title: Dynamic Properties of Magnetorheological Elastomers Based on Iron Sand and Natural Rubber

authors: Shuib, Raa Khimi

subjects: Science & Technology

abstract: In this study, magnetorheological elastomers (MREs) based on iron sand and natural rubber were prepared. The Taguchi method was employed to investigate the effect of a number of factors, namely, the iron sand content, iron sand particle size, and applied magnetic field during curing on the loss tangent (tan δ) and energy dissipated during cyclic loading. Tan δ was measured through dynamic mechanical analysis over a range of frequency (0.01–130 Hz), strain amplitude (0.1–4.5%), and temperature (−100 to 50°C). The energy dissipated was measured with a universal tester under cyclic tensile loading. The data were then statistically analyzed to predict the optimal combination of factors, and finally, experiments were conducted for verification. It was found that the iron sand content had the greatest influence on tan δ when measured over a range of frequency, and the energy dissipated during hysteresis tests. However, none of the factors showed a significant influence on tan δ when measured over a range of strain amplitude. Furthermore, the iron sand content and magnetic field were also found to influence the width of the peak in tan δ as a function of the temperature. The morphological characteristics of the MREs were also examined with scanning electron microscopy.

text: Dynamic Properties of Magnetorheological Elastomers Based on Iron Sand and Natural Rubber In this study, magnetorheological elastomers (MREs) based on iron sand and natural rubber were prepared. The Taguchi method was employed to investigate the effect of a number of factors, namely, the iron sand content, iron sand particle size, and applied magnetic field during curing on the loss tangent (tan δ) and energy dissipated during cyclic loading. Tan δ was measured through dynamic mechanical analysis over a range of frequency (0.01–130 Hz), strain amplitude (0.1–4.5%), and temperature (−100 to 50°C). The energy dissipated was measured with a universal tester under cyclic tensile loading. The data were then statistically analyzed to predict the optimal combination of factors, and finally, experiments were conducted for verification. It was found that the iron sand content had the greatest influence on tan δ when measured over a range of frequency, and the energy dissipated during hysteresis tests. However, none of the factors showed a significant influence on tan δ when measured over a range of strain amplitude. Furthermore, the iron sand content and magnetic field were also found to influence the width of the peak in tan δ as a function of the temperature. The morphological characteristics of the MREs were also examined with scanning electron microscopy.

year: 2015-02-20

title: Factors affecting employer adoption of drug testing in New Zealand

authors: Haar, Jarrod M.

subjects: employee drug testing

abstract: This paper explores employer attitudes towards drug testing in New Zealand to establish under what conditions adoption may be encouraged or discouraged. A survey of 162 New Zealand employers found that adoption rates of drug testing policies were low at 6 per cent. Exploring predictors of the likelihood of drug testing adoption in the next year found that firms that are more compliant to institutional pressures were more likely to seek adoption, as were firms that perceived positive benefits from adoption. Further, firms that perceived negative effects from drug testing, such as union pressures, were less likely to adopt drug testing in the future. Additionally, the moderating effects of organisational size was explored, and significantly affected likely adoption rates, with larger firms being more influenced by institutional pressures and positive effects. However, there was no significant moderation effect towards negative effects of drug testing, which remained strongly negative irrespective of organisational size.

text: Factors affecting employer adoption of drug testing in New Zealand This paper explores employer attitudes towards drug testing in New Zealand to establish under what conditions adoption may be encouraged or discouraged. A survey of 162 New Zealand employers found that adoption rates of drug testing policies were low at 6 per cent. Exploring predictors of the likelihood of drug testing adoption in the next year found that firms that are more compliant to institutional pressures were more likely to seek adoption, as were firms that perceived positive benefits from adoption. Further, firms that perceived negative effects from drug testing, such as union pressures, were less likely to adopt drug testing in the future. Additionally, the moderating effects of organisational size was explored, and significantly affected likely adoption rates, with larger firms being more influenced by institutional pressures and positive effects. However, there was no significant moderation effect towards negative effects of drug testing, which remained strongly negative irrespective of organisational size.

year: 2007

title: The biology and general ecology of the Koaro (Galaxias brevipinnis) in some tributary streams of Lake Taupo

authors: Kusabs, Ian Andrew

abstract: The ecology and general biology of Galaxias brevipinnis were studied in three tributary streams of Lake Taupo between May 1988 and April 1989. Adult koaro were found in relatively high densities in the Waipehi and Omori streams but in low densities in the larger Waiotaka stream. The results of population estimation studies suggest that the distribution and abundance of koaro is negatively correlated with that of trout. There was a general decline in the population density of stream-resident koaro in the winter months. Juvenile koaro were found to migrate into the tributaries from August to December, with migrations being at a peak in October and November.

Population length-frequency distributions and otoliths used to age koaro indicated that there were up to 5 age classes. Growth was allometric and was adequately described by the von Bertalanffy equation after the first year of life. Koaro were found to be in best condition in the Spring and lowest in Winter.

Spawning appeared to occur from December through to April peaking in late Summer to early in the Waipehi Stream was Autumn. The mean fecundity of koaro approximately 5500. A sex-ratio of approximately 1:1 (males: females) were found in the koaro populations in the Omori and Waipehi streams, but during spawning there were always more ripe males than gravid females.

There was considerable overlap in the diets of both koaro and juvenile rainbow trout in the Waipehi and Omori streams, with invertebrates being consumed according to their relative abundance in the benthos. Ephemeroptera larvae were numerically the most important food item in the diet of both species. However, by weight, fish (juvenile koaro) were the most important food · item in the diet of koaro and rainbow trout in the Waipehi stream. In the Omori stream in Winter, trout eggs were the most important food item in terms of weight. Terrestrial prey was found to be of relatively minor importance in the diets of koaro and rainbow trout in the Waipehi and Omori streams.

text: The biology and general ecology of the Koaro (Galaxias brevipinnis) in some tributary streams of Lake Taupo The ecology and general biology of Galaxias brevipinnis were studied in three tributary streams of Lake Taupo between May 1988 and April 1989. Adult koaro were found in relatively high densities in the Waipehi and Omori streams but in low densities in the larger Waiotaka stream. The results of population estimation studies suggest that the distribution and abundance of koaro is negatively correlated with that of trout. There was a general decline in the population density of stream-resident koaro in the winter months. Juvenile koaro were found to migrate into the tributaries from August to December, with migrations being at a peak in October and November.

Population length-frequency distributions and otoliths used to age koaro indicated that there were up to 5 age classes. Growth was allometric and was adequately described by the von Bertalanffy equation after the first year of life. Koaro were found to be in best condition in the Spring and lowest in Winter.

Spawning appeared to occur from December through to April peaking in late Summer to early in the Waipehi Stream was Autumn. The mean fecundity of koaro approximately 5500. A sex-ratio of approximately 1:1 (males: females) were found in the koaro populations in the Omori and Waipehi streams, but during spawning there were always more ripe males than gravid females.

There was considerable overlap in the diets of both koaro and juvenile rainbow trout in the Waipehi and Omori streams, with invertebrates being consumed according to their relative abundance in the benthos. Ephemeroptera larvae were numerically the most important food item in the diet of both species. However, by weight, fish (juvenile koaro) were the most important food · item in the diet of koaro and rainbow trout in the Waipehi stream. In the Omori stream in Winter, trout eggs were the most important food item in terms of weight. Terrestrial prey was found to be of relatively minor importance in the diets of koaro and rainbow trout in the Waipehi and Omori streams.

year: 1989