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The localization of shaking forces acting on an operating machine is an important step to identify vibration and noise sources. The forced vibration response of a linearly vibrating structure is assumed to be linear. However, the energy distribution of a linearly vibrating structure contains “coupled terms” in the modal decomposition of the vibration energy density function. These coupled energy terms represent the cross-modal energy density associated with the exciting force of a dynamic structure under forced vibration. In this research, it is proved analytically that the high-order cross-modal energy densities of a linear dynamic structure are highly correlated to the location of the external exciting force. Using this finding, a new force localization index based on the high-order cross-modal energy densities of a dynamic structure is proposed and tested. Numerical tests on uniform and step beam structures under force excitation with different frequencies and locations have been carried out to test the effectiveness of the proposed force localization method. It is found that the proposed force localization method works well on vibrating beam structures. Experiments are carried out to verify the proposed force localization method.

Annoyance caused by railway operations has gained increasing attention in the Netherlands. This has led to a multimillion research project into different aspects of train passages as a source of vibration. The project is initiated by the Dutch railway operator ProRail. In advance of this project a study has been performed on vibration signals at free field caused by cargo train passages at four different sites. The signals have been compared to trackside measurements. The trackside measurements consist of fibre optic measurements of the rail deflection at pre-installed locations different from the free field vibration measurement sites. Different vibration level indicators have been studied like train speed, axle loads and wheel roughness indicators and their correlation with vibration levels. Vibration levels are defined in several ways, a frequency weighted running mean square value (so-called Veffmax), a 2-second RMS level (unweighted) and levels per frequency band. Special attention is given to the variation in time of the measured vibration signals during the train passage to see whether 'bad quality' wheel passages can be identified. The results give valuable input for a future case study in which wheel quality and its influence on vibration levels will be studied further.

Creation of downhole sources of elastic vibrations for the implementation of vibrowave enhanced oil recovery methods is an urgent task of mining engineering. The paper substantiates the expediency of using an electromagnetic linear drive of a downhole vibration source to generate axial shock pulses. A mathematical model is proposed that describes the dynamics of movement of the striker of electromagnetic impact unit under the action of traction forces of coils, friction forces and aerodynamic resistance, taking into account the elastic constraints at the end of the lower and upper working strokes of the striker. Theoretical dependences of striker displacement and speed on time, obtained using the developed model, are presented, and their high convergence with the experimental data is shown. The mathematical model of electromagnetic impact unit can be used to optimize its parameters, as well as to design new standard sizes of vibration sources that meet the requirements of the oil and gas industry.

There are some studies in the literature in order to make the interpretation of human tissues having different characteristics. Some of these studies focused on the evaluation of human face tissues. Vibration signals generated from vocal cords have been used in these studies about human face tissues. However, any study using the vibration signals recorded by applying the external vibration source having fixed frequency value is not available in the literature. In this study, it is aimed to investigate the frequency characteristics of the vibration signals recorded from the human face. These signals obtained from nine different regions on the faces of subjects are analysed using frequency characteristics. In the analysis stage, median and maximum frequency values are calculated and evaluated. So, the softness and hardness interpretation about these regions on the face can be made and the frequency ranges of these regions can be determined. As a result, it is observed that low-frequency signals are dominant in hard regions and high-frequency signals are dominant in soft regions.

Protecting sensitive and/or valuable facilities is of concern when placing them near a machine foundation. There are methods available and well-studied such as wave barriers to reduce tran...

The article is devoted to the study of the vibrational waves propagation and the estimation of the level of their influence on various objects. The development of adequate mathematical models, methods for the estimation of vibration wave levels at various distances from the earth foundation is an urgent task. In this article, a mathematical model was developed using a variational approach to study the propagation of vibration waves induced by railway transport at various distances. A technique for solving the considered problems was developed using the finite element method. The effect of the level of vibrations propagating from the railway transport motion on buildings located at a certain distance from the vibration source was investigated, when the railroad bed is located at the foundation level or at a certain height from the foundation. It was stated that if the railroad bed is located at a height of 2 m from the level of the earth foundation of the building, then the amplitude of vibration displacements in the building can be reduced from 1.5 to 3.5 times.

