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Isomorphous Substitution of Gallium into MFI-Framework Zeolite Increases 2,5-Dimethylfuran to Aromatics Selectivity and Suppresses Catalyst Deactivation
Get PDFThe valorization of biomass-derived molecules into commodity chemicals is important for the transition to renewable feedstocks. The model platform molecule 2,5-dimethylfuran (2,5-dmf) can be converted into value-added aromatics such as benzene, toluene, and xylenes (BTX) over zeolite catalysts. To explore the role of the zeolite acid site(s) in BTX selectivity, gallium has been isomorphously substituted into the framework, resulting in a Ga-silicate. Compared to the ZSM-5 counterpart, this modification shows enhanced benzene selectivity as well as resistance to deactivation by coke in continuous catalytic performance tests.Guido J. L. de Reijer and Christopher Sauer have contributed equally to this work
Bike-sharing systems rebalancing considering redistribution proportions: A user-based repositioning approach
No full textBike-sharing systems have become an indispensable transportation mode due to the environmental friendliness and shareability in the sustainable cities development process. However, the asymmetry of people\u27s travel patterns during the morning and evening rush hours has contributed to the imbalance in bike inventory. Consequently, station rentals and returns require redistribution to address the rebalancing of bikes. In this paper, a user-based repositioning method through a bi-level programming model is proposed. With the objective of minimizing the repositioning workload, the upper-level model yields redistribution proportions that enable the balance between rentals and returns at the station. In addition, aiming at maximum user profit, the lower-level model calculates a redistribution matrix between station pairs and provides recommended stations for users. Finally, three levels of evaluation indicators for the bike-sharing system, operators, and users are presented. The results indicate that the proposed user-based repositioning is remarkably effective in improving the bike inventory balance and the station\u27s turnover rate. This study provides a novel idea for the bike-sharing repositioning problem and contributes to the improvement of urban transportation
Combined metabolic activators improve metabolic functions in the animal models of neurodegenerative diseases
Get PDFBackground: Neurodegenerative diseases (NDDs), including Alzheimer\u27s disease (AD) and Parkinson\u27s disease (PD), are associated with metabolic abnormalities. Integrative analysis of human clinical data and animal studies have contributed to a better understanding of the molecular and cellular pathways involved in the progression of NDDs. Previously, we have reported that the combined metabolic activators (CMA), which include the precursors of nicotinamide adenine dinucleotide and glutathione can be utilized to alleviate metabolic disorders by activating mitochondrial metabolism. Methods: We first analysed the brain transcriptomics data from AD patients and controls using a brain-specific genome-scale metabolic model (GEM). Then, we investigated the effect of CMA administration in animal models of AD and PD. We evaluated pathological and immunohistochemical findings of brain and liver tissues. Moreover, PD rats were tested for locomotor activity and apomorphine-induced rotation. Findings: Analysis of transcriptomics data with GEM revealed that mitochondrial dysfunction is involved in the underlying molecular pathways of AD. In animal models of AD and PD, we showed significant damage in the high-fat diet groups\u27 brain and liver tissues compared to the chow diet. The histological analyses revealed that hyperemia, degeneration and necrosis in neurons were improved by CMA administration in both AD and PD animal models. These findings were supported by immunohistochemical evidence of decreased immunoreactivity in neurons. In parallel to the improvement in the brain, we also observed dramatic metabolic improvement in the liver tissue. CMA administration also showed a beneficial effect on behavioural functions in PD rats. Interpretation: Overall, we showed that CMA administration significantly improved behavioural scores in parallel with the neurohistological outcomes in the AD and PD animal models and is a promising treatment for improving the metabolic parameters and brain functions in NDDs
Penetration of corrosive species into copper exposed to simulated O2-free groundwater by time-of-flight secondary ion mass spectrometry (ToF-SIMS)
Get PDFToF-SIMS analysis of copper samples after exposures to simulated groundwater with and without sulfide addition was performed to investigate the penetration of corrosive species containing H, S, O, and Cl, into copper. Depth profiles show extent of penetration and 2D/3D images reveal local elemental distribution of the corrosive species at different depths inside copper. Pre-oxidation did not reduce the penetration while sulfide additional in groundwater and exposure at 60 \ub0C significantly promoted the penetration. The extent of penetration of the corrosive species into copper demonstrates the need for risk assessment of complex corrosion forms such as sulfide-induced embrittlement and cracking
