Lifting Frequency Research Articles

Investigation on flow around and through a hygroscopic porous cylinder with consideration of compressibility of moist air

In order to better understand the influence of the physical conditions, such as high temperature, high humidity, and high speed, on porous media in coastal engineering, a compressible, viscous, unsteady flow around and through a hygroscopic porous circular cylinder was discussed in this paper. The effects of the hygroscopicity, the Mach number, and the Darcy number on the flow structure, temperature field, and water content of the porous cylinder are evaluated in detail. The results of numerical simulations show significant effects of compressibility of moist air on the lift and drag of the cylinder. With an increase in the Mach number, the frequency of vortex shedding argument and dimensionless lift and drag of the porous cylindrical surface decrease. Nevertheless, the effect of the Mach number on the magnitude of the vorticity and distribution of temperature is negligible. In our simulation, we also found that an increase in the Darcy number significantly weakens the magnitude of the vorticity and the amplitude of lift and drag of the cylinder. Moreover, the absorption of the porous cylinder may also have a weak effect on accelerating vortex shedding. Considering the high temperature, high humidity, and high speed of the coastal environment, this paper has some significance for the study of wind erosion.

Work Organization Factors Associated with Health and Work Outcomes among Apprentice Construction Workers: Comparison between the Residential and Commercial Sectors.

There are substantial differences in work organization between residential and commercial construction sectors. This paper examined differences in work factors between construction sectors and examined the association between sector and health behaviors, health outcomes, and work outcomes. We surveyed 929 male construction apprentices (44% residential and 56% commercial) and found that residential apprentices reported fewer workplace safety policies, higher frequency of heavy lifting, and greater likelihood of reporting musculoskeletal pain compared to apprentices in commercial work. Residential apprentices reported higher job strain, lower supervisor support, more lost workdays due to pain or injury, and lower productivity related to health than commercial apprentices. Multivariate Poisson regression models controlling for multiple work factors showed that residential construction work, high job strain, heavy lifting, low coworker support, and low supervisor support were each independently associated with one or more work or health outcomes. These findings suggest that interventions should seek to improve coworker and supervisory supportive behaviors, decrease job strain, and reduce organizational stressors, such as mandatory overtime work. Our study shows disparities in health and safety between construction sectors and highlights the need for interventions tailored to the residential sector.

The Safety Profile of Flunixin and its Pharmacological Effects in Chicks

Background: Flunixin meglumine is a non-steroidal anti-inflammatory drug used in the treatment of several conditions in veterinary medicine. Objective: The study was aimed to investigate the analgesic and anti-inflammatory effects of flunixin meglumine in chicks. Methods: The up and down method was used to assess the median lethal dose (LD50) and effective median analgesic dose (ED50) of flunixin meglumine administered intraperitoneally (i.p.) and orally (p.o.) in chicks. From the obtained values we determined the drug safety indices. Electric stimulation method was used to determination the dose-dependent analgesic effect of flunixin meglumine in chicks. Analgesic and anti-inflammatory effects were dignified via the formalin test. Results: The median lethal doses (LD50) of flunixin were 143.24mg/kg intraperitoneally and 170.77mg/kg orally. The effective median analgesic doses (ED50) of flunixin meglumine in chicks were 9.34 mg/kg and 11.75 mg/kg for intraperitoneally and orally respectively. The Therapeutic Index, Standard Safety Margin and Therapeutic Ratio of flunixin through intraperitoneal and oral route were (15.35 , 14.53), (0.15 , 0.14) and ( 5.11 , 4.84) respectively. The dose-dependent analgesic effect of flunixin meglumine at 9 mg/kg, 18 mg/kg ip and 12 mg/kg, 24 mg/kg p.o started at 15 min after treatment and lasted over 120 min of treatment. The analgesic effect peak of flunixin meglumine through intraperitoneal and oral routes was 30 minutes after treatment. In formalin test, flunixin meglumine caused a significant rise in the latency to lift right foot in comparison with the control value, along with a significant decline in foot lifting frequency. A substantial decrease in foot thickness compared to control value has been demonstrated by the anti-inflammatory effects of flunixin meglumine. Conclusion: These results shows that the flunixin has analgesic and anti-inflammatory effects and form the backbone for further pharmacological studies as well as the medication could be safely administered to chicken.

