Average Parameters Research Articles

Practical exponential stability and applications of switched homogeneous nonlinear systems with external inputs and impulses

The practical exponential stability of switched homogeneous nonlinear systems (SHNS) with external inputs and impulses is studied in this paper, which includes two types of continuous-time systems and discrete-time systems. Specifically, we add a kind of nonnegative impulses which is consistent with the switching behaviours for the systems. We first study switched homogeneous positive nonlinear systems (SHPNS) case, then we extend the SHPNS to a time-varying SHNS case. The primary difficulty of this research is the estimation of Lyapunov function value at switching-impulse points under the coupling effects of synchronous switches and state jumps. By employing the max-separable Lyapunov function approach, we present new sufficient stability criteria and design new switching-impulse signals, and successfully establish the new relation between the average dwell time parameter and impulse strength. Then, we apply the obtained results to the time-varying vehicle formation model with impulses. At last, four examples are given to demonstrate the feasibility of our results, which includes the specific algorithm verification process.

Average Star Formation Parameters in the Local Volume of the Universe

Average Star Formation Parameters in the Local Volume of the Universe

Relating Pore‐Scale Observations to Continuum‐Scale Models: Impact of Ganglion Dynamics on Flow Transport Kinetics

AbstractContinuum‐scale models used to model and predict two‐phase flow in the subsurface are often based on averaged flow parameters and do not consider pore‐scale fluid flow phenomena, for example, ganglion dynamics and thin‐film flow. As such, a major challenge in upscaling two‐phase flow for groundwater engineering applications is understanding the impact of disconnected flow and ganglion dynamics on continuum‐scale flow functions such as relative permeability‐saturation and capillary pressure‐saturation curves. In this study, we explored how changes in wettability and fluid velocity affect ganglion dynamics. We conducted pore‐scale numerical simulations with OpenFOAM to investigate the displacement of decane by water. Additionally, we examined how displaced phase saturation (a continuum‐scale flow function) responds to changes in dynamic fluid connectivity. We identified three different fluid flow regimes, that is, the connected pathway flow regime, ganglion dynamics (GD) flow regime, and droplet traffic flow regime, and studied the effects of changes in the wettability of the porous medium and the velocity of the invading fluid on the transitions between these different regimes. Our research showed that transitions between connected and disconnected pore‐scale flow regimes, which are induced by changes in fluid velocity and wettability, have a significant impact on both fluid displacement efficiency and average fluid flow transport kinetics.

Normal cardiac dimensions by magnetic resonance imaging and topographic anatomy of the adult arabian one-humped camel (Camelus dromedarius)

BackgroundDromedaries’ normal heart architecture and size have not been adequately examined utilizing magnetic resonance imaging (MRI) and topographic anatomy.Resultwe aimed to investigate the regular appearance of the heart and its dimensions, using MRI and cross-sectional anatomy, in mature Arabian one-humped camels (Camelus dromedarius). We also analyzed hematological and cardiac biochemical markers. MRI scans were conducted on twelve camel heart cadavers using a closed 1.5-Tesla magnet with fast spin echo (FSE) weighted sequences. Subsequently, the hearts were cross-sectionally sliced. Additionally, hematobiochemical studies were conducted on ten mature live camels. The study analyzed standard cardiac dimensions including HL, BW, RA, LA, RV, LV, IVS, LAD, RAD, RVD, AoD, TCVD, and MVD. The results showed a strong positive correlation between the cardiac dimensions obtained from both gross analysis and MR images, with no significant difference between them. On both gross and MRI images, the usual structures of the heart were identified and labeled. Along with the cardiac markers (creatine kinase and troponin), the average hematological values and standard biochemical parameters were also described.ConclusionAccording to what we know, this investigation demonstrates, for the first time the typical heart structures and dimensions of the heart in dromedaries, and it could serve as a basis for diagnosing cardiac disorders in these animals.

Explainable Reverse Verification of Goodness of Classification of MRI Images by Clinical Experts.

