Experiment Test Research Articles

SNGNN2D-v2: A GNN-Based Model for the Generation of Human-Aware Cost Maps in Dynamic Environments

AbstractNavigating dynamic, human-populated environments is a critical challenge for mobile robots, as they must balance effective pathfinding with minimizing social disruption. Cost maps can combine information from different nature and are more interpretable than final control signals. This paper addresses the generation of real-time cost maps in human-aware navigation (HAN) by introducing SNGNN2D-v2, a graph neural network designed and trained to capture social interactions and respond to dynamic elements in human-populated environments. SNGNN2D-v2 is evaluated through three types of experiments. The first involves deploying a real robot in a controlled indoor environment and assessing the disturbance caused by the robot when driven by the model. The second experiment tests the proposed model under more complex and unfavorable conditions using simulated environments. Both experiments include a comparison with other proposals using social and navigation metrics. The third experiment compares SNGNN2D-v2 with an end-to-end CNN-based method to evaluate how models generalize across changes in the appearance of the environment and its elements. The results from these experiments suggest that SNGNN2D-v2 is an effective model for human-aware cost map generation for dynamic environments. Its ability to capture dynamic information, generalize across scenarios with different appearances, and represent social interactions could contribute to the development of human-friendly robots.

Construction of rhodamine-based fluorescent sensor for fast, on-site quantitative detection of hazardous salicylic acid in practical sample analysis

Salicylic acid (SA) is widely used in food storage, preservatives, additives, healthcare, and the pharmaceutical industry. However, various poisoning symptoms are frequently reported upon ingestion of a large amount of SA. Therefore, discovering new tools for sensing SA with fast, simple, and portable performance is imperative. Herein, five rhodamine-based fluorescent sensors were constructed, and investigated their SA detection profiles. Probe 1 was excellent selective with a rapid response, highly sensitive (LOD = 2.5 μM), good interference resistance, and unaided eye recognition. The spray experiment and paper-based test strips indicating that probe 1 enables to the on-site and quantitatively detect SA on actual food surfaces by using a smartphone identifying the RGB values. The sensing performance was validated in soil samples, water, and various agricultural food samples. Overall, the constructed SA sensor can function as a promising, convenient, and affordable tool for point-of-care detection of SA in diversiform environmental samples.

Mutual Disclosures and Content Intimacy in User Engagement: Evidence from an Online Chat Group

This paper investigates the role of self-disclosure in online chat groups (OCGs), which serve as a communication channel situated between public platforms and private live chats. Our investigation delves into the effects of mutual disclosures, originating from other members and focal users, on user engagement in terms of promptness, positivity, and effort. We also explore the disclosure content and the interplay between mutual disclosures regarding consistency in content intimacy. Using data from a retailer utilizing OCGs for customer service, our findings reveal that mutual disclosures are positively associated with user engagement through the mechanism of liking and uncover multifaceted influences from content intimacy consistency between mutual disclosures. The results are further verified by a controlled experiment and various robustness tests. Moreover, our study differentiates and discusses the roles of group hosts and peer users in facilitating OCG engagement. This research broadens our understanding of how self-related information exchange in online group conversations promotes meaningful engagement. Our fine-grained analysis of disclosure interactions provides clear guidance for firms to strategically manage customer relationships through OCGs and sheds new light on conversational commerce.

Textflows: an open science NLP evaluation approach

AbstractWeb-based platforms offer suitable experimental environments enabling the construction and reuse of natural language processing (NLP) pipelines. However, systematic evaluation of NLP tools in an open science web-based setting is still a challenge, as suitable experimental environments for the construction and reuse of NLP pipelines are still rare. This paper presents TextFlows, an open-source web-based platform, which enables user-friendly construction, sharing, execution, and reuse of NLP pipelines. It demonstrates that TextFlows can be easily used for systematic evaluation of new NLP components by integrating seven publicly available open-source part of speech (POS) taggers from popular NLP libraries, and evaluating them on six annotated corpora. The integration of new tools into TextFlows supports tools reuse, while the use of precomposed algorithm comparison and evaluation workflows supports experiment reproducibility and testing of future algorithms in the same experimental environment. Finally, to showcase the variety of evaluation possibilities offered in the TextFlows platform, the influence of various factors, such as the training corpus length and the use of pre-trained models, have been tested.

