31,613 results on '"Zhang, Meng"'
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2. The Hamin Mangha Site: Mass Deaths and Abandonment of a Late Neolithic Settlement in Northeastern China
- Author
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Zhou, Yawei, Niu, Xiaohui, Ji, Ping, Zhu, Yonggang, Zhu, Hong, and Zhang, Meng
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- 2022
- Full Text
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3. China’s Gilded Age: The Paradox of Economic Boom and Vast Corruption by Yuen Yuen Ang (review)
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Zhang, Meng
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- 2021
4. Absence of altermagnetic spin splitting character in rutile oxide RuO$_2$
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Liu, Jiayu, Zhan, Jie, Li, Tongrui, Liu, Jishan, Cheng, Shufan, Shi, Yuming, Deng, Liwei, Zhang, Meng, Li, Chihao, Ding, Jianyang, Jiang, Qi, Ye, Mao, Liu, Zhengtai, Jiang, Zhicheng, Wang, Siyu, Li, Qian, Xie, Yanwu, Wang, Yilin, Qiao, Shan, Wen, Jinsheng, Sun, Yan, and Shen, Dawei
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Condensed Matter - Materials Science - Abstract
Rutile RuO$_2$ has been posited as a potential $d$-wave altermagnetism candidate, with a predicted significant spin splitting up to 1.4 eV. Despite accumulating theoretical predictions and transport measurements, direct spectroscopic observation of spin splitting has remained elusive. Here, we employ spin- and angle-resolved photoemission spectroscopy to investigate the band structures and spin polarization of thin-film and single-crystal RuO$_2$. Contrary to expectations of altermagnetism, our analysis indicates that RuO$_2$'s electronic structure aligns with those predicted under non-magnetic conditions, exhibiting no evidence of the hypothesized spin splitting. Additionally, we observe significant in-plane spin polarization of the low-lying bulk bands, which is antisymmetric about the high-symmetry plane and contrary to the $d$-wave spin texture due to time-reversal symmetry breaking in altermagnetism. These findings definitively challenge the altermagnetic order previously proposed for rutile RuO$_2$, prompting a reevaluation of its magnetic properties., Comment: 6 pages, 4 figures. Submitted to Physical Review Letters
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- 2024
5. Scalable tensor network algorithm for thermal quantum many-body systems in two dimension
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Zhang, Meng, Zhang, Hao, Wang, Chao, and He, Lixin
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Condensed Matter - Strongly Correlated Electrons - Abstract
Simulating strongly-correlated quantum many-body systems at finite temperatures is a significant challenge in computational physics. In this work, we present a scalable finite-temperature tensor network algorithm for two-dimensional quantum many-body systems. We employ the (fermionic) projected entangled pair state (PEPS) to represent the vectorization of the quantum thermal state and utilize a stochastic reconfiguration method to cool down the quantum states from infinite temperature. We validate our method by benchmarking it against the 2D antiferromagnetic Heisenberg model, the $J_1$-$J_2$ model, and the Fermi-Hubbard model, comparing physical properties such as internal energy, specific heat, and magnetic susceptibility with results obtained from stochastic series expansion (SSE), exact diagonalization, and determinant quantum Monte Carlo (DQMC).
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- 2024
6. Ground-roll Separation From Land Seismic Records Based on Convolutional Neural Network
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Jia, Zhuang, Lu, Wenkai, Zhang, Meng, and Miao, Yongkang
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Computer Science - Computer Vision and Pattern Recognition ,Electrical Engineering and Systems Science - Signal Processing ,Physics - Geophysics - Abstract
Ground-roll wave is a common coherent noise in land field seismic data. This Rayleigh-type surface wave usually has low frequency, low apparent velocity, and high amplitude, therefore obscures the reflection events of seismic shot gathers. Commonly used techniques focus on the differences of ground-roll and reflection in transformed domain such as $f-k$ domain, wavelet domain, or curvelet domain. These approaches use a series of fixed atoms or bases to transform the data in time-space domain into transformed domain to separate different waveforms, thus tend to suffer from the complexity for a delicate design of the parameters of the transform domain filter. To deal with these problems, a novel way is proposed to separate ground-roll from reflections using convolutional neural network (CNN) model based method to learn to extract the features of ground-roll and reflections automatically based on training data. In the proposed method, low-pass filtered seismic data which is contaminated by ground-roll wave is used as input of CNN, and then outputs both ground-roll component and low-frequency part of reflection component simultaneously. Discriminative loss is applied together with similarity loss in the training process to enhance the similarity to their train labels as well as the difference between the two outputs. Experiments are conducted on both synthetic and real data, showing that CNN based method can separate ground roll from reflections effectively, and has generalization ability to a certain extent.
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- 2024
7. Efficient Active Flow Control Strategy for Confined Square Cylinder Wake Using Deep Learning-Based Surrogate Model and Reinforcement Learning
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Zhang, Meng, Yousif, Mustafa Z., Xu, Minze, Zhou, Haifeng, Yu, Linqi, and Lim, HeeChang
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Physics - Fluid Dynamics - Abstract
This study presents a deep learning model-based reinforcement learning (DL-MBRL) approach for active control of two-dimensional (2D) wake flow past a square cylinder using antiphase jets. The DL-MBRL framework alternates between interacting with a deep learning surrogate model (DL-SM) and computational fluid dynamics (CFD) simulations to suppress wake vortex shedding, significantly reducing computational costs. The DL-SM, which combines a Transformer and a multiscale enhanced super-resolution generative adversarial network (MS-ESRGAN), effectively models complex flow dynamics, efficiently emulating the CFD environment. Trained on 2D direct numerical simulation (DNS) data, the Transformer and MS-ESRGAN demonstrated excellent agreement with DNS results, validating the DL-SM's accuracy. Error analysis suggests replacing the DL-SM with CFD every five interactions to maintain reliability. While DL-MBRL showed less robust convergence than model-free reinforcement learning (MFRL) during training, it reduced training time by 49.2%, from 41.87 hours to 20.62 hours. Both MFRL and DL-MBRL achieved a 98% reduction in shedding energy and a 95% reduction in the standard deviation of the lift coefficient (C_L). However, MFRL exhibited a nonzero mean lift coefficient due to insufficient exploration, whereas DL-MBRL improved exploration by leveraging the randomness of the DL-SM, resolving the nonzero mean C_L issue. This study demonstrates that DL-MBRL is not only comparably effective but also superior to MFRL in flow stabilization, with significantly reduced training time, highlighting the potential of combining deep reinforcement learning with DL-SM for enhanced active flow control., Comment: 19 pages, 12 figures
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- 2024
8. MagicID: Flexible ID Fidelity Generation System
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Deng, Zhaoli, Liu, Wen, Wang, Fanyi, Zhang, Junkang, Chen, Fan, Zhang, Meng, Zhang, Wendong, and Mi, Zhenpeng
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Computer Science - Computer Vision and Pattern Recognition - Abstract
Portrait Fidelity Generation is a prominent research area in generative models, with a primary focus on enhancing both controllability and fidelity. Current methods face challenges in generating high-fidelity portrait results when faces occupy a small portion of the image with a low resolution, especially in multi-person group photo settings. To tackle these issues, we propose a systematic solution called MagicID, based on a self-constructed million-level multi-modal dataset named IDZoom. MagicID consists of Multi-Mode Fusion training strategy (MMF) and DDIM Inversion based ID Restoration inference framework (DIIR). During training, MMF iteratively uses the skeleton and landmark modalities from IDZoom as conditional guidance. By introducing the Clone Face Tuning in training stage and Mask Guided Multi-ID Cross Attention (MGMICA) in inference stage, explicit constraints on face positional features are achieved for multi-ID group photo generation. The DIIR aims to address the issue of artifacts. The DDIM Inversion is used in conjunction with face landmarks, global and local face features to achieve face restoration while keeping the background unchanged. Additionally, DIIR is plug-and-play and can be applied to any diffusion-based portrait generation method. To validate the effectiveness of MagicID, we conducted extensive comparative and ablation experiments. The experimental results demonstrate that MagicID has significant advantages in both subjective and objective metrics, and achieves controllable generation in multi-person scenarios.
