Vibration Duration Research Articles

Approximate Experimental Simulation of Clogging of Pervious Concrete Pile Induced by Soil Liquefaction during Earthquake

Abstract It has been reported by previous studies that the pervious concrete pile (PCP) has the advantages of high permeability and strength as a novel ground-improvement technology. However, during an earthquake, the liquefied soil particle is bound to migrate into the PCP under the excess pore water pressure because of dynamic stress. This leads to the clogging of PCP. In this study, a permeability test system for an approximate simulation of this clogging is presented. The experimental results obtained by employing this system were reported and validated. In order to gain insight into the clogging caused by earthquake, the effects of the porosity on pervious concrete were evaluated. Clogging that accounted for the acceleration peak, the frequency, and the duration of vibration were characterized. The thickness of the impervious layer of ground surface and the pile spacing on the clogging were studied as well. Results show that within the scope of this study, the clogging of PCP is significantly related to the aforementioned factors. In addition to the thickness of the impervious soil layer, the clogging becomes more obviously with the increase of the other five factors. However, the overlarge values of some factors, such as the porosity of pervious concrete, the acceleration peak, and the frequency/duration of vibration, cannot obviously aggravate the clogging of pervious concrete. Based on the experimental evidence, a preliminary dynamic clogging model is proposed, which is helpful for the design of PCP composite foundation.

Real-time monitoring for vibration quality of fresh concrete using convolutional neural networks and IoT technology

Vibration quality is critical to ensure the concrete strength, which directly affects the long-term safe operation of concrete structures. The vibration duration and vibration depth are key parameters to guarantee vibration quality. However, traditional manual inspection on concrete surface to judge the vibration duration and estimation of vibration depth is subjective and unreliable. Moreover, existing studies monitor the vibration duration based on the knowledge from prior experiments, ignoring the influence of concrete heterogeneity. Thus, a real-time monitoring method for vibration quality of fresh concrete based on ResNet with 50 layers (ResNet-50) and Internet of Things (IoT) technology is proposed. The IoT-based monitoring framework is proposed to measure vibration depth and capture concrete surface image (CSI). A three-category classification model of CSI is established based on fine-tuned ResNet-50 model using a self-constructed dataset with 15,006 images to determine proper vibration duration. A large-scale hydraulic engineering application verifies the performance of the proposed method.

Combined effects of vertical spacers and segregation on mass transport properties of reinforced concrete

All concrete structures contain reinforcement spacers, and deep sections can be affected by bleeding and segregation without displaying visible indications during casting. However, their effects on mass transport and long-term durability are not well studied. In this paper, reinforced concrete columns were prepared with plastic and cementitious spacers to achieve 50 mm cover, and compacted at different vibration frequencies and durations. 28d cured samples were extracted along the height, conditioned to equilibrium (21 °C, 75% RH or 50 °C, 7% RH), and then subjected to water absorption, electrical conduction, epoxy impregnation and fluorescence imaging. Samples from the top of the column consistently gave higher accessible porosity and mass transport compared to samples from the bottom. Presence of spacers caused additional increases in mass transport because of preferential flow through the spacer-concrete interface which is more porous and microcracked compared to bulk concrete farther away. Image analysis on cross-sections showed that the columns experienced some aggregate segregation despite care taken to avoid over-compaction. The resistance of concrete to ingress of aggressive agents decreases with increasing height due to the combined negative effects of reinforcement spacers and segregation.

The effect of side-alternating vibration therapy on mobility and health outcomes in young children with mild to moderate cerebral palsy: design and rationale for the randomized controlled study

