On the Harmonic Mobius Transformations
Hernandez, R and Martin, MJ
Jan 2022 | JOURNAL OF GEOMETRIC ANALYSIS 32 (1)
It is well-known that two locally univalent analytic functions have equal Schwarzian derivative if and only if each one of them is a composition of the other with a non-constant Mobius transformation. The main goal in this paper is to extend this result to the cases when the functions considered are harmonic. That is, we identify completely the transformations that preserve the (harmonic) Schwarzian derivative of locally univalent harmonic functions. Ver más.

Business perception of obstacles to innovate: Evidence from Chile with pseudo-panel data analysis
Ortiz, R and Fernandez, V
Jan 2022 | RESEARCH IN INTERNATIONAL BUSINESS AND FINANCE 59
The extant literature on firm-level innovation has primarily focused on the driving forces of successful innovation; thus, paying less attention to obstacles associated with innovation inputs and outputs. On the other hand, most studies on innovation impediments have concentrated on financial obstacles, overlooking other kinds of barriers as important for companies engaged in innovation. This article fills this gap by studying the impact of perceived obstacles on a set of inputs to and outputs from the innovation process. Empirical results based on the 6th-10th Chile Business Innovation Surveys confirm that perceived non-financial obstacles, such as knowledge, cooperation, market, demand, and regulation, are as important as perceived financial impediments. Ver más.

Hydrogen supply chain optimisation for the transport sector-Focus on hydrogen purity and purification requirements
Wickham, D; Hawkes, A and Jalil-Vega, F
Jan 1 2022 | APPLIED ENERGY 305
This study presents a spatially-resolved optimisation model to assess cost optimal configurations of hydrogen supply chains for the transport sector up to 2050. The model includes hydrogen grades and separation/purification technologies, offering the possibility to assess the effects that hydrogen grades play in the development of cost-effective hydrogen supply chains, including the decisions to repurpose gas distribution networks or blending hydrogen into them. The model is implemented in a case study of Great Britain, for a set of decarbonisation and learning rate scenarios. A base case with a medium carbon price scenario shows that the total discounted cost of the hydrogen supply chain is significantly higher than shown in previous studies, largely due to the additional costs from purification/separation needed to meet hydrogen purity standards for transport applications. Furthermore, it was shown that producing hydrogen from steam methane reforming with carbon capture and storage; installing new transmission pipelines; repurposing the gas distribution network to supply 100% hydrogen; and purifying hydrogen with a pressure swing adsorption system locally at the refuelling station; is a cost optimal configuration for the given technoeconomic assumptions, providing hydrogen at 6.18 pound per kg at the pump. Purification technologies were found to contribute to 14% and 30% of total discounted investment and operation costs respectively, highlighting the importance of explicitly including them into hydrogen supply chain models for the transport sector. Ver más.

Risk-Based Design of Regular Plane Frames Subject to Damage by Abnormal Events: A Conceptual Study
Beck, AT; Ribeiro, LD; (…); Jensen, H
Jan 1 2022 | JOURNAL OF STRUCTURAL ENGINEERING 148 (1)Enriched Cited References
Constructed facilities should be robust with respect to the loss of load-bearing elements due to abnormal events. Yet, strengthening structures to withstand such damage has a significant impact on construction costs. Strengthening costs should be justified by the threat and should result in smaller expected costs of progressive collapse. In regular frame structures, beams and columns compete for the strengthening budget. Ver más.

Watching the world from my screen: A longitudinal evaluation of the influence of a problematic use of the internet on depressive symptomatology
Hernandez, C; Cottin, M; (…); Behn, A
Jan 2022 | COMPUTERS IN HUMAN BEHAVIOR 126
Previous research has found a consistent association between depressive symptomatology and a problematic use of the Internet, however, the causal pathways responsible for this association are not well known. Following emotion regulation theory, the present study aimed to explore the longitudinal dynamics between using the Internet to distract oneself, difficulties controlling Internet use, and depressive symptoms. Ver más.

