On the Use of an Adaptive, Hybrid-Isentropic Vertical Coordinate in Global Atmospheric Modeling

2010 ◽  
Vol 138 (6) ◽  
pp. 2188-2210 ◽  
Author(s):  
Rainer Bleck ◽  
Stan Benjamin ◽  
Jin Lee ◽  
Alexander E. MacDonald
Keyword(s):  
Hybrid Approach ◽  
Atmospheric Modeling ◽  
Arbitrary Lagrangian Eulerian ◽  
Free Atmosphere ◽  
Vertical Coordinate ◽  
Trade Offs ◽  
Terrain Following ◽  
Spatial Transition ◽  
The Impact

Abstract This article is one in a series describing the functionality of the Flow-Following, Finite-Volume Icosahedral Model (FIM) developed at NOAA’s Earth System Research Laboratory. Emphasis in this article is on the design of the vertical coordinate—the “flow following” aspect of FIM. The coordinate is terrain-following near the ground and isentropic in the free atmosphere. The spatial transition between the two coordinates is adaptive and is based on the arbitrary Lagrangian–Eulerian (ALE) paradigm. The impact of vertical resolution trade-offs between the present hybrid approach and traditional terrain-following coordinates is demonstrated in a three-part case study.

Two-way nesting ocean models with different vertical coordinates

2021 ◽  
Author(s):  
Jerome Chanut ◽  
James Harle ◽  
Tim Graham ◽  
Laurent Debreu
Keyword(s):  
Vertical Direction ◽  
Test Cases ◽  
Numerical Representation ◽  
Arbitrary Lagrangian Eulerian ◽  
Coordinate Systems ◽  
Vertical Coordinate ◽  
Terrain Following ◽  
New Feature ◽  
Polynomial Reconstruction ◽  
Horizontal Grid

<p>The NEMO platform possesses a versatile block-structured refinement capacity thanks to the AGRIF library. It is however restricted up to versions 4.0x, to the horizontal direction only. In the present work, we explain how we extended the nesting capabilities to the vertical direction, a feature which can appear, in some circumstances, as beneficial as refining the horizontal grid.</p><p>Doing so is not a new concept per se, except that we consider here the general case of child and parent grids with possibly different vertical coordinate systems, hence not logically defined from each other as in previous works. This enables connecting together for instance z (geopotential), s (terrain following) or eventually ALE (Arbitrary Lagrangian Eulerian) coordinate systems. In any cases, two-way exchanges are enabled, which is the other novel aspect tackled here.  </p><p>Considering the vertical nesting procedure itself, we describe the use of high order conservative and monotone polynomial reconstruction operators to remap from parent to child grids and vice versa. Test cases showing the feasibility of the approach are presented, with particular attention on the connection of s and z grids in the context of gravity flow modelling. This work can be considered as a preliminary step towards the application of the vertical nesting concept over major overflow regions in global realistic configurations. The numerical representation of these areas is indeed known to be particularly sensitive to the vertical coordinate formulation. More generally, this work illustrates the typical methodology from the development to the validation of a new feature in the NEMO model.</p>

Preliminary Design and Performance of Counter Rotating Turbines for Open Rotors: Part II — 0-D Methodology and Case Study for a 160 PAX Aircraft

2016 ◽  
Author(s):  
Pablo Bellocq ◽  
Inaki Garmendia ◽  
Jordane Legrand ◽  
Vishal Sethi
Keyword(s):  
Design Methodology ◽  
Design Space Exploration ◽  
Design Space ◽  
Space Exploration ◽  
Preliminary Design ◽  
Regulatory Constraints ◽  
Trade Offs ◽  
And Performance ◽  
The Impact

