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The partial C^(0)-estimate along a general continuity path and applications

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Science China Mathematics 2021年第11期64卷 2495-2520页

作者： ke feng Liangming Shen School of Mathematical Sciences University of Electronic Science and Technology of ChinaChengdu 611731China School of Mathematical Sciences Beihang UniversityBeijing 100191China

We establish a new partial C^(0)-estimate along a continuity path mixed with conic singularities along a simple normal crossing divisor and a positive twisted(1,1)-form on Fano *** an application,this estimate enables us to show the reductivity of the automorphism group of the limit space,which leads to a new proof of the Yau-Tian-Donaldson conjecture.

关键词： partial C0-estimate K?hler-Einstein metric conic K?hler metric

Novel algorithm for complex bit reversal:employing vector permutation and branch reduction methods

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第10期10卷 1492-1499页

作者： feng YU Ze-ke WANG Rui-feng GE Department of lnstrument Engineering Zhejiang University Hangzhou 310027 China

We present novel vector permutation and branch reduction methods to minimize the number of execution cycles for bit reversal *** new methods are applied to single instruction multiple data(SIMD) parallel implementation of complex data floating-point fast Fourier transform(FFT).The number of operational clock cycles can be reduced by an average factor of 3.5 by using our vector permutation methods and by 1.1 by using our branch reduction methods,compared with conventional *** on MPC7448(a well-known SIMD reduced instruction set computing processor) demonstrate that our optimal bit-reversal algorithm consistently takes fewer than two cycles per element in complex array operations.

关键词： Bit reversal Vector permutation Branch reduction Single instruction multiple data (SIMD) Fast Fourier transform (FFT)

Modular Invariance and Anomaly Cancellation Formulas in Odd Dimension Ⅱ

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Acta Mathematica Sinica,English Series 2017年第4期33卷 455-469页

作者： ke feng LIU Yong WANG Center of Mathematical Sciences Zhejiang UniversityHangzhou 310027P.R.China Department of Mathematics University of California at Los AngelesLos Angeles CA90095-1555USA School of Mathematics and Statistics Northeast Normal UniversityChangchun 130024P.R.China

By studying modular invariance properties of some characteristic forms, we get some generalized anomaly cancellation formulas on(4 r-1)-dimensional manifolds with no assumption that the 3 rd de-Rham cohomology of manifolds vanishes. These anomaly cancellation formulas generalize our previous anomaly cancellation formulas on(4 r-1)-dimensional manifolds. We also generalize our previous anomaly cancellation formulas on(4 r-1)-dimensional manifolds and the Han–Yu rigidity theorem to the(a, b) case.

关键词： Modular invariance Eisenstein series generalized cancellation formulas in odd dimension Witten rigidity theorem

Minimal Complex Surfaces with Levi–Civita Ricci-flat Metrics

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Acta Mathematica Sinica,English Series 2018年第8期34卷 1195-1207页

作者： ke feng LIU Xiao Kui YANG Department of Mathematics Capital Normal University Beijing 100048 P. R. ChinaDepartment of Mathematics University of California at Los Angeles California 90095 USA Morningside Center of Mathematics Institute of Mathematics Hua Loo-Keng center of Mathematical Sciences Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 P. R. China

This is a continuation of our previous paper [14]. In [14], we introduced the first Aeppli- Chern class on compact complex manifolds, and proved that the （1, 1） curvature form of the Levi-Civita connection represents the first Aeppli-Chern class which is a natural link between Riemannian geometry and complex geometry. In this paper, we study the geometry of compact complex manifolds with Levi- Civita Ricci-flat metrics and classify minimal complex surfaces with Levi-Civita Ricci-flat metrics. More precisely, we show that minimal complex surfaces admitting Levi-Civita Ricci-flat metrics are K/ihler Calabi-Yau surfaces and Hopf surfaces.

关键词： Levi-Civita Ricci-flat metric kodaira dimension classication

New Results on Nonexistence of Perfect p-Ary Sequences and Almost p-Ary Sequences

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Acta Mathematica Sinica,English Series 2016年第1期32卷 2-10页

作者： Hai Ying LIU ke Qin feng School of Mathematical Sciences Peking University Department of Mathematical Sciences Tsinghua University

Complex periodical sequences with lower antocorrelation values are used in CDMA comnmnieation systems and cryptography. In this paper we present new nonexistence results on perfect p-ary sequences and almost p-ary seq... 详细信息

关键词： Perfect sequence p-ary and almost p-ary sequence difference set cyclotomic field imag-inary quadratic field

A new power generation method utilizing a low grade heat source

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2012年第2期13卷 140-145页

作者： Wei-feng WU Xin-ping LONG Xiao-ling YU Quan-ke feng School of Energy and Power Engineering Xi ＇an Jiaotong University Xi ＇an 710049 China School of Power and Mechanical Engineering Wuhan University Wuhan 430072 China

Energy crisis make the effective use of low grade energy more and more urgent. It is still a worldwide difficult conundrum. To efficiently recover low grade heat, this paper deals with a theoretical analysis of a new power generation method driven by a low grade heat source. When the temperature of the low grade heat source exceeds the saturated temperature, it can heat the liquid into steam. If the steam is sealed and cooled in a container, it will lead to a negative pressure condition. The proposed power generation method utilizes the negative pressure condition in the sealed container, called as a condensator. When the condensator is connected to a liquid pool, the liquid will be pumped into it by the negative pressure condition. After the conden- sator is filled by liquid, the liquid flows back into the pool and drives the turbine to generate electricity. According to our analysis, for water, the head pressure of water pumped into the condensator could reach 9.5 m when the temperature of water in the pool is 25 ℃, and the steam temperature is 105 ℃. Theoretical thermal efficiency of this power generation system could reach 3.2% to 5.8% varying with the altitude of the condensator to the water level, ignoring steam leakage loss.