Radiology offers a presumptive diagnosis. The etiology of radiological errors are prevalent, recurrent, and multi-factorial. The pseudo-diagnostic conclusions can arise from varying factors such as, poor technique, failures of visual perception, lack of knowledge, and misjudgments. This retrospective and interpretive errors can influence and alter the Ground Truth (GT) of Magnetic Resonance (MR) imaging which in turn result in faulty class labeling. Wrong class labels can lead to erroneous training and illogical classification outcomes for Computer Aided Diagnosis (CAD) systems. This work aims at verifying and authenticating the accuracy and exactness of the GT of biomedical datasets which are extensively used in binary classification frameworks. Generally such datasets are labeled by only one radiologist. Our article adheres a hypothetical approach to generate few faulty iterations. An iteration here considers simulation of faulty radiologist's perspective in MR image labeling. To achieve this, we try to simulate radiologists who are subjected to human error while taking decision regarding the class labels. In this context, we swap the class labels randomly and force them to be faulty. The experiments are carried out on some iterations (with varying number of brain images) randomly created from the brain MR datasets. The experiments are carried out on two benchmark datasets DS-75 and DS-160 collected from Harvard Medical School website and one larger input pool of self-collected dataset NITR-DHH. To validate our work, average classification parameter values of faulty iterations are compared with that of original dataset. It is presumed that, the presented approach provides a potential solution to verify the genuineness and reliability of the GT of the MR datasets. This approach can be utilized as a standard technique to validate the correctness of any biomedical dataset.

Влияние износа инструмента в процессе физического моделирования шевингования-прикатывания цилиндрических зубчатых колес на параметр шероховатости

The main issues related to the results of an experimental study aimed at modeling of the combined (cutting-deforming) finishing process of a gear processing, i.e. cylindrical gear shaving and rolling, under turning with a special combined cutting-deforming tool, which is a single-tip tool of a cylindrical work, divided into equal working areas. Due to the proprietary exploratory procedure used for prototype process, in one operation of a compact cylindrical work, a gear processing of a sufficiently large batch of horisontal wheels-representatives with average parameters, consisting of several thousand pieces, is simulated on a CNC lathe. The analysis of the results of the experiment was treated, allowing us to obtain information about gear processing of a large batch of gears in laboratory conditions. The roughness parameter of the work on workpiece areas is determined, the boundaries of tool degradation for this parameter are revealed. The revealed pattern of tool degradation appears to be the following: the prevailing wear of the tool occurs along the back surface due to its design feature, i.e. zero angle of its back, aggravated by the technological characteristics of the process (shaving - rolling), in which the back is involved in the surface plastic deformation, in particular, crushing a metal layer under the influence of a significant normal load. This results in frictional load taking place between its back surface and the surface of the proccesed workpiece. Tool degradation along the front surface, accompanied by its tool cutter blunting of its cutting edge, contributes to further deterioration of cutting process conditions (when stock removal of about 0.02 mm), and at the same time increases the proportion of surface plastic deformation (when shaving– rolling). This, as a result, increases the workpiece material share, which should be removed not by cutting, but by surface plastic deformation, thereby further redoubling a wear bit in its back surface.

Investigation of the energetic and exergetic performance of hybrid rotary desiccant-vapor compression cooling systems using different refrigerants

In this study, a desiccant-based hybrid cooling system supported by a vapor compression system and a heat recovery unit (rotary heat wheel) was analyzed from energetic and exergetic perspectives during the daily working hours of an office building in Istanbul to meet the desired comfort conditions. We focus on the impact of different refrigerants; namely R32, R1234yf, R290, R134a, R600a, R245fa, and R717, on hybrid rotary desiccant-vapor compression systems. While the highest electricity consumption was obtained in the system using R1234yf, the lowest electricity consumption was achieved with R717. However, with the effectiveness of the desiccant wheel, the best results were obtained for R1234yf with those pertinent to R717 at the other extreme. Considering the total electricity consumption of the system, the highest energetic and exergetic performance parameters were achieved with the use of R717 as the refrigerant. Compared to R1234yf, the daily average energetic performance parameters obtained with R717 increased by 22.3 % for COPr, 21.8 % for COPel, and 4.7 % for COPth. Similarly, compared to R1234yf, the daily average exergetic performance parameters in R717 presented increases of 13.6 % for COPx,el, 7.5 % for COPx,th, and 8.1 % for ηx.

