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2007

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Articles 6121 - 6150 of 6787

Full-Text Articles in Physical Sciences and Mathematics

Acoustic Measurement And Modeling Of Waves In Estuarine And Coastal Environments, Justin P. Vandever Jan 2007

Acoustic Measurement And Modeling Of Waves In Estuarine And Coastal Environments, Justin P. Vandever

Dissertations, Theses, and Masters Projects

No abstract provided.

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Eddy Correlation Measurements Of The Air/Sea Flux Of Dimethylsulfide Over The North Pacific Ocean, Christa A. Marandino, Warren J. De Bruyn, Scott D. Miller, Eric S. Saltzman Jan 2007

Eddy Correlation Measurements Of The Air/Sea Flux Of Dimethylsulfide Over The North Pacific Ocean, Christa A. Marandino, Warren J. De Bruyn, Scott D. Miller, Eric S. Saltzman

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Shipboard measurements of air/sea fluxes and sea surface concentrations of dimethylsulfide (DMS) were made over the tropical and midlatitude North Pacific Ocean. Atmospheric pressure chemical ionization mass spectrometry was used to measure DMS levels in ambient air and in air equilibrated with surface seawater drawn from a depth of 5 m. Air/sea fluxes were obtained using eddy covariance. Corrections and uncertainties involved in the calculation of fluxes from shipboard data are discussed. The surface ocean DMS concentrations measured during this study ranged from 1 to 10 nM, and atmospheric mixing ratios ranged from 20 to 1000 ppt. Air/sea fluxes ranged …

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Measurement Of The Branching Fraction For The Decay Neutral Kaon(Long) Going To Pion-Antipion-Positron-Electron In The High M(Pi-Pi) Invariant Mass Region, Joshua J. Moss Jan 2007

Measurement Of The Branching Fraction For The Decay Neutral Kaon(Long) Going To Pion-Antipion-Positron-Electron In The High M(Pi-Pi) Invariant Mass Region, Joshua J. Moss

Dissertations, Theses, and Masters Projects

A measurement of the branching fraction for the rare decay K0L → pi+pi-e +e- was performed using data collected from experiment E871 which ran at the AGS of Brookhaven National Laboratory. Analysis of the data revealed 27.7 +/- 7.4 signal events in the signal region, 0.4905 GeV < Mpipiee < 0.505 GeV together with 13.3 +/- 3.7 background events. The branching fractions of ( 8.5+/-2.3stat +/-1.0sys ) x 10-6 using the phenomenological model acceptance and ( 2.3+/-0.6stat +/-0.3sys ) x 10-6 using the chiral perturbation model represent the first measurements for K0L → pi+pi-e +e- in the dipion invariant mass region 0.475 GeV < Mpipi < 0.497 GeV. These results support the prediction of chiral perturbation theory rather than that of the phenomenological model.

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Decoupling Method For Parallel Delaunay Two-Dimensional Mesh Generation, Leonidas Linardakis Jan 2007

Decoupling Method For Parallel Delaunay Two-Dimensional Mesh Generation, Leonidas Linardakis

Dissertations, Theses, and Masters Projects

Parallel mesh generation procedures that are based on geometric domain decompositions require the permanent separators to be of good quality (in terms of their angles and length), in order to maintain the mesh quality. The Medial Axis Domain Decomposition, an innovative geometric domain decomposition procedure that addresses this problem, is introduced. The Medial Axis domain decomposition is of high quality in terms of the formed angles, and provides separators of small size, and also good work-load balance. It presents for the first time a decomposition method suitable for parallel meshing procedures that are based on geometric domain decompositions.;The Decoupling Method …

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Why De Minimis?, Matthew D. Adler Jan 2007

Why De Minimis?, Matthew D. Adler

Faculty Scholarship

De minimis cutoffs are a familiar feature of risk regulation. This includes the quantitative individual risk thresholds for fatality risks employed in many contexts by EPA, FDA, and other agencies, such as the 1-in-1 million lifetime cancer risk cutoff; extreme event cutoffs for addressing natural hazards, such as the 100 - year - flood or 475 - year - earthquake; de minimis failure probabilities for built structures; the exclusion of low - probability causal models; and other policymaking criteria. All these tests have a common structure, as I show in the Article. A de minimis test, broadly defined, tells the …

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A Review Of Studies In Swarm Robotics, Levent Bayindir, Erol Şahi̇n Jan 2007

