Speed Settings Research Articles

Heat partition evaluation during dry drilling of thick CFRP laminates with polycrystalline diamond drills

Since various material properties of carbon fiber-reinforced polymer (CFRP) are temperature dependent, dry drilling of CFRP is a delicate process. Thermal damage can be caused by a rise in temperature during drilling due to a large portion of heat being transferred into the material. Heat partition is used to quantify this, which represents the percentage of total heat being dissipated into the constituent objects during a machining operation. Drill margin and contact conditions at the tool-workpiece interface significantly affect the drilling of CFRP material. Drilling experiments were performed to measure thrust force, torque, and temperatures for five different sets of feed rates and rotational speeds. This study proposes a method for calculating heat partition values during CFRP drilling by developing a finite element-based thermal model. The FE model employs a Gaussian distributed ring-type heat flux that is a function of the equivalent contact length at the interface between the drill and the material surface and the geometry of the workpiece which operates as a moving heat source, emulating the progress of the drill through the CFRP laminate. The tool implements heat fluxes that use characteristic time-point-based step functions to represent the temperature on the drill as it advances through the workpiece during machining. The temperature profiles obtained from the FE analysis and the experiments for the workpiece and tool were subsequently matched iteratively to determine the corresponding heat partition value.

Studying Performance of Wire Electrical Discharge Machining for Multi-pass Cutting Strategy on the Tool Steel SKD 61 Using Recommended Parameters of Machine

This research aims to study the machining efficiency of wire electrical discharge machining for multi-pass cutting. The recommended parameters of the machine are employed for cutting test tool steel grade SKD 61 with the thickness of 40 mm. The brass wire electrode with the diameter of 0.25 mm was used in the cutting test. The recommended parameters for multi-pass tool path cutting consisted of 4 operations. The 1st cut was defined as a full cut that required the removal of a large amount of workpiece material, with the cutting speed set at 2.60 mm/min. The 2nd, 3rd, and 4th cuts involve cutting on the edge of the workpiece to remove only a small amount of work material, with the cutting speed set at 3.20, 3.60, and 6.80 mm/min, respectively. The experimental test showed that the machining performance of the cutting speed for the 1st cut was lower than the expected value by approximately 18.01 percent. The 2nd, 3rd, and 4th cuts found that the cutting speed higher than expected value by approximately 104.34, 128.89 and 4.12 percentage for each cutting pass, respectively. In addition, the surface roughness and dimensional error of the machined part decrease as the number of cutting passes increases. The difference between the expected values and the experimental results is very useful in planning decisions and quality control for cutting workpieces by the process of wire electrical discharge machining.

An Eco-Driving Strategy at Multiple Fixed-Time Signalized Intersections Considering Traffic Flow Effects

To encourage energy saving and emission reduction and improve traffic efficiency in the multiple signalized intersections area, an eco-driving strategy for connected and automated vehicles (CAVs) considering the effects of traffic flow is proposed for the mixed traffic environment. Firstly, the formation and dissipation process of signalized intersection queues are analyzed based on traffic wave theory, and a traffic flow situation estimation model is constructed, which can estimate intersection queue length and rear obstructed fleet length. Secondly, a feasible speed set calculation method for multiple signalized intersections is proposed to enable vehicles to pass through intersections without stopping and obstructing the following vehicles, adopting a trigonometric profile to generate smooth speed trajectory to ensure good riding comfort, and the speed trajectory is optimized with comprehensive consideration of fuel consumption, emissions, and traffic efficiency costs. Finally, the effectiveness of the strategy is verified. The results show that traffic performance and fuel consumption benefits increase as the penetration rate of CAVs increases. When all vehicles on the road are CAVs, the proposed strategy can increase the average speed by 9.5%, reduce the number of stops by 78.2%, reduce the stopped delay by 82.0%, and reduce the fuel consumption, NOx, and HC emissions by 20.4%, 39.4%, and 46.6%, respectively.

