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  • 1
    Publication Date: 2024-04-22
    Description: A preliminary inventory of the composition of zooplancktonic species found in Bayano Lake, between February and September 1981 revealed that there are seven species of Rotifera, five Cladocera, two Copepoda, one Ostracoda and larvae of Macrobrachium (Decapoda) and Chaoborus (Diptera). The composition, abundance and horizontal and monthly distribution of the most important zooplanktonic groups found in Bayano Lake are here presented.
    Description: Published
    Description: Refereed
    Keywords: Limonology ; Abundancia ; Vertical distribution ; Limnology ; Composición
    Repository Name: AquaDocs
    Type: Journal Contribution
    Format: pp.17-24
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  • 2
    Publication Date: 2024-05-20
    Description: To ensure the long-term sustainable use of African Great Lakes (AGL), and to better understand the functioning of these ecosystems, authorities, managers and scientists need regularly collected scientific data and information of key environmental indicators over multi-years to make informed decisions. Monitoring is regularly conducted at some sites across AGL; while at others sites, it is rare or conducted irregularly in response to sporadic funding or short-term projects/studies. Managers and scientists working on the AGL thus often lack critical long-term data to evaluate and gauge ongoing changes. Hence, we propose a multi-lake approach to harmonize data collection modalities for better understanding of regional and global environmental impacts on AGL. Climate variability has had strong impacts on all AGL in the recent past. Although these lakes have specific characteristics, their limnological cycles show many similarities. Because different anthropogenic pressures take place at the different AGL, harmonized multilake monitoring will provide comparable data to address the main drivers of concern (climate versus regional anthropogenic impact). To realize harmonized long-term multi-lake monitoring, the approach will need: (1) support of a wide community of researchers and managers; (2) political goodwill towards a common goal for such monitoring; and (3) sufficient capacity (e.g., institutional, financial, human and logistic resources) for its implementation. This paper presents an assessment of the state of monitoring the AGL and possible approaches to realize a long-term, multi-lake harmonized monitoring strategy. Key parameters are proposed. The support of national and regional authorities is necessary as each AGL crosses international boundaries.
    Description: Published
    Description: 101988
    Description: JCR Journal
    Keywords: Fisheries ; Limnology ; Pollution ; Biodiversity ; Climate change ; Erosion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    Springer Nature | Springer International Publishing
    Publication Date: 2024-04-05
    Description: Chilean Patagonia, located at the southwestern tip of South America, is one of the last regions on earth where highly intact environments predominate. With a coastline that extends along some 100,000 km of fjords, channels, and islands, it has one of the world´s most extensive marine-terrestrial interfaces. Local place-based and Indigenous cultures and management practices are a vital presence across the region, while the long and rich history of conservation efforts have resulted in officially protected areas covering over 50% of the land and 41% of the coastal-marine area. However, Chilean Patagonia is increasingly facing anthropogenic pressures associated with increased infrastructure and access, salmon aquaculture, extractive industries, and the spread of invasive exotic species. Despite widespread recognition that Chilean Patagonia represents a unique global reservoir of socio-natural heritage, to date there has been no region-wide assessment of the scientific evidence of the conservation status of its ecosystems or the priorities for their effective conservation. Conservation in Chilean Patagonia: Assessing the state of knowledge, opportunities, and challenges is the first book to gather and synthesize the available scientific and socio-environmental information related to Patagonian conservation. It presents the collaborative work of 68 researchers and local experts, representing a range of specialties and perspectives, including: biology, ecology, socio-ecology, fisheries, aquaculture, anthropology, economics, geography, tourism, cryosphere, oceanography, climate and global change. The book’s 18 chapters focus on the status of key ecosystems and conservation tools, and provide recommendations toward the construction of a renewed, inclusive, and integrated conservation agenda for the Chilean Patagonian region. It provides an essential primer for anyone interested in the future of this ecologically vital region, as well as lessons on interdisciplinary collaboration and integrated analysis of conservation issues useful for conservation practitioners and scholars. This is an open access book. This book is a translation of an original Spanish edition. The translation was done with the help of artificial intelligence (machine translation by the service DeepL.com). A subsequent human revision was done primarily in terms of content, so that the book will read stylistically differently from a conventional translation.
    Keywords: Ecology ; Limnology ; Oceanography ; Biodiversity ; Marine-terrestrial Interface ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAF Ecological science, the Biosphere ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RN The environment::RNK Conservation of the environment ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RB Earth sciences::RBK Hydrology and the hydrosphere::RBKC Oceanography (seas and oceans) ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RG Geography::RGM Biogeography ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RN The environment::RNC Applied ecology::RNCB Biodiversity
    Language: English
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  • 4
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    Springer Nature | Springer International Publishing
    Publication Date: 2024-01-16
    Description: Chilean Patagonia, located at the southwestern tip of South America, is one of the last regions on earth where highly intact environments predominate. With a coastline that extends along some 100,000 km of fjords, channels, and islands, it has one of the world´s most extensive marine-terrestrial interfaces. Local place-based and Indigenous cultures and management practices are a vital presence across the region, while the long and rich history of conservation efforts have resulted in officially protected areas covering over 50% of the land and 41% of the coastal-marine area. However, Chilean Patagonia is increasingly facing anthropogenic pressures associated with increased infrastructure and access, salmon aquaculture, extractive industries, and the spread of invasive exotic species. Despite widespread recognition that Chilean Patagonia represents a unique global reservoir of socio-natural heritage, to date there has been no region-wide assessment of the scientific evidence of the conservation status of its ecosystems or the priorities for their effective conservation. Conservation in Chilean Patagonia: Assessing the state of knowledge, opportunities, and challenges is the first book to gather and synthesize the available scientific and socio-environmental information related to Patagonian conservation. It presents the collaborative work of 68 researchers and local experts, representing a range of specialties and perspectives, including: biology, ecology, socio-ecology, fisheries, aquaculture, anthropology, economics, geography, tourism, cryosphere, oceanography, climate and global change. The book’s 18 chapters focus on the status of key ecosystems and conservation tools, and provide recommendations toward the construction of a renewed, inclusive, and integrated conservation agenda for the Chilean Patagonian region. It provides an essential primer for anyone interested in the future of this ecologically vital region, as well as lessons on interdisciplinary collaboration and integrated analysis of conservation issues useful for conservation practitioners and scholars. This is an open access book. This book is a translation of an original Spanish edition. The translation was done with the help of artificial intelligence (machine translation by the service DeepL.com). A subsequent human revision was done primarily in terms of content, so that the book will read stylistically differently from a conventional translation.
    Keywords: Ecology ; Limnology ; Oceanography ; Biodiversity ; Marine-terrestrial Interface ; bic Book Industry Communication::R Earth sciences, geography, environment, planning::RN The environment::RNK Conservation of the environment ; bic Book Industry Communication::P Mathematics & science::PS Biology, life sciences::PSA Life sciences: general issues::PSAF Ecological science, the Biosphere ; bic Book Industry Communication::R Earth sciences, geography, environment, planning::RG Geography::RGM Biogeography ; bic Book Industry Communication::R Earth sciences, geography, environment, planning::RN The environment::RNC Applied ecology::RNCB Biodiversity
    Language: English
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  • 5
    Publication Date: 2024-02-26
    Description: Identifcation of ontogenetic age classes plays an important role in the felds of zoology, palaeontology and archaeology, where accurate age classifcations of (sub)fossil remains are a crucial component for the reconstruction \nof past life. Textural ageing\xe2\x80\x94the identifcation of age-related bone surface textures\xe2\x80\x94provides a size-independent \nmethod for age assessment of vertebrate material. However, most of the work so far is limited to qualitative results. \nWhile qualitative approaches provide helpful insights on textural ageing patterns, they are heavily subject to observer \nbias and fall short of quantitative data relevant for detailed statistical analyses and cross-comparisons. Here, we present a pilot study on the application of 3D surface digital microscopy to quantify bone surface textures on the long \nbones of the grey heron (Ardea cinerea) and the Canada goose (Branta canadensis) using internationally verifed \nroughness parameters. Using a standardised measuring protocol, computed roughness values show a strong correlation with qualitative descriptions of textural patterns. Overall, higher roughness values correspond to increased numbers of grooves and pits and vice versa. Most of the roughness parameters allowed distinguishing between diferent \nontogenetic classes and closely followed the typical sigmoidal animal growth curve. Our results show that bone \ntexture quantifcation is a feasible approach to identifying ontogenetic age classes.
    Keywords: General Physics and Astronomy ; General Environmental Science ; General Biochemistry ; Genetics and Molecular Biology ; General Materials Science ; General Chemistry ; Roughness ; Surfaces ; Taphonomy ; Topography ; Bone ; Ontogeny ; Digital microscopy
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 6
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    MDPI - Multidisciplinary Digital Publishing Institute
    Publication Date: 2023-11-30
    Description: Active flow control (AFC) utilizes local active perturbations to induce changes in global flow behavior that result in aero/hydrodynamic performance improvement. It has been a vibrant research area with potential applications in a wide range of engineering fields. This Special Issue is a collection of 11 excellent research papers published in Actuators, showcasing and discussing new advances in both fundamental and applied AFC technologies.
    Keywords: Active flow control ; Actuators ; Aerodynamics ; Synthetic jets&nbsp ; bic Book Industry Communication::T Technology, engineering, agriculture::TB Technology: general issues
    Language: English
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  • 7
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-11
    Description: Some sixty years after the experimental flights of the North American X-15 hypersonic rocket-powered aircraft, sustained hypervelocity travel is still the next frontier in high-speed transportation. Today, there is much excitement and interest regarding hypersonic vehicles. In fact, many aerospace agencies, large industries, and several start-ups are involved in design activities and experimental campaigns both in wind tunnels and in-flight with full-scale experimental flying test beds and prototypes to make hypersonic travel almost as easy and convenient as airliner travel. Achieving this goal will radically revolutionize the future of civil transportation. This book contains valuable contributions that focus on various design issues related to hypersonic aircraft.
    Keywords: Aerodynamics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TG Mechanical engineering and materials::TGM Materials science::TGMF Engineering: Mechanics of fluids::TGMF1 Aerodynamics
    Language: English
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  • 8
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-11
    Description: Aerodynamics, the study of air motion around solid objects, allows us to understand and measure the dominating forces acting on aircrafts, buildings, bridges, automobiles, and other structures. The forces that result in an aircraft overcoming gravity and drag are called thrust and lift. Various parameters such as geometrical configurations of objects, as well as physical properties of air, which may be functions of position and time, affect those forces. This book covers some of the latest studies regarding the application of the principles of aerodynamics to the design of many different engineered objects. This book will be of interest to mechanical and aerospace engineering students, academics, and researchers who are looking for new insights into this fascinating branch of fluid mechanics.
    Keywords: Aerodynamics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TG Mechanical engineering and materials::TGM Materials science
    Language: English
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  • 9
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-11
    Description: Aerodynamics, from a modern point of view, is a branch of physics that study physical laws and their applications, regarding the displacement of a body into a fluid, such concept could be applied to any body moving in a fluid at rest or any fluid moving around a body at rest. This Book covers a small part of the numerous cases of stationary and non stationary aerodynamics; wave generation and propagation; wind energy; flow control techniques and, also, sports aerodynamics. It's not an undergraduate text but is thought to be useful for those teachers and/or researchers which work in the several branches of applied aerodynamics and/or applied fluid dynamics, from experiments procedures to computational methods.