A Review Of Studies In Swarm Robotics, Levent Bayindir, Erol Şahi̇n

Turkish Journal of Electrical Engineering and Computer Sciences

Swarm robotics is a new approach to the coordination of large numbers of relatively simple robots. The approach takes its inspiration from the system-level functioning of social insects which demonstrate three desired characteristics for multi-robot systems: robustness, flexibility and scalability. In this paper we have presented a preliminary taxonomy for swarm robotics and classified existing studies into this taxonomy after investigating the existing surveys related to swarm robotics literature. Our parent taxonomic units are modeling, behavior design, communication, analytical studies and problems. We are classifying existing studies into these main axes. Since existing reviews do not have enough number of …

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Using Angle Of Arrival (Bearing) Information For Localization In Robot Networks, Tolga Eren Jan 2007

Using Angle Of Arrival (Bearing) Information For Localization In Robot Networks, Tolga Eren

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper, we consider using angle of arrival information (bearing) for localization in robot networks. The essential property we require in this paper is that a node can infer heading information from its neighbors. We address the uniqueness of network localization solutions by the theory of globally rigid graphs. We show that while the parallel rigidity problem for formations with bearings is isomorphic to the distance case, the global rigidity of the formation is simpler (in fact identical to the simpler rigidity case) for a network with bearings, compared to formations with distances. We provide the conditions of localization …

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A Vrp-Based Route Planning For A Mobile Robot Group, Osman Parlaktuna, Aydin Si̇pahi̇oğlu, Ahmet Yazici Jan 2007

A Vrp-Based Route Planning For A Mobile Robot Group, Osman Parlaktuna, Aydin Si̇pahi̇oğlu, Ahmet Yazici

Turkish Journal of Electrical Engineering and Computer Sciences

In this study, a vehicle routing problem-based approach is presented to construct non-intersecting routes for the members of a mobile robot team. It is assumed that each robot starts from a central location such as the charging point, completes its route and returns to the starting location. The proposed method consists of three algorithms: a sweep algorithm determines the position of each node in clockwise (or counter clockwise) manner with respect to the starting location; savings algorithm calculates the saving obtained by adding a node to the route of a robot; Dijkstra's shortest path algorithm is used to calculate the …

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Design And Implementation Of An Ad-Hoc Routing Protocol For Mobile Robots, Carlos Agüero, Jose M. Canas, Miguel Ortu˜No, Vicente Matellan Jan 2007

Design And Implementation Of An Ad-Hoc Routing Protocol For Mobile Robots, Carlos Agüero, Jose M. Canas, Miguel Ortu˜No, Vicente Matellan

Turkish Journal of Electrical Engineering and Computer Sciences

Mobile robots need to be able to communicate among themselves, as well as with hosts participating in the task that they are all involved in. Wired networks are obviously not suitable for mobile robots. Current wireless networks based on a fixed infrastructure (GSM, WiFi, etc.) to route packets may not be suitable because this infrastructure does not cover every place and the requirements of its resources. The best choice for mobile robots are Ad-Hoc networks, which are wireless and do not need a fixed infrastructure. This article describes PERA, a complete communications library including link, net, and transport layers for …

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Umts-Hsdpa In High Altitude Platforms (Haps) Communications, Bazil Taha Ahmed, Miguel Calvo Ramon, Leandro De Haro-Ariet Jan 2007

Umts-Hsdpa In High Altitude Platforms (Haps) Communications, Bazil Taha Ahmed, Miguel Calvo Ramon, Leandro De Haro-Ariet

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper, the performance of HAPs (High Altitudes Platforms) UMTS HSDPA (High Speed Downlink Packet Access) is studied for different HAPs height h, different cells radius R and two directions (0° and 30°) within the cell. The network under study is assumed to have 61 ground cells. It is noticed that, for urban zone users, the effective range is lower than the effective range for users in rural zones for a given modulation scheme. Also it is noticed that in rural zone, the HSDPA can support higher modulation schemes. It is noticed that, when 80% of the base station …

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Study Of The Warranty Cost Model For Software Reliability With An Imperfect Debugging Phenomenon, D.R. Prince Williams Jan 2007

Study Of The Warranty Cost Model For Software Reliability With An Imperfect Debugging Phenomenon, D.R. Prince Williams

Turkish Journal of Electrical Engineering and Computer Sciences

Software reliability is one of the most important characteristics of software quality. Its measurement and management technologies employed during the software life-cycle are essential for producing and maintaining quality/reliable software systems. Herein, we discuss a modified approach to calculating the delivery cost of a software product, when warranty is to be provided, with an imperfect debugging phenomenon. Unlike existing cost models, here the strategy was to consider maintenance support given to the customer with an imperfect debugging phenomenon. The optimal release time can be calculated for various reliability levels by minimizing the cost. The delivery cost, reliability of the software …

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On-Road Remote Sensing Of Automobile Emissions In The Denver Area: Year 6, January 2007, Gary A. Bishop, Donald H. Stedman Jan 2007

On-Road Remote Sensing Of Automobile Emissions In The Denver Area: Year 6, January 2007, Gary A. Bishop, Donald H. Stedman

Fuel Efficiency Automobile Test Publications

No abstract provided.