Numerical investigation of flow around a structure using Navier-slip boundary conditions

PurposeComplicated motion of vortex is frequently observed in the wake of islands. These kinds of swirling fluid cause the trap of sediments or pollutants, subsequently inducing the dead zone, odor or poor water quality. Therefore, the understanding of flow past a circular cylinder is significant in predicting water quality and positioning the immersed structures. This study aims to investigate the flow properties around a structure using Navier-slip boundary conditions.Design/methodology/approachBoundary conditions are a major factor affecting the flow pattern because the magnitude of flow detachment on a surface can redistribute the tangential stress on the wall. Therefore, the authors performed an analysis of laminar flow passing through a circular structure to investigate the effect of boundary conditions on the flow pattern.FindingsThe authors examined the relationship between the partial-slip boundary conditions and the flow behavior at low Reynolds number past a circular cylinder considering velocity and vorticity distributions behind the cylinder, lift coefficient and Strouhal number. The amplitude of lift coefficient by the partial slip condition had relatively small value compared with that of no-slip condition, as the wall shear stress acting on the cylinder became smaller by the velocity along the cylinder surface. The frequency of the asymmetrical vortex formation with partial slip velocity was increased compared with no-slip case due to the intrinsic inertial effect of Navier-slip condition.Originality/valueThe ability to engineer slip could have dramatic influences on flow, as the viscous dominated motion can lead to large pressure drops and large axial dispersion. By the slip length control, no-slip, partial-slip and free-slip boundary conditions are tunable, and the velocity distributions at the wall, vortex formation and wake pattern including the amplitude of lift coefficient and frequency were significantly affected by slip length parameter.

Numerical investigation of vortex induced vibration effects on the heat transfer for various aspect ratios ellipse cylinder

The vortex-induced vibration of various aspect ratio (AR=0.75, 1.0, 1.25 and 1.5) ellipse cylinders with convective heat transfer is investigated at Re=150 and m∗=10 for 3≤Ur≤12, where Ur=U/(fnD) and fn is the natural frequency of cylinder in still air. The amplitude and frequency response of displacement, force and the Nusselt number are presented and discussed, the vorticity, temperature contours and wake patterns are studied to understand the effect of AR and Ur on the 1DOF vibration characteristics and the heat transfer of the isothermal cylinder. The results show that the classical Karman shedding (2S) is observed at relative low displacement and the C(2S) occurs when the cylinder undergoes high-amplitude oscillations for the AR considered, and the P+S wake mode which is composed with a single vortex and one pair of counter-rotating vortices during the transition from the initial branch to the VIV lock-in regime. There are multiple frequencies related to the response of Nusselt number, with the 2StNu dominating. And the maximum value of NuA is 11.07, 11.7, 12.1 and 12.35 for AR=0.75, 1.0, 1.25 and 1.5 respectively, which are increased by 7%, 8.7%, 11% and 13.5%, respectively, compared with the corresponding stationary cylinders, indicting an enhanced heat transfer of VIV cylinder. As increasing of the AR to 1.5, an early exit of the VIV lock-in regime and into the desynchronized regime happens due to the strong 2Stn in the lift frequency response when.

Effect of the yaw angle and spanning length on flow characteristics around a near-wall cylindrical structure

Three-dimensional direct numerical simulation is carried out to investigate the effects of the yaw angle and spanning length on the vortex structures and hydrodynamics of flow crossing a near-wall cylindrical structure. Two yaw angles (α = 0°, 45°), and three spanning length ratios (L* = 25, 50, 100) are investigated at Re = 500. Under the normal cylinder condition (α = 0°), a parallel vortex shedding pattern is observed in the wake. The vortex formation lengths are identical for all L*, whereas the spanwise correlation of the vortex shedding declines with the increasing L*, indicating the intensified three-dimensionality. A single dominant peak is found in the lift frequency spectra for each L* case. Under the yawed condition (α = 45°), the flow characteristics are fundamentally changed with negatively-yawed linear vortex shedding tubes being observed in the wake. Different from the normal cases, the vortex formation length for L* = 25 is larger than that of L* = 50 and 100, while the oblique angle of the vortex tube decreases with the increasing L*. It is shown that, at α = 45°, the three-dimensional flow features are fully developed when L* ≥ 50. The lift frequency spectra show multiple peaks while the magnitudes of the secondary peaks are significantly reduced by extending the spanning length. By comparing the results between α = 0° and α = 45°, it is found the Independence Principle (IP) is applicable for predicting the first-order statistics of the hydrodynamic forces and vortex shedding frequency, but fails in predicting the second-order force statistics. The effects of the yaw angle on the pressure and shear stress distributions of the bottom wall are also discussed.

