Numerical Work Research Articles

More accurate solution of mixed convection radiative power law fluid flow over a stretching porous surface with presence of Forchheimer and chemical reaction

In hydraulic analysis, one of the most popular viscosity models for non-Newtonian fluids is the Power Law model. In shear-thinning and shear-thickening, the governing system of partial differential equations is transformed into a system of coupled highly non-linear ordinary differential equations. The effects of emerging parameters on velocities, temperature, and concentration as well as the engineering quantities (friction factor, Nusselt number, and Sherwood number) are presented in tables, graphs, and discussed. Most previous studies do not care about studying the effect of different parameters on stream velocity, and this is one of the advantages of our current study, which can be used by researchers in the future to make comparisons and verify the validity of the solutions. The higher accuracy of fifth-order FDM is tested by comparing it (in the Newtonian case) with previously published works and the results are in excellent agreement with these analytical and numerical works.

Effect of pressure pores size on hydrodynamic and hydroacoustic marine propeller performances under cavitating case

The numerical work presented in the paper investigates the effect of pressure pores on hydrodynamic and hydroacoustic performances. This research aims to reduce cavitation area and underwater noise by mitigating the tip vortex cavitation. Compared to the few studies devoted to the pressure pores technique, several configurations based on the E779A marine propeller have been tested by considering different azimuthal and radial step values, a wider pore region concentrated at the top of the blade, and several pore diameter values. In addition, a numerical simulation was started to verify the effectiveness of the theoretical models in detecting the effect of pressure pores on the acoustic propagation generated by the propellers tested. The numerical approaches combining cavitating flow and noise propagation are performed using a hybrid method, which solves the Ffowcs Williams-Hawkings (FW–H) equation. A validation of the numerical simulation is carried out for cavitating and non-cavitating cases. Open water performances, cavitation area, sound pressure levels, and thrust distributions are analysed for two cavitation numbers. σ= 1,763 and σ= 1,029. The obtained results reveal that the cavitation area decreases as the pressure pore radius increases, but a slight reduction in propulsive efficiency accompanies this. Particularly for the pores radius of 0,00264D, propeller efficiency loss doesn't exceed 2,6 % and 4,05 % for the two cavitation numbers investigated. Nevertheless, this configuration showed better acoustic performances with a diminution of 10 dB in overall sound pressure level compared to the propeller without pressure pores.

Absorption by a Layered Microbolometer Pixel’s Active Element

Microbolometer arrays, i.e., arrays of micro-scale pixels sensing temperature via resistance changes, have proven to be an effective basis for real-time imaging instrumentation in infrared as well as terahertz frequencies. In previous work, a design of THz and IR absorbing nano-laminates of dielectric and metal layers was studied. It was shown via numerical modeling that absorption may be maximized by appropriate choices of thickness, permittivity and conductivity. In this work, an analytical approach to the problem is formulated based on the standard recursive multiple reflection formulas for multi-layered planar structures. The results fully confirm and extend previous numerical work. A previous relationship between wavelength and silicon thickness for maximum absorption, derived numerically for specific parameter combinations, is now generalized in a parametric closed form. The method can be extended to include multiple lossy dielectric layers and may serve as a tool for optimizing the absorption characteristics of more complex layered absorbing structures. This could enhance the sensitivity of the detection scheme of interest, providing benefits in terms of cost, efficiency, precision, and adjustability.

Scientific Works of Academician Rymgali Nurgali

ABSTRACT The relevance is predefined by a necessity for in-depth research and analysis of the scientist generation of various fields, which has made a significant contribution to the development and growth of Kazakh science. The research aims to study the well-known academician, critic, professor, doctor of philological science, writer, scientist, and literature specialist Rymgali Nurgali’s scientific works and peculiarities of research. The primary methodological approach of scientific research is a qualitative combination of theoretical research methods (descriptive and comparative, juxtaposition, generalization, abstraction, analysis, synthesis, comparative-historical, etc.). These methods were employed for the research, detailed investigation, and analysis of Nurgali’s scientific works. The primary value of the study is to determine the relevance of Nurgali’s works for modern Kazakh science, as well as the need for further research and analysis of his works, which are incredibly diverse, detailed, and full of truly aesthetic tone. The results of the scientific research, as well as the conclusions formulated on their basis, are of practical value for literary critics, philologists, teachers, and other specialists who study outstanding personalities in the field of Kazakh literary criticism and analyze their numerous works.

