20 research outputs found
MTSS: Learn from Multiple Domain Teachers and Become a Multi-domain Dialogue Expert
How to build a high-quality multi-domain dialogue system is a challenging
work due to its complicated and entangled dialogue state space among each
domain, which seriously limits the quality of dialogue policy, and further
affects the generated response. In this paper, we propose a novel method to
acquire a satisfying policy and subtly circumvent the knotty dialogue state
representation problem in the multi-domain setting. Inspired by real school
teaching scenarios, our method is composed of multiple domain-specific teachers
and a universal student. Each individual teacher only focuses on one specific
domain and learns its corresponding domain knowledge and dialogue policy based
on a precisely extracted single domain dialogue state representation. Then,
these domain-specific teachers impart their domain knowledge and policies to a
universal student model and collectively make this student model a multi-domain
dialogue expert. Experiment results show that our method reaches competitive
results with SOTAs in both multi-domain and single domain setting.Comment: AAAI 2020, Spotlight Pape
Effect of hydrogel stiffness on nucleus pulposus cell phenotypes in vitro and its repairment of intervertebral disc in vivo
ObjectiveĀ·To investigate the effect of hydrogel stiffness on nucleus pulposus cell phenotype and its function in repairing intervertebral disc degeneration in rats.MethodsĀ·Methacrylate gelatin (GelMA) hydrogels with different concentrations were constructed. The stiffness of the hydrogels was investigated by using rheological analysis and uniaxial compression test. The microstructure and morphology of the hydrogels were observed by scanning electron microscopy (SEM). Nucleus pulposus cells with normal phenotype were inoculated on the surface of GelMA hydrogels. The biocompatibility of the hydrogel was evaluated by live-dead cell staining and the growth pattern of nucleus pulposus cells on hydrogels with different stiffness was observed with phalloidin staining under microscope. Immunofluorescence staining was performed to examine the nuclear localization of Yes-associated protein (YAP) and real-time quantitative reverse transcription PCR (qRT-PCR) was used to detect the expression levels of nucleus pulposus cell-associated genes [neural cell adhesion molecule 1 (Ncam-1), aggrecan (Acan), sex-determing region of Y chromosome (SRY)-box transcription factor 9 (Sox9)]. A rat caudal acupuncture intervertebral disc degeneration model was established. Nucleus pulposus cells cultured on different hydrogels were harvested and injected into the degenerated discs separately. Four weeks after surgery, magnetic resonance imaging (MRI) was performed to analyze the water content of the intervertebral discs in each group. Histological tests were performed to examine the disc structure and proteoglycan levels.ResultsĀ·The elastic modulus of the hydrogels was 1 kPa and 200 kPa when the concentration of GelMA prepolymerisation solution was at 4% and 15% respectively. SEM observation revealed that the hydrogels showed a loose and porous microstructure, and the porosity of hydrogels decreased significantly with the decrease of their stiffness. In vitro experiments demonstrated that both GelMA hydrogel mediums showed good biocompatibility and the ability to support cell proliferation. Nucleus pulposus cells cultured on the soft matrix (4%GelMA) had a lower elongation and spreading area than those cultured on the stiff matrix (15%GelMA), showing a tendency of YAP concentration in the cytoplasm. The gene expression of nucleus pulposus cells was examined and the levels of Sox9, Acan and Ncam-1 in the soft matrix hydrogel group were 23.7, 6.6 and 12.7 times of those in the control group respectively. In vivo experiments on rat disc degeneration showed that the soft hydrogel matrix group had higher disc water content and structural integrity than the stiff hydrogel matrix group.ConclusionĀ·Compared to stiff GelMA hydrogels, hydrogels with low stiffness better maintain the growth phenotypes in the nucleus pulposus cells and have better therapeutic effect on disc degeneration in vivo
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Tuning Oxygen Redox Reaction through the Inductive Effect with Proton Insertion in Li-Rich Oxides.
