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基于GIS的国外文化地理学研究热点演变与趋势

张涵, 李彦辉, 刘博

张涵, 李彦辉, 刘博. 基于GIS的国外文化地理学研究热点演变与趋势[J]. 华南师范大学学报(自然科学版), 2022, 54(5): 1-11. DOI: 10.6054/j.jscnun.2022067
引用本文: 张涵, 李彦辉, 刘博. 基于GIS的国外文化地理学研究热点演变与趋势[J]. 华南师范大学学报(自然科学版), 2022, 54(5): 1-11. DOI: 10.6054/j.jscnun.2022067
ZHANG Han, LI Yanhui, LIU Bo. The Evolution and Trend of Foreign Research Hotspots in GIS-based Cultural Geography[J]. Journal of South China Normal University (Natural Science Edition), 2022, 54(5): 1-11. DOI: 10.6054/j.jscnun.2022067
Citation: ZHANG Han, LI Yanhui, LIU Bo. The Evolution and Trend of Foreign Research Hotspots in GIS-based Cultural Geography[J]. Journal of South China Normal University (Natural Science Edition), 2022, 54(5): 1-11. DOI: 10.6054/j.jscnun.2022067

基于GIS的国外文化地理学研究热点演变与趋势

基金项目: 

国家自然科学基金项目 41971190

国家自然科学基金项目 42001162

国家自然科学基金项目 42201264

广东省哲学社会科学规划学科共建项目 GD22XSH10

详细信息
    通讯作者:

    刘博,Email: 114659591@qq.com

  • 中图分类号: K901.2

The Evolution and Trend of Foreign Research Hotspots in GIS-based Cultural Geography

  • 摘要: 借助文献计量法和科学知识图谱分析法,筛选“Web of Science”核心合集数据库中基于GIS的文化地理研究文献,通过CiteSpace可视化软件绘制发文作者、学科领域和关键词等知识图谱,并进一步追溯核心文献,聚焦研究主题与热点。研究结果表明:(1)该领域研究趋势指向新型地理信息系统,国外研究的高中心性和高突现性文献集中指向批判地理信息系统、历史地理信息系统、质性地理信息系统;(2)核心文献较多采用ArcMAP制图的分层设色模式及核密度分析法来呈现文化地理信息的制图可视化;(3)基于GIS的文化地理研究具有跨学科的优势及良好的研究前景,今后的文化地理学研究在数据获取上可以借助志愿地理信息系统等开放式的地理信息技术平台,在方法上可以探索空间插值等较为精准的空间分析方法。
    Abstract: With the bibliometric method and the scientific knowledge graph analysis method, the research literature on GIS-based cultural geography in the Web of Science database is screened, the knowledge graph of authors, disciplines and keywords is drawn through the CiteSpace visualization software, and then the core literature is traced to focus on the hot research topics. The findings are as follows. First, the literature of high centrality and prominence focuses on criticizing GIS, historical GIS and qualitative GIS. Second, the core literature mainly adopts the hierarchical color setting mode of ArcMAP mapping and the kernel density analysis to present the cartographic visualization of cultural geographic information. Third, the GIS-based cultural geography research has interdisciplinary advantages and good research prospects. In the future, cultural geography research can rely on open geographic information technology platforms such as the voluntary geographic information system for data acquisition and try more accurate spatial analysis methods such as spatial interpolation.
  • Cahn-Hilliard方程在流体力学中具有重要应用,并被许多学者广泛研究.如:应用Cahn-Hilliard理论建立非局部反应扩散模型并采用其渐进展开式与多时间尺度去分析该模型[1];应用Cahn-Hilliard方程表示拓扑相变,并分析如何模拟3个不能混合的流在陡峭界面的运动[2];应用Cahn-Hilliard方程描述不可压缩的流体扩散界面以及相位场[3-4];分析Allen-Cahn方程ut=Δu+ε2(f(u)ελ(t))在含无流边界条件的有界闭域上的质量守恒性,其中,ελ(t)f(u(,t))的平均值,-f是双等位势函数的导子[5];讨论容器带有密度的相位场用平均曲率流近似[6];给出容器V的自由能量表达式:

    E=NVV(F0(c)+k(c)2)dV,

    其中,V表示非均匀结构或非均匀密度的各向同性的空间几何体,NV表示每单位体积的分子数,λ表示结构梯度或密度梯度,F0表示对应均匀系(齐次系统)的每分子的自由能,k是一个参数[7];基于二阶平均向量场方法和拟谱方法,构造了具有多辛结构的复修正KdV方程新的数值格式, 证明了该格式能保方程离散的整体能量守恒特性[8];采用能量不变二次化法来解决一些微分方程的数值近似[9-11].

