Type Boundary Research Articles

Functional division and age differences in cervical spine of males and females

Introduction. The cervical spine from osteopathy point of view, taking into account spine functional division, includes vertebrae of the cervical-thoracic junction, and the approach requires additional coordination. The X-ray examination experience with the entire spine integrity suggests that both cervical vertebrae and vertebrae of cervical-thoracic junction are the place of the greatest age-related changes. The study of gender difference in cervical spine vertebra positions and its age-related dynamics requires additional attention. The purpose of the work: on the basis of digital radiographs to develop an integral indicator for assessing the position of the vertebrae of the middle cervical spine; research objectives: to quantify vertebra positions from CIII–VI; to propose a characteristic of transition smoothness from vertebral CIII–VI group to the vertebral CVII–TIII group; to study the male/female features of age trend in cervical spine shape.Materials and methods. Radiographs of all spine parts in sagittal plane were examined for 141 patients with dorsopathies (57 males and 84 females). The cohort of patients is divided into 4 groups: I (n=31) — 21–44 years (average age 33,1 years); II (n=39) — 45–59 years (average age 52,6 years); III (n=50) — 60–74 years (average age 66,8 years); IV (n=21) — 75–88 years (average age 81,1 years). A single digital X-ray spine image in sagittal plane was obtained for each patient. On the combined digital radiograph, the occipital vertical was drawn along all spine parts, starting from the external tubercle of occipital bone, and anteroposterior axes for CIII–TIII vertebrae (r axes) were drawn. The angles between the occipital vertical and the perpendiculars restored to the axes at the points of their intersection with the occipital vertical were measured. Statistical processing of the data obtained was carried out.Results. The St integral indicator has been developed to quantify the vertebra position of middle cervical spine. It was calculated by formula St = (rCIII+rCIV+rCV +rCVI)/4. Using St the type boundaries are determined, and four displacement types for the cervical vertebra group (from CIII–VI) are identifi ed: I — low start; II — medium start; III — high start; IV — ultra-high start. An age-related trend of changes in CIII–VI vertebra position was detected. The correlation between the position indicator St of the middle cervical vertebrae and indicator ArCT for the vertebrae of cervical-thoracic junction CVII–TIII was proved. Gender differences depending on age were revealed in transition smoothness between these spine parts.Conclusion. Some arguments have been obtained confi rming the validity of attributing the vertebra group of cervical-thoracic junction from CVII to TIII to the functional unity of cervical spine. Quantitative smoothness assessment of transition from the middle cervical spine to the vertebra group of cervical-thoracic junction can be carried out by calculating the difference between the ArCT and St indicators. The difference demonstrates age-related shape features of the spine part for males and females.

A general electroelastic analysis of piezoelectric shells based on levy-type solution and eigenvalue-eigenvector method

Eigenvalue-Eigenvector approach as well as Levy type solution are used for electroelastic analysis of a doubly curved shell made of piezoelectric material based on a shear deformable model and piezoelasticity relations. The electroelastic governing equations are derived using virtual work principle. The solution is proposed for a Levy type boundary conditions with two simply-supported boundary conditions and two clamped ones. After derivation of the governing equations, a solution satisfying two simply supported boundary conditions is assumed to arrive a system of ordinary differential equations. The latest governing equations are solved using Eigenvalue-Eigenvector method to satisfy clamped-clamped boundary conditions. The distribution of displacements, rotations, electric potential, strain and stress is presented along the planar coordinate. Accuracy of the proposed solution is justified through comparison with results of previous papers.

Effect of Twin Spacing and Loading Mode on Mechanical Properties and Deformation Mechanism of NiCoAl Columnar Polycrystalline Alloy

Grain boundary engineering is an effective and feasible metal strengthening strategy to enhance the properties of nanopolycrystalline alloys by changing the number, configuration, and connectivity of different types of grain boundaries, especially for the twin boundaries. In the present contribution, the effect of twin spacing and loading mode on the deformation behavior and mechanism of NiCoAl columnar polycrystalline alloy is investigated. The results show that the nanotwins can not only increase the bearing capacity of dislocations but also emit many dislocations, resulting in the coupling effect of dislocation strengthening and twin strengthening. When the twin spacing is large, intrinsic stacking faults occur and gradually transform into deformation twins. In this stage, Shockley partial dislocation controls plastic deformation. When the twin spacing is small, the high‐density twin layers and stacking faults are more likely to interweave, showing a combination action of Shockley partial dislocation and stair‐rod dislocation. With the loading changing to Z axis, the yield strength decreases due to reduced resistance to the dislocation and a weakened number of Shockley partial dislocations of the emission, leading to less strengthening of the twins. The insights provide a solid theoretical foundation for the further application of NiCoAl in industrial production.

