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Publication Vapor–liquid equilibria for the binary system 2,2−dimethylbutane + 1,1−dimethylpropyl methyl ether (TAME) at 298.15, 318.15, and 338.15 K(Elsevier, 2004-07-30) Río Hernández, Armando del; Coto, Baudilio; Renuncio, Juan A. R.; Pando, ConcepciónVapor–liquid equilibrium (VLE) data are reported for the binary mixtures formed by 2,2-dimethylbutane and the branched ether 1,1-dimethylpropyl methyl ether (tert-amyl methyl ether or TAME). A Gibbs-van Ness type apparatus was used to obtain total vapor pressure measurements as a function of composition at 298.15, 318.15, and 338.15 K. Deviations from Raoult’s law are positive and very small. These VLE data are analyzed together with excess enthalpy (HmE) data previously reported at 298.15 K using the UNIQUAC model. The modified UNIFAC (Dortmund) model is used to predict VLE data.Item Photonic Bandgap Closure and Metamaterial Behavior in 1D Periodic Chains of High-Index Nanobricks(MDPI, 2022-10-01) Díaz Escobar, Evelyn; Mercadé, Laura; Barreda, Ángela; García Rupérez, Jaime; Martínez, Alejandro; Generalitat Valenciana; Ministerio de Universidades (España)It has been shown that the photonic bandgap of one-dimensional (1D) dielectric periodic thin films can vanish at the first Bragg condition for TM modes. Here, we address the case of 1D photonic crystal slabs formed by a chain of high-index dielectric particles with transversal confinement and show that the Bragg bandgap can vanish for both TE- and TM-like modes. Calculations using plane-wave expansion and finite-difference time-domain methods confirm that the PBG vanishes. PBG closure is explained as being a result of the interplay between the electric and magnetic dipole resonances of the isolated nanoparticle with Bragg resonance, as confirmed by calculating the electric and magnetic dipoles of the isolated nanobricks. This can be considered as a manifestation of the metamaterial behavior of the 1D system when using silicon as an underlying material. Our finding may have important consequences for the fields of photonic crystals and all-dielectric metamaterials.Publication Reducing subspaces for rank-one perturbations of normal operators(2023-08-01) Gallardo Gutiérrez, Eva A.; González Doña, Francisco Javier; Ministerio de Ciencia e Innovación (España); Consejo Superior de Investigaciones Científicas (España); Agencia Estatal de Investigación (España)We study the existence of reducing subspaces for rank-one perturbations of diagonal operators and, in general, of normal operators of uniform multiplicity one. As we will show, the spectral picture will play a significant role in order to prove the existence of reducing subspaces for rank-one perturbations of diagonal operators whenever they are not normal. In this regard, the most extreme case is provided when the spectrum of the rank-one perturbation of a diagonal operator T=D+u¿v (uniquely determined by such expression) is contained in a line, since in such a case T has a reducing subspace if and only if T is normal. Nevertheless, we will show that it is possible to exhibit non-normal operators T=D+u¿v with spectrum contained in a circle either having or lacking non-trivial reducing subspaces. Moreover, as far as the spectrum of T is contained in any compact subset of the complex plane, we provide a characterization of the reducing subspaces M of T such that the restriction T¿M is normal. In particular, such characterization allows us to exhibit rank-one perturbations of completely normal diagonal operators (in the sense of Wermer) lacking reducing subspaces. Furthermore, it determines completely the decomposition of the underlying Hilbert space in an orthogonal sum of reducing subspaces in the context of a classical theorem due to Behncke on essentially normal operators.Publication Vapor–liquid equilibria for the binary systems decane + 1,1-dimethylethyl methyl ether (MTBE) and decane + 1,1-dimethylpropyl methyl ether (TAME) at 308.15, 318.15 and 328.15 K.(Elsevier, 2001-09-15) Río Hernández, Armando del; Coto, Baudilio; Pando, Concepción; Renuncio, Juan A. R.Vapor–liquid equilibrium (VLE) data are reported for the binary mixtures formed by decane and the branched ethers 1,1-dimethylpropyl methyl ether (tert-amyl methyl ether or TAME) and 1,1-dimethylethyl methyl ether (tert-butyl methyl ether or MTBE). A Gibbs–Van Ness type apparatus was used to obtain total vapor pressure measurements for the decane+MTBE and decane+TAME systems as a function of composition at 308.15, 318.15 and 328.15 K. Both systems show a nearly ideal behavior. VLE data are analyzed together with excess enthalpy (HmE) data previously obtained at 298.15 K for these mixtures. The UNIQUAC model is used to correlate VLE and HmE data and the original UNIFAC group contribution model and the modified