysis time of 15 min. To overcome challenges related to storage stability and the affinity of antibodies in the manufacturing process, we integrated the P3-CRP peptide as a new bioreceptor for CRP detection. The performance of both the P3-CRP peptide and antibodies was assessed and examined using chronocoulometry. The proposed device exhibited a limit of detection at 47 pg mL−1 with a wide linear range (5 orders of magnitude). To validate its applicability, the device was tested with serum, plasma, and whole blood samples, yielding satisfactory results.

Initial loading of dexmedetomidine and continuous propofol sedation for prevention of delayed recovery: A randomized controlled trial

BackgroundSedation with continuous dexmedetomidine and bolus midazolam administration provides a lower incidence of unacceptable patient movement during procedures but requires a longer recovery time. The authors aimed to compare recovery time and unacceptable patient movement during sedation with initial loading of dexmedetomidine followed by continuous propofol infusion with those during sedation with continuous dexmedetomidine and bolus midazolam administration. MethodsIn this prospective randomized controlled trial, 54 patients undergoing dental surgery and requiring intravenous sedation were assigned to either the dexmedetomidine and propofol group (n = 27, dexmedetomidine administered at 6 μg/kg/h for 5 minutes, followed by continuous propofol infusion using a target-controlled infusion) or the dexmedetomidine and midazolam group (n = 27, dexmedetomidine administered at 0.2-0.7 μg/kg/h continuously after the same initial loading dose with bolus midazolam). A bispectral index of 70 through 80 was maintained during the procedure. Patient movement that interfered with the procedure and time from the end of sedation to achieving a negative Romberg sign were assessed. ResultsTimes from the end of sedation to achieving a negative Romberg sign in the dexmedetomidine and propofol group (median, 14 minutes [interquartile range, 12-15 minutes]) were significantly shorter (P < .001) than in the dexmedetomidine and midazolam group (median, 22 minutes [interquartile range, 17.5-30.5 minutes]). The incidence of unacceptable patient movement was comparable between groups (n = 3 in the dexmedetomidine and propofol group, n = 4 in the dexmedetomidine and midazolam group; P = .999). ConclusionsSedation with a single loading dose of dexmedetomidine followed by continuous propofol infusion can prevent delayed recovery without increasing unacceptable patient movement. Practical ImplicationsThe combination of dexmedetomidine and propofol may provide high-quality sedation for ambulatory dental practice. This clinical trial was registered in the University Hospital Medical Information Network Clinical Trials Registry. The registration number is UMIN000039668.

Photoelastic Stress in Mandibular Overdenture Retained by Two Implants

Objectives: The aim of this study was to verify the effect of occlusal and axial single loads in the photoelastic stress in overdenture retained by two implants placed in the anterior region of the mandible. Materials and Methods: Occlusal load (10, 20, and 30 kgf) was exerted by the conventional maxillary complete denture in occlusion with the overdenture adapted in the mandibular photoelastic model. Axial single load was also exerted on the first left or right molar of the overdenture. Qualitative analysis was made in polariscope images and quantitative analysis by the FRINGES program. Results: Qualitative analysis: The occlusal load showed similar stress in the region between the two implants. Axial single load induced in the first molars promoted stress in the implant apexes, and between the implant and mandible posterior region for the three loads. Quantitative analysis for occlusal load: 10 kgf (T = 265.03; N = 0.57); 20 kgf (T = 989.81; N = 2.11); 30 kgf (T = 1055.40; N = 2.26). Axial single load in the left molar: 10 kgf (T = 267.38; N = 0.57); 20 kgf (T = 270.07; N = 0.58) and 30 kgf (T = 281.84; N = 0.60). Axial single load in the right molar: 10 kgf (T = 952.14; N = 2.03); 20 kgf (T = 1038.58; N = 2.22); and 30 kgf (T = 926.92; N = 1.98). Conclusions: Different photoelastic stress levels occurred in the overdenture retained by two implants when submitted to occlusal or axial single load in the first left or right molar. Clinical Relevance: Artificial teeth intercuspation in the overdenture supported by two implants must have the same importance given to the vertical relationship to relieve the chewing effort.

Titania-supported Cu Single Atom Catalyst for Electrochemical Reduction of Acetylene to Ethylene at Low-Concentrations with Suppressed Hydrogen Evolution.

