Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
1,832
result(s) for
"Micromechanics"
Sort by:
Ultrasonic visualization of destruction processes in nonwoven polymeric matrix for regenerative medicine
The paper depicts the tensile behaviour of a random oriented nonwoven polymer matrix based on poly-3-hydroxybutyrate. The process of alignment, orientation and stretching of polymer fibers in a water filled condition mimicked presence in a living organism was revealed using acoustic microscopy. To describe the micromechanics of electrospun mats the mechanism of ultrasound contrast of small-sized single cylindrical scatterer was described.
Journal Article
Predicting Mechanical Properties of High-Performance Fiber-Reinforced Cementitious Composites by Integrating Micromechanics and Machine Learning
Current development of high-performance fiber-reinforced cementitious composites (HPFRCC) mainly relies on intensive experiments. The main purpose of this study is to develop a machine learning method for effective and efficient discovery and development of HPFRCC. Specifically, this research develops machine learning models to predict the mechanical properties of HPFRCC through innovative incorporation of micromechanics, aiming to increase the prediction accuracy and generalization performance by enriching and improving the datasets through data cleaning, principal component analysis (PCA), and K-fold cross-validation. This study considers a total of 14 different mix design variables and predicts the ductility of HPFRCC for the first time, in addition to the compressive and tensile strengths. Different types of machine learning methods are investigated and compared, including artificial neural network (ANN), support vector regression (SVR), classification and regression tree (CART), and extreme gradient boosting tree (XGBoost). The results show that the developed machine learning models can reasonably predict the concerned mechanical properties and can be applied to perform parametric studies for the effects of different mix design variables on the mechanical properties. This study is expected to greatly promote efficient discovery and development of HPFRCC.
Journal Article
On the modelling of the vibration behaviors via discrete singular convolution method for a high-order sector annular system
This research presents a numerical investigation on the dynamic information of the axisymmetric sandwich annular sector plate via a higher-order continuum elasticity theory. The sandwich annular sector plate comprises multi-hybrid nanocomposite reinforced (MHCR) face sheets in the top, bottom layers, and a honeycomb core. For modeling the thermal situation and the thickness of the structure, three-kinds of thermal loading are presented. For simulating MHCR face sheets, the role of the mixture and Halpin–Tsai micromechanics model is utilized. For obtaining the governing equations and various boundary conditions, first-order shear deformation theory (FSDT), as well as Hamilton’s principle, are presented. For solving the equations and obtaining eigenvalue, and eigenvector of the current structure, discrete singular convolution method (DSCM) as a numerical one is investigated. Consequently, a parametric study is carried out to examine the impacts of honeycomb network angle, thickness to length ratio of the honeycomb, honeycomb to face sheet thickness ratio, fibers angel, outer to inner radius ratio, and weight fraction of CNTs on the dynamics of the current sandwich structure. The results show that for clamped edge and each th/lh, increasing θh/π is a reason for decreasing the natural frequency of the disk. Another consequence is that the impact of temperature changes on the frequency of the disk is hardly dependent on the fiber angle. It means that the effect of temperature changes on the frequencies of the current system is more considerable at 0.2 ≤ θf ⁄π ≤ 0.4 and 0.6 ≤ θf ⁄π ≤ 0.8.
Journal Article
Imposing Dirichlet boundary conditions directly for FFT-based computational micromechanics
We discuss how Dirichlet boundary conditions can be directly imposed for the Moulinec–Suquet discretization on the boundary of rectangular domains in iterative schemes based on the fast Fourier transform (FFT) and computational homogenization problems in mechanics. Classically, computational homogenization methods based on the fast Fourier transform work with periodic boundary conditions. There are applications, however, when Dirichlet (or Neumann) boundary conditions are required. For thermal homogenization problems, it is straightforward to impose such boundary conditions by using discrete sine (and cosine) transforms instead of the FFT. This approach, however, is not readily extended to mechanical problems due to the appearance of mixed derivatives in the Lamé operator of elasticity. Thus, Dirichlet boundary conditions are typically imposed either by using Lagrange multipliers or a “buffer zone” with a high stiffness. Both strategies lead to formulations which do not share the computational advantages of the original FFT-based schemes. The work at hand introduces a technique for imposing Dirichlet boundary conditions directly without the need for indefinite systems. We use a formulation on the deformation gradient—also at small strains—and employ the Green’s operator associated to the vector Laplacian. Then, we develop the Moulinec–Suquet discretization for Dirichlet boundary conditions—requiring carefully selected weights at boundary points—and discuss the seamless integration into existing FFT-based computational homogenization codes based on dedicated discrete sine/cosine transforms. The article culminates with a series of well-chosen numerical examples demonstrating the capabilities of the introduced technology.
Journal Article
Fluorescence lifetime imaging microscopy: fundamentals and advances in instrumentation, analysis, and applications
Significance: Fluorescence lifetime imaging microscopy (FLIM) is a powerful technique to distinguish the unique molecular environment of fluorophores. FLIM measures the time a fluorophore remains in an excited state before emitting a photon, and detects molecular variations of fluorophores that are not apparent with spectral techniques alone. FLIM is sensitive to multiple biomedical processes including disease progression and drug efficacy.
Aim: We provide an overview of FLIM principles, instrumentation, and analysis while highlighting the latest developments and biological applications.
