4,054 research outputs found
Effect of CaO content in raw material on the mineral composition of ferric-rich sulfoaluminate clinker
No full textFerric-rich calcium sulfoaluminate (FR-CSA) cement is an eco-friendly cement. Fe2O3 exists in different minerals of FR-CSA clinker, e.g., Ca4Al2Fe2O10 (C4AF), Ca2Fe2O5 (C2F), and Ca4Al6-2xFe2xSO16 (C4A3-xFxS-). The mineral composition depends on the chemical composition of the raw materials and significantly determines the reactivity of FR-CSA cement. To optimize the phase composition of the FR-CSA clinker, chemical reagent raw mixtures with different amounts of CaO were used to prepare the FR-CSA clinker. X-ray diffraction (XRD) analysis, Rietveld quantitative phase analysis (RQPA), Fourier Transform Infrared spectroscopy (FT-IR), and scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) were used to identify the mineralogical conditions of the FR-CSA clinker. The results indicated that the amounts of CaO in raw materials greatly affected the iron-bearing phase formation in the FR-CSA clinker. With decreasing CaO content involved in calcination reaction, the amounts of Fe2O3 incorporated in C4A3-xFxS- increased up to 17.72 wt% (where x = 0.36). The findings make it possible to optimize the mineral composition of the FR-CSA clinker by changing the CaO content in raw materials. Furthermore, low CaO content in the raw material is beneficial to the formation of C4A3-xFxS-, which enables the use of solid wastes containing low calcium for producing FR-CSA cement.Accepted author manuscriptMaterials and Environmen
Stabilization/Solidification of Nitrobenzene Contaminated Soil based on Hydrophobilized CaO
No full textAbstractLime, one of the common binders used in Solidification/Stabilization (S/S), is not adequate to immobilize toxic organic compounds of high-concentration released into soil by accidents in petrochemical and chemical industries. CaO, the main composition of lime, was hydrophobilized with stearic acid (SA) and silane coupling agent (KH570) to improve its fixation of nitrobenzene in S/S remediation of contaminated soil in present work, and the effect of hydrophobilized CaO on toxic organic compound encapsulation was evaluated through leaching and volatilization tests. Results showed that the binder composed of 20% SA hydrophobilized CaO together with 10% original CaO could reduce nitrobenzene's volatilization ratio to 0.096% and leaching ratio to 8.79%, while the nitrobenzene's volatilization ratio is 0.413% and leaching ratio is 35.48% with 30% original CaO as the binder
A Guiding Vector-Field algorithm for path-following control of nonholonomic mobile robots
No full textIn this paper, we propose an algorithm for path-following control of the nonholonomic mobile robot based on the idea of the guiding vector field (GVF). The desired path may be an arbitrary smooth curve in its implicit form, that is, a level set of a predefined smooth function. Using this function and the robot's kinematic model, we design a GVF, whose integral curves converge to the trajectory. A nonlinear motion controller is then proposed, which steers the robot along such an integral curve, bringing it to the desired path. We establish global convergence conditions for our algorithm and demonstrate its applicability and performance by experiments with wheeled robots.Accepted Author ManuscriptTeam Tamas Keviczk
Structural Characterization of the Chlorophyllide a Oxygenase (CAO) Enzyme Through an In Silico Approach
No full textChlorophyllide a oxygenase (CAO) is responsible for converting chlorophyll a to chlorophyll b in a two-step oxygenation reaction. CAO belongs to the family of Rieske-mononuclear iron oxygenases. Although the structure and reaction mechanism of other Rieske monooxygenases have been described, a member of plant Rieske non-heme iron-dependent monooxygenase has not been structurally characterized. The enzymes in this family usually form a trimeric structure and electrons are transferred between the non-heme iron site and the Rieske center of the adjoining subunits. CAO is supposed to form a similar structural arrangement. However, in Mamiellales such as Micromonas and Ostreococcus, CAO is encoded by two genes where non-heme iron site and Rieske cluster localize on the distinct polypeptides. It is not clear if they can form a similar structural organization to achieve the enzymatic activity. In this study, the tertiary structures of CAO from the model plant Arabidopsis thaliana and the Prasinophyte Micromonas pusilla were predicted by deep learning-based methods, followed by energy minimization and subsequent stereochemical quality assessment of the predicted models. Furthermore, the chlorophyll a binding cavity and the interaction of ferredoxin, which is the electron donor, on the surface of Micromonas CAO were predicted. The electron transfer pathway was predicted in Micromonas CAO and the overall structure of the CAO active site was conserved even though it forms a heterodimeric complex. The structures presented in this study will serve as a basis for understanding the reaction mechanism and regulation of the plant monooxygenase family to which CAO belongs
Residential self-selection in the relationship between the built environment and travel behavior: A literature review and research agenda
