Two-stage Experiment Research Articles

Fusing YOLOv5s-MediaPipe-HRV to classify engagement in E-learning: From the perspective of external observations and internal factors

The rapid advancements in computer vision technology present significant potential for the automatic recognition of learner engagement in E-learning. We conducted a two-stage experiment to assess learner engagement based on behavioural (external observations) and physiological (internal factors) cues. Using computer vision technology and wearable sensors, we extracted three feature sets: action, head posture and heart rate variability (HRV). Subsequently, we integrated our constructed YOLOv5s–MediaPipe behaviour detection model with a physiological detection model based on HRV to comprehensively evaluate learners’ behavioural, affective and cognitive engagement. Additionally, we developed a method and criteria for assessing distraction based on behaviour, ultimately creating a comprehensive, efficient, low-cost and easy-to-use system for the automatic recognition of learner engagement. Experimental results showed that our improved YOLOv5s model achieved a mean average precision of 92.2 %, while halving both the number of parameters and model size. Unlike other deep learning-based methods, using MediaPipe–OpenCV for head posture analysis offers advantages in real-time performance, making it lightweight and easy to deploy. Our proposed long short-term memory classifier, based on sensitive HRV metrics and their normalisation, demonstrated satisfactory performance on the test set, with an accuracy = 80 %, precision = 81 %, recall = 80 % and an F1 score = 80 %.

LinkedOut? A Field Experiment on Discrimination in Job Network Formation

Abstract We assess the impact of discrimination on Black individuals’ job networks across the U.S. using a two-stage field experiment with 400+ fictitious LinkedIn profiles. In the first stage, we vary race via AI-generated images only and find that Black profiles’ connection requests are 13 percent less likely to be accepted. Based on users’ CVs, we find widespread discrimination across social groups. In the second stage, we exogenously endow Black and White profiles with the same networks and ask connected users for career advice. We find no evidence of direct discrimination in information provision. However, when taking into account differences in the composition and size of networks, Black profiles receive substantially fewer replies. Our findings suggest that gatekeeping is a key driver of Black-White disparities.

Key Factors for Improving Predictive Accuracy and Avoiding Overparameterization of the PBPK Absorption Model in Food Effect Studies of Weakly Basic Water-Insoluble Compounds in Immediate Release Formulations.

Background/Objectives: Physiologically based pharmacokinetic (PBPK) absorption models are instrumental for assessing drug absorption prior to clinical food effect studies, though discrepancies in predictive and actual outcomes are observed. This study focused on immediate release formulations of weakly basic water-insoluble compounds, namely rivaroxaban, ticagrelor, and PB-201, to investigate factors that could improve the predictive accuracy of PBPK models regarding food effects. Methods: Comprehensive in vitro experimental results provided the basis for the development of mechanistic absorption models, which were then combined with mechanistic disposition models to predict the systemic exposure of the model drugs in both fasted and fed states. Results: The developed PBPK models showed moderate to high predictive accuracy for food effects in Caucasian populations. For the Chinese population, the ticagrelor model's initial overestimation of fed-state absorption was addressed by updating the permeability parameters from Caco-2 cell assays to those derived from parallel artificial membrane permeability assays in FaSSIF and FeSSIF media. This refinement was also applied to the rivaroxaban and ticagrelor models, leading to a more accurate representation of absorption in Caucasians. Conclusions: This study highlights the importance of apparent permeability in enhancing the predictive accuracy of PBPK absorption models for weakly basic water-insoluble compounds. Furthermore, the precipitation of PB-201 in the two-stage transfer experiments suggests that precipitation may not be a universal phenomenon for such compounds in vivo. Consequently, the precipitation rate constant, a theoretically essential parameter, should be determined based on experimental evidence to avoid overparameterization and ensure robust predictive accuracy of PBPK models.

