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  • 1
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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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  • 2
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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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  • 3
    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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  • 4
    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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  • 5
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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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  • 6
    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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  • 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
    Format: 72pp.
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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
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    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
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    American Physical Society (APS)
    Publication Date: 2018-12-14
    Description: Author(s): Pavel A. Volkov and Sergej Moroz We consider the stability of nodal surfaces in fermionic band systems with respect to the Coulomb repulsion. It is shown that nodal surfaces at the Fermi level are gapped out at low temperatures due to emergent particle-hole orders. Energy dispersion of the nodal surface suppresses the instability t... [Phys. Rev. B 98, 241107(R)] Published Thu Dec 13, 2018
    Keywords: Electronic structure and strongly correlated systems
    Print ISSN: 1098-0121
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  • 49
    Publication Date: 2018-12-14
    Description: Author(s): Xiancong Lu and D. Sénéchal We investigate parity-mixing superconductivity in the two-dimensional Hubbard model with Rashba spin-orbit coupling, using cellular dynamical mean-field theory (CDMFT). A superconducting state with mixed singlet d -wave and triplet p -wave character is found in a wide range of doping. The singlet comp... [Phys. Rev. B 98, 245118] Published Thu Dec 13, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 50
    Publication Date: 2018-07-27
    Description: Author(s): Alireza Habibi, S. A. Jafari, and S. Rouhani We elucidate the reduction of the winding number caused by the on-site disorder in a next-nearest-neighbor XY model. When disorder becomes strong enough, Majorana edge modes become critically extended, beyond which they collapse into Anderson localized (AL) states in the bulk, resulting in a topolog... [Phys. Rev. B 98, 035142] Published Thu Jul 26, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 51
    Publication Date: 2018-07-27
    Description: Author(s): Carsten A. Ullrich To describe noncollinear magnetism in systems such as spiral ferromagnets or spin-frustrated molecules, density-functional methods need to give a proper account of the interplay between broken spin symmetries and exchange-correlation many-body effects. Here, the author develops a class of orbital-dependent exchange-correlation functionals for systems with noncollinear spin, treating correlation via a self-consistent scheme inspired by the Singwi-Tosi-Land-Sjölander method. The approach is applied to a very simple yet nontrivial benchmark system, the asymmetric half-filled Hubbard dimer, and is found to perform well, particularly in the weakly to moderately correlated regime. [Phys. Rev. B 98, 035140] Published Thu Jul 26, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 52
    Publication Date: 2018-07-27
    Description: Author(s): Kai Luo, Valentin V. Karasiev, and S. B. Trickey A simple, unconventional, nonempirical, constraint-based orbital-free generalized gradient approximation (GGA) noninteracting kinetic energy density functional is presented along with illustrative applications. The innovation is adaptation of constraint-based construction to the essential properties... [Phys. Rev. B 98, 041111(R)] Published Thu Jul 26, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 53
    facet.materialart.
