Adjacent Waves Research Articles

Bidirectional association between clustering of health-related behaviours and depression in mid- and older-aged adults: A longitudinal study in China and Japan.

To disentangle the direction between health-related behaviours (HRBs) and depression in East Asia, we examined the bidirectional longitudinal relationship of HRBs clustering and depression in Chinese and Japanese ageing populations gender-specifically. Data were drawn from the China Health and Retirement Longitudinal Study (CHARLS) (N = 18,739) (2011-2015) and the Japan Study of Ageing and Retirement (JSTAR) (N = 7116) (2007-2011). Cross-lagged panel models (CLPM) were applied to assess bidirectional longitudinal relationships between HRB clustering and depression in adjacent waves, stratified by cohort and gender. Sensitivity analyses were conducted to explore key risk factors in risky clusters. The prevalence of baseline depression was approximately 20 % in China and 4 % in Japan, with over 70 % of participants belonging to the risky cluster. A unidirectional negative association between the risky cluster and depression was observed only in Chinese females (βstandardized = -0.039, 95%CI: -0.054 to -0.024, P < 0.001). However, no association was found in Japanese females or males in either country. Further sensitivity analyses revealed that this association was primarily driven by overweight/obesity cluster. Sensitivity analyses also identified a positive effect of depression on the smoking and drinking cluster and a negative effect on the overweight/obesity cluster in Chinese females. This study was limited by reliance on self-report data, the CES-D cannot be used to diagnose depression and some other confounding factors were not considered (e.g., use of antidepressants). Our findings highlight a unidirectional negative association of the risky cluster on depression in Chinese females, with notable variations observed across different countries and genders.

Prediction of simultaneous enhancement of Goos-Hänchen shift and reflectance in VO2 grating structure

Vanadium dioxide (VO2) material stands out in the family of the phase change materials due to its temperature-dependent phase transition properties, which make it a promising candidate for the temperature-dependent optoelectronic devices. Enhancement of the Goos-Hänchen (GH) shift is essential in VO2-based nanostructures for their applications, but it has been limited to the multilayered structures with VO2 materials so far. Here, we theoretically investigate the GH shift and corresponding reflectance in the VO2-based grating structure. We evidence that this structure has two GH peaks (3107λ and 2266λ) and high reflectance values (both up to 1) when VO2 is in the insulating phase as well as the maximum GH valley (−1061λ) and low reflectance (0.19) when VO2 is in the metallic phase. The electromagnetic field distributions in this hybrid structure suggest that the guided mode resonances (GMRs) can be excited no matter whether VO2 is in its insulating or metallic phases due to the couplings between the incident waves and the adjacent evanescent diffracted order waves, which produces their enhanced GH shifts. Different from the former case with the high reflectances and the large GH shifts, the latter has the low maximum magnetic field intensity due to the lossy property of the metallic VO2, which leads to the low reflectance and small GH valley value. Additionally, we have also found that by the alterations of the temperature-dependent conductivity of VO2 and the geometric parameters of the structure allows for the control the magnitude and position of the GH peak or valley. The simultaneously enhanced GH shifts and reflectances in the VO2-based grating structure, associated with its controllable features, enable it an effective configuration for establishing the temperature sensors and optoelectronic switches.

Factors associated with transitions in tobacco product use states among young adults aged 18-29 years.

