Displaying publications 1 - 20 of 147 in total

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  1. Fulltext Intelligent ground vibration prediction in surface mines using an efficient soft computing method based on field data
    Keshtegar B, Piri J, Asnida Abdullah R, Hasanipanah M, Muayad Sabri Sabri M, Nguyen Le B
    Front Public Health, 2022;10:1094771.
    PMID: 36817184 DOI: 10.3389/fpubh.2022.1094771
    Ground vibration induced by blasting operations is considered one of the most common environmental effects of mining projects. A strong ground vibration can destroy buildings and structures, hence its prediction and minimization are of high importance. The aim of this study is to estimate the ground vibration through a hybrid soft computing (SC) method, called RSM-SVR, which comprises two main regression techniques: the response surface model (RSM) and support vector regression (SVR). The RSM-SVR model applies an RSM in the first calibrating process and an SVR in the second calibrating process to improve the accuracy of the ground vibration predictions. The predicted results of an RSM, which are obtained using the input data of problems, are used as the input dataset for the regression process of an SVR. The effectiveness and agreement of the RSM-SVR model were compared to those of an SVR optimized with the particle swarm optimization (PSO) and genetic algorithm (GA), RSM, and multivariate linear regression (MLR) based on several statistical factors. The findings confirmed that the RSM-SVR model was considerably superior to other models in terms of accuracy. The amounts of coefficient of determination (R 2) were 0.896, 0.807, 0.782, 0.752, 0.711, and 0.664 obtained from the RSM-SVR, PSO-SVR, GA-SVR, MLR, SVR, and RSM models, respectively.
    Matched MeSH terms: Vibration*
  2. Fulltext Developed steady-state response for a new hybrid damper mounted on structures
    Ziaee M, Hejazi F
    PLoS One, 2023;18(8):e0290248.
    PMID: 37590241 DOI: 10.1371/journal.pone.0290248
    Coulomb friction is considered as a mechanical approach to diminish the structural responses during the excitations. However, in case of severe oscillations supplementary mechanisms are employed besides the friction to mitigate the destructive effects of the vibrations in structures. Therefore, the main goal of this research is to develop a new Hybrid System (HS) which is a parallel combination of Viscous Damping (VD) and Coulomb friction for structures subjected to dynamic load. To achieve this goal, the effect of viscous damper is embedded in the equation of motion which is proposed by Den Hartog for a Single-Degree-of-Freedom (SDOF) Coulomb system, and has been extensively implemented for past few decades. In the considered numerical example in this study, implementing the proposed HDM in system resulted in decreasing the maximum displacement in the range of 1% to 98% for different amounts of force amplitude and viscous damping ratios. Also, applying the proposed HDM increased the time lag for about up to 24% for the frequency ratios greater than 1. The developed hybridized system in this study can be utilised as new generation of Tuned Mass Damper (TMD) to improve their energy dissipating efficiency under severe excitations.
    Matched MeSH terms: Vibration*
  3. Fulltext Numerical investigation of the vortex-induced vibration of an elastically mounted circular cylinder at high Reynolds number (Re = 104) and low mass ratio using the RANS code
    Khan NB, Ibrahim Z, Nguyen LTT, Javed MF, Jameel M
    PLoS One, 2017;12(10):e0185832.
    PMID: 28982172 DOI: 10.1371/journal.pone.0185832
    This study numerically investigates the vortex-induced vibration (VIV) of an elastically mounted rigid cylinder by using Reynolds-averaged Navier-Stokes (RANS) equations with computational fluid dynamic (CFD) tools. CFD analysis is performed for a fixed-cylinder case with Reynolds number (Re) = 104 and for a cylinder that is free to oscillate in the transverse direction and possesses a low mass-damping ratio and Re = 104. Previously, similar studies have been performed with 3-dimensional and comparatively expensive turbulent models. In the current study, the capability and accuracy of the RANS model are validated, and the results of this model are compared with those of detached eddy simulation, direct numerical simulation, and large eddy simulation models. All three response branches and the maximum amplitude are well captured. The 2-dimensional case with the RANS shear-stress transport k-w model, which involves minimal computational cost, is reliable and appropriate for analyzing the characteristics of VIV.
