Maximum Oscillation Amplitude Research Articles

Joint work of a flat frame and pile foundations under dynamic impacts

In this paper, the basic data of theoretical and experimental studies of a flat frame on pile foundations are presented. Based on theoretical and experimental studies, methods for conducting experimental studies have been developed, the dynamic parameters of the system have been determined, the dynamic calculation scheme has been refined, and a method for calculating a flat frame with a pile foundation under dynamic loads has been developed. Calculation and comparative analysis of the results on the application of pile foundations following building standards are made and the advantage of the work of pile foundations under the condition of dynamic effects is established. Research results allow us to obtain the dynamic characteristics of a flat frame on pile foundations, necessary for subsequent calculations. An analysis of the modes of natural vibrations shows that for a system the 1st form of vibrations is apparently qualitatively different from the vibration form of a conventional single-mass system. To determine the degree of reliability of the developed methodology, the results of theoretical calculations carried out on the basis of the obtained formulas were compared with field tests for structures. The parameters used were adopted on the basis of theoretical calculations. Quantitatively, the discrepancy near the resonant frequency was about 15% in moving micron vs frequencies curves. The maximum amplitude of oscillations on this grillage very closely coincides with each other. With an increase in frequency in both cases, it leads to a decrease in the amplitude of oscillations of the grillage. The discrepancy between the theoretical and experimental values was about 16%.

Conjunto de alcanzabilidad de un sistema mecánico controlable y condiciones de estabilidad robusta

<p>En este trabajo se determina de forma numérica la frontera del conjunto de alcanzabilidad de una ecuación diferencial de segundo orden con una perturbación externa, empleando la solución del problema de la variación máxima de las amplitudes de oscilación de sus soluciones. El método consiste en determinar en un conjunto de funciones dado, la perturbación externa que provoque amplitudes de oscilación máxima en las soluciones de la ecuación diferencial que describe, como caso particular, la dinámica de un sistema mecánico controlable con impactos. Con ayuda de esta perturbación, se determina la existencia de una trayectoria cerrada que describe la frontera del conjunto de alcanzabilidad, lo cual permite establecer condiciones suficientes sobre la estabilidad robusta de las soluciones de la ecuación diferencial. Los resultados se ilustran de forma numérica en casos particulares.</p>

Analytical approximations to primary resonance response of harmonically forced oscillators with strongly general nonlinearity

This paper presents an innovative analytical approximate method for constructing the primary resonance response of harmonically forced oscillators with strongly general nonlinearity. A linearization process is introduced prior to harmonic balancing (HB) of the nonlinear system and a linear system is derived by which the accurate analytical approximation procedure is easily and innovatively implemented. The main cutting edge of the proposed method is that complicated and coupled nonlinear algebraic equations obtained by the classical HB method is avoided. With only one iteration, very accurate analytical approximate primary resonance response can be determined, even for significantly nonlinear systems. Another advantage is the direct determination of the maximum oscillation amplitude. This is due to the appropriate form chosen for the approximation with no extra processing required. It is concluded that the result of an initial approximate solution from the two-term (constant plus the first harmonic term) harmonic balance is not reliable especially for strongly nonlinear systems and a correction to the initial approximation is necessary. The proposed method can be applied to general oscillators with mixed nonlinearities, such as the Helmholtz-Duffing oscillator. Two examples are presented to illustrate the applicability and effectiveness of the proposed technique.

Effects of varying ultrasound parameters on the oscillation of a microbubble near a boundary

Microbubbles are currently used as ultrasound contrast agents. However, microbubbles have the potential to be used in diagnostic imaging and therapeutic applications. Most numerical work on simulating microbubble oscillation involves modelling microbubbles in infinite medium whereas clinical trials and experiments involve microbubbles near a boundary such as an endothelium and blood vessels. This study will extend previous research by investigating the effects of varying the ultrasound parameters on a microbubble near a boundary. The microbubble oscillation was found to become increasingly irregular as the driving pressure amplitude is increased. The maximum amplitude of oscillation was found to decrease with increasing ultrasound frequency.