    Unknown
    American Physical Society (APS)
    Publication Date: 2018-07-27
    Description: Author(s): Dino Novko The unusual Raman spectrum of MgB 2 and its formidable temperature dependence are successfully reproduced by means of a parameter-free ab initio nonadiabatic theory that accounts for the electron-hole pair scattering mechanisms with the system phonons. This example turns out to be a prototypical case... [Phys. Rev. B 98, 041112(R)] Published Thu Jul 26, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 54
    Publication Date: 2018-07-28
    Description: Author(s): W. H. Brito, S. Choi, Y. X. Yao, and G. Kotliar We investigate the normal state of the superconducting compound PuCoGa 5 using the combination of density functional theory (DFT) and dynamical mean-field theory (DMFT), with the continuous time quantum Monte Carlo (CTQMC) and the vertex-corrected one-crossing approximation (OCA) as the impurity solv... [Phys. Rev. B 98, 035143] Published Fri Jul 27, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 55
    Publication Date: 2018-07-28
    Description: Author(s): Yi-Yan Wang (王义炎), Lin-Lin Sun (孙琳琳), Sheng Xu (徐升), Yuan Su (苏园), and Tian-Long Xia (夏天龙) We report the magnetotransport properties of HoSb, a semimetal with antiferromagnetic ground state. HoSb shows extremely large magnetoresistance (XMR) and Shubnikov-de Haas (SdH) oscillation at low temperature and high magnetic field. Different from previous reports in other rare earth monopnictides... [Phys. Rev. B 98, 045137] Published Fri Jul 27, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 56
    Publication Date: 2018-07-28
    Description: Author(s): Irakli Titvinidze, Max E. Sorantin, Antonius Dorda, Wolfgang von der Linden, and Enrico Arrigoni We address the steady-state behavior of a system consisting of several correlated monoatomic layers sandwiched between two metallic leads under the influence of a bias voltage. In particular, we investigate the interplay of the local Hubbard and the long-range Coulomb interaction on the charge redis... [Phys. Rev. B 98, 035146] Published Fri Jul 27, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 57
    Publication Date: 2018-07-31
    Description: Author(s): Akitoshi Nakano, Takumi Hasegawa, Shinya Tamura, Naoyuki Katayama, Satoshi Tsutsui, and Hiroshi Sawa Ta 2 NiSe 5 is considered a promising excitonic insulator (EI) candidate, in which the EI state is due to Coulomb interaction between electrons and holes. In Ta 2 NiSe 5 , the role of phonons is significant since the EI transition is accompanied by an orthorhombic-to-monoclinic structural transition at T s = ... [Phys. Rev. B 98, 045139] Published Mon Jul 30, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 58
    Publication Date: 2018-07-31
    Description: Author(s): F. C. Chen, X. Luo, J. Yan, Y. Sun, H. Y. Lv, W. J. Lu, C. Y. Xi, P. Tong, Z. G. Sheng, X. B. Zhu, W. H. Song, and Y. P. Sun Topological Weyl semimetals (WSMs), a new quantum state of matter, provide the realization of relativistic Weyl fermions in solid-state physics. The appearance of the Weyl nodes will demonstrate novel transport phenomena related to the chiral anomaly. Theoretical prediction hints that the giant plan... [Phys. Rev. B 98, 041114(R)] Published Mon Jul 30, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 59
    Publication Date: 2018-07-31
    Description: Author(s): M. Naseska, A. Pogrebna, G. Cao, Z. A. Xu, D. Mihailovic, and T. Mertelj We report on a systematic excitation-density-dependent all-optical femtosecond time-resolved study of the spin density wave state in iron-based superconductors. The destruction and recovery dynamics are measured by means of the standard and a multipulse pump-probe technique. The experimental data ar... [Phys. Rev. B 98, 035148] Published Mon Jul 30, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 60
    Publication Date: 2018-07-25
    Description: Author(s): Rui-Qi Xing, Laura Classen, and Andrey V. Chubukov We study the structure of the orbital order Γ = d x z † d x z − d y z † d y z in FeSe in light of recent scanning tunneling microscopy and angle-resolved photoemission spectroscopy (ARPES) data, which detect the shapes of the hole and electron pockets in the nematic phase. The geometry of the pockets indicates that... [Phys. Rev. B 98, 041108(R)] Published Tue Jul 24, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 61
    Publication Date: 2018-07-25