UNIFAC (Dortmund model) are used to predict VLE and HmE data for the binary systems decane+MTBE and decane+TAME.Item Tuning and switching effects of quasi-BIC states combining phase change materials with all-dielectric metasurfaces(Optica Publishing Group, 2022-08-01) Barreda, Ángela; Zou, Chengjun; Sinelnik, Artem; Menshikov, Evgenii; Sinev, Ivan; Pertsch, Thomas; Staude, IsabelleEmission enhancement of quantum emitters is particularly relevant in the development of single-photon sources, which are key elements in quantum information and quantum communications. All-dielectric metasurfaces offer a route towards strong enhancement of local density of optical states via engineering of high quality factor optical modes. In particular, the recently proposed concept of quasi-bound states in the continuum (quasi-BIC) allows for precise control of such resonances in lattices with an asymmetric unit cell. Still, the spectral band of emission enhancement is usually fixed by the geometric parameters of the metasurface. Here, we propose to utilize phase change materials to tune the properties of light-emitting metasurfaces designed to support quasi-BIC states in the telecom wavelength range. In our design, a thin layer of a phase change material, which provides strong contrast of refractive index when switched from the amorphous to the crystalline state, is located on top of the resonators made of amorphous silicon (a-Si). Depending on the selected phase change material, we numerically demonstrate different functionalities of the metasurface, In particular, for low-loss Sb2Se3 we evidence spectral tuning effects, whereas for Ge2Sb2Te5, we report an “on”/“off” switching effect of the quasi-BIC resonance. Furthermore, we investigate the influence of the crystallization fraction and the asymmetry parameter of the metasurface on the results. This work provides concrete design blueprints for switchable metasurfaces, offering new opportunities for nanophotonics devices or integrated photonic circuits.Item Aplicación de la transformada wavelet discreta a la detección de roturas catastróficas de herramienta durante el taladrado de componentes aeronáuticos estructurales(2024-07-07) Guerra Sancho, Antonio; Domínguez Monferrer, Carlos; Miguélez Garrido, María Henar; Cantero Guisández, José Luis; Agencia Estatal De Investigación (España)Este trabajo presenta un acercamiento a la detección de roturas catastróficas de herramienta en los procesos de taladrado automático que tienen lugar durante la fase de ensamblaje de componentes estructurales aeronáuticos. Durante la fase de taladrado, los componentes del fuselaje se disponen formando apilados híbridos, que incluyen material compuesto de fibra de carbono y aleación de titanio. Las condiciones de mecanizado varían a lo largo de cada agujero dependiendo del material y número de componentes, sus espesores, los parámetros de corte, el sistema de refrigeración y/o lubricación y la sujeción de las piezas. En el proceso de mecanizado de estos apilados híbridos, el grado de complejidad puede dar lugar a condiciones críticas que lleven a la rotura catastrófica de la herramienta. Esta casuística es especialmente problemática por el coste y el tiempo que conlleva, sobre todo en procesos automáticos. Con el fin de detectar en tiempo real el instante en el que ocurren estos eventos, se plantea un método de detección basado en el análisis en el dominio tiempo-frecuencia de las señales de consumo de potencia del husillo principal. En concreto, se estudia la viabilidad de utilizar las transformadas wavelets discretas Haar, Daubechies, Symlet y Coiflet con diferentes niveles de descomposición para detectar roturas considerando señales orrespondientes a una herramienta del sistema productivo de 4.6 mm de diámetro.Publication MAMOM: Multicriteria Attribution Model for Online Marketing(World Scientific, 2022-11-17) Patricio Guisado, Miguel Ángel; Berlanga de Jesús, Antonio; Palomero Méndez, David; Molina López, José Manuel; Ministerio de Ciencia e Innovación (España); Comunidad de Madrid; Universidad Carlos III de MadridOne of the problems facing online marketing in omni-channel environments is efficient budget allocation to each channel. The complexity of this problem is greater in omni-channel environments due to the greater number of channels and the need to analyze data sources containing user interaction information. To solve this problem, different attribution models have been proposed to assign the weight that each channel has in the acquisition of a product, also known as conversion. Each of these attribution models adopts a strategy to define the weighting of channels. The decision-making strategy is established using the company"s expert knowledge, which can contain different criteria depending on the department to which the expert belongs. The aim of this