Boundary Restrictions Research Articles

Impact of convective tip condition on the transient thermal behavior of wet porous convective radiative exponential profiled inclined longitudinal fin structures subject to heat generation

AbstractA convective‐radiative fully wet porous inclined longitudinal fin of exponential profile is the focus of the current work. The thermal behavior of the fin under unsteady conditions has been analyzed for adiabatic and convective boundary conditions. The exponential fin and its counterpart inverted exponential fin are simultaneously investigated by considering temperature‐relevant thermal conductivity and heat generation. The modeled governing equation upon nondimensionalization reduces to a partial differential equation which is computed by employing the finite difference approach. The impact of relevant parameters like the convective parameter, radiative parameter, wet porous parameter, dimensionless time, exponential index, dimensionless ambient temperature, generation number, thermal conductivity parameter, and angle of inclination on thermal characteristics of exponential and inverted exponential fin structures with adiabatic and convective boundary restrictions have been examined. One of the main outcomes was that the inverted exponential fin with an adiabatic tip gives rise to the highest thermal curve, and the tapered exponential fin with a convective tip resulted in the lowest thermal curve.

Associations among Historical Neighborhood Disinvestment, Hazardous Air Pollutants, and Current Adult Asthma Prevalence

Associations among Historical Neighborhood Disinvestment, Hazardous Air Pollutants, and Current Adult Asthma Prevalence

The Research on the Social Media Addiction and Mental Disorders

Along with the rapid development of media technology, social media has become an indispensable part of human life. Social media enables the spread of information that exceeds the restriction of physical and temporal boundaries. While enhancing the convenience and connectedness of human beings, social media, to some extent, grievously affects people’s internal well-being. The widespread use of media platforms leads to social media addiction, especially among the young generation.This article takes teenagers as the research object, and uses the literature reading method to explore the causes and consequences of social media addiction. According to the research results, the reason about social media additions includes biological reasons, psychological reasons and social reasons. Consequences of social media addition among young generations include the shape of toxic beauty standards, body shaming, beauty and eating disorders. Social media has created a platform where people share only the positive part of themselves; peer pressure has formed under these circumstances. Adolescents are predominantly the victims of mainstream beauty standards. Body shaming and eating disorders are the representative psychological impacts due to the dissatisfaction with one's physical characteristics and the desire to be more "beautiful".

Anatomical Step-by-Step Dissection of Midline Suboccipital Approaches to the Fourth Ventricle for Trainees: Surgical Anatomy of the Telovelar, Transvermian, and Superior Transvelar Routes, Surgical Principles, and Illustrative Cases.

Introduction Safe, effective access to the fourth ventricle for oncologic resection remains challenging given the depth of location, restricted posterior fossa boundaries, and surrounding eloquent neuroanatomy. Despite description in the literature, a practical step-by step dissection guide of the suboccipital approaches to the fourth ventricle targeted to all training levels is lacking. Methods Two formalin-fixed, latex-injected specimens were dissected under microscopic magnification and endoscopic visualization. Dissections of the telovelar, transvermian, and supracerebellar infratentorial-superior transvelar approaches were performed by one neurosurgery resident (D.D.D.), under guidance of senior authors. The dissections were supplemented with representative clinical cases to highlight pertinent surgical principles. Results The telovelar and transvermian corridors afford excellent access to the caudal two-thirds of the fourth ventricle with the former approach offering expanded access to the lateral recess, foramen of Luschka, adjacent skull base, and cerebellopontine angle. The supracerebellar infratentorial-superior transvelar approach reaches the rostral third of the fourth ventricle, the cerebral aqueduct, and dorsal mesencephalon. Key steps described include positioning and skin incision, myofascial dissection, burr hole and craniotomy, durotomy, the aforementioned transventricular routes, and identification of relevant skull base landmarks. Conclusion The midline suboccipital craniotomy represents a foundational cranial approach, particularly for lesions involving the fourth ventricle. Operatively oriented resources that combine stepwise neuroanatomic dissections with representative cases provide a crucial foundation for neurosurgical training. We present a comprehensive guide for trainees in the surgical anatomy laboratory to optimize familiarity with fourth ventricle approaches, mastery of relevant microsurgical anatomy, and simultaneous preparation for learning in the operating room.