A novel coordinate transformation stability criterion and parameter selection for grid-connected inverter

The negative resistance of grid-connected inverter (GCI) and the increasing number of GCI in power grid pose great challenges to the stability of GCI. This paper proposes a coordinate transformation stability criterion (CTSC) based on the single-input single-output (SISO) impedance model for GCI system. A low complexity fractional polynomial model of GCI is derived by the Pade approximation and the SISO impedance model in the αβ domain. CTSC is proposed by applying the Nyquist stability criterion, which simplifies the graph trajectory criterion to a numerical criterion. Since the effect of parameter on stability is usually limited to the neighborhood, average parameter assessment metric (APAM) is proposed based on CTSC to evaluate the impact of each parameter over a wide range. Additionally, joint parameter assessment metric (JPAM) is proposed to simultaneously adjust multiple parameters on stability. Finally, compared with the three criteria for conservatism analysis, CTSC possesses the lowest conservatism. The theory proposed in this paper is verified by experiment.

A novel adjusted real-time decision-making for dynamic distribution in the grocery supply chain

PurposeThe current research has developed a novel method to update the decisions regarding real-time data, named the dynamic adjusted real-time decision-making (DARDEM), for updating the decisions of a grocery supply chain that avoids both frequent modifications of decisions and apathy. The DARDEM method is an integration of unsupervised machine learning and mathematical modeling. This study aims to propose a dynamic proposed a dynamic distribution structure and developed a bi-objective mixed-integer linear program to make distribution decisions along with supplier selection in the supply chain.Design/methodology/approachThe constantly changing environment of the grocery supply chains shows the necessity for dynamic distribution systems. In addition, new disruptive technologies of Industry 4.0, such as the Internet of Things, provide real-time data availability. Under such conditions, updating decisions has a crucial impact on the continued success of the supply chains. Optimization models have traditionally relied on estimated average input parameters, making it challenging to incorporate real-time data into their framework.FindingsThe proposed dynamic distribution and DARDEM method are studied in an e-grocery supply chain to minimize the total cost and complexity of the supply chain simultaneously. The proposed dynamic structure outperforms traditional distribution structures in a grocery supply chain, particularly when there is higher demand dispersion. The study showed that the DARDEM solution, the online solution, achieved an average difference of 1.54% compared to the offline solution, the optimal solution obtained in the presence of complete information. Moreover, the proposed method reduced the number of changes in downstream and upstream decisions by 30.32% and 40%, respectively, compared to the shortsighted approach.Originality/valueIntroducing a dynamic distribution structure in the supply chain that can effectively manage the challenges posed by real-time demand data, providing a balance between distribution stability and flexibility. The research develops a bi-objective mixed-integer linear program to make distribution decisions and supplier selections in the supply chain simultaneously. This model helps minimize the total cost and complexity of the e-grocery supply chain, providing valuable insights into decision-making processes. Developing a novel method to determine the status of the supply chain and online decision-making in the supply chain based on real-time data, enhancing the adaptability of the system to changing conditions. Implementing and analyzing the proposed MILP model and the developed real-time decision-making method in a case study in a grocery supply chain.

Influence of autonomous regulation type on the connective tissue content in the muscular membrane of the chickens’ small intestine

The relationship between the small intestine's muscular membrane structure of chickens and the autonomous regulation type was investigated. Based on electrocardiographic and variational pulsometric studies, adult laying hens of the Isa-Brown breed were divided into two groups: sympathotonic (ST) and sympatho-normotonic (ST-NT). The volume of individual layers and the entire muscle membrane, as well as the volume of connective tissue fibers located in it, was determined in the small intestine of the hens. In general, the relationship between morphological parameters and the autonomous regulation type is similar throughout the whole intestine, but it has certain peculiarities in different intestine parts. An increase in the volume of both the circumferential and longitudinal layers of the intestinal muscular membrane accompanies an increase in sympathetic tonus. This pattern is typical for both groups. The ratio between these layers varies along the intestinal wall: the share of the longitudinal layer increases while that of the circumferential layer decreases. Accordingly, the average volume of the entire small intestine's muscular membrane in ST and ST-NT chickens differs by 590.6 mm3, and the total volume by 1771.7 mm3. Increased sympathetic tonus also contributes to a more significant number of collagen fibers in the circular layer of the muscle membrane. In the average values of the small intestine, its superiority over the longitudinal layer is 5.6 % in ST chickens and 3.4 % in ST-NT chickens. Regarding absolute values of elastic fiber volume, no group of birds has a complete advantage along the small intestine. However, the average values of this section are still dominated by ST chickens, which outnumber the other group by 15.3 mm3 in the circumferential layer and by 11.7 mm3 in the longitudinal layer of the muscle membrane. Birds with persistent sympathotonia also have more collagen fibers per 1 mm3 muscle membrane. Regarding average small intestine parameters, ST-NT chickens demonstrate a lower value (0.005 mm3). However, regarding the number of elastic fibers alone, ST-NT chickens already occupy a dominant position, and the difference between the two groups decreases to 0.004 mm3. The established muscle membrane's morphological features indicate its plasticity in adapting the intestinal wall to the autonomous regulation peculiarities.

