PURPOSES : There has been increasing interest in South Korea on warm-mix asphalt (WMA) and cold-mix asphalt (CMA) technologies that allow production of asphalt pavement mixtures at comparatively lower temperatures than those of hot-mix asphalt (HMA) for use in pavement engineering. This study aims to evaluate the feasibility of replacing HMA pavement with WMA pavement with the goal of reducing CO2 emissions associated with asphalt production for road construction. METHODS : Changes in the dynamic modulus characteristics of WMA and HMA according to short-term and long-term aging were evaluated. In addition, the effects of water damage were evaluated for short- and long-term aging stages. RESULTS : For WMA, in the process of mixing and short-term aging, early-age dynamic modulus decreased owing to low temperature and reduced short-term aging (STA) time. This could result in early damage to the asphalt pavement depending on the applied traffic load and environmental load. CONCLUSIONS : Mastercurves of the dynamic modulus were used for comparative analysis of WMA and HMA. Compared to the dynamic modulus after STA of HMA, the estimated aging time determined by experiments for WMA to achieve the required stiffness was more than 48 hours, which is equiva-lent to approximately 4 to 5 years real service life when converted. It is considered that further studies are needed for performance optimization to achieve early-age performance of the asphalt mixes.

We investigated the mating age for sexual maturity and sperm quality of the bumblebee Bombus terrestris queens and males. In the mating age of sexual maturity of queen, mating rate was 6.7% at just emergence, 85.0% at 10 days of emergence, and decreased thereafter. In case of mating age of sexual maturity of male, mating rate was 38.3% at just emergence and 62.5% to 75.0% at 7 days to 20 days of emergence. The colony development at aging of B. terrestris queen and male was a similar tendency to the mating age of sexual maturity. In case of multiple mating, B. terrestris male was mated by 4 times, which was 74.3% for one time, 50.0% for two times, 22.9% for three times and 8.6% for four times. The number of spermatozoa was increased as the age of male was older until 25days after emergence. The number of spermatozoa of non-mated males of one day and 3 days after emergence was higher at 1.2 and 1.7 times than that of mated males and 18.9 and 36.6 times than that in spermatheca of mated queen. Our results indicate that period favorable for artificial insemination of B. terrestris was from 6 days after emergence for queen and 7 days after emergence for male.

An experiment was carried out to find out the priming effects of rice seeds, Oryza sativa L. (cv. Ilpumbyeo) on. the seedling establishment and early emergence under excess soil moisture conditions. Seeds were primed by soaking in -0.6 MPa polyethylene glycol (PEG) solution at 25~circC for 4 days. The primed seeds were sown in soils with various soil moistures (60, 80, 100, 120, and 140% field capacity) at 17 and 25~circC , respectively. Germination and emergence rates, plumule height, and radicle length of primed seeds were higher than those of untreated seeds at any soil moisture and temperature examined. The time from planting to 50% germination (T50 ) of primed seeds was less than that of untreated seeds by 0.9～3.7 days. Germination rate, emergence rate, plumule height, and radicle length were highest at the soil moisture of 80% field capacity among the soil moistures. Priming effects of rice seeds on germination and emergence rates were more prominent under the unfavorable soil moistures (60, 100, 120, and 140% field capacity) than those under the optimum soil moisture condition (80% field capacity). However, priming effects on seedling growth were greater at near optimum soil moisture compared with too lower or higher soil moistures. Therefore, these findings suggest that priming of rice seeds may be a useful way for better seedling establishment under the adverse soil conditions.