504 research outputs found
Numerical simulation on directional solidification of Al-Ni-Co alloy based on FEM
The ratio, of the temperature gradient at the solidification front to the solidification rate of solid-liquid interface, plays a large part in columnar grain growth. The transient temperature fields of directional solidification of Al-Ni-Co alloy were studied by employing a finite element method. The temperature gradient at the solidification front and the solidification rate were analyzed for molten steels pouring at different temperatures. The results show that with different initial pouring temperatures, the individual ratio of the temperature gradient at solidification front to the solidification rate soars up in the initial stage of solidification, then varies within 2,000-6,000 ℃·s·cm-2, and finally goes down rapidly and even tend to be closed to each other when the solidification thickness reaches 5-6 cm. The simulation result is consistent with the practical production which can provide an available reference for process optimization of directional solidified Al-Ni-Co alloy
Geographic and Climatic Attributions of Autumn Land Surface Phenology Spatial Patterns in the Temperate Deciduous Broadleaf Forest of China
Autumn vegetation phenology plays a critical role in identifying the end of the growing season and its response to climate change. Using the six vegetation indices retrieved from moderate resolution imaging spectroradiometer data, we extracted an end date of the growing season (EOS) in the temperate deciduous broadleaf forest (TDBF) area of China. Then, we validated EOS with the ground-observed leaf fall date (LF) of dominant tree species at 27 sites and selected the best vegetation index. Moreover, we analyzed the spatial pattern of EOS based on the best vegetation index and its dependency on geo-location indicators and seasonal temperature/precipitation. Results show that the plant senescence reflectance index-based EOS agrees most closely with LF. Multi-year averaged EOS display latitudinal, longitudinal and altitudinal gradients. The altitudinal sensitivity of EOS became weaker from 2000 to 2012. Temperature-based spatial phenology modeling indicated that a 1 K spatial shift in seasonal mean temperature can cause a spatial shift of 2.4–3.6 days in EOS. The models explain between 54% and 73% of the variance in the EOS timing. However, the influence of seasonal precipitation on spatial variations of EOS was much weaker. Thus, spatial temperature variation controls the spatial patterns of EOS in TDBF of China, and future temperature increase might lead to more uniform autumn phenology across elevations
GPT4RoI: Instruction Tuning Large Language Model on Region-of-Interest
Instruction tuning large language model (LLM) on image-text pairs has
achieved unprecedented vision-language multimodal abilities. However, their
vision-language alignments are only built on image-level, the lack of
region-level alignment limits their advancements to fine-grained multimodal
understanding. In this paper, we propose instruction tuning on
region-of-interest. The key design is to reformulate the bounding box as the
format of spatial instruction. The interleaved sequences of visual features
extracted by the spatial instruction and the language embedding are input to
LLM, and trained on the transformed region-text data in instruction tuning
format. Our region-level vision-language model, termed as GPT4RoI, brings brand
new conversational and interactive experience beyond image-level understanding.