Work-Related Risk Assessment According to the Revised NIOSH Lifting Equation: A Preliminary Study Using a Wearable Inertial Sensor and Machine Learning.

Many activities may elicit a biomechanical overload. Among these, lifting loads can cause work-related musculoskeletal disorders. Aspiring to improve risk prevention, the National Institute for Occupational Safety and Health (NIOSH) established a methodology for assessing lifting actions by means of a quantitative method based on intensity, duration, frequency and other geometrical characteristics of lifting. In this paper, we explored the machine learning (ML) feasibility to classify biomechanical risk according to the revised NIOSH lifting equation. Acceleration and angular velocity signals were collected using a wearable sensor during lifting tasks performed by seven subjects and further segmented to extract time-domain features: root mean square, minimum, maximum and standard deviation. The features were fed to several ML algorithms. Interesting results were obtained in terms of evaluation metrics for a binary risk/no-risk classification; specifically, the tree-based algorithms reached accuracies greater than 90% and Area under the Receiver operating curve characteristics curves greater than 0.9. In conclusion, this study indicates the proposed combination of features and algorithms represents a valuable approach to automatically classify work activities in two NIOSH risk groups. These data confirm the potential of this methodology to assess the biomechanical risk to which subjects are exposed during their work activity.

A Study on Factors Affecting the Manual Material Handling Capacity of Indian Male Construction Workers

Construction is one of the most hazardous industries involving high manual labour where health and safety risks are plentiful. This study focuses on evaluating the factors affecting the material lifting capacity of Indian male construction workers. A statistical experiment was conducted on selected male construction workers, and ANOVA technique was used to analyse the influence of parameters (like age, body mass index (BMI), material lifting height and lifting frequency) on maximum allowable weight limit (MAWL). From the analysis, maximum allowable weight limit (MAWL) and minimum lifting weight were determined for every worker based on his age and BMI corresponding to three different lift frequencies and lifting heights. The results indicate that for all BMI categories, the MAWL increases with the increase in the age of workers to a certain extent, but it decreases as the age increases. Using the maximum and minimum lifting weight values obtained, it will be easy to assign manual lifting tasks for workers without compromising their health at the same time ensuring optimum utilization of their efficiency.

The Correlation between Body Mass Index and Lifting Frequency with Low Back Pain Complaints on Rice Transport Workers in Warehouse of Perum BULOG Subdivre Pematangsiantar

Introduction: Rice transport workers are at risk for Low Back Pain (LBP) complaints because their workis lifting heavy loads repeatedly and affected by individual characteristics. This research aimed to analyzethe strength of the correlation between body mass index and lifting frequency with LBP complaints on ricetransport workers in Perum BULOG Pematangsiantar Subdivre.Methods: This type of research was an observational research with a cross sectional design. The samplingtechnique used total populated sampling with 30 respondents. The variables researched included body massindex, lifting frequency, and LBP complaints.Data were collected by observation, filling out research questionnaires, and Nordic Body Map (NBM). Thedata analysis used was the Spearman correlation.Results: The strength of the correlation between body mass index with low back pain complaints had a valueof r = 0.203, the strength of the correlation between the lifting frequency with low back pain complaints hada value of r = 0.415.Conclusion: Body mass index with LBP complaints had a weak and positive correlation. The liftingfrequency with LBP complaints had a moderate and positive corelation.

A pilot study to assess a risk of a high-risk group of low back pain membership in workers who perform the manual material handling tasks.

