Impulse Intensity Research Articles

Improving Conductivity in Nano-Conduit Flows by Using Thermal Pulse-Induced Brownian Motion: A Spectral Impulse Intensity Approach

Inter-particle and particle-wall connectivity in suspension flow has profound effects on thermal and electrical conductivity. The spectral impulse generation and the imparting of kinetic energy on the particles is shown through a mathematical analysis to be effective as a means of achieving an approximate equivalent of a Langevin thermostat. However, with dilute suspensions, the quadratic form of the thermal pulse spectra is modified with a damping coefficient to achieve the desired Langevin value. With the dense suspension system, the relaxation time is calculated from the non-linear differential equation, and the fluid properties were supported by the viscosity coefficient. A “smoothed” pulse is used for each time-step of the flow simulation to take care of the near-neighbor interactions of the adjacent particles. An approximate optimal thermostat is achieved when the number of extra pulses introduced within each time step is found to be nearly equal to the co-ordination number of each particle within the assembly. Furthermore, the ratio of the particle kinetic energy and the thermal energy imparted is found to be never quite equal to unity, as they both depend upon the finite values of the pulse duration and the relaxation time.

The Effects of Superimposed Whole-Body Electromyostimulation During Short-Term Strength Training on Physical Fitness in Physically Active Females: A Randomized Controlled Trial.

The aim of this study was to compare the effects of short-term strength training with and without superimposed whole-body electromyostimulation (WB-EMS) on straight sprinting speed (SSS), change of direction speed (CODS), vertical and horizontal jumping, as well as on strength and power in physically active females. Twenty-two active female participants (n = 22; mean ± SD: age: 20.5 ± 2.3 years; height: 171.9 ± 5.5 cm; body mass: 64.0 ± 8.2 kg; strength training experience 5.1 ± 3.6 years) were randomly assigned to two groups: strength training (S) or strength training with superimposed WB-EMS (S+E). Both groups trained twice a week over a period of 4 weeks and differed in the application of free weights or WB-EMS during four strength (e.g., split squats, glute-ham raises) and five sprinting and jumping exercises (e.g., side and box jumps, skippings). The WB-EMS impulse intensity was adjusted to 70% of individual maximal sustainable pain. SSS was tested via 30-m sprinting, CODS by a T-run, vertical and horizontal jumping using four different jump tests at pre-, post-, and retests. Maximal strength (Fmax) and power (Pmax) testing procedures were conducted on the Leg Press (LP), Leg Extension (LE), and Leg Curl (LC) machine. Significant time × group interaction effects revealed significant decreases of contact time of the Drop Jump and split time of CODS (p ≤ 0.043; = 0.15–0.25) for S (≤ 11.6%) compared to S+E (≤ 5.7%). Significant time effects (p < 0.024; = 0.17–0.57) were observed in both groups for SSS (S+E: ≤6.3%; S: ≤8.0%) and CODS (S+E: ≤1.8%; S: ≤2.0%) at retest, for jump test performances (S+E: ≤13.2%; S: ≤9.2%) as well as Fmax and Pmax for LE (S+E: ≤13.5%; S: ≤13.3%) and LC (S+E: ≤18.2%; S: ≤26.7%) at post- and retests. The findings of this study indicate comparable effects of short-term strength training with and without superimposed WB-EMS on physical fitness in physically active females. Therefore, WB-EMS training could serve as a reasonable but not superior alternative to classic training regimes in female exercisers.