    Matched MeSH terms: Vibration*
  4. Fulltext ON NUMERICAL METHODS FOR SECOND-ORDER NON-LINEAR ORDINARY DIFFERENTIAL EQUATIONS (ODEs): A REDUCTION TO A SYSTEM OF FIRST-ORDER ODEs
    Loy Kak Choon, Puteri Nurul Fatihah binti Mohamad Azli
    UMT Journal of Undergraduate Research, 2019;1(4):1-8.
    MyJurnal
    2nd-order ODEs can be found in many applications, e.g., motion of pendulum, vibrating springs, etc. We first convert the 2nd-order nonlinear ODEs to a system of 1st-order ODEs which is easier to deal with. Then, Adams-Bashforth (AB) methods are used to solve the resulting system of 1st-order ODE. AB methods are chosen since they are the explicit schemes and more efficient in terms of shorter computational time. However, the step size is more restrictive since these methods are conditionally stable. We find two test cases (one test problem and one manufactured solution) to be used to validate the AB methods. The exact solution for both test cases are available for the error and convergence analysis later on. The implementation of 1st-, 2nd- and 3rd-order AB methods are done using Octave. The error was computed to retrieve the order of convergence numerically and the CPU time was recorded to analyze their efficiency.
    Matched MeSH terms: Vibration
  5. Fulltext Near-zero metamaterial inspired UHF antenna for nanosatellite communication system
    Alam T, Islam MT, Cho M
    Sci Rep, 2019 Mar 05;9(1):3441.
    PMID: 30837629 DOI: 10.1038/s41598-019-40207-3
    Epsilon-and-mu-near-zero (EMNZ) metamaterial structure inspired UHF antenna for nanosatellite has been proposed in this paper. The antenna consists of 3 × 2-unit cell array on the ground plane and a meander line radiating patch. Coaxial probe feeding technique has been obtained to excite the antenna. The meander line enables the antenna to resonate at lower UHF band and the metamaterial array is used to make the resonant frequency stable by reducing the coupling effect with metallic nanosatellite structure. The metamaterial structure exhibits EMNZ characteristics from 385 MHz to 488.5 MHz, which facilitates stable resonant frequency and higher antenna efficiency when embedded with nanosatellite structure. The proposed EMNZ inspired antenna has achieved measured impedance bandwidth (S11 
    Matched MeSH terms: Vibration
  6. Fulltext Improving the dynamic characteristics of body-in-white structure using structural optimization
    Yahaya Rashid AS, Ramli R, Mohamed Haris S, Alias A
    ScientificWorldJournal, 2014;2014:190214.
    PMID: 25101312 DOI: 10.1155/2014/190214
    The dynamic behavior of a body-in-white (BIW) structure has significant influence on the noise, vibration, and harshness (NVH) and crashworthiness of a car. Therefore, by improving the dynamic characteristics of BIW, problems and failures associated with resonance and fatigue can be prevented. The design objectives attempt to improve the existing torsion and bending modes by using structural optimization subjected to dynamic load without compromising other factors such as mass and stiffness of the structure. The natural frequency of the design was modified by identifying and reinforcing the structure at critical locations. These crucial points are first identified by topology optimization using mass and natural frequencies as the design variables. The individual components obtained from the analysis go through a size optimization step to find their target thickness of the structure. The thickness of affected regions of the components will be modified according to the analysis. The results of both optimization steps suggest several design modifications to achieve the target vibration specifications without compromising the stiffness of the structure. A method of combining both optimization approaches is proposed to improve the design modification process.