Co Modified Pr0.6Sm0.4Mn1O3 Perovskite Enhances the Non‐Radical Pathway for Efficient Removal of Rhodamine B

AbstractBecause of its excellent catalytic activity and stability, perovskite materials are widely used in advanced oxidation processes to remove refractory organic pollutants. In this study, a series of catalysts Pr0.6Sm0.4CoxMn1‐xO3 (x = 0, 0.2, 0.4, 0.5, 0.6,0.8 and 1) with limited range effect are prepared by sol–gel method with the regulation strategy of injecting active metal Co at B site in the crystal lattice of perovskite catalyst Pr0.6Sm0.4MnO3. Under the optimal conditions, the Pr0.6Sm0.4Co0.8Mn0.2O3/PMS/RhB system showed superior catalytic performance, and the removal rate of Rhodamine B (100 mg L−1) is close to 100% within 40 min. In addition, the Pr0.6Sm0.4Co0.8Mn0.2O3 catalyst has a wider pH (2‐10) tolerance range and still has outstanding catalytic properties after multiple cycle tests. The quenching experiment and EPR test confirmed that a variety of active species are produced in the system, and the singlet oxygen as the leading path of a variety of active substances assisted to promote the efficient degradation of Rhodamine B in wastewater. This study provides a new reaction system and regulatory strategy of active structural sites for the design of Fenton‐like catalytic systems based on novel perovskite oxides.

Cotransport of fullerene nanoparticles and clay colloids in porous media: The relation between aggregation and transport

In the study, cotransport of fullerene nanoparticles (nC60) and mobile clay colloids (illite (ILL), kaolinite (KL), montmorillonite (ML)) in aquifer porous media and its relation to the aggregative interaction between these two types of particles was investigated. Minimal interaction occurred between nC60 and ILL, resulting in unaffected transport. Strong heteroaggregation between ML and nC60 resulted in not only significant retention of both particles during their cotransport but also the retention of nC60 in the media pre-injected with ML. Strong homoaggregation of KL caused strong straining effect and consequently retention of both KL and nC60 during their cotransport, however, the pre-emplacement of KL did not cause retention of nC60 during the sequential injection of KL and nC60. Such aggregation behaviors were well demonstrated by the adsorption-sedimentation experiment, microscopic observation, the size and zeta-potential test, and model simulation. Based on the surface chemistry analysis, divalent-cation bridging between ML and nC60 and hydrogen bonding between KL particles were responsible for the heteroaggregation and the homoaggregation, respectively. The study demonstrated the specificity of the aggregation between the mobile clays and nC60 to the chemistry of the clays and its consequent effect on the cotransport of the particles, which is critical for assessment of the environmental risk of nC60.

Cognitive Fatigue, Humor, and Physical Activity: A Field Experiment Testing Whether Humorous Messages Promote Walking in Cognitively Fatigued Individuals

ABSTRACT Despite the success of humorous messages in various health interventions, its role in promoting physical activity (PA) remains understudied. This study addresses this gap by investigating the effectiveness of humorous messages in a 2-week smartphone-based intervention aimed at promoting walking behavior, particularly amongst cognitively fatigued individuals. Female participants (n = 57; M age = 32.00; SD = 4.385) received humorous, nonhumorous, or a mix of both messages (in the form of memes) via a study-specific application, with cognitive fatigue measured daily. Panel linear regression models revealed a significant positive interaction between cognitive fatigue and message type. Our results suggest that the resilience of humorous messages to cognitive fatigue and their potential as motivational tools position them as a more robust choice for promoting PA. Importantly, when cognitively fatigued individuals received humorous messages, their walking behaviors showed no significant change, in contrast to the detrimental impact of nonhumorous messages on exercise. Recognizing the differential effects of cognitive fatigue on message effectiveness and considering the potential of humorous messages as motivational tools offers a valuable perspective for tailoring interventions to individual states.