A New Modeling Approach for Estimating Abiotic and Biotic Stress-Induced de novo Emissions of Biogenic Volatile Organic Compounds From Plants

The emission of biogenic volatile organic compounds (BVOCs) is usually thought to depend on species-specific emission capacities that vary with seasonal and phenological conditions. Actual – so called constitutive - emissions are then calculated from prevailing temperature and radiation. However, various abiotic and biotic stressors such as ozone, extreme radiation and temperature conditions, as well as wounding e.g. from insect feeding, can lead to de-novo emissions of stress-induced BVOCs (sBVOCs) that may excel constitutive emissions by more than an order of magnitude. These emissions often have a considerable different compound composition and are short-lived but can prolong under continuous stress for quite some time. Thus they may easily have a large impact on overall regional BVOC emissions. However, sBVOCs are generally not considered in models since up to date no consistent mechanism has been suggested. This manuscript suggests a new mechanism based on the finding that sBVOCs originate from a handful of biosynthetic pathways which synthesize compounds in the groups of monoterpenes, sesquiterpenes, and green leave volatiles, as well as methyl salicylate, ethanol/acetaldehyde, methanol/formaldehyde, and acetone. Isoprene is also considered but since it is often constitutively emitted, the specific role of stress induction is difficult to determine for this compound. A function is proposed that describes the production of all de-novo sBVOCs sufficiently well and scales with stress intensity. It is hypothesized that the response delay and the form of the function is specific for the production pathway and valid for ozone as well as wounding (herbivory) induced stress. Model parameters are then derived from pooled literature data based on a meta-analysis of suitable induction-response measurements of different plant species. The overall emission amount then derives from the intensity and frequency of the stress impulse. We present a number of literature studies that are used to parameterize the new model as well as a selection of evaluations for single- and multiple-stress inductions. Furthermore, coupling and interaction with constitutive emission models as well as limitations and possible further developments are discussed.

Experimental study on the dynamic responses of foam sandwich panels with different facesheets and core gradients subjected to blast impulse

Sandwich panels with an energy-absorbing core material have exhibited great potential in lightweight structures for blast protection. In this study, the deformation/failure modes of sandwich panels against blast impulse were investigated experimentally. The blast tests were conducted on the aluminum foam-core sandwich panels with different facesheet materials, namely aluminum alloy, steel, and carbon fiber reinforced plastics (CFRP); and the cores involve uniform foam and graded foam. The deformation modes of the whole sandwich panels as well as the front facesheet, foam core, and back facesheet were analyzed systematically. It is shown that the deformation patterns are fairly sensitive to the impulse intensity, facesheet material, and foam core gradient. Based upon the measurements, the back facesheet deflection increases linearly with the impulse, apart from the petal-tearing failure of front facesheet. When considering the specific impulse and the same metallic back facesheets, the blast resistance of the sandwich specimen with CFRP front facesheet is superior to these of the metallic front facesheet specimens. Interestingly, the sandwich panels with the aluminum front and steel back facesheet perform better in blast resistance than those with the steel front and aluminum back facesheet. The blast resistance of sandwich panels with a positive gradient of core density (i.e. core density linearly decreased along the blast direction) is superior to those with a negative gradient of core density; and the performance increases with increasing density difference. Compared with the uniform core, the positively-graded foam core with a larger density difference exhibits a stronger blast resistance, while those with a smaller density difference present a weaker blast resistance. The study is expected to provide some fundamental data and design guide for a more efficient sandwich structure with lighter weight and higher capacity of blast protection.

A comparison of the finite‐difference and finite‐volume methods for a numerical solution of a hyperbolic thermoelasticity problem utilizing the implicit and explicit schemes

AbstractA numerical solution for a coupled hyperbolic thermoelasticity problem of the Lord‐Shulman type is presented. An infinite layer with free boundaries that are kept at a constant temperature is irradiated by a short laser impulse. In this case the problem can be studied in the one‐dimensional formulation. An impact of the laser impulse on a medium is modeled by an internal heat source. The laser impulse intensity decays with a distance from an irradiated surface according to the Bouguer law. The layer is in an unperturbed state at the initial moment of time. The material properties of copper are taken to be the thermo‐mechanical properties of the layer.Two approaches for the boundary value problem are considered: the finite‐difference method (FDM) and the finite‐volume method (FVM). In the first case the system of two second‐order PDE is investigated, in the second case a system of integral balance equations and an integral thermal conductivity equation are composed. To integrate these equations both the explicit and implicit schemes are used. The obtained results are compared with each other and with an analytical solution. A numerical error is estimated for different time and space step sizes. The features inherent in various ways of integration of the coupled hyperbolic thermoelastic problem with the thermal excitation are found.

