Probabilistic analysis of the DoB in axially-loaded tubular KT-joints of offshore structures

The degree of bending (DoB) characterizing the through-the-thickness stress distribution has a profound effect on the fatigue behavior of tubular joints commonly found in steel offshore structures and the determination of DoB values is essential for improving the accuracy of fatigue life estimation. Probability density functions of the involved random variables are necessary for the fatigue reliability analysis of offshore structures. The objective of present research was the derivation of probability density function (PDF) for the DoB in tubular KT-joints commonly found in jacket-type offshore platforms. A total of 162 finite element (FE) analyses were carried out on 81 FE models of KT-joints subjected to two types of axial loading. Generated FE models were validated using experimental data, previous FE results, and available parametric equations. Based on the results of parametric FE study, a sample database was prepared for the DoB values and density histograms were generated for respective samples based on the Freedman-Diaconis rule. Thirteen theoretical PDFs were fitted to the developed histograms and the maximum likelihood (ML) method was applied to evaluate the parameters of fitted PDFs. In each case, the Kolmogorov-Smirnov test was used to evaluate the goodness of fit. Finally, the Generalized Extreme Value model was proposed as the governing probability distribution function for the DoB. After substituting the values of estimated parameters, six fully defined PDFs were presented for the DoB in tubular KT-joints subjected to two types of axial loading.     

pH胁迫对不同规格刺参生长及免疫酶活性的影响

以大、中、小3种不同规格的刺参(Apostichopus japonicus)为对象,在pH为7.3、7.5、8.2、8.7、8.9不同环境中养殖30d,观测刺参行为、生长及溶菌酶(LZM)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性。结果显示:当pH为7.5、8.7时, 3种不同规格刺参均能正常活动、摄食、生长,未表现出异常状况;若超出此范围,刺参出现粪便细短、残饵增多、摄食量减少等现象,尤其在pH 8.9时,中规格刺参有明显棘刺收缩的现象,小规格刺参不同程度地出现身体收缩、棘刺平滑状态,而大规格刺参无明显表观不适现象。不同pH对3种规格刺参的特定生长率(SGR)有显著影响,随着pH升高或者降低,刺参SGR均逐渐下降,与对照组差异显著(P0.05),规格越小刺参受到抑制作用越大;刺参LZM、SOD、CAT活性随pH胁迫时间的延长呈现先升高后下降的趋势,在第10天时达到最高,与对照组差异显著(P0.05),至30 d胁迫结束时,在pH 7.3、8.9条件下,刺参免疫酶活性显著低于对照组(P0.05),而pH为7.5、8.7时,刺参免疫酶活性与对照差异不显著; pH胁迫对不同规格刺参非特异性免疫酶活性的影响存在差异,在相同胁迫条件下,酶活性依次为大规格中规格小规格,当pH7.3、8.9时,小中大规格分别在胁迫20 d、25 d、25 d后免疫酶活性显著低于对照组(P0.05)。研究表明, pH胁迫会对刺参生长及免疫产生明显的影响,在刺参养殖过程中, pH属关键的理化因子之一,应密切关注其变化。     

莱州湾湿地资源价值评估综合研究

文章分析了国内外资源价值评估现状及莱州湾湿地自然资源地理经济概况,构建了价值评估体系,运用价值评估方法对该湾湿地资源的直接和非直接使用价值进行评估计算,结果分别为449 640.5万元/a(其中,水产资源价值220 532万元/a,水资源价值73 887万元/a,原盐资源生产价值147 200万元/a,植物资源生产价值8 021.5万元/a)和85 972.6万元/a(其中,气候调节49 976万元/a,涵养水源27 515万元/a,湿地水质净化4 008万元/a,生物多样性维护4 473.6万元/a),发现水产资源、水资源、矿物资源、气候调节与涵养水源为莱州湾资源价值量较高的前5位。综上所述,本研究认为当地政府、企业及公众在发展经济的同时也应充分利用当地资源优势发展渔业与盐化工产业,以达资源可持续利用及生态保护之目的。     