Modeling of the Complexity Propagation of Crack in a Ductile Material Under Complex Solicitation in Crack Tip: Introduction of a Matrix of Stress Intensity Factors of Bifurcation

In fracture and damage mechanics, modeling of crack propagation has always been a source of difficulties. Numerous works have been carried out on this case at the crack tip, introducing new parameters: the Stress Intensity Factor (K); which is the local Irwin parameter, and also the Rice integral (J), the Griffith's energizing method, in which J and G are the global parameters around the crack tip. The problem of the crack remains very complex and difficult problem to be solved. Several methods are used to investigate the crack problem, namely the method of gradient, the numerical methods by finite elements, as well as the thermodynamic approach and the classical methods of Irwin, Griffith or Rice, according to the Intensity Stress Factor. This study adds to the work already carried out. Using the analytical analysis method of equations, we manage to show that the Stress Intensity Factor has a matrix of rank 3 at the crack tip, which is a better form since it includes complex combination cases of crack mode and bifurcation. Furthermore, when the material is subjected to complex stress, after analysis we emerge from a new singularity in (r) which is different from the classical mode. Finally, we are shown the new form of singularity, which is frequency dependent. This work can explain many situations, for example, the case of certain structural disasters showing the presence of cracks for complex or uncontrollable stress.

A comprehensive study on predicting the elastic modulus and Poisson ratio of hardened cement pastes via micro-scale cement hydration simulations

A comprehensive study was conducted to predict the elastic modulus and Poisson ratio of hardened cement pastes (HCPs), including numerical work, comparison of two modelling approaches, and experimental validation. Modelling approach 1 (M1) applied a continuum micromechanics model (CMM) whereas modelling approach 2 (M2) used finite element analysis (FEA). This study presents a reliable method for predicting the mechanical properties of HCPs by firstly employing the microstructures of HCPs, obtained by CEMHYD3D analysis with random distribution of cement particles as input parameters for both M1 and M2 approaches. The elastic modulus and Poisson ratio predicted by M1 and M2 approaches were verified through the experimental data obtained from compressive tests combined with digital image correlation analysis. The elastic moduli of HCPs were significantly affected by the input C-S-H modulus, with 90% of reported C-S-H elastic moduli falling within the range of 20.25 GPa and 30.4 GPa. The predicted elastic moduli of HCPs were well-matched with experimental data when assigning the elastic modulus, bulk modulus, and shear modulus, of C-S-H, as 20.25, 12.98, and 8.17 GPa, respectively. A sensitivity analysis demonstrated a linear increase in the elastic modulus of HCPs with increase of C-S-H modulus, with correlation coefficients R² of 0.9985 and 0.9996 for HCPs with water-to-cement ratios (w/c) of 0.3 and 0.5, respectively. Additionally, the predicted results showed greater consistency at later age (after 7 d) compared to earlier stages. The integral absolute error values of the elastic moduli obtained via M1 and M2 for HCPs with w/c of 0.3 were 6.32% and 6.23%, respectively while those for HCPs with w/c of 0.5 were 4.8% and 5.67%, respectively. M1 approach is more recommended since it is straightforward with time and cost efficiency compared to M2 approach in addition to the suitable prediction accuracy.

Progress and Challenges of Ferrite Matrix Microwave Absorption Materials.

Intelligent devices, when subjected to multiple interactions, tend to generate electromagnetic pollution, which can disrupt the normal functioning of electronic components. Ferrite, which acts as a microwave-absorbing material (MAM), offers a promising strategy to overcome this issue. To further enhance the microwave absorption properties of ferrite MAM, numerous works have been conducted, including ion doping and combining with other materials. Notably, the microstructure is also key factor that affects the microwave absorption properties of ferrite-based MAM. Thus, this article provides a comprehensive overview of research progress on the influence of the microstructure on ferrite-based MAM. MAMs with sheet and layered structures are also current important research directions. For core-shell structure composites, the solid core-shell structure, hollow core-shell structure, yolk-eggshell structure, and non-spherical core-shell structure are introduced. For porous composites, the biomass porous structure and other porous structures are presented. Finally, the development trends are summarized, and prospects for the structure design and preparation of high-performance MAMs are predicted.