Feasibility study of electrodialysis as an ammonium reuse process for covering the nitrogen demand of an industrial wastewater treatment plant

Electrodialysis (ED) is a cost-effective membrane technology used is a variety of fields for desalination and concentration. This feasibility study explores the potential of ED as an NH4-N recovery technology from anaerobic digestate liquor (ADL), and the use of the concentrate as a nitrogen source in an industrial wastewater treatment plant (WWTP). Three neighboring WWTPs were the focus of this study: Two municipal WWTPs A and B, operating anaerobic sludge stabilization, and a pulp & paper WWTP C, utilizing urea as a nitrogen source. Two-stage bench-scale experiments with the municipal ADL from WWTP A and WWTP B were conducted, and performance indicators were determined. A concentration of approximately 10 g NH4-N/L and 15 g NH4-N/L was obtained in stages 1 and 2, respectively. The NH4-N removal was above 85 % in all experiment, while recovery varied between 25 and 95 %. The specific energy consumption (SEC) was on average 12.9 kWh/kg NH4-N. Moreover, mass and energy balances in a model WWTP demonstrated that an ED side-stream treatment for NH4-N removal coupled with microfiltration (MF) pre-treatment results in a net energy gain, also without the added benefit of the ED concentrate as a nitrogen source.

Investigation of creep damage accumulation under variable loading conditions in nickel-based single crystal superalloys

Nickel-based single crystal (SX) turbine blades typically experience varying load conditions during operation. It is essential to consider the effects of changing stress and temperature when evaluating creep damage. The commonly used time-fraction method, based on the linear damage rule (LDR), has been demonstrated to be inconsistent with experimental results under certain loading conditions. There is a lack of research on damage accumulation under variable loading conditions specifically for SX superalloy. This paper conducted two-stage creep experiments for SX superalloy DD6 at 980 °C with stress levels of 230 MPa and 320 MPa, and at 1050 °C with stress levels of 135 MPa and 230 MPa. The load for the experiment was set based on the typical operating conditions of the SX turbine blades. The evolution of the microstructure under variable loading was observed using scanning electron microscope (SEM) and transmission electron microscope (TEM). The result of creep experiments revealed that the damage accumulation behavior of the SX superalloy does not conform to the LDR. Furthermore, in two-stage loading tests, the creep damage accumulation behavior differs from the classical sequence effect of fatigue loading. SEM and TEM analyses suggested that this phenomenon might be associated with the varying degradation rates of microstructures in SX superalloy.

Impact of Lactobacillus acidophilus and Its Combination with Isoflavone Products on Calcium Status, Calcium Transporters, and Bone Metabolism Biomarkers in a Post-Menopausal Osteoporotic Rat Model.

Osteoporosis in menopausal women requires alternatives to current medications, considering their adverse effects. In this context, probiotics and isoflavone products are promising dietary interventions. The objective of our study was to examine the impacts of Lactobacillus acidophilus and its combination with daidzein and tempeh on calcium status, calcium transporters, and bone metabolism biomarkers in a post-menopausal osteoporotic rat model. A total of 48 female Wistar rats were exposed to a two-stage experiment involving calcium deficit induction and subsequent dietary interventions across six groups. Calcium levels, the gene expression of TRPV5 and TRPV6 calcium transporters, bone histopathology, serum bone metabolism markers, and blood biochemistry were evaluated. The results revealed that, while decreasing serum calcium levels, the groups that received the probiotic L. acidophilus and isoflavone combination exhibited increased bone metabolism biomarkers and decreased calcium transporter expressions, akin to the effects of bisphosphonate. Additionally, significant improvements in bone histopathology were observed in these groups. However, the group receiving probiotic L. acidophilus alone did not exhibit significant changes in bone resorption biomarkers, calcium transporter expression, or various blood parameters. Meanwhile, the combination of probiotic L. acidophilus with tempeh positively influenced hematological parameters and reduced cholesterol and triglyceride levels, but it led to elevated blood glucose levels. Correlation analyses highlighted associations between serum calcium levels, calcium transporter expression, and bone metabolism biomarkers. In conclusion, our findings suggest that the daily consumption of probiotic L. acidophilus in combination with isoflavone products may improve bone health in ovariectomized rats, warranting further research to elucidate potential interactions with other nutrients.