A free boundary problem for a flexible loan based on the borrower asset

In this paper, a restricted free boundary problem model for the remaining loan value under a flexible repayment method is proposed. The model is formulated as a weak coupling problem between parabolic variational inequality and partial differential equation. The existence and uniqueness of the solution are obtained. Some properties of the free boundary, such as boundedness, monotonicity and smoothness, are also studied. Especially, the relationship between the free boundary and its lower bound threshold is discussed. As the expected clear off time of the loan cannot be analytically expressed, numerical calculation is shown. Some numerical results for the free boundary are also presented.

Classification via Structure-Preserved Hypergraph Convolution Network for Hyperspectral Image

Graph convolutional network (GCN) as a combination of deep learning and graph learning has gained increasing attention in hyperspectral image (HSI) classification. However, most GCN methods consider the simple point-to-point structure between two pixels rather than the high-order structure of multiple pixels, which is contradict with the real feature distribution of ground object. And the nonlinear property of HSI also brings challenge for precise structural representation in GCN. To tackle these problems, this work proposes a structure preserved hypergraph convolution network (SPHGCN). It first builds a multiple neighborhood reconstruction (MNR) model to reveal the essential resemblance of multiple pixels in nonlinear spectral feature space. With the high-order structure, SPHGCN designs the hypergraph convolution operation for irregular feature aggregation among similar pixels from different regions, which achieves more discriminative features from multiple pixel nodes. Meanwhile, a structure preservation layer is built to optimize the distribution of convolutional features under the guidance of high-order structure. Moreover, SPHGCN integrates local regular convolution and irregular hypergraph convolution to learn the structured semantic feature of HSI. This strategy breaks the boundary restriction in traditional convolution and aggregates semantic feature across different image patches. Experiments on three HSI data sets indicate that SPHGCN outperforms a few state-of-the-art methods for HSI classification.

Experimental study on the law of transitional gas flow in porous media

There are many nanoscale pores in deep low permeability coal seams. The flow of coalbed methane (gas) in nanoscale pores belongs to the gas flow in porous media with medium and high Knudsen numbers. Its flow mechanism is one of the key unsolved scientific problems. In order to explore the gas transport law in nanopores of coal, a gas transport model based on microscopic boundary restriction was adopted to describe the gas flow law, and its rationality was verified by experimental data. The Field Emission Scanning Electron Microscope was used to scan the nanopores of customized anodized aluminum membrane. Then, the Maximally Stable Extremal Regions (MSER) algorithm of MATLAB and binarization algorithm were employed to quantify the pore structure parameters (equivalent pore size and porosity) of the membrane nanoscale pores. Finally, PMI micro-flow permeability tester was used to carry out different rarefied degree gas penetration experiments through anodized aluminum membranes, and the adopted gas transport model was verified. The results show that the binarization method is more accurate to characterize sample whose theoretical pore sizes are 20–35 nm, while MSER characterizes samples whose theoretical pore sizes are 110–150 nm and 200–300 nm more accurately. In other words, binarization method is more accurate for characterizing mesopores, while MSER algorithm is more accurate for macropores. The results have important reference value for more accurate extraction of nanopore parameters of porous media. Compared with traditional gas transport model, the adopted model considering the microscopic boundary restriction in this paper is closer to the experimental results. Moreover, it is suitable for describing the gas flow law in multiscale nanopores. The study provided important guiding significance for ascertaining the gas migration law in low permeability coal seam, improving the prediction accuracy of gas extraction and taking effective measures to increase production. The research results can further enrich the theoretical system of gas transport in coal, which is conducive to the efficient gas extraction, and is of great significance to promote the realization of carbon peak and carbon neutrality.

