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An inertial micro-switch with multi-threshold acceleration detection capability has been proposed, taking advantage of electromechanical coupling behavior. A mathematical model of electromechanical coupling behavior was established to display the dependence of highly sensitivity on pull-in characteristic and show the ability to detect threshold acceleration by controlling the voltage applied to the inertial micro-switch. The capability of sensitivity and detection that was described in mathematical model was implemented to occur at the inertial switch and showed agreement with that of a simulation. Inertia switches that were comprised of various microstructures with dimensions ranging 3.5 µm from 180 µm were manufactured by means of the micro-electro-mechanical system (MEMS) manufacturing process, and their functions were evaluated by a dropping system. The control method related to the manufacturing of inertial switches was obtained by analyzing the effect of the structural parameters of the inertial switch on threshold voltage and threshold acceleration, resulting in a relatively small error between simulation and experiment. The inertial micro-switch showed high sensitivity to achieving the pull-in effect at 30 V, sense multi-threshold acceleration ranging from 500 g to 2000 g in 2.46 ms and provided enough time for outputting the acceleration signal. Furthermore, the multi-threshold acceleration can be adjusted by controlling the voltage applied to inertial micro-switches. In addition, other functions of inertial micro-switches, such as lower residual stress, high recoverability, and repeatability, have been displayed.

At present, the Newmark Sliding Block Method is adopted as a seismic evaluation method of embankments in Japan. The threshold acceleration during shaking is supposed to be a constant in the Newmark Sliding Block Method. However, threshold acceleration can be varied during strong earthquake motions. In this study, several dynamic centrifuge model tests were carried out to investigate the threshold acceleration of embankments during the shaking. The compensation in the Newmark Sliding Block Method was proposed considering variations in threshold acceleration. The test data indicate that the threshold acceleration of the embankments has a tendency to decrease during an earthquake.

At present, the Newmark Sliding Block Method is adopted as a seismic evaluation method of embankments in Japan. The threshold acceleration during shaking is supposed to be a constant in the Newmark Sliding Block Method. However, threshold acceleration can be varied during strong earthquake motions. In this study, several dynamic centrifuge model tests were carried out to investigate the threshold acceleration of embankments during the shaking. The compensation in the Newmark Sliding Block Method was proposed considering variations in threshold acceleration. The test data indicate that the threshold acceleration of the embankments has a tendency to decrease during an earthquake.

Acceleration switch can trigger switches according to the variation of external acceleration without complex control system and circuit. With the excellent characteristics of integration of sensor and actuator, zero power consumption and high reliability, multi-threshold acceleration switch has great application value in the fields of vehicle safety, aerospace and industrial equipment. In order to reduce the complexity of the measurement system and improve the reliability, we realized the design of a multi-threshold and anti-overloading acceleration switch which can distinguish specific pulse width. Additionally, the magnetic elastic contact is designed to prevent the rebound phenomenon when switch is overloaded. Considering the coupling force of spring, magnetic elastic contact and magnetic, we built the dynamic model and analysed the influence of the acceleration threshold and the pulse width on the switch actuation. The numerical simulation shows that the proposed switch has accurate sensitivity of acceleration excitation with specific threshold and certain pulse width, and it also has the ability of anti-overload. Consequently, the proposed method provides a new method for designing acceleration switch.

A micromachined acceleration switch capable of increasing the threshold acceleration is proposed. Comb drive actuators were used to tune the threshold acceleration. The acceleration switch was successfully fabricated using a silicon-on-glass process. Switching characteristics were measured in a centrifugal chamber and a turn-on response time was 0.38 ms. The threshold acceleration was 11 g without a tuning voltage, and it was effectively increased up to 30 g with a tuning voltage of 30 V at the comb actuators, which is about 270% increased threshold compared to the initial threshold with zero tuning voltage.

To determine the range of the threshold acceleration (a-threshold) for the gravitropic stimulation of Lepidium sativum L. roots and hypocotyls, experiments were performed on a centrifuge-clinostat with two-orthogonal axes. The rotation rate of the clinostat was 4 rpm (or = 1.8 x 10(-4) g), while that of the centrifuge was from 3 to 17 rpm (3 x 10(-3) to 10(-1) g). The gravitropic response was determined: (i) after growth of roots and hypocotyls in their normal vertical position and subsequent gravitropic stimulation for 3 h by accelerations of 4 x 10(-3) to 10(-1) g, and (ii) after continuous stimulation in the lateral direction by centripetal accelerations of 4 x 10(-3) to 10(-1) g. The a-threshold was defined by an extrapolation of the regression line of R = p + rx, where x was either ln a or l/a for 3 h or a continuous stimulation, respectively. The a-threshold estimated after 3 h stimulation was equal to 2.6 x 10(-3) g for roots and 3.1 x 10(-3) g for hypocotyls. The threshold accelerations that were unable to evoke a gravitropic response even with continuous stimulation of cress roots and hypocotyls were approximately 3.1 x 10(-3) g and 3.6 x 10(-3) g, respectively. Increasing the stimulation acceleration up to 4.1 x 10(-3) g led to a statistically confirmed gravitropic response of a definite proportion of both the root and hypocotyl populations. In the experiments where acceleration and stimulation time were variable, the threshold dose (D-threshold) for roots was determined to be about 14 to 22 g x s, depending on the stimulation duration and the range of accelerations. The kinetics of gravitropic response at a near-threshold acceleration (4 x 10(-3) to 1.9 x 10(-2) g) differed from that at 1 g (horizontal stimulation). At low forces, the maximal response dependent on the magnitude of acceleration could not be enhanced by increasing the stimulation time up to at least 210 min.

Human-induced vibration has become a serious serviceability problem due to the larger opening of girder, lighter floor systems and longer spans designed and used in practice. Vibration tests were undertaken in laboratory to research the vibrational characteristics of the arch pre-stressed concrete truss (APT) system spanning 16.0 m. Results from ambient vibration, impulse excitations (heel-drop and jumping) and steady-state incentives (walking and running) were presented. Dynamic characteristics such as natural frequencies, damping ratios, mode shapes and acceleration responses were studied and checked against the existing codes. Experimental results show that the investigated APT girder possesses high fundamental frequency and low damping ratio. Moreover, the perception factors based on the root-mean-square acceleration, vibration dose value (VDV) and psychological comfort data were obtained. Lastly, the threshold accelerations and VDVs were suggested for evaluating the human-induced vibration.

Inertial micro-switches have great potential in the applications of acceleration sensing, due to the integrated advantages of a small size, high integration level, and low or even no power consumption. This paper presents an overview of the recent advancements made in research on the sensitive direction, threshold acceleration, contact effect, and threshold accuracy of inertial micro-switches. The reviewed switches were categorized according to the performance parameters, including multi-directional switches, multi-threshold switches, persistent closed switches, flexible-electrode switches, and low-g high-threshold-accuracy switches. The current challenges and prospects are also discussed.