    YANG等[12]利用能量不变二次化方法,设计了一阶和二阶的时间离散格式, 以求解三组分Cahn-Hilliard方程,但没有考虑时间方向的误差估计.因此,本文基于能量不变二次化方法,对一类非三组分的具有能量泛函

    E(ϕ)=Ω(12|ϕ|2+F(ϕ))dx

    的Cahn-Hilliard方程ϕt=Δ2ϕ+ΔF(ϕ)构造线性数值格式,并讨论该数值格式在时间方向的误差估计.

    为了便于构造线性数值格式,将Cahn-Hilliard方程ϕt=Δ2ϕ+ΔF(ϕ)变形为方程组

    {ϕt=Δω,ω=Δϕ+F(ϕ), (1)

    其中,F(ϕ)=f(ϕ)=ϕ3ϕ,F(ϕ)是非线性的光滑的位势函数, ΩR2的闭集;ϕ(x,t)(xΩ,t(0,T])是混合物中某种物质的浓度,ω是化学势.

    本节采用能量不变二次化法分析Cahn-Hillirad方程的数值近似.能量不变二次化法[9]是指通过变量代换将自由能被积函数变成新变量的二次函数,变换后的能量函数满足能耗规律(Energy Dissipation Law).本文所用的部分记号如下:f(x)g(x)L2内积为(f(x),g(x))=Ωf(x)g(x)dx(xΩR2); f(x)的的L2范数为f=(f,f);q(ϕ)=F(ϕ)+Bg(ϕ)=2ddϕq(ϕ)=f(ϕ)F(ϕ)+B.

    于是,方程组(1)可以写成:

    {ϕt=Δω,ω=Δϕ+g(ϕ)q(ϕ),qt=12g(ϕ)ϕt, (2)

    满足初始条件:

    ϕ|t=0=ϕ0,q|t=0=F(ϕ0)+B,

    并满足以下其中一个边界条件:

    (i) 在边界Ω上,ϕω都是周期性的;

    (ii) 无流边界,即

    nϕ|Ω=nω|Ω=0, (3)

    其中,n为边界上的向外法向量.

    方程组(2)的3个方程分别与ωϕt2qL2内积,整理得

    ddtE(ϕ,q)=Ω|ω|2dx,

    其中,E(ϕ,q)=Ω(12|ϕ|2+q2)dx,这里E(ϕ,q)等价于E(ϕ).

    针对方程组(2),构造如下时间离散格式:

    {ϕn+2ϕn2δt=Δωn+2+ωn2,ωn+2+ωn2=Δϕn+2+ϕn2+gn+1qn+2+qn2,qn+2qn2δt=12gn+1ϕn+2ϕn2δt. (4)

    该格式有如下的能量稳定性,且该格式的解是惟一的.

    定理1    (能量稳定性)方程组(4)的解是具有能量稳定的,即

    E(ϕn+1,qn+1)E(ϕn,qn)δt=14ωn+2+ωn2,

    其中,

    E(ϕn,qn)=14(ϕn+12+ϕn2+2qn2+2qn+12).

    证明  把方程组(4)的第1个方程与2δt(ωn+2+ωn)L2内积,并使用分部积分法,整理得

    (ϕn+2ϕn,ωn+1+ωn)=δtωn+2+ωn2. (5)

    方程组(4)的第2个方程与2(ϕn+2ϕn)L2内积,整理得

    (ωn+2+ωn,ϕn+2ϕn)=ϕn+22ϕn2+(gn+1(qn+2+qn),ϕn+2ϕn). (6)

    方程组(4)的第3个方程与4δtqn+2+qnL2内积,整理得

    2qn+222qn2=(gn+1(ϕn+2ϕn),qn+2+qn). (7)

    结合式(5)~(7),有

    ϕn+22ϕn2+2qn+222qn2=δtωn+2+ωn2,

    从而可以导出结果.证毕.

