Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

An overview of the extended/generalized finite element method (GEFM/XFEM) with emphasis on methodological issues is presented. This method enables the accurate approximation of solutions that involve jumps, kinks, singularities, and other locally non-smooth features within elements. This is achieved by enriching the polynomial approximation space of the classical finite element method. The GEFM/XFEM has shown its potential in a variety of applications that involve non-smooth solutions near interfaces: Among them are the simulation of cracks, shear bands, dislocations, solidification, and multi-field problems. Copyright © 2010 John Wiley & Sons, Ltd.

The extended/generalized finite element method: An overview of the method and its applications

Review of State of Art of Smart Structures and Integrated Systems

A strain sensor has been fabricated from a polymer nanocomposite with multiwalled carbon nanotube (MWNT) fillers. The piezoresistivity
of this nanocomposite strain sensor has been investigated based on an improved three-dimensional (3D) statistical resistor network
model incorporating the tunneling effect between the neighboring carbon nanotubes (CNTs), and a fiber reorientation model. The
numerical results agree very well with the experimental measurements. As compared with traditional strain gauges, much higher sensitivity
can be obtained in the nanocomposite sensors when the volume fraction of CNT is close to the percolation threshold. For a small
CNT volume fraction, weak nonlinear piezoresistivity is observed both experimentally and from numerical simulation. The tunneling
effect is considered to be the principal mechanism of the sensor under small strains.

Tunneling effect in a polymer/carbon nanotube nanocompositestrain sensor

The paper provides a state of the art review of guided wave based structural health monitoring (SHM). First, the fundamental concepts of guided wave propagation and its implementation for SHM is explained. Following sections present the different modeling schemes adopted, developments in the area of transducers for generation, and sensing of wave, signal processing and imaging technique, statistical and machine learning schemes for feature extraction. Next, a section is presented on the recent advancements in nonlinear guided wave for SHM. This is followed by section on Rayleigh and SH waves. Next is a section on real-life implementation of guided wave for industrial problems. The paper, though briefly talks about the early development for completeness,. is primarily focussed on the recent progress made in the last decade. The paper ends by discussing and highlighting the future directions and open areas of research in guided wave based SHM.

https://iopscience.iop.org/article/10.1088/0964-1726/25/5/053001/pdf

Guided wave based structural health monitoring: A review

Simulation has become a prerequisite in engineering and science today for visualization of ideas and concepts. In non-destructive evaluation, simulation is increasingly used to show how an inspection method functions with regard to the component to be inspected and is even used for determining the probability of detection of a respective flaw with regard to the inspection method applied. Probability of detection in non-destructive evaluation is optimized in a way that the best sensor positions, as well as sensor tracking paths, can be found through simulation. In classical non-destructive evaluation, a transducer or transducer array can be virtually moved over the surface of a component to be inspected until a full capture of the component's surface and hopefully volume is achieved in terms of the inspection process. However, with structural health monitoring, no movement of the transducers is possible in case those become an integral and hence fixed part of the component considered. Determining the optimum position of a respective structural health monitoring transducer network can therefore only be achieved through optimization procedures, where numerical simulation is possibly the only viable solution to get this done. Establishing a numerical simulation platform for structural health monitoring purposes has been the major objective of the recently completed INDEUS (Integration of Non-Destructive Evaluation-based Ultrasonic Simulation) project, which is described in this article. The open simulation platform includes different simulation tools, where the requirements and options for further extension of those tools and different test cases applied for validation so far are described. The target is to even simulate real complex structures such as applied in civil, aeronautical, and other engineering disciplines made of metallic and polymer-based monolithic and composite materials where the digital models are inherited from traditional computer-aided design and finite element-based designs. This lays the ground for determining the probability of damage for a given loading condition and structure, and the propagation of guided waves in the structure considered for an undamaged and a damage tolerant condition. From those simulation results, the determination of an optimum configuration of sensing transducers for a given set of actuating transducers is then shown for a guided wave-based structural health monitoring system solution to be designed allowing the tolerable damage to be detected reliably.

Integration of Non-Destructive Evaluation-based Ultrasonic Simulation: A means for simulation in structural health monitoring

In this paper, we present a new nasal sensor system developed using Polyvinylidene fluoride (PVDF) piezo polymer in cantilever configuration and its applicability for measuring human Respiration Rate (RR). Two identical PVDF nasal sensors are mounted on a headphone such that they are located below Right Nostril (RN) and Left Nostril (LN), in such a way that the nasal airflow during inspiration and expiration impinge on sensors. Due to nasal airflow, piezoelectric natured PVDF nasal sensors generate corresponding voltage signals. The RR is the number of breaths per minute (bpm). The RR was determined from the filtered respiratory signals, by computing a power spectral density (PSD) spectrum using Welch method of averaged periodograms. The developed PVDF nasal sensors were capable of identifying different RR corresponding to normal (18.5±1.5 bpm), tachypnea (34.5±4 bpm), and bradypnea (10.5±2.2 bpm) similar to `Gold standard' Respiratory Inductance Plethysmograph (RIP) method and Nasal Prongs (NP).

