Search Results (1,705)

The human pupil changes size in response to processing demands or cognitive (work)load and emotional processing. Therefore, it is important to test if automatic tracking of cognitive load by pupil-size measurement is possible under conditions of varying levels of emotion-related processing. Here, we investigated this question in an experiment simulating a highly relevant applied context in which cognitive load and emotional processing can vary independently: a clinical interview. Our participants conducted a live clinical interview via computer monitor with a confederate as an interviewee. We used eye-tracking and automatic extraction of participants’ pupil size to monitor cognitive load (single vs. dual tasks, between participants), while orthogonally varying the emotional content of the interviewee’s answers (neutral vs. negative, between participants). We ensured participants’ processing of the verbal content of the interview by asking all participants to report on the content of the interview in a subsequent memory test and by asking them to discriminate if the answers of the interviewee referred to only herself or to somebody else (too). In the dual-task condition, participants had to monitor additionally if the facial emotional expressions of the interviewee matched the content of her verbal responses. Results showed that pupil-size extraction reliably discriminated between high and low cognitive load, albeit to a lower degree under negative emotional content conditions. This was possible with an algorithmic online measure of cognitive load as well as with a conventional pupil-size measure, providing proof of the external validity of the algorithm/online measure. Full article

Over the past 30 years, China has emerged as the country with the world’s largest engineering construction industry. However, rockbursts induced by tunnel excavation in rock engineering have resulted in a substantial number of casualties and extensive property damage. Understanding the brittle failure behavior of rock masses and identifying the mechanism of rockbursts have become critical challenges in the field. Physical model tests can provide a more intuitive simulation of the rockburst process. The selection and proportioning of materials similar to brittle rocks are crucial factors for the success of these model tests. This study selected refined iron powder, barite powder, quartz sand, gypsum powder, and a rosin–alcohol solution to prepare rockburst simulation materials characterized by a low strength and high brittleness. The rockburst tendency and brittleness indices were introduced, and an orthogonal experimental design was used to establish 25 different formulation schemes. The influence of the material component proportions on the physical and mechanical properties of the specimens, as well as their brittleness characteristics, was systematically analyzed. A multiple linear regression analysis was conducted to derive linear regression equations for the physical and mechanical parameters of the brittle rock simulation materials. In addition, simulation materials and standard specimens of Jinping marble were prepared. The brittle failure modes and acoustic emission characteristics of the specimens under uniaxial compression and Brazilian splitting conditions were analyzed. The results indicate that component proportions significantly affected the physical and mechanical properties of the specimens. The refined iron powder–barite powder ratio, as well as the concentration of the rosin–alcohol solution, played a primary role in controlling the physical and mechanical parameters of the brittle rock simulation materials. Full article

The floating platform is a critical component of the floating offshore wind turbine (FOWT), and its internal structure design plays a key role in ensuring the safe operation of the FOWT. In this study, the local model of the floating platform was firstly parameterized, and a response surface model was obtained by conducting an orthogonal test. The response surface model was then optimized using a gradient descent algorithm. Finally, the internal structure arrangement was validated through a safety calibration. The optimization results indicate that the maximum stress of the optimized model is reduced by 22.12% compared to the original model, while maintaining the same mass, centroid, and other mass-related parameters. The optimization significantly improves the safety of the structure and provides valuable references for the design and construction of a FOWT platform. Full article

Straw incorporation offers significant advantages in agricultural crop cultivation systems. Mechanized methods constitute the predominant approach, potentially reducing yield costs and enhancing operational efficiency. The imperative to enhance the quality of straw chopping within the field is of particular significance, as suboptimal chopping quality can engender a cascade of issues, particularly seeding blockages. The straw chopping pass rate (CPR) is a pivotal metric for assessing the quality of straw chopping. Therefore, enhancing the CPR during the straw chopping process is necessary. This study introduces a novel maize-straw-chopping device with the ground as its supporting base. This device facilitates the rapid vertical chopping of maize straw through a constant breath cam transmission mechanism. Critical parameters were determined to optimize the performance of the chopping device by establishing mathematical models and kinematic simulation analysis methods. With the help of Rocky 2022.R2 software, the influence of the rotational velocity of the draft, tractor velocity, and blade edge angles on the CPR during the operation of the device was analyzed. The Box–Behnken test methodology was used to carry out a three-factor, three-level orthogonal rotation test to obtain the optimal working parameter combination. The results indicated that the maximum CPR value was achieved with a draft rotational velocity of 245 rpm, a tractor velocity of 3.8 km/h, and a blade edge angle of 20.75°. Finally, field validation experiments were conducted under these optimized conditions, with the average CPR of maize straw reaching an impressive 91.45%. These findings have significant implications for enhancing crop production practices. Full article