Direct Drive Open Rotors (DDORs) have the potential to significantly reduce fuel consumption and emissions relative to conventional turbofans. However, this engine architecture presents many design and operational challenges both at engine and aircraft level. At preliminary design stages, a broad design space exploration is required to identify potential optimum design regions and to understand the main trade offs of this novel engine architecture. These assessments may also aid the development process when compromises need to be performed as a consequence of design, operational or regulatory constraints. Design space exploration assessments are done with 0-D or 1-D models for computational purposes. These simplified 0-D and 1-D models have to capture the impact of the independent variation of the main design and control variables of the engine. Historically, it appears that for preliminary design studies of DDORs, Counter Rotating Turbines (CRTs) have been modelled as conventional turbines and therefore it was not possible to assess the impact of the variation of the number of stages (Nb) of the CRT and rotational speed of the propellers. Additionally, no preliminary design methodology for CRTs was found in the public domain. Part I of this two-part publication proposes a 1-D preliminary design methodology for DDOR CRTs which allows an independent definition of both parts of the CRT. A method for calculating the off-design performance of a known CRT design is also described. In Part II, a 0-D design point efficiency calculation for CRTs is proposed and verified with the 1-D methods. The 1-D and 0-D CRT models were used in an engine control and design space exploration case study of a DDOR with a 4.26m diameter an 10% clipped propeller for a 160 PAX aircraft. For this application: • the design and performance of a 20 stage CRT rotating at 860 rpm (both drums) obtained with the 1-D methods is presented. • differently from geared open rotors, negligible cruise fuel savings can be achieved by an advanced propeller control. • for rotational speeds between 750 and 880 rpm (relatively low speeds for reduced noise), 22 and 20 stages CRTs are required. • engine weight can be kept constant for different design rotational speeds by using the minimum required Nb. • for any target engine weight, TOC and cruise SFC are reduced by reducing the rotational speeds and increasing Nb (also favourable for reducing CRP noise). However additional CRT stages increase engine drag, mechanical complexity and cost.

The Network Runs the Schools: From a Loose to a Tightly Coupled School District

2020 ◽  
Vol 23 (4) ◽  
pp. 47-61
Author(s):  
Patricia M. Virella ◽  
Jennie M. Weiner
Keyword(s):  
Student Achievement ◽  
Hybrid Approach ◽  
Educational Leaders ◽  
Central Office Administrators ◽  
Teacher Student Relationships ◽  
Teacher Student ◽  
Trade Offs ◽  
Tightly Coupled ◽  
Pros And Cons

This case study explores a central office’s attempt to improve its school performance by shifting from a loosely to a more tightly coupled organization through greater oversight and standardization of practice. Educational leaders and, specifically, district-level and central office administrators often negotiate between providing schools autonomy and pursuing greater accountability and uniformity to foster improved student achievement. Educators studying this case will examine the pros and cons of both approaches as well as the potential trade-offs when shifting from one system to another or engaging in a hybrid approach on elements like teacher motivation, teacher–student relationships, school culture, and student achievement.

scholarly journals Temporal changes in greenspace in a highly urbanized region

2011 ◽  
Vol 7 (5) ◽  
pp. 763-766 ◽  
Author(s):  
Martin Dallimer ◽  
Zhiyao Tang ◽  
Peter R. Bibby ◽  
Paul Brindley ◽  
Kevin J. Gaston ◽  
...  
Keyword(s):  
Land Use ◽  
Urban Areas ◽  
National Level ◽  
Urban Land Use ◽  
Policy Reforms ◽  
Trade Offs ◽  
Dramatic Shift ◽  
Urbanized Region ◽  
The Impact

The majority of the world's population now lives in towns and cities, and urban areas are expanding faster than any other land-use type. In response to this phenomenon, two opposing arguments have emerged: whether cities should ‘sprawl’ into the wider countryside, or ‘densify’ through the development of existing urban greenspace. However, these greenspaces are increasingly recognized as being central to the amelioration of urban living conditions, supporting biodiversity conservation and ecosystem service provision. Taking the highly urbanized region of England as a case study, we use data from a variety of sources to investigate the impact of national-level planning policy on temporal patterns in the extent of greenspace in cities. Between 1991 and 2006, greenspace showed a net increase in all but one of 13 cities. However, the majority of this gain occurred prior to 2001, and greenspace has subsequently declined in nine cities. Such a dramatic shift in land use coincides with policy reforms in 2000, which favoured densification. Here, we illustrate the dynamic and policy-responsive nature of urban land use, thereby highlighting the need for a detailed investigation of the trade-offs associated with different mechanisms of urban densification to optimize and secure the diverse benefits associated with greenspaces.

Can the Deforestation Breeze Change the Rainfall in Amazonia? A Case Study for the BR-163 Highway Region

2010 ◽  
Vol 14 (18) ◽  
pp. 1-25 ◽  
Author(s):  
Sandra I. Saad ◽  
Humberto R. da Rocha ◽  
Maria A. F. Silva Dias ◽  
Rafael Rosolem
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Three Dimensional ◽  
Atmospheric Modeling ◽  
Thermal Cell ◽  
Soil Wetness ◽  
Soil Dryness ◽  
Regional Atmospheric Modeling ◽  
The Impact

