中立型时滞抛物方程初边值问题的差分方法

给出了求解中立型时滞抛物方程初边值问题t[u(x ,t) -λu(x ,t-τ) ] =2x2 u(x ,t) +f(x ,t) ,　　　 (x ,t)∈ ( 0 ,l)× ( 0 ,T]u(x ,t) =φ(x ,t) ,　　　 (x ,t)∈ ( 0 ,l)× [-τ ,0 ]u( 0 ,t) =u(l ,t) =0 ,　　　t∈ [-τ,T]的差分方法 ,并获得了该差分格式的收敛性     

赋权图中最重的最长v-路与赋权周长

对2－连通非Hamilton赋权图G,本文证明：若P（u,v)是G中最重的最长路，则G的赋权周长C^w(G)≥d^w(u) d^w(v)，假设G满足文中描述的额外条件C1，C2，则max｛d^w(x),d^w(y)|d(x,y)=2｝≥m/2时，对每个顶点v,G含量最重长v-路P（u,v)使d^w(u)≥m/2，而d^w(x) d^w(y) d^w(z)≥m（当d(x,y,z)=2)时，c^w(G)≥2m/3.改进了非赋权图的周长及赋权图的赋权周长的若干已有结果。     

开发平潭旅游业之我见

平潭素有“千礁岛县”的美誉 ,主岛海坛风景名胜区以优质海滨沙滩和奇特的海蚀地貌被专家誉为海蚀地貌博物馆 ,于 1 994年被国务院确定为国家重点风景名胜区。但几年来平潭旅游在我省的旅游产业发展中却默默无闻 ,本文通过对平潭旅游业发展现状的换位思考 ,提出为适应新经济环境的变化 ,平潭旅游业应长远谋划来做心灵的生意     

栗斑腹鹀种群数量变化的分析

1999年至 2 0 0 1年每年 4～ 7月在吉林省西部地区对栗斑腹种群数量及繁殖情况进行了调查 ,发现三年来栗斑腹种群数量连续下降 .其原因是 :人为干扰导致栗斑腹繁殖成功率及繁殖成活率降低 ,从而导致栗斑腹种群数量下降 ;研究地区内近几年连续高温干旱的天气也导致了栗斑腹种群数量的下降 ,气温升高 (R2 =0 9964 )、降雨量减少 (R2 =0 84 98)对栗斑腹种群数量下降的影响很大 .     

反应精馏过程设计研究

介绍连续反应精馏过程设计的两种研究方法：静态分析法和有限元正交搭配OEFE法，静态分析法是对反应精馏图进行热力学和拓扑学分析，鉴定反应精馏过程的基本可能性，此方法不需要依靠确定的对象的特性，要求最少最反应混合物的物理化学特性，有限元正交配技术应用了把整级评估模型转变成连续的模型。OCFE能精确地吻俣逐板模型的优化设计，而只是使用一套较小的模型公式和避免使用与塔级数有关的总决策变量，用静态分析寻找一个最大转化率稳定态，用OCFE确定反应精馏塔的级数（塔级数）及进行精级（塔板）位置。     

试论现代教学条件下的班级规模

班级规模是影响教学质量的重要因素。本讨论班级规模与教学质量的关系，班级规模变动的原因，以及在现代教学条件下班级规模扩大所产生的利与弊及其应对办法。     

金材网络信息系统的建立与实现

用Windows NT Server4.0、SQL Server7.0、Powerbuilder6.5开发出金属材料供应公司网络管理信息系统。该系统通过拨号连接办公楼（主干）和生产区4个远程站建立金属材料供应公司的局域网。以生产、销售管理为主线，在生产、财务、销售、废钢铁采购、劳资管理及办公自动化等方面全面覆盖公司的各类信息管理工作，实现各科室的信息资源共享，提高了工作效率。     

Loess in the Tian Shan and its implications for the development of the Gurbantunggut Desert and drying of northern Xinjiang

Eolian loess is widely distributed on the various geomorphic surfaces between 700–2400 m a.s.l. on the northern slope of the Tian Shan. It is formed in a synchronous manner with dust transported from the Gurbantunggut Desert in the Junggar Basin. The thickest section of loess was found in the Shawan and Shihezi regions. Paleomagnetic and climatic proxy analyses of over 71 m of a loess-paleosol sequence on the highest terrace of the Qingshui He (River) in the Shawan show that the paleomagnetic Bruhues/Matuyama (B/M) boundary lies at the bottom of paleosol S8, at a depth of 69.5 m, and the bottom of the sequence was estimated to be ∼0.8 Ma. This implies that the extremely dry climatic conditions in the Junggar Basin and the initial Gurbantunggut Desert were present at least by 0.8 Ma. High-resolution grain size series demonstrate that this area and desert expansion experienced two dramatic periods of desert expansions that occurred at ∼0.65 Ma and 0.5 Ma, respectively; and the subsequent continuous enhancement led to the environment presently observed. This tremendous environmental effect, caused by large-scale expansion of the desert and arid region of inner Asia, might be an important driving force for the global temperature drop that occurred in the mid-Pleistocene.     

Nanometer properties of oceanic polymetallic nodules and cobalt-rich crusts

An ammonia leaching process was utilized to extract Co, Ni and Cu from oceanic polymetallic nodules, whereas an acid leaching process was utilized to extract Co, Ni, Cu, Zn and Mn from cobalt-rich crusts. Both processes produced nanometer materials—ammonia leaching residue and acid leaching residue. A systematic study was conducted on the phase, composition and physicochemistry properties of these residues. The result shows that both residues contain a large amount of nanometer minerals. Ammonia l eaching residue mainly consists of rhodochrosite, with the average grain diameter of 17.9 nm; whereas the acid leaching residue mainly consists of well-developed bassanite, with the average grain deameter of 9.5 nm. The bassanite also has a microporous structure, the volume of the pore space is 1.23 × 10⁻² mL/g. Both the ammonia and acid leaching residues have a large specific surface area, and they display a strong adsorption capacity to saturate sodium chloride vapour, N₂ and SO₂. Both residues have high contents of rare earth elements, and most of these elements exist in the state of ionic adsorption. The content of σ FeO is high. The P₂O₅ enrichment is observable in acid leaching residues. The unique composition and nanometer solid properties of the leaching residues displayed their potential value and promised a bright future for their application in the field of environmental protection and materials.     

Carbon isotopic records in paleosols over the Pliocene in Northern China: Implication on vegetation development and Tibetan uplift

Carbon isotopic composition of pedogenic carbonate can be used to estimate the proportion of C₄ and C₃ plants. Here we present carbon isotopic data of carbonate in a red earth section at Xifeng, central Loess Plateau. Results show that C₄ vegetation increased in ∼4.4 Ma B.P., stabilized between 4.0 and 3.0 Ma B.P. The character and timing of C₄ expansion on the Loess Plateau are similar, but different with other localities, e.g. Pakistan and Africa, implying that regional climate changes were main factors driving the expansion of C₄ plants. This event is comparable in timing with increased aridity evidenced by Xifeng grain size and North Pacific eolian dust records. Therefore we argue that the Pliocene expansion of C₄ plants in northern China might have been caused by the increased aridity, which in turn might be related to rapid uplift of the Tibetan Plateau.