Study of the Role of Nitrogen in the Oxidation of Titanium-Based Alloys by Changing the Reaction Gas

AbstractThe role of nitrogen in the oxidation of Ti-2W, Ti-10Al-2W (at.%) and Ti6242S was investigated using experiments in air and in Ar-20%O2, and two-stage experiments where the reaction gas was switched from one mixture to the other. When switching from Ar-20%O2 to air, the oxidation rates first increased during a short period, then decreased. This surge of mass gain following the introduction of air was attributed to N pickup, forming a nitride layer and a N-enriched zone in the alloy, below the oxide layer. The subsequent decrease of oxidation rate was attributed to the formation of nitride and/or N-rich zone, which both act as diffusion barriers for oxygen. Switching from air to Ar-20%O2 caused an increase in the oxidation rate of the W-containing alloys, which was attributed to the consumption of this barrier. The gas change had no significant effect on the oxidation rate of Ti6242S, which formed a much thinner nitride layer in air. The faster the nitride layer grows, the faster it is consumed when removing N from the reaction gas, probably because of a higher diffusion rate of N in W-doped TiO2 compared to TiO2 formed on Ti6242S.

New mathematical model from dynamic dissolution rate tests

In vitro dissolution experiments are becoming increasingly complex attempting to replicate in vivo behavior. The objective of these new methods is to explore the behavior of low-solubility drugs. This is more relevant for drugs classified in subclasses 2a, 2b and 2c of the BCS, considering their pH-dependent solubility and dissolution characteristics.A novel mathematical approach using a modified double Weibull equation is proposed to model the dissolution and precipitation kinetics observed in two-stage and transfer dissolution experiments (dumping test). This approach demonstrates a high level of accuracy in fitting experimental data for two drugs BCS class 2a and two BCS class 2b, providing valuable insights into their dissolution behavior under different conditions.The results highlight the versatility of the proposed model in capturing complex dissolution phenomena, including rapid dissolution, precipitation, and redissolution. The ease of implementation in Excel, using the Solver tool, makes it a practical and accessible tool for pharmaceutical researchers.Overall, the study contributes to the development of more effective in vitro dissolution testing methods, facilitating the formulation and optimization of pharmaceutical products and potentially aiding in the establishment of in vitro-in vivo correlations (IVIVC).

Main focus of parents of children with attention deficit hyperactivity disorder and the effectiveness of early clinical screening.

Attention deficit hyperactivity disorder (ADHD) is a common mental and behavioral disorder among children. To explore the focus of attention deficit hyperactivity disorder parents and the effectiveness of early clinical screening. This study found that the main directions of parents seeking medical help were short attention time for children under 7 years old (16.6%) and poor academic performance for children over 7 years old (12.1%). We employed a two-stage experiment to diagnose ADHD. Among the 5683 children evaluated from 2018 to 2021, 360 met the DSM-5 criteria. Those diagnosed with ADHD underwent assessments for letter, number, and figure attention. Following the exclusion of ADHD-H diagnoses, the detection rate rose to 96.0%, with 310 out of 323 cases identified. This study yielded insights into the primary concerns of parents regarding their children's symptoms and validated the efficacy of a straightforward diagnostic test, offering valuable guidance for directing ADHD treatment, facilitating early detection, and enabling timely intervention. Our research delved into the predominant worries of parents across various age groups. Furthermore, we showcased the precision of the simple exclusion experiment in discerning between ADHD-I and ADHD-C in children. Our study will help diagnose and guide future treatment directions for ADHD.

Is Virtual Reality an Effective Experimental Tool for Window View Studies with Dynamic Content Involved?

ABSTRACT Dynamic content is a desirable quality in window views. However, most researchers have focused on static window scenes, which are inconsistent with real-world window views. The scarcity of studies involving dynamic view content is exacerbated by the lack of suitable evaluation tools, which this study aims to address. A novel method of displaying dynamic content in the virtual scene was presented. A two-stage experiment with forty-eight subjects was designed to compare subjective responses to a dynamic window scene in physical and virtual environments. Virtual reality’s effectiveness was assessed based on the consistency of their responses regarding level of satisfaction with the window view in both environments. Imaging capability, sense of presence, and sense of comfort were also adopted as evaluation criteria in the virtual environment. Responses concerning satisfaction with different view contents in the physical and virtual environments were found to have no statistically significant difference and they also achieved statistical equivalence. It was also established that the novel method used to display dynamic window scenes could retain the clarity of content and attain good scene integration. The virtual environment offered a sense of presence, although some subjects still paid attention to the physical environment. In relation to sense of comfort, most subjects found the headset’s weight to be bearable and it did not compromise the performance of tasks in the virtual environment. However, visual fatigue was identified as a notable drawback which should be addressed to improve the comfort of subjects and accuracy of results. This study affirms virtual reality’s viability as a convenient and effective tool for evaluating dynamic window views.

