Dominant Channel Research Articles

Unravelling ultralow thermal conductivity in perovskite Cs2AgBiBr6: dominant wave-like phonon tunnelling and strong anharmonicity

Understanding the lattice dynamics and heat transport physics in the lead-free halide double perovskites remains an outstanding challenge due to their lattice dynamical instability and strong anharmonicity. In this work, we investigate the microscopic mechanisms of anharmonic lattice dynamics and thermal transport in lead-free halide double perovskite Cs2AgBiBr6 from first principles. We combine self-consistent phonon calculations with bubble diagram correction and a unified theory of lattice thermal transport that considers both the particle-like phonon propagation and wave-like tunnelling of phonons. An ultra-low thermal conductivity at room temperature (~0.21 Wm−1K−1) is predicted with weak temperature dependence( ~ T−0.34), in sharp contrast to the conventional ~T−1 dependence. Particularly, the vibrational properties of Cs2AgBiBr6 are featured by strong anharmonicity and wave-like tunnelling of phonons. Anharmonic phonon renormalization from both the cubic and quartic anharmonicities are found essential in precisely predicting the phase transition temperature in Cs2AgBiBr6 while the negative phonon energy shifts induced by cubic anharmonicity has a significant influence on particle-like phonon propagation. Further, the contribution of the wave-like tunnelling to the total thermal conductivity surpasses that of the particle-like propagation above around 310 K, indicating the breakdown of the phonon gas picture conventionally used in the Peierls-Boltzmann Transport Equation. Importantly, further including four-phonon scatterings is required in achieving the dominance of wave-like tunnelling, as compared to the dominant particle-like propagation channel when considering only three-phonon scatterings. Our work highlights the importance of lattice anharmonicity and wave-like tunnelling of phonons in the thermal transport in lead-free halide double perovskites.

Verification Behaviors and Countermeasures in the Age of Misinformation

Across the globe, social media have become dominant channels of communication and news for many citizens. They also provide online spaces where misleading information can exacerbate social cleavages and political differences in societies, which can then lead to deleterious democratic outcomes. Therefore, much work has sought to understand the ways in which the effects of misinformation can be attenuated. This virtual theme collection highlights eight studies that examined the conditions in which individuals would actively verify information as well as the effectiveness of certain countermeasures designed to help individuals discern information veracity.

Evaluation of Profile Control and Oil Displacement Effect of Starch Gel and Nano-MoS2 Combination System in High-Temperature Heterogeneous Reservoir.

The Henan Oilfield's medium-permeability blocks face challenges such as high temperatures and severe heterogeneity, making conventional flooding systems less effective. The starch gel system is an efficient approach for deep profile control in high-temperature reservoirs, while the nano-MoS2 system is a promising enhanced oil recovery (EOR) technology for high-temperature low-permeability reservoirs. Combining these two may achieve the dual effects of profile control and oil displacement, significantly enhancing oil recovery in high-temperature heterogeneous reservoirs. The basic performance evaluation of the combination system was carried out under reservoir temperature. Displacement experiments were conducted in target blocks under different permeabilities and extreme disparity core flooding to evaluate the combination system's oil displacement effect. Additionally, the displacement effects and mechanisms of the starch gel and nano-MoS2 combination system in heterogeneous reservoirs were evaluated by simulating interlayer and intralayer heterogeneity models. The results show that the single nano-MoS2 system's efficiency decreases with increased core permeability, and its effectiveness is limited in triple and quintuple disparity parallel experiments. After injecting the starch gel-nano-MoS2 combination system, the enhanced oil recovery effect was significant. The interlayer and intralayer heterogeneous models demonstrated that the primary water flooding mainly affected the high-permeability layers, while the starch gel effectively blocked the dominant channels, forcing the nano-MoS2 oil displacement system towards unswept areas. This coordination significantly enhanced oil displacement, with the combination system improving recovery by 15.33 and 12.20 percentage points, respectively. This research indicates that the starch gel and nano-MoS2 combination flooding technique holds promise for enhancing oil recovery in high-temperature heterogeneous reservoirs of Henan Oilfield, providing foundational support for field applications.