Electrochemical acetylene reduction (EAR) is a promising strategy for removing acetylene from ethylene-rich gas streams. However, suppressing the undesirable hydrogen evolution is vital for practical applications in acetylene-insufficient conditions. Herein, weimmobilized Cu single atoms on anatase TiO2 nanoplates (Cu-SA/TiO2 ) for electrochemical acetylene reduction, achieving an ethylene selectivity of ∼97% with a 5vol.% acetylene gas feed (Ar balance). At the optimal Cu single atom loading, Cu-SA/TiO2 wasable to effectively suppress HER and ethylene over-hydrogenation even when using dilute acetylene (0.5vol.%) or ethylene-rich gas feeds, delivering a 99.8% acetylene conversion, providing a turnover frequency of 8.9 × 10-2 s-1 , which is superior to other EAR catalysts reported to date. Theoretical calculations showed that the Cu single atoms and the TiO2 support acted cooperatively to promote charge transfer to adsorbed acetylene molecules, whilst also inhibiting hydrogen generation in alkali environments, thus allowing selective ethylene production with negligible hydrogen evolution at low acetylene concentrations. This article is protected by copyright. All rights reserved.

Effects of Multiple-Metal-Compound Contamination on the Soil Microbial Community in Typical Karst Tea Plantations

In this study, the effects of pollution levels and heavy metal pollution on soil microbial diversity in karst tea plantations are reported. Four tea plantations from plateau hills, under forests, by lakesides and on steep slopes in the South China karst were used as research regions. Soil samples were taken from these tea plantations, the soil heavy metals Cd, Cr, Pb, Zn, Ni and Cu were tested using inductively coupled plasma-mass spectrometry, and Hg and As were tested via atomic fluorescence spectrometry. The soil microbes were analyzed via high-throughput sequencing technology. Heavy metal pollution was evaluated via the single factor index and pollution load index, and the correlation between soil heavy metals and the microbial community was analyzed via SPSS 18.0 and Canoco 5.0 software. The results showed that the studied tea plantation soils were greatly polluted by the heavy metals, Cd and Hg, to a low to moderate degree. The comprehensive pollution of multiple heavy metals occurred only in lakeside tea plantations, in which pollution reached a low degree. It is also suggested that Hg and Cd were the major contributors, followed by Cu. The soil microbial diversity in soil samples from lakeside tea plantations was the highest; however, the discrepancy in its dominant species composition was also the highest. When the pollution load index was close to 0.6, the microbial diversity decreased sharply. Afterward, the diversity and heterogeneity generally gently increased, and the dominant composition was more obvious. These results reveal that the impact of heavy metal pollution on soil microbial diversity was not very distinct, but the impact on the dominant microbial community composition was obvious. In addition, the heavy metals, Cd, Hg and Cu, were the key factors that impacted the soil microbial community composition.

Impact of far-field glacially-induced stresses on fault stability in the eastern Paris Basin

Stable Continental Regions (SCR) feature very low seismicity levels, but historical seismicity reveals that these areas can experience large damaging earthquakes of magnitude up to Mw ≈ 7, on faults that were previously undocumented or thought to be stable. Glacial Isostatic Adjustment (GIA) is commonly considered as a factor of SCR deformation and stress perturbations that can trigger fault failure in formerly glaciated areas. Studies suggest that fault reactivation due to GIA may not only be restricted to glaciated areas, but could also occur in their periphery, several hundreds of kilometers away from the former glaciations. In this study, we model GIA associated to the Alpine, Massif Central, Celtic and Scandinavian glaciations from the last glacial cycle, in order to estimate the impact of this process on fault stability in the eastern Paris Basin, an area featuring very low strain rates and seismic activity, but of particular interest due to the proposed construction of a radioactive waste disposal facility. Our computations predict stress perturbations far (hundreds of kilometers away) from the ice loads, of similar amplitude to those in areas where fault reactivation has been observed (1–8 MPa at LGM, 0.8–2 MPa at present-day in our study area). We also show that the interaction between several GIA systems can impact the timing of maximum fault destabilization in a different way than common models considering only a single ice load. The computed far-field glacially-induced stress perturbations remain small compared to ambient crustal stresses, but they are large enough to potentially destabilize faults close to Andersonian geometries, with known faults in the eastern Paris Basin meeting these criteria, mainly in the Marne and Saint-Martin-de-Bossenay fault systems. Yet, there is no known evidence of Quaternary fault activity in the Paris Basin, and discrepancies between the localization of potentially unstable faults due to GIA and seismically active areas in northern France suggests that other processes must be at play.