Effects of Infill Density and Printing Speed on The Tensile Behaviour of Fused Deposition Modelling 3D Printed PLA Specimens

The mechanical properties such as tensile behavior of a 3D printed object can be influenced by various printing parameters, including printing temperature, orientation, infill density, and printing speed. This study focuses on investigating the effects of infill density and printing speed. Thirty dog-bone specimens were 3D printed using Fused Deposition Modelling (FDM) technique with Polylactic Acid (PLA) filament. Three different infill density settings (40%, 60%, and 80%) and three printing speed settings (30 mm/s, 60 mm/s, and 90 mm/s) were used. Tensile tests were performed on each specimen using a Universal Testing Machine. The experimental results indicate a clear trend of tensile behaviour with infill density. Increasing the infill density leads to improved tensile behaviour in the specimen. The highest Young’s Modulus and ultimate tensile strength (UTS) were achieved at 541.67 MPa and 24.3 MPa, respectively, with an infill density of 80%. On the other hand, printing speed showed an inverse relationship with tensile behaviour. As the printing speed increased, the Young’s Modulus and UTS decreased. However, the effect of printing speed on the mechanical properties was not as significant as that of infill density. When increasing the printing speed from 30 mm/s to 90 mm/s, the UTS only decreased by 5.61%. In contrast, increasing the infill density from 40% to 80% resulted in a UTS increase of 35.23%.

Pulsating waves in a multidimensional reaction-diffusion system of epidemic type

In this work we investigate the existence of front propagation for a two-component reaction -diffusion system of epidemic type posed in a multi-dimensional periodic medium. This system is a spatially heterogeneous version of the well-known Kermack–McKendrick epidemic model with Fickian diffusion. We derive sufficient conditions for the existence of pulsating travelling waves propagating in an arbitrarily given unit direction. Specifically, we prove that the set of admissible wave speeds contains a semi-infinite interval. Then, for each direction of propagation and each admissible speed, there exists a pulsating travelling wave solution of the system which is globally bounded.

Optimal Hydrofluoric Acid Etching Duration and Impact of Silane/Adhesive on Profilometric Properties and Bonding to Lithium Disilicate Glass Ceramics.

This study aimed to assess the surface roughness, surface free energy (SFE), and shear bond strength (SBS) on a lithium disilicate glass-ceramic surface following varying etching protocols (time variation) and application of silane either with or without adhesive material. Lithium disilicate glassceramic (LDGC) computer-aided design and computer-aided manufacture (CAD/CAM) blocks were cut using a slow-speed cutting mechanism. CAD/CAM blocks were then evaluated for surface roughness, 6 groups (n=20); SFE,12 groups (n=5); and SBS, 10 groups (n=10). The cut CAD/CAM blocks were randomly allocated to 28 groups. Groups were based on the following: 30 or 90 seconds of etching with 9% hydrofluoric acid (HF); application or absence of silane coupling agent (Sil); and application or absence of adhesive (Adh).The control group (Cont) had untreated surfaces. Unetched surfaces were surveyed with only silane (Sil), only adhesive (Adh), or silane+adhesive (SilAdh). Further etched groups were HF30 with HF for 30 seconds, HF30-Sil, HF30-Adh, and HF30-SilAdh. Alternative 90-second etching times produced similar groups: HF90, HF90-Sil, HF90-Adh, and HF90-SilAdh. A digital profilometer was used to assess the surface roughness of specimens, and two readings were recorded. Sessile drop analysis was used to examine SFE specimens, and the OWRK model was modified to measure liquid surface tension. A universal testing machine (UltraTester, Ultradent Products, Inc, South Jordan, UT, USA) was utilized for the SBS test, with the crosshead speed set at 0.5 mm/min until failure. Representative treated specimens from each group were submitted to surface morphological evaluation and chemical analysis using scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDXS) (n=3). After data collection, evaluation using one- or two-way analysis of variance and the post-hoc Tukey test (α=5%) was conducted. A longer etching time of 90 seconds produced a rougher surface. After the 90-second etching process, SFE displayed the greatest values; nevertheless, the use of silane did not affect SFE. For every group examined, the application of silane followed by adhesive resulted in an increase in SBS and more stable bonding over time. SEM/EDXS showed that etching times did affect the amount of cerium on the surface and altered surface morphology. Higher and more consistent bond strengths have been observed with longer etching periods. Silane and adhesive application on the ceramic surface showed stronger and enhanced bond strength, specifically when longer etching times were employed.