Abstract The authors simulated the effects of Amazonian mesoscale deforestation in the boundary layer and in rainfall with the Brazilian Regional Atmospheric Modeling System (BRAMS) model. They found that both the area and shape (with respect to wind incidence) of deforestation and the soil moisture status contributed to the state of the atmosphere during the time scale of several weeks, with distinguishable patterns of temperature, humidity, and rainfall. Deforestation resulted in the development of a three-dimensional thermal cell, the so-called deforestation breeze, slightly shifted downwind to large-scale circulation. The boundary layer was warmer and drier above 1000-m height and was slightly wetter up to 2000-m height. Soil wetness affected the circulation energetics proportionally to the soil dryness (for soil wetness below ∼0.6). The shape of the deforestation controlled the impact on rainfall. The horizontal strips lined up with the prevailing wind showed a dominant increase in rainfall, significant up to about 60 000 km2. On the other hand, in the patches aligned in the opposite direction (north–south), there was both increase and decrease in precipitation in two distinct regions, as a result of clearly separated upward and downward branches, which caused the precipitation to increase for patches up to 15 000 km2. The authors’ estimates for the size of deforestation impacting the rainfall contributed to fill up the low spatial resolution in other previous studies.

scholarly journals Germany’s Agricultural Land Footprint and the Impact of Import Pattern Allocation

2021 ◽  
Author(s):  
Klaus Josef Hennenberg ◽  
Swantje Gebhardt ◽  
Florian Wimmer ◽  
Martin Distelkamp ◽  
Christian Lutz ◽  
...  
Keyword(s):  
Land Use ◽  
Agricultural Land ◽  
Methodological Approach ◽  
Hybrid Approach ◽  
Ecosystem Functions ◽  
Land Conversion ◽  
Environmental Goods ◽  
Global Average ◽  
The Impact

Footprints are powerful indicators for evaluating the impact of the bioeconomy of a country on environmental goods, domestically and abroad. In this study, we apply a hybrid approach combining a Multi-Regional Input-Output model and land use modelling to compute the agricultural land footprint (aLF). Furthermore, we added information on land-use change to the analysis and allocated land conversion to specific commodities. The German case study shows that the aLF abroad is larger by a factor of 2.5 to 3 than the aLF in Germany. In 2005 and 2010, conversion of natural and semi-natural land-cover types abroad allocated to Germany due to import increases was 2.5 times higher than the global average. Import increases to Germany slowed down in 2015 and 2020, reducing land conversion attributed to the German bioeconomy to the global average. The case study shows that the applied land footprint provides clear and meaningful information for policymakers and other stakeholders. The presented methodological approach can be applied to other countries and regions covered in the underlying database EXIOBASE. It can be adapted, also for an assessment of other ecosystem functions, such as water or soil fertility.

scholarly journals Hyperspectral system trade-offs for illumination, hardware and analysis methods: a case study of seed mix ingredient discrimination

2020 ◽  
Author(s):  
Carolina Blanch-Pérez del Notario ◽  
Carlos López-Molina ◽  
Andy Lambrechts ◽  
Wouter Saeys
Keyword(s):  
Hyperspectral Imaging ◽  
Spectral Resolution ◽  
Food Industry ◽  
Near Infrared ◽  
Imaging System ◽  
Infrared Range ◽  
Analysis Methods ◽  
Trade Offs ◽  
The Impact

The discrimination power of a hyperspectral imaging system for image segmentation or object detection is determined by the illumination, the camera spatial–spectral resolution, and both the pre-processing and analysis methods used for image processing. In this study, we methodically reviewed the alternatives for each of those factors for a case study from the food industry to provide guidance in the construction and configuration of hyperspectral imaging systems in the visible near infrared range for food quality inspection. We investigated both halogen- and LED-based illuminations and considered cameras with different spatial–spectral resolution trade-offs. At the level of the data analysis, we evaluated the impact of binning, median filtering and bilateral filtering as pre- or post-processing and compared pixel-based classifiers with convolutional neural networks for a challenging application in the food industry, namely ingredient identification in a flour–seed mix. Starting from a basic configuration and by modifying the combination of system aspects we were able to increase the mean accuracy by at least 25 %. In addition, different trade-offs in performance-complexity were identified for different combinations of system parameters, allowing adaptation to diverse application requirements.