Improved Droop Control Strategy for Microgrids Based on Auto Disturbance Rejection Control and LSTM

This thesis proposes an improved droop control strategy design based on active disturbance rejection control and LSTM. This strategy uses the droop control method to coordinately control the distributed generation units (DGs) in a microgrid to achieve stable operation of the microgrid system. Linear-Auto Disturbance Rejection Control (LADRC) is introduced and an improved LADRC is designed based on the error principle. A disturbance compensation link is introduced on the basis of traditional LADRC to form ILADRC and a droop control strategy is used. Instead of improving the PD controller in LADRC, an improved droop control strategy is formed, which not only achieves natural decoupling between powers, but also improves the system’s immunity and transient operation capabilities. At the same time, in order to achieve adaptive parameter tuning in the improved droop control strategy, this article introduces long short-term memory (LSTM) to form an adaptive improved droop control strategy which further improves the system’s immunity and robustness. This article builds a simulation model through the MATLAB/Simulink simulation experiment platform and tests PI control and traditional droop control. The strategy and the improved droop control strategy designed in this thesis are experimentally compared and verified, and simulation analysis and verification are conducted on the two working conditions. The simulation results clearly demonstrate the superiority of the improved droop control strategy over PI control and traditional droop control, indicating that the correctness and reliability under various working conditions are verified.

Alzheimer's Disease-Derived Outer Membrane Vesicles Exacerbate Cognitive Dysfunction, Modulate the Gut Microbiome, and Increase Neuroinflammation and Amyloid-β Production.

Although our understanding of the molecular biology of Alzheimer's disease (AD) continues to improve, the etiology of the disease, particularly the involvement of gut microbiota disturbances, remains a challenge. Outer membrane vesicles (OMVs) play a key role in central nervous system diseases, but the impact of OMVs on AD progression remains unclear. In this study, we hypothesized that AD-derived OMVs (OMVsAD) were a risk factor in AD pathology. To test our hypothesis, young APP/PS1 mice (AD mice) were given OMVsAD by gavage. Young AD mice were euthanized 120days after gavage to assess the intestinal barrier, gut microbiota diversity, mediators of neuroinflammation, glial markers, amyloid burden, and short-chain fatty acid (SCFA) levels. Our results showed that OMVsAD accelerated cognitive dysfunction after 120days of intragastric administration. Morris water maze experiment and new object recognition test showed that OMVsAD caused significantly poorer spatial ability learning and memory of the AD mice. We observed the OMVsAD-treated APP/PS1 mice display OMVs disrupting the intestinal barrier compared with controls of normal human-derived OMVs. Compared with the OMVsHC group, claudin-5 and ZO-1 related to the intestinal barrier were significantly downregulated in the OMVsAD group. The OMVsAD activate microglia in the cerebral cortex and hippocampus of AD mice, and the levels of IL-1β, IL-6, TNF-α, and NF-Κb were upregulated. We also found that OMVsAD increased Aβ production. 16S rRNA sequencing showed that OMVsAD negatively regulated the α- and β-diversity index of intestinal flora and reduced the levels of SCFA. OMVsAD may change the intestinal flora of young AD, damage the intestinal mucosa and blood-brain barrier, and accelerate AD neuropathological damage.

Peridynamics simulations of the damage of reinforced concrete structures under radial blasting

Concrete is prone to damage under explosive loads, which can cause a large number of casualties and property losses. The concrete fragmentation process during explosion is transient and dynamic, and the experimental measurement of such events is difficult and risky to conduct, and the intermediate explosion process is difficult to observe in the experimental tests. Therefore, the numerical simulation is an ideal method to model and simulate the explosion process of concrete. Different from the traditional finite element method, Peridynamics (PD) method uses the spatial integral equation to replace the traditional local differential equation to solve the fragmentation problem with massive and complex discontinuous patterns. In this study, a peridynamics (PD) model is developed to simulate the failure process of reinforced concrete (RC) structures under radial blasting. Concrete PD models with different cavity sizes and reinforcement conditions were established and calibrated with the experimental data. We find that the crack growth and damage pattern obtained in the peridynamics simulation is consistent with the experiment test results, which verifies the feasibility of peridynamics method as a modeling tool for modeling concrete damage under explosive load and for evaluating anti-explosion performance of RC concrete structures.

