| 1. |
-
- 2019
-
Journal article (peer-reviewed)
|
|
| 2. |
- Chen, Jingxuan, et al.
(author)
-
Regulating Thiol Ligands of p-Type Colloidal Quantum Dots for Efficient Infrared Solar Cells
- 2021
-
In: ACS Energy Letters. - : American Chemical Society (ACS). - 2380-8195. ; 6:5, s. 1970-1989
-
Journal article (peer-reviewed)abstract
- The p-type semiconducting colloidal quantum dot (CQD), working as a hole conductor in CQD solar cells (CQDSCs), is critical for charge carrier extraction and therefore, to large extent, determines the device's photovoltaic performance. However, during the preparation of a p-type CQD solid film on the top of an n-type CQD solid film, forming a p-n heterojunction within the CQDSCs, the optoelectronic properties of the underlayered n-type CQD solid film are significantly affected by conventional 1,2-ethanedithiol (EDT) ligands due to its high reactivity. Herein, a series of thiol ligands are comprehensively studied for p-type CQDs, which suggests that, by finely controlling the interaction between the CQDs and thiol ligands during the preparation of p-type CQD solid films, the n-type CQD solid films can be well protected and avoid destruction induced by thiol ligands. The p-type CQD solid film with 4-aminobenzenethiol (ABT) passivating the CQD surface exhibits better optoelectronic properties than the conventional p-type EDT-based CQD solid films, resulting in an improved photovoltaic performance in CQDSCs.
|
|
| 3. |
- Chen, Siyu, et al.
(author)
-
Non-Abelian braiding of Weyl nodes via symmetry-constrained phase transitions
- 2022
-
In: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 105:8
-
Journal article (peer-reviewed)abstract
- Weyl semimetals are arguably the most paradigmatic form of a gapless topological phase. While the stability of Weyl nodes, as quantified by their topological charge, has been extensively investigated, recent interest has shifted to the manipulation of the location of these Weyl nodes for non-Abelian braiding. To accomplish this braiding it is necessary to drive significant Weyl node motion using realistic experimental parameter changes. We show that a family of phase transitions characterized by certain symmetry constraints impose that the Weyl nodes have to reorganize by a large amount, shifting from one high-symmetry plane to another. Additionally, for a subset of pairs of nodes with nontrivial Euler class topology, this reorganization can only occur through a braiding process with adjacent nodes. As a result, the Weyl nodes are forced to move a large distance across the Brillouin zone and to braid, all driven by small temperature changes, a process we illustrate with Cd2Re2O7.
|
|
| 4. |
- Gao, Yaqing, et al.
(author)
-
Housing environment and early childhood development in sub-Saharan Africa: A cross-sectional analysis.
- 2021
-
In: PLoS medicine. - : Public Library of Science (PLoS). - 1549-1676 .- 1549-1277. ; 18:4
-
Research review (peer-reviewed)abstract
- The influence of the safety and security of environments on early childhood development (ECD) has been under-explored. Although housing might be linked to ECD by affecting a child's health and a parent's ability to provide adequate care, only a few studies have examined this factor. We hypothesized that housing environment is associated with ECD in sub-Saharan Africa (SSA).From 92,433 children aged 36 to 59 months who participated in Multiple Indicator Cluster Survey (MICS) in 20 SSA countries, 88,271 were tested for cognitive and social-emotional development using the Early Childhood Development Index (ECDI) questionnaire and were thus included in this cross-sectional analysis. Children's mean age was 47.2 months, and 49.8% were girls. Children were considered developmentally on track in a certain domain if they failed no more than 1 ECDI item in that domain. In each country, we used conditional logistic regression models to estimate the association between improved housing (housing with finished building materials, improved drinking water, improved sanitation facilities, and sufficient living area) and children's cognitive and social-emotional development, accounting for contextual effects and socioeconomic factors. Estimates from each country were pooled using random-effects meta-analyses. Subgroup analyses were conducted by the child's gender, maternal education, and household wealth quintiles. On-track cognitive development was associated with improved housing (odds ratio [OR] = 1.15, 95% CI 1.06 to 1.24, p < 0.001), improved drinking water (OR = 1.07, 95% CI 1.00 to 1.14, p = 0.046), improved sanitation facilities (OR = 1.15, 95% CI 1.03 to 1.28, p = 0.014), and sufficient living area (OR = 1.06, 95% CI 1.01 to 1.10, p = 0.018). On-track social-emotional development was associated with improved housing only in girls (OR = 1.14, 95% CI 1.04 to 1.25, p = 0.006). The main limitations of this study included the cross-sectional nature of the datasets and the use of the ECDI, which lacks sensitivity to measure ECD outcomes.In this study, we observed that improved housing was associated with on-track cognitive development and with on-track social-emotional development in girls. These findings suggest that housing improvement in SSA may be associated not only with benefits for children's physical health but also with broader aspects of healthy child development.
