Speed Line Research Articles

Optimization of Tensile Strength and Cost-Effectiveness of Polyethylene Terephthalate Glycol in Fused Deposition Modeling Using the Taguchi Method and Analysis of Variance

This paper investigates the optimization of tensile strength, tensile strength per unit weight, and tensile strength per unit time of polyethylene terephthalate glycol (PETG) material in fused deposition modeling (FDM) technology using the Taguchi method and analysis of variance (ANOVA). Unlike previous studies that typically focused on optimizing a single mechanical property, our research offers a multi-dimensional evaluation by simultaneously optimizing three critical quality characteristics: tensile strength, tensile strength per unit weight, and tensile strength per unit time. This comprehensive approach provides a broader perspective on both the mechanical performance and production efficiency, contributing new insights into the optimization of PETG in FDM. The Taguchi method (L16 45) was designed and executed, with the layer height, infill density, print temperature, print speed, and infill line direction as the control factors. Sixteen tensile tests were conducted, and ANOVA was employed to identify the main influencing factors for each quality characteristic. For the tensile strength, the infill density was found to have the greatest impact (48.45%), while the print temperature had the least impact (0.78%). The optimal parameter combination reduced the quality loss to 31.28% and standard deviation to 55.93%. For tensile strength per unit weight, the infill line direction had the greatest impact (87.22%), whereas the print temperature had the least impact (0.77%). The optimal parameter combination reduced the quality loss to 54.09% and standard deviation to 73.54%. Regarding the tensile strength per unit time, the layer height had the greatest impact (82.12%), while the print temperature had the least impact (0.08%). The optimal parameter combination reduced the quality loss to 10.81% and standard deviation to 32.87%.

A novel method for aero-engine map calibration using adaptation factor surface

High-fidelity component-level models (CLMs) are essential for aero-engine performance modeling, monitoring, and diagnosis, relying heavily on precise component maps. Inaccuracies in these maps can cause significant deviations between predicted and actual measurements. This study introduces a novel wide-range performance adaptation method (WPAM) utilizing adaptation factor surfaces, enabling precise adjustment of speed line operating points. The adaptation factors for the component maps are calculated based on both steady-state and transient measurements using the Levenberg-Marquardt method, with transient adaptation calculations converted into a steady-state solution. Adaptation factor surfaces are constructed using the moving least squares method to modify component maps in both spool speed and β-value directions. Validated on two engines with distinct maps, WPAM significantly enhances CLM accuracy under steady-state and transient conditions, considering multidimensional engine and CLM map discrepancies. It is applicable to degraded and variable geometry engines, exhibiting robustness in handling noisy measurement data.

Industrial centrifugal gas compressor sound emission comparison across speed lines

Centrifugal gas compressors are widely used in the oil and gas industry. Gas compressors produce sound emissions while operating and are often unenclosed requiring the need to know the sound emissions. Gas compressors create a variety of sound pressure levels across their large operating range. This paper compares sound pressure levels of a compressor operating across three different speed lines and two different pressures. The results show increasing sound levels coincide with increasing mechanical power. Also shown is an increase in sound level as the compressor approaches choke.

Rapid automatised naming is related to reading and arithmetic for different reasons in Chinese: Evidence from Hong Kong third graders

BackgroundRapid automatised naming (RAN) has been found to predict children's reading and arithmetic abilities. However, the underlying mechanisms for its involvement in the two abilities are not clear. This study examines how RAN shared variances with domain‐general and domain‐specific abilities in predicting reading and arithmetic in Chinese children.MethodsOne hundred and sixty‐four children (mean age = 8 years 0 months, SD = 4 months) were administered with RAN tasks, word reading and arithmetic tasks and measures of working memory, processing speed, morphological awareness, phonological awareness and number line estimation.ResultsRAN mainly shared variance with morphological awareness in predicting word reading, while it shared variance with processing speed and number line estimation in predicting arithmetic calculation.ConclusionsThe findings indicated that RAN was related to reading and arithmetic for different reasons. The RAN–reading relationship partly reflected the semantic facilitation of the orthography–phonology links for both RAN stimuli and Chinese characters, while the RAN–arithmetic relationship partly reflected the shared process of retrieving semantic information from long‐term memory embedded in the two tasks.

Research on process parameter optimization of irregular coal face.