An Alternative Reinforcement Learning (ARL) control strategy for data center air-cooled HVAC systems

Energy efficiency of data center is of great concern globally due to their large amount of energy consumption and the foreseeable growth in the demand of digital services in the future. Advanced control strategies are needed to reduce energy consumption. However, the optimization of data center HVAC control is a challenge task due to the complexity of the thermal dynamic models of buildings and uncertainties associated with both server loads and outdoor temperature. In this paper, we propose a new control strategy called Alternately-Reinforcement Learning-control(ARL), which realizes the alternating control of RL and proportional, integral and derivative (PID) for optimizing the control of air-cooled HVAC systems in data centers. The control object of the ARL is the speed set of the compressor and the condensing fan, and the control goal is to minimize energy consumption while maintaining temperature stability. The applied RL algorithm is Deep deterministic policy gradient (DDPG) and Proximal policy optimization (PPO). We pre-train the ARL strategy in offline environment firstly and deploy it in real data center environment for online testing. The test results show that the ARL has significant advantages in maintaining temperature stability while reducing energy consumption, and the PPO algorithm performs better than the DDPG algorithm. Compared with the PID algorithm, the PPO algorithm can save energy by 5.27%, and the temperature control effect can be improved by 3.27%,which indicates the feasibility of the ARL for implementation in real data centers.

Walking balance control in different settings: Effects of walking speed and biological sex

BackgroundPrevious research has suggested that spatiotemporal step parameters differ between settings; however, it remains unclear how different settings influence walking balance control. Research questionHow do settings and sex influence walking balance control during walking at different speeds for young adults? MethodsForty-two adults (21 male (23 ± 4 years), 21 female (24 ± 5 years)) completed overground walking trials in four settings: laboratory (10 m), hallway, indoor open, and outdoor pathway (all 20 m) at three self-selected speeds (slow, preferred, fast) following verbal instructions. Participants wore 17 inertial sensors (Xsens Awinda, Movella, Henderson, NV) to capture total body kinematics. The number of included strides was matched across all conditions, with six strides included in each condition for all participants. Medial-lateral and anterior-posterior total body angular momentum range over each stride was calculated (HML range and HAP range). Setting × speed × sex mixed factorial analysis of variance with repeated measures on setting and speed were used for statistical analysis (α =.05). ResultsSignificant setting × speed interactions (p <.001) were present for both outcomes. HML range was greater in the laboratory and hallway compared to the indoor open and outdoor pathway settings for slow walking speed only. HAP range was lower in the outdoor pathway compared to all indoor settings at slow and preferred walking speeds. Differences in HAP range between settings was more pronounced at the slow speed condition. Across setting and speed conditions, HML range was greater for males compared to females. SignificanceYoung adults may alter their balance control strategy depending on the setting (laboratory, indoor open and outdoor pathway), particularly at slow speeds. Researchers and clinicians are cautioned not to assume walking in laboratory settings reflects walking in all settings nor that males and females can be examined as a single group.

Machinability of gas metal arc based 3D printed Al-Mg 5356 alloy using wire-EDM

Wire-Arc Additive Manufactured (WAAM) is relatively new method of metal 3D printing in which the raw material is heated by the gas metal arc and the molten metal pool is deposited layer-by-layer using a computer numerically controlled axis drive system. Since WAAM needs a finishing process for attaining the final dimensions of the components, there is a need to investigate the machinability aspects of WAAM fabricated materials. This work investigates the machinability of Al-Mg 5356 alloy test samples fabricated by WAAM process using wire-electric discharge machining (Wire-EDM). The test samples were subjected to Wire-EDM and the obtained material removal rate (MRR), kerf width (KW) and surface roughness (Ra) were investigated at different Wire-EDM process settings of voltage, current, pulse-on time (Ton), pulse-off time (Toff) and wire speed (Ws). Statistical analysis revealed that current had a significant influence on MRR. Ton had a strong influence on KW and Ra, whereas Toff exhibited a considerable impact on all these responses. Notably, Ws demonstrated a significant impact on Ra. However, voltage was found to have statistically negligible impact on all the machining responses. Microstructural investigations and compositional analysis were conducted providing valuable information on the cut surfaces. The results derived from the present investigation are useful for predicting the optimum process parameter settings for machining of WAAM-based 3D printed Al-Mg alloy in various manufacturing industries.