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- 2024
9. Flow Reconstruction Using Spatially Restricted Domains Based on Enhanced Super-Resolution Generative Adversarial Networks
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Yousif, Mustafa Z., Zhou, Dan, Yu, Linqi, Zhang, Meng, Mohammadikarachi, Arash, Lee, Jung Sub, and Lim, Hee-Chang
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Physics - Fluid Dynamics - Abstract
This study aims to reconstruct the complete flow field from spatially restricted domain data by utilizing an Enhanced Super-Resolution Generative Adversarial Network (ESRGAN) model. The difficulty in flow field reconstruction lies in accurately capturing and reconstructing large amounts of data under nonlinear, multi-scale, and complex flow while ensuring physical consistency and high computational efficiency. The ESRGAN model has a strong information mapping capability, capturing fluctuating features from local flow fields of varying geometries and sizes. The model effectiveness in reconstructing the whole domain flow field is validated by comparing instantaneous velocity fields, flow statistical properties, and probability density distributions. Using laminar bluff body flow from Direct Numerical Simulation (DNS) as a priori case, the model successfully reconstructs the complete flow field from three non-overlapping limited regions, with flow statistical properties perfectly matching the original data. Validation of the power spectrum density (PSD) for the reconstruction results also proves that the model could conform to the temporal behavior of the real complete flow field. Additionally, tests using DNS turbulent channel flow with a friction Reynolds number ($Re_\tau = 180$) demonstrate the model ability to reconstruct turbulent fields, though the quality of results depends on the number of flow features in the local regions. Finally, the model is applied to reconstruct turbulence flow fields from Particle Image Velocimetry (PIV) experimental measurements, using limited data from the near-wake region to reconstruct a larger field of view. The turbulence statistics closely match the experimental data, indicating that the model can serve as a reliable data-driven method to overcome PIV field-of-view limitations while saving computational costs., Comment: 27 pages, 16 figures
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- 2024
10. Self-Supervised Learning for Effective Denoising of Flow Fields
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Yu, Linqi, Yousif, Mustafa Z., Zhou, Dan, Zhang, Meng, Lee, Jungsub, and Lim, Hee-Chang
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Physics - Fluid Dynamics - Abstract
In this study, we proposed an efficient approach based on a deep learning (DL) denoising autoencoder (DAE) model for denoising noisy flow fields. The DAE operates on a self-learning principle and does not require clean data as training labels. Furthermore, investigations into the denoising mechanism of the DAE revealed that its bottleneck structure with a compact latent space enhances denoising efficacy. Meanwhile, we also developed a deep multiscale DAE for denoising turbulent flow fields. Furthermore, we used conventional noise filters to denoise the flow fields and performed a comparative analysis with the results from the DL method. The effectiveness of the proposed DL models was evaluated using direct numerical simulation data of laminar flow around a square cylinder and turbulent channel flow data at various Reynolds numbers. For every case, synthetic noise was augmented in the data. A separate experiment used particle-image velocimetry data of laminar flow around a square cylinder containing real noise to test DAE denoising performance. Instantaneous contours and flow statistical results were used to verify the alignment between the denoised data and ground truth. The findings confirmed that the proposed method could effectively denoise noisy flow data, including turbulent flow scenarios. Furthermore, the proposed method exhibited excellent generalization, efficiently denoising noise with various types and intensities., Comment: 32 pages, 20 figures
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- 2024
11. Garment Animation NeRF with Color Editing
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Wang, Renke, Zhang, Meng, Li, Jun, and Yan, Jian
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Computer Science - Computer Vision and Pattern Recognition - Abstract
Generating high-fidelity garment animations through traditional workflows, from modeling to rendering, is both tedious and expensive. These workflows often require repetitive steps in response to updates in character motion, rendering viewpoint changes, or appearance edits. Although recent neural rendering offers an efficient solution for computationally intensive processes, it struggles with rendering complex garment animations containing fine wrinkle details and realistic garment-and-body occlusions, while maintaining structural consistency across frames and dense view rendering. In this paper, we propose a novel approach to directly synthesize garment animations from body motion sequences without the need for an explicit garment proxy. Our approach infers garment dynamic features from body motion, providing a preliminary overview of garment structure. Simultaneously, we capture detailed features from synthesized reference images of the garment's front and back, generated by a pre-trained image model. These features are then used to construct a neural radiance field that renders the garment animation video. Additionally, our technique enables garment recoloring by decomposing its visual elements. We demonstrate the generalizability of our method across unseen body motions and camera views, ensuring detailed structural consistency. Furthermore, we showcase its applicability to color editing on both real and synthetic garment data. Compared to existing neural rendering techniques, our method exhibits qualitative and quantitative improvements in garment dynamics and wrinkle detail modeling. Code is available at \url{https://github.com/wrk226/GarmentAnimationNeRF}.
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- 2024
12. Activity Waves in Condensed Phases of Quincke Rollers
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Zhang, Meng Fei, Fan, Bao Ying, Liu, Zeng Tao, and Zhang, Tian Hui
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Condensed Matter - Soft Condensed Matter - Abstract
Wave-exciting is a universal phenomenon in physical and biological excitable systems. Here we show that colloidal systems of Quincke rollers which are driven periodically can condense into active liquids and active crystals, in which waves can be excited. In active liquids, the waves propagate antiparallel to local density gradients via the splitting of dense bands, and cross over each other in collision as sound waves do. The waves in active crystals have a sharp front like that of shock waves, and propagate parallel to local density gradients. The shock waves annihilate or converge as they collide. Detailed investigations on microscopic dynamics reveal that in sound waves, the dynamics of rollers is dominated by electrostatic repulsions; in shock waves, the dynamics is encoded with a density-dependent collective memory. These findings demonstrate a realization of excitable colloidal systems with tunable dynamics. This is of great interests in exploring the principles of self-organization and the fabrication of active functional materials., Comment: 11pages, 10figures
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- 2024
13. Perm: A Parametric Representation for Multi-Style 3D Hair Modeling
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He, Chengan, Sun, Xin, Shu, Zhixin, Luan, Fujun, Pirk, Sören, Herrera, Jorge Alejandro Amador, Michels, Dominik L., Wang, Tuanfeng Y., Zhang, Meng, Rushmeier, Holly, and Zhou, Yi
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Computer Science - Computer Vision and Pattern Recognition ,Computer Science - Graphics - Abstract
We present Perm, a learned parametric model of human 3D hair designed to facilitate various hair-related applications. Unlike previous work that jointly models the global hair shape and local strand details, we propose to disentangle them using a PCA-based strand representation in the frequency domain, thereby allowing more precise editing and output control. Specifically, we leverage our strand representation to fit and decompose hair geometry textures into low- to high-frequency hair structures. These decomposed textures are later parameterized with different generative models, emulating common stages in the hair modeling process. We conduct extensive experiments to validate the architecture design of \textsc{Perm}, and finally deploy the trained model as a generic prior to solve task-agnostic problems, further showcasing its flexibility and superiority in tasks such as 3D hair parameterization, hairstyle interpolation, single-view hair reconstruction, and hair-conditioned image generation. Our code, data, and supplemental can be found at our project page: https://cs.yale.edu/homes/che/projects/perm/, Comment: Project page: https://cs.yale.edu/homes/che/projects/perm/
