Predicting Creep in Alloy 617 Pressurized Tubes Using Uniaxial Bar Test Data

Alloy 617, a nickel‑based alloy, is a leading candidate for application in next‑generation nuclear plants (NGNPs). Creep, a thermally activated, time-dependent deformation process impacts the lifetime and failure of heat exchangers used at the very high operating temperatures and pressures of such plants. Current methods of testing creep are generally limited to bar specimens in uniaxial tension. In an attempt to correlate uniaxial to multiaxial creep behavior a method to test creep in a pressurized tube was developed. Test specimens were pressurized with argon up to 3.5 MPa, and heated to 950°C. Creep rates were measured as strain rates by tracking diametric changes with time. Parallel experimental and modeling efforts were used to characterize creep behavior in the pressurized tubes. The aim of this research was to use the existing body of knowledge concerning creep in Alloy 617 to develop a model to accurately predict creep in tubular components. Towards this end, a constitutive model was developed and computer simulations undertaken which were ultimately verified experimentally.Faculty Sponsor: Dr. Rick Ubi

Predicting Creep in an Alloy 617 Pressure Vessel Using Uniaxial Bar Test Data

Alloy 617 is being investigated as a candidate for application in next generation nuclear plants (NGNPs), including the very high temperature reactor (VHTR). Creep deformation concerns the lifetime and failure of heat exchangers used at the very high operating temperatures and pressures of such plants. In order to meet the American Society of Mechanical Engineers’ Boiler and Pressure Vessel code (ASME B&PV), and be certified for use in NGNPs, a thorough understanding of creep must be demonstrated. Current methods of testing creep have limitations and there remains uncertainty and controversy as to the applicability of these tests to more complex designs[1,2]. The aim of this research is to relate data from uniaxial laboratory creep tests to multiaxially loaded service components

Stereocontrolled Total Synthesis of Bastimolide B Using Iterative Homologation of Boronic Esters

[Image: see text] Bastimolide B is a polyhydroxy macrolide isolated from marine cyanobacteria displaying antimalarial activity. It features a dense array of hydroxylated stereogenic centers with 1,5-relationships along a hydrocarbon chain. These 1,5-polyols represent a particularly challenging motif for synthesis, as the remote position of the stereocenters hampers stereocontrol. Herein, we present a strategy for 1,5-polyol stereocontrolled synthesis based on iterative boronic ester homologation with enantiopure magnesium carbenoids. By merging boronic ester homologation and transition-metal-catalyzed alkene hydroboration and diboration, the acyclic backbone of bastimolide B was rapidly assembled from readily available building blocks with full control over the remote stereocenters, enabling the total synthesis to be completed in 16 steps (LLS)

Automated Storm Tracking and the Lightning Jump Algorithm Using GOES-R Geostationary Lightning Mapper (GLM) Proxy Data

This study develops a fully automated lightning jump system encompassing objective storm tracking, Geostationary Lightning Mapper proxy data, and the lightning jump algorithm (LJA), which are important elements in the transition of the LJA concept from a research to an operational based algorithm. Storm cluster tracking is based on a product created from the combination of a radar parameter (vertically integrated liquid, VIL), and lightning information (flash rate density). Evaluations showed that the spatial scale of tracked features or storm clusters had a large impact on the lightning jump system performance, where increasing spatial scale size resulted in decreased dynamic range of the system's performance. This framework will also serve as a means to refine the LJA itself to enhance its operational applicability. Parameters within the system are isolated and the system's performance is evaluated with adjustments to parameter sensitivity. The system's performance is evaluated using the probability of detection (POD) and false alarm ratio (FAR) statistics. Of the algorithm parameters tested, sigma-level (metric of lightning jump strength) and flash rate threshold influenced the system's performance the most. Finally, verification methodologies are investigated. It is discovered that minor changes in verification methodology can dramatically impact the evaluation of the lightning jump system

Effects of environmental impact labels on the sustainability of food purchases: A randomised controlled trial in an experimental online supermarket

Providing consumers with product-specific environmental impact information for food products (ecolabels) may promote more sustainable purchasing, needed to meet global environmental targets. This UK study (N = 1051 participants) investigated the effectiveness of different ecolabels using an experimental online supermarket platform, comparing three labels against control (no label). Significant reductions were found in the environmental impact score (EIS) for all labels compared to control (labels presented: values for four environmental indicators [-3.9 percentiles, 95%CIs: -5.3, -2.6]; a composite score [taking values from A to E; -3.9, 95%CIs: -5.2,-2.5]; or both together [-3.2, 95%CIs: -4.5, -1.9]). Providing ecolabels is a promising intervention to promote the selection of more sustainable products

Spontaneous mutation accumulation in multiple strains of the green alga, Chlamydomonas reinhardtii

Estimates of mutational parameters, such as the average fitness effect of a new mutation and the rate at which new genetic variation for fitness is created by mutation, are important for the understanding of many biological processes. However, the causes of interspecific variation in mutational parameters and the extent to which they vary within species remain largely unknown. We maintained multiple strains of the unicellular eukaryote Chlamydomonas reinhardtii, for approximately 1000 generations under relaxed selection by transferring a single cell every ∼10 generations. Mean fitness of the lines tended to decline with generations of mutation accumulation whereas mutational variance increased. We did not find any evidence for differences among strains in any of the mutational parameters estimated. The overall change in mean fitness per cell division and rate of input of mutational variance per cell division were more similar to values observed in multicellular organisms than to those in other single-celled microbes. However, after taking into account differences in genome size among species, estimates from multicellular organisms and microbes, including our new estimates from C. reinhardtii, become substantially more similar. Thus, we suggest that variation in genome size is an important determinant of interspecific variation in mutational parameters