This paper reports an analysis on the relationship between the tilt of the proof mass in MEMS switch and the chattering phenomena. Low-g MEMS acceleration switch developed by Kim’s group was modelled in 2D and displacements of each end of the proof mass were analysed using RK 4th method. Some elementary assumptions were made to ease the modelling and analysis. The chattering time of the MEMS switch gets longer as the tilt of the proof mass increases. The reason is that the elongated travel distance of one end of proof mass increases the impact velocity and lengthens the bouncing back time. From the results, we found that the chattering phenomena can last very long even if the tilt of the proof mass is very small.

Squeeze-film damping and acceleration load are two major issues in the design of inertial micro-switches. In order to deeply and systematically study these two issues, this paper proposes a typical vertically-driven inertial micro-switch, wherein the air and electrode gaps were chosen to design the required damping ratio and threshold value, respectively. The switch was modeled by ANSYS Workbench, and the simulation program was optimized for computational accuracy and speed. Transient analysis was employed to investigate the relationship between the damping ratio, acceleration load, and the natural frequency, and the dynamic properties (including contact bounce, contact time, response time, and threshold acceleration) of the switch. The results can be used as a guide in the design of inertial micro-switches to meet various application requirements. For example, increasing the damping ratio can prolong the contact time of the switch activated by short acceleration duration or reduce the contact bounce of the switch activated by long acceleration duration; the threshold value is immune to variations in the damping effect and acceleration duration when the switch is quasi-statically operated; the anti-jamming capability of the switch can be improved by designing the sensing frequency of the switch to be higher than the acceleration duration but much lower than the other order frequencies of the switch.

The equation of motion of a one way (vertical) spanning strip wall, as an assembly of two rigid bodies, is presented. Only one degree of freedom is needed to completely describe the wall response as the bodies are assumed to be perfectly rectangular and are allowed to rock but not to slide horizontally. Furthermore, no arching action occurs since vertical motion of the upper body is not restrained. Consequently, the equation of motion is nonlinear, with non constant coefficients and a Coriolis acceleration term. Phenomena associated with overburden to self weight ratio, motion triggering, impulsive energy dissipation, amplitude dependency of damping and period of vibration, and scale effect are discussed, contributing to a more complete understanding of experimental observations and to an estimation of system parameters based on the wall characteristics, such as intermediate hinge height and energy damping, necessary to perform nonlinear time history analyses. A comparison to a simple standing, or parapet, wall is developed in order to better highlight the characteristics of this assembly.

The purpose of this study is; to develop asystem that can detect road disturbances and can warn the driver. For thispurpose, a measurement method which tracking as a 3-axis of the road situationwith a semiconductor MEMS-based accelerometer has been developed to be used todetect vehicle vibration and drive conditions which has a serious effect on thedriving quality of the road. With the developed measuring system, road wear andtear can be successfully reported. Thanks to theimproved system, the driver can also be warned by detecting vehicle suspensiondamage. In addition, a driver performance report may be drawn up under theproject that is very important for fleet and service owners (universities,municipalities and other similar public and corporate entities). Thus, thedamage caused by the bad use of the vehicles can be reduced to the minimum; theoperating costs can be reduced.The sensor on the measurement card developed for thispurpose is placed at the lower control arm portion point of the vehicle to beused in the test drives (Renault Thalia II/Symbol brand 2012 model). A testing roadwith a length of 135 meters was constructed and test runs were carried out atdifferent speeds (10km/h, 20 km/h, 30 km/h, 40 km/h and 50 km/h). 7 bumps withvarying dimensions were placed on the created road route at intervals of 5meters. The obtained data were recorded on the SD card and then analyzed in theMatlab program by filtering it from the noise. A total of 2099 data wereanalyzed. As a result, driver performances can be categorized successfully(Normal, Medium, Bad, Very Bad, Very Very Bad) for each test drive according tothe speed and condition of the road bumps. Sound and light stimulation of thedriver when the bulge and the pit are entered in the test runs repeated in theresult of the determined threshold acceleration value after the referencedriving has also been successfully achieved., The purpose of this study is; to develop a system that can detect roaddisturbances and can warn the driver. For this purpose, a measurement methodwhich tracking as a 3-axis of the road situation with a semiconductorMEMS-based accelerometer has been developed to be used to detect vehiclevibration and drive conditions which has a serious effect on the drivingquality of the road. With the developed measuring system, road wear and tearcan be successfully reported. Thanks to the improved system, the driver can also bewarned by detecting vehicle suspension damage. In addition, a driverperformance report may be drawn up under the project that is very important forfleet and service owners (universities, municipalities and other similar publicand corporate entities). Thus, the damage caused by the bad use of the vehiclescan be reduced to the minimum; the operating costs can be reduced.The sensor on the measurement card developed for thispurpose is placed at the lower control arm portion point of the vehicle to beused in the test drives (Renault Thalia II/Symbol brand 2012 model). A testing roadwith a length of 135 meters was constructed and test runs were carried out atdifferent speeds (10km/h, 20 km/h, 30 km/h, 40 km/h and 50 km/h). 7 bumps withvarying dimensions were placed on the created road route at intervals of 5meters. The obtained data were recorded on the SD card and then analyzed in theMatlab program by filtering it from the noise. A total of 2099 data wereanalyzed. As a result, driver performances can be categorized successfully(Normal, Medium, Bad, Very Bad, Very Very Bad) for each test drive according tothe speed and condition of the road bumps. Sound and light stimulation of thedriver when the bulge and the pit are entered in the test runs repeated in theresult of the determined threshold acceleration value after the referencedriving has also been successfully achieved.

We present two designs for metal compliant mechanisms for use as threshold accelerometers which require zero external power. Both designs rely on long, thin flexures positioned orthogonally to a flat body. The first design involves cutting or stamping a thin spring-steel sheet and then bending elements to form the necessary thin flexors. The second design uses precut spring-steel flexure elements mounted into a mold which is then filled with molten tin to form a bimetallic device. Accelerations necessary to switch the devices between bistable states were measured using a centrifuge. Both designs showed very little variation in threshold acceleration due to stress relaxation over a period of several weeks. Relatively large variations in threshold acceleration were observed for devices of the same design, most likely due to variations in the angle of the flexor elements relative to the main body of the devices. Keywords: Structural health monitoring, Sensor, Accelerometer, Zero power, Shock, Threshold

Response time is one of the core attributes for threshold acceleration switches for determining the impact severity. Different from single function inertial switches for only converting circuit states, a wireless inertial microswitch incorporating the bistable flexible mechanism was designed and fabricated using multilayered microelectroforming technology, which can be used for remote detection of both the threshold acceleration and the corresponding response time in severe environments. The threshold snap-through characteristic of the nonlinear bistable mechanism has been introduced to achieve the threshold acceleration sensing capability. The switch mainly consists of one wireless module, one proof mass supported by two pairs of ultralong V-shaped slender beams with the dimension of 28.0~μ m × 25.0 μm × 5150.0 μm, and two contact points for recording triggering times through the high speed sending and receiving wireless module. Then, an accurate design model for analyzing the threshold acceleration and the dynamic response time was established. The 20 repeated experimental results are in good agreement under the same triggering threshold acceleration of 32.38 g, in which, the response time with the traveling distance of 530.0~μm is 179.80 ± 0.20 ms.