    Matched MeSH terms: Vibration*
  7. Fulltext Resonant frequency characteristics of a SAW device attached to resonating micropillars
    Ramakrishnan N, Nemade HB, Palathinkal RP
    Sensors (Basel), 2012;12(4):3789-97.
    PMID: 22666001 DOI: 10.3390/s120403789
    Recently we reported experimental and simulation results on an increase in resonance frequency of a SAW resonator caused by mass loading of micropillars made of SU-8, attached normal to the surface of the resonator. We concluded that SAW resonator and the SU-8 micropillars in unison form a system of coupled resonators. We have now extended this work and performed a finite element method simulation to study the resonance frequency characteristics of the SAW-based coupled resonator. In this paper we report the effect of the resonance frequency of the micropillars on the resonance frequency of the system of coupled resonators, and observe the coupling of micropillar resonance and the propagating SAW as described in the well known Dybwad system of coupled resonators.
    Matched MeSH terms: Vibration
  8. Combination of Searches for Higgs Boson Pair Production in Proton-Proton Collisions at sqrt[s]=13  TeV
    Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Phys Rev Lett, 2019 Mar 29;122(12):121803.
    PMID: 30978057 DOI: 10.1103/PhysRevLett.122.121803
    This Letter describes a search for Higgs boson pair production using the combined results from four final states: bbγγ, bbττ, bbbb, and bbVV, where V represents a W or Z boson. The search is performed using data collected in 2016 by the CMS experiment from LHC proton-proton collisions at sqrt[s]=13  TeV, corresponding to an integrated luminosity of 35.9  fb^{-1}. Limits are set on the Higgs boson pair production cross section. A 95% confidence level observed (expected) upper limit on the nonresonant production cross section is set at 22.2 (12.8) times the standard model value. A search for narrow resonances decaying to Higgs boson pairs is also performed in the mass range 250-3000 GeV. No evidence for a signal is observed, and upper limits are set on the resonance production cross section.
    Matched MeSH terms: Vibration
  9. First Measurements of Absolute Branching Fractions of the Ξ_{c}^{0} Baryon at Belle
    Li YB, Shen CP, Yuan CZ, Adachi I, Aihara H, Al Said S, et al.
    Phys Rev Lett, 2019 Mar 01;122(8):082001.
    PMID: 30932568 DOI: 10.1103/PhysRevLett.122.082001
    We present the first measurements of absolute branching fractions of Ξ_{c}^{0} decays into Ξ^{-}π^{+}, ΛK^{-}π^{+}, and pK^{-}K^{-}π^{+} final states. The measurements are made using a dataset comprising (772±11)×10^{6} BB[over ¯] pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB e^{+}e^{-} collider. We first measure the absolute branching fraction for B^{-}→Λ[over ¯]_{c}^{-}Ξ_{c}^{0} using a missing-mass technique; the result is B(B^{-}→Λ[over ¯]_{c}^{-}Ξ_{c}^{0})=(9.51±2.10±0.88)×10^{-4}. We subsequently measure the product branching fractions B(B^{-}→Λ[over ¯]_{c}^{-}Ξ_{c}^{0})B(Ξ_{c}^{0}→Ξ^{-}π^{+}), B(B^{-}→Λ[over ¯]_{c}^{-}Ξ_{c}^{0})B(Ξ_{c}^{0}→ΛK^{-}π^{+}), and B(B^{-}→Λ[over ¯]_{c}^{-}Ξ_{c}^{0})B(Ξ_{c}^{0}→pK^{-}K^{-}π^{+}) with improved precision. Dividing these product branching fractions by the result for B^{-}→Λ[over ¯]_{c}^{-}Ξ_{c}^{0} yields the following branching fractions: B(Ξ_{c}^{0}→Ξ^{-}π^{+})=(1.80±0.50±0.14)%, B(Ξ_{c}^{0}→ΛK^{-}π^{+})=(1.17±0.37±0.09)%, and B(Ξ_{c}^{0}→pK^{-}K^{-}π^{+})=(0.58±0.23±0.05)%. For the above branching fractions, the first uncertainties are statistical and the second are systematic. Our result for B(Ξ_{c}^{0}→Ξ^{-}π^{+}) can be combined with Ξ_{c}^{0} branching fractions measured relative to Ξ_{c}^{0}→Ξ^{-}π^{+} to yield other absolute Ξ_{c}^{0} branching fractions.