    Description: Author(s): A. Amaricci, A. Valli, G. Sangiovanni, B. Trauzettel, and M. Capone We investigate the emergence of antiferromagnetic ordering and its effect on the helical edge states in a quantum spin Hall insulator, in the presence of strong Coulomb interaction. Using dynamical mean-field theory, we show that the breakdown of lattice translational symmetry favors the formation o... [Phys. Rev. B 98, 045133] Published Tue Jul 24, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 62
    Publication Date: 2018-07-25
    Description: Author(s): Peng-Jie Guo, Huan-Cheng Yang, Kai Liu, and Zhong-Yi Lu As a type of fermions without counterpart in high energy physics, triply degenerate fermions show exotic physical properties, which are represented by triply degenerate nodal points in topological semimetals. Here, based on the space group theory analysis, we propose a practical guidance for seeking... [Phys. Rev. B 98, 045134] Published Tue Jul 24, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 63
    Publication Date: 2018-08-07
    Description: Author(s): Shiang Fang, Stephen Carr, Miguel A. Cazalilla, and Efthimios Kaxiras We derive electronic tight-binding Hamiltonians for strained graphene, hexagonal boron nitride, and transition-metal dichalcogenides based on Wannier transformation of ab initio density functional theory calculations. Our microscopic models include strain effects to leading order that respect the he... [Phys. Rev. B 98, 075106] Published Mon Aug 06, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 64
    Publication Date: 2018-08-07
    Description: Author(s): Vojtěch Vlček, Wenfei Li, Roi Baer, Eran Rabani, and Daniel Neuhauser We introduce the concept of sparse stochastic compression, an efficient stochastic sampling of any general function. The technique uses sparse stochastic orbitals (SSOs), short vectors that sample a small number of space points. As a first demonstration, SSOs are applied in conjunction with simple d... [Phys. Rev. B 98, 075107] Published Mon Aug 06, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 65
    Publication Date: 2018-08-07
    Description: Author(s): Daniel Kidd, A. S. Umar, and Kálmán Varga An iterative optimization approach that simultaneously minimizes the energy and optimizes the Lagrange multipliers enforcing desired constraints is presented. The method is tested on previously established benchmark systems and it is proved to be efficient and accurate. The approach can also be effi... [Phys. Rev. B 98, 075108] Published Mon Aug 06, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 66
    Publication Date: 2018-08-07
    Description: Author(s): Alex Thomson, Shubhayu Chatterjee, Subir Sachdev, and Mathias S. Scheurer We present the electronic band structures of states with the same symmetry as the three-sublattice planar antiferromagnetic order of the triangular lattice. Such states can also be defined on the honeycomb lattice provided the spin density waves lie on the bonds. We identify cases which are consiste... [Phys. Rev. B 98, 075109] Published Mon Aug 06, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 67
    Publication Date: 2018-08-08
    Description: Author(s): Andrzej Biborski, Andrzej P. Kądzielawa, and Józef Spałek We discuss electronic properties and their evolution for the linear chain of H 2 molecules in the presence of a uniform external force f acting along the chain. The system is described by an extended Hubbard model within a fully microscopic approach . Explicitly, the microscopic parameters describing ... [Phys. Rev. B 98, 085112] Published Tue Aug 07, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 68
    Publication Date: 2018-08-07
    Description: Author(s): Scott McKechnie, Jarvist M. Frost, Dimitar Pashov, Pooya Azarhoosh, Aron Walsh, and Mark van Schilfgaarde Metal halide perovskites exhibit a materials physics that is distinct from traditional semiconductors. While materials such as CH 3 NH 3 PbI 3 are nonmagnetic, the presence of heavy elements (Pb and I) in a noncentrosymmetric crystal environment result in a spin splitting of the frontier electronic bands... [Phys. Rev. B 98, 085108] Published Mon Aug 06, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 69
    Publication Date: 2018-08-07
    Description: Author(s): Klaus Halterman, Mohammad Alidoust, and Alexander Zyuzin We theoretically study the electromagnetic response of type-I and type-II centrosymmetric Weyl metals. We derive an anisotropic permittivity tensor with off-diagonal elements to describe such gyrotropic media. Our findings reveal that for appropriate Weyl cones tilts, the real part of the transverse... [Phys. Rev. B 98, 085109] Published Mon Aug 06, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 70