The increasing incidence of structural failures, such as cracks and collapses, in rock masses within mines, tunnels, and other civil engineering environments has attracted considerable attention among scholars in recent years. Grouting serves as a principal solution to these issues. The Renlou Coal Mine in the Anhui Province is used as a case study to evaluate the effectiveness of nanosilica (NS) as an additive in ultrafine cement (UC), introducing a novel grouting material for practical applications. This study investigates the physical and microscopic properties of a UC–ultrafine fly ash (UFA) mixed slurry containing powdered NS. Slurries of pure UC, UFA-blended UC, and UFA-blended UC with NS were prepared, and their viscosity, water precipitation rate, and compressive strength were evaluated. Scanning electron microscopy and X-ray diffraction were used for microscopic analyses. The results showed that the addition of UFA and NS to the UC slurry induced a more compact structure with reduced porosity. It was found that the viscosity and 7 d and 28 d compressive strengths of the slurry containing 50% UFA decreased by 91%, 51%, and 29.2%, respectively, and the water separation rate increased by 306.5%. The decrease in early strength was more pronounced, and the UFA content should not exceed 25%. Compared with the slurry without NS, the viscosity and 7 d and 28 d compressive strength of the slurry containing 1.5% NS increased by 216%, 51.2%, and 37%, respectively, and the water separation rate decreased by 45%. Notably, when the NS content is 1.5%, the performance of cement slurry is improved the most, and more C-S-H gel is produced. Cement consumption costs could be lowered and slurry performance improved by replacing a part of the cement with UFA and NS. Finally, orthogonal tests were conducted to select the optimal proportions for cement grouting. The optimal blend was determined to be composed of 20% UFA and 1.5% NS, with a water–cement ratio of 0.6. The study’s results not only demonstrate that NS has a good effect on improving the performance of cement-based grouting materials but also provide new insights for the design and application of grouting support in underground engineering. Full article

The key elements in the operation of modern underwater robotic systems are hydroacoustic communication and navigation systems. Hydroacoustic data transmission channels are designed in such a way that the transmitted information signals must be resistant to various types of interference and distortion, even without preliminary estimates of the channel parameters, due to their significant non-stationarity because of the roughness of the sea surface, currents, and the movement of underwater vehicles. Furthermore, due to the high mobility of underwater vehicles, the transmission time of navigation signals and necessary information packets must be significantly reduced, which can negatively affect the noise immunity of the packages. For these purposes, digital wideband signals and orthogonal frequency division multiplexing (OFDM) are widely used; however, a number of significant drawbacks of these types of modulations often do not allow for the forming of a reliable channel for transmitting information, and for the navigation of mobile underwater systems. Unfortunately, this problem is not comprehensively presented in the literature. The authors propose to use the algorithm of digital data transmission based on the OFDM constant envelope multifrequency modulation (CE-OFDM) with differential symbol coding, which is suitable for non-stationary hydroacoustic environments. The presented algorithm, due to the minimization of the signal peak factor, can improve the signal-to-noise ratio at the receiving end by 5–10 dB, with a number of other advantages, over the classical OFDM method. The authors also numerically found groups of short binary sequences from 14–55 elements long, with the best autocorrelation properties for the formation of synchronization and navigation preambles with high noise immunity to Doppler and multipath effects that are characteristic of the hydroacoustic communication channel. The proposed algorithms were tested on the certain channel models on the Watermark acoustic simulator, as well as in shallow water at distances up to 2 km. Full article

Aiming at the problem of the wheat straw and stubble of the previous crop blocking the opener during the operation of the summer peanut no-tillage seeder under straw incorporation modes, an oblique stubble-cutting and side-throwing anti-blocking device that can simultaneously cut the stubble and throw the straw was designed. The structure and working principle of the device were clarified, and the key structure of the anti-blocking device was designed through theoretical analysis. According to the kinematics analysis of the rotary blade cutting and throwing of the root–soil composite, the key factors affecting the operation quality of the device and the range of values were determined. The quadratic orthogonal rotation combination design test was carried out with the motion inclination angle, bending angle, and advancing velocity as the test factors, and the straw clearance rate, stubble-cutting rate, and operation power consumption as the indexes. The discrete element simulation test was carried out in EDEM. The significance test of the test results was carried out in Design-Expert, and the influence of each factor on the test index and the interaction between the factors were determined. Then the regression model was optimized by multi-objective function, and the optimal parameter combination was obtained as follows: The motion inclination angle was 22°, the bending angle was 58°, and the advance velocity was 7.7 km/h. At this time, the straw clearance rate of the seedling belt was 92.55%, the root stubble-cutting rate was 95%, and the operation power consumption was 1.80 kW. The field test shows that the machine had good passing capacity, the straw clearance rate of the seedling belt was 91.04%, the root stubble-cutting rate was 92.98%, and the operation power consumption of the single group of stubble cutting device was 1.92 kW. The difference between the field test results and the simulation test was less than 6%, which met the local agronomic requirements and proved that the anti-blocking device had good operation quality. Full article

