A robust loop-shaping approach to fast and accurate nanopositioning

Peer reviewedPreprin

Integral Resonant Control for vibration damping and precise tip-positioning of a single-link flexible manipulator

Peer reviewedPostprin

Venous Thromboembolism: Classification, Risk Factors, Diagnosis, and Management

Venous thromboembolism (VTE) is categorised as deep venous thrombosis (DVT) and pulmonary embolism (PE). VTE is associated with high morbidity and causes a huge financial burden on patients, hospitals, and governments. Both acquired and hereditary risks factors contribute to VTE. To diagnose VTE, noninvasive cost-effective diagnostic algorithms including clinical probability assessment and D-dimer measurement may be employed followup by compression ultrasonography for suspected DVT patients and multidetector computed tomography angiography for suspected PE patients. There are pharmacological and mechanical interventions to manage and prevent VTE. The pharmacological approaches mainly target pathways in coagulation cascade nonspecifically: conventional anticoagulants or specifically: new generation of anticoagulants. Excess bleeding is one of the major risk factors for pharmacological interventions. Hence, nonpharmacological or mechanical approaches such as inferior vena cava filters, graduated compression stockings, and intermittent pneumatic compression devices in combination with pharmacological interventions or alone may be a good approach to manage VTE

Failure study of fiber/epoxy composite laminate interface using cohesive multiscale model:

In this study, finite element modeling is performed to investigate the compressive failure of the composite sandwich structures with layered composite shells. An embedded debond area between the layered composite shell and the foam core is assumed as a defect. The composite shells are several plies of equal thickness Kevlar, carbon fiber composite, and E-glass composite with epoxy resin. Three different lay-ups, namely, (0°/90°/0°/90°/0°/90°), (45°/−45°/0°/90°/60°/−30°), and (60°/−30°/90°/0°/30°/90°) are considered for symmetric and asymmetric sequences. The work focuses on the importance of cohesive zone model versus the previously conducted numerical simulation and experimental results for buckling of sandwich composite structures. This enables one to account for delamination growth between shells and core and improve the correlation results with those of experiments. It has been shown that not only the cohesive model is capable of demonstrating delamination propagation, but it also correlates very well with the experimental data. By compiling user-defined cohesive mesoscale model in Abaqus simulation, the local and global buckling of the face-sheets can be precisely detected and response of sandwich structure becomes mesh independent, while mesh size is reduced

Bree\u27s Diagram of A Functionally Graded Thick-walled Cylinder Under Thermo-mechanical Loading Considering Nonlinear Kinematic Hardening

n this paper, elasto-plastic analysis of a thick-walled cylinder made of functionally graded materials (FGMs) subjected to constant internal pressure and cyclic temperature gradient loading is carried out using MATLAB. The material is assumed to be isotropic and independent of tem- perature with constant Poisson\u27s ratio and the material properties vary radially based on a power law volume function relation. The Von Mises’ yield criterion and the Armstrong-Frederick non- linear kinematic hardening model were implemented in this investigation. To obtain the incre- mental plastic strain, return mapping algorithm (RMA) was used. At the end, the Bree\u27s inter- action diagram is plotted in terms of non-dimensional pressure and temperature which represents an engineering index for optimum design under thermo-mechanical loading

Model-based Control of the Scanning Tunneling Microscope: Enabling New Modes of Imaging, Spectroscopy, and Lithography

The invention of scanning tunneling microscope (STM) dates back to the work of Binnig and Rohrer in the early 1980s, whose seminal contribution was rewarded by the 1986 Nobel Prize in Physics for the design of the scanning tunneling microscope. Forty years later, the STM remains the best existing tool for studying electronic, chemical, and physical properties of conducting and semiconducting surfaces with atomic precision. It has opened entirely new fields of research, enabling scientists to gain invaluable insight into properties and structure of matter at the atomic scale. Recent breakthroughs in STM-based automated hydrogen depassivation lithography (HDL) on silicon have resulted in the STM being considered a viable tool for fabrication of error-free silicon-based quantum-electronic devices. Despite the STM's unique ability to interrogate and manipulate matter with atomic precision, it remains a challenging tool to use. It turns out that many issues can be traced back to the STM's feedback control system, which has remained essentially unchanged since its invention about 40 years ago. This article explains the role of feedback control system of the STM and reviews some of the recent progress made possible in imaging, spectroscopy, and lithography by making appropriate changes to the STM's feedback control loop. We believe that the full potential of the STM is yet to be realized, and the key to new innovations will be the application of advanced model-based control and estimation techniques to this system

