Allowable Exposure Time Research Articles

Development of a hybrid intelligent switching hydraulically interconnected suspension system under a multi-objective optimized mode selection strategy with real-world condition

Reduction in vertical acceleration is crucial for car manufacturers. This parameter evaluates the comfort index. Moreover, the handling index is another feature that must be under investigation. The suspension system has an essential impact on these two indices. A hybrid intelligent switching hydraulically interconnected suspension (HISHIS) is proposed. The parallel configuration is combined with the diagonal configuration in the suspension system. A mode selection strategy is discussed to select the layout between diagonal and parallel configurations. The only mode of parallel configuration is called Anti-pitch configuration. The diagonal configuration has three modes, including Anti-roll, Anti-oversteering, and Anti-vibration configuration. According to the mode selection strategy, one of these three diagonal configuration modes might be selected. The origin of roll and pitch generation is inertia force and road inputs. Hopfield neural network can recognize the origin of roll and pitch generation. Therefore, the performance of valves will change according to Hopfield neural network recognition. The results of different maneuvers show the improvement at each targeted parameter in various tasks independently. The data logger gathered the acceleration of the vehicle in real-world conditions. However, the margins of the selection strategy block are multi-objective optimized with a genetic algorithm to reach better responses in real-world conditions. The roll angle, yaw rate, allowable exposure time, and pitch angle are improved by 63%, 5%, 40%, and 99% on average. Also, optimizing the selection strategy improves the allowable exposure time by 9%. Obviously, by combining two layouts, it is possible to have a flexible situation to improve ride comfort and handling situations. In addition, there is a conditional strategy to select different layouts and modes to reach a better response.

A machine learning-based forecasting model for personal maximum allowable exposure time under extremely hot environments

A machine learning-based forecasting model for personal maximum allowable exposure time under extremely hot environments

Small globes and pocket heat stress meters for WBGT and PHS evaluations. A critical analysis under controlled conditions

This paper is aimed at quantifying the effects of the well-known criticalities related to the use of small globes in the assessment of extreme hot thermal environments. Based on the experimental measurements carried out through a special apparatus able to reproduce a black enclosure under controlled conditions, the analysis has been focused on both screening (WBGT) and rational (PHS) assessment methods. Obtained results showed the underestimation of the WBGT values within 1 °C using small globes for measuring the WBGT index according to the Standard ISO 7243 and no relevant errors occur also in the presence of high radiative loads. These errors can be even eliminated if specific correction coefficients for the heat transfer by convection are used. On the other hand, pocket WBGT meters based upon small globes and psychrometric (shielded) sensors – instead of the wet wick – are affected by an unacceptable underestimation (by more than 10 °C) of the WBGT that is particularly enhanced at low air velocity and high radiative loads. Finally, the systematic underestimation of the mean radiant temperature measured through small globes can lead the allowable exposure times predicted by the PHS model to be underestimated by more than 5 h when a 38 mm table-tennis ball is used.

Hand-Arm Vibration Controls for Jackleg Rock Drills: A Pilot Study Assessing Ergonomic Hazards.

Jackleg drill operators are exposed to harmful levels of hand-arm vibration (HAV). Anti-vibration handles and gloves provide modest reductions in HAV exposures and forearm muscle exertion from the use of AV handles and gloves by jackleg drill operators. The goal of this pilot study was to investigate changes in HAV with the use of anti-vibration gloves and handles compared to forearm muscle exertion experienced by operators and measured with surface electromyography (EMG). Five subjects operated the drill under four different cases: no anti-vibration controls, anti-vibration gloves only, anti-vibration handle only, and simultaneous anti-vibration handle and glove use. Muscle exertion was expressed as a percent of maximum voluntary contraction (%MVC) and was compared using Welch's ANOVA with Games-Howell post-hoc comparisons. The case with both anti-vibration controls in use simultaneously (largest grip diameter) was associated with a mean %MVC of 36.13% during operation for all forearm muscles combined, which was significantly higher than the other cases (p < 0.05). There were no statistically significant differences in mean HAV exposures. The anti-vibration handle with anti-vibration glove case only increased the maximum allowable exposure time by eight minutes as compared to the control case without any anti-vibration controls. These results suggest that the modest HAV exposure reductions from the use of anti-vibration handles and gloves may pale in comparison to the increased muscle exertion resulting from their use, and this tradeoff among jackleg drill operators is a potential concern that warrants further investigation.

