Accommodation Mechanism Research Articles

СИНТАКТИЧНАТА АКОМОДАЦИЯ КАТО ЕЗИКОВА ТЕХНИКА И ИНСТРУМЕНТ ЗА ОПИСАНИЕ НА ПРОСТИТЕ СИНТАКТИЧНИ ГРУПИ / SYNTACTIC ACCOMMODATION AS A LANGUAGE TECHNIQUE AND DESCRIPTION TOOL OF SIMPLE SYNTACTIC GROUPS

The article clarifies the notion of syntactic accommodation as a language technique and a main tool in the model of description of simple syntactic groups in connection with the development of a normative grammar of the Bulgarian language. The authors point out the advantages of this approach in descriptions with normative orientation with respect to the derivation of system rules in the language. They go on to study the effect of syntactic accommodation in connecting personal and impersonal verbs with da-constructions as an illustration of the approach. The authors consider the degrees of accommodation in the simple syntactic groups consisting of a personal verb and a da-construction. The mechanism of accommodation is illustrated in more detail by its action in the categories of polarity, person, number and mood in simple syntactic groups with an impersonal verb as a main member and a da-construction as a subordinate member. Keywords: syntactic accommodation, simple syntactic groups, personal verbs, impersonal verbs, da-constructions, degree of accommodation, Bulgarian language

Acoustic signature identification of damage and wear mechanisms in a steel/glass sliding contact

The tribological behavior of a steel/glass ball-on-flat contact was studied by synchronizing the friction measurements with an acoustic emission device and a vision system. The results highlight two distinct friction regimes identified with low and high friction values. Their transition is characterized by a modification of acoustic emission signals. In addition, two main damage and wear mechanisms are identified: the creation and propagation of Hertzian cracks visible on the glass surface and the constitution of an interfacial layer of debris. The different accommodation mechanisms, activated successively or simultaneously, are identified for acoustic emission frequencies between 300 and 700 kHz. Eventually, this approach allows a real-time wear mechanisms identification and gives better insights about acoustic emission signals in relation to tribological systems.

On the warm temperature strain accommodation mechanisms of Ti–6Al–4V alloy holding different starting microstructures

The strain accommodation mechanism of Ti–6Al–4V alloy with different initial microstructure; equiaxed α+β, lamellar α+β, dual phase α+ά, and fully ά martensite was studied in warm temperature deformation regime. Toward this end, a series of tensile tests were performed at room temperature, 400, 500 and 600 °C. The progressive substructure development during tensile deformation of the equiaxed α+β microstructure at 400 °C increased the strain-hardenability (n-exponent) of the material. However, activation of continuous dynamic recrystallization at higher temperature of 600 °C as main strain accommodation mechanisms increases the portion of non-uniform elongation. This was attributed to the resistance against localized deformation and the occurrence of diffused necking. In the case of initial lamellar microstructure, mechanical fragmentation and thermal disintegration of β phase, and globularization of α-phase via boundary splitting mechanism were dominant restoration mechanisms. Martensite reverse transformation and dynamic recrystallization also served as the primary source of softening and strain compensation in dual-phase α+ά initial microstructure. This was led to the development of bimodal/trimodal microstructure representing acceptable balance between strength and ductility. The microstructural evolution in fully ά martensite was relatively analogous to that of α+ά microstructure apart from activation of load transition mechanism. The correlation of strain accommodation capability of each microstructure and tensile formability was discussed in details.

Eye Accommodation, Near Vision, and Far Vision from a Geometrical Optics Point of View

The eye should have a particular focal length in order to see an object. As there are many things to see, the focal length of the eye must vary because these things are not all at the same distance from the eye. We explore the eye accommodation from a geometrical optics point of view and present our results in this paper; the study includes a description of the accommodation mechanism and a scientific definition of near vision and far vision.