Optimization of the optical fiber with triple sector stress elements

• Stress oscillation amplitude reaches the maximum when the expanded angle is equal to 60°. • Stress oscillation amplitude is inversely proportional to the third power of the distance. • Optimized structure of an optical fiber with triple sector stress elements is acquired. The stress distribution characteristics of the optical fiber with triple sector stress elements are studied in detail. The relationship between the stress oscillation amplitude of the optical fiber and the structural parameters is analyzed. The structural parameters include the distance from the stress element center to the core center and the stress element area. The results show that the stress oscillation amplitude of the optical fiber with triple sector stress elements will increase rapidly if the stress element is close to the core while the stress element area is fixed. When the distance from the stress element center to the core center is fixed, the stress oscillation amplitude increases linearly with the increase of the stress element area under the premise of selecting the optimum stress element expanded angle. Based on the drawn conclusion, the optical fiber with triple sector stress elements is optimized. The maximum stress oscillation amplitude and the optical fiber structure with optimal stress distribution are determined to improve the coupling efficiency of the optical fiber and better realize the circular polarization state stable transmission.

РОЗРАХУНОК СИЛ, ЩО ВИНИКАЮТЬ ПРИ СТВОРЕННІ ВІБРАЦІЙ ЗА ДОПОМОГОЮ SMART PIEZOCERAMICS, ТА ДОСЛІДЖЕННЯ ЇХ РОЗПОДІЛУ У ПЛУЖНОМУ ВІДВАЛІ

The main purpose of this article is to calculate and determine the necessary force of smart piezoceramics to create vibrations in the plough dump and to perform simulations on the basis of the calculations. Agriculture is providing the population with food and raw materials for a number of industries. That is why this industry is one of the most important economic spheres present in almost all countries. One of the major problems of agriculture consists in the complexity and efficiency of land cultivation. By energy costs, ploughing is the most energy-intensive operation in technological process of growing crops. In known general purpose hinged ploughs, bolts are attached to the frame by the risers of the plow housings with the housing. During operation of the tiller unit, the traction resistance of the plough produces vibrations that increase the dynamic loads of the components and parts, which lead to their premature destruction. In addition, during oscillatory movements of the tiller unit, the tractor's efforts to move it increase, which leads to increased traction resistance. Improvement of some characteristics aggravates others, in this case when adding additional mechanical devices, their characteristics and disadvantages are placed on the soil tillage plough itself. Determination of the required force to create vibrations in the plough, as well as its own plough oscillations is considered. To determine the force generated, it is necessary to know the magnitude of the force, the oscillation frequencies that appear and act on the plough during ploughing. Thus, in the work, calculations have been carried out to determine the necessary generated force of smart piezoceramics to create vibrations in vibroplough, which is 3.2 kN. Based on the calculated data, we simulate the loading process in the SolidWorks software package. Results of the simulation of plough blade oscillation in SolidWorks software package at different frequencies to 107.88, 212.45, 583.48, 774.94, 874.62 Hz are shown. The maximum oscillation amplitude of the plough blade corresponds to a frequency of 36 Hz.

The COLIBRI experimental program in the CROCUS reactor: characterization of the fuel rods oscillator

The present article presents the mechanical characterization of the fuel rods oscillator developed for the purposes of the COLIBRI experimental program in CROCUS. COLIBRI aims at investigating the radiation noise related to fuel vibrations. The main motivation is the increased amplitudes in the neutron noise distributions recorded in ex- and in-core detectors that have been observed in recent years in Siemens pre-Konvoi type of pressurized water reactors. Several potential explanations have been put forward, but no definitive conclusions could yet be drawn. Among others, changes in fuel assembly or pin vibration patterns, due to recent modifications of assembly structural designs, were pointed out as a possible cause. Computational dynamic tools are currently developed within the Horizon 2020 European project CORTEX, to help with understanding the additional noise amplitude. The COLIBRI program is used for their validation. An in-core device was designed, tested, and licensed between 2015 and 2019 for fuel rods oscillation in CROCUS, in successive steps from out-of-pile tests with dummy fuel rods to critical in-core tests. The characterization of its mechanical behavior is presented, in air and in water, and as a function of the load, for safety and experimental purposes. The device allows simultaneously oscillating up to 18 fuel rods. The maximum oscillation amplitude is 5 mm, while the maximum allowed frequency is 2 Hz, i.e. in the frequency range in which the induced neutron flux fluctuations are most pronounced in nuclear power plants.