Activities of the oral health teams in primary health care: a time-motion study

BackgroundEfficient planning of the oral health workforce in Primary Health Care (PHC) is paramount to ensure equitable community access to services. This requires a meticulous examination of the population’s needs, strategic distribution of oral health professionals, and effective human resource management. In this context, the average time spent on care to meet the needs of users/families/communities is the central variable in healthcare professional workforce planning methods. However, many time measures are solely based on professional judgment or experience.ObjectiveCalculate the average time parameters for the activities carried out by the oral health team in primary health care.MethodThis is a descriptive observational study using the time-motion method carried out in five Primary Health Care Units in the city of São Paulo, SP, Brazil. Direct and continuous observation of oral health team members occurred for 40 h spread over five days of a typical work week.ResultsA total of 696.05 h of observation were conducted with 12 Dentists, three Oral Health Assistants, and five Oral Health Technicians. The Dentists’ main activity was consultation with an average duration of 24.39 min, which took up 42.36% of their working time, followed by documentation with 12.15%. Oral Health Assistants spent 31.57% of their time on infection control, while Oral Health Technicians spent 22.37% on documentation.ConclusionThe study establishes time standards for the activities performed by the dental care team and provides support for the application of workforce planning methods that allow for review and optimization of the work process and public policies.

Recognition of multi-component compounds based on occurrence time of secondary crest in the fluorescence lifetime attenuation curve

Fluorescence lifetime is the main characteristic parameter of fluorescence. It is a widely used to draw fluorescence lifetime attenuation curves and to fit fluorescence lifetime parameters by using gated detection methods to identify the species of substances. However, the fluorescence attenuation of each fluorophore in a multi-component compound interferes with one another, affecting the accuracy of identification. In this paper, we propose a method to accurately identify substances by using the occurrence time of the secondary crest of the fluorescence lifetime attenuation curve based on the principle of gated detection to measure the fluorescence lifetime. Furthermore, we design a fluorescence lifetime imaging measurement system and select the same areas of interest in the images for analysis and comparison. The average lifetime of the fluorescence and the occurrence time of the secondary crest are considered as the characteristic parameters. We use five commercially available motor engine oils as the experimental samples and compare the recognition performance of different kernel functions based on a support vector machine (SVM). The radial basis kernel function presents the best performance in terms of recognition accuracy and speed. The recognition rates of the SVM model with the average fluorescence lifetime and the occurrence time of the secondary crest in the attenuation curve of the fluorescence lifetime as a feature vector are 76.24% and 74.65%, respectively. The recognition rate of the SVM model which combines them as feature vectors reaches 91.88%. The experimental results demonstrate that the occurrence time of the secondary crest in the attenuation curve of the fluorescence lifetime can be employed as the basis for substance identification in the analysis of the fluorescence characteristics of multi-component compounds, whose recognition accuracy is similar to the average fluorescence lifetime parameter. Moreover, the occurrence time of the secondary crest of the fluorescence lifetime attenuation curve can be implemented to identify multi-component compounds when it is used as a characteristic parameter.

Extracting Pole Characteristics of Complex Radar Targets for the Aircraft in Resonance Region Using RMSPSO_ARMA

The extraction algorithm of target characteristics resonance set at the high-frequency band plays a significant role in defense applications like early warning. The paper proposes a new method to extract the characteristic resonance set of radar targets in the resonance frequency region using an autoregressive moving average model optimized by root mean square propagation particle swarm optimization. Considering that the total scattering response in the resonant region consists of early-time and late-time responses, the autoregressive moving average model approximate the total scattering responses to avoid errors caused by intercepting the late-time response. Further, the paper investigated the impact of the swarm optimization algorithm on the accuracy of moving average model parameters when obtaining the resonance set at different target aspects. The extracted characteristic resonance results within a range of azimuth directions through an aircraft target paradigm indicate that the new method is more convenient and precise than the matrix beam prediction method.