    Publication Date: 2018-08-07
    Description: Author(s): Ke Yang, D. I. Khomskii, and Hua Wu While double perovskites A 2 B B ′ O 6 , if ordered, usually form a rock-salt–type structure with a checkerboard B − B ′ ordering, it is surprising that Ca 2 FeMnO 6 has alternate FeO 2 and MnO 2 layers in its perovskite structure. Here, by using density functional calculations, we demonstrate that this unusual la... [Phys. Rev. B 98, 085105] Published Mon Aug 06, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 71
    Publication Date: 2018-06-05
    Description: Author(s): SangEun Han and Eun-Gook Moon Topological states may be protected by a lattice symmetry in a class of topological semimetals. In three spatial dimensions, the Berry flux around gapless excitations in momentum space concretely defines a chirality, so a protecting symmetry may be referred to as a chiral symmetry. Prime examples in... [Phys. Rev. B 97, 241101(R)] Published Mon Jun 04, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 72
    Publication Date: 2018-06-14
    Description: Author(s): Duk Y. Kim, Shi-Zeng Lin, Franziska Weickert, P. F. S. Rosa, Eric D. Bauer, Filip Ronning, J. D. Thompson, and Roman Movshovich The thermal conductivity of heavy-fermion superconductor Ce 0.95 Nd 0.05 CoIn 5 was measured with a magnetic field rotating in the tetragonal a − b plane. The thermal conductivity exhibits a step within the high-field low-temperature (HFLT) phase, which exists above 8 Tesla within the superconducting state... [Phys. Rev. B 97, 245120] Published Wed Jun 13, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 73
    Publication Date: 2018-06-06
    Description: Author(s): Julián Rincón, Elbio Dagotto, and Adrian E. Feiguin We study the photoinduced breakdown of a two-orbital Mott insulator and resulting metallic state. Using time-dependent density matrix renormalization group, we scrutinize the real-time dynamics of the half-filled two-orbital Hubbard model interacting with a resonant radiation field pulse. The breakd... [Phys. Rev. B 97, 235104] Published Tue Jun 05, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 74
    Publication Date: 2018-06-06
    Description: Author(s): Yongping Du, Er-jun Kan, Hu Xu, Sergey Y. Savrasov, and Xiangang Wan A search for new topological quantum systems is challenging due to the requirement of nontrivial band connectivity that leads to protected surface states of electrons. Progress in this field was primarily due to a realization of a band inversion mechanism between even and odd parity states that was ... [Phys. Rev. B 97, 245104] Published Tue Jun 05, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 75
    Publication Date: 2018-06-16
    Description: Author(s): Zheng Zhu, Itamar Kimchi, D. N. Sheng, and Liang Fu We investigate the non-Abelian topological chiral spin-liquid phase in the two-dimensional Kitaev honeycomb model subject to a magnetic field. By combining density matrix renormalization group and exact diagonalization we study the energy spectra, entanglement, topological degeneracy, and expectatio... [Phys. Rev. B 97, 241110(R)] Published Fri Jun 15, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 76
    Publication Date: 2018-06-16
    Description: Author(s): Chunxiao Liu, Xiao Chen, and Leon Balents The Sachdev-Ye-Kitaev (SYK) model is a quantum-mechanical model of fermions interacting with q -body random couplings. For q = 2 , it describes free particles and is nonchaotic in the many-body sense, while for q 〉 2 it is strongly interacting and exhibits many-body chaos. In this work we study the ent... [Phys. Rev. B 97, 245126] Published Fri Jun 15, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 77
    Publication Date: 2018-06-22
    Description: Author(s): Takami Tohyama, Michiyasu Mori, and Shigetoshi Sota The ground state of the t − t ′ − J ladder with four legs favors a striped charge distribution for the parameters corresponding to hole-doped cuprate superconductors. We investigate the dynamical spin and charge structure factors of the model by using the dynamical density matrix renormalization group (D... [Phys. Rev. B 97, 235137] Published Thu Jun 21, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 78
    Publication Date: 2018-06-23
