149 research outputs found
Regional water balance analysis of glacierised river basins in the north-eastern Himalaya applying the J2000 hydrological model
The glacierised basins of the Northeast Himalayan region are highly vulnerable to climate-change impacts. The spatio-temporal hydroclimatic and physiographic variability impact the water balance of these glacierised basins across the region. This study assesses the glaciohydrological processes and dynamics in the data scarce region for the present as well future climate change scenarios by regional water balance analysis. The J2000 hydrological model was adapted to incorporate the frozen ground as well as glacier dynamics in a stepwise, nested basin calibration approach. The modelled ERA-Interim precipitation data cannot capture the high amplitude orographic and convective events. Therefore, Orographic correction factors were used to inversely correct the ERA-Interim precipitation data to account for the orographic as well as cyclonic precipitation in the region from reported glacier mass balance and evapotranspiration estimates. Monthly temperature lapse rate was adopted for correcting the ERA-Interim temperature dataset. The Beki basin was selected as the donor basin for model development and evaluation. The parameters from the Beki basin were regionalised to the receptor Lohit and the Noadihing basins by the Proxy-basin method. Multi-objective optimization criteria such as the Kling-Gupta efficiency (KGE) for temporal dynamics and flow distribution and Bias for overall water balance showed high to moderate conformity between measured and simulated discharge at the corresponding basin outlets. The variability in the water balance and runoff components among the three basins was primarily related to the spatio-temporal variation in the mean annual precipitation, runoff and evapotranspiration estimates. The impact of climate-change scenarios on the study basins indicated that water availability would sustain until the end of the century due to higher projected precipitation even though after the depletion of glaciers in the region
Advanced Technologies for Biomass
The use of biomass and organic waste material as a primary resource for the production of fuels, chemicals, and electric power is of growing significance in light of the environmental issues associated with the use of fossil fuels. For this reason, it is vital that new and more efficient technologies for the conversion of biomass are investigated and developed. Today, various advanced methods can be used for the conversion of biomass. These methods are broadly classified into thermochemical conversion, biochemical conversion, and electrochemical conversion. This book collects papers that consider various aspects of sustainability in the conversion of biomass into valuable products, covering all the technical stages from biomass production to residue management. In particular, it focuses on experimental and simulation studies aiming to investigate new processes and technologies on the industrial, pilot, and bench scales
3D Information Technologies in Cultural Heritage Preservation and Popularisation
This Special Issue of the journal Applied Sciences presents recent advances and developments in the use of digital 3D technologies to protect and preserve cultural heritage. While most of the articles focus on aspects of 3D scanning, modeling, and presenting in VR of cultural heritage objects from buildings to small artifacts and clothing, part of the issue is devoted to 3D sound utilization in the cultural heritage field
The need for disruption in the credit ratings landscape : a model for machine learning computed credit ratings.
I present the results from the research on the topics of (1) credit ratings, which are usually
provided by credit rating agencies, and (2) Artificial Intelligence and Machine Learning as a
form of solving classification tasks, such as credit ratings, without the involvement of human
experts. My research problem is stated as follows: to improve the solutions for the credit
rating problem introduced by other credit rating agencies, I propose a rating system in the
form of an expert system. Then I show that this system is more efficient than traditional rating
systems on different hold-out samples of large-scale, multi-period data for public nonfinancial
corporate entities worldwide, and with respect to different forecasting horizons. I
show that my rating system, which is based on an ensemble machine learning method,
specifically Gradient Boosted Decision Trees, when applied to the rating process, outperforms
incumbent rating systems on the accuracy-stability scale measured by a compound metric
Index of the Quality of Ratings, which I develop and introduce.
In the course of the research in addition to the topic of rating performance evaluation,
I have included the comparison of market-implied ratings with fundamental ratings, ratings
forecasting and replication, mapping of ratings of different providers to the universal scale,
financial effects of qualitative ratings for the investors, the stability of ratings, and the cyclical
effects of ratings. The novelty is in the amount of data that I used, including the number and
diversification of the rated entities, also in the number of other rating providers involved in
performance comparison tests and the number of optional models built and tested. I have
shown performance results for different forecasting horizons. The complexity of the proposed
model, its iterative revisions throughout the estimation periods, as well as mapping of ratings
directly through the default ratios, also mark out my research.
