Calculation Of Coefficients Research Articles

Bubble thermodynamics in cryogenic fluids under ultrasonic field excitation: Theoretical analysis and numerical calculation

In the study of cavitation in room-temperature fluids, the heat transfer between gas and liquid in bubble oscillation is usually assumed to be an adiabatic process for simplification. However, this heat transfer and thermodynamic mechanism is not yet understood in cryogenic fluids, especially under small amplitude oscillation conditions excited by ultrasonic field. This article studies bubble thermodynamic model under an external ultrasonic field based on the heat transfer equation for cryogenic fluids. The temperature changes inside bubbles are calculated, and the heat transfer mechanism is briefly analyzed. The results indicate that the heat transfer mechanism of bubbles depends on the relationship between ultrasonic frequency and bubble resonance frequency. By analyzing two special cases of dual-bubble and high-pressure environment, it is believed that heat transfer can be approximated as an adiabatic process under high-pressure conditions with ultrasonic frequency far from the resonance frequency. This conclusion can provide a theoretical basis for subsequent accurate calculation of heat-transfer polytropic coefficient, or void faction measurement in cryogenic two-phase flow.

A novel interactive prognosis framework with nonlinear Wiener process and multi-sensor fusion for remaining useful life prediction

Accurate remaining useful life (RUL) prediction plays a vital role in increasing the system operation safety and reducing maintenance costs. In industrial applications, there is usually a large amount of multi-sensor data generated. Therefore, how to construct an appropriate health index (HI) based on multi-sensor signals is very important for the RUL prediction. However, existing works treat sensor selection, HI construction, and degradation modeling independently as unrelated parts, which may result in the combination of sensors selected not constituting an optimal HI or the constructed HI not matching the degradation model. In addition, most existing works treat prior units as a whole to obtain a unique set of sensor combinations and fusion coefficients, which cannot reflect unit-to-unit heterogeneity, thus affecting the accuracy of RUL prediction. Therefore, a novel interactive feedback framework is established to construct HI, where the sensor selection, fusion coefficient calculation, and nonlinear Wiener process degradation modeling are incorporated into the feedback. Furthermore, an adaptive weight selection method based on particle swarm optimization and leave-one-out cross-validation (PSO-LV) is proposed to adjust the fusion coefficients in real-time. Then, the RUL is estimated by updating model parameters online, detecting degradation trends, and deriving the probability density function (PDF) of the RUL. Finally, two examples of engine datasets are provided to verify the effectiveness of the proposed method.

Diffusion of curcumin in PLGA-based carriers for drug delivery: a molecular dynamics study

Context:The rapid growth and diversification of drug delivery systems have been significantly supported by advancements in micro- and nano-technologies, alongside the adoption of biodegradable polymeric materials like poly(lactic-co-glycolic acid) (PLGA) as microcarriers. These developments aim to reduce toxicity and enhance target specificity in drug delivery. The use of in silico methods, particularly molecular dynamics (MD) simulations, has emerged as a pivotal tool for predicting the dynamics of species within these systems. This approach aids in investigating drug delivery mechanisms, thereby reducing the costs associated with design and prototyping. In this study, we focus on elucidating the diffusion mechanisms in curcumin-loaded PLGA particles, which are critical for optimizing drug release and efficacy in therapeutic applications.Methods:We utilized MD to explore the diffusion behavior of curcumin in PLGA drug delivery systems. The simulations, executed with GROMACS, modeled curcumin molecules in a representative volume element of PLGA chains and water, referencing molecular structures from the Protein Data Bank and employing the CHARMM force field. We generated PLGA chains of varying lengths using the Polymer Modeler tool and arranged them in a bulk-like environment with Packmol. The simulation protocol included steps for energy minimization, T and p equilibration, and calculation of the isotropic diffusion coefficient from the mean square displacement. The Taguchi method was applied to assess the effects of hydration level, PLGA chain length, and density on diffusion.Results:Our results provide insight into the influence of PLGA chain length, hydration level, and polymer density on the diffusion coefficient of curcumin, offering a mechanistic understanding for the design of efficient drug delivery systems. The sensitivity analysis obtained through the Taguchi method identified hydration level and PLGA density as the most significant input parameters affecting curcumin diffusion, while the effect of PLGA chain length was negligible within the simulated range. We provided a regression equation capable to accurately fit MD results. The regression equation suggests that increases in hydration level and PLGA density result in a decrease in the diffusion coefficient.