A time-domain fatigue damage assessment approach for the tripod structure of offshore wind turbines

Welded features in the tubular joints are one of the most severe sources of fatigue failure in supporting structure for offshore wind turbines (OWTs). Therefore, fatigue resistance becomes a vital design, inspection and maintenance criterion for tripod supporting structures. This paper proposes a time-domain fatigue damage assessment approach for tripod structures by establishing a detailed finite element model for the critical zones and simplified beam model for the remaining regions. The stress influence matrix (SIM) is formed once by utilizing multiple finite element analyses. Based on the equivalent static loads and linear superposition principle, the time-variant stress can be efficiently calculated. By comparing the fatigue damage caused by multiple loads to that caused by a single load in a particular direction, we conclude that the advantage of the proposed method over the conventional stress concentration factors method. Afterwards, we investigate the effects of environmental conditions on the cumulative fatigue damage of critical zones. The fatigue resistances of various structures by altering angles between the main barrel and up brace, and a novel structure inspired by topology optimization, are promptly verified. All results indicate that the present approach can determine the fatigue damage for the tripod structure with precision and efficiency.

Investigation on fatigue life of HAp and rGO hybrid coating on the PEEK artificial screws for dental implant

The mechanical behaviour of dental implants is crucial to their long-term endurance. Despite the demonstrated efficacy of dental implants, mechanical and biological concerns revealed in long-term follow-up studies continue to be a cause for concern. Screw loosening, which is usually caused by masticatory pressures when chewing, and peri-implantitis owing to microleakage are two of them, and if left untreated, they can lead to gradual loss of the supporting crestal bone. This study investigated the influence of hydroxyapatite (HAp) and reduced graphene oxide (rGO) hybrid coatings on the threads of a dental implant retention screw made of polyetheretherketone (PEEK). HAp with different concentrations of rGO (0.25, 0.5, 0.75, and 1%) coatings were investigated. The clamping force (CF) and coefficient of friction (COF) of the screw thread pair, as well as the single load fracture and dynamic fatigue life tests, were assessed to determine the integrity of the implant thread connection. The screw fracture mechanism and screw thread surface erosion morphology were also studied. The results revealed that C4 (HAp/rGO) coating might minimize COF, improve CF, and reduce fracture load. Furthermore, it demonstrated better anti-loosening properties under dynamic load. Most screw fractures happen on the screw's initial thread. The fracture end of a C3 combination coated screw was easily removed, but not that of a C4 combination coated screw.

Hydrodynamic Response of Mocean Wave Energy Converter in Extreme Waves

The design of moored floating wave energy converters (WECs) must take into account extreme responses and mooring line loads in order to ensure their survival and continued wave power generation in the ocean environment. This study focuses on Mocean Energy's hinged raft WEC and aims to provide a comprehensive understanding of its hydrodynamic characteristics in survival wave conditions. To achieve this, a physical model study was conducted on a Froude scale of 1 in 50 at the FloWave Ocean Energy Research Facility, University of Edinburgh.&#x0D; The experiments involved the use of NewWaves focusing of crest and trough at the model hinge location, as well as long irregular waves. Motion responses of the fore and aft bodies of the WEC were measured using a Qualisys camera, and single component load cells were used to measure the forces in the 3-point catenary mooring line. The hydrodynamic characteristics of the WEC were evaluated in terms of response amplitude operators and non-dimensional mooring line loads.&#x0D; Results indicate that the fore and aft bodies of the WEC exhibit similar motion responses, except for the pitch motion. The aft body has a pitch response 2 to 3 times higher than the fore body. Concerning the moorings, the wave load on the mooring line in line with the wave direction was found to be higher than the other two mooring lines which were arranged at an angle to the wave direction.&#x0D; In this paper, a brief discussion of the model set-up, parameters, test procedure, analysis of results, and discussion will be reported. The results will provide insight into the behaviour of the Mocean device in survival wave conditions and will aid with the determination of appropriate design parameters for optimal performance and survival in the ocean environment.