Informing the recruitment crisis in policing: Evaluating which incentives can entice the best candidates among college students

AbstractResearch SummaryScrutiny over the quality of police work continues to increase, at the same time that a recruitment crisis may hinder policing services. Moreover, this crisis exists despite numerous work incentives for officers, which are potentially competitive salaries, early pensions, and legal protections. Using a sample of 604 undergraduate students—a natural recruiting pool for police agencies—this study explores the predictors of students’ interest in a career in policing. In addition, we conducted a randomized survey experiment to identify the effect of work incentives on students’ willingness to apply to be a police officer upon graduation. Specifically, we manipulated the starting salary, years of service until pension eligibility, and the protection afforded against lawsuits. Finally, we tested whether the effect of these incentives differs across the quality of applicants (i.e., grade point average [GPA], ability to pass existing application criteria, and subjective qualities that comprise honesty, teamwork, and compassion) and their preexisting interest in a career in policing. We found that students are generally uninterested in becoming police officers, particularly when their GPA is high. Though the starting salary was the most impactful of all incentives, some lawsuit protection is key for enticing the best students. In contrast, conditions for pension had only modest if any effects.Policy ImplicationsRecruiting is key to improving the quality of policing, particularly when many potential candidates are overlooking the career. However, research on the causes and consequences of police recruitment strategies is limited. This study implements rigorous research methods to investigate how to increase the pool of high‐quality applicants to police agencies. Findings support sensible and potentially cost‐effective policy decisions in regard to police recruiting, which should focus on increasing the starting salary, and on more effectively communicating the value of other existing benefits of the career that comprise lawsuit protection and attractive pension plans.

Development of a fast-running method for prediction of blast propagation in partially confined spaces

In this contribution, a series of findings from Computational Fluid Dynamics (CFD) simulations of blast propagation within fully confined spaces are presented. These numerical works have been carried out as part of an ongoing in-house development towards a fast-running method to predict overpressures and impulses arising from detonations within the various configurations of carparks in Singapore. In land-scarce cities like Singapore, carparks are typically located within the same structural footprints and are integrated with other functions of the building to facilitate convenient access. Design of carparks are required to meet statutory provisions with regards to the layout, headroom clearance and safety. To this end, the present research study has adopted a three-stage approach. First, different representative configurations of carparks are determined by making reference to and rationalising based on the prevailing statutory provisions in Singapore. This is then followed by a series of parametric CFD simulations to obtain essential numerical data in order to characterise the blast propagation within the respective partially confined spaces. Finally, several regression models are employed to derive relationships between the critical parameters and the blast data, with the aim of achieving a fast-running predictive method. This paper seeks to provide detailed descriptions of the first and the second stages, as well as to present the comparisons of numerically converged solutions, which are obtained from preliminary CFD simulations using two mesh sizes, against semi-analytical solutions which are calculated based on guidance from UFC 3-340-02 for fully confined detonation as initial reference cases.

Gedimino laiškai ir pirmosios dominikonų bažnyčios Vilniuje problema

This article seeks to answer a seemingly simple question: did the Dominican church exist in Vilnius during the reign of the Lithuanian grand duke Gediminas (1316–1341)? It is mentioned in a several letters of this ruler that were produced in 1323 and, therefore, the idea that this church was a real thing received wide currency in numerous historiographical works. However, the comprehensible analysis of the contradictory information regarding this subject-matter, and the very absence of its mention in a letter addressed to the Dominicans themselves, allowed the author of this paper to advance a thesis that this church, in all probability and likelihood, did not exist at all. The fact that it was mentioned might be interpreted as an attempt by Gediminas to produce a most positive image of his (pagan) country in the eyes of the intended (Roman Christian) audience. In sum, Gediminas collaborated more closely with the Franciscans, but some Dominican friars also were present at his court in 1323. It would be extremely interesting to know whence they came. However, for the lack of conclusive evidence this question must remain unanswered.