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Fleet Vehicle Smoke Emissions As Measured By On-Road Remote Sensing Using Infrared Scattering: Years 1998 Through 2007, Jeffrey A. Caulfield, Gary A. Bishop, Donald H. Stedman Jan 2007

Fleet Vehicle Smoke Emissions As Measured By On-Road Remote Sensing Using Infrared Scattering: Years 1998 Through 2007, Jeffrey A. Caulfield, Gary A. Bishop, Donald H. Stedman

Fuel Efficiency Automobile Test Publications

No abstract provided.

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Web Search From A Bus, Aruna Balasubramanian, Yun Zhou, Bruce Croft, Brian Neil Levine, Arun Venkataramani Jan 2007

Web Search From A Bus, Aruna Balasubramanian, Yun Zhou, Bruce Croft, Brian Neil Levine, Arun Venkataramani

Computer Science Department Faculty Publication Series

Opportunistic connections to the Internet from open wireless access points is now commonly possible in municipal areas. Vehicular networks can opportunistically connect to the internet for several seconds via open access points. In this paper, we adapt the interactive process of web search and retrieval to vehicular networks with intermittent Internet access. Our system, called Thedu has mobile nodes use an Internet proxy to collect search engine results and prefetch result pages. The mobiles nodes download the pre-fetched web pages from the proxy. Our contribution is a novel set of techniques to make aggressive but selective prefetching practical, resulting in …

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Cryptanalysis Of Two Lightweight Rfid Authentication Schemes, Benessa Defend, Kevin Fu, Ari Juels Jan 2007

Cryptanalysis Of Two Lightweight Rfid Authentication Schemes, Benessa Defend, Kevin Fu, Ari Juels

Computer Science Department Faculty Publication Series

Vajda and Buttyan proposed several lightweight authentication protocols for authenticating RFID tags to readers, and left open the quantifiable cryptographic strength. Our cryptanalysis answers this open question by implementing and measuring attacks against their XOR and SUBSET protocols. A passive eavesdropper can impersonate a tag in the XOR protocol after observing only 70 challenge-response transactions between the tag and reader. In contrast, the theoretical maximum strength of the XOR protocol could have required 16! * 2 observed transactions to break the key. Our experiments also show that a passive eavesdropper can recover the shared secret used in the XOR protocol …

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Simple, Robust, Scalable Semi-Supervised Learning Via Expectation Regularization, Gideon S. Mann Jan 2007

Simple, Robust, Scalable Semi-Supervised Learning Via Expectation Regularization, Gideon S. Mann

Computer Science Department Faculty Publication Series

Although semi-supervised learning has been an active area of research, its use in deployed applications is still relatively rare because the methods are often difficult to implement, fragile in tuning, or lacking in scalability. This paper presents expectation regularization, a semi-supervised learning method for exponential family parametric models that augments the traditional conditional label-likelihood objective function with an additional term that encourages model predictions on unlabeled data to match certain expectations—such as label priors. The method is extremely easy to implement, scales as well as logistic regression, and can handle non-independent features. We present experiments on five different data sets, …

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Anonymizing Social Networks, Michael Hay, Gerome Miklau, David Jensen, Philipp Weis, Siddharth Srivastava Jan 2007

Anonymizing Social Networks, Michael Hay, Gerome Miklau, David Jensen, Philipp Weis, Siddharth Srivastava

Computer Science Department Faculty Publication Series

Advances in technology have made it possible to collect data about individuals and the connections between them, such as email correspondence and friendships. Agencies and researchers who have collected such social network data often have a compelling interest in allowing others to analyze the data. However, in many cases the data describes relationships that are private (e.g., email correspondence) and sharing the data in full can result in unacceptable disclosures. In this paper, we present a framework for assessing the privacy risk of sharing anonymized network data. This includes a model of adversary knowledge, for which we consider several variants …

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Structure Theorem And Strict Alternation Hierarchy For Fo2 On Words, Philipp Weis Jan 2007

Structure Theorem And Strict Alternation Hierarchy For Fo2 On Words, Philipp Weis