Population of Russia: demographic situation, problems and prospects

Analysis of the size, structure and age-sex composition of the population of Russia is the most important task of modern statistics, providing government agencies with the necessary information for developing programs and plans for the development of key sectors of the economy. In times of economic downturns and recessions, it is important for authorities to have reliable and complete information about the state of the population, since it is the population size and its structure that are the basis of human resources for the development of sectors of the economy, including agriculture, which ensures food security and preservation of the population, decides strategic development tasks for the country as a whole. The study is aimed at analyzing the state and identifying patterns of changes in the Russian population, population distribution, identifying trends in the dynamics of the working-age and elderly population, and analyzing the gender and age pyramid of Russia for 2023. To conduct a comprehensive study, the following methods were used: calculation of demographic coefficients, alignment of time series. The results of the study made it possible to propose directions for improving measures within the framework of the existing demographic policy of the state to ensure uniform distribution of the population throughout the country, reduce the tax burden on individuals, and increase labor productivity.

THE DEVELOPMENT AND INITIAL TESTS FOR THE PSYCHOMETRIC PROPERTIES OF THE EQUAL OPPORTUNITY IN EDUCATION SCALE

Although equality of opportunity in education is a current and important issue, most of the studies on this subject are based on theoretical studies rather than empirical studies. The main reason for this can be said to be the lack of a valid and reliable measurement tool in this field. For this reason, this study aims to develop a valid and reliable measurement tool for determining pre-service teachers' perceptions of equality of opportunity in education. For this purpose, data were collected from four different samples using a simple random sampling technique. First, a literature review was conducted, and qualitative interviews were conducted with the first sample on equal opportunities in qualitative education. After the item pool was created, the first application was made in order to determine the factor structure of the measurement tool. Data were collected from a separate sample to test the resulting structure and perform confirmatory factor analysis. Then, in the context of reliability studies of the measurement tool, calculation of the internal consistency coefficient, extracted mean variance, composite reliability and test-retest processes were used. As a result, a valid and reliable scale for determining the perception of equality of opportunity in education consisting of three factors and 23 items has been brought to the education literature. Keywords: equal opportunity in education, factor analysis, validity and reliability, scale development

Learning models and achievements of the most gifted students

The emergency of switching to an online learning model due to the COVID pandemic impacted the educational process in of schools world wide. We conducted an anonymous survey at the elite high schools in Serbia whose students won 45 medals at international Olympiads in mathematics, physics, and computer sciences in the last 4-year period (2019–2022). The impact of switching from in-person to online learning on the achievement of the gifted students was analyzed. The results of the research revealed a downward trend in the final grades and achievements in international Olympiads, which persists even after returning to the face-to-face educational model. This trend is confirmed by calculation of the Pearson correlation coefficient (−0.62) between school years and achievements in international mathematical Olympiads, international physics Olympiads, and international Olympiads in informatics. Gifted students’ satisfaction with online learning during the COVID pandemic was also analyzed using content analysis of open-ended questions. The surveyed gifted students showed a high level of self-criticism and maturity by expressing their opinion about online learning. In the group of gifted students, there is a higher level of agreement about harmful consequences of online learning on the level of their education and work habits than in other research conducted on similar topics. Moreover, the level of agreement is in a positive correlation with students’ achievements and final grades.