    Keywords: Aerodynamics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TG Mechanical engineering and materials::TGM Materials science
    Language: English
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  • 10
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-11
    Description: This book is intended to be a valuable addition to students, engineers, scientists, industrialists, consultants and others providing greater insight into wind tunnel designs and their enormous research potential. It is a compilation of works from world experts on subsonic and supersonic wind tunnel designs, applicable to a diverse range of disciplines. The book is organised in two sections. The first section comprises of three chapters on various aspects of stationary and portable subsonic wind tunnel designs, followed by one chapter on supersonic wind tunnel and the final chapter discusses a method to address unsteadiness effects of fan blade rotation. The second section contains four chapters regarding wind tunnel applications across a multitude of engineering fields including civil, mechanical, chemical and environmental engineering.
    Keywords: Aerodynamics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TG Mechanical engineering and materials::TGM Materials science
    Language: English
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  • 11
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-11
    Description: This book reports the latest development and trends in the low Re number aerodynamics, transition from laminar to turbulence, unsteady low Reynolds number flows, experimental studies, numerical transition modelling, control of low Re number flows, and MAV wing aerodynamics. The contributors to each chapter are fluid mechanics and aerodynamics scientists and engineers with strong expertise in their respective fields. As a whole, the studies presented here reveal important new directions toward the realization of applications of MAV and wind turbine blades.
    Keywords: Aerodynamics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TG Mechanical engineering and materials::TGM Materials science
    Language: English
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  • 12
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    IntechOpen
    Publication Date: 2024-04-04
    Description: Spacecraft attitude maneuvers comply with Euler's moment equations, a set of three nonlinear, coupled differential equations. Nonlinearities complicate the mathematical treatment of the seemingly simple action of rotating, and these complications lead to a robust lineage of research. This book is meant for basic scientifically inclined readers, and commences with a chapter on the basics of spaceflight and leverages this remediation to reveal very advanced topics to new spaceflight enthusiasts. The topics learned from reading this text will prepare students and faculties to investigate interesting spaceflight problems in an era where cube satellites have made such investigations attainable by even small universities. It is the fondest hope of the editor and authors that readers enjoy this book.
    Keywords: Science ; Mechanics ; Aerodynamics ; bic Book Industry Communication::P Mathematics & science::PH Physics::PHD Classical mechanics::PHDF Fluid mechanics ; thema EDItEUR::P Mathematics and Science::PH Physics::PHD Classical mechanics::PHDF Physics: Fluid mechanics
    Language: English
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  • 13
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-11
    Description: Although great advances in computational methods have been made in recent years, wind tunnel tests remain essential for obtaining the full range of data required to guide detailed design decisions for various practical engineering problems. This book collects original and innovative research studies on recent applications in wind tunnel tests, exhibiting various investigation directions and providing a bird’s eye view on this broad subject area. It is composed of seven chapters that have been grouped in two major parts. The first part of the book (chapters 1–4) deals with wind tunnel technologies and devices. The second part (chapters 5–7) deals with the latest applications of wind tunnel testing. The text is addressed not only to researchers but also to professional engineers, engineering lecturers, and students seeking to gain better understanding of the current status of wind tunnels. Through its seven chapters, the reader will have an access to a wide range of works related to wind tunnel testing.
    Keywords: Aerodynamics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TG Mechanical engineering and materials::TGM Materials science
    Language: English
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  • 14
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    MDPI - Multidisciplinary Digital Publishing Institute
    Publication Date: 2022-01-31
    Description: Today, sustainability of a healthy freshwater ecosystem and its associated ecosystem services are hot issues with ever-growing attention placed upon them. We are increasingly recognizing that they are crucial for the survival of the aquatic biota and human beings on our planet. The efficient monitoring of water resources is fundamental for effective management of water quality and aquatic ecosystems. The first stage in sustainable ecosystem management is the evaluation of the current status of target ecosystems. Traditionally, and even today, physico-chemical parameters have mainly been used to evaluate the quality of water resources. However, they have a large limit to grab the wholeness of water system, particularly in the sense of ecosystem health and integrity, for which ecological monitoring should be based on biological factors. Various approaches are applicable to ecosystem health assessment at different levels of the biological hierarchy, from genes to ecosystems. This Special Issue is designed to improve scientific understanding and strategies for sound aquatic ecosystem management and services for researchers, decision makers, and stakeholders.
    Keywords: Limnology ; Aquatic ecosystem assessment Aquatic ecosystem management ; Restoration ; Aquatic ecosystem services ; Aquatic ecology ; Aquatic ecosystem policy ; Conservation ; Ecohydrology ; Aquatic ecosystem monitoring ; Streams/ Rivers/ Lakes/ Wetlands ; Biological indicators
    Language: English
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  • 15
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-11
    Description: Spacecraft attitude maneuvers comply with Euler's moment equations, a set of three nonlinear, coupled differential equations. Nonlinearities complicate the mathematical treatment of the seemingly simple action of rotating, and these complications lead to a robust lineage of research. This book is meant for basic scientifically inclined readers, and commences with a chapter on the basics of spaceflight and leverages this remediation to reveal very advanced topics to new spaceflight enthusiasts. The topics learned from reading this text will prepare students and faculties to investigate interesting spaceflight problems in an era where cube satellites have made such investigations attainable by even small universities. It is the fondest hope of the editor and authors that readers enjoy this book.
    Keywords: Aerodynamics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TG Mechanical engineering and materials::TGM Materials science
    Language: English
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  • 16
    Publication Date: 2019-08-01
    Description: The InSight spacecraft was proposed to be a build-to-print copy of the Phoenix vehicle due to the knowledge that the lander payload would be similar and the trajectory would be similar. However, the InSight aerothermal analysts, based on tests performed in CO2 during the Mars Science Laboratory mission (MSL) and completion of Russian databases, considered radiative heat flux to the aftbody from the wake for the first time for a US Mars mission. The combined convective and radiative heat flux was used to determine if the as-flown Phoenix thermal protection system (TPS) design would be sufficient for InSight. All analyses showed that the design would be adequate. Once the InSight lander was successfully delivered to Mars on November 26, 2018, work began to reconstruct the atmosphere and trajectory in order to evaluate the aerothermal environments that were actually encountered by the spacecraft and to compare them to the design environments.The best estimated trajectory (BET) reconstructed for the InSight atmospheric entry fell between the two trajectories considered for the design, when looking at the velocity versus altitude values. The maximum heat rate design trajectory (MHR) flew at a higher velocity and the maximum heat load design trajectory (MHL) flew at a lower velocity than the BET. For TPS sizing, the MHL trajectory drove the design. Reconstruction has shown that the BET flew for a shorter time than either of the design environments, hence total heat load on the vehicle should have been less than used in design. Utilizing the BET, both DPLR and LAURA were first run to analyze the convective heating on the vehicle with no angle of attack. Both codes were run with axisymmetric, laminar flow in radiative equilibrium and vibrational non-equilibrium with a surface emissivity of 0.8. Eight species Mitcheltree chemistry was assumed with CO2, CO, N2, O2, NO, C, N, and O. Both codes agreed within 1% on the forebody and had the expected differences on the aftbody. The NEQAIR and HARA codes were used to analyze the radiative heating on the vehicle using full spherical ray-tracing. The codes agreed within 5% on most aftbody points of interest.The LAURA code was then used to evaluate the conditions at angle of attack at the peak heating and peak pressure times. Boundary layer properties were investigated to confirm that the flow over the forebody was laminar for the flight.Comparisons of the aerothermal heating determined for the reconstructed trajectory to the design trajectories showed that the as-flown conditions were less severe than design
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN70187 , International Planetary Probe Workshop (IPPW) 2019; Jul 08, 2019 - Jul 12, 2019; Oxford; United Kingdom
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  • 17
    Publication Date: 2019-07-20
    Description: Improvements and results of a new method are presented that computes a pre-test estimate of the precision error of the drag coefficient of a wind tunnel model. The error estimate is defined as the part of the drag coefficient's precision error that is primarily associated with the precision error of the angle of attack measurement and physical characteristics of the chosen strain-gage balance. The method indirectly describes the precision error of the angle of attack measurement by using an assumed balance gage output variation of one microV/V. The physical characteristics of the balance, on the other hand, are described by partial derivatives of the axial and normal forces with respect to the strain-gage outputs. These derivatives can directly be obtained from the data reduction matrix of the balance. The precision error estimate itself is calculated by applying a simple explicit equation that uses the model reference area, the dynamic pressure, the angle of attack, the coefficients of the linear terms of the data reduction matrix, and the electrical output variation of one microvolt per volt as input. Precision errors at constant angle of attack may be visualized as contour plots by plotting them, for example, versus the Mach number and the total pressure. Characteristics of NASA's MC60E balance are used in combination with the reference area of a generic wind tunnel model in order to demonstrate that error estimates are independent of both the balance load format and the units chosen for the description of balance loads, model reference area, and the dynamic pressure. Finally, experimental data from a wind tunnel test of the Ames Check Standard Model in the NASA Ames 11-foot Transonic Wind Tunnel illustrates the application of the method to real-world test data.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN63164 , AIAA SciTech 2019; Jan 07, 2019 - Jan 11, 2019; San Diego, CA; United States
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  • 18
    Publication Date: 2019-07-19
    Description: Wake vortex spacing standards constrict the terminal area throughput and impose severe constraints on the overall capacity and efficiency of the National Airspace System. For more than two decades starting in the early 1990s, the National Aeronautics and Space Administration conducted extensive research on characterizing the formation and evolution of aircraft wakes. This multidisciplinary work included comprehensive field experiments (Pruis et al. 2016), flight tests (Vicroy et al. 1998), and wind tunnel tests (Rossow 1994; Chow et al. 1997). Parametric studies using large eddy simulations (Proctor 1998; Proctor et al. 2006) were conducted in order to develop fast-time models for the prediction of wake transport and decay (Ahmad et al. 2016). Substantial effort was spent on the formulation of acceptable vortex hazard metrics (Tatnall 1995; Hinton and Tatnall 1997). Several wake encounter severity metrics have been suggested in the past, which include the wake circulation strength, vortex-induced rolling moment coefficient (Clv), bank angle, and the roll control ratio (Tatnall 1995; Hinton and Tatnall 1997; Van der Geest 2012). The vortex-induced rolling moment coefficient introduced by Bowles and Tatnall (Tatnall 1995; Gloudemans et al. 2016) has been used extensively for risk and safety analysis of newly proposed air traffic management concepts and procedures. The original method of Bowles and Tatnall assumed a constant wing loading (the wing lift-curve slope, CL is constant), which resulted in an overestimation of the vortexinduced rolling moment coefficient. Bowles (2014) suggested a correction to the original method that provides more accurate values of Clv and which is also consistent with the underlying physics of the problem. The overestimation of Clv in the original method can be corrected by assuming an elliptical lift distribution. Figure 1.1 illustrates the correction in Clv achieved by the modified method.