BackgroundCerebral palsy (CP) is the most common cause of physical disability in early childhood. Vibration therapy (VT) is a promising rehabilitation approach for children with CP with potential to impact mobility, bone and muscle health as demonstrated by extant research. However, it is still unclear how long therapy must be conducted for and what the optimal vibration frequency is in order to gain health benefits.Methods/designThe study is a randomized clinical trial evaluating and comparing the effects of two vibration frequency (20 Hz vs 25 Hz) and duration protocols (12 weeks vs 20 weeks) of side-alternating VT on mobility and other health parameters in children with CP. Children aged 5–12 years old with CP and GMFCS level I-III who are able to understand instruction and safely stand are eligible for the study. Exclusion criteria include bone fracture within 12 weeks of enrolment; acute conditions; the history of significant organic disease; the history of taking anabolic agents, glucocorticoids, growth hormone, and botulinum toxin injection into lower limbs within 3 months of enrolment. All participants will act as their own control with a 12-week lead-in period prior to intervention. The intervention period will consist of 20 weeks of home- or school-based VT 9 min per day, 4 times a week. After the baseline assessment, participants will be randomized to either a 20 Hz or 25 Hz vibration-frequency group. The primary outcome is mobility measured by a 6-min walking test, with analysis performed on the principle of intention to treat. Secondary outcomes include body composition, muscle strength, physical activity level, balance, gross motor function, respiratory function, and quality of life. Participants will undergo four assessment visits over the study period: baseline, at weeks 12, 24, and 32.DiscussionThe results of the study will provide evidence-based insights into the health benefits of side-alternating VT as a therapeutic tool in young children with cerebral palsy. The investigation of different vibration training protocols will help define the optimal parameters of intervention protocols (duration, frequency) of side-alternating VT to maximize outcomes on the health of 5–12-year-old children with CP.Trial registrationAustralian New Zealand Clinical Trials Registry (ANZCTR): 12618002026202 (Registration date 18/12/2018).

Association of disease duration and sensorimotor function in type 2 diabetes mellitus: beyond diabetic peripheral neuropathy

Purpose The aim of the study is to assess association of the duration of diabetes and vibration, proprioception, muscle strength, reaction time and balance measures in people with type 2 diabetes mellitus (DM) without peripheral neuropathy. Methods Forty-seven type 2 diabetics without peripheral neuropathy and 23 healthy controls were recruited for the study. Patients with type 2 DM were further classified into 23 patients who suffered from diabetes for less than 5 years (<5yrDM) and 24 patients who had diabetes for 5 years and above (≥5yrDM). All participants were assessed for Michigan neuropathy screening instrument (MNSI), vibration perception threshold (VPT), proprioception, muscles strength, centre of pressure (COP) range, COP sway and reaction time. Results ≥5yrDM patients were found to significantly differ from healthy control in MNSI score (p ≤ 0.013), VPT score (p ≤ 0.002), reaction time (p ≤ 0.018), COP range (p ≤ 0.005) and COP sway (p ≤ 0.027). A significant difference was found only in reaction time (p < 0.002) except in the back direction (p = 0.089), and COP range (p ≤ 0.016) except in the front (p = 0.101) and right direction (p = 0.085) between <5yrDM patients and healthy controls. Conclusions ≥5yrDM patients exhibit a subtle deterioration in VPT, reaction time, and balance measure while <5yr DM patients were impaired only in COP range and reaction time when compared with healthy control.

Experimental study on the vibration reduction characteristics of the ballasted track with rubber composite sleepers

Impact loads from trains in operation induce vibration on track structure and its surroundings, which causes track deterioration and negative environmental effects over time. In this study, the vibration reduction characteristics of the ballasted track with rubber composite sleeper were measured and compared to that of the ballasted track with concrete sleeper using full-scale in-door laboratory models. The sleepers were subjected to impact excitations through a free-falling hammer weight and the vibration responses of the track components were analysed in both time and frequency-domains. The results show that; 1. The peak acceleration and root-mean-square (RMS) distribution on the ballasted track with rubber composite sleeper are lower than that of the ballasted track with concrete sleeper. This implies better vibration attenuation capacity. 2. The time-domain analysis showed that the track with rubber composite sleeper has lower vibration acceleration energy, reduced velocity and shorter vibration duration. 3. When compared to ballasted track with concrete sleeper, the track with rubber composite sleeper reduced the overall vibration levels of the ballasted track by 1.11 dB, −2.32 dB and 1.69 dB for the sleepers, ballast and ground respectively. Consequently, the ballasted track with rubber composite sleeper has significant vibration reduction effect on the ground.

Modeling of Ground Acceleration Parameters at the Petropavlovsk Station (Kamchatka)

When assessing possible seismic impacts, the important ground motion parameters are the level and duration of seismic vibrations. Based on the earthquake records at the Petropavlovsk seismic station (Kamchatka), expressions are obtained for calculating the maximum amplitude of horizontal acceleration, the duration of the area of vibration section at a level of 0.5 of the maximum amplitude, the RMS amplitude in four frequency bands, and the boundaries of the frequency band in which the maximum accelerations are observed. The calculations used records of 75 regional earthquakes with magnitudes of 3.9−8.3.

Vibrotactile Alphabets: Time and Frequency Patterns to Encode Information.