Surface temperature and free-stream velocity oscillation effects on mixed convention slip flow from surface of a horizontal circular cylinder

The present phenomena address the slip velocity effects on mixed convection flow of electrically conducting fluid with surface temperature and free stream velocity oscillation over a non-conducting horizontal cylinder. To remove the difficulties in illustrating the coupled PDE, the primitive variable formulation for finite dif?ference technique is proposed to transform dimensionless equations into primitive form. The numerical simulations of coupled non-dimensional equations are exam?ined in terms of fluid slip velocity, temperature, and magnetic velocity which are used to calculate the oscillating components of skin friction, heat transfer, and cur?rent density for various emerging parameters magnetic force parameter, ?, mixed convection parameter, ?, magnetic Prandtl number, ?, Prandtl number, and slip factor, SL. It is observed that the effect of slip flow on the non-conducting cylinder is reduced the fluid motion. A minimum oscillating behavior is noted in skin friction at each position but maximum amplitude of oscillation in heat transfer is observed at each position ? = ?/4 and 2?/3. It is further noticed that a fluid velocity increas?es sharply with the impact of slip factor on the fluid-flow mechanism. Moreover, due to frictional forces with lower magnitude between viscous layers, the rise in Prandtl number leads to decrease in skin fiction and heat transfer which is physi?cally in good agreement.

Surface temperature and free-stream velocity oscillation effects on mixed convention slip flow from surface of a horizontal circular cylinder

The present phenomena address the slip velocity effects on mixed convection flow of electrically conducting fluid with surface temperature and free stream velocity oscillation over a non-conducting horizontal cylinder. To remove the difficulties in illustrating the coupled PDE, the primitive variable formulation for finite dif?ference technique is proposed to transform dimensionless equations into primitive form. The numerical simulations of coupled non-dimensional equations are exam?ined in terms of fluid slip velocity, temperature, and magnetic velocity which are used to calculate the oscillating components of skin friction, heat transfer, and cur?rent density for various emerging parameters magnetic force parameter, ?, mixed convection parameter, ?, magnetic Prandtl number, ?, Prandtl number, and slip factor, SL. It is observed that the effect of slip flow on the non-conducting cylinder is reduced the fluid motion. A minimum oscillating behavior is noted in skin friction at each position but maximum amplitude of oscillation in heat transfer is observed at each position ? = ?/4 and 2?/3. It is further noticed that a fluid velocity increas?es sharply with the impact of slip factor on the fluid-flow mechanism. Moreover, due to frictional forces with lower magnitude between viscous layers, the rise in Prandtl number leads to decrease in skin fiction and heat transfer which is physi?cally in good agreement.

Stress distribution optimization of the optical fiber with multiple stress elements

Abstract The stress oscillation amplitude of the multiple stress elements optical fiber with arbitrary stress element shape is studied. The maximum stress oscillation amplitude and the optimal stress distribution structure of the fiber are determined by the expanded angle of the stress element, the shape and number of the stress elements, the area of the stress element, and the distance from the stress element center to the core center. The results show that different stress element shape fibers have different optimum expanded angles to reach the maximum stress oscillation amplitude. The stress oscillation amplitude of the rectangular stress element fiber is the largest, and the stress oscillation amplitude of the triangle stress element fiber is the smallest. For multiple stress elements optical fiber, if the number of stress elements is smaller, the corresponding stress oscillation amplitude is larger. When the stress element area is larger, the corresponding stress oscillation amplitude is larger too. As the distance from the stress element center to the core center increases, the corresponding amplitude of the stress oscillation decreases. Therefore, the maximum stress oscillation amplitude can be obtained by the triple rectangular stress elements fiber. According to these conclusions, an optimal stress distribution structure of the triple rectangular stress elements fiber is designed.