This study examined young adults' tobacco use transitions based on their past 30-day use states, and identified factors associated with their transitions. Participants (N = 12377) were young adults aged 18-29 years at Wave 1 of the Population Assessment of Tobacco and Health (PATH) study. Self-reported tobacco use states were categorized by the number of past-month use days (0, 1-4, 5-8, 9-12, 13-30 days) for cigarettes, electronic cigarettes [e-cigarettes], traditional cigars, filtered cigars, cigarillos, smokeless tobacco (SLT), and hookah. Multistate Markov models examined transitions between use states across Waves 1-5 of unweighted PATH data and multinomial logistic regressions examined predictors of transitions. Most young adults remained nonusers across adjacent waves for all products (88%-99%). Collapsed across waves, transitioning from use at any level to nonuse (average 46%-67%) was more common than transitioning from nonuse to use at any level (average 4%-10%). Several factors that predicted riskier patterns of use (i.e., transitioning to use and/or remaining a user across adjacent waves) were similar across most products: male, Black, Hispanic, lower education levels, and lower harm perceptions. In contrast, other factors predicted riskier patterns for only select products (e.g., e-cigarette and SLT use among Whites). Few sampled young adults escalated their tobacco use over time, and escalations for many products were predicted by similar factors. Prevention and regulatory efforts targeted towards adolescents should continue, but also be expanded into young adulthood. These same efforts should consider both shared and unique factors that influence use transitions.

Trigger waves in an oscillator loop and their applications in voltage‐controlled oscillation with high tuning gain

SummaryTrigger waves, propagating in a loop of a one‐dimensional lattice of tunnel‐diode (TD) oscillators, can be effectively applied to voltage‐controlled oscillation with high tuning gain. The lattice under investigation can generate both phase and trigger waves by varying the bias voltage to the TD. We demonstrate a voltage‐controlled oscillator (VCO) achieving high tuning gain through the utilization of rotating trigger waves. As the loop size decreases, the trigger wave becomes bound to itself or to adjacent waves. At this point, the excitation motion of the individual lattice cell is constrained by the global interaction caused by the trigger wave(s), leading to coherent behavior. Consequently, the bifurcation curve of the trigger wave seamlessly connects to that of the phase wave with changes in the TD bias voltage. Owing to the trigger wave's property of significantly increasing velocity with the TD bias voltage, a VCO with very high tuning gain can be developed, leveraging the seamless dependence of the oscillation frequency on the TD bias voltage.

Understanding individual differences in computational thinking development of primary school students: A three‐wave longitudinal study

AbstractBackgroundComputational thinking (CT) has emerged as a critical component of 21st‐century skills, and increasing effort was seen in exploring the development of CT skills in K–12 students. Despite cumulative research on exploring students' CT acquisition and its influencing factors, learners' development of the skill over time and the underlying mechanism that contributes to individual differences remain unclear.ObjectiveTo bridge this gap, the present study aimed to explore the individual differences in CT acquisition among primary school students and how these differences were shaped over time. Specifically, variations in the development of CT across demographics, including gender and learning experience, were explored.MethodThree waves of data were collected from a sample of 322 primary school students (aged 7–12) across 18 months, with a 9‐month interval between adjacent waves. A time‐lagged model was leveraged for data analysis, and control variables were included in the model to strengthen statistical robustness.Results and ConclusionThe results indicate that male students and those who were more experienced in coding tended to have more positive attitudes toward coding. Additionally, coding interest was found to mediate the relationship between demographics and CT, demonstrating that male students and more experienced learners tended to be more interested in coding, which, in turn, contributed to the development of CT skills in later stages.ConclusionThe study provides valuable insights into the mechanisms underlying individual differences in CT development over time. The findings highlight the importance of nurturing coding interest among female students and promoting coding exposure for novice learners.