The significance of the research is in showing a more reliable, hi-tech, cost- and timeeffective
solution for the problem of credit risk assessment for financial markets participants,
who now rely upon the opinion of credit rating agencies. The key output of the research is
therefore to re-imagine the credit ratings according to modern advances in finance, datascience,
information technology and software. The results of my analysis can be used as a
starting point or proxy for choosing the optimal rating agency for investor’s needs, as a stepby-
step manual to develop a rating system, as a benchmark for the regulation of rating
agencies, or when discussing the quality of ratings in academic and financial papers
Dynamics under Uncertainty: Modeling Simulation and Complexity
The dynamics of systems have proven to be very powerful tools in understanding the behavior of different natural phenomena throughout the last two centuries. However, the attributes of natural systems are observed to deviate from their classical states due to the effect of different types of uncertainties. Actually, randomness and impreciseness are the two major sources of uncertainties in natural systems. Randomness is modeled by different stochastic processes and impreciseness could be modeled by fuzzy sets, rough sets, Dempster–Shafer theory, etc
Mobile Robots Navigation
Mobile robots navigation includes different interrelated activities: (i) perception, as obtaining and interpreting sensory information; (ii) exploration, as the strategy that guides the robot to select the next direction to go; (iii) mapping, involving the construction of a spatial representation by using the sensory information perceived; (iv) localization, as the strategy to estimate the robot position within the spatial map; (v) path planning, as the strategy to find a path towards a goal location being optimal or not; and (vi) path execution, where motor actions are determined and adapted to environmental changes. The book addresses those activities by integrating results from the research work of several authors all over the world. Research cases are documented in 32 chapters organized within 7 categories next described
Sensitive soils of the Puketoka Formation, Hamilton, New Zealand
Sensitive soils are known to cause significant issues in the infrastructure and civil engineering industry, and are prone to sudden, oftentimes catastrophic failures following long periods of stability.
The Walton Subgroup soils deposited through volcanic activity and partially reworked by the ancestral Waikato River are identified within the Hamilton Basin. These materials are of interest to the engineering community, and consultancy groups in the Hamilton area, due to their identified sensitivity. The Puketoka Formation was focused on in this study.
Sampling of material was undertaken at two active construction sites in Hamilton: Dixon Road Roundabout, and Temple View Urban Development. A series of classification tests were completed to determine the samples’ mineralogical and geotechnical characteristics.
Mineralogical testing found that all the materials were silt dominated (55.06 – 81.12 %), with sub-ordinate clay (13.10 – 18.85 %) and sand (5.56 – 25.35 %) fractions. The moisture contents were variable (49 – 65 %). The field moist bulk density varied throughout the samples (1069 – 1576 kg/m3), as did the oven dry bulk densities (645 – 1057 kg/m3). The porosity as a result also varied (36 – 51 %). The void ratios followed the same trend as the porosity values (0.56 – 0.88). The particle densities of the materials also showed variation (1935 – 2487 kg/m3). The activities of all three samples were variable, ranging from inactive (0.60) to active (1.79). The X-Ray Diffraction (XRD) analysis determined that the main clay mineral present within the samples was a kaolinite group clay, either halloysite or kaolinite. The Fieldes & Perrott NaF test to determine the presence of allophane was also completed on the samples. Both tests were negative, confirming the dominance of halloysite. Bulk analysis also determined other constituents of the samples to include quartz, plagioclase, augite and volcanic glass. Scanning Electron Microscopy (SEM) indicated the main halloysite morphologies present to be a combination of short and long tubules, spheroids, plates and book formations. The microstructure was analysed, and the main clay minerals, grains, microaggregates, and pores within the materials described. The microfabric was consistent for all three samples, with each showing an abundance of small pores (< 20 µm). These pores hold significant amounts of water in not readily accessible locations, leading to the highly porous, but poorly permeable nature of the materials. DRAB1 and TV1 showed microstructures consistent with Huppert (1986) and Beattie’s (1990) ‘matrix’ structures, whilst TV2 showed a more dominant ‘skeletal’ to ‘matrix’ structure.
Atterberg limits testing found that the samples had a high liquid limit (59 – 75 %) and plastic limit (41 – 53 %), but a variable plasticity index (8 – 34 %) and liquidity index (0.1 – 2). This placed all three samples within the high plasticity “MH” category upon the Casagrande chart. Consolidated undrained triaxial testing of DRAB1 and TV1 indicated a characteristic normally consolidated response to shear, with the majority of cores showing shear band formation. Only TV1 at 170 kPa displayed an intermediate failure type, potentially occurring due to a combination of material being tested, confining pressure, and the low shear rate allowing time for pressure dissipation. The percentage of axial strain the cores failed at varied (1.81 – 16.35 %), and the peak deviator stress (129 – 277 kPa) and pore water pressure values (717.2 – 879.7 kPa) tended to increase as the confining pressures increased. Graphical outputs show a moderate strain, contractive (MSC) style of failure. The effective shear strength values produced were in keeping with the varying ranges of previously published values (effective cohesion: 0 – 37 kPa, effective friction angle: 27 - 38°). The permeability for all three samples was estimated to be ~10-9 – 10-10. Thin section analyses of failed core sections for DRAB1 at 270 kPa confining pressure and TV1 at 130 and 230 kPa confining pressures found that some degree of shear formation and propagation occurred. The calculated R’ angle for DRAB1 was closely observed in the thin section, however was not for TV1. This was hypothesised to have occurred due to a true shear band failure not occurring, rather the development of intermediate to juvenile shear bands within the soil.