Comparison of 6 Oscillatory Positive Expiratory Pressure Devices During Active Expiratory Flow.

Air-flow oscillations generated by exhaling through oscillatory positive expiratory pressure (OPEP) devices favor airway clearance. Variations in mechanical properties between different devices may influence therapeutic efficacy. The objective of this study was to assess mechanical properties in vitro and to compare the performance of 6 OPEP devices at different resistance levels under active expiratory flow patterns. 4 gravity-dependent OPEP devices (ie, Flutter, Gelomuc, Pari O-PEP, Shaker Medic Plus) and 2 gravity-independent OPEP devices (ie, Acapella Choice and Aerobika) were each tested at low, medium, and high resistance settings. All devices were independently connected to a pulmonary waveform generator that reproduced active exhalation flows. Expiratory flow-volume curves were retrieved from 4 subjects with different stages of obstruction severity and were scaled according to either peak expiratory flow (4, 6, and 8 L/s) or volumes (2, 3 and 4 L), thus amounting to 24 active exhalations. Resulting waveforms were divided into 4 parts and the 2 middle parts were used to extract the following mechanical data: positive expiratory pressure (PEP), maximum expiratory pressure (Ppeak), oscillation frequency, and flow oscillation amplitude. The percentage of tests achieving oscillation frequencies ≥ 12 Hz and PEP ≥ 10 cm H2O was calculated for each device. Mechanistic effects of the Acapella, Aerobika, and Shaker devices were not comparable. The Flutter, Gelomuc, and Pari devices behaved similarly and achieved more tests with optimum oscillation frequency and PEP values than the other devices. These 3 devices also produced the highest oscillation amplitudes at the low-resistance level, whereas the Aerobika elicited higher and consistent oscillation amplitudes at medium and high resistance settings. Operational parameters differed between and within devices, yet the Flutter, Gelomuc, and Pari devices were similar in many aspects. Therapeutic efficacy may depend on the selected OPEP device and set resistance.

РОЗРОБКА П’ЄЗОДВИГУНА ДЛЯ БІОПРОТЕЗА

Currently, worldwide, the development and research of piezoelectric motors is a very relevant and important problem that attracts a large number of researchers. The interest in this problem is due to the prospect of creating small piezoelectric motors. This allows to obtain unique devices in which electric vibrations turn into rotary movement, in addition, the rotating moment that develops on the shaft of such an engine is so large that eliminates the need for a mechanical gearbox to increase the torque. The world leaders in the production of piezoelectric motors are the following companies: Physik Instrumente (PI), New Scale Technologies and others. The main purpose of this paper is to study and improve piezomotors, for the use in bioprostheses as actuators. Piezomotors are the main element of many microelectromechanical systems that are used in military sphere, in particular in robotics, and also in scientific research instruments. But all these piezoelectric motors have a number of disadvantages, the main of which are: high control voltage, small range of movement of the moving parts, the complexity of manufacturing structures, and large dimensions that reduce their application in various fields. Based on the drawbacks of these constructions, we have proposed and developed our own piezoelectric motor design, and simulated one biomorphic plate in the COMSOL Multiphysics program package. With the COMSOL Multiphysics program, forms of mechanical oscillations, deformations, resonance frequency of bending oscillations, and maximum amplitude of oscillations are determined. Also, in this paper, the coefficient of stiffness of bimorph piezoelements is given, thus, a qualitative mathematical model can significantly reduce the time and costs for the development of bimorph piezoelements. The use of bimorph piezoelectric cells in the developed piezoelectric motor increases the ampli-tude of oscillations, and reduces the amplitude of the control signal. The obtained data can be used in the design of devices where piezoceramic actuators are used.