Magnetic field breakout from white dwarf crystallization dynamos

ABSTRACT A convective dynamo operating during the crystallization of white dwarfs is one of the promising channels to produce their observed strong magnetic fields. Although the magnitude of the fields generated by crystallization dynamos is uncertain, their timing may serve as an orthogonal test of this channel’s contribution. The carbon–oxygen cores of $M\approx 0.5-1.0\, {\rm M}_{\odot }$ white dwarfs begin to crystallize at an age tcryst ∝ M−5/3, but the magnetic field is initially trapped in the convection zone – deep inside the CO core. Only once a mass of mcryst has crystallized, the convection zone approaches the white dwarf’s helium layer, such that the magnetic diffusion time through the envelope shortens sufficiently for the field to break out to the surface, where it can be observed. This breakout time is longer than tcryst by a few Gyr, scaling as tbreak ∝ tcrystf−1/2, where f ≡ 1 − mcryst/M depends on the white dwarf’s initial C/O profile before crystallization. The first appearance of strong magnetic fields B ≳ 1 MG in volume-limited samples approximately coincides with our numerically computed tbreak(M) – potentially signalling crystallization dynamos as a dominant magnetization channel. However, some observed magnetic white dwarfs are slightly younger, challenging this scenario. The dependence of the breakout process on the white dwarf’s C/O profile implies that magnetism may probe the CO phase diagram, as well as uncertainties during the core helium burning phase in the white dwarf’s progenitor, such as the 12C(α, γ)16O nuclear reaction.

Importance of stable mass transfer and stellar winds for the formation of gravitational wave sources

ABSTRACT The large number of gravitational wave (GW) detections have revealed the properties of the merging black hole binary population, but how such systems are formed is still heavily debated. Understanding the imprint of stellar physics on the observable GW population will shed light on how we can use the GW data, along with other observations, to constrain the poorly understood evolution of massive binaries. We perform a parameter study on the classical isolated binary formation channel with the population synthesis code seba to investigate how sensitive the properties of the coalescing binary black hole population are on the uncertainties related to first phase of mass transfer and stellar winds. We vary five assumptions: (1) and (2) the mass transfer efficiency and the angular momentum loss during the first mass transfer phase, (3) the mass transfer stability criteria for giant donors with radiative envelopes, (4) the effective temperature at which an evolved star develops a deep convective envelope, and (5) the mass-loss rates of stellar winds. We find that current uncertainties related to first phase of mass transfer have a huge impact on the relative importance of different dominant channels, while the observable demographics of GW sources are not significantly affected. Our varied parameters have a complex, interrelated effect on the population properties of GW sources. Therefore, inference of massive binary physics from GW data alone remains extremely challenging, given the large uncertainties in our current models.

Theoretical study on iso‐pentanol oxidation chemistry: Fuel radical isomerization and decomposition kinetics and mechanism development

AbstractThis study undertakes a detailed theoretical investigation into the iso‐pentanol radical isomerization and decomposition kinetics and the mechanism development of the iso‐pentanol oxidation. The CCSD(T)/CBS//M08‐HX/6‐311+G(2df,2p) method was adopted to calculate the reaction potential energy surface. The reaction rate coefficients were calculated by variational transition state theory (VTST) with multistructural torsional (MS‐T) partition function and small curvature tunneling (SCT) correction. Moreover, the pressure‐dependent rate coefficients were determined using the system‐specific quantum Rice‐Ramsperger‐Kassel theory (SS‐QRRK). The variational and tunneling effects were discussed, and the dominant reaction channels were identified. It reveals that the isomerization reactions play a significant role at low temperatures, while the decomposition reactions dominate the high‐temperature regime. Notably, the quantitative rate expressions for iso‐pentanol radical decomposition reactions were also obtained. Furthermore, a new kinetic model incorporating the calculated rate coefficients was constructed, exhibiting satisfactory prediction performance on ignition delay times and improved predictive accuracy of species mole fractions. This work provides accurate rate data of isomerization and decomposition kinetics and contributes to a more comprehensive understanding of the iso‐pentanol oxidation mechanism.

Experimental Investigation of Solids Production Mechanisms in a Hydraulic Screen-Through Fracturing Well in a Loose Reservoir and Its Control