Based on the engineering background of 1353 working face in Daizhuang Coalmine, the paper identifies three primary issues with the working face mining process: conventional pressure relief means are limited, risk of impact and the length of working face changes, It also proposes comprehensive control measures to improve the blasting roof cutting scheme, optimize mining speed and the location of the stopping line. The three improvement measures mentioned above are simulated numerically, and the effects of the drilling and blasting plan, mining speed, and stopping line location on stress distribution are determined. The results show that by implementing the three improvement measures, the stress variation interval can be efficiently controlled and the working face's production safety can be increased. Finally, it is determined that the 1353 working face of Daizhuang Coalmine adopts the pressure relief method of drilling on one side and cutting the roof 20m deep on the other side, and the mining speed of the working face is 3m/day and the length of the stopping line is 85m. Based on the on-site monitoring results, the implementation of comprehensive treatment measures can effectively improve the surrounding rock state of 1353 working face, which has certain guiding significance for the mining of irregular working face.

Research on speculation method for compressor map of PG9351FA gas turbine

A compressor map is usually represented by a limited number of feature points to speculate the entire operating range. Also, accurate compressor map models can be obtained quickly by using the appropriate methods. In this paper, 9351FA gas turbine is used as the research object, and a set of targeted compressor map speculation scheme is proposed. At 15 data points, high-precision compressor maps are obtained based on BP neural network, and this method is suitable for a large number of data points. At 6 data points, compressor maps are obtained based on the parameter estimation method, and this method is suitable for a small number of data points. The mean square deviation of the compressor map obtained by the neural network is about 0.002, while the minimum mean square deviation of the results of the parameter estimation method is 0.026 and the maximum mean square deviation is 0.088. Since the corrected speed line of 106.4 is almost vertical, the maximum error mean squared deviation and the maximum standard deviation occur on this line. Both methods are suitable for different sample sizes, and the speculated compressor maps are more reliable. The combination of the two methods can provide a set of reference methods for compressor map speculation.

Multi-Purpose Tracker Robot

Abstract: This paper introduces a multi-purpose tracking robot designed with Arduino, ultrasonic, infrared sensors, and motor drivers. The robot is capable of performing diverse tasks such as obstacle avoidance, line following, and object tracking. Its hardware comprises an Arduino Uno microcontroller, ultrasonic sensors for distance measurement, infrared sensors for line detection and obstacle avoidance, and motor drivers for controlling DC motors. The software, developed using Arduino IDE, includes algorithms for sensor data processing, decision-making logic, and motor control. By implementing PID control algorithms, the robot achieves enhanced stability and accuracy in navigation tasks like motor speed control and line following. Experimental results validate its effectiveness in various scenarios, showcasing its potential for advanced robotics and automation applications through intelligent sensor integration and control strategies.

Experimental Study on the Distribution Law of Wind Speed in Rectangular Section Tunnels of Coal Mines

Ventilation is the cornerstone of coal mine safety production, and accurate monitoring of ventilation parameters is the fundamental guarantee for ventilation technology decision-making. A calculation model for the average wind speed line position in rectangular section tunnels of coal mines was established based on the Boussinesk theory and Prandtl turbulence theory to address the issue of difficulty in meeting decision-making needs in wind speed monitoring accuracy. The airflow field of rectangular section tunnels under different wind speed conditions was measured at the coal mine site, and the average position of the measured average wind speed line was obtained. The comparison and verification with the theoretical calculation results were carried out, with an absolute error of less than 5%.

Study on Wind Speed Distribution Law of Mine Roadway Section under Different Conditions

Ventilation is the cornerstone of coal mine safety production, and accurate monitoring of ventilation parameters is the basic guarantee for ventilation technology decision-making. Aiming at the problem that the accuracy of wind speed monitoring in coal mine roadway is difficult to meet the needs of decision-making, this paper studies the position relationship between the average wind speed line and the roadway wall surface by combining theoretical calculation and numerical simulation, and simulates the wind speed distribution law of typical roadway section. The main factors affecting the distribution of wind speed in roadway section include roadway section shape, section size, support form, wind speed, facilities and equipment status, etc. The expression of the position relationship between the average wind speed line of the rectangular and semi-circular arch roadway section and the roadway wall surface is y=elna-1.5. Through 25 groups of model simulation, the wind speed distribution law of different types of roadway sections under different conditions is obtained: the wind speed contour is basically parallel to the roadway wall. The wind speed gradient near the roadway wall is large, and the wind speed gradient in the middle of the roadway is small. The thickness of the boundary layer decreases with the increase of wind speed.