As a parent compound of Li-rich electrodes, Li2MnO3 exhibits high capacity during the initial charge; however, it suffers notoriously low Coulombic efficiency due to oxygen and surface activities. Here, we successfully optimize the oxygen activities toward reversible oxygen redox reactions by intentionally introducing protons into lithium octahedral vacancies in the Li2MnO3 system with its original structural integrity maintained. Combining structural probes, theoretical calculations, and resonant inelastic X-ray scattering results, a moderate coupling between the introduced protons and lattice oxygen at the oxidized state is revealed, which stabilizes the oxygen activities during charging. Such a coupling leads to an unprecedented initial Coulombic efficiency (99.2%) with a greatly improved discharge capacity of 302 mAh g-1 in the protonated Li2MnO3 electrodes. These findings directly demonstrate an effective concept for controlling oxygen activities in Li-rich systems, which is critical for developing high-energy cathodes in batteries
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High-voltage oxide cathodes for high-energy-density lithium-ion batteries
The worldwide electrification of the automobile industry has been strongly pushing the advancement of lithium-ion batteries (LIBs) with high energy density and long service life. Since the cathode is currently the limiting electrode for energy density, safety, and cost of commercial LIBs, extensive efforts have been devoted into investigating next-generation high-performance cathode materials with high capacity and operating voltage. Among the pool of cathodes, high-nickel layered oxide cathodes, LiNiāMāāāOā (M = Co, Mn, Al, etc.; x > 0.7), are regarded as one of the most promising candidates. However, the practical viability of high-Ni cathodes is compromised by their air instability, fast structural and interfacial deteriorations during operation, poor thermal stability, and high cost. On the other hand, another promising cathode, high-voltage spinel LiNiā.ā
Mnā.ā
Oā, exhibits better thermal and structural stabilities, but suffers from rapid performance degradations due to its high operating voltage of > 4.7 V vs. Liāŗ/Li. This dissertation focuses on stabilizing the operation of high-Ni and high-voltage spinel cathodes with diverse modification strategies and advancing the understanding of the degradation mechanisms of cells with high-voltage cathodes assisted by state-of-the-art characterizations. First, the function of atomic scale zinc-doping in a high-Ni cathode LiNiā.āāCoā.āāZnā.āāOā.āā is investigated. The incorporation of Zn greatly mitigates the average voltage and capacity fade by ameliorating the anisotropic lattice distortion, enhancing the structural integrity, and reducing cathode-electrolyte side reactions. Moreover, Zn-doping is proved beneficial to improve the thermal stability. Second, a cobalt- and manganese-free LiNiā.āāAlā.āā
Tiā.āāMgā.āāOā cathode is rationally designed, synthesized, and comprehensively investigated. Collectively, the use of Al, Ti, and Mg in the cathode enables a stable operation of practical full cells over 800 cycles by alleviating electrolyte decomposition reactions, transition-metal crossover, and active lithium loss. Third, single-element doped cathodes, viz., LiNiā.āā
Coā.āā
Oā, LiNiā.āā
Mnā.āā
Oā, and LiNiā.āā
Alā.āā
Oā, along with undoped LiNiOā, are compared through a control of cutoff energy density to elucidate the role of dopants in high-Ni cathodes. Via a group of advanced analytical techniques, it is unveiled that one critical role of dopant is regulating the state-of-charge and the occurrence of H2āH3 phase transition of high-Ni cathodes, which essentially dictates the cycle stability. Finally, electrochemical modifications on the graphite anode and high-voltage spinel cathode are performed and characterized. The results suggest that the graphite anode interphase degradations caused by acidic and transition-metal crossover species generated from the cathode predominately contribute to the cell performance deterioration. Based on in-depth analyses, pathways towards long-life high-voltage full cells are pictured.Materials Science and Engineerin
Degradation Pathways of Cobalt-free LiNiO2 Cathode in Lithium Batteries
Electrode-electrolyte reactivity (EER) and particle cracking (PC) are considered two main causes of capacity fade in high-nickel layered oxide cathodes in lithium-based batteries. However, whether EER or PC is more critical remains debatable. Herein, the fundamental correlation between EER and PC is systematically investigated with LiNiO2 (LNO), the ultimate cobalt-free lithium layered oxide cathode. Specifically, EER is found more critical than secondary particle cracking (SPC) in determining the cycling stability of LNO; EER leads to primary particle cracking (PPC), but contrary to conventional wisdom, prevents SPC. Two surface degradation pathways are identified for cycled LNO under low and high EERs. A common blocking surface reconstruction layer (SRL) containing electrochemically-inactive Ni3O4 spinel and NiO rock-salt phases is formed on LNO at the charged state in an electrolyte with high EER; in contrast, an electrochemically-active SRL featuring regions of electron- and lithium-ion-conductive LiNi2O4 spinel phase is formed on LNO at the charged state in an electrolyte with low EER, even though bulk LiNi2O4 crystals are believed to be non-existent. These findings unveil the intrinsic degradation pathways of LNO cathode and are foreseen to provide new insights into the development of lithium-based batteries with minimized EER and maximized service life