The abrasives of traditional grinding wheels are usually randomly arranged on the substrate, reducing the number of effective abrasive grains involved in the machining during the grinding process. However, there are some problems such as uneven distribution of chip storage space, high grinding temperature, and easy surface burn. In trying to address this issue, an ultrasonic vibration 3D printing method is introduced to fabricate the structured CBN (Cubic Boron Nitride) grinding wheel. The effects of the fabricated process parameters, overlap rate, scanning path, and ultrasonic amplitude were analyzed. The effects of laser power, scanning speed, and powder disk rotation speed on the topography of the printing layer were analyzed by orthogonal tests. The obtained data were input into the GA-BP (Genetic Algorithm-Back Propagation) neural network for training, and the trained model was utilized to derive the optimal process parameters. Then, the experiments were carried out to optimize the overlap rate and the scanning path. The effect of ultrasonic vibration amplitude on the surface topography and the microhardness of the printing layer was observed and investigated. The structured CBN grinding wheels were fabricated using the optimal parameters, and the performance of the grinding wheels was evaluated. The workpiece surface roughness ground by the grinding wheel fabricated with ultrasonic vibration was smaller than that without ultrasonic vibration, and a better workpiece surface quality was obtained. Full article

The aim of this study is to evaluate the indoor temperature of a double-skin façades (DSF) high-rise building in Xi’an under different window opening arrangements, and to assess their impact on the operating time of the air-conditioning system. Compared to conventional buildings, double-skin façade (DSF) buildings can reduce energy consumption. While current research trends focus primarily on heat transfer and materials, there is limited exploration of window opening arrangements. To address this gap, VENT engineering software 2018 was used to simulate indoor temperatures at various window opening angles and determine the optimal arrangement. Additionally, the extreme random tree (ET) algorithm was employed to develop a model for indoor temperature prediction. Climate data were sourced from an online database and processed using the Spearman correlation coefficient method. Window opening arrangements were designed using orthogonal tests, and the performance of the DSF was evaluated with computational fluid dynamics (CFD) software (Fluent) 2023R1. An analysis of temperature variation in the double-skin façade (DSF) curtain wall revealed that the ET algorithm predicted indoor temperatures with 93% accuracy at a 50° window opening angle. Optimal window opening arrangement 2 resulted in a 2.7% reduction in the average interior temperature, a 3.6% reduction at a height of 1.2 m, and a decrease in air-conditioning runtime by 1.33 h. The extreme random tree (ET) algorithm was found to be more accurate than other methods in predicting DSF performance. These findings provide insights for optimizing the control and application of double-skin façades and suggest potential synergies with other systems. Full article

The Ethylene Diamine Tetra-acetic Acid (EDTA) titration test is widely used for determining cement content, but its reliability is influenced by the hydration process of cement, which is affected by factors such as water content and hydration time. Despite their importance, these factors have received limited attention in existing research. This study explores the relationships between the volume of titrant required for stabilization, cement content, water content, and hydration time. Using a regression orthogonal test, the primary and secondary relationships, as well as the interdependencies among these factors, are analyzed. Results reveal a negative linear relationship between the titrant volume and both water content and hydration time. Cement content, water content, and hydration time are identified as the most significant factors, with minimal interdependencies observed. Within the test parameters, calculated values exhibit an error margin below 2.4%. Deviations of 2.9% in water content and 86 min in hydration time correspond to an approximate 0.5% change in cement content. These findings offer valuable insights for optimizing cement content detection in Controlled Low-Strength Material (CLSM) mixes, promoting more sustainable construction practices. Full article