Development and analysis of the two-regime transient tyre model for combined slip
Get PDFThis paper refines the two-regime transient theory developed by Romano et\ua0al.\ua0[Romano L, Bruzelius F, Jacobson B. Unsteady-state brush theory. Vehicle Syst Dyn. 2020;59:11–29. DOI:\ua010.1080/00423114.2020.1774625.] to include the effect of combined slip. A nonlinear system is derived that describes the non-steady generation of tyre forces and considers the coupling between the longitudinal and lateral characteristics. The proposed formulation accounts for both the carcass and the bristle dynamics, and represents a generalisation of the single contact point models. A formal analysis is conducted to investigate the effect of the tyre carcass anisotropy on the properties of the system. It is concluded that a fundamental role is played by the ratio between the longitudinal and lateral relaxation lengths. In particular, it is demonstrated that the maximum slip that guarantees (partial) adhesion conditions does not coincide with the stationary value and decreases considerably for highly anisotropic tyres. The dissipative nature of the model is also analysed using elementary tools borrowed from the classic theory for nonlinear systems. A comparison is performed against the single contact point models, showing a good agreement especially towards the full-nonlinear one. Furthermore, compared to the single contact point models, the two-regime appears to be able to better replicate the exact dynamics of the tyre forces predicted by the complete brush theory. Finally, the transient model is partially validated against experimental results
Literature review on crack retrofitting in steel by Tungsten Inert Gas remelting
Get PDFWelded metallic structures are usually prone to different forms of degradation in the mechanical properties during their life span such as fatigue. Tungsten Inert Gas remelting is a post-weld treatment method that gained increasing interest in the last decades. However, more light should be thrown on the behaviour of the existing cracked structures retrofitted by TIG-remelting. Therefore, fatigue test results of several welded details improved TIG-remelting have been extracted. Around 130 test results with different existing crack sizes are presented and analyzed. The gain factor in fatigue is defined and calculated for the collected data. TIG-remelting shows high potential in life extension. In fact, TIG-remelting is found to give a fair life extension greater than the design life of the new details even when 2 crack mm remains. Besides, toe radius and residual stresses are found to vary significantly after TIG-remelting depending on the remelting parameters and the steel type
Resource renewal in heavy business networks: the case of Modvion starting up in the Swedish wind energy context
Get PDFPurpose: Taking the perspective of a start-up company, the purpose of this paper is to analyse resource renewal in heavy business networks. Design/methodology/approach: The theoretical framework is based on the Industrial Network Approach and, especially, the resource interaction framework, business network settings and studies of starting up in business networks. The basis for the paper is a case study of a start-up in the Swedish wind energy context. Findings: Resource renewal in this case means replacing one resource, having implications for the resource interfaces in the three business network settings. Research limitations/implications: The paper contributes to the area of studies of starting up in business networks by identifying a distinct form of resource renewal in heavy business networks enabled by development of resource interfaces in three business network settings. Practical implications: Managers in start-ups as well as established firms need to interact to create and develop the resource interfaces that are needed to achieve resource renewal. Resource renewal not only is in the hands of start-ups but also requires interactive resource development with various collaboration partners. Originality/value: This study takes a start-up’s perspective to resource renewal of heavy business networks and analyses heaviness based on resource interfaces in three business network settings
A Move Forward: Exploring National Identity Through Non-linear Principal Component Analysis in Germany