Summary Successful cases of hydraulic screen-through fracturing (HSTF) in the Bohai oil field highlight the possibility that hydraulic fracturing can be an alternative method for enhancing the productivity of loose reservoirs. However, a portion of the HSTF wells in the Bohai oil field suffer from severe solids production, meaning that proppants and stratum sands are produced in the wellbore during production and cause wellbore plugging and ensuing debilitation of productivity. In this study, fluid flow amid the stratum, fracture, and HSTF well is simulated experimentally, and pressure drop, flow rate of the fracture, and stratum are monitored to investigate mechanisms and influencing factors of solids production from HSTF wells. Perspectives on solids control optimization are put forward for the Bohai oil field. Results indicate that the formation of an erosion cavity on lip-sealing in fracture and a dominant fluid channel near the wellbore in the stratum are two main mechanisms of solids production. The higher the flow rate and fluid viscosity are, the more severe solids production can be. For the Bohai oil field, with 725-psi-strength resin-coated proppant, the minimum proportion of resin-coated proppant in fractures to prevent solids production can be reduced from the previous 65% to 30%. With 1,073-psi-strength resin-coated proppant, it can be further reduced to 20%. Reducing the proportion of resin-coated proppant can help optimize the conductivity of fractures. This study aims to provide preliminary insight on solving the solids production problem of an HSTF well, thus enhancing the applicability of hydraulic stimulation in loose reservoirs.

Temperature, humidity, and ionisation effect of iodine oxoacid nucleation.

Iodine oxoacids are recognised for their significant contribution to the formation of new particles in marine and polar atmospheres. Nevertheless, to incorporate the iodine oxoacid nucleation mechanism into global simulations, it is essential to comprehend how this mechanism varies under various atmospheric conditions. In this study, we combined measurements from the CLOUD (Cosmic Leaving OUtdoor Droplets) chamber at CERN and simulations with a kinetic model to investigate the impact of temperature, ionisation, and humidity on iodine oxoacid nucleation. Our findings reveal that ion-induced particle formation rates remain largely unaffected by changes in temperature. However, neutral particle formation rates experience a significant increase when the temperature drops from +10 °C to -10 °C. Running the kinetic model with varying ionisation rates demonstrates that the particle formation rate only increases with a higher ionisation rate when the iodic acid concentration exceeds 1.5 × 107 cm-3, a concentration rarely reached in pristine marine atmospheres. Consequently, our simulations suggest that, despite higher ionisation rates, the charged cluster nucleation pathway of iodic acid is unlikely to be enhanced in the upper troposphere by higher ionisation rates. Instead, the neutral nucleation channel is likely to be the dominant channel in that region. Notably, the iodine oxoacid nucleation mechanism remains unaffected by changes in relative humidity from 2% to 80%. However, under unrealistically dry conditions (below 0.008% RH at +10 °C), iodine oxides (I2O4 and I2O5) significantly enhance formation rates. Therefore, we conclude that iodine oxoacid nucleation is the dominant nucleation mechanism for iodine nucleation in the marine and polar boundary layer atmosphere.

Experimental study on the failure process and modes of loess spoil slope induced by rainfall and engineering disturbance.

In this paper, indoor model tests were conducted using image analysis, pore pressure, and displacement measurement methods to investigate the failure evolution process and modes of loess spoil slopes with various components under the influence of rainfall and artificial excavation. The results of the experiments reveal that, under the action of rainfall, there are two types of cracks-to-failure modes for pure loess spoil slopes. One involves the formation of a large gully through the dominant channel, while the other is characterized by step-by-step retreating soil damage between cracks. The failure exhibits three distinct stages, and after failure, the slope angle is relatively large (>45°). The process of rainfall-induced destruction affecting loess spoil containing 25% coarse-grained content similarly unfolds in three stages, ultimately resulting in the formation of a regional landslide. This landslide typically encompasses a broader damage range compared to pure loess spoil, albeit with a shallower depth of damage. After the landslide stops and stabilizes, a tiny slope (45°) is created (<45°). The excavation at the toe of the slope induces loess spoil damage in a progressive multi-stage receding manner. This study provides a reference and basis for disaster prevention and warning of spoiled ground in loess areas.

Preparation of sp2 carbon-bonded π-conjugated COF aerogels by ultrasound-assisted mild solvothermal reaction for multi-functional applications.

Molding COFs into aerogels from monomers can establish interpenetrating spatial network structures on the centimeter scale that increase the accessibility of dominant pore channels and the convenience of real application, which radically gets rid of the difficult reprocessing problems of insoluble and non-fusible powder COFs. However, the construction of bulk COF structures and achieving crystallinity are often incompatible, especially with sp2 carbon-based COFs, whose powder synthesis has been quite demanding. Herein, for the first time, we report an efficient method to prepare sp2 carbon-linked π-conjugated DFB-TMTA-COF (DT-COF) aerogels by an ultrasound-assisted mild solvothermal technique and freeze-drying. Particularly, unlike the typical synthesis methods of vacuum deoxygenation, high temperature and long reaction time, crystalline DT-COF aerogels can be obtained by reacting at 90 °C for 48 h without vacuum sealing. The fluffy, hierarchical porous flower-shaped microsphere clustering of DT-COF aerogels contributes to excellent mechanical properties and better host-guest interactions, which are favorable to utilize the benefits of the highly conjugated structure of channels. As a proof of concept, DT-COF aerogels have been used in absorption, batteries, and sensors, demonstrating enhanced functionality and effectiveness.