Vibration assessment criteria for cosmetic building damage are specified in terms of peak velocity thresholds. For masonry buildings, these thresholds are relatively low compared to vibration levels generated by various sources in the built environment. Therefore they will be exceeded numerous times over the lifetime of most buildings. These exceedances are important when one tries to establish or disprove a causal relation between building damage and a vibration source. Despite the relevance of this information, little is known about the number of times velocity thresholds for cosmetic building damage are exceeded in the built environment. The vibration data collected over a period of more than 5 years in 326 buildings, mostly constructed in masonry and randomly distributed over the Province of Groningen, allowed for a unique opportunity to gain insight. First of all, to determine the number of times these thresholds were exceeded, and secondly to make a comparison between shallow earthquakes and other sources. The number of exceedances and the return period were determined for a set of thresholds (i.e. 0.3, 1, 3, 5, 10, and 20 mm/s), which align with peak velocity thresholds typically encountered in vibration assessment guidelines and standards. The results obtained over a 1 year period with very low seismic activity (only earthquakes with M < 2.0) show that the velocity thresholds for cosmetic damage to masonry buildings (i.e. 1, 3, and 5 mm/s) were exceeded on average less than once a month for 80% of the building sensors. For buildings with a large number of exceedances of these thresholds, the most important sources appear to be traffic, construction work, and hits near the sensor. A subset of 59 building sensors was selected, for which the full operational period of about 5 years was analysed to determine the contribution of earthquakes to the threshold exceedances. Less than 1% of the 1 mm/s exceedances measured by the 59 sensors over their full operational period were caused by earthquakes. Only for building with few exceedances (less than 8), the relative influence of induced earthquakes on the number of exceedances is significant (between 30 and 50%).

We analyze temporal variations in the travel times of both P and S waves (Vp and Vs) for 14 months at Toyohashi (central Japan) with a continuously operating vibration source that could efficiently produce both P and S waves. Seismic waves produced by the source, which is called the accurately controlled routinely operated signal system (ACROSS), are recorded by three nearby seismic stations, and the travel time variation at each station is estimated using the transfer function calculated from the recorded data. Long-term variations in Vp and Vs are observed and can be interpreted by the change in fluid saturation and crack density of the subsurface rocks. The variation in fluid saturation and crack density are consistent with that in the groundwater level, which is measured at the station nearest to the ACROSS. Short-term responses to rainfalls are observed at the station nearest to the ACROSS system; the interpretation of the changes in crack density and saturation is inconsistent with the ground water observation, partly owing to the initial response to rainfall. This can be interpreted as an air–water mixture within pores or cracks on a fine scale.