Design and analysis of a nozzle-less twin-entry turbine volute for automobile application

Due to the increasing demand for improved fuel economy in passenger cars, recent internal combustion engines come with a turbocharger. Turbochargers are a method of engine downsizing that forces more compressed air into the combustion chamber, enabling a high power density. Two main types of turbines are commonly adopted in turbochargers; single-entry and multiple-entry. The multiple-entry type includes twin-entry and double-entry volutes. A twin-entry volute consists of two inlets with a divider that feed the entire circumference of a rotor whereas a double-entry volute has two separate inlets that feed the rotor separately. A twin-entry volute's design is based on a single-entry volute by merely placing a divider into the volute. The conventional design approach of a twin-entry volute gives relatively little consideration to the design aspects such as the divider's length, the divider's width, and the cross-sectional shape of the volute. The above-mentioned design aspects of a twin-entry volute have an impact on the performance of a turbine. This paper intends to design a new twin-entry volute with a specified divider length and width. The volute's profile is based on a single-entry volute. In addition, the performance of this twin-entry turbine is compared with the asymmetric double-entry turbine. The comparison of these configurations relies on consistent criteria, including the A/R ratio, mixed-flow rotor, and cross-sectional of the volute. The simulation was executed at two different turbine speeds; 30k RPM (50 %) and 48k RPM (80 %). The validation simulation shows great agreement with the experimental data with a Root Mean Square Error of less than 5 % for both speed lines. Based on the results obtained, the twin-entry turbine shows a lower swallowing capacity than the asymmetric double-entry turbine at both operating conditions. At both speed lines, the twin-entry turbine's efficiency begins to fall toward the end. The incidence angle of the twin-entry turbine is 24.4° at 50 % operating speed and -3.72° at 80 % operating speed. In both turbines, entropy generation reduces as the speed line increases, and both turbines exhibit a similar entropy generation at both speed lines. The existence of a horseshoe vortex near the hub surface and the tip leakage vortex near the shroud region of the blade substantially influence both the turbines' performance.

Experimental Study on Wind Speed Distribution in Semi-circular Arch Tunnels Based on Mirror Stepped Grid Method

Ventilation is the cornerstone of coal mine safety production. Accurate monitoring of ventilation parameters is the basic guarantee for ventilation technology decision. For the problem that the accuracy of wind speed monitoring in coal mine tunnels is difficult to meet decision-making needs, a combination of theoretical calculation and experimental research was used to study the relationship between the average wind speed line and the position of the tunnel wall. The theoretical calculation obtained the expression of the relationship between the average wind speed line of the semi-circular arch tunnel section and the position of the tunnel wall. The proposed multi section mirror stepped grid format was used to investigate the airflow field in a semi-circular arch roadway under different conditions in the laboratory. The contour map of wind speed distribution was drawn, and the position of the measured average wind speed line was obtained. The absolute error between the measured average wind speed line and the theoretical model calculation results was within 5%, which verified the reliability of the theoretical calculation results.

High performance efficiency of optical networking infrastructure characteristics with maximum speed of commercial fiber optic line cables employment

Abstract Fiber optic communications have made great strides, and it is now the foundation of our telecommunications and data networking infrastructures. Due to its beneficial characteristics, including low attenuation, a large bandwidth, and immunity to electromagnetic interference, optical fiber is frequently acknowledged as a superior transmission medium. Optical fibers have been widely used to create high speed lines that can transmit either a single wavelength channel or many wavelength channels using wavelength division multiplexing due to their special features (WDM). The maximum speed of commercial fiber-optic cables was only 2.5 Gb/s and can be extended to 1 Tb/s for short and medium distance. The study clarifies the possible transmission distance for different transmission media silica/plastic optical fibers with various optical fiber window transmissions versus environmental ambient temperature variations. The study demonstrated the bad effects of the temperature effects on the optical fiber transmission media (silica/plastic fibers) for various transmission windows.