A mechanical trigger inertial micro-switch with spring stationary electrode is proposed and fabricated by surface micromachining. The elastic contact process and stability performance are evaluated through experimental tests performed using a drop hammer. The test results show that the contact time is about 110 &mu, s and 100 &mu, s when the threshold acceleration is 480 g and the overload acceleration is 602 g, respectively. The vibration process of the electrodes is explained through an established physical mode. The elastic contact process is analyzed and discussed by Finite Element Analysis (FEA) simulations, which indicated that the contact time is about 65 &mu, s when the threshold acceleration is 600 g. At the same time, this result also proved that the contact time could be extended effectively by the designed spring stationary electrode. The overload acceleration (800 g) has been applied to the Finite-Element model in ANSYS, the contact process indicated that the proof mass contacted with stationary electrode three times, and there was no bounce phenomenon during contact process, which fully proved that the stable contact process can be realized at high acceleration owing to the designed elastic stationary electrode.

The nonlinearity of the soil may considerably affect the response of structures subjected to seismic events. This paper aims to show under which circumstances geometry, soil, and earthquake-type; the nonlinearity is important. A simple model based on a 1D shear column was developed to calculate the maximum shear strain (γ) in the soil subjected to earthquake excitation. It was found that γ is a function of peak ground acceleration PGA and the maximum horizontal ground displacement (∆). EC8 provides an expression for calculating ∆ that is independent of the soil thickness. It was found that this expression is conservative for shallow layers and underestimates γ for thick ones, as a result, improvements have been suggested. By performing several time history analyses, simple formulas are developed which enable the designer to assess when nonlinearity must be taken into account. Four curves based on soil thickness and peak ground acceleration have been introduced for different soil types (A, B, C, and D) using a limit value of γ = 10–4. These curves show that depending on the soil depth, the threshold acceleration of nonlinear soil behavior is around 0.48, 0.36, 0.29, and 0.10 m/s2 for soil types A, B, C, and D, respectively. Obviously, nonlinear analysis must be performed for shallow soil layers under moderate seismicity.

An increase in the operation speed of high-speed trains often leads to an increase in the loading frequency on subgrade soil. Hence, the long-term dynamic behavior of the subgrade and the service performance of high-speed tracks are affected. To determine the stress–strain characteristics of granular soil under high-frequency loading, a triaxial test setup was modified to investigate the effects of loading acceleration and duration, water content, vibration frequency, cell pressure, and initial soil density. The experimental results indicate that there are reductions in axial stress and volumetric strain during high-frequency loading. The reduction in axial stress is as high as 40%, and that of volumetric strain, which is permanent, could approach 0.1%. The stress reduction, strain compression, and excess pore pressure are found to vary linearly with vibration acceleration when a/g > 0.02, where a is vertical vibration acceleration and g is gravitational acceleration. The reduction in strength and strains are found to depend on the loading acceleration and effective cell pressure, but independent of the loading duration, water content, frequency, and initial density. A threshold acceleration a = 0.02g is observed, below which the changes in the shear strength and volumetric strain induced by vibration are negligible. At high vibration acceleration, the strain amplitude could increase, eventually leading to a collapse of the specimen.

Functional base of support (FBOS), the effective area for center of pressure (COP) movement, decreases with aging, which would reduce one's ability to restore balance during perturbed stance. We investigated the relationship between ankle muscle strength and FBOS as well as the threshold perturbation acceleration that required a heel-rise (HR) or step (STEP) to maintain balance. Standing posture of 16 young and 16 elderly adults was perturbed with a backward support surface translation with the speed ranging from 15 to 70 cm/s. Dorsiflexor (DF) strength was found to significantly correlate with FBOS measures and threshold acceleration for HR. Significant correlations were also found between FBOS measures and threshold accelerations for HR and STEP, except for the backward FBOS and threshold acceleration for STEP. Elderly subjects demonstrated significantly smaller DF strength and FBOS measures than young subjects, but no significant group difference was detected in plantarflexor (PF) strength. Most elderly subjects took a step once they raised their heels, while most young subjects were able to restore balance after heel-rise. These findings, taken together, imply that weakness in ankle dorsiflexors could limit the ability of elderly adults to restore balance while standing on their toes. FBOS measures and ankle dorsiflexor strength could be sensitive measures to detect individuals with declined balance control.

By using low-cost microcontrollers and TinyML, we investigate the feasibility of detecting potential early warning signs of domestic violence and other anti-social behaviors within the home. We created a machine learning model to determine if a door was closed aggressively by analyzing audio data and feeding this into a convolutional neural network to classify the sample. Under test conditions, with no background noise, accuracy of 88.89\% was achieved, declining to 87.50\% when assorted background noises were mixed in at a relative volume of 0.5 times that of the sample. The model is then deployed on an Arduino Nano BLE 33 Sense attached to the door, and only begins sampling once an acceleration greater than a predefined threshold acceleration is detected. The predictions made by the model can then be sent via BLE to another device, such as a smartphone of Raspberry Pi., In Proceedings of the 2022 IEEE/ACM Seventh International Conference on Internet-of-Things Design and Implementation (IoTDI) 2022