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- 2024
14. Topological magnons in a collinear altermagnet
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Zhang, Meng-Han, Xiao, Lu, and Yao, Dao-Xin
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Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Strongly Correlated Electrons - Abstract
We propose a model with Weyl magnons and weak topological magnons ($\mathbb{Z}_2$) in a collinear altermagnet on the honeycomb lattice. Altermagnetic magnon bands can be realized by breaking the symmetry of the second nearest neighbor exchange couplings without the Dzyaloshinskii-Moriya (DM) interaction. Besides the Chern number and $\mathbb{Z}_2$ invariant, chirality is important to describe the band topology. The model shows the nonzero magnon Nernst effect for both the strong and weak topological phases when a longitudinal temperature gradient exists. Furthermore, we find the orbital angular momentum induced purely by the topology of magnons, which can be probed by the Einstein-de Haas effect., Comment: 7 pages, 5 figures
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- 2024
15. Operando probing of nanocracking in CuO-derived Cu during CO$_2$ electroreduction
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Wan, Jiawei, Liu, Ershuai, Choi, Woong, Liang, Jiayun, Zhang, Buyu, Kim, Keon-Han, Sun, Xianhu, Zhang, Meng, Xue, Han, Chen, Yi, Zhang, Qiubo, Wen, Changlian, Yang, Ji, Bustillo, Karen C., Ercius, Peter, Leshchev, Denis, Su, Ji, Balushi, Zakaria Y. Al, Weber, Adam Z., Asta, Mark, Bell, Alexis T., Drisdell, Walter S., and Zheng, Haimei
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Condensed Matter - Materials Science - Abstract
Identifying and controlling active sites in electrocatalysis remains a grand challenge due to restructuring of catalysts in the complex chemical environments during operation. Inactive precatalysts can transform into active catalysts under reaction conditions, such as oxide-derived Cu (OD-Cu) for CO$_2$ electroreduction displaying improved production of multicarbon (C$_{2+}$) chemicals. Revealing the mechanism of active site origin in OD-Cu catalysts requires in situ/operando characterizations of structure, morphology, and valence state evolution with high spatial and temporal resolution. Applying newly developed electrochemical liquid cell transmission electron microscopy combined with X-ray absorption spectroscopy, our multimodal operando techniques unveil the formation pathways of OD-Cu active sites from CuO bicrystal nanowire precatalysts. Rapid reduction of CuO directly to Cu within 60 seconds generates a nanocrack network throughout the nanowire, via formation of "boundary nanocracks" along the twin boundary and "transverse nanocracks" propagating from the surface to the center of the nanowire. The nanocrack network further reconstructs, leading to a highly porous structure rich in Cu nanograins, with a boosted specific surface area and density of active sites for C$_{2+}$ products. These findings suggest a means to optimize active OD-Cu nanostructures through nanocracking by tailoring grain boundaries in CuO precatalysts. More generally, our advanced operando approach opens new opportunities for mechanistic insights to enable improved control of catalyst structure and performance.
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- 2024
16. Beyond Boundaries: efficient Projected Entangled Pair States methods for periodic quantum systems
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Dong, Shaojun, Wang, Chao, Zhang, Hao, Zhang, Meng, and He, Lixin
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Condensed Matter - Strongly Correlated Electrons ,Quantum Physics - Abstract
Projected Entangled Pair States (PEPS) are recognized as a potent tool for exploring two-dimensional quantum many-body systems. However, a significant challenge emerges when applying conventional PEPS methodologies to systems with periodic boundary conditions (PBC), attributed to the prohibitive computational scaling with the bond dimension. This has notably restricted the study of systems with complex boundary conditions. To address this challenge, we have developed a strategy that involves the superposition of PEPS with open boundary conditions (OBC) to treat systems with PBC. This approach significantly reduces the computational complexity of such systems while maintaining their translational invariance and the PBC. We benchmark this method against the Heisenberg model and the $J_1$-$J_2$ model, demonstrating its capability to yield highly accurate results at low computational costs, even for large system sizes. The techniques are adaptable to other boundary conditions, including cylindrical and twisted boundary conditions, and therefore significantly expands the application scope of the PEPS approach, shining new light on numerous applications.
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- 2024
17. TorchGT: A Holistic System for Large-scale Graph Transformer Training
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Zhang, Meng, Sun, Jie, Hu, Qinghao, Sun, Peng, Wang, Zeke, Wen, Yonggang, and Zhang, Tianwei
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Computer Science - Distributed, Parallel, and Cluster Computing ,Computer Science - Artificial Intelligence ,Computer Science - Machine Learning - Abstract
Graph Transformer is a new architecture that surpasses GNNs in graph learning. While there emerge inspiring algorithm advancements, their practical adoption is still limited, particularly on real-world graphs involving up to millions of nodes. We observe existing graph transformers fail on large-scale graphs mainly due to heavy computation, limited scalability and inferior model quality. Motivated by these observations, we propose TorchGT, the first efficient, scalable, and accurate graph transformer training system. TorchGT optimizes training at different levels. At algorithm level, by harnessing the graph sparsity, TorchGT introduces a Dual-interleaved Attention which is computation-efficient and accuracy-maintained. At runtime level, TorchGT scales training across workers with a communication-light Cluster-aware Graph Parallelism. At kernel level, an Elastic Computation Reformation further optimizes the computation by reducing memory access latency in a dynamic way. Extensive experiments demonstrate that TorchGT boosts training by up to 62.7x and supports graph sequence lengths of up to 1M., Comment: Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis (SC), 2024
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- 2024
18. SCATTER: Algorithm-Circuit Co-Sparse Photonic Accelerator with Thermal-Tolerant, Power-Efficient In-situ Light Redistribution
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Yin, Ziang, Gangi, Nicholas, Zhang, Meng, Zhang, Jeff, Huang, Rena, and Gu, Jiaqi
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Computer Science - Hardware Architecture ,Computer Science - Emerging Technologies ,Computer Science - Machine Learning - Abstract
Photonic computing has emerged as a promising solution for accelerating computation-intensive artificial intelligence (AI) workloads. However, limited reconfigurability, high electrical-optical conversion cost, and thermal sensitivity limit the deployment of current optical analog computing engines to support power-restricted, performance-sensitive AI workloads at scale. Sparsity provides a great opportunity for hardware-efficient AI accelerators. However, current dense photonic accelerators fail to fully exploit the power-saving potential of algorithmic sparsity. It requires sparsity-aware hardware specialization with a fundamental re-design of photonic tensor core topology and cross-layer device-circuit-architecture-algorithm co-optimization aware of hardware non-ideality and power bottleneck. To trim down the redundant power consumption while maximizing robustness to thermal variations, we propose SCATTER, a novel algorithm-circuit co-sparse photonic accelerator featuring dynamically reconfigurable signal path via thermal-tolerant, power-efficient in-situ light redistribution and power gating. A power-optimized, crosstalk-aware dynamic sparse training framework is introduced to explore row-column structured sparsity and ensure marginal accuracy loss and maximum power efficiency. The extensive evaluation shows that our cross-stacked optimized accelerator SCATTER achieves a 511X area reduction and 12.4X power saving with superior crosstalk tolerance that enables unprecedented circuit layout compactness and on-chip power efficiency.
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- 2024
19. Network Origins of the Global Economy: East vs. West in a Complex Systems Perspective by Hilton L. Root (review)
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Zhang, Meng
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- 2021
20. Integrated analyses highlight interactions between the three-dimensional genome and DNA, RNA and epigenomic alterations in metastatic prostate cancer.