Electromechanical characterization of 3–2 ceramic-air composites

In this study, a type 3–2 ceramic-air composite was designed, and the impact of varying thicknesses on its electromechanical properties was analyzed. Initially, finite element simulation software was employed to model type 3–2 ceramic-air composites of differing thicknesses. This modeling facilitated the determination of resonance and anti-resonance frequencies, calculation of effective electromechanical coupling coefficients, and assessment of frequency discrepancies corresponding to each thickness. Subsequently, type 3–2 ceramic-air composites of various thicknesses were fabricated using the reverse cutting method. The experimental results corroborated the simulation outcomes, demonstrating consistency. In the final analysis, the performance parameters of conventional type 1–3 piezoelectric composites were evaluated alongside those of type 3–2 composites. Findings indicated an improvement of 0.8 in the thickness electromechanical coupling coefficient for type 3–2 composites compared to conventional type 1–3 composites. Consequently, type 3–2 composites show promise for the development of highly sensitive piezoelectric transducers.

Translation and Cross-Cultural Adaptation, Reliability and Validation Study of the Persian Version of Kansas City Cardiomyopathy Questionnaire

The Kansas City Cardiomyopathy Questionnaire (KCCQ) has been developed to measure the health status of Congestive heart failure (CHF) patients. This study aimed to translate KCCQ into a Persian version and assess its validity and reliability. We used a forward-backward procedure to translate the questionnaire. In a cross-sectional study, 150 CHF patients and 50 healthy subjects over 30 years old were selected to assess the reliability and construct validity of the instrument. The face and content validity were used for the questionnaire's validity. The validity was examined on a population of patients with CHF using the Persian version of the Minnesota Living Heart Failure Questionnaire (MLHF) health survey. Calculation of the Intraclass correlation coefficient (ICC) and Cronbach's alpha was done to evaluate the questionnaire's reliability. Test-retest reliability was examined by re-administering the KCCQ after 2 weeks. Test-retest results demonstrated that the Persian version has excellent reliability (ICC for all domains was higher than 0.93, P≤0.000). Internal consistency was found by Cronbach's alpha to be 0.86 for the clinical summary and 0.87 for the overall summary, respectively. Also, the correlation between the components of KCCQ and MLHQ showed satisfactory construct validity. Good Pearson's Correlation Coefficient was seen between KCCQ and MLHF (r= -0.44, P≤0.000 for the clinical summary; r= -0.45, P≤0.000 for the overall summary). Analysing the data from 50 healthy persons and 150 patients were shown that the Persian version of KCCQ has acceptable discriminate validity for all domains except self-efficacy. The Persian version of the KCCQ had satisfactory reliability and validity for assessing health-related quality of life status for Iranian CHF patients.

The longest multiannual drought in Northeastern Brazil

The Northeastern region of Brazil has long history of drought with impacts on water supply for cities and agriculture. However, the last drought that occurred in the region had unprecedented magnitude and periodicity, making it the longest multiannual drought in Northeastern Brazil. Thus, understanding and characterizing the behavior of this phenomenon is necessary, considering that another episodes may occur. Thus, the objective of this study was to characterize the drought trend in the Northeastern region of Brazil, with the application of the Palmer Drought Severity Index (PDSI). The application of PDSI was carried out with the monthly calculation of the water balance coefficients referring to the soil water balance between the years 2000 and 2019, depending on the relative soil moisture values. The results obtained were submitted to the Mann-Kendall test to identify monthly trends in the index. The annual drought variability in Northeastern Brazil showed moderate to extreme intensity, with the worst drought being observed between the years 2012 and 2019. The monthly drought average shows the Mid-Northern and “Sertão” regions as the most critical, with monthly trend of significant drought severity. The positive trend was observed in the Eastern, Southern and Western coast regions of NEB.

