• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.15 no.3
• /
• pp.213-220
• /
• 2005

Penetration and health effect of fibers was related with their diameters and length. The purpose of this study is to characterize and compare the diameter and length of airborne man-made mineral fibers(MMMF) or synthetic vitreous fibers in the related industries. The average fiber length of the continuous filament glass, rock wool, refractory ceramic, and glass wool fibers production industries approximately 27, 28, 35, $50-105{\mu}m$. Airborne glass fibers were longest in all the type of MMMFs. The average diameters of airborne fibers generated from refractory ceramic, rock wool, glass wool, continuous filament glass fibers production industries were approximately 1.0, 1.6, 1.5-4 and $10{\mu}m$, respectively. The percentages of respirable fibers(<$3{\mu}m$) were 94% for RCFs, 73% for rock wool fibers, 61.0% for glass fibers, and 1.6% for filament glass fibers. The length of glass fibers were the longest in all types of fibers, and length of the others were similar. The refractory ceramic fibers were smallest in diameters and highest in fraction of respirable fibers.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.15 no.3
• /
• pp.221-231
• /
• 2005

In this study, occupational exposures to man-made mineral fibers (MMMFs) including glass wool, rock wool, and continuous glass filament fibers were determined and evaluated on the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV). A total of 171 personal samples collected from 4 glass wool fiber, 2 rock wool fibers, 4 continuous filament glass fiber products manufacturing and a glass fiber and rock wool insulations using industries, and determined respirable fibers concentrations using the National Institute for Occupational Safety and Health (NIOSH) Method 7400, "B counting rule. The fiber concentrations of samples from workers installing thermal insulations in a MMMF using industry showed the highest value: geometric mean (GM) = 0.73 f/cc and maximum = 2.9 f/cc, 70% of them were above the TLV, 1 f/cc. Workers' exposure level (GM= 0.032 f/cc) in the rock wool manufacturing industries was significantly higher than those of glass wool (GM=0.012 f/cc) and continuous filament glass fibers (GM=0.010 f/cc) manufacturing industries (p<0.01). No samples were more than the TLV in the MMMF manufacturing industries. There was a significant difference among companies in airborne fiber levels.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.22 no.2
• /
• pp.134-139
• /
• 2012

Objectives: This study was conducted to study the analytical variability of A & B counting rules in counting using a phase contrast microscope airborne fibers collected on filters in man-made mineral or vitreous fibers (MMMFs) industries. Methods: Fibers in filters were counted using A & B rules of NIOSH Method 7400. Intra-counter and inter-counter variations by fiber type and density were obtained. The types of MMMFs analyzed were glass wool fiber, rock wool fiber, slag wool fiber, and refractory ceramic fibers. The densities of fibers classified were <20 $fibers/mm^2,$ 20 - <50 $fibers/mm^2$, 50 - <100 $fibers/mm^2,$ and ${\geq}100$ $fibers/mm^2,$ respectively. Results: Intra-counter relative standard deviations by rule A were 0.084, 0.102, 0.071 for glass wool fibers, rock wool fibers and refractory ceramic fibers, and those by rule B were 0.139, 0.120 and 0.142, respectively. Inter-counter relative standard deviations by rule A were 0.281, 0.296, 0.180 for glass wool fibers, rock wool fibers and refractory ceramic fibers, and those by rule B were 0.396, 0.337 and 0.238, respectively. Conclusions: Intra-counter variation was not different significantly among fiber types (p>0.05), but B rule variation for ceramic fibers approximately 2 times greater than corresponding A rule estimates, and intra-counter and inter-counter variations were higher in the low fiber density.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.9 no.2
• /
• pp.158-166
• /
• 1999