Numerical study on detonation initiation by multiple hot spots

Detonation initiation is important not only for the development of advanced detonation engines and but also for the control of accidental explosion. There are mainly two types of detonation initiation, i.e., direct initiation and indirect initiation. This work focuses on direct detonation initiation which has a short initiation distance but requires large amount of energy deposition. Specially, we investigate the reduction in the critical initiation energy through replacing the single hot spot by multiple hot spots. The transient detonation initiation process in a stoichiometric H2/O2/Ar mixture is examined through two-dimensional simulations considering detailed chemistry. It is found that under the same initiation energy, detonation initiation fails for a single large hot spot while successful detonation initiation can be achieved by employing six small hot spots. The collisions among adjacent transverse detonation waves induce new local explosions, which play a pivotal role in detonation initiation. To further assess the impact of wave collision, we change the hot spot energy used in the multiple hot spot configuration. For relatively low initiation energy, the blast wave quickly decays and decouples with the reaction zone. Consequently, the collision among transverse shock waves cannot induce new local explosion and detonation initiation fails. Increasing the initiation energy can enhance the blast wave and is favorable to the formation of local explosion, facilitating the rapid detonation initiation. Furthermore, the influence of hot spot number on detonation initiation is assessed. Interestingly the hot spot number is found to have non-monotonic effect on detonation initiation. Splitting a single hot spot into multiple hot spots enhances detonation initiation since the wave collision helps to induce local explosion. However, as the hot spot number increases, the energy of each hot spot is decreased and becomes excessively dispersed, which results in relatively weak blast wave and thereby weak wave interaction. Consequently, local explosion cannot be triggered and detonation initiation fails for relatively large hot spot numbers. This study provides insights on promoting detonation initiation through multiple hot spots.

Уголковые подпорные стены с вертикальными консолями в виде оболочек и складок

The subject of the study is reinforced concrete corner retaining walls, widely used in hydraulic engineering construction. Optimization of the shape of the vertical console of corner retaining walls is important to reduce internal forces and increase the stability of structures. When replacing flat panels with spatial structures in the console, bending moments are reduced; the predominant work of structures for compression or stretching allows reducing their thickness due to more efficient use of materials. The purpose of the study is to determine the optimal shape and nature of reinforcement of vertical retaining wall consoles, depending on their height. The study was conducted in the certified software package “LIRA-CAD2021”. Computational models of corner retaining walls with consoles in the form of multi-wave cylindrical shells and folds have been developed. At the junctions of the waves and the edges of the folds, racks are provided, pinched in the ground. Comparative calculations of structures in the software package “LIRA-CAD2021” were performed. The results of calculations are analyzed. Conclusions are drawn on the optimization of the structures of retaining walls with a vertical console in the form of shells and folds. The study showed that with a retaining wall height of up to 3 m, a retaining wall with a console in the form of a multi-wave shell is more rational in terms of material consumption. At a height of more than 3 m, retaining walls with a console in the form of folds with vertical posts at the interface of the faces become rational. For consoles in the form of shells, double reinforcement is recommended with an increase in the area of the reinforcement in the lower part and at the interface areas of adjacent waves. For consoles in the form of folds, double reinforcement is also recommended, but additional reinforcement is required only in the area of the interface of the panels with the foundation plate.

Investigations of the Atomization Characteristics and Mechanisms of Liquid Jets in Supersonic Crossflow

In the combustion chamber of scramjets, fuel jets interact with supersonic airflow in the form of a liquid jet in crossflow (LJIC). It is difficult to achieve adequate jet–crossflow mixing and the efficient combustion of fuel in an instant. Large eddy simulation (LES), the coupled level-set and volume of fluid (CLSVOF) method, and an adaptive mesh refinement (AMR) framework are used to simulate supersonic LJICs in this article. This way, LJIC atomization characteristics and mechanisms can be further explored and analyzed in detail. It is found that the surface waves of the liquid column exist in a two-dimensional form, including vertical and spanwise directions. Column breakup occurs when all the spanwise surface waves between adjacent vertical surface waves break up. Bow shock waves, composed of multiple connected arcuate shock waves, are dynamic and will change with the evolution of the liquid column. The vortex ring movement of supersonic LJICs, whose trends in the vertical and spanwise directions are different, is relatively complex, which is due to the complex and time-dependent shape of liquid columns.

Experimental investigation of the evolution and energy transmission of a type-a internal solitary wave packet over a gentle slope

Laboratory experiments were conducted to investigate the evolution characteristics of a type-a ISW packet propagating over a gentle slope. The elevation type-a ISW packet was generated by the gravity collapse of stratified density fluid, and its transformation process over the gentle slope was measured by use of the multichannel conductivity-probe arrays. The energy transmission and loss of the ISW packets during its evolution over the gentle slope were further analyzed. The experimental results showed that the evolution and energy transmission of the type-a ISW packet over the gentle slope is closely related to the amplitude of the leading wave in the wave packet. The conversion of the wave packet type is caused by the variations in amplitudes of the leading and tailing waves in the type-a ISW packet due to the topography effect. The distance between the adjacent waves in a type-a ISW packet gradually increases with the increasing propagation distance on the slope, as well as its increase rate is also enlarged. The wave speeds of both the leading and tailing waves always decrease with the propagation distance. The energy loss of the whole ISW packet increases with both the incident wave amplitude and the propagation distance.