Numerical investigation on origin and evolution of polygonal cracks on rock surfaces

We studied the formation and evolution mechanism of polygonal cracks on rock surfaces under cooling by modelling meso-damage mechanics, continuum mechanics and thermodynamics. Factors that affect rock surface damage include ambient temperature, lithology difference and boundary restrictions. We established and simulated a heterogeneous model with a surface weak layer for three types of boundaries. These were biaxial constraint, uniaxial constraint and free boundary. The initiation and propagation of polygonal cracks were reproduced for varying thickness and homogeneity of the weak layer. The results show that the boundary constraints strongly influence the polygonal cracking. Many polygonal or parallel cracks are generated on the rock surface under biaxial or uniaxial constraint. The unconstrained rock surface displays polygonal cracks at the center and parallel cracks in the surrounding areas. The thicker the surface weak layer, the larger the average area of formed blocks. Small blocks and short cracks are more numerous than large blocks and long cracks. As the heterogeneity index increases, the rock layer is more likely to produce blocks with relatively regular shapes. Quadrilateral, pentagonal and hexagonal blocks dominate regardless of changes in layer thickness and heterogeneity. However, the number of edges of the polygonal blocks is sensitive to rock heterogeneity. The polygons tend to become more complex with increasing inhomogeneity. This study contributes to understanding the complex formation mechanisms of polygonal cracks on rock surfaces in nature. Additionally, the simulations of three-dimensional fracture geometry provide a basis for developing algorithms to generate discrete fractures and blocks in discrete fracture network (DFN) analyses.

Analysis of periodic magnetohydrodynamics effects on triple diffusive nonlinear mixed convective flow of Eyring–Powell nanoliquid

AbstractThe article spotlights aspects of the triply diffusive mixed convective flow of Eyring–Powell nanoliquid over a vertical plate. A periodic magnetic field with nonlinear convection is exhibited. The governing partial differential equations (PDEs) with boundary restrictions are the case paradigm transformed into a non‐dimensional system by feasible non‐similar transformations. The quasilinearization technique combined with an implicit finite difference scheme is used for numerical simulation, resulting in a block‐tridiagonal matrix form. Furthermore, a system of algebraic linear equations has been solved through Varga's algorithm. The numerical outcomes are correlated with various physical parameters graphically. The variations in the nonlinear mixed convection parameter and Powell–Eyring liquid parameter raise the skin friction coefficient more than a Newtonian fluid. In a periodic magnetic field, the fluid temperature rises and drops in the corresponding energy transfer rate. Also, wavy variations have been observed because of oscillatory magnetic fields. The current study can find its potential applications in medical, engineering and industrial developments, including polymer sheet manufacture, medicine cover coating, fibre production, crystal growth, heat exchangers and metal extrusion.

BNT‐based relaxor/ferroelectric systems: Improved field‐induced strain property in the layered composite ceramics

AbstractBoth high strain and low driving electric‐field are important characteristics of the piezoelectric actuators for industrial applications, but they are difficult to achieve together in a single material system. In this work, the layered and inlay‐onlay structures of relaxor/ferroelectric composites were prepared by selecting relaxor phase (0.94Bi0.5(Na0.82K0.18)0.5TiO3‐0.06NaNbO3, BNKT‐6NN) and ferroelectric phase (0.9Bi0.5Na0.5TiO3‐0.1Bi0.2Sr0.7TiO3, BNT‐10BST) with the volume ratio of 1:1. By comparing the field‐induced strains under same electric‐field, the S33 of the BNKT‐6NN/BNT‐10BST layered composites (0.17%) was greater than that of the inlay‐onlay composites (0.08%) and exhibited excellent temperature stability. The superiority in field‐induced strain for the layered composite ceramic was originated from the inhomogeneous distribution of internal electric‐field between relaxor and ferroelectric phase and thereby could modulate the polar nanoregions to ferroelectric phase transition. In addition, the restricted phase boundary between relaxor and ferroelectric phase enhanced the potential barrier energy (Ea = 1.47 eV) and hindered the jump of defective ions (mainly oxygen vacancies) of the BNKT‐6NN/BNT‐10BST layered composites. The outstanding electrical properties of layered composite ceramics provide a new idea for further improving field‐induced strain performance.