Quasi-Synchronization of Delayed Memristive Neural Networks via a Hybrid Impulsive Control

This paper investigates the quasi-synchronization of delayed memristive neural networks (MNNs) via a novel hybrid impulsive control algorithm which combines time-triggered and event-triggered impulsive control. The relationship between a predesigned non-negative auxiliary function and a given exponentially decreasing threshold function is used to describe the switching. Under this novel controller, sufficient conditions for the quasi-synchronization are derived by the impulsive differential inequality. In addition, by choosing appropriate parameters or initial conditions such that the initial value of the non-negative auxiliary function is less than that of the event-triggered function, the quasi-synchronization can be realized theoretically as long as the event-triggered impulsive intensity is less than 1. This greatly reduces the conservatism of the existing quasi-synchronization results. Furthermore, the event-triggered rules can avoid the Zeno behavior as long as the event-triggered impulsive intensity is less than 1. This hybrid mechanism can reduce the amount of impulsive control and lessen the network communication. Finally, one example is given to illustrate the validness of the obtained results.

Study on the hydration of young concrete based on dielectric property measurement

A nondestructive device is designed and employed to monitor the hydration of young concrete. The relative dielectric constant and amplitude can be measured by calculating the propagation time and intensity of electromagnetic impulses in young concrete, and the XRD and SEM are applied to investigate the mechanism of correlation between dielectric property and hydration process. Chemical admixtures (citric acid and triethanolamine) are used to verify the application of this method. The test results show that both the amplitude and relative dielectric constant (RDC) are ideal indicators of the hydration process. Microstructure observations demonstrate that the dielectric properties are strongly related to the formation of hydration products and changes of microstructure. The final setting time can also be achieved based on the amplitude measurement. This research provides theoretical and technical foundations for investigating the hydration of concrete, which enables us to have a better understanding of the hydration process.

Dynamic response of circular composite laminates subjected to underwater impulsive loading

The dynamic response and failures of carbon/epoxy composite laminates subjected to underwater impulsive loading are investigated experimentally. The effect of impulsive intensity and thickness of laminates on dynamic deformation, failure modes, and associated mechanisms is identified and quantified respectively. The plates are subjected to underwater impulsive loads of different intensities with a lab-scaled underwater explosive simulator. 3D DIC is employed to capture the dynamic response in terms of response rate, mid-span deflection, and deflection-profile history during the elastic response process, followed by a series of postmortem non-destructive investigation and microscopic examinations to examine the failure modes and its distributions, and analyse the associated mechanisms. The results show that the intensity of impulse, thickness and failure of panels affect the dynamic response of laminate plates significantly. The non-surface failure has very limited influences on the tendency of the deflection-impulse relationship, and the local failure on the surface occurring later than the delamination and fiber fracture through the thickness of laminates. The blast resistance of composite laminates is not enhanced continuously with the increasing thickness due to the inconsistent changes of failure modes. With similar areal mass, meanwhile, composite laminates perform better blast-resistant performance than that of the metallic structures.

Experimental investigation on dynamic failure of carbon/epoxy laminates under underwater impulsive loading

The dynamic response and failure modes of carbon/epoxy laminates subjected to underwater impulsive loading are experimentally investigated in this work. The effects of impulse intensity and fluid-structure interaction (FSI) on the failure modes of the clamped laminates were also assessed. A lab-scale underwater explosive simulator was utilized to impart the controlled impulsive loading with three different decay times on the laminates. The 3D Digital Image Correlation method with high speed photography was used to capture the dynamic response of the laminates. A series of microscopic examinations was conducted to analyze the failure mechanism of the laminates. The results show that the composite laminates provided higher blast resistance than aluminum plates in the same thickness. The fiber breakage, delamination and matrix crack were the main failure modes of the laminates subjected to underwater impulsive loading. The fiber breakage occurring at the center and the boundary of the plate was mainly caused by the stretching and shear-off, respectively. The damage extent of the laminates was increased with the impulsive loading increasing or FSI parameter decreasing. The results obtained in this study provide a potential application guidance for laminates in marine structure lightweight design.