Computer Science Department Faculty Publication Series

It is well-known that every first-order property on words is expressible using at most three variables. The subclass of properties expressible with only two variables is also quite interesting and wellstudied. We prove precise structure theorems that characterize the exact expressive power of first-order logic with two variables on words. Our results apply to FO2[<] and FO 2[<; Suc], the latter of which includes the binary successor relation in addition to the linear ordering on string positions. For both languages, our structuretheorems showexactly whatis expressible using a given quantifier depth, n, and using m blocks of alternating quantifiers, for any m ≤ n. Using these characterizations, we prove, among other results, that there is a strict hierarchy of alternating quantifiers for both languages. The question whether there was such a hierarchy had been completely open. As another consequence of our structural results, we show that satisfiability for FO2[<], which is NEXP-complete in general, becomes NP-complete once we only consider alphabets of a bounded size.

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Learning State-Action Basis Functions For Hierarchical Mdps, Sarah Osentoski Jan 2007

Learning State-Action Basis Functions For Hierarchical Mdps, Sarah Osentoski

Computer Science Department Faculty Publication Series

This paper introduces a new approach to actionvalue function approximation by learning basis functions from a spectral decomposition of the state-action manifold. This paper extends previous work on using Laplacian bases for value function approximation by using the actions of the agent as part of the representation when creating basis functions. The approach results in a nonlinear learned representation particularly suited to approximating action-value functions, without incurring the wasteful duplication of state bases in previous work. We discuss two techniques to create state-action graphs: offpolicy and on-policy. We show that these graphs have a greater expressive power and have better …

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Quantifying Soil Chemical Properties Using Near Infrared Reflectance Spectroscopy, Robert L. Ficklin, Shane M. Foley, Robert E. Kissell Jr. Jan 2007

Quantifying Soil Chemical Properties Using Near Infrared Reflectance Spectroscopy, Robert L. Ficklin, Shane M. Foley, Robert E. Kissell Jr.

Journal of the Arkansas Academy of Science

Methodologies for determining soil chemical properties have evolved dramatically during the past century. Early geochemical analyses were conducted exclusively through the use of wet chemistry techniques that were relatively reliable but painstaking and subject to errors at various stages of analysis. Near infrared reflectance spectroscopy (NIRS) has emerged as a new approach for rapidly analyzing a variety of materials including soils. In this study soil samples were taken from eight study areas across the Ozark Highlands of Arkansas, and NIRS calibration models were developed to determine the accuracy of using NIRS to analyze soils compared with standard soil chemical analysis …

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Measurement And Modeling Of Light Transmission Through Turbid Media, Alois (Al) J. Adams, Michael Fahrenwald, Long Do Jan 2007

Measurement And Modeling Of Light Transmission Through Turbid Media, Alois (Al) J. Adams, Michael Fahrenwald, Long Do

Journal of the Arkansas Academy of Science

No abstract provided.

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Electron Shock Waves: Ionization Rate And Solutions To The Efd Equations, Mostafa Hemmati, Steven Summers, Michael Weller Jan 2007

Electron Shock Waves: Ionization Rate And Solutions To The Efd Equations, Mostafa Hemmati, Steven Summers, Michael Weller

Journal of the Arkansas Academy of Science

This paper describes our numerical investigation into ionizing breakdown waves, primarily antiforce waves. Antiforce waves are waves for which the electric field force on the electronsisin the opposite direction of the wave's propagation. This investigation required us to utilize one-dimensional electron fluid-dynamical equations, which were applied to a pulse wave that transmits into a region of neutral gas and is under the influence of an applied electric field. Two important assumptions were made in applying these equations: electrons were considered to be the main component in the propagation of the pulse wave, and the partial pressure of the electron gas …

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Portable Emission Measurements Of Snowcoaches And Snowmobiles In Yellowstone National Park, Gary A. Bishop, Ryan Stadtmuller, Donald H. Stedman Jan 2007

Portable Emission Measurements Of Snowcoaches And Snowmobiles In Yellowstone National Park, Gary A. Bishop, Ryan Stadtmuller, Donald H. Stedman

Fuel Efficiency Automobile Test Publications

No abstract provided.