Thermo-mechanical coupled three-dimensional finite element simulation analysis of drilling thermoplastic braided carbon fiber composite and optimization of process parameters

Optimizing the process parameters of thermoplastic composites during drilling is paramount for mitigating tearing, delamination, and other forms of damage, while simultaneously enhancing the tensile strength and extending the long-term service life of the overall structure. This study focuses on exploring a thermal-mechanical coupling method for predicting dynamic mechanical progressive failure and determining optimal process parameters during the drilling of Braided Carbon Fiber Reinforced Polyether Ether Ketone (BCF/PEEK). Initially, a thermal conduction constitutive model of BCF/PEEK was developed based on the proposed thermal distribution ratio calculation method. Concurrently, a user-defined material subroutine VUMAT and a bilinear cohesive element model, were implemented on the ABAQUS/Explicit platform to simulate the delamination behaviors of drilling BCF/PEEK using a tapered drill-reamer. Subsequently, a comprehensive BCF/PEEK drilling experiment platform was constructed, and the simulation accuracy of the drilling finite element (FE) model was verified through temperature, thrust force, and hole-wall morphology analyses. Finally, response surface regression models were established for process parameters, and the optimal parameters were predicted and validated. The results indicate that minimum thrust force and temperature can be achieved using the tapered drill-reamer with a spindle speed set at 4878.79/3000 r/min and a feed speed of 34.04/30 mm/min, respectively, with a maximum error of only 8.78 %.

A Comparative and Experimental Study of Parametric Influence on Drilling Process of Hybrid AMMC

Abstract: To aim for the highest quality product quality and a high metal removal rate, metal cutting is crucial. The primary obstacle to attaining optimal quality and high production is the short tool life. The hybrid aluminum metal matrix AA 6082, with reinforcement consisting of titanium dioxide (7.5%) and cenosphere (2.5%), was optimized using the Modified Taguchi optimization method for simultaneous minimization and maximization of surface roughness (Ra), machining time, and material removal rate. The surface finish was affected by different types of geometrical precision values of the CNC drilling process parameters in order to both minimize and maximize the responses. The experiments, including call for the machining of hybrid AMMC and the use of an HSS drill bit, will be performed using a CNC with different process parameters. The L16 orthogonal array will be used for the examinations, and each experiment will be run under a distinct set of circumstances, including feed, speed, and pecking. Using the TAGUCHI design, the optimal geometrical and machining parameters were determined from the experimental output responses, and significant influences were discovered for the corresponding specific output responses.

Finite Speed-Set Model Reference Adaptive System Based on Sensorless Control of Permanent Magnet Synchronous Generators for Wind Turbines

This paper proposes a novel finite speed-set model reference adaptive system (FSS-MRAS) based on the current predictive control (CPC) of a permanent magnet synchronous generator (PMSG) in wind energy turbine systems (WETSs). The mathematical models of wind energy systems (WESs) coupled with a permanent magnet synchronous generator (PMSG) are presented in addition to the implementation of the CPC of PMSGs. The proposed FSS-MRAS is based on eliminating the tuning burden of the conventional MRAS by using a limited set of speeds of the PMSG rotor that are employed to predict the rotor speed of the generator. Consequently, the optimal speed of the rotor is the one resulting from the optimization of a proposed new cost function. Accordingly, the conventional MRAS controller is eliminated and the main disadvantage represented in the tuning burden of the constant-gain proportional-integral (PI) controller has been overcome. The proposed FSS-MRAS observer is validated using MATLAB/Simulink (R2023b) at different operating conditions. The results of the proposed FSS-MRAS have been compared with those of the conventional MRAS, which proved the high robustness and reliability of the proposed observer.