Predictors of successful cardioversion of recent-onset atrial fibrillation to sinus rhythm with orally inhaled flecainide

Abstract Background Height, weight, and body mass index (BMI) are well established risk factors for atrial fibrillation (AF) but whether they are also predictors of successful pharmacological cardioversion of AF is unknown. Data from the open-label INSTANT study of flecainide acetate oral inhalation solution (FlecIH) for acute cardioversion of recent-onset symptomatic AF were examined to determine if these anthropometric measures are predictors of successful cardioversion of AF to sinus rhythm (SR) with FlecIH. Methods Logistic regression was performed on a broad array of patient and disease characteristics to identify predictors of cardioversion success at 90 minutes post-dose, and potential interactions were examined by boundary restriction analysis. Data are presented for patients receiving 120 mg FlecIH. Results Data from 81 patients (32.1% female) with a mean age of 59.8 years (range: 26.0, 84.0) were included in the analysis. This cohort had a mean weight of 87 kg (range: 57, 150), a mean height of 180 cm (range: 156, 199), and a mean BMI of 26.8 kg/m2 (range: 17.2, 37.9). A logistic regression model identified height, weight, and BMI as significant predictors of cardioversion success (p<0.01) and a boundary restriction analysis revealed a negative correlation between BMI and conversion rate across the entire dataset (see Figure 1). Clinically significant conversion rates were observed for patients with BMI values that were considered normal (BMI <25 kg/m2 = 53%; 95% CI: 36, 70), overweight (BMI ≥25 and <30 kg/m2 = 47%; 95% CI: 29, 64), and obese (BMI ≥30 and <35 kg/m2 = 43%; 95% CI: 17, 69); however, none of the severely obese patients (BMI ≥35 mg/m2) had their AF successfully converted to sinus rhythm (see Figure 2). Conclusions Successful cardioversion of recent onset AF with 120 mg FlecIH was observed in normal, overweight, and obese patients with BMI values <35 kg/m2; however, conversion rate decreases with increasing BMI. Further evaluation of FlecIH dosing in severely obese patients is warranted. Funding Acknowledgement Type of funding sources: Private company. Main funding source(s): InCarda Therapeutics

Inverter prototype development for HLFC compressor applications

A key component in Hybrid Laminar Flow Control (HLFC) is a turbo-compressor, which requires an inverter. However, a harsh environment in combination with restrictive boundary conditions make the inverter design very challenging. Moreover, aviation certification standards have to be considered. By reason of its growing significance, a Model-Based Systems Engineering (MBSE) approach is described to break the HLFC system requirements down to the lower level of the inverter. Using the acquired set of requirements, the design of an inverter prototype was initiated. For this, the compressor motor, a Permanent Magnet Synchronous Motor (PMSM) running up to 150,000 text {min}^{text {-1}} at a power of more than 5 kW, was characterized by measurements. Thereafter, a control concept was elaborated and implemented on a preliminary electronics. In the end, feasibility tests were conducted on a testbed, whose results match well with the theory.

Enhanced Stark effect in Dirac materials

The Stark effect in confined geometries is sensitive to boundary conditions. The vanishing wave function required on the boundary of nanostructures described by the infinite-barrier Schrödinger equation means that such states are only weakly polarizable. In contrast, materials described by the Dirac equation are characterized by much less restrictive boundary conditions. Focusing on honeycomb-lattice armchair nanoribbons, we demonstrate an enhancement by more than an order of magnitude. This result follows from an exact Dirac polarizability valid for arbitrary mass, momentum and ribbon width. Moreover, an exact expression for the frequency-dependent dynamic polarizability has been derived. Our analytic Dirac results have been validated by comparison to numerical results from atomistic models.