Experimental observation of molecular-weight growth by the reactions of o-benzyne with benzyl radicals.

The chemistry of ortho-benzyne (o-C6H4) is of fundamental importance due to its role as an essential molecular building block in molecular-weight growth reactions. Here, we report on an experimental investigation of the reaction of o-C6H4 with benzyl (C7H7) radicals in a well-controlled flash pyrolysis experiment using a resistively heated SiC microtubular reactor at temperatures of 800-1600 K and pressures near 30 torr. To this end, the reactants o-C6H4 and C7H7 were pyrolytically generated from 1,2-diiodobenzene and benzyl bromide, respectively. Using molecular-beam time-of-flight mass spectrometry, we found that o-C6H4 associates with the benzyl to form C13H11 radicals, which decompose at higher temperatures via H-loss to form closed-shell C13H10 molecules. Our experimental results agree with earlier theoretical calculations by Matsugi and Miyoshi [Phys. Chem. Chem. Phys., 2012, 14, 9722-9728], who predicted the formation of fluorene (C13H10) + H to be the dominant reaction channel. At temperatures above 1400 K, we also observed the formation of C13H9 radicals, most likely the resonance-stabilized fluorenyl π-radical. Our study confirms that molecular-mass growth via the o-C6H4 + C7H7 reaction provides a versatile pathway for introducing five-membered rings, and hence curved structures, into polycyclic aromatic hydrocarbons.

ASSESSMENT OF COMMUNICATION STRATEGIES OF COMMUNITY AND SOCIAL DEVELOPMENT PROJECTS IN BENUE, NASARAWA, AND TARABA STATES

The study anchored on assessment of communication strategies of Community and Social Development Projects in Benue, Nasarawa and Taraba States in Nigeria. The statement of the problem centred on how effective the communication strategies were in terms of their deployment; the specific communication channels used; the challenges of the use of these communication strategies. The objectives of the study were to: determine the communication strategies, ascertain how the communication strategies are deployed and the challenges of communication strategies used. The theories used were the Developmental State Theory and Alternative Paradigm Model. The aim of this study was to ascertain how the communication strategies are deployed. The methodology adopted in this research designs were survey and Focus Group Discussion (FGD). The population of the study was 11, 468, 425; the sample size was 384, while the sampling techniques were multi-stage, and simple random sampling techniques. The study find out that the respondents were fully-aware of the CSDPs in their communities based on the communication strategies; and that mobile phone calls/text messages and WhatsApp messages have now displaced radio as the dominant communication channels. The finding of the study show that the communication strategies deployed contributed maximally to the success.

Excited-state dynamics of 3-hydroxychromone in gas phase.

In recent years, 3-hydroxychromone (3-HC) and its derivatives have attracted much interest for their applications as molecular photoswitches and fluorescent probes. A clear understanding of their excited-state dynamics is essential for their applications and further development of new functional 3-HC derivatives. However, the deactivation mechanism of the photoexcited 3-HC family is still puzzling as their spectral properties are sensitive to the surrounding medium and substituents. The excited-state relaxation channels of 3-HC have been a matter of intense debate. In the current work, we thoroughly investigated the excited-state decay process of the 3-HC system in the gas phase using high-level electronic structure calculations and on-the-fly excited-state dynamic simulations intending to provide insight into the intrinsic photochemical properties of the 3-HC system. A new deactivation mechanism is proposed in the gas phase, which is different from that in solvents. The excited-state intramolecular proton transfer (ESIPT) process that occurs in solutions is not preferred in the gas phase due to the existence of a sizable energy barrier (∼0.8 eV), and thus, no dual fluorescence is found. On the contrary, the non-radiative decay process is the dominant decay channel, which is driven by photoisomerization combined with ring-puckering and ring-opening processes. The results coincide with the observations of an experiment performed in a supersonic jet by Itoh (M. Itoh, Pure Appl. Chem., 1993, 65(8), 1629-1634). The current work indicates that the solution environment plays an important role in regulating the excited-state dynamic behaviour of the 3-HC system. This study thus provides theoretical guidance for the rational design and improvement of the photochemical properties of the 3-HC system and paves the way for further investigation into its photochemical properties in complex environments.

