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对二维三温热传导方程组提出一类分数步有限差分格式。利用变分形式及能量方法 ,得到离散 H1范数的最优阶先验误差估计及稳定性 相似文献
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对耦合Schr?dinger方程组提出1个线性差分格式并对其进行分析,证明格式保持原方程组的守恒律,证明格式依L2模稳定性和先验误差估计,对孤波碰撞的多种现象进行模拟,得到较为满意的结果. 相似文献
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提出解非线性耦合Schrodinger方程的1种差分格式.理论证明此格式关于时间和空间具有二阶精度,保持了连续方程的2个守恒量,并且是收敛、无条件稳定的.大量的数值试验证明了差分格式的精度以及守恒性. 相似文献
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基于一维阻尼潮波传播方程解析解,从求解数值格式及Heuristic稳定性分析方面,讨论了数值解的精度、计算耗时和摩阻系数选取等问题。研究结果表明:1)Courant数小于1时,潮波方程显格式解的精度略高于隐格式解,计算耗时少于隐格式解;2)为减少计算耗时,潮波方程的隐格式解允许较大的时间步长,但解的精度有所降低,须通过减小底床摩阻系数以保证计算精度;3)隐格式解摩阻系数的选取与Courant数有关,Courant数越大,摩阻系数的选取值比实际值越小,通过理论分析结合数值试验得到了相应的关系式。这些研究结论对实际海域的潮波传播的数值模拟具有重要的应用价值。 相似文献
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利用基于广义梯度近似的密度泛函理论,计算了金刚石(100)表面不同氢吸附密度的平衡态几何结构和态密度.结果表明对于2×1构型,在平行和垂直表面两个方向上发生弛豫,而1×1构型仅在垂直表面方向上发生弛豫.另外,清洁2×1,2×1 ∶0.5H和1×1 ∶1.5H表面,带隙中存在空表面态;而对于1×1 ∶2H和2×1 ∶H两种表面结构,空表面态上移进入导带,带隙中不存在表面态.结合电荷密度分布,探讨了金刚石(100)不同构型和氢吸附密度表面的表面态诱发机理. 相似文献
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缢蛏家系早期生长表现比较 总被引：1，自引：0，他引：1
《中国海洋大学学报(自然科学版)》2015,(10)
采用单对配对方法建立了10个缢蛏家系(A1—F1各家系母本不同,G1和G2同母本,H1和H2同母本),对缢蛏表型性状的相关性进行分析,对家系间不同日龄的生长性状进行比较。结果表明:缢蛏的壳长和壳高有较强的相关性,且达到极显著水平(P0.01);部分家系生长性状差异显著(P0.05)。D1为生长快速家系,各时期各性状上均表现出明显的生长优势。H1和H2由于母性效应的影响,表现出明显的生长优势,G1和G2则表现出相反的生长趋势。各家系中,D1和C1壳长、壳高的Kung育种值、综合评定值均高于其他家系,母系半同胞家系组合中H1的Kung育种值和综合评定值优于其他家系。通过研究发现,D1、C1和H1可作为留选家系,通过进一步的家系内选育或家系间杂交选育出个体大、生长快的优良家系。 相似文献
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Fenton 试剂降解壳聚糖废液的初步研究 总被引：1，自引：0，他引：1
通过单因素分析实验 ,研究了 Fenton试剂降解壳聚糖制备废液过程中各影响因子的作用机制 ,初步得出了其最佳作用范围。通过正交匹配实验 ,确定了最佳操作条件为 :初始 p H=2 .5,终了p H=1 0 ,1 0 g Fe/ L的 Fe2 溶液 1 5m L,30 % H2 O2 2 m L,t(搅拌 ) =80 min,t(静置 ) =8h,T=348K,经验证 COD去除率达到 58.91 %。在常温下 ,利用紫外扫描法简单分析了 Fenton试剂对醋酸钠难降解有机物的降解效率 ,达到了 1 6.39%。 相似文献
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为了研究污染物对流扩散方程中不同时空格式的适用性,针对对流扩散方程的一维﹑二维和三维3种情况,分别建立了预报-校正的有限差分数值模型。在时间步进格式上分别采用了Crank-Nicolson格式或混合4阶Adams-Bashforth-Moulton格式,对对流项分别采用2阶精度或4阶精度,对扩散项采用了2阶精度。利用建立的数值模型求解了经典的污染物浓度场对流扩散,通过数值解与解析解的比较讨论了不同时空格式对数值模型计算结果的影响。结果表明:对空间一次导数采用4阶精度可以避免采用2阶精度带来的误差。采用混合4阶Adams-Bashforth-Moulton格式或Crank-Nicolson格式数值计算结果均与解析解吻合程度较好,但对于数组为[40,40,40]的三维对流扩散问题,前者比后者省时20.7%。 相似文献
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温度、光照、pH值对后棘藻生长及脂肪酸含量的影响 总被引：3，自引：0，他引：3
报道了环境因子对富含 EPA (2 0∶ 5ω3)的海洋微藻后棘藻 (Ellipsoidion sp.) 70 - 0 1的生长速度、总脂及脂肪酸含量的影响。结果表明 ,后棘藻具有较快的生长速度和较高的脂肪酸含量 ,总脂含量为 31～ 36 % ,主要脂肪酸为 14∶ 0、16∶ 0、16∶ 1、18∶ 1ω9、18∶ 1ω7、18∶ 2 ω6、2 0∶ 4 ω6、2 0∶ 5ω3。生长的温度范围为 15～ 30℃ ,2 5℃时生长速度最快。温度对总脂含量影响很小 ,但对EPA和 PUFA含量影响较大。在 2 5℃时有最大的 EPA和 PUFA含量。适宜光强为 10 8.75μmolm-2 s-1～ 2 4 4 .15μmolm-2 s-1,在 145.54μmolm-2 s-1时 EPA产率较大。在起始 p H6 .5～ 9范围内 ,p H8.5时有最大的生长速率和总脂含量 ,而 EPA和 PUFA在起始 p H7.5时最大 ,分别占脂肪酸的 18.77%和 2 3.38%。实验条件下后棘藻 EPA产率最大的条件为温度 2 5℃ ,光强 145.54μmolm-2 s-1,p H为 7.5～ 8.5。 相似文献
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为了评价琼枝麒麟菜多糖(EGP)包括粗提物(CEGP)及大于500 k Da多糖组分(LEGP)抗呼吸道相关病毒活性。采用Reed-muench法计算流感病毒H1N1、H3N2和H5N3,柯萨奇病毒CVB3及呼吸道合胞病毒RSV-long株滴度;采用观察细胞病变效应(CPE)法,确定CEGP和LEGP对犬肾细胞(MDCK),人宫颈癌细胞(He La)和人喉癌上皮细胞(HEp-2)的最大无毒浓度;通过细胞病变观察法(CPE)及四甲基偶氮唑盐微量酶反应比色法(MTT法)测定CEGP和LEGP抑制各病毒产生细胞病变的作用。结果表明:CEGP和LEGP对5种常见的呼吸道病毒H1N1、H3N2和H5N3,CVB3和RSV都有抑制作用,CVB3和RSV对CEGP和LEGP更敏感;CEGP和LEGP有抗多种呼吸道病毒作用,为抗呼吸道病毒新药的研发提供理论依据。 相似文献