Net environmental benefit: introducing a new LCA approach on wastewater treatment systems

2012 ◽  
Vol 65 (9) ◽  
pp. 1624-1631 ◽  
Author(s):  
D. Godin ◽  
C. Bouchard ◽  
P. A. Vanrolleghem
Keyword(s):  
Wastewater Treatment ◽  
Life Cycle ◽  
Wastewater Treatment Plants ◽  
Environmental Benefit ◽  
Trade Offs ◽  
Wastewater Quality ◽  
Potential Impact ◽  
The Impact ◽  
Lca Results

Life cycle assessment (LCA) allows evaluating the potential environmental impacts of a product or a service in relation to its function and over its life cycle. In past LCAs applied to wastewater treatment plants (WWTPs), the system function definition has received little attention despite its great importance. This has led to some limitations in LCA results interpretation. A new methodology to perform LCA on WWTPs is proposed to avoid those limitations. It is based on net environmental benefit (NEB) evaluation and requires assessing the potential impact of releasing wastewater without and with treatment besides assessing the impact of the WWTP's life cycle. The NEB allows showing the environmental trade-offs between avoided impact due to wastewater treatment and induced impact by the WWTP's life cycle. NEB is compared with a standard LCA through the case study of a small municipal WWTP consisting of facultative aerated lagoons. The NEB and standard LCA show similar results for impact categories solely related to the WWTP's life cycle but differ in categories where wastewater treatment environmental benefit is accounted for as NEB considers influent wastewater quality whereas standard LCA does not.

scholarly journals Design Trade-Offs in Common-Mode Feedback Implementations for Highly Linear Three-Stage Operational Transconductance Amplifiers

Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 991
Author(s):  
Joseph Riad ◽  
Sergio Soto-Aguilar ◽  
Johan J. Estrada-López ◽  
Oscar Moreira-Tamayo ◽  
Edgar Sánchez-Sinencio
Keyword(s):  
Cmos Technology ◽  
Common Mode ◽  
Operational Transconductance Amplifiers ◽  
Fully Differential ◽  
Trade Offs ◽  
Active Rc Filter ◽  
Transconductance Amplifiers ◽  
Two Stages ◽  
The Impact

Fully differential amplifiers require the use of common-mode feedback (CMFB) circuits to properly set the amplifier’s operating point. Due to scaling trends in CMOS technology, modern amplifiers increasingly rely on cascading more than two stages to achieve sufficient gain. With multiple gain stages, different topologies for implementing CMFB are possible, whether using a single CMFB loop or multiple ones. However, the impact on performance of each CMFB approach has seldom been studied in the literature. The aim of this work is to guide the choice of the CMFB implementation topology evaluating performance in terms of stability, linearity, noise and common-mode rejection. We present a detailed theoretical analysis, comparing the relative performance of two CMFB configurations for 3-stage OTA topologies in an implementation-agnostic manner. Our analysis is then corroborated through a case study with full simulation results comparing the two topologies at the transistor level and confirming the theoretical intuition. An active-RC filter is used as an example of a high-linearity OTA application, highlighting a 6 dB improvement in P1dB in the multi-loop implementation with respect to the single-loop case.

scholarly journals Quantifying the Benefits of Targeting for Pandemic Response

2021 ◽  
Author(s):  
Sergio Camelo ◽  
Dragos F. Ciocan ◽  
Dan A. Iancu ◽  
Xavier S. Warnes ◽  
Spyros I. Zoumpoulis
Keyword(s):  
Economic Value ◽  
Population Group ◽  
Economic Losses ◽  
Modeling Framework ◽  
Social Contacts ◽  
Policy Makers ◽  
Flexible Modeling ◽  
Trade Offs ◽  
The Impact

To respond to pandemics such as COVID-19, policy makers have relied on interventions that target specific population groups or activities. Such targeting is potentially contentious, so rigorously quantifying its benefits and downsides is critical for designing effective and equitable pandemic control policies. We propose a flexible modeling framework and a set of associated algorithms that compute optimally targeted, time-dependent interventions that coordinate across two dimensions of heterogeneity: population group characteristics and the specific activities that individuals engage in during the normal course of a day. We showcase a complete implementation in a case study focused on the Île-de-France region of France, based on commonly available hospitalization, community mobility, social contacts and economic data. We find that optimized dual-targeted policies have a simple and explainable structure, imposing less confinement on group-activity pairs that generate a relatively high economic value prorated by activity-specific social contacts. When compared to confinements based on uniform or less granular targeting, dual-targeted policies generate substantial complementarities that lead to Pareto improvements, reducing the number of deaths and the economic losses overall and reducing the time in confinement foreach population group. Since dual-targeted policies could lead to increased discrepancies in the confinements faced by distinct groups, we also quantify the impact of requirements that explicitly limit such disparities, and find that satisfactory intermediate trade-offs may be achievable through limited targeting.

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