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Effects of salinity on methane gas hydrate system

Science china Earth sciences 2007年第11期50卷 1733-1745页

作者： YANG DingHui1 & XU WenYue2 1 department of mathematical sciences, tsinghua university, beijing 100084, china 2 School of Earth & Atmospheric sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA department of mathematical sciences Tsinghua University Beijing China School of Earth & Atmospheric sciences Georgia Institute of Technology Atlanta USA

Using an approximately analytical formation, we extend the steady state model of the pure methane hydrate system to include the salinity based on the dynamic model of the methane hydrate system. The top and bottom boundaries of the methane hydrate stability zone (MHSZ) and the actual methane hy-drate zone (MHZ), and the top of free gas occurrence are determined by using numerical methods and the new steady state model developed in this paper. Numerical results show that the MHZ thickness becomes thinner with increasing the salinity, and the stability is lowered and the base of the MHSZ is shifted toward the seafloor in the presence of salts. As a result, the thickness of actual hydrate occur-rence becomes thinner compared with that of the pure water case. On the other hand, since lower solubility reduces the amount of gas needed to form methane hydrate, the existence of salts in sea-water can actually promote methane gas hydrate formation in the hydrate stability zone. Numerical modeling also demonstrates that for the salt-water case the presence of methane within the field of methane hydrate stability is not sufficient to ensure the occurrence of gas hydrate, which can only form when the methane concentration dissolved in solution with salts exceeds the local methane solubility in salt water and if the methane flux exceeds a critical value corresponding to the rate of diffusive methane transport. In order to maintain gas hydrate or to form methane gas hydrate in marine sedi-ments, a persistent supplied methane probably from biogenic or thermogenic processes, is required to overcome losses due to diffusion and advection.

关键词： methane gas hydrate,solubility,stability of hydrate,salinity,phase equilibrium

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BGP reflection functors in root categories

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Science china Mathematics 2005年第8期48卷 1033-1045页

作者： XIAO Jie, ZHANG Guanglian1’2 & ZHU Bin department of mathematical sciences, tsinghua university, beijing 100084, china department of Mathematics, Yancheng Teachers College, Yancheng 224002, china department of mathematical sciences Tsinghua University Beijing China department of Mathematics Yancheng Teachers College Yancheng China

We define the BGP-reflection functors in the derived categories and the root categories. By Ringel's Hall algebra approach, the BGP-reflection functor is applicable to obtain the classical Weyl group action on the Lie... 详细信息

关键词： m-cycle complexes, derived categories, BGP-reflections, Kac-Moody algebras.

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The Elements in Crystal Bases Corresponding to Exceptional Modules

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Chinese Annals of Mathematics,Series B 2010年第1期31卷 1-20页

作者： Yong JIANG Jie SHENG Jie XIAO department of mathematical sciences Tsinghua University Beijing 100084 China

According to the Ringel-Green theorem,the generic composition algebra of the Hall algebra provides a realization of the positive part of the quantum ***,its Drinfeld double can be identified with the whole quantum group,in which the BGP-reflection functors coincide with Lusztig's *** is first asserted that the elements corresponding to exceptional modules lie in the integral generic composition algebra,hence in the integral form of the quantum *** it is proved that these elements lie in the crystal basis up to a ***,it is shown that the sign can be removed by the geometric *** results hold for any type of Cartan datum.

关键词： Crystal basis Hall algebra Exceptional module

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New Monotonicity Formulae for Semi-linear Ellipti and Parabolic Systems

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Chinese Annals of Mathematics,Series B 2010年第3期31卷 411-432页

作者： Li MA Xianfa SONG Lin ZHAO department of mathematical sciences Tsinghua University Beijing 100084 China. department of Mathematics Tianjin University Tianjin 300072 China.

The authors establish a general monotonicity formula for the following elliptic system △ui＋fi（x,ui,…,um）=0 in Ω,where Ω belong to belong to R^n is a regular domain, （fi（x, u1,... ,um）） = △↓F（x,→↑u）, F（x,→↑u ） is a given smooth function of x ∈ R^n and →↑u = （u1,…,um） ∈ R^m. The system comes from understanding the stationary case of Ginzburg-Landau model. A new monotonicity formula is also set up for the following parabolic systemδtui-△ui-fi（x,ui,…,um）=0 in（ti,t2）×R^n,where t1 〈 t2 are two constants, （fi（x,→↑u ） is given as above. The new monotonicity formulae are focused more attention on the monotonicity of nonlinear terms. The new point of the results is that an index β is introduced to measure the monotonicity of the nonlinear terms in the problems. The index β in the study of monotonieity formulae is useful in understanding the behavior of blow-up sequences of solutions. Another new feature is that the previous monotonicity formulae are extended to nonhomogeneous nonlinearities. As applications, the Ginzburg-Landau model and some different generalizations to the free boundary problems are studied.