Higher-derivative field redefinitions in the presence of boundary

Recently it has been proposed that the consistency with T-duality requires the effective action of string theory at order alpha '^n to satisfy the least action principle provided that the values of the massless fields and their derivatives up to order n are known on the boundary. In this paper we speculate that this boundary condition constrains the field redefinitions and the corrections to the T-duality transformations in the presence of boundary, e.g., at order alpha ', the metric does not change, and all other massless fields should change to include only the first derivative of the massless fields. Using the above restricted field redefinitions, we write all gauge invariant bulk and boundary couplings in the bosonic string theory at order alpha ' in a minimal scheme. Then using the assumption that the effective action of string theory at the critical dimension is background independent, we fix the coefficients of the tree-level gauge invariant couplings by imposing O(1, 1) symmetry when the background has a circle and by imposing O(d, d) symmetry when the background has T^d. These constraints fix the bulk action up to an overall factor, and the boundary action up to two parameters. By requiring the gravity couplings in the boundary action to be consistent with those in the Chern-Simons gravity, the two boundary parameters are also fixed. Up to a restricted field redefinition, the bulk and boundary couplings are exactly those in the K.A. Meissner action and its corresponding boundary action.

RSSI Zigbee based prisoner break monitoring and alerting system

This paper deals with the main objective of tracking the prisoner movement inside a restricted boundary. The above mention objective is achieved with the help of GPS and RSSI. The precise location of the prisoner can be traced by the authorities at anytime and anywhere with the help of IoT devices. If any movement of prisoner is noticed by the IoT device through RSSI, it measures the signal strength. If the signal strength measured are within the permissible limit no action is taken, if it exceeds the permissible limit appropriate action is taken either making an alarm or activating the vibration sensor through Arduino Controller

Par-delà le sang et la guerre : les enjeux de la conceptualisation diplomatique de l’Alliance franco-écossaise au Moyen Âge

The history of the relationship between France and Scotland is deeply rooted in the unstable context of late medieval Europe. First drafted in the late 13th century, the yet-to-be Auld Alliance” was to stand for several centuries. Its heritage, overshadowed either by sentimentalism or harsh criticism, is still a matter for debate. This study aims at exploring this narrative and at pushing beyond the usual and restrictive boundaries of traditional warfare. By looking at the diplomatic sources that initially defined and shaped the Alliance, it appears that the Franco-Scottish league was serving more than one purpose, that its military aspects were inherently limited, and that its main ambition was probably not to crush the English might on conventional battlefields. The Alliance was built and promoted in the name of peace, as a public and international display of mutual love between Christian princes, involving their peoples and realms in the process. The Alliance proved to be a powerful tool of legitimacy for the kings of France and Scotland, as well as a political and highly symbolic apparatus aimed at mutually reinforcing the rightful stance of the allies against the cruel and ungodly claims of the English kings.

Thermal performance of unsteady mixed convective Ag/MgO nanohybrid flow near the stagnation point domain of a spinning sphere

Mixed convective flow over a revolving sphere is of immense interest in several industrial and engineering applications starting from polymer deposition, electrolysis management, drug transport, spin-stabilized missiles, cooling of spinning machinery slices, etc. Hybrid nanofluid exhibits promising efficiency in heat transport compared to mono nanofluid. They are widely introduced in nuclear power plants, solar collectors, heat exchangers, microfluidic heat sinks, etc. Such unique promising applicative features drive this investigation to analyse the magnetized mixed convective unsteady Ag/MgO-water hybrid nanofluid stream over a whirling sphere near the stagnation zone. Moreover, the nanofluid motion is treated as thermally radiative. The foremost flow profiles are made dimensionless using appropriate similarity translation. The renovated equations associated with the boundary restrictions are treated numerically. Several schematics are extracted to reconnoiter the requisite noteworthy influence of flow parameters on thermal, velocity, heat transport, and skin frictional profiles. Consequences indicate the increase in x-direction velocity for the unsteadiness parameter and mono nanofluid exhibits higher velocity compared to hybrid nanofluid, while the reverse is detected for z-direction velocity. Thermal enhancement is assured for radiation parameters and nanoparticle concentration, where hybrid nanofluid illustrates a higher magnitude. Heat transport is also higher for hybrid nanofluid compared to the usual nanofluid.

Improving coarse-grained models of protein folding through weighting of polar-polar/hydrophobic-hydrophobic interactions into crowded spaces.

