135 research outputs found
In-Plane Electric Field Induced Orbital Hybridization of Excitonic States In Monolayer WSe2
The giant exciton binding energy and the richness of degrees of freedom make
monolayer transition metal dichalcogenide an unprecedented playground for
exploring exciton physics in 2D systems. Thanks to the well energetically
separated excitonic states, the response of the discrete excitonic states to
the electric field could be precisely examined. Here we utilize the
photocurrent spectroscopy to probe excitonic states under a static in-plane
electric field. We demonstrate that the in-plane electric field leads to a
significant orbital hybridization of Rydberg excitonic states with different
angular momentum (especially orbital hybridization of 2s and 2p) and
consequently optically actives 2p-state exciton. Besides, the electric-field
controlled mixing of the high lying exciton state and continuum band enhances
the oscillator strength of the discrete excited exciton states. This electric
field modulation of the excitonic states in monolayer TMDs provides a paradigm
of the manipulation of 2D excitons for potential applications of the
electro-optical modulation in 2D semiconductors
LLM-empowered Chatbots for Psychiatrist and Patient Simulation: Application and Evaluation
Empowering chatbots in the field of mental health is receiving increasing
amount of attention, while there still lacks exploration in developing and
evaluating chatbots in psychiatric outpatient scenarios. In this work, we focus
on exploring the potential of ChatGPT in powering chatbots for psychiatrist and
patient simulation. We collaborate with psychiatrists to identify objectives
and iteratively develop the dialogue system to closely align with real-world
scenarios. In the evaluation experiments, we recruit real psychiatrists and
patients to engage in diagnostic conversations with the chatbots, collecting
their ratings for assessment. Our findings demonstrate the feasibility of using
ChatGPT-powered chatbots in psychiatric scenarios and explore the impact of
prompt designs on chatbot behavior and user experience
Dynamics and Control of a Flexible Solar Sail
Solar sail can merely make use of solar radiation pressure (SRP) force as the thrust for space missions. The attitude dynamics is obtained for the highly flexible solar sail with control vanes, sliding masses, and a gimbaled control boom. The vibration equations are derived considering the geometric nonlinearity of the sail structure subjected to the forces generated by the control vanes, solar radiation pressure (SRP), and sliding masses. Then the dynamic models for attitude/vibration controller design and dynamic simulation are obtained, respectively. The linear quadratic regulator (LQR) based and optimal proportional-integral (PI) based controllers are designed for the coupled attitude/vibration models with constant disturbance torques caused by the center-of-mass (cm)/center-of-pressure (cp) offset, respectively. It can be concluded from the theoretical analysis and simulation results that the optimal PI based controller performs better than the LQR based controller from the view of eliminating the steady-state errors. The responses with and without the geometrical nonlinearity are performed, and the differences are observed and analyzed. And some suggestions are also presented
Robust Visual Imitation Learning with Inverse Dynamics Representations
Imitation learning (IL) has achieved considerable success in solving complex
sequential decision-making problems. However, current IL methods mainly assume
that the environment for learning policies is the same as the environment for
collecting expert datasets. Therefore, these methods may fail to work when
there are slight differences between the learning and expert environments,
especially for challenging problems with high-dimensional image observations.
However, in real-world scenarios, it is rare to have the chance to collect
expert trajectories precisely in the target learning environment. To address
this challenge, we propose a novel robust imitation learning approach, where we
develop an inverse dynamics state representation learning objective to align
the expert environment and the learning environment. With the abstract state
representation, we design an effective reward function, which thoroughly
measures the similarity between behavior data and expert data not only
element-wise, but also from the trajectory level. We conduct extensive
experiments to evaluate the proposed approach under various visual
perturbations and in diverse visual control tasks. Our approach can achieve a
near-expert performance in most environments, and significantly outperforms the
state-of-the-art visual IL methods and robust IL methods
Semi-Supervised Classification of Hyperspectral Images Based on Extended Label Propagation and Rolling Guidance Filtering
Semi-supervised classification methods result in higher performance for hyperspectral images, because they can utilize the relationship between unlabeled samples and labeled samples to obtain pseudo-labeled samples. However, how generating an effective training sample set is a major challenge for semi-supervised methods, In this paper, we propose a novel semi-supervised classification method based on extended label propagation (ELP) and a rolling guidance filter (RGF) called ELP-RGF, in which ELP is a new two-step process to make full use of unlabeled samples. The first step is to implement the graph-based label propagation algorithm to propagate the label information from labeled samples to the neighboring unlabeled samples. This is then followed by the second step, which uses superpixel propagation to assign the same labels to all pixels within the superpixels that are generated by the image segmentation method, so that some labels wrongly labeled by the above step can be modified. As a result, so obtained pseudo-labeled samples could be used to improve the performance of the classifier. Subsequently, an effective feature extraction method, i.e., RGF is further used to remove the noise and the small texture structures to optimize the features of the initial hyperspectral image. Finally, these produced initial labeled samples and high-confidence pseudo-labeled samples are used as a training set for support vector machine (SVM). The experimental results show that the proposed method can produce better classification performance for three widely-used real hyperspectral datasets, particularly when the number of training samples is relatively small
A non-linear reverse-engineering method for inferring genetic regulatory networks
Hematopoiesis is a highly complex developmental process that produces various types of blood cells. This process is regulated by different genetic networks that control the proliferation, differentiation, and maturation of hematopoietic stem cells (HSCs). Although substantial progress has been made for understanding hematopoiesis, the detailed regulatory mechanisms for the fate determination of HSCs are still unraveled. In this study, we propose a novel approach to infer the detailed regulatory mechanisms. This work is designed to develop a mathematical framework that is able to realize nonlinear gene expression dynamics accurately. In particular, we intended to investigate the effect of possible protein heterodimers and/or synergistic effect in genetic regulation. This approach includes the Extended Forward Search Algorithm to infer network structure (top-down approach) and a non-linear mathematical model to infer dynamical property (bottom-up approach). Based on the published experimental data, we study two regulatory networks of 11 genes for regulating the erythrocyte differentiation pathway and the neutrophil differentiation pathway. The proposed algorithm is first applied to predict the network topologies among 11 genes and 55 non-linear terms which may be for heterodimers and/or synergistic effect. Then, the unknown model parameters are estimated by fitting simulations to the expression data of two different differentiation pathways. In addition, the edge deletion test is conducted to remove possible insignificant regulations from the inferred networks. Furthermore, the robustness property of the mathematical model is employed as an additional criterion to choose better network reconstruction results. Our simulation results successfully realized experimental data for two different differentiation pathways, which suggests that the proposed approach is an effective method to infer the topological structure and dynamic property of genetic regulations
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