No full textThis chapter gives an overview of the current debates on residential self-selection and presents a related research agenda. Here, we define residential self-selection as “the tendency of people to choose residential locations based on their travel abilities, needs and preferences.” Debates relate to theory/causalities (including the role of attitudes), research methods, empirical findings (including the magnitude of the importance of residential self-selection for the influence of the built environment on travel behavior and the dominance of OECD (Organization for Economic Co-operation and Development) countries), and the implications for planning. The main contribution is in translating the current debates into a research agenda. Challenging avenues for future research are partly inspired by these debates, and include changing attitudes, qualitative research, multiple causal structures, extending the scope to other areas than residential areas, the existence of threshold values for the strength of preferences to be important for residential self-selection, the role of perceived accessibility, non-OECD countries, and planning implications.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport and Logistic
Evolutionary Changes in Chlorophyllide a Oxygenase (CAO) Structure Contribute to the Acquisition of a New Light-harvesting Complex in Micromonas
No full textChlorophyll b is found in photosynthetic prokaryotes and primary and secondary endosymbionts, although their light-harvesting systems are quite different. Chlorophyll b is synthesized from chlorophyll a by chlorophyllide a oxygenase (CAO), which is a Rieske-mononuclear iron oxygenase. Comparison of the amino acid sequences of CAO among photosynthetic organisms elucidated changes in the domain structures of CAO during evolution. However, the evolutionary relationship between the light-harvesting system and the domain structure of CAO remains unclear. To elucidate this relationship, we investigated the CAO structure and the pigment composition of chlorophyll-protein complexes in the prasinophyte Micromonas. The Micromonas CAO is composed of two genes, MpCAO1 and MpCAO2, that possess Rieske and mononuclear iron-binding motifs, respectively. Only when both genes were introduced into the chlorophyll b-less Arabidopsis mutant (ch1-1) was chlorophyll b accumulated, indicating that cooperation between the two subunits is required to synthesize chlorophyll b. Although Micromonas has a characteristic light-harvesting system in which chlorophyll b is incorporated into the core antennas of reaction centers, chlorophyll b was also incorporated into the core antennas of reaction centers of the Arabidopsis transformants that contained the two Micromonas CAO proteins. Based on these results, we discuss the evolutionary relationship between the structures of CAO and light-harvesting systems
Du shu cao tang ming shi: si juan.
No full text順德簡朝亮述."排印留版存讀書草堂, 上海中華書局承印"--Title page verso.Shunde Jian Zhaoliang shu."Pai yin liu ban cun Du shu cao tang, Shanghai Zhonghua shu ju cheng yin"--Title page verso
Calciothermic reduction of NiO by molten salt electrolysis of CaO in CaCl2 melt
No full textMetallic nickel powders with low and uniform residual oxygen content were produced from NiO using the molten salt electrolysis of CaO in CaCl2 melt. Suitable amount of CaO for the reduction was in the range of 0.5-3.0 mol% CaO. The electrical isolation of NiO from both electrodes could produce metallic Ni in CaCl2 melt. Separating the metal oxides from the cathode confirmed the mechanism of calciothermic reduction that the electrolysis of dissolved CaO in CaCl2 melt produces Ca, and that the dissolved Ca in molten CaCl2 successfully reduces NiO to metallic Ni. An average of about 600 ppm oxygen in Ni sample was achieved directly from oxide, when NiO was detached from the cathode
Bidirectional branch and bound for controlled variable selection. Part II: exact local method for self-optimizing control
No full textThe selection of controlled variables (CVs) from available measurements through
enumeration of all possible alternatives is computationally forbidding for
large-dimensional problems. In Part I of this work [Cao, Y., & Kariwala, V.
(2008). Bidirectional branch and bound for controlled variable selection: Part
I. Principles and minimum singular value criterion. Comput. Chem. Eng., 32
(10),2306-2319], we proposed a bidirectional branch and bound (BAB) approach for
subset selection problems and demonstrated its efficiency using the minimum
singular value criterion. In this paper, the BAB approach is extended for CV
selection using the exact local method for self-optimizing control. By
redefining the loss expression, we show that the CV selection criterion for
exact local method is bidirectionally monotonic. A number of novel determinant
based criteria are proposed for fast pruning and branching purposes resulting in
a computationally inexpensive BAB approach. We also establish a link between the
problems of selecting a subset and combinations of measurements as CVs and
present a partially bidirectional BAB method for selection of measurements,
whose combinations can be used as CVs. Numerical tests using randomly generated
matrices and binary distillation column case study demonstrate the computational
efficiency of the proposed methods. (C) 2009 Elsevier Ltd. All rights reserved
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