Relationship between the Tensile Properties and Damping Capacity of Fe-22%Mn-12%Cr-4%Co-3%Ni-2%Si Alloys by Fatigue Stress

The relationship between the tensile properties and damping capacity of fatigue-damaged Fe-22%Mn-12%Cr-4%Co-3%Ni-2%Si alloy under various magnitudes of fatigue stress was investigated. Analytical results show that α′- and ε-martensite were formed due to fatigue stress. The formed α′- and ε-martensite followed a specific orientation and surface relief and intersected with each other. TEM observation and pattern analysis reveal that both α′- and ε-martensites formed on the austenite. As a result of X-ray diffraction, with an increase in fatigue stress, the volume fractions of α′- and ε-martensite were increased, and the increasing rate of the volume fraction of α′-martensite was higher than that of the ε-martensite. As the fatigue stress increased, the tensile strength and damping capacity increased, but the elongation decreased. Besides, as the strength increased and the elongation decreased, the damping capacity decreased. This result is inconsistent with the general tendency for metals but similar to that of alloys undergoing deformation-induced martensite transformation.

Dropped Object Impact Analysis Considering Frequency and Consequence for LNG-FPSO Topside Module

Recently, quantitative risk assessment (QRA) has been widely used as a decision-making tool in the offshore industry. This study focused on analyzing dropped objects in the design of a modern offshore platform. A modified QRA procedure was developed for assessing production module protection against accidental external loads. Frequency and consequence analyses were performed using the developed QRA procedure. An exceedance curve was plotted, and a high-risk management item was derived through this process. In particular, simulations and experiments were used to verify the difference between the potential and impact energies according to drop orientation. When the object dropped in a specific orientation, the impact energy was confirmed to be up to 4.7 times greater than the potential energy. To reflect the QRA results in structural design, the proposed procedure should be used to calculate the maximum impact energy. The proposed procedure provides a step-by-step guide to assess the damage capacity of a production area as well as the damage frequency and consequences.

Gaps of saddle connection directions for some branched covers of tori

We compute the gap distribution of directions of saddle connections for two classes of translation surfaces. One class will be the translation surfaces arising from gluing two identical tori along a slit. These yield the first explicit computations of gap distributions for non-lattice translation surfaces. We show that this distribution has support at zero and quadratic tail decay. We also construct examples of translation surfaces in any genus $d>1$ that have the same gap distribution as the gap distribution of two identical tori glued along a slit. The second class we consider are twice-marked tori and saddle connections between distinct marked points with a specific orientation. These results can be interpreted as the gap distribution of slopes of affine lattices. We obtain our results by translating the question of gap distributions to a dynamical question of return times to a transversal under the horocycle flow on an appropriate moduli space.

Adaptation of Drosophila larva foraging in response to changes in food distribution

When foraging, animals combine internal cues and sensory input from their environment to guide sequences of behavioral actions. Drosophila larva executes crawls, turns, and pauses to explore the substrate and find food sources. This exploration has to be flexible in the face of changes in the quality of food so that larvae feed in patches with favorable food and look for another source when the current location does not fulfill their nutritional needs. But which behavioral elements adapt, and what triggers those changes remain elusive. Using experiments and modeling, we investigate the foraging behavior of larvae in homogeneous environments with different food types and in environments where the food sources are patchy. Our work indicates that the speed of larval crawling and frequency of pauses is modulated by the food quality. Interestingly, we found that the genetic dimorphism in the foraging gene influences the exploratory behavior only when larvae crawl on yeast patches. While in a homogeneous substrate larvae maintain a turning bias in a specific orientation, in a patchy substrate larvae orient themselves towards the food when the patch border is reached. Therefore, by adapting different elements in their foraging behavior, larvae either increase the time inside nutritious food patches or continue exploring the substrate in less nutritious environments.