    Description: Author(s): Agnese Tagliavini, Stefan Hummel, Nils Wentzell, Sabine Andergassen, Alessandro Toschi, and Georg Rohringer We present here two alternative schemes designed to correct the high-frequency truncation errors in the numerical treatment of the Bethe-Salpeter equations. The schemes are applicable to all Bethe-Salpeter calculations with a local two-particle irreducible vertex, which is relevant, e.g., for the dy... [Phys. Rev. B 97, 235140] Published Fri Jun 22, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 79
    Publication Date: 2018-06-23
    Description: Author(s): Adam Smith, Johannes Knolle, Roderich Moessner, and Dmitry L. Kovrizhin We study quantum quenches in two-dimensional lattice gauge theories with fermions coupled to dynamical Z 2 gauge fields. Through the identification of an extensive set of conserved quantities, we propose a generic mechanism of charge localization in the absence of quenched disorder both in the Hamilt... [Phys. Rev. B 97, 245137] Published Fri Jun 22, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 80
    Publication Date: 2018-06-28
    Description: Author(s): Juan Rubio-Zuazo, Ashish Chainani, Munetaka Taguchi, Daniel Malterre, Aida Serrano, and German R. Castro We study the electronic structure of well-characterized epitaxial films of FeO (wustite), γ − Fe 2 O 3 (maghemite), and Fe 3 O 4 (magnetite) using hard x-ray photoelectron spectroscopy (HAXPES), x-ray absorption near-edge spectroscopy (XANES), and electron energy loss spectroscopy (EELS). We carry out HAXPE... [Phys. Rev. B 97, 235148] Published Wed Jun 27, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 81
    Publication Date: 2018-06-29
    Description: Author(s): N. Pouse, S. Jang, B. D. White, S. Ran, R. B. Adhikari, C. C. Almasan, and M. B. Maple We report electrical resistivity, magnetization, and specific heat measurements on the correlated electron system Ce 1 − x Sm x CoIn 5 ( 0 ≤ x ≤ 1 ). Superconductivity (SC) in the heavy-fermion compound CeCoIn 5 , which is suppressed with increasing Sm concentration x , and antiferromagnetic (AFM) order of SmCoIn 5 ,... [Phys. Rev. B 97, 235149] Published Thu Jun 28, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 82
    Publication Date: 2018-06-29
    Description: Author(s): J. P. L. Faye, M. N. Kiselev, P. Ram, B. Kumar, and D. Sénéchal The interplay between the Kondo effect and magnetic ordering driven by the Ruderman-Kittel-Kasuya-Yosida interaction is studied within the two-dimensional Hubbard-Kondo lattice model. In addition to the antiferromagnetic exchange interaction J ⊥ between the localized spins and the conduction electron... [Phys. Rev. B 97, 235151] Published Thu Jun 28, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 83
    facet.materialart.
    Unknown
    American Physical Society (APS)
    Publication Date: 2018-12-01
    Description: Author(s): Hennadii Yerzhakov and Joseph Maciejko We study the effect of quenched disorder on the semimetal-superconductor quantum phase transition in a model of two-dimensional Dirac semimetal with N flavors of two-component Dirac fermions, using perturbative renormalization group methods at one-loop order in a double epsilon expansion. For N ≥ 2 we... [Phys. Rev. B 98, 195142] Published Fri Nov 30, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 84
    Publication Date: 2018-12-01
    Description: Author(s): I. Valmianski, P. Y. Wang, S. Wang, Juan Gabriel Ramirez, S. Guénon, and Ivan K. Schuller We report the existence of two competing mechanisms in the current-driven electrical breakdown of vanadium sesquioxide ( V 2 O 3 ) and vanadium dioxide ( V O 2 ) nanodevices. Our experiments and simulations show that the competition between a purely electronic (PE) mechanism and an electrothermal (ET) mechan... [Phys. Rev. B 98, 195144] Published Fri Nov 30, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 85
    Publication Date: 2018-12-01
    Description: Author(s): Sumit Mazumdar We present a valence transition model for electron- and hole-doped cuprates, within which there occurs a discrete jump in ionicity Cu 2 + → Cu 1 + in both families upon doping, at or near optimal doping in the conventionally prepared electron-doped compounds and at the pseudogap phase transition in the ho... [Phys. Rev. B 98, 205153] Published Fri Nov 30, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 86
    Publication Date: 2018-12-04