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Zhao, Shuang, Bootsma, Matthew, Zhou, Stanley, Shrestha, Raunak, Moreno-Rodriguez, Thaidy, Lundberg, Arian, Pan, Chu, Arlidge, Christopher, Hawley, James, Foye, Adam, Weinstein, Alana, Sjöström, Martin, Zhang, Meng, Li, Haolong, Chesner, Lisa, Rydzewski, Nicholas, Helzer, Kyle, Shi, Yue, Lynch, Molly, Dehm, Scott, Lang, Joshua, Alumkal, Joshi, He, Hansen, Wyatt, Alexander, Aggarwal, Rahul, Zwart, Wilbert, Small, Eric, Quigley, David, Lupien, Mathieu, and Feng, Felix
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Humans ,Male ,DNA Methylation ,5-Methylcytosine ,Gene Expression Regulation ,Neoplastic ,Epigenomics ,Neoplasm Metastasis ,Genome ,Human ,Prostatic Neoplasms ,Epigenesis ,Genetic ,Receptors ,Androgen ,Chromatin ,Prostatic Neoplasms ,Castration-Resistant ,Oncogene Proteins ,Fusion ,DNA ,Whole Genome Sequencing ,RNA ,Prognosis - Abstract
The impact of variations in the three-dimensional structure of the genome has been recognized, but solid cancer tissue studies are limited. Here, we performed integrated deep Hi-C sequencing with matched whole-genome sequencing, whole-genome bisulfite sequencing, 5-hydroxymethylcytosine (5hmC) sequencing and RNA sequencing across a cohort of 80 biopsy samples from patients with metastatic castration-resistant prostate cancer. Dramatic differences were present in gene expression, 5-methylcytosine/5hmC methylation and in structural variation versus mutation rate between A and B (open and closed) chromatin compartments. A subset of tumors exhibited depleted regional chromatin contacts at the AR locus, linked to extrachromosomal circular DNA (ecDNA) and worse response to AR signaling inhibitors. We also identified topological subtypes associated with stark differences in methylation structure, gene expression and prognosis. Our data suggested that DNA interactions may predispose to structural variant formation, exemplified by the recurrent TMPRSS2-ERG fusion. This comprehensive integrated sequencing effort represents a unique clinical tumor resource.
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- 2024
21. Effect of Micellar Morphology on the Temperature-Induced Structural Evolution of ABC Polypeptoid Triblock Terpolymers into Two-Compartment Hydrogel Network.
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Jiang, Naisheng, Yu, Tianyi, Zhang, Meng, Barrett, Bailee, Sun, Haofeng, Wang, Jun, Luo, Ying, Sternhagen, Garrett, Xuan, Sunting, Yuan, Guangcui, Kelley, Elizabeth, Qian, Shuo, Bonnesen, Peter, Hong, Kunlun, Li, Dongcui, and Zhang, Donghui
- Abstract
We investigated the temperature-dependent structural evolution of thermoreversible triblock terpolypeptoid hydrogels, namely poly(N-allyl glycine)-b-poly(N-methyl glycine)-b-poly(N-decyl glycine) (AMD), using small-angle neutron scattering (SANS) with contrast matching in conjunction with X-ray scattering and cryogenic transmission electron microscopy (cryo-TEM) techniques. At room temperature, A100M101D10 triblock terpolypeptoids self-assemble into core-corona-type spherical micelles in aqueous solution. Upon heating above the critical gelation temperature (T gel), SANS analysis revealed the formation of a two-compartment hydrogel network comprising distinct micellar cores composed of dehydrated A blocks and hydrophobic D blocks. At T ≳ T gel, the temperature-dependent dehydration of A block further leads to the gradual rearrangement of both A and D domains, forming well-ordered micellar network at higher temperatures. For AMD polymers with either longer D block or shorter A block, such as A101M111D21 and A43M92D9, elongated nonspherical micelles with a crystalline D core were observed at T < T gel. Although these enlarged crystalline micelles still undergo a sharp sol-to-gel transition upon heating, the higher aggregation number of chains results in the immediate association of the micelles into ordered aggregates at the initial stage, followed by a disruption of the spatial ordering as the temperature further increases. On the other hand, fiber-like structures were also observed for AMD with longer A block, such as A153M127D10, due to the crystallization of A domains. This also influences the assembly pathway of the two-compartment network. Our findings emphasize the critical impact of initial micellar morphology on the structural evolution of AMD hydrogels during the sol-to-gel transition, providing valuable insights for the rational design of thermoresponsive hydrogels with tunable network structures at the nanometer scale.
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- 2024
22. Rogue waves excitation on zero-background in the (2+1)-dimensional KdV equation
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Zhang, Jie-Fang, Jin, Mei-zhen, and Zhang, Meng-yang
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Nonlinear Sciences - Pattern Formation and Solitons - Abstract
An analytical method for constructing various coherent localized solutions with short-lived characteristics is proposed based on a novel self-mapping transformation of the (2+1) dimensional KdV equation. The highlight of this method is that it allows one to generate a class of basic two--dimensional rogue waves excited on zero-background for this equation, which includes the line-soliton-induced rogue wave and dromion-induced rogue wave with exponentially decaying as well as the lump-induced rogue wave with algebraically decaying in the -plane. Our finding provides a proper candidate to describe two-dimensional rogue waves and paves a feasible path for studying rogue waves., Comment: 11 pages,3 figures
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- 2024
23. Silicon Photonics Foundry Fabricated, Slow-Light Enhanced, Low Power Thermal Phase Shifter
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Chen, Alexander, Zhang, Meng, Crowley, Daniel, Gangi, Nicholas, Begović, Amir, and Huang, Zhaoran Rena
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Physics - Optics - Abstract
In this research, we developed a low-power silicon photonics foundry-fabricated slow-light thermal phase shifter (SLTPS) where the slow-light (SL) effect is achieved using an integrated Bragg grating (BG) waveguide. Heating the grating induces a red shift in the transmission spectrum, leading to an increased group index $n_g$ during operation, which facilitates a further reduction in the voltage needed for a $\pi$ phase shift, i.e. $V_{\pi}$. Additionally, we investigated a compact Mach-Zehnder Interferometer (MZI) that incorporates the SLTPS in both arms with a phase shifter length of 50 $\mu$m. A detailed theoretical analysis was conducted to address the non-idealities of the SL-MZI due to uneven optical power splitting and unbalanced loss in the two MZI arms. The $V_{\pi}$ and power consumption for a $\pi$ phase shift $(P_{\pi})$ of the SL-MZI were quantified for operation in the slow light regime, demonstrating a $V_{\pi}$ of 1.1 V and a $P_{\pi}$ of 3.63 mW at an operational wavelength near the photonic band edge. The figure of merit (FOM) $P_{\pi} \times \tau$ is commonly used to assess the performance of thermal optical switches. The SL-MZI in this work has achieved a low $P_{\pi} \times \tau$ of 5.1 mW $\mu$s. Insertion loss of the SL-MZI ranges from 1.3 dB to 4.4 dB depending on the operation wavelength, indicating a trade-off with the $V_\pi$ reduction., Comment: 14 pages, 9 figures, 1 table
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- 2024
24. Agent Hospital: A Simulacrum of Hospital with Evolvable Medical Agents
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Li, Junkai, Wang, Siyu, Zhang, Meng, Li, Weitao, Lai, Yunghwei, Kang, Xinhui, Ma, Weizhi, and Liu, Yang
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Computer Science - Artificial Intelligence - Abstract
In this paper, we introduce a simulacrum of hospital called Agent Hospital that simulates the entire process of treating illness. All patients, nurses, and doctors are autonomous agents powered by large language models (LLMs). Our central goal is to enable a doctor agent to learn how to treat illness within the simulacrum. To do so, we propose a method called MedAgent-Zero. As the simulacrum can simulate disease onset and progression based on knowledge bases and LLMs, doctor agents can keep accumulating experience from both successful and unsuccessful cases. Simulation experiments show that the treatment performance of doctor agents consistently improves on various tasks. More interestingly, the knowledge the doctor agents have acquired in Agent Hospital is applicable to real-world medicare benchmarks. After treating around ten thousand patients (real-world doctors may take over two years), the evolved doctor agent achieves a state-of-the-art accuracy of 93.06% on a subset of the MedQA dataset that covers major respiratory diseases. This work paves the way for advancing the applications of LLM-powered agent techniques in medical scenarios.