Analysis of Hyperthermia of Children in Enclosed Vehicle

Aiming at the problem of high temperature hazard in children stranded in cars, based on the thermal environment parameters of the enclosed vehicle during outdoor thermal soaking in summer, the predicted heat strain (PHS) model was used, combined with children’s height, weight, clothing and other factors, to simulate the changes in physiological indicators such as core temperature, rectal temperature and water loss, and to scientifically determined the maximum allowable exposure time. It was predicted that the core temperature of human body exceeded 38°C at 72 minutes, and then the body began to heat exhaustion.

The effect of combined resistance muffler on noise pollution and the allowable driver exposure in Massey-Ferguson tractors (MF 285 and MF 299)

Abstract A tractor is the main element of agricultural mechanization. However, the use of tractors has some problems, including noise emissions. The exhaust system in tractors is responsible in addition to the transmission of gases released from combustion into the atmosphere, reducing engine noise. In this study, a combined resistance exhaust system was used to reduce noise emission in two common tractors in Iran (285 and 299 Massey-Ferguson tractors). Noise emission was measured and compared in ordinary and combined resistance exhaust systems. The tests of this study were carried out based on international standards for product noise emissions (ISO 7216 and ISO 5131) taking into account the type of the exhaust system, the position of the microphone, engine speed (rpm) and gear position. The number of tests for each tractor reached 72, which consisted of 24 treatments replicated three times. The data obtained were analyzed in the form of a factorial test which was based on a completely randomized design. The results showed that the effect of the main factors of engine speed, gear position, type of exhaust and microphone position on the noise emitted from the tractors was significant at 1% probability level. In all treatments, the combined resistance exhaust system reduced the sound pressure level and increased allowable driver exposure time compared to the ordinary exhaust system.

The Effects of Clothing Insulation and Acclimation on the Thermal Comfort of Underground Mine Workers

Excessive heat exposure is among the health and safety hazards that have adverse effects on the mine workers. The very nature of the underground climate makes it a convenient avenue for heat generation and accumulation from several heat sources including autocompression, equipment, and heat from strata. This study investigated the effects of clothing insulation and acclimation on the thermal comfort of mine workers who are exposed to heat in underground working environments. Several clothing ensembles have been considered to analyze the effect of the thermal resistance of clothing on the thermal comfort of workers. To investigate the impact of the clothing insulation, the thermal comfort limit of an underground miner was calculated in the form of maximum allowable exposure time for an 8-h shift. Parametric analyses were subsequently performed using an already developed thermal comfort model using MATLAB software. The results demonstrate that clothing insulation has a significant effect on the thermal comfort of mine workers. Increase in the clothing insulation decreases the maximum allowable exposure time of mine workers. This is especially true for the new and non-acclimated workers. Since acclimatized workers can tolerate a higher level of the dehydration and are capable of losing more water by sweat per shift, the maximum allowable exposure time for the acclimated workers are higher than non-acclimated workers. These analyses have shown that acclimated workers can have more continuous work per shift compared with non-acclimated workers. For example, in an environmental condition with clothing that a non-acclimated worker cannot work more than 5 h, an acclimated worker can work a full 8-h shift.

Vibrations analysis of combine harvester seat in time and frequency domain

Agricultural machineries as one of the main inputs in producing agricultural materials are associated with some problems on occupational health such as vibrations. At the lowest level, vibrations cause different diseases such as those affecting blood vessels, nerves, muscles, etc. The aim of this study was to determine and investigate the seat vibrations in John Deere 1055I combine harvester at different conditions. The experiments were carried out based on ISO 2631 and the Iranian standard number 14133. The tests were done at different engine revolutions and gear ratios with three replications. The collected data were analyzed considering factorial experiments based on completely randomized design. The results of variance analysis related to the effect of the main factors on combine seat vibrations showed a significant difference at the probability level of 1%. Effect of engine revolutions on vibration of the combine seat was higher than that of shifting gears. By calculating the allowable exposure time, there was concluded that for the first and second gears at the engine revolution of 1800 rpm and the first gear at the revolution of 2500 rpm, operators can easily drive the combine harvester for eight hours every day without any problems. The results of this study can be used to optimize the components affecting the vibration of the combine seat.

Study on the Allowable Exposure Time of Temporary Goaf in the Open Stope and Backfill Mining Method with Large Structure Parameters

Based on the uniaxial rheological experiment data of iron ore rock mass and filling body in large‐scale stope obtained by using the rock servo controlling creep equipment, the characteristics of the creep curve were analyzed. The creep models of iron ore and filling body which can show the attenuation creep of rock were constructed. And a nonlinear creep model was obtained. According to the rheological data of the iron ore and the filling body, the parameters of the new nonlinear creep model were identified to obtain the material parameters of the creep model. Then, the creep model parameters were fitted and reduced to calculate the reasonable exposure time of temporary goaf in the large‐scale stope. The results show that the reasonable exposure time of stope is 520 ～ 650 days, and the reasonable exposure time of filling body is 410 ～ 520 days. The model can well describe the initial attenuation creep stage and steady creep stage in the creep curve, which proves the correctness and rationality of the model. The study provides a reference for mining design and safety production of similar mines with large‐scale stope structure.