    Matched MeSH terms: Vibration
  10. Fulltext Schrodinger equation in string theory
    Anuar Alias, Ithnin Abdul Jalil, Tajuddin, W.A.
    Journal of Nuclear and Related Technologies, 2010;2010(2):154-169.
    MyJurnal
    String theory is currently considered as the leading candidate for a unified theory of physics combining the Standard Model of forces and particles with gravity which is best described by Einstein theory of General Relativity. Contrary to classical model of point particle, String theory proposes that matter, force, even space and time are composed of tiny vibrating strings. This paper is to elaborate on the correspondence between string states and quantum fields by initially constructing general time-dependent states from string basis states analogous to general timedependent super-positions of basis states for a point particle. From this derivation we can show that an equation emerges from the 'classical' Schrodinger equation that represents the Schrodinger equation in String theory. This is very interesting to investigate since the Schrodinger equation is at the core of Quantum Mechanics which is the foundation of Standard Model that is the pillar of Nuclear physics.
    Matched MeSH terms: Vibration
  11. Observation of ϒ(4S)→η^{'}ϒ(1S)
    Guido E, Mussa R, Tamponi U, Aihara H, Al Said S, Asner DM, et al.
    Phys Rev Lett, 2018 Aug 10;121(6):062001.
    PMID: 30141661 DOI: 10.1103/PhysRevLett.121.062001
    We report the first observation of the hadronic transition ϒ(4S)→η^{'}ϒ(1S), using 496  fb^{-1} data collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. We reconstruct the η^{'} meson through its decays to ρ^{0}γ and to π^{+}π^{-}η, with η→γγ. We measure B(ϒ(4S)→η^{'}ϒ(1S))=[3.43±0.88(stat)±0.21(syst)]×10^{-5}, with a significance of 5.7σ.
    Matched MeSH terms: Vibration
  12. Fulltext A New Method for a Piezoelectric Energy Harvesting System Using a Backtracking Search Algorithm-Based PI Voltage Controller
    Sarker MR, Mohamed A, Mohamed R
    Micromachines (Basel), 2016 Sep 23;7(10).
    PMID: 30404344 DOI: 10.3390/mi7100171
    This paper presents a new method for a vibration-based piezoelectric energy harvesting system using a backtracking search algorithm (BSA)-based proportional-integral (PI) voltage controller. This technique eliminates the exhaustive conventional trial-and-error procedure for obtaining optimized parameter values of proportional gain (Kp), and integral gain (Ki) for PI voltage controllers. The generated estimate values of Kp and Ki are executed in the PI voltage controller that is developed through the BSA optimization technique. In this study, mean absolute error (MAE) is used as an objective function to minimize output error for a piezoelectric energy harvesting system (PEHS). The model for the PEHS is designed and analyzed using the BSA optimization technique. The BSA-based PI voltage controller of the PEHS produces a significant improvement in minimizing the output error of the converter and a robust, regulated pulse-width modulation (PWM) signal to convert a MOSFET switch, with the best response in terms of rise time and settling time under various load conditions.
    Matched MeSH terms: Vibration
  13. Clusters of gaas prepared by quantum mechanical DFT and the nanowire raman spectra
    AHMAD NAZRUL ROSLI, HASAN ABU KASSIM, SHRIVASTAVA KN
    Sains Malaysiana, 2013;42:1811-1814.