Erzincan Ovasının Kayma Dalga Hızına Bağlı Potansiyel Sıvılaşma AnaliziJeofizik Müh. F. Seçil ŞAYLANÖZDeprem bölgelerinde zeminin sıvılaşma direncinin önceden belirlenmesi, depreme daha iyidayanımlı yapılar oluşturulmasında bir adım olacaktır. Bu amaçla bu tezde, Erzincan ovasıincelenirken bu bölgenin tektoniği ve jeolojisi hakkında geniş bir araştırmaya yer verilmiştir.Sonrasında gerekli zemin parametreleri bulunması ve bunların yardımıyla zeminlerin elastikve plastik yer değişimleri anlatılmıştır. Bundan hareketle zemin sıvılaşma tanımı, çeşitleri verisk hesaplama yöntemleri tanımlanmıştır. lk olarak 1964 Niigata ve Alaska depremlerindeoluşan sıvılaşma olayı incelenerek Standart Penetrasyon Test'ine dayalı zemin sıvılaşmadirenç değerlendirmesi yöntemini geliştirilmiştir. ncelenen diğer yöntemler CPT ile sıvılaşmaanalizi, Becker ve eşik ivme metodu ile sıvılaşma analizleridir. Daha sonra kayma dalgahızına bağlı bir yöntem de bulunmuş ve uygulamada bu yöntem ile Erzincan ovasındasıvılaşma riski taşıyan bölgeler tespit edilmiştir.Kayma dalga hız ile sıvılaşma analizi yönteminde, deprem dalgasının hakim periyodu vekayma dalga hız ölçümleri kullanılmıştır. Bunlar kullanılarak sıvılaşmayı oluşturan devirgerilme oranı tespit edilmiştir. Buradan eşik ivme faktöründe emniyet faktörü sonucuna göresıvılaşma oluşup oluşmayacağı tespit edilmiştir.Bu çalışmada Erzincan Altınbaşak Köyü, Erzincan Merkez Afetevleri, Erzincan GeçitköyAfetevleri, Erzincan Emniyet Lojmanları Yanı, 4 nolu Gecekondu Önleme Bölgesi,Çukurkuyu Afetevleri bölgelerinin sismik ve DES verilerinden yola çıkılarak, tabakaların Vpve Vs veri haritaları çıkarılmış, tabaka kalınlıkları hesaplanmış, Poisson oran haritası çizilmişve sıvılaşma potansiyellerinin olup olmadığı saptanmıştır.Elde edilen sonuçlar, bize Erzincan'daki çalışma yapılan bölgelerde yüksek oranda sıvılaşmariski olduğunu göstermiştir. Bu da bize göstermektedir ki, bu bölgelerde bina ve oturmaalanları yapılırken zemin özellikleri konusunda hasarları önlemek amacı ile gerekli zeminetüdü yapılmalıdır. Gerekirse bu bölgelerde zemin ıslahı yapılmalı veya oturuma izinverilmemelidir. The Analysis Of Erzincan Plain Potential Liquefaction By UsingShear Wave Velocity Measurements.Geophysics Engineer F. Seçil ŞAYLANABSTRACTPredetermination of ground liquefaction resistance in the earthquake regions will be astep to constract buildings more resistant to earthquakes. Thus, this project is based ona wide research on the tectonicks and geology of the region while examining theErzincan plain. This is followed by finding the required ground parameters and elasticand plastic parameters. Ground liquefaction, its types and risk assessment have beendefined accordingly. Firstly, by studying the liquefaction phenomena of 1964 Niigataand Alaska earthquakes soil resistance against liquidification method based on standartpenetration test is developed. Other methods examined are liquefaction analysis throughCPT, liquefaction analysis as per Becker and threshold acceleration methods. Later,another method based on slip wave speed has been found. Areas in Erzincan plain withliquefaction risk have been risk have been through this method.For the method of liquefaction analysis through slip wave speed, the dominant period ofearthquake wave and slip wave speed measurement have been used. By making use ofthese, cycle stretching rate leading to liquefaction has been determined. It has thus beendetermined whether liquefaction would occur according to the results of security factorin the threshold acceleration factor.Vp and Vs maps of the layers are formed, the thickesses of the layers are calculated,poisson ratio maps of the layers are drawn, and liquefaction potentials of this layers areinvestigated using sismic data of Erzincan Altınbasak Koyu, Erzincan MerkezAfetevleri, Erzincan Emniyet Lojmanlari, 4 no?lu Gecekondu Onleme Bolgesi,Cukurkuyu Afetevleri and DES in this study.The results of this study shows that there is a high risk of liquefaction in the first layer ofthe inversigated region. At the same time there is also considerable risk of liquefactionin the second layer of Altınbasak Koyu, Erzincan Merkez Afetevleri, 4 no?lu GecekonduOnleme Bolgesi, Cukurkuyu Afetevleri. Additionally before the construction works ofthe buildings in this region the soil characteristics must be done and necessaryprecautions against surface and underground waters must be taken. 143

Traffic safety is important in reducing death and building a harmonious society. In addition to studies of accident incidences, the perception of driving risk is significant in guiding the implementation of appropriate driving countermeasures. Risk assessment can be conducted in real-time for traffic safety due to the rapid development of communication technology and computing capabilities. This paper aims at the problems of difficult calibration and inconsistent thresholds in the existing risk assessment methods. It proposes a risk assessment model based on the potential field to quantify the driving risk of vehicles. Firstly, virtual energy is proposed as an attribute considering vehicle sizes and velocity. Secondly, the driving risk surrogate(DRS) is proposed based on potential field theory to describe the risk degree of vehicles. Risk factors are quantified by establishing submodels, including an interactive vehicle risk surrogate, a restrictions risk surrogate, and a speed risk surrogate. To unify the risk threshold, acceleration for implementation guidance is derived from the risk field strength. Finally, a naturalistic driving dataset in Nanjing, China, is selected, and 3063 pairs of following naturalistic trajectories are screened out. Based on that, the proposed model and other models use for comparisons are calibrated through the improved particle optimization algorithm. Simulations prove that the proposed model performs better than other algorithms in risk perception and response, car-following trajectory, and velocity estimation. In addition, the proposed model exhibits better car-following ability than existing car-following models.

Heavy vehicles, such as tractor-semitrailers, play an important role in transportation systems. They present more complex dynamical behavior than passenger cars, due to their high centers of gravity, which can vary depending on the load conditions, and are highly susceptible to rollover during cornering. Heavy vehicle rollover on highways occurs as a result of cornering with excessively high speed, cornering on a small radius curve or sudden lane change. However, if rollover threat is predicted using an appropriate algorithm, then the accident can be prevented by the driver's corrective maneuvers. For situations where rollover warning is ineffective, active rollover control is necessary. Most of the rollover warning algorithms use instantaneous rollover-threat index to identify the rollover threat. Since a rollover warning may be issued at 75 % of the rollover threshold acceleration, the time from warning to rollover is too short for the driver to respond effectively. However, if the rollover threat is predicted using the expected maneuvers, a warning can be issued sufficiently in advance of the event. This fact implies that warning systems based on predicted rollover threat can be more effective. Many control strategies have been designed to prevent rollover, most of them based on active speed control and active roll control. However, active roll control is ineffective for sharp turns, since it does not reduce the lateral acceleration, and requires hydraulic actuators which increase the cost considerably. On the other hand, the use of differential braking prevent jack-knifing and loss of direction generated by sudden braking during cornering. Different loading configurations produce different reaction forces on each wheel. This motivates the use of nonlinear robust controllers which have to be able to deal with parametric uncertainties, but most controllers are based on reduced models, in order to lessen the computational requirements. Many mathematical models for tractor semitrailers have been developed in order to derive active control algorithms. The Automotive Research Center of the University of Michigan developed the 33 degrees-of-freedom ArcSim model (UMTRI, 1997) to study the acceleration/braking and handling responses of an US Army 6-axle tractor-semitrailer. In (Hyun & Langari, 2003), the vehicle model for single-unit heavy

An omnidirectional inertial switch with rectangular spring is proposed in this paper, and the prototype has been fabricated by surface micromachining technology. To evaluate the threshold consistency and stability of omnidirectional inertia switch, the stiffness of rectangular suspension springs is analyzed. The simulation result shows that the coupling stiffness of the rectangular spring suspension system in the non-sensitive direction is a little more than that in the sensitive direction, which indicated that the omnidirectional switching system’s stability is reinforced, attributed to the design of rectangular springs. The dynamic response simulation shows that the threshold of the omnidirectional inertial switch using the rectangular suspension spring has high consistency in the horizontal direction. The prototype of an inertial switch is fabricated and tested successfully. The testing results indicate even threshold distribution in the horizontal direction. The threshold acceleration of the designed inertial switch is about 58 g in the X direction and 37 g in the Z direction, the contact time is about 18 μs.