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- 2024
25. Age-minimal Multicast by Graph Attention Reinforcement Learning
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Zhang, Yanning, Liao, Guocheng, Cao, Shengbin, Yang, Ning, and Zhang, Meng
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Computer Science - Networking and Internet Architecture - Abstract
Age of Information (AoI) is an emerging metric used to assess the timeliness of information, gaining research interest in real-time multicast applications such as video streaming and metaverse platforms. In this paper, we consider a dynamic multicast network with energy constraints, where our objective is to minimize the expected time-average AoI through energy-constrained multicast routing and scheduling. The inherent complexity of the problem, given the NP-hardness and intertwined scheduling and routing decisions, makes existing approaches inapplicable. To address these challenges, we decompose the original problem into two subtasks, each amenable to reinforcement learning (RL) methods. Subsequently, we propose an innovative framework based on graph attention networks (GATs) to effectively capture graph information with superior generalization capabilities. To validate our framework, we conduct experiments on three datasets including a real-world dataset called AS-733, and show that our proposed scheme reduces the average weighted AoI by 62.9% and reduces the energy consumption by at most 72.5% compared to baselines.
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- 2024
26. Thermodynamic topology of Phantom AdS Black Holes in Massive Gravity
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Chen, Hao, Wu, Di, Zhang, Meng-Yao, Hassanabadi, Hassan, and Long, Zheng-Wen
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General Relativity and Quantum Cosmology - Abstract
In this work, we explore the thermodynamic topology of phantom AdS black holes in the context of massive gravity. To this end, we evaluate these black holes in two distinct ensembles: the canonical and grand canonical ensembles (GCE). We begin by examining the topological charge linked to the critical point and confirming the existence of a conventional critical point $(CP_{1})$ in the canonical ensemble (CE), this critical point has a topological charge of $-1$ and acts as a point of phase annihilation, this situation can only be considered within the context of the classical Einstein-Maxwell (CEM) theory $(\eta=1)$, while no critical point is identified in the GCE. Furthermore, we consider black holes as a topological defect within the thermodynamic space. To gain an understanding of the local and global topological configuration of this defect, we will analyze its winding numbers, and observe that the total topological charge in the CE consistently remains at $1$. When the system experiences a pressure below the critical threshold, it gives rise to the occurrence of annihilation and generation points. The value of electric potential determines whether the total topological charge in the GCE is zero or one. As a result, we detect a point of generation point or absence of generation/annihilation point. Based on our analysis, it can be inferred that ensembles significantly impact the topological class of phantom AdS black holes in massive gravity., Comment: 12pages, 19 figures
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- 2024
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27. Efficient and Generalizable Certified Unlearning: A Hessian-free Recollection Approach
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Qiao, Xinbao, Zhang, Meng, Tang, Ming, and Wei, Ermin
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Computer Science - Machine Learning ,Computer Science - Artificial Intelligence - Abstract
Machine unlearning strives to uphold the data owners' right to be forgotten by enabling models to selectively forget specific data. Recent advances suggest precomputing and storing statistics extracted from second-order information and implementing unlearning through Newton-style updates. However, the theoretical analysis of these works often depends on restrictive assumptions of convexity and smoothness, and those mentioned operations on Hessian matrix are extremely costly. As a result, applying these works to high-dimensional models becomes challenging. In this paper, we propose an efficient Hessian-free certified unlearning. We propose to maintain a statistical vector for each data, computed through affine stochastic recursion approximation of the difference between retrained and learned models. Our analysis does not involve inverting Hessian and thus can be extended to non-convex non-smooth objectives. Under same assumptions, we demonstrate advancements of proposed method beyond the state-of-the-art theoretical studies, in terms of generalization, unlearning guarantee, deletion capacity, and computation/storage complexity, and we show that the unlearned model of our proposed approach is close to or same as the retrained model. Based on the strategy of recollecting statistics for forgetting data, we develop an algorithm that achieves near-instantaneous unlearning as it only requires a vector addition operation. Experiments demonstrate that the proposed scheme surpasses existing results by orders of magnitude in terms of time/storage costs, while also enhancing accuracy., Comment: 31 pages, 10 figures
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- 2024
28. Cardiovascular events reported in patients with B-cell malignancies treated with zanubrutinib.
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Moslehi, Javid, Furman, Richard, Tam, Constantine, Salem, Joe-Elie, Flowers, Christopher, Cohen, Aileen, Zhang, Meng, Zhang, Jun, Chen, Lipeng, Ma, Han, and Brown, Jennifer
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Humans ,Pyrimidines ,Pyrazoles ,Piperidines ,Male ,Aged ,Female ,Protein Kinase Inhibitors ,Middle Aged ,Cardiovascular Diseases ,Adenine ,Agammaglobulinaemia Tyrosine Kinase ,Incidence ,Atrial Fibrillation ,Aged ,80 and over - Abstract
First-generation Bruton tyrosine kinase (BTK) inhibitor, ibrutinib, has been associated with an increased risk of cardiovascular toxicities. Zanubrutinib is a more selective, next-generation BTK inhibitor. In this analysis, incidence rates of atrial fibrillation, symptomatic (grade ≥2) ventricular arrhythmia, and hypertension were evaluated in a pooled analysis of 10 clinical studies with zanubrutinib monotherapy in patients (N = 1550) with B-cell malignancies and a pooled analysis of head-to-head studies comparing zanubrutinib with ibrutinib (ASPEN cohort 1; ALPINE). Among the 10 studies, most patients (median age, 67 years) were male (66.3%) and had CLL/SLL (60.5%). Overall incidence and exposure-adjusted incidence rates (EAIR) for atrial fibrillation, symptomatic ventricular arrhythmia, and hypertension were lower with zanubrutinib than ibrutinib. Despite a similar prevalence of preexisting cardiovascular events in ASPEN and ALPINE, atrial fibrillation/flutter incidence rates (6.1% vs 15.6%) and EAIR (0.2 vs 0.64 persons per 100 person-months; P < .0001) were lower with zanubrutinib than with ibrutinib. Symptomatic ventricular arrhythmia incidence was low for both zanubrutinib (0.7%) and ibrutinib (1.7%) with numerically lower EAIR (0.02 vs 0.06 persons per 100 person-months, respectively) for zanubrutinib. The hypertension EAIR was lower with zanubrutinib than ibrutinib in ASPEN but similar between treatment arms in ALPINE. The higher hypertension EAIR in ALPINE was inconsistent with other zanubrutinib studies. However, fewer discontinuations (1 vs 14) and deaths (0 vs 6) due to cardiac disorders occurred with zanubrutinib versus ibrutinib in ALPINE. These data support zanubrutinib as a treatment option with improved cardiovascular tolerability compared with ibrutinib for patients with B-cell malignancies in need of BTK inhibitors. These trials were registered at www.ClinicalTrials.gov as # NCT03053440, NCT03336333, NCT03734016, NCT04170283, NCT03206918, NCT03206970, NCT03332173, NCT03846427, NCT02343120, and NCT03189524.