Indonesia merupakan salah satu negara dengan gunungapi terbanyak di dunia. Rangkaian gunungapi membentang dari Pulau Sumatera, Jawa, Bali dan Nusa Tenggara. Dari kepulauan di Laut Bdana sampai bagian utara Pulau Sulawesi merupakan daerah gunungapi terpanjang di dunia. Indonesia memiliki 129 gunungapi aktif, 70 buah diantaranya berancaman dan 500 buah tidak aktif. Sejak tahun 1800, paling tidak telag tercatat 600 kali letusan oleh 70 gunungapi di Indonesia. Karena itu, Indonesia dapat dikatakan sebagai negara yang rawan bencana, terutama ancaman bencana gunung berapi. Pengamatan, pemantauan, pencatatan, penyebaran informasi dan peringatan tanda bahaya terhadap aktivitas gunungapi menjadi salah satu fokus dalam penanggulangan bencana gunungapi. Untuk mendukung hal tersebut diperlukan instrumentasi deteksi aktivitas vulkanik gunungapi. Salah satu instrumentasi yang digunakan untuk memantau aktivitas gunung berapi Gunung Merapi adalah Real-time Seismic Amplitude Measurement (RSAM). RSAM adalah sistem yang menyediakan pengukuran kontinu dari amplitudo seismik rata-rata absolut dari jumlah stasiun seismik. RSAM menempati peran strategis dalam memantau aktivitas seismik gunung berapi terutama pada saat krisis sebelum letusan. Dalam penelitian ini, perancangan sistem RSAM menggunakan sensor geophone untuk mendeteksi getaran seismik. Frekuensi tes yang diberikan dalam penelitian ini termasuk 10 Hz, 30 Hz, dan 50 Hz. Sistem yang telah dirancang bangun dapat mendeteksi frekuensi dengan baik sebagaimana dibuktikan bahwa semakin besar frekuensi uji maka semakin banyak output grafik yang dihasilkan. Selain itu, besaran yang dihasilkan juga semakin besar. Pada frekuensi 10 Hz, magnitudo yang dihasilkan adalah 0,997, pada 30 Hz magnitudo yang dihasilkan 1,559 sedangkan pada 50 Hz magnitudo yang dihasilkan adalah 1,962. Sistem RSAM yang dirancang bangun menghasilkan amplitudo yang memiliki hubungan linier dengan besarnya getaran sumber disediakan..

The challenges we are faced with in localizing objects are the complex environments, such as tunnels, high-rise areas and underground parking lots. This paper develops a bionic vibration source localization device to estimate the direction of the object which is inspired by the unique and precise hunting localization mechanism of scorpions. The localization device uses the sensor array, which is patterned after the scorpions’ biological sensory structure, and imitates the coding mode of scorpions’ sensory neurons for determination of the prey (vibration source) bearing. To verify the effectiveness of the localization device, some experiments were performed through real collected vibration signals. The Average Estimated Error (AEE) and the Relative Estimated Error (REE) of the experimental results were calculated to be 3.64° ± 2.44° and −1.43° ± 4.14°, respectively. It indicates that the device has a good performance to estimate the bearings of vibration sources at different distances and azimuths. This bionic localization device lays the foundation for the development of locating the moving object in some special conditions.

Due to the structural characteristics of railway turnouts, as well as their vulnerability to damage and other problems, the environmental vibrations induced by urban rail transit often have a greater effect on the railway turnouts than that on an ordinary line. Therefore, it is necessary to carry out an in-depth study on the characteristics of vibration source on the turnouts. In this paper, a group of representative turnouts is selected for field testing on four typical lines of different operational times in a Chinese city. The profile and rail irregularity of the turnouts are measured to evaluate the service condition of the turnouts and the wheel–rail interaction. The vibration acceleration of the track structure and tunnel wall is measured as the train passes the turnout by setting the measuring points in the two main vibration sources, including the switch and the crossing section. The time–frequency domain analysis method is used to analyze these data. It is found that the source strength of the tunnel wall in the crossing section is much greater than that in the switch section, and that the lateral vibration level is often greater than the vertical vibration level. Unexpectedly, there is a low positive correlation between the vibration level and the train speed, while the healthy state of the turnout rails has a great influence on the vibration level. According to the results of the research, the sources of vibration excitation in the turnouts are complex; therefore, it is necessary to comprehensively evaluate their environmental impact and take corresponding vibration control measures.

Vibrations propagating through the soil into the building can not only be harmful to the building structure or cause its accelerated wear, but can also effect on the vibrational comfort in the rooms. They can also be annoying for residents and building users, and in extreme cases can lead to sleep disorders, headaches and neurotic conditions. Especially vibrations from the low frequency range from 5 to 25 Hz are undesirable, because there are resonance frequencies of human internal organs in this frequency range. The human perception of vibrations in buildings, despite many researches made in the past, despite standards and requirements in this area, is still a topic not fully understood mainly due to the subjective nature of the perception of vibrations by various people. It is widely known that the type of transport vibration source has an impact on human perception. Vibrations generated by above-ground sources are more felt on the upper floors as opposed to vibrations generated from the underground. In this paper three types of transport vibrations are analyzed on one chosen building located in Warsaw. Human perception of vibration is evaluated according to two methods: root mean squared (RMS) and vibration dose value (VDV).