    定理2   (解的唯一性)方程组(4)的解是唯一的.

    证明   由方程组(4)的第3个方程可得

    qn+2=qn+12gn+1(ϕn+2ϕn), (8)

    则方程组(4)可写成

    {ϕn+2δtΔωn+2=Q1,P(ϕn+2)ωn+2=Q2, (9)

    其中,Q1=ϕn+δtωn, Q2=Δϕn+gn+1(12gn+1ϕn2qn) + ωn,P(ϕ)=Δϕ+12(gn+1)2ϕ.

    于是,由方程组(9)直接推导得(ϕn+2,ωn+2)从而由式(8)推导得qn+2.进一步地,当任意的φ满足边界条件(i)或条件(ii)时,有

    (P(ϕ),φ)=(ϕ,φ)+12((gn+1)2ϕ,φ)=(φ,P(ϕ)),

    则线性算子P(ϕ)是对称的.又当Ωϕdx=0时,有

    (P(ϕ),ϕ)=ϕ2+12gn+1ϕ20,

    则线性算子P(ϕ)是正定的.

    通过方程组(4)的第1个方程与1作L2内积,可推导出

    Ωϕn+2dx=Ωϕndx==Ωϕ0dx.

    vϕ=1|Ω|Ωϕ0dx,vω=1|Ω|Ωωn+2dx并记

    ˆϕn+2=ϕn+2vϕ,ˆωn+2=ωn+2vω.

    结合方程组(9),可知(ˆϕn+2,ˆωn+2)是以下方程组的解:

    {ϕδtΔω=f,1P(ϕ)ωvω=f2, (10)

    其中, Ωdx=0,Ωdx=0.

    记逆算子u=Δ1ρ如下:

    {Δu=ρ,Ωudx=0,

    其中, u满足边界条件(i)或条件(ii).将Δ1作用到方程组(10)的第1个方程,整理得到

    Δ1ϕ+δtP(ϕ)δtvω=Δ1f1+δtf2. (11)

    记式(11)为Γϕ =Ζ,则对任意满足Ωϕdx=0Ωφdx=0ϕφ,有

    (Γϕ,φ)=(Δ1ϕ+δtP(ϕ)δtvω,φ)=(ϕ,Δ1φ+δtP(φ)δtvω)=(ϕ,Γφ).

    (Γϕ,ϕ)=(Δ1ϕ+δtP(ϕ)δtvω,ϕ)=ϕ2H1+δt(P(ϕ),ϕ)0,

    Γ是对称的,也是正定的,从而由Lax-Milgram定理[13]可知方程组(9)存在唯一解.证毕.

    定义误差enϕ=ϕ(tn)ϕn,enω=ω(tn)ωn, enq=q(tn)qn.记误差函数

    rn+11Δ=ϕ(tn+2)ϕ(tn)2δtϕt(tn+1),
    rn+12Δ=q(tn+2)q(tn)2δtqt(tn+1),
    rn+13Δ=q(tn+1)q(tn+2)+q(tn)2,
    rn+14Δ=ω(tn+1)ω(tn+2)+ω(tn)2,
    rn+15Δ=ϕ(tn+1)ϕ(tn+2)+ϕ(tn)2.

    应用泰勒展式,有

    rn+11Cδt2,rn+12Cδt2,rn+13Cδt2,rn+14Cδt2,rn+15Cδt2.

    引理1  设函数F(x)ϕ满足以下条件:

    (a) F(x)>A,A<B,x(,+);

    (b) F(x)C2(,+);

    (c) 存在一个正的常数C0,使得

    maxnk{ϕ(tn+1)L,ϕn+1L}C0.

    则有

    maxnk{F(χn+1)L,f(χn+1)L,f(χn+1)L,F(χn+1)+BL}C1, (12)

    其中,χn+1=εϕ(tn+1)+(1ε)ϕn+1,ε[0,1].进而有

    g(ϕ(tn+1))gn+1C2ϕ(tn+1)ϕn+1,

    其中,C2是依赖于C0C1AB的常数.