Micro-mechanical behaviour of selective laser melted Ti6Al4V under compression

The mechanical properties and deformation behaviour of a selective laser melted (SLMed) Ti6Al4V alloy were investigated at the micro-scale via in situ micro-pillar compression. The microstructure of the alloy consists of acicular martensite (α′) compared to the bi-modal α/β microstructure of a mill-annealed alloy of similar composition. This microstructure, together with loading direction with respect to build direction, affects the mechanical properties and gives rise to anisotropy. Irrespective of build orientation, both the yield and the ultimate compressive strength of the alloy is about 1.8 times more than that of the mill-annealed alloy. The rise of anisotropy was related to the presence of prior β grain orientation with that of the loading direction and is discussed in relation to predominant fracture mechanisms. TEM investigation on the deformed micropillars showed the existence of a vast network of dislocations, stacking faults and compression twinning{101‾2}; which was identified as a load accommodation mechanism during deformation.

Understanding the unobserved influences on the careers of ethnic minority women: implications for human resource management

If HR managers wish to influence the careers of professional staff, it is important to understand their career aspirations and what determines them. This paper reports a study of the experiences of black, Asian and minority ethnic (BAME) women professionals that shape their careers and working lives. Qualitative data from 39 interviews identifies a distinct set of influences on their career decisions linked to the intersection of their gender and ethnic identities. In particular, it reveals how the mechanisms of fit and accommodation play a role in shaping career adjustment. The paper contributes to career theory by demonstrating the role of mesostructures in the form of career scripts in exploring the interplay between individual agency and structure. It also contributes by incorporating reference group theory and highlighting the role of reference groups in shaping and transmitting career scripts. In so doing it reveals the potential longer-term implications for careers of relational influences on career choice. The analysis highlights the need for HR managers and HR researchers to be aware of the hidden influences on the career decisions of BAME women.

In Situ Mechanical Loading and Neutron Bragg-edge Imaging, Applied to Polygranular Graphite On IMAT@ISIS

BackgroundBragg edge imaging have seen significant developments in the last decade with the availability of new time-resolved detectors, however, there have been no studies of changes in local coherent scattering from grain reorientation and deformation with load. Such damage accommodation mechanism may occur in (quasi)-brittle materials.ObjectiveWe developed a novel method using in-situ Bragg imaging at the ISIS spallation neutron and muon source on the IMAT (Imaging and MATerials science and engineering) instrument using an energy-resolved detector setup. We collected and analysed data of a proof-of-concept experiment demonstrating the use of the method.MethodsWe have developed a loading apparatus that addresses the constraints posed by Bragg imaging, allowing us to resolve features in the material microstructure. We use energy-resolved neutron imaging to obtain images in energy bins and we have developed a set of codes to register and correlate these images, as well as detect changes in local coherent scattering, in situ.ResultsPreliminary results from this method on Gilsocarbon nuclear graphite allow qualitative observation of local changes in Bragg contrast, which may be due to deformation or grain reorientation.ConclusionsWe have demonstrated that we can track changes in local coherent scattering under mechanical load, with sufficient resolution to track features with a size above 100 microns. This method, apparatus and accompanying codes may be used on the IMAT instruments by users interested to better understand deformation in their materials.

Adaptive Instability: Aligning Integration with Responsiveness through Value Management

Multinational corporations face the task of managing tensions between global integration and local responsiveness. However, the field is short of understanding the facilitative mechanisms between the two strategic orientations. This paper fills in this gap by investigating how MNCs’ normative integration improves local responsiveness. Relying on an adaptive instability view of organizational identity and the knowledge management literature, we theorize that the level of alignment between global integration and local responsiveness (I-R alignment) depends on how MNCs manage the local construction of the instability of headquarter (HQ) values. A multiple-case study of MNCs’ value management in China reveals that value instability breeds alienation, manipulation, and fragmentation as barriers to local responsiveness. These barriers reduce the quality of local information available to the HQ and undermine intra-subsidiary collaboration, leading to low I-R alignment. In contrast, routinely and sequentially engaging in anchoring, affirmation, and accommodation mechanisms can address these barriers and transform value instability into an MNC’s adaptive capability. These findings generate a value management model of I-R alignment. The adaptive instability view extends the theorizing on global integration and enriches the understanding of local managers' role as a knowledge creator in the process of global integration.