Methodology to capture the single blade loads on a cross-flow tidal turbine flume model

The OPTIDE project aims to improve the efficiency and durability of Hydro-kinetic cross-flow tidal turbines (CFTT). These turbines are attractive for the exploitation of tidal energy, as the area-based power density of such turbine arrays is higher in comparison to those from horizontal-axis turbines. CFTT also generally feature a simpler design and the ability to operate under varying flow conditions. Nevertheless, the efficiency of single CFTT is lower relative to the most commonly used axial turbine type. Furthermore the life time can be affected by alternating and pulsating stresses, caused by continuous variations of the angle of attack and hydraulic loads during the rotation. These stresses may lead to structural damage and fatigue-induced material failures. A promising approach to overcome these drawbacks is intracycle blade pitching. In this case the angle of attack is continuously adjusted individually for each blade during the rotation. The consequence is smoothed peaks of the load alternations and a higher power coefficient CP . The project aims to explore the influence of active blade pitching on CFTTs and to optimize it with numerical and experimental means. Therefore, a lab-scaled three-bladed experimental turbine with embedded pitch actuators is developed. The model will subsequently be tested in the lab flume of the Institute of Fluid Dynamics and Thermodynamics of the Otto-von-Guericke University Magdeburg. Blade forces in tangential and radial components as well as the machine torque and the rotational speed are measured during the experiments. The turbine is equipped with two full-bridges of strain gauges for the detection of the blade loads, from which the structural stress is calculated subsequently. To ensure the turbine model’s mechanical durability, weakly coupled fluid-solid-interaction (FSI) simulations have been performed and will be presented. To this purpose, a 2D flow analysis, employing the open-source CFD toolkit OpenFOAM (v2206), has been coupled with a 3D structural analysis, using the Mechanical module of the commercial software package Ansys Workbench (2020 R2). The FSI simulations show that the current setup only allows for the measurement of the radial blade load component, because the pitching moment at blade level interferes with the measurements as soon as the profile stalls. The measurements are further distorted by secondary force paths from the loads on the other rotor blades. Possible measures for an improved instrumentation strategy on the flume model will be presented and discussed. It is shown that multiple equipment options allow for a decent investigation of the forces on blade level.

Hybrid fatigue crack propagation analysis using damage and fracture mechanics methods

AbstractSteel structures are frequently exposed to high‐cycle loading in which fatigue cracks initiate and propagate in the service life. The development of crack(s) will affect the structural integrity. In extreme cases, e.g., earthquakes and impacts, structures may be overloaded in several cycles or even a single loading cycle with the development of significant plastic deformation and macro cracks. Service loads, e.g., traffic and waves, will afterwards still be experienced in these damaged structures. The aforementioned two types of deformation are currently analyzed using damage and fracture mechanics methods, respectively. The cycle‐by‐cycle calculation and jump strategy relying on the Paris' equation, are employed for the low (including monotonic) and high‐cycle problems, using elastoplastic and linear‐elastic materials, respectively. The two calculation methods were developed independently, which presents a challenge in analyzing overloaded high‐cycle fatigue problems. This paper presents and executes a hybrid analysis using damage and fracture mechanics models for the single‐edge notch bend specimen. Either linear‐elastic or elasto‐plastic materials is employed in finite element simulations. The hybrid analysis with the combination of damage and linear‐elastic fracture mechanics shows the potential of a promising solution for assessing the fatigue behaviour of steel structures experiencing extreme loading and associated stepwise material damage. Some challenges are addressed in the combination of the ductile fracture followed by the high cycle fatigue calculation.

