2,291 research outputs found
The Informativeness of Estimation Moments
This paper introduces measures for how each moment contributes to the
precision of parameter estimates in GMM settings. For example, one of the
measures asks what would happen to the variance of the parameter estimates if a
particular moment was dropped from the estimation. The measures are all easy to
compute. We illustrate the usefulness of the measures through two simple
examples as well as an application to a model of joint retirement planning of
couples. We estimate the model using the UK-BHPS, and we find evidence of
complementarities in leisure. Our sensitivity measures illustrate that the
estimate of the complementarity is primarily informed by the distribution of
differences in planned retirement dates. The estimated econometric model can be
interpreted as a bivariate ordered choice model that allows for simultaneity.
This makes the model potentially useful in other applications
Fully automated landmarking and facial segmentation on 3D photographs
Three-dimensional facial stereophotogrammetry provides a detailed
representation of craniofacial soft tissue without the use of ionizing
radiation. While manual annotation of landmarks serves as the current gold
standard for cephalometric analysis, it is a time-consuming process and is
prone to human error. The aim in this study was to develop and evaluate an
automated cephalometric annotation method using a deep learning-based approach.
Ten landmarks were manually annotated on 2897 3D facial photographs by a single
observer. The automated landmarking workflow involved two successive
DiffusionNet models and additional algorithms for facial segmentation. The
dataset was randomly divided into a training and test dataset. The training
dataset was used to train the deep learning networks, whereas the test dataset
was used to evaluate the performance of the automated workflow. The precision
of the workflow was evaluated by calculating the Euclidean distances between
the automated and manual landmarks and compared to the intra-observer and
inter-observer variability of manual annotation and the semi-automated
landmarking method. The workflow was successful in 98.6% of all test cases. The
deep learning-based landmarking method achieved precise and consistent landmark
annotation. The mean precision of 1.69 (+/-1.15) mm was comparable to the
inter-observer variability (1.31 +/-0.91 mm) of manual annotation. The
Euclidean distance between the automated and manual landmarks was within 2 mm
in 69%. Automated landmark annotation on 3D photographs was achieved with the
DiffusionNet-based approach. The proposed method allows quantitative analysis
of large datasets and may be used in diagnosis, follow-up, and virtual surgical
planning.Comment: 13 pages, 4 figures, 7 tables, repository
https://github.com/rumc3dlab/3dlandmarkdetection
Effect of Fuel Ethanol Content on Exhaust Emissions of a Flexible Fuel Vehicle
The European Union is aiming at increasing the market share of biofuels in order to improve the security of supply of transport fuel and to reduce CO2 emissions. The target is to reach a 10% of biofuels on energy basis in the transport sector by 2020.
Bioethanol and biodiesel represent the only biofuels currently available on the market in big quantities and technologically mature and bioethanol is probably the most widely use alternative fuel in the world (mainly in Brazil and in the USA).
According to the literature, the success of bioethanol as alternative fuel is linked to some clear advantages but there are also disadvantages:
Advantages:
- Very high octane number
- As a renewable fuel produces lower CO2 emissions compare to conventional fuels
- It reduces some pollutant emissions
- Its ozone forming potential is lower than that of gasoline and diesel
- It contains no sulphur and is biodegradable
Disadvantages:
- It increases evaporative emissions (when blended with gasoline at low percentages)
- Because of the lower vapour pressure and high latent heat of vaporization of neat ethanol, it makes cold start in cooler climates more difficult.
- It increase acetaldehyde emissions but reduces those of formaldehyde.
- E85 vehicles give higher unregulated emissions (ethane and acetaldehyde) than gasoline fuelled vehicles.
Due to its characteristics neat ethanol cannot be used as transport fuel mainly because its high heat of vaporization and low volatility make cold start very difficult especially in cold climates.
The most common way to overcome this problem is to blend ethanol with a small fraction of a much more volatile fuel such as gasoline; the most popular blend is E85 which consists of 85% ethanol and 15% gasoline by volume. Although E85 has been extensively used worldwide, engine manufacturers guarantee problem-free operation without any modification only to catalyst equipped cars fuelled with gasoline containing no more than 5% ethanol. However modern catalyst-equipped cars are probably able to run without any material problem with up to 20% ethanol which seems to be the upper limit for cold climates.
An experimental activity has been planned and carried out at the JRC to investigate the emissions of a flexible fuel vehicle using different ethanol/gasoline blends. The results of this experimental programme are briefly summarized here below. The details of the work and the complete results are described in the first part of this document (
In particular, three different fuels have been tested: a standard commercial summer gasoline marketed in Italy used as base fuel and two gasoline/ethanol blends, which have been obtained by splash blending ethanol in the standard gasoline. The two gasoline/ethanol blends contained respectively 10% ethanol (E10) and 85% ethanol (E85).
The test vehicle was a passenger car currently marketed in Europe and one of the most popular models belonging to the flexible fuel vehicle category.