Photocatalytic Bacterial Destruction and Mineralization by TiO2-Based Photocatalysts: A Mini Review

This work presents an overview of the reports on the bacterial cell photocatalytic destruction and mineralization process in the presence of TiO2-based photocatalysts. The presented research included experiments conducted in air and water. Numerous works confirmed that a photocatalytic process with TiO2 led to bacteria and their organic residues’ mineralization. Additionally, based on the obtained results, a possible two-stage mechanism of photocatalytic mineralization in the presence of TiO2-based materials was proposed. To help future studies, challenges of photocatalytic microorganism mineralization are also proposed. There are some aspects that need to be addressed, such as the lack of standardization of conducted research or relatively small amount of research on photocatalytic microorganism mineralization. According to our best knowledge, in the available literature, no work regarding a summary of previous research on photocatalytic bacterial mineralization process was found.

Geometrical investigation of forced convective flows over staggered arrangement of cylinders employing constructal design

The current numerical work conducted a geometrical investigation of forced convective flows over a staggered arrangement of four cylinders applying constructal design. The main objectives are to determine designs maximizing the Nusselt number (NuD) and minimizing the drag coefficient (CD) of the cylinders at three distinct Reynolds numbers (ReD = 10, 40, and 150) considering Pr = 0.71. The problem involves two constraints: cross-sectional area of the cylinders and the occupation area of the arrangement, and three degrees of freedom: ST/D, SL1/D and SL2/D. These represent the ratios between the transversal pitch, the longitudinal pitch between the frontal and intermediate cylinders, and the longitudinal pitch between the intermediate and posterior cylinders over the diameter. The introduction of two longitudinal pitches enabled an exploration of the generation of asymmetrical patterns in the flow direction. Results indicated a strong dependency of the arrangement design on the Reynolds number. Moreover, asymmetrical configurations generally benefited both performance indicators for the present conditions. The most favorable arrangements for the fluid dynamics were achieved with the lowest ST/D, more concentrated longitudinal pitches for ReD = 10, and asymmetrical pitches for ReD = 40 and 150. Concerning the thermal purpose, the highest magnitude of ST/D and asymmetrical longitudinal pitches led to the highest NuD. For ReD = 10, the intermediate cylinders are near the upstream one; for ReD = 40 the length of the arrangement increases with the intermediate cylinders near the downstream one, and for ReD = 150, the arrangement occupied all the length of occupation area with slight asymmetry.

Thermosolutal and hydromagnetic performance of radiative hybrid nanofluid in a wavy porous enclosure with a plus-shaped baffle

The objective of this article is to explore the thermosolutal transmission rates with hydromagnetic Fe3O4-H2O nanofluid and Fe3O4-Cu-H2O hybrid nanofluid flow in a partially heated wavy porous enclosure with a plus-shaped baffle. A portion of length b on the bottom border is heated and soluted uniformly, while the rest portions of the bottom wall are assumed as adiabatic. The side curved borders are considered as cold and low concentration, while the adiabatic condition is imposed in the upper flat border. A plus-shaped cold baffle is located at the geometric center of the chamber. The porous cabinet is filled with a radiative Fe3O4-H2O nanofluid and Fe3O4-Cu-H2O hybrid nanofluid. The streamfunction (ψ)- vorticity (ζ) form incorporating the energy and species transport equations of coupled Navier-Stokes governing equations are solved by an efficient compact scheme. We have validated our in-house computational code with reliable published numerical and experimental works. This work explores the impacts of various well-defined parameters such as Rayleigh number (104≤Ra≤106), Hartmann number (0≤Ha≤40), Darcy number (10−4≤Da≤10−2), buoyancy ratio (N=1), Lewis number (1≤Le≤20), radiation parameter (1≤Rd≤10), heater size (0.2≤b≤0.8), volumetric heat source/sink coefficient (−10≤Q≤10) and solid volume fraction (0.0≤ϕhnp≤0.04) of the hybrid nanofluid. We have found that for the change in the radiation parameter (Rd) from 1 to 10, energy transfer is improved by 150.67% for Fe3O4-Cu-H2O hybrid nanofluid and 149.80% for Fe3O4-H2O nanofluid whereas solutal transfer is diminished by 4.76% and 4.83%, respectively. Our result revealed that Fe3O4-Cu-H2O hybrid nanofluid is more useful than Fe3O4-H2O nanofluid in the case of double diffusion.