Analysis of consumer preferences for new electric vehicle technologies: Can future vehicle steering system steer consumer's purchase intention?

As the mainstream of vehicle industry is moving from internal combustion engine vehicles to electric vehicles (EVs), a multi-perspective analysis of consumer preference for the new EV technology is required. Therefore, this study proposes a new framework for consumer preference analysis—a two-stage choice experiment—and conducts an empirical analysis of the four-wheel independent steering system (4-WISS). In the first stage, we analyzed consumer preference for the availability of 4-WISS in EVs. In the second stage, we investigated consumer preference for the specific technology of 4-WISS in EVs. Stated preference data were collected through a choice experiment survey, and a mixed logit model was used to quantitatively analyze consumer preference and willingness-to-pay. Results show that consumers are willing to pay KRW 19,045,098.6 (USD 13,513.9) to use 4-WISS in high-end EVs. Furthermore, consumers who are female, older, and have more knowledge of autonomous vehicles prefer 4-WISS more. We found that consumers prefer the parallel movement among 4-WISS modes, the touch display for selecting 4-WISS, the steering wheel for operating 4-WISS mode, and dashboard for displaying information. We finally discuss the new business model in the vehicle industry and suggest automakers to establish an effective strategy for the initial market for EVs with 4-WISS.

Stage–discharge prediction in the multi-stage ice-covered compound channel

The multi-stage compound channel, which is a common pattern in natural alluvial rivers and the regulation projects of urban rivers, inevitably freezes in winter when it is situated in cold northern areas with high latitudes. Given that ascertaining the stage–discharge relationship for rivers is the foundation for the development of flood control schemes and water resources management, this study concentrates on proposing an analytical model for predicting the stage–discharge curves of multi-stage ice-covered compound channels. In deducing the analytical model, the cross section of the channel is first segmented into several homogeneous subregions that can be grouped into seven categories according to the geometric characteristics. Through analyzing the momentum transfer between adjacent subregions, the force balance equation for each subregion is then established to get the bulk mean velocity for the corresponding subregion, thereby obtaining the discharge by solving a tridiagonal matrix. Subsequently, measurements from two-stage and three-stage ice-covered compound channel experiments and three sets of experimental data from the literature are used to validate the performance of the proposed model. Good agreement between the predictions and the measured data suggests that the deduced model can accurately estimate the discharge for the multi-stage ice-covered compound channels when the flow depth is given. Finally, sensitivity analysis indicates that Manning's roughness coefficient of the channel bed has a more pronounced impact on the stage–discharge relationship than that of the ice cover. Moreover, when compared to the two-stage ice-covered compound channel, the multi-stage ice-covered compound channel offers greater potential for water resource utilization.

Police compliance with the social contract as an antecedent of police legitimacy, of satisfaction with the police, and of willingness to obey: findings from a two-stage vignette experiment

Abstract Objectives Test the effects of police compliance with the restrictions on their authority embedded in Social Contract Theory (SCT) on police legitimacy, satisfaction with the police, and willingness to obey police officers. Methods A two-stage vignette experiment. In the first, 1356 participants were randomly assigned to one of four study conditions: control, procedural justice (PJ), police performance (PP), and compliance with the social contract (SC). In the follow-up stage, 660 participants were randomly assigned to either a control or proportionality/least restrictive alternative (PL) condition. Results Compared to the control condition, the SC manipulation improved evaluations of all three dependent variables. For legitimacy, its effect was no different than that of PJ and PP. For satisfaction, it was similar to that of PP and stronger than the effect of PJ. For willingness to obey, it was no different than the effect of PJ, but stronger than that of PP. The second stage of the experiment revealed that compared to the control condition, the two unique components of the SC model (PL) significantly improved the scores of all three DVs. Conclusions Police adherence to the SC, and particularly to its two unique components, is an important determinant of police legitimacy and other outcomes, and should thus be acknowledged by researchers and practitioners. Future research is encouraged to disentangle the relative effects of the “building blocks” making up PJ, PP, and compliance with the SC.