    Keywords: Aerodynamics
    Type: NF1676L-33235 , NASA/TM-2019-220285 , L-21029
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  • 19
    Publication Date: 2019-07-20
    Description: National airspace, the management for access and operation of these vehicles is required. This management is being developed under the unmanned aircraft system traffic management system (UTM) program. To determine the aerodynamic characteristics of drones, wind tunnel experiments and computation fluid dynamic (CFD) analysis have been conducted. These experiments and analyses are undertaken to understand the flight capabilities of these vehicles in variable head and cross wind conditions. The results of these investigations will provide metrics for the safe operation of these vehicles in and around civil populations and in urban settings. The focus of this paper is to model a drone installed in a wind tunnel for varying pitch attitudes and rotor rpm settings. Specifically, the IRIS drone is modeled in the NASA-Ames 7x10 ft. W/T. The tunnel mounting hardware and the tunnel enclosure are modeled with the IRIS drone geometry. The rotors of the drone are modeled using two methodologies: a rotor disk model and individual blade representations. The results of the analysis are compared with available experimental data to validate the computational approach.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN64165 , AIAA Science and Technology Forum and Exposition 2019; Jan 07, 2019 - Jan 11, 2019; San Diego, CA; United States
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  • 20
    Publication Date: 2019-07-20
    Description: The Mid-Lift-to-Drag ratio Rigid Vehicle (MRV) is a candidate in the NASA multi-center effort to determine the most cost effective vehicle to deliver a large-mass payload to the surface of Mars for a human mission. Products of this effort include six-degree-of-freedom (6DoF) entry-to-descent trajectory performance studies for each candidate vehicle. These high fidelity analyses help determine the best guidance and control (G&C) strategies for a feasible, robust trajectory. This paper presents an analysis of the MRV's G&C design by applying common entry and descent associated uncertainties using a Fully Numerical Predictor-corrector Entry Guidance (FNPEG) and tunable Apollo powered descent guidance.
    Keywords: Aerodynamics
    Type: JSC-E-DAA-TN64439 , 2019 AAS/AIAA Space Flight Mechanics Meeting; Jan 13, 2019 - Jan 17, 2019; Ka''anapali, HI; United States
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  • 21
    Publication Date: 2019-07-13
    Description: Artificial ice shapes of various geometric fidelity were tested on a wing model based on the Common Research Model. Low Reynolds number test were conducted at Wichita State University's Walter H. Beech Memorial Wind utilizing an 8.9% scale model, and high Reynolds number tests were conducted at ONERA's F1 wind tunnel utilizing a 13.3% scale model. Several identical geometrically-scaled ice shapes were tested at both facilities, and the results were compared at overlapping Reynolds and Mach numbers. This was to ensure that the results and trends observed at low Reynolds number could be applied and continued to high, near-flight Reynolds number. The data from Wichita State University and ONERA F1 agreed well at matched Reynolds and Mach numbers. The lift and pitching moment curves agreed very well for most configurations. This confirmed results from previous tests with other ice shapes that indicated the data from the low Reynolds number tests could be used to understand ice-swept-wing aerodynamics at high Reynolds number. This allows ice aerodynamics testing to be performed at low Reynolds number facilities with much lower operating costs and generate results that are applicable to flight Reynolds number.
    Keywords: Aerodynamics
    Type: GRC-E-DAA-TN67168 , International Conference on Icing of Aircraft, Engines and Structures; Jun 17, 2019 - Jun 21, 2019; Minneapolis, MN; United States
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  • 22
    Publication Date: 2019-06-11
    Description: The intermediate wakes of thin flat plates with circular trailing edges (TEs) are investigated here with direct numerical simulations (DNSs). The separating boundary layers are turbulent in all cases. The near wake in two thin-plate cases (IN & NS), with a focus on the vortex shedding process, was explored in a recent article. Intermittent shedding was observed in Case IN. Case NS, with half the TE diameter of Case IN, was an essentially non-shedding case. A third case (ST) with a sharp trailing edge was also investigated and found to exhibit an intermittent wake instability. The objectives of the present study are twofold. The first is to determine if the wake instability found in Case ST exists in Cases IN and NS as well. The second is to provide the distributions of the turbulent normal intensities and shear stress in the wake and to understand these distributions via the budget terms in the corresponding transport equations. The results show that both Cases IN & NS exhibit a wake instability in the intermediate wake region, that is similar to that found earlier in Case ST. We note that in Case IN, the presence of an intermediate-wake instability results in the co-existence of two different types of instability within a single wake. The distributions of the turbulent normal intensities and shear stress, and the budget terms for the streamwise intensity are included and discussed here. All the budget terms contribute appreciably to the overall budget in the transport equation for streamwise normal intensity.
    Keywords: Aerodynamics
    Type: NASA/TM-2019-220195 , ARC-E-DAA-TN67460
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  • 23
    Publication Date: 2019-08-01
    Description: US Army MC-4/5 ram-air parachutes were tested in the 80- by 120-Ft test section of the National Full-Scale Aerodynamics Complex. Arrays of targets on the upper and lower surfaces of the central cell of the canopies were measured by stereo photogrammetry, and the target positions were used to estimate both the shape of the cell and angle of attack of the canopy. Forces and moments were measured by a six-axis load cell. Based on the photogrammetry and load-cell measurements, the relationships between lift, drag, and angle of attack were determined over a range of trailing-edge flap deflections, front riser lengths, and free-stream airspeeds. This paper describes the test, with an emphasis on the photogrammetry measurements, and presents a summary of results.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN68756 , 2019 AIAA Aviation and Aeronautics Forum and Exposition; Jun 17, 2019 - Jun 21, 2019; Indianapolis, IN; United States
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  • 24
    Publication Date: 2019-08-01
    Description: The Advanced Supersonic Parachute Inflation Research Experiments (ASPIRE) project waslaunched to develop the capability for testing supersonic parachutes at Mars-relevant conditions.Three initial parachute tests, targeted as a risk-reduction activity for NASA's upcomingMars2020 mission, successfully tested two candidate parachute designs and provided valuabledata on parachute inflation, forces, and aerodynamic behavior. Design of the flight tests dependedon flight mechanics simulations which in turn required aerodynamic models for the payload, andthe parachute. Computational Fluid Dynamics (CFD) was used to generate these models preflightand are compared against the flight data after the tests. For the payload, the reconstructedaerodynamic behavior is close to the pre-flight predictions, but the uncertainties in thereconstructed data are high due to the low dynamic pressures and accelerations during the flightperiod of comparison. For the parachute, the predicted time to inflation agrees well with the preflightmodel; the peak aerodynamic force and the steady state drag on the parachute are withinthe bounds of the pre-flight models, even as the models over-predict the parachute drag atsupersonic Mach numbers. Notably, the flight data does not show the transonic drag decreasepredicted by the pre-flight model. The ASPIRE flight tests provide previously unavailablevaluable data on the performance of a large full-scale parachute behind a slender leading bodyat Mars-relevant Mach number, dynamic pressure and parachute loads. This data is used topropose a new model for the parachute drag behind slender bodies to aid future experiments.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN68662 , AIAA Aviation Forum 2019; May 17, 2019 - May 21, 2019; Dallas, TX; United States
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  • 25
    Publication Date: 2019-07-31
    Description: Objectives: Reliable evaluation of mass flow rates through permeable boundaries - Estimate and control discretization error- Consider both computational domain outflow and inflow- Applicable to simulating propulsion-system effects, as well as secondary flow paths - Explore feasibility of handling more general outputs at domain boundaries. Design optimization subject to mass-flow-rate constraints - Improve aerodynamic performance and reduce noise due to sonic boom - Control discretization error in design space to improve confidence in final designs.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN69972 , AIAA Aviation and Aeronautics Forum (Aviation 2019); Jun 17, 2019 - Jun 21, 2019; Dallas, TX; United States
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  • 26
    Publication Date: 2019-08-28
    Description: The experimental, fully electric X-57 Maxwell is designed to enable lower energy con-sumption at cruise compare to a fuel burning baseline. This is to be achieved using a sumof subsystem benefits incorporated in the electric, airframe, and propulsion systems. AMission Planning Tool captures the three stages of X-57 development in order to assess thedesign of each subsystem in the context of the whole aircraft. The Mission Planning Toolfor the fully electric X-57 Maxwell captures the aerodynamics, propulsion, heat transfer,and power system of the aircraft with trajectory optimization capabilities. It is able tomodel these subsystems through all phases of flight, from taxi to landing. Through thismultidisciplinary approach, we are able to predict the benefit of each subsystem and theeffect of key design assumptions and how the aircraft will react if they are not met or ex-ceeded. As the aircraft progresses and systems are tested, we can use the Mission PlanningTool to continue to predict performance. This paper details the continued development ofthe X-57 Mission Planning Tool and demonstrates its capabilities.
    Keywords: Aerodynamics
    Type: GRC-E-DAA-TN71098 , AIAA/IEEE Electric Aircraft Technologies Symposium (EATS); Aug 22, 2019 - Aug 24, 2019; Indianapolis, IN; United States
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  • 27
    Publication Date: 2019-10-04
    Description: NASAs Advanced Air Transport Technology (AATT) project is investigating boundary layer ingesting (BLI) propulsors for advanced subsonic commercial vehicle concepts to enable the reduction of fuel burn. A multidisciplinary team of researchers from NASA, United Technologies Research Center (UTRC), Virginia Polytechnic University, and the Air Force Arnold Engineering Development Complex developed and tested an embedded BLI inlet and distortion-tolerant fan (BLI2DTF) system in the NASA Glenn Research Center (GRC) 8- foot by 6-foot (8x6) transonic wind tunnel. The test demonstrated the component performance goals necessary for an overall fuel burn reduction of 3 to 5 percent on a large hybrid wing body (HWB) aircraft. Special test equipment, including a raised floor with flow effectors and a bleed system, was developed for use in the 8x6 to produce the appropriate incoming boundary layer representative of an HWB application. Detailed measurements were made to determine the inlet total pressure loss and distortion, fan stage efficiency, and aeromechanic performance including blade vibration stress and displacement response. Results from this test were used as input to a vehicle-level system study performed by the AATT project to assess the impact of BLI on an alternative advanced concept aircraft referred to as the NASA D8 (ND8), which is somewhat similar to the HWB in its integration of the propulsor. This paper will provide an overview of the project timeline, special test equipment needed in the wind tunnel to develop the appropriate incoming boundary layer, and the difficulties in designing a propulsor for the test. The paper will conclude with some representative aerodynamic and aeromechanic data from the test itself and conclude with how this data was used in the ND8 system study.
    Keywords: Aerodynamics
    Type: ISABE-2019-24264 , GRC-E-DAA-TN72111 , International Society for Air Breathing Engines (ISABE) Conference; Sep 22, 2019 - Sep 27, 2019; Canberra; Australia
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  • 28
    Publication Date: 2019-11-30
    Description: This manual describes the installation and execution of FUN3D version 13.6, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.
    Keywords: Aerodynamics
    Type: NF1676L-34707 , NASA/TM-2019-220416
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  • 29
    Publication Date: 2019-10-29
    Description: _NASA's Advanced Air Transport Technology (AATT) project is investigating boundary layer ingesting (BLI) propulsors for advanced subsonic commercial vehicle concepts to enable the reduction of fuel burn. A multidisciplinary team of researchers from NASA, United Technologies Research Center (UTRC), Virginia Polytechnic University, and the Air Force Arnold Engineering Development Complex developed and tested an embedded BLI inlet and distortion-tolerant fan (BLI2DTF) system in the NASA Glenn Research Center (GRC) 8-foot by 6-foot (8x6) transonic wind tunnel. The test demonstrated the component performance goals necessary for an overall fuel burn reduction of 3 to 5 percent on a large hybrid wing body (HWB) aircraft. Special test equipment, including a raised floor with flow effectors and a bleed system, was developed for use in the 8x6 to produce the appropriate incoming boundary layer representative of an HWB application. Detailed measurements were made to determine the inlet total pressure loss and distortion, fan stage efficiency, and aeromechanic performance including blade vibration stress and displacement response. Results from this test were used as input to a vehicle-level system study performed by the AATT project to assess the impact of BLI on an alternative advanced concept aircraft referred to as the NASA D8 (ND8), which is somewhat similar to the HWB in its integration of the propulsor. This paper will provide an overview of the project timeline, special test equipment needed in the wind tunnel to develop the appropriate incoming boundary layer, and the difficulties in designing a propulsor for the test. The paper will conclude with some representative aerodynamic and aeromechanic data from the test itself and conclude with how this data was used in the ND8 system study.