Herein were tested 7 hydrophobic-polar sequences in two types of 2D-square space lattices, homogeneous and correlated, the latter simulating molecular crowding included as a geometric boundary restriction. Optimization of 2D structures was carried out using a variant of Dill's model, inspired by convex function, taking into account both hydrophobic (Dill's model) and polar interactions, including more structural information to reach better folding solutions. While using correlated networks, degrees of freedom in the folding of sequences were limited; as a result in all cases, more successful structural trials were found in comparison to a homogeneous lattice. The majority of employed sequences were designed by our workgroup, two of them were folded with other approaches, and another is a modified version of a previous sequence, initial forms of the other two have been employed but without taking into account polar-polar contributions. Three of them are newly proposed, intended to test the conjoint hydrophobic-hydrophobic and polar-polar contributions in crowded spaces. One sequence turned out to be the most difficult of the seven folded, this perhaps due to intrinsic (i) degrees of freedom and (ii) motifs of the expected 2D HP structure. Meanwhile two-sequence, although optimal folding was not achieved for neither of the two approaches, folding with correlated network approach not only produced better results than homogeneous space, but for them the best values found with crowding were very close to the expected optimal fitness. In general, five sequences were better folded with medium lattice units for correlated media; instead, another two sequences were better folded with a bit larger degree of lattice unit, revealing that depending on the degrees of freedom and particular folding, motifs in each sequence would require tuned crowding to achieve better folding. Therefore, the main goal herein was to obtain a modified 2D HP lattice model to mimic folding of proteins or secondary structures, like β-sheets, taking into account both hydrophobic-hydrophobic and polar-polar interactions, and fold them in a crowded environment. This simple but enough construction would be conducted to determine the needed information to fold sequences in a sort of a minimal but complete heuristic model. Finally, we claim that all folded sequences into crowded spaces achieve better results than homogeneous ones.

Experimental correlation of thermal conductivity with dielectric properties of wood and wood-based materials: Possibilities for rapid in-situ building energy evaluation

In-situ measurement of thermal transmittance properties of building envelopes is important yet remains elusive. Several studies have pointed to the discrepancy between assumed and actual thermal transmittance of building envelope components; however, the measurement is not usually carried out because the available methods are time-consuming and have restrictive boundary conditions. Nonetheless, this measurement is crucial as it is a key predictor of building performance and energy consumption. This paper proposes an approach to predict thermal conductivity using dielectric properties. The objective of our study is to find a correlation between thermal conductivity and dielectric properties of wood and wood-based materials with the intent of facilitating in-situ measurement of thermal transmittance properties of building envelopes in the future. These two material properties are each proportional to the density of the medium, thereby making any interrelationship highly likely. To verify this correlation, 30 solid wood and 17 wood-based materials were tested. The coefficient of determination between thermal conductivity and relative dielectric constant for the aggregate was found to be 0.87, which is stronger than its correlation with density. 72% of the data points were found to be within 10% of the regression line, revealing the strength of the correlation. Both wood and wood-based materials were found to fall within the same regression line. This correlation is the first step towards inferring thermal transmittance of wood-based materials using devices that can quickly measure dielectric properties. Future studies are needed to determine whether this correlation persists for insulations and wall assemblies.

Influence of geometry constraint in finite space on impact resistance of shear thickening fluid

The shear thickening area formed by impact load and the restriction boundary conditions play an important role in the impact resistance and energy absorption characteristics of the shear thickening fluid (STF). In order to reveal the low speed impact resistance of STF under finite space constraints, this paper carried out research through the preparation of STF, viscosity test and design of low speed drop weight impact experiment. Firstly, STF samples with different mass fractions were prepared by self-made. Then, the rheological tests were implemented to obtain the characteristics of STF viscosity under different shear rate loads. Next, a straightforward test through rapidly pulling the glass rod out of the STF was adopted to observe the shear thickening mechanism of STF. After that, two kinds of STF samples with different mass fractions and good shear thickening performance were selected for low speed drop weight test. In the drop weight test, three containers with different geometries were designed to equivalent the finite space constraints to reveal the low speed impact resistance of STF under finite space constraints. Finally, combined with the experimental results, a series of numerical models are established to study the influence of geometric parameters in finite space on the impact resistance of STF. Through the research of this paper, the influence of geometry constraint in finite space on impact resistance of STF was obtained, which can provide reference for the geometric design of protective structure filled with STF.