Numerical study of flow-induced vibration of a circular cylinder with attached flexible splitter plate at low

Flow-induced vibration (FIV) of an elastically mounted circular cylinder with an attached splitter plate in uniform flow is studied numerically via a stabilized space–time finite element method. The Reynolds number based on the cylinder diameter $D$ and the free-stream speed is restricted to 150. The ratio of the density of the body to that of the fluid, for the major part of the study, is 10. Two different reduced speeds are defined to quantify the compliance of the elastic support and flexibility of the splitter plate, respectively: $U_{s}^{\ast }$ based on the natural frequency of the spring–mass system and $U_{p}^{\ast }$ based on the fundamental natural frequency of the plate. Flow past a stationary cylinder ($U_{s}^{\ast }=0$) with a flexible splitter plate of length $3.5D$ is studied at different values of $U_{p}^{\ast }$. The vibration response of the plate exhibits lock-in with various eigenmodes of the plate in different ranges of $U_{p}^{\ast }$. The onsets of these lock-in regions are abrupt and hysteretic. The elastically mounted cylinder, without the splitter plate, undergoes large-amplitude vortex-induced vibration (VIV) for $4<U_{s}^{\ast }<7$. These large-amplitude oscillations are a consequence of synchronization, wherein the vortex shedding frequency locks in to the cylinder oscillation frequency. A rigid splitter plate attached to the cylinder reduces significantly the peak amplitude during VIV. Increasing the length of the plate from $1.5D$ to $3.5D$ only marginally affects the peak amplitude. It, however, leads to a wider range of lock-in. Unlike the case of an isolated cylinder, the lock-in and desynchronization regimes are not well demarcated in the presence of the splitter plate. Further, galloping is observed beyond a critical value of $U_{s}^{\ast }$; the amplitude of vibration increases with an increase in $U_{s}^{\ast }$ while the vibration frequency is relatively low and remains nearly constant. Increase in plate length delays, in terms of $U_{s}^{\ast }$, the onset of galloping. It is also found that the flexibility of the plate affects the maximum oscillation amplitude in the VIV regime. It also dictates the presence/absence of galloping. The system behaves similar to an isolated cylinder for a very flexible plate. The response is devoid of galloping, but relatively large amplitude of oscillation is observed during lock-in. The behaviour of the cylinder with a stiff plate is similar to that with the rigid one. The galloping instability sets in when the flexibility of the plate is less than a certain value ($U_{p}^{\ast }<4.7$, approximately for $U_{s}^{\ast }=22$). The VIV and galloping are separated by a range of $U_{s}^{\ast }$ in which the flow is either steady, for longer plates, or exhibits very weak vortex shedding. In the VIV regime, the plate tip and cylinder vibrate in phase for low $U_{p}^{\ast }$; their motion is out of phase for larger $U_{p}^{\ast }$. The change in phase is also associated with change in the frequency of vibration. At low $U_{p}^{\ast }$, the frequency of vibration is close to the first natural frequency of the system, while at high $U_{p}^{\ast }$ it becomes closer to the second natural frequency. The vibration amplitude of the cylinder is close to maximum in the VIV regime for $U_{s}^{\ast }=6$. Computations for various $U_{p}^{\ast }$, for $U_{s}^{\ast }=6$ and $22$, are utilized to determine optimal flexibility that leads to minimal FIV. The effect of the length of the flexible splitter plate, mass ratio and damping ratio is studied. A strategy is proposed to utilize the computations from various combinations of $U_{s}^{\ast }$ and $U_{p}^{\ast }$ to choose the appropriate flexibility of the attached splitter plate to minimize FIV.