Effects of Boundary Conditions on Performance Prediction of Deep-Buried Ground Heat Exchangers for Geothermal Energy Utilization

An accurate prediction for deep-buried ground heat exchangers (DBGHEs) is the premise for efficient utilization of geothermal energy. Due to the complexity of the geological composition spanning thousands of meters, the configuration of boundary conditions plays a critical role in evaluating DBGHE thermal performance. This paper proposed a three-dimensional model of full-scale DBGHE involving both conductive and convective heat transfer in aquifuge and aquifer layers. The constant inlet temperature and constant heating power boundaries in the DBGHE domain, and the surface–bottom temperature and heat flux boundaries in the rock-soil domain were examined. It was found that the differences in the performance prediction caused by different DBGHE boundary conditions were closely related to the system’s operating time. The relative differences in heat extraction amount and average borehole temperature of 2000 m DBGHE caused by the two inlet boundaries on the 30th day were, respectively, 19.5% and 18.3%, while these differences on the 120th day were decreased to 8.4% and 9.9%, respectively. It was found that the constant inlet temperature boundary was more appropriate than the constant heating power condition for estimating aquifer effects on the performance of DBGHE. For the rock-soil domain, the results showed that the heat extraction amount of DBGHE under the heat flux boundary was 12.6%–13.6% higher than that under the surface–bottom temperature boundary. Particularly, when considering the velocity change of groundwater in the aquifer, the relative difference in heat extraction amount increments caused by the two types of rock-soil boundaries can reach 26.6% on the 120th day. It was also found that the thermal influence radius at the end of a heating season was hardly affected by either the DBGHE inlet or rock-soil domain boundary conditions.

아트헤어의 다각적 표현을 위한 엑소노메트릭 연구

This study intends to explore masterpieces which are characteristic concerning ancient Greek and Roman mythologies and to analyze the underlying meanings behind the allergories of the Gods and Goddesses of Mount Olympus. With the help of computer graphics and 2D Axonometric projection, this study to realize the devised hair artwork by drawing inspiration form the assessed allegories. The significance of computer graphics id that they can be used to create pieces whose expression by hand is simply impossible and try different types of expressions with various new expressive techniques that may be employed in the Beauty sector. Digital beauty design utilizing Photo-shop may empower all specialists of the beauty industry to develop their work if the innumerable possibilities and benefits which may be represented through Photo- shop are employed.This demonstrates that manifold and also nuanced approaches in general may be applied to Art hair through employing different tools, making it simple to adapt and change patterns. Graphic approaches that surpass the boundaries of realistic types of expression. especially, can be used to produce visually creative works in the realm of Beauty Art, indicating their versatility.

Fracture strength and failure mechanism of graphene-containing grain boundaries and pores

Grain boundaries and pores commonly manifest in graphene sheets during experimental preparation. Additionally, pores have been intentionally incorporated into graphene to fulfill specific functions for various applications. However, how does the simultaneous presence of pores and grain boundaries impact the mechanical properties of graphene? This paper establishes uniaxial tension models of single-layer graphene-containing pores and three types of experimentally observed. The effect of interaction between pores and grain boundaries on the fracture strength of graphene was studied respectively for three types of grain boundaries by employing molecular dynamics simulations and considering factors such as pore size, the distance between pores and grain boundaries, and loading angle. A competitive mechanism between the intrinsic strength of pristine graphene with grain boundaries (referred to as pristine GGBs), which varies with the loading angle and the fracture strength of graphene sheets with pores that changes with the size of the pores, governs the fracture strength and failure modes of GGBs with pores. When the former exceeds the latter, the fracture strength of GGBs with pores primarily depends on the size of the pores, and fractures occur at the edges of the pores. Conversely, when the former is lower, the fracture strength of GGBs with pores relies on the loading angle and the distance between pores and grain boundaries, leading to grain boundary rupture. If the two strengths are comparable, the failure modes are influenced by the distance between pores and grain boundaries as well as the loading angle. The findings further elucidate the impact of coexisting grain boundaries and pores on the fracture behavior of graphene, providing valuable guidance for the precise design of graphene-based devices in the future.