Additive Manufacturing (AM) of three-dimensional objects is now being progressively realised with its ad-hoc approach with minimal material wastage (lean manufacturing) being one of its benefit by default. It could also be considered as an evolutional paradigm in the manufacturing industry with its long list of application as of late. Artificial Intelligence is currently finding its usefulness in predictive modelling to provide intelligent, efficient, customisable, high-quality and sustainable-oriented production process. This paper presents a comprehensive survey on commonly used predictive models based on heuristic algorithms and discusses their applications toward making AM “smart”. This paper summarises AM’s current trend, future opportunity, gaps, and requirements together with recommendations for technology and research for inter-industry collaboration, educational training and technology transfer in the AI perspective in-line with the Industry 4.0 developmental process. Moreover, machine learning algorithms are presented for detecting product defects in the cyber-physical system of additive manufacturing. Based on reviews on various applications, printability with multi-indicators, reduction of design complexity threshold, acceleration of prefabrication, real-time control, enhancement of security and defect detection for customised designs are seen of as prospective opportunities for further research.

Background: Various technologies have been developed to quantify the pivot shift, as it is regarded as a key indicator of anterolateral rotatory laxity of the knee. Purpose: To determine the usefulness of a commercially available triaxial accelerometer (Kinematic Rapid Assessment [KiRA]) in numerically quantifying the pivot shift in patients under anesthesia with an anterior cruciate ligament (ACL)–deficient knee. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: Both knees of 50 patients (26 male [mean age, 30.4 years], 24 female [mean age, 26.6 years]) under anesthesia were assessed immediately before unilateral ACL reconstruction by an orthopaedic fellow and 1 of 3 experienced knee surgeons. The pivot-shift grade and 2 KiRA outputs (range of acceleration and slope of acceleration change) were compared. Results: The surgeon and fellow recorded the same pivot-shift grade for 45 of 50 patients (90%). Data from the 5 patients with no agreement and 1 patient with extreme outlying data were excluded from subsequent analysis. Using the KiRA range and slope data, the surgeon identified the injured knee in 74% and 76% of patients, respectively, while the fellow’s rate of injured knee identification was 74% and 80%, respectively. A correlation could be found only between pivot-shift grade and surgeon-derived range data ( ρ = 0.40; P < .01) but not slope data or any fellow-derived outputs. Using the surgeon-derived range data, there was a significant difference between a grade 3 pivot (>5 m/s2) and a grade 1 or 2 pivot (2) ( P = .01). Conclusion: Although a correlation between KiRA output data and pivot-shift grade was found when the device was used by an experienced surgeon, there was no correlation when used by a well-trained but less experienced orthopaedic fellow. Furthermore, the KiRA output data identified the ACL-deficient knee correctly in only 74% of patients. Although a threshold acceleration range value could be identified, above which the value was associated with a grade 3 pivot shift, this was dependent on the examiner, and distinction between other grades could not be made.

Investigation of damping of gravity–capillary waves (GCW) on the surface of turbulent fluid is a classical problem which geophysical applications are related to the problems of swell damping, interpretation of radar and optical images of ship wakes, development of physical mechanisms of wind wave suppression, etc. Analysis of the relevant literature reveals the necessity of setting reliable experiments to study the effect of damping of GCW due to turbulence. An original laboratory method of investigation of surface wave damping due to turbulence is described. The method is based on the parametric excitation of standing surface waves (so-called Faraday ripples) and simultaneous and independent generation of turbulence. The wave damping coefficient is determined by a threshold acceleration corresponding to the surface wave parametric excitation. The disadvantages of the previously used methods are eliminated or significantly reduced in the presented method, and the results are formulated in terms of eddy viscosity. It is revealed that the eddy viscosity coefficient is proportional to the rms velocity of turbulent pulsations, and achieves a maximum as a function of GCW frequency, when the GCW wavelengths are of order of the scales of turbulent eddies. This effect has never been mentioned in the literature, since the previous studies were focused on the investigation of wave damping due to small-scale (relative to the GCW wavelengths) turbulence. Applications of the obtained results to real-sea conditions are discussed.

A proof of concept of a triboelectric threshold shock sensor and its characterization are presented. Shock sensors are used in many applications in the automotive, shipping and other industries, mainly to determine if acceleration thresholds are met. Many shock sensors are only mechanical, so the only way to know if the threshold has been reached is to physically check the device. There are noticeable advantages of using triboelectric transduction and bi-stability to create a shock sensor. By combining a buckled-beam structure and a triboelectric generator, we created a proof of concept of a tunable threshold shock sensor. The sensor generates a voltage peak only if the base acceleration is beyond a threshold. In addition, the sensor produces voltage proportional to the base acceleration beyond the threshold acceleration. This means the output signal provides more information about the strength of the shock that the device experiences. The sensor concept is illustrated for a threshold shock of 3.26g, but the threshold can be tuned by increasing the compressive axial force of the buckled beam. Increasing this axial force increases the threshold shock the sensor can detect. Thus, the combined system is a tunable threshold shock sensor with enhanced functionality. We presented a mathematical model that captures important observations of the experiments and can be used as a design tool for more precise, high-resolution triboelectric shock sensors.

To assess the seismic performance of soil-nailed walls, a series of 1g shaking table tests was conducted on 0.8 m high wall models with different nail lengths. It was found that the seismic deformation mode of walls highly depends on the nail length and input motion parameters. The combination of a base sliding and rotating deformation mode was observed as the predominant mode of deformation and the length to height (L/H) ratio of 0.7 was presented as the critical ratio in seismic conditions. The pattern of the observed failure mechanisms was similar to a third-degree polynomial failure surface with a specific inflection point. Irrespective of different nail lengths, the threshold acceleration corresponding to the onset of plastic displacements was similar and equal to 0.5g for all models. Based on the formation of initial cracks, a range of Δx/H = 0.33%–0.56% (where Δx is the lateral displacement of the facing) was found as a transitional level from quasi-elastic to plastic state. Also, based on the initial development of the active wedge failure, a range of Δx/H = 3.3%–4.3% was found as a transitional level from plastic to failure state.

A rotating wheel experimental facility was developed to investigate incompressible Rayleigh-Taylor instability in elastic-plastic materials. A soft solid (mayonnaise) was chosen as the elastic-plastic material for experiments; material properties that include shear modulus and yield strength were fully characterized using a vane spindle type rheometer. Initial perturbations of varying amplitudes and wavelengths were generated on the interface of the soft solid using sinusoidal cutting guides. A backlit imaging technique was used in conjunction with a high-speed camera to track the motion of the interface at various phases of the instability. Results for both two- and three-dimensional perturbations were compared to study the acceleration required for instability and the growth after the interface yielded. Exponential growth rates were observed after instability was reached with trends of increasing growth rates for lower initial amplitudes. It was found that the acceleration required for instability increased when initial amplitude and wavelength decreased. Three-dimensional interfaces were found to be more stable. For both cases, a decrease in initial amplitude produced a more stable interface that increased the threshold acceleration required for the instability. Critical amplitude conditions for instability were calculated and compared with various analytical models and other experimental results.