|
|
| 5. |
- Gao, Yaqing, et al.
(author)
-
Inequality in measles vaccination coverage in the "big six" countries of the WHO South-East Asia region.
- 2020
-
In: Human vaccines & immunotherapeutics. - : Informa UK Limited. - 2164-554X .- 2164-5515. ; 16:7, s. 1485-1497
-
Journal article (peer-reviewed)abstract
- The "big six" countries (Bangladesh, India, Indonesia, Myanmar, Nepal, and Thailand) in the World Health Organization South-East Asia Region (WHO SEAR) are currently facing severe challenges in measles elimination and consequent childhood mortality reduction, with inadequacies and inequalities in the coverage of the measles-containing-vaccine first-dose (MCV1) being major obstacles. However, these issues of inequality in MCV1 coverage have not yet been systematically examined. We used data from the latest Demographic and Health Surveys and Multiple Indicator Cluster Surveys. To provide a comprehensive picture of existing MCV1 coverage gaps, data were disaggregated by geographic location, as well as by socioeconomic and nutritional dimensions. National MCV1 coverage ranged from 77% in Myanmar to 92% in Thailand. Only nine of the 104 sub-national districts had achieved the 95% MCV1 coverage goal as set by the WHO. Geographic inequalities were more pronounced in countries with lower coverage levels. Areas in clusters with poor MCV1 coverage performances as well as disadvantaged socioeconomic profiles require increased attention. Inequalities were evident in all countries, except Thailand, and were more pronounced in the sectors of wealth, education, antenatal care (ANC) status, and vitamin A supplementation (VAS) when compared against the areas of gender and urban/rural residence. Wealth-related inequality in Bangladesh, education-related inequality in Indonesia, ANC-related inequalities in Myanmar and Nepal, and VAS-related inequalities in Indonesia and Myanmar were all noteworthy. Equity-oriented changes in policies focusing on health promotion and integrated interventions among disadvantaged populations need to be implemented in order to increase MCV1 coverage and reduce childhood mortality.
|
|
| 6. |
- Geng, Huifang, et al.
(author)
-
Controlled synthesis of highly stable lead-free bismuth halide perovskite nanocrystals : tructures and photophysics
- 2023
-
In: SCIENCE CHINA Materials. - : Springer Science and Business Media LLC. - 2095-8226 .- 2199-4501. ; 66:5, s. 2079-2089
-
Journal article (peer-reviewed)abstract
- Recently, cesium bismuth halide perovskites have emerged as potential substitutes to their counterparts, cesium lead halide perovskites, owing to their low toxicity. However, the photophysics of cesium-bismuth halides nanocrystals (NCs) have not yet been fully rationalized because their structures remain highly debated. The ultraviolet-visible (UV-vis) absorption along with other photophysical properties such as the nature and lifetime of the excited states vary considerably across the previous reports. Here, we successfully synthesize pure Cs3BiBr6 and Cs3Bi2Br9 NCs via a modified hot-injection method, where the structure can be easily controlled by tuning the reaction temperature. The UV-vis absorption spectrum of the pure Cs3Bi2Br9 NCs features two characteristic peaks originating from the absorption of the first exciton and second exciton, respectively, which ultimately clarifies the debate in the previous reports. Using femtosecond transient absorption spectroscopy, we systematically investigate the excited state dynamics of the Cs3Bi2Br9 NCs and reveal that the photoexcited carriers undergo a self-trapping process within 3 ps after excitation. More intriguingly, the Cs3Bi2Br9 NCs prepared by this method show much better photostability than those prepared by the ligand-assisted reprecipitation process. Photodetectors based on these Cs3Bi2Br9 NCs show a sensitive light response, demonstrating the definite potential for breakthrough optoelectronic applications. [Figure not available: see fulltext.].
|
|
| 7. |
- Jia, Donglin, et al.