Neuromuscular electrical stimulation reduces sludge in the popliteal vein

The common peroneal nerve stimulator (CPNS) is a UK-approved device for reducing venous thromboembolism (VTE) risk. It resembles a wrist watch and is placed over the common peroneal nerve, discharging electricity at a rate of 1 impulse/s. It has been presumed that as blood flow slows, erythrocytes aggregate into ultrasound-detectable echogenic particles, described as venous sludge. The aim of the study was to determine whether the CPNS reduces venous sludge by using an ultrasound-derived gray-scale (0-255) venous sludge index (VSI). Twenty-five healthy volunteers had their right popliteal vein video recorded using B-mode ultrasound at 22frames/s in longitudinal and transverse views, standing and lying. This was performed first with the CPNS off and then with the CPNS on. The CPNS impulse intensity used was set from 1 to 7 for each individual, and the level was sufficient to cause an outward jerking movement of the foot. A single frame of the possible 154 frames, lasting 7seconds, was selected using a random number generator for the image analysis. The "brightness" of the erythrocyte aggregates (pixels) within a circular sampling area was quantified using the VSI. The brighter the sample, the greater the sludge. Values are expressed as median (interquartile range). On standing with the device off, there was a significantly higher VSI (P< .0005) compared with lying (longitudinal view, 27.7 [18.8-41.4] vs 11.7 [5.5-17.5]; transverse view, 20.7 [13.6-32.2] vs 11.4 [6.3-15.9]). Activation of the CPNS significantly reduced all the VSI values (P< .0005) shown (longitudinal view, 2 [1.1-3.2] and 1.5 [0.5-3.1]; transverse view, 1.1 [0.6-2.7] and 0.8 [0.5-2.1]). The CPNS device significantly reduces venous sludge within the popliteal vein irrespective of whether the subject is standing or lying down or of the longitudinal or transverse position of the ultrasound transducer. The principal mode of action of the device in the claim that it may reduce venous thromboembolism risk may be through a reduction of venous sludge. However, the relationship between erythrocyte aggregation, venous stasis, and venous thromboembolism risk requires more investigation.

A theoretical analysis for mean exit time of a Bi-stable system under combined Gaussian and Poisson white noise excitations

In this work, an approximate method is proposed to simultaneously compute an analytic solution for the mean exit time statistics in a bi-stable system with combined Gaussian and Poisson white noise excitations. Firstly, the method employs a perturbation scheme coupled with the Laplace integral method to estimate the mean exit time analytically. Then, a bi-stable system under both external and parametric excitations of combined Gaussian and Poisson white noises are investigated illustratively with the proposed technique, and effects of noise intensity and random magnitude of impulses on the mean exit time are discussed respectively. Finally, the effectiveness of the theoretical results is verified by means of Monte Carlo simulation, and good agreement will be observed.

Dynamic response and failure of sandwich plates with PVC foam core subjected to impulsive loading

This paper presents an experimental study on dynamic response of clamped sandwich plates with PVC foam core subjected to lab-scale impulsive loading. DIC-3D method and post-test are presented to investigate the permanent deformation, dynamic response and failure modes of the plates. Failure modes of PVC foam layers with three densities as well as front and rear metallic sheets are identified and discussed. Comparison methodologies concerning the blast resistance and energy absorption performance of four configurations in same mass with three densities and thicknesses are carried out. It is indicated that configuration 3 performs well in reducing permanent deformation of structure, and configuration 1 performs well in protecting the structure from destruction and have advantage in blast resistance under high impulsive intensity. The descending order of core densities have advantage in blast resistance than the core with ascending order of densities. Choosing the most efficient density, thickness and sequence of core layers is very helpful in structural optimization design, and especially in blast resistance for a prescribed load.