Critical implications of ion-surface energy accommodation and neutralization mechanism in hollow cathode physics

Self-heating thermionic hollow cathodes are essential components in modern plasma thrusters. To fully understand their operation, three interdependent physical domains must be considered: plasma discharge physics, thermal response of the cathode structure, and chemical evolution of plasma exposed surfaces. In this work, we develop the first self-consistently coupled plasma–thermal–chemical simulation platform for hollow cathode operation using lanthanum hexaboride (LaB6) and Xe and study its performance against our experimentally determined temperature measurements. Results show that the customary assumptions of single-step resonant neutralization and full energy accommodation in ion-surface collisions fail to reproduce our empirical observations. We propose a two-step neutralization mechanism that consists of resonant neutralization to the first excited state of xenon followed by Auger de-excitation to the ground state, along with system specific accommodation factors. In this way, the agreement between the results of the simulations and experiments was achieved. These fundamental processes could govern neutralization in other cathode technologies where low work function emitters are employed and should therefore be accounted for in physical models. In addition, the new simulation platform allows us to better estimate the equilibrium work function of LaB6 hollow cathode emitters. In the cathode studied here, we found that the effective work function is 2.25 eV, which is significantly lower than previous estimates, and leads to better than expected cathode material performance with important implications for space missions.

Mechanism of large strain accommodation assisted by shear localization in a precipitation-hardened Cu–Be alloy

The influence of the structural state on deformation mechanisms under large strains was investigated in a Cu – 2 wt.% Be alloy. Torque evolutions during straining exhibit serrations typical of structural relaxations in the precipitation-hardened alloy, but not in the solid solution state. Microstructure characterization revealed that homogeneous deformation of the solid solution led to strong grain size reduction (20 nm), while localization occurred in the precipitated state with numerous shear bands. The role of CuBe precipitates on hindering dislocation glide and the resulting shear localization under large strain is discussed.

The enhanced warm temperature ductility of Ti-6Al-4V alloy through strain induced martensite reversion and recrystallization

Two different initial microstructures of Ti-6Al-4V alloy, α+ά dual phase and fully ά-martensite, were deformed in tensile mode at warm temperatures of 300 °C and 600 °C. The simultaneous occurrence of martensite reverse transformation and dynamic recrystallization were identified as the main responsible to enhance the ductility values. A bimodal/trimodal microstructure arose during the thermomechanical processing of the dual phase α+ά at 600 °C which resulted in an acceptable balance between strength and ductility. The lower ductility of full ά martensite than dual phase α+ά microstructure was related to the lower extent of involved strain accommodation mechanisms and absence of load transition mechanism.

The role of tectonic inheritance in the development of a fold-thrust belt and superimposed rift: An example from the São Francisco basin, eastern Brazil

