Critical velocities of a two-layer composite tube under a uniform internal pressure moving at a constant velocity are analytically determined. The formulation is based on a Love–Kirchhoff thin shell ...theory that incorporates the rotary inertia and material anisotropy. The composite tube consists of two perfectly bonded axisymmetric circular cylindrical layers of dissimilar materials, which can be orthotropic, transversely isotropic, cubic or isotropic. Closed-form expressions for the critical velocities and radial displacement of the two-layer composite tube are first derived for the general case by including the effects of material anisotropy, rotary inertia and radial stress. The formulas for composite tubes without the rotary inertia effect and/or the radial stress effect and with various types of material symmetry for each layer are then obtained as special cases. In addition, it is shown that the model for single-layer, homogeneous tubes can be recovered from the current model as a special case. To illustrate the new model, a composite tube with an isotropic inner layer and an orthotropic outer layer is analyzed as an example. All four critical velocities of the composite tube are calculated using the newly derived closed-form formulas. Six values of the lowest critical velocity of the two-layer composite tube are computed using three sets of the new formulas, which compare fairly well with existing results.
Abstract
The macula, located near the center of the retina in the human eye, is responsible for providing critical functions, such as central, sharp vision. Structural changes in the macula are ...associated with many ocular diseases, including age-related macular degeneration (AMD) and glaucoma. Although macular thickness is a highly heritable trait, there are no prior reported genome-wide association studies (GWASs) of it. Here we describe the first GWAS of macular thickness, which was measured by spectral-domain optical coherence tomography using 68 423 participants from the UK Biobank cohort. We identified 139 genetic loci associated with macular thickness at genome-wide significance (P < 5 × 10−8). The most significant loci were LINC00461 (P = 5.1 × 10−120), TSPAN10 (P = 1.2 × 10−118), RDH5 (P = 9.2 × 10−105) and SLC6A20 (P = 1.4 × 10−71). Results from gene expression demonstrated that these genes are highly expressed in the retina. Other hits included many previously reported AMD genes, such as NPLOC4 (P = 1.7 × 10−103), RAD51B (P = 9.1 × 10−14) and SLC16A8 (P = 1.7 × 10−8), further providing functional significance of the identified loci. Through cross-phenotype analysis, these genetic loci also exhibited pleiotropic effects with myopia, neurodegenerative diseases (e.g. Parkinson's disease, schizophrenia and Alzheimer's disease), cancer (e.g. breast, ovarian and lung cancers) and metabolic traits (e.g. body mass index, waist circumference and type 2 diabetes). Our findings provide the first insight into the genetic architecture of macular thickness and may further elucidate the pathogenesis of related ocular diseases, such as AMD.
Several types of multiphase solid (MS) inclusions are identified in garnet from ultrahigh‐pressure (UHP) eclogite in the Dabie orogen. The mineralogy of MS inclusions ranges from pure K‐feldspar to ...pure quartz, with predominance of intermediate types consisting of K‐feldspar + quartz ± silicate (plagioclase or epidote) ± barite. The typical MS inclusions are usually surrounded with radial cracks in the host garnet, similar to where garnet contains relict coesite. Barite aggregates display significant heterogeneity in major element composition, with total contents of only 57–73% and highly variable SiO2 contents of 0.32–25.85% that are positively correlated with BaO and SO3 contents. The occurrence of MS inclusions provides petrographic evidence for partial melting in the UHP metamorphic rock. The occurrence of barite aggregates with variably high SiO2 contents suggests the coexistence of aqueous fluid with hydrous melt under HP eclogite facies conditions. Thus, local dehydration melting is inferred to take place inside the UHP metamorphic slice during continental collision. This is ascribed to phengite breakdown during ‘hot’ exhumation of the deeply subducted continental crust. As a consequence, the aqueous fluid is internally buffered in chemical composition and its local sink is a basic trigger to the partial melting during the continental subduction‐zone metamorphism.
Realizing quantum speedup for practically relevant, computationally hard problems is a central challenge in quantum information science. Using Rydberg atom arrays with up to 289 qubits in two spatial ...dimensions, we experimentally investigate quantum algorithms for solving the Maximum Independent Set problem. We use a hardware-efficient encoding associated with Rydberg blockade, realize closed-loop optimization to test several variational algorithms, and subsequently apply them to systematically explore a class of graphs with programmable connectivity. We find the problem hardness is controlled by the solution degeneracy and number of local minima, and experimentally benchmark the quantum algorithm's performance against classical simulated annealing. On the hardest graphs, we observe a superlinear quantum speedup in finding exact solutions in the deep circuit regime and analyze its origins.
•Variation pattern of system state estimated through variation pattern of sensing data.•Two system degradation stages revealed by mapping from sensing data to system state.•Prediction performance of ...LSTM improves after initial stage of degradation.•LSTM effective in engine remaining life prediction using C-MAPSS dataset.