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The New Zealand Waters Pollution Regulations 1963, referring to recreational water to which the public can gain access, states that the “coliform bacteria content shall not consistently exceed 1,000/100 ml”. This standard is now under revision, and the suggested new standard is a median faecal coliform index of 200/100 ml with a maximum value not exceeding 400/100 ml. Recent literature supports the use of faecal coliform sub‐group bacteria as the best indicator of faecal pollution and reference is made to the membership of this sub‐group. Inherent inaccuracies of the Most Probable Number (MPN) method of assessing bacterial populations are pointed out, such as experimental variations with different cultural media, and possible errors in interpretation of results. In North America, there is evidence that an MPN for the total coliform group of 1000/100 ml indicates a faecal coliform sub‐group MPN of 200/100 ml, and epidemiological experience supports these values as standards. We tabulate and discuss evidence that the usual ratio of faecal coliforms : coliform group bacteria is typically 1 : 1 in fresh and marine waters of the Wellington region, and that a more attainable standard would be 500 faecal coliforms/100 ml. In ratios quoted in this paper, ‘coliform group’ means the remainder of the coliform group excluding faecal coliforms. The World Health Organisation (1963) definition, of the entire group of coliforms, is not intended. The ratio is different in other parts of New Zealand; in Auckland, for example, the ratio is close to that found in the United States. 相似文献
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《Marine Policy》2015
This paper systematically reviews and synthesizes peer-reviewed, English-language scientific publications (n=212) to identify relevant research about how Ecosystem-Based Adaptation (EBA) is integrated with coastal planning. Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) methodology is applied in this study. Attention was given to studies concerning human-environment interactions as opposed to physical or biological climate change issues alone because the coastal planning and EBA approach addresses the management of human actions in nature. The literature references include the issue of climate change (77%); however, limited evidence of EBA in coastal areas are reported (18%), and it is evident that the issues have become relevant in the scientific literature published in recent years. Broad texts demonstrate that SLR is one of the major long-term impacts (68%), and all of these papers recognize the most affected ecosystems in the tropics would be mangroves. EBA is an emerging option that can offset anticipated ecosystem losses and improve coastal planning to cope with SLR because it provides benefits beyond climate change stressors. There is a need to synthesize a road map for incorporation of mangrove regulations into local planning instruments and for building capacity for their implementation. Application of PRISMA in marine science will enhance future reviews, facilitate the systematic search and adequately document any theme, and also be useful in determining research gaps or information needs. 相似文献
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《Marine Policy》2014