Stability Analysis of Planetary Rotor with Variable Speed Self Rotation and Uniform Eccentric Revolution in the Rubber Tapping Machinery

Natural rubber is a critical material that is essential to industry and transportation. In order to reduce the cost of rubber tapping and improve the efficiency and profitability of rubber production, the 4GXJ-2 portable electric rubber cutter and automatic rubber tapping robot have been developed. In their vibration tool holder, the planetary rotor with variable speed self rotation and uniform eccentric revolution is the most important transmission component, and its instability will cause irregular vibration of the tapping tool, thereby reducing the accuracy of vibration cutting and increasing noise. Base on the ANCF (Absolute Nodal Coordinate Formulation) 3D-beam element and 3D REF (3D Ring on Elastic Foundation), a novel eccentric 3D REF model of a planetary rotor is proposed. By introducing multiple coordinate systems, the coupled motion of uniform eccentric revolution, variable speed self rotation and flexible deformation is decomposed and the influences of these motions on the centrifugal force and Coriolis force are more clearly derived. The model is degraded and validated by comparing with other examples of a rotating circular ring model and uniformly eccentrically revolving annular plate. According to the Floquet theory and Runge−Kutta method, the unstable region of revolution speed of a planetary rotor in rubber tapping machinery is predicted as [817 rad/s, 909 rad/s], [1017 rad/s, 1095 rad/s] and [1263 rad/s,1312 rad/s]. Compared with the rubber-tapping experiment of rubber tapping machinery, the validity of the proposed model is further verified. This model provides important design references for the speed settings of those rubber tapping machines.

Mechanical and microstructural characterization of AISI SAE 4130 steel welded joints made by robotic gas metal arc welding process: influence of electrode work angle in 'T' welded joints

Microstructural variations within welded metals, specifically in terms of phases and their corresponding volume fractions, play a crucial role in influencing weld strength and other mechanical properties. Welded joints in a ‘T’ configuration pose a unique challenge due to the dynamic heat distribution caused by changes in the electrode work angle (EWA) between perpendicularly aligned plates. This study focuses on characterizing the microstructure and micro-hardness of ‘T’ welded joints in a 6 mm thick plate of AISI SAE 4130, welded using the robotic gas metal arc welding process. The examination covers three distinct zones: the base material (BM), the fusion zone (FZ), and the heat-affected zone (HAZ). The extent of the HAZ is meticulously measured on both the vertical and horizontal plates within the weld zones. The x-ray diffraction (XRD) analysis results indicated that the average crystallite size of the base metal and fusion zone is 25.75 nm and 24.51 nm respectively. As per the scanning electron microscope (SEM) image observations, the higher wire feed rate yields to brittle fracture surface. The torch angles notably influence the dimensions of the HAZ on the vertical and horizontal plates of a ‘T’-Joint. Welding at higher EWA and contact-tip-work-distance, results in a larger HAZ on the vertical plate. Conversely, employing a flattened EWA and an increased contact-tip-work-distance leads to a greater extent of the HAZ on the horizontal plate. Furthermore, the micro-hardness of the fusion zone and heat-affected zone demonstrates an increase at higher settings of wire feed rate and travel speed. This phenomenon is attributed to the elevated heat inputs, which contribute to the formation of a finer microstructure within the weldment.

Prediction of TBM penetration rate for different surrounding rocks and cutter head diameters

The penetration rate (PR) of tunnel boring machines (TBMs) is often used to evaluate tunneling performance and predict construction period costs. However, most penetration rate (PR) prediction models are based on a single specific project, which leads to poor universality of the models.Furthermore, the value of the cutter head speed set for the prediction of the construction period in the survey and planning stages depends on manual experience and lacks theoretical guidance. Therefore, based on a set of engineering data from TBM of different surrounding rocks and diameters, this study statistically analyzed the distribution law of the cutter head speed (N) and the relationship between the field penetration index (FPI), geological parameters (uniaxial compressive strength (UCS) and the integrity coefficient of the rock mass (Kv)), and penetration (P). The results show that the FPI is strongly correlated with the geological parameters and the P. The geological and tunnelling parameters are the main factors affecting the penetration rate (PR). On the basis of this, prediction models of the FPI and P and a calculation model of the cutter head speed were developed, and a prediction model of the PR was obtained. The accuracy and reliability of this model were verified and analyzed for the EHe (EH) project. The average prediction error was 15.15 %.