    证明  由条件(c)可知χn+1是一致有界的,再结合条件(b),可以得到式(12).应用拉格朗日中值定理,有

    g(ϕ(tn+1))gn+1=f(ϕ(tn+1))F(ϕ(tn+1))+Bf(ϕn+1)F(ϕn+1)+B=f(ϕ(tn+1))F(ϕn+1)+Bf(ϕn+1)F(ϕ(tn+1))+BF(ϕ(tn+1))+BF(ϕn+1)+Bf(ϕ(tn+1))(F(ϕn+1)+BF(ϕ(tn+1))+B)F(ϕ(tn+1))+BF(ϕn+1)+B+F(ϕ(tn+1))+B(f(ϕ(tn+1))f(ϕn+1))F(ϕ(tn+1))+BF(ϕn+1)+B(C12(BA)3f(χn+11)ϕ(tn+1)ϕn+1+C1BAf(χn+12)ϕ(tn+1)ϕn+1)C2ϕ(tn+1)ϕn+1.

    引理2  设函数F(x)ϕ满足以下条件:

    (a) F(x)>A,A<B,x(,+);

    (b) F(x)C3(,+);

    (c) 存在一个正的常数C3,使得

    maxnk{ϕ(tn+1)L,ϕn+1L}C3.

    则有

    maxnk{F(χn+1)L,f(χn+1)L,f(χn+1)L,
    f(χn+1)L,F(χn+1)+BL}C4,

    其中,χn+1=εϕ(tn+1)+(1ε)ϕn+1,ε[0,1]进而有

    g(ϕ(tn+1))gn+1C5ϕ(tn+1)ϕn+1,

    这里的C5是依赖于C3C4AB的常数.

    引理2的证明过程与引理1的类似,在此略.

    引理3   设{un}N2n=0Ω上的函数列,则有

    un+2nm=0um+2+um+u0.

    证明  使用数学归纳法证明.当n=0时,易证得

    u2u2+u0+u0.

    假设n=k-1时,有

    uk+1k1m=0um+2+um+u0.

    n=k时,有

    uk+2u0=uk+2uk+1+uk+1u0k1m=0um+2+um+uk+2uk+1k1m=0um+2+um+uk+2+uk+1=km=0um+2+um.

    则引理3得证.

    为了更好地证明方程组(2)的数值近似的误差估计,定义v为:

    v=max0tTϕ(t)L+1.

    引理4  设F(x)>A,A<B,x(,+)F(x)C3(,+),方程组(2)的精确解满足正则性假设条件ϕL(0,T;H2(Ω))L(0,T;W1,(Ω)), ϕtL2(0,T;H1(Ω))L(0,T;L(Ω)),qL(0,T; W1,(Ω)),ωL(0,T;H1(Ω)),qtt,ϕttL2(0,T;L2(Ω)),则对于正数τ0,当δt<τ0时,有

    ϕnLv(n=0,1,2,;K=T/(δt)).

    证明   使用数学归纳法证明.当n=0时,易知ϕ0Lv.现假设ϕk+1Lv成立,下面将要证明ϕk+2Lv.先不考虑方程组(4),而把方程组(2)在tn+1处重新表述,将方程组(2)的3个方程分别与φθψL2内积,整理得

    (en+2ϕenϕ2δt,φ)=(en+2ω+enω2,φ)+(rn+11+Δrn+14,φ), (13)
    (en+2ω+enω2,θ)=(rn+14+Δrn+15,θ)(Δen+2ϕ+enϕ2,θ)+(g(ϕ(tn+1))q(ϕ(tn+1))gn+1qn+1+qn2,)θ, (14)
    (en+2qenq2δt,ψ)=(rn+12,ψ)+12(g(ϕ(tn+1))ϕt(tn+1)gn+1ϕn+2ϕn2δt,φ). (15)

    在式(13)中,令φ=2δt(en+2ω+enω), 得

    (en+2ϕenϕ,en+2ω+enω)+δten+2ω+enω2=2δt(rn+11+Δrn+14,en+2ω+enω). (16)

