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We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD2 taken with Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3), Spitzer Space Telescope/Infrared Array Camera (Spitzer/IRAC), and the GROWTH telescope network, visible spectroscopy from Keck/Low-Resolution Imaging Spectrometer (LRIS), and archival Zwicky Transient Facility observations taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD2 has a radius between 0.2 and 1.8 km assuming a 0.08 albedo and a coma dominated by ∼100 μm-scale dust ejected at ∼1 m s−1 speeds with a ∼1′ jet pointing in the southwest direction. LD2 experienced a total dust mass loss of ∼108 kg at a loss rate of ∼6 kg s−1 with Afρ/cross section varying between ∼85 cm/125 km2 and ∼200 cm/310 km2 from 2019 April 9 to 2019 November 8. If the increase in Afρ/cross section remained constant, it implies LD2's activity began ∼2018 November when within 4.8 au of the Sun, implying the onset of H2O sublimation. We measure CO/CO2 gas production of ≲1027 mol s−1/≲1026 mol s−1 from our 4.5 μm Spitzer observations; g–r = 0.59 ± 0.03, r–i = 0.18 ± 0.05, and i–z = 0.01 ± 0.07 from GROWTH observations; and H2O gas production of ≲80 kg s−1 scaling from our estimated C 2 production of mol s−1 from Keck/LRIS spectroscopy. We determine that the long-term orbit of LD2 is similar to Jupiter-family comets having close encounters with Jupiter within ∼0.5 Hill radius in the last ∼3 y and within 0.8 Hill radius in ∼9 y. Additionally, 78.8% of our orbital clones are ejected from the solar system within 1 × 106 yr, having a dynamical half-life of 3.4 × 105 yr.

a three-dimensional hydrodynamic and mud transport modelling system MIKE 3-FM is used to study the flow circulation and the sediment plume fate in the Randle Reef (RR) area of Hamilton Harbour.It was found that the simulated plume extents can be very sensitive to transport model mesh resolution because of the additional numerical advection induced in the calculations. Detailed discussion of this particular issue has not been observed in other publications.The results of the simulation provide useful information for remediation project managers to plan and guide the environmental monitoring of dredging operations. In addition, the methodology used in this study can be adapted to other dredging projects.

The objective of this paper is to describe a method for selecting optimal engine technology solution sets while simultaneously accounting for the presence of technology risk. This method uses a genetic algorithm in conjunction with Technology Identification, Evaluation, and Selection methods to find optimal combinations of technologies. The unique feature of this method is that the technology evaluation itself is probabilistic in nature. This allows the performance impact and associated risk of each technology to be quantified in terms of a distribution on key engine technology metrics. The resulting method can best be characterized as a concurrent genetic algorithm/Monte Carlo analysis that yields a performance- and risk-optimal technology solution set. This solution set is inherently a robust solution because the method will naturally strive to find those technologies representing the best compromise between performance improvement and technology risk. Finally, a practical demonstration of the method and accompanying results is given for a typical commercial aircraft engine technology selection problem.

The purpose of this study was to investigate the highest bottom shear stress, induced by wind in an area of Hamilton Harbour, Ontario, Canada known as Randle Reef. The study was conducted in support of a component of a contaminated sediment remediation plan utilizing a thin layer of sand to manage contaminated sediments. Toward this end, four acoustic Doppler current profilers (ADCPs) were deployed at two locations in the study region to measure velocity profiles for the purpose of indirectly measuring bottom shear stress (BSS) and model verification. There is no easy way to directly measure BSS in the field. As a result, the use of the logarithmic-profile method from the ADCP measured high resolution velocity profiles in the bottom layer was explored. This approach, according to our best knowledge, has not been published for a wind driven flow in a small open water body. To use the indirectly measured BSS to estimate the highest BSS in the study area, a three-dimensional hydrodynamic model was adopted to provide the spatial and temporal information of the bottom flow. The results showed that the modeled and measured flow velocity components agreed reasonably well at most of the water depths with the correlation coefficients being greater than 0.6. However, agreements between the modeled and measured bottom flow speeds were worse than expected due to the error contributions from both the modeled velocity components. Therefore, the modeled flow speed required rescaling based on ADCP velocity measurements before it could be deemed reliable. This is especially important in estimation of the BSS with a quadratic formula because the calculated BSS is proportional to the square of the speed.Résumé : La présente étude avait pour but d'examiner la contrainte de cisaillement de fond la plus élevée induite par les vents dans un secteur du port d'Hamilton, Ontario, Canada, connu sous le nom du récif Randle. L'étude a été réalisée dans le cadre d'un plan de remise en état de sédiments contaminés utilisant une couche mince de sable pour gérer les sédiments contaminés. Dans ce but, quatre profileur de courant à effet Doppler (ADCP) ont été placés en deux endroits de la région à l'étude dans le but de mesurer les profils de vitesse afin de mesurer indirectement la contrainte de cisaillement de fond (BSS) et vérifier le modèle. Il n'existe aucune méthode facile de mesurer directement la BBS sur le terrain. La méthode du profil logarithmique de l'ADCP pour mesurer des profils de vitesse à haute résolution dans la couche de fond a été examinée. Cette approche, au meilleur de notre connaissance, n'a jamais été publiée pour un courant dû au vent dans un petit plan d'eau libre. Un modèle hydrodynamique tridimensionnel a été adopté pour fournir de l'information spatiale et temporelle sur l'écoulement de fond afin d'utiliser la BSS mesurée indirectement pour évaluer la plus haute BSS dans la région à l'étude. Les résultats montrent que les composantes de vitesse de débit modélisée et mesurée concordent assez bien à la plupart des profo...