    We studied the clusters of GaAs by using the density functional theory simulation to optimize the structure. We determined the binding energy, bond lengths, Fermi energy and vibrational frequencies for all of the clusters. We use the Raman data of nanowires of GaAs to compare our calculated values with the experimental values of the vibrational frequencies. The nanowire of GaAs gives a Raman line at 256 cm-1 whereas in the bipyramidal Ga2As3 the calculated value is 256.33 cm-1. Similarly 285 cm-1 found in the experimental Raman data agrees with 286.21 cm-1 found in the values calculated for Ga2As2 (linear) showing that linear bonds occur in the nanowire. The GaAs is found in two structures zinc-blend as well as wurtzite structures. In the nanowire mixed structures as well as clusters are formed.
    Matched MeSH terms: Vibration
  14. The clinical features of hand-arm vibration syndrome in a warm environment--a review of the literature
    Su AT, Darus A, Bulgiba A, Maeda S, Miyashita K
    J Occup Health, 2012;54(5):349-60.
    PMID: 22863899
    The internationally accepted limit values and the health effects of hand-transmitted vibration exposure have been described extensively in the literature from temperate climate countries but not from a tropical climate environment.

    OBJECTIVES: We conducted a systematic review of the health effects of hand-transmitted vibration exposure in tropical countries to determine the characteristics of hand-arm vibration syndrome in a warm environment and compared the findings with the results of the systematic reviews published by the US NIOSH.

    METHODS: We searched major medical databases including MEDLINE, PubMed, Embase, CINAHL, Ovid and Cochrane based on the terms "hand arm vibration syndrome," "hand transmitted vibration," "vibration white finger" and "Raynaud" up to January 2011. Only studies conducted in a tropical or subtropical environment were selected for the review. The quality of the selected papers was assessed independently by two investigators using predefined criteria. A standard set of information was abstracted from the papers for review.

    RESULTS: Only six papers from tropical countries and three papers from subtropical countries were available in the literature. No vibration white finger was reported in the tropical countries. Neurological symptoms were prevalent in the vibration-exposed workers. Finger coldness seems to be an important surrogate for vascular disorder in a tropical environment. Meta-analysis could not be performed due to inadequacy of the information reported in these papers.

    CONCLUSIONS: The current dose-response relationship in ISO5349-1 for hand-transmitted vibration exposure is not applicable to a tropical environment. Further studies on hand-arm vibration syndromes in tropical countries are needed.

    Matched MeSH terms: Hand-Arm Vibration Syndrome/physiopathology*
  15. Lifetime vibration dose correlates with severity of the neurological component of hand-arm vibration syndrome among tyre shop workers in Kelantan, Malaysia
    Qamruddin AA, Husain NRN, Sidek MY, Hanafi MH, Ripin ZM, Ali N
    Int J Occup Saf Ergon, 2021 Jun;27(2):410-415.
    PMID: 30940001 DOI: 10.1080/10803548.2019.1600872
    Introduction. Cumulative lifetime exposure to vibration is believed to contribute to more severe complications of hand-arm vibration syndrome (HAVS). Objectives. To determine prevalence of the neurological component of HAVS and the correlation between lifetime vibration dose (LVD) and neurological severity of HAVS among tyre shop workers in Kelantan. Methods. The cross-sectional study involved 200 tyre shop workers from two districts in Kelantan. Part one data were collected in the field using a questionnaire and hand-arm vibration was measured. Part two involved a set of hand clinical examinations (Purdue pegboard, Semmes-Weinstein monofilament and two-point discrimination tests) carried out for neurological component severity staging. LVD for each worker was calculated from data gathered in part one. For workers who had neurological symptoms, staging according to Stockholm workshop scales was done according to part two data. The strength of correlation between LVD and neurological stages was then determined using Spearman correlation. Results. Prevalence of neurological component was 37%. Spearman correlation between LVD and the neurological stages showed a moderate positive correlation. Conclusion. Cumulative lifetime exposure to hand-transmitted vibration is likely to be related to neurological severity of HAVS and therefore must be considered when assessing workers' exposure to hand-arm vibration.