Harvesting energy from ambient vibration sources is challenging due to its low characteristic amplitude and frequencies. In this purpose, this work presents a compact hybrid vibration converter based on electromagnetic and magnetoelectric principles working for a frequency bandwidth and under real vibration source properties. The combination of especially these two principles is mainly due to the fact that both converters can use the same changes of the magnetic field for energy harvesting. The converter was investigated using finite element analysis and validated experimentally. Results have shown that a frequency bandwidth up to 12 Hz with a characteristic resonant frequency at 24 Hz and a power density of 0.11mW/cm3 can be reached.

When a high-power vibrating roller compact the subgrade, the vibration wave will quickly propagate along the surface of the subgrade and generate hazards to surrounding environment and structure. To study the vibration propagation rules of the roller, the vibration acceleration of the high-power vibrating roller was measured on the surface of the rock subgrade, coarse-grained soil subgrade and fine-grained soil subgrade. The respective relations between vibration acceleration and the distance from a vibration source in the vertical, horizontal radial and horizontal circumferential direction have been discovered. The research results show that the vibration peak frequency generated by the vibrating roller on the subgrade approximates vibration frequency. The vibration effective influence distance varies from 10m to14m, and the horizontal radial vibration is greater than that of vertical and horizontal circumferential direction. The vibration of the rock subgrade attenuates the most slowly and propagates the most remotely.

The tank vibration of power transformers comes from alternating forces acting on the core and windings. It is meaningful to study the vibration sources and the transmission characteristics in transformers for interpreting the constitution of the tank vibration specifically. This paper experimentally investigates the coupling between the winding vibration and the core vibration, as well as the vibration transmission characteristics on a single phase power transformer the winding vibration coupled with the core vibration has a broader frequency band than the responses caused by the electromagnetic force. For transmission characteristics, the oil-borne transmission is the main path for the winding vibration, while the structure-borne transmission highly depends on the modal characteristics of the tank. This work improves the understanding of the relationship between the internal vibrations and the tank responses.

Operational transfer path analysis is applied in this study to identify the vibration source and its critical transfer path. A simple analytical five-degrees-of-freedom mechanical isolation system is first taken as an example to illustrate the analysis flow and to validate the accuracy of operational transfer path analysis. The acceleration amplitude spectrum of the receiver is used to prove the accuracy, and the path contribution of each path is used to identify the critical path. Operational transfer path analysis is then applied to the cab mount system of a heavy commercial vehicle to identify the vibration source and its critical transfer path. The vibration energy propagation capabilities from the four cab mounts to the driver’s seat are analyzed by operational transfer path analysis with the path contribution analysis, and the maximum vibration source is identified by the path operation contribution analysis. The analysis and evaluation method of the operational transfer path analysis introduced in this study can provide a research foundation and reference for vibration or noise source identification in mechanical systems.

Offshore wind turbines (OWTs) are more and more widely used to produce electrical energy nowadays. Besides the constant wind and wave loads, earthquake excitation can be another important vibration source to the OWTs since many OWTs have been/will be constructed in the seismic prone areas. Extensive research works have been carried out to understand the dynamic behaviours of OWTs when they are subjected to multi-hazards (e.g. the simultaneous wind, wave and/or earthquake loadings). However, when seismic excitations are considered, the onshore earthquake records are normally used as inputs in the analyses due to the lack of offshore data and the difficulty in synthesizing the offshore seismic motions. This practice may lead to inaccurate structural response estimations since it is well known that the seawater can significantly suppress the seafloor vertical motions near the P wave resonant frequencies of the seawater layer, which in turn results in the different characteristics of onshore and offshore earthquake recordings. Moreover, the earthquake motions along the pile of OWTs are different from those at the ground surface, i.e. the earthquake motions vary with the soil depth. Recently, a method to stochastically simulate the earthquake ground motions on the offshore site was proposed, in which the influence of seawater layer was considered and the earthquake motions at any soil depth could be obtained. This paper carries out numerical simulations on the dynamic behaviours of OWTs subjected to the combined wind, wave and earthquake loadings, and the depth-varying offshore seismic motions are used as inputs in the analyses. The seismic responses of OWTs obtained from the onshore and offshore earthquake motions are calculated and compared. The influence of depth-varying ground motions on the dynamic responses of OWTs is discussed.