    在式(13)中,令φ=2δt(en+2ϕ+enϕ), 得

    en+2ϕ2enϕ2=δt(en+2ω+enω,en+2ϕ+enϕ)+2δt(rn+11+Δrn+14,en+2ϕ+enϕ). (17)

    在式(14)中,令θ=2(en+2ϕ+enϕ), 得

    (en+2ω+enω,en+2ϕenϕ)=2(rn+14+Δrn+15,en+2ϕenϕ)+en+2ϕ2Δenϕ2+2(g(ϕ(tn+1))q(ϕ(tn+1))gn+1qn+2+qn2,en+2ϕenϕ). (18)

    在式(14)中,令θ=2δt(en+2ω+enω), 得

    δten+2ω+enω2=2δt(rn+14+Δrn+15,en+2ω+enω)+δt((en+2ϕ+enϕ),(en+2ω+enω))+2δt(g(ϕ(tn+1))q(ϕ(tn+1))gn+1qn+2+qn2,en+2ω+enω). (19)

    在式(15)中,令ψ=4δt(en+2q+enq), 得

    2en+2q22enq2=4δt(rn+12,en+2q+enq)+2δt(g(ϕ(tn+1))ϕt(tn+1)gn+1ϕn+2ϕn2δt,en+2q+enq). (20)

    组合式(16)~(20),并整理得

    en+2ϕ21enϕ21+2en+2q22enq2+δten+2ω+enω21=2δt(rn+11+Δrn+14rn+14Δrn+15,en+2ω+enω)+2δt(rn+11+Δrn+14,en+2ϕ+enϕ)+2(rn+14+Δrn+15,en+2ϕenϕ)+4δt(rn+12,en+2q+enq)2(g(ϕ(tn+1))q(ϕ(tn+1))gn+1qn+2+qn2,en+2ϕenϕ)+2δt(g(ϕ(tn+1))q(ϕ(tn+1))gn+1qn+2+qn2,en+2ω+enω)+2δt(g(ϕ(tn+1))ϕt(tn+1)gn+1ϕn+2ϕn2δt,en+2q+enq). (21)

    注意到

    g(ϕ(tn+1))q(ϕ(tn+1))gn+1qn+2+qn2=q(ϕ(tn+1))(g(ϕ(tn+1))gn+1)+gn+1(q(ϕ(tn+1))qn+2+qn2)=q(ϕ(tn+1))(g(ϕ(tn+1))gn+1)+gn+1(q(ϕ(tn+1))q(ϕ(tn+2))+q(ϕ(tn))2)+gn+1(q(ϕ(tn+2))+q(ϕ(tn))2qn+2+qn2)=q(ϕ(tn+1))(g(ϕ(tn+1))gn+1)+gn+1rn+13+gn+1en+2q+enq2,

    g(ϕ(tn+1))ϕt(tn+1)gn+1ϕn+2ϕn2δt=ϕt(tn+1)(g(ϕ(tn+1))gn+1)+gn+1(ϕt(tn+1)ϕn+2ϕn2δt)=ϕt(tn+1)(g(ϕ(tn+1))gn+1)gn+1rn+11+gn+1en+2ϕenϕ2δt.

    应用Gronwall和Young不等式,式(21)等号的右端可以放缩如下:

    2δt(rn+11+Δrn+14rn+14Δrn+15,en+2ω+enω)Cδt5+δt4en+2ω+enω2, (22)
    2δt(rn+11+Δrn+14,en+2ϕ+enϕ)Cδt5+δten+2ϕ+enϕ2, (23)
    4δt(rn+12+en+2ϕ+enϕ)Cδt5+δten+2ϕ+enϕ2, (24)
    2(rn+14+Δrn+15,en+2ϕenϕ)=4δt(rn+14+Δrn+15,Δen+2ω+enω2+rn+11+Δrn+14)Cδt5+δt4en+2ω+enω2. (25)

    应用引理1, 式(21)的右端非线性项估计如下:

    2(g(ϕ(tn+1))q(ϕ(tn+1))gn+1qn+2+qn2,en+2ϕenϕ)+2δt(g(ϕ(tn+1))ϕt(tn+1)gn+1ϕn+2ϕn2δt,en+2q+enq)=2(q(ϕ(tn+1))(g(ϕ(tn+1))gn+1)+gn+1rn+13+gn+1en+2q+enq2,en+2ϕenϕ)+2δt(ϕt(tn+1)(g(ϕ(tn+1))gn+1)gn+1rn+11+gn+1en+2ϕenϕ2δt,en+2q+enq)=2(q(ϕ(tn+1))(g(ϕ(tn+1))gn+1)+gn+1rn+13,en+2ϕenϕ)+2δt(ϕt(tn+1)(g(ϕ(tn+1))gn+1)gn+1rn+11,en+2q+enq)Cδt(δt4+en+2ϕ+enϕ2+en+1ϕ21)+δt4en+2ω+enω2, (26)
    2δt(g(ϕ(tn+1))q(ϕ(tn+1))gn+1qn+2+qn2,en+2ω+enω)=2δt(q(ϕ(tn+1))(g(ϕ(tn+1))gn+1)+gn+1rn+13+gn+1en+2q+enq2,en+2ω+enω)Cδt(δt4+en+1ϕ2+en+2q+enq2)+δt4en+2ω+enω2. (27)

    将式(22)~(27)代入式(21),整理得

    en+2ϕ21enϕ21+2en+2q22enq2+δt2en+2ω+enω21Cδt5+Cδt(en+1ϕ21+en+2q+enq2+en+2ϕ+enϕ2). (28)

    在式(28)中,令n=0, 1, 2…, k,并求和,整理得

    ek+2ϕ21+ek+1ϕ21+2ek+2q2+2ek+1q2+δt2kn=0en+2ω+enω21e1ϕ21+2e1q2+Cδt4+Cδtkn=0(en+1ϕ21+en+2ϕ2+enϕ2+en+2q2+enq2).

    容易证得

    e1ϕ21+2e1q2

    应用Gronwall不等式,存在一个正数 {\tau _1},当 \delta t < {\tau _1}时,有

    \begin{array}{*{20}{c}} {\left\| {e_\phi ^{k + 2}} \right\|_1^2 + \left\| {e_\phi ^{k + 1}} \right\|_1^2 + {{\left\| {e_q^{k + 2}} \right\|}^2} + {{\left\| {e_q^{k + 1}} \right\|}^2} + }\\ {\delta t\sum\limits_{n = 0}^k {\left\| {e_\omega ^{n + 2} + e_\omega ^n} \right\|_1^2} \le {C_6}\delta {t^4}.} \end{array} (29)

    由方程组(2)、(4)知

    \begin{array}{*{20}{l}} {\left\| {\Delta e_\phi ^{n + 2} + \Delta e_\phi ^n} \right\| \le 2{{\left\| {r_1^{n + 1}} \right\|}^2} + 2{{\left\| {r_5^{n + 1}} \right\|}^2} + \left\| {e_\omega ^{n + 2} + e_\omega ^n} \right\| + }\\ {{\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} \left\| {g(\phi ({t_{n + 1}}))q(\phi ({t_{n + 1}})) - {g^{n + 1}}\frac{{{q^{n + 2}} + {q^n}}}{2}} \right\| \le {C_7}\delta {t^2}.} \end{array}

    由引理3可知

    \left\| {\Delta e_\phi ^{k + 2}} \right\| \le \sum\limits_{n = 0}^k {\left\| {\Delta e_\phi ^{n + 2} + \Delta e_\phi ^n} \right\| + \left\| {\Delta e_\phi ^0} \right\|} \le {C_8}\delta t.

