Impact of Boundary Conditions on Entrainment and Transport in Gravity Currents

Gravity currents have been studied numerically and experimentally both in the laboratory and in the ocean. The question of appropriate boundary conditions is still challenging for most complex flows. Gravity currents make no exception - appropriate, physically and mathematically sound boundary conditions are yet to be found. This task is further complicated by the technical limitations imposed by the current oceanographic techniques. In this paper, we make a first step toward a better understanding of the impact of boundary conditions on gravity currents. Specifically, we use direct numerical simulations to investigate the effect that the popular Neumann, and less popular Dirichlet boundary conditions on the bottom continental shelf have on the entrainment and transport of gravity currents. The finding is that gravity currents under these two different boundary conditions differ most in the way they transport heat from the top towards the bottom. This major difference occurs at medium temperature ranges. Entrainment and transport at high temperatures also show significant differences

Chaotic advection in a steady, three-dimensional, Ekman-driven eddy

Author Posting. © Cambridge University Press, 2013. This article is posted here by permission of Cambridge University Press for personal use, not for redistribution. The definitive version was published in Journal of Fluid Mechanics 738 (2014): 143-183, doi:10.1017/jfm.2013.583.We investigate and quantify stirring due to chaotic advection within a steady, three-dimensional, Ekman-driven, rotating cylinder flow. The flow field has vertical overturning and horizontal swirling motion, and is an idealization of motion observed in some ocean eddies. The flow is characterized by strong background rotation, and we explore variations in Ekman and Rossby numbers, E and Ro, over ranges appropriate for the ocean mesoscale and submesoscale. A high-resolution spectral element model is used in conjunction with linear analytical theory, weakly nonlinear resonance analysis and a kinematic model in order to map out the barriers, manifolds, resonance layers and other objects that provide a template for chaotic stirring. As expected, chaos arises when a radially symmetric background state is perturbed by a symmetry-breaking disturbance. In the background state, each trajectory lives on a torus and some of the latter survive the perturbation and act as barriers to chaotic transport, a result consistent with an extension of the KAM theorem for three-dimensional, volume-preserving flow. For shallow eddies, where E is O(1), the flow is dominated by thin resonant layers sandwiched between KAM-type barriers, and the stirring rate is weak. On the other hand, eddies with moderately small E experience thicker resonant layers, wider-spread chaos and much more rapid stirring. This trend reverses for sufficiently small E, corresponding to deep eddies, where the vertical rigidity imposed by strong rotation limits the stirring. The bulk stirring rate, estimated from a passive tracer release, confirms the non-monotonic variation in stirring rate with E. This result is shown to be consistent with linear Ekman layer theory in conjunction with a resonant width calculation and the Taylor–Proudman theorem. The theory is able to roughly predict the value of E at which stirring is maximum. For large disturbances, the stirring rate becomes monotonic over the range of Ekman numbers explored. We also explore variation in the eddy aspect ratio.L.J.P., I.I.R., T.M.O. and P.W. have been supported on DOD (MURI) grant N000141110087, administered by the Office of Naval Research. I.I.R. and L.J.P. received additional support from Grant NSF-OCE-0725796 from the National Science Foundation.2014-12-0

Submesoscale dispersion in the vicinity of the Deepwater Horizon spill

Reliable forecasts for the dispersion of oceanic contamination are important for coastal ecosystems, society and the economy as evidenced by the Deepwater Horizon oil spill in the Gulf of Mexico in 2010 and the Fukushima nuclear plant incident in the Pacific Ocean in 2011. Accurate prediction of pollutant pathways and concentrations at the ocean surface requires understanding ocean dynamics over a broad range of spatial scales. Fundamental questions concerning the structure of the velocity field at the submesoscales (100 meters to tens of kilometers, hours to days) remain unresolved due to a lack of synoptic measurements at these scales. \textcolor{black} {Using high-frequency position data provided by the near-simultaneous release of hundreds of accurately tracked surface drifters, we study the structure of submesoscale surface velocity fluctuations in the Northern Gulf Mexico. Observed two-point statistics confirm the accuracy of classic turbulence scaling laws at 200m$-$50km scales and clearly indicate that dispersion at the submesoscales is \textit{local}, driven predominantly by energetic submesoscale fluctuations.} The results demonstrate the feasibility and utility of deploying large clusters of drifting instruments to provide synoptic observations of spatial variability of the ocean surface velocity field. Our findings allow quantification of the submesoscale-driven dispersion missing in current operational circulation models and satellite altimeter-derived velocity fields.Comment: 9 pages, 6 figure

