High repetition rate femtosecond laser heat accumulation and ablation thresholds in cobalt-binder and binderless tungsten carbides

Femtosecond (fs) laser ablation has been studied for the potential of fast, high precision machining of difficult-to-machine materials like binderless tungsten carbide. Obstacles that have limited its efficiency include melting from heat accumulation (HA), particle shielding, and plasma shielding. To address HA without shielding effects, high repetition rate (57.4 MHz), ultra-low fluence fs laser irradiation is performed to study the incubation effect and subsequent HA-ablation threshold of fine-grained tungsten carbides. Exposure times on the order of 100 ms were conducted in air with fluences (1.82 to 9.09 mJ/cm2) two orders of magnitude below the single fs pulse ablation thresholds reported in literature (0.4 J/cm2). Heat accumulation at high repetition rate explains the ultra-low fluence melt threshold behavior resulting in melt crowns around ablated holes and grooves. The results of this study aid in predicting heat buildup in high repetition rate laser irradiation for applications that wish to achieve high ablation rates of difficult-to-machine, ultrahard materials and help enable shaping of binderless tungsten carbide for use in applications too extreme for bindered tungsten carbide

Influence of oxygen pressure on the fs laserinduced oxidation of molybdenum thin films

We present a study of femtosecond (1028 nm, 230 fs, 54.7 MHz) laser processing on molybdenum (Mo) thin films. Irradiations were done under ambient air as well as pure oxygen (O2) at various gauge pressures (4, 8, 12 and 16 psi). Our results indicate that the high heating rates associated with laser processing allow the production of different molybdenum oxides. Raman spectroscopy and scanning electron microscopy are used to characterize the molybdenum oxidation for the different irradiation and oxygen pressures parameters chosen showing a high correlation between well-defined oxidation zones and the oxygen pressure surrounding the samples during the irradiation of the Mo thin films

Monitoring strawberry production to get grip on strawberry quality : GreenCHAINge Fruit & Vegetables WP3

The Greenchainge project is a large project financially supported by the industry and Foundation TKI Horticulture comprising different sub-projects focussing on different fruit and vegetable products. One of the sub-projects (work package 3) is dedicated to strawberry and is carried out with and by Driscoll’s BV, Bakker Barendrecht BV and Wageningen Food and Biobased Research (WFBR). One of the main goals of the soft fruit project is to contribute to the understanding of strawberry quality and as such pave the way towards controlling quality to supply high and constant strawberry quality. Therefore, one of the key research question in this project is which chain parameters affect quality directly. Hence, a large-scale quality monitoring research was set up together with the companies involved in the project. The main goal of this monitoring research was to get insight in the pre and post-harvest parameters that influence the quality of strawberries, meaning the quality at harvest and shelf life

Active Class Incremental Learning for Imbalanced Datasets

Incremental Learning (IL) allows AI systems to adapt to streamed data. Most existing algorithms make two strong hypotheses which reduce the realism of the incremental scenario: (1) new data are assumed to be readily annotated when streamed and (2) tests are run with balanced datasets while most real-life datasets are actually imbalanced. These hypotheses are discarded and the resulting challenges are tackled with a combination of active and imbalanced learning. We introduce sample acquisition functions which tackle imbalance and are compatible with IL constraints. We also consider IL as an imbalanced learning problem instead of the established usage of knowledge distillation against catastrophic forgetting. Here, imbalance effects are reduced during inference through class prediction scaling. Evaluation is done with four visual datasets and compares existing and proposed sample acquisition functions. Results indicate that the proposed contributions have a positive effect and reduce the gap between active and standard IL performance.Comment: Accepted in IPCV workshop from ECCV202

Plasma oxyphytosterols most likely originate from hepatic oxidation and subsequent spill-over in the circulation

We evaluated oxyphytosterol (OPS) concentrations in plasma and various tissues of two genetically modified mouse models with either increased cholesterol (apoE KO mice) or increased cholesterol and plant sterol (PS) concentrations (apoExABCG8 dKO mice). Sixteen female apoE KO and 16 dKO mice followed the same standard, low OPS-chow diet. Animals were euthanized at 36 weeks to measure PS and OPS concentrations in plasma, brain, liver and aortic tissue. Cholesterol and oxysteml (OS) concentrations were analyzed as reference for sterol oxidation in general. Plasma campesterol (24.1 +/- 4.3 vs. 11.8 +/- 3.0 mg/dL) and sitosterol (67.4 +/- 12.7 vs. 4.9 +/- 1.1 mg/dL) concentrations were severely elevated in the dKO compared to the apoE KO mice (p < 0.001). Also, in aortic and brain tissue, PS levels were significantly elevated in dKO. However, plasma, aortic and brain OPS concentrations were comparable or even lower in the dKO mice. In contrast, in liver tissue, both PS and OPS concentrations were severely elevated in the dKO compared to apoE KO mice (sum OPS: 7.4 +/- 1.6 vs. 4.1 +/- 0.8 ng/mg, p < 0.001). OS concentrations followed cholesterol concentrations in plasma and all tissues suggesting ubiquitous oxidation. Despite severely elevated PS concentrations, OPS concentrations were only elevated in liver tissue, suggesting that OPS are primarily formed in the liver and plasma concentrations originate from hepatic spill-over into the circulation