Soft ground micro TBM jack speed and torque prediction using machine learning models through operator data and micro TBM-log data synchronization

Tunnel Boring Machines (TBMs) are pivotal in underground projects like subways, highways, and water supply tunnels. Predicting and monitoring jack speed and torque is crucial for optimizing TBM excavation efficiency. Conventionally, skilled operators manually adjust numerous tunnelling parameters to regulate the machine's progress. In contrast, machine learning (ML) algorithms offer a promising avenue where computers learn from operator actions to establish parameter relationships autonomously. This study introduces an innovative approach to enhancing operator monitoring and TBM data comprehension. A robust correlation between TBM operator behaviour and TBM logged data is established by leveraging an Optuna-assisted ML methodology—the research light on the intricate dynamics influencing TBM advance rate parameters. Operational data is collected from micro slurry tunnel boring machine (MSTBM) umbrella support excavations. The proposed framework harnesses Optuna, an advanced hyperparameter optimization platform, to dynamically refine jack speed and torque settings. Through meticulous analysis of the interplay between TBM operator decisions and real-time logged data, the AI model discerns patterns, empowering informed decision-making. Using Optuna, a range of models, including random forest (RF), K-nearest neighbours (kNN), decision tree (DT), XGBoost, Support Vector Machine (SVM), and Artificial Neural Network (ANN) were automatically compared and tuned. The best model's (RF) performance is evaluated through a correlation coefficient (R2) of 96%, mean squared error (MSE) of 119.7, and mean absolute error (MAE) of 4.42 for jack speed decision making while 83% of R2, MSE of 0.62, and MAE of 0.42 for the torque decision making. This intelligent model can assist the TBM operator in making decisions about TBM control.

Optimizing Carding Speed Parameters and C-60 RSB Draft to Improve Sliver Quality

ABSTRACT The optimization of settings of spinning machinery is one of the technically most urgent tasks when it comes to achieving the best possible raw material utilization for a high-quality yarn. Carding, as part of an integrated draw frame, is the very critical process in spinning preparation for open end rotor spun yarn manufacturing. The aim of the integrated draw frame process in a spinning line is to produce uniform slivers (with low deviation in mass per unit length) where the fibers are laid parallel and the sliver has relatively low neps, short fiber, trash and dust contents. This work examined the potential effects of a range of speed settings on the physical properties of sliver. Optimization results of the study showed that 3.5 CVm% and 2.8 U% of sliver achieved with 96.3% desirability with optimum predicted value of neps 252 cnt/g, short fiber content by number 25.8%, trash 29 cnt/g and dust 234 cnt/g satisfied at licker in speed of 1250 rpm, cylinder speed of 650 rpm, flat speed 0.29 m/min, and C 60 RSB total draft of 2.11 for processing the cotton variety of Deltapine 90 (DP-90).

Measurements and Modelling of the Discharge Cycle of a Grid-Connected Hydro-Pneumatic Energy Storage System

Hydro-pneumatic energy storage is a form of compressed-air energy storage that can provide the long-duration storage required for integrating intermittent renewable energies into electrical power grids. This paper presents results based on numerical modelling and laboratory tests for a kilowatt-scale HPES system tested at the University of Malta. This paper presents measurements of the discharge cycle, in which energy stored in compressed air within a pressure vessel is hydro-pneumatically converted back into electricity via a Pelton turbine and fed into the national electricity grid. The tests were conducted using a hydraulic turbine operated under different fixed-turbine rotational speed settings, with the pressure being allowed to decrease gradually during the HPES system’s discharge cycle. The system’s overall efficiency accounted for flow losses, turbine inefficiencies, and electrical losses. The tests showed that this efficiency was practically independent of the compressed-air pressure of specific water turbine runner speeds, despite the water turbine operating at fixed speeds. A numerical model developed in MATLAB Simulink (R2022a) was also presented for use simulating the hydraulic performance of the system during the discharge cycle. The model used secondary loss coefficients for the hydraulic circuit and derived velocity coefficients from computational fluid dynamics (CFD) for the Pelton turbine nozzle. We achieved very good agreement between the predictions based on numerical modelling and the measurements taken during laboratory testing.