The São Francisco intracratonic basin, eastern Brazil, hosts multiple sedimentary successions younger than 1.8Ga that witnessed major plate reorganizations since its generation. During the Brasiliano/Pan-African Gondwana amalgamation, in the Ediacaran-Cambrian boundary, the western half of the basin was involved in the Brasília foreland fold-thrust belt, which propagated eastwards deforming its Proterozoic-Paleozoic strata. Lately, as the South Atlantic rift evolved giving rise to the Brazilian continental margin, the basin was affected by extensional tectonism leading to the development of the Cretaceous Abaeté half-graben. During this episode, elements related to a prominent structure of the Brasília foreland fold-thrust belt, the João Pinheiro fault, were reactivated controlling the graben architecture. Aiming to unravel the evolutionary history of the fault zone since its nucleation until its Cretaceous extensional reactivation, we conducted a structural investigation based on field, well-tied 2D seismic data, and paleostress analysis. Our study revealed that the fault represents an emergent ramp of the basal detachment of the Brasilia foreland fold-thrust belt. Formed under EW-oriented shortening, the structure exhibits a gentle recces-salient geometry in map view, which reflects variations in the detachment depth influenced by pre-orogenic rift structures. Trains of NS-trending chevron folds are abundant and their high symmetry and dominance are expressions of the control exerted by mechanical stratigraphy and low-friction basal detachment. The superposed Abaeté half-graben developed under an extensional regime with a NE-trending maximum extension. Under this condition, a stratigraphic interface along the João Pinheiro fault zone was reactivated giving rise to the graben border fault. NS- to NW-oriented preexisting bedding planes were activated as small normal faults. Although newly-formed faults are present, reactivation is the most effective mechanism of extension accommodation. Therefore, this study provides insights on the influence of tectonic inheritance on the architecture, deformation pattern, strain/stress partitioning and evolution of both extensional and compressional intracontinental systems.

Accommodation mechanisms in strain-transformable titanium alloys

A new β-metastable Ti-alloy is designed with the aim to obtain a TWIP alloy but positioned at the limit between the TRIP/TWIP and the TWIP dominated regime. The designed alloy exhibits a large ductility combined with an elevated and stable work-hardening rate. Deformation occurring by formation and multiplication of {332}<113> twins is evidenced and followed by in-situ electron microscopy, and no primary stress induced martensite is observed. Since microstructural investigations of the deformation mechanisms show a highly heterogeneous deformation, the reason of the large ductility is then investigated. The spatial strain distribution is characterized by micro-scale digital image correlation, and the highly deformed regions are found to stand at the crossover between twins, or at the intersection between deformation twins and grain boundaries. Detailed electron back-scattered imaging in such regions of interest finally allowed to evidence the formation of thin needles of stress induced martensite. The latter is thus interpreted as an accommodation mechanism, relaxing the local high strain fields, which ensures a large and stable plastic deformation of this newly designed Ti-alloy.

Accommodation in L2 English: Measuring dialect convergence in Nigerian Englishes

To what extent can we speak of second dialect acquisition in English L2, and the mechanisms of accommodation in L2 contexts? In contact between different dialects, accommodation is deemed social or mechanical—thus consequent on speaker attitude or frequency of interaction with the new dialect. Drawing on sociophonetics, this study investigates the workings of accommodation between L2 English dialects, using data from mobile Igbo English speakers and lifelong Yoruba counterparts in Southwest Nigeria. The Igbo speakers come from Eyinmba Central Igbo (ECI) region whose L1 lacks the open-mid vowel [ɛ], resulting in the fusion of dress/ɛ/ with face/e/ in their English. An emergence of contrast between the phonemes might be indicative of new dialect aquisition. Overall, a process of convergence as an outcome of accommodation to Yoruba English was established. Younger speakers converged more, while variation within the older speaker-group signalled ethnic bias and social network. The findings suggest that the influence of speaker attitude, age-group and interactional frequency can be composite, and synchronously correlative with the degrees of convergence.

Constraining the effects of dynamic topography on the development of Late Cretaceous Cordilleran foreland basin, western United States