Extending the admissible control-loop delays for the inverted pendulum by fractional-order proportional-derivative controller

Stabilization of the inverted pendulum by fractional-order proportional-derivative (PD) feedback with two delays is investigated. This feedback law is obtained as a combination of PD feedback with two delays and fractional-order PD feedback with a single delay. Different types of stabilizability boundaries and the corresponding geometric and multiplicity conditions are determined using the D-subdivision method. The stabilizable region is depicted in the plane of the delay parameters for given fractional derivative orders. Several special cases and the concept of delay detuning are also discussed. It is shown that the admissible delay can be slightly increased compared to the integer-order PD feedback by introducing a fractional-order feedback term.

Effect of hydrogen-vacancy cluster on the tensile strength of alpha-titanium twin boundaries: A first-principles investigation

This study investigated the formation of hydrogen-vacancy cluster at twin boundaries (TBs) in alpha-titanium and their impact on TB strength. Using first-principles calculations, it is found that a single vacancy (VA) on the {10−12} TB plane can trap up to five hydrogen atoms, while the single VA on the {10−11} TB plane can accommodate up to eight hydrogen atoms. The presence of VA weakens TBs by reducing the number of Ti-Ti bonds near the TBs. However, in the {10−12} TB with VAH5, the enhancement effect of Ti-H-Ti bonds dominates over the weakening effect of electron transfer, resulting in a slight increase in tensile strength compared to {10−12} TB with VA. On the other hand, in the {10−11} TB with VAH8, the weakening effect of electron transfer dominates, leading to a further reduction in tensile strength relative to {10−11} TB with VA. Therefore, the effect of hydrogen-vacancy cluster on the strength of twin boundaries is sensitive to the type of twin boundary. These findings provide valuable insights into the role of hydrogen in the embrittlement of alpha-titanium.

De Sitter space, extremal surfaces, and time entanglement

We refine previous investigations on de Sitter space and extremal surfaces anchored at the future boundary $I^+$. Since such surfaces do not return, they require extra data or boundary conditions in the past (interior). In entirely Lorentzian de Sitter spacetime, this leads to future-past timelike surfaces stretching between $I^\pm$. Apart from an overall $-i$ factor (relative to spacelike surfaces in $AdS$) their areas are real and positive. With a no-boundary type boundary condition, the top half of these timelike surfaces joins with a spacelike part on the hemisphere giving a complex-valued area. Motivated by these, we describe two aspects of "time-entanglement" in simple toy models in quantum mechanics. One is based on a future-past thermofield double type state entangling timelike separated states, which leads to entirely positive structures. Another is based on the time evolution operator and reduced transition amplitudes, which leads to complex-valued entropy.

A coupled domain–boundary type meshless method for phase-field modelling of dendritic solidification with the fluid flow

PurposeThis study aims to simulate the dendritic growth in Stokes flow by iteratively coupling a domain and boundary type meshless method.Design/methodology/approachA preconditioned phase-field model for dendritic solidification of a pure supercooled melt is solved by the strong-form space-time adaptive approach based on dynamic quadtree domain decomposition. The domain-type space discretisation relies on monomial augmented polyharmonic splines interpolation. The forward Euler scheme is used for time evolution. The boundary-type meshless method solves the Stokes flow around the dendrite based on the collocation of the moving and fixed flow boundaries with the regularised Stokes flow fundamental solution. Both approaches are iteratively coupled at the moving solid–liquid interface. The solution procedure ensures computationally efficient and accurate calculations. The novel approach is numerically implemented for a 2D case.FindingsThe solution procedure reflects the advantages of both meshless methods. Domain one is not sensitive to the dendrite orientation and boundary one reduces the dimensionality of the flow field solution. The procedure results agree well with the reference results obtained by the classical numerical methods. Directions for selecting the appropriate free parameters which yield the highest accuracy and computational efficiency are presented.Originality/valueA combination of boundary- and domain-type meshless methods is used to simulate dendritic solidification with the influence of fluid flow efficiently.