    Matched MeSH terms: Vibration/adverse effects
  16. Fulltext Linear Segmented Arc-Shaped Piezoelectric Branch Beam Energy Harvester for Ultra-Low Frequency Vibrations
    Piyarathna IE, Thabet AM, Ucgul M, Lemckert C, Lim YY, Tang ZS
    Sensors (Basel), 2023 Jun 01;23(11).
    PMID: 37299984 DOI: 10.3390/s23115257
    Piezoelectric energy harvesting systems have been drawing the attention of the research community over recent years due to their potential for recharging/replacing batteries embedded in low-power-consuming smart electronic devices and wireless sensor networks. However, conventional linear piezoelectric energy harvesters (PEH) are often not a viable solution in such advanced practices, as they suffer from a narrow operating bandwidth, having a single resonance peak present in the frequency spectrum and very low voltage generation, which limits their ability to function as a standalone energy harvester. Generally, the most common PEH is the conventional cantilever beam harvester (CBH) attached with a piezoelectric patch and a proof mass. This study investigated a novel multimode harvester design named the arc-shaped branch beam harvester (ASBBH), which combined the concepts of the curved beam and branch beam to improve the energy-harvesting capability of PEH in ultra-low-frequency applications, in particular, human motion. The key objectives of the study were to broaden the operating bandwidth and enhance the harvester's effectiveness in terms of voltage and power generation. The ASBBH was first studied using the finite element method (FEM) to understand the operating bandwidth of the harvester. Then, the ASBBH was experimentally assessed using a mechanical shaker and real-life human motion as excitation sources. It was found that ASBBH achieved six natural frequencies within the ultra-low frequency range (<10 Hz), in comparison with only one natural frequency achieved by CBH within the same frequency range. The proposed design significantly broadened the operating bandwidth, favouring ultra-low-frequency-based human motion applications. In addition, the proposed harvester achieved an average output power of 427 μW at its first resonance frequency under 0.5 g acceleration. The overall results of the study demonstrated that the ASBBH design can achieve a broader operating bandwidth and significantly higher effectiveness, in comparison with CBH.
    Matched MeSH terms: Vibration*
  17. A cross sectional study on hand-arm vibration syndrome among a group of tree fellers in a tropical environment
    Su AT, Maeda S, Fukumoto J, Miyai N, Isahak M, Yoshioka A, et al.
    Ind Health, 2014;52(4):367-76.
    PMID: 24739764
    This study aimed to explore the clinical characteristics of hand arm vibration syndrome (HAVS) in a group of tree fellers in a tropical environment. We examined all tree fellers and selected control subjects in a logging camp of central Sarawak for vibration exposure and presence of HAVS symptoms utilizing vibrotactile perception threshold test (VPT) and cold water provocation test (CWP). None of the subjects reported white finger. The tree fellers reported significantly higher prevalence of finger coldness as compared to the control subjects (OR=10.32, 95%CI=1.21-87.94). A lower finger skin temperature, longer fingernail capillary return time and higher VPT were observed among the tree fellers as compared to the control subjects in all fingers (effect size >0.5). The VPT following CWP of the tree fellers was significantly higher (repeated measures ANOVA p=0.002, partial η(2)=0.196) than the control subject. The A (8) level was associated with finger tingling, numbness and dullness (effect size=0.983) and finger coldness (effect size=0.524) among the tree fellers. Finger coldness and finger tingling, numbness and dullness are important symptoms for HAVS in tropical environment that may indicate vascular and neurological damage due to hand-transmitted vibration exposure.
    Matched MeSH terms: Vibration/adverse effects; Hand-Arm Vibration Syndrome/etiology; Hand-Arm Vibration Syndrome/epidemiology*
  18. Musculoskeletal complications of hand-arm vibration syndrome among tyre shop workers in Kelantan, Malaysia
    Qamruddin AA, Husain NRN, Sidek MY, Hanafi MH, Ripin ZM, Ali N
    Int J Occup Saf Ergon, 2020 Dec 03.