BackgroundWe conducted this experimental study to estimate a risk of a high-risk group of low back pain (LBP) membership in workers who perform the manual material handling (MMH) tasks in an actual workplace setting.MethodsThe subjects include healthy workers who were engaged in 12 MMH tasks at 6 manufacturing companies. We assessed the dynamic motion of trunk or lumbar spine using an industrial lumbar motion monitor (BioDynamics Laboratory of Ohio State University). The subjects were evaluated for the age, gender, years of working and anthropometric measurements (e.g., height, weight, shoulder height, elbow height, iliac height, leg length, trunk length, trunk circumference, iliac width, iliac depth, xiphoid width and xiphoid depth). Moreover, they were also evaluated for a risk of a high-risk group of LBP membership based on lift frequency, average twisting velocity, maximum moment, maximum sagittal flexion and maximum lateral velocity.ResultsThe subjects who were engaged in a packaging at a detergent manufacturing company are at the greatest risk of LBP (63.76%). This was followed by packaging at a leather product manufacturing company (57.06%), packaging at a non-metallic casting material manufacturing company (57.03%), manual injection at a non-metallic casting material manufacturing company (52.00%), toggling at a leather product manufacturing company (46.09%), non-metallic casting material manufacturing company (42.88%), rolling at a non-metallic mineral product manufacturing company (42.12%), shooting at a non-metallic casting material manufacturing company (40.99%), vacuum processes at a leather product manufacturing company (35.00%), looping at a general industrial machinery manufacturing company (33.93%), setting at a leather product manufacturing company (30.22%) and packaging at a general metal product manufacturing company (22.02%).ConclusionsOur approach indicates that there is a risk of a high-risk group of LBP membership in workers who perform the MMH tasks.

Periodic Response and Stability of a Maglev System with Delayed Feedback Control Under Aerodynamic Lift

In this research, the periodic response and stability of a nonlinear maglev system under the combined effects of steady and unsteady aerodynamic lifts is investigated, considering time delay in the feedback control loop. First, a nonlinear maglev system with a single levitation point that accounts for the nonlinearity of the electromagnetic force, time delay in the feedback control loop, and effect of aerodynamic lift is established. Then the periodic solutions of the maglev system with aerodynamic lift and time delays are obtained by an incremental harmonic balance analysis, in which the explicit time-delay action matrices used indicate that the effect of time delay on the response of the maglev system is periodic. The stability of the periodic solutions based on a finite difference continuous time approximation method and Floquet theory is studied, from which the critical time delay is obtained. Also, the relationship between the periodic vibration amplitude and the time delay is examined, along with the steady aerodynamic lift coefficient, and frequency of the unsteady aerodynamic lift, as well as the variation of critical delay with respect to the position feedback and velocity feedback with the control gain parameters. In addition, the stability boundary for the simultaneous time-delayed position and velocity feedback is obtained.

Digital pen technology for conducting cognitive assessments: a cross-over study with older adults

Many digitalized cognitive assessments exist to increase reliability, standardization, and objectivity. Particularly in older adults, the performance of digitized cognitive assessments can lead to poorer test results if they are unfamiliar with the computer, mouse, keyboard, or touch screen. In a cross-over design study, 40 older adults (age M = 74.4 ± 4.1 years) conducted the Trail Making Test A and B with a digital pen (digital pen tests, DPT) and a regular pencil (pencil tests, PT) to identify differences in performance. Furthermore, the tests conducted with a digital pen were analyzed manually (manual results, MR) and electronically (electronic results, ER) by an automized system algorithm to determine the possibilities of digital pen evaluation. ICC(2,k) showed a good level of agreement for TMT A (ICC(2,k) = 0.668) and TMT B (ICC(2,k) = 0.734) between PT and DPT. When comparing MR and ER, ICC(2,k) showed an excellent level of agreement in TMT A (ICC(2,k) = 0.999) and TMT B (ICC(2,k) = 0.994). The frequency of pen lifting correlates significantly with the execution time in TMT A (r = 0.372, p = 0.030) and TMT B (r = 0.567, p < 0.001). A digital pen can be used to perform the Trail Making Test, as it has been shown that there is no difference in the results due to the type of pen used. With a digital pen, the advantages of digitized testing can be used without having to accept the disadvantages.