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- 2024
29. AF1q is a universal marker of neuroblastoma that sustains N-Myc expression and drives tumorigenesis.
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Lee, Joanna, Asgharzadeh, Shahab, Khan, Ranjha, Zhang, Meng, Weisbrod, Julia, Choi, Youn-Jeong, Puri, Latika, Aguilar, Ana, Zhao, Piming, Saba, Julie, and Oskouian, Babak
- Subjects
Child ,Humans ,N-Myc Proto-Oncogene Protein ,Neuroblastoma ,Oncogene Proteins ,Cell Transformation ,Neoplastic ,Transcription Factors ,Carcinogenesis ,Cell Line ,Tumor ,Gene Expression Regulation ,Neoplastic - Abstract
Neuroblastoma is the most common extracranial malignant tumor of childhood, accounting for 15% of all pediatric cancer deaths. Despite significant advances in our understanding of neuroblastoma biology, five-year survival rates for high-risk disease remain less than 50%, highlighting the importance of identifying novel therapeutic targets to combat the disease. MYCN amplification is the most frequent and predictive molecular aberration correlating with poor outcome in neuroblastoma. N-Myc is a short-lived protein primarily due to its rapid proteasomal degradation, a potentially exploitable vulnerability in neuroblastoma. AF1q is an oncoprotein with established roles in leukemia and solid tumor progression. It is normally expressed in brain and sympathetic neurons and has been postulated to play a part in neural differentiation. However, no role for AF1q in tumors of neural origin has been reported. In this study, we found AF1q to be a universal marker of neuroblastoma tumors. Silencing AF1q in neuroblastoma cells caused proteasomal degradation of N-Myc through Ras/ERK and AKT/GSK3β pathways, activated p53 and blocked cell cycle progression, culminating in cell death via the intrinsic apoptotic pathway. Moreover, silencing AF1q attenuated neuroblastoma tumorigenicity in vivo signifying AF1qs importance in neuroblastoma oncogenesis. Our findings reveal AF1q to be a novel regulator of N-Myc and potential therapeutic target in neuroblastoma.
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- 2024
30. Financing Market-Oriented Reforestation: Securitization of Timberlands and Shareholding Practices in Southwest China, 1750–1900
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Zhang, Meng
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- 2017
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31. Topology of dyonic AdS black holes with quasitopological electromagnetism in Einstein-Gauss-Bonnet gravity
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Chen, Hao, Zhang, Meng-Yao, Hassanabadi, Hassan, Lütfüoğlu, Bekir Can, and Long, Zheng-Wen
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General Relativity and Quantum Cosmology - Abstract
In this study, we employ the thermodynamic topological method to classify critical points for the dyonic AdS black holes with quasitopological electromagnetism in the Einstein-Gauss-Bonnet background. To this end, we find a small/large black hole phase transition in all dimensions of space-time, the existence of a conventional critical point implies a total topological charge of $Q_t=-1$. The coupling constant $\alpha$ gives rise to a more intricate phase structure, with the emergence of a triple points requires $\alpha\geq0.5$ and $d=6$. Interestingly, the condition for the occurrence of small/intermediate/large phase transition is that the coupling constant a takes a special value ($\alpha=0.5$), the two conventional critical points $CP_{1},CP_{2}$ of the black hole are physical critical point, and the novel critical point $CP_{3}$ that lacks the capability to minimize the Gibbs free energy. The critical points $CP_{1}$ and $CP_{2}$ are observed to occur at the maximum extreme points of temperature in the isobaric curve, while the critical point $CP_{3}$, emerges at the minimum extreme points of temperature. Furthermore, the number of phases at the novel critical point exhibits an upward trend, followed by a subsequent decline at the conventional critical points. With the increase of the coupling constant ($\alpha = 1$), although the system has three critical points, only the conventional $CP_{1}$ is a (physical) critical point, and the conventional $CP_{2}$ serves as the phase annihilation point. This means that the coupling constant $\alpha$ has a non-negligible effect on the phase structure., Comment: 10 pages, 18 figures
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- 2024
32. Characterization of Large Language Model Development in the Datacenter
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Hu, Qinghao, Ye, Zhisheng, Wang, Zerui, Wang, Guoteng, Zhang, Meng, Chen, Qiaoling, Sun, Peng, Lin, Dahua, Wang, Xiaolin, Luo, Yingwei, Wen, Yonggang, and Zhang, Tianwei
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Computer Science - Distributed, Parallel, and Cluster Computing ,Computer Science - Machine Learning - Abstract
Large Language Models (LLMs) have presented impressive performance across several transformative tasks. However, it is non-trivial to efficiently utilize large-scale cluster resources to develop LLMs, often riddled with numerous challenges such as frequent hardware failures, intricate parallelization strategies, and imbalanced resource utilization. In this paper, we present an in-depth characterization study of a six-month LLM development workload trace collected from our GPU datacenter Acme. Specifically, we investigate discrepancies between LLMs and prior task-specific Deep Learning (DL) workloads, explore resource utilization patterns, and identify the impact of various job failures. Our analysis summarizes hurdles we encountered and uncovers potential opportunities to optimize systems tailored for LLMs. Furthermore, we introduce our system efforts: (1) fault-tolerant pretraining, which enhances fault tolerance through LLM-involved failure diagnosis and automatic recovery. (2) decoupled scheduling for evaluation, which achieves timely performance feedback via trial decomposition and scheduling optimization.
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- 2024
33. Model-Free Load Frequency Control of Nonlinear Power Systems Based on Deep Reinforcement Learning
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Chen, Xiaodi, Zhang, Meng, Wu, Zhengguang, Wu, Ligang, and Guan, Xiaohong
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Electrical Engineering and Systems Science - Systems and Control ,Computer Science - Artificial Intelligence - Abstract
Load frequency control (LFC) is widely employed in power systems to stabilize frequency fluctuation and guarantee power quality. However, most existing LFC methods rely on accurate power system modeling and usually ignore the nonlinear characteristics of the system, limiting controllers' performance. To solve these problems, this paper proposes a model-free LFC method for nonlinear power systems based on deep deterministic policy gradient (DDPG) framework. The proposed method establishes an emulator network to emulate power system dynamics. After defining the action-value function, the emulator network is applied for control actions evaluation instead of the critic network. Then the actor network controller is effectively optimized by estimating the policy gradient based on zeroth-order optimization (ZOO) and backpropagation algorithm. Simulation results and corresponding comparisons demonstrate the designed controller can generate appropriate control actions and has strong adaptability for nonlinear power systems.