    Keywords: Aerodynamics
    Type: GRC-E-DAA-TN73213 , International Society for Air Breathing Engines (ISABE) Conference; Sep 22, 2019 - Sep 27, 2019; Canberra; Australia
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  • 30
    Publication Date: 2020-01-22
    Description: Thermal Protection System (TPS) modeling requires accurate representation and prediction of the thermomechanical behavior of ablative materials. State-of-the-art TPS materials such as Phenolic Impregnated Carbon Ablator (PICA) have a proven flight record and demonstrate exceptional capabilities for handling extreme aerothermal heating conditions. The constant push for lightweight materials that are flexible in their design and performance, and hence allow for a wide range of mission profiles, has led NASA over the past years to develop its Heatshield for Extreme Entry Environment Technology (HEEET). HEEET is based primarily on a dual layer woven carbon fiber architecture and the technology has successfully been tested in arc-jet facilities. These recent developments have sparked interest in the accurate micro-scale modeling of composite weave architectures, to predict the structural response of macro-scale heatshields upon atmospheric entry. This effort can be extended to incorporate in-depth failure mechanics analyses as a result of local thermal gradients or high-velocity particle impact.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN73345 , Ablation Workshop; Sep 16, 2019 - Sep 17, 2019; Minneapolis, MN; United States
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  • 31
    Publication Date: 2020-01-17
    Description: Prediction and control of the onset of transition and the associated variation in aerothermodynamic parameters in high-speed flows is key to optimize the performance and design of Thermal Protection Systems (TPS) of next-generation aerospace vehicles [1]. Boundary Layer Transition (BLT) characteristics can influence the surface heating budget determining the TPS thickness and consequently its weight penalty. Ablative heatshields are designed to alleviate the high heat flux at the surface through pyrolysis of their polymeric matrix and subsequent fiber ablation [2]. Pyrolysis leads to out-gassing and non-uniform ablation lead to surface roughness, both of which are known to influence the transition process. An ablator impacts BLT through three main routes: gas injecting into the boundary layer from the wall, changing the surface heat transfer due to wall-flow chemical reactions, and modifying surface roughness [3]. In preparation to Mars 2020 mission post-flight analysis, the predictive transition capability has been initiated toward hard-coupling porous material response analysis and aerothermal environment calculation.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN73347 , Ablation Workshop; Sep 16, 2019 - Sep 17, 2019; Minneapolis, MN; United States
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  • 32
    Publication Date: 2020-01-17
    Description: The Mars Science Laboratory (MSL) Entry, Descent and Landing Instrumentation (MEDLI) collected in-flight data largely used by the ablation community to verify and validate physics-based models for the response of the Phenolic Impregnated Carbon Ablator (PICA) material [1-4]. MEDLI data were recently used to guide the development of NASAs high-fidelity material response models for PICA, implemented in the Porous material Analysis Toolbox based on OpenFOAM (PATO) software [5-6]. A follow-up instrumentation suite, MEDLI2, is planned for the upcoming Mars 2020 mission [7] after the large scientific impact of MEDLI. Recent analyses performed as part of MEDLI2 development draw the attention to significant effects of a protective coating to the aerothermal response of PICA. NuSil, a silicone-based overcoat sprayed onto the MSL heatshield as contamination control, is currently neglected in PICA ablation models. To mitigate the spread of phenolic dust from PICA, NuSil was applied to the entire MSL heatshield, including the MEDLI plugs. NuSil is a space grade designation of the siloxane copolymer, primarily used to protect against atomic oxygen erosion in the Low Earth Orbit environment. Ground testing of PICA-NuSil (PICA-N) models all exhibited surface temperature jumps of the order of 200 K due to oxide scale formation and subsequent NuSil burn-off. It is therefore critical to include a model for the aerothermal response of the coating in ongoing code development and validation efforts.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN73344 , Ablation Workshop; Sep 16, 2019 - Sep 17, 2019; Minneapolis, MN; United States
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  • 33
    Publication Date: 2019-07-13
    Description: NASA is investigating the potential of integrating acoustic liners into fan cases to reduce fan noise, while maintaining the fans aerodynamic performance. An experiment was conducted to quantify the aerodynamic impact of circumferentially grooved fan cases with integrated acoustic liners on a 1.5 pressure ratio turbofan rotor. In order to improve the ability to measure small performance changes, fan performance calculations were updated to include real gas effects including the effect of humidity. For all fan cases tested, the measured difference in fan isentropic efficiency was found to be less than the measurement repeatability for a torque-based efficiency calculation (approx. = 0.2%), however, an unintended tip clearance difference between configurations makes it difficult to determine if circumferentially grooved fan cases degraded fan performance. Fan exit turbulence measurements showed a 1.5% reduction in total turbulence intensity between hardwall and circumferentially grooved fan cases in the tip vortex region, which is attributed to a disruption in the formation of the tip leakage vortex. This decrease in fan exit turbulence could potentially lead to a 1-2dB reduction in broadband rotor-stator interaction noise. Reduced aerodynamic performance losses associated with over-the-rotor liners could enable further fan noise reduction.
    Keywords: Aerodynamics
    Type: GRC-E-DAA-TN62158 , ASME Turbo Expo 2019 Turbomachinery Technical Conference & Exposition; Jun 17, 2019 - Jun 21, 2019; Phoenix, AZ; United States
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  • 34
    Publication Date: 2019-07-13
    Description: A full-scale isolated proprotor test is currently being conducted in the USAF National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Foot Wind Tunnel at NASA Ames. The test article is a 3-bladed research rotor derived from the right-hand rotor of the AW609; this rotor was manufactured by Bell Helicopter under contract to NASA. In this paper, this research rotor is referred to as "699". The test, nearly completed, is an integral part of the initial checkout test of the newly developed Tiltrotor Test Rig (TTR), whose purpose is to test advanced, full-scale proprotors in the NFAC. Figure 1 shows the TTR/699 installed in the 40- by 80-Foot test section. The TTR rotor axis is horizontal and the rig rotates in yaw on the wind tunnel turntable for conversion (transition) and helicopter mode testing. To date, a substantial amount of wind tunnel test data has already been acquired. The completed operational conditions include hover, airplane mode (cruise, wind tunnel airspeed V=61 to 267 knots), and the helicopter and conversion conditions (with a comprehensive sweep of the TTR yaw angle ranging, to date, from 90-deg yaw helicopter mode to 30-deg yaw conversion mode, at varying airspeeds). This 699 proprotor performance and loads correlation study uses these newly acquired wind tunnel test data. This paper represents the third analytical study, coming after two earlier analytical studies on the TTR/699; that is, a 2018 paper on pre-test predictions of 699 performance and loads, Ref. 1, and an upcoming January 2019 paper on aeroelastic stability analysis of the TTR/699 installed in the 40- by 80-Foot Wind Tunnel, Ref. 2. Reference 8 will present an overview of the entire TTR/699 test program. For completeness, Ref. 3 addresses the development and initial testing of the TTR. Background information on the TTR effort at NASA Ames can be found at the Aeromechanics website: https://rotorcraft.arc.nasa.gov/Research/Facilities/ttr.html. To the authors' knowledge, the full-scale results presented in this paper are the first of their kind. A literature survey brought up several existing correlation studies, but these were either based on small-scale test data (for example, the studies performed by the University of Maryland) or full-scale aircraft flight test data (for example, flight tests conducted by Bell Helicopter). Separately, the 2009 NASA study involving the JVX rotor is relevant (see Ref.4). The JVX is closely similar to the 699 in size and aerodynamics, and is accordingly a good reference for performance calculations. In Ref. 1 (as mentioned above), pre-test reality checks of the current analytical model were made by comparing JVX and 699 predictions in hover and forward flight (airplane mode).
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN61869 , Vertical Flight Society''s Annual Forum and Technology Display; May 13, 2019 - May 16, 2019; Philadelphia, PA; United States
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  • 35
    Publication Date: 2019-07-13
    Description: Two full seven-equation turbulence models have been implemented into the FUN3D code to evaluate their ability to improve the computation of challenging flows encountered in aerospace propulsion, including mixing flows. These models are the SSG/LRR and Wilcox full second-moment Reynolds stress models. They solve equations for the six components of the Reynolds stress and a seventh equation for the mixing length. Two standard eddy viscosity models are also evaluated for comparison, the Spalart-Allmaras (SA) one-equation model and the Menter Shear Stress Transport (SST-V) two-equation turbulence model. Flow through an axisymmetric reference nozzle is examined at three flow conditions: subsonic unheated, subsonic heated, and near sonic unheated. Centerline profiles of velocity and turbulent kinetic energy and radial profiles of velocity, turbulent kinetic energy and turbulent stresses are examined. characteristics, no significant changes in the downstream flow behavior compared to the baseline case are observed. Furthermore, the total power consumed by the fans for different incoming flow conditions also remain marginally the same. It is hoped that the results, albeit obtained at very low speeds. would serve as a database for this technologically interesting flow field that has not been explored adequately before.
    Keywords: Aerodynamics
    Type: GRC-E-DAA-TN63722 , AIAA Science and Technology Forum (AIAA SciTech); Jan 07, 2019 - Jan 11, 2019; San Diego, CA; United States
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  • 36
    Publication Date: 2019-09-13
    Description: Heated ethane (C2H6) has been proposed as an alternative to inert gases for use as a motive fluid in the experimental simulation of rocket exhaust plumes. By adjusting stagnation temperature, the isentropic exponent of ethane can be tuned to approximate those produced by common rocket propellants including hydrogen, hypergols, alcohols, and hydrocarbons. As a result, ethane can be made to follow a nozzle expansion process which is nearly identical to realistic rocket engine flow fields. Additionally, its high auto-ignition temperature and resistance to condensation enable the testing of expansion ratios much larger than conventional inertgas testing. NASA SSC has performed quasi-one-dimensional analyses using the Chemical Equilibrium with Applications (CEA) code as a preliminary means to compare flow fields produced by non-reacting ethane to those of reacting combustion products. A LO2/LH2 rocket engine operating at a chamber pressure of 5.0 MPa and a mixture ratio of 6.1 was used as an example case to demonstrate ethanes efficacy as a simulant. Errors for key similarity parameters were compared to legacy cold-flow test methods. Additional errors induced by machining tolerances and chemical impurities were also examined. Results suggest that at a 3% geometric scale and ~500 K ethane stagnation temperature, an error of less than 2.5% throughout the flow field is realistically achievable along the dimensions of Mach number, Reynolds number, pressure ratio, and isentropic exponent. The development of an experimental test bed for validation of this configuration is currently underway.
    Keywords: Aerodynamics
    Type: NASA/TM-2019-220446 , SREP-2220-0003
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  • 37
    Publication Date: 2019-10-03
    Description: A 13.49-percent-thick, slotted, natural-laminar-flow airfoil, the S207, for a transport aircraft has been designed and analyzed theoretically. The two primary objectives of high maximum lift, insensitive to roughness, and low profile drag have been achieved. The drag-divergence Mach number is predicted to be greater than 0.70.