Predicting Wood Density Using Resistance Drilling: The Effect of Varying Feed Speed and RPM

The IML PD series Resi is a device used to assess the drilling resistance of wood. The IML PD series Resi instrument is being widely adopted for commercial wood quality assessment due to its speed, cost-effectiveness, and precision when combined with web-based trace processing. Collecting Resi data with fixed feed speed and RPM settings is challenging due to inherent basic density variations within and between tree species. Altering these settings affects the drilling resistance amplitude of the Resi data, impacting basic density predictions. This study introduces the concept of chip thickness to combine feed speed and RPM into a single parameter to minimise the effects of different sampling conditions on the basic density predictions. Regression models, with chip thickness as the regressor variable, account for 97% to 99% of variance in mean Resi outerwood amplitude across six species. The demonstrated adaptability of chip thickness for adjusting feed speed and RPM settings, along with species-specific functions correlating it with Resi amplitude, holds promise for standardizing amplitude values across diverse feed speeds and RPM settings. Optimal sampling conditions needed to predict basic density lie within the 30%–40% amplitude range. To drill a ~30 cm diameter tree, the recommended fastest settings were 200 cm/min and 3500 RPM for Southern Pine (Pinus elliottii var. elliottii (Engelm) × Pinus caribaea var. hondurensis (Sénéclauze)) and Radiata Pine (Pinus radiata (D. Don.)), 200 cm/min and 2500 RPM for Hoop Pine (Araucaria cunninghamii (Mudie)), 50 cm/min and 5000 RPM for Spotted Gum (Corymbia citriodora subsp. variegata (F. Muell.)), 200 cm/min and 4500 RPM for White Cypress (Callitris glaucophylla (Thompson &amp; Johnson)), and 150 cm/min and 3500 RPM for Shining Gum (Eucalyptus nitens (H. Deane &amp; Maiden) Maiden) based on the billets sampled.

Comparative Evaluation of Antimicrobial Effectiveness and Compressive Strength in Neem and Lemongrass-Modified Glass Ionomer Cement: An In Vitro Study.

Background Glass ionomer cement (GIC) demonstrates biocompatibility and fluoride ion release, indicating their potential to inhibit a wide range of bacteria, although this remains uncertain. Lemongrass and neem are recognized for their potent antimicrobial activity against numerous pathogenic microorganisms. The objective of the study is to evaluate the antimicrobial effectiveness and compressive strength of GIC modified with neem and lemongrass. Methodology Lemongrass and neem were incorporated into conventional GIC at varying concentrations. Group I - neem-modified GIC (0.5%, 1%, 2%), group II - lemongrass-modified GIC (0.5%, 1%, 2%), and group III (non-modified GIC as a control group). The disk-shaped specimens were then compared to unmodified GIC (control). Antimicrobial effectiveness was assessed using the minimal inhibitory concentration (MIC) assay against Streptococcus mutans and Lactobacillus. Compressive strength was assessed using a Universal Testing Machine, with a crosshead speed set to 0.5 mm per minute. Statistical analysis was conducted with a significance level set at p < 0.05. Results Neem modification displayed superior antimicrobial effectiveness against both Streptococcus mutans and Lactobacillus at all concentrations when compared to the control, with 2% showing the least mean value of 0.262. In contrast, lemongrass modification exhibited a significant difference in effectiveness against Streptococcus mutans but no difference against Lactobacillus. Neem modification demonstrated superior performance compared to lemongrass (p < 0.05). Both modified groups showed no significant impact on compressive strength. Conclusions Neem-modified GIC demonstrated the highest antimicrobial efficacy against Streptococcus mutans and Lactobacillus without altering its compressive strength. This suggests its potential as a promising alternative material in restorative dentistry. Additional in vivo investigations are needed to assess the extended-term effectiveness of the material.