Emission tests were carried out both following the European certification procedure (NEDC cycle) and using a US driving cycle (US 06). Regulated and unregulated emissions were measured.JRC.H.4-Transport and air qualit
Towards harmonizing natural resources as an area of protection in life cycle impact assessment
Purpose. In this paper, we summarize the discussion and present the findings of an expert group effort under the umbrella of the United Nations Environment Programme (UNEP)/Society of Environmental Toxicology and Chemistry (SETAC) Life Cycle Initiative proposing natural resources as an Area of Protection (AoP) in Life Cycle Impact Assessment (LCIA).
Methods: As a first step, natural resources have been defined for the LCA context with reference to the overall UNEP/SETAC Life Cycle Impact Assessment (LCIA) framework. Second, existing LCIA methods have been reviewed and discussed. The reviewed methods have been evaluated according to the considered type of natural resources and their underlying principles followed (use-to-availability ratios, backup technology approaches, or thermodynamic accounting methods).
Results and discussion. There is currently no single LCIA method available that addresses impacts for all natural resource categories, nor do existing methods and models addressing different natural resource categories do so in a consistent way across categories. Exceptions are exergy and solar energy-related methods, which cover the widest range of resource categories. However, these methods do not link exergy consumption to changes in availability or provisioning capacity of a specific natural resource (e.g., mineral, water, land etc.). So far, there is no agreement in the scientific community on the most relevant type of future resource indicators (depletion, increased energy use or cost due to resource extraction, etc.). To address this challenge, a framework based on the concept of stock/fund/flow resources is proposed to identify, across natural resource categories, whether depletion/dissipation (of stocks and funds) or competition (for flows) is the main relevant aspect.
Conclusions. An LCIA method—or a set of methods—that consistently address all natural resource categories is needed in order to avoid burden shifting from the impact associated with one resource to the impact associated with another resource. This paper is an important basis for a step forward in the direction of consistently integrating the various natural resources as an Area of Protection into LCA
Advancing on large-scale trends of apparent organic matter reactivity in marine sediments and patterns of benthic carbon transformation
The sweet spot in sustainability: a framework for corporate assessment in sugar manufacturing
The assessment of corporate sustainability has become an increasingly important topic, both within academia and in industry. For manufacturing companies to conform to their commitments to sustainable development, a standard and reliable measurement framework is required. There is, however, a lack of sector-specific and empirical research in many areas, including the sugar industry. This paper presents an empirically developed framework for the assessment of corporate sustainability within the Thai sugar industry. Multiple case studies were conducted, and a survey using questionnaires was also employed to enhance the power of generalisation. The developed framework is an accurate and reliable measurement instrument of corporate sustainability, and guidelines to assess qualitative criteria are put forward. The proposed framework can be used for a company’s self-assessment and for guiding practitioners in performance improvement and policy decision-maki
Exploring the brown dwarf desert : new substellar companions from the SDSS-III MARVELS survey
Planet searches using the radial velocity technique show a paucity of companions to solar-type stars within ∼5 au in the mass range of ∼10–80 MJup. This deficit, known as the brown dwarf desert, currently has no conclusive explanation. New substellar companions in this region help assess the reality of the desert and provide insight to the formation and evolution of these objects. Here, we present 10 new brown dwarf and 2 low-mass stellar companion candidates around solar-type stars from the Multi-object APO Radial Velocity Exoplanet Large-Area Survey (MARVELS) of the Sloan Digital Sky Survey III. These companions were selected from processed MARVELS data using the latest University of Florida Two Dimensional pipeline, which shows significant improvement and reduction of systematic errors over previous pipelines. The 10 brown dwarf companions range in mass from ∼13 to 76 MJup and have orbital radii of less than 1 au. The two stellar companions have minimum masses of ∼98 and 100 MJup. The host stars of the MARVELS brown dwarf sample have a mean metallicity of [Fe/H] = 0.03 ± 0.08 dex. Given our stellar sample we estimate the brown dwarf occurrence rate around solar-type stars with periods less than ∼300 d to be ∼0.56 per cent
Sulfated seaweed polysaccharides as multifunctional materials in drug delivery applications
In the last decades, the discovery of metabolites from marine resources showing biological activity has increased significantly. Among marine resources, seaweed is a valuable source of structurally diverse bioactive compounds. The cell walls of marine algae are rich in sulfated polysaccharides, including carrageenan in red algae, ulvan in green algae and fucoidan in brown algae. Sulfated polysaccharides have been increasingly studied over the years in the pharmaceutical field, given their potential usefulness in applications such as the design of drug delivery systems. The purpose of this review is to discuss potential applications of these polymers in drug delivery systems, with a focus on carrageenan, ulvan and fucoidan. General information regarding structure, extraction process and physicochemical properties is presented, along with a brief reference to reported biological activities. For each material, specific applications under the scope of drug delivery are described, addressing in privileged manner particulate carriers, as well as hydrogels and beads. A final section approaches the application of sulfated polysaccharides in targeted drug delivery, focusing with particular interest the capacity for macrophage targeting
Testicular Microlithiasis: Prevalence and Clinical Significance in a Population Referred for Scrotal Ultrasonography
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