Fabrication of Two-Dimensional Bi2MoO6 Nanosheet-Decorated Bi2MoO6/Bi4O5Br2 Type II Heterojunction and the Enhanced Photocatalytic Degradation of Antibiotics

This article successfully synthesized a series of Bi2MoO6/Bi4O5Br2 heterojunctions using a two-step solvothermal method followed by calcination, and the photocatalytic activity by degradation of tetracycline hydrochloride (TC) was investigated. Compared with pure Bi4O5Br2 and Bi2MoO6, a series of Bi2MoO6/Bi4O5Br2 heterojunctions exhibit higher photocatalytic activity, which can be attributed to the heterostructures with strong interfacial interaction, improving the charge separation. The 2% Bi2MoO6/Bi4O5Br2 heterojunction shows the best photocatalytic activity under visible light irradiation, which is 1.9 times and 1.8 times that of Bi2MoO6 and Bi4O5Br2, respectively. In addition, cyclic experiments have shown that 2% Bi2MoO6/Bi4O5Br2 heterojunction has high stability, with a degradation efficiency only decreasing by 3% after 5 cycles. From the capture agent experiment and ESR test, it can be seen that ·O2− and h+ are the main active species. A possible photocatalytic mechanism of 2% Bi2MoO6/Bi4O5Br2 heterojunction under visible light irradiation was proposed.

Cascade Model Predictive Control for Enhancing UAV Quadcopter Stability and Energy Efficiency in Wind Turbulent Mangrove Forest Environment

Unmanned aerial vehicle (UAV) modelling and control, particularly in quadrotors with high position-orientation coupling, present significant challenges for practical applications, such as environmental monitoring missions in windy mangrove forests. Conventional control strategies like the PID controller, often employed in simulations due to their simplicity, often underperform in real-world scenarios due to their linear assumptions. This research proposes a novel hierarchical cascaded model predictive control system for altitude, attitude, and battery efficiency for quadrotor in mangrove area. This control system addresses computational complexity by decomposing the overall MPC strategy into two distinct schemes, one for translational displacements and another for rotational movements, enhancing the UAV's resilience to wind turbulence, a significant disturbance factor in mangrove environments. Rigorous simulation and experiment test flight involving complex trajectory tracking and windy conditions demonstrate the proposed controller's superior performance compared to conventional PID controller, particularly in terms of stability, disturbance rejection, underscoring its potential for UAV applications in challenging environments.

Aerodynamic Performance and Numerical Validation Study of a Scaled-Down and Full-Scale Wind Turbine Models

Understanding the aerodynamic performance of scaled-down models is vital for providing crucial insights into wind energy optimization. In this study, the aerodynamic performance of a scaled-down model (12%) was investigated. This validates the findings of the unsteady aerodynamic experiment (UAE) test sequence H. UAE tests provide information on the configuration and conditions of wind tunnel testing to measure the pressure coefficient distribution on the blade surface and the aerodynamic performance of the wind turbine. The computational simulations used shear stress transport and kinetic energy (SST K-Omega) and transitional shear stress transport (SST) turbulence models, with wind speeds ranging from 5 m/s to 25 m/s for the National Renewable Energy Laboratory (NREL) Phase VI and 4 m/s to 14 m/s for the 12% scaled-down model. The aerodynamic performance of both cases was assessed at representative wind speeds of 7 m/s for low, 10 m/s for medium, and 20 m/s for high flow speeds for NREL Phase VI and 7 m/s for low, 9 m/s medium, and 12 m/s for the scaled-down model. The results of the SST K-Omega and transitional SST models were aligned with experimental test measurement data at low wind speeds. However, the SST K-Omega torque values exhibited a slight deviation. The transitional SST and SST K-Omega models yielded aerodynamic properties that were comparable to those of the 12% scaled-down model. The torque values obtained from the simulation for the full-scale NREL Phase VI and the scaled-down model were 1686.5 Nm and 0.8349 Nm, respectively. Both turbulence models reliably predicted torque and pressure coefficient values that were consistent with the experimental data, considering specific flow regimes. The pressure coefficient was maximum at the leading edge of the wind turbine blade on the windward side and minimum on the leeward side. For the 12% scaled-down model, the flow simulation results bordering the low-pressure region of the blade varied slightly.

The Evolution of Social Anxiety: Tests of Two Theories

Social anxiety, the psychological state of showing fear and avoidance in social situations, remains prevalent in modern society. The research in this article is based on the theoretical background of social threat, which states that people in group life need social anxiety to avoid potential threats that may affect social status or accessible social resources. The prediction of the article is that Social Rank Theory and Social Bonds Theory can be successfully tested, with one relating to social hierarchies in which people maintain their social status by avoiding conflict and maintaining a positive image through social anxiety, while the other states that social anxiety can help maintain existing social bonds. The experiment tests whether the loss of social status and social bonds produces social anxiety. By setting up scenarios and collecting data about participants’ individual levels of social anxiety, it will eventually be possible to conclude how the potential threats present in the different scenarios affect people’s anxiety levels, and whether the possible experimental results can test the two theories.