Distinct REV-ERBα Conformational State Predicted by GaMD Simulations Leads to the Structure-Based Discovery of Novel REV-ERBα Antagonist

REV-ERBα is a nuclear hormone receptor that plays important role in the regulation of many physiological processes such as circadian clock regulation, inflammation, and metabolism. Despite its importance, few chemical tools are available to study this receptor. In addition, there is no available X-ray crystal structures of REV-ERB bound with synthetic ligands, hampering the development of targeted therapeutics. SR8278 is the only identified synthetic antagonist of REV-ERB. We have performed Gaussian accelerated molecular dynamics (GaMD) simulations to sample the binding pathway of SR8278 and associated conformational changes to REV-ERBα. The simulations revealed a novel and more energetically favorable conformational state than the starting conformation. The new conformation allows ligand binding to the orthosteric binding site in a specific orientation. This state is reached after a tryptophan (Trp436) rotameric switch coupled with H3-H6 distance change. We used the newly identified GaMD conformational state in structure-based virtual screening of one million compounds library which led to the identification of novel REV-ERBα antagonist. This study is the first that demonstrates a synthetic ligand binding pathway to REV-ERBα, which provided important insights into the REV-ERBα functional mechanism and lead to the discovery of novel REV-ERBα antagonists. This study further emphasizes the power of computational chemistry methods in advancing drug discovery research.

Cubesat attitude determination

When satellites are placed in orbit, often times a specific orientation is required to achieve mission purposes. Different factors (such as atmospheric drag, magnetic fields, solar winds) or tumbling upon deployment from the launch vehicle, may result in an undesirable satellite orientation. To address these challenges, the ability to control the orientation, termed as attitude determination, becomes critical to any mission. This thesis will focus on developing an earth-pointing and sun-pointing mode in order to meet the objectives of the ESSENCE CubeSat. The earth-pointing mode orients the vehicle to point towards a desired target on the earth surface, and the sun-pointing mode orients the vehicle such that the maximum solar array surface area is exposed to the sun when the vehicle is out of eclipse.

Cubesat attitude determination

When satellites are placed in orbit, often times a specific orientation is required to achieve mission purposes. Different factors (such as atmospheric drag, magnetic fields, solar winds) or tumbling upon deployment from the launch vehicle, may result in an undesirable satellite orientation. To address these challenges, the ability to control the orientation, termed as attitude determination, becomes critical to any mission. This thesis will focus on developing an earth-pointing and sun-pointing mode in order to meet the objectives of the ESSENCE CubeSat. The earth-pointing mode orients the vehicle to point towards a desired target on the earth surface, and the sun-pointing mode orients the vehicle such that the maximum solar array surface area is exposed to the sun when the vehicle is out of eclipse.

Widening Inborn Constraints for Language Ability: The Case for Autism

What does the way autistics bypass, learn, and eventually master language tell us about human linguistic ability? Here, we argue that non-social acquisition of language, in addition to representing a strong argument for nativist models of human language, may be encompassed within the human-specific orientation and mastery of complex embedded structures, of which language represents one realization. Non-social language learning could thus represent the extension of available linguistic, and non-linguistic material processed by human genetic constraints, allowing language acquisition. This deviation from typical developmental language acquisition may ultimately allow access to language, sometimes in its most elaborate forms, and also explains the possibility of the absence of its development when applied to primarily non-linguistic structured material. However, such enlargement of material-specificity does not cast doubts about its human nature. Regardless of the adaptive success or failure of non-social language learning, it is up to science, legal policies, and ethical principles to strive to maintain autism as a human potentiality to further foster our vision of a plural society.

The Shadows of the Past and the Work of the Future: Frederick Douglass's Temporal Theory of Democracy

Throughout his career, Frederick Douglass linked the achievement of an egalitarian, multiracial democracy to Americans’ perception of their collective past and future. In so doing, I argue, Douglass developed a distinctive, temporal account of democratic peoplehood. For Douglass, temporal continuity lent force and content to demands for equality—demands which would succeed only if the whole demos cultivated a specific orientation to its collective past, present, and future. Douglass offers a productive contrast to contemporary democratic theory, which often misses the importance of temporality suggested by his account and thereby risks surrendering its powerful egalitarian resources. Moreover, temporality provides a new lens on what many interpreters see as an episode of inconsistency in Douglass's thought: his brief, quickly abandoned contemplation of colonization proposals in the spring of 1861. Ultimately, Douglass turned to temporality in order to decide whether democracy for African Americans required affiliation with, or disaffiliation from, the United States.