KINETICS OF DRYING OF DISPERSED MATERIAL IN THE APPARATUS OF PERIODIC ACTION WITH FLUIDIZED BED

A theoretical method for calculating a periodically operating fluidized bed dryer is presented based on the zonal method for describing kinetics and an example of calculation is given in relation to the drying of pea grain. In the calculation, it is assumed that the solid phase in the apparatus is completely mixed, and the gas is ideally displaced, the particles have a spherical shape and are the same in size. Accounting for changes in the parameters of the drying agent in the layer is carried out on the basis of the equations of material and thermal balance for the layer with the division of the entire range of changes in the moisture content of the material into a number of concentration zones. The change in the temperature of the dried particles during the process is calculated based on the analytical solution of the linear heat conduction problem at a constant ambient temperature and the condition that moisture evaporation occurs at the surface of the particles (there is no internal evaporation). The calculation is carried out using the method of successive approximations. First, the duration of drying of the material in the concentration zone under consideration is set, then the average air parameters are determined by the height of the layer and by the drying time, and, using these data, by solving the problem of mass conductivity (moisture diffusion), the drying duration in the zone under consideration is determined and compared with the preset one. If there is a significant discrepancy, a second calculation iteration is carried out, taking the drying time found in the first calculation iteration. Calculations are carried out until an acceptable match between the previously accepted and calculated drying time. Then they move on to the second concentration zone, for which they do the same. The total drying time is equal to the sum of the times in the concentration zones. This technique was tested using the example of calculating the drying of pea grains. In the calculations, we used data previously found by the authors on the coefficient of mass conductivity (moisture diffusion), as well as literary reference data on the coefficients of thermal conductivity, thermal diffusivity and heat capacity of this material. Heat and mass transfer coefficients were calculated using criterion equations given in the literature. To select the operating air speed, the speed of the beginning of fluidization was calculated; the operating air speed was taken at a fluidization number of 1.05. The calculation of the Biothermal and mass transfer criteria showed that the thermal problem is mixed (the Biothermal number is 5.81), i.e. the heat transfer process is influenced by both internal and external heat transfer. The problem of mass transfer is purely internal (the modified mass transfer Bio number is 122.5), which was taken into account when calculating the drying time. The calculated drying curve was compared with the experimental one. A diagram of the experimental setup is given and a description of the experiment is given. Satisfactory agreement between the calculated and experimental drying curves indicates the correctness of the calculation method under consideration, which can be recommended for engineering use. For citation: Rudobashta S.P., Zueva G.A., Babicheva E.L. Kinetics of drying of dispersed material in the apparatus of periodic action with fluidized bed. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 6. P. 109-118. DOI: 10.6060/ivkkt.20246706.6968.

Extracting macroscopic quantities in crowd behaviour with deep learning

Abnormal behaviours in crowded populations can pose significant threats to public safety, with the occurrence of such anomalies often corresponding to changes in macroscopic quantities of the complex system. Therefore, the automatic extraction and prediction of macroscopic quantities in pedestrian collective behaviour becomes significant. In this study, we generated pedestrian evacuation data through simulation, and calculated the average kinetic energy, entropy and order parameter of the system based on principles of statistical physics. These macroscopic quantities can characterize the changes in crowd behaviour patterns over time and can also assist in detecting abnormalities. Subsequently, we designed deep convolutional neural networks(CNNs) to estimate these macroscopic quantities directly from frame-by-frame image data. In the end, a convolutional auto-encoder(CAE) model is trained to learn the underlying physics unsupervisedly. Successful results indicate that deep learning methods can directly extract macroscopic information from crowd dynamics, aiding in analysing collective behaviour.