Simulation and experimental analysis of traveling wave resonance of flexible spiral bevel gear system

Considering the traveling wave resonance (TWR) phenomenon of the spiral bevel gear system in the aero engine accessory casing, the flexible spiral bevel gear model is established by three-dimensional (3D) shell element and beam element. The dynamic model of flexible bevel gear system considering the change of meshing teeth pairs in the operating process is established by component mode synthesis (CMS) method and rotational modal projection method. The proposed model is verified by finite element (FE) solid model and experiment test results. On this basis, the TWR phenomenon of the bevel gear system is studied in combination with dynamic response and vibration stress experimental test. The results show that the bevel gear system has 3 nodal diameter resonance speeds within the actual operating speed range, which are one 1st nodal diameter resonance of pinion and two 1st nodal diameter resonance of gear. When the bevel gear system operates at TWR state, the amplitude corresponding to fm ± m·fr (fm is meshing frequency, m is nodal diameter number, fr is shaft rotational frequency) is larger than that corresponding to fm in the Fast Fourier transform (FFT) spectrum of the of the gear foundation vibration stress, and the vibration stress cloud map of the gear foundation shows the corresponding nodal diameter vibration shape. The research results provide a theoretical basis for feature recognition and influence law evaluation of TWR of bevel gear system.

Enhanced Plant Growth Through Composite Inoculation of Phosphate-Solubilizing Bacteria: Insights from Plate and Soil Experiments

Excessive application of phosphorus (P) fertilizers does not alleviate P deficiency in soils and may cause water eutrophication. The available P in acidic soils is bound to minerals, such as iron and aluminum, in forms that are difficult to utilize by plants. The low availability of P is detrimental to soil health and crop growth. To address the P imbalance in the soil, different bioremediation techniques, such as phosphate-solubilizing bacteria (PSB) application, have been employed. However, the systematic analysis of the effects of composite inoculation of PSB on crops remains elusive. In this study, the effects of composite-inoculated PSB on plant growth were systematically evaluated by two scales: plate experiment and soil test. This study employed six different strains of PSB including Lelliottia amnigena 1-1 (A), Kluyvera intermedia 1-2 (B), Pseudomonas tolaasii 1-6 (C), Burkholderia cepacia 2-5 (D), Pseudomonas frederiksbergensis 2-11 (E), and Pseudomonas rhodesiae 2-47 (F). Among the 57 different combinations of these strains, four combinations (AE, AF, ADF, and AEF) indicated higher phosphate-solubilizing abilities than the single strains. These combinations were used for subsequent experiments. The plate experiment revealed that composite strains were more effective than single strains in promoting the growth and development of seedlings and roots of oilseed rape. Furthermore, AE, AF, and AEF combinations indicated excellent growth-promoting effects. Moreover, the soil test revealed that the composite inoculation of AE and AEF significantly enhanced biomass accumulation and root development in oilseed rape. The increased growth-promoting effects of the composite strains were observed to be associated with to their phosphate-solubilizing capacities. Both scales confirmed that compared to single inoculation, composite inoculation of PSB is more beneficial for plant growth. This study provides composite inoculation materials and foundational data to support the bioremediation of P imbalance in soil.

Chiral FeNC single-atom nanozymes with multi-enzyme activity for dye degradation

The application of single-atom nanozymes in the removal of organic dye pollution by advanced oxidation process (AOPs) have been widely concerned. However, the application of single-atom nanozymes in AOPs is rarely reported. In this work, a kind of Fe-and nitrogen-codoped carbon (Fe-N-C) with peroxidase-like and laccase-like activities was prepared by calcining Fe-doped MOF, then the chiral peptides were introduced into single-atom nanozymes, and chiral single-atom nanozymes (L-Au@FeNC) were successfully prepared. The L-Au@FeNC can effectively activate PMS to degrade different kinds of organic dyes and also shows high cycle stability. In addition, the results of quenching experiment and electron paramagnetic resonance (EPR) test show that 1O2 produced during PMS activation plays an important role in the degradation of organic dyes, and O2·-, ·OH, and SO4·- are also produced during PMS activation, suggesting that the degradation of selected organic dyes include radical and non-radical pathways. It should be noted that L-Au@FeNC showed higher activity than D-Au@FeNC in enzyme-like activity (laccase-like and peroxidase-like) experiment and organic dye degradation, the results of molecular docking simulation indicated that it may be due to the better binding force of L peptide to the substrate of enzyme-like reaction and organic dye than D peptide. This chiral single-atom nanozymes provide a new idea for the application of organic dye degradation and enzyme-like catalysis design.

