Author name cluster

Zhen Zhou

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8 papers

2 author rows

IROS Conference 2025 Conference Paper

Decentralized Multi-robot Navigation Policy with Enhanced Security Using Graph GRU Policy Network

Lin Chen
Yuxuan Ao
Zhen Zhou
Yaonan Wang
Danwei Wang

Formulating a multi-robot obstacle avoidance policy is essential for enabling safe and efficient navigation in multi-robot environments, forming a critical component of the effective operation of multi-robot systems. Recently, reinforcement learning has been applied to improve the performance of decentralized, policy-driven robots in task execution. However, ensuring the safety of these agents during movement remains a significant challenge due to the inherent risks associated with the reinforcement learning process, such as frequent collisions. To address this issue and enhance the safety of policy-guided multi-robot navigation, we propose a novel policy based on imitation learning. This framework introduces a novel policy neural network that integrates a graph attention mechanism with the GRU network structure. The key innovation lies in utilizing the interactions between neighboring robots to enhance the safety of their movements. In a multi-robot simulation environment, robot behaviors are directed by the proposed policy. A comparative analysis was conducted between our approach and RL-RVO, one of the advanced methods in the field. The results demonstrate that our approach outperforms RL-RVO, achieving a higher success rate and significantly improving safety performance.

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IROS Conference 2023 Conference Paper

An Energy-Efficient Lane-Keeping System Using 3D LiDAR Based on Spiking Neural Network

Genghang Zhuang
Zhenshan Bing
Zhen Zhou
Xiangtong Yao
Yuhong Huang
Kai Huang 0001
Alois C. Knoll

Lane keeping, as a fundamental functionality of autonomous navigation, remains a challenging task for autonomous robots and vehicles. Recently, spiking neural networks (SNNs) have gained attention and research interest due to their biological plausibility and application potential on neuromorphic processors. SNNs have also been successfully deployed on robots to solve autonomous navigation problems. However, lane keeping with a LiDAR sensor is still an open problem for SNNs. In this work, we propose an end-to-end approach based on an SNN to solve the lane-keeping problem using a 3D LiDAR sensor. For the first time, we explore the capability of the proposed SNN controller to perceive the LiDAR input and exploit the features to perform reward-based feedback learning. To ensure the effectiveness of the controller, the proposed method is deployed and evaluated on two high-fidelity simulators. The experimental results demonstrate the high applicability and performance in different scenarios. Furthermore, experiments show that the SNN is capable of performing lane keeping in a simulated urban environment with only 18 control neurons and 32 synapse connections, producing on average only a 17cm deviation from lane center, which is 4. 3 % of the lane width.

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JBHI Journal 2023 Journal Article

Multiple Adversarial Learning Based Angiography Reconstruction for Ultra-Low-Dose Contrast Medium CT

Weiwei Zhang
Zhen Zhou
Zhifan Gao
Guang Yang
Lei Xu
Weiwen Wu
Heye Zhang

Iodinated contrast medium (ICM) dose reduction is beneficial for decreasing potential health risk to renal-insufficiency patients in CT scanning. Due to the low-intensity vessel in ultra-low-dose-ICM CT angiography, it cannot provide clinical diagnosis of vascular diseases. Angiography reconstruction for ultra-low-dose-ICM CT can enhance vascular intensity for directly vascular diseases diagnosis. However, the angiography reconstruction is challenging since patient individual differences and vascular disease diversity. In this paper, we propose a Multiple Adversarial Learning based Angiography Reconstruction (i. e. , MALAR) framework to enhance vascular intensity. Specifically, a bilateral learning mechanism is developed for mapping a relationship between source and target domains rather than the image-to-image mapping. Then, a dual correlation constraint is introduced to characterize both distribution uniformity from across-domain features and sample inconsistency within domain simultaneously. Finally, an adaptive fusion module by combining multi-scale information and long-range interactive dependency is explored to alleviate the interference of high-noise metal. Experiments are performed on CT sequences with different ICM doses. Quantitative results based on multiple metrics demonstrate the effectiveness of our MALAR on angiography reconstruction. Qualitative assessments by radiographers confirm the potential of our MALAR for the clinical diagnosis of vascular diseases.