(1) Controllability: Users can interact with our model by both language and
spatial instructions to flexibly adjust the detail level of the question. (2)
Capacities: Our model supports not only single-region spatial instruction but
also multi-region. This unlocks more region-level multimodal capacities such as
detailed region caption and complex region reasoning. (3) Composition: Any
off-the-shelf object detector can be a spatial instruction provider so as to
mine informative object attributes from our model, like color, shape, material,
action, relation to other objects, etc. The code, data, and demo can be found
at https://github.com/jshilong/GPT4RoI.Comment: Code has been released at https://github.com/jshilong/GPT4Ro
Fundamental Aspects of Ceria Supported Au Catalysts Probed by In Situ/Operando Spectroscopy and TAP Reactor Studies
The discovery of the activity of dispersed gold nanoparticles three decades ago paved the way for a new era in catalysis. The unusual behavior of these catalysts sparked many questions about their working mechanism. In particular, Au/CeO2 proved to be an efficient catalyst in several reactions such as CO oxidation, water gas shift, and CO2 reduction. Here, by employing findings from operando X-ray absorption spectroscopy at the near and extended Au and Ce LIII energy edges, we focus on the fundamental aspects of highly active Au/CeO2 catalysts, mainly in the CO oxidation for understanding their complex structure-reactivity relationship. These results were combined with findings from in situ diffuse reflectance FTIR and Raman spectroscopy, highlighting the changes of adlayer and ceria defects. For a comprehensive understanding, the spectroscopic findings will be supplemented by results of the dynamics of O2 activation obtained from Temporal Analysis of Products (TAP). Merging these results illuminates the complex relationship among the oxidation state, size of the Au nanoparticles, the redox properties of CeO2 support, and the dynamics of O2 activation
Robust tracking control of a flexible manipulator with limited control input based on backstepping and the Nussbaum function
A flexible manipulator is a versatile automated device with a wide range of applications, capable of performing various tasks. However, these manipulators are often vulnerable to external disturbances and face limitations in their ability to control actuators. These factors significantly impact the precision of tracking control in such systems. This study delves into the problem of attitude tracking control for a flexible manipulator under the constraints of control input limitations and the influence of external disturbances. To address these challenges effectively, we first introduce the backstepping method, aiming to achieve precise state tracking and tackle the issue of external disturbances. Additionally, recognizing the constraints posed by control input limitations in the flexible manipulator's actuator control system, we employ a design approach based on the Nussbaum function. This method is designed to overcome these limitations, allowing for more robust control. To validate the effectiveness and disturbance rejection capabilities of the proposed control strategy, we conduct comparative numerical simulations using MATLAB/Simulink. These simulations provide further evidence of the robustness and reliability of the control strategy, even in the presence of external disturbances and control input limitations
Research on Energy Consumption Calculation of Prefabricated Cabin Type Lithium Iron Phosphate Battery Energy Storage Power Station
[Introduction] The paper proposes an energy consumption calculation method for prefabricated cabin type lithium iron phosphate battery energy storage power station based on the energy loss sources and the detailed classification of equipment attributes in the station. [Method] From the perspective of an energy storage power station, this paper discussed the main factors to be considered in the energy consumption calculation of prefabricated cabin type lithium iron phosphate battery energy storage power station, and then divided the energy consumption of the energy storage power station into two parts, namely, the energy consumption of the energy storage system and the energy consumption of the auxiliary equipment operation. Besides, it also provided the calculation method for the energy consumption of each part and the selection method of efficiency value respectively. [Result] Through a practical calculation example, the whole-day energy consumption of a 2 MW/2 MWh energy storage battery prefabrication cabin in a certain operation mode is analyzed and compared with the field test results. The difference between the field test results and the theoretical analysis results is analyzed from the perspective of the heat produced by the energy storage battery and the heat transmitted by the air conditioner, and suggestions are put forward for the energy consumption statistics of the energy storage power station. [Conclusion] The energy consumption calculation method proposed in the study comprehensively discusses the main factors affecting the energy consumption index of the prefabricated cabin type lithium iron phosphate battery energy storage power station and gives the energy consumption calculation method for the main equipment according to the detailed classification of equipment attributes, which has a good engineering reference value
Large Language Models Are Neurosymbolic Reasoners
A wide range of real-world applications is characterized by their symbolic
nature, necessitating a strong capability for symbolic reasoning. This paper
investigates the potential application of Large Language Models (LLMs) as
symbolic reasoners. We focus on text-based games, significant benchmarks for
agents with natural language capabilities, particularly in symbolic tasks like
math, map reading, sorting, and applying common sense in text-based worlds. To
facilitate these agents, we propose an LLM agent designed to tackle symbolic
challenges and achieve in-game objectives. We begin by initializing the LLM
agent and informing it of its role. The agent then receives observations and a
set of valid actions from the text-based games, along with a specific symbolic
module. With these inputs, the LLM agent chooses an action and interacts with
the game environments. Our experimental results demonstrate that our method
significantly enhances the capability of LLMs as automated agents for symbolic
reasoning, and our LLM agent is effective in text-based games involving
symbolic tasks, achieving an average performance of 88% across all tasks.Comment: Accepted by AAAI 202
- …