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Nano Research 2025年第1期18卷 351-361页

作者： tie liu School of Chemistry and Chemical Engineering Heze UniversityHeze 274015China

The constituents and geometric design of cathodic electrocatalyst to achieve high activity and durability are effective but challenging for the development of high-performance Li-O_(2)*** study employs a mild solution precipitation method followed by thermolysis to construct a faveolate open-structured Ru-N/C matrix with a loosely braided network morphology as a bifunctional *** details prove that this hybrid structure is composed of ultrafine Ru globular nanoparticles(ca.2 nm)coated with an N-enriched carbon film and exhibits a valuable beehive through-hole character for rapid mass transport during oxygen redox *** synergistic effect of open-structured and reticular network matrix with metal-N4 coordination induces asymmetric charge distributions with moderate adsorption/desorption behaviour with oxygen ***,this particular Ru-N/C matrix cathode provides a promising Li_(2)O_(2)accommodation space and exhibits superior electrochemical performance in terms of a positive discharge plateau and low charge ***,the assembled batteries also present a high discharge capacity and a long cycle life(exceeding 283 cycles).The density functional theory(DFT)calculations also corroborate the assertion that the Ru-N/C catalyst exhibits robust electronic coupling transfer and superior bifunctional *** such,our work demonstrates that this type of open-structured Ru-N/C matrix is promising for fabricating high-performance quasi solid-state Li-O_(2)batteries.

关键词： ruthenium nitride nitrogen-doped carbon electrocatalyst Li-O_(2)battery

Monitoring recent changes in snow cover in Central Asia using improved MODIS snow-cover products

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Journal of Arid Land 2017年第5期9卷 763-777页

作者： liu Jinping ZHANG Wanchang liu tie Key Laboratory of Digital Earth Science Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences Beijing 100094 China University of Chinese Academy of Sciences Beijing 100039 China State Key Laboratory of Desert and Oasis Ecology Xinjiang Institute of Ecology and Geography Chinese Academy of Sciences Urumqi 830011 China

Snow cover plays an important role in the fields of climatology and cryospheric science. Remotely-sensed data have been proven to be effective in monitoring snow covers. Improved methods to process the 8-day snow-cover products derived from MODIS Terra/Aqua data can dramatically increase the data quality and reduce noise. A five-step algorithm for removing cloud effects was designed to improve the quality of MODIS snow products, and the overall accuracy of the MODIS snow data without cloud（defined as cloud-free snow-cover dataset） was enhanced by more than 90% based on direct and indirect validation methods. The snow-cover frequency（SCF） and snow-cover rate（SCR） of Central Asia were analyzed from 2000 to 2015 using trend analysis and empirical orthogonal functions（EOFs）. Over the plain regions, the SCF displayed a significant north-south declining trend with a rate of 0.03 per degree of latitude, and the SCR showed a similar north-south gradient. In the mountainous areas, the SCF significantly increased with altitude by 0.12 per kilometer. Within the study area, the SCF in 65% of the study area experienced an increasing trend, but only 4.3% of the SCF-increasing pixels passed a significance test. The remaining 35% of the area underwent a decreasing trend of SCF, but only 5.2% of the SCF-decreasing pixels passed a significance test. For the entire Central Asia, the inter-annual variations of snow-cover presented a slight and insignificant increase trend from 2000 to 2015. However, the change trends of snow cover are different between the plain and mountainous regions. That is, the annual mean SCR in the plain areas displayed an increasing trend, but a decreasing trend was found in the mountainous areas.

关键词： snow-cover MODIS cloud-removing empirical orthogonal function Central Asia

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Computational pricing in Internet era

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Frontiers of Computer Science 2018年第1期12卷 40-54页

作者： Fei TIAN Tao QIN tie-Yan liu Microsoft Research Asia Beijing 100080 China

Pricing plays a central rule to a company＇s prof- itability, and therefore has been extensively studied in the literature of economics. When designing a pricing mech- anism/model, an important principle to consider is ＂price discrimination＂, which refers to selling the same resources with different prices according to different values of buy- ers. To meet the ＂price discrimination＂ principle, especially when the number of buyers is large, computational methods, which act in a more accurate and principled way, are usu- ally needed to determine the optimal allocation of sellers＇ re- sources （whom to sell to） and the optimal payment of buyers （what to charge）. Nowadays, in the Internet era in which quite a lot of buy and sell processes are conducted through Internet, the design of computational pricing models faces both new challenges and opportunities, considering that （i） nearly real- time interactions between people enable the buyers to reveal their needs and enable the sellers to expose their information in a more expressive manner, （ii） the large-scale interaction data require powerful methods for more efficient processing and enable the sellers to model different buyers in a more precise manner. In this paper, we review recent advances on the analysis and design of computational pricing models for representative Internet industries, e.g., online advertising and cloud computing. In particular, we introduce how computa- tional approaches can be used to analyze buyer＇s behaviors （i.e., equilibrium analysis）, improve resource utilization （i.e., social welfare analysis）, and boost seller＇s profit （i.e., revenue analysis）. We also discuss how machine learning techniques can be used to better understand buyer＇s behaviors and design more effective pricing mechanisms, given the availability oflarge scale data. Moreover, we make discussions on future re- search directions on computational pricing, which hopefully can inspire more researchers to contribute to this important