Comprehensive analysis of hazard of ultraviolet radiation emitted during arc welding of cast iron.

ObjectivesUltraviolet radiation (UVR) emitted during arc welding frequently causes keratoconjunctivitis and skin erythema. The extent of the hazard of UVR varies depending on the welding process and conditions. Therefore, it is important to identify the levels of UVR present under different conditions. The purpose of this study was to investigate the degree of hazard of UVR emitted by the different types of arc welding of cast iron frequently used in industry.MethodsIn this study, we experimentally measured the UVR emitted during gas tungsten arc welding (GTAW), shielded metal arc welding (SMAW), and gas metal arc welding (GMAW) of cast iron. The degree of hazard of UVR was quantitatively evaluated in accordance with the guidelines of the American Conference of Governmental Industrial Hygienists.ResultsEffective irradiances measured in this study were in the range 0.045‐2.2 mW/cm2 at a distance of 500 mm from the welding arc. The maximum allowable exposure times corresponding to these levels were only 1.4‐67 s/day.ConclusionsUVR emitted during arc welding of cast iron has the following characteristics: (a) It is more hazardous at higher welding currents. (b) The magnitude of the hazard, which depends on the welding process, increases in the order of GMAW > SMAW > GTAW. (c) It is influenced by the filler material used; that is, the components contained in the filler material affect the hazard of UVR. The effect is Fe > Ni, Cr

Modification of the Predicted Heat Strain (PHS) model in predicting human thermal responses for Chinese workers in hot environments

The Predicted Heat Strain (PHS) model predicts physiological responses of European people to heat stress; while its performance for Chinese population remains underexplored. The study conducted a heat exposure experiment (temperature: 35 °C/38 °C/40 °C, relative humidity (RH): 25%/40%/60%) in a well-controlled climate chamber. 10 male Chinese workers were recruited to perform exercises on the treadmill at a speed of 0.5 m/s for 120min, to simulate moderate metabolic rate. Rectal temperature(Tre), skin temperature(Tsk), sweat rate(SR) and heart rate(HR) were monitored continuously; the corresponding predicted values were obtained by the PHS model. The results showed that the measured Tre, Tsk, SR increased significantly with increased temperature and RH. The PHS model overestimated the maximum allowable exposure time of subjects but underestimated the final Tre and Tsk. Bland–Altman analysis showed that the differences and 95%CI between the observed and predicted values increased with increasing temperature, RH and exposure time, indicating the significant prediction deviation of the PHS model. Through adjusting the initial Tre from 36.8 °C to 37 °C, the protection efficacy was improved from original 24.7% to57.1% for the PHS model. The protection efficacies were further improved to 71.2% through adjusting the maximum HR based on ages, and to 68.2% through adopting the real-time HR to predict metabolic rates. The proposed three methods improve the heat strain prediction in the PHS model for Chinese workers and are more applicable in practical hot working place. This benefits to policy decisions and occupational safety protection for Chinese workers with heat exposure risks.

Analysis of bus users' vibration exposure time

The paper analyzes the effects of vibrations on allowable vibration exposure time in intercity bus users for the criterion of reduced comfort according to the ISO 2631/1985 standard. The analysis was carried out using a validated spatial oscillatory model of 65 degrees of freedom (DOF) built in the ADAMS/View module of the MSC.ADAMS package. Simulation results revealed that passengers on the bus front and rear overhang have very short allowed exposure time. In order to extend the exposure time, by using Design of Experiments (DOE) analysis, new oscillatory parameters for passengers' seats are proposed. With new oscillatory parameters, the exposure time is significantly extended for the assistant driver and passengers on the front and rear bus overhang. For the passenger on the last row seat, power spectral density of weighted vertical acceleration is of lower intensities even at frequencies above 4 Hz.Relevance to industry: Bus users (passengers and drivers) are exposed to harmful effects of vibrations. Vibrations influence comfort, work ability, and if increasingly intense can affect human health. Allowable vibration exposure time referring to oscillatory comfort has a particular importance for intercity bus' passengers when traveling longer distances. Vibration time could be extended by proper selection of seat oscillatory parameters. Results of such an analysis can significantly help bus manufacturers and designers in order to improve ride comfort for bus' passengers.