    Description: Author(s): Vedran Jovic, Roland J. Koch, Swarup K. Panda, Helmuth Berger, Philippe Bugnon, Arnaud Magrez, Kevin E. Smith, Silke Biermann, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, and Simon Moser The efficiency and stability of RuO 2 in electrocatalysis has made this material a subject of intense fundamental and industrial interest. The surface functionality is rooted in its electronic and magnetic properties, determined by a complex interplay of lattice-, spin-rotational, and time-reversal s... [Phys. Rev. B 98, 241101(R)] Published Mon Dec 03, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 87
    Publication Date: 2018-12-04
    Description: Author(s): Iman Mahyaeh and Eddy Ardonne In this paper, we generalized the Peschel-Emery line of the interacting transverse field Ising model to a model based on three-state clock variables. Along this line, the model has exactly degenerate ground states, which can be written as product states. In addition, we present operators that transf... [Phys. Rev. B 98, 245104] Published Mon Dec 03, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 88
    Publication Date: 2018-12-04
    Description: Author(s): V. Brouet, L. Serrier-Garcia, A. Louat, L. Fruchter, F. Bertran, P. Le Fèvre, J. Rault, A. Forget, and D. Colson In Sr 2 IrO 4 and Sr 3 Ir 2 O 7 , correlations, magnetism, and spin-orbit coupling compete on similar energy scales, creating a new context to study metal-insulator transitions (MIT). We use here angle-resolved photoemission to investigate the MIT as a function of hole and electron doping in Sr 3 Ir 2 O 7 , obtain... [Phys. Rev. B 98, 235101] Published Mon Dec 03, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 89
    Publication Date: 2018-12-04
    Description: Author(s): Thomas Mertz, Karim Zantout, and Roser Valentí We introduce the concept of self-energy dispersion as an error bound on local theories and apply it to the two-dimensional Hubbard model on the square lattice at half filling. Since the self-energy has no single-particle analog and is not directly measurable in experiments, its general behavior as a... [Phys. Rev. B 98, 235105] Published Mon Dec 03, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 90
    Publication Date: 2018-12-04
    Description: Author(s): P. Thunström, O. Gunnarsson, Sergio Ciuchi, and G. Rohringer The local two-particle Green’s function and its generalized susceptibility are central building blocks in state-of-the-art theoretical descriptions of strongly correlated many-electron systems. The unexpected discovery of singular points in the generalized susceptibility, resulting in divergences of the two-particle irreducible vertex function and in multivaluedness of the Luttinger-Ward functional, has therefore attracted considerable interest. Unfortunately, almost no analytical results for irreducible vertices are available for correlated electrons. Here, the authors fill this gap by presenting fully analytical expressions for all irreducible vertex function of a simple, yet prototypical, correlated model, the single-orbital Hubbard atom. This gives highly relevant insights into the energy dependence of these functions. [Phys. Rev. B 98, 235107] Published Mon Dec 03, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 91
    Publication Date: 2018-12-04
    Description: Author(s): Sander H. Kooi, Guido van Miert, and Carmine Ortix We prove the existence of higher-order topological insulators with protected chiral hinge modes in quasi-two-dimensional systems made out of coupled layers stacked in an inversion-symmetric manner. In particular, we show that a homogeneous external magnetic field slightly tilted away from the stacki... [Phys. Rev. B 98, 245102] Published Mon Dec 03, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 92
    Publication Date: 2018-12-04
    Description: Author(s): Jörn W. F. Venderbos and Rafael M. Fernandes The recent observation of superconductivity in proximity to an insulating phase in twisted bilayer graphene (TBG) at small “magic” twist angles has been linked to the existence of nearly flat bands, which make TBG a fresh playground to investigate the interplay between correlations and superconducti... [Phys. Rev. B 98, 245103] Published Mon Dec 03, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 93
    Publication Date: 2018-12-04
    Description: Author(s): Hongkee Yoon, Jae-Hoon Sim, and Myung Joon Han We present a machine-learning approach to a long-standing issue in quantum many-body physics, namely, analytic continuation. This notorious ill-conditioned problem of obtaining spectral function from an imaginary time Green's function has been a focus of new method developments for past decades. Her... [Phys. Rev. B 98, 245101] Published Mon Dec 03, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 94