关键词： Low grade heat Power generation Condensation Energ-v storage Renewable energy

MEASUREMENT OF A WALL-BOUNDED TURBULENT MIXING LAYER FLOW

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Journal of Hydrodynamics 2005年第6期17卷 681-685页

作者： ke feng LIU Ying-zheng CHEN Han-ping School of Mechanical and Power Engineering Shanghai jiaotong University Shanghai 200030 China

Turbulence properties of a wall bounded turbulent mixing layer associated with an opening step were extensively measured using I-and X-type hntwires. The turbu lent mixing layer flow was analyzed in terms of wall static pressure distribution, turbulence intensity, Reynolds stress, streamwise velocity profile and continuous wavelet transform coefficients, Development of vortical structures embedded in the turbulent mixing layer was temporally and spatially re solved by using continuous wavelet transform. The constraint of the downstream solid wall on the mixing layer flow was de lineated.

关键词： turbulent flow mixing layer coherent structure

Estimation of non-point source pollution loads with flux method in Danjiangkou Reservoir area,China

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Water Science and Engineering 2017年第2期10卷 134-142页

作者： Xiao-kang Xin Wei Yin ke-feng Li State key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Changjiang Water Resources Protection Institute Changjiang Water Resources Commission

The estimation of non-point source pollution loads into the Danjiangkou Reservoir is highly significant to environmental protection in the watershed. In order to overcome the drawbacks of traditional watershed numerical models, a base flow separation method was established coupled with a digital filtering method and a flux method. The digital filtering method has been used to separate the base flows of the Hanjiang,Tianhe, Duhe, Danjiang, Laoguan, and Qihe rivers. Based on daily discharge, base flow, and pollutant concentration data, the flux method was used to calculate the point source pollution load and non-point source pollution load. The results show that:(1) In the year 2013, the total inflow of the six rivers mentioned above accounted for 95.9% of the total inflow to the Danjiangkou Reservoir. The total pollution loads of chemical oxygen demand(CODMn) and total phosphorus(TP) from the six rivers were 58.20 103 t and 1.863 10~3 t, respectively, and the non-point source pollution loads were 39.82 10~3 t and 1.544 10~3 t, respectively, indicating that the non-point source pollution is a major factor(with a contribution rate of 68.4% for CODMnand 82.9% for TP).(2) The Hanjiang River is the most significant contributor of pollution loads to the Danjiangkou Reservoir, and its CODMnand TP contribution rates reached 79.3% and 83.2%, respectively. The Duhe River took the second place.(3) Non-point source pollution mainly occurred in the wet season in 2013, accounting for 80.8% and 90.9% of the total pollution loads of CODMnand TP, respectively. It is concluded that the emphasis of pollution control should be placed on non-point source pollution.

关键词： Danjiangkou Reservoir Non-point source pollution Base flow separation Digital filtering method (DFM) Flux method

Effect of total dissolved gas supersaturated water on early life of David's schizothoracin (Schizothorax davidi)

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2013年第7期14卷 632-639页

作者： Rui-feng LIANG Bo LI ke-feng LI You-cai TUO State key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Changjiang River Scientific Research Institute

The effect of total dissolved gas （TDG） supersaturation on fish living downstream of dams is one of the main ecological risks of high dam construction. A strategy for mitigating the negative effects is needed urgently since many high dams are under construction in the upper reaches of the Yangtze River in China. Experiments on the hatching process of David＇s schizothoracin were carried out and the results show that the hatching rate decreased with increasing TDG levels, and that most eggs hatched within a very short time in the higher TDG saturation groups. By using a stereomicroscope, damages to the head, yolk sac, body, anus, etc. were found in larvae which hatched in TDG supersaturated water. Results show that the lesion rate increased with increasing TDG levels. Furthermore, 7-d-old David＇s schizothoracin were exposed to TDG supersaturated water levels of 100%, 105%, 110%, 115%, 120%, 125%, 130%, 135%, and 140% for testing their tolerance to TDG supersaturation. We found that the median lethal concentrations （LC50） for 13, 14, 20, 35, 52, 73, and 96 h exposure were 138%, 138%, 134%, 130%, 129%, 128%, and 126%, respectively. The median lethal times （LTs0） were 7.49, 11.04, 19.25, and 35.38 h for exposure to water with TDG levels of 145%, 140%, 135%, and 130%, respectively.

关键词： Total dissolved gas (TDG) TDG supersaturation David's schizothoracin Hatch Larvae