22 research outputs found
Ultrafast interfacial energy transfer and interlayer excitons in the monolayer WS<sub>2</sub>/CsPbBr<sub>3</sub> quantum dot heterostructure
No full textThe idea of fabricating artificial solids with band structures tailored to particular applications has long fascinated condensed matter physicists.</p
A Dynamic Bayesian Network model to evaluate the availability of machinery systems in Maritime Autonomous Surface Ships
No full textFunding Information: The research was supported by the Hubei Provincial Natural Science Foundation of China (2019CFA039), the National Natural Science Foundation of China (51920105014; 52071247), and the Innovation and entrepreneurship team import project of Shaoguan city (201212176230928). Publisher Copyright: © 2023 Elsevier LtdWith their complex structure, multiple failure modes and lack of maintenance crew, the safety problem of Maritime Autonomous Surface Ships’ (MASS) machinery systems are becoming an important research topic. The present study presents an availability model for ship machinery systems incorporating a maintenance strategy based on Dynamic Bayesian Networks (DBN). First, the availability of conventional ship machinery systems is evaluated and used as a benchmark based on the configuration and planned maintenance strategy. Secondly, the availability of MASS machinery systems is compared to the benchmark, before the introduction of any changes to the ship's configuration and planned maintenance strategy. Finally, the availability improvement strategies, including redundant designs and planned maintenance strategies at port, are proposed based on sensitivity analysis and planned maintenance cost minimization. To exemplify the model's application, a case study of a cooling water system is explored. Based on a sensitivity analysis using the model, it is possible to decide which components need to be redundant. Different redundancy designs and corresponding planned maintenance strategies can be adopted to meet the availability demand. It is also shown that redundancy and enhanced detection capabilities reduce much of the planned maintenance cost. This framework can be used in the early design stages to determine whether the MASS machinery systems’ availability is at least equivalent to that of conventional ships, and has certain reference significance for redundant configuration designs and MASS planned maintenance strategy schedule.Peer reviewe
COLREGs-Adaptive trajectory planning and decision-making in maritime autonomous surface ships
No full textDecision-making for collision avoidance and trajectory planning are critical technologies for maritime autonomous surface ships. These systems must align with regulatory frameworks such as the International Regulations for Preventing Collisions at Sea (COLREGs) and account for the ship’s maneuvering capabilities for effective control and tracking. This study introduces a novel framework integrating regulatory consideration into the path-searching process, enhancing collision avoidance in both COLREG-compliant and non-compliant scenarios. The framework recasts the trajectory-planning problem into an optimal control problem and employs virtual obstacles and spatial–temporal navigation corridors consistent with collision-free decisions as constraints for trajectory optimization, improving navigation efficiency and comfort. The framework is validated through various encounter scenarios, and the results demonstrate that the proposed framework can produce superior collision avoidance decisions, while planning shorter navigation time and smoother collision-free trajectories, significantly improving the collision avoidance capability of maritime autonomous surface ships
COLREGs-Adaptive trajectory planning and decision-making in maritime autonomous surface ships
No full textPublisher Copyright: © 2024 Elsevier LtdDecision-making for collision avoidance and trajectory planning are critical technologies for maritime autonomous surface ships. These systems must align with regulatory frameworks such as the International Regulations for Preventing Collisions at Sea (COLREGs) and account for the ship's maneuvering capabilities for effective control and tracking. This study introduces a novel framework integrating regulatory consideration into the path-searching process, enhancing collision avoidance in both COLREG-compliant and non-compliant scenarios. The framework recasts the trajectory-planning problem into an optimal control problem and employs virtual obstacles and spatial–temporal navigation corridors consistent with collision-free decisions as constraints for trajectory optimization, improving navigation efficiency and comfort. The framework is validated through various encounter scenarios, and the results demonstrate that the proposed framework can produce superior collision avoidance decisions, while planning shorter navigation time and smoother collision-free trajectories, significantly improving the collision avoidance capability of maritime autonomous surface ships.Peer reviewe
Use of Hybrid Causal Logic Method for Preliminary Hazard Analysis of Maritime Autonomous Surface Ships
No full textFunding Information: The research was supported by the Hubei Provincial Natural Science Foundation of China (2019CFA039), the Natural Science Foundation of China (No.52071247) and the innovation and entrepreneurship team import project of Shaoguan city (201208176230693). Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Recently, the safety issue of maritime autonomous surface ships (MASS) has become a hot topic. Preliminary hazard analysis of MASS can assist autonomous ship design and ensure safe and reliable operation. However, since MASS technology is still at its early stage, there are not enough data for comprehensive hazard analysis. Hence, this paper attempts to combine conventional ship data and MASS experiments to conduct a preliminary hazard analysis for autonomy level III MASS using the hybrid causal logic (HCL) method. Firstly, the hazardous scenario of autonomy level III MASS is developed using the event sequence diagram (ESD). Furthermore, the fault tree (FT) method is utilized to analyze mechanical events in ESD. The events involving human factors and related to MASS in the ESD are analyzed using Bayesian Belief Network (BBN). Finally, the accident probability of autonomy level III MASS is calculated in practice through historical data and a test ship with both an autonomous and a remote navigation mode in Wuhan and Nanjing, China. Moreover, the key influence factors are found, and the accident-causing event chains are identified, thus providing a reference for MASS design and safety assessment process. This process is applied to the preliminary hazard analysis of the test ship.Peer reviewe