Evolution of turbulent liquid films on the corrugated plate—rivulets and slender water columns necking rupture

The evolution of turbulent liquid film on the corrugated plate is experimentally studied with the help of ultrasonic Doppler velocimetry and a high-speed camera, revealing the formation mechanism of rivulets and water columns necking rupture. The results show that the flow pattern of the liquid film on the corrugated plate is divided into three regions: stable region, fluctuating region, and oscillating region. In the fluctuating region, the connection between adjacent solitary waves leads to the generation of primary rivulets. In contrast, the formation of secondary rivulets mainly comes from the extinction of solitary waves. In the oscillating region, the collision between secondary rivulets promotes the formation of slender water columns. The necking diameter of the water column tended to decrease exponentially with time. The increase in Rel (liquid phase Reynolds number) promotes the necking rupture process of the water column due to the presence of corrugated structures. When Rel increased from 1.72 × 104 to 2.57 × 104, the characteristic time of necking rupture was shortened by about 25.7%.

A unified model for large-scale thickness measurement of lubricating film based on ultrasonic lag phase slope

A unified model based on the ultrasonic lag phase slope is developed for measuring the lubricating film thickness at a large scale. The ultrasonic lag phase of adjacent waves instead of the phase of overlapped waves is calculated as a function of the ultrasonic frequency and film thickness. The slope of the ultrasonic lag phase is determined correspondingly, which is linearly proportional to the lubricating film thickness. Both the finite element analysis and tests on the lubricating film thickness are performed to verify the proposed method. The results show that despite the fluctuations of the lag phase, the lag phase slope can be used for measuring the lubricating film thickness at a large scale from 0.1 μm to 170 μm.

Influence of Aerodynamic Interaction on Performance of Contrarotating Propeller/Wing System

This paper gives a quantitative account of the influence of slipstream on the aerodynamic performance of a contrarotating propeller (CRP)/wing system, and compares it with the CRP and clean wing. To accurately evaluate the complex aerodynamic interaction, the unsteady Reynolds-averaged Navier–Stokes approach using the sliding mesh method is performed at a typical freestream velocity of 30 m/s. Four different critical parameters, including the freestream angle of attack (AoA), axial spacing between the front propeller (FP) and rear propeller (RP), number of blades, and rotational speed, are considered in the present work. The results show that the thrust coefficient, power coefficient, and propulsion efficiency of the CRP/wing system change sharply and the difference in amplitude between adjacent waves is large. In particular, the propeller slipstream has a significant impact on the lift–drag performance of the wing in the case of a nonzero AoA. The presence of a wing also increases the efficiency of propulsion due to the recovery of vortices. In the case of a small axial spacing, the thrust coefficient value of the FP is significantly smaller than that of the RP. However, when the axial spacing exceeds a certain value, the opposite relationship is obtained. When the rotational speed increases from 3695 RPM to 8867 RPM, the lift coefficient and drag coefficient of the wing gradually increase.

Reciprocal associations between peer victimization and depressive symptoms among Chinese children and adolescents: Between- and within-person effects.