Assessing attitudes towards biostatistics education among medical students: adaptation and preliminary evaluation of the Chinese version survey of attitudes towards statistics (SATS-36)

BackgroundDespite the numerous advantages of mastering biostatistics, medical students generally perceive biostatistics as a difficult and challenging subject and even experience anxiety during the courses. Evidence for the correlation between students’ academic achievements and their attitudes, indicating that attitudes at the beginning of the biostatistics course may affect cognitive competence at the end of the course and subsequently influence student academic performance. However, there are current disagreements regarding the measurement and evaluation of attitudes related to statistics. Thus, there is a need for standard instruments to assess them. This study was conducted to develop a Chinese version of the Survey of Attitudes Toward Statistics (SATS-36) in order to acquire a valid instrument to measure medical students’ attitudes toward biostatistics under Chinese medical educational background.MethodsThe Chinese version SATS-36 was developed through translation and back-translation of the original scale, with subsequent revisions based on expert advice to ensure the most appropriate item content. The local adaption was performed with a cohort of 1709 Chinese-speaking medical undergraduate and graduate students enrolled in biostatistics courses. And then, the reliability, validity and discrimination of the questionnaires were evaluated through correlation coefficient calculation, factor analysis, parallel analysis and other methods.ResultsThe Chinese version SATS-36 consisted of 36 items and loaded a five-factor structure by factor analysis, which offered an alternative similar but not equal to that original six-factor structure. The cumulative variance contribution rate was 62.20%, the Cronbach’s α coefficient was 0.908, the Guttman split-half reliability coefficient was 0.905 and the test–retest reliability coefficient was 0.752. Discriminant analysis revealed small to large significant differences in the five attitude subscales.ConclusionsThe Chinese version SATS-36 with good validity and reliability in this study can be used to evaluate the learning framework of Chinese medical students.

Analytical Determination of Nusselt Numbers for Convective Heat Transfer Coefficients in Channel Macroporous Absorbers.

This article introduces a novel analytical equation for computing the Nusselt number within the macroporous structures of channel absorbers utilized in high-temperature solar receivers. The equation incorporates heat and mass transfer processes occurring within boundary layers as fluid flows through complex-shaped macroporous absorber channels. The importance of accounting for the length of the thermodynamic boundary layer within channel-type macroporous media when calculating heat transfer coefficients using the Nusselt equation is demonstrated. By incorporating proposed indicators of porosity and flow characteristics, this method significantly enhances the accuracy of heat transfer coefficient calculations for such media. Discrepancies observed in existing calculation relationships and experiments are attributed to the omission of certain proposed values in the Nusselt number for macroporous media. To address this, empirical coefficients for the Nusselt number are derived using statistical methods. The resulting semi-empirical equation is applied to macroporous absorbers in solar receivers. The findings enable more accurate predictions of future absorber characteristics, enhancing their efficiency. The derived equation is successfully validated against numerical data across various geometric structures of absorbers in concentrated solar power plants.

Fine-tuning digital FIR filters with gray wolf optimization for peak performance

The design of optimum filters constitutes a fundamental aspect within the realm of signal processing applications. The process entails the calculation of ideal coefficients for a filter in order to get a passband with a flat response and an unlimited level of attenuation in the stopband. The objective of this work is to solve the FIR filter design problem and to compare the optimal solutions obtained from evolutionary algorithms. The design of optimal FIR low pass (LP), high pass (HP), and band stop (BS) filters is achieved by the utilization of nature-inspired optimization approaches, namely gray wolf optimization ,cuckoo search, particle swarm optimization, and genetic algorithm. The filters are evaluated in terms of their stop band attenuation, pass band ripples, and departure from the anticipated response. In addition, this study compares the optimization strategies applied in the context of algorithm execution time which is achievement of global optimal outcomes for the design of digital finite impulse response (FIR) filters. The results indicate that when the Gray wolf algorithm is applied to the development of a finite impulse response (FIR) filter, it produces a higher level of performance than other approaches, as supported by enhanced design precision, decreased execution time, and achievement of an optimal solution.