The contribution of plyometric exercises assisted by sensory technology on vertical jump parameters in U15 female volleyball players

Background and Study Aim. Volleyball requires high vertical jump skills for crucial actions like attacking and blocking, making jump training a focus for players, especially in youth categories. The main goal of the study was to highlight (with some specific data) the strengths and weaknesses of integrating sensory technology into the physical training program, during the entire competitive period. Material and Methods. The study included both an experimental and a control group, each consisting of 16 female athletes from the volleyball section of the Cetate Sports High School in Deva. During the competitive season of 2022/2023, both groups underwent daily training sessions from Monday to Saturday, totaling 120 minutes per day. The BlazePod Flash Reflex Training system was employed in this research. It integrates cognitive training to enhance thinking speed and clarity with physical exercises aimed at maximizing motor skills. Performance evaluations of the athletes utilized eight predefined tests from the OptoJump Next optical measuring system and the Myotest accelerometric system. To analyze the data, paired (dependent) sample t-tests were conducted to compare average parameters between matched samples. Repeated measures ANOVA was utilized to compare the average outcomes, ensuring the participants were consistent across the evaluated conditions. Results. The experimental group showed significant improvements in the height reached from the center of gravity and flight time for the following tests: Countermovement Jump, Countermovement Jump with Arm Swing, Squat Jump, Squat Jump with Arm Swing, and Drop Jump from 30 cm. All improvements reached statistical significance: p<0.05. Significant enhancements were also observed in average jump height, jump power, force of jumps, and ascensional speed, demonstrating statistical significance (p<0.05). Furthermore, the use of an arm swing during jumps notably improved performance compared to when jumps were performed with hands on hips. This indicates that an arm swing can significantly increase the height of the vertical jump (p<0.05). Conclusions. The study confirms that the integration of sensory technology into the training programs for junior volleyball teams is effective in enhancing training outcomes. This approach not only improves the vertical jump capabilities of young athletes but also positively affects their ability to perform technical moves that require elevation from the ground. It underscores the potential of innovative training methods in advancing athletic performance in youth sports.

The changes in health-related quality of life in stable coronary artery disease patients and intermediante coronary lesions after elective percutaneous coronary intervention

The aim – to analyze the factors, associated with the change in health-related quality of life (HRQoL) in stable coronary artery disease (SCAD) patients with intermediate coronary lesions at 3-months follow-up after elective percutaneous coronary intervention (PCI).Materials and methods. A prospective single-center study enrolled 84 SCAD patients (mean age 64±8 years; males – 73 %) with intermediate coronary lesions (stenosis 50-90 %) (by invasive coronary angiography [ICA]), consecutively enrolled and hospitalized with the aim of elective PCI to be performed. HRQoL was evaluated by SF-36 (physical health summary [PHsum] and mental health summary [МНsum]) and SAQ (Seattle Angina Questionnaire»; the domains «physical limitation» [PL], «angina stability» [AS], «angina frequency» [AF], «treatment satisfaction» [TS] and «disease perception» [DP]), – at baseline and 3-months follow-up. The enrolled sample was subdivided in a dichotomous manner into the HRQoL «improvement» or «non-improvement» patterns, based on the cut-off-values (COVs) of clinically meaningful change of the certain HRQoL parameter score at 3-months follow-up after PCI.Results and discussion. We revealed an improvement of average (median) HRQoL parameters at 3-months follow-up after PCI, namely PHsum (score increase from 38.8 to 43.1; р < 0.001), SAQ-AS (25 to 75; р < 0.001), SAQ-AF (70 to 80; р < 0.001), SAQ-TS (58.8 to 70.6; р < 0.001) and SAQ-DP (45.8 to 66.7; р < 0.001). The clinically meaningful HRQoL improvement ranged from 14 % to 71 % cases, depending on the certain HRQoL parameter and the COVs of its change at follow-up after PCI. The worse baseline HRQoL, older age and higher baseline total cholesterol level were the factors, associated with the increased probability of HRQoL to be meaningfully improved after revascularization. In addition, a presence of diabetes mellitus, a history of acute cerebrovascular accident, and the ICA data on multivessel disease and in-stent restenosis after previous PCI, – all were associated with the lower odds of HRQoL «improvement» status to be achieved.Conclusions. A PCI favored the HRQoL improvement in SCAD patients at 3-months follow-up. The clinical and angiographic factors, associated with the post-procedure change in HRQoL, should be considered for a better selection of SCAD patients with intermediate coronary lesions for PCI.