Determining the Efficiency of Small-Scale Propellers via Slipstream Monitoring

A large part of small-sized UAVs that are used for surface scanning, video- and photography, or other similar applications are of the multirotor type. These small aircraft perform mainly in hovering or nearly hovering flight mode, and the endurance of these vehicles depends greatly on the efficiency of their motors and the aerodynamic efficiency of their thrust-generating systems, including propellers, ducted fans, etc. Propellers may therefore work in different regimes: in a regime where the propeller performs work to move the vehicle through the air, and the static or hovering regime, in which standing air is accelerated. In both cases, the concept of efficiency can be used to describe the propeller’s performance. There have been several previous studies on static and advancing propellers’ performances. In these studies, when determining the efficiency of a static propeller, the thrust and power coefficients are most commonly compared to evaluate the propeller’s performance. Sometimes, the inducted velocities are calculated via the momentum theory. As small-scale propellers work on very low Reynolds (Re) numbers below 500,000, the flow type transition and boundary layer separation make it very hard to predict the actual efficiency of the propellers in static mode. Therefore, the aim of this paper is to introduce a method to determine the static efficiency of small-scale propellers directly and empirically via a comparison between the output and input power, wherein the output power is determined via the measured thrust and mean induced velocity. The used method combines thrust, torque, and angular velocity measurements with slipstream monitoring. The performed tests showed a decrease in efficiency, with the Re number rising in spite of the rising values of the thrust coefficient. This study led to two main conclusions: thrust and power coefficients are not always the key parameters to determine the efficiency of a propeller; the role of the Re number in the propeller’s efficiency is not yet clear and requires further investigation. The presence of Re number effects has been proven in numerous works, but the impact of those effects seems to not be as trivial as the claim that the lower the Re number, the weaker the propeller’s performance.

Atomistically informed phase field study of austenite grain growth

Atomistically-informed phase field simulations have been performed to investigate the effect of five common alloying elements (Nb, Ti, Mo, V, Mn) on austenite grain growth. The anisotropic simulations based on the segregation energy profiles of the solutes to four different grain boundary (GB) types from density functional theory calculations suggest a secondary role of solute drag anisotropy on grain growth. Hence, the solute trends are determined to be the same for all investigated GBs, and as a result, the Σ5(310)[001] GB can be considered as a representative GB for solute trend predictions. The decrease in grain growth rates due to solute additions is quantitatively described using a solute trend parameter. The following hierarchy of the solute’s effectiveness to retard austenite grain growth has been determined based on the results of the presented model calculations in agreement with the experimental observations: Nb>Ti>Mo>V≈Mn. The limitations and the strengths of the proposed approach are discussed in detail, and a potential application of this approach to steel design is suggested.

Effect of bainitic or martensitic microstructure of a pressure vessel steel on grain boundary segregation induced by step cooling simulating thermal aging

During operating lifetime of a nuclear power plant, the pressure boundary components, usually in 16MND5 (SA508 Cl. 3) steel, are subjected to thermal aging that may induce phosphorus intergranular segregation. This is known to decrease brittle fracture stress and induce intergranular fracture, which causes reversible temper embrittlement. Large components such as the reactor pressure vessel presents microstructure heterogeneity due to forging and welding. Tempered martensite can locally be found in the nominally bainitic steel. The question of microstructure susceptibility to reversible temper embrittlement has been raised in literature suggesting that tempered martensite has higher sensibility to phosphorus intergranular segregation than tempered bainite. In this paper, a comparative study of intergranular segregation in tempered bainitic and martensitic 16MND5 steel after thermal aging is conducted using energy dispersive X-ray spectroscopy on transmission electron microscope. Focus ion beam is used to precisely prepare lamellae at prior austenite grain boundaries on step cooled bainitic and martensitic samples. Different types of grain boundaries are identified using precession assisted crystal orientation mapping and then the local chemical composition is analyzed. Phosphorus, nickel, manganese and molybdenum were observed at all types of grain boundaries in both microstructures. The segregation levels are higher in prior austenitic grain boundaries than in other types of boundaries for both microstructures. Taking into account the segregation amount in different types of boundaries, the phosphorus bulk depletion is shown negligible. The results show similar segregation levels in the two studied microstructures, indicating that the susceptibility to thermally induced grain boundary segregation between the tempered bainite and tempered martensite is the same.