关键词： computational pricing price discrimination on-line advertising cloud computing mechanism design

Well-defined carbon nanoframes containing bimetal-N-C active sites as efficient bi-functional electrocatalysts for Li-Ch batterie

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Nano Research 2019年第3期12卷 517-523页

作者： tie liu Leidanyang Wang Tao Huang Aishui Yu Department of Chemistry Collaborative Innovation Center of Chemistry for Energy Materials Institute of New Energy Fudan University Shanghai 200438 China Laboratory of Advanced Materials Fudan University Shanghai 200438 China

Design and fabrication of framework-structured porous precursors have been regarded as a prospective albeit challenging strategy to obtain bimetal/NC-enriched bifunctional elecrocatalysts. In this work, an effective bottom-up approach involving solution-based self-assembly and a post-annealing process was developed to confine (Co, Zn)-N-C active sites into N-enriched graphitic carbon nanocages. This novel architecture containing N-doped-C stabilized bimetallic nanoparticles derived from ZIF precursors was well-studied by a series of characterization and analysis techniques. Details were given that these well-dispersed (Co, Zn) nanoparticles were encapsulated into the pyridinic-N-dominated graphitic carbon nanocage with a total metal loading of approximately 7.4 at.%. This favorable hierarchical structure not only enhances the electron conductivity, but also owns a sufficient BET surface area facilitating the gas-liquid-solid triphase reaction and producing more space to store discharge products. Importantly, results infer that the interesting nanoframes manifests a satisfying ORR/OER activity and enhanced cell performance whether liquid or solid-state electrolytes are used. As such, our work rationalizes that this type of cage-shaped bimetal-N-C material is promising for high-performance Li-O2 batteries.

关键词： bifunctional electrocatalyst Li-oxygen battery nitrogen-doped carbon zinc-cobalt

New results on multilevel diversity coding with secure regeneration

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Science China(Information Sciences) 2018年第10期61卷 130-143页

作者： Shuo SHAO tie liu Chao TIAN Cong SHEN Department of Electrical Engineering Shanghai Jiaotong University Department of Electrical Engineering Texas A&M University School of Information Science and Technology University of Science & Technology of China

The problem of multilevel diversity coding with secure regeneration is revisited. Under the assumption that the eavesdropper can access the repair data for all compromised storage nodes, Shao et *** a precise characterization of the minimum-bandwidth-regeneration(MBR) point of the achievable normalized storage-capacity repair-bandwidth tradeoff region. In this paper, it is shown that the MBR point of the achievable normalized storage-capacity repair-bandwidth tradeoff region remains the same even if we assume that the eavesdropper can access the repair data for some compromised storage nodes(defined as the type II compromised nodes) but only the data contents of the remaining compromised nodes(defined as the type I compromised nodes), as long as the number of type I compromised nodes is no greater than that of type II compromised nodes.

关键词： distributed storage regenerating code exact repair secrecy constraint MBR point

HAPNet: a head-aware pedestrian detection network associated with the affinity field

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Science China(Information Sciences) 2022年第6期65卷 17-32页

作者： Jiali DING tie liu Yun ZHAO Zejian YUAN Yuanyuan SHANG College of Information Engineering Capital Normal University College of Artificial Intelligence Xi'an Jiaotong University

Pedestrian detection has made great progress with the rapid development of deep learning, but pedestrian detection under occlusion remains a challenge. To solve the occlusion problem, some research endeavors have been carried out based on visible parts, such as the body, but there is still substantial room for improvement due to the introduction of additional calculation. Aiming to improve the detection performance under occlusion, this paper proposes a head-aware pedestrian detection network(HAPNet) by using the inherent structural relationship between the human body and head. The postprocessing stage is redesigned to include a scoring module and an augmented non-maximum suppression(NMS) ***, HAPNet detects head and body simultaneously through different layers of a feature map. We then propose a head-side affinity model, which can represent the association between the head and body sides. Detection and affinity prediction tasks are implemented through different branches of HAPNet. In the scoring module, the head and body detection scores are fused to match the head-body pairs to improve the detection performance. On this basis, an enhanced NMS algorithm is proposed, which achieves a good balance between reducing false positives and missing detection. The experimental results verify the effectiveness of this method in pedestrian detection under occlusion.