    进而有

    \begin{array}{l} {\left\| {{\phi ^{k + 2}}} \right\|_{{L^\infty }}} \le {\left\| {e_\phi ^{k + 2}} \right\|_{{L^\infty }}} + {\left\| {\phi ({t_{k + 2}})} \right\|_{{L^\infty }}} \le \\ {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {C_\varOmega }\left\| {e_\phi ^{k + 2}} \right\|_1^{\frac{1}{2}}\left\| {e_\phi ^{k + 2}} \right\|_2^{\frac{1}{2}} + {\left\| {\phi ({t_{k + 2}})} \right\|_{{L^\infty }}} \le \\ {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {C_9}\delta {t^{\frac{3}{2}}} + {\left\| {\phi ({t_{k + 2}})} \right\|_{{L^\infty }}}. \end{array}

    {C_9}\delta {t^{\frac{3}{2}}} \le 1,则 \left\|\phi^{k+2}\right\|_{L^{\infty}} \leqslant 1+\left\|\phi\left(t_{k+2}\right)\right\|_{L^{\infty}} \leqslant v.证毕.

    定理3  设F(x) > - A, A < B, \forall x \in ( - \infty , + \infty ) F(x) \in {C^3}( - \infty , + \infty ),Cahn-Hilliard方程组的精确解满足正则性假设条件\phi \in {L^\infty }\left( {0, T;{H^2}(\mathit{\Omega } )} \right) \cap {L^\infty }(0, \left. {T;{W^{1, \infty }}(\mathit{\Omega } )} \right), {\phi _t} \in {L^2}\left( {0, T;{H^1}(\mathit{\Omega } )} \right) \cap {L^\infty }\left( {0, T;{L^\infty }(\mathit{\Omega } )} \right) , q \in {L^\infty }\left( {0, T;{W^{1, \infty }}(\mathit{\Omega } )} \right), \omega \in {L^\infty }\left( {0, T;{H^1}(\mathit{\Omega } )} \right), {q_{tt}}, {\phi _{tt}} \in {L^2}\left( {0, T;{L^2}(\mathit{\Omega } )} \right) ,则有

    \begin{array}{l} {\left\| {\phi ({t_{k + 2}}) - {\phi ^{k + 2}}} \right\|_1} + \left\| {q(\phi ({t_{k + 2}})) - q({\phi ^{k + 2}})} \right\| + \\ {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} \delta t\sum\limits_{n = 0}^k {{{\left\| {\omega ({t_{n + 2}}) + \omega ({t_n}) - ({\omega ^{n + 2}} + {\omega ^n})} \right\|}_1}} \le C\delta {t^2}. \end{array}

    证明  因为{\left\| {{\phi ^n}} \right\|_{L\infty }} \le v, 0 \le n \le T/\delta t , 采用相同的方法,可以证得式(29), 从而定理3得证.

    下面采用数值例子验证理论分析的准确性.实验中,为了测试Cahn-Hilliard方程数值解的时间精度,选取如下初始值:

    {\phi (x,y,0) = \frac{1}{2}\left( {1 + \tanh \left( {\frac{{R - 0.15}}{\varepsilon }} \right)} \right),\varepsilon = 0.01,}
    {R = \sqrt {{{(x - 0.5)}^2} + {{(y - 0.5)}^2}} .}

    由基于能量不变二次化法的Cahn-Hilliard方程的数值解在L2范数下的误差和时间精度(表 1)可知:Cahn-Hilliard方程数值解在时间方向上基本达到二阶精度,从而验证了定理3的准确性.

    表  1  能量不变二次化法的Cahn-Hilliard方程的数值结果
    Table  1.  The numerical results of invariant energy quadratization approach of Cahn-Hilliard equation
    δt L2范数下的误差
    0.01 0.008 235
    0.005 0.005 224 1.651 101
    0.002 5 0.002 406 1.752 124
    0.001 25 0.001 126 1.861 113
    0.000 625 0.000 722 1.924 021
    0.000 312 5 0.000 465 1.945 233
    下载: 导出CSV 
    | 显示表格

    为了清楚看到相位变化过程,取T=1, 计算区域为Ω=[0, 1]×[0, 1], 初始条件为 \phi \left( {x, t = 0} \right) = {10^{ - 3}}{\rm{rand}}( - 1, 1).由基于能量不变二次化法的Cahn-Hilliard方程的数值解在t=1与t=2时刻的相位图(图 1)可知:所构造的数值格式能够有效地模拟Cahn-Hilliard方程的相位变化过程.