As drivers age, their risk of being involved in a car collision decreases. The present study investigated if this trend is due, in part, to some risky drivers having a collision early in their driving lives and subsequently reducing their risky driving after that negative experience. Accelerometers and video cameras were installed in the vehicles of 16- to 17-year-old drivers ( N = 254), allowing coders to measure the number of g-force events (i.e., events in which a threshold acceleration level was exceeded) per 1,000 miles and the number of collisions. Among the 41 participants who experienced a severe collision, the rate of g-force events dropped significantly in the 1st month after the collision, remained unchanged for the 2nd month, and increased significantly in the 3rd month. There were no changes in the rate of g-force events at comparable time points for the drivers not involved in a collision. Being involved in a collision led to a decrease in risky driving, but this may have been a temporary effect.

Microelectromechanical systems (MEMS)-based high-performance accelerometers are ubiquitously used in various electronic devices. However, there is an existing need to detect physical impacts using low-cost devices with no electronic circuits or a battery. We designed and fabricated an impact sensor prototype using a commercial stereolithography apparatus that only consists of a plastic housing and working fluids. The sensor device responds to the instantaneous acceleration (impact) by deformation and pinch off of a water droplet that is suspended in oil in a sensor cavity. We tested the various geometrical and physical parameters of the impact sensor to identify their relations to threshold acceleration values. We show that the state diagram that is plotted against the dimensionless Archimedes and Bond numbers adequately describes the response of the proposed sensor.

On 23 October 2011, a Mw = 7.2 earthquake occurred in the Van Province in eastern Turkey, killing 604 people. The earthquake was triggered by a thrust fault due to a compression stress in the region, and caused extensive damage over a large area. Many structures in the earthquake region collapsed, and the damage spread from the city of Van to the town of Erciş, in a distance of 60 km. The earthquake generated several slope movements and liquefaction failures in the region, and this study evaluates these processes from the perspective of engineering geology, and presents field and laboratory results related to these processes. Attenuation relationships were used for estimation of peak ground accelerations (PGAs), and an empirical liquefaction evaluation method employing ground accelerations was used to define threshold accelerations initiating the liquefaction. The results demonstrate that landslides were widespread and more frequently observed in the field in comparison with earthflows and rockfalls. Flow-type liquefaction and lateral spreading was found to be widespread and more common than the liquefaction-related settlement. The minimum threshold acceleration value for the initiation of soil liquefaction was calculated to be 188.87 cm s−2 (~0.19 g) in the earthquake region. Laboratory results indicated that the soil liquefaction was closely associated with grain size. The slope instabilities, liquefaction and associated ground failures occurred mainly in rural areas, and their impact on structures was quite low as compared to the human loss and structural damage by the earthquake.

On 23 October 2011, a Mw = 7.2 earthquake occurred in the Van Province in eastern Turkey, killing 604 people. The earthquake was triggered by a thrust fault due to a compression stress in the region, and caused extensive damage over a large area. Many structures in the earthquake region collapsed, and the damage spread from the city of Van to the town of Erciş, in a distance of 60 km. The earthquake generated several slope movements and liquefaction failures in the region, and this study evaluates these processes from the perspective of engineering geology, and presents field and laboratory results related to these processes. Attenuation relationships were used for estimation of peak ground accelerations (PGAs), and an empirical liquefaction evaluation method employing ground accelerations was used to define threshold accelerations initiating the liquefaction. The results demonstrate that landslides were widespread and more frequently observed in the field in comparison with earthflows and rockfalls. Flow-type liquefaction and lateral spreading was found to be widespread and more common than the liquefaction-related settlement. The minimum threshold acceleration value for the initiation of soil liquefaction was calculated to be 188.87 cm s−2 (~0.19 g) in the earthquake region. Laboratory results indicated that the soil liquefaction was closely associated with grain size. The slope instabilities, liquefaction and associated ground failures occurred mainly in rural areas, and their impact on structures was quite low as compared to the human loss and structural damage by the earthquake.

We have demonstrated a batch-fabricated inertial microswitch with extended contact time using carbon nanotube (CNT)-contact pads. Self-assembled and aligned CNT bundles, as deformable electromechanical contact pads are selectively synthesized on fully fabricated single crystal silicon microstructures. Outstanding mechanical flexibility and resilience, as well as electrical conductivity of CNTs, make them suitable as an electromechanical contact material. It is experimentally verified that the elastic deformation of CNTs dramatically enhances the contact time of the inertial microswitch from 7.5 μs to 114 μs. Due to the prolonged contact time, the presented inertial microswitch provides reliable and easy detection of threshold acceleration, which is crucial in diverse commercial applications such as airbag restraint systems in vehicles or geriatric healthcare systems.

© Published under licence by IOP Publishing Ltd. We proposed an autoparametric excitation harvester employing a microfabricated leaf spring for the base beam and a synchronized switch harvesting on inductor (SSHI) interface. Our harvester achieved miniaturization, low threshold acceleration of the autoparametric excitation, and increase in output power, compared with the previous work. The base beam for amplifying the excitation was microfabricated from a stainless steel film, through the photolithography followed by the wet-chemical etching. To trigger the autoparametric excitation, the main and the base beams are designed such that the resonance frequency for the base beam becomes twice higher than that for the main beam. The resonance frequencies obtained in experiment for the main and the base beams were 26.6 and 53.1 Hz, respectively. This study employed a self-powered parallel SSHI interface, which can increase the piezoelectric voltage and thus the output power, consuming only a small portion of the harvested energy. The harvester connected with the self-powered SSHI interface successfully displayed the autoparametric excitation at acceleration greater than 1.0 m/s2, and the output power showed 1.12 mW at the frequency of 53.1 Hz under the acceleration of 2.0 m/s2, which is 1.43-fold increase over the standard AC-DC interface.

