To prepare high molecular weight (HMW) poly(vinyl pivalate) (PVPi) with high yield and high linearity which is a promising precursor for syndiotactic poly (vinyl alcohol) (PVA), vinyl pivalate (VPi) was emulsion polymerized, using 2,2 0 -azobis(2-amidinopropane) dihydrochloride (AAPH) as an initiator and sodium dodecyl sulfate (SDS) as an emulsifier. The effect of the polymerization conditions on the conversion, molecular weight, and degree of branching was investigated. PVA with maximum number-average degree of polymerization (P n ) of 6200 could be prepared by complete saponification of PVPi, with P n of 13,300-16,700 obtained at polymerization tem-perature of 508C, using SDS and AAPH concentration of 2.0 Â 10 À3 mol/L of water and 1.0 Â 10 À3 mol/L of water, respectively, and the maximum conversion was about 90%. From the emulsion polymerization of VPi, spherical PVPi with high yield was effectively prepared, which might be useful for the precursor of syndiotactic PVA micro-and nano-spheres with various surface properties.

This study was conducted to provide field-based harvesting study information which can be used to select an optimal cable system for certain work conditions on steep grounds (>20° ground slope) in Korea. To accomplish this study objectives, we evaluated three cable yarding systems (RME-300T tower-yarder, Chuncheon tower-yarder, FARMI tractor winch) working in typical work conditions for their yarding productivity and operational efficiency. Those yarders are commonly used for removing logs or trees on steep grounds in Korea. Under the same work conditions (average DBH of tree to be cut, 20 cm; yarding distance, 60 m; lateral yarding distance, 10 m; and machine utilization rate, 70%), the average productivities were 33.04 m 3 /day, 38.47 m 3 /day, and 14.17 m 3 /day for RME-300T, Chuncheon tower-yarder, and FARMI, respectively. Our standardized cost comparison study also showed that the yarding cost was highest at 37,835 won/m 3 with FARMI, followed by RME-300T at 25,105 won/m 3 for the same work conditions. We found the lowest yarding cost with the Chuncheon tower-yarder at 20,520 won/m 3 which was resulted primarily from high yarding productivity at the yarding distance (60 m). Our analysis suggested that a small machine such as FARMI could be a low-cost yarding machine option for a cable yarding job with a short yarding distance (40 m or less). The Chuncheon tower-yarder is well suited for a mid-range yarding distance job in Korea, ranged between 40 to 140 m. If yarding distance were longer than 140 m, the RME-300T tower yarder appears to be most cost-effective.

The effects of three major molecular parameters of poly(vinyl alcohol)-the number-average degree of polymerization, degree of saponification, and syndiotactic dyad content-on the characteristics of poly(vinyl alcohol) films were investigated. Various poly(vinyl alcohol) films were prepared by a casting method. Then, the films were characterized with atomic force microscopy, differential scanning calorimetry, wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, and Instron instrumentation. On the basis of atomic force microscopy images and calculated average roughness values, it was determined that the surface roughness of poly(vinyl alcohol) films increased with increasing molecular parameters. The crystallinities obtained with differential scanning calorimetry and wideangle X-ray diffraction analyses were also enhanced with increasing molecular parameters, especially the degree of saponification. The tensile properties were improved with higher molecular parameters. This might be ascribed to the fact that the higher the molecular parameters were, the stronger the hydrogen bonding was.

Logging equipment and method have a major influence on harvesting productivity and cost. This study investigated the productivity and operational costs of tree-length cable yarding system using HAM300, a domestically developed tower yarder. We tested HAM300 for thinning operation in Pinus densiflora stands at Gangreung, Gangwon-do on April, 2014. To assess the productivity we conducted time study for each stage of the operation. When the average time/cycle was examined for each stage of the operation, the longest was for yarding (241 sec), followed by delimbing (237 sec), felling (153 sec), and processing (103 sec). Furthermore, productivity for felling was 8.6 m 3 /hr, followed by delimbing (5.1 m 3 /hr), yarding (3.5 m 3 /hr), and processing (8.1 m 3 /hr). The total cost for the tree-length logging system was 58,446 won/m 3 , of which the majority was incurred by the yarding cost at 46,217 won/m 3 (79.3%), whereas the lowest cost was for felling at 2,359 won/m 3 (4.1%). We suggest that it is necessary to foster specialized operators and provide training in operating the tower yarder thereby implementing efficient harvesting system resulting from low-cost yarding.

No abstract