    图  1  数值解在t=1与t=2时刻的相位图
    Figure  1.  The phase diagram of the numerical results on t=1 and t=2

    基于能量不变二次化法,本文对Cahn-Hilliard方程构造有效的时间离散数值格式.对该数值格式的时间误差进行的分析结果表明:该数值格式在时间方向上是二阶精度的.数值例子也验证了该分析结果的准确性.本文所构造的时间离散数值格式能够使得非线性项离散化且在时间水平上保持能量稳定,能够解决Cahn-Hilliard方程数值近似中遇到的主要难题,为进一步考虑Cahn-Hilliard方程在时间和空间方向上同时离散数值逼近奠定一定的基础.

  • 图  1   基于GIS的文化地理文献发文量年度分布图(1993—2022年)

    Figure  1.   The annual distribution of literature in the cultural geo-graphy and GIS domain from 1993 to 2022

    图  2   基于GIS的文化地理文献共被引网络图谱(1993—2022年)

    Figure  2.   The co-citation network map of literature in the cultural geography and GIS domain from 1993 to 2022

    图  3   基于GIS的文化地理研究关键词的时间序列图

    注:图中圆圈符号越大表示该关键词被引频率越高。

    Figure  3.   The time series graph of keywords in GIS-based cultural geography research

    表  1   基于GIS的文化地理研究的关键文献

    Table  1   The key node literature of GIS and cultural geography research

    关键文献 作者 发文期刊 年份 中心性 共被引频次
    《Negotiating knowledge production: the everyday inclusions, exclusions, and contradictions of participatory GIS research》 ELWOOD S 《Professional Geographer》 2006 0.02 4
    《Walter Benjamin's dionysian adventures on Google Earth》 KINGSBURY P 《Geoforum》 2009 0.02 2
    《Location-based services, conspicuous mo-bility, and the location-aware future》 WILSON M W 《Geoforum》 2012 0.01 3
    《Feminist geographies of new spatial me-dia》 LESZCZYNSKI A 《The Canadian Geographer》 2015 0.01 2
    《Affecting geospatial technologies: toward a feminist politics of emotion》 KWAN M P 《Professional Geographer》 2007 0.01 3
    《New spatial media, new knowledge politics》 ELWOOD S 《Transactions of the Institute of British Geographers》 2012 0.01 2
    下载: 导出CSV

    表  2   基于GIS的文化地理研究的期刊发文情况

    Table  2   The journal publication of GIS and cultural geography research

    期刊名 发文量 影响因子(2020年) Journal Citation Report(JCR) 分区(2020年)
    《Applied Geography》 6 4.24 Q1
    《Isprs International Journal of Geo Information》 4 2.90 Q2
    《Journal of Geography in Higher Education》 4 2.46 Q2
    《Professional Geographer》 4 2.38 Q3
    《Annals of the Association of American Geographers》 3 4.68 Q1
    《Journal of Archaeological Science》 3 3.22 Q1
    《Transactions in GIS》 3 2.41 Q3
    《Journal of Geography》 3 2.40 Q3
    《Geographical Review》 3 1.58 Q4
    《Progress in Human Geography》 2 10.22 Q1
    《Land Use Policy》 2 5.40 Q1
    《Journal of Historical Geography》 2 1.39 Q1
    《Cultural Geographies》 2 3.55 Q3
    下载: 导出CSV

    表  3   基于GIS的文化地理研究前15名突现关键词(按突现起始年排序)

    Table  3   The top 15 prominent keywords in GIS-based cultural geography (in order of the beginning year of prominencne)

    关键词 突现度 起始年份 终止年份
    ecology 1.23 1993 2004
    cultural geography 1.21 2005 2016
    map 1.79 2008 2013
    space 1.69 2008 2013
    policy 1.61 2008 2013
    knowledge 1.54 2008 2010
    city 1.53 2008 2013
    world 1.49 2008 2013
    landscape 1.14 2008 2013
    critical GI 1.32 2014 2019
    geography 2.55 2017 2022
    place 1.72 2017 2022
    science 1.7 2017 2019
    land use 1.24 2017 2022
    historical geography 1.22 2020 2022
    下载: 导出CSV
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出版历程
  • 收稿日期:  2022-09-09
  • 网络出版日期:  2022-12-15
  • 刊出日期:  2022-10-24

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