    Keywords: Aerodynamics
    Type: NF1676L-34040 , NASA-CR-2019-220403
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  • 38
    Publication Date: 2019-08-09
    Description: NASA's ASPIRE (Advanced Supersonic Parachute Inflation Research Experiments) project was launched to investigate the supersonic deployment, inflation and aerodynamics of full-scale disk-gap-band (DGB) parachutes. Three flight tests (October 2017, March 2018 and July 2018) deployed and examined parachutes meant for the upcoming "Mars 2020" mission. Mars-relevant conditions were achieved by performing the tests at high altitudes over Earth on a sounding rocket platform, with the parachute deploying behind a slender body (roughly 1/6-th the diameter of the capsule that will use this parachute for descent at Mars). All three tests were successful and delivered valuable data and imagery on parachute deployment and performance. CFD simulations were used in designing the flight test, interpreting the flight data, and extrapolating the results obtained during the flight test to predict parachute behavior at Mars behind a blunt capsule. This presentation will provide a brief overview of the test program and flight test data, with emphasis on differences in parachute performance due to the leading body geometry.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN71648 , Annual Meeting of the APS Division of Fluid Dynamics; Nov 23, 2019 - Nov 26, 2019; Seattle, WA; United States
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  • 39
    Publication Date: 2019-08-07
    Description: Aerodynamic assessment of icing effects on swept wings is an important component of a larger effort to improve three-dimensional icing simulation capabilities. An understanding of ice-shape geometric fidelity and Reynolds and Mach number effects on iced-wing aerodynamics is needed to guide the development and validation of ice-accretion simulation tools. To this end, wind-tunnel testing was carried out for 8.9% and 13.3% scale semispan wing models based upon the Common Research Model airplane configuration. Various levels of geometric fidelity of an artificial ice shape representing a realistic glaze-ice accretion on a swept wing were investigated. The highest fidelity artificial ice shape reproduced all of the three-dimensional features associated with the glaze ice accretion. The lowest fidelity artificial ice shapes were simple, spanwise-varying horn ice geometries intended to represent the maximum ice thickness on the wing upper surface. The results presented in this paper show that changes in Reynolds and Mach number have only a small effect on the iced-wing aerodynamics relative to the clean-wing configuration. Furthermore, the addition of grit roughness to some lower-fidelity artificial ice shapes resulted in favorable lift and pitching moment comparisons to the wing with the highest fidelity artificial ice shape. For the wing with simple horn ice shapes, the dependence of maximum lift coefficient on horn height and angle are generally consistent with the trends observed for similar experiments conducted on iced airfoils in past research. In terms of usable lift however, the horn height did have a significant effect even for lower horn angles. This could be an important finding since usable lift may be more indicative of the impending iced-swept wing stall and need for additional pitch control than maximum lift coefficient.
    Keywords: Aerodynamics
    Type: GRC-E-DAA-TN66891 , International Conference on Icing of Aircraft, Engines, and Structures; Jun 17, 2019 - Jun 21, 2019; Minneapolic, MN; United States
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  • 40
    Publication Date: 2019-09-13
    Description: Swept wings and control surfaces are common elements of modern aircraft, and it has been shown both experimentally and theoretically that laminar-to-turbulent transition of the three-dimensional boundary layer that develops over them is highly sensitive to surface roughness. Numerous studies have been conducted on the effect of discrete roughness elements or distributed roughness elements on swept flow transition, however so far limited computational effort has been dedicated to the study of transition over swept wings with randomly distributed micron-sized roughness. In the present work, we set up to reproduce the extensive experimental data base generated by Dagenhart et al for the infinite swept wing NLF(2)-0415. To this purpose, we perform scale-resolving simulations of flow transition over smooth and rough surfaces using a high-order space-time spectral-element Discontinuous-Galerkin solver. Different types of surface roughnesses are implemented by elastically deforming the original mesh. The study shows that the experimental results cannot be accounted for by a perfectly smooth wing and reveals a strong sensitivity of the transition process to the representation of the surface roughness. The crossflow patterns and transition location approach those measured for some of the surface profiles, however a correlation between the wavenumber spectrum of the surface, grid resolution and boundary layer stability is yet to be established.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN69562 , AIAA AVIATION Forum 2019; Jun 17, 2019 - Jun 21, 2019; Dallas, TX; United States
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  • 41
    Publication Date: 2021-05-19
    Description: Aquaculture activity is restricted mainly to rainbow trout in cold waters and carps in warm waters in inland waters of Iran as well as Fars Province. Probably for this reason saline waters of south and southeast Fars have not been used for aquaculture. These rivers are ecosystems with a diverse biota, it is predictable that can be found some there endemic aquatic organisms with a potential for aquaculture. Finding a suitable organism can help increase wise use of this natural resource, and local production and recruitment. However, it is highly needed to investigate various environmental elements prior to any use to obtain an estimation of the environmental consequences, parallel to finding usage potentials. In This study, we investigated Dehram saline river in south of Fars Province. Hydrological and physiographical properties, chemical composition of the river, and aquatic populations were sampled and measured monthly in 3 stations in one year. Salinity, electrical conductivity, and total dissolved solids increased from station 1 to 3, reaching from 6.6 g/L, 14.3 g/L, and 12800 µs/cm to 13.5 g/L, 17.7 g/L, and 16500 µs/cm, respectively. Dissolved oxygen and oxygen saturation were higher in station 3, and in autumn and winter. Nitrite showed lowest values in winter (0.006 mg/L) and highest values in spring (0.013 mg/L). Nitrate showed the lowest concentration in station 3 (0.43 mg/L), but no differences were seen among seasons. Ammonium showed no differences among stations or seasons. Phosphate levels in station 1 and 3 were 0.13 mg/L‌to 0.17 mg/L, with the highest level (0.29 mg/L) seen in the spring. Five species of fishes were identified in the river, which all were widely favored by local people. Some of these have been categorized as edible in previous studies, others as ornamental. On the other hand, intensive growth of an algal species throughout the river demonstrates a potential for algal cultivation. Significant role of algae in production of food for both man and livestock is now well recognized in aquaculture industry.
    Description: Iranian Fisheries Science Research Institute
    Description: Published
    Keywords: Ecology ; Dehram River ; Limnology ; Saline water ; Physico-chemical parameters ; Aquaculture
    Repository Name: AquaDocs
    Type: Report , Refereed
    Format: 62pp.
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  • 42
    Publication Date: 2021-05-19
    Description: Limnological factors of brackish water pounds of the rainbow trout, Onchorhynchus mykiss were studied at Bafgh region in Yazd province. Physicochemical factors, phytoplankton, zooplankton and benthic populations of pools, supply and drainage channels from different farms were studied in aquaculture cycle in 2002 and 2003. Means were compared using Tukey HSD and t tests. Meanings of factors in 2002 and 2003 were respectively: and 9.3 0.2ppt; dissolved oxygen 7.9 0.2mg/l water temperature 13.8 0.3°c and 14.9 0.6°c; salinity 12.3 0.2ppt and 7.2 0.1mg/l; pH between 7.8 to 9.2 and 8.1 to 9.5; depth of hyalinity 0.85 0.1m and 1.1 0.1m; ammonium 0.1-0.5mg/l; and nitrate 1.8-21mg/l. Main phytoplankton were diatoms specially Chaetoceros, and Cyanophyta. Rotifera were the dominant zooplankton. Benthic fauna mainly included immature Chironomids. Final mean lengths were between 24.7cm to 31.5cm, mean weights between 11179.9gr to 434.6gr. FCR between 1.16 to 1.6; DGR between 1.04gr/day to 3.03gr/day; production 0.03kg/m2 to 0.84 kg/m2. Supply channels had the optimum limnological condition for trout aquaculture. Limnological factors were often not significantly different between pools and drainage channels. Saeeid and Rangin-Kaman farms were the most successful farms.
    Description: Iranian Fisheries Science Research Institute
    Description: Published
    Keywords: Limnology ; Brackish water ; Onchorhynchus mykiss ; Rainbow trout ; Phytoplankton ; Zooplankton ; Chaetoceros ; Survey ; Pond culture
    Repository Name: AquaDocs
    Type: Report , Refereed
    Format: 175pp.
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  • 43
    Publication Date: 2021-05-19
    Description: Gahar-roud is in 18 kilometer far from Doroud city from East of lorestan province . This river orginated from internal part of Oshteran-kouh mountain altitude and Gahar-Lake . Survey on Gahar roud Limnology began from the end of 2001 year and during the 18 month achived, at first on the length of 20 kilometer five station of sampling was selected and biological, physical and chemical character of this river was surveyed this river in all path of it feeding with large and small spring, little rivers and water of icehouse. The amount water of this river is different and maximum water is about 21 m/s in April month. Specifity of this river is be enough the temperature of water for fish. Minimum in the Jan is about 3 centigrad deegree and maximum is July and Aug about 24 centigrade deegree phis between 6.5-8.2 and is few basic . solauble oxigen is enough and is between 8.5-13 mg/lit.during the year.This river is very bright and haven t the source of polution and during the path of river and be enaugh the dosage of mineral in water are the important physical and chemical character of this river. Gahar-roud is not biological hardness quality. About 31 genus and species from 5 family of phytoplangton and 42 genus from 26 family from the order of insects, molusca, worms and crustacea and 9 species from 12 family from the side aquatic. Plants was collected and recognized. Based on ecological potential of this region, because Gahar- roud river is poor for food material and classified in oligotroph river and hasn t high biological value. And also have a few population and in fact haven t any population and based on the safer system belong to the quatiy elass of oligotroph and amount of water, regular circulation of water with microclima condition rate of natural resource land around river, having program for culture of cold water fish is important but it is better that use from culture of fish, be regulated key word limnology, Gahar-roud, river plangton, bentoz, fish.
    Description: Iranian Fisheries Science Research Institute
    Description: Published
    Keywords: Limnology ; Fish ; Bentos ; Plankton
    Repository Name: AquaDocs
    Type: Report , Refereed
    Format: 84pp.
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  • 44
    Publication Date: 2021-05-19
    Description: Dorudzan reservoir is the main provider of drinking water for the capital Shiraz, as well as the most significant storage of water in the Kor river course. In addition of eroded material, a load of agricultural outputs from upstream are moved to the lake every year. Main physiographic, physical and chemical, and biological components of the lake were monthly sampled and analysed from Novembr 2010 to October 2011. Mean annual measures were water temperature 16.7 ˚C (SD=5.8), pH 8.2 (SD=0.3), dissolved oxygen 7.6 mg/l (SD=1.7), ammonium 0.05 mg/l (SD=0.08), nitrite 0.004 mg/l (SD=0.003), nitrate 0.44 mg/l (SD=0.44), phosphate 0.20 mg/l (SD=0.23), silicate 7.00 mg/l (SD=2.49), BOD 2.29 mg/l (SD=1.00), COD 24.49 mg/l (SD=15.47), electrical conductivity 720 µs/cm (SD=219), total dissolved solids 457.67 mg/l (SD=138.72), calcium hardness 61.30 mg/l (SD=13.45), and magnesium hardness 20.23 mg/l (SD=9.18). Living parts of the ecosystem including species of fish, orders and families of benthic invertebrates, zooplanktons, and phytoplanktons were investigated. Benthic macroinvertebrates included various nematodes, oligochates, gastropods, bivalves, and insect larvae (dipteral and coleptera), most abundant of which were dipteran larvae, mollusks, and nematodes. Dominant zooplankton was Bosmina, with Daphnia and Cyclops in next ranks. Among rotifer, Trichocera was more abundant than Lecanae. Bosmina showed the most abundance in summer and Daphnia in spring. Trichocera had its most abundance in summer as well, while Lecanae was more abundant in Automn and winter. A total of 41 algal genera from 8 divisions were found. Dominant phytoplankton division was Chlorophyta, with genus Pediastrum. Dominant microalga was Dynobrion (Chrysophyta) in Spring, Cylindrospermum and (both Cyanophyta) in Summer, Microsystis in Automn, and Ceratium (Dynophyta) in Winter. Ceratium were found in all seasons in most of the sampling sites, and showed highest abundance compared to other genera of its division. Dominant genus of diatoms was Fragilaria. Fish populations include Alburnus mossulensis, Capoeta aculeate, Capoeta damascina, Carasobarbus luteus, Carassius gibelio, Cyprinus carpio, and Hypophthalmichthys molitrix. Main different parts of the lake showed quite different composition of fish species. An epidemic occurance of the crustacean ectoparasite Lernea cyprinacea among most fishes was another important finding. These findings will serve as a base for future studies as a set point of drought situations.