Although many tactual communication methods have been developed over the past decades, few of them have been widely adopted in everyday lives. In this paper, we investigate the ability to deliver text messages using patterns of vibrations. By manipulating the duration and frequency of vibrations, we designed two vibrotactile alphabets, i.e. 3F Vibraille and 2F Vibraille, along with their corresponding numbers and symbols. The main difference between 3F Vibraille and 2F Vibraille is the number of frequency levels utilised. Both alphabets were evaluated through human experiments in terms of training time, learning process and recognition accuracy of words and symbols. For both alphabets, the results demonstrated that participants were able to recognise words and symbols at an accuracy of over 90% after 6-8 hours of training. The main difference between the alphabets was that 3F Vibraille achieved a higher transmission rate while 2F Vibraille required less training time.

Post removal techniques: a systematic review and meta-analysis

Aim: This systematic review aimed to answer what is the best way to remove prefabricated metallic, fiber or cast metal posts. Methodology: An electronic search was conducted in Medline and Scopus databases to identify clinical and in vitro studies that assessed post removal techniques from 1950 to October 2018. Tables were generated to summarize the included studies and reports were assessed for bias using the Cochrane risk of bias tool. A meta-analysis was performed to evaluate the force necessary to remove posts (α=5%). Results: Of the 2,951 studies identified in the initial search, 33 were selected. The duration of using ultrasonic vibrations (and the number of surfaces where the vibration was applied) led to less time spent and less force needed to dislodge a metal post. Dentist’s expertise (more than 10 years) was also related to easier post removal. The use of adhesive cements resulted in a more difficult protocol for post removal. Conclusions: Although there is need for more consistent results, the data summarized and meta-analysis points toward the use of ultrasonic energy as the first option to remove posts, with best results for metal posts.

Crystallization of amorphous Ti40.7Hf9.5Ni41.8Cu8 alloy during the low-frequency mechanical vibrations at room temperature

The influence of the low-frequency vibrations at room temperature on the structure of an amorphous Ti40.7Hf9.5Ni41.8Cu8 thin ribbon was studied by X-ray diffraction and high-resolution transmission electron microscopy. It was found that mechanical vibrations for 1 h led to the formation of crystalline clusters that were several nanometres in size. An increase in the duration of the mechanical vibrations to 4 h resulted in the growth of the clusters until the formation of crystalline walls that surrounded amorphous islands. It was assumed that this process was due to the β relaxation that occurred during the low-frequency vibration.

Efficacy of whole body vibration therapy on pain and functional ability in people with non-specific low back pain: a systematic review

BackgroundWhole body vibration (WBV) is currently increasing in popularity as a treatment modality for musculoskeletal disorders and improving health-related quality of life. Recent research has shown that WBV can reduce low back pain and improve the functional abilities for patients, however, optimal frequency and duration of vibration for therapeutic use is unclear. This review was conducted to summarize and determine the efficacy of whole body vibration therapy on individuals with non-specific low back pain (NLBP) and evaluated methodological quality of the included studies.MethodsOnline literature searches through the Web of Science, PubMed, Cochrane Library databases, PEDro, Ovid, EBSCO (Medline) and Scopus were conducted up to December 2019. Randomized controlled trials investigating the effect of WBV on pain intensity and/or functional ability in individuals with non-specific low back pain (NLBP) were included. Details of the sample characteristics, treatment of the comparison group, WBV parameters and outcome measures were recorded, and methodological quality appraised using the PEDro scale.Results7 published RCTs (418 patients) were included in the systematic review. Due to heterogeneity in vibration parameters and prescriptions, and small number of studies, no meta-analysis was performed. Four out of the six included studies using pain as an outcome measure showed that WBV had a beneficial effect on pain compared with the control group, whereas only two trials were considered to be of high methodological quality. Among the six studies which measured functional ability, three studies with good quality reported significant between-group differences in favor of WBV.ConclusionsThere is limited evidence suggests that WBV is beneficial for NLBP when compared with other forms of interventions (stability training, classic physiotherapy, routine daily activity). Due to the small sample sizes and statistical heterogeneity, we still cannot draw conclusions that WBV is an effective intervention. Further high-quality studies are needed before clinical recommendations can be provided to support its use in a general population with NLBP and to explore the optimal treatment protocol.Trial registrationPROSPERO registration number: CRD42017074775.

Prospects for harmonization of domestic vibration standards with international standards

Full vibration acceleration, as an estimated and normalized parameter of the vibration characteristics of machines and vibration acting on a person, is used to regulate the effect of vibration in the regulatory documents of the European Union (EU). In Russian practice, the maximum «corrected vibration acceleration» measured for each direction of the basicentric coordinate system is used for these purposes. Both evaluation principles are compared using examples of vibration measurements from various sources for the maximum safe duration of vibration in typical operating conditions of vibroactive equipment. For vibration exposures from most manual machines, vehicles and transport and technological machines, the assessment of vibration exposures under Directive 2002/44 / EU will in almost all cases be more «rigid» than under SanPiN 2.2.4.3359-16.