research is to present a new multicriteria attribution model for online marketing (MAMOM) based on Analytical Hierarchical Process, that resolves this type of problem. MAMOM is a meta-model that takes as input information related to channel features, user interactions and even decisions from other strategies. This information is integrated to enable the integration of interdepartmental strategies as well as to obtain a dynamic attribution model based on expert interviews. The expert assessment procedure is carried out subjectively and simply with a pairwise assessment of the criteria, finally MAMOM obtains a final formulation to calculate the investment to be made in each channel if the experts opinions are considered. Results show that first five channels selected by the MAMOM are nearly identical to those that would be obtained with the traditional models but with a different sequence caused by experts knowledge. This result shows the capacity of MAMOM to factor in expert opinion and experience for making the investment outcome more aligned with the tactical and strategic objectives of a given online marketing campaign.Publication Improving time series forecasting using information fusion in local agricultural markets(Elsevier, 2021-09-10) Padilla, Washington R.; García Herrero, Jesús; Molina López, José Manuel; Ministerio De Economía, Comercio Y EmpresaThis research explores the capacity of Information Fusion and Data Mining to extract knowledge about associations among agricultural products and achieve better predictions for future consumption in local markets in the Andean region of Ecuador. This commercial activity is performed using Alternative Marketing Circuits (CIALCO), seeking to establish a direct relationship between producer and consumer prices, and promote buying and selling among family groups. The time-series forecasting, presented as a machine learning formulation, is enhanced with multi-variate predictions based on association rules extracted from transactions data analysis. These transactional data are used to learn the best association rules between products sold in different local markets, knowledge that allows the system to gain a significant improvement in forecasting accuracy by including these variables in multi-variate forecasting models. In the results we see that, from establishing best association rules valid in the original dataset, we can achieve a considerable improvement in prediction accuracy, validated with independent test subsequences of agricultural products using non-linear regression techniques including neural networks with a varying number of hidden layers.Publication Vapor−Liquid Equilibria for the Binary System Hexane + 1,1-Dimethylpropyl Methyl Ether at 298.15, 308.15, 318.15, and 328.15 K(ACS Publications, 2002-03-01) Río Hernández, Armando del; Coto, Baudilio; Pando, Concepción; Renuncio, Juan A. R.; Ministerio de Educación, Cultura y Deporte (España)Vapor-liquid equilibrium (VLE) data are reported for the binary mixtures formed by hexane and the branched ether 1,1-dimethylpropyl methyl ether (tert-amyl methyl ether or TAME). A Gibbs-van Ness type apparatus was used to obtain total vapor pressure measurements as a function of composition at 298.15, 308.15, 318.15, and 328.15 K. The system shows positive deviations from Raoult’s law. VLE data are analyzed together with excess enthalpy (Hm) and excess volume (Vm) data previously obtained at 298.15 K for these mixtures. The UNIQUAC model, the lattice-fluid model, and the Flory theory are used to simultaneously correlate VLE and Hm data and to correlate or predict Vm data. The original UNIFAC group contribution model and the modified UNIFAC (Dortmund model) are used to predict VLE data.Publication Vapor–liquid equilibria and excess properties of octane + 1,1-dimethylpropyl methyl ether (TAME) mixtures(Elsevier, 2002-07-15) Río Hernández, Armando del; Coto, Baudilio; Pando, Concepción; Renuncio, Juan A. R.Vapor–liquid equilibrium (VLE) data are reported for the binary mixtures formed by octane and the branched ether 1,1-dimethylpropyl methyl ether (tert-amyl methyl ether or TAME). A Gibbs–van Ness type apparatus was used to obtain total vapor pressure measurements as a function of composition at 298.15, 308.15, 318.15 and 328.15 K. The system shows positive deviations from Raoult’s law. These VLE data are analyzed together with data previously reported for octane+TAME mixtures: VLE data at 323.15 and 423.15 K, excess enthalpy (HmE) data at 298.15 and 313.15 K and excess volume (VmE) data at 298.15 K. The UNIQUAC model, the lattice–fluid (LF) model, and the Flory theory are used to simultaneously correlate VLE and HmE data. The two latter models are then used to predict VmE data. The original UNIFAC group contribution model and the modified UNIFAC (Dortmund model) are used to