The purpose of this study was to determine the effect of selected vibratory strengthening machining factors on the properties of CuZn30 brass. Vibratory strengthening machining was carried out using metal media dedicated to polishing processes, which also contributed to strengthening the treated surfaces. The test samples were cut with an abrasive water jet and recrystallized to obtain a soft microstructure. An orthogonal, two-factor five-level plan was used for the study. The effect of vibration frequency and vibratory machining time on selected changes in parameters of the geometric structure of the surface and hardness of the surface layer was determined using Statistica software version 10 (64-bit). Higher vibration frequencies for vibratory machining increased the hardness of machined surfaces by as much as 50 HV_0.02. The arithmetic mean deviation of the height of surface irregularities from the reference plane, Sa, decreases with increasing the time of vibratory machining. A value of Sa = 0.168 µm was obtained after 87 min of consolidation, compared to an initial surface of S_a = 0.65 µm. Full article

To overcome the limitations of phase sampling points in testing aspherical surface wavefronts using traditional interferometers, we propose a high-spatial-resolution method based on multi-directional orthogonal lateral shearing interferometry. In this study, we provide a detailed description of the methodology, which includes the theoretical foundations and experimental setup, along with the results from simulations and experiments. By establishing a relational model between the multi-directional differential wavefront and differential Zernike polynomials, we demonstrate high-spatial-resolution wavefront reconstruction using multi-directional orthogonal lateral shearing interferometry. Theoretical calculations and simulations of aspherical surface wavefront testing are followed by experimental verification on an aspherical surface with a known asphericity. Comparing the measurement results with those from the LuphoScan profilometer, we achieve a relative measurement error with an RMS precision better than λ/100. Full article

The Longwangmiao Formation gas reservoir in the Moxi block of the Sichuan Basin is a complex carbonate reservoir characterized by a low porosity and permeability, strong heterogeneity, developed natural fractures, and active water bodies. The existence of natural fractures allows water bodies to easily channel along these fractures, resulting in a more complicated mechanism and dynamic law of gas-well water production, which seriously impacts reservoir development. Therefore, a core-based simulation experiment was designed for oil–water two-phase flow. Three main factors influencing the water production of the gas reservoir, namely fracture permeability, fracture penetration, and water volume multiple, were analyzed using the orthogonal test method. The experimental results showed that the influences of the experimental parameters on the recovery factor and average water production can be ranked as water volume multiple > fracture penetration > fracture permeability, with the influence of the water volume multiple being slightly greater than that of the other two parameters. It provides a certain theoretical basis for water control of the gas reservoir. Full article

This study designed and investigated a solid particle spreader, as well as parameter optimization and experimental for a groove wheel, to mitigate the problems of low uniformity and poor control accuracy of solid particulate material UAV spreading. The discrete element method was used to simulate and analyze the displacement range and stability of each grooved wheel at low speeds. Furthermore, orthogonal regression and response surface analyses were used to analyze the influence of each factor on the stability of the discharge rate and pulsation amplitude. The results showed that the helix angle, sharpness, and length of the groove significantly influenced the application performance, whereas the number of grooves had no significant influence. The groove shape was eccentric, the helix angle was 50°, the length was 35 mm, and the number of grooves was 7. Additionally, the bench test results showed that in the range of 10–60 rpm, the relative deviation of the discharging rate between the simulation and bench test is from 0.47% to 10.39%, and the average relative deviation is 3.93%. Between the groove wheel rotation speed and discharge rate, R² was 0.991, and the adjustable range of the discharge amount was between 3.68 and 23.43 g/s. The minimum and maximum variation coefficients of the average discharge rate among individual applicators were 1.01% and 2.79%, respectively, whereas the standard deviations were 0.09 and 0.46 g/s, respectively. In conclusion, the discharge stability and adjustable range of the spreader using the optimized groove wheel satisfied the requirements for solid particulate material discharge. Full article

With the continuous advancement of electromagnetic countermeasures, new types of interference signals (e.g., multi-polarization suppression interference) pose a significant threat to conventional Global Navigation Satellite System (GNSS) services, even when the receiver employs a right-handed circularly polarized (RHCP) anti-jamming array. This paper proposes a receiving signal model for orthogonal circularly polarized (OCP) interference signals based on conventional arrays, following an analysis of the non-ideal characteristics of actual arrays. Furthermore, the mechanism by which OCP interference signals affect anti-jamming performance is examined. Power inversion (PI) and linear constrained minimum variance (LCMV) techniques, applied to both uniform linear arrays and central circular arrays, are utilized to verify the impact of these interference signals. Simulation and physical testing demonstrate that OCP interference significantly affects the interference subspace of the conventional RHCP array, potentially leading to a reduction in the anti-jamming performance of the receiver. To effectively suppress multi-polarization interference, anti-jamming GNSS receivers must either ensure the consistency of cross-polarization among the elements of the array or adopt polarization-sensitive arrays. Full article