(author)
-
Highly Stabilized Quantum Dot Ink for Efficient Infrared Light Absorbing Solar Cells
- 2019
-
In: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 9:44
-
Journal article (peer-reviewed)abstract
- Liquid-state ligand exchange provides an efficient approach to passivate a quantum dot (QD) surface with small binding species and achieve a QD ink toward scalable QD solar cell (QDSC) production. Herein, experimental studies and theoretical simulations are combined to establish the physical principles of QD surface properties induced charge carrier recombination and collection in QDSCs. Ammonium iodide (AI) is used to thoroughly replace the native oleic acid ligand on the PbS QD surface forming a concentrated QD ink, which has high stability of more than 30 d. The ink can be directly applied for the preparation of a thick QD solid film using a single deposition step method and the QD solid film shows better characteristics compared with that of the film prepared with the traditional PbX2 (X = I or Br) post-treated QD ink. Infrared light-absorbing QDSC devices are fabricated using the PbS-AI QD ink and the devices give a higher photovoltaic performance compared with the devices fabricated with the traditional PbS-PbX2 QD ink. The improved photovoltaic performance in PbS-AI-based QDSC is attributed to diminished charge carrier recombination induced by the sub-bandgap traps in QDs. A theoretical simulation is carried out to atomically link the relationship of QDSC device function with the QD surface properties.
|
|
| 8. |
|
|
| 9. |
- Liu, Wei, et al.
(author)
-
Microencapsulated phase change material through cellulose nanofibrils stabilized Pickering emulsion templating
- 2023
-
In: advanced composites and hybrid materials. - 2522-0128. ; 6:4
-
Journal article (peer-reviewed)abstract
- Phase change materials (PCMs) possess remarkable capability to store and release substantial amounts of energy during the processes of melting and crystallization across a wide temperature range, thus holding great promise in applications related to temperature regulation and thermal energy storage. Herein, to effectively address PCM leakage and enhance thermal conduction, PCM microcapsules with melamine-formaldehyde resin (MF) shell were prepared using in situ polymerization of Pickering emulsions stabilized by cellulose nanofibrils (CNFs). CNFs were selected as the stabilizers for the Pickering emulsions and as reinforcing nanofillers for the MF shell, owing to their excellent emulsifying capability, high mechanical strength, and sustainable nature. Paraffin wax (PW) was utilized as the PCM material. The resulting PCM microcapsules with MF resin shells and PW core had a diameter ranging from 2 to 4 & mu;m. Results showed that microcapsule with the core-shell ratio of 2 (Micro-2.0) exhibited the highest latent heat of crystallization and latent heat of fusion, measuring approximately 128.40 J/g and 120.23 J/g, respectively. The encapsulation efficiency of Micro-2.0 was determined to be approximately 79.84%.
|
|
| 10. |
- Luan, Siyu, et al.
(author)
-
LRP-based network pruning and policy distillation of robust and non-robust DRL agents for embedded systems
- 2023
-
In: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 35:19
-
Journal article (peer-reviewed)abstract
- Reinforcement learning (RL) is an effective approach to developing control policies by maximizing the agent's reward. Deep reinforcement learning uses deep neural networks (DNNs) for function approximation in RL, and has achieved tremendous success in recent years. Large DNNs often incur significant memory size and computational overheads, which may impede their deployment into resource-constrained embedded systems. For deployment of a trained RL agent on embedded systems, it is necessary to compress the policy network of the RL agent to improve its memory and computation efficiency. In this article, we perform model compression of the policy network of an RL agent by leveraging the relevance scores computed by layer-wise relevance propagation (LRP), a technique for Explainable AI (XAI), to rank and prune the convolutional filters in the policy network, combined with fine-tuning with policy distillation. Performance evaluation based on several Atari games indicates that our proposed approach is effective in reducing model size and inference time of RL agents. We also consider robust RL agents trained with RADIAL-RL versus standard RL agents, and show that a robust RL agent can achieve better performance (higher average reward) after pruning than a standard RL agent for different attack strengths and pruning rates.
|
|