Power Absorbed by the Standing Human Body During Whole-Body Vibration Training.

Absorbed power (AP) is a biodynamic response that is directly related to the magnitude and duration of vibration. No work has previously investigated the power absorbed by the standing human body during the exposure to vibration training conditions or otherwise. This article reports the power absorbed by the standing human body under whole-body vibration (WBV) training conditions. In this work, the force and acceleration used to calculate the apparent mass by Nawayseh and Hamdan (2019, "Apparent Mass of the Standing Human Body When Using a Whole-Body Vibration Training Machine: Effect of Knee Angle and Input Frequency," J. Biomech., 82, pp. 291-298) were reanalyzed to obtain the AP. The reported acceleration was integrated to obtain the velocity needed to calculate the AP. The effects of bending the knees (knee angles of 180 deg, 165 deg, 150 deg, and 135 deg) and vibration frequency (17-42 Hz) on the power absorbed by 12 standing subjects were investigated. Due to the different vibration magnitudes at different frequencies, the AP was normalized by dividing it by the power spectral density (PSD) of the input acceleration to obtain the normalized AP (NAP). The results showed a dependency of the data on the input frequency as well as the knee angle. A peak in the data was observed between 20 and 24 Hz. Below and above the peak, the AP and NAP tend to increase with more bending of the knees indicating an increase in the damping of the system. This may indicate the need for an optimal knee angle during WBV training to prevent possible injuries especially with prolonged exposure to vibration at high vibration intensities.

Developing Sustainable Concrete Compaction using a Proposed Multi-vibration Technique

This study seeks to develop a sustainable construction technique based on the introduction of a specific method for improving concrete compressive strength through a proposed multi-vibration compaction method. An experimental program is performed to evaluate the effect of the proposed compaction technique on fresh silica fume concrete undergoing the initial setting. Multi-vibration intends to minimize concrete production cost because it upgrades the compressive strength of the same materials with better utilization of the vibration energy required for compaction. The collected experimental data presented assign relationships among vibration duration, vibration cycles or phases, and compressive strength upgrading of single vibrated, revibrated, and multi-vibrated specimens for analysis and discussion. This study shows that multi-vibration phases, rather than single vibration or revibration techniques, are powerful techniques for improving concrete compressive strength. The results indicated that the existence of an optimum multi-vibration mode was dominated by phase number and vibration duration and confirm the reliability vibration overall time duration recommended by ACI 309 which relates to a single vibration time limit to be considered in the case of multi vibration technique. Multi-vibration Mode 8 (subjected to three vibration phases 10, 20, and 30 sec ) has the best effect for the considered mixtures among the specific vibration modes. The maximum improvement ratio is 1.25, which is associated with the plastic mixture.

Ultrasonic-Assisted Semi-Solid Forming Method and Microstructure Evolution of Aluminum/Copper Brazed Joints

Aluminum/Copper dissimilar metal connection devices have been widely used in equipment manufacturing. Ultrasonic vibration assisted semi-solid brazing technology is beneficial to improve brazing quality by using the good flow ability and strong deformation resistance of brazing alloy when it is in a semi-solid state. In this study, a new ultrasound-assisted high-frequency induction brazing method was used to braze aluminum and copper dissimilar metals under non-vacuum conditions with non-prefabrication of brazing filler metal. In a short time, uniform semi-solid brazed joint was obtained. Detailed investigations on the effects of aluminum-substrate side (Abbreviated as Al side) heat dissipation rate and ultrasonic vibration duration on the microstructure evolution and mechanical properties of semisolid weld were conducted. The results show that the welding seam obtained by the modification method increases the microstructure uniformity of brazing joint.

Nonlinear Parametric Vibration Analysis of Radial Gates

In this work, based on dynamic characteristics of radial gates, a nonlinear differential equation of motion&nbsp;for&nbsp;the radial gate arm&nbsp;is established. Excitation conditions of principal&nbsp;parametric resonance and subharmonic parametric resonance are obtained by using multi-scale method and numerical method. The parameter analysis shows that: comparing with traditional calculation method of dynamic instability region division, the presented method is more suitable to analysis of parametric vibration for radial gates as considering the end moment, vibration duration and amplitude. The vibration amplitudes of arm increase with the increase of its length and excitation amplitude, as well as the decrease of arm inclination angle. Moreover, the parametric resonance is easier to be excited and its resonance region become wider&nbsp;with the initial end moment increasing. Since the vibration response of the arm is influenced by the nonlinear term in the equation, the damping effect is limited. Thus, energy transfer method (e.g. tuned mass damper)&nbsp;can&nbsp;be adopted to achieve vibration control.