A simplified analytical model for radiation dominated ignition of solid fuels exposed to multiple non-steady heat fluxes
Parot, R; Rivera, JI; (…); Fuentes, A
Mar 2022 | COMBUSTION AND FLAME 237
Heat fluxes from fires are strongly time-dependent. Historically, the thermal ignition theory in its classical form has neglected this time dependency until recent years, where theories have been developed to include time-varying incident heat fluxes. This article proposes a simplified general model formulation for the heating of solid fuels exposed to four different heat flux behaviors, considering the penetration of radiation into the medium. The incident heat flux cases developed where: Constant, Linear, Exponential and Polynomial, which represent different situations related to structural and wildland fires. The analytical models consider a spatially averaged medium temperature and exact and approximate solutions are presented, based on the critical ignition temperature criterion, which are valid for solids of any optical thickness. The results were validated by comparison with various models presented in the literature, where the model granted in this work was capable to adjust to all of them, especially when high heat fluxes are involved. Therefore, the proposed model acquires a significant engineering utility since it provides a single model to be used as a general and versatile tool to predict the ignition delay time in a manageable way for solid fuels exposed to different fire conditions. (c) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved. Ver más.

Isogeometric multilevel quadrature for forward and inverse random acoustic scattering
Dolz, J; Harbrecht, H; (…); Multerer, M
Jan 1 2022 | COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 388
We study the numerical solution of forward and inverse time-harmonic acoustic scattering problems by randomly shaped obstacles in three-dimensional space using a fast isogeometric boundary element method. Within the isogeometric framework, realizations of the random scatterer can efficiently be computed by simply updating the NURBS mappings which represent the scatterer. Ver más.

Performance of a two-stage partial nitritation-anammox system treating the supernatant of a sludge anaerobic digester pretreated by a thermal hydrolysis process
Valenzuela-Heredia, D; Panatt, C; (…); Campos, JL
Feb 1 2022 | CHEMICAL ENGINEERING JOURNAL 429
A two-stage system (partial nitritation (PN) and anammox processes) was used to remove nitrogen from the dewatering liquor originating from the thermal hydrolysis/anaerobic digestion (THP/AD) of municipal WWTP sludge. Two strategies were tested to start up the PN reactor: 1) maintaining a fixed hydraulic retention time (HRT) and increasing the ammonium loading rate (ALR) by decreasing the feeding dilution ratio and 2) feeding undiluted dewatering liquor and gradually decreasing the HRT. With diluted feeding, the reactor performance had destabilization episodes that were statistically correlated with the application of high specific ammonium (> 0.6 g NH4+-N/(g TSS.d)) and organic (> 0.7 g COD/(g TSS.d)) loading rates. The second strategy allowed stable PN reactor operation while treating ALR up to 4.8 g NH4+-N/(L.d) and demonstrating that dilution of THP/AD effluents is not required. The operating conditions promoted the presence of free nitrous acid levels (> 0.14 mg HNO2-N/L) inside the PN reactor that inhibited the proliferation of nitrite oxidizing bacteria.

Batch activity tests showed that the inhibitory effects of organic compounds present in the THP/AD dewatering liquor on the ammonia oxidizing bacteria activity can be removed in the PN reactor. Thus, aerobic pretreatment would not be necessary when two-stage systems are used. The PN reactor effluent was successfully treated by an anammox reactor.

An economic analysis showed that using two-stage systems is advantageous for treating THP/AD dewatering liquor. The implementation of an aerobic pre-treatment unit is recommended for WWTPs capacities higher than 5.10(5) inhabitants equivalent when one-stage systems are used. Ver más.

Ocean acidification alters anti-predator responses in a competitive dominant intertidal mussel
Jahnsen-Guzman, N; Lagos, NA; (…); Duarte, C
Feb 2022 | CHEMOSPHERE 288
Widespread intertidal mussels are exposed to a variety of natural and anthropogenic stressors. Even so, our understanding of the combined influence of stressors such as predation risk and ocean acidification (OA) on these species remains limited. This study examined the response of the purple mussel (Perumytilus purpuratus), a species distributed along Pacific southeastern rocky shores, to the effects of predation risk and OA. Ver más.

Data-driven and active learning of variance-based sensitivity indices with Bayesian probabilistic integration
Song, JW; Wei, PF; (…); Beer, M
Jan 15 2022 | MECHANICAL SYSTEMS AND SIGNAL PROCESSING 163
Variance-based sensitivity indices play an important role in scientific computation and data mining, thus the significance of developing numerical methods for efficient and reliable estimation of these sensitivity indices based on (expensive) computer simulators and/or data cannot be emphasized too much. In this article, the estimation of these sensitivity indices is treated as a statistical inference problem. Ver más.