Influence of tubing/oil-blanket lifting on construction and geometries of two-well-horizontal salt caverns

Underground TWH (Two-well-horizontal) salt caverns are an ideal storage medium for large-scale energy storage, having large usable volumes and high construction efficiency. Different tubing/oil-blanket lifting techniques relate to different solution mining rates and help define cavern geometries based on the previous experience of SWV (Single-well-vertical)-cavern construction. In this study, we present a complete and comprehensive evaluation of the influence of a particular tubing/oil-blanket lifting method on TWH-cavern leaching and geometric shapes. Based on the solution mining numerical simulation original program TWHSMC V2.0 (Two-well-horizontal solution mining cavern V2.0), we carried out a set of numerical simulations, such that the cavern construction process is real-time display and easily recorded. The results demonstrate that with a matching water injection rate, the outlet brine concentration is not sensitive to tubing/oil-blanket lifting. During construction of a horizontal cavern with a volume of 300,000 m3, lifting tubing on both sides simultaneously yields the shortest leaching time (near 307 days). Only lift the tubing on one side will form an asymmetrical cavern, with the height of the cavity near the side being higher than on the opposite side. The lower the frequency of tubing and oil blanket lifting, the smaller the height/length ratio coefficient is, meaning the cavern is closer to the horizontal. Therefore, when constructing TWH-caverns in thinly-bedded rocksalt formations, simultaneously lifting the both sides of tubing and oil-blanket, in addition to a lower lifting rate, are required. This research provides theoretical basis and engineering guidance for TWH-cavern constructing in thinly bedded rocksalt formations.

Effect of hypoxia, safety shoe type, and lifting frequency on cardiovascular and ventilation responses

ObjectiveThere is limited work on the physiological demands of lifting activities at different altitudes and different lifting frequencies when wearing different types of shoes. This study aimed to examine the heart rate variability (HRV) and ventilation responses of individuals in normobaric hypoxia (ambient oxygen of 15%, 18%, and 21%) while doing lifting tasks and wearing three types of different safety shoes (“light, medium, and heavy-duty”) at two different lifting frequencies (“1 lift/min and 4 lifts/min”). MethodsUsing an experimental study design, two sessions were conducted by ten male university students that included an acclimatization and training session followed by experimental lifting. The study used a four-way repeated measures design (4 independent and twenty-one responses, i.e., twelve HRV and nine ventilation responses). ResultsThe findings highlighted substantial low HRV and ventilation parameters for the light workload stress in the form of higher ambient oxygen content and lowered lifting frequency while wearing light safety shoe type. It also presented an increase in the physical demand, followed by increased lifting frequency and replication with increased mean heart rate and decreased mean RR, very low frequency (VLF) power, low frequency (LF) power, and low frequency to a high-frequency ratio (LF/HF). ConclusionOur findings suggest that if a safe lifting load limit is applied for workers in the industrial environment, the risk of musculoskeletal disorders will be mainly decreased, and the rate of production will be better with ambient oxygen content and appropriate safety shoes. This research would safeguard industrial workers' physical capacities and future health risks.

Improving sustainability in combined manual material handling through enhanced lot-sizing models

Lot-sizing models play an important role in optimizing the performance of internal logistics systems that involve a large amount of manual material handling (MMH) tasks. The performance of MMH tasks should be assessed using multiple criteria rather than being merely cost-oriented, considering the fact that the lot size affects the workload and can result in work-related musculoskeletal disorders (WMSDs). This study aims to integrate biomechanical and physiological guidelines into a cost-based performance optimization model of MMH tasks. In this study, we consider the impact of lot size on lifting frequency, which is reflected in the Composite Lifting Index (CLI), an extension of the National Institute for Occupational Safety and Health (NIOSH). In addition, the energy expenditure rates of operators are estimated by applying an established physiological method. The energy expenditure results are used to calculate rest allowance during a handling process that help keep workload levels acceptable. To make the model more general, we consider different manual material shipping scenarios and intermodal replenishment cases. Finally, a sustainable lot-sizing model is applied in a two-stage intermodal replenishment case and several numerical experiments to determine the influence of item weight, speed, distance, and opportunity cost. The results indicate that the proposed model can ease the ergonomic strain of operators without compromising economic efficiency.