The movement and mechanical characteristics of oil-tea camellia fruit coupling with flower simultaneously during the harvest period were studied to provide an indispensable theoretical guideline for the mechanized picking machine. The mechanical properties of Camellia oleifera were obtained by investigating its flowers and fruits, and the vibration harvesting of Camellia oleifera was studied by using dynamic vibration device. The i-Speed3 high-speed camera was used to record the harvesting process, and the image analysis and calculation were carried out by its own Control-Pro software. The results showed that different varieties of Camellia oleifera had different flowering periods, ranging from 30 to 55 days; their weight also varied among varieties; there was no inevitable relationship between the binding force (pulling force and torque) of fruit stalks and their varieties, locations and diameter of fruit stalks. More importantly, during the vibration process, the fruit peeling speed is related to the vibration source clamping position and vibration parameters. Under the condition of short clamping distance and high frequency and low amplitude, the fruit is more likely to fall off.

Requirement of oil and gas industry in increasing of rate of hydrocarbon extraction from deposits contributes to development of science-based methods of oil production increasing. Vibrowave impact to productive seam is related to such methods. This impact can be effectively carried out with hole seismic signal sources. In the work results of study of load-bearing element of hole electro-magnetic pulse source are represented. Objective of the work is the study of static and dynamic strains of casing pipe, determination of values of pressure pulses at modified load-bearing element during its work with electro-magnetic striking center. Values of static and dynamic strains of casing pipe under the action of thrust force are experimentally determined. The values are located in flexible zone and make 1mm at the static load and from 0.35 up to 0.6mm at the pulse load. As the results of tests of vibration source prototype, dependence of pulse pressure value at load-bearing element on voltage of striking center supply under the pressure of preliminary pumping 20MPa is obtained. Pulse amplitude raises proportionally voltage in the range from 14.2 MPa up to 19.7 MPa. Experiments with increasing of pumping pressure in the range from 20 MPa up to 27 MPa have shown that ratio of pulse value to pumping pressure linearly reduces when voltage of striking center supply is constant. Obtained results are scientific basic for designing of load-bearing elements destined for work at pulse impact transfer mode.

The surface finish of ground workpieces often presents periodic marks related to different vibration frequencies. In some cases, however, the identification of the vibration source is not straightforward. Even low amplitude vibrations could create visually unacceptable surface waviness due to beating frequencies appearance. This paper introduces this phenomenon during the dressing process as an origin of the undesirable surface topography in grinding operations. The effect of dynamic and process parameters in this phenomenon has been analysed and a procedure to overcome the problem has been proposed. Finally, an experimental validation to demonstrate the validity of the methodology is shown.

The article describes a project proposed to determine the epicenter of a future short-focus earthquake tens of hours before and to reduce the magnitude of an impending catastrophic earthquake. It focuses on developing a physical model to determine the conditions necessary for the start of an earthquake, for a method based on the registration of flows of mercury vapor in the gas rising from the Earth. This model gives an explanation of why an earthquake precursor appears so early (such a long period of time can range from a few to hundreds of hours). Normally, the characteristic times of an earthquake precursor for seismic methods are tens of seconds. The project is based on the physical and mathematical models of an earthquake. The derived formula for the time of the precursor of a future earthquake allows us to explain and to describe the time increase for the precursor, depending on the magnitude of the earthquake. The method of reducing the magnitude of an impending catastrophic earthquake is based on the proposed physical model of the onset of an earthquake and is implemented by the action of a vibration source in the region of the detected earthquake epicenter. The proposed system should save citizens, lives from future short-focus earthquakes.