A sequence-to-sequence model for joint bridge response forecasting

Knowledge of the structural response of bridges is extremely important for highway asset management and bridge structural health monitoring. Instrumenting every bridge in a road network and maintaining the monitoring instrumentation over decades of service can be financially infeasible. Mechanical intuition suggests a significant relationship exists between responses of two sets of bridges reasonably similar in design exposed to an identical load. This study explores the use of data-driven models to forecast the response of one bridge to a given truck load using the response of another bridge to the same loading profile. By deploying a modern monitoring system in multiple bridges in the same highway corridor integrated in a cyber-physical systems (CPS) framework, and utilizing advanced computer vision algorithms, the authors have gathered a unique dataset consisting of pairs of bridge responses to the same truck load from live traffic moving across a 32.2 km (20 miles) stretch of the I-275 highway in southeast Michigan. Signal processing techniques have been employed to isolate the response of the bridges to a single truck load in a time series of recorded responses. Then, a deep-learning-based time series forecasting framework using the encoder-decoder architecture with gated recurrent unit (GRU) and long short-term memory (LSTM) cells has been used for bridge response forecasting. Baseline models based on linear time series models are also developed to which the deep-learning forecasting models can be compared. After training the models, it is observed that deep-learning-based models can accurately forecast the response of one bridge using the response of another and reduce the forecasting root-mean-squared error (RMSE) by at least 20% relative to baseline linear models. The forecasting capabilities of the encoder-decoder architecture proposed herein outperform traditional approaches to response forecasting. Trained versions of the encoder-decoder forecasting model can be used to provide reliable estimates of bridge response using a single instrumented bridge in a corridor, thereby enhancing the value of data from instrumented bridges for asset management of bridge networks.

Single-Atom Pt Embedded in Defective Layered Double Hydroxide for Efficient and Durable Hydrogen Evolution.

Electrocatalysis in neutral conditions is appealing for hydrogen production by utilizing abundant wastewater or seawater resources. Single-atom catalysts (SACs) immobilized on supports are considered one of the most promising strategies for electrocatalysis research. While they have principally exhibited breakthrough activity and selectivity for the hydrogen evolution reaction (HER) electrocatalysis in alkaline or acidic conditions, few SACs were reported for HER in neutral media. Herein, we report a facile strategy to tailor the water dissociation active sites on the NiFe LDH by inducing Mo species and an ultralow single atomic Pt loading. The defected NiFeMo LDH (V-NiFeMo LDH) shows HER activity with an overpotential of 89 mV at 10 mA cm-2 in 1 M phosphate buffer solutions. The induced Mo species and the transformed NiO/Ni phases after etching significantly increase the electron conductivity and the catalytic active sites. A further enhancement can be achieved by modulating the ultralow single atom Pt anchored on the V-NiFeMo LDH by potentiostatic polarization. A potential as low as 37 mV is obtained at 10 mA cm-2 with a pronounced long-term durability over 110 h, surpassing its crystalline LDH materials and most of the HER catalysts in neutral medium. Experimental and density functional theory calculation results have demonstrated that the synergistic effects of Mo/SAs Pt and phase transformation into NiFe LDH reduce the kinetic energy barrier of the water dissociation process and promote the H* conversion for accelerating the neutral HER.

On the influence of head motion on the swimming kinematics of robotic fish.

Up to now bio-inspired fish-mimicking robots fail when competing with the swimming performance of real fish. While tail motion has been studied extensively, the influence of the head motion is still not fully understood and its active control is challenging. In this experimental study, we show that head yawing strongly impacts on the propulsion force and determines the optimal fin actuation amplitude and tail beat frequency when aiming for a maximal propulsion force. In a parametric experimental study on a tethered 367 mm long fish robot the pivot point location of the head yaw has been varied along with tail beat frequency and actuation amplitude. The experiments took place in a still water tank and the swimming force has been measured with a single axis load cell. The robot is actuated with non-conventional area actuators based on micro fiber composites. 105 parameter sets have been investigated while the highest pivot point distance of roughly 0.36 body length from the nose tip provided the highest propulsion force of 500 mN with the lowest actuation frequency of 2.5 Hz and the highest head motion amplitude of a magnitude of 0.18 body length. Even though the pivot point location on a free swimming robot is a consequence of the complex fluid-structure interactions of fish and fluid, the results provide valuable information for the design of fish mimicking robots and questions the paradigm that head yaw is a simple recoil effect from tail motion and has to be minimized for an effective propulsion.