Wavelet-based correlations of the global magnetic field in connection to strongest earthquakes

We consider 3-component records of the magnetic field strength with a time step of 1 min at 153 stations of the INTERMAGNET network for 31 years, 1991–2021. Data analysis is based on the calculation of pairwise correlation coefficients between wavelet coefficients in successive time windows 1 day long (1440 min counts). To describe the state of the magnetic field, the maxima of the average values of all pairwise correlation coefficients between stations were chosen, calculated over all detail levels of the wavelet decomposition and over all components of the magnetic field strength vector. The daily time series of such maxima is called wavelet correlation. The division of the network stations into 7 clusters is considered, and a time series of wavelet correlations is calculated for each cluster. In a sliding time window with a length of 365 days, correlation measures of synchronization of wavelet correlations from different clusters are calculated, which are compared with the strongest earthquakes with a magnitude of at least 8.5. For the global time series of wavelet correlations, the method of influence matrices is used to study the relationship between the maximum correlation responses to a change in the length of the day and a sequence of earthquakes with a magnitude of at least 7. As a result of the analysis, precursor effects are identified, and the important role of the Maule earthquake in Chile on February 27, 2010 in the behavior of the response of magnetic field for the preparation of strong seismic events is shown.

The First Estimation of the Ambipolar Diffusivity Coefficient from Multi-scale Observations of the Class 0/I Protostar, HOPS-370

Protostars are born in magnetized environments. As a consequence, the formation of protostellar disks can be suppressed by the magnetic field, efficiently removing the angular momentum of the infalling material. Nonideal MHD effects are proposed as one way to allow protostellar disks to form. Thus, it is important to understand their contributions to observations of protostellar systems. We derive an analytical equation to estimate the ambipolar diffusivity coefficient at the edge of the protostellar disk in the Class 0/I protostar, HOPS-370, for the first time, under the assumption that the disk radius is set by ambipolar diffusion. Using previous results of the protostellar mass, disk mass, disk radius, density and temperature profiles, and magnetic field strength, we estimate the ambipolar diffusivity coefficient to be 1.7−1.4+1.5×1019cm2s−1 . We quantify the contribution of ambipolar diffusion by estimating its dimensionless Elsässer number to be ∼1.7−1.0+1.0 , indicating its dynamical importance in this region. We compare our results to those of the chemical calculations of the ambipolar diffusivity coefficient using the Non-Ideal Magnetohydrodynamics Coefficients and Ionization Library, which are consistent with our results. In addition, we compare our derived ambipolar diffusivity coefficient to the diffusivity coefficients for ohmic dissipation and the Hall effect, and find ambipolar diffusion is dominant in our density regime. These results demonstrate a new methodology to understand nonideal MHD effects in observations of protostellar disks. More detailed modeling of the magnetic field, envelope, and microphysics, along with a larger sample of protostellar systems, is needed to further understand the contributions of nonideal MHD.

Noncollinear phase matching and effective nonlinear coefficient calculations for biaxial crystal out of the principal plane

Noncollinear phase matching and effective nonlinear coefficient calculations for biaxial crystal out of the principal plane

Coupling coefficient calculation method of circular coil with bilateral finite magnetic shields at horizontal misalignment in wireless power transfer systems

AbstractThe coupling coefficient determines the transfer efficiency of the wireless power transfer (WPT) system. The magnetic leakage can be reduced, and the coupling coefficient of the coil can be enhanced by adding a magnetic shield. Thus, the transfer efficiency of the WPT system can be improved. However, when the receiving coil is added with magnetic shield and occurs horizontally misaligned, the coupling coefficients between the coils with the magnetic shield can only be calculated by finite element simulation, and there is no calculation method for the coupling coefficient of two circular coils with bilateral finite magnetic shield at horizontal misalignment. Therefore, based on Maxwell's equations and Bessel's function, the formula of the coupling coefficient between circular coils at coaxial is derived by the subdomain hierarchical analysis (SHA) method. On this basis, the coupling coefficient calculation formula between circular coils at horizontal misalignment is further derived by using the boundary vector equivalence (BVE) method. The results show that the maximum experimental error is not more than 5.58%, and the longest average time of the algorithm is not more than 1.282 s, which verifies the effectiveness and rapidity of the proposed method.