Operators of hand tractors are exposed to high levels of hand transmitted vibration (HTV). This vibration, which can be both irksome and hazardous to human health, is imparted to the operator via his or her hands and arms. However, a standardized method for measuring HTV of hand tractors has yet to be defined. The aim of the study was to present an experimental method for the investigation of the biodynamic response and vibration transmissibility of the hand-arm system during the operation of a hand tractor in a stationary mode. Measurements were performed with ten subjects using three grip forces and three handle vibration levels to examine the influences of the hand pressure and frequency on hand transmitted vibration (HTV). The results indicate that the tightness of grip on the handle influences the vibration response of the hand-arm system, especially at frequencies between 20 and 100 Hz. The transmission of lower frequencies in the hand-arm system was relatively unattenuated. In comparison, attenuation was found to be quite marked for higher frequencies during the operation of the hand tractor. The vibration transmissibility to different parts of the hand-arm system decreased with the increase of the distance from the vibration source. The proposed methodology contributes to the collection of consistent data for the evaluation of operator vibration exposure and the ergonomics development of hand tractors.

This study investigated the localization ability of an impulse vibration source outside the body in two-dimensional space. We tested whether humans can recognize the direction or distance of an impulse vibration source when using their hand to detect spatiotemporal vibrotactile information provided by the propagated vibrational wave from the source. Specifically, we had users put their hands on a silicone rubber sheet in several postures. We asked users to indicate the position of the vibration source when a location on the sheet was indented. Experimental results suggested that the direction of the impact vibration source can be recognized to some extent, although recognition accuracy depends on hand posture and the position of the vibration source. The best results were achieved when the fingers and palm were grounded and a vibration source was presented around the middle fingertip, and the directional recognition error in this case was 6 degree. In contrast, results suggest it is difficult to accurately recognize the distance of the vibration. The results of this study suggest a new possibility for directional display where vibrotactile actuators are embedded at a distance from the user's hand.

Arachnids including sand scorpions and spiders use their tactile sense organs, called basitarsal compound slit sensilla (BCSS), to detect their prey. The sense organs consisting of mechanoreceptors are located at or near joints in the cuticle, and they can sense a vibrational signal caused by prey movement. The nocturnal sand scorpion Paruroctonus mesaensis has a distinguished capability of finding their prey only with these tactile senses. The sand scorpions show their orientation behaviour of positioning themselves directly towards their prey and then run into the prey when there is a vibration disturbance caused by the prey. According to the biological researches (Brownell & Farley, 1979, Brownell, 1984), it is presumed that the sand scorpions respond to Rayleigh waves, surface waves of sand, to detect the direction of a vibration source and possibly longitudinal vibrations to estimate the distance. Especially, the time delay between arrival of a vibration signal at the BCSS sense organs is an important cue to determine the direction of their prey (Brownell & Farley, 1979). The central nervous system should process stimulus-locked neuron firings of the sense organs on their eight legs to induce the orientation behaviour. How the nervous system is organized to handle the orientation behaviour is still an open question. Only a few studies explain this behaviour mechanism. Stuerzl et al. (2000) introduced a neuronal mechanism to support the orientation behaviour of scorpions, and it is based on the difference of the arrival time of stimulus signals produced at sense organs on their legs. They argued that the brain of sand scorpions receives sensor signals from mechanoreceptors on their eight legs and processes an inhibition mechanism among a set of command neurons projected from the sense organs on each leg. This inhibitory interaction leads to more accumulated firings of the command neurons near the prey source and less firings at the opposite sides. The accumulated neuron firings thus form a tuning curve for a specific resource direction. Then the distribution of neuron firings can vote to determine the resource direction. In fact, arachnids have sensory projections to the central nervous system for each leg (Babu & Barth, 1989, Anton & Barth, 1993). Previously Brownell and Farley (1979) suggested that eight command neurons (or eight clusters of neurons in the brain) accumulate neuron firings from mechanoreceptors on the eight legs of scorpions, respectively and also interact each other with triad inhibitions. According to the triad inhibition hypothesis, early arrival of vibration stimulus to mechanoreceptors on a leg excites the corresponding command O pe n A cc es s D at ab as e w w w .in te ch w eb .o rg