Formation of low-mass protostars and their circumstellar disks

Understanding circumstellar disks is of prime importance in astrophysics; however, their birth process remains poorly constrained due to observational and numerical challenges. Recent numerical works have shown that the small-scale physics, often wrapped into a sub-grid model, play a crucial role in disk formation and evolution. This calls for a combined approach in which both the protostar and circumstellar disk are studied in concert. We aim to elucidate the small-scale physics and constrain sub-grid parameters commonly chosen in the literature by resolving the star-disk interaction. We carried out a set of very high resolution 3D radiative-hydrodynamics simulations that self-consistently describe the collapse of a turbulent, dense molecular cloud core to stellar densities. We studied the birth of the protostar, the circumstellar disk, and its early evolution ($<6\ yr $ after protostellar formation). Following the second gravitational collapse, the nascent protostar quickly reaches breakup velocity and sheds its surface material, thus forming a hot ($ K $), dense, and highly flared circumstellar disk. The protostar is embedded within the disk such that material can flow without crossing any shock fronts. The circumstellar disk mass quickly exceeds that of the protostar, and its kinematics are dominated by self-gravity. Accretion onto the disk is highly anisotropic, and accretion onto the protostar mainly occurs through material that slides on the disk surface. The polar mass flux is negligible in comparison. The radiative behavior also displays a strong anisotropy, as the polar accretion shock was shown to be supercritical, whereas its equatorial counterpart is subcritical. We also find a remarkable convergence of our results with respect to initial conditions. These results reveal the structure and kinematics in the smallest spatial scales relevant to protostellar and circumstellar disk evolution. They can be used to describe accretion onto regions commonly described by sub-grid models in simulations studying larger-scale physics.

The effects on heat and oxygen transport of different heat shield and sidewall insulation designs during continuous Czochralski silicon crystal growth

Numerical work has been done to optimize the hot zone for the continuous Czochralski growth of 8-inch diameter silicon crystals using a double-crucible system. Thicker insulation layers on a high-heel-shaped heat shield and the sidewall insulation led to a reduction in the heater power of more than 40%, a decrease in the oxygen content, and a significant flattening of the growth interface. This design also allowed a stronger argon gas flow near the outer free melt surface and the quartz crucible wall, which prevented the generation of an argon gas vortex in this area. Stronger flow of argon gas would assist in moving more SiO gas and dust out of the chamber. However, the reduction in the outer melt temperature compared to the original design could slow down the melting of the silicon granules.

Гален как представитель греческой paideia эпохи Второй софистики

Thanks to the extensive corpus of Galen's writings, which includes numerous autobiographical works and individual notes, we possess a wealth of information regarding his upbringing and education. According to a fami-ly tradition, he received a classical Greek education (known as paideia), which allowed him to transition from a provincial intellectual to one of the influential figures in Roman society and achieve the status of a court physi-cian. His brilliant command of language, extensive erudition, and active participation in the intellectual life of the Roman elite justify considering Galen as one of the authors of the so-called "Second Sophistic." This article scrutinizes Galen's various accounts of his mentors, early education, and scholastic experiences, with their veracity corroborated by contemporaneous testimonials. In addition to reading and scrutinizing the classical texts that formed the cornerstone of Greek paideia, Galen's education placed great emphasis on the study of exact sciences such as Euclidean geometry and arithmetic, which, together with Aristotle's logic, enabled Galen to adhere to the evidence-based method in medicine. An analysis of Galen's citation fre-quency of classical authors revealed that his foundational education was similar to other authors of his time, whereas the citation of medical authors is unparalleled in ancient literature. Unfortunately, we can only form a vague notion of his library since much of it was lost in a fire during Galen's lifetime in 192 AD. However, his collection of texts is a mix of various knowledge, rare writings, and quotes. Galen's interest in language and words, which confirmed his status as an intellectual, suggests his association with the "Second Sophistic" group. He wrote several works on ancient grammar, word usage, and rhetoric, criticiz-ing both extreme linguistic purism and loose interpretations of old-fashioned Attic language. This paints Galen not just as a doctor but also as a knowledgeable figure of his time.