In-vehicle fragrance administration as a countermeasure for driver fatigue

Driver fatigue is a contributing factor in about 10–30% of all fatal crashes. Prevention of fatigue-related crashes relies on robust detection of driver fatigue and application of effective countermeasures. A potential countermeasure is fragrance administration since odors can have alerting effects on humans. The aim here was to investigate if a fragrance incorporating trigeminal components could be used as an in-vehicle countermeasure for driver fatigue.The fragrance was tested in a driving simulator with 21 healthy but sleep-deprived participants. Each participant performed a monotonous driving task twice, once with active fragrance containing a trigeminal component and once with olfactory fragrance, in a cross-over single-blind design. The order of trigeminal/olfactory fragrance was randomized and blinded to the participants. Both fragrances (trigeminal/olfactory) were administered either when the participant fell asleep (defined as eye closure > 3 s) or after approximately 45 min if the participant did not fall asleep.Self-reported sleepiness was assessed using the Karolinska Sleepiness Scale (KSS) every 5 min during driving. Variability in speed and lateral position and line crossing frequency were logged for each drive to measure driving performance. Heart rate measurements (ECG) and eye blinks (EOG) were collected to investigate potential arousing effects of the fragrance and to track objective signs of sleepiness.Mean blink duration, which was used as an objective measure of sleepiness, decreased significantly, after fragrance exposure, as did the frequency of line crossings, but there were no statistically significant differences between the fragrance with trigeminal stimulus and the pure olfactory fragrance.The results are in line with the effects found for other commonly used fatigue countermeasures, like playing loud music. These countermeasures can restore alertness and driving performance for a short while. Whether this is sufficient to support driving performance until the driver can make a safe stop in real traffic remains a topic for future studies.

Influence of pneumatic tube delivery system on laboratory results.

The pneumatic tube system (PTS) is an automated and fast modality of transportation of biological samples, but it has been reported to induce preanalytical errors. To study the influence of transportation by PTS on biochemistry tests which are particularly sensitive to haemolysis and atmospheric pressure variation. We compared laboratory results of arterial blood gas, sodium, potassium, chloride, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, glucose and haemolysis index of samples conveyed simultaneously by PTS and by courier. We recruited 30 patients from the sampling room and 40 patients from the intensive care unit. Transport through PTS resulted in a significant increase in aspartate aminotransferase and potassium without exceeding the limits of acceptability. Potassium was significantly more increased for samples transported in a higher speed line (p = .048) but without exceeding the limits of acceptability. No significant impact was noted on haemolysis indices. The pO2 variations due to PTS transportation exceeded the limit of acceptability with significant intra-individual variations. Our PTS is validated for biochemistry tests results. It reduces turnaround times without affecting sample quality. However, the interpretation of arterial blood gas results should be careful for samples transported by PTS.

Numerical Simulation Analysis of the Influence of Entrance Wind Speed on the Wind Speed Distribution of Coal Mine Tunnel Sections

In order to further accurately obtain the wind speed of coal mine tunnels and achieve intelligent ventilation, taking the Wuhushan coal mine tunnel as the research object, the COMSOL Multiphysics numerical simulation software was used to simulate and analyze the influence of inlet wind speed on the wind speed distribution on the tunnel section, and the wind speed distribution law of the semi circular arch tunnel section under different inlet wind speed conditions was obtained. The research results indicate that the wind speed contour is basically parallel to the tunnel wall, and the wind speed gradient near the tunnel wall is large, while the wind speed gradient in the middle of the tunnel is small. The thickness of the boundary layer decreases with increasing wind speed. The ratio of the maximum wind speed to the average wind speed of the tunnel section is approximately 1.2125. The distance between the average wind speed line of the semi circular arch tunnel and the roof is 10.76%~11.02% of the tunnel height, and the error between the simulation results and theoretical calculation results is within 4%. The research results provide strong support for precise measurement of the average wind speed at fixed points in coal mine underground tunnels.