Background and Objective Chronic exposure to resonant environment may cause more serious injuries to human lumbar spine than other vibrations. On the condition that the natural frequency of human lumbar spine is known, excitation frequency from an external vibration source can be optimized to keep away from the natural frequency and thus avoid lumbar resonance. Therefore, this study aimed to present an approach to predict the natural frequency of the human lumbar spine. Methods Four poroelastic finite element models of human L2–L3 spinal motion segments with different degrees of degeneration were established. Dynamic finite element analyses of these models during 1 h of vibration were then conducted. The mechanical parameters of these models under vibrations at different excitation frequencies were predicted. The excitation frequencies that resulted in the greatest changes in the lumbar mechanical parameters were identified as the natural frequencies of the established L2–L3 spinal motion segments. Results Simulation results showed that the natural frequencies of the healthy and mildly degenerated L2–L3 spinal motion segments, moderately degenerated L2–L3 spinal motion segments, and seriously degenerated L2–L3 spinal motion segments were in the range of 5–7, 3–5, and 1–3 Hz, respectively. Conclusions The predicted results indicated that the natural frequencies of the human L2–L3 spinal motion segments gradually decreased with the severity of degeneration. These phenomena may be related to changes in the lumbar structures and materials because of degeneration. This study provided a feasible method to predict the lumbar natural frequencies for different populations, which may be helpful in optimizing external vibration sources to avoid lumbar resonance.

Ground vibrations induced by large flood discharge from a dam can damage surrounding buildings and impact the quality of life of local residents. If ground vibrations could be predicted during flood discharge, the ground vibration intensity could be mitigated by controlling or tuning the discharge conditions by, for example, changing the flow rate, changing the opening method of the orifice, and changing the upstream or downstream water level, thereby effectively preventing damage. This study proposes a prediction method with a modified frequency response function (FRF) and applies it to the in situ measured data of Xiangjiaba Dam. A multiple averaged power spectrum FRF (MP-FRF) is derived by analyzing four major factors when the FRF is used: noise, system nonlinearity, spectral leakages, and signal latency. The effects of the two types of vibration source as input are quantified. The impact of noise on the predicted amplitude is corrected based on the characteristics of the measured signal. The proposed method involves four steps: signal denoising, MP-FRF estimation, vibration prediction, and noise correction. The results show that when the vibration source and ground vibrations are broadband signals and two or more bands with relative high energies, the frequency distribution of ground vibration can be predicted with MP-FRF by filtering both the input and output. The amplitude prediction loss caused by filtering can be corrected by adding a constructed white noise signal to the prediction result. Compared with using the signal at multiple vibration sources after superimposed as input, using the main source as input improves the accuracy of the predicted frequency distribution. The proposed method can predict the dominant frequency and the frequency bands with relative high energies of the ground vibration downstream of Xiangjiaba Dam. The predicted amplitude error is 9.26%.

During a print, friction-induced vibration can occur in a toner fixing device of a recent copier and a printer. The toner fixing device comprises a fixing sleeve, a heat source, a pressure roller including an elastic layer, and a pad. The inner surface of the fixing sleeve slides on the pad. In some operational conditions, the uncomfortable noise occurs by friction-induced vibration. The purpose of this study is to clarify the generation mechanism of friction-induced vibration. The present study investigates the friction torque between the fixing sleeve and the pad and the main vibration sources experimentally. As a result of experiments, it was made clear that the noise is likely to occur in a region where the friction torque has a negative slope with respect to velocity. Further, it is clarified that the vibration mode of the fixing sleeve is the main vibration source of friction-induced vibration from the measurement of the actual operating vibration mode of the fixing sleeve and the pressure roller.