Peer victimization is detrimental to child mental health. Research has indicated a reciprocal relationship between peer victimization and mental health problems. Yet limited evidence was from children and adolescents in China. The present study used the random intercepts cross-lagged panel model (RI-CLPM) to examine both between-person and within-person associations between peer victimization and depressive symptoms among Chinese children and adolescents. Participants were 1205 Chinese students (Mage = 11.27 years; ranged from 9 to 15 years; SD = 1.75; 55% boys) who completed four surveys (Time 1 to Time 4) between 2017 and 2019 on demographics, peer victimization, and depressive symptoms. At the between-person level, peer victimization was positively associated with depressive symptoms. Controlling for between-person effects, RI-CLPM suggested positive within-person effects from peer victimization to depressive symptoms across adjacent waves. The model also suggested a positive within-person effect from Time 2 depressive symptoms to Time 3 peer victimization. The multi-group analysis showed that these effects did not differ by gender, age, or subjective socioeconomic status. Peer victimization and depression appear to be reciprocally related at the transitioning period between late childhood and early adolescence in Chinese students. Mental health interventions should attend to peer victimization for children and adolescents in China.

Multi-wave tabu search for the boolean quadratic programming problem with generalized upper bound constraints

The boolean quadratic programming problem with generalized upper bound constraints (BQP-GUB) is an NP-hard problem with many practical applications. In this study, we propose an effective multi-wave tabu search algorithm for solving BQP-GUB. The algorithm performs a sequence of search waves, where each wave alternates between the forward and reverse phases, and the transition between two adjacent waves depends on a hybrid perturbation phase. The forward phase employs tabu search to reach a critical solution and the reverse phase follows to reverse previously performed moves and perform an equal number of moves by referring to the search information gathered from the latest search process. The hybrid perturbation phase randomly chooses a directed strategy, a frequency guided strategy and a recency guided strategy to achieve search diversification. Experimental results on 78 standard instances indicate that the proposed algorithm is able to improve the lower bounds for 6 instances and match the best solutions in the literature for most instances within competitive time.

0–5 Hz deterministic 3-D ground motion simulations for the 2014 La Habra, California, Earthquake

SUMMARYWe have simulated 0–5 Hz deterministic wave propagation for a suite of 17 models of the 2014 Mw 5.1 La Habra, CA, earthquake with the Southern California Earthquake Center Community Velocity Model Version S4.26-M01 using a finite-fault source. Strong motion data at 259 sites within a 148 km × 140 km area are used to validate our simulations. Our simulations quantify the effects of statistical distributions of small-scale crustal heterogeneities (SSHs), frequency-dependent attenuation Q(f), surface topography and near-surface low-velocity material (via a 1-D approximation) on the resulting ground motion synthetics. The shear wave quality factor QS(f) is parametrized as QS, 0 and QS, 0fγ for frequencies less than and higher than 1 Hz, respectively. We find the most favourable fit to data for models using ratios of QS, 0 to shear wave velocity VS of 0.075–1.0 and γ values less than 0.6, with the best-fitting amplitude drop-off for the higher frequencies obtained for γ values of 0.2–0.4. Models including topography and a realistic near-surface weathering layer tend to increase peak velocities at mountain peaks and ridges, with a corresponding decrease behind the peaks and ridges in the direction of wave propagation. We find a clear negative correlation between the effects on peak ground velocity amplification and duration lengthening, suggesting that topography redistributes seismic energy from the large-amplitude first arrivals to the adjacent coda waves. A weathering layer with realistic near-surface low velocities is found to enhance the amplification at mountain peaks and ridges, and may partly explain the underprediction of the effects of topography on ground motions found in models. Our models including topography tend to improve the fit to data, as compared to models with a flat free surface, while our distributions of SSHs with constraints from borehole data fail to significantly improve the fit. Accuracy of the velocity model, particularly the near-surface low velocities, as well as the source description, controls the resolution with which the anelastic attenuation can be determined. Our results demonstrate that it is feasible to use fully deterministic physics-based simulations to estimate ground motions for seismic hazard analysis up to 5 Hz. Here, the effects of, and trade-offs with, near-surface low-velocity material, topography, SSHs and Q(f) become increasingly important as frequencies increase towards 5 Hz, and should be included in the calculations. Future improvement in community velocity models, wider access to computational resources, more efficient numerical codes and guidance from this study are bound to further constrain the ground motion models, leading to more accurate seismic hazard analysis.