Investigation on the effect of strain rate on standard involute and asymmetric polymer gears using the newly design fixture for single tooth testing method

Effect of strain rate on the single tooth strength of nylon-based gear has been investigated using a newly designed testing fixture. An adjustable single tooth testing fixture has been designed and developed for the purposed of single tooth loading test which is able to accommodate the gear with varying thickness. Injection molded nylon-6 and SLS (selective laser sintering) printed glass filled nylon-6 standard involute and asymmetric gear tooth have been investigated for their single tooth loading test at three different strain rates of 0.0003, 0.003, and 0.01 per sec. Single tooth strength for both injection and printed gear is found to increase with the increase in strain rate. Injection molded single gear tooth undergone bending failure whereas SLS printed gear tooth shows fracture failure. Resistance to single tooth deflection at higher strain rate has drastically increased for injection molded standard involute (IS) gear tooth by 23% whereas, asymmetric gear tooth IA20 followed by IA34 shows slight increment. SLS printed asymmetric gear tooth PAG20/34 exhibits maximum single tooth strength among all three types of printed gears at all the three strain rates. At higher strain rate of 0.01 per sec, single tooth strength dominates by tooth profile geometry whereas, at lower strain rate of 0.0003 per sec, it dominates by tooth profile geometry and microstructure.

Generation of traffic input for flexible pavement design

Layered elastic theory (LET) was performed by Burmister. It helped to build mechanistic – empirical (M-E) pavement design. In this study, three different approaches were used to predict Cumulative Equivalent single axle load (C-ESAL) over the design period. Two were based on M-E and one was empirical. In each of these cases, standard axle loads were used as well as weight limits and vehicle classification, according to their axle configurations (single, tandem, tridem). Traffic data came from annual traffic census campaigns over the past ten years. Gross vehicle weight (GVW) and axle weight (AW) data came from a fixed weighing station performed during 31 days in 2020. Two road axis were considered: One having a weighing station (reference road) and one under technical studies (specific road). Traffic road data were used to perform regression analyses and predictions. AW and GVW helped to calculate Axle load equivalency factors (ALEF) and Truck equivalency factors (TEF) on the reference road. These values were projected on the specific road. Frequency distribution, gross vehicle weight distribution, axle load distribution of heavy vehicles are applied on the reference road. We performed overload AW and overload GVW analyses. Comparisons were done for the three approaches and an evaluation of technical studies was proposed, including traffic and AW monitoring and management systems. This work came as a basis for the transposition of M-E calculation of traffic inputs, more accurate and used over the passed fifty years, in Higher Income countries, called AASHTO method for USA, LCPC-SETRA method for France, to Cameroon and Sub-sahara African countries, that have been using empirical generation of traffic inputs over the same period, called CEBTP method.

Influence of ceramic thickness and dental substrate on the survival rate and failure load of non-retentive occlusal veneers after fatigue.

To investigate the effect of ceramic thickness and dental substrate (enamel vs. dentin/enamel) on the survival rate and failure load of non-retentive occlusal veneers. Human maxillary molars (n = 60) were divided into five test-groups (n = 12). The groups (named DE-1.5, DE-1.0, DE-0.5, E-1.0, E-0.5) differed in their dental substrate (E = enamel, DE = dentin/enamel) and restoration thickness (standard: 1.5 mm, thin: 1.0 mm, ultrathin: 0.5 mm). All teeth were prepared for non-retentive monolithic lithium-disilicate occlusal veneers (IPS e.max Press, Ivoclar). Restorations were adhesively cemented (Syntac Classic/Variolink II, Ivoclar) and exposed to thermomechanical fatigue (1.2 million cycles, 1.6 Hz, 49 N/ 5-55°C). Single load to failure was performed using a universal testing-machine. A linear-regression model was applied, pairwise comparisons used the Student-Newman-Keuls method (p < 0.05). Three dentin-based occlusal veneers (one DE-1.0, two DE-0.5) revealed cracks after fatigue exposure, which corresponds to an overall-survival rate of 95%. Load to failure resulted in the following ranking: 2142 N(DE-0.5) > 2105 N(E-1.0) > 2075 N(E-0.5) > 1440 N(DE-1.5) > 1430 N(DE-1.0). Thin (E-1.0) and ultrathin enamel-based occlusal veneers (E-0.5) revealed high failure loads and surpassed the standard thickness dentin-based veneers (DE-1.5) significantly (p = 0.044, p = 0.022). All tested monolithic lithium disilicate occlusal veneers obtained failure loads above physiological chewing forces. Thin and ultrathin enamel-based occlusal veneers outperformed the standard thick dentin-based occlusal veneers. Minimally invasive enamel-based occlusal veneer restorations with non-retentive preparation design may serve as a conservative treatment option.