Comparison of serum concentrations of pregnancy-associated glycoproteins and estrone sulphate during pregnancy in eutocia and dystocia beef cattle

Preventing dystocia can stabilise beef cattle management. This study aimed to investigate the relationship between serum pregnancy-associated glycoproteins (PAGs) S-N values and estrone sulphate (E1S) concentrations during pregnancy and the calf birth weight in beef cattle and to evaluate their usefulness as new predictive parameters for dystocia due to foetal overgrowth. Thirty-eight pregnant Japanese Black cattle were used. Blood samples were collected at 40, 70, 100, 150, 200, 250, 280, and 285 days after artificial insemination (AI), and birth weight of the offspring was measured. Serum PAGs S-N values and E1S concentrations were measured, and the area under the curve (AUC) and the ratio of change based on 70 days after AI were calculated, followed by calculation of the correlation coefficient with the birth weight of the offspring and comparison between the eutocia (n = 32) and dystocia (n = 6) groups. The birth weight of the offspring was moderately positively correlated with the AUC of serum PAGs S-N values and E1S concentrations in the second (r = 0.425, P < 0.01) and third (r = 0.595, P < 0.01) trimesters, respectively. The ratio of change in serum E1S concentrations between 70 and 280 days after AI was greater (P < 0.05) in the dystocia group (1276.6 ± 229.1 %) than in the eutocia group (852.6 ± 69.6 %). These results suggest that blood PAGs S-N values at mid-pregnancy (100–199 days after AI) and the ratio of changes in blood E1S concentrations between 70 and 280 days after AI may be new parameters for predicting dystocia.

Duality between predictability and reconstructability in complex systems

Predicting the evolution of a large system of units using its structure of interaction is a fundamental problem in complex system theory. And so is the problem of reconstructing the structure of interaction from temporal observations. Here, we find an intricate relationship between predictability and reconstructability using an information-theoretical point of view. We use the mutual information between a random graph and a stochastic process evolving on this random graph to quantify their codependence. Then, we show how the uncertainty coefficients, which are intimately related to that mutual information, quantify our ability to reconstruct a graph from an observed time series, and our ability to predict the evolution of a process from the structure of its interactions. We provide analytical calculations of the uncertainty coefficients for many different systems, including continuous deterministic systems, and describe a numerical procedure when exact calculations are intractable. Interestingly, we find that predictability and reconstructability, even though closely connected by the mutual information, can behave differently, even in a dual manner. We prove how such duality universally emerges when changing the number of steps in the process. Finally, we provide evidence that predictability-reconstruction dualities may exist in dynamical processes on real networks close to criticality.

Calculation of Time-Independent Maneuvering Coefficients of an Underwater Vehicle Based on Single Grid Structure

Calculation of Time-Independent Maneuvering Coefficients of an Underwater Vehicle Based on Single Grid Structure

MASSTRANSFER FEATURES IN THE APPARATUSES WITH A MOVING NOZZLE IN A THREE-PHASE FOAM LAYER

The improvement of heat and mass exchange equipment for sorption processes in the countercurrent contact of gas and liquid in combined block elements with a weighted spherical nozzle, as well as a more in-depth study of this process, is an urgent task of chemical technology. A fundamentally new type of ball-shaped three-dimensional mesh fluidized nozzle was developed and researched, the bodies of which are made of polymer layers with holes, and a freely coiled metal or polymer mesh is located inside. The nozzle has a high specific surface area, developed free volume and low bulk density. The study of mass transfer in the liquid and gas phases was carried out and the corresponding calculation equations were obtained. Dependencies for the calculation of the mass transfer coefficients and the efficiency of the combined block element on the mode and design parameters are established. The results of calculations based on the obtained dependencies show a sufficient correlation with the experimental data. The proposed model of the desorption process of carbon dioxide from water, which allows predicting the values of the efficiency indicators of the decarbonization process. It was established that the use of a combined block element with a ball-shaped nozzle allows to increase the mass transfer coefficients compared to the failure plate. The industrial implementation of absorption processes in the foam layer and the use of the gas-liquid layer stabilization method significantly expands the scope of application of foam apparatuses and opens up new opportunities for intensifying technological processes. Previously expressed assumption about the perspective of using mesh materials for the manufacture of nozzle bodies was confirmed by experiments, but the peculiarity of the operation of devices with similar nozzles should be emphasized.