Development and Validation of Empirical Formulations for Predicting the Frequency of Historic Masonry Towers

ABSTRACT In the present work, a large database comprising a set of features related to geometry, type of boundary condition, type of material and experimental value of the first natural frequency for 184 historic masonry towers is collected. The database is then used to develop empirical formulas for the estimation of the fundamental frequency related to the first bending mode. The data are divided into a training set and a validation set for a correct assessment of the empirical equations, generated through power regression and artificial neural network. Different combinations of features are exploited as independent variables to investigate their influence on the dynamic behaviour of masonry towers. To improve the accuracy of the prediction, distinct models are generated for specific clusters with likely homogeneous behaviour, according to the boundary conditions (isolated or bounded) and type of materials (brick, stone or mixed masonry).

The Synergistic Effects of Boron and Impression Creep Testing during Paced Controlling of Temperature for P91 Steels

This article induces the quadruple knowledge on effects of 100 ppm (P91B) and 22 ppm (P91) boron in as‐received 9Cr steels in normalized and tempered conditions (NT) and impression crept conditions (ICC). Herein, impression creep testing is improved through paced temperature to fast evaluate creep performance. P91B performs the utmost by advancing activation energy and 30% better creep life, leading to same targeted creep life to 574 °C than P91 at 550 °C. Further, it incisively discusses variations in microstructure, precipitate size, geometrically necessary dislocations (GNDs), pseudo‐rocking curve, grain size (GS), several types of grain boundaries (GBs), effective GB energy, and elastic stiffness. Novel phenomenological mechanisms like GB hardening/softening; antithetical mechanisms; boron‐dependent mosaicity; grain refinement/fragmentation/coarsening/homogenization; interaction among various types of GBs, triggering re/degeneration of dislocations and Σ boundaries as Σ reactions; super‐continuous and geometric dynamic recrystallizations; enhanced creep immunity of like‐oriented GBs than unlike oriented GBs; primary/secondary recrystallization; specialness; boron/NT/ICC‐dependent stiffness; high stiffness is dependent on low GNDs and big GS, and vice versa are observed. The synergistic effects of [100 ppm boron in NT/ICC] and ICC in manifestation of 22/100 ppm boron are ascertained. However, dependency [proportionally and antithetically] and independency of GB character on creep‐microstructural reciprocity discourse and converse into the mathematical relationship.

Twin density and twin thickness evolution in sputtered Al–Mg alloys

Twinned Al–Mg alloys have been reported. However, the role of Mg solute in facilitating the formation of growth twins remains unclear. By using a precession-assisted crystal orientation mapping technique (PACOM) coupled with transmission electron microscopy (known as ASTAR), we examined the evolution of twin boundaries in Al, Al–1Mg, and Al–2.2Mg (at. %) films. The twinned grain fraction elevates with increasing film thickness until it reaches a peak when the film thickness is 120–160 nm. The Al–Mg alloys exhibited greater twinned grain fractions than pure Al. To investigate the fluctuation of twinned grain fraction, two types of twin boundaries were classified including intergranular and intragranular twins. The initial increase in twin density is attributed to the impingement of twinned grains during island coalescence and the twinned grains are more likely to survive during the grain growth process. Whereas the decrease in twinned grain fraction in thicker films is related to the removal of intragranular twins, and a lack of formation mechanisms of new twins.