Identification of different respiratory rate by a piezo polymer based nasal sensor

In the field of photovoltaics, methylammonium lead iodide (MAPbI3) is the most emerging light absorber material because of its excellent optoelectronic properties. Perovskite solar cells with P–I–N device architecture were fabricated with thermally evaporated metal electrodes from different sources like silver nanoparticles and bulk silver shots. Film topography, surface morphology, structure, and grain size were observed using various characterization techniques. Top electrodes with better roughness matching with the transport layer were obtained by thermal evaporation of metal nanopowder. Various electrical characterization techniques, including current density (J) vs voltage (V) and capacitance measurements, were carried out under light and dark conditions for investigating the device performance. Devices with electrodes thermally evaporated using nanopowder showed enhancement in device performance with a lower series resistance and a higher shunt resistance, as observed from J–V characteristics. An open-circuit voltage improvement of ∼14% and a power conversion efficiency enhancement of ∼13% have been observed. A considerable improvement in contact resistances has also been noted. The idea about the recombination of devices can be obtained from J–V measurements with varying illumination intensities. The higher carrier concentration in the device based on a Ag NP electrode can be related to the contribution of the less recombination because of the reduced number of traps. These findings support the purpose of using metal nanopowder instead of the bulk form of metals for thermally evaporated top electrodes in perovskite solar cells. 

Electrode Transport Layer–Metal Electrode Interface Morphology Tailoring for Enhancing the Performance of Perovskite Solar Cells

Objetivos: Este estudo foi desenvolvido para investigar a eficacia e a seguranca do acidozoledronico (ZOL) e do propranolol (PRO) como monoterapia e terapia combinada em ummodelo de rato com osteoporose pos-menopausica. Metodos: Ratas Wistar femeas foram ovariectomizadas (OVX) ou submetidas a cirurgia simulada (placebo) aos tres meses de idade. Doze semanas depois da cirurgia, as ratas foram divididas em seis grupos: (1) placebo + veiculo; (2) OVX + veiculo; (3) OVX + ZOL (100 µg/kg, dose unica intravenosa); (4) OVX + ZOL (50 µg/kg, dose unica intravenosa); (5) OVX + PRO (0,1 mg/kg, via subcutânea, cinco dias por semana); (6) OVX + ZOL (50 µg/kg, dose unica intravenosa) + PRO (0,1 mg/kg, via subcutânea, cinco dias por semana) durante 12 semanas. Depois do tratamento, testou-se a densidade ossea, a porosidade e a microarquitetura tra-becular dos femures. Tambem foram avaliados marcadores bioquimicos sericos e urinarios. Resultados: A terapia combinada com ZOL mais PRO foi mais eficaz em corrigir a diminuicao do calcio serico e o aumento do nivel serico de fosfatase alcalina e fosfatase acida resistenteao tartarato do que a monoterapia com ZOL ou PRO. Alem disso, a terapia combinada comZOL mais PRO foi mais eficaz em corrigir o aumento dos niveis urinarios de calcio, fosforo ecreatinina do que a monoterapia com ZOL ou PRO. A terapia combinada com ZOL mais PRO tambem preservou a microarquitetura trabecular e a porosidade do osso cortical. Conclusao: Os resultados sugerem que a terapia combinada com ZOL mais PRO pode ser aabordagem mais eficaz para o tratamento da osteoporose grave em humanos.

http://www.scielo.br/pdf/rbr/v55n2/en_0482-5004-rbr-55-02-0103.pdf

Efeitos combinados do ácido zoledrônico e do propranolol sobre a densidade óssea e marcadores bioquímicos de remodelação óssea em ratas osteopênicas submetidas à ovariectomia

Prognosis regarding durability of composite structures using various Structural Health Monitoring (SHM) techniques is
an important and challenging topic of research. Ultrasonic SHM systems with embedded transducers have potential
application here due to their instant monitoring capability, compact packaging potential toward unobtrusiveness and noninvasiveness
as compared to non-contact ultrasonic and eddy current techniques which require disassembly of the
structure. However, embedded sensors pose a risk to the structure by acting as a flaw thereby reducing life. The present
paper focuses on the determination of strength and fatigue life of the composite laminate with embedded film sensors
like CNT nanocomposite, PVDF thin films and piezoceramic films. First, the techniques of embedding these sensors in
composite laminates is described followed by the determination of static strength and fatigue life at coupon level testing
in Universal Testing Machine (UTM). Failure mechanisms of the composite laminate with embedded sensors are studied
for static and dynamic loading cases. The coupons are monitored for loading and failure using the embedded sensors. A
comparison of the performance of these three types of embedded sensors is made to study their suitability in various
applications. These three types of embedded sensors cover a wide variety of applications, and prove to be viable in
embedded sensor based SHM of composite structures.

D. Roy Mahapatra

Papers

Integration of Non-Destructive Evaluation-based Ultrasonic Simulation: A means for simulation in structural health monitoring

Identification of different respiratory rate by a piezo polymer based nasal sensor

Electrode Transport Layer–Metal Electrode Interface Morphology Tailoring for Enhancing the Performance of Perovskite Solar Cells

Efeitos combinados do ácido zoledrônico e do propranolol sobre a densidade óssea e marcadores bioquímicos de remodelação óssea em ratas osteopênicas submetidas à ovariectomia

Strength and fatigue life evaluation of composite laminate with embedded sensors