Decision-making for substitutable products in a retailer dominant channel involving a third-party logistics provider

Decision-making for substitutable products in a retailer dominant channel involving a third-party logistics provider

Theoretical investigation of the OH-initiated atmospheric degradation mechanism of CX2CHX (X = H, F, Cl) by advanced quantum chemical and transition state theory methods.

Halogenated olefins are anthropogenic compounds with many industrial applications but at the same time raising many environmental and health concerns. Gas-phase electrophilic addition of the OH radical to the olefinic CC bond represents the primary sink for these chemicals in the atmosphere, with the degree and type of halogenation playing a significant role in their overall reactivity. In this work, we present a theoretical investigation of the reaction mechanisms and kinetics for the reactions between the OH radical and CH2CH2 (ethylene, ETH), CF2CHF (trifluoroethylene, TFE) and CCl2CHCl (trichloroethylene, TCE), simulated by state-of-the-art protocols and methods, with the aim of providing a detailed interpretation of the available experimental results, as well as new data of relevance to tropospheric chemistry. Specifically, potential energy surfaces (PESs) are obtained using the jun-Cheap (jChS) composite scheme, whereas temperature and pressure dependent rate coefficients and product distributions in the 100-600 K temperature range are calculated within the Rice-Ramsperger-Kassel-Marcus/master equation (RRKM/ME) framework. The rates for barrierless channels are obtained from variable reaction coordinate-variational transition state theory (VRC-VTST) combined with the two transition state model. While the reactions with ETH and TFE proceed mainly via the formation of addition adducts at P = 1 atm and T = 298 K, the dominant channel for TCE is the Cl-elimination reaction. Global rate constants for the two halogenated olefins, TFE and TCE, are found to be pressure-independent, contrary to the case of ETH. The computed rate constants, as well as their temperature and pressure dependence, are in remarkable agreement with the available experimental data, and they are used to derive atmospheric lifetimes (τ) for both TFE and TCE as a function of altitude (h) in the atmosphere, by taking into account variations in the rate coefficients (k (T, P)) and [OH] concentration.

Fluorescence and lasing of neutral nitrogen molecules inside femtosecond laser filaments in air: mechanism and applications.

High power femtosecond laser pulses launched in air undergo nonlinear filamentary propagation, featuring a bright and thin plasma channel in air with its length much longer than the Rayleigh length of the laser beam. During this nonlinear propagation process, the laser pulses experience rich and complex spatial and temporal transformations. With its applications ranging from supercontinuum generation, laser pulse compression, remote sensing to triggering of lightning, the underlying physical mechanism of filamentation has been intensively studied. In this review, we will focus on the fluorescence and cavity-free lasing effect of the plasma filaments in air. The different mechanisms underlying the fluorescence of the excited neutral nitrogen molecules will be throughly examined and it is concluded that the electron collision excitation is the dominant channel for the formation of the excited nitrogen molecules. The recently discovered "air lasing" effect, a cavity-free bidirectional lasing emission emitted by the filaments, will be introduced and its main properties will be emphasized. The applications of the fluorescence and lasing effect of the neutral nitrogen molecules will be introduced, with two examples on spectroscopy and detection of electric field. Finally, we discuss the quenching effect of the lasing effect in atmosphere and the mechanisms responsible will be analyzed. An outlook for the achievement of backward lasing in air will be briefly presented.

HCS-Net: Multi-level deformation strategy combined with quadruple attention for image registration

Background and objectiveNon-rigid image registration plays a significant role in computer-aided diagnosis and surgical navigation for brain diseases. Registration methods that utilize convolutional neural networks (CNNs) have shown excellent accuracy when applied to brain magnetic resonance images (MRI). However, CNNs have limitations in understanding long-range spatial relationships in images, which makes it challenging to incorporate contextual information. And in intricate image registration tasks, it is difficult to achieve a satisfactory dense prediction field, resulting in poor registration performance. MethodsThis paper proposes a multi-level deformable unsupervised registration model that combines Transformer and CNN to achieve non-rigid registration of brain MRI. Firstly, utilizing a dual encoder structure to establish the dependency relationship between the global features of two images and to merge features of varying scales, as well as to preserve the relative spatial position information of feature maps at different scales. Then the proposed multi-level deformation strategy utilizes different deformable fields of varying resolutions generated by the decoding structure to progressively deform the moving image. Ultimately, the proposed quadruple attention module is incorporated into the decoding structure to merge feature information from various directions and emphasize the spatial features in the dominant channels. ResultsThe experimental results on multiple brain MR datasets demonstrate that the promising network could provide accurate registration and is comparable to state-of-the-art methods. ConclusionThe proposed registration model can generate superior deformable fields and achieve more precise registration effects, enhancing the auxiliary role of medical image registration in various fields and advancing the development of computer-aided diagnosis, surgical navigation, and related domains.