Wind loading of a finite prism: aspect ratio, incidence and boundary layer thickness effects

A systematic set of low-speed wind tunnel experiments was performed at Re = 6.5x104 and 1.1x105 to study the mean wind loading experienced by surface-mounted finite-height square prisms for different aspect ratios, incidence angles, and boundary layer thicknesses. The aspect ratio of the prism was varied from AR = 1 to 11 in small increments and the incidence angle was changed from α = 0° to 45° in increments of 1°. Two different boundary layer thicknesses were used: a thin boundary layer with δ/D = 0.8 and a thick boundary layer with δ/D = 2.0–2.2. The mean drag and lift coefficients were strong functions of AR, α, and δ/D, while the Strouhal number was mostly influenced by α. The critical incidence angle, at which the prism experiences minimum drag, maximum lift, and highest vortex shedding frequency, increased with AR, converged to a value of αc = 18° ± 2° once AR was sufficiently high, and was relatively insensitive to changes in δ/D. A local maximum value of mean drag coefficient was identified for higher-AR prisms at low α. The overall behaviour of the force coefficients and Strouhal number with AR suggests the possibility of three flow regimes.

Balance Training in Older Adults Using Exergames: Game Speed and Cognitive Elements Affect How Seniors Play.

Falls in older adults are a serious threat to their health and independence, and a prominent reason for institutionalization. Incorrect weight shifts and poor executive functioning have been identified as important causes for falling. Exergames are increasingly used to train both balance and executive functions in older adults, but it is unknown how game characteristics affect the movements of older adults during exergaming. The aim of this study was to investigate how two key game elements, game speed, and the presence of obstacles, influence movement characteristics in older adults playing a balance training exergame. Fifteen older adults (74 ± 4.4 years) played a step-based balance training exergame, designed specifically for seniors to elicit weight shifts and arm stretches. The task consisted of moving sideways to catch falling grapes and avoid obstacles (falling branches), and of raising the arms to catch stationary chickens that appeared above the avatar. No steps in anterior-posterior direction were required in the game. Participants played the game for eight 2 min trials in total, at two speed settings and with or without obstacles, in a counterbalanced order across participants. A 3D motion capture system was used to capture position data of 22 markers fixed to upper and lower body. Calculated variables included step size, step frequency, single leg support, arm lift frequency, and horizontal trunk displacement. Increased game speed resulted in a decrease in mean single support time, step size, and arm lift frequency, and an increase in cadence, game score, and number of error messages. The presence of obstacles resulted in a decrease in single support ratio, step size, cadence, frequency of arm lifts, and game score. In addition, step size increased from the first to the second trial repetition. These results show that both game speed and the presence of obstacles influence players' movement characteristics, but only some of these effects are considered beneficial for balance training whereas others are detrimental. These findings underscore that an informed approach is necessary when designing exergames so that game settings contribute to rather than hinder eliciting the required movements for effective balance training.

Effects of Lifting Method, Safety Shoe Type, and Lifting Frequency on Maximum Acceptable Weight of Lift, Physiological Responses, and Safety Shoes Discomfort Rating.

This study aimed to investigate the physical effects of precision lifting tasks on the maximal acceptable weight of a lift (i.e., psychophysiological lifting capacity where the workers adjust the lifting weight in order to work without any fatigue or strain at the end of the work while wearing common safety shoe types). Additionally, the physical difference between the precise and non-precise lifting conditions associated with wearing safety shoes were assessed by respiration responses and shoe discomfort ratings. To achieve the objective of the study, ten healthy male workers were selected by age (between 25 to 35 years old). Their anthropometric characteristics, including knuckle height, knee height, and body mass index (BMI), were measured. A three-way repeated measures design with three independent variables was used; the variables included—the (1) lifting method (precise and non-precise), (2) lifting frequency (1 and 4 lifts per min), and (3) safety shoe type (light-duty, medium-duty, and heavy-duty). The physiological response variables and one of the subjective factors of this study were—(1) respiration responses, and (2) shoe discomfort rating, respectively. The data were analyzed using the Mauchly’s test of sphericity, Shapiro–Wilk normality test, and analysis of variance (ANOVA). The results showed that the use of heavy-duty safety shoes typically increased the shoe discomfort rating under precise lifting methods. Additionally, the lifting frequency was determined to be one of the main factors affecting respiratory responses and shoe discomfort rating. This study also found that respiration responses rose on four lifts per min as compared to 1 lift per min, regardless of the lifting method type. This study indicated that the replacement of some types of ordinary safety shoes used in some workplaces with those selected appropriately might significantly reduce the rating effort required to lift objects or tools. However, the benefits should be carefully evaluated before replacing the safety shoes.