    Publication Date: 2018-12-05
    Description: Author(s): Xiaoting Zhou, Chuang-Han Hsu, Tay-Rong Chang, Hung-Ju Tien, Qiong Ma, Pablo Jarillo-Herrero, Nuh Gedik, Arun Bansil, Vitor M. Pereira, Su-Yang Xu, Hsin Lin, and Liang Fu Topological crystalline insulators (TCIs) are insulating electronic phases of matter with nontrivial topology originating from crystalline symmetries. Recent theoretical advances have proposed new TCI states protected by rotational symmetries and provided powerful guidelines to search for TCIs in re... [Phys. Rev. B 98, 241104(R)] Published Tue Dec 04, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 95
    Publication Date: 2018-12-06
    Description: Author(s): Lang Peng, Jing-Jing Xian, Peizhe Tang, Angel Rubio, Shou-Cheng Zhang, Wenhao Zhang, and Ying-Shuang Fu Freestanding single bilayer Bi(111) is a two-dimensional topological insulator with edge states propagating along its perimeter. Given the interlayer coupling experimentally, the topological nature of Bi(111) thin films and the impact of the supporting substrate on the topmost Bi bilayer are still u... [Phys. Rev. B 98, 245108] Published Wed Dec 05, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 96
    Publication Date: 2018-12-06
    Description: Author(s): J. Sánchez-Barriga, I. Aguilera, L. V. Yashina, D. Y. Tsukanova, F. Freyse, A. N. Chaika, C. Callaert, A. M. Abakumov, J. Hadermann, A. Varykhalov, E. D. L. Rienks, G. Bihlmayer, S. Blügel, and O. Rader The authors investigate the electronic and spin structure of topological surface states across a topological quantum phase transition. They find a surface band gap opening at the Dirac point of the topological surface states, giving rise to massive fermions with nonzero spin polarization on both sides of the phase transition. A mechanism of bulk-mediated scattering processes that increase with decreasing spin-orbit coupling strength is proposed as an explanation for the problem of the unconventional transformation between spin Dirac phases. [Phys. Rev. B 98, 235110] Published Wed Dec 05, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 97
    facet.materialart.
    Unknown
    American Physical Society (APS)
    Publication Date: 2018-12-06
    Description: Author(s): Janis Erdmanis, Árpád Lukács, and Yuli V. Nazarov A variety of quantum systems exhibit Weyl points in their spectra where two bands cross in a point of three-dimensional parameter space with conical dispersion in the vicinity of the point. We consider theoretically the soft constraint regime where the parameters are dynamical quantum variables. We ... [Phys. Rev. B 98, 241105(R)] Published Wed Dec 05, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 98
    Publication Date: 2018-12-07
    Description: Author(s): Kamil Czelej, Marcin Roland Zemła, Piotr Śpiewak, and Krzysztof J. Kurzydłowski Hydrogen plays an essential role in the growth process of artificial diamond and can easily form complexes with lattice vacancies. Despite substantial efforts to resolve the electronic structure and the ground-state properties of the hydrogen-vacancy (HV) center, the final remarks are ambiguous, whi... [Phys. Rev. B 98, 235111] Published Thu Dec 06, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 99
    Publication Date: 2018-12-08
    Description: Author(s): Tao Zhu, Paolo E. Trevisanutto, Teguh Citra Asmara, Lei Xu, Yuan Ping Feng, and Andrivo Rusydi Recently, an anomalous generation of multiple plasmons with large spectral weight transfer in the visible to ultraviolet range (energies below the band gap) has been experimentally observed in the insulatinglike phase of oxygen-rich strontium niobium oxides ( SrNbO 3 + δ ). Here, we investigate the groun... [Phys. Rev. B 98, 235115] Published Fri Dec 07, 2018
    Keywords: Electronic structure and strongly correlated systems
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  • 100
    Publication Date: 2018-12-08
    Description: Author(s): O. Abdurazakov, D. Nevola, A. Rustagi, J. K. Freericks, D. B. Dougherty, and A. F. Kemper We study the role of excited phonon populations in the relaxation rates of nonequilibrium electrons using a nonequilibrium Green's function formalism. The transient modifications in the phononic properties are accounted for by self-consistently solving the Dyson equation for the electron and phonon ... [Phys. Rev. B 98, 245110] Published Fri Dec 07, 2018
    Keywords: Electronic structure and strongly correlated systems
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