不同条件因子对海月水母胃丝蛋白酶活性的影响

本实验采用福林-酚法测定了海月水母(Aureliaaurita)胃丝酶粗提液中蛋白酶的活性,并系统地研究了不同温度、pH和金属离子对海月水母胃丝蛋白酶活性的影响。结果表明,海月水母胃丝蛋白酶具有很高的活性,且蛋白酶的最适温度为37℃,最适pH值为8.5。Mn~(2+)离子对海月水母蛋白酶活性具有良好的促进作用,而Cu~(2+)和Zn~(2+)对蛋白酶具有很强的抑制作用, Mg~(2+)、K~+、Ca~(2+)对蛋白酶活性没有明显影响。     

海洋酸度变化下孔石莼对农药硫丹的生态响应研究

硫丹作为一种持久性有机氯农药,其对水生生物的毒性已引起广泛关注。本文以大型海藻孔石莼为材料,探究了海洋酸度变化下硫丹对孔石莼的生态毒理学效应。实验结果表明,低浓度硫丹对孔石莼的生长、光合色素及2种抗氧化酶均有明显的促进效应,50μg/L的硫丹促进效应最为显著,然而随着硫丹浓度的升高或暴露时间的延长,抑制作用明显增强。pH=7.9会促进孔石莼的生长,但会降低藻体内光合色素的含量。低pH环境会进一步加剧硫丹对孔石莼的毒性效应,两者的交互作用在不同时间段发挥不同的主效应。     

几种降水pH值预报方法效果对比分析

将4种预报pH值的模式(欧拉酸沉降数值预报模式、神经网络预报模式、动态统计预报模式和集成预报模式),对2005年汛期(5～9月)的预报资料进行了对比,分析了这几种模式预报效果.结果显示:欧拉数值模式有较严重的计算数据溢出;4种预报模式均存在本地化不足问题,预报准确率受城市降水本身的pH值高低影响;内陆城市与沿海城市酸雨可能有不同的发生机制,并对各模式的预报效果产生影响;部分没有阴阳离子的模式在一些城市的预报效果可以接近有阴阳离子的模式.     

菲律宾蛤仔血淋巴溶菌酶活性的研究

通过不同的反应条件对菲律宾蛤仔(Ruditapes philippinarum)血淋巴溶菌酶活力的影响实验,发现各反应条件与菲律宾蛤仔血淋巴溶菌活力密切相关:随着血淋巴添加量的增加,菲律宾蛤仔血淋巴溶菌活力逐渐升高,添加量在150~250μL之间时,两者呈现直线关系;溶菌活力随着温度和pH的升高呈峰值变化,分别在反应温度为50℃和pH为6.4时达到最大值,但统计分析显示pH在5.2~6.4之间时,溶菌活力差异不显著(P>0.05);溶菌活力随着反应时间的延长逐渐升高,当反应时间大于100 min后趋于稳定。这为探讨菲律宾蛤仔免疫力的不同变化提供基础性的数据。     

Interpreting Economics,Rhetoric and Sustainable Development: Some implications for policy determination

Many of the controversies about environmental resource use relate to the perceived conflict between economics and conservation. This conflict might have been resolved with general acceptance of the concept of sustainable development, and with a more transparent and honest use of economics terminology. However, interpretation and application of this concept appear to have led to some further conflicts between perceptions of economics and the environment, partly because commerce and development are sometimes portrayed as having the same meaning. Commercial activity resulting from the use of natural resources is often held to promote social good, while conservation of natural resources, many argue, renders the wealth which may be obtained from such resources unavailable. The latter is deemed to be bad for society. However, although in contemporary parlance economics is usually restricted implicitly to issues concerning commerce, finance and profit, economic theory requires the consideration also of intangible values, such as environmental damage. Environmental and other economists have worked hard to stress the importance of non-financial values in economic theory, and to ensure that they are included in economic analysis. However, these latter aspects of economics are not generally known to the wider public, partly because of the tendentious manner in which interested parties often use economics. When positions are argued on the basis of economics, the arguments are frequently expressed in language designed to persuade members of the community that all commercial activity is in the interests of society, while incurring minimal costs. In these circumstances, economics might be viewed as a form of rhetoric. Anyone assessing the merits of such arguments ought to consider carefully what this rhetoric really means. This is especially important in discussions concerning sustainable development, which is understood by some to mean sustainable, or sustained, commerce.     

