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Capacity analysis of transmit beamforming with variable feedback delay

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Journal of Systems Engineering and Electronics 2012年第1期23卷 24-31页

作者： lei zhu Yong Xiong Xiumei Yang Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 R R. China Shanghai Research Center for Wireless Communications Shanghai 200335 R R. China

The feedback delay can severely affect the quality of the channel state information at the transmitter （CSIT） which is fed back from the receiver. The outdated CSIT will cause large performance loss in the transmit beamforming systems. The effect of variable feedback delay on the capacity of transmit beamforming systems over Rayleigh fading channels is studied. First, the case of fixed feedback delay is considered and a closed-form expression of system capacity is derived. Based on the results of fixed delay, the delay following certain distributions in variable delay case is assumed and the closed-form expressions of capacities are derived. The closed-form expressions show that the capacity is significantly affected by the statistical characteristics of the feedback delay. The obtained results provide an analytical insight into the effects caused by variable delay on the system capacity.

关键词： multiple input single output capacity feedback delay transmit beamforming (TB).

A NON-LINEAR MODEL FOR ESTIMATING THE COST OF ACHIEVING EMISSION REDUCTION TARGETS:THE CASE OF THE U.S.,CHINA AND INDIA

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Journal of Systems Science and Systems Engineering 2012年第3期21卷 297-315页

作者： lei zhu Xiao-Bing ZHANG Ying FAN Center for Energy & Environmental Policy Research Institute of Policy and Management Chinese Academy of Sciences Beijing 100190 China Department of Economics University of Gothenburg SE 40530 G teborg Sweden

With the world talking about climate change, the United States （U.S.）, China and India have announced their carbon emission reduction targets. For these three countries to achieve their targets, significant questions arise, shch as what will be the annual emission reduction efforts to achieve those targets, how much it would cost and what would be the economic effects. This paper puts the carbon intensity reduction targets of China and India together with the absolute emission reduction target of the U.S. into the same non-linear model to quantitatively study the optimal emission control strategies and associated total cost for achieving those targets by the year 2020, and estimate and compare the minimized total costs of the three countries to reach their targets. Our results show that the total cost for the U.S. to achieve its emission reduction target is greater than those of China and India in terms of absolute amount. However, in terms of proportion of total cost to GDP, China and India＇s ratios are significantly greater than that of the U.S., indicating that for the developing countries such as China and India, the achievement of emission reduction targets needs relatively greater effort.

关键词： Emission reduction cost analysis emission reduction strategy optimization model

Unprecedented self-assembly of precise molecular particles

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National Science Review 2016年第1期3卷 3-4页

作者： lei zhu Ming Jiang Department of Macromolecular Science and Engineering Case Western Reserve University Department of Macromolecular Science and The State Key Laboratory of Molecular Engineering of Polymers Fudan University

Atomic self-assembly in pure metals and metal alloys can lead into various conventional(cubic,hexagonal closepacked(hcp),and icosahedron)and non-conventional(Frank–Kasper and quasicrystal[1])*** nonconventional cryst... 详细信息

关键词： Unprecedented self-assembly of precise molecular particles

GIS-based logistic regression method for landslide susceptibility mapping in regional scale

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第12期7卷 2007-2017页

作者： zhu lei HUANG Jing-feng Department of Natural Science. Zhejiang University Hangzhou 310029 China Institute of Agricultural Remote Sensing and Information Technology Application Zhejiang University Hangzhou 310029 China Shandong Agriculture Administrators College Jinan 250100 China