The sensitivity of the Puketoka Formation and wider Walton Subgroup is hypothesised to have been derived from the reworking and weathering the materials experienced. This in turn influenced the porosity and permeability of the materials, which I believe govern the sensitivity of the soils to a degree. Therefore, I believe the Puketoka Formation materials are representative of a silt-dominated, minimally reworked deposit of volcanic origin, that showed appreciable differences compared with the previously studied Tauranga soils.
The remediation strategies used in the engineering industry were also analysed, and the suitability of the strategies in the context of the Puketoka Formation discussed. This assessment provides an overview of why traditional strategies for remediation may not be beneficial in some cases for the Walton Subgroup materials, which could be of benefit to key engineering groups that encounter these soil materials.
The results of this study provide a set of data which can be used as an initial reference point. The findings and hypotheses made could be of use to key groups including local engineering consultancies, who handle these materials regularly
Overview and update of the SPARC Data Initiative: comparison of stratospheric composition measurements from satellite limb sounders
The Stratosphere-troposphere Processes and their Role in Climate (SPARC) Data Initiative (SPARC, 2017) performed the first comprehensive assessment of currently available stratospheric composition measurements obtained from an international suite of space-based limb sounders. The initiative's main objectives were (1) to assess the state of data availability, (2) to compile time series of vertically resolved, zonal monthly mean trace gas and aerosol fields, and (3) to perform a detailed intercomparison of these time series, summarizing useful information and highlighting differences among datasets. The datasets extend over the region from the upper troposphere to the lower mesosphere (300–0.1 hPa) and are provided on a common latitude–pressure grid. They cover 26 different atmospheric constituents including the stratospheric trace gases of primary interest, ozone (O3) and water vapor (H2O), major long-lived trace gases (SF6, N2O, HF, CCl3F, CCl2F2, NOy), trace gases with intermediate lifetimes (HCl, CH4, CO, HNO3), and shorter-lived trace gases important to stratospheric chemistry including nitrogen-containing species (NO, NO2, NOx, N2O5, HNO4), halogens (BrO, ClO, ClONO2, HOCl), and other minor species (OH, HO2, CH2O, CH3CN), and aerosol. This overview of the SPARC Data Initiative introduces the updated versions of the SPARC Data Initiative time series for the extended time period 1979–2018 and provides information on the satellite instruments included in the assessment: LIMS, SAGE I/II/III, HALOE, UARS-MLS, POAM II/III, OSIRIS, SMR, MIPAS, GOMOS, SCIAMACHY, ACE-FTS, ACE-MAESTRO, Aura-MLS, HIRDLS, SMILES, and OMPS-LP. It describes the Data Initiative's top-down climatological validation approach to compare stratospheric composition measurements based on zonal monthly mean fields, which provides upper bounds to relative inter-instrument biases and an assessment of how well the instruments are able to capture geophysical features of the stratosphere. An update to previously published evaluations of O3 and H2O monthly mean time series is provided. In addition, example trace gas evaluations of methane (CH4), carbon monoxide (CO), a set of nitrogen species (NO, NO2, and HNO3), the reactive nitrogen family (NOy), and hydroperoxyl (HO2) are presented. The results highlight the quality, strengths and weaknesses, and representativeness of the different datasets. As a summary, the current state of our knowledge of stratospheric composition and variability is provided based on the overall consistency between the datasets. As such, the SPARC Data Initiative datasets and evaluations can serve as an atlas or reference of stratospheric composition and variability during the “golden age” of atmospheric limb sounding. The updated SPARC Data Initiative zonal monthly mean time series for each instrument are publicly available and accessible via the Zenodo data archive (Hegglin et al., 2020)
Wave Propagation
A wave is one of the basic physics phenomena observed by mankind since ancient time. The wave is also one of the most-studied physics phenomena that can be well described by mathematics. The study may be the best illustration of what is “science”, which approximates the laws of nature by using human defined symbols, operators, and languages. Having a good understanding of waves and wave propagation can help us to improve the quality of life and provide a pathway for future explorations of the nature and universe. This book introduces some exciting applications and theories to those who have general interests in waves and wave propagations, and provides insights and references to those who are specialized in the areas presented in the book
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