    PMID: 33148113 DOI: 10.1080/10803548.2020.1846924
    Objectives. Exposure to hand-arm vibration (HAV) is associated with hand-arm vascular syndrome (HAVS), which is characterized by musculoskeletal complications. However, evidence on this matter has been inconclusive. Therefore, this study aimed to determine and compare the prevalence of musculoskeletal complications of HAVS between a high-exposure (≥5 m·s-2) group and a low-moderate-exposure (<5 m·s-2) group and to explore the factors associated with the musculoskeletal complications of HAVS among tyre shop workers in Kelantan, Malaysia. Methods. A cross-sectional study involving 200 tyre shop workers was carried out. HAV was measured by a vibration meter. The workers were divided into two exposure groups - according to their 8-h time-weighted average, A(8), of vibration exposure - and compared. Results. Almost half of the workers reported musculoskeletal complications of the upper limbs and neck. Only the lifetime vibration dose (LVD) was significantly associated with the development of musculoskeletal complications. Conclusion. The high-exposure group had a higher prevalence of musculoskeletal complications. Only the LVD was significantly associated with complications. However, all factors of the work system, such as ergonomics, handgrip force and posture, might contribute to the development of musculoskeletal complications of HAVS and should be included in assessments.
    Matched MeSH terms: Vibration; Hand-Arm Vibration Syndrome
  19. Resonance condition of a microfiber knot resonator immersed in liquids
    Lim KS, Jasim AA, Damanhuri SS, Harun SW, Rahman BM, Ahmad H
    Appl Opt, 2011 Oct 20;50(30):5912-6.
    PMID: 22015420 DOI: 10.1364/AO.50.005912
    Effects of immersing a microfiber knot resonator (MKR) in liquid solutions that have refractive indices close to that of silica are experimentally demonstrated and theoretically analyzed. Significant improvement in resonance extinction ratio within 2 to 10 dB was observed. To achieve a better understanding, a qualitative analysis of the coupling ratio and round-trip attenuation of the MKR is performed by using a curve-fitting method. It was observed that the coupling coefficient at the knot region increased when immersed in liquids. However, depending on the initial state of the coupling and the quantity of the increment in the coupling coefficient when immersed in a liquid, it is possible that the MKR may experience a deficit in the coupling parameter due to the sinusoidal relationship with the coupling coefficient.
    Matched MeSH terms: Vibration
  20. Optimization of the operating parameters of a grass trimming machine
    Mallick Z
    Appl Ergon, 2010 Mar;41(2):260-5.
    PMID: 19762006 DOI: 10.1016/j.apergo.2009.07.010
    Hand-arm vibration syndrome (HAVS) is very common among the workers operating power tools and doing similar nature of work for long hours. Grass trimming is one of the operations that involves use of vibrating cutter, and results in hand-arm vibration among workers. In this study, the influence of several operating parameters (length of nylon cutting thread, engine speed and handle material) is investigated in terms of HAV. Data are analyzed via orthogonal array, main effect, signal-to-noise (S/N) ratio, and analysis of variance to determine the appropriate operating parameter levels to minimize HAV. Operating parameters under investigation are found to be influential in controlling HAV generation during grass trimming operation. Experiments are carried out for measuring hand-arm vibration using tri-axial accelerometer conforming the effectiveness of this approach. Results show that 100mm length of nylon thread, 3000+/-400rpm of engine speed and ABS handle material combination results in minimum HAV (HARM) of magnitude 2.76m/s(2). Through this study not only the optimal operating parameter levels for GTM are obtained, but also the main process parameters that affect the HAV are determined. The optimum HAV obtained through appropriate level selection of operating parameters, significantly reduces the occurrence of HAVS among the grass trimmers.
    Matched MeSH terms: Vibration/adverse effects*; Hand-Arm Vibration Syndrome/etiology*
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