This paper summarises research and options for sustainable sea transport in Oceania with a focus on domestic shipping. This debate is situated initially within the context of the current Pacific domestic shipping scenario, a region of minute economies connected by some of the longest sea transport routes in the world. All current options are fossil fuel powered and increasingly uneconomic and unsustainable. Many routes are marginal or unviable and a vicious cycle of old ships replaced with old ships prevails. Although a central and essential issue of many Pacific communities, the option of pursuing sustainable sea transport is currently invisible within the policy space at all levels. Various renewable energy options are possible and increasingly available. Recent research finds that these have strong potential for providing benefits across multiple wellbeings. The barriers to pursing this agenda are complex and poorly understood but are perceptual and institutional more than technological. A small number of critical experiments during the last oil crisis provide critical lessons and direction. 相似文献
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《Marine Policy》2017
Marine conservation actions are promoted to conserve natural values and support human wellbeing. Yet the quality of governance processes and the social consequences of some marine conservation initiatives have been the subject of critique and even human rights complaints. These types of governance and social issues may jeopardize the legitimacy of, support for and long-term effectiveness of marine conservation. Thus, we argue that a clearly articulated and comprehensive set of social standards - a code of conduct - is needed to guide marine conservation. In this paper, we draw on the results of an expert meeting and scoping review to present key principles that might be taken into account in a code of conduct, to propose a draft set of foundational elements for inclusion in a code of conduct, to discuss the benefits and challenges of such a document, and to propose next steps to develop and facilitate the uptake of a broadly applicable code of conduct within the marine conservation community. The objectives of developing such a code of conduct are to promote fair conservation governance and decision-making, socially just conservation actions and outcomes, and accountable conservation practitioners and organizations. The uptake and implementation of a code of conduct would enable marine conservation to be both socially acceptable and ecologically effective, thereby contributing to a truly sustainable ocean. 相似文献
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提出了一种用于对不连续压力采样序列的傅立叶分析方法.此方法将周期函数展开成傅立叶级数,但在数值积分时取函数周期内有采样值的区间作为积分域,然后求解线性方程组得到傅立叶级数的系数值.为了检验本方法的有效性,利用此方法对解析函数进行了拟合,当一个周期内的取样时间大于1/2周期时,利用此方法能够得到满意的结果.利用实验方法研究了波浪作用下截断圆柱表面的压力分布.在波浪作用下静水面附近的测点在露出水面时没有压力值.利用所提出的傅立叶分析方法对略低于静水面位置的实测压力进行了分析,拟合结果与实测结果吻合很好,说明此方法在处理物理模型实验中间断采样得到的数据是有效的.利用数值方法对波浪压力进行了计算,并将一阶和二阶波压力的数值结果与实测值进行了比较. 相似文献
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《Coastal Engineering》1999,36(3):263-269
Using the logarithmic wind profile and typical values of dimensionless sea roughness for different sea states, simple power expressions are derived for the wind profile over water. The power expressions are useful for correcting measured wind speed data at a given elevation (up to an elevation of 60 m) to the standard elevation of 10 m commonly used in coastal engineering studies. The analysis shows that the 1/7 power expression (suggested in [U.S. Army Corps of Engineers, 1984. Shore Protection Manual, Vol. 1. Coastal Engineering Research Center, Vicksburg, USA.] and commonly used today) is a good approximation (<3% error) of the logarithmic profile for various sea states up to an elevation of 20 m. Above this elevation, the 1/7 power expression underestimates the wind speed for moderate to fully developed sea states. 相似文献