ИСПОЛЬЗОВАНИЕ SMART PIEZOCERAMICS ДЛЯ ОБРАБОТКИ ПОЧВЫ В СЕЛЬСКОМ ХОЗЯЙСТВЕ

The agriculture is a sector of the economy aimed at providing the population with food and obtaining raw materials for a number of industries. The agricultural industry is one of the most important sectors and is represented in almost all countries. The food security of states depends on the state of this industry. The plow is the main tool for cultivating the soil in agriculture. At present, we can observe various improvements in the technology for tillage and harvesting, while the main organ of cultivation has not undergone major changes, except for the introduction of more durable and reliable materials. However, tillage is still one of the most energy intensive operations in modern agricultural production. The use of the latest high-performance machinery and equipment while reducing metal consumption and energy consumption is one of the main objectives of the development of modern engineering. However, in this way there are limitations to the performance of traditional machines, the efficiency of which varies in the range of 0.19-0.38. One of the ways to improve tillage and reduce friction between the soil and the plow consists in the use of vibration technologies, which can have a significant effect. Vibration technique and technology are radically different from traditional prototypes. The use of vibration methods in various spheres of human activities and, in particular, in agriculture offers great prospects for accelerating technological progress on a qualitatively new basis. The aim of the work is to improve the cultivation working bodies by reducing the total amount of traction resistance (friction) of the soil on the surface of the ploughshare and reducing the sticking of the working bodies by using SMART PIEZOCERAMICS and vibration principles. The main features of smart designs are: embedded or surface mounted sensors; built-in or surface-mounted actuators; control element diagrams for the implementation of the monitoring system (which allow to process the data from the sensors to make an appropriate decision). The essence of this technology when used in the cultivation of the soil is as follows. The piezoceramic element is tightly located on the surface of the plow blade. Due to the presence of the piezoelectric element of direct and reverse piezoelectric effect, it can be used as an actuator (vibrator) or sensor. To determine the amplitude of oscillations of a piezoceramic element, numerical simulation has been performed using the COMSOL Multiphysics software package. By mathematical modeling, it has been established that the main resonant frequencies of the developed plow design correspond to 150, 2950, 4750, 6050, 13350, 17950, 18550 Hz. The maximum oscillation amplitude of the plow blade corresponds to a frequency of 18,550 Hz.

Quantitative evaluation of n-butane concentration on knock severity of a natural gas heavy-duty SI engine

Knocking combustion of a natural gas spark ignition engine with the addition of n-butane was investigated. Specially, the effects of n-butane concentration on knock severity were quantitatively evaluated with engine full-load at various engine speeds. The results show that with an increase in n-butane concentration, the peaks of in-cylinder pressure and heat release rate increase, combustion duration is shortened, and CA50 is advanced. At high speeds, n-butane concentration has a more pronounced influence on combustion and knock. With increased n-butane concentration, cyclic pressure traces oscillate more and more violently, the maximum pressure rise rate (MPRR) and the maximum amplitude of pressure oscillation (MAPO) in some cycles increase significantly. Here the MPRR threshold of light knock cycle is defined at 1.0 MPa/CAD, and the one of heavy knock cycle is 4.0 MPa/CAD. Meanwhile the MAPO threshold of light knock cycle is set at 0.1 MPa, and the one of heavy knock cycle is 0.3 MPa. Based on these thresholds and the probability of knock severity, light and heavy knock conditions are identified. Moreover, the combustion close to light knock may increase thermal efficiency, and heavy knock has caused the erosion of aluminum piston crown and top land in the experiment.

Oscillations around tidal pseudo-synchronous solutions for circumbinary planets

AbstractTidal evolution of low-eccentric circumbinary planets is expected to drive the rotational evolution toward a pseudo-synchronous solution. In this work, we present a study of the oscillation amplitudes around this state by considering that the two central stars exert creep tides on the planet. These amplitudes are computed by direct numerical integrations of the creep equations and also by means of the calculation of the coefficients of the periodic terms in this stationary solution. As in the two-body-problem, the planetary spin and lag-angle are observed to have maximum oscillation amplitudes for stiff bodies and almost null oscillation for the gaseous regime, while the opposite behaviour is observed in the equatorial and polar flattenings. Our analytical approximation shows to be very accurate and specially necessary for very-low eccentric planets. However, the magnitudes of the oscillation amplitudes around the pseudo-synchronous solution in the circumbinary problem appears to be very small respect to the mean value. Thus, considering these oscillation in the computation of the tidal energy dissipation may not have a substantial contribution in the results, at least compared to the case in which only the mean values are taken into account.