Standardization of the apex beat in the full left lateral position and its diagnostic value in detecting left ventricular dilatation.

The aims of this study were to determine the characteristics of the apex beat in the full left lateral position in healthy adults, and to assess its value in the diagnosis of left ventricular dilatation. 77 healthy adults and 27 patients with left ventricular dilatation were evaluated by history, physical examination, electrocardiography, apexcardiography and complete transthoracic echocardiographic examination. The location, size and quality of the apex beat were determined in the 90-degree left lateral position. A palpable apex beat, located in the 5th or 6th intercostal space, was recorded in 87% of the healthy adults. The lateral margin was palpated in a 3-cm-wide area from the left anterior axillary line (LAAL) towards the mid-clavicular line (MCL). The mean diameter and area were 2.5 +/- 0.5 cm and 5.0 +/- 2.5 cm2, respectively. In 51% the apex impulse intensity was of medium degree, in 25% weak and in 24% strong. It was palpable in all patients with left ventricular enlargement in the 5th, 6th or 7th intercostal space. The lateral margin was located in a 4.5-cm-wide area, 3.5 cm left from the LAAL to 1 cm right from it. The mean diameter and area were 5.0 +/- 1.0 cm and 20.0 +/- 7.0 cm2, repectively. The intensity was weak in 56% and medium degree in the rest. The diameter > or = 4.0 cm was sensitive (96%) and specific (96%) for the enlarged left ventricle. The location of the apex beat with the cut-off point in the LAAL was equally sensitive but less specific (63%) for left ventricular dilatation. Palpation of the apex beat in the full left lateral position is very suitable for detecting the left ventricular dilatation at bedside. The size of the apex beat appears to be a more reliable diagnostic sign of left ventricular dilatation than its location.

Dylematy uzależnienia – impulsywność i radzenie sobie ze stresem u mężczyzn uczestniczących w terapii uzależnień

Dotychczasowe badania nad osobami uzależnionymi koncentrowały się głównie na aspekcie reaktywnego radzenia sobie, natomiast proaktywne podejście było zignorowane. Aspekt impulsywności również okazuje się mało zbadany ze względu na różnorodność zastosowanych perspektyw badawczych. W związku z powyższym celem niniejszego artykułu było zbadanie różnic w zakresie impulsywności oraz reaktywnego i proaktywnego radzenia sobie wśród mężczyzn uzależnionych oraz bez uzależnienia. Artykuł składa się z trzech części. Pierwsza skupia się na przeglądzie teorii i badań z dziedziny uzależnień, impulsywności i radzenia sobie ze stresem. W drugiej części przedstawiono metodologię badań, a w trzeciej – wyniki i ich dyskusję. W celu zweryfikowania hipotez przeprowadzono badania na grupie 160 mężczyzn. W grupie eksperymentalnej było 80 uzależnionych mężczyzn, podczas gdy grupa kontrolna składała się z tej samej liczby mężczyzn bez uzależnienia. Zostały zastosowane trzy narzędzia badawcze: kwestionariusz impulsywności IVE, kwestionariusz radzenia sobie w sytuacjach stresowych CISS i kwestionariusz reakcji na codziennie wydarzenia PCI. W celu przeprowadzenia analizy statystycznej użyto pakietu STATISTICA. Analiza wyników wykazała istnienie znaczących różnic między grupami badanych mężczyzn. Mężczyźni uzależnieni charakteryzowali się wyższą impulsywnością, wykorzystaniem ucieczkowej strategii radzenia sobie oraz proaktywnych strategii związanych z poszukiwaniem wsparcia instrumentalnego i emocjonalnego, a także radzenia sobie skoncentrowanego na unikaniu. Mężczyźni bez uzależnienia w porównaniu z mężczyznami z grupy eksperymentalnej częściej stosowali proaktywne i refleksyjne radzenie sobie, strategiczne planowanie oraz prewencyjne radzenie sobie.