Competition mode and soil nutrient status shape the role of soil microbes in the diversity-invasibility relationship.

Understanding the relationship between plant diversity and invasibility is essential in invasion ecology. Species-rich communities are hypothesized to be more resistant to invasions than species-poor communities. However, while soil microorganisms play a crucial role in regulating this diversity-invasibility relationship, the effects of plant competition mode and soil nutrient status on their role remain unclear. To address this, we conducted a two-stage greenhouse experiment. Soils were first conditioned by growing nine native species separately in them for 1 year, then mixed in various configurations with soils conditioned using one, three, or six species, respectively. Next, we inoculated the mixed soil into sterilized substrate soil and planted the alien species Rhus typhina and native species Ailanthus altissima as test plants. We set up two competition modes (intraspecific and interspecific) and two nutrient levels (fertilization using slow-release fertilizer and nonfertilization). Under intraspecific competition, regardless of fertilization, the biomass of the alien species was higher in soil conditioned by six native species. By contrast, under interspecific competition, the biomass increased without fertilization but remained stable with fertilization in soil conditioned by six native species. Analysis of soil microbes suggests that pathogens and symbiotic fungi in diverse plant communities influenced R. typhina growth, which varied with competition mode and nutrient status. Our findings suggest that the soil microbiome is pivotal in mediating the diversity-invasibility relationship, and this influence varies according to competition mode and nutrient status.

Selective separation of lithium from the hydrochloric acid leachate of lithium ores via the extraction system containing TBP-FeCl3

The elevation of comprehensive lithium recovery remains a formidable challenge in lithium extraction from lithium bearing ores due to the equilibrium solubility constraints affecting the lithium precipitation reaction. Hence, this work drew inspirations from lithium extraction techniques in salt lakes by characterizing the hydrochloric acid leachate of lithium ores as a distinct brine. The leachate composition was regulated and solvent extraction technology for selective lithium extraction was developed. By employing the loaded organic phase with Fe3+ (2TBP-NaFeCl4) to extract the leachate, and utilizing a four-stage countercurrent extraction process, the extraction efficiency of lithium could be achieved at 99 % at least. Following three-stage scrubbing and two-stage countercurrent stripping experiments, the stabilized stripping efficiency of lithium was 99.24 %. The concentration of Li+ in the stripping solution was enriched up to 16.404 g/L, while the total concentration of impurity ions was only 0.424 g/L. The resulting lithium-enriched solution could be utilized to prepare high-purity lithium chloride. This process has achieved a highly selective and efficient extraction of lithium, thereby enhancing the overall lithium extraction efficiency. The Density Functional Theory results indicate that the loaded organic phase selectively extracted lithium through ion exchange.

Public Reactions to Communication of Uncertainty: How Long-Term Benefits Can Outweigh Short-Term Costs

Abstract Uncertainty is a fact of political life but not a fact of political communication. Elites are prone to make confident predictions and downplay uncertainty about future outcomes, presumably fearing that the acknowledgement of uncertainty would undermine public confidence in their predictions and the evidence they are based on. But this calculation might both exaggerate the costs and downplay the potential benefits of reporting uncertainty. On costs, the evidence from previous studies is mixed; on benefits, previous research has neglected the possibility that, by acknowledging that outcomes may be worse than expected, those communicating uncertainty will dampen public reactions to the bad news. Here, based on a two-stage online survey experiment (N = 2,165) from December 2020 about COVID-19 vaccines, we find results suggesting that governments are well advised to communicate uncertainty. The costs at Stage 1 were low: reporting a confidence interval around the safety and effectiveness of a hypothetical COVID-19 vaccine did not undermine belief in the statistics or intentions to take the vaccine. And there were indeed benefits at Stage 2: when outcomes turned out to be worse than expected but within that confidence interval, confidence in the vaccine was partly insulated from negative effects.

The compensation effect of competence frustration and its behavioral manifestations.

