Acceleration In Vertical Direction Research Articles

Simplified solution to analyse seismic stability of reinforced soil wall

ABSTRACT The normalized tensile reinforcement force for the seismic stability of reinforced soil walls using some rigorous methods considering the pseudo-static seismic forces is mostly used by the earlier researchers in the design of retaining walls backfilled with cohesive soil. Few studies have been presented using horizontal slice method without taking effect of the seismic acceleration in vertical direction. In the present study, a simplified solution has been presented using the pseudo-static equilibrium of the reinforced soil wall taking the effect of seismic accelerations in the horizontal and in the vertical direction. The seismic stability analysis presented here accounts the required total reinforcement strength in terms of the maximum value of reinforcement force coefficient and the critical inclination of failure plane. Taking some geometrical values of retaining wall and soil characteristics based on the literature, a detailed and comparative parametric study presented here accounts the effect of cohesion of the backfill, angle of internal friction of soil, horizontal seismic coefficient, vertical seismic coefficient and surcharge loading.

A study on evaluation of ship motion in irregular waves

In this paper, the results of evaluating the passenger comfort due to the standard deviation of acceleration in vertical and lateral direction regarding the ship response in irregular wave by ordinary strip method in regular wave and energy spectrum using linear superposition theory in order to evaluate the motion of experimental ship are as follows. According to the results of ship response, it was possible to find that, in order to reduce the motion of ship, a ship operating in bow sea was more stable than in quartering sea. In the results of analyzing the standard deviation of acceleration in vertical direction according to each component wave pattern, when there was a wave length of 56m and an average wave period of 6 sec, most of cases showed the peak value. And among them, the standard deviation was 0.35 which was the highest in head sea. And in case of lateral direction, the maximum value was shown in a wave length of 100m and an average wave period of 8 sec. And it was 0.16 in beam sea and   . In the evaluation of passenger comfort due to standard acceleration in vertical and lateral direction, it was 80% in head and bow sea. On the other hand, it was shown to be 15% in follow sea. Accordingly, when the expected wave height in a sea area where a training ship was intended to operate was known, it was possible to predict the routing of ship. And altering her course could reduce the passenger comfort by approximately 50%.

A Novel Artificial Neural Network Biodynamic Model for Prediction Seated Human Body Head Acceleration in Vertical Direction

Nowadays, usage of vehicles increases due to modern lifestyles, and many people are exposed to vibrations in vehicles. Vibrations in low frequency range cause some serious long-term diseases in both aspects physically and psychologically. Vibration model helps researchers to have better interpretation of vibrations transmitting to human organs. Lumped models are very popular in this field, and different types of models with various degrees of freedom have been introduced. The main disadvantage of lumped models is that due to its fixed weight, some modifications need to be made to new subjects. Therefore, a new biodynamic model with artificial neural network method was constructed to simulate transmitted vibration to head for seated human body by conducting indoor vertical vibration experiments. Five healthy males participated in the tests. They were subjected to vertical vibration, and their responses were recorded. A neural network model was trained by input-output accelerations. The developed model was able to predict head acceleration from exciting vibration at the pelvic. In addition, weight and height of human body were considered as input factors. The comparison between the model evaluation results and the experimental and other lumped models affirmed high accuracy of the achieved artificial neural network biodynamic model.