Stability and Change in Asexuality: Relationship Between Sexual/Romantic Attraction and Sexual Desire

ABSTRACT This study examined the stability and change in asexuality in terms of sexual orientation identity, sexual/romantic attraction, and sexual desire. Data were collected in three waves at 12-month intervals (n = 168). In each wave, the participants completed measures of sexual/romantic orientation identity, sexual/romantic attraction, the Sexual Desire Inventory, and the Asexuality Identification Scale (AIS). Approximately 83% of asexual and gray-asexual individuals maintained their sexual orientation identity between two adjacent waves. The latent growth models indicated an increased tendency for sexual/romantic attraction and solitary sexual desire, while a decreased tendency for AIS over time was established. Only the sexual attraction slope significantly predicted asexual identity, indicating a longitudinal effect of sexual attraction on asexual identification. Initial levels of sexual attraction, and scores on the AIS and dyadic sexual desire (DSD) were associated with stability and changes in asexual identity. Asexual individuals who reported low sexual attraction, low DSD, and high AIS maintained their asexual identity, whereas those who reported high sexual attraction, high DSD, and low AIS were more likely to change their sexual orientation. The current findings indicate the relative stability of asexuality, which supports the notion that asexuality could be deemed a fourth sexual orientation.

Failure mechanism of unequal parameters metal bellows under repeated bending process

The metal bellows used for flexible connection of oxygen lance in metallurgical converter compensate the displacement of pipeline by its bending deformation. Due to the waveform structure, the adjacent waves at the fixed end of the metal bellows are squeezed together, leading to premature fracture. In order to explore the influence of waveform structure parameters on the failure mechanism of the metal bellows, a U-shaped metal bellows with different waveform structure parameters was designed in this paper. The ultimate repeated bending process of the metal bellows was numerically simulated by ABAQUS finite element software. The influence law of waveform structure parameters on equivalent stress, equivalent strain and ultimate bending angular displacement of the metal bellows were obtained. Then, the repeated bending fatigue life of the bellows was tested on the fatigue testing machine, and the influence law of the waveform structure parameters on the fatigue life of the bellows under ultimate bending angular displacement amplitudes was obtained. The experimental results verify the accuracy of the finite element simulation. Finally, X-ray diffraction peaks confirmed the proved that the plasticity accumulation at the wave trough of the equal parameters metal bellows (EPMB) is large, so the hardness value is large. The micro morphology of the fracture and the surrounding area was analyzed by scanning electron microscope (SEM), and the crack propagation and the ultimate repeated bending failure mechanism of the bellows with different waveform structures was revealed. The initial cracks appear in the inner and outer surfaces of the wave trough, distribute along the circumferential direction, and propagate from the inner and outer surfaces to the central layer. Among them, the fracture morphology of the EPMB is mainly composed of fatigue fracture and plastic fracture. However, the fracture morphology of the unequal parameters metal bellows (Un-EPMB) is dominated by fatigue fracture. The results show that the fatigue life and bending fracture resistance of metal bellows can be improved by designing waveform structure with unequal parameters.

Controls on Gas Emission Distribution on the Continental Slope of the Western Black Sea