AbstractDynamic topography refers to the vertical deflection (i.e., uplift and subsidence) of the Earth's surface generated in response to mantle flow. Although dynamic subsidence has been increasingly invoked to explain the subsidence and migration of depocenters in the Late Cretaceous North American Cordilleran foreland basin (CFB), it remains a challenging task to discriminate the effects of dynamic mantle processes from other subsidence mechanisms, and the spatial and temporal scales of dynamic topography is not well known. To unravel the relationship between sedimentary systems, accommodation, and subsidence mechanisms of the CFB through time and space, a high-resolution chronostratigraphic framework was developed for the Upper Cretaceous strata based on a dense data set integrating &amp;gt;600 well logs from multiple basins/regions in Wyoming, Utah, Colorado, and New Mexico, USA. The newly developed stratigraphic framework divides the Upper Cretaceous strata into four chronostratigraphic packages separated by chronostratigraphic surfaces that can be correlated regionally and constrained by ammonite biozones. Regional isopach patterns and shoreline trends constructed for successive time intervals suggest that dynamic subsidence influenced accommodation creation in the CFB starting from ca. 85 Ma, and this wave of subsidence increasingly affected the CFB by ca. 80 Ma as subsidence migrated from the southwest to northeast. During 100–75 Ma, the depocenter migrated from central Utah (dominantly flexural subsidence) to north-central Colorado (dominantly dynamic subsidence). Subsidence within the CFB during 75–66 Ma was controlled by the combined effects of flexural subsidence induced by local Laramide uplifts and dynamic subsidence. Results from this study provide new constraints on the spatio-temporal footprint and migration of large-scale (&amp;gt;400 km × 400 km) dynamic topography at an average rate ranging from ~120 to 60 km/m.y. in the CFB through the Late Cretaceous. The wavelength and location of dynamic topography (subsidence and uplift) generated in response to the subduction of the conjugate Shatsky Rise highly varied through both space and time, probably depending on the evolution of the oceanic plateau (e.g., changes in its location, subduction angle and depth, and buoyancy). Careful, high-resolution reconstruction of regional stratigraphic frameworks using three-dimensional data sets is critical to constrain the influence of dynamic topography. The highly transitory effects of dynamic topography need to be incorporated into future foreland basin models to better reconstruct and predict the formation of foreland basins that may have formed under the combined influence of upper crustal flexural loading and dynamic subcrustal loading associated with large-scale mantle flows.

IMI Accommodation and Binocular Vision in Myopia Development and Progression.

The role of accommodation in myopia development and progression has been debated for decades. More recently, the understanding of the mechanisms involved in accommodation and the consequent alterations in ocular parameters has expanded. This International Myopia Institute white paper reviews the variations in ocular parameters that occur with accommodation and the mechanisms involved in accommodation and myopia development and progression. Convergence is synergistically linked with accommodation and the impact of this on myopia has also been critiqued. Specific topics reviewed included accommodation and myopia, role of spatial frequency, and contrast of the task of objects in the near environment, color cues to accommodation, lag of accommodation, accommodative-convergence ratio, and near phoria status. Aspects of retinal blur from the lag of accommodation, the impact of spatial frequency at near and a short working distance may all be implicated in myopia development and progression. The response of the ciliary body and its links with changes in the choroid remain to be explored. Further research is critical to understanding the factors underlying accommodative and binocular mechanisms for myopia development and its progression and to guide recommendations for targeted interventions to slow myopia progression.

Thermodynamic model for lattice point defect-mediated semi-coherent precipitation in alloys

The formation of precipitates with an atomic volume different from their parent phase eventually leads to a loss of the lattice continuity at the matrix–precipitate interface. Here, we show the creation or removal of lattice sites mediated by lattice point defects is an accommodation mechanism of the coherency loss and even a precipitation driving force. We introduce a thermodynamic approach that rationalizes the selection of phases resulting from chemical and crystallographic constraints in relation to point defect properties. The resulting semi-coherent phase diagram and the precipitation kinetic model depend on the equilibrium phase diagram, the eigenstrain of the precipitating phase, and the chemical potential of point defects. From a joint experimental and modeling study, we uncover the prominent role of excess point defects in unforeseen phase transformations of the Fe–Ni metallic system under irradiation. By addressing the fundamental role of lattice point defects in the accommodation mechanisms of precipitation, we provide a step torwards the understanding of semi-coherent phase transformations occurring in solid materials upon synthesis and in use.