The role of pre-onset hair hormone in predicting the prognosis of patients with severe pneumonia and acute COVID-19 outbreak

Numerous research works have investigated the potential impact of endocrine hormones on the severity of COVID-19-related pneumonia in individuals. However, there are few studies on the effect of pre-onset neuroendocrine hormones on the prognosis of COVID-19 patients. This study looked into the prognostic value of pre-onset hair hormone levels in COVID-19 infected individuals. This study included 27 patients with COVID-19 and collected patient information and laboratory indicators. The hormone levels in hair were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Within 28 days, 63 % of the patients in this study passed away. With 28-day mortality as the outcome index, urea nitrogen, CURB-65 score and pneumonia severity score (PSI) of 2 groups were statistically significant (P < 0.05). Among all hormone levels detected in hair, only progesterone level was substantially correlated negatively with COVID-19 patients' 28-day mortality(P < 0.05). The level of progesterone in hair was substantially adversely connected with the death rate at 28 days of COVID-19 patients, according to correlation and logistic regression analysis(P < 0.05). Among patients with COVID-19 pneumonia, hair progesterone levels were strongly associated with 28-day mortality, which emphasizes hair progesterone's importance as a prognostic factor.

Microfinance: A bibliometric exploration of the knowledge landscape

Microfinance has gained significant attention as a social innovation, offering flexible and low-cost financial services to households who are otherwise excluded from formal financial services. Over the years, numerous research works have expanded the knowledge base of microfinance. Applying bibliometrics, we summarise findings from 1599 articles published between 1987 and 2022. Our performance analysis reveals insights into the research trend, including its geographical distribution, the theories under examination, and the most influential publications. More importantly, the knowledge foundation and thematic analysis categorize microfinance research into three broad themes, viz. impact of microfinance, management of microfinance and performance and efficiency of microfinance. Furthermore, we trace the evolution of various research topics and forecast future trends using periodical average publication years over time. This study, therefore, serves as a valuable reference in microfinance research both for new researchers and seasoned academics, as well as policymakers, providing insights into research trends, seminal works, and future directions.

The dynamics of champagne cork popping revisited through high-speed schlieren imaging and computational fluid dynamics simulations

Cork popping represents a rich and complex fluid dynamics process, involving up to three phases (liquid, gas, and solid), three main chemical compounds (ethanol, water, CO2), and a moving cork gradually opening the bottle and blocking the fast progression of the expanding gas. In this work, we used high-speed, high-sensitivity schlieren imaging setups to provide a fresh perspective on this dynamical phenomenon. Our experimental results are systematically compared and interpreted on the basis of new computational fluid dynamics simulations. Our combined experimental and numerical works confirm the establishment of two supersonic expansions during cork popping from a champagne bottle.

EU regulations on reporting sustainable development as a determinant of limiting the environmental pressure of chemical enterprises in Poland

The period of validity of Directive 2014/95/EU, which imposed on enterprises the obligation to present non-financial information in separate non-financial reports, the so-called ESG was aimed to check its effects, complementary regulations and actual actions in the environmental area. Numerous works have analysed various aspects of non-financial reporting in the context of the directive, including several on ESG reporting in relation to air pollution emissions. However, it has not been examined yet whether there is a relationship between the level of reporting and the effects of pro-environmental activities in the context of the impact of regulations on it. A research gap in this area was identified, and therefore, the aim of the paper is to examine how selected chemical companies in Poland adapt to the EU guidelines on ESG reporting in the environmental dimension and whether it has an impact on reducing their pressure on the environment. The research period is 2010-2022, and the three-stage study used a quantitative-qualitative methodological approach. In the first and third stages, descriptive statistics and time series analysis methods were used. The second one includes methods such as content analysis, case analysis, GES Risk Rating, and expert analysis. The research carried out made it possible to conclude on the impact of non-financial reporting regulations on the environmental pressure.