Algorithmic progress in computer vision

We investigate algorithmic progress in image classification on ImageNet, perhaps the most well-known test bed for computer vision. We estimate a model, informed by work on neural scaling laws, and infer a decomposition of progress into the scaling of compute, data, and algorithms. Using Shapley values to attribute performance improvements, we find that algorithmic improvements have been roughly as important as the scaling of compute for progress computer vision. Our estimates indicate that algorithmic innovations mostly take the form of compute-augmenting algorithmic advances (which enable researchers to get better performance from less compute), not data-augmenting algorithmic advances. We find that compute-augmenting algorithmic advances are made at a pace more than twice as fast as the rate usually associated with Moore's law. In particular, we estimate that compute-augmenting innovations halve compute requirements every nine months (95\% confidence interval: 4 to 25 months)

A Standard Method Verification for Determination of Sugar Content of Commercial Fruit Juices by HPLC

This study aimed to verify the standard test method TS EN 12630 and determine the sugar contents of commercially available fruit juices by high pressure liquid chromatography. A laboratory should verify the standard test method parameters in order to show its performance for the analysis, under consideration. For this purpose, Sucrose, Glucose and Fructose were analysed in orange juices obtained from the market. The principle of the method is based on the separation of sugars on a cation-exchange resin by isocratic elution with mobile phase, detection using a differential refractive index (RI) detector and external standard method. Accuracy and precision were performed via intraday and inter day studies to determine of accuracy and the precision (generally accepted as repeatability and reproducibility) for the standard test method. The recovery values of the sugars added into juice sample were found 92%, 99% and 96% for sucrose, glucose and fructose, respectively

The learnability level of rhythm named “zencîr usûlü” with Dalcroze teaching method in Turkish music rhythm education : Türk mûsıkîsi usûl eğitiminde Dalcroze öğretim yöntemi ile zencîr usûlünün öğrenilebilirlik düzeyi

In this study, by using the Dalcroze teaching method in the education of special talented students, practices focused on the perception of the Turkish musical “zencîr usûlü” with the support of the musical element and the determination of the level of learnability. However, with the applied curriculum, it is aimed to develop rhythmic perception and musical sensitivity by using interdisciplinary method technique and Dalcroze teaching method technique. The subject study group of the study was formed from the students of the music department studying in Akhisar Science and Art Center affiliated to the Ministry of National Education. In this study; A curriculum suitable for students' levels was prepared by foreseeing that gifted students grasped and progressed in a process three times faster than their peers, and that many activities would be easier for them than their peers. Based on the saying "Body movement with music is one, it cannot be separated" mentioned in Ancient Greece, the evaluation of the teaching technique we envisioned with the Turkish musical procedural technique, the pre-test post-test experimental design with control group Handled using. In order to determine whether there is a significant difference between test results, Mann - Whitney U Test, and "SPSS 20" package program was used for pre-test and post-test results. In order to determine the reliability of the study, an expert opinion form regarding the rubric and rubric was used at the pre-test and post-test stages. In the control group, the lessons were taught with the traditional teaching system, while in the experimental group, the teaching model was handled. According to the findings obtained in the study, it was determined that the experimental group in which the teaching model based strategies were applied was more successful than the control group in which the traditional method technique was used.   Özet Bu çalışmada, özel yetenekli öğrenci eğitiminde Dalcroze öğretim yöntemi kullanılarak, Türk mûsıkîsi zencîr usûlünün müzik unsuru ile desteklenerek algılanması ve öğrenilebilirlik düzeyinin tespiti üzerinde yoğunlaşılan uygulamalar yapılmıştır. Bununla birlikte, uygulanan öğretim programıyla disiplinlerarası yöntem tekniği ve Dalcroze öğretim yöntem tekniği kullanılarak ritmik algı ve müzikal duyarlılığın geliştirilmesi amaçlanmıştır. Araştırmanın denek çalışma grubu, Milli Eğitim Bakanlığına bağlı Akhisar Bilim ve Sanat Merkezinde öğrenim gören müzik bölümü öğrencilerinden oluşturulmuştur. Bu araştırmada; özel yetenekli öğrencilerin, yaşıtlarına göre normalden üç kat daha hızlı bir süreçte konuyu kavradıkları ve ilerledikleri, yaşıtlarına göre pek çok etkinliğin onlara daha kolay gelebileceği ön görülerek öğrencilerin seviyelerine uygun bir öğretim programı hazırlanmıştır. Antik Yunan’da zikredilen “Müzikle beden hareketi birdir, ayrılamaz” sözünden yola çıkarak, Türk mûsıkîsi usûl icra tekniği (meşk sistemi) ile öngördüğümüz öğretim tekniğinin değerlendirmesi, söz konusu tekniğin, bedensel hareket ve koordinasyon eşliğinde uygulandığı ön test son test kontrol gruplu deneysel desen kullanılarak ele alınmıştır. Test sonuçları arasında anlamlı bir fark olup olmadığını belirlemek amacı ile Mann - Whitney U Testi, ön test ve son test sonuçlarında ise “SPSS 20” paket programı kullanılmıştır. Çalışmanın güvenirliğinin tespiti için de, ön test - son test aşamalarında dereceli puanlama anahtarı ve dereceli puanlama anahtarına ilişkin uzman görüşü alma formu kullanılmıştır. Kontrol gurubunda dersler geleneksel öğretim sistemiyle işlenirken, deney grubunda ise öğretim modeli ele alınarak işlenmiştir. Araştırmada elde edilen bulgulara göre, geleneksel yöntem tekniğinin kullanıldığı kontrol grubuna nazaran öğretim modeline dayalı stratejilerin uygulandığı deney grubunun daha başarılı olduğu saptanmıştır