International audience; Triggering large-scale motion by imposing vibrations to a system can be encountered in many situations, from daily-life shaking of saltcellar to silo unclogging or dynamic earthquakes triggering. In the well-known situation of solid or granular friction, the acceleration of imposed vibrations has often been proposed as the governing parameter for the transition between stick-slip motion and continuous sliding. The threshold acceleration for the onset of continuous slip motion or system unjamming is usually found of the order of the gravitational acceleration. These conclusions are mostly drawn from numerical studies. Here, we investigate, in the laboratory, granular friction by shearing a layer of grains subjected to horizontal vibrations. We show that, in contrast with previous results, the quantity that controls the frictional properties is the characteristic velocity, and not the acceleration, of the imposed mechanical vibrations. Thus, when the system is statically loaded, the typical acceleration of the vibrations which trigger large slip events is much smaller than the gravitational acceleration. These results may be relevant to understand dynamic earthquake triggering by small ground perturbations. Granular assemblies are athermal systems, often used as paradigms to study the dynamics of industrial or natural processes, such as fault gouge and earthquake nucleation 1–6. When submitted to mechanical vibrations, granular media can behave as thermalized fluids when the vibrations are large enough, or remain in a solid-like state for small enough vibrations. Such a transition between jammed and unjammed states has been reported to occur when the peak-acceleration characterizing the vibration is of the order of the gravitational acceleration 7,8

This paper presents a complete threshold acceleration detection microsystem comprising an array of threshold accelerometers and a low power interface circuit. The sensors were designed and fabricated using the bulk-silicon dissolved-wafer process. The process offers a wide latitude in sensor threshold levels, as demonstrated in the fabrication of devices with levels of 1.5–1000 g, bandwidths of 45 Hz to 40 kHz, with mass sizes ranging from 0.015 µ gt o 0.7µg, and low-resistance gold–gold contacts for the switch. The interface circuit dissipates less than 300 µW, measures 2. 2m m× 2.2 mm; it was fabricated in-house using a standard 3 µm, p-well CMOS (complementary metal oxide semiconductor) process, and is connected to the sensor chip in a multi-chip module. The key aspects of the microsystem are the implementation of sensor redundancy and supporting circuit logic to improve detection accuracy and fault tolerance, which are crucial factors in many applications. In addition, the microsystem supports communication with a standard microcontroller bus in a smart sensor network.

Currently, the seismic design method of a container crane is adopted the 'seismic coefficient method'(pseudo static method). In case of extremely high intensity input seismic motion such as Level 2, the dynamic behavior of a container crane is expressed in terms of lift off of the legs from the rails and locking motion. The current design method can not treat the behaviors mentioned above. To evaluate and develop the design method for the Level 2 input motion, 1/15 scale model shake tsets, simple mass-spring numerical analyses and 3-D dynamic FEM analyses were conducted. From the model shake test results, a threshold acceleration level of the lift off of the legs from the rails showed good agreement with a pseudo static horizontal acceleration of lift off the legs predicted in the design method. Proposed 3-D FEM model of container crane can simulate the dynamic behavior of a crane model during a shake table test even when the legs lifted off from the rails. The simple mass-spring model is also a useful numerical method for the case of smaller acceleration level when the legs do not lift off.

This paper deals with nearly inviscid, capillary–gravity, modulated waves parametrically excited by monochromatic horizontal vibrations in liquid containers whose width and depth are both large compared with the wavelength of the excited waves. A general linear amplitude equation is derived with appropriate boundary conditions that provides the threshold acceleration and associated spatiotemporal patterns, which compare very well with experimental measurements and visualizations. The primary instability is associated with a pair of complex Floquet multipliers that are close to (but strictly different from) −1, meaning that the instability is not strictly (2:1) subharmonic. The resulting (quasi-periodic) waves are generally oblique, not perpendicular to the vibrating endwalls. The extension of the theory to other confined systems such as vibrating containers of arbitrary shape and vibrating drops is also considered.

We consider layers of non-cohesive granular materials lying on a vertically vibrating surface. Above a threshold acceleration, Γ = Γc internal convective motion begins, and the free surface of the granular material becomes unstable to the formation of a heap. As Γ increases further, there are several higher order instabilities, traveling surface waves, subharmonic bifurcations, and bubbling. We find that for particles of diameter d ≤ 1 mm, the pressure P of the surrounding gas plays a key role in the instabilities. We propose criteria to determine when gas effects are relevant.

Summary Oyster larvae (Crassostrea virginica) could enhance their settlement success by moving toward the seafloor in strong turbulence associated with coastal habitats. We characterized the behavior of individual oyster larvae in grid-generated turbulence by measuring larval velocities and flow velocities simultaneously using infrared particle image velocimetry. We estimated larval behavioral velocities and propulsive forces as functions of the kinetic energy dissipation rate ε, strain rate γ, vorticity ξ, and acceleration α. In calm water most larvae had near-zero vertical velocities despite propelling themselves upward (swimming). In stronger turbulence all larvae used more propulsive force, but relative to the larval axis, larvae propelled themselves downward (diving) instead of upward more frequently and more forcefully. Vertical velocity magnitudes of both swimmers and divers increased with turbulence, but the swimming velocity leveled off as larvae were rotated away from their stable, velum-up orientation in strong turbulence. Diving speeds rose steadily with turbulence intensity to several times the terminal fall velocity in still water. Rapid dives may require a switch from ciliary swimming to another propulsive mode such as flapping the velum, which would become energetically efficient at the intermediate Reynolds numbers attained by larvae in strong turbulence. We expected larvae to respond to spatial or temporal velocity gradients, but although the diving frequency changed abruptly at a threshold acceleration, the variation in propulsive force and behavioral velocity was best explained by the dissipation rate. Downward propulsion could enhance oyster larval settlement by raising the probability of larval contact with oyster reef patches.

SUMMARY Determining temporal and spatial variation in feeding rates is essential for understanding the relationship between habitat features and the foraging behavior of top predators. In this study we examined the utility of head movement as a proxy of prey encounter rates in medium-sized Antarctic penguins, under the presumption that the birds should move their heads actively when they encounter and peck prey. A field study of free-ranging chinstrap and gentoo penguins was conducted at King George Island, Antarctica. Head movement was recorded using small accelerometers attached to the head, with simultaneous monitoring for prey encounter or body angle. The main prey was Antarctic krill (>99% in wet mass) for both species. Penguin head movement coincided with a slow change in body angle during dives. Active head movements were extracted using a high-pass filter (5 Hz acceleration signals) and the remaining acceleration peaks (higher than a threshold acceleration of 1.0 g) were counted. The timing of head movements coincided well with images of prey taken from the back-mounted cameras: head movement was recorded within ±2.5 s of a prey image on 89.1±16.1% (N=7 trips) of images. The number of head movements varied largely among dive bouts, suggesting large temporal variations in prey encounter rates. Our results show that head movement is an effective proxy of prey encounter, and we suggest that the method will be widely applicable for a variety of predators.

apital investment in national infrastructure is significant. The need to maintain and protect critical infrastructure links has led in recent years to significant developments in the area of structural health monitoring. The objective is to track a structure’s long-term performance, typically using sensors, and to successively compare the most recently measured responses with prior response history. During construction of the West Street On-Ramp, a curved concrete box girder bridge, located in the city of Anaheim (California), eleven accelerometers were permanently installed on its bridge deck. The associated data acquisition system was configured to record once a specified threshold acceleration response was exceeded; during the period 2002–2010 a total of 1350 datasets including six earthquakes, for each of the eleven sensors, were acquired. This automatically acquired data was supplemented, during the summer of 2009, with responses measured during controlled vehicle tests. Six accelerometers were additionally installed on the frame of the weighed test vehicle. This paper presents the findings of the analyses of these measured data sets and serves to inform owners and managers as to the potential feedback from their instrumentation investment. All response histories were analyzed using frequency domain techniques for system identification. Extraction of the modal characteristics revealed a continuous reduction, of approximately 5%, in the first three natural frequencies over the period of the study. The measured responses from the vehicle sensors are discussed in the context of identifying the potential for bridge frequency measurement using instrumented vehicles. Deposited by bulk import

