Thermomechanical Analysis of a Damaged Thermal Protection System.

Research on the effects of damage on the thermomechanical performance and structural integrity of thermal protection systems (TPS) has been limited. The objective of this research is to address this need by conducting experiments and finite element (FE) analysis on damaged TPS. The TPS selected for study is the High-Temperature Reusable Insulation (HRSI) tiles used on NASA's Space Shuttle Orbiter. The TPS consists of a LI-900 tile, the strain isolator pad and the underlying structure, is subjected to the thermal loading and re-entry static pressure of the Access to Space reference vehicle. The damage to the TPS emulates hypervelocity-impact-type damage. Preliminary FE analysis using several simplifying assumptions, was conducted to determine the accuracy of using an approximate axisymmetric model compared to a complete three-dimensional model. Temperature results were found to be reasonable close; however, thermal stress results displayed significant differences. The sensitivity of the FE results to the various simplifying assumptions was also examined and it was concluded that for reliable results, the simplifying assumptions were not acceptable. Subsequently, an exact three-dimensional model was developed and validated by comparison with experimental data. Re-entry static pressures and temperatures were simulated using a high-temperature experimental facility that consists of a quartz radiant heater and a vacuum chamber with appropriate instrumentation. This facility was developed during the course of this dissertation. Temperatures on the top and bottom surfaces of the TPS specimen as well as strains in the underlying structure were recorded for FE model validation. The validated FE model was then combined with improved thermal loads based on the interactions of hypersonic flow past a cavity representing the damage. Damage increases the thermal loads on the TPS and significantly reduces the heat rejection capability of the surface of the tile, resulting in elevated temperatures. The higher temperatures coupled with the stress concentrations introduced by the damage cause a substantial increase in thermal stresses. For the damage sizes considered, the elevated thermal stresses alone are not likely to cause material failure. However, a modest damage size of 0.5" is capable of raising temperatures in the tile to exceed its melting point.Ph.D.Aerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/57597/2/whn_1.pd

Thermomechanical Analysis of a Thermal Protection System with Defects and Heat Shorts

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77124/1/AIAA-2006-2212-827.pd

Investigation of failure mode interaction in laminated composites subjected to compression loading

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90657/1/AIAA-2011-1792-899.pd

Thermomechanical Behavior of Damaged TPS Including Hypersonic Flow Effects

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76198/1/AIAA-2006-7951-158.pd

Computational modeling of failure in composite structures including uncertainties in material and geometrical properties

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90654/1/AIAA-2011-1722-752.pd

Mental awareness improved mild cognitive impairment and modulated gut microbiome

There is ample scientific and clinical evidence of the effects of gut microbiota on the brain but no definitive evidence that the brain can affect changes in gut microbiota under the bi-directional gut-brain axis concept. As there is no pharmacotherapeutic intervention for the early stages of cognitive decline, research has focused on cognitive stimulation in reversing or slowing the impairment. Elderly patients diagnosed with mild cognitive impairment underwent a randomized-control trial of mindful awareness practice. Neuropsychological assessments, inflammatory markers, and gut microbiota profiles were tested. Here, we report that their cognitive impairment was improved and associated with changes in gut bacterial profile. A cognition-score-dependent-abundance was observed in Ruminococcus vs Recognition Trials (RT), Digit Span Backward (DSB), Semantic Fluency Span (SFS) and Memory Domain (MD); Coprococcus vs DSB, Color Trails Test 2 (CTT2) and Block Design (BD); Parabacteroides vs DSB and SFS; Fusobacterium vs DSB and CTT2; Enterobacteriaceae vs BD and SFS; Ruminococcaceae vs DSB; Phascolarctobacterium vs MD. The study showed for the first-time, alteration in the cognitive capacity leading to the corresponding changes in microbiota profiles. This strongly suggests that signals from the different segments of brain could dictate directly or indirectly the abundances of specific gut microbes

Two new species of blackwater catfishes (Siluriformes: Siluridae and Clariidae) from the Natuna Archipelago, Indonesia

Low, Bi Wei, Ng, Heok Hee, Tan, Heok Hui (2022): Two new species of blackwater catfishes (Siluriformes: Siluridae and Clariidae) from the Natuna Archipelago, Indonesia. Raffles Bulletin of Zoology 70: 385-396, DOI: 10.26107/RBZ-2022-002

Fig. 1 in Two new species of blackwater catfishes (Siluriformes: Siluridae and Clariidae) from the Natuna Archipelago, Indonesia

Fig. 1. Lateral views of head region of A) Silurichthys insulanus, new species, MZB 17239 holotype, 41.9 mm SL; B) S. marmoratus, ZRC 40107, 41.7 mm SL, Brunei; C) S. gibbiceps, ZRC 40328 paratype, 47.2 mm SL, Barito (not to scale).Published as part of Low, Bi Wei, Ng, Heok Hee & Tan, Heok Hui, 2022, Two new species of blackwater catfishes (Siluriformes: Siluridae and Clariidae) from the Natuna Archipelago, Indonesia, pp. 385-396 in Raffles Bulletin of Zoology 70 on page 387, DOI: 10.26107/RBZ-2022-0020, http://zenodo.org/record/717485

Fig. 2 in Two new species of blackwater catfishes (Siluriformes: Siluridae and Clariidae) from the Natuna Archipelago, Indonesia

Fig. 2. Lateral view of Silurichthys insulanus, new species, MZB 17239 holotype, 41.9 mm SL (composite of the same fish, top with black background, bottom with white background).Published as part of <i>Low, Bi Wei, Ng, Heok Hee & Tan, Heok Hui, 2022, Two new species of blackwater catfishes (Siluriformes: Siluridae and Clariidae) from the Natuna Archipelago, Indonesia, pp. 385-396 in Raffles Bulletin of Zoology 70</i> on page 388, DOI: 10.26107/RBZ-2022-0020, <a href="http://zenodo.org/record/7174851">http://zenodo.org/record/7174851</a&gt

Mental awareness improved mild cognitive impairment and modulated gut microbiome

10.18632/aging.202277AGING-US122324371-24393complete