Get PDFIn research on national identity, scholars have developed a wide variety of approaches to measure and better understand this ubiquitous yet complex concept. To date, most of these approaches have been theory-driven, while only a very few have been data-driven. In this article, we aim to contribute to the latter by introducing a new data-driven method that has not been applied yet—that of non-linear principal component analysis (NLPCA). In contrast to other commonly used methods such as factor analysis, NLPCA distinguishes itself by making relatively few assumptions about the data and by allowing for greater flexibility when discovering underlying dimensions of such a complex concept as national identity. Drawing on the 2013 ISSP National Identity module, our analysis focuses on the case of Germany, also taking into account Western and Eastern Germany. Running an NLPCA, we find four dimensions that cover the multidimensionality of national identity: nationalistic attitudes, national pride and attachment, cosmopolitan beliefs, and membership criteria defining national belonging. This article contributes to the empirical debate on measuring national identity by suggesting a new and flexible methodological approach that better grasps the concept’s complexity and which we believe can move empirical research on national identity forward in and beyond Germany
Catalytic Conversion of Hydrocarbons and Formation of Carbon Nanofilaments in Porous Pellets
Get PDFCatalytic conversion of hydrocarbons occurring at metal nanoparticles in porous pellets is often accompanied by the formation of coke in the form of growing heterogeneous film-like aggregates or carbon nanofilaments. The latter processes result in deactivation of metal nanoparticles. The corresponding kinetic models imply the formation and growth of film-like coke aggregates. Herein, I present an alternative generic kinetic model focused on the formation and growth of carbon nanofilaments. These processes are considered to deactivate metal nanoparticles and reduce the rate of reactant diffusion in pores. In this framework, the kinetically limited reaction regime is described by simple analytical expressions. The diffusion-limited regime can be described as well but only numerically. The model presented can be used for interpretation of experimental results. [GRAPHICS]
Disruption Mitigation in Tokamaks with Massive Material Injection
Get PDFThe sudden loss of confinement of the energy content of fusion plasmas in off-normal events, called disruptions, is among the most severe threats to the future of fusion energy based on the tokamak design. An efficient disruption mitigation system will therefore be of utmost importance for future large, high-current devices such as ITER. The potentially greatest threat to be mitigated is posed by currents carried by highly energetic electrons, called runaway electrons, which may cause severe damage upon wall impact. The disruption mitigation system must also ensure a sufficiently homogeneous deposition of the thermal energy on the plasma-facing components, and avoid excessive forces on the machine due to currents flowing in the surrounding structures. The currently envisaged mitigation method is to initiate a massive material injection, e.g. in the form of a pressurized gas or a shattered cryogenic pellet, when an emerging disruption is detected, and so attempt to better control the plasma cooling and energy dissipation. In this thesis, we develop modeling tools for the various physical phenomena present during a tokamak disruption mitigated by a massive material injection. This includes extending the numerical tools GO and DREAM with the capability to handle more advanced geometry, effects of partial ionization in the cooling plasma on the generation of runaway electrons, and the material assimilation in the plasma following a shattered pellet injection. These tools are then used to perform integrated numerical simulations, assessing the mitigation performance for a wide range of injection scenarios in reactor-scale tokamak devices. Finally, we also develop an analytical model for the radial transport of the relatively cold and dense material recently ablated from a shattered pellet upon exposure to the hot plasma.Our results indicate that the severity of a disruption in a reactor-scale device can be significantly reduced by a carefully chosen injection scheme and composition of the injected material. In particular, a two-stage shattered pellet injection might efficiently reduce the localised heat loads and the runaway generation due to the hot-tail mechanism, by allowing for an intermediate equilibration of the superthermal electron population between the injections. However, the strong runaway avalanche associated with a high plasma current was found to be able to amplify even a very small runaway seed, such as those produced by tritium decay and Compton scattering during nuclear operation, to several mega-amperes. The reason is that the intense cooling from the injected material leads to a high induced electric field and a substantial recombination, resulting in an enhanced avalanche multiplication. Our calculations also indicate that this mitigation scheme might be further complicated by a relatively large outward drift of the recently ablated pellet material