Transverse vortex-induced vibration of a circular cylinder on a viscoelastic support at low Reynolds number

The effect of a viscoelastic-type structural support on vortex-induced vibration (VIV) of a circular cylinder has been studied computationally for a fixed mass ratio (m∗=2.546) and Reynolds number (Re=150). Unlike the classical case of VIV where the structural support consists of a spring and damper in parallel, this study considers two springs and one damper, where the two springs are in parallel and the damper is in series with one of the springs. This spring/damper arrangement is similar to the Standard Linear Solid (SLS) model used for modelling viscoelastic behaviour. The viscoelastic support (SLS type) is governed by the following two parameters: (a) the ratio of spring constants (R), and (b) the damping ratio (ζ). The focus of the present study is to examine and understand the varied response of the cylinder to VIV as these parameters are varied. For small ζ and R, the cylinder response shows characteristics similar to the classical case, where the amplitude response is composed of an upper- and the lower-type branch. The presence of upper-type branch at low Re is evident through the peak lift force, frequency and phase response of the cylinder. As the damping ratio is increased, the vibration amplitude decreases and hence the upper-type branch disappears. There exists a critical value of ζ=1 beyond which the amplitude again increases asymptotically. The non-monotonic variation of amplitude response with ζ is presented in the form of the ”Griffin plot”. The amplitude, force, frequency and phase-difference response of cylinder were found to be mirror symmetric in log(ζ) about ζ=1. In addition, the effect of R at the critical value of damping, ζ=1, was studied. This show that the amplitude decreases with an increase of R, with suppression of the response branches for high R values. The results suggest that a careful tuning of the damping may be effectively employed both to enhance power output for energy extraction applications or to suppress flow-induced vibration.

Using Electroencephalography (EEG) Power Responses to Investigate the Effects of Ambient Oxygen Content, Safety Shoe Type, and Lifting Frequency on the Worker's Activities.

Objective The study assesses the changes in electroencephalography (EEG) power spectral density of individuals in hypoxia when wearing a different type of safety shoes under different lifting frequencies. It also assesses the EEG response behavior induced via the process of lifting loads related to these variables. Methods The study was conducted in two consecutive phases: training and acclimatization phase and experimental lifting phase. Ten male college students participated in this study. A four-way repeated measures design was used in this research with independent variables: ambient oxygen content (“15%, 18%, and 20%”), safety shoes type (“light-duty, medium-duty, and heavy-duty”), lifting frequency (“1 and 4 lifts/min”), and replication (“first and second”). And the dependent variables were alpha, theta, beta, gamma, θ/α, θ/β, α/β, β/α, (θ + α)/β, and (θ + α)/(α + β). The participant was allowed to determine his maximum acceptable weight of lift (MAWL) in fifteen minutes of lifting using psychophysically technique. Then, he continued lifting the MAWL for another five minutes, where all the data were collected. Results Results showed that the EEG responses at lower levels of the independent variables were significantly high than at higher levels; except for oxygen content, the EEG responses at lower levels were considerably lower than at a higher level. It also showed that an upsurge in the physical demand increased lifting frequency and replication and caused decreasing in alpha power, theta/beta, alpha/beta, (theta + alpha)/beta, (theta + alpha)/(alpha + beta) and increasing in the theta power and the gamma power. Furthermore, several interactions among independent variables had significant effects on the EEG responses. Conclusion The EEG implementation for the investigation of neural responses to physical demands allows for the possibility of newer nontraditional and faster methods of human performance monitoring. These methods provide effective and reliable results as compared to other traditional methods. This study will safeguard the physical capabilities and possible health risks of industrial workers. And the applications of these tasks can occur in almost all working environments (factories, warehouses, airports, building sites, farms, hospitals, offices, etc.) that are at high altitudes. It can include lifting boxes at a packaging line, handling construction materials, handling patients in hospitals, and cleaning.