Germinal disc region: an appropriate source for obtaining maternal DNA from eggs
No full textEggs may serve as an alternative source for DNA extraction. The quality of DNA extracted from eggshell, whole egg liquid (WEL) and germinal disc region (GDR) was compared based on the spectrophotometric, electrophoretic, PCR and reduced-representation library sequencing (RRLS) results. Although these DNAs were all invisible on the gel and can not be measured spectrophotometrically, the GDR DNA was superior to the eggshell and WEL DNA in PCR efficiency. After the whole genome amplification (WGA) was introduced, the yield of GDR DNA was significantly increased. The obtaining DNA had overwhelming superiority over the eggshell and WEL DNA in the ratio of captured genome and the number of called
SNP. The GDR DNA extraction followed by the WGA provides a method to obtain sufficient DNA from a single egg.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
High-efficient visible-light photocatalyst based on graphene incorporated Ag3PO4 nanocomposite applicable for the degradation of a wide variety of dyes
No full textIrreparable Defects Produced by the Patching of h-BN Frontiers on Strongly Interacting Re(0001) and Their Electronic Properties
No full textClarifying the origin and the electronic properties of defects in materials is crucial since the mechanical, electronic and magnetic properties can be tuned by defects. Herein, we find that, for the growth of h-BN monolayer on Re(0001), the patching frontiers of different domains can be classified into three types, i.e., the patching of B- and N-terminated (BlN-terminated) frontiers, BIB-terminated frontiers and NlN-terminated frontiers, which introduce three types of defects, i.e., the "heart" shaped moire-level defect, the nonbonded and bonded line defects, respectively. These defects were found to bring significant modulations to the electronic properties of h-BN, by introducing band gap reductions and in-gap states, comparing with perfect h-BN on Re(0001) with a band gap of similar to 3.7 eV. The intrinsic binary composition nature of h-BN and the strong h-BN-Re(0001) interaction are proposed to be cooperatively responsible for the formation of these three types of defects. The former one provides different types of h-BN frontiers for domain patching. And the later one induces multinucleation but aligned growth of h-BN domains on Re(0001), thus precluding their subsequent coalescence to some extent. This work offers a deep insight into the categories of defects introduced from the patching growth of two-dimensional layered materials, as well as their electronic property modulation through the defect engineering.National Key Research and Development Program of China [2016YFA0200103]; Beijing Municipal Science and Technology Commission [Z161100002116020]; Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics [KF201601]; National Natural Science Foundation of China [51290272, 51472008, 51432002, 50121091, 21201012]; National Basic Research Program of China [2013CB932603, 2014CB921002]SCI(E)ARTICLE165849-585613
Strong Adlayer-Substrate Interactions "Break" the Patching Growth of h-BN onto Graphene on Re(0001)
No full textHetero-epitaxial growth of hexagonal boron nitride (h-BN) from the edges of graphene domains or vice versa has been widely observed during synthesis of in-plane heterostructures of h-BN-G on Rh(111), Ir(111), and even Cu foil. We report that, on a strongly coupled Re(0001) substrate via a similar two-step sequential growth strategy, h-BN preferably nucleated on the edges of Re(0001) steps rather than on the edges of existing graphene domains. Statistically, one-third of the domain boundaries of graphene and h-BN were patched seamlessly, and the others were characterized by obvious "defect lines" when the total coverage approached a full monolayer. This imperfect merging behavior can be explained by translational misalignment and lattice mismatch of the resulting separated component domains. According to density functional theory calculations, this coexisting patching and non-patching growth behavior was radically mediated by the strong adlayer substrate (A-S) interactions, as well as the disparate formation energies of the attachment of B-N pairs or B-N lines along the edges of the Re(0001) steps versus the graphene domains. This work will be of fundamental significance for the controllable synthesis of in-plane heterostructures constructed from two-dimensional layered materials with consideration of A-S interactions.National Key Research and Development Program of China [2016YFA0200103]; National Natural Science Foundation of China [51290272, 51472008, 51432002, 50121091, 21201012]; National Basic Research Program of China [2013CB932603, 2012CB933404, 2014CB921002]; Open Research Fund Program of the State Key Laboratory of Low Dimensional Quantum Physics [KF201601]; Open Research Fund Program of State Key Laboratory of Coal-based Low-carbon Energy (ENN Group Co., Ltd.), Langfang, ChinaSCI(E)ARTICLE21807-18151
All-in-One Tuning and Structural Pruning for Domain-Specific LLMs
No full textExisting pruning techniques for large language models (LLMs) targeting domain-specific applications typically follow a two-stage process: pruning the pretrained general-purpose LLMs and then fine-tuning the pruned LLMs on specific domains. However, the pruning decisions, derived from the pretrained weights, remain unchanged during fine-tuning, even if the weights have been updated. Therefore, such a combination of the pruning decisions and the finetuned weights may be suboptimal, leading to non-negligible performance degradation. To address these limitations, we propose ATP: All-in-One Tuning and Structural Pruning, a unified one-stage structural pruning and fine-tuning approach that dynamically identifies the current optimal substructure throughout the fine-tuning phase via a trainable pruning decision generator. Moreover, given the limited available data for domain-specific applications, Low-Rank Adaptation (LoRA) becomes a common technique to fine-tune the LLMs. In ATP, we introduce LoRA-aware forward and sparsity regularization to ensure that the substructures corresponding to the learned pruning decisions can be directly removed after the ATP process. ATP outperforms the state-of-the-art two-stage pruning methods on tasks in the legal and healthcare domains. More specifically, ATP recovers up to 88% and 91% performance of the dense model when pruning 40% parameters of LLaMA2-7B and LLaMA3-8B models, respectively.Updated a typo in the author list