    Description: Iranian Fisheries Science Research Institute
    Description: Published
    Keywords: Limnology ; Reservoir ; Plankton ; Fish ; Alburnus mossulensis ; Capoeta aculeate ; Capoeta damascina ; Carasobarbus luteus ; Carassius gibelio ; Cyprinus carpio ; Hypophthalmichthys molitrix
    Repository Name: AquaDocs
    Type: Report , Refereed
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  • 45
    Publication Date: 2021-05-19
    Description: Abbarik River is an important river in Kerman. Study of limnology of Abbarik River for aquatics & culture was started from Mehr 1381 to Day 1382. Base of this study was physical- chemical and Biological factors. In this research 3 stations was appointed. PH- oxygen- salinity- Ca- Mg- Na- K- Cl and was majored and bentetic- fish was recognized. This study was achievement in 4 season and twice in month. Bentosis recognize was Ephemeroptera- Diptera- Anisoptera- Cleoptera Trichoptera Fishes recognize was Capoeta damascina- Nemachilus sargadensis- Cyprinion watsoni.
    Description: Iranian Fisheries Science Research Institute
    Description: Published
    Keywords: Physical ; Chemical ; Biological ; Limnology ; Bentosis fish ; Aquatic ; Culture ; PH ; Salinity ; Oxygen ; Ephemeroptera ; Diptera ; Anisoptera ; Cleoptera Trichoptera ; Capoeta damascina ; Nemachilus sargadensis ; Cyprinion watsoni
    Repository Name: AquaDocs
    Type: Report , Refereed
    Format: 44pp.
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  • 46
    Publication Date: 2021-05-19
    Description: The shiroud river is one of the important riveres in point of view of fisheries matter which located in western part of Mazndran provience. The project of Limnological study have done in this river during June/ 2002 - Jun / 2003 for more and better underestanding situations, of biological and nonbiological parameters like as phytoplankton, zooplonkton, benthoses, Ichthyology, physico - chemical and pesticides of water. - Physico- chemical paramaters by ASTM methods and spectrophotometer and pestisides by US-EPA- method and GC- ECD determined. The procedures of detemination of zooplanklon and phytoplankton by manuals of Newell, 1970 and Sorina, 1974 idantify and determined respectinely. In Ichthyology, by manual procedure Berg, 1949 identifind. The sampeling have been in four stations during four seasons and result as follow: - The maximum and minimum amount of pH were in station 5 (spring) and Station no. 4 (summer) 8.19 and 7.75 respectively. - The maximum and minimum temperature of water were in station no. 8 (summer) and stations no. 2 (winter) 27.7 c and 7.7c respectively. The fluctuatcions of nutroients datas of this study and other studies done during last 5 years showed, there were not big diffrence between them but also these datas were very close to each other. - The maximum residues of pesticides for heptachlor Epoxide (Winter ) and Lindane (spring) betweenresidues of sixteen pesticdes were 79.4 and 3.7 ppb respectively. - The maximum and minimum amount of phytoplankton biomass belong to chrysophyta during four seasons were 2572 through 1081 mg/m3. - The percentage of zooplankton belong to Rotatoria , Protozoa , Copepoda , Cladocera and Zoobenthos were in 41 , 31 , 12 , 4 and 12 percent recpectively. - The maximum aboundant percentage of bentheic animals belong to Diptera with 42 percent and were dominate whole sampeling stations . - The abundence of fishes in this river belong to two species of C. capoeta gracilis and Al. bipunctatus were catched in four seasons at eight stations . The percentages of C. capoeta gracilis species were catched in four seasons at eight stations during winter, summer , spring and fall with 96 ,81 , 73 and 67 percent respectively. The percentages of Al. bipunctatus species were catched in four seasons at eight stations during winter, summer , spring and fall with 47 , 44 , 43 and 40 percent respectively.
    Description: Iranian Fisheries Science Research Institute
    Description: Published
    Keywords: Pesticdes residues ; Phytoplankton ; Zooplankton ; Riverine fishes ; Nutrients ; Limnology ; ASTM ; Rotatoria ; Protozoa ; Copepoda ; Cladocera ; Zoobenthos
    Repository Name: AquaDocs
    Type: Report , Refereed
    Format: 127pp.
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  • 47
    facet.materialart.
    Unknown
    Woods Hole Oceanographic Institution
    Publication Date: 2022-05-26
    Description: This is a report describing activities associated with the Matamek program in 1977. Research was conducted on biological, chemical and physical factors related to salmonid production in Matamek River and Matamek Lake. Canadian universities, the Quebec government and Woods Hole Oceanographic Institution cooperated in the program.
    Description: Supported by Woods Hole Oceanographic Institution and the Department of Tourism, Fish and Game of the Province of Quebec.
    Keywords: Ecology ; Limnology
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 48
    Publication Date: 2018-03-13
    Description: Author(s): Tianxing Ma, Lufeng Zhang, Chia-Chen Chang, Hsiang-Hsuan Hung, and Richard T. Scalettar Using exact quantum Monte Carlo calculations, we examine the interplay between localization of electronic states driven by many-body correlations and that by randomness in a two-dimensional system featuring linearly vanishing density of states at the Fermi level. A novel disorder-induced nonmagnetic... [Phys. Rev. Lett. 120, 116601] Published Mon Mar 12, 2018
    Keywords: Condensed Matter: Electronic Properties, etc.
    Print ISSN: 0031-9007
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  • 49
    Publication Date: 2018-07-26
    Description: Author(s): M. Klaas, E. Schlottmann, H. Flayac, F. P. Laussy, F. Gericke, M. Schmidt, M. v. Helversen, J. Beyer, S. Brodbeck, H. Suchomel, S. Höfling, S. Reitzenstein, and C. Schneider By counting the photons emitted from a microcavity, researchers shed light on the nature of an exotic condensate of quasiparticles contained in the cavity. [Phys. Rev. Lett. 121, 047401] Published Wed Jul 25, 2018
    Keywords: Condensed Matter: Electronic Properties, etc.
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  • 50
    Publication Date: 2018-07-27
    Description: Author(s): J. P. Carbotte, E. J. Nicol, and T. Timusk We present a new technique for measuring the critical temperature T c in the high pressure, high T c electron-phonon-driven superconducting hydrides. This technique does not require connecting leads to the sample. In the region of the absorption spectrum above the sum of the optical gap and maximum ph... [Phys. Rev. Lett. 121, 047002] Published Thu Jul 26, 2018
    Keywords: Condensed Matter: Electronic Properties, etc.
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  • 51
    Publication Date: 2018-07-25
    Description: Author(s): Wen-Yu He, Xiao Yan Xu, Gang Chen, K. T. Law, and Patrick A. Lee 1 T − Ta S 2 is a cluster Mott insulator on the triangular lattice with 13 Ta atoms forming a star of David cluster as the unit cell. We derive a two-dimensional X X Z spin- 1 / 2 model with a four-spin ring exchange term to describe the effective low energy physics of a monolayer 1 T − Ta S 2 , where the effective... [Phys. Rev. Lett. 121, 046401] Published Tue Jul 24, 2018
    Keywords: Condensed Matter: Electronic Properties, etc.
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  • 52
    Publication Date: 2018-08-02
    Description: Author(s): Koshi Kurashima, Tadashi Adachi, Kensuke M. Suzuki, Yasushi Fukunaga, Takayuki Kawamata, Takashi Noji, Hitoshi Miyasaka, Isao Watanabe, Masanori Miyazaki, Akihiro Koda, Ryosuke Kadono, and Yoji Koike We demonstrate the presence of ferromagnetic (FM) fluctuations in the superconducting and nonsuperconducting heavily overdoped regimes of high-temperature superconducting copper oxides, using ( Bi , Pb ) 2 Sr 2 CuO 6 + δ (Bi-2201) single crystals. Magnetization curves exhibit a tendency to be saturated in high... [Phys. Rev. Lett. 121, 057002] Published Wed Aug 01, 2018
    Keywords: Condensed Matter: Electronic Properties, etc.
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  • 53
    Publication Date: 2018-08-04
    Description: Author(s): Konstantin Klyukin, L. L. Tao, Evgeny Y. Tsymbal, and Vitaly Alexandrov Recent experimental results have demonstrated ferroelectricity in thin films of SrTiO 3 induced by antisite Ti Sr defects. This opens a possibility to use SrTiO 3 as a barrier layer in ferroelectric tunnel junctions (FTJs)—emerging electronic devices promising for applications in nanoelectronics. Here ... [Phys. Rev. Lett. 121, 056601] Published Fri Aug 03, 2018
    Keywords: Condensed Matter: Electronic Properties, etc.
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  • 54
    Publication Date: 2018-08-08
    Description: Author(s): Yafis Barlas The Landau bands of mirror symmetric 2D Dirac semimetals (e.g., odd layers of A B A graphene) can be identified by their parity with respect to mirror symmetry. This symmetry facilitates a new class of counterpropagating Hall states. We predict the presence of a Laughlin-like correlated liquid state, ... [Phys. Rev. Lett. 121, 066602] Published Tue Aug 07, 2018
    Keywords: Condensed Matter: Electronic Properties, etc.
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  • 55
    Publication Date: 2018-08-08
    Description: Author(s): Peter Cristofolini, Z. Hatzopoulos, Pavlos G. Savvidis, and Jeremy J. Baumberg Exciton polaritons in high quality semiconductor microcavities can travel long macroscopic distances ( 〉 100     μ m ) due to their ultralight effective mass. The polaritons are repelled from optically pumped exciton reservoirs where they are formed; however, their spatial dynamics is not as expected fo... [Phys. Rev. Lett. 121, 067401] Published Tue Aug 07, 2018
    Keywords: Condensed Matter: Electronic Properties, etc.
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  • 56
    Publication Date: 2018-06-12
    Description: Author(s): Yao Wang, Edwin W. Huang, Brian Moritz, and Thomas P. Devereaux Understanding spin excitations and their connection to unconventional superconductivity have remained central issues since the discovery of cuprates. Direct measurement of the dynamical spin structure factor in the parent compounds can provide key information on important interactions relevant in th... [Phys. Rev. Lett. 120, 246401] Published Mon Jun 11, 2018
    Keywords: Condensed Matter: Electronic Properties, etc.
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  • 57
    Publication Date: 2018-06-06
    Description: Author(s): Fengmiao Li and George A. Sawatzky The recent observation of replica bands in single-layer FeSe / SrTiO 3 by angle-resolved photoemission spectroscopy (ARPES) has triggered intense discussions concerning the potential influence of the FeSe electrons coupling with substrate phonons on the superconducting transition temperature. Here we p... [Phys. Rev. Lett. 120, 237001] Published Tue Jun 05, 2018
    Keywords: Condensed Matter: Electronic Properties, etc.
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  • 58
    Publication Date: 2018-06-16
    Description: Author(s): Toshikaze Kariyado, Takahiro Morimoto, and Yasuhiro Hatsugai We show that the Z N Berry phase (Berry phase quantized into 2 π / N ) provides a useful tool to characterize symmetry protected topological phases with correlation that can be directly computed through numerics of a relatively small system size. The Z N Berry phase is defined in a N − 1 -dimensional paramet... [Phys. Rev. Lett. 120, 247202] Published Fri Jun 15, 2018
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  • 59
    Publication Date: 2018-06-28
    Description: Author(s): Jennifer Cano, Barry Bradlyn, Zhijun Wang, L. Elcoro, M. G. Vergniory, C. Felser, M. I. Aroyo, and B. Andrei Bernevig A new topological invariant—a movable but unremovable Dirac cone—is identified by considering symmorphic and non-symmorphic space groups of gapped elementary band representations. [Phys. Rev. Lett. 120, 266401] Published Wed Jun 27, 2018
    Keywords: Condensed Matter: Electronic Properties, etc.
