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Table 1 Hot topics with the strongest positive trend

From: Reflecting trends in the academic landscape of sustainable energy using probabilistic topic modeling

Topic no.

Slope rank

Superordinate theme

Topic interpretation

Top 20 topic terms ordered by decreasing probability for each topic

57

1

Electrical energy storage

Materials for electrochemical energy storage via batteries or supercapacitors

electrode, battery, carbon, electrolyte, electrochemical, cycle, cell, cathode, energy_storage, low_cost, electrode_material, report, anode, discharge, lithium, exhibit, supercapacitor, material, redox, graphene

13

2

Fuel cells

Materials for catalysis in fuel cells

catalyst, activity, electrochemical, graphene, active, electrocatalyst, cobalt, efficient, surface, exhibit, highly, stability, report, electrode, platinum, fuel_cell, oxidation, active_site, superior, catalytic

63

3

Hydrogen production

Photosensitive materials and photocatalysis for water splitting

tio_two, photocatalyst, semiconductor, photocatalytic, tio, water_splitting, visible_light, photo, cds, exhibit, photocatalysis, degradation, electron, solar_energy, dye, light, photoanode, band, photocurrent, report

154

4

Nanotechnology

Synthesis of nanomaterials

scan, characterize, synthesis, nanoparticle, prepare, sample, characterization, technique, synthesize, zno, obtain, confirm, property, morphology, precursor, material, ion, x_ray_diffraction, observe, oxide

109

12

Nanotechnology

Properties of materials

material, structure, property, nanomaterial, molecule, bond, nano, functional, compound, shell, sulfur, molecular, formation, exhibit, surface, unique, excellent, electron, report, layer

262

15

Nanotechnology

Structure of nanomaterials

particle, polymer, nanoparticle, nanocomposite, preparation, fabrication, powder, size, prepare, porous, spray, synthesis, matrix, agent, formation, poly, highly, silica, simple, rgo

242

5

Chemical catalysis

Chemical catalysis for various types of reactions

reaction, catalyst, catalytic, methanol, oxidation, ligand, conversion, complex, compound, intermediate, selective, catalysis, acid, synthesis, yield, oxygen, chemical, highly, metal, molecular

255

6

Digital network communication

Wireless sensor networks and real-time data for energy applications

algorithm, node, power, network, wireless, transmission, protocol, energy_harvesting, user, communication, technique, sensor, sensor_node, spectrum, data, scheme, channel, battery, maximize, distribute

111

7

Mechanical energy harvesting

Triboelectric nanogenerator and piezoelectric effect for small scale applications

mechanical, power, teng, powered, harvest, device, motion, vibration, energy_harvesting, sensor, flexible, output, generate, electrical, circuit, electronics, power_source, magnetic, drive, piezoelectric

125

8

Sustainable building materials

Alternative blendings or replacement materials for cement

concrete, cement, brick, material, aggregate, strength, fly_ash, property, durability, mortar, compressive_strength, binder, block, sand, produce, lime, replacement, clay, replace, specimen

253

9

Biofuels

Biofuel from algal biomass

biodiesel, microalgae, algae, biodiesel_production, lipid, cultivation, algal, yield, produce, feedstock, culture, microalgal, transesterification, nutrient, biofuel, oil, fuel, potential, algal_biomass, content

251

10

Biofuels

Production of biomethanol by fermentation of biomass

fermentation, sugar, pretreatment, glucose, enzyme, yield, obtain, cellulose, hydrolysis, produce, lignin, substrate, lignocellulosic_biomass, g_l, pulp, carbohydrate, biomass, pretreated, ethanol, acid

172

13

Biofuels

Bio-based materials from lignocellulosic feedstocks

extraction, separation, solvent, extract, acid, lignin, recovery, cellulose, liquid, leach, water, yield, ionic_liquid, compound, chemical, surfactant, step, distillation, separate, recover

74

14

Biofuels

Biogas production from anaerobic digestion

bioga, anaerobic_digestion, produce, methane, manure, sludge, biogas, fertilizer, substrate, bioga_production, digestate, biomethane, organic_waste, food_waste, digester, bioga_plant, anaerobic, digestion, biogas_production, compost

90

11

Modeling and optimization

Optimization models and algorithms for power systems operation and markets

optimal, optimization, optimize, constraint, minimize, algorithm, objective, maximize, solution, scheduling, multi_objective, optimization_model, solve, minimization, formulate, objective_function, search, simultaneously, trade, genetic_algorithm

  1. Topics equal to or above the 95% quantile regarding the slope of the linear models; topics are clustered according to superordinate themes; the order of themes follows the topic with the highest rank belonging to a theme; rank 1 indicates the topic with the strongest positive trend