Using multi-robot active olfaction method to locate time-varying contaminant source in indoor environment

Prevention of indoor contaminant source leak disasters is becoming an urgent issue in the indoor environment and public safety fields. Quickly locating such a source is a prerequisite for effective implementation of source control, and a key basis for further guidance on evacuation and emergency rescue. Indoor contaminant sources have many forms because of source characteristic variation. The current research focuses on continuous release from a source with constant intensity and instantaneous release from a source with impulse intensity. There are few studies of sources with varying release intensity. The main goal of the present research study was to develop a source localization method for a time-varying source. A computational fluid dynamics model of leakage for an indoor time-varying contaminant source is established, together with a search strategy using multi-robot active olfaction. Based on the time-varying leakage source localization method, the robots are used to verify method effectiveness through indoor two-dimensional ventilation room simulation experiments. The influence of factors such as intensity change, position and obstacles on the localization is analyzed, which provides a foundation for further study of contaminant source identification in an unsteady flow field.

Nuo alkoholio priklausomų žmonių emocijų raiškos skirtumai, esant skirtingoms motyvacijų stadijoms atsisakyti vartoti alkoholį

Objective. The aim of this study is to evaluate differences in emotional expressivity according to the motivation to refuse alcohol in a sample of alcohol dependent patients. Methods . The study sample consists of 142 alcohol-dependent patients (96 males and 46 females) undergoing treatment in Lithuania, Kaunas centre for addictive disorders. Emotional expressivity, motivation to refuse alcohol and alcohol dependency are measured by Lithuanian versions of The Stages of Change Readiness and Treatment Eagerness Scale (SOCRATES), Five Expressivity Facet Scale and AUDIT test. Results. Highly motivated alcohol-dependent males express more positive and negative emotions; also, they have significantly higher expressive confidence and higher emotional impulse intensity than those alcohol-dependent males with low motivation to refuse alcohol. Highly motivated alcohol-dependent females have higher emotional impulse intensity and they express more positive emotions comparing to low motivated females. Conclusions . Increased motivation to refuse alcohol is significantly related to some positive aspects of emotional expressivity. Highly motivated alcohol-dependent patients (both males and females) show higher emotional impulse intensity and higher expression of positive emotions. So, applied psychosocial interventions make significant changes in emotional expressivity and this perhaps is significant for the development of new perception of alcohol dependency and for making behavioural changes.

How passion and impulsivity influence a player's choice of videogame, intensity of playing and time spent playing

Videogames have received much attention in addiction research due to their popularity and frequent use. However, few studies have addressed the effect of passion and impulsivity in gamers. Therefore, the aim of the current study was to examine the influence of passion and impulsivity on the intensity of play, playing time, and choice of Massive Multiplayer Online Role Play Game (MMORPG) vs. non-MMORPG. A sample of 630 university students (40.7% Colombian, 59.3% Spanish) responded to a questionnaire on gaming habits, the Passion scale and the Inventory of Impulsivity. Results showed that men preferred sports and MMORPG games and women played more simulation and strategy games and mini-games. The predictor variables for Intensity of Play were: playing MMORPG games, harmonious and obsessive passion and dysfunctional impulsivity. The predictor variables for Hours of Play were: age, harmonious passion and dysfunctional impulsivity. Age, both passions, and functional impulsivity predicted preference for MMORPGs. Impulsivity and passion help explain how players engage with videogames. Dysfunctional impulsivity is related to higher hours and intensity of play and functional impulsivity is a defining feature of MMORPG players. The presence of both passions was related to a higher intensity of play, however only harmonious passion was positively associated with playing for a longer time. These results suggest that the different types of passion and impulsivity have distinct influences on the manner of game play and the experience of that play.