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  • 60
    Publication Date: 2018-06-29
    Description: Author(s): Marija Todorić, Dario Jukić, Danko Radić, Marin Soljačić, and Hrvoje Buljan Composites formed from charged particles and magnetic flux tubes, proposed by Wilczek, are one model for anyons—particles obeying fractional statistics. Here we propose a scheme for realizing charged flux tubes, in which a charged object with an intrinsic magnetic dipole moment is placed between two... [Phys. Rev. Lett. 120, 267201] Published Thu Jun 28, 2018
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  • 61
    Publication Date: 2018-11-29
    Description: Author(s): Dongfang Li, Sinan Karaveli, Sébastien Cueff, Wenhao Li, and Rashid Zia We experimentally demonstrate that the radiative decay rate of a quantum emitter is determined by the combined electric and magnetic local density of optical states (LDOS). A Drexhage-style experiment was performed for two distinct quantum emitters, divalent nickel ions in magnesium oxide and trival... [Phys. Rev. Lett. 121, 227403] Published Wed Nov 28, 2018
    Keywords: Condensed Matter: Electronic Properties, etc.
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  • 62
    Publication Date: 2018-12-01
    Description: Author(s): Shuyi Liu, Martin Wolf, and Takashi Kumagai We report plasmon-assisted resonant electron tunneling from a Ag or Au tip to field emission resonances (FERs) of a Ag(111) surface induced by cw laser excitation of a scanning tunneling microscope (STM) junction at visible wavelengths. As a hallmark of the plasmon-assisted resonant tunneling, we ob... [Phys. Rev. Lett. 121, 226802] Published Fri Nov 30, 2018
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  • 63
    Publication Date: 2018-12-04
    Description: Author(s): Jeffrey G. Rau, Paul A. McClarty, and Roderich Moessner In systems with competing interactions, continuous degeneracies can appear which are accidental, in that they are not related to any symmetry of the Hamiltonian. Accordingly, the pseudo-Goldstone modes associated with these degeneracies are also unprotected. Indeed, through a process known as “order... [Phys. Rev. Lett. 121, 237201] Published Mon Dec 03, 2018
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  • 64
    Publication Date: 2018-12-13
    Description: Author(s): T. Mittiga, S. Hsieh, C. Zu, B. Kobrin, F. Machado, P. Bhattacharyya, N. Z. Rui, A. Jarmola, S. Choi, D. Budker, and N. Y. Yao Nitrogen-vacancy centers in diamond are found to be more affected by local charge than expected, which has implications for the use of the defects as quantum sensors. [Phys. Rev. Lett. 121, 246402] Published Wed Dec 12, 2018
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  • 65
    Publication Date: 2018-12-14
    Description: Author(s): D. Blosser, V. K. Bhartiya, D. J. Voneshen, and A. Zheludev By means of inelastic neutron scattering we investigate finite temperature dynamics in the quantum spin ladder compound ( C 5 H 12 N ) 2 CuBr 4 (BPCB) near the magnetic field induced quantum critical point with dynamical exponent z = 2 . We observe universal finite-temperature scaling of the transverse local dy... [Phys. Rev. Lett. 121, 247201] Published Thu Dec 13, 2018
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  • 66
    Publication Date: 2018-12-14
    Description: Author(s): Riccardo Pisoni, Andor Kormányos, Matthew Brooks, Zijin Lei, Patrick Back, Marius Eich, Hiske Overweg, Yongjin Lee, Peter Rickhaus, Kenji Watanabe, Takashi Taniguchi, Atac Imamoglu, Guido Burkard, Thomas Ihn, and Klaus Ensslin The strong spin-orbit coupling and the broken inversion symmetry in monolayer transition metal dichalcogenides results in spin-valley coupled band structures. Such a band structure leads to novel applications in the fields of electronics and optoelectronics. Density functional theory calculations as... [Phys. Rev. Lett. 121, 247701] Published Thu Dec 13, 2018
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  • 67
    Publication Date: 2018-12-15
    Description: Author(s): Jorge I. Facio, Dmitri Efremov, Klaus Koepernik, Jhih-Shih You, Inti Sodemann, and Jeroen van den Brink Transitions between topologically distinct electronic states have been predicted in different classes of materials and observed in some. A major goal is the identification of measurable properties that directly expose the topological nature of such transitions. Here, we focus on the giant Rashba mat... [Phys. Rev. Lett. 121, 246403] Published Fri Dec 14, 2018
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  • 68
    Publication Date: 2018-08-09
    Description: Author(s): Zhiwei Zhang, R. Sutarto, F. He, F. C. Chou, L. Udby, S. L. Holm, Z. H. Zhu, W. A. Hines, J. I. Budnick, and B. O. Wells In this Letter, we report a resonant x-ray scattering measurement of stripelike charge order in the 1/8th doped component of electronically phase-separated, orthorhombic La 2 CuO 4 + y . This observation is coupled to the absence of any resonant (001) peak, which at different resonant energies has been id... [Phys. Rev. Lett. 121, 067602] Published Wed Aug 08, 2018
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  • 69
    facet.materialart.
    Unknown
    American Physical Society (APS)
    Publication Date: 2018-08-09
    Description: Author(s): Ming Xie and A. H. MacDonald The ground state of two-dimensional (2D) electron systems with equal low densities of electrons and holes in nearby layers is an exciton fluid. We show that a reservoir for excitons can be established by contacting the two layers separately and maintaining the chemical potential difference at a valu... [Phys. Rev. Lett. 121, 067702] Published Wed Aug 08, 2018
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  • 70
    Publication Date: 2018-08-09
    Description: Author(s): Sandro Sorella, Kazuhiro Seki, Oleg O. Brovko, Tomonori Shirakawa, Shohei Miyakoshi, Seiji Yunoki, and Erio Tosatti The phase diagram of isotropically expanded graphene cannot be correctly predicted by ignoring either electron correlations, or mobile carbons, or the effect of applied stress, as was done so far. We calculate the ground state enthalpy (not just energy) of strained graphene by an accurate off-lattic... [Phys. Rev. Lett. 121, 066402] Published Wed Aug 08, 2018
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  • 71
    Publication Date: 2018-08-09
    Description: Author(s): Xingye Lu, Daniel D. Scherer, David W. Tam, Wenliang Zhang, Rui Zhang, Huiqian Luo, Leland W. Harriger, H. C. Walker, D. T. Adroja, Brian M. Andersen, and Pengcheng Dai Understanding magnetic interactions in the parent compounds of high-temperature superconductors forms the basis for determining their role for the mechanism of superconductivity. For parent compounds of iron pnictide superconductors such as A Fe 2 As 2 ( A = Ba , Ca, Sr), although spin excitations have been... [Phys. Rev. Lett. 121, 067002] Published Wed Aug 08, 2018
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  • 72
    Publication Date: 2018-08-15
    Description: Author(s): Daniel Yates, Yonah Lemonik, and Aditi Mitra Periodically driven Kitaev chains show a rich phase diagram as the amplitude and frequency of the drive is varied, with topological phase transitions separating regions with different number of Majorana zero and π modes. We explore whether the critical point separating different phases of the period... [Phys. Rev. Lett. 121, 076802] Published Tue Aug 14, 2018
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  • 73
    Publication Date: 2018-08-15
    Description: Author(s): L. Petit, J. M. Boter, H. G. J. Eenink, G. Droulers, M. L. V. Tagliaferri, R. Li, D. P. Franke, K. J. Singh, J. S. Clarke, R. N. Schouten, V. V. Dobrovitski, L. M. K. Vandersypen, and M. Veldhorst We investigate the magnetic field and temperature dependence of the single-electron spin lifetime in silicon quantum dots and find a lifetime of 2.8 ms at a temperature of 1.1 K. We develop a model based on spin-valley mixing and find that Johnson noise and two-phonon processes limit relaxation at l... [Phys. Rev. Lett. 121, 076801] Published Tue Aug 14, 2018
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  • 74
    Publication Date: 2018-08-16
    Description: Author(s): S. V. Mironov, D. Yu. Vodolazov, Y. Yerin, A. V. Samokhvalov, A. S. Mel’nikov, and A. Buzdin We show that a wide class of layered superconductor-ferromagnet ( S / F ) hybrids demonstrates the emergence of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase well below the superconducting transition temperature. By decreasing the temperature, one can switch the system from uniform to the FFLO state... [Phys. Rev. Lett. 121, 077002] Published Wed Aug 15, 2018
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  • 75
    Publication Date: 2018-08-16
    Description: Author(s): Alexander J. E. Kreil, Dmytro A. Bozhko, Halyna Yu. Musiienko-Shmarova, Vitaliy I. Vasyuchka, Victor S. L’vov, Anna Pomyalov, Burkard Hillebrands, and Alexander A. Serga Evolution of an overpopulated gas of magnons to a Bose-Einstein condensate and excitation of a magnon supercurrent, propelled by a phase gradient in the condensate wave function, can be observed at room temperature by means of the Brillouin light scattering spectroscopy in an yttrium iron garnet mat... [Phys. Rev. Lett. 121, 077203] Published Wed Aug 15, 2018
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  • 76
    Publication Date: 2018-08-18
    Description: Author(s): R. P. Day, G. Levy, M. Michiardi, B. Zwartsenberg, M. Zonno, F. Ji, E. Razzoli, F. Boschini, S. Chi, R. Liang, P. K. Das, I. Vobornik, J. Fujii, W. N. Hardy, D. A. Bonn, I. S. Elfimov, and A. Damascelli We report on the influence of spin-orbit coupling (SOC) in Fe-based superconductors via application of circularly polarized spin and angle-resolved photoemission spectroscopy. We combine this technique in representative members of both the Fe-pnictides (LiFeAs) and Fe-chalcogenides (FeSe) with tight... [Phys. Rev. Lett. 121, 076401] Published Fri Aug 17, 2018
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  • 77
    facet.materialart.