Approach: This review covers FLIM principles and theory, including advantages over intensity-based fluorescence measurements. Fundamentals of FLIM instrumentation in time- and frequency-domains are summarized, along with recent developments. Image segmentation and analysis strategies that quantify spatial and molecular features of cellular heterogeneity are reviewed. Finally, representative applications are provided including high-resolution FLIM of cell- and organelle-level molecular changes, use of exogenous and endogenous fluorophores, and imaging protein-protein interactions with Förster resonance energy transfer (FRET). Advantages and limitations of FLIM are also discussed.
Conclusions: FLIM is advantageous for probing molecular environments of fluorophores to inform on fluorophore behavior that cannot be elucidated with intensity measurements alone. Development of FLIM technologies, analysis, and applications will further advance biological research and clinical assessments.
Journal Article
Mesoporous carbon spheres with programmable interiors as efficient nanoreactors for H2O2 electrosynthesis
The nanoreactor holds great promise as it emulates the natural processes of living organisms to facilitate chemical reactions, offering immense potential in catalytic energy conversion owing to its unique structural functionality. Here, we propose the utilization of precisely engineered carbon spheres as building blocks, integrating micromechanics and controllable synthesis to explore their catalytic functionalities in two-electron oxygen reduction reactions. After conducting rigorous experiments and simulations, we present compelling evidence for the enhanced mass transfer and microenvironment modulation effects offered by these mesoporous hollow carbon spheres, particularly when possessing a suitably sized hollow architecture. Impressively, the pivotal achievement lies in the successful screening of a potent, selective, and durable two-electron oxygen reduction reaction catalyst for the direct synthesis of medical-grade hydrogen peroxide disinfectant. Serving as an exemplary demonstration of nanoreactor engineering in catalyst screening, this work highlights the immense potential of various well-designed carbon-based nanoreactors in extensive applications.
Nanoreactors, with biomimetic features and distinct catalytic functions, show promise in catalytic energy conversion. Here the authors propose the utilization of precisely engineered mesoporous carbon spheres with tunable hollow sizes as nanoreactors, leveraging their catalytic functionalities for enhanced diffusion and microenvironment modulation effects to achieve efficient hydrogen peroxide electrosynthesis.
Journal Article
Remote quantum entanglement between two micromechanical oscillators
Entanglement, an essential feature of quantum theory that allows for inseparable quantum correlations to be shared between distant parties, is a crucial resource for quantum networks
1
. Of particular importance is the ability to distribute entanglement between remote objects that can also serve as quantum memories. This has been previously realized using systems such as warm
2
,
3
and cold atomic vapours
4
,
5
, individual atoms
6
and ions
7
,
8
, and defects in solid-state systems
9
–
11
. Practical communication applications require a combination of several advantageous features, such as a particular operating wavelength, high bandwidth and long memory lifetimes. Here we introduce a purely micromachined solid-state platform in the form of chip-based optomechanical resonators made of nanostructured silicon beams. We create and demonstrate entanglement between two micromechanical oscillators across two chips that are separated by 20 centimetres . The entangled quantum state is distributed by an optical field at a designed wavelength near 1,550 nanometres. Therefore, our system can be directly incorporated in a realistic fibre-optic quantum network operating in the conventional optical telecommunication band. Our results are an important step towards the development of large-area quantum networks based on silicon photonics.
Remote quantum entanglement is demonstrated in a micromachined solid-state system comprising two optomechanical oscillators across two chips physically separated by 20 cm and with an optical separation of around 70 m.
Journal Article
Electronically integrated, mass-manufactured, microscopic robots
Fifty years of Moore’s law scaling in microelectronics have brought remarkable opportunities for the rapidly evolving field of microscopic robotics
1
–
5
. Electronic, magnetic and optical systems now offer an unprecedented combination of complexity, small size and low cost
6
,
7
, and could be readily appropriated for robots that are smaller than the resolution limit of human vision (less than a hundred micrometres)
8
–
11
. However, a major roadblock exists: there is no micrometre-scale actuator system that seamlessly integrates with semiconductor processing and responds to standard electronic control signals. Here we overcome this barrier by developing a new class of voltage-controllable electrochemical actuators that operate at low voltages (200 microvolts), low power (10 nanowatts) and are completely compatible with silicon processing. To demonstrate their potential, we develop lithographic fabrication-and-release protocols to prototype sub-hundred-micrometre walking robots. Every step in this process is performed in parallel, allowing us to produce over one million robots per four-inch wafer. These results are an important advance towards mass-manufactured, silicon-based, functional robots that are too small to be resolved by the naked eye.
A new class of voltage-controllable electrochemical actuators that are compatible with silicon processing are used to produce over one million sub-hundred-micrometre walking robots on a single four-inch wafer.
Journal Article
The microstructure and micromechanics of the tendon–bone insertion
The exceptional mechanical properties of the load-bearing connection of tendon to bone rely on an intricate interplay of its biomolecular composition, microstructure and micromechanics. Here we identify that the Achilles tendon–bone insertion is characterized by an interface region of ∼500 μm with a distinct fibre organization and biomolecular composition. Within this region, we identify a heterogeneous mechanical response by micromechanical testing coupled with multiscale confocal microscopy. This leads to localized strains that can be larger than the remotely applied strain. The subset of fibres that sustain the majority of loading in the interface area changes with the angle of force application. Proteomic analysis detects enrichment of 22 proteins in the interfacial region that are predominantly involved in cartilage and skeletal development as well as proteoglycan metabolism. The presented mechanisms mark a guideline for further biomimetic strategies to rationally design hard–soft interfaces.
High-resolution imaging, composition analysis and mechanical testing provide a new insight into the structure and function of the Achilles enthesis.
Journal Article