Morphological focus and its agreement features in Kakabe

The paper explores the morphological expression of focus on the example of Focus Particle (FP) in Kakabe. The analysis addresses questions that are rarely if ever investigated with respect to morphological focus: i) how FP is related to the boundaries of a focus constituent, in particular, VP and IP focus; ii) how givenness affects the position of FP; iii) FP with respect to types of CP and CP boundaries. I demonstrate that, even though FP resembles prosodic focus in some respects, its distribution cannot be fitted into a prosodic account of focus, contra Büring 2010 and Féry 2013. More specifically, I propose that Kakabe has a Focus operator located lower than CP. Similarly to Cable’s (2006, 2010) Q-operator that can be involved a bi-partite agreement relationship, Foc operator agrees at a time with C0 above it and with the DP below it. I demonstrate how the pattern of FP distribution follows, in particular, from the conditions on Agree (Chomsky 2000, 2001), such as locality, superiority and activity conditions.

Innovation on technological “islands”: domain contrast, boundary spanning, knowledge depth and breadth

Abstract Prior literature has long examined innovation as a recombination process within or across the boundaries of technological domains. However, limited attention is paid to boundaries per se. Building upon recent development of categorical contrast, this study distinguishes domains with crisp boundaries from those with fuzzy boundaries and examines their effects on innovation outputs. Analyzing a large sample of US patents, we find that spanning crisp boundaries is more likely to generate impactful inventions but at the same time leads to significantly higher recombinant uncertainty. We continue to explore what types of inventors are better able to span such types of domain boundaries. Focusing specifically on the role of inventors’ knowledge expertise, we find that while both knowledge depth and breadth enhance the impact of technologies that span crisp boundaries, knowledge breadth is also found to escalate the associated uncertainty. Our emphasis on the contrast of technological domains contributes to the literature on recombinative innovation and boundary spanning.

Influence of type of drainage boundary on coefficient of horizontal consolidation

Vertical drains are used widely to accelerate the consolidation of soft clay deposits when preloading is used as a ground improvement technique. One of the essential input parameters required in Barron's theory is the coefficient of horizontal consolidation, ch. The values of ch can be determined by the radial consolidation test, using either a central sand drain or a porous plastic peripheral drain. This paper presents the laboratory tests carried out to understand the reason for the difference in values of ch determined from inward and outward radial flow consolidations tests. A 150 mm wide instrumented consolidation cell was used to carry out the inward or outward radial consolidation tests. The total stress measurements during consolidation showed non-uniform stress distribution in clay with higher effective stress values close to the drainage boundary. This stiffening of the clay close to the drain retards the consolidation rate resulting in reduced values of ch. As a result, the ch values determined by radially outward consolidation tests with a larger drainage boundary area are lower to those obtained by inward radial flow tests. The pore water pressure measurements showed significantly higher undissipated pore water pressure away from the drainage boundary for the outward flow tests.

Molecular Dynamics Study on the Effects of Substrate Grain Boundaries on the Adsorption State of Graphene: Implications for Nanoscale Lubrication

Graphene on polycrystalline surfaces, such as stainless steel, exhibits frictional strengthening properties during nanofriction. The adsorption state of graphene is directly related to the nanofriction behavior, and graphene’s adsorption state is affected by substrate grain boundaries. However, the mechanism of the influence of the substrate grain boundaries on the adsorption state of graphene is not clear. Herein, the adsorption states of graphene on different stainless-steel grain boundary surfaces are analyzed, and the mechanism of the substrate grain boundaries regulating the surface graphene bulge is revealed. The notion that graphene bulges are related to the type of substrate grain boundaries has been confirmed. Moreover, we demonstrate that the difference in the crystal surfaces on both sides of the grain boundaries and the gradient of adsorption energy are the key factors regulating the graphene bulge. Graphene bulging can only be caused by the existence of crystal surface differences in the grain boundary structure; therefore, the tilt grain boundaries are unable to cause graphene bulging. In addition, the adsorption energy distribution within the grain boundary will also influence graphene bulging if there is a grain surface difference in the grain boundary structure. When the direction of the adsorption energy gradient is perpendicular to the grain boundary, such a grain boundary structure favors the appearance of graphene bulges. In contrast, graphene bulging is suppressed when the direction of the adsorption energy gradient is parallel to the grain boundary. It provides a theoretical basis for explaining graphene’s nanofriction on polycrystalline substrates such as stainless steel. It is important for the use of graphene for the nano-lubrication of stainless-steel components in microelectromechanical systems.