An evaluation of vibration and other effects on the accuracy of grip and push force recall

Operators of vibratory hand tools can be at risk of developing health problems associated with repeated forceful actions and exposure to intense hand-transmitted vibration. To better assess health risks, comprehensive risk evaluations of these tasks must include quantitative assessments of hand-tool coupling forces. Researchers have used instrumentation for such measurements; but those techniques may be ill-suited for certain field environments. Psychophysical force-recall techniques have been proposed as alternatives to handle instrumentation. This study comprised two experiments that examined the effects of vibration and other factors upon force-recall accuracy and reliability. In each experiment, participants applied specific grip and push forces to an instrumented handle mounted on a shaker system. Participants were exposed to sinusoidal vibration at frequencies that ranged from 0 Hz to 250 Hz. Three levels of applied force and two levels of vibration magnitude were examined. During the vibration exposure period, participants were provided with visual feedback while they attempted to memorize their applied grip and push forces. Following vibration exposure and a rest period, participants tried to duplicate the hand forces without visual feedback. Vibration frequencies, magnitudes, and hand force levels were randomized from trial to trial. To evaluate test-retest reliability, the test was repeated on a later day with each participant. Participants overestimated grip and push forces. Depending on exposure conditions, error means ranged from 2 N to 10 N. The ANOVA revealed that force-recall errors for exposures between 31.5 Hz and 63 Hz were significantly higher than those at other vibration frequencies. Errors were greater when participants were exposed to the higher vibration magnitude when compared with the lower vibration magnitude. The average error for females was significantly less than that for males. The effects of force level were mixed. This method demonstrated strong test-retest reliability as correlations for all but one participant were found to be significant. Overall, recalled force errors were relatively small over the range of operationally-relevant hand-handle coupling forces and vibration exposure conditions. This force-recall technique shows promise as an alternative to expensive and fragile force-sensing instrumentation

Review and Evaluation of Hand–Arm Coordinate Systems for Measuring Vibration Exposure, Biodynamic Responses, and Hand Forces

AbstractThe hand coordinate systems for measuring vibration exposures and biodynamic responses have been standardized, but they are not actually used in many studies. This contradicts the purpose of the standardization. The objectives of this study were to identify the major sources of this problem, and to help define or identify better coordinate systems for the standardization. This study systematically reviewed the principles and definition methods, and evaluated typical hand coordinate systems. This study confirms that, as accelerometers remain the major technology for vibration measurement, it is reasonable to standardize two types of coordinate systems: a tool-based basicentric (BC) system and an anatomically based biodynamic (BD) system. However, these coordinate systems are not well defined in the current standard. Definition of the standard BC system is confusing, and it can be interpreted differently; as a result, it has been inconsistently applied in various standards and studies. The standard hand BD system is defined using the orientation of the third metacarpal bone. It is neither convenient nor defined based on important biological or biodynamic features. This explains why it is rarely used in practice. To resolve these inconsistencies and deficiencies, we proposed a revised method for defining the realistic handle BC system and an alternative method for defining the hand BD system. A fingertip-based BD system for measuring the principal grip force is also proposed based on an important feature of the grip force confirmed in this study

Estimation of the biodynamic responses distributed at fingers and palm based on the total response of the hand–arm system

The major objective of this study is to develop a modeling method for estimating the biodynamic responses distributed at the fingers and the palm of the hand based on the total driving-point mechanical impedance of the entire hand–arm system. A five degrees-of-freedom (DOF) model with a set of constraints proposed in this study was used in the estimation. Three sets of mechanical impedance data measured at the fingers and palm of the hand were used to examine the validity of the proposed method. The estimated response distributed at the palm was consistent with the measured data even when the real part of the impedance alone was used in the modeling (coefficient of correlation, r2 ≥ 0.902). Better agreements between the estimated and measured responses were obtained (r2 ≥ 0.929) when the magnitude and phase of the total impedance or the magnitude alone were used in the modeling estimation. In each case, the estimated response distributed at the fingers was also reliably correlated with the experimental data (r2 ≥ 0.726) but it was not as consistent with the experimental data as that distributed at the palm. The applications of the proposed method were also demonstrated using five other sets of reported experimental data. This study also demonstrated that the modeling method may also be used to assess the quality of the experimental data in some cases. As a special application of the acceptable data identified in this study, this study also defined a 2-DOF model for the construction of a hand–arm simulator for tool tests. The results of this study and the proposed modeling method are expected to contribute to the revision of ISO 10068 (1998)

Non-Formal Education in a World Context

During the past decade the role of non-formal education throughout the world has become an important topic. Educators realize that the formal system cannot solve the diversified and complex problems which face a society today. As a consequence a closer look is now being taken at educational activities outside the established system--especially those non-formal processes which have a relationship to socio-economic development. While many societies have a long tradition of non-formal education, little attempt has been made to utilize this base to provide individuals with a flexible and diversified range of useful learning opportunities. Recently, however, the innate potential of non-formal education is being realized. Today education is being viewed as a life-long process rather than the specified knowledge transmitted in a formal school system. As interest in the field of non-formal education developed, attempts have been made to collect and exchange useful information. Toward this end, the Center for International Education, University of Massachusetts, hosted a World Education Conference and invited educators to share ideas on non-formal education. This booklet contains the papers delivered at that Conference. Some papers are exploratory and some definitive, some are brief overviews, and others are detailed accounts; however, all the papers make a worthwhile contribution to the field. The papers have been organized according to geographical areas