Surface-sediment and epilithic diatom pH calibration sets for remote European mountain lakes (AL:PE Project) and their comparison with the Surface Waters Acidification Programme (SWAP) calibration set

A modern diatom-pH calibration data-set consisting of surface-sediment diatom assemblages from 118 lakes and 530 taxa is presented. The AL:PE data-set is from high-altitude or high-latitude lakes in the Alps, Norway, Svalbard, Kola Peninsula, UK, Slovenia, Slovakia, Poland, Portugal, and Spain (pH range = 4.5-8.0; DOC range = 0.2-3.2 mg l^-1). In addition, 92 epilithon samples from 22 high-altitude or high-latitude lakes comprise an AL:PE epilithon diatom-pH data-set. Weighted averaging partial least squares regression is used to develop pH-inference models. The AL:PE data-set has a root-mean-square-error of prediction (RMSEP) of 0.33 and a maximum bias of 0.36 pH units and r² of 0.82, as assessed by leave-one-out cross-validation. The epilithon data-set has, after data-screening and the deletion of one very obvious outlier, a RMSEP of 0.23 and a maximum bias of 0.18 pH units and r² of 0.88. The 167 sample SWAP diatom-pH data-set from lowland or upland lakes in the UK, Norway, and Sweden has a RMSEP of 0.29 and a maximum bias of 0.23 pH units and r² of 0.86.The pH optima, as estimated by weighted averaging and Gaussian regression, are compared for the three data-sets (AL:PE, SWAP, AL:PE epilithon). There is a good correspondence between the AL:PE and the AL:PE epilithon optima, but a consistent bias between the AL:PE and SWAP optima, with the SWAP optima being lower than the AL:PE estimates.The predictive performances of the AL:PE and SWAP calibration data-sets are compared using independent test samples and six core sequences, all from high-altitude lakes, one in south-east Siberia and five in eastern Scotland. The results show the importance of using the AL:PE data-set for inferring lake-water pH from diatom assemblages in high-altitude or high latitude lakes with low DOC concentrations.     

Diatom responses to late-glacial and early-Holocene environmental changes at Kråkenes, western Norway

A stratigraphic diatom sequence is presented for the period from 13,870-9,170 cal BP from Kråkenes Lake, western Norway. Changes in species assemblages are discussed with reference to the changing environmental conditions in the Allerød, Younger Dryas, and the early Holocene and to the development of the aquatic ecosystem. The site is sensitive to acidification, and diatom-based transfer functions are applied to estimate the past pH status. The combination of rapid sediment accumulation together with an excellent calibrated radiocarbon chronology means that the rate of inferred pH change and associated increase in [H⁺] can be assessed and compared with recent, anthropogenically acidified situations.The Allerød diatom assemblages are dominated by benthic taxa particularly Fragilaria species, indicating an unproductive, alkaline, turbid, and immature system. Diatoms are absent in the early part of the Younger Dryas, but subsequently a sparse planktonic flora develops reflecting decreased turbidity and/or increased nutrient supply. A clear sequence of diatom assemblages is seen in the early Holocene. A short-lived peak of Stephanodiscus species indicating a period of increased nutrient availability occurred at ca. 11,500 cal BP. Throughout the early Holocene, acid-tolerant species increasingly replaced less acidophilous, circumneutral taxa.The lake became slightly more acid during the Allerød, but this was statistically insignificant in a trend test involving regression of pH or [H⁺] in relation to age. Diatom-inferred pH declined rapidly during the early Holocene period investigated (9,175-11,525 cal BP) with a statistically significant overall rate of 0.024 pH units per 100 yrs. This consisted of an older (ca. 11,525-10,255 cal BP) phase, where pH fell more rapidly at up to 0.095 pH units per 100 yrs; and a younger phase after ca. 10,500 cal BP where the pH fall was extremely slow (0.008 pH units per 100 yrs) and was not statistically significant.In the Allerød a combination of low catchment productivity together with disturbance, weathering, and minerogenic inwash ensured that the base-cation status remained relatively high. In the Holocene the catchment soils stabilised and base cations were sequestered by terrestrial vegetation and soil. This resulted in reduced base-cation leaching and this, together with the production of organic acids caused the lake to acidify, reaching an equilibrium by ca. 10,000 cal BP.