From experimentation to scaling: what shapes the funnel of AI adoption?

ABSTRACT Firms tend to manage the diffusion of complex and uncertain technologies through a ‘funnel', whereby firms first experiment (test and learn), then decide to exploit and scale technology. We study how internal and external factors typically affecting Artificial Intelligence (AI) adoption influence the successive steps of the funnel for a sample of large firms worldwide. We demonstrate that competition influences AI adoption more at the exploitation than at the experimentation phase. Conversely, technology complements are more relevant at the start of the funnel, in contrast to organizational complements which are most relevant to ensure embedding of AI technologies in business practices.

The carbon crater: Comparing anthropogenic greenhouse gas emissions to historical planetary events

Equilibrium climate sensitivity modeling relies heavily on paleoclimate records that were affected by meteorite impacts and volcanic explosions. This paper conducts a thought experiment by re-assembling known data and theories to shed new light on anthropogenic carbon waste. Anthropogenic activity, meteorite impacts and volcanic explosions all extract material from the Earth’s crust and deposit it in the atmosphere. This thought experiment tests if the mass of anthropogenic greenhouse gas emissions from 1851 to 2021 is comparable to the mass of atmospheric emissions from historical planetary events. Approximately 3.60 trillion tons of anthropogenic carbon dioxide equivalents are converted into volume and then transformed into the shape of a meteorite impact structure named the “Carbon Crater.” The 35 km crater (bounded by 34%–68% confidence intervals of 25–45 km) would rank 23rd on the list of known impact structures. The 2.6 km projectile required to create the Crater would be a 10 on the 1–10 Torino hazard scale described as “. . .capable of causing global climatic catastrophe. . .” The estimated re-occurrence interval for a projectile of this size is 5.3 million years. An interval of this time in Earth’s recent history predates homo sapiens. The Crater’s volume is exponentially larger than the 1883 eruption of Krakatoa and ranks as an 8 (“mega-colossal”) on the 0–8 Volcanic Explosivity Index. The thought experiment indicates that the Carbon Crater’s scale is comparable with large historical biospheric events. These results likely confer few direct implications for the study of the paleoclimate in climate modeling but might change conceptual understandings of atmospheric human waste. Additional empirical research is required to understand the potential impact of the Carbon Crater on conceptual change.

A Quantitative Study of Axial Performance of Rockbolts with an Elastic–Debonding Model

Full-length anchorage rockbolts are widely used in roadway reinforcement and rock controlling in underground mining. This article proposes using an elastic–debonding (ED) model to analyse the axial performance of rockbolts. The advantage of this ED model was that the full force–deformation curve of rockbolts comprised only three phases, which was relatively simpler to calculate. Its effectiveness was compared with experiment tests. Based on the ED model, a series of parameter studies was conducted. Results showed that for cross-section area of rock, there was a critical range. Once the cross-section area of rock was beyond that critical range, external rock had a mild impact on the axial performance of rockbolts. Rockbolt diameter significantly affected the axial performance of rockbolts. When rock diameter increased, the peak force of rockbolts increased linearly, while deformation at the peak force decreased non-linearly. The corresponding calculation equation between the peak force, deformation at the peak force, and rockbolt diameter was obtained. Borehole diameter had a mild impact on the axial performance of rockbolts. Increasing rockbolt length benefits improving the peak force of rockbolts. Rockbolt modulus of elasticity had a more apparent impact on the deformation at peak force. Mechanical properties of the bolt/grout (b/g) face affected the axial performance of rockbolts. Increasing the b/g face strength improved the peak force of rockbolts. Slippage at the ultimate load had a more apparent impact on the turning point between the elastic phase and the elastic–softening phase.