Hydration monitoring and strength prediction of cement-based materials based on the dielectric properties

A nondestructive testing method is developed to monitor the hydration process and predict the strength development of cement-based materials by applying the ground penetrating radar (GPR) and a non-contacting electrical resistivity device. These two instruments allow the measurements of the relative dielectric constant (RDC), the relative amplitude reflected electromagnetic (EM) wave and the electrical conductivity. The RDC and relative amplitude can be measured by calculating the propagation time and the intensity of electromagnetic impulses in material, while the electrical conductivity can be obtained directly by using the non-contacting electrical resistivity device. The results show that both of the relative amplitude and RDC are ideal indicators of the hydration process. The electrical resistivity shifts are well related to the dielectric properties. Linear relationships between the dielectric properties and compressive strength are observed, and a theoretical model is proposed to describe this relation based on the measurements of the dielectric constant and the relative amplitude at early age. This study provides additional theoretical and technical foundations for investigating the hydration progress and estimating the strength, which further helps to have a better understanding of the hydration process and promotes the quality control of cement-based materials.

Evaluating the intensity of the acoustic radiation force impulse (ARFI) in intravascular ultrasound (IVUS) imaging: Preliminary in vitro results

The ability to measure the elastic properties of plaques and vessels is significant in clinical diagnosis, particularly for detecting a vulnerable plaque. A novel concept of combining intravascular ultrasound (IVUS) imaging and acoustic radiation force impulse (ARFI) imaging has recently been proposed. This method has potential in elastography for distinguishing between the stiffness of plaques and arterial vessel walls. However, the intensity of the acoustic radiation force requires calibration as a standard for the further development of an ARFI–IVUS imaging device that could be used in clinical applications. In this study, a dual-frequency transducer with 11MHz and 48MHz was used to measure the association between the biological tissue displacement and the applied acoustic radiation force. The output intensity of the acoustic radiation force generated by the pushing element ranged from 1.8 to 57.9mW/cm2, as measured using a calibrated hydrophone. The results reveal that all of the acoustic intensities produced by the transducer in the experiments were within the limits specified by FDA regulations and could still displace the biological tissues. Furthermore, blood clots with different hematocrits, which have elastic properties similar to the lipid pool of plaques, with stiffness ranging from 0.5 to 1.9kPa could be displaced from 1 to 4μm, whereas the porcine arteries with stiffness ranging from 120 to 291kPa were displaced from 0.4 to 1.3μm when an acoustic intensity of 57.9mW/cm2 was used. The in vitro ARFI images of the artery with a blood clot and artificial arteriosclerosis showed a clear distinction of the stiffness distributions of the vessel wall. All the results reveal that ARFI–IVUS imaging has the potential to distinguish the elastic properties of plaques and vessels. Moreover, the acoustic intensity used in ARFI imaging has been experimentally quantified. Although the size of this two-element transducer is unsuitable for IVUS imaging, the experimental results reported herein can be applied in ARFI–IVUS imaging applications.

Compressive response of sandwich plates to water-based impulsive loading

The compressive response of sandwich plates with polyvinyl chloride (PVC) foam cores and aluminum facesheets to water-based impulsive loading is analyzed using an instrumented impulsive loading apparatus called the underwater shock loading simulator (USLS) and a fully-dynamic 3-D computational framework. The loading conditions analyzed are similar to those in underwater blasts. The study focuses on the overall deformation, strain recovery and impulse transmission which are quantified as functions of structural attributes such as core density, front and backface masses, and incident impulsive load intensity. Measurements obtained using high-speed digital imaging and pressure and force sensors allow the computational models to be calibrated and verified. Quantitative loading–structure–performance maps are developed between the response variables and structural and load attributes. The results reveal that core density has the most pronounced influence on core compressive strain and impulse transmission. Specifically, for severe impulse intensities, a 100% increase in core density leads to a 200% decrease in compressive strain and a 500% increase in normalized transmitted impulse. On the other hand, structures with low density cores are susceptible to collapse at high impulse intensities. Additionally, the compressive strains and transmitted impulses increase monotonically as the mass of the frontface increases, but are unaffected by backface mass. For the same core density, a 100% increase in facesheet thickness leads to a 25% and 50% increase in the core strain and normalized transmitted impulse, respectively. The results and performance maps are useful for designing marine structures with restricts, such as hull sections and pipelines backed by water or machinery.