Reliable tracking of performance degradation in dynamical systems such as manufacturing machines or aircraft engines and consequently, prediction of the remaining useful life (RUL) are one of the major challenges in realizing smart manufacturing. Traditional machine learning algorithms are often constrained in adapting to the complex and non-linear characteristics of manufacturing systems and processes. With the rapid development of modern computational hardware, Deep Learning has emerged as a promising computational technique for dynamical system prediction due to its enhanced capability to characterize the system complexity, overcoming the shortcomings of those traditional methods. In this paper, a new approach based on the Long Short-Term Memory (LSTM) network, an architecture that is specialized in discovering the underlying patterns embedded in time series, is proposed to track the system degradation and consequently, to predict the RUL. The objectives of this paper are: 1) translating the raw sensor data to an interpretable health index with the aim of better describing the system health condition; and 2) tracking the historical system degradation for accurate prediction of its future health condition. Evaluation using NASA’s C-MAPSS dataset verifies the effectiveness of the proposed method. Compared with other machine learning techniques, LSTM turns out to be more powerful and accurate in revealing degradation patterns, enabled by its time-dependent structure in nature.
Closed-form expressions for critical velocities and middle-surface displacements of anisotropic tubes subjected to a uniform internal pressure moving at a constant speed are derived using a ...first-order shear deformation (FSD) model for axisymmetric orthotropic cylindrical shells. The FSD shell model is first formulated employing a variational method based on Hamilton’s principle, which incorporates both the transverse shear and rotary inertia effects. The general 3-D constitutive relations for orthotropic elastic materials are utilized to describe the tube anisotropy, which enables a unified treatment of orthotropic, transversely isotropic, cubic and isotropic tubes representing various composite and metallic cylindrical shells. Closed-form formulas for four critical velocities of the anisotropic tube are derived for the general case with the transverse shear, rotary inertia and radial stress effects, which divide the range of the pressure velocity into four segments. For each of these segments, closed-form expressions for the mid-surface radial displacement are obtained. By suppressing the transverse shear, rotary inertia or radial stress effect, the general formulas are reduced to those for special cases. In particular, when the transverse shear, rotary inertia and radial stress effects are all neglected, the newly derived critical velocity formulas for orthotropic and isotropic tubes recover the two existing ones for thin tubes. To quantitatively illustrate the new model, a numerical example is provided for an isotropic tube, where eight values of the lowest critical velocity are directly determined using newly derived formulas and compared with an existing value computationally obtained by others.
Critical velocities of a two-layer composite tube subjected to a uniform internal pressure moving at a constant velocity are analytically derived by using a first-order shear deformation shell theory ...incorporating the transverse shear, rotary inertia and material anisotropy. The composite tube consists of two perfectly bonded axisymmetric circular cylindrical layers of dissimilar materials, which can be orthotropic, transversely isotropic, cubic or isotropic. Closed-form expressions for four critical velocities are first derived for the general case by including the effects of transverse shear, rotary inertia, material orthotropy and radial stress. The formulas for composite tubes without the transverse shear, rotary inertia or radial stress effect and with simpler anisotropy are then obtained as special cases. In addition, it is shown that the model for a single-layer, homogeneous tube is included in the current model as a special case. To illustrate the newly derived closed-form formulas, a composite tube with an isotropic inner layer and an orthotropic outer layer is analyzed as an example. The numerical values of the lowest critical velocity of the two-layer composite tube predicted by the new formulas compare well with existing data.
A new model for determining band gaps for wave propagation in two-dimensional (2-D) periodic three-phase composites containing coated star-shaped inclusions and an orthotropic matrix is developed ...using an extended version of the modified couple stress theory. An improved plane wave expansion method and the Bloch theorem for periodic media are employed to solve the 2-D elastic wave equations, which are converted to an eigenvalue problem. The shape functions for the newly proposed three-phase composites are analytically derived and utilized for the first time. The new model reduces to the classical elasticity-based counterpart when the microstructure effects are suppressed. To quantitatively illustrate the newly developed model, a parametric study is conducted. The numerical results reveal that the first band gap size predicted by the current non-classical model is larger than that given by the classical elasticity-based model, and the difference between the two sets of band gap values is significant when the unit cell size is very small. Also, it is seen that the inclusion geometry and coating thickness have significant effects on the band gap size. These indicate that large band gaps can be attained by tailoring microstructural parameters including the unit cell size and geometrical variables for the inclusion and coating.
A detailed variational formulation is provided for a simplified strain gradient elasticity theory by using the principle of minimum total potential energy. This leads to the simultaneous ...determination of the equilibrium equations and the complete boundary conditions of the theory for the first time. To supplement the stress-based formulation, the coordinate-invariant displacement form of the simplified strain gradient elasticity theory is also derived anew. In view of the lack of a consistent and complete formulation, derivation details are included for the tutorial purpose. It is shown that both the stress and displacement forms of the simplified strain gradient elasticity theory obtained reduce to their counterparts in classical elasticity when the strain gradient effect (a measure of the underlying material microstructure) is not considered. As a direct application of the newly obtained displacement form of the theory, the problem of a pressurized thick-walled cylinder is analytically solved. The solution contains a material length scale parameter and can account for microstructural effects, which is qualitatively different from Lamé’s solution in classical elasticity. In the absence of the strain gradient effect, this strain gradient elasticity solution reduces to Lamé’s solution. The numerical results reveal that microstructural effects can be large and Lamé’s solution may not be accurate for materials exhibiting significant microstructure dependence.
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