Impact of Dopants on Suppressing Gas Evolution from High-Nickel Layered Oxide Cathodes
Gas release from high-Ni layered
oxide cathodes (LiNixMn1āxāyāzCoyAlzO2; x > 0.8) can jeopardize the
overall performance and safety characteristics of the cell. A comprehensive
assessment of rational cathode design with common dopants, such as
Ni, Co, Al, and Mn, to suppress gas evolution is crucial for battery
safety, yet it remains to be conducted. Here, we present an in situ
gas analysis of nine high-Ni cathode materials with online electrochemical
mass spectrometry (OEMS). We show that, regardless of the dopant,
reactive oxygen release from the cathode lattice remains a critical
process for gas evolution. A series of comparisons reveals that the
intensity and onset point of gas release are strongly dependent on
the cathode composition. Notably, Al and Mn are the most effective
dopants to suppress gas evolution from the cathode at 4.4 V. We further
highlight lattice stability limits, across these nine compositions,
between 85% and 93% state-of-charge
Advanced microfluidic devices for fabricating multiāstructural hydrogel microsphere
Abstract Hydrogel microspheres are a novel functional material, arousing much attention in various fields. Microfluidics, a technology that controls and manipulates fluids at the micron scale, has emerged as a promising method for fabricating hydrogel microspheres due to its ability to generate uniform microspheres with controlled geometry. With the development of microfluidic devices, more complicated hydrogel microspheres with multiple structures can be constructed. This review presents an overview of advances in microfluidics for designing and engineering hydrogel microspheres. It starts with an introduction to the features of hydrogel microspheres and microfluidic techniques, followed by a discussion of material selection for fabricating microfluidic devices. Then the progress of microfluidic devices for singleācomponent and composite hydrogel microspheres is described, and the method for optimizing microfluidic devices is also given. Finally, this review discusses the key research directions and applications of microfluidics for hydrogel microsphere in the future
Faba Bean (<i>Vicia faba</i> L.) Yield Estimation Based on Dual-Sensor Data
Faba bean is an important member of legumes, which has richer protein levels and great development potential. Yield is an important phenotype character of crops, and early yield estimation can provide a reference for field inputs. To facilitate rapid and accurate estimation of the faba bean yield, the dual-sensor (RGB and multi-spectral) data based on unmanned aerial vehicle (UAV) was collected and analyzed. For this, support vector machine (SVM), ridge regression (RR), partial least squares regression (PLS), and k-nearest neighbor (KNN) were used for yield estimation. Additionally, the fusing data from different growth periods based on UAV was first used for estimating faba bean yield to obtain better estimation accuracy. The results obtained are as follows: for a single-growth period, S2 (12 July 2019) had the best accuracy of the estimation model. For fusion data from the muti-growth period, S2 + S3 (12 August 2019) obtained the best estimation results. Furthermore, the coefficient of determination (R2) values for RF were higher than other machine learning algorithms, followed by PLS, and the estimation effects of fusion data from a dual-sensor were evidently better than from a single sensor. In a word, these results indicated that it was feasible to estimate the faba bean yield with high accuracy through data fusion based on dual-sensor data and different growth periods
Nanorod In<sub>2</sub>O<sub>3</sub>@C Modified Separator with Improved Adsorption and Catalytic Conversion of Soluble Polysulfides for High-Performance LithiumāSulfur Batteries
The shuttle effect of soluble lithium polysulfides (LiPSs)
poses
a crucial challenge for commercializing lithiumāsulfur batteries.
The functionalization of the separator is an effective strategy for
enhancing the cell lifespan through the capture and reuse of LiPSs.
Herein, a novel In2O3 nanorod with an ultrathin
carbon layer (In2O3@C) was coated on a polypropylene
separator. The results demonstrate the adsorption and catalysis of
In2O3 on polysulfides, effectively inhibiting
the shuttle effect and improving the redox kinetics of LiPSs. Besides,
the ultrathin carbon layer increases the reaction sites and accelerates
the electrochemical reaction rate. The cell with the In2O3@C interlayer displays excellent reversibility and stability
with a 0.029% capacity decay each cycle in 2000 cycles at 2C. In addition,
the In2O3@C interlayer significantly improves
the cell performance under high current (888.2 mA h gā1 at 2C and room temperature) and low temperature (1007.8 mA h gā1 at 0.1C and ā20 Ā°C) conditions