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YNIMG Journal 2023 Journal Article

Multiscale functional connectivity patterns of the aging brain learned from harmonized rsfMRI data of the multi-cohort iSTAGING study

Zhen Zhou
Hongming Li
Dhivya Srinivasan
Ahmed Abdulkadir
Ilya M. Nasrallah
Junhao Wen
Jimit Doshi
Guray Erus

To learn multiscale functional connectivity patterns of the aging brain, we built a brain age prediction model of functional connectivity measures at seven scales on a large fMRI dataset, consisting of resting-state fMRI scans of 4186 individuals with a wide age range (22 to 97 years, with an average of 63) from five cohorts. We computed multiscale functional connectivity measures of individual subjects using a personalized functional network computational method, harmonized the functional connectivity measures of subjects from multiple datasets in order to build a functional brain age model, and finally evaluated how functional brain age gap correlated with cognitive measures of individual subjects. Our study has revealed that functional connectivity measures at multiple scales were more informative than those at any single scale for the brain age prediction, the data harmonization significantly improved the brain age prediction performance, and the data harmonization in the functional connectivity measures' tangent space worked better than in their original space. Moreover, brain age gap scores of individual subjects derived from the brain age prediction model were significantly correlated with clinical and cognitive measures. Overall, these results demonstrated that multiscale functional connectivity patterns learned from a large-scale multi-site rsfMRI dataset were informative for characterizing the aging brain and the derived brain age gap was associated with cognitive and clinical measures.

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JBHI Journal 2022 Journal Article

Divergent and Convergent Imaging Markers Between Bipolar and Unipolar Depression Based on Machine Learning

Huifeng Zhang
Zhen Zhou
Lei Ding
Chuangxin Wu
Meihui Qiu
Yueqi Huang
Feng Jin
Ting Shen

Distinguishing bipolar depression (BD) from unipolar depression (UD) based on symptoms only is challenging. Brain functional connectivity (FC), especially dynamic FC, has emerged as a promising approach to identify possible imaging markers for differentiating BD from UD. However, most of such studies utilized conventional FC and group-level statistical comparisons, which may not be sensitive enough to quantify subtle changes in the FC dynamics between BD and UD. In this paper, we present a more effective individualized differentiation model based on machine learning and the whole-brain “high-order functional connectivity (HOFC)” network. The HOFC, capturing temporal synchronization among the dynamic FC time series, a more complex “chronnectome” metric compared to the conventional FC, was used to classify 52 BD, 73 UD, and 76 healthycontrols (HC). We achieved a satisfactory accuracy (70. 40%) in BD vs. UD differentiation. The resultant contributing features revealed the involvement of the coordinated flexible interactions among sensory (e. g. , olfaction, vision, and audition), motor, and cognitive systems. Despite sharing common chronnectome of cognitive and affective impairments, BD and UD also demonstrated unique dynamic FC synchronization patterns. UD is more associated with abnormal visual-somatomotor inter-network connections, while BD is more related to impaired ventral attention-frontoparietal inter-network connections. Moreover, we found that the illness duration modulated the BD vs. UD separation, with the differentiation performance hampered by the secondary disease effects. Our findings suggest that BD and UD may have divergent and convergent neural substrates, which further expand our knowledge of the two different mental disorders.