Redesign of a turbocharger compressor based on multi-component full-passage optimization

Self-recirculation casing treatment (SRCT) is often used to improve the flow stability of turbocharger compressors. However, it usually introduces penalties of the peak efficiency or the choke margin of compressors though assisted by auto-optimizations. For this, a multi-component optimization of SRCT and diffuser for a turbocharger compressor is implemented based on the full-passage computational model with a volute. As a result, the aerodynamic performances of the compressor are improved over the whole speed line. Specifically, the efficiency and pressure ratio at the design condition are increased by 1.23% and 1.31% respectively, those at the near-stall condition are improved by 1.84% and 3.13% respectively. The choke flow rate is improved by 1.44%, and the stable flow range is expanded by 2.7 percentage points. The flow mechanisms are as follows. Firstly, the bleed slot width is increased, then the recirculation flow rates in different impeller passages are improved and the low-energy fluids in corresponding passages are removed. The blockages and the circumferential asymmetry in impeller passages are reduced, hence, the flow stability is improved. Secondly, the flow area of diffuser passages is enlarged due to the reduced solidity of vaned diffuser, and then the swallowing capacity of the compressor is improved. Also, the mismatching effect introduced by the SRCT is compensated by the reduced solidity of vaned diffuser. Finally, the injection slot angle and height are decreased, then the distortions and mixing losses in impeller inlet are reduced. Also, the aerodynamic losses in impeller inducer are reduced by removing more stagnation fluids near inducer shroud due to the increased bleed slot width.

What drives broadband traffic?

Worldwide there is an ongoing policy and regulatory push to make very high speed broadband available as widely as possible. Underlying the policy interventions to support higher speeds is an implicit assumption that higher speeds will enable different (and socially valuable) use. In this paper we empirically test whether higher speed lines are associated with greater household data usage in the UK. We find that after allowing for demographic factors, higher speed in fact has a very limited relationship to traffic. This suggests that mid-speed broadband is not in fact a constraint on household usage (as measured by traffic), and thus the benefits of policy interventions to support higher speeds remain somewhat speculative.

Detecting mechanical property anomalies along railway earthworks by Bayesian appraisal of MASW data

The techniques traditionally used to estimate the mechanical properties of railway earthworks (RE) are costly and of low performance. There is a great need for the development of non-destructive methods, which would allow a fast and efficient diagnosis of RE. Seismic surface-wave (SW) methods, also known as multi-channel analysis of surface waves (MASW), were rescaled here for there systematic implementation on RE. A test site was chosen along the North European High Speed Line (HSL) for its well-known correspondence between discontinuity in mechanical properties and anomalous maintenance forces. With the proposed acquisition and processing strategy, a contrast in SW propagation velocity was correlated with the change in shear modulus of the soil layers beneath the track, previously evaluated in the laboratory. Bayesian inversion of the SW data also allowed to integrate the strong a priori knowledge available on these HSL lines and to provide quantitative results with a confidence index to help end-users in their decisions.

Martian flow characterization using tunable diode laser absorption spectroscopy, in high enthalpy facilities

This research aims at analyzing thermo-chemical properties of the hypersonic high-enthalpy flow in the L2K wind tunnel, situated in Köln at the German Aerospace Center (DLR). In the L2K wind tunnel, Martian atmosphere can be created, and the facility can simulate heat load conditions encountered during atmospheric entry of Martian missions. The focus of this project is the analysis of the non-intrusive experimental technique “Tunable Diode Laser Absorption Spectroscopy” (TDLAS), based on line of sight absorption spectroscopy, and applied to hypersonic flow. A simplified Martian atmosphere (97% CO2 and 3% N2) was used. A new interpretation for CO-TDLAS experimental technique applied to hypersonic wind tunnel flow analysis was developed. Numerical simulations with the DLR-TAU non-equilibrium flow solver were used as support of this analysis, and match between simulations and experiments was observed. Flow speed and absorption line’s width were measured, and the knowledge of L2K’s flow structure was extended.

Numerical Investigation of Rotating Instability Development in a Wide Tip Gap Centrifugal Compressor

In the current study, full-stage unsteady simulations were performed to investigate rotating instability inception mechanisms in a particularly large tip clearance centrifugal compressor with a vaneless diffuser and a volute. Four operating points along a speed line were analysed to understand the influence of the mass flow reduction on flow structures. Close to the peak efficiency, an unsteady interaction between the tip clearance vortices and splitter blades was observed. Considering other studies, the influence of the tip gap size was analysed. Then, a large-scale vortex shedding from the leading edges of the main blades was detected when the stage operated near the maximum pressure ratio. It was demonstrated that shed vortices were caused by the combination of the radial gradient of the tangential velocity under the tip vortex and the reverse backflow near the casing. Previous studies on axial compressors refer to these vortical structures as backflow vortices. These vortices cause a significant increase in the incidence angle in the tip region.