The continental slopes of the Black Sea show abundant manifestations of gas seepage in water depth of &amp;lt;720 m, but underlying controls are still not fully understood. Here, we investigate gas seepage along the Bulgarian and Romanian Black Sea margin using acoustic multibeam water column, bathymetry, backscatter, and sub-bottom profiler data to determine linkages between sub-seafloor structures, seafloor gas seeps, and gas discharge into the water column. More than 10,000 seepage sites over an area of ∼3,000 km2were identified. The maximum water depth of gas seepage is controlled by the onset of the structure I gas hydrate stability zone in ∼720 m depth. However, gas seepage is not randomly distributed elsewhere. We classify three factors controlling on gas seepage locations into depositional, erosional, and tectonic factors. Depositional factors are associated with regionally occurring sediment waves forming focusing effects and mass-transport deposits (MTDs) with limited sediment drape. Elongated seafloor depressions linked to faulting and gas seepage develop at the base between adjacent sediment waves. The elongated depressions become progressively wider and deeper toward shallow water depths and culminate in some locations into clusters of pockmarks. MTDs cover larger regions and level out paleo-topography. Their surface morphology results in fault-like deformation patterns of the sediment drape on top of the MTDs that is locally utilized for gas migration. Erosional factors are seen along channels and canyons as well as slope failures, where gas discharge occurs along head-scarps and ridges. Sediment that was removed by slope failures cover larger regions down-slope. Those regions are devoid of gas seepage either by forming impermeable barriers to gas migration or by removal of the formerly gas-rich sediments. Deep-rooted tectonic control on gas migration is seen in the eastern study region with wide-spread normal faulting promoting gas migration. Overall, gas seepage is widespread along the margin. Gas migration appears more vigorous in shallow waters below ∼160 m water depth, but the number of flare sites is not necessarily an indicator of the total volume of gas released.

An Effective Method for Distinguishing Sleep Apnea and Hypopnea Based on ECG Signals

Good sleep quality is essential to our life and work. The two major challenges in evaluating sleep quality are the scoring of sleep stages and sleep apnea detection. In addition to sleep apnea, hypopnea is also a respiratory event that occurs at an equal or even higher frequency compared to that of apnea. However, the two phenomena are not only different in terms of physical manifestation, there are also significant differences in the methods and means of clinical treatment. Therefore, in this study we propose an effective algorithm to distinguish between hypopnea and apnea events. We consider two aspects of feature extraction. On the one hand, from the original time-domain waveform of electrocardiogram signals, we extract the time difference sequence between the appearance of the R-R wave in two adjacent QRS waves (RR intervals) and explore the way they change when apnea and hypopnea event occur. On the other hand, considering that the degree of sequence disorder caused by hypopnea and apnea events is different, multi-scale entropy and complexity are chosen as the features that describe this change. The results obtained using the proposed algorithm show that the classification between hypopnea events and any type of apnea events all reach an accuracy rate greater than 90%. For obstructive apnea events, which occur most frequently among the three different types of apneas, the classification accuracy, sensitivity, specificity and F1-score were 91.78%, 92.21%, 91.30%, 92.20%, respectively. The classification results between central apnea events and hypopnea events reached an accuracy of 93.18%, sensitivity of 95.00%, specificity of 91.67% and F1-score of 92.68%. At the same time, the algorithm achieved an accuracy of 92.59%, sensitivity of 90.38%, specificity of 94.64% and F1-score of 92.16% when classifying mixed apnea and hypopnea events. In the classification of normal breathing, hypopnea events and apnea events, the total accuracy rate achieved was 91.92%, with that for normal breathing reaching 93.62%, for hypopnea events reaching 90.39%, and 91.91% for apnea events, with a Kappa coefficient of 0.99. The algorithm proposed in this study constitutes an efficient and convenient approach for apnea and hypopnea event detection and classification.

Flow and Force for Plate Undergoing Stopping Motion in Supersonic Flow

Linear and nonlinear models have been studied in the past for supersonic starting flow due to forward step motion of an airfoil where the airfoil gains an angle of attack. This Paper considers the inverse problem, supersonic stopping flow due to backward step motion of a flat plate, where the plate initially having an angle of attack reduces its angle of attack to a smaller one. The wave structures and their time evolution are clarified numerically, and a theory is built to predict the pressure along the airfoil, various wave speeds and indicial force. It is found that shock and rarefaction waves are produced to replace or complement the initial flow structure and the interaction between two adjacent new waves produces secondary waves with dimple-shape pressure profile. The indicial force first drops from the initial value to a smaller one and then evolves following a three-stage behavior. The force increases or decreases during the first stage where the secondary waves are upstream of the trailing edge, drops monotonically during the second stage where the secondary waves are leaving the trailing edge, and reaches its final steady state value after the secondary waves have left the trailing edge.