Grain-size effect on cracking accumulation in yttria-doped zirconia ceramics during cyclic martensitic transformations

Bulk polycrystalline zirconia-based ceramics generally crack as they undergo martensitic transformations, largely due to the transformation mismatch stresses. Polycrystals subjected to cyclic transformations bodily lose individual grains and progressively comminute, but it is not yet clear how the grain size of a polycrystal affects such cyclic degradation. We explore this issue in 1.5 mol% yttria-doped zirconia by varying the grain size from 0.6 to 7.9 µm in pellets of fixed composition and sample size and subjecting them to multiple thermal cycles through the transformation. A smaller grain size is found to increase the number of cycles required to disaggregate the pellet because of the larger amount of grain boundary area that must crack. Calorimetry analysis shows that the energy relieved through cracking decreases with increasing grain size and suggests an apparent material length scale of ~2 micrometers for the stress relief zone. For grain diameters below this critical length scale, complete stress relief is suggested, while at larger grain sizes, intergranular cracking apparently does not fully relieve the transformation mismatch stresses. Alternate accommodation mechanisms are required including the formation of multiple variants and even some transgranular fracture.

A finite strain thermomechanically-coupled constitutive model for phase transformation and (transformation-induced) plastic deformation in NiTi single crystals

A 3D finite-strain constitutive model for the deformation response of NiTi at the single crystal level is proposed. The model accounts for reversible phase transformation from austenite to martensite habit plane variants, plastic deformation in the austenite phase, and rate effects induced from latent heat. It is developed within the formalism of irreversible thermodynamics with internal state variables based on the Eulerian logarithmic strain and its corrotational objective rate. The inelastic deformation is defined as an average over a representative volume element as classical in the micromechanics-based modeling approach. Transformation-induced plastic deformation is viewed as a mechanism for accommodation of the local deformation incompatibility at the austenite–martensite interface. It is accounted for by introducing an interaction term in the free energy, which is described through the Eshelby tensor by regarding the habit plane variants as ellipsoidal inclusions embedded in the austenite matrix, in order to accurately reflect the internal stress states that contribute to dislocation slipping. The numerical implementation of the model in an efficient scheme and its calibration are described in detail. The proposed model is validated by comparing simulations with available experimental data in single NiTi crystals. Numerical simulations of polycrystals are performed to obtain an insight into the interaction between phase transformation and plastic deformation induced by intergrannular constraints. The efficiency of the numerical implementation of the model is verified by simulations of indentation tests.

The action of ciliary muscle contraction on accommodation of the lens explored with a 3D model

The eye's accommodative mechanism changes optical power for near vision. In accommodation, ciliary muscle excursion relieves lens tension, allowing it to return to its more convex shape. Lens deformation alters its refractive properties, but the mechanics of ciliary muscle actions are difficult to intuit due to the complex architecture of the tissues involved. The muscle itself comprises three sections of dissimilarly oriented cells. These cells contract, transmitting forces through the zonule fibers and extralenticular structures. This study aims to create a finite element model (FEM) to predict how the action of the ciliary muscle sections leads to lens displacement. The FEM incorporates initialization of the disaccommodated lens state and ciliary muscle contraction, with three muscle sections capable of independent activation, to drive accommodative movement. Model inputs were calibrated to replicate experimentally measured disaccommodated lens and accommodated ciliary muscle shape changes. Additional imaging studies were used to validate model predictions of accommodative lens deformation. Models were analyzed to quantify mechanical actions of ciliary muscle sections in lens deformation and position modulation. Analyses revealed that ciliary muscle sections act synergistically: the circular section contributes most to increasing lens thickness, while longitudinal and radial sections can oppose this action. Conversely, longitudinal and radial sections act to translate the lens anteriorly with opposition from the circular section. This FEM demonstrates the complex interplay of the three sections of ciliary muscle in deforming and translating the lens during accommodation, providing a useful framework for future investigations of accommodative dysfunction that occurs with age in presbyopia.