The purpose of this study was to investigate the correlation between airborne total dust and man-made mineral fibers (MMMF), and to estimate total dust concentration to maintain below the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV$^{(R)}$) for the MMMF. The regression coefficients between airborne total dust concentrations and fiber concentrations determined in the industries producing glass fibers, rock wool. refractory ceramic and continuous filament glass fibers products were 0.41, 0.42, 0.20 and 0.19, respectively. The size characteristics of fibers as well as the amounts of contaminated non-fibrous dusts could affect the correlation intensities. When total dust and fiber exposure data were compared with the occupational exposure limits, there was a large gap between two evaluation results. The regression coefficient between total dust and fiber data was increased ($r^2=0.88$) in the process of insulation installation generating in the higher levels of glass or rock wool fibers. In this case, an estimated total dust concentration of glass wool or rock wool fibers complying with the ACGIH TLV (1 f/cc) was $1.7mg/m^3$. In conclusion, the total dust and fibers concentrations was highly correlated at the higher exposure levels so that total dust-monitoring data could be used to control simply and economically and to estimate worker's exposure to fibers.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.16 no.1
• /
• pp.11-16
• /
• 2006

There are many counting rules for analyzing man-made mineral fibers. The representatives are the NIOSH Method 7400 A and B counting rules. The two rules have different rules of length-to-width ratio(aspect ratio) and diameter. The A rule counts only fibers $>5{\mu}m$ in length, and only fibers with aspect ratio >3:1. The B rule counts only ends of fibers $>5{\mu}m$ in length and $<3{\mu}m$ in diameter, and only fibers with aspect ratio ${\geq}5:1$. The A counting rule had been used before the B counting rule was introduced. The purpose of this study is to compare the A and B counting rules for airborne fibers from various man-made mineral fibers(glass wool fibers, rock wool fibers, refractory ceramic fibers, and continuous filament glass fibers) industries. There were significantly differences between the paired counts of A and B rules in all types of fibers(p<0.05). A rule counts/B rule counts(A/B ratios) were 1.52 for glass fibers, 1.53 for rock wool fibers, 1.19 for RCF, and 1.82 for continuous filament glass fibers. The counting results by A and B counting rules were highly correlated in glass wool fibers, rock wool fibers and refractory ceramic fibers(RCF) samples (r=0.96 for all types of fibers) except continuous filament glass fibers(r=0.82). Regression equations to correct for the differences between counting rules were presented in this paper.

• Journal of Food Hygiene and Safety
• /
• v.7 no.4
• /
• pp.165-172
• /
• 1992

Among the nutrients of biological importance, minerals are of particular interest in human nutrition because the range of adequate intake is so narrow. As the results of a series of interaction experiments between dietary fiber sources and minerals, there are many inconsistencies in the experimental data regarding the effect of dietary fibers on mineral bioavailability. the mechanism by which dietary fiber might influence mineral absorption is related to its physicochemical properties. These properties involve the ability of dietary fiber to (1) act as a weak cation exchanger, (2) decrease transit time, (3) dilute mineral concentration by increasing fecal bulk and (4) resist digestion in the large bowel. Regardless of the large number of human and animal studies available, a carful review of these publications dose not provide the answer as to whether the adverse effect of dietary fibers on mineral absorption is the fiber itself or some associated dietary factors( e.g. phytate, oxalate, ascorbate, citrate and protein, mineral-mineral interaction, etc) that are responsible for this action. As a result of the complexity of interaction that may take place between minerals. dietary fiber, and other component of food ; it becomes very difficult to blame fiber alone as a negative factor of mineral nutrition. We absolutely need more research with advanced tools rather than metabolic balance study.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.41 no.5
• /
• pp.33-37
• /
• 2009

Hanji is a traditional Korean handmade paper, made of bast fibers of the paper mulberry. Its fiber furnish is much more expensive than wood fiber furnish. Hanji with a low basis weight requires additional opacity and smoothness for better writing and printing. Filler such as calcium carbonate can not be used to raise the opacity of Hanji because of its low retention in low basis weight paper and the high freeness of the Hanji fiber furnish. Addition of red algae pulp, which is prepared from marine red algae to the Hanji fiber furnish negated retention problems happening in the case of mineral filler addition, and produced a substantial improvement in the opacity and smoothness of Hanji. The higher retention was due to the much larger size of the red algae fibers compared to the mineral fillers. The improvement in opacity and smoothness were also due to the shape of the red algae fibers: that red algae fibers are narrower in widths and shorter in lengths than wood fibers results in increased surface area and smoothness.