关键词： Elliptic systems Parabolic system Monotonicity formula Ginzburg-Landau model

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On (2~m + 1)-variable symmetric Boolean functions with submaximum algebraic immunity 2^(m-1)

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Science china Mathematics 2009年第1期52卷 17-28页

作者： LIAO QunYing1, LIU Feng2 & FENG KeQin2 1 College of Mathematics and Software sciences, Sichuan Normal university, Chengdu 610066, china 2 department of mathematical sciences, tsinghua university, beijing 100084, china College of Mathematics and Software sciences Sichuan Normal University Chengdu China department of mathematical sciences Tsinghua University Beijing China

All (2m +1)-variable symmetric Boolean functions with submaximal algebraic immunity 2m-1 are described and constructed. The total number of such Boolean functions is 32 ·22m-3 +3m-2 · 24 - 2 for m≥2.

关键词： symmetric Boolean function algebraic immunity cryptography

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A Fuzzy Control System with Application to Production Planning Problem

A Fuzzy Control System with Application to Production Planni...

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第六届中国不确定系统年会

作者： Zhongfeng Qin department of mathematical sciences,tsinghua university,beijing 100084,china

＜正＞There is a considerable literature devoted to the field of fuzzy *** this paper,an alter- native fuzzy control system is introduced to describe a dynamic system with fuzzy white *** order to find optimal ways to control such system with some objective,fuzzy optimal control theory is further de- ***,a linear quadratic model is for- mulated and *** an application,production planning model is formulated,and some economic in- terpretations are given to illustrate the meaning of the solution.

关键词： Credibility theory Production planning Optimal control Fuzzy control system Liu process

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Some Ranking Methods to Data Envelopment Analysis

Some Ranking Methods to Data Envelopment Analysis

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第五届中国不确定系统年会

作者： Meilin Wen department of mathematical sciences tsinghua university,beijing 100084,china

＜正＞Most efficiency measures in DEA estimate the distance between DMUs to an efficient frontier as their relative *** there comes forth another method which uses the distance to the inef- ficient frontier to estimate the *** paper wants to rank all the DMUs by the Hurwicz criterion, which attempts to find a middle ground between the distances to the efficient frontier and to the inefficient *** varying the parameter in the Hurwicz cri- terion,the ranking method can present various forms. This method can rank all the DMUs including effi- cient ones and inefficient *** many cases,the inputs and outputs can not be given exactly,which can be considered to be *** order to rank the DMUs with fuzzy data,we give the ranking method in DEA under fuzzy environment based on credibility ***,we provide some numerical exam- ples to illustrate the ranking methods that this paper introduced.

关键词： Data Envelopment Analysis Ranking Method Credibility Measure Hurwicz Criterion Fuzzy Programming

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Sufficient and Necessary Condition of Credibility Measure

Sufficient and Necessary Condition of Credibility Measure

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第三届不确定系统年会

作者： Xiang Li department of mathematical sciences, tsinghua university, beijing 100084, china

＜正＞ Possibility measure is widely used in fuzzy set theory. However, possibility measure is not self-dual. Credibility measure is a self-dual one. This paper proves the uniqueness theorem between possibility measur... 详细信息

关键词： Fuzzy variable Possibility measure Credibility measure

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A Method to Introduce Additional Separated Variables for Binary Constrained Flows

A Method to Introduce Additional Separated Variables for Bin...

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中国数学力学物理学高新技术交叉研究会第8届学术研讨会

作者： Yunbo Zeng~* (department of mathematical sciences,tsinghua university beijing 100084 china)

＜正＞Degrees of freedom for binary constrained flows of soliton equations admitting 2×2 Lax matrices are *** is known that N pairs of canonical separated variables for their separation of variables can be introduced directly via their Lax *** have presented a method in[23]to construct the other N pairs of canonical separated *** present paper we propose a different method to introduce the additional N pairs of canonical separated variables and N additional separated *** Jacobi inversion problems for binary constrained flows and for soliton equations are also established.

关键词： Separation of variables Jacobi inversion problem binary constrained flow Lax representation factorization of soliton equations

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Some Properties of Continuous Uncertain Measure

Some Properties of Continuous Uncertain Measure

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第五届中国不确定系统年会

作者： Xin Gao department of mathematical sciences,tsinghua university beijing 100084,china

＜正＞In this paper,we discuss some proper- ties in uncertainty theory when uncertain measure is ***,the judgement conditions of con- tinuous uncertain measure are ***, basic properties of uncertainty distribution and... 详细信息

关键词： uncertainty theory uncertain measure uncertain variable continuous

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