Theory of electrostatically induced shape transitions in carbon nanotubes

A mechanically bistable single-walled carbon nanotube can act as a variable-shaped capacitor with a voltage-controlled transition between collapsed and inflated states. This external control parameter provides a means to tune the system so that collapsed and inflated states are degenerate, at which point the tube's susceptibility to diverse external stimuli-- temperature, voltage, trapped atoms -- diverges following a universal curve, yielding an exceptionally sensitive sensor or actuator that is characterized by a vanishing energy scale. For example, the boundary between collapsed and inflated states can shift hundreds of Angstroms in response to the presence or absence of a single gas atom in the core of the tube. Several potential nano-electromechanical devices can be based on this electrically tuned crossover between near-degenerate collapsed and inflated configurations

Performance Analysis of an Electromagnetically Coupled Piezoelectric Energy Scavenger

The deliberate introduction of nonlinearities is widely used as an effective technique for the bandwidth broadening of conventional linear energy harvesting devices. This approach not only results in a more uniform behavior of the output power within a wider frequency band through bending the resonance response, but also contributes to energy harvesting from low-frequency excitations by activation of superharmonic resonances. This article investigates the nonlinear dynamics of a monostable piezoelectric harvester under a self-powered electromagnetic actuation. To this end, the governing nonlinear partial differential equations of the proposed harvester are order-reduced and solved by means of the perturbation method of multiple scales. The results indicate that, according to the excitation amplitude and load resistance, different responses can be distinguished at the primary resonance. The system behavior may involve the traditional bending of response curves, Hopf bifurcations, and instability regions. Furthermore, an order-two superharmonic resonance is observed, which is activated at lower excitations in comparison to order-three conventional resonances of the Duffing-type resonator. This secondary resonance makes it possible to extract considerable amounts of power at fractions of natural frequency, which is very beneficial in micro-electro-mechanical systems (MEMS)-based harvesters with generally high resonance frequencies. The extracted power in both primary and superharmonic resonances are analytically calculated, then verified by a numerical solution where a good agreement is observed between the results

Life cycle analysis of milking of microalgae for renewable hydrocarbon production

Botryococcus braunii is a unique microalga which can repeatedly produce the hydrocarbons after their non-destructive extraction - the process called milking. Botryococcus braunii hydrocarbons can be converted to high-quality fuel or used as other high-value products. In this study, we conduct the life cycle analysis of the milking process for renewable hydrocarbon production focusing on the GHG emissions, the fossil energy consumption, the freshwater consumption and the land use of the process. The total-CO2 emissions and the GHG emissions over 100-year time span for production of B. braunii hydrocarbons were estimated to be -0.39 kg CO2-eq/kg hydrocarbons and -0.90 kg CO2-eq/kg hydrocarbons, respectively. The fossil energy ratio of the process was found to be 1.04 MJ produced/MJ fossil energy consumed. The fresh water consumption of the process and the land use were estimated to be 1802 kg/kg hydrocarbons and 0.85m2/kg of hydrocarbons, respectively

Symmetrical and Antisymmetrical Sequenced Fibers with Epoxy Resin on Rectangular Reinforced Structures under Axial Loading

In this study, Finite element Method (FEM) evaluation is performed for the compressive failure of reinforced structures with layered composite shells under axial loading. In addition, embedded delamination between the reinforcing layered composite shells and the core is considered as a defect. The layered composite shells are made of 12 plies of equal thickness of Kevlar, CFC, and E-Glass with epoxy resin. Considering the orientation and laminate, three different layered composite shells, (0°/90°/0°/90°/0°/90°), (45°/-45°/0°/90°/60°/-30°), and (60°/-30°/90°/0°/30°/90°), are considered for symmetrical and antisymmetrical sequences. These results are obtained through ABAQUS simulations and subsequent analysis. The results show that symmetrical and antisymmetrical sequences can be used as an index for quality control and as a safety factor of composite shells produced by the hand lay-up technique in certain industrial processes. The delamination growth is also investigated with the help of cohesive elements. Buckling phenomenon occurred abruptly due to the fast propagation of delamination, having face/core debond