Three point bending tests of single edge notched beam (SENB) specimens were carried out to evaluate the fracture behavior of the fine-grain isotropic nuclear grade graphite, IG-11. To measure the crack initiation point and the subsequent crack growth, the direct current potential drop (DCPD) method and a traveling microscope were used. The effects of test variables like initial crack length, specimen thickness, notch type and loading rate on the measured fracture toughness, KQ, were investigated. Based on the test results, the ranges of the test variables to measure the reliable fracture toughness value were proposed. During the crack growth, the rising R-curve behavior was observed in IG-11 graphite when the superficial crack length measured on the specimen surface was used. The increase of crack growth resistance was discussed in terms of crack bridging, crack meandering, crack branching, microcracking and crack deflection, which increase the surface energy and friction force.

Grain size is one of the most important trait determining yield in cereal crops, apart from number of grains per panicle, number of panicles per plant and 1000 seed weight. Other than grain characteristics, plant architecture is another very important factor influencing yield by affecting the amount plant surface area directly exposed to the sun light. Erect panicle is important morphological characteristic which helps in enhancing the yield by allowing sun light to fall directly on leaves unlike curved panicle which blocks sunlight and consequently reduce photosynthesis. A small round grain and erect panicle mutant was obtained by treating Hwacheong rice (japonica) with MNU (N-methyl-N-nitrosourea) chemical mutagen. Through bulked segregant analysis (BSA) using STS (Sequence-Tagged Sites) and SS-STS (Sub-species Specific Sequence-Tagged Site) markers we located the mutated gene on the long arm of chromosome 7 and narrowed down candidate region to 168.75kbp through fine mapping. Mutant manifested characteristics like reduced grain size and plant height, dense and erect panicle and relatively erect plant compared to the wild type. When we crossed the mutant with its parent (Hwacheong), F1 panicle and grain characteristics showed intermediate phenotype, therefore, we concluded that wild type allele of this gene shows incomplete dominance. Scanning electron microscopy(SEM) result shows that increase in width of mutant grain, which changes its shape, is due to increase in width of glume cells. Phenotypic examination shows that dense and erect panicle phenotype is result of reduction in length of rachis, primary and secondary branch.

When GA4 was applied to heading stage, it was examined to understand the change of plant hormones and starch during grain filling and ripening. Exogenous gibberellin caused a dramatic decrease in endogenous ABA content. Endogenous GA4 content in both superior and inferior part was more promoted in GA4-treated rice grain than in the control. GA1 content of an inferior part was not detected in the control and GA4-treated rice otherwise GA4 was detected in all grain parts. Ripened grain rate in GA4-treated rice grain was lower than that of the control plant. Amylopectin from GA4-treated grain contained more very short chains with degree of polymerization (DP) between 4 and 8 than amylopectin from the control plant. It suggests strongly that fine structure of rice endosperm may be changed by exogenously applied GA4 in rice plants.