    Unknown
    American Physical Society (APS)
    Publication Date: 2018-08-18
    Description: Author(s): M. Horio et al. We present a soft x-ray angle-resolved photoemission spectroscopy study of overdoped high-temperature superconductors. In-plane and out-of-plane components of the Fermi surface are mapped by varying the photoemission angle and the incident photon energy. No k z dispersion is observed along the nodal ... [Phys. Rev. Lett. 121, 077004] Published Fri Aug 17, 2018
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  • 78
    Publication Date: 2018-08-18
    Description: Author(s): Y. Yamane, T. Onimaru, K. Wakiya, K. T. Matsumoto, K. Umeo, and T. Takabatake Electrical resistivity ρ ( T ) and specific heat C ( T ) measurements have been made on the diluted 4 f 2 system Y ( Pr ) Ir 2 Zn 20 . Both data of ρ and magnetic specific heat C m per Pr ion are well scaled as a function of T / T 0 , where T 0 is a characteristic temperature of non-Fermi-liquid (NFL) behaviors. Furtherm... [Phys. Rev. Lett. 121, 077206] Published Fri Aug 17, 2018
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  • 79
    Publication Date: 2018-08-18
    Description: Author(s): S. Komori, A. Di Bernardo, A. I. Buzdin, M. G. Blamire, and J. W. A. Robinson At a superconductor-ferromagnet ( S / F ) interface, the F layer can introduce a magnetic exchange field within the S layer, which acts to locally spin split the superconducting density of states. The effect of magnetic exchange fields on superconductivity has been thoroughly explored at S -ferromagnet i... [Phys. Rev. Lett. 121, 077003] Published Fri Aug 17, 2018
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  • 80
    Publication Date: 2018-08-22
    Description: Author(s): Martin Hohenadler and Fakher F. Assaad Quantum Monte Carlo simulations reveal an exotic metallic phase with a single-particle gap but gapless spin and charge excitations and a nonsaturating resistivity in a two-dimensional SU(2) Falicov-Kimball model. An exact duality between this model and an unconstrained slave-spin theory leads to a c... [Phys. Rev. Lett. 121, 086601] Published Tue Aug 21, 2018
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  • 81
    Publication Date: 2018-08-25
    Description: Author(s): Manas Ranjan Sahu, Xin Liu, Arup Kumar Paul, Sourin Das, Pratap Raychaudhuri, J. K. Jain, and Anindya Das Superconductivity and the quantum Hall effect are distinct states of matter occurring in apparently incompatible physical conditions. Recent theoretical developments suggest that the coupling of the quantum Hall effect with a superconductor can provide fertile ground for realizing exotic topological... [Phys. Rev. Lett. 121, 086809] Published Fri Aug 24, 2018
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  • 82
    Publication Date: 2018-08-25
    Description: Author(s): Zhengzheng Shao, Zhizhen Yin, Helun Song, Wei Liu, Xiujian Li, Jubo Zhu, Klaus Biermann, Luis L. Bonilla, Holger T. Grahn, and Yaohui Zhang The effect of a coherence resonance is observed experimentally in a GaAs / Al 0.45 Ga 0.55 As superlattice under dc bias at room temperature, which is driven by noise. For an applied voltage, for which no current self-oscillations are observed, regular current self-oscillations with a frequency of about 8... [Phys. Rev. Lett. 121, 086806] Published Fri Aug 24, 2018
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  • 83
    facet.materialart.
    Unknown
    American Physical Society (APS)
    Publication Date: 2018-08-25
    Description: Author(s): Xuzhe Ying and Alex Kamenev We show that sharply defined topological quantum phase transitions are not limited to states of matter with gapped electronic spectra. Such transitions may also occur between two gapless metallic states both with extended Fermi surfaces. The transition is characterized by a discontinuous, but not qu... [Phys. Rev. Lett. 121, 086810] Published Fri Aug 24, 2018
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  • 84
    Publication Date: 2018-08-25
    Description: Author(s): Kenny Choo, Curt W. von Keyserlingk, Nicolas Regnault, and Titus Neupert Entanglement properties are routinely used to characterize phases of quantum matter in theoretical computations. For example, the spectrum of the reduced density matrix, or so-called “entanglement spectrum”, has become a widely used diagnostic for universal topological properties of quantum phases. ... [Phys. Rev. Lett. 121, 086808] Published Fri Aug 24, 2018
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  • 85
    Publication Date: 2018-08-25
    Description: Author(s): Emanuel Mompo, Miguel Ruiz-Garcia, Manuel Carretero, Holger T. Grahn, Yaohui Zhang, and Luis L. Bonilla Collective electron transport causes a weakly coupled semiconductor superlattice under dc voltage bias to be an excitable system with 2 N + 2 degrees of freedom: electron densities and fields at N superlattice periods plus the total current and the field at the injector. External noise of sufficient am... [Phys. Rev. Lett. 121, 086805] Published Fri Aug 24, 2018
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  • 86
    Publication Date: 2018-08-29
    Description: Author(s): Michalis Charilaou, Hans-Benjamin Braun, and Jörg F. Löffler We predict that complete magnetization reversal in simple metallic ferromagnetic nanoparticles is directly linked to the pair creation of topological point defects in the form of hedgehog-antihedgehog pairs. These dynamical point defects move at exceptionally high speeds in excess of 1500     m / s , fast... [Phys. Rev. Lett. 121, 097202] Published Tue Aug 28, 2018
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  • 87
    Publication Date: 2018-08-30
    Description: Author(s): Miguel A. Sierra, Rosa López, and Jong Soo Lim The archetypal two-impurity Kondo problem in a serially coupled double quantum dot is investigated in the presence of a thermal bias θ . The slave-boson formulation is employed to obtain the nonlinear thermal and thermoelectrical responses. When the Kondo correlations prevail over the antiferromagnet... [Phys. Rev. Lett. 121, 096801] Published Wed Aug 29, 2018
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  • 88
    Publication Date: 2018-09-07
    Description: Author(s): Sheng-Chin Ho, Heng-Jian Chang, Chia-Hua Chang, Shun-Tsung Lo, Graham Creeth, Sanjeev Kumar, Ian Farrer, David Ritchie, Jonathan Griffiths, Geraint Jones, Michael Pepper, and Tse-Ming Chen Using a nanowire with controllable width, researchers have created a type of Wigner crystal in which electrons form an ordered zigzag pattern. [Phys. Rev. Lett. 121, 106801] Published Thu Sep 06, 2018
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  • 89
    Publication Date: 2018-09-07
    Description: Author(s): Jukka I. Väyrynen, Dmitry I. Pikulin, and Jason Alicea The observed imperfect conductance quantization in 2D topological insulators may be due to time-dependent electronic noise from charge puddles. [Phys. Rev. Lett. 121, 106601] Published Thu Sep 06, 2018
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  • 90
    Publication Date: 2018-09-08
    Description: Author(s): Daniel Richardson, Boris A. Kalinikos, Lincoln D. Carr, and Mingzhong Wu Exact fractals of nonlinear waves that rely on strong dispersion and nonlinearity and arise spontaneously out of magnetic media were observed for the first time. The experiments make use of a microwave to excite a spin wave in a quasi-one-dimensional magnonic crystal. When the power of the input mic... [Phys. Rev. Lett. 121, 107204] Published Fri Sep 07, 2018
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  • 91
    Publication Date: 2018-09-18
    Description: Author(s): Jian Gou, Bingyu Xia, Hang Li, Xuguang Wang, Longjuan Kong, Peng Cheng, Hui Li, Weifeng Zhang, Tian Qian, Hong Ding, Yong Xu, Wenhui Duan, Kehui Wu, and Lan Chen A honeycomb structure of Bi and Sn atoms on a Si substrate has a pronounced electron-hole asymmetry, providing a platform to explore applications in nanodevices. [Phys. Rev. Lett. 121, 126801] Published Mon Sep 17, 2018
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  • 92
    Publication Date: 2018-09-18
    Description: Author(s): J. Stapmanns, P. Corboz, F. Mila, A. Honecker, B. Normand, and S. Wessel We consider the finite-temperature phase diagram of the S = 1 / 2 frustrated Heisenberg bilayer. Although this two-dimensional system may show magnetic order only at zero temperature, we demonstrate the presence of a line of finite-temperature critical points related to the line of first-order transitio... [Phys. Rev. Lett. 121, 127201] Published Mon Sep 17, 2018
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  • 93
    Publication Date: 2018-09-21
    Description: Author(s): Jinsong Xu, Tiancong Zhu, Yunqiu Kelly Luo, Yuan-Ming Lu, and Roland K. Kawakami Two groups have shown they can create long-lived, polarized spin currents in bilayer graphene. [Phys. Rev. Lett. 121, 127703] Published Thu Sep 20, 2018
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  • 94
    Publication Date: 2018-09-21
    Description: Author(s): Z. Su, A. Zarassi, J.-F. Hsu, P. San-Jose, E. Prada, R. Aguado, E. J. H. Lee, S. Gazibegovic, R. L. M. Op het Veld, D. Car, S. R. Plissard, M. Hocevar, M. Pendharkar, J. S. Lee, J. A. Logan, C. J. Palmstrøm, E. P. A. M. Bakkers, and S. M. Frolov We study transport mediated by Andreev bound states formed in InSb nanowire quantum dots. Two kinds of superconducting source and drain contacts are used: epitaxial Al/InSb devices exhibit a doubling of tunneling resonances, while, in NbTiN / InSb devices, Andreev spectra of the dot appear to be repli... [Phys. Rev. Lett. 121, 127705] Published Thu Sep 20, 2018
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  • 95
    Publication Date: 2018-09-21
    Description: Author(s): Johannes Christian Leutenantsmeyer, Josep Ingla-Aynés, Jaroslav Fabian, and Bart J. van Wees Two groups have shown they can create long-lived, polarized spin currents in bilayer graphene. [Phys. Rev. Lett. 121, 127702] Published Thu Sep 20, 2018
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  • 96
    Publication Date: 2018-09-21
    Description: Author(s): Joshua O. Island, Marvin Ostermann, Lee Aspitarte, Ethan D. Minot, Daniele Varsano, Elisa Molinari, Massimo Rontani, and Gary A. Steele Carbon nanotubes continue to be model systems for studies of confinement and interactions. This is particularly true in the case of so-called “ultraclean” carbon nanotube devices offering the study of quantum dots with extremely low disorder. The quality of such systems, however, has increasingly re... [Phys. Rev. Lett. 121, 127704] Published Thu Sep 20, 2018
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  • 97
    Publication Date: 2018-09-22
    Description: Author(s): Renjun Du (杜人君), Ming-Hao Liu (劉明豪), Jens Mohrmann, Fan Wu (吴凡), Ralph Krupke, Hilbert von Löhneysen, Klaus Richter, and Romain Danneau We show that in gapped bilayer graphene, quasiparticle tunneling and the corresponding Berry phase can be controlled such that they exhibit features of single-layer graphene such as Klein tunneling. The Berry phase is detected by a high-quality Fabry-Pérot interferometer based on bilayer graphene. B... [Phys. Rev. Lett. 121, 127706] Published Fri Sep 21, 2018
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  • 98
    facet.materialart.
    Unknown
    American Physical Society (APS)
    Publication Date: 2018-09-25
    Description: Author(s): Shunyu Yao, Fei Song, and Zhong Wang The relation between chiral edge modes and bulk Chern numbers of quantum Hall insulators is a paradigmatic example of bulk-boundary correspondence. We show that the chiral edge modes are not strictly tied to the Chern numbers defined by a non-Hermitian Bloch Hamiltonian. This breakdown of convention... [Phys. Rev. Lett. 121, 136802] Published Mon Sep 24, 2018
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  • 99
    Publication Date: 2018-09-26
    Description: Author(s): Satoru Hayami and Yukitoshi Motome We theoretically study noncoplanar spin textures in polar magnetic conductors. Starting from the Kondo lattice model with the Rashba spin-orbit coupling, we derive an effective spin model with generalized Ruderman-Kittel-Kasuya-Yosida interactions including the anisotropic and antisymmetric exchange... [Phys. Rev. Lett. 121, 137202] Published Tue Sep 25, 2018
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  • 100
    Publication Date: 2018-09-26
    Description: Author(s): N. Xu, Z. W. Wang, A. Magrez, P. Bugnon, H. Berger, C. E. Matt, V. N. Strocov, N. C. Plumb, M. Radovic, E. Pomjakushina, K. Conder, J. H. Dil, J. Mesot, R. Yu, H. Ding, and M. Shi Using soft x-ray angle-resolved photoemission spectroscopy we probed the bulk electronic structure of T d − MoTe 2 . We found that on-site Coulomb interaction leads to a Lifshitz transition, which is essential for a precise description of the electronic structure. A hybrid Weyl semimetal state with a pai... [Phys. Rev. Lett. 121, 136401] Published Tue Sep 25, 2018
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