Landslide susceptibility map is one of the study fields portraying the spatial distribution of future slope failure sus- ceptibility. This paper deals with past methods for producing landslide susceptibility map and divides these methods into 3 types. The logistic linear regression approach is further elaborated on by crosstabs method, which is used to analyze the relationship between the categorical or binary response variable and one or more continuous or categorical or binary explanatory variables derived from samples. It is an objective assignment of coefficients serving as weights of various factors under considerations while expert opinions make great difference in heuristic approaches. Different from deterministic approach, it is very applicable to regional scale. In this study, double logistic regression is applied in the study area. The entire study area is first analyzed. The logistic regression equation showed that elevation, proximity to road, river and residential area are main factors triggering land- slide occurrence in this area. The prediction accuracy of the first landslide susceptibility map was showed to be 80%. Along the road and residential area, almost all areas are in high landslide susceptibility zone. Some non-landslide areas are incorrectly divided into high and medium landslide susceptibility zone. In order to improve the status, a second logistic regression was done in high landslide susceptibility zone using landslide cells and non-landslide sample cells in this area. In the second logistic regression analysis, only engineering and geological conditions are important in these areas and are entered in the new logistic regression equation indicating that only areas with unstable engineering and geological conditions are prone to landslide during large scale engineering activity. Taking these two logistic regression results into account yields a new landslide susceptibility map. Double logistic regression analysis improved the non-landslid

关键词： Landslide Susceptibility Logistic regression GIS Spatial analysis

Alteration of estuarine circulation pattern due to channel modification in the North Passage of the Changjiang River Estuary

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Acta Oceanologica Sinica 2021年第1期40卷 162-172页

作者： lei zhu Xiaodong Chen Zhimo Wu School of Marine Science Sun Yat-sen UniversityGuangzhou 510275China Southern Marine Science and Engineering Guangdong Laboratory(zhuhai) Zhuhai 519090China

The exchange flow structure was examined in the North Passage of Changjiang River Estuary,where a deep waterway project(DWP)was carried out to improve the *** the construction of the DWP,the friction effect played a significant role in shaping the transverse structure of the exchange *** turbulent eddy viscosity generated near the seabed can be transferred to the upper water column,which facilitated vertical momentum *** a result,the landward inflow extended to–2 m below the water surface and the seaward outflow was concentrated on the shallow shoal on the southern side of the cross *** the construction of the DWP,the turbulent mixing was suppressed as a result of density *** friction felt by the water was constrained in the lower half of the water column and the vertical momentum exchange was ***,the channel became dynamically narrowed with a Kelvin number of ***,the Coriolis played a minor role in shaping the transverse structure of the exchange *** a consequence,the exchange flow featured a vertically-sheared pattern,with outflow at the surface and inflow ***,the gravitational circulation was enhanced due to increase in along-channel density gradient and *** exchange flow components associated with the lateral processes(residual currents induced by eddy viscosityshear covariance and lateral advective acceleration)were reduced,which suggests that lateral processes played a minor role in modifying the along-channel dynamics when the estuary becomes dynamically-narrowed.

关键词： exchange flow stratification lateral circulation Changjiang River Estuary

Graph CA: Learning From Graph Counterfactual Augmentation for Knowledge Tracing

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IEEE/CAA Journal of Automatica Sinica 2023年第11期10卷 2108-2123页

作者： Xinhua Wang Shasha Zhao lei Guo lei zhu Chaoran Cui Liancheng Xu School of Information Science and Engineering Shandong Normal UniversityJinan 250358China School of Computer Science and Technology Shandong University of Finance and EconomicsJinan 250014China

With the popularity of online learning in educational settings, knowledge tracing(KT) plays an increasingly significant role. The task of KT is to help students learn more effectively by predicting their next mastery of knowledge based on their historical exercise sequences. Nowadays, many related works have emerged in this field, such as Bayesian knowledge tracing and deep knowledge tracing methods. Despite the progress that has been made in KT, existing techniques still have the following limitations: 1) Previous studies address KT by only exploring the observational sparsity data distribution, and the counterfactual data distribution has been largely ignored. 2) Current works designed for KT only consider either the entity relationships between questions and concepts, or the relations between two concepts, and none of them investigates the relations among students, questions, and concepts, simultaneously, leading to inaccurate student modeling. To address the above limitations,we propose a graph counterfactual augmentation method for knowledge tracing. Concretely, to consider the multiple relationships among different entities, we first uniform students, questions, and concepts in graphs, and then leverage a heterogeneous graph convolutional network to conduct representation *** model the counterfactual world, we conduct counterfactual transformations on students’ learning graphs by changing the corresponding treatments and then exploit the counterfactual outcomes in a contrastive learning framework. We conduct extensive experiments on three real-world datasets, and the experimental results demonstrate the superiority of our proposed Graph CA method compared with several state-of-the-art baselines.