predict VLE data.Publication Isothermal Vapor−Liquid Equilibrium and Excess Enthalpy Data for the Binary Systems Methyl tert-Butyl Ether + Cyclohexane and Ethyl tert-Butyl Ether + Cyclohexane, n-Hexane, and n-Heptane in a Temperature Range from 298.15 to 393.15 K(ACS Publications, 2001-09-01) Río Hernández, Armando del; Horstmann, Sven; Renuncio, Juan A. R.; Gmehling, JürgenIsothermal vapor−liquid equilibrium (VLE) and excess enthalpy (HE) data are reported for binary systems containing branched ethers and hydrocarbons. The vapor−liquid equilibrium data for methyl tert-butyl ether (MTBE) + cyclohexane at 308.15 K, for ethyl tert-butyl ether (ETBE) + cyclohexane, n-hexane + ethyl tert-butyl ether, and ethyl tert-butyl ether + n-heptane from 298.15 to 363.15 K were measured by means of a computer-controlled static apparatus. An isothermal flow calorimeter was used to obtain excess enthalpy data for the systems containing ethyl tert-butyl ether at 313.15 and 393.15 K. The experimental VLE and HE data were compared with the data of other authors and have been used simultaneously for the correlation of temperature-dependent UNIQUAC parameters.Publication Vapor−Liquid Equilibria and Excess Properties of Cyclohexane−1,1-Dimethylpropyl Methyl Ether (TAME) Mixtures(ACS Publications, 2001-01-01) Río Hernández, Armando del; Coto, Baudilio; Pando, Concepción; Renuncio, Juan A. R.; Ministerio de Educación, Cultura y Deporte (España)Vapor−liquid equilibrium (VLE) data are reported for the binary mixtures formed by cyclohexane and the branched ether 1,1-dimethylpropyl methyl ether (tert-amyl methyl ether or TAME). A Gibbs−Van Ness type apparatus was used to obtain total vapor pressure measurements for cyclohexane−TAME mixtures as a function of composition at 298.15, 308.15, 318.15, and 328.15 K. These data are analyzed together with isothermal VLE data previously obtained at 313.15 K and excess enthalpies and volumes previously determined at 298.15 K for these mixtures. The Peng−Robinson equation of state and the Wong−Sandler mixing rule, the lattice-fluid (LF) model, the Flory theory, the UNIQUAC model, and the modified UNIFAC (Dortmund) model are used to correlate or predict the VLE data and excess properties of cyclohexane−TAME mixtures.Publication Assessment of measurement methods to characterize the producer gas from biomass gasification with steam in a fluidized bed(Elsevier, 2022-08-01) Anca Couce, Andres; Von Berg, Lukas; Pongratz, Gernot; Scharler, Robert; Hochenauer, Christoph; Geusebroek, Marco; Kuipers, Johan; Mourao Vilela, Carlos; Kraia, Tzouliana; Panopoulos, Kyriakos; Funcia, Ibai; Dieguez Alonso, Alba; Almuina Villar, Hernan; Tsiotsias, Timotheos; Kienzl, Norbert; Martini, Stefan; European CommissionMeasuring the producer gas from biomass gasification is very challenging and the use of several methods is required to achieve a complete characterization. Various techniques are available for these measurements, offering very different affordability or time demand requirements and the reliability of these techniques is often unknown. In this work an assessment of commonly employed measuring methods is conducted with a round robin. The main permanent gases, light hydrocarbons, tars, sulfur and nitrogen compounds were measured by several partners employing a producer gas obtained from fluidized bed gasification of wood and miscanthus with steam. Online and offline methods were used for this purpose and their accuracy, repeatability and reproducibility are here discussed. The results demonstrate the reliability of gas chromatography for measuring the main permanent gases, light hydrocarbons, benzene and H2S, validating the obtained results with other methods. An online method could also measure NH3 with a reasonable accuracy, but deviations were present for compounds at even lower concentrations. Regarding tar sampling and analysis, the main source of variability in the results was the analysis of the liquid samples, especially for heavier compounds. The presented work pointed out the need for a complementary use of several techniques to achieve a complete characterization of the producer gas from biomass gasification, and the suitability of certain online techniques as well as their limitations.Publication A year in lockdown: how the waves of COVID-19 impact internet traffic(ACM Digital Library, 2021-06-21) Feldmann, Anja; Gasser, Oliver; Lichtblau, Franziska; Pujol, Enric; Poese, Ingmar; Dietzel, Christoph; Wagner, Daniel; Wichtlhuber, Matthias; Estévez Tapiador, Juan Manuel; Vallina-Rodriguez, Narseo; Hohlfeld, Oliver; Smaragdakis, Georgios; Comunidad de Madrid; Agencia Estatal De Investigacion (España); Ministerio de Ciencias y Universidades (España)In March 2020, the World Health Organization declared the Corona Virus 2019 (COVID-19) outbreak a global pandemic. As a