Evaluation of occupation hot exposure in industrial workplaces in a subtropical country.

The objective of this study has been to evaluate the occupational heat exposure of 12 workers at 5 plants in a subtropical country. The heat stresses and strain on workers in 5 plants were assessed by the International Organization for Standardization (ISO) 7243 index (wet bulb globe temperature - WBGT) and the ISO 7933 index (maximum allowable exposure time - Dlim). Results indicated that 42% of the subjects (5 workers) surpassed the WBGT limits. According to the Dlim, 42% of the subjects could not continue working in the hot environments. The relationships between the various heat stress indices and the WBGT index were also correlated. However, further studies from different heat environments and more subjects should be performed. The sensitive dependence of skin temperature on meteorological and physiological indices for each subject was clearly observed. Obviously, the heart rate response to metabolic rate was much greater than that caused by environmental heat alone. The exponential relationship between workers' duration-limited exposure time, predicted by various estimated criteria, and WBGT were also found. Int J Occup Med Environ Health 2017;30(3):379-395.

Hazard of ultraviolet radiation emitted in gas metal arc welding of mild steel.

Ultraviolet radiation (UVR) emitted during arc welding frequently causes keratoconjunctivitis and erythema in the workplace. The degree of hazard from UVR exposure depends on the welding method and conditions. Therefore, it is important to identify the UVR levels present under various conditions. We experimentally evaluated the UVR levels emitted in gas metal arc welding (GMAW) of mild steel. We used both a pulsed welding current and a non-pulsed welding current. The shielding gases were 80% Ar + 20% CO2 and 100% CO2. The effective irradiance defined in the American Conference of Governmental Industrial Hygienists guidelines was used to quantify the UVR hazard. The effective irradiance measured in this study was in the range of 0.51-12.9 mW/cm2 at a distance of 500 mm from the arc. The maximum allowable exposure times at these levels are only 0.23-5.9 s/day. The following conclusions were made regarding the degree of hazard from UVR exposure during the GMAW of mild steel: (1) It is more hazardous at higher welding currents than at lower welding currents. (2) At higher welding currents, it is more hazardous when 80% Ar + 20% CO2 is used as a shielding gas than when 100% CO2 is used. (3) It is more hazardous for pulsed welding currents than for non-pulsed welding currents. (4) It appears to be very hazardous when metal transfer is the spray type. This study demonstrates that unprotected exposure to UVR emitted by the GMAW of mild steel is quite hazardous.

Interlaboratory Evaluation of Ultraviolet Radiation Emissions from Compact Fluorescent Lamps.

There have been many recent reports regarding the potential risks of UV emissions from compact fluorescent lamps (CFLs). In some of these reports, the robustness of the measurements was difficult to discern. We conducted round-robin measurements, involving three lamp manufacturers and two government research laboratories to gather reliable data on the UV emissions from commercially available CFLs. The initial sample of lamps consisted of 71 spiral-shaped CFLs purchased from local retailers. From the initial sample, 14 "high UV emitting" CFLs were chosen for further evaluation. We compared the UV emissions at a distance of 20cm with the UV exposure limits (ELs) published by the International Commission on Non-ionizing Radiation Protection (ICNIRP). We found that the allowable exposure time for measured lamps ranged from 21 to 415h. This indicates that the emissions would not exceed the short-term ELs that have been established by the ICNIRP for healthy individuals. We also evaluated the potential long-term risk and found it to be insignificant. There was a large variation in the UV emissions found, even for lamps from a single package, indicating that it is impossible to predict the UV output of a CFL based on its physical appearance and model designation.

Hazard of ultraviolet radiation emitted in gas tungsten arc welding of aluminum alloys.

Ultraviolet radiation (UVR) emitted during arc welding frequently causes keratoconjunctivitis and erythema. The extent of the hazard of UVR varies depending on the welding method and conditions. Therefore, it is important to identify the levels of UVR that are present under various conditions. In this study, we experimentally evaluated the hazard of UVR emitted in gas tungsten arc welding (GTAW) of aluminum alloys. The degree of hazard of UVR is measured by the effective irradiance defined in the American Conference of Governmental Industrial Hygienists guidelines. The effective irradiances measured in this study are in the range 0.10–0.91 mW/cm2 at a distance of 500 mm from the welding arc. The maximum allowable exposure times corresponding to these levels are only 3.3–33 s/day. This demonstrates that unprotected exposure to UVR emitted by GTAW of aluminum alloys is quite hazardous in practice. In addition, we found the following properties of the hazard of UVR. (1) It is more hazardous at higher welding currents than at lower welding currents. (2) It is more hazardous when magnesium is included in the welding materials than when it is not. (3) The hazard depends on the direction of emission from the arc.