Estimating the Complier Average Causal Effect with Non-Ignorable Missing Outcomes Using Likelihood Analysis

Missing data problems arise in randomized trials, which complicates the inference of causal effects if the missing mechanism is non-ignorable. We tackle the challenge of identifying and estimating the complier average causal effect parameters under non-ignorable missingness by increasing the covariates to mitigate the sensitivity to the violation of specific identification assumptions. The missing data mechanism is assumed to follow a logistic model, wherein the absence of the outcome is explained by the outcome itself, the treatment received, and the covariates. We establish the identifiability of the models under mild conditions by assuming that the outcome follows a normal distribution. We develop a computational method to estimate model parameters through a two-step likelihood estimation approach, employing subgroup analysis. The bootstrap method is employed for variance estimation, and the effectiveness of our approach is confirmed through simulation. We applied the proposed method to analyze the household income dataset from the Chinese Household Income Project Survey 2013.

The Impact of In-Flight Acceleration Environments on the Performance of a Phase-Change Heat Exchanger Unit with Layered Porous Media

The Phase-Change Heat Exchanger Unit in Layered Porous Media (PCEU-LPM) is obtained through frozen pouring processing, and exhibits characteristics such as high thermal conductivity, high latent heat, and high permeability, making it suitable for dissipating heat in airborne electronic devices. This study numerically investigates the impact of aircraft speed acceleration conditions, which lead to weightlessness or overload, on the performance of the PCHEU-LPM, with a particular focus on the influence of natural convection in the liquid-phase region. Initially, a microscale thermal analysis model is established based on the Navier–Stokes equation scanning electron micrograph to calculate the effective thermal conductivity and permeability of the PCHEU-LPM under different porosities. Subsequently, these parameters are incorporated into a macroscale thermal analysis model based on Darcy’s law, employing an average parameter approach. Using the macroscale thermal analysis model, temperature and velocity fields are computed under various porosities, acceleration magnitudes, and directions. The calculation results indicate that as the acceleration increases from α = 0 to α = 10 g, the interface temperature of the PCHTU-LPM decreases by approximately 5.2 K, and the temperature fluctuation decreases by 2.4 K. If the porosity of the PCHTU-LPM is increased from ε = 70% to ε = 85%, the influence of acceleration change on natural convection will be further amplified, resulting in a decrease in the interface temperature of the PCHTU-LPM by approximately 10.2 K and a decrease in temperature fluctuation by 5.8 K. When the acceleration direction is +z, the interface temperature of the PCHTU-LPM is at its lowest, while it is highest when the acceleration direction is −z, with a maximum difference of 15.4 K between the two. When the acceleration direction is ±x and ±y, the interface temperature lies between the former two cases, with the interface temperature slightly higher for ±y compared to ±x, with a maximum difference of 3.9 K between them.

Static and dynamic atom displacements in nanocrystalline powders from diffraction analysis at finite temperature

We evaluate the accuracy of x-ray diffraction analysis performed by Rietveld refinement in extracting the static and dynamic atomic displacement parameters of spherical gold nanocrystals with sizes of 30 nm and below and within a temperature interval of 10–300 K. A self-consistent computational workflow composed of real- and reciprocal- space analyses is designed for this purpose. We obtain average lattice parameters, static and thermal atomic displacements as well as their temperature and particle size dependence in an ideally monodispersed and realistic nanocrystalline powder generated by molecular dynamics simulations. Then, we compare crystallographic parameters obtained from real- and reciprocal- space analyses to evaluate the accuracy of diffraction analysis. We also extend the comparison to local variations of crystallographic parameters in the nanocrystals and show how Rietveld refinement relates to the average parameters of the core and surface regions separately. We show that 1) average lattice parameters obtained from Rietveld refinement are greater than the mean lattice parameter of small nanocrystals and converge to the core lattice parameter with increasing particle size, 2) Rietveld refinement significantly underestimates static atom displacements of surface atoms in small nanocrystals, 3) dynamic atomic displacements in nanocrystalline gold powders are reliably obtained within 5 % error by Rietveld refinement, provided that thermal diffuse scattering is adequately removed from the diffraction data, 4) the discrepancy between real- and reciprocal-space analysis increases for the smallest gold nanocrystal.