result, billions of people were either encouraged or forced by their governments to stay home to reduce the spread of the virus. This caused many to turn to the Internet for work, education, social interaction, and entertainment. With the Internet demand rising at an unprecedented rate, the question of whether the Internet could sustain this additional load emerged. To answer this question, this paper will review the impact of the first year of the COVID-19 pandemic on Internet traffic in order to analyze its performance. In order to keep our study broad, we collect and analyze Internet traffic data from multiple locations at the core and edge of the Internet. From this, we characterize how traffic and application demands change, to describe the "new normal" and explain how the Internet reacted during these unprecedented times.Publication Vapour–liquid equilibria for the binary system cyclohexane–1,1-dimethylethyl methyl ether (MTBE) at 298.15, 308.15 and 318.15 K(Royal Society of Chemistry, 1999-11) Río Hernández, Armando del; Coto, Baudilio; Pando, Concepción; Renuncio, Juan A. R.; Ministerio de Educación, Cultura y Deporte (España)Vapour–liquid equilibrium data are reported for the binary mixtures formed by cyclohexane and the branched ether 1,1-dimethylethyl methyl ether (tert-butyl methyl ether or MTBE). A Gibbs–Van Ness type apparatus was used to obtain total vapour pressure measurements for cyclohexane–MTBE mixtures at 298.15, 308.15 and 318.15 K. The system exhibits very small deviations from Raoult's law with a nearly ideal behaviour. No temperature effect on vapour compositions is observed. Results are analysed in terms of the Peng–Robinson equation of state and the Wong–Sandler mixing rule, the lattice-fluid model, the UNIQUAC model, and the UNIFAC and modified UNIFAC models.Item Applications of Hybrid Metal-Dielectric Nanostructures: State of the Art(Wiley, 2022-04-01) Barreda, Ángela; Vitale, Francesco; Minovich, Alexander E.; Ronning, Carsten; Staude, IsabelleEnhancing the light-matter interactions is important for many different applications like sensing, surface enhanced spectroscopies, solar energy harvesting, and for quantum effects such as nonlinear frequency generation or spontaneous and stimulated emission. Hybrid metal-dielectric nanostructures have shown extraordinary performance in this respect, demonstrating their superiority with respect to bare metallic or high refractive index dielectric nanostructures. Such hybrid nanostructures can combine the best of two worlds: strong confinement of the electromagnetic energy by metallic structures and high scattering directivity and low losses of the dielectric ones. In this review, following a general overview of the properties of metal-dielectric nanostructures, some of their most relevant applications including directional scattering, sensing, surface enhanced Raman spectroscopy, absorption enhancement, fluorescence and quantum dot emission enhancement, nonlinear effects, as well as lasing, are summarized.Publication Simultaneous desalination and consolidation treatment through the application of electrokinetic techniques(Elsevier, 2023-12-08) Feijoo, J.; Gómez Villalba, Luz Stella; Fort, R.; Rabanal Jiménez, María Eugenia; Comunidad de MadridThe vast majority of building materials that are heavily affected by salts require desalination and subsequent consolidation treatments. This double intervention entails a risk associated with the loss of material due to continuous contact with the affected surface. This study evaluates the effectiveness of an electrokinetic process of simultaneous desalination-consolidation of two types of stones (dolostone and limestone). The results show that it is possible to reduce the salts up to percentages of 100% and at the same time to fill the pores and fractures with insoluble compounds compatible with the materials to be treated, such as calcium-magnesium carbonates.Item Investigation of dipole emission near a dielectric metasurface using a dual-tip scanning near-field optical microscope(De Gruyter, 2021-12-01) Abbasirad, Najmeh; Barreda, Ángela; Arslan, Dennis; Steinert, Michael; Fasold, Stefan; Rockstuhl, Carsten; Staude, Isabelle; Setzpfandt, Frank; Pertsch, Thomas; European CommissionA wide variety of near-field optical phenomena are described by the interaction of dipole radiation with a nanophotonic system. The electromagnetic field due to the dipole excitation is associated with the Green’s function. It is of great interest to investigate the dipole interaction with a photonic system and measure the near-field Green’s function and the quantities it describes, e.g., the local and cross density of optical states. However, measuring the near-field Green’s function requires a point-source excitation and simultaneous near-field detection below the diffraction limit. Conventional