장기 공용 후, 디스크받침이 설치된 판형교의 동적 거동 평가

철도판형교에 설치된 디스크받침의 장기간 공용 후의 판형교 및 디스크받침의 거동을 평가하기 위해서 디스크받침 설치 직후와 5.5년의 공용 후에 차량 주행에 의한 동적 응답을 측정하고 분석하였다. 본 연구에서 12 m 판형교를 대상으로 연구를 수행하였으며, 교량의 수직 변위 및 가속도, 교량받침의 수직 변형량 및 고유진동수의 변화를 비교 분석하였다. 또한, 디스크받침의 수직 강성을 추정하였으며, 이를 이용하여 계산된 디스크받침의 변형과 측정된 응답을 비교하였다. 교량의 중앙 수직변위, 디스크받침의 고정단의 변형 및 1차 모드 고유진동수는 5.5년의 공용에 의해서 크게 변하지 않았으나, 가동단의 변형이 상대적으로 크게 증가하는 현상이 발생하였다. This study conducts two field tests of a steel railway bridge supported disk bearings to assess the long-term dynamic behavior of the steel railway bridge and a disk bearing in the service for 5.5 years; the length of the bridge is 12 m. Displacement and acceleration in vertical direction, deformation of disk bearings and natural frequency of the first mode are measured and analyzed. In addition, the vertical stiffness of the disk bearing is estimated, and the deformation of the disk bearing due to static loading is calculated using the estimated stiffness and compared to the measured dynamic response. Vertical displacement at mid-span, deformation of a fixed disk bearing, and the first natural frequency do not vary due to the 5.5 year service. However, deformation of an expansion disk bearing increases sharply comparing to other components.

Functional changes in cerebral and paraspinal muscle physiology of healthy women during exposure to whole-body vibration

The objective of this study was to investigate the effects of whole-body vibration on multiple tissues simultaneously in fourteen healthy women. On three separate days, participants were exposed to frequencies, 3, 4.5, or 6 Hz (at 0.9 g r.m.s acceleration in vertical direction) per day on a simulator for 16 min. While sitting ‘with’ and ‘without’ backrest support, participants also performed handgrip contractions for 1 min. Cerebral and lumbar muscle oxygenation and blood volume responses were measured using near-infrared spectroscopy. Cardiorespiratory responses were collected using a metabolic cart. In general, cerebral and cardiorespiratory responses increased with vibration compared to without vibration, whereas in the lumbar region oxygenation and blood volume responses decreased. Greatest cerebral responses were observed at 6 Hz ( P < 0.05). When compared to exposure to vibration without performing work, significant decrease in lumbar responses was observed during handgrip contractions in both conditions of sitting ‘with’ and ‘without’ a backrest ( P < 0.05). Such decreases in the lumbar responses suggest postural load due to prolonged sitting combined with physical activity during vibration, might reduce vascular supply to the paraspinal muscles. This study reiterates the importance of understanding the physiological basis for various health disorders in women due to exposure to whole-body vibration.

On Possible Nature of Pre-eclipse Dips in Light Curves of Semi-detached Systems with Steady-state Disks

In order to explain pre-eclipse dips at phases ∼0.7 in light curves of cataclysmic variables, the hypothesis of the thickening at the outer edge of the accretion disk is usually used. Shock-free nature of the interaction between the stream and the steady-state disk in the stationary solution poses the question on the cause of the of matter presence at significant height above the accretion disk in systems of this type. The results of 3D modeling have shown that in the absence of direct collision between the stream and the disk the formation of thickening of the halo above the disk is also possible. In the framework of the hot line model the significant part of the matter gets the acceleration in vertical direction. Gas movement in the vertical direction together with its movement along the outer edge of the disk leads to the gradual increase of the near-disk halo width. Maximum of the calculated thickening located above the outer part of the disk corresponds to the ∼0.7 phase that is in agreement with the observed values for cataclysmic variables with steady-state disks. This fact confirms the hot line model suggested earlier for description of the flow structure in semi-detached binaries and gives new opportunities for the interpretation of the light curves of such systems.

RETRACTED: Design of artificial neural networks for rotor dynamics analysis of rotating machine systems

A Neural Network predictor investigation is presented for analyzing vibration parameters of the rotating system. The vibration parameters of the system such as amplitude, velocity and acceleration in vertical direction were measured at the bearing points. The system's vibration and noise were analyzed for different working conditions. The designed neural predictor has three layers which are input, hidden and output layers. In the hidden layer 10 neurons were used for this approximation. The results showed that the network would be used as analyzer of such systems in experimental applications.