Globular clusters are useful to test the validity of Newtonian dynamics in the low acceleration regime typical of galaxies, without the complications of non-baryonic dark matter. Specifically, in absence of disturbing effects, e.g. tidal heating, their velocity dispersion is expected to vanish at large radii. If such behaviour is not observed, and in particular if, as observed in elliptical galaxies, the dispersion is found constant at large radii below a certain threshold acceleration, this might indicate a break down of Newtonian dynamics. To minimise the effects of tidal heating in this paper we study the velocity dispersion profile of two distant globular clusters, NGC 1851 and NGC 1904. The velocity dispersion profile is derived from accurate radial velocities measurements, obtained at the ESO 8m VLT telescope. Reliable data for 184 and 146 bona fide cluster star members, respectively for NGC 1851 and NGC 1904, were obtained. These data allow to trace the velocity dispersion profile up to ~2r0, where r0 is the radius at which the cluster internal acceleration of gravity is a0 = 10e-8 cm/s/s. It is found that in both clusters the velocity dispersion becomes constant beyond ~r0. These new results are fully in agreement with those found for other five globular clusters previously investigated as part of this project. Taken all together, these 7 clusters support the claim that the velocity dispersion is constant beyond r0, irrespectively of the specific physical properties of the clusters: mass, size, dynamical history, and distance from the Milky Way. The strong similarly with the constant velocity dispersion observed in elliptical galaxies beyond r0 is suggestive of a common origin for this phenomenon in the two class of objects, and might indicate a breakdown of Newtonian dynamics below a0., Comment: Accepted for publication by A&A main journal. 12 pages, 12 figures

When an oil droplet is placed on a quiescent oil bath, it eventually collapses into the bath due to gravity. The resulting coalescence may be eliminated when the bath is vertically vibrated. The droplet bounces periodically on the bath, and the air layer between the droplet and the bath is replenished at each bounce. This sustained bouncing motion is achieved when the forcing acceleration is higher than a threshold value. When the droplet has a sufficiently low viscosity, it significantly deforms : spherical harmonic \boldmath{$Y_{\ell}^m$} modes are excited, resulting in resonant effects on the threshold acceleration curve. Indeed, a lower acceleration is needed when $\ell$ modes with $m=0$ are excited. Modes $m \ne 0$ are found to decrease the bouncing ability of the droplet. When the mode $\ell=2$ and $m=1$ is excited, the droplet rolls on the vibrated surface without touching it, leading to a new self-propulsion mode., 4 pages, 6 figures

The permanent displacement of a slope in Noshiro city during the 1983 Nihonkai-Chubu earthquake is simulated by Distinct Element Analysis. The slope of 2.6 degrees average inclination and 200m length is modeled as 3180 element Distinct Element Model (DEM). A FEM model of 611 quadrilateral elements is utilized to verify the DEM model in the small displacement range. In quasi-static analysis using lateral seismic coefficients of 0.1-0.3, both FEM and DEM models are found to give similar failure surface and critical acceleration, i. e., threshold acceleration for initiating failure. Some subsurface layers are supposed to have been liquefied during the earthquake ground motion. In the model, both the stiffness and shearing resistance of these layers are reduced to account for their volumetric change and liquefaction. The movement of the slope due to subsurface soil liquefaction is simulated realistically with the DEM model including vertical crack and settlement at the top of the slope and lateral sliding of the surface layers. From parametric studies, volumetric change of the liquefied layer is found to be the most influential factor to induce deformation of the slope.

International audience; Seismic vulnerability in wide areas is usually assessed in the basis of inventories of structural parameters of the building stock, especially in high hazard countries like USA or Italy. France is a country with moderate seismicity so that it requires lower-cost methods. Ambient vibrations analyses seem to be an alternative way to determine the vulnerability of buildings. The modal parameters we extract from these recordings give us a 1D model for each class of building found in the study area. We then study the response of these models to realistic seismic excitations (scenarios) including site effects in order to determine a threshold acceleration sustained by this class of building which we interpret as a vulnerability index. The distribution of the classes in the city will lead to a vulnerability map. In order to validate this method, we compare the modal parameters of a building in Grenoble (France) determined under ambient noise and during a stronger excitation: the demolition of a nearby bridge. A statistical study of recordings using time windowing gives uncertainties and leads us to conclude that the modal parameters are equal.

The effect of low-frequency mechanical vibration, applied during the solidification process, on the microstructure and mechanical performance of aluminium sand-casting was investigated. Both green-sand moulds and chemically bounded sand moulds were used. The vibration was applied to the moulds along the vertical axe. The investigated acceleration range was included between 0.1g and 15g. The effect of different sections and cooling rate was considered, as well as the influence of using different amplitude at constant acceleration. The microstructure and porosity of the ingots was evaluated by optical microscopy and image analysis. The mechanical properties were investigated by tensile tests performed both on cylindrical and different section flat specimens. Microstructure modification of dynamically solidified castings was achieved, consisting on a refined or a completely non-dendritic microstructure, with a globular aspect and quite rare dendrite fragments. The effective threshold acceleration in order to modify the microstructure of the different section considered was assessed. The ingots presenting modified microstructure revealed interesting mechanical performance, that means mainly higher fracture strain.

The mode of gravisensing in higher plants is not yet elucidated. Although, it is generally accepted that the amyloplasts (statoliths) in the root cap cells (statocytes) are responsible for susception of gravity. However, the hypothesis that the whole protoplast acts as gravisusceptor cannot be dismissed. The nature of the sensor that is able to transduce and amplify the mechanical energy into a biochemical factor is even more controversial. Several cell structures could potentially serve as gravireceptors: the endoplasmic reticulum, the actin network, the plasma membrane, or the cytoskeleton associated with this membrane. The nature of the gravisusceptors and gravisensors is discussed by taking into account the characteristics of the gravitropic reaction with respect to the presentation time, the threshold acceleration, the reciprocity rule, the deviation from the sine rule, the movement of the amyloplasts, the pre-inversion effect, the response of starch free and intermediate mutants and the effects of cytochalasin treatment. From this analysis, it can be concluded that both the amyloplasts and the protoplast could be the gravisusceptors, the former being more efficient than the latter since they can focus pressure on limited areas. The receptor should be located in the plasma membrane and could be a stretch-activated ion channel.

A proof is developed from first principles, independent of general relativity and of thermodynamics, that there exists a threshold acceleration above which radiation (real particle creation) from the vacuum must occur. The radiation is not expected to follow a Planckian distribution. PACS Codes: 03.65.Bz 04.70.-s 26.35.+c, v. 1.5 adds minor clarification on nonthermal distribution