关键词： pedestrian detection head detection head-aware pedestrian network affinity module occlusion

Learning Better Word Embedding by Asymmetric Low-Rank Projection of Knowledge Graph

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Journal of Computer Science & Technology 2016年第3期31卷 624-634页

作者： Fei Tian Bin Gao En-Hong Chen tie-Yah liu School of Computer Science and Technology University of Science and Technology of China Hefei 230027 China Microsoft Research Asia Beijing 100080 China

Word embedding, which refers to low-dimensional dense vector representations of natural words, has demon- strated its power in many natural language processing tasks. However, it may suffer from the inaccurate and incomplete information contained in the free text corpus as training data. To tackle this challenge, there have been quite a few studies that leverage knowledge graphs as an additional information source to improve the quality of word embedding. Although these studies have achieved certain success, they have neglected some important facts about knowledge graphs： 1） many relationships in knowledge graphs are many-to-one, one-to-many or even many-to-many, rather than simply one-to-one; 2） most head entities and tail entities in knowledge graphs come from very different semantic spaces. To address these issues, in this paper, we propose a new algorithm named ProjectNet. ProjectNet models the relationships between head and tail entities after transforming them with different low-rank projection matrices. The low-rank projection can allow non one- to-one relationships between entities, while different projection matrices for head and tail entities allow them to originate in different semantic spaces. The experimental results demonstrate that ProjectNet yields more accurate word embedding than previous studies, and thus leads to clear improvements in various natural language processing tasks.

关键词： natural language processing word embedding neural network knowledge graph

Automatic salient object sequence rebuilding for video segment analysis

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Science China(Information Sciences) 2018年第1期61卷 249-260页

作者： tie liu Haibin DUAN Yuanyuan SHANG Zejian YUAN Nanning ZHENG School of Automation Science and Electrical Engineering Beihang University Information Engineering College Capital Normal University The School of Electronic and Information Engineering Xi'an Jiaotong University

Detection of salient object sequences from video data is challenging when the salient object changes between consecutive frames. In this study, we addressed the salient object sequence rebuilding problem with video segment analysis. We reformulated the problem as a binary labeling problem, analyzed the potential salient object sequences in the video using a clustering method, and separated the salient object sequence from the background by applying an energy optimization method. Our proposed approach determines whether temporal consecutive pixels belong to the same salient object sequence. The conditional random field is then learned to effectively integrate the salient features and the sequence consecutive constraints.A dynamic programming algorithm was developed to resolve the energy minimization problem *** results confirmed the ability of our approach to address the salient object rebuilding problem in automatic visual attention applications and video content analysis.

关键词： salient object video attention sequence segment analysis conditional random model

A search for massive young stellar objects with 98 CH_3OH maser sources

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Research in Astronomy and Astrophysics 2010年第1期10卷 67-82页

作者： tie liu Yue-Fang Wu Ke Wang Department of Astronomy Peking University Beijing 100871 China

Using the 13.7 m telescope of the Purple Mountain Observatory （PMO）, a survey of the 3 = 1 - 0 lines of CO and its isotopes was carried out on 98 methanol maser sources in January 2008. Eighty-five sources have infrared counterparts within one arcmin. In the survey, except for 43 sources showing complex or multiple-peak profiles, almost all the ^13CO line profiles of the other 55 sources have large line widths of 4.5km s^-1 on average and are usually asymmetric. Fifty corresponding Infrared Astronomical Satellite （IRAS） sources of these 55 sources have Lbdl larger than 10^3 L⊙, which can be identified as possible high-mass young stellar sources. Statistics show that the ^13CO line widths correlate with the bolometric luminosity of the associated IRAS sources. Here, we also report the mapping results of two sources; IRAS 06117＋1350 and IRAS 07299-1651. Two cores were found in IRAS 06117＋1350 and one core was detected in IRAS 07299-1651. The northwest core in IRAS 06117＋1350 and the core in IRAS 07299-1651 can be identified as precursors of UC HII regions or high-mass protostellar objects （HMPOs）. The southeast core of IRAS 06117＋1350 has no infrared counterpart, seeming to be at a younger stage than the pre-UC HII phase.

关键词： stars formation -- ISM clouds -- ISM methanol maser

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Chinese Physics Letters 2014年第3期31卷 14-17页

作者： ZHAO Hu LI tie-Fu liu Jian-She CHEN Wei Institute of Microelectronics Tsinghua National Laboratory of Information Science and Technology Tsinghua University Beijing 100084

A phase-slip flux qubit, exactly dual to a charge qubit, is composed of a superconducting loop interrupted by a phase-slip junction. We propose a tunable phase-slip flux qubit by replacing the phase-slip junction with a charge-related superconducting quantum interference device （SQUID） consisting of two phase-slip junctions connected in series with a superconducting island. This charge-SQUID acts as an effective phase-slip junction controlled by the applied gate voltage and can be used to tune the energy-level splitting of the qubit. In addition, we show that a large inductance inserted in the loop can reduce the inductance energy and consequently suppress the dominating flux noise of the phase-slip flux qubit. This enhanced phase-slip flux qubit is exactly dual to a transmon qubit.

关键词： SQUIDs