Produksi Lateks Pekat Melalui Proses Pendadihan Dengan Pengaturan Waktu Dan Kecepatan Penggetaran

Increasing concentrated latex production is the important things to supply rubber industries, and reduce imports. The quality of latex is evidently altered by shock during transportation, thus providing important information in improving creaming processes. The study aimed to find the duration and speed shaking in accelerating the formation of concentrated latex with creaming technique. The study was arranged factorialin Randomized Block Design with duration (24, 48, and 72 hours) and speed shaker (0, 150, 200, and 250 rpm). The observed wereprocessing time separation between latex and serum (hour), concentrated latex yield (%), total soluble content (%), dry rubber content, pH, colour, and the smell of latex. The results showed that the duration of vibration did not affect time separation between latex and serum, concentrated latex yield, total soluble content, and dry rubber content. The speed of vibration speeds up the processing time separation between latex and serum, affecting the yield and dry rubber content of concentrated latex. The combination of duration and speed of vibration affects the processing time separation between latex and serum. The fastest processing time separation is 32 hours on 48 hours of duration with 150 and 200 rpm speed vibration of orbital shaker. Keyword: concentrated latex, creaming, duration and speed vibration, orbital shaking

Effect of ultrasonication duration of polyvinyl alcohol (PVA) gel on characterizations of PVA film

Many works reported a PVA based film prepared using ultrasonication, however, information on the effect of this treatment on changes of PVA’s properties is still limited. The main objective of this work was to study the effect of ultrasonication duration on the properties of PVA film. The PVA gel was sonicated using a 360 W ultrasonic probe for 2.5, 5, 7.5 and 10 min. Ultrasonication duration for 7.5 min results in a significant effect (p ≤ 0.05) on an increase in tensile strength, but not on tensile modulus and strain at the break of the film. After this vibration duration, tensile strength increased by almost 29 %, strain at break decreased by 30 %, opacity decreased by 22 %, and water vapor permeability decreased by 11 %. On the other hand, moisture resistance decreased significantly (almost 12 %). The sonicated film underwent larger lattice strain and had higher crystal structure compared to non-sonicated film. This work informs that ultrasonication on PVA gel is a potential method to fulfil some properties of PVA film for food packaging material.

Influence of duration of single dynamical events on the result of evaluation of human perception of vibration in buildings

The duration of vibration taken to the analysis influence on the result of evaluation of human perception of vibration. In this paper the relationship between the duration of individual events and the result of RMS and VDV analysis was investigated. The analysis was carried out on two buildings located close to Warsaw Metro line 1. The chosen buildings are typical masonry buildings located in the city center and subjected to three sources of traffic vibrations: subway, tramway and road. Evaluation of human perception of vibration was made using two different methods, the most popular, root mean squared method (RMS) and vibration dose value method (VDV). Methodology of these two methods is also described in the paper. The results from RMS and VDV methods are compared by using HPVR (human perception of vibration ratio) for RMS analysis. It is ratio discovered by prof. Stypula and it is very useful for the diagnosis. The conclusion from analysis are given.

The effect of vibropressing compaction process on the compressive strength based concrete paving blocks

Concrete paving blocks are a mixture of cement and aggregates, which using compressive energy blocks. Paving concrete is a dry concrete category, so it requires block energy in the compaction process. Block energy consists of manual blocks, block presses, and vibropressing blocks. They are pressing blocks to use hydraulics with a strong push of 75 kg/cm² with a 1, 2, and 3 s durations. Then the blocky vibropressing method, namely by making variations on the vibrating length between 4-8 seconds and a frequency of 25-50 Hz and pressing 75 kg/cm². All test specimens with the same volume ratio composition of 1 cement:4 sand:4 crushed stone ash 0-5 mm, and the water and cement ratio are 0.6. The results showed that the manual block and the pressing block did not have a sharp increase in compressive strength even though more blows in the manual bock and increased time in the bock pressing method. The vibropressing process shows a significant and linear growth in compressive strength with increase vibrations and frequencies. The conclusion is that the compressive strength of paving block concrete is very dependent on blocked in terms of the frequency and duration of vibrations.