single-tip near-field optical microscope (SNOM) provides either a point source excitation or amplitude and phase detection with subwavelength spatial resolution. The automated dual-tip SNOM, composed of two tips, has overcome the experimental challenges for simultaneous near-field excitation and detection. Here, we investigate the dipole emission in the near-field of a dielectric metasurface using the automated dual-tip SNOM. We have analyzed the near-field pattern and directional mode propagation depending on the position of the dipole emission relative to the metasurface. This study is one further step toward measuring the dyadic Green’s function and related quantities such as cross density of optical states in complex nanophotonic systems for both visible and near-infrared spectra.Item Metal, dielectric and hybrid nanoantennas for enhancing the emission of single quantum dots: A comparative study(Elsevier, 2021-12-01) Barreda, Ángela; Hell, S.; Weissflog, M. A.; Minovich, A.; Pertsch, T.; Staude, IsabelleThe confinement of electromagnetic energy to subwavelength volumes through nanoscale antennas can be used to enhance the spontaneous emission of quantum emitters. With this aim, different configura- tions of metallic and high refractive index dielectric nanoparticles have been explored. Here, we carry out a comparative analysis of planar metallic, high refractive index dielectric, and hybrid nanoantennas considering three different parameters: the Purcell factor enhancement, radiation efficiency, and directionality properties. We focus our study on different geometries and material combinations of a dimer of cylinders. A dimer made of two gold nanocylinders is the most promising candidate for improving the spontaneous emission. While most previous works have paid attention to the redirection of the scattered emission in the nanoparticle plane, our proposed nanostructure of two large gold cylinders ( R = λ/ 4) emits most of the radiation upwards. This effect is due to the strong quadrupolar electric contribution to the resonant mode. With the aim to further improve the directionality properties, additional silicon nanocylinders are used as directors of the scattered radiation, increasing the directivity by a factor of 2.4 with respect to the gold dimer without directors. All in all, a hybrid structure composed of a gold dimer and silicon nanoparticles is proposed to enhance the spontaneous emission of a single quantum dot and to govern its emission pattern. The results shown in this work could be useful in fluorescence enhance- ment or in quantum photonics. They are particularly interesting for the development of single-photon sources based on quantum dots and other nanoscale emitters.Publication Untangling connections between challenges in the adoption of learning analytics in higher education(Springer, 2022-04-01) Alzahrani, Asma; Tsai, Yi-Shan; Iqbal, Sehrish; Moreno Marcos, Pedro Manuel; Scheffel, Maren; Drachsler, Hendrik; Delgado Kloos, Carlos; Aljohani, Naif; Gasevic, DraganPotential benefits of learning analytics (LA) for improving students performance, predicting students success, and enhancing teaching and learning practice have increasingly been recognized in higher education. However, the adoption of LA in higher education institutions (HEIs) to date remains sporadic and predominantly small in scale due to several socio-technical challenges. To better understand why HEIs struggle to scale LA adoption, it is needed to untangle adoption challenges and their related factors. This paper presents the findings of a study that sought to investigate the associations of adoption factors with challenges HEIs face in the adoption of LA and how these associations are compared among HEIs at different scopes of adoption. The study was based on a series of semi-structured interviews with senior managers in HEIs. The interview data were thematically analysed to identify the main challenges in LA adoption. The connections between challenges and other factors related to LA adoption were analysed using epistemic network analysis (ENA). From senior managers viewpoints, ethical issues of informed consent and resistance culture had the strongest links with challenges of learning analytic adoption in HEI; this was especially true for those institutions that had not adopted LA or who were in the initial phase of adoption (i.e., preparing for or partially implementing LA). By contrast, among HEIs that had fully adopted LA, the main challenges were found to be associated with centralized leadership, gaps in the analytic capabilities, external stakeholders, and evaluations of technology. Based on the results, we discuss implications for LA strategy that can be useful for institutions at various stages of LA adoption, from early stages of interest to the full adoption phase.