关键词： Contrastive learning counterfactual representation graph neural network knowledge tracing

Molecular Cores in Different Evolutionary Stages near Luminous IRAS Sources and UC HII Regions

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Chinese Journal of Astronomy and Astrophysics 2007年第3期7卷 331-334页

作者： lei zhu Yue-Fang Wu Department of Astronomy Peking University Beijing 100871

We report the results of ^12CO of Ultra-Compact （UC） HII regions with and ^13CO J=1-0 observations of eight candidates the Purple Mountain Observatory （PMO） Qinghai 13.7 -m telescope, which resulted in revealing 11 molecular cores. Their masses range from 130 to 1.7 × 10^4 M⊙, with different spatial scales （1 - 6 pc）. Also presented are the relevant HCO＋ j=1-0 maps, which enabled us to investigate more detailed structures of these cores. Further comparisons show that four of the cores deviated from the centers of infrared （MIR） emission of Midcourse Space Experiment （MSX）, while others correspond either to bright MIR sources or diffuse MIR background. This indicates various evolutionary phases of the cores, including quite early ones for those without MIR sources.

关键词： stars formation- ISM clouds- ISM molecules- ISM evolution

Joint empirical likelihood confidence regions for a finite number of quantiles under strong mixing samples

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Applied Mathematics(A Journal of Chinese Universities) 2015年第1期30卷 44-54页

作者： lei Qing-zhu QIN Yong-song Department of Mathematics Guangxi Normal University

In this paper, we obtain the joint empirical likelihood confidence regions for a finite number of quantiles under strong mixing samples. As an application of this result, the empirical likelihood confidence intervals ... 详细信息

关键词： strong mixing sample quantile confidence region blockwise empirical likelihood.

A potentiometric cobalt-based phosphate sensor based on screen-printing technology

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Frontiers of Environmental Science & Engineering 2014年第6期8卷 945-951页

作者： lei zhu Xiaohong ZHOU Hanchang SHI School of Environment Tsinghua University Beijing 100084 China Division of Ecology and Environment Yangtze Delta Region Institute of Tsinghua University Jiaxing 314006 China

A potentiometric cobalt-based screen-pritning sensor was fabricated by electroplating cobalt on the surface of a screen-printing electrode as the sensitive layer for the determination of dihydrogenphosphate （H2PO4） in wastewater samples. The electrochemical performance of this sensor was fully examined to determine its detection calibration, detection limit, response time, selectivity, and interference with pH, various ions, and dissolved oxygen （DO）. The cobalt-based phosphate sensor showed a phosphate-selective potential response in the range of 10 5mol·L^-1 to 10^-1 mol^-1, yielding a detection limit of 3.16 × 10μmol·L^l and a slope of -37.51 mV·decade＇ in an acidic solution （pH 4.0） of H2PO4-. DO and pH were found to interfere with sensor responses to phosphate. Ultimately, the performance of the sensor was validated for detecting wastewater samples from the Xiaojiahe Waste- water Treatment Plant against the standard speetrophotometric methods for HzPO4 analysis. The discrepancy between the two methods was generally ＋5% （relative standard deviation）. Aside from its high selectivity, sensitivity, and stability, which are comparable with conventional bulk Co-wire sensors, the proposed phosphate sensor presents many other advantages, such as low price, compactness, ease of use, and the possibility of integration with other analytical devices, such as flow injectors.

关键词： phosphate cobalt screen-printing technology electroplate wastewater