The investigation of isomeric states in neutron-rich nuclei provides useful insights into the underlying nuclear configurations, and understanding their occurrence along an isotopic chain can inform about shell evolution. Recent studies on neutron-rich Si isotopes near the magic number N = 20 and approaching N = 28 have revealed the presence of low-lying states with intruder configurations, resulting from multiple-particle, multiple-hole excitations across closed shell gaps. The characterization of these states involves measuring their half-lives and transition probabilities. In this study, a new low-energy (7/2−1) isomer at 68 keV in 37Si was accessed via beta decay and characterized. To achieve this, radioactive 37Al and 38Al ions were produced through the projectile fragmentation reaction of a 48Ca beam and implanted into a CeBr3 detector, leading to the population of states in 37Si. The 68-keV isomer was directly populated in the beta-delayed one neutron emission decay of implanted 38Al ions. Ancillary detector arrays comprising HPGe and LaBr3(Ce) detectors were employed for the detection of beta-delayed gamma rays. The choice of detectors was driven by their excellent energy and timing resolutions, respectively. The beta-gamma timing method was utilized to measure the half-life of the new isomeric state in 37Si. This dissertation also discusses other timing techniques employed to search for and characterize isomeric states following beta decay of implanted ions. Notably, the half-life of the newly observed (7/2−1) isomeric state in 37Si was measured to be 9.1(7) ns. The half-life of the previously observed closely-lying (3/2−1) state at 156 keV was determined to be 3.20(4) ns, consistent with previously reported values. Reduced ground-state transition probabilities associated with the gamma-ray decay from these excited states were in agreement with results obtained from shell model calculations. In addition to the investigation of isomeric states in 37Si, isomeric 0+ states in 34Si and 32Mg nuclei belonging to the N = 20 “island of inversion” were characterized and searched for, respectively. The isomeric 0+ state in 34Si was populated following the beta decay of implanted 34Mg ions and its 34Al daughter nucleus. Similarly, the 0+ state in 32Mg was searched for via the beta-delayed one neutron emission decay of implanted 33Na ions.

The ASTM E119 is a large-scale test used to qualify assemblies for fire resistance, including heat transmission and structural integrity. The test requires specialized furnaces and full-scale assemblies that are 3.0 m (10 ft) or more on each side, making it very expensive to perform. In this study, we investigated the feasibility of the scaling methodology for a reduced-scale fire resistance test on different types of wood-based structures, specifically commercially available intumescent coating applied onto wood and bolted lap joints in wood. We build upon a previously developed scaling methodology for wood and gypsum boards, which integrated geometric scaling, Fourier number time scaling, and furnace boundary condition matching. Intumescent coating presents a particular challenge in scaling in that it expands when exposed to fire conditions. To account for this expansion, we identified a relationship between initial dry film thickness and final expanded thickness through cone calorimeter tests and integrated it into a modified scaling methodology. This approach was then validated through fire exposure tests in furnace on wood samples painted with intumescent coating at full, half, and quarter scales. Finally, we demonstrated the scaling laws for joints under combined thermo-structural loading, by subjecting wood-based half-lap joint samples to combined bending and thermal loading at half and quarter scale. The samples were subjected to static three-point bending with the load scaled to achieve structural similitude, while simultaneously being exposed to a scaled fire exposure on the bottom surface. Our study provides insights into the practical application of scaling methodology for testing the fire resistance of joints and fire-resistant coated wood, paving the way for more cost-effective and quicker fire testing for the wood-based composite industry. / Master of Science / The ASTM E119 is a critical test standard that evaluates the fire resistance of various building materials, including wood-based structures. However, the standard tests are quite expensive due to the need for specialized equipment and large-scale samples. In this study, we explored the potential of using a scaled-down fire resistance test on different types of wood-based materials, including commercially available fire-resistant coated wood and joints. We built on existing scaling methods for wood and gypsum boards and adapted it to account for the unique properties of intumescent coating - a fire-resistant material that expands when exposed to high temperatures. By conducting a series of tests, we developed a modified scaling approach to accommodate the expansion of the coating. We then validated this new method by performing fire exposure tests at various scales on wood samples coated with intumescent coating. Finally, we adapted the scaling methods to account for wood based bolted joints. We tested the fire resistance of wood-based half-lap joints under combined heat and structural stress at smaller scales. Our study offers valuable insights into a more cost-effective and efficient method for testing fire resistance in wood-based structures. By providing a reliable scaling approach for fire-resistant coated wood and joints, our work has the potential to make fire testing more accessible for the wood composite industry, ultimately leading to safer and better-performing buildings.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.