Who is leading in AI? An analysis of industry AI research

AI research is increasingly industry-driven, making it crucial to understand company contributions to this field. We compare leading AI companies by research publications, citations, size of training runs, and contributions to algorithmic innovations. Our analysis reveals the substantial role played by Google, OpenAI and Meta. We find that these three companies have been responsible for some of the largest training runs, developed a large fraction of the algorithmic innovations that underpin large language models, and led in various metrics of citation impact. In contrast, leading Chinese companies such as Tencent and Baidu had a lower impact on many of these metrics compared to US counterparts. We observe many industry labs are pursuing large training runs, and that training runs from relative newcomers -- such as OpenAI and Anthropic -- have matched or surpassed those of long-standing incumbents such as Google. The data reveals a diverse ecosystem of companies steering AI progress, though US labs such as Google, OpenAI and Meta lead across critical metrics

Over what area did the oil and gas spread during the 2010 Deepwater Horizon oil spill?

Author Posting. © The Oceanography Society, 2016. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 29, no. 3 (2016): 96–107, doi:10.5670/oceanog.2016.74.The 2010 Deepwater Horizon (DWH) oil spill in the Gulf of Mexico resulted in the collection of a vast amount of situ and remotely sensed data that can be used to determine the spatiotemporal extent of the oil spill and test advances in oil spill models, verifying their utility for future operational use. This article summarizes observations of hydrocarbon dispersion collected at the surface and at depth and our current understanding of the factors that affect the dispersion, as well as our improved ability to model and predict oil and gas transport. As a direct result of studying the area where oil and gas spread during the DWH oil spill, our forecasting capabilities have been greatly enhanced. State-of-the-art oil spill models now include the ability to simulate the rise of a buoyant plume of oil from sources at the seabed to the surface. A number of efforts have focused on improving our understanding of the influences of the near-surface oceanic layer and the atmospheric boundary layer on oil spill dispersion, including the effects of waves. In the future, oil spill modeling routines will likely be included in Earth system modeling environments, which will link physical models (hydrodynamic, surface wave, and atmospheric) with marine sediment and biogeochemical components.This research was made possible by a grant from BP/The Gulf of Mexico Research Initiative to the CARTHE and Deep-C Consortia, and by contract M12PC00003 from the Bureau of Ocean Energy Management (BOEM)