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YNICL Journal 2019 Journal Article

Structural connectome alterations in patients with disorders of consciousness revealed by 7-tesla magnetic resonance imaging

Xufei Tan
Zhen Zhou
Jian Gao
Fanxia Meng
Yamei Yu
Jie Zhang
Fangping He
Ruili Wei

Although the functional connectivity of patients with disorders of consciousness (DOC) has been widely examined, less is known about brain white matter connectivity. The aim of this study was to explore structural network alterations for the diagnosis and prognosis of patients with chronic DOC. Eleven DOC patients and 11 sex- and age-matched controls were included in the study. Participants underwent diffusion magnetic resonance imaging (MRI) and T1-weighted structural MRI at 7 tesla (7 T). Graph-theoretical analysis and network-based statistics were used to analyze the group differences. Two patients were scanned twice for a longitudinal study to examine the relationship between connectome metrics and the patients' prognoses. Compared with healthy controls, DOC patients showed significantly elevated transitivity (p < .001), local efficiency (p = .009), and clustering coefficient (p = .039). When comparing the connectome metrics within the three groups (healthy controls, minimally conscious state (MCS), and vegetative state/unresponsive wakefulness syndrome (VS/UWS)), significant group differences were observed in transitivity (p < .001) and local efficiency (p = .031). Significantly increased transitivity was observed in vegetative state/unresponsive wakefulness syndrome compared with minimally conscious state (p = .0217, Bonferroni corrected). Transitivity showed significant negative correlations with the Coma Recovery Scale-Revised score (r = -0.6902, p = .023), consistent with the longitudinal study results. A subnetwork with significantly decreased structural connections was identified using network-based statistical analysis comparing DOC patients with healthy controls, which was mainly located in the frontal cortex, limbic system, and occipital and parietal lobes. This preliminary study suggests that graph theoretical approaches for assessing white matter connectivity may enable various states of DOC to be distinguished. Of the metrics analyzed, transitivity had a critical role in distinguishing the diagnostic groups. Larger cohorts will be necessary to confirm the predictive value of 7 T MRI in the prognosis of DOC patients.

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YNICL Journal 2014 Journal Article

Multimodal neuroimaging in presurgical evaluation of drug-resistant epilepsy

Jing Zhang
Weifang Liu
Hui Chen
Hong Xia
Zhen Zhou
Shanshan Mei
Qingzhu Liu
Yunlin Li

Intracranial EEG (icEEG) monitoring is critical in epilepsy surgical planning, but it has limitations. The advances of neuroimaging have made it possible to reveal epileptic abnormalities that could not be identified previously and improve the localization of the seizure focus and the vital cortex. A frequently asked question in the field is whether non-invasive neuroimaging could replace invasive icEEG or reduce the need for icEEG in presurgical evaluation. This review considers promising neuroimaging techniques in epilepsy presurgical assessment in order to address this question. In addition, due to large variations in the accuracies of neuroimaging across epilepsy centers, multicenter neuroimaging studies are reviewed, and there is much need for randomized controlled trials (RCTs) to better reveal the utility of presurgical neuroimaging. The results of multiple studies indicate that non-invasive neuroimaging could not replace invasive icEEG in surgical planning especially in non-lesional or extratemporal lobe epilepsies, but it could reduce the need for icEEG in certain cases. With technical advances, multimodal neuroimaging may play a greater role in presurgical evaluation to reduce the costs and risks of epilepsy surgery, and provide surgical options for more patients with drug-resistant epilepsy.

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TCS Journal 2005 Journal Article

On queuing lengths in on-line switching

Peter Damaschke
Zhen Zhou

Queues that temporarily store fixed-length packets are ubiquitous in network switches. Scheduling algorithms that prevent packet-loss are always desirable. LONGEST-QUEUE-FIRST (LQF) is an on-line greedy algorithm widely exploited because of its simplicity and efficiency. In this paper, we give improved bounds on the competitive ratio of LQF in terms of the worst-case queuing length, parameterized with respect to the optimal queuing length of a clairvoyant adversary. This gives a better picture of LQF's performance under heavy traffic than the usual (unparameterized) competitive ratio. We also discuss randomization, and we conclude with some intriguing open problems regarding a two-dimensional generalization of the problem.

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