Underwater image contrast enhancement through an intensity-randomised approach incorporating a swarm intelligence technique with unsupervised dual-step fusion

ABSTRACT Analysing objects in an underwater medium is difficult due to light problems in such an environment. Low contrast and visibility in water medium result in restricted information extraction. Some previous methods inadequately reduce underwater colour cast and improve the image contrast minimally. This work proposes intensity-randomised underwater image contrast enhancement (IRUCE), an improved enhancement method that integrates an unsupervised dual-step fusion technique to reduce blue-green colour cast, improve contrast, and enhance image brightness, especially in turbid and deep underwater media. IRUCE enhances the inferior colour channels and moderates the dominant colour channel to reduce the colour cast before the intensity-randomised approach is implemented. The intensity-randomised approach is designed to effectively distribute image intensity across all intensity levels. Next, a swarm intelligence algorithm is fused to perform median equalisation on all colour channels. The median intensity values of inferior colour channels are shifted towards the dominant colour channel. The unsharp masking technique is employed in the last step to increase image sharpness. The effectiveness of this approach is validated through quantitative and qualitative evaluations, and the results are compared with those of other state-of-the-art methods. Outcomes indicate that the proposed method improves underwater image quality significantly and outperforms other contemporary techniques.

Marketing and Value Chain Analysis of Mandarin at Jorayal Rural Municipality of Doti, Nepal

The yearly decline in mandarin production, one of the important citrus fruit in the mid-hills of Nepal could be attributed to underdeveloped and non-systematic market and lack of value-chain participation by farmers leading to low profitability and hence reducing their motivation. So, this research explores market and value chain of mandarin sub-sector through survey of 100 households from Jorayal rural municipality of Doti district using semi-structured questionnaires. Results showed that the average production of selected mandarin farmers is 1.8 Mt with income of Rs. 24,059 but considering family labor gross margins are negative. The dominant marketing channel is FarmersàCollectors, with around 92% of sales volume. Among the different types of collectors, local ones are dominant market players although price offered is higher for those coming from outside the district (Rs.58/kg) compared to local collectors (Rs. 50/kg), with producer's share being 40% and 35%, respectively. Monopoly of local collectors is high but for local relationship farmers are compelled to sell to them. Due to remoteness of the area, there are low/no value chain actors and hence marketing efficiency is also low. The major problem in marketing is found to be the low market price along with the unavailability of storage facilities or collection centers. Low networking of farmers is also contributing to reduction of the marketing efficiency and hence they are found not to be interested to scale-up their mandarin farms. Cooperative marketing may be one of the best options to increase the bargaining power of small-scale and scattered farmers.

Max–Min Fair 3D Trajectory Design and Transmission Scheduling for Solar-Powered Fixed-Wing UAV-Assisted Data Collection

This paper presents a new three-dimensional (3D) trajectory design approach for a solar-powered, fixed-wing unmanned aerial vehicle (UAV) to harvest solar energy and collect data from multiple smart devices (SDs). The trajectory is optimized based on max-min fairness to balance the total amount of uploaded data and the fairness among the SDs. The key idea is that we develop non-trivial variable substitution and successive convex approximation (SCA) techniques to convexify data transmission, UAV energy consumption and mobility, and energy harvesting constraints under a persistent round-robin transmission schedule of the SDs. The resulting algorithm guarantees a locally optimal trajectory satisfying the Karush-Kuhn-Tucker (KKT) conditions. Another important aspect is that we further jointly optimize the transmission schedule along with the trajectory, and prove that absolute fairness in terms of uploaded data can be achieved among the SDs under the max-min fairness. The new algorithms apply to both line-of-sight (LoS)-dominant and probabilistic SD-UAV channels. Numerical results show that a 3D trajectory increases the uploaded data by 111%, compared to a two-dimensional (2D) trajectory. The proposed algorithms can balance the energy harvesting and data collection, and achieve fairness in both LoS-dominant and probabilistic SD-UAV channels.