Gaussian process modelling of granulation and oscillations in red giant stars

ABSTRACTThe analysis of photometric time series in the context of transiting planet surveys suffers from the presence of stellar signals, often dubbed ‘stellar noise’. These signals, caused by stellar oscillations and granulation, can usually be disregarded for main-sequence stars, as the stellar contributions average out when phase-folding the light curve. For evolved stars, however, the amplitudes of such signals are larger and the timescales similar to the transit duration of short-period planets, requiring that they be modelled alongside the transit. With the promise of TESS delivering of the order of ∼105 light curves for stars along the red giant branch, there is a need for a method capable of describing the ‘stellar noise’ while simultaneously modelling an exoplanet’s transit. In this work, a Gaussian process regression framework is used to model stellar light curves and the method validated by applying it to TESS-like artificial data. Furthermore, the method is used to characterize the stellar oscillations and granulation of a sample of well-studied Kepler low-luminosity red giant branch stars. The parameters determined are compared to equivalent ones obtained by modelling the power spectrum of the light curve. Results show that the method presented is capable of describing the stellar signals in the time domain and can also return an accurate and precise measurement of νmax, i.e. the frequency of maximum oscillation amplitude. Preliminary results show that using the method in transit modelling improves the precision and accuracy of the ratio between the planetary and stellar radius, Rp/R⋆. The method’s implementation is publicly available.1

In-vitro experimental study on the fluid-structure interaction in an image-based flexible model with a lateral cerebral aneurysm

Aiming to experimentally investigate the effect of aspect ratio (AR) of image-based aneurysm on wall deformation oscillation under different pulsatile flow conditions with considering the fluid-structure interaction. In this study, three silicon aneurysm models with different AR (0.8, 1.0, and 1.2) were constructed. It was found that the detected wall deformation oscillation of patient-specific aneurysm increased with pulsatile inflow frequency increases, which was greater and more obvious oscillation than that in the ideal lateral aneurysm. In addition, the maximum amplitude of wall deformations oscillation of the aneurysm at the dome during the systolic phase decrease and the oscillation of wall deformation become obvious as AR increases. These results could provide more knowledge about the effect of AR and pulsatile flow on the wall deformation of aneurysm and will be helpful for understanding the aneurysm rupture risk.

A real-time pressure wave model for knock prediction and control

This article develops a control-oriented real-time zero-dimensional knock pressure wave model for spark-ignited engines based on the reaction-based two-zone combustion model developed earlier. This knock pressure wave model is capable of predicting the in-cylinder pressure oscillations under knocking combustion in real-time and can be used for the model-based knock prediction and control. A pressure wave equation including the knock deadening behavior is proposed, simplified, and used to calculate the pressure perturbations generated by knock combustion. The boundary and initial conditions at knock onset are analyzed and the analytic solution of the pressure wave equation is obtained. The model is calibrated and validated over two engine operating conditions at knock limit. The chemical kinetic-based Arrhenius integral and the maximum amplitude of pressure oscillations are used as the evaluation methods for knock onset and intensity prediction, and the knock frequency is studied using a fast Fourier transform of the filtered in-cylinder pressure oscillations. The simulation results show that the proposed knock pressure wave model is able to predict the knock onset timing, frequency, and intensity accurately under two engine operating conditions. Furthermore, the knock characteristics associated with gas mixture properties at intake valve closing is analyzed based on the experimental data, and their effect to knock cycle-to-cycle variation is also studied for the proposed model.

Comparison of geometric and drive-induced nonlinearities in doubly clamped,thermoelastic nanoelectromechanical systems

The performance of resonant sensors based on nanoelectromechanical systems depends critically on the maximum amplitude of oscillation reached in the linear regime. The maximum linear amplitude is determined by nonlinear mechanisms that can originate from the material, geometric and transduction mechanism related factors. Here we compare the two competing effects, the geometric and drive-induced nonlinearities, for a commonly used device family, the thermoelastically driven, doubly clamped beams. We find that the geometric nonlinearity dominates for most of the device designs used in the literature, however the drive-induced nonlinearity becomes the determining factor for thicker beams with small electrode lengths.