The frustration of competence, one of the three basic psychological needs proposed by self-determination theory, has been widely demonstrated to negatively influence one's motivation and well-being in both work and life. However, research on the recovery mechanism of competence is still in the nascent stage. In this study, a two-stage behavioral experiment was conducted to examine the restoration of competence and the potential moderating role of resilience. Results showed that individuals who were asked to recall experience of competence frustration performed better on subsequent tasks, manifesting their behavioral efforts of competence restoration. However, resilience does not play a significant moderating role in competence restoration. Through convergent behavioral evidence, findings of this study demonstrate the compensation effect of competence frustration.

Coupled effect of prestrain and intermediate annealing on mechanical properties and microstructural evolution of GH5188 superalloy

The forming of sheet metal parts with complex structures often requires multiple processing. The Co-based superalloy GH5188 sheet is taken as the research object for two-stage uniaxial tensile experiments including intermediate heat treatment, where the prestrain is 10%, 20% and 30%, respectively, in the first stage. The results indicate that the macroscopic residual stress increases with increasing prestrain, which is manifested as the increase of the initial yield strength, the deterioration of ductility and work hardening ability. The increase in dislocation density in the plastic deformation process is the decisive factor. After annealing, the number of deformed grains greatly reduces, and the grain size is refined, resulting in a corresponding reduction in dislocation density. Intermediate heat treatment can eliminate dislocation stacking and stress concentration in the alloy and reduce the influence of internal stress generated during work hardening. Furthermore, the intermediate annealing can decrease the initial yield stress and increase the elongation of the predeformed sheet, while retaining desirable work hardening ability and tensile strength, ultimately enhancing the subsequent work performance.

Vacuum ammonia stripping from liquid digestate: Effects of pH, alkalinity, temperature, negative pressure and process optimization

High ammonia-nitrogen digestate has become a key bottleneck limiting the anaerobic digestion of organic solid waste. Vacuum ammonia stripping can simultaneously remove and recover ammonia nitrogen, which has attracted a lot of attention in recent years. To investigate the parameter effects on the efficiency and mass transfer, five combination conditions (53 °C 15 kPa, 60 °C 20 kPa, 65 °C 25 kPa, 72 °C 35 kPa, and 81 °C 50 kPa) were conducted for ammonia stripping of sludge digestate. The results showed that 80% of ammonia nitrogen was stripped in 45 min for all experimental groups, but the ammonia transfer coefficient varied under different conditions, which increased with the rising of boiling point temperature, and reached the maximum value (39.0 mm/hr) at 81 °C 50 kPa. The ammonia nitrogen removal efficiency was more than 80% for 30 min vacuum stripping after adjusting the initial pH to above 9.5, and adjustment of the initial alkalinity also affects the pH value of liquid digestate. It was found that pH and alkalinity are the key factors influencing the ammonia nitrogen dissociation and removal efficiency, while temperature and vacuum mainly affect the ammonia nitrogen mass transfer and removal velocity. In terms of the mechanism of vacuum ammonia stripping, it underwent alkalinity destruction, pH enhancement, ammonia nitrogen dissociation, and free ammonia removal. In this study, two-stage experiments of alkalinity destruction and ammonia removal were also carried out, which showed that the two-stage configuration was beneficial for ammonia removal. It provides a theoretical basis and practical technology for the vacuum ammonia stripping from liquid digestate of organic solid waste.

The role of consciousness in Chinese nominal metaphor processing: a psychophysical approach

Abstract Conceptual metaphor theory (CMT) holds that most conceptual metaphors are processed unconsciously. However, whether multiple words can be integrated into a holistic metaphoric sentence without consciousness remains controversial in cognitive science and psychology. This study aims to investigate the role of consciousness in processing Chinese nominal metaphoric sentences ‘A是B’ (A is[like] B) with a psychophysical experimental paradigm referred to as breaking continuous flash suppression (b-CFS). We manipulated sentence types (metaphoric, literal and anomalous) and word forms (upright, inverted) in a two-staged experiment (CFS and non-CFS). No difference was found in the breakthrough times among all three types of sentences in the CFS stage, while literal sentences were detected more slowly than either metaphoric or anomalous sentences in the non-CFS stage. The results suggest that the integration of multiple words may not succeed without the participation of consciousness, let alone metaphoric processing. These findings may redefine ‘unconscious’ in CMT as ‘preconscious’ and support the indirect access view regarding how the metaphoric meaning is processed in the brain.