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- 2024
34. A Miniaturized Device for Ultrafast On-demand Drug Release based on a Gigahertz Ultrasonic Resonator
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Zhou, Yangchao, Jeong, Moonkwang, Zhang, Meng, Duan, Xuexin, and Qiu, Tian
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Computer Science - Robotics ,Physics - Biological Physics ,J.3 - Abstract
On-demand controlled drug delivery is essential for the treatment of a wide range of chronic diseases. As the drug is released at the time when required, its efficacy is boosted and the side effects are minimized. However, so far, drug delivery devices often rely on the passive diffusion process for a sustained release, which is slow and uncontrollable. Here, we present a miniaturized microfluidic device for wirelessly controlled ultrafast active drug delivery, driven by an oscillating solid-liquid interface. The oscillation generates acoustic streaming in the drug reservoir, which opens an elastic valve to deliver the drug. High-speed microscopy reveals the fast response of the valve on the order of 1 ms, which is more than three orders of magnitude faster than the start-of-the-art. The amount of the released drug exhibits a linear relationship with the working time and the electric power applied to the ultrasonic resonator. The trigger of the release is wirelessly controlled via a magnetic field, and the system shows stable output in a continuous experiment for two weeks. The integrated system shows great promise as a long-term controlled drug delivery implant for chronic diseases., Comment: 19 pages, 6 figures, 1 table
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- 2024
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35. Exponential contractivity and propagation of chaos for Langevin dynamics of McKean-Vlasov type with L\'evy noises
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Liu, Yao, Wang, Jian, and Zhang, Meng-ge
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Mathematics - Probability - Abstract
By the probabilistic coupling approach which combines a new refined basic coupling with the synchronous coupling for L\'evy processes, we obtain explicit exponential contraction rates in terms of the standard $L^1$-Wasserstein distance for the following Langevin dynamic $(X_t,Y_t)_{t\ge0}$ of McKean-Vlasov type on $\mathbb{R}^{2d}$: \begin{equation*}\left\{\begin{array}{l} dX_t=Y_tdt,\\ dY_t=\left(b(X_t)+\displaystyle\int_{\mathbb{R}^d}\tilde{b}(X_t,z)\mu^X_t(dz)-\gamma Y_t\right)dt+dL_t,\quad \mu^X_t={\rm Law}(X_t),\end{array}\right. \end{equation*} where $\gamma>0$, $b:\mathbb{R}^d\rightarrow\mathbb{R}^d$ and $\tilde{b}:\mathbb{R}^{2d}\rightarrow\mathbb{R}^d$ are two globally Lipschitz continuous functions, and $(L_t)_{t\ge0}$ is an $\mathbb{R}^d$-valued pure jump L\'evy process. The proof is also based on a novel distance function, which is designed according to the distance of the marginals associated with the constructed coupling process. Furthermore, by applying the coupling technique above with some modifications, we also provide the propagation of chaos uniformly in time for the corresponding mean-field interacting particle systems with L\'evy noises in the standard $L^1$-Wasserstein distance as well as with explicit bounds.
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- 2024
36. Do Rogue Wave Exist in the Kadomtesv-Petviashivili I Equation ?
- Author
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Zhang, Jie-Fang, Zhang, Zhao, Zhang, Meng-yang, and Jin, Mei-zhen
- Subjects
Nonlinear Sciences - Pattern Formation and Solitons - Abstract
There is considerable fundamental theoretical and applicative interest in obtaining two-dimensional rogue wave similar to one-dimensional rogue wave of the nonlinear Schr\"odinger equation. Here, we first time proposes a self-mapping transformation and analytically predict the existence of a family of novel spatio-temporal rogue wave solutions for the Kadomtesv-Petviashivili equation. We discover that these spatio-temporal rogue waves showing a strong analogy characteristics of the short-lives with rogue waves of the NLS equation. Our fingdings can also provide a solid mathematical basis for theory and application in shallow water, plasma and optics. This technique could be available to construct rogue-like waves of (2+1)-dimensional nonlinear wave models. Also, these studies could be helpful to deepen our understandings and enrich our knowledge about rogue waves., Comment: 15 pages,2 figures,54 references
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- 2024
37. TeMPO: Efficient Time-Multiplexed Dynamic Photonic Tensor Core for Edge AI with Compact Slow-Light Electro-Optic Modulator
- Author
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Zhang, Meng, Yin, Dennis, Gangi, Nicholas, Begović, Amir, Chen, Alexander, Huang, Zhaoran Rena, and Gu, Jiaqi
- Subjects
Computer Science - Emerging Technologies ,Computer Science - Artificial Intelligence ,Computer Science - Machine Learning - Abstract
Electronic-photonic computing systems offer immense potential in energy-efficient artificial intelligence (AI) acceleration tasks due to the superior computing speed and efficiency of optics, especially for real-time, low-energy deep neural network (DNN) inference tasks on resource-restricted edge platforms. However, current optical neural accelerators based on foundry-available devices and conventional system architecture still encounter a performance gap compared to highly customized electronic counterparts. To bridge the performance gap due to lack of domain specialization, we present a time-multiplexed dynamic photonic tensor accelerator, dubbed TeMPO, with cross-layer device/circuit/architecture customization. At the device level, we present foundry-compatible, customized photonic devices, including a slow-light electro-optic modulator with experimental demonstration, optical splitters, and phase shifters that significantly reduce the footprint and power in input encoding and dot-product calculation. At the circuit level, partial products are hierarchically accumulated via parallel photocurrent aggregation, lightweight capacitive temporal integration, and sequential digital summation, considerably relieving the analog-to-digital conversion bottleneck. We also employ a multi-tile, multi-core architecture to maximize hardware sharing for higher efficiency. Across diverse edge AI workloads, TeMPO delivers digital-comparable task accuracy with superior quantization/noise tolerance. We achieve a 368.6 TOPS peak performance, 22.3 TOPS/W energy efficiency, and 1.2 TOPS/mm$^2$ compute density, pushing the Pareto frontier in edge AI hardware. This work signifies the power of cross-layer co-design and domain-specific customization, paving the way for future electronic-photonic accelerators with even greater performance and efficiency., Comment: 17 pages, 19 figures
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- 2024
38. Determining Stellar Elemental Abundances from DESI Spectra with the Data-Driven Payne
- Author
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Zhang, Meng, Xiang, Maosheng, Ting, Yuan-Sen, Wang, Jiahui, Li, Haining, Zou, Hu, Nie, Jundan, Mou, Lanya, Wu, Tianmin, Wu, Yaqian, and Liu, Jifeng
- Subjects
Astrophysics - Astrophysics of Galaxies ,Astrophysics - Solar and Stellar Astrophysics - Abstract
Stellar abundances for a large number of stars are key information for the study of Galactic formation history. Large spectroscopic surveys such as DESI and LAMOST take median-to-low resolution ($R\lesssim5000$) spectra in the full optical wavelength range for millions of stars. However, line blending effect in these spectra causes great challenges for the elemental abundances determination. Here we employ the DD-PAYNE, a data-driven method regularised by differential spectra from stellar physical models, to the DESI EDR spectra for stellar abundance determination. Our implementation delivers 15 labels, including effective temperature $T_{\rm eff}$, surface gravity $\log g$, microturbulence velocity $v_{\rm mic}$, and abundances for 12 individual elements, namely C, N, O, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Ni. Given a spectral signal-to-noise ratio of 100 per pixel, internal precision of the label estimates are about 20 K for $T_{\rm eff}$, 0.05 dex for $\log~g$, and 0.05 dex for most elemental abundances. These results are agree with theoretical limits from the Cr\'amer-Rao bound calculation within a factor of two. The Gaia-Enceladus-Sausage that contributes the majority of the accreted halo stars are discernible from the disk and in-situ halo populations in the resultant [Mg/Fe]-[Fe/H] and [Al/Fe]-[Fe/H] abundance spaces. We also provide distance and orbital parameters for the sample stars, which spread a distance out to $\sim$100 kpc. The DESI sample has a significant higher fraction of distant (or metal-poor) stars than other existed spectroscopic surveys, making it a powerful data set to study the Galactic outskirts. The catalog is publicly available., Comment: 18 pages, 12 figures. Submitted to ApJS