Simplified methods of using probit analysis in consequence analysis

Ensuring personnel can safely shelter during a chemical release is critical. The probit function is useful in determining maximum safe sheltering time.Probits provide a link between probability of expected response and the exposure of a population to a specific event. Probit analysis can provide an estimate of the percentage of sheltered occupants with potential for adverse response to a chemical release.Probits can be used to estimate duration of exposure for probability of nuisance‐level response, loss of consciousness, or fatal exposures.Dispersion modeling tools provide data on predicted effects in response to long‐term exposure (typically 1 h). However, these tools do not define the maximum allowable exposure time for building occupants before loss of consciousness or fatalities are seen.This article provides methodology for estimating critical exposure duration. This article provides a methodology with existing MS Excel formulas in measuring probits to arrive at probability of response to a toxic release.While data on probit values for some chemicals is readily available, there is minimal guidance in the open literature on developing estimates of probit constants where they do not currently exist or are not published. This article presents a methodology for estimating probit constants based on toxicological data. © 2014 American Institute of Chemical Engineers Process Saf Prog 34: 58–63, 2015

Application of the Predicted Heat Strain Model in Development of Localized, Threshold-based Heat Stress Management Guidelines for the Construction Industry

Existing heat stress risk management guidelines recommended by international standards are not practical for the construction industry which needs site supervision staff to make instant managerial decisions to mitigate heat risks. The ability of the predicted heat strain (PHS) model [ISO 7933 (2004). Ergonomics of the thermal environment analytical determination and interpretation of heat stress using calculation of the predicted heat strain. Geneva: International Standard Organisation] to predict maximum allowable exposure time (D lim) has now enabled development of localized, action-triggering and threshold-based guidelines for implementation by lay frontline staff on construction sites. This article presents a protocol for development of two heat stress management tools by applying the PHS model to its full potential. One of the tools is developed to facilitate managerial decisions on an optimized work-rest regimen for paced work. The other tool is developed to enable workers' self-regulation during self-paced work.

Analysis of vibration effects on the comfort of intercity bus users by oscillatory model with ten degrees of freedom

The paper analyzes the effects of vibrations on the comfort of intercity bus IK-301 users. Evaluation of vibration effects was carried out according to the criteria set out in the 1997 ISO 2631-1 standard for comfort in public means of transport. Comfort is determined for the space of a driver, passenger in the middle part of the bus and passenger in the rear overhang. Also, the allowable exposure time to vibrations in drivers for the reduced comfort criterion was determined according to the 1978 ISO 2631-1 standard. The bus spatial oscillatory model with ten degrees of freedom was developed for the needs of the analysis. Bus excitation was generated applying the Power Spectral Density of the asphalt-concrete road roughness, as described by the H. Braun model. The allowable vibration exposure time for the driver’s body decreases as the spring stiffness of the driver’s seat suspension system increases. Simulation was performed using the MATLAB software.

Ultraviolet Radiation Exposure from UV-Transilluminators

UV-transilluminators use ultraviolet radiation (UVR) to visualize proteins, DNA, RNA, and their precursors in a gel electrophoresis procedure. This study was initiated to evaluate workers' exposure to UVR during their use of UV-transillumin- ators. The levels of irradiance of UV-A, UV-B, and UV-C were determined for 29 UV-transilluminators at arbitrary measuring locations of 6, 25, 62, and 125 cm from the center of the UV-transilluminator's filter surface in the direction of the operator's head. The operators (faculty, research staff, and graduate students) worked within 62 cm of the transilluminators, with most subjects commonly working at ≤25 cm from the UV-transilluminator's filter surface. Daily exposure time ranged from 1 to 60 min. Actinic hazard (effective irradiance level of UVR) was also determined for three representative UV-transilluminators at arbitrary measuring locations of 2.5, 5, 10, 15, 20, 30, 40, and 50 cm from these sets' filter surface in the direction of the operator's head. The allowable exposure time for these instruments was less than 20 sec within 15 cm, less than 35 sec within 25 cm, and less than 2 min within 50 cm from the UV-transilluminators' filter surface. The results of this study suggest that the use of UV-transilluminators exposes operators to levels of UVR in excess of exposure guidelines. It is recommended that special safety training be provided for the affected employees and that exposure should be controlled by one or the combination of automation, substitution, isolation, posted warning signs, shielding, and/or personal protective equipment.