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Time-Temperature And Relative Humidity Profiles Of Chilled And Frozen Foods In Retail Outlets Nationwide, And Evaluation Of Related Practices, Caroline Garvan Jan 2007

Time-Temperature And Relative Humidity Profiles Of Chilled And Frozen Foods In Retail Outlets Nationwide, And Evaluation Of Related Practices, Caroline Garvan

Masters

Temperature abuse combined with poor operational practices are the dominant factors in the mishandling of food products which can result in outbreaks of food borne disease. The objective of this work was to determine efficacy of temperature and relative humidity control using recorded data and to assess the food safety management systems in operation in retail outlets in the Republic of Ireland. This study also aims to examine food safety risk to consumers as a result of inadequate temperature control and poor food hygiene practices using microbial analysis and predictive modelling. External air temperature, core temperature and relative humidity of …

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A Novel Tio2 / Pvc Layer For Use In A Photoelectrochemical Cell, Faiza Touati, John Cassidy, Kevin Mcguigan Jan 2007

A Novel Tio2 / Pvc Layer For Use In A Photoelectrochemical Cell, Faiza Touati, John Cassidy, Kevin Mcguigan

Articles

A novel method of coating titanium dioxide on a glassy carbon electrode as a polyvinylchloride composite , is described. On illumination , there is an enhanced voltammetric current at this TiO2/PVC composite in aqueous formic acid solution. This electrode is used as the basis of a formic acid fuel cell where oxygen is reduced at a platinum cathode. The system yields 100 cm-2 for 0.01 mol dm-3 HCOOH in 0.1 mol dm-3 NaOH under illumination from a 150 W xenon lamp. The current without illumination is 0.5 cm-2.

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An Experiment Using A Simple Photoassisted Fuel Cell Designed To Remediate Simulated Wastewater, John Cassidy, Faisa Touati, Kevin Mcguigan Jan 2007

An Experiment Using A Simple Photoassisted Fuel Cell Designed To Remediate Simulated Wastewater, John Cassidy, Faisa Touati, Kevin Mcguigan

Articles

Work in photochemistry work peaked in the 1980’s where there was the prospect of using sunlight shining on suspensions of titanium dioxide in order to catalytically cleave water into hydrogen and oxygen [1-5]. In this way a clean and efficient method of producing hydrogen as a fuel was envisaged. However, there was a requirement to use a rather high energy light to achieve the splitting and it was not as efficient with visible light[5]. Doped TiO2 layers have been used in a three electrode system for formic acid degradation[6]. In this work, the system uses an electrode coated with TiO2 …

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Improved Nitrate Sensing Using Ion Selective Electrodes Based On Urea–Calixarene Ionophores, Benjamin Schazmann, Dermot Diamond Jan 2007

Improved Nitrate Sensing Using Ion Selective Electrodes Based On Urea–Calixarene Ionophores, Benjamin Schazmann, Dermot Diamond

Articles

Urea–calix[4]arenes 1 and 2 were synthesised and incorporated into ISE membranes for assessment as sensors for inorganic anions in water. 1 revealed a strong response to all anions following the Hofmeister selectivity order. For ISEs of 2, the response to a portion of the anion series was suppressed, increasing the margin of selectivity of nitrate over chloride, a common interferant of nitrate in fresh and marine water samples. The performance of ISEs containing 2 was compared to commercially available alkylammonium nitrate ion-exchange salts used for nitrate sensing. Our ISEs performed favourably in terms of sensitivity, linear range and LOD performing …

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A Note On Clean Abelian Groups, Brendan Goldsmith, P. Vamos Jan 2007

A Note On Clean Abelian Groups, Brendan Goldsmith, P. Vamos

Articles

Nicholson defined a ring to be clean if every element is the sum of a unit and an idempotent. A module is clean if its endomorphism algebra is clean. We show that torsion-complete Abelian p-groups are clean and characterize the clean groups among the class of totally projective p-groups. An example is given of a clean p-group which is neither totally projective nor torsion- complete

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Some Transitivity Results For Torsion Abelian Groups, Brendan Goldsmith, Lutz Strungmann Jan 2007

Some Transitivity Results For Torsion Abelian Groups, Brendan Goldsmith, Lutz Strungmann

Articles

We introduce a new class of fully transitive and transitive Abelian p-groups and study the new concept of weak transitivity which is the missing link between full transitivity and transitivity.

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Slow Flow Between Concentric Cones, O. Hall, C. P. Hills, A. D. Gilbert Jan 2007

Slow Flow Between Concentric Cones, O. Hall, C. P. Hills, A. D. Gilbert

Articles

This paper considers the low-Reynolds-number flow of an incompressible fluid contained in the gap between two coaxial cones with coincident apices and bounded by a spherical lid. The two cones and the lid are allowed to rotate independently about their common axis, generating a swirling motion. The swirl induces a secondary, meridional circulation through inertial effects. For specific configurations complex eigenmodes representing an infinite sequence of eddies, analogous to those found in two-dimensional corner flows and some three-dimensional geometries, form a component of this secondary circulation. When the cones rotate these eigenmodes, arising from the geometry, compete with the forced …

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