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- 2024
39. Critical behavior and Joule-Thomson expansion of charged AdS black holes surrounded by exotic fluid with modified Chaplygin equation of state
- Author
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Zhang, Meng-Yao, Chen, Hao, Hassanabadi, Hassan, Long, Zheng-Wen, and Yang, Hui
- Subjects
General Relativity and Quantum Cosmology - Abstract
By considering the concept of a unified single fluid model, referred to as the modified Chaplygin gas (MCG), which amalgamates dark energy and dark matter. In this study, we explore the thermodynamic characteristics of charged anti-de Sitter (AdS) black holes existing in an unconventional fluid accompanied by MCG. To accomplish this objective, we derive the equations of state by regarding the charge $Q^{2}$ as a thermodynamic variable. The impact of MCG parameters on the critical thermodynamic quantities ($\psi_{c}$, $T_{c}$, $Q_{c}^{2}$) are examined, followed by a detailed analysis of the $Q^{2}-\psi$ diagram. To provide a clearer explanation of the phase transition, we present an analysis of the Gibbs free energy. It is important to note that if the Hawking temperature exceeds the critical temperature, there is a distinct pattern observed known as swallowtail behavior. This indicates that the system undergoes a first-order phase transition from a smaller black hole to a larger one. The critical exponent of the system is found to be in complete agreement with that of the van der Waals fluid system. Furthermore, we investigate the impact of MCG parameters and black hole charge on the Joule-Thomson (J-T) expansion in the extended phase space. The J-T coefficient is examined to pinpoint the exact region experiencing cooling or heating, the observation reveals that the presence of negative heat capacity results in the occurrence of a cooling process. In addition, it is worth noting that the certain parameters exert a significant influence on the ratio $\frac{T_{min}}{T_{c}}$. The parameters $\gamma$ and $\beta$ have a non-negligible effect on the isenthalpy curve., Comment: 11 pages,8 figures
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- 2024
40. LESSON: Multi-Label Adversarial False Data Injection Attack for Deep Learning Locational Detection
- Author
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Tian, Jiwei, Shen, Chao, Wang, Buhong, Xia, Xiaofang, Zhang, Meng, Lin, Chenhao, and Li, Qian
- Subjects
Computer Science - Cryptography and Security - Abstract
Deep learning methods can not only detect false data injection attacks (FDIA) but also locate attacks of FDIA. Although adversarial false data injection attacks (AFDIA) based on deep learning vulnerabilities have been studied in the field of single-label FDIA detection, the adversarial attack and defense against multi-label FDIA locational detection are still not involved. To bridge this gap, this paper first explores the multi-label adversarial example attacks against multi-label FDIA locational detectors and proposes a general multi-label adversarial attack framework, namely muLti-labEl adverSarial falSe data injectiON attack (LESSON). The proposed LESSON attack framework includes three key designs, namely Perturbing State Variables, Tailored Loss Function Design, and Change of Variables, which can help find suitable multi-label adversarial perturbations within the physical constraints to circumvent both Bad Data Detection (BDD) and Neural Attack Location (NAL). Four typical LESSON attacks based on the proposed framework and two dimensions of attack objectives are examined, and the experimental results demonstrate the effectiveness of the proposed attack framework, posing serious and pressing security concerns in smart grids., Comment: Accepted by TDSC
- Published
- 2024
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41. Velocity acoustic oscillations on Cosmic Dawn 21 cm power spectrum as a probe of small-scale density fluctuations
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Zhang, Xin, Lin, Hengjie, Zhang, Meng, Yue, Bin, Gong, Yan, Xu, Yidong, and Chen, Xuelei
- Subjects
Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
We investigate the feasibility of using the velocity acoustic oscillations (VAO) features on the Cosmic Dawn 21 cm power spectrum to probe small-scale density fluctuations. In the standard cold dark matter (CDM) model, Pop III stars form in minihalos and affect the 21 cm signal through Ly$\alpha$ and X-ray radiation. Such a process is modulated by the relative motion between dark matter and baryons, generating the VAO wiggles on the 21 cm power spectrum. In the fuzzy or warm dark matter models for which the number of minihalos is reduced, the VAO wiggles are weaker or even fully invisible. We investigate the wiggle features in the CDM with different astrophysical models and in different dark matter models. We find: 1) In the CDM model the relative streaming velocities can generate the VAO wiggles for broad ranges of parameters $f_*$, $\zeta_X$ and $f_{\rm esc,LW}\zeta_{\rm LW}$, though for different parameters the wiggles would appear at different redshifts and have different amplitudes. 2) For the axion model with $m_{\rm a} \lesssim10^{-19}$ eV, the VAO wiggles are negligible. In the mixed model, the VAO signal is sensitive to the axion fraction. For example, the wiggles almost disappear when $f_{\rm a} \gtrsim 10\%$ for $m_{\rm a}=10^{-21}$ eV. Therefore, the VAO signal can be an effective indicator for small-scale density fluctuations and a useful probe of the nature of dark matter. The SKA-low with $\sim$2000 hour observation time has the ability to detect the VAO signal and constraint dark matter models., Comment: 22 pages, 21 figures, accepted for publication by ApJ
- Published
- 2024
42. Genome-wide Analysis of Developmental Stage-specific Transcriptome in Spodoptera litura for the Identification of Effective Control Method
- Author
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Wang, Fei-Feng, Qin, Peng, Zhang, Meng-Ke, Xiong, Ze-En, Cuthbertson, Andrew G. S., Alharbi, Sulaiman Ali, Fiaz, Sajid, Alfarraj, Saleh, Ansari, Mohammad Javed, Azeem, Farrukh, Meng, Jian-Yu, and Sang, Wen
- Published
- 2024
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- View/download PDF
43. ART altered DNA methylation of the imprinted gene H19 in fetal tissue after multifetal pregnancy reduction
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Wu, Wenbin, Ji, Menglu, Yang, Jingjing, Zhang, Meng, Hao, Dayong, Zhao, Xinyan, Li, Saisai, Guan, Yichun, and Wang, Xingling
- Published
- 2024
- Full Text
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44. Grading of products utilizing bamboo as a substitute for plastic based on environmental effects
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Zhang, Meng, Zhou, Guomo, Gu, Lei, and Wang, Wenshuo
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- 2024
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45. The brain networks of alternative use task: a meta-analytic connectivity modeling analysis
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Ma, Ruina, Si, Xiaoyu, Ma, Huanke, Zou, Feng, Wang, Yufeng, Zhang, Meng, and Wu, Xin
- Published
- 2024
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46. Electrochemical co-reduction of Mg(II), Al(III) and Nd(III) in the LiCl-NaCl-MgCl2-AlF3 melts
- Author
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Li, Mei, Guo, Xuan, Liu, Yaochen, Liu, Rugeng, Zhang, Meng, Sun, Yang, and Han, Wei
- Published
- 2024
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- View/download PDF
47. Tough Polymeric Hydrogels Based on Amino Acid Derivative Mediated Dynamic Metal Coordination Bonds
- Author
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Li, Meng, Zhang, Meng-Yuan, Lei, Wu-Xuan, Lv, Zhu-Ting, Shang, Qing-Hua, Zhao, Zheng, Li, Jiang-Tao, and Cheng, Yi-Long
- Published
- 2024
- Full Text
- View/download PDF
48. Land use change impacts on climate extremes over the historical period
- Author
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Zhang, Meng, Gao, Yanhong, Wang, Aihui, Zhang, Liao, and Yang, Kunpeng
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- 2024
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49. Synergistic enhancement of electrochemical performance in reversible solid oxide cells via deficiency-induced oxygen vacancy and nanoparticle generation
- Author
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Zhang, Meng-Yun, Tian, Yun-Feng, Zou, Lu, Pu, Jian, and Chi, Bo
- Published
- 2024
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50. Research on Paleoearthquake and Recurrence Characteristics of Strong Earthquakes in Active Faults of Mainland China
- Author
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Zhang, Yao-Hu, Pan, Hua, Cheng, Jiang, and Zhang, Meng
- Published
- 2024
- Full Text
- View/download PDF
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