• Journal of Environmental Health Sciences
• /
• v.26 no.4
• /
• pp.21-28
• /
• 2000

Various man-made mineral fibers(MMMF) including refractory ceramic fiber(RCF) have been used widely in industries as insulation materials. The effect of fibrous dust on human health depends on fiber size, concentration (exposure level), and durability in biological system. Therefore, these parameters should be determined to evaluate accurately the potential risk of fibers on human health. The purpose of this study was to characterize the size of airborne fiber and the workers＇ exposure to airborne fibers in refractory ceramic fiber manufacturing and processing factories. Airborne fibers were collected on 25-mm mixed cellulose ester membrane filters at personal breathing zones, and analyzed by A and B counting rules of the National Institute for Occupational Safety and Health(NIOSH) Method # 7400. The average ratios of the fiber density by B rule to the fiber density by A rule was 0.84. This result indicates that the proportion of respirable fibers (<3 ${\mu}{\textrm}{m}$ diameter) in air samples was high. The average diameter and length of airborne fibers were 1.05${\mu}{\textrm}{m}$ and 35${\mu}{\textrm}{m}$, respectively. The average fiber concentrations (GM) of all personal samples was 0.26f/cc, and the average concentration was highest at blanket cutting and packing processes. The fifty seven percent of personal air samples was exceeded the proposed American Conference of Governmental Industrial Hygienists(ACGIH) Threshold Limit Value(TLV), i.e. 0.2 f/cc. It was concluded that the RCF industrial workers had the higher potential health risk due to small fiber diameter, long fiber length, and high exposure level to the airborne fibers.

• Journal of Korea Foundry Society
• /
• v.26 no.5
• /
• pp.222-226
• /
• 2006

Steel making slag has gained a considerable attraction as one candidate of eco-materials in research fields for recycling resources. Thus, many researches have been performed but were limited to development of substitute for cement being used in the construction field. A little research work also has been done on development of higher value-added materials, including heat resistant and sound absorbing materials. For this reason, the present study were focused on macrostructure characterization of fabricated slag fibers which are applicable to heat resistant materials. The slag fibers were fabricated through a modified melt extraction method. The processing variables employed were the wheel speed and molten slag temperature. The synthesized fibers were characterized by optical microscope and scanning electron microscopy. It was found that the wheel speed of 1400 rpm generated better quality of mineral fibers in terms of the relative amount of shot, diameter and length. This was attributed to the relative extent of contact width between the flowing melt and the rotating wheel. The thickness of the slag fibers also were decreased with increasing the slag melt temperature due mainly to significant decrease in the viscosity of the slag melt. In addition, the lower melt temperature caused an increase in number of shots plus the mineral fibers.

• Computers and Concrete
• /
• v.18 no.5
• /
• pp.999-1018
• /
• 2016

Enhanced tensile properties of fiber reinforced concrete make it suitable for strengthening of reinforced concrete elements due to their superior corrosion resistance and high tensile strength properties. Recently, the use of fibers as strengthening material has increased motivating the development of numerical tools for the design of this type of intervention technique. This paper presents numerical analysis results carried out on a set of concrete beams reinforced with short fibers. To this purpose, a database of experimental results was collected from an available literature. A reliable and simple three-dimensional Finite Element (FE) model was defined. The linear and nonlinear behavior of all materials was adequately modeled by employing appropriate constitutive laws in the numerical simulations. To simulate the fiber reinforced concrete cracking tensile behavior an approach grounded on the solid basis of micromechanics was used. The results reveal that the developed models can accurately capture the performance and predict the load-carrying capacity of such reinforced concrete members. Furthermore, a parametric study is conducted using the validated models to investigate the effect of fiber material type, fiber volume fraction, and concrete compressive strength on the performance of concrete beams.