Denitrification and total nitrate uptake in streams of a tropical landscape

Author Posting. © Ecological Society of America, 2010. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 20 (2010): 2104-2115, doi:10.1890/09-1110.1.Rapid increases in nitrogen (N) loading are occurring in many tropical watersheds, but the fate of N in tropical streams is not well documented. Rates of nitrate uptake and denitrification were measured in nine tropical low-order streams with contrasting land use as part of the Lotic Intersite Nitrogen eXperiment II (LINX II) in Puerto Rico using short term (24-hour) additions of K15NO3 and NaBr. Background nitrate concentrations ranged from 105 to 997 μg N/L, and stream nitrate uptake lengths were long, varying from 315 to 8480 m (median of 1200 m). Other indices of nitrate uptake (mass transfer coefficient, Vf [cm/s], and whole-stream nitrate uptake rate, U [μg N·m−2·s−1]) were low in comparison to other regions and were related to chemical, biological, and physical parameters. Denitrification rates were highly variable (0–133 μg N·m−2·min−1; median = 15 μg N·m−2·min−1), were dominated by the end product N2 (rather than N2O), and were best predicted by whole-stream respiration rates and stream NO3 concentration. Denitrification accounted for 1–97% of nitrate uptake with five of nine streams having 35% or more of nitrate uptake via denitrification, showing that denitrification is a substantial sink for nitrate in tropical streams. Whole-stream nitrate uptake and denitrification in our study streams closely followed first-order uptake kinetics, indicating that NO3 uptake is limited by delivery of substrate (NO3) to the organisms involved in uptake or denitrification. In the context of whole-catchment nitrogen budgets, our finding that in-stream denitrification results in lower proportional production of N2O than terrestrial denitrification suggests that small streams can be viewed as the preferred site of denitrification in a watershed in order to minimize greenhouse gas N2O emissions. Conservation of small streams is thus critical in tropical ecosystem management.This research was part of the Lotic Intersite Nitrogen eXperiment II (LINX II) funded by the National Science Foundation (DEB-0111410). Additional support was provided by the National Science Foundation to the Institute of Terrestrial Ecology at the University of Puerto Rico and the International Institute of Tropical Forestry (DEB-0218039 and DEB-0620919) through the Luquillo Long Term Ecological Research (LUQ LTER) program

Characterising the impact of sex on severe asthma (SA) in the UK Severe Asthma Registry (UKSAR)

Peer reviewedPostprin

Mechanical impedances distributed at the fingers and palm of the human hand in three orthogonal directions

The objective of this study is to investigate the basic characteristics of the three axis mechanical impedances distributed at the fingers and palm of the hand subjected to vibrations along three orthogonal directions (xh, yh, and zh). Seven subjects participated in the experiment on a novel three-dimensional (3-D) hand–arm vibration test system equipped with a 3-D instrumented handle. The total impedance of the entire hand–arm system was obtained by performing a sum of the distributed impedances. Two major resonances were observed in the impedance data in each direction. For the hand forces (30 N grip and 50 N push) and body postures applied in this study, the first resonance was in the range of 20–40 Hz, and it was primarily observed in the impedance at the palm. The second resonance was generally observed in the impedance at the fingers, while the resonance frequency varied greatly with the subject and vibration direction, ranging from 100 to 200 Hz in the xh direction, 60 to 120 Hz in the yh direction, and 160 to 300 Hz in the zh direction. The impedance at the palm was greater than that at the fingers below a certain frequency in the range of 50–100 Hz, depending on the vibration direction. At higher frequencies, however, the impedance magnitude at the fingers either approached or exceeded that at the palm. The impedance in the zh direction was generally higher than those in the other directions, but it became comparable with that in the xh direction at frequencies above 250 Hz, while the impedance in the yh direction was the lowest. The frequency dependencies of the vibration power absorptions for the entire hand–arm system in the three directions were different, but their basic trends were similar to that of the frequency weighting defined in the current ISO standard. The implications of the results are discussed

The Far-Infrared Spectral Energy Distributions of X-ray-selected Active Galaxies

[Abridged] We present ISO far-infrared (IR) observations of 21 hard X-ray selected AGN from the HEAO-1 A2 sample. We compare the far-IR to X-ray spectral energy distributions (SEDs) of this sample with various radio and optically selected AGN samples. The hard-X-ray selected sample shows a wider range of optical/UV shapes extending to redder near-IR colors. The bluer objects are Seyfert 1s, while the redder AGN are mostly intermediate or type 2 Seyferts. This is consistent with a modified unification model in which the amount of obscuring material increases with viewing angle and may be clumpy. Such a scenario, already suggested by differing optical/near-IR spectroscopic and X-ray AGN classifications, allows for different amounts of obscuration of the continuum emission in different wavebands and of the broad emission line region which results in a mixture of behaviors for AGN with similar optical emission line classifications. The resulting limits on the column density of obscuring material through which we are viewing the redder AGN are 100 times lower than for the standard optically thick torus models. The resulting decrease in optical depth of the obscuring material allows the AGN to heat more dust at larger radial distances. We show that an AGN-heated, flared, dusty disk with mass 10^9 solar and size of few hundred pc is able to generate optical-far-IR SEDs which reproduce the wide range of SEDs present in our sample with no need for an additional starburst component to generate the long-wavelength, cooler part of the IR continuum.Comment: 40 pages, 14 figures, accepted for publication in Astrophysical Journal, V. 590, June 10, 200